Build 32-bit hex value of a custom RISC-V R-type instruction.

new_instruction.py

import re 

def reg_index(reg_name):
    return [
            'zero', # always zero (x0)
            'ra', # return address
            'sp', # stack pointer
            'gp', # global pointer
            'tp', # thread pointer
            't0',
            't1',
            't2',
            's0', # frame pointer (fp)
            's1', 
            'a0', # return value
            'a1',
            'a2',
            'a3',
            'a4',
            'a5',
            'a6',
            'a7',
            's2',
            's3',
            's4',
            's5',
            's6',
            's7',
            's8',
            's9',
            's10',
            's11',
            't3',
            't4',
            't5',
            't6'
            ].index(reg_name)

def reg_index_to_5_bits(i):
    return f'{i:05b}'

def reg_name_to_bits(name):
    i = reg_index(name)
    # print(i)
    return reg_index_to_5_bits(i)

def r_type_instr(func7, rs2_name, rs1_name, func3, rd_name, opcode):
    rs2 = reg_name_to_bits(rs2_name)
    rs1 = reg_name_to_bits(rs1_name)
    rd = reg_name_to_bits(rd_name)
    # print(rs2_name, rs2, rs1_name, rs1)
    instr = ''.join([func7, rs2, rs1, func3, rd, opcode])
    instr = int(instr, 2)
    return instr

def str_to_r_type_instr(s):
    s = re.sub(r'[^10]+', '', s)
    instr = int(s, 2)
    return instr

def print_instr(instr):
    print(f'.word 0x{instr:08x}')
    print(f'{instr:032b}')

# instr = r_type_instr(
#         '0000101', # func7
#         't3',      # rs2_name
#         't4',      # rs1_name
#         '101',     # func3
#         't5',      # rd_name 
#         '0110011', # opcode
#         )

instr = r_type_instr(
        '0000101', # func7
        't3',      # rs2_name
        't4',      # rs1_name
        '100',     # func3
        't0',      # rd_name 
        '0110011', # opcode
        )

print_instr(instr)

instr = r_type_instr(
        '0000101', # func7
        't3',      # rs2_name
        't4',      # rs1_name
        '110',     # func3
        't1',      # rd_name 
        '0110011', # opcode
        )

print_instr(instr)