[Bug middle-end/35290] Missing dead store elimination

[Bug middle-end/35290] Missing dead store elimination

[xinliangli at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290

--- Comment #2 from davidxl <xinliangli at gmail dot com> 2010-11-09 23:11:38 UTC ---
This seems resolved in trunk gcc.

David

[Bug tree-optimization/35290] Missing dead store elimination

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |TREE
   Last reconfirmed|2008-02-22 10:48:57         |2010-11-09 10:48:57
          Component|middle-end                  |tree-optimization

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-11-09 23:21:50 UTC ---
The tree level DSE does not do it though.  The RTL level has been fixed since
the DF branch was merged in.

[Bug tree-optimization/35290] Missing dead store elimination

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-10 12:32:16 UTC ---
Well, it's not working on the tree level to make it cheaper:

  /* We deliberately stop on clobbering statements and not only on
     killing ones to make walking cheaper.  Otherwise we can just
     continue walking until both stores have equal reference trees.  */
  while (!stmt_may_clobber_ref_p (temp, gimple_assign_lhs (stmt)));

changing that to

  while (!stmt_kills_ref_p (temp, gimple_assign_lhs (stmt)));

will make it work (and slower).

Also needs (possibly unsafe in general if used cross loop iteration)

Index: gcc/tree-ssa-alias.c
===================================================================
--- gcc/tree-ssa-alias.c        (revision 166526)
+++ gcc/tree-ssa-alias.c        (working copy)
@@ -1577,7 +1577,12 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref
       base = get_ref_base_and_extent (lhs, &offset, &size, &max_size);
       /* We can get MEM[symbol: sZ, index: D.8862_1] here,
         so base == ref->base does not always hold.  */
-      if (base == ref->base)
+      if (base == ref->base
+         || (TREE_CODE (base) == MEM_REF
+             && TREE_CODE (ref->base) == MEM_REF
+             && TREE_OPERAND (base, 0) == TREE_OPERAND (ref->base, 0)
+             && tree_int_cst_equal (TREE_OPERAND (base, 1),
+                                    TREE_OPERAND (ref->base, 1))))
        {
          /* For a must-alias check we need to be able to constrain
             the accesses properly.  */

[Bug tree-optimization/35290] Missing dead store elimination

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
                 CC|                            |glisse at gcc dot gnu.org
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.0

--- Comment #5 from Marc Glisse <glisse at gcc dot gnu.org> ---
This was fixed on trunk recently by Richard.

[Bug middle-end/35290] New: Missing dead store elimination

[xinliangli at gmail dot com]

void foo(int*p, int*q)
{
    *p = 10;   // <<--- dead, but not removed
    *q = 20;
    *p = 30;
}

int g;
void bar(int* p)
{
   *p = 10;  // Dead -- not removed.
   g = 1;
   *p = 10;
}


-- 
           Summary: Missing dead store elimination
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290

[Bug middle-end/35290] Missing dead store elimination

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-02-22 10:48 -------
Confirmed.  DSE is too dumb for this.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2008-02-22 10:48:57
               date|                            |
            Version|unknown                     |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290