From d13b0bfdacb84b1653245fa1d0ac66819b84cd62 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Sun, 23 Apr 2017 16:03:00 +0000 Subject: [InstCombine] add pattern matches for commuted variants of xor-to-xor There's probably some better way to write this that eliminates the code duplication without hurting readability, but at least this eliminates the logic holes and is hopefully slightly more efficient than creating new instructions. llvm-svn: 301129 --- .../Transforms/InstCombine/InstCombineAndOrXor.cpp | 89 +++++++++++++--------- 1 file changed, 55 insertions(+), 34 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index f320f125bf6..17a6fb9a402 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2374,6 +2374,58 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) { return Changed ? &I : nullptr; } +/// A ^ B can be specified using other logic ops in a variety of patterns. We +/// can fold these early and efficiently by morphing an existing instruction. +static Instruction *foldXorToXor(BinaryOperator &I) { + assert(I.getOpcode() == Instruction::Xor); + Value *Op0 = I.getOperand(0); + Value *Op1 = I.getOperand(1); + Value *A, *B; + + // There are 4 commuted variants for each of the basic patterns. + + // (A & B) ^ (A | B) -> A ^ B + // (A & B) ^ (B | A) -> A ^ B + // (A | B) ^ (A & B) -> A ^ B + // (A | B) ^ (B & A) -> A ^ B + if ((match(Op0, m_And(m_Value(A), m_Value(B))) && + match(Op1, m_c_Or(m_Specific(A), m_Specific(B)))) || + (match(Op0, m_Or(m_Value(A), m_Value(B))) && + match(Op1, m_c_And(m_Specific(A), m_Specific(B))))) { + I.setOperand(0, A); + I.setOperand(1, B); + return &I; + } + + // (A | ~B) ^ (~A | B) -> A ^ B + // (~B | A) ^ (~A | B) -> A ^ B + // (~A | B) ^ (A | ~B) -> A ^ B + // (B | ~A) ^ (A | ~B) -> A ^ B + if ((match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) && + match(Op1, m_Or(m_Not(m_Specific(A)), m_Specific(B)))) || + (match(Op0, m_c_Or(m_Not(m_Value(A)), m_Value(B))) && + match(Op1, m_Or(m_Specific(A), m_Not(m_Specific(B)))))) { + I.setOperand(0, A); + I.setOperand(1, B); + return &I; + } + + // (A & ~B) ^ (~A & B) -> A ^ B + // (~B & A) ^ (~A & B) -> A ^ B + // (~A & B) ^ (A & ~B) -> A ^ B + // (B & ~A) ^ (A & ~B) -> A ^ B + if ((match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) && + match(Op1, m_And(m_Not(m_Specific(A)), m_Specific(B)))) || + (match(Op0, m_c_And(m_Not(m_Value(A)), m_Value(B))) && + match(Op1, m_And(m_Specific(A), m_Not(m_Specific(B)))))) { + I.setOperand(0, A); + I.setOperand(1, B); + return &I; + } + + return nullptr; +} + // FIXME: We use commutative matchers (m_c_*) for some, but not all, matches // here. We should standardize that construct where it is needed or choose some // other way to ensure that commutated variants of patterns are not missed. @@ -2387,6 +2439,9 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) { if (Value *V = SimplifyXorInst(Op0, Op1, DL, &TLI, &DT, &AC)) return replaceInstUsesWith(I, V); + if (Instruction *NewXor = foldXorToXor(I)) + return NewXor; + // (A&B)^(A&C) -> A&(B^C) etc if (Value *V = SimplifyUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); @@ -2569,40 +2624,6 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) { { Value *A, *B, *C, *D; - // (A & B)^(A | B) -> A ^ B - if (match(Op0, m_And(m_Value(A), m_Value(B))) && - match(Op1, m_Or(m_Value(C), m_Value(D)))) { - if ((A == C && B == D) || (A == D && B == C)) - return BinaryOperator::CreateXor(A, B); - } - // (A | B)^(A & B) -> A ^ B - if (match(Op0, m_Or(m_Value(A), m_Value(B))) && - match(Op1, m_And(m_Value(C), m_Value(D)))) { - if ((A == C && B == D) || (A == D && B == C)) - return BinaryOperator::CreateXor(A, B); - } - // (A | ~B) ^ (~A | B) -> A ^ B - // (~B | A) ^ (~A | B) -> A ^ B - if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) && - match(Op1, m_Or(m_Not(m_Specific(A)), m_Specific(B)))) - return BinaryOperator::CreateXor(A, B); - - // (~A | B) ^ (A | ~B) -> A ^ B - if (match(Op0, m_Or(m_Not(m_Value(A)), m_Value(B))) && - match(Op1, m_Or(m_Specific(A), m_Not(m_Specific(B))))) { - return BinaryOperator::CreateXor(A, B); - } - // (A & ~B) ^ (~A & B) -> A ^ B - // (~B & A) ^ (~A & B) -> A ^ B - if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) && - match(Op1, m_And(m_Not(m_Specific(A)), m_Specific(B)))) - return BinaryOperator::CreateXor(A, B); - - // (~A & B) ^ (A & ~B) -> A ^ B - if (match(Op0, m_And(m_Not(m_Value(A)), m_Value(B))) && - match(Op1, m_And(m_Specific(A), m_Not(m_Specific(B))))) { - return BinaryOperator::CreateXor(A, B); - } // (A ^ C)^(A | B) -> ((~A) & B) ^ C if (match(Op0, m_Xor(m_Value(D), m_Value(C))) && match(Op1, m_Or(m_Value(A), m_Value(B)))) { -- cgit v1.2.3