diff options
| author | Nick Lewycky <nicholas@mxc.ca> | 2008-11-02 02:41:50 +0000 |
|---|---|---|
| committer | Nick Lewycky <nicholas@mxc.ca> | 2008-11-02 02:41:50 +0000 |
| commit | 8e39432ea9751917d5cef1f18f6c32382c384d58 (patch) | |
| tree | 9d162738d97b827638c42c0c8d9526395f19726a | |
| parent | 21440acc06b6451ad5c0678e3f15ee08b1f1d206 (diff) | |
| download | llvm-8e39432ea9751917d5cef1f18f6c32382c384d58.tar.gz llvm-8e39432ea9751917d5cef1f18f6c32382c384d58.tar.bz2 llvm-8e39432ea9751917d5cef1f18f6c32382c384d58.tar.xz | |
Fix demanded bits analysis with srem by negative number. Based on a patch
by Richard Osborne.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58555 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 6 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/2008-11-01-SRemDemandedBits.ll | 8 |
2 files changed, 11 insertions, 3 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 75a1ffea6b..3210b12cbb 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -1274,12 +1274,12 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask, break; case Instruction::SRem: if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { - APInt RA = Rem->getValue(); - if (RA.isPowerOf2() || (-RA).isPowerOf2()) { + APInt RA = Rem->getValue().abs(); + if (RA.isPowerOf2()) { if (DemandedMask.ule(RA)) // srem won't affect demanded bits return UpdateValueUsesWith(I, I->getOperand(0)); - APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA; + APInt LowBits = RA - 1; APInt Mask2 = LowBits | APInt::getSignBit(BitWidth); if (SimplifyDemandedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, Depth+1)) diff --git a/test/Transforms/InstCombine/2008-11-01-SRemDemandedBits.ll b/test/Transforms/InstCombine/2008-11-01-SRemDemandedBits.ll new file mode 100644 index 0000000000..46e98eb362 --- /dev/null +++ b/test/Transforms/InstCombine/2008-11-01-SRemDemandedBits.ll @@ -0,0 +1,8 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i1 true} +; PR2993 + +define i1 @foo(i32 %x) { + %1 = srem i32 %x, -1 + %2 = icmp eq i32 %1, 0 + ret i1 %2 +} |