RISC-V: Add permutation C/C++ support

gcc/ChangeLog:

	* config/riscv/riscv-protos.h (enum vlen_enum): New enum.
	(slide1_sew64_helper): New function.
	* config/riscv/riscv-v.cc (compute_vlmax): Ditto.
	(get_unknown_min_value): Ditto.
	(force_vector_length_operand): Ditto.
	(gen_no_side_effects_vsetvl_rtx): Ditto.
	(get_vl_x2_rtx): Ditto.
	(slide1_sew64_helper): Ditto.
	* config/riscv/riscv-vector-builtins-bases.cc (class slideop): New class.
	(class vrgather): Ditto.
	(class vrgatherei16): Ditto.
	(class vcompress): Ditto.
	(BASE): Ditto.
	* config/riscv/riscv-vector-builtins-bases.h: Ditto.
	* config/riscv/riscv-vector-builtins-functions.def (vslideup): Ditto.
	(vslidedown): Ditto.
	(vslide1up): Ditto.
	(vslide1down): Ditto.
	(vfslide1up): Ditto.
	(vfslide1down): Ditto.
	(vrgather): Ditto.
	(vrgatherei16): Ditto.
	(vcompress): Ditto.
	* config/riscv/riscv-vector-builtins-types.def (DEF_RVV_EI16_OPS): New macro.
	(vint8mf8_t): Ditto.
	(vint8mf4_t): Ditto.
	(vint8mf2_t): Ditto.
	(vint8m1_t): Ditto.
	(vint8m2_t): Ditto.
	(vint8m4_t): Ditto.
	(vint16mf4_t): Ditto.
	(vint16mf2_t): Ditto.
	(vint16m1_t): Ditto.
	(vint16m2_t): Ditto.
	(vint16m4_t): Ditto.
	(vint16m8_t): Ditto.
	(vint32mf2_t): Ditto.
	(vint32m1_t): Ditto.
	(vint32m2_t): Ditto.
	(vint32m4_t): Ditto.
	(vint32m8_t): Ditto.
	(vint64m1_t): Ditto.
	(vint64m2_t): Ditto.
	(vint64m4_t): Ditto.
	(vint64m8_t): Ditto.
	(vuint8mf8_t): Ditto.
	(vuint8mf4_t): Ditto.
	(vuint8mf2_t): Ditto.
	(vuint8m1_t): Ditto.
	(vuint8m2_t): Ditto.
	(vuint8m4_t): Ditto.
	(vuint16mf4_t): Ditto.
	(vuint16mf2_t): Ditto.
	(vuint16m1_t): Ditto.
	(vuint16m2_t): Ditto.
	(vuint16m4_t): Ditto.
	(vuint16m8_t): Ditto.
	(vuint32mf2_t): Ditto.
	(vuint32m1_t): Ditto.
	(vuint32m2_t): Ditto.
	(vuint32m4_t): Ditto.
	(vuint32m8_t): Ditto.
	(vuint64m1_t): Ditto.
	(vuint64m2_t): Ditto.
	(vuint64m4_t): Ditto.
	(vuint64m8_t): Ditto.
	(vfloat32mf2_t): Ditto.
	(vfloat32m1_t): Ditto.
	(vfloat32m2_t): Ditto.
	(vfloat32m4_t): Ditto.
	(vfloat32m8_t): Ditto.
	(vfloat64m1_t): Ditto.
	(vfloat64m2_t): Ditto.
	(vfloat64m4_t): Ditto.
	(vfloat64m8_t): Ditto.
	* config/riscv/riscv-vector-builtins.cc (DEF_RVV_EI16_OPS): Ditto.
	* config/riscv/riscv.md: Adjust RVV instruction types.
	* config/riscv/vector-iterators.md (down): New iterator.
	(=vd,vr): New attribute.
	(UNSPEC_VSLIDE1UP): New unspec.
	* config/riscv/vector.md (@pred_slide<ud><mode>): New pattern.
	(*pred_slide<ud><mode>): Ditto.
	(*pred_slide<ud><mode>_extended): Ditto.
	(@pred_gather<mode>): Ditto.
	(@pred_gather<mode>_scalar): Ditto.
	(@pred_gatherei16<mode>): Ditto.
	(@pred_compress<mode>): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/binop_vx_constraint-167.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-168.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-169.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-170.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-171.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-172.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-173.c: New test.
	* gcc.target/riscv/rvv/base/binop_vx_constraint-174.c: New test.