Function std::intrinsics::powif64

pub unsafe extern "rust-intrinsic" fn powif64(a: f64, x: i32) -> f64

🔬 This is a nightly-only experimental API. (core_intrinsics)

intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library

将 f64 提升为整数幂。

此内联函数的稳定版本是 f64::powi