X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=e65da3cf9ba13e161f746f46ea9174e62929e835;hp=691ac841a295c8db495d11509041387b4850acf8;hb=90ce88a0a9b5611416e592a6ff96781ba884975f;hpb=362b461d2149160d36840342add162bf84d6212d diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index 691ac84..e65da3c 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -10,13 +10,6 @@ in that the @Rec@/@NonRec@/etc structure is thrown away (whereas at lower levels it is preserved with @let@/@letrec@s). \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 DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsCoercion, AutoScc(..) @@ -30,19 +23,21 @@ import {-# SOURCE #-} Match( matchWrapper ) import DsMonad import DsGRHSs import DsUtils +import OccurAnal import HsSyn -- lots of things import CoreSyn -- lots of things +import MkCore import CoreUtils import CoreFVs -import TcHsSyn ( mkArbitraryType ) -- Mis-placed? +import TcHsSyn ( mkArbitraryType ) -- Mis-placed? import TcType -import OccurAnal import CostCentre import Module import Id -import Var ( TyVar ) +import MkId ( seqId ) +import Var ( Var, TyVar ) import VarSet import Rules import VarEnv @@ -53,7 +48,8 @@ import Maybes import Bag import BasicTypes hiding ( TopLevel ) import FastString -import Util ( mapSnd ) +import StaticFlags ( opt_DsMultiTyVar ) +import Util ( mapSnd, mapAndUnzip, lengthExceeds ) import Control.Monad import Data.List @@ -90,7 +86,7 @@ dsHsBind :: AutoScc -> HsBind Id -> DsM [(Id,CoreExpr)] -- Result -dsHsBind auto_scc rest (VarBind var expr) = do +dsHsBind _ rest (VarBind var expr) = do core_expr <- dsLExpr expr -- Dictionary bindings are always VarMonoBinds, so @@ -98,57 +94,139 @@ dsHsBind auto_scc rest (VarBind var expr) = do core_expr' <- addDictScc var core_expr return ((var, core_expr') : rest) -dsHsBind auto_scc rest (FunBind { fun_id = L _ fun, fun_matches = matches, +dsHsBind _ rest (FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn, fun_tick = tick, fun_infix = inf }) = do (args, body) <- matchWrapper (FunRhs (idName fun) inf) matches body' <- mkOptTickBox tick body rhs <- dsCoercion co_fn (return (mkLams args body')) return ((fun,rhs) : rest) -dsHsBind auto_scc rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) = do +dsHsBind _ rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) = do body_expr <- dsGuarded grhss ty sel_binds <- mkSelectorBinds pat body_expr return (sel_binds ++ rest) --- Note [Rules and inlining] --- Common special case: no type or dictionary abstraction --- This is a bit less trivial than you might suppose --- The naive way woudl be to desguar to something like --- f_lcl = ...f_lcl... -- The "binds" from AbsBinds --- M.f = f_lcl -- Generated from "exports" --- But we don't want that, because if M.f isn't exported, --- it'll be inlined unconditionally at every call site (its rhs is --- trivial). That would be ok unless it has RULES, which would --- thereby be completely lost. Bad, bad, bad. --- --- Instead we want to generate --- M.f = ...f_lcl... --- f_lcl = M.f --- Now all is cool. The RULES are attached to M.f (by SimplCore), --- and f_lcl is rapidly inlined away. --- --- This does not happen in the same way to polymorphic binds, --- because they desugar to --- M.f = /\a. let f_lcl = ...f_lcl... in f_lcl --- Although I'm a bit worried about whether full laziness might --- float the f_lcl binding out and then inline M.f at its call site +{- Note [Rules and inlining] + ~~~~~~~~~~~~~~~~~~~~~~~~~ + Common special case: no type or dictionary abstraction + This is a bit less trivial than you might suppose + The naive way woudl be to desguar to something like + f_lcl = ...f_lcl... -- The "binds" from AbsBinds + M.f = f_lcl -- Generated from "exports" + But we don't want