X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FdeSugar%2FDsUtils.lhs;h=79e757c94348f7fad5fb195a8ec3a3318cfe0acd;hb=3721dd37a707d2aacb5cac814410a78096e28a2c;hp=a26082fb8348e49487232846f6a54e1f0168fc77;hpb=7e602b0a11e567fcb035d1afd34015aebcf9a577;p=ghc-hetmet.git diff --git a/ghc/compiler/deSugar/DsUtils.lhs b/ghc/compiler/deSugar/DsUtils.lhs index a26082f..79e757c 100644 --- a/ghc/compiler/deSugar/DsUtils.lhs +++ b/ghc/compiler/deSugar/DsUtils.lhs @@ -10,48 +10,166 @@ module DsUtils ( CanItFail(..), EquationInfo(..), MatchResult(..), EqnNo, EqnSet, + tidyLitPat, tidyNPat, + + mkDsLet, + cantFailMatchResult, extractMatchResult, combineMatchResults, adjustMatchResult, adjustMatchResultDs, mkCoLetsMatchResult, mkGuardedMatchResult, mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult, - mkErrorAppDs, + mkErrorAppDs, mkNilExpr, mkConsExpr, mkListExpr, + mkIntExpr, mkCharExpr, + mkStringLit, mkStringLitFS, mkIntegerExpr, - mkSelectorBinds, mkTupleExpr, mkTupleSelector, + mkSelectorBinds, mkTupleExpr, mkTupleSelector, + mkTupleType, mkTupleCase, mkBigCoreTup, + mkCoreTup, mkCoreTupTy, + + dsReboundNames, lookupReboundName, - selectMatchVar + selectMatchVarL, selectMatchVar ) where #include "HsVersions.h" -import {-# SOURCE #-} Match ( matchSimply ) +import {-# SOURCE #-} Match ( matchSimply ) +import {-# SOURCE #-} DsExpr( dsLExpr ) -import HsSyn ( OutPat(..) ) -import TcHsSyn ( TypecheckedPat ) -import DsHsSyn ( outPatType, collectTypedPatBinders ) +import HsSyn +import TcHsSyn ( hsPatType ) import CoreSyn - +import Constants ( mAX_TUPLE_SIZE ) import DsMonad -import CoreUtils ( coreExprType ) -import PrelVals ( iRREFUT_PAT_ERROR_ID ) -import Id ( idType, Id, mkWildId ) -import Const ( Literal(..), Con(..) ) +import CoreUtils ( exprType, mkIfThenElse, mkCoerce, bindNonRec ) +import MkId ( iRREFUT_PAT_ERROR_ID, mkReboxingAlt, mkNewTypeBody ) +import Id ( idType, Id, mkWildId, mkTemplateLocals, mkSysLocal ) +import Name ( Name ) +import Literal ( Literal(..), inIntRange, tARGET_MAX_INT ) import TyCon ( isNewTyCon, tyConDataCons ) -import DataCon ( DataCon ) -import Type ( mkFunTy, isUnLiftedType, splitAlgTyConApp, - Type - ) -import TysWiredIn ( unitDataCon, tupleCon, stringTy, unitTy, unitDataCon ) +import DataCon ( DataCon, dataConSourceArity ) +import Type ( mkFunTy, isUnLiftedType, Type, splitTyConApp ) +import TcType ( tcTyConAppTyCon, isIntTy, isFloatTy, isDoubleTy ) +import TysPrim ( intPrimTy ) +import TysWiredIn ( nilDataCon, consDataCon, + tupleCon, mkTupleTy, + unitDataConId, unitTy, + charTy, charDataCon, + intTy, intDataCon, + floatDataCon, + doubleDataCon, + stringTy, isPArrFakeCon ) +import BasicTypes ( Boxity(..) ) import UniqSet ( mkUniqSet, minusUniqSet, isEmptyUniqSet, UniqSet ) +import UniqSupply ( splitUniqSupply, uniqFromSupply, uniqsFromSupply ) +import PrelNames ( unpackCStringName, unpackCStringUtf8Name, + plusIntegerName, timesIntegerName, smallIntegerDataConName, + lengthPName, indexPName ) import Outputable +import UnicodeUtil ( intsToUtf8, stringToUtf8 ) +import SrcLoc ( Located(..), unLoc, noLoc ) +import Util ( isSingleton, notNull, zipEqual ) +import ListSetOps ( assocDefault ) +import FastString +\end{code} + + + +%************************************************************************ +%* * + Rebindable syntax +%* * +%************************************************************************ + +\begin{code} +dsReboundNames :: ReboundNames Id + -> DsM ([CoreBind], -- Auxiliary bindings + [(Name,Id)]) -- Maps the standard name to its value + +dsReboundNames rebound_ids + = mapAndUnzipDs mk_bind rebound_ids `thenDs` \ (binds_s, prs) -> + return (concat binds_s, prs) + where + -- The cheapo special