farlands/langs/wmc/wmc.py

#!/usr/bin/python

import os
import os.path
import re
import sys

import lark

GRAMMAR = r"""
start: toplevel+
?toplevel: include
         | funcdef
         | arrdec ";"
         | vardec ";"
         | varinit ";"
         | arrinit ";"
         | asm ";"

include: "#" "include" FILENAME 
FILENAME: "<" /.+/ ">"
funcdef: NAME "(" params ")" block
varinit: NAME
arrinit: NAME "[" INTEGER "]"
vardec: NAME "=" expr
arrdec: NAME "[" expr "]" ("=" expr)?

params:
      | NAME ("," NAME)*

block: "{" op* "}"

asm: "asm" "(" STRING+ ")"

?op: block
   | label
   | goto ";"
   | break ";"
   | continue ";"
   | vardec ";"
   | arrdec ";"
   | return ";"
   | varinit ";"
   | arrinit ";"
   | inc ";"
   | dec ";"
   | rinc ";"
   | rdec ";"
   | asm ";"
   | funcall ";"
   | switch
   | if
   | while
   | for
label: NAME ":"
goto: "goto" NAME
break: "break"
continue: "continue"
switch: "switch" "(" expr ")" "{" case+ default? "}"
case: "case" atom2 ":" op*
default: "default" ":" op+
if: "if" "(" expr ")" op ("else" op)?
while: "while" "(" expr ")" op
for: "for" "(" vardec ";" expr ";" (inc|dec|rinc|rdec|vardec|funcall) ")" op
return: "return" expr?
inc: NAME ("[" expr "]")? "++"
dec: NAME ("[" expr "]")? "--"
rinc: "++" NAME ("[" expr "]")?
rdec: "--" NAME ("[" expr "]")?

funcall: NAME "(" args ")"
args:
    | [expr ("," expr)*]

?expr: op1
     | op1 "?" op1 ":" expr -> ifexpr
?op1: op2
    | vardec
    | arrdec
    | op1 "==" op1 -> equals
    | op1 "!=" op1 -> not_equals
    | op1 "+" op2 -> plus
    | op1 "-" op2 -> minus
?op2: op3
    | op2 "*" op2 -> times
    | op2 "/" op3 -> divide
    | op2 "%" op3 -> modulo
    | op2 "<" op3 -> less
    | op2 ">" op3 -> greater
    | op2 "<=" op3 -> less_or_equals
    | op2 ">=" op3 -> greater_or_equals
?op3: op4
    | op3 "**" op4 -> raise
?op4: op5
    | op4 "||" op4 -> or
    | op4 "&&" op4 -> and
    | "!" atom -> not
    | "*" atom -> deref
?op5: atom
    | op5 "[" op1 "]" -> index
?atom: "(" op1 ")"
     | atom2
     | funcall
     | inc
     | dec
     | rinc
     | rdec
?atom2: NAME
      | INTEGER
      | FLOAT
      | CHAR
      | STRING
      | "-" atom -> negate
      | array
array: "{" atom ("," atom)* "}"

NAME: /[A-Za-z_][a-zA-Z0-9_]*/
INTEGER: /[0-9]+/
FLOAT: /[0-9]+\.[0-9]+/
CHAR: /'(.|(\\.))'/
_STRING_INNER: /(.|\n)*?/
_STRING_ESC_INNER: _STRING_INNER /(?<!\\)(\\\\)*?/ 
STRING: "\"" _STRING_ESC_INNER "\""

IG: /[ \t\r\n]+/
COM: /\/\*(.|\!)*\*\//
%ignore IG
%ignore COM
"""

def parse_escape(s):
  return bytes(s, "utf-8").decode("unicode_escape")

class ASMWalker:
  def __init__(self, asm):
    self.asm = asm
    self.pos = -1
    self.size = len(asm)

  def step(self):
    if self.pos >= self.size:
      return False

    self.pos += 1

    return True

  def skip(self, offset):
    for i in range(self.pos, self.pos+offset):
      if i >= self.size:
        break

      self.asm[i] = f"#{self.asm[i]}"

