[maemo-developers] Java acceleration/Jazelle

[From: Sebastian Mancke]

Hi Simon,

sincerely I don't found the time to test your code yet.

> 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)?
This is not a typo. I don't understand the reason, but it had only
worked with the integer array, not with bytes - don't know why.

--Sebastian

Simon Pickering schrieb:
> 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
> 


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