[yjftsjthsd-h]

Yeah, I don't know the breakdown between better hardware and better compiler optimizations (even in the default settings) and less differentiation between processors, but I've done some minor not-very-scientific tests of compiling packages with O3/march=mtune=native and in my limited experience it wasn't particularly useful. Like, not just small benefits, but zero or below the noise floor benefits in my benchmarks. Obviously this is super dependent on your workload and maybe hardware; it's an area where if you care, you have to do your own testing.

[jeffbee]

Tune for native sometimes makes a difference but not always. Targeting a platform that is known to have AVX2, instead of detecting AVX2 at runtime and bouncing through the PLT, can make a large difference. PGO remains the largest opportunity.

[account42]

PGO is not something Gentoo does (outside a few packages like Firefox that have it in their build system) because the profiling cannot be done automatically for arbitrary packages.