Function std::intrinsics::fmaf64

pub unsafe extern "rust-intrinsic" fn fmaf64(
    a: f64, 
    b: f64, 
    c: f64
) -> f64

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

为 f64 值返回 a * b + c。

此内部函数的稳定版本是 f64::mul_add