X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fspecialise%2FSpecConstr.lhs;h=74944da983bd1021eaee75e78bb68dfc84983f39;hb=df85c4b4a403c1e17d3f79fe91109ffbe6ba60b7;hp=0d7589548482dd81125ce329d43b410beccf1823;hpb=12e6a9a58473f8b24e831c2171bf62d256da8a85;p=ghc-hetmet.git diff --git a/ghc/compiler/specialise/SpecConstr.lhs b/ghc/compiler/specialise/SpecConstr.lhs index 0d75895..74944da 100644 --- a/ghc/compiler/specialise/SpecConstr.lhs +++ b/ghc/compiler/specialise/SpecConstr.lhs @@ -12,26 +12,32 @@ module SpecConstr( import CoreSyn import CoreLint ( showPass, endPass ) -import CoreUtils ( exprType, exprIsConApp_maybe, eqExpr ) +import CoreUtils ( exprType, tcEqExpr, mkPiTypes ) import CoreFVs ( exprsFreeVars ) -import DataCon ( isExistentialDataCon ) -import PprCore ( pprCoreRules ) -import Id ( Id, idName, idSpecialisation, mkUserLocal, mkSysLocal ) +import CoreSubst ( Subst, mkSubst, substExpr ) +import CoreTidy ( tidyRules ) +import PprCore ( pprRules ) +import WwLib ( mkWorkerArgs ) +import DataCon ( dataConRepArity, isVanillaDataCon ) +import Type ( tyConAppArgs, tyVarsOfTypes ) +import Unify ( coreRefineTys ) +import Id ( Id, idName, idType, isDataConWorkId_maybe, + mkUserLocal, mkSysLocal ) import Var ( Var ) import VarEnv import VarSet import Name ( nameOccName, nameSrcLoc ) -import Rules ( addIdSpecialisations ) +import Rules ( addIdSpecialisations, mkLocalRule, rulesOfBinds ) import OccName ( mkSpecOcc ) import ErrUtils ( dumpIfSet_dyn ) -import CmdLineOpts ( DynFlags, DynFlag(..) ) -import Outputable - +import DynFlags ( DynFlags, DynFlag(..) ) +import BasicTypes ( Activation(..) ) import Maybes ( orElse ) -import Util ( mapAccumL ) +import Util ( mapAccumL, lengthAtLeast, notNull ) import List ( nubBy, partition ) import UniqSupply import Outputable +import FastString \end{code} ----------------------------------------------------- @@ -176,7 +182,7 @@ specConstrProgram dflags us binds endPass dflags "SpecConstr" Opt_D_dump_spec binds' dumpIfSet_dyn dflags Opt_D_dump_rules "Top-level specialisations" - (vcat (map dump_specs (concat (map bindersOf binds')))) + (pprRules (tidyRules emptyTidyEnv (rulesOfBinds binds'))) return binds' where @@ -184,41 +190,136 @@ specConstrProgram dflags us binds go env (bind:binds) = scBind env bind `thenUs` \ (env', _, bind') -> go env' binds `thenUs` \ binds' -> returnUs (bind' : binds') - -dump_specs var = pprCoreRules var (idSpecialisation var) \end{code} %************************************************************************ %* * -\subsection{Environments and such} +\subsection{Environment: goes downwards} %* * %************************************************************************ \begin{code} -type ScEnv = VarEnv HowBound +data ScEnv = SCE { scope :: VarEnv HowBound, + -- Binds all non-top-level variables in scope -emptyScEnv = emptyVarEnv + cons :: ConstrEnv + } + +type ConstrEnv = IdEnv ConValue +data ConValue = CV AltCon [CoreArg] + -- Variables known to be bound to a constructor + -- in a particular case alternative + +refineConstrEnv :: Subst -> ConstrEnv -> ConstrEnv +-- The substitution is a type substitution only +refineConstrEnv subst env = mapVarEnv refine_con_value env + where + refine_con_value (CV con args) = CV con (map (substExpr subst) args) + +emptyScEnv = SCE { scope = emptyVarEnv, cons = emptyVarEnv } data HowBound = RecFun -- These are the recursive functions for which -- we seek interesting call patterns + | RecArg -- These are those functions' arguments; we are -- interested to see if those arguments are scrutinised + | Other -- We track