Assembly codes in jitinterfacex86.cpp

Hi,
 Is there any documentation regarding the opcodes used in the file
jitinterfacex86.cpp and how the intel opcodes are mapped onto these codes
  for example this is a piece of code from vm/i386/cgencpu.cpp,

      // cmp ebx,0
      Emit16(0xfb83);
      Emit8(0);
if one needs to write
     // cmp edx,0

what parameter should be passed to Emit16 etc..

Thanks,
archana