This seems like a strange thing to say. Fine grained feature detection was around long before "microarchitecture levels" and never went away. The microarchitecture levels were introduced because they were easier to use.

[0] https://github.com/ronnychevalier/cargo-multivers

The same conclusion: v2 as baseline, v3 where possible.

I'm really surprised it's not standard in every toolchain to support arch levels like this today.

Some compilers like Clang allow multiple arch versions in one binary, runtime dispatched. I would love to implement this in our toolchain too.

[0] Please forgive the SEO-style title, it's, well, to get search engines to recognise what's in the article: https://blogs.remobjects.com/2026/01/26/fast-math-in-six-lan...

It's not entirely free; the cost is that the resulting binary will no longer run on processors that lack the instruction. Which, admittedly, is ≈2007 or older. But still! I have a 2012 CPU still in service, and as much as I'd love to obsolete it, gestures at the price tag of RAM these days.

… a 2012 CPU is surprisingly competitive relative to today's tech, too, I'd add. The gap between 2012 and 2026 is nothing compared to the equivalent gap between 1998 and 2012: 1998 is like 500MHz single-core, 32-bit. 2012 is 4 core, 8 hyper threads, 64-bit, 3.5 GHz. (… perhaps more remarkably, my next-oldest machine, a 2017 laptop, is only 2.8 GHz, with the same 4(/8) cores. It also uses like half the power, too. That's mostly the "laptop" bit, though.)

(That same CPU is also incapable of "v3".)

I suspect that heavily optimised code either uses intrinsics or carefully written assembler code.

Ubuntu started allowing defaulting to v3 packages, and I opted in. I already use the -C native to enable AVX512 when compiling binaries for local use. This matters a lot for compute/analytics workloads in my experience.

Speaking of Dr Lemire's suggestion of a V5 architecture level, would that make any sense given the fragmentation of AVX512? None on Intel consumer devices, but it is on the last few generations of AMD.

I wonder if this is a natural law, or emergent behavior of complex systems?