    #self.pos += offset

  def match(self, offset, *args):
    offset = self.pos + offset

    if offset >= self.size:
      return None

    asm = self.asm[offset]
    args = " ".join(args) 
    
    return re.match(f"^{args}$", asm)

  def rule2(self, rule1, rule2, skip=2):
    m = self.match(0, *rule1)
    if m:
      if self.match(1, *map(lambda s: s.format(m=m[1]), rule2)):
        self.skip(skip)

  def get(self):   
    return self.asm[self.pos]

  @property
  def end(self):
    return self.pos >= self.size

class Buffer:
  def __init__(self, *init):
    self.buffer = list(init)

  def emit(self, asm, *args):
    if type(asm) is list:
      self.buffer.extend(asm)
    elif type(asm) is Buffer:
      self.buffer.extend(asm.buffer)
    else:
      self.buffer.append(asm.format(*args))

  def optimize(self):
    buffer = Buffer()
    walker = ASMWalker(self.buffer)

    while walker.step():
      walker.rule2(
        ("jmp", "(.+)"),
        ("{m}:",),
        skip=1
      )
      walker.rule2(
        ("push", "(.+)"),
        ("pop {m}",)
      )

      if walker.end:
        break

      buffer.emit(walker.get())

    return buffer

  def generate(self):
    return "\n".join(self.buffer)

  def __add__(self, other):
    if type(other) is Buffer:
      return Buffer(
        *self.buffer + other.buffer
      )

    raise TypeError

class Scope:
  def __init__(self):
    self.scopes = []
    self.ndx = 0

    self.names = set()

  def new(self):
    self.scopes.append((self.ndx, {}, {}))
    self.ndx += 1

  def leave(self):
    self.scopes.pop()

  def add_label(self, name):
    renamed = f"__{self.scopes[-1][0]}l_{name}"

    self.scopes[-1][2][name] = renamed

    return renamed

  def get_label(self, name):
    if name not in self.scopes[-1][2]:
      raise Exception(f"Undeclared label: '{name}`.")

    return self.scopes[-1][2][name]

  def is_local(self, name):
    return name in self.scopes[-1][1]

  def insert(self, name):
    renamed = f"__{self.scopes[-1][0]}_{name}"

    self.scopes[-1][1][name] = renamed

    self.names.add(renamed)

    return renamed

  def find(self, name):
    for _, scope, _ in self.scopes[::-1]:
      if name in scope:
        return scope[name]

    raise Exception(f"Undeclared identifier: '{name}`.")

  def __contains__(self, name):
    for _, scope, _ in self.scopes[::-1]:
      if name in scope:
        return True

    return False

  def __getitem__(self, name):
    if name in self:
      return self.find(name)

    return self.insert(name)

  def __iter__(self):
    for _, scope, _ in self.scopes[::-1]:
      for name in scope:
        yield (name, scope[name])

  @property
  def is_toplevel(self):
    return self.scopes[-1][0] == 0

class Func:
  def __init__(self, argc, params):
    self.argc = argc
    self.params = params

class WMC:
  def __init__(self):
    self.funcs = {}
    self.used_symbols = {}
    self.where = "toplevel"

    self.scope = Scope()
    self.scope.new()

    self.compiled_funcs = {}

    self.arrays_buffer = Buffer()
    self.init_buffer = Buffer()
    self.buffer = Buffer(
      "jw __main",
      "pop Y",
      "mov 80 _dirBuf",
      "mov Y _dirBuf+1",
      "dir _dirBuf",
      "hlt",
      "_dirBuf:0*4",
    )

    self.label_ndx = 0

    self.included_files = set()

    self.parser = lark.Lark(GRAMMAR)

    self.loops = []

  def record_usage(self, name):
    if name in self.used_symbols:
      self.used_symbols[name].add(self.where)
    else:
      self.used_symbols[name] = set([self.where])

  def is_used(self, name):
    if name in ("main", "toplevel"):
      return True

    if name not in self.used_symbols:
      return False

    for other in self.used_symbols[name]:
      if other == name:
        continue

      if self.is_used(other):
        return True

    return False

  def make_label(self):
    name = f"__{self.label_ndx}l"

