X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=e9ab4e897c7eb186cde265224308eda0b83b5974;hp=2a1f74f33924e297d8cc9812629a280c18bb95b3;hb=d95ce839533391e7118257537044f01cbb1d6694;hpb=2bbec92eb827c0d70b25f4006a954d95ae3088bf diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index 2a1f74f..e9ab4e8 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -23,33 +23,33 @@ import {-# SOURCE #-} Match( matchWrapper ) import DsMonad import DsGRHSs import DsUtils -import DsBreakpoint +import OccurAnal import HsSyn -- lots of things import CoreSyn -- lots of things +import MkCore import CoreUtils +import CoreUnfold +import CoreFVs -import TcHsSyn ( mkArbitraryType ) -- Mis-placed? -import OccurAnal +import TcHsSyn ( mkArbitraryType ) -- Mis-placed? +import TcType import CostCentre import Module import Id +import Var ( Var, TyVar ) +import VarSet import Rules -import Var ( TyVar, Var ) import VarEnv import Type -import TysWiredIn import Outputable import SrcLoc import Maybes import Bag import BasicTypes hiding ( TopLevel ) import FastString -import Util ( mapSnd ) - -import Name -import OccName -import Literal +import StaticFlags ( opt_DsMultiTyVar ) +import Util ( mapSnd, count, mapAndUnzip, lengthExceeds ) import Control.Monad import Data.List @@ -63,21 +63,7 @@ import Data.List \begin{code} dsTopLHsBinds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)] -dsTopLHsBinds auto_scc binds = do - mb_mod_name_ref <- getModNameRefDs - case mb_mod_name_ref of - Just _ -> ds_lhs_binds auto_scc binds - Nothing -> do -- Inject a CAF with the module name as literal - mod <- getModuleDs - mod_name_ref <- do - u <- newUnique - let n = mkSystemName u (mkVarOcc "_module") - return (mkLocalId n stringTy) - let mod_name = moduleNameFS$ moduleName mod - mod_lit <- dsExpr (HsLit (HsString mod_name)) - withModNameRefDs mod_name_ref $ do - res <- ds_lhs_binds auto_scc binds - return$ (mod_name_ref, mod_lit) : res +dsTopLHsBinds auto_scc binds = ds_lhs_binds auto_scc binds dsLHsBinds :: LHsBinds Id -> DsM [(Id,CoreExpr)] dsLHsBinds binds = ds_lhs_binds NoSccs binds @@ -85,6 +71,7 @@ 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) @@ -100,99 +87,202 @@ dsHsBind :: AutoScc -> HsBind Id -> DsM [(Id,CoreExpr)] -- Result -dsHsBind auto_scc rest (VarBind var expr) - = dsLExpr expr `thenDs` \ core_expr -> - - -- Dictionary bindings are always VarMonoBinds, so - -- we only need do this here - addDictScc var core_expr `thenDs` \ core_expr' -> - returnDs ((var, core_expr') : rest) - -dsHsBind auto_scc rest (FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn, fun_tick = tick }) - = matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, body) -> - mkOptTickBox tick body `thenDs` \ body' -> - dsCoercion co_fn (return (mkLams args body')) `thenDs` \ rhs -> - returnDs ((fun,rhs) : rest) - -dsHsBind auto_scc rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) - = dsGuarded grhss ty `thenDs` \ body_expr -> - mkSelectorBinds pat body_expr `thenDs` \ sel_binds -> - returnDs (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 expr 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 + ; 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 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, _, prags) <- lookupVarEnv env lcl_id + = makeCorePair gbl_id (lookupArity ar_env lcl_id) prags $ + 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 + + 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') + | 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 + -- So do self-recursive bindings, and recursive bindings + -- that have been chopped up with type signatures 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 ) - ds_lhs_binds NoSccs binds `thenDs` \ core_prs -> - let - -- Always treat the binds as recursive, because the typechecker - -- makes rather mixed-up dictionary bindings - core_bind = Rec core_prs - in - mappM (dsSpec all_tyvars dicts tyvars global local core_bind) - prags `thenDs` \ mb_specs -> - 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' - in - returnDs (bind : spec_binds ++ rest) + 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 inl_arity core_bind) prags + + ; let (spec_binds, rules) = unzip (catMaybes