<div dir="ltr"><br><br><div class="gmail_quote">On Wed, Mar 25, 2015 at 5:14 PM Robinson, Paul <<a href="mailto:Paul_Robinson@playstation.sony.com">Paul_Robinson@playstation.sony.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div>
<p class="MsoNormal" style="margin-left:.5in">"What caused you to notice not running the DAG combiner was a problem?"<u></u><u></u></p>
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</div></div><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><a name="msg-f:1496662810302868882__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">A fuzzer that we wrote generated some functions with 'optnone' and they crashed the compiler with instruction-selection failures.<u></u><u></u></span></a></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Being mostly vector-related, Andrea looked at them, and didn't take long to point the finger at DAG combine (or lack thereof!).<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Should I take this to imply you'd rather have one of the causes-a-crash functions as the test, instead of this one?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"></span></p></div></div></blockquote><div>Probably both, but definitely a comment going "this is currently necessary for correct code generation due to <blah>".</div><div><br></div><div>-eric</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">--paulr<u></u><u></u></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""> Eric Christopher [mailto:<a href="mailto:echristo@gmail.com" target="_blank">echristo@gmail.com</a>]
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<b>Sent:</b> Wednesday, March 25, 2015 4:44 PM<br>
<b>To:</b> <a href="mailto:reviews%2BD8614%2Bpublic%2B1ca59dfb9fe35dfd@reviews.llvm.org" target="_blank">reviews+D8614+public+1ca59dfb9fe35dfd@reviews.llvm.org</a>; Robinson, Paul; <a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a><br>
<b>Cc:</b> <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
<b>Subject:</b> Re: [PATCH] Verify 'optnone' can run DAG combiner when appropriate<u></u><u></u></span></p>
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<p class="MsoNormal">On Wed, Mar 25, 2015 at 1:28 PM Eric Christopher <<a href="mailto:echristo@gmail.com" target="_blank">echristo@gmail.com</a>> wrote:<u></u><u></u></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Inline comment.<br>
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================<br>
Comment at: test/CodeGen/X86/dag-optnone.ll:7<br>
@@ +6,3 @@<br>
+; that the combine is expected.<br>
+; Note, this will start failing if somebody decides that this combine should<br>
+; not occur at -O0 (because 'optnone' essentially sets -O0 for the function).<br>
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Could you describe the problem that would occur were the dag combiner not run? That hasn't been clear either in this test or in your original commit reverting.<u></u><u></u></p>
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<p class="MsoNormal">Resending because I typoed and it's unclear I think:<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">"What caused you to notice not running the DAG combiner was a problem?"<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">-eric<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal"><a href="http://reviews.llvm.org/D8614" target="_blank">http://reviews.llvm.org/D8614</a><br>
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