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Cheng Shao pushed to branch wip/gbc-faster-internal-names at Glasgow Haskell Compiler / GHC

Commits:

0633b3af

by Cheng Shao at 2026-04-23T14:52:42+00:00

compiler: avoid unique OccNames for internal Names in bytecode objects

This patch improves bytecode object serialization logic by avoiding
the construction of unique `OccName`s when serializing/deserializing
internal `Name`s. Closes #27213.

-------------------------
Metric Decrease:
    LinkableUsage01
-------------------------

1 changed file:

compiler/GHC/ByteCode/Binary.hs

Changes:

compiler/GHC/ByteCode/Binary.hs

@@ -20,7 +20,7 @@ module GHC.ByteCode.Binary (
  import GHC.Prelude
  import GHC.ByteCode.Types
 -import GHC.Data.FastString
 +import qualified GHC.Data.Word64Map.Strict as Word64Map
  import GHC.Types.Name
  import GHC.Types.Name.Cache
  import GHC.Types.Name.Env
@@ -269,9 +269,8 @@ addBinNameWriter bh' = do
          | otherwise -> do
              putByte bh 1
              key <- getBinNameKey env_ref nm
 -            -- Delimit the OccName from the deterministic counter to keep the
 -            -- encoding injective, avoiding collisions like "foo1" vs "foo#1".
 -            put_ bh (occNameFS (occName nm) `appendFS` mkFastString ('#' : show key))
 +            put_ bh $ occNameFS $ occName nm
 +            put_ bh key
    where
      -- Find a deterministic key for local names. This
      getBinNameKey ref name = do
@@ -282,7 +281,7 @@ addBinNameWriter bh' = do
  addBinNameReader :: NameCache -> ReadBinHandle -> IO ReadBinHandle
  addBinNameReader nc bh' = do
 -  env_ref <- newIORef emptyOccEnv
 +  env_ref <- newIORef Word64Map.empty
    pure $ flip addReaderToUserData bh' $ BinaryReader $ \bh -> do
      t <- getByte bh
      case t of
@@ -291,15 +290,16 @@ addBinNameReader nc bh' = do
          pure $ BinName nm
 -> do
          occ <- mkVarOccFS <$> get bh
 +        key <- get bh
          -- We don't want to get a new unique from the NameCache each time we
          -- see a name.
          nm' <- unsafeInterleaveIO $ do
            u <- takeUniqFromNameCache nc
            evaluate $ mkInternalName u occ noSrcSpan
          fmap BinName $ atomicModifyIORef' env_ref $ \env ->
 -          case lookupOccEnv env occ of
 +          case Word64Map.lookup key env of
              Just nm -> (env, nm)
 -            _ -> nm' `seq` (extendOccEnv env occ nm', nm')
 +            _ -> nm' `seq` (Word64Map.insert key nm' env, nm')
        _ -> panic "Binary BinName: invalid byte"
  -- Note [Serializing Names in bytecode]