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llvm/llvm-project/6b26457a0ef2994de54606eb5c356cb897cadda2/./llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
blob: df52a84e0d3f344a059b41424b4efd8abf6be8f3 [file]
//===- InstCombineCasts.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the visit functions for cast operations.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/STLFunctionalExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Transforms/InstCombine/InstCombiner.h"
#include <optional>
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
using EvaluatedMap = SmallDenseMap<Value *, Value *, 8>;
static Value *EvaluateInDifferentTypeImpl(Value *V, Type *Ty, bool isSigned,
InstCombinerImpl &IC,
EvaluatedMap &Processed) {
// Since we cover transformation of instructions with multiple users, we might
// come to the same node via multiple paths. We should not create a
// replacement for every single one of them though.
if (Value *Result = Processed.lookup(V))
return Result;
if (Constant *C = dyn_cast<Constant>(V))
return ConstantFoldIntegerCast(C, Ty, isSigned, IC.getDataLayout());
// Otherwise, it must be an instruction.
Instruction *I = cast<Instruction>(V);
Instruction *Res = nullptr;
unsigned Opc = I->getOpcode();
switch (Opc) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::AShr:
case Instruction::LShr:
case Instruction::Shl:
case Instruction::UDiv:
case Instruction::URem: {
Value *LHS = EvaluateInDifferentTypeImpl(I->getOperand(0), Ty, isSigned, IC,
Processed);
Value *RHS = EvaluateInDifferentTypeImpl(I->getOperand(1), Ty, isSigned, IC,
Processed);
Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
if (Opc == Instruction::LShr || Opc == Instruction::AShr)
Res->setIsExact(I->isExact());
break;
}
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
// If the source type of the cast is the type we're trying for then we can
// just return the source. There's no need to insert it because it is not
// new.
if (I->getOperand(0)->getType() == Ty)
return I->getOperand(0);
// Otherwise, must be the same type of cast, so just reinsert a new one.
// This also handles the case of zext(trunc(x)) -> zext(x).
Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty,
Opc == Instruction::SExt);
if (auto *Trunc = dyn_cast<TruncInst>(I)) {
if (auto *NewTrunc = dyn_cast<TruncInst>(Res)) {
if (Trunc->getType()->getScalarSizeInBits() <=
Ty->getScalarSizeInBits()) {
NewTrunc->setHasNoSignedWrap(Trunc->hasNoSignedWrap());
NewTrunc->setHasNoUnsignedWrap(Trunc->hasNoUnsignedWrap());
}
} else if (auto *NewZExt = dyn_cast<ZExtInst>(Res)) {
if (Trunc->hasNoUnsignedWrap())
NewZExt->setNonNeg();
}
}
break;
case Instruction::Select: {
Value *True = EvaluateInDifferentTypeImpl(I->getOperand(1), Ty, isSigned,
IC, Processed);
Value *False = EvaluateInDifferentTypeImpl(I->getOperand(2), Ty, isSigned,
IC, Processed);
Res = SelectInst::Create(I->getOperand(0), True, False);
break;
}
case Instruction::PHI: {
PHINode *OPN = cast<PHINode>(I);
PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues());
for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
Value *V = EvaluateInDifferentTypeImpl(OPN->getIncomingValue(i), Ty,
isSigned, IC, Processed);
NPN->addIncoming(V, OPN->getIncomingBlock(i));
}
Res = NPN;
break;
}
case Instruction::FPToUI:
case Instruction::FPToSI:
Res = CastInst::Create(static_cast<Instruction::CastOps>(Opc),
I->getOperand(0), Ty);
break;
case Instruction::Call:
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default:
llvm_unreachable("Unsupported call!");
case Intrinsic::vscale: {
Function *Fn = Intrinsic::getOrInsertDeclaration(
I->getModule(), Intrinsic::vscale, {Ty});
Res = CallInst::Create(Fn->getFunctionType(), Fn);
break;
}
case Intrinsic::umin:
case Intrinsic::umax:
case Intrinsic::smin:
case Intrinsic::smax: {
Value *Op0 = EvaluateInDifferentTypeImpl(II->getArgOperand(0), Ty,
isSigned, IC, Processed);
Value *Op1 = EvaluateInDifferentTypeImpl(II->getArgOperand(1), Ty,
isSigned, IC, Processed);
Function *Fn = Intrinsic::getOrInsertDeclaration(
I->getModule(), II->getIntrinsicID(), {Ty});
Res = CallInst::Create(Fn->getFunctionType(), Fn, {Op0, Op1});
break;
}
case Intrinsic::abs: {
Value *Arg = EvaluateInDifferentTypeImpl(II->getArgOperand(0), Ty,
isSigned, IC, Processed);
Function *Fn = Intrinsic::getOrInsertDeclaration(
I->getModule(), II->getIntrinsicID(), {Ty});
Res = CallInst::Create(Fn->getFunctionType(), Fn,
{Arg, ConstantInt::getFalse(I->getContext())});
break;
}
}
}
break;
case Instruction::ShuffleVector: {
auto *ScalarTy = cast<VectorType>(Ty)->getElementType();
auto *VTy = cast<VectorType>(I->getOperand(0)->getType());
auto *FixedTy = VectorType::get(ScalarTy, VTy->getElementCount());
Value *Op0 = EvaluateInDifferentTypeImpl(I->getOperand(0), FixedTy,
isSigned, IC, Processed);
Value *Op1 = EvaluateInDifferentTypeImpl(I->getOperand(1), FixedTy,
isSigned, IC, Processed);
Res = new ShuffleVectorInst(Op0, Op1,
cast<ShuffleVectorInst>(I)->getShuffleMask());
break;
}
default:
// TODO: Can handle more cases here.
llvm_unreachable("Unreachable!");
}
Res->takeName(I);
Value *Result = IC.InsertNewInstWith(Res, I->getIterator());
// There is no need in keeping track of the old value/new value relationship
// when we have only one user, we came have here from that user and no-one
// else cares.
if (!V->hasOneUse())
Processed[V] = Result;
return Result;
}
/// Given an expression that CanEvaluateTruncated or CanEvaluateSExtd returns
/// true for, actually insert the code to evaluate the expression.
Value *InstCombinerImpl::EvaluateInDifferentType(Value *V, Type *Ty,
bool isSigned) {
EvaluatedMap Processed;
return EvaluateInDifferentTypeImpl(V, Ty, isSigned, *this, Processed);
}
Instruction::CastOps
InstCombinerImpl::isEliminableCastPair(const CastInst *CI1,
const CastInst *CI2) {
Type *SrcTy = CI1->getSrcTy();
Type *MidTy = CI1->getDestTy();
Type *DstTy = CI2->getDestTy();
Instruction::CastOps firstOp = CI1->getOpcode();
Instruction::CastOps secondOp = CI2->getOpcode();
Type *SrcIntPtrTy =
SrcTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(SrcTy) : nullptr;
Type *DstIntPtrTy =
DstTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(DstTy) : nullptr;
unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
DstTy, &DL);
// We don't want to form an inttoptr or ptrtoint that converts to an integer
// type that differs from the pointer size.
if ((Res == Instruction::IntToPtr && SrcTy != DstIntPtrTy) ||
(Res == Instruction::PtrToInt && DstTy != SrcIntPtrTy))
Res = 0;
return Instruction::CastOps(Res);
}
/// Implement the transforms common to all CastInst visitors.
Instruction *InstCombinerImpl::commonCastTransforms(CastInst &CI) {
Value *Src = CI.getOperand(0);
Type *Ty = CI.getType();
if (Value *Res =
simplifyCastInst(CI.getOpcode(), Src, Ty, SQ.getWithInstruction(&CI)))
return replaceInstUsesWith(CI, Res);
// Try to eliminate a cast of a cast.
if (auto *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
if (Instruction::CastOps NewOpc = isEliminableCastPair(CSrc, &CI)) {
// The first cast (CSrc) is eliminable so we need to fix up or replace
// the second cast (CI). CSrc will then have a good chance of being dead.
auto *Res = CastInst::Create(NewOpc, CSrc->getOperand(0), Ty);
// Point debug users of the dying cast to the new one.
if (CSrc->hasOneUse())
replaceAllDbgUsesWith(*CSrc, *Res, CI, DT);
return Res;
}
}
if (auto *Sel = dyn_cast<SelectInst>(Src)) {
// We are casting a select. Try to fold the cast into the select if the
// select does not have a compare instruction with matching operand types
// or the select is likely better done in a narrow type.
// Creating a select with operands that are different sizes than its
// condition may inhibit other folds and lead to worse codegen.
Value *Cond = Sel->getCondition();
if (!isa<CmpInst, TruncInst>(Cond) ||
cast<Instruction>(Cond)->getOperand(0)->getType() != Sel->getType() ||
(CI.getOpcode() == Instruction::Trunc &&
shouldChangeType(CI.getSrcTy(), CI.getType()))) {
// If it's a bitcast involving vectors, make sure it has the same number
// of elements on both sides.
if (CI.getOpcode() != Instruction::BitCast ||
match(&CI, m_ElementWiseBitCast(m_Value()))) {
if (Instruction *NV = FoldOpIntoSelect(CI, Sel)) {
replaceAllDbgUsesWith(*Sel, *NV, CI, DT);
return NV;
}
}
}
}
// If we are casting a PHI, then fold the cast into the PHI.
if (auto *PN = dyn_cast<PHINode>(Src)) {
// Don't do this if it would create a PHI node with an illegal type from a
// legal type.
if (!Src->getType()->isIntegerTy() || !CI.getType()->isIntegerTy() ||
shouldChangeType(CI.getSrcTy(), CI.getType()))
if (Instruction *NV = foldOpIntoPhi(CI, PN))
return NV;
}
// Canonicalize a unary shuffle after the cast if neither operation changes
// the size or element size of the input vector.
// TODO: We could allow size-changing ops if that doesn't harm codegen.
// cast (shuffle X, Mask) --> shuffle (cast X), Mask
Value *X;
ArrayRef<int> Mask;
if (match(Src, m_OneUse(m_Shuffle(m_Value(X), m_Poison(), m_Mask(Mask))))) {
// TODO: Allow scalable vectors?
auto *SrcTy = dyn_cast<FixedVectorType>(X->getType());
auto *DestTy = dyn_cast<FixedVectorType>(Ty);
if (SrcTy && DestTy &&
SrcTy->getNumElements() == DestTy->getNumElements() &&
SrcTy->getPrimitiveSizeInBits() == DestTy->getPrimitiveSizeInBits()) {
Value *CastX = Builder.CreateCast(CI.getOpcode(), X, DestTy);
return new ShuffleVectorInst(CastX, Mask);
}
}
return nullptr;
}
namespace {
/// Helper class for evaluating whether a value can be computed in a different
/// type without changing its value. Used by cast simplification transforms.
class TypeEvaluationHelper {
public:
/// Return true if we can evaluate the specified expression tree as type Ty
/// instead of its larger type, and arrive with the same value.
/// This is used by code that tries to eliminate truncates.
[[nodiscard]] static bool canEvaluateTruncated(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI);
/// Determine if the specified value can be computed in the specified wider
/// type and produce the same low bits. If not, return false.
[[nodiscard]] static bool canEvaluateZExtd(Value *V, Type *Ty,
unsigned &BitsToClear,
InstCombinerImpl &IC,
Instruction *CtxI);
/// Return true if we can take the specified value and return it as type Ty
/// without inserting any new casts and without changing the value of the
/// common low bits.
[[nodiscard]] static bool canEvaluateSExtd(Value *V, Type *Ty);
private:
/// Constants and extensions/truncates from the destination type are always
/// free to be evaluated in that type.
[[nodiscard]] static bool canAlwaysEvaluateInType(Value *V, Type *Ty);
/// Check if we traversed all the users of the multi-use values we've seen.
[[nodiscard]] bool allPendingVisited() const {
return llvm::all_of(Pending,
[this](Value *V) { return Visited.contains(V); });
}
/// A generic wrapper for canEvaluate* recursions to inject visitation
/// tracking and enforce correct multi-use value evaluations.
[[nodiscard]] bool
canEvaluate(Value *V, Type *Ty,
llvm::function_ref<bool(Value *, Type *Type)> Pred) {
if (canAlwaysEvaluateInType(V, Ty))
return true;
auto *I = dyn_cast<Instruction>(V);
if (I == nullptr)
return false;
// We insert false by default to return false when we encounter user loops.
const auto [It, Inserted] = Visited.insert({V, false});
// There are three possible cases for us having information on this value
// in the Visited map:
// 1. We properly checked it and concluded that we can evaluate it (true)
// 2. We properly checked it and concluded that we can't (false)
// 3. We started to check it, but during the recursive traversal we came
// back to it.
//
// For cases 1 and 2, we can safely return the stored result. For case 3, we
// can potentially have a situation where we can evaluate recursive user
// chains, but that can be quite tricky to do properly and isntead, we
// return false.
//
// In any case, we should return whatever was there in the map to begin
// with.
if (!Inserted)
return It->getSecond();
// We can easily make a decision about single-user values whether they can
// be evaluated in a different type or not, we came from that user. This is
// not as simple for multi-user values.
//
// In general, we have the following case (inverted control-flow, users are
// at the top):
//
// Cast %A
// ____|
// /
// %A = Use %B, %C
// ________| |
// / |
// %B = Use %D |
// ________| |
// / |
// %D = Use %C |
// ________|___|
// /
// %C = ...
//
// In this case, when we check %A, %B and %D, we are confident that we can
// make the decision here and now, since we came from their only users.
//
// For %C, it is harder. We come there twice, and when we come the first
// time, it's hard to tell if we will visit the second user (technically
// it's not hard, but we might need a lot of repetitive checks with non-zero
// cost).
//
// In the case above, we are allowed to evaluate %C in different type
// because all of it users were part of the traversal.
//
// In the following case, however, we can't make this conclusion:
//
// Cast %A
// ____|
// /
// %A = Use %B, %C
// ________| |
// / |
// %B = Use %D |
// ________| |
// / |
// %D = Use %C |
// | |
// foo(%C) | | <- never traversing foo(%C)
// ________|___|
// /
// %C = ...
//
// In this case, we still can evaluate %C in a different type, but we'd need
// to create a copy of the original %C to be used in foo(%C). Such
// duplication might be not profitable.
//
// For this reason, we collect all users of the mult-user values and mark
// them as "pending" and defer this decision to the very end. When we are
// done and and ready to have a positive verdict, we should double-check all
// of the pending users and ensure that we visited them. allPendingVisited
// predicate checks exactly that.
if (!I->hasOneUse()) {
for (Use &U : I->uses()) {
// For most instructions, evaluating them in a different type will
// change the type of all operands. This is not the case for select
// conditions. Make sure we don't retain an extra use via the select
// condition.
if (isa<SelectInst>(U.getUser()) && U.getOperandNo() == 0)
return false;
Pending.push_back(U.getUser());
}
}
const bool Result = Pred(V, Ty);
// We have to set result this way and not via It because Pred is recursive
// and it is very likely that we grew Visited and invalidated It.
Visited[V] = Result;
return Result;
}
/// Filter out values that we can not evaluate in the destination type for
/// free.
[[nodiscard]] bool canNotEvaluateInType(Value *V, Type *Ty);
[[nodiscard]] bool canEvaluateTruncatedImpl(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI);
[[nodiscard]] bool canEvaluateTruncatedPred(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI);
[[nodiscard]] bool canEvaluateZExtdImpl(Value *V, Type *Ty,
unsigned &BitsToClear,
InstCombinerImpl &IC,
Instruction *CtxI);
[[nodiscard]] bool canEvaluateSExtdImpl(Value *V, Type *Ty);
[[nodiscard]] bool canEvaluateSExtdPred(Value *V, Type *Ty);
/// A bookkeeping map to memorize an already made decision for a traversed
/// value.
SmallDenseMap<Value *, bool, 8> Visited;
/// A list of pending values to check in the end.
SmallVector<Value *, 8> Pending;
};
} // anonymous namespace
/// Constants and extensions/truncates from the destination type are always
/// free to be evaluated in that type. This is a helper for canEvaluate*.
bool TypeEvaluationHelper::canAlwaysEvaluateInType(Value *V, Type *Ty) {
if (isa<Constant>(V))
return match(V, m_ImmConstant());
Value *X;
if (match(V, m_ZExtOrSExt(m_SpecificType(Ty, X))) ||
match(V, m_Trunc(m_SpecificType(Ty, X))))
return true;
return false;
}
/// Filter out values that we can not evaluate in the destination type for free.
/// This is a helper for canEvaluate*.
bool TypeEvaluationHelper::canNotEvaluateInType(Value *V, Type *Ty) {
if (!isa<Instruction>(V))
return true;
// We don't extend or shrink something that has multiple uses -- doing so
// would require duplicating the instruction which isn't profitable.
if (!V->hasOneUse())
return true;
return false;
}
/// Return true if we can evaluate the specified expression tree as type Ty
/// instead of its larger type, and arrive with the same value.
/// This is used by code that tries to eliminate truncates.
///
/// Ty will always be a type smaller than V. We should return true if trunc(V)
/// can be computed by computing V in the smaller type. If V is an instruction,
/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
/// makes sense if x and y can be efficiently truncated.
///
/// This function works on both vectors and scalars.
///
bool TypeEvaluationHelper::canEvaluateTruncated(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI) {
TypeEvaluationHelper TYH;
return TYH.canEvaluateTruncatedImpl(V, Ty, IC, CtxI) &&
// We need to check whether we visited all users of multi-user values,
// and we have to do it at the very end, outside of the recursion.
TYH.allPendingVisited();
}
bool TypeEvaluationHelper::canEvaluateTruncatedImpl(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI) {
return canEvaluate(V, Ty, [this, &IC, CtxI](Value *V, Type *Ty) {
return canEvaluateTruncatedPred(V, Ty, IC, CtxI);
});
}
bool TypeEvaluationHelper::canEvaluateTruncatedPred(Value *V, Type *Ty,
InstCombinerImpl &IC,
Instruction *CtxI) {
auto *I = cast<Instruction>(V);
Type *OrigTy = V->getType();
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators can all arbitrarily be extended or truncated.
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
case Instruction::UDiv:
case Instruction::URem: {
// UDiv and URem can be truncated if all the truncated bits are zero.