that, because if M.f isn't exported, + it'll be inlined unconditionally at every call site (its rhs is + trivial). That would be ok unless it has RULES, which would + thereby be completely lost. Bad, bad, bad. + + Instead we want to generate + M.f = ...f_lcl... + f_lcl = M.f + Now all is cool. The RULES are attached to M.f (by SimplCore), + and f_lcl is rapidly inlined away. + + This does not happen in the same way to polymorphic binds, + because they desugar to + M.f = /\a. let f_lcl = ...f_lcl... in f_lcl + Although I'm a bit worried about whether full laziness might + float the f_lcl binding out and then inline M.f at its call site -} dsHsBind auto_scc rest (AbsBinds [] [] exports binds) = do { core_prs <- ds_lhs_binds NoSccs binds ; let env = mkABEnv exports - do_one (lcl_id, rhs) | Just (gbl_id, prags) <- lookupVarEnv env lcl_id + do_one (lcl_id, rhs) | Just (_, gbl_id, _, prags) <- lookupVarEnv env lcl_id = addInlinePrags prags gbl_id $ addAutoScc auto_scc gbl_id rhs | otherwise = (lcl_id, rhs) locals' = [(lcl_id, Var gbl_id) | (_, gbl_id, lcl_id, _) <- exports] + -- Note [Rules and inlining] ; return (map do_one core_prs ++ locals' ++ rest) } -- No Rec needed here (contrast the other AbsBinds cases) -- because we can rely on the enclosing dsBind to wrap in Rec + +{- Note [Abstracting over tyvars only] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + When abstracting over type variable only (not dictionaries), we don't really need to + built a tuple and select from it, as we do in the general case. Instead we can take + + AbsBinds [a,b] [ ([a,b], fg, fl, _), + ([b], gg, gl, _) ] + { fl = e1 + gl = e2 + h = e3 } + + and desugar it to + + fg = /\ab. let B in e1 + gg = /\b. let a = () in let B in S(e2) + h = /\ab. let B in e3 + + where B is the *non-recursive* binding + fl = fg a b + gl = gg b + h = h a b -- See (b); note shadowing! + + Notice (a) g has a different number of type variables to f, so we must + use the mkArbitraryType thing to fill in the gaps. + We use a type-let to do that. + + (b) The local variable h isn't in the exports, and rather than + clone a fresh copy we simply replace h by (h a b), where + the two h's have different types! Shadowing happens here, + which looks confusing but works fine. + + (c) The result is *still* quadratic-sized if there are a lot of + small bindings. So if there are more than some small + number (10), we filter the binding set B by the free + variables of the particular RHS. Tiresome. + + Why got to this trouble? It's a common case, and it removes the + quadratic-sized tuple desugaring. Less clutter, hopefullly faster + compilation, especially in a case where there are a *lot* of + bindings. +-} + + +dsHsBind auto_scc rest (AbsBinds tyvars [] exports binds) + | opt_DsMultiTyVar -- This (static) debug flag just lets us + -- switch on and off this optimisation to + -- see if it has any impact; it is on by default + = -- Note [Abstracting over tyvars only] + do { core_prs <- ds_lhs_binds NoSccs binds + ; arby_env <- mkArbitraryTypeEnv tyvars exports + ; let (lg_binds, core_prs') = mapAndUnzip do_one core_prs + bndrs = mkVarSet (map fst core_prs) + + add_lets | core_prs `lengthExceeds` 10 = add_some + | otherwise = mkLets lg_binds + add_some rhs = mkLets [ NonRec b r | NonRec b r <- lg_binds + , b `elemVarSet` fvs] rhs + where + fvs = exprSomeFreeVars (`elemVarSet` bndrs) rhs + + env = mkABEnv exports + + do_one (lcl_id, rhs) + | Just (id_tvs, gbl_id, _, prags) <- lookupVarEnv env lcl_id + = (NonRec lcl_id (mkTyApps (Var gbl_id) (mkTyVarTys id_tvs)), + addInlinePrags prags gbl_id $ + addAutoScc auto_scc gbl_id $ + mkLams id_tvs $ + mkLets [ NonRec tv (Type (lookupVarEnv_NF arby_env tv)) + | tv <- tyvars, not (tv `elem` id_tvs)] $ + add_lets