Implement -XStaticValues.wip/static-pointers

Contains contributions from Alexander Vershilov and Mathieu Boespflug.

As proposed in [1], this extension introduces a new syntactic form
`static e`, where `e :: a` can be any closed expression. The static form
produces a value of type `StaticPtr a`, which works as a reference that
programs can "dereference" to get the value of `e` back. References are
like `Ptr`s, except that they are stable across invocations of a
program.

In essence the extension collects the arguments of the static form into
a global static pointer table. The expressions can be looked up by a
fingerprint computed from the package, the module and a fresh name
given to the expression. For more details we refer to the users guide
section contained in the patch.

The extension is a contribution to the Cloud Haskell ecosystem
(distributed-process and related), and thus has the potential to foster
Haskell as a programming language for distributed systems.

The immediate improvement brought by the extension is the elimination of
remote tables from Cloud Haskell applications. Such applications contain
table fragments spread throughout multiple modules and packages.
Eliminating these fragments saves the programmer the burden required to
construct and assemble the global remote table, a verbose and
error-prone process, even with the help of Template Haskell, that
moreover pollutes the export lists of all modules.

[1] Jeff Epstein, Andrew P. Black, and Simon Peyton-Jones. Towards
Haskell in the cloud. SIGPLAN Not., 46(12):118–129, September 2011. ISSN
0362-1340.

6 files changed, 215 insertions, 16 deletions

diff --git a/compiler/deSugar/Coverage.lhs b/compiler/deSugar/Coverage.lhs
index 5e7289f00c..935f24e36b 100644
--- a/compiler/deSugar/Coverage.lhs
+++ b/compiler/deSugar/Coverage.lhs
@@ -534,6 +534,9 @@ addTickHsExpr (ExplicitPArr ty es) =
         liftM2 ExplicitPArr
                 (return ty)
                 (mapM (addTickLHsExpr) es)
+
+addTickHsExpr e@(HsStatic _) = return e
+
 addTickHsExpr (RecordCon id ty rec_binds) =
         liftM3 RecordCon
                 (return id)
diff --git a/compiler/deSugar/Desugar.lhs b/compiler/deSugar/Desugar.lhs
index e2170e7dd4..2ec2aebbe8 100644
--- a/compiler/deSugar/Desugar.lhs
+++ b/compiler/deSugar/Desugar.lhs
@@ -49,6 +49,7 @@ import Coverage
 import Util
 import MonadUtils
 import OrdList
+import SPT
 import Data.List
 import Data.IORef
 import Control.Monad( when )
@@ -91,7 +92,8 @@ deSugar hsc_env
                             tcg_tcs          = tcs,
                             tcg_insts        = insts,
                             tcg_fam_insts    = fam_insts,
-                            tcg_hpc          = other_hpc_info })
+                            tcg_hpc          = other_hpc_info,
+                            tcg_static_binds = static_binds_var })
 
   = do { let dflags = hsc_dflags hsc_env
              print_unqual = mkPrintUnqualified dflags rdr_env
@@ -121,23 +123,36 @@ deSugar hsc_env
                           ; (ds_fords, foreign_prs) <- dsForeigns fords
                           ; ds_rules <- mapMaybeM dsRule rules
                           ; ds_vects <- mapM dsVect vects
+                          ; stBinds <- dsGetStaticBindsVar >>= liftIO . readIORef
+                          ; let core_prs' = core_prs `appOL` toOL stBinds
                           ; let hpc_init
                                   | gopt Opt_Hpc dflags = hpcInitCode mod ds_hpc_info
                                   | otherwise = empty
+                          ; -- Collects the sptEntries of the module
+                            let spt_init = sptInitCode mod stBinds
                           ; return ( ds_ev_binds
-                                   , foreign_prs `appOL` core_prs `appOL` spec_prs
+                                   , foreign_prs `appOL` core_prs' `appOL` spec_prs
                                    , spec_rules ++ ds_rules, ds_vects
-                                   , ds_fords `appendStubC` hpc_init) }
+                                   , ds_fords `appendStubC` hpc_init `appendStubC` spt_init) }
 