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
assert(BitWidth < OrigBitWidth && "Unexpected bitwidths!");
APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
// Do not preserve the original context instruction. Simplifying div/rem
// based on later context may introduce a trap.
if (IC.MaskedValueIsZero(I->getOperand(0), Mask, I) &&
IC.MaskedValueIsZero(I->getOperand(1), Mask, I)) {
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
}
break;
}
case Instruction::Shl: {
// If we are truncating the result of this SHL, and if it's a shift of an
// inrange amount, we can always perform a SHL in a smaller type.
uint32_t BitWidth = Ty->getScalarSizeInBits();
KnownBits AmtKnownBits =
llvm::computeKnownBits(I->getOperand(1), IC.getDataLayout());
if (AmtKnownBits.getMaxValue().ult(BitWidth))
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
break;
}
case Instruction::LShr: {
// If this is a truncate of a logical shr, we can truncate it to a smaller
// lshr iff we know that the bits we would otherwise be shifting in are
// already zeros.
// TODO: It is enough to check that the bits we would be shifting in are
// zero - use AmtKnownBits.getMaxValue().
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
KnownBits AmtKnownBits = IC.computeKnownBits(I->getOperand(1), CtxI);
APInt MaxShiftAmt = AmtKnownBits.getMaxValue();
APInt ShiftedBits = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
if (MaxShiftAmt.ult(BitWidth)) {
// If the only user is a trunc then we can narrow the shift if any new
// MSBs are not going to be used.
if (auto *Trunc = dyn_cast<TruncInst>(V->user_back())) {
auto DemandedBits = Trunc->getType()->getScalarSizeInBits();
if ((MaxShiftAmt + DemandedBits).ule(BitWidth))
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
}
if (IC.MaskedValueIsZero(I->getOperand(0), ShiftedBits, CtxI))
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
}
break;
}
case Instruction::AShr: {
// If this is a truncate of an arithmetic shr, we can truncate it to a
// smaller ashr iff we know that all the bits from the sign bit of the
// original type and the sign bit of the truncate type are similar.
// TODO: It is enough to check that the bits we would be shifting in are
// similar to sign bit of the truncate type.
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
KnownBits AmtKnownBits =
llvm::computeKnownBits(I->getOperand(1), IC.getDataLayout());
unsigned ShiftedBits = OrigBitWidth - BitWidth;
if (AmtKnownBits.getMaxValue().ult(BitWidth) &&
ShiftedBits < IC.ComputeNumSignBits(I->getOperand(0), CtxI))
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
break;
}
case Instruction::Trunc:
// trunc(trunc(x)) -> trunc(x)
return true;
case Instruction::ZExt:
case Instruction::SExt:
// trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest
// trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest
return true;
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
return canEvaluateTruncatedImpl(SI->getTrueValue(), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(SI->getFalseValue(), Ty, IC, CtxI);
}
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// get into trouble with cyclic PHIs here because canEvaluate handles use
// chain loops.
PHINode *PN = cast<PHINode>(I);
return llvm::all_of(
PN->incoming_values(), [this, Ty, &IC, CtxI](Value *IncValue) {
return canEvaluateTruncatedImpl(IncValue, Ty, IC, CtxI);
});
}
case Instruction::FPToUI:
case Instruction::FPToSI: {
// If the integer type can hold the max FP value, it is safe to cast
// directly to that type. Otherwise, we may create poison via overflow
// that did not exist in the original code.
Type *InputTy = I->getOperand(0)->getType()->getScalarType();
const fltSemantics &Semantics = InputTy->getFltSemantics();
uint32_t MinBitWidth = APFloatBase::semanticsIntSizeInBits(
Semantics, I->getOpcode() == Instruction::FPToSI);
return Ty->getScalarSizeInBits() >= MinBitWidth;
}
case Instruction::ShuffleVector:
return canEvaluateTruncatedImpl(I->getOperand(0), Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(I->getOperand(1), Ty, IC, CtxI);
case Instruction::Call: {
Value *AbsOp;
if (match(I, m_Intrinsic<Intrinsic::abs>(m_Value(AbsOp), m_Value()))) {
if (IC.ComputeMaxSignificantBits(AbsOp, CtxI) > Ty->getScalarSizeInBits())
return false;
return canEvaluateTruncatedImpl(AbsOp, Ty, IC, CtxI);
}
auto *MM = dyn_cast<MinMaxIntrinsic>(I);
if (!MM)
return false;
// The min/max can be performed in the narrow type when each operand has
// zero high bits (for umin/umax) or enough sign bits (for smin/smax).
Value *Op0 = MM->getLHS();
Value *Op1 = MM->getRHS();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (MM->isSigned()) {
if (IC.ComputeMaxSignificantBits(Op0, CtxI) > BitWidth ||
IC.ComputeMaxSignificantBits(Op1, CtxI) > BitWidth)
break;
} else {
APInt Mask =
APInt::getBitsSetFrom(OrigTy->getScalarSizeInBits(), BitWidth);
if (!IC.MaskedValueIsZero(Op0, Mask, CtxI) ||
!IC.MaskedValueIsZero(Op1, Mask, CtxI))
break;
}
return canEvaluateTruncatedImpl(Op0, Ty, IC, CtxI) &&
canEvaluateTruncatedImpl(Op1, Ty, IC, CtxI);
}
default:
// TODO: Can handle more cases here.
break;
}
return false;
}
/// Given a vector that is bitcast to an integer, optionally logically
/// right-shifted, and truncated, convert it to an extractelement.
/// Example (big endian):
/// trunc (lshr (bitcast <4 x i32> %X to i128), 32) to i32
/// --->
/// extractelement <4 x i32> %X, 1
static Instruction *foldVecTruncToExtElt(TruncInst &Trunc,
InstCombinerImpl &IC) {
Value *TruncOp = Trunc.getOperand(0);
Type *DestType = Trunc.getType();
if (!TruncOp->hasOneUse() || !isa<IntegerType>(DestType))
return nullptr;
Value *VecInput = nullptr;
ConstantInt *ShiftVal = nullptr;
if (!match(TruncOp, m_CombineOr(m_BitCast(m_Value(VecInput)),
m_LShr(m_BitCast(m_Value(VecInput)),
m_ConstantInt(ShiftVal)))) ||
!isa<VectorType>(VecInput->getType()))
return nullptr;
VectorType *VecType = cast<VectorType>(VecInput->getType());
unsigned VecWidth = VecType->getPrimitiveSizeInBits();
unsigned DestWidth = DestType->getPrimitiveSizeInBits();
unsigned ShiftAmount = ShiftVal ? ShiftVal->getZExtValue() : 0;
if ((VecWidth % DestWidth != 0) || (ShiftAmount % DestWidth != 0))
return nullptr;
// If the element type of the vector doesn't match the result type,
// bitcast it to a vector type that we can extract from.
unsigned NumVecElts = VecWidth / DestWidth;
if (VecType->getElementType() != DestType) {
VecType = FixedVectorType::get(DestType, NumVecElts);
VecInput = IC.Builder.CreateBitCast(VecInput, VecType, "bc");
}
unsigned Elt = ShiftAmount / DestWidth;
if (IC.getDataLayout().isBigEndian())
Elt = NumVecElts - 1 - Elt;
return ExtractElementInst::Create(VecInput, IC.Builder.getInt32(Elt));
}
/// Whenever an element is extracted from a vector, optionally shifted down, and
/// then truncated, canonicalize by converting it to a bitcast followed by an
/// extractelement.
///
/// Examples (little endian):
/// trunc (extractelement <4 x i64> %X, 0) to i32
/// --->
/// extractelement <8 x i32> (bitcast <4 x i64> %X to <8 x i32>), i32 0
///
/// trunc (lshr (extractelement <4 x i32> %X, 0), 8) to i8
/// --->
/// extractelement <16 x i8> (bitcast <4 x i32> %X to <16 x i8>), i32 1
static Instruction *foldVecExtTruncToExtElt(TruncInst &Trunc,
InstCombinerImpl &IC) {
Value *Src = Trunc.getOperand(0);
Type *SrcType = Src->getType();
Type *DstType = Trunc.getType();
// Only attempt this if we have simple aliasing of the vector elements.
// A badly fit destination size would result in an invalid cast.
unsigned SrcBits = SrcType->getScalarSizeInBits();
unsigned DstBits = DstType->getScalarSizeInBits();
uint64_t TruncRatio = SrcBits / DstBits;
if ((SrcBits % DstBits) != 0)
return nullptr;
Value *VecOp;
ConstantInt *Cst;
const APInt *ShiftAmount = nullptr;
if (!match(Src, m_OneUse(m_ExtractElt(m_Value(VecOp), m_ConstantInt(Cst)))) &&
!match(Src,
m_OneUse(m_LShr(m_ExtractElt(m_Value(VecOp), m_ConstantInt(Cst)),
m_APInt(ShiftAmount)))))
return nullptr;
auto *VecOpTy = cast<VectorType>(VecOp->getType());
auto VecElts = VecOpTy->getElementCount();
uint64_t BitCastNumElts = VecElts.getKnownMinValue() * TruncRatio;
// Computed in 64-bit above to avoid a 32-bit overflow. Bail out if the
// element count exceeds IntegerType::MAX_INT_BITS, as we cannot create a
// wider vector type.
if (BitCastNumElts > IntegerType::MAX_INT_BITS)
return nullptr;
// Make sure we don't overflow in the calculation of the new index.
// (VecOpIdx + 1) * TruncRatio should not overflow.
if (Cst->uge(std::numeric_limits<uint64_t>::max() / TruncRatio))
return nullptr;
uint64_t VecOpIdx = Cst->getZExtValue();
uint64_t NewIdx = IC.getDataLayout().isBigEndian()
? (VecOpIdx + 1) * TruncRatio - 1
: VecOpIdx * TruncRatio;
// Adjust index by the whole number of truncated elements.
if (ShiftAmount) {
// Check shift amount is in range and shifts a whole number of truncated
// elements.
if (ShiftAmount->uge(SrcBits) || ShiftAmount->urem(DstBits) != 0)
return nullptr;
uint64_t IdxOfs = ShiftAmount->udiv(DstBits).getZExtValue();
// IdxOfs is guaranteed to be less than TruncRatio, so we won't overflow in
// the adjustment.
assert(IdxOfs < TruncRatio &&
"IdxOfs is expected to be less than TruncRatio.");
NewIdx = IC.getDataLayout().isBigEndian() ? (NewIdx - IdxOfs)
: (NewIdx + IdxOfs);
}
auto *BitCastTo =
VectorType::get(DstType, BitCastNumElts, VecElts.isScalable());
Value *BitCast = IC.Builder.CreateBitCast(VecOp, BitCastTo);
return ExtractElementInst::Create(BitCast, IC.Builder.getInt64(NewIdx));
}
/// Funnel/Rotate left/right may occur in a wider type than necessary because of
/// type promotion rules. Try to narrow the inputs and convert to funnel shift.
Instruction *InstCombinerImpl::narrowFunnelShift(TruncInst &Trunc) {
assert((isa<VectorType>(Trunc.getSrcTy()) ||
shouldChangeType(Trunc.getSrcTy(), Trunc.getType())) &&
"Don't narrow to an illegal scalar type");
// Bail out on strange types. It is possible to handle some of these patterns
// even with non-power-of-2 sizes, but it is not a likely scenario.
Type *DestTy = Trunc.getType();
unsigned NarrowWidth = DestTy->getScalarSizeInBits();
unsigned WideWidth = Trunc.getSrcTy()->getScalarSizeInBits();
if (!isPowerOf2_32(NarrowWidth))
return nullptr;
// First, find an or'd pair of opposite shifts:
// trunc (or (lshr ShVal0, ShAmt0), (shl ShVal1, ShAmt1))
BinaryOperator *Or0, *Or1;
if (!match(Trunc.getOperand(0), m_OneUse(m_Or(m_BinOp(Or0), m_BinOp(Or1)))))
return nullptr;
Value *ShVal0, *ShVal1, *ShAmt0, *ShAmt1;
if (!match(Or0, m_OneUse(m_LogicalShift(m_Value(ShVal0), m_Value(ShAmt0)))) ||
!match(Or1, m_OneUse(m_LogicalShift(m_Value(ShVal1), m_Value(ShAmt1)))) ||
Or0->getOpcode() == Or1->getOpcode())
return nullptr;
// Canonicalize to or(shl(ShVal0, ShAmt0), lshr(ShVal1, ShAmt1)).
if (Or0->getOpcode() == BinaryOperator::LShr) {
std::swap(Or0, Or1);
std::swap(ShVal0, ShVal1);
std::swap(ShAmt0, ShAmt1);
}
assert(Or0->getOpcode() == BinaryOperator::Shl &&
Or1->getOpcode() == BinaryOperator::LShr &&
"Illegal or(shift,shift) pair");
// Match the shift amount operands for a funnel/rotate pattern. This always
// matches a subtraction on the R operand.
auto matchShiftAmount = [&](Value *L, Value *R, unsigned Width) -> Value * {
// The shift amounts may add up to the narrow bit width:
// (shl ShVal0, L) | (lshr ShVal1, Width - L)
// If this is a funnel shift (different operands are shifted), then the
// shift amount can not over-shift (create poison) in the narrow type.
unsigned MaxShiftAmountWidth = Log2_32(NarrowWidth);
APInt HiBitMask = ~APInt::getLowBitsSet(WideWidth, MaxShiftAmountWidth);
if (ShVal0 == ShVal1 || MaskedValueIsZero(L, HiBitMask))
if (match(R, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(L)))))
return L;
// The following patterns currently only work for rotation patterns.
// TODO: Add more general funnel-shift compatible patterns.
if (ShVal0 != ShVal1)
return nullptr;
// The shift amount may be masked with negation:
// (shl ShVal0, (X & (Width - 1))) | (lshr ShVal1, ((-X) & (Width - 1)))
Value *X;
unsigned Mask = Width - 1;
if (match(L, m_And(m_Value(X), m_SpecificInt(Mask))) &&
match(R, m_And(m_Neg(m_Specific(X)), m_SpecificInt(Mask))))
return X;
// Same as above, but the shift amount may be extended after masking:
if (match(L, m_ZExt(m_And(m_Value(X), m_SpecificInt(Mask)))) &&
match(R, m_ZExt(m_And(m_Neg(m_Specific(X)), m_SpecificInt(Mask)))))
return X;
return nullptr;
};
Value *ShAmt = matchShiftAmount(ShAmt0, ShAmt1, NarrowWidth);
bool IsFshl = true; // Sub on LSHR.
if (!ShAmt) {
ShAmt = matchShiftAmount(ShAmt1, ShAmt0, NarrowWidth);
IsFshl = false; // Sub on SHL.
}
if (!ShAmt)
return nullptr;
// The right-shifted value must have high zeros in the wide type (for example
// from 'zext', 'and' or 'shift'). High bits of the left-shifted value are
// truncated, so those do not matter.
APInt HiBitMask = APInt::getHighBitsSet(WideWidth, WideWidth - NarrowWidth);
if (!MaskedValueIsZero(ShVal1, HiBitMask, &Trunc))
return nullptr;
// Adjust the width of ShAmt for narrowed funnel shift operation:
// - Zero-extend if ShAmt is narrower than the destination type.
// - Truncate if ShAmt is wider, discarding non-significant high-order bits.
// This prepares ShAmt for llvm.fshl.i8(trunc(ShVal), trunc(ShVal),
// zext/trunc(ShAmt)).
Value *NarrowShAmt = Builder.CreateZExtOrTrunc(ShAmt, DestTy);
Value *X, *Y;
X = Y = Builder.CreateTrunc(ShVal0, DestTy);
if (ShVal0 != ShVal1)
Y = Builder.CreateTrunc(ShVal1, DestTy);
Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr;
Function *F =
Intrinsic::getOrInsertDeclaration(Trunc.getModule(), IID, DestTy);
return CallInst::Create(F, {X, Y, NarrowShAmt});
}
/// Try to narrow the width of math or bitwise logic instructions by pulling a
/// truncate ahead of binary operators.
