private static DecodedInstruction decodeRegisterRange(
      InstructionCodec format, int opcodeUnit, CodeInput in) throws EOFException {
    int opcode = byte0(opcodeUnit);
    int registerCount = byte1(opcodeUnit);
    int index = in.read();
    int a = in.read();
    IndexType indexType = OpcodeInfo.getIndexType(opcode);
    return new RegisterRangeDecodedInstruction(
        format, opcode, index, indexType, 0, 0L, a, registerCount);
  }
Helper method that decodes any of the three-unit register-range formats.
android/android_framework/dex-maker/src/main/java/com/android/dx/io/instructions/InstructionCodec.java