| //===- InstCombineSimplifyDemanded.cpp ------------------------------------===// | |
| // | |
| // The LLVM Compiler Infrastructure | |
| // | |
| // This file is distributed under the University of Illinois Open Source | |
| // License. See LICENSE.TXT for details. | |
| // | |
| //===----------------------------------------------------------------------===// | |
| // | |
| // This file contains logic for simplifying instructions based on information | |
| // about how they are used. | |
| // | |
| //===----------------------------------------------------------------------===// | |
| #include "InstCombine.h" | |
| #include "llvm/Target/TargetData.h" | |
| #include "llvm/IntrinsicInst.h" | |
| using namespace llvm; | |
| /// ShrinkDemandedConstant - 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, | |
| APInt Demanded) { | |
| assert(I && "No instruction?"); | |
| assert(OpNo < I->getNumOperands() && "Operand index too large"); | |
| // If the operand is not a constant integer, nothing to do. | |
| ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo)); | |
| if (!OpC) return false; | |
| // If there are no bits set that aren't demanded, nothing to do. | |
| Demanded = Demanded.zextOrTrunc(OpC->getValue().getBitWidth()); | |
| if ((~Demanded & OpC->getValue()) == 0) | |
| return false; | |
| // This instruction is producing bits that are not demanded. Shrink the RHS. | |
| Demanded &= OpC->getValue(); | |
| I->setOperand(OpNo, ConstantInt::get(OpC->getType(), Demanded)); | |
| return true; | |
| } | |
| /// SimplifyDemandedInstructionBits - 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(); | |
| APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); | |
| APInt DemandedMask(APInt::getAllOnesValue(BitWidth)); | |
| Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask, | |
| KnownZero, KnownOne, 0); | |
| if (V == 0) return false; | |
| if (V == &Inst) return true; | |
| ReplaceInstUsesWith(Inst, V); | |
| return true; | |
| } | |
| /// SimplifyDemandedBits - 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(Use &U, APInt DemandedMask, | |
| APInt &KnownZero, APInt &KnownOne, | |
| unsigned Depth) { | |
| Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, | |
| KnownZero, KnownOne, Depth); | |
| if (NewVal == 0) return false; | |
| U = NewVal; | |
| return true; | |
| } | |
| /// SimplifyDemandedUseBits - 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. KnownZero 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. KnownOne and KnownZero always follow the invariant that | |
| /// KnownOne & KnownZero == 0. That is, a bit can't be both 1 and 0. Note that | |
| /// the bits in KnownOne and KnownZero may only be accurate for those bits set | |
| /// in DemandedMask. Note also that the bitwidth of V, DemandedMask, KnownZero | |
| /// and KnownOne 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, | |
| APInt &KnownZero, APInt &KnownOne, | |
| unsigned Depth) { | |
| assert(V != 0 && "Null pointer of Value???"); | |
| assert(Depth <= 6 && "Limit Search Depth"); | |
| uint32_t BitWidth = DemandedMask.getBitWidth(); | |
| Type *VTy = V->getType(); | |
| assert((TD || !VTy->isPointerTy()) && | |
| "SimplifyDemandedBits needs to know bit widths!"); | |
| assert((!TD || TD->getTypeSizeInBits(VTy->getScalarType()) == BitWidth) && | |
| (!VTy->isIntOrIntVectorTy() || | |
| VTy->getScalarSizeInBits() == BitWidth) && | |
| KnownZero.getBitWidth() == BitWidth && | |
| KnownOne.getBitWidth() == BitWidth && | |
| "Value *V, DemandedMask, KnownZero and KnownOne " | |
| "must have same BitWidth"); | |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { | |
| // We know all of the bits for a constant! | |
| KnownOne = CI->getValue() & DemandedMask; | |
| KnownZero = ~KnownOne & DemandedMask; | |
| return 0; | |
| } | |
| if (isa<ConstantPointerNull>(V)) { | |
| // We know all of the bits for a constant! | |
| KnownOne.clearAllBits(); | |
| KnownZero = DemandedMask; | |
| return 0; | |
| } | |
| KnownZero.clearAllBits(); | |
| KnownOne.clearAllBits(); | |
| if (DemandedMask == 0) { // Not demanding any bits from V. | |
| if (isa<UndefValue>(V)) | |
