Function has_stibp 

pub fn has_stibp(cpuid: &impl Cpuid, always_on_mode: bool) -> bool

Whether Single Thread Indirect Branch Predictors (STIBP) are supported. The “always on” mode refers to an optimization in which STIBP need only be enabled once.

https://software.intel.com/security-software-guidance/deep-dives/deep-dive-single-thread-indirect-branch-predictors.