X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=65cb8157daaef65e72e26a0e92b9ac83f1628106;hp=04c84cd77b3d8e17ec91e8491e9d13810a88cb50;hb=b2524b3960999fffdb3767900f58825903f6560f;hpb=98de5f474de6eb5dc9b2e2ec582e02902fdb3856 diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index 04c84cd..65cb815 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -10,9 +10,9 @@ in that the @Rec@/@NonRec@/etc structure is thrown away (whereas at lower levels it is preserved with @let@/@letrec@s). \begin{code} -module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, - dsCoercion, - AutoScc(..) +module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsSpec, + dsHsWrapper, dsTcEvBinds, dsEvBinds, wrapDsEvBinds, + DsEvBind(..), AutoScc(..) ) where #include "HsVersions.h" @@ -29,32 +29,37 @@ import CoreSyn -- lots of things import CoreSubst import MkCore import CoreUtils +import CoreArity ( etaExpand ) import CoreUnfold import CoreFVs +import Digraph import TcType +import Type +import Coercion import TysPrim ( anyTypeOfKind ) import CostCentre import Module import Id +import TyCon ( tyConDataCons ) +import Class +import DataCon ( dataConRepType ) +import Name ( localiseName ) import MkId ( seqId ) -import Var ( Var, TyVar, tyVarKind ) -import IdInfo ( vanillaIdInfo ) +import Var import VarSet import Rules import VarEnv import Outputable import SrcLoc import Maybes +import OrdList import Bag import BasicTypes hiding ( TopLevel ) import FastString -import StaticFlags ( opt_DsMultiTyVar ) -import Util ( count, lengthExceeds ) +import Util import MonadUtils -import Control.Monad -import Data.List \end{code} %************************************************************************ @@ -64,33 +69,28 @@ import Data.List %************************************************************************ \begin{code} -dsTopLHsBinds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)] +dsTopLHsBinds :: AutoScc -> LHsBinds Id -> DsM (OrdList (Id,CoreExpr)) dsTopLHsBinds auto_scc binds = ds_lhs_binds auto_scc binds dsLHsBinds :: LHsBinds Id -> DsM [(Id,CoreExpr)] -dsLHsBinds binds = ds_lhs_binds NoSccs binds - +dsLHsBinds binds = do { binds' <- ds_lhs_binds NoSccs binds + ; return (fromOL binds') } ------------------------ -ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)] +ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM (OrdList (Id,CoreExpr)) -- scc annotation policy (see below) -ds_lhs_binds auto_scc binds = foldM (dsLHsBind auto_scc) [] (bagToList binds) +ds_lhs_binds auto_scc binds = do { ds_bs <- mapBagM (dsLHsBind auto_scc) binds + ; return (foldBag appOL id nilOL ds_bs) } -dsLHsBind :: AutoScc - -> [(Id,CoreExpr)] -- Put this on the end (avoid quadratic append) - -> LHsBind Id - -> DsM [(Id,CoreExpr)] -- Result -dsLHsBind auto_scc rest (L loc bind) - = putSrcSpanDs loc $ dsHsBind auto_scc rest bind +dsLHsBind :: AutoScc -> LHsBind Id -> DsM (OrdList (Id,CoreExpr)) +dsLHsBind auto_scc (L loc bind) + = putSrcSpanDs loc $ dsHsBind auto_scc bind -dsHsBind :: AutoScc - -> [(Id,CoreExpr)] -- Put this on the end (avoid quadratic append) - -> HsBind Id - -> DsM [(Id,CoreExpr)] -- Result +dsHsBind :: AutoScc -> HsBind Id -> DsM (OrdList (Id,CoreExpr)) -dsHsBind _ rest (VarBind { var_id = var, var_rhs = expr, var_inline = inline_regardless }) - = do { core_expr <- dsLExpr expr +dsHsBind _ (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 @@ -98,212 +98,92 @@ dsHsBind _ rest (VarBind { var_id = var, var_rhs = expr, var_inline = inline_reg ; let var' | inline_regardless = var `setIdUnfolding` mkCompulsoryUnfolding core_expr' | otherwise = var - ; return ((var', core_expr') : rest) } + ; return (unitOL (makeCorePair var' False 0 core_expr')) } -dsHsBind _ rest - (FunBind { fun_id = L _ fun, fun_matches = matches, - fun_co_fn = co_fn, fun_tick = tick, fun_infix = inf }) +dsHsBind auto_scc (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) } + ; wrap_fn' <- dsHsWrapper co_fn + ; let rhs = addAutoScc auto_scc fun $ wrap_fn' (mkLams args body') + ; return (unitOL (makeCorePair fun False 0 rhs)) } -dsHsBind _ rest - (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) +dsHsBind auto_scc (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 - 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. + -- We silently ignore inline pragmas; no makeCorePair + -- Not so cool, but really doesn't matter + ; let sel_binds' = [ (v, addAutoScc auto_scc v expr) + | (v, expr) <- sel_binds ] + ; return (toOL sel_binds') } - 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 + -- A 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) +dsHsBind auto_scc (AbsBinds { abs_tvs = all_tyvars, abs_ev_vars = dicts + , abs_exports = [(tyvars, global, local, prags)] + , abs_ev_binds = ev_binds, abs_binds = binds }) = ASSERT( all (`elem` tyvars) all_tyvars ) - do { core_prs <- ds_lhs_binds NoSccs binds + do { bind_prs <- ds_lhs_binds NoSccs binds + ; ds_ev_binds <- dsTcEvBinds ev_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 + ; let core_bind = Rec (fromOL bind_prs) + rhs = addAutoScc auto_scc global $ + mkLams tyvars $ mkLams dicts $ + wrapDsEvBinds ds_ev_binds $ + Let core_bind $ + Var local - ; (spec_binds, rules) <- dsSpecs all_tyvars dicts tyvars global - local inl_arity core_bind prags + ; (spec_binds, rules) <- dsSpecs rhs 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 + main_bind = makeCorePair global' (isDefaultMethod prags) + (dictArity dicts) rhs - ; return (main_bind : spec_binds ++ rest) } + ; return (main_bind `consOL` spec_binds) } -dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) - = do { core_prs <- ds_lhs_binds NoSccs binds +dsHsBind auto_scc (AbsBinds { abs_tvs = all_tyvars, abs_ev_vars = dicts + , abs_exports = exports, abs_ev_binds = ev_binds + , abs_binds = binds }) + = do { bind_prs <- ds_lhs_binds NoSccs binds + ; ds_ev_binds <- dsTcEvBinds ev_binds ; let env = mkABEnv exports - 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) + core_bind = Rec (map do_one (fromOL bind_prs)) + -- Monomorphic recursion possible, hence Rec - 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 + tup_expr = mkBigCoreVarTup locals + tup_ty = exprType tup_expr + poly_tup_rhs = mkLams all_tyvars $ mkLams dicts $ + wrapDsEvBinds ds_ev_binds $ + Let core_bind $ + tup_expr + locals = [local | (_, _, local, _) <- exports] + local_tys = map idType locals - ; poly_tup_id <- newSysLocalDs (exprType poly_tup_expr) + ; poly_tup_id <- newSysLocalDs (exprType poly_tup_rhs) - ; let mk_bind ((tyvars, global, local, spec_prags), n) -- locals!!n == local + ; let mk_bind ((tyvars, global, _, 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) - ; (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 $ + ; let rhs = mkLams tyvars $ mkLams dicts $ mkTupleSelector locals' (locals' !! n) tup_id $ mkVarApps (mkTyApps (Var poly_tup_id) ty_args) dicts - ; return ((global', rhs) : spec_binds) } + full_rhs = Let (NonRec poly_tup_id poly_tup_rhs) rhs + ; (spec_binds, rules) <- dsSpecs full_rhs spec_prags + + ; let global' = addIdSpecialisations global rules + ; return ((global', rhs) `consOL` spec_binds) } where mk_ty_arg all_tyvar | all_tyvar `elem` tyvars = mkTyVarTy all_tyvar @@ -312,60 +192,237 @@ dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds) ; export_binds_s <- mapM mk_bind (exports `zip` [0..]) -- Don't scc (auto-)annotate the tuple itself. - ; return ((poly_tup_id, poly_tup_expr) : - (concat export_binds_s ++ rest)) } + ; return ((poly_tup_id, poly_tup_rhs) `consOL` + concatOL export_binds_s) } + +-------------------------------------- +data DsEvBind + = LetEvBind -- Dictionary or coercion + CoreBind -- recursive or non-recursive + | CaseEvBind -- Coercion binding by superclass selection + -- Desugars to case d of d { K _ g _ _ _ -> ... } + DictId -- b The dictionary + AltCon -- K Its constructor + [CoreBndr] -- _ g _ _ _ The binders in the alternative + +wrapDsEvBinds :: [DsEvBind] -> CoreExpr -> CoreExpr +wrapDsEvBinds ds_ev_binds body = foldr wrap_one body ds_ev_binds + where + body_ty = exprType body + wrap_one (LetEvBind b) body = Let b body + wrap_one (CaseEvBind x k xs) body = Case (Var x) x body_ty [(k,xs,body)] + +dsTcEvBinds :: TcEvBinds -> DsM [DsEvBind] +dsTcEvBinds (TcEvBinds {}) = panic "dsEvBinds" -- Zonker has got rid of this +dsTcEvBinds (EvBinds bs) = dsEvBinds bs + +dsEvBinds :: Bag EvBind -> DsM [DsEvBind] +dsEvBinds bs = return (map dsEvGroup sccs) + where + sccs :: [SCC EvBind] + sccs = stronglyConnCompFromEdgedVertices edges + + edges :: [(EvBind, EvVar, [EvVar])] + edges = foldrBag ((:) . mk_node) [] bs + + mk_node :: EvBind -> (EvBind, EvVar, [EvVar]) + mk_node b@(EvBind var term) = (b, var, free_vars_of term) + + free_vars_of :: EvTerm -> [EvVar] + free_vars_of (EvId v) = [v] + free_vars_of (EvCast v co) = v : varSetElems (tyCoVarsOfCo co) + free_vars_of (EvCoercion co) = varSetElems (tyCoVarsOfCo co) + free_vars_of (EvDFunApp _ _ vs) = vs + free_vars_of (EvSuperClass d _) = [d] + +dsEvGroup :: SCC EvBind -> DsEvBind +dsEvGroup (AcyclicSCC (EvBind co_var (EvSuperClass dict n))) + | isCoVar co_var -- An equality superclass + = ASSERT( null other_data_cons ) + CaseEvBind dict (DataAlt data_con) bndrs + where + (cls, tys) = getClassPredTys (evVarPred dict) + (data_con:other_data_cons) = tyConDataCons (classTyCon cls) + (ex_tvs, theta, rho) = tcSplitSigmaTy (applyTys (dataConRepType data_con) tys) + (arg_tys, _) = splitFunTys rho + bndrs = ex_tvs ++ map mk_wild_pred (theta `zip` [0..]) + ++ map mkWildValBinder arg_tys + mk_wild_pred (p, i) | i==n = ASSERT( p `eqPred` (coVarPred co_var)) + co_var + | otherwise = mkWildEvBinder p + +dsEvGroup (AcyclicSCC (EvBind v r)) + = LetEvBind (NonRec v (dsEvTerm r)) + +dsEvGroup (CyclicSCC bs) + = LetEvBind (Rec (map ds_pair bs)) + where + ds_pair (EvBind v r) = (v, dsEvTerm r) + +dsEvTerm :: EvTerm -> CoreExpr +dsEvTerm (EvId v) = Var v +dsEvTerm (EvCast v co) = Cast (Var v) co +dsEvTerm (EvDFunApp df tys vars) = Var df `mkTyApps` tys `mkVarApps` vars +dsEvTerm (EvCoercion co) = Coercion co +dsEvTerm (EvSuperClass d n) + = ASSERT( isClassPred (classSCTheta cls !! n) ) + -- We can only select *dictionary* superclasses + -- in terms. Equality superclasses are dealt with + -- in dsEvGroup, where they can generate a case expression + Var