diff options
| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-03-12 17:18:11 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-03-12 17:18:11 +0000 |
| commit | 14b2a59301e9e4065c7b9b07a0c68462b6037a4f (patch) | |
| tree | 24e22757d901ffa8e83af49a47da3746e6333b75 | |
| parent | 879d3a98a2d64793a49e747b3d64020db74c5a3e (diff) | |
Teach ComputeMaskedBits about sub nsw.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127548 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 24 | ||||
| -rw-r--r-- | test/Transforms/InstSimplify/compare.ll | 23 |
2 files changed, 39 insertions, 8 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 6c33d2d508..c36f68c2ae 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -431,16 +431,24 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } // Are we still trying to solve for the sign bit? - if (I->getOpcode() == Instruction::Add && - Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){ + if (Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){ OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(I); if (OBO->hasNoSignedWrap()) { - // Adding two positive numbers can't wrap into negative ... - if (LHSKnownZero.isNegative() && KnownZero2.isNegative()) - KnownZero |= APInt::getSignBit(BitWidth); - // and adding two negative numbers can't wrap into positive. - else if (LHSKnownOne.isNegative() && KnownOne2.isNegative()) - KnownOne |= APInt::getSignBit(BitWidth); + if (I->getOpcode() == Instruction::Add) { + // Adding two positive numbers can't wrap into negative + if (LHSKnownZero.isNegative() && KnownZero2.isNegative()) + KnownZero |= APInt::getSignBit(BitWidth); + // and adding two negative numbers can't wrap into positive. + else if (LHSKnownOne.isNegative() && KnownOne2.isNegative()) + KnownOne |= APInt::getSignBit(BitWidth); + } else { + // Subtracting a negative number from a positive one can't wrap + if (LHSKnownZero.isNegative() && KnownOne2.isNegative()) + KnownZero |= APInt::getSignBit(BitWidth); + // neither can subtracting a positive number from a negative one. + else if (LHSKnownOne.isNegative() && KnownZero2.isNegative()) + KnownOne |= APInt::getSignBit(BitWidth); + } } } diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll index 75a36b499e..d2c564f567 100644 --- a/test/Transforms/InstSimplify/compare.ll +++ b/test/Transforms/InstSimplify/compare.ll @@ -271,6 +271,29 @@ define i1 @srem2(i16 %X, i32 %Y) { %D = icmp slt i32 %C, 0 ret i1 %D } + +; CHECK: @srem3 +; CHECK-NEXT: ret i1 false +define i1 @srem3(i16 %X, i32 %Y) { + %A = zext i16 %X to i32 + %B = or i32 2147483648, %A + %C = sub nsw i32 1, %B + %D = srem i32 %C, %Y + %E = icmp slt i32 %D, 0 + ret i1 %E +} + +; CHECK: @srem4 +; CHECK-NEXT: ret i1 false +define i1 @srem4(i16 %X, i32 %Y) { + %A = zext i16 %X to i32 + %B = or i32 2147483648, %A + %C = sub nsw i32 %A, %B + %D = srem i32 %C, %Y + %E = icmp slt i32 %D, 0 + ret i1 %E +} + define i1 @udiv1(i32 %X) { ; CHECK: @udiv1 %A = udiv i32 %X, 1000000 |