Function svextb_s16_m 

pub fn svextb_s16_m(
    inactive: svint16_t,
    pg: svbool_t,
    op: svint16_t,
) -> svint16_t

🔬This is a nightly-only experimental API. (stdarch_aarch64_sve #145052)

Available on (AArch64 or ARM64EC) and target feature sve only.

Sign-extend the low 8 bits Arm’s documentation