sc_sel_id `mkTyApps` tys `App` Var d + where + sc_sel_id = classSCSelId cls n -- Zero-indexed + (cls, tys) = getClassPredTys (evVarPred d) + ------------------------ -makeCorePair :: Id-> Arity -> CoreExpr -> (Id, CoreExpr) -makeCorePair gbl_id arity rhs - = (addInline gbl_id arity rhs, rhs) +makeCorePair :: Id -> Bool -> Arity -> CoreExpr -> (Id, CoreExpr) +makeCorePair gbl_id is_default_method dict_arity rhs + | is_default_method -- Default methods are *always* inlined + = (gbl_id `setIdUnfolding` mkCompulsoryUnfolding rhs, rhs) + + | otherwise + = case inlinePragmaSpec inline_prag of + EmptyInlineSpec -> (gbl_id, rhs) + NoInline -> (gbl_id, rhs) + Inlinable -> (gbl_id `setIdUnfolding` inlinable_unf, rhs) + Inline -> inline_pair + + where + inline_prag = idInlinePragma gbl_id + inlinable_unf = mkInlinableUnfolding rhs + inline_pair + | Just arity <- inlinePragmaSat inline_prag + -- Add an Unfolding for an INLINE (but not for NOINLINE) + -- And eta-expand the RHS; see Note [Eta-expanding INLINE things] + , let real_arity = dict_arity + arity + -- NB: The arity in the InlineRule takes account of the dictionaries + = ( gbl_id `setIdUnfolding` mkInlineUnfolding (Just real_arity) rhs + , etaExpand real_arity rhs) + + | otherwise + = pprTrace "makeCorePair: arity missing" (ppr gbl_id) $ + (gbl_id `setIdUnfolding` mkInlineUnfolding Nothing rhs, rhs) + + +dictArity :: [Var] -> Arity +-- Don't count coercion variables in arity +dictArity dicts = count isId dicts + ------------------------ -type AbsBindEnv = VarEnv ([TyVar], Id, Id, [LSpecPrag]) +type AbsBindEnv = VarEnv ([TyVar], Id, Id, TcSpecPrags) -- Maps the "lcl_id" for an AbsBind to -- its "gbl_id" and associated pragmas, if any -mkABEnv :: [([TyVar], Id, Id, [LSpecPrag])] -> AbsBindEnv +mkABEnv :: [([TyVar], Id, Id, TcSpecPrags)] -> 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] +\end{code} -mkArityEnv :: LHsBinds Id -> IdEnv Arity - -- Maps a local to the arity of its definition -mkArityEnv binds = foldrBag (plusVarEnv . lhsBindArity) emptyVarEnv binds +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 [Specialising in no-dict case] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Even if there are no tyvars or dicts, we may have specialisation pragmas. +Class methods can generate + AbsBinds [] [] [( ... spec-prag] + { AbsBinds [tvs] [dicts] ...blah } +So the overloading is in the nested AbsBinds. A good example is in GHC.Float: + + class (Real a, Fractional a) => RealFrac a where + round :: (Integral b) => a -> b + + instance RealFrac Float where + {-# SPECIALIZE round :: Float -> Int #-} + +The top-level AbsBinds for $cround has no tyvars or dicts (because the +instance does not). But the method is locally overloaded! + +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 -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 + AbsBinds [a,b] [ ([a,b], fg, fl, _), + ([b], gg, gl, _) ] + { fl = e1 + gl = e2 + h = e3 } -lhsBindArity _ = emptyVarEnv -- PatBind/VarBind +and desugar it to -dictArity :: [Var] -> Arity --- Don't count coercion variables in arity -dictArity dicts = count isId dicts + fg = /\ab. let B in e1 + gg = /\b. let a = () in let B in S(e2) + h = /\ab. let B in e3 -lookupArity :: IdEnv Arity -> Id -> Arity -lookupArity ar_env id = lookupVarEnv ar_env id `orElse` 0 +where B is the *non-recursive* binding + fl = fg a b + gl = gg b + h = h a b -- See (b); note