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llvm / llvm-project / ee17ca77e50a2170dd79f31e109f6751235e098e / . / llvm / lib / Transforms / InstCombine / InstructionCombining.cpp
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//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
// instructions. This pass does not modify the CFG. This pass is where
// algebraic simplification happens.
//
// This pass combines things like:
// %Y = add i32 %X, 1
// %Z = add i32 %Y, 1
// into:
// %Z = add i32 %X, 2
//
// This is a simple worklist driven algorithm.
//
// This pass guarantees that the following canonicalizations are performed on
// the program:
// 1. If a binary operator has a constant operand, it is moved to the RHS
// 2. Bitwise operators with constant operands are always grouped so that
// shifts are performed first, then or's, then and's, then xor's.
// 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible
// 4. All cmp instructions on boolean values are replaced with logical ops
// 5. add X, X is represented as (X*2) => (X << 1)
// 6. Multiplies with a power-of-two constant argument are transformed into
// shifts.
// ... etc.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LastRunTrackingAnalysis.h"
#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/Utils/Local.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/EHPersonalities.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.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/Metadata.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/KnownFPClass.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <memory>
#include <optional>
#include <string>
#include <utility>
#define DEBUG_TYPE "instcombine"
#include "llvm/Transforms/Utils/InstructionWorklist.h"
#include <optional>
using namespace llvm;
using namespace llvm::PatternMatch;
STATISTIC(NumWorklistIterations,
"Number of instruction combining iterations performed");
STATISTIC(NumOneIteration, "Number of functions with one iteration");
STATISTIC(NumTwoIterations, "Number of functions with two iterations");
STATISTIC(NumThreeIterations, "Number of functions with three iterations");
STATISTIC(NumFourOrMoreIterations,
"Number of functions with four or more iterations");
STATISTIC(NumCombined , "Number of insts combined");
STATISTIC(NumConstProp, "Number of constant folds");
STATISTIC(NumDeadInst , "Number of dead inst eliminated");
STATISTIC(NumSunkInst , "Number of instructions sunk");
STATISTIC(NumExpand, "Number of expansions");
STATISTIC(NumFactor , "Number of factorizations");
STATISTIC(NumReassoc , "Number of reassociations");
DEBUG_COUNTER(VisitCounter, "instcombine-visit",
"Controls which instructions are visited");
static cl::opt<bool>
EnableCodeSinking("instcombine-code-sinking", cl::desc("Enable code sinking"),
cl::init(true));
static cl::opt<unsigned> MaxSinkNumUsers(
"instcombine-max-sink-users", cl::init(32),
cl::desc("Maximum number of undroppable users for instruction sinking"));
static cl::opt<unsigned>
MaxArraySize("instcombine-maxarray-size", cl::init(1024),
cl::desc("Maximum array size considered when doing a combine"));
// FIXME: Remove this flag when it is no longer necessary to convert
// llvm.dbg.declare to avoid inaccurate debug info. Setting this to false
// increases variable availability at the cost of accuracy. Variables that
// cannot be promoted by mem2reg or SROA will be described as living in memory
// for their entire lifetime. However, passes like DSE and instcombine can
// delete stores to the alloca, leading to misleading and inaccurate debug
// information. This flag can be removed when those passes are fixed.
static cl::opt<unsigned> ShouldLowerDbgDeclare("instcombine-lower-dbg-declare",
cl::Hidden, cl::init(true));
std::optional<Instruction *>
InstCombiner::targetInstCombineIntrinsic(IntrinsicInst &II) {
// Handle target specific intrinsics
if (II.getCalledFunction()->isTargetIntrinsic()) {
return TTIForTargetIntrinsicsOnly.instCombineIntrinsic(*this, II);
}
return std::nullopt;
}
std::optional<Value *> InstCombiner::targetSimplifyDemandedUseBitsIntrinsic(
IntrinsicInst &II, APInt DemandedMask, KnownBits &Known,
bool &KnownBitsComputed) {
// Handle target specific intrinsics
if (II.getCalledFunction()->isTargetIntrinsic()) {
return TTIForTargetIntrinsicsOnly.simplifyDemandedUseBitsIntrinsic(
*this, II, DemandedMask, Known, KnownBitsComputed);
}
return std::nullopt;
}
std::optional<Value *> InstCombiner::targetSimplifyDemandedVectorEltsIntrinsic(
IntrinsicInst &II, APInt DemandedElts, APInt &PoisonElts,
APInt &PoisonElts2, APInt &PoisonElts3,
std::function<void(Instruction *, unsigned, APInt, APInt &)>
SimplifyAndSetOp) {
// Handle target specific intrinsics
if (II.getCalledFunction()->isTargetIntrinsic()) {
return TTIForTargetIntrinsicsOnly.simplifyDemandedVectorEltsIntrinsic(
*this, II, DemandedElts, PoisonElts, PoisonElts2, PoisonElts3,
SimplifyAndSetOp);
}
return std::nullopt;
}
bool InstCombiner::isValidAddrSpaceCast(unsigned FromAS, unsigned ToAS) const {
// Approved exception for TTI use: This queries a legality property of the
// target, not an profitability heuristic. Ideally this should be part of
// DataLayout instead.
return TTIForTargetIntrinsicsOnly.isValidAddrSpaceCast(FromAS, ToAS);
}
Value *InstCombinerImpl::EmitGEPOffset(GEPOperator *GEP, bool RewriteGEP) {
if (!RewriteGEP)
return llvm::emitGEPOffset(&Builder, DL, GEP);
IRBuilderBase::InsertPointGuard Guard(Builder);
auto *Inst = dyn_cast<Instruction>(GEP);
if (Inst)
Builder.SetInsertPoint(Inst);
Value *Offset = EmitGEPOffset(GEP);
// If a non-trivial GEP has other uses, rewrite it to avoid duplicating
// the offset arithmetic.
if (Inst && !GEP->hasOneUse() && !GEP->hasAllConstantIndices() &&
!GEP->getSourceElementType()->isIntegerTy(8)) {
replaceInstUsesWith(
*Inst, Builder.CreateGEP(Builder.getInt8Ty(), GEP->getPointerOperand(),
Offset, "", GEP->getNoWrapFlags()));
eraseInstFromFunction(*Inst);
}
return Offset;
}
/// Legal integers and common types are considered desirable. This is used to
/// avoid creating instructions with types that may not be supported well by the
/// the backend.
/// NOTE: This treats i8, i16 and i32 specially because they are common
/// types in frontend languages.
bool InstCombinerImpl::isDesirableIntType(unsigned BitWidth) const {
switch (BitWidth) {
case 8:
case 16:
case 32:
return true;
default:
return DL.isLegalInteger(BitWidth);
}
}
/// Return true if it is desirable to convert an integer computation from a
/// given bit width to a new bit width.
/// We don't want to convert from a legal or desirable type (like i8) to an
/// illegal type or from a smaller to a larger illegal type. A width of '1'
/// is always treated as a desirable type because i1 is a fundamental type in
/// IR, and there are many specialized optimizations for i1 types.
/// Common/desirable widths are equally treated as legal to convert to, in
/// order to open up more combining opportunities.
bool InstCombinerImpl::shouldChangeType(unsigned FromWidth,
unsigned ToWidth) const {
bool FromLegal = FromWidth == 1 || DL.isLegalInteger(FromWidth);
bool ToLegal = ToWidth == 1 || DL.isLegalInteger(ToWidth);
// Convert to desirable widths even if they are not legal types.
// Only shrink types, to prevent infinite loops.
if (ToWidth < FromWidth && isDesirableIntType(ToWidth))
return true;
// If this is a legal or desiable integer from type, and the result would be
// an illegal type, don't do the transformation.
if ((FromLegal || isDesirableIntType(FromWidth)) && !ToLegal)
return false;
// Otherwise, if both are illegal, do not increase the size of the result. We
// do allow things like i160 -> i64, but not i64 -> i160.
if (!FromLegal && !ToLegal && ToWidth > FromWidth)
return false;
return true;
}
/// Return true if it is desirable to convert a computation from 'From' to 'To'.
/// We don't want to convert from a legal to an illegal type or from a smaller
/// to a larger illegal type. i1 is always treated as a legal type because it is
/// a fundamental type in IR, and there are many specialized optimizations for
/// i1 types.
bool InstCombinerImpl::shouldChangeType(Type *From, Type *To) const {
// TODO: This could be extended to allow vectors. Datalayout changes might be
// needed to properly support that.
if (!From->isIntegerTy() || !To->isIntegerTy())
return false;
unsigned FromWidth = From->getPrimitiveSizeInBits();
unsigned ToWidth = To->getPrimitiveSizeInBits();
return shouldChangeType(FromWidth, ToWidth);
}
// Return true, if No Signed Wrap should be maintained for I.
// The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C",
// where both B and C should be ConstantInts, results in a constant that does
// not overflow. This function only handles the Add/Sub/Mul opcodes. For
// all other opcodes, the function conservatively returns false.
static bool maintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) {
auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
if (!OBO || !OBO->hasNoSignedWrap())
return false;
const APInt *BVal, *CVal;
if (!match(B, m_APInt(BVal)) || !match(C, m_APInt(CVal)))
return false;
// We reason about Add/Sub/Mul Only.
bool Overflow = false;
switch (I.getOpcode()) {
case Instruction::Add:
(void)BVal->sadd_ov(*CVal, Overflow);
break;
case Instruction::Sub:
(void)BVal->ssub_ov(*CVal, Overflow);
break;
case Instruction::Mul:
(void)BVal->smul_ov(*CVal, Overflow);
break;
default:
// Conservatively return false for other opcodes.
return false;
}
return !Overflow;
}
static bool hasNoUnsignedWrap(BinaryOperator &I) {
auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
return OBO && OBO->hasNoUnsignedWrap();
}
static bool hasNoSignedWrap(BinaryOperator &I) {
auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
return OBO && OBO->hasNoSignedWrap();
}
/// Conservatively clears subclassOptionalData after a reassociation or
/// commutation. We preserve fast-math flags when applicable as they can be
/// preserved.
static void ClearSubclassDataAfterReassociation(BinaryOperator &I) {
FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I);
if (!FPMO) {
I.clearSubclassOptionalData();
return;
}
FastMathFlags FMF = I.getFastMathFlags();
I.clearSubclassOptionalData();
I.setFastMathFlags(FMF);
}
/// Combine constant operands of associative operations either before or after a
/// cast to eliminate one of the associative operations:
/// (op (cast (op X, C2)), C1) --> (cast (op X, op (C1, C2)))
/// (op (cast (op X, C2)), C1) --> (op (cast X), op (C1, C2))
static bool simplifyAssocCastAssoc(BinaryOperator *BinOp1,
InstCombinerImpl &IC) {
auto *Cast = dyn_cast<CastInst>(BinOp1->getOperand(0));
if (!Cast || !Cast->hasOneUse())
return false;
// TODO: Enhance logic for other casts and remove this check.
auto CastOpcode = Cast->getOpcode();
if (CastOpcode != Instruction::ZExt)
return false;
// TODO: Enhance logic for other BinOps and remove this check.
if (!BinOp1->isBitwiseLogicOp())
return false;
auto AssocOpcode = BinOp1->getOpcode();
auto *BinOp2 = dyn_cast<BinaryOperator>(Cast->getOperand(0));
if (!BinOp2 || !BinOp2->hasOneUse() || BinOp2->getOpcode() != AssocOpcode)
return false;
Constant *C1, *C2;
if (!match(BinOp1->getOperand(1), m_Constant(C1)) ||
!match(BinOp2->getOperand(1), m_Constant(C2)))
return false;
// TODO: This assumes a zext cast.
// Eg, if it was a trunc, we'd cast C1 to the source type because casting C2
// to the destination type might lose bits.
// Fold the constants together in the destination type:
// (op (cast (op X, C2)), C1) --> (op (cast X), FoldedC)
const DataLayout &DL = IC.getDataLayout();
Type *DestTy = C1->getType();
Constant *CastC2 = ConstantFoldCastOperand(CastOpcode, C2, DestTy, DL);
if (!CastC2)
return false;
Constant *FoldedC = ConstantFoldBinaryOpOperands(AssocOpcode, C1, CastC2, DL);
if (!FoldedC)
return false;
IC.replaceOperand(*Cast, 0, BinOp2->getOperand(0));
IC.replaceOperand(*BinOp1, 1, FoldedC);
BinOp1->dropPoisonGeneratingFlags();
Cast->dropPoisonGeneratingFlags();
return true;
}
// Simplifies IntToPtr/PtrToInt RoundTrip Cast.
// inttoptr ( ptrtoint (x) ) --> x
Value *InstCombinerImpl::simplifyIntToPtrRoundTripCast(Value *Val) {
auto *IntToPtr = dyn_cast<IntToPtrInst>(Val);
if (IntToPtr && DL.getTypeSizeInBits(IntToPtr->getDestTy()) ==
DL.getTypeSizeInBits(IntToPtr->getSrcTy())) {
auto *PtrToInt = dyn_cast<PtrToIntInst>(IntToPtr->getOperand(0));
Type *CastTy = IntToPtr->getDestTy();
if (PtrToInt &&
CastTy->getPointerAddressSpace() ==
PtrToInt->getSrcTy()->getPointerAddressSpace() &&
DL.getTypeSizeInBits(PtrToInt->getSrcTy()) ==
DL.getTypeSizeInBits(PtrToInt->getDestTy()))
return PtrToInt->getOperand(0);
}
return nullptr;
}
/// This performs a few simplifications for operators that are associative or
/// commutative:
///
/// Commutative operators:
///
/// 1. Order operands such that they are listed from right (least complex) to
/// left (most complex). This puts constants before unary operators before
/// binary operators.
///
/// Associative operators:
///
/// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
/// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
///
/// Associative and commutative operators:
///
/// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
/// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
/// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
/// if C1 and C2 are constants.
bool InstCombinerImpl::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
Instruction::BinaryOps Opcode = I.getOpcode();
bool Changed = false;
do {
// Order operands such that they are listed from right (least complex) to
// left (most complex). This puts constants before unary operators before
// binary operators.
if (I.isCommutative() && getComplexity(I.getOperand(0)) <
getComplexity(I.getOperand(1)))
Changed = !I.swapOperands();
if (I.isCommutative()) {
if (auto Pair = matchSymmetricPair(I.getOperand(0), I.getOperand(1))) {
replaceOperand(I, 0, Pair->first);
replaceOperand(I, 1, Pair->second);
Changed = true;
}
}
BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0));
BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1));
if (I.isAssociative()) {
// Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
if (Op0 && Op0->getOpcode() == Opcode) {
Value *A = Op0->getOperand(0);
Value *B = Op0->getOperand(1);
Value *C = I.getOperand(1);
// Does "B op C" simplify?
if (Value *V = simplifyBinOp(Opcode, B, C, SQ.getWithInstruction(&I))) {
// It simplifies to V. Form "A op V".
replaceOperand(I, 0, A);
replaceOperand(I, 1, V);
bool IsNUW = hasNoUnsignedWrap(I) && hasNoUnsignedWrap(*Op0);
bool IsNSW = maintainNoSignedWrap(I, B, C) && hasNoSignedWrap(*Op0);
// Conservatively clear all optional flags since they may not be
// preserved by the reassociation. Reset nsw/nuw based on the above
// analysis.
ClearSubclassDataAfterReassociation(I);
// Note: this is only valid because SimplifyBinOp doesn't look at
// the operands to Op0.
if (IsNUW)
I.setHasNoUnsignedWrap(true);
if (IsNSW)
I.setHasNoSignedWrap(true);
Changed = true;
++NumReassoc;
continue;
}
}
// Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
if (Op1 && Op1->getOpcode() == Opcode) {
Value *A = I.getOperand(0);
Value *B = Op1->getOperand(0);
Value *C = Op1->getOperand(1);
// Does "A op B" simplify?
if (Value *V = simplifyBinOp(Opcode, A, B, SQ.getWithInstruction(&I))) {
// It simplifies to V. Form "V op C".
replaceOperand(I, 0, V);
replaceOperand(I, 1, C);
// Conservatively clear the optional flags, since they may not be
// preserved by the reassociation.
ClearSubclassDataAfterReassociation(I);
Changed = true;
++NumReassoc;
continue;
}
}
}
if (I.isAssociative() && I.isCommutative()) {
if (simplifyAssocCastAssoc(&I, *this)) {
Changed = true;
++NumReassoc;
continue;
}
// Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
if (Op0 && Op0->getOpcode() == Opcode) {
Value *A = Op0->getOperand(0);
Value *B = Op0->getOperand(1);
Value *C = I.getOperand(1);
// Does "C op A" simplify?
if (Value *V = simplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) {
// It simplifies to V. Form "V op B".
replaceOperand(I, 0, V);
replaceOperand(I, 1, B);
// Conservatively clear the optional flags, since they may not be
// preserved by the reassociation.
ClearSubclassDataAfterReassociation(I);
Changed = true;
++NumReassoc;
continue;
}
}
// Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
if (Op1 && Op1->getOpcode() == Opcode) {
Value *A = I.getOperand(0);
Value *B = Op1->getOperand(0);
Value *C = Op1->getOperand(1);
// Does "C op A" simplify?
if (Value *V = simplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) {
// It simplifies to V. Form "B op V".
replaceOperand(I, 0, B);
replaceOperand(I, 1, V);
// Conservatively clear the optional flags, since they may not be
// preserved by the reassociation.
ClearSubclassDataAfterReassociation(I);
Changed = true;
++NumReassoc;
continue;
}
}
// Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
// if C1 and C2 are constants.
Value *A, *B;
Constant *C1, *C2, *CRes;
if (Op0 && Op1 &&
Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode &&
match(Op0, m_OneUse(m_BinOp(m_Value(A), m_Constant(C1)))) &&
match(Op1, m_OneUse(m_BinOp(m_Value(B), m_Constant(C2)))) &&
(CRes = ConstantFoldBinaryOpOperands(Opcode, C1, C2, DL))) {
bool IsNUW = hasNoUnsignedWrap(I) &&
hasNoUnsignedWrap(*Op0) &&
hasNoUnsignedWrap(*Op1);
BinaryOperator *NewBO = (IsNUW && Opcode == Instruction::Add) ?
BinaryOperator::CreateNUW(Opcode, A, B) :
BinaryOperator::Create(Opcode, A, B);
if (isa<FPMathOperator>(NewBO)) {
FastMathFlags Flags = I.getFastMathFlags() &
Op0->getFastMathFlags() &
Op1->getFastMathFlags();
NewBO->setFastMathFlags(Flags);
}
InsertNewInstWith(NewBO, I.getIterator());
NewBO->takeName(Op1);
replaceOperand(I, 0, NewBO);
replaceOperand(I, 1, CRes);
// Conservatively clear the optional flags, since they may not be
// preserved by the reassociation.
ClearSubclassDataAfterReassociation(I);
if (IsNUW)
I.setHasNoUnsignedWrap(true);
Changed = true;
continue;
}
}
// No further simplifications.
return Changed;
} while (true);
}
/// Return whether "X LOp (Y ROp Z)" is always equal to
/// "(X LOp Y) ROp (X LOp Z)".
static bool leftDistributesOverRight(Instruction::BinaryOps LOp,
Instruction::BinaryOps ROp) {
// X & (Y | Z) <--> (X & Y) | (X & Z)
// X & (Y ^ Z) <--> (X & Y) ^ (X & Z)
if (LOp == Instruction::And)
return ROp == Instruction::Or || ROp == Instruction::Xor;
// X | (Y & Z) <--> (X | Y) & (X | Z)
if (LOp == Instruction::Or)
return ROp == Instruction::And;
// X * (Y + Z) <--> (X * Y) + (X * Z)
// X * (Y - Z) <--> (X * Y) - (X * Z)
if (LOp == Instruction::Mul)
return ROp == Instruction::Add || ROp == Instruction::Sub;
return false;
}
/// Return whether "(X LOp Y) ROp Z" is always equal to
/// "(X ROp Z) LOp (Y ROp Z)".
static bool rightDistributesOverLeft(Instruction::BinaryOps LOp,
Instruction::BinaryOps ROp) {
if (Instruction::isCommutative(ROp))
return leftDistributesOverRight(ROp, LOp);
// (X {&|^} Y) >> Z <--> (X >> Z) {&|^} (Y >> Z) for all shifts.
return Instruction::isBitwiseLogicOp(LOp) && Instruction::isShift(ROp);
// TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z",
// but this requires knowing that the addition does not overflow and other
// such subtleties.
}
/// This function returns identity value for given opcode, which can be used to
/// factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1).
static Value *getIdentityValue(Instruction::BinaryOps Opcode, Value *V) {
if (isa<Constant>(V))
return nullptr;
return ConstantExpr::getBinOpIdentity(Opcode, V->getType());
}
/// This function predicates factorization using distributive laws. By default,
/// it just returns the 'Op' inputs. But for special-cases like
/// 'add(shl(X, 5), ...)', this function will have TopOpcode == Instruction::Add
/// and Op = shl(X, 5). The 'shl' is treated as the more general 'mul X, 32' to
/// allow more factorization opportunities.
static Instruction::BinaryOps
getBinOpsForFactorization(Instruction::BinaryOps TopOpcode, BinaryOperator *Op,
Value *&LHS, Value *&RHS, BinaryOperator *OtherOp) {
assert(Op && "Expected a binary operator");
LHS = Op->getOperand(0);
RHS = Op->getOperand(1);
if (TopOpcode == Instruction::Add || TopOpcode == Instruction::Sub) {
Constant *C;
if (match(Op, m_Shl(m_Value(), m_ImmConstant(C)))) {
// X << C --> X * (1 << C)
RHS = ConstantFoldBinaryInstruction(
Instruction::Shl, ConstantInt::get(Op->getType(), 1), C);
assert(RHS && "Constant folding of immediate constants failed");
return Instruction::Mul;
}
// TODO: We can add other conversions e.g. shr => div etc.
}
if (Instruction::isBitwiseLogicOp(TopOpcode)) {
if (OtherOp && OtherOp->getOpcode() == Instruction::AShr &&
match(Op, m_LShr(m_NonNegative(), m_Value()))) {
// lshr nneg C, X --> ashr nneg C, X
return Instruction::AShr;
}
}
return Op->getOpcode();
}
/// This tries to simplify binary operations by factorizing out common terms
/// (e. g. "(A*B)+(A*C)" -> "A*(B+C)").
static Value *tryFactorization(BinaryOperator &I, const SimplifyQuery &SQ,
InstCombiner::BuilderTy &Builder,
Instruction::BinaryOps InnerOpcode, Value *A,
Value *B, Value *C, Value *D) {
assert(A && B && C && D && "All values must be provided");
Value *V = nullptr;
Value *RetVal = nullptr;
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
// Does "X op' Y" always equal "Y op' X"?
bool InnerCommutative = Instruction::isCommutative(InnerOpcode);
// Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"?
if (leftDistributesOverRight(InnerOpcode, TopLevelOpcode)) {
// Does the instruction have the form "(A op' B) op (A op' D)" or, in the
// commutative case, "(A op' B) op (C op' A)"?
if (A == C || (InnerCommutative && A == D)) {
if (A != C)
std::swap(C, D);
// Consider forming "A op' (B op D)".
// If "B op D" simplifies then it can be formed with no cost.
V = simplifyBinOp(TopLevelOpcode, B, D, SQ.getWithInstruction(&I));
// If "B op D" doesn't simplify then only go on if one of the existing
// operations "A op' B" and "C op' D" will be zapped as no longer used.
if (!V && (LHS->hasOneUse() || RHS->hasOneUse()))
V = Builder.CreateBinOp(TopLevelOpcode, B, D, RHS->getName());
if (V)
RetVal = Builder.CreateBinOp(InnerOpcode, A, V);
}
}
// Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"?
if (!RetVal && rightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) {
// Does the instruction have the form "(A op' B) op (C op' B)" or, in the
// commutative case, "(A op' B) op (B op' D)"?
if (B == D || (InnerCommutative && B == C)) {
if (B != D)
std::swap(C, D);
// Consider forming "(A op C) op' B".
// If "A op C" simplifies then it can be formed with no cost.
V = simplifyBinOp(TopLevelOpcode, A, C, SQ.getWithInstruction(&I));
// If "A op C" doesn't simplify then only go on if one of the existing
// operations "A op' B" and "C op' D" will be zapped as no longer used.
if (!V && (LHS->hasOneUse() || RHS->hasOneUse()))
V = Builder.CreateBinOp(TopLevelOpcode, A, C, LHS->getName());
if (V)
RetVal = Builder.CreateBinOp(InnerOpcode, V, B);
}
}
if (!RetVal)
return nullptr;
++NumFactor;
RetVal->takeName(&I);
// Try to add no-overflow flags to the final value.
if (isa<BinaryOperator>(RetVal)) {
bool HasNSW = false;
bool HasNUW = false;
if (isa<OverflowingBinaryOperator>(&I)) {
HasNSW = I.hasNoSignedWrap();
HasNUW = I.hasNoUnsignedWrap();
}
if (auto *LOBO = dyn_cast<OverflowingBinaryOperator>(LHS)) {
HasNSW &= LOBO->hasNoSignedWrap();
HasNUW &= LOBO->hasNoUnsignedWrap();
}
if (auto *ROBO = dyn_cast<OverflowingBinaryOperator>(RHS)) {
HasNSW &= ROBO->hasNoSignedWrap();
HasNUW &= ROBO->hasNoUnsignedWrap();
}
if (TopLevelOpcode == Instruction::Add && InnerOpcode == Instruction::Mul) {
// We can propagate 'nsw' if we know that
// %Y = mul nsw i16 %X, C
// %Z = add nsw i16 %Y, %X
// =>
// %Z = mul nsw i16 %X, C+1
//
// iff C+1 isn't INT_MIN
const APInt *CInt;
if (match(V, m_APInt(CInt)) && !CInt->isMinSignedValue())
cast<Instruction>(RetVal)->setHasNoSignedWrap(HasNSW);
// nuw can be propagated with any constant or nuw value.
cast<Instruction>(RetVal)->setHasNoUnsignedWrap(HasNUW);
}
}
return RetVal;
}
// If `I` has one Const operand and the other matches `(ctpop (not x))`,
// replace `(ctpop (not x))` with `(sub nuw nsw BitWidth(x), (ctpop x))`.
