X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=85487e6e816b16434b402a2b451cb82767e5e76a;hp=5f0bdb7a605b193ab21cd638a3daea070c829e50;hb=cad6d4688bdc309b3e9953bf091535a8eeaa2515;hpb=dd99b6f8c61f393087d03cd697c06051a43ca4e9 diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index 5f0bdb7..85487e6 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -17,7 +17,7 @@ module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, #include "HsVersions.h" -import {-# SOURCE #-} DsExpr( dsLExpr, dsExpr ) +import {-# SOURCE #-} DsExpr( dsLExpr ) import {-# SOURCE #-} Match( matchWrapper ) import DsMonad @@ -26,28 +26,34 @@ import DsUtils import HsSyn -- lots of things import CoreSyn -- lots of things +import CoreSubst +import MkCore import CoreUtils +import CoreArity ( etaExpand ) +import CoreUnfold import CoreFVs -import TcHsSyn ( mkArbitraryType ) -- Mis-placed? import TcType -import OccurAnal +import TysPrim ( anyTypeOfKind ) import CostCentre import Module import Id -import 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 import Bag import BasicTypes hiding ( TopLevel ) import FastString -import Util ( mapSnd ) +import StaticFlags ( opt_DsMultiTyVar ) +import Util ( count, lengthExceeds ) +import MonadUtils import Control.Monad import Data.List \end{code} @@ -68,6 +74,7 @@ dsLHsBinds binds = ds_lhs_binds NoSccs binds ------------------------ ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)] + -- scc annotation policy (see below) ds_lhs_binds auto_scc binds = foldM (dsLHsBind auto_scc) [] (bagToList binds) @@ -83,87 +90,191 @@ dsHsBind :: AutoScc -> HsBind Id -> DsM [(Id,CoreExpr)] -- Result -dsHsBind _ rest (VarBind var expr) = do - core_expr <- dsLExpr expr - - -- Dictionary bindings are always VarMonoBinds, so - -- we only need do this here - core_expr' <- addDictScc var core_expr - return ((var, core_expr') : rest) - -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 _ 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 +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 + + ; return ((var', core_expr') : rest) } + +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 + ; 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 }) + = 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 -} 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 - = addInlinePrags prags gbl_id $ - addAutoScc auto_scc gbl_id rhs - | otherwise = (lcl_id, rhs) + ar_env = mkArityEnv binds + do_one (lcl_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) + 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 + ; let arby_env = mkArbitraryTypeEnv tyvars exports + bndrs = mkVarSet (map fst core_prs) + + add_lets | core_prs `lengthExceeds` 10 = add_some + | 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 + + 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 + = 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 -- Non-recursive bindings come through this way + -- So do self-recursive bindings, and recursive bindings + -- that have been chopped up with type signatures dsHsBind auto_scc rest (AbsBinds all_tyvars dicts [(tyvars, global, local, prags)] binds) - = ASSERT( all (`elem` tyvars) all_tyvars ) do - core_prs <- ds_lhs_binds NoSccs binds - let - -- Always treat the binds as recursive, because the typechecker - -- makes rather mixed-up dictionary bindings - core_bind = Rec core_prs + = ASSERT( all (`elem` tyvars) all_tyvars ) + do { core_prs <- ds_lhs_binds NoSccs binds + + ; let -- Always treat the binds as recursive, because the typechecker + -- makes rather mixed-up dictionary bindings + core_bind = Rec core_prs + inl_arity = lookupArity (mkArityEnv binds) local - mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global local core_bind) prags - let - (spec_binds, rules) = unzip (catMaybes mb_specs) - global' = addIdSpecialisations global rules - rhs' = mkLams tyvars $ mkLams dicts $ Let core_bind (Var local) - bind = addInlinePrags prags global' $ addAutoScc auto_scc global' rhs' + ; (spec_binds, rules) <- dsSpecs all_tyvars dicts tyvars global + local inl_arity core_bind prags + + ; 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 + dictArity dicts) rhs - return (bind : spec_binds ++ rest) + ; return (main_bind : spec_binds ++ 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 - = addInlinePrags prags lcl_id $ - addAutoScc auto_scc gbl_id rhs + ar_env = mkArityEnv binds + do_one (lcl_id,rhs) | Just (_, gbl_id, _, _prags) <- lookupVarEnv env lcl_id + = (lcl_id, addAutoScc auto_scc gbl_id rhs) | otherwise = (lcl_id,rhs) -- Rec because of mixed-up dictionary bindings @@ -178,47 +289,122 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) ; 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 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..]) - -- don't scc (auto-)annotate the tuple itself. + -- Don't scc (auto-)annotate the tuple itself. ; return ((poly_tup_id, poly_tup_expr) : (concat export_binds_s ++ rest)) } -mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> VarEnv (Id, [LPrag]) +------------------------ +makeCorePair :: Id-> Arity -> CoreExpr -> (Id, CoreExpr) +makeCorePair gbl_id arity rhs + | isInlinePragma (idInlinePragma gbl_id) + -- Add an Unfolding for an INLINE (but not for NOINLINE) + -- And eta-expand the RHS; see Note [Eta-expanding INLINE things] + = (gbl_id `setIdUnfolding` mkInlineRule InlSat rhs arity, + etaExpand arity rhs) + | otherwise + = (gbl_id, rhs) + +------------------------ +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, [LSpecPrag])] -> AbsBindEnv -- 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] + +mkArityEnv :: LHsBinds Id -> IdEnv Arity + -- Maps a local to the arity of its definition +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 +\end{code} +Note [Eta-expanding INLINE things] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + foo :: Eq a => a -> a + {-# INLINE foo #-} + foo x = ... -dsSpec :: [TyVar] -> [DictId] -> [TyVar] - -> Id -> Id -- Global, local - -> CoreBind -> LPrag - -> DsM (Maybe ((Id,CoreExpr), -- Binding for specialised Id - CoreRule)) -- Rule for the Global Id +If (foo d) ever gets floated out as a common sub-expression (which can +happen as a result of method sharing), there's a danger that we never +get to do the inlining, which is a Terribly Bad thing given that the +user said "inline"! +To avoid this we pre-emptively eta-expand the definition, so that foo +has arity 2 (one for the Eq and one for x); and that in turn should +mean that (foo d) is a PAP and we don't share it. + + +Note [Nested arities] +~~~~~~~~~~~~~~~~~~~~~ +For reasons that are not entirely clear, method bindings come out looking like +this: + + 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 #-} @@ -242,72 +428,105 @@ 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 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 - ; 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 - - -- 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 -> - - case mb_lhs of - Nothing -> do { warnDs decomp_msg; return Nothing } - - Just (_, args) -> 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_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)) - -- 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 (addInlineInfo inl spec_id 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 - 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")) - 2 (ppr spec_expr) - -dsMkArbitraryType :: TcTyVar -> DsM Type -dsMkArbitraryType tv = mkArbitraryType warn tv + decomp_msg spec_co + = hang (ptext (sLit "Specialisation too complicated to desugar; ignored")) + 2 (pprHsWrapper (ppr poly_id) spec_co) + + +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 - warn span msg = putSrcSpanDs span (warnDs msg) + go env [] = env + go env ((ltvs, _, _, _) : exports) + = go env' exports + where + env' = foldl extend env [tv | tv <- tyvars + , not (tv `elem` ltvs) + , not (tv `elemVarEnv` env)] + + extend env tv = extendVarEnv env tv (dsMkArbitraryType tv) + +dsMkArbitraryType :: TcTyVar -> Type +dsMkArbitraryType tv = anyTypeOfKind (tyVarKind tv) \end{code} Note [Unused spec binders] @@ -337,13 +556,16 @@ 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 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. %************************************************************************ @@ -353,64 +575,43 @@ 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 collectArgs body of + (Var fn, args) -> Just (bndrs, fn, args) + + (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 - -- 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) - _ -> 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 --- (c) Ids only; no types are substituted --- --- (b) is the reason we can't use CoreSubst... and it's no longer relevant --- so really we should replace simpleSubst -simpleSubst subst expr - = go expr - 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] - -addInlinePrags :: [LPrag] -> Id -> CoreExpr -> (Id,CoreExpr) -addInlinePrags prags bndr rhs - = case [inl | L _ (InlinePrag inl) <- prags] of - [] -> (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) - where - attach_phase bndr phase - | isAlwaysActive phase = bndr -- Default phase - | otherwise = bndr `setInlinePragma` phase - - wrap_inline True body = mkInlineMe body - wrap_inline False body = body + (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. + %************************************************************************ %* * @@ -463,22 +664,19 @@ 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 id) thing_inside = do { expr <- thing_inside - ; return (App expr (Var id)) } -dsCoercion (WpTyApp ty) thing_inside = do { expr <- thing_inside - ; return (App expr (Type ty)) } -dsCoercion WpInline thing_inside = do { expr <- thing_inside - ; return (mkInlineMe expr) } -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}