删除字符串中的空格，MIPS程序集

Question

我正在尝试编写的程序存在一个小问题。基本上我提示用户输入。然后我计算字符串中的空格数，并显示计数。我还需要删除空格打印出原始字符串。

我遇到的错误是当我在没有空格的字符串中添加字符时，它只添加第一个字符。 $ t2是保存要添加的字符的寄存器，我在运行时检查了寄存器，以确保其中的值发生了变化。我不知道在哪里可以看。

    .data
str:        .space 81   # buffer for input string
strNS:      .space 81   # buffer for string w/o spaces
prompt:     .asciiz "Enter a string up to 80 characters\n"
head1:      .asciiz "\nOriginal String:  "
head2:      .asciiz "\nNumber of spaces:  "
head3:      .asciiz "\nWith spaces removed:  "

.text   
main:   
    #print the first prompt and get the input string from console
    li      $v0, 4          #load syscall value to print string into $v0
    la      $a0, prompt     #address of prompt to print
    syscall                 #print prompt to console
    li      $v0, 8          #load syscall value to read input string
    la      $a0, str        #addr of allocated space for input string is now in $a0
    li      $a1, 81
    syscall 

    jal     countSpace

    addi    $t1, $v0, 0     #the count of spaces is in $v0, save it into $t1
    li      $v0, 4          #print header then the count
    la      $a0, head1  
    syscall
    la      $a0, str        #print the original string
    syscall
    la      $a0, head2      #print second header before printing count
    syscall
    li      $v0, 1      
    addi    $a0, $t1, 0     #place the count in $a0
    syscall                 #print the count

    li      $v0, 4
    la      $a0, head3      #print the third header
    syscall
    la      $a0, strNS      #print no spaces string
    syscall


End:    
    li      $v0, 10         #load syscall value for exit
    syscall                 #exit

countSpace:
    la      $s0, strNS
    addi    $sp, $sp, -12   #adjust the stack pointer for saving
    sw      $s0, 8($sp)     #store addr of nospace string
    sw      $ra, 4($sp)     #store return addr on the stack
    sw      $a0, 0($sp)     #store the count on the stack

    #Begin counting spaces
    addi    $t3, $a0, 0     #$t3 has addr of user input
    addi    $t5, $s0, 0     #$t5 has addr of string with no spaces
    li      $t6, 0          #$t6 holds index of string with no spaces 
    li      $t0, 0          #$t0 will hold the count of spaces
    li      $t4, 0          #$t4 holds the index of the string
loop:   
    add     $t1, $t3, $t4   #$t1 = addr of str[i]
    lb      $t2, 0($t1)     #$t2 = character in str[i]
    beq     $t2, $zero, exitCS  #break from loop if $t2 contains null character
    addi    $a0, $t2, 0     #place value to be checked in $a0

    #save values onto stack from temp registers to preserve them
    addi    $sp, $sp, -28   #adjust the stack pointer for 5 values
    sw      $t6, 24($sp)    #save index of string with no spaces
    sw      $t5, 20($sp)    #save addr of string with no spaces
    sw      $t4, 16($sp)    #save index of user input
    sw      $t3, 12($sp)    #save the addr of user input
    sb      $t2, 8($sp)     #save the character in str[i]
    sw      $t1, 4($sp)     #save the address of str[i] 
    sw      $t0, 0($sp)     #save the count of spaces

    jal     isSpace         #result from this jump and link will be in $v0 after call

    #pop saved values from the stack, then reset the pointer
    lw      $t6, 24($sp)
    lw      $t5, 20($sp)
    lw      $t4, 16($sp)
    lw      $t3, 12($sp)
    lb      $t2, 8($sp)
    lw      $t1, 4($sp)
    lw      $t0, 0($sp)
    addi    $sp, $sp, 28    #reset stack pointer
    beq     $v0, $zero, addTo   #if not a space, continue to next character
    addi    $t0, $t0, 1     #if it is a space, increment count
addTo:  
    bne     $v0, $zero, nextChar #If character is a space, branch
    sll     $t7, $t6, 2     #index if nospaces string stores width of 4
    add     $t7, $t7, $t5   #now $t7 points at nospaces[i]
    sb      $t2, 0($t7)     #store the character in the nospaces string
    addi    $t6, $t6, 1     #increment the index of nospaces

nextChar:

    addi    $t4, $t4, 1     #increment the index value
    j       loop            #jump back to loop and continue processing

exitCS:
    addi    $v0, $t0, 0     #count of spaces placed into $v0
    addi    $v1, $t5, 0
    lw      $ra, 4($sp)     #load return addr from the stack
    lw      $a0, 0($sp)     #load value to check from the stack
    addi    $sp, $sp, 8     #reset stack pointer
    jr      $ra             #return

isSpace:
    addi    $sp, $sp, -12   #adjust stack pointer to make room
    sw      $s0, 8($sp)
    sw      $ra, 4($sp)     #store value of return addr onto stack
    sw      $a0, 0($sp)     #store value to check onto stack

    #Check to see if the character is a space
    li      $t0, 32         #ascii value for space character loaded into $t0
    li      $v0, 0          #Set default return to 0, or "not a space character"
    bne     $t0, $a0, endSC #if ascii values match, character is a space
    li      $v0, 1          #$v0 = 1 means it is a space character

endSC:  
    lw      $s0, 8($sp)
    lw      $ra, 4($sp)     #restore return address
    lw      $a0, 0($sp)     #restore addr of str
    addi    $sp, $sp, 12    #reset the stack pointer

end:    jr $ra

Answer 1

将sll $t7, $t6, 2更改为move $t7, $t6。无需手动对齐任何内容。

这是使用输入here's some spaces运行后程序的数据段。一旦看到错误，修复就应该很明显了。