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<p>Hi, Klarke,</p>
<p>Does adding __builtin_assume(n > 0); before the loop currently accomplish what you're trying to do?</p>
<p> -Hal<br>
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<div class="moz-cite-prefix">On 10/15/2018 09:37 PM, Qianyi (Compiler) via llvm-dev wrote:<br>
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<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">To whom it may concern,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">I’m implementing one pragma to optimize “for” loop.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">We assume the loop will run at least 1 times when we set following pragma:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:14.0pt"><span style="font-size:14.0pt;color:#0070C0" lang="EN-US">#pragma clang loop min(1)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:14.0pt"><span style="font-size:14.0pt;color:#0070C0" lang="EN-US">for(i = 0; i < n; I ++)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">Then we can remove the first branch which go to exit block when “n < =0”.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">This is one picture which show llvm how to do loop rotation.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><img id="图片_x0020_1" src="cid:part1.E82CD81F.F5E8AB60@anl.gov" class="" width="558" height="362"></span><span style="font-size:14.0pt" lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">Is it the proper place(LoopRotation.cpp) to implement my feature?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">Or is there more suitable place to do it?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt" lang="EN-US">Klarke</span><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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