On: SSE code 6 times slower without VZEROUPPER on Skyl...

[gnufx]

For code using intrinsics (not assembler) https://simd-everywhere.github.io/blog/ might be helpful, including on x86_64, though it doesn't provide runtime dispatch. GCC itself knows a level (sse4.2?) of x86_64 intrinsics on ppc64le.