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Diffstat (limited to 'contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp')
| -rw-r--r-- | contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 2691 |
1 files changed, 2691 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp new file mode 100644 index 000000000000..3639edb5df4d --- /dev/null +++ b/contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -0,0 +1,2691 @@ +//===- 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/SetVector.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/DIBuilder.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/Support/KnownBits.h" +#include <numeric> +using namespace llvm; +using namespace PatternMatch; + +#define DEBUG_TYPE "instcombine" + +/// Analyze 'Val', seeing if it is a simple linear expression. +/// If so, decompose it, returning some value X, such that Val is +/// X*Scale+Offset. +/// +static Value *decomposeSimpleLinearExpr(Value *Val, unsigned &Scale, + uint64_t &Offset) { + if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) { + Offset = CI->getZExtValue(); + Scale = 0; + return ConstantInt::get(Val->getType(), 0); + } + + if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) { + // Cannot look past anything that might overflow. + OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val); + if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) { + Scale = 1; + Offset = 0; + return Val; + } + + if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { + if (I->getOpcode() == Instruction::Shl) { + // This is a value scaled by '1 << the shift amt'. + Scale = UINT64_C(1) << RHS->getZExtValue(); + Offset = 0; + return I->getOperand(0); + } + + if (I->getOpcode() == Instruction::Mul) { + // This value is scaled by 'RHS'. + Scale = RHS->getZExtValue(); + Offset = 0; + return I->getOperand(0); + } + + if (I->getOpcode() == Instruction::Add) { + // We have X+C. Check to see if we really have (X*C2)+C1, + // where C1 is divisible by C2. + unsigned SubScale; + Value *SubVal = + decomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset); + Offset += RHS->getZExtValue(); + Scale = SubScale; + return SubVal; + } + } + } + + // Otherwise, we can't look past this. + Scale = 1; + Offset = 0; + return Val; +} + +/// If we find a cast of an allocation instruction, try to eliminate the cast by +/// moving the type information into the alloc. +Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI, + AllocaInst &AI) { + PointerType *PTy = cast<PointerType>(CI.getType()); + + IRBuilderBase::InsertPointGuard Guard(Builder); + Builder.SetInsertPoint(&AI); + + // Get the type really allocated and the type casted to. + Type *AllocElTy = AI.getAllocatedType(); + Type *CastElTy = PTy->getElementType(); + if (!AllocElTy->isSized() || !CastElTy->isSized()) return nullptr; + + Align AllocElTyAlign = DL.getABITypeAlign(AllocElTy); + Align CastElTyAlign = DL.getABITypeAlign(CastElTy); + if (CastElTyAlign < AllocElTyAlign) return nullptr; + + // If the allocation has multiple uses, only promote it if we are strictly + // increasing the alignment of the resultant allocation. If we keep it the + // same, we open the door to infinite loops of various kinds. + if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return nullptr; + + uint64_t AllocElTySize = DL.getTypeAllocSize(AllocElTy); + uint64_t CastElTySize = DL.getTypeAllocSize(CastElTy); + if (CastElTySize == 0 || AllocElTySize == 0) return nullptr; + + // If the allocation has multiple uses, only promote it if we're not + // shrinking the amount of memory being allocated. + uint64_t AllocElTyStoreSize = DL.getTypeStoreSize(AllocElTy); + uint64_t CastElTyStoreSize = DL.getTypeStoreSize(CastElTy); + if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return nullptr; + + // See if we can satisfy the modulus by pulling a scale out of the array + // size argument. + unsigned ArraySizeScale; + uint64_t ArrayOffset; + Value *NumElements = // See if the array size is a decomposable linear expr. + decomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset); + + // If we can now satisfy the modulus, by using a non-1 scale, we really can + // do the xform. + if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 || + (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return nullptr; + + unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize; + Value *Amt = nullptr; + if (Scale == 1) { + Amt = NumElements; + } else { + Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale); + // Insert before the alloca, not before the cast. + Amt = Builder.CreateMul(Amt, NumElements); + } + + if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) { + Value *Off = ConstantInt::get(AI.getArraySize()->getType(), + Offset, true); + Amt = Builder.CreateAdd(Amt, Off); + } + + AllocaInst *New = Builder.CreateAlloca(CastElTy, Amt); + New->setAlignment(AI.getAlign()); + New->takeName(&AI); + New->setUsedWithInAlloca(AI.isUsedWithInAlloca()); + + // If the allocation has multiple real uses, insert a cast and change all + // things that used it to use the new cast. This will also hack on CI, but it + // will die soon. + if (!AI.hasOneUse()) { + // New is the allocation instruction, pointer typed. AI is the original + // allocation instruction, also pointer typed. Thus, cast to use is BitCast. + Value *NewCast = Builder.CreateBitCast(New, AI.getType(), "tmpcast"); + replaceInstUsesWith(AI, NewCast); + eraseInstFromFunction(AI); + } + return replaceInstUsesWith(CI, New); +} + +/// Given an expression that CanEvaluateTruncated or CanEvaluateSExtd returns +/// true for, actually insert the code to evaluate the expression. +Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty, + bool isSigned) { + if (Constant *C = dyn_cast<Constant>(V)) { + C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/); + // If we got a constantexpr back, try to simplify it with DL info. + return ConstantFoldConstant(C, DL, &TLI); + } + + // 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 = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned); + Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); + Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS); + 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); + break; + case Instruction::Select: { + Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); + Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned); + 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 = + EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned); + NPN->addIncoming(V, OPN->getIncomingBlock(i)); + } + Res = NPN; + break; + } + default: + // TODO: Can handle more cases here. + llvm_unreachable("Unreachable!"); + } + + Res->takeName(I); + return InsertNewInstWith(Res, *I); +} + +Instruction::CastOps InstCombiner::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 *MidIntPtrTy = + MidTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(MidTy) : nullptr; + Type *DstIntPtrTy = + DstTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(DstTy) : nullptr; + unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, + DstTy, SrcIntPtrTy, MidIntPtrTy, + DstIntPtrTy); + + // 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 *InstCombiner::commonCastTransforms(CastInst &CI) { + Value *Src = CI.getOperand(0); + + // 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 *Ty = CI.getType(); + 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. + auto *Cmp = dyn_cast<CmpInst>(Sel->getCondition()); + if (!Cmp || Cmp->getOperand(0)->getType() != Sel->getType() || + (CI.getOpcode() == Instruction::Trunc && + shouldChangeType(CI.getSrcTy(), CI.getType()))) { + 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; + } + + return nullptr; +} + +/// Constants and extensions/truncates from the destination type are always +/// free to be evaluated in that type. This is a helper for canEvaluate*. +static bool canAlwaysEvaluateInType(Value *V, Type *Ty) { + if (isa<Constant>(V)) + return true; + Value *X; + if ((match(V, m_ZExtOrSExt(m_Value(X))) || match(V, m_Trunc(m_Value(X)))) && + X->getType() == Ty) + return true; + + return false; +} + +/// Filter out values that we can not evaluate in the destination type for free. +/// This is a helper for canEvaluate*. +static bool canNotEvaluateInType(Value *V, Type *Ty) { + assert(!isa<Constant>(V) && "Constant should already be handled."); + 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. +/// +static bool canEvaluateTruncated(Value *V, Type *Ty, InstCombiner &IC, + Instruction *CxtI) { + if (canAlwaysEvaluateInType(V, Ty)) + return true; + if (canNotEvaluateInType(V, Ty)) + return false; + + 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 canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) && + canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI); + + 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); + if (IC.MaskedValueIsZero(I->getOperand(0), Mask, 0, CxtI) && + IC.MaskedValueIsZero(I->getOperand(1), Mask, 0, CxtI)) { + return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) && + canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI); + } + 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 canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) && + canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI); + 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 = + llvm::computeKnownBits(I->getOperand(1), IC.getDataLayout()); + APInt ShiftedBits = APInt::getBitsSetFrom(OrigBitWidth, BitWidth); + if (AmtKnownBits.getMaxValue().ult(BitWidth) && + IC.MaskedValueIsZero(I->getOperand(0), ShiftedBits, 0, CxtI)) { + return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) && + canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI); + } + 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), 0, CxtI)) + return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) && + canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI); + 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 canEvaluateTruncated(SI->getTrueValue(), Ty, IC, CxtI) && + canEvaluateTruncated(SI->getFalseValue(), Ty, IC, CxtI); + } + 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); + for (Value *IncValue : PN->incoming_values()) + if (!canEvaluateTruncated(IncValue, Ty, IC, CxtI)) + return false; + return true; + } + 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, InstCombiner &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)); +} + +/// 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 *InstCombiner::narrowRotate(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(); + if (!isPowerOf2_32(NarrowWidth)) + return nullptr; + + // First, find an or'd pair of opposite shifts with the same shifted operand: + // trunc (or (lshr ShVal, ShAmt0), (shl ShVal, ShAmt1)) + Value *Or0, *Or1; + if (!match(Trunc.getOperand(0), m_OneUse(m_Or(m_Value(Or0), m_Value(Or1))))) + return nullptr; + + Value *ShVal, *ShAmt0, *ShAmt1; + if (!match(Or0, m_OneUse(m_LogicalShift(m_Value(ShVal), m_Value(ShAmt0)))) || + !match(Or1, m_OneUse(m_LogicalShift(m_Specific(ShVal), m_Value(ShAmt1))))) + return nullptr; + + auto ShiftOpcode0 = cast<BinaryOperator>(Or0)->getOpcode(); + auto ShiftOpcode1 = cast<BinaryOperator>(Or1)->getOpcode(); + if (ShiftOpcode0 == ShiftOpcode1) + return nullptr; + + // Match the shift amount operands for a 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 ShVal, L) | (lshr ShVal, Width - L) + if (match(R, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(L))))) + return L; + + // The shift amount may be masked with negation: + // (shl ShVal, (X & (Width - 1))) | (lshr ShVal, ((-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 SubIsOnLHS = false; + if (!ShAmt) { + ShAmt = matchShiftAmount(ShAmt1, ShAmt0, NarrowWidth); + SubIsOnLHS = true; + } + if (!ShAmt) + return nullptr; + + // The shifted value must have high zeros in the wide type. Typically, this + // will be a zext, but it could also be the result of an 'and' or 'shift'. + unsigned WideWidth = Trunc.getSrcTy()->getScalarSizeInBits(); + APInt HiBitMask = APInt::getHighBitsSet(WideWidth, WideWidth - NarrowWidth); + if (!MaskedValueIsZero(ShVal, HiBitMask, 0, &Trunc)) + return nullptr; + + // We have an unnecessarily wide rotate! + // trunc (or (lshr ShVal, ShAmt), (shl ShVal, BitWidth - ShAmt)) + // Narrow the inputs and convert to funnel shift intrinsic: + // llvm.fshl.i8(trunc(ShVal), trunc(ShVal), trunc(ShAmt)) + Value *NarrowShAmt = Builder.CreateTrunc(ShAmt, DestTy); + Value *X = Builder.CreateTrunc(ShVal, DestTy); + bool IsFshl = (!SubIsOnLHS && ShiftOpcode0 == BinaryOperator::Shl) || + (SubIsOnLHS && ShiftOpcode1 == BinaryOperator::Shl); + Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr; + Function *F = Intrinsic::getDeclaration(Trunc.getModule(), IID, DestTy); + return IntrinsicInst::Create(F, { X, X, NarrowShAmt }); +} + +/// Try to narrow the width of math or bitwise logic instructions by pulling a +/// truncate ahead of binary operators. +/// TODO: Transforms for truncated shifts should be moved into here. +Instruction *InstCombiner::narrowBinOp(TruncInst &Trunc) { + Type *SrcTy = Trunc.getSrcTy(); + Type *DestTy = Trunc.getType(); + 