I'm curious if anyone here has any good resources (papers, or things of that sort) on empirical data about what works and what doesn't in an ISA. It seems to me that a lot of arguments about instruction set design rely on intuition and received wisdom. Sometimes that's helpful and sometimes it isn't. I've been doing a (admittedly, cursory) literature review on this subject and was surprised just how seemingly little publicly available information there is.

When I say "empirical data" I mean specifically things like, how large immediates you actually need, what kind branching ops actually get used (i.e. do we need the full gamut of integer comparisons, or are equals/does not equal zero enough?), &c.

The question re: immediate size is especially interesting to me. The only real data I could find on this is from H&P and as far as I could see they don't really delve into their methodology. What they do show suggests that the log2 of immediates is bimodal which kind of intuitively makes sense to me.