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<p class="MsoNormal"><span lang="FR-CA" style="mso-fareast-language:EN-US">Hello James,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR-CA" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">The compiler is not multi-threaded when you build a single file. There was a long thread on the subject last year:
<a href="https://lists.llvm.org/pipermail/llvm-dev/2020-March/139606.html">https://lists.llvm.org/pipermail/llvm-dev/2020-March/139606.html</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">But it’s not something trivial to achieve.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">The LLD linker however is multithreaded in part. Are you running on Windows or Linux?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">If Windows, you can do:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="mso-fareast-language:EN-US">$ clang-cl /c -gcodeview-ghash file.cpp<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="mso-fareast-language:EN-US">$ lld-link /DEBUG:GHASH file.obj …<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">..to reduce build times a bit. With LLD 12.0 the linker will be faster when using these flags.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">You can also try disabling optimizations with /Od to save some time in the compiler.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Precompiled headers or modules will certainly help as well when iterating:
<a href="https://clang.llvm.org/docs/PCHInternals.html">https://clang.llvm.org/docs/PCHInternals.html</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Alex.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="FR">De :</span></b><span lang="FR"> cfe-dev <cfe-dev-bounces@lists.llvm.org>
<b>De la part de</b> James Courtier-Dutton via cfe-dev<br>
<b>Envoyé :</b> April 2, 2021 6:48 AM<br>
<b>À :</b> cfe-dev@lists.llvm.org Developers <cfe-dev@lists.llvm.org><br>
<b>Objet :</b> [cfe-dev] clang multi-threaded compiling<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,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I am working on a C++ project using Eclipse IDE.<o:p></o:p></p>
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<p class="MsoNormal">When I edit some code, and then go to debug it, it takes time to compile the one .cpp file I was editing, and then link it, and then the debugger starts.<o:p></o:p></p>
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<p class="MsoNormal">I have a 16 CPU Cores PC, but I have noticed for the use case:<o:p></o:p></p>
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<p class="MsoNormal">"one compile then one link"<o:p></o:p></p>
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<p class="MsoNormal">It is only using 1 CPU Core.<o:p></o:p></p>
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<p class="MsoNormal">It is therefore slow to cycle between edit code, and debug it.<o:p></o:p></p>
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<p class="MsoNormal">How do I get clang to use more than one core when compiling a single .cpp file?<o:p></o:p></p>
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<p class="MsoNormal">How do I get clang to use more than one core when linking?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Essentially, any way to speed up the "one compile then one link" use case would help me.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The build tool is "ninja", so a way for ninja to use clang in this way would help.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Kind Regards<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">James<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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