def compile_while_statement(self, context: Context, root: TreeNode):
it = root.get_iterator()
label_count = context.next_label_count(Keyword.WHILE)
exp_label = f"WHILE_EXP{label_count}"
end_label = f"WHILE_END{label_count}"
self.writer.write_label(exp_label)
_ = Helper.eat_keyword(it, Keyword.WHILE)
# expression
_ = Helper.eat_symbol(it, "(")
expression = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, expression)
_ = Helper.eat_symbol(it, ")")
# check end condition
self.writer.write_arithmetic(ArithmeticCommand.NOT)
self.writer.write_if(end_label)
# statements
_ = Helper.eat_symbol(it, "{")
statements = Helper.eat_nonterminal(it, NonTerminalType.STATEMETNS)
self.compile_statements(context, statements)
# loop top
self.writer.write_goto(exp_label)
_ = Helper.eat_symbol(it, "}")
self.writer.write_label(end_label)
def compile_expression(self, context: Context, root: TreeNode):
"""term (op term)*
x
x + y
x + (y * z)
"""
it = root.get_iterator()
term = Helper.eat(it)
if not it.has_next():
self.compile_term(context, term)
else:
symbol = Helper.eat_symbol(it)
other = Helper.eat(it)
self.compile_term(context, term)
self.compile_term(context, other)
# handle operation
if symbol.token == "*":
self.writer.write_call("Math.multiply", 2)
elif symbol.token == "/":
self.writer.write_call("Math.divide", 2)
else:
# to avoid confusion with neg
if symbol.token == "-":
cmd = ArithmeticCommand.SUB
else:
cmd = ArithmeticCommand.from_symbol(symbol.token)
self.writer.write_arithmetic(cmd)
def compile_subroutine_body(self, context: Context, root: TreeNode):
it = root.get_iterator()
_ = Helper.eat_symbol(it, "{")
# variables
variables = []
nlocals = 0
while it.has_next():
node = Helper.eat(it)
if not NonTerminalType.VAR_DEC.is_same(node.name):
break
variables.append(node)
nlocals += Helper.count_variables(node)
self.writer.write_functions(context["function_name"], nlocals)
if context["function_type"] == Keyword.CONSTRUCTOR:
nfields = context["nfields"]
self.writer.write_push(Segment.CONSTANT, nfields)
self.writer.write_call("Memory.alloc", 1)
self.writer.write_pop(Segment.POINTER, 0)
elif context["function_type"] == Keyword.METHOD:
# push the first arugment = this to pointer 0
self.writer.write_push(Segment.ARGUMENT, 0)
self.writer.write_pop(Segment.POINTER, 0)
for var in variables:
self.compile_var_decl(context, var)
self.compile_statements(context, node)
_ = Helper.eat_symbol(it)
def compile_class(self, root: TreeNode):
if not Helper.is_nonterminal(root, NonTerminalType.CLASS):
raise SyntaxError(f"expect 'class' but got '{root.name}'")
context = Context()
it = root.get_iterator()
# should be 'class' keyword
_ = Helper.eat_keyword(it, Keyword.CLASS)
# class name
node = Helper.eat_identifier(it)
context["class"] = node.token
context["nfields"] = 0
# {
_ = Helper.eat_symbol(it, "{")
# TODO static
# TODO constructor
# TODO method
while it.has_next():
node = Helper.eat(it)
# class variables
if Helper.is_nonterminal(node, NonTerminalType.CLASS_VAR_DEC):
context["nfields"] += Helper.count_fields(node)
self.compile_class_var_decl(context, node)
continue
if Helper.is_symbol(node, "}"):
break
# print(node.name)
self.compile_subroutine(context, node)
def count_fields(cls, node: TreeNode) -> int:
if NonTerminalType.CLASS_VAR_DEC.is_same(node.name):
it = node.get_iterator()
k = Helper.eat_keyword(it)
if Helper.is_keyword(k, Keyword.FIELD):
return cls.count_variables(node)
else:
return 0
else:
raise ValueError
def compile_class_var_decl(self, context: Context, root: TreeNode):
it = root.get_iterator()
kwd = Helper.eat_keyword(it)
if Helper.is_keyword(kwd, Keyword.FIELD):
self.process_variable_decl(root, context.global_symbols,
SymbolKind.FIELD)
elif Helper.is_keyword(kwd, Keyword.STATIC):
self.process_variable_decl(root, context.global_symbols,
SymbolKind.STATIC)
else:
raise ValueError
def process_variable_decl(self, root: TreeNode, table: SymbolTable,
kind: SymbolKind):
it = root.get_iterator()
_ = Helper.eat_keyword(it)
type = Helper.eat(it).token
# name
while it.has_next():
name = Helper.eat_identifier(it).token
table.define(name, type, kind)
symbol = Helper.eat_symbol(it)
if symbol.token == ";":
break
def compile_parameter_list(self, context, root: TreeNode):
"""define arguments in local symbol table
int x, int y
"""
it = root.get_iterator()
while it.has_next():
type = Helper.eat(it).token
name = Helper.eat(it).token
context.local_symbols.define(name, type, SymbolKind.ARG)
if it.has_next():
_ = Helper.eat_symbol(it, ",")
else:
break
def compile_let_statement(self, context: Context, root: TreeNode):
it = root.get_iterator()
_ = Helper.eat_keyword(it, Keyword.LET)
# variable
identifier = Helper.eat_identifier(it)
name = identifier.token
symbol = context.lookup_symbol(name)
index = symbol.index
segment = Helper.symbol_kind_to_segment(symbol.kind)
