[1] https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
Examples of what's missing: interleaved load/store, compress/expand, software AES/CLMUL, popcount, lzcnt, saturated add/sub, 128-bit compare/minmax, fixed-point mul, mask find/set, masked load/store, scatter/gather, reductions.
Highway supports those (and >200 operations in total) on all platforms.
[1] https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html