Efficient C++ Programming for Modern 64-bit CPUs: Chapter 4/part 2

what if a language would allow to elegantly pack Optional values?

so the physical layout has a bit vector with one bit for each optional. and a popcnt over that bitvector (masked up to the value we're interested in) will give the actual slot to look into?

would also make sense to reorder / bucket fields by (byte) size

if you want to do that in any low level language (rust, c++) you have to deviate from their standard syntax for optionals, and you have to manually keep track of slot order. but for domains with many optional/default values, this amy really reduce cache pressure, no?

In higher level languages you can fake the effect (with flyweight facades), so from python such a packed "dataclass"-like class can look neat and clean. however at the low level there is no abstraction that allows to create your own data layout.

at least I didn't find anything yet.

I'm somewhat dubious about anything talking about low level performance programming at the instruction level that doesn't distinguish between latency and throughput, never mind mention the incredibly out-of-order nature of modern desktop/server class CPU cores.

Article title should be "Efficient C++ Programming for Modern 64-bit CPUs...".

See also a 3-part article; Advanced C++ Optimization Techniques for High-Performance Applications here - https://news.ycombinator.com/item?id=48265690

Virtual functions cost a lot less here than I expected.

C++ CPUs?

If people are interested in this stuff, this is the house style guide that I've ended up with in mid 2026, its great-great-great grandparents were at Google, which informed Greg Badros and Mark Rabkin and Andrei Alexandrescu when they did the one at FB, which informed a bunch of trading work, which informed a bunch of GPU work.

It's opinionated but it has served me well.

https://gist.github.com/b7r6/5dde648f5dc1dea1e9039f2211f5d40...

This looks like something that every serious C++ programmer should be reading.