Just some trivial spots I found recently:

• Some of those promoteToFullBuild (and analogously named) methods can be made private since they aren't used in child classes
• Removed dead import import org.jruby.EvalType;
• Fixed logger for MixedModeIRBlockBody (it was using the wrong class to bind to)
• Removed two redundant sets of the callcount to -1 (callCount = -1; is not necessary since context.runtime.getJITCompiler().buildThresholdReached(context, this); will do this:

    public void buildThresholdReached(ThreadContext context, final Compilable method) {
        final RubyInstanceConfig config = context.runtime.getInstanceConfig();

        // Disable any other jit tasks from entering queue
        method.setCallCount(-1);

=> sets the -1 here either way.