fibofucked.s

.intel_syntax noprefix

.section .rodata
FORMAT_STRING:
.string "%d %d\n"

.section .text
splittable64:
    // rdi: x
    // rax: a
    mov rax, rdi
    shr rax, 30
    xor rdi, rax
    mov rcx, 0xbf58476d1ce4e5b9
    imul rdi, rcx
    mov rax, rdi
    shr rax, 27
    xor rdi, rax
    mov rcx, 0x94d049bb133111eb
    imul rdi, rcx
    mov rax, rdi
    shr rax, 31
    xor rax, rdi
    ret

fjump:
    # Save all caller saved registers, because it makes calling this
    # garbage at least a bit less painful
    push rax
    mov rax, [rsp + 0x8] # Return address
    push rdi # Used by splittable64
    push rcx # Used by splittable64
    push rdx # Used internally

    sub rax, r12
    mov rdx, rax
    mov rdi, rax
    call splittable64
    and rax, 0xF
    add rax, rdx
    add rax, r12

    pop rdx
    pop rcx
    pop rdi
    mov [rsp + 0x8], rax
    pop rax
    ret

fibonacci:
    // edi: index
    // ecx: val1
    // eax: val2
    // edx: counter
    // esi: oldval
    cmp edi, 0
    je fibonacci_zero
    lea r12, [rip]
    mov ecx, 0
    call fjump
    mov ebx, 1
    sub rsp, 0x8
    mov eax, 1
    mov edx, 1
    call fjump
    mov edi, edx
    add esi, 1
    mov ecx, esi
    call fjump
fibonacci_loop_top:
    cmp edx, edi
    jge fibonacci_loop_end
    call fjump
    add esi, 1
    and esi, 0xF
    call fjump
    mov esi, eax
    add eax, ecx
    call fjump
    mov edx, 1
    add ecx, 1
    call fjump
    mov ecx, esi
    add edx, 1
    jmp fibonacci_loop_top
fibonacci_loop_end:
    ret
fibonacci_zero:
    mov eax, 0
    ret

.global main
main:
    // ecx: i
    // edx: fib
    push rbx
    mov ebx, 0
main_loop_top:
    cmp ebx, 20
    jge main_loop_end
    mov edi, ebx
    call fibonacci
    lea rdi, [rip + FORMAT_STRING]
    mov esi, ebx
    mov edx, eax
    mov eax, 0
    call printf
    add ebx, 1
    jmp main_loop_top
main_loop_end:
    mov eax, 0
    pop rbx
    ret