.section .data
    .align 4
value:
    .word 0x04030201

    .section .text
    .globl _start
_start:
    ldr r0, =value  @ Load the address of value into r0
    ldr r1, [r0]    @ Load the 4-byte value from memory into r1
    rev r2, r1      @ Reverse the byte order