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Fold (X|C1)^C2 -> X^(C1|C2) when possible. This implements 

InstCombine/or.ll:test23.

llvm-svn: 26385
This commit is contained in:
Chris Lattner 2006-02-26 19:57:54 +00:00
parent 69c68c3c3e
commit f78df7c14d
1 changed files with 14 additions and 0 deletions
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14
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2846,6 +2846,20 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
ConstantInt::get(I.getType(), 1)),
Op0I->getOperand(0));
}
} else if (Op0I->getOpcode() == Instruction::Or) {
// (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
if (MaskedValueIsZero(Op0I->getOperand(0), Op0CI->getZExtValue())) {
Constant *NewRHS = ConstantExpr::getOr(Op0CI, RHS);
// Anything in both C1 and C2 is known to be zero, remove it from
// NewRHS.
Constant *CommonBits = ConstantExpr::getAnd(Op0CI, RHS);
NewRHS = ConstantExpr::getAnd(NewRHS,
ConstantExpr::getNot(CommonBits));
WorkList.push_back(Op0I);
I.setOperand(0, Op0I->getOperand(0));
I.setOperand(1, NewRHS);
return &I;
}
}
}