[PATCH] D120993: [PassManager] Add pretty stack entries before P->run() call.

Thu Mar 10 07:24:30 PST 2022

fhahn added a comment.

In D120993#3370296 <https://reviews.llvm.org/D120993#3370296>, @aeubanks wrote:

> In D120993#3370129 <https://reviews.llvm.org/D120993#3370129>, @fhahn wrote:
>
>> In D120993#3370083 <https://reviews.llvm.org/D120993#3370083>, @nikic wrote:
>>
>>> FYI it looks like this isn't as free as I would have expected: http://llvm-compile-time-tracker.com/compare.php?from=338dfcd60f843082bb589b287d890dbd9394eb82&to=128745cc2681c284bc6d0150a319673a6d6e8424&stat=instructions
>>
>> Yeah that's not great. I'll revert it in a bit and check if there's anything in particular that's very expensive.
>
> If I had to guess, it might be eagerly retrieving loop names or cgscc names since they can be pretty big if the scc contains a lot of functions or if the loop has a lot of blocks
> we could start without the cgscc name and using the function name for loop passes

I tried splitting off the loop & CGSCC handling into separate classes that only take pointers to Loop/ SCC. The compile-time impact is better, but still noticeable (worst config: +0.17% on ReleastThinLTO - https://llvm-compile-time-tracker.com/compare.php?from=af98b0af6705df3859ee3c98525b57025d40d9e8&to=bc328a534f528fbf8d7a37eaf08e70bd78b75896&stat=instructions)

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https://reviews.llvm.org/D120993