rhs) + | otherwise + = (NonRec lcl_id (mkTyApps (Var non_exp_gbl_id) (mkTyVarTys tyvars)), + (non_exp_gbl_id, mkLams tyvars (add_lets rhs))) + where + non_exp_gbl_id = setIdType lcl_id (mkForAllTys tyvars (idType lcl_id)) + + ; return (core_prs' ++ rest) } + -- Another common case: one exported variable -- Non-recursive bindings come through this way dsHsBind auto_scc rest - (AbsBinds all_tyvars dicts exports@[(tyvars, global, local, prags)] binds) + (AbsBinds all_tyvars dicts [(tyvars, global, local, prags)] binds) = ASSERT( all (`elem` tyvars) all_tyvars ) do core_prs <- ds_lhs_binds NoSccs binds let @@ -168,7 +246,7 @@ dsHsBind auto_scc rest dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) = do { core_prs <- ds_lhs_binds NoSccs binds ; let env = mkABEnv exports - do_one (lcl_id,rhs) | Just (gbl_id, prags) <- lookupVarEnv env lcl_id + do_one (lcl_id,rhs) | Just (_, gbl_id, _, prags) <- lookupVarEnv env lcl_id = addInlinePrags prags lcl_id $ addAutoScc auto_scc gbl_id rhs | otherwise = (lcl_id,rhs) @@ -213,11 +291,10 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) ; return ((poly_tup_id, poly_tup_expr) : (concat export_binds_s ++ rest)) } -mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> VarEnv (Id, [LPrag]) +mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> VarEnv ([TyVar], Id, Id, [LPrag]) -- Takes the exports of a AbsBinds, and returns a mapping --- lcl_id -> (gbl_id, prags) -mkABEnv exports = mkVarEnv [ (lcl_id, (gbl_id, prags)) - | (_, gbl_id, lcl_id, prags) <- exports] +-- lcl_id -> (tyvars, gbl_id, lcl_id, prags) +mkABEnv exports = mkVarEnv [ (lcl_id, export) | export@(_, _, lcl_id, _) <- exports] dsSpec :: [TyVar] -> [DictId] -> [TyVar] @@ -249,7 +326,7 @@ dsSpec :: [TyVar] -> [DictId] -> [TyVar] -- -- It is *possible* that 'es' does not mention all of the dictionaries 'ds' -- (a bit silly, because then the -dsSpec all_tvs dicts tvs poly_id mono_id mono_bind (L _ (InlinePrag {})) +dsSpec _ _ _ _ _ _ (L _ (InlinePrag {})) = return Nothing dsSpec all_tvs dicts tvs poly_id mono_id mono_bind @@ -258,23 +335,16 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind do { let poly_name = idName poly_id ; spec_name <- newLocalName poly_name ; ds_spec_expr <- dsExpr spec_expr - ; let (bndrs, body) = collectBinders (occurAnalyseExpr ds_spec_expr) - -- The occurrence-analysis does two things - -- (a) identifies unused binders: Note [Unused spec binders] - -- (b) sorts dict bindings into NonRecs - -- so they can be inlined by decomposeRuleLhs - mb_lhs = decomposeRuleLhs body + ; case (decomposeRuleLhs ds_spec_expr) of { + Nothing -> do { warnDs decomp_msg; return Nothing } ; - -- Check for dead binders: Note [Unused spec binders] - ; case filter isDeadBinder bndrs of { - bs | not (null bs) -> do { warnDs (dead_msg bs); return Nothing } - | otherwise -> + Just (bndrs, _fn, args) -> - case mb_lhs of - Nothing -> do { warnDs decomp_msg; return Nothing } + -- Check for dead binders: Note [Unused spec binders] + case filter isDeadBinder bndrs of { + bs | not (null bs) -> do { warnDs (dead_msg bs); return Nothing } + | otherwise -> do - Just (var, args) -> do - { f_body <- fix_up (Let mono_bind (Var mono_id)) ; let local_poly = setIdNotExported poly_id @@ -284,7 +354,9 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind spec_rhs = Let (NonRec local_poly poly_f_body) ds_spec_expr poly_f_body = mkLams (tvs ++ dicts) f_body - extra_dict_bndrs = filter isDictId (varSetElems (exprFreeVars ds_spec_expr)) + extra_dict_bndrs = [localiseId d -- See Note [Constant rule dicts] + | d <- varSetElems (exprFreeVars ds_spec_expr) + , isDictId d] -- Note [Const rule dicts] rule = mkLocalRule (mkFastString ("SPEC " ++ showSDoc (ppr poly_name))) @@ -292,7 +364,7 