[Bug tree-optimization/117692] New: The VRP pass is introducing new signed integer overflow

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117692

            Bug ID: 117692
           Summary: The VRP pass is introducing new signed integer
                    overflow
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kristerw at gcc dot gnu.org
  Target Milestone: ---

The VRP pass is introducing new signed integer overflow when compiling the
following function for X86_64 with -O3:

int
f4 (int x)
{
  if (x & 7)
    __builtin_unreachable ();
  x /= 8;
  x += 4;
  return x * 200;
}

The original function does not invoke UB when called as f4(-85899368), but the
VRP pass is changing

  x_3 = x_2(D) / 8;
  x_4 = x_3 + 4;
  _5 = x_4 * 200;
  return _5;

to

  _7 = x_2(D) * 25;
  _5 = _7 + 800;
  return _5;

which has a signed overflow for
  _7 = x_2(D) * 25;