[Bug tree-optimization/22325] New: missed optimization in loop

[Bug tree-optimization/22325] New: missed optimization in loop

[pinskia at gcc dot gnu dot org]

The following two functions should be the same:
int foo(int a) {
int i;
for (i=0; i<200; i++) {
a = a + 5;
}
return a;
}
int foo(int a) {
int i;
for (i=0; i<200; i++) ;
return a+5*200;
}

The RTL optimizers catch this on ppc but not on x86.

-- 
           Summary: missed optimization in loop
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, TREE
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-06 15:23 -------
And then we can remove the empty loop which is PR 17640.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |17640


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-07 19:57 -------
The old RTL loop optimizer is the one which catches this as shown by adding -floop-optimize2 to 
disable the old RTL loop optimizer.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-07 20:02 -------
Assigning to Zdenek as requested by Honza.
I will note if the start of a was a constant we do the optimization at the tree level.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rakdver at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-07-07 20:02:45
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-07-07 20:06 -------
This is related to Bug 18687. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |18687


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-07 20:16 -------
This looks related to PR 20656.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |20656
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

-- 
Bug 22325 depends on bug 17640, which changed state.

Bug 17640 Summary: empty loop not removed after optimization
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17640

           What    |Old Value                   |New Value
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-15 17:01 -------
Patch posted here: <http://gcc.gnu.org/ml/gcc-patches/2005-07/msg01038.html>.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2005-
                   |                            |07/msg01038.html
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-07-27 13:27 -------
Subject: Bug 22325

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rakdver@gcc.gnu.org	2005-07-27 13:26:56

Modified files:
	gcc            : ChangeLog tree-flow.h tree-scalar-evolution.c 
	                 tree-ssa-loop-ivopts.c 

Log message:
	PR tree-optimization/22325
	* tree-flow.h (compute_phi_arg_on_exit, force_expr_to_var_cost):
	Declare.
	* tree-scalar-evolution.c (scev_const_prop): Add generic final
	value replacement.
	* tree-ssa-loop-ivopts.c (force_expr_to_var_cost): Split from ...
	(force_var_cost): ... this function.
	(compute_phi_arg_on_exit): Export.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.9563&r2=2.9564
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-flow.h.diff?cvsroot=gcc&r1=2.130&r2=2.131
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-scalar-evolution.c.diff?cvsroot=gcc&r1=2.31&r2=2.32
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-ssa-loop-ivopts.c.diff?cvsroot=gcc&r1=2.85&r2=2.86



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325

[Bug tree-optimization/22325] missed optimization in loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-27 13:56 -------
Fixed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22325