[Bug tree-optimization/102149] New: wrong code at -O3 on x86_64-linux-gnu

[Bug tree-optimization/102149] New: wrong code at -O3 on x86_64-linux-gnu

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

            Bug ID: 102149
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: qrzhang at gatech dot edu
  Target Milestone: ---

Seems to be a recent regression.


$ gcc-trunk -v
gcc version 12.0.0 20210831 (experimental) [master revision
5e57bacf6f3:a82c79a304b:de7a795c321e76826d123c92b99e73e144666b60] (GCC)


$ gcc-trunk abc.c ; ./a.out
1

$ gcc-trunk abc.c ; ./a.out
0

$ cat abc.c
int a[8];
int *b = &a[6];
char c;
int main() {
  int d = 7;
  for (; d >= 0; d--) {
    *b = 1;
    c = a[d] >> 3;
    a[d] = c;
  }
  printf("%d\n", a[6]);
}

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[qrzhang at gatech dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

--- Comment #1 from Qirun Zhang <qrzhang at gatech dot edu> ---
My bisection points to g:89f33f44addbf9853bc3e6677d

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r12-3222-g89f33f44addbf9853bc3e6677db1fa941713cb6c
but got fixed with r12-3250-g67927342290c61d7e054430f1d7a7281f1f97fae
So I think we just want to add the testcase to the testsuite and close.

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #2)
> Started with r12-3222-g89f33f44addbf9853bc3e6677db1fa941713cb6c
> but got fixed with r12-3250-g67927342290c61d7e054430f1d7a7281f1f97fae
> So I think we just want to add the testcase to the testsuite and close.

That might mean -fno-vect-cost-model might be able to reproduce this still on
the trunk I think.

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2021-09-01

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine for the testcase & investigation.

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

--- Comment #5 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:e6bd9c42b0ad0cc4a615135612599adb829f2d9c

commit r12-3279-ge6bd9c42b0ad0cc4a615135612599adb829f2d9c
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Sep 1 08:06:48 2021 +0200

    tree-optimization/102149 - add testcase for fixed bug

    This adds the testcase from the PR.

    2021-09-01  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/102149
            * gcc.dg/torture/pr102149.c: New testcase.

[Bug tree-optimization/102149] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102149

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |12.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.