Use byteSwapX# in WORDS_BIGENDIAN

Author: sgraf812

CHANGELOG.md

@@ -1,3 +1,8 @@
+## Changes in 3.5.2.0
+
+* Use `byteSwap16#` and `byteSwap32#` on big-endian architectures instead of
+  handrolling the implementation.
+
 ## Changes in 3.5.1.0
 
 * Drop generating output for GHC < 6.4.

data/AlexTemplate.hs

@@ -44,18 +44,15 @@ data AlexAddr = AlexA# Addr#
 {-# INLINE alexIndexInt16OffAddr #-}
 alexIndexInt16OffAddr :: AlexAddr -> Int# -> Int#
 alexIndexInt16OffAddr (AlexA# arr) off =
-#ifdef WORDS_BIGENDIAN
-  narrow16Int# i
-  where
-        i    = word2Int# ((high `uncheckedShiftL#` 8#) `or#` low)
-        high = int2Word# (ord# (indexCharOffAddr# arr (off' +# 1#)))
-        low  = int2Word# (ord# (indexCharOffAddr# arr off'))
-        off' = off *# 2#
-#else
 #if __GLASGOW_HASKELL__ >= 901
-  GHC.Exts.int16ToInt#
+  GHC.Exts.int16ToInt# -- qualified import because it doesn't exist on older GHC's
 #endif
-    (indexInt16OffAddr# arr off)
+#ifdef WORDS_BIGENDIAN
+  (GHC.Exts.word16ToInt16# (GHC.Exts.wordToWord16# (GHC.Exts.byteSwap16# (GHC.Exts.word16ToWord# (GHC.Exts.int16ToWord16#
+#endif
+  (indexInt16OffAddr# arr off)
+#ifdef WORDS_BIGENDIAN
+  )))))
 #endif
 #else
 alexIndexInt16OffAddr = (Data.Array.!)
@@ -65,22 +62,15 @@ alexIndexInt16OffAddr = (Data.Array.!)
 {-# INLINE alexIndexInt32OffAddr #-}
 alexIndexInt32OffAddr :: AlexAddr -> Int# -> Int#
 alexIndexInt32OffAddr (AlexA# arr) off =
-#ifdef WORDS_BIGENDIAN
-  narrow32Int# i
-  where
-   i    = word2Int# ((b3 `uncheckedShiftL#` 24#) `or#`
-                     (b2 `uncheckedShiftL#` 16#) `or#`
-                     (b1 `uncheckedShiftL#` 8#) `or#` b0)
-   b3   = int2Word# (ord# (indexCharOffAddr# arr (off' +# 3#)))
-   b2   = int2Word# (ord# (indexCharOffAddr# arr (off' +# 2#)))
-   b1   = int2Word# (ord# (indexCharOffAddr# arr (off' +# 1#)))
-   b0   = int2Word# (ord# (indexCharOffAddr# arr off'))
-   off' = off *# 4#
-#else
 #if __GLASGOW_HASKELL__ >= 901
-  GHC.Exts.int32ToInt#
+  GHC.Exts.int32ToInt# -- qualified import because it doesn't exist on older GHC's
 #endif
-    (indexInt32OffAddr# arr off)
+#ifdef WORDS_BIGENDIAN
+  (GHC.Exts.word32ToInt32# (GHC.Exts.wordToWord32# (GHC.Exts.byteSwap32# (GHC.Exts.word32ToWord# (GHC.Exts.int32ToWord32#
+#endif
+  (indexInt32OffAddr# arr off)
+#ifdef WORDS_BIGENDIAN
+  )))))
 #endif
 #else
 alexIndexInt32OffAddr = (Data.Array.!)