.intel_syntax noprefix
    .text
    .global merge
merge:
/*
    rdi - *res
    rsi - from
    rdx - mid
    rcx - to
 */
 //сохранили регистры
    push rbp
    mov rbp, rsp
    push r12
    push r13



    push rdi    //rsp + 24 -*res
    push rsi    //rsp + 16 - from
    push rdx    //rsp + 8 - mid
    push rcx    //rsp  - to

    mov rax, [rsp + 16] //start1 -rdi
    mul r8
    mov rdi, [rsp + 24]
    add rdi, rax

    mov rax, [rsp + 8] //start2 - rsi
    mul r8
    mov rsi, [rsp + 24]
    add rax, 4
    add rsi, rax

    mov rax, [rsp + 8] //mid - r12
    mul r8
    mov r12, [rsp + 24]
    add r12, rax

    mov rax, [rsp] //end - r13
    mul r8
    mov r13, [rsp + 24]
    add r13, rax

merge_loop:
    cmp r12, rdi // mid  , start1
    jl next_merge_step

    cmp r13, rsi //end, start2
    jl next_merge_step

    mov r8, [rdi] // a[start1]
    mov r9, [rsi] //a[start2]

    mov rcx, rsi // start2
    sub rcx, rdi //start1
    mov rdx, rsi //index

    cmp r9, r8
    jl change_loop

    add rdi, 4
    jmp merge_loop

change_loop:

    mov r8, rdx
    sub r8, 4
    mov r8, [r8]
    mov [rdx], r8

    sub rdx, 4

    loop change_loop

    mov [rdi], r9
    add rdi, 4
    add rsi, 4
    add r12, 4
    jmp merge_loop

next_merge_step:
    add rsp, 32
    pop r13
    pop r12
    pop rbp
    ret