<div dir="ltr"><div>I'm not the person to ask DExTer questions (I just fixed a few tests that were causing me bother with regards to the cross-project-tests proposal). You'll want someone like Jeremy Morse (CC'ed).</div><div><br></div><div>James<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 10 Mar 2021 at 20:02, Alexandre Ganea <<a href="mailto:alexandre.ganea@ubisoft.com">alexandre.ganea@ubisoft.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal"><b><span lang="FR">De :</span></b><span lang="FR"> Alexandre Ganea
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<b>Envoyé :</b> March 10, 2021 3:02 PM<br>
<b>À :</b> 'Tobias Hieta' <<a href="mailto:tobias@plexapp.com" target="_blank">tobias@plexapp.com</a>>; Adrian McCarthy <<a href="mailto:amccarth@google.com" target="_blank">amccarth@google.com</a>>; 'James Henderson' <<a href="mailto:jh7370.2008@my.bristol.ac.uk" target="_blank">jh7370.2008@my.bristol.ac.uk</a>><br>
<b>Objet :</b> RE: [llvm-dev] Debug information with clang-cl on Windows<u></u><u></u></span></p>
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<p class="MsoNormal"><span>DExTer can probably help bisecting to the specific optimization pass(es) that cause the debug infos to be omitted?
<a href="https://lists.llvm.org/pipermail/llvm-dev/2018-August/125780.html" target="_blank">https://lists.llvm.org/pipermail/llvm-dev/2018-August/125780.html</a><u></u><u></u></span></p>
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<p class="MsoNormal"><span>+James.<u></u><u></u></span></p>
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<p class="MsoNormal"><b><span lang="FR">De :</span></b><span lang="FR"> llvm-dev <<a href="mailto:llvm-dev-bounces@lists.llvm.org" target="_blank">llvm-dev-bounces@lists.llvm.org</a>>
<b>De la part de</b> Tobias Hieta via llvm-dev<br>
<b>Envoyé :</b> March 10, 2021 2:26 PM<br>
<b>À :</b> Adrian McCarthy <<a href="mailto:amccarth@google.com" target="_blank">amccarth@google.com</a>><br>
<b>Cc :</b> llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>><br>
<b>Objet :</b> Re: [llvm-dev] Debug information with clang-cl on Windows<u></u><u></u></span></p>
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<p class="MsoNormal">Hello,<u></u><u></u></p>
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<p class="MsoNormal">Thanks for your reply!<u></u><u></u></p>
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<p class="MsoNormal">Is it possible to disable optimisations with clang-cl and see if that makes a difference?<u></u><u></u></p>
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<p class="MsoNormal">I will also try to build with clang 12 instead and see if there is any improvement. <u></u><u></u></p>
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<p class="MsoNormal">Happy to try to reproduce or fix the issue - but I am unfamiliar with this debug info on windows and how to even start looking into it, any pointers are appreciated. <u></u><u></u></p>
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<p class="MsoNormal">Thanks,<u></u><u></u></p>
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<p class="MsoNormal">Tobias. <u></u><u></u></p>
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<p class="MsoNormal">On Wed, 10 Mar 2021 at 00:45, Adrian McCarthy <<a href="mailto:amccarth@google.com" target="_blank">amccarth@google.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">I believe that, even with `/Od` (that's Microsoft for "disable optimizations"), clang-cl applies some optimizations.<u></u><u></u></p>
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<p class="MsoNormal">People on my team have been fixing debug info quality bugs for Windows for a while. I don't have specific knowledge of these issues, but it's possible newer versions (like 12 or head) may have solved this. We're somewhat more focused
on 64-bit than 32-bit builds, so you might encounter some differences there.<u></u><u></u></p>
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<p class="MsoNormal">If you can reproduce the problem with a reduced code sample, please file a bug with all the deets. If you do some debugging yourself, please let us know what you find.<u></u><u></u></p>
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<p class="MsoNormal">On Tue, Mar 9, 2021 at 2:46 PM David Blaikie via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">I would guess there's no one bug here - debug info quality (specifically/especially the location of variables when compiling with optimizations enabled) is a long tail/sliding scale of issues. LLVM is, on the whole, not spectacular at this
- a matter of bugs to fix, some small/simple, others more systemic/representational.<br>
<br>
If you're interested in contributing to this work - generally the first step is to isolate the problem - first thing you can do is if you have some experience dumping/examining debug info in object files, you can dump/examine the relevant object files then
try to reduce/remove code from the relevant objects, etc, to see what the minimal example is that'll make it easier to figure out how to fix.<u></u><u></u></p>
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<p class="MsoNormal">On Tue, Mar 9, 2021 at 12:37 AM Tobias Hieta via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Hello,<br>
<br>
We recently switched our windows builds from the CL compiler to<br>
clang-cl. This was a pretty big jump in terms of code generation and<br>
having a uniform compiler across all the major platforms.<br>
<br>
Our setup is that our Windows developer use MSVC as the IDE and<br>
compile with our own build of clang-cl and link with lld-link.<br>
<br>
Some of the developers noticed that some of the debug information are<br>
not as good as with CL. Or rather some variables seems to be optimized<br>
out, this is what the IDE says, see attached screenshot. I have tried<br>
to figure out if there is a rhyme and reason to what variables are<br>
gone - but I have not been able to see any pattern.<br>
<br>
Our command line is:<br>
<br>
clang-cl.exe /nologo -DUNICODE -DUSE_BREAKPAD -DWIN32<br>
-DWIN32_LEAN_AND_MEAN -DWINVER=0x0601 -D_CRT_NONSTDC_NO_DEPRECATE<br>
-D_CRT_SECURE_NO_WARNINGS -D_LEGACY_NAT_TRAVERSAL_ -D_REENTRANT<br>
-D_SCL_SECURE_NO_WARNINGS -D_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS<br>
-D_UNICODE -D_WIN32_WINNT=0x0601 -D_WINSOCK_DEPRECATED_NO_WARNINGS<br>
-Iincludes -m32 -fdiagnostics-absolute-paths<br>
--target=i686-windows-msvc -m32 /DWIN32 /D_WINDOWS /GR /EHsc /Zi /Ob0<br>
/Od /RTC1 -MDd /Zm512 /EHsc /bigobj /W3 -Werror -Wsign-compare<br>
-Wno-reorder-ctor -Wno-delete-non-virtual-dtor -Wunused-variable<br>
-Wuninitialized -std:c++14<br>
<br>
Is there any good way to debug this or is it a known limitation with<br>
clang-cl or 32 bit (we don't do 64 yet - but with clang-cl we hope to<br>
move towards that soon). Or am I missing some flags?<br>
<br>
Thanks,<br>
Tobias<br>
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