[PATCH] D102920: [SLP]Better detection of perfect/shuffles matches for gather nodes.

Tue Jun 1 09:38:55 PDT 2021

ABataev added a comment.

In D102920#2791168 <https://reviews.llvm.org/D102920#2791168>, @nikic wrote:

> FYI there seems to be some (but not very large) compile-time impact on ClamAV: https://llvm-compile-time-tracker.com/compare.php?from=e60f147324b64f7740de58e6b936cdc0e26daadd&to=36911971a58d1ba8b15e97790ac816eaadb0603e&stat=instructions
>
> The file with the largest impact is libclamav_htmlnorm.c with 3.4% regression in NewPM-O3 (and 5.6% in NewPM-ReleaseLTO-g). Might be worth taking a look.

Checked it, caused by the different order of the checks for gathered scalars introduced in this patch. Unfortunately, we cannot change the order back, it was incorrect and produced incorrect cost in some cases. Had to implement a special check to fix this bug, it affects compile time in some cases.

Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D102920/new/

https://reviews.llvm.org/D102920