Remove bitcount; use popCount directly (#1031)

Author: meooow25

containers-tests/tests/IntSetValidity.hs

@@ -7,7 +7,6 @@ import Data.IntSet.Internal
 import Data.List (intercalate)
 import Numeric (showHex)
 import Test.Tasty.QuickCheck (Property, counterexample, property, (.&&.))
-import Utils.Containers.Internal.BitUtil (bitcount)
 
 {--------------------------------------------------------------------
   Assertions

containers/src/Data/IntSet/Internal.hs

@@ -367,7 +367,7 @@ size :: IntSet -> Int
 size = go 0
   where
     go !acc (Bin _ l r) = go (go acc l) r
-    go acc (Tip _ bm) = acc + bitcount 0 bm
+    go acc (Tip _ bm) = acc + popCount bm
     go acc Nil = acc
 
 -- | \(O(\min(n,W))\). Is the value a member of the set?

containers/src/Utils/Containers/Internal/BitUtil.hs

@@ -1,7 +1,4 @@
 {-# LANGUAGE CPP #-}
-#if __GLASGOW_HASKELL__
-{-# LANGUAGE MagicHash #-}
-#endif
 #if !defined(TESTING) && defined(__GLASGOW_HASKELL__)
 {-# LANGUAGE Safe #-}
 #endif
@@ -31,38 +28,16 @@
 -- closely.
 
 module Utils.Containers.Internal.BitUtil
-    ( bitcount
-    , highestBitMask
+    ( highestBitMask
     , shiftLL
     , shiftRL
     , wordSize
     ) where
 
-import Data.Bits (popCount, unsafeShiftL, unsafeShiftR
+import Data.Bits (unsafeShiftL, unsafeShiftR
     , countLeadingZeros, finiteBitSize
     )
 
-
-{----------------------------------------------------------------------
-  [bitcount] as posted by David F. Place to haskell-cafe on April 11, 2006,
-  based on the code on
-  http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan,
-  where the following source is given:
-    Published in 1988, the C Programming Language 2nd Ed. (by Brian W.
-    Kernighan and Dennis M. Ritchie) mentions this in exercise 2-9. On April
-    19, 2006 Don Knuth pointed out to me that this method "was first published
-    by Peter Wegner in CACM 3 (1960), 322. (Also discovered independently by
-    Derrick Lehmer and published in 1964 in a book edited by Beckenbach.)"
-----------------------------------------------------------------------}
-
-bitcount :: Int -> Word -> Int
-bitcount a x = a + popCount x
-{-# INLINE bitcount #-}
-
--- The highestBitMask implementation is based on
--- http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
--- which has been put in the public domain.
-
 -- | Return a word where only the highest bit is set.
 highestBitMask :: Word -> Word
 highestBitMask w = shiftLL 1 (wordSize - 1 - countLeadingZeros w)