| return 0; | |
| return UndefValue::get(VTy); | |
| } | |
| if (Depth == 6) // Limit search depth. | |
| return 0; | |
| APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); | |
| APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0); | |
| Instruction *I = dyn_cast<Instruction>(V); | |
| if (!I) { | |
| ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth); | |
| return 0; // 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()) { | |
| // Despite the fact that we can't simplify this instruction in all User's | |
| // context, we can at least compute the knownzero/knownone 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. | |
| if (I->getOpcode() == Instruction::And) { | |
| // If either the LHS or the RHS are Zero, the result is zero. | |
| ComputeMaskedBits(I->getOperand(1), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1); | |
| ComputeMaskedBits(I->getOperand(0), DemandedMask & ~RHSKnownZero, | |
| LHSKnownZero, LHSKnownOne, Depth+1); | |
| // 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 & ~LHSKnownZero & RHSKnownOne) == | |
| (DemandedMask & ~LHSKnownZero)) | |
| return I->getOperand(0); | |
| if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) == | |
| (DemandedMask & ~RHSKnownZero)) | |
| return I->getOperand(1); | |
| // If all of the demanded bits in the inputs are known zeros, return zero. | |
| if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask) | |
| return Constant::getNullValue(VTy); | |
| } else if (I->getOpcode() == 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. | |
| ComputeMaskedBits(I->getOperand(1), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1); | |
| ComputeMaskedBits(I->getOperand(0), DemandedMask & ~RHSKnownOne, | |
| LHSKnownZero, LHSKnownOne, Depth+1); | |
| // 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 & ~LHSKnownOne & RHSKnownZero) == | |
| (DemandedMask & ~LHSKnownOne)) | |
| return I->getOperand(0); | |
| if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) == | |
| (DemandedMask & ~RHSKnownOne)) | |
| return I->getOperand(1); | |
| // If all of the potentially set bits on one side are known to be set on | |
| // the other side, just use the 'other' side. | |
| if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) == | |
| (DemandedMask & (~RHSKnownZero))) | |
| return I->getOperand(0); | |
| if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) == | |
| (DemandedMask & (~LHSKnownZero))) | |
| return I->getOperand(1); | |
| } | |
| // Compute the KnownZero/KnownOne bits to simplify things downstream. | |
| ComputeMaskedBits(I, DemandedMask, KnownZero, KnownOne, Depth); | |
| return 0; | |
| } | |
| // 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 = APInt::getAllOnesValue(BitWidth); | |
| switch (I->getOpcode()) { | |
| default: | |
| ComputeMaskedBits(I, DemandedMask, KnownZero, KnownOne, Depth); | |
| break; | |
| case Instruction::And: | |
| // If either the LHS or the RHS are Zero, the result is zero. | |
| if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownZero, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?"); | |
| assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?"); | |
| // 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 & ~LHSKnownZero & RHSKnownOne) == | |
| (DemandedMask & ~LHSKnownZero)) | |
| return I->getOperand(0); | |
| if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) == | |
| (DemandedMask & ~RHSKnownZero)) | |
| return I->getOperand(1); | |
| // If all of the demanded bits in the inputs are known zeros, return zero. | |
| if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask) | |
| return Constant::getNullValue(VTy); | |
| // If the RHS is a constant, see if we can simplify it. | |
| if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnownZero)) | |
| return I; | |
| // Output known-1 bits are only known if set in both the LHS & RHS. | |
| KnownOne = RHSKnownOne & LHSKnownOne; | |
| // Output known-0 are known to be clear if zero in either the LHS | RHS. | |
| KnownZero = RHSKnownZero | LHSKnownZero; | |
| break; | |
| case Instruction::Or: | |
| // If either the LHS or the RHS are One, the result is One. | |
