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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 chandler,<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 give more details about my ideas on this patch in <a href="http://reviews.llvm.org/D4954">http://reviews.llvm.org/D4954</a>.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I think you concern about when the narrow LOADs are folded back, we can’t fuse the narrow STOREs back. Am I get your point?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>But I think the narrow LOADs won’t be folded back, as the SROA checks such LOAD can be split and removed. So if the narrow LOADs won’t exist, there are two choices for us:<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span style='mso-list:Ignore'>(1)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The additional ZEXT/SHL/OR and wide STORE.<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span style='mso-list:Ignore'>(2)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Two narrow STOREs.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I still prefer the (2) than the (1). I think a better optimization for (1) is to split the STORE. Even if there are other optimizations to change the wide STORE, we’ll still have ZEXT/SHL/OR left. Such code with bit math seems not the best choice.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>If we believe the (2) is the best choice, why don’t we do it at the very beginning?<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'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>-Hao<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"'> chandlerc@google.com [mailto:chandlerc@google.com] <b>On Behalf Of </b>Chandler Carruth<br><b>Sent:</b> Tuesday, August 26, 2014 9:35 AM<br><b>To:</b> Chandler Carruth<br><b>Cc:</b> reviews+D4954+public+39a520765005fb8e@reviews.llvm.org; Hao Liu; Commit Messages and Patches for LLVM<br><b>Subject:</b> Re: [PATCH] [PATCH][SROA]Also slice the STORE when slicing a LOAD in AllocaSliceRewriter<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>On Mon, Aug 25, 2014 at 6:33 PM, Chandler Carruth <<a href="mailto:chandlerc@gmail.com" target="_blank">chandlerc@gmail.com</a>> wrote:<o:p></o:p></p><p class=MsoNormal>In particular, why did the load need to be sliced up but the store didn't? That doesn't really make sense.<o:p></o:p></p></div><p class=MsoNormal><br>Oh, I see, you have a store into a non-alloca region from a value loaded from the alloca.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I think preserving the wide store is correct here as it represents strictly more freedom in the optimizer. We should do store narrowing to remove bit math in the backend (or late in the optimizer).<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>To see why we would want to use the wider store: consider when we actually can eventually fold the loads together. Once we split up a store, we can in many cases never fuse them back together. =/<span style='color:#1F497D'><o:p></o:p></span></p></div></div></div></div></body></html>