case can happen when we + -- make an intermediate HsDo when desugaring a RecStmt + mk_bind (std_name, L _ (HsVar id)) = return ([], (std_name, id)) + mk_bind (std_name, expr) + = dsLExpr expr `thenDs` \ rhs -> + newSysLocalDs (exprType rhs) `thenDs` \ id -> + return ([NonRec id rhs], (std_name, id)) + +lookupReboundName :: [(Name,Id)] -> Name -> CoreExpr +lookupReboundName prs std_name + = Var (assocDefault (mk_panic std_name) prs std_name) + where + mk_panic std_name = pprPanic "dsReboundNames" (ptext SLIT("Not found:") <+> ppr std_name) +\end{code} + + +%************************************************************************ +%* * +\subsection{Tidying lit pats} +%* * +%************************************************************************ + +\begin{code} +tidyLitPat :: HsLit -> LPat Id -> LPat Id +tidyLitPat (HsChar c) pat = mkCharLitPat c +tidyLitPat lit pat = pat + +tidyNPat :: HsLit -> Type -> LPat Id -> LPat Id +tidyNPat (HsString s) _ pat + | lengthFS s <= 1 -- Short string literals only + = foldr (\c pat -> mkPrefixConPat consDataCon [mkCharLitPat c,pat] stringTy) + (mkNilPat stringTy) (unpackFS s) + -- The stringTy is the type of the whole pattern, not + -- the type to instantiate (:) or [] with! + where + +tidyNPat lit lit_ty default_pat + | isIntTy lit_ty = mkPrefixConPat intDataCon [noLoc $ LitPat (mk_int lit)] lit_ty + | isFloatTy lit_ty = mkPrefixConPat floatDataCon [noLoc $ LitPat (mk_float lit)] lit_ty + | isDoubleTy lit_ty = mkPrefixConPat doubleDataCon [noLoc $ LitPat (mk_double lit)] lit_ty + | otherwise = default_pat + + where + mk_int (HsInteger i _) = HsIntPrim i + + mk_float (HsInteger i _) = HsFloatPrim (fromInteger i) + mk_float (HsRat f _) = HsFloatPrim f + + mk_double (HsInteger i _) = HsDoublePrim (fromInteger i) + mk_double (HsRat f _) = HsDoublePrim f \end{code} %************************************************************************ %* * -%* Selecting match variables +\subsection{Building lets} +%* * +%************************************************************************ + +Use case, not let for unlifted types. The simplifier will turn some +back again. + +\begin{code} +mkDsLet :: CoreBind -> CoreExpr -> CoreExpr +mkDsLet (NonRec bndr rhs) body + | isUnLiftedType (idType bndr) = Case rhs bndr [(DEFAULT,[],body)] +mkDsLet bind body + = Let bind body + +mkDsLets :: [CoreBind] -> CoreExpr -> CoreExpr +mkDsLets binds body = foldr mkDsLet body binds +\end{code} + + +%************************************************************************ +%* * +\subsection{ Selecting match variables} %* * %************************************************************************ @@ -61,11 +179,14 @@ hand, which should indeed be bound to the pattern as a whole, then use it; otherwise, make one up. \begin{code} -selectMatchVar :: TypecheckedPat -> DsM Id +selectMatchVarL :: LPat Id -> DsM Id +selectMatchVarL pat = selectMatchVar (unLoc pat) + selectMatchVar (VarPat var) = returnDs var -selectMatchVar (AsPat var pat) = returnDs var -selectMatchVar (LazyPat pat) = selectMatchVar pat -selectMatchVar other_pat = newSysLocalDs (outPatType other_pat) -- OK, better make up one... +selectMatchVar (AsPat var pat) = returnDs (unLoc var) +selectMatchVar (LazyPat pat) = selectMatchVarL pat +selectMatchVar other_pat = newSysLocalDs (hsPatType (noLoc other_pat)) + -- OK, better make up one... \end{code} @@ -93,7 +214,7 @@ data EquationInfo -- of the *first* thing matched in this group. -- Should perhaps be a list of them all! - [TypecheckedPat] -- The patterns for an eqn + [Pat Id] -- The patterns for an eqn MatchResult -- Encapsulates the guards and bindings \end{code} @@ -126,7 +247,7 @@ extractMatchResult (MatchResult CantFail