| if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownOne, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?"); | |
| assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?"); | |
| // 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 & ~LHSKnownOne & RHSKnownZero) == | |
| (DemandedMask & ~LHSKnownOne)) | |
| return I->getOperand(0); | |
| if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) == | |
| (DemandedMask & ~RHSKnownOne)) | |
| return I->getOperand(1); | |
| // If all of the potentially set bits on one side are known to be set on | |
| // the other side, just use the 'other' side. | |
| if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) == | |
| (DemandedMask & (~RHSKnownZero))) | |
| return I->getOperand(0); | |
| if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) == | |
| (DemandedMask & (~LHSKnownZero))) | |
| return I->getOperand(1); | |
| // If the RHS is a constant, see if we can simplify it. | |
| if (ShrinkDemandedConstant(I, 1, DemandedMask)) | |
| return I; | |
| // Output known-0 bits are only known if clear in both the LHS & RHS. | |
| KnownZero = RHSKnownZero & LHSKnownZero; | |
| // Output known-1 are known to be set if set in either the LHS | RHS. | |
| KnownOne = RHSKnownOne | LHSKnownOne; | |
| break; | |
| case Instruction::Xor: { | |
| if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(0), DemandedMask, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?"); | |
| assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?"); | |
| // 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 & RHSKnownZero) == DemandedMask) | |
| return I->getOperand(0); | |
| if ((DemandedMask & LHSKnownZero) == DemandedMask) | |
| 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 & ~RHSKnownZero & ~LHSKnownZero) == 0) { | |
| 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 & (RHSKnownZero|RHSKnownOne)) == DemandedMask) { | |
| // all known | |
| if ((RHSKnownOne & LHSKnownOne) == RHSKnownOne) { | |
| Constant *AndC = Constant::getIntegerValue(VTy, | |
| ~RHSKnownOne & 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)) && | |
| (LHSKnownOne & RHSKnownOne & DemandedMask) != 0) { | |
| ConstantInt *AndRHS = cast<ConstantInt>(LHSInst->getOperand(1)); | |
| ConstantInt *XorRHS = cast<ConstantInt>(I->getOperand(1)); | |
| APInt NewMask = ~(LHSKnownOne & RHSKnownOne & 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. | |
| KnownZero= (RHSKnownZero & LHSKnownZero) | (RHSKnownOne & LHSKnownOne); | |
| // Output known-1 are known to be set if set in only one of the LHS, RHS. | |
| KnownOne = (RHSKnownZero & LHSKnownOne) | (RHSKnownOne & LHSKnownZero); | |
| break; | |
| } | |
| case Instruction::Select: | |
| if (SimplifyDemandedBits(I->getOperandUse(2), DemandedMask, | |
| RHSKnownZero, RHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(1), DemandedMask, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?"); | |
| assert(!(LHSKnownZero & LHSKnownOne) && "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. | |
| KnownOne = RHSKnownOne & LHSKnownOne; | |
| KnownZero = RHSKnownZero & LHSKnownZero; | |
| break; | |
| case Instruction::Trunc: { | |
| unsigned truncBf = I->getOperand(0)->getType()->getScalarSizeInBits(); | |
| DemandedMask = DemandedMask.zext(truncBf); | |
| KnownZero = KnownZero.zext(truncBf); | |
| KnownOne = KnownOne.zext(truncBf); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| DemandedMask = DemandedMask.trunc(BitWidth); | |
| KnownZero = KnownZero.trunc(BitWidth); | |
| KnownOne = KnownOne.trunc(BitWidth); | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| break; | |
| } | |
| case Instruction::BitCast: | |
| if (!I->getOperand(0)->getType()->isIntOrIntVectorTy()) | |
| return 0; // 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 0; | |
| } else | |
| // Don't touch a scalar-to-vector bitcast. | |
| return 0; | |
| } else if (I->getOperand(0)->getType()->isVectorTy()) | |
| // Don't touch a vector-to-scalar bitcast. | |
| return 0; | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| break; | |
| case Instruction::ZExt: { | |
