[PATCH] D69732: [WIP][LTO] Apply SamplePGO pipeline tunes for ThinLTO pre-link to full LTO

Tue Jul 14 14:18:00 PDT 2020

hoyFB added a comment.

In D69732#1771950 <https://reviews.llvm.org/D69732#1771950>, @ormris wrote:

> I've done testing with the following global parameters.
>
> - The base for the branch is llvmorg-10-init-8655-g94a4a2c97f8
> - Used llvm, clang, lld, and llvm-ar from this branch.
> - The sqlite kvtest program was the test payload.
>
>   This test compared an unmodified compiler from the base of the branch with a modified compiler with this patch applied and the loop optimisation passes mentioned above moved to the backend. The results were as follows. All numbers in seconds.
>
>   |Run|Modified LTO|Modified SPGO+LTO|Unmodified SPGO+LTO| |---|------------|-----------------|-------------------| |1|42.00|41.73|42.08| |2|42.30|39.49|42.45| |3|41.21|42.46|42.49| |AVG:|41.84|41.23|42.34|
>
>   TL;DR the average run using a compiler built with the modified SPGO pipeline is about a second faster. Definitely a positive initial result.
>
> In D69732#1730732 <https://reviews.llvm.org/D69732#1730732>, @tejohnson wrote:
>
> > This probably needs to be taken over by someone who cares about full LTO performance (@wristow or @ormris ?). This patch was some cleanup of the full LTO sample PGO pipeline, but has a number of issues I enumerate in the summary.
>
>
> Given the performance improvements here, I'd like to develop this patch further.

@ormris I'd like to follow up on this. We had a similar change internally which led up to some gains when combined with SPGO, and we'd like to help move forward with this patch here. Would you mind sharing the plan or progress on your side? Thanks!

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https://reviews.llvm.org/D69732