/3rd_party/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
C++ | 1285 lines | 850 code | 144 blank | 291 comment | 288 complexity | bae04db3ea642572d1f62d633a49082c MD5 | raw file
Possible License(s): LGPL-2.1, BSD-3-Clause, JSON, MPL-2.0-no-copyleft-exception, GPL-2.0, GPL-3.0, LGPL-3.0, BSD-2-Clause
- //===- 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/IR/DataLayout.h"
- #include "llvm/IR/IntrinsicInst.h"
- #include "llvm/Support/PatternMatch.h"
- using namespace llvm;
- using namespace llvm::PatternMatch;
- /// 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, 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), RHSKnownZero, RHSKnownOne, Depth+1);
- ComputeMaskedBits(I->getOperand(0), 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), RHSKnownZero, RHSKnownOne, Depth+1);
- ComputeMaskedBits(I->getOperand(0), 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);
- } else if (I->getOpcode() == 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.
- ComputeMaskedBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth+1);
- ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
- // If all of the demanded bits are known zero on one side, return the
- // other.
- if ((DemandedMask & RHSKnownZero) == DemandedMask)
- return I->getOperand(0);
- if ((DemandedMask & LHSKnownZero) == DemandedMask)
- return I->getOperand(1);
- }
- // Compute the KnownZero/KnownOne bits to simplify things downstream.
- ComputeMaskedBits(I, 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, 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, KnownZero, KnownOne, Depth);
- // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
- // zero.
- if (ConstantInt *C0 = dyn_cast<ConstantInt>(I->getOperand(0))) {
- APInt I0 = C0->getValue();
- if ((I0 + 1).isPowerOf2() && (I0 | KnownZero).isAllOnesValue()) {
- Instruction *Xor = BinaryOperator::CreateXor(I->getOperand(1), C0);
- return InsertNewInstWith(Xor, *I);
- }
- }
- break;
- case Instruction::Shl:
- if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
- {
- Value *VarX; ConstantInt *C1;
- if (match(I->getOperand(0), m_Shr(m_Value(VarX), m_ConstantInt(C1)))) {
- Instruction *Shr = cast<Instruction>(I->getOperand(0));
- Value *R = SimplifyShrShlDemandedBits(Shr, I, DemandedMask,
- KnownZero, KnownOne);
- if (R)
- 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 |= 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.
- BinaryOperator *NewVal = BinaryOperator::CreateLShr(I->getOperand(0),
- SA, I->getName());
- NewVal->setIsExact(cast<BinaryOperator>(I)->isExact());
- 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 LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
- ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
- // If it's known zero, our sign bit is also zero.
- if (LHSKnownZero.isNegative())
- KnownZero.setBit(KnownZero.getBitWidth() - 1);
- }
- 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_64:
- KnownZero = APInt::getHighBitsSet(64, 32);
- return 0;
- }
- }
- ComputeMaskedBits(V, 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;
- }
- /// 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,
- Instruction *Shl, APInt DemandedMask, APInt &KnownZero, APInt &KnownOne) {
- const APInt &ShlOp1 = cast<ConstantInt>(Shl->getOperand(1))->getValue();
- const APInt &ShrOp1 = cast<ConstantInt>(Shr->getOperand(1))->getValue();
- if (!ShlOp1 || !ShrOp1)
- return 0; // Noop.
- Value *VarX = Shr->getOperand(0);
- Type *Ty = VarX->getType();
- unsigned BitWidth = Ty->getIntegerBitWidth();
- if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
- return 0; // Undef.
- unsigned ShlAmt = ShlOp1.getZExtValue();
- unsigned ShrAmt = ShrOp1.getZExtValue();
- KnownOne.clearAllBits();
- KnownZero = APInt::getBitsSet(KnownZero.getBitWidth(), 0, ShlAmt-1);
- KnownZero &= 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 0;
- 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 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;
- // Handle ConstantAggregateZero, ConstantVector, ConstantDataSequential.
- if (Constant *C = dyn_cast<Constant>(V)) {
- // 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 *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 == 0) return 0;
- 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 : 0;
- }
- // 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.
- 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: {
- APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
- if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
- for (unsigned i = 0; i < VWidth; i++) {
- if (CV->getAggregateElement(i)->isNullValue())
- LeftDemanded.clearBit(i);
- else
- RightDemanded.clearBit(i);
- }
- }
- TmpV = SimplifyDemandedVectorElts(I->getOperand(1), LeftDemanded,
- UndefElts, Depth+1);
- if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
- TmpV = SimplifyDemandedVectorElts(I->getOperand(2), RightDemanded,
- UndefElts2, Depth+1);
- if (TmpV) { I->setOperand(2, TmpV); MadeChange = true; }
- // Output elements are undefined if both are undefined.
- UndefElts &= UndefElts2;
- 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::FPTrunc:
- case Instruction::FPExt:
- TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
- UndefElts, Depth+1);
- if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
- 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;
- }