[Bug tree-optimization/103596] [9/10/11/12 Regression] ICE: tree check: expected class 'type', have 'exceptional' (error_mark) in useless_type_conversion_p, at gimple-expr.c:88

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103596

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |7.5.0
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-12-07
      Known to fail|                            |8.1.0

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
Reduced testcase:
int n;

void qux (int a){}
int baz (void)
{
  return -1;
}

__attribute__ ((returns_twice)) int
bar (int b)
{
  if (n != 0)
    {
      switch (b) {
          default:  return n + b;
          case 0:
          case 2:;
      }
      if (n == 2)
        return 0;
    }
    __builtin_unreachable();
}
void
foo (void)
{
  qux (n);
  bar (baz ());
}
-------- CUT -----
Only -O3 is needed to produce the ICE with the above testcase.
And it was working in GCC 7.5.0 with the above one and started to fail in GCC
8.1.0.