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llvm / llvm-project / llvm / 0f046bf7abbdfa40aeef31d86835b7adb530511f / . / lib / Analysis / ValueTracking.cpp
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//===- ValueTracking.cpp - Walk computations to compute properties --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains routines that help analyze properties that chains of
// computations have.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumeBundleQueries.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DomConditionCache.h"
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/Analysis/WithCache.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/EHPersonalities.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/IR/IntrinsicsAMDGPU.h"
#include "llvm/IR/IntrinsicsRISCV.h"
#include "llvm/IR/IntrinsicsX86.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/TargetParser/RISCVTargetParser.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <optional>
#include <utility>
using namespace llvm;
using namespace llvm::PatternMatch;
// Controls the number of uses of the value searched for possible
// dominating comparisons.
static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses",
cl::Hidden, cl::init(20));
/// Returns the bitwidth of the given scalar or pointer type. For vector types,
/// returns the element type's bitwidth.
static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
if (unsigned BitWidth = Ty->getScalarSizeInBits())
return BitWidth;
return DL.getPointerTypeSizeInBits(Ty);
}
// Given the provided Value and, potentially, a context instruction, return
// the preferred context instruction (if any).
static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
// If we've been provided with a context instruction, then use that (provided
// it has been inserted).
if (CxtI && CxtI->getParent())
return CxtI;
// If the value is really an already-inserted instruction, then use that.
CxtI = dyn_cast<Instruction>(V);
if (CxtI && CxtI->getParent())
return CxtI;
return nullptr;
}
static const Instruction *safeCxtI(const Value *V1, const Value *V2, const Instruction *CxtI) {
// If we've been provided with a context instruction, then use that (provided
// it has been inserted).
if (CxtI && CxtI->getParent())
return CxtI;
// If the value is really an already-inserted instruction, then use that.
CxtI = dyn_cast<Instruction>(V1);
if (CxtI && CxtI->getParent())
return CxtI;
CxtI = dyn_cast<Instruction>(V2);
if (CxtI && CxtI->getParent())
return CxtI;
return nullptr;
}
static bool getShuffleDemandedElts(const ShuffleVectorInst *Shuf,
const APInt &DemandedElts,
APInt &DemandedLHS, APInt &DemandedRHS) {
if (isa<ScalableVectorType>(Shuf->getType())) {
assert(DemandedElts == APInt(1,1));
DemandedLHS = DemandedRHS = DemandedElts;
return true;
}
int NumElts =
cast<FixedVectorType>(Shuf->getOperand(0)->getType())->getNumElements();
return llvm::getShuffleDemandedElts(NumElts, Shuf->getShuffleMask(),
DemandedElts, DemandedLHS, DemandedRHS);
}
static void computeKnownBits(const Value *V, const APInt &DemandedElts,
KnownBits &Known, unsigned Depth,
const SimplifyQuery &Q);
void llvm::computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
const SimplifyQuery &Q) {
// Since the number of lanes in a scalable vector is unknown at compile time,
// we track one bit which is implicitly broadcast to all lanes. This means
// that all lanes in a scalable vector are considered demanded.
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
::computeKnownBits(V, DemandedElts, Known, Depth, Q);
}
void llvm::computeKnownBits(const Value *V, KnownBits &Known,
const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
computeKnownBits(
V, Known, Depth,
SimplifyQuery(DL, DT, AC, safeCxtI(V, CxtI), UseInstrInfo));
}
KnownBits llvm::computeKnownBits(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return computeKnownBits(
V, Depth, SimplifyQuery(DL, DT, AC, safeCxtI(V, CxtI), UseInstrInfo));
}
KnownBits llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return computeKnownBits(
V, DemandedElts, Depth,
SimplifyQuery(DL, DT, AC, safeCxtI(V, CxtI), UseInstrInfo));
}
static bool haveNoCommonBitsSetSpecialCases(const Value *LHS, const Value *RHS,
const SimplifyQuery &SQ) {
// Look for an inverted mask: (X & ~M) op (Y & M).
{
Value *M;
if (match(LHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
match(RHS, m_c_And(m_Specific(M), m_Value())) &&
isGuaranteedNotToBeUndef(M, SQ.AC, SQ.CxtI, SQ.DT))
return true;
}
// X op (Y & ~X)
if (match(RHS, m_c_And(m_Not(m_Specific(LHS)), m_Value())) &&
isGuaranteedNotToBeUndef(LHS, SQ.AC, SQ.CxtI, SQ.DT))
return true;
// X op ((X & Y) ^ Y) -- this is the canonical form of the previous pattern
// for constant Y.
Value *Y;
if (match(RHS,
m_c_Xor(m_c_And(m_Specific(LHS), m_Value(Y)), m_Deferred(Y))) &&
isGuaranteedNotToBeUndef(LHS, SQ.AC, SQ.CxtI, SQ.DT) &&
isGuaranteedNotToBeUndef(Y, SQ.AC, SQ.CxtI, SQ.DT))
return true;
// Peek through extends to find a 'not' of the other side:
// (ext Y) op ext(~Y)
if (match(LHS, m_ZExtOrSExt(m_Value(Y))) &&
match(RHS, m_ZExtOrSExt(m_Not(m_Specific(Y)))) &&
isGuaranteedNotToBeUndef(Y, SQ.AC, SQ.CxtI, SQ.DT))
return true;
// Look for: (A & B) op ~(A | B)
{
Value *A, *B;
if (match(LHS, m_And(m_Value(A), m_Value(B))) &&
match(RHS, m_Not(m_c_Or(m_Specific(A), m_Specific(B)))) &&
isGuaranteedNotToBeUndef(A, SQ.AC, SQ.CxtI, SQ.DT) &&
isGuaranteedNotToBeUndef(B, SQ.AC, SQ.CxtI, SQ.DT))
return true;
}
return false;
}
bool llvm::haveNoCommonBitsSet(const WithCache<const Value *> &LHSCache,
const WithCache<const Value *> &RHSCache,
const SimplifyQuery &SQ) {
const Value *LHS = LHSCache.getValue();
const Value *RHS = RHSCache.getValue();
assert(LHS->getType() == RHS->getType() &&
"LHS and RHS should have the same type");
assert(LHS->getType()->isIntOrIntVectorTy() &&
"LHS and RHS should be integers");
if (haveNoCommonBitsSetSpecialCases(LHS, RHS, SQ) ||
haveNoCommonBitsSetSpecialCases(RHS, LHS, SQ))
return true;
return KnownBits::haveNoCommonBitsSet(LHSCache.getKnownBits(SQ),
RHSCache.getKnownBits(SQ));
}
bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *I) {
return !I->user_empty() && all_of(I->users(), [](const User *U) {
ICmpInst::Predicate P;
return match(U, m_ICmp(P, m_Value(), m_Zero())) && ICmpInst::isEquality(P);
});
}
static bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
const SimplifyQuery &Q);
bool llvm::isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
bool OrZero, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::isKnownToBeAPowerOfTwo(
V, OrZero, Depth,
SimplifyQuery(DL, DT, AC, safeCxtI(V, CxtI), UseInstrInfo));
}
static bool isKnownNonZero(const Value *V, const APInt &DemandedElts,
const SimplifyQuery &Q, unsigned Depth);
bool llvm::isKnownNonNegative(const Value *V, const SimplifyQuery &SQ,
unsigned Depth) {
return computeKnownBits(V, Depth, SQ).isNonNegative();
}
bool llvm::isKnownPositive(const Value *V, const SimplifyQuery &SQ,
unsigned Depth) {
if (auto *CI = dyn_cast<ConstantInt>(V))
return CI->getValue().isStrictlyPositive();
// If `isKnownNonNegative` ever becomes more sophisticated, make sure to keep
// this updated.
KnownBits Known = computeKnownBits(V, Depth, SQ);
return Known.isNonNegative() &&
(Known.isNonZero() || isKnownNonZero(V, SQ, Depth));
}
bool llvm::isKnownNegative(const Value *V, const SimplifyQuery &SQ,
unsigned Depth) {
return computeKnownBits(V, Depth, SQ).isNegative();
}
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q);
bool llvm::isKnownNonEqual(const Value *V1, const Value *V2,
const DataLayout &DL, AssumptionCache *AC,
const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
return ::isKnownNonEqual(
V1, V2, 0,
SimplifyQuery(DL, DT, AC, safeCxtI(V2, V1, CxtI), UseInstrInfo));
}
bool llvm::MaskedValueIsZero(const Value *V, const APInt &Mask,
const SimplifyQuery &SQ, unsigned Depth) {
KnownBits Known(Mask.getBitWidth());
computeKnownBits(V, Known, Depth, SQ);
return Mask.isSubsetOf(Known.Zero);
}
static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q);
static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
const SimplifyQuery &Q) {
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
return ComputeNumSignBits(V, DemandedElts, Depth, Q);
}
unsigned llvm::ComputeNumSignBits(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::ComputeNumSignBits(
V, Depth, SimplifyQuery(DL, DT, AC, safeCxtI(V, CxtI), UseInstrInfo));
}
unsigned llvm::ComputeMaxSignificantBits(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
unsigned SignBits = ComputeNumSignBits(V, DL, Depth, AC, CxtI, DT);
return V->getType()->getScalarSizeInBits() - SignBits + 1;
}
static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
bool NSW, bool NUW,
const APInt &DemandedElts,
KnownBits &KnownOut, KnownBits &Known2,
unsigned Depth, const SimplifyQuery &Q) {
computeKnownBits(Op1, DemandedElts, KnownOut, Depth + 1, Q);
// If one operand is unknown and we have no nowrap information,
// the result will be unknown independently of the second operand.
if (KnownOut.isUnknown() && !NSW && !NUW)
return;
computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
KnownOut = KnownBits::computeForAddSub(Add, NSW, NUW, Known2, KnownOut);
}
static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
const APInt &DemandedElts, KnownBits &Known,
KnownBits &Known2, unsigned Depth,
const SimplifyQuery &Q) {
computeKnownBits(Op1, DemandedElts, Known, Depth + 1, Q);
computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
bool isKnownNegative = false;
bool isKnownNonNegative = false;
// If the multiplication is known not to overflow, compute the sign bit.
if (NSW) {
if (Op0 == Op1) {
// The product of a number with itself is non-negative.
isKnownNonNegative = true;
} else {
bool isKnownNonNegativeOp1 = Known.isNonNegative();
bool isKnownNonNegativeOp0 = Known2.isNonNegative();
bool isKnownNegativeOp1 = Known.isNegative();
bool isKnownNegativeOp0 = Known2.isNegative();
// The product of two numbers with the same sign is non-negative.
isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
(isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
// The product of a negative number and a non-negative number is either
// negative or zero.
if (!isKnownNonNegative)
isKnownNegative =
(isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
Known2.isNonZero()) ||
(isKnownNegativeOp0 && isKnownNonNegativeOp1 && Known.isNonZero());
}
}
bool SelfMultiply = Op0 == Op1;
if (SelfMultiply)
SelfMultiply &=
isGuaranteedNotToBeUndef(Op0, Q.AC, Q.CxtI, Q.DT, Depth + 1);
Known = KnownBits::mul(Known, Known2, SelfMultiply);
// Only make use of no-wrap flags if we failed to compute the sign bit
// directly. This matters if the multiplication always overflows, in
// which case we prefer to follow the result of the direct computation,
// though as the program is invoking undefined behaviour we can choose
// whatever we like here.
if (isKnownNonNegative && !Known.isNegative())
Known.makeNonNegative();
else if (isKnownNegative && !Known.isNonNegative())
Known.makeNegative();
}
void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
KnownBits &Known) {
unsigned BitWidth = Known.getBitWidth();
unsigned NumRanges = Ranges.getNumOperands() / 2;
assert(NumRanges >= 1);
Known.Zero.setAllBits();
Known.One.setAllBits();
for (unsigned i = 0; i < NumRanges; ++i) {
ConstantInt *Lower =
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
ConstantInt *Upper =
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
ConstantRange Range(Lower->getValue(), Upper->getValue());
// The first CommonPrefixBits of all values in Range are equal.
unsigned CommonPrefixBits =
(Range.getUnsignedMax() ^ Range.getUnsignedMin()).countl_zero();
APInt Mask = APInt::getHighBitsSet(BitWidth, CommonPrefixBits);
APInt UnsignedMax = Range.getUnsignedMax().zextOrTrunc(BitWidth);
Known.One &= UnsignedMax & Mask;
Known.Zero &= ~UnsignedMax & Mask;
}
}
static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
SmallVector<const Value *, 16> WorkSet(1, I);
SmallPtrSet<const Value *, 32> Visited;
SmallPtrSet<const Value *, 16> EphValues;
// The instruction defining an assumption's condition itself is always
// considered ephemeral to that assumption (even if it has other
// non-ephemeral users). See r246696's test case for an example.
if (is_contained(I->operands(), E))
return true;
while (!WorkSet.empty()) {
const Value *V = WorkSet.pop_back_val();
if (!Visited.insert(V).second)
continue;
// If all uses of this value are ephemeral, then so is this value.
if (llvm::all_of(V->users(), [&](const User *U) {
return EphValues.count(U);
})) {
if (V == E)
return true;
if (V == I || (isa<Instruction>(V) &&
!cast<Instruction>(V)->mayHaveSideEffects() &&
!cast<Instruction>(V)->isTerminator())) {
EphValues.insert(V);
if (const User *U = dyn_cast<User>(V))
append_range(WorkSet, U->operands());
}
}
}
return false;
}
// Is this an intrinsic that cannot be speculated but also cannot trap?
bool llvm::isAssumeLikeIntrinsic(const Instruction *I) {
if (const IntrinsicInst *CI = dyn_cast<IntrinsicInst>(I))
return CI->isAssumeLikeIntrinsic();
return false;
}
bool llvm::isValidAssumeForContext(const Instruction *Inv,
const Instruction *CxtI,
const DominatorTree *DT,
bool AllowEphemerals) {
// There are two restrictions on the use of an assume:
// 1. The assume must dominate the context (or the control flow must
// reach the assume whenever it reaches the context).
// 2. The context must not be in the assume's set of ephemeral values
// (otherwise we will use the assume to prove that the condition
// feeding the assume is trivially true, thus causing the removal of
// the assume).
if (Inv->getParent() == CxtI->getParent()) {
// If Inv and CtxI are in the same block, check if the assume (Inv) is first
// in the BB.
if (Inv->comesBefore(CxtI))
return true;
// Don't let an assume affect itself - this would cause the problems
// `isEphemeralValueOf` is trying to prevent, and it would also make
// the loop below go out of bounds.
if (!AllowEphemerals && Inv == CxtI)
return false;
// The context comes first, but they're both in the same block.
// Make sure there is nothing in between that might interrupt
// the control flow, not even CxtI itself.
// We limit the scan distance between the assume and its context instruction
// to avoid a compile-time explosion. This limit is chosen arbitrarily, so
// it can be adjusted if needed (could be turned into a cl::opt).
auto Range = make_range(CxtI->getIterator(), Inv->getIterator());
if (!isGuaranteedToTransferExecutionToSuccessor(Range, 15))
return false;
return AllowEphemerals || !isEphemeralValueOf(Inv, CxtI);
}
// Inv and CxtI are in different blocks.
if (DT) {
if (DT->dominates(Inv, CxtI))
return true;
} else if (Inv->getParent() == CxtI->getParent()->getSinglePredecessor()) {
// We don't have a DT, but this trivially dominates.
return true;
}
return false;
}
// TODO: cmpExcludesZero misses many cases where `RHS` is non-constant but
// we still have enough information about `RHS` to conclude non-zero. For
// example Pred=EQ, RHS=isKnownNonZero. cmpExcludesZero is called in loops
// so the extra compile time may not be worth it, but possibly a second API
// should be created for use outside of loops.
static bool cmpExcludesZero(CmpInst::Predicate Pred, const Value *RHS) {
// v u> y implies v != 0.
if (Pred == ICmpInst::ICMP_UGT)
return true;
// Special-case v != 0 to also handle v != null.
if (Pred == ICmpInst::ICMP_NE)
return match(RHS, m_Zero());
// All other predicates - rely on generic ConstantRange handling.
const APInt *C;
auto Zero = APInt::getZero(RHS->getType()->getScalarSizeInBits());
if (match(RHS, m_APInt(C))) {
ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(Pred, *C);
return !TrueValues.contains(Zero);
}
auto *VC = dyn_cast<ConstantDataVector>(RHS);
if (VC == nullptr)
return false;
for (unsigned ElemIdx = 0, NElem = VC->getNumElements(); ElemIdx < NElem;
++ElemIdx) {
ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(
Pred, VC->getElementAsAPInt(ElemIdx));
if (TrueValues.contains(Zero))
return false;
}
return true;
}
static bool isKnownNonZeroFromAssume(const Value *V, const SimplifyQuery &Q) {
// Use of assumptions is context-sensitive. If we don't have a context, we
// cannot use them!
if (!Q.AC || !Q.CxtI)
return false;
for (AssumptionCache::ResultElem &Elem : Q.AC->assumptionsFor(V)) {
if (!Elem.Assume)
continue;
AssumeInst *I = cast<AssumeInst>(Elem.Assume);
assert(I->getFunction() == Q.CxtI->getFunction() &&
"Got assumption for the wrong function!");
if (Elem.Index != AssumptionCache::ExprResultIdx) {
if (!V->getType()->isPointerTy())
continue;
if (RetainedKnowledge RK = getKnowledgeFromBundle(
*I, I->bundle_op_info_begin()[Elem.Index])) {
if (RK.WasOn == V &&
(RK.AttrKind == Attribute::NonNull ||
(RK.AttrKind == Attribute::Dereferenceable &&
!NullPointerIsDefined(Q.CxtI->getFunction(),
V->getType()->getPointerAddressSpace()))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT))
return true;
}
continue;
}
// Warning: This loop can end up being somewhat performance sensitive.
// We're running this loop for once for each value queried resulting in a
// runtime of ~O(#assumes * #values).
Value *RHS;
CmpInst::Predicate Pred;
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
if (!match(I->getArgOperand(0), m_c_ICmp(Pred, m_V, m_Value(RHS))))
return false;
if (cmpExcludesZero(Pred, RHS) && isValidAssumeForContext(I, Q.CxtI, Q.DT))
return true;
}
return false;
}
static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
Value *LHS, Value *RHS, KnownBits &Known,
const SimplifyQuery &Q) {
if (RHS->getType()->isPointerTy()) {
// Handle comparison of pointer to null explicitly, as it will not be
// covered by the m_APInt() logic below.
if (LHS == V && match(RHS, m_Zero())) {
switch (Pred) {
case ICmpInst::ICMP_EQ:
Known.setAllZero();
break;
case ICmpInst::ICMP_SGE:
case ICmpInst::ICMP_SGT:
Known.makeNonNegative();
break;
case ICmpInst::ICMP_SLT:
Known.makeNegative();
break;
default:
break;
}
}
return;
}
unsigned BitWidth = Known.getBitWidth();
auto m_V =
m_CombineOr(m_Specific(V), m_PtrToIntSameSize(Q.DL, m_Specific(V)));
Value *Y;
const APInt *Mask, *C;
uint64_t ShAmt;
switch (Pred) {
case ICmpInst::ICMP_EQ:
// assume(V = C)
if (match(LHS, m_V) && match(RHS, m_APInt(C))) {
Known = Known.unionWith(KnownBits::makeConstant(*C));
// assume(V & Mask = C)
} else if (match(LHS, m_c_And(m_V, m_Value(Y))) &&
match(RHS, m_APInt(C))) {
// For one bits in Mask, we can propagate bits from C to V.
Known.One |= *C;
if (match(Y, m_APInt(Mask)))
Known.Zero |= ~*C & *Mask;
// assume(V | Mask = C)
} else if (match(LHS, m_c_Or(m_V, m_Value(Y))) && match(RHS, m_APInt(C))) {
// For zero bits in Mask, we can propagate bits from C to V.
Known.Zero |= ~*C;
if (match(Y, m_APInt(Mask)))
Known.One |= *C & ~*Mask;
// assume(V ^ Mask = C)
} else if (match(LHS, m_Xor(m_V, m_APInt(Mask))) &&
match(RHS, m_APInt(C))) {
// Equivalent to assume(V == Mask ^ C)
Known = Known.unionWith(KnownBits::makeConstant(*C ^ *Mask));
// assume(V << ShAmt = C)
} else if (match(LHS, m_Shl(m_V, m_ConstantInt(ShAmt))) &&
match(RHS, m_APInt(C)) && ShAmt < BitWidth) {
// For those bits in C that are known, we can propagate them to known
// bits in V shifted to the right by ShAmt.
KnownBits RHSKnown = KnownBits::makeConstant(*C);
RHSKnown.Zero.lshrInPlace(ShAmt);
RHSKnown.One.lshrInPlace(ShAmt);
Known = Known.unionWith(RHSKnown);
// assume(V >> ShAmt = C)
} else if (match(LHS, m_Shr(m_V, m_ConstantInt(ShAmt))) &&
match(RHS, m_APInt(C)) && ShAmt < BitWidth) {
KnownBits RHSKnown = KnownBits::makeConstant(*C);
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
Known.Zero |= RHSKnown.Zero << ShAmt;
Known.One |= RHSKnown.One << ShAmt;
}
break;
case ICmpInst::ICMP_NE: {
// assume (V & B != 0) where B is a power of 2
const APInt *BPow2;
if (match(LHS, m_And(m_V, m_Power2(BPow2))) && match(RHS, m_Zero()))
Known.One |= *BPow2;
break;
}
default:
if (match(RHS, m_APInt(C))) {
const APInt *Offset = nullptr;
if (match(LHS, m_CombineOr(m_V, m_AddLike(m_V, m_APInt(Offset))))) {
ConstantRange LHSRange = ConstantRange::makeAllowedICmpRegion(Pred, *C);
if (Offset)
LHSRange = LHSRange.sub(*Offset);
Known = Known.unionWith(LHSRange.toKnownBits());
}
// X & Y u> C -> X u> C && Y u> C
if ((Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) &&
match(LHS, m_c_And(m_V, m_Value()))) {
Known.One.setHighBits(
(*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
}
// X | Y u< C -> X u< C && Y u< C
if ((Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) &&
match(LHS, m_c_Or(m_V, m_Value()))) {
Known.Zero.setHighBits(
(*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
}
}
break;
}
}
static void computeKnownBitsFromICmpCond(const Value *V, ICmpInst *Cmp,
KnownBits &Known,
const SimplifyQuery &SQ, bool Invert) {
ICmpInst::Predicate Pred =
Invert ? Cmp->getInversePredicate() : Cmp->getPredicate();
Value *LHS = Cmp->getOperand(0);
Value *RHS = Cmp->getOperand(1);
// Handle icmp pred (trunc V), C
if (match(LHS, m_Trunc(m_Specific(V)))) {
KnownBits DstKnown(LHS->getType()->getScalarSizeInBits());
computeKnownBitsFromCmp(LHS, Pred, LHS, RHS, DstKnown, SQ);
Known = Known.unionWith(DstKnown.anyext(Known.getBitWidth()));
return;
}
computeKnownBitsFromCmp(V, Pred, LHS, RHS, Known, SQ);
}
static void computeKnownBitsFromCond(const Value *V, Value *Cond,
KnownBits &Known, unsigned Depth,
const SimplifyQuery &SQ, bool Invert) {
Value *A, *B;
if (Depth < MaxAnalysisRecursionDepth &&
match(Cond, m_LogicalOp(m_Value(A), m_Value(B)))) {
KnownBits Known2(Known.getBitWidth());
KnownBits Known3(Known.getBitWidth());
computeKnownBitsFromCond(V, A, Known2, Depth + 1, SQ, Invert);
computeKnownBitsFromCond(V, B, Known3, Depth + 1, SQ, Invert);
if (Invert ? match(Cond, m_LogicalOr(m_Value(), m_Value()))
: match(Cond, m_LogicalAnd(m_Value(), m_Value())))
Known2 = Known2.unionWith(Known3);
else
Known2 = Known2.intersectWith(Known3);
Known = Known.unionWith(Known2);
}
if (auto *Cmp = dyn_cast<ICmpInst>(Cond))
computeKnownBitsFromICmpCond(V, Cmp, Known, SQ, Invert);
}
void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
unsigned Depth, const SimplifyQuery &Q) {
if (!Q.CxtI)
return;
if (Q.DC && Q.DT) {
// Handle dominating conditions.
for (BranchInst *BI : Q.DC->conditionsFor(V)) {
BasicBlockEdge Edge0(BI->getParent(), BI->getSuccessor(0));
if (Q.DT->dominates(Edge0, Q.CxtI->getParent()))
computeKnownBitsFromCond(V, BI->getCondition(), Known, Depth, Q,
/*Invert*/ false);
BasicBlockEdge Edge1(BI->getParent(), BI->getSuccessor(1));
if (Q.DT->dominates(Edge1, Q.CxtI->getParent()))
computeKnownBitsFromCond(V, BI->getCondition(), Known, Depth, Q,
/*Invert*/ true);
}
if (Known.hasConflict())
Known.resetAll();
}
if (!Q.AC)
return;
unsigned BitWidth = Known.getBitWidth();
// Note that the patterns below need to be kept in sync with the code
// in AssumptionCache::updateAffectedValues.
for (AssumptionCache::ResultElem &Elem : Q.AC->assumptionsFor(V)) {
if (!Elem.Assume)
continue;
AssumeInst *I = cast<AssumeInst>(Elem.Assume);
assert(I->getParent()->getParent() == Q.CxtI->getParent()->getParent() &&
"Got assumption for the wrong function!");
if (Elem.Index != AssumptionCache::ExprResultIdx) {
if (!V->getType()->isPointerTy())
continue;
if (RetainedKnowledge RK = getKnowledgeFromBundle(
*I, I->bundle_op_info_begin()[Elem.Index])) {
if (RK.WasOn == V && RK.AttrKind == Attribute::Alignment &&
isPowerOf2_64(RK.ArgValue) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT))
Known.Zero.setLowBits(Log2_64(RK.ArgValue));
}
continue;
}
// Warning: This loop can end up being somewhat performance sensitive.
// We're running this loop for once for each value queried resulting in a
// runtime of ~O(#assumes * #values).
Value *Arg = I->getArgOperand(0);
if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
assert(BitWidth == 1 && "assume operand is not i1?");
(void)BitWidth;
Known.setAllOnes();
return;
}
if (match(Arg, m_Not(m_Specific(V))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
assert(BitWidth == 1 && "assume operand is not i1?");
(void)BitWidth;
Known.setAllZero();
return;
}
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth == MaxAnalysisRecursionDepth)
continue;
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
if (!Cmp)
continue;
if (!isValidAssumeForContext(I, Q.CxtI, Q.DT))
continue;
computeKnownBitsFromICmpCond(V, Cmp, Known, Q, /*Invert=*/false);
}
// Conflicting assumption: Undefined behavior will occur on this execution
// path.
if (Known.hasConflict())
Known.resetAll();
}
/// Compute known bits from a shift operator, including those with a
/// non-constant shift amount. Known is the output of this function. Known2 is a
/// pre-allocated temporary with the same bit width as Known and on return
/// contains the known bit of the shift value source. KF is an
/// operator-specific function that, given the known-bits and a shift amount,
/// compute the implied known-bits of the shift operator's result respectively
/// for that shift amount. The results from calling KF are conservatively
/// combined for all permitted shift amounts.
static void computeKnownBitsFromShiftOperator(
const Operator *I, const APInt &DemandedElts, KnownBits &Known,
KnownBits &Known2, unsigned Depth, const SimplifyQuery &Q,
function_ref<KnownBits(const KnownBits &, const KnownBits &, bool)> KF) {
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
// To limit compile-time impact, only query isKnownNonZero() if we know at
// least something about the shift amount.
bool ShAmtNonZero =
Known.isNonZero() ||
(Known.getMaxValue().ult(Known.getBitWidth()) &&
isKnownNonZero(I->getOperand(1), DemandedElts, Q, Depth + 1));
Known = KF(Known2, Known, ShAmtNonZero);
}
static KnownBits
getKnownBitsFromAndXorOr(const Operator *I, const APInt &DemandedElts,
const KnownBits &KnownLHS, const KnownBits &KnownRHS,
unsigned Depth, const SimplifyQuery &Q) {
unsigned BitWidth = KnownLHS.getBitWidth();
KnownBits KnownOut(BitWidth);
bool IsAnd = false;
bool HasKnownOne = !KnownLHS.One.isZero() || !KnownRHS.One.isZero();
Value *X = nullptr, *Y = nullptr;
switch (I->getOpcode()) {
case Instruction::And:
KnownOut = KnownLHS & KnownRHS;
IsAnd = true;
// and(x, -x) is common idioms that will clear all but lowest set
// bit. If we have a single known bit in x, we can clear all bits
// above it.
// TODO: instcombine often reassociates independent `and` which can hide
// this pattern. Try to match and(x, and(-x, y)) / and(and(x, y), -x).
if (HasKnownOne && match(I, m_c_And(m_Value(X), m_Neg(m_Deferred(X))))) {
// -(-x) == x so using whichever (LHS/RHS) gets us a better result.
if (KnownLHS.countMaxTrailingZeros() <= KnownRHS.countMaxTrailingZeros())
KnownOut = KnownLHS.blsi();
else
KnownOut = KnownRHS.blsi();
}
break;
case Instruction::Or:
KnownOut = KnownLHS | KnownRHS;
break;
case Instruction::Xor:
KnownOut = KnownLHS ^ KnownRHS;
// xor(x, x-1) is common idioms that will clear all but lowest set
// bit. If we have a single known bit in x, we can clear all bits
// above it.
// TODO: xor(x, x-1) is often rewritting as xor(x, x-C) where C !=
// -1 but for the purpose of demanded bits (xor(x, x-C) &
// Demanded) == (xor(x, x-1) & Demanded). Extend the xor pattern
// to use arbitrary C if xor(x, x-C) as the same as xor(x, x-1).
if (HasKnownOne &&
match(I, m_c_Xor(m_Value(X), m_c_Add(m_Deferred(X), m_AllOnes())))) {
const KnownBits &XBits = I->getOperand(0) == X ? KnownLHS : KnownRHS;
KnownOut = XBits.blsmsk();
}
break;
default:
llvm_unreachable("Invalid Op used in 'analyzeKnownBitsFromAndXorOr'");
}
// and(x, add (x, -1)) is a common idiom that always clears the low bit;
// xor/or(x, add (x, -1)) is an idiom that will always set the low bit.
// here we handle the more general case of adding any odd number by
// matching the form and/xor/or(x, add(x, y)) where y is odd.
// TODO: This could be generalized to clearing any bit set in y where the
// following bit is known to be unset in y.
if (!KnownOut.Zero[0] && !KnownOut.One[0] &&
(match(I, m_c_BinOp(m_Value(X), m_c_Add(m_Deferred(X), m_Value(Y)))) ||
match(I, m_c_BinOp(m_Value(X), m_Sub(m_Deferred(X), m_Value(Y)))) ||
match(I, m_c_BinOp(m_Value(X), m_Sub(m_Value(Y), m_Deferred(X)))))) {
KnownBits KnownY(BitWidth);
computeKnownBits(Y, DemandedElts, KnownY, Depth + 1, Q);
if (KnownY.countMinTrailingOnes() > 0) {
if (IsAnd)
KnownOut.Zero.setBit(0);
else
KnownOut.One.setBit(0);
}
}
return KnownOut;
}
// Public so this can be used in `SimplifyDemandedUseBits`.
KnownBits llvm::analyzeKnownBitsFromAndXorOr(const Operator *I,
const KnownBits &KnownLHS,
const KnownBits &KnownRHS,
unsigned Depth,
const SimplifyQuery &SQ) {
auto *FVTy = dyn_cast<FixedVectorType>(I->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
return getKnownBitsFromAndXorOr(I, DemandedElts, KnownLHS, KnownRHS, Depth,
SQ);
}
ConstantRange llvm::getVScaleRange(const Function *F, unsigned BitWidth) {
Attribute Attr = F->getFnAttribute(Attribute::VScaleRange);
// Without vscale_range, we only know that vscale is non-zero.
if (!Attr.isValid())
return ConstantRange(APInt(BitWidth, 1), APInt::getZero(BitWidth));
unsigned AttrMin = Attr.getVScaleRangeMin();
// Minimum is larger than vscale width, result is always poison.
if ((unsigned)llvm::bit_width(AttrMin) > BitWidth)
return ConstantRange::getEmpty(BitWidth);
APInt Min(BitWidth, AttrMin);
std::optional<unsigned> AttrMax = Attr.getVScaleRangeMax();
if (!AttrMax || (unsigned)llvm::bit_width(*AttrMax) > BitWidth)
return ConstantRange(Min, APInt::getZero(BitWidth));
return ConstantRange(Min, APInt(BitWidth, *AttrMax) + 1);
}
static void computeKnownBitsFromOperator(const Operator *I,
const APInt &DemandedElts,
KnownBits &Known, unsigned Depth,
const SimplifyQuery &Q) {
unsigned BitWidth = Known.getBitWidth();
KnownBits Known2(BitWidth);
switch (I->getOpcode()) {
default: break;
case Instruction::Load:
if (MDNode *MD =
Q.IIQ.getMetadata(cast<LoadInst>(I), LLVMContext::MD_range))
computeKnownBitsFromRangeMetadata(*MD, Known);
break;
case Instruction::And:
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known = getKnownBitsFromAndXorOr(I, DemandedElts, Known2, Known, Depth, Q);
break;
case Instruction::Or:
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known = getKnownBitsFromAndXorOr(I, DemandedElts, Known2, Known, Depth, Q);
break;
case Instruction::Xor:
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known = getKnownBitsFromAndXorOr(I, DemandedElts, Known2, Known, Depth, Q);
break;
case Instruction::Mul: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, DemandedElts,
Known, Known2, Depth, Q);
break;
}
case Instruction::UDiv: {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known =
KnownBits::udiv(Known, Known2, Q.IIQ.isExact(cast<BinaryOperator>(I)));
break;
}
case Instruction::SDiv: {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known =
KnownBits::sdiv(Known, Known2, Q.IIQ.isExact(cast<BinaryOperator>(I)));
break;
}
case Instruction::Select: {
auto ComputeForArm = [&](Value *Arm, bool Invert) {
KnownBits Res(Known.getBitWidth());
computeKnownBits(Arm, Res, Depth + 1, Q);
// If we have a constant arm, we are done.
if (Res.isConstant())
return Res;
// See what condition implies about the bits of the two select arms.
KnownBits CondRes(Res.getBitWidth());
computeKnownBitsFromCond(Arm, I->getOperand(0), CondRes, Depth + 1, Q,
Invert);
// If we don't get any information from the condition, no reason to
// proceed.
if (CondRes.isUnknown())
return Res;
// We can have conflict if the condition is dead. I.e if we have
// (x | 64) < 32 ? (x | 64) : y
// we will have conflict at bit 6 from the condition/the `or`.
// In that case just return. Its not particularly important
// what we do, as this select is going to be simplified soon.
CondRes = CondRes.unionWith(Res);
if (CondRes.hasConflict())
return Res;
// Finally make sure the information we found is valid. This is relatively
// expensive so it's left for the very end.
if (!isGuaranteedNotToBeUndef(Arm, Q.AC, Q.CxtI, Q.DT, Depth + 1))
return Res;
// Finally, we know we get information from the condition and its valid,
// so return it.
return CondRes;
};
// Only known if known in both the LHS and RHS.
Known =
ComputeForArm(I->getOperand(1), /*Invert=*/false)
.intersectWith(ComputeForArm(I->getOperand(2), /*Invert=*/true));
break;
}
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::SIToFP:
case Instruction::UIToFP:
break; // Can't work with floating point.
case Instruction::PtrToInt:
case Instruction::IntToPtr:
// Fall through and handle them the same as zext/trunc.
[[fallthrough]];
case Instruction::ZExt:
case Instruction::Trunc: {
Type *SrcTy = I->getOperand(0)->getType();
unsigned SrcBitWidth;
// Note that we handle pointer operands here because of inttoptr/ptrtoint
// which fall through here.
Type *ScalarTy = SrcTy->getScalarType();
SrcBitWidth = ScalarTy->isPointerTy() ?
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
Q.DL.getTypeSizeInBits(ScalarTy);
assert(SrcBitWidth && "SrcBitWidth can't be zero");
Known = Known.anyextOrTrunc(SrcBitWidth);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
if (auto *Inst = dyn_cast<PossiblyNonNegInst>(I);
Inst && Inst->hasNonNeg() && !Known.isNegative())
Known.makeNonNegative();
Known = Known.zextOrTrunc(BitWidth);
break;
}
case Instruction::BitCast: {
Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy->isIntOrPtrTy() &&
// TODO: For now, not handling conversions like:
// (bitcast i64 %x to <2 x i32>)
!I->getType()->isVectorTy()) {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
break;
}
// Handle cast from vector integer type to scalar or vector integer.
auto *SrcVecTy = dyn_cast<FixedVectorType>(SrcTy);
if (!SrcVecTy || !SrcVecTy->getElementType()->isIntegerTy() ||
!I->getType()->isIntOrIntVectorTy() ||
isa<ScalableVectorType>(I->getType()))
break;
// Look through a cast from narrow vector elements to wider type.
// Examples: v4i32 -> v2i64, v3i8 -> v24
unsigned SubBitWidth = SrcVecTy->getScalarSizeInBits();
if (BitWidth % SubBitWidth == 0) {
// Known bits are automatically intersected across demanded elements of a
// vector. So for example, if a bit is computed as known zero, it must be
// zero across all demanded elements of the vector.
//
// For this bitcast, each demanded element of the output is sub-divided
// across a set of smaller vector elements in the source vector. To get
// the known bits for an entire element of the output, compute the known
// bits for each sub-element sequentially. This is done by shifting the
// one-set-bit demanded elements parameter across the sub-elements for
// consecutive calls to computeKnownBits. We are using the demanded
// elements parameter as a mask operator.
//
// The known bits of each sub-element are then inserted into place
// (dependent on endian) to form the full result of known bits.
unsigned NumElts = DemandedElts.getBitWidth();
unsigned SubScale = BitWidth / SubBitWidth;
APInt SubDemandedElts = APInt::getZero(NumElts * SubScale);
for (unsigned i = 0; i != NumElts; ++i) {
if (DemandedElts[i])
SubDemandedElts.setBit(i * SubScale);
}
KnownBits KnownSrc(SubBitWidth);
for (unsigned i = 0; i != SubScale; ++i) {
computeKnownBits(I->getOperand(0), SubDemandedElts.shl(i), KnownSrc,
Depth + 1, Q);
unsigned ShiftElt = Q.DL.isLittleEndian() ? i : SubScale - 1 - i;
Known.insertBits(KnownSrc, ShiftElt * SubBitWidth);
}
}
break;
}
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
Known = Known.trunc(SrcBitWidth);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
Known = Known.sext(BitWidth);
break;
}
case Instruction::Shl: {
bool NUW = Q.IIQ.hasNoUnsignedWrap(cast<OverflowingBinaryOperator>(I));
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
auto KF = [NUW, NSW](const KnownBits &KnownVal, const KnownBits &KnownAmt,
bool ShAmtNonZero) {
return KnownBits::shl(KnownVal, KnownAmt, NUW, NSW, ShAmtNonZero);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
// Trailing zeros of a right-shifted constant never decrease.
const APInt *C;
if (match(I->getOperand(0), m_APInt(C)))
Known.Zero.setLowBits(C->countr_zero());
break;
}
case Instruction::LShr: {
bool Exact = Q.IIQ.isExact(cast<BinaryOperator>(I));
auto KF = [Exact](const KnownBits &KnownVal, const KnownBits &KnownAmt,
bool ShAmtNonZero) {
return KnownBits::lshr(KnownVal, KnownAmt, ShAmtNonZero, Exact);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
// Leading zeros of a left-shifted constant never decrease.
const APInt *C;
if (match(I->getOperand(0), m_APInt(C)))
Known.Zero.setHighBits(C->countl_zero());
break;
}
case Instruction::AShr: {
bool Exact = Q.IIQ.isExact(cast<BinaryOperator>(I));
auto KF = [Exact](const KnownBits &KnownVal, const KnownBits &KnownAmt,
bool ShAmtNonZero) {
return KnownBits::ashr(KnownVal, KnownAmt, ShAmtNonZero, Exact);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
break;
}
case Instruction::Sub: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
bool NUW = Q.IIQ.hasNoUnsignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW, NUW,
DemandedElts, Known, Known2, Depth, Q);
break;
}
case Instruction::Add: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
bool NUW = Q.IIQ.hasNoUnsignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW, NUW,
DemandedElts, Known, Known2, Depth, Q);
break;
}
case Instruction::SRem:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::srem(Known, Known2);
break;
case Instruction::URem:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::urem(Known, Known2);
break;
case Instruction::Alloca:
Known.Zero.setLowBits(Log2(cast<AllocaInst>(I)->getAlign()));
break;
case Instruction::GetElementPtr: {
// Analyze all of the subscripts of this getelementptr instruction
// to determine if we can prove known low zero bits.
