Godmar Back wrote:
| 
| >
| > JIT, in general, should be faster than interpreted.  However, there is
| > overhead: the JIT must compile the code to begin with.  If it takes longer
| > for the JIT to run than you save on the code, then overall, JIT will be
| > slower.  That's why newer VMs such as Sun's HotSpot only JIT when they "know"
| > that a method will be frequently used.
| 
| Well, if we ever get Senthil Kumar's efforts on integrating intrp and jit,
| kaffe will have that too.

I would be interested in integrating intrp and jit for other reasons:
- Debugging: debugging JIT is too machine-dependent, so debug intrp only,
  but it may call JIT methods.
- Faster intrp: use the JIT engine to re-write the bytecode into a different
  bytecode that can be interpreted 2-4x faster.

[ Re: pre-JIT ]

| The not-so-weird way how this will work is by using egcs's gcj Java front-end.
| Other groups (HP India) have already reported success in combining egcs-
| generated code with their VMs.
| 
| With Cygnus's run-time library being rooted in an earlier version of Kaffe 
| (Per Bothner used to be contributor to Kaffe), this should certainly be
| possible.  Tim tried it and reported partial success a few months ago.
| 
| If anybody wanted to tackle this project, it would be very welcome.
| At this point, the difficulty is that Cygnus hasn't published the interfaces
| to their run-time lib yet, so you'll have to look hard at the egcs source and 
| at the assembly code generated by egcs to find out what they are.
| Also, exception handling is done differently.  But that would be a very,
| very useful project.  For extra credit, create documentation of the
| interfaces.

I see two ways that this can be done:

1. Use egcs/gcj to make native-method versions of everything, assuming that
   its output can conform to the JNI.

2. Make an add-on to kaffe that does JIT to produce PIC, then re-write the
   class files, embedding the PIC in an attribute instead of the original
   bytecode.  The resulting class file will sit with compilers and other
   java tools (except for javap/javad) just fine, but only kaffe can execute
   it.

I'd rather not delve into the bowels of ecgs - trying to figure out something
by looking at that code is not easy.