{-# LANGUAGE GADTs, BangPatterns, RecordWildCards, GeneralizedNewtypeDeriving, NondecreasingIndentation, TupleSections #-} module CmmBuildInfoTables ( CAFSet, CAFEnv, cafAnal , doSRTs, ModuleSRTInfo, emptySRT ) where import GhcPrelude hiding (succ) import Id import BlockId import Hoopl.Block import Hoopl.Graph import Hoopl.Label import Hoopl.Collections import Hoopl.Dataflow import Module import Platform import Digraph import CLabel import PprCmmDecl () import Cmm import CmmUtils import DynFlags import Maybes import Outputable import SMRep import UniqSupply import CostCentre import StgCmmHeap import PprCmm() import Control.Monad import Data.Map (Map) import qualified Data.Map as Map import Data.Set (Set) import qualified Data.Set as Set import Data.Tuple import Control.Monad.Trans.State import Control.Monad.Trans.Class {- Note [SRTs] SRTs are the mechanism by which the garbage collector can determine the live CAFs in the program. Representation ^^^^^^^^^^^^^^ +------+ | info | | | +-----+---+---+---+ | -------->|SRT_2| | | | | 0 | |------| +-----+-|-+-|-+---+ | | | | | code | | | | | v v An SRT is simply an object in the program's data segment. It has the same representation as a static constructor. There are 16 pre-compiled SRT info tables: stg_SRT_1_info, .. stg_SRT_16_info, representing SRT objects with 1-16 pointers, respectively. The entries of an SRT object point to static closures, which are either - FUN_STATIC, THUNK_STATIC or CONSTR - Another SRT (actually just a CONSTR) The final field of the SRT is the static link field, used by the garbage collector to chain together static closures that it visits and to determine whether a static closure has been visited or not. (see Note [STATIC_LINK fields]) By traversing the transitive closure of an SRT, the GC will reach all of the CAFs that are reachable from the code associated with this SRT. If we need to create an SRT with more than 16 entries, we build a chain of SRT objects with all but the last having 16 entries. +-----+---+- -+---+---+ |SRT16| | | | | | 0 | +-----+-|-+- -+-|-+---+ | | v v +----+---+---+---+ |SRT2| | | | | 0 | +----+-|-+-|-+---+ | | | | v v Referring to an SRT from the info table ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The following things have SRTs: - Static functions (FUN) - Static thunks (THUNK), ie. CAFs - Continuations (RET_SMALL, etc.) In each case, the info table points to the SRT. - info->srt is zero if there's no SRT, otherwise: - info->srt == 1 and info->f.srt_offset points to the SRT e.g. for a FUN with an SRT: StgFunInfoTable +------+ info->f.srt_offset | ------------> offset to SRT object StgStdInfoTable +------+ info->layout.ptrs | ... | info->layout.nptrs | ... | info->srt | 1 | info->type | ... | |------| On x86_64, we optimise the info table representation further. The offset to the SRT can be stored in 32 bits (all code lives within a 2GB region in x86_64's small memory model), so we can save a word in the info table by storing the srt_offset in the srt field, which is half a word. On x86_64 with TABLES_NEXT_TO_CODE (except on MachO, due to #15169): - info->srt is zero if there's no SRT, otherwise: - info->srt is an offset from the info pointer to the SRT object StgStdInfoTable +------+ info->layout.ptrs | | info->layout.nptrs | | info->srt | ------------> offset to SRT object |------| EXAMPLE ^^^^^^^ f = \x. ... g ... where g = \y. ... h ... c1 ... h = \z. ... c2 ... c1 & c2 are CAFs g and h are local functions, but they have no static closures. When we generate code for f, we start with a CmmGroup of four CmmDecls: [ f_closure, f_entry, g_entry, h_entry ] we process each CmmDecl separately in cpsTop, giving us a list of CmmDecls. e.g. for f_entry, we might end up with [ f_entry, f1_ret, f2_proc ] where f1_ret is a return point, and f2_proc is a proc-point. We have a CAFSet for each of these CmmDecls, let's suppose they are [ f_entry{g_info}, f1_ret{g_info}, f2_proc{} ] [ g_entry{h_info, c1_closure} ] [ h_entry{c2_closure} ] Next, we make an SRT for each of these functions: f_srt : [g_info] g_srt : [h_info, c1_closure] h_srt : [c2_closure] Now, for g_info and h_info, we want to refer to the SRTs for g and h respectively, which we'll label g_srt and h_srt: f_srt : [g_srt] g_srt : [h_srt, c1_closure] h_srt : [c2_closure] Now, when an SRT has a single entry, we don't actually generate an SRT closure for it, instead we just replace references to it with its single element. So, since h_srt == c2_closure, we have f_srt : [g_srt] g_srt : [c2_closure, c1_closure] h_srt : [c2_closure] and the only SRT closure we generate is g_srt = SRT_2 [c2_closure, c1_closure] Optimisations ^^^^^^^^^^^^^ To reduce the code size overhead and the cost of traversing SRTs in the GC, we want to simplify SRTs where possible. We therefore apply the following optimisations. Each has a [keyword]; search for the keyword in the code below to see where the optimisation is implemented. 1. [Inline] we never create an SRT with a single entry, instead we point to the single entry directly from the info table. i.e. instead of +------+ | info | | | +-----+---+---+ | -------->|SRT_1| | | 0 | |------| +-----+-|-+---+ | | | | code | | | | v C we can point directly to the closure: +------+ | info | | | | -------->C |------| | | | code | | | Furthermore, the SRT for any code that refers to this info table can point directly to C. The exception to this is when we're doing dynamic linking. In that case, if the closure is not locally defined then we can't point to it directly from the info table, because this is the text section which cannot contain runtime relocations. In this case we skip this optimisation and generate the singleton SRT, becase SRTs are in the data section and *can* have relocatable references. 2. [FUN] A static function closure can also be an SRT, we simply put the SRT entries as fields in the static closure. This makes a lot of sense: the static references are just like the free variables of the FUN closure. i.e. instead of f_closure: +-----+---+ | | | 0 | +- |--+---+ | +------+ | | info | f_srt: | | | +-----+---+---+---+ | | -------->|SRT_2| | | | + 0 | `----------->|------| +-----+-|-+-|-+---+ | | | | | code | | | | | v v We can generate: f_closure: +-----+---+---+---+ | | | | | | | 0 | +- |--+-|-+-|-+---+ | | | +------+ | v v | info | | | | | | 0 | `----------->|------| | | | code | | | (note: we can't do this for THUNKs, because the thunk gets overwritten when it is entered, so we wouldn't be able to share this SRT with other info tables that want to refer to it (see [Common] below). FUNs are immutable so don't have this problem.) 3. [Common] Identical SRTs can be commoned up. 4. [Filter] If an SRT A refers to an SRT B and a closure C, and B also refers to C (perhaps transitively), then we can omit the reference to C from A. Note that there are many other optimisations that we could do, but aren't implemented. In general, we could omit any reference from an SRT if everything reachable from it is also reachable from the other fields in the SRT. Our [Filter] optimisation is a special case of this. Another opportunity we don't exploit is this: A = {X,Y,Z} B = {Y,Z} C = {X,B} Here we could use C = {A} and therefore [Inline] C = A. -} -- --------------------------------------------------------------------- {- Note [Invalid optimisation: shortcutting] You might think that if we have something like A's SRT = {B} B's SRT = {X} that we could replace the reference to B in A's SRT with X. A's SRT = {X} B's SRT = {X} and thereby perhaps save a little work at runtime, because we don't have to visit B. But this is NOT valid. Consider these cases: 0. B can't be a constructor, because constructors don't have SRTs 1. B is a CAF. This is the easy one. Obviously we want A's SRT to point to B, so that it keeps B alive. 