One issue with packed fields is that on many architectures you can't quite
do subword reads or writes. So it might not always be a win.
There's also the issue that c-- as it exists in ghc doesn't have any notion
of subword sized types.
That said, I do support making word/int64/32 # types more first class /
built in. (I hit some issues which tie into this topic in the process of
working on my still in progress safeword package. )
Point being: I support improving what we have, but it's got a bit of
surface area. Please let me know how I can help you dig into this though
On Tue, Aug 1, 2017 at 9:37 AM Michal Terepeta
Hi all,
I'm working on making it possible to pack constructor fields [1], example:
``` data Foo = Foo {-# UNPACK #-} !Float {-# UNPACK #-} !Int32 ```
should only require 4 bytes for unpacked `Float` and 4 bytes for unpacked `Int32`, which on 64-bit arch would take just 1 word (instead of 2 it currently does).
The diff to support packing of fields is in review [2], but to really take advantage of it I think we need to introduce new primitive types: - Int{8,16,32}# - Word{8,16,32}# along with some corresponding primops and with some other follow-up changes like extending `PrimRep`.
Then we could use them in definitions of `Int{8,16,32}` and `Word{8,16,32}` (they're currently just wrapping `Int#` and `Word#`).
Does that sound ok with everyone? (just making sure that this makes sense before I invest more time into this :)
Thanks, Michal
[1] https://ghc.haskell.org/trac/ghc/ticket/13825 [2] https://phabricator.haskell.org/D3809
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