Pure function for only some arguments

[Florian Weimer via Gcc-help <gcc-help@xxxxxxxxxxx>]

Is it possible to declare an extern function pure for just some
arguments?

To clarify, let's assume I have a function

  extern int *func (int);

and I want it to be pure for func (0), func (1), func (3), but not for
func (2).  Is this possible?

Will something like this work?

static inline int *
func (int i)
{
  if (i == 2)
    {
      extern int *func_alias_1 (int) __asm__ ("func");
      return func_alias_1 (i);
    }
  else
    {
      extern int *func_alias_2 (int) __asm__ ("func") __attribute__ ((pure));
      return func_alias_2 (i);
    }
}

Thanks,
Florian