[Bug c/110141] New: Wrong code at -O2 on x86_64-linux-gnu

[Bug c/110141] New: Wrong code at -O2 on x86_64-linux-gnu

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

            Bug ID: 110141
           Summary: Wrong code at -O2 on x86_64-linux-gnu
           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 since 12 emits the wrong code at -O2.

Compiler explorer: https://godbolt.org/z/reGo6jqGK

$ cat a.c
int printf(const char *, ...);
int h, i = 1, m;
int *j = &i, *k = &i, *l;
short n(short b, short c, int d) {
  short e[] = {71, c, c, 40, 28, 57, 3, 8, 79, 19, c};
  int f = d, a = b;
  short *g = e;
  while (f > 1) {
    a += *g++;
    f -= 2;
  }
  a += *g -= 255;
  return a;
}
int fn2() {
  h = 0;
  for (;; h = 5) {
    int o[4];
    m = 0;
    for (; m < 4; m++)
      o[n(6, 7, 19) - 70 + m] = 6;
    if (h) {
      for (;;) {
        int p = 0;
        if (*k)
          break;
        l = &p;
      }
      *j = o[0];
      return 0;
    }
  }
}
int main() {
  fn2();
  printf("%d\n", i);
}
$
$ gcc-tk -O0 a.c && ./a.out
6
$ gcc-tk -O2 a.c && ./a.out
0
$

[Bug middle-end/110141] Wrong code at -O2 on x86_64-linux-gnu

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another -fstack-reuse= issue.

[Bug middle-end/110141] Wrong code at -O2 on x86_64-linux-gnu

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

--- Comment #2 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
I tried to bisect this case and I bisected it to r12-4790-g4b3a325f07a

[Bug middle-end/110141] [12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Wrong code at -O2 on        |[12/13/14 Regression] Wrong
                   |x86_64-linux-gnu            |code at -O2 on
                   |                            |x86_64-linux-gnu
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-12-17
   Target Milestone|---                         |12.4
             Status|UNCONFIRMED                 |NEW

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug middle-end/110141] [12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
                 CC|                            |law at gcc dot gnu.org

[Bug middle-end/110141] [12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
           Priority|P1                          |P2

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 12-13 has been released with this bug, so P2.

[Bug middle-end/110141] [12/13/14/15 Regression] Wrong code at -O2 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110141

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|12.4                        |12.5

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 12.4 is being released, retargeting bugs to GCC 12.5.