Why this code run into infinite loop in ARM

问题:

I am learning ARM assembly and compiled a code which simply ran a loop 5 times but when ran it goes to infinite loop

.global main
main:
push {ip.lr}
sub r1,r1,r1
well:
ldr r0,=message
bl printf
add r1,r1,#1
cmp r1,#6
bne well
pop {ip,pc}
message:
       .ascii "Amit Singh Tomar\n"

Why this code runs in to infinite Loop?

回答1:

printf call destroys your r1. Save your loop invariant in non-scratch register.

回答2:

R1 gets trashed by the call to printf - use a non-volatile register instead or save/restore R1 around the call to printf.