X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FOccurAnal.lhs;h=5c8c11d5991a9b9925c47204f8cf80d9935eaf15;hb=58de6cb725982dd1f57803cc838f233d5fd9c42c;hp=f56bc71f8b30616195854b0291fc5338a2e14da2;hpb=1cc3d6d110594517f2c7adc72d7b4f99db287277;p=ghc-hetmet.git diff --git a/compiler/simplCore/OccurAnal.lhs b/compiler/simplCore/OccurAnal.lhs index f56bc71..5c8c11d 100644 --- a/compiler/simplCore/OccurAnal.lhs +++ b/compiler/simplCore/OccurAnal.lhs @@ -11,25 +11,20 @@ The occurrence analyser re-typechecks a core expression, returning a new core expression with (hopefully) improved usage information. \begin{code} -{-# OPTIONS -w #-} --- The above warning supression flag is a temporary kludge. --- While working on this module you are encouraged to remove it and fix --- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings --- for details - module OccurAnal ( occurAnalysePgm, occurAnalyseExpr ) where +-- XXX This define is a bit of a hack, and should be done more nicely +#define FAST_STRING_NOT_NEEDED 1 #include "HsVersions.h" import CoreSyn -import CoreFVs ( idRuleVars ) +import CoreFVs import CoreUtils ( exprIsTrivial, isDefaultAlt ) import Id import IdInfo -import BasicTypes ( OccInfo(..), isOneOcc, InterestingCxt ) +import BasicTypes import VarSet import VarEnv @@ -38,7 +33,7 @@ import Maybes ( orElse ) import Digraph ( stronglyConnCompR, SCC(..) ) import PrelNames ( buildIdKey, foldrIdKey, runSTRepIdKey, augmentIdKey ) import Unique ( Unique ) -import UniqFM ( keysUFM, intersectsUFM ) +import UniqFM ( keysUFM, intersectUFM_C, foldUFM_Directly ) import Util ( mapAndUnzip ) import Outputable @@ -60,7 +55,7 @@ occurAnalysePgm binds = snd (go initOccEnv binds) where go :: OccEnv -> [CoreBind] -> (UsageDetails, [CoreBind]) - go env [] + go _ [] = (emptyDetails, []) go env (bind:binds) = (final_usage, bind' ++ binds') @@ -95,38 +90,36 @@ occAnalBind env (NonRec binder rhs) body_usage = (body_usage, []) | otherwise -- It's mentioned in the body - = (body_usage' +++ addRuleUsage rhs_usage binder, -- Note [RulesOnly] + = (body_usage' +++ addRuleUsage rhs_usage binder, -- Note [Rules are extra RHSs] [NonRec tagged_binder rhs']) where (body_usage', tagged_binder) = tagBinder body_usage binder (rhs_usage, rhs') = occAnalRhs env tagged_binder rhs \end{code} +Note [Dead code] +~~~~~~~~~~~~~~~~ Dropping dead code for recursive bindings is done in a very simple way: the entire set of bindings is dropped if none of its binders are mentioned in its body; otherwise none are. This seems to miss an obvious improvement. -@ + letrec f = ...g... g = ...f... in ...g... - ===> - letrec f = ...g... g = ...(...g...)... in ...g... -@ -Now @f@ is unused. But dependency analysis will sort this out into a -@letrec@ for @g@ and a @let@ for @f@, and then @f@ will get dropped. -It isn't easy to do a perfect job in one blow. Consider +Now 'f' is unused! But it's OK! Dependency analysis will sort this +out into a letrec for 'g' and a 'let' for 'f', and then 'f' will get +dropped. It isn't easy to do a perfect job in one blow. Consider -@ letrec f = ...g... g = ...h... h = ...k... @@ -134,29 +127,202 @@ It isn't easy to do a perfect job in one blow. Consider m = ...m... in ...m... -@ + + +Note [Loop breaking and RULES] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Loop breaking is surprisingly subtle. First read the section 4 of +"Secrets of the GHC inliner". This describes our basic plan. + +However