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
// Accumulate the constant indices in a separate variable
// to minimize the number of calls to computeForAddSub.
APInt AccConstIndices(BitWidth, 0, /*IsSigned*/ true);
gep_type_iterator GTI = gep_type_begin(I);
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
// TrailZ can only become smaller, short-circuit if we hit zero.
if (Known.isUnknown())
break;
Value *Index = I->getOperand(i);
// Handle case when index is zero.
Constant *CIndex = dyn_cast<Constant>(Index);
if (CIndex && CIndex->isZeroValue())
continue;
if (StructType *STy = GTI.getStructTypeOrNull()) {
// Handle struct member offset arithmetic.
assert(CIndex &&
"Access to structure field must be known at compile time");
if (CIndex->getType()->isVectorTy())
Index = CIndex->getSplatValue();
unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
const StructLayout *SL = Q.DL.getStructLayout(STy);
uint64_t Offset = SL->getElementOffset(Idx);
AccConstIndices += Offset;
continue;
}
// Handle array index arithmetic.
Type *IndexedTy = GTI.getIndexedType();
if (!IndexedTy->isSized()) {
Known.resetAll();
break;
}
unsigned IndexBitWidth = Index->getType()->getScalarSizeInBits();
KnownBits IndexBits(IndexBitWidth);
computeKnownBits(Index, IndexBits, Depth + 1, Q);
TypeSize IndexTypeSize = GTI.getSequentialElementStride(Q.DL);
uint64_t TypeSizeInBytes = IndexTypeSize.getKnownMinValue();
KnownBits ScalingFactor(IndexBitWidth);
// Multiply by current sizeof type.
// &A[i] == A + i * sizeof(*A[i]).
if (IndexTypeSize.isScalable()) {
// For scalable types the only thing we know about sizeof is
// that this is a multiple of the minimum size.
ScalingFactor.Zero.setLowBits(llvm::countr_zero(TypeSizeInBytes));
} else if (IndexBits.isConstant()) {
APInt IndexConst = IndexBits.getConstant();
APInt ScalingFactor(IndexBitWidth, TypeSizeInBytes);
IndexConst *= ScalingFactor;
AccConstIndices += IndexConst.sextOrTrunc(BitWidth);
continue;
} else {
ScalingFactor =
KnownBits::makeConstant(APInt(IndexBitWidth, TypeSizeInBytes));
}
IndexBits = KnownBits::mul(IndexBits, ScalingFactor);
// If the offsets have a different width from the pointer, according
// to the language reference we need to sign-extend or truncate them
// to the width of the pointer.
IndexBits = IndexBits.sextOrTrunc(BitWidth);
// Note that inbounds does *not* guarantee nsw for the addition, as only
// the offset is signed, while the base address is unsigned.
Known = KnownBits::computeForAddSub(
/*Add=*/true, /*NSW=*/false, /* NUW=*/false, Known, IndexBits);
}
if (!Known.isUnknown() && !AccConstIndices.isZero()) {
KnownBits Index = KnownBits::makeConstant(AccConstIndices);
Known = KnownBits::computeForAddSub(
/*Add=*/true, /*NSW=*/false, /* NUW=*/false, Known, Index);
}
break;
}
case Instruction::PHI: {
const PHINode *P = cast<PHINode>(I);
BinaryOperator *BO = nullptr;
Value *R = nullptr, *L = nullptr;
if (matchSimpleRecurrence(P, BO, R, L)) {
// Handle the case of a simple two-predecessor recurrence PHI.
// There's a lot more that could theoretically be done here, but
// this is sufficient to catch some interesting cases.
unsigned Opcode = BO->getOpcode();
// If this is a shift recurrence, we know the bits being shifted in.
// We can combine that with information about the start value of the
// recurrence to conclude facts about the result.
if ((Opcode == Instruction::LShr || Opcode == Instruction::AShr ||
Opcode == Instruction::Shl) &&
BO->getOperand(0) == I) {
// We have matched a recurrence of the form:
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = shift_op %iv, L
// Recurse with the phi context to avoid concern about whether facts
// inferred hold at original context instruction. TODO: It may be
// correct to use the original context. IF warranted, explore and
// add sufficient tests to cover.
SimplifyQuery RecQ = Q;
RecQ.CxtI = P;
computeKnownBits(R, DemandedElts, Known2, Depth + 1, RecQ);
switch (Opcode) {
case Instruction::Shl:
// A shl recurrence will only increase the tailing zeros
Known.Zero.setLowBits(Known2.countMinTrailingZeros());
break;
case Instruction::LShr:
// A lshr recurrence will preserve the leading zeros of the
// start value
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
break;
case Instruction::AShr:
// An ashr recurrence will extend the initial sign bit
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
Known.One.setHighBits(Known2.countMinLeadingOnes());
break;
};
}
// Check for operations that have the property that if
// both their operands have low zero bits, the result
// will have low zero bits.
if (Opcode == Instruction::Add ||
Opcode == Instruction::Sub ||
Opcode == Instruction::And ||
Opcode == Instruction::Or ||
Opcode == Instruction::Mul) {
// Change the context instruction to the "edge" that flows into the
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
SimplifyQuery RecQ = Q;
unsigned OpNum = P->getOperand(0) == R ? 0 : 1;
Instruction *RInst = P->getIncomingBlock(OpNum)->getTerminator();
Instruction *LInst = P->getIncomingBlock(1-OpNum)->getTerminator();
// Ok, we have a PHI of the form L op= R. Check for low
// zero bits.
RecQ.CxtI = RInst;
computeKnownBits(R, Known2, Depth + 1, RecQ);
// We need to take the minimum number of known bits
KnownBits Known3(BitWidth);
RecQ.CxtI = LInst;
computeKnownBits(L, Known3, Depth + 1, RecQ);
Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(),
Known3.countMinTrailingZeros()));
auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(BO);
if (OverflowOp && Q.IIQ.hasNoSignedWrap(OverflowOp)) {
// If initial value of recurrence is nonnegative, and we are adding
// a nonnegative number with nsw, the result can only be nonnegative
// or poison value regardless of the number of times we execute the
// add in phi recurrence. If initial value is negative and we are
// adding a negative number with nsw, the result can only be
// negative or poison value. Similar arguments apply to sub and mul.
//
// (add non-negative, non-negative) --> non-negative
// (add negative, negative) --> negative
if (Opcode == Instruction::Add) {
if (Known2.isNonNegative() && Known3.isNonNegative())
Known.makeNonNegative();
else if (Known2.isNegative() && Known3.isNegative())
Known.makeNegative();
}
// (sub nsw non-negative, negative) --> non-negative
// (sub nsw negative, non-negative) --> negative
else if (Opcode == Instruction::Sub && BO->getOperand(0) == I) {
if (Known2.isNonNegative() && Known3.isNegative())
Known.makeNonNegative();
else if (Known2.isNegative() && Known3.isNonNegative())
Known.makeNegative();
}
// (mul nsw non-negative, non-negative) --> non-negative
else if (Opcode == Instruction::Mul && Known2.isNonNegative() &&
Known3.isNonNegative())
Known.makeNonNegative();
}
break;
}
}
// Unreachable blocks may have zero-operand PHI nodes.
if (P->getNumIncomingValues() == 0)
break;
// Otherwise take the unions of the known bit sets of the operands,
// taking conservative care to avoid excessive recursion.
if (Depth < MaxAnalysisRecursionDepth - 1 && Known.isUnknown()) {
// Skip if every incoming value references to ourself.
if (isa_and_nonnull<UndefValue>(P->hasConstantValue()))
break;
Known.Zero.setAllBits();
Known.One.setAllBits();
for (unsigned u = 0, e = P->getNumIncomingValues(); u < e; ++u) {
Value *IncValue = P->getIncomingValue(u);
// Skip direct self references.
if (IncValue == P) continue;
// Change the context instruction to the "edge" that flows into the
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
SimplifyQuery RecQ = Q;
RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
Known2 = KnownBits(BitWidth);
// Recurse, but cap the recursion to one level, because we don't
// want to waste time spinning around in loops.
// TODO: See if we can base recursion limiter on number of incoming phi
// edges so we don't overly clamp analysis.
computeKnownBits(IncValue, Known2, MaxAnalysisRecursionDepth - 1, RecQ);
// See if we can further use a conditional branch into the phi
// to help us determine the range of the value.
if (!Known2.isConstant()) {
ICmpInst::Predicate Pred;
const APInt *RHSC;
BasicBlock *TrueSucc, *FalseSucc;
// TODO: Use RHS Value and compute range from its known bits.
if (match(RecQ.CxtI,
m_Br(m_c_ICmp(Pred, m_Specific(IncValue), m_APInt(RHSC)),
m_BasicBlock(TrueSucc), m_BasicBlock(FalseSucc)))) {
// Check for cases of duplicate successors.
if ((TrueSucc == P->getParent()) != (FalseSucc == P->getParent())) {
// If we're using the false successor, invert the predicate.
if (FalseSucc == P->getParent())
Pred = CmpInst::getInversePredicate(Pred);
// Get the knownbits implied by the incoming phi condition.
auto CR = ConstantRange::makeExactICmpRegion(Pred, *RHSC);
KnownBits KnownUnion = Known2.unionWith(CR.toKnownBits());
// We can have conflicts here if we are analyzing deadcode (its
// impossible for us reach this BB based the icmp).
if (KnownUnion.hasConflict()) {
// No reason to continue analyzing in a known dead region, so
// just resetAll and break. This will cause us to also exit the
// outer loop.
Known.resetAll();
break;
}
Known2 = KnownUnion;
}
}
}
Known = Known.intersectWith(Known2);
// If all bits have been ruled out, there's no need to check
// more operands.
if (Known.isUnknown())
break;
}
}
break;
}
case Instruction::Call:
case Instruction::Invoke: {
// If range metadata is attached to this call, set known bits from that,
// and then intersect with known bits based on other properties of the
// function.
if (MDNode *MD =
Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
computeKnownBitsFromRangeMetadata(*MD, Known);
const auto *CB = cast<CallBase>(I);
if (std::optional<ConstantRange> Range = CB->getRange())
Known = Known.unionWith(Range->toKnownBits());
if (const Value *RV = CB->getReturnedArgOperand()) {
if (RV->getType() == I->getType()) {
computeKnownBits(RV, Known2, Depth + 1, Q);
Known = Known.unionWith(Known2);
// If the function doesn't return properly for all input values
// (e.g. unreachable exits) then there might be conflicts between the
// argument value and the range metadata. Simply discard the known bits
// in case of conflicts.
if (Known.hasConflict())
Known.resetAll();
}
}
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::abs: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
bool IntMinIsPoison = match(II->getArgOperand(1), m_One());
Known = Known2.abs(IntMinIsPoison);
break;
}
case Intrinsic::bitreverse:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known.Zero |= Known2.Zero.reverseBits();
Known.One |= Known2.One.reverseBits();
break;
case Intrinsic::bswap:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known.Zero |= Known2.Zero.byteSwap();
Known.One |= Known2.One.byteSwap();
break;
case Intrinsic::ctlz: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// If we have a known 1, its position is our upper bound.
unsigned PossibleLZ = Known2.countMaxLeadingZeros();
// If this call is poison for 0 input, the result will be less than 2^n.
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
PossibleLZ = std::min(PossibleLZ, BitWidth - 1);
unsigned LowBits = llvm::bit_width(PossibleLZ);
Known.Zero.setBitsFrom(LowBits);
break;
}
case Intrinsic::cttz: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// If we have a known 1, its position is our upper bound.
unsigned PossibleTZ = Known2.countMaxTrailingZeros();
// If this call is poison for 0 input, the result will be less than 2^n.
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
PossibleTZ = std::min(PossibleTZ, BitWidth - 1);
unsigned LowBits = llvm::bit_width(PossibleTZ);
Known.Zero.setBitsFrom(LowBits);
break;
}
case Intrinsic::ctpop: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// We can bound the space the count needs. Also, bits known to be zero
// can't contribute to the population.
unsigned BitsPossiblySet = Known2.countMaxPopulation();
unsigned LowBits = llvm::bit_width(BitsPossiblySet);
Known.Zero.setBitsFrom(LowBits);
// TODO: we could bound KnownOne using the lower bound on the number
// of bits which might be set provided by popcnt KnownOne2.
break;
}
case Intrinsic::fshr:
case Intrinsic::fshl: {
const APInt *SA;
if (!match(I->getOperand(2), m_APInt(SA)))
break;
// Normalize to funnel shift left.
uint64_t ShiftAmt = SA->urem(BitWidth);
if (II->getIntrinsicID() == Intrinsic::fshr)
ShiftAmt = BitWidth - ShiftAmt;
KnownBits Known3(BitWidth);
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known3, Depth + 1, Q);
Known.Zero =
Known2.Zero.shl(ShiftAmt) | Known3.Zero.lshr(BitWidth - ShiftAmt);
Known.One =
Known2.One.shl(ShiftAmt) | Known3.One.lshr(BitWidth - ShiftAmt);
break;
}
case Intrinsic::uadd_sat:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::uadd_sat(Known, Known2);
break;
case Intrinsic::usub_sat:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::usub_sat(Known, Known2);
break;
case Intrinsic::sadd_sat:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::sadd_sat(Known, Known2);
break;
case Intrinsic::ssub_sat:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::ssub_sat(Known, Known2);
break;
// for min/max/and/or reduce, any bit common to each element in the
// input vec is set in the output.
case Intrinsic::vector_reduce_and:
case Intrinsic::vector_reduce_or:
case Intrinsic::vector_reduce_umax:
case Intrinsic::vector_reduce_umin:
case Intrinsic::vector_reduce_smax:
case Intrinsic::vector_reduce_smin:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
break;
case Intrinsic::vector_reduce_xor: {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
// The zeros common to all vecs are zero in the output.
// If the number of elements is odd, then the common ones remain. If the
// number of elements is even, then the common ones becomes zeros.
auto *VecTy = cast<VectorType>(I->getOperand(0)->getType());
// Even, so the ones become zeros.
bool EvenCnt = VecTy->getElementCount().isKnownEven();
if (EvenCnt)
Known.Zero |= Known.One;
// Maybe even element count so need to clear ones.
if (VecTy->isScalableTy() || EvenCnt)
Known.One.clearAllBits();
break;
}
case Intrinsic::umin:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::umin(Known, Known2);
break;
case Intrinsic::umax:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::umax(Known, Known2);
break;
case Intrinsic::smin:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::smin(Known, Known2);
break;
case Intrinsic::smax:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::smax(Known, Known2);
break;
case Intrinsic::ptrmask: {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
const Value *Mask = I->getOperand(1);
Known2 = KnownBits(Mask->getType()->getScalarSizeInBits());
computeKnownBits(Mask, Known2, Depth + 1, Q);
// TODO: 1-extend would be more precise.
Known &= Known2.anyextOrTrunc(BitWidth);
break;
}
case Intrinsic::x86_sse42_crc32_64_64:
Known.Zero.setBitsFrom(32);
break;
case Intrinsic::riscv_vsetvli:
case Intrinsic::riscv_vsetvlimax: {
bool HasAVL = II->getIntrinsicID() == Intrinsic::riscv_vsetvli;
const ConstantRange Range = getVScaleRange(II->getFunction(), BitWidth);
uint64_t SEW = RISCVVType::decodeVSEW(
cast<ConstantInt>(II->getArgOperand(HasAVL))->getZExtValue());
RISCVII::VLMUL VLMUL = static_cast<RISCVII::VLMUL>(
cast<ConstantInt>(II->getArgOperand(1 + HasAVL))->getZExtValue());
// The Range is [Lower, Upper), so we need to subtract 1 here to get the
// real upper value.
uint64_t MaxVLEN =
(Range.getUpper().getZExtValue() - 1) * RISCV::RVVBitsPerBlock;
uint64_t MaxVL = MaxVLEN / RISCVVType::getSEWLMULRatio(SEW, VLMUL);
// Result of vsetvli must be not larger than AVL.
if (HasAVL)
if (auto *CI = dyn_cast<ConstantInt>(II->getArgOperand(0)))
MaxVL = std::min(MaxVL, CI->getZExtValue());
unsigned KnownZeroFirstBit = Log2_32(MaxVL) + 1;
if (BitWidth > KnownZeroFirstBit)
Known.Zero.setBitsFrom(KnownZeroFirstBit);
break;
}
case Intrinsic::vscale: {
if (!II->getParent() || !II->getFunction())
break;
Known = getVScaleRange(II->getFunction(), BitWidth).toKnownBits();
break;
}
}
}
break;
}
case Instruction::ShuffleVector: {
auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
// FIXME: Do we need to handle ConstantExpr involving shufflevectors?
if (!Shuf) {
Known.resetAll();
return;
}
// For undef elements, we don't know anything about the common state of
// the shuffle result.
APInt DemandedLHS, DemandedRHS;
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS)) {
Known.resetAll();
return;
}
Known.One.setAllBits();
Known.Zero.setAllBits();
if (!!DemandedLHS) {
const Value *LHS = Shuf->getOperand(0);
computeKnownBits(LHS, DemandedLHS, Known, Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
}
if (!!DemandedRHS) {
const Value *RHS = Shuf->getOperand(1);
computeKnownBits(RHS, DemandedRHS, Known2, Depth + 1, Q);
Known = Known.intersectWith(Known2);
}
break;
}
case Instruction::InsertElement: {
if (isa<ScalableVectorType>(I->getType())) {
Known.resetAll();
return;
}
const Value *Vec = I->getOperand(0);
const Value *Elt = I->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
unsigned NumElts = DemandedElts.getBitWidth();
APInt DemandedVecElts = DemandedElts;
bool NeedsElt = true;
// If we know the index we are inserting too, clear it from Vec check.
if (CIdx && CIdx->getValue().ult(NumElts)) {
DemandedVecElts.clearBit(CIdx->getZExtValue());
NeedsElt = DemandedElts[CIdx->getZExtValue()];
}
Known.One.setAllBits();
Known.Zero.setAllBits();
if (NeedsElt) {
computeKnownBits(Elt, Known, Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
}
if (!DemandedVecElts.isZero()) {
computeKnownBits(Vec, DemandedVecElts, Known2, Depth + 1, Q);
Known = Known.intersectWith(Known2);
}
break;
}
case Instruction::ExtractElement: {
// Look through extract element. If the index is non-constant or
// out-of-range demand all elements, otherwise just the extracted element.
const Value *Vec = I->getOperand(0);
const Value *Idx = I->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(Idx);
if (isa<ScalableVectorType>(Vec->getType())) {
// FIXME: there's probably *something* we can do with scalable vectors
Known.resetAll();
break;
}
unsigned NumElts = cast<FixedVectorType>(Vec->getType())->getNumElements();
APInt DemandedVecElts = APInt::getAllOnes(NumElts);
if (CIdx && CIdx->getValue().ult(NumElts))
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
computeKnownBits(Vec, DemandedVecElts, Known, Depth + 1, Q);
break;
}
case Instruction::ExtractValue:
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
const ExtractValueInst *EVI = cast<ExtractValueInst>(I);
if (EVI->getNumIndices() != 1) break;
if (EVI->getIndices()[0] == 0) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::uadd_with_overflow:
case Intrinsic::sadd_with_overflow:
computeKnownBitsAddSub(
true, II->getArgOperand(0), II->getArgOperand(1), /*NSW=*/false,
/* NUW=*/false, DemandedElts, Known, Known2, Depth, Q);
break;
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow:
computeKnownBitsAddSub(
false, II->getArgOperand(0), II->getArgOperand(1), /*NSW=*/false,
/* NUW=*/false, DemandedElts, Known, Known2, Depth, Q);
break;
case Intrinsic::umul_with_overflow:
case Intrinsic::smul_with_overflow:
computeKnownBitsMul(II->getArgOperand(0), II->getArgOperand(1), false,
DemandedElts, Known, Known2, Depth, Q);
break;
}
}
}
break;
case Instruction::Freeze:
if (isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
Depth + 1))
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
break;
}
}
/// Determine which bits of V are known to be either zero or one and return
/// them.
KnownBits llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q) {
KnownBits Known(getBitWidth(V->getType(), Q.DL));
::computeKnownBits(V, DemandedElts, Known, Depth, Q);
return Known;
}
/// Determine which bits of V are known to be either zero or one and return
/// them.
KnownBits llvm::computeKnownBits(const Value *V, unsigned Depth,
const SimplifyQuery &Q) {
KnownBits Known(getBitWidth(V->getType(), Q.DL));
computeKnownBits(V, Known, Depth, Q);
return Known;
}
/// Determine which bits of V are known to be either zero or one and return
/// them in the Known bit set.
///
/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
/// we cannot optimize based on the assumption that it is zero without changing
/// it to be an explicit zero. If we don't change it to zero, other code could
/// optimized based on the contradictory assumption that it is non-zero.
/// Because instcombine aggressively folds operations with undef args anyway,
/// this won't lose us code quality.
///
/// This function is defined on values with integer type, values with pointer
/// type, and vectors of integers. In the case
/// where V is a vector, known zero, and known one values are the
/// same width as the vector element, and the bit is set only if it is true
/// for all of the demanded elements in the vector specified by DemandedElts.
void computeKnownBits(const Value *V, const APInt &DemandedElts,
KnownBits &Known, unsigned Depth,
const SimplifyQuery &Q) {
if (!DemandedElts) {
// No demanded elts, better to assume we don't know anything.
Known.resetAll();
return;
}
assert(V && "No Value?");
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
#ifndef NDEBUG
Type *Ty = V->getType();
unsigned BitWidth = Known.getBitWidth();
assert((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) &&
"Not integer or pointer type!");
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
assert(
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements");
} else {
assert(DemandedElts == APInt(1, 1) &&
"DemandedElt width should be 1 for scalars or scalable vectors");
}
Type *ScalarTy = Ty->getScalarType();
if (ScalarTy->isPointerTy()) {
assert(BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth");
} else {
assert(BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth");
}
#endif
const APInt *C;
if (match(V, m_APInt(C))) {
// We know all of the bits for a scalar constant or a splat vector constant!
Known = KnownBits::makeConstant(*C);
return;
}
// Null and aggregate-zero are all-zeros.
if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) {
Known.setAllZero();
return;
}
// Handle a constant vector by taking the intersection of the known bits of
// each element.
if (const ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(V)) {
assert(!isa<ScalableVectorType>(V->getType()));
// We know that CDV must be a vector of integers. Take the intersection of
// each element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (unsigned i = 0, e = CDV->getNumElements(); i != e; ++i) {
if (!DemandedElts[i])
continue;
APInt Elt = CDV->getElementAsAPInt(i);
Known.Zero &= ~Elt;
Known.One &= Elt;
}
if (Known.hasConflict())
Known.resetAll();
return;
}
if (const auto *CV = dyn_cast<ConstantVector>(V)) {
assert(!isa<ScalableVectorType>(V->getType()));
// We know that CV must be a vector of integers. Take the intersection of
// each element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
if (!DemandedElts[i])
continue;
Constant *Element = CV->getAggregateElement(i);
if (isa<PoisonValue>(Element))
continue;
auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
if (!ElementCI) {
Known.resetAll();
return;
}
const APInt &Elt = ElementCI->getValue();
Known.Zero &= ~Elt;
Known.One &= Elt;
}
if (Known.hasConflict())
Known.resetAll();
return;
}
// Start out not knowing anything.
Known.resetAll();
// We can't imply anything about undefs.
if (isa<UndefValue>(V))
return;
// There's no point in looking through other users of ConstantData for
// assumptions. Confirm that we've handled them all.
assert(!isa<ConstantData>(V) && "Unhandled constant data!");
if (const auto *A = dyn_cast<Argument>(V))
if (std::optional<ConstantRange> Range = A->getRange())
Known = Range->toKnownBits();
// All recursive calls that increase depth must come after this.
if (Depth == MaxAnalysisRecursionDepth)
return;
// A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
// the bits of its aliasee.
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (!GA->isInterposable())
computeKnownBits(GA->getAliasee(), Known, Depth + 1, Q);
return;
}
if (const Operator *I = dyn_cast<Operator>(V))
computeKnownBitsFromOperator(I, DemandedElts, Known, Depth, Q);
else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (std::optional<ConstantRange> CR = GV->getAbsoluteSymbolRange())
Known = CR->toKnownBits();
}
// Aligned pointers have trailing zeros - refine Known.Zero set
if (isa<PointerType>(V->getType())) {
Align Alignment = V->getPointerAlignment(Q.DL);
Known.Zero.setLowBits(Log2(Alignment));
}
// computeKnownBitsFromContext strictly refines Known.
// Therefore, we run them after computeKnownBitsFromOperator.
// Check whether we can determine known bits from context such as assumes.
computeKnownBitsFromContext(V, Known, Depth, Q);
assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
}
/// Try to detect a recurrence that the value of the induction variable is
/// always a power of two (or zero).
static bool isPowerOfTwoRecurrence(const PHINode *PN, bool OrZero,
unsigned Depth, SimplifyQuery &Q) {
BinaryOperator *BO = nullptr;
Value *Start = nullptr, *Step = nullptr;
if (!matchSimpleRecurrence(PN, BO, Start, Step))
return false;
// Initial value must be a power of two.
for (const Use &U : PN->operands()) {
if (U.get() == Start) {
// Initial value comes from a different BB, need to adjust context
// instruction for analysis.
Q.CxtI = PN->getIncomingBlock(U)->getTerminator();
if (!isKnownToBeAPowerOfTwo(Start, OrZero, Depth, Q))
return false;
}
}
// Except for Mul, the induction variable must be on the left side of the
// increment expression, otherwise its value can be arbitrary.
if (BO->getOpcode() != Instruction::Mul && BO->getOperand(1) != Step)
return false;
Q.CxtI = BO->getParent()->getTerminator();
switch (BO->getOpcode()) {
case Instruction::Mul:
// Power of two is closed under multiplication.
return (OrZero || Q.IIQ.hasNoUnsignedWrap(BO) ||
Q.IIQ.hasNoSignedWrap(BO)) &&
isKnownToBeAPowerOfTwo(Step, OrZero, Depth, Q);
case Instruction::SDiv:
// Start value must not be signmask for signed division, so simply being a
// power of two is not sufficient, and it has to be a constant.
if (!match(Start, m_Power2()) || match(Start, m_SignMask()))
return false;
[[fallthrough]];
case Instruction::UDiv:
// Divisor must be a power of two.
// If OrZero is false, cannot guarantee induction variable is non-zero after
// division, same for Shr, unless it is exact division.
return (OrZero || Q.IIQ.isExact(BO)) &&
isKnownToBeAPowerOfTwo(Step, false, Depth, Q);
case Instruction::Shl:
return OrZero || Q.IIQ.hasNoUnsignedWrap(BO) || Q.IIQ.hasNoSignedWrap(BO);
case Instruction::AShr:
if (!match(Start, m_Power2()) || match(Start, m_SignMask()))
return false;
[[fallthrough]];
case Instruction::LShr:
return OrZero || Q.IIQ.isExact(BO);
default:
return false;
}
}
/// Return true if the given value is known to have exactly one
/// bit set when defined. For vectors return true if every element is known to
/// be a power of two when defined. Supports values with integer or pointer
/// types and vectors of integers.
bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
const SimplifyQuery &Q) {
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
if (isa<Constant>(V))
return OrZero ? match(V, m_Power2OrZero()) : match(V, m_Power2());
// i1 is by definition a power of 2 or zero.
if (OrZero && V->getType()->getScalarSizeInBits() == 1)
return true;
auto *I = dyn_cast<Instruction>(V);
if (!I)
return false;
if (Q.CxtI && match(V, m_VScale())) {
const Function *F = Q.CxtI->getFunction();
// The vscale_range indicates vscale is a power-of-two.
return F->hasFnAttribute(Attribute::VScaleRange);
}
// 1 << X is clearly a power of two if the one is not shifted off the end. If
// it is shifted off the end then the result is undefined.
if (match(I, m_Shl(m_One(), m_Value())))
return true;
// (signmask) >>l X is clearly a power of two if the one is not shifted off
// the bottom. If it is shifted off the bottom then the result is undefined.
if (match(I, m_LShr(m_SignMask(), m_Value())))
return true;
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth++ == MaxAnalysisRecursionDepth)
return false;
switch (I->getOpcode()) {
case Instruction::ZExt:
return isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
case Instruction::Trunc:
return OrZero && isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
case Instruction::Shl:
if (OrZero || Q.IIQ.hasNoUnsignedWrap(I) || Q.IIQ.hasNoSignedWrap(I))
return isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
return false;
case Instruction::LShr:
if (OrZero || Q.IIQ.isExact(cast<BinaryOperator>(I)))
return isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
return false;
case Instruction::UDiv:
if (Q.IIQ.isExact(cast<BinaryOperator>(I)))
return isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
return false;
case Instruction::Mul:
return isKnownToBeAPowerOfTwo(I->getOperand(1), OrZero, Depth, Q) &&
isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q) &&
(OrZero || isKnownNonZero(I, Q, Depth));
case Instruction::And:
// A power of two and'd with anything is a power of two or zero.
if (OrZero &&
(isKnownToBeAPowerOfTwo(I->getOperand(1), /*OrZero*/ true, Depth, Q) ||
isKnownToBeAPowerOfTwo(I->getOperand(0), /*OrZero*/ true, Depth, Q)))
return true;
// X & (-X) is always a power of two or zero.
if (match(I->getOperand(0), m_Neg(m_Specific(I->getOperand(1)))) ||
match(I->getOperand(1), m_Neg(m_Specific(I->getOperand(0)))))
return OrZero || isKnownNonZero(I->getOperand(0), Q, Depth);
return false;
case Instruction::Add: {
// Adding a power-of-two or zero to the same power-of-two or zero yields
// either the original power-of-two, a larger power-of-two or zero.
const OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
if (OrZero || Q.IIQ.hasNoUnsignedWrap(VOBO) ||
Q.IIQ.hasNoSignedWrap(VOBO)) {
if (match(I->getOperand(0),
m_c_And(m_Specific(I->getOperand(1)), m_Value())) &&
isKnownToBeAPowerOfTwo(I->getOperand(1), OrZero, Depth, Q))
return true;
if (match(I->getOperand(1),
m_c_And(m_Specific(I->getOperand(0)), m_Value())) &&
isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q))
return true;
unsigned BitWidth = V->getType()->getScalarSizeInBits();
KnownBits LHSBits(BitWidth);
computeKnownBits(I->getOperand(0), LHSBits, Depth, Q);
KnownBits RHSBits(BitWidth);
computeKnownBits(I->getOperand(1), RHSBits, Depth, Q);
// If i8 V is a power of two or zero:
// ZeroBits: 1 1 1 0 1 1 1 1
// ~ZeroBits: 0 0 0 1 0 0 0 0
if ((~(LHSBits.Zero & RHSBits.Zero)).isPowerOf2())
// If OrZero isn't set, we cannot give back a zero result.
// Make sure either the LHS or RHS has a bit set.
if (OrZero || RHSBits.One.getBoolValue() || LHSBits.One.getBoolValue())
return true;
}
return false;
}
case Instruction::Select:
return isKnownToBeAPowerOfTwo(I->getOperand(1), OrZero, Depth, Q) &&
isKnownToBeAPowerOfTwo(I->getOperand(2), OrZero, Depth, Q);
case Instruction::PHI: {
// A PHI node is power of two if all incoming values are power of two, or if
// it is an induction variable where in each step its value is a power of
// two.
auto *PN = cast<PHINode>(I);
SimplifyQuery RecQ = Q;
// Check if it is an induction variable and always power of two.
if (isPowerOfTwoRecurrence(PN, OrZero, Depth, RecQ))
return true;
// Recursively check all incoming values. Limit recursion to 2 levels, so
// that search complexity is limited to number of operands^2.
unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
return llvm::all_of(PN->operands(), [&](const Use &U) {
// Value is power of 2 if it is coming from PHI node itself by induction.
if (U.get() == PN)
return true;
// Change the context instruction to the incoming block where it is
// evaluated.
RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
return isKnownToBeAPowerOfTwo(U.get(), OrZero, NewDepth, RecQ);
});
}
case Instruction::Invoke:
case Instruction::Call: {
if (auto *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
case Intrinsic::umax:
case Intrinsic::smax:
case Intrinsic::umin:
case Intrinsic::smin:
return isKnownToBeAPowerOfTwo(II->getArgOperand(1), OrZero, Depth, Q) &&
isKnownToBeAPowerOfTwo(II->getArgOperand(0), OrZero, Depth, Q);
// bswap/bitreverse just move around bits, but don't change any 1s/0s
// thus dont change pow2/non-pow2 status.
case Intrinsic::bitreverse:
case Intrinsic::bswap:
return isKnownToBeAPowerOfTwo(II->getArgOperand(0), OrZero, Depth, Q);
case Intrinsic::fshr:
case Intrinsic::fshl:
// If Op0 == Op1, this is a rotate. is_pow2(rotate(x, y)) == is_pow2(x)
if (II->getArgOperand(0) == II->getArgOperand(1))
return isKnownToBeAPowerOfTwo(II->getArgOperand(0), OrZero, Depth, Q);
break;
default:
break;
}
}
return false;
}
default:
return false;
}
}
/// Test whether a GEP's result is known to be non-null.
///
/// Uses properties inherent in a GEP to try to determine whether it is known
/// to be non-null.
///
/// Currently this routine does not support vector GEPs.
static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
const SimplifyQuery &Q) {
const Function *F = nullptr;
if (const Instruction *I = dyn_cast<Instruction>(GEP))
F = I->getFunction();
if (!GEP->isInBounds() ||
NullPointerIsDefined(F, GEP->getPointerAddressSpace()))
return false;
// FIXME: Support vector-GEPs.
assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP");
// If the base pointer is non-null, we cannot walk to a null address with an
// inbounds GEP in address space zero.
if (isKnownNonZero(GEP->getPointerOperand(), Q, Depth))
return true;
// Walk the GEP operands and see if any operand introduces a non-zero offset.
// If so, then the GEP cannot produce a null pointer, as doing so would
// inherently violate the inbounds contract within address space zero.
for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
GTI != GTE; ++GTI) {
// Struct types are easy -- they must always be indexed by a constant.
if (StructType *STy = GTI.getStructTypeOrNull()) {
ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
unsigned ElementIdx = OpC->getZExtValue();
const StructLayout *SL = Q.DL.getStructLayout(STy);
uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
if (ElementOffset > 0)
return true;
continue;
}
// If we have a zero-sized type, the index doesn't matter. Keep looping.
if (GTI.getSequentialElementStride(Q.DL).isZero())
continue;
// Fast path the constant operand case both for efficiency and so we don't
// increment Depth when just zipping down an all-constant GEP.
if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
if (!OpC->isZero())
return true;
continue;
}
// We post-increment Depth here because while isKnownNonZero increments it
// as well, when we pop back up that increment won't persist. We don't want
// to recurse 10k times just because we have 10k GEP operands. We don't
// bail completely out because we want to handle constant GEPs regardless
// of depth.
if (Depth++ >= MaxAnalysisRecursionDepth)
continue;
if (isKnownNonZero(GTI.getOperand(), Q, Depth))
return true;
}
return false;
}
static bool isKnownNonNullFromDominatingCondition(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT) {
assert(!isa<Constant>(V) && "Called for constant?");
if (!CtxI || !DT)
return false;
unsigned NumUsesExplored = 0;
for (const auto *U : V->users()) {
// Avoid massive lists
if (NumUsesExplored >= DomConditionsMaxUses)
break;
NumUsesExplored++;
// If the value is used as an argument to a call or invoke, then argument
// attributes may provide an answer about null-ness.
if (const auto *CB = dyn_cast<CallBase>(U))
if (auto *CalledFunc = CB->getCalledFunction())
for (const Argument &Arg : CalledFunc->args())
if (CB->getArgOperand(Arg.getArgNo()) == V &&
Arg.hasNonNullAttr(/* AllowUndefOrPoison */ false) &&
DT->dominates(CB, CtxI))
return true;
// If the value is used as a load/store, then the pointer must be non null.
if (V == getLoadStorePointerOperand(U)) {
const Instruction *I = cast<Instruction>(U);
if (!NullPointerIsDefined(I->getFunction(),
V->getType()->getPointerAddressSpace()) &&
DT->dominates(I, CtxI))
return true;
}
if ((match(U, m_IDiv(m_Value(), m_Specific(V))) ||
match(U, m_IRem(m_Value(), m_Specific(V)))) &&
isValidAssumeForContext(cast<Instruction>(U), CtxI, DT))
return true;
// Consider only compare instructions uniquely controlling a branch
Value *RHS;
CmpInst::Predicate Pred;
if (!match(U, m_c_ICmp(Pred, m_Specific(V), m_Value(RHS))))
continue;
bool NonNullIfTrue;
if (cmpExcludesZero(Pred, RHS))
NonNullIfTrue = true;
else if (cmpExcludesZero(CmpInst::getInversePredicate(Pred), RHS))
NonNullIfTrue = false;
else
continue;
SmallVector<const User *, 4> WorkList;
SmallPtrSet<const User *, 4> Visited;
for (const auto *CmpU : U->users()) {
assert(WorkList.empty() && "Should be!");
if (Visited.insert(CmpU).second)
WorkList.push_back(CmpU);
while (!WorkList.empty()) {
auto *Curr = WorkList.pop_back_val();
// If a user is an AND, add all its users to the work list. We only
// propagate "pred != null" condition through AND because it is only
// correct to assume that all conditions of AND are met in true branch.
// TODO: Support similar logic of OR and EQ predicate?
if (NonNullIfTrue)
if (match(Curr, m_LogicalAnd(m_Value(), m_Value()))) {
for (const auto *CurrU : Curr->users())
if (Visited.insert(CurrU).second)
WorkList.push_back(CurrU);
continue;
}
if (const BranchInst *BI = dyn_cast<BranchInst>(Curr)) {
assert(BI->isConditional() && "uses a comparison!");
BasicBlock *NonNullSuccessor =
BI->getSuccessor(NonNullIfTrue ? 0 : 1);
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
return true;
} else if (NonNullIfTrue && isGuard(Curr) &&
DT->dominates(cast<Instruction>(Curr), CtxI)) {
return true;
}
}
}
}
return false;
}
/// Does the 'Range' metadata (which must be a valid MD_range operand list)
/// ensure that the value it's attached to is never Value? 'RangeType' is
/// is the type of the value described by the range.
static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value) {
const unsigned NumRanges = Ranges->getNumOperands() / 2;
assert(NumRanges >= 1);
for (unsigned i = 0; i < NumRanges; ++i) {
ConstantInt *Lower =
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 0));
ConstantInt *Upper =
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 1));
ConstantRange Range(Lower->getValue(), Upper->getValue());
if (Range.contains(Value))
return false;
}
return true;
}
/// Try to detect a recurrence that monotonically increases/decreases from a
/// non-zero starting value. These are common as induction variables.
static bool isNonZeroRecurrence(const PHINode *PN) {
BinaryOperator *BO = nullptr;
Value *Start = nullptr, *Step = nullptr;
const APInt *StartC, *StepC;
if (!matchSimpleRecurrence(PN, BO, Start, Step) ||
!match(Start, m_APInt(StartC)) || StartC->isZero())
return false;
switch (BO->getOpcode()) {
case Instruction::Add:
// Starting from non-zero and stepping away from zero can never wrap back
// to zero.
return BO->hasNoUnsignedWrap() ||
(BO->hasNoSignedWrap() && match(Step, m_APInt(StepC)) &&
StartC->isNegative() == StepC->isNegative());
case Instruction::Mul:
return (BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap()) &&
match(Step, m_APInt(StepC)) && !StepC->isZero();
case Instruction::Shl:
return BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap();
case Instruction::AShr:
case Instruction::LShr:
return BO->isExact();
default:
return false;
}
}
static bool isNonZeroAdd(const APInt &DemandedElts, unsigned Depth,
const SimplifyQuery &Q, unsigned BitWidth, Value *X,
Value *Y, bool NSW, bool NUW) {
if (NUW)
return isKnownNonZero(Y, DemandedElts, Q, Depth) ||
isKnownNonZero(X, DemandedElts, Q, Depth);
KnownBits XKnown = computeKnownBits(X, DemandedElts, Depth, Q);
KnownBits YKnown = computeKnownBits(Y, DemandedElts, Depth, Q);
// If X and Y are both non-negative (as signed values) then their sum is not
// zero unless both X and Y are zero.
if (XKnown.isNonNegative() && YKnown.isNonNegative())
if (isKnownNonZero(Y, DemandedElts, Q, Depth) ||
isKnownNonZero(X, DemandedElts, Q, Depth))
return true;
// If X and Y are both negative (as signed values) then their sum is not
// zero unless both X and Y equal INT_MIN.
if (XKnown.isNegative() && YKnown.isNegative()) {
APInt Mask = APInt::getSignedMaxValue(BitWidth);
// The sign bit of X is set. If some other bit is set then X is not equal
// to INT_MIN.
if (XKnown.One.intersects(Mask))
return true;
// The sign bit of Y is set. If some other bit is set then Y is not equal
// to INT_MIN.
if (YKnown.One.intersects(Mask))
return true;
}
// The sum of a non-negative number and a power of two is not zero.
if (XKnown.isNonNegative() &&
isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
return true;
if (YKnown.isNonNegative() &&
isKnownToBeAPowerOfTwo(X, /*OrZero*/ false, Depth, Q))
return true;
return KnownBits::computeForAddSub(/*Add=*/true, NSW, NUW, XKnown, YKnown)
.isNonZero();
}
static bool isNonZeroSub(const APInt &DemandedElts, unsigned Depth,
const SimplifyQuery &Q, unsigned BitWidth, Value *X,
Value *Y) {
// TODO: Move this case into isKnownNonEqual().
if (auto *C = dyn_cast<Constant>(X))
if (C->isNullValue() && isKnownNonZero(Y, DemandedElts, Q, Depth))
return true;
return ::isKnownNonEqual(X, Y, Depth, Q);
}
static bool isNonZeroMul(const APInt &DemandedElts, unsigned Depth,
const SimplifyQuery &Q, unsigned BitWidth, Value *X,
Value *Y, bool NSW, bool NUW) {
// If X and Y are non-zero then so is X * Y as long as the multiplication
// does not overflow.
if (NSW || NUW)
return isKnownNonZero(X, DemandedElts, Q, Depth) &&
isKnownNonZero(Y, DemandedElts, Q, Depth);
// If either X or Y is odd, then if the other is non-zero the result can't
// be zero.
