4. Quick look at the disassembly

• 
      y = y + x;
  
  

  A disassembly of a debug build on Windows 32-bit platform shows

      mov eax, dword ptr [y]  ; load y from memory into CPU register EAX
  
      add eax, dword ptr [x]  ; compute EAX + x, save result in EAX
  
      mov dword ptr [y], eax  ; save result from EAX in memory that belongs to y
  

   

  • Only one instruction (add) deals with the math.

  • The other two instructions (mov) transfer values to/from memory.

  • Can CPU add two memory values in one step?