[Bug c/69825] New: False -Wdiv-by-zero warning when it should be short-circuited

[dgilbert at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69825

            Bug ID: 69825
           Summary: False -Wdiv-by-zero warning when it should be
                    short-circuited
           Product: gcc
           Version: 5.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dgilbert at redhat dot com
  Target Milestone: ---

gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC) 

$ cat bug.c
void bug(void)
{
    static unsigned int counter = 0;
    static const unsigned int frequency = 0;

    if (frequency && (!(counter % frequency))) {
    }

    counter++;
}


$ gcc bug.c -Wall -c -O2
bug.c: In function ‘bug’:
bug.c:6:33: warning: division by zero [-Wdiv-by-zero]
     if (frequency && (!(counter % frequency))) {
                                 ^


I'm told it also triggers on trunk, 4.6, 5.3 but not 4.8.5