2. B is a function. This is the tricky one. The reason we can't shortcut in this case is that we aren't allowed to resurrect static objects. == How does this cause a problem? == The particular case that cropped up when we tried this was #15544. - A is a thunk - B is a static function - X is a CAF - suppose we GC when A is alive, and B is not otherwise reachable. - B is "collected", meaning that it doesn't make it onto the static objects list during this GC, but nothing bad happens yet. - Next, suppose we enter A, and then call B. (remember that A refers to B) At the entry point to B, we GC. This puts B on the stack, as part of the RET_FUN stack frame that gets pushed when we GC at a function entry point. - This GC will now reach B - But because B was previous "collected", it breaks the assumption that static objects are never resurrected. See Note [STATIC_LINK fields] in rts/sm/Storage.h for why this is bad. - In practice, the GC thinks that B has already been visited, and so doesn't visit X, and catastrophe ensues. == Isn't this caused by the RET_FUN business? == Maybe, but could you prove that RET_FUN is the only way that resurrection can occur? So, no shortcutting. -} -- --------------------------------------------------------------------- -- Label types -- Labels that come from cafAnal can be: -- - _closure labels for static functions or CAFs -- - _info labels for dynamic functions, thunks, or continuations -- - _entry labels for functions or thunks -- -- Meanwhile the labels on top-level blocks are _entry labels. -- -- To put everything in the same namespace we convert all labels to -- closure labels using toClosureLbl. Note that some of these -- labels will not actually exist; that's ok because we're going to -- map them to SRTEntry later, which ranges over labels that do exist. -- newtype CAFLabel = CAFLabel CLabel deriving (Eq,Ord,Outputable) type CAFSet = Set CAFLabel type CAFEnv = LabelMap CAFSet mkCAFLabel :: CLabel -> CAFLabel mkCAFLabel lbl = CAFLabel (toClosureLbl lbl) -- This is a label that we can put in an SRT. It *must* be a closure label, -- pointing to either a FUN_STATIC, THUNK_STATIC, or CONSTR. newtype SRTEntry = SRTEntry CLabel deriving (Eq, Ord, Outputable) -- --------------------------------------------------------------------- -- CAF analysis -- | -- For each code block: -- - collect the references reachable from this code block to FUN, -- THUNK or RET labels for which hasCAF == True -- -- This gives us a `CAFEnv`: a mapping from code block to sets of labels -- cafAnal :: LabelSet -- The blocks representing continuations, ie. those -- that will get RET info tables. These labels will -- get their own SRTs, so we don't aggregate CAFs from -- references to these labels, we just use the label. -> CLabel -- The top label of the proc -> CmmGraph -> CAFEnv cafAnal contLbls topLbl cmmGraph = analyzeCmmBwd cafLattice (cafTransfers contLbls (g_entry cmmGraph) topLbl) cmmGraph mapEmpty cafLattice :: DataflowLattice CAFSet cafLattice = DataflowLattice Set.empty add where add (OldFact old) (NewFact new) = let !new' = old `Set.union` new in changedIf (Set.size new' > Set.size old) new' cafTransfers :: LabelSet -> Label -> CLabel -> TransferFun CAFSet cafTransfers contLbls entry topLbl (BlockCC eNode middle xNode) fBase = let joined = cafsInNode xNode $! live' !result = foldNodesBwdOO cafsInNode middle joined facts = mapMaybe successorFact (successors xNode) live' = joinFacts cafLattice facts successorFact s -- If this is a loop back to the entry, we can refer to the -- entry label. | s == entry = Just (add topLbl Set.empty) -- If this is a continuation, we want to refer to the -- SRT for the continuation's info table | s `setMember` contLbls = Just (Set.singleton (mkCAFLabel (infoTblLbl s))) -- Otherwise, takes the CAF references from the destination | otherwise = lookupFact s fBase cafsInNode :: CmmNode e x -> CAFSet -> CAFSet cafsInNode node set = foldExpDeep addCaf node set addCaf expr !set = case expr of CmmLit (CmmLabel c) -> add c set CmmLit (CmmLabelOff c _) -> add c set CmmLit (CmmLabelDiffOff c1 c2 _ _) -> add c1 $! add c2 set _ -> set add l s | hasCAF l = Set.insert (mkCAFLabel l) s | otherwise = s in mapSingleton (entryLabel eNode) result -- ----------------------------------------------------------------------------- -- ModuleSRTInfo data ModuleSRTInfo = ModuleSRTInfo { thisModule :: Module -- ^ Current module being compiled. Required for calling labelDynamic. , dedupSRTs :: Map (Set SRTEntry) SRTEntry -- ^ previous SRTs we've emitted, so we can de-duplicate. -- Used to implement the [Common] optimisation. , flatSRTs :: Map SRTEntry (Set SRTEntry) -- ^ The reverse mapping, so that we can remove redundant -- entries. e.g. if we have an SRT [a,b,c], and we know that b -- points to [c,d], we can omit c and emit [a,b]. -- Used to implement the [Filter] optimisation. } instance Outputable ModuleSRTInfo where ppr ModuleSRTInfo{..} = text "ModuleSRTInfo:" <+> ppr dedupSRTs <+> ppr flatSRTs emptySRT :: Module -> ModuleSRTInfo emptySRT mod = ModuleSRTInfo { thisModule = mod , dedupSRTs = Map.empty , flatSRTs = Map.empty } -- ----------------------------------------------------------------------------- -- Constructing SRTs {- Implementation notes - In each CmmDecl there is a mapping info_tbls from Label -> CmmInfoTable - The entry in info_tbls corresponding to g_entry is the closure info table, the rest are continuations. - Each entry in info_tbls possibly needs an SRT. We need to make a label for each of these. - We get the CAFSet for each entry from the CAFEnv -} -- | Return a (Label,CLabel) pair for each labelled block of a CmmDecl, -- where the label is -- - the info label for a continuation or dynamic closure -- - the closure label for a top-level function (not a CAF) getLabelledBlocks :: CmmDecl -> [(Label, CAFLabel)] getLabelledBlocks (CmmData _ _) = [] getLabelledBlocks (CmmProc top_info _ _ _) = [ (blockId, mkCAFLabel (cit_lbl info)) | (blockId, info) <- mapToList (info_tbls top_info) , let rep = cit_rep info , not (isStaticRep rep) || not (isThunkRep rep) ] -- | Put the labelled blocks that we will be annotating with SRTs into -- dependency order. This is so that we can process them one at a -- time, resolving references to earlier blocks to point to their -- SRTs. CAFs themselves are not included here; see getCAFs below. depAnalSRTs :: CAFEnv -> [CmmDecl] -> [SCC (Label, CAFLabel, Set CAFLabel)] depAnalSRTs cafEnv decls = srtTrace "depAnalSRTs" (ppr graph) graph where labelledBlocks = concatMap getLabelledBlocks decls labelToBlock = Map.fromList (map swap labelledBlocks) graph = stronglyConnCompFromEdgedVerticesOrd [ let cafs' = Set.delete lbl cafs in DigraphNode (l,lbl,cafs') l (mapMaybe (flip Map.lookup labelToBlock) (Set.toList cafs')) | (l, lbl) <- labelledBlocks , Just cafs <- [mapLookup l cafEnv] ] -- | Get (Label, CAFLabel, Set CAFLabel) for each block that represents a CAF. -- These are treated differently from other labelled blocks: -- - we never shortcut a reference to a CAF to the contents of its -- SRT, since the point of SRTs is to keep CAFs alive. -- - CAFs therefore don't take part in the dependency analysis in depAnalSRTs. -- instead we generate their SRTs after everything else. getCAFs :: CAFEnv -> [CmmDecl] -> [(Label, CAFLabel, Set CAFLabel)] getCAFs cafEnv decls = [ (g_entry g, mkCAFLabel topLbl, cafs) | CmmProc top_info topLbl _ g <- decls , Just info <- [mapLookup (g_entry g) (info_tbls top_info)] , let rep = cit_rep info , isStaticRep rep && isThunkRep rep , Just cafs <- [mapLookup (g_entry g) cafEnv] ] -- | Get the list of blocks that correspond to the entry points for -- FUN_STATIC closures. These are the blocks for which if we have an -- SRT we can merge it with the static closure. [FUN] getStaticFuns :: [CmmDecl] -> [(BlockId, CLabel)] getStaticFuns decls = [ (g_entry g, lbl) | CmmProc top_info _ _ g <- decls , Just info <- [mapLookup (g_entry