diff options
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineShifts.cpp | 46 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/shift.ll | 19 |
2 files changed, 44 insertions, 21 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp index 628d7a8ef0..6d85adde9b 100644 --- a/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -208,11 +208,12 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, return I; case Instruction::Shl: { - unsigned TypeWidth = I->getType()->getScalarSizeInBits(); + BinaryOperator *BO = cast<BinaryOperator>(I); + unsigned TypeWidth = BO->getType()->getScalarSizeInBits(); // We only accept shifts-by-a-constant in CanEvaluateShifted. - ConstantInt *CI = cast<ConstantInt>(I->getOperand(1)); - + ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1)); + // We can always fold shl(c1)+shl(c2) -> shl(c1+c2). if (isLeftShift) { // If this is oversized composite shift, then unsigned shifts get 0. @@ -220,7 +221,9 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, if (NewShAmt >= TypeWidth) return Constant::getNullValue(I->getType()); - I->setOperand(1, ConstantInt::get(I->getType(), NewShAmt)); + BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt)); + BO->setHasNoUnsignedWrap(false); + BO->setHasNoSignedWrap(false); return I; } @@ -228,11 +231,11 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, // zeros. if (CI->getValue() == NumBits) { APInt Mask(APInt::getLowBitsSet(TypeWidth, TypeWidth - NumBits)); - V = IC.Builder->CreateAnd(I->getOperand(0), - ConstantInt::get(I->getContext(), Mask)); + V = IC.Builder->CreateAnd(BO->getOperand(0), + ConstantInt::get(BO->getContext(), Mask)); if (Instruction *VI = dyn_cast<Instruction>(V)) { - VI->moveBefore(I); - VI->takeName(I); + VI->moveBefore(BO); + VI->takeName(BO); } return V; } @@ -240,23 +243,27 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, // We turn shl(c1)+shr(c2) -> shl(c3)+and(c4), but only when we know that // the and won't be needed. assert(CI->getZExtValue() > NumBits); - I->setOperand(1, ConstantInt::get(I->getType(), - CI->getZExtValue() - NumBits)); - return I; + BO->setOperand(1, ConstantInt::get(BO->getType(), + CI->getZExtValue() - NumBits)); + BO->setHasNoUnsignedWrap(false); + BO->setHasNoSignedWrap(false); + return BO; } case Instruction::LShr: { - unsigned TypeWidth = I->getType()->getScalarSizeInBits(); + BinaryOperator *BO = cast<BinaryOperator>(I); + unsigned TypeWidth = BO->getType()->getScalarSizeInBits(); // We only accept shifts-by-a-constant in CanEvaluateShifted. - ConstantInt *CI = cast<ConstantInt>(I->getOperand(1)); + ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1)); // We can always fold lshr(c1)+lshr(c2) -> lshr(c1+c2). if (!isLeftShift) { // If this is oversized composite shift, then unsigned shifts get 0. unsigned NewShAmt = NumBits+CI->getZExtValue(); if (NewShAmt >= TypeWidth) - return Constant::getNullValue(I->getType()); + return Constant::getNullValue(BO->getType()); - I->setOperand(1, ConstantInt::get(I->getType(), NewShAmt)); + BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt)); + BO->setIsExact(false); return I; } @@ -265,7 +272,7 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, if (CI->getValue() == NumBits) { APInt Mask(APInt::getHighBitsSet(TypeWidth, TypeWidth - NumBits)); V = IC.Builder->CreateAnd(I->getOperand(0), - ConstantInt::get(I->getContext(), Mask)); + ConstantInt::get(BO->getContext(), Mask)); if (Instruction *VI = dyn_cast<Instruction>(V)) { VI->moveBefore(I); VI->takeName(I); @@ -276,9 +283,10 @@ static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift, // We turn lshr(c1)+shl(c2) -> lshr(c3)+and(c4), but only when we know that // the and won't be needed. assert(CI->getZExtValue() > NumBits); - I->setOperand(1, ConstantInt::get(I->getType(), - CI->getZExtValue() - NumBits)); - return I; + BO->setOperand(1, ConstantInt::get(BO->getType(), + CI->getZExtValue() - NumBits)); + BO->setIsExact(false); + return BO; } case Instruction::Select: diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll index d9ac9cbfe9..132d51a660 100644 --- a/test/Transforms/InstCombine/shift.ll +++ b/test/Transforms/InstCombine/shift.ll @@ -525,5 +525,20 @@ define i32 @test43(i32 %a, i32 %b) nounwind { ; CHECK-NEXT: ret } - - +define i32 @test44(i32 %a) nounwind { + %y = shl nuw i32 %a, 1 + %z = shl i32 %y, 4 + ret i32 %z +; CHECK: @test44 +; CHECK-NEXT: %y = shl i32 %a, 5 +; CHECK-NEXT: ret i32 %y +} + +define i32 @test45(i32 %a) nounwind { + %y = lshr exact i32 %a, 1 + %z = lshr i32 %y, 4 + ret i32 %z +; CHECK: @test45 +; CHECK-NEXT: %y = lshr i32 %a, 5 +; CHECK-NEXT: ret i32 %y +} |