Add infrastructure to support -mcpu=future to represent a future

Add infrastructure to support -mcpu=future to represent a future
architecture level, as yet unnamed.

[gcc]

2019-05-22  Bill Schmidt  <wschmidt@linux.ibm.com>
	    Michael Meissner  <meissner@linux.ibm.com>
	    Segher Boessenkool  <segher@kernel.crashing.org>

	* config.gcc: Add future cpu.
	* config/rs6000/driver-rs6000.c (asm_names): Add future cpu.
	* config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): New
	#define.
	(POWERPC_MASKS): Add OPTION_MASK_FUTURE.
	(RS6000_CPU): New instantiation for future cpu.
	* config/rs6000/rs6000-opts.h (enum processor_type): Add
	PROCESSOR_FUTURE.
	* config/rs6000/rs6000-string.c (expand_compare_loop): Treat
	PROCESSOR_FUTURE like PROCESSOR_POWER9 for now.
	* config/rs6000/rs6000-tables.opt: Regenerate.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Treat
	PROCESSOR_FUTURE similarly to PROCESSOR_POWER9 for now.
	(rs6000_machine_from_flags): Handle future cpu.
	(rs6000_reassociation_width): Treat PROCESSOR_FUTURE like
	PROCESSOR_POWER9 for now.
	(rs6000_adjust_cost): Likewise.
	(rs6000_issue_rate): Likewise.
	(rs6000_register_move_cost): Likewise.
	(rs6000_opt_mask): Add entry for future.
	* config/rs6000/rs6000.h (ASM_CPU_SPEC): Add future cpu.
	(MASK_FUTURE): New #define.
	* config/rs6000/rs6000.md (define_attr "cpu"): Add future cpu.
	* config/rs6000/rs6000.opt (mfuture): New target option.
	* doc/invoke.texi (mcpu): Add future cpu.

[gcc/testsuite]

2019-05-22  Bill Schmidt  <wschmidt@linux.ibm.com>

	* gcc.target/powerpc/cpu-future.c: New test.

Co-Authored-By: Michael Meissner <meissner@linux.ibm.com>
Co-Authored-By: Segher Boessenkool <segher@kernel.crashing.org>
From-SVN: r271567