我正在尝试以非常脏的方式实施合并排序算法，因为我们的老师告诉我这样做。
该程序从用户获取输入整数数组，并在每次调用sort时打印数组的值（仅用于测试。我稍后会更正）。它完全依赖于堆栈。我被告知首先以这种方式实现它，然后进一步改进算法。
但是，每次我得到0作为输出而不是输入的数字。为了测试我运行了4个数字（作为输入）的代码，如下所示
.data
Array1 : .word 0:20
Array2 : .word 0:20
.text
.globl main
main :
#initial activation record ... send the three arguments to sort......0
li $v0, 5 # system call for read_int
syscall
move $t4, $v0 # number read is put in $t0
li $v0, 5 # system call for read_int
syscall
move $t5, $v0 # number read is put in $t1
li $v0, 5 # system call for read_int
syscall
move $t6, $v0 # number read is put in $t2
li $v0, 5 # system call for read_int
syscall
move $t7, $v0 # number read is put in $t3
#do the syscall for array 1 and array 2(empty)(no syscall) and size save them in t0 , t1 , t2 respectively which are then send to stack
la $t0 , Array1
sw $t4 , 0($t0)
sw $t5 , 4($t0)
sw $t6 , 8($t0)
sw $t7 , 12($t0)
la $t1 , Array2
li $t2 , 4
sw $t0, -12($sp)
sw $t1, -8($sp)
sw $t2, -4($sp)
addi $sp, $sp, -184
jal sort
#.........display the result stored in B and then clear the stack (exit the program) ...........#
li $v0, 10 # system call for exit
syscall
#....................................................................0
#creating the initial activation record .............1
sort:
# a0 mein A (initial one) and a1 mein B (initial one) a2 mein initial n which will be taken as system call
sw $ra, 168($sp)
#//already done addi $sp , $sp , -184
#for n1 and n2
lw $t2 , 180($sp) #($t2 = n)
srl $t0 , $t2 , 1 #($t0 = n1 = n/2)
sra $t0 , $t2 , 1
sub $t1 , $t2 , $t0 #($t1 = n2 = n - n1)
sw $t1 , 164($sp) #(stored n2)
sw $t0 , 160($sp) #(stored n1)
#la $t0 , Array1
#la $t1 , Array2
#sw $t1 , 80($sp) #stored ARRAY2
#sw $t0 , 0($sp) #stored ARRAY1
#....................................................1
#SORT FUNC FIRST PART................................2
#ASSUMPTIONS:
#a0 = A
#a1 = B
#a2 = n
#BASE CASE
li $t0 , 1 #t0 = 1
bne $t0 , $t2 , firstL #((t2 = n) != 1) then go to firstL
lw $t1 , 172($sp) #t1 = &A
lw $t1 , 0($t1) #t1 = A[0]
lw $t2 , 176($sp) #t2 = &B
sw $t1 , 0($t2) #B[0] = A[0]
#sw $t2 , 176($sp) #stored &B at the desired position in stack
jr $ra
#First Loop
firstL :
#........................................................2
#CALLING SORT ...........................................3
lw $t8, 172($sp) #loading &A
sw $t8, -12($sp) #storing &A at the desired location
add $t8, $sp, $zero #loading &A1
sw $t8, -8($sp) #storing &A1 at the desired location
lw $t8, 160($sp) #loading n1
sw $t8, -4($sp) #storing n1 at the desired location
addi $sp, $sp, -184
jal sort
#.........................................................3
#CALLING SORT AGAIN ......................................4
lw $t8, 172($sp) #loading &A
lw $t7, 160($sp) #loading n1
sll $t7 , $t7 , 2 #n1*= 4 for mips address
add $t8 , $t8 , $t7 #adding &A + n1
sw $t8, -12($sp) #storing &A + n1
addi $t8, $sp, 80 #loading &A2
sw $t8, -8($sp) #storing A2
lw $t8, 164($sp) #loading n2
sw $t8, -4($sp)
addi $sp, $sp, -184
jal sort
#calling merge...........................................5
add $a0, $sp, $zero #a0 = &A1
addi $a1, $sp, 80 #a1 = &A2
lw $a2, 176($sp) #a2 = &B
lw $t8, 160($sp)
sw $t8, -8($sp) #stored p
lw $t8, 164($sp)
sw $t8, -4($sp) #stored q
addi $sp, $sp, -12
jal merge
#........................................................5
#return from sort........................................8
lw $ra, 168($sp)
lw $t0 , 176($sp)
lw $t1 , 0($t0)
lw $t2 , 4($t0)
lw $t3 , 8($t0)
lw $t4 , 12($t0)
li $v0, 1 # system call for print_int
move $a0, $t1 # number in $t3 is to be printed
syscall
li $v0, 1 # system call for print_int
move $a0, $t2 # number in $t3 is to be printed
syscall
li $v0, 1 # system call for print_int
move $a0, $t3 # number in $t3 is to be printed
syscall
li $v0, 1 # system call for print_int
move $a0, $t4 # number in $t3 is to be printed
syscall
addi $sp , $sp , 184
jr $ra
#........................................................8
#Merge ..................................................6
merge:
sw $ra, 0($sp) #stored ra .........