shadowing! -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} +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. -Nested arities -~~~~~~~~~~~~~~ + (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. + + +Note [Eta-expanding INLINE things] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + foo :: Eq a => a -> a + {-# INLINE foo #-} + foo x = ... + +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 the arity with which it is declared in the source code. In this +example it has arity 2 (one for the Eq and one for x). Doing this +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: @@ -381,138 +438,205 @@ gotten from the binding for fromT_1. It might be better to have just one level of AbsBinds, but that requires more thought! +Note [Implementing SPECIALISE pragmas] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Example: + f :: (Eq a, Ix b) => a -> b -> Bool + {-# SPECIALISE f :: (Ix p, Ix q) => Int -> (p,q) -> Bool #-} + f = + +From this the typechecker generates + + AbsBinds [ab] [d1,d2] [([ab], f, f_mono, prags)] binds + + SpecPrag (wrap_fn :: forall a b. (Eq a, Ix b) => XXX + -> forall p q. (Ix p, Ix q) => XXX[ Int/a, (p,q)/b ]) + +Note that wrap_fn can transform *any* function with the right type prefix + forall ab. (Eq a, Ix b) => XXX +regardless of XXX. It's sort of polymorphic in XXX. This is +useful: we use the same wrapper to transform each of the class ops, as +well as the dict. + +From these we generate: + + Rule: forall p, q, (dp:Ix p), (dq:Ix q). + f Int (p,q) dInt ($dfInPair dp dq) = f_spec p q dp dq + + Spec bind: f_spec = wrap_fn + +Note that + + * The LHS of the rule may mention dictionary *expressions* (eg + $dfIxPair dp dq), and that is essential because the dp, dq are + needed on the RHS. + + * The RHS of f_spec, has a *copy* of 'binds', so that it + can fully specialise it. \begin{code} ------------------------ -dsSpecs :: [TyVar] -> [DictId] -> [TyVar] - -> Id -> Id -> Arity -- Global, local, arity of local - -> CoreBind -> [LSpecPrag] - -> DsM ( [(Id,CoreExpr)] -- Binding for specialised Ids +dsSpecs :: CoreExpr -- Its rhs + -> TcSpecPrags + -> DsM ( OrdList (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 #-} --- --- AbsBinds [ab] [d1,d2] [([ab], f, f_mono, prags)] binds --- --- SpecPrag (/\b.\(d:Ix b). f Int b dInt d) --- (forall b. Ix b => Int -> b -> b) --- --- Rule: forall b,(d:Ix b). f Int b dInt d = f_spec b d --- --- Spec bind: f_spec = Let f = /\ab \(d1:Eq a)(d2:Ix b). let binds in f_mono --- /\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 --- --- 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 - -dsSpecs all_tvs dicts tvs poly_id mono_id inl_arity mono_bind prags - = do { pairs <- mapMaybeM spec_one prags +-- See Note [Implementing SPECIALISE pragmas] +dsSpecs _ IsDefaultMethod = return (nilOL, []) +dsSpecs poly_rhs (SpecPrags sps) + = do { pairs <- mapMaybeM (dsSpec (Just poly_rhs)) sps ; 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 = 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:"), - 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 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) + ; return (concatOL spec_binds_s, rules) } + +dsSpec :: Maybe CoreExpr -- Just rhs => RULE is for a local binding + -- Nothing => RULE is for an imported Id + -- rhs is in the Id's unfolding + -> Located TcSpecPrag + -> DsM (Maybe (OrdList (Id,CoreExpr), CoreRule)) +dsSpec mb_poly_rhs (L loc (SpecPrag poly_id