X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsExpr.lhs;h=eed7f87d8f304c49d989ff832729f5325d368fb0;hp=97c5d15afbaea7a5a49eb0d26de6134ce58f2582;hb=27de38efce6d73d2a0209f803cfa98c82773e773;hpb=ad94d40948668032189ad22a0ad741ac1f645f50 diff --git a/compiler/deSugar/DsExpr.lhs b/compiler/deSugar/DsExpr.lhs index 97c5d15..eed7f87 100644 --- a/compiler/deSugar/DsExpr.lhs +++ b/compiler/deSugar/DsExpr.lhs @@ -6,18 +6,17 @@ Desugaring exporessions. \begin{code} -{-# OPTIONS -w #-} +{-# OPTIONS -fno-warn-incomplete-patterns #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and fix -- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings -- for details module DsExpr ( dsExpr, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where #include "HsVersions.h" - import Match import MatchLit import DsBinds @@ -43,7 +42,9 @@ import TcType import Type import CoreSyn import CoreUtils +import MkCore +import DynFlags import CostCentre import Id import PrelInfo @@ -73,19 +74,20 @@ dsLocalBinds (HsIPBinds binds) body = dsIPBinds binds body ------------------------- dsValBinds :: HsValBinds Id -> CoreExpr -> DsM CoreExpr -dsValBinds (ValBindsOut binds _) body = foldrDs ds_val_bind body binds +dsValBinds (ValBindsOut binds _) body = foldrM ds_val_bind body binds ------------------------- +dsIPBinds :: HsIPBinds Id -> CoreExpr -> DsM CoreExpr dsIPBinds (IPBinds ip_binds dict_binds) body = do { prs <- dsLHsBinds dict_binds ; let inner = Let (Rec prs) body -- The dict bindings may not be in -- dependency order; hence Rec - ; foldrDs ds_ip_bind inner ip_binds } + ; foldrM ds_ip_bind inner ip_binds } where ds_ip_bind (L _ (IPBind n e)) body - = dsLExpr e `thenDs` \ e' -> - returnDs (Let (NonRec (ipNameName n) e') body) + = do e' <- dsLExpr e + return (Let (NonRec (ipNameName n) e') body) ------------------------- ds_val_bind :: (RecFlag, LHsBinds Id) -> CoreExpr -> DsM CoreExpr @@ -113,34 +115,34 @@ ds_val_bind (NonRecursive, hsbinds) body case bind of FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn, fun_tick = tick, fun_infix = inf } - -> matchWrapper (FunRhs (idName fun ) inf) matches `thenDs` \ (args, rhs) -> - ASSERT( null args ) -- Functions aren't lifted - ASSERT( isIdHsWrapper co_fn ) - mkOptTickBox tick rhs `thenDs` \ rhs' -> - returnDs (bindNonRec fun rhs' body_w_exports) + -> do (args, rhs) <- matchWrapper (FunRhs (idName fun ) inf) matches + MASSERT( null args ) -- Functions aren't lifted + MASSERT( isIdHsWrapper co_fn ) + rhs' <- mkOptTickBox tick rhs + return (bindNonRec fun rhs' body_w_exports) PatBind {pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty } -> -- let C x# y# = rhs in body -- ==> case rhs of C x# y# -> body putSrcSpanDs loc $ - do { rhs <- dsGuarded grhss ty - ; let upat = unLoc pat - eqn = EqnInfo { eqn_pats = [upat], - eqn_rhs = cantFailMatchResult body_w_exports } - ; var <- selectMatchVar upat - ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body) - ; return (scrungleMatch var rhs result) } + do { rhs <- dsGuarded grhss ty + ; let upat = unLoc pat + eqn = EqnInfo { eqn_pats = [upat], + eqn_rhs = cantFailMatchResult body_w_exports } + ; var <- selectMatchVar upat + ; result <- matchEquations PatBindRhs [var] [eqn] (exprType body) + ; return (scrungleMatch var rhs result) } - other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body) + _ -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body) -- Ordinary case for bindings; none should be unlifted -ds_val_bind (is_rec, binds) body +ds_val_bind (_is_rec, binds) body = do { prs <- dsLHsBinds binds ; ASSERT( not (any (isUnLiftedType . idType . fst) prs) ) case prs of - [] -> return body - other -> return (Let (Rec prs) body) } + [] -> return body + _ -> return (Let (Rec prs) body) } -- Use a Rec regardless of is_rec. -- Why? Because it allows the binds to be all -- mixed up, which