[maemo-developers] Java acceleration/Jazelle

[From: Simon Pickering]

Hi Scott (& all),

> The following describes an experiment I suggested:
> Create an array with opcodes 204 to 255 in it.  Create one handler for
> all opcodes.
> Set up R14 to point to opcode 204.
> Set up R12 to your handler.
> Push the address you want to return to onto the stack.
> Write your handler in C and printf to the console what opcode you are
> handling as long as the opcode is <= 253.  Setup R14 to point to the
> next opcode, and R12 to point to your handler.  For opcodes 254, 255 pop
> the return address off the stack and continue.
>
> I believe this will chew through all the opcodes in the array, dumping
> output to the console until opcode 254 is encountered.  At that point
> execution of Java bytecodes will stop.  This should occur whether
> Jazelle is enable or not.

I sat down and wrote a bit of code that I hope will do this 
(eventually). The one issue I've not sorted out yet is how to print 
something to the screen from assembly. Is there some secret incantation 
(CALL for example), or do I need to define my own printf function in 
assembly)?

http://people.bath.ac.uk/enpsgp/nokia770/jazelle/test_jazelle7.c

> Simon, you have done a great deal of work, and gotten quite far.   Good
> work!

Many thanks and thank you for your detailed summary of the patent, it's 
good to have you on board,


Simon