         ; case mb_res of {
            Nothing -> return (msgs, Nothing) ;
-           Just (ds_ev_binds, all_prs, all_rules, vects0, ds_fords) -> do
+           Just (ds_ev_binds, all_prs, {-st_binds,-} all_rules, vects0, ds_fords) ->
 
-     do {       -- Add export flags to bindings
-          keep_alive <- readIORef keep_var
+     do { st_binds' <- readIORef static_binds_var
+          -- Add export flags to bindings
+        ; keep_alive <- readIORef keep_var
+        -- ; let static_names = map (map (idName . fst)) $ [ st_binds', st_binds ]
+        --      keep_alive_all = foldl addListToNameSet keep_alive static_names
         ; let (rules_for_locals, rules_for_imps) = partition isLocalRule all_rules
-              final_prs = addExportFlagsAndRules target export_set keep_alive
-                                                 rules_for_locals (fromOL all_prs)
+              final_prs = addExportFlagsAndRules
+                            target export_set keep_alive
+                            rules_for_locals $ fromOL $ all_prs
+
+                            -- target export_set keep_alive_all
+                            -- rules_for_locals $ fromOL $
+                            --   all_prs `appOL`
+                            --  toOL st_binds' `appOL` toOL st_binds
 
               final_pgm = combineEvBinds ds_ev_binds final_prs
         -- Notice that we put the whole lot in a big Rec, even the foreign binds
diff --git a/compiler/deSugar/DsExpr.lhs b/compiler/deSugar/DsExpr.lhs
index ce2d5a5d4a..e9c06fa812 100644
--- a/compiler/deSugar/DsExpr.lhs
+++ b/compiler/deSugar/DsExpr.lhs
@@ -62,6 +62,10 @@ import Bag
 import Outputable
 import FastString
 
+import IdInfo
+-- import Module ( HasModule(..), lookupWithDefaultModuleEnv, extendModuleEnv )
+import Data.IORef       ( atomicModifyIORef, modifyIORef )
+
 import Control.Monad
 \end{code}
 
@@ -413,6 +417,51 @@ dsExpr (PArrSeq _ _)
 \end{code}
 
 \noindent
+\underline{\bf Static Pointers}
+%              ~~~~~~~~~~~~~~~
+\begin{verbatim}
+    static f
+==>
+    StaticPtr (StaticName "pkg id of f" "module of f" "f")
+\end{verbatim}
+
+\begin{code}
+dsExpr (HsStatic expr@(L loc _)) = do
+    expr_ds <- dsLExpr expr
+    let ty = exprType expr_ds
+    case dropTypeApps expr_ds of
+      Var _ -> return ()
+      _ -> do
+        failWithDs $ cat
+          [ ptext (sLit "The argument of a static form can be only a name")
+          , ptext (sLit "but found: static") <+> parens (ppr expr)
+          ]
+    n' <- mkSptEntryName loc
+    static_binds_var <- dsGetStaticBindsVar
+
+    let mod = nameModule n'
+        pkgKey = modulePackageKey mod
+        pkgName = packageKeyString pkgKey
+
+    -- create static name
+    nm <- fmap (mkConApp staticNameDataCon) $
+            mapM mkStringExprFS
+                 [ fsLit pkgName
+                 , moduleNameFS $ moduleName mod
+                 , occNameFS $ nameOccName n'
+                 ]
+    let tvars = varSetElems $ tyVarsOfType ty
+        speId = mkExportedLocalId VanillaId n' staticSptEntryTy
+        spe   = mkConApp staticSptEntryDataCon
+                  [Type (mkForAllTys tvars ty), nm, mkLams tvars expr_ds]
+    liftIO $ modifyIORef static_binds_var ((speId, spe) :)
+    putSrcSpanDs loc $ return $ mkConApp staticPtrDataCon [Type ty, nm, expr_ds]
+  where
+    dropTypeApps (App e (Type _)) = dropTypeApps e
+    dropTypeApps e = e
+\end{code}
+
+\noindent
 \underline{\bf Record construction and update}
 %              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 For record construction we do this (assuming T has three arguments)
@@ -887,3 +936,32 @@ badMonadBind rhs elt_ty flag_doc
               2 (quotes $ ptext (sLit "_ <-") <+> ppr rhs)
          , ptext (sLit "or by using the flag") <+>  flag_doc ]
 \end{code}
+
+%************************************************************************
+%*                                                                      *
+\subsection{Static pointers}
+%*                                                                      *
+%************************************************************************
+
+
+-- mkStaticRhs :: CoreExpr ->
+
+\begin{code}
+mkSptEntryName :: SrcSpan -> DsM Name
+mkSptEntryName loc = do
+    uniq <- newUnique
+    mod  <- getModule
+    occ  <- mkWrapperName "sptEntry"
+    return $ mkExternalName uniq mod occ loc
+  where
+    mkWrapperName what
+      = do dflags <- getDynFlags
+           thisMod <- getModule
+           let -- Note [Generating fresh names for ccall wrapper]
+               -- in compiler/typecheck/TcEnv.hs
+               wrapperRef = nextWrapperNum dflags
+           wrapperNum <- liftIO $ atomicModifyIORef wrapperRef $ \mod_env ->
+               let num = lookupWithDefaultModuleEnv mod_env 0 thisMod
+                in (extendModuleEnv mod_env thisMod (num+1), num)
+           return $ mkVarOcc $ what ++ ":" ++ show wrapperNum
+\end{code}
diff --git a/compiler/deSugar/DsMeta.hs b/compiler/deSugar/DsMeta.hs
index 083c466baa..e344070df1 100644
--- a/compiler/deSugar/DsMeta.hs
+++ b/compiler/deSugar/DsMeta.hs
@@ -1075,6 +1075,7 @@ repE (ArithSeq _ _ aseq) =
                              repFromThenTo ds1 ds2 ds3
 