Instruction *InstCombinerImpl::narrowBinOp(TruncInst &Trunc) {
Type *SrcTy = Trunc.getSrcTy();
Type *DestTy = Trunc.getType();
unsigned SrcWidth = SrcTy->getScalarSizeInBits();
unsigned DestWidth = DestTy->getScalarSizeInBits();
if (!isa<VectorType>(SrcTy) && !shouldChangeType(SrcTy, DestTy))
return nullptr;
BinaryOperator *BinOp;
if (!match(Trunc.getOperand(0), m_OneUse(m_BinOp(BinOp))))
return nullptr;
Value *BinOp0 = BinOp->getOperand(0);
Value *BinOp1 = BinOp->getOperand(1);
switch (BinOp->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul: {
Constant *C;
if (match(BinOp0, m_Constant(C))) {
// trunc (binop C, X) --> binop (trunc C', X)
Constant *NarrowC = ConstantExpr::getTrunc(C, DestTy);
Value *TruncX = Builder.CreateTrunc(BinOp1, DestTy);
return BinaryOperator::Create(BinOp->getOpcode(), NarrowC, TruncX);
}
if (match(BinOp1, m_Constant(C))) {
// trunc (binop X, C) --> binop (trunc X, C')
Constant *NarrowC = ConstantExpr::getTrunc(C, DestTy);
Value *TruncX = Builder.CreateTrunc(BinOp0, DestTy);
return BinaryOperator::Create(BinOp->getOpcode(), TruncX, NarrowC);
}
Value *X;
if (match(BinOp0, m_ZExtOrSExt(m_SpecificType(DestTy, X)))) {
// trunc (binop (ext X), Y) --> binop X, (trunc Y)
Value *NarrowOp1 = Builder.CreateTrunc(BinOp1, DestTy);
return BinaryOperator::Create(BinOp->getOpcode(), X, NarrowOp1);
}
if (match(BinOp1, m_ZExtOrSExt(m_SpecificType(DestTy, X)))) {
// trunc (binop Y, (ext X)) --> binop (trunc Y), X
Value *NarrowOp0 = Builder.CreateTrunc(BinOp0, DestTy);
return BinaryOperator::Create(BinOp->getOpcode(), NarrowOp0, X);
}
break;
}
case Instruction::LShr:
case Instruction::AShr: {
// trunc (*shr (trunc A), C) --> trunc(*shr A, C)
Value *A;
Constant *C;
if (match(BinOp0, m_Trunc(m_Value(A))) && match(BinOp1, m_Constant(C))) {
unsigned MaxShiftAmt = SrcWidth - DestWidth;
// If the shift is small enough, all zero/sign bits created by the shift
// are removed by the trunc.
if (match(C, m_SpecificInt_ICMP(ICmpInst::ICMP_ULE,
APInt(SrcWidth, MaxShiftAmt)))) {
auto *OldShift = cast<Instruction>(Trunc.getOperand(0));
bool IsExact = OldShift->isExact();
if (Constant *ShAmt = ConstantFoldIntegerCast(C, A->getType(),
/*IsSigned*/ true, DL)) {
ShAmt = Constant::mergeUndefsWith(ShAmt, C);
Value *Shift =
OldShift->getOpcode() == Instruction::AShr
? Builder.CreateAShr(A, ShAmt, OldShift->getName(), IsExact)
: Builder.CreateLShr(A, ShAmt, OldShift->getName(), IsExact);
return CastInst::CreateTruncOrBitCast(Shift, DestTy);
}
}
}
break;
}
default: break;
}
if (Instruction *NarrowOr = narrowFunnelShift(Trunc))
return NarrowOr;
return nullptr;
}
/// Try to narrow the width of a splat shuffle. This could be generalized to any
/// shuffle with a constant operand, but we limit the transform to avoid
/// creating a shuffle type that targets may not be able to lower effectively.
static Instruction *shrinkSplatShuffle(TruncInst &Trunc,
InstCombiner::BuilderTy &Builder) {
Value *Shuf = Trunc.getOperand(0), *ShufVec;
ArrayRef<int> SplatMask;
if (match(Shuf, m_OneUse(m_Shuffle(m_Value(ShufVec), m_Poison(),
m_Mask(SplatMask)))) &&
match(SplatMask, m_SplatMask()) &&
ElementCount::isKnownGE(
cast<VectorType>(Shuf->getType())->getElementCount(),
cast<VectorType>(ShufVec->getType())->getElementCount())) {
// trunc (shuf X, poison, SplatMask) --> shuf (trunc X), poison, SplatMask
Type *NewTruncTy =
ShufVec->getType()->getWithNewType(Trunc.getType()->getScalarType());
Value *NarrowOp = Builder.CreateTrunc(ShufVec, NewTruncTy);
return new ShuffleVectorInst(NarrowOp, SplatMask);
}
return nullptr;
}
/// Try to narrow the width of an insert element. This could be generalized for
/// any vector constant, but we limit the transform to insertion into poison to
/// avoid potential backend problems from unsupported insertion widths. This
/// could also be extended to handle the case of inserting a scalar constant
/// into a vector variable.
static Instruction *shrinkInsertElt(CastInst &Trunc,
InstCombiner::BuilderTy &Builder) {
Instruction::CastOps Opcode = Trunc.getOpcode();
assert((Opcode == Instruction::Trunc || Opcode == Instruction::FPTrunc) &&
"Unexpected instruction for shrinking");
Value *Elt, *Index;
if (match(Trunc.getOperand(0),
m_OneUse(m_InsertElt(m_Poison(), m_Value(Elt), m_Value(Index))))) {
// trunc (inselt poison, X, Index) --> inselt poison, (trunc X), Index
// fptrunc (inselt poison, X, Index) --> inselt poison, (fptrunc X), Index
auto *NarrowPoison = PoisonValue::get(Trunc.getType());
Value *NarrowOp =
Builder.CreateCast(Opcode, Elt, Trunc.getType()->getScalarType());
return InsertElementInst::Create(NarrowPoison, NarrowOp, Index);
}
return nullptr;
}
Instruction *InstCombinerImpl::visitTrunc(TruncInst &Trunc) {
if (Instruction *Result = commonCastTransforms(Trunc))
return Result;
Value *Src = Trunc.getOperand(0);
Type *DestTy = Trunc.getType(), *SrcTy = Src->getType();
unsigned DestWidth = DestTy->getScalarSizeInBits();
unsigned SrcWidth = SrcTy->getScalarSizeInBits();
// Attempt to truncate the entire input expression tree to the destination
// type. Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
if ((DestTy->isVectorTy() || shouldChangeType(SrcTy, DestTy)) &&
TypeEvaluationHelper::canEvaluateTruncated(Src, DestTy, *this, &Trunc)) {
// If this cast is a truncate, evaluting in a different type always
// eliminates the cast, so it is always a win.
LLVM_DEBUG(
dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid cast: "
<< Trunc << '\n');
Value *Res = EvaluateInDifferentType(Src, DestTy, false);
assert(Res->getType() == DestTy);
return replaceInstUsesWith(Trunc, Res);
}
// For integer types, check if we can shorten the entire input expression to
// DestWidth * 2, which won't allow removing the truncate, but reducing the
// width may enable further optimizations, e.g. allowing for larger
// vectorization factors.
if (auto *DestITy = dyn_cast<IntegerType>(DestTy)) {
if (DestWidth * 2 < SrcWidth) {
auto *NewDestTy = DestITy->getExtendedType();
if (shouldChangeType(SrcTy, NewDestTy) &&
TypeEvaluationHelper::canEvaluateTruncated(Src, NewDestTy, *this,
&Trunc)) {
LLVM_DEBUG(
dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to reduce the width of operand of"
<< Trunc << '\n');
Value *Res = EvaluateInDifferentType(Src, NewDestTy, false);
return new TruncInst(Res, DestTy);
}
}
}
Value *X;
if (DestWidth == 1 &&
(Trunc.hasNoUnsignedWrap() || Trunc.hasNoSignedWrap()) &&
match(Src, m_Exact(m_Shr(m_Value(X), m_Value()))))
return new ICmpInst(ICmpInst::ICMP_NE, X, Constant::getNullValue(SrcTy));
// See if we can simplify any instructions used by the input whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(Trunc))
return &Trunc;
if (DestWidth == 1) {
Value *Zero = Constant::getNullValue(SrcTy);
const APInt *C1;
Constant *C2;
if (match(Src, m_OneUse(m_Shr(m_Shl(m_Power2(C1), m_Value(X)),
m_ImmConstant(C2))))) {
// trunc ((C1 << X) >> C2) to i1 --> X == (C2-cttz(C1)), where C1 is pow2
Constant *Log2C1 = ConstantInt::get(SrcTy, C1->exactLogBase2());
Constant *CmpC = ConstantExpr::getSub(C2, Log2C1);
return new ICmpInst(ICmpInst::ICMP_EQ, X, CmpC);
}
if (match(Src, m_Shr(m_Value(X), m_SpecificInt(SrcWidth - 1)))) {
// trunc (ashr X, BW-1) to i1 --> icmp slt X, 0
// trunc (lshr X, BW-1) to i1 --> icmp slt X, 0
return new ICmpInst(ICmpInst::ICMP_SLT, X, Zero);
}
Constant *C;
if (match(Src, m_OneUse(m_LShr(m_Value(X), m_ImmConstant(C))))) {
// trunc (lshr X, C) to i1 --> icmp ne (and X, C'), 0
Constant *One = ConstantInt::get(SrcTy, APInt(SrcWidth, 1));
Value *MaskC = Builder.CreateShl(One, C);
Value *And = Builder.CreateAnd(X, MaskC);
return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
}
if (match(Src, m_OneUse(m_c_Or(m_LShr(m_Value(X), m_ImmConstant(C)),
m_Deferred(X))))) {
// trunc (or (lshr X, C), X) to i1 --> icmp ne (and X, C'), 0
Constant *One = ConstantInt::get(SrcTy, APInt(SrcWidth, 1));
Value *MaskC = Builder.CreateShl(One, C);
Value *And = Builder.CreateAnd(X, Builder.CreateOr(MaskC, One));
return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
}
{
const APInt *C;
if (match(Src, m_Shl(m_APInt(C), m_Value(X))) && (*C)[0] == 1) {
// trunc (C << X) to i1 --> X == 0, where C is odd
return new ICmpInst(ICmpInst::Predicate::ICMP_EQ, X, Zero);
}
}
if (Trunc.hasNoUnsignedWrap() || Trunc.hasNoSignedWrap()) {
Value *X, *Y;
if (match(Src, m_Xor(m_Value(X), m_Value(Y))))
return new ICmpInst(ICmpInst::ICMP_NE, X, Y);
}
if (match(Src,
m_OneUse(m_Intrinsic<Intrinsic::usub_sat>(m_One(), m_Value(X)))))
return new ICmpInst(ICmpInst::ICMP_EQ, X,
ConstantInt::getNullValue(SrcTy));
}
Value *A, *B;
Constant *C;
// trunc(u/smin(zext(a) + zext(b), MAX)) --> uadd.sat(a, b)
if (match(Src, m_OneUse(m_CombineOr(
m_UMin(m_OneUse(m_Add(m_ZExt(m_SpecificType(DestTy, A)),
m_ZExt(m_SpecificType(DestTy, B)))),
m_SpecificInt(APInt::getMaxValue(DestWidth))),
m_SMin(m_OneUse(m_Add(m_ZExt(m_SpecificType(DestTy, A)),
m_ZExt(m_SpecificType(DestTy, B)))),
m_SpecificInt(APInt::getMaxValue(DestWidth))))))) {
return replaceInstUsesWith(
Trunc, Builder.CreateBinaryIntrinsic(Intrinsic::uadd_sat, A, B));
}
// trunc(smax(zext(a) - zext(b), 0)) --> usub.sat(a, b)
if (match(Src,
m_OneUse(m_SMax(m_OneUse(m_Sub(m_ZExt(m_SpecificType(DestTy, A)),
m_ZExt(m_SpecificType(DestTy, B)))),
m_Zero())))) {
return replaceInstUsesWith(
Trunc, Builder.CreateBinaryIntrinsic(Intrinsic::usub_sat, A, B));
}
if (match(Src, m_LShr(m_SExt(m_Value(A)), m_Constant(C)))) {
unsigned AWidth = A->getType()->getScalarSizeInBits();
unsigned MaxShiftAmt = SrcWidth - std::max(DestWidth, AWidth);
auto *OldSh = cast<Instruction>(Src);
bool IsExact = OldSh->isExact();
// If the shift is small enough, all zero bits created by the shift are
// removed by the trunc.
if (match(C, m_SpecificInt_ICMP(ICmpInst::ICMP_ULE,
APInt(SrcWidth, MaxShiftAmt)))) {
auto GetNewShAmt = [&](unsigned Width) {
Constant *MaxAmt = ConstantInt::get(SrcTy, Width - 1, false);
Constant *Cmp =
ConstantFoldCompareInstOperands(ICmpInst::ICMP_ULT, C, MaxAmt, DL);
Constant *ShAmt = ConstantFoldSelectInstruction(Cmp, C, MaxAmt);
return ConstantFoldCastOperand(Instruction::Trunc, ShAmt, A->getType(),
DL);
};
// trunc (lshr (sext A), C) --> ashr A, C
if (A->getType() == DestTy) {
Constant *ShAmt = GetNewShAmt(DestWidth);
ShAmt = Constant::mergeUndefsWith(ShAmt, C);
return IsExact ? BinaryOperator::CreateExactAShr(A, ShAmt)
: BinaryOperator::CreateAShr(A, ShAmt);
}
// The types are mismatched, so create a cast after shifting:
// trunc (lshr (sext A), C) --> sext/trunc (ashr A, C)
if (Src->hasOneUse()) {
Constant *ShAmt = GetNewShAmt(AWidth);
Value *Shift = Builder.CreateAShr(A, ShAmt, "", IsExact);
return CastInst::CreateIntegerCast(Shift, DestTy, true);
}
}
// TODO: Mask high bits with 'and'.
}
if (Instruction *I = narrowBinOp(Trunc))
return I;
if (Instruction *I = shrinkSplatShuffle(Trunc, Builder))
return I;
if (Instruction *I = shrinkInsertElt(Trunc, Builder))
return I;
if (Src->hasOneUse() &&
(isa<VectorType>(SrcTy) || shouldChangeType(SrcTy, DestTy))) {
// Transform "trunc (shl X, cst)" -> "shl (trunc X), cst" so long as the
// dest type is native and cst < dest size.
if (match(Src, m_Shl(m_Value(A), m_Constant(C))) &&
!match(A, m_Shr(m_Value(), m_Constant()))) {
// Skip shifts of shift by constants. It undoes a combine in
// FoldShiftByConstant and is the extend in reg pattern.
APInt Threshold = APInt(C->getType()->getScalarSizeInBits(), DestWidth);
if (match(C, m_SpecificInt_ICMP(ICmpInst::ICMP_ULT, Threshold))) {
// If neither the wide shift nor the truncate wrap, propagate the wrap
// flags on the new truncate and shift.
auto *WideShl = cast<OverflowingBinaryOperator>(Src);
bool NUW = Trunc.hasNoUnsignedWrap() && WideShl->hasNoUnsignedWrap();
bool NSW = Trunc.hasNoSignedWrap() && WideShl->hasNoSignedWrap();
Value *NewTrunc = Builder.CreateTrunc(A, DestTy, A->getName() + ".tr",
/*IsNUW=*/NUW, /*IsNSW=*/NSW);
auto *NewShl = BinaryOperator::Create(
Instruction::Shl, NewTrunc, ConstantExpr::getTrunc(C, DestTy));
NewShl->setHasNoUnsignedWrap(NUW);
NewShl->setHasNoSignedWrap(NSW);
return NewShl;
}
}
}
// trunc (select(icmp_ult(A, DestTy_umax+1), A, sext(icmp_sgt(A, 0)))) -->
// trunc (smin(smax(0, A), DestTy_umax))
// Also handle the inverted form:
// trunc (select(icmp_ugt(A, DestTy_umax), sext(icmp_sgt(A, 0)), A))
CmpPredicate Pred;
const APInt *CmpC;
Value *TVal, *FVal;
if (SrcTy->isIntegerTy() && isPowerOf2_64(SrcWidth) &&
isPowerOf2_64(DestWidth) &&
match(Src,
m_OneUse(m_Select(m_OneUse(m_ICmp(Pred, m_Value(A), m_APInt(CmpC))),
m_Value(TVal), m_Value(FVal))))) {
APInt TruncatedMax = APInt::getLowBitsSet(SrcWidth, DestWidth);
Value *SExtVal = nullptr;
// Check the select arm first so that A is known to have type SrcTy.
if (Pred == ICmpInst::ICMP_ULT && TVal == A && *CmpC == TruncatedMax + 1)
SExtVal = FVal;
else if (Pred == ICmpInst::ICMP_UGT && FVal == A && *CmpC == TruncatedMax)
SExtVal = TVal;
if (SExtVal &&
match(SExtVal, m_OneUse(m_SExt(m_OneUse(m_SpecificICmp(
ICmpInst::ICMP_SGT, m_Specific(A), m_Zero())))))) {
Value *SMax = Builder.CreateIntrinsic(Intrinsic::smax, {SrcTy},
{ConstantInt::get(SrcTy, 0), A});
Value *SMin = Builder.CreateIntrinsic(
Intrinsic::smin, {SrcTy},
{SMax, ConstantInt::get(SrcTy, TruncatedMax)});
return new TruncInst(SMin, DestTy);
}
}
if (Instruction *I = foldVecTruncToExtElt(Trunc, *this))
return I;
if (Instruction *I = foldVecExtTruncToExtElt(Trunc, *this))
return I;
// trunc (ctlz_i32(zext(A), B) --> add(ctlz_i16(A, B), C)
if (match(Src, m_OneUse(m_Ctlz(m_ZExt(m_Value(A)), m_Value(B))))) {
unsigned AWidth = A->getType()->getScalarSizeInBits();
if (AWidth == DestWidth && AWidth > Log2_32(SrcWidth)) {
Value *WidthDiff = ConstantInt::get(A->getType(), SrcWidth - AWidth);
Value *NarrowCtlz =
Builder.CreateIntrinsic(Intrinsic::ctlz, {Trunc.getType()}, {A, B});
return BinaryOperator::CreateAdd(NarrowCtlz, WidthDiff);
}
}
if (match(Src, m_VScale())) {
if (Trunc.getFunction() &&
Trunc.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
Attribute Attr =
Trunc.getFunction()->getFnAttribute(Attribute::VScaleRange);
if (std::optional<unsigned> MaxVScale = Attr.getVScaleRangeMax())
if (Log2_32(*MaxVScale) < DestWidth)
return replaceInstUsesWith(Trunc, Builder.CreateVScale(DestTy));
}
}
// trunc(scmp(x, y)) -> scmp(x, y) with a narrower result type.
// trunc(ucmp(x, y)) -> ucmp(x, y) with a narrower result type.
// scmp/ucmp produce only -1, 0, or 1, so any result type with at least 2
// bits can represent every possible value and the truncation is lossless.
if (DestWidth >= 2)
if (auto *CI = dyn_cast<CmpIntrinsic>(Src); CI && CI->hasOneUse())
return replaceInstUsesWith(
Trunc, Builder.CreateIntrinsic(DestTy, CI->getIntrinsicID(),
{CI->getLHS(), CI->getRHS()}));
if (DestWidth == 1 &&
(Trunc.hasNoUnsignedWrap() || Trunc.hasNoSignedWrap()) &&
isKnownNonZero(Src, SQ.getWithInstruction(&Trunc)))
return replaceInstUsesWith(Trunc, ConstantInt::getTrue(DestTy));
bool Changed = false;
if (!Trunc.hasNoSignedWrap() &&
ComputeMaxSignificantBits(Src, &Trunc) <= DestWidth) {
Trunc.setHasNoSignedWrap(true);
Changed = true;
}
if (!Trunc.hasNoUnsignedWrap() &&
MaskedValueIsZero(Src, APInt::getBitsSetFrom(SrcWidth, DestWidth),
&Trunc)) {
Trunc.setHasNoUnsignedWrap(true);
Changed = true;
}
const APInt *C1;
Value *V1;
// OP = { lshr, ashr }
// trunc ( OP i8 C1, V1) to i1 -> icmp eq V1, log_2(C1) iff C1 is power of 2
if (DestWidth == 1 && match(Src, m_Shr(m_Power2(C1), m_Value(V1)))) {
Value *Right = ConstantInt::get(V1->getType(), C1->countr_zero());
return new ICmpInst(ICmpInst::ICMP_EQ, V1, Right);
}
// OP = { lshr, ashr }
// trunc ( OP i8 C1, V1) to i1 -> icmp ult V1, log_2(C1 + 1) iff (C1 + 1) is
// power of 2
if (DestWidth == 1 && match(Src, m_Shr(m_LowBitMask(C1), m_Value(V1)))) {
Value *Right = ConstantInt::get(V1->getType(), C1->countr_one());
return new ICmpInst(ICmpInst::ICMP_ULT, V1, Right);
}
// OP = { lshr, ashr }
// trunc ( OP i8 C1, V1) to i1 -> icmp ugt V1, cttz(C1) - 1 iff (C1) is
// negative power of 2
if (DestWidth == 1 && match(Src, m_Shr(m_NegatedPower2(C1), m_Value(V1)))) {
Value *Right = ConstantInt::get(V1->getType(), C1->countr_zero());
return new ICmpInst(ICmpInst::ICMP_UGE, V1, Right);
}
return Changed ? &Trunc : nullptr;
}
Instruction *InstCombinerImpl::transformZExtICmp(ICmpInst *Cmp,
ZExtInst &Zext) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// to an integer, then shift the bit to the appropriate place and then
// cast to integer to avoid the comparison.
