> Then, a bit later, we need to very quickly finish populating the structs.

I am finding it extremely hard to envision a circumstance where this is a bottleneck for anything. Care to clarify the context?

I also find the struct layout really odd; why not just move c?

Your benchmarks are also probably broken; branch predictors use global state so will almost certainly predict fine the way you've used things. You need to repopulate a significantly-sized array each time with randomly chosen values. You can't use the same array because it'll be learnt, and you can't use a short array because it'll be predicted globally.