That still just gets you autovectorization, and generally locks you out of the performance you could have with direct SIMD intrinsics.

Granted, the number of cases this distinction matters is relatively small, making a function faster only makes a program appreciably faster if that function is a bottleneck.

Starts to get a bit philosophical on what constitutes "portable" but JIT compilers would emit an opcode based off of whatever the frontend/IR is saying to do surely?