[llvm-dev] [cfe-dev] State of NaCl in monorepo?

Mon Apr 20 16:57:51 PDT 2020

> On Apr 20, 2020, at 4:32 PM, Chris Lattner via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> 
> 
>> On Apr 20, 2020, at 1:47 PM, James Y Knight via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> 
>> But the most recent NaCL toolchain release is based on LLVM 3.7 from 2015.
>> 
>> Unless you're planning to upgrade the NaCL toolchain to use a new release based on LLVM devhead (which would seem a rather expensive thing to attempt now, given the plan to desupport it in a year), I don't think keeping the code in LLVM is actually useful for anyone at this point.
> 
> Right, I think this is the key issue.  If the community cannot use the code that is in tree, there isn’t a strong reason for the community to maintain it.

IIUC, Derek is saying that a build of Chrome uses the limited NaCl support, but they plan to stop this on June 2021. It’s therefore usable in a limited manner, and I don’t think there's much of a cost to the LLVM community if we leave in until June 2021. Keeping it in likely makes his life easier because they don’t need to maintain downstream patches while the turn NaCl down. I imagine that Derek has already implicitly signed up for this maintenance, if ever is required, as well as for the removal in June 2021.

I see ~zero cost, and upsides for Derek’s team, in keeping this for now.

> -Chris
> 
>> 
>> 
>> On Mon, Apr 20, 2020 at 4:22 PM Derek Schuff via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> Hi Fangrui,
>> As you noted we are working on helping our NaCl users transition to WebAssembly and new web APIs that cover the functionality offered by NaCl. In terms of actually turning down the platform features, we recently announced a timeline at https://blog.chromium.org/2020/01/moving-forward-from-chrome-apps.html <https://blog.chromium.org/2020/01/moving-forward-from-chrome-apps.html>. 
>> 
>> In terms of LLM, I would prefer to keep the support we have in the tree until we complete the turndown as long as the support isn't unusually onerous. Not all of our NaCl toolchain code is upstream, but we are actually about to redo part of our current downstream code soon to improve Chromium's C++ support until we complete the platform turndown. And of course we continue to be available to support it upstream as needed, especially if there is some particular problem you're looking to solve by removing this code. 
>> Feel free to contact me directly as well (aside from the usual channels like this list of course) if you want more on NaCl or PNaCl.
>> 
>> 
>> On Sat, Apr 18, 2020 at 10:25 PM Petr Hosek via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> On Sat, Apr 18, 2020 at 7:43 PM Fangrui Song via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
>> Hi all,
>> 
>> LLVM/Clang supports an OS called 'NaCl' (llvm/include/llvm/ADT/Triple.h).
>> It apparently hasn't had any development since 2015.
>> 
>> This page https://developer.chrome.com/native-client/migration <https://developer.chrome.com/native-client/migration>
>> mentions that NaCl is deprecated.
>> 
>> Is it still used? If not, I would propose that we remove it.
>> I created a patch https://reviews.llvm.org/D78441 <https://reviews.llvm.org/D78441> which I think can
>> delete 90% of the related code.
>> 
>> There are still a few references left (noticeably aligned bundling in
>> MC) https://sites.google.com/a/chromium.org/dev/nativeclient/pnacl/aligned-bundling-support-in-llvm <https://sites.google.com/a/chromium.org/dev/nativeclient/pnacl/aligned-bundling-support-in-llvm>
>> I will delete that as a follow-up.
>> 
>> AFAIK aligned bundling has other users (e.g. the author of https://reviews.llvm.org/D19924 <https://reviews.llvm.org/D19924> mentioned interested in using bundle locked groups for Hexagon) so its removal should be probably treated as a separate proposal.
>>  
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