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_Value(X))) && X->getType() == DestTy) { + // 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_Value(X))) && X->getType() == DestTy) { + // trunc (binop Y, (ext X)) --> binop (trunc Y), X + Value *NarrowOp0 = Builder.CreateTrunc(BinOp0, DestTy); + return BinaryOperator::Create(BinOp->getOpcode(), NarrowOp0, X); + } + break; + } + + default: break; + } + + if (Instruction *NarrowOr = narrowRotate(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) { + auto *Shuf = dyn_cast<ShuffleVectorInst>(Trunc.getOperand(0)); + if (Shuf && Shuf->hasOneUse() && isa<UndefValue>(Shuf->getOperand(1)) && + is_splat(Shuf->getShuffleMask()) && + Shuf->getType() == Shuf->getOperand(0)->getType()) { + // trunc (shuf X, Undef, SplatMask) --> shuf (trunc X), Undef, SplatMask + Constant *NarrowUndef = UndefValue::get(Trunc.getType()); + Value *NarrowOp = Builder.CreateTrunc(Shuf->getOperand(0), Trunc.getType()); + return new ShuffleVectorInst(NarrowOp, NarrowUndef, Shuf->getShuffleMask()); + } + + 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 undef 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"); + + auto *InsElt = dyn_cast<InsertElementInst>(Trunc.getOperand(0)); + if (!InsElt || !InsElt->hasOneUse()) + return nullptr; + + Type *DestTy = Trunc.getType(); + Type *DestScalarTy = DestTy->getScalarType(); + Value *VecOp = InsElt->getOperand(0); + Value *ScalarOp = InsElt->getOperand(1); + Value *Index = InsElt->getOperand(2); + + if (isa<UndefValue>(VecOp)) { + // trunc (inselt undef, X, Index) --> inselt undef, (trunc X), Index + // fptrunc (inselt undef, X, Index) --> inselt undef, (fptrunc X), Index + UndefValue *NarrowUndef = UndefValue::get(DestTy); + Value *NarrowOp = Builder.CreateCast(Opcode, ScalarOp, DestScalarTy); + return InsertElementInst::Create(NarrowUndef, NarrowOp, Index); + } + + return nullptr; +} + +Instruction *InstCombiner::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(); + ConstantInt *Cst; + + // 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)) && + 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) && + 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); + } + } + } + + // Test if the trunc is the user of a select which is part of a + // minimum or maximum operation. If so, don't do any more simplification. + // Even simplifying demanded bits can break the canonical form of a + // min/max. + Value *LHS, *RHS; + if (SelectInst *Sel = dyn_cast<SelectInst>(Src)) + if (matchSelectPattern(Sel, LHS, RHS).Flavor != SPF_UNKNOWN) + return nullptr; + + // 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); + if (DestTy->isIntegerTy()) { + // Canonicalize trunc x to i1 -> icmp ne (and x, 1), 0 (scalar only). + // TODO: We canonicalize to more instructions here because we are probably + // lacking equivalent analysis for trunc relative to icmp. There may also + // be codegen concerns. If those trunc limitations were removed, we could + // remove this transform. + Value *And = Builder.CreateAnd(Src, ConstantInt::get(SrcTy, 1)); + return new ICmpInst(ICmpInst::ICMP_NE, And, Zero); + } + + // For vectors, we do not canonicalize all truncs to icmp, so optimize + // patterns that would be covered within visitICmpInst. + Value *X; + Constant *C; + if (match(Src, m_OneUse(m_LShr(m_Value(X), m_Constant(C))))) { + // trunc (lshr X, C) to i1 --> icmp ne (and X, C'), 0 + Constant *One = ConstantInt::get(SrcTy, APInt(SrcWidth, 1)); + Constant *MaskC = ConstantExpr::getShl(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_Constant(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)); + Constant *MaskC = ConstantExpr::getShl(One, C); + MaskC = ConstantExpr::getOr(MaskC, One); + Value *And = Builder.CreateAnd(X, MaskC); + return new ICmpInst(ICmpInst::ICMP_NE, And, Zero); + } + } + + // FIXME: Maybe combine the next two transforms to handle the no cast case + // more efficiently. Support vector types. Cleanup code by using m_OneUse. + + // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion. + Value *A = nullptr; + if (Src->hasOneUse() && + match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) { + // We have three types to worry about here, the type of A, the source of + // the truncate (MidSize), and the destination of the truncate. We know that + // ASize < MidSize and MidSize > ResultSize, but don't know the relation + // between ASize and ResultSize. + unsigned ASize = A->getType()->getPrimitiveSizeInBits(); + + // If the shift amount is larger than the size of A, then the result is + // known to be zero because all the input bits got shifted out. + if (Cst->getZExtValue() >= ASize) + return replaceInstUsesWith(Trunc, Constant::getNullValue(DestTy)); + + // Since we're doing an lshr and a zero extend, and know that the shift + // amount is smaller than ASize, it is always safe to do the shift in A's + // type, then zero extend or truncate to the result. + Value *Shift = Builder.CreateLShr(A, Cst->getZExtValue()); + Shift->takeName(Src); + return CastInst::CreateIntegerCast(Shift, DestTy, false); + } + + const APInt *C; + if (match(Src, m_LShr(m_SExt(m_Value(A)), m_APInt(C)))) { + unsigned AWidth = A->getType()->getScalarSizeInBits(); + unsigned MaxShiftAmt = SrcWidth - std::max(DestWidth, AWidth); + + // If the shift is small enough, all zero bits created by the shift are + // removed by the trunc. + if (C->getZExtValue() <= MaxShiftAmt) { + // trunc (lshr (sext A), C) --> ashr A, C + if (A->getType() == DestTy) { + unsigned ShAmt = std::min((unsigned)C->getZExtValue(), DestWidth - 1); + return BinaryOperator::CreateAShr(A, ConstantInt::get(DestTy, ShAmt)); + } + // The types are mismatched, so create a cast after shifting: + // trunc (lshr (sext A), C) --> sext/trunc (ashr A, C) + if (Src->hasOneUse()) { + unsigned ShAmt = std::min((unsigned)C->getZExtValue(), AWidth - 1); + Value *Shift = Builder.CreateAShr(A, ShAmt); + 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<IntegerType>(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_ConstantInt(Cst))) && + !