// FIXME: This set of transforms does not check for extra uses and/or creates
// an extra instruction (an optional final cast is not included
// in the transform comments). We may also want to favor icmp over
// shifts in cases of equal instructions because icmp has better
// analysis in general (invert the transform).
const APInt *Op1CV;
if (match(Cmp->getOperand(1), m_APInt(Op1CV))) {
// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
if (Cmp->getPredicate() == ICmpInst::ICMP_SLT && Op1CV->isZero()) {
Value *In = Cmp->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getScalarSizeInBits() - 1);
In = Builder.CreateLShr(In, Sh, In->getName() + ".lobit");
if (In->getType() != Zext.getType())
In = Builder.CreateIntCast(In, Zext.getType(), false /*ZExt*/);
return replaceInstUsesWith(Zext, In);
}
// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
// zext (X != 0) to i32 --> X iff X has only the low bit set.
// zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
if (Op1CV->isZero() && Cmp->isEquality()) {
// Exactly 1 possible 1? But not the high-bit because that is
// canonicalized to this form.
KnownBits Known = computeKnownBits(Cmp->getOperand(0), &Zext);
APInt KnownZeroMask(~Known.Zero);
uint32_t ShAmt = KnownZeroMask.logBase2();
bool IsExpectShAmt = KnownZeroMask.isPowerOf2() &&
(Zext.getType()->getScalarSizeInBits() != ShAmt + 1);
if (IsExpectShAmt &&
(Cmp->getOperand(0)->getType() == Zext.getType() ||
Cmp->getPredicate() == ICmpInst::ICMP_NE || ShAmt == 0)) {
Value *In = Cmp->getOperand(0);
if (ShAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = Builder.CreateLShr(In, ConstantInt::get(In->getType(), ShAmt),
In->getName() + ".lobit");
}
// Toggle the low bit for "X == 0".
if (Cmp->getPredicate() == ICmpInst::ICMP_EQ)
In = Builder.CreateXor(In, ConstantInt::get(In->getType(), 1));
if (Zext.getType() == In->getType())
return replaceInstUsesWith(Zext, In);
Value *IntCast = Builder.CreateIntCast(In, Zext.getType(), false);
return replaceInstUsesWith(Zext, IntCast);
}
}
}
if (Cmp->isEquality()) {
// Test if a bit is clear/set using a shifted-one mask:
// zext (icmp eq (and X, (1 << ShAmt)), 0) --> and (lshr (not X), ShAmt), 1
// zext (icmp ne (and X, (1 << ShAmt)), 0) --> and (lshr X, ShAmt), 1
Value *X, *ShAmt;
if (Cmp->hasOneUse() && match(Cmp->getOperand(1), m_ZeroInt()) &&
match(Cmp->getOperand(0),
m_OneUse(m_c_And(m_Shl(m_One(), m_Value(ShAmt)), m_Value(X))))) {
auto *And = cast<BinaryOperator>(Cmp->getOperand(0));
Value *Shift = And->getOperand(X == And->getOperand(0) ? 1 : 0);
if (Zext.getType() == And->getType() ||
Cmp->getPredicate() != ICmpInst::ICMP_EQ || Shift->hasOneUse()) {
if (Cmp->getPredicate() == ICmpInst::ICMP_EQ)
X = Builder.CreateNot(X);
Value *Lshr = Builder.CreateLShr(X, ShAmt);
Value *And1 =
Builder.CreateAnd(Lshr, ConstantInt::get(X->getType(), 1));
return replaceInstUsesWith(
Zext, Builder.CreateZExtOrTrunc(And1, Zext.getType()));
}
}
}
return nullptr;
}
/// Determine if the specified value can be computed in the specified wider type
/// and produce the same low bits. If not, return false.
///
/// If this function returns true, it can also return a non-zero number of bits
/// (in BitsToClear) which indicates that the value it computes is correct for
/// the zero extend, but that the additional BitsToClear bits need to be zero'd
/// out. For example, to promote something like:
///
/// %B = trunc i64 %A to i32
/// %C = lshr i32 %B, 8
/// %E = zext i32 %C to i64
///
/// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be
/// set to 8 to indicate that the promoted value needs to have bits 24-31
/// cleared in addition to bits 32-63. Since an 'and' will be generated to
/// clear the top bits anyway, doing this has no extra cost.
///
/// This function works on both vectors and scalars.
bool TypeEvaluationHelper::canEvaluateZExtd(Value *V, Type *Ty,
unsigned &BitsToClear,
InstCombinerImpl &IC,
Instruction *CtxI) {
TypeEvaluationHelper TYH;
return TYH.canEvaluateZExtdImpl(V, Ty, BitsToClear, IC, CtxI);
}
bool TypeEvaluationHelper::canEvaluateZExtdImpl(Value *V, Type *Ty,
unsigned &BitsToClear,
InstCombinerImpl &IC,
Instruction *CtxI) {
BitsToClear = 0;
if (canAlwaysEvaluateInType(V, Ty))
return true;
// We stick to the one-user limit for the ZExt transform due to the fact
// that this predicate returns two values: predicate result and BitsToClear.
if (canNotEvaluateInType(V, Ty))
return false;
auto *I = cast<Instruction>(V);
unsigned Tmp;
switch (I->getOpcode()) {
case Instruction::ZExt: // zext(zext(x)) -> zext(x).
case Instruction::SExt: // zext(sext(x)) -> sext(x).
case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x)
return true;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
if (!canEvaluateZExtdImpl(I->getOperand(0), Ty, BitsToClear, IC, CtxI) ||
!canEvaluateZExtdImpl(I->getOperand(1), Ty, Tmp, IC, CtxI))
return false;
// These can all be promoted if neither operand has 'bits to clear'.
if (BitsToClear == 0 && Tmp == 0)
return true;
// If the operation is an AND/OR/XOR and the bits to clear are zero in the
// other side, BitsToClear is ok.
if (Tmp == 0 && I->isBitwiseLogicOp()) {
// We use MaskedValueIsZero here for generality, but the case we care
// about the most is constant RHS.
unsigned VSize = V->getType()->getScalarSizeInBits();
if (IC.MaskedValueIsZero(I->getOperand(1),
APInt::getHighBitsSet(VSize, BitsToClear),
CtxI)) {
// If this is an And instruction and all of the BitsToClear are
// known to be zero we can reset BitsToClear.
if (I->getOpcode() == Instruction::And)
BitsToClear = 0;
return true;
}
}
// Otherwise, we don't know how to analyze this BitsToClear case yet.
return false;
case Instruction::Shl: {
// We can promote shl(x, cst) if we can promote x. Since shl overwrites the
// upper bits we can reduce BitsToClear by the shift amount.
uint64_t ShiftAmt;
if (match(I->getOperand(1), m_ConstantInt(ShiftAmt))) {
if (!canEvaluateZExtdImpl(I->getOperand(0), Ty, BitsToClear, IC, CtxI))
return false;
BitsToClear = ShiftAmt < BitsToClear ? BitsToClear - ShiftAmt : 0;
return true;
}
return false;
}
case Instruction::LShr: {
// We can promote lshr(x, cst) if we can promote x. This requires the
// ultimate 'and' to clear out the high zero bits we're clearing out though.
uint64_t ShiftAmt;
if (match(I->getOperand(1), m_ConstantInt(ShiftAmt))) {
if (!canEvaluateZExtdImpl(I->getOperand(0), Ty, BitsToClear, IC, CtxI))
return false;
BitsToClear += ShiftAmt;
if (BitsToClear > V->getType()->getScalarSizeInBits())
BitsToClear = V->getType()->getScalarSizeInBits();
return true;
}
// Cannot promote variable LSHR.
return false;
}
case Instruction::Select:
if (!canEvaluateZExtdImpl(I->getOperand(1), Ty, Tmp, IC, CtxI) ||
!canEvaluateZExtdImpl(I->getOperand(2), Ty, BitsToClear, IC, CtxI) ||
// TODO: If important, we could handle the case when the BitsToClear are
// known zero in the disagreeing side.
Tmp != BitsToClear)
return false;
return true;
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// get into trouble with cyclic PHIs here because we only consider
// instructions with a single use.
PHINode *PN = cast<PHINode>(I);
if (!canEvaluateZExtdImpl(PN->getIncomingValue(0), Ty, BitsToClear, IC,
CtxI))
return false;
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
if (!canEvaluateZExtdImpl(PN->getIncomingValue(i), Ty, Tmp, IC, CtxI) ||
// TODO: If important, we could handle the case when the BitsToClear
// are known zero in the disagreeing input.
Tmp != BitsToClear)
return false;
return true;
}
case Instruction::Call:
// llvm.vscale() can always be executed in larger type, because the
// value is automatically zero-extended.
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
if (II->getIntrinsicID() == Intrinsic::vscale)
return true;
return false;
default:
// TODO: Can handle more cases here.
return false;
}
}
Instruction *InstCombinerImpl::visitZExt(ZExtInst &Zext) {
// If this zero extend is only used by a truncate, let the truncate be
// eliminated before we try to optimize this zext.
if (Zext.hasOneUse() && isa<TruncInst>(Zext.user_back()) &&
!isa<Constant>(Zext.getOperand(0)))
return nullptr;
// If one of the common conversion will work, do it.
if (Instruction *Result = commonCastTransforms(Zext))
return Result;
if (auto *NewI = foldExtractionOfVectorDeinterleave(Zext))
return NewI;
Value *Src = Zext.getOperand(0);
Type *SrcTy = Src->getType(), *DestTy = Zext.getType();
// zext nneg bool x -> 0
if (SrcTy->isIntOrIntVectorTy(1) && Zext.hasNonNeg())
return replaceInstUsesWith(Zext, Constant::getNullValue(Zext.getType()));
// zext nneg means Src is non-negative and we can treat this as an sext.
// Evaluating as a signed type means that any constant operands will be
// sign-extended instead of zero-extended, which means that, if the
// expression tree contains only no-signed-wrap arithmetic, the sign bits in
// the final result should be enough that we avoid having to clear the high
// bits.
bool EvaluateAsSigned =
Zext.hasNonNeg() && TypeEvaluationHelper::canEvaluateSExtd(Src, DestTy);
// Try to extend the entire expression tree to the wide destination type.
unsigned BitsToClear = 0;
if (shouldChangeType(SrcTy, DestTy) &&
(EvaluateAsSigned || TypeEvaluationHelper::canEvaluateZExtd(
Src, DestTy, BitsToClear, *this, &Zext))) {
assert(BitsToClear <= SrcTy->getScalarSizeInBits() &&
"Can't clear more bits than in SrcTy");
// Okay, we can transform this! Insert the new expression now.
LLVM_DEBUG(
dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid zero extend: "
<< Zext << '\n');
Value *Res = EvaluateInDifferentType(Src, DestTy, EvaluateAsSigned);
assert(Res->getType() == DestTy);
// Preserve debug values referring to Src if the zext is its last use.
if (auto *SrcOp = dyn_cast<Instruction>(Src))
if (SrcOp->hasOneUse())
replaceAllDbgUsesWith(*SrcOp, *Res, Zext, DT);
uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits() - BitsToClear;
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
// If the high bits are already filled with zeros, just replace this
// cast with the result. If we've evaluated as a signed expressions then
// instead check that the high bits are the sign bit, which we know is zero.
if (EvaluateAsSigned
? (ComputeNumSignBits(Res, &Zext) > DestBitSize - SrcBitsKept)
: MaskedValueIsZero(
Res,
APInt::getHighBitsSet(DestBitSize, DestBitSize - SrcBitsKept),
&Zext))
return replaceInstUsesWith(Zext, Res);
// We need to emit an AND to clear the high bits.
Constant *C = ConstantInt::get(Res->getType(),
APInt::getLowBitsSet(DestBitSize, SrcBitsKept));
return BinaryOperator::CreateAnd(Res, C);
}
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
// types and if the sizes are just right we can convert this into a logical
// 'and' which will be much cheaper than the pair of casts.
if (auto *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
// TODO: Subsume this into EvaluateInDifferentType.
// Get the sizes of the types involved. We know that the intermediate type
// will be smaller than A or C, but don't know the relation between A and C.
Value *A = CSrc->getOperand(0);
unsigned SrcSize = A->getType()->getScalarSizeInBits();
unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
unsigned DstSize = DestTy->getScalarSizeInBits();
// If we're actually extending zero bits, then if
// SrcSize < DstSize: zext(a & mask)
// SrcSize == DstSize: a & mask
// SrcSize > DstSize: trunc(a) & mask
if (SrcSize < DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
Value *And = Builder.CreateAnd(A, AndConst, CSrc->getName() + ".mask");
return new ZExtInst(And, DestTy);
}
if (SrcSize == DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(),
AndValue));
}
if (SrcSize > DstSize) {
Value *Trunc = Builder.CreateTrunc(A, DestTy);
APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
return BinaryOperator::CreateAnd(Trunc,
ConstantInt::get(Trunc->getType(),
AndValue));
}
}
if (auto *Cmp = dyn_cast<ICmpInst>(Src))
return transformZExtICmp(Cmp, Zext);
Constant *C;
Value *X;
// zext((trunc(X) & C) ^ C) -> ((X & zext(C)) ^ zext(C)).
Value *And;
if (match(Src, m_OneUse(m_Xor(m_Value(And), m_Constant(C)))) &&
match(And, m_OneUse(m_And(m_Trunc(m_SpecificType(DestTy, X)),
m_Specific(C))))) {
Value *ZC = Builder.CreateZExt(C, DestTy);
return BinaryOperator::CreateXor(Builder.CreateAnd(X, ZC), ZC);
}
// zext(sub(0, trunc(X))) -> and(sub(0, X), mask)
if (match(Src, m_Sub(m_Zero(), m_Trunc(m_SpecificType(DestTy, X))))) {
APInt Mask = APInt::getLowBitsSet(DestTy->getScalarSizeInBits(),
SrcTy->getScalarSizeInBits());
Value *Neg = Builder.CreateSub(ConstantInt::get(DestTy, 0), X);
return BinaryOperator::CreateAnd(Neg, ConstantInt::get(DestTy, Mask));
}
// If we are truncating, masking, and then zexting back to the original type,
// that's just a mask. This is not handled by canEvaluateZextd if the
// intermediate values have extra uses. This could be generalized further for
// a non-constant mask operand.
// zext (and (trunc X), C) --> and X, (zext C)
if (match(Src, m_And(m_Trunc(m_SpecificType(DestTy, X)), m_Constant(C)))) {
Value *ZextC = Builder.CreateZExt(C, DestTy);
return BinaryOperator::CreateAnd(X, ZextC);
}
Value *Y;
if (match(Src, m_OneUse(m_c_BitwiseLogic(
m_NUWTrunc(m_SpecificType(DestTy, X)), m_Value(Y))))) {
Value *ZextY = Builder.CreateZExt(Y, DestTy);
return BinaryOperator::Create(cast<BinaryOperator>(Src)->getOpcode(), X,
ZextY);
}
if (match(Src, m_VScale())) {
if (Zext.getFunction() &&
Zext.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
Attribute Attr =
Zext.getFunction()->getFnAttribute(Attribute::VScaleRange);
if (std::optional<unsigned> MaxVScale = Attr.getVScaleRangeMax()) {
unsigned TypeWidth = Src->getType()->getScalarSizeInBits();
if (Log2_32(*MaxVScale) < TypeWidth)
return replaceInstUsesWith(Zext, Builder.CreateVScale(DestTy));
}
}
}
if (!Zext.hasNonNeg()) {
// If this zero extend is only used by a shift, add nneg flag.
if (Zext.hasOneUse() &&
SrcTy->getScalarSizeInBits() >
Log2_64_Ceil(DestTy->getScalarSizeInBits()) &&
match(Zext.user_back(), m_Shift(m_Value(), m_Specific(&Zext)))) {
Zext.setNonNeg();
return &Zext;
}
if (isKnownNonNegative(Src, SQ.getWithInstruction(&Zext))) {
Zext.setNonNeg();
return &Zext;
}
}
return nullptr;
}
/// Transform (sext icmp) to bitwise / integer operations to eliminate the icmp.
Instruction *InstCombinerImpl::transformSExtICmp(ICmpInst *Cmp,
SExtInst &Sext) {
Value *Op0 = Cmp->getOperand(0), *Op1 = Cmp->getOperand(1);
ICmpInst::Predicate Pred = Cmp->getPredicate();
// Don't bother if Op1 isn't of vector or integer type.
if (!Op1->getType()->isIntOrIntVectorTy())
return nullptr;
if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_ZeroInt())) {
// sext (x <s 0) --> ashr x, 31 (all ones if negative)
Value *Sh = ConstantInt::get(Op0->getType(),
Op0->getType()->getScalarSizeInBits() - 1);
Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
if (In->getType() != Sext.getType())
In = Builder.CreateIntCast(In, Sext.getType(), true /*SExt*/);
return replaceInstUsesWith(Sext, In);
}
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
// If we know that only one bit of the LHS of the icmp can be set and we
// have an equality comparison with zero or a power of 2, we can transform
// the icmp and sext into bitwise/integer operations.
if (Cmp->hasOneUse() &&
Cmp->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){
KnownBits Known = computeKnownBits(Op0, &Sext);
APInt KnownZeroMask(~Known.Zero);
if (KnownZeroMask.isPowerOf2()) {
Value *In = Cmp->getOperand(0);
// If the icmp tests for a known zero bit we can constant fold it.
if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) {
Value *V = Pred == ICmpInst::ICMP_NE ?