 repE (HsSpliceE _ splice)  = repSplice splice
+repE (HsStatic e)        = repLE e >>= rep2 staticEName . (:[]) . unC
 repE e@(PArrSeq {})        = notHandled "Parallel arrays" (ppr e)
 repE e@(HsCoreAnn {})      = notHandled "Core annotations" (ppr e)
 repE e@(HsSCC {})          = notHandled "Cost centres" (ppr e)
@@ -2105,7 +2106,7 @@ templateHaskellNames = [
     tupEName, unboxedTupEName,
     condEName, multiIfEName, letEName, caseEName, doEName, compEName,
     fromEName, fromThenEName, fromToEName, fromThenToEName,
-    listEName, sigEName, recConEName, recUpdEName,
+    listEName, sigEName, recConEName, recUpdEName, staticEName,
     -- FieldExp
     fieldExpName,
     -- Body
@@ -2287,7 +2288,7 @@ clauseName = libFun (fsLit "clause") clauseIdKey
 varEName, conEName, litEName, appEName, infixEName, infixAppName,
     sectionLName, sectionRName, lamEName, lamCaseEName, tupEName,
     unboxedTupEName, condEName, multiIfEName, letEName, caseEName,
-    doEName, compEName :: Name
+    doEName, compEName, staticEName :: Name
 varEName        = libFun (fsLit "varE")        varEIdKey
 conEName        = libFun (fsLit "conE")        conEIdKey
 litEName        = libFun (fsLit "litE")        litEIdKey
@@ -2318,6 +2319,7 @@ listEName       = libFun (fsLit "listE")       listEIdKey
 sigEName        = libFun (fsLit "sigE")        sigEIdKey
 recConEName     = libFun (fsLit "recConE")     recConEIdKey
 recUpdEName     = libFun (fsLit "recUpdE")     recUpdEIdKey
+staticEName     = libFun (fsLit "staticE")     staticEIdKey
 
 -- type FieldExp = ...
 fieldExpName :: Name
@@ -2657,7 +2659,7 @@ varEIdKey, conEIdKey, litEIdKey, appEIdKey, infixEIdKey, infixAppIdKey,
     unboxedTupEIdKey, condEIdKey, multiIfEIdKey,
     letEIdKey, caseEIdKey, doEIdKey, compEIdKey,
     fromEIdKey, fromThenEIdKey, fromToEIdKey, fromThenToEIdKey,
-    listEIdKey, sigEIdKey, recConEIdKey, recUpdEIdKey :: Unique
+    listEIdKey, sigEIdKey, recConEIdKey, recUpdEIdKey, staticEIdKey :: Unique
 varEIdKey         = mkPreludeMiscIdUnique 270
 conEIdKey         = mkPreludeMiscIdUnique 271
 litEIdKey         = mkPreludeMiscIdUnique 272
@@ -2684,6 +2686,7 @@ listEIdKey        = mkPreludeMiscIdUnique 292
 sigEIdKey         = mkPreludeMiscIdUnique 293
 recConEIdKey      = mkPreludeMiscIdUnique 294
 recUpdEIdKey      = mkPreludeMiscIdUnique 295
+staticEIdKey      = mkPreludeMiscIdUnique 296
 
