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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 c/110243] New: Wrong code at -O3 on x86_64-linux-gnu
Date: Tue, 13 Jun 2023 21:10:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110243

            Bug ID: 110243
           Summary: Wrong code at -O3 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: ---

Since GCC-13, gcc at -O3 produces wrong code.

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

$ cat a.c
#define X 1100000000
char a;
long b =3D X;
int c[9][1];
unsigned d;
static long *e =3D &b, *f =3D &b;
int g() {
  if (a && a <=3D '9')
    return '0';
  if (a)
    return 10;
  return -1;
}
int main() {
  d =3D 0;
  for (; (int)*f -(X-1) + d < 9; d++)
    c[g() + (int)*f + ((int)*e - X) -(X-1) + d]
     [0] =3D 0;
}
$
$ gcc-tk -O3 a.c &&./a.out
Segmentation fault
$
$ gcc-tk -O0 a.c &&./a.out
$
$ gcc-tk -fsanitize=3Daddress,undefined a.c &&./a.out
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=3Dgcc-tk
COLLECT_LTO_WRAPPER=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-bf470=
895905e9152424076d1630a9d2c60de023b/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/=
lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=3Dc,c++
--prefix=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-bf470895905e9152=
424076d1630a9d2c60de023b
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230612 (experimental) (GCC)
$=