| // Compute the bits in the result that are not present in the input. | |
| unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits(); | |
| DemandedMask = DemandedMask.trunc(SrcBitWidth); | |
| KnownZero = KnownZero.trunc(SrcBitWidth); | |
| KnownOne = KnownOne.trunc(SrcBitWidth); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| DemandedMask = DemandedMask.zext(BitWidth); | |
| KnownZero = KnownZero.zext(BitWidth); | |
| KnownOne = KnownOne.zext(BitWidth); | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| // The top bits are known to be zero. | |
| KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); | |
| 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 & | |
| APInt::getLowBitsSet(BitWidth, SrcBitWidth); | |
| APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth)); | |
| // If any of the sign extended bits are demanded, we know that the sign | |
| // bit is demanded. | |
| if ((NewBits & DemandedMask) != 0) | |
| InputDemandedBits.setBit(SrcBitWidth-1); | |
| InputDemandedBits = InputDemandedBits.trunc(SrcBitWidth); | |
| KnownZero = KnownZero.trunc(SrcBitWidth); | |
| KnownOne = KnownOne.trunc(SrcBitWidth); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), InputDemandedBits, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| InputDemandedBits = InputDemandedBits.zext(BitWidth); | |
| KnownZero = KnownZero.zext(BitWidth); | |
| KnownOne = KnownOne.zext(BitWidth); | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| // If the sign bit of the input is known set or clear, then we know the | |
| // top bits of the result. | |
| // If the input sign bit is known zero, or if the NewBits are not demanded | |
| // convert this into a zero extension. | |
| if (KnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) { | |
| // Convert to ZExt cast | |
| CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName()); | |
| return InsertNewInstWith(NewCast, *I); | |
| } else if (KnownOne[SrcBitWidth-1]) { // Input sign bit known set | |
| KnownOne |= NewBits; | |
| } | |
| break; | |
| } | |
| case Instruction::Add: { | |
| // Figure out what the input bits are. If the top bits of the and result | |
| // are not demanded, then the add doesn't demand them from its input | |
| // either. | |
| unsigned NLZ = DemandedMask.countLeadingZeros(); | |
| // If there is a constant on the RHS, there are a variety of xformations | |
| // we can do. | |
| if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { | |
| // If null, this should be simplified elsewhere. Some of the xforms here | |
| // won't work if the RHS is zero. | |
| if (RHS->isZero()) | |
| break; | |
| // If the top bit of the output is demanded, demand everything from the | |
| // input. Otherwise, we demand all the input bits except NLZ top bits. | |
| APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ)); | |
| // Find information about known zero/one bits in the input. | |
| if (SimplifyDemandedBits(I->getOperandUse(0), InDemandedBits, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| // If the RHS of the add has bits set that can't affect the input, reduce | |
| // the constant. | |
| if (ShrinkDemandedConstant(I, 1, InDemandedBits)) | |
| return I; | |
| // Avoid excess work. | |
| if (LHSKnownZero == 0 && LHSKnownOne == 0) | |
| break; | |
| // Turn it into OR if input bits are zero. | |
| if ((LHSKnownZero & RHS->getValue()) == RHS->getValue()) { | |
| Instruction *Or = | |
| BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1), | |
| I->getName()); | |
| return InsertNewInstWith(Or, *I); | |
| } | |
| // We can say something about the output known-zero and known-one bits, | |
| // depending on potential carries from the input constant and the | |
| // unknowns. For example if the LHS is known to have at most the 0x0F0F0 | |
| // bits set and the RHS constant is 0x01001, then we know we have a known | |
| // one mask of 0x00001 and a known zero mask of 0xE0F0E. | |
| // To compute this, we first compute the potential carry bits. These are | |
| // the bits which may be modified. I'm not aware of a better way to do | |
| // this scan. | |
| const APInt &RHSVal = RHS->getValue(); | |
| APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal)); | |
| // Now that we know which bits have carries, compute the known-1/0 sets. | |
| // Bits are known one if they are known zero in one operand and one in the | |
| // other, and there is no input carry. | |
| KnownOne = ((LHSKnownZero & RHSVal) | | |
| (LHSKnownOne & ~RHSVal)) & ~CarryBits; | |
| // Bits are known zero if they are known zero in both operands and there | |
| // is no input carry. | |
| KnownZero = LHSKnownZero & ~RHSVal & ~CarryBits; | |
| } else { | |
| // If the high-bits of this ADD are not demanded, then it does not demand | |
| // the high bits of its LHS or RHS. | |
| if (DemandedMask[BitWidth-1] == 0) { | |
| // Right fill the mask of bits for this ADD to demand the most | |
| // significant bit and all those below it. | |
| APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps, | |
| LHSKnownZero, LHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| } | |
| } | |
| break; | |
| } | |
| case Instruction::Sub: | |
| // If the high-bits of this SUB are not demanded, then it does not demand | |
| // the high bits of its LHS or RHS. | |
| if (DemandedMask[BitWidth-1] == 0) { | |
| // Right fill the mask of bits for this SUB to demand the most | |
| // significant bit and all those below it. | |
| uint32_t NLZ = DemandedMask.countLeadingZeros(); | |
| APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps, | |
| LHSKnownZero, LHSKnownOne, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| } | |
| // Otherwise just hand the sub off to ComputeMaskedBits to fill in | |
| // the known zeros and ones. | |
| ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth); | |
| break; | |
| case Instruction::Shl: | |
| if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { | |
| 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 |= APInt::getHighBitsSet(BitWidth, ShiftAmt+1); | |
| else if (IOp->hasNoUnsignedWrap()) | |
| DemandedMaskIn |= APInt::getHighBitsSet(BitWidth, ShiftAmt); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| KnownZero <<= ShiftAmt; | |
| KnownOne <<= ShiftAmt; | |
| // low bits known zero. | |
| if (ShiftAmt) | |
| KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt); | |
| } | |
| break; | |
| case Instruction::LShr: | |
| // For a logical shift right | |
| if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { | |
| 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 |= APInt::getLowBitsSet(BitWidth, ShiftAmt); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); | |
| KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); | |
| if (ShiftAmt) { | |
| // Compute the new bits that are at the top now. | |
| APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt)); | |
| KnownZero |= HighBits; // 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 == 1) { | |
| // 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.isSignBit()) | |
| return I->getOperand(0); | |
| if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { | |
| 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.setBit(BitWidth-1); | |
| // If the shift is exact, then it does demand the low bits (and knows that | |
| // they are zero). | |
| if (cast<AShrOperator>(I)->isExact()) | |
| DemandedMaskIn |= APInt::getLowBitsSet(BitWidth, ShiftAmt); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn, | |
| KnownZero, KnownOne, Depth+1)) | |
| return I; | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| // Compute the new bits that are at the top now. | |
| APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt)); | |
| KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); | |
| KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); | |
| // Handle the sign bits. | |
| APInt SignBit(APInt::getSignBit(BitWidth)); | |
| // Adjust to where it is now in the mask. | |
| SignBit = APIntOps::lshr(SignBit, 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. | |
| if (BitWidth <= ShiftAmt || KnownZero[BitWidth-ShiftAmt-1] || | |
| (HighBits & ~DemandedMask) == HighBits) { | |
| // Perform the logical shift right. | |
| Instruction *NewVal = BinaryOperator::CreateLShr( | |
| I->getOperand(0), SA, I->getName()); | |
