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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Pete,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I’ve pinged Zhaoshi and Ana using our internal emails. Hopefully, they can provide some feedback shortly.<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'> Chad<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><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><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'> Pete Cooper [mailto:peter_cooper@apple.com] <br><b>Sent:</b> Tuesday, April 21, 2015 6:51 PM<br><b>To:</b> mcrosier@codeaurora.org<br><b>Cc:</b> zhaoshiz@codeaurora.org; apazos@codeaurora.org; Tim Northover; Jiangning Liu; sdmitrouk@accesssoftek.com; llvm-commits<br><b>Subject:</b> [PATCH] Check Dest Register Liveness using MRI in CondOpt pass<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hi Chad<o:p></o:p></p><div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><a href="http://reviews.llvm.org/D6048">http://reviews.llvm.org/D6048</a> (everyone CCed here was CCed on it) added register liveness checking to the CondOpt pass. It does this with<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><blockquote style='margin-left:30.0pt;margin-right:0in'><div><p class=MsoNormal>if (I->getOperand(0).isDead())<o:p></o:p></p></div></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>However, this requires that some kind of liveness has been run beforehand, so the pass had to require live intervals. Looking at the pass manager dump, we then invalidated live intervals shortly after CondOpt because other passes don’t preserve it.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Attached is a patch which removes the dependency on LiveIntervals by checking if the def has any uses. If it has no uses then it was going to be marked dead anyway, so this is equivalent to your original code. I’ve verified that this passes ‘make check’ and specifically stepped through the examples in combine-comparisons-by-cse.ll in lldb to ensure the behavior was the same.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>When building a bitcode containing all of llc with/without this change, it results in one less run of LiveIntervals per MF and saves 4s out of 80s total compile time.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Thanks,<o:p></o:p></p></div><div><p class=MsoNormal>Pete<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>