Function assembly code analysis

[Littell]

Can anyone comment on the prologue and epilogue of following code, particularly the content of r7 when the routine returns?

{
   0:	b480      	push	{r7}
   2:	af00      	add	r7, sp, #0

    if ((ANADIG_MISC->MISC_DIFPROG & ANADIG_MISC_MISC_DIFPROG_CHIPID(0x10U)) != 0U)
   4:	4b0b      	ldr	r3, [pc, #44]	@ (34 <RamBased_ROM_API_Init+0x34>)
   6:	f8d3 3800 	ldr.w	r3, [r3, #2048]	@ 0x800
   a:	f003 0310 	and.w	r3, r3, #16
   e:	2b00      	cmp	r3, #0
  10:	d005      	beq.n	1e <RamBased_ROM_API_Init+0x1e>
    {
        g_bootloaderTree = ((bootloader_api_entry_t *)*(uint32_t *)0x0021001cU);
  12:	4b09      	ldr	r3, [pc, #36]	@ (38 <RamBased_ROM_API_Init+0x38>)
  14:	681b      	ldr	r3, [r3, #0]
  16:	461a      	mov	r2, r3
  18:	4b08      	ldr	r3, [pc, #32]	@ (3c <RamBased_ROM_API_Init+0x3c>)
  1a:	601a      	str	r2, [r3, #0]
    }
    else
    {
        g_bootloaderTree = ((bootloader_api_entry_t *)*(uint32_t *)0x0020001cU);
    }
}
  1c:	e004      	b.n	28 <RamBased_ROM_API_Init+0x28>
        g_bootloaderTree = ((bootloader_api_entry_t *)*(uint32_t *)0x0020001cU);
  1e:	4b08      	ldr	r3, [pc, #32]	@ (40 <RamBased_ROM_API_Init+0x40>)
  20:	681b      	ldr	r3, [r3, #0]
  22:	461a      	mov	r2, r3
  24:	4b05      	ldr	r3, [pc, #20]	@ (3c <RamBased_ROM_API_Init+0x3c>)
  26:	601a      	str	r2, [r3, #0]
}

  28:	bf00      	nop
  2a:	46bd      	mov	sp, r7
  2c:	f85d 7b04 	ldr.w	r7, [sp], #4
  30:	4770      	bx	lr
  32:	bf00      	nop

  34:	40c84000 	.word	0x40c84000
  38:	0021001c 	.word	0x0021001c
  3c:	80981070 	.word	0x80981070
  40:	0020001c 	.word	0x0020001c

Thanks very much!

[Littell]

So you guys are completely stumped by a tiny bit of assembly? 

[Pablo_Ramos]

Hi @Littell,

Could you help me with the following information?

Which MCU are you using?

Could you explain what is the expected behavior of the application?

[Littell]

It's an RT1176 (CM7) and the expected behavior isn't relevant - I'm asking for an analysis of the assembly code, in particular the contents of r7 when the function returns.

[Pablo_Ramos]

My apologies for the late reply.

I understand may not be able to share more information about the application, however, custom code and assembly code is out of the scope of support through this channel.
If you need help with any ARM related instructions in particular, I would recommend contacting ARM support. For NXP products related questions you may also contact your NXP Distributor for help.

Please let me know if there’s anything else that I can do for you.
Regards,