| //===- 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 "InstCombineInternal.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/PatternMatch.h" |
| |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| #define DEBUG_TYPE "instcombine" |
| |
| /// 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, &Inst); |
| if (!V) 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) { |
| auto *UserI = dyn_cast<Instruction>(U.getUser()); |
| Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, KnownZero, |
| KnownOne, Depth, UserI); |
| if (!NewVal) 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, |
| Instruction *CxtI) { |
| assert(V != nullptr && "Null pointer of Value???"); |
| assert(Depth <= 6 && "Limit Search Depth"); |
| uint32_t BitWidth = DemandedMask.getBitWidth(); |
| Type *VTy = V->getType(); |
| assert( |
| (!VTy->isIntOrIntVectorTy() || VTy->getScalarSizeInBits() == BitWidth) && |
| 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 nullptr; |
| } |
| if (isa<ConstantPointerNull>(V)) { |
| // We know all of the bits for a constant! |
| KnownOne.clearAllBits(); |
| KnownZero = DemandedMask; |
| return nullptr; |
| } |
| |
| KnownZero.clearAllBits(); |
| KnownOne.clearAllBits(); |
| if (DemandedMask == 0) { // Not demanding any bits from V. |
| if (isa<UndefValue>(V)) |
| return nullptr; |
| return UndefValue::get(VTy); |
| } |
| |
| if (Depth == 6) // Limit search depth. |
| return nullptr; |
| |
| APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); |
| APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0); |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) { |
| computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); |
| return nullptr; // Only analyze instructions. |
| } |
| |
| // If there are multiple uses of this value and we aren't at the root, then |
| // we can't do any simplifications of the operands, because DemandedMask |
| // only reflects the bits demanded by *one* of the users. |
| if (Depth != 0 && !I->hasOneUse()) { |
| // 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. |
| computeKnownBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth + 1, |
| CxtI); |
| computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, |
| CxtI); |
| |
| // 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. |
| computeKnownBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth + 1, |
| CxtI); |
| computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, |
| CxtI); |
| |
| // 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. |
| |
| computeKnownBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth + 1, |
| CxtI); |
| computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, |
| CxtI); |
| |
| // 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. |
| computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); |
| return nullptr; |
| } |
| |
| // 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: |
| computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); |
| 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 the client is only demanding bits that we know, return the known |
| // constant. |
| if ((DemandedMask & ((RHSKnownZero | LHSKnownZero)| |
| (RHSKnownOne & LHSKnownOne))) == DemandedMask) |
| return Constant::getIntegerValue(VTy, RHSKnownOne & LHSKnownOne); |
| |
| // 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 the client is only demanding bits that we know, return the known |
| // constant. |
| if ((DemandedMask & ((RHSKnownZero & LHSKnownZero)| |
| (RHSKnownOne | LHSKnownOne))) == DemandedMask) |
| return Constant::getIntegerValue(VTy, RHSKnownOne | LHSKnownOne); |
| |
| // 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?"); |
| |
| // Output known-0 bits are known if clear or set in both the LHS & RHS. |
| APInt IKnownZero = (RHSKnownZero & LHSKnownZero) | |
| (RHSKnownOne & LHSKnownOne); |
| // Output known-1 are known to be set if set in only one of the LHS, RHS. |
| APInt IKnownOne = (RHSKnownZero & LHSKnownOne) | |
| (RHSKnownOne & LHSKnownZero); |
| |
| // If the client is only demanding bits that we know, return the known |
| // constant. |
| if ((DemandedMask & (IKnownZero|IKnownOne)) == DemandedMask) |
| return Constant::getIntegerValue(VTy, IKnownOne); |
| |
| // If all of the demanded bits are known zero on one side, return the other. |
| // These bits cannot contribute to the result of the 'xor'. |
| if ((DemandedMask & 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 this is a select as part of a min/max pattern, don't simplify any |
