How to duplicate values in memory fast?

Dear all,

This is my code:

//Duplicate points
__asm  {
      mov      esi, offsetCount
      mov      edx, memLocation1
      mov      eax, memLocation2

      mov ecx,DWORD PTR[eax+esi*4]  //last value1
      mov edi,DWORD PTR[edx+esi*4]  //last value2
     
               //duplicate the last values 3 times
      mov DWORD PTR[eax+esi*4+4], ecx
                mov DWORD PTR[eax+esi*4+8], ecx
      mov DWORD PTR[eax+esi*4+12], ecx
      mov DWORD PTR[edx+esi*4+4], edi
      mov DWORD PTR[edx+esi*4+8], edi
      mov DWORD PTR[edx+esi*4+12], edi

      add      esi, 3
      shr      esi, 2 //make divisable by 4
      mov      offsetCount, esi
}

THis code seems to be a bit slow. Is there a better way of doing it?

thank you.