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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">So here is the patch. For now, my computing of the register class intersection assumes register classes are either disjoint, or nicely nested; I will have to
modify it to support weird architecture, where you can have overlapping register classes. I am thinking of doing that by modifying createInterferenceEdge to detect when a zero matrix would be added, cache the empty-intersection result between the register
classes (and not add the edge </span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">J</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">) --- unless there is an easier way to compute if 2 register classes
are disjoint.<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">The failing regression test (when you apply my patch) is in-tree: test/CodeGen/AArch64/PBQP-csr.ll. It fails the machine instr verification step. Reverting
your fix (r227942) is enough to make it pass.<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">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Arnaud<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Lang Hames [mailto:lhames@gmail.com]
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<b>Sent:</b> 04 February 2015 00:33<br>
<b>To:</b> Arnaud De Grandmaison<br>
<b>Cc:</b> LLVM Developers Mailing List<br>
<b>Subject:</b> Re: [PBQP] Are edges between nodes from totally disjoint register classes necessary ?<o:p></o:p></span></p>
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<p class="MsoNormal">Hi Arnaud,<o:p></o:p></p>
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<p class="MsoNormal">That sounds good to me. If you send me the patch I'd like to have a look too.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Cheers,<o:p></o:p></p>
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<p class="MsoNormal">Lang.<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 Tue, Feb 3, 2015 at 4:06 PM, Arnaud A. de Grandmaison <<a href="mailto:arnaud.degrandmaison@arm.com" target="_blank">arnaud.degrandmaison@arm.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">Hi Lang,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">While working on improving the debug dumps of the PBQP graphs, I found out that we can have some edges between nodes which belong to totally disjoint register classes (for example,
on AArch64, this would be an int and a floating point register). Although it is true those 2 registers interferes, in the sense they are alive at the same time, they never have any physical interference, and this shows up as a zero matrix.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I was wondering if it could make sense to skip adding such edges to the graph, as they do not add useful information, they increases the nodes degrees … and ultimately make the
allocation take longer time.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I have a patch ready prototyping this. It unfortunately breaks with the last fix you made (@ r227942), but if I revert it, it just works fine. if you believe this could be worth
it, then I will investigate where the failure comes from.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Cheers,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">--<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Arnaud A. de Grandmaison<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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