KnownBits XKnown = computeKnownBits(X, DemandedElts, Depth, Q);
if (XKnown.One[0])
return isKnownNonZero(Y, DemandedElts, Q, Depth);
KnownBits YKnown = computeKnownBits(Y, DemandedElts, Depth, Q);
if (YKnown.One[0])
return XKnown.isNonZero() || isKnownNonZero(X, DemandedElts, Q, Depth);
// If there exists any subset of X (sX) and subset of Y (sY) s.t sX * sY is
// non-zero, then X * Y is non-zero. We can find sX and sY by just taking
// the lowest known One of X and Y. If they are non-zero, the result
// must be non-zero. We can check if LSB(X) * LSB(Y) != 0 by doing
// X.CountLeadingZeros + Y.CountLeadingZeros < BitWidth.
return (XKnown.countMaxTrailingZeros() + YKnown.countMaxTrailingZeros()) <
BitWidth;
}
static bool isNonZeroShift(const Operator *I, const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q,
const KnownBits &KnownVal) {
auto ShiftOp = [&](const APInt &Lhs, const APInt &Rhs) {
switch (I->getOpcode()) {
case Instruction::Shl:
return Lhs.shl(Rhs);
case Instruction::LShr:
return Lhs.lshr(Rhs);
case Instruction::AShr:
return Lhs.ashr(Rhs);
default:
llvm_unreachable("Unknown Shift Opcode");
}
};
auto InvShiftOp = [&](const APInt &Lhs, const APInt &Rhs) {
switch (I->getOpcode()) {
case Instruction::Shl:
return Lhs.lshr(Rhs);
case Instruction::LShr:
case Instruction::AShr:
return Lhs.shl(Rhs);
default:
llvm_unreachable("Unknown Shift Opcode");
}
};
if (KnownVal.isUnknown())
return false;
KnownBits KnownCnt =
computeKnownBits(I->getOperand(1), DemandedElts, Depth, Q);
APInt MaxShift = KnownCnt.getMaxValue();
unsigned NumBits = KnownVal.getBitWidth();
if (MaxShift.uge(NumBits))
return false;
if (!ShiftOp(KnownVal.One, MaxShift).isZero())
return true;
// If all of the bits shifted out are known to be zero, and Val is known
// non-zero then at least one non-zero bit must remain.
if (InvShiftOp(KnownVal.Zero, NumBits - MaxShift)
.eq(InvShiftOp(APInt::getAllOnes(NumBits), NumBits - MaxShift)) &&
isKnownNonZero(I->getOperand(0), DemandedElts, Q, Depth))
return true;
return false;
}
static bool isKnownNonZeroFromOperator(const Operator *I,
const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q) {
unsigned BitWidth = getBitWidth(I->getType()->getScalarType(), Q.DL);
switch (I->getOpcode()) {
case Instruction::Alloca:
// Alloca never returns null, malloc might.
return I->getType()->getPointerAddressSpace() == 0;
case Instruction::GetElementPtr:
if (I->getType()->isPointerTy())
return isGEPKnownNonNull(cast<GEPOperator>(I), Depth, Q);
break;
case Instruction::BitCast: {
// We need to be a bit careful here. We can only peek through the bitcast
// if the scalar size of elements in the operand are smaller than and a
// multiple of the size they are casting too. Take three cases:
//
// 1) Unsafe:
// bitcast <2 x i16> %NonZero to <4 x i8>
//
// %NonZero can have 2 non-zero i16 elements, but isKnownNonZero on a
// <4 x i8> requires that all 4 i8 elements be non-zero which isn't
// guranteed (imagine just sign bit set in the 2 i16 elements).
//
// 2) Unsafe:
// bitcast <4 x i3> %NonZero to <3 x i4>
//
// Even though the scalar size of the src (`i3`) is smaller than the
// scalar size of the dst `i4`, because `i3` is not a multiple of `i4`
// its possible for the `3 x i4` elements to be zero because there are
// some elements in the destination that don't contain any full src
// element.
//
// 3) Safe:
// bitcast <4 x i8> %NonZero to <2 x i16>
//
// This is always safe as non-zero in the 4 i8 elements implies
// non-zero in the combination of any two adjacent ones. Since i8 is a
// multiple of i16, each i16 is guranteed to have 2 full i8 elements.
// This all implies the 2 i16 elements are non-zero.
Type *FromTy = I->getOperand(0)->getType();
if ((FromTy->isIntOrIntVectorTy() || FromTy->isPtrOrPtrVectorTy()) &&
(BitWidth % getBitWidth(FromTy->getScalarType(), Q.DL)) == 0)
return isKnownNonZero(I->getOperand(0), Q, Depth);
} break;
case Instruction::IntToPtr:
// Note that we have to take special care to avoid looking through
// truncating casts, e.g., int2ptr/ptr2int with appropriate sizes, as well
// as casts that can alter the value, e.g., AddrSpaceCasts.
if (!isa<ScalableVectorType>(I->getType()) &&
Q.DL.getTypeSizeInBits(I->getOperand(0)->getType()).getFixedValue() <=
Q.DL.getTypeSizeInBits(I->getType()).getFixedValue())
return isKnownNonZero(I->getOperand(0), Q, Depth);
break;
case Instruction::PtrToInt:
// Similar to int2ptr above, we can look through ptr2int here if the cast
// is a no-op or an extend and not a truncate.
if (!isa<ScalableVectorType>(I->getType()) &&
Q.DL.getTypeSizeInBits(I->getOperand(0)->getType()).getFixedValue() <=
Q.DL.getTypeSizeInBits(I->getType()).getFixedValue())
return isKnownNonZero(I->getOperand(0), Q, Depth);
break;
case Instruction::Sub:
return isNonZeroSub(DemandedElts, Depth, Q, BitWidth, I->getOperand(0),
I->getOperand(1));
case Instruction::Or:
// X | Y != 0 if X != 0 or Y != 0.
return isKnownNonZero(I->getOperand(1), DemandedElts, Q, Depth) ||
isKnownNonZero(I->getOperand(0), DemandedElts, Q, Depth);
case Instruction::SExt:
case Instruction::ZExt:
// ext X != 0 if X != 0.
return isKnownNonZero(I->getOperand(0), Q, Depth);
case Instruction::Shl: {
// shl nsw/nuw can't remove any non-zero bits.
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(I);
if (Q.IIQ.hasNoUnsignedWrap(BO) || Q.IIQ.hasNoSignedWrap(BO))
return isKnownNonZero(I->getOperand(0), Q, Depth);
// shl X, Y != 0 if X is odd. Note that the value of the shift is undefined
// if the lowest bit is shifted off the end.
KnownBits Known(BitWidth);
computeKnownBits(I->getOperand(0), DemandedElts, Known, Depth, Q);
if (Known.One[0])
return true;
return isNonZeroShift(I, DemandedElts, Depth, Q, Known);
}
case Instruction::LShr:
case Instruction::AShr: {
// shr exact can only shift out zero bits.
const PossiblyExactOperator *BO = cast<PossiblyExactOperator>(I);
if (BO->isExact())
return isKnownNonZero(I->getOperand(0), Q, Depth);
// shr X, Y != 0 if X is negative. Note that the value of the shift is not
// defined if the sign bit is shifted off the end.
KnownBits Known =
computeKnownBits(I->getOperand(0), DemandedElts, Depth, Q);
if (Known.isNegative())
return true;
return isNonZeroShift(I, DemandedElts, Depth, Q, Known);
}
case Instruction::UDiv:
case Instruction::SDiv: {
// X / Y
// div exact can only produce a zero if the dividend is zero.
if (cast<PossiblyExactOperator>(I)->isExact())
return isKnownNonZero(I->getOperand(0), DemandedElts, Q, Depth);
std::optional<bool> XUgeY;
KnownBits XKnown =
computeKnownBits(I->getOperand(0), DemandedElts, Depth, Q);
// If X is fully unknown we won't be able to figure anything out so don't
// both computing knownbits for Y.
if (XKnown.isUnknown())
return false;
KnownBits YKnown =
computeKnownBits(I->getOperand(1), DemandedElts, Depth, Q);
if (I->getOpcode() == Instruction::SDiv) {
// For signed division need to compare abs value of the operands.
XKnown = XKnown.abs(/*IntMinIsPoison*/ false);
YKnown = YKnown.abs(/*IntMinIsPoison*/ false);
}
// If X u>= Y then div is non zero (0/0 is UB).
XUgeY = KnownBits::uge(XKnown, YKnown);
// If X is total unknown or X u< Y we won't be able to prove non-zero
// with compute known bits so just return early.
return XUgeY && *XUgeY;
}
case Instruction::Add: {
// X + Y.
// If Add has nuw wrap flag, then if either X or Y is non-zero the result is
// non-zero.
auto *BO = cast<OverflowingBinaryOperator>(I);
return isNonZeroAdd(DemandedElts, Depth, Q, BitWidth, I->getOperand(0),
I->getOperand(1), Q.IIQ.hasNoSignedWrap(BO),
Q.IIQ.hasNoUnsignedWrap(BO));
}
case Instruction::Mul: {
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(I);
return isNonZeroMul(DemandedElts, Depth, Q, BitWidth, I->getOperand(0),
I->getOperand(1), Q.IIQ.hasNoSignedWrap(BO),
Q.IIQ.hasNoUnsignedWrap(BO));
}
case Instruction::Select: {
// (C ? X : Y) != 0 if X != 0 and Y != 0.
// First check if the arm is non-zero using `isKnownNonZero`. If that fails,
// then see if the select condition implies the arm is non-zero. For example
// (X != 0 ? X : Y), we know the true arm is non-zero as the `X` "return" is
// dominated by `X != 0`.
auto SelectArmIsNonZero = [&](bool IsTrueArm) {
Value *Op;
Op = IsTrueArm ? I->getOperand(1) : I->getOperand(2);
// Op is trivially non-zero.
if (isKnownNonZero(Op, DemandedElts, Q, Depth))
return true;
// The condition of the select dominates the true/false arm. Check if the
// condition implies that a given arm is non-zero.
Value *X;
CmpInst::Predicate Pred;
if (!match(I->getOperand(0), m_c_ICmp(Pred, m_Specific(Op), m_Value(X))))
return false;
if (!IsTrueArm)
Pred = ICmpInst::getInversePredicate(Pred);
return cmpExcludesZero(Pred, X);
};
if (SelectArmIsNonZero(/* IsTrueArm */ true) &&
SelectArmIsNonZero(/* IsTrueArm */ false))
return true;
break;
}
case Instruction::PHI: {
auto *PN = cast<PHINode>(I);
if (Q.IIQ.UseInstrInfo && isNonZeroRecurrence(PN))
return true;
// Check if all incoming values are non-zero using recursion.
SimplifyQuery RecQ = Q;
unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
return llvm::all_of(PN->operands(), [&](const Use &U) {
if (U.get() == PN)
return true;
RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
// Check if the branch on the phi excludes zero.
ICmpInst::Predicate Pred;
Value *X;
BasicBlock *TrueSucc, *FalseSucc;
if (match(RecQ.CxtI,
m_Br(m_c_ICmp(Pred, m_Specific(U.get()), m_Value(X)),
m_BasicBlock(TrueSucc), m_BasicBlock(FalseSucc)))) {
// Check for cases of duplicate successors.
if ((TrueSucc == PN->getParent()) != (FalseSucc == PN->getParent())) {
// If we're using the false successor, invert the predicate.
if (FalseSucc == PN->getParent())
Pred = CmpInst::getInversePredicate(Pred);
if (cmpExcludesZero(Pred, X))
return true;
}
}
// Finally recurse on the edge and check it directly.
return isKnownNonZero(U.get(), DemandedElts, RecQ, NewDepth);
});
}
case Instruction::InsertElement: {
if (isa<ScalableVectorType>(I->getType()))
break;
const Value *Vec = I->getOperand(0);
const Value *Elt = I->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
unsigned NumElts = DemandedElts.getBitWidth();
APInt DemandedVecElts = DemandedElts;
bool SkipElt = false;
// If we know the index we are inserting too, clear it from Vec check.
if (CIdx && CIdx->getValue().ult(NumElts)) {
DemandedVecElts.clearBit(CIdx->getZExtValue());
SkipElt = !DemandedElts[CIdx->getZExtValue()];
}
// Result is zero if Elt is non-zero and rest of the demanded elts in Vec
// are non-zero.
return (SkipElt || isKnownNonZero(Elt, Q, Depth)) &&
(DemandedVecElts.isZero() ||
isKnownNonZero(Vec, DemandedVecElts, Q, Depth));
}
case Instruction::ExtractElement:
if (const auto *EEI = dyn_cast<ExtractElementInst>(I)) {
const Value *Vec = EEI->getVectorOperand();
const Value *Idx = EEI->getIndexOperand();
auto *CIdx = dyn_cast<ConstantInt>(Idx);
if (auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType())) {
unsigned NumElts = VecTy->getNumElements();
APInt DemandedVecElts = APInt::getAllOnes(NumElts);
if (CIdx && CIdx->getValue().ult(NumElts))
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
return isKnownNonZero(Vec, DemandedVecElts, Q, Depth);
}
}
break;
case Instruction::ShuffleVector: {
auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
if (!Shuf)
break;
APInt DemandedLHS, DemandedRHS;
// For undef elements, we don't know anything about the common state of
// the shuffle result.
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
break;
// If demanded elements for both vecs are non-zero, the shuffle is non-zero.
return (DemandedRHS.isZero() ||
isKnownNonZero(Shuf->getOperand(1), DemandedRHS, Q, Depth)) &&
(DemandedLHS.isZero() ||
isKnownNonZero(Shuf->getOperand(0), DemandedLHS, Q, Depth));
}
case Instruction::Freeze:
return isKnownNonZero(I->getOperand(0), Q, Depth) &&
isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
Depth);
case Instruction::Load: {
auto *LI = cast<LoadInst>(I);
// A Load tagged with nonnull or dereferenceable with null pointer undefined
// is never null.
if (auto *PtrT = dyn_cast<PointerType>(I->getType())) {
if (Q.IIQ.getMetadata(LI, LLVMContext::MD_nonnull) ||
(Q.IIQ.getMetadata(LI, LLVMContext::MD_dereferenceable) &&
!NullPointerIsDefined(LI->getFunction(), PtrT->getAddressSpace())))
return true;
} else if (MDNode *Ranges = Q.IIQ.getMetadata(LI, LLVMContext::MD_range)) {
return rangeMetadataExcludesValue(Ranges, APInt::getZero(BitWidth));
}
// No need to fall through to computeKnownBits as range metadata is already
// handled in isKnownNonZero.
return false;
}
case Instruction::ExtractValue: {
const WithOverflowInst *WO;
if (match(I, m_ExtractValue<0>(m_WithOverflowInst(WO)))) {
switch (WO->getBinaryOp()) {
default:
break;
case Instruction::Add:
return isNonZeroAdd(DemandedElts, Depth, Q, BitWidth,
WO->getArgOperand(0), WO->getArgOperand(1),
/*NSW=*/false,
/*NUW=*/false);
case Instruction::Sub:
return isNonZeroSub(DemandedElts, Depth, Q, BitWidth,
WO->getArgOperand(0), WO->getArgOperand(1));
case Instruction::Mul:
return isNonZeroMul(DemandedElts, Depth, Q, BitWidth,
WO->getArgOperand(0), WO->getArgOperand(1),
/*NSW=*/false, /*NUW=*/false);
break;
}
}
break;
}
case Instruction::Call:
case Instruction::Invoke: {
const auto *Call = cast<CallBase>(I);
if (I->getType()->isPointerTy()) {
if (Call->isReturnNonNull())
return true;
if (const auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
return isKnownNonZero(RP, Q, Depth);
} else {
if (MDNode *Ranges = Q.IIQ.getMetadata(Call, LLVMContext::MD_range))
return rangeMetadataExcludesValue(Ranges, APInt::getZero(BitWidth));
if (std::optional<ConstantRange> Range = Call->getRange()) {
const APInt ZeroValue(Range->getBitWidth(), 0);
if (!Range->contains(ZeroValue))
return true;
}
if (const Value *RV = Call->getReturnedArgOperand())
if (RV->getType() == I->getType() && isKnownNonZero(RV, Q, Depth))
return true;
}
if (auto *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
case Intrinsic::sshl_sat:
case Intrinsic::ushl_sat:
case Intrinsic::abs:
case Intrinsic::bitreverse:
case Intrinsic::bswap:
case Intrinsic::ctpop:
return isKnownNonZero(II->getArgOperand(0), DemandedElts, Q, Depth);
// NB: We don't do usub_sat here as in any case we can prove its
// non-zero, we will fold it to `sub nuw` in InstCombine.
case Intrinsic::ssub_sat:
return isNonZeroSub(DemandedElts, Depth, Q, BitWidth,
II->getArgOperand(0), II->getArgOperand(1));
case Intrinsic::sadd_sat:
return isNonZeroAdd(DemandedElts, Depth, Q, BitWidth,
II->getArgOperand(0), II->getArgOperand(1),
/*NSW=*/true, /* NUW=*/false);
// umin/smin/smax/smin/or of all non-zero elements is always non-zero.
case Intrinsic::vector_reduce_or:
case Intrinsic::vector_reduce_umax:
case Intrinsic::vector_reduce_umin:
case Intrinsic::vector_reduce_smax:
case Intrinsic::vector_reduce_smin:
return isKnownNonZero(II->getArgOperand(0), Q, Depth);
case Intrinsic::umax:
case Intrinsic::uadd_sat:
return isKnownNonZero(II->getArgOperand(1), DemandedElts, Q, Depth) ||
isKnownNonZero(II->getArgOperand(0), DemandedElts, Q, Depth);
case Intrinsic::smax: {
// If either arg is strictly positive the result is non-zero. Otherwise
// the result is non-zero if both ops are non-zero.
auto IsNonZero = [&](Value *Op, std::optional<bool> &OpNonZero,
const KnownBits &OpKnown) {
if (!OpNonZero.has_value())
OpNonZero = OpKnown.isNonZero() ||
isKnownNonZero(Op, DemandedElts, Q, Depth);
return *OpNonZero;
};
// Avoid re-computing isKnownNonZero.
std::optional<bool> Op0NonZero, Op1NonZero;
KnownBits Op1Known =
computeKnownBits(II->getArgOperand(1), DemandedElts, Depth, Q);
if (Op1Known.isNonNegative() &&
IsNonZero(II->getArgOperand(1), Op1NonZero, Op1Known))
return true;
KnownBits Op0Known =
computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q);
if (Op0Known.isNonNegative() &&
IsNonZero(II->getArgOperand(0), Op0NonZero, Op0Known))
return true;
return IsNonZero(II->getArgOperand(1), Op1NonZero, Op1Known) &&
IsNonZero(II->getArgOperand(0), Op0NonZero, Op0Known);
}
case Intrinsic::smin: {
// If either arg is negative the result is non-zero. Otherwise
// the result is non-zero if both ops are non-zero.
KnownBits Op1Known =
computeKnownBits(II->getArgOperand(1), DemandedElts, Depth, Q);
if (Op1Known.isNegative())
return true;
KnownBits Op0Known =
computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q);
if (Op0Known.isNegative())
return true;
if (Op1Known.isNonZero() && Op0Known.isNonZero())
return true;
}
[[fallthrough]];
case Intrinsic::umin:
return isKnownNonZero(II->getArgOperand(0), DemandedElts, Q, Depth) &&
isKnownNonZero(II->getArgOperand(1), DemandedElts, Q, Depth);
case Intrinsic::cttz:
return computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q)
.Zero[0];
case Intrinsic::ctlz:
return computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q)
.isNonNegative();
case Intrinsic::fshr:
case Intrinsic::fshl:
// If Op0 == Op1, this is a rotate. rotate(x, y) != 0 iff x != 0.
if (II->getArgOperand(0) == II->getArgOperand(1))
return isKnownNonZero(II->getArgOperand(0), DemandedElts, Q, Depth);
break;
case Intrinsic::vscale:
return true;
case Intrinsic::experimental_get_vector_length:
return isKnownNonZero(I->getOperand(0), Q, Depth);
default:
break;
}
break;
}
return false;
}
}
KnownBits Known(BitWidth);
computeKnownBits(I, DemandedElts, Known, Depth, Q);
return Known.One != 0;
}
/// Return true if the given value is known to be non-zero when defined. For
/// vectors, return true if every demanded element is known to be non-zero when
/// defined. For pointers, if the context instruction and dominator tree are
/// specified, perform context-sensitive analysis and return true if the
/// pointer couldn't possibly be null at the specified instruction.
/// Supports values with integer or pointer type and vectors of integers.
bool isKnownNonZero(const Value *V, const APInt &DemandedElts,
const SimplifyQuery &Q, unsigned Depth) {
Type *Ty = V->getType();
#ifndef NDEBUG
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
assert(
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements");
} else {
assert(DemandedElts == APInt(1, 1) &&
"DemandedElt width should be 1 for scalars");
}
#endif
if (auto *C = dyn_cast<Constant>(V)) {
if (C->isNullValue())
return false;
if (isa<ConstantInt>(C))
// Must be non-zero due to null test above.
return true;
// For constant vectors, check that all elements are poison or known
// non-zero to determine that the whole vector is known non-zero.
if (auto *VecTy = dyn_cast<FixedVectorType>(Ty)) {
for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
if (!DemandedElts[i])
continue;
Constant *Elt = C->getAggregateElement(i);
if (!Elt || Elt->isNullValue())
return false;
if (!isa<PoisonValue>(Elt) && !isa<ConstantInt>(Elt))
return false;
}
return true;
}
// A global variable in address space 0 is non null unless extern weak
// or an absolute symbol reference. Other address spaces may have null as a
// valid address for a global, so we can't assume anything.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (!GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
GV->getType()->getAddressSpace() == 0)
return true;
}
// For constant expressions, fall through to the Operator code below.
if (!isa<ConstantExpr>(V))
return false;
}
if (const auto *A = dyn_cast<Argument>(V))
if (std::optional<ConstantRange> Range = A->getRange()) {
const APInt ZeroValue(Range->getBitWidth(), 0);
if (!Range->contains(ZeroValue))
return true;
}
if (!isa<Constant>(V) && isKnownNonZeroFromAssume(V, Q))
return true;
// Some of the tests below are recursive, so bail out if we hit the limit.
if (Depth++ >= MaxAnalysisRecursionDepth)
return false;
// Check for pointer simplifications.
if (PointerType *PtrTy = dyn_cast<PointerType>(Ty)) {
// A byval, inalloca may not be null in a non-default addres space. A
// nonnull argument is assumed never 0.
if (const Argument *A = dyn_cast<Argument>(V)) {
if (((A->hasPassPointeeByValueCopyAttr() &&
!NullPointerIsDefined(A->getParent(), PtrTy->getAddressSpace())) ||
A->hasNonNullAttr()))
return true;
}
}
if (const auto *I = dyn_cast<Operator>(V))
if (isKnownNonZeroFromOperator(I, DemandedElts, Depth, Q))
return true;
if (!isa<Constant>(V) &&
isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
return true;
return false;
}
bool llvm::isKnownNonZero(const Value *V, const SimplifyQuery &Q,
unsigned Depth) {
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
return ::isKnownNonZero(V, DemandedElts, Q, Depth);
}
/// If the pair of operators are the same invertible function, return the
/// the operands of the function corresponding to each input. Otherwise,
/// return std::nullopt. An invertible function is one that is 1-to-1 and maps
/// every input value to exactly one output value. This is equivalent to
/// saying that Op1 and Op2 are equal exactly when the specified pair of
/// operands are equal, (except that Op1 and Op2 may be poison more often.)
static std::optional<std::pair<Value*, Value*>>
getInvertibleOperands(const Operator *Op1,
const Operator *Op2) {
if (Op1->getOpcode() != Op2->getOpcode())
return std::nullopt;
auto getOperands = [&](unsigned OpNum) -> auto {
return std::make_pair(Op1->getOperand(OpNum), Op2->getOperand(OpNum));
};
switch (Op1->getOpcode()) {
default:
break;
case Instruction::Or:
if (!cast<PossiblyDisjointInst>(Op1)->isDisjoint() ||
!cast<PossiblyDisjointInst>(Op2)->isDisjoint())
break;
[[fallthrough]];
case Instruction::Xor:
case Instruction::Add: {
Value *Other;
if (match(Op2, m_c_BinOp(m_Specific(Op1->getOperand(0)), m_Value(Other))))
return std::make_pair(Op1->getOperand(1), Other);
if (match(Op2, m_c_BinOp(m_Specific(Op1->getOperand(1)), m_Value(Other))))
return std::make_pair(Op1->getOperand(0), Other);
break;
}
case Instruction::Sub:
if (Op1->getOperand(0) == Op2->getOperand(0))
return getOperands(1);
if (Op1->getOperand(1) == Op2->getOperand(1))
return getOperands(0);
break;
case Instruction::Mul: {
// invertible if A * B == (A * B) mod 2^N where A, and B are integers
// and N is the bitwdith. The nsw case is non-obvious, but proven by
// alive2: https://alive2.llvm.org/ce/z/Z6D5qK
auto *OBO1 = cast<OverflowingBinaryOperator>(Op1);
auto *OBO2 = cast<OverflowingBinaryOperator>(Op2);
if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
(!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
break;
// Assume operand order has been canonicalized
if (Op1->getOperand(1) == Op2->getOperand(1) &&
isa<ConstantInt>(Op1->getOperand(1)) &&
!cast<ConstantInt>(Op1->getOperand(1))->isZero())
return getOperands(0);
break;
}
case Instruction::Shl: {
// Same as multiplies, with the difference that we don't need to check
// for a non-zero multiply. Shifts always multiply by non-zero.
auto *OBO1 = cast<OverflowingBinaryOperator>(Op1);
auto *OBO2 = cast<OverflowingBinaryOperator>(Op2);
if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
(!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
break;
if (Op1->getOperand(1) == Op2->getOperand(1))
return getOperands(0);
break;
}
case Instruction::AShr:
case Instruction::LShr: {
auto *PEO1 = cast<PossiblyExactOperator>(Op1);
auto *PEO2 = cast<PossiblyExactOperator>(Op2);
if (!PEO1->isExact() || !PEO2->isExact())
break;
if (Op1->getOperand(1) == Op2->getOperand(1))
return getOperands(0);
break;
}
case Instruction::SExt:
case Instruction::ZExt:
if (Op1->getOperand(0)->getType() == Op2->getOperand(0)->getType())
return getOperands(0);
break;
case Instruction::PHI: {
const PHINode *PN1 = cast<PHINode>(Op1);
const PHINode *PN2 = cast<PHINode>(Op2);
// If PN1 and PN2 are both recurrences, can we prove the entire recurrences
// are a single invertible function of the start values? Note that repeated
// application of an invertible function is also invertible
BinaryOperator *BO1 = nullptr;
Value *Start1 = nullptr, *Step1 = nullptr;
BinaryOperator *BO2 = nullptr;
Value *Start2 = nullptr, *Step2 = nullptr;
if (PN1->getParent() != PN2->getParent() ||
!matchSimpleRecurrence(PN1, BO1, Start1, Step1) ||
!matchSimpleRecurrence(PN2, BO2, Start2, Step2))
break;
auto Values = getInvertibleOperands(cast<Operator>(BO1),
cast<Operator>(BO2));
if (!Values)
break;
// We have to be careful of mutually defined recurrences here. Ex:
// * X_i = X_(i-1) OP Y_(i-1), and Y_i = X_(i-1) OP V
// * X_i = Y_i = X_(i-1) OP Y_(i-1)
// The invertibility of these is complicated, and not worth reasoning
// about (yet?).
if (Values->first != PN1 || Values->second != PN2)
break;
return std::make_pair(Start1, Start2);
}
}
return std::nullopt;
}
/// Return true if V1 == (binop V2, X), where X is known non-zero.
/// Only handle a small subset of binops where (binop V2, X) with non-zero X
/// implies V2 != V1.
static bool isModifyingBinopOfNonZero(const Value *V1, const Value *V2,
unsigned Depth, const SimplifyQuery &Q) {
const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
if (!BO)
return false;
switch (BO->getOpcode()) {
default:
break;
case Instruction::Or:
if (!cast<PossiblyDisjointInst>(V1)->isDisjoint())
break;
[[fallthrough]];
case Instruction::Xor:
case Instruction::Add:
Value *Op = nullptr;
if (V2 == BO->getOperand(0))
Op = BO->getOperand(1);
else if (V2 == BO->getOperand(1))
Op = BO->getOperand(0);
else
return false;
return isKnownNonZero(Op, Q, Depth + 1);
}
return false;
}
/// Return true if V2 == V1 * C, where V1 is known non-zero, C is not 0/1 and
/// the multiplication is nuw or nsw.
static bool isNonEqualMul(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
const APInt *C;
return match(OBO, m_Mul(m_Specific(V1), m_APInt(C))) &&
(OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
!C->isZero() && !C->isOne() && isKnownNonZero(V1, Q, Depth + 1);
}
return false;
}
/// Return true if V2 == V1 << C, where V1 is known non-zero, C is not 0 and
/// the shift is nuw or nsw.
static bool isNonEqualShl(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
const APInt *C;
return match(OBO, m_Shl(m_Specific(V1), m_APInt(C))) &&
(OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
!C->isZero() && isKnownNonZero(V1, Q, Depth + 1);
}
return false;
}
static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
unsigned Depth, const SimplifyQuery &Q) {
// Check two PHIs are in same block.
if (PN1->getParent() != PN2->getParent())
return false;
SmallPtrSet<const BasicBlock *, 8> VisitedBBs;
bool UsedFullRecursion = false;
for (const BasicBlock *IncomBB : PN1->blocks()) {
if (!VisitedBBs.insert(IncomBB).second)
continue; // Don't reprocess blocks that we have dealt with already.
const Value *IV1 = PN1->getIncomingValueForBlock(IncomBB);
const Value *IV2 = PN2->getIncomingValueForBlock(IncomBB);
const APInt *C1, *C2;
if (match(IV1, m_APInt(C1)) && match(IV2, m_APInt(C2)) && *C1 != *C2)
continue;
// Only one pair of phi operands is allowed for full recursion.
if (UsedFullRecursion)
return false;
SimplifyQuery RecQ = Q;
RecQ.CxtI = IncomBB->getTerminator();
if (!isKnownNonEqual(IV1, IV2, Depth + 1, RecQ))
return false;
UsedFullRecursion = true;
}
return true;
}
static bool isNonEqualSelect(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
const SelectInst *SI1 = dyn_cast<SelectInst>(V1);
if (!SI1)
return false;
if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2)) {
const Value *Cond1 = SI1->getCondition();
const Value *Cond2 = SI2->getCondition();
if (Cond1 == Cond2)
return isKnownNonEqual(SI1->getTrueValue(), SI2->getTrueValue(),
Depth + 1, Q) &&
isKnownNonEqual(SI1->getFalseValue(), SI2->getFalseValue(),
Depth + 1, Q);
}
return isKnownNonEqual(SI1->getTrueValue(), V2, Depth + 1, Q) &&
isKnownNonEqual(SI1->getFalseValue(), V2, Depth + 1, Q);
}
// Check to see if A is both a GEP and is the incoming value for a PHI in the
// loop, and B is either a ptr or another GEP. If the PHI has 2 incoming values,
// one of them being the recursive GEP A and the other a ptr at same base and at
// the same/higher offset than B we are only incrementing the pointer further in
// loop if offset of recursive GEP is greater than 0.
static bool isNonEqualPointersWithRecursiveGEP(const Value *A, const Value *B,
const SimplifyQuery &Q) {
if (!A->getType()->isPointerTy() || !B->getType()->isPointerTy())
return false;
auto *GEPA = dyn_cast<GEPOperator>(A);
if (!GEPA || GEPA->getNumIndices() != 1 || !isa<Constant>(GEPA->idx_begin()))
return false;
// Handle 2 incoming PHI values with one being a recursive GEP.
auto *PN = dyn_cast<PHINode>(GEPA->getPointerOperand());
if (!PN || PN->getNumIncomingValues() != 2)
return false;
// Search for the recursive GEP as an incoming operand, and record that as
// Step.
Value *Start = nullptr;
Value *Step = const_cast<Value *>(A);
if (PN->getIncomingValue(0) == Step)
Start = PN->getIncomingValue(1);
else if (PN->getIncomingValue(1) == Step)
Start = PN->getIncomingValue(0);
else
return false;
// Other incoming node base should match the B base.
// StartOffset >= OffsetB && StepOffset > 0?
// StartOffset <= OffsetB && StepOffset < 0?
// Is non-equal if above are true.
// We use stripAndAccumulateInBoundsConstantOffsets to restrict the
// optimisation to inbounds GEPs only.
unsigned IndexWidth = Q.DL.getIndexTypeSizeInBits(Start->getType());
APInt StartOffset(IndexWidth, 0);
Start = Start->stripAndAccumulateInBoundsConstantOffsets(Q.DL, StartOffset);
APInt StepOffset(IndexWidth, 0);
Step = Step->stripAndAccumulateInBoundsConstantOffsets(Q.DL, StepOffset);
// Check if Base Pointer of Step matches the PHI.
if (Step != PN)
return false;
APInt OffsetB(IndexWidth, 0);
B = B->stripAndAccumulateInBoundsConstantOffsets(Q.DL, OffsetB);
return Start == B &&
((StartOffset.sge(OffsetB) && StepOffset.isStrictlyPositive()) ||
(StartOffset.sle(OffsetB) && StepOffset.isNegative()));
}
/// Return true if it is known that V1 != V2.
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
if (V1 == V2)
return false;
if (V1->getType() != V2->getType())
// We can't look through casts yet.
return false;
if (Depth >= MaxAnalysisRecursionDepth)
return false;
// See if we can recurse through (exactly one of) our operands. This
// requires our operation be 1-to-1 and map every input value to exactly
// one output value. Such an operation is invertible.
auto *O1 = dyn_cast<Operator>(V1);
auto *O2 = dyn_cast<Operator>(V2);
if (O1 && O2 && O1->getOpcode() == O2->getOpcode()) {
if (auto Values = getInvertibleOperands(O1, O2))
return isKnownNonEqual(Values->first, Values->second, Depth + 1, Q);
if (const PHINode *PN1 = dyn_cast<PHINode>(V1)) {
const PHINode *PN2 = cast<PHINode>(V2);
// FIXME: This is missing a generalization to handle the case where one is
// a PHI and another one isn't.
if (isNonEqualPHIs(PN1, PN2, Depth, Q))
return true;
};
}
if (isModifyingBinopOfNonZero(V1, V2, Depth, Q) ||
isModifyingBinopOfNonZero(V2, V1, Depth, Q))
return true;
if (isNonEqualMul(V1, V2, Depth, Q) || isNonEqualMul(V2, V1, Depth, Q))
return true;
if (isNonEqualShl(V1, V2, Depth, Q) || isNonEqualShl(V2, V1, Depth, Q))
return true;
if (V1->getType()->isIntOrIntVectorTy()) {
// Are any known bits in V1 contradictory to known bits in V2? If V1
// has a known zero where V2 has a known one, they must not be equal.
KnownBits Known1 = computeKnownBits(V1, Depth, Q);
if (!Known1.isUnknown()) {
KnownBits Known2 = computeKnownBits(V2, Depth, Q);
if (Known1.Zero.intersects(Known2.One) ||
Known2.Zero.intersects(Known1.One))
return true;
}
}
if (isNonEqualSelect(V1, V2, Depth, Q) || isNonEqualSelect(V2, V1, Depth, Q))
return true;
if (isNonEqualPointersWithRecursiveGEP(V1, V2, Q) ||
isNonEqualPointersWithRecursiveGEP(V2, V1, Q))
return true;
Value *A, *B;
// PtrToInts are NonEqual if their Ptrs are NonEqual.
// Check PtrToInt type matches the pointer size.
if (match(V1, m_PtrToIntSameSize(Q.DL, m_Value(A))) &&
match(V2, m_PtrToIntSameSize(Q.DL, m_Value(B))))
return isKnownNonEqual(A, B, Depth + 1, Q);
return false;
}
// Match a signed min+max clamp pattern like smax(smin(In, CHigh), CLow).
// Returns the input and lower/upper bounds.
static bool isSignedMinMaxClamp(const Value *Select, const Value *&In,
const APInt *&CLow, const APInt *&CHigh) {
assert(isa<Operator>(Select) &&
cast<Operator>(Select)->getOpcode() == Instruction::Select &&
"Input should be a Select!");
const Value *LHS = nullptr, *RHS = nullptr;
SelectPatternFlavor SPF = matchSelectPattern(Select, LHS, RHS).Flavor;
if (SPF != SPF_SMAX && SPF != SPF_SMIN)
return false;
if (!match(RHS, m_APInt(CLow)))
return false;
const Value *LHS2 = nullptr, *RHS2 = nullptr;
SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor;
if (getInverseMinMaxFlavor(SPF) != SPF2)
return false;
if (!match(RHS2, m_APInt(CHigh)))
return false;
if (SPF == SPF_SMIN)
std::swap(CLow, CHigh);
In = LHS2;
return CLow->sle(*CHigh);
}
static bool isSignedMinMaxIntrinsicClamp(const IntrinsicInst *II,
const APInt *&CLow,
const APInt *&CHigh) {
assert((II->getIntrinsicID() == Intrinsic::smin ||
II->getIntrinsicID() == Intrinsic::smax) && "Must be smin/smax");
Intrinsic::ID InverseID = getInverseMinMaxIntrinsic(II->getIntrinsicID());
auto *InnerII = dyn_cast<IntrinsicInst>(II->getArgOperand(0));
if (!InnerII || InnerII->getIntrinsicID() != InverseID ||
!match(II->getArgOperand(1), m_APInt(CLow)) ||
!match(InnerII->getArgOperand(1), m_APInt(CHigh)))
return false;
if (II->getIntrinsicID() == Intrinsic::smin)
std::swap(CLow, CHigh);
return CLow->sle(*CHigh);
}
/// For vector constants, loop over the elements and find the constant with the
/// minimum number of sign bits. Return 0 if the value is not a vector constant
/// or if any element was not analyzed; otherwise, return the count for the
/// element with the minimum number of sign bits.
static unsigned computeNumSignBitsVectorConstant(const Value *V,
const APInt &DemandedElts,
unsigned TyBits) {
const auto *CV = dyn_cast<Constant>(V);
if (!CV || !isa<FixedVectorType>(CV->getType()))
return 0;
unsigned MinSignBits = TyBits;
unsigned NumElts = cast<FixedVectorType>(CV->getType())->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
if (!DemandedElts[i])
continue;
// If we find a non-ConstantInt, bail out.
auto *Elt = dyn_cast_or_null<ConstantInt>(CV->getAggregateElement(i));
if (!Elt)
return 0;
MinSignBits = std::min(MinSignBits, Elt->getValue().getNumSignBits());
}
return MinSignBits;
}
static unsigned ComputeNumSignBitsImpl(const Value *V,
const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q);
static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q) {
unsigned Result = ComputeNumSignBitsImpl(V, DemandedElts, Depth, Q);
assert(Result > 0 && "At least one sign bit needs to be present!");
return Result;
}
/// Return the number of times the sign bit of the register is replicated into
/// the other bits. We know that at least 1 bit is always equal to the sign bit
/// (itself), but other cases can give us information. For example, immediately
/// after an "ashr X, 2", we know that the top 3 bits are all equal to each
/// other, so we return 3. For vectors, return the number of sign bits for the
/// vector element with the minimum number of known sign bits of the demanded
/// elements in the vector specified by DemandedElts.
static unsigned ComputeNumSignBitsImpl(const Value *V,
const APInt &DemandedElts,
unsigned Depth, const SimplifyQuery &Q) {
Type *Ty = V->getType();
#ifndef NDEBUG
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
assert(
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements");
} else {
assert(DemandedElts == APInt(1, 1) &&
"DemandedElt width should be 1 for scalars");
}
#endif
// We return the minimum number of sign bits that are guaranteed to be present
// in V, so for undef we have to conservatively return 1. We don't have the
// same behavior for poison though -- that's a FIXME today.
