% % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[SCCfinal]{Modify and collect code generation for final STG program} This is now a sort-of-normal STG-to-STG pass (WDP 94/06), run by stg2stg. - Traverses the STG program collecting the cost centres. These are required to declare the cost centres at the start of code generation. Note: because of cross-module unfolding, some of these cost centres may be from other modules. But will still have to give them "extern" declarations. - Puts on CAF cost-centres if the user has asked for individual CAF cost-centres. - Ditto for individual DICT cost-centres. - Boxes top-level inherited functions passed as arguments. - "Distributes" given cost-centres to all as-yet-unmarked RHSs. \begin{code}

    module SCCfinal ( stgMassageForProfiling ) where

    #include "HsVersions.h"

    import StgSyn

    import CostCentre       -- lots of things
    import Id
    import Name
    import Module
    import UniqSupply       ( splitUniqSupply, UniqSupply )
    #ifdef PROF_DO_BOXING
    import UniqSupply       ( uniqFromSupply )
    #endif
    import VarSet
    import ListSetOps       ( removeDups )
    import Outputable
    import DynFlags

\end{code} \begin{code}

    stgMassageForProfiling
            :: DynFlags
            -> PackageId
            -> Module                       -- module name
            -> UniqSupply                   -- unique supply
            -> [StgBinding]                 -- input
            -> (CollectedCCs, [StgBinding])

    stgMassageForProfiling dflags this_pkg mod_name us stg_binds
      = let
            ((local_ccs, extern_ccs, cc_stacks),
             stg_binds2)
              = initMM mod_name us (do_top_bindings stg_binds)

            (fixed_ccs, fixed_cc_stacks)
              = if dopt Opt_AutoSccsOnIndividualCafs dflags
                then ([],[])  -- don't need "all CAFs" CC
                              -- (for Prelude, we use PreludeCC)
                else ([all_cafs_cc], [all_cafs_ccs])

            local_ccs_no_dups  = fst (removeDups cmpCostCentre local_ccs)
            extern_ccs_no_dups = fst (removeDups cmpCostCentre extern_ccs)
        in
        ((fixed_ccs ++ local_ccs_no_dups,
          extern_ccs_no_dups,
          fixed_cc_stacks ++ cc_stacks), stg_binds2)
      where

        all_cafs_cc  = mkAllCafsCC mod_name
        all_cafs_ccs = mkSingletonCCS all_cafs_cc

        ----------
        do_top_bindings :: [StgBinding] -> MassageM [StgBinding]

        do_top_bindings [] = return []

        do_top_bindings (StgNonRec b rhs : bs) = do
            rhs' <- do_top_rhs b rhs
            addTopLevelIshId b $ do
               bs' <- do_top_bindings bs
               return (StgNonRec b rhs' : bs')

        do_top_bindings (StgRec pairs : bs)
          = addTopLevelIshIds binders $ do
               pairs2 <- mapM do_pair pairs
               bs' <- do_top_bindings bs
               return (StgRec pairs2 : bs')
          where
            binders = map fst pairs
            do_pair (b, rhs) = do
                 rhs2 <- do_top_rhs b rhs
                 return (b, rhs2)

        ----------
        do_top_rhs :: Id -> StgRhs -> MassageM StgRhs

        do_top_rhs _ (StgRhsClosure _ _ _ _ _ [] (StgSCC cc (StgConApp con args)))
          | not (isSccCountCostCentre cc) && not (isDllConApp this_pkg con args)
            -- Trivial _scc_ around nothing but static data
            -- Eliminate _scc_ ... and turn into StgRhsCon

            -- isDllConApp checks for LitLit args too
          = return (StgRhsCon dontCareCCS con args)