// This is only useful is the new subtract can fold so we only handle the
// following cases:
// 1) (add/sub/disjoint_or C, (ctpop (not x))
// -> (add/sub/disjoint_or C', (ctpop x))
// 1) (cmp pred C, (ctpop (not x))
// -> (cmp pred C', (ctpop x))
Instruction *InstCombinerImpl::tryFoldInstWithCtpopWithNot(Instruction *I) {
unsigned Opc = I->getOpcode();
unsigned ConstIdx = 1;
switch (Opc) {
default:
return nullptr;
// (ctpop (not x)) <-> (sub nuw nsw BitWidth(x) - (ctpop x))
// We can fold the BitWidth(x) with add/sub/icmp as long the other operand
// is constant.
case Instruction::Sub:
ConstIdx = 0;
break;
case Instruction::ICmp:
// Signed predicates aren't correct in some edge cases like for i2 types, as
// well since (ctpop x) is known [0, log2(BitWidth(x))] almost all signed
// comparisons against it are simplfied to unsigned.
if (cast<ICmpInst>(I)->isSigned())
return nullptr;
break;
case Instruction::Or:
if (!match(I, m_DisjointOr(m_Value(), m_Value())))
return nullptr;
[[fallthrough]];
case Instruction::Add:
break;
}
Value *Op;
// Find ctpop.
if (!match(I->getOperand(1 - ConstIdx),
m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(Op)))))
return nullptr;
Constant *C;
// Check other operand is ImmConstant.
if (!match(I->getOperand(ConstIdx), m_ImmConstant(C)))
return nullptr;
Type *Ty = Op->getType();
Constant *BitWidthC = ConstantInt::get(Ty, Ty->getScalarSizeInBits());
// Need extra check for icmp. Note if this check is true, it generally means
// the icmp will simplify to true/false.
if (Opc == Instruction::ICmp && !cast<ICmpInst>(I)->isEquality()) {
Constant *Cmp =
ConstantFoldCompareInstOperands(ICmpInst::ICMP_UGT, C, BitWidthC, DL);
if (!Cmp || !Cmp->isZeroValue())
return nullptr;
}
// Check we can invert `(not x)` for free.
bool Consumes = false;
if (!isFreeToInvert(Op, Op->hasOneUse(), Consumes) || !Consumes)
return nullptr;
Value *NotOp = getFreelyInverted(Op, Op->hasOneUse(), &Builder);
assert(NotOp != nullptr &&
"Desync between isFreeToInvert and getFreelyInverted");
Value *CtpopOfNotOp = Builder.CreateIntrinsic(Ty, Intrinsic::ctpop, NotOp);
Value *R = nullptr;
// Do the transformation here to avoid potentially introducing an infinite
// loop.
switch (Opc) {
case Instruction::Sub:
R = Builder.CreateAdd(CtpopOfNotOp, ConstantExpr::getSub(C, BitWidthC));
break;
case Instruction::Or:
case Instruction::Add:
R = Builder.CreateSub(ConstantExpr::getAdd(C, BitWidthC), CtpopOfNotOp);
break;
case Instruction::ICmp:
R = Builder.CreateICmp(cast<ICmpInst>(I)->getSwappedPredicate(),
CtpopOfNotOp, ConstantExpr::getSub(BitWidthC, C));
break;
default:
llvm_unreachable("Unhandled Opcode");
}
assert(R != nullptr);
return replaceInstUsesWith(*I, R);
}
// (Binop1 (Binop2 (logic_shift X, C), C1), (logic_shift Y, C))
// IFF
// 1) the logic_shifts match
// 2) either both binops are binops and one is `and` or
// BinOp1 is `and`
// (logic_shift (inv_logic_shift C1, C), C) == C1 or
//
// -> (logic_shift (Binop1 (Binop2 X, inv_logic_shift(C1, C)), Y), C)
//
// (Binop1 (Binop2 (logic_shift X, Amt), Mask), (logic_shift Y, Amt))
// IFF
// 1) the logic_shifts match
// 2) BinOp1 == BinOp2 (if BinOp == `add`, then also requires `shl`).
//
// -> (BinOp (logic_shift (BinOp X, Y)), Mask)
//
// (Binop1 (Binop2 (arithmetic_shift X, Amt), Mask), (arithmetic_shift Y, Amt))
// IFF
// 1) Binop1 is bitwise logical operator `and`, `or` or `xor`
// 2) Binop2 is `not`
//
// -> (arithmetic_shift Binop1((not X), Y), Amt)
Instruction *InstCombinerImpl::foldBinOpShiftWithShift(BinaryOperator &I) {
const DataLayout &DL = I.getDataLayout();
auto IsValidBinOpc = [](unsigned Opc) {
switch (Opc) {
default:
return false;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
// Skip Sub as we only match constant masks which will canonicalize to use
// add.
return true;
}
};
// Check if we can distribute binop arbitrarily. `add` + `lshr` has extra
// constraints.
auto IsCompletelyDistributable = [](unsigned BinOpc1, unsigned BinOpc2,
unsigned ShOpc) {
assert(ShOpc != Instruction::AShr);
return (BinOpc1 != Instruction::Add && BinOpc2 != Instruction::Add) ||
ShOpc == Instruction::Shl;
};
auto GetInvShift = [](unsigned ShOpc) {
assert(ShOpc != Instruction::AShr);
return ShOpc == Instruction::LShr ? Instruction::Shl : Instruction::LShr;
};
auto CanDistributeBinops = [&](unsigned BinOpc1, unsigned BinOpc2,
unsigned ShOpc, Constant *CMask,
Constant *CShift) {
// If the BinOp1 is `and` we don't need to check the mask.
if (BinOpc1 == Instruction::And)
return true;
// For all other possible transfers we need complete distributable
// binop/shift (anything but `add` + `lshr`).
if (!IsCompletelyDistributable(BinOpc1, BinOpc2, ShOpc))
return false;
// If BinOp2 is `and`, any mask works (this only really helps for non-splat
// vecs, otherwise the mask will be simplified and the following check will
// handle it).
if (BinOpc2 == Instruction::And)
return true;
// Otherwise, need mask that meets the below requirement.
// (logic_shift (inv_logic_shift Mask, ShAmt), ShAmt) == Mask
Constant *MaskInvShift =
ConstantFoldBinaryOpOperands(GetInvShift(ShOpc), CMask, CShift, DL);
return ConstantFoldBinaryOpOperands(ShOpc, MaskInvShift, CShift, DL) ==
CMask;
};
auto MatchBinOp = [&](unsigned ShOpnum) -> Instruction * {
Constant *CMask, *CShift;
Value *X, *Y, *ShiftedX, *Mask, *Shift;
if (!match(I.getOperand(ShOpnum),
m_OneUse(m_Shift(m_Value(Y), m_Value(Shift)))))
return nullptr;
if (!match(I.getOperand(1 - ShOpnum),
m_c_BinOp(m_CombineAnd(
m_OneUse(m_Shift(m_Value(X), m_Specific(Shift))),
m_Value(ShiftedX)),
m_Value(Mask))))
return nullptr;
// Make sure we are matching instruction shifts and not ConstantExpr
auto *IY = dyn_cast<Instruction>(I.getOperand(ShOpnum));
auto *IX = dyn_cast<Instruction>(ShiftedX);
if (!IY || !IX)
return nullptr;
// LHS and RHS need same shift opcode
unsigned ShOpc = IY->getOpcode();
if (ShOpc != IX->getOpcode())
return nullptr;
// Make sure binop is real instruction and not ConstantExpr
auto *BO2 = dyn_cast<Instruction>(I.getOperand(1 - ShOpnum));
if (!BO2)
return nullptr;
unsigned BinOpc = BO2->getOpcode();
// Make sure we have valid binops.
if (!IsValidBinOpc(I.getOpcode()) || !IsValidBinOpc(BinOpc))
return nullptr;
if (ShOpc == Instruction::AShr) {
if (Instruction::isBitwiseLogicOp(I.getOpcode()) &&
BinOpc == Instruction::Xor && match(Mask, m_AllOnes())) {
Value *NotX = Builder.CreateNot(X);
Value *NewBinOp = Builder.CreateBinOp(I.getOpcode(), Y, NotX);
return BinaryOperator::Create(
static_cast<Instruction::BinaryOps>(ShOpc), NewBinOp, Shift);
}
return nullptr;
}
// If BinOp1 == BinOp2 and it's bitwise or shl with add, then just
// distribute to drop the shift irrelevant of constants.
if (BinOpc == I.getOpcode() &&
IsCompletelyDistributable(I.getOpcode(), BinOpc, ShOpc)) {
Value *NewBinOp2 = Builder.CreateBinOp(I.getOpcode(), X, Y);
Value *NewBinOp1 = Builder.CreateBinOp(
static_cast<Instruction::BinaryOps>(ShOpc), NewBinOp2, Shift);
return BinaryOperator::Create(I.getOpcode(), NewBinOp1, Mask);
}
// Otherwise we can only distribute by constant shifting the mask, so
// ensure we have constants.
if (!match(Shift, m_ImmConstant(CShift)))
return nullptr;
if (!match(Mask, m_ImmConstant(CMask)))
return nullptr;
// Check if we can distribute the binops.
if (!CanDistributeBinops(I.getOpcode(), BinOpc, ShOpc, CMask, CShift))
return nullptr;
Constant *NewCMask =
ConstantFoldBinaryOpOperands(GetInvShift(ShOpc), CMask, CShift, DL);
Value *NewBinOp2 = Builder.CreateBinOp(
static_cast<Instruction::BinaryOps>(BinOpc), X, NewCMask);
Value *NewBinOp1 = Builder.CreateBinOp(I.getOpcode(), Y, NewBinOp2);
return BinaryOperator::Create(static_cast<Instruction::BinaryOps>(ShOpc),
NewBinOp1, CShift);
};
if (Instruction *R = MatchBinOp(0))
return R;
return MatchBinOp(1);
}
// (Binop (zext C), (select C, T, F))
// -> (select C, (binop 1, T), (binop 0, F))
//
// (Binop (sext C), (select C, T, F))
// -> (select C, (binop -1, T), (binop 0, F))
//
// Attempt to simplify binary operations into a select with folded args, when
// one operand of the binop is a select instruction and the other operand is a
// zext/sext extension, whose value is the select condition.
Instruction *
InstCombinerImpl::foldBinOpOfSelectAndCastOfSelectCondition(BinaryOperator &I) {
// TODO: this simplification may be extended to any speculatable instruction,
// not just binops, and would possibly be handled better in FoldOpIntoSelect.
Instruction::BinaryOps Opc = I.getOpcode();
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
Value *A, *CondVal, *TrueVal, *FalseVal;
Value *CastOp;
auto MatchSelectAndCast = [&](Value *CastOp, Value *SelectOp) {
return match(CastOp, m_ZExtOrSExt(m_Value(A))) &&
A->getType()->getScalarSizeInBits() == 1 &&
match(SelectOp, m_Select(m_Value(CondVal), m_Value(TrueVal),
m_Value(FalseVal)));
};
// Make sure one side of the binop is a select instruction, and the other is a
// zero/sign extension operating on a i1.
if (MatchSelectAndCast(LHS, RHS))
CastOp = LHS;
else if (MatchSelectAndCast(RHS, LHS))
CastOp = RHS;
else
return nullptr;
auto NewFoldedConst = [&](bool IsTrueArm, Value *V) {
bool IsCastOpRHS = (CastOp == RHS);
bool IsZExt = isa<ZExtInst>(CastOp);
Constant *C;
if (IsTrueArm) {
C = Constant::getNullValue(V->getType());
} else if (IsZExt) {
unsigned BitWidth = V->getType()->getScalarSizeInBits();
C = Constant::getIntegerValue(V->getType(), APInt(BitWidth, 1));
} else {
C = Constant::getAllOnesValue(V->getType());
}
return IsCastOpRHS ? Builder.CreateBinOp(Opc, V, C)
: Builder.CreateBinOp(Opc, C, V);
};
// If the value used in the zext/sext is the select condition, or the negated
// of the select condition, the binop can be simplified.
if (CondVal == A) {
Value *NewTrueVal = NewFoldedConst(false, TrueVal);
return SelectInst::Create(CondVal, NewTrueVal,
NewFoldedConst(true, FalseVal));
}
if (match(A, m_Not(m_Specific(CondVal)))) {
Value *NewTrueVal = NewFoldedConst(true, TrueVal);
return SelectInst::Create(CondVal, NewTrueVal,
NewFoldedConst(false, FalseVal));
}
return nullptr;
}
Value *InstCombinerImpl::tryFactorizationFolds(BinaryOperator &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
Value *A, *B, *C, *D;
Instruction::BinaryOps LHSOpcode, RHSOpcode;
if (Op0)
LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B, Op1);
if (Op1)
RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D, Op0);
// The instruction has the form "(A op' B) op (C op' D)". Try to factorize
// a common term.
if (Op0 && Op1 && LHSOpcode == RHSOpcode)
if (Value *V = tryFactorization(I, SQ, Builder, LHSOpcode, A, B, C, D))
return V;
// The instruction has the form "(A op' B) op (C)". Try to factorize common
// term.
if (Op0)
if (Value *Ident = getIdentityValue(LHSOpcode, RHS))
if (Value *V =
tryFactorization(I, SQ, Builder, LHSOpcode, A, B, RHS, Ident))
return V;
// The instruction has the form "(B) op (C op' D)". Try to factorize common
// term.
if (Op1)
if (Value *Ident = getIdentityValue(RHSOpcode, LHS))
if (Value *V =
tryFactorization(I, SQ, Builder, RHSOpcode, LHS, Ident, C, D))
return V;
return nullptr;
}
/// This tries to simplify binary operations which some other binary operation
/// distributes over either by factorizing out common terms
/// (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this results in
/// simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is a win).
/// Returns the simplified value, or null if it didn't simplify.
Value *InstCombinerImpl::foldUsingDistributiveLaws(BinaryOperator &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
// Factorization.
if (Value *R = tryFactorizationFolds(I))
return R;
// Expansion.
if (Op0 && rightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) {
// The instruction has the form "(A op' B) op C". See if expanding it out
// to "(A op C) op' (B op C)" results in simplifications.
Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op'
// Disable the use of undef because it's not safe to distribute undef.
auto SQDistributive = SQ.getWithInstruction(&I).getWithoutUndef();
Value *L = simplifyBinOp(TopLevelOpcode, A, C, SQDistributive);
Value *R = simplifyBinOp(TopLevelOpcode, B, C, SQDistributive);
// Do "A op C" and "B op C" both simplify?
if (L && R) {
// They do! Return "L op' R".
++NumExpand;
C = Builder.CreateBinOp(InnerOpcode, L, R);
C->takeName(&I);
return C;
}
// Does "A op C" simplify to the identity value for the inner opcode?
if (L && L == ConstantExpr::getBinOpIdentity(InnerOpcode, L->getType())) {
// They do! Return "B op C".
++NumExpand;
C = Builder.CreateBinOp(TopLevelOpcode, B, C);
C->takeName(&I);
return C;
}
// Does "B op C" simplify to the identity value for the inner opcode?
if (R && R == ConstantExpr::getBinOpIdentity(InnerOpcode, R->getType())) {
// They do! Return "A op C".
++NumExpand;
C = Builder.CreateBinOp(TopLevelOpcode, A, C);
C->takeName(&I);
return C;
}
}
if (Op1 && leftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) {
// The instruction has the form "A op (B op' C)". See if expanding it out
// to "(A op B) op' (A op C)" results in simplifications.
Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op'
// Disable the use of undef because it's not safe to distribute undef.
auto SQDistributive = SQ.getWithInstruction(&I).getWithoutUndef();
Value *L = simplifyBinOp(TopLevelOpcode, A, B, SQDistributive);
Value *R = simplifyBinOp(TopLevelOpcode, A, C, SQDistributive);
// Do "A op B" and "A op C" both simplify?
if (L && R) {
// They do! Return "L op' R".
++NumExpand;
A = Builder.CreateBinOp(InnerOpcode, L, R);
A->takeName(&I);
return A;
}
// Does "A op B" simplify to the identity value for the inner opcode?
if (L && L == ConstantExpr::getBinOpIdentity(InnerOpcode, L->getType())) {
// They do! Return "A op C".
++NumExpand;
A = Builder.CreateBinOp(TopLevelOpcode, A, C);
A->takeName(&I);
return A;
}
// Does "A op C" simplify to the identity value for the inner opcode?
if (R && R == ConstantExpr::getBinOpIdentity(InnerOpcode, R->getType())) {
// They do! Return "A op B".
++NumExpand;
A = Builder.CreateBinOp(TopLevelOpcode, A, B);
A->takeName(&I);
return A;
}
}
return SimplifySelectsFeedingBinaryOp(I, LHS, RHS);
}
static std::optional<std::pair<Value *, Value *>>
matchSymmetricPhiNodesPair(PHINode *LHS, PHINode *RHS) {
if (LHS->getParent() != RHS->getParent())
return std::nullopt;
if (LHS->getNumIncomingValues() < 2)
return std::nullopt;
if (!equal(LHS->blocks(), RHS->blocks()))
return std::nullopt;
Value *L0 = LHS->getIncomingValue(0);
Value *R0 = RHS->getIncomingValue(0);
for (unsigned I = 1, E = LHS->getNumIncomingValues(); I != E; ++I) {
Value *L1 = LHS->getIncomingValue(I);
Value *R1 = RHS->getIncomingValue(I);
if ((L0 == L1 && R0 == R1) || (L0 == R1 && R0 == L1))
continue;
return std::nullopt;
}
return std::optional(std::pair(L0, R0));
}
std::optional<std::pair<Value *, Value *>>
InstCombinerImpl::matchSymmetricPair(Value *LHS, Value *RHS) {
Instruction *LHSInst = dyn_cast<Instruction>(LHS);
Instruction *RHSInst = dyn_cast<Instruction>(RHS);
if (!LHSInst || !RHSInst || LHSInst->getOpcode() != RHSInst->getOpcode())
return std::nullopt;
switch (LHSInst->getOpcode()) {
case Instruction::PHI:
return matchSymmetricPhiNodesPair(cast<PHINode>(LHS), cast<PHINode>(RHS));
case Instruction::Select: {
Value *Cond = LHSInst->getOperand(0);
Value *TrueVal = LHSInst->getOperand(1);
Value *FalseVal = LHSInst->getOperand(2);
if (Cond == RHSInst->getOperand(0) && TrueVal == RHSInst->getOperand(2) &&
FalseVal == RHSInst->getOperand(1))
return std::pair(TrueVal, FalseVal);
return std::nullopt;
}
case Instruction::Call: {
// Match min(a, b) and max(a, b)
MinMaxIntrinsic *LHSMinMax = dyn_cast<MinMaxIntrinsic>(LHSInst);
MinMaxIntrinsic *RHSMinMax = dyn_cast<MinMaxIntrinsic>(RHSInst);
if (LHSMinMax && RHSMinMax &&
LHSMinMax->getPredicate() ==
ICmpInst::getSwappedPredicate(RHSMinMax->getPredicate()) &&
((LHSMinMax->getLHS() == RHSMinMax->getLHS() &&
LHSMinMax->getRHS() == RHSMinMax->getRHS()) ||
(LHSMinMax->getLHS() == RHSMinMax->getRHS() &&
LHSMinMax->getRHS() == RHSMinMax->getLHS())))
return std::pair(LHSMinMax->getLHS(), LHSMinMax->getRHS());
return std::nullopt;
}
default:
return std::nullopt;
}
}
Value *InstCombinerImpl::SimplifySelectsFeedingBinaryOp(BinaryOperator &I,
Value *LHS,
Value *RHS) {
Value *A, *B, *C, *D, *E, *F;
bool LHSIsSelect = match(LHS, m_Select(m_Value(A), m_Value(B), m_Value(C)));
bool RHSIsSelect = match(RHS, m_Select(m_Value(D), m_Value(E), m_Value(F)));
if (!LHSIsSelect && !RHSIsSelect)
return nullptr;
FastMathFlags FMF;
BuilderTy::FastMathFlagGuard Guard(Builder);
if (isa<FPMathOperator>(&I)) {
FMF = I.getFastMathFlags();
Builder.setFastMathFlags(FMF);
}
Instruction::BinaryOps Opcode = I.getOpcode();
SimplifyQuery Q = SQ.getWithInstruction(&I);
Value *Cond, *True = nullptr, *False = nullptr;
// Special-case for add/negate combination. Replace the zero in the negation
// with the trailing add operand:
// (Cond ? TVal : -N) + Z --> Cond ? True : (Z - N)
// (Cond ? -N : FVal) + Z --> Cond ? (Z - N) : False
auto foldAddNegate = [&](Value *TVal, Value *FVal, Value *Z) -> Value * {
// We need an 'add' and exactly 1 arm of the select to have been simplified.
if (Opcode != Instruction::Add || (!True && !False) || (True && False))
return nullptr;
Value *N;
if (True && match(FVal, m_Neg(m_Value(N)))) {
Value *Sub = Builder.CreateSub(Z, N);
return Builder.CreateSelect(Cond, True, Sub, I.getName());
}
if (False && match(TVal, m_Neg(m_Value(N)))) {
Value *Sub = Builder.CreateSub(Z, N);
return Builder.CreateSelect(Cond, Sub, False, I.getName());
}
return nullptr;
};
if (LHSIsSelect && RHSIsSelect && A == D) {
// (A ? B : C) op (A ? E : F) -> A ? (B op E) : (C op F)
Cond = A;
True = simplifyBinOp(Opcode, B, E, FMF, Q);
False = simplifyBinOp(Opcode, C, F, FMF, Q);
if (LHS->hasOneUse() && RHS->hasOneUse()) {
if (False && !True)
True = Builder.CreateBinOp(Opcode, B, E);
else if (True && !False)
False = Builder.CreateBinOp(Opcode, C, F);
}
} else if (LHSIsSelect && LHS->hasOneUse()) {
// (A ? B : C) op Y -> A ? (B op Y) : (C op Y)
Cond = A;
True = simplifyBinOp(Opcode, B, RHS, FMF, Q);
False = simplifyBinOp(Opcode, C, RHS, FMF, Q);
if (Value *NewSel = foldAddNegate(B, C, RHS))
return NewSel;
} else if (RHSIsSelect && RHS->hasOneUse()) {
// X op (D ? E : F) -> D ? (X op E) : (X op F)
Cond = D;
True = simplifyBinOp(Opcode, LHS, E, FMF, Q);
False = simplifyBinOp(Opcode, LHS, F, FMF, Q);
if (Value *NewSel = foldAddNegate(E, F, LHS))
return NewSel;
}
if (!True || !False)
return nullptr;
Value *SI = Builder.CreateSelect(Cond, True, False);
SI->takeName(&I);
return SI;
}
/// Freely adapt every user of V as-if V was changed to !V.
/// WARNING: only if canFreelyInvertAllUsersOf() said this can be done.
void InstCombinerImpl::freelyInvertAllUsersOf(Value *I, Value *IgnoredUser) {
assert(!isa<Constant>(I) && "Shouldn't invert users of constant");
for (User *U : make_early_inc_range(I->users())) {
if (U == IgnoredUser)
continue; // Don't consider this user.
switch (cast<Instruction>(U)->getOpcode()) {
case Instruction::Select: {
auto *SI = cast<SelectInst>(U);
SI->swapValues();
SI->swapProfMetadata();
break;
}
case Instruction::Br: {
BranchInst *BI = cast<BranchInst>(U);
BI->swapSuccessors(); // swaps prof metadata too
if (BPI)
BPI->swapSuccEdgesProbabilities(BI->getParent());
break;
}
case Instruction::Xor:
replaceInstUsesWith(cast<Instruction>(*U), I);
// Add to worklist for DCE.
addToWorklist(cast<Instruction>(U));
break;
default:
llvm_unreachable("Got unexpected user - out of sync with "
"canFreelyInvertAllUsersOf() ?");
}
}
}
/// Given a 'sub' instruction, return the RHS of the instruction if the LHS is a
/// constant zero (which is the 'negate' form).
Value *InstCombinerImpl::dyn_castNegVal(Value *V) const {
Value *NegV;
if (match(V, m_Neg(m_Value(NegV))))
return NegV;
// Constants can be considered to be negated values if they can be folded.
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantExpr::getNeg(C);
if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V))
if (C->getType()->getElementType()->isIntegerTy())
return ConstantExpr::getNeg(C);
if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
Constant *Elt = CV->getAggregateElement(i);
if (!Elt)
return nullptr;
if (isa<UndefValue>(Elt))
continue;
if (!isa<ConstantInt>(Elt))
return nullptr;
}
return ConstantExpr::getNeg(CV);
}
// Negate integer vector splats.
if (auto *CV = dyn_cast<Constant>(V))
if (CV->getType()->isVectorTy() &&
CV->getType()->getScalarType()->isIntegerTy() && CV->getSplatValue())
return ConstantExpr::getNeg(CV);
return nullptr;
}
// Try to fold:
// 1) (fp_binop ({s|u}itofp x), ({s|u}itofp y))
// -> ({s|u}itofp (int_binop x, y))
// 2) (fp_binop ({s|u}itofp x), FpC)
// -> ({s|u}itofp (int_binop x, (fpto{s|u}i FpC)))
//
// Assuming the sign of the cast for x/y is `OpsFromSigned`.
Instruction *InstCombinerImpl::foldFBinOpOfIntCastsFromSign(
BinaryOperator &BO, bool OpsFromSigned, std::array<Value *, 2> IntOps,
Constant *Op1FpC, SmallVectorImpl<WithCache<const Value *>> &OpsKnown) {
Type *FPTy = BO.getType();
Type *IntTy = IntOps[0]->getType();
unsigned IntSz = IntTy->getScalarSizeInBits();
// This is the maximum number of inuse bits by the integer where the int -> fp
// casts are exact.
unsigned MaxRepresentableBits =
APFloat::semanticsPrecision(FPTy->getScalarType()->getFltSemantics());
// Preserve known number of leading bits. This can allow us to trivial nsw/nuw
// checks later on.
unsigned NumUsedLeadingBits[2] = {IntSz, IntSz};
// NB: This only comes up if OpsFromSigned is true, so there is no need to
// cache if between calls to `foldFBinOpOfIntCastsFromSign`.
auto IsNonZero = [&](unsigned OpNo) -> bool {
if (OpsKnown[OpNo].hasKnownBits() &&
OpsKnown[OpNo].getKnownBits(SQ).isNonZero())
return true;
return isKnownNonZero(IntOps[OpNo], SQ);
};
auto IsNonNeg = [&](unsigned OpNo) -> bool {
// NB: This matches the impl in ValueTracking, we just try to use cached
// knownbits here. If we ever start supporting WithCache for
// `isKnownNonNegative`, change this to an explicit call.
return OpsKnown[OpNo].getKnownBits(SQ).isNonNegative();
};
// Check if we know for certain that ({s|u}itofp op) is exact.
auto IsValidPromotion = [&](unsigned OpNo) -> bool {
// Can we treat this operand as the desired sign?
if (OpsFromSigned != isa<SIToFPInst>(BO.getOperand(OpNo)) &&
!IsNonNeg(OpNo))
return false;
// If fp precision >= bitwidth(op) then its exact.
// NB: This is slightly conservative for `sitofp`. For signed conversion, we
// can handle `MaxRepresentableBits == IntSz - 1` as the sign bit will be
// handled specially. We can't, however, increase the bound arbitrarily for
// `sitofp` as for larger sizes, it won't sign extend.
if (MaxRepresentableBits < IntSz) {
// Otherwise if its signed cast check that fp precisions >= bitwidth(op) -
// numSignBits(op).
