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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/109778] New: Wrong code at -O3 on x86_64-linux-gnu since
 GCC-12.2
Date: Mon, 08 May 2023 19:18:28 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 14.0
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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=3D109778

            Bug ID: 109778
           Summary: Wrong code at -O3 on x86_64-linux-gnu since GCC-12.2
           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: ---

gcc trunk at -O3 emits wrong code. This seems to be a bug since gcc-12.2

Compiler explorer: https://godbolt.org/z/E5aqnMK6Y


$ cat a.c
int printf(const char *, ...);
int a, b, c, d;
int *e =3D &c;
unsigned f(unsigned char g) {
  g =3D 1 | g << 1;
  g =3D g >> 4 | g << 4;
  return g;
}
void h(unsigned g) { *e =3D 8 > f(g + 86) - 86; }
int main() {
  d =3D a && b;
  h(d + 4);
  printf("%d\n", c);
}
$
$ gcc-tk -O0 a.c && ./a.out
1
$ gcc-tk -O3 a.c && ./a.out
0
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=3Dgcc-tk
COLLECT_LTO_WRAPPER=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-b7fe3=
8c14e5f1bc32950c7b2ffc8537c7c381af4/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-b7fe38c14e5f1bc3=
2950c7b2ffc8537c7c381af4
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230506 (experimental) (GCC)
$=