things are made quite a bit more complicated by RULES. Remember + + * Note [Rules are extra RHSs] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~ + A RULE for 'f' is like an extra RHS for 'f'. That way the "parent" + keeps the specialised "children" alive. If the parent dies + (because it isn't referenced any more), then the children will die + too (unless they are already referenced directly). + + To that end, we build a Rec group for each cyclic strongly + connected component, + *treating f's rules as extra RHSs for 'f'*. + + When we make the Rec groups we include variables free in *either* + LHS *or* RHS of the rule. The former might seems silly, but see + Note [Rule dependency info]. + + So in Example [eftInt], eftInt and eftIntFB will be put in the + same Rec, even though their 'main' RHSs are both non-recursive. + + * Note [Rules are visible in their own rec group] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + We want the rules for 'f' to be visible in f's right-hand side. + And we'd like them to be visible in other functions in f's Rec + group. E.g. in Example [Specialisation rules] we want f' rule + to be visible in both f's RHS, and fs's RHS. + + This means that we must simplify the RULEs first, before looking + at any of the definitions. This is done by Simplify.simplRecBind, + when it calls addLetIdInfo. + + * Note [Choosing loop breakers] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + We avoid infinite inlinings by choosing loop breakers, and + ensuring that a loop breaker cuts each loop. But what is a + "loop"? In particular, a RULES is like an equation for 'f' that + is *always* inlined if it are applicable. We do *not* disable + rules for loop-breakers. It's up to whoever makes the rules to + make sure that the rules themselves alwasys terminate. See Note + [Rules for recursive functions] in Simplify.lhs + + Hence, if + f's RHS mentions g, and + g has a RULE that mentions h, and + h has a RULE that mentions f + + then we *must* choose f to be a loop breaker. In general, take the + free variables of f's RHS, and augment it with all the variables + reachable by RULES from those starting points. That is the whole + reason for computing rule_fv_env in occAnalBind. (Of course we + only consider free vars that are also binders in this Rec group.) + + Note that when we compute this rule_fv_env, we only consider variables + free in the *RHS* of the rule, in contrast to the way we build the + Rec group in the first place (Note [Rule dependency info]) + + Note that in Example [eftInt], *neither* eftInt *nor* eftIntFB is + chosen as a loop breaker, because their RHSs don't mention each other. + And indeed both can be inlined safely. + + Note that the edges of the graph we use for computing loop breakers + are not the same as the edges we use for computing the Rec blocks. + That's why we compute + rec_edges for the Rec block analysis + loop_breaker_edges for the loop breaker analysis + + + * Note [Weak loop breakers] + ~~~~~~~~~~~~~~~~~~~~~~~~~ + There is a last nasty wrinkle. Suppose we have + + Rec { f = f_rhs + RULE f [] = g + + h = h_rhs + g = h + ...more... + } + + Remmber that we simplify the RULES before any RHS (see Note + [Rules are visible in their own rec group] above). + + So we must *not* postInlineUnconditionally 'g', even though + its RHS turns out to be trivial. (I'm assuming that 'g' is + not choosen as a loop