Simplify (A & ~B) in icmp if A is a power of 2
The transform will execute like so:
(A & ~B) == 0 --> (A & B) != 0
(A & ~B) != 0 --> (A & B) == 0
llvm-svn: 179386
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 4d5fa87..4c252c0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2669,6 +2669,15 @@
}
{ 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)))) {