[kaffe] JIT optimization questions

gonzo Robert.N.Gonzalez at williams.edu
Wed Jul 24 12:06:04 PDT 2002

in bytecode.h constants CHECKCAST_FAST and INSTANCEOF_FAST are declared,
and their only usage in the source code seems to be in code-analyse.c,
where their use is commented out!

so i have a few questions on our JIT compilation and proposed paths for

first, what, if any, code analysis is currently done for the JIT before
it's run (and where is that analysis done).

second, is there a good reference (or two) out there on JIT optimizations
and code analysis techniques used for them that someone could point me to.

third, if we plan on using the code analysis done at the verifier stage
for JIT optimization (as opposed to doing analysis for verification and
optimization in two separate steps), then it would make the verifier
plugin API that i was thinking of putting in useless and require us to go
with our own in-house verifier that adds the information required by the
JIT compiler.  what are the thoughts of everyone on this?  i personally
like the API idea (ie - do the verification and analysis for optimization 
completely separately) as it makes finding holes in the verifier much
easier for us.  though if we do decide to do all the analysis at the
same time, the authors of the verifier patch (which is almost 1.0.7 ready)
claim that their verifier is complete but too strict in the case of
implementing multiple interfaces (ie - it won't accept some code that it
should, but other than that it's fine) so we could use that as a
preliminary verifier in which to put our optimization analysis.

thanks :)

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