x86 assembly (MASM) - Square root of a 64-bit integer?

Question

I\'m coding a simple primality tester program for Windows in x86 assembly language (MASM32), which involves calculating a square root of a (64-bit) integer. My question is:

Answer 1

Here is my original 64-bit Square root routine:

// X:int64    
// sqrt64(X)
....
  asm      
   push ESI  {preserve ESI,EDI and EBX}
   push EDI
   push EBX

   mov ESI,dword ptr X      
   mov EDI,dword ptr X+4

   xor Eax,Eax
   xor Ebx,Ebx
   mov cx,32
@next:
  // Add ESI,ESI   //old RCL ESI,1  -  Peter Cordes suggestion 
  // ADC EDI,EDI   //old RCL EDI,1     ~1.38x faster! 
  // ADC EBX,EBX   //old RCL Ebx,1     

   //Add ESI,ESI   //old RCL ESI,1
   //ADC EDI,EDI   //old RCL EDI,1
   //ADC EBX,EBX   //old RCL Ebx,1

   shld ebx, edi, 2   //-  Peter Cordes 41% speed up!
   shld edi, esi, 2
   lea esi, [esi*4]

   //mov EDX,EAX
   //Add EDX,EDX   //old shl Edx,1
   //stc
   //ADC EDX,EDX   //old RCL Edx,1    {+01}
   lea edx, [eax*4 + 1]   //-  Peter Cordes   +20% speed up

   cmp EBX,EDX   {if BX>=DX -> BX-DX}
  JC @skip
   sub EBX,EDX
@skip:
   cmc           {invert C}
   ADC EAX,EAX   //old  RCL Eax,1
   dec cx
   jnz @next     // -  Peter Cordes  +40% speed up
  //LOOP @next

   pop EBX
   pop EDI
   pop ESI

   mov result,Eax
 end;
....