    self.label_ndx += 1

    return name

  def make_array(self, value):
    name = self.make_label()

    self.arrays_buffer.emit(
      "{}:{}",
      name, value
    )

    return name

  def compile_literal(self, node):
    if type(node) is lark.Token:
      if node.type == "NAME":        
        value = self.scope.find(node.value)

        self.record_usage(value)

        return value
      elif node.type in ("INTEGER", "FLOAT"):
        return node.value
      elif node.type == "CHAR":
        return str(ord(parse_escape(node.value[1:-1])))
      elif node.type == "STRING":
        value = parse_escape(node.value[1:-1])
        value = map(ord, value)
        value = map(str, value)
        value = " ".join(value)
        value += " 0"

        return value
    elif node.data == "array":
      value = []
      for child in node.children:
        value.append(
          self.compile_literal(child)
        )

      return " ".join(value)

    raise Exception(f"Not implemented: {node}")

  def compile_unary_expr(self, node, *ops):
    buffer = Buffer()

    buffer.emit(
      self.compile_expr(
        node.children[0]
      )
    )

    for op in ops:
      buffer.emit(op)

    return buffer

  def compile_binary_expr(self, node):
    buffer = Buffer()

    buffer.emit(
      self.compile_expr(
        node.children[0]
      )
    )
    buffer.emit('push Y')

    buffer.emit(
      self.compile_expr(
        node.children[1]
      )
    )
    buffer.emit('push Y')

    buffer.emit('pop X')
    buffer.emit('pop Y')

    return buffer

  def compile_compare_expr(self, node, *ops, true='1', false='0'):
    buffer = Buffer()

    ret_label = self.make_label()
    exit_label = self.make_label()

    buffer.emit(
      self.compile_binary_expr(
        node        
      )
    )

    for op in ops:
      buffer.emit(
        op,
        ret_label
      )

    buffer.emit(
      "mov {} Y",
      false
    )
    buffer.emit(
      "jmp {}",
      exit_label
    )

    buffer.emit(
      "{}:",
      ret_label
    )
    buffer.emit(
      "mov {} Y",
      true
    )      

    buffer.emit(
      "{}:",
      exit_label
    )

    return buffer

  def compile_expr(self, node):
    buffer = Buffer()

    if type(node) is lark.Token:
      if node.type == "NAME":
        buffer.emit(
          "mov {} Y",
          self.compile_literal(node)
        )
      elif node.type in ("INTEGER", "FLOAT"):
        buffer.emit(
          "mov {} Y",
          self.compile_literal(node)
        )
      elif node.type == "CHAR":
        buffer.emit(
          "mov {} Y",
          self.compile_literal(node)
        )
      elif node.type == "STRING":
        buffer.emit(
          "ld {} Y",
          self.make_array(
            self.compile_literal(node)
          )
        )
      else:
        raise Exception(f"Not implemented: {node}")
    elif node.data == "ifexpr":
      else_label = self.make_label()
      exit_label = self.make_label()

      buffer.emit(
        self.compile_expr(
          node.children[0]
        )
      )

      buffer.emit(
        "nbnz Y {}",
        else_label
      )

      buffer.emit(
        self.compile_expr(
          node.children[1]
        )
      )
      buffer.emit(
        "jmp {}",
        exit_label
      )

      buffer.emit(
        "{}:",
        else_label
      )
      buffer.emit(
        self.compile_expr(
          node.children[2]
        )
      )