breaker.) + + We "solve" this by making g a "weak" or "rules-only" loop breaker, + with OccInfo = IAmLoopBreaker True. A normal "strong" loop breaker + has IAmLoopBreaker False. So + + Inline postInlineUnconditinoally + IAmLoopBreaker False no no + IAmLoopBreaker True yes no + other yes yes + + The **sole** reason for this kind of loop breaker is so that + postInlineUnconditionally does not fire. Ugh. + + * Note [Rule dependency info] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~ + The VarSet in a SpecInfo is used for dependency analysis in the + occurrence analyser. We must track free vars in *both* lhs and rhs. Why both? + Consider + x = y + RULE f x = 4 + Then if we substitute y for x, we'd better do so in the + rule's LHS too, so we'd better ensure the dependency is respected + + +Example [eftInt] +~~~~~~~~~~~~~~~ +Example (from GHC.Enum): + + eftInt :: Int# -> Int# -> [Int] + eftInt x y = ...(non-recursive)... + + {-# INLINE [0] eftIntFB #-} + eftIntFB :: (Int -> r -> r) -> r -> Int# -> Int# -> r + eftIntFB c n x y = ...(non-recursive)... + + {-# RULES + "eftInt" [~1] forall x y. eftInt x y = build (\ c n -> eftIntFB c n x y) + "eftIntList" [1] eftIntFB (:) [] = eftInt + #-} + +Example [Specialisation rules] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider this group, which is typical of what SpecConstr builds: + + fs a = ....f (C a).... + f x = ....f (C a).... + {-# RULE f (C a) = fs a #-} + +So 'f' and 'fs' are in the same Rec group (since f refers to fs via its RULE). + +But watch out! If 'fs' is not chosen as a loop breaker, we may get an infinite loop: + - the RULE is applied in f's RHS (see Note [Self-recursive rules] in Simplify + - fs is inlined (say it's small) + - now there's another opportunity to apply the RULE + +This showed up when compiling Control.Concurrent.Chan.getChanContents. \begin{code} occAnalBind env (Rec pairs) body_usage - = foldr ({-# SCC "occAnalBind.dofinal" #-} do_final_bind) (body_usage, []) sccs + | not (any (`usedIn` body_usage) bndrs) -- NB: look at body_usage, not total_usage + = (body_usage, []) -- Dead code + | otherwise + = (final_usage, map ({-# SCC "occAnalBind.dofinal" #-} do_final_bind) sccs) where - analysed_pairs :: [Details] - analysed_pairs = [ (bndr, rhs_usage, rhs') - | (bndr, rhs) <- pairs, - let (rhs_usage, rhs') = occAnalRhs env bndr rhs - ] + bndrs = map fst pairs + bndr_set = mkVarSet bndrs + + --------------------------------------- + -- See Note [Loop breaking] + --------------------------------------- + + -------------Dependency analysis ------------------------------ + occ_anald :: [(Id, (UsageDetails, CoreExpr))] + -- The UsageDetails here are strictly those arising from the RHS + -- *not* from any rules in the Id + occ_anald = [(bndr, occAnalRhs env bndr rhs) | (bndr,rhs) <- pairs] + + total_usage = foldl add_usage body_usage occ_anald + add_usage body_usage (bndr, (rhs_usage, _)) + = body_usage +++ addRuleUsage rhs_usage bndr + + (final_usage, tagged_bndrs) = tagBinders total_usage bndrs + final_bndrs | isEmptyVarSet all_rule_fvs = tagged_bndrs + | otherwise = map tag_rule_var tagged_bndrs + + tag_rule_var bndr | bndr `elemVarSet` all_rule_fvs = makeLoopBreaker True bndr + | otherwise = bndr + all_rule_fvs = bndr_set `intersectVarSet` foldr (unionVarSet . idRuleVars) emptyVarSet bndrs + -- Mark the binder with OccInfo saying "no preInlineUnconditionally" if + -- it is used in any rule (lhs or