[PATCH] D93838: [LLVM] [SCCP] : Add Function Specialization pass

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

In D93838#2693588 <https://reviews.llvm.org/D93838#2693588>, @ChuanqiXu wrote:

> In D93838#2691276 <https://reviews.llvm.org/D93838#2691276>, @SjoerdMeijer wrote:
>
>>> ! In D93838#2691075 <https://reviews.llvm.org/D93838#2691075>, @fhahn wrote:
>>
>> Thanks for sharing those sobering numbers. These seem to indicate that just adjusting the threshold may not be enough to control the excessive compile-time.
>
> Since the pass only run in LTO in LegacyPM, I wonder if the excessive compile-time is OK because LTO are time-consuming naturally. Although it looks like to be running as a module pass in NewPM, I don't know it's by design or just a miss.

It should run at the same place in both LegacyPM and NewPM.  The fact that LTO is slow already is not a strong argument to make it substantially slower again :) In the end, it is always a trade-off between the benefits and the extra compile-time. I think one of the main concerns with the numbers you shared is that there appears to be couple of substantial increases in compile-time without any noticeable benefits. This is only a small sample of course and we probably need more data.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93838/new/

https://reviews.llvm.org/D93838