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From: "shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111631] New: Wrong code at -Os on
 x86_64-linux-gnu since r14-3217-g4d6132e5932
Date: Thu, 28 Sep 2023 13:57:53 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111631

            Bug ID: 111631
           Summary: Wrong code at -Os on x86_64-linux-gnu since
                    r14-3217-g4d6132e5932
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
                CC: rguenth at gcc dot gnu.org
  Target Milestone: ---

gcc at -Os produced the wrong code.

Bisected to r14-3217-g4d6132e5932

Compiler explorer: https://godbolt.org/z/Yj9bq1ecs

$ cat a.c
int printf(const char *, ...);
short a, f, i;
static const int *e;
short *g;
long h;
int main() {
  {
    unsigned j =3D i;
    a =3D 1;
    for (; a; a++) {
      {
        long b =3D j, d =3D h;
        int c =3D 0;
        while (d--)
          *(char *)b++ =3D c;
      }
      if (e)
        break;
    }
    j && (*g)--;
    const int **k =3D &e;
    *k =3D 0;
  }
  printf("%d\n", f);
}
$
$ gcc -O0 a.c && ./a.out
0
$ gcc -Os a.c && ./a.out
Segmentation fault
$ gcc -fsanitize=3Daddress,undefined a.c && ./a.out
0
$=