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<p class="MsoNormal">So, I thought that the whole idea of the ‘incubator’ was to take up tiers 2/3 until they were sufficiently baked for tier 1. Is this intended to go against that for some things (that is, Bazel in this case)?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>Geoffrey Martin-Noble via llvm-dev<br>
<b>Sent:</b> Friday, October 30, 2020 11:57 AM<br>
<b>To:</b> Jacques Pienaar <jpienaar@google.com><br>
<b>Cc:</b> LLVM Dev <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] Policy on support tiers<o:p></o:p></p>
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<p class="MsoNormal">On Fri, Oct 30, 2020 at 11:36 AM Jacques Pienaar <<a href="mailto:jpienaar@google.com">jpienaar@google.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><a href="mailto:gcmn@google.com" target="_blank">+Geoffrey Martin-Noble</a> <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 Fri, Oct 30, 2020 at 8:45 AM Renato Golin 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>
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<p class="MsoNormal">Hi all,<o:p></o:p></p>
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<p class="MsoNormal">It seems the BAZEL[1] discussion is going round in circles and many have suggested we encode the policy on the tiers of support we want from the community.<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 is not what I think is the best, just what I have interpreted the "consensus" seems to think is the best. I may be completely wrong, please don't assume anything other than a faulty attempt at getting it right.<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 tried to use different words like "must", "should", "could", "will", etc. to convey the right meaning, but I'm not a native English speaker, so feel free to tweak that to get the right balance.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Here it goes.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">*** Tier 1: the core compiler, which *must* work at all times.<o:p></o:p></p>
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<p class="MsoNormal"> * Front-ends, back-ends, middle-ends, libraries, core APIs, official projects and tools.<o:p></o:p></p>
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<p class="MsoNormal"> * The CMake build infrastructure.<o:p></o:p></p>
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<p class="MsoNormal"> * Builds on all first class citizen combinations of targets x OSs. [2]<o:p></o:p></p>
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<p class="MsoNormal"> * Vim support (kidding!! :)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It must:<o:p></o:p></p>
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<p class="MsoNormal"> * have noisy green bots<o:p></o:p></p>
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<p class="MsoNormal"> * revert on failure policy<o:p></o:p></p>
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<p class="MsoNormal"> * etc?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">*** Tier 2: side projects that integrate with the compiler and that *should* work at all times.<o:p></o:p></p>
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<p class="MsoNormal"> * Experimental targets, infrastructure and APIs, non-default cmd-line options<o:p></o:p></p>
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<p class="MsoNormal"> * Alternative build systems (ex. GN, Bazel)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It must not:<o:p></o:p></p>
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<p class="MsoNormal"> * Break or hinder tier 1<o:p></o:p></p>
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<p class="MsoNormal"> * Increase validation noise beyond its scope<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It should:<o:p></o:p></p>
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<p class="MsoNormal"> * Have green buildbots, handled by the sub-community that cares about it<o:p></o:p></p>
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<p class="MsoNormal"> * Have notifications only to those interested when things break (avoid bitrot)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Sub-communities that care about it *must* fix issues in them, but the rest of the community has no obligations to support it. Lack of maintenance *could* be subject to removal.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">*** Tier 3: miscellaneous accessories<o:p></o:p></p>
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<p class="MsoNormal"> * Helper scripts, editor files, debugger scripts, etc.<o:p></o:p></p>
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<p class="MsoNormal"> * Whatever is detached enough that bit rot is irrelevant<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 think bit rot is never really totally "irrelevant". Perhaps "detached and small enough that bit rot is a minor concern"? <o:p></o:p></p>
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<p class="MsoNormal">It must not:<o:p></o:p></p>
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<p class="MsoNormal"> * Break or hinder tiers 1 or 2<o:p></o:p></p>
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<p class="MsoNormal"> * Increase validation noise beyond its scope<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It should:<o:p></o:p></p>
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<p class="MsoNormal"> * Have a sub-community that cares about it and maintain 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">Sub-communities that care about it *should* fix issues in them, but the rest of the community has no obligations to support it. Lack of maintenance *will* be subject to removal.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">cheers,<o:p></o:p></p>
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<p class="MsoNormal">--renato<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">[1] <a href="http://lists.llvm.org/pipermail/llvm-dev/2020-October/146138.html" target="_blank">
http://lists.llvm.org/pipermail/llvm-dev/2020-October/146138.html</a><o:p></o:p></p>
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<p class="MsoNormal">[2] Existing definition of "first-class", could be updated / moved here.<o:p></o:p></p>
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<p class="MsoNormal">_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_blank">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><o:p></o:p></p>
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<p class="MsoNormal">Thanks for kicking this off Renato. This looks very similar to what I would've written after that discussion except that I'm not sure I see the clear distinction between when something should be considered tier 2 vs 3. It seems like if
something is sufficiently big it's not *allowed* to be tier 3 and must have a buildbot and remain green? And tier 2 seems to be largely an extension of the "experimental targets" policy, but encompassing things that aren't targets.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Some additional constraints I would add:<o:p></o:p></p>
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<p class="MsoNormal">1. Something in a higher tier may never depend on something in a lower tier.<o:p></o:p></p>
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<p class="MsoNormal">2. Items in tiers <1 must always be simple to remove (`rm -rf /path/to/thing` ideally, although experimental backends also include some CMake options).<o:p></o:p></p>
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<p class="MsoNormal">3. Items in tiers <1 must have clear documentation accompanying them indicating their less-supported status.<o:p></o:p></p>
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