match_fn) fail_expr extractMatchResult (MatchResult CanFail match_fn) fail_expr = mkFailurePair fail_expr `thenDs` \ (fail_bind, if_it_fails) -> match_fn if_it_fails `thenDs` \ body -> - returnDs (Let fail_bind body) + returnDs (mkDsLet fail_bind body) combineMatchResults :: MatchResult -> MatchResult -> MatchResult @@ -156,7 +277,7 @@ adjustMatchResultDs encl_fn (MatchResult can_it_fail body_fn) mkCoLetsMatchResult :: [CoreBind] -> MatchResult -> MatchResult mkCoLetsMatchResult binds match_result - = adjustMatchResult (mkLets binds) match_result + = adjustMatchResult (mkDsLets binds) match_result mkGuardedMatchResult :: CoreExpr -> MatchResult -> MatchResult @@ -171,11 +292,11 @@ mkCoPrimCaseMatchResult var match_alts = MatchResult CanFail mk_case where mk_case fail - = mapDs (mk_alt fail) match_alts `thenDs` \ alts -> - returnDs (Case (Var var) var (alts ++ [(DEFAULT, [], fail)])) + = mappM (mk_alt fail) match_alts `thenDs` \ alts -> + returnDs (Case (Var var) var ((DEFAULT, [], fail) : alts)) mk_alt fail (lit, MatchResult _ body_fn) = body_fn fail `thenDs` \ body -> - returnDs (Literal lit, [], body) + returnDs (LitAlt lit, [], body) mkCoAlgCaseMatchResult :: Id -- Scrutinee @@ -184,26 +305,27 @@ mkCoAlgCaseMatchResult :: Id -- Scrutinee mkCoAlgCaseMatchResult var match_alts | isNewTyCon tycon -- Newtype case; use a let - = ASSERT( newtype_sanity ) - mkCoLetsMatchResult [coercion_bind] match_result + = ASSERT( null (tail match_alts) && null (tail arg_ids) ) + mkCoLetsMatchResult [NonRec arg_id newtype_rhs] match_result + + | isPArrFakeAlts match_alts -- Sugared parallel array; use a literal case + = MatchResult CanFail mk_parrCase | otherwise -- Datatype case; use a case = MatchResult fail_flag mk_case where -- Common stuff scrut_ty = idType var - (tycon, tycon_arg_tys, _) = splitAlgTyConApp scrut_ty + tycon = tcTyConAppTyCon scrut_ty -- Newtypes must be opaque here -- Stuff for newtype - (con_id, arg_ids, match_result) = head match_alts - arg_id = head arg_ids - coercion_bind = NonRec arg_id (Note (Coerce (idType arg_id) scrut_ty) (Var var)) - newtype_sanity = null (tail match_alts) && null (tail arg_ids) - + (_, arg_ids, match_result) = head match_alts + arg_id = head arg_ids + newtype_rhs = mkNewTypeBody tycon (idType arg_id) (Var var) + -- Stuff for data types - data_cons = tyConDataCons tycon - - match_results = [match_result | (_,_,match_result) <- match_alts] + data_cons = tyConDataCons tycon + match_results = [match_result | (_,_,match_result) <- match_alts] fail_flag | exhaustive_case = foldr1 orFail [can_it_fail | MatchResult can_it_fail _ <- match_results] @@ -211,12 +333,13 @@ mkCoAlgCaseMatchResult var match_alts = CanFail wild_var = mkWildId (idType var) - mk_case fail = mapDs (mk_alt fail) match_alts `thenDs` \ alts -> - returnDs (Case (Var var) wild_var (alts ++ mk_default fail)) + mk_case fail = mappM (mk_alt fail) match_alts `thenDs` \ alts -> + returnDs (Case (Var var) wild_var (mk_default fail ++ alts)) mk_alt fail (con, args, MatchResult _ body_fn) - = body_fn fail `thenDs` \ body -> - returnDs (DataCon con, args, body) + = body_fn fail `thenDs` \ body -> + newUniqueSupply `thenDs` \ us -> + returnDs (mkReboxingAlt (uniqsFromSupply us) con args body) mk_default fail | exhaustive_case = [] | otherwise = [(DEFAULT, [], fail)] @@ -225,9 +348,73 @@ mkCoAlgCaseMatchResult var match_alts = mkUniqSet data_cons `minusUniqSet` mkUniqSet [ con | (con, _, _) <- match_alts] exhaustive_case = isEmptyUniqSet un_mentioned_constructors - + -- Stuff for parallel arrays + -- + -- * the following is to desugar cases over fake constructors for + -- parallel arrays, which are introduced by `tidy1' in the `PArrPat' + -- case + -- + -- Concerning `isPArrFakeAlts': + -- + -- * it is *not* sufficient to just check the type of the type + -- constructor, as we have to be careful not to confuse the real + -- representation of parallel arrays with the fake constructors; + -- moreover, a list of alternatives must not mix fake and real + -- constructors (this is checked earlier on) + -- + -- FIXME: We actually go through the whole list and make sure that + -- either all or none of the constructors are fake parallel + -- array constructors. This is to spot equations that mix fake + -- constructors with the real representation defined in + -- `PrelPArr'. It would be nicer to spot this situation + -- earlier and raise a proper error message, but it can really + -- only happen in `PrelPArr' anyway. + -- + isPArrFakeAlts [(dcon, _, _)] = isPArrFakeCon dcon + isPArrFakeAlts ((dcon, _, _):alts) = + case (isPArrFakeCon dcon, isPArrFakeAlts alts) of + (True , True ) -> True + (False, False) -> False + _ -> + panic "DsUtils: You may not mix `[:...:]' with `PArr' patterns" + -- + mk_parrCase fail = + dsLookupGlobalId lengthPName `thenDs` \lengthP -> + unboxAlt `thenDs` \alt -> + returnDs (Case (len lengthP) (mkWildId intTy) [alt]) + where + elemTy = case splitTyConApp (idType var) of + (_, [elemTy]) -> elemTy + _ -> panic panicMsg + panicMsg = "DsUtils.mkCoAlgCaseMatchResult: not a parallel array?" + len lengthP = mkApps (Var lengthP) [Type elemTy, Var var] + -- + unboxAlt = + newSysLocalDs intPrimTy `thenDs` \l -> + dsLookupGlobalId indexPName `thenDs` \indexP -> + mappM (mkAlt indexP) match_alts `thenDs` \alts -> + returnDs (DataAlt intDataCon, [l], (Case (Var l) wild (dft : alts))) + where + wild = mkWildId intPrimTy + dft = (DEFAULT, [], fail) + -- + -- each alternative matches one array length (corresponding to one + -- fake array constructor), so the match is on a literal; each + -- alternative's body is extended by a local binding for each + -- constructor argument, which are bound to array elements starting + -- with the first + -- + mkAlt indexP (con, args, MatchResult _ bodyFun) = + bodyFun fail `thenDs` \body -> + returnDs (LitAlt lit, [], mkDsLets binds body) + where + lit = MachInt $ toInteger (dataConSourceArity con) + binds = [NonRec arg (indexExpr i) | (i, arg) <- zip [1..] args] + -- + indexExpr i = mkApps (Var indexP) [Type elemTy, Var var, mkIntExpr i] \end{code} + %************************************************************************ %* * \subsection{Desugarer's versions of some Core functions} @@ -241,13 +428,90 @@ mkErrorAppDs :: Id -- The error function -> DsM CoreExpr mkErrorAppDs err_id ty msg - = getSrcLocDs `thenDs` \ src_loc -> + = getSrcSpanDs `thenDs` \ src_loc -> let full_msg = showSDoc (hcat [ppr src_loc, text "|", text msg]) + core_msg = Lit (MachStr (mkFastString (stringToUtf8 full_msg))) in - returnDs (mkApps (Var err_id) [Type ty, mkStringLit full_msg]) + returnDs (mkApps (Var err_id) [Type ty, core_msg]) \end{code} + +************************************************************* +%* * +\subsection{Making literals} +%* * +%************************************************************************ + +\begin{code} +mkCharExpr :: Char -> CoreExpr -- Returns C# c :: Int +mkIntExpr :: Integer -> CoreExpr -- Returns I# i :: Int +mkIntegerExpr :: Integer -> DsM CoreExpr -- Result :: Integer +mkStringLit :: String -> DsM CoreExpr -- Result :: String +mkStringLitFS :: FastString -> DsM CoreExpr -- Result :: String + +mkIntExpr i = mkConApp intDataCon [mkIntLit i] +mkCharExpr c = mkConApp charDataCon [mkLit (MachChar c)] + +mkIntegerExpr i + | inIntRange i -- Small enough, so start from an Int + = dsLookupDataCon smallIntegerDataConName `thenDs` \ integer_dc -> + returnDs (mkSmallIntegerLit integer_dc i) + +-- Special case for integral literals with a large magnitude: +-- They are transformed into an expression involving only smaller +-- integral literals. This improves constant folding. + + | otherwise -- Big, so start from a string + = dsLookupGlobalId plusIntegerName `thenDs` \ plus_id -> + dsLookupGlobalId timesIntegerName `thenDs` \ times_id -> + dsLookupDataCon smallIntegerDataConName `thenDs` \ integer_dc -> + let + lit i = mkSmallIntegerLit integer_dc i + plus a b = Var plus_id `App` a `App` b + times a b = Var times_id `App` a `App` b + + -- Transform i into (x1 + (x2 + (x3 + (...) * b) * b) * b) with abs xi <= b + horner :: Integer -> Integer -> CoreExpr + horner b i | abs q <= 1 = if r == 0 || r == i + then lit i + else lit r `plus` lit (i-r) + | r == 0 = horner b q `times` lit b + | otherwise = lit r `plus` (horner b q `times` lit b) + where + (q,r) = i `quotRem` b + + in + returnDs (horner tARGET_MAX_INT i) + +mkSmallIntegerLit small_integer_data_con i = mkConApp small_integer_data_con [mkIntLit i] + +mkStringLit str = mkStringLitFS (mkFastString str) + +mkStringLitFS str + | nullFastString str + = returnDs (mkNilExpr charTy) + + | lengthFS str == 1 + = let + the_char = mkCharExpr (headFS str) + in + returnDs (mkConsExpr charTy the_char (mkNilExpr charTy)) + + | all safeChar int_chars + = dsLookupGlobalId unpackCStringName `thenDs` \ unpack_id -> + returnDs (App (Var unpack_id) (Lit (MachStr str))) + + | otherwise + = dsLookupGlobalId unpackCStringUtf8Name `thenDs` \ unpack_id -> + returnDs (App (Var unpack_id) (Lit (MachStr (mkFastString (intsToUtf8 int_chars))))) + + where + int_chars = unpackIntFS str + safeChar c = c >= 1 && c <= 0xFF +\end{code} + + %************************************************************************ %* * \subsection[mkSelectorBind]{Make a selector bind} @@ -256,10 +520,10 @@ mkErrorAppDs err_id ty msg This is used in various places to do with lazy patterns. For each binder $b$ in the pattern, we create a binding: - +\begin{verbatim} b = case v of pat' -> b' - -where pat' is pat with each binder b cloned into b'. +\end{verbatim} +where @pat'@ is @pat@ with each binder @b@ cloned into @b'@. ToDo: making these bindings should really depend on whether there's much work to be done per binding. If the pattern is complex, it @@ -271,76 +535,132 @@ even more helpful. Something very similar happens for pattern-bound expressions. \begin{code} -mkSelectorBinds :: TypecheckedPat -- The pattern - -> CoreExpr -- Expression to which the pattern is bound +mkSelectorBinds :: LPat Id -- The pattern + -> CoreExpr -- Expression to which the pattern is bound -> DsM [(Id,CoreExpr)] -mkSelectorBinds (VarPat v) val_expr +mkSelectorBinds (L _ (VarPat v)) val_expr = returnDs [(v, val_expr)] mkSelectorBinds pat val_expr - | length binders == 1 || is_simple_pat pat - = newSysLocalDs (coreExprType val_expr) `thenDs` \ val_var -> - - -- For the error message we don't use mkErrorAppDs to avoid - -- duplicating the string literal each time - newSysLocalDs stringTy `thenDs` \ msg_var -> - getSrcLocDs `thenDs` \ src_loc -> - let - full_msg = showSDoc (hcat [ppr src_loc, text "|", ppr pat]) - in - mapDs (mk_bind val_var msg_var) binders `thenDs` \ binds -> + | isSingleton binders || is_simple_lpat pat + = -- Given p = e, where p binds x,y + -- we are going to make + -- v = p (where v is fresh) + -- x = case v of p -> x + -- y = case v of p -> x + + -- Make up 'v' + -- NB: give it the type of *pattern* p, not the type of the *rhs* e. + -- This does not matter after desugaring, but there's a subtle + -- issue with implicit parameters. Consider + -- (x,y) = ?i + -- Then, ?i is given type {?i :: Int}, a PredType, which is opaque + -- to the desugarer. (Why opaque? Because newtypes have to be. Why + -- does it get that type? So that when we abstract over it we get the + -- right top-level type (?i::Int) => ...) + -- + -- So to get the type of 'v', use the pattern not the rhs. Often more + -- efficient too. + newSysLocalDs (hsPatType pat) `thenDs` \ val_var -> + + -- For the error message we make one error-app, to avoid duplication. + -- But we need it at different types... so we use coerce for that + mkErrorAppDs iRREFUT_PAT_ERROR_ID + unitTy (showSDoc (ppr pat)) `thenDs` \ err_expr -> + newSysLocalDs unitTy `thenDs` \ err_var -> + mappM (mk_bind val_var err_var) binders `thenDs` \ binds -> returnDs ( (val_var, val_expr) : - (msg_var, mkStringLit full_msg) : + (err_var, err_expr) : binds ) | otherwise - = mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (showSDoc (ppr pat)) `thenDs` \ error_expr -> - matchSimply val_expr LetMatch pat local_tuple error_expr `thenDs` \ tuple_expr -> + = mkErrorAppDs iRREFUT_PAT_ERROR_ID + tuple_ty (showSDoc (ppr pat)) `thenDs` \ error_expr -> + matchSimply val_expr PatBindRhs pat local_tuple error_expr `thenDs` \ tuple_expr -> newSysLocalDs tuple_ty `thenDs` \ tuple_var -> let - mk_tup_bind binder = (binder, mkTupleSelector binders binder tuple_var (Var tuple_var)) + mk_tup_bind binder + = (binder, mkTupleSelector binders binder tuple_var (Var tuple_var)) in returnDs ( (tuple_var, tuple_expr) : map mk_tup_bind binders ) where - binders = collectTypedPatBinders pat + binders = collectPatBinders pat local_tuple = mkTupleExpr binders - tuple_ty = coreExprType local_tuple + tuple_ty = exprType local_tuple - mk_bind scrut_var msg_var bndr_var - -- (mk_bind sv bv) generates - -- bv = case sv of { pat -> bv; other -> error-msg } + mk_bind scrut_var err_var bndr_var + -- (mk_bind sv err_var) generates + -- bv = case sv of { pat -> bv; other -> coerce (type-of-bv) err_var } -- Remember, pat binds bv - = matchSimply (Var scrut_var) LetMatch pat + = matchSimply (Var scrut_var) PatBindRhs pat (Var bndr_var) error_expr `thenDs` \ rhs_expr -> returnDs (bndr_var, rhs_expr) where - binder_ty = idType bndr_var - error_expr = mkApps (Var iRREFUT_PAT_ERROR_ID) [Type binder_ty, Var msg_var] + error_expr = mkCoerce (idType bndr_var) (Var err_var) - is_simple_pat (TuplePat ps True{-boxed-}) = all is_triv_pat ps - is_simple_pat (ConPat _ _ _ _ ps) = all is_triv_pat ps - is_simple_pat (VarPat _) = True - is_simple_pat (RecPat _ _ _ _ ps) = and [is_triv_pat p | (_,p,_) <- ps] - is_simple_pat other = False + is_simple_lpat p = is_simple_pat (unLoc p) + + is_simple_pat (TuplePat ps Boxed) = all is_triv_lpat ps + is_simple_pat (ConPatOut _ ps _ _ _) = all is_triv_lpat (hsConArgs ps) + is_simple_pat (VarPat _) = True + is_simple_pat (ParPat p) = is_simple_lpat p + is_simple_pat other = False + + is_triv_lpat p = is_triv_pat (unLoc p) is_triv_pat (VarPat v) = True is_triv_pat (WildPat _) = True + is_triv_pat (ParPat p) = is_triv_lpat p is_triv_pat other = False \end{code} -@mkTupleExpr@ builds a tuple; the inverse to @mkTupleSelector@. If it -has only one element, it is the identity function. +%************************************************************************ +%* * + Tuples +%* * +%************************************************************************ + +@mkTupleExpr@ builds a tuple; the inverse to @mkTupleSelector@. + +* If it has only one element, it is the identity function. + +* If there are more elements than a big tuple can have, it nests + the tuples. + +Nesting policy. Better a 2-tuple of 10-tuples (3 objects) than +a 10-tuple of 2-tuples (11 objects). So we want the leaves to be