rhs) of the recursive group + ---- stuff for dependency analysis of binds ------------------------------- sccs :: [SCC (Node Details)] - sccs = {-# SCC "occAnalBind.scc" #-} stronglyConnCompR edges - + sccs = {-# SCC "occAnalBind.scc" #-} stronglyConnCompR rec_edges - ---- stuff for dependency analysis of binds ------------------------------- - edges :: [Node Details] - edges = {-# SCC "occAnalBind.assoc" #-} - [ (details, idUnique id, edges_from id rhs_usage) - | details@(id, rhs_usage, rhs) <- analysed_pairs - ] + rec_edges :: [Node Details] -- The binders are tagged with correct occ-info + rec_edges = {-# SCC "occAnalBind.assoc" #-} zipWith make_node final_bndrs occ_anald + make_node tagged_bndr (_bndr, (rhs_usage, rhs)) + = ((tagged_bndr, rhs, rhs_fvs), idUnique tagged_bndr, out_edges) + where + rhs_fvs = intersectUFM_C (\b _ -> b) bndr_set rhs_usage + out_edges = keysUFM (rhs_fvs `unionVarSet` idRuleVars tagged_bndr) + -- (a -> b) means a mentions b -- Given the usage details (a UFM that gives occ info for each free var of @@ -167,55 +333,57 @@ 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 :: Id -> UsageDetails -> [Unique] - edges_from bndr rhs_usage = {-# SCC "occAnalBind.edges_from" #-} - keysUFM (addRuleUsage rhs_usage bndr) ---- Stuff to "re-constitute" bindings from dependency-analysis info ------ + do_final_bind (AcyclicSCC ((bndr, rhs, _), _, _)) = NonRec bndr rhs + do_final_bind (CyclicSCC cycle) + | no_rules = Rec (reOrderCycle cycle) + | otherwise = Rec (concatMap reOrderRec (stronglyConnCompR loop_breaker_edges)) + where -- See Note [Choosing loop breakers] for looop_breker_edges + loop_breaker_edges = map mk_node cycle + mk_node (details@(_bndr, _rhs, rhs_fvs), k, _) = (details, k, new_ks) + where + new_ks = keysUFM (extendFvs rule_fv_env rhs_fvs rhs_fvs) - -- Non-recursive SCC - do_final_bind (AcyclicSCC ((bndr, rhs_usage, rhs'), _, _)) (body_usage, binds_so_far) - | not (bndr `usedIn` body_usage) - = (body_usage, binds_so_far) -- Dead code - | otherwise - = (body_usage' +++ addRuleUsage rhs_usage bndr, new_bind : binds_so_far) - where - (body_usage', tagged_bndr) = tagBinder body_usage bndr - new_bind = NonRec tagged_bndr rhs' - - -- Recursive SCC - do_final_bind (CyclicSCC cycle) (body_usage, binds_so_far) - | not (any (`usedIn` body_usage) bndrs) -- NB: look at body_usage, not total_usage - = (body_usage, binds_so_far) -- Dead code - | otherwise -- If any is used, they all are - = (final_usage, final_bind : binds_so_far) - where - details = [details | (details, _, _) <- cycle] - bndrs = [bndr | (bndr, _, _) <- details] - bndr_usages = [addRuleUsage rhs_usage bndr | (bndr, rhs_usage, _) <- details] - total_usage = foldr (+++) body_usage bndr_usages - (final_usage, tagged_cycle) = mapAccumL tag_bind total_usage cycle - tag_bind usg ((bndr,rhs_usg,rhs),k,ks) = (usg', ((bndr',rhs_usg,rhs),k,ks)) - where - (usg', bndr') = tagBinder usg bndr - final_bind = Rec (reOrderCycle (mkVarSet bndrs) tagged_cycle) - -{- An alternative; rebuild the edges. No semantic difference, but perf might change - - -- Hopefully 'bndrs' is a relatively small group now - -- Now get ready for the loop-breaking phase - -- We've done dead-code elimination already, so no worries about un-referenced binders - keys = map idUnique bndrs - mk_node tagged_bndr (_, rhs_usage, rhs') - = ((tagged_bndr, rhs'), idUnique tagged_bndr, used) - where - used = [key | key <- keys, used_outside_rule