The method I talked about would work diffrent let me expand a little. I can imagen that jumping between two jits is problematic spezially if there is an interpreter throwen in. The method I talk about would use a simple method jit that generates assembly and the code to enable tracing. This compiler would not optimize anything only get rid of the interpreter overhead. Then the trace jit would jump in if it finds a worthy trace. There would be no switching between the two only from one to the other. In the LtU thread they talk about this too.

I don't read anywhere that the method-jit is better in optimizing, i only that the trace-jit dosn't find enought stuff to win. Once you have a good trace you can optimize it like crazy.

Mozilla seams to move in this direction, they have thrown out Tracemonky but in the longrun add one again and as far as I know the want to throw out spidermonky too. The diffrence would be that they would have more power in the method jit and less in the trace jit.

The reason I said that they would have reimplemented alot is that for the intepreter/simple-jit method and trace-jit to work well you need a nicly designed bytecode and I'm not sure they have one atm (I don't really know). There existing implmentation would have to be reworked to use a new bytecode.