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Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 1733 |
1 files changed, 1733 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp new file mode 100644 index 000000000000..d30ab8001897 --- /dev/null +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -0,0 +1,1733 @@ +//===- InstCombineSimplifyDemanded.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 contains logic for simplifying instructions based on information +// about how they are used. +// +//===----------------------------------------------------------------------===// + +#include "InstCombineInternal.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/Support/KnownBits.h" + +using namespace llvm; +using namespace llvm::PatternMatch; + +#define DEBUG_TYPE "instcombine" + +namespace { + +struct AMDGPUImageDMaskIntrinsic { + unsigned Intr; +}; + +#define GET_AMDGPUImageDMaskIntrinsicTable_IMPL +#include "InstCombineTables.inc" + +} // end anonymous namespace + +/// Check to see if the specified operand of the specified instruction is a +/// constant integer. If so, check to see if there are any bits set in the +/// constant that are not demanded. If so, shrink the constant and return true. +static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo, + const APInt &Demanded) { + assert(I && "No instruction?"); + assert(OpNo < I->getNumOperands() && "Operand index too large"); + + // The operand must be a constant integer or splat integer. + Value *Op = I->getOperand(OpNo); + const APInt *C; + if (!match(Op, m_APInt(C))) + return false; + + // If there are no bits set that aren't demanded, nothing to do. + if (C->isSubsetOf(Demanded)) + return false; + + // This instruction is producing bits that are not demanded. Shrink the RHS. + I->setOperand(OpNo, ConstantInt::get(Op->getType(), *C & Demanded)); + + return true; +} + + + +/// Inst is an integer instruction that SimplifyDemandedBits knows about. See if +/// the instruction has any properties that allow us to simplify its operands. +bool InstCombiner::SimplifyDemandedInstructionBits(Instruction &Inst) { + unsigned BitWidth = Inst.getType()->getScalarSizeInBits(); + KnownBits Known(BitWidth); + APInt DemandedMask(APInt::getAllOnesValue(BitWidth)); + + Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask, Known, + 0, &Inst); + if (!V) return false; + if (V == &Inst) return true; + replaceInstUsesWith(Inst, V); + return true; +} + +/// This form of SimplifyDemandedBits simplifies the specified instruction +/// operand if possible, updating it in place. It returns true if it made any +/// change and false otherwise. +bool InstCombiner::SimplifyDemandedBits(Instruction *I, unsigned OpNo, + const APInt &DemandedMask, + KnownBits &Known, + unsigned Depth) { + Use &U = I->getOperandUse(OpNo); + Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, Known, + Depth, I); + if (!NewVal) return false; + U = NewVal; + return true; +} + + +/// This function attempts to replace V with a simpler value based on the +/// demanded bits. When this function is called, it is known that only the bits +/// set in DemandedMask of the result of V are ever used downstream. +/// Consequently, depending on the mask and V, it may be possible to replace V +/// with a constant or one of its operands. In such cases, this function does +/// the replacement and returns true. In all other cases, it returns false after +/// analyzing the expression and setting KnownOne and known to be one in the +/// expression. Known.Zero contains all the bits that are known to be zero in +/// the expression. These are provided to potentially allow the caller (which +/// might recursively be SimplifyDemandedBits itself) to simplify the +/// expression. +/// Known.One and Known.Zero always follow the invariant that: +/// Known.One & Known.Zero == 0. +/// That is, a bit can't be both 1 and 0. Note that the bits in Known.One and +/// Known.Zero may only be accurate for those bits set in DemandedMask. Note +/// also that the bitwidth of V, DemandedMask, Known.Zero and Known.One must all +/// be the same. +/// +/// This returns null if it did not change anything and it permits no +/// simplification. This returns V itself if it did some simplification of V's +/// operands based on the information about what bits are demanded. This returns +/// some other non-null value if it found out that V is equal to another value +/// in the context where the specified bits are demanded, but not for all users. +Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, + KnownBits &Known, unsigned Depth, + Instruction *CxtI) { + assert(V != nullptr && "Null pointer of Value???"); + assert(Depth <= 6 && "Limit Search Depth"); + uint32_t BitWidth = DemandedMask.getBitWidth(); + Type *VTy = V->getType(); + assert( + (!VTy->isIntOrIntVectorTy() || VTy->getScalarSizeInBits() == BitWidth) && + Known.getBitWidth() == BitWidth && + "Value *V, DemandedMask and Known must have same BitWidth"); + + if (isa<Constant>(V)) { + computeKnownBits(V, Known, Depth, CxtI); + return nullptr; + } + + Known.resetAll(); + if (DemandedMask.isNullValue()) // Not demanding any bits from V. + return UndefValue::get(VTy); + + if (Depth == 6) // Limit search depth. + return nullptr; + + Instruction *I = dyn_cast<Instruction>(V); + if (!I) { + computeKnownBits(V, Known, Depth, CxtI); + return nullptr; // Only analyze instructions. + } + + // If there are multiple uses of this value and we aren't at the root, then + // we can't do any simplifications of the operands, because DemandedMask + // only reflects the bits demanded by *one* of the users. + if (Depth != 0 && !I->hasOneUse()) + return SimplifyMultipleUseDemandedBits(I, DemandedMask, Known, Depth, CxtI); + + KnownBits LHSKnown(BitWidth), RHSKnown(BitWidth); + + // If this is the root being simplified, allow it to have multiple uses, + // just set the DemandedMask to all bits so that we can try to simplify the + // operands. This allows visitTruncInst (for example) to simplify the + // operand of a trunc without duplicating all the logic below. + if (Depth == 0 && !V->hasOneUse()) + DemandedMask.setAllBits(); + + switch (I->getOpcode()) { + default: + computeKnownBits(I, Known, Depth, CxtI); + break; + case Instruction::And: { + // If either the LHS or the RHS are Zero, the result is zero. + if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) || + SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.Zero, LHSKnown, + Depth + 1)) + return I; + assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?"); + assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?"); + + // Output known-0 are known to be clear if zero in either the LHS | RHS. + APInt IKnownZero = RHSKnown.Zero | LHSKnown.Zero; + // Output known-1 bits are only known if set in both the LHS & RHS. + APInt IKnownOne = RHSKnown.One & LHSKnown.One; + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(VTy, IKnownOne); + + // If all of the demanded bits are known 1 on one side, return the other. + // These bits cannot contribute to the result of the 'and'. + if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One)) + return I->getOperand(1); + + // If the RHS is a constant, see if we can simplify it. + if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnown.Zero)) + return I; + + Known.Zero = std::move(IKnownZero); + Known.One = std::move(IKnownOne); + break; + } + case Instruction::Or: { + // If either the LHS or the RHS are One, the result is One. + if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) || + SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.One, LHSKnown, + Depth + 1)) + return I; + assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?"); + assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?"); + + // Output known-0 bits are only known if clear in both the LHS & RHS. + APInt IKnownZero = RHSKnown.Zero & LHSKnown.Zero; + // Output known-1 are known. to be set if s.et in either the LHS | RHS. + APInt IKnownOne = RHSKnown.One | LHSKnown.One; + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(VTy, IKnownOne); + + // If all of the demanded bits are known zero on one side, return the other. + // These bits cannot contribute to the result of the 'or'. + if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero)) + return I->getOperand(1); + + // If the RHS is a constant, see if we can simplify it. + if (ShrinkDemandedConstant(I, 1, DemandedMask)) + return I; + + Known.Zero = std::move(IKnownZero); + Known.One = std::move(IKnownOne); + break; + } + case Instruction::Xor: { + if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) || + SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1)) + return I; + assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?"); + assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?"); + + // Output known-0 bits are known if clear or set in both the LHS & RHS. + APInt IKnownZero = (RHSKnown.Zero & LHSKnown.Zero) | + (RHSKnown.One & LHSKnown.One); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + APInt IKnownOne = (RHSKnown.Zero & LHSKnown.One) | + (RHSKnown.One & LHSKnown.Zero); + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(VTy, IKnownOne); + + // If all of the demanded bits are known zero on one side, return the other. + // These bits cannot contribute to the result of the 'xor'. + if (DemandedMask.isSubsetOf(RHSKnown.Zero)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(LHSKnown.Zero)) + return I->getOperand(1); + + // If all of the demanded bits are known to be zero on one side or the + // other, turn this into an *inclusive* or. + // e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0 + if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.Zero)) { + Instruction *Or = + BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1), + I->getName()); + return InsertNewInstWith(Or, *I); + } + + // If all of the demanded bits on one side are known, and all of the set + // bits on that side are also known to be set on the other side, turn this + // into an AND, as we know the bits will be cleared. + // e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2 + if (DemandedMask.isSubsetOf(RHSKnown.Zero|RHSKnown.One) && + RHSKnown.One.isSubsetOf(LHSKnown.One)) { + Constant *AndC = Constant::getIntegerValue(VTy, + ~RHSKnown.One & DemandedMask); + Instruction *And = BinaryOperator::CreateAnd(I->getOperand(0), AndC); + return InsertNewInstWith(And, *I); + } + + // If the RHS is a constant, see if we can simplify it. + // FIXME: for XOR, we prefer to force bits to 1 if they will make a -1. + if (ShrinkDemandedConstant(I, 1, DemandedMask)) + return I; + + // If our LHS is an 'and' and if it has one use, and if any of the bits we + // are flipping are known to be set, then the xor is just resetting those + // bits to zero. We can just knock out bits from the 'and' and the 'xor', + // simplifying both of them. + if (Instruction *LHSInst = dyn_cast<Instruction>(I->getOperand(0))) + if (LHSInst->getOpcode() == Instruction::And && LHSInst->hasOneUse() && + isa<ConstantInt>(I->getOperand(1)) && + isa<ConstantInt>(LHSInst->getOperand(1)) && + (LHSKnown.One & RHSKnown.One & DemandedMask) != 0) { + ConstantInt *AndRHS = cast<ConstantInt>(LHSInst->getOperand(1)); + ConstantInt *XorRHS = cast<ConstantInt>(I->getOperand(1)); + APInt NewMask = ~(LHSKnown.One & RHSKnown.One & DemandedMask); + + Constant *AndC = + ConstantInt::get(I->getType(), NewMask & AndRHS->getValue()); + Instruction *NewAnd = BinaryOperator::CreateAnd(I->getOperand(0), AndC); + InsertNewInstWith(NewAnd, *I); + + Constant *XorC = + ConstantInt::get(I->getType(), NewMask & XorRHS->getValue()); + Instruction *NewXor = BinaryOperator::CreateXor(NewAnd, XorC); + return InsertNewInstWith(NewXor, *I); + } + + // Output known-0 bits are known if clear or set in both the LHS & RHS. + Known.Zero = std::move(IKnownZero); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + Known.One = std::move(IKnownOne); + break; + } + case Instruction::Select: { + Value *LHS, *RHS; + SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor; + if (SPF == SPF_UMAX) { + // UMax(A, C) == A if ... + // The lowest non-zero bit of DemandMask is higher than the highest + // non-zero bit of C. + const APInt *C; + unsigned CTZ = DemandedMask.countTrailingZeros(); + if (match(RHS, m_APInt(C)) && CTZ >= C->getActiveBits()) + return LHS; + } else if (SPF == SPF_UMIN) { + // UMin(A, C) == A if ... + // The lowest non-zero bit of DemandMask is higher than the highest + // non-one bit of C. + // This comes from using DeMorgans on the above umax example. + const APInt *C; + unsigned CTZ = DemandedMask.countTrailingZeros(); + if (match(RHS, m_APInt(C)) && + CTZ >= C->getBitWidth() - C->countLeadingOnes()) + return LHS; + } + + // If this is a select as part of any other min/max pattern, don't simplify + // any further in case we break the structure. + if (SPF != SPF_UNKNOWN) + return nullptr; + + if (SimplifyDemandedBits(I, 2, DemandedMask, RHSKnown, Depth + 1) || + SimplifyDemandedBits(I, 1, DemandedMask, LHSKnown, Depth + 1)) + return I; + assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?"); + assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?"); + + // If the operands are constants, see if we can simplify them. + if (ShrinkDemandedConstant(I, 1, DemandedMask) || + ShrinkDemandedConstant(I, 2, DemandedMask)) + return I; + + // Only known if known in both the LHS and RHS. + Known.One = RHSKnown.One & LHSKnown.One; + Known.Zero = RHSKnown.Zero & LHSKnown.Zero; + break; + } + case Instruction::ZExt: + case Instruction::Trunc: { + unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); + + APInt InputDemandedMask = DemandedMask.zextOrTrunc(SrcBitWidth); + KnownBits InputKnown(SrcBitWidth); + if (SimplifyDemandedBits(I, 0, InputDemandedMask, InputKnown, Depth + 1)) + return I; + assert(InputKnown.getBitWidth() == SrcBitWidth && "Src width changed?"); + Known = InputKnown.zextOrTrunc(BitWidth, + true /* ExtendedBitsAreKnownZero */); + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + break; + } + case Instruction::BitCast: + if (!I->getOperand(0)->getType()->isIntOrIntVectorTy()) + return nullptr; // vector->int or fp->int? + + if (VectorType *DstVTy = dyn_cast<VectorType>(I->getType())) { + if (VectorType *SrcVTy = + dyn_cast<VectorType>(I->getOperand(0)->getType())) { + if (DstVTy->getNumElements() != SrcVTy->getNumElements()) + // Don't touch a bitcast between vectors of different element counts. + return nullptr; + } else + // Don't touch a scalar-to-vector bitcast. + return nullptr; + } else if (I->getOperand(0)->getType()->isVectorTy()) + // Don't touch a vector-to-scalar bitcast. + return nullptr; + + if (SimplifyDemandedBits(I, 0, DemandedMask, Known, Depth + 1)) + return I; + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + break; + case Instruction::SExt: { + // Compute the bits in the result that are not present in the input. + unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); + + APInt InputDemandedBits = DemandedMask.trunc(SrcBitWidth); + + // If any of the sign extended bits are demanded, we know that the sign + // bit is demanded. + if (DemandedMask.getActiveBits() > SrcBitWidth) + InputDemandedBits.setBit(SrcBitWidth-1); + + KnownBits InputKnown(SrcBitWidth); + if (SimplifyDemandedBits(I, 0, InputDemandedBits, InputKnown, Depth + 1)) + return I; + + // If the input sign bit is known zero, or if the NewBits are not demanded + // convert this into a zero extension. + if (InputKnown.isNonNegative() || + DemandedMask.getActiveBits() <= SrcBitWidth) { + // Convert to ZExt cast. + CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName()); + return InsertNewInstWith(NewCast, *I); + } + + // If the sign bit of the input is known set or clear, then we know the + // top bits of the result. + Known = InputKnown.sext(BitWidth); + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + break; + } + case Instruction::Add: + case Instruction::Sub: { + /// If the high-bits of an ADD/SUB are not demanded, then we do not care + /// about the high bits of the operands. + unsigned NLZ = DemandedMask.countLeadingZeros(); + // Right fill the mask of bits for this ADD/SUB to demand the most + // significant bit and all those below it. + APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); + if (ShrinkDemandedConstant(I, 0, DemandedFromOps) || + SimplifyDemandedBits(I, 0, DemandedFromOps, LHSKnown, Depth + 1) || + ShrinkDemandedConstant(I, 1, DemandedFromOps) || + SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1)) { + if (NLZ > 0) { + // Disable the nsw and nuw flags here: We can no longer guarantee that + // we won't wrap after simplification. Removing the nsw/nuw flags is + // legal here because the top bit is not demanded. + BinaryOperator &BinOP = *cast<BinaryOperator>(I); + BinOP.setHasNoSignedWrap(false); + BinOP.setHasNoUnsignedWrap(false); + } + return I; + } + + // If we are known to be adding/subtracting zeros to every bit below + // the highest demanded bit, we just return the other side. + if (DemandedFromOps.isSubsetOf(RHSKnown.Zero)) + return I->getOperand(0); + // We can't do this with the LHS for subtraction, unless we are only + // demanding the LSB. + if ((I->getOpcode() == Instruction::Add || + DemandedFromOps.isOneValue()) && + DemandedFromOps.isSubsetOf(LHSKnown.Zero)) + return I->getOperand(1); + + // Otherwise just compute the known bits of the result. + bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap(); + Known = KnownBits::computeForAddSub(I->getOpcode() == Instruction::Add, + NSW, LHSKnown, RHSKnown); + break; + } + case Instruction::Shl: { + const APInt *SA; + if (match(I->getOperand(1), m_APInt(SA))) { + const APInt *ShrAmt; + if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt)))) + if (Instruction *Shr = dyn_cast<Instruction>(I->getOperand(0))) + if (Value *R = simplifyShrShlDemandedBits(Shr, *ShrAmt, I, *SA, + DemandedMask, Known)) + return R; + + uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1); + APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt)); + + // If the shift is NUW/NSW, then it does demand the high bits. + ShlOperator *IOp = cast<ShlOperator>(I); + if (IOp->hasNoSignedWrap()) + DemandedMaskIn.setHighBits(ShiftAmt+1); + else if (IOp->hasNoUnsignedWrap()) + DemandedMaskIn.setHighBits(ShiftAmt); + + if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) + return I; + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + Known.Zero <<= ShiftAmt; + Known.One <<= ShiftAmt; + // low bits known zero. + if (ShiftAmt) + Known.Zero.setLowBits(ShiftAmt); + } + break; + } + case Instruction::LShr: { + const APInt *SA; + if (match(I->getOperand(1), m_APInt(SA))) { + uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1); + + // Unsigned shift right. + APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt)); + + // If the shift is exact, then it does demand the low bits (and knows that + // they are zero). + if (cast<LShrOperator>(I)->isExact()) + DemandedMaskIn.setLowBits(ShiftAmt); + + if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) + return I; + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + Known.Zero.lshrInPlace(ShiftAmt); + Known.One.lshrInPlace(ShiftAmt); + if (ShiftAmt) + Known.Zero.setHighBits(ShiftAmt); // high bits known zero. + } + break; + } + case Instruction::AShr: { + // If this is an arithmetic shift right and only the low-bit is set, we can + // always convert this into a logical shr, even if the shift amount is + // variable. The low bit of the shift cannot be an input sign bit unless + // the shift amount is >= the size of the datatype, which is undefined. + if (DemandedMask.isOneValue()) { + // Perform the logical shift right. + Instruction *NewVal = BinaryOperator::CreateLShr( + I->getOperand(0), I->getOperand(1), I->getName()); + return InsertNewInstWith(NewVal, *I); + } + + // If the sign bit is the only bit demanded by this ashr, then there is no + // need to do it, the shift doesn't change the high bit. + if (DemandedMask.isSignMask()) + return I->getOperand(0); + + const APInt *SA; + if (match(I->getOperand(1), m_APInt(SA))) { + uint32_t ShiftAmt = SA->getLimitedValue(BitWidth-1); + + // Signed shift right. + APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt)); + // If any of the high bits are demanded, we should set the sign bit as + // demanded. + if (DemandedMask.countLeadingZeros() <= ShiftAmt) + DemandedMaskIn.setSignBit(); + + // If the shift is exact, then it does demand the low bits (and knows that + // they are zero). + if (cast<AShrOperator>(I)->isExact()) + DemandedMaskIn.setLowBits(ShiftAmt); + + if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) + return I; + + unsigned SignBits = ComputeNumSignBits(I->getOperand(0), Depth + 1, CxtI); + + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + // Compute the new bits that are at the top now plus sign bits. + APInt HighBits(APInt::getHighBitsSet( + BitWidth, std::min(SignBits + ShiftAmt - 1, BitWidth))); + Known.Zero.lshrInPlace(ShiftAmt); + Known.One.lshrInPlace(ShiftAmt); + + // If the input sign bit is known to be zero, or if none of the top bits + // are demanded, turn this into an unsigned shift right. + assert(BitWidth > ShiftAmt && "Shift amount not saturated?"); + if (Known.Zero[BitWidth-ShiftAmt-1] || + !DemandedMask.intersects(HighBits)) { + BinaryOperator *LShr = BinaryOperator::CreateLShr(I->getOperand(0), + I->getOperand(1)); + LShr->setIsExact(cast<BinaryOperator>(I)->isExact()); + return InsertNewInstWith(LShr, *I); + } else if (Known.One[BitWidth-ShiftAmt-1]) { // New bits are known one. + Known.One |= HighBits; + } + } + break; + } + case Instruction::UDiv: { + // UDiv doesn't demand low bits that are zero in the divisor. + const APInt *SA; + if (match(I->getOperand(1), m_APInt(SA))) { + // If the shift is exact, then it does demand the low bits. + if (cast<UDivOperator>(I)->isExact()) + break; + + // FIXME: Take the demanded mask of the result into account. + unsigned RHSTrailingZeros = SA->countTrailingZeros(); + APInt DemandedMaskIn = + APInt::getHighBitsSet(BitWidth, BitWidth - RHSTrailingZeros); + if (SimplifyDemandedBits(I, 0, DemandedMaskIn, LHSKnown, Depth + 1)) + return I; + + // Propagate zero bits from the input. + Known.Zero.setHighBits(std::min( + BitWidth, LHSKnown.Zero.countLeadingOnes() + RHSTrailingZeros)); + } + break; + } + case Instruction::SRem: + if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { + // X % -1 demands all the bits because we don't want to introduce + // INT_MIN % -1 (== undef) by accident. + if (Rem->isMinusOne()) + break; + APInt RA = Rem->getValue().abs(); + if (RA.isPowerOf2()) { + if (DemandedMask.ult(RA)) // srem won't affect demanded bits + return I->getOperand(0); + + APInt