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| author | Nick Lewycky <nicholas@mxc.ca> | 2011-02-28 06:52:12 +0000 |
|---|---|---|
| committer | Nick Lewycky <nicholas@mxc.ca> | 2011-02-28 06:52:12 +0000 |
| commit | 346018bbe7301f73b4c77a0aa89a4a938ab6af26 (patch) | |
| tree | 22361dad8f0b908784412622ceeae99dafcb7b6f /lib/Analysis | |
| parent | f71720231f6de9b2b7fe28edd179ae217a105329 (diff) | |
| download | llvm-346018bbe7301f73b4c77a0aa89a4a938ab6af26.tar.gz llvm-346018bbe7301f73b4c77a0aa89a4a938ab6af26.tar.bz2 llvm-346018bbe7301f73b4c77a0aa89a4a938ab6af26.tar.xz | |
Teach ValueTracking to look at the dividend when determining the sign bit of an
srem instruction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126637 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis')
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 1060bc5349..fac0407da5 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -460,6 +460,18 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); } } + if (Mask.isNegative()) { // We're looking for the sign bit. + APInt Mask2 = APInt::getSignBit(BitWidth); + KnownZero2 = 0; + KnownOne2 = 0; + ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, + Depth+1); + if (KnownOne2[BitWidth-1]) + KnownOne |= Mask2; + if (KnownZero2[BitWidth-1]) + KnownZero |= Mask2; + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); + } break; case Instruction::URem: { if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { |