static final Map<Class, _MethodCache> callOpt_cache = newDangerousWeakHashMap();

static O callOpt_cached(O o, S methodName, O... args) ctex {
  if (o == null) null;
  
  if (o instanceof Class) {
    Class c = (Class) o;
    _MethodCache cache = callOpt_getCache(c);
    
    // TODO: (super-rare) case where method exists static and non-static
    // with different args
    
    Method me = cache.findMethod(methodName, args);
    if (me == null || (me.getModifiers() & Modifier.STATIC) == 0) null;
    ret invokeMethod(me, null, args);
  } else {
    Class c = o.getClass();
    _MethodCache cache = callOpt_getCache(c);

    Method me = cache.findMethod(methodName, args);
    if (me == null) null;
    ret invokeMethod(me, o, args);
  }
}

// no longer synchronizes! (see #1102990)
static _MethodCache callOpt_getCache(Class c) {
  _MethodCache cache = callOpt_cache.get(c);
  if (cache == null)
    callOpt_cache.put(c, cache = _MethodCache(c));
  ret cache;
}

Began life as a copy of #1005583