Patch for Word64

[Matt]

Bulat Ziganshin wrote:
> Hello Simon,
>
> Wednesday, November 23, 2005, 2:28:26 PM, you wrote:
>
>>   int64ToWord64# = unsafeCoerce#
>>   word64ToInt64# = unsafeCoerce#
>
>> this should reduce the cost of the conversions to zero, which is a
>> simpler way to fix the performance bug (if it works).
>
>> If you confirm that this also improves performance, I'll commit it.
>> If not, I'll commit your patch instead.
>
> please don't forget about:
>
>  int32ToWord32#
>  word32ToInt32#
>  intToInt32#
>  int32ToInt#
>  wordToWord32#
>  word32ToWord#
>  int2Word#
>  word2Int#

These are already free, as I understand. When I compare Int, Word, Int#, 
Word#, Int32 (same thing as Int), and Word32 (same thing as Word), they have 
identical performance. It is Int64/Word64/Int64#/Word64# that are abysmal.

I will continue as time allows and make the suggested changes, but I thought 
that the original patch also makes sense. Compare these definitions from the 
original Word.hs file:
    (W# x#) + (W# y#)      = W# (x# `plusWord#` y#)
    (W8# x#) + (W8# y#)    = W8# (narrow8Word# (x# `plusWord#` y#))
    (W16# x#) + (W16# y#)  = W16# (narrow16Word# (x# `plusWord#` y#))
    (W32# x#) + (W32# y#)  = W32# (narrow32Word# (x# `plusWord#` y#))
    (W64# x#) + (W64# y#)  = W64# (int64ToWord64# (word64ToInt64# x# 
`plusInt64#` word64ToInt64# y#))

The definitions are those used on a 32-bit architecture. So, when it is 
cheap the plusWord# function is used, but when it is "relatively expensive" 
then extra conversions are added. Wouldn't it make sense to avoid the 
conversions in all cases, regardless of whether they are free or not? If so, 
then I will keep the old changes in the next patch I submit. If not, then I 
will discard them.

-Matt or [ricebowl, wearkilts, soysauce] on #haskell on Freenode