[Bug target/57952] AVX/AVX2 no ymm registers used in a trivial reduction

[mmokrejs at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57952

--- Comment #9 from mmokrejs at gmail dot com ---
Thank you, I updated https://wiki.gentoo.org/wiki/GCC_optimization and added
the notes on -ftree-vectorize option.