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Simplify (A & ~B) in icmp if A is a power of 2

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The transform will execute like so:
(A & ~B) == 0 --> (A & B) != 0
(A & ~B) != 0 --> (A & B) == 0


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179386 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2013-04-12 17:25:07 +00:00
parent dda4b6bf25
commit fb1cd69b90
2 changed files with 35 additions and 0 deletions
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9
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@@ -2669,6 +2669,15 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
}
{ Value *A, *B;
// Transform (A & ~B) == 0 --> (A & B) != 0
// and (A & ~B) != 0 --> (A & B) == 0
// if A is a power of 2.
if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(A) && I.isEquality())
return new ICmpInst(I.getInversePredicate(),
Builder->CreateAnd(A, B),
Op1);
// ~x < ~y --> y < x
// ~x < cst --> ~cst < x
if (match(Op0, m_Not(m_Value(A)))) {