Function vpaddl_s8 

pub fn vpaddl_s8(a: int8x8_t) -> int16x4_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.

Signed Add and Accumulate Long Pairwise. Arm’s documentation