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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'>Hi James,<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 style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><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"'> mankeyrabbit@gmail.com [mailto:mankeyrabbit@gmail.com] <b>On Behalf Of </b>James Molloy<br><b>Sent:</b> Monday, October 27, 2014 11:38 PM<br><b>To:</b> reviews+D5864+public+2de5fd757ea4c578@reviews.llvm.org<br><b>Cc:</b> Hao Liu; Tim Northover; ssijaric@codeaurora.org; Chad Rosier; Jingyue Wu; LLVM Commits<br><b>Subject:</b> Re: [PATCH] [AArch64] Improve and enable the SeparateConstOffsetFromGEP for AArch64 backend.<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Hi Hao,<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I'm not sure about this. Firstly I have concerns about the statistical significance of the difference in results - we've seen swings of +/- 1% on A57, and here we're talking about a 0.5% difference. Are you satisfied that the difference is genuine?<o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>[Hao Liu] I’m also curious about the result. I suspect both versions should have not big difference. But I think the difference is genuine. The benchmark astar is quite stable and should never have variance about +/- 1%.</span></i></b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p></div><div><p class=MsoNormal>Secondly, I don't see a good reason why useAA should be worse than !useAA. To my mind, if there is a regression when useAA is enabled, it should be one of two things:<o:p></o:p></p></div><div><p class=MsoNormal> 1) A legitimate regression, in which case let's fix useAA!<o:p></o:p></p></div><div><p class=MsoNormal> 2) Random code permutation outside of the compiler's model. If this is the case we shouldn't be adjusting the compiler to compensate.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>useAA has the potential to improve codegen. We're not really using it at the moment, but it's good that it's available to use in the future. If we rip it out, we should have a good reason for it, I think!<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Can I suggest that you make the initial commit, which improves performance, then have a look at why !useAA is better and fix that incrementally?<o:p></o:p></p></div><div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>[Hao Liu] OK, I’d like to do that. Thanks.</span></i></b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p></div><div><p class=MsoNormal>Cheers,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>James<span style='color:#1F497D'><o:p></o:p></span></p></div></div></div></div></body></html>