// TODO: If we add support for `WithCache` in `ComputeNumSignBits`, change
// `IntOps[OpNo]` arguments to `KnownOps[OpNo]`.
if (OpsFromSigned)
NumUsedLeadingBits[OpNo] = IntSz - ComputeNumSignBits(IntOps[OpNo]);
// Finally for unsigned check that fp precision >= bitwidth(op) -
// numLeadingZeros(op).
else {
NumUsedLeadingBits[OpNo] =
IntSz - OpsKnown[OpNo].getKnownBits(SQ).countMinLeadingZeros();
}
}
// NB: We could also check if op is known to be a power of 2 or zero (which
// will always be representable). Its unlikely, however, that is we are
// unable to bound op in any way we will be able to pass the overflow checks
// later on.
if (MaxRepresentableBits < NumUsedLeadingBits[OpNo])
return false;
// Signed + Mul also requires that op is non-zero to avoid -0 cases.
return !OpsFromSigned || BO.getOpcode() != Instruction::FMul ||
IsNonZero(OpNo);
};
// If we have a constant rhs, see if we can losslessly convert it to an int.
if (Op1FpC != nullptr) {
// Signed + Mul req non-zero
if (OpsFromSigned && BO.getOpcode() == Instruction::FMul &&
!match(Op1FpC, m_NonZeroFP()))
return nullptr;
Constant *Op1IntC = ConstantFoldCastOperand(
OpsFromSigned ? Instruction::FPToSI : Instruction::FPToUI, Op1FpC,
IntTy, DL);
if (Op1IntC == nullptr)
return nullptr;
if (ConstantFoldCastOperand(OpsFromSigned ? Instruction::SIToFP
: Instruction::UIToFP,
Op1IntC, FPTy, DL) != Op1FpC)
return nullptr;
// First try to keep sign of cast the same.
IntOps[1] = Op1IntC;
}
// Ensure lhs/rhs integer types match.
if (IntTy != IntOps[1]->getType())
return nullptr;
if (Op1FpC == nullptr) {
if (!IsValidPromotion(1))
return nullptr;
}
if (!IsValidPromotion(0))
return nullptr;
// Final we check if the integer version of the binop will not overflow.
BinaryOperator::BinaryOps IntOpc;
// Because of the precision check, we can often rule out overflows.
bool NeedsOverflowCheck = true;
// Try to conservatively rule out overflow based on the already done precision
// checks.
unsigned OverflowMaxOutputBits = OpsFromSigned ? 2 : 1;
unsigned OverflowMaxCurBits =
std::max(NumUsedLeadingBits[0], NumUsedLeadingBits[1]);
bool OutputSigned = OpsFromSigned;
switch (BO.getOpcode()) {
case Instruction::FAdd:
IntOpc = Instruction::Add;
OverflowMaxOutputBits += OverflowMaxCurBits;
break;
case Instruction::FSub:
IntOpc = Instruction::Sub;
OverflowMaxOutputBits += OverflowMaxCurBits;
break;
case Instruction::FMul:
IntOpc = Instruction::Mul;
OverflowMaxOutputBits += OverflowMaxCurBits * 2;
break;
default:
llvm_unreachable("Unsupported binop");
}
// The precision check may have already ruled out overflow.
if (OverflowMaxOutputBits < IntSz) {
NeedsOverflowCheck = false;
// We can bound unsigned overflow from sub to in range signed value (this is
// what allows us to avoid the overflow check for sub).
if (IntOpc == Instruction::Sub)
OutputSigned = true;
}
// Precision check did not rule out overflow, so need to check.
// TODO: If we add support for `WithCache` in `willNotOverflow`, change
// `IntOps[...]` arguments to `KnownOps[...]`.
if (NeedsOverflowCheck &&
!willNotOverflow(IntOpc, IntOps[0], IntOps[1], BO, OutputSigned))
return nullptr;
Value *IntBinOp = Builder.CreateBinOp(IntOpc, IntOps[0], IntOps[1]);
if (auto *IntBO = dyn_cast<BinaryOperator>(IntBinOp)) {
IntBO->setHasNoSignedWrap(OutputSigned);
IntBO->setHasNoUnsignedWrap(!OutputSigned);
}
if (OutputSigned)
return new SIToFPInst(IntBinOp, FPTy);
return new UIToFPInst(IntBinOp, FPTy);
}
// Try to fold:
// 1) (fp_binop ({s|u}itofp x), ({s|u}itofp y))
// -> ({s|u}itofp (int_binop x, y))
// 2) (fp_binop ({s|u}itofp x), FpC)
// -> ({s|u}itofp (int_binop x, (fpto{s|u}i FpC)))
Instruction *InstCombinerImpl::foldFBinOpOfIntCasts(BinaryOperator &BO) {
std::array<Value *, 2> IntOps = {nullptr, nullptr};
Constant *Op1FpC = nullptr;
// Check for:
// 1) (binop ({s|u}itofp x), ({s|u}itofp y))
// 2) (binop ({s|u}itofp x), FpC)
if (!match(BO.getOperand(0), m_SIToFP(m_Value(IntOps[0]))) &&
!match(BO.getOperand(0), m_UIToFP(m_Value(IntOps[0]))))
return nullptr;
if (!match(BO.getOperand(1), m_Constant(Op1FpC)) &&
!match(BO.getOperand(1), m_SIToFP(m_Value(IntOps[1]))) &&
!match(BO.getOperand(1), m_UIToFP(m_Value(IntOps[1]))))
return nullptr;
// Cache KnownBits a bit to potentially save some analysis.
SmallVector<WithCache<const Value *>, 2> OpsKnown = {IntOps[0], IntOps[1]};
// Try treating x/y as coming from both `uitofp` and `sitofp`. There are
// different constraints depending on the sign of the cast.
// NB: `(uitofp nneg X)` == `(sitofp nneg X)`.
if (Instruction *R = foldFBinOpOfIntCastsFromSign(BO, /*OpsFromSigned=*/false,
IntOps, Op1FpC, OpsKnown))
return R;
return foldFBinOpOfIntCastsFromSign(BO, /*OpsFromSigned=*/true, IntOps,
Op1FpC, OpsKnown);
}
/// A binop with a constant operand and a sign-extended boolean operand may be
/// converted into a select of constants by applying the binary operation to
/// the constant with the two possible values of the extended boolean (0 or -1).
Instruction *InstCombinerImpl::foldBinopOfSextBoolToSelect(BinaryOperator &BO) {
// TODO: Handle non-commutative binop (constant is operand 0).
// TODO: Handle zext.
// TODO: Peek through 'not' of cast.
Value *BO0 = BO.getOperand(0);
Value *BO1 = BO.getOperand(1);
Value *X;
Constant *C;
if (!match(BO0, m_SExt(m_Value(X))) || !match(BO1, m_ImmConstant(C)) ||
!X->getType()->isIntOrIntVectorTy(1))
return nullptr;
// bo (sext i1 X), C --> select X, (bo -1, C), (bo 0, C)
Constant *Ones = ConstantInt::getAllOnesValue(BO.getType());
Constant *Zero = ConstantInt::getNullValue(BO.getType());
Value *TVal = Builder.CreateBinOp(BO.getOpcode(), Ones, C);
Value *FVal = Builder.CreateBinOp(BO.getOpcode(), Zero, C);
return SelectInst::Create(X, TVal, FVal);
}
static Value *simplifyOperationIntoSelectOperand(Instruction &I, SelectInst *SI,
bool IsTrueArm) {
SmallVector<Value *> Ops;
for (Value *Op : I.operands()) {
Value *V = nullptr;
if (Op == SI) {
V = IsTrueArm ? SI->getTrueValue() : SI->getFalseValue();
} else if (match(SI->getCondition(),
m_SpecificICmp(IsTrueArm ? ICmpInst::ICMP_EQ
: ICmpInst::ICMP_NE,
m_Specific(Op), m_Value(V))) &&
isGuaranteedNotToBeUndefOrPoison(V)) {
// Pass
} else {
V = Op;
}
Ops.push_back(V);
}
return simplifyInstructionWithOperands(&I, Ops, I.getDataLayout());
}
static Value *foldOperationIntoSelectOperand(Instruction &I, SelectInst *SI,
Value *NewOp, InstCombiner &IC) {
Instruction *Clone = I.clone();
Clone->replaceUsesOfWith(SI, NewOp);
Clone->dropUBImplyingAttrsAndMetadata();
IC.InsertNewInstBefore(Clone, I.getIterator());
return Clone;
}
Instruction *InstCombinerImpl::FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
bool FoldWithMultiUse) {
// Don't modify shared select instructions unless set FoldWithMultiUse
if (!SI->hasOneUse() && !FoldWithMultiUse)
return nullptr;
Value *TV = SI->getTrueValue();
Value *FV = SI->getFalseValue();
// Bool selects with constant operands can be folded to logical ops.
if (SI->getType()->isIntOrIntVectorTy(1))
return nullptr;
// Test if a FCmpInst instruction is used exclusively by a select as
// part of a minimum or maximum operation. If so, refrain from doing
// any other folding. This helps out other analyses which understand
// non-obfuscated minimum and maximum idioms. And in this case, at
// least one of the comparison operands has at least one user besides
// the compare (the select), which would often largely negate the
// benefit of folding anyway.
if (auto *CI = dyn_cast<FCmpInst>(SI->getCondition())) {
if (CI->hasOneUse()) {
Value *Op0 = CI->getOperand(0), *Op1 = CI->getOperand(1);
if ((TV == Op0 && FV == Op1) || (FV == Op0 && TV == Op1))
return nullptr;
}
}
// Make sure that one of the select arms folds successfully.
Value *NewTV = simplifyOperationIntoSelectOperand(Op, SI, /*IsTrueArm=*/true);
Value *NewFV =
simplifyOperationIntoSelectOperand(Op, SI, /*IsTrueArm=*/false);
if (!NewTV && !NewFV)
return nullptr;
// Create an instruction for the arm that did not fold.
if (!NewTV)
NewTV = foldOperationIntoSelectOperand(Op, SI, TV, *this);
if (!NewFV)
NewFV = foldOperationIntoSelectOperand(Op, SI, FV, *this);
return SelectInst::Create(SI->getCondition(), NewTV, NewFV, "", nullptr, SI);
}
static Value *simplifyInstructionWithPHI(Instruction &I, PHINode *PN,
Value *InValue, BasicBlock *InBB,
const DataLayout &DL,
const SimplifyQuery SQ) {
// NB: It is a precondition of this transform that the operands be
// phi translatable!
SmallVector<Value *> Ops;
for (Value *Op : I.operands()) {
if (Op == PN)
Ops.push_back(InValue);
else
Ops.push_back(Op->DoPHITranslation(PN->getParent(), InBB));
}
// Don't consider the simplification successful if we get back a constant
// expression. That's just an instruction in hiding.
// Also reject the case where we simplify back to the phi node. We wouldn't
// be able to remove it in that case.
Value *NewVal = simplifyInstructionWithOperands(
&I, Ops, SQ.getWithInstruction(InBB->getTerminator()));
if (NewVal && NewVal != PN && !match(NewVal, m_ConstantExpr()))
return NewVal;
// Check if incoming PHI value can be replaced with constant
// based on implied condition.
BranchInst *TerminatorBI = dyn_cast<BranchInst>(InBB->getTerminator());
const ICmpInst *ICmp = dyn_cast<ICmpInst>(&I);
if (TerminatorBI && TerminatorBI->isConditional() &&
TerminatorBI->getSuccessor(0) != TerminatorBI->getSuccessor(1) && ICmp) {
bool LHSIsTrue = TerminatorBI->getSuccessor(0) == PN->getParent();
std::optional<bool> ImpliedCond = isImpliedCondition(
TerminatorBI->getCondition(), ICmp->getCmpPredicate(), Ops[0], Ops[1],
DL, LHSIsTrue);
if (ImpliedCond)
return ConstantInt::getBool(I.getType(), ImpliedCond.value());
}
return nullptr;
}
Instruction *InstCombinerImpl::foldOpIntoPhi(Instruction &I, PHINode *PN,
bool AllowMultipleUses) {
unsigned NumPHIValues = PN->getNumIncomingValues();
if (NumPHIValues == 0)
return nullptr;
// We normally only transform phis with a single use. However, if a PHI has
// multiple uses and they are all the same operation, we can fold *all* of the
// uses into the PHI.
bool OneUse = PN->hasOneUse();
bool IdenticalUsers = false;
if (!AllowMultipleUses && !OneUse) {
// Walk the use list for the instruction, comparing them to I.
for (User *U : PN->users()) {
Instruction *UI = cast<Instruction>(U);
if (UI != &I && !I.isIdenticalTo(UI))
return nullptr;
}
// Otherwise, we can replace *all* users with the new PHI we form.
IdenticalUsers = true;
}
// Check that all operands are phi-translatable.
for (Value *Op : I.operands()) {
if (Op == PN)
continue;
// Non-instructions never require phi-translation.
auto *I = dyn_cast<Instruction>(Op);
if (!I)
continue;
// Phi-translate can handle phi nodes in the same block.
if (isa<PHINode>(I))
if (I->getParent() == PN->getParent())
continue;
// Operand dominates the block, no phi-translation necessary.
if (DT.dominates(I, PN->getParent()))
continue;
// Not phi-translatable, bail out.
return nullptr;
}
// Check to see whether the instruction can be folded into each phi operand.
// If there is one operand that does not fold, remember the BB it is in.
SmallVector<Value *> NewPhiValues;
SmallVector<unsigned int> OpsToMoveUseToIncomingBB;
bool SeenNonSimplifiedInVal = false;
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InVal = PN->getIncomingValue(i);
BasicBlock *InBB = PN->getIncomingBlock(i);
if (auto *NewVal = simplifyInstructionWithPHI(I, PN, InVal, InBB, DL, SQ)) {
NewPhiValues.push_back(NewVal);
continue;
}
// Handle some cases that can't be fully simplified, but where we know that
// the two instructions will fold into one.
auto WillFold = [&]() {
if (!InVal->hasOneUser())
return false;
// icmp of ucmp/scmp with constant will fold to icmp.
const APInt *Ignored;
if (isa<CmpIntrinsic>(InVal) &&
match(&I, m_ICmp(m_Specific(PN), m_APInt(Ignored))))
return true;
// icmp eq zext(bool), 0 will fold to !bool.
if (isa<ZExtInst>(InVal) &&
cast<ZExtInst>(InVal)->getSrcTy()->isIntOrIntVectorTy(1) &&
match(&I,
m_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(PN), m_Zero())))
return true;
return false;
};
if (WillFold()) {
OpsToMoveUseToIncomingBB.push_back(i);
NewPhiValues.push_back(nullptr);
continue;
}
if (!OneUse && !IdenticalUsers)
return nullptr;
if (SeenNonSimplifiedInVal)
return nullptr; // More than one non-simplified value.
SeenNonSimplifiedInVal = true;
// If there is exactly one non-simplified value, we can insert a copy of the
// operation in that block. However, if this is a critical edge, we would
// be inserting the computation on some other paths (e.g. inside a loop).
// Only do this if the pred block is unconditionally branching into the phi
// block. Also, make sure that the pred block is not dead code.
BranchInst *BI = dyn_cast<BranchInst>(InBB->getTerminator());
if (!BI || !BI->isUnconditional() || !DT.isReachableFromEntry(InBB))
return nullptr;
NewPhiValues.push_back(nullptr);
OpsToMoveUseToIncomingBB.push_back(i);
// If the InVal is an invoke at the end of the pred block, then we can't
// insert a computation after it without breaking the edge.
if (isa<InvokeInst>(InVal))
if (cast<Instruction>(InVal)->getParent() == InBB)
return nullptr;
// Do not push the operation across a loop backedge. This could result in
// an infinite combine loop, and is generally non-profitable (especially
// if the operation was originally outside the loop).
if (isBackEdge(InBB, PN->getParent()))
return nullptr;
}
// Clone the instruction that uses the phi node and move it into the incoming
// BB because we know that the next iteration of InstCombine will simplify it.
SmallDenseMap<BasicBlock *, Instruction *> Clones;
for (auto OpIndex : OpsToMoveUseToIncomingBB) {
Value *Op = PN->getIncomingValue(OpIndex);
BasicBlock *OpBB = PN->getIncomingBlock(OpIndex);
Instruction *Clone = Clones.lookup(OpBB);
if (!Clone) {
Clone = I.clone();
for (Use &U : Clone->operands()) {
if (U == PN)
U = Op;
else
U = U->DoPHITranslation(PN->getParent(), OpBB);
}
Clone = InsertNewInstBefore(Clone, OpBB->getTerminator()->getIterator());
Clones.insert({OpBB, Clone});
}
NewPhiValues[OpIndex] = Clone;
}
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues());
InsertNewInstBefore(NewPN, PN->getIterator());
NewPN->takeName(PN);
NewPN->setDebugLoc(PN->getDebugLoc());
for (unsigned i = 0; i != NumPHIValues; ++i)
NewPN->addIncoming(NewPhiValues[i], PN->getIncomingBlock(i));
if (IdenticalUsers) {
for (User *U : make_early_inc_range(PN->users())) {
Instruction *User = cast<Instruction>(U);
if (User == &I)
continue;
replaceInstUsesWith(*User, NewPN);
eraseInstFromFunction(*User);
}
OneUse = true;
}
if (OneUse) {
replaceAllDbgUsesWith(const_cast<PHINode &>(*PN),
const_cast<PHINode &>(*NewPN),
const_cast<PHINode &>(*PN), DT);
}
return replaceInstUsesWith(I, NewPN);
}
Instruction *InstCombinerImpl::foldBinopWithPhiOperands(BinaryOperator &BO) {
// TODO: This should be similar to the incoming values check in foldOpIntoPhi:
// we are guarding against replicating the binop in >1 predecessor.
// This could miss matching a phi with 2 constant incoming values.
auto *Phi0 = dyn_cast<PHINode>(BO.getOperand(0));
auto *Phi1 = dyn_cast<PHINode>(BO.getOperand(1));
if (!Phi0 || !Phi1 || !Phi0->hasOneUse() || !Phi1->hasOneUse() ||
Phi0->getNumOperands() != Phi1->getNumOperands())
return nullptr;
// TODO: Remove the restriction for binop being in the same block as the phis.
if (BO.getParent() != Phi0->getParent() ||
BO.getParent() != Phi1->getParent())
return nullptr;
// Fold if there is at least one specific constant value in phi0 or phi1's
// incoming values that comes from the same block and this specific constant
// value can be used to do optimization for specific binary operator.
// For example:
// %phi0 = phi i32 [0, %bb0], [%i, %bb1]
// %phi1 = phi i32 [%j, %bb0], [0, %bb1]
// %add = add i32 %phi0, %phi1
// ==>
// %add = phi i32 [%j, %bb0], [%i, %bb1]
Constant *C = ConstantExpr::getBinOpIdentity(BO.getOpcode(), BO.getType(),
/*AllowRHSConstant*/ false);
if (C) {
SmallVector<Value *, 4> NewIncomingValues;
auto CanFoldIncomingValuePair = [&](std::tuple<Use &, Use &> T) {
auto &Phi0Use = std::get<0>(T);
auto &Phi1Use = std::get<1>(T);
if (Phi0->getIncomingBlock(Phi0Use) != Phi1->getIncomingBlock(Phi1Use))
return false;
Value *Phi0UseV = Phi0Use.get();
Value *Phi1UseV = Phi1Use.get();
if (Phi0UseV == C)
NewIncomingValues.push_back(Phi1UseV);
else if (Phi1UseV == C)
NewIncomingValues.push_back(Phi0UseV);
else
return false;
return true;
};
if (all_of(zip(Phi0->operands(), Phi1->operands()),
CanFoldIncomingValuePair)) {
PHINode *NewPhi =
PHINode::Create(Phi0->getType(), Phi0->getNumOperands());
assert(NewIncomingValues.size() == Phi0->getNumOperands() &&
"The number of collected incoming values should equal the number "
"of the original PHINode operands!");
for (unsigned I = 0; I < Phi0->getNumOperands(); I++)
NewPhi->addIncoming(NewIncomingValues[I], Phi0->getIncomingBlock(I));
return NewPhi;
}
}
if (Phi0->getNumOperands() != 2 || Phi1->getNumOperands() != 2)
return nullptr;
// Match a pair of incoming constants for one of the predecessor blocks.
BasicBlock *ConstBB, *OtherBB;
Constant *C0, *C1;
if (match(Phi0->getIncomingValue(0), m_ImmConstant(C0))) {
ConstBB = Phi0->getIncomingBlock(0);
OtherBB = Phi0->getIncomingBlock(1);
} else if (match(Phi0->getIncomingValue(1), m_ImmConstant(C0))) {
ConstBB = Phi0->getIncomingBlock(1);
OtherBB = Phi0->getIncomingBlock(0);
} else {
return nullptr;
}
if (!match(Phi1->getIncomingValueForBlock(ConstBB), m_ImmConstant(C1)))
return nullptr;
// The block that we are hoisting to must reach here unconditionally.
// Otherwise, we could be speculatively executing an expensive or
// non-speculative op.
auto *PredBlockBranch = dyn_cast<BranchInst>(OtherBB->getTerminator());
if (!PredBlockBranch || PredBlockBranch->isConditional() ||
!DT.isReachableFromEntry(OtherBB))
return nullptr;
// TODO: This check could be tightened to only apply to binops (div/rem) that
// are not safe to speculatively execute. But that could allow hoisting
// potentially expensive instructions (fdiv for example).
for (auto BBIter = BO.getParent()->begin(); &*BBIter != &BO; ++BBIter)
if (!isGuaranteedToTransferExecutionToSuccessor(&*BBIter))
return nullptr;
// Fold constants for the predecessor block with constant incoming values.
Constant *NewC = ConstantFoldBinaryOpOperands(BO.getOpcode(), C0, C1, DL);
if (!NewC)
return nullptr;
// Make a new binop in the predecessor block with the non-constant incoming
// values.
Builder.SetInsertPoint(PredBlockBranch);
Value *NewBO = Builder.CreateBinOp(BO.getOpcode(),
Phi0->getIncomingValueForBlock(OtherBB),
Phi1->getIncomingValueForBlock(OtherBB));
if (auto *NotFoldedNewBO = dyn_cast<BinaryOperator>(NewBO))
NotFoldedNewBO->copyIRFlags(&BO);
// Replace the binop with a phi of the new values. The old phis are dead.
PHINode *NewPhi = PHINode::Create(BO.getType(), 2);
NewPhi->addIncoming(NewBO, OtherBB);
NewPhi->addIncoming(NewC, ConstBB);
return NewPhi;
}
Instruction *InstCombinerImpl::foldBinOpIntoSelectOrPhi(BinaryOperator &I) {
if (!isa<Constant>(I.getOperand(1)))
return nullptr;
if (auto *Sel = dyn_cast<SelectInst>(I.getOperand(0))) {
if (Instruction *NewSel = FoldOpIntoSelect(I, Sel))
return NewSel;
} else if (auto *PN = dyn_cast<PHINode>(I.getOperand(0))) {
if (Instruction *NewPhi = foldOpIntoPhi(I, PN))
return NewPhi;
}
return nullptr;
}
static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) {
// If this GEP has only 0 indices, it is the same pointer as
// Src. If Src is not a trivial GEP too, don't combine
// the indices.
if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() &&
!Src.hasOneUse())
return false;
return true;
}
Instruction *InstCombinerImpl::foldVectorBinop(BinaryOperator &Inst) {
if (!isa<VectorType>(Inst.getType()))
return nullptr;
BinaryOperator::BinaryOps Opcode = Inst.getOpcode();
Value *LHS = Inst.getOperand(0), *RHS = Inst.getOperand(1);
assert(cast<VectorType>(LHS->getType())->getElementCount() ==
cast<VectorType>(Inst.getType())->getElementCount());
assert(cast<VectorType>(RHS->getType())->getElementCount() ==
cast<VectorType>(Inst.getType())->getElementCount());
// If both operands of the binop are vector concatenations, then perform the
// narrow binop on each pair of the source operands followed by concatenation
// of the results.
Value *L0, *L1, *R0, *R1;
ArrayRef<int> Mask;
if (match(LHS, m_Shuffle(m_Value(L0), m_Value(L1), m_Mask(Mask))) &&
match(RHS, m_Shuffle(m_Value(R0), m_Value(R1), m_SpecificMask(Mask))) &&
LHS->hasOneUse() && RHS->hasOneUse() &&
cast<ShuffleVectorInst>(LHS)->isConcat() &&
cast<ShuffleVectorInst>(RHS)->isConcat()) {
// This transform does not have the speculative execution constraint as
// below because the shuffle is a concatenation. The new binops are
// operating on exactly the same elements as the existing binop.
// TODO: We could ease the mask requirement to allow different undef lanes,
// but that requires an analysis of the binop-with-undef output value.
Value *NewBO0 = Builder.CreateBinOp(Opcode, L0, R0);
if (auto *BO = dyn_cast<BinaryOperator>(NewBO0))
BO->copyIRFlags(&Inst);
Value *NewBO1 = Builder.CreateBinOp(Opcode, L1, R1);
if (auto *BO = dyn_cast<BinaryOperator>(NewBO1))
BO->copyIRFlags(&Inst);
return new ShuffleVectorInst(NewBO0, NewBO1, Mask);
}
auto createBinOpReverse = [&](Value *X, Value *Y) {
Value *V = Builder.CreateBinOp(Opcode, X, Y, Inst.getName());
if (auto *BO = dyn_cast<BinaryOperator>(V))
BO->copyIRFlags(&Inst);
Module *M = Inst.getModule();
Function *F = Intrinsic::getOrInsertDeclaration(
M, Intrinsic::vector_reverse, V->getType());
return CallInst::Create(F, V);
};
// NOTE: Reverse shuffles don't require the speculative execution protection
// below because they don't affect which lanes take part in the computation.
Value *V1, *V2;
if (match(LHS, m_VecReverse(m_Value(V1)))) {
// Op(rev(V1), rev(V2)) -> rev(Op(V1, V2))
if (match(RHS, m_VecReverse(m_Value(V2))) &&
(LHS->hasOneUse() || RHS->hasOneUse() ||
(LHS == RHS && LHS->hasNUses(2))))
return createBinOpReverse(V1, V2);
// Op(rev(V1), RHSSplat)) -> rev(Op(V1, RHSSplat))
if (LHS->hasOneUse() && isSplatValue(RHS))
return createBinOpReverse(V1, RHS);
}
// Op(LHSSplat, rev(V2)) -> rev(Op(LHSSplat, V2))
else if (isSplatValue(LHS) && match(RHS, m_OneUse(m_VecReverse(m_Value(V2)))))
return createBinOpReverse(LHS, V2);
// It may not be safe to reorder shuffles and things like div, urem, etc.
// because we may trap when executing those ops on unknown vector elements.
// See PR20059.
if (!isSafeToSpeculativelyExecuteWithVariableReplaced(&Inst))
return nullptr;
auto createBinOpShuffle = [&](Value *X, Value *Y, ArrayRef<int> M) {
Value *XY = Builder.CreateBinOp(Opcode, X, Y);
if (auto *BO = dyn_cast<BinaryOperator>(XY))
BO->copyIRFlags(&Inst);
return new ShuffleVectorInst(XY, M);
};
// If both arguments of the binary operation are shuffles that use the same
// mask and shuffle within a single vector, move the shuffle after the binop.
if (match(LHS, m_Shuffle(m_Value(V1), m_Poison(), m_Mask(Mask))) &&
match(RHS, m_Shuffle(m_Value(V2), m_Poison(), m_SpecificMask(Mask))) &&
V1->getType() == V2->getType() &&
(LHS->hasOneUse() || RHS->hasOneUse() || LHS == RHS)) {
// Op(shuffle(V1, Mask), shuffle(V2, Mask)) -> shuffle(Op(V1, V2), Mask)
return createBinOpShuffle(V1, V2, Mask);
}
// If both arguments of a commutative binop are select-shuffles that use the
// same mask with commuted operands, the shuffles are unnecessary.
if (Inst.isCommutative() &&
match(LHS, m_Shuffle(m_Value(V1), m_Value(V2), m_Mask(Mask))) &&
match(RHS,
m_Shuffle(m_Specific(V2), m_Specific(V1), m_SpecificMask(Mask)))) {
auto *LShuf = cast<ShuffleVectorInst>(LHS);
auto *RShuf = cast<ShuffleVectorInst>(RHS);
// TODO: Allow shuffles that contain undefs in the mask?
