[Bug other/17106] New: Opportunity to eliminate loads from TOC.

[Bug other/17106] New: Opportunity to eliminate loads from TOC.

[gcc-bugzilla at gcc dot gnu dot org]

Description:
A non-optimal code sequence is illustraded.    Duplicate using gcc 3.5 and
command line:

gcc -O3 -m64 -c test.c


Testcase:
static int s1, s2, s3;
void no_common_toc1 ()
{

  s1 = 1;
  s2 = 2;
  s3 = 3;
}

Assembly:
The code generated by gcc 3.5 contains loads the address from the TOC for
each
target location:

.no_common_toc1:
      ld 11,.LC0@toc(2)
      li 0,1
      li 9,2
      ld 8,.LC2@toc(2)
      ld 10,.LC1@toc(2)
      stw 0,0(11)
      li 0,3
      stw 9,0(10)
      stw 0,0(8)
      blr

A single load of the base of the TOC is all that is needed:

.no_common_toc1:
      ld 11,.LC0@toc(2)
      li 0,1
      li 9,2
      stw 0,0(11)
      li 0,3
      stw 9,4(11)
      stw 0,8(11)
      blr




-- 
           Summary: Opportunity to eliminate loads from TOC.
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P1
         Component: other
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steinmtz at us dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org,steinmtz at us dot ibm
                    dot com
 GCC build triplet: powerpc64-linux
  GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17106

[Bug tree-optimization/17106] Opportunity to eliminate loads from TOC.

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-08-19 15:21 -------
Confirmed, what needs to happen here is that GCC needs to put these variables in a struct like so:
static struct {int s1, s2, s3; }t;
void no_common_toc1 ()
{
  t.s1 = 1;
  t.s2 = 2;
  t.s3 = 3;
}

Which will produce the optimial code.  This also helps powerpc-apple-darwin.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|other                       |tree-optimization
     Ever Confirmed|                            |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2004-08-19 15:21:33
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17106

[Bug tree-optimization/17106] Opportunity to eliminate loads from TOC.

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Last reconfirmed|2004-08-19 15:21:33         |2004-11-06 20:37:23
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17106

[Bug tree-optimization/17106] Opportunity to eliminate loads from TOC.

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-10 18:02 -------
This should be helped or fixed by:
http://gcc.gnu.org/wiki/Section%20Anchor%20Optimisations

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2005-05-08 18:55:21         |2005-09-10 18:02:38
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17106