[ARC] Add basic support for double load and store instructions

[ARC] Add basic support for double load and store instructions

gcc/
2016-01-25  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (TARGET_DWARF_REGISTER_SPAN): Define.
	(arc_init): Check validity mll64 option.
	(arc_save_restore): Use double load/store instruction.
	(arc_expand_movmem): Likewise.
	(arc_split_move): Don't split if we have double load/store
	instructions. Returns a boolean.
	(arc_process_double_reg_moves): Change function to return boolean
	instead of a sequence of instructions.
	(arc_dwarf_register_span): New function.
	* config/arc/arc-protos.h (arc_split_move): Change prototype.
	* config/arc/arc.h (TARGET_CPU_CPP_BUILTINS): Define __ARC_LL64__.
	* config/arc/arc.md (*movdi_insn): Emit ldd/std instructions.
	(*movdf_insn): Likewise.
	* config/arc/arc.opt (mll64): New option.
	* config/arc/predicates.md (even_register_operand): New predicate.
	* doc/invoke.texi (ARC Options): Add mll64 documentation.

From-SVN: r232788