Inlining heuristic trouble

[John Rose]

On Jun 20, 2011, at 1:11 PM, Mark Roos wrote:

> So we do not have a path that can be assumed to be not taken (except the last in the chain). 
> 
> Perhaps in the JVM this is a poor choice for implementation of a small polymorphic inline cache.  Here I defer to the real experts 

Both monomorphic and polymorphic inline caches are a central use case for invokedynamic.  For more details and references, see the VMIL paper linked here:
  http://blogs.oracle.com/jrose/entry/vmil_paper_on_invokedynamic

See section 5, "Case Study: Inline Caches and invokedynamic".

A small (non-megamorphic) polymorphic cache can be represented as a cascade or decision tree of GWT combinators, probably with a control block of some sort that can rebalance from time to time.

A megamorphic call site can be represented using the class pattern of a two-step dispatch plus indirect function call. The foldArguments combinator is intended to support this pattern.  (You fold some arguments together, yielding a MH to prepend to the argument list, and then you jump to an invoker.)  This can support vtable or metaclass dispatches, or more subtle ones like the CLOS dispatch via a hash of relevant argument attributes.

(I'm getting hungry for Remi's cookbook, because it will have this sort of example in it nicely worked out.)

-- John