// That is legal, but it reduces undef knowledge.
// TODO: Allow arbitrary shuffles by shuffling after binop?
// That might be legal, but we have to deal with poison.
if (LShuf->isSelect() &&
!is_contained(LShuf->getShuffleMask(), PoisonMaskElem) &&
RShuf->isSelect() &&
!is_contained(RShuf->getShuffleMask(), PoisonMaskElem)) {
// Example:
// LHS = shuffle V1, V2, <0, 5, 6, 3>
// RHS = shuffle V2, V1, <0, 5, 6, 3>
// LHS + RHS --> (V10+V20, V21+V11, V22+V12, V13+V23) --> V1 + V2
Instruction *NewBO = BinaryOperator::Create(Opcode, V1, V2);
NewBO->copyIRFlags(&Inst);
return NewBO;
}
}
// If one argument is a shuffle within one vector and the other is a constant,
// try moving the shuffle after the binary operation. This canonicalization
// intends to move shuffles closer to other shuffles and binops closer to
// other binops, so they can be folded. It may also enable demanded elements
// transforms.
Constant *C;
auto *InstVTy = dyn_cast<FixedVectorType>(Inst.getType());
if (InstVTy &&
match(&Inst, m_c_BinOp(m_OneUse(m_Shuffle(m_Value(V1), m_Poison(),
m_Mask(Mask))),
m_ImmConstant(C))) &&
cast<FixedVectorType>(V1->getType())->getNumElements() <=
InstVTy->getNumElements()) {
assert(InstVTy->getScalarType() == V1->getType()->getScalarType() &&
"Shuffle should not change scalar type");
// Find constant NewC that has property:
// shuffle(NewC, ShMask) = C
// If such constant does not exist (example: ShMask=<0,0> and C=<1,2>)
// reorder is not possible. A 1-to-1 mapping is not required. Example:
// ShMask = <1,1,2,2> and C = <5,5,6,6> --> NewC = <undef,5,6,undef>
bool ConstOp1 = isa<Constant>(RHS);
ArrayRef<int> ShMask = Mask;
unsigned SrcVecNumElts =
cast<FixedVectorType>(V1->getType())->getNumElements();
PoisonValue *PoisonScalar = PoisonValue::get(C->getType()->getScalarType());
SmallVector<Constant *, 16> NewVecC(SrcVecNumElts, PoisonScalar);
bool MayChange = true;
unsigned NumElts = InstVTy->getNumElements();
for (unsigned I = 0; I < NumElts; ++I) {
Constant *CElt = C->getAggregateElement(I);
if (ShMask[I] >= 0) {
assert(ShMask[I] < (int)NumElts && "Not expecting narrowing shuffle");
Constant *NewCElt = NewVecC[ShMask[I]];
// Bail out if:
// 1. The constant vector contains a constant expression.
// 2. The shuffle needs an element of the constant vector that can't
// be mapped to a new constant vector.
// 3. This is a widening shuffle that copies elements of V1 into the
// extended elements (extending with poison is allowed).
if (!CElt || (!isa<PoisonValue>(NewCElt) && NewCElt != CElt) ||
I >= SrcVecNumElts) {
MayChange = false;
break;
}
NewVecC[ShMask[I]] = CElt;
}
// If this is a widening shuffle, we must be able to extend with poison
// elements. If the original binop does not produce a poison in the high
// lanes, then this transform is not safe.
// Similarly for poison lanes due to the shuffle mask, we can only
// transform binops that preserve poison.
// TODO: We could shuffle those non-poison constant values into the
// result by using a constant vector (rather than an poison vector)
// as operand 1 of the new binop, but that might be too aggressive
// for target-independent shuffle creation.
if (I >= SrcVecNumElts || ShMask[I] < 0) {
Constant *MaybePoison =
ConstOp1
? ConstantFoldBinaryOpOperands(Opcode, PoisonScalar, CElt, DL)
: ConstantFoldBinaryOpOperands(Opcode, CElt, PoisonScalar, DL);
if (!MaybePoison || !isa<PoisonValue>(MaybePoison)) {
MayChange = false;
break;
}
}
}
if (MayChange) {
Constant *NewC = ConstantVector::get(NewVecC);
// It may not be safe to execute a binop on a vector with poison elements
// because the entire instruction can be folded to undef or create poison
// that did not exist in the original code.
// TODO: The shift case should not be necessary.
if (Inst.isIntDivRem() || (Inst.isShift() && ConstOp1))
NewC = getSafeVectorConstantForBinop(Opcode, NewC, ConstOp1);
// Op(shuffle(V1, Mask), C) -> shuffle(Op(V1, NewC), Mask)
// Op(C, shuffle(V1, Mask)) -> shuffle(Op(NewC, V1), Mask)
Value *NewLHS = ConstOp1 ? V1 : NewC;
Value *NewRHS = ConstOp1 ? NewC : V1;
return createBinOpShuffle(NewLHS, NewRHS, Mask);
}
}
// Try to reassociate to sink a splat shuffle after a binary operation.
if (Inst.isAssociative() && Inst.isCommutative()) {
// Canonicalize shuffle operand as LHS.
if (isa<ShuffleVectorInst>(RHS))
std::swap(LHS, RHS);
Value *X;
ArrayRef<int> MaskC;
int SplatIndex;
Value *Y, *OtherOp;
if (!match(LHS,
m_OneUse(m_Shuffle(m_Value(X), m_Undef(), m_Mask(MaskC)))) ||
!match(MaskC, m_SplatOrPoisonMask(SplatIndex)) ||
X->getType() != Inst.getType() ||
!match(RHS, m_OneUse(m_BinOp(Opcode, m_Value(Y), m_Value(OtherOp)))))
return nullptr;
// FIXME: This may not be safe if the analysis allows undef elements. By
// moving 'Y' before the splat shuffle, we are implicitly assuming
// that it is not undef/poison at the splat index.
if (isSplatValue(OtherOp, SplatIndex)) {
std::swap(Y, OtherOp);
} else if (!isSplatValue(Y, SplatIndex)) {
return nullptr;
}
// X and Y are splatted values, so perform the binary operation on those
// values followed by a splat followed by the 2nd binary operation:
// bo (splat X), (bo Y, OtherOp) --> bo (splat (bo X, Y)), OtherOp
Value *NewBO = Builder.CreateBinOp(Opcode, X, Y);
SmallVector<int, 8> NewMask(MaskC.size(), SplatIndex);
Value *NewSplat = Builder.CreateShuffleVector(NewBO, NewMask);
Instruction *R = BinaryOperator::Create(Opcode, NewSplat, OtherOp);
// Intersect FMF on both new binops. Other (poison-generating) flags are
// dropped to be safe.
if (isa<FPMathOperator>(R)) {
R->copyFastMathFlags(&Inst);
R->andIRFlags(RHS);
}
if (auto *NewInstBO = dyn_cast<BinaryOperator>(NewBO))
NewInstBO->copyIRFlags(R);
return R;
}
return nullptr;
}
/// Try to narrow the width of a binop if at least 1 operand is an extend of
/// of a value. This requires a potentially expensive known bits check to make
/// sure the narrow op does not overflow.
Instruction *InstCombinerImpl::narrowMathIfNoOverflow(BinaryOperator &BO) {
// We need at least one extended operand.
Value *Op0 = BO.getOperand(0), *Op1 = BO.getOperand(1);
// If this is a sub, we swap the operands since we always want an extension
// on the RHS. The LHS can be an extension or a constant.
if (BO.getOpcode() == Instruction::Sub)
std::swap(Op0, Op1);
Value *X;
bool IsSext = match(Op0, m_SExt(m_Value(X)));
if (!IsSext && !match(Op0, m_ZExt(m_Value(X))))
return nullptr;
// If both operands are the same extension from the same source type and we
// can eliminate at least one (hasOneUse), this might work.
CastInst::CastOps CastOpc = IsSext ? Instruction::SExt : Instruction::ZExt;
Value *Y;
if (!(match(Op1, m_ZExtOrSExt(m_Value(Y))) && X->getType() == Y->getType() &&
cast<Operator>(Op1)->getOpcode() == CastOpc &&
(Op0->hasOneUse() || Op1->hasOneUse()))) {
// If that did not match, see if we have a suitable constant operand.
// Truncating and extending must produce the same constant.
Constant *WideC;
if (!Op0->hasOneUse() || !match(Op1, m_Constant(WideC)))
return nullptr;
Constant *NarrowC = getLosslessTrunc(WideC, X->getType(), CastOpc);
if (!NarrowC)
return nullptr;
Y = NarrowC;
}
// Swap back now that we found our operands.
if (BO.getOpcode() == Instruction::Sub)
std::swap(X, Y);
// Both operands have narrow versions. Last step: the math must not overflow
// in the narrow width.
if (!willNotOverflow(BO.getOpcode(), X, Y, BO, IsSext))
return nullptr;
// bo (ext X), (ext Y) --> ext (bo X, Y)
// bo (ext X), C --> ext (bo X, C')
Value *NarrowBO = Builder.CreateBinOp(BO.getOpcode(), X, Y, "narrow");
if (auto *NewBinOp = dyn_cast<BinaryOperator>(NarrowBO)) {
if (IsSext)
NewBinOp->setHasNoSignedWrap();
else
NewBinOp->setHasNoUnsignedWrap();
}
return CastInst::Create(CastOpc, NarrowBO, BO.getType());
}
/// Determine nowrap flags for (gep (gep p, x), y) to (gep p, (x + y))
/// transform.
static GEPNoWrapFlags getMergedGEPNoWrapFlags(GEPOperator &GEP1,
GEPOperator &GEP2) {
return GEP1.getNoWrapFlags().intersectForOffsetAdd(GEP2.getNoWrapFlags());
}
/// Thread a GEP operation with constant indices through the constant true/false
/// arms of a select.
static Instruction *foldSelectGEP(GetElementPtrInst &GEP,
InstCombiner::BuilderTy &Builder) {
if (!GEP.hasAllConstantIndices())
return nullptr;
Instruction *Sel;
Value *Cond;
Constant *TrueC, *FalseC;
if (!match(GEP.getPointerOperand(), m_Instruction(Sel)) ||
!match(Sel,
m_Select(m_Value(Cond), m_Constant(TrueC), m_Constant(FalseC))))
return nullptr;
// gep (select Cond, TrueC, FalseC), IndexC --> select Cond, TrueC', FalseC'
// Propagate 'inbounds' and metadata from existing instructions.
// Note: using IRBuilder to create the constants for efficiency.
SmallVector<Value *, 4> IndexC(GEP.indices());
GEPNoWrapFlags NW = GEP.getNoWrapFlags();
Type *Ty = GEP.getSourceElementType();
Value *NewTrueC = Builder.CreateGEP(Ty, TrueC, IndexC, "", NW);
Value *NewFalseC = Builder.CreateGEP(Ty, FalseC, IndexC, "", NW);
return SelectInst::Create(Cond, NewTrueC, NewFalseC, "", nullptr, Sel);
}
// Canonicalization:
// gep T, (gep i8, base, C1), (Index + C2) into
// gep T, (gep i8, base, C1 + C2 * sizeof(T)), Index
static Instruction *canonicalizeGEPOfConstGEPI8(GetElementPtrInst &GEP,
GEPOperator *Src,
InstCombinerImpl &IC) {
if (GEP.getNumIndices() != 1)
return nullptr;
auto &DL = IC.getDataLayout();
Value *Base;
const APInt *C1;
if (!match(Src, m_PtrAdd(m_Value(Base), m_APInt(C1))))
return nullptr;
Value *VarIndex;
const APInt *C2;
Type *PtrTy = Src->getType()->getScalarType();
unsigned IndexSizeInBits = DL.getIndexTypeSizeInBits(PtrTy);
if (!match(GEP.getOperand(1), m_AddLike(m_Value(VarIndex), m_APInt(C2))))
return nullptr;
if (C1->getBitWidth() != IndexSizeInBits ||
C2->getBitWidth() != IndexSizeInBits)
return nullptr;
Type *BaseType = GEP.getSourceElementType();
if (isa<ScalableVectorType>(BaseType))
return nullptr;
APInt TypeSize(IndexSizeInBits, DL.getTypeAllocSize(BaseType));
APInt NewOffset = TypeSize * *C2 + *C1;
if (NewOffset.isZero() ||
(Src->hasOneUse() && GEP.getOperand(1)->hasOneUse())) {
Value *GEPConst =
IC.Builder.CreatePtrAdd(Base, IC.Builder.getInt(NewOffset));
return GetElementPtrInst::Create(BaseType, GEPConst, VarIndex);
}
return nullptr;
}
Instruction *InstCombinerImpl::visitGEPOfGEP(GetElementPtrInst &GEP,
GEPOperator *Src) {
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction with matching element type, combine the
// indices of the two getelementptr instructions into a single instruction.
if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src))
return nullptr;
if (auto *I = canonicalizeGEPOfConstGEPI8(GEP, Src, *this))
return I;
// For constant GEPs, use a more general offset-based folding approach.
Type *PtrTy = Src->getType()->getScalarType();
if (GEP.hasAllConstantIndices() &&
(Src->hasOneUse() || Src->hasAllConstantIndices())) {
// Split Src into a variable part and a constant suffix.
gep_type_iterator GTI = gep_type_begin(*Src);
Type *BaseType = GTI.getIndexedType();
bool IsFirstType = true;
unsigned NumVarIndices = 0;
for (auto Pair : enumerate(Src->indices())) {
if (!isa<ConstantInt>(Pair.value())) {
BaseType = GTI.getIndexedType();
IsFirstType = false;
NumVarIndices = Pair.index() + 1;
}
++GTI;
}
// Determine the offset for the constant suffix of Src.
APInt Offset(DL.getIndexTypeSizeInBits(PtrTy), 0);
if (NumVarIndices != Src->getNumIndices()) {
// FIXME: getIndexedOffsetInType() does not handled scalable vectors.
if (BaseType->isScalableTy())
return nullptr;
SmallVector<Value *> ConstantIndices;
if (!IsFirstType)
ConstantIndices.push_back(
Constant::getNullValue(Type::getInt32Ty(GEP.getContext())));
append_range(ConstantIndices, drop_begin(Src->indices(), NumVarIndices));
Offset += DL.getIndexedOffsetInType(BaseType, ConstantIndices);
}
// Add the offset for GEP (which is fully constant).
if (!GEP.accumulateConstantOffset(DL, Offset))
return nullptr;
// Convert the total offset back into indices.
SmallVector<APInt> ConstIndices =
DL.getGEPIndicesForOffset(BaseType, Offset);
if (!Offset.isZero() || (!IsFirstType && !ConstIndices[0].isZero()))
return nullptr;
GEPNoWrapFlags NW = getMergedGEPNoWrapFlags(*Src, *cast<GEPOperator>(&GEP));
SmallVector<Value *> Indices;
append_range(Indices, drop_end(Src->indices(),
Src->getNumIndices() - NumVarIndices));
for (const APInt &Idx : drop_begin(ConstIndices, !IsFirstType)) {
Indices.push_back(ConstantInt::get(GEP.getContext(), Idx));
// Even if the total offset is inbounds, we may end up representing it
// by first performing a larger negative offset, and then a smaller
// positive one. The large negative offset might go out of bounds. Only
// preserve inbounds if all signs are the same.
if (Idx.isNonNegative() != ConstIndices[0].isNonNegative())
NW = NW.withoutNoUnsignedSignedWrap();
if (!Idx.isNonNegative())
NW = NW.withoutNoUnsignedWrap();
}
return replaceInstUsesWith(
GEP, Builder.CreateGEP(Src->getSourceElementType(), Src->getOperand(0),
Indices, "", NW));
}
if (Src->getResultElementType() != GEP.getSourceElementType())
return nullptr;
SmallVector<Value*, 8> Indices;
// Find out whether the last index in the source GEP is a sequential idx.
bool EndsWithSequential = false;
for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
I != E; ++I)
EndsWithSequential = I.isSequential();
// Can we combine the two pointer arithmetics offsets?
if (EndsWithSequential) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
Value *GO1 = GEP.getOperand(1);
// If they aren't the same type, then the input hasn't been processed
// by the loop above yet (which canonicalizes sequential index types to
// intptr_t). Just avoid transforming this until the input has been
// normalized.
if (SO1->getType() != GO1->getType())
return nullptr;
Value *Sum =
simplifyAddInst(GO1, SO1, false, false, SQ.getWithInstruction(&GEP));
// Only do the combine when we are sure the cost after the
// merge is never more than that before the merge.
if (Sum == nullptr)
return nullptr;
Indices.append(Src->op_begin()+1, Src->op_end()-1);
Indices.push_back(Sum);
Indices.append(GEP.op_begin()+2, GEP.op_end());
} else if (isa<Constant>(*GEP.idx_begin()) &&
cast<Constant>(*GEP.idx_begin())->isNullValue() &&
Src->getNumOperands() != 1) {
// Otherwise we can do the fold if the first index of the GEP is a zero
Indices.append(Src->op_begin()+1, Src->op_end());
Indices.append(GEP.idx_begin()+1, GEP.idx_end());
}
if (!Indices.empty())
return replaceInstUsesWith(
GEP, Builder.CreateGEP(
Src->getSourceElementType(), Src->getOperand(0), Indices, "",
getMergedGEPNoWrapFlags(*Src, *cast<GEPOperator>(&GEP))));
return nullptr;
}
Value *InstCombiner::getFreelyInvertedImpl(Value *V, bool WillInvertAllUses,
BuilderTy *Builder,
bool &DoesConsume, unsigned Depth) {
static Value *const NonNull = reinterpret_cast<Value *>(uintptr_t(1));
// ~(~(X)) -> X.
Value *A, *B;
if (match(V, m_Not(m_Value(A)))) {
DoesConsume = true;
return A;
}
Constant *C;
// Constants can be considered to be not'ed values.
if (match(V, m_ImmConstant(C)))
return ConstantExpr::getNot(C);
if (Depth++ >= MaxAnalysisRecursionDepth)
return nullptr;
// The rest of the cases require that we invert all uses so don't bother
// doing the analysis if we know we can't use the result.
if (!WillInvertAllUses)
return nullptr;
// Compares can be inverted if all of their uses are being modified to use
// the ~V.
if (auto *I = dyn_cast<CmpInst>(V)) {
if (Builder != nullptr)
return Builder->CreateCmp(I->getInversePredicate(), I->getOperand(0),
I->getOperand(1));
return NonNull;
}
// If `V` is of the form `A + B` then `-1 - V` can be folded into
// `(-1 - B) - A` if we are willing to invert all of the uses.
if (match(V, m_Add(m_Value(A), m_Value(B)))) {
if (auto *BV = getFreelyInvertedImpl(B, B->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateSub(BV, A) : NonNull;
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateSub(AV, B) : NonNull;
return nullptr;
}
// If `V` is of the form `A ^ ~B` then `~(A ^ ~B)` can be folded
// into `A ^ B` if we are willing to invert all of the uses.
if (match(V, m_Xor(m_Value(A), m_Value(B)))) {
if (auto *BV = getFreelyInvertedImpl(B, B->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateXor(A, BV) : NonNull;
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateXor(AV, B) : NonNull;
return nullptr;
}
// If `V` is of the form `B - A` then `-1 - V` can be folded into
// `A + (-1 - B)` if we are willing to invert all of the uses.
if (match(V, m_Sub(m_Value(A), m_Value(B)))) {
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateAdd(AV, B) : NonNull;
return nullptr;
}
// If `V` is of the form `(~A) s>> B` then `~((~A) s>> B)` can be folded
// into `A s>> B` if we are willing to invert all of the uses.
if (match(V, m_AShr(m_Value(A), m_Value(B)))) {
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateAShr(AV, B) : NonNull;
return nullptr;
}
Value *Cond;
// LogicOps are special in that we canonicalize them at the cost of an
// instruction.
bool IsSelect = match(V, m_Select(m_Value(Cond), m_Value(A), m_Value(B))) &&
!shouldAvoidAbsorbingNotIntoSelect(*cast<SelectInst>(V));
// Selects/min/max with invertible operands are freely invertible
if (IsSelect || match(V, m_MaxOrMin(m_Value(A), m_Value(B)))) {
bool LocalDoesConsume = DoesConsume;
if (!getFreelyInvertedImpl(B, B->hasOneUse(), /*Builder*/ nullptr,
LocalDoesConsume, Depth))
return nullptr;
if (Value *NotA = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
LocalDoesConsume, Depth)) {
DoesConsume = LocalDoesConsume;
if (Builder != nullptr) {
Value *NotB = getFreelyInvertedImpl(B, B->hasOneUse(), Builder,
DoesConsume, Depth);
assert(NotB != nullptr &&
"Unable to build inverted value for known freely invertable op");
if (auto *II = dyn_cast<IntrinsicInst>(V))
return Builder->CreateBinaryIntrinsic(
getInverseMinMaxIntrinsic(II->getIntrinsicID()), NotA, NotB);
return Builder->CreateSelect(Cond, NotA, NotB);
}
return NonNull;
}
}
if (PHINode *PN = dyn_cast<PHINode>(V)) {
bool LocalDoesConsume = DoesConsume;
SmallVector<std::pair<Value *, BasicBlock *>, 8> IncomingValues;
for (Use &U : PN->operands()) {
BasicBlock *IncomingBlock = PN->getIncomingBlock(U);
Value *NewIncomingVal = getFreelyInvertedImpl(
U.get(), /*WillInvertAllUses=*/false,
/*Builder=*/nullptr, LocalDoesConsume, MaxAnalysisRecursionDepth - 1);
if (NewIncomingVal == nullptr)
return nullptr;
// Make sure that we can safely erase the original PHI node.
if (NewIncomingVal == V)
return nullptr;
if (Builder != nullptr)
IncomingValues.emplace_back(NewIncomingVal, IncomingBlock);
}
DoesConsume = LocalDoesConsume;
if (Builder != nullptr) {
IRBuilderBase::InsertPointGuard Guard(*Builder);
Builder->SetInsertPoint(PN);
PHINode *NewPN =
Builder->CreatePHI(PN->getType(), PN->getNumIncomingValues());
for (auto [Val, Pred] : IncomingValues)
NewPN->addIncoming(Val, Pred);
return NewPN;
}
return NonNull;
}
if (match(V, m_SExtLike(m_Value(A)))) {
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateSExt(AV, V->getType()) : NonNull;
return nullptr;
}
if (match(V, m_Trunc(m_Value(A)))) {
if (auto *AV = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
DoesConsume, Depth))
return Builder ? Builder->CreateTrunc(AV, V->getType()) : NonNull;
return nullptr;
}
// De Morgan's Laws:
// (~(A | B)) -> (~A & ~B)
// (~(A & B)) -> (~A | ~B)
auto TryInvertAndOrUsingDeMorgan = [&](Instruction::BinaryOps Opcode,
bool IsLogical, Value *A,
Value *B) -> Value * {
bool LocalDoesConsume = DoesConsume;
if (!getFreelyInvertedImpl(B, B->hasOneUse(), /*Builder=*/nullptr,
LocalDoesConsume, Depth))
return nullptr;
if (auto *NotA = getFreelyInvertedImpl(A, A->hasOneUse(), Builder,
LocalDoesConsume, Depth)) {
auto *NotB = getFreelyInvertedImpl(B, B->hasOneUse(), Builder,
LocalDoesConsume, Depth);
DoesConsume = LocalDoesConsume;
if (IsLogical)
return Builder ? Builder->CreateLogicalOp(Opcode, NotA, NotB) : NonNull;
return Builder ? Builder->CreateBinOp(Opcode, NotA, NotB) : NonNull;
}
return nullptr;
};
if (match(V, m_Or(m_Value(A), m_Value(B))))
return TryInvertAndOrUsingDeMorgan(Instruction::And, /*IsLogical=*/false, A,
B);
if (match(V, m_And(m_Value(A), m_Value(B))))
return TryInvertAndOrUsingDeMorgan(Instruction::Or, /*IsLogical=*/false, A,
B);
if (match(V, m_LogicalOr(m_Value(A), m_Value(B))))
return TryInvertAndOrUsingDeMorgan(Instruction::And, /*IsLogical=*/true, A,
B);
if (match(V, m_LogicalAnd(m_Value(A), m_Value(B))))
return TryInvertAndOrUsingDeMorgan(Instruction::Or, /*IsLogical=*/true, A,
B);
return nullptr;
}
/// Return true if we should canonicalize the gep to an i8 ptradd.
static bool shouldCanonicalizeGEPToPtrAdd(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
Type *GEPEltType = GEP.getSourceElementType();
if (GEPEltType->isIntegerTy(8))
return false;
// Canonicalize scalable GEPs to an explicit offset using the llvm.vscale
// intrinsic. This has better support in BasicAA.
if (GEPEltType->isScalableTy())
return true;
// gep i32 p, mul(O, C) -> gep i8, p, mul(O, C*4) to fold the two multiplies
// together.
if (GEP.getNumIndices() == 1 &&
match(GEP.getOperand(1),
m_OneUse(m_CombineOr(m_Mul(m_Value(), m_ConstantInt()),
m_Shl(m_Value(), m_ConstantInt())))))
return true;
// gep (gep %p, C1), %x, C2 is expanded so the two constants can
// possibly be merged together.
auto PtrOpGep = dyn_cast<GEPOperator>(PtrOp);
return PtrOpGep && PtrOpGep->hasAllConstantIndices() &&
any_of(GEP.indices(), [](Value *V) {
const APInt *C;
return match(V, m_APInt(C)) && !C->isZero();
});
}
static Instruction *foldGEPOfPhi(GetElementPtrInst &GEP, PHINode *PN,
IRBuilderBase &Builder) {
auto *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0));
if (!Op1)
return nullptr;
// Don't fold a GEP into itself through a PHI node. This can only happen
// through the back-edge of a loop. Folding a GEP into itself means that
// the value of the previous iteration needs to be stored in the meantime,
// thus requiring an additional register variable to be live, but not
// actually achieving anything (the GEP still needs to be executed once per
// loop iteration).
if (Op1 == &GEP)
return nullptr;
GEPNoWrapFlags NW = Op1->getNoWrapFlags();
int DI = -1;
for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) {
auto *Op2 = dyn_cast<GetElementPtrInst>(*I);
if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands() ||
Op1->getSourceElementType() != Op2->getSourceElementType())
return nullptr;
// As for Op1 above, don't try to fold a GEP into itself.
if (Op2 == &GEP)
return nullptr;
// Keep track of the type as we walk the GEP.
Type *CurTy = nullptr;
for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) {
if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType())
return nullptr;
if (Op1->getOperand(J) != Op2->getOperand(J)) {
if (DI == -1) {
// We have not seen any differences yet in the GEPs feeding the
// PHI yet, so we record this one if it is allowed to be a
// variable.
