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Implement: (A|B)^B == A & (~B)

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llvm-svn: 5728
This commit is contained in:
Chris Lattner 2003-03-10 18:24:17 +00:00
parent 0c461ded59
commit 5e6fb8b8d5
1 changed files with 25 additions and 0 deletions
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25
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -493,6 +493,31 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
if (Op1I->getOpcode() == Instruction::Or)
if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
cast<BinaryOperator>(Op1I)->swapOperands();
I.swapOperands();
std::swap(Op0, Op1);
} else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
I.swapOperands();
std::swap(Op0, Op1);
}
if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
cast<BinaryOperator>(Op0I)->swapOperands();
if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
WorkList.push_back(cast<Instruction>(NotB));
return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
NotB);
}
}
return Changed ? &I : 0;
}