我已经在C中获得了两个我需要转换为MIPS32指令的函数。
我是编程新手。到目前为止，我已经尝试了解C中实际发生的事情，然后使用MIPS指令将C代码转换为汇编语言。我主要使用跳转指令来跳过代码的不同部分。我相信可能有更好的方法来使用寄存器来使代码简洁，但在这一点上，我只是想让我的概念正确并理解字符串操作。之后，我将致力于优化代码。
C代码：
char firstmatch(char *s1, char *s2) {
char *temp;
temp = s1;
do {
if (strchr(s2, *temp) != 0)
return temp;
temp++;
} while (*temp != 0);
return 0;
}
char *strchr(register const char *s, int c) {
do {
if (*s == c) {
return (char*)s;
}
} while (*s++);
return (0);
}
MIPS代码：
.data
str1: .asciiz "hello \n" #String 1
str2: .asciiz "meh \n" #String 2
char_found: .asciiz " is the first character in string s1 that is also in s2 \n"
char_not_found: .asciiz "No character match between the two strings \n"
.text
main:
la $a0, str1 #Loading address of string 1 into register $a0
la $a1, str2 #Loading address of string 2 into register $a1
firstmatch:
move $t0, $a0 #Passing address of str1 from $a0 to $t0
move $t1, $a1 #Passing address of str1 from $a1 to $t1
addi $t2,$t0,0 #Using $t2 register for the temp variable
Load_Bytes:
lb $t4, 0($t1) #Loading the first character of str2
lb $t3, 0($t2) #Loading the first character of str1
strchr:
beq $t4,$t3,Label_1 #Checking for character match.
j Label_2 #No match, go to Label_2
Label_1: #Label to Print character as well as char_found string
li $v0, 4
la $s0, ($t4)
syscall
la $t5, char_found
syscall
Label_2:
addi $t2, $t2, 1 #Incrementing temp by 1
lb $t6, 0($t2) #Using t6 to check for NULL character
beqz $t6, Label_4 #Checking if value at $t2 is 0.
j Load_Bytes
Label_3: #Label to print when no character match
li $v0, 4
la $t5, char_not_found
syscall
Label_4:
addi $t1, $t1, 1 #Increment str2 byte by 1 after string 1 iteration reaches the NULLL character
lb $t7, 0($t1) #Using t7 to check for NULL character
beqz $t7, Label_3 #Checking if value at str 2($t1) is 0
addi $t2, $t0, 0 #Re-initialize string 1
j Load_Bytes
目前，我的代码一直无休止地运行并打印字符串1.我怀疑要么我不理解正确加载地址和字节的概念，要么存在不断重复程序的跳转条件。任何帮助，将不胜感激。
.data
str1: .asciiz "HeLlo" #String 1
str2: .asciiz "mEadow" #String 2
char_found: .asciiz " is the first character in string s1 that is also in s2 \n" #To be printed when character is found
char_not_found: .asciiz "No character match between the two strings \n" #To be printed if there is no match
.text
main:
la $a1,str1 #Loading address of string 1 into register $a1
la $a2,str2 #Loading address of string 2 into register $a2
move $t0,$a1 #Passing address of str1 from $a1 to temp register $t0
move $t1,$a2 #Passing address of str1 from $a2 to temp register $t1
addi $t2,$t0,0 #Using $t2 register for the temp variable in the code
Load_Bytes:
lb $t4, 0($t1) #Loading the first character of str2 from memory address $t1 to $t4
lb $t3, 0($t2) #Loading the first character of str1 from memory address $t2 to $t3
strchr:
beq $t3,$t4,Label_1 #Checking for character match. If yes, going to Label_1. If not, continue
jal firstmatch
addi $t1, $t1, 1 #Increment str2 byte by 1 after string 1 iteration reaches the NULLL character
lb $t7, 0($t1) #Using t7 as temporary register to check for NULL character in the next step
beqz $t7, Label_2 #Checking if value at string 2($t1) is 0. If yes, go to Label_5
addi $t2, $t0, 0 #Re-initialize string 1 to start the compare loop again
j Load_Bytes
firstmatch:
addi $t2, $t2, 1 #Incrementing temp by 1
lb $t6, 0($t2) #Using t6 as temporary register to check for NULL character in the next step
bnez $t6, Load_Bytes #Checking if value at $t2 is 0. If yes, going to Label_2. If not, continue and iterate the loop
jr $ra
Label_1: #Label to Print character as well as char_found string above simultaneously
la $a0,($t4)
li $v0, 11
syscall
la $a0, char_found
li $v0, 4
syscall
li $v0,10
syscall
Label_2: #Label to print when no character match is found
la $a0, char_not_found
li $v0, 4
syscall
li $v0, 10
syscall