rhs_usage key ] - - used_outside_rule usage uniq = case lookupUFM_Directly usage uniq of - Nothing -> False - Just RulesOnly -> False -- Ignore rules - other -> True --} + + ------------------------------------ + rule_fv_env :: IdEnv IdSet -- Variables from this group mentioned in RHS of rules + -- Domain is *subset* of bound vars (others have no rule fvs) + rule_fv_env = rule_loop init_rule_fvs + + no_rules = null init_rule_fvs + init_rule_fvs = [(b, rule_fvs) + | b <- bndrs + , let rule_fvs = idRuleRhsVars b `intersectVarSet` bndr_set + , not (isEmptyVarSet rule_fvs)] + + rule_loop :: [(Id,IdSet)] -> IdEnv IdSet -- Finds fixpoint + rule_loop fv_list + | no_change = env + | otherwise = rule_loop new_fv_list + where + env = mkVarEnv init_rule_fvs + (no_change, new_fv_list) = mapAccumL bump True fv_list + bump no_change (b,fvs) + | new_fvs `subVarSet` fvs = (no_change, (b,fvs)) + | otherwise = (False, (b,new_fvs `unionVarSet` fvs)) + where + new_fvs = extendFvs env emptyVarSet fvs + +idRuleRhsVars :: Id -> VarSet +-- Just the variables free on the *rhs* of a rule +-- See Note [Choosing loop breakers] +idRuleRhsVars id = foldr (unionVarSet . ruleRhsFreeVars) emptyVarSet (idCoreRules id) + +extendFvs :: IdEnv IdSet -> IdSet -> IdSet -> IdSet +-- (extendFVs env fvs s) returns (fvs `union` env(s)) +extendFvs env fvs id_set + = foldUFM_Directly add fvs id_set + where + add uniq _ fvs + = case lookupVarEnv_Directly env uniq of + Just fvs' -> fvs' `unionVarSet` fvs + Nothing -> fvs \end{code} @reOrderRec@ is applied to the list of (binder,rhs) pairs for a cyclic @@ -255,37 +423,38 @@ Perhaps something cleverer would suffice. \begin{code} type Node details = (details, Unique, [Unique]) -- The Ints are gotten from the Unique, -- which is gotten from the Id. -type Details = (Id, UsageDetails, CoreExpr) +type Details = (Id, -- Binder + CoreExpr, -- RHS + IdSet) -- RHS free vars (*not* include rules) -reOrderRec :: IdSet -- Binders of this group - -> SCC (Node Details) +reOrderRec :: SCC (Node Details) -> [(Id,CoreExpr)] -- Sorted into a plausible order. Enough of the Ids have -- IAmALoopBreaker pragmas that there are no loops left. -reOrderRec bndrs (AcyclicSCC ((bndr, _, rhs), _, _)) = [(bndr, rhs)] -reOrderRec bndrs (CyclicSCC cycle) = reOrderCycle bndrs cycle +reOrderRec (AcyclicSCC ((bndr, rhs, _), _, _)) = [(bndr, rhs)] +reOrderRec (CyclicSCC cycle) = reOrderCycle cycle -reOrderCycle :: IdSet -> [Node Details] -> [(Id,CoreExpr)] -reOrderCycle bndrs [] +reOrderCycle :: [Node Details] -> [(Id,CoreExpr)] +reOrderCycle [] = panic "reOrderCycle" -reOrderCycle bndrs [bind] -- Common case of simple self-recursion - = [(makeLoopBreaker bndrs rhs_usg bndr, rhs)] +reOrderCycle [bind] -- Common case of simple self-recursion + = [(makeLoopBreaker False bndr, rhs)] where - ((bndr, rhs_usg, rhs), _, _) = bind + ((bndr, rhs, _), _, _) = bind -reOrderCycle bndrs (bind : binds) +reOrderCycle (bind : binds) = -- Choose a loop breaker, mark it no-inline, -- do SCC analysis on the rest, and recursively sort them out - concatMap (reOrderRec bndrs) (stronglyConnCompR unchosen) ++ - [(makeLoopBreaker bndrs rhs_usg bndr, rhs)] + concatMap reOrderRec (stronglyConnCompR unchosen) ++ + [(makeLoopBreaker False bndr, rhs)] where (chosen_bind, unchosen) = choose_loop_breaker bind (score bind) [] binds - (bndr, rhs_usg, rhs) = chosen_bind + (bndr, rhs, _) = chosen_bind -- This loop looks for