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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/112616] New: wrong code at -O{s,2,3} on
 x86_64-linux-gnu
Date: Sun, 19 Nov 2023 05:24:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112616

            Bug ID: 112616
           Summary: wrong code at -O{s,2,3} 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 appears to be a regression from 9.*, and affects 10.* and later.

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


[510] % 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/14.0.0/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 14.0.0 20231118 (experimental) (GCC)=20
[511] %=20
[511] % gcctk -O1 small.c; ./a.out
[512] %=20
[512] % gcctk -O3 small.c
[513] % ./a.out
Segmentation fault
[514] %=20
[514] % cat small.c
unsigned a;
int b, d, e, f =3D 2, g, h =3D 1, *i =3D &b;
volatile int c =3D 1;
static int *o() {
  long m =3D ~a;
  int j =3D f / b, k =3D f - 1, n =3D m << -1 / ~g / k;
  if (j && n)
    c;
  return &e;
}
static long p() {
  int *q =3D 0, **r =3D &q;
  if (c) {
    *i =3D h;
    *r =3D o();
  }
  return *q;
}
int main() {
  p();
  int *l =3D 0;
  if (d)
    c =3D *l;
  return 0;
}=