SQRT TABLE FOR LOG CALCULATION

; input one single double precision number and get the table for successive square roots
; warning: no error checking options are added
; assemble using `nasm -f elf64 -o output.o file.asm`
; link using `gcc -o output output.o`
    extern  printf
    extern  scanf
    section     .data
two     dq      2.0
fmt     db      "iter#%02d: sqrt(%.10lf) = %.10lf",10,0
fmt2    db      "%lf"
    section     .bss
b   resq        1
    section     .text
    global  main
main:
    push    rbp
    mov     rbp, rsp
    sub     rsp, 0x30

input:
    mov     rdi, fmt2
    mov     rsi, b
    call    scanf

    xor     r12, r12
    mov     rax, qword [b]
    movsd   xmm0, qword [b]

    movsd   xmm1, xmm0
log_loop:
    mov     ecx, 6
sqrt_loop:
    movsd   xmm2, xmm0
    divsd   xmm2, xmm1
    addsd   xmm1, xmm2
    movsd   xmm2, qword [two]
    divsd   xmm1, xmm2
    movq    rax, xmm1
    loop sqrt_loop

    inc     r12
    movsd   xmm2, xmm1
    mov     rdi, fmt
    mov     rsi, r12
    mov     rax, 2
    call    printf

    movsd   xmm0, xmm2
    movsd   xmm1, xmm2
    cmp     r12, 34
    jle     log_loop

    mov     rsp, rbp
    pop     rbp
    ret