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Add a canonicalization that got lost, fixing PowerPC/fold-li.ll:SUB 

llvm-svn: 23693
This commit is contained in:
Chris Lattner 2005-10-11 06:07:15 +00:00
parent cc6e53e6ee
commit c38fb8e2a1
1 changed files with 5 additions and 3 deletions
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8
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -517,9 +517,11 @@ SDOperand DAGCombiner::visitSUB(SDNode *N) {
if (N0C && N1C)
return DAG.getConstant(N0C->getValue() - N1C->getValue(),
N->getValueType(0));
// fold (sub x, 0) -> x
if (N1C && N1C->isNullValue())
return N0;
// fold (sub x, c) -> (add x, -c)
if (N1C)
return DAG.getNode(ISD::ADD, N0.getValueType(), N0,
DAG.getConstant(-N1C->getValue(), N0.getValueType()));
// fold (A+B)-A -> B
if (N0.getOpcode() == ISD::ADD && N0.getOperand(0) == N1)
return N0.getOperand(1);