g) (info_tbls top_info)] , Just (id, _) <- [cit_clo info] , let rep = cit_rep info , isStaticRep rep && isFunRep rep , let lbl = mkLocalClosureLabel (idName id) (idCafInfo id) ] -- | Maps labels from 'cafAnal' to the final CLabel that will appear -- in the SRT. -- - closures with singleton SRTs resolve to their single entry -- - closures with larger SRTs map to the label for that SRT -- - CAFs must not map to anything! -- - if a labels maps to Nothing, we found that this label's SRT -- is empty, so we don't need to refer to it from other SRTs. type SRTMap = Map CAFLabel (Maybe SRTEntry) -- | resolve a CAFLabel to its SRTEntry using the SRTMap resolveCAF :: SRTMap -> CAFLabel -> Maybe SRTEntry resolveCAF srtMap lbl@(CAFLabel l) = Map.findWithDefault (Just (SRTEntry (toClosureLbl l))) lbl srtMap -- | Attach SRTs to all info tables in the CmmDecls, and add SRT -- declarations to the ModuleSRTInfo. -- doSRTs :: DynFlags -> ModuleSRTInfo -> [(CAFEnv, [CmmDecl])] -> IO (ModuleSRTInfo, [CmmDecl]) doSRTs dflags moduleSRTInfo tops = do us <- mkSplitUniqSupply 'u' -- Ignore the original grouping of decls, and combine all the -- CAFEnvs into a single CAFEnv. let (cafEnvs, declss) = unzip tops cafEnv = mapUnions cafEnvs decls = concat declss staticFuns = mapFromList (getStaticFuns decls) -- Put the decls in dependency order. Why? So that we can implement -- [Inline] and [Filter]. If we need to refer to an SRT that has -- a single entry, we use the entry itself, which means that we -- don't need to generate the singleton SRT in the first place. But -- to do this we need to process blocks before things that depend on -- them. let sccs = depAnalSRTs cafEnv decls cafsWithSRTs = getCAFs cafEnv decls -- On each strongly-connected group of decls, construct the SRT -- closures and the SRT fields for info tables. let result :: [ ( [CmmDecl] -- generated SRTs , [(Label, CLabel)] -- SRT fields for info tables , [(Label, [SRTEntry])] -- SRTs to attach to static functions ) ] ((result, _srtMap), moduleSRTInfo') = initUs_ us $ flip runStateT moduleSRTInfo $ flip runStateT Map.empty $ do nonCAFs <- mapM (doSCC dflags staticFuns) sccs cAFs <- forM cafsWithSRTs $ \(l, cafLbl, cafs) -> oneSRT dflags staticFuns [l] [cafLbl] True{-is a CAF-} cafs return (nonCAFs ++ cAFs) (declss, pairs, funSRTs) = unzip3 result -- Next, update the info tables with the SRTs let srtFieldMap = mapFromList (concat pairs) funSRTMap = mapFromList (concat funSRTs) decls' = concatMap (updInfoSRTs dflags srtFieldMap funSRTMap) decls return (moduleSRTInfo', concat declss ++ decls') -- | Build the SRT for a strongly-connected component of blocks doSCC :: DynFlags -> LabelMap CLabel -- which blocks are static function entry points -> SCC (Label, CAFLabel, Set CAFLabel) -> StateT SRTMap (StateT ModuleSRTInfo UniqSM) ( [CmmDecl] -- generated SRTs , [(Label, CLabel)] -- SRT fields for info tables , [(Label, [SRTEntry])] -- SRTs to attach to static functions ) doSCC dflags staticFuns (AcyclicSCC (l, cafLbl, cafs)) = oneSRT dflags staticFuns [l] [cafLbl] False cafs doSCC dflags staticFuns (CyclicSCC nodes) = do -- build a single SRT for the whole cycle, see Note [recursive SRTs] let (blockids, lbls, cafsets) = unzip3 nodes cafs = Set.unions cafsets oneSRT dflags staticFuns blockids lbls False cafs {- Note [recursive SRTs] If the dependency analyser has found us a recursive group of declarations, then we build a single SRT for the whole group, on the grounds that everything in the group is reachable from everything else, so we lose nothing by having a single SRT. However, there are a couple of wrinkles to be aware of. * The Set CAFLabel for this SRT will contain labels in the group itself. The SRTMap will therefore not contain entries for these labels yet, so we can't turn them into SRTEntries using resolveCAF. BUT we can just remove recursive references from the Set CAFLabel before generating the SRT - the SRT will still contain all