ConstantInt::getAllOnesValue(Sext.getType()) :
ConstantInt::getNullValue(Sext.getType());
return replaceInstUsesWith(Sext, V);
}
if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) {
// sext ((x & 2^n) == 0) -> (x >> n) - 1
// sext ((x & 2^n) != 2^n) -> (x >> n) - 1
unsigned ShiftAmt = KnownZeroMask.countr_zero();
// Perform a right shift to place the desired bit in the LSB.
if (ShiftAmt)
In = Builder.CreateLShr(In,
ConstantInt::get(In->getType(), ShiftAmt));
// At this point "In" is either 1 or 0. Subtract 1 to turn
// {1, 0} -> {0, -1}.
In = Builder.CreateAdd(In,
ConstantInt::getAllOnesValue(In->getType()),
"sext");
} else {
// sext ((x & 2^n) != 0) -> (x << bitwidth-n) a>> bitwidth-1
// sext ((x & 2^n) == 2^n) -> (x << bitwidth-n) a>> bitwidth-1
unsigned ShiftAmt = KnownZeroMask.countl_zero();
// Perform a left shift to place the desired bit in the MSB.
if (ShiftAmt)
In = Builder.CreateShl(In,
ConstantInt::get(In->getType(), ShiftAmt));
// Distribute the bit over the whole bit width.
In = Builder.CreateAShr(In, ConstantInt::get(In->getType(),
KnownZeroMask.getBitWidth() - 1), "sext");
}
if (Sext.getType() == In->getType())
return replaceInstUsesWith(Sext, In);
return CastInst::CreateIntegerCast(In, Sext.getType(), true/*SExt*/);
}
}
}
return nullptr;
}
/// Return true if we can take the specified value and return it as type Ty
/// without inserting any new casts and without changing the value of the common
/// low bits. This is used by code that tries to promote integer operations to
/// a wider types will allow us to eliminate the extension.
///
/// This function works on both vectors and scalars.
///
bool TypeEvaluationHelper::canEvaluateSExtd(Value *V, Type *Ty) {
TypeEvaluationHelper TYH;
return TYH.canEvaluateSExtdImpl(V, Ty) && TYH.allPendingVisited();
}
bool TypeEvaluationHelper::canEvaluateSExtdImpl(Value *V, Type *Ty) {
return canEvaluate(V, Ty, [this](Value *V, Type *Ty) {
return canEvaluateSExtdPred(V, Ty);
});
}
bool TypeEvaluationHelper::canEvaluateSExtdPred(Value *V, Type *Ty) {
assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() &&
"Can't sign extend type to a smaller type");
auto *I = cast<Instruction>(V);
switch (I->getOpcode()) {
case Instruction::SExt: // sext(sext(x)) -> sext(x)
case Instruction::ZExt: // sext(zext(x)) -> zext(x)
case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x)
return true;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
// These operators can all arbitrarily be extended if their inputs can.
return canEvaluateSExtdImpl(I->getOperand(0), Ty) &&
canEvaluateSExtdImpl(I->getOperand(1), Ty);
// case Instruction::Shl: TODO
// case Instruction::LShr: TODO
case Instruction::Select:
return canEvaluateSExtdImpl(I->getOperand(1), Ty) &&
canEvaluateSExtdImpl(I->getOperand(2), Ty);
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// get into trouble with cyclic PHIs here because canEvaluate handles use
// chain loops.
PHINode *PN = cast<PHINode>(I);
for (Value *IncValue : PN->incoming_values())
if (!canEvaluateSExtdImpl(IncValue, Ty))
return false;
return true;
}
default:
// TODO: Can handle more cases here.
break;
}
return false;
}
Instruction *InstCombinerImpl::visitSExt(SExtInst &Sext) {
// If this sign extend is only used by a truncate, let the truncate be
// eliminated before we try to optimize this sext.
if (Sext.hasOneUse() && isa<TruncInst>(Sext.user_back()))
return nullptr;
if (Instruction *I = commonCastTransforms(Sext))
return I;
Value *Src = Sext.getOperand(0);
Type *SrcTy = Src->getType(), *DestTy = Sext.getType();
unsigned SrcBitSize = SrcTy->getScalarSizeInBits();
unsigned DestBitSize = DestTy->getScalarSizeInBits();
// If the value being extended is zero or positive, use a zext instead.
if (isKnownNonNegative(Src, SQ.getWithInstruction(&Sext))) {
auto CI = CastInst::Create(Instruction::ZExt, Src, DestTy);
CI->setNonNeg(true);
return CI;
}
// Try to extend the entire expression tree to the wide destination type.
bool ShouldExtendExpression = true;
Value *TruncSrc = nullptr;
// It is not desirable to extend expression in the trunc + sext pattern when
// destination type is narrower than original (pre-trunc) type.
if (match(Src, m_Trunc(m_Value(TruncSrc))))
if (TruncSrc->getType()->getScalarSizeInBits() > DestBitSize)
ShouldExtendExpression = false;
if (ShouldExtendExpression && shouldChangeType(SrcTy, DestTy) &&
TypeEvaluationHelper::canEvaluateSExtd(Src, DestTy)) {
// Okay, we can transform this! Insert the new expression now.
LLVM_DEBUG(
dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid sign extend: "
<< Sext << '\n');
Value *Res = EvaluateInDifferentType(Src, DestTy, true);
assert(Res->getType() == DestTy);
// If the high bits are already filled with sign bit, just replace this
// cast with the result.
if (ComputeNumSignBits(Res, &Sext) > DestBitSize - SrcBitSize)
return replaceInstUsesWith(Sext, Res);
// We need to emit a shl + ashr to do the sign extend.
Value *ShAmt = ConstantInt::get(DestTy, DestBitSize - SrcBitSize);
return BinaryOperator::CreateAShr(Builder.CreateShl(Res, ShAmt, "sext"),
ShAmt);
}
Value *X = TruncSrc;
if (X) {
// If the input has more sign bits than bits truncated, then convert
// directly to final type.
unsigned XBitSize = X->getType()->getScalarSizeInBits();
bool HasNSW = cast<TruncInst>(Src)->hasNoSignedWrap();
if (HasNSW || (ComputeNumSignBits(X, &Sext) > XBitSize - SrcBitSize)) {
auto *Res = CastInst::CreateIntegerCast(X, DestTy, /* isSigned */ true);
if (auto *ResTrunc = dyn_cast<TruncInst>(Res); ResTrunc && HasNSW)
ResTrunc->setHasNoSignedWrap(true);
return Res;
}
// If input is a trunc from the destination type, then convert into shifts.
if (Src->hasOneUse() && X->getType() == DestTy) {
// sext (trunc X) --> ashr (shl X, C), C
Constant *ShAmt = ConstantInt::get(DestTy, DestBitSize - SrcBitSize);
return BinaryOperator::CreateAShr(Builder.CreateShl(X, ShAmt), ShAmt);
}
// If we are replacing shifted-in high zero bits with sign bits, convert
// the logic shift to arithmetic shift and eliminate the cast to
// intermediate type:
// sext (trunc (lshr Y, C)) --> sext/trunc (ashr Y, C)
Value *Y;
if (Src->hasOneUse() &&
match(X, m_LShr(m_Value(Y),
m_SpecificIntAllowPoison(XBitSize - SrcBitSize)))) {
Value *Ashr = Builder.CreateAShr(Y, XBitSize - SrcBitSize);
return CastInst::CreateIntegerCast(Ashr, DestTy, /* isSigned */ true);
}
}
if (auto *Cmp = dyn_cast<ICmpInst>(Src))
return transformSExtICmp(Cmp, Sext);
// If the input is a shl/ashr pair of a same constant, then this is a sign
// extension from a smaller value. If we could trust arbitrary bitwidth
// integers, we could turn this into a truncate to the smaller bit and then
// use a sext for the whole extension. Since we don't, look deeper and check
// for a truncate. If the source and dest are the same type, eliminate the
// trunc and extend and just do shifts. For example, turn:
// %a = trunc i32 %i to i8
// %b = shl i8 %a, C
// %c = ashr i8 %b, C
// %d = sext i8 %c to i32
// into:
// %a = shl i32 %i, 32-(8-C)
// %d = ashr i32 %a, 32-(8-C)
Value *A = nullptr;
// TODO: Eventually this could be subsumed by EvaluateInDifferentType.
Constant *BA = nullptr, *CA = nullptr;
if (match(Src,
m_AShr(m_Shl(m_Trunc(m_SpecificType(DestTy, A)), m_Constant(BA)),
m_ImmConstant(CA))) &&
BA->isElementWiseEqual(CA)) {
Constant *WideCurrShAmt =
ConstantFoldCastOperand(Instruction::SExt, CA, DestTy, DL);
assert(WideCurrShAmt && "Constant folding of ImmConstant cannot fail");
Constant *NumLowbitsLeft = ConstantExpr::getSub(
ConstantInt::get(DestTy, SrcTy->getScalarSizeInBits()), WideCurrShAmt);
Constant *NewShAmt = ConstantExpr::getSub(
ConstantInt::get(DestTy, DestTy->getScalarSizeInBits()),
NumLowbitsLeft);
NewShAmt =
Constant::mergeUndefsWith(Constant::mergeUndefsWith(NewShAmt, BA), CA);
A = Builder.CreateShl(A, NewShAmt, Sext.getName());
return BinaryOperator::CreateAShr(A, NewShAmt);
}
// Splatting a bit of constant-index across a value:
// sext (ashr (trunc iN X to iM), M-1) to iN --> ashr (shl X, N-M), N-1
// If the dest type is different, use a cast (adjust use check).
if (match(Src, m_OneUse(m_AShr(m_Trunc(m_Value(X)),
m_SpecificInt(SrcBitSize - 1))))) {
Type *XTy = X->getType();
unsigned XBitSize = XTy->getScalarSizeInBits();
Constant *ShlAmtC = ConstantInt::get(XTy, XBitSize - SrcBitSize);
Constant *AshrAmtC = ConstantInt::get(XTy, XBitSize - 1);
if (XTy == DestTy)
return BinaryOperator::CreateAShr(Builder.CreateShl(X, ShlAmtC),
AshrAmtC);
if (cast<BinaryOperator>(Src)->getOperand(0)->hasOneUse()) {
Value *Ashr = Builder.CreateAShr(Builder.CreateShl(X, ShlAmtC), AshrAmtC);
return CastInst::CreateIntegerCast(Ashr, DestTy, /* isSigned */ true);
}
}
if (match(Src, m_VScale())) {
if (Sext.getFunction() &&
Sext.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
Attribute Attr =
Sext.getFunction()->getFnAttribute(Attribute::VScaleRange);
if (std::optional<unsigned> MaxVScale = Attr.getVScaleRangeMax())
if (Log2_32(*MaxVScale) < (SrcBitSize - 1))
return replaceInstUsesWith(Sext, Builder.CreateVScale(DestTy));
}
}
// sext(scmp(x, y)) -> scmp(x, y) with a wider result type.
// sext(ucmp(x, y)) -> ucmp(x, y) with a wider result type.
// scmp/ucmp return only -1, 0, or 1, which sign-extend correctly to any
// wider integer type, so we can sink the extension into the intrinsic.
if (auto *CI = dyn_cast<CmpIntrinsic>(Src); CI && CI->hasOneUse())
return replaceInstUsesWith(
Sext, Builder.CreateIntrinsic(DestTy, CI->getIntrinsicID(),
{CI->getLHS(), CI->getRHS()}));
Value *Y;
if (match(Src, m_OneUse(m_c_BitwiseLogic(
m_NSWTrunc(m_SpecificType(DestTy, X)), m_Value(Y))))) {
Value *SextY = Builder.CreateSExt(Y, DestTy);
return BinaryOperator::Create(cast<BinaryOperator>(Src)->getOpcode(), X,
SextY);
}
return nullptr;
}
/// Return a Constant* for the specified floating-point constant if it fits
/// in the specified FP type without changing its value.
static bool fitsInFPType(APFloat F, const fltSemantics &Sem) {
bool losesInfo;
(void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo);
return !losesInfo;
}
static Type *shrinkFPConstant(LLVMContext &Ctx, const APFloat &F,
bool PreferBFloat) {
// See if the value can be truncated to bfloat and then reextended.
if (PreferBFloat && fitsInFPType(F, APFloat::BFloat()))
return Type::getBFloatTy(Ctx);
// See if the value can be truncated to half and then reextended.
if (!PreferBFloat && fitsInFPType(F, APFloat::IEEEhalf()))
return Type::getHalfTy(Ctx);
// See if the value can be truncated to float and then reextended.
if (fitsInFPType(F, APFloat::IEEEsingle()))
return Type::getFloatTy(Ctx);
if (&F.getSemantics() == &APFloat::IEEEdouble())
return nullptr; // Won't shrink.
// See if the value can be truncated to double and then reextended.
if (fitsInFPType(F, APFloat::IEEEdouble()))
return Type::getDoubleTy(Ctx);
// Don't try to shrink to various long double types.
return nullptr;
}
static Type *shrinkFPConstant(ConstantFP *CFP, bool PreferBFloat) {
Type *Ty = CFP->getType();
if (Ty->getScalarType()->isPPC_FP128Ty())
return nullptr; // No constant folding of this.
Type *ShrinkTy =
shrinkFPConstant(CFP->getContext(), CFP->getValueAPF(), PreferBFloat);
if (ShrinkTy)
if (auto *VecTy = dyn_cast<VectorType>(Ty))
ShrinkTy = VectorType::get(ShrinkTy, VecTy);
return ShrinkTy;
}
// Determine if this is a vector of ConstantFPs and if so, return the minimal
// type we can safely truncate all elements to.
static Type *shrinkFPConstantVector(Value *V, bool PreferBFloat) {
auto *CV = dyn_cast<Constant>(V);
auto *CVVTy = dyn_cast<FixedVectorType>(V->getType());
if (!CV || !CVVTy)
return nullptr;
Type *MinType = nullptr;
unsigned NumElts = CVVTy->getNumElements();
// For fixed-width vectors we find the minimal type by looking
// through the constant values of the vector.
for (unsigned I = 0; I != NumElts; ++I) {
if (match(CV->getAggregateElement(I), m_Poison()))
continue;
auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(I));
if (!CFP)
return nullptr;
Type *T = shrinkFPConstant(CFP, PreferBFloat);
if (!T)
return nullptr;
// If we haven't found a type yet or this type has a larger mantissa than
// our previous type, this is our new minimal type.
if (!MinType || T->getFPMantissaWidth() > MinType->getFPMantissaWidth())
MinType = T;
}
// Make a vector type from the minimal type.
return MinType ? FixedVectorType::get(MinType, NumElts) : nullptr;
}
/// Find the minimum FP type we can safely truncate to.
static Type *getMinimumFPType(Value *V, Type *PreferredTy, InstCombiner &IC) {
if (auto *FPExt = dyn_cast<FPExtInst>(V))
return FPExt->getOperand(0)->getType();
Value *Src;
if (match(V, m_IToFP(m_Value(Src))) &&
IC.canBeCastedExactlyIntToFP(Src, PreferredTy, isa<SIToFPInst>(V),
cast<Instruction>(V)))
return PreferredTy;
bool PreferBFloat = PreferredTy->getScalarType()->isBFloatTy();
// If this value is a constant, return the constant in the smallest FP type
// that can accurately represent it. This allows us to turn
// (float)((double)X+2.0) into x+2.0f.
if (auto *CFP = dyn_cast<ConstantFP>(V))
if (Type *T = shrinkFPConstant(CFP, PreferBFloat))
return T;
// Try to shrink scalable and fixed splat vectors.
if (auto *FPC = dyn_cast<Constant>(V))
if (auto *VTy = dyn_cast<VectorType>(V->getType()))
if (auto *Splat = dyn_cast_or_null<ConstantFP>(FPC->getSplatValue()))
if (Type *T = shrinkFPConstant(Splat, PreferBFloat))
return VectorType::get(T, VTy);
// Try to shrink a vector of FP constants. This returns nullptr on scalable
// vectors
if (Type *T = shrinkFPConstantVector(V, PreferBFloat))
return T;
return V->getType();
}
bool InstCombiner::canBeCastedExactlyIntToFP(Value *V, Type *FPTy,
bool IsSigned,
const Instruction *CtxI) const {
Type *SrcTy = V->getType();
assert(SrcTy->isIntOrIntVectorTy() && "Expected an integer type");
int SrcSize = (int)SrcTy->getScalarSizeInBits() - IsSigned;
int DestNumSigBits = FPTy->getFPMantissaWidth();
// Easy case - if the source integer type has less bits than the FP mantissa,
// then the cast must be exact.
if (SrcSize <= DestNumSigBits)
return true;
// Cast from FP to integer and back to FP is independent of the intermediate
// integer width because of poison on overflow.
Value *F;
if (match(V, m_FPToI(m_Value(F)))) {
// If this is uitofp (fptosi F), the source needs an extra bit to avoid
// potential rounding of negative FP input values.
int SrcNumSigBits = F->getType()->getFPMantissaWidth();
if (!IsSigned && match(V, m_FPToSI(m_Value())))
SrcNumSigBits++;
// [su]itofp (fpto[su]i F) --> exact if the source type has less or equal
// significant bits than the destination (and make sure neither type is
// weird -- ppc_fp128).
if (SrcNumSigBits > 0 && DestNumSigBits > 0 &&
SrcNumSigBits <= DestNumSigBits)
return true;
}
// Try harder to find if the source integer type has less significant bits.
// Compute number of sign bits or determine trailing zeros.
KnownBits SrcKnown = computeKnownBits(V, CtxI);
int SigBits = (int)SrcTy->getScalarSizeInBits() -
SrcKnown.countMinLeadingZeros() -
SrcKnown.countMinTrailingZeros();
if (SigBits <= DestNumSigBits)
return true;
// For sitofp, the sign maps to the FP sign bit, so only magnitude bits
// (BitWidth - NumSignBits) consume mantissa.
if (IsSigned) {
SigBits = (int)SrcTy->getScalarSizeInBits() - ComputeNumSignBits(V, CtxI);
if (SigBits <= DestNumSigBits)
return true;
}
return false;
}
bool InstCombiner::isKnownExactCastIntToFP(CastInst &I) const {
CastInst::CastOps Opcode = I.getOpcode();
assert((Opcode == CastInst::SIToFP || Opcode == CastInst::UIToFP) &&
"Unexpected cast");
Value *Src = I.getOperand(0);
Type *FPTy = I.getType();
return canBeCastedExactlyIntToFP(Src, FPTy, Opcode == CastInst::SIToFP, &I);
}
Instruction *InstCombinerImpl::visitFPTrunc(FPTruncInst &FPT) {
if (Instruction *I = commonCastTransforms(FPT))
return I;
// If we have fptrunc(OpI (fpextend x), (fpextend y)), we would like to
// simplify this expression to avoid one or more of the trunc/extend
// operations if we can do so without changing the numerical results.
