amdgcn: Add Accelerator VGPR registers

amdgcn: Add Accelerator VGPR registers

Add the new CDNA register file.  We don't support any of the specialized
instructions that use these registers, but they're useful to relieve
register pressure without spilling to stack.

Co-authored-by: Andrew Jenner  <andrew@codesourcery.com>
gcc/ChangeLog:

	* config/gcn/constraints.md: Add "a" AVGPR constraint.
	* config/gcn/gcn-valu.md (*mov<mode>): Add AVGPR alternatives.
	(*mov<mode>_4reg): Likewise.
	(@mov<mode>_sgprbase): Likewise.
	(gather<mode>_insn_1offset<exec>): Likewise.
	(gather<mode>_insn_1offset_ds<exec>): Likewise.
	(gather<mode>_insn_2offsets<exec>): Likewise.
	(scatter<mode>_expr<exec_scatter>): Likewise.
	(scatter<mode>_insn_1offset_ds<exec_scatter>): Likewise.
	(scatter<mode>_insn_2offsets<exec_scatter>): Likewise.
	* config/gcn/gcn.cc (MAX_NORMAL_AVGPR_COUNT): Define.
	(gcn_class_max_nregs): Handle AVGPR_REGS and ALL_VGPR_REGS.
	(gcn_hard_regno_mode_ok): Likewise.
	(gcn_regno_reg_class): Likewise.
	(gcn_spill_class): Allow spilling to AVGPRs on TARGET_CDNA1_PLUS.
	(gcn_sgpr_move_p): Handle AVGPRs.
	(gcn_secondary_reload): Reload AVGPRs via VGPRs.
	(gcn_conditional_register_usage): Handle AVGPRs.
	(gcn_vgpr_equivalent_register_operand): New function.
	(gcn_valid_move_p): Check for validity of AVGPR moves.
	(gcn_compute_frame_offsets): Handle AVGPRs.
	(gcn_memory_move_cost): Likewise.
	(gcn_register_move_cost): Likewise.
	(gcn_vmem_insn_p): Handle TYPE_VOP3P_MAI.
	(gcn_md_reorg): Handle AVGPRs.
	(gcn_hsa_declare_function_name): Likewise.
	(print_reg): Likewise.
	(gcn_dwarf_register_number): Likewise.
	* config/gcn/gcn.h (FIRST_AVGPR_REG): Define.
	(AVGPR_REGNO): Define.
	(LAST_AVGPR_REG): Define.
	(SOFT_ARG_REG): Update.
	(FRAME_POINTER_REGNUM): Update.
	(DWARF_LINK_REGISTER): Update.
	(FIRST_PSEUDO_REGISTER): Update.
	(AVGPR_REGNO_P): Define.
	(enum reg_class): Add AVGPR_REGS and ALL_VGPR_REGS.
	(REG_CLASS_CONTENTS): Add new register classes and add entries for
	AVGPRs to all classes.
	(REGISTER_NAMES): Add AVGPRs.
	* config/gcn/gcn.md (FIRST_AVGPR_REG, LAST_AVGPR_REG): Define.
	(AP_REGNUM, FP_REGNUM): Update.
	(define_attr "type"): Add vop3p_mai.
	(define_attr "unit"): Handle vop3p_mai.
	(define_attr "gcn_version"): Add "cdna2".
	(define_attr "enabled"): Handle cdna2.
	(*mov<mode>_insn): Add AVGPR alternatives.
	(*movti_insn): Likewise.
	* config/gcn/mkoffload.cc (isa_has_combined_avgprs): New.
	(process_asm): Process avgpr_count.
	* config/gcn/predicates.md (gcn_avgpr_register_operand): New.
	(gcn_avgpr_hard_register_operand): New.
	* doc/md.texi: Document the "a" constraint.

gcc/testsuite/ChangeLog:

	* gcc.target/gcn/avgpr-mem-double.c: New test.
	* gcc.target/gcn/avgpr-mem-int.c: New test.
	* gcc.target/gcn/avgpr-mem-long.c: New test.
	* gcc.target/gcn/avgpr-mem-short.c: New test.
	* gcc.target/gcn/avgpr-spill-double.c: New test.
	* gcc.target/gcn/avgpr-spill-int.c: New test.
	* gcc.target/gcn/avgpr-spill-long.c: New test.
	* gcc.target/gcn/avgpr-spill-short.c: New test.

libgomp/ChangeLog:

	* plugin/plugin-gcn.c (max_isa_vgprs): New.
	(run_kernel): CDNA2 devices have more VGPRs.