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind (extra_dict_bndrs ++ bndrs) args (mkVarApps (Var spec_id) bndrs) ; return (Just (addInlineInfo inl spec_id spec_rhs, rule)) - } } } + } } } } where -- Bind to Any any of all_ptvs that aren't -- relevant for this particular function @@ -302,15 +374,34 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind void_tvs = all_tvs \\ tvs - dead_msg bs = vcat [ sep [ptext SLIT("Useless constraint") <> plural bs - <+> ptext SLIT("in specialied type:"), + dead_msg bs = vcat [ sep [ptext (sLit "Useless constraint") <> plural bs + <+> ptext (sLit "in specialied type:"), nest 2 (pprTheta (map get_pred bs))] - , ptext SLIT("SPECIALISE pragma ignored")] + , ptext (sLit "SPECIALISE pragma ignored")] get_pred b = ASSERT( isId b ) expectJust "dsSpec" (tcSplitPredTy_maybe (idType b)) - decomp_msg = hang (ptext SLIT("Specialisation too complicated to desugar; ignored")) + decomp_msg = hang (ptext (sLit "Specialisation too complicated to desugar; ignored")) 2 (ppr spec_expr) + + +mkArbitraryTypeEnv :: [TyVar] -> [([TyVar], a, b, c)] -> DsM (TyVarEnv Type) +-- If any of the tyvars is missing from any of the lists in +-- the second arg, return a binding in the result +mkArbitraryTypeEnv tyvars exports + = go emptyVarEnv exports + where + go env [] = return env + go env ((ltvs, _, _, _) : exports) + = do { env' <- foldlM extend env [tv | tv <- tyvars + , not (tv `elem` ltvs) + , not (tv `elemVarEnv` env)] + ; go env' exports } + + extend env tv = do { ty <- dsMkArbitraryType tv + ; return (extendVarEnv env tv ty) } + +dsMkArbitraryType :: TcTyVar -> DsM Type dsMkArbitraryType tv = mkArbitraryType warn tv where warn span msg = putSrcSpanDs span (warnDs msg) @@ -350,6 +441,9 @@ And from that we want the rule RULE forall dInt. f Int dInt = f_spec f_spec = let f = in f Int dInt +But be careful! That dInt might be GHC.Base.$fOrdInt, which is an External +Name, and you can't bind them in a lambda or forall without getting things +confused. Hence the use of 'localiseId' to make it Internal. %************************************************************************ @@ -359,31 +453,54 @@ And from that we want the rule %************************************************************************ \begin{code} -decomposeRuleLhs :: CoreExpr -> Maybe (Id, [CoreExpr]) +decomposeRuleLhs :: CoreExpr -> Maybe ([Var], Id, [CoreExpr]) +-- Take apart the LHS of a RULE. It's suuposed to look like +-- /\a. f a Int dOrdInt +-- or /\a.\d:Ord a. let { dl::Ord [a] = dOrdList a d } in f [a] dl +-- That is, the RULE binders are lambda-bound -- Returns Nothing if the LHS isn't of the expected shape decomposeRuleLhs lhs - = go emptyVarEnv (occurAnalyseExpr lhs) -- Occurrence analysis sorts out the dict - -- bindings so we know if they are recursive + = case (decomp emptyVarEnv body) of + Nothing -> Nothing + Just (fn, args) -> Just (bndrs, fn, args) where - -- Substitute dicts in the LHS args, so that there - -- aren't any lets getting in the way - -- Note that we substitute the function too; we might have this as - -- a LHS: let f71 = M.f Int in f71 - go env (Let (NonRec dict rhs) body) - = go (extendVarEnv env dict (simpleSubst env rhs)) body - go env body - = case collectArgs (simpleSubst env body) of - (Var fn, args) -> Just (fn, args) - other -> Nothing + occ_lhs = occurAnalyseExpr lhs + -- The occurrence-analysis does two things + -- (a) identifies unused binders: Note [Unused spec binders] + -- (b) sorts dict bindings into NonRecs + -- so they can be inlined by 'decomp' + (bndrs, body) = collectBinders occ_lhs + + -- Substitute dicts in the LHS args, so that there + -- aren't any lets getting in the way + -- Note that we substitute the function too; we might have this as + -- a LHS: let