2. Registers and Basic arithmetic

두 r# 레지스터를 더하는 방법

• sum01.s

    .global main
  
    main:
        mov r1, #3      /* r1 <- 3 */
        mov r2, #4      /* r2 <- 4 */
        add r0, r1, r2  /* r0 <- r1 + r2 */
        bx lr
  

  r1 r2를 더해 r0 에 저장

• sum02.s

    .global main
  
    main:
        mov r0, #3      /* r0 <- 3 */
        mov r1, #4      /* r1 <- 4 */
        add r0, r0, r1  /* r0 <- r0 + r1 */
        bx lr
  

  r0 를 재활용함.

• Run on the target RPI after compile

     $ ./sum01 ; echo $?
     7
  
     $ ./sum02 ; echo $?
     7