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From: "zhendong.su at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114552] New: wrong code at -O1 and above on
 x86_64-linux-gnu
Date: Mon, 01 Apr 2024 19:34:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114552

            Bug ID: 114552
           Summary: wrong code at -O1 and above on x86_64-linux-gnu
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhendong.su at inf dot ethz.ch
  Target Milestone: ---

It is a regression from 12.3, and affects 13.* and the trunk.=20

Compiler Explorer: https://godbolt.org/z/bznEs9bao

[656] % gcctk -v
Using built-in specs.
COLLECT_GCC=3Dgcctk
COLLECT_LTO_WRAPPER=3D/local/suz-local/software/local/gcc-trunk/libexec/gcc=
/x86_64-pc-linux-gnu/14.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=3Dyes --prefix=3D/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=3Dc,c++ --disable-werror --enable-mu=
ltilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.1 20240401 (experimental) (GCC)=20
[657] %=20
[657] % gcctk -O0 small.c; ./a.out
[658] %=20
[658] % gcctk -O1 small.c
[659] % ./a.out
Segmentation fault
[660] %=20
[660] % cat small.c
#pragma pack(1)
struct a {
  short b;
  int c;
};
struct d {
  struct a b;
  int e;
};
short f, g, h;
int i, j, o;
const struct d k =3D {{1,0},0};
short *l =3D &h, *m =3D &g, *n =3D &f;
void p() { *n =3D (o > 0) > o; }
void q(struct a n) {
  j =3D 0;
  for (; j < 5; j++)
    i =3D *m =3D *l !=3D 0;
  p();
}
int main() {
  q(k.b);
  return 0;
}=