 -- type FieldExp = ...
 fieldExpIdKey :: Unique
diff --git a/compiler/deSugar/DsMonad.lhs b/compiler/deSugar/DsMonad.lhs
index c017a7cc01..ea4f581880 100644
--- a/compiler/deSugar/DsMonad.lhs
+++ b/compiler/deSugar/DsMonad.lhs
@@ -21,7 +21,7 @@ module DsMonad (
         mkPrintUnqualifiedDs,
         newUnique, 
         UniqSupply, newUniqueSupply,
-        getGhcModeDs, dsGetFamInstEnvs,
+        getGhcModeDs, dsGetFamInstEnvs, dsGetStaticBindsVar,
         dsLookupGlobal, dsLookupGlobalId, dsDPHBuiltin, dsLookupTyCon, dsLookupDataCon,
         
         PArrBuiltin(..), 
@@ -167,6 +167,8 @@ data DsGblEnv
                                                 -- exported entities of 'Data.Array.Parallel' iff
                                                 -- '-XParallelArrays' was given; otherwise, empty
         , ds_parr_bi :: PArrBuiltin             -- desugarar names for '-XParallelArrays'
+        , ds_static_binds :: IORef [(Id,CoreExpr)]
+          -- ^ Bindings resulted from floating static forms
         }
 
 instance ContainsModule DsGblEnv where
@@ -197,8 +199,11 @@ initDs :: HscEnv
 
 initDs hsc_env mod rdr_env type_env fam_inst_env thing_inside
   = do  { msg_var <- newIORef (emptyBag, emptyBag)
+        ; static_binds_var <- newIORef []
         ; let dflags                   = hsc_dflags hsc_env
-              (ds_gbl_env, ds_lcl_env) = mkDsEnvs dflags mod rdr_env type_env fam_inst_env msg_var
+              (ds_gbl_env, ds_lcl_env) = mkDsEnvs dflags mod rdr_env type_env
+                                                  fam_inst_env msg_var
+                                                  static_binds_var
 
         ; either_res <- initTcRnIf 'd' hsc_env ds_gbl_env ds_lcl_env $
                           loadDAP $
@@ -276,12 +281,15 @@ initDsTc thing_inside
         ; let type_env = tcg_type_env tcg_env
               rdr_env  = tcg_rdr_env tcg_env
               fam_inst_env = tcg_fam_inst_env tcg_env
-              ds_envs  = mkDsEnvs dflags this_mod rdr_env type_env fam_inst_env msg_var
+              static_binds_var = tcg_static_binds tcg_env
+              ds_envs  = mkDsEnvs dflags this_mod rdr_env type_env fam_inst_env
+                                  msg_var static_binds_var
         ; setEnvs ds_envs thing_inside
         }
 
