JavaScript:ActionMonkey

ActionMonkey is the code-name for the project to integrate Tamarin and SpiderMonkey as part of Mozilla 2.

Want to help? Write to jason dot orendorff at gmail dot com. Or visit irc://irc.mozilla.org/jslang and say hi.

Goals

The goals are:

• Preservation (with necessary additions and as few deletions as possible) of jsapi.h.
• SpiderMonkey's thread safety and property tree integrated/reimplemented in Tamarin.
• Replacement of SpiderMonkey's decompiler with a better decompiler that can work with ABC.
• Replacement of SpiderMonkey's GC with Tamarin:MMgc, evolved as needed.
• Replacement of SpiderMonkey's interpreter by an evolved version of Tamarin's.
• Advanced JIT optimization for hot paths and untyped code, inspired by Trace Trees.
• Information flow VM support for better security models.

The ActionMonkey development environment

All ActionMonkey work is happening in the http://hg.mozilla.org/actionmonkey and http://hg.mozilla.org/actionmonkey-tamarin Mercurial repositories.

(These repositories are a hard hat area, one step removed from the primary mozilla-central repository. This is because we expect things will break intermittently. Also because some of the people working on this aren't CVS committers yet, myself included. -jorendorff)

How to build: Things work slightly differently in Mercurial land. You'll want to be familiar with building in CVS first. After you're comfortable with that, try this:

• Install Mercurial. (On Mac with MacPorts, sudo port install mercurial)
• Install Python 2.4 or later. (sudo port install python24)
• hg clone http://hg.mozilla.org/actionmonkey
• cd actionmonkey
• python client.py
• Then build as you normally would.

You should be able to build a working JS shell, Firefox, or other app this way. If it doesn't work for you, please file a bug with "ActionMonkey" in the summary and assign it to jorendorff.

Stage 0

Replace SpiderMonkey's GC with Tamarin's GC (MMgc). See JavaScript:ActionMonkey:Stage 0 Whiteboard.

Stage 1

Integrate SpiderMonkey more closely with MMgc.

• Make MMgc::Mark() call SpiderMonkey trace() methods. The plan is to add a per-page type tag to MMgc; this takes over the job of the type bits in SpiderMonkey's GCThingFlags.

• Get rid of js_GetGCThingFlags.
  • The type bits: move to an MMgc page-level type tag. (Note: The cycle collector sneakily uses these, in nsXPConnect.cpp; it will be changed.)
  • The GCF_LOCK bit: mainly replaced by allowing MMgc to scan rt->gcLocksHash. There is also a string optimization that uses this bit. It's yet to be determined what to do about that.
  • The GCF_MUTABLE bit: move into JSString.
  • The GCF_SYSTEM bit: To be determined.

• Drop weak roots, newborns, and local root scopes (if they're not already gone in stage 0). These will be replaced by MMgc's conservative stack scanning.