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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">We could implement /Zi with LLD running on the side, during the compilation, and have clang pass the debuginfo along to
LLD through shared memory pages. However most of us use distributed builds, I’m not sure how practical that would be. We would need to maintain a PDB per project, per remote worker, and get it back once all CPPs are done compiling. Unless you compile all CPPs
from a project on the same remote worker, there wouldn’t be much gain?<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">An alternative would be to start merging (debug info) locally as soon as the remote worker(s) sends back OBJs. You would
still have the OBJ in the OS cache, so that could speed up linking a bit; especially if your local host is idle waiting for remote CPPs to finish compiling. All this would require for LLD to run in some kind of daemon mode (start with the build process, and
end when all OBJs are available, to emit the final EXE and PDB).<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Zachary what do you think?<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Zachary Turner <zturner@google.com>
<br>
<b>Sent:</b> Wednesday, February 27, 2019 6:27 PM<br>
<b>To:</b> Leonardo Santagada <santagada@gmail.com><br>
<b>Cc:</b> Reid Kleckner <rnk@google.com>; Alexandre Ganea <alexandre.ganea@ubisoft.com>; llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] Making LLD PDB generation faster<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">On Wed, Feb 27, 2019 at 3:17 PM Leonardo Santagada <</span><a href="mailto:santagada@gmail.com"><span lang="EN-US">santagada@gmail.com</span></a><span lang="EN-US">> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Also we are investigating why we have 420 million types being linked while it appears that 95-99 % of them are not being used. De anyone know if pch can help here? My feeling is not much as template instantiation still
generates a ton of weak symbols on the pch users, but I might be confused.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">This probably has to do with the fact that most types are duplicates. If there is a class Foo in a header file, and you include that header file in 100 different translation units, all 100 of them of them will get full
type information for that class in its object file. This is the /Z7 semantics that clang-cl implements. The alternative is /Zi which uses a type server (out of process de-duplicater) to do this merging at compile time, which is what cl uses by default, and
which clang-cl doesn't support. <o:p></o:p></span></p>
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