      buffer.emit(
        "{}:",
        exit_label
      )      
    elif node.data == "equals":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "sblez X Y !",
          "nbnz Y {}",
          true='1',
          false='0'
        )
      )
    elif node.data == "not_equals":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "sblez X Y !",
          "nbnz Y {}",
          true='0',
          false='1'
        )
      )
    elif node.data == "plus":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "ablez X Y !"
      )
    elif node.data == "minus":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "sblez X Y !"
      )
    elif node.data == "times":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "mbnz X Y !"
      )
    elif node.data == "divide":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "vblz X Y !"
      )
    elif node.data == "modulo":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "modbz X Y !"
      )
    elif node.data == "raise":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "mov 12 _dirBuf"
      )
      buffer.emit(
        "mov X _dirBuf+1"
      )
      buffer.emit(
        "mov Y _dirBuf+2"
      )
      buffer.emit(
        "dir _dirBuf"
      )
      buffer.emit(
        "mov _dirBuf+2 Y"
      )
    elif node.data == "or":
      true_label = self.make_label()
      exit_label = self.make_label()

      buffer.emit(
        self.compile_expr(
          node.children[0]
        )
      )

      buffer.emit(
        "nbnz Y !"
      )
      buffer.emit(
        "nbnz Y {}",
        true_label
      )

      buffer.emit(
        self.compile_expr(
        node.children[1]
        )
      )

      buffer.emit(
        "jmp {}",
        exit_label
      )
      buffer.emit(
        "{}:",
        true_label
      )
      buffer.emit(
        "mov 1 Y"
      )
      buffer.emit(
        "{}:",
        exit_label
      )
    elif node.data == "and":
      false_label = self.make_label()
      exit_label = self.make_label()

      buffer.emit(
        self.compile_expr(
          node.children[0]
        )
      )

      buffer.emit(
        "nbnz Y {}",
        false_label
      )

      buffer.emit(
        self.compile_expr(
        node.children[1]
        )
      )

      buffer.emit(
        "jmp {}",
        exit_label
      )
      buffer.emit(
        "{}:",
        false_label
      )
      buffer.emit(
        "mov 0 Y"
      )
      buffer.emit(
        "{}:",
        exit_label
      )
    elif node.data == "less":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "inc Y",
          "sblez X Y {}"
        )
      )
    elif node.data == "greater":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "dec Y",
          "sblez X Y {}",
          true='0',
          false='1'
        )
      )
    elif node.data == "less_or_equals":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "sblez X Y {}"
        )
      )
    elif node.data == "greater_or_equals":
      buffer.emit(
        self.compile_compare_expr(
          node,
          "inc Y",
          "sblez X Y {}",
          true='0',
          false='1'
        )
      )
    elif node.data == "not":
      buffer.emit(
        self.compile_unary_expr(
          node,
          "nbnz Y !"
        )
      )
    elif node.data == "deref":
      buffer.emit(
        self.compile_unary_expr(
          node,
          "la Y Y"
        )
      )
    elif node.data == "index":
      buffer.emit(
        self.compile_binary_expr(
          node        
        )
      )

      buffer.emit(
        "ablez X Y !"
      )
      buffer.emit(
        "la Y Y"
      )
    elif node.data == "negate":
      buffer.emit(
        self.compile_unary_expr(
          node,
          "mov Y X",
          "sblez X Y !",
          "sblez X Y !",
        )
      )
    elif node.data == "array":
      buffer.emit(
        "ld {} Y",
        self.make_array(
          self.compile_literal(node)
        )
      )   
    elif node.data == "inc":
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "mov {} Y",
        name
      )
      buffer.emit(
        "inc {}",
        name
      )     
    elif node.data == "dec":
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "mov {} Y"
      )
      buffer.emit(
        "dec {}",
        name
      )     
    elif node.data == "rinc":
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "inc {}",
        name
      )  
      buffer.emit(
        "mov {} Y",
        name
      )  
    elif node.data == "rdec":
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "dec {}",
        name
      )  
      buffer.emit(
        "mov {} Y"
      )
    elif node.data == "funcall":
      buffer.emit(
        self.compile_funcall(node, dest='Y')
      )
    elif node.data == "vardec":
      buffer.emit(
        self.compile_op(node)
      )
    elif node.data == "arrdec":
      buffer.emit(
        self.compile_arrdec(node)
      )
    else:
      raise Exception(f"Not implemented: {node}")

    return buffer

  def compile_funcall(self, node, dest='Y'):
    buffer = Buffer()

    name = node.children[0].value

    if name not in self.funcs:
      raise Exception(f"Call to an undeclared function: '{name}`.")

