64-bit Assembly Language: Aarch64 VS. X84_64
Published: 2022-02-28 07:30:41


In this blog post, you can read about my experiment with assembler on the x86_64 and aarch64 servers. 

If you didn't ever see assembler language instructions, here is the ready source code for the Aarch64 system for this lab. 

#### Aarch64

```
.text
.globl _start

min = 0                          /* starting value for the loop index; note that this is a symbol (constant), not a variable */
max = 31                         /* loop exits when the index hits this number (loop condition is i<max) */

_start:

        mov     x19, min
        mov     x17, 10

loop:
        mov     x0, 1           /* file descriptor: 1 is stdout */
        adr     x1, msg         /* message location (memory address) */
        mov     x2, len         /* message length (bytes) */

        mov     x18, x19        /*mov x19 into x18 */
        udiv    x9, x18, x17
        add     x13, x9, 0x30
        msub    x10, x9, x17, x18 /*get remainder*/
        add     x14, x10, 0x30
        adr     x15, msg
        strb    w13, [x15, 13]

        strb    w14, [x15, 14]
        mov     x8, 64          /* write is syscall #64 */
        svc     0               /* invoke syscall */

        add     x19, x19, 1
        cmp     x19, max
        b.ne    loop

.data

msg:    .ascii      "Hello, World  #\n"
len=    . - msg
```

This is how we build this code on a specific _[server](https://wiki.cdot.senecacollege.ca/wiki/SPO600_Servers)_ 

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/z2gtf84xuja2zoh9x53v.png)
This is the output of our source code:
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8z1s1onwbji5ghzgdrvm.png)
For those interested in how my tree looks right now on the Israel server. 
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ut9vo4zp420ks5i0d0gu.png)

#### X84_64

Here is almost the same code, but for a different system.

```
/* 
   This is a 'hello world' program in x86_64 assembler using the 
   GNU assembler (gas) syntax. Note that this program runs in 64-bit
   mode.

   CTyler, Seneca College, 2014-01-20
   Licensed under GNU GPL v2+
*/

.text
.globl  _start


_start:

        movq     $0, %r15                        /* Loop counter */
        movq     $0x30, %r12                     /* value of 0 in Ascii */

loop:
        movq     $0, %rdx                        /* clearing reminder for division */
        movq     %r15, %rax                      /* set rax to be divide */
        movq     $10, %r10                       /* set divisor */
        div      %r10                            /* divide */
        movq     %rax, %r14                      /* store quotient */
        movq     %rdx, %r13                      /* store remainder */

        add      $0x30, %r14                     /* quotient to ascii */
        add      $0x30, %r13                     /* remainder to ascii */
        mov      %r13b, msg+14                   /* Modify 1 byte inmsg with remainder */

        cmp      %r12, %r14
        mov      %r14b, msg+13                   /* Modify 1 byte in msg with quotient */

        movq     $len, %rdx                      /* message length */
        movq     $msg, %rsi                      /* message location */
        movq     $1, %rdi                                /* file descriptor stdout */
        movq     $1, %rax                                /* syscall sys_write */
        syscall

        inc     %r15                            /* increment counter */
        cmp     $31, %r15                               /* see if we're done */
        jne     loop                            /* if not, loop */

        movq     $0, %rdi                                /* exit status */
        movq     $60, %rax                       /* syscall sys_exit */
        syscall

.section .data

        msg:    .ascii   "Hello World:   \n"
        len = . - msg

~             
```

On a different server.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jtss07e0ly03h9w19z24.png)
 

### Conclusion

⚠️ Computer Architecture Blog Post: Link

### Links

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_p.s This post was made for my Software Portability and Optimization class.