* combine.c: Include "output.h" to define dump_file.
	(uid_insn_cost, last_insn_cost): New global variables.
	(combine_insn_cost): New function to estimate cost of an insn.
	(combine_validate_cost): New function to determine whether a
	try_combine replacement sequence is cheaper than the original.
	(combine_instructions): Allocate and populate uid_insn_cost
	array at the start of the combine pass, and deallocate it after.
	(try_combine): Check combine_validate_cost to determine whether
	a "recombination" should be rejected as being more expensive.
	* Makefile.in (combine.o): Add dependency upon output.h.

From-SVN: r83908