re PR rtl-optimization/25130 (miscompilation in GCSE)

	* fold-const.c (operand_equal_p): Accept a NULL operand 0 for
	COMPONENT_REFs.
	* emit-rtl.c (mem_attrs_htab_eq): Use iterative_hash_expr for
	hashing trees instead of a pointer hash.
	(mem_attrs_htab_eq): Do a deep compare instead of a pointer
	compare for MEM_EXPR.

	PR rtl-optimization/25130
	* cse.c (exp_equiv_p): Compare MEM_ATTRS instead of MEM_ALIAS_SET
	when comparing MEMs for GCSE

From-SVN: r109264