// The first two arguments can vary for any GEP, the rest have to be
// static for struct slots
if (J > 1) {
assert(CurTy && "No current type?");
if (CurTy->isStructTy())
return nullptr;
}
DI = J;
} else {
// The GEP is different by more than one input. While this could be
// extended to support GEPs that vary by more than one variable it
// doesn't make sense since it greatly increases the complexity and
// would result in an R+R+R addressing mode which no backend
// directly supports and would need to be broken into several
// simpler instructions anyway.
return nullptr;
}
}
// Sink down a layer of the type for the next iteration.
if (J > 0) {
if (J == 1) {
CurTy = Op1->getSourceElementType();
} else {
CurTy =
GetElementPtrInst::getTypeAtIndex(CurTy, Op1->getOperand(J));
}
}
}
NW &= Op2->getNoWrapFlags();
}
// If not all GEPs are identical we'll have to create a new PHI node.
// Check that the old PHI node has only one use so that it will get
// removed.
if (DI != -1 && !PN->hasOneUse())
return nullptr;
auto *NewGEP = cast<GetElementPtrInst>(Op1->clone());
NewGEP->setNoWrapFlags(NW);
if (DI == -1) {
// All the GEPs feeding the PHI are identical. Clone one down into our
// BB so that it can be merged with the current GEP.
} else {
// All the GEPs feeding the PHI differ at a single offset. Clone a GEP
// into the current block so it can be merged, and create a new PHI to
// set that index.
PHINode *NewPN;
{
IRBuilderBase::InsertPointGuard Guard(Builder);
Builder.SetInsertPoint(PN);
NewPN = Builder.CreatePHI(Op1->getOperand(DI)->getType(),
PN->getNumOperands());
}
for (auto &I : PN->operands())
NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI),
PN->getIncomingBlock(I));
NewGEP->setOperand(DI, NewPN);
}
NewGEP->insertBefore(*GEP.getParent(), GEP.getParent()->getFirstInsertionPt());
return NewGEP;
}
Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
SmallVector<Value *, 8> Indices(GEP.indices());
Type *GEPType = GEP.getType();
Type *GEPEltType = GEP.getSourceElementType();
if (Value *V =
simplifyGEPInst(GEPEltType, PtrOp, Indices, GEP.getNoWrapFlags(),
SQ.getWithInstruction(&GEP)))
return replaceInstUsesWith(GEP, V);
// For vector geps, use the generic demanded vector support.
// Skip if GEP return type is scalable. The number of elements is unknown at
// compile-time.
if (auto *GEPFVTy = dyn_cast<FixedVectorType>(GEPType)) {
auto VWidth = GEPFVTy->getNumElements();
APInt PoisonElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnes(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&GEP, AllOnesEltMask,
PoisonElts)) {
if (V != &GEP)
return replaceInstUsesWith(GEP, V);
return &GEP;
}
// TODO: 1) Scalarize splat operands, 2) scalarize entire instruction if
// possible (decide on canonical form for pointer broadcast), 3) exploit
// undef elements to decrease demanded bits
}
// Eliminate unneeded casts for indices, and replace indices which displace
// by multiples of a zero size type with zero.
bool MadeChange = false;
// Index width may not be the same width as pointer width.
// Data layout chooses the right type based on supported integer types.
Type *NewScalarIndexTy =
DL.getIndexType(GEP.getPointerOperandType()->getScalarType());
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); I != E;
++I, ++GTI) {
// Skip indices into struct types.
if (GTI.isStruct())
continue;
Type *IndexTy = (*I)->getType();
Type *NewIndexType =
IndexTy->isVectorTy()
? VectorType::get(NewScalarIndexTy,
cast<VectorType>(IndexTy)->getElementCount())
: NewScalarIndexTy;
// If the element type has zero size then any index over it is equivalent
// to an index of zero, so replace it with zero if it is not zero already.
Type *EltTy = GTI.getIndexedType();
if (EltTy->isSized() && DL.getTypeAllocSize(EltTy).isZero())
if (!isa<Constant>(*I) || !match(I->get(), m_Zero())) {
*I = Constant::getNullValue(NewIndexType);
MadeChange = true;
}
if (IndexTy != NewIndexType) {
// If we are using a wider index than needed for this platform, shrink
// it to what we need. If narrower, sign-extend it to what we need.
// This explicit cast can make subsequent optimizations more obvious.
*I = Builder.CreateIntCast(*I, NewIndexType, true);
MadeChange = true;
}
}
if (MadeChange)
return &GEP;
// Canonicalize constant GEPs to i8 type.
if (!GEPEltType->isIntegerTy(8) && GEP.hasAllConstantIndices()) {
APInt Offset(DL.getIndexTypeSizeInBits(GEPType), 0);
if (GEP.accumulateConstantOffset(DL, Offset))
return replaceInstUsesWith(
GEP, Builder.CreatePtrAdd(PtrOp, Builder.getInt(Offset), "",
GEP.getNoWrapFlags()));
}
if (shouldCanonicalizeGEPToPtrAdd(GEP)) {
Value *Offset = EmitGEPOffset(cast<GEPOperator>(&GEP));
Value *NewGEP =
Builder.CreatePtrAdd(PtrOp, Offset, "", GEP.getNoWrapFlags());
return replaceInstUsesWith(GEP, NewGEP);
}
// Check to see if the inputs to the PHI node are getelementptr instructions.
if (auto *PN = dyn_cast<PHINode>(PtrOp)) {
if (Value *NewPtrOp = foldGEPOfPhi(GEP, PN, Builder))
return replaceOperand(GEP, 0, NewPtrOp);
}
if (auto *Src = dyn_cast<GEPOperator>(PtrOp))
if (Instruction *I = visitGEPOfGEP(GEP, Src))
return I;
if (GEP.getNumIndices() == 1) {
unsigned AS = GEP.getPointerAddressSpace();
if (GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
DL.getIndexSizeInBits(AS)) {
uint64_t TyAllocSize = DL.getTypeAllocSize(GEPEltType).getFixedValue();
if (TyAllocSize == 1) {
// Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X)) to (bitcast Y),
// but only if the result pointer is only used as if it were an integer,
// or both point to the same underlying object (otherwise provenance is
// not necessarily retained).
Value *X = GEP.getPointerOperand();
Value *Y;
if (match(GEP.getOperand(1),
m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X)))) &&
GEPType == Y->getType()) {
bool HasSameUnderlyingObject =
getUnderlyingObject(X) == getUnderlyingObject(Y);
bool Changed = false;
GEP.replaceUsesWithIf(Y, [&](Use &U) {
bool ShouldReplace = HasSameUnderlyingObject ||
isa<ICmpInst>(U.getUser()) ||
isa<PtrToIntInst>(U.getUser());
Changed |= ShouldReplace;
return ShouldReplace;
});
return Changed ? &GEP : nullptr;
}
} else if (auto *ExactIns =
dyn_cast<PossiblyExactOperator>(GEP.getOperand(1))) {
// Canonicalize (gep T* X, V / sizeof(T)) to (gep i8* X, V)
Value *V;
if (ExactIns->isExact()) {
if ((has_single_bit(TyAllocSize) &&
match(GEP.getOperand(1),
m_Shr(m_Value(V),
m_SpecificInt(countr_zero(TyAllocSize))))) ||
match(GEP.getOperand(1),
m_IDiv(m_Value(V), m_SpecificInt(TyAllocSize)))) {
return GetElementPtrInst::Create(Builder.getInt8Ty(),
GEP.getPointerOperand(), V,
GEP.getNoWrapFlags());
}
}
if (ExactIns->isExact() && ExactIns->hasOneUse()) {
// Try to canonicalize non-i8 element type to i8 if the index is an
// exact instruction. If the index is an exact instruction (div/shr)
// with a constant RHS, we can fold the non-i8 element scale into the
// div/shr (similiar to the mul case, just inverted).
const APInt *C;
std::optional<APInt> NewC;
if (has_single_bit(TyAllocSize) &&
match(ExactIns, m_Shr(m_Value(V), m_APInt(C))) &&
C->uge(countr_zero(TyAllocSize)))
NewC = *C - countr_zero(TyAllocSize);
else if (match(ExactIns, m_UDiv(m_Value(V), m_APInt(C)))) {
APInt Quot;
uint64_t Rem;
APInt::udivrem(*C, TyAllocSize, Quot, Rem);
if (Rem == 0)
NewC = Quot;
} else if (match(ExactIns, m_SDiv(m_Value(V), m_APInt(C)))) {
APInt Quot;
int64_t Rem;
APInt::sdivrem(*C, TyAllocSize, Quot, Rem);
// For sdiv we need to make sure we arent creating INT_MIN / -1.
if (!Quot.isAllOnes() && Rem == 0)
NewC = Quot;
}
if (NewC.has_value()) {
Value *NewOp = Builder.CreateBinOp(
static_cast<Instruction::BinaryOps>(ExactIns->getOpcode()), V,
ConstantInt::get(V->getType(), *NewC));
cast<BinaryOperator>(NewOp)->setIsExact();
return GetElementPtrInst::Create(Builder.getInt8Ty(),
GEP.getPointerOperand(), NewOp,
GEP.getNoWrapFlags());
}
}
}
}
}
// We do not handle pointer-vector geps here.
if (GEPType->isVectorTy())
return nullptr;
if (!GEP.isInBounds()) {
unsigned IdxWidth =
DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
APInt BasePtrOffset(IdxWidth, 0);
Value *UnderlyingPtrOp =
PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL, BasePtrOffset);
bool CanBeNull, CanBeFreed;
uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
DL, CanBeNull, CanBeFreed);
if (!CanBeNull && !CanBeFreed && DerefBytes != 0) {
if (GEP.accumulateConstantOffset(DL, BasePtrOffset) &&
BasePtrOffset.isNonNegative()) {
APInt AllocSize(IdxWidth, DerefBytes);
if (BasePtrOffset.ule(AllocSize)) {
return GetElementPtrInst::CreateInBounds(
GEP.getSourceElementType(), PtrOp, Indices, GEP.getName());
}
}
}
}
// nusw + nneg -> nuw
if (GEP.hasNoUnsignedSignedWrap() && !GEP.hasNoUnsignedWrap() &&
all_of(GEP.indices(), [&](Value *Idx) {
return isKnownNonNegative(Idx, SQ.getWithInstruction(&GEP));
})) {
GEP.setNoWrapFlags(GEP.getNoWrapFlags() | GEPNoWrapFlags::noUnsignedWrap());
return &GEP;
}
// These rewrites are trying to preserve inbounds/nuw attributes. So we want
// to do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
// Given (gep p, x+y) we want to determine the common nowrap flags for both
// geps if transforming into (gep (gep p, x), y).
auto GetPreservedNoWrapFlags = [&](bool AddIsNUW) {
// We can preserve both "inbounds nuw", "nusw nuw" and "nuw" if we know
// that x + y does not have unsigned wrap.
if (GEP.hasNoUnsignedWrap() && AddIsNUW)
return GEP.getNoWrapFlags();
return GEPNoWrapFlags::none();
};
// Try to replace ADD + GEP with GEP + GEP.
Value *Idx1, *Idx2;
if (match(GEP.getOperand(1),
m_OneUse(m_AddLike(m_Value(Idx1), m_Value(Idx2))))) {
// %idx = add i64 %idx1, %idx2
// %gep = getelementptr i32, ptr %ptr, i64 %idx
// as:
// %newptr = getelementptr i32, ptr %ptr, i64 %idx1
// %newgep = getelementptr i32, ptr %newptr, i64 %idx2
bool NUW = match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value()));
GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW);
auto *NewPtr =
Builder.CreateGEP(GEP.getSourceElementType(), GEP.getPointerOperand(),
Idx1, "", NWFlags);
return replaceInstUsesWith(GEP,
Builder.CreateGEP(GEP.getSourceElementType(),
NewPtr, Idx2, "", NWFlags));
}
ConstantInt *C;
if (match(GEP.getOperand(1), m_OneUse(m_SExtLike(m_OneUse(m_NSWAddLike(
m_Value(Idx1), m_ConstantInt(C))))))) {
// %add = add nsw i32 %idx1, idx2
// %sidx = sext i32 %add to i64
// %gep = getelementptr i32, ptr %ptr, i64 %sidx
// as:
// %newptr = getelementptr i32, ptr %ptr, i32 %idx1
// %newgep = getelementptr i32, ptr %newptr, i32 idx2
bool NUW = match(GEP.getOperand(1),
m_NNegZExt(m_NUWAddLike(m_Value(), m_Value())));
GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW);
auto *NewPtr = Builder.CreateGEP(
GEP.getSourceElementType(), GEP.getPointerOperand(),
Builder.CreateSExt(Idx1, GEP.getOperand(1)->getType()), "", NWFlags);
return replaceInstUsesWith(
GEP,
Builder.CreateGEP(GEP.getSourceElementType(), NewPtr,
Builder.CreateSExt(C, GEP.getOperand(1)->getType()),
"", NWFlags));
}
}
if (Instruction *R = foldSelectGEP(GEP, Builder))
return R;
return nullptr;
}
static bool isNeverEqualToUnescapedAlloc(Value *V, const TargetLibraryInfo &TLI,
Instruction *AI) {
if (isa<ConstantPointerNull>(V))
return true;
if (auto *LI = dyn_cast<LoadInst>(V))
return isa<GlobalVariable>(LI->getPointerOperand());
// Two distinct allocations will never be equal.
return isAllocLikeFn(V, &TLI) && V != AI;
}
/// Given a call CB which uses an address UsedV, return true if we can prove the
/// call's only possible effect is storing to V.
static bool isRemovableWrite(CallBase &CB, Value *UsedV,
const TargetLibraryInfo &TLI) {
if (!CB.use_empty())
// TODO: add recursion if returned attribute is present
return false;
if (CB.isTerminator())
// TODO: remove implementation restriction
return false;
if (!CB.willReturn() || !CB.doesNotThrow())
return false;
// If the only possible side effect of the call is writing to the alloca,
// and the result isn't used, we can safely remove any reads implied by the
// call including those which might read the alloca itself.
std::optional<MemoryLocation> Dest = MemoryLocation::getForDest(&CB, TLI);
return Dest && Dest->Ptr == UsedV;
}
static bool isAllocSiteRemovable(Instruction *AI,
SmallVectorImpl<WeakTrackingVH> &Users,
const TargetLibraryInfo &TLI) {
SmallVector<Instruction*, 4> Worklist;
const std::optional<StringRef> Family = getAllocationFamily(AI, &TLI);
Worklist.push_back(AI);
do {
Instruction *PI = Worklist.pop_back_val();
for (User *U : PI->users()) {
Instruction *I = cast<Instruction>(U);
switch (I->getOpcode()) {
default:
// Give up the moment we see something we can't handle.
return false;
case Instruction::AddrSpaceCast:
case Instruction::BitCast:
case Instruction::GetElementPtr:
Users.emplace_back(I);
Worklist.push_back(I);
continue;
case Instruction::ICmp: {
ICmpInst *ICI = cast<ICmpInst>(I);
// We can fold eq/ne comparisons with null to false/true, respectively.
// We also fold comparisons in some conditions provided the alloc has
// not escaped (see isNeverEqualToUnescapedAlloc).
if (!ICI->isEquality())
return false;
unsigned OtherIndex = (ICI->getOperand(0) == PI) ? 1 : 0;
if (!isNeverEqualToUnescapedAlloc(ICI->getOperand(OtherIndex), TLI, AI))
return false;
// Do not fold compares to aligned_alloc calls, as they may have to
// return null in case the required alignment cannot be satisfied,
// unless we can prove that both alignment and size are valid.
auto AlignmentAndSizeKnownValid = [](CallBase *CB) {
// Check if alignment and size of a call to aligned_alloc is valid,
// that is alignment is a power-of-2 and the size is a multiple of the
// alignment.
const APInt *Alignment;
const APInt *Size;
return match(CB->getArgOperand(0), m_APInt(Alignment)) &&
match(CB->getArgOperand(1), m_APInt(Size)) &&
Alignment->isPowerOf2() && Size->urem(*Alignment).isZero();
};
auto *CB = dyn_cast<CallBase>(AI);
LibFunc TheLibFunc;
if (CB && TLI.getLibFunc(*CB->getCalledFunction(), TheLibFunc) &&
TLI.has(TheLibFunc) && TheLibFunc == LibFunc_aligned_alloc &&
!AlignmentAndSizeKnownValid(CB))
return false;
Users.emplace_back(I);
continue;
}
case Instruction::Call:
// Ignore no-op and store intrinsics.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default:
return false;
case Intrinsic::memmove:
case Intrinsic::memcpy:
case Intrinsic::memset: {
MemIntrinsic *MI = cast<MemIntrinsic>(II);
if (MI->isVolatile() || MI->getRawDest() != PI)
return false;
[[fallthrough]];
}
case Intrinsic::assume:
case Intrinsic::invariant_start:
case Intrinsic::invariant_end:
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
case Intrinsic::objectsize:
Users.emplace_back(I);
continue;
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
Users.emplace_back(I);
Worklist.push_back(I);
continue;
}
}
if (isRemovableWrite(*cast<CallBase>(I), PI, TLI)) {
Users.emplace_back(I);
continue;
}
if (getFreedOperand(cast<CallBase>(I), &TLI) == PI &&
getAllocationFamily(I, &TLI) == Family) {
assert(Family);
Users.emplace_back(I);
continue;
}
if (getReallocatedOperand(cast<CallBase>(I)) == PI &&
getAllocationFamily(I, &TLI) == Family) {
assert(Family);
Users.emplace_back(I);
Worklist.push_back(I);
continue;
}
return false;
case Instruction::Store: {
StoreInst *SI = cast<StoreInst>(I);
if (SI->isVolatile() || SI->getPointerOperand() != PI)
return false;
Users.emplace_back(I);
continue;
}
}
llvm_unreachable("missing a return?");
}
} while (!Worklist.empty());
return true;
}
Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
assert(isa<AllocaInst>(MI) || isRemovableAlloc(&cast<CallBase>(MI), &TLI));
// If we have a malloc call which is only used in any amount of comparisons to
// null and free calls, delete the calls and replace the comparisons with true
// or false as appropriate.
// This is based on the principle that we can substitute our own allocation
// function (which will never return null) rather than knowledge of the
// specific function being called. In some sense this can change the permitted
// outputs of a program (when we convert a malloc to an alloca, the fact that
// the allocation is now on the stack is potentially visible, for example),
// but we believe in a permissible manner.
SmallVector<WeakTrackingVH, 64> Users;
// If we are removing an alloca with a dbg.declare, insert dbg.value calls
// before each store.
SmallVector<DbgVariableIntrinsic *, 8> DVIs;
SmallVector<DbgVariableRecord *, 8> DVRs;
std::unique_ptr<DIBuilder> DIB;
if (isa<AllocaInst>(MI)) {
findDbgUsers(DVIs, &MI, &DVRs);
DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false));
}
if (isAllocSiteRemovable(&MI, Users, TLI)) {
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
// Lowering all @llvm.objectsize calls first because they may
// use a bitcast/GEP of the alloca we are removing.
if (!Users[i])
continue;
Instruction *I = cast<Instruction>(&*Users[i]);
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
if (II->getIntrinsicID() == Intrinsic::objectsize) {
SmallVector<Instruction *> InsertedInstructions;
Value *Result = lowerObjectSizeCall(
II, DL, &TLI, AA, /*MustSucceed=*/true, &InsertedInstructions);
for (Instruction *Inserted : InsertedInstructions)
Worklist.add(Inserted);
replaceInstUsesWith(*I, Result);
eraseInstFromFunction(*I);
Users[i] = nullptr; // Skip examining in the next loop.
}
}
}
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
if (!Users[i])
continue;
Instruction *I = cast<Instruction>(&*Users[i]);
if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
replaceInstUsesWith(*C,
ConstantInt::get(Type::getInt1Ty(C->getContext()),
C->isFalseWhenEqual()));
} else if (auto *SI = dyn_cast<StoreInst>(I)) {
for (auto *DVI : DVIs)
if (DVI->isAddressOfVariable())
ConvertDebugDeclareToDebugValue(DVI, SI, *DIB);
for (auto *DVR : DVRs)
if (DVR->isAddressOfVariable())
ConvertDebugDeclareToDebugValue(DVR, SI, *DIB);
} else {
// Casts, GEP, or anything else: we're about to delete this instruction,
// so it can not have any valid uses.
replaceInstUsesWith(*I, PoisonValue::get(I->getType()));
}
eraseInstFromFunction(*I);
}
if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
// Replace invoke with a NOP intrinsic to maintain the original CFG
Module *M = II->getModule();
Function *F = Intrinsic::getOrInsertDeclaration(M, Intrinsic::donothing);
auto *NewII = InvokeInst::Create(
F, II->getNormalDest(), II->getUnwindDest(), {}, "", II->getParent());
NewII->setDebugLoc(II->getDebugLoc());
}
// Remove debug intrinsics which describe the value contained within the
// alloca. In addition to removing dbg.{declare,addr} which simply point to
// the alloca, remove dbg.value(<alloca>, ..., DW_OP_deref)'s as well, e.g.:
//
// ```
// define void @foo(i32 %0) {
// %a = alloca i32 ; Deleted.
// store i32 %0, i32* %a
// dbg.value(i32 %0, "arg0") ; Not deleted.
// dbg.value(i32* %a, "arg0", DW_OP_deref) ; Deleted.
// call void @trivially_inlinable_no_op(i32* %a)
// ret void
// }
// ```
//
// This may not be required if we stop describing the contents of allocas
// using dbg.value(<alloca>, ..., DW_OP_deref), but we currently do this in
// the LowerDbgDeclare utility.
//
// If there is a dead store to `%a` in @trivially_inlinable_no_op, the
// "arg0" dbg.value may be stale after the call. However, failing to remove
// the DW_OP_deref dbg.value causes large gaps in location coverage.
//
// FIXME: the Assignment Tracking project has now likely made this
// redundant (and it's sometimes harmful).
for (auto *DVI : DVIs)
if (DVI->isAddressOfVariable() || DVI->getExpression()->startsWithDeref())
DVI->eraseFromParent();
for (auto *DVR : DVRs)
if (DVR->isAddressOfVariable() || DVR->getExpression()->startsWithDeref())
DVR->eraseFromParent();
return eraseInstFromFunction(MI);
}
return nullptr;
}
/// Move the call to free before a NULL test.
///
/// Check if this free is accessed after its argument has been test
/// against NULL (property 0).
/// If yes, it is legal to move this call in its predecessor block.
///
/// The move is performed only if the block containing the call to free
/// will be removed, i.e.:
/// 1. it has only one predecessor P, and P has two successors
/// 2. it contains the call, noops, and an unconditional branch
/// 3. its successor is the same as its predecessor's successor
///
/// The profitability is out-of concern here and this function should
/// be called only if the caller knows this transformation would be
/// profitable (e.g., for code size).
static Instruction *tryToMoveFreeBeforeNullTest(CallInst &FI,
const DataLayout &DL) {
Value *Op = FI.getArgOperand(0);
BasicBlock *FreeInstrBB = FI.getParent();
BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor();
// Validate part of constraint #1: Only one predecessor
// FIXME: We can extend the number of predecessor, but in that case, we
// would duplicate the call to free in each predecessor and it may
// not be profitable even for code size.
if (!PredBB)
return nullptr;
// Validate constraint #2: Does this block contains only the call to
// free, noops, and an unconditional branch?
BasicBlock *SuccBB;
Instruction *FreeInstrBBTerminator = FreeInstrBB->getTerminator();
if (!match(FreeInstrBBTerminator, m_UnconditionalBr(SuccBB)))
return nullptr;
// If there are only 2 instructions in the block, at this point,
// this is the call to free and unconditional.
// If there are more than 2 instructions, check that they are noops
// i.e., they won't hurt the performance of the generated code.
if (FreeInstrBB->size() != 2) {
for (const Instruction &Inst : FreeInstrBB->instructionsWithoutDebug()) {
if (&Inst == &FI || &Inst == FreeInstrBBTerminator)
continue;
auto *Cast = dyn_cast<CastInst>(&Inst);
if (!Cast || !Cast->isNoopCast(DL))
return nullptr;
}
}
// Validate the rest of constraint #1 by matching on the pred branch.
Instruction *TI = PredBB->getTerminator();
BasicBlock *TrueBB, *FalseBB;
CmpPredicate Pred;
if (!match(TI, m_Br(m_ICmp(Pred,
m_CombineOr(m_Specific(Op),
m_Specific(Op->stripPointerCasts())),
m_Zero()),
TrueBB, FalseBB)))
return nullptr;
if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE)
return nullptr;
// Validate constraint #3: Ensure the null case just falls through.
if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB))
return nullptr;
assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) &&
"Broken CFG: missing edge from predecessor to successor");
// At this point, we know that everything in FreeInstrBB can be moved
// before TI.
for (Instruction &Instr : llvm::make_early_inc_range(*FreeInstrBB)) {
if (&Instr == FreeInstrBBTerminator)
break;
Instr.moveBeforePreserving(TI->getIterator());
}
assert(FreeInstrBB->size() == 1 &&
"Only the branch instruction should remain");
// Now that we've moved the call to free before the NULL check, we have to
// remove any attributes on its parameter that imply it's non-null, because
// those attributes might have only been valid because of the NULL check, and
// we can get miscompiles if we keep them. This is conservative if non-null is
// also implied by something other than the NULL check, but it's guaranteed to
// be correct, and the conservativeness won't matter in practice, since the
// attributes are irrelevant for the call to free itself and the pointer
// shouldn't be used after the call.
AttributeList Attrs = FI.getAttributes();
Attrs = Attrs.removeParamAttribute(FI.getContext(), 0, Attribute::NonNull);
Attribute Dereferenceable = Attrs.getParamAttr(0, Attribute::Dereferenceable);
if (Dereferenceable.isValid()) {
uint64_t Bytes = Dereferenceable.getDereferenceableBytes();
Attrs = Attrs.removeParamAttribute(FI.getContext(), 0,
Attribute::Dereferenceable);
Attrs = Attrs.addDereferenceableOrNullParamAttr(FI.getContext(), 0, Bytes);
}
FI.setAttributes(Attrs);
return &FI;
}
Instruction *InstCombinerImpl::visitFree(CallInst &FI, Value *Op) {
// free undef -> unreachable.
if (isa<UndefValue>(Op)) {
// Leave a marker since we can't modify the CFG here.
CreateNonTerminatorUnreachable(&FI);
return eraseInstFromFunction(FI);
}
// If we have 'free null' delete the instruction. This can happen in stl code
// when lots of inlining happens.
if (isa<ConstantPointerNull>(Op))
return eraseInstFromFunction(FI);
// If we had free(realloc(...)) with no intervening uses, then eliminate the
// realloc() entirely.
