[Bug middle-end/127285] GCC generates redundant `test + sete`

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127285

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Reduced testcase:
```
bool f(char *a, char *b)
{
  return __builtin_memcmp (a, b, 3) == 0;
}