X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FBits.hs;h=cbf7b37015b3d1b8f732ee8a048dad9b9dd9a843;hb=HEAD;hp=ded147a762993ac4a7a73247f437e338d483cbb7;hpb=47b53f7aa91d79eb538e14d4ccbf0ef9f25b7938;p=ghc-base.git diff --git a/Data/Bits.hs b/Data/Bits.hs index ded147a..cbf7b37 100644 --- a/Data/Bits.hs +++ b/Data/Bits.hs @@ -1,4 +1,5 @@ -{-# OPTIONS_GHC -fno-implicit-prelude #-} +{-# LANGUAGE CPP, NoImplicitPrelude, BangPatterns, MagicHash #-} + ----------------------------------------------------------------------------- -- | -- Module : Data.Bits @@ -9,11 +10,11 @@ -- Stability : experimental -- Portability : portable -- --- This module defines bitwise operations for signed and unsigned --- integers. Instances of the class 'Bits' for the 'Int' and --- 'Integer' types are available from this module, and instances for --- explicitly sized integral types are available from the --- "Data.Int" and "Data.Word" modules. +-- This module defines bitwise operations for signed and unsigned +-- integers. Instances of the class 'Bits' for the 'Int' and +-- 'Integer' types are available from this module, and instances for +-- explicitly sized integral types are available from the +-- "Data.Int" and "Data.Word" modules. -- ----------------------------------------------------------------------------- @@ -48,7 +49,6 @@ module Data.Bits ( #ifdef __GLASGOW_HASKELL__ import GHC.Num -import GHC.Real import GHC.Base #endif @@ -84,31 +84,34 @@ class Num a => Bits a where {-| Reverse all the bits in the argument -} complement :: a -> a - {-| Shift the argument left by the specified number of bits. - Right shifts (signed) are specified by giving a negative value. + {-| @'shift' x i@ shifts @x@ left by @i@ bits if @i@ is positive, + or right by @-i@ bits otherwise. + Right shifts perform sign extension on signed number types; + i.e. they fill the top bits with 1 if the @x@ is negative + and with 0 otherwise. - An instance can define either this unified 'shift' or 'shiftL' and - 'shiftR', depending on which is more convenient for the type in - question. -} + An instance can define either this unified 'shift' or 'shiftL' and + 'shiftR', depending on which is more convenient for the type in + question. -} shift :: a -> Int -> a - x `shift` i | i<0 = x `shiftR` (-i) - | i==0 = x - | i>0 = x `shiftL` i + x `shift` i | i<0 = x `shiftR` (-i) + | i>0 = x `shiftL` i + | otherwise = x - {-| Rotate the argument left by the specified number of bits. - Right rotates are specified by giving a negative value. + {-| @'rotate' x i@ rotates @x@ left by @i@ bits if @i@ is positive, + or right by @-i@ bits otherwise. For unbounded types like 'Integer', 'rotate' is equivalent to 'shift'. - An instance can define either this unified 'rotate' or 'rotateL' and - 'rotateR', depending on which is more convenient for the type in - question. -} + An instance can define either this unified 'rotate' or 'rotateL' and + 'rotateR', depending on which is more convenient for the type in + question. -} rotate :: a -> Int -> a - x `rotate` i | i<0 = x `rotateR` (-i) - | i==0 = x - | i>0 = x `rotateL` i + x `rotate` i | i<0 = x `rotateR` (-i) + | i>0 = x `rotateL` i + | otherwise = x {- -- Rotation can be implemented in terms of two shifts, but care is @@ -124,7 +127,7 @@ class Num a => Bits a where | i>0 = (x `shift` i) .|. (x `shift` (i-bitSize x)) -} - -- | @bit i@ is a value with the @i@th bit set + -- | @bit i@ is a value with the @i@th bit set and all other bits clear bit :: Int -> a -- | @x \`setBit\` i@ is the same as @x .|. bit i@ @@ -140,15 +143,20 @@ class Num a => Bits a where testBit :: a -> Int -> Bool {-| Return the number of bits in the type of the argument. The actual - value of the argument is ignored. The function 'bitSize' is - undefined for types that do not have a fixed bitsize, like 'Integer'. - -} + value of the argument is ignored. The function 'bitSize' is + undefined for types that do not have a fixed bitsize, like 'Integer'. + -} bitSize :: a -> Int {-| Return 'True' if the argument is a signed type. The actual value of the argument is ignored -} isSigned :: a -> Bool + {-# INLINE bit #-} + {-# INLINE setBit #-} + {-# INLINE clearBit #-} + {-# INLINE complementBit #-} + {-# INLINE testBit #-} bit i = 1 `shiftL` i x `setBit` i = x .