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. + if (Cst->getValue().ult(DestWidth)) { + Value *NewTrunc = Builder.CreateTrunc(A, DestTy, A->getName() + ".tr"); + + return BinaryOperator::Create( + Instruction::Shl, NewTrunc, + ConstantInt::get(DestTy, Cst->getValue().trunc(DestWidth))); + } + } + } + + if (Instruction *I = foldVecTruncToExtElt(Trunc, *this)) + return I; + + // Whenever an element is extracted from a vector, and then truncated, + // canonicalize by converting it to a bitcast followed by an + // extractelement. + // + // Example (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 + Value *VecOp; + if (match(Src, m_OneUse(m_ExtractElt(m_Value(VecOp), m_ConstantInt(Cst))))) { + auto *VecOpTy = cast<VectorType>(VecOp->getType()); + unsigned VecNumElts = VecOpTy->getNumElements(); + + // A badly fit destination size would result in an invalid cast. + if (SrcWidth % DestWidth == 0) { + uint64_t TruncRatio = SrcWidth / DestWidth; + uint64_t BitCastNumElts = VecNumElts * TruncRatio; + uint64_t VecOpIdx = Cst->getZExtValue(); + uint64_t NewIdx = DL.isBigEndian() ? (VecOpIdx + 1) * TruncRatio - 1 + : VecOpIdx * TruncRatio; + assert(BitCastNumElts <= std::numeric_limits<uint32_t>::max() && + "overflow 32-bits"); + + auto *BitCastTo = FixedVectorType::get(DestTy, BitCastNumElts); + Value *BitCast = Builder.CreateBitCast(VecOp, BitCastTo); + return ExtractElementInst::Create(BitCast, Builder.getInt32(NewIdx)); + } + } + + return nullptr; +} + +Instruction *InstCombiner::transformZExtICmp(ICmpInst *Cmp, ZExtInst &Zext, + bool DoTransform) { + // 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. + const APInt *Op1CV; + if (match(Cmp->getOperand(1), m_APInt(Op1CV))) { + + // zext (x <s 0) to i32 --> x>>u31 true if signbit set. + // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear. + if ((Cmp->getPredicate() == ICmpInst::ICMP_SLT && Op1CV->isNullValue()) || + (Cmp->getPredicate() == ICmpInst::ICMP_SGT && Op1CV->isAllOnesValue())) { + if (!DoTransform) return Cmp; + + 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*/); + + if (Cmp->getPredicate() == ICmpInst::ICMP_SGT) { + Constant *One = ConstantInt::get(In->getType(), 1); + In = Builder.CreateXor(In, One, In->getName() + ".not"); + } + + 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 == 1) to i32 --> X iff X has only the low bit set. + // zext (X == 2) to i32 --> X>>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. + // zext (X != 1) to i32 --> X^1 iff X has only the low bit set. + // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. + if ((Op1CV->isNullValue() || Op1CV->isPowerOf2()) && + // This only works for EQ and NE + Cmp->isEquality()) { + // If Op1C some other power of two, convert: + KnownBits Known = computeKnownBits(Cmp->getOperand(0), 0, &Zext); + + APInt KnownZeroMask(~Known.Zero); + if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1? + if (!DoTransform) return Cmp; + + bool isNE = Cmp->getPredicate() == ICmpInst::ICMP_NE; + if (!Op1CV->isNullValue() && (*Op1CV != KnownZeroMask)) { + // (X&4) == 2 --> false + // (X&4) != 2 --> true + Constant *Res = ConstantInt::get(Zext.getType(), isNE); + return replaceInstUsesWith(Zext, Res); + } + + uint32_t ShAmt = KnownZeroMask.logBase2(); + 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"); + } + + if (!Op1CV->isNullValue() == isNE) { // Toggle the low bit. + Constant *One = ConstantInt::get(In->getType(), 1); + In = Builder.CreateXor(In, One); + } + + if (Zext.getType() == In->getType()) + return replaceInstUsesWith(Zext, In); + + Value *IntCast = Builder.CreateIntCast(In, Zext.getType(), false); + return replaceInstUsesWith(Zext, IntCast); + } + } + } + + // icmp ne A, B is equal to xor A, B when A and B only really have one bit. + // It is also profitable to transform icmp eq into not(xor(A, B)) because that + // may lead to additional simplifications. + if (Cmp->isEquality() && Zext.getType() == Cmp->getOperand(0)->getType()) { + if (IntegerType *ITy = dyn_cast<IntegerType>(Zext.getType())) { + Value *LHS = Cmp->getOperand(0); + Value *RHS = Cmp->getOperand(1); + + KnownBits KnownLHS = computeKnownBits(LHS, 0, &Zext); + KnownBits KnownRHS = computeKnownBits(RHS, 0, &Zext); + + if (KnownLHS.Zero == KnownRHS.Zero && KnownLHS.One == KnownRHS.One) { + APInt KnownBits = KnownLHS.Zero | KnownLHS.One; + APInt UnknownBit = ~KnownBits; + if (UnknownBit.countPopulation() == 1) { + if (!DoTransform) return Cmp; + + Value *Result = Builder.CreateXor(LHS, RHS); + + // Mask off any bits that are set and won't be shifted away. + if (KnownLHS.One.uge(UnknownBit)) + Result = Builder.CreateAnd(Result, + ConstantInt::get(ITy, UnknownBit)); + + // Shift the bit we're testing down to the lsb. + Result = Builder.CreateLShr( + Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros())); + + if (Cmp->getPredicate() == ICmpInst::ICMP_EQ) + Result = Builder.CreateXor(Result, ConstantInt::get(ITy, 1)); + Result->takeName(Cmp); + return replaceInstUsesWith(Zext, Result); + } + } + } + } + + 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. +static bool canEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear, + InstCombiner &IC, Instruction *CxtI) { + BitsToClear = 0; + if (canAlwaysEvaluateInType(V, Ty)) + return true; + 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 (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI) || + !canEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI)) + 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), + 0, CxtI)) { + // 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. + const APInt *Amt; + if (match(I->getOperand(1), m_APInt(Amt))) { + if (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI)) + return false; + uint64_t ShiftAmt = Amt->getZExtValue(); + 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. + const APInt *Amt; + if (match(I->getOperand(1), m_APInt(Amt))) { + if (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI)) + return false; + BitsToClear += Amt->getZExtValue(); + if (BitsToClear > V->getType()->getScalarSizeInBits()) + BitsToClear = V->getType()->getScalarSizeInBits(); + return true; + } + // Cannot promote variable LSHR. + return false; + } + case Instruction::Select: + if (!canEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI) || + !canEvaluateZExtd(I->getOperand(2), Ty, BitsToClear, IC, CxtI) || + // 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 (!canEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear, IC, CxtI)) + return false; + for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) + if (!canEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp, IC, CxtI) || + // TODO: If important, we could handle the case when the BitsToClear + // are known zero in the disagreeing input. + Tmp != BitsToClear) + return false; + return true; + } + default: + // TODO: Can handle more cases here. + return false; + } +} + +Instruction *InstCombiner::visitZExt(ZExtInst &CI) { + // If this zero extend is only used by a truncate, let the truncate be + // eliminated before we try to optimize this zext. + if (CI.hasOneUse() && isa<TruncInst>(CI.user_back())) + return nullptr; + + // If one of the common