mips-stack-saver.py

from sys import argv
import re

use = """
python3 mipsstacksaver.py [OPTION] filename
OPTIONS:
    -m:     merges the output to the input file
    -s:     prints the output to the standard output
Example use in source file:
    myroutine:
        # this is a comment
        ##save ra,s0,s1,s2,s3
        $addi  $s1, $zero, 0
        $addi  $s2, $zero, 0
        $move  $s3, $zero
        $move  $s4, $zero
        ##load 1,2,3,4
        # BE CAREFUL! The order of registers after the "load"
        # must be the same as the order of registers
        # after the "save"
This program is intented for use with MIPS32/MIPS64 architecture.
"""

outmode = ""

def substitute(filename):
    file = open(filename, "r+")
    newfile = []

    for line in file:
        if (re.fullmatch(r"\s*##((load)|(save)) (\w\w,)*(\w\w)\s*", line[:-1])):
            line = line.rstrip()
            leading = re.match(r"^\s*##", line).regs[0][1]
            rest = line[leading-2:]
            leading = line[:leading-2]
            args = re.split(" ", line[2:])
            regs = re.split(",", args[1])
            if args[0] == "save":
                newfile.append("{}addi $sp, $sp, -{}\n".format(leading, len(regs)*4))
                for i in range(0, len(regs)*4, 4):
                    newfile.append("{}sw ${}, {}($sp)\n".format(leading, regs[int(i/4)], i))
            else:
                for i in range(0, len(regs)*4, 4):
                    newfile.append("{}lw ${}, {}($sp)\n".format(leading, regs[int(i/4)], i))
                newfile.append("{}addi $sp, $sp, {}\n". format(leading, len(regs)*4))
        else:
            newfile.append(line)

    global outmode
    if outmode == "-s":
        for i in newfile:
            print(i)
    elif outmode == "-m":
        file.seek(0, 0)
        file.writelines(newfile)
    else:
        print_use()

    file.close() # also flushed the buffer

def print_use():
    print(use)

if __name__ == "__main__":
    if len(argv) >= 3:
        outmode = argv[1]
        substitute(argv[2])
    else:
        print_use()