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From Steve Blackburn <Steve.Blackb...@anu.edu.au>
Subject Re: Other interesting papers and research
Date Tue, 24 May 2005 11:08:05 GMT
shudo@computer.org wrote:

>>They automatically build themselves
>>simple JIT backends (by extracting fragments produced by the ahead of
>>time compiler).  This sounds like a great way to achieve portability
>>while achiving better performance than a conventional interpreter.
>>    
>>
>
>I guess it's a bit better or just comparable with a good interpreter.
>  
>
They say it is a lot better: "speedups of up to 1.87 over the fastest 
previous interpreter based technique, and performance comparable to 
simple native code compilers. The effort required for retargeting our 
implementation from the 386 to the PPC architecture was less than a 
person day."

>In 1998, I have written such a JIT compiler concatinate code fragments
>generated by GCC for each JVM instruction.
>
Very interesting!

>Unfortunately, the JIT was
>slightly slower than an interpreter in Sun's Classic VM. The
>interpreter was written in x86 assembly language and implements
>dynamic stack caching with 2 registers and 3 states. It performs much
>better than the previous interpreter written in C.
>
>Then I rewrote the JIT.
>  
>
It would be interesting to hear your perspective on Ertl & Gregg's 
approach.  Did they do something you had not done?  Do they have any 
particular insight?  You are in an excellent position to make a critical 
assessment of their work.

>I am not very sure which is better for us, having a portable and so-so
>baseline compiler or a good interpreter which is possibly less
>portable than the compiler. There will be a trade off between memory
>consumption, portability and so on.
>  
>
Ideally we will have both as components and the  capacity to choose 
either or both depending on the build we are targetting.

Cheers,

--Steve

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