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| 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 | 50a281a871ee64ad76c6c44f4b60b8d47f88f4c3 (patch) | |
| tree | 2bdb208e12d06b63d708679879c5f1bbd6ee6bba /llvm/lib/Transforms | |
| parent | 1473c9a7c484590a842120c0517974ca1d3584b3 (diff) | |
| download | bcm5719-llvm-50a281a871ee64ad76c6c44f4b60b8d47f88f4c3.tar.gz bcm5719-llvm-50a281a871ee64ad76c6c44f4b60b8d47f88f4c3.zip | |
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.
llvm-svn: 128777
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 32ab123f103..6f70de86576 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/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 |