Type *ScalarTy = Ty->getScalarType();
unsigned TyBits = ScalarTy->isPointerTy() ?
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
Q.DL.getTypeSizeInBits(ScalarTy);
unsigned Tmp, Tmp2;
unsigned FirstAnswer = 1;
// Note that ConstantInt is handled by the general computeKnownBits case
// below.
if (Depth == MaxAnalysisRecursionDepth)
return 1;
if (auto *U = dyn_cast<Operator>(V)) {
switch (Operator::getOpcode(V)) {
default: break;
case Instruction::SExt:
Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q) + Tmp;
case Instruction::SDiv: {
const APInt *Denominator;
// sdiv X, C -> adds log(C) sign bits.
if (match(U->getOperand(1), m_APInt(Denominator))) {
// Ignore non-positive denominator.
if (!Denominator->isStrictlyPositive())
break;
// Calculate the incoming numerator bits.
unsigned NumBits = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
// Add floor(log(C)) bits to the numerator bits.
return std::min(TyBits, NumBits + Denominator->logBase2());
}
break;
}
case Instruction::SRem: {
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
const APInt *Denominator;
// srem X, C -> we know that the result is within [-C+1,C) when C is a
// positive constant. This let us put a lower bound on the number of sign
// bits.
if (match(U->getOperand(1), m_APInt(Denominator))) {
// Ignore non-positive denominator.
if (Denominator->isStrictlyPositive()) {
// Calculate the leading sign bit constraints by examining the
// denominator. Given that the denominator is positive, there are two
// cases:
//
// 1. The numerator is positive. The result range is [0,C) and
// [0,C) u< (1 << ceilLogBase2(C)).
//
// 2. The numerator is negative. Then the result range is (-C,0] and
// integers in (-C,0] are either 0 or >u (-1 << ceilLogBase2(C)).
//
// Thus a lower bound on the number of sign bits is `TyBits -
// ceilLogBase2(C)`.
unsigned ResBits = TyBits - Denominator->ceilLogBase2();
Tmp = std::max(Tmp, ResBits);
}
}
return Tmp;
}
case Instruction::AShr: {
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
// ashr X, C -> adds C sign bits. Vectors too.
const APInt *ShAmt;
if (match(U->getOperand(1), m_APInt(ShAmt))) {
if (ShAmt->uge(TyBits))
break; // Bad shift.
unsigned ShAmtLimited = ShAmt->getZExtValue();
Tmp += ShAmtLimited;
if (Tmp > TyBits) Tmp = TyBits;
}
return Tmp;
}
case Instruction::Shl: {
const APInt *ShAmt;
if (match(U->getOperand(1), m_APInt(ShAmt))) {
// shl destroys sign bits.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (ShAmt->uge(TyBits) || // Bad shift.
ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
Tmp2 = ShAmt->getZExtValue();
return Tmp - Tmp2;
}
break;
}
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: // NOT is handled here.
// Logical binary ops preserve the number of sign bits at the worst.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp != 1) {
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
FirstAnswer = std::min(Tmp, Tmp2);
// We computed what we know about the sign bits as our first
// answer. Now proceed to the generic code that uses
// computeKnownBits, and pick whichever answer is better.
}
break;
case Instruction::Select: {
// If we have a clamp pattern, we know that the number of sign bits will
// be the minimum of the clamp min/max range.
const Value *X;
const APInt *CLow, *CHigh;
if (isSignedMinMaxClamp(U, X, CLow, CHigh))
return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
Tmp = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp == 1) break;
Tmp2 = ComputeNumSignBits(U->getOperand(2), Depth + 1, Q);
return std::min(Tmp, Tmp2);
}
case Instruction::Add:
// Add can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
// Special case decrementing a value (ADD X, -1):
if (const auto *CRHS = dyn_cast<Constant>(U->getOperand(1)))
if (CRHS->isAllOnesValue()) {
KnownBits Known(TyBits);
computeKnownBits(U->getOperand(0), Known, Depth + 1, Q);
// If the input is known to be 0 or 1, the output is 0/-1, which is
// all sign bits set.
if ((Known.Zero | 1).isAllOnes())
return TyBits;
// If we are subtracting one from a positive number, there is no carry
// out of the result.
if (Known.isNonNegative())
return Tmp;
}
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp2 == 1) break;
return std::min(Tmp, Tmp2) - 1;
case Instruction::Sub:
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp2 == 1) break;
// Handle NEG.
if (const auto *CLHS = dyn_cast<Constant>(U->getOperand(0)))
if (CLHS->isNullValue()) {
KnownBits Known(TyBits);
computeKnownBits(U->getOperand(1), Known, Depth + 1, Q);
// If the input is known to be 0 or 1, the output is 0/-1, which is
// all sign bits set.
if ((Known.Zero | 1).isAllOnes())
return TyBits;
// If the input is known to be positive (the sign bit is known clear),
// the output of the NEG has the same number of sign bits as the
// input.
if (Known.isNonNegative())
return Tmp2;
// Otherwise, we treat this like a SUB.
}
// Sub can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
return std::min(Tmp, Tmp2) - 1;
case Instruction::Mul: {
// The output of the Mul can be at most twice the valid bits in the
// inputs.
unsigned SignBitsOp0 = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (SignBitsOp0 == 1) break;
unsigned SignBitsOp1 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (SignBitsOp1 == 1) break;
unsigned OutValidBits =
(TyBits - SignBitsOp0 + 1) + (TyBits - SignBitsOp1 + 1);
return OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
}
case Instruction::PHI: {
const PHINode *PN = cast<PHINode>(U);
unsigned NumIncomingValues = PN->getNumIncomingValues();
// Don't analyze large in-degree PHIs.
if (NumIncomingValues > 4) break;
// Unreachable blocks may have zero-operand PHI nodes.
if (NumIncomingValues == 0) break;
// Take the minimum of all incoming values. This can't infinitely loop
// because of our depth threshold.
SimplifyQuery RecQ = Q;
Tmp = TyBits;
for (unsigned i = 0, e = NumIncomingValues; i != e; ++i) {
if (Tmp == 1) return Tmp;
RecQ.CxtI = PN->getIncomingBlock(i)->getTerminator();
Tmp = std::min(
Tmp, ComputeNumSignBits(PN->getIncomingValue(i), Depth + 1, RecQ));
}
return Tmp;
}
case Instruction::Trunc: {
// If the input contained enough sign bits that some remain after the
// truncation, then we can make use of that. Otherwise we don't know
// anything.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
unsigned OperandTyBits = U->getOperand(0)->getType()->getScalarSizeInBits();
if (Tmp > (OperandTyBits - TyBits))
return Tmp - (OperandTyBits - TyBits);
return 1;
}
case Instruction::ExtractElement:
// Look through extract element. At the moment we keep this simple and
// skip tracking the specific element. But at least we might find
// information valid for all elements of the vector (for example if vector
// is sign extended, shifted, etc).
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
case Instruction::ShuffleVector: {
// Collect the minimum number of sign bits that are shared by every vector
// element referenced by the shuffle.
auto *Shuf = dyn_cast<ShuffleVectorInst>(U);
if (!Shuf) {
// FIXME: Add support for shufflevector constant expressions.
return 1;
}
APInt DemandedLHS, DemandedRHS;
// For undef elements, we don't know anything about the common state of
// the shuffle result.
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
return 1;
Tmp = std::numeric_limits<unsigned>::max();
if (!!DemandedLHS) {
const Value *LHS = Shuf->getOperand(0);
Tmp = ComputeNumSignBits(LHS, DemandedLHS, Depth + 1, Q);
}
// If we don't know anything, early out and try computeKnownBits
// fall-back.
if (Tmp == 1)
break;
if (!!DemandedRHS) {
const Value *RHS = Shuf->getOperand(1);
Tmp2 = ComputeNumSignBits(RHS, DemandedRHS, Depth + 1, Q);
Tmp = std::min(Tmp, Tmp2);
}
// If we don't know anything, early out and try computeKnownBits
// fall-back.
if (Tmp == 1)
break;
assert(Tmp <= TyBits && "Failed to determine minimum sign bits");
return Tmp;
}
case Instruction::Call: {
if (const auto *II = dyn_cast<IntrinsicInst>(U)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::abs:
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
// Absolute value reduces number of sign bits by at most 1.
return Tmp - 1;
case Intrinsic::smin:
case Intrinsic::smax: {
const APInt *CLow, *CHigh;
if (isSignedMinMaxIntrinsicClamp(II, CLow, CHigh))
return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
}
}
}
}
}
}
// Finally, if we can prove that the top bits of the result are 0's or 1's,
// use this information.
// If we can examine all elements of a vector constant successfully, we're
// done (we can't do any better than that). If not, keep trying.
if (unsigned VecSignBits =
computeNumSignBitsVectorConstant(V, DemandedElts, TyBits))
return VecSignBits;
KnownBits Known(TyBits);
computeKnownBits(V, DemandedElts, Known, Depth, Q);
// If we know that the sign bit is either zero or one, determine the number of
// identical bits in the top of the input value.
return std::max(FirstAnswer, Known.countMinSignBits());
}
Intrinsic::ID llvm::getIntrinsicForCallSite(const CallBase &CB,
const TargetLibraryInfo *TLI) {
const Function *F = CB.getCalledFunction();
if (!F)
return Intrinsic::not_intrinsic;
if (F->isIntrinsic())
return F->getIntrinsicID();
// We are going to infer semantics of a library function based on mapping it
// to an LLVM intrinsic. Check that the library function is available from
// this callbase and in this environment.
LibFunc Func;
if (F->hasLocalLinkage() || !TLI || !TLI->getLibFunc(CB, Func) ||
!CB.onlyReadsMemory())
return Intrinsic::not_intrinsic;
switch (Func) {
default:
break;
case LibFunc_sin:
case LibFunc_sinf:
case LibFunc_sinl:
return Intrinsic::sin;
case LibFunc_cos:
case LibFunc_cosf:
case LibFunc_cosl:
return Intrinsic::cos;
case LibFunc_exp:
case LibFunc_expf:
case LibFunc_expl:
return Intrinsic::exp;
case LibFunc_exp2:
case LibFunc_exp2f:
case LibFunc_exp2l:
return Intrinsic::exp2;
case LibFunc_log:
case LibFunc_logf:
case LibFunc_logl:
return Intrinsic::log;
case LibFunc_log10:
case LibFunc_log10f:
case LibFunc_log10l:
return Intrinsic::log10;
case LibFunc_log2:
case LibFunc_log2f:
case LibFunc_log2l:
return Intrinsic::log2;
case LibFunc_fabs:
case LibFunc_fabsf:
case LibFunc_fabsl:
return Intrinsic::fabs;
case LibFunc_fmin:
case LibFunc_fminf:
case LibFunc_fminl:
return Intrinsic::minnum;
case LibFunc_fmax:
case LibFunc_fmaxf:
case LibFunc_fmaxl:
return Intrinsic::maxnum;
case LibFunc_copysign:
case LibFunc_copysignf:
case LibFunc_copysignl:
return Intrinsic::copysign;
case LibFunc_floor:
case LibFunc_floorf:
case LibFunc_floorl:
return Intrinsic::floor;
case LibFunc_ceil:
case LibFunc_ceilf:
case LibFunc_ceill:
return Intrinsic::ceil;
case LibFunc_trunc:
case LibFunc_truncf:
case LibFunc_truncl:
return Intrinsic::trunc;
case LibFunc_rint:
case LibFunc_rintf:
case LibFunc_rintl:
return Intrinsic::rint;
case LibFunc_nearbyint:
case LibFunc_nearbyintf:
case LibFunc_nearbyintl:
return Intrinsic::nearbyint;
case LibFunc_round:
case LibFunc_roundf:
case LibFunc_roundl:
return Intrinsic::round;
case LibFunc_roundeven:
case LibFunc_roundevenf:
case LibFunc_roundevenl:
return Intrinsic::roundeven;
case LibFunc_pow:
case LibFunc_powf:
case LibFunc_powl:
return Intrinsic::pow;
case LibFunc_sqrt:
case LibFunc_sqrtf:
case LibFunc_sqrtl:
return Intrinsic::sqrt;
}
return Intrinsic::not_intrinsic;
}
/// Return true if it's possible to assume IEEE treatment of input denormals in
/// \p F for \p Val.
static bool inputDenormalIsIEEE(const Function &F, const Type *Ty) {
Ty = Ty->getScalarType();
return F.getDenormalMode(Ty->getFltSemantics()).Input == DenormalMode::IEEE;
}
static bool inputDenormalIsIEEEOrPosZero(const Function &F, const Type *Ty) {
Ty = Ty->getScalarType();
DenormalMode Mode = F.getDenormalMode(Ty->getFltSemantics());
return Mode.Input == DenormalMode::IEEE ||
Mode.Input == DenormalMode::PositiveZero;
}
static bool outputDenormalIsIEEEOrPosZero(const Function &F, const Type *Ty) {
Ty = Ty->getScalarType();
DenormalMode Mode = F.getDenormalMode(Ty->getFltSemantics());
return Mode.Output == DenormalMode::IEEE ||
Mode.Output == DenormalMode::PositiveZero;
}
bool KnownFPClass::isKnownNeverLogicalZero(const Function &F, Type *Ty) const {
return isKnownNeverZero() &&
(isKnownNeverSubnormal() || inputDenormalIsIEEE(F, Ty));
}
bool KnownFPClass::isKnownNeverLogicalNegZero(const Function &F,
Type *Ty) const {
return isKnownNeverNegZero() &&
(isKnownNeverNegSubnormal() || inputDenormalIsIEEEOrPosZero(F, Ty));
}
bool KnownFPClass::isKnownNeverLogicalPosZero(const Function &F,
Type *Ty) const {
if (!isKnownNeverPosZero())
return false;
// If we know there are no denormals, nothing can be flushed to zero.
if (isKnownNeverSubnormal())
return true;
DenormalMode Mode = F.getDenormalMode(Ty->getScalarType()->getFltSemantics());
switch (Mode.Input) {
case DenormalMode::IEEE:
return true;
case DenormalMode::PreserveSign:
// Negative subnormal won't flush to +0
return isKnownNeverPosSubnormal();
case DenormalMode::PositiveZero:
default:
// Both positive and negative subnormal could flush to +0
return false;
}
llvm_unreachable("covered switch over denormal mode");
}
void KnownFPClass::propagateDenormal(const KnownFPClass &Src, const Function &F,
Type *Ty) {
KnownFPClasses = Src.KnownFPClasses;
// If we aren't assuming the source can't be a zero, we don't have to check if
// a denormal input could be flushed.
if (!Src.isKnownNeverPosZero() && !Src.isKnownNeverNegZero())
return;
// If we know the input can't be a denormal, it can't be flushed to 0.
if (Src.isKnownNeverSubnormal())
return;
DenormalMode Mode = F.getDenormalMode(Ty->getScalarType()->getFltSemantics());
if (!Src.isKnownNeverPosSubnormal() && Mode != DenormalMode::getIEEE())
KnownFPClasses |= fcPosZero;
if (!Src.isKnownNeverNegSubnormal() && Mode != DenormalMode::getIEEE()) {
if (Mode != DenormalMode::getPositiveZero())
KnownFPClasses |= fcNegZero;
if (Mode.Input == DenormalMode::PositiveZero ||
Mode.Output == DenormalMode::PositiveZero ||
Mode.Input == DenormalMode::Dynamic ||
Mode.Output == DenormalMode::Dynamic)
KnownFPClasses |= fcPosZero;
}
}
void KnownFPClass::propagateCanonicalizingSrc(const KnownFPClass &Src,
const Function &F, Type *Ty) {
propagateDenormal(Src, F, Ty);
propagateNaN(Src, /*PreserveSign=*/true);
}
/// Given an exploded icmp instruction, return true if the comparison only
/// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if
/// the result of the comparison is true when the input value is signed.
bool llvm::isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
bool &TrueIfSigned) {
switch (Pred) {
case ICmpInst::ICMP_SLT: // True if LHS s< 0
TrueIfSigned = true;
return RHS.isZero();
case ICmpInst::ICMP_SLE: // True if LHS s<= -1
TrueIfSigned = true;
return RHS.isAllOnes();
case ICmpInst::ICMP_SGT: // True if LHS s> -1
TrueIfSigned = false;
return RHS.isAllOnes();
case ICmpInst::ICMP_SGE: // True if LHS s>= 0
TrueIfSigned = false;
return RHS.isZero();
case ICmpInst::ICMP_UGT:
// True if LHS u> RHS and RHS == sign-bit-mask - 1
TrueIfSigned = true;
return RHS.isMaxSignedValue();
case ICmpInst::ICMP_UGE:
// True if LHS u>= RHS and RHS == sign-bit-mask (2^7, 2^15, 2^31, etc)
TrueIfSigned = true;
return RHS.isMinSignedValue();
case ICmpInst::ICMP_ULT:
// True if LHS u< RHS and RHS == sign-bit-mask (2^7, 2^15, 2^31, etc)
TrueIfSigned = false;
return RHS.isMinSignedValue();
case ICmpInst::ICMP_ULE:
// True if LHS u<= RHS and RHS == sign-bit-mask - 1
TrueIfSigned = false;
return RHS.isMaxSignedValue();
default:
return false;
}
}
/// Returns a pair of values, which if passed to llvm.is.fpclass, returns the
/// same result as an fcmp with the given operands.
std::pair<Value *, FPClassTest> llvm::fcmpToClassTest(FCmpInst::Predicate Pred,
const Function &F,
Value *LHS, Value *RHS,
bool LookThroughSrc) {
const APFloat *ConstRHS;
if (!match(RHS, m_APFloatAllowUndef(ConstRHS)))
return {nullptr, fcAllFlags};
return fcmpToClassTest(Pred, F, LHS, ConstRHS, LookThroughSrc);
}
std::pair<Value *, FPClassTest>
llvm::fcmpToClassTest(FCmpInst::Predicate Pred, const Function &F, Value *LHS,
const APFloat *ConstRHS, bool LookThroughSrc) {
auto [Src, ClassIfTrue, ClassIfFalse] =
fcmpImpliesClass(Pred, F, LHS, *ConstRHS, LookThroughSrc);
if (Src && ClassIfTrue == ~ClassIfFalse)
return {Src, ClassIfTrue};
return {nullptr, fcAllFlags};
}
/// Return the return value for fcmpImpliesClass for a compare that produces an
/// exact class test.
static std::tuple<Value *, FPClassTest, FPClassTest> exactClass(Value *V,
FPClassTest M) {
return {V, M, ~M};
}
std::tuple<Value *, FPClassTest, FPClassTest>
llvm::fcmpImpliesClass(CmpInst::Predicate Pred, const Function &F, Value *LHS,
FPClassTest RHSClass, bool LookThroughSrc) {
assert(RHSClass != fcNone);
Value *Src = LHS;
if (Pred == FCmpInst::FCMP_TRUE)
return exactClass(Src, fcAllFlags);
if (Pred == FCmpInst::FCMP_FALSE)
return exactClass(Src, fcNone);
const FPClassTest OrigClass = RHSClass;
const bool IsNegativeRHS = (RHSClass & fcNegative) == RHSClass;
const bool IsPositiveRHS = (RHSClass & fcPositive) == RHSClass;
const bool IsNaN = (RHSClass & ~fcNan) == fcNone;
if (IsNaN) {
// fcmp o__ x, nan -> false
// fcmp u__ x, nan -> true
return exactClass(Src, CmpInst::isOrdered(Pred) ? fcNone : fcAllFlags);
}
// fcmp ord x, zero|normal|subnormal|inf -> ~fcNan
if (Pred == FCmpInst::FCMP_ORD)
return exactClass(Src, ~fcNan);
// fcmp uno x, zero|normal|subnormal|inf -> fcNan
if (Pred == FCmpInst::FCMP_UNO)
return exactClass(Src, fcNan);
const bool IsFabs = LookThroughSrc && match(LHS, m_FAbs(m_Value(Src)));
if (IsFabs)
RHSClass = llvm::inverse_fabs(RHSClass);
const bool IsZero = (OrigClass & fcZero) == OrigClass;
if (IsZero) {
assert(Pred != FCmpInst::FCMP_ORD && Pred != FCmpInst::FCMP_UNO);
// Compares with fcNone are only exactly equal to fcZero if input denormals
// are not flushed.
// TODO: Handle DAZ by expanding masks to cover subnormal cases.
if (!inputDenormalIsIEEE(F, LHS->getType()))
return {nullptr, fcAllFlags, fcAllFlags};
switch (Pred) {
case FCmpInst::FCMP_OEQ: // Match x == 0.0
return exactClass(Src, fcZero);
case FCmpInst::FCMP_UEQ: // Match isnan(x) || (x == 0.0)
return exactClass(Src, fcZero | fcNan);
case FCmpInst::FCMP_UNE: // Match (x != 0.0)
return exactClass(Src, ~fcZero);
case FCmpInst::FCMP_ONE: // Match !isnan(x) && x != 0.0
return exactClass(Src, ~fcNan & ~fcZero);
case FCmpInst::FCMP_ORD:
// Canonical form of ord/uno is with a zero. We could also handle
// non-canonical other non-NaN constants or LHS == RHS.
return exactClass(Src, ~fcNan);
case FCmpInst::FCMP_UNO:
return exactClass(Src, fcNan);
case FCmpInst::FCMP_OGT: // x > 0
return exactClass(Src, fcPosSubnormal | fcPosNormal | fcPosInf);
case FCmpInst::FCMP_UGT: // isnan(x) || x > 0
return exactClass(Src, fcPosSubnormal | fcPosNormal | fcPosInf | fcNan);
case FCmpInst::FCMP_OGE: // x >= 0
return exactClass(Src, fcPositive | fcNegZero);
case FCmpInst::FCMP_UGE: // isnan(x) || x >= 0
return exactClass(Src, fcPositive | fcNegZero | fcNan);
case FCmpInst::FCMP_OLT: // x < 0
return exactClass(Src, fcNegSubnormal | fcNegNormal | fcNegInf);
case FCmpInst::FCMP_ULT: // isnan(x) || x < 0
return exactClass(Src, fcNegSubnormal | fcNegNormal | fcNegInf | fcNan);
case FCmpInst::FCMP_OLE: // x <= 0
return exactClass(Src, fcNegative | fcPosZero);
case FCmpInst::FCMP_ULE: // isnan(x) || x <= 0
return exactClass(Src, fcNegative | fcPosZero | fcNan);
default:
llvm_unreachable("all compare types are handled");
}
return {nullptr, fcAllFlags, fcAllFlags};
}
const bool IsDenormalRHS = (OrigClass & fcSubnormal) == OrigClass;
const bool IsInf = (OrigClass & fcInf) == OrigClass;
if (IsInf) {
FPClassTest Mask = fcAllFlags;
switch (Pred) {
case FCmpInst::FCMP_OEQ:
case FCmpInst::FCMP_UNE: {
// Match __builtin_isinf patterns
//
// fcmp oeq x, +inf -> is_fpclass x, fcPosInf
// fcmp oeq fabs(x), +inf -> is_fpclass x, fcInf
// fcmp oeq x, -inf -> is_fpclass x, fcNegInf
// fcmp oeq fabs(x), -inf -> is_fpclass x, 0 -> false
//
// fcmp une x, +inf -> is_fpclass x, ~fcPosInf
// fcmp une fabs(x), +inf -> is_fpclass x, ~fcInf
// fcmp une x, -inf -> is_fpclass x, ~fcNegInf
// fcmp une fabs(x), -inf -> is_fpclass x, fcAllFlags -> true
if (IsNegativeRHS) {
Mask = fcNegInf;
if (IsFabs)
Mask = fcNone;
} else {
Mask = fcPosInf;
if (IsFabs)
Mask |= fcNegInf;
}
break;
}
case FCmpInst::FCMP_ONE:
case FCmpInst::FCMP_UEQ: {
// Match __builtin_isinf patterns
// fcmp one x, -inf -> is_fpclass x, fcNegInf
// fcmp one fabs(x), -inf -> is_fpclass x, ~fcNegInf & ~fcNan
// fcmp one x, +inf -> is_fpclass x, ~fcNegInf & ~fcNan
// fcmp one fabs(x), +inf -> is_fpclass x, ~fcInf & fcNan
//
// fcmp ueq x, +inf -> is_fpclass x, fcPosInf|fcNan
// fcmp ueq (fabs x), +inf -> is_fpclass x, fcInf|fcNan
// fcmp ueq x, -inf -> is_fpclass x, fcNegInf|fcNan
// fcmp ueq fabs(x), -inf -> is_fpclass x, fcNan
if (IsNegativeRHS) {
Mask = ~fcNegInf & ~fcNan;
if (IsFabs)
Mask = ~fcNan;
} else {
Mask = ~fcPosInf & ~fcNan;
if (IsFabs)
Mask &= ~fcNegInf;
}
break;
}
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_UGE: {
if (IsNegativeRHS) {
// No value is ordered and less than negative infinity.
// All values are unordered with or at least negative infinity.
// fcmp olt x, -inf -> false
// fcmp uge x, -inf -> true
Mask = fcNone;
break;
}
// fcmp olt fabs(x), +inf -> fcFinite
// fcmp uge fabs(x), +inf -> ~fcFinite
// fcmp olt x, +inf -> fcFinite|fcNegInf
// fcmp uge x, +inf -> ~(fcFinite|fcNegInf)
Mask = fcFinite;
if (!IsFabs)
Mask |= fcNegInf;
break;
}
case FCmpInst::FCMP_OGE:
case FCmpInst::FCMP_ULT: {
if (IsNegativeRHS) {
// fcmp oge x, -inf -> ~fcNan
// fcmp oge fabs(x), -inf -> ~fcNan
// fcmp ult x, -inf -> fcNan
// fcmp ult fabs(x), -inf -> fcNan
Mask = ~fcNan;
break;
}
// fcmp oge fabs(x), +inf -> fcInf
// fcmp oge x, +inf -> fcPosInf
// fcmp ult fabs(x), +inf -> ~fcInf
// fcmp ult x, +inf -> ~fcPosInf
Mask = fcPosInf;
if (IsFabs)
Mask |= fcNegInf;
break;
}
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_ULE: {
if (IsNegativeRHS) {
// fcmp ogt x, -inf -> fcmp one x, -inf
// fcmp ogt fabs(x), -inf -> fcmp ord x, x
// fcmp ule x, -inf -> fcmp ueq x, -inf
// fcmp ule fabs(x), -inf -> fcmp uno x, x
Mask = IsFabs ? ~fcNan : ~(fcNegInf | fcNan);
break;
}
// No value is ordered and greater than infinity.
Mask = fcNone;
break;
}
case FCmpInst::FCMP_OLE:
case FCmpInst::FCMP_UGT: {
if (IsNegativeRHS) {
Mask = IsFabs ? fcNone : fcNegInf;
break;
}
// fcmp ole x, +inf -> fcmp ord x, x
// fcmp ole fabs(x), +inf -> fcmp ord x, x
// fcmp ole x, -inf -> fcmp oeq x, -inf
// fcmp ole fabs(x), -inf -> false
Mask = ~fcNan;
break;
}
default:
llvm_unreachable("all compare types are handled");
}
// Invert the comparison for the unordered cases.
if (FCmpInst::isUnordered(Pred))
Mask = ~Mask;
return exactClass(Src, Mask);
}
if (Pred == FCmpInst::FCMP_OEQ)
return {Src, RHSClass, fcAllFlags};
if (Pred == FCmpInst::FCMP_UEQ) {
FPClassTest Class = RHSClass | fcNan;
return {Src, Class, ~fcNan};
}
if (Pred == FCmpInst::FCMP_ONE)
return {Src, ~fcNan, RHSClass | fcNan};
if (Pred == FCmpInst::FCMP_UNE)
return {Src, fcAllFlags, RHSClass};
assert((RHSClass == fcNone || RHSClass == fcPosNormal ||
RHSClass == fcNegNormal || RHSClass == fcNormal ||
RHSClass == fcPosSubnormal || RHSClass == fcNegSubnormal ||
RHSClass == fcSubnormal) &&
"should have been recognized as an exact class test");
if (IsNegativeRHS) {
// TODO: Handle fneg(fabs)
if (IsFabs) {
// fabs(x) o> -k -> fcmp ord x, x
// fabs(x) u> -k -> true
// fabs(x) o< -k -> false
// fabs(x) u< -k -> fcmp uno x, x
switch (Pred) {
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE:
return {Src, ~fcNan, fcNan};
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
return {Src, fcAllFlags, fcNone};
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE:
return {Src, fcNone, fcAllFlags};
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
return {Src, fcNan, ~fcNan};
default:
break;
}
return {nullptr, fcAllFlags, fcAllFlags};
}
FPClassTest ClassesLE = fcNegInf | fcNegNormal;
FPClassTest ClassesGE = fcPositive | fcNegZero | fcNegSubnormal;
if (IsDenormalRHS)
ClassesLE |= fcNegSubnormal;
else
ClassesGE |= fcNegNormal;
switch (Pred) {
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE:
return {Src, ClassesGE, ~ClassesGE | RHSClass};
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
return {Src, ClassesGE | fcNan, ~(ClassesGE | fcNan) | RHSClass};
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE:
return {Src, ClassesLE, ~ClassesLE | RHSClass};
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
return {Src, ClassesLE | fcNan, ~(ClassesLE | fcNan) | RHSClass};
default:
break;
}
} else if (IsPositiveRHS) {
FPClassTest ClassesGE = fcPosNormal | fcPosInf;
FPClassTest ClassesLE = fcNegative | fcPosZero | fcPosSubnormal;
if (IsDenormalRHS)
ClassesGE |= fcPosSubnormal;
else
ClassesLE |= fcPosNormal;
if (IsFabs) {
ClassesGE = llvm::inverse_fabs(ClassesGE);
ClassesLE = llvm::inverse_fabs(ClassesLE);
}
switch (Pred) {
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE:
return {Src, ClassesGE, ~ClassesGE | RHSClass};
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
return {Src, ClassesGE | fcNan, ~(ClassesGE | fcNan) | RHSClass};
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE:
return {Src, ClassesLE, ~ClassesLE | RHSClass};
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
return {Src, ClassesLE | fcNan, ~(ClassesLE | fcNan) | RHSClass};
default:
break;
}
}
return {nullptr, fcAllFlags, fcAllFlags};
}
std::tuple<Value *, FPClassTest, FPClassTest>
llvm::fcmpImpliesClass(CmpInst::Predicate Pred, const Function &F, Value *LHS,
const APFloat &ConstRHS, bool LookThroughSrc) {
// We can refine checks against smallest normal / largest denormal to an
// exact class test.
if (!ConstRHS.isNegative() && ConstRHS.isSmallestNormalized()) {
Value *Src = LHS;
const bool IsFabs = LookThroughSrc && match(LHS, m_FAbs(m_Value(Src)));
FPClassTest Mask;
// Match pattern that's used in __builtin_isnormal.
switch (Pred) {
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_UGE: {
// fcmp olt x, smallest_normal -> fcNegInf|fcNegNormal|fcSubnormal|fcZero
// fcmp olt fabs(x), smallest_normal -> fcSubnormal|fcZero
// fcmp uge x, smallest_normal -> fcNan|fcPosNormal|fcPosInf
// fcmp uge fabs(x), smallest_normal -> ~(fcSubnormal|fcZero)
Mask = fcZero | fcSubnormal;
if (!IsFabs)
Mask |= fcNegNormal | fcNegInf;
break;
}
case FCmpInst::FCMP_OGE:
case FCmpInst::FCMP_ULT: {
// fcmp oge x, smallest_normal -> fcPosNormal | fcPosInf
// fcmp oge fabs(x), smallest_normal -> fcInf | fcNormal
// fcmp ult x, smallest_normal -> ~(fcPosNormal | fcPosInf)
// fcmp ult fabs(x), smallest_normal -> ~(fcInf | fcNormal)
Mask = fcPosInf | fcPosNormal;
if (IsFabs)
Mask |= fcNegInf | fcNegNormal;
break;
}
default:
return fcmpImpliesClass(Pred, F, LHS, ConstRHS.classify(),
LookThroughSrc);
}
// Invert the comparison for the unordered cases.
if (FCmpInst::isUnordered(Pred))
Mask = ~Mask;
return exactClass(Src, Mask);
}
return fcmpImpliesClass(Pred, F, LHS, ConstRHS.classify(), LookThroughSrc);
}
std::tuple<Value *, FPClassTest, FPClassTest>
llvm::fcmpImpliesClass(CmpInst::Predicate Pred, const Function &F, Value *LHS,
Value *RHS, bool LookThroughSrc) {
const APFloat *ConstRHS;
if (!match(RHS, m_APFloatAllowUndef(ConstRHS)))
return {nullptr, fcAllFlags, fcAllFlags};
// TODO: Just call computeKnownFPClass for RHS to handle non-constants.
return fcmpImpliesClass(Pred, F, LHS, *ConstRHS, LookThroughSrc);
}
static void computeKnownFPClassFromCond(const Value *V, Value *Cond,
bool CondIsTrue,
const Instruction *CxtI,
KnownFPClass &KnownFromContext) {
CmpInst::Predicate Pred;
Value *LHS;
uint64_t ClassVal = 0;
const APFloat *CRHS;
const APInt *RHS;
if (match(Cond, m_FCmp(Pred, m_Value(LHS), m_APFloat(CRHS)))) {
auto [CmpVal, MaskIfTrue, MaskIfFalse] = fcmpImpliesClass(
Pred, *CxtI->getParent()->getParent(), LHS, *CRHS, LHS != V);
if (CmpVal == V)
KnownFromContext.knownNot(~(CondIsTrue ? MaskIfTrue : MaskIfFalse));
} else if (match(Cond, m_Intrinsic<Intrinsic::is_fpclass>(
m_Value(LHS), m_ConstantInt(ClassVal)))) {
FPClassTest Mask = static_cast<FPClassTest>(ClassVal);
KnownFromContext.knownNot(CondIsTrue ? ~Mask : Mask);
} else if (match(Cond, m_ICmp(Pred, m_ElementWiseBitCast(m_Value(LHS)),
m_APInt(RHS)))) {
bool TrueIfSigned;
if (!isSignBitCheck(Pred, *RHS, TrueIfSigned))
return;
if (TrueIfSigned == CondIsTrue)
KnownFromContext.signBitMustBeOne();
else
KnownFromContext.signBitMustBeZero();
}
}
static KnownFPClass computeKnownFPClassFromContext(const Value *V,
const SimplifyQuery &Q) {
KnownFPClass KnownFromContext;
if (!Q.CxtI)
return KnownFromContext;
if (Q.DC && Q.DT) {
// Handle dominating conditions.
for (BranchInst *BI : Q.DC->conditionsFor(V)) {
Value *Cond = BI->getCondition();
BasicBlockEdge Edge0(BI->getParent(), BI->getSuccessor(0));
if (Q.DT->dominates(Edge0, Q.CxtI->getParent()))
computeKnownFPClassFromCond(V, Cond, /*CondIsTrue=*/true, Q.CxtI,
KnownFromContext);
BasicBlockEdge Edge1(BI->getParent(), BI->getSuccessor(1));
if (Q.DT->dominates(Edge1, Q.CxtI->getParent()))
computeKnownFPClassFromCond(V, Cond, /*CondIsTrue=*/false, Q.CxtI,
KnownFromContext);
}
}
if (!Q.AC)
return KnownFromContext;
// Try to restrict the floating-point classes based on information from
// assumptions.
for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
if (!AssumeVH)
continue;
CallInst *I = cast<CallInst>(AssumeVH);
assert(I->getFunction() == Q.CxtI->getParent()->getParent() &&
"Got assumption for the wrong function!");
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
"must be an assume intrinsic");
if (!isValidAssumeForContext(I, Q.CxtI, Q.DT))
continue;
computeKnownFPClassFromCond(V, I->getArgOperand(0), /*CondIsTrue=*/true,
Q.CxtI, KnownFromContext);
}
return KnownFromContext;
}
void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
FPClassTest InterestedClasses, KnownFPClass &Known,
unsigned Depth, const SimplifyQuery &Q);
static void computeKnownFPClass(const Value *V, KnownFPClass &Known,
FPClassTest InterestedClasses, unsigned Depth,
const SimplifyQuery &Q) {
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
computeKnownFPClass(V, DemandedElts, InterestedClasses, Known, Depth, Q);
}
static void computeKnownFPClassForFPTrunc(const Operator *Op,
const APInt &DemandedElts,
FPClassTest InterestedClasses,
KnownFPClass &Known, unsigned Depth,
const SimplifyQuery &Q) {
if ((InterestedClasses &
(KnownFPClass::OrderedLessThanZeroMask | fcNan)) == fcNone)
return;
KnownFPClass KnownSrc;
computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedClasses,
KnownSrc, Depth + 1, Q);
// Sign should be preserved
// TODO: Handle cannot be ordered greater than zero
if (KnownSrc.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
Known.propagateNaN(KnownSrc, true);
// Infinity needs a range check.
}
void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
FPClassTest InterestedClasses, KnownFPClass &Known,
unsigned Depth, const SimplifyQuery &Q) {
assert(Known.isUnknown() && "should not be called with known information");
if (!DemandedElts) {
// No demanded elts, better to assume we don't know anything.
Known.resetAll();
return;
}
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
if (auto *CFP = dyn_cast<ConstantFP>(V)) {
Known.KnownFPClasses = CFP->getValueAPF().classify();
Known.SignBit = CFP->isNegative();
return;
}
if (isa<ConstantAggregateZero>(V)) {
Known.KnownFPClasses = fcPosZero;
Known.SignBit = false;
return;
}
if (isa<PoisonValue>(V)) {
Known.KnownFPClasses = fcNone;
Known.SignBit = false;
return;
}
// Try to handle fixed width vector constants
auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
const Constant *CV = dyn_cast<Constant>(V);
if (VFVTy && CV) {
Known.KnownFPClasses = fcNone;
bool SignBitAllZero = true;
bool SignBitAllOne = true;
// For vectors, verify that each element is not NaN.
unsigned NumElts = VFVTy->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
if (!DemandedElts[i])
continue;
Constant *Elt = CV->getAggregateElement(i);
if (!Elt) {
Known = KnownFPClass();
return;
}
if (isa<UndefValue>(Elt))
continue;
auto *CElt = dyn_cast<ConstantFP>(Elt);
if (!CElt) {
Known = KnownFPClass();
return;
}
const APFloat &C = CElt->getValueAPF();
Known.KnownFPClasses |= C.classify();
if (C.isNegative())
SignBitAllZero = false;
else
SignBitAllOne = false;
}
if (SignBitAllOne != SignBitAllZero)
Known.SignBit = SignBitAllOne;
return;
}
FPClassTest KnownNotFromFlags = fcNone;
if (const auto *CB = dyn_cast<CallBase>(V))
KnownNotFromFlags |= CB->getRetNoFPClass();
else if (const auto *Arg = dyn_cast<Argument>(V))
KnownNotFromFlags |= Arg->getNoFPClass();
const Operator *Op = dyn_cast<Operator>(V);
if (const FPMathOperator *FPOp = dyn_cast_or_null<FPMathOperator>(Op)) {
if (FPOp->hasNoNaNs())
KnownNotFromFlags |= fcNan;
if (FPOp->hasNoInfs())
KnownNotFromFlags |= fcInf;
}
KnownFPClass AssumedClasses = computeKnownFPClassFromContext(V, Q);
KnownNotFromFlags |= ~AssumedClasses.KnownFPClasses;
// We no longer need to find out about these bits from inputs if we can
// assume this from flags/attributes.
