X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FdeSugar%2FDsListComp.lhs;h=d6b00657d7cb98297510f126a97384cfc8b25362;hb=f714e6b642fd614a9971717045ae47c3d871275e;hp=fd38e6201f8440ab63ad352a0e2a36bfda84c64e;hpb=111cee3f1ad93816cb828e38b38521d85c3bcebb;p=ghc-hetmet.git diff --git a/ghc/compiler/deSugar/DsListComp.lhs b/ghc/compiler/deSugar/DsListComp.lhs index fd38e62..d6b0065 100644 --- a/ghc/compiler/deSugar/DsListComp.lhs +++ b/ghc/compiler/deSugar/DsListComp.lhs @@ -1,33 +1,38 @@ % % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -\section[DsListComp]{Desugaring list comprehensions} +\section[DsListComp]{Desugaring list comprehensions and array comprehensions} \begin{code} -module DsListComp ( dsListComp ) where +module DsListComp ( dsListComp, dsPArrComp ) where #include "HsVersions.h" -import {-# SOURCE #-} DsExpr ( dsExpr, dsLet ) +import {-# SOURCE #-} DsExpr ( dsLExpr, dsLet ) -import HsSyn ( Stmt(..), HsExpr ) -import TcHsSyn ( TypecheckedStmt, TypecheckedHsExpr ) -import DsHsSyn ( outPatType ) +import BasicTypes ( Boxity(..) ) +import HsSyn +import TcHsSyn ( hsPatType ) import CoreSyn import DsMonad -- the monadery used in the desugarer import DsUtils -import CmdLineOpts ( opt_FoldrBuildOn ) -import CoreUtils ( exprType ) +import CmdLineOpts ( DynFlag(..), dopt, opt_RulesOff ) +import CoreUtils ( exprType, mkIfThenElse ) import Id ( idType ) -import Var ( Id, TyVar ) -import PrelInfo ( foldrId, buildId ) -import Type ( mkTyVarTy, mkForAllTy, mkFunTys, mkFunTy, Type ) -import TysPrim ( alphaTyVar, alphaTy ) -import TysWiredIn ( nilDataCon, consDataCon, listTyCon ) +import Var ( Id ) +import Type ( mkTyVarTy, mkFunTys, mkFunTy, Type, + splitTyConApp_maybe ) +import TysPrim ( alphaTyVar ) +import TysWiredIn ( nilDataCon, consDataCon, trueDataConId, falseDataConId, + unitDataConId, unitTy, mkListTy, parrTyCon ) import Match ( matchSimply ) -import Outputable +import PrelNames ( foldrName, buildName, replicatePName, mapPName, + filterPName, zipPName, crossPName ) +import PrelInfo ( pAT_ERROR_ID ) +import SrcLoc ( noLoc, unLoc ) +import Panic ( panic ) \end{code} List comprehensions may be desugared in one of two ways: ``ordinary'' @@ -37,26 +42,38 @@ turned on'' (if you read Gill {\em et al.}'s paper on the subject). There will be at least one ``qualifier'' in the input. \begin{code} -dsListComp :: [TypecheckedStmt] +dsListComp :: [LStmt Id] -> Type -- Type of list elements -> DsM CoreExpr - -dsListComp quals elt_ty - | not opt_FoldrBuildOn -- Be boring - = deListComp quals (mkNilExpr elt_ty) - - | otherwise -- foldr/build lives! - = newTyVarsDs [alphaTyVar] `thenDs` \ [n_tyvar] -> +dsListComp lquals elt_ty + = getDOptsDs `thenDs` \dflags -> + let + quals = map unLoc lquals + in + if opt_RulesOff || dopt Opt_IgnoreInterfacePragmas dflags + -- Either rules are switched off, or we are ignoring what there are; + -- Either way foldr/build won't happen, so use the more efficient + -- Wadler-style desugaring + || isParallelComp quals + -- Foldr-style desugaring can't handle + -- parallel list comprehensions + then deListComp quals (mkNilExpr elt_ty) + + else -- Foldr/build should be enabled, so desugar + -- into foldrs and builds + newTyVarsDs [alphaTyVar] `thenDs` \ [n_tyvar] -> let n_ty = mkTyVarTy n_tyvar c_ty = mkFunTys [elt_ty, n_ty] n_ty in - newSysLocalsDs [c_ty,n_ty] `thenDs` \ [c, n] -> - - dfListComp c n quals `thenDs` \ result -> - - returnDs (Var buildId `App` Type elt_ty - `App` mkLams [n_tyvar, c, n] result) + newSysLocalsDs [c_ty,n_ty] `thenDs` \ [c, n] -> + dfListComp c n quals `thenDs` \ result -> + dsLookupGlobalId buildName `thenDs` \ build_id -> + returnDs (Var build_id `App` Type elt_ty + `App` mkLams [n_tyvar, c, n] result) + + where isParallelComp (ParStmt bndrstmtss : _) = True + isParallelComp _ = False \end{code} %************************************************************************ @@ -102,16 +119,62 @@ TQ << [ e | p <- L1, qs ] ++ L2 >> = is the TE translation scheme. Note that we carry around the @L@ list already desugared. @dsListComp@ does the top TE rule mentioned above. +To the above, we add an additional rule to deal with parallel list +comprehensions. The translation goes roughly as follows: + [ e | p1 <- e11, let v1 = e12, p2 <- e13 + | q1 <- e21, let v2 = e22, q2 <- e23] + => + [ e | ((x1, .., xn), (y1, ..., ym)) <- + zip [(x1,..,xn) | p1 <- e11, let v1 = e12, p2 <- e13] + [(y1,..,ym) | q1 <- e21, let v2 = e22, q2 <- e23]] +where (x1, .., xn) are the variables bound in p1, v1, p2 + (y1, .., ym) are the variables bound in q1, v2, q2 + +In the translation below, the ParStmt branch translates each parallel branch +into a sub-comprehension, and desugars each independently. The resulting lists +are fed to a zip function, we create a binding for all the variables bound in all +the comprehensions, and then we hand things off the the desugarer for bindings. +The zip function is generated here a) because it's small, and b) because then we +don't have to deal with arbitrary limits on the number of zip functions in the +prelude, nor which library the zip function came from. +The introduced tuples are Boxed, but only because I couldn't get it to work +with the Unboxed variety. \begin{code} -deListComp :: [TypecheckedStmt] -> CoreExpr -> DsM CoreExpr +deListComp :: [Stmt Id] -> CoreExpr -> DsM CoreExpr + +deListComp (ParStmt stmtss_w_bndrs : quals) list + = mappM do_list_comp stmtss_w_bndrs `thenDs` \ exps -> + mkZipBind qual_tys `thenDs` \ (zip_fn, zip_rhs) -> + + -- Deal with [e | pat <- zip l1 .. ln] in example above + deBindComp pat (Let (Rec [(zip_fn, zip_rhs)]) (mkApps (Var zip_fn) exps)) + quals list + + where + bndrs_s = map snd stmtss_w_bndrs + + -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above + pat = noLoc (TuplePat pats Boxed) + pats = map mk_hs_tuple_pat bndrs_s + + -- Types of (x1,..,xn), (y1,..,yn) etc + qual_tys = map mk_bndrs_tys bndrs_s -deListComp [ReturnStmt expr] list -- Figure 7.4, SLPJ, p 135, rule C above - = dsExpr expr `thenDs` \ core_expr -> + do_list_comp (stmts, bndrs) + = dsListComp (stmts ++ [noLoc $ ResultStmt (mk_hs_tuple_expr bndrs)]) + (mk_bndrs_tys bndrs) + + mk_bndrs_tys bndrs = mkCoreTupTy (map idType bndrs) + + -- Last: the one to return +deListComp [ResultStmt expr] list -- Figure 7.4, SLPJ, p 135, rule C above + = dsLExpr expr `thenDs` \ core_expr -> returnDs (mkConsExpr (exprType core_expr) core_expr list) -deListComp (GuardStmt