add draw condition and fix not-so good but also not terrible issue with rbx register not being reserved in makeAIMove

game.s

@@ -1,11 +1,9 @@
-; TODO out of moves check
-
 global _start
 
 section .text
 
 checkVictory:
-  mov rax, 0
+  mov eax, 0
   
   mov cl, [fieldBuffer + 12]
   and cl, [fieldBuffer + 14]
@@ -64,25 +62,26 @@ checkVictory:
 
 makeAIMove:
   rdtsc
-  mov rbx, rax
+  mov r8, rax
 .loop:
   ; RAND from wiki https://en.wikipedia.org/wiki/Linear_congruential_generator. Numerical Recipes ranqd1, Chapter 7.1, §An Even Quicker Generator, Eq. 7.1.6 parameters from Knuth and H. W. Lewis
   mov rdx, 1664525
   mul rdx
   add rax, 1013904223
-  mov rbx, rax
+  mov r8, rax
 
   ; clamping to 1-3 range and moving to rdi
   mov rsi, 3
   mov rax, 0
-  mov ah, bh
+  mov al, r8b
   mov dx, 0
   div si ;TODO for some reason div sil causes division by zero
   inc dx
   mov di, dx
   shl di, 8
   mov rax, 0
-  mov ah, bl
+  mov ax, r8w
+  shr ax, 8
   mov dx, 0
   div si
   inc dx
@@ -91,7 +90,7 @@ makeAIMove:
   call placeChar
   cmp rax, 0
   je .return
-  mov rax, rbx
+  mov rax, r8
   jmp .loop
   
 .return:
@@ -175,6 +174,7 @@ _start:
   mov rdx, readInputsMessageLen        ; size
   syscall                       ; 
 
+  mov rbp, 0 ; number of moves done
 .loop:
   ;reading input 
   call readXY
@@ -196,12 +196,17 @@ _start:
   ; failed to place a char
   jne .printOccupiedError
 
+  inc rbp
+
   ;check win condition
   mov rdi, 'x'
   call checkVictory
   cmp rax, 0
   jne .printYouWon
 
+  cmp rbp, 5 ; player did 5 moves, time to go
+  je .printDraw
+
   ;drawing field again
   call drawField
 
@@ -274,6 +279,15 @@ _start:
   syscall                       ;
   jmp .exit
 
+.printDraw:
+  call drawField
+  mov rax, 1                    ; sys_write
+  mov rdi, 1                    ; out
+  mov rsi, drawMessage           ; str
+  mov rdx, drawMessageLen        ; size
+  syscall                       ;
+  jmp .exit
+
 .printYouLost:
   call drawField
   mov rax, 1                    ; sys_write
@@ -301,6 +315,8 @@ section .rodata
   youWonMessageLen: equ $ - youWonMessage
   youLostMessage: db "you lost T_T", 0xA
   youLostMessageLen: equ $ - youLostMessage
+  drawMessage: db "it's a draw", 0xA
+  drawMessageLen: equ $ - drawMessage
   aiThinkingMessage: db "AI thinking"
   aiThinkingMessageLen: equ $ - aiThinkingMessage
   aiThinkingDotMessage: db "."