InterestedClasses &= ~KnownNotFromFlags;
auto ClearClassesFromFlags = make_scope_exit([=, &Known] {
Known.knownNot(KnownNotFromFlags);
if (!Known.SignBit && AssumedClasses.SignBit) {
if (*AssumedClasses.SignBit)
Known.signBitMustBeOne();
else
Known.signBitMustBeZero();
}
});
if (!Op)
return;
// All recursive calls that increase depth must come after this.
if (Depth == MaxAnalysisRecursionDepth)
return;
const unsigned Opc = Op->getOpcode();
switch (Opc) {
case Instruction::FNeg: {
computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedClasses,
Known, Depth + 1, Q);
Known.fneg();
break;
}
case Instruction::Select: {
Value *Cond = Op->getOperand(0);
Value *LHS = Op->getOperand(1);
Value *RHS = Op->getOperand(2);
FPClassTest FilterLHS = fcAllFlags;
FPClassTest FilterRHS = fcAllFlags;
Value *TestedValue = nullptr;
FPClassTest MaskIfTrue = fcAllFlags;
FPClassTest MaskIfFalse = fcAllFlags;
uint64_t ClassVal = 0;
const Function *F = cast<Instruction>(Op)->getFunction();
CmpInst::Predicate Pred;
Value *CmpLHS, *CmpRHS;
if (F && match(Cond, m_FCmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)))) {
// If the select filters out a value based on the class, it no longer
// participates in the class of the result
// TODO: In some degenerate cases we can infer something if we try again
// without looking through sign operations.
bool LookThroughFAbsFNeg = CmpLHS != LHS && CmpLHS != RHS;
std::tie(TestedValue, MaskIfTrue, MaskIfFalse) =
fcmpImpliesClass(Pred, *F, CmpLHS, CmpRHS, LookThroughFAbsFNeg);
} else if (match(Cond,
m_Intrinsic<Intrinsic::is_fpclass>(
m_Value(TestedValue), m_ConstantInt(ClassVal)))) {
FPClassTest TestedMask = static_cast<FPClassTest>(ClassVal);
MaskIfTrue = TestedMask;
MaskIfFalse = ~TestedMask;
}
if (TestedValue == LHS) {
// match !isnan(x) ? x : y
FilterLHS = MaskIfTrue;
} else if (TestedValue == RHS) { // && IsExactClass
// match !isnan(x) ? y : x
FilterRHS = MaskIfFalse;
}
KnownFPClass Known2;
computeKnownFPClass(LHS, DemandedElts, InterestedClasses & FilterLHS, Known,
Depth + 1, Q);
Known.KnownFPClasses &= FilterLHS;
computeKnownFPClass(RHS, DemandedElts, InterestedClasses & FilterRHS,
Known2, Depth + 1, Q);
Known2.KnownFPClasses &= FilterRHS;
Known |= Known2;
break;
}
case Instruction::Call: {
const CallInst *II = cast<CallInst>(Op);
const Intrinsic::ID IID = II->getIntrinsicID();
switch (IID) {
case Intrinsic::fabs: {
if ((InterestedClasses & (fcNan | fcPositive)) != fcNone) {
// If we only care about the sign bit we don't need to inspect the
// operand.
computeKnownFPClass(II->getArgOperand(0), DemandedElts,
InterestedClasses, Known, Depth + 1, Q);
}
Known.fabs();
break;
}
case Intrinsic::copysign: {
KnownFPClass KnownSign;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
Known, Depth + 1, Q);
computeKnownFPClass(II->getArgOperand(1), DemandedElts, InterestedClasses,
KnownSign, Depth + 1, Q);
Known.copysign(KnownSign);
break;
}
case Intrinsic::fma:
case Intrinsic::fmuladd: {
if ((InterestedClasses & fcNegative) == fcNone)
break;
if (II->getArgOperand(0) != II->getArgOperand(1))
break;
// The multiply cannot be -0 and therefore the add can't be -0
Known.knownNot(fcNegZero);
// x * x + y is non-negative if y is non-negative.
KnownFPClass KnownAddend;
computeKnownFPClass(II->getArgOperand(2), DemandedElts, InterestedClasses,
KnownAddend, Depth + 1, Q);
if (KnownAddend.cannotBeOrderedLessThanZero())
Known.knownNot(fcNegative);
break;
}
case Intrinsic::sqrt:
case Intrinsic::experimental_constrained_sqrt: {
KnownFPClass KnownSrc;
FPClassTest InterestedSrcs = InterestedClasses;
if (InterestedClasses & fcNan)
InterestedSrcs |= KnownFPClass::OrderedLessThanZeroMask;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedSrcs,
KnownSrc, Depth + 1, Q);
if (KnownSrc.isKnownNeverPosInfinity())
Known.knownNot(fcPosInf);
if (KnownSrc.isKnownNever(fcSNan))
Known.knownNot(fcSNan);
// Any negative value besides -0 returns a nan.
if (KnownSrc.isKnownNeverNaN() && KnownSrc.cannotBeOrderedLessThanZero())
Known.knownNot(fcNan);
// The only negative value that can be returned is -0 for -0 inputs.
Known.knownNot(fcNegInf | fcNegSubnormal | fcNegNormal);
// If the input denormal mode could be PreserveSign, a negative
// subnormal input could produce a negative zero output.
const Function *F = II->getFunction();
if (Q.IIQ.hasNoSignedZeros(II) ||
(F && KnownSrc.isKnownNeverLogicalNegZero(*F, II->getType()))) {
Known.knownNot(fcNegZero);
if (KnownSrc.isKnownNeverNaN())
Known.signBitMustBeZero();
}
break;
}
case Intrinsic::sin:
case Intrinsic::cos: {
// Return NaN on infinite inputs.
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
KnownSrc, Depth + 1, Q);
Known.knownNot(fcInf);
if (KnownSrc.isKnownNeverNaN() && KnownSrc.isKnownNeverInfinity())
Known.knownNot(fcNan);
break;
}
case Intrinsic::maxnum:
case Intrinsic::minnum:
case Intrinsic::minimum:
case Intrinsic::maximum: {
KnownFPClass KnownLHS, KnownRHS;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
KnownLHS, Depth + 1, Q);
computeKnownFPClass(II->getArgOperand(1), DemandedElts, InterestedClasses,
KnownRHS, Depth + 1, Q);
bool NeverNaN = KnownLHS.isKnownNeverNaN() || KnownRHS.isKnownNeverNaN();
Known = KnownLHS | KnownRHS;
// If either operand is not NaN, the result is not NaN.
if (NeverNaN && (IID == Intrinsic::minnum || IID == Intrinsic::maxnum))
Known.knownNot(fcNan);
if (IID == Intrinsic::maxnum) {
// If at least one operand is known to be positive, the result must be
// positive.
if ((KnownLHS.cannotBeOrderedLessThanZero() &&
KnownLHS.isKnownNeverNaN()) ||
(KnownRHS.cannotBeOrderedLessThanZero() &&
KnownRHS.isKnownNeverNaN()))
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
} else if (IID == Intrinsic::maximum) {
// If at least one operand is known to be positive, the result must be
// positive.
if (KnownLHS.cannotBeOrderedLessThanZero() ||
KnownRHS.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
} else if (IID == Intrinsic::minnum) {
// If at least one operand is known to be negative, the result must be
// negative.
if ((KnownLHS.cannotBeOrderedGreaterThanZero() &&
KnownLHS.isKnownNeverNaN()) ||
(KnownRHS.cannotBeOrderedGreaterThanZero() &&
KnownRHS.isKnownNeverNaN()))
Known.knownNot(KnownFPClass::OrderedGreaterThanZeroMask);
} else {
// If at least one operand is known to be negative, the result must be
// negative.
if (KnownLHS.cannotBeOrderedGreaterThanZero() ||
KnownRHS.cannotBeOrderedGreaterThanZero())
Known.knownNot(KnownFPClass::OrderedGreaterThanZeroMask);
}
// Fixup zero handling if denormals could be returned as a zero.
//
// As there's no spec for denormal flushing, be conservative with the
// treatment of denormals that could be flushed to zero. For older
// subtargets on AMDGPU the min/max instructions would not flush the
// output and return the original value.
//
if ((Known.KnownFPClasses & fcZero) != fcNone &&
!Known.isKnownNeverSubnormal()) {
const Function *Parent = II->getFunction();
if (!Parent)
break;
DenormalMode Mode = Parent->getDenormalMode(
II->getType()->getScalarType()->getFltSemantics());
if (Mode != DenormalMode::getIEEE())
Known.KnownFPClasses |= fcZero;
}
if (Known.isKnownNeverNaN()) {
if (KnownLHS.SignBit && KnownRHS.SignBit &&
*KnownLHS.SignBit == *KnownRHS.SignBit) {
if (*KnownLHS.SignBit)
Known.signBitMustBeOne();
else
Known.signBitMustBeZero();
} else if ((IID == Intrinsic::maximum || IID == Intrinsic::minimum) ||
((KnownLHS.isKnownNeverNegZero() ||
KnownRHS.isKnownNeverPosZero()) &&
(KnownLHS.isKnownNeverPosZero() ||
KnownRHS.isKnownNeverNegZero()))) {
if ((IID == Intrinsic::maximum || IID == Intrinsic::maxnum) &&
(KnownLHS.SignBit == false || KnownRHS.SignBit == false))
Known.signBitMustBeZero();
else if ((IID == Intrinsic::minimum || IID == Intrinsic::minnum) &&
(KnownLHS.SignBit == true || KnownRHS.SignBit == true))
Known.signBitMustBeOne();
}
}
break;
}
case Intrinsic::canonicalize: {
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
KnownSrc, Depth + 1, Q);
// This is essentially a stronger form of
// propagateCanonicalizingSrc. Other "canonicalizing" operations don't
// actually have an IR canonicalization guarantee.
// Canonicalize may flush denormals to zero, so we have to consider the
// denormal mode to preserve known-not-0 knowledge.
Known.KnownFPClasses = KnownSrc.KnownFPClasses | fcZero | fcQNan;
// Stronger version of propagateNaN
// Canonicalize is guaranteed to quiet signaling nans.
if (KnownSrc.isKnownNeverNaN())
Known.knownNot(fcNan);
else
Known.knownNot(fcSNan);
const Function *F = II->getFunction();
if (!F)
break;
// If the parent function flushes denormals, the canonical output cannot
// be a denormal.
const fltSemantics &FPType =
II->getType()->getScalarType()->getFltSemantics();
DenormalMode DenormMode = F->getDenormalMode(FPType);
if (DenormMode == DenormalMode::getIEEE()) {
if (KnownSrc.isKnownNever(fcPosZero))
Known.knownNot(fcPosZero);
if (KnownSrc.isKnownNever(fcNegZero))
Known.knownNot(fcNegZero);
break;
}
if (DenormMode.inputsAreZero() || DenormMode.outputsAreZero())
Known.knownNot(fcSubnormal);
if (DenormMode.Input == DenormalMode::PositiveZero ||
(DenormMode.Output == DenormalMode::PositiveZero &&
DenormMode.Input == DenormalMode::IEEE))
Known.knownNot(fcNegZero);
break;
}
case Intrinsic::vector_reduce_fmax:
case Intrinsic::vector_reduce_fmin:
case Intrinsic::vector_reduce_fmaximum:
case Intrinsic::vector_reduce_fminimum: {
// reduce min/max will choose an element from one of the vector elements,
// so we can infer and class information that is common to all elements.
Known = computeKnownFPClass(II->getArgOperand(0), II->getFastMathFlags(),
InterestedClasses, Depth + 1, Q);
// Can only propagate sign if output is never NaN.
if (!Known.isKnownNeverNaN())
Known.SignBit.reset();
break;
}
case Intrinsic::trunc:
case Intrinsic::floor:
case Intrinsic::ceil:
case Intrinsic::rint:
case Intrinsic::nearbyint:
case Intrinsic::round:
case Intrinsic::roundeven: {
KnownFPClass KnownSrc;
FPClassTest InterestedSrcs = InterestedClasses;
if (InterestedSrcs & fcPosFinite)
InterestedSrcs |= fcPosFinite;
if (InterestedSrcs & fcNegFinite)
InterestedSrcs |= fcNegFinite;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedSrcs,
KnownSrc, Depth + 1, Q);
// Integer results cannot be subnormal.
Known.knownNot(fcSubnormal);
Known.propagateNaN(KnownSrc, true);
// Pass through infinities, except PPC_FP128 is a special case for
// intrinsics other than trunc.
if (IID == Intrinsic::trunc || !V->getType()->isMultiUnitFPType()) {
if (KnownSrc.isKnownNeverPosInfinity())
Known.knownNot(fcPosInf);
if (KnownSrc.isKnownNeverNegInfinity())
Known.knownNot(fcNegInf);
}
// Negative round ups to 0 produce -0
if (KnownSrc.isKnownNever(fcPosFinite))
Known.knownNot(fcPosFinite);
if (KnownSrc.isKnownNever(fcNegFinite))
Known.knownNot(fcNegFinite);
break;
}
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::exp10: {
Known.knownNot(fcNegative);
if ((InterestedClasses & fcNan) == fcNone)
break;
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
KnownSrc, Depth + 1, Q);
if (KnownSrc.isKnownNeverNaN()) {
Known.knownNot(fcNan);
Known.signBitMustBeZero();
}
break;
}
case Intrinsic::fptrunc_round: {
computeKnownFPClassForFPTrunc(Op, DemandedElts, InterestedClasses, Known,
Depth, Q);
break;
}
case Intrinsic::log:
case Intrinsic::log10:
case Intrinsic::log2:
case Intrinsic::experimental_constrained_log:
case Intrinsic::experimental_constrained_log10:
case Intrinsic::experimental_constrained_log2: {
// log(+inf) -> +inf
// log([+-]0.0) -> -inf
// log(-inf) -> nan
// log(-x) -> nan
if ((InterestedClasses & (fcNan | fcInf)) == fcNone)
break;
FPClassTest InterestedSrcs = InterestedClasses;
if ((InterestedClasses & fcNegInf) != fcNone)
InterestedSrcs |= fcZero | fcSubnormal;
if ((InterestedClasses & fcNan) != fcNone)
InterestedSrcs |= fcNan | (fcNegative & ~fcNan);
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedSrcs,
KnownSrc, Depth + 1, Q);
if (KnownSrc.isKnownNeverPosInfinity())
Known.knownNot(fcPosInf);
if (KnownSrc.isKnownNeverNaN() && KnownSrc.cannotBeOrderedLessThanZero())
Known.knownNot(fcNan);
const Function *F = II->getFunction();
if (F && KnownSrc.isKnownNeverLogicalZero(*F, II->getType()))
Known.knownNot(fcNegInf);
break;
}
case Intrinsic::powi: {
if ((InterestedClasses & fcNegative) == fcNone)
break;
const Value *Exp = II->getArgOperand(1);
Type *ExpTy = Exp->getType();
unsigned BitWidth = ExpTy->getScalarType()->getIntegerBitWidth();
KnownBits ExponentKnownBits(BitWidth);
computeKnownBits(Exp, isa<VectorType>(ExpTy) ? DemandedElts : APInt(1, 1),
ExponentKnownBits, Depth + 1, Q);
if (ExponentKnownBits.Zero[0]) { // Is even
Known.knownNot(fcNegative);
break;
}
// Given that exp is an integer, here are the
// ways that pow can return a negative value:
//
// pow(-x, exp) --> negative if exp is odd and x is negative.
// pow(-0, exp) --> -inf if exp is negative odd.
// pow(-0, exp) --> -0 if exp is positive odd.
// pow(-inf, exp) --> -0 if exp is negative odd.
// pow(-inf, exp) --> -inf if exp is positive odd.
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, fcNegative,
KnownSrc, Depth + 1, Q);
if (KnownSrc.isKnownNever(fcNegative))
Known.knownNot(fcNegative);
break;
}
case Intrinsic::ldexp: {
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
KnownSrc, Depth + 1, Q);
Known.propagateNaN(KnownSrc, /*PropagateSign=*/true);
// Sign is preserved, but underflows may produce zeroes.
if (KnownSrc.isKnownNever(fcNegative))
Known.knownNot(fcNegative);
else if (KnownSrc.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
if (KnownSrc.isKnownNever(fcPositive))
Known.knownNot(fcPositive);
else if (KnownSrc.cannotBeOrderedGreaterThanZero())
Known.knownNot(KnownFPClass::OrderedGreaterThanZeroMask);
// Can refine inf/zero handling based on the exponent operand.
const FPClassTest ExpInfoMask = fcZero | fcSubnormal | fcInf;
if ((InterestedClasses & ExpInfoMask) == fcNone)
break;
if ((KnownSrc.KnownFPClasses & ExpInfoMask) == fcNone)
break;
const fltSemantics &Flt =
II->getType()->getScalarType()->getFltSemantics();
unsigned Precision = APFloat::semanticsPrecision(Flt);
const Value *ExpArg = II->getArgOperand(1);
ConstantRange ExpRange = computeConstantRange(
ExpArg, true, Q.IIQ.UseInstrInfo, Q.AC, Q.CxtI, Q.DT, Depth + 1);
const int MantissaBits = Precision - 1;
if (ExpRange.getSignedMin().sge(static_cast<int64_t>(MantissaBits)))
Known.knownNot(fcSubnormal);
const Function *F = II->getFunction();
const APInt *ConstVal = ExpRange.getSingleElement();
if (ConstVal && ConstVal->isZero()) {
// ldexp(x, 0) -> x, so propagate everything.
Known.propagateCanonicalizingSrc(KnownSrc, *F, II->getType());
} else if (ExpRange.isAllNegative()) {
// If we know the power is <= 0, can't introduce inf
if (KnownSrc.isKnownNeverPosInfinity())
Known.knownNot(fcPosInf);
if (KnownSrc.isKnownNeverNegInfinity())
Known.knownNot(fcNegInf);
} else if (ExpRange.isAllNonNegative()) {
// If we know the power is >= 0, can't introduce subnormal or zero
if (KnownSrc.isKnownNeverPosSubnormal())
Known.knownNot(fcPosSubnormal);
if (KnownSrc.isKnownNeverNegSubnormal())
Known.knownNot(fcNegSubnormal);
if (F && KnownSrc.isKnownNeverLogicalPosZero(*F, II->getType()))
Known.knownNot(fcPosZero);
if (F && KnownSrc.isKnownNeverLogicalNegZero(*F, II->getType()))
Known.knownNot(fcNegZero);
}
break;
}
case Intrinsic::arithmetic_fence: {
computeKnownFPClass(II->getArgOperand(0), DemandedElts, InterestedClasses,
Known, Depth + 1, Q);
break;
}
case Intrinsic::experimental_constrained_sitofp:
case Intrinsic::experimental_constrained_uitofp:
// Cannot produce nan
Known.knownNot(fcNan);
// sitofp and uitofp turn into +0.0 for zero.
Known.knownNot(fcNegZero);
// Integers cannot be subnormal
Known.knownNot(fcSubnormal);
if (IID == Intrinsic::experimental_constrained_uitofp)
Known.signBitMustBeZero();
// TODO: Copy inf handling from instructions
break;
default:
break;
}
break;
}
case Instruction::FAdd:
case Instruction::FSub: {
KnownFPClass KnownLHS, KnownRHS;
bool WantNegative =
Op->getOpcode() == Instruction::FAdd &&
(InterestedClasses & KnownFPClass::OrderedLessThanZeroMask) != fcNone;
bool WantNaN = (InterestedClasses & fcNan) != fcNone;
bool WantNegZero = (InterestedClasses & fcNegZero) != fcNone;
if (!WantNaN && !WantNegative && !WantNegZero)
break;
FPClassTest InterestedSrcs = InterestedClasses;
if (WantNegative)
InterestedSrcs |= KnownFPClass::OrderedLessThanZeroMask;
if (InterestedClasses & fcNan)
InterestedSrcs |= fcInf;
computeKnownFPClass(Op->getOperand(1), DemandedElts, InterestedSrcs,
KnownRHS, Depth + 1, Q);
if ((WantNaN && KnownRHS.isKnownNeverNaN()) ||
(WantNegative && KnownRHS.cannotBeOrderedLessThanZero()) ||
WantNegZero || Opc == Instruction::FSub) {
// RHS is canonically cheaper to compute. Skip inspecting the LHS if
// there's no point.
computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedSrcs,
KnownLHS, Depth + 1, Q);
// Adding positive and negative infinity produces NaN.
// TODO: Check sign of infinities.
if (KnownLHS.isKnownNeverNaN() && KnownRHS.isKnownNeverNaN() &&
(KnownLHS.isKnownNeverInfinity() || KnownRHS.isKnownNeverInfinity()))
Known.knownNot(fcNan);
// FIXME: Context function should always be passed in separately
const Function *F = cast<Instruction>(Op)->getFunction();
if (Op->getOpcode() == Instruction::FAdd) {
if (KnownLHS.cannotBeOrderedLessThanZero() &&
KnownRHS.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
if (!F)
break;
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
if ((KnownLHS.isKnownNeverLogicalNegZero(*F, Op->getType()) ||
KnownRHS.isKnownNeverLogicalNegZero(*F, Op->getType())) &&
// Make sure output negative denormal can't flush to -0
outputDenormalIsIEEEOrPosZero(*F, Op->getType()))
Known.knownNot(fcNegZero);
} else {
if (!F)
break;
// Only fsub -0, +0 can return -0
if ((KnownLHS.isKnownNeverLogicalNegZero(*F, Op->getType()) ||
KnownRHS.isKnownNeverLogicalPosZero(*F, Op->getType())) &&
// Make sure output negative denormal can't flush to -0
outputDenormalIsIEEEOrPosZero(*F, Op->getType()))
Known.knownNot(fcNegZero);
}
}
break;
}
case Instruction::FMul: {
// X * X is always non-negative or a NaN.
if (Op->getOperand(0) == Op->getOperand(1))
Known.knownNot(fcNegative);
if ((InterestedClasses & fcNan) != fcNan)
break;
// fcSubnormal is only needed in case of DAZ.
const FPClassTest NeedForNan = fcNan | fcInf | fcZero | fcSubnormal;
KnownFPClass KnownLHS, KnownRHS;
computeKnownFPClass(Op->getOperand(1), DemandedElts, NeedForNan, KnownRHS,
Depth + 1, Q);
if (!KnownRHS.isKnownNeverNaN())
break;
computeKnownFPClass(Op->getOperand(0), DemandedElts, NeedForNan, KnownLHS,
Depth + 1, Q);
if (!KnownLHS.isKnownNeverNaN())
break;
if (KnownLHS.SignBit && KnownRHS.SignBit) {
if (*KnownLHS.SignBit == *KnownRHS.SignBit)
Known.signBitMustBeZero();
else
Known.signBitMustBeOne();
}
// If 0 * +/-inf produces NaN.
if (KnownLHS.isKnownNeverInfinity() && KnownRHS.isKnownNeverInfinity()) {
Known.knownNot(fcNan);
break;
}
const Function *F = cast<Instruction>(Op)->getFunction();
if (!F)
break;
if ((KnownRHS.isKnownNeverInfinity() ||
KnownLHS.isKnownNeverLogicalZero(*F, Op->getType())) &&
(KnownLHS.isKnownNeverInfinity() ||
KnownRHS.isKnownNeverLogicalZero(*F, Op->getType())))
Known.knownNot(fcNan);
break;
}
case Instruction::FDiv:
case Instruction::FRem: {
if (Op->getOperand(0) == Op->getOperand(1)) {
// TODO: Could filter out snan if we inspect the operand
if (Op->getOpcode() == Instruction::FDiv) {
// X / X is always exactly 1.0 or a NaN.
Known.KnownFPClasses = fcNan | fcPosNormal;
} else {
// X % X is always exactly [+-]0.0 or a NaN.
Known.KnownFPClasses = fcNan | fcZero;
}
break;
}
const bool WantNan = (InterestedClasses & fcNan) != fcNone;
const bool WantNegative = (InterestedClasses & fcNegative) != fcNone;
const bool WantPositive =
Opc == Instruction::FRem && (InterestedClasses & fcPositive) != fcNone;
if (!WantNan && !WantNegative && !WantPositive)
break;
KnownFPClass KnownLHS, KnownRHS;
computeKnownFPClass(Op->getOperand(1), DemandedElts,
fcNan | fcInf | fcZero | fcNegative, KnownRHS,
Depth + 1, Q);
bool KnowSomethingUseful =
KnownRHS.isKnownNeverNaN() || KnownRHS.isKnownNever(fcNegative);
if (KnowSomethingUseful || WantPositive) {
const FPClassTest InterestedLHS =
WantPositive ? fcAllFlags
: fcNan | fcInf | fcZero | fcSubnormal | fcNegative;
computeKnownFPClass(Op->getOperand(0), DemandedElts,
InterestedClasses & InterestedLHS, KnownLHS,
Depth + 1, Q);
}
const Function *F = cast<Instruction>(Op)->getFunction();
if (Op->getOpcode() == Instruction::FDiv) {
// Only 0/0, Inf/Inf produce NaN.
if (KnownLHS.isKnownNeverNaN() && KnownRHS.isKnownNeverNaN() &&
(KnownLHS.isKnownNeverInfinity() ||
KnownRHS.isKnownNeverInfinity()) &&
((F && KnownLHS.isKnownNeverLogicalZero(*F, Op->getType())) ||
(F && KnownRHS.isKnownNeverLogicalZero(*F, Op->getType())))) {
Known.knownNot(fcNan);
}
// X / -0.0 is -Inf (or NaN).
// +X / +X is +X
if (KnownLHS.isKnownNever(fcNegative) && KnownRHS.isKnownNever(fcNegative))
Known.knownNot(fcNegative);
} else {
// Inf REM x and x REM 0 produce NaN.
if (KnownLHS.isKnownNeverNaN() && KnownRHS.isKnownNeverNaN() &&
KnownLHS.isKnownNeverInfinity() && F &&
KnownRHS.isKnownNeverLogicalZero(*F, Op->getType())) {
Known.knownNot(fcNan);
}
// The sign for frem is the same as the first operand.
if (KnownLHS.cannotBeOrderedLessThanZero())
Known.knownNot(KnownFPClass::OrderedLessThanZeroMask);
if (KnownLHS.cannotBeOrderedGreaterThanZero())
Known.knownNot(KnownFPClass::OrderedGreaterThanZeroMask);
// See if we can be more aggressive about the sign of 0.
if (KnownLHS.isKnownNever(fcNegative))
Known.knownNot(fcNegative);
if (KnownLHS.isKnownNever(fcPositive))
Known.knownNot(fcPositive);
}
break;
}
case Instruction::FPExt: {
// Infinity, nan and zero propagate from source.
computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedClasses,
Known, Depth + 1, Q);
const fltSemantics &DstTy =
Op->getType()->getScalarType()->getFltSemantics();
const fltSemantics &SrcTy =
Op->getOperand(0)->getType()->getScalarType()->getFltSemantics();
// All subnormal inputs should be in the normal range in the result type.
if (APFloat::isRepresentableAsNormalIn(SrcTy, DstTy)) {
if (Known.KnownFPClasses & fcPosSubnormal)
Known.KnownFPClasses |= fcPosNormal;
if (Known.KnownFPClasses & fcNegSubnormal)
Known.KnownFPClasses |= fcNegNormal;
Known.knownNot(fcSubnormal);
}
// Sign bit of a nan isn't guaranteed.
if (!Known.isKnownNeverNaN())
Known.SignBit = std::nullopt;
break;
}
case Instruction::FPTrunc: {
computeKnownFPClassForFPTrunc(Op, DemandedElts, InterestedClasses, Known,
Depth, Q);
break;
}
case Instruction::SIToFP:
case Instruction::UIToFP: {
// Cannot produce nan
Known.knownNot(fcNan);
// Integers cannot be subnormal
Known.knownNot(fcSubnormal);
// sitofp and uitofp turn into +0.0 for zero.
Known.knownNot(fcNegZero);
if (Op->getOpcode() == Instruction::UIToFP)
Known.signBitMustBeZero();
if (InterestedClasses & fcInf) {
// Get width of largest magnitude integer (remove a bit if signed).
// This still works for a signed minimum value because the largest FP
// value is scaled by some fraction close to 2.0 (1.0 + 0.xxxx).
int IntSize = Op->getOperand(0)->getType()->getScalarSizeInBits();
if (Op->getOpcode() == Instruction::SIToFP)
--IntSize;
// If the exponent of the largest finite FP value can hold the largest
// integer, the result of the cast must be finite.
Type *FPTy = Op->getType()->getScalarType();
if (ilogb(APFloat::getLargest(FPTy->getFltSemantics())) >= IntSize)
Known.knownNot(fcInf);
}
break;
}
case Instruction::ExtractElement: {
// Look through extract element. If the index is non-constant or
// out-of-range demand all elements, otherwise just the extracted element.
const Value *Vec = Op->getOperand(0);
const Value *Idx = Op->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(Idx);
if (auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType())) {
unsigned NumElts = VecTy->getNumElements();
APInt DemandedVecElts = APInt::getAllOnes(NumElts);
if (CIdx && CIdx->getValue().ult(NumElts))
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
return computeKnownFPClass(Vec, DemandedVecElts, InterestedClasses, Known,
Depth + 1, Q);
}
break;
}
case Instruction::InsertElement: {
if (isa<ScalableVectorType>(Op->getType()))
return;
const Value *Vec = Op->getOperand(0);
const Value *Elt = Op->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(Op->getOperand(2));
unsigned NumElts = DemandedElts.getBitWidth();
APInt DemandedVecElts = DemandedElts;
bool NeedsElt = true;
// If we know the index we are inserting to, clear it from Vec check.
if (CIdx && CIdx->getValue().ult(NumElts)) {
DemandedVecElts.clearBit(CIdx->getZExtValue());
NeedsElt = DemandedElts[CIdx->getZExtValue()];
}
// Do we demand the inserted element?
if (NeedsElt) {
computeKnownFPClass(Elt, Known, InterestedClasses, Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
} else {
Known.KnownFPClasses = fcNone;
}
// Do we need anymore elements from Vec?
if (!DemandedVecElts.isZero()) {
KnownFPClass Known2;
computeKnownFPClass(Vec, DemandedVecElts, InterestedClasses, Known2,
Depth + 1, Q);
Known |= Known2;
}
break;
}
case Instruction::ShuffleVector: {
// For undef elements, we don't know anything about the common state of
// the shuffle result.
APInt DemandedLHS, DemandedRHS;
auto *Shuf = dyn_cast<ShuffleVectorInst>(Op);
if (!Shuf || !getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
return;
if (!!DemandedLHS) {
const Value *LHS = Shuf->getOperand(0);
computeKnownFPClass(LHS, DemandedLHS, InterestedClasses, Known,
Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
} else {
Known.KnownFPClasses = fcNone;
}
if (!!DemandedRHS) {
KnownFPClass Known2;
const Value *RHS = Shuf->getOperand(1);
computeKnownFPClass(RHS, DemandedRHS, InterestedClasses, Known2,
Depth + 1, Q);
Known |= Known2;
}
break;
}
case Instruction::ExtractValue: {
const ExtractValueInst *Extract = cast<ExtractValueInst>(Op);
ArrayRef<unsigned> Indices = Extract->getIndices();
const Value *Src = Extract->getAggregateOperand();
if (isa<StructType>(Src->getType()) && Indices.size() == 1 &&
Indices[0] == 0) {
if (const auto *II = dyn_cast<IntrinsicInst>(Src)) {
switch (II->getIntrinsicID()) {
case Intrinsic::frexp: {
Known.knownNot(fcSubnormal);
KnownFPClass KnownSrc;
computeKnownFPClass(II->getArgOperand(0), DemandedElts,
InterestedClasses, KnownSrc, Depth + 1, Q);
const Function *F = cast<Instruction>(Op)->getFunction();
if (KnownSrc.isKnownNever(fcNegative))
Known.knownNot(fcNegative);
else {
if (F && KnownSrc.isKnownNeverLogicalNegZero(*F, Op->getType()))
Known.knownNot(fcNegZero);
if (KnownSrc.isKnownNever(fcNegInf))
Known.knownNot(fcNegInf);
}
if (KnownSrc.isKnownNever(fcPositive))
Known.knownNot(fcPositive);
else {
if (F && KnownSrc.isKnownNeverLogicalPosZero(*F, Op->getType()))
Known.knownNot(fcPosZero);
if (KnownSrc.isKnownNever(fcPosInf))
Known.knownNot(fcPosInf);
}
Known.propagateNaN(KnownSrc);
return;
}
default:
break;
}
}
}
computeKnownFPClass(Src, DemandedElts, InterestedClasses, Known, Depth + 1,
Q);
break;
}
case Instruction::PHI: {
const PHINode *P = cast<PHINode>(Op);
// Unreachable blocks may have zero-operand PHI nodes.
if (P->getNumIncomingValues() == 0)
break;
// Otherwise take the unions of the known bit sets of the operands,
// taking conservative care to avoid excessive recursion.
const unsigned PhiRecursionLimit = MaxAnalysisRecursionDepth - 2;
if (Depth < PhiRecursionLimit) {
// Skip if every incoming value references to ourself.
if (isa_and_nonnull<UndefValue>(P->hasConstantValue()))
break;
bool First = true;
for (const Use &U : P->operands()) {
Value *IncValue = U.get();
// Skip direct self references.
if (IncValue == P)
continue;
KnownFPClass KnownSrc;
// Recurse, but cap the recursion to two levels, because we don't want
// to waste time spinning around in loops. We need at least depth 2 to
// detect known sign bits.
computeKnownFPClass(
IncValue, DemandedElts, InterestedClasses, KnownSrc,
PhiRecursionLimit,
Q.getWithInstruction(P->getIncomingBlock(U)->getTerminator()));
if (First) {
Known = KnownSrc;
First = false;
} else {
Known |= KnownSrc;
}
if (Known.KnownFPClasses == fcAllFlags)
break;
}
}
break;
}
default:
break;
}
}
KnownFPClass llvm::computeKnownFPClass(const Value *V,
const APInt &DemandedElts,
FPClassTest InterestedClasses,
unsigned Depth,
const SimplifyQuery &SQ) {
KnownFPClass KnownClasses;
::computeKnownFPClass(V, DemandedElts, InterestedClasses, KnownClasses, Depth,
SQ);
return KnownClasses;
}
KnownFPClass llvm::computeKnownFPClass(const Value *V,
FPClassTest InterestedClasses,
unsigned Depth,
const SimplifyQuery &SQ) {
KnownFPClass Known;
::computeKnownFPClass(V, Known, InterestedClasses, Depth, SQ);
return Known;
}
Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
// All byte-wide stores are splatable, even of arbitrary variables.
if (V->getType()->isIntegerTy(8))
return V;
LLVMContext &Ctx = V->getContext();
// Undef don't care.
auto *UndefInt8 = UndefValue::get(Type::getInt8Ty(Ctx));
if (isa<UndefValue>(V))
return UndefInt8;
// Return Undef for zero-sized type.
if (DL.getTypeStoreSize(V->getType()).isZero())
return UndefInt8;
Constant *C = dyn_cast<Constant>(V);
if (!C) {
// Conceptually, we could handle things like:
// %a = zext i8 %X to i16
// %b = shl i16 %a, 8
// %c = or i16 %a, %b
// but until there is an example that actually needs this, it doesn't seem
// worth worrying about.
return nullptr;
}
// Handle 'null' ConstantArrayZero etc.
if (C->isNullValue())
return Constant::getNullValue(Type::getInt8Ty(Ctx));
// Constant floating-point values can be handled as integer values if the
// corresponding integer value is "byteable". An important case is 0.0.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
Type *Ty = nullptr;
if (CFP->getType()->isHalfTy())
Ty = Type::getInt16Ty(Ctx);
else if (CFP->getType()->isFloatTy())
Ty = Type::getInt32Ty(Ctx);
else if (CFP->getType()->isDoubleTy())
Ty = Type::getInt64Ty(Ctx);
// Don't handle long double formats, which have strange constraints.
return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
: nullptr;
}
// We can handle constant integers that are multiple of 8 bits.
if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
if (CI->getBitWidth() % 8 == 0) {
assert(CI->getBitWidth() > 8 && "8 bits should be handled above!");
if (!CI->getValue().isSplat(8))
return nullptr;
return ConstantInt::get(Ctx, CI->getValue().trunc(8));
}
}
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::IntToPtr) {
if (auto *PtrTy = dyn_cast<PointerType>(CE->getType())) {
unsigned BitWidth = DL.getPointerSizeInBits(PtrTy->getAddressSpace());
if (Constant *Op = ConstantFoldIntegerCast(
CE->getOperand(0), Type::getIntNTy(Ctx, BitWidth), false, DL))
return isBytewiseValue(Op, DL);
}
}
}
auto Merge = [&](Value *LHS, Value *RHS) -> Value * {
if (LHS == RHS)
return LHS;
if (!LHS || !RHS)
return nullptr;
if (LHS == UndefInt8)
return RHS;
if (RHS == UndefInt8)
return LHS;
return nullptr;
};
if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
Value *Val = UndefInt8;
for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I), DL))))
return nullptr;
return Val;
}
if (isa<ConstantAggregate>(C)) {
Value *Val = UndefInt8;
for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I), DL))))
return nullptr;
return Val;
}
// Don't try to handle the handful of other constants.
return nullptr;
}
// This is the recursive version of BuildSubAggregate. It takes a few different
// arguments. Idxs is the index within the nested struct From that we are
// looking at now (which is of type IndexedType). IdxSkip is the number of
// indices from Idxs that should be left out when inserting into the resulting
// struct. To is the result struct built so far, new insertvalue instructions
// build on that.
static Value *BuildSubAggregate(Value *From, Value *To, Type *IndexedType,
SmallVectorImpl<unsigned> &Idxs,
unsigned IdxSkip,
BasicBlock::iterator InsertBefore) {
StructType *STy = dyn_cast<StructType>(IndexedType);
if (STy) {
// Save the original To argument so we can modify it
Value *OrigTo = To;
// General case, the type indexed by Idxs is a struct
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
// Process each struct element recursively
Idxs.push_back(i);
Value *PrevTo = To;
To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
InsertBefore);
Idxs.pop_back();
if (!To) {
// Couldn't find any inserted value for this index? Cleanup
while (PrevTo != OrigTo) {
InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
PrevTo = Del->getAggregateOperand();
Del->eraseFromParent();
}
// Stop processing elements
break;
}
}
// If we successfully found a value for each of our subaggregates
if (To)
return To;
}
// Base case, the type indexed by SourceIdxs is not a struct, or not all of
// the struct's elements had a value that was inserted directly. In the latter
// case, perhaps we can't determine each of the subelements individually, but
// we might be able to find the complete struct somewhere.
// Find the value that is at that particular spot
Value *V = FindInsertedValue(From, Idxs);
if (!V)
return nullptr;
// Insert the value in the new (sub) aggregate
return InsertValueInst::Create(To, V, ArrayRef(Idxs).slice(IdxSkip), "tmp",
InsertBefore);
}
// This helper takes a nested struct and extracts a part of it (which is again a
// struct) into a new value. For example, given the struct:
// { a, { b, { c, d }, e } }
// and the indices "1, 1" this returns
// { c, d }.
//
// It does this by inserting an insertvalue for each element in the resulting
// struct, as opposed to just inserting a single struct. This will only work if
// each of the elements of the substruct are known (ie, inserted into From by an
// insertvalue instruction somewhere).
//
// All inserted insertvalue instructions are inserted before InsertBefore
static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range,
BasicBlock::iterator InsertBefore) {
Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
idx_range);
Value *To = PoisonValue::get(IndexedType);
SmallVector<unsigned, 10> Idxs(idx_range.begin(), idx_range.end());
unsigned IdxSkip = Idxs.size();
return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
}
/// Given an aggregate and a sequence of indices, see if the scalar value
/// indexed is already around as a register, for example if it was inserted
/// directly into the aggregate.
///
/// If InsertBefore is not null, this function will duplicate (modified)
/// insertvalues when a part of a nested struct is extracted.
Value *
llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
std::optional<BasicBlock::iterator> InsertBefore) {
// Nothing to index? Just return V then (this is useful at the end of our
// recursion).
if (idx_range.empty())
return V;
// We have indices, so V should have an indexable type.
assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&
"Not looking at a struct or array?");
assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&
"Invalid indices for type?");
if (Constant *C = dyn_cast<Constant>(V)) {
C = C->getAggregateElement(idx_range[0]);
if (!C) return nullptr;
return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
}
if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
// Loop the indices for the insertvalue instruction in parallel with the
// requested indices
const unsigned *req_idx = idx_range.begin();
for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
i != e; ++i, ++req_idx) {
if (req_idx == idx_range.end()) {
// We can't handle this without inserting insertvalues
if (!InsertBefore)
return nullptr;
// The requested index identifies a part of a nested aggregate. Handle
// this specially. For example,
// %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
// %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
// %C = extractvalue {i32, { i32, i32 } } %B, 1
// This can be changed into
// %A = insertvalue {i32, i32 } undef, i32 10, 0
// %C = insertvalue {i32, i32 } %A, i32 11, 1
// which allows the unused 0,0 element from the nested struct to be
// removed.
return BuildSubAggregate(V, ArrayRef(idx_range.begin(), req_idx),
*InsertBefore);
}
// This insert value inserts something else than what we are looking for.
