[Bug middle-end/87831] New: Guard variable is not eliminated when there's nothing to guard

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87831

            Bug ID: 87831
           Summary: Guard variable is not eliminated when there's nothing
                    to guard
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Consider the example:

struct base {
    base() {}
};

base& test() {
    static base val;
    return val;
}

For that example a lot of assembly is generated, including empty initialization
under the guard:

.L14:
     ; nothing to initialize
  mov edi, OFFSET FLAT:guard variable for test()::val
  call __cxa_guard_release
  mov eax, OFFSET FLAT:_ZZ4testvE3val
  add rsp, 8
  ret

Consider removing all the guard variable instructions if there's no
instructions for initialization.