RISC-V: Add indexed loads/stores C/C++ intrinsic support

RISC-V: Add indexed loads/stores C/C++ intrinsic support

gcc/ChangeLog:

	* config/riscv/riscv-protos.h (get_vector_mode): New function.
	* config/riscv/riscv-v.cc (get_vector_mode): Ditto.
	* config/riscv/riscv-vector-builtins-bases.cc (enum lst_type): New enum.
	(class loadstore): Adjust for indexed loads/stores support.
	(BASE): Ditto.
	* config/riscv/riscv-vector-builtins-bases.h: New function declare.
	* config/riscv/riscv-vector-builtins-functions.def (vluxei8): Ditto.
	(vluxei16): Ditto.
	(vluxei32): Ditto.
	(vluxei64): Ditto.
	(vloxei8): Ditto.
	(vloxei16): Ditto.
	(vloxei32): Ditto.
	(vloxei64): Ditto.
	(vsuxei8): Ditto.
	(vsuxei16): Ditto.
	(vsuxei32): Ditto.
	(vsuxei64): Ditto.
	(vsoxei8): Ditto.
	(vsoxei16): Ditto.
	(vsoxei32): Ditto.
	(vsoxei64): Ditto.
	* config/riscv/riscv-vector-builtins-shapes.cc
	(struct indexed_loadstore_def): New class.
	(SHAPE): Ditto.
	* config/riscv/riscv-vector-builtins-shapes.h: Ditto.
	* config/riscv/riscv-vector-builtins.cc (required_extensions_p): Adjust
	for indexed loads/stores support.
	(check_required_extensions): Ditto.
	(rvv_arg_type_info::get_base_vector_type): New function.
	(rvv_arg_type_info::get_tree_type): Ditto.
	(function_builder::add_unique_function): Adjust for indexed loads/stores
	support.
	(function_expander::use_exact_insn): New function.
	* config/riscv/riscv-vector-builtins.h (enum rvv_base_type): Adjust for
	indexed loads/stores support.
	(struct rvv_arg_type_info): Ditto.
	(function_expander::index_mode): New function.
	(function_base::apply_tail_policy_p): Ditto.
	(function_base::apply_mask_policy_p): Ditto.
	* config/riscv/vector-iterators.md (unspec): New unspec.
	* config/riscv/vector.md (unspec): Ditto.
	(@pred_indexed_<order>load<VNX1_QHSD:mode><VNX1_QHSDI:mode>): New
	pattern.
	(@pred_indexed_<order>store<VNX1_QHSD:mode><VNX1_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX2_QHSD:mode><VNX2_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>store<VNX2_QHSD:mode><VNX2_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX4_QHSD:mode><VNX4_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>store<VNX4_QHSD:mode><VNX4_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX8_QHSD:mode><VNX8_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>store<VNX8_QHSD:mode><VNX8_QHSDI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX16_QHS:mode><VNX16_QHSI:mode>): Ditto.
	(@pred_indexed_<order>store<VNX16_QHS:mode><VNX16_QHSI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX32_QH:mode><VNX32_QHI:mode>): Ditto.
	(@pred_indexed_<order>store<VNX32_QH:mode><VNX32_QHI:mode>): Ditto.
	(@pred_indexed_<order>load<VNX64_Q:mode><VNX64_Q:mode>): Ditto.
	(@pred_indexed_<order>store<VNX64_Q:mode><VNX64_Q:mode>): Ditto.