[PATCH] D119880: [FuncSpec] Support function specialization across multiple arguments.

Wed Feb 16 04:08:43 PST 2022

labrinea added a comment.

> ! In D119880#3325445 <https://reviews.llvm.org/D119880#3325445>, @SjoerdMeijer wrote:
>  My request would be to split this up and do one thing at a time if possible. There also seems to a bit of refactoring and NFC changes in here, probably also best split off.
>  Regarding the compile-times, thanks for measuring that. I think you also need to report how many functions were specialised, also compared to previous version. But I think the compile-times discussion is for another time, when we start the discussion of possibly enabling this by default (don't think it is should be recorded/included as a code comment).

Could you clarify which bits to split up, as I don't see how I could further break down this patch? Regarding the number of functions specialized in comparison to the previous version, I believe the llvm-test-suite reports statistics so I might be able to provide that information. Cheers.

> ! In D119880#3325448 <https://reviews.llvm.org/D119880#3325448>, @SjoerdMeijer wrote:
>  Compile times are important of course. But what I want to say is that we should aim to lift some of these arbitrary restrictions, like you mentioned, by providing new options/ways to control things but try to be as NFC or close to the original behaviour as possible. That was tuned to specialise very infrequently and a special case, so everything lifting of restrictions will increase compile times. Thus, the way I look at this that you put the infrastructure in place, so that perhaps later we can change things, or decisions can be manually overridden.

Indeed this pass is profitable for spec-int-mcf. The two interesting functions we get to specialize have a gain about 4M. I experimented with the default value of `MinGainThreshold` among {1, 1K, 10K, 100K, 1M}. Using the llvm-test-suite for measuring compilation times anything above 10K had more or less the same effect, so I chose that one.

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https://reviews.llvm.org/D119880