guard locn : quals) list -- rule B above - = dsExpr guard `thenDs` \ core_guard -> + -- Non-last: must be a guard +deListComp (ExprStmt guard ty : quals) list -- rule B above + = dsLExpr guard `thenDs` \ core_guard -> deListComp quals list `thenDs` \ core_rest -> returnDs (mkIfThenElse core_guard core_rest list) @@ -120,13 +183,19 @@ deListComp (LetStmt binds : quals) list = deListComp quals list `thenDs` \ core_rest -> dsLet binds core_rest -deListComp (BindStmt pat list1 locn : quals) core_list2 -- rule A' above - = dsExpr list1 `thenDs` \ core_list1 -> - let +deListComp (BindStmt pat list1 : quals) core_list2 -- rule A' above + = dsLExpr list1 `thenDs` \ core_list1 -> + deBindComp pat core_list1 quals core_list2 +\end{code} + + +\begin{code} +deBindComp pat core_list1 quals core_list2 + = let u3_ty@u1_ty = exprType core_list1 -- two names, same thing -- u1_ty is a [alpha] type, and u2_ty = alpha - u2_ty = outPatType pat + u2_ty = hsPatType pat res_ty = exprType core_list2 h_ty = u1_ty `mkFunTy` res_ty @@ -139,7 +208,7 @@ deListComp (BindStmt pat list1 locn : quals) core_list2 -- rule A' above letrec_body = App (Var h) core_list1 in deListComp quals core_fail `thenDs` \ rest_expr -> - matchSimply (Var u2) ListCompMatch pat + matchSimply (Var u2) (StmtCtxt ListComp) pat rest_expr core_fail `thenDs` \ core_match -> let rhs = Lam u1 $ @@ -150,6 +219,49 @@ deListComp (BindStmt pat list1 locn : quals) core_list2 -- rule A' above \end{code} +\begin{code} +mkZipBind :: [Type] -> DsM (Id, CoreExpr) +-- mkZipBind [t1, t2] +-- = (zip, \as1:[t1] as2:[t2] +-- -> case as1 of +-- [] -> [] +-- (a1:as'1) -> case as2 of +-- [] -> [] +-- (a2:as'2) -> (a2,a2) : zip as'1 as'2)] + +mkZipBind elt_tys + = mappM newSysLocalDs list_tys `thenDs` \ ass -> + mappM newSysLocalDs elt_tys `thenDs` \ as' -> + mappM newSysLocalDs list_tys `thenDs` \ as's -> + newSysLocalDs zip_fn_ty `thenDs` \ zip_fn -> + let + inner_rhs = mkConsExpr ret_elt_ty + (mkCoreTup (map Var as')) + (mkVarApps (Var zip_fn) as's) + zip_body = foldr mk_case inner_rhs (zip3 ass as' as's) + in + returnDs (zip_fn, mkLams ass zip_body) + where + list_tys = map mkListTy elt_tys + ret_elt_ty = mkCoreTupTy elt_tys + zip_fn_ty = mkFunTys list_tys (mkListTy ret_elt_ty) + + mk_case (as, a', as') rest + = Case (Var as) as [(DataAlt nilDataCon, [], mkNilExpr ret_elt_ty), + (DataAlt consDataCon, [a', as'], rest)] + +-- Helper functions that makes an HsTuple only for non-1-sized tuples +mk_hs_tuple_expr :: [Id] -> LHsExpr Id +mk_hs_tuple_expr [] = nlHsVar unitDataConId +mk_hs_tuple_expr [id] = nlHsVar id +mk_hs_tuple_expr ids = noLoc $ ExplicitTuple [ nlHsVar i | i <- ids ] Boxed + +mk_hs_tuple_pat :: [Id] -> LPat Id +mk_hs_tuple_pat [b] = nlVarPat b +mk_hs_tuple_pat bs = noLoc $ TuplePat (map nlVarPat bs) Boxed +\end{code} + + %************************************************************************ %* * \subsection[DsListComp-foldr-build]{Foldr/Build desugaring of list comprehensions} @@ -171,15 +283,17 @@ TE[ e | p <- l , q ] c n = let \begin{code} dfListComp :: Id -> Id -- 'c' and 'n' - -> [TypecheckedStmt] -- the rest of the qual's + -> [Stmt Id] -- the rest of the qual's -> DsM CoreExpr -dfListComp c_id n_id [ReturnStmt