lecture6-1, Assembly

Language: Layout:

;File: index1.asm
;
;This program demonstrates the use of an indexed addressing mode
;to access array elements
;
;This program has no I/O. Use the debugger to examine its effects
;
;nasm -felf64 -g index1.asm -o index1.o
;ld -o index1 index1.o
;

section .data
arr: dd 0,1,2,3,4,5,6,7,8,9 ; ten 32-bit words
base: equ arr - 4

section .text
global _start

_start:
        ;Add 5 to each element of the array stored in arr
        ;Simulate
        ;
        ; for (i=0; i<10l i++) {
        ;   arr[i] += 5;
        ; }

init:   mov rcx,0                       ;rcx simulates i
loop1:  cmp rcx,10                      ; i<10
        jge done1
        add [rcx*4+arr], dword 5        ; arr[i] += 5
        inc rcx                         ; i++
        jmp loop1
done1:
        ;another way
init2:  mov rcx,9                       ; i=9
loop2:  add [rcx*4+arr], dword 5        ; arr[i] += 5
        dec rcx                         ; i--
        jge loop2                       ; loop while rcx >= 0

;another way
init3:  mov rdi,base                    ; base computed by ld
        mov rcx,10                      ; i = 10
loop3:  add [rdi+rcx*4], dword 5        ; arr[i] += 5
        loop loop3                      ; loop = dec rcx, jne

alldone:
        mov rax,60
        xor rdi,rdi
        syscall

Show compiler warnings [ + ] Show input