<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 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>I see the BackendUtil.cpp of Clang creates the TargetMachine with the optimization level based on below mentioned logic<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> CodeGenOpt::Level OptLevel = CodeGenOpt::Default;<o:p></o:p></p><p class=MsoNormal> switch (CodeGenOpts.OptimizationLevel) {<o:p></o:p></p><p class=MsoNormal> default: break;<o:p></o:p></p><p class=MsoNormal> case 0: OptLevel = CodeGenOpt::None; break;<o:p></o:p></p><p class=MsoNormal> case 3: OptLevel = CodeGenOpt::Aggressive; break;<o:p></o:p></p><p class=MsoNormal> }<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>As per my understanding, the correspondence between optimization level and CodeGenOpt is as below<o:p></o:p></p><p class=MsoNormal>O0 - none<o:p></o:p></p><p class=MsoNormal>O1 - less<o:p></o:p></p><p class=MsoNormal>O2 - default<o:p></o:p></p><p class=MsoNormal>O3 - aggressive<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>My goal is to turn on a target dependent codegen optimization at –O1(less). The TargetMachine is constructed with “CodeGenOpt::Default”. Is there a way I could do this in LLVM ? What is the standard way of doing this ? Also, the code in BackendUtil.cpp seem somewhat offbeat to me.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>--Sumanth G<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>