CallInst *CI = dyn_cast<CallInst>(Op);
if (CI && CI->hasOneUse())
if (Value *ReallocatedOp = getReallocatedOperand(CI))
return eraseInstFromFunction(*replaceInstUsesWith(*CI, ReallocatedOp));
// If we optimize for code size, try to move the call to free before the null
// test so that simplify cfg can remove the empty block and dead code
// elimination the branch. I.e., helps to turn something like:
// if (foo) free(foo);
// into
// free(foo);
//
// Note that we can only do this for 'free' and not for any flavor of
// 'operator delete'; there is no 'operator delete' symbol for which we are
// permitted to invent a call, even if we're passing in a null pointer.
if (MinimizeSize) {
LibFunc Func;
if (TLI.getLibFunc(FI, Func) && TLI.has(Func) && Func == LibFunc_free)
if (Instruction *I = tryToMoveFreeBeforeNullTest(FI, DL))
return I;
}
return nullptr;
}
Instruction *InstCombinerImpl::visitReturnInst(ReturnInst &RI) {
Value *RetVal = RI.getReturnValue();
if (!RetVal)
return nullptr;
Function *F = RI.getFunction();
Type *RetTy = RetVal->getType();
if (RetTy->isPointerTy()) {
bool HasDereferenceable =
F->getAttributes().getRetDereferenceableBytes() > 0;
if (F->hasRetAttribute(Attribute::NonNull) ||
(HasDereferenceable &&
!NullPointerIsDefined(F, RetTy->getPointerAddressSpace()))) {
if (Value *V = simplifyNonNullOperand(RetVal, HasDereferenceable))
return replaceOperand(RI, 0, V);
}
}
if (!AttributeFuncs::isNoFPClassCompatibleType(RetTy))
return nullptr;
FPClassTest ReturnClass = F->getAttributes().getRetNoFPClass();
if (ReturnClass == fcNone)
return nullptr;
KnownFPClass KnownClass;
Value *Simplified =
SimplifyDemandedUseFPClass(RetVal, ~ReturnClass, KnownClass, 0, &RI);
if (!Simplified)
return nullptr;
return ReturnInst::Create(RI.getContext(), Simplified);
}
// WARNING: keep in sync with SimplifyCFGOpt::simplifyUnreachable()!
bool InstCombinerImpl::removeInstructionsBeforeUnreachable(Instruction &I) {
// Try to remove the previous instruction if it must lead to unreachable.
// This includes instructions like stores and "llvm.assume" that may not get
// removed by simple dead code elimination.
bool Changed = false;
while (Instruction *Prev = I.getPrevNonDebugInstruction()) {
// While we theoretically can erase EH, that would result in a block that
// used to start with an EH no longer starting with EH, which is invalid.
// To make it valid, we'd need to fixup predecessors to no longer refer to
// this block, but that changes CFG, which is not allowed in InstCombine.
if (Prev->isEHPad())
break; // Can not drop any more instructions. We're done here.
if (!isGuaranteedToTransferExecutionToSuccessor(Prev))
break; // Can not drop any more instructions. We're done here.
// Otherwise, this instruction can be freely erased,
// even if it is not side-effect free.
// A value may still have uses before we process it here (for example, in
// another unreachable block), so convert those to poison.
replaceInstUsesWith(*Prev, PoisonValue::get(Prev->getType()));
eraseInstFromFunction(*Prev);
Changed = true;
}
return Changed;
}
Instruction *InstCombinerImpl::visitUnreachableInst(UnreachableInst &I) {
removeInstructionsBeforeUnreachable(I);
return nullptr;
}
Instruction *InstCombinerImpl::visitUnconditionalBranchInst(BranchInst &BI) {
assert(BI.isUnconditional() && "Only for unconditional branches.");
// If this store is the second-to-last instruction in the basic block
// (excluding debug info) and if the block ends with
// an unconditional branch, try to move the store to the successor block.
auto GetLastSinkableStore = [](BasicBlock::iterator BBI) {
BasicBlock::iterator FirstInstr = BBI->getParent()->begin();
do {
if (BBI != FirstInstr)
--BBI;
} while (BBI != FirstInstr && BBI->isDebugOrPseudoInst());
return dyn_cast<StoreInst>(BBI);
};
if (StoreInst *SI = GetLastSinkableStore(BasicBlock::iterator(BI)))
if (mergeStoreIntoSuccessor(*SI))
return &BI;
return nullptr;
}
void InstCombinerImpl::addDeadEdge(BasicBlock *From, BasicBlock *To,
SmallVectorImpl<BasicBlock *> &Worklist) {
if (!DeadEdges.insert({From, To}).second)
return;
// Replace phi node operands in successor with poison.
for (PHINode &PN : To->phis())
for (Use &U : PN.incoming_values())
if (PN.getIncomingBlock(U) == From && !isa<PoisonValue>(U)) {
replaceUse(U, PoisonValue::get(PN.getType()));
addToWorklist(&PN);
MadeIRChange = true;
}
Worklist.push_back(To);
}
// Under the assumption that I is unreachable, remove it and following
// instructions. Changes are reported directly to MadeIRChange.
void InstCombinerImpl::handleUnreachableFrom(
Instruction *I, SmallVectorImpl<BasicBlock *> &Worklist) {
BasicBlock *BB = I->getParent();
for (Instruction &Inst : make_early_inc_range(
make_range(std::next(BB->getTerminator()->getReverseIterator()),
std::next(I->getReverseIterator())))) {
if (!Inst.use_empty() && !Inst.getType()->isTokenTy()) {
replaceInstUsesWith(Inst, PoisonValue::get(Inst.getType()));
MadeIRChange = true;
}
if (Inst.isEHPad() || Inst.getType()->isTokenTy())
continue;
// RemoveDIs: erase debug-info on this instruction manually.
Inst.dropDbgRecords();
eraseInstFromFunction(Inst);
MadeIRChange = true;
}
SmallVector<Value *> Changed;
if (handleUnreachableTerminator(BB->getTerminator(), Changed)) {
MadeIRChange = true;
for (Value *V : Changed)
addToWorklist(cast<Instruction>(V));
}
// Handle potentially dead successors.
for (BasicBlock *Succ : successors(BB))
addDeadEdge(BB, Succ, Worklist);
}
void InstCombinerImpl::handlePotentiallyDeadBlocks(
SmallVectorImpl<BasicBlock *> &Worklist) {
while (!Worklist.empty()) {
BasicBlock *BB = Worklist.pop_back_val();
if (!all_of(predecessors(BB), [&](BasicBlock *Pred) {
return DeadEdges.contains({Pred, BB}) || DT.dominates(BB, Pred);
}))
continue;
handleUnreachableFrom(&BB->front(), Worklist);
}
}
void InstCombinerImpl::handlePotentiallyDeadSuccessors(BasicBlock *BB,
BasicBlock *LiveSucc) {
SmallVector<BasicBlock *> Worklist;
for (BasicBlock *Succ : successors(BB)) {
// The live successor isn't dead.
if (Succ == LiveSucc)
continue;
addDeadEdge(BB, Succ, Worklist);
}
handlePotentiallyDeadBlocks(Worklist);
}
Instruction *InstCombinerImpl::visitBranchInst(BranchInst &BI) {
if (BI.isUnconditional())
return visitUnconditionalBranchInst(BI);
// Change br (not X), label True, label False to: br X, label False, True
Value *Cond = BI.getCondition();
Value *X;
if (match(Cond, m_Not(m_Value(X))) && !isa<Constant>(X)) {
// Swap Destinations and condition...
BI.swapSuccessors();
if (BPI)
BPI->swapSuccEdgesProbabilities(BI.getParent());
return replaceOperand(BI, 0, X);
}
// Canonicalize logical-and-with-invert as logical-or-with-invert.
// This is done by inverting the condition and swapping successors:
// br (X && !Y), T, F --> br !(X && !Y), F, T --> br (!X || Y), F, T
Value *Y;
if (isa<SelectInst>(Cond) &&
match(Cond,
m_OneUse(m_LogicalAnd(m_Value(X), m_OneUse(m_Not(m_Value(Y))))))) {
Value *NotX = Builder.CreateNot(X, "not." + X->getName());
Value *Or = Builder.CreateLogicalOr(NotX, Y);
BI.swapSuccessors();
if (BPI)
BPI->swapSuccEdgesProbabilities(BI.getParent());
return replaceOperand(BI, 0, Or);
}
// If the condition is irrelevant, remove the use so that other
// transforms on the condition become more effective.
if (!isa<ConstantInt>(Cond) && BI.getSuccessor(0) == BI.getSuccessor(1))
return replaceOperand(BI, 0, ConstantInt::getFalse(Cond->getType()));
// Canonicalize, for example, fcmp_one -> fcmp_oeq.
CmpPredicate Pred;
if (match(Cond, m_OneUse(m_FCmp(Pred, m_Value(), m_Value()))) &&
!isCanonicalPredicate(Pred)) {
// Swap destinations and condition.
auto *Cmp = cast<CmpInst>(Cond);
Cmp->setPredicate(CmpInst::getInversePredicate(Pred));
BI.swapSuccessors();
if (BPI)
BPI->swapSuccEdgesProbabilities(BI.getParent());
Worklist.push(Cmp);
return &BI;
}
if (isa<UndefValue>(Cond)) {
handlePotentiallyDeadSuccessors(BI.getParent(), /*LiveSucc*/ nullptr);
return nullptr;
}
if (auto *CI = dyn_cast<ConstantInt>(Cond)) {
handlePotentiallyDeadSuccessors(BI.getParent(),
BI.getSuccessor(!CI->getZExtValue()));
return nullptr;
}
// Replace all dominated uses of the condition with true/false
// Ignore constant expressions to avoid iterating over uses on other
// functions.
if (!isa<Constant>(Cond) && BI.getSuccessor(0) != BI.getSuccessor(1)) {
for (auto &U : make_early_inc_range(Cond->uses())) {
BasicBlockEdge Edge0(BI.getParent(), BI.getSuccessor(0));
if (DT.dominates(Edge0, U)) {
replaceUse(U, ConstantInt::getTrue(Cond->getType()));
addToWorklist(cast<Instruction>(U.getUser()));
continue;
}
BasicBlockEdge Edge1(BI.getParent(), BI.getSuccessor(1));
if (DT.dominates(Edge1, U)) {
replaceUse(U, ConstantInt::getFalse(Cond->getType()));
addToWorklist(cast<Instruction>(U.getUser()));
}
}
}
DC.registerBranch(&BI);
return nullptr;
}
// Replaces (switch (select cond, X, C)/(select cond, C, X)) with (switch X) if
// we can prove that both (switch C) and (switch X) go to the default when cond
// is false/true.
static Value *simplifySwitchOnSelectUsingRanges(SwitchInst &SI,
SelectInst *Select,
bool IsTrueArm) {
unsigned CstOpIdx = IsTrueArm ? 1 : 2;
auto *C = dyn_cast<ConstantInt>(Select->getOperand(CstOpIdx));
if (!C)
return nullptr;
BasicBlock *CstBB = SI.findCaseValue(C)->getCaseSuccessor();
if (CstBB != SI.getDefaultDest())
return nullptr;
Value *X = Select->getOperand(3 - CstOpIdx);
CmpPredicate Pred;
const APInt *RHSC;
if (!match(Select->getCondition(),
m_ICmp(Pred, m_Specific(X), m_APInt(RHSC))))
return nullptr;
if (IsTrueArm)
Pred = ICmpInst::getInversePredicate(Pred);
// See whether we can replace the select with X
ConstantRange CR = ConstantRange::makeExactICmpRegion(Pred, *RHSC);
for (auto Case : SI.cases())
if (!CR.contains(Case.getCaseValue()->getValue()))
return nullptr;
return X;
}
Instruction *InstCombinerImpl::visitSwitchInst(SwitchInst &SI) {
Value *Cond = SI.getCondition();
Value *Op0;
ConstantInt *AddRHS;
if (match(Cond, m_Add(m_Value(Op0), m_ConstantInt(AddRHS)))) {
// Change 'switch (X+4) case 1:' into 'switch (X) case -3'.
for (auto Case : SI.cases()) {
Constant *NewCase = ConstantExpr::getSub(Case.getCaseValue(), AddRHS);
assert(isa<ConstantInt>(NewCase) &&
"Result of expression should be constant");
Case.setValue(cast<ConstantInt>(NewCase));
}
return replaceOperand(SI, 0, Op0);
}
ConstantInt *SubLHS;
if (match(Cond, m_Sub(m_ConstantInt(SubLHS), m_Value(Op0)))) {
// Change 'switch (1-X) case 1:' into 'switch (X) case 0'.
for (auto Case : SI.cases()) {
Constant *NewCase = ConstantExpr::getSub(SubLHS, Case.getCaseValue());
assert(isa<ConstantInt>(NewCase) &&
"Result of expression should be constant");
Case.setValue(cast<ConstantInt>(NewCase));
}
return replaceOperand(SI, 0, Op0);
}
uint64_t ShiftAmt;
if (match(Cond, m_Shl(m_Value(Op0), m_ConstantInt(ShiftAmt))) &&
ShiftAmt < Op0->getType()->getScalarSizeInBits() &&
all_of(SI.cases(), [&](const auto &Case) {
return Case.getCaseValue()->getValue().countr_zero() >= ShiftAmt;
})) {
// Change 'switch (X << 2) case 4:' into 'switch (X) case 1:'.
OverflowingBinaryOperator *Shl = cast<OverflowingBinaryOperator>(Cond);
if (Shl->hasNoUnsignedWrap() || Shl->hasNoSignedWrap() ||
Shl->hasOneUse()) {
Value *NewCond = Op0;
if (!Shl->hasNoUnsignedWrap() && !Shl->hasNoSignedWrap()) {
// If the shift may wrap, we need to mask off the shifted bits.
unsigned BitWidth = Op0->getType()->getScalarSizeInBits();
NewCond = Builder.CreateAnd(
Op0, APInt::getLowBitsSet(BitWidth, BitWidth - ShiftAmt));
}
for (auto Case : SI.cases()) {
const APInt &CaseVal = Case.getCaseValue()->getValue();
APInt ShiftedCase = Shl->hasNoSignedWrap() ? CaseVal.ashr(ShiftAmt)
: CaseVal.lshr(ShiftAmt);
Case.setValue(ConstantInt::get(SI.getContext(), ShiftedCase));
}
return replaceOperand(SI, 0, NewCond);
}
}
// Fold switch(zext/sext(X)) into switch(X) if possible.
if (match(Cond, m_ZExtOrSExt(m_Value(Op0)))) {
bool IsZExt = isa<ZExtInst>(Cond);
Type *SrcTy = Op0->getType();
unsigned NewWidth = SrcTy->getScalarSizeInBits();
if (all_of(SI.cases(), [&](const auto &Case) {
const APInt &CaseVal = Case.getCaseValue()->getValue();
return IsZExt ? CaseVal.isIntN(NewWidth)
: CaseVal.isSignedIntN(NewWidth);
})) {
for (auto &Case : SI.cases()) {
APInt TruncatedCase = Case.getCaseValue()->getValue().trunc(NewWidth);
Case.setValue(ConstantInt::get(SI.getContext(), TruncatedCase));
}
return replaceOperand(SI, 0, Op0);
}
}
// Fold switch(select cond, X, Y) into switch(X/Y) if possible
if (auto *Select = dyn_cast<SelectInst>(Cond)) {
if (Value *V =
simplifySwitchOnSelectUsingRanges(SI, Select, /*IsTrueArm=*/true))
return replaceOperand(SI, 0, V);
if (Value *V =
simplifySwitchOnSelectUsingRanges(SI, Select, /*IsTrueArm=*/false))
return replaceOperand(SI, 0, V);
}
KnownBits Known = computeKnownBits(Cond, 0, &SI);
unsigned LeadingKnownZeros = Known.countMinLeadingZeros();
unsigned LeadingKnownOnes = Known.countMinLeadingOnes();
// Compute the number of leading bits we can ignore.
// TODO: A better way to determine this would use ComputeNumSignBits().
for (const auto &C : SI.cases()) {
LeadingKnownZeros =
std::min(LeadingKnownZeros, C.getCaseValue()->getValue().countl_zero());
LeadingKnownOnes =
std::min(LeadingKnownOnes, C.getCaseValue()->getValue().countl_one());
}
unsigned NewWidth = Known.getBitWidth() - std::max(LeadingKnownZeros, LeadingKnownOnes);
// Shrink the condition operand if the new type is smaller than the old type.
// But do not shrink to a non-standard type, because backend can't generate
// good code for that yet.
// TODO: We can make it aggressive again after fixing PR39569.
if (NewWidth > 0 && NewWidth < Known.getBitWidth() &&
shouldChangeType(Known.getBitWidth(), NewWidth)) {
IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
Builder.SetInsertPoint(&SI);
Value *NewCond = Builder.CreateTrunc(Cond, Ty, "trunc");
for (auto Case : SI.cases()) {
APInt TruncatedCase = Case.getCaseValue()->getValue().trunc(NewWidth);
Case.setValue(ConstantInt::get(SI.getContext(), TruncatedCase));
}
return replaceOperand(SI, 0, NewCond);
}
if (isa<UndefValue>(Cond)) {
handlePotentiallyDeadSuccessors(SI.getParent(), /*LiveSucc*/ nullptr);
return nullptr;
}
if (auto *CI = dyn_cast<ConstantInt>(Cond)) {
handlePotentiallyDeadSuccessors(SI.getParent(),
SI.findCaseValue(CI)->getCaseSuccessor());
return nullptr;
}
return nullptr;
}
Instruction *
InstCombinerImpl::foldExtractOfOverflowIntrinsic(ExtractValueInst &EV) {
auto *WO = dyn_cast<WithOverflowInst>(EV.getAggregateOperand());
if (!WO)
return nullptr;
Intrinsic::ID OvID = WO->getIntrinsicID();
const APInt *C = nullptr;
if (match(WO->getRHS(), m_APIntAllowPoison(C))) {
if (*EV.idx_begin() == 0 && (OvID == Intrinsic::smul_with_overflow ||
OvID == Intrinsic::umul_with_overflow)) {
// extractvalue (any_mul_with_overflow X, -1), 0 --> -X
if (C->isAllOnes())
return BinaryOperator::CreateNeg(WO->getLHS());
// extractvalue (any_mul_with_overflow X, 2^n), 0 --> X << n
if (C->isPowerOf2()) {
return BinaryOperator::CreateShl(
WO->getLHS(),
ConstantInt::get(WO->getLHS()->getType(), C->logBase2()));
}
}
}
// We're extracting from an overflow intrinsic. See if we're the only user.
// That allows us to simplify multiple result intrinsics to simpler things
// that just get one value.
if (!WO->hasOneUse())
return nullptr;
// Check if we're grabbing only the result of a 'with overflow' intrinsic
// and replace it with a traditional binary instruction.
if (*EV.idx_begin() == 0) {
Instruction::BinaryOps BinOp = WO->getBinaryOp();
Value *LHS = WO->getLHS(), *RHS = WO->getRHS();
// Replace the old instruction's uses with poison.
replaceInstUsesWith(*WO, PoisonValue::get(WO->getType()));
eraseInstFromFunction(*WO);
return BinaryOperator::Create(BinOp, LHS, RHS);
}
assert(*EV.idx_begin() == 1 && "Unexpected extract index for overflow inst");
// (usub LHS, RHS) overflows when LHS is unsigned-less-than RHS.
if (OvID == Intrinsic::usub_with_overflow)
return new ICmpInst(ICmpInst::ICMP_ULT, WO->getLHS(), WO->getRHS());
// smul with i1 types overflows when both sides are set: -1 * -1 == +1, but
// +1 is not possible because we assume signed values.
if (OvID == Intrinsic::smul_with_overflow &&
WO->getLHS()->getType()->isIntOrIntVectorTy(1))
return BinaryOperator::CreateAnd(WO->getLHS(), WO->getRHS());
// extractvalue (umul_with_overflow X, X), 1 -> X u> 2^(N/2)-1
if (OvID == Intrinsic::umul_with_overflow && WO->getLHS() == WO->getRHS()) {
unsigned BitWidth = WO->getLHS()->getType()->getScalarSizeInBits();
// Only handle even bitwidths for performance reasons.
if (BitWidth % 2 == 0)
return new ICmpInst(
ICmpInst::ICMP_UGT, WO->getLHS(),
ConstantInt::get(WO->getLHS()->getType(),
APInt::getLowBitsSet(BitWidth, BitWidth / 2)));
}
// If only the overflow result is used, and the right hand side is a
// constant (or constant splat), we can remove the intrinsic by directly
// checking for overflow.
if (C) {
// Compute the no-wrap range for LHS given RHS=C, then construct an
// equivalent icmp, potentially using an offset.
ConstantRange NWR = ConstantRange::makeExactNoWrapRegion(
WO->getBinaryOp(), *C, WO->getNoWrapKind());
CmpInst::Predicate Pred;
APInt NewRHSC, Offset;
NWR.getEquivalentICmp(Pred, NewRHSC, Offset);
auto *OpTy = WO->getRHS()->getType();
auto *NewLHS = WO->getLHS();
if (Offset != 0)
NewLHS = Builder.CreateAdd(NewLHS, ConstantInt::get(OpTy, Offset));
return new ICmpInst(ICmpInst::getInversePredicate(Pred), NewLHS,
ConstantInt::get(OpTy, NewRHSC));
}
return nullptr;
}
static Value *foldFrexpOfSelect(ExtractValueInst &EV, IntrinsicInst *FrexpCall,
SelectInst *SelectInst,
InstCombiner::BuilderTy &Builder) {
// Helper to fold frexp of select to select of frexp.
if (!SelectInst->hasOneUse() || !FrexpCall->hasOneUse())
return nullptr;
Value *Cond = SelectInst->getCondition();
Value *TrueVal = SelectInst->getTrueValue();
Value *FalseVal = SelectInst->getFalseValue();
const APFloat *ConstVal = nullptr;
Value *VarOp = nullptr;
bool ConstIsTrue = false;
if (match(TrueVal, m_APFloat(ConstVal))) {
VarOp = FalseVal;
ConstIsTrue = true;
} else if (match(FalseVal, m_APFloat(ConstVal))) {
VarOp = TrueVal;
ConstIsTrue = false;
} else {
return nullptr;
}
Builder.SetInsertPoint(&EV);
CallInst *NewFrexp =
Builder.CreateCall(FrexpCall->getCalledFunction(), {VarOp}, "frexp");
NewFrexp->copyIRFlags(FrexpCall);
Value *NewEV = Builder.CreateExtractValue(NewFrexp, 0, "mantissa");
int Exp;
APFloat Mantissa = frexp(*ConstVal, Exp, APFloat::rmNearestTiesToEven);
Constant *ConstantMantissa = ConstantFP::get(TrueVal->getType(), Mantissa);
Value *NewSel = Builder.CreateSelectFMF(
Cond, ConstIsTrue ? ConstantMantissa : NewEV,
ConstIsTrue ? NewEV : ConstantMantissa, SelectInst, "select.frexp");
return NewSel;
}
Instruction *InstCombinerImpl::visitExtractValueInst(ExtractValueInst &EV) {
Value *Agg = EV.getAggregateOperand();
if (!EV.hasIndices())
return replaceInstUsesWith(EV, Agg);
if (Value *V = simplifyExtractValueInst(Agg, EV.getIndices(),
SQ.getWithInstruction(&EV)))
return replaceInstUsesWith(EV, V);
Value *Cond, *TrueVal, *FalseVal;
if (match(&EV, m_ExtractValue<0>(m_Intrinsic<Intrinsic::frexp>(m_Select(
m_Value(Cond), m_Value(TrueVal), m_Value(FalseVal)))))) {
auto *SelInst =
cast<SelectInst>(cast<IntrinsicInst>(Agg)->getArgOperand(0));
if (Value *Result =
foldFrexpOfSelect(EV, cast<IntrinsicInst>(Agg), SelInst, Builder))
return replaceInstUsesWith(EV, Result);
}
if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
// We're extracting from an insertvalue instruction, compare the indices
const unsigned *exti, *exte, *insi, *inse;
for (exti = EV.idx_begin(), insi = IV->idx_begin(),
exte = EV.idx_end(), inse = IV->idx_end();
exti != exte && insi != inse;
++exti, ++insi) {
if (*insi != *exti)
// The insert and extract both reference distinctly different elements.
// This means the extract is not influenced by the insert, and we can
// replace the aggregate operand of the extract with the aggregate
// operand of the insert. i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 0
// with
// %E = extractvalue { i32, { i32 } } %A, 0
return ExtractValueInst::Create(IV->getAggregateOperand(),
EV.getIndices());
}
if (exti == exte && insi == inse)
// Both iterators are at the end: Index lists are identical. Replace
// %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %C = extractvalue { i32, { i32 } } %B, 1, 0
// with "i32 42"
return replaceInstUsesWith(EV, IV->getInsertedValueOperand());
if (exti == exte) {
// The extract list is a prefix of the insert list. i.e. replace
// %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %E = extractvalue { i32, { i32 } } %I, 1
// with
// %X = extractvalue { i32, { i32 } } %A, 1
// %E = insertvalue { i32 } %X, i32 42, 0
// by switching the order of the insert and extract (though the
// insertvalue should be left in, since it may have other uses).
Value *NewEV = Builder.CreateExtractValue(IV->getAggregateOperand(),
EV.getIndices());
return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
ArrayRef(insi, inse));
}
if (insi == inse)
// The insert list is a prefix of the extract list
// We can simply remove the common indices from the extract and make it
// operate on the inserted value instead of the insertvalue result.
// i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 1, 0
// with
// %E extractvalue { i32 } { i32 42 }, 0
return ExtractValueInst::Create(IV->getInsertedValueOperand(),
ArrayRef(exti, exte));
}
if (Instruction *R = foldExtractOfOverflowIntrinsic(EV))
return R;
if (LoadInst *L = dyn_cast<LoadInst>(Agg)) {
// Bail out if the aggregate contains scalable vector type
if (auto *STy = dyn_cast<StructType>(Agg->getType());
STy && STy->isScalableTy())
return nullptr;
// If the (non-volatile) load only has one use, we can rewrite this to a
// load from a GEP. This reduces the size of the load. If a load is used
// only by extractvalue instructions then this either must have been
// optimized before, or it is a struct with padding, in which case we
// don't want to do the transformation as it loses padding knowledge.
if (L->isSimple() && L->hasOneUse()) {
// extractvalue has integer indices, getelementptr has Value*s. Convert.
SmallVector<Value*, 4> Indices;
// Prefix an i32 0 since we need the first element.
Indices.push_back(Builder.getInt32(0));
for (unsigned Idx : EV.indices())
Indices.push_back(Builder.getInt32(Idx));
// We need to insert these at the location of the old load, not at that of
// the extractvalue.
Builder.SetInsertPoint(L);
Value *GEP = Builder.CreateInBoundsGEP(L->getType(),
L->getPointerOperand(), Indices);
Instruction *NL = Builder.CreateLoad(EV.getType(), GEP);
// Whatever aliasing information we had for the orignal load must also
// hold for the smaller load, so propagate the annotations.
NL->setAAMetadata(L->getAAMetadata());
// Returning the load directly will cause the main loop to insert it in
// the wrong spot, so use replaceInstUsesWith().
return replaceInstUsesWith(EV, NL);
}
}
if (auto *PN = dyn_cast<PHINode>(Agg))
if (Instruction *Res = foldOpIntoPhi(EV, PN))
return Res;
// Canonicalize extract (select Cond, TV, FV)
// -> select cond, (extract TV), (extract FV)
if (auto *SI = dyn_cast<SelectInst>(Agg))
if (Instruction *R = FoldOpIntoSelect(EV, SI, /*FoldWithMultiUse=*/true))
return R;
// We could simplify extracts from other values. Note that nested extracts may
// already be simplified implicitly by the above: extract (extract (insert) )
// will be translated into extract ( insert ( extract ) ) first and then just
// the value inserted, if appropriate. Similarly for extracts from single-use
// loads: extract (extract (load)) will be translated to extract (load (gep))
// and if again single-use then via load (gep (gep)) to load (gep).
