I guess it's not clearly readable (nested), but Relfos did it just the other way round:
Code:
{$IFDEF CPU64}
...
{$ELSE}
  ...
  Asm
    mov myself, ECX;
  End;
  ...
{$ENDIF}
Hm, adding that calling convention thiscall would probably make little sense without additional mechanisms for accessing C++ classes. Would be nice if one could declare a whole pascal class as "cppdecl" or whatever, so that somehow the linker would be able to access the C++ classes symbols/properties within a DLL ...