[Bug rtl-optimization/43491] Unnecessary temporary for global register variable

["ibolton at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #1 from ibolton at gcc dot gnu dot org  2010-09-08 16:21 -------
reg is assigned to a temporary (reg.0) at the very first tree pass, as shown by
this 004t.gimple dump:

d ()
{
  struct b * const reg.0;
  unsigned int * D.2019;
  int D.2020;

  goto <D.1276>;
  <D.1275>:
  c ();
  <D.1276>:
  reg.0 = reg;
  D.2019 = &reg.0->j;
  D.2020 = diff (D.2019);
  if (D.2020 != 0) goto <D.1275>; else goto <D.1277>;
  <D.1277>:
}

I'm thinking that this is perfectly normal thing to do, and that the redundant
move is meant to disappear in a later pass.  My guess is that IRA is choosing
not to assign the pseudo to r4, but I do not know why at the moment.


-- 

ibolton at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization, ra
      Known to fail|                            |4.5.3 4.6.0
   Last reconfirmed|0000-00-00 00:00:00         |2010-09-08 16:21:50
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43491