mb_specs) + 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 + + ; 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 core_bind = Rec (map do_one core_prs) - tup_expr = mkTupleExpr locals + tup_expr = mkBigCoreVarTup locals tup_ty = exprType tup_expr poly_tup_expr = mkLams all_tyvars $ mkLams dicts $ Let core_bind tup_expr 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 @@ -200,38 +290,80 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) 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 { locals' <- newSysLocalsDs (map substitute local_tys) + do { ty_args <- mapM mk_ty_arg all_tyvars + ; let 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) + ; 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 rhs = mkLams tyvars $ mkLams dicts $ mkTupleSelector locals' (locals' !! n) tup_id $ mkApps (mkTyApps (Var poly_tup_id) ty_args) dict_args - ; returnDs ((global', rhs) : spec_binds) } + ; return ((global', rhs) : spec_binds) } where - mk_ty_arg all_tyvar | all_tyvar `elem` tyvars = mkTyVarTy all_tyvar - | otherwise = mkArbitraryType all_tyvar - ty_args = map mk_ty_arg all_tyvars - substitute = substTyWith all_tyvars ty_args + mk_ty_arg all_tyvar + | all_tyvar `elem` tyvars = return (mkTyVarTy all_tyvar) + | otherwise = dsMkArbitraryType all_tyvar - ; export_binds_s <- mappM mk_bind (exports `zip` [0..]) - -- don't scc (auto-)annotate the tuple itself. + ; export_binds_s <- mapM mk_bind (exports `zip` [0..]) + -- Don't scc (auto-)annotate the tuple itself. - ; returnDs ((poly_tup_id, poly_tup_expr) : + ; return ((poly_tup_id, poly_tup_expr) : (concat export_binds_s ++ rest)) } -mkABEnv :: [([TyVar], Id, Id, [Prag])] -> VarEnv (Id, [Prag]) +------------------------ +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") ] + +------------------------ +type AbsBindEnv = VarEnv ([TyVar], Id, Id, [LPrag]) + -- Maps the "lcl_id" for an AbsBind to + -- its "gbl_id" and associated pragmas, if any + +mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> 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 = 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 + +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 + +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 +------------------------ dsSpec :: [TyVar] -> [DictId] -> [TyVar] - -> Id -> Id -- Global, local - -> CoreBind -> Prag + -> Id -> Id -> Arity -- Global, local, arity of local + -> CoreBind -> LPrag -> DsM (Maybe ((Id,CoreExpr), -- Binding for specialised Id CoreRule)) -- Rule for the Global Id @@ -250,54 +382,135 @@ dsSpec :: [TyVar] -> [DictId] -> [TyVar] -- /\b.\(d:Ix b). in f Int b dInt d -- The idea is that f occurs just once, so it'll be -- inlined and specialised - -dsSpec all_tvs dicts tvs poly_id mono_id mono_bind (InlinePrag {}) +-- +-- Given SpecPrag (/\as.\ds. f es) t, we have +-- the defn f_spec as ds = let-nonrec f = /\fas\fds. let f_mono = in f_mono +-- in f es +-- and the RULE forall as, ds. f es = f_spec as ds +-- +-- 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 - (SpecPrag spec_expr spec_ty const_dicts inl) - = do { let poly_name = idName poly_id +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 - ; let (bndrs, body) = collectBinders ds_spec_expr - mb_lhs = decomposeRuleLhs (bndrs ++ const_dicts) body + ; case (decomposeRuleLhs ds_spec_expr) of { + Nothing -> do { warnDs decomp_msg; return Nothing } ; - ; case mb_lhs of - Nothing -> do { warnDs msg; return Nothing } + Just (bndrs, _fn, args) -> - Just (bndrs', var, args) -> return (Just (addInlineInfo inl spec_id spec_rhs, rule)) - where - local_poly = setIdNotExported poly_id + -- 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) $ - fix_up (Let mono_bind (Var mono_id)) - - -- Quantify over constant dicts on the LHS, since - -- their value depends only on their type - -- The ones we are interested in may even be imported - -- e.g. GHC.Base.dEqInt + 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 - bndrs' -- Includes constant dicts - args + (extra_dict_bndrs ++ bndrs) args (mkVarApps (Var spec_id) bndrs) - } + ; return (Just ((spec_id1, spec_rhs), rule)) + } } } } where -- Bind to Any any of all_ptvs that aren't -- relevant for this particular