| return InsertNewInstWith(NewVal, *I); | |
| } else if ((KnownOne & SignBit) != 0) { // New bits are known one. | |
| KnownOne |= HighBits; | |
| } | |
| } | |
| 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->isAllOnesValue()) | |
| 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::getSignBit(BitWidth); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), Mask2, | |
| LHSKnownZero, LHSKnownOne, Depth+1)) | |
| return I; | |
| // The low bits of LHS are unchanged by the srem. | |
| KnownZero = LHSKnownZero & LowBits; | |
| KnownOne = LHSKnownOne & LowBits; | |
| // If LHS is non-negative or has all low bits zero, then the upper bits | |
| // are all zero. | |
| if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits)) | |
| KnownZero |= ~LowBits; | |
| // If LHS is negative and not all low bits are zero, then the upper bits | |
| // are all one. | |
| if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0)) | |
| KnownOne |= ~LowBits; | |
| assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); | |
| } | |
| } | |
| // The sign bit is the LHS's sign bit, except when the result of the | |
| // remainder is zero. | |
| if (DemandedMask.isNegative() && KnownZero.isNonNegative()) { | |
| APInt Mask2 = APInt::getSignBit(BitWidth); | |
| APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); | |
| ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, | |
| Depth+1); | |
| // If it's known zero, our sign bit is also zero. | |
| if (LHSKnownZero.isNegative()) | |
| KnownZero |= LHSKnownZero; | |
| } | |
| break; | |
| case Instruction::URem: { | |
| APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0); | |
| APInt AllOnes = APInt::getAllOnesValue(BitWidth); | |
| if (SimplifyDemandedBits(I->getOperandUse(0), AllOnes, | |
| KnownZero2, KnownOne2, Depth+1) || | |
| SimplifyDemandedBits(I->getOperandUse(1), AllOnes, | |
| KnownZero2, KnownOne2, Depth+1)) | |
| return I; | |
| unsigned Leaders = KnownZero2.countLeadingOnes(); | |
| Leaders = std::max(Leaders, | |
| KnownZero2.countLeadingOnes()); | |
| KnownZero = 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::x86_sse42_crc32_64_8: | |
| case Intrinsic::x86_sse42_crc32_64_64: | |
| KnownZero = APInt::getHighBitsSet(64, 32); | |
| return 0; | |
| } | |
| } | |
| ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth); | |
| break; | |
| } | |
| // If the client is only demanding bits that we know, return the known | |
| // constant. | |
| if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) | |
| return Constant::getIntegerValue(VTy, KnownOne); | |
| return 0; | |
| } | |
| /// SimplifyDemandedVectorElts - The specified value produces a vector with | |
| /// any number of elements. DemandedElts contains the set of elements that are | |
| /// actually used by the caller. This method analyzes which elements of the | |
| /// operand are undef and returns that information in UndefElts. | |
| /// | |
| /// 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) { | |
| unsigned VWidth = cast<VectorType>(V->getType())->getNumElements(); | |
| 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 0; | |
| } | |
| if (DemandedElts == 0) { // If nothing is demanded, provide undef. | |
| UndefElts = EltMask; | |
| return UndefValue::get(V->getType()); | |
| } | |
| UndefElts = 0; | |
| if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) { | |
| Type *EltTy = cast<VectorType>(V->getType())->getElementType(); | |
| Constant *Undef = UndefValue::get(EltTy); | |
| std::vector<Constant*> Elts; | |
| for (unsigned i = 0; i != VWidth; ++i) | |
| if (!DemandedElts[i]) { // If not demanded, set to undef. | |
| Elts.push_back(Undef); | |
| UndefElts.setBit(i); | |
| } else if (isa<UndefValue>(CV->getOperand(i))) { // Already undef. | |
| Elts.push_back(Undef); | |
| UndefElts.setBit(i); | |
| } else { // Otherwise, defined. | |
| Elts.push_back(CV->getOperand(i)); | |
| } | |
| // If we changed the constant, return it. | |
| Constant *NewCP = ConstantVector::get(Elts); | |
| return NewCP != CV ? NewCP : 0; | |
| } | |
| if (isa<ConstantAggregateZero>(V)) { | |