conversion will work, do it. + if (Instruction *Result = commonCastTransforms(CI)) + return Result; + + Value *Src = CI.getOperand(0); + Type *SrcTy = Src->getType(), *DestTy = CI.getType(); + + // Try to extend the entire expression tree to the wide destination type. + unsigned BitsToClear; + if (shouldChangeType(SrcTy, DestTy) && + canEvaluateZExtd(Src, DestTy, BitsToClear, *this, &CI)) { + 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: " + << CI << '\n'); + Value *Res = EvaluateInDifferentType(Src, DestTy, false); + 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, CI, 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 (MaskedValueIsZero(Res, + APInt::getHighBitsSet(DestBitSize, + DestBitSize-SrcBitsKept), + 0, &CI)) + return replaceInstUsesWith(CI, 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 (TruncInst *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 = CI.getType()->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, CI.getType()); + } + + 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, CI.getType()); + APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize)); + return BinaryOperator::CreateAnd(Trunc, + ConstantInt::get(Trunc->getType(), + AndValue)); + } + } + + if (ICmpInst *Cmp = dyn_cast<ICmpInst>(Src)) + return transformZExtICmp(Cmp, CI); + + BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src); + if (SrcI && SrcI->getOpcode() == Instruction::Or) { + // zext (or icmp, icmp) -> or (zext icmp), (zext icmp) if at least one + // of the (zext icmp) can be eliminated. If so, immediately perform the + // according elimination. + ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0)); + ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1)); + if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() && + (transformZExtICmp(LHS, CI, false) || + transformZExtICmp(RHS, CI, false))) { + // zext (or icmp, icmp) -> or (zext icmp), (zext icmp) + Value *LCast = Builder.CreateZExt(LHS, CI.getType(), LHS->getName()); + Value *RCast = Builder.CreateZExt(RHS, CI.getType(), RHS->getName()); + Value *Or = Builder.CreateOr(LCast, RCast, CI.getName()); + if (auto *OrInst = dyn_cast<Instruction>(Or)) + Builder.SetInsertPoint(OrInst); + + // Perform the elimination. + if (auto *LZExt = dyn_cast<ZExtInst>(LCast)) + transformZExtICmp(LHS, *LZExt); + if (auto *RZExt = dyn_cast<ZExtInst>(RCast)) + transformZExtICmp(RHS, *RZExt); + + return replaceInstUsesWith(CI, Or); + } + } + + // zext(trunc(X) & C) -> (X & zext(C)). + Constant *C; + Value *X; + if (SrcI && + match(SrcI, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Constant(C)))) && + X->getType() == CI.getType()) + return BinaryOperator::CreateAnd(X, ConstantExpr::getZExt(C, CI.getType())); + + // zext((trunc(X) & C) ^ C) -> ((X & zext(C)) ^ zext(C)). + Value *And; + if (SrcI && match(SrcI, m_OneUse(m_Xor(m_Value(And), m_Constant(C)))) && + match(And, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Specific(C)))) && + X->getType() == CI.getType()) { + Constant *ZC = ConstantExpr::getZExt(C, CI.getType()); + return BinaryOperator::CreateXor(Builder.CreateAnd(X, ZC), ZC); + } + + return nullptr; +} + +/// Transform (sext icmp) to bitwise / integer operations to eliminate the icmp. +Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) { + Value *Op0 = ICI->getOperand(0), *Op1 = ICI->getOperand(1); + ICmpInst::Predicate Pred = ICI->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())) || + (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))) { + // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if negative + // (x >s -1) ? -1 : 0 -> not (ashr x, 31) -> all ones if positive + Value *Sh = ConstantInt::get(Op0->getType(), + Op0->getType()->getScalarSizeInBits() - 1); + Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit"); + if (In->getType() != CI.getType()) + In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/); + + if (Pred == ICmpInst::ICMP_SGT) + In = Builder.CreateNot(In, In->getName() + ".not"); + return replaceInstUsesWith(CI, 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 (ICI->hasOneUse() && + ICI->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){ + KnownBits Known = computeKnownBits(Op0, 0, &CI); + + APInt KnownZeroMask(~Known.Zero); + if (KnownZeroMask.isPowerOf2()) { + Value *In = ICI->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(CI.getType()) : + ConstantInt::getNullValue(CI.getType()); + return replaceInstUsesWith(CI, 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.countTrailingZeros(); + // 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.countLeadingZeros(); + // 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 (CI.getType() == In->getType()) + return replaceInstUsesWith(CI, In); + return CastInst::CreateIntegerCast(In, CI.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. +/// +static bool canEvaluateSExtd(Value *V, Type *Ty) { + assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() && + "Can't sign extend type to a smaller type"); + if (canAlwaysEvaluateInType(V, Ty)) + return true; + if (canNotEvaluateInType(V, Ty)) + return false; + + 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 canEvaluateSExtd(I->getOperand(0), Ty) && + canEvaluateSExtd(I->getOperand(1), Ty); + + //case Instruction::Shl: TODO + //case Instruction::LShr: TODO + + case Instruction::Select: + return canEvaluateSExtd(I->getOperand(1), Ty) && + canEvaluateSExtd(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 we only consider + // instructions with a single use. + PHINode *PN = cast<PHINode>(I); + for (Value *IncValue : PN->incoming_values()) + if (!canEvaluateSExtd(IncValue, Ty)) return false; + return true; + } + default: + // TODO: Can handle more cases here. + break; + } + + return false; +} + +Instruction *InstCombiner::visitSExt(SExtInst &CI) { + // If this sign extend is only used by a truncate, let the truncate be + // eliminated before we try to optimize this sext. + if (CI.hasOneUse() && isa<TruncInst>(CI.user_back())) + return nullptr; + + if (Instruction *I = commonCastTransforms(CI)) + return I; + + Value *Src = CI.getOperand(0); + Type *SrcTy = Src->getType(), *DestTy = CI.getType(); + + // If we know that the value being extended is positive, we can use a zext + // instead. + KnownBits Known = computeKnownBits(Src, 0, &CI); + if (Known.isNonNegative()) + return CastInst::Create(Instruction::ZExt, Src, DestTy); + + // Try to extend the entire expression tree to the wide destination type. + if (shouldChangeType(SrcTy, DestTy) && 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: " + << CI << '\n'); + Value *Res = EvaluateInDifferentType(Src, DestTy, true); + assert(Res->getType() == DestTy); + + uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); + uint32_t DestBitSize = DestTy->getScalarSizeInBits(); + + // If the high bits are already filled with sign bit, just replace this + // cast with the result. + if (ComputeNumSignBits(Res, 0, &CI) > DestBitSize - SrcBitSize) + return replaceInstUsesWith(CI, 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); + } + + // If the input is a trunc from the destination type, then turn sext(trunc(x)) + // into shifts. + Value *X; + if (match(Src, m_OneUse(m_Trunc(m_Value(X)))) && X->getType() == DestTy) { + // sext(trunc(X)) --> ashr(shl(X, C), C) + unsigned SrcBitSize = SrcTy->getScalarSizeInBits(); + unsigned DestBitSize = DestTy->getScalarSizeInBits(); + Constant *ShAmt = ConstantInt::get(DestTy, DestBitSize - SrcBitSize); + return BinaryOperator::CreateAShr(Builder.CreateShl(X, ShAmt), ShAmt); + } + + if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) + return transformSExtICmp(ICI, CI); + + // 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, 6 + // %c = ashr i8 %b, 6 + // %d = sext i8 %c to i32 + // into: + // %a = shl i32 %i, 30 + // %d = ashr i32 %a, 30 + 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_Value(A)), m_Constant(BA)), + m_Constant(CA))) && + BA == CA && A->getType() == CI.getType()) { + unsigned MidSize = Src->getType()->getScalarSizeInBits(); + unsigned SrcDstSize = CI.getType()->getScalarSizeInBits(); + Constant *SizeDiff = ConstantInt::get(CA->getType(), SrcDstSize - MidSize); + Constant *ShAmt = ConstantExpr::getAdd(CA, SizeDiff); + Constant *ShAmtExt = ConstantExpr::getSExt(ShAmt, CI.getType()); + A = Builder.CreateShl(A, ShAmtExt, CI.getName()); + return BinaryOperator::CreateAShr(A, ShAmtExt); + } + + 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(ConstantFP *CFP, const fltSemantics &Sem) { + bool losesInfo; + APFloat F = CFP->getValueAPF(); + (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo); + return !losesInfo; +} + +static Type *shrinkFPConstant(ConstantFP *CFP) { + if (CFP->getType() == Type::getPPC_FP128Ty(CFP->getContext())) + return nullptr; // No constant folding of this. + // See if the value can be truncated to half and then reextended. + if (fitsInFPType(CFP, APFloat::IEEEhalf())) + return Type::getHalfTy(CFP->getContext()); + // See if the value can be truncated to float and then reextended. + if (fitsInFPType(CFP, APFloat::IEEEsingle())) + return Type::getFloatTy(CFP->getContext()); + if (CFP->getType()->isDoubleTy()) + return nullptr; // Won't shrink. + if (fitsInFPType(CFP, APFloat::IEEEdouble())) + return Type::getDoubleTy(CFP->getContext()); + // Don't try to shrink to various long double types. + return nullptr; +} + +// Determine if this is a vector of ConstantFPs and if so, return the minimal +// type we can safely truncate all elements to. +// TODO: Make these support undef elements. +static Type *shrinkFPConstantVector(Value *V) { + auto *CV = dyn_cast<Constant>(V); + auto *CVVTy = dyn_cast<VectorType>(V->getType()); + if (!CV || !CVVTy) + return nullptr; + + Type *MinType = nullptr; + + unsigned NumElts = CVVTy->getNumElements(); + for (unsigned i = 0; i != NumElts; ++i) { + auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i)); + if (!CFP) + return nullptr; + + Type *T = shrinkFPConstant(CFP); + 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 FixedVectorType::get(MinType, NumElts); +} + +/// Find the minimum FP type we can safely truncate to. +static Type *getMinimumFPType(Value *V) { + if (auto *FPExt = dyn_cast<FPExtInst>(V)) + return FPExt->getOperand(0)->getType(); + + // 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)) + return T; + + // Try to shrink a vector of FP constants. + if (Type *T = shrinkFPConstantVector(V)) + return T; + + return V->getType(); +} + +/// Return true if the cast from integer to FP can be proven to be exact for all +/// possible inputs (the conversion does not lose any precision). +static bool isKnownExactCastIntToFP(CastInst &I) { + CastInst::CastOps Opcode = I.getOpcode(); + assert((Opcode == CastInst::SIToFP || Opcode == CastInst::UIToFP) && + "Unexpected cast"); + Value *Src = I.getOperand(0); + Type *SrcTy = Src->getType(); + Type *FPTy = I.getType(); + bool IsSigned = Opcode == Instruction::SIToFP; + int SrcSize = (int)SrcTy->getScalarSizeInBits() - IsSigned; + + // Easy case - if the source integer type has less bits than the FP mantissa, + // then the cast must be exact. + int DestNumSigBits = FPTy->getFPMantissaWidth(); + 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(Src, m_FPToSI(m_Value(F))) || match(Src, m_FPToUI(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(Src, 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; + } + + // TODO: + // Try harder to find if the source integer type has less significant bits. + // For example, compute number of sign bits or compute low bit mask. + return false; +} + +Instruction *InstCombiner::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)); + Type *RHSMinType = getMinimumFPType(BO->getOperand(1)); + unsigned OpWidth = BO->getType()->getFPMantissaWidth(); + unsigned LHSWidth = LHSMinType->getFPMantissaWidth(); + unsigned RHSWidth = RHSMinType->getFPMantissaWidth(); + unsigned SrcWidth = std::max(LHSWidth, RHSWidth); + unsigned DstWidth = Ty->getFPMantissaWidth(); + 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->copyFastMathFlags(BO); + 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, BO); + } + 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, BO); + } + 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()) { + // FIXME: The FMF should propagate from the fptrunc, not the source op. + IRBuilder<>::FastMathFlagGuard FMFG(Builder); + if (isa<FPMathOperator>(Op)) + Builder.setFastMathFlags(Op->getFastMathFlags()); + + if (match(Op, m_FNeg(m_Value(X)))) { + Value *InnerTrunc = Builder.CreateFPTrunc(X, Ty); + + return UnaryOperator::CreateFNegFMF(InnerTrunc, Op); + } + + // 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_Value(X)), m_Value(Y))) && + X->getType() == Ty) { + // fptrunc (select Cond, (fpext X), Y --> select Cond, X, (fptrunc Y) + Value *NarrowY = Builder.CreateFPTrunc(Y, Ty); + Value *Sel = Builder.CreateSelect(Cond, X, NarrowY, "narrow.sel", Op); + return replaceInstUsesWith(FPT, Sel); + } + if (match(Op, m_Select(m_Value(Cond), m_Value(Y), m_FPExt(m_Value(X)))) && + X->getType() == Ty) { + // fptrunc (select Cond, Y, (fpext X) --> select Cond, (fptrunc Y), X + Value *NarrowY = Builder.CreateFPTrunc(Y, Ty); + Value *Sel = Builder.CreateSelect(Cond, NarrowY, X, "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::getDeclaration(FPT.getModule(), + II->getIntrinsicID(), Ty); + SmallVector<OperandBundleDef, 1> OpBundles; + II->getOperandBundlesAsDefs(OpBundles); + CallInst *NewCI = + CallInst::Create(Overload, {InnerTrunc}, OpBundles, II->getName()); + NewCI->copyFastMathFlags(II); + 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 *InstCombiner::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({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. +Instruction *InstCombiner::foldItoFPtoI(CastInst &FI) { + 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 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)) { + // 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 undefined behavior. + int OutputSize = (int)DestType->getScalarSizeInBits() - IsOutputSigned; + if (OutputSize > OpI->getType()->getFPMantissaWidth()) + return nullptr; + } + + if (DestType->getScalarSizeInBits() > XType->getScalarSizeInBits()) { + bool IsInputSigned = isa<SIToFPInst>(OpI); + if (IsInputSigned && IsOutputSigned) + return new SExtInst(X, DestType); + return new ZExtInst(X, DestType); + } + if (DestType->getScalarSizeInBits() < XType->getScalarSizeInBits()) + return new TruncInst(X, DestType); + + assert(XType == DestType && "Unexpected types for int to FP to int casts"); + return replaceInstUsesWith(FI, X); +} + +Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) { + if (Instruction *I = foldItoFPtoI(FI)) + return I; + + return commonCastTransforms(FI); +} + +Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) { + if (Instruction *I = foldItoFPtoI(FI)) + return I; + + return commonCastTransforms(FI); +} + +Instruction *InstCombiner::visitUIToFP(CastInst &CI) { + return commonCastTransforms(CI); +} + +Instruction *InstCombiner::visitSIToFP(CastInst &CI) { + return commonCastTransforms(CI); +} + +Instruction *InstCombiner::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 = DL.getIntPtrType(CI.getContext(), AS); + // Handle vectors of pointers. + if (auto *CIVTy = dyn_cast<VectorType>(CI.getType())) + Ty = VectorType::get(Ty, CIVTy->getElementCount()); + + Value *P = Builder.CreateZExtOrTrunc(CI.getOperand(0), Ty); + return new IntToPtrInst(P, CI.getType()); + } + + if (Instruction *I = commonCastTransforms(CI)) + return I; + + return nullptr; +} + +/// Implement the transforms for cast of pointer (bitcast/ptrtoint) +Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) { + Value *Src = CI.getOperand(0); + + if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) { + // If casting the result of a getelementptr instruction with no offset, turn + // this into a cast of the original pointer! + if (GEP->hasAllZeroIndices() && + // If CI is an addrspacecast and GEP changes the poiner type, merging + // GEP into CI would undo canonicalizing addrspacecast with different + // pointer types, causing infinite loops. + (!isa<AddrSpaceCastInst>(CI) || + GEP->getType() == GEP->getPointerOperandType())) { + // Changing the cast operand is usually not a good idea but it is safe + // here because the pointer operand is being replaced with another + // pointer operand so the opcode doesn't need to change. + return replaceOperand(CI, 0, GEP->getOperand(0)); + } + } + + return commonCastTransforms(CI); +} + +Instruction *InstCombiner::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. + + Type *Ty = CI.getType(); + unsigned AS = CI.getPointerAddressSpace(); + + if (Ty->getScalarSizeInBits() == DL.getPointerSizeInBits(AS)) + return commonPointerCastTransforms(CI); + + Type *PtrTy = DL.getIntPtrType(CI.getContext(), AS); + if (auto *VTy = dyn_cast<VectorType>(Ty)) { + // Handle vectors of pointers. + // FIXME: what should happen for scalable vectors? + PtrTy = FixedVectorType::get(PtrTy, VTy->getNumElements()); + } + + Value *P = Builder.CreatePtrToInt(CI.getOperand(0), PtrTy); + return CastInst::CreateIntegerCast(P, Ty, /*isSigned=*/false); +} + +/// 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, + InstCombiner &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(), SrcTy->getNumElements()); + InVal = IC.Builder.CreateBitCast(InVal, SrcTy); + } + + bool IsBigEndian = IC.getDataLayout().isBigEndian(); + unsigned SrcElts = SrcTy->getNumElements(); + unsigned DestElts = 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. + SmallVector<int, 16> ShuffleMaskStorage; + ArrayRef<int> ShuffleMask; + Value *V2; + + // Produce an identify shuffle mask for the src vector. + ShuffleMaskStorage.resize(SrcElts); + std::iota(ShuffleMaskStorage.begin(), ShuffleMaskStorage.end(), 0); + + 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 undef as the second shuffle + // input. + V2 = UndefValue::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"); + + // Undef values never contribute useful bits to the result. + if (isa<UndefValue>(V)) 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 = Shift+i*ElementSize; + Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(), + ShiftI)); + Piece = ConstantExpr::getTrunc(Piece, ElementIntTy); + if (!collectInsertionElements(Piece, ShiftI, 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: + 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, + InstCombiner &IC) { + VectorType *DestVecTy = cast<VectorType>(CI.getType()); + Value *IntInput = CI.getOperand(0); + + 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], + IC.Builder.getInt32(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, + InstCombiner &IC) { + // TODO: Create and use a pattern matcher for ExtractElementInst. + auto *ExtElt = dyn_cast<ExtractElementInst>(BitCast.getOperand(0)); + if (!ExtElt || !ExtElt->hasOneUse()) + 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(); + if (!VectorType::isValidElementType(DestType)) + return nullptr; + + unsigned NumElts = ExtElt->getVectorOperandType()->getNumElements(); + auto *NewVecType = FixedVectorType::get(DestType, NumElts); + auto *NewBC = IC.Builder.CreateBitCast(ExtElt->getVectorOperand(), + NewVecType, "bc"); + return ExtractElementInst::Create(NewBC, ExtElt->getIndexOperand()); +} + +/// 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 (!DestTy->isIntOrIntVectorTy() || + !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; + + Value *X; + if (match(BO->getOperand(0), m_OneUse(m_BitCast(m_Value(X)))) && + X->getType() == DestTy && !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_Value(X)))) && + X->getType() == DestTy && !