ilp32 far pointers

[David McQuillan]

Has there been an implementation or design of a way of representing 64 
bit pointers with ilp32 on a 64 bit system? I know this sounds like it 
is rather pushing the boundary and one should just use the lp64 but I 
believe it could save effort in a number of circumstances. What I was 
thinking of is something like say
char __attribute__((longptr)) *abc; would hold the address with the top 
part zero, or even with a full 64 bit address if there was enough 
support but that sounds a lot more work.

David