public final short getAUnit() {
    int a = getA();

    if ((a & ~0xffff) != 0) {
      throw new DexException("Register A out of range: " + Hex.u8(a));
    }

    return (short) a;
  }
Gets the A register number, as a code unit. This will throw if the value is out of the range of
an unsigned code unit.
android/android_framework/dex-maker/src/main/java/com/android/dx/io/instructions/DecodedInstruction.java