is what happens in one rare case @@ -154,7 +156,7 @@ ds_val_bind (is_rec, binds) body isUnboxedTupleBind :: HsBind Id -> Bool isUnboxedTupleBind (PatBind { pat_rhs_ty = ty }) = isUnboxedTupleType ty -isUnboxedTupleBind other = False +isUnboxedTupleBind _ = False scrungleMatch :: Id -> CoreExpr -> CoreExpr -> CoreExpr -- Returns something like (let var = scrut in body) @@ -181,7 +183,7 @@ scrungleMatch var scrut body scrungle (Let binds body) = Let binds (scrungle body) scrungle other = panic ("scrungleMatch: tuple pattern:\n" ++ showSDoc (ppr other)) -\end{code} +\end{code} %************************************************************************ %* * @@ -197,25 +199,20 @@ dsLExpr (L loc e) = putSrcSpanDs loc $ dsExpr e dsExpr :: HsExpr Id -> DsM CoreExpr dsExpr (HsPar e) = dsLExpr e dsExpr (ExprWithTySigOut e _) = dsLExpr e -dsExpr (HsVar var) = returnDs (Var var) -dsExpr (HsIPVar ip) = returnDs (Var (ipNameName ip)) +dsExpr (HsVar var) = return (Var var) +dsExpr (HsIPVar ip) = return (Var (ipNameName ip)) dsExpr (HsLit lit) = dsLit lit dsExpr (HsOverLit lit) = dsOverLit lit dsExpr (HsWrap co_fn e) = dsCoercion co_fn (dsExpr e) dsExpr (NegApp expr neg_expr) - = do { core_expr <- dsLExpr expr - ; core_neg <- dsExpr neg_expr - ; return (core_neg `App` core_expr) } - -dsExpr expr@(HsLam a_Match) - = matchWrapper LambdaExpr a_Match `thenDs` \ (binders, matching_code) -> - returnDs (mkLams binders matching_code) - -dsExpr expr@(HsApp fun arg) - = dsLExpr fun `thenDs` \ core_fun -> - dsLExpr arg `thenDs` \ core_arg -> - returnDs (core_fun `mkDsApp` core_arg) + = App <$> dsExpr neg_expr <*> dsLExpr expr + +dsExpr (HsLam a_Match) + = uncurry mkLams <$> matchWrapper LambdaExpr a_Match + +dsExpr (HsApp fun arg) + = mkCoreApp <$> dsLExpr fun <*> dsLExpr arg \end{code} Operator sections. At first it looks as if we can convert @@ -241,53 +238,48 @@ will sort it out. \begin{code} dsExpr (OpApp e1 op _ e2) - = dsLExpr op `thenDs` \ core_op -> - -- for the type of y, we need the type of op's 2nd argument - dsLExpr e1 `thenDs` \ x_core -> - dsLExpr e2 `thenDs` \ y_core -> - returnDs (mkDsApps core_op [x_core, y_core]) + = -- for the type of y, we need the type of op's 2nd argument + mkCoreApps <$> dsLExpr op <*> mapM dsLExpr [e1, e2] dsExpr (SectionL expr op) -- Desugar (e !) to ((!) e) - = dsLExpr op `thenDs` \ core_op -> - dsLExpr expr `thenDs` \ x_core -> - returnDs (mkDsApp core_op x_core) + = mkCoreApp <$> dsLExpr op <*> dsLExpr expr -- dsLExpr (SectionR op expr) -- \ x -> op x expr -dsExpr (SectionR op expr) - = dsLExpr op `thenDs` \ core_op -> +dsExpr (SectionR op expr) = do + core_op <- dsLExpr op -- for the type of x, we need the type of op's 2nd argument - let - (x_ty:y_ty:_, _) = splitFunTys (exprType core_op) - -- See comment with SectionL - in - dsLExpr expr `thenDs` \ y_core -> - newSysLocalDs x_ty `thenDs` \ x_id -> - newSysLocalDs y_ty `thenDs` \ y_id -> - - returnDs (bindNonRec y_id y_core $ - Lam x_id (mkDsApps core_op [Var x_id, Var y_id])) + let (x_ty:y_ty:_, _) = splitFunTys (exprType core_op) + -- See comment with SectionL + y_core <- dsLExpr expr + x_id <- newSysLocalDs x_ty + y_id <- newSysLocalDs y_ty + return (bindNonRec y_id y_core $ + Lam x_id (mkCoreApps core_op [Var x_id, Var y_id])) -dsExpr (HsSCC cc expr) - = dsLExpr expr `thenDs` \ core_expr -> - getModuleDs `thenDs` \ mod_name -> - returnDs (Note (SCC (mkUserCC cc mod_name)) core_expr) +dsExpr (HsSCC cc expr) = do + mod_name <- getModuleDs + Note (SCC (mkUserCC cc mod_name)) <$> dsLExpr expr -- hdaume: core annotation dsExpr (HsCoreAnn fs expr) - = dsLExpr expr `thenDs` \ core_expr -> - returnDs (Note (CoreNote $ unpackFS fs) core_expr) + = Note (CoreNote $ unpackFS fs) <$> dsLExpr expr -dsExpr (HsCase discrim matches) - = dsLExpr discrim `thenDs` \ core_discrim -> - matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) -> - returnDs (scrungleMatch discrim_var core_discrim matching_code) +dsExpr (HsCase discrim matches@(MatchGroup _ rhs_ty)) + | isEmptyMatchGroup matches -- A Core 'case' is always non-empty + = -- So desugar empty HsCase to error call + mkErrorAppDs pAT_ERROR_ID (funResultTy rhs_ty) "case" + + | otherwise + = do { core_discrim <- dsLExpr discrim + ; ([discrim_var], matching_code) <- matchWrapper CaseAlt matches + ; return (scrungleMatch discrim_var core_discrim matching_code) } -- Pepe: The binds are in scope in the body but NOT in the binding group -- This is to avoid silliness in breakpoints -dsExpr (HsLet binds body) - = dsLExpr body `thenDs` \ body' -> +dsExpr (HsLet binds body) = do + body' <- dsLExpr body dsLocalBinds binds body' -- We need the `ListComp' form to use `deListComp' (rather than the "do" form) @@ -312,10 +304,7 @@ dsExpr (HsDo PArrComp stmts body result_ty) [elt_ty] = tcTyConAppArgs result_ty dsExpr (HsIf guard_expr then_expr else_expr) - = dsLExpr guard_expr `thenDs` \ core_guard -> - dsLExpr then_expr `thenDs` \ core_then -> - dsLExpr else_expr `thenDs` \ core_else -> - returnDs (mkIfThenElse core_guard core_then core_else) + = mkIfThenElse <$> dsLExpr guard_expr <*> dsLExpr then_expr <*> dsLExpr else_expr \end{code} @@ -323,13 +312,8 @@ dsExpr (HsIf guard_expr then_expr else_expr) \underline{\bf Various data construction things} % ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \begin{code} -dsExpr (ExplicitList ty xs) - = go xs - where - go [] = returnDs (mkNilExpr ty) - go (x:xs) = dsLExpr x `thenDs` \ core_x -> - go xs `thenDs` \ core_xs -> - returnDs (mkConsExpr ty core_x core_xs) +dsExpr (ExplicitList elt_ty xs) + = dsExplicitList elt_ty xs -- we create a list from the array elements and convert them into a list using -- `PrelPArr.toP' @@ -341,54 +325,35 @@ dsExpr (ExplicitList ty xs) -- that we can exploit the fact that we already know the length of the array -- here at compile time -- -dsExpr (ExplicitPArr ty xs) - = dsLookupGlobalId toPName `thenDs` \toP -> - dsExpr (ExplicitList ty xs) `thenDs` \coreList -> - returnDs (mkApps (Var toP) [Type ty, coreList]) +dsExpr (ExplicitPArr ty xs) = do + toP <- dsLookupGlobalId toPName + coreList <- dsExpr (ExplicitList ty xs) + return (mkApps (Var toP) [Type ty, coreList]) -dsExpr (ExplicitTuple expr_list boxity) - = mappM dsLExpr expr_list `thenDs` \ core_exprs -> - returnDs (mkConApp (tupleCon boxity (length expr_list)) - (map (Type . exprType) core_exprs ++ core_exprs)) +dsExpr (ExplicitTuple expr_list boxity) = do + core_exprs <- mapM dsLExpr expr_list + return (mkConApp (tupleCon boxity (length expr_list)) + (map (Type . exprType) core_exprs ++ core_exprs)) dsExpr (ArithSeq expr (From from)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - returnDs (App expr2 from2) + = App <$> dsExpr expr <*> dsLExpr from -dsExpr (ArithSeq expr (FromTo from two)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - dsLExpr two `thenDs` \ two2 -> - returnDs (mkApps expr2 [from2, two2]) +dsExpr (ArithSeq expr (FromTo from to)) + = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, to] dsExpr (ArithSeq expr (FromThen from thn)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - dsLExpr thn `thenDs` \ thn2 -> - returnDs (mkApps expr2 [from2, thn2]) - -dsExpr (ArithSeq expr (FromThenTo from thn two)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - dsLExpr thn `thenDs` \ thn2 -> - dsLExpr two `thenDs` \ two2 -> - returnDs (mkApps expr2 [from2, thn2, two2]) - -dsExpr (PArrSeq expr (FromTo from two)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - dsLExpr two `thenDs` \ two2 -> - returnDs (mkApps expr2 [from2, two2]) - -dsExpr (PArrSeq expr (FromThenTo from thn two)) - = dsExpr expr `thenDs` \ expr2 -> - dsLExpr from `thenDs` \ from2 -> - dsLExpr thn `thenDs` \ thn2 -> - dsLExpr