| // Simplify the CAZ to a ConstantVector where the non-demanded elements are | |
| // set to undef. | |
| // Check if this is identity. If so, return 0 since we are not simplifying | |
| // anything. | |
| if (DemandedElts.isAllOnesValue()) | |
| return 0; | |
| Type *EltTy = cast<VectorType>(V->getType())->getElementType(); | |
| Constant *Zero = Constant::getNullValue(EltTy); | |
| Constant *Undef = UndefValue::get(EltTy); | |
| std::vector<Constant*> Elts; | |
| for (unsigned i = 0; i != VWidth; ++i) { | |
| Constant *Elt = DemandedElts[i] ? Zero : Undef; | |
| Elts.push_back(Elt); | |
| } | |
| UndefElts = DemandedElts ^ EltMask; | |
| return ConstantVector::get(Elts); | |
| } | |
| // Limit search depth. | |
| if (Depth == 10) | |
| return 0; | |
| // 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 0; | |
| // Conservatively assume that all elements are needed. | |
| DemandedElts = EltMask; | |
| } | |
| Instruction *I = dyn_cast<Instruction>(V); | |
| if (!I) return 0; // Only analyze instructions. | |
| bool MadeChange = false; | |
| APInt UndefElts2(VWidth, 0); | |
| Value *TmpV; | |
| switch (I->getOpcode()) { | |
| default: 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 == 0) { | |
| // Note that we can't propagate undef elt info, because we don't know | |
| // which elt is getting updated. | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts, | |
| UndefElts2, Depth+1); | |
| if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } | |
| break; | |
| } | |
| // If this is inserting an element that isn't demanded, remove this | |
| // insertelement. | |
| unsigned IdxNo = Idx->getZExtValue(); | |
| if (IdxNo >= VWidth || !DemandedElts[IdxNo]) { | |
| Worklist.Add(I); | |
| return I->getOperand(0); | |
| } | |
| // Otherwise, the element inserted overwrites whatever was there, so the | |
| // input demanded set is simpler than the output set. | |
| APInt DemandedElts2 = DemandedElts; | |
| DemandedElts2.clearBit(IdxNo); | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts2, | |
| UndefElts, Depth+1); | |
| if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } | |
| // The inserted element is defined. | |
| UndefElts.clearBit(IdxNo); | |
| break; | |
| } | |
| case Instruction::ShuffleVector: { | |
| ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I); | |
| uint64_t LHSVWidth = | |
| cast<VectorType>(Shuffle->getOperand(0)->getType())->getNumElements(); | |
| 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 UndefElts4(LHSVWidth, 0); | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(0), LeftDemanded, | |
| UndefElts4, Depth+1); | |
| if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } | |
| APInt UndefElts3(LHSVWidth, 0); | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(1), RightDemanded, | |
| UndefElts3, Depth+1); | |
| if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; } | |
| bool NewUndefElts = false; | |
| 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 (UndefElts4[MaskVal]) { | |
| NewUndefElts = true; | |
| UndefElts.setBit(i); | |
| } | |
| } else { | |
| if (UndefElts3[MaskVal - LHSVWidth]) { | |
| NewUndefElts = true; | |
| UndefElts.setBit(i); | |
| } | |
| } | |
| } | |
| if (NewUndefElts) { | |
| // Add additional discovered undefs. | |
| std::vector<Constant*> 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::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); | |
| 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) { | |
| // Untested so far. | |
| break; | |
| // If there are more elements in the result than there are in the source, | |
| // 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 { | |
| // Untested so far. | |
| break; | |
| // If there are more elements in the source than there are in the result, | |
| // 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); | |
| } | |
| // div/rem demand all inputs, because they don't want divide by zero. | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(0), InputDemandedElts, | |
| UndefElts2, Depth+1); | |
| if (TmpV) { | |
| I->setOperand(0, TmpV); | |
| MadeChange = true; | |
| } | |
| UndefElts = UndefElts2; | |
| if (VWidth > InVWidth) { | |