| // further in case we break the structure. |
| Value *LHS, *RHS; |
| if (matchSelectPattern(I, LHS, RHS).Flavor != SPF_UNKNOWN) |
| return nullptr; |
| |
| 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 nullptr; // vector->int or fp->int? |
| |
| if (VectorType *DstVTy = dyn_cast<VectorType>(I->getType())) { |
| if (VectorType *SrcVTy = |
| dyn_cast<VectorType>(I->getOperand(0)->getType())) { |
| if (DstVTy->getNumElements() != SrcVTy->getNumElements()) |
| // Don't touch a bitcast between vectors of different element counts. |
| return nullptr; |
| } else |
| // Don't touch a scalar-to-vector bitcast. |
| return nullptr; |
| } else if (I->getOperand(0)->getType()->isVectorTy()) |
| // Don't touch a vector-to-scalar bitcast. |
| return nullptr; |
| |
| if (SimplifyDemandedBits(I->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: |
| case Instruction::Sub: { |
| /// If the high-bits of an ADD/SUB are not demanded, then we do not care |
| /// about the high bits of the operands. |
| unsigned NLZ = DemandedMask.countLeadingZeros(); |
| if (NLZ > 0) { |
| // Right fill the mask of bits for this ADD/SUB to demand the most |
| // significant bit and all those below it. |
| APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); |
| if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps, |
| LHSKnownZero, LHSKnownOne, Depth + 1) || |
| ShrinkDemandedConstant(I, 1, DemandedFromOps) || |
| SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps, |
| LHSKnownZero, LHSKnownOne, Depth + 1)) { |
| // Disable the nsw and nuw flags here: We can no longer guarantee that |
| // we won't wrap after simplification. Removing the nsw/nuw flags is |
| // legal here because the top bit is not demanded. |
| BinaryOperator &BinOP = *cast<BinaryOperator>(I); |
| BinOP.setHasNoSignedWrap(false); |
| BinOP.setHasNoUnsignedWrap(false); |
| return I; |
| } |
| } |
| |
| // Otherwise just hand the add/sub off to computeKnownBits to fill in |
| // the known zeros and ones. |
| computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); |
| 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); |
| computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, |
| CxtI); |
| // 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 nullptr; |
| } |
| } |
| computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); |
| 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 nullptr; |
| } |
| |
| /// Helper routine of SimplifyDemandedUseBits. It tries to simplify |
| /// "E1 = (X lsr C1) << C2", where the C1 and C2 are constant, into |
| /// "E2 = X << (C2 - C1)" or "E2 = X >> (C1 - C2)", depending on the sign |
| /// of "C2-C1". |
| /// |
| /// Suppose E1 and E2 are generally different in bits S={bm, bm+1, |
| /// ..., bn}, without considering the specific value X is holding. |
| /// This transformation is legal iff one of following conditions is hold: |
| /// 1) All the bit in S are 0, in this case E1 == E2. |
| /// 2) We don't care those bits in S, per the input DemandedMask. |
| /// 3) Combination of 1) and 2). Some bits in S are 0, and we don't care the |
| /// rest bits. |
| /// |
| /// Currently we only test condition 2). |
| /// |
| /// As with SimplifyDemandedUseBits, it returns NULL if the simplification was |
| /// not successful. |
| Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr, |
| 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 nullptr; // Noop. |
| |
| Value *VarX = Shr->getOperand(0); |
| Type *Ty = VarX->getType(); |
| unsigned BitWidth = Ty->getIntegerBitWidth(); |
| if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth)) |
| return nullptr; // 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 nullptr; |
| |
| BinaryOperator *New; |
| if (ShrAmt < ShlAmt) { |
| Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt); |
| New = BinaryOperator::CreateShl(VarX, Amt); |
| BinaryOperator *Orig = cast<BinaryOperator>(Shl); |
| New->setHasNoSignedWrap(Orig->hasNoSignedWrap()); |
| New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap()); |
| } else { |
| Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt); |
| New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) : |
| BinaryOperator::CreateAShr(VarX, Amt); |
| if (cast<BinaryOperator>(Shr)->isExact()) |
| New->setIsExact(true); |
| } |
| |
| return InsertNewInstWith(New, *Shl); |
| } |
| |
| return nullptr; |
| } |
| |
| /// 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 nullptr; |
| } |
| |
| 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 nullptr; |
| |
| Type *EltTy = cast<VectorType>(V->getType())->getElementType(); |
