tree.c (commutative_tree_code, [...]): New functions.

tree.c (commutative_tree_code, [...]): New functions.

	* tree.c (commutative_tree_code, associative_tree_code): New
	functions.
	(iterative_hash_expr): Use commutative_tree_code.
	* tree.h (commutative_tree_code, associative_tree_code): Declare.
	* fold-const.c (operand_equal_p): Use commutative_tree_code
	rather than inlining the commutativity check.
	(fold): Likewise.

Co-Authored-By: Roger Sayle <roger@eyesopen.com>
From-SVN: r77152