X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FOccurAnal.lhs;h=8b6c5bb135cdbba187737efefe7515cd28850ea3;hb=36d22a1cb608e8572776ab6d402fd0c1a9287dc5;hp=87927ece4821662041495ee0492cbd1d73ee5e6c;hpb=cfcebde74cf826af12143a92bcffa8c995eee135;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/OccurAnal.lhs b/ghc/compiler/simplCore/OccurAnal.lhs index 87927ec..8b6c5bb 100644 --- a/ghc/compiler/simplCore/OccurAnal.lhs +++ b/ghc/compiler/simplCore/OccurAnal.lhs @@ -12,38 +12,31 @@ core expression with (hopefully) improved usage information. \begin{code} module OccurAnal ( - occurAnalyseBinds, occurAnalyseExpr, occurAnalyseGlobalExpr, - markBinderInsideLambda, tagBinders, - UsageDetails + occurAnalysePgm, occurAnalyseGlobalExpr, occurAnalyseRule, ) where #include "HsVersions.h" -import BinderInfo -import CmdLineOpts ( SimplifierSwitch(..) ) import CoreSyn import CoreFVs ( idRuleVars ) import CoreUtils ( exprIsTrivial ) -import Const ( Con(..), Literal(..) ) -import Id ( isSpecPragmaId, - getInlinePragma, setInlinePragma, - isExportedId, modifyIdInfo, idInfo, - getIdSpecialisation, +import Id ( isDataConWorkId, isOneShotBndr, setOneShotLambda, + idOccInfo, setIdOccInfo, + isExportedId, idArity, idSpecialisation, idType, idUnique, Id ) -import IdInfo ( InlinePragInfo(..), OccInfo(..), copyIdInfo ) +import BasicTypes ( OccInfo(..), isOneOcc ) import VarSet import VarEnv -import ThinAir ( noRepStrIds, noRepIntegerIds ) -import Name ( isLocallyDefined ) -import Type ( splitFunTy_maybe, splitForAllTys ) -import Maybes ( maybeToBool ) +import Type ( isFunTy, dropForAlls ) +import Maybes ( orElse ) import Digraph ( stronglyConnCompR, SCC(..) ) -import Unique ( u2i, buildIdKey, foldrIdKey, runSTRepIdKey, augmentIdKey ) +import PrelNames ( buildIdKey, foldrIdKey, runSTRepIdKey, augmentIdKey ) +import Unique ( Unique ) import UniqFM ( keysUFM ) -import Util ( zipWithEqual, mapAndUnzip, count ) +import Util ( zipWithEqual, mapAndUnzip ) import Outputable \end{code} @@ -57,152 +50,34 @@ import Outputable Here's the externally-callable interface: \begin{code} -occurAnalyseExpr :: (Id -> Bool) -- Tells if a variable is interesting - -> CoreExpr - -> (IdEnv BinderInfo, -- Occ info for interesting free vars - CoreExpr) - -occurAnalyseExpr interesting expr - = occAnal initial_env expr +occurAnalysePgm :: [CoreBind] -> [CoreBind] +occurAnalysePgm binds + = snd (go (initOccEnv emptyVarSet) binds) where - initial_env = OccEnv interesting emptyVarSet [] + go :: OccEnv -> [CoreBind] -> (UsageDetails, [CoreBind]) + go env [] + = (emptyDetails, []) + go env (bind:binds) + = (final_usage, bind' ++ binds') + where + new_env = env `addNewCands` (bindersOf bind) + (bs_usage, binds') = go new_env binds + (final_usage, bind') = occAnalBind env bind bs_usage occurAnalyseGlobalExpr :: CoreExpr -> CoreExpr occurAnalyseGlobalExpr expr = -- Top level expr, so no interesting free vars, and -- discard occurence info returned - snd (occurAnalyseExpr (\_ -> False) expr) -\end{code} - - -%************************************************************************ -%* * -\subsection{Top level stuff} -%* * -%************************************************************************ - -In @occAnalTop@ we do indirection-shorting. That is, if we have this: - - loc = - ... - exp = loc + snd (occAnal (initOccEnv emptyVarSet) expr) -where exp is exported, and loc is not, then we replace it with this: - - loc = exp - exp = - ... - -Without this we never get rid of the exp = loc thing. -This save a gratuitous jump -(from \tr{x_exported} to \tr{x_local}), and makes strictness -information propagate better. -This used to happen in the final phase, but it's tidier to do it here. - - -If more than one exported thing is equal to a local thing (i.e., the -local thing really is shared), then we do one only: -\begin{verbatim} - x_local = .... - x_exported1 = x_local - x_exported2 = x_local -==> - x_exported1 = .... - - x_exported2 = x_exported1 -\end{verbatim} - -We rely on prior eta reduction to simplify things like -\begin{verbatim} - x_exported = /\ tyvars -> x_local tyvars -==> - x_exported = x_local -\end{verbatim} -Hence,there's a possibility of leaving unchanged something like this: -\begin{verbatim} - x_local = .... - x_exported1 = x_local Int -\end{verbatim} -By the time we've thrown away the types in STG land this -could be eliminated. But I don't think it's very common -and it's dangerous to do this fiddling in STG land -because we might elminate a binding that's mentioned in the -unfolding for something. - -\begin{code} -occurAnalyseBinds :: [CoreBind] -> [CoreBind] - -occurAnalyseBinds binds - = binds' +occurAnalyseRule :: CoreRule -> CoreRule +occurAnalyseRule rule@(BuiltinRule _ _) = rule +occurAnalyseRule (Rule str act tpl_vars tpl_args rhs) + -- Add occ info to tpl_vars, rhs + = Rule str act tpl_vars' tpl_args rhs' where - (_, _, binds') = go initialTopEnv binds - - go :: OccEnv -> [CoreBind] - -> (UsageDetails, -- Occurrence info - IdEnv Id, -- Indirection elimination info - [CoreBind]) - - go env [] = (emptyDetails, emptyVarEnv, []) - - go env (bind : binds) - = let - new_env = env `addNewCands` (bindersOf bind) - (scope_usage, ind_env, binds') = go new_env binds - (final_usage, new_binds) = occAnalBind env (zapBind ind_env bind) scope_usage - -- NB: I zap before occur-analysing, so - -- I don't need to worry about getting the - -- occ info on the new bindings right. - in - case bind of - NonRec exported_id (Var local_id) - | shortMeOut ind_env exported_id local_id - -- Special case for eliminating indirections - -- Note: it's a shortcoming that this only works for - -- non-recursive bindings. Elminating indirections - -- makes perfect sense for recursive bindings too, but - -- it's more complicated to implement, so I haven't done so - -> (scope_usage, ind_env', binds') - where - ind_env' = extendVarEnv ind_env local_id exported_id - - other -> -- Ho ho! The normal case - (final_usage, ind_env, new_binds ++ binds') - -initialTopEnv = OccEnv isLocallyDefined -- Anything local is interesting - emptyVarSet - [] - - --- Deal with any indirections -zapBind ind_env (NonRec bndr rhs) - | bndr `elemVarEnv` ind_env = Rec (zap ind_env (bndr,rhs)) - -- The Rec isn't strictly necessary, but it's convenient -zapBind ind_env (Rec pairs) - | or [id `elemVarEnv` ind_env | (id,_) <- pairs] = Rec (concat (map (zap ind_env) pairs)) - -zapBind ind_env bind = bind - -zap ind_env pair@(bndr,rhs) - = case lookupVarEnv ind_env bndr of - Nothing -> [pair] - Just exported_id -> [(bndr, Var exported_id), - (exported_id_w_info, rhs)] - where - exported_id_w_info = modifyIdInfo (copyIdInfo (idInfo bndr)) exported_id - -- See notes with copyIdInfo about propagating IdInfo from - -- one to t'other - -shortMeOut ind_env exported_id local_id - = isExportedId exported_id && -- Only if this is exported - - isLocallyDefined local_id && -- Only if this one is defined in this - -- module, so that we *can* change its - -- binding to be the exported thing! - - not (isExportedId local_id) && -- Only if this one is not itself exported, - -- since the transformation will nuke it - - not (local_id `elemVarEnv` ind_env) -- Only if not already substituted for + (rhs_uds, rhs') = occAnal (initOccEnv (mkVarSet tpl_vars)) rhs + (_, tpl_vars') = tagBinders rhs_uds tpl_vars \end{code} @@ -218,7 +93,7 @@ Bindings \begin{code} type IdWithOccInfo = Id -- An Id with fresh PragmaInfo attached -type Node details = (details, Int, [Int]) -- The Ints are gotten from the Unique, +type Node details = (details, Unique, [Unique]) -- The Ints are gotten from the Unique, -- which is gotten from the Id. type Details1 = (Id, UsageDetails, CoreExpr) type Details2 = (IdWithOccInfo, CoreExpr) @@ -240,7 +115,7 @@ occAnalBind env (NonRec binder rhs) body_usage where (final_body_usage, tagged_binder) = tagBinder body_usage binder - (rhs_usage, rhs') = occAnalRhs env binder rhs + (rhs_usage, rhs') = occAnalRhs env tagged_binder rhs \end{code} Dropping dead code for recursive bindings is done in a very simple way: @@ -282,8 +157,6 @@ It isn't easy to do a perfect job in one blow. Consider occAnalBind env (Rec pairs) body_usage = foldr (_scc_ "occAnalBind.dofinal" do_final_bind) (body_usage, []) sccs where - pp_item (_, bndr, _) = ppr bndr - binders = map fst pairs rhs_env = env `addNewCands` binders @@ -300,7 +173,7 @@ occAnalBind env (Rec pairs) body_usage ---- stuff for dependency analysis of binds ------------------------------- edges :: [Node Details1] edges = _scc_ "occAnalBind.assoc" - [ (details, IBOX(u2i (idUnique id)), edges_from rhs_usage) + [ (details, idUnique id, edges_from rhs_usage) | details@(id, rhs_usage, rhs) <- analysed_pairs ] @@ -313,7 +186,7 @@ occAnalBind env (Rec pairs) body_usage -- maybeToBool (lookupVarEnv rhs_usage bndr)] -- which has n**2 cost, and this meant that edges_from alone -- consumed 10% of total runtime! - edges_from :: UsageDetails -> [Int] + edges_from :: UsageDetails -> [Unique] edges_from rhs_usage = _scc_ "occAnalBind.edges_from" keysUFM rhs_usage @@ -416,7 +289,7 @@ reOrderRec env (AcyclicSCC (bind, _, _)) = [bind] -- Common case of simple self-recursion reOrderRec env (CyclicSCC [bind]) - = [(setInlinePragma tagged_bndr IAmALoopBreaker, rhs)] + = [(setIdOccInfo tagged_bndr IAmALoopBreaker, rhs)] where ((tagged_bndr, rhs), _, _) = bind @@ -425,7 +298,7 @@ reOrderRec env (CyclicSCC (bind : binds)) -- do SCC analysis on the rest, and recursively sort them out concat (map (reOrderRec env) (stronglyConnCompR unchosen)) ++ - [(setInlinePragma tagged_bndr IAmALoopBreaker, rhs)] + [(setIdOccInfo tagged_bndr IAmALoopBreaker, rhs)] where (chosen_pair, unchosen) = choose_loop_breaker bind (score bind) [] binds @@ -447,21 +320,29 @@ reOrderRec env (CyclicSCC (bind : binds)) score :: Node Details2 -> Int -- Higher score => less likely to be picked as loop breaker score ((bndr, rhs), _, _) - | exprIsTrivial rhs && - not (isExportedId bndr) = 3 -- Practically certain to be inlined - | inlineCandidate bndr rhs = 3 -- Likely to be inlined - | not_fun_ty (idType bndr) = 2 -- Data types help with cases - | not (isEmptyCoreRules (getIdSpecialisation bndr)) = 1 + | exprIsTrivial rhs = 4 -- Practically certain to be inlined + -- Used to have also: && not (isExportedId bndr) + -- But I found this sometimes cost an extra iteration when we have + -- rec { d = (a,b); a = ...df...; b = ...df...; df = d } + -- where df is the exported dictionary. Then df makes a really + -- bad choice for loop breaker + + | not_fun_ty (idType bndr) = 3 -- Data types help with cases + -- This used to have a lower score than inlineCandidate, but + -- it's *really* helpful if dictionaries get inlined fast, + -- so I'm experimenting with giving higher priority to data-typed things + + | inlineCandidate bndr rhs = 2 -- Likely to be inlined + + | not (isEmptyCoreRules (idSpecialisation bndr)) = 1 -- Avoid things with specialisations; we'd like -- to take advantage of them in the subsequent bindings + | otherwise = 0 inlineCandidate :: Id -> CoreExpr -> Bool inlineCandidate id (Note InlineMe _) = True - inlineCandidate id rhs = case getInlinePragma id of - IMustBeINLINEd -> True - ICanSafelyBeINLINEd _ _ -> True - other -> False + inlineCandidate id rhs = isOneOcc (idOccInfo id) -- Real example (the Enum Ordering instance from PrelBase): -- rec f = \ x -> case d of (p,q,r) -> p x @@ -473,9 +354,7 @@ reOrderRec env (CyclicSCC (bind : binds)) -- we didn't stupidly choose d as the loop breaker. -- But we won't because constructor args are marked "Many". - not_fun_ty ty = not (maybeToBool (splitFunTy_maybe rho_ty)) - where - (_, rho_ty) = splitForAllTys