diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 40 |
1 files changed, 17 insertions, 23 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp index edd51baf2a8..61716ca4d7f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -373,24 +373,6 @@ foldShiftByConstOfShiftByConst(BinaryOperator &I, const APInt *COp1, if (ShiftAmt2 < ShiftAmt1) { uint32_t ShiftDiff = ShiftAmt1 - ShiftAmt2; - // (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2) - if (I.getOpcode() == Instruction::LShr && - ShiftOp->getOpcode() == Instruction::Shl) { - ConstantInt *ShiftDiffCst = ConstantInt::get(Ty, ShiftDiff); - if (ShiftOp->hasNoUnsignedWrap()) { - // (X <<nuw C1) >>u C2 --> X <<nuw (C1-C2) - BinaryOperator *NewShl = - BinaryOperator::Create(Instruction::Shl, X, ShiftDiffCst); - NewShl->setHasNoUnsignedWrap(true); - return NewShl; - } - Value *Shift = Builder->CreateShl(X, ShiftDiffCst); - - APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2)); - return BinaryOperator::CreateAnd(Shift, - ConstantInt::get(I.getContext(), Mask)); - } - // We can't handle (X << C1) >>s C2, it shifts arbitrary bits in. However, // we can handle (X <<nsw C1) >>s C2 since it only shifts in sign bits. if (I.getOpcode() == Instruction::AShr && @@ -740,11 +722,6 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) { const APInt *ShlAmtAPInt; if (match(Op0, m_Shl(m_Value(X), m_APInt(ShlAmtAPInt)))) { unsigned ShlAmt = ShlAmtAPInt->getZExtValue(); - if (ShlAmt == ShAmt) { - // (X << C) >>u C --> X & (-1 >>u C) - APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); - return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); - } if (ShlAmt < ShAmt) { Constant *ShiftDiff = ConstantInt::get(Ty, ShAmt - ShlAmt); if (cast<BinaryOperator>(Op0)->hasNoUnsignedWrap()) { @@ -758,6 +735,23 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) { APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); return BinaryOperator::CreateAnd(NewLShr, ConstantInt::get(Ty, Mask)); } + if (ShlAmt > ShAmt) { + Constant *ShiftDiff = ConstantInt::get(Ty, ShlAmt - ShAmt); + if (cast<BinaryOperator>(Op0)->hasNoUnsignedWrap()) { + // (X <<nuw C1) >>u C2 --> X <<nuw (C1 - C2) + auto *NewShl = BinaryOperator::CreateShl(X, ShiftDiff); + NewShl->setHasNoUnsignedWrap(true); + return NewShl; + } + // (X << C1) >>u C2 --> X << (C1 - C2) & (-1 >> C2) + Value *NewShl = Builder->CreateShl(X, ShiftDiff); + APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(NewShl, ConstantInt::get(Ty, Mask)); + } + assert(ShlAmt == ShAmt); + // (X << C) >>u C --> X & (-1 >>u C) + APInt Mask(APInt::getLowBitsSet(BitWidth, BitWidth - ShAmt)); + return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); } // If the shifted-out value is known-zero, then this is an exact shift. |