big. \begin{code} mkTupleExpr :: [Id] -> CoreExpr +mkTupleExpr ids = mkBigCoreTup (map Var ids) + +-- corresponding type +mkTupleType :: [Id] -> Type +mkTupleType ids = mkBigTuple mkCoreTupTy (map idType ids) + +mkBigCoreTup :: [CoreExpr] -> CoreExpr +mkBigCoreTup = mkBigTuple mkCoreTup -mkTupleExpr [] = mkConApp unitDataCon [] -mkTupleExpr [id] = Var id -mkTupleExpr ids = mkConApp (tupleCon (length ids)) - (map (Type . idType) ids ++ [ Var i | i <- ids ]) +mkBigTuple :: ([a] -> a) -> [a] -> a +mkBigTuple small_tuple as = mk_big_tuple (chunkify as) + where + -- Each sub-list is short enough to fit in a tuple + mk_big_tuple [as] = small_tuple as + mk_big_tuple as_s = mk_big_tuple (chunkify (map small_tuple as_s)) + +chunkify :: [a] -> [[a]] +-- The sub-lists of the result all have length <= mAX_TUPLE_SIZE +-- But there may be more than mAX_TUPLE_SIZE sub-lists +chunkify xs + | n_xs <= mAX_TUPLE_SIZE = {- pprTrace "Small" (ppr n_xs) -} [xs] + | otherwise = {- pprTrace "Big" (ppr n_xs) -} (split xs) + where + n_xs = length xs + split [] = [] + split xs = take mAX_TUPLE_SIZE xs : split (drop mAX_TUPLE_SIZE xs) \end{code} @@ -353,20 +673,147 @@ are in scope. If there is just one id in the ``tuple'', then the selector is just the identity. +If it's big, it does nesting + mkTupleSelector [a,b,c,d] b v e + = case e of v { + (p,q) -> case p of p { + (a,b) -> b }} +We use 'tpl' vars for the p,q, since shadowing does not matter. + +In fact, it's more convenient to generate it innermost first, getting + + case (case e of v + (p,q) -> p) of p + (a,b) -> b + \begin{code} -mkTupleSelector :: [Id] -- The tuple args - -> Id -- The selected one - -> Id -- A variable of the same type as the scrutinee - -> CoreExpr -- Scrutinee +mkTupleSelector :: [Id] -- The tuple args + -> Id -- The selected one + -> Id -- A variable of the same type as the scrutinee + -> CoreExpr -- Scrutinee -> CoreExpr -mkTupleSelector [var] should_be_the_same_var scrut_var scrut +mkTupleSelector vars the_var scrut_var scrut + = mk_tup_sel (chunkify vars) the_var + where + mk_tup_sel [vars] the_var = mkCoreSel vars the_var scrut_var scrut + mk_tup_sel vars_s the_var = mkCoreSel group the_var tpl_v $ + mk_tup_sel (chunkify tpl_vs) tpl_v + where + tpl_tys = [mkCoreTupTy (map idType gp) | gp <- vars_s] + tpl_vs = mkTemplateLocals tpl_tys + [(tpl_v, group)] = [(tpl,gp) | (tpl,gp) <- zipEqual "mkTupleSelector" tpl_vs vars_s, + the_var `elem` gp ] +\end{code} + +A generalization of @mkTupleSelector@, allowing the body +of the case to be an arbitrary expression. + +If the tuple is big, it is nested: + + mkTupleCase uniqs [a,b,c,d] body v e + = case e of v { (p,q) -> + case p of p { (a,b) -> + case q of q { (c,d) -> + body }}} + +To avoid shadowing, we use uniqs to invent new variables p,q. + +ToDo: eliminate cases where none of the variables are needed. + +\begin{code} +mkTupleCase + :: UniqSupply -- for inventing names of intermediate variables + -> [Id] -- the tuple args + -> CoreExpr -- body of the case + -> Id -- a variable of the same type as the scrutinee + -> CoreExpr -- scrutinee + -> CoreExpr + +mkTupleCase uniqs vars body scrut_var scrut + = mk_tuple_case uniqs (chunkify vars) body + where + mk_tuple_case us [vars] body + = mkSmallTupleCase vars body scrut_var scrut + mk_tuple_case us vars_s body + = let + (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s + in + mk_tuple_case us' (chunkify vars') body' + one_tuple_case chunk_vars (us, vs, body) + = let + (us1, us2) = splitUniqSupply us + scrut_var = mkSysLocal FSLIT("ds") (uniqFromSupply us1) + (mkCoreTupTy (map idType chunk_vars)) + body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var) + in (us2, scrut_var:vs, body') +\end{code} + +The