spec_co spec_inl)) + = putSrcSpanDs loc $ + do { let poly_name = idName poly_id + ; spec_name <- newLocalName poly_name + ; wrap_fn <- dsHsWrapper spec_co + ; let (bndrs, ds_lhs) = collectBinders (wrap_fn (Var poly_id)) + spec_ty = mkPiTypes bndrs (exprType ds_lhs) + ; case decomposeRuleLhs bndrs ds_lhs of { + Left msg -> do { warnDs msg; return Nothing } ; + Right (final_bndrs, _fn, args) -> do + + { (spec_unf, unf_pairs) <- specUnfolding wrap_fn spec_ty (realIdUnfolding poly_id) + + ; let 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 + + rule = mkRule False {- Not auto -} is_local_id + (mkFastString ("SPEC " ++ showSDoc (ppr poly_name))) + AlwaysActive poly_name + final_bndrs args + (mkVarApps (Var spec_id) bndrs) + + spec_rhs = wrap_fn poly_rhs + spec_pair = makeCorePair spec_id False (dictArity bndrs) spec_rhs + + ; return (Just (spec_pair `consOL` unf_pairs, rule)) + } } } + where + is_local_id = isJust mb_poly_rhs + poly_rhs | Just rhs <- mb_poly_rhs + = rhs -- Local Id; this is its rhs + | Just unfolding <- maybeUnfoldingTemplate (realIdUnfolding poly_id) + = unfolding -- Imported Id; this is its unfolding + -- Use realIdUnfolding so we get the unfolding + -- even when it is a loop breaker. + -- We want to specialise recursive functions! + | otherwise = pprPanic "dsImpSpecs" (ppr poly_id) + -- The type checker has checked that it *has* an unfolding + +specUnfolding :: (CoreExpr -> CoreExpr) -> Type + -> Unfolding -> DsM (Unfolding, OrdList (Id,CoreExpr)) +{- [Dec 10: TEMPORARILY commented out, until we can straighten out how to + generate unfoldings for specialised DFuns + +specUnfolding wrap_fn spec_ty (DFunUnfolding _ _ 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 [] = 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) + ; return (mkDFunUnfolding spec_ty (map Var spec_ids), toOL (spec_ids `zip` spec_rhss)) } +-} +specUnfolding _ _ _ + = return (noUnfolding, nilOL) dsMkArbitraryType :: TcTyVar -> Type dsMkArbitraryType tv = anyTypeOfKind (tyVarKind tv) \end{code} +%************************************************************************ +%* * +\subsection{Adding inline pragmas} +%* * +%************************************************************************ + +\begin{code} +decomposeRuleLhs :: [Var] -> CoreExpr -> Either SDoc ([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 bndrs lhs + = -- Note [Simplifying the left-hand side of a RULE] + case collectArgs opt_lhs of + (Var fn, args) -> check_bndrs fn args + + (Case scrut bndr ty [(DEFAULT, _, body)], args) + | isDeadBinder bndr -- Note [Matching seqId] + -> check_bndrs seqId (args' ++ args) + where + args' = [Type (idType bndr), Type ty, scrut, body] + + _other -> Left bad_shape_msg + where + opt_lhs = simpleOptExpr lhs + + check_bndrs fn args + | null (dead_bndrs) = Right (extra_dict_bndrs ++ bndrs, fn, args) + | otherwise = Left (vcat (map dead_msg dead_bndrs)) + where + arg_fvs = exprsFreeVars args + + -- Check for dead binders: Note [Unused spec binders] + dead_bndrs = filterOut (`elemVarSet` arg_fvs) bndrs + + -- Add extra dict binders: Note [Constant rule dicts] + extra_dict_bndrs = [ mkLocalId (localiseName (idName d)) (idType d) + | d <- varSetElems (arg_fvs `delVarSetList` bndrs) + , isDictId d] + + + bad_shape_msg = hang (ptext (sLit "RULE left-hand side too complicated to desugar")) + 2 (ppr opt_lhs) + dead_msg bndr = hang (sep [ ptext (sLit "Forall'd") <+> pp_bndr