X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=04c84cd77b3d8e17ec91e8491e9d13810a88cb50;hb=1b62d143650231ead9571ce1ebea12ac8c547a82;hp=e9ab4e897c7eb186cde265224308eda0b83b5974;hpb=d95ce839533391e7118257537044f01cbb1d6694;p=ghc-hetmet.git diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index e9ab4e8..04c84cd 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -17,31 +17,32 @@ module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, #include "HsVersions.h" -import {-# SOURCE #-} DsExpr( dsLExpr, dsExpr ) +import {-# SOURCE #-} DsExpr( dsLExpr ) import {-# SOURCE #-} Match( matchWrapper ) import DsMonad import DsGRHSs import DsUtils -import OccurAnal import HsSyn -- lots of things import CoreSyn -- lots of things +import CoreSubst import MkCore import CoreUtils import CoreUnfold import CoreFVs -import TcHsSyn ( mkArbitraryType ) -- Mis-placed? import TcType +import TysPrim ( anyTypeOfKind ) import CostCentre import Module import Id -import Var ( Var, TyVar ) +import MkId ( seqId ) +import Var ( Var, TyVar, tyVarKind ) +import IdInfo ( vanillaIdInfo ) import VarSet import Rules import VarEnv -import Type import Outputable import SrcLoc import Maybes @@ -49,8 +50,9 @@ import Bag import BasicTypes hiding ( TopLevel ) import FastString import StaticFlags ( opt_DsMultiTyVar ) -import Util ( mapSnd, count, mapAndUnzip, lengthExceeds ) +import Util ( count, lengthExceeds ) +import MonadUtils import Control.Monad import Data.List \end{code} @@ -87,14 +89,14 @@ dsHsBind :: AutoScc -> HsBind Id -> DsM [(Id,CoreExpr)] -- Result -dsHsBind _ rest (VarBind var expr inline_regardless) +dsHsBind _ rest (VarBind { var_id = var, var_rhs = expr, var_inline = inline_regardless }) = do { core_expr <- dsLExpr expr -- Dictionary bindings are always VarBinds, -- so we only need do this here ; core_expr' <- addDictScc var core_expr ; let var' | inline_regardless = var `setIdUnfolding` mkCompulsoryUnfolding core_expr' - | otherwise = var + | otherwise = var ; return ((var', core_expr') : rest) } @@ -102,9 +104,9 @@ 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) } + ; body' <- mkOptTickBox tick body + ; wrap_fn' <- dsCoercion co_fn + ; return ((fun, wrap_fn' (mkLams args body')) : rest) } dsHsBind _ rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) @@ -141,9 +143,10 @@ dsHsBind auto_scc rest (AbsBinds [] [] exports binds) ; let env = mkABEnv exports ar_env = mkArityEnv binds do_one (lcl_id, rhs) - | Just (_, gbl_id, _, prags) <- lookupVarEnv env lcl_id - = makeCorePair gbl_id (lookupArity ar_env lcl_id) prags $ - addAutoScc auto_scc gbl_id rhs + | Just (_, gbl_id, _, spec_prags) <- lookupVarEnv env lcl_id + = WARN( not (null spec_prags), ppr gbl_id $$ ppr spec_prags ) -- Not overloaded + makeCorePair gbl_id (lookupArity ar_env lcl_id) + (addAutoScc auto_scc gbl_id rhs) | otherwise = (lcl_id, rhs) @@ -203,35 +206,42 @@ dsHsBind auto_scc rest (AbsBinds tyvars [] exports binds) -- see if it has any impact; it is on by default = -- Note [Abstracting over tyvars only] do { core_prs <- ds_lhs_binds NoSccs binds - ; arby_env <- mkArbitraryTypeEnv tyvars exports - ; let (lg_binds, core_prs') = mapAndUnzip do_one core_prs + ; let arby_env = mkArbitraryTypeEnv tyvars exports bndrs = mkVarSet (map fst core_prs) add_lets | core_prs `lengthExceeds` 10 = add_some - | otherwise = mkLets lg_binds - add_some