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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/114796] New: wrong code at -O2 with
 "-fno-tree-fre -fno-inline -fselective-scheduling2" on x86_64-linux-gnu
Date: Sun, 21 Apr 2024 16:32:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114796

            Bug ID: 114796
           Summary: wrong code at -O2 with "-fno-tree-fre -fno-inline
                    -fselective-scheduling2" 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: ---

This seems quite long-latent and affects all versions 9.* and later.=20

Compiler Explorer: https://godbolt.org/z/nKx6f4hjK

[526] % 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 20240421 (experimental) (GCC)=20
[527] %=20
[527] % gcctk -O0 small.c
[528] % ./a.out
[529] %=20
[529] % gcctk -O2 -fno-tree-fre -fno-inline -fselective-scheduling2 small.c
[530] % ./a.out
Aborted
[531] %=20
[531] % cat small.c
int printf(const char *, ...);
int a, b, c =3D -3, h, j, k;
struct d {
  int e;
  char f;
  char g;
};
int i, l, m;
char n[10][9] =3D {{1}};
struct d o =3D {1,0,0};
unsigned p;
void q(int s) { b =3D a; }
void r() {
  k =3D 0;
  while (k)
    while (l)
      while (i)
        if (m)
          while (1)
            ;
  for (; p < 1; p++) {
    if (j) {
      q(n[j][c]);
      if (h)
        printf("\n");
    }
    n[p][k] =3D 1;
  }
}
int main() {
  r();
  if (o.g !=3D 0)
    __builtin_abort();
  return 0;
}=