[arch] JIT interfaces

[Shih-wei Liao <li...@gmail.com>]

I would like to find out how other Harmony developers want to solve
some basic JIT/VM interfacing.  One area is stack maps for precise
enumeration of live object references.  There are many options on how
the VM and JIT can handle this info.  For example, the JIT can store
the stack maps internally, then produce a list of live references on
the stack when requested.  Another approach would be to cache the
stack map info in the VM.

We cache the stack map info in the VM.  VM only handles the storage,
but JIT controls the interpretation.  The rationale is that we want to
let JIT focus on compilation, not on storage.  However, since JIT
controls the interpretation, unified format on stack map is not
required.  It may be beneficial for multiple JITs to agree on a
format.  Does anyone know how other open source JVMs do the above?

  Thanks,
    Steve Liao, Intel

Re: [arch] JIT interfaces

[Archie Cobbs <ar...@dellroad.org>]

Shih-wei Liao wrote:
> We cache the stack map info in the VM.  VM only handles the storage,
> but JIT controls the interpretation.  The rationale is that we want to
> let JIT focus on compilation, not on storage.  However, since JIT
> controls the interpretation, unified format on stack map is not
> required.  It may be beneficial for multiple JITs to agree on a
> format.  Does anyone know how other open source JVMs do the above?

JCVM performs conservative scanning of the thread stacks, to
generate a root set, and then exact GC after that. This keeps
things simple.

-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com