ty + not_fun_ty ty = not (isFunTy (dropForAlls ty)) \end{code} @occAnalRhs@ deals with the question of bindings where the Id is marked @@ -492,12 +371,34 @@ ToDo: try using the occurrence info for the inline'd binder. \begin{code} occAnalRhs :: OccEnv -> Id -> CoreExpr -- Binder and rhs + -- For non-recs the binder is alrady tagged + -- with occurrence info -> (UsageDetails, CoreExpr) occAnalRhs env id rhs = (final_usage, rhs') where - (rhs_usage, rhs') = occAnal (zapCtxt env) rhs + (rhs_usage, rhs') = occAnal ctxt rhs + ctxt | certainly_inline id = env + | otherwise = rhsCtxt env + -- Note that we generally use an rhsCtxt. This tells the occ anal n + -- that it's looking at an RHS, which has an effect in occAnalApp + -- + -- But there's a problem. Consider + -- x1 = a0 : [] + -- x2 = a1 : x1 + -- x3 = a2 : x2 + -- g = f x3 + -- First time round, it looks as if x1 and x2 occur as an arg of a + -- let-bound constructor ==> give them a many-occurrence. + -- But then x3 is inlined (unconditionally as it happens) and + -- next time round, x2 will be, and the next time round x1 will be + -- Result: multiple simplifier iterations. Sigh. + -- Crude solution: use rhsCtxt for things that occur just once... + + certainly_inline id = case idOccInfo id of + OneOcc in_lam one_br -> not in_lam && one_br + other -> False -- [March 98] A new wrinkle is that if the binder has specialisations inside -- it then we count the specialised Ids as "extra rhs's". That way @@ -505,8 +406,14 @@ occAnalRhs env id rhs -- dies (because it isn't referenced any more), then the children will -- die too unless they are already referenced directly. - final_usage = foldVarSet add rhs_usage (idRuleVars id) - add v u = addOneOcc u v noBinderInfo -- Give a non-committal binder info + final_usage = addRuleUsage rhs_usage id + +addRuleUsage :: UsageDetails -> Id -> UsageDetails +-- Add the usage from RULES in Id to the usage +addRuleUsage usage id + = foldVarSet add usage (idRuleVars id) + where + add v u = addOneOcc u v NoOccInfo -- Give a non-committal binder info -- (i.e manyOcc) because many copies -- of the specialised thing can appear \end{code} @@ -524,7 +431,7 @@ occAnal env (Type t) = (emptyDetails, Type t) occAnal env (Var v) = (var_uds, Var v) where - var_uds | isCandidate env v = unitVarEnv v funOccZero + var_uds | isCandidate env v = unitVarEnv v oneOcc | otherwise = emptyDetails -- At one stage, I gathered the idRuleVars for v here too, @@ -552,35 +459,7 @@ If we aren't careful we duplicate the (expensive x) call! Constructors are rather like lambdas in this way. \begin{code} - -- For NoRep literals we have to report an occurrence of - -- the things which tidyCore will later add, so that when - -- we are compiling the very module in which those thin-air Ids - -- are defined we have them in scope! -occAnal env expr@(Con (Literal lit) args) - = ASSERT( null args ) - (mk_lit_uds lit, expr) - where - mk_lit_uds (NoRepStr _ _) = try noRepStrIds - mk_lit_uds (NoRepInteger _ _) = try noRepIntegerIds - mk_lit_uds lit = emptyDetails - - try vs = foldr add emptyDetails vs - add v uds | isCandidate env v = extendVarEnv uds v funOccZero - | otherwise = uds - -occAnal env (Con con args) - = case occAnalArgs env args of { (arg_uds, args') -> - let - -- We mark the free vars of the argument of a constructor as "many" - -- This means that nothing gets inlined into a constructor argument - -- position, which is what we want. Typically those constructor - -- arguments are just variables, or trivial expressions. - final_arg_uds = case con of - DataCon _ -> mapVarEnv markMany arg_uds - other -> arg_uds - in - (final_arg_uds, Con con args') - } +occAnal env expr@(Lit lit) = (emptyDetails, expr) \end{code} \begin{code} @@ -602,7 +481,7 @@ occAnal env (Note note body) \begin{code} occAnal env app@(App fun arg) - = occAnalApp env (collectArgs app) + = occAnalApp