[Bug tree-optimization/73457] Missed optimizations: count_if on std::array of constants.

[Bug tree-optimization/73457] Missed optimizations: count_if on std::array of constants.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=73457

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
testcase:
#include <array>
#include <algorithm>

enum event {
  stuff,
  crap
};

template<typename Cont>
auto count_event(event e, Cont const& events) {
        return std::count(events.begin(), events.end(), e);
}

int main() {
  std::array<event, 4> events = { stuff, crap, stuff, stuff };
  return count_event(stuff, events);
}

[Bug tree-optimization/73457] Missed optimizations: count_if on std::array of constants.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=73457

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 8+ can handle this at -O3 and above because we can vectorize the loop
(which GCC 7 could not do, I have not looked into why) so DOM is able to
optimize it after unrolling.

GCC 10+ can handle this at -O3 -fno-tree-loop-vectorize (with SLP still
happening) because of r10-1420.


I do think we should be able to optimize this for -O2 though.