RISC-V: Support Zcmp push/pop instructions.

RISC-V: Support Zcmp push/pop instructions.

Support zcmp extension push/pop/popret and popret zero instructions.
The `reg_list' is a list containing 1 to 13 registers, we can use:
"{ra}, {ra, s0}, {ra, s0-s1}, {ra, s0-s2} ... {ra, s0-sN}"
to present this feature.

Passed gcc/binutils regressions of riscv-gnu-toolchain.

Most of work was finished by Sinan Lin.
Co-Authored by: Charlie Keaney <charlie.keaney@embecosm.com>
Co-Authored by: Mary Bennett <mary.bennett@embecosm.com>
Co-Authored by: Nandni Jamnadas <nandni.jamnadas@embecosm.com>
Co-Authored by: Sinan Lin <sinan.lin@linux.alibaba.com>
Co-Authored by: Simon Cook <simon.cook@embecosm.com>
Co-Authored by: Shihua Liao <shihua@iscas.ac.cn>
Co-Authored by: Yulong Shi <yulong@iscas.ac.cn>

bfd/ChangeLog:

        * elfxx-riscv.c (riscv_implicit_subset): Imply zca for zcmp.
	(riscv_supported_std_z_ext): Added zcmp with version 1.0.
	(riscv_parse_check_conflicts): Zcmp conflicts with d/zcd.
        (riscv_multi_subset_supports): Handle zcmp.
        (riscv_multi_subset_supports_ext): Ditto.

gas/ChangeLog:

	* NEWS: Updated.
        * config/tc-riscv.c (regno_to_reg_list): New function, used to map
	register to reg_list number.
        (reglist_lookup): Called reglist_lookup_internal.  Return false if
	reg_list number is zero, which is an invalid value.
	(reglist_lookup_internal): Parse register list, and return the last
	register by regno_to_reg_list.
        (validate_riscv_insn):  New operators.
        (riscv_ip): Ditto.
	* testsuite/gas/riscv/march-help.l: Updated.
        * testsuite/gas/riscv/zcmp-push-pop-fail.d: New test.
        * testsuite/gas/riscv/zcmp-push-pop-fail.l: New test.
        * testsuite/gas/riscv/zcmp-push-pop-fail.s: New test.
        * testsuite/gas/riscv/zcmp-push-pop.d: New test.
        * testsuite/gas/riscv/zcmp-push-pop.s: New test.

include/ChangeLog:

        * opcode/riscv-opc.h (MATCH/MASK_CM_PUSH): New macros for zcmp.
        (MATCH/MASK_CM_POP): Ditto.
        (MATCH/MASK_CM_POPRET): Ditto.
        (MATCH/MASK_CM_POPRETZ): Ditto.
        (DECLARE_INSN): New declarations for zcmp.
        * opcode/riscv.h (EXTRACT/ENCODE/VALID_ZCMP_SPIMM): Handle spimm
	operand for zcmp.
        (OP_MASK_REG_LIST): Handle operand for zcmp register list.
        (OP_SH_REG_LIST): Ditto.
        (ZCMP_SP_ALIGNMENT): New argument, used in riscv_get_sp_base.
        (X_S0, X_S1, X_S2, X_S10, X_S11): New register numbers.
        (enum riscv_insn_class): Added INSN_CLASS_ZCMP.
        (extern riscv_get_sp_base): Added.

opcodes/ChangeLog:

        * riscv-dis.c (print_reg_list): New function, used to get zcmp
	reg_list field.
        (riscv_get_spimm): New function, used to get zcmp sp adjustment
	immediate.
        (print_insn_args): Handle new operands for zcmp.
        * riscv-opc.c (riscv_get_sp_base): New function, used by gas and
	objdump.  Get sp base adjustment.
	(riscv_opcodes): Added zcmp instructions.