combine.c (unmentioned_reg_p): New function to check whether an expression is a ...

combine.c (unmentioned_reg_p): New function to check whether an expression is a "specialization" of another, i.e.

	* combine.c (unmentioned_reg_p): New function to check whether an
	expression is a "specialization" of another, i.e. that there are
	no registers or memory references mentioned in the first that don't
	appear in the second.
	(unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
	(combine_instructions): Also try combining instructions using the
	REG_EQUAL note from a preceding log-linked instruction.

From-SVN: r79398