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Fold (A^B) == A -> B == 0

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and  (A-B) == A  ->  B == 0


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26394 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-27 01:44:11 +00:00
parent e047eedc04
commit 26ab9a9218
1 changed files with 26 additions and 0 deletions
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26
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3876,6 +3876,32 @@ Instruction *InstCombiner::visitSetCondInst(SetCondInst &I) {
if (Instruction *R = visitSetCondInstWithCastAndCast(I))
return R;
}
if (I.getOpcode() == Instruction::SetNE ||
I.getOpcode() == Instruction::SetEQ) {
Value *A, *B;
if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1)) {
// (A^B) == A -> B == 0
Value *OtherVal = A == Op1 ? B : A;
return BinaryOperator::create(I.getOpcode(), OtherVal,
Constant::getNullValue(A->getType()));
} else if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
(A == Op0 || B == Op0)) {
// A == (A^B) -> B == 0
Value *OtherVal = A == Op0 ? B : A;
return BinaryOperator::create(I.getOpcode(), OtherVal,
Constant::getNullValue(A->getType()));
} else if (match(Op0, m_Sub(m_Value(A), m_Value(B))) && A == Op1) {
// (A-B) == A -> B == 0
return BinaryOperator::create(I.getOpcode(), B,
Constant::getNullValue(B->getType()));
} else if (match(Op1, m_Sub(m_Value(A), m_Value(B))) && A == Op0) {
// A == (A-B) -> B == 0
return BinaryOperator::create(I.getOpcode(), B,
Constant::getNullValue(B->getType()));
}
}
return Changed ? &I : 0;
}