mips汇编简单实例——一个小计算器

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http://blog.csdn.net/oncoding/archive/2009/07/14/4346531.aspx

其实开始的时候一直在看 mips的指令格式，看了、忘了，没什么效果。

现在通过这个例子，简单训练一下： mips汇编中：

常用寄存器的使用；

系统调用： 1(print_int),4(print_str),5(read_int),10(exit)；

算术运算： add,sub,mul,div；

逻辑运算及跳转；

上代码：(汇编写的少，代码书写、风格还很差劲，感谢请大虾指教)：

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#sample example 'a small calculater’
.text                       # text section
.globl main                 # call main by SPIM
main:
    la $t0, 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)

    la $a0,msg1
    li $v0,4
    syscall             #print "first num:"

    li $v0, 5
    syscall
    sw $v0, 0($t0)

    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"
#sample example 'a small calculater’
.text       # text section
.globl main     # call main by SPIM
main:
la $t0, 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)

la $a0,msg1
    li $v0,4
    syscall    #print "first num:"

li $v0, 5
syscall
sw $v0, 0($t0)

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"

运行效果截图如下：

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