env (collectArgs app) False -- Ignore type variables altogether -- (a) occurrences inside type lambdas only not marked as InsideLam @@ -623,9 +502,13 @@ occAnal env expr@(Lam x body) | isTyVar x -- Then, the simplifier is careful when partially applying lambdas. occAnal env expr@(Lam _ _) - = case occAnal (env_body `addNewCands` binders) body of { (body_usage, body') -> + = case occAnal env_body body of { (body_usage, body') -> let (final_usage, tagged_binders) = tagBinders body_usage binders + -- URGH! Sept 99: we don't seem to be able to use binders' here, because + -- we get linear-typed things in the resulting program that we can't handle yet. + -- (e.g. PrelShow) TODO + really_final_usage = if linear then final_usage else @@ -634,21 +517,36 @@ occAnal env expr@(Lam _ _) (really_final_usage, mkLams tagged_binders body') } where - (binders, body) = collectBinders expr - (linear, env_body) = getCtxt env (count isId binders) - -occAnal env (Case scrut bndr alts) - = case mapAndUnzip (occAnalAlt alt_env) alts of { (alts_usage_s, alts') -> - case occAnal (zapCtxt env) scrut of { (scrut_usage, scrut') -> + (binders, body) = collectBinders expr + (linear, env1, _) = oneShotGroup env binders + env2 = env1 `addNewCands` binders -- Add in-scope binders + env_body = vanillaCtxt env2 -- Body is (no longer) an RhsContext + +occAnal env (Case scrut bndr ty alts) + = case mapAndUnzip (occAnalAlt alt_env bndr) alts of { (alts_usage_s, alts') -> + case occAnal (vanillaCtxt env) scrut of { (scrut_usage, scrut') -> + -- No need for rhsCtxt let alts_usage = foldr1 combineAltsUsageDetails alts_usage_s - (alts_usage1, tagged_bndr) = tagBinder alts_usage bndr + alts_usage' = addCaseBndrUsage alts_usage + (alts_usage1, tagged_bndr) = tagBinder alts_usage' bndr total_usage = scrut_usage `combineUsageDetails` alts_usage1 in - total_usage `seq` (total_usage, Case scrut' tagged_bndr alts') }} + total_usage `seq` (total_usage, Case scrut' tagged_bndr ty alts') }} where alt_env = env `addNewCand` bndr + -- The case binder gets a usage of either "many" or "dead", never "one". + -- Reason: we like to inline single occurrences, to eliminate a binding, + -- but inlining a case binder *doesn't* eliminate a binding. + -- We *don't* want to transform + -- case x of w { (p,q) -> f w } + -- into + -- case x of w { (p,q) -> f (p,q) } + addCaseBndrUsage usage = case lookupVarEnv usage bndr of + Nothing -> usage + Just occ -> extendVarEnv usage bndr (markMany occ) + occAnal env (Let bind body) = case occAnal new_env body of { (body_usage, body') -> case occAnalBind env bind body_usage of { (final_usage, new_binds) -> @@ -660,7 +558,7 @@ occAnalArgs env args = case mapAndUnzip (occAnal arg_env) args of { (arg_uds_s, args') -> (foldr combineUsageDetails emptyDetails arg_uds_s, args')} where - arg_env = zapCtxt env + arg_env = vanillaCtxt env \end{code} Applications are dealt with specially because we want @@ -668,45 +566,75 @@ the "build hack" to work. \begin{code} -- Hack for build, fold, runST -occAnalApp env (Var fun, args) +occAnalApp env (Var fun, args) is_rhs = case args_stuff of { (args_uds, args') -> let - final_uds = fun_uds `combineUsageDetails` args_uds + -- We mark the free vars of the argument of a constructor or PAP + -- as "many", if it is the RHS of a let(rec). + -- This means that nothing gets inlined into a constructor argument + -- position, which is what we want. Typically those constructor + -- arguments are just variables, or trivial expressions. + -- + -- This is the *whole point* of the isRhsEnv predicate + final_args_uds + | isRhsEnv env, + isDataConWorkId fun || valArgCount args < idArity fun + = mapVarEnv markMany args_uds + | otherwise = args_uds in - (final_uds, mkApps (Var fun) args') } + (fun_uds `combineUsageDetails` final_args_uds, mkApps (Var fun) args') } where fun_uniq = idUnique fun - fun_uds | isCandidate