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<p class="MsoNormal">I found a bug in the expansion code for SUB going back to at least LLVM 2.6 and still shows up in trunk.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">case ISD::SUB: {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> EVT VT = Node->getValueType(0);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> assert(TLI.isOperationLegalOrCustom(ISD::ADD, VT) &&<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> TLI.isOperationLegalOrCustom(ISD::XOR, VT) &&<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> "Don't know how to expand this subtraction!");<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> Tmp1 = DAG.getNode(ISD::XOR, dl, VT, Node->getOperand(1),<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> DAG.getConstant(APInt::getAllOnesValue(VT.getSizeInBits()), VT));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> Tmp1 = DAG.getNode(ISD::ADD, dl, VT, Tmp2, DAG.getConstant(1, VT));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> Results.push_back(DAG.getNode(ISD::ADD, dl, VT, Node->getOperand(0), Tmp1));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> break;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> }<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The problem is Tmp2 is not initialized and should be Tmp1 instead. This code only is hit if the architecture does not support ‘SUB’ and you need to expand it.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Patch is attached, please commit if good.<o:p></o:p></p>
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