<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle18
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:#1F497D;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Sorry, Dead Store Elimination.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><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"'> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu] <b>On Behalf Of </b>Michael Smith<br><b>Sent:</b> Monday, November 21, 2011 12:20 PM<br><b>To:</b> Cameron Zwarich<br><b>Cc:</b> llvmdev@cs.uiuc.edu<br><b>Subject:</b> Re: [LLVMdev] Optimization of array access<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='color:#1F497D'>Dead Code Elimination. I’m going to try re-working it following some of the insights Don Quixote provided.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><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"'> Cameron Zwarich [mailto:zwarich@apple.com] <br><b>Sent:</b> Monday, November 21, 2011 12:17 PM<br><b>To:</b> Michael Smith<br><b>Cc:</b> llvmdev@cs.uiuc.edu<br><b>Subject:</b> Re: [LLVMdev] Optimization of array access<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Where does the -time-passes option say the time is going?<br><br>Sent from my iPhone<o:p></o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><br>On Nov 21, 2011, at 8:58 AM, Michael Smith <<a href="mailto:Michael.Smith@synopsys.com">Michael.Smith@synopsys.com</a>> wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>I’ve attached a 2 examples of patterns for updating an array. They’re simplified examples of some code generation I’m doing where I need to pass a large, unknown number of arguments (ints, doubles, pointers to other information) to a function.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>The two patterns are:<o:p></o:p></p><p class=MsoNormal> Stack[0] = 0;<o:p></o:p></p><p class=MsoNormal> Stack[1] = 1;<o:p></o:p></p><p class=MsoNormal> Stack[2] = 42;<o:p></o:p></p><p class=MsoNormal>And<o:p></o:p></p><p class=MsoNormal> Int I = 0;<o:p></o:p></p><p class=MsoNormal> Stack[i++] = 0;<o:p></o:p></p><p class=MsoNormal> Stack[i++] = 1;<o:p></o:p></p><p class=MsoNormal> Stack[i++] = 42;<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>I’ve found that the optimizer is much faster at handling the 2<sup>nd</sup> pattern than the 1<sup>st</sup>. With 3000 assignments - as in the examples attached – “opt –std-compile-opts –S func1.ll –o func1.opt” takes 10 seconds, while func2.ll takes 0.2s. Anyone have any ideas why?<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>I’ve tested with LLVM 2.9, and LLVM 3.0 RC1.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Regards,<o:p></o:p></p><p class=MsoNormal>Michael<o:p></o:p></p></div></blockquote><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><opt.zip><o:p></o:p></span></p></div></blockquote><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>_______________________________________________<br>LLVM Developers mailing list<br><a href="mailto:LLVMdev@cs.uiuc.edu">LLVMdev@cs.uiuc.edu</a> <a href="http://llvm.cs.uiuc.edu">http://llvm.cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a><o:p></o:p></span></p></div></blockquote></div></body></html>