diff options
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineShifts.cpp | 47 |
1 files changed, 13 insertions, 34 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp index e5ce8a612f..cfff0a9ba7 100644 --- a/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -59,7 +59,7 @@ Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) { Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, BinaryOperator &I) { bool isLeftShift = I.getOpcode() == Instruction::Shl; - + // See if we can simplify any instructions used by the instruction whose sole // purpose is to compute bits we don't care about. uint32_t TypeBits = Op0->getType()->getScalarSizeInBits(); @@ -288,39 +288,17 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, ConstantInt::get(Ty, AmtSum)); } - if (ShiftOp->getOpcode() == Instruction::LShr && - I.getOpcode() == Instruction::AShr) { - if (AmtSum >= TypeBits) - return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); - - // ((X >>u C1) >>s C2) -> (X >>u (C1+C2)) since C1 != 0. - return BinaryOperator::CreateLShr(X, ConstantInt::get(Ty, AmtSum)); - } - - if (ShiftOp->getOpcode() == Instruction::AShr && - I.getOpcode() == Instruction::LShr) { - // ((X >>s C1) >>u C2) -> ((X >>s (C1+C2)) & mask) since C1 != 0. - if (AmtSum >= TypeBits) - AmtSum = TypeBits-1; - - Value *Shift = Builder->CreateAShr(X, ConstantInt::get(Ty, AmtSum)); - - APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2)); - return BinaryOperator::CreateAnd(Shift, - ConstantInt::get(I.getContext(), Mask)); - } - - // Okay, if we get here, one shift must be left, and the other shift must be - // right. See if the amounts are equal. if (ShiftAmt1 == ShiftAmt2) { // If we have ((X >>? C) << C), turn this into X & (-1 << C). - if (I.getOpcode() == Instruction::Shl) { + if (I.getOpcode() == Instruction::Shl && + ShiftOp->getOpcode() != Instruction::Shl) { APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1)); return BinaryOperator::CreateAnd(X, ConstantInt::get(I.getContext(),Mask)); } // If we have ((X << C) >>u C), turn this into X & (-1 >>u C). - if (I.getOpcode() == Instruction::LShr) { + if (I.getOpcode() == Instruction::LShr && + ShiftOp->getOpcode() == Instruction::Shl) { APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt1)); return BinaryOperator::CreateAnd(X, ConstantInt::get(I.getContext(), Mask)); @@ -329,7 +307,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, uint32_t ShiftDiff = ShiftAmt2-ShiftAmt1; // (X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2) - if (I.getOpcode() == Instruction::Shl) { + if (I.getOpcode() == Instruction::Shl && + ShiftOp->getOpcode() != Instruction::Shl) { assert(ShiftOp->getOpcode() == Instruction::LShr || ShiftOp->getOpcode() == Instruction::AShr); Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff)); @@ -340,7 +319,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, } // (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2) - if (I.getOpcode() == Instruction::LShr) { + if (I.getOpcode() == Instruction::LShr && + ShiftOp->getOpcode() == Instruction::Shl) { assert(ShiftOp->getOpcode() == Instruction::Shl); Value *Shift = Builder->CreateLShr(X, ConstantInt::get(Ty, ShiftDiff)); @@ -355,9 +335,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, uint32_t ShiftDiff = ShiftAmt1-ShiftAmt2; // (X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2) - if (I.getOpcode() == Instruction::Shl) { - assert(ShiftOp->getOpcode() == Instruction::LShr || - ShiftOp->getOpcode() == Instruction::AShr); + if (I.getOpcode() == Instruction::Shl && + ShiftOp->getOpcode() != Instruction::Shl) { Value *Shift = Builder->CreateBinOp(ShiftOp->getOpcode(), X, ConstantInt::get(Ty, ShiftDiff)); @@ -367,8 +346,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1, } // (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2) - if (I.getOpcode() == Instruction::LShr) { - assert(ShiftOp->getOpcode() == Instruction::Shl); + if (I.getOpcode() == Instruction::LShr && + ShiftOp->getOpcode() == Instruction::Shl) { Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff)); APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2)); |