def p_term(p):
"""
term : ASTERISK term %prec DE_REF
| AMPERSAND ID %prec ADDR_OF
| ID
"""
global global_symbol_table, symbol_table_stack
if len(p) == 2:
try:
_id = p[1]
sym = access_variable_symbol(_id, global_symbol_table,
symbol_table_stack)
p[0] = ASTNode('VAR', _id), sym.type, sym.deref_depth
except KeyError:
panic('Symbol accessed without declaration')
elif len(p) == 3:
if p[1] == '*':
child_ast_node, _type, deref_depth = p[2]
if deref_depth == 0:
panic('Symbol de-referenced too many times')
node = ASTNode('DEREF', '*%s' % child_ast_node.value)
node.append_child(child_ast_node)
p[0] = node, _type, deref_depth - 1
elif p[1] == '&':
try:
_id = p[2]
sym = access_variable_symbol(_id, global_symbol_table,
symbol_table_stack)
node = ASTNode('ADDR', '&%s' % _id)
id_node = ASTNode('VAR', _id)
node.append_child(id_node)
p[0] = node, sym.type, sym.deref_depth + 1
except KeyError:
panic('Symbol accessed without declaration')
def p_return_statement(p):
"""
return_statement : RETURN expression SEMICOLON
| RETURN SEMICOLON
|
"""
global symbol_table_stack, global_symbol_table
fun = symbol_table_stack[-1]
fun_type = fun.type
fun_deref_depth = fun.deref_depth
if len(p) == 4:
ast_node, _type, deref_depth = p[2]
if fun_type != _type or fun_deref_depth != deref_depth:
panic('Improper return type in function implementation')
node = ASTNode('RETURN', 'return')
node.append_child(ast_node)
p[0] = node, True
elif len(p) == 3 or len(p) == 1:
if fun_type != 'void':
panic('Improper return type in function implementation')
node = ASTNode('RETURN', 'return')
if len(p) == 3:
p[0] = node, True
elif len(p) == 1:
p[0] = node, False
def p_while_block(p):
"""
while_block : WHILE L_PAREN compound_condition R_PAREN if_else_while_common_body
"""
while_block = ASTNode('WHILE', 'while')
while_block.append_child(p[3])
while_block.append_child(p[5])
p[0] = while_block
def p_if_block(p):
"""
if_block : IF L_PAREN compound_condition R_PAREN if_else_while_common_body
| IF L_PAREN compound_condition R_PAREN if_else_while_common_body ELSE if_block
| IF L_PAREN compound_condition R_PAREN if_else_while_common_body ELSE if_else_while_common_body
"""
if_block = ASTNode('IF', 'if')
if_block.append_child(p[3])
if_block.append_child(p[5])
if len(p) == 8:
if_block.append_child(p[7])
p[0] = if_block
def p_if_else_while_common_body(p):
"""
if_else_while_common_body : SEMICOLON
| assignment SEMICOLON
| L_CURLY body R_CURLY
"""
if len(p) == 2:
p[0] = ASTNode('BODY', 'body')
elif len(p) == 3:
body = ASTNode('BODY', 'body')
body.append_child(p[1])
p[0] = body
elif len(p) == 4:
p[0] = p[2]
def p_compound_condition(p):
"""
compound_condition : compound_condition LOGICAL_AND compound_condition
| compound_condition LOGICAL_OR compound_condition
| L_PAREN compound_condition R_PAREN
| EXCLAMATION L_PAREN compound_condition R_PAREN
| EXCLAMATION condition
| condition
"""
if len(p) == 4:
if p[2] == '&&':
node = ASTNode('AND', '&&', p[1].is_constant and p[3].is_constant)
node.append_child(p[1])
node.append_child(p[3])
p[0] = node
elif p[2] == '||':
node = ASTNode('OR', '||', p[1].is_constant and p[3].is_constant)
node.append_child(p[1])
node.append_child(p[3])
p[0] = node
elif p[1] == '(' and p[3] == ')':
p[0] = p[2]
elif len(p) == 3:
node = ASTNode('NOT', '!', p[2][0].is_constant)
node.append_child(p[2][0])
p[0] = node
elif len(p) == 5:
node = ASTNode('NOT', '!', p[3].is_constant)
node.append_child(p[3])
p[0] = node
elif len(p) == 2:
p[0] = p[1][0]
def p_function_term_r(p):
"""
function_term_r : ASTERISK function_term_r
| ID
"""
# p[0] = ast_node, id, deref_depth
if len(p) == 2:
_id = p[1]
p[0] = ASTNode('VAR', _id), _id, 0
elif len(p) == 3:
child_ast_node, _id, deref_depth = p[2]
node = ASTNode('DEREF', '*%s' % child_ast_node.value)
node.append_child(child_ast_node)
p[0] = node, _id, deref_depth + 1
def p_arg_list_non_empty(p):
"""
arg_list_non_empty : arg_list_non_empty COMMA expression
| expression
"""
