mips汇编简单实例——一个小计算器

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：