| Constant *Undef = UndefValue::get(EltTy); |
| |
| SmallVector<Constant*, 16> Elts; |
| for (unsigned i = 0; i != VWidth; ++i) { |
| if (!DemandedElts[i]) { // If not demanded, set to undef. |
| Elts.push_back(Undef); |
| UndefElts.setBit(i); |
| continue; |
| } |
| |
| Constant *Elt = C->getAggregateElement(i); |
| if (!Elt) return nullptr; |
| |
| if (isa<UndefValue>(Elt)) { // Already undef. |
| Elts.push_back(Undef); |
| UndefElts.setBit(i); |
| } else { // Otherwise, defined. |
| Elts.push_back(Elt); |
| } |
| } |
| |
| // If we changed the constant, return it. |
| Constant *NewCV = ConstantVector::get(Elts); |
| return NewCV != C ? NewCV : nullptr; |
| } |
| |
| // Limit search depth. |
| if (Depth == 10) |
| return nullptr; |
| |
| // If multiple users are using the root value, proceed with |
| // simplification conservatively assuming that all elements |
| // are needed. |
| if (!V->hasOneUse()) { |
| // Quit if we find multiple users of a non-root value though. |
| // They'll be handled when it's their turn to be visited by |
| // the main instcombine process. |
| if (Depth != 0) |
| // TODO: Just compute the UndefElts information recursively. |
| return nullptr; |
| |
| // Conservatively assume that all elements are needed. |
| DemandedElts = EltMask; |
| } |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return nullptr; // Only analyze instructions. |
| |
| bool MadeChange = false; |
| 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) { |
| // 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++) { |
| Constant *CElt = CV->getAggregateElement(i); |
| // Method isNullValue always returns false when called on a |
| // ConstantExpr. If CElt is a ConstantExpr then skip it in order to |
| // to avoid propagating incorrect information. |
| if (isa<ConstantExpr>(CElt)) |
| continue; |
| if (CElt->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); |
| UndefElts2 = APInt(InVWidth, 0); |
| unsigned Ratio; |
| |
| if (VWidth == InVWidth) { |
| // If we are converting from <4 x i32> -> <4 x f32>, we demand the same |
| // elements as are demanded of us. |
| Ratio = 1; |
| InputDemandedElts = DemandedElts; |
| } else if ((VWidth % InVWidth) == 0) { |
| // If the number of elements in the output is a multiple of the number of |
| // elements in the input then an input element is live if any of the |
| // corresponding output elements are live. |
| Ratio = VWidth / InVWidth; |
| for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) |
| if (DemandedElts[OutIdx]) |
| InputDemandedElts.setBit(OutIdx / Ratio); |
| } else if ((InVWidth % VWidth) == 0) { |
| // If the number of elements in the input is a multiple of the number of |
| // elements in the output then an input element is live if the |
| // corresponding output element is live. |
| Ratio = InVWidth / VWidth; |
| for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx) |
| if (DemandedElts[InIdx / Ratio]) |
| InputDemandedElts.setBit(InIdx); |
| } else { |
| // Unsupported so far. |
| break; |
| } |
| |
| // 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; |
| } |
| |
| if (VWidth == InVWidth) { |
| UndefElts = UndefElts2; |
| } else if ((VWidth % InVWidth) == 0) { |
| // If the number of elements in the output is a multiple of the number of |
| // elements in the input then an output element is undef if the |
| // corresponding input element is undef. |
| for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) |
| if (UndefElts2[OutIdx / Ratio]) |
| UndefElts.setBit(OutIdx); |
| } else if ((InVWidth % VWidth) == 0) { |
| // If the number of elements in the input is a multiple of the number of |
| // elements in the output then an output element is undef if all of the |
| // corresponding input elements are undef. |
| for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) { |
| APInt SubUndef = UndefElts2.lshr(OutIdx * Ratio).zextOrTrunc(Ratio); |
| if (SubUndef.countPopulation() == Ratio) |
| UndefElts.setBit(OutIdx); |
| } |
| } else { |
| llvm_unreachable("Unimp"); |
| } |
| break; |
| } |
| case Instruction::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; |
| |
| // SSE4A instructions leave the upper 64-bits of the 128-bit result |
| // in an undefined state. |
| case Intrinsic::x86_sse4a_extrq: |
| case Intrinsic::x86_sse4a_extrqi: |
| case Intrinsic::x86_sse4a_insertq: |
| case Intrinsic::x86_sse4a_insertqi: |
| UndefElts |= APInt::getHighBitsSet(VWidth, VWidth / 2); |
| break; |
| } |
| break; |
| } |
| } |
| return MadeChange ? I : nullptr; |
| } |
