[Bug target/117438] x86's pass_align_tight_loops may cause performance regression in nested loops

[liuhongt at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117438

--- Comment #4 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
(In reply to Mayshao-oc from comment #0)
> Created attachment 59530 [details]
> gcc -O1 loop.c
> 
> Pass_align_tight_loops align the inner loop aggressively, this may cause
> significant performance regression of some nested loops.The attached loop.c
> could be compiled by gcc -O1 to reproduce the scenario.

For the testcase, on SPR, align is 25% better than no_align. Looks like nops is
not an issue on SPR.