diff options
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 77 |
1 files changed, 62 insertions, 15 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 1b42d3d..ad6983a 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -43,6 +43,20 @@ static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo, // This instruction is producing bits that are not demanded. Shrink the RHS. Demanded &= OpC->getValue(); I->setOperand(OpNo, ConstantInt::get(OpC->getType(), Demanded)); + + // If either 'nsw' or 'nuw' is set and the constant is negative, + // removing *any* bits from the constant could make overflow occur. + // Remove 'nsw' and 'nuw' from the instruction in this case. + if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(I)) { + assert(OBO->getOpcode() == Instruction::Add); + if (OBO->hasNoSignedWrap() || OBO->hasNoUnsignedWrap()) { + if (OpC->getValue().isNegative()) { + cast<BinaryOperator>(OBO)->setHasNoSignedWrap(false); + cast<BinaryOperator>(OBO)->setHasNoUnsignedWrap(false); + } + } + } + return true; } @@ -57,7 +71,7 @@ bool InstCombiner::SimplifyDemandedInstructionBits(Instruction &Inst) { APInt DemandedMask(APInt::getAllOnesValue(BitWidth)); Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask, - KnownZero, KnownOne, 0); + KnownZero, KnownOne, 0, &Inst); if (!V) return false; if (V == &Inst) return true; ReplaceInstUsesWith(Inst, V); @@ -71,7 +85,8 @@ bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask, APInt &KnownZero, APInt &KnownOne, unsigned Depth) { Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, - KnownZero, KnownOne, Depth); + KnownZero, KnownOne, Depth, + dyn_cast<Instruction>(U.getUser())); if (!NewVal) return false; U = NewVal; return true; @@ -101,7 +116,8 @@ bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask, /// 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) { + unsigned Depth, + Instruction *CxtI) { assert(V != nullptr && "Null pointer of Value???"); assert(Depth <= 6 && "Limit Search Depth"); uint32_t BitWidth = DemandedMask.getBitWidth(); @@ -144,7 +160,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, Instruction *I = dyn_cast<Instruction>(V); if (!I) { - computeKnownBits(V, KnownZero, KnownOne, Depth); + computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); return nullptr; // Only analyze instructions. } @@ -158,8 +174,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // 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); - computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1); + 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 @@ -180,8 +198,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // 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); - computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1); + 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 @@ -205,8 +225,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // 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); - computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1); + 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. @@ -217,7 +239,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, } // Compute the KnownZero/KnownOne bits to simplify things downstream. - computeKnownBits(I, KnownZero, KnownOne, Depth); + computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); return nullptr; } @@ -230,7 +252,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, switch (I->getOpcode()) { default: - computeKnownBits(I, KnownZero, KnownOne, Depth); + computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); break; case Instruction::And: // If either the LHS or the RHS are Zero, the result is zero. @@ -242,6 +264,12 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, 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) == @@ -274,6 +302,12 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, 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) == @@ -310,6 +344,18 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, 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) @@ -581,7 +627,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // Otherwise just hand the sub off to computeKnownBits to fill in // the known zeros and ones. - computeKnownBits(V, KnownZero, KnownOne, Depth); + computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known // zero. @@ -752,7 +798,8 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // remainder is zero. if (DemandedMask.isNegative() && KnownZero.isNonNegative()) { APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); - computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1); + 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); @@ -814,7 +861,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, return nullptr; } } - computeKnownBits(V, KnownZero, KnownOne, Depth); + computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); break; } |