[Bug target/121994] [16 Regression] 15% slowdown of 538.imagick_r and 6% slowdown of 454.calculix on AMD Zen2 since r16-3396-g9823624395a946

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121994

--- Comment #2 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
I guess it's related to register pressure and can be tuned by adjusting   
reduc_lat_mult_thr. I don't have Zen2 machine, so for simplity, I'll just
disable unroll in vectorizer for Zen2.