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<p class="MsoNormal">> > Even then, are we seriously ignoring the fact that even if you did clone<br>
> > the whole repository including everything, that you can still build just<br>
> > the libc++ and sanitiser runtimes if you wanted to?<br>
><br>
> Is it that easy to build a subset of a large checked-out tree? I haven't<br>
> tried it but my impression is: not so much.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It's possible to disable subsets of an LLVM build by setting the various 'LLVM_TOOL_*_BUILD' options to 'OFF' in cmake. For example, 'LLVM_TOOL_COMPILER_RT_BUILD=OFF' will prevent the build for projects/compiler-rt, and 'LLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD=OFF'
will disable the tools/projects/clang/tools/extra (I've just double checked the latter). IIRC, these are the variables that disable the build for projects that aren't checked out.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Also, I haven’t tried this myself but we should still be able to do standalone builds of particular projects by picking the initial CMakeLists.txt like so:<o:p></o:p></p>
<p class="MsoNormal"> cmake ../llvm/projects/compiler-rt<o:p></o:p></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>Bruce Hoult via llvm-dev<br>
<b>Sent:</b> 29 July 2016 15:52<br>
<b>To:</b> Robinson, Paul<br>
<b>Cc:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> Re: [llvm-dev] [RFC] One or many git repositories?<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"><o:p> </o:p></p>
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<p class="MsoNormal">On Sat, Jul 30, 2016 at 2:26 AM, Robinson, Paul via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal"><br>
> Even then, are we seriously ignoring the fact that even if you did clone<br>
> the whole repository including everything, that you can still build just<br>
> the libc++ and sanitiser runtimes if you wanted to?<br>
<br>
Is it that easy to build a subset of a large checked-out tree? I haven't<br>
tried it but my impression is: not so much. Certainly the advertised<br>
tactics for configuring/building don't tell you how to do that. Somebody<br>
figuring out what it takes would be very constructive here, instead of<br>
just asserting it can't possibly be that hard.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Right now, no. The build system assumes that if you checked someone out then you want to build it.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This needs to change.<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 believe David Chisnall up-thread cited a difference in checkout times<o:p></o:p></p>
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<p class="MsoNormal">on the order of a handful of seconds versus a couple of minutes. While<br>
naively it might seem not a big deal, over time and depending on what you<br>
are trying to do yes it can be a big burden<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">That's a one time cost, not every time you do an update.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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