<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=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@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:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","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-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
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 lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi,<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'>If you're looking for something incredibly simple to get started with it might be fruitful to implement replacement of particular function calls of constant arguments with the appropriate result. (That might also then lead to opportunities for a constant propagation pass.) This would involve quite a bit of API usage without being actually that involved, and if you're doing it just for the learning experience you probably neededn't bother too much about the corner cases that make this tricky in general.<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'>Dave<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-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><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"'> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu] <b>On Behalf Of </b>Rekha R<br><b>Sent:</b> 06 October 2013 13:24<br><b>To:</b> LLVM Developers Mailing List<br><b>Subject:</b> [LLVMdev] Suggestion on simple optimization pass for a beginner?<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><div><div><div><div><p class=MsoNormal style='margin-bottom:12.0pt'>Hello,<o:p></o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>I am a beginner in LLVM development with the aim of writing a new optimization pass. But then before I could do that, I thought of writing simple passes. I could successfully implement the Hello pass as given in the doc. Then I wrote a simple Constant Folding pass - evaluate instructions of the form c=10+20 and replace all uses of c with 30. Only later did I realize that Clang does this optimization while building the IR. Hence I couldn't check whether my constant folding pass is "working". I have two questions:<o:p></o:p></p></div><p class=MsoNormal>1. Is there a way to disable constant folding during IR development by clang?<o:p></o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>2. If not, can someone suggest a simple optimization (simple in complexity on the lines of constant folding) to get started?<o:p></o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>My intention is to get used to the APIs in LLVM and not get cluttered by the optimization itself. (Hence I chose constant folding in the first place.)<o:p></o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'>Any opinion will be appreciated :)<o:p></o:p></p></div><p class=MsoNormal>Regards,<o:p></o:p></p><div><div><div><div><div><div><p class=MsoNormal>Rekha <o:p></o:p></p></div></div></div></div></div></div></div></div></body></html>