[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 2 commits: Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types

22 Sep 2026


      Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC


Commits:
4cc0d181 by ARATA Mizuki at 2026-09-22T08:42:55-04:00
Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types

bitReverse{16,32}# and byteSwap{16,32}# have the type
Word# -> Word#, but their C correspondents took and
returned StgWord{16,32}.

The mismatch on bitReverse16# led to the problem reported
in #27299. Although no similar issue is reported for
bitReverse32# and byteSwap{16,32}#, it seemed wise to
change them proactively.

This commit fixes the mismatch by changing the C type.

Fixes #27299

- - - - -
43ddbbba by fendor at 2026-09-22T08:42:56-04:00
Don't lose instances from shadowed imported modules with the same name

When we look for instances below the current module, we need to check
the unit id as well when we check for whether the module is the current
module, otherwise we ignore modules we import that have the same name as
the import module.

Adds regression test.

- - - - -


16 changed files:

- + changelog.d/26610
- compiler/GHC/Driver/Env.hs
- rts/include/stg/Prim.h
- rts/prim/bitrev.c
- rts/prim/bswap.c
- + testsuite/tests/ghci/prog-mhu008/Makefile
- + testsuite/tests/ghci/prog-mhu008/a/M.hs
- + testsuite/tests/ghci/prog-mhu008/all.T
- + testsuite/tests/ghci/prog-mhu008/b/M.hs
- + testsuite/tests/ghci/prog-mhu008/prog-mhu008.script
- + testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout
- + testsuite/tests/ghci/prog-mhu008/unitA
- + testsuite/tests/ghci/prog-mhu008/unitB
- + testsuite/tests/primops/should_run/T27299.hs
- + testsuite/tests/primops/should_run/T27299.stdout
- testsuite/tests/primops/should_run/all.T


Changes:

=====================================
changelog.d/26610
=====================================
@@ -0,0 +1,7 @@
+section: compiler
+synopsis: Fix instance resolution for shadowed modules
+description:
+  Instances imported from modules with the same module name as the importing module
+  were dropped accidentally since we didn't account for the unit id of the imported module.
+mrs: !16648
+issues: #26610


=====================================
compiler/GHC/Driver/Env.hs
=====================================
@@ -263,13 +263,13 @@ hugCompleteSigsBelow hsc uid mn = foldr (++) [] <$>
 -- | Find instances visible from the given set of imports
 hugInstancesBelow :: HscEnv -> UnitId -> ModuleNameWithIsBoot -> IO (InstEnv, [FamInst])
 hugInstancesBelow hsc_env uid mnwib = do
- let mn = gwib_mod mnwib
+ let mn = mkModule uid (gwib_mod mnwib)
  (insts, famInsts) <-
      unzip . concat <$>
        hugSomeThingsBelowUs (\mod_info ->
                                   let details = hm_details mod_info
                                   -- Don't include instances for the current module
-                                  in if moduleName (mi_module (hm_iface mod_info)) == mn
+                                  in if fmap toUnitId (mi_module (hm_iface mod_info)) == mn
                                        then []
                                        else [(md_insts details, md_fam_insts details)])
                           True -- Include -hi-boot


=====================================
rts/include/stg/Prim.h
=====================================
@@ -59,16 +59,16 @@ StgWord hs_xchg32(StgWord x, StgWord val);
 StgWord64 hs_xchg64(StgWord x, StgWord64 val);
 
 /* rts/prim/bswap.c */
-StgWord16 hs_bswap16(StgWord16 x);
-StgWord32 hs_bswap32(StgWord32 x);
+StgWord hs_bswap16(StgWord x);
+StgWord hs_bswap32(StgWord x);
 StgWord64 hs_bswap64(StgWord64 x);
 
 /* rts/prim/bitrev.c
 This was done as part of issue #16164.
 See Note [Bit reversal primop] for more details about the implementation.*/
 StgWord hs_bitrev8(StgWord x);
-StgWord16 hs_bitrev16(StgWord16 x);
-StgWord32 hs_bitrev32(StgWord32 x);
+StgWord hs_bitrev16(StgWord x);
+StgWord hs_bitrev32(StgWord x);
 StgWord64 hs_bitrev64(StgWord64 x);
 
 /* rts/prim/longlong.c */


=====================================
rts/prim/bitrev.c
=====================================
@@ -36,8 +36,8 @@ hs_bitrev8(StgWord x)
   return x;
 }
 
-StgWord16
-hs_bitrev16(StgWord16 x)
+StgWord
+hs_bitrev16(StgWord x)
 {
   x = ((x >> 1) & 0x5555) | ((x & 0x5555) << 1 );
   x = ((x >> 2) & 0x3333) | ((x & 0x3333) << 2 );
@@ -46,14 +46,14 @@ hs_bitrev16(StgWord16 x)
   return x;
 }
 
-StgWord32
-hs_bitrev32(StgWord32 x)
+StgWord
+hs_bitrev32(StgWord x)
 {
-  x = ((x >> 1) & 0x55555555) | ((x & 0x55555555) << 1 );
-  x = ((x >> 2) & 0x33333333) | ((x & 0x33333333) << 2 );
-  x = ((x >> 4) & 0x0F0F0F0F) | ((x & 0x0F0F0F0F) << 4 );
-  x = ((x >> 8) & 0x00FF00FF) | ((x & 0x00FF00FF) << 8 );
-  x = ( x >> 16             ) | ( x << 16              );
+  x = ((x >> 1)  & 0x55555555) | ((x & 0x55555555) << 1 );
+  x = ((x >> 2)  & 0x33333333) | ((x & 0x33333333) << 2 );
+  x = ((x >> 4)  & 0x0F0F0F0F) | ((x & 0x0F0F0F0F) << 4 );
+  x = ((x >> 8)  & 0x00FF00FF) | ((x & 0x00FF00FF) << 8 );
+  x = ((x >> 16) & 0x0000FFFF) | ((x & 0x0000FFFF) << 16);
   return x;
 }
 