# can be = or []
# a[i] = ...
# a =
# array
# push base_addr
# push index_expr
# add
# pop pointer 1 (THAT)
if Helper.is_symbol(Helper.eat_symbol(it), "["):
# push the variable
index_expr = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, index_expr)
self.compile_variable(context, identifier)
_ = Helper.eat_symbol(it, "]")
_ = Helper.eat_symbol(it, "=")
self.writer.write_arithmetic(ArithmeticCommand.ADD)
# rhs
expression = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, expression)
# stack (bottom)
# | addr of a[i] |
# | rhs |
# (top)
# *(a+i) = rhs
# copy the top to (result of rhs) to temp0
self.writer.write_pop(Segment.TEMP, 0)
# set THAT ot address of a[i]
self.writer.write_pop(Segment.POINTER, 1)
# pop rhs stored in temp
self.writer.write_push(Segment.TEMP, 0)
self.writer.write_pop(Segment.THAT, 0)
else:
# rhs
expression = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, expression)
# pop the stack top to the variable
self.writer.write_pop(segment, index)
def compile_expression_list(self, context: Context, root: TreeNode):
"""<expression> (, <expression>)*
"""
it = root.get_iterator()
# empty list
if not it.has_next():
return
# at least one expression
expression = next(it)
self.compile_expression(context, expression)
# more expressions
while it.has_next():
_ = Helper.eat_symbol(it, ",")
expression = next(it)
self.compile_expression(context, expression)
def compile_subroutine(self, context: Context, root: TreeNode):
"""
<function_type> <function_name>
{
(<var statement>)*
<statements>
}
"""
# clear context
context.clear_local_symbols()
context.clear_label_count()
it = root.get_iterator()
# expect 'constructor', 'function' or 'method
node = Helper.eat_keyword(it)
function_type = Keyword.from_str(node.token)
context['function_type'] = function_type
return_type: TreeNode = Helper.eat(it)
context["return_type"] = return_type.token
function_name = f"{context['class']}.{Helper.eat_identifier(it).token}"
# skip symbol
_ = Helper.eat_symbol(it, "(")
# parameters
parametert_list = Helper.eat_nonterminal(
it, NonTerminalType.PARAMETER_LIST)
nargs = Helper.parameter_size(parametert_list)
self.compile_parameter_list(context, parametert_list)
# skip symbol
_ = Helper.eat_symbol(it, ")")
# 'function' instruction needs the number of local variables.
# delegate it to compiler of subroutine body.
context["function_name"] = function_name
# subroutine body
body = Helper.eat_nonterminal(it, NonTerminalType.SUBROUTINE_BODY)
self.compile_subroutine_body(context, body)
# moved out of function. remove it!
del context["function_name"]
del context["function_type"]
del context["return_type"]
context.clear_local_symbols()
def compile_return_statement(self, context: Context, root: TreeNode):
it = root.get_iterator()
_ = Helper.eat_keyword(it)
if context["return_type"] == "void":
# push dummy
self.writer.write_push(Segment.CONSTANT, 0)
elif context["function_type"] == Keyword.CONSTRUCTOR:
# expect return this;
expr = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
term = Helper.eat_nonterminal(expr.get_iterator(),
NonTerminalType.TERM)
_ = Helper.eat_keyword(term.get_iterator(), Keyword.THIS)
self.writer.write_push(Segment.POINTER, 0)
else:
expr = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, expr)
self.writer.write_return()
def compile_do_statement(self, context: Context, root: TreeNode):
"""calls a function returning nothing
"""