LowBits = RA - 1; + APInt Mask2 = LowBits | APInt::getSignMask(BitWidth); + if (SimplifyDemandedBits(I, 0, Mask2, LHSKnown, Depth + 1)) + return I; + + // The low bits of LHS are unchanged by the srem. + Known.Zero = LHSKnown.Zero & LowBits; + Known.One = LHSKnown.One & LowBits; + + // If LHS is non-negative or has all low bits zero, then the upper bits + // are all zero. + if (LHSKnown.isNonNegative() || LowBits.isSubsetOf(LHSKnown.Zero)) + Known.Zero |= ~LowBits; + + // If LHS is negative and not all low bits are zero, then the upper bits + // are all one. + if (LHSKnown.isNegative() && LowBits.intersects(LHSKnown.One)) + Known.One |= ~LowBits; + + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); + break; + } + } + + // The sign bit is the LHS's sign bit, except when the result of the + // remainder is zero. + if (DemandedMask.isSignBitSet()) { + computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI); + // If it's known zero, our sign bit is also zero. + if (LHSKnown.isNonNegative()) + Known.makeNonNegative(); + } + break; + case Instruction::URem: { + KnownBits Known2(BitWidth); + APInt AllOnes = APInt::getAllOnesValue(BitWidth); + if (SimplifyDemandedBits(I, 0, AllOnes, Known2, Depth + 1) || + SimplifyDemandedBits(I, 1, AllOnes, Known2, Depth + 1)) + return I; + + unsigned Leaders = Known2.countMinLeadingZeros(); + Known.Zero = APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask; + break; + } + case Instruction::Call: + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { + switch (II->getIntrinsicID()) { + default: break; + case Intrinsic::bswap: { + // If the only bits demanded come from one byte of the bswap result, + // just shift the input byte into position to eliminate the bswap. + unsigned NLZ = DemandedMask.countLeadingZeros(); + unsigned NTZ = DemandedMask.countTrailingZeros(); + + // Round NTZ down to the next byte. If we have 11 trailing zeros, then + // we need all the bits down to bit 8. Likewise, round NLZ. If we + // have 14 leading zeros, round to 8. + NLZ &= ~7; + NTZ &= ~7; + // If we need exactly one byte, we can do this transformation. + if (BitWidth-NLZ-NTZ == 8) { + unsigned ResultBit = NTZ; + unsigned InputBit = BitWidth-NTZ-8; + + // Replace this with either a left or right shift to get the byte into + // the right place. + Instruction *NewVal; + if (InputBit > ResultBit) + NewVal = BinaryOperator::CreateLShr(II->getArgOperand(0), + ConstantInt::get(I->getType(), InputBit-ResultBit)); + else + NewVal = BinaryOperator::CreateShl(II->getArgOperand(0), + ConstantInt::get(I->getType(), ResultBit-InputBit)); + NewVal->takeName(I); + return InsertNewInstWith(NewVal, *I); + } + + // TODO: Could compute known zero/one bits based on the input. + break; + } + case Intrinsic::fshr: + case Intrinsic::fshl: { + const APInt *SA; + if (!match(I->getOperand(2), m_APInt(SA))) + break; + + // Normalize to funnel shift left. APInt shifts of BitWidth are well- + // defined, so no need to special-case zero shifts here. + uint64_t ShiftAmt = SA->urem(BitWidth); + if (II->getIntrinsicID() == Intrinsic::fshr) + ShiftAmt = BitWidth - ShiftAmt; + + APInt DemandedMaskLHS(DemandedMask.lshr(ShiftAmt)); + APInt DemandedMaskRHS(DemandedMask.shl(BitWidth - ShiftAmt)); + if (SimplifyDemandedBits(I, 0, DemandedMaskLHS, LHSKnown, Depth + 1) || + SimplifyDemandedBits(I, 1, DemandedMaskRHS, RHSKnown, Depth + 1)) + return I; + + Known.Zero = LHSKnown.Zero.shl(ShiftAmt) | + RHSKnown.Zero.lshr(BitWidth - ShiftAmt); + Known.One = LHSKnown.One.shl(ShiftAmt) | + RHSKnown.One.lshr(BitWidth - ShiftAmt); + break; + } + case Intrinsic::x86_mmx_pmovmskb: + case Intrinsic::x86_sse_movmsk_ps: + case Intrinsic::x86_sse2_movmsk_pd: + case Intrinsic::x86_sse2_pmovmskb_128: + case Intrinsic::x86_avx_movmsk_ps_256: + case Intrinsic::x86_avx_movmsk_pd_256: + case Intrinsic::x86_avx2_pmovmskb: { + // MOVMSK copies the vector elements' sign bits to the low bits + // and zeros the high bits. + unsigned ArgWidth; + if (II->getIntrinsicID() == Intrinsic::x86_mmx_pmovmskb) { + ArgWidth = 8; // Arg is x86_mmx, but treated as <8 x i8>. + } else { + auto Arg = II->getArgOperand(0); + auto ArgType = cast<VectorType>(Arg->getType()); + ArgWidth = ArgType->getNumElements(); + } + + // If we don't need any of low bits then return zero, + // we know that DemandedMask is non-zero already. + APInt DemandedElts = DemandedMask.zextOrTrunc(ArgWidth); + if (DemandedElts.isNullValue()) + return ConstantInt::getNullValue(VTy); + + // We know that the upper bits are set to zero. + Known.Zero.setBitsFrom(ArgWidth); + return nullptr; + } + case Intrinsic::x86_sse42_crc32_64_64: + Known.Zero.setBitsFrom(32); + return nullptr; + } + } + computeKnownBits(V, Known, Depth, CxtI); + break; + } + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(Known.Zero|Known.One)) + return Constant::getIntegerValue(VTy, Known.One); + return nullptr; +} + +/// Helper routine of SimplifyDemandedUseBits. It computes Known +/// bits. It also tries to handle simplifications that can be done based on +/// DemandedMask, but without modifying the Instruction. +Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, + const APInt &DemandedMask, + KnownBits &Known, + unsigned Depth, + Instruction *CxtI) { + unsigned BitWidth = DemandedMask.getBitWidth(); + Type *ITy = I->getType(); + + KnownBits LHSKnown(BitWidth); + KnownBits RHSKnown(BitWidth); + + // Despite the fact that we can't simplify this instruction in all User's + // context, we can at least compute the known bits, and we can + // do simplifications that apply to *just* the one user if we know that + // this instruction has a simpler value in that context. + switch (I->getOpcode()) { + case Instruction::And: { + // If either the LHS or the RHS are Zero, the result is zero. + computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI); + computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, + CxtI); + + // Output known-0 are known to be clear if zero in either the LHS | RHS. + APInt IKnownZero = RHSKnown.Zero | LHSKnown.Zero; + // Output known-1 bits are only known if set in both the LHS & RHS. + APInt IKnownOne = RHSKnown.One & LHSKnown.One; + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(ITy, IKnownOne); + + // If all of the demanded bits are known 1 on one side, return the other. + // These bits cannot contribute to the result of the 'and' in this + // context. + if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One)) + return I->getOperand(1); + + Known.Zero = std::move(IKnownZero); + Known.One = std::move(IKnownOne); + break; + } + case Instruction::Or: { + // We can simplify (X|Y) -> X or Y in the user's context if we know that + // only bits from X or Y are demanded. + + // If either the LHS or the RHS are One, the result is One. + computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI); + computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, + CxtI); + + // Output known-0 bits are only known if clear in both the LHS & RHS. + APInt IKnownZero = RHSKnown.Zero & LHSKnown.Zero; + // Output known-1 are known to be set if set in either the LHS | RHS. + APInt IKnownOne = RHSKnown.One | LHSKnown.One; + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(ITy, IKnownOne); + + // If all of the demanded bits are known zero on one side, return the + // other. These bits cannot contribute to the result of the 'or' in this + // context. + if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero)) + return I->getOperand(1); + + Known.Zero = std::move(IKnownZero); + Known.One = std::move(IKnownOne); + break; + } + case