[Haskell] GHC 64bit?

[Ketil Malde]

Axel Simon <A.Simon at kent.ac.uk> writes:

>> There is an IA64 port somewhere, and I suspect other 64-bit
>> architectures as well.  Presumably they support >4Gb?

> I wonder if such an effort is worthwhile. If all pointers are suddenly
> twice the size then the footprint of a program roughly doubles. 

Unless you do additional tricks.  Since we're still some way from 2^64
memory, perhaps part of the pointers could contain data (tags, say) as
well?  This means more than a straightforward port, though, and I've
no idea how feasible it would be to implement.

> Hence to run a program that that needs more than 4GB of RAM on a 32
> bit architecture you would need more than 8GB of RAM on a 64 bit
> machine (and e.g. Apples G5 machines only support 8GB of on-board
> memory).

Well - so be it.  There are 64bit machines out there that supports
more than 8Gb. It'll be expensive, but at least possible.

> It would be interesting if Haskell programs could run in the lower 4 GB 
> while running in 64 bit mode. Then you could have large data structures 
> (or memory mapped files) in C land.

That's an interesting possibility -- at least part of my program is a
large UArray of Word8, which could probably be FFI'ed relatively
easily. 

-kzm
-- 
If I haven't seen further, it is by standing in the footprints of giants