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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/110640] New: Wrong code at -O2/3 on x86_64-linux-gnu since
 GCC-13
Date: Wed, 12 Jul 2023 12:45:14 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110640

            Bug ID: 110640
           Summary: Wrong code at -O2/3 on x86_64-linux-gnu since GCC-13
           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: ---

This looks like a regression since GCC-13. gcc produces wrong code at -O2/3.

Compiler explorer: https://godbolt.org/z/5MWe6eK8M

$ cat a.c
unsigned short a =3D 65535;
int b, f, g;
int *c =3D &b;
long d;
short e;
static int *h(int);
void i() { h(a); }
int *h(int j) {
  unsigned char k;
  for (; e !=3D 8; e =3D e + 4)
    k =3D 0;
  for (; (unsigned char)(j-181249535) + k <=3D 1; k++) {
    *c =3D d;
    for (; f; f++)
      ;
  }
  return &g;
}
int main() { i(); }
$
$ gcc-tk -O0 a.c && ./a.out
$
$ gcc-tk -O2 a.c
$ ./a.out
Killed
$ gcc-tk -O3 a.c
$ ./a.out
Killed
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=3Dgcc-tk
COLLECT_LTO_WRAPPER=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-322d1=
7ae51ea0137167424e0018d7fa355948f9f/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-322d17ae51ea0137=
167424e0018d7fa355948f9f
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230711 (experimental) (GCC)
$=