[Bug tree-optimization/110060] Adding optimizer hints to std::vector causes a new -Wstringop-overread false positive

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110060

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note you can reduce main to just:
```
int main()
{
  std::vector<int> v(5);
  const std::vector<int> w(1);

  v.resize(1);
//  v.insert(v.begin(), 0);
  //v.insert(v.begin(), 1, 0);
//  v.insert(v.begin(), w.begin(), w.end());
  v = w;

  return 0;
}
```
And get the warning still at -O2.

With the above main in .optimized we get:
```
  MEM[(struct _Vector_base *)&w]._M_impl.D.25239._M_start = _53;
  _46 = _53 + 4;
  MEM[(struct _Vector_base *)&w]._M_impl.D.25239._M_end_of_storage = _46;
  *_53 = 0;
  w.D.25935._M_impl.D.25239._M_finish = _46;
  v.D.25935._M_impl.D.25239._M_finish = __first_33;
  __xlen_82 = std::vector<int>::size (&w);
  if (__xlen_82 > 5)
    goto <bb 4>; [33.00%]
  else
    goto <bb 10>; [67.00%]
```

std::vector<int>::size is literally just:
```
        movq    8(%rdi), %rax
        subq    (%rdi), %rax
        sarq    $2, %rax
        ret
```

So that is definitely an issue there.