    if self.funcs[name].argc != len(node.children[1].children):
      raise Exception(f"Function '{name}` expects {self.funcs[name].argc} arguments, but got {node.children[1].children}.")

    for arg in node.children[1].children[::-1]:
      buffer.emit(
        self.compile_expr(arg)
      )
      buffer.emit(
        "push Y"
      )

    buffer.emit(
      "jw __{}",
      name
    )
    buffer.emit(
      "pop {}",
      dest
    )

    self.record_usage(name)

    return buffer

  def compile_asm(self, node):
    buffer = Buffer()

    table = {}
    for name, renamed in self.scope:
      table[name] = renamed

    for child in node.children:
      value = parse_escape(child.value[1:-1])

      for name in table:
        if f"{{{name}}}" in value:
          self.record_usage(table[name])

      try:
        value = value.format(
          **table
        )
      except:
        raise Exception("Malformed asm directive.")

      buffer.emit(value)

    return buffer

  def compile_arrdec(self, node):
    buffer = Buffer()

    name = node.children[0].value

    if name in self.scope and len(node.children) == 3: # Index assignment.
      name = self.scope.find(name)

      self.record_usage(name)

      buffer.emit(
        self.compile_expr(
          node.children[1]
        )
      )

      buffer.emit(
        "mov {} X",
        name
      )
      buffer.emit(
        "ablez X Y !"
      )
      buffer.emit(
        "push Y"
      )

      buffer.emit(
        self.compile_expr(
          node.children[2]
        )
      )

      buffer.emit(
        "pop X"
      )
      buffer.emit(
        "str Y X"
      )

      return buffer

    if not self.scope.is_toplevel and self.scope.is_local(name):
      raise Exception(f"Duplicated declaration of a local variable: '{node.children[0].value}`.")

    name = self.scope[name]

    self.record_usage(name)

    count = int(node.children[1].value)

    if count <= 0:
      raise Exception(f"Illegal array declaration '{node.children[0].value}`: array size should be >0, but it is {count}.")

    if len(node.children) == 3:
      value = self.compile_literal(node.children[2])
      size = len(value.split(" ")) # Dirty.

      if size < count:
        value += f" 0*{count-size}"
      elif size != count:
        raise Exception(f"Illegal array declaration '{node.children[0].value}`: value size is {size}, but expected {count}.")

      buffer.emit(
        "ld {} Y",
        self.make_array(value)
      )
    else:
      buffer.emit(
        "ld {} Y",
        self.make_array(f"0*{count}")
      )

    buffer.emit(
      "mov Y {}",
      name
    )

    return buffer

  def compile_op(self, node):
    buffer = Buffer()

    if node.data == "block":
      buffer.emit(
        self.compile_block(
          node
        )
      )
    elif node.data == "label":
      buffer.emit(
        "{}:",
        self.scope.get_label(node.children[0].value)
      )
    elif node.data == "goto":
      buffer.emit(
        "jmp {}",
        self.scope.get_label(node.children[0].value)
      )
    elif node.data == "break":
      if len(self.loops) < 1:
        raise Exception("'break` outside of a loop/switch.")

      labels = self.loops[-1]

      buffer.emit(
        "jmp {}",
        labels[0] if len(labels) == 1 else labels[1]
      )
    elif node.data == "continue":
      if len(self.loops) < 1 or len(self.loops[-1]) != 2:
        raise Exception("'continue` outside of a loop.")

      buffer.emit(
        "jmp {}",
        self.loops[-1][0]
      ) 
    elif node.data == "varinit":
      name = node.children[0].value

      if self.scope.is_local(name):
        raise Exception(f"Duplicated declaration of a local variable: '{name}`.")
        
