def _compile_if_statement(self, node: ParseTreeNode):
condition_node = node.get_child("bool")
self.oreo_to_tac(condition_node)
condition_is_false_label = Label('if_false')
# IfZ a Goto L1;
# > result=L1 op=IfFalseGoto, arg1=a
self._add_instruction(
arg1=condition_node.result,
op=IF_FALSE_GOTO,
result_var=condition_is_false_label
)
# the if statement was true
self.oreo_to_tac(node.get_child("compound"))
if node.has_child("optional_else"):
end_of_else_block_label = Label('else_end')
# if condition held, skip the else block
self._add_goto_instruction(end_of_else_block_label)
# the else block
self.program.append(condition_is_false_label)
self.oreo_to_tac(node.get_child("optional_else"))
self.program.append(end_of_else_block_label)
else:
# there's no else block: if condition doesn't hold, just jump down here
self.program.append(condition_is_false_label)
def _compile_print_expression(self, node: ParseTreeNode):
if node.has_child("GET"):
return self._add_instruction(
op="GET"
)
else:
self._add_instruction(
result_var=node.get_child("expression").result,
op=node.get_a_child(["PRINT", "PRINTLN"]).content.token.name
)
return "NULL RESULT"
def oreo_to_tac(self, node: ParseTreeNode):
if hasattr(node, "result"):
return # this node has already been processed, no need to do it again
if node.is_non_terminal("p"):
# ignore the top level program declaration, just process the program compound itself
self.oreo_to_tac(node.get_child("compound"))
return
# if statements and while loops are carefully compiled in order, so the right things are in the right labels
elif node.is_non_terminal("i"):
self._compile_if_statement(node)
return
elif node.is_non_terminal("w"):
self._compile_while_statement(node)
return
for child in node.children:
self.oreo_to_tac(child)
if node.is_terminal("NUMBER") or node.is_terminal("STRING"):
literal = node.content.token.attribute
if node.is_terminal("NUMBER"):
literal = int(literal)
node.result = NodeResult(literal=literal)
elif node.is_terminal("TRUE") or node.is_terminal("FALSE"):
bool_literal = TRUE_TAC if node.is_terminal("TRUE") else FALSE_TAC
node.result = NodeResult(literal=bool_literal)
elif node.is_terminal("ID"):
node.result = NodeResult(variable=self._get_variable(node.content.token.attribute, create=True))
elif node.is_in(["term", "factor", "simple_expr", "compare_expr", "bool"]):
node.result = self._compile_optional_combiner(node)
elif node.is_non_terminal("expression"):
node.result = self._compile_optional_combiner(node, specific_combiners=["and_or_b"])
elif node.is_non_terminal("a"):
self._compile_assignment(node.get_child("ID"), node.get_child("expression"))
elif node.is_non_terminal("v") and node.has_child("var_assign"):
self._compile_assignment(node.get_child("ID"), node.get_child("var_assign").get_child("expression"))
elif node.is_non_terminal("pr"):
node.result = self._compile_print_expression(node)
if hasattr(node, "result"):
assert isinstance(node.result, NodeResult)
else:
node.result = "NULL RESULT" # to prevent reprocessing processed nodes which do not have a result
def _analyse(node: ParseTreeNode, scope):
node.scope = scope
if node.is_non_terminal("function_definition"):
_analyse_func_definition(node)
elif node.is_non_terminal(
"v"): # variable declaration, with optional assignment
_analyse_variable_assignment(node, scope, is_declaration=True)
elif node.is_non_terminal(
"a"): # assignment of an already declared variable
_analyse_variable_assignment(node, scope, is_declaration=False)
elif node.is_non_terminal("pr") and node.has_child(
"GET"): # assign declared variable to user input
_analyse_variable_assignment(node, scope, is_declaration=False)
elif node.is_terminal("ID"):
scope.use_var(node)
elif node.children:
for child in node.children:
_analyse(child, scope)