// However, double extracts from e.g. function arguments or return values
// aren't handled yet.
return nullptr;
}
/// Return 'true' if the given typeinfo will match anything.
static bool isCatchAll(EHPersonality Personality, Constant *TypeInfo) {
switch (Personality) {
case EHPersonality::GNU_C:
case EHPersonality::GNU_C_SjLj:
case EHPersonality::Rust:
// The GCC C EH and Rust personality only exists to support cleanups, so
// it's not clear what the semantics of catch clauses are.
return false;
case EHPersonality::Unknown:
return false;
case EHPersonality::GNU_Ada:
// While __gnat_all_others_value will match any Ada exception, it doesn't
// match foreign exceptions (or didn't, before gcc-4.7).
return false;
case EHPersonality::GNU_CXX:
case EHPersonality::GNU_CXX_SjLj:
case EHPersonality::GNU_ObjC:
case EHPersonality::MSVC_X86SEH:
case EHPersonality::MSVC_TableSEH:
case EHPersonality::MSVC_CXX:
case EHPersonality::CoreCLR:
case EHPersonality::Wasm_CXX:
case EHPersonality::XL_CXX:
case EHPersonality::ZOS_CXX:
return TypeInfo->isNullValue();
}
llvm_unreachable("invalid enum");
}
static bool shorter_filter(const Value *LHS, const Value *RHS) {
return
cast<ArrayType>(LHS->getType())->getNumElements()
<
cast<ArrayType>(RHS->getType())->getNumElements();
}
Instruction *InstCombinerImpl::visitLandingPadInst(LandingPadInst &LI) {
// The logic here should be correct for any real-world personality function.
// However if that turns out not to be true, the offending logic can always
// be conditioned on the personality function, like the catch-all logic is.
EHPersonality Personality =
classifyEHPersonality(LI.getParent()->getParent()->getPersonalityFn());
// Simplify the list of clauses, eg by removing repeated catch clauses
// (these are often created by inlining).
bool MakeNewInstruction = false; // If true, recreate using the following:
SmallVector<Constant *, 16> NewClauses; // - Clauses for the new instruction;
bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup.
SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already.
for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) {
bool isLastClause = i + 1 == e;
if (LI.isCatch(i)) {
// A catch clause.
Constant *CatchClause = LI.getClause(i);
Constant *TypeInfo = CatchClause->stripPointerCasts();
// If we already saw this clause, there is no point in having a second
// copy of it.
if (AlreadyCaught.insert(TypeInfo).second) {
// This catch clause was not already seen.
NewClauses.push_back(CatchClause);
} else {
// Repeated catch clause - drop the redundant copy.
MakeNewInstruction = true;
}
// If this is a catch-all then there is no point in keeping any following
// clauses or marking the landingpad as having a cleanup.
if (isCatchAll(Personality, TypeInfo)) {
if (!isLastClause)
MakeNewInstruction = true;
CleanupFlag = false;
break;
}
} else {
// A filter clause. If any of the filter elements were already caught
// then they can be dropped from the filter. It is tempting to try to
// exploit the filter further by saying that any typeinfo that does not
// occur in the filter can't be caught later (and thus can be dropped).
// However this would be wrong, since typeinfos can match without being
// equal (for example if one represents a C++ class, and the other some
// class derived from it).
assert(LI.isFilter(i) && "Unsupported landingpad clause!");
Constant *FilterClause = LI.getClause(i);
ArrayType *FilterType = cast<ArrayType>(FilterClause->getType());
unsigned NumTypeInfos = FilterType->getNumElements();
// An empty filter catches everything, so there is no point in keeping any
// following clauses or marking the landingpad as having a cleanup. By
// dealing with this case here the following code is made a bit simpler.
if (!NumTypeInfos) {
NewClauses.push_back(FilterClause);
if (!isLastClause)
MakeNewInstruction = true;
CleanupFlag = false;
break;
}
bool MakeNewFilter = false; // If true, make a new filter.
SmallVector<Constant *, 16> NewFilterElts; // New elements.
if (isa<ConstantAggregateZero>(FilterClause)) {
// Not an empty filter - it contains at least one null typeinfo.
assert(NumTypeInfos > 0 && "Should have handled empty filter already!");
Constant *TypeInfo =
Constant::getNullValue(FilterType->getElementType());
// If this typeinfo is a catch-all then the filter can never match.
if (isCatchAll(Personality, TypeInfo)) {
// Throw the filter away.
MakeNewInstruction = true;
continue;
}
// There is no point in having multiple copies of this typeinfo, so
// discard all but the first copy if there is more than one.
NewFilterElts.push_back(TypeInfo);
if (NumTypeInfos > 1)
MakeNewFilter = true;
} else {
ConstantArray *Filter = cast<ConstantArray>(FilterClause);
SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements.
NewFilterElts.reserve(NumTypeInfos);
// Remove any filter elements that were already caught or that already
// occurred in the filter. While there, see if any of the elements are
// catch-alls. If so, the filter can be discarded.
bool SawCatchAll = false;
for (unsigned j = 0; j != NumTypeInfos; ++j) {
Constant *Elt = Filter->getOperand(j);
Constant *TypeInfo = Elt->stripPointerCasts();
if (isCatchAll(Personality, TypeInfo)) {
// This element is a catch-all. Bail out, noting this fact.
SawCatchAll = true;
break;
}
// Even if we've seen a type in a catch clause, we don't want to
// remove it from the filter. An unexpected type handler may be
// set up for a call site which throws an exception of the same
// type caught. In order for the exception thrown by the unexpected
// handler to propagate correctly, the filter must be correctly
// described for the call site.
//
// Example:
//
// void unexpected() { throw 1;}
// void foo() throw (int) {
// std::set_unexpected(unexpected);
// try {
// throw 2.0;
// } catch (int i) {}
// }
// There is no point in having multiple copies of the same typeinfo in
// a filter, so only add it if we didn't already.
if (SeenInFilter.insert(TypeInfo).second)
NewFilterElts.push_back(cast<Constant>(Elt));
}
// A filter containing a catch-all cannot match anything by definition.
if (SawCatchAll) {
// Throw the filter away.
MakeNewInstruction = true;
continue;
}
// If we dropped something from the filter, make a new one.
if (NewFilterElts.size() < NumTypeInfos)
MakeNewFilter = true;
}
if (MakeNewFilter) {
FilterType = ArrayType::get(FilterType->getElementType(),
NewFilterElts.size());
FilterClause = ConstantArray::get(FilterType, NewFilterElts);
MakeNewInstruction = true;
}
NewClauses.push_back(FilterClause);
// If the new filter is empty then it will catch everything so there is
// no point in keeping any following clauses or marking the landingpad
// as having a cleanup. The case of the original filter being empty was
// already handled above.
if (MakeNewFilter && !NewFilterElts.size()) {
assert(MakeNewInstruction && "New filter but not a new instruction!");
CleanupFlag = false;
break;
}
}
}
// If several filters occur in a row then reorder them so that the shortest
// filters come first (those with the smallest number of elements). This is
// advantageous because shorter filters are more likely to match, speeding up
// unwinding, but mostly because it increases the effectiveness of the other
// filter optimizations below.
for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) {
unsigned j;
// Find the maximal 'j' s.t. the range [i, j) consists entirely of filters.
for (j = i; j != e; ++j)
if (!isa<ArrayType>(NewClauses[j]->getType()))
break;
// Check whether the filters are already sorted by length. We need to know
// if sorting them is actually going to do anything so that we only make a
// new landingpad instruction if it does.
for (unsigned k = i; k + 1 < j; ++k)
if (shorter_filter(NewClauses[k+1], NewClauses[k])) {
// Not sorted, so sort the filters now. Doing an unstable sort would be
// correct too but reordering filters pointlessly might confuse users.
std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j,
shorter_filter);
MakeNewInstruction = true;
break;
}
// Look for the next batch of filters.
i = j + 1;
}
// If typeinfos matched if and only if equal, then the elements of a filter L
// that occurs later than a filter F could be replaced by the intersection of
// the elements of F and L. In reality two typeinfos can match without being
// equal (for example if one represents a C++ class, and the other some class
// derived from it) so it would be wrong to perform this transform in general.
// However the transform is correct and useful if F is a subset of L. In that
// case L can be replaced by F, and thus removed altogether since repeating a
// filter is pointless. So here we look at all pairs of filters F and L where
// L follows F in the list of clauses, and remove L if every element of F is
// an element of L. This can occur when inlining C++ functions with exception
// specifications.
for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) {
// Examine each filter in turn.
Value *Filter = NewClauses[i];
ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType());
if (!FTy)
// Not a filter - skip it.
continue;
unsigned FElts = FTy->getNumElements();
// Examine each filter following this one. Doing this backwards means that
// we don't have to worry about filters disappearing under us when removed.
for (unsigned j = NewClauses.size() - 1; j != i; --j) {
Value *LFilter = NewClauses[j];
ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType());
if (!LTy)
// Not a filter - skip it.
continue;
// If Filter is a subset of LFilter, i.e. every element of Filter is also
// an element of LFilter, then discard LFilter.
SmallVectorImpl<Constant *>::iterator J = NewClauses.begin() + j;
// If Filter is empty then it is a subset of LFilter.
if (!FElts) {
// Discard LFilter.
NewClauses.erase(J);
MakeNewInstruction = true;
// Move on to the next filter.
continue;
}
unsigned LElts = LTy->getNumElements();
// If Filter is longer than LFilter then it cannot be a subset of it.
if (FElts > LElts)
// Move on to the next filter.
continue;
// At this point we know that LFilter has at least one element.
if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros.
// Filter is a subset of LFilter iff Filter contains only zeros (as we
// already know that Filter is not longer than LFilter).
if (isa<ConstantAggregateZero>(Filter)) {
assert(FElts <= LElts && "Should have handled this case earlier!");
// Discard LFilter.
NewClauses.erase(J);
MakeNewInstruction = true;
}
// Move on to the next filter.
continue;
}
ConstantArray *LArray = cast<ConstantArray>(LFilter);
if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros.
// Since Filter is non-empty and contains only zeros, it is a subset of
// LFilter iff LFilter contains a zero.
assert(FElts > 0 && "Should have eliminated the empty filter earlier!");
for (unsigned l = 0; l != LElts; ++l)
if (LArray->getOperand(l)->isNullValue()) {
// LFilter contains a zero - discard it.
NewClauses.erase(J);
MakeNewInstruction = true;
break;
}
// Move on to the next filter.
continue;
}
// At this point we know that both filters are ConstantArrays. Loop over
// operands to see whether every element of Filter is also an element of
// LFilter. Since filters tend to be short this is probably faster than
// using a method that scales nicely.
ConstantArray *FArray = cast<ConstantArray>(Filter);
bool AllFound = true;
for (unsigned f = 0; f != FElts; ++f) {
Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts();
AllFound = false;
for (unsigned l = 0; l != LElts; ++l) {
Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts();
if (LTypeInfo == FTypeInfo) {
AllFound = true;
break;
}
}
if (!AllFound)
break;
}
if (AllFound) {
// Discard LFilter.
NewClauses.erase(J);
MakeNewInstruction = true;
}
// Move on to the next filter.
}
}
// If we changed any of the clauses, replace the old landingpad instruction
// with a new one.
if (MakeNewInstruction) {
LandingPadInst *NLI = LandingPadInst::Create(LI.getType(),
NewClauses.size());
for (Constant *C : NewClauses)
NLI->addClause(C);
// A landing pad with no clauses must have the cleanup flag set. It is
// theoretically possible, though highly unlikely, that we eliminated all
// clauses. If so, force the cleanup flag to true.
if (NewClauses.empty())
CleanupFlag = true;
NLI->setCleanup(CleanupFlag);
return NLI;
}
// Even if none of the clauses changed, we may nonetheless have understood
// that the cleanup flag is pointless. Clear it if so.
if (LI.isCleanup() != CleanupFlag) {
assert(!CleanupFlag && "Adding a cleanup, not removing one?!");
LI.setCleanup(CleanupFlag);
return &LI;
}
return nullptr;
}
Value *
InstCombinerImpl::pushFreezeToPreventPoisonFromPropagating(FreezeInst &OrigFI) {
// Try to push freeze through instructions that propagate but don't produce
// poison as far as possible. If an operand of freeze follows three
// conditions 1) one-use, 2) does not produce poison, and 3) has all but one
// guaranteed-non-poison operands then push the freeze through to the one
// operand that is not guaranteed non-poison. The actual transform is as
// follows.
// Op1 = ... ; Op1 can be posion
// Op0 = Inst(Op1, NonPoisonOps...) ; Op0 has only one use and only have
// ; single guaranteed-non-poison operands
// ... = Freeze(Op0)
// =>
// Op1 = ...
// Op1.fr = Freeze(Op1)
// ... = Inst(Op1.fr, NonPoisonOps...)
auto *OrigOp = OrigFI.getOperand(0);
auto *OrigOpInst = dyn_cast<Instruction>(OrigOp);
// While we could change the other users of OrigOp to use freeze(OrigOp), that
// potentially reduces their optimization potential, so let's only do this iff
// the OrigOp is only used by the freeze.
if (!OrigOpInst || !OrigOpInst->hasOneUse() || isa<PHINode>(OrigOp))
return nullptr;
// We can't push the freeze through an instruction which can itself create
// poison. If the only source of new poison is flags, we can simply
// strip them (since we know the only use is the freeze and nothing can
// benefit from them.)
if (canCreateUndefOrPoison(cast<Operator>(OrigOp),
/*ConsiderFlagsAndMetadata*/ false))
return nullptr;
// If operand is guaranteed not to be poison, there is no need to add freeze
// to the operand. So we first find the operand that is not guaranteed to be
// poison.
Use *MaybePoisonOperand = nullptr;
for (Use &U : OrigOpInst->operands()) {
if (isa<MetadataAsValue>(U.get()) ||
isGuaranteedNotToBeUndefOrPoison(U.get()))
continue;
if (!MaybePoisonOperand)
MaybePoisonOperand = &U;
else
return nullptr;
}
OrigOpInst->dropPoisonGeneratingAnnotations();
// If all operands are guaranteed to be non-poison, we can drop freeze.
if (!MaybePoisonOperand)
return OrigOp;
Builder.SetInsertPoint(OrigOpInst);
auto *FrozenMaybePoisonOperand = Builder.CreateFreeze(
MaybePoisonOperand->get(), MaybePoisonOperand->get()->getName() + ".fr");
replaceUse(*MaybePoisonOperand, FrozenMaybePoisonOperand);
return OrigOp;
}
Instruction *InstCombinerImpl::foldFreezeIntoRecurrence(FreezeInst &FI,
PHINode *PN) {
// Detect whether this is a recurrence with a start value and some number of
// backedge values. We'll check whether we can push the freeze through the
// backedge values (possibly dropping poison flags along the way) until we
// reach the phi again. In that case, we can move the freeze to the start
// value.
Use *StartU = nullptr;
SmallVector<Value *> Worklist;
for (Use &U : PN->incoming_values()) {
if (DT.dominates(PN->getParent(), PN->getIncomingBlock(U))) {
// Add backedge value to worklist.
Worklist.push_back(U.get());
continue;
}
// Don't bother handling multiple start values.
if (StartU)
return nullptr;
StartU = &U;
}
if (!StartU || Worklist.empty())
return nullptr; // Not a recurrence.
Value *StartV = StartU->get();
BasicBlock *StartBB = PN->getIncomingBlock(*StartU);
bool StartNeedsFreeze = !isGuaranteedNotToBeUndefOrPoison(StartV);
// We can't insert freeze if the start value is the result of the
// terminator (e.g. an invoke).
if (StartNeedsFreeze && StartBB->getTerminator() == StartV)
return nullptr;
SmallPtrSet<Value *, 32> Visited;
SmallVector<Instruction *> DropFlags;
while (!Worklist.empty()) {
Value *V = Worklist.pop_back_val();
if (!Visited.insert(V).second)
continue;
if (Visited.size() > 32)
return nullptr; // Limit the total number of values we inspect.
// Assume that PN is non-poison, because it will be after the transform.
if (V == PN || isGuaranteedNotToBeUndefOrPoison(V))
continue;
Instruction *I = dyn_cast<Instruction>(V);
if (!I || canCreateUndefOrPoison(cast<Operator>(I),
/*ConsiderFlagsAndMetadata*/ false))
return nullptr;
DropFlags.push_back(I);
append_range(Worklist, I->operands());
}
for (Instruction *I : DropFlags)
I->dropPoisonGeneratingAnnotations();
if (StartNeedsFreeze) {
Builder.SetInsertPoint(StartBB->getTerminator());
Value *FrozenStartV = Builder.CreateFreeze(StartV,
StartV->getName() + ".fr");
replaceUse(*StartU, FrozenStartV);
}
return replaceInstUsesWith(FI, PN);
}
bool InstCombinerImpl::freezeOtherUses(FreezeInst &FI) {
Value *Op = FI.getOperand(0);
if (isa<Constant>(Op) || Op->hasOneUse())
return false;
// Move the freeze directly after the definition of its operand, so that
// it dominates the maximum number of uses. Note that it may not dominate
// *all* uses if the operand is an invoke/callbr and the use is in a phi on
// the normal/default destination. This is why the domination check in the
// replacement below is still necessary.
BasicBlock::iterator MoveBefore;
if (isa<Argument>(Op)) {
MoveBefore =
FI.getFunction()->getEntryBlock().getFirstNonPHIOrDbgOrAlloca();
} else {
auto MoveBeforeOpt = cast<Instruction>(Op)->getInsertionPointAfterDef();
if (!MoveBeforeOpt)
return false;
MoveBefore = *MoveBeforeOpt;
}
// Don't move to the position of a debug intrinsic.
if (isa<DbgInfoIntrinsic>(MoveBefore))
MoveBefore = MoveBefore->getNextNonDebugInstruction()->getIterator();
// Re-point iterator to come after any debug-info records, if we're
// running in "RemoveDIs" mode
MoveBefore.setHeadBit(false);
bool Changed = false;
if (&FI != &*MoveBefore) {
FI.moveBefore(*MoveBefore->getParent(), MoveBefore);
Changed = true;
}
Op->replaceUsesWithIf(&FI, [&](Use &U) -> bool {
bool Dominates = DT.dominates(&FI, U);
Changed |= Dominates;
return Dominates;
});
return Changed;
}
// Check if any direct or bitcast user of this value is a shuffle instruction.
static bool isUsedWithinShuffleVector(Value *V) {
for (auto *U : V->users()) {
if (isa<ShuffleVectorInst>(U))
return true;
else if (match(U, m_BitCast(m_Specific(V))) && isUsedWithinShuffleVector(U))
return true;
}
return false;
}
Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
Value *Op0 = I.getOperand(0);
if (Value *V = simplifyFreezeInst(Op0, SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
// freeze (phi const, x) --> phi const, (freeze x)
if (auto *PN = dyn_cast<PHINode>(Op0)) {
if (Instruction *NV = foldOpIntoPhi(I, PN))
return NV;
if (Instruction *NV = foldFreezeIntoRecurrence(I, PN))
return NV;
}
if (Value *NI = pushFreezeToPreventPoisonFromPropagating(I))
return replaceInstUsesWith(I, NI);
// If I is freeze(undef), check its uses and fold it to a fixed constant.
// - or: pick -1
// - select's condition: if the true value is constant, choose it by making
// the condition true.
// - default: pick 0
//
// Note that this transform is intentionally done here rather than
// via an analysis in InstSimplify or at individual user sites. That is
// because we must produce the same value for all uses of the freeze -
// it's the reason "freeze" exists!
//
// TODO: This could use getBinopAbsorber() / getBinopIdentity() to avoid
// duplicating logic for binops at least.
auto getUndefReplacement = [&](Type *Ty) {
Value *BestValue = nullptr;
Value *NullValue = Constant::getNullValue(Ty);
for (const auto *U : I.users()) {
Value *V = NullValue;
if (match(U, m_Or(m_Value(), m_Value())))
V = ConstantInt::getAllOnesValue(Ty);
else if (match(U, m_Select(m_Specific(&I), m_Constant(), m_Value())))
V = ConstantInt::getTrue(Ty);
else if (match(U, m_c_Select(m_Specific(&I), m_Value(V)))) {
if (!isGuaranteedNotToBeUndefOrPoison(V, &AC, &I, &DT))
V = NullValue;
}
if (!BestValue)
BestValue = V;
else if (BestValue != V)
BestValue = NullValue;
}
assert(BestValue && "Must have at least one use");
return BestValue;
};
if (match(Op0, m_Undef())) {
// Don't fold freeze(undef/poison) if it's used as a vector operand in
// a shuffle. This may improve codegen for shuffles that allow
// unspecified inputs.
if (isUsedWithinShuffleVector(&I))
return nullptr;
return replaceInstUsesWith(I, getUndefReplacement(I.getType()));
}
auto getFreezeVectorReplacement = [](Constant *C) -> Constant * {
Type *Ty = C->getType();
auto *VTy = dyn_cast<FixedVectorType>(Ty);
if (!VTy)
return nullptr;
unsigned NumElts = VTy->getNumElements();
Constant *BestValue = Constant::getNullValue(VTy->getScalarType());
for (unsigned i = 0; i != NumElts; ++i) {
Constant *EltC = C->getAggregateElement(i);
if (EltC && !match(EltC, m_Undef())) {
BestValue = EltC;
break;
}
}
return Constant::replaceUndefsWith(C, BestValue);
};
Constant *C;
if (match(Op0, m_Constant(C)) && C->containsUndefOrPoisonElement() &&
!C->containsConstantExpression()) {
if (Constant *Repl = getFreezeVectorReplacement(C))
return replaceInstUsesWith(I, Repl);
}
// Replace uses of Op with freeze(Op).
if (freezeOtherUses(I))
return &I;
return nullptr;
}
/// Check for case where the call writes to an otherwise dead alloca. This
/// shows up for unused out-params in idiomatic C/C++ code. Note that this
/// helper *only* analyzes the write; doesn't check any other legality aspect.
static bool SoleWriteToDeadLocal(Instruction *I, TargetLibraryInfo &TLI) {
auto *CB = dyn_cast<CallBase>(I);
if (!CB)
// TODO: handle e.g. store to alloca here - only worth doing if we extend
// to allow reload along used path as described below. Otherwise, this
// is simply a store to a dead allocation which will be removed.
return false;
std::optional<MemoryLocation> Dest = MemoryLocation::getForDest(CB, TLI);
if (!Dest)
return false;
auto *AI = dyn_cast<AllocaInst>(getUnderlyingObject(Dest->Ptr));
if (!AI)
// TODO: allow malloc?
return false;
// TODO: allow memory access dominated by move point? Note that since AI
// could have a reference to itself captured by the call, we would need to
// account for cycles in doing so.
SmallVector<const User *> AllocaUsers;
SmallPtrSet<const User *, 4> Visited;
auto pushUsers = [&](const Instruction &I) {
for (const User *U : I.users()) {
if (Visited.insert(U).second)
AllocaUsers.push_back(U);
}
};
pushUsers(*AI);
while (!AllocaUsers.empty()) {
auto *UserI = cast<Instruction>(AllocaUsers.pop_back_val());
if (isa<GetElementPtrInst>(UserI) || isa<AddrSpaceCastInst>(UserI)) {
pushUsers(*UserI);
continue;
}
if (UserI == CB)
continue;
// TODO: support lifetime.start/end here
return false;
}
return true;
}
/// Try to move the specified instruction from its current block into the
/// beginning of DestBlock, which can only happen if it's safe to move the
/// instruction past all of the instructions between it and the end of its
/// block.
bool InstCombinerImpl::tryToSinkInstruction(Instruction *I,
BasicBlock *DestBlock) {
BasicBlock *SrcBlock = I->getParent();
// Cannot move control-flow-involving, volatile loads, vaarg, etc.
if (isa<PHINode>(I) || I->isEHPad() || I->mayThrow() || !I->willReturn() ||
I->isTerminator())
return false;
// Do not sink static or dynamic alloca instructions. Static allocas must
// remain in the entry block, and dynamic allocas must not be sunk in between
// a stacksave / stackrestore pair, which would incorrectly shorten its
// lifetime.
if (isa<AllocaInst>(I))
return false;
// Do not sink into catchswitch blocks.
if (isa<CatchSwitchInst>(DestBlock->getTerminator()))
return false;
// Do not sink convergent call instructions.
if (auto *CI = dyn_cast<CallInst>(I)) {
if (CI->isConvergent())
return false;
}
// Unless we can prove that the memory write isn't visibile except on the
// path we're sinking to, we must bail.
if (I->mayWriteToMemory()) {
if (!SoleWriteToDeadLocal(I, TLI))
return false;
}
// We can only sink load instructions if there is nothing between the load and
// the end of block that could change the value.
if (I->mayReadFromMemory() &&
!I->hasMetadata(LLVMContext::MD_invariant_load)) {
// We don't want to do any sophisticated alias analysis, so we only check
// the instructions after I in I's parent block if we try to sink to its
// successor block.
if (DestBlock->getUniquePredecessor() != I->getParent())
return false;
for (BasicBlock::iterator Scan = std::next(I->getIterator()),
E = I->getParent()->end();
Scan != E; ++Scan)
if (Scan->mayWriteToMemory())
return false;
}
I->dropDroppableUses([&](const Use *U) {
auto *I = dyn_cast<Instruction>(U->getUser());
if (I && I->getParent() != DestBlock) {
Worklist.add(I);
return true;
}
return false;
});
/// FIXME: We could remove droppable uses that are not dominated by
/// the new position.
BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt();
I->moveBefore(*DestBlock, InsertPos);
++NumSunkInst;
// Also sink all related debug uses from the source basic block. Otherwise we
// get debug use before the def. Attempt to salvage debug uses first, to
// maximise the range variables have location for. If we cannot salvage, then
// mark the location undef: we know it was supposed to receive a new location
// here, but that computation has been sunk.
SmallVector<DbgVariableIntrinsic *, 2> DbgUsers;
SmallVector<DbgVariableRecord *, 2> DbgVariableRecords;
findDbgUsers(DbgUsers, I, &DbgVariableRecords);
if (!DbgUsers.empty())
tryToSinkInstructionDbgValues(I, InsertPos, SrcBlock, DestBlock, DbgUsers);
if (!DbgVariableRecords.empty())
tryToSinkInstructionDbgVariableRecords(I, InsertPos, SrcBlock, DestBlock,
DbgVariableRecords);
// PS: there are numerous flaws with this behaviour, not least that right now
// assignments can be re-ordered past other assignments to the same variable
// if they use different Values. Creating more undef assignements can never be
// undone. And salvaging all users outside of this block can un-necessarily
// alter the lifetime of the live-value that the variable refers to.
// Some of these things can be resolved by tolerating debug use-before-defs in
// LLVM-IR, however it depends on the instruction-referencing CodeGen backend
// being used for more architectures.
return true;
}
void InstCombinerImpl::tryToSinkInstructionDbgValues(
Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
BasicBlock *DestBlock, SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers) {
// For all debug values in the destination block, the sunk instruction
// will still be available, so they do not need to be dropped.
SmallVector<DbgVariableIntrinsic *, 2> DbgUsersToSalvage;
for (auto &DbgUser : DbgUsers)
if (DbgUser->getParent() != DestBlock)
DbgUsersToSalvage.push_back(DbgUser);
// Process the sinking DbgUsersToSalvage in reverse order, as we only want
// to clone the last appearing debug intrinsic for each given variable.
