Gameboy Emulation in Javascript and HTML5

I did this last year: http://daeken.github.com/Dyna6502Asm/

I took the awesome 6502 emulator from http://6502asm.com/ and converted it to accumulate instructions from each basic block, turn them into functions, caches them, and let the JIT do its magic. While I never benchmarked it, I'd say it got between a 5x and 20x speedup on most things. It breaks certain self-modifying code (never bothered to add cache invalidation), but overall it works well.

Am I misunderstanding or does his "tracing" stop at the basic block level? While basic blocks are completely predictable traces through the program, they are usually very short. You can get much more benefit by finding long common traces through multiple basic blocks and compiling the whole thing as a unit, providing tests and/or fixup code in case you find you actually needed to branch somewhere else in the middle of a trace. This is what I think most compiler people would call a "tracing JIT."

It'll be a lot less than 10 years. We can already play Quake2 running on JavaScript in the browser.

http://tatari.se:8080/GwtQuake.html