Use byteSwapX# in WORDS_BIGENDIAN

.github/workflows/emulated.yml

@@ -0,0 +1,49 @@
+name: emulated
+on:
+  - push
+  - pull_request
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  # Emulation is incredibly slow and memory demanding. It seems that any
+  # executable with GHC RTS takes at least 7-8 Gb of RAM, so we can run
+  # `cabal` or `ghc` on their own, but cannot run them both at the same time,
+  # striking out `cabal test`. Instead we rely on system packages and invoke
+  # `ghc --make` manually, and even so `ghc -O` is prohibitively expensive.
+  emulated:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+      matrix:
+        arch: ['s390x', 'ppc64le']
+    steps:
+    - uses: actions/checkout@v3
+    - uses: uraimo/[email protected]
+      timeout-minutes: 60
+      with:
+        arch: ${{ matrix.arch }}
+        distro: ubuntu_rolling
+        githubToken: ${{ github.token }}
+        install: |
+          apt-get update -y
+          apt-get install -y ghc alex happy
+        run: |
+          (cd src/; alex -g Scan.x; happy -ag Parser.y)
+          # Need to remove mention of the Cabal path module, and then substitutes
+          #   getDataDir  |->  return "/pwd/data/"
+          #   version     |->  undefined
+          sed -i '/^import Paths_alex.*$/d' src/Main.hs #
+          # The nested sed here escapes / into \/ so that the outer sed doesn't
+          # interpret the forward slashes. You're welcome.
+          sed -i "s/getDataDir/\(return \"$(pwd | sed 's/\//\\\//g')\\/data\"\)/g" src/Main.hs
+          sed -i "s/version/undefined/g" src/Main.hs
+          ghc -XHaskell2010 -XPatternSynonyms -XFlexibleContexts -XMagicHash -XCPP -XNondecreasingIndentation -XScopedTypeVariables -XTupleSections \
+              -package array -package containers -package directory \
+              -isrc src/Main.hs \
+              -o alex
+          ./alex -g tests/simple.x
+          ghc -package array tests/simple.hs -o simple
+          ./simple +RTS -s

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.!)