Instruction::Xor: { + // We can simplify (X^Y) -> X or Y in the user's context if we know that + // only bits from X or Y are demanded. + + computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI); + computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, + CxtI); + + // Output known-0 bits are known if clear or set in both the LHS & RHS. + APInt IKnownZero = (RHSKnown.Zero & LHSKnown.Zero) | + (RHSKnown.One & LHSKnown.One); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + APInt IKnownOne = (RHSKnown.Zero & LHSKnown.One) | + (RHSKnown.One & LHSKnown.Zero); + + // If the client is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(IKnownZero|IKnownOne)) + return Constant::getIntegerValue(ITy, IKnownOne); + + // If all of the demanded bits are known zero on one side, return the + // other. + if (DemandedMask.isSubsetOf(RHSKnown.Zero)) + return I->getOperand(0); + if (DemandedMask.isSubsetOf(LHSKnown.Zero)) + return I->getOperand(1); + + // Output known-0 bits are known if clear or set in both the LHS & RHS. + Known.Zero = std::move(IKnownZero); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + Known.One = std::move(IKnownOne); + break; + } + default: + // Compute the Known bits to simplify things downstream. + computeKnownBits(I, Known, Depth, CxtI); + + // If this user is only demanding bits that we know, return the known + // constant. + if (DemandedMask.isSubsetOf(Known.Zero|Known.One)) + return Constant::getIntegerValue(ITy, Known.One); + + break; + } + + return nullptr; +} + + +/// Helper routine of SimplifyDemandedUseBits. It tries to simplify +/// "E1 = (X lsr C1) << C2", where the C1 and C2 are constant, into +/// "E2 = X << (C2 - C1)" or "E2 = X >> (C1 - C2)", depending on the sign +/// of "C2-C1". +/// +/// Suppose E1 and E2 are generally different in bits S={bm, bm+1, +/// ..., bn}, without considering the specific value X is holding. +/// This transformation is legal iff one of following conditions is hold: +/// 1) All the bit in S are 0, in this case E1 == E2. +/// 2) We don't care those bits in S, per the input DemandedMask. +/// 3) Combination of 1) and 2). Some bits in S are 0, and we don't care the +/// rest bits. +/// +/// Currently we only test condition 2). +/// +/// As with SimplifyDemandedUseBits, it returns NULL if the simplification was +/// not successful. +Value * +InstCombiner::simplifyShrShlDemandedBits(Instruction *Shr, const APInt &ShrOp1, + Instruction *Shl, const APInt &ShlOp1, + const APInt &DemandedMask, + KnownBits &Known) { + if (!ShlOp1 || !ShrOp1) + return nullptr; // No-op. + + Value *VarX = Shr->getOperand(0); + Type *Ty = VarX->getType(); + unsigned BitWidth = Ty->getScalarSizeInBits(); + if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth)) + return nullptr; // Undef. + + unsigned ShlAmt = ShlOp1.getZExtValue(); + unsigned ShrAmt = ShrOp1.getZExtValue(); + + Known.One.clearAllBits(); + Known.Zero.setLowBits(ShlAmt - 1); + Known.Zero &= DemandedMask; + + APInt BitMask1(APInt::getAllOnesValue(BitWidth)); + APInt BitMask2(APInt::getAllOnesValue(BitWidth)); + + bool isLshr = (Shr->getOpcode() == Instruction::LShr); + BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) : + (BitMask1.ashr(ShrAmt) << ShlAmt); + + if (ShrAmt <= ShlAmt) { + BitMask2 <<= (ShlAmt - ShrAmt); + } else { + BitMask2 = isLshr ? BitMask2.lshr(ShrAmt - ShlAmt): + BitMask2.ashr(ShrAmt - ShlAmt); + } + + // Check if condition-2 (see the comment to this function) is satified. + if ((BitMask1 & DemandedMask) == (BitMask2 & DemandedMask)) { + if (ShrAmt == ShlAmt) + return VarX; + + if (!Shr->hasOneUse()) + return nullptr; + + BinaryOperator *New; + if (ShrAmt < ShlAmt) { + Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt); + New = BinaryOperator::CreateShl(VarX, Amt); + BinaryOperator *Orig = cast<BinaryOperator>(Shl); + New->setHasNoSignedWrap(Orig->hasNoSignedWrap()); + New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap()); + } else { + Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt); + New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) : + BinaryOperator::CreateAShr(VarX, Amt); + if (cast<BinaryOperator>(Shr)->isExact()) + New->setIsExact(true); + } + + return InsertNewInstWith(New, *Shl); + } + + return nullptr; +} + +/// Implement SimplifyDemandedVectorElts for amdgcn buffer and image intrinsics. +/// +/// Note: This only supports non-TFE/LWE image intrinsic calls; those have +/// struct returns. +Value *InstCombiner::simplifyAMDGCNMemoryIntrinsicDemanded(IntrinsicInst *II, + APInt DemandedElts, + int DMaskIdx) { + + // FIXME: Allow v3i16/v3f16 in buffer intrinsics when the types are fully supported. + if (DMaskIdx < 0 && + II->getType()->getScalarSizeInBits() != 32 && + DemandedElts.getActiveBits() == 3) + return nullptr; + + unsigned VWidth = II->getType()->getVectorNumElements(); + if (VWidth == 1) + return nullptr; + + ConstantInt *NewDMask = nullptr; + + if (DMaskIdx < 0) { + // Pretend that a prefix of elements is demanded to simplify the code + // below. + DemandedElts = (1 << DemandedElts.getActiveBits()) - 1; + } else { + ConstantInt *DMask = cast<ConstantInt>(II->getArgOperand(DMaskIdx)); + unsigned DMaskVal = DMask->getZExtValue() & 0xf; + + // Mask off values that are undefined because the dmask doesn't cover them + DemandedElts &= (1 << countPopulation(DMaskVal)) - 1; + + unsigned NewDMaskVal = 0; + unsigned OrigLoadIdx = 0; + for (unsigned SrcIdx = 0; SrcIdx < 4; ++SrcIdx) { + const unsigned Bit = 1 << SrcIdx; + if (!!(DMaskVal & Bit)) { + if (!!DemandedElts[OrigLoadIdx]) + NewDMaskVal |= Bit; + OrigLoadIdx++; + } + } + + if (DMaskVal != NewDMaskVal) + NewDMask = ConstantInt::get(DMask->getType(), NewDMaskVal); + } + + unsigned NewNumElts = DemandedElts.countPopulation(); + if (!NewNumElts) + return UndefValue::get(II->getType()); + + if (NewNumElts >= VWidth && DemandedElts.isMask()) { + if (NewDMask) + II->setArgOperand(DMaskIdx, NewDMask); + return nullptr; + } + + // Determine the overload types of the original intrinsic. + auto IID = II->getIntrinsicID(); + SmallVector<Intrinsic::IITDescriptor, 16> Table; + getIntrinsicInfoTableEntries(IID, Table); + ArrayRef<Intrinsic::IITDescriptor> TableRef = Table; + + // Validate function argument and return types, extracting overloaded types + // along the way. + FunctionType *FTy = II->getCalledFunction()->getFunctionType(); + SmallVector<Type *, 6> OverloadTys; + Intrinsic::matchIntrinsicSignature(FTy, TableRef, OverloadTys); + + Module *M = II->getParent()->getParent()->getParent(); + Type *EltTy = II->getType()->getVectorElementType(); + Type *NewTy = (NewNumElts == 1) ? EltTy : VectorType::get(EltTy, NewNumElts); + + OverloadTys[0] = NewTy; + Function *NewIntrin = Intrinsic::getDeclaration(M, IID, OverloadTys); + + SmallVector<Value *, 16> Args; + for (unsigned I = 0, E = II->getNumArgOperands(); I != E; ++I) + Args.push_back(II->getArgOperand(I)); + + if (NewDMask) + Args[DMaskIdx] = NewDMask; + + IRBuilderBase::InsertPointGuard Guard(Builder); + Builder.SetInsertPoint(II); + + CallInst *NewCall = Builder.CreateCall(NewIntrin, Args); + NewCall->takeName(II); + NewCall->copyMetadata(*II); + + if (NewNumElts == 1) { + return Builder.CreateInsertElement(UndefValue::get(II->getType()), NewCall, + DemandedElts.countTrailingZeros()); + } + + SmallVector<uint32_t, 8> EltMask; + unsigned NewLoadIdx = 0; + for (unsigned OrigLoadIdx = 0; OrigLoadIdx < VWidth; ++OrigLoadIdx) { + if (!!DemandedElts[OrigLoadIdx]) + EltMask.push_back(NewLoadIdx++); + else + EltMask.push_back(NewNumElts); + } + + Value *Shuffle = + Builder.CreateShuffleVector(NewCall, UndefValue::get(NewTy), EltMask); + + return Shuffle; +} + +/// The specified value produces a vector with any number of elements. +/// This method analyzes which elements of the operand are undef and returns +/// that information in UndefElts. +/// +/// DemandedElts contains the set of elements that are actually used by the +/// caller, and by default (AllowMultipleUsers equals false) the value is +/// simplified only if it has a single caller. If AllowMultipleUsers is set +/// to true, DemandedElts refers to the union of sets of elements that are +/// used by all callers. +/// +/// If the information about demanded elements can be used to simplify the +/// operation, the operation is simplified, then the resultant value is +/// returned. This returns null if no change was made. +Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, + APInt &UndefElts, + unsigned Depth, + bool AllowMultipleUsers) { + unsigned VWidth = V->getType()->getVectorNumElements(); + APInt EltMask(APInt::getAllOnesValue(VWidth)); + assert((DemandedElts & ~EltMask) == 0 && "Invalid DemandedElts!"); + + if (isa<UndefValue>(V)) { + // If the entire vector is undefined, just return this info. + UndefElts = EltMask; + return nullptr; + } + + if (DemandedElts.isNullValue()) { // If nothing is demanded, provide undef. + UndefElts = EltMask; + return UndefValue::get(V->getType()); + } + + UndefElts = 0; + + if (auto *C = dyn_cast<Constant>(V)) { + // Check if this is identity. If so, return 0 since we are not simplifying + // anything. + if (DemandedElts.isAllOnesValue()) + return nullptr; + + Type *EltTy = cast<VectorType>(V->getType())->getElementType(); + Constant *Undef = UndefValue::get(EltTy); + SmallVector<Constant*, 16> Elts; + for (unsigned i = 0; i != VWidth; ++i) { + if (!DemandedElts[i]) { // If not demanded, set to undef. + Elts.push_back(Undef); + UndefElts.setBit(i); + continue; + } + + Constant *Elt = C->getAggregateElement(i); + if (!Elt) return nullptr; + + if (isa<UndefValue>(Elt)) { // Already undef. + Elts.push_back(Undef); + UndefElts.setBit(i); + } else { // Otherwise, defined. + Elts.push_back(Elt); + } + } + + // If we changed the constant, return it. + Constant *NewCV = ConstantVector::get(Elts); + return NewCV != C ? NewCV : nullptr; + } + + // Limit search depth. + if (Depth == 10) + return nullptr; + + if (!AllowMultipleUsers) { + // If multiple users are using the root value, proceed with + // simplification conservatively assuming that all elements + // are needed. + if (!V->hasOneUse()) { + // Quit if we find multiple users of a non-root value though. + // They'll be handled when it's their turn to be visited by + // the main instcombine process. + if (Depth != 0) + // TODO: Just compute the UndefElts information recursively. + return nullptr; + + // Conservatively assume that all elements are needed. + DemandedElts = EltMask; + } + } + + Instruction *I = dyn_cast<Instruction>(V); + if (!I) return nullptr; // Only analyze instructions. + + bool MadeChange = false; + auto simplifyAndSetOp = [&](Instruction *Inst, unsigned OpNum, + APInt Demanded, APInt &Undef) { + auto *II = dyn_cast<IntrinsicInst>(Inst); + Value *Op = II ? II->getArgOperand(OpNum) : Inst->getOperand(OpNum); + if (Value *V = SimplifyDemandedVectorElts(Op, Demanded, Undef, Depth + 1)) { + if (II) + II->setArgOperand(OpNum, V); + else + Inst->setOperand(OpNum, V); + MadeChange = true; + } + }; + + APInt UndefElts2(VWidth, 0); + APInt UndefElts3(VWidth, 0); + switch (I->getOpcode()) { + default: break; + + case Instruction::GetElementPtr: { + // The LangRef requires that struct geps have all constant indices. As + // such, we can't convert any operand to partial undef. + auto mayIndexStructType = [](GetElementPtrInst &GEP) { + for (auto I = gep_type_begin(GEP), E = gep_type_end(GEP); + I != E; I++) + if (I.isStruct()) + return true;; + return false; + }; + if (mayIndexStructType(cast<GetElementPtrInst>(*I))) + break; + + // Conservatively track the demanded elements back through any vector + // operands we may have. We know there must be at least one, or we + // wouldn't have a vector result to get here. Note that we intentionally + // merge the undef bits here since gepping with either an undef base or + // index results in undef. + for (unsigned i = 0; i < I->getNumOperands(); i++) { + if (isa<UndefValue>(I->getOperand(i))) { + // If the entire vector is undefined, just return this info. + UndefElts = EltMask; + return nullptr; + } + if (I->getOperand(i)->getType()->isVectorTy()) { + APInt UndefEltsOp(VWidth, 0); + simplifyAndSetOp(I, i, DemandedElts, UndefEltsOp); + UndefElts |= UndefEltsOp; + } + } + + break; + } + case Instruction::InsertElement: { + // If this is a variable index, we don't know which element it overwrites. + // demand exactly the same input as we produce. + ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2)); + if (!Idx) { + // Note that we can't propagate undef elt info, because we don't know + // which elt is getting updated. + simplifyAndSetOp(I, 0, DemandedElts, UndefElts2); + break; + } + + // The element inserted overwrites whatever was there, so the input demanded + // set is simpler than the output set. + unsigned IdxNo = Idx->getZExtValue(); + APInt PreInsertDemandedElts = DemandedElts; + if (IdxNo < VWidth) + PreInsertDemandedElts.clearBit(IdxNo); + + simplifyAndSetOp(I, 0, PreInsertDemandedElts, UndefElts); + + // If this is inserting an element that isn't demanded, remove this + // insertelement. + if (IdxNo >= VWidth || !DemandedElts[IdxNo]) { + Worklist.Add(I); + return I->getOperand(0); + } + + // The inserted element is defined. + UndefElts.clearBit(IdxNo); + break; + } + case Instruction::ShuffleVector: { + ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I); + unsigned LHSVWidth = + Shuffle->getOperand(0)->getType()->getVectorNumElements(); + APInt LeftDemanded(LHSVWidth, 0), RightDemanded(LHSVWidth, 0); + for (unsigned i = 0; i < VWidth; i++) { + if (DemandedElts[i]) { + unsigned MaskVal = Shuffle->getMaskValue(i); + if (MaskVal != -1u) { + assert(MaskVal < LHSVWidth * 2 && + "shufflevector mask index out of range!"); + if (MaskVal < LHSVWidth) + LeftDemanded.setBit(MaskVal); + else + RightDemanded.setBit(MaskVal - LHSVWidth); + } + } + } + + APInt LHSUndefElts(LHSVWidth, 0); + simplifyAndSetOp(I, 0, LeftDemanded, LHSUndefElts); + + APInt RHSUndefElts(LHSVWidth, 0); + simplifyAndSetOp(I, 1, RightDemanded, RHSUndefElts); + + bool NewUndefElts = false; + unsigned LHSIdx = -1u, LHSValIdx = -1u; + unsigned RHSIdx = -1u, RHSValIdx = -1u; + bool LHSUniform = true; + bool RHSUniform = true; + for (unsigned i = 0; i < VWidth; i++) { + unsigned MaskVal = Shuffle->getMaskValue(i); + if (MaskVal == -1u) { + UndefElts.setBit(i); + } else if (!DemandedElts[i]) { + NewUndefElts = true; + UndefElts.setBit(i); + } else if (MaskVal < LHSVWidth) { + if (LHSUndefElts[MaskVal]) { + NewUndefElts = true; + UndefElts.setBit(i); + } else { + LHSIdx = LHSIdx == -1u ? i : LHSVWidth; + LHSValIdx = LHSValIdx == -1u ? MaskVal : LHSVWidth; + LHSUniform = LHSUniform && (MaskVal == i); + } + } else { + if (RHSUndefElts[MaskVal - LHSVWidth]) { + NewUndefElts = true; + UndefElts.setBit(i); + } else { + RHSIdx = RHSIdx == -1u ? i : LHSVWidth; + RHSValIdx = RHSValIdx == -1u ? MaskVal - LHSVWidth : LHSVWidth; + RHSUniform = RHSUniform && (MaskVal - LHSVWidth == i); + } + } + } + + // Try to transform shuffle with constant vector and single element from + // this constant vector to single insertelement instruction. + // shufflevector V, C, <v1, v2, .., ci, .., vm> -> + // insertelement