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fold nested and's early to avoid inefficiencies in MaskedValueIsZero. This

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fixes a very slow compile in PR639.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24011 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-10-26 17:18:16 +00:00
parent a7ad198f89
commit e9f15e538a
1 changed files with 9 additions and 0 deletions
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9
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1725,6 +1725,15 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
// and X, -1 == X
if (AndRHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op0);
// and (and X, c1), c2 -> and (x, c1&c2). Handle this case here, before
// calling MaskedValueIsZero, to avoid inefficient cases where we traipse
// through many levels of ands.
{
Value *X; ConstantInt *C1;
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))))
return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS));
}
if (MaskedValueIsZero(Op0, AndRHS)) // LHS & RHS == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));