[Bug tree-optimization/115568] New: wrong code at -O2 with "-fno-tree-sink -fno-tree-ter -fschedule-insns" on x86_64-linux-gnu

[Bug tree-optimization/115568] New: wrong code at -O2 with "-fno-tree-sink -fno-tree-ter -fschedule-insns" on x86_64-linux-gnu

[zhendong.su at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115568

            Bug ID: 115568
           Summary: wrong code at -O2 with "-fno-tree-sink -fno-tree-ter
                    -fschedule-insns" 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 11.*, and affects 12.* and later.

Compiler Explorer: https://godbolt.org/z/dT39sfGd6

[524] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=yes --prefix=/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.0 20240620 (experimental) (GCC) 
[525] % 
[525] % gcctk -O2 small.c; ./a.out
[526] % 
[526] % gcctk -O2 -fno-tree-sink -fno-tree-ter -fschedule-insns small.c
[527] % ./a.out
Floating point exception
[528] % 
[528] % cat small.c
int a, c, d = 1, e, f = 1, h, i, j;
unsigned b = 1, g;
int main() {
  for (; h < 2; h++) {
    int k = ~(b || 0), l = ((~e - j) ^ a % b) % k, m = (b ^ -1) + e;
    unsigned o = ~a % ~1;
    if (f) {
      l = d;
      m = 10;
      i = e;
      d = -(~e + b);
      g = o % m;
      e = -1;
    n:
      a = a % ~i;
      b = ~k;
      if (!g) {
        b = e + o % -1;
        continue;
      }
      if (!l)
        break;
    }
    int q = (~d + g) << ~e, p = (~d - q) & a >> b;
    unsigned s = ~((g & e) + (p | (b ^ (d + k))));
    int r = (e & s) + p, u = d | ~a,
        t = ((~(q + (~a + (s + e)))) & u) | (-g & (c << d ^ p));
    if (t)
      if (!r)
        goto n;
    g = m;
    e = i;
  }
  return 0;
}

[Bug rtl-optimization/115568] wrong code at -O2 with "-fno-tree-sink -fno-tree-ter -fschedule-insns" on x86_64-linux-gnu

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115568

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I wonder if the scheduler is moving the divide (by zero) incorrectly.

[Bug rtl-optimization/115568] [12/13/14/15 Regression] wrong code at -O2 with "-fno-tree-sink -fno-tree-ter -fschedule-insns" on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115568

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |needs-bisection
            Summary|wrong code at -O2 with      |[12/13/14/15 Regression]
                   |"-fno-tree-sink             |wrong code at -O2 with
                   |-fno-tree-ter               |"-fno-tree-sink
                   |-fschedule-insns" on        |-fno-tree-ter
                   |x86_64-linux-gnu            |-fschedule-insns" on
                   |                            |x86_64-linux-gnu
   Target Milestone|---                         |12.5
            Version|unknown                     |15.0