#ASSUMPTION :
#a0 = P #available from stack though.....
#a1 = Q
#a2 = R
#s1 = p
#s2 = q
lw $s1 , 4($sp)
lw $s2 , 8($sp)
move $t0 , $zero # t0 = i , t1 = j, t2 = k (= 0)
move $t1 , $zero
move $t2 , $zero
While1:
sll $t3 , $t0 , 2
add $t3 , $t3 , $a0 #t3 = &P[i]
sll $t4 , $t1 , 2
add $t4 , $t4 , $a1 #t4 = &Q[j]
lw $t5 , 0($t3) #t5 = P[i]
lw $t6 , 0($t4) #t6 = Q[j]
sll $t7 , $t2 , 2
add $t7 , $t7 , $a2 #t7 = &R[k]
bge $t0 , $s1 , While2
bge $t1 , $s2 , While2 # exit loop 1 if j>=q or i>=p
bge $t5 , $t6 , While12
sw $t5 , 0($t7) #R[k] = P[i]
addi $t0 , $t0 , 1 #incremented i and k
addi $t2 , $t2 , 1
j While1
While12:
sw $t6 , 0($t7) #R[K] = Q[j]
addi $t1 , $t1 , 1 #incremented j and k
addi $t2 , $t2 , 1
j While1
While2:
bge $t0 , $s1 , While3 #exit loop if i >= p
sw $t5 , 0($t7) #R[k] = P[i]
addi $t0 , $t0 , 1 #incremented i and k
addi $t2 , $t2 , 1
j While1
While3:
bge $t1 , $s2 , Exit #exit loop if j>= q
sw $t6 , 0($t7) #R[k] = Q[j]
addi $t1 , $t1 , 1 #incremented j and k
addi $t2 , $t2 , 1
j While1
Exit :
#.........................................................6
#return from merge........................................7
lw $ra, 0($sp)
addi $sp, $sp, 12
jr $ra
#..........................................................7
#....................... END ..................................#
请告诉我它为什么不起作用。我已经尝试了很多。
我非常感谢正确的答案。
答案 0 :(得分：2)
这很困难，但我弄清楚错误是什么。
在BASE CASE部分中，我必须在原始点恢复堆栈。 这是因为在返回排序之前，每次都将值184添加到堆栈中。 我忘了基本情况也是排序程序本身的一个实例。 因此，必须在那里添加值184。
更正的程序（仅基础案例部分）：
li $t0 , 1 #t0 = 1
bne $t0 , $t2 , firstL #((t2 = n) != 1) then go to firstL
lw $t1 , 172($sp) #t1 = &A
lw $t1 , 0($t1) #t1 = A[0]
lw $t2 , 176($sp) #t2 = &B
sw $t1 , 0($t2) #B[0] = A[0]
addi $sp , $sp , 184 #THE CORRECTION
jr $ra