[Bug tree-optimization/31914] New: FRE does not do const or copy propagation while it could

[Bug tree-optimization/31914] New: FRE does not do const or copy propagation while it could

[rguenth at gcc dot gnu dot org]

FRE has all the information available, it's simply not used because eliminate()
does not consider copy statements (and does not run elimination on PHI
arguments
for the same reason).  Also for full const/copy propagation COND_EXPRs need to
be value-numbered.

This would let us get rid of a copyprop and a ccp pass.

I have a prototype patch (still lacks COND_EXPR VN).


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           Summary: FRE does not do const or copy propagation while it could
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
 BugsThisDependsOn: 30997


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31914

[Bug tree-optimization/31914] FRE does not do const or copy propagation while it could

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-11-04 15:51 -------
Confirmed.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-11-04 15:51:43
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31914

[Bug tree-optimization/31914] FRE does not do const or copy propagation while it could

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2008-01-07 12:11 -------
Created an attachment (id=14893)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14893&action=view)
patch for copyprop in the simple case

Produced while working on PR34683 (though doesn't help that significantly).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31914

[Bug tree-optimization/31914] FRE does not do const or copy propagation while it could

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2009-04-04 17:58 -------
I think we don't want this one being fixed.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31914