all others so we know what's in scope + -- This is used in spec_one to check what needs to be + -- passed as a parameter and what is in scope at the + -- function definition site + +instance Outputable HowBound where + ppr RecFun = text "RecFun" + ppr RecArg = text "RecArg" + ppr Other = text "Other" + +lookupScopeEnv env v = lookupVarEnv (scope env) v + +extendBndrs env bndrs = env { scope = extendVarEnvList (scope env) [(b,Other) | b <- bndrs] } +extendBndr env bndr = env { scope = extendVarEnv (scope env) bndr Other } + + -- When we encounter + -- case scrut of b + -- C x y -> ... + -- we want to bind b, and perhaps scrut too, to (C x y) +extendCaseBndrs :: ScEnv -> Id -> CoreExpr -> AltCon -> [Var] -> ScEnv +extendCaseBndrs env case_bndr scrut DEFAULT alt_bndrs + = extendBndrs env (case_bndr : alt_bndrs) + +extendCaseBndrs env case_bndr scrut con@(LitAlt lit) alt_bndrs + = ASSERT( null alt_bndrs ) extendAlt env case_bndr scrut (CV con []) [] + +extendCaseBndrs env case_bndr scrut con@(DataAlt data_con) alt_bndrs + | isVanillaDataCon data_con + = extendAlt env case_bndr scrut (CV con vanilla_args) alt_bndrs + + | otherwise -- GADT + = extendAlt env1 case_bndr scrut (CV con gadt_args) alt_bndrs + where + vanilla_args = map Type (tyConAppArgs (idType case_bndr)) ++ + map varToCoreExpr alt_bndrs + + gadt_args = map (substExpr subst . varToCoreExpr) alt_bndrs + + (alt_tvs, _) = span isTyVar alt_bndrs + Just (tv_subst, is_local) = coreRefineTys data_con alt_tvs (idType case_bndr) + subst = mkSubst in_scope tv_subst emptyVarEnv -- No Id substitition + in_scope = mkInScopeSet (tyVarsOfTypes (varEnvElts tv_subst)) + + env1 | is_local = env + | otherwise = env { cons = refineConstrEnv subst (cons env) } + + + +extendAlt :: ScEnv -> Id -> CoreExpr -> ConValue -> [Var] -> ScEnv +extendAlt env case_bndr scrut val alt_bndrs + = let + env1 = SCE { scope = extendVarEnvList (scope env) [(b,Other) | b <- case_bndr : alt_bndrs], + cons = extendVarEnv (cons env) case_bndr val } + in + case scrut of + Var v -> -- Bind the scrutinee in the ConstrEnv if it's a variable + -- Also forget if the scrutinee is a RecArg, because we're + -- now in the branch of a case, and we don't want to + -- record a non-scrutinee use of v if we have + -- case v of { (a,b) -> ...(f v)... } + SCE { scope = extendVarEnv (scope env1) v Other, + cons = extendVarEnv (cons env1) v val } + other -> env1 + + -- When we encounter a recursive function binding + -- f = \x y -> ... + -- we want to extend the scope env with bindings + -- that record that f is a RecFn and x,y are RecArgs +extendRecBndr env fn bndrs + = env { scope = scope env `extendVarEnvList` + ((fn,RecFun): [(bndr,RecArg) | bndr <- bndrs]) } +\end{code} -extendBndrs env bndrs = extendVarEnvList env [(b,Other) | b <- bndrs] -extendBndr env bndr = extendVarEnv env bndr Other +%************************************************************************ +%* * +\subsection{Usage information: flows upwards} +%* * +%************************************************************************ + +\begin{code} data ScUsage = SCU { - calls :: !(IdEnv ([[CoreArg]])), -- Calls - -- The functions are a subset of the - -- RecFuns in the ScEnv + calls :: !(IdEnv ([Call])), -- Calls + -- The functions are a subset of the + -- RecFuns in the ScEnv occs :: !