; THIS CODE HAS BEEN TESTED AND IS FULLY OPERATIONAL.

; Problem Statement: Write 80387 ALP to find the roots of the quadratic equation. All the possible cases must be considered in calculating the roots.

; Code from Microprocessor (SPPU - Second Year - Computer Engineering - Content) repository on KSKA Git: https://git.kska.io/sppu-se-comp-content/Microprocessor/


; BEGINNING OF CODE
section .data
msg1 db "Complex Root",10
msglen1 equ $-msg1
msg2 db "Root 1: "
msglen2 equ $-msg2
msg3 db 10, "Root 2: "
msglen3 equ $-msg3
a dd 1.00
b dd -6.00
c dd 8.00
four dd 4.00
two dd 2.00

hdec dq 100
point db "."

section .bss

	root1 resd 1
	root2 resd 1
	resbuff rest 1
	temp resb 2
	disc resd 1

%macro write 2        ;macro for display
	mov rax,1
	mov rdi,1
	mov rsi,%1
	mov rdx,%2
	syscall
%endmacro

%macro read 2         ;macro for input
       mov rax,0
       mov rdi,0
       mov rsi,%1
       mov rdx,%2
       syscall
%endmacro


%macro exit 0         ;macro for exit
	mov rax,60
	xor rdi,rdi
	syscall
%endmacro

section .text
  global _start
  _start:

  finit               ;initialise 80387 co-processor
  fld dword[b]        ;stack: b

  fmul dword[b]       ;stack: b*b

  fld dword[a]        ;stack: a, b*b

  fmul dword[c]       ;stack: a*c, b*b

  fmul dword[four]    ;stack: 4*a*c,b*b

  fsub                ;stack: b*b - 4*a*c

  ftst                ;compares ST0 and 0
  jb no_real_solutions

  fsqrt               ;stack: sqrt(b*b - 4*a*c)
  fst dword[disc]     ;store disc= sqrt(b*b - 4*a*c)

  fsub dword[b]       ;stack: disc-b

  fdiv dword[a]       ;stack: disc-b/2*a or (-b+disc)/2a


  fdiv dword[two]

  write msg2,msglen2

  call disp_proc

  fldz                ;stack:0
  fsub dword[disc]    ;stack:-disc
  fsub dword[b]       ;stack: -disc - b
  fdiv dword[a]       ;stack: (-b - disc)/(2*a)
  fdiv dword[two]

  write msg3,msglen3
  call disp_proc
  jmp exi

no_real_solutions:
write msg1,msglen1
exi :

mov rax,60
mov rdi,1
syscall


disp_proc:
	FIMUL dword[hdec]
	FBSTP tword[resbuff]
	mov rsi,resbuff+9
	mov rcx,09
  next1:

  	push rcx
  	push rsi

  	mov bl,[rsi]
  	call disp

  	pop rsi
  	pop rcx

   	dec rsi
  	loop next1

    push rsi
  	write point,1
    pop rsi
  	mov bl,[rsi]
  	call disp
    ret


disp:
    	mov rdi,temp            ;mov dnum address into edi
    	mov rcx,02              ;initialize ecx with 2
    	dispup1:
    	    rol bl,4            ;rotate bl by 4 bits
            mov dl,bl         ;move bl into dl
            and dl,0fh        ;and of dl with 0fh
            add dl,30h        ;add 30h into dl
            cmp dl,39h        ;compare dl with 39h
            jbe dispskip1     ;jump if below and equal to dispskip1
            add dl,07h        ;add 7h into dl
            dispskip1:
                mov [rdi],dl  ;mov dl into dnum
                inc rdi       ;increament edi by a byte
            loop dispup1      ;loop dispup1 while ecx not zero
            write temp,2      ;Display dnum by calling macro
          ret                 ;return from procedure
; END OF CODE