Re: wip-rtl native closure creation

[Stefan Israelsson Tampe <stefan.itampe@gmail.com>]

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Hi,

When code is both VM and native it's nice to be able to have both code
blocks as a unit because then
we can freely compile a function without needing to do graph analysis. It
simply makes the life easier to maintain the two setups. And incrementally
compile to native on a per uses base and not in one go very much like JIT
ing. Also the overhead on the VM side is low but the native execution will
of cause be a
little bit slower because of an extra indirection. I don't expect the
slowdown to be too bad though. Perhaps we could mark the beginning of a
code block in a program as

0     -> the rest of the vector is VM code
1     -> the rest of the vector is Native code
addr -> there is native code at the addr indirection

Then we can skip the expensive extra inderection for native code when
suitable.
To note here I assume that picking a[0],a[1] is less expensive then
a[0],*a[0].

At some stage we may leave the VM and perhaps enter into a Native only
mode. Then we can restructure.

/Stefan

On Mon, Aug 6, 2012 at 11:32 AM, Andy Wingo <wingo@pobox.com> wrote:

> On Sun 05 Aug 2012 17:19, Stefan Israelsson Tampe <stefan.itampe@gmail.com>
> writes:
>
> > Probably it is best to have the first qword / dword in the code to be
> > 0 or the native adress e.g. I propose to add that feature to the
> > rtl-branch.
>
> Good question!  Given the different tradeoffs, that seems workable.
> Another possibility would be to use a different TC7 for native
> procedures.  After all, the only calls we need to make cheaply are
> native->native and bytecode->bytecode, and the rest can go through a
> general dispatch loop (possibly with inline caching).  WDYT?  (Also note
> that RTL words are 32 bits wide, which may or may not be sufficient for
> native code pointers.)
>
> Andy
> --
> http://wingolog.org/
>

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