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add a simple xform 

llvm-svn: 21203
This commit is contained in:
Chris Lattner 2005-04-10 04:04:49 +00:00
parent b076731713
commit f2bff92411
1 changed files with 6 additions and 0 deletions
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6
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -892,6 +892,12 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
return getNode(ISD::SUB, VT, N1, N2.getOperand(0));
if (N1.getOpcode() == ISD::FNEG) // ((-A)+B) -> B-A
return getNode(ISD::SUB, VT, N2, N1.getOperand(0));
if (N1.getOpcode() == ISD::SUB && isa<ConstantSDNode>(N1.getOperand(0)) &&
cast<ConstantSDNode>(N1.getOperand(0))->getValue() == 0)
return getNode(ISD::SUB, VT, N2, N1.getOperand(1)); // (0-A)+B -> B-A
if (N2.getOpcode() == ISD::SUB && isa<ConstantSDNode>(N2.getOperand(0)) &&
cast<ConstantSDNode>(N2.getOperand(0))->getValue() == 0)
return getNode(ISD::SUB, VT, N1, N2.getOperand(1)); // A+(0-B) -> A-B
break;
case ISD::SUB:
if (N1.getOpcode() == ISD::ADD) {