Earlier quoted context omitted.
Hot currently is defined as "function called more than X times" and "function contains a loop that took a backedge more than Y times". So it is defined per-function basis. I can hardly speculate how V8 will behave on some abstract application. That is really highly dependent on how code looks like. But ultimately V8 will try to optimize everything that falls under criteria outlined above.
I see, thanks. I ask because performance of small benchmarks has been quite good, except for the uint32 issue mentioned above, often around 3x slower than native code - but on very large codebases it is often much slower, and I do not know why.
Unfortunately (as you probably know yourself) I don't have a magical answer that would speed everything up. As for V8 there is quite a number of limits that you might be hitting with generated code (e.g. number of locals, size of the function etc) and there can be some bugs or non-done-yet thingies affecting performance. Profiling and looking at the generated code (and filing bugs) is the only suggesting I can give here.