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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/110491] New: Wrong code at -O2 on x86_64-linux-gnu (a recent
 regression)
Date: Fri, 30 Jun 2023 01:38:10 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 14.0
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X-Bugzilla-Who: shaohua.li at inf dot ethz.ch
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110491

            Bug ID: 110491
           Summary: Wrong code at -O2 on x86_64-linux-gnu (a recent
                    regression)
           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 at -O2 produced wrong code.

Compiler explorer: https://godbolt.org/z/cbM1q13G7

$ cat a.c
int printf(const char *, ...);
int a, c, d, e;
short b;
void f(int *g) { c &=3D *g; }
void h(void);
void i() {
  a =3D 1;
  h();
  f(&a);
}
void h() {
  int *j =3D &c;
  *j =3D 5;
k:
  for (; 4 + b <=3D 0;)
    ;
  for (; d;) {
    c =3D e =3D=3D 0;
    goto k;
  }
}
int main() {
  i();
  printf("%d\n", c);
}
$
$ gcc-tk -O0 a.c &&./a.out
1
$ gcc-tk -O2 a.c && ./a.out
-2003318871
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=3Dgcc-tk
COLLECT_LTO_WRAPPER=3D/zdata/shaoli/compilers/ccbuilder-compilers/gcc-5f590=
ee3174cf6058ac882c3a84a96ae639349c8/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-5f590ee3174cf605=
8ac882c3a84a96ae639349c8
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230629 (experimental) (GCC)
$=