same, but with a tuple small enough not to need nesting. + +\begin{code} +mkSmallTupleCase + :: [Id] -- the tuple args + -> CoreExpr -- body of the case + -> Id -- a variable of the same type as the scrutinee + -> CoreExpr -- scrutinee + -> CoreExpr + +mkSmallTupleCase [var] body _scrut_var scrut + = bindNonRec var scrut body +mkSmallTupleCase vars body scrut_var scrut + = Case scrut scrut_var [(DataAlt (tupleCon Boxed (length vars)), vars, body)] +\end{code} + +%************************************************************************ +%* * +\subsection[mkFailurePair]{Code for pattern-matching and other failures} +%* * +%************************************************************************ + +Call the constructor Ids when building explicit lists, so that they +interact well with rules. + +\begin{code} +mkNilExpr :: Type -> CoreExpr +mkNilExpr ty = mkConApp nilDataCon [Type ty] + +mkConsExpr :: Type -> CoreExpr -> CoreExpr -> CoreExpr +mkConsExpr ty hd tl = mkConApp consDataCon [Type ty, hd, tl] + +mkListExpr :: Type -> [CoreExpr] -> CoreExpr +mkListExpr ty xs = foldr (mkConsExpr ty) (mkNilExpr ty) xs + + +-- The next three functions make tuple types, constructors and selectors, +-- with the rule that a 1-tuple is represented by the thing itselg +mkCoreTupTy :: [Type] -> Type +mkCoreTupTy [ty] = ty +mkCoreTupTy tys = mkTupleTy Boxed (length tys) tys + +mkCoreTup :: [CoreExpr] -> CoreExpr +-- Builds exactly the specified tuple. +-- No fancy business for big tuples +mkCoreTup [] = Var unitDataConId +mkCoreTup [c] = c +mkCoreTup cs = mkConApp (tupleCon Boxed (length cs)) + (map (Type . exprType) cs ++ cs) + +mkCoreSel :: [Id] -- The tuple args + -> Id -- The selected one + -> Id -- A variable of the same type as the scrutinee + -> CoreExpr -- Scrutinee + -> CoreExpr +-- mkCoreSel [x,y,z] x v e +-- ===> case e of v { (x,y,z) -> x +mkCoreSel [var] should_be_the_same_var scrut_var scrut = ASSERT(var == should_be_the_same_var) scrut -mkTupleSelector vars the_var scrut_var scrut - = ASSERT( not (null vars) ) - Case scrut scrut_var [(DataCon (tupleCon (length vars)), vars, Var the_var)] +mkCoreSel vars the_var scrut_var scrut + = ASSERT( notNull vars ) + Case scrut scrut_var + [(DataAlt (tupleCon Boxed (length vars)), vars, Var the_var)] \end{code} @@ -390,7 +837,7 @@ fail-variable, and use that variable if the thing fails: Then \begin{itemize} \item -If the case can't fail, then there'll be no mention of fail.33, and the +If the case can't fail, then there'll be no mention of @fail.33@, and the simplifier will later discard it. \item @@ -401,7 +848,7 @@ Only if it is used more than once will the let-binding remain. \end{itemize} There's a problem when the result of the case expression is of -unboxed type. Then the type of fail.33 is unboxed too, and +unboxed type. Then the type of @fail.33@ is unboxed too, and there is every chance that someone will change the let into a case: \begin{verbatim} case error "Help" of @@ -422,7 +869,7 @@ for the primitive case: p4 -> ... \end{verbatim} -Now fail.33 is a function, so it can be let-bound. +Now @fail.33@ is a function, so it can be let-bound. \begin{code} mkFailurePair :: CoreExpr -- Result type of the whole case expression @@ -435,14 +882,13 @@ mkFailurePair expr = newFailLocalDs (unitTy `mkFunTy` ty) `thenDs` \ fail_fun_var -> newSysLocalDs unitTy `thenDs` \ fail_fun_arg -> returnDs (NonRec fail_fun_var (Lam fail_fun_arg expr), - App (Var fail_fun_var) (mkConApp unitDataCon [])) + App (Var fail_fun_var) (Var unitDataConId)) | otherwise = newFailLocalDs ty `thenDs` \ fail_var -> returnDs (NonRec fail_var expr, Var fail_var) where - ty = coreExprType expr + ty = exprType expr \end{code} -