JavaScript:SpiderMonkey:GC Futures

JS GC Futures

Brain-dump of work items:

• Speed up allocator
• Speed up collector
• Remove byte flag per thing design

 * Bad cache effects of flags and things allocated from opposite ends of same arena
 * Don't want generality of different thing-types allocated from same size class
   * Can put finalizer or other index/info in the pool, not in each flag's low bits
   * Compress flags to mark bit in bitmap?

• Add new JNI-like (handles, "clothed" not "naked") global rooting API
• Make old JS global rooting API be #ifdef JS_NAKED_GC_ROOTS (enabled at first)
• Convert mozilla-central to use new global rooting API
• Disable JS_NAKED_GC_ROOTS
• Write barrier for all code including JITted code
• Write barrier in API
• Fast generational copying allocation and collection