-mkDsEnvs :: DynFlags -> Module -> GlobalRdrEnv -> TypeEnv -> FamInstEnv -> IORef Messages -> (DsGblEnv, DsLclEnv)
-mkDsEnvs dflags mod rdr_env type_env fam_inst_env msg_var
+mkDsEnvs :: DynFlags -> Module -> GlobalRdrEnv -> TypeEnv -> FamInstEnv
+         -> IORef Messages -> IORef [(Id, CoreExpr)] -> (DsGblEnv, DsLclEnv)
+mkDsEnvs dflags mod rdr_env type_env fam_inst_env msg_var static_binds_var
   = let if_genv = IfGblEnv { if_rec_types = Just (mod, return type_env) }
         if_lenv = mkIfLclEnv mod (ptext (sLit "GHC error in desugarer lookup in") <+> ppr mod)
         gbl_env = DsGblEnv { ds_mod     = mod
@@ -291,6 +299,7 @@ mkDsEnvs dflags mod rdr_env type_env fam_inst_env msg_var
                            , ds_msgs    = msg_var
                            , ds_dph_env = emptyGlobalRdrEnv
                            , ds_parr_bi = panic "DsMonad: uninitialised ds_parr_bi"
+                           , ds_static_binds = static_binds_var
                            }
         lcl_env = DsLclEnv { ds_meta = emptyNameEnv
                            , ds_loc  = noSrcSpan
@@ -496,6 +505,9 @@ dsLookupMetaEnv name = do { env <- getLclEnv; return (lookupNameEnv (ds_meta env
 dsExtendMetaEnv :: DsMetaEnv -> DsM a -> DsM a
 dsExtendMetaEnv menv thing_inside
   = updLclEnv (\env -> env { ds_meta = ds_meta env `plusNameEnv` menv }) thing_inside
+
+dsGetStaticBindsVar :: DsM (IORef [(Id,CoreExpr)])
+dsGetStaticBindsVar = fmap ds_static_binds getGblEnv
 \end{code}
 
 \begin{code}
diff --git a/compiler/deSugar/SPT.lhs b/compiler/deSugar/SPT.lhs
new file mode 100644
index 0000000000..b5823413e0
--- /dev/null
+++ b/compiler/deSugar/SPT.lhs
@@ -0,0 +1,88 @@
+%
+% Code generation for the Static Pointer Table
+%
+% (c) 2014 I/O Tweag
+%
+\begin{code}
+module SPT (sptInitCode) where
+
+import CoreSyn
+import Module
+import Outputable
+import Id
+import Name
+import CLabel
+import FastString
+import Foreign.Ptr
+import GHC.Fingerprint
+import qualified Data.ByteString.Unsafe as BS
+import System.IO.Unsafe (unsafePerformIO)
+\end{code}
+
+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)
+{
+ extern StgPtr Main_sptEntryZC0_closure;
+ extern StgPtr Main_sptEntryZC1_closure;
+ hs_spt_insert( (StgWord64[2]){16252233376642134256ULL,7370534374097506082ULL}
+              , &Main_sptEntryZC0_closure
+              );
+ hs_spt_insert( (StgWord64[2]){12545634534567898323ULL,5409674567544156781ULL}
+              , &Main_sptEntryZC1_closure
+              );
+}
+
+where constants are values of a fingerprint of the triplet
+(package_id, module_name, sptEntry:N).
+
+\begin{code}
+sptInitCode :: Module -> [(Id,CoreExpr)] -> SDoc
+sptInitCode _ [] = Outputable.empty
+sptInitCode 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 $
+        [  ptext (sLit "extern StgPtr ")
+        <> (ppr $ mkClosureLabel (idName n) (idCafInfo n))
+        <> semi
+        |  (n, _) <- entries ] ++
+        [  ptext (sLit "hs_spt_insert")
+        <> parens (hcat $ punctuate comma
+            [ pprFingerprint $ fingerprintId n
+            , ptext (sLit "&") <> ppr (mkClosureLabel (idName n) (idCafInfo n))
+            ])
+        <> semi
+        |  (n, _) <- entries ]
+    ]
+\end{code}
+
+\begin{code}
+fingerprintId :: Id -> Fingerprint
+fingerprintId n =
+   fingerprintString (unpackFS name)
+ where
+   name = concatFS [ packageKeyFS $ modulePackageKey $ nameModule $ idName n
+                   , fsLit ":"
+                   , moduleNameFS (moduleName $ nameModule $ idName n)
+                   , fsLit "."
+                   , occNameFS $ occName $ idName n
+                   ]
+
+pprFingerprint :: Fingerprint -> SDoc
+pprFingerprint (Fingerprint w1 w2) =
+   ptext (sLit "(StgWord64[2])")
+   <> (braces $ hcat $ punctuate comma [integer (fromIntegral w1) <> ptext  (sLit "ULL")
+                                       ,integer (fromIntegral w2) <> ptext (sLit "ULL")
+                                       ])
+\end{code}
+