[kaffe] Differences between JIT and JIT3

Jeremy Brown jbbrown at fastmail.us
Mon Mar 15 15:48:04 PST 2004

I think I can answer some of what you asked. JIT is older and not as 
good. JIT3 is "better" (faster?) and newer. I don't really know any more 
details than that. JIT3 isn't available on all platforms. For example, I 
am using an Alpha machine, and there is no JIT3 for that yet. When you 
configure, it configures for one or the other (or neither if nobody's 
implemented either for your platform). Unless you specify otherwise (eg 
--with-engine=INTRP), it will automatically decide whether to use JIT3, 
JIT, or INTRP. As I understand it, you get one or the other when you 
compile. They don't mix and you can't specify which you want at runtime.

I make no guarantees as to the absolute accuracy of what I've said, but 
I think most of it's right :-) I know I didn't get to a lot of those 
details you mentioned. I'm sure other people can give more detail if 


Ben Stephenson wrote:

>I'm wondering if someone can point me at a document that summarizes the
>differences between the JIT and JIT3 configurations.  Failing that, could
>someone take a minute and briefly comment on any differences in
>implementation strategy, optimizations performed, frequency of application
>(ie does one only get applied to 'hot' methods and one get applied on
>first invocation of the method) and performance.
>Any help would be greatly appreciated.
>Ben Stephenson
>ben at csd.uwo.ca
>bdstephe at csd.uwo.ca
>kaffe mailing list
>kaffe at kaffe.org

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