The Funtoo Linux project has transitioned to "Hobby Mode" and this wiki is now read-only.
Funtoo ARM64 CPU WIKI
https://www.funtoo.org/Funtoo_CPU_Database
Unfortunately This page has nil for Arm64 CPU's and documentation however THIS page below Will hopefully grow till added to above.
https://wiki.gentoo.org/wiki/Safe_CFLAGS#ARM still has older Settings , included for reference and or adding in.
RPI4/Rock64 Rock64pro and Pinebookpro laptop.
filename=/etc/portage/make.conf
COMMON_FLAGS="-O2 -pipe -march=armv8-a+crc+crypto -mcpu=cortex-a72.cortex-a53 ${GRAPHITE} ${CPU_FLAGS_ARM64}"
CPU_FLAGS_ARM64="edsp neon thumb vfp vfpv3 vfpv4 vfp-d32 crc32 v4 v5 v6 v7 v8 thumb2"
https://raw.githubusercontent.com/necrose99/arm64-portage/master/package.use/00cpu-flags (app-portage/cpuid2cpuflags output)
For Rpi4 soon Vulkan-vc? gpu for now Vc4 , Odroid-X4 ? Rock64/Pine64/Pinebook varriants also mali/bifrost panfrost kernel mode drivers , Panfrost being opensource. https://raw.githubusercontent.com/necrose99/arm64-portage/master/mesa template ...