the bind with the lowest score -- to pick as the loop breaker. The rest accumulate in - choose_loop_breaker (details,_,_) loop_sc acc [] + choose_loop_breaker (details,_,_) _loop_sc acc [] = (details, acc) -- Done choose_loop_breaker loop_bind loop_sc acc (bind : binds) @@ -298,7 +467,7 @@ reOrderCycle bndrs (bind : binds) sc = score bind score :: Node Details -> Int -- Higher score => less likely to be picked as loop breaker - score ((bndr, _, rhs), _, _) + score ((bndr, rhs, _), _, _) | workerExists (idWorkerInfo bndr) = 10 -- Note [Worker inline loop] @@ -309,12 +478,6 @@ reOrderCycle bndrs (bind : binds) -- where df is the exported dictionary. Then df makes a really -- bad choice for loop breaker - | idHasRules bndr = 3 - -- Avoid things with specialisations; we'd like - -- to take advantage of them in the subsequent bindings - -- Also vital to avoid risk of divergence: - -- Note [Recursive rules] - | is_con_app rhs = 2 -- Data types help with cases -- Note [conapp] @@ -324,8 +487,8 @@ reOrderCycle bndrs (bind : binds) | otherwise = 0 inlineCandidate :: Id -> CoreExpr -> Bool - inlineCandidate id (Note InlineMe _) = True - inlineCandidate id rhs = isOneOcc (idOccInfo id) + inlineCandidate _ (Note InlineMe _) = True + inlineCandidate id _ = isOneOcc (idOccInfo id) -- Note [conapp] -- @@ -353,19 +516,14 @@ reOrderCycle bndrs (bind : binds) -- Note [Closure conversion] is_con_app (Var v) = isDataConWorkId v is_con_app (App f _) = is_con_app f - is_con_app (Lam b e) = is_con_app e + is_con_app (Lam _ e) = is_con_app e is_con_app (Note _ e) = is_con_app e - is_con_app other = False - -makeLoopBreaker :: VarSet -- Binders of this group - -> UsageDetails -- Usage of this rhs (neglecting rules) - -> Id -> Id --- Set the loop-breaker flag, recording whether the thing occurs only in --- the RHS of a RULE (in this recursive group) -makeLoopBreaker bndrs rhs_usg bndr - = setIdOccInfo bndr (IAmALoopBreaker rules_only) - where - rules_only = bndrs `intersectsUFM` rhs_usg + is_con_app _ = False + +makeLoopBreaker :: Bool -> Id -> Id +-- Set the loop-breaker flag +-- See Note [Weak loop breakers] +makeLoopBreaker weak bndr = setIdOccInfo bndr (IAmALoopBreaker weak) \end{code} Note [Worker inline loop] @@ -387,25 +545,6 @@ nofib/spectral/minimax. If the repTree wrapper is chosen as the loop breaker then compiling Game.hs goes into an infinite loop (this happened when we gave is_con_app a lower score than inline candidates). -Note [Recursive rules] -~~~~~~~~~~~~~~~~~~~~~~ -Consider this group, which is typical of what SpecConstr builds: - - fs a = ....f (C a).... - f x = ....f (C a).... - {-# RULE f (C a) = fs a #-} - -So 'f' and 'fs' are mutually recursive. If we choose 'fs' as the loop breaker, -all is well; the RULE is applied, and 'fs' becomes self-recursive. - -But if we choose 'f' as the loop breaker, we may get an infinite loop: - - the RULE is applied in f's RHS (see Note [Self-recursive rules] in Simplify - - fs is inlined (say it's small) - - now there's another opportunity to apply the RULE - -So it's very important not to choose the RULE-variable as the loop breaker. -This showed up when compiling Control.Concurrent.Chan.getChanContents. - Note [Closure conversion] ~~~~~~~~~~~~~~~~~~~~~~~~~ We treat (\x. C p q) as a high-score candidate in the letrec scoring algorithm. @@ -469,42 +608,12 @@ occAnalRhs env id rhs certainly_inline id = case idOccInfo id of OneOcc in_lam