[kaba0]

I am by no means an expert, but I believe what you have in mind would likely fit in i-cache without a problem, so you wouldn’t see a significant difference.

There is an interesting talk titled ‘the death of optimizing compilers’ that argues that for most code these optimizations are almost completely meaningless, and in the hot loops where it actually matters, they are not good compared to humans (and sometimes 100x or more improvements are possible and left on the table). While I don’t completely agree with its points, it is a good talk/slides to read through.

[EVa5I7bHFq9mnYK]

Its not that compilers are stupid, they just dont know what humans know about their data, it's ranges, invariants, symmetries etc. They work on most general case, which can be horribly inefficient.