ARMv8 Printing Multiple Strings with Same Number Reference

Question

Here's my code, before I explain my problem:

I'm new to ARM by the way, so I'm a super newbie. For now, I just cut out the unnecessary bits of my code. x0 - x7 being the "argument" registers, x29 is the frame pointer and x30 is the link register. x19 and x20 are just callee saved registers.

string1:        .string "constant = %d   low value = %d \n\n"
string2:        .string "constant = %d \n"


                .balign 4
                .global main

main:           stp     x29,    x30,    [sp,    -16]!
                mov     x29,    sp

                mov     x20,    -1000         // Setting values
                mov     x19,    5

print:          adrp    x0,    string1
                add     x0,    x0,     :lo12:string1
                mov     x1,    x19
                mov     x2,    x20
                bl      printf

print2:         adrp    x0,    string2
                add     x0,    x0,     :lo12:string2
                mov     x3,    x19
                bl      printf


done:           mov x0, 0

end:            ldp     x29,   x30,   [sp],   16
                ret

Now for some reason, during "print", it prints out "constant = 5" just fine. However when it goes to "print2", it prints out "constant = 0". What's happening and why does it not print to 5 even though I haven't manipulated register x19 yet? I don't have quite the full grasp of how these work.

Result:

  constant = 5    low value = -1000

  constant = 0

thanks

Answer 1

In the event you want to create regular functions, as compared to inserting such functions within the body of your main code section, here's some code to prime the ARMv8 pump. My .include is just for my macros (i.e., push2 & pop2, etc); which is the same code you are using.

 .data
        string1:        .string "constant = %d low value = %d\n\n"
        string2:        .string "constant = %d \n"
.text
        .global main
        .include "mymac_armv8.s"        // for push2, pop2, and _exit macros

main:
        movn x20, 1000
        mov x19, 5

        bl write1
        bl write2

_exit

write1:
        push2 x29, x30
        push2 x1, x2
        ldr x0,=string1
        mov x1, x19
        mov x2, x20
        bl printf
        pop2 x1, x2
        pop2 x29, x30
        ret

write2:
        push2 x29, x30
        push2 x1, x2
        ldr x0,=string2
        mov x1, x19
        mov x2, x20
        bl printf
        pop2 x1, x2
        pop2 x29, x30
        ret