rhs = mkLets [ NonRec b r | NonRec b r <- lg_binds - , b `elemVarSet` fvs] rhs + | otherwise = mkLets + add_some lg_binds rhs = mkLets [ NonRec b r | NonRec b r <- lg_binds + , b `elemVarSet` fvs] rhs where fvs = exprSomeFreeVars (`elemVarSet` bndrs) rhs ar_env = mkArityEnv binds env = mkABEnv exports - do_one (lcl_id, rhs) - | Just (id_tvs, gbl_id, _, prags) <- lookupVarEnv env lcl_id - = let rhs' = addAutoScc auto_scc gbl_id $ - mkLams id_tvs $ - mkLets [ NonRec tv (Type (lookupVarEnv_NF arby_env tv)) - | tv <- tyvars, not (tv `elem` id_tvs)] $ - add_lets rhs - in (NonRec lcl_id (mkTyApps (Var gbl_id) (mkTyVarTys id_tvs)), - makeCorePair gbl_id (lookupArity ar_env lcl_id) prags rhs') + mk_lg_bind lcl_id gbl_id tyvars + = NonRec (setIdInfo lcl_id vanillaIdInfo) + -- Nuke the IdInfo so that no old unfoldings + -- confuse use (it might mention something not + -- even in scope at the new site + (mkTyApps (Var gbl_id) (mkTyVarTys tyvars)) + + do_one lg_binds (lcl_id, rhs) + | Just (id_tvs, gbl_id, _, spec_prags) <- lookupVarEnv env lcl_id + = WARN( not (null spec_prags), ppr gbl_id $$ ppr spec_prags ) -- Not overloaded + (let rhs' = 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 lg_binds rhs + in return (mk_lg_bind lcl_id gbl_id id_tvs, + makeCorePair gbl_id (lookupArity ar_env lcl_id) 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)) + = do { non_exp_gbl_id <- newUniqueId lcl_id (mkForAllTys tyvars (idType lcl_id)) + ; return (mk_lg_bind lcl_id non_exp_gbl_id tyvars, + (non_exp_gbl_id, mkLams tyvars (add_lets lg_binds rhs))) } + ; (_, core_prs') <- fixDs (\ ~(lg_binds, _) -> mapAndUnzipM (do_one lg_binds) core_prs) ; return (core_prs' ++ rest) } -- Another common case: one exported variable @@ -248,14 +258,13 @@ dsHsBind auto_scc rest core_bind = Rec core_prs inl_arity = lookupArity (mkArityEnv binds) local - ; mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global - local inl_arity core_bind) prags + ; (spec_binds, rules) <- dsSpecs all_tyvars dicts tyvars global + local inl_arity core_bind prags - ; let (spec_binds, rules) = unzip (catMaybes mb_specs) - global' = addIdSpecialisations global rules + ; let global' = addIdSpecialisations global rules rhs = addAutoScc auto_scc global $ mkLams tyvars $ mkLams dicts $ Let core_bind (Var local) - main_bind = makeCorePair global' (inl_arity + length dicts) prags rhs + main_bind = makeCorePair global' (inl_arity + dictArity dicts) rhs ; return (main_bind : spec_binds ++ rest) } @@ -277,35 +286,27 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) locals = [local | (_, _, local, _) <- exports] local_tys = map idType locals - inl_prags :: [(Id, SrcSpan)] - inl_prags = [(id, loc) | (_, id, _, prags) <- exports - , L loc (InlinePrag {}) <- prags ] - - ; mapM_ discardedInlineWarning inl_prags - ; poly_tup_id <- newSysLocalDs (exprType poly_tup_expr) - ; let dict_args = map Var dicts - - mk_bind ((tyvars, global, local, prags), n) -- locals !! n == local - = -- Need to make fresh locals to bind in the selector, because - -- some of the tyvars will be bound to 'Any' - do { ty_args <- mapM mk_ty_arg all_tyvars - ; let substitute = substTyWith all_tyvars ty_args + ; let mk_bind ((tyvars, global, local, spec_prags), n) -- locals!!n == local + = -- Need to make fresh locals to bind in the selector, + -- because some of the tyvars will be bound