John Rose @ Sun: John Rose's weblog at Sun Microsystems

It is Autumn, and tail recursion is in the air. A JSR 292 colleague, Samuele Pedroni, just raised the question of how invokedynamic might interact with a tail call feature in the JVM. Here are a few thoughts on that subject, which I hope will provoke further discussion. The first few are (I think) not very controversial, but I try to get a little crazy toward the end. Where, do you suppose, is the boundary? [Read More]

I have written a paper for VMIL '09 on invokedynamic, which my fellow JVM and JIT geeks may find interesting:

Bytecodes meet Combinators: invokedynamic on the JVM
John Rose, VMIL '09 Workshop at OOPSLA, Orlando, October 2009

The focus of the paper is on evaluating the architectural effect of adding invokedynamic to JVM bytecodes. The description of JSR 292 is partial and provisional but I expect the part I have described is mostly stable. There is a lot of overview of (a) current implementation techniques for JVM languages, (b) how these techniques adapt to invokedynamic, and (c) how a JVM might optimize invokedynamic. The treatment is not specific to HotSpot. I hope it is useful to JVM teams and to dynamic language implementors.

Start with one generously sized conference room. Fill it to capacity with language and VM implementors. Stir vigorously for three days, folding in talks and workshops in successive layers. Garnish with professional videography. Yield: One JVM Language Summit, about 80 servings.

It's been wonderful so far, and I'm looking forward to the final day tomorrow. You can see what we've been talking about by clicking on the talk links in the agenda; most of the slide decks are uploaded there...[Read More]

If you (like me) are someone who actually enjoys contemplating the details of how languages turn into bytecodes and thence into wicked-fast machine code... If you lose sleep wondering about the joint future of programming languages and managed runtimes (especially the JVM)... If you think VM and language designers can save the world from a dystopian future of multi-core computers with no software to run on them... Please read the enclosed Call for Participation![Read More]

Christian Thalinger, Charlie Nutter, and I just finished a talk (my last of three!), called JSR 292 Cookbook. Thanks for your help, guys!

...I have posted the slides. The code examples are also on-line.[Read More]

It has been a busy day, of course. For those interested, I have posted the talk Brian Goetz and I gave on the Da Vinci Machine Project. We divided our attention between a “grand vision” of what VMs are and where they are going, and the exciting particulars of how invokedynamic and method handles work...[Read More]

Today’s talk at CommunityOne (San Francisco) about the Da Vinci Machine Project surveyed the history and status of the project to date. In the same spirit, I have updated the project page to include more pointers to recent talks, including my three talks this week at JavaOne. See you there!

I'm enjoying Microsoft's Lang.NET Symposium. Lars Bak just told us about the V8 JavaScript engine. As usual with his work, the virtues are overall simplicity, with a few careful choices about what to optimize. (The recipe is fixnums + stateful Self-like hidden classes + monomorphic inline caches + generational GC + simple JIT.) Here's the slide deck for my talk (up next) on new JVM features.

May 8 update: After the conference I enjoyed a video chat with Charles Torre of Microsoft Channel 9 about the Da Vinci Machine Project. Charles has posted a number of very good interviews from Lang.NET; check out those with Lars, Gilad, Anders, and Erik. Also, the Lang.NET organizers have posted synchronized slides and audio of the talks.

I was at the PyCon VM summit; it was great! There were about 20 talks (in the 10-20 minute range). Since "Sun" comes late in the alphabet, I had the pleasure of watching my fellow summiteers go first. When everybody was good and tired, I gave a presentation on the Da Vinci Machine Project. Here are some notes on a few of the other talks...[Read More]

JSR 292 is adding a fifth invocation instruction, invokedynamic. Like the other four invocation instructions, it is statically typed. What is new is that an invokedynamic instruction is dynamically linked under program control. In this blog, I will be giving “recipes” to demonstrate some of its applications. For today, here is a light aperitif showing how invokedynamic could be used to simulate the other invocation instructions. Caution: This blog post is for people who enjoy their bytecodes full strength and without mixers.[Read More]

Last week some Sun engineers and I invited our colleagues over to Sun Santa Clara to talk about the future of VMs and languages. We called the meeting the JVM Language Summit. It was a blast; I’d like to tell you why, and what I learned.

Pizza with extra MOP

Here are my top-level takeaways:

• The invokedynamic design is sound, but the exposition needs more work.
• The synergy of JSR 292 with Attila Szegedi’s MOP looks very promising.
• Interface injection is going to be helpful to a lot of people, and it is not hard to implement (on top of method handles).
• Tailcall and value types will never go away. We have to plan for them.
• Unless we do this sort of innovation on the JVM, crucial multicore research will move elsewhere.
• We have to do this again next year.

[Read More]

I have been working furiously this summer, patching the OpenJDK HotSpot JVM for the JSR 292 implementation of dynamic invocation.

In the wee hours of this morning, the JVM has for the first time processed a full bootstrap cycle for invokedynamic instructions, linking the constant pool entries, creating the reified call site object, finding and calling the per-class bootstrap method, linking the reified call site to a method handle, and then calling the linked call site 999 more times through the method handle, at full speed. The method names mentioned by the caller and the callee were different, though the signatures were the same. The linkage was done by random, hand-written Java code inside the bootstrap methdod.

The Email thread of the announcement is truly international, since Guillaume Laforge celebrated by sending virtual champagne.

The example code is included in the Email, and also posted (as a truly rebarbative test in a NetBeans project) with the patches. As for the JVM code, it only works on x86/32; the next step is to move the assembler code into the right files, and finish the support for x86/64 and SPARC.

Happy International Invokedynamic Day!

(And by a curious anagrammatic permutation of letters, it could also be International Davinci-Monkey Day. My co-workers, who watched me pounding on my keyboard all summer, claim to see some significance in this.)

Invited by some friends at Google, I went to Google I/O this week to find out about Android, and specifically their Java story. I went to a few talks and had some excellent chats with various colleagues.

Here are the top ten things I learned about Android and the Dalvik VM...[Read More]

After a successful meeting at JavaOne, the JSR 292 EG (expert group) has published its EDR (early draft review) for the invokedynamic instruction. This draft will be updated from time to time (in response to your comments), until August 17, which is the end of the 90-day review period. Check it out!

Update: There are some good conversations going on about the EDR at the jvm-languages Google group. Here are some rough changes to the EDR I will be proposing in response; the EG may choose to make these changes (or something like them) official with an EDR update pushed through the JCP (Java Community Process).

In the Java cosmos we can reckon time in terms of JavaOne conferences. For programming languages on the JVM, the just-finished epoch has seen much progress, and the next epoch looks even better. Here is some of the progress that I am excited about, after bouncing around at JavaOne...

In other news, today (May 10th) is National Train Day. On this day 139 years ago, a ceremonial golden spike was driven at Promontory Summit, Utah, joining the Central Pacific and Union Pacific railways into a single transcontinental line. The continent was very suddenly smaller, because people, goods, and mail could be moved more quickly from coast to coast, a task which was previously done with wagons, horses, and boats. In the years leading up to this watershed event, two railroads were built, with great difficulty and ingenuity, from each coast, to meet at Promontory Summit.

There is a Promontory Summit and a golden spike in our future also... [Read More]