Function vext_u16 

pub fn vext_u16(a: uint16x4_t, b: uint16x4_t, const N: i32) -> uint16x4_t

Available on (AArch64 or ARM64EC) and (AArch64 or ARM64EC or target feature v7) and (ARM or AArch64 or ARM64EC) and target feature neon only.

Extract vector from pair of vectors Arm’s documentation