LoongArch: Add some vector pack/unpack patterns

gcc/ChangeLog:

	* config/loongarch/lasx.md (vec_unpacks_lo_<mode>): Redefine.
	(vec_unpacku_lo_<mode>): Ditto.
	(lasx_vext2xv_h<u>_b<u>): Replaced by vec_unpack<su>_lo_v32qi.
	(vec_unpack<su>_lo_v32qi): New insn.
	(lasx_vext2xv_w<u>_h<u>): Replaced by vec_unpack<su>_lo_v16hi.
	(vec_unpack<su>_lo_v16qi_internal): New insn, for 128 bits.
	(vec_unpack<su>_lo_v16hi): New insn.
	(lasx_vext2xv_d<u>_w<u>): Replaced by vec_unpack<su>_lo_v8si.
	(vec_unpack<su>_lo_v8hi_internal): New insn, for 128 bits.
	(vec_unpack<su>_lo_v8si): New insn.
	(vec_unpack<su>_lo_v4si_internal): New insn, for 128 bits.
	(vec_packs_float_v4di): New expander.
	(vec_pack_sfix_trunc_v4df): Ditto.
	(vec_unpacks_float_hi_v8si): Ditto.
	(vec_unpacks_float_lo_v8si): Ditto.
	(vec_unpack_sfix_trunc_hi_v8sf): Ditto.
	(vec_unpack_sfix_trunc_lo_v8sf): Ditto.
	* config/loongarch/loongarch-builtins.cc
	(CODE_FOR_lsx_vftintrz_w_d): Rename.
	(CODE_FOR_lsx_vftintrzh_l_s): Ditto.
	(CODE_FOR_lsx_vftintrzl_l_s): Ditto.
	(CODE_FOR_lsx_vffint_s_l): Ditto.
	(CODE_FOR_lsx_vffinth_d_w): Ditto.
	(CODE_FOR_lsx_vffintl_d_w): Ditto.
	(CODE_FOR_lsx_vexth_h_b): Ditto.
	(CODE_FOR_lsx_vexth_w_h): Ditto.
	(CODE_FOR_lsx_vexth_d_w): Ditto.
	(CODE_FOR_lsx_vexth_hu_bu): Ditto.
	(CODE_FOR_lsx_vexth_wu_hu): Ditto.
	(CODE_FOR_lsx_vexth_du_wu): Ditto.
	(CODE_FOR_lsx_vfcvth_d_s): Ditto.
	(CODE_FOR_lsx_vfcvtl_d_s): Ditto.
	(CODE_FOR_lasx_vext2xv_h_b): Ditto.
	(CODE_FOR_lasx_vext2xv_w_h): Ditto.
	(CODE_FOR_lasx_vext2xv_d_w): Ditto.
	(CODE_FOR_lasx_vext2xv_hu_bu): Ditto.
	(CODE_FOR_lasx_vext2xv_wu_hu): Ditto.
	(CODE_FOR_lasx_vext2xv_du_wu): Ditto.
	(loongarch_expand_builtin_insn): Swap source operands in
	CODE_FOR_lsx_vftintrz_w_d and CODE_FOR_lsx_vffint_s_l.
	* config/loongarch/loongarch-protos.h
	(loongarch_expand_vec_unpack): Remove useless parameter high_p.
	* config/loongarch/loongarch.cc (loongarch_expand_vec_unpack):
	Rewrite.
	* config/loongarch/lsx.md (vec_unpacks_hi_v4sf): Redefine.
	(vec_unpacks_lo_v4sf): Ditto.
	(vec_unpacks_hi_<mode>): Ditto.
	(vec_unpacku_hi_<mode>): Ditto.
	(lsx_vfcvth_d_s): Replaced by vec_unpacks_hi_v4sf.
	(lsx_vfcvtl_d_s): Replaced by vec_unpacks_lo_v4sf.
	(lsx_vffint_s_l): Replaced by vec_packs_float_v2di.
	(vec_packs_float_v2di): New insn.
	(lsx_vftintrz_w_d): Replaced by vec_pack_sfix_trunc_v2df.
	(vec_pack_sfix_trunc_v2df): New insn.
	(lsx_vffinth_d_w): Replaced by vec_unpacks_float_hi_v4si.
	(vec_unpacks_float_hi_v4si): New insn.
	(lsx_vffintl_d_w): Replaced by vec_unpacks_float_lo_v4si.
	(vec_unpacks_float_lo_v4si): New insn.
	(lsx_vftintrzh_l_s): Replaced by vec_unpack_sfix_trunc_hi_v4sf.
	(vec_unpack_sfix_trunc_hi_v4sf): New insn.
	(lsx_vftintrzl_l_s): Replaced by vec_unpack_sfix_trunc_lo_v4sf.
	(vec_unpack_sfix_trunc_lo_v4sf): New insn.
	(lsx_vexth_h<u>_b<u>): Replaced by vec_unpack<su>_hi_v16qi.
	(vec_unpack<su>_hi_v16qi): New insn.
	(lsx_vexth_w<u>_h<u>): Replaced by vec_unpack<su>_hi_v8hi.
	(vec_unpack<su>_hi_v8hi): New insn.
	(lsx_vexth_d<u>_w<u>): Replaced by vec_unpack<su>_hi_v4si.
	(vec_unpack<su>_hi_v4si): New insn.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/vec_pack_unpack_128.c: New test.
	* gcc.target/loongarch/vec_pack_unpack_256.c: New test.