f71 = M.f Int in f71 + decomp env (Let (NonRec dict rhs) body) + = decomp (extendVarEnv env dict (simpleSubst env rhs)) body + + decomp env (Case scrut bndr ty [(DEFAULT, _, body)]) + | isDeadBinder bndr -- Note [Matching seqId] + = Just (seqId, [Type (idType bndr), Type ty, + simpleSubst env scrut, simpleSubst env body]) + + decomp env body + = case collectArgs (simpleSubst env body) of + (Var fn, args) -> Just (fn, args) + _ -> Nothing simpleSubst :: IdEnv CoreExpr -> CoreExpr -> CoreExpr -- Similar to CoreSubst.substExpr, except that --- (a) takes no account of capture; dictionary bindings use new names --- (b) can have a GlobalId (imported) in its domain +-- (a) Takes no account of capture; at this point there is no shadowing +-- (b) Can have a GlobalId (imported) in its domain -- (c) Ids only; no types are substituted +-- (d) Does not insist (as does CoreSubst.lookupIdSubst) that the +-- in-scope set mentions all LocalIds mentioned in the argument of the subst -- --- (b) is the reason we can't use CoreSubst... and it's no longer relevant --- so really we should replace simpleSubst +-- (b) and (d) are the reasons we can't use CoreSubst +-- +-- (I had a note that (b) is "no longer relevant", and indeed it doesn't +-- look relevant here. Perhaps there was another caller of simpleSubst.) + simpleSubst subst expr = go expr where @@ -406,17 +523,23 @@ addInlinePrags prags bndr rhs (inl:_) -> addInlineInfo inl bndr rhs addInlineInfo :: InlineSpec -> Id -> CoreExpr -> (Id,CoreExpr) -addInlineInfo (Inline phase is_inline) bndr rhs - = (attach_phase bndr phase, wrap_inline is_inline rhs) +addInlineInfo (Inline prag is_inline) bndr rhs + = (attach_pragma bndr prag, wrap_inline is_inline rhs) where - attach_phase bndr phase - | isAlwaysActive phase = bndr -- Default phase - | otherwise = bndr `setInlinePragma` phase + attach_pragma bndr prag + | isDefaultInlinePragma prag = bndr + | otherwise = bndr `setInlinePragma` prag wrap_inline True body = mkInlineMe body wrap_inline False body = body \end{code} +Note [Matching seq] +~~~~~~~~~~~~~~~~~~~ +The desugarer turns (seq e r) into (case e of _ -> r), via a special-case hack +and this code turns it back into an application of seq! +See Note [Rules for seq] in MkId for the details. + %************************************************************************ %* * @@ -445,7 +568,8 @@ If profiling and dealing with a dict binding, wrap the dict in @_scc_ DICT @: \begin{code} -addDictScc var rhs = return rhs +addDictScc :: Id -> CoreExpr -> DsM CoreExpr +addDictScc _ rhs = return rhs {- DISABLED for now (need to somehow make up a name for the scc) -- SDM | not ( opt_SccProfilingOn && opt_AutoSccsOnDicts) @@ -471,14 +595,17 @@ addDictScc var rhs = return rhs dsCoercion :: HsWrapper -> DsM CoreExpr -> DsM CoreExpr dsCoercion WpHole thing_inside = thing_inside dsCoercion (WpCompose c1 c2) thing_inside = dsCoercion c1 (dsCoercion c2 thing_inside) -dsCoercion (WpCo co) thing_inside = do { expr <- thing_inside +dsCoercion (WpCast co) thing_inside = do { expr <- thing_inside ; return (Cast expr co) } dsCoercion (WpLam id) thing_inside = do { expr <- thing_inside ; return (Lam id expr) } dsCoercion (WpTyLam tv) thing_inside = do { expr <- thing_inside ; return (Lam tv expr) } -dsCoercion (WpApp id) thing_inside = do { expr <- thing_inside - ; return (App expr (Var id)) } +dsCoercion (WpApp v) thing_inside + | isTyVar v = do { expr <- thing_inside + {- Probably a coercion var -} ; return (App expr (Type (mkTyVarTy v))) } + | otherwise = do { expr <- thing_inside + {- An Id -} ; return (App expr (Var v)) } dsCoercion (WpTyApp ty) thing_inside = do { expr <- thing_inside ; return (App expr (Type ty)) } dsCoercion WpInline thing_inside = do { expr <- thing_inside