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<div class="moz-cite-prefix">My speculation here is that we
originally didn't have the check for cycles and someone (maybe
even the original author) added it to prevent stack overflow due
to infinite recursion.š I do not see a strong reason not to handle
phi cycles in this code.š Curious if anyone else disagrees?š Or
was around for the design of this?<br>
<br>
Philip<br>
<br>
On 06/29/2017 08:47 PM, Serguei Katkov via llvm-dev wrote:<br>
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<p class="MsoNormal">Dear Community,<o:p></o:p></p>
<p class="MsoNormal"><o:p>š</o:p></p>
<p class="MsoNormal">I'm trying to implement optimization
described in PR26223 and meet the following bail out condition
in CodeGenPrepare::optimizeMemoryInst.<o:p></o:p></p>
<p class="MsoNormal"><o:p>š</o:p></p>
<p class="MsoNormal">ššš // Break use-def graph loops.<o:p></o:p></p>
<p class="MsoNormal">ššš if (!Visited.insert(V).second) {<o:p></o:p></p>
<p class="MsoNormal">ššššš Consensus = nullptr;<o:p></o:p></p>
<p class="MsoNormal">ššššš break;<o:p></o:p></p>
<p class="MsoNormal">ššš }<o:p></o:p></p>
<p class="MsoNormal"><o:p>š</o:p></p>
<p class="MsoNormal">So while traversing thorough phi nodes from
memory instruction to find addr mode we bail out if we meet
some instruction twice.<o:p></o:p></p>
<p class="MsoNormal">Does anybody know/remember what is the
reason for this checks.<o:p></o:p></p>
<p class="MsoNormal">From the first glance it seems that it will
be ok if we just mark it as visited and continue processing
worklist.<o:p></o:p></p>
<p class="MsoNormal">I did this change and make check passed. <o:p></o:p></p>
<p class="MsoNormal"><o:p>š</o:p></p>
<p class="MsoNormal">So I seek for a help to explain this
decision.<o:p></o:p></p>
<p class="MsoNormal"><o:p>š</o:p></p>
<p class="MsoNormal">Thank you in advance,<o:p></o:p></p>
<p class="MsoNormal">Serguei.<o:p></o:p></p>
<p class="MsoNormal"><span lang="RU"><o:p>š</o:p></span></p>
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