[Bug tree-optimization/117279] std::string bounds check from -D_GLIBCXX_ASSERTIONS not optimised out

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117279

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-10-24
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We don't optimize away the load of `p._M_string_length` after the printf. 

```
  __builtin_memcpy (&p.D.27115._M_local_buf, "Hello world", 11);
  p._M_string_length = 11;
  MEM[(char_type &)&p + 27] = 0;
  _22 = (long unsigned int) index_8(D);
  _20 = &p.D.27115._M_local_buf + _22;
  _3 = *_20;
  _4 = (int) _3;
  __builtin_printf ("%c\n", _4);

  <bb 4> [local count: 472360499]:
  _21 = p._M_string_length;
```

We must think p escapes somehow. I have not looked into why though.