[ARC] Use TARGET_INSN_COST.

[ARC] Use TARGET_INSN_COST.

TARGET_INSN_COST gives us a better control over the instruction costs
than classical RTX_COSTS.  A simple cost scheme is in place for the
time being, when optimizing for size, the cost is given by the
instruction length. When optimizing for speed, the cost is 1 for any
recognized instruction, and 2 for any load/store instruction.  The
latter one can be overwritten by using cost attribute for an
instruction.  Due to this change, we need to update also a number of
instruction patterns with a new predicate to better reflect the costs.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (arc_insn_cost): New function.
	(TARGET_INSN_COST): Define.
	* config/arc/arc.md (cost): New attribute.
	(add_n): Use arc_nonmemory_operand.
	(ashlsi3_insn): Likewise, also update constraints.
	(ashrsi3_insn): Likewise.
	(rotrsi3): Likewise.
	(add_shift): Likewise.
	* config/arc/predicates.md (arc_nonmemory_operand): New predicate.

testsuite/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* gcc.target/arc/or-cnst-size2.c: Update test.