On Tue, 11 Jul 2006, Charles O Nutter defenestrated me: > > Been thinking through compilation a bit more. Here's a little > pseudo-bytecode for the fib function. > def fib: arity 1 > PUSH local var 2 > PUSH literal 2 > CALL '<' arity 1 > JMP_FALSE to XX > PUSH local var 2 > RETURN > XX: PUSH local var 2 > PUSH literal 2 > CALL '-' arity 1 > FCALL 'fib' arity 1 > PUSH local var 2 > PUSH literal 1 > CALL '-' arity 1 > FCALL 'fib' > CALL '+' > RETURN > end > It's obviously modeling a stack-based machine rather than > register-based, which makes sense since we'll be running on a Java VM. > It's also not far off from what the actual Java bytecodes would look > like; the big difference is the calls for <, -, + and so on (which > really just increases the number of calls) and the fact that there's > no typing (which just means everything is an IRubyObject, i.e. a Java > reference type). Coming up with the bytecode isn't really the hard > part though...it's properly traversing the AST to execute in the > proper order. For example, we can't do any of the calls before we > determine the receiver and the arguments, but the call nodes are > encountered first. The current interpreter recurses to handle that, > traversing the receiver and arg nodes before returning to make the > call, but the compiler will want to receive the nodes serially. > For those of you keeping score, the ruby "bytecodes" CALL and FCALL > above could eventually translate to INVOKEDYNAMIC JVM calls. The > trouble with INVOKEDYNAMIC is that you still need to have the method > on a Java class somewhere, and you can't move methods around once the > class is generated. It might, however, be possible to replace old > classes with new when they're modified ( i.e. for every reopening of a > class), but it would be VERY important to keep that class churn to a > minimum. The dynamic-invoked classes would have to just be method bags > though, since you can't change the type of an instantiated object (and > therefore couldn't associate it with the new generated class).
During Gilad's JSR292 talk at JavaOne he mentioned the idea that a special flag could be added to a class definition so it is marked as dynamic. This would allow replacement/addition/removal of methods. The extra flag would be a cue that all this crazy stuff can happen in that particular class. He stated this is only a wild idea he has not put much thought into. He also mentioned allowing a low level handler to be invokable when method_missing happens. -Tom -- + http://www.tc.umn.edu/~enebo +---- mailto:[EMAIL PROTECTED] ----+ | Thomas E Enebo, Protagonist | "Luck favors the prepared | | | mind." -Louis Pasteur | ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Jruby-devel mailing list Jruby-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jruby-devel