to 'Any' + do { let ty_args = map mk_ty_arg all_tyvars + substitute = substTyWith all_tyvars ty_args ; locals' <- newSysLocalsDs (map substitute local_tys) ; tup_id <- newSysLocalDs (substitute tup_ty) - ; mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global local - (lookupArity ar_env local) core_bind) - prags - ; let (spec_binds, rules) = unzip (catMaybes mb_specs) - global' = addIdSpecialisations global rules + ; (spec_binds, rules) <- dsSpecs all_tyvars dicts tyvars global local + (lookupArity ar_env local) core_bind + spec_prags + ; let global' = addIdSpecialisations global rules rhs = mkLams tyvars $ mkLams dicts $ mkTupleSelector locals' (locals' !! n) tup_id $ - mkApps (mkTyApps (Var poly_tup_id) ty_args) dict_args + mkVarApps (mkTyApps (Var poly_tup_id) ty_args) + dicts ; return ((global', rhs) : spec_binds) } where mk_ty_arg all_tyvar - | all_tyvar `elem` tyvars = return (mkTyVarTy all_tyvar) + | all_tyvar `elem` tyvars = mkTyVarTy all_tyvar | otherwise = dsMkArbitraryType all_tyvar ; export_binds_s <- mapM mk_bind (exports `zip` [0..]) @@ -315,58 +316,79 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) (concat export_binds_s ++ rest)) } ------------------------ -makeCorePair :: Id-> Arity -> [LPrag] -> CoreExpr -> (Id, CoreExpr) -makeCorePair gbl_id arity prags rhs - = (addInline gbl_id arity rhs prags, rhs) - ------------------------- -discardedInlineWarning :: (Id, SrcSpan) -> DsM () -discardedInlineWarning (id, loc) - = putSrcSpanDs loc $ - warnDs $ sep [ ptext (sLit "Discarding INLINE pragma for") <+> ppr id - , ptext (sLit "because it is bound by a pattern, or a mutual recursion") ] +makeCorePair :: Id-> Arity -> CoreExpr -> (Id, CoreExpr) +makeCorePair gbl_id arity rhs + = (addInline gbl_id arity rhs, rhs) ------------------------ -type AbsBindEnv = VarEnv ([TyVar], Id, Id, [LPrag]) +type AbsBindEnv = VarEnv ([TyVar], Id, Id, [LSpecPrag]) -- Maps the "lcl_id" for an AbsBind to -- its "gbl_id" and associated pragmas, if any -mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> AbsBindEnv +mkABEnv :: [([TyVar], Id, Id, [LSpecPrag])] -> AbsBindEnv -- Takes the exports of a AbsBinds, and returns a mapping -- lcl_id -> (tyvars, gbl_id, lcl_id, prags) mkABEnv exports = mkVarEnv [ (lcl_id, export) | export@(_, _, lcl_id, _) <- exports] mkArityEnv :: LHsBinds Id -> IdEnv Arity -- Maps a local to the arity of its definition -mkArityEnv binds = mkVarEnv (mapCatMaybes get_arity (bagToList binds)) - where - get_arity (L _ (FunBind { fun_id = id, fun_matches = ms })) = Just (unLoc id, matchGroupArity ms) - get_arity _ = Nothing +mkArityEnv binds = foldrBag (plusVarEnv . lhsBindArity) emptyVarEnv binds + +lhsBindArity :: LHsBind Id -> IdEnv Arity +lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) + = unitVarEnv (unLoc id) (matchGroupArity ms) +lhsBindArity (L _ (AbsBinds { abs_exports = exports + , abs_dicts = dicts + , abs_binds = binds })) + = mkVarEnv [ (gbl, lookupArity ar_env lcl + n_val_dicts) + | (_, gbl, lcl, _) <- exports] + where -- See Note [Nested arities] + ar_env = mkArityEnv binds + n_val_dicts = dictArity dicts + +lhsBindArity _ = emptyVarEnv -- PatBind/VarBind + +dictArity :: [Var] -> Arity +-- Don't count coercion variables in arity +dictArity dicts = count isId dicts lookupArity :: IdEnv Arity -> Id -> Arity lookupArity ar_env id = lookupVarEnv ar_env