X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FOccurAnal.lhs;h=90a565f4ddd0782795ac95badfa4a84172cd0daa;hb=1eeb06aa5afa12474f8e73d9d8bd082b3dde76b9;hp=afe7ac0993db47ee4e8f753a368ae520e7647e9d;hpb=cae34044d89a87bd3da83b0e867b4a5d6994079a;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/OccurAnal.lhs b/ghc/compiler/simplCore/OccurAnal.lhs index afe7ac0..90a565f 100644 --- a/ghc/compiler/simplCore/OccurAnal.lhs +++ b/ghc/compiler/simplCore/OccurAnal.lhs @@ -12,31 +12,30 @@ core expression with (hopefully) improved usage information. \begin{code} module OccurAnal ( - occurAnalyseBinds, occurAnalyseGlobalExpr, occurAnalyseRule + occurAnalysePgm, occurAnalyseExpr ) where #include "HsVersions.h" -import BinderInfo import CoreSyn import CoreFVs ( idRuleVars ) -import CoreUtils ( exprIsTrivial ) -import Id ( isSpecPragmaId, isDataConId, isOneShotLambda, setOneShotLambda, - idOccInfo, setIdOccInfo, - isExportedId, modifyIdInfo, idInfo, - idSpecialisation, +import CoreUtils ( exprIsTrivial, isDefaultAlt ) +import Id ( isDataConWorkId, isOneShotBndr, setOneShotLambda, + idOccInfo, setIdOccInfo, isLocalId, + isExportedId, idArity, idSpecialisation, idType, idUnique, Id ) -import IdInfo ( OccInfo(..), insideLam, shortableIdInfo, copyIdInfo ) +import IdInfo ( isEmptySpecInfo ) +import BasicTypes ( OccInfo(..), isOneOcc, InterestingCxt ) import VarSet import VarEnv -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 ) import Outputable @@ -52,169 +51,22 @@ 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 - where - initial_env = OccEnv interesting emptyVarSet [] - -occurAnalyseGlobalExpr :: CoreExpr -> CoreExpr -occurAnalyseGlobalExpr expr - = -- Top level expr, so no interesting free vars, and - -- discard occurence info returned - snd (occurAnalyseExpr (\_ -> False) expr) - -occurAnalyseRule :: CoreRule -> CoreRule -occurAnalyseRule rule@(BuiltinRule _) = rule -occurAnalyseRule (Rule str tpl_vars tpl_args rhs) - -- Add occ info to tpl_vars, rhs - = Rule str tpl_vars' tpl_args rhs' +occurAnalysePgm :: [CoreBind] -> [CoreBind] +occurAnalysePgm binds + = snd (go initOccEnv binds) where - (rhs_uds, rhs') = occurAnalyseExpr isLocallyDefined rhs - (_, tpl_vars') = tagBinders rhs_uds tpl_vars -\end{code} - - -%************************************************************************ -%* * -\subsection{Top level stuff} -%* * -%************************************************************************ - -In @occAnalTop@ we do indirection-shorting. That is, if we have this: - - x_local = - ... - x_exported = loc - -where exp is exported, and loc is not, then we replace it with this: - - x_local = x_exported - x_exported = - ... - -Without this we never get rid of the x_exported = x_local 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] + go :: OccEnv -> [CoreBind] -> (UsageDetails, [CoreBind]) + go env [] + = (emptyDetails, []) + go env (bind:binds) + = (final_usage, bind' ++ binds') + where + (bs_usage, binds') = go env binds + (final_usage, bind') = occAnalBind env bind bs_usage -occurAnalyseBinds binds - = binds' - where - (_, _, binds') = go initialTopEnv binds - - go :: OccEnv -> [CoreBind] - -> (UsageDetails, -- Occurrence info - IdEnv Id, -- Indirection elimination info - -- Maps local-id -> exported-id, but it embodies - -- bindings of the form exported-id = local-id in - -- the argument to go - [CoreBind]) -- Occ-analysed bindings, less the exported-id=local-id ones - - 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@(local_id,rhs) - = case lookupVarEnv ind_env local_id of - Nothing -> [pair] - Just exported_id -> [(local_id, Var exported_id), - (exported_id', rhs)] - where - exported_id' = modifyIdInfo (copyIdInfo (idInfo local_id)) exported_id - -shortMeOut ind_env exported_id local_id --- The if-then-else stuff is just so I can get a pprTrace to see --- how often I don't get shorting out becuase of IdInfo stuff - = if 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 - then - if shortableIdInfo (idInfo exported_id) -- Only if its IdInfo is 'shortable' - -- (see the defn of IdInfo.shortableIdInfo - then True - else pprTrace "shortMeOut:" (ppr exported_id) False - else - False +occurAnalyseExpr :: CoreExpr -> CoreExpr + -- Do occurrence analysis, and discard occurence