[bluGill]

My understanding is the layout is the hint. Modern CPUs would not want to use cache space for any hints, not to mention all the silicon to decode the hint.

Compiler writers are smart people and can layout code to give the CPU the right hints, so long as they know what the CPU does. CPU manufactures want the compilers writers to do this as the compiler is a significant factor in making one CPU faster than the competition in benchmarks.

[hyperpape]

It seems to me that it's misleading to call that a hint. Rather, certain code paths create hard-to-predict branches, and others create predictable branches. A hint would be some kind of metadata that says "you'll want to predict this branch this way based on your algorithm, but please don't!"

[hyperpape]

s/code paths/code patterns/