id `orElse` 0 -addInline :: Id -> Arity -> CoreExpr -> [LPrag] -> Id -addInline id arity rhs prags - = case [inl | L _ (InlinePrag inl) <- prags] of - [] -> id - (inl_spec : _) -> addInlineToId id arity rhs inl_spec +addInline :: Id -> Arity -> CoreExpr -> Id +addInline id arity rhs + | isInlinePragma (idInlinePragma id) + -- Add an Unfolding for an INLINE (but not for NOINLINE) + = id `setIdUnfolding` mkInlineRule InlSat rhs arity + | otherwise + = id +\end{code} -addInlineToId :: Id -> Arity -> CoreExpr -> InlineSpec -> Id -addInlineToId id inl_arity rhs (Inline phase is_inline) - = id `setInlinePragma` phase - `setIdUnfolding` inline_rule - where - inline_rule | is_inline = mkInlineRule rhs inl_arity - | otherwise = noUnfolding +Nested arities +~~~~~~~~~~~~~~ +For reasons that are not entirely clear, method bindings come out looking like +this: ------------------------- -dsSpec :: [TyVar] -> [DictId] -> [TyVar] - -> Id -> Id -> Arity -- Global, local, arity of local - -> CoreBind -> LPrag - -> DsM (Maybe ((Id,CoreExpr), -- Binding for specialised Id - CoreRule)) -- Rule for the Global Id + AbsBinds [] [] [$cfromT <= [] fromT] + $cfromT [InlPrag=INLINE] :: T Bool -> Bool + { AbsBinds [] [] [fromT <= [] fromT_1] + fromT :: T Bool -> Bool + { fromT_1 ((TBool b)) = not b } } } + +Note the nested AbsBind. The arity for the InlineRule on $cfromT should be +gotten from the binding for fromT_1. + +It might be better to have just one level of AbsBinds, but that requires more +thought! + +\begin{code} +------------------------ +dsSpecs :: [TyVar] -> [DictId] -> [TyVar] + -> Id -> Id -> Arity -- Global, local, arity of local + -> CoreBind -> [LSpecPrag] + -> DsM ( [(Id,CoreExpr)] -- Binding for specialised Ids + , [CoreRule] ) -- Rules for the Global Ids -- Example: -- f :: (Eq a, Ix b) => a -> b -> b -- {-# SPECIALISE f :: Ix b => Int -> b -> b #-} @@ -390,53 +412,65 @@ dsSpec :: [TyVar] -> [DictId] -> [TyVar] -- -- It is *possible* that 'es' does not mention all of the dictionaries 'ds' -- (a bit silly, because then the -dsSpec _ _ _ _ _ _ _ (L _ (InlinePrag {})) - = return Nothing - -dsSpec all_tvs dicts tvs poly_id mono_id inl_arity mono_bind - (L loc (SpecPrag spec_expr spec_ty inl)) - = putSrcSpanDs loc $ - do { let poly_name = idName poly_id - ; spec_name <- newLocalName poly_name - ; ds_spec_expr <- dsExpr spec_expr - ; case (decomposeRuleLhs ds_spec_expr) of { - Nothing -> do { warnDs decomp_msg; return Nothing } ; - - Just (bndrs, _fn, args) -> - - -- 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 - - { f_body <- fix_up (Let mono_bind (Var mono_id)) - - ; let local_poly = setIdNotExported poly_id - -- Very important to make the 'f' non-exported, - -- else it won't be inlined! - spec_id = mkLocalId spec_name spec_ty - spec_id1 = addInlineToId spec_id (inl_arity + count isDictId bndrs) - spec_rhs inl - spec_rhs = Let (NonRec local_poly poly_f_body) ds_spec_expr - poly_f_body = mkLams (tvs ++ dicts) f_body - - 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))) - AlwaysActive poly_name - (extra_dict_bndrs ++ bndrs) args - (mkVarApps (Var spec_id) bndrs) - ; return (Just ((spec_id1, spec_rhs), rule)) - } } } } - where + +dsSpecs all_tvs dicts tvs poly_id mono_id inl_arity mono_bind prags + = do { pairs <- mapMaybeM spec_one prags + ; let (spec_binds_s, rules) = unzip pairs + ; return (concat spec_binds_s, rules) } + where + spec_one :: LSpecPrag -> DsM (Maybe ([(Id,CoreExpr)], CoreRule)) + spec_one (L loc (SpecPrag spec_co spec_inl)) + = putSrcSpanDs loc $ + do { let poly_name = idName poly_id + ; spec_name <- newLocalName poly_name + ; wrap_fn <- dsCoercion spec_co + ; let ds_spec_expr = wrap_fn (Var poly_id) + ; case decomposeRuleLhs ds_spec_expr of { + Nothing -> do { warnDs (decomp_msg spec_co) + ; return Nothing } ; + + Just (bndrs, _fn, args) -> + + -- 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 + + { (spec_unf, unf_pairs) <- specUnfolding wrap_fn (idUnfolding poly_id) + + ; let f_body = fix_up (Let mono_bind (Var mono_id)) + spec_ty = exprType ds_spec_expr + spec_id = mkLocalId spec_name spec_ty + `setInlinePragma` inl_prag + `setIdUnfolding` spec_unf + inl_prag | isDefaultInlinePragma spec_inl = idInlinePragma poly_id + | otherwise = spec_inl + -- Get the INLINE pragma from SPECIALISE declaration, or, + -- failing that, from the original Id + + spec_id_arity = inl_arity + count isDictId bndrs + + 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))) + AlwaysActive poly_name + (extra_dict_bndrs ++ bndrs) args + (mkVarApps (Var spec_id) bndrs) + + spec_rhs = wrap_fn (mkLams (tvs ++ dicts) f_body) + spec_pair = makeCorePair spec_id spec_id_arity spec_rhs + + ; return (Just (spec_pair : unf_pairs, rule)) + } } } } + -- Bind to Any any of all_ptvs that aren't -- relevant for this particular function - fix_up body | null void_tvs = return body - | otherwise = do { void_tys <- mapM dsMkArbitraryType void_tvs - ; return (mkTyApps (mkLams void_tvs body) void_tys) } + fix_up body | null void_tvs = body + | otherwise = mkTyApps (mkLams void_tvs body) $ + map dsMkArbitraryType void_tvs void_tvs = all_tvs \\ tvs @@ -446,31 +480,37 @@ dsSpec all_tvs dicts tvs poly_id mono_id inl_arity mono_bind , 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")) - 2 (ppr spec_expr) + decomp_msg spec_co + = hang (ptext (sLit "Specialisation too complicated to desugar; ignored")) + 2 (pprHsWrapper (ppr poly_id) spec_co) -mkArbitraryTypeEnv :: [TyVar] -> [([TyVar], a, b, c)] -> DsM (TyVarEnv Type) +specUnfolding :: (CoreExpr -> CoreExpr) -> Unfolding -> DsM (Unfolding, [(Id,CoreExpr)]) +specUnfolding wrap_fn (DFunUnfolding con ops) + = do { let spec_rhss = map wrap_fn ops + ; spec_ids <- mapM (mkSysLocalM (fsLit "spec") . exprType) spec_rhss + ; return (DFunUnfolding con (map Var spec_ids), spec_ids `zip` spec_rhss) } +specUnfolding _ _ + = return (noUnfolding, []) + +mkArbitraryTypeEnv :: [TyVar] -> [([TyVar], a, b, c)] -> 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 [] = env go env ((ltvs, _, _, _) : exports) - = do { env' <- foldlM extend env [tv | tv <- tyvars - , not (tv `elem` ltvs) - , not (tv `elemVarEnv` env)] - ; go env' exports } + = go env' exports + where + env' = foldl extend env [tv | tv <- tyvars + , not (tv `elem` ltvs) + , not (tv `elemVarEnv` env)] - extend env tv = do { ty <- dsMkArbitraryType tv - ; return (extendVarEnv env tv ty) } + extend env tv = extendVarEnv env tv (dsMkArbitraryType tv) - -dsMkArbitraryType :: TcTyVar -> DsM Type -dsMkArbitraryType tv = mkArbitraryType warn tv - where - warn span msg = putSrcSpanDs span (warnDs msg) +dsMkArbitraryType :: TcTyVar -> Type +dsMkArbitraryType tv = anyTypeOfKind (tyVarKind tv) \end{code} Note [Unused spec