Implement a function in assembly that would do the following: . loop through a s

Question

Implement a function in assembly that would do the following: . loop through a sequence of characters and swap them such that the end result is the original strinq in reverse . before looping, call another assembly function to extract the number of characters in the string . for swapping characters, call another assembly function to do just that Submit just your .cppl/.c and .asm files. The three assembly functions should be called something appropriate like reverse(). getLength(),swap(). Your C++ code should initialize a C-string (null terminated) and call just the reverse function. Display the resulting string. Comments are always a good idea.

Explanation / Answer

revwords isn't a function in my attempt, i put it in main for now until i get it working. I created the rev function and tested it and it works for a string. Then i went on to create the other one and thats where i'm having issues. It goes through the words and everything but the output i get is LucyLove_I_ whrere _ are spaces. I've tried to fix it where the space is still in the correct location but I cannot figure it out. The code is posted below, if anyone has any suggestions it would really help, I've spent hours trying to fix this little bug and i've lost hope. .data string: .asciiz "I Love Lucy" endl: .asciiz " " space: .asciiz " " .text .globl main rev: #la $s0, string #addi $a1, $0, 7 add $t2, $0, $0 # set the counter variable to 0 srl $t0, $a1, 1 # divide the number of characters by 2 add $t1, $0, $a1 # put the number of characters into t1 addi $t1, $t1, -1 # subtract 1 from the number of characters add $t1, $a0, $t1 # add to the beginning address to get to the end address loop: lb $t6, 0($a0) # load the byte into t6 (left half) lb $t7, 0($t1) # load the byte into $t7 (right half) sb $t6, 0($t1) # store t6 at position t1, basically swap sb $t7, 0($a0) # store t7 at position a0, swapping addi $a0, $a0, 1 # get the address of the next pixel by adding 1 addi $t1, $t1, -1 # get the address of the previous pixel from end by adding -1 addi $t2,$t2, 1 # increment the counter by 1 bne $t0, $t2, loop # while the counter is not equal to half the number of characters loop jr $ra # jump back to where the function was called main: la $a0, string # load the address of the string into a0 addi $sp, $sp, -12 # make space on the stack for a0 sw $a0, 0($sp) # store a0 sw $ra, 4($sp) # store ra addi $a1, $0, 11 # 11 = total number of characters jal rev # call rev with whole string la $a0, string # print the string and an end line li $v0, 4 syscall la $a0, endl syscall lw $a0, 0($sp) # load the string back into a0, since rev changed the variable addi $t3, $0, 32 # t3 holds the value for a space, 32 add $s0, $a0, $0 # s0 is a0 outerLoop: add $a1, $0, $0 # set the num of characters counter to 0 add $a0, $s0, $0 # set a0 to s0 innerLoop: addi $a0, $a0, 1 # add 1 to the current address addi $a1, $a1, 1 # add 1 to the counter lb $t8, 0($a0) # load the byte at a0 beq $t8, $0, after # if it is the end jump to after bne $t8, $t3, innerLoop # if there is not a space loop again after: add $s0, $a0, $0 # add a0 to s0 for storage sub $a0, $a0, $a1 # subtract a1 from a0 to get to the beginning of the word jal rev add $a0, $s0, $0 # restore a0 after function call lb $t8, 0($a0) # load the byte into t0 bne $t8, $0, outerLoop # if its not the end loop again la $a0, string li $v0, 4 syscall

Reference https://www.physicsforums.com/threads/mips-assembly-loop-help.395942/

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