two `thenDs` \ two2 -> - returnDs (mkApps expr2 [from2, thn2, two2]) - -dsExpr (PArrSeq expr _) + = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn] + +dsExpr (ArithSeq expr (FromThenTo from thn to)) + = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn, to] + +dsExpr (PArrSeq expr (FromTo from to)) + = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, to] + +dsExpr (PArrSeq expr (FromThenTo from thn to)) + = mkApps <$> dsExpr expr <*> mapM dsLExpr [from, thn, to] + +dsExpr (PArrSeq _ _) = panic "DsExpr.dsExpr: Infinite parallel array!" -- the parser shouldn't have generated it and the renamer and typechecker -- shouldn't have let it through @@ -416,30 +381,28 @@ We also handle @C{}@ as valid construction syntax for an unlabelled constructor @C@, setting all of @C@'s fields to bottom. \begin{code} -dsExpr (RecordCon (L _ data_con_id) con_expr rbinds) - = dsExpr con_expr `thenDs` \ con_expr' -> +dsExpr (RecordCon (L _ data_con_id) con_expr rbinds) = do + con_expr' <- dsExpr con_expr let - (arg_tys, _) = tcSplitFunTys (exprType con_expr') - -- A newtype in the corner should be opaque; - -- hence TcType.tcSplitFunTys - - mk_arg (arg_ty, lbl) -- Selector id has the field label as its name - = case findField (rec_flds rbinds) lbl of - (rhs:rhss) -> ASSERT( null rhss ) - dsLExpr rhs - [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showSDoc (ppr lbl)) - unlabelled_bottom arg_ty = mkErrorAppDs rEC_CON_ERROR_ID arg_ty "" - - labels = dataConFieldLabels (idDataCon data_con_id) - -- The data_con_id is guaranteed to be the wrapper id of the constructor - in - - (if null labels - then mappM unlabelled_bottom arg_tys - else mappM mk_arg (zipEqual "dsExpr:RecordCon" arg_tys labels)) - `thenDs` \ con_args -> - - returnDs (mkApps con_expr' con_args) + (arg_tys, _) = tcSplitFunTys (exprType con_expr') + -- A newtype in the corner should be opaque; + -- hence TcType.tcSplitFunTys + + mk_arg (arg_ty, lbl) -- Selector id has the field label as its name + = case findField (rec_flds rbinds) lbl of + (rhs:rhss) -> ASSERT( null rhss ) + dsLExpr rhs + [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showSDoc (ppr lbl)) + unlabelled_bottom arg_ty = mkErrorAppDs rEC_CON_ERROR_ID arg_ty "" + + labels = dataConFieldLabels (idDataCon data_con_id) + -- The data_con_id is guaranteed to be the wrapper id of the constructor + + con_args <- if null labels + then mapM unlabelled_bottom arg_tys + else mapM mk_arg (zipEqual "dsExpr:RecordCon" arg_tys labels) + + return (mkApps con_expr' con_args) \end{code} Record update is a little harder. Suppose we have the decl: @@ -548,10 +511,8 @@ dsExpr (HsBinTick ixT ixF e) = do \begin{code} -#ifdef DEBUG -- HsSyn constructs that just shouldn't be here: dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig" -#endif findField :: [HsRecField Id arg] -> Name -> [arg] @@ -562,6 +523,64 @@ findField rbinds lbl %-------------------------------------------------------------------- +Note [Desugaring explicit lists] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Explicit lists are desugared in a cleverer way to prevent some +fruitless allocations. Essentially, whenever we see a list literal +[x_1, ..., x_n] we: + +1. Find the tail of the list that can be allocated statically (say + [x_k, ..., x_n]) by later stages and ensure we desugar that + normally: this makes sure that we don't cause a code size increase + by having the cons in that expression fused (see later) and hence + being unable to statically allocate any more + +2. For the prefix of the list which cannot be allocated statically, + say [x_1, ..., x_(k-1)], we turn it into an expression involving + build so that if we find any foldrs over it it will fuse away + entirely! + + So in this example we will desugar to: + build (\c n -> x_1 `c` x_2 `c` .... `c` foldr c n [x_k, ..., x_n] + + If