[Bug tree-optimization/16306] New: restrict and copying pointers problem

[Bug tree-optimization/16306] New: restrict and copying pointers problem

[dann at godzilla dot ics dot uci dot edu]

The current mainline does not optimize away the "link_error" call for this function:

void bar00 (int *a1, int *a2)
{
  int * __restrict__ cpy_res1 = a1;
  int * __restrict__ cpy_res2 = a2;
  cpy_res1[0] = 1;
  cpy_res2[0] = 1;
  if (cpy_res1[0] != 1)
    link_error ();
}

gcc-3.0 optimizes it. 

What happens is that the dom1 pass replaces the uses of cpy_res[12] (which are
restricted pointers)  with a[12] (which are not), so the RTL optimizers cannot
know that the "if" can be optimized away. 

This issue might be sort of related to PR14187. 


PR 14187

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           Summary: restrict and copying pointers problem
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [3.5 Regression] restrict and copying pointers problem

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-07-01 01:35 -------
Confirmed.

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           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |missed-optimization
      Known to fail|                            |3.5.0
      Known to work|                            |3.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2004-07-01 01:35:29
               date|                            |
            Summary|restrict and copying        |[3.5 Regression] restrict
                   |pointers problem            |and copying pointers problem
   Target Milestone|---                         |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0 Regression] restrict and copying pointers problem

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-26 05:51 -------
First part to fix it: <http://gcc.gnu.org/ml/gcc-patches/2004-12/msg01931.html>, The next part is 
because TER is getting in the way.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.0                       |4.0.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.1                       |4.0.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.2                       |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[mmitchel at gcc dot gnu dot org]

------- Comment #5 from mmitchel at gcc dot gnu dot org  2005-10-30 22:41 -------
To better support restrict, we should copy around the set of "based on"
pointers when copying other pointer attributes.

However, I don't think this is a sufficiently serious missed optimization to
warrant holding up a release.  

Downgraded to P5.


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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[steven at gcc dot gnu dot org]

------- Comment #3 from steven at gcc dot gnu dot org  2005-10-12 20:58 -------
The patch mentioned in #2 is not sufficient anymore.  copy propagation and VRP
also propagate copies of this kind.  And may_propagate_copy is not used in most
places, and even when it _is_ used, it doesn't help because it allows this kind
of copies to be performed.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306

[Bug tree-optimization/16306] [4.0/4.1 Regression] restrict and copying pointers problem

[steven at gcc dot gnu dot org]

------- Comment #4 from steven at gcc dot gnu dot org  2005-10-12 20:58 -------
Mark, this is probably not fixable for GCC 4.1.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16306