the CAFLabels that we need to refer to from this group's SRT. * That is, EXCEPT for static function closures. For the same reason described in Note [Invalid optimisation: shortcutting], we cannot omit references to static function closures. - But, since we will merge the SRT with one of the static function closures (see [FUN]), we can omit references to *that* static function closure from the SRT. -} -- | Build an SRT for a set of blocks oneSRT :: DynFlags -> LabelMap CLabel -- which blocks are static function entry points -> [Label] -- blocks in this set -> [CAFLabel] -- labels for those blocks -> Bool -- True <=> this SRT is for a CAF -> Set CAFLabel -- SRT for this set -> StateT SRTMap (StateT ModuleSRTInfo UniqSM) ( [CmmDecl] -- SRT objects we built , [(Label, CLabel)] -- SRT fields for these blocks' itbls , [(Label, [SRTEntry])] -- SRTs to attach to static functions ) oneSRT dflags staticFuns blockids lbls isCAF cafs = do srtMap <- get topSRT <- lift get let -- Can we merge this SRT with a FUN_STATIC closure? (maybeFunClosure, otherFunLabels) = case [ (l,b) | b <- blockids, Just l <- [mapLookup b staticFuns] ] of [] -> (Nothing, []) ((l,b):xs) -> (Just (l,b), map (mkCAFLabel . fst) xs) -- Remove recursive references from the SRT, except for (all but -- one of the) static functions. See Note [recursive SRTs]. nonRec = cafs `Set.difference` (Set.fromList lbls `Set.difference` Set.fromList otherFunLabels) -- First resolve all the CAFLabels to SRTEntries -- Implements the [Inline] optimisation. resolved = Set.fromList $ catMaybes (map (resolveCAF srtMap) (Set.toList nonRec)) -- The set of all SRTEntries in SRTs that we refer to from here. allBelow = Set.unions [ lbls | caf <- Set.toList resolved , Just lbls <- [Map.lookup caf (flatSRTs topSRT)] ] -- Remove SRTEntries that are also in an SRT that we refer to. -- Implements the [Filter] optimisation. filtered = Set.difference resolved allBelow srtTrace "oneSRT:" (ppr cafs <+> ppr resolved <+> ppr allBelow <+> ppr filtered) $ return () let isStaticFun = isJust maybeFunClosure -- For a label without a closure (e.g. a continuation), we must -- update the SRTMap for the label to point to a closure. It's -- important that we don't do this for static functions or CAFs, -- see Note [Invalid optimisation: shortcutting]. updateSRTMap srtEntry = when (not isCAF && not isStaticFun) $ do let newSRTMap = Map.fromList [(cafLbl, srtEntry) | cafLbl <- lbls] put (Map.union newSRTMap srtMap) this_mod = thisModule topSRT case Set.toList filtered of [] -> do srtTrace "oneSRT: empty" (ppr lbls) $ return () updateSRTMap Nothing return ([], [], []) -- [Inline] - when we have only one entry there is no need to -- build an SRT object at all, instead we put the singleton SRT -- entry in the info table. [one@(SRTEntry lbl)] | -- Info tables refer to SRTs by offset (as noted in the section -- "Referring to an SRT from the info table" of Note [SRTs]). However, -- when dynamic linking is used we cannot guarantee that the offset -- between the SRT and the info table will fit in the offset field. -- Consequently we build a singleton SRT in in this case. not (labelDynamic dflags this_mod lbl) -- MachO relocations can't express offsets between compilation units at -- all, so we are always forced to build a singleton SRT in this case. && (not (osMachOTarget $ platformOS $ targetPlatform dflags) || isLocalCLabel this_mod lbl) -> do -- If we have a static function closure, then it becomes the -- SRT object, and everything else points to it. (the only way -- we could have multiple labels here is if this is a -- recursive group, see Note [recursive SRTs]) case maybeFunClosure of Just (staticFunLbl,staticFunBlock) -> return ([], withLabels, []) where withLabels = [ (b, if b == staticFunBlock then lbl else staticFunLbl) | b <- blockids ] Nothing -> do updateSRTMap (Just one) return ([], map (,lbl) blockids, []) cafList -> -- Check whether an SRT with the same