[Bug tree-optimization/58010] New: ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[Bug tree-optimization/58010] New: ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[antoine.balestrat at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

            Bug ID: 58010
           Summary: ICE in vect_create_epilog_for_reduction, at
                    tree-vect-loop.c:4378
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoine.balestrat at gmail dot com

Hello !
Using GCC 4.9.0 as of 20130728 :

$ cat vect.c
short a, b, c, d;

void f(void)
{
    short e;

    for(; e; e++)
        for(; b; b++);

    for(d = 0; d < 4; d++)
        a ^= (e ^= 1) || c ? : e;
}

$ xgcc -O2 -funswitch-loops -ftree-vectorize vect.c
vect.c: In function ‘f’:
vect.c:3:6: internal compiler error: in vect_create_epilog_for_reduction, at
tree-vect-loop.c:4378
 void f(void)
      ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
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Subject: [Bug fortran/58009] Elements with same value in vector subscript in variable definition context
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX009

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
... and it would be nice to diagnose it (with a hard
error) whenever possible.

[Bug tree-optimization/58010] [4.8/4.9 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-08-02
                 CC|                            |mpolacek at gcc dot gnu.org
      Known to work|                            |4.7.3
   Target Milestone|---                         |4.8.2
            Summary|ICE in                      |[4.8/4.9 Regression] ICE in
                   |vect_create_epilog_for_redu |vect_create_epilog_for_redu
                   |ction, at                   |ction, at
                   |tree-vect-loop.c:4378       |tree-vect-loop.c:4378
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.1, 4.9.0

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.

[Bug tree-optimization/58010] [4.8/4.9 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[wschmidt at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

--- Comment #3 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
r189527 is probably a red herring.  That just changed the cost model to be
turned on by default at -O3.  Somebody who's actively working on the vectorizer
should probably have a look at this.

If you want to narrow it down further, try turning on -fvect-cost-model and
bisecting.  The problem will probably show up as being introduced further back
if you do this.

This also suggests a workaround for the OP of using -fno-vect-cost-model, if a
workaround is needed.

[Bug tree-optimization/58010] [4.8/4.9 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.

[Bug tree-optimization/58010] [4.8/4.9 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
In the loop in question we have a dead scalar cycle for which we do not
insert loop-closed PHI nodes.  Hm.

The correct fix looks easy though - simply remove the assert.  We'll vectorize
dead code, but who cares.

Testing that.

[Bug tree-optimization/58010] [4.8/4.9 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Fri Aug 30 07:47:54 2013
New Revision: 202095

URL: http://gcc.gnu.org/viewcvs?rev=202095&root=gcc&view=rev
Log:
2013-08-30  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/58010
    * tree-vect-loop.c (vect_create_epilog_for_reduction): Remove
    assert that we have a loop-closed PHI.

    * gcc.dg/pr58010.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/pr58010.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-loop.c

[Bug tree-optimization/58010] [4.8 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.9.0
            Summary|[4.8/4.9 Regression] ICE in |[4.8 Regression] ICE in
                   |vect_create_epilog_for_redu |vect_create_epilog_for_redu
                   |ction, at                   |ction, at
                   |tree-vect-loop.c:4378       |tree-vect-loop.c:4378
      Known to fail|4.9.0                       |

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk sofar.

[Bug tree-optimization/58010] [4.8 Regression] ICE in vect_create_epilog_for_reduction, at tree-vect-loop.c:4378

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58010

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

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

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.