(IdEnv ArgOcc) -- Information on argument occurrences } -- The variables are a subset of the -- RecArg in the ScEnv +type Call = (ConstrEnv, [CoreArg]) + -- The arguments of the call, together with the + -- env giving the constructor bindings at the call site + nullUsage = SCU { calls = emptyVarEnv, occs = emptyVarEnv } combineUsage u1 u2 = SCU { calls = plusVarEnv_C (++) (calls u1) (calls u2), @@ -248,6 +349,9 @@ combineOcc _ _ = Both %* * %************************************************************************ +The main recursive function gathers up usage information, and +creates specialised versions of functions. + \begin{code} scExpr :: ScEnv -> CoreExpr -> UniqSM (ScUsage, CoreExpr) -- The unique supply is needed when we invent @@ -261,19 +365,19 @@ scExpr env (Note n e) = scExpr env e `thenUs` \ (usg,e') -> scExpr env (Lam b e) = scExpr (extendBndr env b) e `thenUs` \ (usg,e') -> returnUs (usg, Lam b e') -scExpr env (Case scrut b alts) +scExpr env (Case scrut b ty alts) = sc_scrut scrut `thenUs` \ (scrut_usg, scrut') -> mapAndUnzipUs sc_alt alts `thenUs` \ (alts_usgs, alts') -> returnUs (combineUsages alts_usgs `combineUsage` scrut_usg, - Case scrut' b alts') + Case scrut' b ty alts') where sc_scrut e@(Var v) = returnUs (varUsage env v CaseScrut, e) sc_scrut e = scExpr env e - sc_alt (con,bs,rhs) = scExpr env rhs `thenUs` \ (usg,rhs') -> + sc_alt (con,bs,rhs) = scExpr env1 rhs `thenUs` \ (usg,rhs') -> returnUs (usg, (con,bs,rhs')) where - env1 = extendBndrs env (b:bs) + env1 = extendCaseBndrs env b scrut con bs scExpr env (Let bind body) = scBind env bind `thenUs` \ (env', bind_usg, bind') -> @@ -288,8 +392,9 @@ scExpr env e@(App _ _) let arg_usg = combineUsages usgs fn_usg | Var f <- fn, - Just RecFun <- lookupVarEnv env f - = SCU { calls = unitVarEnv f [args], occs = emptyVarEnv } + Just RecFun <- lookupScopeEnv env f + = SCU { calls = unitVarEnv f [(cons env, args)], + occs = emptyVarEnv } | otherwise = nullUsage in @@ -300,16 +405,21 @@ scExpr env e@(App _ _) ---------------------- scBind :: ScEnv -> CoreBind -> UniqSM (ScEnv, ScUsage, CoreBind) scBind env (Rec [(fn,rhs)]) - | not (null val_bndrs) - = scExpr env' body `thenUs` \ (usg@(SCU { calls = calls, occs = occs }), body') -> + | notNull val_bndrs + = scExpr env_fn_body body `thenUs` \ (usg, body') -> + let + SCU { calls = calls, occs = occs } = usg + in specialise env fn bndrs body usg `thenUs` \ (rules, spec_prs) -> - returnUs (extendBndrs env bndrs, + returnUs (extendBndr env fn, -- For the body of the letrec, just + -- extend the env with Other to record + -- that it's in scope; no funny RecFun business SCU { calls = calls `delVarEnv` fn, occs = occs `delVarEnvList` val_bndrs}, Rec ((fn `addIdSpecialisations` rules, mkLams bndrs body') : spec_prs)) where (bndrs,body) = collectBinders rhs val_bndrs = filter isId bndrs - env' = env `extendVarEnvList` ((fn,RecFun): [(bndr,RecArg) | bndr <- bndrs]) + env_fn_body = extendRecBndr env fn bndrs scBind env (Rec prs) = mapAndUnzipUs do_one prs `thenUs` \ (usgs, prs') -> @@ -324,8 +434,9 @@ scBind env (NonRec bndr rhs) ---------------------- varUsage env v use - | Just RecArg <- lookupVarEnv env v = SCU { calls = emptyVarEnv, occs = unitVarEnv v use } - | otherwise = nullUsage + | Just RecArg <- lookupScopeEnv env v = SCU { calls = emptyVarEnv, + occs = unitVarEnv v use } + | otherwise = nullUsage \end{code} @@ -350,32 +461,29 @@ specialise env fn bndrs body (SCU {calls=calls, occs=occs}) good_calls :: [[CoreArg]] good_calls = [ pats - | call_args <- all_calls, - length call_args >= n_bndrs, -- App is saturated + | (con_env, call_args) <- all_calls, + call_args `lengthAtLeast` n_bndrs, -- App is saturated let call = (bndrs `zip` call_args), - any (good_arg occs) call, - let (_, pats) = argsToPats us call_args + any (good_arg con_env occs) call, -- At least one arg is a constr