[Bug tree-optimization/24001] New: Simple redundancy not eliminated

[Bug tree-optimization/24001] New: Simple redundancy not eliminated

[falk at debian dot org]

For this code:

int f(int *ptr, int t) {
    if (t)
        return  *ptr;
    else
        return  *ptr;
}

the jump is not eliminated:

f:      beq $17,$L2
        ldl $0,0($16)
        ret
$L2:    ldl $0,0($16)
        ret

This used to work with 2.95 (not sure whether that still counts as 
regression...), but not with 3.3, 3.4, 4.0, or 4.1.0 20050915.

-- 
           Summary: Simple redundancy not eliminated
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: falk at debian dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: alpha-linux-gnu
  GCC host triplet: alpha-linux-gnu
GCC target triplet: alpha-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24001

[Bug tree-optimization/24001] Simple redundancy not eliminated

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-21 16:32 -------
Try with -Os and you will see it is eliminated.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24001

[Bug tree-optimization/24001] Simple redundancy not eliminated

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2005-09-22 08:31 -------
load-pre should sink the load and fix the problem at the tree level.

GCSE does it at rtl level for both -O2 and -Os on i686, so maybe costs on
alpha are weird enough to prevent it from doing its work at -O2?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24001

Re: [Bug tree-optimization/24001] Simple redundancy not eliminated

[Daniel Berlin]

On Thu, 2005-09-22 at 08:31 +0000, rguenth at gcc dot gnu dot org wrote:
> ------- Additional Comments From rguenth at gcc dot gnu dot org  2005-09-22 08:31 -------
> load-pre should sink the load and fix the problem at the tree level.

Uh, load PRE doesn't sink loads, it would lift it.

[Bug tree-optimization/24001] Simple redundancy not eliminated

[dberlin at dberlin dot org]

------- Additional Comments From dberlin at gcc dot gnu dot org  2005-09-22 18:40 -------
Subject: Re:  Simple redundancy not eliminated

On Thu, 2005-09-22 at 08:31 +0000, rguenth at gcc dot gnu dot org wrote:
> ------- Additional Comments From rguenth at gcc dot gnu dot org  2005-09-22 08:31 -------
> load-pre should sink the load and fix the problem at the tree level.

Uh, load PRE doesn't sink loads, it would lift it.






-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24001

[Bug tree-optimization/24001] Simple redundancy not eliminated

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-25 04:31 -------
Confirmed, on most targets (ppc and x86 at least) this is done at the rtl level, I don't know why it is not 
done for alpha.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
  GCC build triplet|alpha-linux-gnu             |
   GCC host triplet|alpha-linux-gnu             |
           Keywords|                            |TREE
   Last reconfirmed|0000-00-00 00:00:00         |2005-09-25 04:31:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24001