MIPS 中的递归最大公约数

Question

在MIPS中，我试图使用欧几里得算法计算正整数对的最大公约数(GCD(。 例如，6 和 9 的 GCD 是 3，而 10 和 25 的 GCD 是 5。

C 代码是这样的

uint32_t m_w = 50000;
uint32_t m_z = 60000;
uint32_t hcf(uint32_t n1, uint32_t n2)
{
if (n2 != 0)
return hcf(n2, n1%n2);
else 
return n1;
}

我正在编写MIPS程序，但我不确定如何使用n1%n2。这是我第一次做递归，我不确定语法是否正确

.data
n1: .word 6
n2: .word 9
.text
.globl main
main:
lw $a0,n1  # load value n1
lw $a1,n2  #load value n2
jal GCD # call funtion GCD
add $a0,$v0,$zero 
li $v0,1
syscall # print result
li $v0, 10 # exit program 
syscall
GCD:
#GCD(n1, n2)
# n1 = $a0
# n2 = $a1
addi $sp, $sp, -12
sw $ra, 0($sp) # save function into stack
sw $s0, 4($sp) # save value $s0 into stack 
sw $s1, 8($sp) # save value $s1 into stack 
add $s0, $a0, $zero # s0 = a0 ( value n1 ) 
add $s1, $a1, $zero # s1 = a1 ( value n2 ) 
addi $t1, $zero, 0 # $t1 = 0
beq $s1, $t1, returnn1 # if s1 == 0 returnn1
addi $a0, $zero, $s1 # make a0 = $s1
addi $a1, .... #  (n1%n2)
jal GCD
exitGCD:
lw $ra, 0 ($sp)  # read registers from stack
lw $s0, 4 ($sp)
lw $s1, 8 ($sp)
addi $sp,$sp , 12 # bring back stack pointer
jr $ra
returnn1:
li $v0, $s0 # return $v0 = $s0 ( n1)
j exitGCD

Answer 1

你快到了。就像@Micheal说的div和mfhi是你所需要的。模(% 是取模运算符(只是提醒两个整数之间的除法。

.data
n1: .word 60
n2: .word 45
.text
.globl main
main:
lw $a0,n1  # load value n1
lw $a1,n2  #load value n2
jal GCD # call funtion GCD
add $a0,$v0,$zero 
li $v0,1
syscall # print result
li $v0, 10 # exit program 
syscall
GCD:
#GCD(n1, n2)
# n1 = $a0
# n2 = $a1
addi $sp, $sp, -12
sw $ra, 0($sp) # save function into stack
sw $s0, 4($sp) # save value $s0 into stack 
sw $s1, 8($sp) # save value $s1 into stack 
add $s0, $a0, $zero # s0 = a0 ( value n1 ) 
add $s1, $a1, $zero # s1 = a1 ( value n2 ) 
addi $t1, $zero, 0 # $t1 = 0
beq $s1, $t1, returnn1 # if s1 == 0 returnn1
add $a0, $zero, $s1 # make a0 = $s1
div $s0, $s1 # n1/n2
mfhi $a1 # reminder of n1/n2 which is equal to n1%n2
jal GCD
exitGCD:
lw $ra, 0 ($sp)  # read registers from stack
lw $s0, 4 ($sp)
lw $s1, 8 ($sp)
addi $sp,$sp , 12 # bring back stack pointer
jr $ra
returnn1:
add $v0, $zero, $s0 # return $v0 = $s0 ( n1)
j exitGCD

您的代码也存在一些语法问题。 你可以在这里阅读关于div，mhfi