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From Egor Pasko <egor.pa...@gmail.com>
Subject Re: [general] Google Android
Date Fri, 30 Nov 2007 06:45:27 GMT
On the 0x39E day of Apache Harmony Dan Bornstein wrote:
> > I wonder if there any possibility of code reuse
> > between DRLVM and Dalvik.
> >
> > Which chances have JIT, GC, a verifier, or any other part of DRLVM to
> > be reused?
> 
> If the JIT or verifier are based on the bytecode you might find in a
> typical .class file, then I doubt those components will be reusable.
> Dalvik uses a different bytecode. We already verify it, and if/when we
> do a JIT, the JIT would be taking Dalvik bytecode / .dex files as
> input.

In case some Android phone runs on an x86 processor (doubtful,
but..why not?), we could reuse the optimizing code-generator from
Harmony JIT (Jitrino). It uses register-based IR, so writing a
translator from .dex should be fairly simple.

Though, it is reasonable for Android to start from IR-less JIT like
Jitrino.JET. And I see no obvious field for reuse here. So, it is too
early to speak about reusing Harmony JIT in Android.

> Our allocator today is a fairly simple one built on top of dlmalloc. I
> know we will want something a bit more complex at some point, and the
> DRLVM related code very well may fit the bill. The overriding concerns
> we will have will be minimizing memory overhead and maximizing cache
> locality. We already know, for example, that we will want to do stuff
> to ensure that we can have a (section of the) heap which is shared
> copy-on-write between processes, but where running gc wouldn't force a
> copy; this means that mark bits would have to be segregated from the
> objects that are being marked.
> 
> > Are you interested in developing common runtime building
> > blocks in Apache?
> 
> Put perhaps overly bluntly: I am interested in shipping a good solid
> Android 1.0. I am also interested in sharing as much of the Android
> work as makes sense. But shipping is my #1 priority.
> 
> -dan
> 

-- 
Egor Pasko


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