From 1a08accbb7e5430b41045d67eec09367ee96495e Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Fri, 12 Apr 2013 17:25:07 +0000 Subject: 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 --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 4d5fa8776e9..4c252c03d08 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -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)))) { -- cgit v1.2.3