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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/110582] New: Wrong code at -O2/3 on x86_64-linux-gnu
Date: Fri, 07 Jul 2023 08:03:05 +0000
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X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110582

            Bug ID: 110582
           Summary: Wrong code at -O2/3 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: ---

This seems to be a recent regression. gcc at -O2 and -O3 produce wrong code.

Compiler explorer: https://godbolt.org/z/qWxPW34ch

$ cat a.c
int a, b;
int main() {
  char c =3D a =3D 0;
  for (; c !=3D -3; c++) {
    int d =3D 2;
    d ^=3D 2 && a;
    b =3D a =3D=3D 0 ? d : d / a;
    a =3D b;
  }
  for (; (1 + 95 << 24) + b + 1 + 686658714L + b - 2297271457;)
    ;
}
$
$ gcc-tk -O0 a.c && ./a.out
$
$ gcc-tk -O2 a.c
$=20
$ ./a.out
Killed
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=3Dgcc-tk
COLLECT_LTO_WRAPPER=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-55900=
189ab517906efe08f8d17f3e4a310ee7fff/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-55900189ab517906=
efe08f8d17f3e4a310ee7fff
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230707 (experimental) (GCC)
$=