amdgcn: minimal V64TImode vector support

amdgcn: minimal V64TImode vector support

Just enough support for TImode vectors to exist, load, store, move,
without any real instructions available.

This is primarily for the use of divmodv64di4, which uses TImode to
return a pair of DImode values.

gcc/ChangeLog:

	* config/gcn/gcn-protos.h (vgpr_4reg_mode_p): New function.
	* config/gcn/gcn-valu.md (V_4REG, V_4REG_ALT): New iterators.
	(V_MOV, V_MOV_ALT): Likewise.
	(scalar_mode, SCALAR_MODE): Add TImode.
	(vnsi, VnSI, vndi, VnDI): Likewise.
	(vec_merge, vec_merge_with_clobber, vec_merge_with_vcc): Use V_MOV.
	(mov<mode>, mov<mode>_unspec): Use V_MOV.
	(*mov<mode>_4reg): New insn.
	(mov<mode>_exec): New 4reg variant.
	(mov<mode>_sgprbase): Likewise.
	(reload_in<mode>, reload_out<mode>): Use V_MOV.
	(vec_set<mode>): Likewise.
	(vec_duplicate<mode><exec>): New 4reg variant.
	(vec_extract<mode><scalar_mode>): Likewise.
	(vec_extract<V_ALL:mode><V_ALL_ALT:mode>): Rename to ...
	(vec_extract<V_MOV:mode><V_MOV_ALT:mode>): ... this, and use V_MOV.
	(vec_extract<V_4REG:mode><V_4REG_ALT:mode>_nop): New 4reg variant.
	(fold_extract_last_<mode>): Use V_MOV.
	(vec_init<V_ALL:mode><V_ALL_ALT:mode>): Rename to ...
	(vec_init<V_MOV:mode><V_MOV_ALT:mode>): ... this, and use V_MOV.
	(gather_load<mode><vnsi>, gather<mode>_expr<exec>,
	gather<mode>_insn_1offset<exec>, gather<mode>_insn_1offset_ds<exec>,
	gather<mode>_insn_2offsets<exec>): Use V_MOV.
	(scatter_store<mode><vnsi>, scatter<mode>_expr<exec_scatter>,
	scatter<mode>_insn_1offset<exec_scatter>,
	scatter<mode>_insn_1offset_ds<exec_scatter>,
	scatter<mode>_insn_2offsets<exec_scatter>): Likewise.
	(maskload<mode>di, maskstore<mode>di, mask_gather_load<mode><vnsi>,
	mask_scatter_store<mode><vnsi>): Likewise.
	* config/gcn/gcn.cc (gcn_class_max_nregs): Use vgpr_4reg_mode_p.
	(gcn_hard_regno_mode_ok): Likewise.
	(GEN_VNM): Add TImode support.
	(USE_TI): New macro. Separate TImode operations from non-TImode ones.
	(gcn_vector_mode_supported_p): Add V64TImode, V32TImode, V16TImode,
	V8TImode, and V2TImode.
	(print_operand):  Add 'J' and 'K' print codes.

(cherry picked from commit 8aeabd9f63d8a54a5fa0b038ad4425a999e1cc75)