//
// The exact manner in which the widths of the operands interact to limit
// what we can and cannot do safely varies from operation to operation, and
// is explained below in the various case statements.
Type *Ty = FPT.getType();
auto *BO = dyn_cast<BinaryOperator>(FPT.getOperand(0));
if (BO && BO->hasOneUse()) {
Type *LHSMinType = getMinimumFPType(BO->getOperand(0), Ty, *this);
Type *RHSMinType = getMinimumFPType(BO->getOperand(1), Ty, *this);
unsigned OpWidth = BO->getType()->getFPMantissaWidth();
unsigned LHSWidth = LHSMinType->getFPMantissaWidth();
unsigned RHSWidth = RHSMinType->getFPMantissaWidth();
unsigned SrcWidth = std::max(LHSWidth, RHSWidth);
unsigned DstWidth = Ty->getFPMantissaWidth();
// Narrowing recomputes the binop in a smaller type, which can overflow to
// inf where the wide op was finite. Therefore we can only keep ninf if
// both the binop and the fptrunc have that flag.
FastMathFlags NarrowFMF = BO->getFastMathFlags();
NarrowFMF.setNoInfs(NarrowFMF.noInfs() && FPT.hasNoInfs());
switch (BO->getOpcode()) {
default: break;
case Instruction::FAdd:
case Instruction::FSub:
// For addition and subtraction, the infinitely precise result can
// essentially be arbitrarily wide; proving that double rounding
// will not occur because the result of OpI is exact (as we will for
// FMul, for example) is hopeless. However, we *can* nonetheless
// frequently know that double rounding cannot occur (or that it is
// innocuous) by taking advantage of the specific structure of
// infinitely-precise results that admit double rounding.
//
// Specifically, if OpWidth >= 2*DstWdith+1 and DstWidth is sufficient
// to represent both sources, we can guarantee that the double
// rounding is innocuous (See p50 of Figueroa's 2000 PhD thesis,
// "A Rigorous Framework for Fully Supporting the IEEE Standard ..."
// for proof of this fact).
//
// Note: Figueroa does not consider the case where DstFormat !=
// SrcFormat. It's possible (likely even!) that this analysis
// could be tightened for those cases, but they are rare (the main
// case of interest here is (float)((double)float + float)).
if (OpWidth >= 2*DstWidth+1 && DstWidth >= SrcWidth) {
Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
Instruction *RI = BinaryOperator::Create(BO->getOpcode(), LHS, RHS);
RI->setFastMathFlags(NarrowFMF);
return RI;
}
break;
case Instruction::FMul:
// For multiplication, the infinitely precise result has at most
// LHSWidth + RHSWidth significant bits; if OpWidth is sufficient
// that such a value can be exactly represented, then no double
// rounding can possibly occur; we can safely perform the operation
// in the destination format if it can represent both sources.
if (OpWidth >= LHSWidth + RHSWidth && DstWidth >= SrcWidth) {
Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
return BinaryOperator::CreateFMulFMF(LHS, RHS, NarrowFMF);
}
break;
case Instruction::FDiv:
// For division, we use again use the bound from Figueroa's
// dissertation. I am entirely certain that this bound can be
// tightened in the unbalanced operand case by an analysis based on
// the diophantine rational approximation bound, but the well-known
// condition used here is a good conservative first pass.
// TODO: Tighten bound via rigorous analysis of the unbalanced case.
if (OpWidth >= 2*DstWidth && DstWidth >= SrcWidth) {
Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
return BinaryOperator::CreateFDivFMF(LHS, RHS, NarrowFMF);
}
break;
case Instruction::FRem: {
// Remainder is straightforward. Remainder is always exact, so the
// type of OpI doesn't enter into things at all. We simply evaluate
// in whichever source type is larger, then convert to the
// destination type.
if (SrcWidth == OpWidth)
break;
Value *LHS, *RHS;
if (LHSWidth == SrcWidth) {
LHS = Builder.CreateFPTrunc(BO->getOperand(0), LHSMinType);
RHS = Builder.CreateFPTrunc(BO->getOperand(1), LHSMinType);
} else {
LHS = Builder.CreateFPTrunc(BO->getOperand(0), RHSMinType);
RHS = Builder.CreateFPTrunc(BO->getOperand(1), RHSMinType);
}
Value *ExactResult = Builder.CreateFRemFMF(LHS, RHS, BO);
return CastInst::CreateFPCast(ExactResult, Ty);
}
}
}
// (fptrunc (fneg x)) -> (fneg (fptrunc x))
Value *X;
Instruction *Op = dyn_cast<Instruction>(FPT.getOperand(0));
if (Op && Op->hasOneUse()) {
FastMathFlags FMF = FPT.getFastMathFlags();
if (auto *FPMO = dyn_cast<FPMathOperator>(Op))
FMF &= FPMO->getFastMathFlags();
if (match(Op, m_FNeg(m_Value(X)))) {
Value *InnerTrunc = Builder.CreateFPTruncFMF(X, Ty, FMF);
Value *Neg = Builder.CreateFNegFMF(InnerTrunc, FMF);
return replaceInstUsesWith(FPT, Neg);
}
// If we are truncating a select that has an extended operand, we can
// narrow the other operand and do the select as a narrow op.
Value *Cond, *X, *Y;
if (match(Op, m_Select(m_Value(Cond), m_FPExt(m_SpecificType(Ty, X)),
m_Value(Y)))) {
// fptrunc (select Cond, (fpext X), Y --> select Cond, X, (fptrunc Y)
Value *NarrowY = Builder.CreateFPTruncFMF(Y, Ty, FMF);
Value *Sel =
Builder.CreateSelectFMF(Cond, X, NarrowY, FMF, "narrow.sel", Op);
return replaceInstUsesWith(FPT, Sel);
}
if (match(Op, m_Select(m_Value(Cond), m_Value(Y),
m_FPExt(m_SpecificType(Ty, X))))) {
// fptrunc (select Cond, Y, (fpext X) --> select Cond, (fptrunc Y), X
Value *NarrowY = Builder.CreateFPTruncFMF(Y, Ty, FMF);
Value *Sel =
Builder.CreateSelectFMF(Cond, NarrowY, X, FMF, "narrow.sel", Op);
return replaceInstUsesWith(FPT, Sel);
}
}
if (auto *II = dyn_cast<IntrinsicInst>(FPT.getOperand(0))) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::ceil:
case Intrinsic::fabs:
case Intrinsic::floor:
case Intrinsic::nearbyint:
case Intrinsic::rint:
case Intrinsic::round:
case Intrinsic::roundeven:
case Intrinsic::trunc: {
Value *Src = II->getArgOperand(0);
if (!Src->hasOneUse())
break;
// Except for fabs, this transformation requires the input of the unary FP
// operation to be itself an fpext from the type to which we're
// truncating.
if (II->getIntrinsicID() != Intrinsic::fabs) {
FPExtInst *FPExtSrc = dyn_cast<FPExtInst>(Src);
if (!FPExtSrc || FPExtSrc->getSrcTy() != Ty)
break;
}
// Do unary FP operation on smaller type.
// (fptrunc (fabs x)) -> (fabs (fptrunc x))
Value *InnerTrunc = Builder.CreateFPTrunc(Src, Ty);
Function *Overload = Intrinsic::getOrInsertDeclaration(
FPT.getModule(), II->getIntrinsicID(), Ty);
SmallVector<OperandBundleDef, 1> OpBundles;
II->getOperandBundlesAsDefs(OpBundles);
CallInst *NewCI =
CallInst::Create(Overload, {InnerTrunc}, OpBundles, II->getName());
// A normal value may be converted to an infinity. It means that we cannot
// propagate ninf from the intrinsic. So we propagate FMF from fptrunc.
NewCI->copyFastMathFlags(&FPT);
return NewCI;
}
}
}
if (Instruction *I = shrinkInsertElt(FPT, Builder))
return I;
Value *Src = FPT.getOperand(0);
if (isa<SIToFPInst>(Src) || isa<UIToFPInst>(Src)) {
auto *FPCast = cast<CastInst>(Src);
if (isKnownExactCastIntToFP(*FPCast))
return CastInst::Create(FPCast->getOpcode(), FPCast->getOperand(0), Ty);
}
return nullptr;
}
Instruction *InstCombinerImpl::visitFPExt(CastInst &FPExt) {
// If the source operand is a cast from integer to FP and known exact, then
// cast the integer operand directly to the destination type.
Type *Ty = FPExt.getType();
Value *Src = FPExt.getOperand(0);
if (isa<SIToFPInst>(Src) || isa<UIToFPInst>(Src)) {
auto *FPCast = cast<CastInst>(Src);
if (isKnownExactCastIntToFP(*FPCast))
return CastInst::Create(FPCast->getOpcode(), FPCast->getOperand(0), Ty);
}
return commonCastTransforms(FPExt);
}
/// fpto{s/u}i[.sat]({u/s}itofp(X)) --> X or zext(X) or sext(X) or trunc(X)
/// This is safe if the intermediate type has enough bits in its mantissa to
/// accurately represent all values of X. For example, this won't work with
/// i64 -> float -> i64.
template <typename FPToIntTy>
Instruction *InstCombinerImpl::foldItoFPtoI(FPToIntTy &FI) {
constexpr bool IsSaturating = std::is_same_v<FPToIntTy, IntrinsicInst>;
if (!isa<UIToFPInst>(FI.getOperand(0)) && !isa<SIToFPInst>(FI.getOperand(0)))
return nullptr;
auto *OpI = cast<CastInst>(FI.getOperand(0));
Value *X = OpI->getOperand(0);
Type *XType = X->getType();
Type *DestType = FI.getType();
bool IsInputSigned = isa<SIToFPInst>(OpI);
bool IsOutputSigned;
if constexpr (IsSaturating)
IsOutputSigned = FI.getIntrinsicID() == Intrinsic::fptosi_sat;
else
IsOutputSigned = isa<FPToSIInst>(FI);
// Since we can assume the conversion won't overflow, our decision as to
// whether the input will fit in the float should depend on the minimum
// of the input range and output range.
// This means this is also safe for a signed input and unsigned output, since
// a negative input would lead to undefined behavior.
if (!isKnownExactCastIntToFP(*OpI)) {
if constexpr (!IsSaturating) {
// The first cast may not round exactly based on the source integer width
// and FP width, but the overflow UB rules can still allow this to fold.
// If the destination type is narrow, that means the intermediate FP value
// must be large enough to hold the source value exactly.
//
// For example, (uint8_t)((float)(uint32_t 16777217) is UB.
int OutputSize = (int)DestType->getScalarSizeInBits();
if (OutputSize > OpI->getType()->getFPMantissaWidth())
return nullptr;
} else {
// Sat intrinsics produce a defined saturated value on overflow, so
// the UB-based shortcut is invalid. Require exactness.
return nullptr;
}
}
unsigned SrcWidth = XType->getScalarSizeInBits();
unsigned DestWidth = DestType->getScalarSizeInBits();
if constexpr (IsSaturating) {
// TODO: cross-sign and narrowing cases could be handled with range
// analysis to prove the source fits in the destination.
if (IsInputSigned != IsOutputSigned || DestWidth < SrcWidth)
return nullptr;
}
if (DestWidth > SrcWidth) {
if (IsInputSigned && IsOutputSigned)
return new SExtInst(X, DestType);
return new ZExtInst(X, DestType);
}
if (DestWidth < SrcWidth)
return new TruncInst(X, DestType);
assert(XType == DestType && "Unexpected types for int to FP to int casts");
return replaceInstUsesWith(FI, X);
}
template Instruction *InstCombinerImpl::foldItoFPtoI<CastInst>(CastInst &);
template Instruction *
InstCombinerImpl::foldItoFPtoI<IntrinsicInst>(IntrinsicInst &);
static Instruction *foldFPtoI(Instruction &FI, InstCombiner &IC) {
// fpto{u/s}i non-norm --> 0
FPClassTest Mask =
FI.getOpcode() == Instruction::FPToUI ? fcPosNormal : fcNormal;
KnownFPClass FPClass = computeKnownFPClass(
FI.getOperand(0), Mask, IC.getSimplifyQuery().getWithInstruction(&FI));
if (FPClass.isKnownNever(Mask))
return IC.replaceInstUsesWith(FI, ConstantInt::getNullValue(FI.getType()));
// fpto{u/s}i (fdiv ({u/s}itofp X to F), C_fp) --> {u/s}div X, C
//
// F has precision p (significand bits incl. hidden bit); C_fp is the exact FP
// value of the integer constant C. Given N = integer width, this is safe if:
// Unsigned: C > 0 and N <= p.
// Signed: C != 0 and N - 1 <= p, excluding (X == INT_MIN, C == -1) since
// sdiv INT_MIN, -1 is UB while the FP path only yields poison.
// fdiv X, -1 gets transformed to fneg in InstCombine regardless.
//
// The bounds make {u/s}itofp and C_fp exact (every |int| <= 2^p is exact),
// and ensure the rounded quotient never crosses an integer boundary:
// Rounding lemma: for 0 <= A <= 2^p, 1 <= B <= 2^p, q = floor(A/B),
// trunc(R_p(A/B)) = q.
// For r = A - qB > 0, m = q+1, half-gap H(m) <= q/2^p and
// m - A/B = (B-r)/B >= 1/B > q/2^p >= H(m), so R_p(A/B) < m; q = 0 is
// similar (H(1) = 2^(-p-1) < 2^-p <= 1/B).
// Signed case: by symmetry R_p(-z) = -R_p(z), so fptosi yields s*q = sdiv.
bool IsSigned = FI.getOpcode() == Instruction::FPToSI;
Value *X;
const APFloat *APF;
if (IsSigned) {
if (!match(FI.getOperand(0),
m_OneUse(m_FDiv(m_SIToFP(m_Value(X)), m_APFloat(APF)))))
return nullptr;
} else {
if (!match(FI.getOperand(0),
m_OneUse(m_FDiv(m_UIToFP(m_Value(X)), m_APFloat(APF)))))
return nullptr;
}
Type *IntTy = X->getType();
if (FI.getType() != IntTy)
return nullptr;
unsigned IntWidth = IntTy->getScalarSizeInBits();
unsigned Precision = APFloat::semanticsPrecision(APF->getSemantics());
if (Precision + IsSigned < IntWidth)
return nullptr;
if (!APF->isInteger())
return nullptr;
APSInt Divisor(IntWidth, !IsSigned);
bool IsExact = false;
APF->convertToInteger(Divisor, APFloat::rmTowardZero, &IsExact);
if (!IsExact)
return nullptr;
if (Divisor.isZero())
return nullptr;
// sdiv INT_MIN, -1 is UB, not poison, so this isn't valid if X == INT_MIN.
// fdiv X, -1 gets transformed to fneg anyways, so we do not handle C == -1.
if (IsSigned && Divisor.isAllOnes())
return nullptr;
Constant *C = ConstantInt::get(IntTy, Divisor);
return IsSigned ? BinaryOperator::CreateSDiv(X, C)
: BinaryOperator::CreateUDiv(X, C);
}
Instruction *InstCombinerImpl::visitFPToUI(FPToUIInst &FI) {
if (Instruction *I = foldItoFPtoI(FI))
return I;
if (Instruction *I = foldFPtoI(FI, *this))
return I;
return commonCastTransforms(FI);
}
Instruction *InstCombinerImpl::visitFPToSI(FPToSIInst &FI) {
if (Instruction *I = foldItoFPtoI(FI))
return I;
if (Instruction *I = foldFPtoI(FI, *this))
return I;
return commonCastTransforms(FI);
}
Instruction *InstCombinerImpl::visitUIToFP(CastInst &CI) {
if (Instruction *R = commonCastTransforms(CI))
return R;
if (!CI.hasNonNeg() && isKnownNonNegative(CI.getOperand(0), SQ)) {
CI.setNonNeg();
return &CI;
}
// uitofp (and (trunc X), Mask) --> uitofp (and X, zext(Mask))
Value *Src = CI.getOperand(0);
Value *X;
Constant *Mask;
if (match(Src, m_OneUse(m_And(m_OneUse(m_Trunc(m_Value(X))),
m_ImmConstant(Mask))))) {
unsigned SourceWidth = Src->getType()->getScalarSizeInBits();
unsigned InputWidth = X->getType()->getScalarSizeInBits();
if (!DL.isLegalInteger(SourceWidth) &&
shouldChangeType(SourceWidth, InputWidth)) {
Value *MaskedX =
Builder.CreateAnd(X, Builder.CreateZExt(Mask, X->getType()));
auto *NewUIToFP =
CastInst::Create(Instruction::UIToFP, MaskedX, CI.getType());
NewUIToFP->setNonNeg(CI.hasNonNeg());
return NewUIToFP;
}
}
return nullptr;
}
Instruction *InstCombinerImpl::visitSIToFP(CastInst &CI) {
if (Instruction *R = commonCastTransforms(CI))
return R;
if (isKnownNonNegative(CI.getOperand(0), SQ)) {
auto *UI =
CastInst::Create(Instruction::UIToFP, CI.getOperand(0), CI.getType());
UI->setNonNeg(true);
// nnan/afn/reassoc/contract/arcp carry no meaning for a value-preserving
// cast, but ninf/nsz are semantically meaningful for {u,s}itofp and
// remain valid after reinterpreting the operand as unsigned.
UI->setHasNoInfs(CI.hasNoInfs());
UI->setHasNoSignedZeros(CI.hasNoSignedZeros());
return UI;
}
return nullptr;
}
Instruction *InstCombinerImpl::visitIntToPtr(IntToPtrInst &CI) {
// If the source integer type is not the intptr_t type for this target, do a
// trunc or zext to the intptr_t type, then inttoptr of it. This allows the
// cast to be exposed to other transforms.
unsigned AS = CI.getAddressSpace();
if (CI.getOperand(0)->getType()->getScalarSizeInBits() !=
DL.getPointerSizeInBits(AS)) {
Type *Ty = CI.getOperand(0)->getType()->getWithNewType(
DL.getIntPtrType(CI.getContext(), AS));
Value *P = Builder.CreateZExtOrTrunc(CI.getOperand(0), Ty);
return new IntToPtrInst(P, CI.getType());
}
// Replace (inttoptr (add (ptrtoint %Base), %Offset)) with
// (getelementptr i8, %Base, %Offset) if the pointer is only used as integer
// value.
