[project @ 2001-12-07 11:34:48 by sewardj]

[ghc-hetmet.git] / ghc / lib / std / PrelBits.lhs

diff --git a/ghc/lib/std/PrelBits.lhs b/ghc/lib/std/PrelBits.lhs
index 716ee84..594eb56 100644 (file)
--- a/ghc/lib/std/PrelBits.lhs
+++ b/ghc/lib/std/PrelBits.lhs
@@ -8,11 +8,11 @@ See library document for details on the semantics of the
 individual operations.
 
 \begin{code}
+{-# OPTIONS -fno-implicit-prelude #-}
 #include "MachDeps.h"
 
 module PrelBits where
 
-import Prelude         -- To generate the dependency
 #ifdef __GLASGOW_HASKELL__
 import PrelGHC
 import PrelBase
@@ -61,22 +61,21 @@ instance Bits Int where
     (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#)
+        | i# ==# 0#     = I# x#
+        | i# >=# wsib   = 0
+        | i# ># 0#      = I# (x# `uncheckedIShiftL#` i#)
+        | i# <=# nwsib  = I# (if x# <# 0# then -1# else 0#)
+        | otherwise     = I# (x# `uncheckedIShiftRA#` negateInt# i#)
+          where
+            wsib  = WORD_SIZE_IN_BITS#   {- work around preprocessor problem (??) -}
+             nwsib = negateInt# wsib
     (I# x#) `rotate` (I# i#) =
-#if WORD_SIZE_IN_BYTES == 4
-        I# (word2Int# ((x'# `shiftL#` i'#) `or#`
-                       (x'# `shiftRL#` (32# -# i'#))))
+        I# (word2Int# ((x'# `uncheckedShiftL#` i'#) `or#`
+                       (x'# `uncheckedShiftRL#` (wsib -# i'#))))
         where
-        x'# = int2Word# x#
-        i'# = word2Int# (int2Word# i# `and#` int2Word# 31#)
-#else
-        I# (word2Int# ((x'# `shiftL#` i'#) `or#`
-                       (x'# `shiftRL#` (64# -# i'#))))
-        where
-        x'# = int2Word# x#
-        i'# = word2Int# (int2Word# i# `and#` int2Word# 63#)
-#endif
-    bitSize  _                 = WORD_SIZE_IN_BYTES * 8
+           x'#   = int2Word# x#
+           i'#   = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#))
+          wsib  = WORD_SIZE_IN_BITS#
+    bitSize  _                 = WORD_SIZE_IN_BITS
     isSigned _                 = True
 \end{code}