fusion fails to occur then build will get inlined and (since we + defined a RULE for foldr (:) []) we will get back exactly the + normal desugaring for an explicit list. + +This optimisation can be worth a lot: up to 25% of the total +allocation in some nofib programs. Specifically + + Program Size Allocs Runtime CompTime + rewrite +0.0% -26.3% 0.02 -1.8% + ansi -0.3% -13.8% 0.00 +0.0% + lift +0.0% -8.7% 0.00 -2.3% + +Of course, if rules aren't turned on then there is pretty much no +point doing this fancy stuff, and it may even be harmful. +\begin{code} + +dsExplicitList :: PostTcType -> [LHsExpr Id] -> DsM CoreExpr +-- See Note [Desugaring explicit lists] +dsExplicitList elt_ty xs = do + dflags <- getDOptsDs + xs' <- mapM dsLExpr xs + if not (dopt Opt_RewriteRules dflags) + then return $ mkListExpr elt_ty xs' + else mkBuildExpr elt_ty (mkSplitExplicitList (thisPackage dflags) xs') + where + mkSplitExplicitList this_package xs' (c, _) (n, n_ty) = do + let (dynamic_prefix, static_suffix) = spanTail (rhsIsStatic this_package) xs' + static_suffix' = mkListExpr elt_ty static_suffix + + folded_static_suffix <- mkFoldrExpr elt_ty n_ty (Var c) (Var n) static_suffix' + let build_body = foldr (App . App (Var c)) folded_static_suffix dynamic_prefix + return build_body + +spanTail :: (a -> Bool) -> [a] -> ([a], [a]) +spanTail f xs = (reverse rejected, reverse satisfying) + where (satisfying, rejected) = span f $ reverse xs +\end{code} + Desugar 'do' and 'mdo' expressions (NOT list comprehensions, they're handled in DsListComp). Basically does the translation given in the Haskell 98 report: @@ -572,7 +591,7 @@ dsDo :: [LStmt Id] -> Type -- Type of the whole expression -> DsM CoreExpr -dsDo stmts body result_ty +dsDo stmts body _result_ty = go (map unLoc stmts) where go [] = dsLExpr body @@ -581,7 +600,7 @@ dsDo stmts body result_ty = do { rhs2 <- dsLExpr rhs ; then_expr2 <- dsExpr then_expr ; rest <- go stmts - ; returnDs (mkApps then_expr2 [rhs2, rest]) } + ; return (mkApps then_expr2 [rhs2, rest]) } go (LetStmt binds : stmts) = do { rest <- go stmts @@ -589,14 +608,16 @@ dsDo stmts body result_ty go (BindStmt pat rhs bind_op fail_op : stmts) = - do { body <- go stmts + do { body <- go stmts + ; rhs' <- dsLExpr rhs + ; bind_op' <- dsExpr bind_op ; var <- selectSimpleMatchVarL pat + ; let bind_ty = exprType bind_op' -- rhs -> (pat -> res1) -> res2 + res1_ty = funResultTy (funArgTy (funResultTy bind_ty)) ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat - result_ty (cantFailMatchResult body) + res1_ty (cantFailMatchResult body) ; match_code <- handle_failure pat match fail_op - ; rhs' <- dsLExpr rhs - ; bind_op' <- dsExpr bind_op - ; returnDs (mkApps bind_op' [rhs', Lam var match_code]) } + ; return (mkApps bind_op' [rhs', Lam var match_code]) } -- In a do expression, pattern-match failure just calls -- the monadic 'fail' rather than throwing an exception @@ -608,6 +629,7 @@ dsDo stmts body result_ty | otherwise = extractMatchResult match (error "It can't fail") +mk_fail_msg :: Located e -> String mk_fail_msg pat = "Pattern match failure in do expression at " ++ showSDoc (ppr (getLoc pat)) \end{code} @@ -646,7 +668,7 @@ dsMDo tbl stmts body result_ty go (ExprStmt rhs _ rhs_ty : stmts) = do { rhs2 <- dsLExpr rhs ; rest <- go stmts - ; returnDs (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) } + ; return (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) } go (BindStmt pat rhs _ _ : stmts) = do { body <- go stmts @@ -658,7 +680,7 @@ dsMDo tbl stmts body result_ty ; match_code <- extractMatchResult match fail_expr ; rhs' <- dsLExpr rhs - ; returnDs (mkApps (Var bind_id) [Type (hsLPatType pat), Type b_ty, + ; return (mkApps (Var bind_id) [Type (hsLPatType pat), Type b_ty, rhs', Lam var match_code]) } go (RecStmt rec_stmts later_ids rec_ids rec_rets binds : stmts)