In F#, there's the NativePtr module, but it seems to only support 32 bit offsets for its’ add/get/set functions, just like System.IntPtr does.

Is there a way to add a 64 bit offset to a native pointer (nativeptr<'a>) in F#? Of course I could convert all addresses to 64 bit integers, do normal integer operations and then convert the result again to nativeptr<'a>, but this would cost additional add and imul instructions. I really want the AGUs to perform the address calculations.

For instance, using unsafe in C# you could do something like

void* ptr = Marshal.AllocHGlobal(...).ToPointer();
int64 offset = ...;
T* newAddr = (T*)ptr + offset; // T has to be an unmanaged type

Well actually you can't, because there is no "unmanaged" constraint for type parameters, but at least you can do general pointer arithmetic in a non-generic way.

In F# we finally got the unmanaged constraint; but how do I do the pointer arithmetic?