env fun = unitVarEnv fun funOccZero + fun_uds | isCandidate env fun = unitVarEnv fun oneOcc | otherwise = emptyDetails args_stuff | fun_uniq == buildIdKey = appSpecial env 2 [True,True] args | fun_uniq == augmentIdKey = appSpecial env 2 [True,True] args | fun_uniq == foldrIdKey = appSpecial env 3 [False,True] args - | fun_uniq == runSTRepIdKey = appSpecial env 2 [True] args - | otherwise = occAnalArgs env args - -occAnalApp env (fun, args) - = case occAnal (zapCtxt env) fun of { (fun_uds, fun') -> - case occAnalArgs env args of { (args_uds, args') -> + | fun_uniq == runSTRepIdKey = appSpecial env 2 [True] args + -- (foldr k z xs) may call k many times, but it never + -- shares a partial application of k; hence [False,True] + -- This means we can optimise + -- foldr (\x -> let v = ...x... in \y -> ...v...) z xs + -- by floating in the v + + | otherwise = occAnalArgs env args + + +occAnalApp env (fun, args) is_rhs + = case occAnal (addAppCtxt env args) fun of { (fun_uds, fun') -> + -- The addAppCtxt is a bit cunning. One iteration of the simplifier + -- often leaves behind beta redexs like + -- (\x y -> e) a1 a2 + -- Here we would like to mark x,y as one-shot, and treat the whole + -- thing much like a let. We do this by pushing some True items + -- onto the context stack. + + case occAnalArgs env args of { (args_uds, args') -> let final_uds = fun_uds `combineUsageDetails` args_uds in (final_uds, mkApps fun' args') }} -appSpecial :: OccEnv -> Int -> CtxtTy -> [CoreExpr] -> (UsageDetails, [CoreExpr]) +appSpecial :: OccEnv + -> Int -> CtxtTy -- Argument number, and context to use for it + -> [CoreExpr] + -> (UsageDetails, [CoreExpr]) appSpecial env n ctxt args = go n args where + arg_env = vanillaCtxt env + go n [] = (emptyDetails, []) -- Too few args go 1 (arg:args) -- The magic arg - = case occAnal (setCtxt env ctxt) arg of { (arg_uds, arg') -> - case occAnalArgs env args of { (args_uds, args') -> + = case occAnal (setCtxt arg_env ctxt) arg of { (arg_uds, arg') -> + case occAnalArgs env args of { (args_uds, args') -> (combineUsageDetails arg_uds args_uds, arg':args') }} go n (arg:args) - = case occAnal env arg of { (arg_uds, arg') -> + = case occAnal arg_env arg of { (arg_uds, arg') -> case go (n-1) args of { (args_uds, args') -> (combineUsageDetails arg_uds args_uds, arg':args') }} \end{code} @@ -714,31 +642,53 @@ appSpecial env n ctxt args Case alternatives ~~~~~~~~~~~~~~~~~ +If the case binder occurs at all, the other binders effectively do too. +For example + case e of x { (a,b) -> rhs } +is rather like + let x = (a,b) in rhs +If e turns out to be (e1,e2) we indeed get something like + let a = e1; b = e2; x = (a,b) in rhs + \begin{code} -occAnalAlt env (con, bndrs, rhs) +occAnalAlt env case_bndr (con, bndrs, rhs) = case occAnal (env `addNewCands` bndrs) rhs of { (rhs_usage, rhs') -> let (final_usage, tagged_bndrs) = tagBinders rhs_usage bndrs + final_bndrs | case_bndr `elemVarEnv` final_usage = bndrs + | otherwise = tagged_bndrs + -- Leave the binders untagged if the case + -- binder occurs at all; see note above in - (final_usage, (con, tagged_bndrs, rhs')) } + (final_usage, (con, final_bndrs, rhs')) } \end{code} %************************************************************************ %* * -\subsection[OccurAnal-types]{Data types} +\subsection[OccurAnal-types]{OccEnv} %* * %************************************************************************ \begin{code} --- We gather inforamtion for variables that are either --- (a) in scope or --- (b) interesting - -data OccEnv = - OccEnv (Id -> Bool) -- Tells whether an Id occurrence is interesting, - IdSet -- In-scope Ids - CtxtTy -- Tells about linearity +data OccEnv + = OccEnv IdSet -- In-scope Ids; we gather info about these only + OccEncl -- Enclosing context information + CtxtTy -- Tells about linearity + +-- OccEncl is used to control whether to inline into