=====================================
rts/prim/bswap.c
=====================================
@@ -1,16 +1,18 @@
 #include "Rts.h"
 
-StgWord16
-hs_bswap16(StgWord16 x)
+StgWord
+hs_bswap16(StgWord x)
 {
-  return ((x >> 8) | (x << 8));
+  x = (StgWord16)x;
+  return (StgWord16)((x >> 8) | (x << 8));
 }
 
-StgWord32
-hs_bswap32(StgWord32 x)
+StgWord
+hs_bswap32(StgWord x)
 {
-  return ((x >> 24) | ((x >> 8) & 0xff00) |
-          (x << 24) | ((x & 0xff00) << 8));
+  x = (StgWord32)x;
+  return (StgWord32)((x >> 24) | ((x >> 8) & 0xff00) |
+                     (x << 24) | ((x & 0xff00) << 8));
 }
 
 StgWord64


=====================================
testsuite/tests/ghci/prog-mhu008/Makefile
=====================================
@@ -0,0 +1,3 @@
+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk


=====================================
testsuite/tests/ghci/prog-mhu008/a/M.hs
=====================================
@@ -0,0 +1,4 @@
+module M (T (..)) where
+
+newtype T = MkT Int
+  deriving (Eq, Ord)


=====================================
testsuite/tests/ghci/prog-mhu008/all.T
=====================================
@@ -0,0 +1,5 @@
+test('prog-mhu008',
+     [extra_files(['a/', 'b/', 'unitA', 'unitB']),
+     cmd_prefix('ghciWayFlags=' + config.ghci_way_flags),
+     req_interp],
+     ghci_multiunit_script, [['unitA', 'unitB'], 'prog-mhu008.script'])


=====================================
testsuite/tests/ghci/prog-mhu008/b/M.hs
=====================================
@@ -0,0 +1,11 @@
+{-# LANGUAGE PackageImports #-}
+
+module M
+  ( module Export
+  , cmp
+  ) where
+
+import "a" M as Export
+
+cmp :: T -> T -> Bool
+cmp x y = x <= y


=====================================
testsuite/tests/ghci/prog-mhu008/prog-mhu008.script
=====================================
@@ -0,0 +1,5 @@
+:set -XPackageImports
+import "a" M qualified as MA
+import "b" M qualified as MB
+
+MB.cmp (MA.MkT 1) (MA.MkT 2)


=====================================
testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout
=====================================
@@ -0,0 +1 @@
+True


=====================================
testsuite/tests/ghci/prog-mhu008/unitA
=====================================
@@ -0,0 +1,5 @@
+-this-unit-id a-0-inplace
+-this-package-name a
+-i
+-ia
+M


=====================================
testsuite/tests/ghci/prog-mhu008/unitB
=====================================
@@ -0,0 +1,6 @@
+-this-unit-id b-0-inplace
+-this-package-name b
+-package-id a-0-inplace
+-i
+-ib
+M


=====================================
testsuite/tests/primops/should_run/T27299.hs
=====================================
@@ -0,0 +1,23 @@
+{-# LANGUAGE MagicHash #-}
+import GHC.Exts
+import GHC.Word
+import Numeric
+
+main :: IO ()
+main = do
+  putStrLn $ showHex (W# (bitReverse8# 0x55##)) ""
+  putStrLn $ showHex (W# (bitReverse8# 0xAA##)) ""
+  putStrLn $ showHex (W# (bitReverse16# 0x5555##)) ""
+  putStrLn $ showHex (W# (bitReverse16# 0xAAAA##)) ""
+  putStrLn $ showHex (W# (bitReverse32# 0x5555_5555##)) ""
+  putStrLn $ showHex (W# (bitReverse32# 0xAAAA_AAAA##)) ""
+  putStrLn $ showHex (W# (byteSwap16# 0xABCD##)) ""
+  putStrLn $ showHex (W# (byteSwap32# 0xABCD_EF12##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse8# 0x55##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse8# 0xAA##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse16# 0x5555##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse16# 0xAAAA##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse32# 0x5555_5555##)) ""
+  putStrLn $ showHex (W# (noinline bitReverse32# 0xAAAA_AAAA##)) ""
+  putStrLn $ showHex (W# (noinline byteSwap16# 0xABCD##)) ""
+  putStrLn $ showHex (W# (noinline byteSwap32# 0xABCD_EF12##)) ""


=====================================
testsuite/tests/primops/should_run/T27299.stdout
=====================================
@@ -0,0 +1,16 @@
+aa
+55
+aaaa
+5555
+aaaaaaaa
+55555555
+cdab
+12efcdab
+aa
+55
+aaaa
+5555
+aaaaaaaa
+55555555
+cdab
+12efcdab


=====================================
testsuite/tests/primops/should_run/all.T
=====================================
@@ -91,3 +91,4 @@ test('T24496'
       ]
     , compile_and_run, ['-O'])
 test('T6026', normal, compile_and_run, [''])
+test('T27299', normal, compile_and_run, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/94826f172cdf346491c288c25e9ce4b...

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/94826f172cdf346491c288c25e9ce4b...
You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

    

Marge Bot (＠marge-bot)

tags

participants (1)