[Bug c/122705] Add function attributes to mark functions that return a pointer parameter, verbatim or derived

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122705

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
```
int
gimple_call_return_flags (const gcall *stmt)
{
  if (gimple_call_flags (stmt) & ECF_MALLOC)
    return ERF_NOALIAS;

  attr_fnspec fnspec = gimple_call_fnspec (stmt);

  unsigned int arg_no;
  if (fnspec.returns_arg (&arg_no))
    return ERF_RETURNS_ARG | arg_no;

  if (fnspec.returns_noalias_p ())
    return ERF_NOALIAS;
  return 0;
}
```

I am not if we want to expose this though.