[Bug middle-end/91709] Missed optimization for multiplication on 1.5 and 1.25

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91709
--- Comment #1 from Antony Polukhin <antoshkka at gmail dot com> ---
Godbolt playground: https://godbolt.org/z/rHQj2w