"compiled" js - what's the current state of this?

Is there a page listing what does and doesn't work with compiled js?

I know that method calls aren't supported, but loops and if/then are, but right now the specifics are scattered among a bunch of threads. I'm wondering if there's a page that

I've been making another push on the 433 mhz communication with those cheap modules, and this is going to inevitably bring me back to receiving on an Espruino.

Also, what is the current situation w/regards to using compiled JS for IRQ?

This is the function that I was using as the watch before, and which I was hoping could be made faster, as an example of what I'd like to compile.

function sigOff(e) {
  var d=e.time-e.lastTime;
  if (d>0.0005 && d<0.0013) n+=d>0.0008?1:0;
  else{
    n="";
  }
  if (n.length==z)  parseRx(n);
}