[Bug rtl-optimization/26069] [4.0/4.1/4.2 Regression] Runtime endian-ness check is no longer optimized out.

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-02-02 05:19 -------
If you used GCC's extension of using an union as not violating aliasing rules,
it works there but does not with using the portable ways:
bool tell_endian() {
  unsigned x = 1;
  return *(char*)&x;
}

bool tell_endian1()
{
  char a;
  int x = 1;
  __builtin_memcpy(&a, &x, 1);
  return a;
}
bool tell_endian_good()
{
  union{int i;char c;}a;
  a.i = 1;
  return a.c;
}
-----

Only tell_endian_good produces good result.

This looks like the removal of addressof RTL caused this.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |normal
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   GCC host triplet|linux-x86-elf               |
 GCC target triplet|linux-x86-elf               |
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2006-02-02 05:19:37
               date|                            |
            Summary|Runtime endian-ness check is|[4.0/4.1/4.2 Regression]
                   |no longer optimized out.    |Runtime endian-ness check is
                   |                            |no longer optimized out.
   Target Milestone|---                         |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26069