one_br _ -> not in_lam && one_br - other -> False + _ -> False \end{code} -Note [RulesOnly] -~~~~~~~~~~~~~~~~~~ -If the binder has RULES inside it then we count the specialised Ids as -"extra rhs's". That way the "parent" keeps the specialised "children" -alive. If the parent dies (because it isn't referenced any more), -then the children will die too unless they are already referenced -directly. - -That's the basic idea. However in a recursive situation we want to be a bit -cleverer. Example (from GHC.Enum): - - eftInt :: Int# -> Int# -> [Int] - eftInt x y = ...(non-recursive)... - - {-# INLINE [0] eftIntFB #-} - eftIntFB :: (Int -> r -> r) -> r -> Int# -> Int# -> r - eftIntFB c n x y = ...(non-recursive)... - - {-# RULES - "eftInt" [~1] forall x y. eftInt x y = build (\ c n -> eftIntFB c n x y) - "eftIntList" [1] eftIntFB (:) [] = eftInt - #-} - -The two look mutually recursive only because of their RULES; we don't want -that to inhibit inlining! - -So when we identify a LoopBreaker, we mark it to say whether it only mentions -the other binders in its recursive group in a RULE. If so, we can inline it, -because doing so will not expose new occurrences of binders in its group. \begin{code} - addRuleUsage :: UsageDetails -> Id -> UsageDetails -- Add the usage from RULES in Id to the usage addRuleUsage usage id @@ -523,11 +632,11 @@ occAnal :: OccEnv -> (UsageDetails, -- Gives info only about the "interesting" Ids CoreExpr) -occAnal env (Type t) = (emptyDetails, Type t) +occAnal _ (Type t) = (emptyDetails, Type t) 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. - -- Btu that went wrong right after specialisation, when + -- But 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. @@ -549,7 +658,7 @@ If we aren't careful we duplicate the (expensive x) call! Constructors are rather like lambdas in this way. \begin{code} -occAnal env expr@(Lit lit) = (emptyDetails, expr) +occAnal _ expr@(Lit _) = (emptyDetails, expr) \end{code} \begin{code} @@ -558,7 +667,7 @@ occAnal env (Note InlineMe body) (mapVarEnv markMany usage, Note InlineMe body') } -occAnal env (Note note@(SCC cc) body) +occAnal env (Note note@(SCC _) body) = case occAnal env body of { (usage, body') -> (mapVarEnv markInsideSCC usage, Note note body') } @@ -578,14 +687,14 @@ occAnal env (Cast expr co) \end{code} \begin{code} -occAnal env app@(App fun arg) - = occAnalApp env (collectArgs app) False +occAnal env app@(App _ _) + = occAnalApp env (collectArgs app) -- Ignore type variables altogether -- (a) occurrences inside type lambdas only not marked as InsideLam -- (b) type variables not in environment -occAnal env expr@(Lam x body) | isTyVar x +occAnal env (Lam x body) | isTyVar x = case occAnal env body of { (body_usage, body') -> (body_usage, Lam x body') } @@ -650,7 +759,7 @@ occAnal env (Case scrut bndr ty alts) 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 + occ_anal_scrut scrut _alts = occAnal vanillaCtxt scrut -- No need for rhsCtxt occAnal env (Let bind body) @@ -658,7 +767,8 @@ occAnal env (Let bind body) case occAnalBind env bind body_usage of { (final_usage, new_binds) -> (final_usage, mkLets new_binds body') }} -occAnalArgs env args +occAnalArgs :: OccEnv -> [CoreExpr] -> (UsageDetails, [CoreExpr]) +occAnalArgs _env args = case mapAndUnzip (occAnal arg_env) args of { (arg_uds_s, args') -> (foldr (+++) emptyDetails arg_uds_s, args')} where @@ -669,7 +779,10 @@ Applications are dealt