Value *Base;
Value *Offset;
auto UsesPointerAsInt = [](User *U) {
if (isa<ICmpInst, PtrToIntInst>(U))
return true;
if (auto *P = dyn_cast<PHINode>(U))
return P->hasOneUse() && isa<ICmpInst, PtrToIntInst>(*P->user_begin());
return false;
};
if (match(CI.getOperand(0),
m_OneUse(m_c_Add(m_PtrToIntSameSize(DL, m_Value(Base)),
m_Value(Offset)))) &&
CI.getType()->getPointerAddressSpace() ==
Base->getType()->getPointerAddressSpace() &&
all_of(CI.users(), UsesPointerAsInt)) {
return GetElementPtrInst::Create(Builder.getInt8Ty(), Base, Offset);
}
if (Instruction *I = commonCastTransforms(CI))
return I;
return nullptr;
}
Value *InstCombinerImpl::foldPtrToIntOrAddrOfGEP(Type *IntTy, Value *Ptr) {
// Look through chain of one-use GEPs.
Type *PtrTy = Ptr->getType();
SmallVector<GEPOperator *> GEPs;
while (true) {
auto *GEP = dyn_cast<GEPOperator>(Ptr);
if (!GEP || !GEP->hasOneUse())
break;
GEPs.push_back(GEP);
Ptr = GEP->getPointerOperand();
}
// Don't handle case where GEP converts from pointer to vector.
if (GEPs.empty() || PtrTy != Ptr->getType())
return nullptr;
// Check whether we know the integer value of the base pointer.
Value *Res;
Type *IdxTy = DL.getIndexType(PtrTy);
if (match(Ptr, m_OneUse(m_IntToPtr(m_Value(Res)))) &&
Res->getType() == IntTy && IntTy == IdxTy) {
// pass
} else if (isa<ConstantPointerNull>(Ptr)) {
Res = Constant::getNullValue(IdxTy);
} else {
return nullptr;
}
// Perform the entire operation on integers instead.
for (GEPOperator *GEP : reverse(GEPs)) {
Value *Offset = EmitGEPOffset(GEP);
Res = Builder.CreateAdd(Res, Offset, "", GEP->hasNoUnsignedWrap());
}
return Builder.CreateZExtOrTrunc(Res, IntTy);
}
Instruction *InstCombinerImpl::visitPtrToInt(PtrToIntInst &CI) {
// If the destination integer type is not the intptr_t type for this target,
// do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast
// to be exposed to other transforms.
Value *SrcOp = CI.getPointerOperand();
Type *SrcTy = SrcOp->getType();
Type *Ty = CI.getType();
unsigned AS = CI.getPointerAddressSpace();
unsigned TySize = Ty->getScalarSizeInBits();
unsigned PtrSize = DL.getPointerSizeInBits(AS);
if (TySize != PtrSize) {
Type *IntPtrTy =
SrcTy->getWithNewType(DL.getIntPtrType(CI.getContext(), AS));
Value *P = Builder.CreatePtrToInt(SrcOp, IntPtrTy);
return CastInst::CreateIntegerCast(P, Ty, /*isSigned=*/false);
}
// (ptrtoint (ptrmask P, M))
// -> (and (ptrtoint P), M)
// This is generally beneficial as `and` is better supported than `ptrmask`.
Value *Ptr, *Mask;
if (match(SrcOp, m_OneUse(m_Intrinsic<Intrinsic::ptrmask>(
m_Value(Ptr), m_SpecificType(Ty, Mask)))))
return BinaryOperator::CreateAnd(Builder.CreatePtrToInt(Ptr, Ty), Mask);
if (Value *V = foldPtrToIntOrAddrOfGEP(Ty, SrcOp))
return replaceInstUsesWith(CI, V);
Value *Vec, *Scalar, *Index;
if (match(SrcOp, m_OneUse(m_InsertElt(m_IntToPtr(m_SpecificType(Ty, Vec)),
m_Value(Scalar), m_Value(Index))))) {
assert(Vec->getType()->getScalarSizeInBits() == PtrSize && "Wrong type");
// Convert the scalar to int followed by insert to eliminate one cast:
// p2i (ins (i2p Vec), Scalar, Index --> ins Vec, (p2i Scalar), Index
Value *NewCast = Builder.CreatePtrToInt(Scalar, Ty->getScalarType());
return InsertElementInst::Create(Vec, NewCast, Index);
}
return commonCastTransforms(CI);
}
Instruction *InstCombinerImpl::visitPtrToAddr(PtrToAddrInst &CI) {
Value *SrcOp = CI.getPointerOperand();
Type *Ty = CI.getType();
// (ptrtoaddr (ptrmask P, M))
// -> (and (ptrtoaddr P), M)
// This is generally beneficial as `and` is better supported than `ptrmask`.
Value *Ptr, *Mask;
if (match(SrcOp, m_OneUse(m_Intrinsic<Intrinsic::ptrmask>(
m_Value(Ptr), m_SpecificType(Ty, Mask)))))
return BinaryOperator::CreateAnd(Builder.CreatePtrToAddr(Ptr), Mask);
if (Value *V = foldPtrToIntOrAddrOfGEP(Ty, SrcOp))
return replaceInstUsesWith(CI, V);
// FIXME: Implement variants of ptrtoint folds.
return commonCastTransforms(CI);
}
/// This input value (which is known to have vector type) is being zero extended
/// or truncated to the specified vector type. Since the zext/trunc is done
/// using an integer type, we have a (bitcast(cast(bitcast))) pattern,
/// endianness will impact which end of the vector that is extended or
/// truncated.
///
/// A vector is always stored with index 0 at the lowest address, which
/// corresponds to the most significant bits for a big endian stored integer and
/// the least significant bits for little endian. A trunc/zext of an integer
/// impacts the big end of the integer. Thus, we need to add/remove elements at
/// the front of the vector for big endian targets, and the back of the vector
/// for little endian targets.
///
/// Try to replace it with a shuffle (and vector/vector bitcast) if possible.
///
/// The source and destination vector types may have different element types.
static Instruction *
optimizeVectorResizeWithIntegerBitCasts(Value *InVal, VectorType *DestTy,
InstCombinerImpl &IC) {
// We can only do this optimization if the output is a multiple of the input
// element size, or the input is a multiple of the output element size.
// Convert the input type to have the same element type as the output.
VectorType *SrcTy = cast<VectorType>(InVal->getType());
if (SrcTy->getElementType() != DestTy->getElementType()) {
// The input types don't need to be identical, but for now they must be the
// same size. There is no specific reason we couldn't handle things like
// <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten
// there yet.
if (SrcTy->getElementType()->getPrimitiveSizeInBits() !=
DestTy->getElementType()->getPrimitiveSizeInBits())
return nullptr;
SrcTy =
FixedVectorType::get(DestTy->getElementType(),
cast<FixedVectorType>(SrcTy)->getNumElements());
InVal = IC.Builder.CreateBitCast(InVal, SrcTy);
}
bool IsBigEndian = IC.getDataLayout().isBigEndian();
unsigned SrcElts = cast<FixedVectorType>(SrcTy)->getNumElements();
unsigned DestElts = cast<FixedVectorType>(DestTy)->getNumElements();
assert(SrcElts != DestElts && "Element counts should be different.");
// Now that the element types match, get the shuffle mask and RHS of the
// shuffle to use, which depends on whether we're increasing or decreasing the
// size of the input.
auto ShuffleMaskStorage = llvm::to_vector<16>(llvm::seq<int>(0, SrcElts));
ArrayRef<int> ShuffleMask;
Value *V2;
if (SrcElts > DestElts) {
// If we're shrinking the number of elements (rewriting an integer
// truncate), just shuffle in the elements corresponding to the least
// significant bits from the input and use poison as the second shuffle
// input.
V2 = PoisonValue::get(SrcTy);
// Make sure the shuffle mask selects the "least significant bits" by
// keeping elements from back of the src vector for big endian, and from the
// front for little endian.
ShuffleMask = ShuffleMaskStorage;
if (IsBigEndian)
ShuffleMask = ShuffleMask.take_back(DestElts);
else
ShuffleMask = ShuffleMask.take_front(DestElts);
} else {
// If we're increasing the number of elements (rewriting an integer zext),
// shuffle in all of the elements from InVal. Fill the rest of the result
// elements with zeros from a constant zero.
V2 = Constant::getNullValue(SrcTy);
// Use first elt from V2 when indicating zero in the shuffle mask.
uint32_t NullElt = SrcElts;
// Extend with null values in the "most significant bits" by adding elements
// in front of the src vector for big endian, and at the back for little
// endian.
unsigned DeltaElts = DestElts - SrcElts;
if (IsBigEndian)
ShuffleMaskStorage.insert(ShuffleMaskStorage.begin(), DeltaElts, NullElt);
else
ShuffleMaskStorage.append(DeltaElts, NullElt);
ShuffleMask = ShuffleMaskStorage;
}
return new ShuffleVectorInst(InVal, V2, ShuffleMask);
}
static bool isMultipleOfTypeSize(unsigned Value, Type *Ty) {
return Value % Ty->getPrimitiveSizeInBits() == 0;
}
static unsigned getTypeSizeIndex(unsigned Value, Type *Ty) {
return Value / Ty->getPrimitiveSizeInBits();
}
/// V is a value which is inserted into a vector of VecEltTy.
/// Look through the value to see if we can decompose it into
/// insertions into the vector. See the example in the comment for
/// OptimizeIntegerToVectorInsertions for the pattern this handles.
/// The type of V is always a non-zero multiple of VecEltTy's size.
/// Shift is the number of bits between the lsb of V and the lsb of
/// the vector.
///
/// This returns false if the pattern can't be matched or true if it can,
/// filling in Elements with the elements found here.
static bool collectInsertionElements(Value *V, unsigned Shift,
SmallVectorImpl<Value *> &Elements,
Type *VecEltTy, bool isBigEndian) {
assert(isMultipleOfTypeSize(Shift, VecEltTy) &&
"Shift should be a multiple of the element type size");
// Poison values never contribute useful bits to the result.
if (match(V, m_Poison()))
return true;
// If we got down to a value of the right type, we win, try inserting into the
// right element.
if (V->getType() == VecEltTy) {
// Inserting null doesn't actually insert any elements.
if (Constant *C = dyn_cast<Constant>(V))
if (C->isNullValue())
return true;
unsigned ElementIndex = getTypeSizeIndex(Shift, VecEltTy);
if (isBigEndian)
ElementIndex = Elements.size() - ElementIndex - 1;
// Fail if multiple elements are inserted into this slot.
if (Elements[ElementIndex])
return false;
Elements[ElementIndex] = V;
return true;
}
if (Constant *C = dyn_cast<Constant>(V)) {
// Figure out the # elements this provides, and bitcast it or slice it up
// as required.
unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(),
VecEltTy);
// If the constant is the size of a vector element, we just need to bitcast
// it to the right type so it gets properly inserted.
if (NumElts == 1)
return collectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy),
Shift, Elements, VecEltTy, isBigEndian);
// Okay, this is a constant that covers multiple elements. Slice it up into
// pieces and insert each element-sized piece into the vector.
if (!isa<IntegerType>(C->getType()))
C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(),
C->getType()->getPrimitiveSizeInBits()));
unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits();
Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize);
for (unsigned i = 0; i != NumElts; ++i) {
unsigned ShiftI = i * ElementSize;
Constant *Piece = ConstantFoldBinaryInstruction(
Instruction::LShr, C, ConstantInt::get(C->getType(), ShiftI));
if (!Piece)
return false;
Piece = ConstantExpr::getTrunc(Piece, ElementIntTy);
if (!collectInsertionElements(Piece, ShiftI + Shift, Elements, VecEltTy,
isBigEndian))
return false;
}
return true;
}
if (!V->hasOneUse()) return false;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
switch (I->getOpcode()) {
default: return false; // Unhandled case.
case Instruction::BitCast:
if (I->getOperand(0)->getType()->isVectorTy())
return false;
return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
isBigEndian);
case Instruction::ZExt:
if (!isMultipleOfTypeSize(
I->getOperand(0)->getType()->getPrimitiveSizeInBits(),
VecEltTy))
return false;
return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
isBigEndian);
case Instruction::Or:
return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
isBigEndian) &&
collectInsertionElements(I->getOperand(1), Shift, Elements, VecEltTy,
isBigEndian);
case Instruction::Shl: {
// Must be shifting by a constant that is a multiple of the element size.
ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
if (!CI) return false;
Shift += CI->getZExtValue();
if (!isMultipleOfTypeSize(Shift, VecEltTy)) return false;
return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
isBigEndian);
}
}
}
/// If the input is an 'or' instruction, we may be doing shifts and ors to
/// assemble the elements of the vector manually.
/// Try to rip the code out and replace it with insertelements. This is to
/// optimize code like this:
///
/// %tmp37 = bitcast float %inc to i32
/// %tmp38 = zext i32 %tmp37 to i64
/// %tmp31 = bitcast float %inc5 to i32
/// %tmp32 = zext i32 %tmp31 to i64
/// %tmp33 = shl i64 %tmp32, 32
/// %ins35 = or i64 %tmp33, %tmp38
/// %tmp43 = bitcast i64 %ins35 to <2 x float>
///
/// Into two insertelements that do "buildvector{%inc, %inc5}".
static Value *optimizeIntegerToVectorInsertions(BitCastInst &CI,
InstCombinerImpl &IC) {
auto *DestVecTy = cast<FixedVectorType>(CI.getType());
Value *IntInput = CI.getOperand(0);
// if the int input is just an undef value do not try to optimize to vector
// insertions as it will prevent undef propagation
if (isa<UndefValue>(IntInput))
return nullptr;
SmallVector<Value*, 8> Elements(DestVecTy->getNumElements());
if (!collectInsertionElements(IntInput, 0, Elements,
DestVecTy->getElementType(),
IC.getDataLayout().isBigEndian()))
return nullptr;
// If we succeeded, we know that all of the element are specified by Elements
// or are zero if Elements has a null entry. Recast this as a set of
// insertions.
Value *Result = Constant::getNullValue(CI.getType());
for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
if (!Elements[i]) continue; // Unset element.
Result = IC.Builder.CreateInsertElement(Result, Elements[i], i);
}
return Result;
}
/// Canonicalize scalar bitcasts of extracted elements into a bitcast of the
/// vector followed by extract element. The backend tends to handle bitcasts of
/// vectors better than bitcasts of scalars because vector registers are
/// usually not type-specific like scalar integer or scalar floating-point.
static Instruction *canonicalizeBitCastExtElt(BitCastInst &BitCast,
InstCombinerImpl &IC) {
Value *VecOp, *Index;
if (!match(BitCast.getOperand(0),
m_OneUse(m_ExtractElt(m_Value(VecOp), m_Value(Index)))))
return nullptr;
// The bitcast must be to a vectorizable type, otherwise we can't make a new
// type to extract from.
Type *DestType = BitCast.getType();
VectorType *VecType = cast<VectorType>(VecOp->getType());
if (VectorType::isValidElementType(DestType)) {
auto *NewVecType = VectorType::get(DestType, VecType);
auto *NewBC = IC.Builder.CreateBitCast(VecOp, NewVecType, "bc");
return ExtractElementInst::Create(NewBC, Index);
}
// Only solve DestType is vector to avoid inverse transform in visitBitCast.
// bitcast (extractelement <1 x elt>, dest) -> bitcast(<1 x elt>, dest)
auto *FixedVType = dyn_cast<FixedVectorType>(VecType);
if (DestType->isVectorTy() && FixedVType && FixedVType->getNumElements() == 1)
return CastInst::Create(Instruction::BitCast, VecOp, DestType);
return nullptr;
}
/// Change the type of a bitwise logic operation if we can eliminate a bitcast.
static Instruction *foldBitCastBitwiseLogic(BitCastInst &BitCast,
InstCombiner::BuilderTy &Builder) {
Type *DestTy = BitCast.getType();
BinaryOperator *BO;
if (!match(BitCast.getOperand(0), m_OneUse(m_BinOp(BO))) ||
!BO->isBitwiseLogicOp())
return nullptr;
// FIXME: This transform is restricted to vector types to avoid backend
// problems caused by creating potentially illegal operations. If a fix-up is
// added to handle that situation, we can remove this check.
if (!DestTy->isVectorTy() || !BO->getType()->isVectorTy())
return nullptr;
if (DestTy->isFPOrFPVectorTy()) {
Value *X, *Y;
// bitcast(logic(bitcast(X), bitcast(Y))) -> bitcast'(logic(bitcast'(X), Y))
if (match(BO->getOperand(0), m_OneUse(m_BitCast(m_Value(X)))) &&
match(BO->getOperand(1), m_OneUse(m_BitCast(m_Value(Y))))) {
if (X->getType()->isFPOrFPVectorTy() &&
Y->getType()->isIntOrIntVectorTy()) {
Value *CastedOp =
Builder.CreateBitCast(BO->getOperand(0), Y->getType());
Value *NewBO = Builder.CreateBinOp(BO->getOpcode(), CastedOp, Y);
return CastInst::CreateBitOrPointerCast(NewBO, DestTy);
}
if (X->getType()->isIntOrIntVectorTy() &&
Y->getType()->isFPOrFPVectorTy()) {
Value *CastedOp =
Builder.CreateBitCast(BO->getOperand(1), X->getType());
Value *NewBO = Builder.CreateBinOp(BO->getOpcode(), CastedOp, X);
return CastInst::CreateBitOrPointerCast(NewBO, DestTy);
}
}
return nullptr;
}
if (!DestTy->isIntOrIntVectorTy())
return nullptr;
Value *X;
if (match(BO->getOperand(0),
m_OneUse(m_BitCast(m_SpecificType(DestTy, X)))) &&
!isa<Constant>(X)) {
// bitcast(logic(bitcast(X), Y)) --> logic'(X, bitcast(Y))
Value *CastedOp1 = Builder.CreateBitCast(BO->getOperand(1), DestTy);
return BinaryOperator::Create(BO->getOpcode(), X, CastedOp1);
}
if (match(BO->getOperand(1),
m_OneUse(m_BitCast(m_SpecificType(DestTy, X)))) &&
!isa<Constant>(X)) {
// bitcast(logic(Y, bitcast(X))) --> logic'(bitcast(Y), X)
Value *CastedOp0 = Builder.CreateBitCast(BO->getOperand(0), DestTy);
return BinaryOperator::Create(BO->getOpcode(), CastedOp0, X);
}
// Canonicalize vector bitcasts to come before vector bitwise logic with a
// constant. This eases recognition of special constants for later ops.
