I have an existing VC++ code, its a DLL, along with its MSI setup. Now I have to convert the whole process into 64-bit, therefore if I simply compile it with X64 compiler, will it be sufficient or do I have to convert all the datatypes and functiona into 64-bit too?

What will be the possible consequence if I just compile it with 64-bit compiler and don't convert the datatypes and functions?

Thanks in Advance