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<p class="MsoNormal"><span lang="EN-US">Sure, I’ll take a look at the legacy pass manager’s implementation and see if I can send a patch.</span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks,</span></p>
<p class="MsoNormal"><span lang="EN-US">Chibin Zhang</span></p>
<p class="MsoNormal"><span lang="EN-US">2021.5.12</span><span lang="EN-US" style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal" style="border:none;padding:0cm"><b>发件人<span lang="EN-US">: </span>
</b><span lang="EN-US"><a href="mailto:aeubanks@google.com">Arthur Eubanks</a><br>
</span><b>发送时间<span lang="EN-US">: </span></b><span lang="EN-US">2021</span>年<span lang="EN-US">5</span>月<span lang="EN-US">11</span>日<span lang="EN-US"> 3:40<br>
</span><b>收件人<span lang="EN-US">: </span></b><span lang="EN-US"><a href="mailto:zhangchb1@shanghaitech.edu.cn"><span lang="EN-US"><span lang="EN-US">张驰斌</span></span></a><br>
</span><b>抄送<span lang="EN-US">: </span></b><span lang="EN-US"><a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a><br>
</span><b>主题<span lang="EN-US">: </span></b><span lang="EN-US">Re: [llvm-dev] A Few Questions Regarding The New Pass Manager, LTO, and LLD</span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:SimSun"><o:p> </o:p></span></p>
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<p class="MsoNormal" align="left" style="text-align:left"><span lang="EN-US" style="font-size:12.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">On Sat, May 8, 2021 at 8:15 AM </span>张驰斌<span lang="EN-US"> via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:</span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">LLVM Developers,</span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> Hi!</span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> There is a scenario where I want to do full program analysis, ideally after link time optimization is done and before assembly is emitted, when all symbols
are in LLVM IR form and contained in a single module. But after some time browsing stackoverflow, lld documentation, and the mailing lists, I still have little clue how to do it</span>…<span lang="EN-US"> I am aware of the email sent by Y Liu and titled
</span>“<span lang="EN-US">how to add my own passes to LTO pass</span>”<span lang="EN-US">. But it doesn</span>’<span lang="EN-US">t seem to work for the new pass manager. A few questions:</span></p>
<p class="gmail-m6733311334807343348msolistparagraph" style="margin-left:39.0pt">
<span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">1.</span></span><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US" style="font-size:7.0pt;font-family:"Times New Roman",serif">
</span></span><span lang="EN-US">The legacy pass manager has an extension point, `PassManagerBuilder::EP_FullLinkTimeOptimizationLast`. Unfortunately, I can</span>’<span lang="EN-US">t find a alternative in the new pass manager. The `Bye` example seems to suggest
using `PB.<span class="gmail-m6733311334807343348pl-c1">registerVectorizerStartEPCallback`. I am not sure whether doing so will result in my module pass being ran at compile or link time?</span></span></p>
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<p class="MsoNormal"><span lang="EN-US">Feel free to create a patch to add a PassBuilder equivalent of EP_FullLinkTimeOptimizationLast. </span></p>
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<span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">2.</span></span><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US" style="font-size:7.0pt;font-family:"Times New Roman",serif">
</span><span lang="EN-US">I wonder how does clang communicates passes that need to be run at lto to lld. The command line that I attempt to get lto running is `clang -fexperimental-new-pass-manager -fpass-plugin=libmymodulepass.so -flto -fuse-ld=lld
</span>…<span lang="EN-US">`. I straced the command for execv calls, and expected to see libmymodulepass.so to be passed to ld.lld as an argument, but found out it wasn</span>’<span lang="EN-US">t. Could you shed some light on how clang and lld cope with each
other during lto?</span></span></p>
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<p class="MsoNormal"><span lang="EN-US">I don't know pass plugins that well, but maybe llvm/examples/Bye/Bye.cpp and its surrounding infrastructure may help?</span></p>
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<span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">3.</span></span><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US" style="font-size:7.0pt;font-family:"Times New Roman",serif">
</span><span lang="EN-US">Greping `ld.lld --help` reveals an interesting option: `--lto-newpm-passes=<value>`. Does the <value> here mean built-in pass names like `dce`/`mem2reg`, or is it an option to insert our plugin like libmymodulepass.so?</span></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:21.0pt">
<span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">I</span>’<span lang="EN-US">ve looking into this for a while but haven</span>’<span lang="EN-US">t made much progress</span>…<span lang="EN-US">Any examples / command line on how to do this are
greatly appreciated!</span></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US"> </span></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">Best Wishes,</span></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">Chibin Zhang</span></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span class="gmail-m6733311334807343348pl-c1"><span lang="EN-US">2021.5.8</span></span></p>
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<p class="MsoNormal" style="margin-left:4.8pt"><span lang="EN-US">_______________________________________________<br>
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<a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_BLANK">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:SimSun"><o:p> </o:p></span></p>
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