    {- Can't do this one with cost-centre stacks:  --SDM
        do_top_rhs binder (StgRhsClosure no_cc bi fv u [] (StgSCC ty cc expr))
          | (noCCSAttached no_cc || currentOrSubsumedCCS no_cc)
            && not (isSccCountCostCentre cc)
            -- Top level CAF without a cost centre attached
            -- Attach and collect cc of trivial _scc_ in body
          = do collectCC cc
               expr' <- set_prevailing_cc cc (do_expr expr)
               return (StgRhsClosure cc bi fv u [] expr')
    -}

        do_top_rhs binder (StgRhsClosure no_cc bi fv u srt [] body)
          | noCCSAttached no_cc || currentOrSubsumedCCS no_cc = do
            -- Top level CAF without a cost centre attached
            -- Attach CAF cc (collect if individual CAF ccs)
            caf_ccs <- if dopt Opt_AutoSccsOnIndividualCafs dflags
                       then let cc = mkAutoCC binder modl CafCC
                                ccs = mkSingletonCCS cc
                                       -- careful: the binder might be :Main.main,
                                       -- which doesn't belong to module mod_name.
                                       -- bug #249, tests prof001, prof002
                                modl | Just m <- nameModule_maybe (idName binder) = m
                                     | otherwise = mod_name
                            in do
                            collectNewCC  cc
                            collectCCS ccs
                            return ccs
                       else
                            return all_cafs_ccs
            body' <- set_prevailing_cc caf_ccs (do_expr body)
            return (StgRhsClosure caf_ccs bi fv u srt [] body')

        do_top_rhs _ (StgRhsClosure cc _ _ _ _ [] _)
            -- Top level CAF with cost centre attached
            -- Should this be a CAF cc ??? Does this ever occur ???
          = pprPanic "SCCfinal: CAF with cc:" (ppr cc)

        do_top_rhs _ (StgRhsClosure no_ccs bi fv u srt args body)
            -- Top level function, probably subsumed
          | noCCSAttached no_ccs
          = do body' <- set_lambda_cc (do_expr body)
               return (StgRhsClosure subsumedCCS bi fv u srt args body')

          | otherwise
          = pprPanic "SCCfinal: CAF with cc:" (ppr no_ccs)

        do_top_rhs _ (StgRhsCon _ con args)
            -- Top-level (static) data is not counted in heap
            -- profiles; nor do we set CCCS from it; so we
            -- just slam in dontCareCostCentre
          = return (StgRhsCon dontCareCCS con args)

        ------
        do_expr :: StgExpr -> MassageM StgExpr

        do_expr (StgLit l) = return (StgLit l)

        do_expr (StgApp fn args)
          = boxHigherOrderArgs (StgApp fn) args

        do_expr (StgConApp con args)
          = boxHigherOrderArgs (\args -> StgConApp con args) args

        do_expr (StgOpApp con args res_ty)
          = boxHigherOrderArgs (\args -> StgOpApp con args res_ty) args

        do_expr (StgSCC cc expr) = do -- Ha, we found a cost centre!
            collectCC cc
            expr' <- do_expr expr
            return (StgSCC cc expr')

        do_expr (StgCase expr fv1 fv2 bndr srt alt_type alts) = do
            expr' <- do_expr expr
            alts' <- mapM do_alt alts
            return (StgCase expr' fv1 fv2 bndr srt alt_type alts')
          where
            do_alt (id, bs, use_mask, e) = do
                e' <- do_expr e
                return (id, bs, use_mask, e')

        do_expr (StgLet b e) = do
              (b,e) <- do_let b e
              return (StgLet b e)

        do_expr (StgLetNoEscape lvs1 lvs2 b e) = do
              (b,e) <- do_let b e
              return (StgLetNoEscape lvs1 lvs2 b e)

        do_expr (StgTick m n expr) = do
              expr' <- do_expr expr
              return (StgTick m n expr')

        do_expr other = pprPanic "SCCfinal.do_expr" (ppr other)

        ----------------------------------

        do_let (StgNonRec b rhs) e = do
            rhs' <- do_rhs rhs
            addTopLevelIshId b $ do
              e' <- do_expr e
              return (StgNonRec b rhs',e')

        do_let (StgRec pairs) e
          = addTopLevelIshIds binders $ do
               pairs' <- mapM do_pair pairs
               e' <- do_expr e
               return (StgRec pairs', e')
          where
            binders = map fst pairs
            do_pair (b, rhs) = do
                 rhs2 <- do_rhs rhs
                 return (b, rhs2)

        ----------------------------------
        do_rhs :: StgRhs -> MassageM StgRhs
            -- We play much the same game as we did in do_top_rhs above;
            -- but we don't have to worry about cafs etc.

