Function vmull_laneq_s16 

pub fn vmull_laneq_s16(a: int16x4_t, b: int16x8_t, const LANE: i32) -> int32x4_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.

Vector long multiply by scalar Arm’s documentation