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(); + if (auto *CondVTy = dyn_cast<VectorType>(CondTy)) { + if (!DestTy->isVectorTy()) + return nullptr; + if (cast<VectorType>(DestTy)->getNumElements() != CondVTy->getNumElements()) + return nullptr; + } + + // 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 (DestTy->isVectorTy() != TVal->getType()->isVectorTy()) + return nullptr; + + auto *Sel = cast<Instruction>(BitCast.getOperand(0)); + Value *X; + if (match(TVal, m_OneUse(m_BitCast(m_Value(X)))) && X->getType() == DestTy && + !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_Value(X)))) && X->getType() == DestTy && + !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 *InstCombiner::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; + 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.count(PHI) == 0) + 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, UndefValue::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 (auto It = OldPN->user_begin(), End = OldPN->user_end(); It != End; ) { + User *V = *It; + // We may remove this user, advance to avoid iterator invalidation. + ++It; + 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.count(PHI) > 0); + (void) PHI; + } else { + llvm_unreachable("all uses should be handled"); + } + } + } + + return RetVal; +} + +Instruction *InstCombiner::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<PointerType>(SrcTy) && isa<PointerType>(DestTy)) { + PointerType *SrcPTy = cast<PointerType>(SrcTy); + PointerType *DstPTy = cast<PointerType>(DestTy); + Type *DstElTy = DstPTy->getElementType(); + Type *SrcElTy = SrcPTy->getElementType(); + + // Casting pointers between the same type, but with different address spaces + // is an addrspace cast rather than a bitcast. + if ((DstElTy == SrcElTy) && + (DstPTy->getAddressSpace() != SrcPTy->getAddressSpace())) + return new AddrSpaceCastInst(Src, DestTy); + + // If we are casting a alloca to a pointer to a type of the same + // size, rewrite the allocation instruction to allocate the "right" type. + // There is no need to modify malloc calls because it is their bitcast that + // needs to be cleaned up. + if (AllocaInst *AI = dyn_cast<AllocaInst>(Src)) + if (Instruction *V = PromoteCastOfAllocation(CI, *AI)) + return V; + + // When the type pointed to is not sized the cast cannot be + // turned into a gep. + Type *PointeeType = + cast<PointerType>(Src->getType()->getScalarType())->getElementType(); + if (!PointeeType->isSized()) + return nullptr; + + // If the source and destination are pointers, and this cast is equivalent + // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep. + // This can enhance SROA and other transforms that want type-safe pointers. + unsigned NumZeros = 0; + while (SrcElTy && SrcElTy != DstElTy) { + SrcElTy = GetElementPtrInst::getTypeAtIndex(SrcElTy, (uint64_t)0); + ++NumZeros; + } + + // If we found a path from the src to dest, create the getelementptr now. + if (SrcElTy == DstElTy) { + SmallVector<Value *, 8> Idxs(NumZeros + 1, Builder.getInt32(0)); + GetElementPtrInst *GEP = + GetElementPtrInst::Create(SrcPTy->getElementType(), Src, Idxs); + + // If the source pointer is dereferenceable, then assume it points to an + // allocated object and apply "inbounds" to the GEP. + bool CanBeNull; + if (Src->getPointerDereferenceableBytes(DL, CanBeNull)) { + // In a non-default address space (not 0), a null pointer can not be + // assumed inbounds, so ignore that case (dereferenceable_or_null). + // The reason is that 'null' is not treated differently in these address + // spaces, and we consequently ignore the 'gep inbounds' special case + // for 'null' which allows 'inbounds' on 'null' if the indices are + // zeros. + if (SrcPTy->getAddressSpace() == 0 || !CanBeNull) + GEP->setIsInBounds(); + } + return GEP; + } + } + + if (FixedVectorType *DestVTy = dyn_cast<FixedVectorType>(DestTy)) { + // Beware: messing with this target-specific oddity may cause trouble. + if (DestVTy->getNumElements() == 1 && SrcTy->isX86_MMXTy()) { + Value *Elem = Builder.CreateBitCast(Src, DestVTy->getElementType()); + return InsertElementInst::Create(UndefValue::get(DestTy), Elem, + Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); + } + + 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, + Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); + 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); + } + } + + 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); + unsigned NumShufElts = Shuf->getType()->getNumElements(); + unsigned NumSrcVecElts = + cast<VectorType>(ShufOp0->getType())->getNumElements(); + if (Shuf->hasOneUse() && DestTy->isVectorTy() && + cast<VectorType>(DestTy)->getNumElements() == NumShufElts && + NumShufElts == NumSrcVecElts) { + 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-reversing shuffle is better recognized as + // a byte-swap: + // bitcast <N x i8> (shuf X, undef, <N, N-1,...0>) --> bswap (bitcast X) + // TODO: We should match the related pattern for bitreverse. + if (DestTy->isIntegerTy() && + DL.isLegalInteger(DestTy->getScalarSizeInBits()) && + SrcTy->getScalarSizeInBits() == 8 && NumShufElts % 2 == 0 && + Shuf->hasOneUse() && Shuf->isReverse()) { + assert(ShufOp0->getType() == SrcTy && "Unexpected shuffle mask"); + assert(isa<UndefValue>(ShufOp1) && "Unexpected shuffle op"); + Function *Bswap = + Intrinsic::getDeclaration(CI.getModule(), Intrinsic::bswap, DestTy); + Value *ScalarX = Builder.CreateBitCast(ShufOp0, DestTy); + return IntrinsicInst::Create(Bswap, { 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 (SrcTy->isPointerTy()) + return commonPointerCastTransforms(CI); + return commonCastTransforms(CI); +} + +Instruction *InstCombiner::visitAddrSpaceCast(AddrSpaceCastInst &CI) { + // If the destination pointer element type is not the same as the source's + // first do a bitcast to the destination type, and then the addrspacecast. + // This allows the cast to be exposed to other transforms. + Value *Src = CI.getOperand(0); + PointerType *SrcTy = cast<PointerType>(Src->getType()->getScalarType()); + PointerType *DestTy = cast<PointerType>(CI.getType()->getScalarType()); + + Type *DestElemTy = DestTy->getElementType(); + if (SrcTy->getElementType() != DestElemTy) { + Type *MidTy = PointerType::get(DestElemTy, SrcTy->getAddressSpace()); + if (VectorType *VT = dyn_cast<VectorType>(CI.getType())) { + // Handle vectors of pointers. + // FIXME: what should happen for scalable vectors? + MidTy = FixedVectorType::get(MidTy, VT->getNumElements()); + } + + Value *NewBitCast = Builder.CreateBitCast(Src, MidTy); + return new AddrSpaceCastInst(NewBitCast, CI.getType()); + } + + return commonPointerCastTransforms(CI); +} |