app + let (_, pats) = argsToPats con_env us call_args ] in - pprTrace "specialise" (ppr all_calls $$ ppr good_calls) $ mapAndUnzipUs (spec_one env fn (mkLams bndrs body)) (nubBy same_call good_calls `zip` [1..]) where n_bndrs = length bndrs - same_call as1 as2 = and (zipWith eqExpr as1 as2) + same_call as1 as2 = and (zipWith tcEqExpr as1 as2) --------------------- -good_arg :: IdEnv ArgOcc -> (CoreBndr, CoreArg) -> Bool -good_arg arg_occs (bndr, arg) - = case exprIsConApp_maybe arg of -- exprIsConApp_maybe looks - Just (dc,_) -> not (isExistentialDataCon dc) -- through unfoldings - && bndr_usg_ok arg_occs bndr arg +good_arg :: ConstrEnv -> IdEnv ArgOcc -> (CoreBndr, CoreArg) -> Bool +good_arg con_env arg_occs (bndr, arg) + = case is_con_app_maybe con_env arg of + Just _ -> bndr_usg_ok arg_occs bndr arg other -> False bndr_usg_ok :: IdEnv ArgOcc -> Var -> CoreArg -> Bool bndr_usg_ok arg_occs bndr arg - = pprTrace "bndr_ok" (ppr bndr <+> ppr (lookupVarEnv arg_occs bndr)) $ - case lookupVarEnv arg_occs bndr of + = case lookupVarEnv arg_occs bndr of Just CaseScrut -> True -- Used only by case scrutiny Just Both -> case arg of -- Used by case and elsewhere App _ _ -> True -- so the arg should be an explicit con app @@ -384,71 +492,134 @@ bndr_usg_ok arg_occs bndr arg --------------------- -argsToPats :: UniqSupply -> [CoreArg] -> (UniqSupply, [CoreExpr]) -argsToPats us args = mapAccumL argToPat us args - -argToPat :: UniqSupply -> CoreArg -> (UniqSupply, CoreExpr) --- C a (D (f x) (g y)) ==> C p1 (D p2 p3) -argToPat us (Type ty) - = (us, Type ty) - -argToPat us arg - | Just (dc,args) <- exprIsConApp_maybe arg - = let - (us',args') = argsToPats us args - in - (us', mkConApp dc args') - -argToPat us (Var v) -- Don't uniqify existing vars, - = (us, Var v) -- so that we can spot when we pass them twice - -argToPat us arg - = (us1, Var (mkSysLocal SLIT("sc") (uniqFromSupply us2) (exprType arg))) - where - (us1,us2) = splitUniqSupply us - ---------------------- spec_one :: ScEnv -> Id -- Function -> CoreExpr -- Rhs of the original function -> ([CoreArg], Int) -> UniqSM (CoreRule, (Id,CoreExpr)) -- Rule and binding +-- spec_one creates a specialised copy of the function, together +-- with a rule for using it. I'm very proud of how short this +-- function is, considering what it does :-). + {- Example In-scope: a, x::a - f = /\b \y::[(a,b)] -> ....f (b,c) ((:) (a,(b,c)) v (h v))... - [c is presumably bound by the (...) part] + f = /\b \y::[(a,b)] -> ....f (b,c) ((:) (a,(b,c)) (x,v) (h w))... + [c::*, v::(b,c) are presumably bound by the (...) part] ==> - f_spec = /\ b c \ v::(a,(b,c)) -> - (...entire RHS of f...) (b,c) ((:) (a,(b,c)) v (h v)) + f_spec = /\ b c \ v::(b,c) hw::[(a,(b,c))] -> + (...entire RHS of f...) (b,c) ((:) (a,(b,c)) (x,v) hw) - RULE: forall b c, - y::[(a,(b,c))], - v::(a,(b,c)), - h::(a,(b,c))->[(a,(b,c))] . + RULE: forall b::* c::*, -- Note, *not* forall a, x + v::(b,c), + hw::[(a,(b,c))] . - f (b,c) ((:) (a,(b,c)) v (h v)) = f_spec b c v + f (b,c) ((:) (a,(b,c)) (x,v) hw) = f_spec b c v hw -} -spec_one env fn rhs (pats, n) - = getUniqueUs `thenUs` \ spec_uniq -> +spec_one env fn rhs (pats, rule_number) + = getUniqueUs `thenUs` \ spec_uniq -> let fn_name = idName fn fn_loc = nameSrcLoc fn_name spec_occ = mkSpecOcc (nameOccName fn_name) pat_fvs = varSetElems (exprsFreeVars pats) vars_to_bind = filter not_avail pat_fvs - not_avail v = not (v `elemVarEnv` env) - -- Put the type variables first just for tidiness + not_avail v = not (v `elemVarEnv` scope env) + -- Put the type variables first; the type of a term + -- variable may mention a type variable (tvs, ids) = partition isTyVar vars_to_bind bndrs = tvs ++ ids + spec_body = mkApps rhs pats + body_ty = exprType spec_body - rule_name = _PK_ ("SC:" ++ showSDoc (ppr fn <> int n)) - spec_rhs = mkLams bndrs (mkApps rhs pats) - spec_id = mkUserLocal spec_occ spec_uniq (exprType spec_rhs) fn_loc - rule = Rule rule_name pat_fvs pats (mkVarApps (Var spec_id) bndrs) + (spec_lam_args, spec_call_args) = mkWorkerArgs bndrs body_ty + -- Usual w/w hack to avoid generating + -- a spec_rhs of unlifted type and no args + + rule_name = mkFastString ("SC:" ++ showSDoc (ppr fn <> int rule_number)) + spec_rhs = mkLams spec_lam_args spec_body + spec_id = mkUserLocal spec_occ spec_uniq (mkPiTypes spec_lam_args body_ty) fn_loc + rule_rhs = mkVarApps (Var spec_id) spec_call_args + rule = mkLocalRule rule_name specConstrActivation fn_name bndrs pats rule_rhs in returnUs (rule, (spec_id, spec_rhs)) + +-- In which phase should the specialise-constructor rules be active? +-- Originally I made them always-active, but Manuel found that +-- this defeated some clever user-written rules. So Plan B +-- is to make them active only in Phase 0; after all, currently, +-- the specConstr transformation is only run after the simplifier +-- has reached Phase 0. In general one would want it to be +-- flag-controllable, but for now I'm leaving it baked in +-- [SLPJ Oct 01] +specConstrActivation :: Activation +specConstrActivation = ActiveAfter 0 -- Baked in; see comments above +\end{code} + +%************************************************************************ +%* * +\subsection{Argument analysis} +%* * +%************************************************************************ + +This code deals with analysing call-site arguments to see whether +they are constructor applications. + +\begin{code} + -- argToPat takes an actual argument, and returns an abstracted + -- version, consisting of just the "constructor skeleton" of the + -- argument, with non-constructor sub-expression replaced by new + -- placeholder variables. For example: + -- C a (D (f x) (g y)) ==> C p1 (D p2 p3) + +argToPat :: ConstrEnv -> UniqSupply -> CoreArg -> (UniqSupply, CoreExpr) +argToPat env us (Type ty) + = (us, Type ty) + +argToPat env us arg + | Just (CV dc args) <- is_con_app_maybe env arg + = let + (us',args') = argsToPats env us args + in + (us', mk_con_app dc args') + +argToPat env us (Var v) -- Don't uniqify existing vars, + = (us, Var v) -- so that we can spot when we pass them twice + +argToPat env us arg + = (us1, Var (mkSysLocal FSLIT("sc") (uniqFromSupply us2) (exprType arg))) + where + (us1,us2) = splitUniqSupply us + +argsToPats :: ConstrEnv -> UniqSupply -> [CoreArg] -> (UniqSupply, [CoreExpr]) +argsToPats env us args = mapAccumL (argToPat env) us args +\end{code} + + +\begin{code} +is_con_app_maybe :: ConstrEnv -> CoreExpr -> Maybe ConValue +is_con_app_maybe env (Var v) + = lookupVarEnv env v + -- You might think we could look in the idUnfolding here + -- but that doesn't take account of which branch of a + -- case we are in, which is the whole point + +is_con_app_maybe env (Lit lit) + = Just (CV (LitAlt lit) []) + +is_con_app_maybe env expr + = case collectArgs expr of + (Var fun, args) | Just con <- isDataConWorkId_maybe fun, + args `lengthAtLeast` dataConRepArity con + -- Might be > because the arity excludes type args + -> Just (CV (DataAlt con) args) + + other -> Nothing + +mk_con_app :: AltCon -> [CoreArg] -> CoreExpr +mk_con_app (LitAlt lit) [] = Lit lit +mk_con_app (DataAlt con) args = mkConApp con args \end{code}