constructor arguments +-- For example: +-- x = (p,q) -- Don't inline p or q +-- y = /\a -> (p a, q a) -- Still don't inline p or q +-- z = f (p,q) -- Do inline p,q; it may make a rule fire +-- So OccEncl tells enought about the context to know what to do when +-- we encounter a contructor application or PAP. + +data OccEncl + = OccRhs -- RHS of let(rec), albeit perhaps inside a type lambda + -- Don't inline into constructor args here + | OccVanilla -- Argument of function, body of lambda, scruintee of case etc. + -- Do inline into constructor args here type CtxtTy = [Bool] -- [] No info @@ -750,49 +700,84 @@ type CtxtTy = [Bool] -- be applied many times; but when it is, -- the CtxtTy inside applies +initOccEnv :: VarSet -> OccEnv +initOccEnv vars = OccEnv vars OccRhs [] + +isRhsEnv (OccEnv _ OccRhs _) = True +isRhsEnv (OccEnv _ OccVanilla _) = False + isCandidate :: OccEnv -> Id -> Bool -isCandidate (OccEnv ifun cands _) id = id `elemVarSet` cands || ifun id +isCandidate (OccEnv cands encl _) id = id `elemVarSet` cands addNewCands :: OccEnv -> [Id] -> OccEnv -addNewCands (OccEnv ifun cands ctxt) ids - = OccEnv ifun (cands `unionVarSet` mkVarSet ids) ctxt +addNewCands (OccEnv cands encl ctxt) ids + = OccEnv (extendVarSetList cands ids) encl ctxt addNewCand :: OccEnv -> Id -> OccEnv -addNewCand (OccEnv ifun cands ctxt) id - = OccEnv ifun (extendVarSet cands id) ctxt +addNewCand (OccEnv cands encl ctxt) id + = OccEnv (extendVarSet cands id) encl ctxt setCtxt :: OccEnv -> CtxtTy -> OccEnv -setCtxt (OccEnv ifun cands _) ctxt = OccEnv ifun cands ctxt +setCtxt (OccEnv cands encl _) ctxt = OccEnv cands encl ctxt + +oneShotGroup :: OccEnv -> [CoreBndr] -> (Bool, OccEnv, [CoreBndr]) + -- True <=> this is a one-shot linear lambda group + -- The [CoreBndr] are the binders. + + -- The result binders have one-shot-ness set that they might not have had originally. + -- This happens in (build (\cn -> e)). Here the occurrence analyser + -- linearity context knows that c,n are one-shot, and it records that fact in + -- the binder. This is useful to guide subsequent float-in/float-out tranformations + +oneShotGroup (OccEnv cands encl ctxt) bndrs + = case go ctxt bndrs [] of + (new_ctxt, new_bndrs) -> (all is_one_shot new_bndrs, OccEnv cands encl new_ctxt, new_bndrs) + where + is_one_shot b = isId b && isOneShotBndr b + + go ctxt [] rev_bndrs = (ctxt, reverse rev_bndrs) + + go (lin_ctxt:ctxt) (bndr:bndrs) rev_bndrs + | isId bndr = go ctxt bndrs (bndr':rev_bndrs) + where + bndr' | lin_ctxt = setOneShotLambda bndr + | otherwise = bndr + + go ctxt (bndr:bndrs) rev_bndrs = go ctxt bndrs (bndr:rev_bndrs) + -getCtxt :: OccEnv -> Int -> (Bool, OccEnv) -- True <=> this is a linear lambda - -- The Int is the number of lambdas -getCtxt env@(OccEnv ifun cands []) n = (False, env) -getCtxt (OccEnv ifun cands ctxt) n = (and (take n ctxt), OccEnv ifun cands (drop n ctxt)) - -- Only return True if *all* the lambdas are linear +vanillaCtxt (OccEnv cands _ _) = OccEnv cands OccVanilla [] +rhsCtxt (OccEnv cands _ _) = OccEnv cands OccRhs [] + +addAppCtxt (OccEnv cands encl ctxt) args + = OccEnv cands encl (replicate (valArgCount args) True ++ ctxt) +\end{code} -zapCtxt env@(OccEnv ifun cands []) = env -zapCtxt (OccEnv ifun cands _ ) = OccEnv ifun cands [] +%************************************************************************ +%* * +\subsection[OccurAnal-types]{OccEnv} +%* * +%************************************************************************ -type UsageDetails = IdEnv BinderInfo -- A finite map from ids to their usage +\begin{code} +type UsageDetails = IdEnv OccInfo -- A finite map from ids to their usage combineUsageDetails, combineAltsUsageDetails :: UsageDetails -> UsageDetails -> UsageDetails combineUsageDetails usage1 usage2 - = plusVarEnv_C addBinderInfo usage1 usage2 + = plusVarEnv_C addOccInfo usage1 usage2 combineAltsUsageDetails