Question

有谁知道如何将其转换为mips 32？请出示代码并为我解释。非常感谢你

int service (int n) {
    if (n <= 10) 
        return n;
    else
        return n + service(n+1) + service (n+2);
}

Answer 1

请注意评论，并尝试按说明理解正在发生的事情。

 service:   
        lw      $t0, $a0        # Load word from memory to $t0. $a0 is the argument of the function (int n).
        addi    $t1, 10         # $t1 = 10

        bne     $t0, $t1, cont  # If n != 10 , continue 
        slti    $t2, $t1, $t0   # If 10 < n $t2 = 1, else $t2 = 0
        bne     $t2, $t0, cont  # If $t2 != 0 , then $t2 = 1 so 10 < n , so continue
        addi    $v0, $t0, $0    # Else return n;
        jr $ra
    cont:
        addi    $sp, $sp, -4    # Room on stack for 4 bytes
        sw      $ra, 0($sp)     # Save $ra, recursion
        addi    $a0, $a0, 1     # n+1
        jal     service         # Call service(n+1)
        addi    $a0, $a0, 1     # (n+1) + 1 = n+2
        jal     service         # Call service(n+2)
        lw      $ra, 0($sp)     # restore $sp
        addi    $sp, $sp, 4     # Restore room on stack
        jr      $ra

Answer 2

这是我的澄清尝试

# assuming $a0 is the parameter n

service:
    bgt $a0, 10, else   # if $a0 > 10 branch to else part
    move    $v0, $a0    # $v0 = $a0, to return the value
    jr  $ra     # return n;
else: 
    addiu   $sp, $sp, -8    # using stack to store $ra, $a0 each 4 bytes we need 8 bytes
    sw  $a0, 0($sp) # store the value of a0 in the stack
    sw  $ra, 4($sp) # store the caller addrs. 
    addiu   $a0, $a0, 1 # parameter of the first function call (n+1)
    jal service     # service(n+1)
    move    $s0, $v0    # s0 = result of service(n+1)
    lw  $a0, 0($sp) # $a0 = n
    addiu   $a0, $a0, 2 # parameter of the second function call (n+2)
    jal service     # service(n+1)
    move    $s1, $v0    # s1 = result of service(n+1)
    lw  $a0, 0($sp) # $a0 = n
    addu    $v0, $a0, $s0   # $v0 = n + service(n+1)
    addu    $v0, $v0, $s1   # $v0 = n + service(n+1) + service(n+2)
    lw  $ra, 4($sp) # $ra = old caller return addrs.
    addiu   $sp, $sp, 8 # freeing the stack
    jr  $ra     # return

将c转换为Mips的练习

2 个答案: