-- | Code generation for the Static Pointer Table -- -- (c) 2014 I/O Tweag -- -- Each module that uses 'static' keyword declares an initialization function of -- the form hs_spt_init_\<module>() which is emitted into the _stub.c file and -- annotated with __attribute__((constructor)) so that it gets executed at -- startup time. -- -- The function's purpose is to call hs_spt_insert to insert the static -- pointers of this module in the hashtable of the RTS, and it looks something -- like this: -- -- > static void hs_hpc_init_Main(void) __attribute__((constructor)); -- > static void hs_hpc_init_Main(void) { -- > -- > static StgWord64 k0[2] = {16252233372134256ULL,7370534374096082ULL}; -- > extern StgPtr Main_r2wb_closure; -- > hs_spt_insert(k0, &Main_r2wb_closure); -- > -- > static StgWord64 k1[2] = {12545634534567898ULL,5409674567544151ULL}; -- > extern StgPtr Main_r2wc_closure; -- > hs_spt_insert(k1, &Main_r2wc_closure); -- > -- > } -- -- where the constants are fingerprints produced from the static forms. -- -- The linker must find the definitions matching the @extern StgPtr <name>@ -- declarations. For this to work, the identifiers of static pointers need to be -- exported. This is done in 'GHC.Core.Opt.SetLevels.newLvlVar'. -- -- There is also a finalization function for the time when the module is -- unloaded. -- -- > static void hs_hpc_fini_Main(void) __attribute__((destructor)); -- > static void hs_hpc_fini_Main(void) { -- > -- > static StgWord64 k0[2] = {16252233372134256ULL,7370534374096082ULL}; -- > hs_spt_remove(k0); -- > -- > static StgWord64 k1[2] = {12545634534567898ULL,5409674567544151ULL}; -- > hs_spt_remove(k1); -- > -- > } -- {-# LANGUAGE ViewPatterns, TupleSections #-} module GHC.Iface.Tidy.StaticPtrTable ( sptCreateStaticBinds , sptModuleInitCode ) where {- Note [Grand plan for static forms] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Static forms go through the compilation phases as follows. Here is a running example: f x = let k = map toUpper in ...(static k)... * The renamer looks for out-of-scope names in the body of the static form, as always. If all names are in scope, the free variables of the body are stored in AST at the location of the static form. * The typechecker verifies that all free variables occurring in the static form are floatable to top level (see Note [Meaning of IdBindingInfo] in GHC.Tc.Types). In our example, 'k' is floatable. Even though it is bound in a nested let, we are fine. * The desugarer replaces the static form with an application of the function 'makeStatic' (defined in module GHC.StaticPtr.Internal of base). So we get f x = let k = map toUpper in ...fromStaticPtr (makeStatic location k)... * The simplifier runs the FloatOut pass which moves the calls to 'makeStatic' to the top level. Thus the FloatOut pass is always executed, even when optimizations are disabled. So we get k = map toUpper static_ptr = makeStatic location k f x = ...fromStaticPtr static_ptr... The FloatOut pass is careful to produce an /exported/ Id for a floated 'makeStatic' call, so the binding is not removed or inlined by the simplifier. E.g. the code for `f` above might look like static_ptr = makeStatic location k f x = ...(case static_ptr of ...)... which might be simplified to f x = ...(case makeStatic location k of ...)... BUT the top-level binding for static_ptr must remain, so that it can be collected to populate the Static Pointer Table. Making the binding exported also has a necessary effect during the CoreTidy pass. * The CoreTidy pass replaces all bindings of the form b = /\ ... -> makeStatic location value with b = /\ ... -> StaticPtr key (StaticPtrInfo "pkg key" "module" location) value where a distinct key is generated for each binding. * If we are compiling to object code we insert a C stub (generated by sptModuleInitCode) into the final object which runs when the module is loaded, inserting the static forms defined by the module into the RTS's static pointer table. * 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'). -} import GHC.Prelude import GHC.Cmm.CLabel import GHC.Core import GHC.Core.Utils (collectMakeStaticArgs) import GHC.Core.DataCon import GHC.Driver.Session import GHC.Driver.Types import GHC.Types.Id import GHC.Core.Make (mkStringExprFSWith) import GHC.Unit.Module import GHC.Types.Name import GHC.Utils.Outputable as Outputable import GHC.Platform import GHC.Builtin.Names import GHC.Tc.Utils.Env (lookupGlobal) import GHC.Core.Type import Control.Monad.Trans.Class (lift) import Control.Monad.Trans.State import Data.List import Data.Maybe import GHC.Fingerprint import qualified GHC.LanguageExtensions as LangExt -- | Replaces all bindings of the form -- -- > b = /\ ... -> makeStatic location value -- -- with -- -- > b = /\ ... -> -- > StaticPtr key (StaticPtrInfo "pkg key" "module" location) value -- -- where a distinct key is generated for each binding. -- -- It also yields the C stub that inserts these bindings into the static -- pointer table. sptCreateStaticBinds :: HscEnv -> Module -> CoreProgram -> IO ([SptEntry], CoreProgram) sptCreateStaticBinds hsc_env this_mod binds | not (xopt LangExt.StaticPointers dflags) = return ([], binds) | otherwise = do -- Make sure the required interface files are loaded. _ <- lookupGlobal hsc_env unpackCStringName (fps, binds') <- evalStateT (go [] [] binds) 0 return (fps, binds') where go fps bs xs = case xs of [] -> return (reverse fps, reverse bs) bnd : xs' -> do (fps', bnd') <- replaceStaticBind bnd go (reverse fps' ++ fps) (bnd' : bs) xs' dflags = hsc_dflags hsc_env platform = targetPlatform dflags -- Generates keys and replaces 'makeStatic' with 'StaticPtr'. -- -- The 'Int' state is used to produce a different key for each binding. replaceStaticBind :: CoreBind -> StateT Int IO ([SptEntry], CoreBind) replaceStaticBind (NonRec b e) = do (mfp, (b', e')) <- replaceStatic b e return (maybeToList mfp, NonRec b' e') replaceStaticBind (Rec rbs) = do (mfps, rbs') <- unzip <$> mapM (uncurry replaceStatic) rbs return (catMaybes mfps, Rec rbs') replaceStatic :: Id -> CoreExpr -> StateT Int IO (Maybe SptEntry, (Id, CoreExpr)) replaceStatic b e@(collectTyBinders -> (tvs, e0)) = case collectMakeStaticArgs e0 of Nothing -> return (Nothing, (b, e)) Just (_, t, info, arg) -> do (fp, e') <- mkStaticBind t info arg return (Just (SptEntry b fp), (b, foldr Lam e' tvs)) mkStaticBind :: Type -> CoreExpr -> CoreExpr -> StateT Int IO (Fingerprint, CoreExpr) mkStaticBind t srcLoc e = do i <- get put (i + 1) staticPtrInfoDataCon <- lift $ lookupDataConHscEnv staticPtrInfoDataConName let fp@(Fingerprint w0 w1) = mkStaticPtrFingerprint i info <- mkConApp staticPtrInfoDataCon <$> (++[srcLoc]) <$> mapM (mkStringExprFSWith (lift . lookupIdHscEnv)) [ unitFS $ moduleUnit this_mod , moduleNameFS $ moduleName this_mod ] -- The module interface of GHC.StaticPtr should be loaded at least -- when looking up 'fromStatic' during type-checking. staticPtrDataCon <- lift $ lookupDataConHscEnv staticPtrDataConName return (fp, mkConApp staticPtrDataCon [ Type t , mkWord64LitWordRep platform w0 , mkWord64LitWordRep platform w1 , info , e ]) mkStaticPtrFingerprint :: Int -> Fingerprint mkStaticPtrFingerprint n = fingerprintString $ intercalate ":" [ unitString $ moduleUnit this_mod , moduleNameString $ moduleName this_mod , show n ] -- Choose either 'Word64#' or 'Word#' to represent the arguments of the -- 'Fingerprint' data constructor. mkWord64LitWordRep platform = case platformWordSize platform of PW4 -> mkWord64LitWord64 PW8 -> mkWordLit platform . toInteger lookupIdHscEnv :: Name -> IO Id lookupIdHscEnv n = lookupTypeHscEnv hsc_env n >>= maybe (getError n) (return . tyThingId) lookupDataConHscEnv :: Name -> IO DataCon lookupDataConHscEnv n = lookupTypeHscEnv hsc_env n >>= maybe (getError n) (return . tyThingDataCon) getError n = pprPanic "sptCreateStaticBinds.get: not found" $ text "Couldn't find" <+> ppr n -- | @sptModuleInitCode module fps@ is a C stub to insert the static entries -- of @module@ into the static pointer table. -- -- @fps@ is a list associating each binding corresponding to a static entry with -- its fingerprint. sptModuleInitCode :: Module -> [SptEntry] -> SDoc sptModuleInitCode _ [] = Outputable.empty sptModuleInitCode this_mod entries = vcat [ text "static void hs_spt_init_" <> ppr this_mod <> text "(void) __attribute__((constructor));" , text "static void hs_spt_init_" <> ppr this_mod <> text "(void)" , braces $ vcat $ [ text "static StgWord64 k" <> int i <> text "[2] = " <> pprFingerprint fp <> semi $$ text "extern StgPtr " <> (ppr $ mkClosureLabel (idName n) (idCafInfo n)) <> semi $$ text "hs_spt_insert" <> parens (hcat $ punctuate comma [ char 'k' <> int i , char '&' <> ppr (mkClosureLabel (idName n) (idCafInfo n)) ] ) <> semi | (i, SptEntry n fp) <- zip [0..] entries ] , text "static void hs_spt_fini_" <> ppr this_mod <> text "(void) __attribute__((destructor));" , text "static void hs_spt_fini_" <> ppr this_mod <> text "(void)" , braces $ vcat $ [ text "StgWord64 k" <> int i <> text "[2] = " <> pprFingerprint fp <> semi $$ text "hs_spt_remove" <> parens (char 'k' <> int i) <> semi | (i, (SptEntry _ fp)) <- zip [0..] entries ] ] where pprFingerprint :: Fingerprint -> SDoc pprFingerprint (Fingerprint w1 w2) = braces $ hcat $ punctuate comma [ integer (fromIntegral w1) <> text "ULL" , integer (fromIntegral w2) <> text "ULL" ]