[Bug c/109925] New: Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[Bug c/109925] New: Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

            Bug ID: 109925
           Summary: Wrong code at -O2 on x86_64-linux-gnu since GCC-12
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
  Target Milestone: ---

For the following code, gcc trunk emits wrong code at -O2.

Compiler explorer: https://godbolt.org/z/hcnaxoPaP

$ cat a.c
int printf(const char *, ...);
int a, c, f;
int main() {
  int g[2];
  c = 0;
  for (; c < 2; c++) {
    {
      char h[20];
      char *b = h;
      int d = 48, e = 0;
      while (d && e < 5)
        b[e++] = d /= 10;
      f = e;
    }
    g[f - 2 + c] = 0;
  }
  for (;;) {
    for (; a <= 4; a++)
      if (g[0])
        break;
    break;
  }
  printf("%d\n", a);
}
$
$ gcc-tk -O0 a.c && ./a.out
5
$ gcc-tk -O2 a.c && ./a.out
0
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-f211757f6fa9515e3fd1a4f66f1a8b48e500c9de/bin/gcc
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-f211757f6fa9515e3fd1a4f66f1a8b48e500c9de/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-f211757f6fa9515e3fd1a4f66f1a8b48e500c9de
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230521 (experimental) (GCC)
$

[Bug tree-optimization/109925] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org
   Target Milestone|---                         |10.5
          Component|c                           |tree-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-05-21
            Summary|Wrong code at -O2 on        |[10/11/12/13/14 Regression]
                   |x86_64-linux-gnu since      |Wrong code at -O2 on
                   |GCC-12                      |x86_64-linux-gnu since
                   |                            |GCC-12

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
With
int a, c, f;

int
main ()
{
  int g[2];
  for (c = 0; c < 2; c++)
    {
      {
        char h[20], *b = h;
        int d = 48, e = 0;
        while (d && e < 5)
          b[e++] = d /= 10;
        f = e;
      }
      g[f - 2 + c] = 0;
    }
  for (;;)
    {
      for (; a <= 4; a++)
        if (g[0])
          break;
      break;
    }
  if (a != 5)
    __builtin_abort ();
  return 0;
}
at -O2 this started with r7-1513-g1dc8d15bc6d7d55c7731093e

[Bug tree-optimization/109925] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
-fstack-reuse=none fixes this, the testcase looks similar to PR109967.

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Doesn't reproduce on the trunk since
r14-4089-gd45ddc2c04e471d0dcee016b6edacc00b8341b16
Doesn't reproduce on 13 branch either, the PR113372 fixed it there.
So, I think we should just add the testcase to the testsuite and remove 13/14
markers.
Will handle that.
PR113372 hasn't been backported to 12/11 yet.

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:7942558f27038461f948ca10140a156ae678cdf8

commit r14-9704-g7942558f27038461f948ca10140a156ae678cdf8
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 28 11:58:26 2024 +0100

    testsuite: Add testcase for already fixed PR [PR109925]

    This testcase was made latent by r14-4089 and got fixed both
    on the trunk and 13 branch with PR113372 fix.

    Adding testcase to the testsuite and will close the PR as a dup.

    2024-03-28  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/109925
            * gcc.c-torture/execute/pr109925.c: New test.

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed some time ago.

*** This bug has been marked as a duplicate of bug 113372 ***

[Bug tree-optimization/109925] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu since GCC-12

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109925

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:43022dd24e82a8625895e35da2b7e5a45f3b7483

commit r13-8524-g43022dd24e82a8625895e35da2b7e5a45f3b7483
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 28 11:58:26 2024 +0100

    testsuite: Add testcase for already fixed PR [PR109925]

    This testcase was made latent by r14-4089 and got fixed both
    on the trunk and 13 branch with PR113372 fix.

    Adding testcase to the testsuite and will close the PR as a dup.

    2024-03-28  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/109925
            * gcc.c-torture/execute/pr109925.c: New test.

    (cherry picked from commit 7942558f27038461f948ca10140a156ae678cdf8)