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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100864] (a&!b) | b is not opimized to a | b
 for comparisons
Date: Mon, 14 Jun 2021 22:04:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100864

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So what is done for A && !B (and A || !B), is the following:
/* Simple range test simplifications.  */
/* A < B || A >=3D B -> true.  */
(for test1 (lt le le le ne ge)
     test2 (ge gt ge ne eq ne)
 (simplify
  (bit_ior:c (test1 @0 @1) (test2 @0 @1))
  (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
       || VECTOR_INTEGER_TYPE_P (TREE_TYPE (@0)))
   { constant_boolean_node (true, type); })))
/* A < B && A >=3D B -> false.  */
(for test1 (lt lt lt le ne eq)
     test2 (ge gt eq gt eq gt)
 (simplify
  (bit_and:c (test1 @0 @1) (test2 @0 @1))
  (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
       || VECTOR_INTEGER_TYPE_P (TREE_TYPE (@0)))
   { constant_boolean_node (false, type); })))

But this could be expanded to other non-integer types.
For float types e.g (with -ffast-math):
int f(float a, float b)
{
  int c =3D a =3D=3D b;
  int d =3D a !=3D b;
  return c & d;
}
Is not optimized until reassoc1.  I will change that to be similar what I H=
ave
too.=