[Bug c++/122727] Efficient String Concatenation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122727

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to M Welinder from comment #6)
> I don't think sorting out the pointer aliases is going to do much here.  To
> see that, let's side step it completely and consider the code you would have
> if you somehow managed to optimize the temporaries away:

Except that still has aliasing issues because of escaping is not flow sensative
in GCC:
  MEM[(struct basic_string *)res_5(D)]._M_string_length = _100;
  _107 = MEM[(const struct basic_string *)res_5(D)]._M_dataplus._M_p;
  _108 = _107 + _100;
  MEM[(char_type &)_108] = 0;
  __sz_146 = MEM[(const struct basic_string *)res_5(D)]._M_string_length;

So there is still some aliasing issues.