On Fri, 26 Jun 2015, Richard Biener wrote:
+ /* Equality compare simplifications from fold_binary */
+ (for cmp (eq ne)
+
+ /* If we have (A | C) == D where C & ~D != 0, convert this into 0.
+ Similarly for NE_EXPR. */
+ (simplify
+ (cmp (convert?@3 (bit_ior @0 INTEGER_CST@1)) INTEGER_CST@2)
+ (if (tree_nop_conversion_p (TREE_TYPE (@3), TREE_TYPE (@0))
+ && wi::bit_and_not (@1, @2) != 0)
+ { constant_boolean_node (cmp == NE_EXPR, type); }))
+
+ /* (X ^ Y) == 0 becomes X == Y, and (X ^ Y) != 0 becomes X != Y. */
+ (simplify
+ (cmp (bit_xor @0 @1) integer_zerop)
+ (cmp @0 @1))
+
+ /* (X ^ Y) == Y becomes X == 0.
+ Likewise (X ^ Y) == X becomes Y == 0. */
+ (simplify
+ (cmp (bit_xor:c @0 @1) @0)
Don't you need cmp:c for this one? The transformation still somehow
happens through forward_propagate_into_comparison, but it looks like an
accident.
+ (cmp @1 { build_zero_cst (TREE_TYPE (@1)); }))
+
+ /* (X ^ C1) op C2 can be rewritten as X op (C1 ^ C2). */
+ (simplify
+ (cmp (convert?@3 (bit_xor @0 INTEGER_CST@1)) INTEGER_CST@2)
+ (if (tree_nop_conversion_p (TREE_TYPE (@3), TREE_TYPE (@0)))
+ (cmp @0 (bit_xor @1 (convert @2))))))
I guess we'll have to generalize this to vectors at some point...
--
Marc Glisse