    {-
        do_rhs (StgRhsClosure closure_cc bi fv u [] (StgSCC ty cc (StgCon (DataCon con) args _)))
          | not (isSccCountCostCentre cc)
          = do collectCC cc
               return (StgRhsCon cc con args)
    -}

        do_rhs (StgRhsClosure _ bi fv u srt args expr) = do
            (expr', ccs) <- slurpSCCs currentCCS expr
            expr'' <- do_expr expr'
            return (StgRhsClosure ccs bi fv u srt args expr'')
          where
            slurpSCCs ccs (StgSCC cc e)
                 = do collectCC cc
                      slurpSCCs (cc `pushCCOnCCS` ccs) e
            slurpSCCs ccs e
                 = return (e, ccs)

        do_rhs (StgRhsCon _ con args)
          = return (StgRhsCon currentCCS con args)

\end{code} %************************************************************************ %* * \subsection{Boxing higher-order args} %* * %************************************************************************ Boxing is *turned off* at the moment, until we can figure out how to do it properly in general. \begin{code}

    boxHigherOrderArgs
        :: ([StgArg] -> StgExpr)
                            -- An application lacking its arguments
        -> [StgArg]         -- arguments which we might box
        -> MassageM StgExpr

    #ifndef PROF_DO_BOXING
    boxHigherOrderArgs almost_expr args
       = return (almost_expr args)
    #else
    boxHigherOrderArgs almost_expr args = do
        ids <- getTopLevelIshIds
        (let_bindings, new_args) <- mapAccumLM (do_arg ids) [] args
        return (foldr (mk_stg_let currentCCS) (almost_expr new_args) let_bindings)
      where
        ---------------

        do_arg ids bindings arg@(StgVarArg old_var)
            |  (not (isLocalVar old_var) || elemVarSet old_var ids)
            && isFunTy (dropForAlls var_type)
          = do    -- make a trivial let-binding for the top-level function
            uniq <- getUniqueMM
            let
                new_var = mkSysLocal (fsLit "sf") uniq var_type
            return ( (new_var, old_var) : bindings, StgVarArg new_var )
          where
            var_type = idType old_var

        do_arg ids bindings arg = return (bindings, arg)

        ---------------
        mk_stg_let :: CostCentreStack -> (Id, Id) -> StgExpr -> StgExpr

        mk_stg_let cc (new_var, old_var) body
          = let
                rhs_body    = StgApp old_var [{-args-}]
                rhs_closure = StgRhsClosure cc stgArgOcc [{-fvs-}] ReEntrant NoSRT{-eeek!!!-} [{-args-}] rhs_body
            in
            StgLet (StgNonRec new_var rhs_closure) body
          where
            bOGUS_LVs = emptyUniqSet -- easier to print than: panic "mk_stg_let: LVs"
    #endif

\end{code} %************************************************************************ %* * \subsection{Boring monad stuff for this} %* * %************************************************************************ \begin{code}

    newtype MassageM result
      = MassageM {
          unMassageM :: Module              -- module name
                     -> CostCentreStack     -- prevailing CostCentre
                                            -- if none, subsumedCosts at top-level
                                            -- currentCostCentre at nested levels
                     -> UniqSupply
                     -> VarSet              -- toplevel-ish Ids for boxing
                     -> CollectedCCs
                     -> (CollectedCCs, result)
        }

    instance Monad MassageM where
        return x = MassageM (\_ _ _ _ ccs -> (ccs, x))
        (>>=) = thenMM
        (>>)  = thenMM_

