[Bug tree-optimization/110919] [14 Regression] Dead Code Elimination Regression at -O3 since r14-1691-gbc5a2c2e793

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110919

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
After reassoc1 we have:


  _19 = _6 == iftmp.1_8;
  _3 = iftmp.1_8 ^ 1;
  _21 = (_Bool) _3;
  _23 = _6 != 0;
  _10 = _19 & _23;
  _5 = _10 & _21;


Which is: (_6 != 0) & (_6 == iftmp.1_8) But since we know that iftmp.1_8 only
has 2 values, we could optimize this to: (_6 == 1) & (iftmp.1_8 == 1)


Reduced testcase:
```
_Bool f(int a, int b)
{
  b &= 1;
  _Bool t = a == b;
  int c = b^1;
  _Bool d = c;
  _Bool e = a;
  _Bool g = t & d;
  _Bool h = g & e;
  return h;
}
```
This should return false always.

So something like:
(simplify
 (bit_and:c (eq:c @0 @1) (ne:c @0 INTEGER_CST@2))
 (if (has_two_value_range (@1))
  (with {
     tree other_value = ...;
   }
   (bit_and (eq @0 { other_value; }) (eq @1 { other_value; }))
  )
 )
)