// Example:
// icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
Constant *C;
if (match(BO->getOperand(1), m_Constant(C))) {
// bitcast (logic X, C) --> logic (bitcast X, C')
Value *CastedOp0 = Builder.CreateBitCast(BO->getOperand(0), DestTy);
Value *CastedC = Builder.CreateBitCast(C, DestTy);
return BinaryOperator::Create(BO->getOpcode(), CastedOp0, CastedC);
}
return nullptr;
}
/// Change the type of a select if we can eliminate a bitcast.
static Instruction *foldBitCastSelect(BitCastInst &BitCast,
InstCombiner::BuilderTy &Builder) {
Value *Cond, *TVal, *FVal;
if (!match(BitCast.getOperand(0),
m_OneUse(m_Select(m_Value(Cond), m_Value(TVal), m_Value(FVal)))))
return nullptr;
// A vector select must maintain the same number of elements in its operands.
Type *CondTy = Cond->getType();
Type *DestTy = BitCast.getType();
auto *DestVecTy = dyn_cast<VectorType>(DestTy);
if (auto *CondVTy = dyn_cast<VectorType>(CondTy))
if (!DestVecTy ||
CondVTy->getElementCount() != DestVecTy->getElementCount())
return nullptr;
auto *Sel = cast<Instruction>(BitCast.getOperand(0));
auto *SrcVecTy = dyn_cast<VectorType>(TVal->getType());
if ((isa<Constant>(TVal) || isa<Constant>(FVal)) &&
(!DestVecTy ||
(SrcVecTy && ElementCount::isKnownLE(DestVecTy->getElementCount(),
SrcVecTy->getElementCount())))) {
// Avoid introducing select of vector (or select of vector with more
// elements) until the backend can undo this transformation.
Value *CastedTVal = Builder.CreateBitCast(TVal, DestTy);
Value *CastedFVal = Builder.CreateBitCast(FVal, DestTy);
return SelectInst::Create(Cond, CastedTVal, CastedFVal, "", nullptr, Sel);
}
// FIXME: This transform is restricted from changing the select between
// scalars and vectors to avoid backend problems caused by creating
// potentially illegal operations. If a fix-up is added to handle that
// situation, we can remove this check.
if ((DestVecTy != nullptr) != (SrcVecTy != nullptr))
return nullptr;
Value *X;
if (match(TVal, m_OneUse(m_BitCast(m_SpecificType(DestTy, X)))) &&
!isa<Constant>(X)) {
// bitcast(select(Cond, bitcast(X), Y)) --> select'(Cond, X, bitcast(Y))
Value *CastedVal = Builder.CreateBitCast(FVal, DestTy);
return SelectInst::Create(Cond, X, CastedVal, "", nullptr, Sel);
}
if (match(FVal, m_OneUse(m_BitCast(m_SpecificType(DestTy, X)))) &&
!isa<Constant>(X)) {
// bitcast(select(Cond, Y, bitcast(X))) --> select'(Cond, bitcast(Y), X)
Value *CastedVal = Builder.CreateBitCast(TVal, DestTy);
return SelectInst::Create(Cond, CastedVal, X, "", nullptr, Sel);
}
return nullptr;
}
/// Check if all users of CI are StoreInsts.
static bool hasStoreUsersOnly(CastInst &CI) {
for (User *U : CI.users()) {
if (!isa<StoreInst>(U))
return false;
}
return true;
}
/// This function handles following case
///
/// A -> B cast
/// PHI
/// B -> A cast
///
/// All the related PHI nodes can be replaced by new PHI nodes with type A.
/// The uses of \p CI can be changed to the new PHI node corresponding to \p PN.
Instruction *InstCombinerImpl::optimizeBitCastFromPhi(CastInst &CI,
PHINode *PN) {
// BitCast used by Store can be handled in InstCombineLoadStoreAlloca.cpp.
if (hasStoreUsersOnly(CI))
return nullptr;
Value *Src = CI.getOperand(0);
Type *SrcTy = Src->getType(); // Type B
Type *DestTy = CI.getType(); // Type A
SmallVector<PHINode *, 4> PhiWorklist;
SmallSetVector<PHINode *, 4> OldPhiNodes;
// Find all of the A->B casts and PHI nodes.
// We need to inspect all related PHI nodes, but PHIs can be cyclic, so
// OldPhiNodes is used to track all known PHI nodes, before adding a new
// PHI to PhiWorklist, it is checked against and added to OldPhiNodes first.
PhiWorklist.push_back(PN);
OldPhiNodes.insert(PN);
while (!PhiWorklist.empty()) {
auto *OldPN = PhiWorklist.pop_back_val();
for (Value *IncValue : OldPN->incoming_values()) {
if (isa<Constant>(IncValue))
continue;
if (auto *LI = dyn_cast<LoadInst>(IncValue)) {
// If there is a sequence of one or more load instructions, each loaded
// value is used as address of later load instruction, bitcast is
// necessary to change the value type, don't optimize it. For
// simplicity we give up if the load address comes from another load.
Value *Addr = LI->getOperand(0);
if (Addr == &CI || isa<LoadInst>(Addr))
return nullptr;
// Don't tranform "load <256 x i32>, <256 x i32>*" to
// "load x86_amx, x86_amx*", because x86_amx* is invalid.
// TODO: Remove this check when bitcast between vector and x86_amx
// is replaced with a specific intrinsic.
if (DestTy->isX86_AMXTy())
return nullptr;
if (LI->hasOneUse() && LI->isSimple())
continue;
// If a LoadInst has more than one use, changing the type of loaded
// value may create another bitcast.
return nullptr;
}
if (auto *PNode = dyn_cast<PHINode>(IncValue)) {
if (OldPhiNodes.insert(PNode))
PhiWorklist.push_back(PNode);
continue;
}
auto *BCI = dyn_cast<BitCastInst>(IncValue);
// We can't handle other instructions.
if (!BCI)
return nullptr;
// Verify it's a A->B cast.
Type *TyA = BCI->getOperand(0)->getType();
Type *TyB = BCI->getType();
if (TyA != DestTy || TyB != SrcTy)
return nullptr;
}
}
// Check that each user of each old PHI node is something that we can
// rewrite, so that all of the old PHI nodes can be cleaned up afterwards.
for (auto *OldPN : OldPhiNodes) {
for (User *V : OldPN->users()) {
if (auto *SI = dyn_cast<StoreInst>(V)) {
if (!SI->isSimple() || SI->getOperand(0) != OldPN)
return nullptr;
} else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
// Verify it's a B->A cast.
Type *TyB = BCI->getOperand(0)->getType();
Type *TyA = BCI->getType();
if (TyA != DestTy || TyB != SrcTy)
return nullptr;
} else if (auto *PHI = dyn_cast<PHINode>(V)) {
// As long as the user is another old PHI node, then even if we don't
// rewrite it, the PHI web we're considering won't have any users
// outside itself, so it'll be dead.
if (!OldPhiNodes.contains(PHI))
return nullptr;
} else {
return nullptr;
}
}
}
// For each old PHI node, create a corresponding new PHI node with a type A.
SmallDenseMap<PHINode *, PHINode *> NewPNodes;
for (auto *OldPN : OldPhiNodes) {
Builder.SetInsertPoint(OldPN);
PHINode *NewPN = Builder.CreatePHI(DestTy, OldPN->getNumOperands());
NewPNodes[OldPN] = NewPN;
}
// Fill in the operands of new PHI nodes.
for (auto *OldPN : OldPhiNodes) {
PHINode *NewPN = NewPNodes[OldPN];
for (unsigned j = 0, e = OldPN->getNumOperands(); j != e; ++j) {
Value *V = OldPN->getOperand(j);
Value *NewV = nullptr;
if (auto *C = dyn_cast<Constant>(V)) {
NewV = ConstantExpr::getBitCast(C, DestTy);
} else if (auto *LI = dyn_cast<LoadInst>(V)) {
// Explicitly perform load combine to make sure no opposing transform
// can remove the bitcast in the meantime and trigger an infinite loop.
Builder.SetInsertPoint(LI);
NewV = combineLoadToNewType(*LI, DestTy);
// Remove the old load and its use in the old phi, which itself becomes
// dead once the whole transform finishes.
replaceInstUsesWith(*LI, PoisonValue::get(LI->getType()));
eraseInstFromFunction(*LI);
} else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
NewV = BCI->getOperand(0);
} else if (auto *PrevPN = dyn_cast<PHINode>(V)) {
NewV = NewPNodes[PrevPN];
}
assert(NewV);
NewPN->addIncoming(NewV, OldPN->getIncomingBlock(j));
}
}
// Traverse all accumulated PHI nodes and process its users,
// which are Stores and BitcCasts. Without this processing
// NewPHI nodes could be replicated and could lead to extra
// moves generated after DeSSA.
// If there is a store with type B, change it to type A.
// Replace users of BitCast B->A with NewPHI. These will help
// later to get rid off a closure formed by OldPHI nodes.
Instruction *RetVal = nullptr;
for (auto *OldPN : OldPhiNodes) {
PHINode *NewPN = NewPNodes[OldPN];
for (User *V : make_early_inc_range(OldPN->users())) {
if (auto *SI = dyn_cast<StoreInst>(V)) {
assert(SI->isSimple() && SI->getOperand(0) == OldPN);
Builder.SetInsertPoint(SI);
auto *NewBC =
cast<BitCastInst>(Builder.CreateBitCast(NewPN, SrcTy));
SI->setOperand(0, NewBC);
Worklist.push(SI);
assert(hasStoreUsersOnly(*NewBC));
}
else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
Type *TyB = BCI->getOperand(0)->getType();
Type *TyA = BCI->getType();
assert(TyA == DestTy && TyB == SrcTy);
(void) TyA;
(void) TyB;
Instruction *I = replaceInstUsesWith(*BCI, NewPN);
if (BCI == &CI)
RetVal = I;
} else if (auto *PHI = dyn_cast<PHINode>(V)) {
assert(OldPhiNodes.contains(PHI));
(void) PHI;
} else {
llvm_unreachable("all uses should be handled");
}
}
}
return RetVal;
}
/// Fold (bitcast (or (and (bitcast X to int), signmask), nneg Y) to fp) to
/// copysign((bitcast Y to fp), X)
static Value *foldCopySignIdioms(BitCastInst &CI,
InstCombiner::BuilderTy &Builder,
const SimplifyQuery &SQ) {
Value *X, *Y;
Type *FTy = CI.getType();
if (!FTy->isFPOrFPVectorTy())
return nullptr;
if (!match(&CI, m_ElementWiseBitCast(m_c_Or(
m_And(m_ElementWiseBitCast(m_Value(X)), m_SignMask()),
m_Value(Y)))))
return nullptr;
if (X->getType() != FTy)
return nullptr;
if (!isKnownNonNegative(Y, SQ))
return nullptr;
return Builder.CreateCopySign(Builder.CreateBitCast(Y, FTy), X);
}
Instruction *InstCombinerImpl::visitBitCast(BitCastInst &CI) {
// If the operands are integer typed then apply the integer transforms,
// otherwise just apply the common ones.
Value *Src = CI.getOperand(0);
Type *SrcTy = Src->getType();
Type *DestTy = CI.getType();
// Get rid of casts from one type to the same type. These are useless and can
// be replaced by the operand.
if (DestTy == Src->getType())
return replaceInstUsesWith(CI, Src);
if (isa<FixedVectorType>(DestTy)) {
if (isa<IntegerType>(SrcTy)) {
// If this is a cast from an integer to vector, check to see if the input
// is a trunc or zext of a bitcast from vector. If so, we can replace all
// the casts with a shuffle and (potentially) a bitcast.
if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) {
CastInst *SrcCast = cast<CastInst>(Src);
if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0)))
if (isa<VectorType>(BCIn->getOperand(0)->getType()))
if (Instruction *I = optimizeVectorResizeWithIntegerBitCasts(
BCIn->getOperand(0), cast<VectorType>(DestTy), *this))
return I;
}
// If the input is an 'or' instruction, we may be doing shifts and ors to
// assemble the elements of the vector manually. Try to rip the code out
// and replace it with insertelements.
if (Value *V = optimizeIntegerToVectorInsertions(CI, *this))
return replaceInstUsesWith(CI, V);
}
}
if (FixedVectorType *SrcVTy = dyn_cast<FixedVectorType>(SrcTy)) {
if (SrcVTy->getNumElements() == 1) {
// If our destination is not a vector, then make this a straight
// scalar-scalar cast.
if (!DestTy->isVectorTy()) {
Value *Elem = Builder.CreateExtractElement(Src, uint64_t{0});
return CastInst::Create(Instruction::BitCast, Elem, DestTy);
}
// Otherwise, see if our source is an insert. If so, then use the scalar
// component directly:
// bitcast (inselt <1 x elt> V, X, 0) to <n x m> --> bitcast X to <n x m>
if (auto *InsElt = dyn_cast<InsertElementInst>(Src))
return new BitCastInst(InsElt->getOperand(1), DestTy);
}
// Convert an artificial vector insert into more analyzable bitwise logic.
unsigned BitWidth = DestTy->getScalarSizeInBits();
Value *X, *Y;
uint64_t IndexC;
if (match(Src, m_OneUse(m_InsertElt(
m_OneUse(m_BitCast(m_SpecificType(DestTy, X))),
m_Value(Y), m_ConstantInt(IndexC)))) &&
DestTy->isIntegerTy() && Y->getType()->isIntegerTy() &&
isDesirableIntType(BitWidth)) {
// Adjust for big endian - the LSBs are at the high index.
if (DL.isBigEndian())
IndexC = SrcVTy->getNumElements() - 1 - IndexC;
// We only handle (endian-normalized) insert to index 0. Any other insert
// would require a left-shift, so that is an extra instruction.
if (IndexC == 0) {
// bitcast (inselt (bitcast X), Y, 0) --> or (and X, MaskC), (zext Y)
unsigned EltWidth = Y->getType()->getScalarSizeInBits();
APInt MaskC = APInt::getHighBitsSet(BitWidth, BitWidth - EltWidth);
Value *AndX = Builder.CreateAnd(X, MaskC);
Value *ZextY = Builder.CreateZExt(Y, DestTy);
return BinaryOperator::CreateOr(AndX, ZextY);
}
}
}
if (auto *Shuf = dyn_cast<ShuffleVectorInst>(Src)) {
// Okay, we have (bitcast (shuffle ..)). Check to see if this is
// a bitcast to a vector with the same # elts.
Value *ShufOp0 = Shuf->getOperand(0);
Value *ShufOp1 = Shuf->getOperand(1);
auto ShufElts = cast<VectorType>(Shuf->getType())->getElementCount();
auto SrcVecElts = cast<VectorType>(ShufOp0->getType())->getElementCount();
if (Shuf->hasOneUse() && DestTy->isVectorTy() &&
cast<VectorType>(DestTy)->getElementCount() == ShufElts &&
ShufElts == SrcVecElts) {
BitCastInst *Tmp;
// If either of the operands is a cast from CI.getType(), then
// evaluating the shuffle in the casted destination's type will allow
// us to eliminate at least one cast.
if (((Tmp = dyn_cast<BitCastInst>(ShufOp0)) &&
Tmp->getOperand(0)->getType() == DestTy) ||
((Tmp = dyn_cast<BitCastInst>(ShufOp1)) &&
Tmp->getOperand(0)->getType() == DestTy)) {
Value *LHS = Builder.CreateBitCast(ShufOp0, DestTy);
Value *RHS = Builder.CreateBitCast(ShufOp1, DestTy);
// Return a new shuffle vector. Use the same element ID's, as we
// know the vector types match #elts.
return new ShuffleVectorInst(LHS, RHS, Shuf->getShuffleMask());
}
}
// A bitcasted-to-scalar and byte/bit reversing shuffle is better recognized
// as a byte/bit swap:
// bitcast <N x i8> (shuf X, undef, <N, N-1,...0>) -> bswap (bitcast X)
// bitcast <N x i1> (shuf X, undef, <N, N-1,...0>) -> bitreverse (bitcast X)
if (DestTy->isIntegerTy() && ShufElts.getKnownMinValue() % 2 == 0 &&
Shuf->hasOneUse() && Shuf->isReverse() && match(ShufOp1, m_Poison())) {
unsigned IntrinsicNum = 0;
if (DL.isLegalInteger(DestTy->getScalarSizeInBits()) &&
SrcTy->getScalarSizeInBits() == 8) {
IntrinsicNum = Intrinsic::bswap;
} else if (SrcTy->getScalarSizeInBits() == 1) {
IntrinsicNum = Intrinsic::bitreverse;
}
if (IntrinsicNum != 0) {
assert(ShufOp0->getType() == SrcTy && "Unexpected shuffle mask");
Function *BswapOrBitreverse = Intrinsic::getOrInsertDeclaration(
CI.getModule(), IntrinsicNum, DestTy);
Value *ScalarX = Builder.CreateBitCast(ShufOp0, DestTy);
return CallInst::Create(BswapOrBitreverse, {ScalarX});
}
}
}
// Handle the A->B->A cast, and there is an intervening PHI node.
if (PHINode *PN = dyn_cast<PHINode>(Src))
if (Instruction *I = optimizeBitCastFromPhi(CI, PN))
return I;
if (Instruction *I = canonicalizeBitCastExtElt(CI, *this))
return I;
if (Instruction *I = foldBitCastBitwiseLogic(CI, Builder))
return I;
if (Instruction *I = foldBitCastSelect(CI, Builder))
return I;
if (Value *V = foldCopySignIdioms(CI, Builder, SQ.getWithInstruction(&CI)))
return replaceInstUsesWith(CI, V);
return commonCastTransforms(CI);
}
Instruction *InstCombinerImpl::visitAddrSpaceCast(AddrSpaceCastInst &CI) {
return commonCastTransforms(CI);
}