[Bug tree-optimization/123332] Missing optimization of loop to __builtin_popcount()

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123332

--- Comment #1 from Antony Polukhin <antoshkka at gmail dot com> ---
godbolt playground: https://godbolt.org/z/qhecThhav