|. bit i x `clearBit` i = x .&. complement (bit i) @@ -156,58 +164,74 @@ class Num a => Bits a where x `testBit` i = (x .&. bit i) /= 0 {-| Shift the argument left by the specified number of bits - (which must be non-negative). + (which must be non-negative). - An instance can define either this and 'shiftR' or the unified - 'shift', depending on which is more convenient for the type in - question. -} + An instance can define either this and 'shiftR' or the unified + 'shift', depending on which is more convenient for the type in + question. -} shiftL :: a -> Int -> a + {-# INLINE shiftL #-} x `shiftL` i = x `shift` i - {-| Shift the argument right (signed) by the specified number of bits - (which must be non-negative). + {-| Shift the first argument right by the specified number of bits + (which must be non-negative). + Right shifts perform sign extension on signed number types; + i.e. they fill the top bits with 1 if the @x@ is negative + and with 0 otherwise. - An instance can define either this and 'shiftL' or the unified - 'shift', depending on which is more convenient for the type in - question. -} + An instance can define either this and 'shiftL' or the unified + 'shift', depending on which is more convenient for the type in + question. -} shiftR :: a -> Int -> a + {-# INLINE shiftR #-} x `shiftR` i = x `shift` (-i) {-| Rotate the argument left by the specified number of bits - (which must be non-negative). + (which must be non-negative). - An instance can define either this and 'rotateR' or the unified - 'rotate', depending on which is more convenient for the type in - question. -} + An instance can define either this and 'rotateR' or the unified + 'rotate', depending on which is more convenient for the type in + question. -} rotateL :: a -> Int -> a + {-# INLINE rotateL #-} x `rotateL` i = x `rotate` i {-| Rotate the argument right by the specified number of bits - (which must be non-negative). + (which must be non-negative). - An instance can define either this and 'rotateL' or the unified - 'rotate', depending on which is more convenient for the type in - question. -} + An instance can define either this and 'rotateL' or the unified + 'rotate', depending on which is more convenient for the type in + question. -} rotateR :: a -> Int -> a + {-# INLINE rotateR #-} x `rotateR` i = x `rotate` (-i) instance Bits Int where + {-# INLINE shift #-} + #ifdef __GLASGOW_HASKELL__ (I# x#) .&. (I# y#) = I# (word2Int# (int2Word# x# `and#` int2Word# y#)) + (I# x#) .|. (I# y#) = I# (word2Int# (int2Word# x# `or#` int2Word# y#)) + (I# x#) `xor` (I# y#) = I# (word2Int# (int2Word# x# `xor#` int2Word# y#)) + complement (I# x#) = I# (word2Int# (int2Word# x# `xor#` int2Word# (-1#))) + (I# x#) `shift` (I# i#) | i# >=# 0# = I# (x# `iShiftL#` i#) | otherwise = I# (x# `iShiftRA#` negateInt# i#) + + {-# INLINE rotate #-} -- See Note [Constant folding for rotate] (I# x#) `rotate` (I# i#) = - I# (word2Int# ((x'# `shiftL#` i'#) `or#` - (x'# `shiftRL#` (wsib -# i'#)))) - where - x'# = int2Word# x# - i'# = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#)) - wsib = WORD_SIZE_IN_BITS# {- work around preprocessor problem (??) -} + I# (word2Int# ((x'# `uncheckedShiftL#` i'#) `or#` + (x'# `uncheckedShiftRL#` (wsib -# i'#)))) + where + !x'# = int2Word# x# + !i'# = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#)) + !wsib = WORD_SIZE_IN_BITS# {- work around preprocessor problem (??) -} bitSize _ = WORD_SIZE_IN_BITS + #else /* !__GLASGOW_HASKELL__ */ #ifdef __HUGS__ @@ -230,12 +254,12 @@ instance Bits Int where #endif /* __NHC__ */ x `rotate` i - | i<0 && x<0 = let left = i+bitSize x in + | i<0 && x<0 = let left = i+bitSize x in ((x `shift` i) .