Neil Henning via llvm-dev
2021-May-20 07:04 UTC
[llvm-dev] How to use a custom InlineAdvisor with the new pass manager
So what I need is for the default LLVM inliner to be able to use my InlineAdvisor in some fashion - without modifying tip LLVM *locally *to do so. So what I think I will have to do is land one of the proposals I stated originally (or a better idea from any of you fine folk) into LLVM *before *the LLVM 13 cutoff, so that when we pick up the LLVM 13 release in future we'll have the APIs available to set our own InlinerAdvisor. So to be clear - I'm totally ok to do a patch to LLVM to fix this, I just can't patch LLVM myself *locally *post-release because we are provided with a pre-built LLVM for some platforms we support. Hopefully that makes it a bit clearer? On Wed, May 19, 2021 at 4:21 PM Mircea Trofin <mtrofin at google.com> wrote:> > On Wed, May 19, 2021 at 5:27 AM Neil Henning via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hey list, >> >> I'm currently porting our HPC# Burst compiler over from the legacy pass >> manager to the new pass manager. While nearly everything went fine, I've >> hit one major hiccup that I can't seem to workaround - how can we have a >> custom `InlineAdvisor` for Burst without modifying tip LLVM. >> > > I'm trying to understand this better - you mean you'd want to load the > InlineAdvisor from a dynamic library, or something like that? > > >> >> At present I've managed to completely bodge this locally by getting >> access to the `OwnedAdvisor` member of `InlinerPass` through very UB means >> (make a class of the same layout, casteroo, assign the field). Now this >> works in that I don't have codegen regressions anymore, but obviously this >> isn't the solution I want to ship! >> >> I was wondering if the list would object to us either: >> >> 1. Making the `OwnedAdvisor` field of `InlinerPass` protected, so I >> could derive from `InlinerPass` and set the advisor. >> 2. I could make the `getAdvisor` virtual, and assign it that way. >> 3. Probably the 'best' fix would be to make `InlineAdvisorAnalysis` >> somehow able to take a user-provided `InlineAdvisor` - although I'd rather >> not use the static option `UseInlineAdvisor` to set this. I don't really >> know how this solution would look if I'm honest. >> >> I'm trying to understand what amount of changes to tip of tree are OK for > your scenario. Option 1 means modifying a .h; maybe option 2 needs a > recompile though (because virtual). So would option 3 (at this point, we > can talk about purpose-building support for your scenario, basically - if > rebuilding the compiler binaries is on the table) > > Thoughts from anyone? This is a blocker for us in the LLVM 13 timeframe >> when we hope to enable the new pass manager as the default. >> >> Cheers, >> -Neil. >> >> -- >> Neil Henning >> Senior Software Engineer Compiler >> unity.com >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >-- Neil Henning Senior Software Engineer Compiler unity.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210520/f1b2cf62/attachment.html>
Mircea Trofin via llvm-dev
2021-May-20 14:16 UTC
[llvm-dev] How to use a custom InlineAdvisor with the new pass manager
Ah, I see. There's a precedent for using custom InlineAdvisors, see for instance (in Inliner.cpp) how the ReplayInlineAdvisor is handled. I suppose you could do the same? On Thu, May 20, 2021 at 12:04 AM Neil Henning <neil.henning at unity3d.com> wrote:> So what I need is for the default LLVM inliner to be able to use my > InlineAdvisor in some fashion - without modifying tip LLVM *locally *to > do so. > > So what I think I will have to do is land one of the proposals I stated > originally (or a better idea from any of you fine folk) into LLVM *before > *the LLVM 13 cutoff, so that when we pick up the LLVM 13 release in > future we'll have the APIs available to set our own InlinerAdvisor. > > So to be clear - I'm totally ok to do a patch to LLVM to fix this, I just > can't patch LLVM myself *locally *post-release because we are provided > with a pre-built LLVM for some platforms we support. > > Hopefully that makes it a bit clearer? > > On Wed, May 19, 2021 at 4:21 PM Mircea Trofin <mtrofin at google.com> wrote: > >> >> On Wed, May 19, 2021 at 5:27 AM Neil Henning via llvm-dev < >> llvm-dev at lists.llvm.org> wrote: >> >>> Hey list, >>> >>> I'm currently porting our HPC# Burst compiler over from the legacy pass >>> manager to the new pass manager. While nearly everything went fine, I've >>> hit one major hiccup that I can't seem to workaround - how can we have a >>> custom `InlineAdvisor` for Burst without modifying tip LLVM. >>> >> >> I'm trying to understand this better - you mean you'd want to load the >> InlineAdvisor from a dynamic library, or something like that? >> >> >>> >>> At present I've managed to completely bodge this locally by getting >>> access to the `OwnedAdvisor` member of `InlinerPass` through very UB means >>> (make a class of the same layout, casteroo, assign the field). Now this >>> works in that I don't have codegen regressions anymore, but obviously this >>> isn't the solution I want to ship! >>> >>> I was wondering if the list would object to us either: >>> >>> 1. Making the `OwnedAdvisor` field of `InlinerPass` protected, so I >>> could derive from `InlinerPass` and set the advisor. >>> 2. I could make the `getAdvisor` virtual, and assign it that way. >>> 3. Probably the 'best' fix would be to make `InlineAdvisorAnalysis` >>> somehow able to take a user-provided `InlineAdvisor` - although I'd rather >>> not use the static option `UseInlineAdvisor` to set this. I don't really >>> know how this solution would look if I'm honest. >>> >>> I'm trying to understand what amount of changes to tip of tree are OK >> for your scenario. Option 1 means modifying a .h; maybe option 2 needs a >> recompile though (because virtual). So would option 3 (at this point, we >> can talk about purpose-building support for your scenario, basically - if >> rebuilding the compiler binaries is on the table) >> >> Thoughts from anyone? This is a blocker for us in the LLVM 13 timeframe >>> when we hope to enable the new pass manager as the default. >>> >>> Cheers, >>> -Neil. >>> >>> -- >>> Neil Henning >>> Senior Software Engineer Compiler >>> unity.com >>> _______________________________________________ >>> LLVM Developers mailing list >>> llvm-dev at lists.llvm.org >>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>> >> > > -- > Neil Henning > Senior Software Engineer Compiler > unity.com >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210520/57168903/attachment.html>