      self.scope.insert(name)
    elif node.data == "vardec":
      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        self.compile_expr(node.children[1])
      )
      buffer.emit(
        "mov Y {}",
        name
      )
    elif node.data in ("arrdec", "arrinit"):
      buffer.emit(
        self.compile_arrdec(node)
      )
    elif node.data in ("inc", "rinc"):
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "inc {}",
        name
      )
    elif node.data == ("dec", "rdec"):
      if len(node.children) == 2:
        raise Exception(f"Not implemented: {node}")

      name = self.scope[node.children[0].value]

      self.record_usage(name)

      buffer.emit(
        "dec {}",
        name
      )
    elif node.data == "funcall":
      buffer.emit(
        self.compile_funcall(node, dest='ZZ')
      )
    elif node.data == "return":
      if len(node.children) == 1:
        buffer.emit(
          self.compile_expr(
            node.children[0]
          )
        )
        buffer.emit("push Y")
      else:
        buffer.emit("push Z")
      
      buffer.emit("ret")
    elif node.data == "asm":
      buffer.emit(
        self.compile_asm(node)
      )
    elif node.data == "switch":
      default_label = self.make_label()
      exit_label = self.make_label()

      buffer.emit(
        self.compile_expr(node.children[0])
      )
      buffer.emit(
        "push Y"
      )

      self.loops.append((exit_label,))

      labels = {}
      for child in node.children[1:]:
        if child.data == "default":
          label = default_label

          ops = child.children
        else:
          label = self.make_label()

          buffer.emit(
            self.compile_expr(child.children[0])
          )
          buffer.emit(
            "peek X"
          )
          buffer.emit(
            "sblez X Y !"
          )
          buffer.emit(
            "nbnz Y {}",
            label
          )

          ops = child.children[1:]
        
        subbuffer = Buffer()

        for op in ops:
          subbuffer.emit(
            self.compile_op(op)
          )

        labels[label] = subbuffer

      self.loops.pop()

      buffer.emit(
        "pop ZZ"
      )
      buffer.emit(
        "jmp {}",
        default_label if default_label in labels else exit_label
      )

      for name in labels:
        buffer.emit(
          "{}:",
          name
        )

        buffer.emit(
          labels[name]
        )

      buffer.emit(
        "{}:",
        exit_label
      )
    elif node.data == "if":
      else_label = self.make_label()
      exit_label = self.make_label()

      buffer.emit(
        self.compile_expr(
          node.children[0]
        )
      )

      buffer.emit(
        "nbnz Y {}",
        else_label
      )

      buffer.emit(
        self.compile_op(
          node.children[1]
        )
      )

      buffer.emit(
        "jmp {}",
        exit_label
      )
      buffer.emit(
        "{}:",
        else_label
      )

      if len(node.children) == 3:
        buffer.emit(
          self.compile_op(
            node.children[2]
          )
        )

      buffer.emit(
        "{}:",
        exit_label
      )
    elif node.data == "while":
      loop_label = self.make_label()
      exit_label = self.make_label()

      self.loops.append((loop_label, exit_label))

      buffer.emit(
        "{}:",
        loop_label
      )

      buffer.emit(
        self.compile_expr(
          node.children[0]
        )
      )

      buffer.emit(
        "nbnz Y {}",
        exit_label
      )

      buffer.emit(
        self.compile_op(
          node.children[1]
        )
      )

      self.loops.pop()

      buffer.emit(
        "jmp {}",
        loop_label
      )
      buffer.emit(
        "{}:",
        exit_label
      )
    elif node.data == "for":
      loop_label = self.make_label()
      exit_label = self.make_label()

      self.loops.append((loop_label, exit_label))

      self.scope.new()

      buffer.emit(
        self.compile_op(
          node.children[0]
        )
      )

      buffer.emit(
        "{}:",
        loop_label
      )

      buffer.emit(
        self.compile_expr(
          node.children[1]
        )
      )

      buffer.emit(
        "nbnz Y {}",
        exit_label
      )

      buffer.emit(
        self.compile_op(
          node.children[3]
        )
      )

      buffer.emit(
        self.compile_op(
          node.children[2]
        )
      )

      self.scope.leave()

      self.loops.pop()

      buffer.emit(
        "jmp {}",
        loop_label
      )
      buffer.emit(
        "{}:",
        exit_label
      )
    else:
      raise Exception(f"Not implemented: {node}")