with specially because we want the "build hack" to work. \begin{code} -occAnalApp env (Var fun, args) is_rhs +occAnalApp :: OccEnv + -> (Expr CoreBndr, [Arg CoreBndr]) + -> (UsageDetails, Expr CoreBndr) +occAnalApp env (Var fun, args) = case args_stuff of { (args_uds, args') -> let final_args_uds = markRhsUds env is_pap args_uds @@ -694,7 +807,7 @@ occAnalApp env (Var fun, args) is_rhs | otherwise = occAnalArgs env args -occAnalApp env (fun, args) is_rhs +occAnalApp env (fun, args) = 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 @@ -735,7 +848,7 @@ appSpecial env n ctxt args where arg_env = vanillaCtxt - go n [] = (emptyDetails, []) -- Too few args + go _ [] = (emptyDetails, []) -- Too few args go 1 (arg:args) -- The magic arg = case occAnal (setCtxt arg_env ctxt) arg of { (arg_uds, arg') -> @@ -764,7 +877,11 @@ Note [Aug 06]: I don't think this is necessary any more, and it helpe isDeadBinder in Simplify.mkDupableAlt \begin{code} -occAnalAlt env case_bndr (con, bndrs, rhs) +occAnalAlt :: OccEnv + -> CoreBndr + -> CoreAlt + -> (UsageDetails, Alt IdWithOccInfo) +occAnalAlt env _case_bndr (con, bndrs, rhs) = case occAnal env rhs of { (rhs_usage, rhs') -> let (final_usage, tagged_bndrs) = tagBinders rhs_usage bndrs @@ -818,9 +935,13 @@ type CtxtTy = [Bool] initOccEnv :: OccEnv initOccEnv = OccEnv OccRhs [] +vanillaCtxt :: OccEnv vanillaCtxt = OccEnv OccVanilla [] + +rhsCtxt :: OccEnv rhsCtxt = OccEnv OccRhs [] +isRhsEnv :: OccEnv -> Bool isRhsEnv (OccEnv OccRhs _) = True isRhsEnv (OccEnv OccVanilla _) = False @@ -837,10 +958,10 @@ oneShotGroup :: OccEnv -> [CoreBndr] -> [CoreBndr] -- 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 encl ctxt) bndrs +oneShotGroup (OccEnv _encl ctxt) bndrs = go ctxt bndrs [] where - go ctxt [] rev_bndrs = reverse rev_bndrs + go _ [] rev_bndrs = reverse rev_bndrs go (lin_ctxt:ctxt) (bndr:bndrs) rev_bndrs | isId bndr = go ctxt bndrs (bndr':rev_bndrs) @@ -850,6 +971,7 @@ oneShotGroup (OccEnv encl ctxt) bndrs go ctxt (bndr:bndrs) rev_bndrs = go ctxt bndrs (bndr:rev_bndrs) +addAppCtxt :: OccEnv -> [Arg CoreBndr] -> OccEnv addAppCtxt (OccEnv encl ctxt) args = OccEnv encl (replicate (valArgCount args) True ++ ctxt) \end{code} @@ -877,6 +999,7 @@ addOneOcc usage id info = plusVarEnv_C addOccInfo usage (unitVarEnv id info) -- ToDo: make this more efficient +emptyDetails :: UsageDetails emptyDetails = (emptyVarEnv :: UsageDetails) usedIn :: Id -> UsageDetails -> Bool @@ -913,7 +1036,7 @@ setBinderOcc usage bndr | isTyVar bndr = bndr | isExportedId bndr = case idOccInfo bndr of NoOccInfo -> bndr - other -> setIdOccInfo bndr NoOccInfo + _ -> 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" @@ -932,14 +1055,14 @@ setBinderOcc usage bndr \begin{code} mkOneOcc :: OccEnv -> Id -> InterestingCxt -> UsageDetails -mkOneOcc env id int_cxt +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 +markMany _ = NoOccInfo markInsideSCC occ = markMany occ @@ -950,17 +1073,17 @@ addOccInfo, orOccInfo :: OccInfo -> OccInfo -> OccInfo addOccInfo IAmDead info2 = info2 addOccInfo info1 IAmDead = info1 -addOccInfo info1 info2 = NoOccInfo +addOccInfo _ _ = 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) +orOccInfo (OneOcc in_lam1 _ int_cxt1) + (OneOcc in_lam2 _ int_cxt2) = OneOcc (in_lam1 || in_lam2) False -- False, because it occurs in both branches (int_cxt1 && int_cxt2) -orOccInfo info1 info2 = NoOccInfo +orOccInfo _ _ = NoOccInfo \end{code}