[PATCH] tree-optimization/103514 Missing XOR-EQ-AND Optimization

[Marc Glisse]

+/* (a & b) ^ (a == b) -> !(a | b) */
+/* (a & b) == (a ^ b) -> !(a | b) */
+(for first_op (bit_xor eq)
+     second_op (eq bit_xor)
+ (simplify
+  (first_op:c (bit_and:c @0 @1) (second_op:c @0 @1))
+   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+        && types_match (TREE_TYPE (@0), TREE_TYPE (@1)))
+    (convert (bit_not (bit_ior @0 @1))))))

I don't think you need types_match, if both are operands of bit_and, their 
types must already match.

It isn't clear what the INTEGRAL_TYPE_P test is for. Your 2 
transformations don't seem that similar to me. The first one requires that 
a and b have the same type as the result of ==, so they are boolean-like. 
The second one makes sense for more general integers, but then it looks 
like it should produce (a|b)==0.

It doesn't look like we have a canonical representation between a^b and 
a!=b for booleans :-(

(sorry for the broken thread, I was automatically unsubscribed because 
mailman doesn't like greylisting)

-- 
Marc Glisse