V, C[ci], ci-n + if (LHSVWidth == Shuffle->getType()->getNumElements()) { + Value *Op = nullptr; + Constant *Value = nullptr; + unsigned Idx = -1u; + + // Find constant vector with the single element in shuffle (LHS or RHS). + if (LHSIdx < LHSVWidth && RHSUniform) { + if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(0))) { + Op = Shuffle->getOperand(1); + Value = CV->getOperand(LHSValIdx); + Idx = LHSIdx; + } + } + if (RHSIdx < LHSVWidth && LHSUniform) { + if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(1))) { + Op = Shuffle->getOperand(0); + Value = CV->getOperand(RHSValIdx); + Idx = RHSIdx; + } + } + // Found constant vector with single element - convert to insertelement. + if (Op && Value) { + Instruction *New = InsertElementInst::Create( + Op, Value, ConstantInt::get(Type::getInt32Ty(I->getContext()), Idx), + Shuffle->getName()); + InsertNewInstWith(New, *Shuffle); + return New; + } + } + if (NewUndefElts) { + // Add additional discovered undefs. + SmallVector<Constant*, 16> Elts; + for (unsigned i = 0; i < VWidth; ++i) { + if (UndefElts[i]) + Elts.push_back(UndefValue::get(Type::getInt32Ty(I->getContext()))); + else + Elts.push_back(ConstantInt::get(Type::getInt32Ty(I->getContext()), + Shuffle->getMaskValue(i))); + } + I->setOperand(2, ConstantVector::get(Elts)); + MadeChange = true; + } + break; + } + case Instruction::Select: { + // If this is a vector select, try to transform the select condition based + // on the current demanded elements. + SelectInst *Sel = cast<SelectInst>(I); + if (Sel->getCondition()->getType()->isVectorTy()) { + // TODO: We are not doing anything with UndefElts based on this call. + // It is overwritten below based on the other select operands. If an + // element of the select condition is known undef, then we are free to + // choose the output value from either arm of the select. If we know that + // one of those values is undef, then the output can be undef. + simplifyAndSetOp(I, 0, DemandedElts, UndefElts); + } + + // Next, see if we can transform the arms of the select. + APInt DemandedLHS(DemandedElts), DemandedRHS(DemandedElts); + if (auto *CV = dyn_cast<ConstantVector>(Sel->getCondition())) { + for (unsigned i = 0; i < VWidth; i++) { + // isNullValue() always returns false when called on a ConstantExpr. + // Skip constant expressions to avoid propagating incorrect information. + Constant *CElt = CV->getAggregateElement(i); + if (isa<ConstantExpr>(CElt)) + continue; + // TODO: If a select condition element is undef, we can demand from + // either side. If one side is known undef, choosing that side would + // propagate undef. + if (CElt->isNullValue()) + DemandedLHS.clearBit(i); + else + DemandedRHS.clearBit(i); + } + } + + simplifyAndSetOp(I, 1, DemandedLHS, UndefElts2); + simplifyAndSetOp(I, 2, DemandedRHS, UndefElts3); + + // Output elements are undefined if the element from each arm is undefined. + // TODO: This can be improved. See comment in select condition handling. + UndefElts = UndefElts2 & UndefElts3; + break; + } + case Instruction::BitCast: { + // Vector->vector casts only. + VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType()); + if (!VTy) break; + unsigned InVWidth = VTy->getNumElements(); + APInt InputDemandedElts(InVWidth, 0); + UndefElts2 = APInt(InVWidth, 0); + unsigned Ratio; + + if (VWidth == InVWidth) { + // If we are converting from <4 x i32> -> <4 x f32>, we demand the same + // elements as are demanded of us. + Ratio = 1; + InputDemandedElts = DemandedElts; + } else if ((VWidth % InVWidth) == 0) { + // If the number of elements in the output is a multiple of the number of + // elements in the input then an input element is live if any of the + // corresponding output elements are live. + Ratio = VWidth / InVWidth; + for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) + if (DemandedElts[OutIdx]) + InputDemandedElts.setBit(OutIdx / Ratio); + } else if ((InVWidth % VWidth) == 0) { + // If the number of elements in the input is a multiple of the number of + // elements in the output then an input element is live if the + // corresponding output element is live. + Ratio = InVWidth / VWidth; + for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx) + if (DemandedElts[InIdx / Ratio]) + InputDemandedElts.setBit(InIdx); + } else { + // Unsupported so far. + break; + } + + simplifyAndSetOp(I, 0, InputDemandedElts, UndefElts2); + + if (VWidth == InVWidth) { + UndefElts = UndefElts2; + } else if ((VWidth % InVWidth) == 0) { + // If the number of elements in the output is a multiple of the number of + // elements in the input then an output element is undef if the + // corresponding input element is undef. + for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) + if (UndefElts2[OutIdx / Ratio]) + UndefElts.setBit(OutIdx); + } else if ((InVWidth % VWidth) == 0) { + // If the number of elements in the input is a multiple of the number of + // elements in the output then an output element is undef if all of the + // corresponding input elements are undef. + for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) { + APInt SubUndef = UndefElts2.lshr(OutIdx * Ratio).zextOrTrunc(Ratio); + if (SubUndef.countPopulation() == Ratio) + UndefElts.setBit(OutIdx); + } + } else { + llvm_unreachable("Unimp"); + } + break; + } + case Instruction::FPTrunc: + case Instruction::FPExt: + simplifyAndSetOp(I, 0, DemandedElts, UndefElts); + break; + + case Instruction::Call: { + IntrinsicInst *II = dyn_cast<IntrinsicInst>(I); + if (!II) break; + switch (II->getIntrinsicID()) { + case Intrinsic::masked_gather: // fallthrough + case Intrinsic::masked_load: { + // Subtlety: If we load from a pointer, the pointer must be valid + // regardless of whether the element is demanded. Doing otherwise risks + // segfaults which didn't exist in the original program. + APInt DemandedPtrs(APInt::getAllOnesValue(VWidth)), + DemandedPassThrough(DemandedElts); + if (auto *CV = dyn_cast<ConstantVector>(II->getOperand(2))) + for (unsigned i = 0; i < VWidth; i++) { + Constant *CElt = CV->getAggregateElement(i); + if (CElt->isNullValue()) + DemandedPtrs.clearBit(i); + else if (CElt->isAllOnesValue()) + DemandedPassThrough.clearBit(i); + } + if (II->getIntrinsicID() == Intrinsic::masked_gather) + simplifyAndSetOp(II, 0, DemandedPtrs, UndefElts2); + simplifyAndSetOp(II, 3, DemandedPassThrough, UndefElts3); + + // Output elements are undefined if the element from both sources are. + // TODO: can strengthen via mask as well. + UndefElts = UndefElts2 & UndefElts3; + break; + } + case Intrinsic::x86_xop_vfrcz_ss: + case Intrinsic::x86_xop_vfrcz_sd: + // The instructions for these intrinsics are speced to zero upper bits not + // pass them through like other scalar intrinsics. So we shouldn't just + // use Arg0 if DemandedElts[0] is clear like we do for other intrinsics. + // Instead we should return a zero vector. + if (!DemandedElts[0]) { + Worklist.Add(II); + return ConstantAggregateZero::get(II->getType()); + } + + // Only the lower element is used. + DemandedElts = 1; + simplifyAndSetOp(II, 0, DemandedElts, UndefElts); + + // Only the lower element is undefined. The high elements are zero. + UndefElts = UndefElts[0]; + break; + + // Unary scalar-as-vector operations that work column-wise. + case Intrinsic::x86_sse_rcp_ss: + case Intrinsic::x86_sse_rsqrt_ss: + simplifyAndSetOp(II, 0, DemandedElts, UndefElts); + + // If lowest element of a scalar op isn't used then use Arg0. + if (!DemandedElts[0]) { + Worklist.Add(II); + return II->getArgOperand(0); + } + // TODO: If only low elt lower SQRT to FSQRT (with