assembly code analysis

[David Littell]

Can anyone comment on the prologue and epilogue of following CM7 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!