&. complement ((-1) `shift` left)) .|. (x `shift` left) - | i<0 = (x `shift` i) .|. (x `shift` (i+bitSize x)) - | i==0 = x - | i>0 = (x `shift` i) .|. (x `shift` (i-bitSize x)) + | i<0 = (x `shift` i) .|. (x `shift` (i+bitSize x)) + | i==0 = x + | i>0 = (x `shift` i) .|. (x `shift` (i-bitSize x)) #endif /* !__GLASGOW_HASKELL__ */ @@ -251,57 +275,39 @@ foreign import ccall nhc_primIntCompl :: Int -> Int #endif /* __NHC__ */ instance Bits Integer where -#ifdef __GLASGOW_HASKELL__ - (S# x) .&. (S# y) = S# (word2Int# (int2Word# x `and#` int2Word# y)) - x@(S# _) .&. y = toBig x .&. y - x .&. y@(S# _) = x .&. toBig y - (J# s1 d1) .&. (J# s2 d2) = - case andInteger# s1 d1 s2 d2 of - (# s, d #) -> J# s d - - (S# x) .|. (S# y) = S# (word2Int# (int2Word# x `or#` int2Word# y)) - x@(S# _) .|. y = toBig x .|. y - x .|. y@(S# _) = x .|. toBig y - (J# s1 d1) .|. (J# s2 d2) = - case orInteger# s1 d1 s2 d2 of - (# s, d #) -> J# s d - - (S# x) `xor` (S# y) = S# (word2Int# (int2Word# x `xor#` int2Word# y)) - x@(S# _) `xor` y = toBig x `xor` y - x `xor` y@(S# _) = x `xor` toBig y - (J# s1 d1) `xor` (J# s2 d2) = - case xorInteger# s1 d1 s2 d2 of - (# s, d #) -> J# s d - - complement (S# x) = S# (word2Int# (int2Word# x `xor#` int2Word# (0# -# 1#))) - complement (J# s d) = case complementInteger# s d of (# s, d #) -> J# s d +#if defined(__GLASGOW_HASKELL__) + (.&.) = andInteger + (.|.) = orInteger + xor = xorInteger + complement = complementInteger + shift x i@(I# i#) | i >= 0 = shiftLInteger x i# + | otherwise = shiftRInteger x (negateInt# i#) #else -- reduce bitwise binary operations to special cases we can handle x .&. y | x<0 && y<0 = complement (complement x `posOr` complement y) - | otherwise = x `posAnd` y + | otherwise = x `posAnd` y x .|. y | x<0 || y<0 = complement (complement x `posAnd` complement y) - | otherwise = x `posOr` y + | otherwise = x `posOr` y x `xor` y | x<0 && y<0 = complement x `posXOr` complement y - | x<0 = complement (complement x `posXOr` y) - | y<0 = complement (x `posXOr` complement y) - | otherwise = x `posXOr` y + | x<0 = complement (complement x `posXOr` y) + | y<0 = complement (x `posXOr` complement y) + | otherwise = x `posXOr` y -- assuming infinite 2's-complement arithmetic complement a = -1 - a -#endif - shift x i | i >= 0 = x * 2^i - | otherwise = x `div` 2^(-i) + | otherwise = x `div` 2^(-i) +#endif rotate x i = shift x i -- since an Integer never wraps around bitSize _ = error "Data.Bits.bitSize(Integer)" isSigned _ = True -#ifndef __GLASGOW_HASKELL__ +#if !defined(__GLASGOW_HASKELL__) -- Crude implementation of bitwise operations on Integers: convert them -- to finite lists of Ints (least significant first), zip and convert -- back again. @@ -324,7 +330,7 @@ toInts n | n == 0 = [] | otherwise = mkInt (n `mod` numInts):toInts (n `div` numInts) where mkInt n | n > toInteger(maxBound::Int) = fromInteger (n-numInts) - | otherwise = fromInteger n + | otherwise = fromInteger n fromInts :: [Int] -> Integer fromInts = foldr catInt 0 @@ -332,3 +338,30 @@ fromInts = foldr catInt 0 numInts = toInteger (maxBound::Int) - toInteger (minBound::Int) + 1 #endif /* !__GLASGOW_HASKELL__ */ + +{- Note [Constant folding for rotate] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The INLINE on the Int instance of rotate enables it to be constant +folded. For example: + sumU . mapU (`rotate` 3) . replicateU 10000000 $ (7 :: Int) +goes to: + Main.$wfold = + \ (ww_sO7 :: Int#) (ww1_sOb :: Int#) -> + case ww1_sOb of wild_XM { + __DEFAULT -> Main.$wfold (+# ww_sO7 56) (+# wild_XM 1); + 10000000 -> ww_sO7 +whereas before it was left as a call to $wrotate. + +All other Bits instances seem to inline well enough on their +own to enable constant folding; for example 'shift': + sumU . mapU (`shift` 3) . replicateU 10000000 $ (7 :: Int) + goes to: + Main.$wfold = + \ (ww_sOb :: Int#) (ww1_sOf :: Int#) -> + case ww1_sOf of wild_XM { + __DEFAULT -> Main.$wfold (+# ww_sOb 56) (+# wild_XM 1); + 10000000 -> ww_sOb + } +-} + +