GitLab

Matthew Pickering pushed to branch wip/ghc-upsweep-spt at Glasgow Haskell Compiler / GHC

Commits:

290f8357

by Matthew Pickering at 2025-09-29T11:50:38+01:00

driver: Load bytecode static pointer entries during linking

Previously the entries were loaded too eagerly, during upsweep, but we
should delay loading them until we know that the relevant bytecode
object is demanded.

Towards #25230

4 changed files:

compiler/GHC/Driver/Main.hs
compiler/GHC/Driver/Make.hs
compiler/GHC/Iface/Tidy/StaticPtrTable.hs
compiler/GHC/Linker/Loader.hs

Changes:

compiler/GHC/Driver/Main.hs

@@ -102,7 +102,6 @@ module GHC.Driver.Main
      , dumpIfaceStats
      , ioMsgMaybe
      , showModuleIndex
 -    , hscAddSptEntries
      , writeInterfaceOnlyMode
      , loadByteCode
      , genModDetails
@@ -2515,9 +2514,6 @@ hscParsedDecls hsc_env decls = runInteractiveHsc hsc_env $ do
      let src_span = srcLocSpan interactiveSrcLoc
      _ <- liftIO $ loadDecls interp hsc_env src_span linkable
 -    {- Load static pointer table entries -}
 -    liftIO $ hscAddSptEntries hsc_env (cg_spt_entries tidy_cg)
+-
      let tcs = filterOut isImplicitTyCon (mg_tcs simpl_mg)
          patsyns = mg_patsyns simpl_mg
@@ -2539,18 +2535,6 @@ hscParsedDecls hsc_env decls = runInteractiveHsc hsc_env $ do
                                                  fam_insts defaults fix_env
      return (new_tythings, new_ictxt)
 --- | Load the given static-pointer table entries into the interpreter.
 --- See Note [Grand plan for static forms] in "GHC.Iface.Tidy.StaticPtrTable".
 -hscAddSptEntries :: HscEnv -> [SptEntry] -> IO ()
 -hscAddSptEntries hsc_env entries = do
 -    let interp = hscInterp hsc_env
 -    let add_spt_entry :: SptEntry -> IO ()
 -        add_spt_entry (SptEntry n fpr) = do
 -            -- These are only names from the current module
 -            (val, _, _) <- loadName interp hsc_env n
 -            addSptEntry interp fpr val
 -    mapM_ add_spt_entry entries
+-
  {-
    Note [Fixity declarations in GHCi]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

compiler/GHC/Driver/Make.hs

@@ -56,8 +56,6 @@ import GHC.Tc.Utils.Monad  ( initIfaceCheck, concatMapM )
  import GHC.Runtime.Interpreter
  import qualified GHC.Linker.Loader as Linker
 -import GHC.Linker.Types
+-
  import GHC.Driver.Config.Diagnostic
  import GHC.Driver.Pipeline
@@ -72,8 +70,6 @@ import GHC.Driver.MakeSem
  import GHC.Driver.Downsweep
  import GHC.Driver.MakeAction
 -import GHC.ByteCode.Types
+-
  import GHC.Iface.Load      ( cannotFindModule, readIface )
  import GHC.IfaceToCore     ( typecheckIface )
  import GHC.Iface.Recomp    ( RecompileRequired(..), CompileReason(..) )
@@ -1232,31 +1228,9 @@ upsweep_mod :: HscEnv
  upsweep_mod hsc_env mHscMessage old_hmi summary mod_index nmods =  do
    hmi <- compileOne' mHscMessage hsc_env summary
            mod_index nmods (hm_iface <$> old_hmi) (maybe emptyHomeModInfoLinkable hm_linkable old_hmi)
+-
 -  -- MP: This is a bit janky, because before you add the entries you have to extend the HPT with the module
 -  -- you just compiled. Another option, would be delay adding anything until after upsweep has finished, but I
 -  -- am unsure if this is sound (wrt running TH splices for example).
 -  -- This function only does anything if the linkable produced is a BCO, which
 -  -- used to only happen with the bytecode backend, but with
 -  -- @-fprefer-byte-code@, @HomeModInfo@ has bytecode even when generating
 -  -- object code, see #25230.
    hscInsertHPT hmi hsc_env
 -  addSptEntries (hsc_env)
 -                (homeModInfoByteCode hmi)
+-
    return hmi
 --- | Add the entries from a BCO linkable to the SPT table, see
 --- See Note [Grand plan for static forms] in GHC.Iface.Tidy.StaticPtrTable.
 -addSptEntries :: HscEnv -> Maybe Linkable -> IO ()
 -addSptEntries hsc_env mlinkable =
 -  hscAddSptEntries hsc_env
 -     [ spt
 -     | linkable <- maybeToList mlinkable
 -     , bco <- linkableBCOs linkable
 -     , spt <- bc_spt_entries bco
 -     ]
+-
  -- Note [When source is considered modified]
  -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

compiler/GHC/Iface/Tidy/StaticPtrTable.hs

@@ -124,7 +124,7 @@ Here is a running example:
  * If we are compiling for the byte-code interpreter, we instead explicitly add
    the SPT entries (recorded in CgGuts' cg_spt_entries field) to the interpreter
    process' SPT table using the addSptEntry interpreter message. This happens
 -  in upsweep after we have compiled the module (see GHC.Driver.Make.upsweep').
 +  when the bytecode object is linked in `dynLinkBCOs`.
  -}
  import GHC.Prelude

compiler/GHC/Linker/Loader.hs

@@ -717,6 +717,7 @@ loadDecls interp hsc_env span linkable = do
            let ce2  = extendClosureEnv (closure_env le2) nms_fhvs
                !pls2 = pls { linker_env = le2 { closure_env = ce2 }
                            , linked_breaks = lb2 }
 +          mapM_ (linkSptEntry interp ce2) (concatMap bc_spt_entries cbcs)
            return (pls2, (nms_fhvs, links_needed, units_needed))
    where
      cbcs = linkableBCOs linkable
@@ -950,10 +951,28 @@ dynLinkBCOs interp pls bcos = do
          -- Wrap finalizers on the ones we want to keep
          new_binds <- makeForeignNamedHValueRefs interp to_add
++
          let ce2 = extendClosureEnv (closure_env le2) new_binds
++
 +        -- Add SPT entries
 +        mapM_ (linkSptEntry interp ce2) (concatMap bc_spt_entries cbcs)
++
          return $! pls1 { linker_env = le2 { closure_env = ce2 }
                         , linked_breaks = lb2 }
 +-- | Register SPT entries for this module in the interpreter
 +-- Assumes that the name from the SPT has already been loaded into the interpreter.
 +linkSptEntry :: Interp -> ClosureEnv -> SptEntry -> IO ()
 +linkSptEntry interp ce (SptEntry name fpr) = do
 +  case lookupNameEnv ce name of
 +    -- The SPT entries only point to locally defined names, which should have already been
 +    -- loaded into the interpreter before this function is called.
 +    Nothing -> pprPanic "linkSptEntry" (ppr name)
 +    Just (_, hval) -> addSptEntry interp fpr hval
++
++
++
++
  -- Link a bunch of BCOs and return references to their values
  linkSomeBCOs :: Interp
               -> PkgsLoaded