Function svpfirst_b 

pub fn svpfirst_b(pg: svbool_t, op: svbool_t) -> svbool_t

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

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

Set the first active predicate element to true Arm’s documentation