// See if the (aggregate) value inserted into has the value we are
// looking for, then.
if (*req_idx != *i)
return FindInsertedValue(I->getAggregateOperand(), idx_range,
InsertBefore);
}
// If we end up here, the indices of the insertvalue match with those
// requested (though possibly only partially). Now we recursively look at
// the inserted value, passing any remaining indices.
return FindInsertedValue(I->getInsertedValueOperand(),
ArrayRef(req_idx, idx_range.end()), InsertBefore);
}
if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
// If we're extracting a value from an aggregate that was extracted from
// something else, we can extract from that something else directly instead.
// However, we will need to chain I's indices with the requested indices.
// Calculate the number of indices required
unsigned size = I->getNumIndices() + idx_range.size();
// Allocate some space to put the new indices in
SmallVector<unsigned, 5> Idxs;
Idxs.reserve(size);
// Add indices from the extract value instruction
Idxs.append(I->idx_begin(), I->idx_end());
// Add requested indices
Idxs.append(idx_range.begin(), idx_range.end());
assert(Idxs.size() == size
&& "Number of indices added not correct?");
return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
}
// Otherwise, we don't know (such as, extracting from a function return value
// or load instruction)
return nullptr;
}
bool llvm::isGEPBasedOnPointerToString(const GEPOperator *GEP,
unsigned CharSize) {
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
// Make sure the index-ee is a pointer to array of \p CharSize integers.
// CharSize.
ArrayType *AT = dyn_cast<ArrayType>(GEP->getSourceElementType());
if (!AT || !AT->getElementType()->isIntegerTy(CharSize))
return false;
// Check to make sure that the first operand of the GEP is an integer and
// has value 0 so that we are sure we're indexing into the initializer.
const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
if (!FirstIdx || !FirstIdx->isZero())
return false;
return true;
}
// If V refers to an initialized global constant, set Slice either to
// its initializer if the size of its elements equals ElementSize, or,
// for ElementSize == 8, to its representation as an array of unsiged
// char. Return true on success.
// Offset is in the unit "nr of ElementSize sized elements".
bool llvm::getConstantDataArrayInfo(const Value *V,
ConstantDataArraySlice &Slice,
unsigned ElementSize, uint64_t Offset) {
assert(V && "V should not be null.");
assert((ElementSize % 8) == 0 &&
"ElementSize expected to be a multiple of the size of a byte.");
unsigned ElementSizeInBytes = ElementSize / 8;
// Drill down into the pointer expression V, ignoring any intervening
// casts, and determine the identity of the object it references along
// with the cumulative byte offset into it.
const GlobalVariable *GV =
dyn_cast<GlobalVariable>(getUnderlyingObject(V));
if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
// Fail if V is not based on constant global object.
return false;
const DataLayout &DL = GV->getParent()->getDataLayout();
APInt Off(DL.getIndexTypeSizeInBits(V->getType()), 0);
if (GV != V->stripAndAccumulateConstantOffsets(DL, Off,
/*AllowNonInbounds*/ true))
// Fail if a constant offset could not be determined.
return false;
uint64_t StartIdx = Off.getLimitedValue();
if (StartIdx == UINT64_MAX)
// Fail if the constant offset is excessive.
return false;
// Off/StartIdx is in the unit of bytes. So we need to convert to number of
// elements. Simply bail out if that isn't possible.
if ((StartIdx % ElementSizeInBytes) != 0)
return false;
Offset += StartIdx / ElementSizeInBytes;
ConstantDataArray *Array = nullptr;
ArrayType *ArrayTy = nullptr;
if (GV->getInitializer()->isNullValue()) {
Type *GVTy = GV->getValueType();
uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy).getFixedValue();
uint64_t Length = SizeInBytes / ElementSizeInBytes;
Slice.Array = nullptr;
Slice.Offset = 0;
// Return an empty Slice for undersized constants to let callers
// transform even undefined library calls into simpler, well-defined
// expressions. This is preferable to making the calls although it
// prevents sanitizers from detecting such calls.
Slice.Length = Length < Offset ? 0 : Length - Offset;
return true;
}
auto *Init = const_cast<Constant *>(GV->getInitializer());
if (auto *ArrayInit = dyn_cast<ConstantDataArray>(Init)) {
Type *InitElTy = ArrayInit->getElementType();
if (InitElTy->isIntegerTy(ElementSize)) {
// If Init is an initializer for an array of the expected type
// and size, use it as is.
Array = ArrayInit;
ArrayTy = ArrayInit->getType();
}
}
if (!Array) {
if (ElementSize != 8)
// TODO: Handle conversions to larger integral types.
return false;
// Otherwise extract the portion of the initializer starting
// at Offset as an array of bytes, and reset Offset.
Init = ReadByteArrayFromGlobal(GV, Offset);
if (!Init)
return false;
Offset = 0;
Array = dyn_cast<ConstantDataArray>(Init);
ArrayTy = dyn_cast<ArrayType>(Init->getType());
}
uint64_t NumElts = ArrayTy->getArrayNumElements();
if (Offset > NumElts)
return false;
Slice.Array = Array;
Slice.Offset = Offset;
Slice.Length = NumElts - Offset;
return true;
}
/// Extract bytes from the initializer of the constant array V, which need
/// not be a nul-terminated string. On success, store the bytes in Str and
/// return true. When TrimAtNul is set, Str will contain only the bytes up
/// to but not including the first nul. Return false on failure.
bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
bool TrimAtNul) {
ConstantDataArraySlice Slice;
if (!getConstantDataArrayInfo(V, Slice, 8))
return false;
if (Slice.Array == nullptr) {
if (TrimAtNul) {
// Return a nul-terminated string even for an empty Slice. This is
// safe because all existing SimplifyLibcalls callers require string
// arguments and the behavior of the functions they fold is undefined
// otherwise. Folding the calls this way is preferable to making
// the undefined library calls, even though it prevents sanitizers
// from reporting such calls.
Str = StringRef();
return true;
}
if (Slice.Length == 1) {
Str = StringRef("", 1);
return true;
}
// We cannot instantiate a StringRef as we do not have an appropriate string
// of 0s at hand.
return false;
}
// Start out with the entire array in the StringRef.
Str = Slice.Array->getAsString();
// Skip over 'offset' bytes.
Str = Str.substr(Slice.Offset);
if (TrimAtNul) {
// Trim off the \0 and anything after it. If the array is not nul
// terminated, we just return the whole end of string. The client may know
// some other way that the string is length-bound.
Str = Str.substr(0, Str.find('\0'));
}
return true;
}
// These next two are very similar to the above, but also look through PHI
// nodes.
// TODO: See if we can integrate these two together.
/// If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
static uint64_t GetStringLengthH(const Value *V,
SmallPtrSetImpl<const PHINode*> &PHIs,
unsigned CharSize) {
// Look through noop bitcast instructions.
V = V->stripPointerCasts();
// If this is a PHI node, there are two cases: either we have already seen it
// or we haven't.
if (const PHINode *PN = dyn_cast<PHINode>(V)) {
if (!PHIs.insert(PN).second)
return ~0ULL; // already in the set.
// If it was new, see if all the input strings are the same length.
uint64_t LenSoFar = ~0ULL;
for (Value *IncValue : PN->incoming_values()) {
uint64_t Len = GetStringLengthH(IncValue, PHIs, CharSize);
if (Len == 0) return 0; // Unknown length -> unknown.
if (Len == ~0ULL) continue;
if (Len != LenSoFar && LenSoFar != ~0ULL)
return 0; // Disagree -> unknown.
LenSoFar = Len;
}
// Success, all agree.
return LenSoFar;
}
// strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs, CharSize);
if (Len1 == 0) return 0;
uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs, CharSize);
if (Len2 == 0) return 0;
if (Len1 == ~0ULL) return Len2;
if (Len2 == ~0ULL) return Len1;
if (Len1 != Len2) return 0;
return Len1;
}
// Otherwise, see if we can read the string.
ConstantDataArraySlice Slice;
if (!getConstantDataArrayInfo(V, Slice, CharSize))
return 0;
if (Slice.Array == nullptr)
// Zeroinitializer (including an empty one).
return 1;
// Search for the first nul character. Return a conservative result even
// when there is no nul. This is safe since otherwise the string function
// being folded such as strlen is undefined, and can be preferable to
// making the undefined library call.
unsigned NullIndex = 0;
for (unsigned E = Slice.Length; NullIndex < E; ++NullIndex) {
if (Slice.Array->getElementAsInteger(Slice.Offset + NullIndex) == 0)
break;
}
return NullIndex + 1;
}
/// If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
uint64_t llvm::GetStringLength(const Value *V, unsigned CharSize) {
if (!V->getType()->isPointerTy())
return 0;
SmallPtrSet<const PHINode*, 32> PHIs;
uint64_t Len = GetStringLengthH(V, PHIs, CharSize);
// If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
// an empty string as a length.
return Len == ~0ULL ? 1 : Len;
}
const Value *
llvm::getArgumentAliasingToReturnedPointer(const CallBase *Call,
bool MustPreserveNullness) {
assert(Call &&
"getArgumentAliasingToReturnedPointer only works on nonnull calls");
if (const Value *RV = Call->getReturnedArgOperand())
return RV;
// This can be used only as a aliasing property.
if (isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
Call, MustPreserveNullness))
return Call->getArgOperand(0);
return nullptr;
}
bool llvm::isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
const CallBase *Call, bool MustPreserveNullness) {
switch (Call->getIntrinsicID()) {
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
case Intrinsic::aarch64_irg:
case Intrinsic::aarch64_tagp:
// The amdgcn_make_buffer_rsrc function does not alter the address of the
// input pointer (and thus preserve null-ness for the purposes of escape
// analysis, which is where the MustPreserveNullness flag comes in to play).
// However, it will not necessarily map ptr addrspace(N) null to ptr
// addrspace(8) null, aka the "null descriptor", which has "all loads return
// 0, all stores are dropped" semantics. Given the context of this intrinsic
// list, no one should be relying on such a strict interpretation of
// MustPreserveNullness (and, at time of writing, they are not), but we
// document this fact out of an abundance of caution.
case Intrinsic::amdgcn_make_buffer_rsrc:
return true;
case Intrinsic::ptrmask:
return !MustPreserveNullness;
default:
return false;
}
}
/// \p PN defines a loop-variant pointer to an object. Check if the
/// previous iteration of the loop was referring to the same object as \p PN.
static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
const LoopInfo *LI) {
// Find the loop-defined value.
Loop *L = LI->getLoopFor(PN->getParent());
if (PN->getNumIncomingValues() != 2)
return true;
// Find the value from previous iteration.
auto *PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(0));
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(1));
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
return true;
// If a new pointer is loaded in the loop, the pointer references a different
// object in every iteration. E.g.:
// for (i)
// int *p = a[i];
// ...
if (auto *Load = dyn_cast<LoadInst>(PrevValue))
if (!L->isLoopInvariant(Load->getPointerOperand()))
return false;
return true;
}
const Value *llvm::getUnderlyingObject(const Value *V, unsigned MaxLookup) {
if (!V->getType()->isPointerTy())
return V;
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
if (auto *GEP = dyn_cast<GEPOperator>(V)) {
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast ||
Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
V = cast<Operator>(V)->getOperand(0);
if (!V->getType()->isPointerTy())
return V;
} else if (auto *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->isInterposable())
return V;
V = GA->getAliasee();
} else {
if (auto *PHI = dyn_cast<PHINode>(V)) {
// Look through single-arg phi nodes created by LCSSA.
if (PHI->getNumIncomingValues() == 1) {
V = PHI->getIncomingValue(0);
continue;
}
} else if (auto *Call = dyn_cast<CallBase>(V)) {
// CaptureTracking can know about special capturing properties of some
// intrinsics like launder.invariant.group, that can't be expressed with
// the attributes, but have properties like returning aliasing pointer.
// Because some analysis may assume that nocaptured pointer is not
// returned from some special intrinsic (because function would have to
// be marked with returns attribute), it is crucial to use this function
// because it should be in sync with CaptureTracking. Not using it may
// cause weird miscompilations where 2 aliasing pointers are assumed to
// noalias.
if (auto *RP = getArgumentAliasingToReturnedPointer(Call, false)) {
V = RP;
continue;
}
}
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
}
return V;
}
void llvm::getUnderlyingObjects(const Value *V,
SmallVectorImpl<const Value *> &Objects,
LoopInfo *LI, unsigned MaxLookup) {
SmallPtrSet<const Value *, 4> Visited;
SmallVector<const Value *, 4> Worklist;
Worklist.push_back(V);
do {
const Value *P = Worklist.pop_back_val();
P = getUnderlyingObject(P, MaxLookup);
if (!Visited.insert(P).second)
continue;
if (auto *SI = dyn_cast<SelectInst>(P)) {
Worklist.push_back(SI->getTrueValue());
Worklist.push_back(SI->getFalseValue());
continue;
}
if (auto *PN = dyn_cast<PHINode>(P)) {
// If this PHI changes the underlying object in every iteration of the
// loop, don't look through it. Consider:
// int **A;
// for (i) {
// Prev = Curr; // Prev = PHI (Prev_0, Curr)
// Curr = A[i];
// *Prev, *Curr;
//
// Prev is tracking Curr one iteration behind so they refer to different
// underlying objects.
if (!LI || !LI->isLoopHeader(PN->getParent()) ||
isSameUnderlyingObjectInLoop(PN, LI))
append_range(Worklist, PN->incoming_values());
else
Objects.push_back(P);
continue;
}
Objects.push_back(P);
} while (!Worklist.empty());
}
/// This is the function that does the work of looking through basic
/// ptrtoint+arithmetic+inttoptr sequences.
static const Value *getUnderlyingObjectFromInt(const Value *V) {
do {
if (const Operator *U = dyn_cast<Operator>(V)) {
// If we find a ptrtoint, we can transfer control back to the
// regular getUnderlyingObjectFromInt.
if (U->getOpcode() == Instruction::PtrToInt)
return U->getOperand(0);
// If we find an add of a constant, a multiplied value, or a phi, it's
// likely that the other operand will lead us to the base
// object. We don't have to worry about the case where the
// object address is somehow being computed by the multiply,
// because our callers only care when the result is an
// identifiable object.
if (U->getOpcode() != Instruction::Add ||
(!isa<ConstantInt>(U->getOperand(1)) &&
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
!isa<PHINode>(U->getOperand(1))))
return V;
V = U->getOperand(0);
} else {
return V;
}
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
} while (true);
}
/// This is a wrapper around getUnderlyingObjects and adds support for basic
/// ptrtoint+arithmetic+inttoptr sequences.
/// It returns false if unidentified object is found in getUnderlyingObjects.
bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
SmallVectorImpl<Value *> &Objects) {
SmallPtrSet<const Value *, 16> Visited;
SmallVector<const Value *, 4> Working(1, V);
do {
V = Working.pop_back_val();
SmallVector<const Value *, 4> Objs;
getUnderlyingObjects(V, Objs);
for (const Value *V : Objs) {
if (!Visited.insert(V).second)
continue;
if (Operator::getOpcode(V) == Instruction::IntToPtr) {
const Value *O =
getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
if (O->getType()->isPointerTy()) {
Working.push_back(O);
continue;
}
}
// If getUnderlyingObjects fails to find an identifiable object,
// getUnderlyingObjectsForCodeGen also fails for safety.
if (!isIdentifiedObject(V)) {
Objects.clear();
return false;
}
Objects.push_back(const_cast<Value *>(V));
}
} while (!Working.empty());
return true;
}
AllocaInst *llvm::findAllocaForValue(Value *V, bool OffsetZero) {
AllocaInst *Result = nullptr;
SmallPtrSet<Value *, 4> Visited;
SmallVector<Value *, 4> Worklist;
auto AddWork = [&](Value *V) {
if (Visited.insert(V).second)
Worklist.push_back(V);
};
AddWork(V);
do {
V = Worklist.pop_back_val();
assert(Visited.count(V));
if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
if (Result && Result != AI)
return nullptr;
Result = AI;
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
AddWork(CI->getOperand(0));
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
for (Value *IncValue : PN->incoming_values())
AddWork(IncValue);
} else if (auto *SI = dyn_cast<SelectInst>(V)) {
AddWork(SI->getTrueValue());
AddWork(SI->getFalseValue());
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
if (OffsetZero && !GEP->hasAllZeroIndices())
return nullptr;
AddWork(GEP->getPointerOperand());
} else if (CallBase *CB = dyn_cast<CallBase>(V)) {
Value *Returned = CB->getReturnedArgOperand();
if (Returned)
AddWork(Returned);
else
return nullptr;
} else {
return nullptr;
}
} while (!Worklist.empty());
return Result;
}
static bool onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
const Value *V, bool AllowLifetime, bool AllowDroppable) {
for (const User *U : V->users()) {
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
if (!II)
return false;
if (AllowLifetime && II->isLifetimeStartOrEnd())
continue;
if (AllowDroppable && II->isDroppable())
continue;
return false;
}
return true;
}
bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
V, /* AllowLifetime */ true, /* AllowDroppable */ false);
}
bool llvm::onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V) {
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
V, /* AllowLifetime */ true, /* AllowDroppable */ true);
}
bool llvm::mustSuppressSpeculation(const LoadInst &LI) {
if (!LI.isUnordered())
return true;
const Function &F = *LI.getFunction();
// Speculative load may create a race that did not exist in the source.
return F.hasFnAttribute(Attribute::SanitizeThread) ||
// Speculative load may load data from dirty regions.
F.hasFnAttribute(Attribute::SanitizeAddress) ||
F.hasFnAttribute(Attribute::SanitizeHWAddress);
}
bool llvm::isSafeToSpeculativelyExecute(const Instruction *Inst,
const Instruction *CtxI,
AssumptionCache *AC,
const DominatorTree *DT,
const TargetLibraryInfo *TLI) {
return isSafeToSpeculativelyExecuteWithOpcode(Inst->getOpcode(), Inst, CtxI,
AC, DT, TLI);
}
bool llvm::isSafeToSpeculativelyExecuteWithOpcode(
unsigned Opcode, const Instruction *Inst, const Instruction *CtxI,
AssumptionCache *AC, const DominatorTree *DT,
const TargetLibraryInfo *TLI) {
#ifndef NDEBUG
if (Inst->getOpcode() != Opcode) {
// Check that the operands are actually compatible with the Opcode override.
auto hasEqualReturnAndLeadingOperandTypes =
[](const Instruction *Inst, unsigned NumLeadingOperands) {
if (Inst->getNumOperands() < NumLeadingOperands)
return false;
const Type *ExpectedType = Inst->getType();
for (unsigned ItOp = 0; ItOp < NumLeadingOperands; ++ItOp)
if (Inst->getOperand(ItOp)->getType() != ExpectedType)
return false;
return true;
};
assert(!Instruction::isBinaryOp(Opcode) ||
hasEqualReturnAndLeadingOperandTypes(Inst, 2));
assert(!Instruction::isUnaryOp(Opcode) ||
hasEqualReturnAndLeadingOperandTypes(Inst, 1));
}
#endif
switch (Opcode) {
default:
return true;
case Instruction::UDiv:
case Instruction::URem: {
// x / y is undefined if y == 0.
const APInt *V;
if (match(Inst->getOperand(1), m_APInt(V)))
return *V != 0;
return false;
}
case Instruction::SDiv:
case Instruction::SRem: {
// x / y is undefined if y == 0 or x == INT_MIN and y == -1
const APInt *Numerator, *Denominator;
if (!match(Inst->getOperand(1), m_APInt(Denominator)))
return false;
// We cannot hoist this division if the denominator is 0.
if (*Denominator == 0)
return false;
// It's safe to hoist if the denominator is not 0 or -1.
if (!Denominator->isAllOnes())
return true;
// At this point we know that the denominator is -1. It is safe to hoist as
// long we know that the numerator is not INT_MIN.
if (match(Inst->getOperand(0), m_APInt(Numerator)))
return !Numerator->isMinSignedValue();
// The numerator *might* be MinSignedValue.
return false;
}
case Instruction::Load: {
const LoadInst *LI = dyn_cast<LoadInst>(Inst);
if (!LI)
return false;
if (mustSuppressSpeculation(*LI))
return false;
const DataLayout &DL = LI->getModule()->getDataLayout();
return isDereferenceableAndAlignedPointer(LI->getPointerOperand(),
LI->getType(), LI->getAlign(), DL,
CtxI, AC, DT, TLI);
}
case Instruction::Call: {
auto *CI = dyn_cast<const CallInst>(Inst);
if (!CI)
return false;
const Function *Callee = CI->getCalledFunction();
// The called function could have undefined behavior or side-effects, even
// if marked readnone nounwind.
return Callee && Callee->isSpeculatable();
}
case Instruction::VAArg:
case Instruction::Alloca:
case Instruction::Invoke:
case Instruction::CallBr:
case Instruction::PHI:
case Instruction::Store:
case Instruction::Ret:
case Instruction::Br:
case Instruction::IndirectBr:
case Instruction::Switch:
case Instruction::Unreachable:
case Instruction::Fence:
case Instruction::AtomicRMW:
case Instruction::AtomicCmpXchg:
case Instruction::LandingPad:
case Instruction::Resume:
case Instruction::CatchSwitch:
case Instruction::CatchPad:
case Instruction::CatchRet:
case Instruction::CleanupPad:
case Instruction::CleanupRet:
return false; // Misc instructions which have effects
}
}
bool llvm::mayHaveNonDefUseDependency(const Instruction &I) {
if (I.mayReadOrWriteMemory())
// Memory dependency possible
return true;
if (!isSafeToSpeculativelyExecute(&I))
// Can't move above a maythrow call or infinite loop. Or if an
// inalloca alloca, above a stacksave call.
return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
// 1) Can't reorder two inf-loop calls, even if readonly
// 2) Also can't reorder an inf-loop call below a instruction which isn't
// safe to speculative execute. (Inverse of above)
return true;
return false;
}
/// Convert ConstantRange OverflowResult into ValueTracking OverflowResult.
static OverflowResult mapOverflowResult(ConstantRange::OverflowResult OR) {
switch (OR) {
case ConstantRange::OverflowResult::MayOverflow:
return OverflowResult::MayOverflow;
case ConstantRange::OverflowResult::AlwaysOverflowsLow:
return OverflowResult::AlwaysOverflowsLow;
case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
return OverflowResult::AlwaysOverflowsHigh;
case ConstantRange::OverflowResult::NeverOverflows:
return OverflowResult::NeverOverflows;
}
llvm_unreachable("Unknown OverflowResult");
}
/// Combine constant ranges from computeConstantRange() and computeKnownBits().
ConstantRange
llvm::computeConstantRangeIncludingKnownBits(const WithCache<const Value *> &V,
bool ForSigned,
const SimplifyQuery &SQ) {
ConstantRange CR1 =
ConstantRange::fromKnownBits(V.getKnownBits(SQ), ForSigned);
ConstantRange CR2 = computeConstantRange(V, ForSigned, SQ.IIQ.UseInstrInfo);
ConstantRange::PreferredRangeType RangeType =
ForSigned ? ConstantRange::Signed : ConstantRange::Unsigned;
return CR1.intersectWith(CR2, RangeType);
}
OverflowResult llvm::computeOverflowForUnsignedMul(const Value *LHS,
const Value *RHS,
const SimplifyQuery &SQ) {
KnownBits LHSKnown = computeKnownBits(LHS, /*Depth=*/0, SQ);
KnownBits RHSKnown = computeKnownBits(RHS, /*Depth=*/0, SQ);
ConstantRange LHSRange = ConstantRange::fromKnownBits(LHSKnown, false);
ConstantRange RHSRange = ConstantRange::fromKnownBits(RHSKnown, false);
return mapOverflowResult(LHSRange.unsignedMulMayOverflow(RHSRange));
}
OverflowResult llvm::computeOverflowForSignedMul(const Value *LHS,
const Value *RHS,
const SimplifyQuery &SQ) {
// Multiplying n * m significant bits yields a result of n + m significant
// bits. If the total number of significant bits does not exceed the
// result bit width (minus 1), there is no overflow.
// This means if we have enough leading sign bits in the operands
// we can guarantee that the result does not overflow.
// Ref: "Hacker's Delight" by Henry Warren
unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
// Note that underestimating the number of sign bits gives a more
// conservative answer.
unsigned SignBits =
::ComputeNumSignBits(LHS, 0, SQ) + ::ComputeNumSignBits(RHS, 0, SQ);
// First handle the easy case: if we have enough sign bits there's
// definitely no overflow.
if (SignBits > BitWidth + 1)
return OverflowResult::NeverOverflows;
// There are two ambiguous cases where there can be no overflow:
// SignBits == BitWidth + 1 and
// SignBits == BitWidth
// The second case is difficult to check, therefore we only handle the
// first case.
if (SignBits == BitWidth + 1) {
// It overflows only when both arguments are negative and the true
// product is exactly the minimum negative number.
// E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
// For simplicity we just check if at least one side is not negative.
KnownBits LHSKnown = computeKnownBits(LHS, /*Depth=*/0, SQ);
KnownBits RHSKnown = computeKnownBits(RHS, /*Depth=*/0, SQ);
if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
return OverflowResult::NeverOverflows;
}
return OverflowResult::MayOverflow;
}
OverflowResult
llvm::computeOverflowForUnsignedAdd(const WithCache<const Value *> &LHS,
const WithCache<const Value *> &RHS,
const SimplifyQuery &SQ) {
ConstantRange LHSRange =
computeConstantRangeIncludingKnownBits(LHS, /*ForSigned=*/false, SQ);
ConstantRange RHSRange =
computeConstantRangeIncludingKnownBits(RHS, /*ForSigned=*/false, SQ);
return mapOverflowResult(LHSRange.unsignedAddMayOverflow(RHSRange));
}
static OverflowResult
computeOverflowForSignedAdd(const WithCache<const Value *> &LHS,
const WithCache<const Value *> &RHS,
const AddOperator *Add, const SimplifyQuery &SQ) {
if (Add && Add->hasNoSignedWrap()) {
return OverflowResult::NeverOverflows;
}
// If LHS and RHS each have at least two sign bits, the addition will look
// like
//
// XX..... +
// YY.....
//
// If the carry into the most significant position is 0, X and Y can't both
// be 1 and therefore the carry out of the addition is also 0.
//
// If the carry into the most significant position is 1, X and Y can't both
// be 0 and therefore the carry out of the addition is also 1.
//
// Since the carry into the most significant position is always equal to
// the carry out of the addition, there is no signed overflow.
if (::ComputeNumSignBits(LHS, 0, SQ) > 1 &&
::ComputeNumSignBits(RHS, 0, SQ) > 1)
return OverflowResult::NeverOverflows;
ConstantRange LHSRange =
computeConstantRangeIncludingKnownBits(LHS, /*ForSigned=*/true, SQ);
ConstantRange RHSRange =
computeConstantRangeIncludingKnownBits(RHS, /*ForSigned=*/true, SQ);
OverflowResult OR =
mapOverflowResult(LHSRange.signedAddMayOverflow(RHSRange));
if (OR != OverflowResult::MayOverflow)
return OR;
// The remaining code needs Add to be available. Early returns if not so.
if (!Add)
return OverflowResult::MayOverflow;
// If the sign of Add is the same as at least one of the operands, this add
// CANNOT overflow. If this can be determined from the known bits of the
// operands the above signedAddMayOverflow() check will have already done so.
// The only other way to improve on the known bits is from an assumption, so
// call computeKnownBitsFromContext() directly.
bool LHSOrRHSKnownNonNegative =
(LHSRange.isAllNonNegative() || RHSRange.isAllNonNegative());
bool LHSOrRHSKnownNegative =
(LHSRange.isAllNegative() || RHSRange.isAllNegative());
if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) {
KnownBits AddKnown(LHSRange.getBitWidth());
computeKnownBitsFromContext(Add, AddKnown, /*Depth=*/0, SQ);
if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) ||
(AddKnown.isNegative() && LHSOrRHSKnownNegative))
return OverflowResult::NeverOverflows;
}
return OverflowResult::MayOverflow;
}
OverflowResult llvm::computeOverflowForUnsignedSub(const Value *LHS,
const Value *RHS,
const SimplifyQuery &SQ) {
// X - (X % ?)
// The remainder of a value can't have greater magnitude than itself,
// so the subtraction can't overflow.
// X - (X -nuw ?)
// In the minimal case, this would simplify to "?", so there's no subtract
// at all. But if this analysis is used to peek through casts, for example,
// then determining no-overflow may allow other transforms.
// TODO: There are other patterns like this.
// See simplifyICmpWithBinOpOnLHS() for candidates.
if (match(RHS, m_URem(m_Specific(LHS), m_Value())) ||
match(RHS, m_NUWSub(m_Specific(LHS), m_Value())))
if (isGuaranteedNotToBeUndef(LHS, SQ.AC, SQ.CxtI, SQ.DT))
return OverflowResult::NeverOverflows;
// Checking for conditions implied by dominating conditions may be expensive.
// Limit it to usub_with_overflow calls for now.
if (match(SQ.CxtI,
m_Intrinsic<Intrinsic::usub_with_overflow>(m_Value(), m_Value())))
if (auto C = isImpliedByDomCondition(CmpInst::ICMP_UGE, LHS, RHS, SQ.CxtI,
SQ.DL)) {
if (*C)
return OverflowResult::NeverOverflows;
return OverflowResult::AlwaysOverflowsLow;
}
ConstantRange LHSRange =
computeConstantRangeIncludingKnownBits(LHS, /*ForSigned=*/false, SQ);
ConstantRange RHSRange =
computeConstantRangeIncludingKnownBits(RHS, /*ForSigned=*/false, SQ);
return mapOverflowResult(LHSRange.unsignedSubMayOverflow(RHSRange));
}
OverflowResult llvm::computeOverflowForSignedSub(const Value *LHS,
const Value *RHS,
const SimplifyQuery &SQ) {
// X - (X % ?)
// The remainder of a value can't have greater magnitude than itself,
// so the subtraction can't overflow.
// X - (X -nsw ?)
// In the minimal case, this would simplify to "?", so there's no subtract
// at all. But if this analysis is used to peek through casts, for example,
// then determining no-overflow may allow other transforms.
if (match(RHS, m_SRem(m_Specific(LHS), m_Value())) ||
match(RHS, m_NSWSub(m_Specific(LHS), m_Value())))
if (isGuaranteedNotToBeUndef(LHS, SQ.AC, SQ.CxtI, SQ.DT))
return OverflowResult::NeverOverflows;
// If LHS and RHS each have at least two sign bits, the subtraction
// cannot overflow.
if (::ComputeNumSignBits(LHS, 0, SQ) > 1 &&
::ComputeNumSignBits(RHS, 0, SQ) > 1)
return OverflowResult::NeverOverflows;
ConstantRange LHSRange =
computeConstantRangeIncludingKnownBits(LHS, /*ForSigned=*/true, SQ);
ConstantRange RHSRange =
computeConstantRangeIncludingKnownBits(RHS, /*ForSigned=*/true, SQ);
return mapOverflowResult(LHSRange.signedSubMayOverflow(RHSRange));
}
bool llvm::isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
const DominatorTree &DT) {
SmallVector<const BranchInst *, 2> GuardingBranches;
SmallVector<const ExtractValueInst *, 2> Results;
for (const User *U : WO->users()) {
if (const auto *EVI = dyn_cast<ExtractValueInst>(U)) {
assert(EVI->getNumIndices() == 1 && "Obvious from CI's type");
if (EVI->getIndices()[0] == 0)
Results.push_back(EVI);
else {
assert(EVI->getIndices()[0] == 1 && "Obvious from CI's type");
for (const auto *U : EVI->users())
if (const auto *B = dyn_cast<BranchInst>(U)) {
assert(B->isConditional() && "How else is it using an i1?");
GuardingBranches.push_back(B);
}
}
} else {
// We are using the aggregate directly in a way we don't want to analyze
// here (storing it to a global, say).
return false;
}
}
auto AllUsesGuardedByBranch = [&](const BranchInst *BI) {
BasicBlockEdge NoWrapEdge(BI->getParent(), BI->getSuccessor(1));
if (!NoWrapEdge.isSingleEdge())
return false;
// Check if all users of the add are provably no-wrap.
for (const auto *Result : Results) {
// If the extractvalue itself is not executed on overflow, the we don't
// need to check each use separately, since domination is transitive.
if (DT.dominates(NoWrapEdge, Result->getParent()))
continue;
for (const auto &RU : Result->uses())
if (!DT.dominates(NoWrapEdge, RU))
return false;
}
return true;
};
return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
}
/// Shifts return poison if shiftwidth is larger than the bitwidth.
static bool shiftAmountKnownInRange(const Value *ShiftAmount) {
auto *C = dyn_cast<Constant>(ShiftAmount);
if (!C)
return false;
// Shifts return poison if shiftwidth is larger than the bitwidth.
SmallVector<const Constant *, 4> ShiftAmounts;
if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
unsigned NumElts = FVTy->getNumElements();
for (unsigned i = 0; i < NumElts; ++i)
ShiftAmounts.push_back(C->getAggregateElement(i));
} else if (isa<ScalableVectorType>(C->getType()))
return false; // Can't tell, just return false to be safe
else
ShiftAmounts.push_back(C);
bool Safe = llvm::all_of(ShiftAmounts, [](const Constant *C) {
auto *CI = dyn_cast_or_null<ConstantInt>(C);
return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
});
return Safe;
}
enum class UndefPoisonKind {
PoisonOnly = (1 << 0),
UndefOnly = (1 << 1),
UndefOrPoison = PoisonOnly | UndefOnly,
};
static bool includesPoison(UndefPoisonKind Kind) {
return (unsigned(Kind) & unsigned(UndefPoisonKind::PoisonOnly)) != 0;
}
static bool includesUndef(UndefPoisonKind Kind) {
return (unsigned(Kind) & unsigned(UndefPoisonKind::UndefOnly)) != 0;
}
static bool canCreateUndefOrPoison(const Operator *Op, UndefPoisonKind Kind,
bool ConsiderFlagsAndMetadata) {
if (ConsiderFlagsAndMetadata && includesPoison(Kind) &&
Op->hasPoisonGeneratingFlagsOrMetadata())
return true;
unsigned Opcode = Op->getOpcode();
// Check whether opcode is a poison/undef-generating operation
switch (Opcode) {
case Instruction::Shl:
case Instruction::AShr:
case Instruction::LShr:
return includesPoison(Kind) && !shiftAmountKnownInRange(Op->getOperand(1));
case Instruction::FPToSI:
case Instruction::FPToUI:
// fptosi/ui yields poison if the resulting value does not fit in the
// destination type.
return true;
case Instruction::Call:
if (auto *II = dyn_cast<IntrinsicInst>(Op)) {
switch (II->getIntrinsicID()) {
// TODO: Add more intrinsics.
case Intrinsic::ctlz:
case Intrinsic::cttz:
case Intrinsic::abs:
if (cast<ConstantInt>(II->getArgOperand(1))->isNullValue())
return false;
break;
case Intrinsic::ctpop:
case Intrinsic::bswap:
case Intrinsic::bitreverse:
case Intrinsic::fshl:
case Intrinsic::fshr:
case Intrinsic::smax:
case Intrinsic::smin:
case Intrinsic::umax:
case Intrinsic::umin:
case Intrinsic::ptrmask:
case Intrinsic::fptoui_sat:
case Intrinsic::fptosi_sat:
case Intrinsic::sadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::umul_with_overflow:
case Intrinsic::sadd_sat:
case Intrinsic::uadd_sat:
case Intrinsic::ssub_sat:
case Intrinsic::usub_sat:
return false;
case Intrinsic::sshl_sat:
case Intrinsic::ushl_sat:
return includesPoison(Kind) &&
!shiftAmountKnownInRange(II->getArgOperand(1));
case Intrinsic::fma:
case Intrinsic::fmuladd:
case Intrinsic::sqrt:
case Intrinsic::powi:
case Intrinsic::sin:
case Intrinsic::cos:
case Intrinsic::pow:
case Intrinsic::log:
case Intrinsic::log10:
case Intrinsic::log2:
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::exp10:
case Intrinsic::fabs:
case Intrinsic::copysign:
case Intrinsic::floor:
case Intrinsic::ceil:
case Intrinsic::trunc:
case Intrinsic::rint:
case Intrinsic::nearbyint:
case Intrinsic::round:
case Intrinsic::roundeven:
case Intrinsic::fptrunc_round:
case Intrinsic::canonicalize:
case Intrinsic::arithmetic_fence:
case Intrinsic::minnum:
case Intrinsic::maxnum:
case Intrinsic::minimum:
case Intrinsic::maximum:
case Intrinsic::is_fpclass:
case Intrinsic::ldexp:
case Intrinsic::frexp:
return false;
case Intrinsic::lround:
case Intrinsic::llround:
case Intrinsic::lrint:
case Intrinsic::llrint:
// If the value doesn't fit an unspecified value is returned (but this
// is not poison).
return false;
}
}
[[fallthrough]];
case Instruction::CallBr:
case Instruction::Invoke: {
const auto *CB = cast<CallBase>(Op);
return !CB->hasRetAttr(Attribute::NoUndef);
}
case Instruction::InsertElement:
case Instruction::ExtractElement: {
// If index exceeds the length of the vector, it returns poison
auto *VTy = cast<VectorType>(Op->getOperand(0)->getType());
unsigned IdxOp = Op->getOpcode() == Instruction::InsertElement ? 2 : 1;
auto *Idx = dyn_cast<ConstantInt>(Op->getOperand(IdxOp));
if (includesPoison(Kind))
return !Idx ||
Idx->getValue().uge(VTy->getElementCount().getKnownMinValue());
return false;
}
case Instruction::ShuffleVector: {
ArrayRef<int> Mask = isa<ConstantExpr>(Op)
? cast<ConstantExpr>(Op)->getShuffleMask()
: cast<ShuffleVectorInst>(Op)->getShuffleMask();
return includesPoison(Kind) && is_contained(Mask, PoisonMaskElem);
}
case Instruction::FNeg:
case Instruction::PHI:
case Instruction::Select:
case Instruction::URem:
case Instruction::SRem:
case Instruction::ExtractValue:
case Instruction::InsertValue:
case Instruction::Freeze:
case Instruction::ICmp:
case Instruction::FCmp:
case Instruction::FAdd:
case Instruction::FSub:
case Instruction::FMul:
case Instruction::FDiv:
case Instruction::FRem:
return false;
case Instruction::GetElementPtr:
// inbounds is handled above
// TODO: what about inrange on constexpr?
return false;
default: {
const auto *CE = dyn_cast<ConstantExpr>(Op);
if (isa<CastInst>(Op) || (CE && CE->isCast()))
return false;
else if (Instruction::isBinaryOp(Opcode))
return false;
// Be conservative and return true.
return true;
}
}
}
bool llvm::canCreateUndefOrPoison(const Operator *Op,
bool ConsiderFlagsAndMetadata) {
return ::canCreateUndefOrPoison(Op, UndefPoisonKind::UndefOrPoison,
ConsiderFlagsAndMetadata);
}
bool llvm::canCreatePoison(const Operator *Op, bool ConsiderFlagsAndMetadata) {
return ::canCreateUndefOrPoison(Op, UndefPoisonKind::PoisonOnly,
ConsiderFlagsAndMetadata);
}
static bool directlyImpliesPoison(const Value *ValAssumedPoison, const Value *V,
unsigned Depth) {
if (ValAssumedPoison == V)
return true;
const unsigned MaxDepth = 2;
if (Depth >= MaxDepth)
return false;
if (const auto *I = dyn_cast<Instruction>(V)) {
if (any_of(I->operands(), [=](const Use &Op) {
return propagatesPoison(Op) &&
directlyImpliesPoison(ValAssumedPoison, Op, Depth + 1);
}))
return true;
// V = extractvalue V0, idx
// V2 = extractvalue V0, idx2
// V0's elements are all poison or not. (e.g., add_with_overflow)
const WithOverflowInst *II;
if (match(I, m_ExtractValue(m_WithOverflowInst(II))) &&
(match(ValAssumedPoison, m_ExtractValue(m_Specific(II))) ||
llvm::is_contained(II->args(), ValAssumedPoison)))
return true;
}
return false;
}
static bool impliesPoison(const Value *ValAssumedPoison, const Value *V,
unsigned Depth) {
if (isGuaranteedNotToBePoison(ValAssumedPoison))
return true;
if (directlyImpliesPoison(ValAssumedPoison, V, /* Depth */ 0))
return true;
const unsigned MaxDepth = 2;
if (Depth >= MaxDepth)
return false;
const auto *I = dyn_cast<Instruction>(ValAssumedPoison);
if (I && !canCreatePoison(cast<Operator>(I))) {
return all_of(I->operands(), [=](const Value *Op) {
return impliesPoison(Op, V, Depth + 1);
});
}
return false;
}
bool llvm::impliesPoison(const Value *ValAssumedPoison, const Value *V) {
return ::impliesPoison(ValAssumedPoison, V, /* Depth */ 0);
}
static bool programUndefinedIfUndefOrPoison(const Value *V, bool PoisonOnly);
static bool isGuaranteedNotToBeUndefOrPoison(
const Value *V, AssumptionCache *AC, const Instruction *CtxI,
const DominatorTree *DT, unsigned Depth, UndefPoisonKind Kind) {
if (Depth >= MaxAnalysisRecursionDepth)
return false;
if (isa<MetadataAsValue>(V))
return false;
if (const auto *A = dyn_cast<Argument>(V)) {
if (A->hasAttribute(Attribute::NoUndef) ||
A->hasAttribute(Attribute::Dereferenceable) ||
A->hasAttribute(Attribute::DereferenceableOrNull))
return true;
}
if (auto *C = dyn_cast<Constant>(V)) {
if (isa<PoisonValue>(C))
return !includesPoison(Kind);
if (isa<UndefValue>(C))
return !includesUndef(Kind);
if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
isa<ConstantPointerNull>(C) || isa<Function>(C))
return true;
if (C->getType()->isVectorTy() && !isa<ConstantExpr>(C))
return (!includesUndef(Kind) ? !C->containsPoisonElement()
: !C->containsUndefOrPoisonElement()) &&
!C->containsConstantExpression();
}
// Strip cast operations from a pointer value.
