rs6000: Add base support and types for defining MMA built-ins.

Add the new -mmma option as well as the initial MMA support, which includes
the target specific __vector_pair and __vector_quad types, the POImode and
PXImode partial integer modes they are mapped to, and their associated
move patterns.  Support for the restrictions on the registers these modes
can be assigned to as also been added.

2020-06-20  Peter Bergner  <bergner@linux.ibm.com>
	    Michael Meissner  <meissner@linux.ibm.com>

gcc/
	* config/rs6000/mma.md: New file.
	* config/rs6000/rs6000-c.c (rs6000_target_modify_macros): Define
	__MMA__ for mma.
	* config/rs6000/rs6000-call.c (rs6000_init_builtins): Add support
	for __vector_pair and __vector_quad types.
	* config/rs6000/rs6000-cpus.def (OTHER_FUTURE_MASKS): Add
	OPTION_MASK_MMA.
	(POWERPC_MASKS): Likewise.
	* config/rs6000/rs6000-modes.def (OI, XI): New integer modes.
	(POI, PXI): New partial integer modes.
	* config/rs6000/rs6000.c (TARGET_INVALID_CONVERSION): Define.
	(rs6000_hard_regno_nregs_internal): Use VECTOR_ALIGNMENT_P.
	(rs6000_hard_regno_mode_ok_uncached): Likewise.
	Add support for POImode being allowed in VSX registers and PXImode
	being allowed in FP registers.
	(rs6000_modes_tieable_p): Adjust comment.
	Add support for POImode and PXImode.
	(rs6000_debug_reg_global) <print_tieable_modes>: Add OImode, POImode
	XImode, PXImode, V2SImode, V2SFmode and CCFPmode..
	(rs6000_setup_reg_addr_masks): Use VECTOR_ALIGNMENT_P.
	Set up appropriate addr_masks for vector pair and vector quad addresses.
	(rs6000_init_hard_regno_mode_ok): Add support for vector pair and
	vector quad registers.  Setup reload handlers for POImode and PXImode.
	(rs6000_builtin_mask_calculate): Add support for RS6000_BTM_MMA.
	(rs6000_option_override_internal): Error if -mmma is specified
	without -mcpu=future.
	(rs6000_slow_unaligned_access): Use VECTOR_ALIGNMENT_P.
	(quad_address_p): Change size test to less than 16 bytes.
	(reg_offset_addressing_ok_p): Add support for ISA 3.1 vector pair
	and vector quad instructions.
	(avoiding_indexed_address_p): Likewise.
	(rs6000_emit_move): Disallow POImode and PXImode moves involving
	constants.
	(rs6000_preferred_reload_class): Prefer VSX registers for POImode
	and FP registers for PXImode.
	(rs6000_split_multireg_move): Support splitting POImode and PXImode
	move instructions.
	(rs6000_mangle_type): Adjust comment.  Add support for mangling
	__vector_pair and __vector_quad types.
	(rs6000_opt_masks): Add entry for mma.
	(rs6000_builtin_mask_names): Add RS6000_BTM_MMA and RS6000_BTM_FUTURE.
	(rs6000_function_value): Use VECTOR_ALIGNMENT_P.
	(address_to_insn_form): Likewise.
	(reg_to_non_prefixed): Likewise.
	(rs6000_invalid_conversion): New function.
	* config/rs6000/rs6000.h (MASK_MMA): Define.
	(BIGGEST_ALIGNMENT): Set to 512 if MMA support is enabled.
	(VECTOR_ALIGNMENT_P): New helper macro.
	(ALTIVEC_VECTOR_MODE): Use VECTOR_ALIGNMENT_P.
	(RS6000_BTM_MMA): Define.
	(RS6000_BTM_COMMON): Add RS6000_BTM_MMA and RS6000_BTM_FUTURE.
	(rs6000_builtin_type_index): Add RS6000_BTI_vector_pair and
	RS6000_BTI_vector_quad.
	(vector_pair_type_node): New.
	(vector_quad_type_node): New.
	* config/rs6000/rs6000.md: Include mma.md.
	(define_mode_iterator RELOAD): Add POI and PXI.
	* config/rs6000/t-rs6000 (MD_INCLUDES): Add mma.md.
	* config/rs6000/rs6000.opt (-mmma): New.
	* doc/invoke.texi: Document -mmma.