The tools are there in the instruction set, but that still leaves the issues of time and effort to implement in compilers, and enough performance improvement on enough machines in some market (browsers, games, etc) capable of running it all before any of this possibility becomes real.
The skylake-xeon/icelake false start here really can’t have helped. It’s still a much more pragmatic thing to target the haswell feature set that all the intel chips and most amd chips can run (and run well).
I know game console emulators use it to great effect with significant performance increases.
1: https://www.tomshardware.com/news/ps3-emulation-i9-12900k-vs...
Sometimes the second comer to a game has the advantage of taking their time to implement something, with fewer compromises and a better overall fit.
My question is just... does it? (And does it use AVX-512 profitably?)
Depends on a couple factors (i.e. Ice Lake client only has 1 FMA unit) but I'd be surprised if Tiger Lake was a major regression relative to Ice Lake. It seems like they had it in an OK spot by then.
I'm not rebuilding specifically for this one potential optimization.
Unless you have a very specific AVX-512 workload or you need to run AVX-512 code for local testing, you won’t see any net benefit of keeping your older AVX-512 part.
Newer parts will have higher clock speed and better performance that will benefit you everywhere. Skipping that for the possibility of maybe having some workload in the future where AVX-512 might help is a net loss.
AMD Phoenix is far better than any current Intel mobile CPU anyway, so it is an easy choice (and it compiles code much faster than Intel Raptor Lake, which counts for a Gentoo user or developer).
The only reason to not choose an AMD Phoenix for an upgrade would be to wait for an Intel Meteor Lake a.k.a. Intel Core Ultra. Meteor Lake will be faster in single-thread (the relative performance in multi-thread is unknown) and it will have a bigger GPU (with 1024 FP32 ALUs vs. 768 for AMD).
However, Meteor Lake will not have AVX-512 support.
For compiling code, the AVX-512 support should not matter, but it should matter a lot for the code generated by the compiler, as it enables the efficient auto-vectorization of many loops that cannot be vectorized efficiently with AVX2.
While gcc and clang will never be as smart as hand-written code, their automatic use of AVX-512 can be improved a lot and announcements like that linked by you show progress in this direction.
However, compilers have so far been slow to implement this, with the relevant patches only going into GCC right now.
Maybe this doesn't matter, almost certainly wouldn't for most people, but I'm compiling the whole system myself so the compiler at least has the freedom to use AVX-512 wherever it pleases. Does anyone know if AVX-512 actually makes a difference in workloads that aren't specifically tuned for it?
My guess is that given news like https://www.phoronix.com/news/GCC-AVX-512-Fully-Masked-Vecto... that compilers basically don't do anything interesting with AVX-512 without hand-written code.