usage1 usage2 - = plusVarEnv_C orBinderInfo usage1 usage2 + = plusVarEnv_C orOccInfo usage1 usage2 -addOneOcc :: UsageDetails -> Id -> BinderInfo -> UsageDetails +addOneOcc :: UsageDetails -> Id -> OccInfo -> UsageDetails addOneOcc usage id info - = plusVarEnv_C addBinderInfo usage (unitVarEnv id info) + = plusVarEnv_C addOccInfo usage (unitVarEnv id info) -- ToDo: make this more efficient emptyDetails = (emptyVarEnv :: UsageDetails) -unitDetails id info = (unitVarEnv id info :: UsageDetails) - usedIn :: Id -> UsageDetails -> Bool v `usedIn` details = isExportedId v || v `elemVarEnv` details @@ -804,7 +789,7 @@ tagBinders :: UsageDetails -- Of scope tagBinders usage binders = let usage' = usage `delVarEnvList` binders - uss = map (setBinderPrag usage) binders + uss = map (setBinderOcc usage) binders in usage' `seq` (usage', uss) @@ -816,56 +801,61 @@ tagBinder :: UsageDetails -- Of scope tagBinder usage binder = let usage' = usage `delVarEnv` binder - binder' = setBinderPrag usage binder + binder' = setBinderOcc usage binder in usage' `seq` (usage', binder') +setBinderOcc :: UsageDetails -> CoreBndr -> CoreBndr +setBinderOcc usage bndr + | isTyVar bndr = bndr + | isExportedId bndr = case idOccInfo bndr of + NoOccInfo -> bndr + other -> setIdOccInfo bndr NoOccInfo + -- Don't use local usage info for visible-elsewhere things + -- BUT *do* erase any IAmALoopBreaker annotation, because we're + -- about to re-generate it and it shouldn't be "sticky" + + | otherwise = setIdOccInfo bndr occ_info + where + occ_info = lookupVarEnv usage bndr `orElse` IAmDead +\end{code} -setBinderPrag :: UsageDetails -> CoreBndr -> CoreBndr -setBinderPrag usage bndr - | isTyVar bndr - = bndr - | otherwise - = case old_prag of - NoInlinePragInfo -> new_bndr - IAmDead -> new_bndr -- The next three are annotations - ICanSafelyBeINLINEd _ _ -> new_bndr -- from the previous iteration of - IAmALoopBreaker -> new_bndr -- the occurrence analyser +%************************************************************************ +%* * +\subsection{Operations over OccInfo} +%* * +%************************************************************************ + +\begin{code} +oneOcc :: OccInfo +oneOcc = OneOcc False True - other | its_now_dead -> new_bndr -- Overwrite the others iff it's now dead - | otherwise -> bndr +markMany, markInsideLam, markInsideSCC :: OccInfo -> OccInfo - where - old_prag = getInlinePragma bndr - new_bndr = setInlinePragma bndr new_prag +markMany IAmDead = IAmDead +markMany other = NoOccInfo - its_now_dead = case new_prag of - IAmDead -> True - other -> False +markInsideSCC occ = markMany occ - new_prag = occInfoToInlinePrag occ_info +markInsideLam (OneOcc _ one_br) = OneOcc True one_br +markInsideLam occ = occ - occ_info - | isExportedId bndr = noBinderInfo - -- Don't use local usage info for visible-elsewhere things - -- But NB that we do set NoInlinePragma for exported things - -- thereby nuking any IAmALoopBreaker from a previous pass. +addOccInfo, orOccInfo :: OccInfo -> OccInfo -> OccInfo - | otherwise = case lookupVarEnv usage bndr of - Nothing -> deadOccurrence - Just info -> info +addOccInfo IAmDead info2 = info2 +addOccInfo info1 IAmDead = info1 +addOccInfo info1 info2 = NoOccInfo -markBinderInsideLambda :: CoreBndr -> CoreBndr -markBinderInsideLambda bndr - | isTyVar bndr - = bndr +-- (orOccInfo orig new) is used +-- when combining occurrence info from branches of a case - | otherwise - = case getInlinePragma bndr of - ICanSafelyBeINLINEd not_in_lam nalts - -> bndr `setInlinePragma` ICanSafelyBeINLINEd InsideLam nalts - other -> bndr +orOccInfo IAmDead info2 = info2 +orOccInfo info1 IAmDead = info1 +orOccInfo (OneOcc in_lam1 one_branch1) + (OneOcc in_lam2 one_branch2) + = OneOcc (in_lam1 || in_lam2) + False -- False, because it occurs in both branches -funOccZero = funOccurrence 0 +orOccInfo info1 info2 = NoOccInfo \end{code}