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<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">Given the function:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">long simpleExample(long x) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"> return x;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">RDF produces the following data-flow graph:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">DFG dump:[<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">f1: Function: simpleExample<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">b2: --- %bb.0 --- preds(0): succs(0):<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">p8: phi [+d9<DIH:0000000000000001>(,,u15"):]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">p10: phi [+d11<DIL:0000000000000001>(,,u14"):]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">p12: phi [+d13<HDI:0000000000000001>(,,u5"):]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">s3: COPY [d4<RAX>(,,u7):, u5"<RDI>(+d13):, u14"<RDI>(+d11):, u15"<RDI>(+d9):]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">s6: RET [u7<RAX>!(d4):]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">Why is the argument in RDI split into three lanes that do not fully span RDI? It would seem more natural to just have a single phi for RDI.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">I think the RDF code responsible for this behavior is located here:
<a href="https://github.com/llvm/llvm-project/blob/55d887b833646baeea0e3371fd2cbbd7550a8d4d/llvm/lib/CodeGen/RDFGraph.cpp#L903">
https://github.com/llvm/llvm-project/blob/55d887b833646baeea0e3371fd2cbbd7550a8d4d/llvm/lib/CodeGen/RDFGraph.cpp#L903</a>, but I admit I do not fully understand what is going on.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">Thanks in advance,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif">Scott Constable<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Intel Clear",sans-serif"><o:p> </o:p></span></p>
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