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Add another permutation where we should get rid of a-a.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61401 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen
2008-12-23 23:01:27 +00:00
parent c7a37d4ff2
commit f9cbc1f9ac
2 changed files with 35 additions and 4 deletions
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15
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@@ -1177,13 +1177,20 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
return N0.getOperand(1);
// fold (A+B)-B -> A
if (N0.getOpcode() == ISD::ADD && N0.getOperand(1) == N1)
return N0.getOperand(0);
// fold ((A+(B-C))-B) -> A-C
return N0.getOperand(0);
// fold ((A+(B+-C))-B) -> A+-C
if (N0.getOpcode() == ISD::ADD &&
N0.getOperand(1).getOpcode() == ISD::SUB &&
(N0.getOperand(1).getOpcode() == ISD::SUB ||
N0.getOperand(1).getOpcode() == ISD::ADD) &&
N0.getOperand(1).getOperand(0) == N1)
return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
return DAG.getNode(N0.getOperand(1).getOpcode(), VT, N0.getOperand(0),
N0.getOperand(1).getOperand(1));
// fold ((A+(C+B))-B) -> A+C
if (N0.getOpcode() == ISD::ADD &&
N0.getOperand(1).getOpcode() == ISD::ADD &&
N0.getOperand(1).getOperand(1) == N1)
return DAG.getNode(ISD::ADD, VT, N0.getOperand(0),
N0.getOperand(1).getOperand(0));
// fold ((A-(B-C))-C) -> A-B
if (N0.getOpcode() == ISD::SUB &&
N0.getOperand(1).getOpcode() == ISD::SUB &&