From 5624046453adfd1e6807be4dd08f67f9e33a48ba Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Wed, 30 Jul 2014 21:26:37 +0000 Subject: [PATCH] InstCombine: Simplify (A ^ B) or/and (A ^ B ^ C) While we can already transform A | (A ^ B) into A | B, things get bad once we have (A ^ B) | (A ^ B ^ Cst) because reassociation will morph this into (A ^ B) | ((A ^ Cst) ^ B). Our existing patterns fail once this happens. To fix this, we add a new pattern which looks through the tree of xor binary operators to see that, in fact, there exists a redundant xor operation. What follows bellow is a correctness proof of the transform using CVC3. $ cat t.cvc A, B, C : BITVECTOR(64); QUERY BVXOR(A, B) | BVXOR(BVXOR(B, C), A) = BVXOR(A, B) | C; QUERY BVXOR(BVXOR(A, C), B) | BVXOR(A, B) = BVXOR(A, B) | C; QUERY BVXOR(A, B) & BVXOR(BVXOR(B, C), A) = BVXOR(A, B) & ~C; QUERY BVXOR(BVXOR(A, C), B) & BVXOR(A, B) = BVXOR(A, B) & ~C; $ cvc3 < t.cvc Valid. Valid. Valid. Valid. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214342 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../InstCombine/InstCombineAndOrXor.cpp | 24 +++++++++++++++++++ test/Transforms/InstCombine/or-xor.ll | 20 ++++++++++++++++ test/Transforms/InstCombine/xor2.ll | 20 ++++++++++++++++ 3 files changed, 64 insertions(+) diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 718cf29f184..51564088e67 100644 --- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -1283,6 +1283,18 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) { if (match(Op1, m_Or(m_Not(m_Specific(Op0)), m_Value(A))) || match(Op1, m_Or(m_Value(A), m_Not(m_Specific(Op0))))) return BinaryOperator::CreateAnd(A, Op0); + + // (A ^ B) & ((B ^ C) ^ A) -> (A ^ B) & ~C + if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) + if (match(Op1, m_Xor(m_Xor(m_Specific(B), m_Value(C)), m_Specific(A)))) + if (Op1->hasOneUse() || cast(Op1)->hasOneUse()) + return BinaryOperator::CreateAnd(Op0, Builder->CreateNot(C)); + + // ((A ^ C) ^ B) & (B ^ A) -> (B ^ A) & ~C + if (match(Op0, m_Xor(m_Xor(m_Value(A), m_Value(C)), m_Value(B)))) + if (match(Op1, m_Xor(m_Specific(B), m_Specific(A)))) + if (Op0->hasOneUse() || cast(Op0)->hasOneUse()) + return BinaryOperator::CreateAnd(Op1, Builder->CreateNot(C)); } if (ICmpInst *RHS = dyn_cast(Op1)) @@ -2080,6 +2092,18 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) { } } + // (A ^ B) | ((B ^ C) ^ A) -> (A ^ B) | C + if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) + if (match(Op1, m_Xor(m_Xor(m_Specific(B), m_Value(C)), m_Specific(A)))) + if (Op1->hasOneUse() || cast(Op1)->hasOneUse()) + return BinaryOperator::CreateOr(Op0, C); + + // ((A ^ C) ^ B) | (B ^ A) -> (B ^ A) | C + if (match(Op0, m_Xor(m_Xor(m_Value(A), m_Value(C)), m_Value(B)))) + if (match(Op1, m_Xor(m_Specific(B), m_Specific(A)))) + if (Op0->hasOneUse() || cast(Op0)->hasOneUse()) + return BinaryOperator::CreateOr(Op1, C); + // (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts. if (BinaryOperator *SI1 = dyn_cast(Op1)) { if (BinaryOperator *SI0 = dyn_cast(Op0)) diff --git a/test/Transforms/InstCombine/or-xor.ll b/test/Transforms/InstCombine/or-xor.ll index cec36f119a9..3f247e27522 100644 --- a/test/Transforms/InstCombine/or-xor.ll +++ b/test/Transforms/InstCombine/or-xor.ll @@ -92,3 +92,23 @@ define i32 @test9(i32 %x, i32 %y) nounwind { ; CHECK-NEXT: %z = or i32 %y.not, %x ; CHECK-NEXT: ret i32 %z } + +define i32 @test10(i32 %A, i32 %B) { + %xor1 = xor i32 %B, %A + %not = xor i32 %A, -1 + %xor2 = xor i32 %not, %B + %or = or i32 %xor1, %xor2 + ret i32 %or +; CHECK-LABEL: @test10( +; CHECK-NEXT: ret i32 -1 +} + +define i32 @test11(i32 %A, i32 %B) { + %xor1 = xor i32 %B, %A + %not = xor i32 %A, -1 + %xor2 = xor i32 %not, %B + %or = or i32 %xor1, %xor2 + ret i32 %or +; CHECK-LABEL: @test11( +; CHECK-NEXT: ret i32 -1 +} diff --git a/test/Transforms/InstCombine/xor2.ll b/test/Transforms/InstCombine/xor2.ll index 4ae50a140e1..6318afe51bf 100644 --- a/test/Transforms/InstCombine/xor2.ll +++ b/test/Transforms/InstCombine/xor2.ll @@ -125,3 +125,23 @@ define i32 @test10(i32 %b, i32 %c) { ; CHECK-LABEL: @test10( ; CHECK-NEXT: %xor2 = or i32 %b, %c } + +define i32 @test11(i32 %A, i32 %B) { + %xor1 = xor i32 %B, %A + %not = xor i32 %A, -1 + %xor2 = xor i32 %not, %B + %and = and i32 %xor1, %xor2 + ret i32 %and +; CHECK-LABEL: @test11( +; CHECK-NEXT: ret i32 0 +} + +define i32 @test12(i32 %A, i32 %B) { + %xor1 = xor i32 %B, %A + %not = xor i32 %A, -1 + %xor2 = xor i32 %not, %B + %and = and i32 %xor1, %xor2 + ret i32 %and +; CHECK-LABEL: @test12( +; CHECK-NEXT: ret i32 0 +}