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Constant exprs are not efficiently negatable in practice. This disables

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turning X - (constantexpr) into X + (-constantexpr) among other things.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18935 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-12-14 20:08:06 +00:00
parent 3b0cc78c60
commit 0ce8580fcd
1 changed files with 3 additions and 4 deletions
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7
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -309,10 +309,9 @@ static inline Value *dyn_castNegVal(Value *V) {
if (BinaryOperator::isNeg(V))
return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
// Constants can be considered to be negated values if they can be folded...
if (Constant *C = dyn_cast<Constant>(V))
if (!isa<UndefValue>(C))
return ConstantExpr::getNeg(C);
// Constants can be considered to be negated values if they can be folded.
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantExpr::getNeg(C);
return 0;
}