assembler.py 文件源码

def jump(self, op, arg=None):
        def jump_target(offset):
            target = offset
            if op not in hasjabs:
                target = target - (posn + 3)
                if target < 0:
                    raise AssertionError("Relative jumps can't go backwards")
                if target > 0xFFFF:
                    target = offset - (posn + 6)
            return target

        def backpatch(offset):
            target = jump_target(offset)
            if target > 0xFFFF:
                raise AssertionError("Forward jump span must be <64K bytes")
            self.patch_arg(posn, 0, target)
            self.branch_stack(offset, old_level)

        if op == FOR_ITER:
            old_level = self.stack_size = self.stack_size - 1
            self.stack_size += 2
        else:
            old_level = self.stack_size
        self.stack_size -= (op in (JUMP_IF_TRUE_OR_POP, JUMP_IF_FALSE_OR_POP))
        posn = self.here()
        if arg is not None:
            self.emit_arg(op, jump_target(arg))
            self.branch_stack(arg, old_level)
            lbl = None
        else:
            self.emit_arg(op, 0)

            def lbl(code=None):
                backpatch(self.here())
        if op in (JUMP_FORWARD, JUMP_ABSOLUTE, CONTINUE_LOOP):
            self.stack_unknown()
        return lbl