如何用汇编语言循环

Question

我如何计算斐波那契数列中的前 12 个值并将其放入 EAX 寄存器中？并显示调用 DumpRegs？使用间接寻址我知道我需要一个 for 循环，但我不知道如何去做。任何帮助或提示表示赞赏。

      INCLUDE Irvine32.inc

; (insert symbol definitions here)

.data

; (insert variables here)
   Fibonacci BYTE 1, 1, 10 DUP (?)

.code
main PROC

; (insert executable instructions here)


    ; (This below will show hexa contents of string.)
      mov   esi, OFFSET Fibonacci       ; offset the variables
      mov   ebx,1                   ; byte format
      mov   ecx, SIZEOF Fibonacci       ; counter
      call  dumpMem 


    exit        ; exit to operating system
main ENDP

; (insert additional procedures here)

END main

Answer 1

您可以创建如下循环：

mov ecx,12
your_label:
; your code
loop your_label

循环指令递减 ecx 并跳转到指定标签，除非 ecx 等于 0。您还可以像这样构建相同的循环：

mov ecx,12
your_label:
; your code
dec ecx
jnz your_label

Answer 2

您确定需要一个 for 循环来实现您的目标，因此也许 for 循环的 C 实现（在汇编中）将帮助您：

Code Generation for For Loop

for (i=0; i < 100; i++)
{
  . . .
}

      * Data Register D2 is used to implement i.
      * Set D2 to zero (i=0)
      CLR.L D2

  L1  
      . . .
      * Increment i for (i++)
      ADDQ.L #1, D2
      * Check for the for loop exit condition ( i < 100)
      CMPI.L #100, D2
      * Branch to the beginning of for loop if less than flag is set
      BLT.S L1

来源：eventhelix.com

Answer 3

.model small
.stack 100h
.data
   msg db 'Enter height of the square form 1-9: 

   hash db '#

   height db 1
   length db 0
   ctr dw 0
   msgagain db 13,10,'Do you want to repeat the program? 

   msgend db 13,10,'Program Terminated! Press any key to exit..

.code
   mov ax, @data
   mov ds, ax
REPEAT:   
   mov ax, 03
   int 10h

   mov ah, 09
   lea dx, msg
   int 21h

   mov ah, 01
   int 21h

   cmp al, '1'
   jl REPEAT
   cmp al, '9'
   jg REPEAT

   sub al, 48
   mov length, al
   mov bl, 1
   mul bl

   mov height, 1  
   mov di, 1 
   mov ctr, ax

   mov cx, ax
   nextline:
      dec length

      mov ah, 02
      mov bh, 00
      mov dl, length
      mov dh, height
      int 10h

      mov cx, di
      hashtags:
         mov ah, 09
         lea dx, hash
         int 21h
      loop hashtags      

      inc di
      inc height
      mov cx, ctr
      dec ctr
   loop nextline

   mov ah, 09
   lea dx, msgagain
   int 21h

   mov ah, 01
   int 21h

   cmp al, 'Y'
   je REPEAT
   cmp al, 'y'
   je REPEAT   

   mov ah, 09
   lea dx, msgend
   int 21h

   mov ah, 01
   int 21h

   mov ah, 4ch
   int 21h

END