learn mips

可以使用MARS来编汇编,MARS是一个用java编的IDE,它是一个模拟环境.

样例:重要的句子输出三遍

.data 
   str: .asciiz "weidiao is great
"
.text
j main
f:
   la $a0,str
   li $v0,4
   syscall
   jr $ra
main:
   li $t1,0
   li $t2,3
loop:
   bgt $t1,$t2,over
   addi $t1,$t1,1
   jal f
   j loop
over:   li $v0,10
   syscall

指令文档:链接

下面程序为一个四则运算程序,学习汇编就是要大量的阅读实例.实例学习在编程技术中至关重要.

    #simple example :a small calculater’  
    .text                       # text section  
    .globl main                 # call main by SPIM  
    main:  
        la $t0, value      
        #t0 is the address of the value
                  # load address "value" into $t0  
        la $a0,msg0  
        li $v0,4          
        syscall             #print "please choose the operation:"  
          
        li  $v0, 5    
        syscall  
        sw  $v0, 8($t0)  #operation is stored to t0+8---the second byte
          
        la $a0,msg1  #v0 controls the syscall.a0 controls the output_data;
        li $v0,4          
        syscall             #print "first num:"  
          
        li  $v0, 5    #load integer 5 to v0,this is the read operation.
        syscall  
        sw  $v0, 0($t0)  #store $v0
          
        la $a0,msg2  
        li $v0,4          
        syscall             #print " second num:"  
          
          
        li  $v0, 5    
        syscall  
        sw  $v0, 4($t0)         #read the other num   
          
        la $a0,newline  
        li $v0,4          
        syscall             #print "/n"  
          
        lw $t1, 0($t0)          # load the first num  
        lw $t2, 4($t0)          # load the second num  
        lw $t3, 8($t0)          # load the operation  
          
        beq $t3,1,addOp         # if +  
        beq $t3,2,subOp         # if -  
        beq $t3,3,mulOp         # if *  
        beq $t3,4,divOp         # if /  
          
    addOp:  
        add $t4, $t1, $t2       # $t1 + $t2 = $t4     
        sw $t4, 12($t0)         #   
        la $t5,addFlag  
        j printResult  
    subOp:  
        sub $t4, $t1, $t2       # $t1 - $t2 = $t4     
        sw $t4, 12($t0)           
        la $t5,subFlag  
        j printResult  
    mulOp:  
        mul $t4, $t1, $t2       # $t1 * $t2 = $t4     
        sw $t4, 12($t0)  
        la $t5,mulFlag  
        j printResult  
    divOp:  
        div $t4, $t1, $t2       # $t1 / $t2 = $t4     
        sw $t4, 12($t0)   
        la $t5,divFlag  
        j printResult  
          
    printResult:  
        lw $a0,0($t0)  
        li $v0,1          
        syscall             #read first number  
          
        la $a0,0($t5)  
        li $v0,4   
        syscall             #print opflag  
          
        lw $a0,4($t0)  
        li $v0,1          
        syscall             #print second number  
          
        la $a0,equalStr  
        li $v0,4   
        syscall             #print " = "  
          
        lw $a0,12($t0)  
        li $v0,1          
        syscall             # print sum result  
        j exit  
          
    exit:  
        la $a0,newline  
        li $v0,4   
        syscall             #print " /n "  
          
        li $v0,10         
        syscall             # exit  
    # data section  
    .data                 
    value:  .word 0, 0, 0 ,0 ,0     # 0: first num ,4 : second num , 8 : operation , 12:result  
    msg0        :   .asciiz " please choose the operation(1~4):/n/t/t1 : +,addition /n/t/t2 : -,subtracter/n/t/t3 : * multiplication /n/t/t4 : /,division/n"  
    msg1        :   .asciiz "first num:"  
    msg2        :   .asciiz "second num:"  
    addFlag     :   .asciiz " + "  
    subFlag     :   .asciiz " - "  
    mulFlag     :   .asciiz " * "  
    divFlag     :   .asciiz " / "  
    equalStr    :   .asciiz " = "  
    newline     :   .asciiz "/n===============================/n"   

 样例:打印九九乘法表

.data
  op :.asciiz "*"
  eq:.asciiz "="
  line:.asciiz "
"
  space:.asciiz " "
.text
  j main
  print:
    move $a0,$t1
    li $v0,1
    syscall
    
    la $a0,op
    li $v0,4
    syscall
    
    move $a0,$t2
    li $v0,1
    syscall
    
    la $a0,eq
    li $v0,4
    syscall
    
    mult $t1,$t2
    mflo $a0
    li $v0,1
    syscall
    
    la $a0,space
    li $v0,4 
    syscall
    
    blt $t2,$t1,ret
    la $a0,line
    syscall
    
    ret:
    jr $ra
  main:
    li $t1,0
    for1:
      addi $t1,$t1,1
      bgt $t1,9,for1_out
      li $t2,0
      for2:
        addi $t2,$t2,1
        bgt $t2,$t1,for1
        jal print
        j for2
      j for1
    for1_out:
      li $v0,10
      syscall