entries has been emitted already. -- Implements the [Common] optimisation. case Map.lookup filtered (dedupSRTs topSRT) of Just srtEntry@(SRTEntry srtLbl) -> do srtTrace "oneSRT [Common]" (ppr lbls <+> ppr srtLbl) $ return () updateSRTMap (Just srtEntry) return ([], map (,srtLbl) blockids, []) Nothing -> do -- No duplicates: we have to build a new SRT object srtTrace "oneSRT: new" (ppr lbls <+> ppr filtered) $ return () (decls, funSRTs, srtEntry) <- case maybeFunClosure of Just (fun,block) -> return ( [], [(block, cafList)], SRTEntry fun ) Nothing -> do (decls, entry) <- lift . lift $ buildSRTChain dflags cafList return (decls, [], entry) updateSRTMap (Just srtEntry) let allBelowThis = Set.union allBelow filtered oldFlatSRTs = flatSRTs topSRT newFlatSRTs = Map.insert srtEntry allBelowThis oldFlatSRTs newDedupSRTs = Map.insert filtered srtEntry (dedupSRTs topSRT) lift (put (topSRT { dedupSRTs = newDedupSRTs , flatSRTs = newFlatSRTs })) let SRTEntry lbl = srtEntry return (decls, map (,lbl) blockids, funSRTs) -- | build a static SRT object (or a chain of objects) from a list of -- SRTEntries. buildSRTChain :: DynFlags -> [SRTEntry] -> UniqSM ( [CmmDecl] -- The SRT object(s) , SRTEntry -- label to use in the info table ) buildSRTChain _ [] = panic "buildSRT: empty" buildSRTChain dflags cafSet = case splitAt mAX_SRT_SIZE cafSet of (these, []) -> do (decl,lbl) <- buildSRT dflags these return ([decl], lbl) (these,those) -> do (rest, rest_lbl) <- buildSRTChain dflags (head these : those) (decl,lbl) <- buildSRT dflags (rest_lbl : tail these) return (decl:rest, lbl) where mAX_SRT_SIZE = 16 buildSRT :: DynFlags -> [SRTEntry] -> UniqSM (CmmDecl, SRTEntry) buildSRT dflags refs = do id <- getUniqueM let lbl = mkSRTLabel id srt_n_info = mkSRTInfoLabel (length refs) fields = mkStaticClosure dflags srt_n_info dontCareCCS [ CmmLabel lbl | SRTEntry lbl <- refs ] [] -- no padding [mkIntCLit dflags 0] -- link field [] -- no saved info return (mkDataLits (Section Data lbl) lbl fields, SRTEntry lbl) -- | Update info tables with references to their SRTs. Also generate -- static closures, splicing in SRT fields as necessary. updInfoSRTs :: DynFlags -> LabelMap CLabel -- SRT labels for each block -> LabelMap [SRTEntry] -- SRTs to merge into FUN_STATIC closures -> CmmDecl -> [CmmDecl] updInfoSRTs dflags srt_env funSRTEnv (CmmProc top_info top_l live g) | Just (_,closure) <- maybeStaticClosure = [ proc, closure ] | otherwise = [ proc ] where proc = CmmProc top_info { info_tbls = newTopInfo } top_l live g newTopInfo = mapMapWithKey updInfoTbl (info_tbls top_info) updInfoTbl l info_tbl | l == g_entry g, Just (inf, _) <- maybeStaticClosure = inf | otherwise = info_tbl { cit_srt = mapLookup l srt_env } -- Generate static closures [FUN]. Note that this also generates -- static closures for thunks (CAFs), because it's easier to treat -- them uniformly in the code generator. maybeStaticClosure :: Maybe (CmmInfoTable, CmmDecl) maybeStaticClosure | Just info_tbl@CmmInfoTable{..} <- mapLookup (g_entry g) (info_tbls top_info) , Just (id, ccs) <- cit_clo , isStaticRep cit_rep = let (newInfo, srtEntries) = case mapLookup (g_entry g) funSRTEnv of Nothing -> -- if we don't add SRT entries to this closure, then we -- want to set the srt field in its info table as usual (info_tbl { cit_srt = mapLookup (g_entry g) srt_env }, []) Just srtEntries -> srtTrace "maybeStaticFun" (ppr res) (info_tbl { cit_rep = new_rep }, res) where res = [ CmmLabel lbl | SRTEntry lbl <- srtEntries ] fields = mkStaticClosureFields dflags info_tbl ccs (idCafInfo id) srtEntries new_rep = case cit_rep of HeapRep sta ptrs nptrs ty -> HeapRep sta (ptrs + length srtEntries) nptrs ty _other -> panic "maybeStaticFun" lbl = mkLocalClosureLabel (idName id) (idCafInfo id) in Just (newInfo, mkDataLits (Section Data lbl) lbl fields) | otherwise = Nothing updInfoSRTs _ _ _ t = [t] srtTrace :: String -> SDoc -> b -> b -- srtTrace = pprTrace srtTrace _ _ b = b