[maemo-developers] Java acceleration/Jazelle

[From: Simon Pickering]

Hi all,

Sebastian, in this link:

> You can find a small example in my jalimo slides from linuxtag2007
> (slide 33ff).
> 
> http://www.jalimo.org/wiki/doku.php?id=news:linuxtag2007 

(direct link:
http://www.jalimo.org/documents/jalimo-slides_english_linuxtag2007.pdf)

Did you make a typo in your declaration (on p34) of int code[]? Should this not
be unsigned char code[] as bytecodes are 1x byte not n x byte long (I'm assuming
you're running on a machine with sizeof(int)>1)? Just wondering if this is a
typo when you were writing the presentation or whether it might have affected
your results. On the other hand it may be my misunderstanding the declaration.

> It might be possible to test at least some aspects of my 'new improved' 
> theory. The one that comes to mind is to try a BXJ to an unhandled Java 
> instruction immediately. This should then branch back to whatever ARM 
> code is at R12 straight away (not needing to know the pointer table 
> base address). This could prove a number of things, including 
> the stack pointer, R12 & R14 contents, etc.

I've written a piece of test code, but not tested it yet (no compiler here at
work). I must admit that I've only learned extended inline asm this week, so it
may not work correctly ;). If anyone spots any mistakes, please let me know.

http://people.bath.ac.uk/enpsgp/nokia770/jazelle/test_jazelle.c
http://people.bath.ac.uk/enpsgp/nokia770/jazelle/to_compile_do_this.txt

I'll post some results tomorrow/later on, one way or the other.

Cheers,


Si