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Remove explicit check for: not (not X) = X, it is already handled because xor is commutative 

- InstCombine: (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
  - InstCombine: (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2

llvm-svn: 7282
This commit is contained in:
Chris Lattner 2003-07-23 21:37:07 +00:00
parent 2326ef6484
commit 9763859e8d
1 changed files with 16 additions and 10 deletions
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26
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -625,22 +625,28 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (ConstantIntegral *Op1C = dyn_cast<ConstantIntegral>(Op1)) {
if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
// xor X, 0 == X
if (Op1C->isNullValue())
if (RHS->isNullValue())
return ReplaceInstUsesWith(I, Op0);
// Is this a "NOT" instruction?
if (Op1C->isAllOnesValue()) {
// xor (xor X, -1), -1 = not (not X) = X
if (Value *X = dyn_castNotVal(Op0))
return ReplaceInstUsesWith(I, X);
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
// xor (setcc A, B), true = not (setcc A, B) = setncc A, B
if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0))
if (SCI->use_size() == 1)
if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
if (RHS == ConstantBool::True && SCI->use_size() == 1)
return new SetCondInst(SCI->getInverseCondition(),
SCI->getOperand(0), SCI->getOperand(1));
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Op0I->getOpcode() == Instruction::And) {
// (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
if ((*RHS & *Op0CI)->isNullValue())
return BinaryOperator::create(Instruction::Or, Op0, RHS);
} else if (Op0I->getOpcode() == Instruction::Or) {
// (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
if ((*RHS & *Op0CI) == RHS)
return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
}
}
}