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| author | Jakub Staszak <kubastaszak@gmail.com> | 2012-12-31 00:34:55 +0000 |
|---|---|---|
| committer | Jakub Staszak <kubastaszak@gmail.com> | 2012-12-31 00:34:55 +0000 |
| commit | d60b8ac64fa161646d50c49d6171cb49e6a2c7ee (patch) | |
| tree | 96b9e6304e1c6187584c90a8124206f1608929e0 /lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | |
| parent | 6eb7a4270bc411342f459bc574f8fe4ef5eeff28 (diff) | |
| download | llvm-d60b8ac64fa161646d50c49d6171cb49e6a2c7ee.tar.gz llvm-d60b8ac64fa161646d50c49d6171cb49e6a2c7ee.tar.bz2 llvm-d60b8ac64fa161646d50c49d6171cb49e6a2c7ee.tar.xz | |
Transform (A == C1 || A == C2) into (A & ~(C1 ^ C2)) == C1
if C1 and C2 differ only with one bit.
Fixes PR14708.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171270 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineAndOrXor.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index ecae3b6045..0fd1e2b2e4 100644 --- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -1524,6 +1524,18 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS) { AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst); return Builder->CreateICmpULT(Add, AddCST); } + + if (LHS->getOperand(0) == RHS->getOperand(0)) { + // if LHSCst and RHSCst differ with only one bit: + // (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1 + APInt Xor = LHSCst->getValue() ^ RHSCst->getValue(); + if (Xor.isPowerOf2()) { + Value *NegCst = Builder->getInt(~Xor); + Value *And = Builder->CreateAnd(LHS->getOperand(0), NegCst); + return Builder->CreateICmp(ICmpInst::ICMP_EQ, And, LHSCst); + } + } + break; // (X == 13 | X == 15) -> no change case ICmpInst::ICMP_UGT: // (X == 13 | X u> 14) -> no change case ICmpInst::ICMP_SGT: // (X == 13 | X s> 14) -> no change |