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Add a dag combine pattern for folding C2-(A+C1) -> (C2-C1)-A

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Fixes rdar://9761830

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135123 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Christopher
2011-07-14 01:12:15 +00:00
parent 4fcfcf4984
commit 7332e6ee25
1 changed files with 10 additions and 2 deletions
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12
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1001,7 +1001,7 @@ void DAGCombiner::Run(CombineLevel AtLevel) {
dbgs() << "\nWith: ";
RV.getNode()->dump(&DAG);
dbgs() << '\n');
// Transfer debug value.
DAG.TransferDbgValues(SDValue(N, 0), RV);
WorkListRemover DeadNodes(*this);
@ -1566,6 +1566,8 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
SDValue N1 = N->getOperand(1);
ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0.getNode());
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.getNode());
ConstantSDNode *N1C1 = N1.getOpcode() != ISD::ADD ? 0 :
dyn_cast<ConstantSDNode>(N1.getOperand(1).getNode());
EVT VT = N0.getValueType();
// fold vector ops
@ -1597,6 +1599,12 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
// fold (A+B)-B -> A
if (N0.getOpcode() == ISD::ADD && N0.getOperand(1) == N1)
return N0.getOperand(0);
// fold C2-(A+C1) -> (C2-C1)-A
if (N1.getOpcode() == ISD::ADD && N0C && N1C1) {
SDValue NewC = DAG.getConstant((N0C->getAPIntValue() - N1C1->getAPIntValue()), VT);
return DAG.getNode(ISD::SUB, N->getDebugLoc(), VT, NewC,
N1.getOperand(0));
}
// fold ((A+(B+or-C))-B) -> A+or-C
if (N0.getOpcode() == ISD::ADD &&
(N0.getOperand(1).getOpcode() == ISD::SUB ||
@ -2571,7 +2579,7 @@ SDValue DAGCombiner::MatchBSwapHWordLow(SDNode *N, SDValue N0, SDValue N1,
(!LookPassAnd0 || !LookPassAnd1) &&
!DAG.MaskedValueIsZero(N10, APInt::getHighBitsSet(OpSizeInBits, 16)))
return SDValue();
SDValue Res = DAG.getNode(ISD::BSWAP, N->getDebugLoc(), VT, N00);
if (OpSizeInBits > 16)
Res = DAG.getNode(ISD::SRL, N->getDebugLoc(), VT, Res,