[Bug tree-optimization/25553] New: Missed removal of load

[Bug tree-optimization/25553] New: Missed removal of load

[pinskia at gcc dot gnu dot org]

I don't know what this optimization is called but we miss the removal of the
load of a global variable:

int t;
int g(int);
int f(int tt)
{
  if (tt)
    t = 2;
  else
    t = 3;
  return g(t);
}


I should note I found this while looking at LAPACK.


-- 
           Summary: Missed removal of load
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2005-12-24 01:51 -------
I should mention this shows up semi a lot in fortran code as what happens is
that t is not really a global variable but instead a local variable which is
passed to another function.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-01-28 04:06 -------
We should be able to create a PHI for this case.

Hmm, maybe I don't understand load PRE but for some reason I thought it would
be able to do this case:
int *t;
int g(int);
int f(int tt)
{
  int *t1 = t;
  if (*t1)
    *t1 = 2;
  return g(*t1);
}


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-01-28 04:06:19
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-02-06 16:19 -------
(In reply to comment #2)
> We should be able to create a PHI for this case.
> 
> Hmm, maybe I don't understand load PRE but for some reason I thought it would
> be able to do this case:

This load PRE issue has been fixed.

But the orginal testcase is not been fixed because it is a seperate
optimization.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2007-04-03 20:00 -------
*** Bug 31460 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl at lucon dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2007-04-03 20:40 -------
Micha, this one is "similar" to hmmer


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matz at suse dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2007-07-01 01:18 -------
Note for the Cell this is even more important so you don't run into the LHS
hazzard.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2006-01-28 04:06:19         |2007-07-01 01:18:12
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2008-02-23 05:39 -------
*** Bug 35304 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553

[Bug tree-optimization/25553] Missed removal of load

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2008-04-07 01:44 -------
This turns out to be PRE for global decl issue as the following is done
correctly (at least on the trunk):
int g(int);
int f(int tt, int *t)
{
  if (tt)
    *t = 2;
  else
    *t = 3;
  return g(*t);
}
--- CUT ---
f (tt, t)
{
  int prephitmp.9;
  int D.1182;

<bb 2>:
  if (tt != 0)
    goto <bb 3>;
  else
    goto <bb 4>;

<bb 3>:
  *t = 2;
  prephitmp.9 = 2;
  goto <bb 5>;

<bb 4>:
  *t = 3;
  prephitmp.9 = 3;

<bb 5>:
  D.1182 = g (prephitmp.9) [tail call];
  return D.1182;

}


*** This bug has been marked as a duplicate of 23455 ***


-- 

pinskia at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25553