binders] @@ -500,7 +540,7 @@ So for example when you have {-# SPECIALISE f :: Int -> Int #-} Then we get the SpecPrag - SpecPrag (f Int dInt) Int + SpecPrag (f Int dInt) And from that we want the rule @@ -526,57 +566,36 @@ decomposeRuleLhs :: CoreExpr -> Maybe ([Var], Id, [CoreExpr]) -- That is, the RULE binders are lambda-bound -- Returns Nothing if the LHS isn't of the expected shape decomposeRuleLhs lhs - = case (decomp emptyVarEnv body) of - Nothing -> Nothing - Just (fn, args) -> Just (bndrs, fn, args) - where - 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 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; 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) 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.) + = case collectArgs body of + (Var fn, args) -> Just (bndrs, fn, args) -simpleSubst subst expr - = go expr + (Case scrut bndr ty [(DEFAULT, _, body)], args) + | isDeadBinder bndr -- Note [Matching seqId] + -> Just (bndrs, seqId, args' ++ args) + where + args' = [Type (idType bndr), Type ty, scrut, body] + + _other -> Nothing -- Unexpected shape where - go (Var v) = lookupVarEnv subst v `orElse` Var v - go (Cast e co) = Cast (go e) co - go (Type ty) = Type ty - go (Lit lit) = Lit lit - go (App fun arg) = App (go fun) (go arg) - go (Note note e) = Note note (go e) - go (Lam bndr body) = Lam bndr (go body) - go (Let (NonRec bndr rhs) body) = Let (NonRec bndr (go rhs)) (go body) - go (Let (Rec pairs) body) = Let (Rec (mapSnd go pairs)) (go body) - go (Case scrut bndr ty alts) = Case (go scrut) bndr ty - [(c,bs,go r) | (c,bs,r) <- alts] + (bndrs, body) = collectBinders (simpleOptExpr lhs) + -- simpleOptExpr occurrence-analyses and simplifies the lhs + -- and thereby + -- (a) identifies unused binders: Note [Unused spec binders] + -- (b) sorts dict bindings into NonRecs + -- so they can be inlined by 'decomp' + -- (c) substitute trivial lets so that they don't get in the way + -- Note that we substitute the function too; we might + -- have this as a LHS: let f71 = M.f Int in f71 + -- NB: tcSimplifyRuleLhs is very careful not to generate complicated + -- dictionary expressions that we might have to match \end{code} +Note [Matching seqId] +~~~~~~~~~~~~~~~~~~~ +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. + %************************************************************************ %* * @@ -629,23 +648,19 @@ addDictScc _ rhs = return rhs \begin{code} -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 (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 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 (WpLet bs) thing_inside = do { prs <- dsLHsBinds bs - ; expr <- thing_inside - ; return (Let (Rec prs) expr) } +dsCoercion :: HsWrapper -> DsM (CoreExpr -> CoreExpr) +dsCoercion WpHole = return (\e -> e) +dsCoercion (WpCompose c1 c2) = do { k1 <- dsCoercion c1 + ; k2 <- dsCoercion c2 + ; return (k1 . k2) } +dsCoercion (WpCast co) = return (\e -> Cast e co) +dsCoercion (WpLam id) = return (\e -> Lam id e) +dsCoercion (WpTyLam tv) = return (\e -> Lam tv e) +dsCoercion (WpApp v) | isTyVar v -- Probably a coercion var + = return (\e -> App e (Type (mkTyVarTy v))) + | otherwise + = return (\e -> App e (Var v)) +dsCoercion (WpTyApp ty) = return (\e -> App e (Type ty)) +dsCoercion (WpLet bs) = do { prs <- dsLHsBinds bs + ; return (\e -> Let (Rec prs) e) } \end{code}