# need a symbol table here!
it = root.get_iterator()
_ = Helper.eat_keyword(it, Keyword.DO)
# method call
# do foo(x, y)
# static function call
# do Output.printInt(123)
# method call
# do p1.dist(p2)
# in any case, start with identifier
self.compile_call(context, it)
# remove dummy return value
self.writer.write_pop(Segment.TEMP, 0)
def compile_term(self, context: Context, root: TreeNode):
"""
x
-x
((x+y)*2)
Memory.peek(8000)
variable
"abcdefg"
"""
it = root.get_iterator()
node = Helper.eat(it)
# integer constant
if node.is_terminal() and node.token_type == TokenType.INT_CONST:
value = int(node.token)
self.writer.write_push(Segment.CONSTANT, value)
# string constant
elif node.is_terminal() and node.token_type == TokenType.STRING_CONST:
self.compile_string_const(context, node)
# unary operation
elif Helper.is_symbol(node, "-"):
term = Helper.eat_nonterminal(it, NonTerminalType.TERM)
self.compile_term(context, term)
self.writer.write_arithmetic(ArithmeticCommand.NEG)
elif Helper.is_symbol(node, "~"):
term = Helper.eat_nonterminal(it, NonTerminalType.TERM)
self.compile_term(context, term)
self.writer.write_arithmetic(ArithmeticCommand.NOT)
# boolean
elif Helper.is_keyword(node, Keyword.TRUE):
# push -1
self.writer.write_push(Segment.CONSTANT, 0)
self.writer.write_arithmetic(ArithmeticCommand.NOT)
elif Helper.is_keyword(node, Keyword.FALSE):
self.writer.write_push(Segment.CONSTANT, 0)
# null
elif Helper.is_keyword(node, Keyword.NULL):
# push -1
self.writer.write_push(Segment.CONSTANT, 0)
# this
elif Helper.is_keyword(node, Keyword.THIS):
self.writer.write_push(Segment.POINTER, 0)
# expression enclosed by parentheses
elif Helper.is_symbol(node, "("):
expression = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
self.compile_expression(context, expression)
_ = Helper.eat_symbol(it, ")")
elif Helper.is_identifier(node):
if it.has_next():
# is array?
nxt = it.current_value()
if Helper.is_symbol(nxt, "["):
# index
_ = Helper.eat(it)
expr = Helper.eat_nonterminal(it,
NonTerminalType.EXPRESSION)
self.compile_expression(context, expr)
self.compile_variable(context, node)
_ = Helper.eat(it)
# address = base address + index
self.writer.write_arithmetic(ArithmeticCommand.ADD)
# THAT
self.writer.write_pop(Segment.POINTER, 1)
# push *that
self.writer.write_push(Segment.THAT, 0)
# otherwise should be function call
else:
self.compile_call(context, root.get_iterator())
# variable
else:
self.compile_variable(context, node)
else:
print("term not defined: ", root)
def compile_if_statement(self, context: Context, root: TreeNode):
"""
<expr>
if-goto IFTRUE
goto IFFLASE
label IFTRUE
<true_statements>
goto IFEND
label IFFALSE (else)
<false_statements>
label IFEND
"""
it = root.get_iterator()
# labels
n = context.next_label_count(Keyword.IF)
if_true_label = f"IF_TRUE{n}"
if_false_label = f"IF_FALSE{n}"
if_end_label = f"IF_END{n}"
has_else = False
# if (expr)
_ = Helper.eat_keyword(it, Keyword.IF)
_ = Helper.eat_symbol(it, "(")
expr = Helper.eat_nonterminal(it, NonTerminalType.EXPRESSION)
_ = Helper.eat_symbol(it, ")")
# if true statements
_ = Helper.eat_symbol(it, "{")
true_statements = Helper.eat_nonterminal(it,
NonTerminalType.STATEMETNS)
_ = Helper.eat_symbol(it, "}")
# else statement (optional)
if it.has_next():
has_else = True
_ = Helper.eat_keyword(it, Keyword.ELSE)
_ = Helper.eat_symbol(it, "{")
false_statements = Helper.eat_nonterminal(
it, NonTerminalType.STATEMETNS)
_ = Helper.eat_symbol(it, "}")
self.compile_expression(context, expr)
if has_else:
self.writer.write_if(if_true_label) # if-statement
self.writer.write_goto(if_false_label) # else-statement
# true
self.writer.write_label(if_true_label)
self.compile_statements(context, true_statements)
self.writer.write_goto(if_end_label)
# false
self.writer.write_label(if_false_label)
self.compile_statements(context, false_statements)
self.writer.write_label(if_end_label)
else:
self.writer.write_if(if_true_label) # if-statement
self.writer.write_goto(if_false_label) # else-statement
# true
self.writer.write_label(if_true_label)
self.compile_statements(context, true_statements)
self.writer.write_label(if_false_label)