# p[0] := ast_node, [(type, deref_depth, arg_index), ...]
if len(p) == 2:
expr_ast_node, _type, deref_depth = p[1]
node = ASTNode('ARG_LIST', 'arg_list')
node.append_child(expr_ast_node)
arg_list = [(_type, deref_depth, 0)]
p[0] = node, arg_list
elif len(p) == 4:
node, arg_list = p[1]
expr_ast_node, _type, deref_depth = p[3]
node.append_child(expr_ast_node)
current_arg = [(_type, deref_depth, len(arg_list))]
arg_list = arg_list + current_arg
p[0] = node, arg_list
def p_func_expr(p):
"""
func_expr : ID L_PAREN arg_list R_PAREN
"""
if len(p) == 5:
_id = p[1]
func_symbol = None
arg_list_ast_node, arg_types = p[3]
if global_symbol_table.symbol_exists(_id):
func_symbol = global_symbol_table.get_symbol(_id)
if func_symbol.is_function():
param_list = func_symbol.its_child_table.get_param_signature()
if param_list != arg_types:
panic('Function %s arguments are mismatched' % _id)
else:
panic('Symbol %s is not a function' % _id)
else:
panic('Function called without declaration %s' % _id)
node = ASTNode('FUNCTION_CALL', 'function_call')
id_node = ASTNode('VAR', p[1])
node.append_child(id_node)
node.append_child(arg_list_ast_node)
p[0] = node, func_symbol.type, func_symbol.deref_depth
def p_assignment(p):
"""
assignment : ID EQUALS expression
| ASTERISK term EQUALS expression %prec DE_REF
"""
global no_assignments
no_assignments += 1
global global_symbol_table, symbol_table_stack
if len(p) == 4:
# ID = expr
expr_ast_node, expr_type, expr_deref_depth = p[3]
if expr_ast_node.is_constant:
panic(
'Constant cannot be assigned directly without de-referencing')
_id = p[1]
lhs_symbol = None
try:
lhs_symbol = access_variable_symbol(_id, global_symbol_table,
symbol_table_stack)
except KeyError:
panic('Symbol %s accessed without declaration' % _id)
if lhs_symbol.deref_depth == 0:
panic('Scalar %s cannot be directly assigned' % _id)
if lhs_symbol.type != expr_type or lhs_symbol.deref_depth != expr_deref_depth:
panic('Type mismatch while assigning %s' % _id)
id_node = ASTNode('VAR', _id)
node = ASTNode('ASGN', '=')
node.append_child(id_node)
node.append_child(expr_ast_node)
p[0] = node
elif len(p) == 5:
term_node, term_type, term_deref_depth = p[2]
expr_ast_node, expr_type, expr_deref_depth = p[4]
if term_deref_depth <= 0:
panic('Symbol de-referenced too many times')
if term_type != expr_type or term_deref_depth - 1 != expr_deref_depth:
panic('Type mismatch at assignment')
asterisk_node = ASTNode('DEREF', '*%s' % term_node.value)
asterisk_node.append_child(term_node)
node = ASTNode('ASGN', '=')
node.append_child(asterisk_node)
node.append_child(expr_ast_node)
p[0] = node
def p_expression_uminus(p):
"""expression : MINUS expression %prec U_MINUS"""
child_ast_node, _type, deref_depth = p[2]
node = ASTNode('UMINUS', '-', child_ast_node.is_constant)
node.append_child(child_ast_node)
p[0] = node, _type, deref_depth
def p_expression_binary_op(p):
"""
expression : expression PLUS expression
| expression MINUS expression
| expression ASTERISK expression
| expression DIVIDE expression
"""
left_child_node, left_type, left_deref_depth = p[1]
right_child_node, right_type, right_deref_depth = p[3]
if left_type != right_type or left_deref_depth != right_deref_depth:
panic('Type mismatch for operation %s' % p[2])
if left_deref_depth != 0:
panic('Pointer Arthmatic is not allowed')
if p[2] == '+':
node = ASTNode(
'PLUS', '+', left_child_node.is_constant
and right_child_node.is_constant)
node.append_child(left_child_node)
node.append_child(right_child_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '-':
node = ASTNode(
'MINUS', '-', left_child_node.is_constant
and right_child_node.is_constant)
node.append_child(left_child_node)
node.append_child(right_child_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '*':
