オーケー配列インデックス計算するときに、あなたが書かなければならなかった機能が間違ったレジスタを使用していました：
変更：
sll $t2,$t2,2 # compute 4i in $t2
を中へ：
sll $t2,$t1,2 # compute 4i in $t2
しかし、あなたの機能にはさらに多くのものがありましたひどいバグ。関数の先頭に戻り、処理中にの複数のスタックフレームを作成していました。私はあなたがExit: [mainの一部です]にジャンプして機能を補償して終了しようとした理由を、これをあるレベルで認識したと思います。
また、計算機能は、最初の最大値を見つけた後も早期に終了します。 ではなく、は、より良い（つまり大きな）値を見つけるために配列の残りの部分をループし続けます。
他にも多数のバグがありました。
私はあなたのプログラムの2つのバージョンを作成しました。バグに関する注釈付きのもの。そして、2番目のバージョンは、クリーンアップし、作業しています。ここで
注釈付きバージョンは、[無償スタイルのクリーンアップをご容赦ください]である。ここで
.data # data segment
nl: .asciiz "\n" # ASCII for a new line
separator: .asciiz ":" # string that seprates index from number
msg1: .asciiz "The function returned "
# NOTE/BUG: these "li" are misplaced and have no meaning
msg2: .asciiz "\nThe maximum value is "
###li $v0,$t5
msg3: .asciiz "\nThe address of the word is "
# .asciiz
# .asciiz
###li $v0,$t6
.align 2 # important for words
###buffer: .space 4096 # allocate space for 1K words
buffer: .space 128 # allocate space for 1K words
bufe:
.text # Code segment
.globl main # declare main to be global
main:
addi $sp,$sp,-4 # allocate space on the stack for $s0
sw $s0,($sp) # save $s0
# specify the size of the array, must be less than 1024
la $s1,bufe # get address of array end
la $a0,buffer # get address of array
subu $s1,$s1,$a0 # get byte length of array
srl $s0,$s1,2 # get word count of array
# NOTE/BUG: "name" is undefined
###la $a0,name # load the address of "name" into $a0
###li $v0,4 # system call, type 4, print an string, *$a0
###syscall # call the "OS"
# call
la $a0,buffer
move $a1,$s0
jal init_array # initialize the array with random values
la $a0,buffer
move $a1,$s0
jal print_array # call print. You can comment it out.
# call your find_max function
la $a0,buffer
move $a1,$s0
# NOTE/BUG: these serve no purpose
lw $t0,0($a0)
la $t5,0($a0)
jal find_max # call find_max
# NOTE/BUG: these serve no purpose
lw $v0,0($t0)
lw $v1,0($t5)
# NOTE/BUG: the messages are printed below, but not the actual values
# add code to print the results
# print the returned value
la $a0,msg1 # print mssage 1
li $v0,4
syscall
# print the maximum value
la $a0,msg2 # print mssage 2
li $v0,4
syscall
# print the address of the value (in hex).
la $a0,msg3 # print mssage 3
li $v0,4
syscall
la $a0,nl # print end of line
syscall
# restore $s0. You can check $sp here to make sure the stack is maintained correctly.
lw $s0,($sp) # load $s0
addi $sp,$sp,4 # restore $sp
Exit:
# NOTE/BUG: these serve no purpose
lw $v0,0($t5)
lw $v1,0($t6)
# NOTE/BUG: the "li" should _not_ be commented out
# li $v0,10 # System call, type 10, standard exit
syscall # ...and call the OS
# your implementation of find_max
#
# arguments:
# a0 -- buffer address
# a1 -- buffer count
#
# registers:
#
find_max:
addi $sp,$sp,-16 # allocate stack space for four registers
sw $s0,($sp) # save $s0
sw $s1,4($sp) # save $s1
sw $s2,8($sp) # save $s2
sw $s3,12($sp) # save $s3
# NOTE/BUG: the "max" value is never initialized to anything
# put your code below.
# You can use temporary registers and $s0 to $s3
# NOTE/BUG: $t1 has _not_ been initialized
add $t1,$t1,1 # increment index i by 1
# NOTE/BUG: we just want to exit the function and _not_ the program -- this
# bug is linked to the one below
beq $t1,$s0,Exit # if all elements examined, quit
# NOTE/BUG: this should be:
# sll $t2,$t1,2
###sll $t2,$t2,2 # compute 4i in $t2
sll $t2,$t1,2 # compute 4i in $t2
add $t2,$t2,$s1 # form address of A[i] in $t2
# THIS IS THE LINE GIVING PROBLEMS
# NOTE/FIX: with the bugfix it won't
lw $t3,0($t2) # load value of A[i] into $t3
slt $t4,$t0,$t3 # maximum < A[i]?
# NOTE/BUG: this should _not_ loop back to find_max as that will create
# _multiple_ stack frames -- it is because of _this_ bug that you
# tried to compensate and leave this function by jumping to Exit
beq $t4,$zero,find_max # if not, repeat with no change
# NOTE/BUG: if you set a new maximum, you still have to loop back and _not_
# just exit this function. you may have found the _first_ maximum but there
# could be others (i.e. larger values)
addi $t0,$t3,0 # if so, A[i] is the new maximum
addi $t5,$t2,0
# restore saved registers.
# make sure $sp is restored if you changed it.
lw $s0,($sp)
lw $s1,4($sp)
lw $s2,8($sp)
lw $s3,12($sp)
addi $sp,$sp,16 # restore $sp
jr $ra # return to calling routine
# init_array -- initialize array with random values
#
# arguments:
# a0 -- array address
# a1 -- array count
#
# registers:
# t0 -- array address
# t1 -- array count
init_array:
move $t0,$a0 # prevent value from being clobbered
move $t1,$a1 # prevent value from being clobbered
init_loop:
li $v0,41 # syscall for random int
li $a0,0 # specify which generator to use
syscall
sw $a0,0($t0) # store into array
addiu $t0,$t0,4 # advance to next array element
subi $t1,$t1,1 # decrement count
bgtz $t1,init_loop # more to do? if yes, loop
jr $ra # return
# print_array -- initialize array with random values
#
# arguments:
# a0 -- array address
# a1 -- array count
#
# registers:
# t0 -- array address
# t1 -- array index
print_array:
move $t0,$a0 # prevent value from being clobbered
li $t1,0 # array index
print_array_loop:
move $a0,$t1 # index value
li $v0,1 # syscall for print int
syscall
la $a0,separator
li $v0,4
syscall
lw $a0,0($t0) # get array value
li $v0,1 # syscall for print int
syscall
# output a newline
la $a0,nl
li $v0,4
syscall
addiu $t0,$t0,4 # advance to next array element
addi $t1,$t1,1 # increment index
blt $t1,$a1,print_array_loop # more to do? if yes, loop
jr $ra # return
は固定し、実行しているバージョンです。私は不足しているinit_arrayとprint_arrayの機能と結果の印刷を追加しました。あなたが与えたボイラープレートコードにも、私が修正したいくつかの[マイナー]バグがありました。私はあなたのfind_maxコードに忠実にしようとしましたが、残念ながら、私はそれをリファクタリングする必要がありました。
はまた、MIPSの下ABIは、$v*、$a*、および$t*がいかなる目的のために呼び出される関数で使用することができるという事実をメモしておきます。したがって、$s*レジスタを変更することは、内部的にはfind_maxの問題ではありませんでした。
.data # data segment
.align 2 # important for words
###buffer: .space 4096 # allocate space for 1K words
buffer: .space 128 # allocate space for 1K words
bufe:
nl: .asciiz "\n" # ASCII for a new line
separator: .asciiz ":" # string that seprates index from number
msg1: .asciiz "The function returned "
msg2: .asciiz "\nThe maximum value is "
msg3: .asciiz "\nThe address of the word is "
.text # Code segment
.globl main # declare main to be global
main:
addiu $sp,$sp,-4 # allocate space on the stack for $s0
sw $s0,($sp) # save $s0
# specify the size of the array, must be less than 1024
la $s0,bufe # get address of array end
la $a0,buffer # get address of array
subu $s0,$s0,$a0 # get byte length of array
srl $s0,$s0,2 # get word count of array
la $a0,buffer
move $a1,$s0
jal init_array # initialize the array with random values
la $a0,buffer
move $a1,$s0
jal print_array # call print. You can comment it out.