SmallVector<DbgVariableIntrinsic *, 2> DbgUsersToSink;
for (DbgVariableIntrinsic *DVI : DbgUsersToSalvage)
if (DVI->getParent() == SrcBlock)
DbgUsersToSink.push_back(DVI);
llvm::sort(DbgUsersToSink,
[](auto *A, auto *B) { return B->comesBefore(A); });
SmallVector<DbgVariableIntrinsic *, 2> DIIClones;
SmallSet<DebugVariable, 4> SunkVariables;
for (auto *User : DbgUsersToSink) {
// A dbg.declare instruction should not be cloned, since there can only be
// one per variable fragment. It should be left in the original place
// because the sunk instruction is not an alloca (otherwise we could not be
// here).
if (isa<DbgDeclareInst>(User))
continue;
DebugVariable DbgUserVariable =
DebugVariable(User->getVariable(), User->getExpression(),
User->getDebugLoc()->getInlinedAt());
if (!SunkVariables.insert(DbgUserVariable).second)
continue;
// Leave dbg.assign intrinsics in their original positions and there should
// be no need to insert a clone.
if (isa<DbgAssignIntrinsic>(User))
continue;
DIIClones.emplace_back(cast<DbgVariableIntrinsic>(User->clone()));
if (isa<DbgDeclareInst>(User) && isa<CastInst>(I))
DIIClones.back()->replaceVariableLocationOp(I, I->getOperand(0));
LLVM_DEBUG(dbgs() << "CLONE: " << *DIIClones.back() << '\n');
}
// Perform salvaging without the clones, then sink the clones.
if (!DIIClones.empty()) {
salvageDebugInfoForDbgValues(*I, DbgUsersToSalvage, {});
// The clones are in reverse order of original appearance, reverse again to
// maintain the original order.
for (auto &DIIClone : llvm::reverse(DIIClones)) {
DIIClone->insertBefore(InsertPos);
LLVM_DEBUG(dbgs() << "SINK: " << *DIIClone << '\n');
}
}
}
void InstCombinerImpl::tryToSinkInstructionDbgVariableRecords(
Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
BasicBlock *DestBlock,
SmallVectorImpl<DbgVariableRecord *> &DbgVariableRecords) {
// Implementation of tryToSinkInstructionDbgValues, but for the
// DbgVariableRecord of variable assignments rather than dbg.values.
// Fetch all DbgVariableRecords not already in the destination.
SmallVector<DbgVariableRecord *, 2> DbgVariableRecordsToSalvage;
for (auto &DVR : DbgVariableRecords)
if (DVR->getParent() != DestBlock)
DbgVariableRecordsToSalvage.push_back(DVR);
// Fetch a second collection, of DbgVariableRecords in the source block that
// we're going to sink.
SmallVector<DbgVariableRecord *> DbgVariableRecordsToSink;
for (DbgVariableRecord *DVR : DbgVariableRecordsToSalvage)
if (DVR->getParent() == SrcBlock)
DbgVariableRecordsToSink.push_back(DVR);
// Sort DbgVariableRecords according to their position in the block. This is a
// partial order: DbgVariableRecords attached to different instructions will
// be ordered by the instruction order, but DbgVariableRecords attached to the
// same instruction won't have an order.
auto Order = [](DbgVariableRecord *A, DbgVariableRecord *B) -> bool {
return B->getInstruction()->comesBefore(A->getInstruction());
};
llvm::stable_sort(DbgVariableRecordsToSink, Order);
// If there are two assignments to the same variable attached to the same
// instruction, the ordering between the two assignments is important. Scan
// for this (rare) case and establish which is the last assignment.
using InstVarPair = std::pair<const Instruction *, DebugVariable>;
SmallDenseMap<InstVarPair, DbgVariableRecord *> FilterOutMap;
if (DbgVariableRecordsToSink.size() > 1) {
SmallDenseMap<InstVarPair, unsigned> CountMap;
// Count how many assignments to each variable there is per instruction.
for (DbgVariableRecord *DVR : DbgVariableRecordsToSink) {
DebugVariable DbgUserVariable =
DebugVariable(DVR->getVariable(), DVR->getExpression(),
DVR->getDebugLoc()->getInlinedAt());
CountMap[std::make_pair(DVR->getInstruction(), DbgUserVariable)] += 1;
}
// If there are any instructions with two assignments, add them to the
// FilterOutMap to record that they need extra filtering.
SmallPtrSet<const Instruction *, 4> DupSet;
for (auto It : CountMap) {
if (It.second > 1) {
FilterOutMap[It.first] = nullptr;
DupSet.insert(It.first.first);
}
}
// For all instruction/variable pairs needing extra filtering, find the
// latest assignment.
for (const Instruction *Inst : DupSet) {
for (DbgVariableRecord &DVR :
llvm::reverse(filterDbgVars(Inst->getDbgRecordRange()))) {
DebugVariable DbgUserVariable =
DebugVariable(DVR.getVariable(), DVR.getExpression(),
DVR.getDebugLoc()->getInlinedAt());
auto FilterIt =
FilterOutMap.find(std::make_pair(Inst, DbgUserVariable));
if (FilterIt == FilterOutMap.end())
continue;
if (FilterIt->second != nullptr)
continue;
FilterIt->second = &DVR;
}
}
}
// Perform cloning of the DbgVariableRecords that we plan on sinking, filter
// out any duplicate assignments identified above.
SmallVector<DbgVariableRecord *, 2> DVRClones;
SmallSet<DebugVariable, 4> SunkVariables;
for (DbgVariableRecord *DVR : DbgVariableRecordsToSink) {
if (DVR->Type == DbgVariableRecord::LocationType::Declare)
continue;
DebugVariable DbgUserVariable =
DebugVariable(DVR->getVariable(), DVR->getExpression(),
DVR->getDebugLoc()->getInlinedAt());
// For any variable where there were multiple assignments in the same place,
// ignore all but the last assignment.
if (!FilterOutMap.empty()) {
InstVarPair IVP = std::make_pair(DVR->getInstruction(), DbgUserVariable);
auto It = FilterOutMap.find(IVP);
// Filter out.
if (It != FilterOutMap.end() && It->second != DVR)
continue;
}
if (!SunkVariables.insert(DbgUserVariable).second)
continue;
if (DVR->isDbgAssign())
continue;
DVRClones.emplace_back(DVR->clone());
LLVM_DEBUG(dbgs() << "CLONE: " << *DVRClones.back() << '\n');
}
// Perform salvaging without the clones, then sink the clones.
if (DVRClones.empty())
return;
salvageDebugInfoForDbgValues(*I, {}, DbgVariableRecordsToSalvage);
// The clones are in reverse order of original appearance. Assert that the
// head bit is set on the iterator as we _should_ have received it via
// getFirstInsertionPt. Inserting like this will reverse the clone order as
// we'll repeatedly insert at the head, such as:
// DVR-3 (third insertion goes here)
// DVR-2 (second insertion goes here)
// DVR-1 (first insertion goes here)
// Any-Prior-DVRs
// InsertPtInst
assert(InsertPos.getHeadBit());
for (DbgVariableRecord *DVRClone : DVRClones) {
InsertPos->getParent()->insertDbgRecordBefore(DVRClone, InsertPos);
LLVM_DEBUG(dbgs() << "SINK: " << *DVRClone << '\n');
}
}
bool InstCombinerImpl::run() {
while (!Worklist.isEmpty()) {
// Walk deferred instructions in reverse order, and push them to the
// worklist, which means they'll end up popped from the worklist in-order.
while (Instruction *I = Worklist.popDeferred()) {
// Check to see if we can DCE the instruction. We do this already here to
// reduce the number of uses and thus allow other folds to trigger.
// Note that eraseInstFromFunction() may push additional instructions on
// the deferred worklist, so this will DCE whole instruction chains.
if (isInstructionTriviallyDead(I, &TLI)) {
eraseInstFromFunction(*I);
++NumDeadInst;
continue;
}
Worklist.push(I);
}
Instruction *I = Worklist.removeOne();
if (I == nullptr) continue; // skip null values.
// Check to see if we can DCE the instruction.
if (isInstructionTriviallyDead(I, &TLI)) {
eraseInstFromFunction(*I);
++NumDeadInst;
continue;
}
if (!DebugCounter::shouldExecute(VisitCounter))
continue;
// See if we can trivially sink this instruction to its user if we can
// prove that the successor is not executed more frequently than our block.
// Return the UserBlock if successful.
auto getOptionalSinkBlockForInst =
[this](Instruction *I) -> std::optional<BasicBlock *> {
if (!EnableCodeSinking)
return std::nullopt;
BasicBlock *BB = I->getParent();
BasicBlock *UserParent = nullptr;
unsigned NumUsers = 0;
for (Use &U : I->uses()) {
User *User = U.getUser();
if (User->isDroppable())
continue;
if (NumUsers > MaxSinkNumUsers)
return std::nullopt;
Instruction *UserInst = cast<Instruction>(User);
// Special handling for Phi nodes - get the block the use occurs in.
BasicBlock *UserBB = UserInst->getParent();
if (PHINode *PN = dyn_cast<PHINode>(UserInst))
UserBB = PN->getIncomingBlock(U);
// Bail out if we have uses in different blocks. We don't do any
// sophisticated analysis (i.e finding NearestCommonDominator of these
// use blocks).
if (UserParent && UserParent != UserBB)
return std::nullopt;
UserParent = UserBB;
// Make sure these checks are done only once, naturally we do the checks
// the first time we get the userparent, this will save compile time.
if (NumUsers == 0) {
// Try sinking to another block. If that block is unreachable, then do
// not bother. SimplifyCFG should handle it.
if (UserParent == BB || !DT.isReachableFromEntry(UserParent))
return std::nullopt;
auto *Term = UserParent->getTerminator();
// See if the user is one of our successors that has only one
// predecessor, so that we don't have to split the critical edge.
// Another option where we can sink is a block that ends with a
// terminator that does not pass control to other block (such as
// return or unreachable or resume). In this case:
// - I dominates the User (by SSA form);
// - the User will be executed at most once.
// So sinking I down to User is always profitable or neutral.
if (UserParent->getUniquePredecessor() != BB && !succ_empty(Term))
return std::nullopt;
assert(DT.dominates(BB, UserParent) && "Dominance relation broken?");
}
NumUsers++;
}
// No user or only has droppable users.
if (!UserParent)
return std::nullopt;
return UserParent;
};
auto OptBB = getOptionalSinkBlockForInst(I);
if (OptBB) {
auto *UserParent = *OptBB;
// Okay, the CFG is simple enough, try to sink this instruction.
if (tryToSinkInstruction(I, UserParent)) {
LLVM_DEBUG(dbgs() << "IC: Sink: " << *I << '\n');
MadeIRChange = true;
// We'll add uses of the sunk instruction below, but since
// sinking can expose opportunities for it's *operands* add
// them to the worklist
for (Use &U : I->operands())
if (Instruction *OpI = dyn_cast<Instruction>(U.get()))
Worklist.push(OpI);
}
}
// Now that we have an instruction, try combining it to simplify it.
Builder.SetInsertPoint(I);
Builder.CollectMetadataToCopy(
I, {LLVMContext::MD_dbg, LLVMContext::MD_annotation});
#ifndef NDEBUG
std::string OrigI;
#endif
LLVM_DEBUG(raw_string_ostream SS(OrigI); I->print(SS););
LLVM_DEBUG(dbgs() << "IC: Visiting: " << OrigI << '\n');
if (Instruction *Result = visit(*I)) {
++NumCombined;
// Should we replace the old instruction with a new one?
if (Result != I) {
LLVM_DEBUG(dbgs() << "IC: Old = " << *I << '\n'
<< " New = " << *Result << '\n');
// We copy the old instruction's DebugLoc to the new instruction, unless
// InstCombine already assigned a DebugLoc to it, in which case we
// should trust the more specifically selected DebugLoc.
if (!Result->getDebugLoc())
Result->setDebugLoc(I->getDebugLoc());
// We also copy annotation metadata to the new instruction.
Result->copyMetadata(*I, LLVMContext::MD_annotation);
// Everything uses the new instruction now.
I->replaceAllUsesWith(Result);
// Move the name to the new instruction first.
Result->takeName(I);
// Insert the new instruction into the basic block...
BasicBlock *InstParent = I->getParent();
BasicBlock::iterator InsertPos = I->getIterator();
// Are we replace a PHI with something that isn't a PHI, or vice versa?
if (isa<PHINode>(Result) != isa<PHINode>(I)) {
// We need to fix up the insertion point.
if (isa<PHINode>(I)) // PHI -> Non-PHI
InsertPos = InstParent->getFirstInsertionPt();
else // Non-PHI -> PHI
InsertPos = InstParent->getFirstNonPHIIt();
}
Result->insertInto(InstParent, InsertPos);
// Push the new instruction and any users onto the worklist.
Worklist.pushUsersToWorkList(*Result);
Worklist.push(Result);
eraseInstFromFunction(*I);
} else {
LLVM_DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n'
<< " New = " << *I << '\n');
// If the instruction was modified, it's possible that it is now dead.
// if so, remove it.
if (isInstructionTriviallyDead(I, &TLI)) {
eraseInstFromFunction(*I);
} else {
Worklist.pushUsersToWorkList(*I);
Worklist.push(I);
}
}
MadeIRChange = true;
}
}
Worklist.zap();
return MadeIRChange;
}
// Track the scopes used by !alias.scope and !noalias. In a function, a
// @llvm.experimental.noalias.scope.decl is only useful if that scope is used
// by both sets. If not, the declaration of the scope can be safely omitted.
// The MDNode of the scope can be omitted as well for the instructions that are
// part of this function. We do not do that at this point, as this might become
// too time consuming to do.
class AliasScopeTracker {
SmallPtrSet<const MDNode *, 8> UsedAliasScopesAndLists;
SmallPtrSet<const MDNode *, 8> UsedNoAliasScopesAndLists;
public:
void analyse(Instruction *I) {
// This seems to be faster than checking 'mayReadOrWriteMemory()'.
if (!I->hasMetadataOtherThanDebugLoc())
return;
auto Track = [](Metadata *ScopeList, auto &Container) {
const auto *MDScopeList = dyn_cast_or_null<MDNode>(ScopeList);
if (!MDScopeList || !Container.insert(MDScopeList).second)
return;
for (const auto &MDOperand : MDScopeList->operands())
if (auto *MDScope = dyn_cast<MDNode>(MDOperand))
Container.insert(MDScope);
};
Track(I->getMetadata(LLVMContext::MD_alias_scope), UsedAliasScopesAndLists);
Track(I->getMetadata(LLVMContext::MD_noalias), UsedNoAliasScopesAndLists);
}
bool isNoAliasScopeDeclDead(Instruction *Inst) {
NoAliasScopeDeclInst *Decl = dyn_cast<NoAliasScopeDeclInst>(Inst);
if (!Decl)
return false;
assert(Decl->use_empty() &&
"llvm.experimental.noalias.scope.decl in use ?");
const MDNode *MDSL = Decl->getScopeList();
assert(MDSL->getNumOperands() == 1 &&
"llvm.experimental.noalias.scope should refer to a single scope");
auto &MDOperand = MDSL->getOperand(0);
if (auto *MD = dyn_cast<MDNode>(MDOperand))
return !UsedAliasScopesAndLists.contains(MD) ||
!UsedNoAliasScopesAndLists.contains(MD);
// Not an MDNode ? throw away.
return true;
}
};
/// Populate the IC worklist from a function, by walking it in reverse
/// post-order and adding all reachable code to the worklist.
///
/// This has a couple of tricks to make the code faster and more powerful. In
/// particular, we constant fold and DCE instructions as we go, to avoid adding
/// them to the worklist (this significantly speeds up instcombine on code where
/// many instructions are dead or constant). Additionally, if we find a branch
/// whose condition is a known constant, we only visit the reachable successors.
bool InstCombinerImpl::prepareWorklist(Function &F) {
bool MadeIRChange = false;
SmallPtrSet<BasicBlock *, 32> LiveBlocks;
SmallVector<Instruction *, 128> InstrsForInstructionWorklist;
DenseMap<Constant *, Constant *> FoldedConstants;
AliasScopeTracker SeenAliasScopes;
auto HandleOnlyLiveSuccessor = [&](BasicBlock *BB, BasicBlock *LiveSucc) {
for (BasicBlock *Succ : successors(BB))
if (Succ != LiveSucc && DeadEdges.insert({BB, Succ}).second)
for (PHINode &PN : Succ->phis())
for (Use &U : PN.incoming_values())
if (PN.getIncomingBlock(U) == BB && !isa<PoisonValue>(U)) {
U.set(PoisonValue::get(PN.getType()));
MadeIRChange = true;
}
};
for (BasicBlock *BB : RPOT) {
if (!BB->isEntryBlock() && all_of(predecessors(BB), [&](BasicBlock *Pred) {
return DeadEdges.contains({Pred, BB}) || DT.dominates(BB, Pred);
})) {
HandleOnlyLiveSuccessor(BB, nullptr);
continue;
}
LiveBlocks.insert(BB);
for (Instruction &Inst : llvm::make_early_inc_range(*BB)) {
// ConstantProp instruction if trivially constant.
if (!Inst.use_empty() &&
(Inst.getNumOperands() == 0 || isa<Constant>(Inst.getOperand(0))))
if (Constant *C = ConstantFoldInstruction(&Inst, DL, &TLI)) {
LLVM_DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << Inst
<< '\n');
Inst.replaceAllUsesWith(C);
++NumConstProp;
if (isInstructionTriviallyDead(&Inst, &TLI))
Inst.eraseFromParent();
MadeIRChange = true;
continue;
}
// See if we can constant fold its operands.
for (Use &U : Inst.operands()) {
if (!isa<ConstantVector>(U) && !isa<ConstantExpr>(U))
continue;
auto *C = cast<Constant>(U);
Constant *&FoldRes = FoldedConstants[C];
if (!FoldRes)
FoldRes = ConstantFoldConstant(C, DL, &TLI);
if (FoldRes != C) {
LLVM_DEBUG(dbgs() << "IC: ConstFold operand of: " << Inst
<< "\n Old = " << *C
<< "\n New = " << *FoldRes << '\n');
U = FoldRes;
MadeIRChange = true;
}
}
// Skip processing debug and pseudo intrinsics in InstCombine. Processing
// these call instructions consumes non-trivial amount of time and
// provides no value for the optimization.
if (!Inst.isDebugOrPseudoInst()) {
InstrsForInstructionWorklist.push_back(&Inst);
SeenAliasScopes.analyse(&Inst);
}
}
// If this is a branch or switch on a constant, mark only the single
// live successor. Otherwise assume all successors are live.
Instruction *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI); BI && BI->isConditional()) {
if (isa<UndefValue>(BI->getCondition())) {
// Branch on undef is UB.
HandleOnlyLiveSuccessor(BB, nullptr);
continue;
}
if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
bool CondVal = Cond->getZExtValue();
HandleOnlyLiveSuccessor(BB, BI->getSuccessor(!CondVal));
continue;
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
if (isa<UndefValue>(SI->getCondition())) {
// Switch on undef is UB.
HandleOnlyLiveSuccessor(BB, nullptr);
continue;
}
if (auto *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
HandleOnlyLiveSuccessor(BB,
SI->findCaseValue(Cond)->getCaseSuccessor());
continue;
}
}
}
// Remove instructions inside unreachable blocks. This prevents the
// instcombine code from having to deal with some bad special cases, and
// reduces use counts of instructions.
for (BasicBlock &BB : F) {
if (LiveBlocks.count(&BB))
continue;
unsigned NumDeadInstInBB;
unsigned NumDeadDbgInstInBB;
std::tie(NumDeadInstInBB, NumDeadDbgInstInBB) =
removeAllNonTerminatorAndEHPadInstructions(&BB);
MadeIRChange |= NumDeadInstInBB + NumDeadDbgInstInBB > 0;
NumDeadInst += NumDeadInstInBB;
}
// Once we've found all of the instructions to add to instcombine's worklist,
// add them in reverse order. This way instcombine will visit from the top
// of the function down. This jives well with the way that it adds all uses
// of instructions to the worklist after doing a transformation, thus avoiding
// some N^2 behavior in pathological cases.
Worklist.reserve(InstrsForInstructionWorklist.size());
for (Instruction *Inst : reverse(InstrsForInstructionWorklist)) {
// DCE instruction if trivially dead. As we iterate in reverse program
// order here, we will clean up whole chains of dead instructions.
if (isInstructionTriviallyDead(Inst, &TLI) ||
SeenAliasScopes.isNoAliasScopeDeclDead(Inst)) {
++NumDeadInst;
LLVM_DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
salvageDebugInfo(*Inst);
Inst->eraseFromParent();
MadeIRChange = true;
continue;
}
Worklist.push(Inst);
}
return MadeIRChange;
}
void InstCombiner::computeBackEdges() {
// Collect backedges.
SmallPtrSet<BasicBlock *, 16> Visited;
for (BasicBlock *BB : RPOT) {
Visited.insert(BB);
for (BasicBlock *Succ : successors(BB))
if (Visited.contains(Succ))
BackEdges.insert({BB, Succ});
}
ComputedBackEdges = true;
}
static bool combineInstructionsOverFunction(
Function &F, InstructionWorklist &Worklist, AliasAnalysis *AA,
AssumptionCache &AC, TargetLibraryInfo &TLI, TargetTransformInfo &TTI,
DominatorTree &DT, OptimizationRemarkEmitter &ORE, BlockFrequencyInfo *BFI,
BranchProbabilityInfo *BPI, ProfileSummaryInfo *PSI,
const InstCombineOptions &Opts) {
auto &DL = F.getDataLayout();
bool VerifyFixpoint = Opts.VerifyFixpoint &&
!F.hasFnAttribute("instcombine-no-verify-fixpoint");
/// Builder - This is an IRBuilder that automatically inserts new
/// instructions into the worklist when they are created.
IRBuilder<TargetFolder, IRBuilderCallbackInserter> Builder(
F.getContext(), TargetFolder(DL),
IRBuilderCallbackInserter([&Worklist, &AC](Instruction *I) {
Worklist.add(I);
if (auto *Assume = dyn_cast<AssumeInst>(I))
AC.registerAssumption(Assume);
}));
ReversePostOrderTraversal<BasicBlock *> RPOT(&F.front());
// Lower dbg.declare intrinsics otherwise their value may be clobbered
// by instcombiner.
bool MadeIRChange = false;
if (ShouldLowerDbgDeclare)
MadeIRChange = LowerDbgDeclare(F);
// Iterate while there is work to do.
unsigned Iteration = 0;
while (true) {
++Iteration;
if (Iteration > Opts.MaxIterations && !VerifyFixpoint) {
LLVM_DEBUG(dbgs() << "\n\n[IC] Iteration limit #" << Opts.MaxIterations
<< " on " << F.getName()
<< " reached; stopping without verifying fixpoint\n");
break;
}
++NumWorklistIterations;
LLVM_DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
<< F.getName() << "\n");
InstCombinerImpl IC(Worklist, Builder, F.hasMinSize(), AA, AC, TLI, TTI, DT,
ORE, BFI, BPI, PSI, DL, RPOT);
IC.MaxArraySizeForCombine = MaxArraySize;
bool MadeChangeInThisIteration = IC.prepareWorklist(F);
MadeChangeInThisIteration |= IC.run();
if (!MadeChangeInThisIteration)
break;
MadeIRChange = true;
if (Iteration > Opts.MaxIterations) {
report_fatal_error(
"Instruction Combining on " + Twine(F.getName()) +
" did not reach a fixpoint after " + Twine(Opts.MaxIterations) +
" iterations. " +
"Use 'instcombine<no-verify-fixpoint>' or function attribute "
"'instcombine-no-verify-fixpoint' to suppress this error.",
/*GenCrashDiag=*/false);
}
}
if (Iteration == 1)
++NumOneIteration;
else if (Iteration == 2)
++NumTwoIterations;
else if (Iteration == 3)
++NumThreeIterations;
else
++NumFourOrMoreIterations;
return MadeIRChange;
}
InstCombinePass::InstCombinePass(InstCombineOptions Opts) : Options(Opts) {}
void InstCombinePass::printPipeline(
raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
static_cast<PassInfoMixin<InstCombinePass> *>(this)->printPipeline(
OS, MapClassName2PassName);
OS << '<';
OS << "max-iterations=" << Options.MaxIterations << ";";
OS << (Options.VerifyFixpoint ? "" : "no-") << "verify-fixpoint";
OS << '>';
}
char InstCombinePass::ID = 0;
PreservedAnalyses InstCombinePass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &LRT = AM.getResult<LastRunTrackingAnalysis>(F);
// No changes since last InstCombine pass, exit early.
if (LRT.shouldSkip(&ID))
return PreservedAnalyses::all();
auto &AC = AM.getResult<AssumptionAnalysis>(F);
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
auto &TTI = AM.getResult<TargetIRAnalysis>(F);
auto *AA = &AM.getResult<AAManager>(F);
auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
ProfileSummaryInfo *PSI =
MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
auto *BFI = (PSI && PSI->hasProfileSummary()) ?
&AM.getResult<BlockFrequencyAnalysis>(F) : nullptr;
auto *BPI = AM.getCachedResult<BranchProbabilityAnalysis>(F);
if (!combineInstructionsOverFunction(F, Worklist, AA, AC, TLI, TTI, DT, ORE,
BFI, BPI, PSI, Options)) {
// No changes, all analyses are preserved.
LRT.update(&ID, /*Changed=*/false);
return PreservedAnalyses::all();
}
// Mark all the analyses that instcombine updates as preserved.
PreservedAnalyses PA;
LRT.update(&ID, /*Changed=*/true);
PA.preserve<LastRunTrackingAnalysis>();
PA.preserveSet<CFGAnalyses>();
return PA;
}
void InstructionCombiningPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<AAResultsWrapperPass>();
AU.addPreserved<BasicAAWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU);
}
bool InstructionCombiningPass::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
// Required analyses.
auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &ORE = getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
// Optional analyses.
ProfileSummaryInfo *PSI =
&getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
BlockFrequencyInfo *BFI =
(PSI && PSI->hasProfileSummary()) ?
&getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() :
nullptr;
BranchProbabilityInfo *BPI = nullptr;
if (auto *WrapperPass =
getAnalysisIfAvailable<BranchProbabilityInfoWrapperPass>())
BPI = &WrapperPass->getBPI();
return combineInstructionsOverFunction(F, Worklist, AA, AC, TLI, TTI, DT, ORE,
BFI, BPI, PSI, InstCombineOptions());
}
char InstructionCombiningPass::ID = 0;
InstructionCombiningPass::InstructionCombiningPass() : FunctionPass(ID) {
initializeInstructionCombiningPassPass(*PassRegistry::getPassRegistry());
}
INITIALIZE_PASS_BEGIN(InstructionCombiningPass, "instcombine",
"Combine redundant instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LazyBlockFrequencyInfoPass)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_END(InstructionCombiningPass, "instcombine",
"Combine redundant instructions", false, false)
// Initialization Routines
void llvm::initializeInstCombine(PassRegistry &Registry) {
initializeInstructionCombiningPassPass(Registry);
}
FunctionPass *llvm::createInstructionCombiningPass() {
return new InstructionCombiningPass();
}