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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">There’s two things going on here:<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">Firstly, extension points interact in a slightly odd way with optimization levels:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">* At -O0 the only extension points used are EP_EarlyAsPossible and EP_EnabledOnOptLevel0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">* At -O1 and higher all extension points are used
<i>except</i> EP_EnabledOnOptLevel0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">so when you’re not seeing the crash it’s because you’re using an optimization level (probably -O0 because that’s<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">the default) where the extension point you’re using isn’t used.<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">Secondly, CGSCC passes can only be added to a GCSCC pass manager. If you use a debug build of clang then the<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">crash becomes an assertion failure which (somewhat) tells you this:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">CallGraphSCCPass.cpp:575: virtual void llvm::CallGraphSCCPass::assignPassManager(llvm::PMStack&, llvm::PassManagerType): Assertion `!PMS.empty() && "Unable
to handle Call Graph Pass"' failed.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">From some experimentation it looks like it’s only EP_EarlyAsPossible where we get this error, because (looking<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">at PassManagerBuilder::populateFunctionPassManager) that extension point uses a Function Pass Manager<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">whereas all the others look like they use a Module Pass Manager.<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">John<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>
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<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""> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Alberto Barbaro via llvm-dev<br>
<b>Sent:</b> 16 November 2018 18:34<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [llvm-dev] Help with a pass<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi all,<o:p></o:p></p>
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<p class="MsoNormal">I was able to create a pass following [1]. Now goal is amend the pass and try to dump the call graph. I think I have properly amended the source extending my pass from CallGraphSCCPass but unfortunately every time I run it, it crashes.
I tried with llvm-6 and llvm-7. I notice that if I change EP_EarlyAsPossible to anything else it does not crash but I don't see the expected string printed by the runOnSCC.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Could you help me to solve this problem? How should I create the pass?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks for your time<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">[1] <a href="https://www.cs.cornell.edu/~asampson/blog/llvm.html">https://www.cs.cornell.edu/~asampson/blog/llvm.html</a><o:p></o:p></p>
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