[Bug tree-optimization/115347] [12/13/14/15 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115347

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=112859
            Version|unknown                     |14.1.1

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
it's loop distribution doing

t2.c:7:12: optimized: Loop nest 1 distributed: split to 2 loops and 0 library
calls.

We get

  for (; f < 1; f++) {
    for (h = 0; h < 2; h++) {
      d = e[f];
    }
  }
  for (; f < 1; f++) {
    for (h = 0; h < 2; h++) {
      g = e[1].c;
      e[f].c = 1;
    }
  }

I think this is similar to the other still open issue where zero-distance
inner loop dependences (&e[f].c doesnt't vary in the inner loop) cause
issues with the interpretation of classical dependence analysis.

I'm somewhat lost there.  PR112859.