[llvm-dev] [RFC] Moving tools/llvm-mca/lib into lib/MCA (original) (raw)

Clement Courbet via llvm-dev llvm-dev at lists.llvm.org
Sun Dec 16 23:24:15 PST 2018

Thanks for the comments. I'm going to submit this as there seem to be no objections.

On Wed, Dec 12, 2018 at 10:37 PM David Greene <dag at cray.com> wrote:

+1. Great work!

-David Andrea Di Biagio via llvm-dev <llvm-dev at lists.llvm.org> writes: > Thanks Clement for working on this. > > I like the idea of moving the core abstractions of llvm-mca in > llvm/lib, as it potentially enables a number of interesting use cases > and future developments. > > As you wrote, the patch is very simple (a pretty mechanical change). > From my point of view, this all looks good. Let see if other people > have the same opinion on this. > > -Andrea > > On Wed, Dec 12, 2018 at 11:58 AM Clement Courbet <courbet at google.com> > wrote: > > (on the correct mailing list) > > > Hi all, > > tl;dr: We'd like to propose moving tools/llvm-mca/lib into lib/MCA > and create a new MCA library in LLVM. > > llvm-mca has recently been split into its core part and the tool > part. > > * The core part simulates the execution of a basic block of > machine instructions as modeled by the llvm SchedModel. > > * The tool part deals with the plumbing and interacting with > the user. > > The core part can be used by parts of LLVM that deal with cost > modeling (e.g. scheduling and vectorization). MCA provides a more > realistic target for optimization than the heuristics typically > used to drive these passes. We think that using approaches based > on fine-grained cost modeling can greatly improve the performance > of critically hot code, by trading compile time for performance. > > As an example of how MCA can be used to improve scheduling, we > have built a prototype machine scheduler that optimizes the > simulated latency of a block of code under the constraints of the > scheduling DAG. We've had interesting wins of 2-3% on assembly > kernels for webp and gemmlowp*. > > The patch is completely mechanical and can be seen here. It only > moves the files and updates all references. > > We'd like to hear if there are any things comments/objections to > this change. > > Thanks ! > > *note: We did this before llvm-mca was released and were using a > different simulator, but the idea remains the same. > > > On Wed, Dec 12, 2018 at 11:44 AM Clement Courbet > <courbet at google.com> wrote: > > > Hi all, > > tl;dr: We'd like to propose moving tools/llvm-mca/lib into > lib/MCA and create a new MCA library in LLVM. > > llvm-mca has recently been split into its core part and the > tool part. > > * The core part simulates the execution of a basic > block of machine instructions as modeled by the llvm > SchedModel. > > * The tool part deals with the plumbing and > interacting with the user. > > The core part can be used by parts of LLVM that deal with cost > modeling (e.g. scheduling and vectorization). MCA provides a > more realistic target for optimization than the heuristics > typically used to drive these passes. We think that using > approaches based on fine-grained cost modeling can greatly > improve the performance of critically hot code, by trading > compile time for performance. > > As an example of how MCA can be used to improve scheduling, we > have built a prototype machine scheduler that optimizes the > simulated latency of a block of code under the constraints of > the scheduling DAG. We've had interesting wins of 2-3% on > assembly kernels for webp and gemmlowp*. > > The patch is completely mechanical and can be seen here. It > only moves the files and updates all references. > > We'd like to hear if there are any things comments/objections > to this change. > > Thanks ! > > *note: We did this before llvm-mca was released and were using > a different simulator, but the idea remains the same. > > _> ________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181217/4bf05568/attachment-0001.html>

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