Unable to compile IcedTea with CACAO under Fedora 17

[Greg Johnson]

>>No, they're using the same VM.  The problem is that Raspberry Pi
>>doesn't support the Thumb2 instruction set, and the ARM JIT in OpenJDK
>>needs it.  I've been hoping that some day a brave soul will come along
>>and convert the Thumb2 JIT to generate ARM code instead of Thumb2
>>code, but there haven't been any takers.

Under Debian, I have this:
# java -version
java version "1.6.0_18"
OpenJDK Runtime Environment (IcedTea6 1.8.13) (6b18-1.8.13-0+squeeze1)
OpenJDK Zero VM (build 14.0-b16, mixed mode)


Under Fedora, I have this:
# java -version
java version "1.7.0_b147-icedtea"
OpenJDK Runtime Environment (fedora-2.1.fc17.6-arm)
OpenJDK Zero VM (build 22.0-b10, interpreted mode)


Both are using Zero VM, but with different modes. Then I received this explanation from the Raspberry Pi forums:
--------------------------------------
The main reason why you see a magnitude difference in the Debian vs Fedora results really boils down to that there exist two variants of Zero.

In Fedora you have installed OpenJDK Zero VM (build 22.0-b10, interpreted mode)
This is using the C++ interpreter only.

In Debian you have installed OpenJDK Zero VM (build 14.0-b16, mixed mode)
The "mixed mode" version contains two addons, designed by Edward Nevill, on top of the generic Zero C++ interpreter, a rewritten interpreter main loop in ARM assembly this speeds up the jvm about a factor x3 this do benefit the Pi.
The "mixed mode" also include a Thumb2 JIT that improves speed for ARMv7 cores and later, the Pi could benefit from this JIT if it got rewritten from Thumb2 to target generic ARM or Thumb1 assembly.

-----------------------------------------

The Thumb2 info is out of my league. However, the disparity on performance was drastic, thus I searched out other avenues. Cacao was suggested, so I thought I'd try it out. Since it won't compile on 32bit x86, I have no hope of compiling it on ARM. I guess my search continues.... :-(  Stefan suggested JamVM as a possibility. Off I go. :-)
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