[Bug tree-optimization/118947] Missed optimization: GCC forgets stack buffer contents across function call

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118947

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|rtl-optimization            |tree-optimization

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Oh optimize_memcpy_to_memset does not understand "" either. I will add that
support too.


Here is a testcase to show the vdef issue and not related to the "" issue:
```
void* aaa();
void* bbb()
{
    aaa();
    static int buf2[32];
    int buf[32] = {};
    __builtin_memcpy(buf2, buf, sizeof(buf2));
    return buf2;
}
void* ccc()
{
    int buf[32] = {};
    aaa();
    static int buf2[32];
    __builtin_memcpy(buf2, buf,  sizeof(buf2));
    return buf2;
}
```