ARM ASM label addressing/dereferencing note

arm_adressing.s

        .syntax unified
        .cpu cortex-m4
        .thumb
        .thumb_func

foo:
        ldr r0, =timer                  @ load address of label
        ldr r1, [r0, #4]                @ load word following bar ( => SysTick_VAL => 8 )
        ldr r0, [r0]			@ deref label addr => SysTick_BASE
        ldr r0, [r0, r1]		@ => val of [SysTick_BASE + SysTick_VAL]
        
        ldr r0, timer                	@ load word at label ( => SysTick_Base )
        ldr r0, [r0, #4]                @ deref addr + 4 (=> val of [SysTick_BASE + SysTick_LOAD])
        ldr r0, [r0, SysTick_VAL]       @ => val of [SysTick_BASE + SysTick_VAL]
        
        .equ SysTick_Base, 0xE000E100
        .equ SysTick_CTRL, 0x00
        .equ SysTick_LOAD, 0x04
        .equ SysTick_VAL, 0x08
        
timer:
        .word SysTick_Base
        .word SysTick_VAL