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From "Nick Lothian" <nloth...@educationau.edu.au>
Subject RE: JIT vs. WAT
Date Fri, 13 May 2005 03:03:21 GMT
> Nick Lothian wrote:
> >>GCJ begins to fall short where you wish to use Java's dynamic 
> >>loading/linking capabilities.  Classes must be loaded
> > 
> > Most modern Java programs make extensive use of dynamic loading & 
> > linking, and that usage is increasing.
> > 
> > Recent releases of the Sun VM have put a lot of emphasis on 
> speeding 
> > up the performance of reflection and this has been one of the big 
> > performance boosters in these VMs.
> IMHO both JITs and pre-compiling have their place.. it 
> depends on the application whether one is definitely better 
> than the other.
> Ideally, the design of harmony would allow for people to 
> pursue both approaches and the two could coexist peacefully. 
> E.g., it may be common for people to precompile all of the 
> core classes, leaving everything else for runtime. This is 
> where a well thought out design can lead to a very powerful 
> and flexible system...
> there will be people who care about optimizing their 
> particular scenario, and hopefully all such people can 
> contribute to make the overall system more valuable to everyone, etc.
> Just rambling here.. imagine a "code object" contained 
> executable machine code plus meta-data describing the 
> assumptions behind any optimizations taken. Then the 
> filesysytem could contain pre-compiled code objects that 
> could be used, if appropriate, at runtime. New code objects 
> would be created at runtime by the JIT, and optionally cached.
> Then the core VM becomes just a code object executor. It 
> calls out to the JIT, the "JIT cache", etc. on demand and 
> provides any relevant runtime information, etc.

JRockit does this, see:


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