    -- the initMM function also returns the final CollectedCCs

    initMM :: Module        -- module name, which we may consult
           -> UniqSupply
           -> MassageM a
           -> (CollectedCCs, a)

    initMM mod_name init_us (MassageM m) = m mod_name noCCS init_us emptyVarSet ([],[],[])

    thenMM  :: MassageM a -> (a -> MassageM b) -> MassageM b
    thenMM_ :: MassageM a -> (MassageM b) -> MassageM b

    thenMM expr cont = MassageM $ \mod scope_cc us ids ccs ->
        case splitUniqSupply us of { (s1, s2) ->
        case unMassageM expr mod scope_cc s1 ids ccs of { (ccs2, result) ->
        unMassageM (cont result) mod scope_cc s2 ids ccs2 }}

    thenMM_ expr cont = MassageM $ \mod scope_cc us ids ccs ->
        case splitUniqSupply us of { (s1, s2) ->
        case unMassageM expr mod scope_cc s1 ids ccs of { (ccs2, _) ->
        unMassageM cont mod scope_cc s2 ids ccs2 }}

    #ifdef PROF_DO_BOXING
    getUniqueMM :: MassageM Unique
    getUniqueMM = MassageM \mod scope_cc us ids ccs -> (ccs, uniqFromSupply us)
    #endif

    addTopLevelIshId :: Id -> MassageM a -> MassageM a
    addTopLevelIshId id scope
       = MassageM $ \mod scope_cc us ids ccs ->
          if isCurrentCCS scope_cc then unMassageM scope mod scope_cc us ids ccs
                                   else unMassageM scope mod scope_cc us (extendVarSet ids id) ccs

    addTopLevelIshIds :: [Id] -> MassageM a -> MassageM a
    addTopLevelIshIds [] cont = cont
    addTopLevelIshIds (id:ids) cont
      = addTopLevelIshId id (addTopLevelIshIds ids cont)

    #ifdef PROF_DO_BOXING
    getTopLevelIshIds :: MassageM VarSet
    getTopLevelIshIds = MassageM $ \_mod _scope_cc _us ids ccs -> (ccs, ids)
    #endif

\end{code} The prevailing CCS is used to tell whether we're in a top-levelish position, where top-levelish is defined as "not inside a lambda". Prevailing CCs used to be used for something much more complicated, I'm sure --SDM \begin{code}

    set_lambda_cc :: MassageM a -> MassageM a
    set_lambda_cc action
       =    MassageM $     \mod _scope_cc  us ids ccs
       -> unMassageM action mod currentCCS us ids ccs

    set_prevailing_cc :: CostCentreStack -> MassageM a -> MassageM a
    set_prevailing_cc cc_to_set_to action
       =    MassageM $     \mod _scope_cc    us ids ccs
       -> unMassageM action mod cc_to_set_to us ids ccs

\end{code} \begin{code}

    collectCC :: CostCentre -> MassageM ()
    collectCC cc
     = MassageM $ \mod_name _scope_cc _us _ids (local_ccs, extern_ccs, ccss)
      -> ASSERT(not (noCCAttached cc))
         if (cc `ccFromThisModule` mod_name) then
            ((cc : local_ccs, extern_ccs, ccss), ())
         else -- must declare it "extern"
            ((local_ccs, cc : extern_ccs, ccss), ())

    -- Version of collectCC used when we definitely want to declare this
    -- CC as local, even if its module name is not the same as the current
    -- module name (eg. the special :Main module) see bug #249, #1472,
    -- test prof001,prof002.
    collectNewCC :: CostCentre -> MassageM ()
    collectNewCC cc
     = MassageM $ \_mod_name _scope_cc _us _ids (local_ccs, extern_ccs, ccss)
                  -> ((cc : local_ccs, extern_ccs, ccss), ())

    collectCCS :: CostCentreStack -> MassageM ()

    collectCCS ccs
     = MassageM $ \_mod_name _scope_cc _us _ids (local_ccs, extern_ccs, ccss)
                  -> ASSERT(not (noCCSAttached ccs))
                           ((local_ccs, extern_ccs, ccs : ccss), ())

\end{code}