Ahead-of-time RPN compiler.

RPNJit.py

import ctypes, mmap, struct
DEBUG = True
try:
    VirtualAlloc = ctypes.windll.kernel32.VirtualAlloc
    raise Exception("Windows not supported.")
except(AttributeError):
    libc = ctypes.CDLL("libc.so.6")
    libc.valloc.restype = ctypes.c_void_p
    def valloc(size):
        addr = libc.valloc(size)
        if not addr or libc.mprotect(addr, size, 0x07):
            raise RuntimeError("Cannot allocate RWX memory")
        return addr

def pack_number(term):
    number = float(term)
    return struct.pack('f', number)

def compile(rpn_code):
    size = mmap.PAGESIZE
    page = valloc(size)
    # cdecl header, compatible with python ctype
    buffer = push("rbp") + \
             mov('rbp', 'rsp')

    sp = 0
    for term in rpn_code.split():
        try:
            buffer += \
                push(pack_number(term))
            sp += 1
        except(ValueError):
            header = fld("[rsp]") + \
                     pop("rax") + \
                     fld("[rsp]") + \
                     "%s" + \
                     fst("[rsp]")
            dictionary = {
                "+" : header % fadd,
                "-" : header % fsub,
                "*" : header % fmul,
                "/" : header % fdiv,
                "//": header % (fdiv + frndint),
                "%" : header % fprem,
                "^" : header % FPOW,
            }

            sp -= 1
            buffer += dictionary[term]

    buffer += pop("rax") * sp # clear the stack into the return slot
    buffer += mov("rsp", "rbp") + \
              pop('rbp') + \
              ret

    if not ctypes.memmove(page, buffer, min(len(buffer), size)):
        raise RuntimeError("Input cannot not fit into memory.")

    if DEBUG: print(''.join(map(lambda x: '%02x' % ord(x), buffer)))
    return ctypes.CFUNCTYPE(ctypes.c_int)(page)

# fake mnemonics
push = lambda r: "\x55" if r == 'rbp' else ("\x68" + str(r))
mov = lambda r1, r2: "\x48\x89" + ("\xe5" if (r1, r2) == ("rbp", "rsp") else "\xec" if (r1, r2) == ("rsp", "rbp") else None)
pop = lambda r: "\x58" if r == "rax" else "\x5d" if r == "rbp" else None
fld = lambda r: "\xD9\x44\x24\x00" if r == "[rsp]" else None
fst = lambda r: "\xD9\x54\x24\x00" if r == "[rsp]" else None
ret = "\xc3"
fadd = "\xd8\xc1"
fsub = "\xd8\xe1"
fmul = "\xd8\xc9"
fdiv = "\xd8\xf1"
fprem = "\xd9\xf8"
frndint = "\xD9\xFC"
FPOW = "\xD9\xF1\xDB\x14\x24\xDB\x04\x24\xDE\xE9\xD9\xF0\xD9\xE8\xDE\xC1\xDB\x04\x24\xD9\xC9\xD9\xFD"

def rpn(code):
    f = compile(code)
    return struct.unpack('f', struct.pack('i', f()))[0]

if __name__ == '__main__':
    import sys
    DEBUG = True if len(sys.argv) > 2 and sys.argv[2] == '--debug' else False
    print(rpn(sys.argv[1] if len(sys.argv) > 1 else "2 0.5 ^"))