def _while(env, args):
if len(args) < 2:
raise CompileTimeError, 'while -- Missing blocks %r' % args
pred = args[0]
codes = args[1:]
# create some labels
loop_start_label = NewLabel('loop_start')
loop_next_label = NewLabel('loop_next')
loop_end_label = NewLabel('loop_end')
env.while_stack.append((loop_start_label, loop_end_label))
env.emit(tac.label(loop_start_label))
# emit code for looping
tmp_pred = env.eval_(pred)
if not tmp_pred.can_cast_to_type('int'):
print 'WARNING: while -- casting %r to boolean type' % tmp_pred
env.print_block()
# loop labels
env.emit(tac.cbranch(tmp_pred.tacn, loop_next_label))
env.emit(tac.branch(loop_end_label))
env.emit(tac.label(loop_next_label))
ret_val = env.exec_block(codes) # XXX: the block need to know how to jump
# out of this loop! hmm... a stack?
env.emit(tac.branch(loop_start_label))
env.emit(tac.label(loop_end_label))
env.while_stack.pop() # remove while stack
# while should not have a return value... things should be changed
# by side effects. this is what loops are intended to do
return obtype.Token('void')
def _cond(env, args):
to_ret = []
# tac preparations
pred_labels = [NewLabel('case') for i in xrange(len(args))]
block_labels = [NewLabel('iftrue') for i in xrange(len(args))]
else_label = NewLabel('else')
final_label = NewLabel('final')
final_result = NewVar()
# for each predicate and code block:
for i, pred_todo in enumerate(args):
if len(pred_todo) == 1: # no todo?
raise CompileTimeError, 'cond -- Missing code block '\
'after predicate %r' % (pred_todo)
pred = pred_todo[0]
codes = pred_todo[1:]
# XXX: here i dont check whether the else is placed at the last
if isinstance(pred, obtype.Token) and pred.symbolp() \
and pred.n == 'else': # is else
env.emit(tac.label(else_label))
ret_val = env.exec_block(codes)
env.emit(tac.assign(final_result, ret_val.tacn))
else: # is predcate
if i != 0:
env.emit(tac.label(pred_labels[i])) # at case i
pred = env.eval_(pred) # eval and emit code block
if not pred.can_cast_to_type('int'):
print 'WARNING: cond -- casting %r to boolean type' % pred
env.print_block()
env.emit(tac.cbranch(pred.tacn, block_labels[i])) # if true
if i == len(args) - 1:
# is the last case. XXX: somehow dirty..
env.emit(tac.branch(final_label))
elif isinstance(args[i + 1][0], obtype.Token) and \
args[i + 1][0].n == 'else':
env.emit(tac.branch(else_label))
else: # still have more cases to check
env.emit(tac.branch(pred_labels[i + 1]))
env.emit(tac.label(block_labels[i])) # exec block
ret_val = env.exec_block(codes)
env.emit(tac.assign(final_result, ret_val.tacn))
env.emit(tac.branch(final_label))
to_ret.append(ret_val)
# cond over, the final label
env.emit(tac.label(final_label))
if not to_ret:
return obtype.Token('void')
else:
first = to_ret[0]
first.tacn = final_result # it's created on the fly so dont worry
# about the side effect ^ ^
for item in to_ret:
if not first.can_cast_to(item):
print 'WARNING: cond -- returning different types: %r %r' % (
first, item)
env.print_block()
return first