ifcvt: Clarify if_info.original_cost.

ifcvt: Clarify if_info.original_cost.

Before noce_find_if_block processes a block it sets up an if_info
structure that holds the original costs.  At that point the costs of
the then/else blocks have not been added so we only care about the
"if" cost.

The code originally used BRANCH_COST for that but was then changed
to COST_N_INSNS (2) - a compare and a jump.

This patch computes the jump costs via
  insn_cost (if_info.jump, ...)
under the assumption that the target takes BRANCH_COST into account
when costing a jump instruction.

In noce_convert_multiple_sets we keep track of the need for the initial
CC comparison.  If needed for the generated sequence we add its
cost in default_noce_conversion_profitable_p.

gcc/ChangeLog:

	* ifcvt.cc (noce_convert_multiple_sets_1): Add use_cond_earliest
	param.
	(noce_convert_multiple_sets): Set use_cond_earliest.
	(noce_process_if_block): Just use original cost.
	(noce_find_if_block): Use insn_cost (jump_insn).

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/addsieq.c: Remove xfail and expect conversion
	through noce_convert_multiple_sets.
	* gcc.target/riscv/addsifeq.c: Ditto.
	* gcc.target/riscv/addsifge.c: Ditto.
	* gcc.target/riscv/addsifgt.c: Ditto.
	* gcc.target/riscv/addsifle.c: Ditto.
	* gcc.target/riscv/addsiflt.c: Ditto.
	* gcc.target/riscv/addsifne.c: Ditto.
	* gcc.target/riscv/addsige.c: Ditto.
	* gcc.target/riscv/addsigeu.c: Ditto.
	* gcc.target/riscv/addsigt.c: Ditto.
	* gcc.target/riscv/addsigtu.c: Ditto.
	* gcc.target/riscv/addsile.c: Ditto.
	* gcc.target/riscv/addsileu.c: Ditto.
	* gcc.target/riscv/addsilt.c: Ditto.
	* gcc.target/riscv/addsiltu.c: Ditto.