node = ASTNode(
'MUL', '*', left_child_node.is_constant
and right_child_node.is_constant)
node.append_child(left_child_node)
node.append_child(right_child_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '/':
node = ASTNode(
'DIV', '/', left_child_node.is_constant
and right_child_node.is_constant)
node.append_child(left_child_node)
node.append_child(right_child_node)
p[0] = node, left_type, left_deref_depth
def p_condition(p):
"""
condition : expression EE expression
| expression NE expression
| expression GE expression
| expression GT expression
| expression LE expression
| expression LT expression
"""
left_ast_node, left_type, left_deref_depth = p[1]
right_ast_node, right_type, right_deref_depth = p[3]
if left_type != right_type or left_deref_depth != right_deref_depth:
panic('Type mismatch at boolean operator %s' % p[2])
if left_deref_depth != 0:
panic('Pointer Comparision is not allowed')
if p[2] == '==':
node = ASTNode(
'EQ', '==', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '!=':
node = ASTNode(
'NE', '!=', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '>=':
node = ASTNode(
'GE', '>=', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '>':
node = ASTNode(
'GT', '>', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '<=':
node = ASTNode(
'LE', '<=', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
elif p[2] == '<':
node = ASTNode(
'LT', '<', left_ast_node.is_constant
and right_ast_node.is_constant)
node.append_child(left_ast_node)
node.append_child(right_ast_node)
p[0] = node, left_type, left_deref_depth
def p_function_implementation(p):
"""
function : function_head L_PAREN param_list R_PAREN L_CURLY body return_statement R_CURLY
"""
global symbol_table_stack
global global_symbol_table
current_symbol_table = symbol_table_stack[-1]
type_node, id_node, _id, _type, deref_depth = p[1]
param_list_node = p[3]
body_node = p[6]
return_node, return_existence = p[7]
if _id == 'main':
if len(param_list_node.children) != 0:
panic('main function cannot have parameters')
if return_existence:
panic('main function cannot have return statement')
if not global_symbol_table.symbol_exists(_id):
# New function implementation
symbol = Symbol(_id,
_type,
Symbol.GLOBAL_SCOPE,
deref_depth,
its_child_table=current_symbol_table,
is_prototype=False)
global_symbol_table.add_symbol(symbol)
symbol_table_stack.pop()
else:
existing_symbol = global_symbol_table.get_symbol(_id)
if not existing_symbol.is_function():
# Existing symbol is not a function
panic('Function implementation : Symbol already exists')
else:
if existing_symbol.is_prototype:
if existing_symbol.type == _type and existing_symbol.deref_depth == deref_depth:
param_symbols1 = current_symbol_table.get_param_signature()
param_symbols2 = existing_symbol.its_child_table.get_param_signature(
)
if param_symbols1 == param_symbols2:
symbol = Symbol(_id,
_type,
Symbol.GLOBAL_SCOPE,
deref_depth,
its_child_table=current_symbol_table,
is_prototype=False)
prototype_symbol_tables.append(
(_id, existing_symbol.its_child_table))
global_symbol_table.add_symbol(symbol)
symbol_table_stack.pop()
else:
# Params mismatch
panic('Params mismatch in function implementation')
else:
# Return type mismatch
panic('Return type mismatch')
else:
# Already implemented function
panic('Multiple function implementation')
function_node = ASTNode('FUNCTION', _id)
type_node_val = type_node.value
for i in range(deref_depth):
type_node_val = '*' + type_node_val
type_node.value = type_node_val
function_node.append_child(type_node)
function_node.append_child(id_node)
function_node.append_child(param_list_node)
function_node.append_child(body_node)
function_node.append_child(return_node)
p[0] = function_node