如何比較MIPS寄存器中的值？

Question

我想創建一個函數，提示用戶輸入一個介於3和30之間的數字，如果數字小於3，它將顯示「你的數字小於3」，如果數字大於30，將顯示「你的號碼大於30」。這可能是愚蠢的，但我是MIPS新手，我不太明白我做錯了什麼。

謝謝

.data 
prompt: .asciiz "Enter your number (3-30):" 
message: .asciiz "\n Your number is " 
message2: .asciiz "\n Your number is less than 3" 
message3: .asciiz "\n Your number is more than 30" 
.text 
# Prompt the user to enter the number 
li $v0, 4 
la $a0, prompt 
syscall 

# Get the number 
li $v0, 5 #get an integer from the user 
syscall 

# Store the result in t0 
move $t0, $v0 

main: #syscall to end the program 
    addi $t1, $zero, 0 
    addi $t2, $zero, 3 
    addi $t3, $zero, 30 

    ble $t0, $t1, numberSmaller 
    bge $t0, $t2, numberLarger 

    li $v0, 10 
    syscall 

numberSmaller: 
    li $v0, 4 
    la $a0, message2 
    syscall 
numberLarger: 
    li $v0, 4 
    la $a0, message3 
    syscall 

Answer 1

你實際上是相當接近。

main:標籤位於錯誤的地方，所以在某些模擬器下，可能不會執行前幾條指令。

此外，該程序[有點]不完整，因爲在採用條件分支之後，程序「脫離世界的盡頭」。

但是，問題的核心是兩個分支需要不同的分支條件和需要改變在每個第二寄存器：

變化：

ble $t0, $t1, numberSmaller 

分爲：

blt $t0, $t2, numberSmaller 

更改：

bge $t0, $t2, numberLarger 

分爲：

bgt $t0, $t3, numberLarger 

---

所以，這裏的全部糾正的程序：

.data 
prompt:  .asciiz  "Enter your number (3-30):" 
message: .asciiz  "\n Your number is " 
message2: .asciiz  "\n Your number is less than 3" 
message3: .asciiz  "\n Your number is more than 30" 

    .text 
    .globl main 
main: 
    # Prompt the user to enter the number 
    li  $v0,4 
    la  $a0,prompt 
    syscall 

    # Get the number 
    li  $v0,5     # get an integer from the user 
    syscall 

    # Store the result in t0 
    move $t0,$v0 

    addi $t1,$zero,0 
    addi $t2,$zero,3 
    addi $t3,$zero,30 

    blt  $t0,$t2,numberSmaller 
    bgt  $t0,$t3,numberLarger 

    # output message to show the number 
    li  $v0,4 
    la  $a0,message 
    syscall 

    # show the number 
    li  $v0,1 
    move $a0,$t0 
    syscall 

exit: 
    li  $v0,10     # syscall to end the program 
    syscall 

numberSmaller: 
    li  $v0,4 
    la  $a0,message2 
    syscall 
    j  exit 

numberLarger: 
    li  $v0,4 
    la  $a0,message3 
    syscall 
    j  exit 

---

這裏有一個稍微更嚴格的版本：

.data 
prompt:  .asciiz  "Enter your number (3-30):" 
message: .asciiz  "\n Your number is " 
message2: .asciiz  "\n Your number is less than 3" 
message3: .asciiz  "\n Your number is more than 30" 

    .text 
    .globl main 
main: 
    # Prompt the user to enter the number 
    li  $v0,4 
    la  $a0,prompt 
    syscall 

    # Get the number 
    li  $v0,5     # get an integer from the user 
    syscall 

    # Store the result in t0 
    move $t0,$v0 

    li  $t1,3 
    blt  $t0,$t1,numberSmaller 

    li  $t1,30 
    bgt  $t0,$t1,numberLarger 

    # output message to show the number 
    li  $v0,4 
    la  $a0,message 
    syscall 

    # show the number 
    li  $v0,1 
    move $a0,$t0 
    syscall 

exit: 
    li  $v0,10     # syscall to end the program 
    syscall 

numberSmaller: 
    li  $v0,4 
    la  $a0,message2 
    syscall 
    j  exit 

numberLarger: 
    li  $v0,4 
    la  $a0,message3 
    syscall 
    j  exit