diff options
| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-02 18:50:58 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-02 18:50:58 +0000 |
| commit | f5b75932b8c23db5789ad19687c98070c551e896 (patch) | |
| tree | 666688ebfc02511c84e8dee776c5b995421861e6 /lib/Transforms/InstCombine/InstCombineCasts.cpp | |
| parent | 0b7bc77e305d8d4bd5615e54cf61f32cd0cac9c2 (diff) | |
While SimplifyDemandedBits constant folds this, we can't rely on it here.
It's possible to craft an input that hits the recursion limits in a way
that SimplifyDemandedBits doesn't simplify the icmp but ComputeMaskedBits
can infer which bits are zero.
No test case as it depends on too many other things. Fixes PR9609.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128777 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineCasts.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCasts.cpp | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp index 32ab123f10..6f70de8657 100644 --- a/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -913,8 +913,13 @@ Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) { if (KnownZeroMask.isPowerOf2()) { Value *In = ICI->getOperand(0); - assert((Op1C->isZero() || Op1C->getValue() == KnownZeroMask) && - "Constant icmp not folded?"); + // If the icmp tests for a known zero bit we can constant fold it. + if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) { + Value *V = Pred == ICmpInst::ICMP_NE ? + ConstantInt::getAllOnesValue(CI.getType()) : + ConstantInt::getNullValue(CI.getType()); + return ReplaceInstUsesWith(CI, V); + } if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) { // sext ((x & 2^n) == 0) -> (x >> n) - 1 |