// Note that stripPointerCastsSameRepresentation can strip off getelementptr
// inbounds with zero offset. To guarantee that the result isn't poison, the
// stripped pointer is checked as it has to be pointing into an allocated
// object or be null `null` to ensure `inbounds` getelement pointers with a
// zero offset could not produce poison.
// It can strip off addrspacecast that do not change bit representation as
// well. We believe that such addrspacecast is equivalent to no-op.
auto *StrippedV = V->stripPointerCastsSameRepresentation();
if (isa<AllocaInst>(StrippedV) || isa<GlobalVariable>(StrippedV) ||
isa<Function>(StrippedV) || isa<ConstantPointerNull>(StrippedV))
return true;
auto OpCheck = [&](const Value *V) {
return isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth + 1, Kind);
};
if (auto *Opr = dyn_cast<Operator>(V)) {
// If the value is a freeze instruction, then it can never
// be undef or poison.
if (isa<FreezeInst>(V))
return true;
if (const auto *CB = dyn_cast<CallBase>(V)) {
if (CB->hasRetAttr(Attribute::NoUndef) ||
CB->hasRetAttr(Attribute::Dereferenceable) ||
CB->hasRetAttr(Attribute::DereferenceableOrNull))
return true;
}
if (const auto *PN = dyn_cast<PHINode>(V)) {
unsigned Num = PN->getNumIncomingValues();
bool IsWellDefined = true;
for (unsigned i = 0; i < Num; ++i) {
auto *TI = PN->getIncomingBlock(i)->getTerminator();
if (!isGuaranteedNotToBeUndefOrPoison(PN->getIncomingValue(i), AC, TI,
DT, Depth + 1, Kind)) {
IsWellDefined = false;
break;
}
}
if (IsWellDefined)
return true;
} else if (!::canCreateUndefOrPoison(Opr, Kind,
/*ConsiderFlagsAndMetadata*/ true) &&
all_of(Opr->operands(), OpCheck))
return true;
}
if (auto *I = dyn_cast<LoadInst>(V))
if (I->hasMetadata(LLVMContext::MD_noundef) ||
I->hasMetadata(LLVMContext::MD_dereferenceable) ||
I->hasMetadata(LLVMContext::MD_dereferenceable_or_null))
return true;
if (programUndefinedIfUndefOrPoison(V, !includesUndef(Kind)))
return true;
// CxtI may be null or a cloned instruction.
if (!CtxI || !CtxI->getParent() || !DT)
return false;
auto *DNode = DT->getNode(CtxI->getParent());
if (!DNode)
// Unreachable block
return false;
// If V is used as a branch condition before reaching CtxI, V cannot be
// undef or poison.
// br V, BB1, BB2
// BB1:
// CtxI ; V cannot be undef or poison here
auto *Dominator = DNode->getIDom();
while (Dominator) {
auto *TI = Dominator->getBlock()->getTerminator();
Value *Cond = nullptr;
if (auto BI = dyn_cast_or_null<BranchInst>(TI)) {
if (BI->isConditional())
Cond = BI->getCondition();
} else if (auto SI = dyn_cast_or_null<SwitchInst>(TI)) {
Cond = SI->getCondition();
}
if (Cond) {
if (Cond == V)
return true;
else if (!includesUndef(Kind) && isa<Operator>(Cond)) {
// For poison, we can analyze further
auto *Opr = cast<Operator>(Cond);
if (any_of(Opr->operands(),
[V](const Use &U) { return V == U && propagatesPoison(U); }))
return true;
}
}
Dominator = Dominator->getIDom();
}
if (getKnowledgeValidInContext(V, {Attribute::NoUndef}, CtxI, DT, AC))
return true;
return false;
}
bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT,
unsigned Depth) {
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth,
UndefPoisonKind::UndefOrPoison);
}
bool llvm::isGuaranteedNotToBePoison(const Value *V, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT, unsigned Depth) {
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth,
UndefPoisonKind::PoisonOnly);
}
bool llvm::isGuaranteedNotToBeUndef(const Value *V, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT, unsigned Depth) {
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth,
UndefPoisonKind::UndefOnly);
}
/// Return true if undefined behavior would provably be executed on the path to
/// OnPathTo if Root produced a posion result. Note that this doesn't say
/// anything about whether OnPathTo is actually executed or whether Root is
/// actually poison. This can be used to assess whether a new use of Root can
/// be added at a location which is control equivalent with OnPathTo (such as
/// immediately before it) without introducing UB which didn't previously
/// exist. Note that a false result conveys no information.
bool llvm::mustExecuteUBIfPoisonOnPathTo(Instruction *Root,
Instruction *OnPathTo,
DominatorTree *DT) {
// Basic approach is to assume Root is poison, propagate poison forward
// through all users we can easily track, and then check whether any of those
// users are provable UB and must execute before out exiting block might
// exit.
// The set of all recursive users we've visited (which are assumed to all be
// poison because of said visit)
SmallSet<const Value *, 16> KnownPoison;
SmallVector<const Instruction*, 16> Worklist;
Worklist.push_back(Root);
while (!Worklist.empty()) {
const Instruction *I = Worklist.pop_back_val();
// If we know this must trigger UB on a path leading our target.
if (mustTriggerUB(I, KnownPoison) && DT->dominates(I, OnPathTo))
return true;
// If we can't analyze propagation through this instruction, just skip it
// and transitive users. Safe as false is a conservative result.
if (I != Root && !any_of(I->operands(), [&KnownPoison](const Use &U) {
return KnownPoison.contains(U) && propagatesPoison(U);
}))
continue;
if (KnownPoison.insert(I).second)
for (const User *User : I->users())
Worklist.push_back(cast<Instruction>(User));
}
// Might be non-UB, or might have a path we couldn't prove must execute on
// way to exiting bb.
return false;
}
OverflowResult llvm::computeOverflowForSignedAdd(const AddOperator *Add,
const SimplifyQuery &SQ) {
return ::computeOverflowForSignedAdd(Add->getOperand(0), Add->getOperand(1),
Add, SQ);
}
OverflowResult
llvm::computeOverflowForSignedAdd(const WithCache<const Value *> &LHS,
const WithCache<const Value *> &RHS,
const SimplifyQuery &SQ) {
return ::computeOverflowForSignedAdd(LHS, RHS, nullptr, SQ);
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
// Note: An atomic operation isn't guaranteed to return in a reasonable amount
// of time because it's possible for another thread to interfere with it for an
// arbitrary length of time, but programs aren't allowed to rely on that.
// If there is no successor, then execution can't transfer to it.
if (isa<ReturnInst>(I))
return false;
if (isa<UnreachableInst>(I))
return false;
// Note: Do not add new checks here; instead, change Instruction::mayThrow or
// Instruction::willReturn.
//
// FIXME: Move this check into Instruction::willReturn.
if (isa<CatchPadInst>(I)) {
switch (classifyEHPersonality(I->getFunction()->getPersonalityFn())) {
default:
// A catchpad may invoke exception object constructors and such, which
// in some languages can be arbitrary code, so be conservative by default.
return false;
case EHPersonality::CoreCLR:
// For CoreCLR, it just involves a type test.
return true;
}
}
// An instruction that returns without throwing must transfer control flow
// to a successor.
return !I->mayThrow() && I->willReturn();
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
// TODO: This is slightly conservative for invoke instruction since exiting
// via an exception *is* normal control for them.
for (const Instruction &I : *BB)
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
return false;
return true;
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(
BasicBlock::const_iterator Begin, BasicBlock::const_iterator End,
unsigned ScanLimit) {
return isGuaranteedToTransferExecutionToSuccessor(make_range(Begin, End),
ScanLimit);
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(
iterator_range<BasicBlock::const_iterator> Range, unsigned ScanLimit) {
assert(ScanLimit && "scan limit must be non-zero");
for (const Instruction &I : Range) {
if (isa<DbgInfoIntrinsic>(I))
continue;
if (--ScanLimit == 0)
return false;
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
return false;
}
return true;
}
bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
const Loop *L) {
// The loop header is guaranteed to be executed for every iteration.
//
// FIXME: Relax this constraint to cover all basic blocks that are
// guaranteed to be executed at every iteration.
if (I->getParent() != L->getHeader()) return false;
for (const Instruction &LI : *L->getHeader()) {
if (&LI == I) return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&LI)) return false;
}
llvm_unreachable("Instruction not contained in its own parent basic block.");
}
bool llvm::propagatesPoison(const Use &PoisonOp) {
const Operator *I = cast<Operator>(PoisonOp.getUser());
switch (I->getOpcode()) {
case Instruction::Freeze:
case Instruction::PHI:
case Instruction::Invoke:
return false;
case Instruction::Select:
return PoisonOp.getOperandNo() == 0;
case Instruction::Call:
if (auto *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
// TODO: Add more intrinsics.
case Intrinsic::sadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::umul_with_overflow:
// If an input is a vector containing a poison element, the
// two output vectors (calculated results, overflow bits)'
// corresponding lanes are poison.
return true;
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
case Intrinsic::abs:
case Intrinsic::smax:
case Intrinsic::smin:
case Intrinsic::umax:
case Intrinsic::umin:
case Intrinsic::bitreverse:
case Intrinsic::bswap:
case Intrinsic::sadd_sat:
case Intrinsic::ssub_sat:
case Intrinsic::sshl_sat:
case Intrinsic::uadd_sat:
case Intrinsic::usub_sat:
case Intrinsic::ushl_sat:
return true;
}
}
return false;
case Instruction::ICmp:
case Instruction::FCmp:
case Instruction::GetElementPtr:
return true;
default:
if (isa<BinaryOperator>(I) || isa<UnaryOperator>(I) || isa<CastInst>(I))
return true;
// Be conservative and return false.
return false;
}
}
/// Enumerates all operands of \p I that are guaranteed to not be undef or
/// poison. If the callback \p Handle returns true, stop processing and return
/// true. Otherwise, return false.
template <typename CallableT>
static bool handleGuaranteedWellDefinedOps(const Instruction *I,
const CallableT &Handle) {
switch (I->getOpcode()) {
case Instruction::Store:
if (Handle(cast<StoreInst>(I)->getPointerOperand()))
return true;
break;
case Instruction::Load:
if (Handle(cast<LoadInst>(I)->getPointerOperand()))
return true;
break;
// Since dereferenceable attribute imply noundef, atomic operations
// also implicitly have noundef pointers too
case Instruction::AtomicCmpXchg:
if (Handle(cast<AtomicCmpXchgInst>(I)->getPointerOperand()))
return true;
break;
case Instruction::AtomicRMW:
if (Handle(cast<AtomicRMWInst>(I)->getPointerOperand()))
return true;
break;
case Instruction::Call:
case Instruction::Invoke: {
const CallBase *CB = cast<CallBase>(I);
if (CB->isIndirectCall() && Handle(CB->getCalledOperand()))
return true;
for (unsigned i = 0; i < CB->arg_size(); ++i)
if ((CB->paramHasAttr(i, Attribute::NoUndef) ||
CB->paramHasAttr(i, Attribute::Dereferenceable) ||
CB->paramHasAttr(i, Attribute::DereferenceableOrNull)) &&
Handle(CB->getArgOperand(i)))
return true;
break;
}
case Instruction::Ret:
if (I->getFunction()->hasRetAttribute(Attribute::NoUndef) &&
Handle(I->getOperand(0)))
return true;
break;
case Instruction::Switch:
if (Handle(cast<SwitchInst>(I)->getCondition()))
return true;
break;
case Instruction::Br: {
auto *BR = cast<BranchInst>(I);
if (BR->isConditional() && Handle(BR->getCondition()))
return true;
break;
}
default:
break;
}
return false;
}
void llvm::getGuaranteedWellDefinedOps(
const Instruction *I, SmallVectorImpl<const Value *> &Operands) {
handleGuaranteedWellDefinedOps(I, [&](const Value *V) {
Operands.push_back(V);
return false;
});
}
/// Enumerates all operands of \p I that are guaranteed to not be poison.
template <typename CallableT>
static bool handleGuaranteedNonPoisonOps(const Instruction *I,
const CallableT &Handle) {
if (handleGuaranteedWellDefinedOps(I, Handle))
return true;
switch (I->getOpcode()) {
// Divisors of these operations are allowed to be partially undef.
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
return Handle(I->getOperand(1));
default:
return false;
}
}
void llvm::getGuaranteedNonPoisonOps(const Instruction *I,
SmallVectorImpl<const Value *> &Operands) {
handleGuaranteedNonPoisonOps(I, [&](const Value *V) {
Operands.push_back(V);
return false;
});
}
bool llvm::mustTriggerUB(const Instruction *I,
const SmallPtrSetImpl<const Value *> &KnownPoison) {
return handleGuaranteedNonPoisonOps(
I, [&](const Value *V) { return KnownPoison.count(V); });
}
static bool programUndefinedIfUndefOrPoison(const Value *V,
bool PoisonOnly) {
// We currently only look for uses of values within the same basic
// block, as that makes it easier to guarantee that the uses will be
// executed given that Inst is executed.
//
// FIXME: Expand this to consider uses beyond the same basic block. To do
// this, look out for the distinction between post-dominance and strong
// post-dominance.
const BasicBlock *BB = nullptr;
BasicBlock::const_iterator Begin;
if (const auto *Inst = dyn_cast<Instruction>(V)) {
BB = Inst->getParent();
Begin = Inst->getIterator();
Begin++;
} else if (const auto *Arg = dyn_cast<Argument>(V)) {
if (Arg->getParent()->isDeclaration())
return false;
BB = &Arg->getParent()->getEntryBlock();
Begin = BB->begin();
} else {
return false;
}
// Limit number of instructions we look at, to avoid scanning through large
// blocks. The current limit is chosen arbitrarily.
unsigned ScanLimit = 32;
BasicBlock::const_iterator End = BB->end();
if (!PoisonOnly) {
// Since undef does not propagate eagerly, be conservative & just check
// whether a value is directly passed to an instruction that must take
// well-defined operands.
for (const auto &I : make_range(Begin, End)) {
if (isa<DbgInfoIntrinsic>(I))
continue;
if (--ScanLimit == 0)
break;
if (handleGuaranteedWellDefinedOps(&I, [V](const Value *WellDefinedOp) {
return WellDefinedOp == V;
}))
return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
break;
}
return false;
}
// Set of instructions that we have proved will yield poison if Inst
// does.
SmallSet<const Value *, 16> YieldsPoison;
SmallSet<const BasicBlock *, 4> Visited;
YieldsPoison.insert(V);
Visited.insert(BB);
while (true) {
for (const auto &I : make_range(Begin, End)) {
if (isa<DbgInfoIntrinsic>(I))
continue;
if (--ScanLimit == 0)
return false;
if (mustTriggerUB(&I, YieldsPoison))
return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
return false;
// If an operand is poison and propagates it, mark I as yielding poison.
for (const Use &Op : I.operands()) {
if (YieldsPoison.count(Op) && propagatesPoison(Op)) {
YieldsPoison.insert(&I);
break;
}
}
// Special handling for select, which returns poison if its operand 0 is
// poison (handled in the loop above) *or* if both its true/false operands
// are poison (handled here).
if (I.getOpcode() == Instruction::Select &&
YieldsPoison.count(I.getOperand(1)) &&
YieldsPoison.count(I.getOperand(2))) {
YieldsPoison.insert(&I);
}
}
BB = BB->getSingleSuccessor();
if (!BB || !Visited.insert(BB).second)
break;
Begin = BB->getFirstNonPHI()->getIterator();
End = BB->end();
}
return false;
}
bool llvm::programUndefinedIfUndefOrPoison(const Instruction *Inst) {
return ::programUndefinedIfUndefOrPoison(Inst, false);
}
bool llvm::programUndefinedIfPoison(const Instruction *Inst) {
return ::programUndefinedIfUndefOrPoison(Inst, true);
}
static bool isKnownNonNaN(const Value *V, FastMathFlags FMF) {
if (FMF.noNaNs())
return true;
if (auto *C = dyn_cast<ConstantFP>(V))
return !C->isNaN();
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
if (!C->getElementType()->isFloatingPointTy())
return false;
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
if (C->getElementAsAPFloat(I).isNaN())
return false;
}
return true;
}
if (isa<ConstantAggregateZero>(V))
return true;
return false;
}
static bool isKnownNonZero(const Value *V) {
if (auto *C = dyn_cast<ConstantFP>(V))
return !C->isZero();
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
if (!C->getElementType()->isFloatingPointTy())
return false;
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
if (C->getElementAsAPFloat(I).isZero())
return false;
}
return true;
}
return false;
}
/// Match clamp pattern for float types without care about NaNs or signed zeros.
/// Given non-min/max outer cmp/select from the clamp pattern this
/// function recognizes if it can be substitued by a "canonical" min/max
/// pattern.
static SelectPatternResult matchFastFloatClamp(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS) {
// Try to match
// X < C1 ? C1 : Min(X, C2) --> Max(C1, Min(X, C2))
// X > C1 ? C1 : Max(X, C2) --> Min(C1, Max(X, C2))
// and return description of the outer Max/Min.
// First, check if select has inverse order:
if (CmpRHS == FalseVal) {
std::swap(TrueVal, FalseVal);
Pred = CmpInst::getInversePredicate(Pred);
}
// Assume success now. If there's no match, callers should not use these anyway.
LHS = TrueVal;
RHS = FalseVal;
const APFloat *FC1;
if (CmpRHS != TrueVal || !match(CmpRHS, m_APFloat(FC1)) || !FC1->isFinite())
return {SPF_UNKNOWN, SPNB_NA, false};
const APFloat *FC2;
switch (Pred) {
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_OLE:
case CmpInst::FCMP_ULT:
case CmpInst::FCMP_ULE:
if (match(FalseVal,
m_CombineOr(m_OrdFMin(m_Specific(CmpLHS), m_APFloat(FC2)),
m_UnordFMin(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
*FC1 < *FC2)
return {SPF_FMAXNUM, SPNB_RETURNS_ANY, false};
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_OGE:
case CmpInst::FCMP_UGT:
case CmpInst::FCMP_UGE:
if (match(FalseVal,
m_CombineOr(m_OrdFMax(m_Specific(CmpLHS), m_APFloat(FC2)),
m_UnordFMax(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
*FC1 > *FC2)
return {SPF_FMINNUM, SPNB_RETURNS_ANY, false};
break;
default:
break;
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// Recognize variations of:
/// CLAMP(v,l,h) ==> ((v) < (l) ? (l) : ((v) > (h) ? (h) : (v)))
static SelectPatternResult matchClamp(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal) {
// Swap the select operands and predicate to match the patterns below.
if (CmpRHS != TrueVal) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(TrueVal, FalseVal);
}
const APInt *C1;
if (CmpRHS == TrueVal && match(CmpRHS, m_APInt(C1))) {
const APInt *C2;
// (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
if (match(FalseVal, m_SMin(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->slt(*C2) && Pred == CmpInst::ICMP_SLT)
return {SPF_SMAX, SPNB_NA, false};
// (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
if (match(FalseVal, m_SMax(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->sgt(*C2) && Pred == CmpInst::ICMP_SGT)
return {SPF_SMIN, SPNB_NA, false};
// (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
if (match(FalseVal, m_UMin(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->ult(*C2) && Pred == CmpInst::ICMP_ULT)
return {SPF_UMAX, SPNB_NA, false};
// (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
if (match(FalseVal, m_UMax(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->ugt(*C2) && Pred == CmpInst::ICMP_UGT)
return {SPF_UMIN, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// Recognize variations of:
/// a < c ? min(a,b) : min(b,c) ==> min(min(a,b),min(b,c))
static SelectPatternResult matchMinMaxOfMinMax(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TVal, Value *FVal,
unsigned Depth) {
// TODO: Allow FP min/max with nnan/nsz.
assert(CmpInst::isIntPredicate(Pred) && "Expected integer comparison");
Value *A = nullptr, *B = nullptr;
SelectPatternResult L = matchSelectPattern(TVal, A, B, nullptr, Depth + 1);
if (!SelectPatternResult::isMinOrMax(L.Flavor))
return {SPF_UNKNOWN, SPNB_NA, false};
Value *C = nullptr, *D = nullptr;
SelectPatternResult R = matchSelectPattern(FVal, C, D, nullptr, Depth + 1);
if (L.Flavor != R.Flavor)
return {SPF_UNKNOWN, SPNB_NA, false};
// We have something like: x Pred y ? min(a, b) : min(c, d).
// Try to match the compare to the min/max operations of the select operands.
// First, make sure we have the right compare predicate.
switch (L.Flavor) {
case SPF_SMIN:
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_SMAX:
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_UMIN:
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_UMAX:
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
default:
return {SPF_UNKNOWN, SPNB_NA, false};
}
// If there is a common operand in the already matched min/max and the other
// min/max operands match the compare operands (either directly or inverted),
// then this is min/max of the same flavor.
// a pred c ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
// ~c pred ~a ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
if (D == B) {
if ((CmpLHS == A && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
match(A, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// a pred d ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
// ~d pred ~a ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
if (C == B) {
if ((CmpLHS == A && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
match(A, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// b pred c ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
// ~c pred ~b ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
if (D == A) {
if ((CmpLHS == B && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
match(B, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// b pred d ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
// ~d pred ~b ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
if (C == A) {
if ((CmpLHS == B && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
match(B, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// If the input value is the result of a 'not' op, constant integer, or vector
/// splat of a constant integer, return the bitwise-not source value.
/// TODO: This could be extended to handle non-splat vector integer constants.
static Value *getNotValue(Value *V) {
Value *NotV;
if (match(V, m_Not(m_Value(NotV))))
return NotV;
const APInt *C;
if (match(V, m_APInt(C)))
return ConstantInt::get(V->getType(), ~(*C));
return nullptr;
}
/// Match non-obvious integer minimum and maximum sequences.
static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS,
unsigned Depth) {
// Assume success. If there's no match, callers should not use these anyway.
LHS = TrueVal;
RHS = FalseVal;
SelectPatternResult SPR = matchClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal);
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
return SPR;
SPR = matchMinMaxOfMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, Depth);
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
return SPR;
// Look through 'not' ops to find disguised min/max.
// (X > Y) ? ~X : ~Y ==> (~X < ~Y) ? ~X : ~Y ==> MIN(~X, ~Y)
// (X < Y) ? ~X : ~Y ==> (~X > ~Y) ? ~X : ~Y ==> MAX(~X, ~Y)
if (CmpLHS == getNotValue(TrueVal) && CmpRHS == getNotValue(FalseVal)) {
switch (Pred) {
case CmpInst::ICMP_SGT: return {SPF_SMIN, SPNB_NA, false};
case CmpInst::ICMP_SLT: return {SPF_SMAX, SPNB_NA, false};
case CmpInst::ICMP_UGT: return {SPF_UMIN, SPNB_NA, false};
case CmpInst::ICMP_ULT: return {SPF_UMAX, SPNB_NA, false};
default: break;
}
}
// (X > Y) ? ~Y : ~X ==> (~X < ~Y) ? ~Y : ~X ==> MAX(~Y, ~X)
// (X < Y) ? ~Y : ~X ==> (~X > ~Y) ? ~Y : ~X ==> MIN(~Y, ~X)
if (CmpLHS == getNotValue(FalseVal) && CmpRHS == getNotValue(TrueVal)) {
switch (Pred) {
case CmpInst::ICMP_SGT: return {SPF_SMAX, SPNB_NA, false};
case CmpInst::ICMP_SLT: return {SPF_SMIN, SPNB_NA, false};
case CmpInst::ICMP_UGT: return {SPF_UMAX, SPNB_NA, false};
case CmpInst::ICMP_ULT: return {SPF_UMIN, SPNB_NA, false};
default: break;
}
}
if (Pred != CmpInst::ICMP_SGT && Pred != CmpInst::ICMP_SLT)
return {SPF_UNKNOWN, SPNB_NA, false};
const APInt *C1;
if (!match(CmpRHS, m_APInt(C1)))
return {SPF_UNKNOWN, SPNB_NA, false};
// An unsigned min/max can be written with a signed compare.
const APInt *C2;
if ((CmpLHS == TrueVal && match(FalseVal, m_APInt(C2))) ||
(CmpLHS == FalseVal && match(TrueVal, m_APInt(C2)))) {
// Is the sign bit set?
// (X <s 0) ? X : MAXVAL ==> (X >u MAXVAL) ? X : MAXVAL ==> UMAX
// (X <s 0) ? MAXVAL : X ==> (X >u MAXVAL) ? MAXVAL : X ==> UMIN
if (Pred == CmpInst::ICMP_SLT && C1->isZero() && C2->isMaxSignedValue())
return {CmpLHS == TrueVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
// Is the sign bit clear?
// (X >s -1) ? MINVAL : X ==> (X <u MINVAL) ? MINVAL : X ==> UMAX
// (X >s -1) ? X : MINVAL ==> (X <u MINVAL) ? X : MINVAL ==> UMIN
if (Pred == CmpInst::ICMP_SGT && C1->isAllOnes() && C2->isMinSignedValue())
return {CmpLHS == FalseVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
assert(X && Y && "Invalid operand");
// X = sub (0, Y) || X = sub nsw (0, Y)
if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
(NeedNSW && match(X, m_NSWNeg(m_Specific(Y)))))
return true;
// Y = sub (0, X) || Y = sub nsw (0, X)
if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
(NeedNSW && match(Y, m_NSWNeg(m_Specific(X)))))
return true;
// X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
Value *A, *B;
return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
(NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
}
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
FastMathFlags FMF,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS,
unsigned Depth) {
bool HasMismatchedZeros = false;
if (CmpInst::isFPPredicate(Pred)) {
// IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one
// 0.0 operand, set the compare's 0.0 operands to that same value for the
// purpose of identifying min/max. Disregard vector constants with undefined
// elements because those can not be back-propagated for analysis.
Value *OutputZeroVal = nullptr;
if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) &&
!cast<Constant>(TrueVal)->containsUndefOrPoisonElement())
OutputZeroVal = TrueVal;
else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) &&
!cast<Constant>(FalseVal)->containsUndefOrPoisonElement())
OutputZeroVal = FalseVal;
if (OutputZeroVal) {
if (match(CmpLHS, m_AnyZeroFP()) && CmpLHS != OutputZeroVal) {
HasMismatchedZeros = true;
CmpLHS = OutputZeroVal;
}
if (match(CmpRHS, m_AnyZeroFP()) && CmpRHS != OutputZeroVal) {
HasMismatchedZeros = true;
CmpRHS = OutputZeroVal;
}
}
}
LHS = CmpLHS;
RHS = CmpRHS;
// Signed zero may return inconsistent results between implementations.
// (0.0 <= -0.0) ? 0.0 : -0.0 // Returns 0.0
// minNum(0.0, -0.0) // May return -0.0 or 0.0 (IEEE 754-2008 5.3.1)
// Therefore, we behave conservatively and only proceed if at least one of the
// operands is known to not be zero or if we don't care about signed zero.
switch (Pred) {
default: break;
case CmpInst::FCMP_OGT: case CmpInst::FCMP_OLT:
case CmpInst::FCMP_UGT: case CmpInst::FCMP_ULT:
if (!HasMismatchedZeros)
break;
[[fallthrough]];
case CmpInst::FCMP_OGE: case CmpInst::FCMP_OLE:
case CmpInst::FCMP_UGE: case CmpInst::FCMP_ULE:
if (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
!isKnownNonZero(CmpRHS))
return {SPF_UNKNOWN, SPNB_NA, false};
}
SelectPatternNaNBehavior NaNBehavior = SPNB_NA;
bool Ordered = false;
// When given one NaN and one non-NaN input:
// - maxnum/minnum (C99 fmaxf()/fminf()) return the non-NaN input.
// - A simple C99 (a < b ? a : b) construction will return 'b' (as the
// ordered comparison fails), which could be NaN or non-NaN.
// so here we discover exactly what NaN behavior is required/accepted.
if (CmpInst::isFPPredicate(Pred)) {
bool LHSSafe = isKnownNonNaN(CmpLHS, FMF);
bool RHSSafe = isKnownNonNaN(CmpRHS, FMF);
if (LHSSafe && RHSSafe) {
// Both operands are known non-NaN.
NaNBehavior = SPNB_RETURNS_ANY;
} else if (CmpInst::isOrdered(Pred)) {
// An ordered comparison will return false when given a NaN, so it
// returns the RHS.
Ordered = true;
if (LHSSafe)
// LHS is non-NaN, so if RHS is NaN then NaN will be returned.
NaNBehavior = SPNB_RETURNS_NAN;
else if (RHSSafe)
NaNBehavior = SPNB_RETURNS_OTHER;
else
// Completely unsafe.
return {SPF_UNKNOWN, SPNB_NA, false};
} else {
Ordered = false;
// An unordered comparison will return true when given a NaN, so it
// returns the LHS.
if (LHSSafe)
// LHS is non-NaN, so if RHS is NaN then non-NaN will be returned.
NaNBehavior = SPNB_RETURNS_OTHER;
else if (RHSSafe)
NaNBehavior = SPNB_RETURNS_NAN;
else
// Completely unsafe.
return {SPF_UNKNOWN, SPNB_NA, false};
}
}
if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
std::swap(CmpLHS, CmpRHS);
Pred = CmpInst::getSwappedPredicate(Pred);
if (NaNBehavior == SPNB_RETURNS_NAN)
NaNBehavior = SPNB_RETURNS_OTHER;
else if (NaNBehavior == SPNB_RETURNS_OTHER)
NaNBehavior = SPNB_RETURNS_NAN;
Ordered = !Ordered;
}
// ([if]cmp X, Y) ? X : Y
if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
switch (Pred) {
default: return {SPF_UNKNOWN, SPNB_NA, false}; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return {SPF_UMAX, SPNB_NA, false};
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return {SPF_SMAX, SPNB_NA, false};
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return {SPF_UMIN, SPNB_NA, false};
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return {SPF_SMIN, SPNB_NA, false};
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE: return {SPF_FMAXNUM, NaNBehavior, Ordered};
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE: return {SPF_FMINNUM, NaNBehavior, Ordered};
}
}
if (isKnownNegation(TrueVal, FalseVal)) {
// Sign-extending LHS does not change its sign, so TrueVal/FalseVal can
// match against either LHS or sext(LHS).
auto MaybeSExtCmpLHS =
m_CombineOr(m_Specific(CmpLHS), m_SExt(m_Specific(CmpLHS)));
auto ZeroOrAllOnes = m_CombineOr(m_ZeroInt(), m_AllOnes());
auto ZeroOrOne = m_CombineOr(m_ZeroInt(), m_One());
if (match(TrueVal, MaybeSExtCmpLHS)) {
// Set the return values. If the compare uses the negated value (-X >s 0),
// swap the return values because the negated value is always 'RHS'.
LHS = TrueVal;
RHS = FalseVal;
if (match(CmpLHS, m_Neg(m_Specific(FalseVal))))
std::swap(LHS, RHS);
// (X >s 0) ? X : -X or (X >s -1) ? X : -X --> ABS(X)
// (-X >s 0) ? -X : X or (-X >s -1) ? -X : X --> ABS(X)
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
return {SPF_ABS, SPNB_NA, false};
// (X >=s 0) ? X : -X or (X >=s 1) ? X : -X --> ABS(X)
if (Pred == ICmpInst::ICMP_SGE && match(CmpRHS, ZeroOrOne))
return {SPF_ABS, SPNB_NA, false};
// (X <s 0) ? X : -X or (X <s 1) ? X : -X --> NABS(X)
// (-X <s 0) ? -X : X or (-X <s 1) ? -X : X --> NABS(X)
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
return {SPF_NABS, SPNB_NA, false};
}
else if (match(FalseVal, MaybeSExtCmpLHS)) {
// Set the return values. If the compare uses the negated value (-X >s 0),
// swap the return values because the negated value is always 'RHS'.
LHS = FalseVal;
RHS = TrueVal;
if (match(CmpLHS, m_Neg(m_Specific(TrueVal))))
std::swap(LHS, RHS);
// (X >s 0) ? -X : X or (X >s -1) ? -X : X --> NABS(X)
// (-X >s 0) ? X : -X or (-X >s -1) ? X : -X --> NABS(X)
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
return {SPF_NABS, SPNB_NA, false};
// (X <s 0) ? -X : X or (X <s 1) ? -X : X --> ABS(X)
// (-X <s 0) ? X : -X or (-X <s 1) ? X : -X --> ABS(X)
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
return {SPF_ABS, SPNB_NA, false};
}
}
if (CmpInst::isIntPredicate(Pred))
return matchMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS, Depth);
// According to (IEEE 754-2008 5.3.1), minNum(0.0, -0.0) and similar
// may return either -0.0 or 0.0, so fcmp/select pair has stricter
// semantics than minNum. Be conservative in such case.
if (NaNBehavior != SPNB_RETURNS_ANY ||
(!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
!isKnownNonZero(CmpRHS)))
return {SPF_UNKNOWN, SPNB_NA, false};
return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
}
/// Helps to match a select pattern in case of a type mismatch.
///
/// The function processes the case when type of true and false values of a
/// select instruction differs from type of the cmp instruction operands because
/// of a cast instruction. The function checks if it is legal to move the cast
/// operation after "select". If yes, it returns the new second value of
/// "select" (with the assumption that cast is moved):
/// 1. As operand of cast instruction when both values of "select" are same cast
/// instructions.
/// 2. As restored constant (by applying reverse cast operation) when the first
/// value of the "select" is a cast operation and the second value is a
/// constant.
/// NOTE: We return only the new second value because the first value could be
/// accessed as operand of cast instruction.
static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
Instruction::CastOps *CastOp) {
auto *Cast1 = dyn_cast<CastInst>(V1);
if (!Cast1)
return nullptr;
*CastOp = Cast1->getOpcode();
Type *SrcTy = Cast1->getSrcTy();
if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
// If V1 and V2 are both the same cast from the same type, look through V1.
if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
return Cast2->getOperand(0);
return nullptr;
}
auto *C = dyn_cast<Constant>(V2);
if (!C)
return nullptr;
const DataLayout &DL = CmpI->getModule()->getDataLayout();
Constant *CastedTo = nullptr;
switch (*CastOp) {
case Instruction::ZExt:
if (CmpI->isUnsigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy);
break;
case Instruction::SExt:
if (CmpI->isSigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
break;
case Instruction::Trunc:
Constant *CmpConst;
if (match(CmpI->getOperand(1), m_Constant(CmpConst)) &&
CmpConst->getType() == SrcTy) {
// Here we have the following case:
//
// %cond = cmp iN %x, CmpConst
// %tr = trunc iN %x to iK
// %narrowsel = select i1 %cond, iK %t, iK C
//
// We can always move trunc after select operation:
//
// %cond = cmp iN %x, CmpConst
// %widesel = select i1 %cond, iN %x, iN CmpConst
// %tr = trunc iN %widesel to iK
//
// Note that C could be extended in any way because we don't care about
// upper bits after truncation. It can't be abs pattern, because it would
// look like:
//
// select i1 %cond, x, -x.
//
// So only min/max pattern could be matched. Such match requires widened C
// == CmpConst. That is why set widened C = CmpConst, condition trunc
// CmpConst == C is checked below.
CastedTo = CmpConst;
} else {
unsigned ExtOp = CmpI->isSigned() ? Instruction::SExt : Instruction::ZExt;
CastedTo = ConstantFoldCastOperand(ExtOp, C, SrcTy, DL);
}
break;
case Instruction::FPTrunc:
CastedTo = ConstantFoldCastOperand(Instruction::FPExt, C, SrcTy, DL);
break;
case Instruction::FPExt:
CastedTo = ConstantFoldCastOperand(Instruction::FPTrunc, C, SrcTy, DL);
break;
case Instruction::FPToUI:
CastedTo = ConstantFoldCastOperand(Instruction::UIToFP, C, SrcTy, DL);
break;
case Instruction::FPToSI:
CastedTo = ConstantFoldCastOperand(Instruction::SIToFP, C, SrcTy, DL);
break;
case Instruction::UIToFP:
CastedTo = ConstantFoldCastOperand(Instruction::FPToUI, C, SrcTy, DL);
break;
case Instruction::SIToFP:
CastedTo = ConstantFoldCastOperand(Instruction::FPToSI, C, SrcTy, DL);
break;
default:
break;
}
if (!CastedTo)
return nullptr;
// Make sure the cast doesn't lose any information.
Constant *CastedBack =
ConstantFoldCastOperand(*CastOp, CastedTo, C->getType(), DL);
if (CastedBack && CastedBack != C)
return nullptr;
return CastedTo;
}
SelectPatternResult llvm::matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
Instruction::CastOps *CastOp,
unsigned Depth) {
if (Depth >= MaxAnalysisRecursionDepth)
return {SPF_UNKNOWN, SPNB_NA, false};
SelectInst *SI = dyn_cast<SelectInst>(V);
if (!SI) return {SPF_UNKNOWN, SPNB_NA, false};
CmpInst *CmpI = dyn_cast<CmpInst>(SI->getCondition());
if (!CmpI) return {SPF_UNKNOWN, SPNB_NA, false};
Value *TrueVal = SI->getTrueValue();
Value *FalseVal = SI->getFalseValue();
return llvm::matchDecomposedSelectPattern(CmpI, TrueVal, FalseVal, LHS, RHS,
CastOp, Depth);
}
SelectPatternResult llvm::matchDecomposedSelectPattern(
CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS,
Instruction::CastOps *CastOp, unsigned Depth) {
CmpInst::Predicate Pred = CmpI->getPredicate();
Value *CmpLHS = CmpI->getOperand(0);
Value *CmpRHS = CmpI->getOperand(1);
FastMathFlags FMF;
if (isa<FPMathOperator>(CmpI))
FMF = CmpI->getFastMathFlags();
// Bail out early.
if (CmpI->isEquality())
return {SPF_UNKNOWN, SPNB_NA, false};
// Deal with type mismatches.
if (CastOp && CmpLHS->getType() != TrueVal->getType()) {
if (Value *C = lookThroughCast(CmpI, TrueVal, FalseVal, CastOp)) {
// If this is a potential fmin/fmax with a cast to integer, then ignore
// -0.0 because there is no corresponding integer value.
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
FMF.setNoSignedZeros();
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
cast<CastInst>(TrueVal)->getOperand(0), C,
LHS, RHS, Depth);
}
if (Value *C = lookThroughCast(CmpI, FalseVal, TrueVal, CastOp)) {
// If this is a potential fmin/fmax with a cast to integer, then ignore
// -0.0 because there is no corresponding integer value.
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
FMF.setNoSignedZeros();
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
C, cast<CastInst>(FalseVal)->getOperand(0),
LHS, RHS, Depth);
}
}
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS, TrueVal, FalseVal,
LHS, RHS, Depth);
}
CmpInst::Predicate llvm::getMinMaxPred(SelectPatternFlavor SPF, bool Ordered) {
if (SPF == SPF_SMIN) return ICmpInst::ICMP_SLT;
if (SPF == SPF_UMIN) return ICmpInst::ICMP_ULT;
if (SPF == SPF_SMAX) return ICmpInst::ICMP_SGT;
if (SPF == SPF_UMAX) return ICmpInst::ICMP_UGT;
if (SPF == SPF_FMINNUM)
return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT;
if (SPF == SPF_FMAXNUM)
return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT;
llvm_unreachable("unhandled!");
}
SelectPatternFlavor llvm::getInverseMinMaxFlavor(SelectPatternFlavor SPF) {
if (SPF == SPF_SMIN) return SPF_SMAX;
if (SPF == SPF_UMIN) return SPF_UMAX;
if (SPF == SPF_SMAX) return SPF_SMIN;
if (SPF == SPF_UMAX) return SPF_UMIN;
llvm_unreachable("unhandled!");
}
Intrinsic::ID llvm::getInverseMinMaxIntrinsic(Intrinsic::ID MinMaxID) {
switch (MinMaxID) {
case Intrinsic::smax: return Intrinsic::smin;
case Intrinsic::smin: return Intrinsic::smax;
case Intrinsic::umax: return Intrinsic::umin;
case Intrinsic::umin: return Intrinsic::umax;
// Please note that next four intrinsics may produce the same result for
// original and inverted case even if X != Y due to NaN is handled specially.
case Intrinsic::maximum: return Intrinsic::minimum;
case Intrinsic::minimum: return Intrinsic::maximum;
case Intrinsic::maxnum: return Intrinsic::minnum;
case Intrinsic::minnum: return Intrinsic::maxnum;
default: llvm_unreachable("Unexpected intrinsic");
}
}
APInt llvm::getMinMaxLimit(SelectPatternFlavor SPF, unsigned BitWidth) {
switch (SPF) {
case SPF_SMAX: return APInt::getSignedMaxValue(BitWidth);
case SPF_SMIN: return APInt::getSignedMinValue(BitWidth);
case SPF_UMAX: return APInt::getMaxValue(BitWidth);
case SPF_UMIN: return APInt::getMinValue(BitWidth);
default: llvm_unreachable("Unexpected flavor");
}
}
std::pair<Intrinsic::ID, bool>
llvm::canConvertToMinOrMaxIntrinsic(ArrayRef<Value *> VL) {
// Check if VL contains select instructions that can be folded into a min/max
// vector intrinsic and return the intrinsic if it is possible.
// TODO: Support floating point min/max.
bool AllCmpSingleUse = true;
SelectPatternResult SelectPattern;
SelectPattern.Flavor = SPF_UNKNOWN;
if (all_of(VL, [&SelectPattern, &AllCmpSingleUse](Value *I) {
Value *LHS, *RHS;
auto CurrentPattern = matchSelectPattern(I, LHS, RHS);
if (!SelectPatternResult::isMinOrMax(CurrentPattern.Flavor) ||
CurrentPattern.Flavor == SPF_FMINNUM ||
CurrentPattern.Flavor == SPF_FMAXNUM ||
!I->getType()->isIntOrIntVectorTy())
return false;
if (SelectPattern.Flavor != SPF_UNKNOWN &&
SelectPattern.Flavor != CurrentPattern.Flavor)
return false;
SelectPattern = CurrentPattern;
AllCmpSingleUse &=
match(I, m_Select(m_OneUse(m_Value()), m_Value(), m_Value()));
return true;
})) {
switch (SelectPattern.Flavor) {
case SPF_SMIN:
return {Intrinsic::smin, AllCmpSingleUse};
case SPF_UMIN:
return {Intrinsic::umin, AllCmpSingleUse};
case SPF_SMAX:
return {Intrinsic::smax, AllCmpSingleUse};
case SPF_UMAX:
return {Intrinsic::umax, AllCmpSingleUse};
default:
llvm_unreachable("unexpected select pattern flavor");
}
}
return {Intrinsic::not_intrinsic, false};
}
bool llvm::matchSimpleRecurrence(const PHINode *P, BinaryOperator *&BO,
Value *&Start, Value *&Step) {
// Handle the case of a simple two-predecessor recurrence PHI.
// There's a lot more that could theoretically be done here, but
// this is sufficient to catch some interesting cases.
if (P->getNumIncomingValues() != 2)
return false;
for (unsigned i = 0; i != 2; ++i) {
Value *L = P->getIncomingValue(i);
Value *R = P->getIncomingValue(!i);
auto *LU = dyn_cast<BinaryOperator>(L);
if (!LU)
continue;
unsigned Opcode = LU->getOpcode();
switch (Opcode) {
default:
continue;
// TODO: Expand list -- xor, div, gep, uaddo, etc..
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:
case Instruction::Or:
case Instruction::Mul:
case Instruction::FMul: {
Value *LL = LU->getOperand(0);
Value *LR = LU->getOperand(1);
// Find a recurrence.
if (LL == P)
L = LR;
else if (LR == P)
L = LL;
else
continue; // Check for recurrence with L and R flipped.
break; // Match!
}
};
// We have matched a recurrence of the form:
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = binop %iv, L
// OR
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = binop L, %iv
BO = LU;
Start = R;
Step = L;
return true;
}
return false;
}
bool llvm::matchSimpleRecurrence(const BinaryOperator *I, PHINode *&P,
Value *&Start, Value *&Step) {
BinaryOperator *BO = nullptr;
P = dyn_cast<PHINode>(I->getOperand(0));
if (!P)
P = dyn_cast<PHINode>(I->getOperand(1));
return P && matchSimpleRecurrence(P, BO, Start, Step) && BO == I;
}
/// Return true if "icmp Pred LHS RHS" is always true.
static bool isTruePredicate(CmpInst::Predicate Pred, const Value *LHS,
const Value *RHS) {
if (ICmpInst::isTrueWhenEqual(Pred) && LHS == RHS)
return true;
switch (Pred) {
default:
return false;
case CmpInst::ICMP_SLE: {
const APInt *C;
// LHS s<= LHS +_{nsw} C if C >= 0
// LHS s<= LHS | C if C >= 0
if (match(RHS, m_NSWAdd(m_Specific(LHS), m_APInt(C))) ||
match(RHS, m_Or(m_Specific(LHS), m_APInt(C))))
return !C->isNegative();
// LHS s<= smax(LHS, V) for any V
if (match(RHS, m_c_SMax(m_Specific(LHS), m_Value())))
return true;
// smin(RHS, V) s<= RHS for any V
if (match(LHS, m_c_SMin(m_Specific(RHS), m_Value())))
return true;
// Match A to (X +_{nsw} CA) and B to (X +_{nsw} CB)
const Value *X;
const APInt *CLHS, *CRHS;
if (match(LHS, m_NSWAddLike(m_Value(X), m_APInt(CLHS))) &&
match(RHS, m_NSWAddLike(m_Specific(X), m_APInt(CRHS))))
return CLHS->sle(*CRHS);
return false;
}
case CmpInst::ICMP_ULE: {
// LHS u<= LHS +_{nuw} V for any V
if (match(RHS, m_c_Add(m_Specific(LHS), m_Value())) &&
cast<OverflowingBinaryOperator>(RHS)->hasNoUnsignedWrap())
return true;
// LHS u<= LHS | V for any V
if (match(RHS, m_c_Or(m_Specific(LHS), m_Value())))
return true;
// LHS u<= umax(LHS, V) for any V
if (match(RHS, m_c_UMax(m_Specific(LHS), m_Value())))
return true;
// RHS >> V u<= RHS for any V
if (match(LHS, m_LShr(m_Specific(RHS), m_Value())))
return true;
// RHS u/ C_ugt_1 u<= RHS
const APInt *C;
if (match(LHS, m_UDiv(m_Specific(RHS), m_APInt(C))) && C->ugt(1))
return true;
// RHS & V u<= RHS for any V
if (match(LHS, m_c_And(m_Specific(RHS), m_Value())))
return true;
// umin(RHS, V) u<= RHS for any V
if (match(LHS, m_c_UMin(m_Specific(RHS), m_Value())))
return true;
// Match A to (X +_{nuw} CA) and B to (X +_{nuw} CB)
const Value *X;
const APInt *CLHS, *CRHS;
if (match(LHS, m_NUWAddLike(m_Value(X), m_APInt(CLHS))) &&
match(RHS, m_NUWAddLike(m_Specific(X), m_APInt(CRHS))))
return CLHS->ule(*CRHS);
return false;
}
}
}
/// Return true if "icmp Pred BLHS BRHS" is true whenever "icmp Pred
/// ALHS ARHS" is true. Otherwise, return std::nullopt.
static std::optional<bool>
isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
const Value *ARHS, const Value *BLHS, const Value *BRHS) {
switch (Pred) {
default:
return std::nullopt;
case CmpInst::ICMP_SLT:
case CmpInst::ICMP_SLE:
if (isTruePredicate(CmpInst::ICMP_SLE, BLHS, ALHS) &&
isTruePredicate(CmpInst::ICMP_SLE, ARHS, BRHS))
return true;
return std::nullopt;
case CmpInst::ICMP_SGT:
case CmpInst::ICMP_SGE:
if (isTruePredicate(CmpInst::ICMP_SLE, ALHS, BLHS) &&
isTruePredicate(CmpInst::ICMP_SLE, BRHS, ARHS))
return true;
return std::nullopt;
case CmpInst::ICMP_ULT:
case CmpInst::ICMP_ULE:
if (isTruePredicate(CmpInst::ICMP_ULE, BLHS, ALHS) &&
isTruePredicate(CmpInst::ICMP_ULE, ARHS, BRHS))
return true;
return std::nullopt;
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_UGE:
if (isTruePredicate(CmpInst::ICMP_ULE, ALHS, BLHS) &&
isTruePredicate(CmpInst::ICMP_ULE, BRHS, ARHS))
return true;
return std::nullopt;
}
}
/// Return true if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is true.
/// Return false if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is false.
/// Otherwise, return std::nullopt if we can't infer anything.
static std::optional<bool>
isImpliedCondMatchingOperands(CmpInst::Predicate LPred,
CmpInst::Predicate RPred) {
if (CmpInst::isImpliedTrueByMatchingCmp(LPred, RPred))
return true;
if (CmpInst::isImpliedFalseByMatchingCmp(LPred, RPred))
return false;
return std::nullopt;
}
/// Return true if "icmp LPred X, LC" implies "icmp RPred X, RC" is true.
/// Return false if "icmp LPred X, LC" implies "icmp RPred X, RC" is false.
/// Otherwise, return std::nullopt if we can't infer anything.
static std::optional<bool> isImpliedCondCommonOperandWithConstants(
CmpInst::Predicate LPred, const APInt &LC, CmpInst::Predicate RPred,
const APInt &RC) {
ConstantRange DomCR = ConstantRange::makeExactICmpRegion(LPred, LC);
ConstantRange CR = ConstantRange::makeExactICmpRegion(RPred, RC);
ConstantRange Intersection = DomCR.intersectWith(CR);
ConstantRange Difference = DomCR.difference(CR);
if (Intersection.isEmptySet())
return false;
if (Difference.isEmptySet())
return true;
return std::nullopt;
}
/// Return true if LHS implies RHS (expanded to its components as "R0 RPred R1")
/// is true. Return false if LHS implies RHS is false. Otherwise, return
/// std::nullopt if we can't infer anything.
static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
CmpInst::Predicate RPred,
const Value *R0, const Value *R1,
const DataLayout &DL,
bool LHSIsTrue) {
Value *L0 = LHS->getOperand(0);
Value *L1 = LHS->getOperand(1);
// The rest of the logic assumes the LHS condition is true. If that's not the
// case, invert the predicate to make it so.
CmpInst::Predicate LPred =
LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
// We can have non-canonical operands, so try to normalize any common operand
// to L0/R0.
if (L0 == R1) {
std::swap(R0, R1);
RPred = ICmpInst::getSwappedPredicate(RPred);
}
if (R0 == L1) {
std::swap(L0, L1);
LPred = ICmpInst::getSwappedPredicate(LPred);
}
if (L1 == R1) {
// If we have L0 == R0 and L1 == R1, then make L1/R1 the constants.
if (L0 != R0 || match(L0, m_ImmConstant())) {
std::swap(L0, L1);
LPred = ICmpInst::getSwappedPredicate(LPred);
std::swap(R0, R1);
RPred = ICmpInst::getSwappedPredicate(RPred);
}
}
// Can we infer anything when the 0-operands match and the 1-operands are
// constants (not necessarily matching)?
const APInt *LC, *RC;
if (L0 == R0 && match(L1, m_APInt(LC)) && match(R1, m_APInt(RC)))
return isImpliedCondCommonOperandWithConstants(LPred, *LC, RPred, *RC);
// Can we infer anything when the two compares have matching operands?
if (L0 == R0 && L1 == R1)
return isImpliedCondMatchingOperands(LPred, RPred);
// L0 = R0 = L1 + R1, L0 >=u L1 implies R0 >=u R1, L0 <u L1 implies R0 <u R1
if (L0 == R0 &&
(LPred == ICmpInst::ICMP_ULT || LPred == ICmpInst::ICMP_UGE) &&
(RPred == ICmpInst::ICMP_ULT || RPred == ICmpInst::ICMP_UGE) &&
match(L0, m_c_Add(m_Specific(L1), m_Specific(R1))))
return LPred == RPred;
if (LPred == RPred)
return isImpliedCondOperands(LPred, L0, L1, R0, R1);
return std::nullopt;
}
/// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
/// false. Otherwise, return std::nullopt if we can't infer anything. We
/// expect the RHS to be an icmp and the LHS to be an 'and', 'or', or a 'select'
/// instruction.
static std::optional<bool>
isImpliedCondAndOr(const Instruction *LHS, CmpInst::Predicate RHSPred,
const Value *RHSOp0, const Value *RHSOp1,
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
// The LHS must be an 'or', 'and', or a 'select' instruction.
assert((LHS->getOpcode() == Instruction::And ||
LHS->getOpcode() == Instruction::Or ||
LHS->getOpcode() == Instruction::Select) &&
"Expected LHS to be 'and', 'or', or 'select'.");
assert(Depth <= MaxAnalysisRecursionDepth && "Hit recursion limit");
// If the result of an 'or' is false, then we know both legs of the 'or' are
// false. Similarly, if the result of an 'and' is true, then we know both
// legs of the 'and' are true.
const Value *ALHS, *ARHS;
if ((!LHSIsTrue && match(LHS, m_LogicalOr(m_Value(ALHS), m_Value(ARHS)))) ||
(LHSIsTrue && match(LHS, m_LogicalAnd(m_Value(ALHS), m_Value(ARHS))))) {
// FIXME: Make this non-recursion.
if (std::optional<bool> Implication = isImpliedCondition(
ALHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
return Implication;
if (std::optional<bool> Implication = isImpliedCondition(
ARHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
return Implication;
return std::nullopt;
}
return std::nullopt;
}
std::optional<bool>
llvm::isImpliedCondition(const Value *LHS, CmpInst::Predicate RHSPred,
const Value *RHSOp0, const Value *RHSOp1,
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
// Bail out when we hit the limit.
if (Depth == MaxAnalysisRecursionDepth)
return std::nullopt;
// A mismatch occurs when we compare a scalar cmp to a vector cmp, for
// example.
if (RHSOp0->getType()->isVectorTy() != LHS->getType()->isVectorTy())
return std::nullopt;
assert(LHS->getType()->isIntOrIntVectorTy(1) &&
"Expected integer type only!");
// Match not
if (match(LHS, m_Not(m_Value(LHS))))
LHSIsTrue = !LHSIsTrue;
// Both LHS and RHS are icmps.
const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
if (LHSCmp)
return isImpliedCondICmps(LHSCmp, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue);
/// The LHS should be an 'or', 'and', or a 'select' instruction. We expect
/// the RHS to be an icmp.
/// FIXME: Add support for and/or/select on the RHS.
if (const Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if ((LHSI->getOpcode() == Instruction::And ||
LHSI->getOpcode() == Instruction::Or ||
LHSI->getOpcode() == Instruction::Select))
return isImpliedCondAndOr(LHSI, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue,
Depth);
}
return std::nullopt;
}
std::optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
const DataLayout &DL,
bool LHSIsTrue, unsigned Depth) {
// LHS ==> RHS by definition
if (LHS == RHS)
return LHSIsTrue;
// Match not
bool InvertRHS = false;
if (match(RHS, m_Not(m_Value(RHS)))) {
if (LHS == RHS)
return !LHSIsTrue;
InvertRHS = true;
}
if (const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS)) {
if (auto Implied = isImpliedCondition(
LHS, RHSCmp->getPredicate(), RHSCmp->getOperand(0),
RHSCmp->getOperand(1), DL, LHSIsTrue, Depth))
return InvertRHS ? !*Implied : *Implied;
return std::nullopt;
}
if (Depth == MaxAnalysisRecursionDepth)
return std::nullopt;
// LHS ==> (RHS1 || RHS2) if LHS ==> RHS1 or LHS ==> RHS2
// LHS ==> !(RHS1 && RHS2) if LHS ==> !RHS1 or LHS ==> !RHS2
const Value *RHS1, *RHS2;
if (match(RHS, m_LogicalOr(m_Value(RHS1), m_Value(RHS2)))) {
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS1, DL, LHSIsTrue, Depth + 1))
if (*Imp == true)
return !InvertRHS;
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS2, DL, LHSIsTrue, Depth + 1))
if (*Imp == true)
return !InvertRHS;
}
if (match(RHS, m_LogicalAnd(m_Value(RHS1), m_Value(RHS2)))) {
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS1, DL, LHSIsTrue, Depth + 1))
if (*Imp == false)
return InvertRHS;
if (std::optional<bool> Imp =
isImpliedCondition(LHS, RHS2, DL, LHSIsTrue, Depth + 1))
if (*Imp == false)
return InvertRHS;
}
return std::nullopt;
}
// Returns a pair (Condition, ConditionIsTrue), where Condition is a branch
// condition dominating ContextI or nullptr, if no condition is found.
static std::pair<Value *, bool>
getDomPredecessorCondition(const Instruction *ContextI) {
if (!ContextI || !ContextI->getParent())
return {nullptr, false};
// TODO: This is a poor/cheap way to determine dominance. Should we use a
// dominator tree (eg, from a SimplifyQuery) instead?
const BasicBlock *ContextBB = ContextI->getParent();
const BasicBlock *PredBB = ContextBB->getSinglePredecessor();
if (!PredBB)
return {nullptr, false};
// We need a conditional branch in the predecessor.
Value *PredCond;
BasicBlock *TrueBB, *FalseBB;
if (!match(PredBB->getTerminator(), m_Br(m_Value(PredCond), TrueBB, FalseBB)))
return {nullptr, false};
// The branch should get simplified. Don't bother simplifying this condition.
if (TrueBB == FalseBB)
return {nullptr, false};
assert((TrueBB == ContextBB || FalseBB == ContextBB) &&
"Predecessor block does not point to successor?");
// Is this condition implied by the predecessor condition?
return {PredCond, TrueBB == ContextBB};
}
std::optional<bool> llvm::isImpliedByDomCondition(const Value *Cond,
const Instruction *ContextI,
const DataLayout &DL) {
assert(Cond->getType()->isIntOrIntVectorTy(1) && "Condition must be bool");
auto PredCond = getDomPredecessorCondition(ContextI);
if (PredCond.first)
return isImpliedCondition(PredCond.first, Cond, DL, PredCond.second);
return std::nullopt;
}
std::optional<bool> llvm::isImpliedByDomCondition(CmpInst::Predicate Pred,
const Value *LHS,
const Value *RHS,
const Instruction *ContextI,
const DataLayout &DL) {
auto PredCond = getDomPredecessorCondition(ContextI);
if (PredCond.first)
return isImpliedCondition(PredCond.first, Pred, LHS, RHS, DL,
PredCond.second);
return std::nullopt;
}
static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
APInt &Upper, const InstrInfoQuery &IIQ,
bool PreferSignedRange) {
unsigned Width = Lower.getBitWidth();
const APInt *C;
switch (BO.getOpcode()) {
case Instruction::Add:
if (match(BO.getOperand(1), m_APInt(C)) && !C->isZero()) {
bool HasNSW = IIQ.hasNoSignedWrap(&BO);
bool HasNUW = IIQ.hasNoUnsignedWrap(&BO);
// If the caller expects a signed compare, then try to use a signed range.
// Otherwise if both no-wraps are set, use the unsigned range because it
// is never larger than the signed range. Example:
// "add nuw nsw i8 X, -2" is unsigned [254,255] vs. signed [-128, 125].
if (PreferSignedRange && HasNSW && HasNUW)
HasNUW = false;
if (HasNUW) {
// 'add nuw x, C' produces [C, UINT_MAX].
Lower = *C;
} else if (HasNSW) {
if (C->isNegative()) {
// 'add nsw x, -C' produces [SINT_MIN, SINT_MAX - C].
Lower = APInt::getSignedMinValue(Width);
Upper = APInt::getSignedMaxValue(Width) + *C + 1;
} else {
// 'add nsw x, +C' produces [SINT_MIN + C, SINT_MAX].
Lower = APInt::getSignedMinValue(Width) + *C;
Upper = APInt::getSignedMaxValue(Width) + 1;
}
}
}
break;
case Instruction::And:
if (match(BO.getOperand(1), m_APInt(C)))
// 'and x, C' produces [0, C].
Upper = *C + 1;
// X & -X is a power of two or zero. So we can cap the value at max power of
// two.
if (match(BO.getOperand(0), m_Neg(m_Specific(BO.getOperand(1)))) ||
match(BO.getOperand(1), m_Neg(m_Specific(BO.getOperand(0)))))
Upper = APInt::getSignedMinValue(Width) + 1;
break;
case Instruction::Or:
if (match(BO.getOperand(1), m_APInt(C)))
// 'or x, C' produces [C, UINT_MAX].
Lower = *C;
break;
case Instruction::AShr:
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
// 'ashr x, C' produces [INT_MIN >> C, INT_MAX >> C].
Lower = APInt::getSignedMinValue(Width).ashr(*C);
Upper = APInt::getSignedMaxValue(Width).ashr(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
unsigned ShiftAmount = Width - 1;
if (!C->isZero() && IIQ.isExact(&BO))
ShiftAmount = C->countr_zero();
if (C->isNegative()) {
// 'ashr C, x' produces [C, C >> (Width-1)]
Lower = *C;
Upper = C->ashr(ShiftAmount) + 1;
} else {
// 'ashr C, x' produces [C >> (Width-1), C]
Lower = C->ashr(ShiftAmount);
Upper = *C + 1;
}
}
break;
case Instruction::LShr:
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
// 'lshr x, C' produces [0, UINT_MAX >> C].
Upper = APInt::getAllOnes(Width).lshr(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
// 'lshr C, x' produces [C >> (Width-1), C].
unsigned ShiftAmount = Width - 1;
if (!C->isZero() && IIQ.isExact(&BO))
ShiftAmount = C->countr_zero();
Lower = C->lshr(ShiftAmount);
Upper = *C + 1;
}
break;
case Instruction::Shl:
if (match(BO.getOperand(0), m_APInt(C))) {
if (IIQ.hasNoUnsignedWrap(&BO)) {
// 'shl nuw C, x' produces [C, C << CLZ(C)]
Lower = *C;
Upper = Lower.shl(Lower.countl_zero()) + 1;
} else if (BO.hasNoSignedWrap()) { // TODO: What if both nuw+nsw?
if (C->isNegative()) {
// 'shl nsw C, x' produces [C << CLO(C)-1, C]
unsigned ShiftAmount = C->countl_one() - 1;
Lower = C->shl(ShiftAmount);
Upper = *C + 1;
} else {
// 'shl nsw C, x' produces [C, C << CLZ(C)-1]
unsigned ShiftAmount = C->countl_zero() - 1;
Lower = *C;
Upper = C->shl(ShiftAmount) + 1;
}
} else {
// If lowbit is set, value can never be zero.
if ((*C)[0])
Lower = APInt::getOneBitSet(Width, 0);
// If we are shifting a constant the largest it can be is if the longest
// sequence of consecutive ones is shifted to the highbits (breaking
// ties for which sequence is higher). At the moment we take a liberal
// upper bound on this by just popcounting the constant.
// TODO: There may be a bitwise trick for it longest/highest
// consecutative sequence of ones (naive method is O(Width) loop).
Upper = APInt::getHighBitsSet(Width, C->popcount()) + 1;
}
} else if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
Upper = APInt::getBitsSetFrom(Width, C->getZExtValue()) + 1;
}
break;
case Instruction::SDiv:
if (match(BO.getOperand(1), m_APInt(C))) {
APInt IntMin = APInt::getSignedMinValue(Width);
APInt IntMax = APInt::getSignedMaxValue(Width);
if (C->isAllOnes()) {
// 'sdiv x, -1' produces [INT_MIN + 1, INT_MAX]
// where C != -1 and C != 0 and C != 1
Lower = IntMin + 1;
Upper = IntMax + 1;
} else if (C->countl_zero() < Width - 1) {
// 'sdiv x, C' produces [INT_MIN / C, INT_MAX / C]
// where C != -1 and C != 0 and C != 1
Lower = IntMin.sdiv(*C);
Upper = IntMax.sdiv(*C);
if (Lower.sgt(Upper))
std::swap(Lower, Upper);
Upper = Upper + 1;
assert(Upper != Lower && "Upper part of range has wrapped!");
}
} else if (match(BO.getOperand(0), m_APInt(C))) {
if (C->isMinSignedValue()) {
// 'sdiv INT_MIN, x' produces [INT_MIN, INT_MIN / -2].
Lower = *C;
Upper = Lower.lshr(1) + 1;
} else {
// 'sdiv C, x' produces [-|C|, |C|].
Upper = C->abs() + 1;
Lower = (-Upper) + 1;
}
}
break;
case Instruction::UDiv:
if (match(BO.getOperand(1), m_APInt(C)) && !C->isZero()) {
// 'udiv x, C' produces [0, UINT_MAX / C].
Upper = APInt::getMaxValue(Width).udiv(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
// 'udiv C, x' produces [0, C].
Upper = *C + 1;
}
break;
case Instruction::SRem:
if (match(BO.getOperand(1), m_APInt(C))) {
// 'srem x, C' produces (-|C|, |C|).
Upper = C->abs();
Lower = (-Upper) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
if (C->isNegative()) {
// 'srem -|C|, x' produces [-|C|, 0].
Upper = 1;
Lower = *C;
} else {
// 'srem |C|, x' produces [0, |C|].
Upper = *C + 1;
}
}
break;
case Instruction::URem:
if (match(BO.getOperand(1), m_APInt(C)))
// 'urem x, C' produces [0, C).
Upper = *C;
else if (match(BO.getOperand(0), m_APInt(C)))
// 'urem C, x' produces [0, C].
Upper = *C + 1;
break;
default:
break;
}
}
static ConstantRange getRangeForIntrinsic(const IntrinsicInst &II) {
unsigned Width = II.getType()->getScalarSizeInBits();
const APInt *C;
switch (II.getIntrinsicID()) {
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
// Maximum of set/clear bits is the bit width.
return ConstantRange::getNonEmpty(APInt::getZero(Width),
APInt(Width, Width + 1));
case Intrinsic::uadd_sat:
// uadd.sat(x, C) produces [C, UINT_MAX].
if (match(II.getOperand(0), m_APInt(C)) ||
match(II.getOperand(1), m_APInt(C)))
return ConstantRange::getNonEmpty(*C, APInt::getZero(Width));
break;
case Intrinsic::sadd_sat:
if (match(II.getOperand(0), m_APInt(C)) ||
match(II.getOperand(1), m_APInt(C))) {
if (C->isNegative())
// sadd.sat(x, -C) produces [SINT_MIN, SINT_MAX + (-C)].
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width),
APInt::getSignedMaxValue(Width) + *C +
1);
// sadd.sat(x, +C) produces [SINT_MIN + C, SINT_MAX].
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width) + *C,
APInt::getSignedMaxValue(Width) + 1);
}
break;
case Intrinsic::usub_sat:
// usub.sat(C, x) produces [0, C].
if (match(II.getOperand(0), m_APInt(C)))
return ConstantRange::getNonEmpty(APInt::getZero(Width), *C + 1);
// usub.sat(x, C) produces [0, UINT_MAX - C].
if (match(II.getOperand(1), m_APInt(C)))
return ConstantRange::getNonEmpty(APInt::getZero(Width),
APInt::getMaxValue(Width) - *C + 1);
break;
case Intrinsic::ssub_sat:
if (match(II.getOperand(0), m_APInt(C))) {
if (C->isNegative())
// ssub.sat(-C, x) produces [SINT_MIN, -SINT_MIN + (-C)].
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width),
*C - APInt::getSignedMinValue(Width) +
1);
// ssub.sat(+C, x) produces [-SINT_MAX + C, SINT_MAX].
return ConstantRange::getNonEmpty(*C - APInt::getSignedMaxValue(Width),
APInt::getSignedMaxValue(Width) + 1);
} else if (match(II.getOperand(1), m_APInt(C))) {
if (C->isNegative())
// ssub.sat(x, -C) produces [SINT_MIN - (-C), SINT_MAX]:
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width) - *C,
APInt::getSignedMaxValue(Width) + 1);
// ssub.sat(x, +C) produces [SINT_MIN, SINT_MAX - C].
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width),
APInt::getSignedMaxValue(Width) - *C +
1);
}
break;
case Intrinsic::umin:
case Intrinsic::umax:
case Intrinsic::smin:
case Intrinsic::smax:
if (!match(II.getOperand(0), m_APInt(C)) &&
!match(II.getOperand(1), m_APInt(C)))
break;
switch (II.getIntrinsicID()) {
case Intrinsic::umin:
return ConstantRange::getNonEmpty(APInt::getZero(Width), *C + 1);
case Intrinsic::umax:
return ConstantRange::getNonEmpty(*C, APInt::getZero(Width));
case Intrinsic::smin:
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(Width),
*C + 1);
case Intrinsic::smax:
return ConstantRange::getNonEmpty(*C,
APInt::getSignedMaxValue(Width) + 1);
default:
llvm_unreachable("Must be min/max intrinsic");
}
break;
case Intrinsic::abs:
// If abs of SIGNED_MIN is poison, then the result is [0..SIGNED_MAX],
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
if (match(II.getOperand(1), m_One()))
return ConstantRange::getNonEmpty(APInt::getZero(Width),
APInt::getSignedMaxValue(Width) + 1);
return ConstantRange::getNonEmpty(APInt::getZero(Width),
APInt::getSignedMinValue(Width) + 1);
case Intrinsic::vscale:
if (!II.getParent() || !II.getFunction())
break;
return getVScaleRange(II.getFunction(), Width);
default:
break;
}
return ConstantRange::getFull(Width);
}
static ConstantRange getRangeForSelectPattern(const SelectInst &SI,
const InstrInfoQuery &IIQ) {
unsigned BitWidth = SI.getType()->getScalarSizeInBits();
const Value *LHS = nullptr, *RHS = nullptr;
SelectPatternResult R = matchSelectPattern(&SI, LHS, RHS);
if (R.Flavor == SPF_UNKNOWN)
return ConstantRange::getFull(BitWidth);
if (R.Flavor == SelectPatternFlavor::SPF_ABS) {
// If the negation part of the abs (in RHS) has the NSW flag,
// then the result of abs(X) is [0..SIGNED_MAX],
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
if (match(RHS, m_Neg(m_Specific(LHS))) &&
IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
return ConstantRange::getNonEmpty(APInt::getZero(BitWidth),
APInt::getSignedMaxValue(BitWidth) + 1);
return ConstantRange::getNonEmpty(APInt::getZero(BitWidth),
APInt::getSignedMinValue(BitWidth) + 1);
}
if (R.Flavor == SelectPatternFlavor::SPF_NABS) {
// The result of -abs(X) is <= 0.
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(BitWidth),
APInt(BitWidth, 1));
}
const APInt *C;
if (!match(LHS, m_APInt(C)) && !match(RHS, m_APInt(C)))
return ConstantRange::getFull(BitWidth);
switch (R.Flavor) {
case SPF_UMIN:
return ConstantRange::getNonEmpty(APInt::getZero(BitWidth), *C + 1);
case SPF_UMAX:
return ConstantRange::getNonEmpty(*C, APInt::getZero(BitWidth));
case SPF_SMIN:
return ConstantRange::getNonEmpty(APInt::getSignedMinValue(BitWidth),
*C + 1);
case SPF_SMAX:
return ConstantRange::getNonEmpty(*C,
APInt::getSignedMaxValue(BitWidth) + 1);
default:
return ConstantRange::getFull(BitWidth);
}
}
static void setLimitForFPToI(const Instruction *I, APInt &Lower, APInt &Upper) {
// The maximum representable value of a half is 65504. For floats the maximum
// value is 3.4e38 which requires roughly 129 bits.
unsigned BitWidth = I->getType()->getScalarSizeInBits();
if (!I->getOperand(0)->getType()->getScalarType()->isHalfTy())
return;
if (isa<FPToSIInst>(I) && BitWidth >= 17) {
Lower = APInt(BitWidth, -65504);
Upper = APInt(BitWidth, 65505);
}
if (isa<FPToUIInst>(I) && BitWidth >= 16) {
// For a fptoui the lower limit is left as 0.
Upper = APInt(BitWidth, 65505);
}
}
ConstantRange llvm::computeConstantRange(const Value *V, bool ForSigned,
bool UseInstrInfo, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT,
unsigned Depth) {
assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction");
if (Depth == MaxAnalysisRecursionDepth)
return ConstantRange::getFull(V->getType()->getScalarSizeInBits());
const APInt *C;
if (match(V, m_APInt(C)))
return ConstantRange(*C);
unsigned BitWidth = V->getType()->getScalarSizeInBits();
if (auto *VC = dyn_cast<ConstantDataVector>(V)) {
ConstantRange CR = ConstantRange::getEmpty(BitWidth);
for (unsigned ElemIdx = 0, NElem = VC->getNumElements(); ElemIdx < NElem;
++ElemIdx)
CR = CR.unionWith(VC->getElementAsAPInt(ElemIdx));
return CR;
}
InstrInfoQuery IIQ(UseInstrInfo);
ConstantRange CR = ConstantRange::getFull(BitWidth);
if (auto *BO = dyn_cast<BinaryOperator>(V)) {
APInt Lower = APInt(BitWidth, 0);
APInt Upper = APInt(BitWidth, 0);
// TODO: Return ConstantRange.
setLimitsForBinOp(*BO, Lower, Upper, IIQ, ForSigned);
CR = ConstantRange::getNonEmpty(Lower, Upper);
} else if (auto *II = dyn_cast<IntrinsicInst>(V))
CR = getRangeForIntrinsic(*II);
else if (auto *SI = dyn_cast<SelectInst>(V)) {
ConstantRange CRTrue = computeConstantRange(
SI->getTrueValue(), ForSigned, UseInstrInfo, AC, CtxI, DT, Depth + 1);
ConstantRange CRFalse = computeConstantRange(
SI->getFalseValue(), ForSigned, UseInstrInfo, AC, CtxI, DT, Depth + 1);
CR = CRTrue.unionWith(CRFalse);
CR = CR.intersectWith(getRangeForSelectPattern(*SI, IIQ));
} else if (isa<FPToUIInst>(V) || isa<FPToSIInst>(V)) {
APInt Lower = APInt(BitWidth, 0);
APInt Upper = APInt(BitWidth, 0);
// TODO: Return ConstantRange.
setLimitForFPToI(cast<Instruction>(V), Lower, Upper);
CR = ConstantRange::getNonEmpty(Lower, Upper);
} else if (const auto *A = dyn_cast<Argument>(V))
if (std::optional<ConstantRange> Range = A->getRange())
CR = *Range;
if (auto *I = dyn_cast<Instruction>(V)) {
if (auto *Range = IIQ.getMetadata(I, LLVMContext::MD_range))
CR = CR.intersectWith(getConstantRangeFromMetadata(*Range));
if (const auto *CB = dyn_cast<CallBase>(V))
if (std::optional<ConstantRange> Range = CB->getRange())
CR = CR.intersectWith(*Range);
}
if (CtxI && AC) {
// Try to restrict the range based on information from assumptions.
for (auto &AssumeVH : AC->assumptionsFor(V)) {
if (!AssumeVH)
continue;
CallInst *I = cast<CallInst>(AssumeVH);
assert(I->getParent()->getParent() == CtxI->getParent()->getParent() &&
"Got assumption for the wrong function!");
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
"must be an assume intrinsic");
if (!isValidAssumeForContext(I, CtxI, DT))
continue;
Value *Arg = I->getArgOperand(0);
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
// Currently we just use information from comparisons.
if (!Cmp || Cmp->getOperand(0) != V)
continue;
// TODO: Set "ForSigned" parameter via Cmp->isSigned()?
ConstantRange RHS =
computeConstantRange(Cmp->getOperand(1), /* ForSigned */ false,
UseInstrInfo, AC, I, DT, Depth + 1);
CR = CR.intersectWith(
ConstantRange::makeAllowedICmpRegion(Cmp->getPredicate(), RHS));
}
}
return CR;
}
static void
addValueAffectedByCondition(Value *V,
function_ref<void(Value *)> InsertAffected) {
assert(V != nullptr);
if (isa<Argument>(V) || isa<GlobalValue>(V)) {
InsertAffected(V);
} else if (auto *I = dyn_cast<Instruction>(V)) {
InsertAffected(V);
// Peek through unary operators to find the source of the condition.
Value *Op;
if (match(I, m_CombineOr(m_PtrToInt(m_Value(Op)), m_Trunc(m_Value(Op))))) {
if (isa<Instruction>(Op) || isa<Argument>(Op))
InsertAffected(Op);
}
}
}
void llvm::findValuesAffectedByCondition(
Value *Cond, bool IsAssume, function_ref<void(Value *)> InsertAffected) {
auto AddAffected = [&InsertAffected](Value *V) {
addValueAffectedByCondition(V, InsertAffected);
};
auto AddCmpOperands = [&AddAffected, IsAssume](Value *LHS, Value *RHS) {
if (IsAssume) {
AddAffected(LHS);
AddAffected(RHS);
} else if (match(RHS, m_Constant()))
AddAffected(LHS);
};
SmallVector<Value *, 8> Worklist;
SmallPtrSet<Value *, 8> Visited;
Worklist.push_back(Cond);
while (!Worklist.empty()) {
Value *V = Worklist.pop_back_val();
if (!Visited.insert(V).second)
continue;
CmpInst::Predicate Pred;
Value *A, *B, *X;
if (IsAssume) {
AddAffected(V);
if (match(V, m_Not(m_Value(X))))
AddAffected(X);
}
if (match(V, m_LogicalOp(m_Value(A), m_Value(B)))) {
// assume(A && B) is split to -> assume(A); assume(B);
// assume(!(A || B)) is split to -> assume(!A); assume(!B);
// Finally, assume(A || B) / assume(!(A && B)) generally don't provide
// enough information to be worth handling (intersection of information as
// opposed to union).
if (!IsAssume) {
Worklist.push_back(A);
Worklist.push_back(B);
}
} else if (match(V, m_ICmp(Pred, m_Value(A), m_Value(B)))) {
AddCmpOperands(A, B);
if (ICmpInst::isEquality(Pred)) {
if (match(B, m_ConstantInt())) {
Value *Y;
// (X & C) or (X | C) or (X ^ C).
// (X << C) or (X >>_s C) or (X >>_u C).
if (match(A, m_BitwiseLogic(m_Value(X), m_ConstantInt())) ||
match(A, m_Shift(m_Value(X), m_ConstantInt())))
AddAffected(X);
else if (match(A, m_And(m_Value(X), m_Value(Y))) ||
match(A, m_Or(m_Value(X), m_Value(Y)))) {
AddAffected(X);
AddAffected(Y);
}
}
} else {
if (match(B, m_ConstantInt())) {
// Handle (A + C1) u< C2, which is the canonical form of
// A > C3 && A < C4.
if (match(A, m_AddLike(m_Value(X), m_ConstantInt())))
AddAffected(X);
Value *Y;
// X & Y u> C -> X >u C && Y >u C
// X | Y u< C -> X u< C && Y u< C
if (ICmpInst::isUnsigned(Pred) &&
(match(A, m_And(m_Value(X), m_Value(Y))) ||
match(A, m_Or(m_Value(X), m_Value(Y))))) {
AddAffected(X);
AddAffected(Y);
}
}
// Handle icmp slt/sgt (bitcast X to int), 0/-1, which is supported
// by computeKnownFPClass().
if (match(A, m_ElementWiseBitCast(m_Value(X)))) {
if (Pred == ICmpInst::ICMP_SLT && match(B, m_Zero()))
InsertAffected(X);
else if (Pred == ICmpInst::ICMP_SGT && match(B, m_AllOnes()))
InsertAffected(X);
}
}
} else if (match(Cond, m_FCmp(Pred, m_Value(A), m_Value(B)))) {
AddCmpOperands(A, B);
// fcmp fneg(x), y
// fcmp fabs(x), y
// fcmp fneg(fabs(x)), y
if (match(A, m_FNeg(m_Value(A))))
AddAffected(A);
if (match(A, m_FAbs(m_Value(A))))
AddAffected(A);
} else if (match(V, m_Intrinsic<Intrinsic::is_fpclass>(m_Value(A),
m_Value()))) {
// Handle patterns that computeKnownFPClass() support.
AddAffected(A);
}
}
}