Function __smusd 

pub unsafe fn __smusd(a: int16x2_t, b: int16x2_t) -> i32

🔬This is a nightly-only experimental API. (stdarch_arm_dsp #117237)

Available on ARM and (target feature v6 and non-target feature mclass, or target features mclass and dsp) only.

Signed Dual Multiply Subtract.

Returns the equivalent of

res = a[0] * b[0] - a[1] * b[1]

and sets the Q flag if overflow occurs on the addition.