How to deal with branch prediction when using a switch case in CPU emulation

Question

I recently read the question here Why is it faster to process a sorted array than an unsorted array? and found the answer to be absolutely fascinating and it has completely chan

Answer 1

I thought I'd add something since no one mentioned it.

Granted, the indirect jump is likely to be the best option.

However, should you go with the N-compare way, there are two things that come to my mind:

First, instead of doing N equality compares, you could do log(N) inequality compares, testing your instructions based on their numerical opcode by dichotomy (or test the number bit by bit if the value space is near to full) .This is a bit like a hashtable, you implement a static tree to find the final element.

Second, you could run an analysis on the binary code you want to execute. You could even do that per binary, before execution, and runtime-patch your emulator. This analysis would build a histogram representing the frequency of instructions, and then you would organize your tests so that the most frequent instructions get predicted correctly.

But I cant see this being faster than a medium 15 cycles penalty, unless you have 99% of MOV and you put an equality for the MOV opcode before the other tests.