<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">+backend guys</div><div class=""><br class=""></div><div class="">Hi Laurin,</div><div class=""><br class=""></div><div class="">Would you mind sharing more details about your project? What is your goal here?</div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class="">Jan<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 18 Sep 2018, at 15:13, Laurin Brandner via clangd-dev <<a href="mailto:clangd-dev@lists.llvm.org" class="">clangd-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">Hi Sam,
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<div class="">Thank you very much for your help. I will prototype this and see where it goes :)</div>
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Cheers,
<div class="">Laurin</div>
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<div name="messageReplySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class="">On 17 Sep 2018, 16:43 +0200, Sam McCall <<a href="mailto:sammccall@google.com" class="">sammccall@google.com</a>>, wrote:<br class="">
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<div dir="ltr" class="">Hi Laurin,
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<div class="">I'm not really familiar with clang/LLVM backends, but here's a guess.</div>
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<div class="">The simplest idea is to change the existing code that parses the file and generates diagnostics.</div>
<div class="">At least to prototype, I think you might want to change clangd::ClangdFrontendAction (in ClangdUnit.cpp) to subclass clang::EmitCodeGenOnlyAction (or one of the other CodeGenActions) instead of clang::SyntaxOnlyAction. And then add the relevant flags.</div>
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<div class="">However I'm not sure that's going to work well:</div>
<div class=""> - with the backend enabled, everything is going to get a lot slower</div>
<div class=""> - we have optimizations (like not parsing function bodies in the preamble) that probably aren't compatible with codegen</div>
<div class=""> - doing codegen is probably going to force clang to deserialize all of the preamble, which is also slow</div>
<div class=""> - obviously it means linking in the backend, which is quite a big thing for a release build if this is a niche feature</div>
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<div class="">For performance, I'm not sure how feasible it is to run codegen for code directly referenced by the main file only (again, not a backend person!), this would be the analogue to how we keep frontend diagnostics fast.</div>
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<div class="">We have a vague wish to support some more-expensive diagnostics (template expansions, clang-tidy analysis) that can't be computed every loop, but haven't come up with a good design yet.</div>
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<div class="">Cheers, Sam</div>
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<div dir="ltr" class="">On Mon, Sep 17, 2018 at 2:24 PM Laurin Brandner via clangd-dev <<a href="mailto:clangd-dev@lists.llvm.org" class="">clangd-dev@lists.llvm.org</a>> wrote:<br class=""></div>
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<div name="messageBodySection" style="font-size:14px;font-family:-apple-system,BlinkMacSystemFont,sans-serif" class="">Hi,
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<div class="">I’m fairly new to this community so I hope I’m not asking a very trivial question.</div>
<div class="">Anyways, I’m looking into the possibility of returning optimization remarks like the option -Rpass=loop-vectorize would do. By looking at clangd’s source code I realized that clangd only preprocesses the project but does not really invoke the backend.</div>
<div class="">Thus, I would like to implement an action that enables the output of optimization remarks. Could I maybe get some guidance on to what I need to do to achieve this? I saw that I most likely need to subclass Action but I’m not quite sure what subclass I should have a closer look at. </div>
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<div class="">Thanks a lot for any kind of help.</div>
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<div name="messageSignatureSection" style="font-size:14px;font-family:-apple-system,BlinkMacSystemFont,sans-serif" class=""><br class="">
Cheers,
<div class="">Laurin</div>
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