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From: "aosman9xx9 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107212] New: -O2 and -O3 optimizer bug
Date: Tue, 11 Oct 2022 08:06:30 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 12.2.0
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X-Bugzilla-Who: aosman9xx9 at gmail dot com
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107212

            Bug ID: 107212
           Summary: -O2 and -O3 optimizer bug
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: aosman9xx9 at gmail dot com
  Target Milestone: ---

There seams to be an optimizer bug in the recent gcc version.

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D

[root@archlinux ~]# gcc --version
gcc (GCC) 12.2.0
(the current gcc version in Archlinux)

[root@archlinux ~]# cat GccError.c
#include <stdio.h>

int main() {
    unsigned int tab[6][2] =3D { {69, 73}, {36, 40}, {24, 16}, {16, 11}, {4=
, 5},
{3, 1} };

    int flag =3D 1;
    int sum_0 =3D 0;
    int sum_1 =3D 0;

    for(int t=3D0; t<6; t++) {
        sum_0 +=3D tab[t][0];
        sum_1 +=3D tab[t][1];
    }

    int x1 =3D (sum_0 < 100);
    int x2 =3D (sum_0 > 200);
    int x3 =3D (x1 || x2);

    if(sum_1 > 200) {
        flag=3D0;
    }

    printf("sum_0: %d\n", sum_0);
    printf("sum_1: %d\n", sum_1);
    printf("x1: %d\n", x1);
    printf("x2: %d\n", x2);
    printf("x1 || x2: %d\n", x3);
    printf("flag: %d\n", flag);

    return 0;
}

[root@archlinux ~]# gcc -O2 -Wall -Wextra -o GccError GccError.c

[root@archlinux ~]# ./GccError
sum_0: 152
sum_1: 146
x1: 0
x2: 0
x1 || x2: 1
flag: 1

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D
The expected result of (x1 || x2) is 0, because x1 and x2 is 0. But the res=
ult
is 1. This only happens with -O2 or -O3 optimization.=