@stedolan doesn't this PR suggest an alternative fix for #1345 that would degrade performances less? Instead of completely disabling the cache lookup (that is currently inlined within generated code), maybe you could define its logic as a function in CamlinternalOO?

(I'm planning to eventually merge this (in trunk only), but would like to leave a few days for people to chime in if they wish to.)

I agree that the approach in stedolan/ocaml-afl-persistent#2 is promising-but-work.

Using this approach as an alternative to #1345 is challenging. Since class initialisation imports an arbitrary amount of stuff from the current environment, it can't easily be pulled out to a library function (at least, not without allocating a new closure, which would defeat the point of the optimisation). For instance, compiling fun a b c -> object method a = a method b = b method c = c end results in the following lambda:

(let
  (shared/1326 =a [0: #"a" #"b" #"c"]
   shared/1319 =a [0: #"c" #"b" #"a"]
   class_tables/1307 =a (makemutable 0 0a 0a 0a))
  (function a/1290 b/1291 c/1292
    (funct-body //toplevel//(1):0-62
      (before //toplevel//(1):13-62
        (let (cached/1325 =a class_tables/1307)
          (seq
            (if (field 0 cached/1325) 0a
              (let
                (class/1311 =
                   (apply (field 15 (global CamlinternalOO!)) shared/1326)
                 env_init/1322 =
                   (... complicated code mentioning a, b, c ...))
                (seq (apply (field 16 (global CamlinternalOO!)) class/1311)
                  (setfield_ptr 0 cached/1325 env_init/1322))))
            (let (envs/1324 =a (makeblock 0 c/1292 b/1291 a/1290))
              (apply (field 0 cached/1325) envs/1324))))))))