[Bug tree-optimization/15452] New: [tree-ssa] Optimize cascaded a = a == 0;

[Bug tree-optimization/15452] New: [tree-ssa] Optimize cascaded a = a == 0;

[kazu at cs dot umass dot edu]

This is very similar to PR 14758.

int
foo (int a)
{
  a = !a;
  a = !a;
  a = !a;
  a = !a;
  a = !a;
  return a;
}

I get:

foo (a)
{
<bb 0>:
  a_2 = a_1 == 0;
  a_3 = a_2 == 0;
  a_4 = a_3 == 0;
  a_5 = a_4 == 0;
  a_6 = a_5 == 0;
  return a_6;

}

Do the obvious optimization.

-- 
           Summary: [tree-ssa] Optimize cascaded a = a == 0;
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Keywords: pessimizes-code
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-15 03:40 -------
Confirmed, I think this is what a TREE combiner (just like the rtl one) would do just like a couple of your 
other bugs.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |TREE
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-15 03:40:47
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-17 01:58 -------
Definitely will be fixed when PR 15459 is fixed.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-30 04:55 -------
Mine.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-21 05:14 -------
Will be submitting my tree combiner tonight.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452
Bug 15452 depends on bug 15459, which changed state.

Bug 15459 Summary: [meta-bug] there should be a tree combiner like the rtl one
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15459

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2009-04-22 21:05 -------
This has been fixed for a while now, at least since 4.4.0.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

Re: [Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[Daniel Berlin]

pinskia at gcc dot gnu dot org wrote:
> ------- Comment #6 from pinskia at gcc dot gnu dot org  2006-08-24 04:27 -------
> Another interesting case would be (but which could be handled by VRP):
> int
> foo (int a)
> {
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   return a;
> }
> Which should be optimized to:
> int foo(int a) { return a!=0;}
> 
> 
Uh, FRE could also optimize this to the same thing, I just don't
remember whether it bothers to look at conditionals as eliminable
expressions.

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[dberlin at dberlin dot org]

------- Comment #7 from dberlin at gcc dot gnu dot org  2006-08-24 14:43 -------
Subject: Re:  [tree-ssa] Optimize cascaded a
 = a == 0;

pinskia at gcc dot gnu dot org wrote:
> ------- Comment #6 from pinskia at gcc dot gnu dot org  2006-08-24 04:27 -------
> Another interesting case would be (but which could be handled by VRP):
> int
> foo (int a)
> {
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   a = a!=0;
>   return a;
> }
> Which should be optimized to:
> int foo(int a) { return a!=0;}
> 
> 
Uh, FRE could also optimize this to the same thing, I just don't
remember whether it bothers to look at conditionals as eliminable
expressions.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2006-08-24 04:27 -------
Another interesting case would be (but which could be handled by VRP):
int
foo (int a)
{
  a = a!=0;
  a = a!=0;
  a = a!=0;
  a = a!=0;
  a = a!=0;
  return a;
}
Which should be optimized to:
int foo(int a) { return a!=0;}


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452

[Bug tree-optimization/15452] [tree-ssa] Optimize cascaded a = a == 0;

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-07-12 21:26 -------
It might be a while for me to rewrite the tree combiner so unassigning for now.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15452