rounding/exceptions + // checks). + break; + + // Binary scalar-as-vector operations that work column-wise. The high + // elements come from operand 0. The low element is a function of both + // operands. + case Intrinsic::x86_sse_min_ss: + case Intrinsic::x86_sse_max_ss: + case Intrinsic::x86_sse_cmp_ss: + case Intrinsic::x86_sse2_min_sd: + case Intrinsic::x86_sse2_max_sd: + case Intrinsic::x86_sse2_cmp_sd: { + simplifyAndSetOp(II, 0, DemandedElts, UndefElts); + + // If lowest element of a scalar op isn't used then use Arg0. + if (!DemandedElts[0]) { + Worklist.Add(II); + return II->getArgOperand(0); + } + + // Only lower element is used for operand 1. + DemandedElts = 1; + simplifyAndSetOp(II, 1, DemandedElts, UndefElts2); + + // Lower element is undefined if both lower elements are undefined. + // Consider things like undef&0. The result is known zero, not undef. + if (!UndefElts2[0]) + UndefElts.clearBit(0); + + break; + } + + // Binary scalar-as-vector operations that work column-wise. The high + // elements come from operand 0 and the low element comes from operand 1. + case Intrinsic::x86_sse41_round_ss: + case Intrinsic::x86_sse41_round_sd: { + // Don't use the low element of operand 0. + APInt DemandedElts2 = DemandedElts; + DemandedElts2.clearBit(0); + simplifyAndSetOp(II, 0, DemandedElts2, UndefElts); + + // If lowest element of a scalar op isn't used then use Arg0. + if (!DemandedElts[0]) { + Worklist.Add(II); + return II->getArgOperand(0); + } + + // Only lower element is used for operand 1. + DemandedElts = 1; + simplifyAndSetOp(II, 1, DemandedElts, UndefElts2); + + // Take the high undef elements from operand 0 and take the lower element + // from operand 1. + UndefElts.clearBit(0); + UndefElts |= UndefElts2[0]; + break; + } + + // Three input scalar-as-vector operations that work column-wise. The high + // elements come from operand 0 and the low element is a function of all + // three inputs. + case Intrinsic::x86_avx512_mask_add_ss_round: + case Intrinsic::x86_avx512_mask_div_ss_round: + case Intrinsic::x86_avx512_mask_mul_ss_round: + case Intrinsic::x86_avx512_mask_sub_ss_round: + case Intrinsic::x86_avx512_mask_max_ss_round: + case Intrinsic::x86_avx512_mask_min_ss_round: + case Intrinsic::x86_avx512_mask_add_sd_round: + case Intrinsic::x86_avx512_mask_div_sd_round: + case Intrinsic::x86_avx512_mask_mul_sd_round: + case Intrinsic::x86_avx512_mask_sub_sd_round: + case Intrinsic::x86_avx512_mask_max_sd_round: + case Intrinsic::x86_avx512_mask_min_sd_round: + simplifyAndSetOp(II, 0, DemandedElts, UndefElts); + + // If lowest element of a scalar op isn't used then use Arg0. + if (!DemandedElts[0]) { + Worklist.Add(II); + return II->getArgOperand(0); + } + + // Only lower element is used for operand 1 and 2. + DemandedElts = 1; + simplifyAndSetOp(II, 1, DemandedElts, UndefElts2); + simplifyAndSetOp(II, 2, DemandedElts, UndefElts3); + + // Lower element is undefined if all three lower elements are undefined. + // Consider things like undef&0. The result is known zero, not undef. + if (!UndefElts2[0] || !UndefElts3[0]) + UndefElts.clearBit(0); + + break; + + case Intrinsic::x86_sse2_packssdw_128: + case Intrinsic::x86_sse2_packsswb_128: + case Intrinsic::x86_sse2_packuswb_128: + case Intrinsic::x86_sse41_packusdw: + case Intrinsic::x86_avx2_packssdw: + case Intrinsic::x86_avx2_packsswb: + case Intrinsic::x86_avx2_packusdw: + case Intrinsic::x86_avx2_packuswb: + case Intrinsic::x86_avx512_packssdw_512: + case Intrinsic::x86_avx512_packsswb_512: + case Intrinsic::x86_avx512_packusdw_512: + case Intrinsic::x86_avx512_packuswb_512: { + auto *Ty0 = II->getArgOperand(0)->getType(); + unsigned InnerVWidth = Ty0->getVectorNumElements(); + assert(VWidth == (InnerVWidth * 2) && "Unexpected input size"); + + unsigned NumLanes = Ty0->getPrimitiveSizeInBits() / 128; + unsigned VWidthPerLane = VWidth / NumLanes; + unsigned InnerVWidthPerLane = InnerVWidth / NumLanes; + + // Per lane, pack the elements of the first input and then the second. + // e.g. + // v8i16 PACK(v4i32 X, v4i32 Y) - (X[0..3],Y[0..3]) + // v32i8 PACK(v16i16 X, v16i16 Y) - (X[0..7],Y[0..7]),(X[8..15],Y[8..15]) + for (int OpNum = 0; OpNum != 2; ++OpNum) { + APInt OpDemandedElts(InnerVWidth, 0); + for (unsigned Lane = 0; Lane != NumLanes; ++Lane) { + unsigned LaneIdx = Lane * VWidthPerLane; + for (unsigned Elt = 0; Elt != InnerVWidthPerLane; ++Elt) { + unsigned Idx = LaneIdx + Elt + InnerVWidthPerLane * OpNum; + if (DemandedElts[Idx]) + OpDemandedElts.setBit((Lane * InnerVWidthPerLane) + Elt); + } + } + + // Demand elements from the operand. + APInt OpUndefElts(InnerVWidth, 0); + simplifyAndSetOp(II, OpNum, OpDemandedElts, OpUndefElts); + + // Pack the operand's UNDEF elements, one lane at a time. + OpUndefElts = OpUndefElts.zext(VWidth); + for (unsigned Lane = 0; Lane != NumLanes; ++Lane) { + APInt LaneElts = OpUndefElts.lshr(InnerVWidthPerLane * Lane); + LaneElts = LaneElts.getLoBits(InnerVWidthPerLane); + LaneElts <<= InnerVWidthPerLane * (2 * Lane + OpNum); + UndefElts |= LaneElts; + } + } + break; + } + + // PSHUFB + case Intrinsic::x86_ssse3_pshuf_b_128: + case Intrinsic::x86_avx2_pshuf_b: + case Intrinsic::x86_avx512_pshuf_b_512: + // PERMILVAR + case Intrinsic::x86_avx_vpermilvar_ps: + case Intrinsic::x86_avx_vpermilvar_ps_256: + case Intrinsic::x86_avx512_vpermilvar_ps_512: + case Intrinsic::x86_avx_vpermilvar_pd: + case Intrinsic::x86_avx_vpermilvar_pd_256: + case Intrinsic::x86_avx512_vpermilvar_pd_512: + // PERMV + case Intrinsic::x86_avx2_permd: + case Intrinsic::x86_avx2_permps: { + simplifyAndSetOp(II, 1, DemandedElts, UndefElts); + break; + } + + // SSE4A instructions leave the upper 64-bits of the 128-bit result + // in an undefined state. + case Intrinsic::x86_sse4a_extrq: + case Intrinsic::x86_sse4a_extrqi: + case Intrinsic::x86_sse4a_insertq: + case Intrinsic::x86_sse4a_insertqi: + UndefElts.setHighBits(VWidth / 2); + break; + case Intrinsic::amdgcn_buffer_load: + case Intrinsic::amdgcn_buffer_load_format: + case Intrinsic::amdgcn_raw_buffer_load: + case Intrinsic::amdgcn_raw_buffer_load_format: + case Intrinsic::amdgcn_raw_tbuffer_load: + case Intrinsic::amdgcn_struct_buffer_load: + case Intrinsic::amdgcn_struct_buffer_load_format: + case Intrinsic::amdgcn_struct_tbuffer_load: + case Intrinsic::amdgcn_tbuffer_load: + return simplifyAMDGCNMemoryIntrinsicDemanded(II, DemandedElts); + default: { + if (getAMDGPUImageDMaskIntrinsic(II->getIntrinsicID())) + return simplifyAMDGCNMemoryIntrinsicDemanded(II, DemandedElts, 0); + + break; + } + } // switch on IntrinsicID + break; + } // case Call + } // switch on Opcode + + // TODO: We bail completely on integer div/rem and shifts because they have + // UB/poison potential, but that should be refined. + BinaryOperator *BO; + if (match(I, m_BinOp(BO)) && !BO->isIntDivRem() && !BO->isShift()) { + simplifyAndSetOp(I, 0, DemandedElts, UndefElts); + simplifyAndSetOp(I, 1, DemandedElts, UndefElts2); + + // Any change to an instruction with potential poison must clear those flags + // because we can not guarantee those constraints now. Other analysis may + // determine that it is safe to re-apply the flags. + if (MadeChange) + BO->dropPoisonGeneratingFlags(); + + // Output elements are undefined if both are undefined. Consider things + // like undef & 0. The result is known zero, not undef. + UndefElts &= UndefElts2; + } + + // If we've proven all of the lanes undef, return an undef value. + // TODO: Intersect w/demanded lanes + if (UndefElts.isAllOnesValue()) + return UndefValue::get(I->getType());; + + return MadeChange ? I : nullptr; +} |