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from back.tac import *
from front.scope import Scope
class Register(object):
__shared_state = {}
__current_function = None
__function_registers = {}
count = 0
def __init__(self):
self.__dict__ = self.__shared_state
def new(self):
self.count += 1
self.__function_registers[self.__current_function].append(self.count)
return self.count
def set_function(self, name):
self.__current_function = name
self.__function_registers[self.__current_function] = []
def get_registers(self, name):
return self.__function_registers[name]
class Generator(object):
def __init__(self):
self.tac_list = TACList()
self.__op_list = []
def emit(self, op, tac = None):
if tac:
self.__op_list[self.__op_list.index(tac)] = op
else:
self.__op_list.append(op)
# this cde will appear before every function
# sets bp, pushes used registers and variables
def generate_prologue(self, name):
Scope().set_function(name)
self.emit(Label(name))
self.emit("PUSH bp")
self.emit("ADD bp, r0, sp")
for variable in Scope().get_variables()[1]:
self.emit("PUSH r0")
for register in Register().get_registers(name):
self.emit("PUSH r%d" % register)
# this code will appear after every function
# restores registers, sp, bp
def generate_epilogue(self, name):
for variable in Scope().get_variables()[1]:
self.emit("POP r0")
Register().get_registers(name).reverse()
for register in Register().get_registers(name):
self.emit("POP r%d" % register)
Register().get_registers(name).reverse()
self.emit("ADD sp, r0, bp")
self.emit("POP bp")
self.emit("RET")
def generate(self):
# pass 1 - generate ops, but not labels yet
for tac in self.tac_list:
if isinstance(tac, TAC):
if tac.op in [Op.ADD, Op.SUB, Op.MUL, Op.DIV, Op.MOD, Op.AND, Op.OR]:
self.emit("%s r%d, r%d, r%d" % (tac.op, tac.arg1, tac.arg1, tac.arg2))
elif tac.op == Op.NOT:
self.emit("CMP r%d, r0" % tac.arg1)
self.emit("EQ r%d" % tac.arg1)
elif tac.op == Op.MINUS:
self.emit("SUB r%d, r0, r%d" % (tac.arg1, tac.arg1))
elif tac.op in [Op.STORE, Op.LOAD]:
offset = Scope().get_variable_offset(tac.arg1)
op = {Op.STORE: "SW", Op.LOAD: "LW"}[tac.op]
self.emit("%s bp, r%d, %d" % (op, tac.arg2, offset * 4))
elif tac.op == Op.MOV:
self.emit("MOV r%d, %d" % (tac.arg1, tac.arg2))
elif tac.op == Op.CMP:
self.emit("CMP r%d, r%d" % (tac.arg1, tac.arg2))
elif tac.op in [Op.EQ, Op.NE, Op.LT, Op.LE, Op.GE, Op.GT]:
self.emit("%s r%d" % (tac.op, tac.arg1))
elif tac.op in [Op.BEZ, Op.JMP]:
self.emit(tac)
elif tac.op in [Op.PUSH, Op.POP]:
self.emit("%s r%d" % (tac.op, tac.arg1))
elif tac.op == Op.CALL:
self.emit(tac)
self.emit("ADD r%d, r0, rv" % tac.arg2)
elif tac.op == Op.RETURN:
self.emit("ADD rv, r0, r%d" % tac.arg1)
self.emit(tac)
elif tac.op == Op.PRINT:
r = Register().new()
self.emit("PUSH r%d" % tac.arg1)
self.emit("MOV r%d, %d" % (r, 1))
self.emit("PUSH r%d" % r)
self.emit("SYS")
self.emit("POP r0")
self.emit("POP r0")
elif tac.op == Op.SYS:
self.emit("SYS")
else:
raise Exception("%s is not a valid TAC operator" % tac.op)
elif isinstance(tac, FunctionPrologue):
self.generate_prologue(tac.name)
elif isinstance(tac, FunctionEpilogue):
self.generate_epilogue(tac.name)
elif isinstance(tac, Label):
self.emit(Label(tac.name))
else:
raise Exception("%s is not a valid TACList element" % repr(tac))
# pass 2 - generate label ops (ignores still present labels)
for op in self.__op_list:
if isinstance(op, TAC):
if op.op == Op.BEZ:
offset = self.get_label_offset(op.arg2, op)
self.emit("BEZ r%d, %d" % (op.arg1, offset), op)
elif op.op == Op.JMP:
offset = self.get_label_offset(op.arg1, op)
self.emit("JMP %d" % offset, op)
elif op.op == Op.CALL:
offset = self.get_label_offset(op.arg1, op)
self.emit("CALL %d" % offset, op)
elif op.op == Op.RETURN:
offset = self.get_label_offset("L%d" % op.arg2, op)
self.emit("JMP %d" % offset, op)
# pass 3 - remove labels
self.__op_list = filter(lambda x: not isinstance(x, Label), self.__op_list)
# pass 4 - replace the pseudo registers with their register numbers
def replace_pseudo_regs(op):
regs = Register().count
bp = "r%d" % (regs + 1) # base pointer
sp = "r%d" % (regs + 2) # stack pointer
rv = "r%d" % (regs + 3) # return value
return op.replace("bp", bp).replace("sp", sp).replace("rv", rv)
self.__op_list = map(replace_pseudo_regs, self.__op_list)
self.__op_list = [".REGS %d" % Register().count] + self.__op_list
# finally, print the generated code
print "\n".join(self.__op_list)
# find the line number to which the given label leads
def get_label_offset(self, name, tac):
tac_index = 0
for op in self.__op_list:
if isinstance(op, Label):
continue
if op == tac:
break
tac_index += 1
name_index = 0
for op in self.__op_list:
if isinstance(op, Label):
if op.name == name:
return name_index - tac_index
continue
name_index += 1
raise Exception("label %s does not exist" % name)
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