    return buffer

  def collect_labels(self, node):
    for child in node.children:
      if child.data == "label":
        self.scope.add_label(child.children[0].value)       

  def compile_block(self, node, *prepend_names, scope=True):
    if scope:
      self.scope.new()

      for name in prepend_names:
        self.scope.insert(name)

    buffer = Buffer()

    self.collect_labels(node)

    for child in node.children:
      buffer.emit(
        self.compile_op(child)
      )

    if scope:
      self.scope.leave()

    return buffer

  def compile_toplevel(self, node):
    buffer = Buffer()

    if node.data == "funcdef":
      name = node.children[0].value
      params = self.funcs[name].params

      buffer.emit("__{}:", name)

      for param in params:
        buffer.emit(
          "pop __{}_{}",
          self.scope.ndx, param
        )

      self.where = name

      buffer.emit(
        self.compile_block(
          node.children[2],
          *params
        )
      )

      buffer.emit(
        "push Z"
      )
      buffer.emit(
        "ret"
      )
    elif node.data == "vardec":
      name = node.children[0].value

      self.init_buffer.emit(
        self.compile_expr(node.children[1])
      )
      self.init_buffer.emit(
        "mov Y __0_{}",
        name
      )

      self.record_usage(f"__0__{name}")
    elif node.data in ("arrdec", "arrinit"):
      self.init_buffer.emit(
        self.compile_arrdec(node)
      )
    elif node.data == "asm":
      buffer.emit(
        self.compile_asm(node)
      )
    elif node.data == "include":
      filename = node.children[0].value[1:-1]

      if not os.path.isfile(filename):
        filename = os.path.join(os.getenv("WC_I"), filename)

      if not os.path.isfile(filename):
        raise Exception(f"No such file: '{os.path.basename(filename)}`.")

      if filename not in self.included_files:
        with open(filename, "r") as f:
          self.compile_program(f.read())

        self.included_files.add(filename)
    elif node.data == "varinit":
      pass
    else:
      raise Exception(f"Not implemented: {node}")

    return buffer

  def collect_toplevel(self, ast):
    for node in ast.children:
      if node.data == "funcdef":
        name = node.children[0].value

        if name in self.funcs:
          raise Exception(f"Duplicated function declaration: '{name}`.")

        self.funcs[name] = Func(
          len(node.children[1].children),
          tuple(map(lambda t: t.value, node.children[1].children))
        )
      elif node.data in ("varinit", "vardec", "arrinit", "arrdec"):
        name = node.children[0].value

        if name in self.scope:
          raise Exception(f"Duplicated top-level variable declaration: '{name}`.")

        self.scope.insert(name) # Because we're at the top-level rn.

  def compile_program(self, text):
    ast = self.parser.parse(text)

    #print(ast.pretty())

    self.collect_toplevel(ast)

    for node in ast.children:
      buffer = self.compile_toplevel(node)

      if node.data == "funcdef":
        self.compiled_funcs[node.children[0].value] = buffer
      else:
        self.buffer.emit(buffer)

  def compile(self, text):
    self.compile_program(text)

    for name in self.compiled_funcs:
      if self.is_used(name):
        self.buffer.emit(self.compiled_funcs[name])

        for param in self.funcs[name].params:
          self.record_usage(param)

    self.buffer = self.init_buffer + self.buffer + self.arrays_buffer

    for name in self.scope.names:
      if self.is_used(name):
        self.buffer.emit(
          "{}:0", name
        )

    if "main" not in self.funcs:
      raise Exception("Missing 'main` function.")

    self.buffer = self.buffer.optimize()

    return self.buffer.generate() + "\n"

wmc = WMC()

try:
  if len(sys.argv) == 3:
    with open(sys.argv[1], "r") as fin:
      with open(sys.argv[2], "w") as fout:
        fout.write(wmc.compile(fin.read()))
  else:
    sys.stdout.write(wmc.compile(sys.stdin.read()))
except Exception as e:
  #__import__('traceback').print_exc()

  print(e)

  sys.exit(1)