[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |changpeng.fang at amd dot
                   |                            |com

--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-19 11:28:19 UTC ---
*** Bug 43425 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning or PRE

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |snagavallis at outlook dot com

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
*** Bug 57223 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning or PRE

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

Richard Biener <rguenth at gcc dot gnu.org> changed:

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

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
*** Bug 56595 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning or PRE

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Still happens for partially loop invariant loads (partially loop invariant as
in blocked by a following aliasing store in the loop body).  Like seen in
PR57223.

[Bug tree-optimization/35229] New: Vectorizer doesn't support dependence created by predictive commoning

[irar at il dot ibm dot com]

The following type of dependence, similar to such that would be created by
predictive commoning (or even PRE), is not supported by the vectorizer: 

 for (i = 1; i <= i_2; ++i)
   {
     a[i] = (b[i] + x) * .5f;
     x = b[i];
   }


-- 
           Summary: Vectorizer doesn't  support dependence created by
                    predictive commoning
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: irar at il dot ibm dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2009-02-25 14:12 -------
Indeed.  Proper testcase:

float res[1024], data[1024];

void foo(void)
{
  int i;
  float tmp = data[0];
  for (i = 1; i < 1024; ++i)
    {
      float tmp2 = data[i];
      res[i] = tmp + tmp2;
      tmp = tmp2;
    }
}

manually "optimized" from

      res[i] = data[i] + data[i-1];


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
OtherBugsDependingO|                            |39300
              nThis|                            |
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-02-25 14:12:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2009-02-25 14:33 -------
Or like the following, which is just a bunch of reductions of two elements

float data[1024];

void foo(void)
{
  int i;
  for (i = 1; i < 1024; ++i)
    data[i] = data[i] + data[i-1];
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[irar at il dot ibm dot com]

------- Comment #3 from irar at il dot ibm dot com  2009-03-17 13:33 -------
(In reply to comment #2)
> Or like the following, which is just a bunch of reductions of two elements
> float data[1024];
> void foo(void)
> {
>   int i;
>   for (i = 1; i < 1024; ++i)
>     data[i] = data[i] + data[i-1];
> }

Actually, this loop is not vectorizable. res and data have to be different
arrays, otherwise we get read after write dependence with distance 1.

Ira


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229

[Bug tree-optimization/35229] Vectorizer doesn't support dependence created by predictive commoning

[matz at gcc dot gnu dot org]

------- Comment #4 from matz at gcc dot gnu dot org  2009-07-22 15:31 -------
Subject: Bug 35229

Author: matz
Date: Wed Jul 22 15:30:50 2009
New Revision: 149942

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=149942
Log:
        PR tree-optimization/35229
        PR tree-optimization/39300

        * tree-ssa-pre.c (includes): Include tree-scalar-evolution.h.
        (inhibit_phi_insertion): New function.
        (insert_into_preds_of_block): Call it for REFERENCEs.
        (init_pre): Initialize and finalize scalar evolutions.
        * Makefile.in (tree-ssa-pre.o): Depend on tree-scalar-evolution.h .

testsuite/
        * gcc.dg/vect/vect-pre-interact.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/vect/vect-pre-interact.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-pre.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35229