On Friday, 13 January 2012 at 16:02 , Antonio Cuni wrote:

> Hello Michał,
>  
> On 01/12/2012 09:24 PM, Michał Bendowski wrote:
> > Hello everyone,  
> >  
> > Back in the summer I asked on this mailing list if there's interest in 
> > moving the JVM backend forward. Back then there was some enthusiasm, so I 
> > got back to it when I had the chance, which unfortunately was a few months 
> > later. The suggestion back then was to look into using JPype to integrate 
> > more closely with Java-side code, and that's what I would like to do.
> >  
> > But before that, I noticed that the JVM backend fails to translate the 
> > standard interpreter and spent some time lately getting to know the code 
> > and trying to get it to work. What I have right now is a version that 
> > outputs valid Jasmin files, which unfortunately still contain some invalid 
> > bytecodes (longs vs ints from what I've seen, I'll look into it next).
>  
> the long vs int problems are likely due to the fact that you are translating
> on a 64 bit machine. The translator toolchain assumes that the "native" long
> type of the target platform is the same as the source one, but this is not the
> case if you are targeting the JVM (where long is 32 bit) on a 64 bit linux
> (where long is 64 bit).
>  
> This problem is not easily solvable, so my suggestion is just to translate
> pypy-jvm inside a 32bit chroot for now.
>  
> > It would be awesome if someone could take a look at my changes. What's the 
> > best way to submit them? Bitbucket pull requests? They will need to go 
> > through some review - do you have a workflow for that?
>  
> we don't have any precise workflow, although a bitbucket pull request might be
> the easiest thing to do. I'll be glad to review it.
>  
> > Here's a short list of stuff I found and fixed (hopefully):
> > - support the ll_getlength method of StringBuilders in ootype,
> > - make compute_unique_id work on built-ins (StringBuilders again).
>  
>  
>  
> not sure what you mean here. What is the relation between compute_unique_id
> and StringBuilder?
>  
> > - provide oo implementations (or stubs) for pypy__rotateLeft, 
> > pypy__longlong2float etc.
> > - handle rffi.SHORT and rffi.INT showing up in graphs. For now I try to 
> > emit something that makes sense (seemed easier), but the right solution is 
> > probably to see if the code in question (rbigint, rsha) can be implemented 
> > on the java level.
>  
>  
>  
> yes, this is another issue that has been around for a long time. In theory, we
> would like to be able to write per-backend specific code which overrides the
> default implementation. This would be useful for rbigint and rsha, but also
> e.g. for rlib.streamio. However, we never wrote the infrastructure to do that.
>  
> > - handle the jit_is_virtual opcode - I had no idea how to "safely ignore" 
> > it for now, is False the safe answer?
>  
> yes. Look at translator/c/funcgen.py:848: this is how jit_is_virtual is
> implemented by the C backend, you can see that it always returns 0/
>  
> > I hope someone can help me to submit the changes and maybe guide with 
> > further work.
>  
> Please put your work on bitbucket, I'll review it. I'd greatly appreciate if
> you committed small checkins (one for each fix/feature you are doing) instead
> of one giant commit with all the changes :-)



OK, I got myself a 32bit environment and created the pull request (. I'll be 
grateful for any feedback. One thing I didn't do was to create regression tests 
against the problems I found - I didn't know where to put the tests and what 
(and how) exactly to test. If you can shed some light on it, that would be 
awesome.

Here's the URL: 
https://bitbucket.org/pypy/pypy/pull-request/19/improvements-to-the-jvm-backend

Thank you,

Michał
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