[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.