[m2m-dev] Re: [ATL] Adding operation to ATL VM

[Dennis Wagelaar <dennis.wagelaar@xxxxxxxxx>]

Hmm, perhaps this kind of information is better posted on the 
development mailing list: m2m-dev@xxxxxxxxxxx

I'll add it in CC...

Eric MAES schreef:
> Are there some limitations adding operations to the ATL VM ?
> What are the consequences of addind a huge amount of operations ?
>
> I'd like to add about thousand simple operations to the ATL VM. Does 
> anyone has tried such an experience and can tell me about his feeling on 
> ATL's possibilities and behavior ?
>
> Thanks,
> Regards

I assume you mean adding VM instructions? I found that the biggest 
performance factor in the standard ATL VM is the creation of stackframes 
with every method invocation. Interpreting instructions only plays a 
small part.

Of course, there are currently only 22 instructions, which are 
interpreted through a big if-then statement inside a while loop in the 
ASMOperation class. I'm afraid that this solution does not scale up to 
1000 instructions.

You may try to refactor the current approach to a more object-oriented 
approach with an interpreter pattern. You can extend the ASMInstruction 
and ASMInstructionWithOperand classes with new subclasses for each 
instruction (in their own "instr" package, probably).

The behaviour for each instruction can be implemented in the instruction 
class itself and ASMOperation only needs to call instr.exec(frame). 
Instruction parsing is then done only once when the asm file is loaded. 
ASMInstruction objects are created by the ASMEmitter class. Probably a 
good idea to add an ASMInstructionFactory class that creates the correct 
object for each mnemonic.

This may be a lot of work, but you probably need to do this if you don't 
want the runtime transformation performance to become worse.

Regards,
Dennis