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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/113756] New: Wrong code at -O2 on
 x86_64-linux-gnu since r14-2780-g39f117d6c87
Date: Sun, 04 Feb 2024 14:14:50 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: shaohua.li at inf dot ethz.ch
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113756

            Bug ID: 113756
           Summary: Wrong code at -O2 on x86_64-linux-gnu since
                    r14-2780-g39f117d6c87
           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: aldyh at redhat dot com
  Target Milestone: ---

gcc at -O2 produced the wrong code.

Bisected to r14-2780-g39f117d6c87

Compiler explorer: https://godbolt.org/z/qWd4196h6

% cat reduced.c
int printf(const char *, ...);
int d, e, i, k, l =3D -8;
char h, j;
int m(int n, int o, int p3) {
  int a =3D o - p3, b =3D n - p3, c =3D a + b, f =3D -b, g =3D c < 0 ? -c :=
 c;
  return a <=3D f && a <=3D g ? o : p3;
}
void q(int *n, unsigned short o) {
  unsigned p =3D 8896;
  for (; e >=3D 0; e--)
    p =3D 5377;
  for (; h <=3D 0; h++)
    for (; j <=3D 0; j++) {
      *n =3D 1611581749;
      i =3D m(34, p - 5294, *n - 1611581687);
      k =3D i + p + 65535 + o + *n - 1611718251;
      printf("%d\n", k);
    }
}
int main() {
  q(&l, l);
}
%
% gcc -O0 reduced.c &&./a.out
0
% gcc -O2 reduced.c &&./a.out
21
%=