[Bug c/111336] New: Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[Bug c/111336] New: Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

            Bug ID: 111336
           Summary: Wrong code at -O2/3 since r14-2472-g14b10ff30ad
           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
                CC: hubicka at gcc dot gnu.org
  Target Milestone: ---

gcc at -O2/3 produced the wrong code on the following testcase.

Bisected to r14-2472-g14b10ff30ad

Compiler explorer: https://godbolt.org/z/njdcv5aK8

$ cat a.c
int printf(const char *, ...);
int a, b;
long c = 3521733542;
int d[2];
int e(int f, int g) {
  if (f == 0)
    return 0;
  if (f > 200)
    return 0;
  if (g)
    return 5 * f;
  return 0;
}
int main() {
  int h = 0;
  for (; e((int)c + 773233762, c + 60) + 773163185 + h < 2; h++)
    d[h] = b;
  printf("%X\n", a);
}
$
$ gcc -O0 a.c && ./a.out
0
$ gcc -O2 a.c && ./a.out
Segmentation fault
$

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Wrong code at -O2/3 since   |[14 Regression] Wrong code
                   |r14-2472-g14b10ff30ad       |at -O2/3 since
                   |                            |r14-2472-g14b10ff30ad
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-09-08
     Ever confirmed|0                           |1
          Component|c                           |tree-optimization

--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Confirmed.

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

Shaohua Li <shaohua.li at inf dot ethz.ch> changed:

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

--- Comment #2 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
I have another similar test case that even affects GCC-12 (bisected to
r12-6087-g51a24e4a984)

Compiler explorer: https://godbolt.org/z/d6hjfGqzj

I reported another bug111331, which also looks similar but has different
bisection point.

$ cat a.c
int printf(const char *, ...);
int a, b;
long c = 3521733542;
int d[2];
int e(int f, int g) {
  if (f == 0)
    return 0;
  if (f > 200)
    return 0;
  if (g)
    return 5000 * f;
  return 0;
}
int main() {
  int h = 0;
  for (;e((int)c + 773233762, c + 773233760) + (int)c + 773228714 + h < 2; h++)
    d[h] = b;
  printf("%d\n", a);
}
$

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note -fwrapv or -fno-ivopts causes the issue to disappear.

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #4 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #3)
> Note -fwrapv or -fno-ivopts causes the issue to disappear.

Does your patch for PR111331 work for this one too?

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #4)
> (In reply to Andrew Pinski from comment #3)
> > Note -fwrapv or -fno-ivopts causes the issue to disappear.
> 
> Does your patch for PR111331 work for this one too?

No because it is unrelated, there was no min or max in the IR either.

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
   Last reconfirmed|2023-09-08 00:00:00         |2023-10-17

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=110243

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Goes away with my fix for PR110243, so I think it's related or even the same.

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

--- Comment #7 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:44e7e4498c3cdc27e087ab80aa76dac41819702f

commit r14-4789-g44e7e4498c3cdc27e087ab80aa76dac41819702f
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Oct 20 14:08:46 2023 +0200

    tree-optimization/110243 - IVOPTs introducing undefined overflow

    The following addresses IVOPTs rewriting expressions in its
    strip_offset without caring for definedness of overflow.  Rather
    than the earlier attempt of just using the proper
    split_constant_offset from data-ref analysis the following adjusts
    IVOPTs helper trying to minimize changes from this fix, possibly
    easing backports.

            PR tree-optimization/110243
            PR tree-optimization/111336
            * tree-ssa-loop-ivopts.cc (strip_offset_1): Rewrite
            operations with undefined behavior on overflow to
            unsigned arithmetic.

            * gcc.dg/torture/pr110243.c: New testcase.
            * gcc.dg/torture/pr111336.c: Likewise.

[Bug tree-optimization/111336] [14 Regression] Wrong code at -O2/3 since r14-2472-g14b10ff30ad

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111336

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

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

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