info returned +occurAnalyseExpr expr = snd (occAnal initOccEnv expr) \end{code} @@ -230,7 +82,7 @@ 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) @@ -252,7 +104,7 @@ 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: @@ -294,13 +146,10 @@ 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 - binders = map fst pairs - rhs_env = env `addNewCands` binders - analysed_pairs :: [Details1] analysed_pairs = [ (bndr, rhs_usage, rhs') | (bndr, rhs) <- pairs, - let (rhs_usage, rhs') = occAnalRhs rhs_env bndr rhs + let (rhs_usage, rhs') = occAnalRhs env bndr rhs ] sccs :: [SCC (Node Details1)] @@ -310,7 +159,7 @@ 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 ] @@ -323,7 +172,7 @@ 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 @@ -471,7 +320,7 @@ reOrderRec env (CyclicSCC (bind : binds)) | inlineCandidate bndr rhs = 2 -- Likely to be inlined - | not (isEmptyCoreRules (idSpecialisation bndr)) = 1 + | not (isEmptySpecInfo (idSpecialisation bndr)) = 1 -- Avoid things with specialisations; we'd like -- to take advantage of them in the subsequent bindings @@ -479,9 +328,7 @@ reOrderRec env (CyclicSCC (bind : binds)) inlineCandidate :: Id -> CoreExpr -> Bool inlineCandidate id (Note InlineMe _) = True - inlineCandidate id rhs = case idOccInfo id of - OneOcc _ _ -> 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 @@ -493,9 +340,7 @@ 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 @@ -512,12 +357,34 @@ 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 + -- 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 @@ -525,8 +392,14 @@ 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} @@ -540,20 +413,13 @@ occAnal :: OccEnv CoreExpr) occAnal env (Type t) = (emptyDetails, Type t) - -occAnal env (Var v) - = (var_uds, Var v) - where - var_uds | isCandidate env v = unitVarEnv v funOccZero - | otherwise = emptyDetails - +occAnal env (Var v) = (mkOneOcc env v False, Var v) -- At one stage, I gathered the idRuleVars for v here too, -- which in a way is the right thing to do. - -- But that went wrong right after specialisation, when + -- Btu that went wrong right after specialisation, when -- the *occurrences* of the overloaded function didn't have any -- rules in them, so the *specialised* versions looked as if they -- weren't used at all. - \end{code} We regard variables that occur as constructor arguments as "dangerousToDup": @@ -594,7 +460,7 @@ 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 @@ -615,7 +481,7 @@ 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 @@ -630,22 +496,23 @@ occAnal env expr@(Lam _ _) (really_final_usage, mkLams tagged_binders body') } where - (binders, body) = collectBinders expr - (linear, env_body, _) = oneShotGroup env 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') -> + env_body = vanillaCtxt -- Body is (no longer) an RhsContext + (binders, body) = collectBinders expr + binders' = oneShotGroup env binders + linear = all is_one_shot binders' + is_one_shot b = isId b && isOneShotBndr b + +occAnal env (Case scrut bndr ty alts) + = case occ_anal_scrut scrut alts of { (scrut_usage, scrut') -> + case mapAndUnzip (occAnalAlt env bndr) alts of { (alts_usage_s, alts') -> let alts_usage = foldr1 combineAltsUsageDetails alts_usage_s 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. @@ -657,18 +524,22 @@ occAnal env (Case scrut bndr alts) Nothing -> usage Just occ -> extendVarEnv usage bndr (markMany occ) + occ_anal_scrut (Var v) (alt1 : other_alts) + | not (null other_alts) || not (isDefaultAlt alt1) + = (mkOneOcc env v True, Var v) + occ_anal_scrut scrut alts = occAnal vanillaCtxt scrut + -- No need for rhsCtxt + occAnal env (Let bind body) - = case occAnal new_env body of { (body_usage, body') -> + = case occAnal env body of { (body_usage, body') -> case occAnalBind env bind body_usage of { (final_usage, new_binds) -> (final_usage, mkLets new_binds body') }} - where - new_env = env `addNewCands` (bindersOf bind) 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 \end{code} Applications are dealt with specially because we want @@ -676,54 +547,72 @@ 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 - | otherwise = emptyDetails - + fun_uds = mkOneOcc env fun (valArgCount args > 0) 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 - - | isDataConId fun = case occAnalArgs env args of - (arg_uds, args') -> (mapVarEnv markMany arg_uds, args') - -- 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. - - | 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 + 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} @@ -731,31 +620,52 @@ 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) - = case occAnal (env `addNewCands` bndrs) rhs of { (rhs_usage, rhs') -> +occAnalAlt env case_bndr (con, bndrs, rhs) + = case occAnal env 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 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 @@ -767,36 +677,28 @@ type CtxtTy = [Bool] -- be applied many times; but when it is, -- the CtxtTy inside applies -isCandidate :: OccEnv -> Id -> Bool -isCandidate (OccEnv ifun cands _) id = id `elemVarSet` cands || ifun id +initOccEnv :: OccEnv +initOccEnv = OccEnv OccRhs [] -addNewCands :: OccEnv -> [Id] -> OccEnv -addNewCands (OccEnv ifun cands ctxt) ids - = OccEnv ifun (cands `unionVarSet` mkVarSet ids) ctxt +vanillaCtxt = OccEnv OccVanilla [] +rhsCtxt = OccEnv OccRhs [] -addNewCand :: OccEnv -> Id -> OccEnv -addNewCand (OccEnv ifun cands ctxt) id - = OccEnv ifun (extendVarSet cands id) ctxt +isRhsEnv (OccEnv OccRhs _) = True +isRhsEnv (OccEnv OccVanilla _) = False setCtxt :: OccEnv -> CtxtTy -> OccEnv -setCtxt (OccEnv ifun cands _) ctxt = OccEnv ifun cands ctxt - -oneShotGroup :: OccEnv -> [CoreBndr] -> (Bool, OccEnv, [CoreBndr]) - -- True <=> this is a one-shot linear lambda group - -- The [CoreBndr] are the binders. +setCtxt (OccEnv encl _) ctxt = OccEnv encl ctxt +oneShotGroup :: OccEnv -> [CoreBndr] -> [CoreBndr] -- 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 ifun cands ctxt) bndrs - = case go ctxt bndrs [] of - (new_ctxt, new_bndrs) -> (all is_one_shot new_bndrs, OccEnv ifun cands new_ctxt, new_bndrs) +oneShotGroup (OccEnv encl ctxt) bndrs + = go ctxt bndrs [] where - is_one_shot b = isId b && isOneShotLambda b - - go ctxt [] rev_bndrs = (ctxt, reverse rev_bndrs) + go ctxt [] rev_bndrs = reverse rev_bndrs go (lin_ctxt:ctxt) (bndr:bndrs) rev_bndrs | isId bndr = go ctxt bndrs (bndr':rev_bndrs) @@ -806,30 +708,35 @@ oneShotGroup (OccEnv ifun cands ctxt) bndrs go ctxt (bndr:bndrs) rev_bndrs = go ctxt bndrs (bndr:rev_bndrs) +addAppCtxt (OccEnv encl ctxt) args + = OccEnv 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 @@ -857,23 +764,60 @@ tagBinder usage binder in usage' `seq` (usage', binder') - setBinderOcc :: UsageDetails -> CoreBndr -> CoreBndr setBinderOcc usage bndr | isTyVar bndr = bndr - | isExportedId bndr - = -- 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" - case idOccInfo bndr of - NoOccInfo -> bndr - other -> setIdOccInfo bndr NoOccInfo + | 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 + | otherwise = setIdOccInfo bndr occ_info where - occ_info = case lookupVarEnv usage bndr of - Nothing -> IAmDead - Just info -> binderInfoToOccInfo info + occ_info = lookupVarEnv usage bndr `orElse` IAmDead +\end{code} + + +%************************************************************************ +%* * +\subsection{Operations over OccInfo} +%* * +%************************************************************************ + +\begin{code} +mkOneOcc :: OccEnv -> Id -> InterestingCxt -> UsageDetails +mkOneOcc env id int_cxt + | isLocalId id = unitVarEnv id (OneOcc False True int_cxt) + | otherwise = emptyDetails + +markMany, markInsideLam, markInsideSCC :: OccInfo -> OccInfo + +markMany IAmDead = IAmDead +markMany other = NoOccInfo + +markInsideSCC occ = markMany occ + +markInsideLam (OneOcc _ one_br int_cxt) = OneOcc True one_br int_cxt +markInsideLam occ = occ + +addOccInfo, orOccInfo :: OccInfo -> OccInfo -> OccInfo + +addOccInfo IAmDead info2 = info2 +addOccInfo info1 IAmDead = info1 +addOccInfo info1 info2 = NoOccInfo + +-- (orOccInfo orig new) is used +-- when combining occurrence info from branches of a case + +orOccInfo IAmDead info2 = info2 +orOccInfo info1 IAmDead = info1 +orOccInfo (OneOcc in_lam1 one_branch1 int_cxt1) + (OneOcc in_lam2 one_branch2 int_cxt2) + = OneOcc (in_lam1 || in_lam2) + False -- False, because it occurs in both branches + (int_cxt1 && int_cxt2) -funOccZero = funOccurrence 0 +orOccInfo info1 info2 = NoOccInfo \end{code}