function - fix_up body | null void_tvs = body - | otherwise = mkTyApps (mkLams void_tvs body) - (map mkArbitraryType void_tvs) + fix_up body | null void_tvs = return body + | otherwise = do { void_tys <- mapM dsMkArbitraryType void_tvs + ; return (mkTyApps (mkLams void_tvs body) void_tys) } + void_tvs = all_tvs \\ tvs - msg = hang (ptext SLIT("Specialisation too complicated to desugar; ignored")) - 2 (ppr spec_expr) + 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")] + 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) + + +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) \end{code} +Note [Unused spec binders] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + f :: a -> a + {-# SPECIALISE f :: Eq a => a -> a #-} +It's true that this *is* a more specialised type, but the rule +we get is something like this: + f_spec d = f + RULE: f = f_spec d +Note that the rule is bogus, becuase it mentions a 'd' that is +not bound on the LHS! But it's a silly specialisation anyway, becuase +the constraint is unused. We could bind 'd' to (error "unused") +but it seems better to reject the program because it's almost certainly +a mistake. That's what the isDeadBinder call detects. + +Note [Const rule dicts] +~~~~~~~~~~~~~~~~~~~~~~~ +When the LHS of a specialisation rule, (/\as\ds. f es) has a free dict, +which is presumably in scope at the function definition site, we can quantify +over it too. *Any* dict with that type will do. + +So for example when you have + f :: Eq a => a -> a + f = + {-# SPECIALISE f :: Int -> Int #-} + +Then we get the SpecPrag + SpecPrag (f Int dInt) Int + +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. + %************************************************************************ %* * @@ -306,45 +519,47 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind %************************************************************************ \begin{code} -decomposeRuleLhs :: [Var] -> CoreExpr -> Maybe ([Var], 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 --- The argument 'all_bndrs' includes the "constant dicts" of the LHS, --- and they may be GlobalIds, which we can't forall-ify. --- So we substitute them out instead -decomposeRuleLhs all_bndrs lhs - = go init_env (occurAnalyseExpr lhs) -- Occurrence analysis sorts out the dict - -- bindings so we know if they are recursive +decomposeRuleLhs lhs + = case (decomp emptyVarEnv body) of + Nothing -> Nothing + Just (fn, args) -> Just (bndrs, fn, args) where - - -- all_bndrs may include top-level imported dicts, - -- imported things with a for-all. - -- So we localise them and subtitute them out - bndr_prs = [ (id, Var (localise id)) | id <- all_bndrs, isGlobalId id ] - localise d = mkLocalId (idName d) (idType d) - - init_env = mkVarEnv bndr_prs - all_bndrs' = map subst_bndr all_bndrs - subst_bndr bndr = case lookupVarEnv init_env bndr of - Just (Var bndr') -> bndr' - Just other -> panic "decomposeRuleLhs" - Nothing -> bndr - - -- 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 (all_bndrs', 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 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) 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 @@ -360,23 +575,6 @@ simpleSubst subst expr 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 :: [Prag] -> Id -> CoreExpr -> (Id,CoreExpr) -addInlinePrags prags bndr rhs - = case [inl | 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 \end{code} @@ -407,17 +605,18 @@ If profiling and dealing with a dict binding, wrap the dict in @_scc_ DICT @: \begin{code} -addDictScc var rhs = returnDs 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) || not (isDictId var) - = returnDs rhs -- That's easy: do nothing + = return rhs -- That's easy: do nothing | otherwise - = getModuleAndGroupDs `thenDs` \ (mod, grp) -> + = do (mod, grp) <- getModuleAndGroupDs -- ToDo: do -dicts-all flag (mark dict things with individual CCs) - returnDs (Note (SCC (mkAllDictsCC mod grp False)) rhs) + return (Note (SCC (mkAllDictsCC mod grp False)) rhs) -} \end{code} @@ -433,14 +632,17 @@ addDictScc var rhs = returnDs 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 (WpLet bs) thing_inside = do { prs <- dsLHsBinds bs