bndr + , ptext (sLit "is not bound in RULE lhs")]) + 2 (ppr opt_lhs) + pp_bndr bndr + | isTyVar bndr = ptext (sLit "type variable") <+> quotes (ppr bndr) + | isEvVar bndr = ptext (sLit "constraint") <+> quotes (ppr (evVarPred bndr)) + | otherwise = ptext (sLit "variable") <+> quotes (ppr bndr) +\end{code} + +Note [Simplifying the left-hand side of a RULE] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +simpleOptExpr occurrence-analyses and simplifies the lhs +and thereby +(a) sorts dict bindings into NonRecs and inlines them +(b) 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 +(c) does eta reduction + +For (c) consider the fold/build rule, which without simplification +looked like: + fold k z (build (/\a. g a)) ==> ... +This doesn't match unless you do eta reduction on the build argument. +Similarly for a LHS like + augment g (build h) +we do not want to get + augment (\a. g a) (build h) +otherwise we don't match when given an argument like + augment (\a. h a a) (build h) + +NB: tcSimplifyRuleLhs is very careful not to generate complicated + dictionary expressions that we might have to match + +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. + Note [Unused spec binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider @@ -528,7 +652,7 @@ 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] +Note [Constant 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 @@ -549,52 +673,9 @@ And from that we want the rule 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. - - -%************************************************************************ -%* * -\subsection{Adding inline pragmas} -%* * -%************************************************************************ - -\begin{code} -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 - = 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 - (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. +confused. Likewise it might have an InlineRule or something, which would be +utterly bogus. So we really make a fresh Id, with the same unique and type +as the old one, but with an Internal name and no IdInfo. %************************************************************************ @@ -607,6 +688,7 @@ See Note [Rules for seq] in MkId for the details. data AutoScc = NoSccs | AddSccs Module (Id -> Bool) -- The (Id->Bool) says which Ids to add SCCs to +-- But we never add a SCC to function marked INLINE addAutoScc :: AutoScc -> Id -- Binder @@ -615,6 +697,8 @@ addAutoScc :: AutoScc addAutoScc NoSccs _ rhs = rhs +addAutoScc _ id rhs | isInlinePragma (idInlinePragma id) + = rhs addAutoScc (AddSccs mod add_scc) id rhs | add_scc id = mkSCC (mkAutoCC id mod NotCafCC) rhs | otherwise = rhs @@ -648,19 +732,16 @@ addDictScc _ rhs = return rhs \begin{code} -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) } +dsHsWrapper :: HsWrapper -> DsM (CoreExpr -> CoreExpr) +dsHsWrapper WpHole = return (\e -> e) +dsHsWrapper (WpTyApp ty) = return (\e -> App e (Type ty)) +dsHsWrapper (WpLet ev_binds) = do { ds_ev_binds <- dsTcEvBinds ev_binds + ; return (wrapDsEvBinds ds_ev_binds) } +dsHsWrapper (WpCompose c1 c2) = do { k1 <- dsHsWrapper c1 + ; k2 <- dsHsWrapper c2 + ; return (k1 . k2) } +dsHsWrapper (WpCast co) = return (\e -> Cast e co) +dsHsWrapper (WpEvLam ev) = return (\e -> Lam ev e) +dsHsWrapper (WpTyLam tv) = return (\e -> Lam tv e) +dsHsWrapper (WpEvApp evtrm) = return (\e -> App e (dsEvTerm evtrm)) \end{code}