# call your find_max function
la $a0,buffer
move $a1,$s0
jal find_max # call find_max
move $t0,$v0 # save address
move $t1,$v1 # save value
# add code to print the results
# print the maximum value
la $a0,msg2 # print mssage 2
li $v0,4
syscall
move $a0,$t1 # get max value
li $v0,1
syscall
la $a0,nl
li $v0,4
syscall
# print the address of the value (in hex).
la $a0,msg3 # print mssage 3
li $v0,4
syscall
move $a0,$t0 # get address of max value
li $v0,34
syscall
la $a0,nl
li $v0,4
syscall
# restore $s0. You can check $sp here to make sure the stack is maintained correctly.
lw $s0,($sp) # load $s0
addiu $sp,$sp,4 # restore $sp
li $v0,10 # exit program
syscall # ...and call the OS
# your implementation of find_max
#
# RETURNS:
# v0 -- address of maximum value
# v1 -- maximum value
#
# arguments:
# a0 -- buffer address
# a1 -- buffer count
#
# registers:
# t0 -- current value
# t1 -- test/temporary
find_max:
addiu $sp,$sp,-16 # allocate stack space for four registers
sw $s0,($sp) # save $s0
sw $s1,4($sp) # save $s1
sw $s2,8($sp) # save $s2
sw $s3,12($sp) # save $s3
# put your code below.
# You can use temporary registers and $s0 to $s3
# initialize the maximum value from the first element
move $v0,$a0 # get the address
lw $v1,0($a0) # get the value
find_max_loop:
addiu $a0,$a0,4 # advance buffer pointer
subi $a1,$a1,1 # decrement remaining count
blez $a1,find_max_done # more to do? if no, return
lw $t0,0($a0) # get current value
slt $t1,$v1,$t0 # got new maximum?
beqz $t1,find_max_loop # no, loop
move $v0,$a0 # set new maximum pointer
move $v1,$t0 # set new maximum value
j find_max_loop # try next value
# restore saved registers.
# make sure $sp is restored if you changed it.
find_max_done:
lw $s0,($sp)
lw $s1,4($sp)
lw $s2,8($sp)
lw $s3,12($sp)
addiu $sp,$sp,16 # restore $sp
jr $ra # return to calling routine
# init_array -- initialize array with random values
#
# arguments:
# a0 -- array address
# a1 -- array count
#
# registers:
# t0 -- array address
# t1 -- array count
init_array:
move $t0,$a0 # prevent value from being clobbered
move $t1,$a1 # prevent value from being clobbered
# seed the generator
li $v0,40
li $a0,0
li $a1,0x12345678
syscall
init_loop:
li $v0,41 # syscall for random int
li $a0,0 # specify which generator to use
syscall
sw $a0,0($t0) # store into array
addiu $t0,$t0,4 # advance to next array element
subi $t1,$t1,1 # decrement count
bgtz $t1,init_loop # more to do? if yes, loop
jr $ra # return
# print_array -- initialize array with random values
#
# arguments:
# a0 -- array address
# a1 -- array count
#
# registers:
# t0 -- array address
# t1 -- array index
print_array:
move $t0,$a0 # prevent value from being clobbered
li $t1,0 # array index
print_array_loop:
move $a0,$t1 # index value
li $v0,1 # syscall for print int
syscall
la $a0,separator
li $v0,4
syscall
lw $a0,0($t0) # get array value
li $v0,1 # syscall for print int
syscall
# output a newline
la $a0,nl
li $v0,4
syscall
addiu $t0,$t0,4 # advance to next array element
addi $t1,$t1,1 # increment index
blt $t1,$a1,print_array_loop # more to do? if yes, loop
jr $ra # return