expr] - = dsExpr expr `thenDs` \ core_expr -> + -- Last: the one to return +dfListComp c_id n_id [ResultStmt expr] + = dsLExpr expr `thenDs` \ core_expr -> returnDs (mkApps (Var c_id) [core_expr, Var n_id]) -dfListComp c_id n_id (GuardStmt guard locn : quals) - = dsExpr guard `thenDs` \ core_guard -> + -- Non-last: must be a guard +dfListComp c_id n_id (ExprStmt guard ty : quals) + = dsLExpr guard `thenDs` \ core_guard -> dfListComp c_id n_id quals `thenDs` \ core_rest -> returnDs (mkIfThenElse core_guard core_rest (Var n_id)) @@ -188,12 +302,12 @@ dfListComp c_id n_id (LetStmt binds : quals) = dfListComp c_id n_id quals `thenDs` \ core_rest -> dsLet binds core_rest -dfListComp c_id n_id (BindStmt pat list1 locn : quals) +dfListComp c_id n_id (BindStmt pat list1 : quals) -- evaluate the two lists - = dsExpr list1 `thenDs` \ core_list1 -> + = dsLExpr list1 `thenDs` \ core_list1 -> -- find the required type - let x_ty = outPatType pat + let x_ty = hsPatType pat b_ty = idType n_id in @@ -204,16 +318,159 @@ dfListComp c_id n_id (BindStmt pat list1 locn : quals) dfListComp c_id b quals `thenDs` \ core_rest -> -- build the pattern match - matchSimply (Var x) ListCompMatch pat core_rest (Var b) `thenDs` \ core_expr -> + matchSimply (Var x) (StmtCtxt ListComp) + pat core_rest (Var b) `thenDs` \ core_expr -> -- now build the outermost foldr, and return + dsLookupGlobalId foldrName `thenDs` \ foldr_id -> returnDs ( - Var foldrId `App` Type x_ty - `App` Type b_ty - `App` mkLams [x, b] core_expr - `App` Var n_id - `App` core_list1 + Var foldr_id `App` Type x_ty + `App` Type b_ty + `App` mkLams [x, b] core_expr + `App` Var n_id + `App` core_list1 ) \end{code} +%************************************************************************ +%* * +\subsection[DsPArrComp]{Desugaring of array comprehensions} +%* * +%************************************************************************ +\begin{code} + +-- entry point for desugaring a parallel array comprehension +-- +-- [:e | qss:] = <<[:e | qss:]>> () [:():] +-- +dsPArrComp :: [Stmt Id] + -> Type -- Don't use; called with `undefined' below + -> DsM CoreExpr +dsPArrComp qs _ = + dsLookupGlobalId replicatePName `thenDs` \repP -> + let unitArray = mkApps (Var repP) [Type unitTy, + mkIntExpr 1, + mkCoreTup []] + in + dePArrComp qs (noLoc (TuplePat [] Boxed)) unitArray + +-- the work horse +-- +dePArrComp :: [Stmt Id] + -> LPat Id -- the current generator pattern + -> CoreExpr -- the current generator expression + -> DsM CoreExpr +-- +-- <<[:e' | :]>> pa ea = mapP (\pa -> e') ea +-- +dePArrComp [ResultStmt e'] pa cea = + dsLookupGlobalId mapPName `thenDs` \mapP -> + let ty = parrElemType cea + in + deLambda ty pa e' `thenDs` \(clam, + ty'e') -> + returnDs $ mkApps (Var mapP) [Type ty, Type ty'e', clam, cea] +-- +-- <<[:e' | b, qs:]>> pa ea = <<[:e' | qs:]>> pa (filterP (\pa -> b) ea) +-- +dePArrComp (ExprStmt b _ : qs) pa cea = + dsLookupGlobalId filterPName `thenDs` \filterP -> + let ty = parrElemType cea + in + deLambda ty pa b `thenDs` \(clam,_) -> + dePArrComp qs pa (mkApps (Var filterP) [Type ty, clam, cea]) +-- +-- <<[:e' | p <- e, qs:]>> pa ea = +-- let ef = filterP (\x -> case x of {p -> True; _ -> False}) e +-- in +-- <<[:e' | qs:]>> (pa, p) (crossP ea ef) +-- +dePArrComp (BindStmt p e : qs) pa cea = + dsLookupGlobalId filterPName `thenDs` \filterP -> + dsLookupGlobalId crossPName `thenDs` \crossP -> + dsLExpr e `thenDs` \ce -> + let ty'cea = parrElemType cea + ty'ce = parrElemType ce + false = Var falseDataConId + true = Var trueDataConId + in + newSysLocalDs ty'ce `thenDs` \v -> + matchSimply (Var v) (StmtCtxt PArrComp) p true false `thenDs` \pred -> + let cef = mkApps (Var filterP) [Type ty'ce, mkLams [v] pred, ce] + ty'cef = ty'ce -- filterP preserves the type + pa' = noLoc (TuplePat [pa, p] Boxed) + in + dePArrComp qs pa' (mkApps (Var crossP) [Type ty'cea, Type ty'cef, cea, cef]) +-- +-- <<[:e' | let ds, qs:]>> pa ea = +-- <<[:e' | qs:]>> (pa, (x_1, ..., x_n)) +-- (mapP (\v@pa -> (v, let ds in (x_1, ..., x_n))) ea) +-- where +-- {x_1, ..., x_n} = DV (ds) -- Defined Variables +-- +dePArrComp (LetStmt ds : qs) pa cea = + dsLookupGlobalId mapPName `thenDs` \mapP -> + let xs = map unLoc (collectGroupBinders ds) + ty'cea = parrElemType cea + in + newSysLocalDs ty'cea `thenDs` \v -> + dsLet ds (mkCoreTup (map Var xs)) `thenDs` \clet -> + newSysLocalDs (exprType clet) `thenDs` \let'v -> + let projBody = mkDsLet (NonRec let'v clet) $ + mkCoreTup [Var v, Var let'v] + errTy = exprType projBody + errMsg = "DsListComp.dePArrComp: internal error!" + in + mkErrorAppDs pAT_ERROR_ID errTy errMsg `thenDs` \cerr -> + matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr `thenDs` \ccase -> + let pa' = noLoc $ TuplePat [pa, noLoc (TuplePat (map nlVarPat xs) Boxed)] Boxed + proj = mkLams [v] ccase + in + dePArrComp qs pa' (mkApps (Var mapP) [Type ty'cea, proj, cea]) +-- +-- <<[:e' | qs | qss:]>> pa ea = +-- <<[:e' | qss:]>> (pa, (x_1, ..., x_n)) +-- (zipP ea <<[:(x_1, ..., x_n) | qs:]>>) +-- where +-- {x_1, ..., x_n} = DV (qs) +-- +dePArrComp (ParStmt [] : qss2) pa cea = dePArrComp qss2 pa cea +dePArrComp (ParStmt ((qs, xs):qss) : qss2) pa cea = + dsLookupGlobalId zipPName `thenDs` \zipP -> + let pa' = noLoc $ TuplePat [pa, noLoc (TuplePat (map nlVarPat xs) Boxed)] Boxed + ty'cea = parrElemType cea + resStmt = ResultStmt (noLoc $ ExplicitTuple (map nlHsVar xs) Boxed) + in + dsPArrComp (map unLoc qs ++ [resStmt]) undefined `thenDs` \cqs -> + let ty'cqs = parrElemType cqs + cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs] + in + dePArrComp (ParStmt qss : qss2) pa' cea' + +-- generate Core corresponding to `\p -> e' +-- +deLambda :: Type -- type of the argument + -> LPat Id -- argument pattern + -> LHsExpr Id -- body + -> DsM (CoreExpr, Type) +deLambda ty p e = + newSysLocalDs ty `thenDs` \v -> + dsLExpr e `thenDs` \ce -> + let errTy = exprType ce + errMsg = "DsListComp.deLambda: internal error!" + in + mkErrorAppDs pAT_ERROR_ID errTy errMsg `thenDs` \cerr -> + matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr `thenDs` \res -> + returnDs (mkLams [v] res, errTy) + +-- obtain the element type of the parallel array produced by the given Core +-- expression +-- +parrElemType :: CoreExpr -> Type +parrElemType e = + case splitTyConApp_maybe (exprType e) of + Just (tycon, [ty]) | tycon == parrTyCon -> ty + _ -> panic + "DsListComp.parrElemType: not a parallel array type" +\end{code}