Herbert would you like to open a ticket, saying what's wrong and how to reproduce it? Simon | -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of | git@git.haskell.org | Sent: 01 March 2014 13:53 | To: ghc-commits@haskell.org | Subject: [commit: packages/base] ghc-7.8: Workaround failed constant- | folding for zeroBits (591142f) | | Repository : ssh://git@git.haskell.org/base | | On branch : ghc-7.8 | Link : | http://ghc.haskell.org/trac/ghc/changeset/591142f8aead4c28bdaa5656d79e6 | dc38273e685/base | | >--------------------------------------------------------------- | | commit 591142f8aead4c28bdaa5656d79e6dc38273e685 | Author: Herbert Valerio Riedel | Date: Sat Mar 1 14:45:48 2014 +0100 | | Workaround failed constant-folding for zeroBits | | For some reason GHC fails to constant fold `zeroBits :: Int` and | `zeroBits :: Integer`; `ghc -show-iface` shows | | $fBitsInt_$czeroBits :: GHC.Types.Int | {- Strictness: m, | Unfolding: (GHC.Types.I# (GHC.Prim.andI# 1 (GHC.Prim.notI# | 1))) -} | | Otoh, constant-folding works as expected, reducing `zeroBits` to 0 | constant | for the other integer-types (= {Word,Int}{8,16,32,64}` and `Word`). | So this | quickfix is actually just treating the symptom rather than the | cause. | | Signed-off-by: Herbert Valerio Riedel | (cherry picked from commit | 2dbfcd70e53845d9119389cecc88411b47b70644) | | | >--------------------------------------------------------------- | | 591142f8aead4c28bdaa5656d79e6dc38273e685 | Data/Bits.hs | 3 +++ | 1 file changed, 3 insertions(+) | | diff --git a/Data/Bits.hs b/Data/Bits.hs | index e771624..28cd024 100644 | --- a/Data/Bits.hs | +++ b/Data/Bits.hs | @@ -363,6 +363,8 @@ instance Bits Int where | {-# INLINE bit #-} | {-# INLINE testBit #-} | | + zeroBits = 0 | + | bit = bitDefault | | testBit = testBitDefault | @@ -437,6 +439,7 @@ instance Bits Integer where | | otherwise = shiftRInteger x (negateInt# i#) | testBit x (I# i) = testBitInteger x i | | + zeroBits = 0 | bit = bitDefault | popCount = popCountDefault | | | _______________________________________________ | ghc-commits mailing list | ghc-commits@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-commits