| llvm_unreachable("Unimp"); | |
| // If there are more elements in the result than there are in the source, | |
| // 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 (VWidth < InVWidth) { | |
| llvm_unreachable("Unimp"); | |
| // If there are more elements in the source than there are in the result, | |
| // then a result element is undef if all of the corresponding input | |
| // elements are undef. | |
| UndefElts = ~0ULL >> (64-VWidth); // Start out all undef. | |
| for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx) | |
| if (!UndefElts2[InIdx]) // Not undef? | |
| UndefElts.clearBit(InIdx/Ratio); // Clear undef bit. | |
| } | |
| break; | |
| } | |
| case Instruction::And: | |
| case Instruction::Or: | |
| case Instruction::Xor: | |
| case Instruction::Add: | |
| case Instruction::Sub: | |
| case Instruction::Mul: | |
| // div/rem demand all inputs, because they don't want divide by zero. | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts, | |
| UndefElts, Depth+1); | |
| if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } | |
| TmpV = SimplifyDemandedVectorElts(I->getOperand(1), DemandedElts, | |
| UndefElts2, Depth+1); | |
| if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; } | |
| // Output elements are undefined if both are undefined. Consider things | |
| // like undef&0. The result is known zero, not undef. | |
| UndefElts &= UndefElts2; | |
| break; | |
| case Instruction::Call: { | |
| IntrinsicInst *II = dyn_cast<IntrinsicInst>(I); | |
| if (!II) break; | |
| switch (II->getIntrinsicID()) { | |
| default: break; | |
| // Binary vector operations that work column-wise. A dest element is a | |
| // function of the corresponding input elements from the two inputs. | |
| case Intrinsic::x86_sse_sub_ss: | |
| case Intrinsic::x86_sse_mul_ss: | |
| case Intrinsic::x86_sse_min_ss: | |
| case Intrinsic::x86_sse_max_ss: | |
| case Intrinsic::x86_sse2_sub_sd: | |
| case Intrinsic::x86_sse2_mul_sd: | |
| case Intrinsic::x86_sse2_min_sd: | |
| case Intrinsic::x86_sse2_max_sd: | |
| TmpV = SimplifyDemandedVectorElts(II->getArgOperand(0), DemandedElts, | |
| UndefElts, Depth+1); | |
| if (TmpV) { II->setArgOperand(0, TmpV); MadeChange = true; } | |
| TmpV = SimplifyDemandedVectorElts(II->getArgOperand(1), DemandedElts, | |
| UndefElts2, Depth+1); | |
| if (TmpV) { II->setArgOperand(1, TmpV); MadeChange = true; } | |
| // If only the low elt is demanded and this is a scalarizable intrinsic, | |
| // scalarize it now. | |
| if (DemandedElts == 1) { | |
| switch (II->getIntrinsicID()) { | |
| default: break; | |
| case Intrinsic::x86_sse_sub_ss: | |
| case Intrinsic::x86_sse_mul_ss: | |
| case Intrinsic::x86_sse2_sub_sd: | |
| case Intrinsic::x86_sse2_mul_sd: | |
| // TODO: Lower MIN/MAX/ABS/etc | |
| Value *LHS = II->getArgOperand(0); | |
| Value *RHS = II->getArgOperand(1); | |
| // Extract the element as scalars. | |
| LHS = InsertNewInstWith(ExtractElementInst::Create(LHS, | |
| ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U)), *II); | |
| RHS = InsertNewInstWith(ExtractElementInst::Create(RHS, | |
| ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U)), *II); | |
| switch (II->getIntrinsicID()) { | |
| default: llvm_unreachable("Case stmts out of sync!"); | |
| case Intrinsic::x86_sse_sub_ss: | |
| case Intrinsic::x86_sse2_sub_sd: | |
| TmpV = InsertNewInstWith(BinaryOperator::CreateFSub(LHS, RHS, | |
| II->getName()), *II); | |
| break; | |
| case Intrinsic::x86_sse_mul_ss: | |
| case Intrinsic::x86_sse2_mul_sd: | |
| TmpV = InsertNewInstWith(BinaryOperator::CreateFMul(LHS, RHS, | |
| II->getName()), *II); | |
| break; | |
| } | |
| Instruction *New = | |
| InsertElementInst::Create( | |
| UndefValue::get(II->getType()), TmpV, | |
| ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U, false), | |
| II->getName()); | |
| InsertNewInstWith(New, *II); | |
| return New; | |
| } | |
| } | |
| // Output elements are undefined if both are undefined. Consider things | |
| // like undef&0. The result is known zero, not undef. | |
| UndefElts &= UndefElts2; | |
| break; | |
| } | |
| break; | |
| } | |
| } | |
| return MadeChange ? I : 0; | |
| } |