[Bug tree-optimization/99253] New: tree-vect-loop wrong code

[Bug tree-optimization/99253] New: tree-vect-loop wrong code

[stefansf at linux dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

            Bug ID: 99253
           Summary: tree-vect-loop wrong code
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: stefansf at linux dot ibm.com
  Target Milestone: ---
            Target: s390x, x86_64-*-*

int a = 0;
static int b = 0;
long c = 0;

int
main() {
  for (int d = 0; d < 8; d++) {
    a ^= c;
    b = a;
    a ^= 1;
  }
  if (b != 1)
    __builtin_abort();
  return 0;
}

Aborts when built with:
gcc -O3 t.c

Bisection stops at commit 04bff1bbfc11a974342c0eb0c0d65d902e36e82e on IBM Z and
at commit b7ff7cef5005721e78d6936bed3ae1c059b4e8d2 on x86 ¯\_(ツ)_/¯

[Bug tree-optimization/99253] [10/11 Regression] tree-vect-loop wrong code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |10.2.1
            Summary|tree-vect-loop wrong code   |[10/11 Regression]
                   |                            |tree-vect-loop wrong code
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
   Target Milestone|---                         |10.3
   Last reconfirmed|                            |2021-02-25
      Known to work|                            |9.3.0
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
More likely b7ff7cef5005.  Try -fno-vect-cost-model on Z.  Mine.

[Bug tree-optimization/99253] [10/11 Regression] tree-vect-loop wrong code

[stefansf at linux dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

--- Comment #2 from Stefan Schulze Frielinghaus <stefansf at linux dot ibm.com> ---
Still aborts with -fno-vect-cost-model on IBM Z.

[Bug tree-optimization/99253] [10/11 Regression] tree-vect-loop wrong code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:1193d05465acd39b6e3c7095274d8351a1e2cd44

commit r11-7385-g1193d05465acd39b6e3c7095274d8351a1e2cd44
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Feb 25 09:36:33 2021 +0100

    tree-optimization/99253 - fix reduction path check

    This fixes an ordering problem with verifying that no intermediate
    computations in a reduction path are used outside of the chain.  The
    check was disabled for value-preserving conversions at the tail
    but whether a stmt was a conversion or not was only computed after
    the first use.  The following fixes this by re-ordering things
    accordingly.

    2021-02-25  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/99253
            * tree-vect-loop.c (check_reduction_path): First compute
            code, then verify out-of-loop uses.

            * gcc.dg/vect/pr99253.c: New testcase.

[Bug tree-optimization/99253] [10 Regression] tree-vect-loop wrong code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[10/11 Regression]          |[10 Regression]
                   |tree-vect-loop wrong code   |tree-vect-loop wrong code
           Priority|P3                          |P2
      Known to work|                            |11.0

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk sofar.

[Bug tree-optimization/99253] [10 Regression] tree-vect-loop wrong code

[stefansf at linux dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

Stefan Schulze Frielinghaus <stefansf at linux dot ibm.com> changed:

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

--- Comment #5 from Stefan Schulze Frielinghaus <stefansf at linux dot ibm.com> ---
Can confirm, fixed on IBM Z.  Thanks!

[Bug tree-optimization/99253] [10 Regression] tree-vect-loop wrong code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

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

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

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Sill needs to be backported.

[Bug tree-optimization/99253] [10 Regression] tree-vect-loop wrong code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:65767abfdc07547b5435083a5af6ab085e013a4d

commit r10-9447-g65767abfdc07547b5435083a5af6ab085e013a4d
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Feb 25 09:36:33 2021 +0100

    tree-optimization/99253 - fix reduction path check

    This fixes an ordering problem with verifying that no intermediate
    computations in a reduction path are used outside of the chain.  The
    check was disabled for value-preserving conversions at the tail
    but whether a stmt was a conversion or not was only computed after
    the first use.  The following fixes this by re-ordering things
    accordingly.

    2021-02-25  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/99253
            * tree-vect-loop.c (check_reduction_path): First compute
            code, then verify out-of-loop uses.

            * gcc.dg/vect/pr99253.c: New testcase.

    (cherry picked from commit 1193d05465acd39b6e3c7095274d8351a1e2cd44)

[Bug tree-optimization/99253] [10 Regression] tree-vect-loop wrong code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99253

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
      Known to fail|10.2.1                      |10.2.0
      Known to work|                            |10.2.1

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