Signed Double and Add, saturating the result to the signed
range -231 ≤
QDADD instruction calculates
SAT(. Saturation can
occur on the doubling operation, on the addition, or on both. If
saturation occurs on the doubling but not on the addition, the Q
flag is set but the final result is unsaturated.
Rn * 2))
All values are treated as two’s complement signed integers by this instruction.