From 0e07248704fa97f6c7d9e007f82db17116fbaf78 Mon Sep 17 00:00:00 2001 From: David Bolvansky Date: Wed, 4 Sep 2019 17:30:53 +0000 Subject: [InstCombine] Fold sub (and A, B) (or A, B)) to neg (xor A, B) Summary: ``` Name: sub(and(x, y), or(x, y)) -> neg(xor(x, y)) %or = or i32 %y, %x %and = and i32 %x, %y %sub = sub i32 %and, %or => %sub1 = xor i32 %x, %y %sub = sub i32 0, %sub1 Optimization: sub(and(x, y), or(x, y)) -> neg(xor(x, y)) Done: 1 Optimization is correct! ``` https://rise4fun.com/Alive/VI6 Found by @lebedev.ri. Also author of the proof. Reviewers: lebedev.ri, spatel Reviewed By: lebedev.ri Subscribers: llvm-commits, lebedev.ri Tags: #llvm Differential Revision: https://reviews.llvm.org/D67155 llvm-svn: 370934 --- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 776bef36abf..fbd0165cd2d 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1725,6 +1725,15 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { return BinaryOperator::CreateXor(A, B); } + // (sub (and A, B) (or A, B)) --> neg (xor A, B) + { + Value *A, *B; + if (match(Op0, m_And(m_Value(A), m_Value(B))) && + match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) && + (Op0->hasOneUse() || Op1->hasOneUse())) + return BinaryOperator::CreateNeg(Builder.CreateXor(A, B)); + } + // (sub (or A, B), (xor A, B)) --> (and A, B) { Value *A, *B; -- cgit v1.2.3