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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">@dblaikie does that answer the question? Sorry I should have pinged this a while ago.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> llvm-commits [mailto:llvm-commits-bounces@lists.llvm.org]
<b>On Behalf Of </b>Robinson, Paul via llvm-commits<br>
<b>Sent:</b> Tuesday, September 26, 2017 2:05 PM<br>
<b>To:</b> David Blaikie; reviews+D38088+public+4bc8f3de9212eeb7@reviews.llvm.org; Voss, Matthew; craig.topper@gmail.com; echristo@gmail.com<br>
<b>Cc:</b> llvm-commits@lists.llvm.org<br>
<b>Subject:</b> RE: [PATCH] D38088: Fix out-of-order stepping behavior in programs with hoisted constants.<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:4.8pt">Doesn't need to be merged with the insertion point, I don't think? Does this merge across basic blocks? or just raise the uses of a constant to the beginning of a single basic block?<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">I read the pass as looking for a dominating insertion point across multiple basic blocks. Doesn't mean the insertion point necessarily is in a different block,
but I *think* it could be.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<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>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> David Blaikie [mailto:dblaikie@gmail.com]
<br>
<b>Sent:</b> Monday, September 25, 2017 5:06 PM<br>
<b>To:</b> Robinson, Paul; reviews+D38088+public+4bc8f3de9212eeb7@reviews.llvm.org; Voss, Matthew; craig.topper@gmail.com; echristo@gmail.com<br>
<b>Cc:</b> llvm-commits@lists.llvm.org<br>
<b>Subject:</b> Re: [PATCH] D38088: Fix out-of-order stepping behavior in programs with hoisted constants.<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" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">On Fri, Sep 22, 2017 at 12:22 PM Robinson, Paul <<a href="mailto:paul.robinson@sony.com">paul.robinson@sony.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">(re-adding llvm-commits)</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">If this is motivated by SPGO issues - should it be using mergeDebugLocations, then (& thus only changing the location if they come from different basic blocks)?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Well, you could consider it a merge of all the uses, but then it should also be merged with the insertion
point, which is chosen to dominate the uses.</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Doesn't need to be merged with the insertion point, I don't think? Does this merge across basic blocks? or just raise the uses of a constant to the beginning of a single basic block?<br>
<br>
If it does work across basic block, then yeah, merging the location may be insufficient (since the location could be the same but still be merging across basic blocks... - not sure what the best way to detect/handle that is)<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="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> Intuitively it seemed unlikely this would ever produce a real debug location. (Also, in a sense
this is an artificially generated instruction and from that perspective having no source location is also appropriate.)</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Do you want us to pursue the extra bookkeeping? I'm having a hard time imagining this coming up
in the wild (i.e., not convinced it's worth the effort, but you're a lot better at that than I am).</span><o:p></o:p></p>
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<p class="MsoNormal"><br>
I'd guess at a macro that uses the same constant a few times (in which case they'll have the same location) or maybe a single line statement (with column info disabled) using the constant a few times/in a few places.<br>
<br>
I'd think it'd be worth checking how this works for some simple cases with a single basic block, etc. Maybe seeing how often that such a merge would fire on a real codebase maybe, etc.<br>
<br>
- Dave<br>
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><a href="https://reviews.llvm.org/D38088" target="_blank">https://reviews.llvm.org/D38088</a><o:p></o:p></p>
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