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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi Daniel,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">please take a look into
</span><a href="https://reviews.llvm.org/D36073" target="_blank">https://reviews.llvm.org/D36073</a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">It contains a couple of tests which shows the patterns I'm trying to resolve.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">In reality the pattern might be more complex.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">shortly for the case<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">BB1:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">p1 = b1 + 40<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">p2 = b2 + 40<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">br cond, BB2, BB3<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">BB2:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">br BB3<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">BB3:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">p = phi [p1, BB2], [p2, BB3]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">v = load p<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I want to see in BB3:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">b = phi [b1, BB2], [b2, BB3]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">p.b = b + 40<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">v = load p.b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">(after that p, p1, p2 will be eliminated)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Please note that in the original test
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">p = phi [p1, BB3], [p2, BB2]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">then I need<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">b = phi [b1, BB3], [b2, BB2]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="RU" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thank you,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Serguei.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="RU" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Daniel Berlin [mailto:dberlin@dberlin.org]
<br>
<b>Sent:</b> Tuesday, August 1, 2017 12:39 AM<br>
<b>To:</b> reviews+D35474+public+a0659378412bff14@reviews.llvm.org<br>
<b>Cc:</b> Serguei Katkov <serguei.katkov@azul.com>; Pete Cooper <peter_cooper@apple.com>; sabre+phabricator@nondot.org; Bob Wilson <bob.wilson@apple.com>; Friedman, Eli <efriedma@codeaurora.org>; llvm-commits <llvm-commits@lists.llvm.org><br>
<b>Subject:</b> Re: [PATCH] D35474: SSAUpdater: Add mode when Phi creation is not allowed<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Mon, Jul 31, 2017 at 12:21 AM, Serguei Katkov via Phabricator <<a href="mailto:reviews@reviews.llvm.org" target="_blank">reviews@reviews.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">skatkov abandoned this revision.<br>
skatkov added a comment.<br>
<br>
Hi Daniel,<br>
<br>
I've come up with the following implementation basing on your idea: <a href="https://reviews.llvm.org/D36073" target="_blank">
https://reviews.llvm.org/D36073</a><br>
<br>
Please take into account that finally I realized that I could not use SSAUpdater API because it is possible that I can observe the base instruction in the same BB but the difference might be in the path I can get it.<br>
Simple example:<br>
p1 = b1 + 40<br>
p2 = b2 + 40<br>
p = p1<br>
if (cond) p = p2<br>
v = *(p)<br>
<br>
So I have p1 and p2 in the same basic block, so I cannot say to SSA update that I saw b1 and b2 in the same basic block to get the right phi node merging b1 and b2.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">(I assume this if is turning into a select)<o:p></o:p></p>
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<p class="MsoNormal">Right, you have to write/read the definitions in the right order, even with the new API.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It's possible toavoid this issue by adding local dominance info using ordered instructions, and then you could just add them in any order.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I'm pretty sure we could design something that worked a little better for you.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Do you have an example of what you want the above output fo actually produce in terms of phi nodes?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">I hope the right implementation may b found in
<a href="https://reviews.llvm.org/D36073" target="_blank">https://reviews.llvm.org/D36073</a><br>
<br>
<br>
<a href="https://reviews.llvm.org/D35474" target="_blank">https://reviews.llvm.org/D35474</a><br>
<br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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