Update

Author: INIT-REF

019.asm

@@ -10,28 +10,25 @@ main:
  mov ebx, 1900 ;year (to be increased soon)
  mov edi, 2 ;1901/01/01 was a Tuesday
  mov esi, 1 ;day in month counter
- mov r8d, 4 ;for leap year divisions
- xor r9d, r9d ;sum
+ xor r8d, r8d ;sum
 
 nextyear:
  mov ecx, 1 ;set month to January
  inc ebx ;next year
  cmp ebx, 2001 ;check if we are finished
  je print ;if yes, print result
  mov dword [dim + 8], 28 ;reset febuary
- xor edx, edx ;reset remainder
- mov eax, ebx ;year in eax
- div r8d ;divide by 4
- test edx, edx ;check remainder
- jnz count ;if not zero go to count
+ bsr eax, ebx ;year divisible by 4 when last two bits are 0
+ cmp eax, 2 ;result 2?
+ jne count ;if not, go to count
  mov dword [dim + 8], 29 ;if zero, set febuary to 29 days
 
 count:
  cmp esi, 1 ;check if first of month
  jne continue ;if not, continue
  cmp edi, 7 ;check if it is Sunday
  jne continue ;if not, continue
- inc r9d ;else increase count
+ inc r8d ;else increase count
 
 continue:
  inc edi ;increase weekday
@@ -61,7 +58,7 @@ back:
 print: ;printing routine, differs slightly from OS to OS
  push rbp
  mov edi, msg
- mov esi, r9d
+ mov esi, r8d
  call printf
  pop rbp