Hello Ian,
Monday, October 9, 2006, 6:51:46 PM, you wrote:
> * Inline shift in GHC's Bits instances for {Int,Word}{,8,16,32,64}
> M ./Data/Bits.hs +2
> M ./GHC/Int.hs +12
> M ./GHC/Word.hs +14
i think that it will be not enough for proper specialization of
constant-width shifts. look for example at the following code:
instance Bits Int8 where
{-# INLINE shift #-}
(I8# x#) `shift` (I# i#)
| i# >=# 0# = I8# (narrow8Int# (x# `iShiftL#` i#))
| otherwise = I8# (x# `iShiftRA#` negateInt# i#)
here we call iShiftL# and iShiftRA# operations. but they are not
primitives! GHC.Base contains their definitions:
iShiftL# :: Int# -> Int# -> Int#
a `iShiftL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
| otherwise = a `uncheckedIShiftL#` b
iShiftRA# :: Int# -> Int# -> Int#
a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
| otherwise = a `uncheckedIShiftRA#` b
as you can see, these are not inlined, so we probably get the same
problems. i think that we need to add inlining either to
iShiftL#/iShiftRA# definitions or usage sites
--
Best regards,
Bulat mailto:[EMAIL PROTECTED]
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