%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[DsUtils]{Utilities for desugaring}
CanItFail(..), EquationInfo(..), MatchResult(..),
EqnNo, EqnSet,
- combineGRHSMatchResults,
- combineMatchResults,
- dsExprToAtomGivenTy, DsCoreArg,
- mkCoAlgCaseMatchResult,
- mkAppDs, mkConDs, mkPrimDs, mkErrorAppDs,
- mkCoLetsMatchResult,
- mkCoPrimCaseMatchResult,
- mkFailurePair,
- mkGuardedMatchResult,
- mkSelectorBinds,
- mkTupleExpr,
- mkTupleSelector,
- selectMatchVars,
- showForErr
+ tidyLitPat, tidyNPat,
+
+ mkDsLet, mkDsLets,
+
+ cantFailMatchResult, extractMatchResult,
+ combineMatchResults,
+ adjustMatchResult, adjustMatchResultDs,
+ mkCoLetsMatchResult, mkGuardedMatchResult,
+ mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult,
+
+ mkErrorAppDs, mkNilExpr, mkConsExpr, mkListExpr,
+ mkIntExpr, mkCharExpr,
+ mkStringLit, mkStringLitFS, mkIntegerExpr,
+
+ mkSelectorBinds, mkTupleExpr, mkTupleSelector,
+ mkTupleType, mkTupleCase, mkBigCoreTup,
+ mkCoreTup, mkCoreSel, mkCoreTupTy,
+
+ dsReboundNames, lookupReboundName,
+
+ selectMatchVar
) where
#include "HsVersions.h"
-import {-# SOURCE #-} Match ( matchSimply )
+import {-# SOURCE #-} Match ( matchSimply )
+import {-# SOURCE #-} DsExpr( dsExpr )
-import HsSyn ( OutPat(..), Stmt, DoOrListComp )
-import TcHsSyn ( TypecheckedPat )
-import DsHsSyn ( outPatType, collectTypedPatBinders )
+import HsSyn
+import TcHsSyn ( TypecheckedPat, hsPatType )
import CoreSyn
-
+import Constants ( mAX_TUPLE_SIZE )
import DsMonad
-import CoreUtils ( coreExprType, mkCoreIfThenElse )
-import PrelVals ( iRREFUT_PAT_ERROR_ID, voidId )
-import Id ( idType, dataConArgTys,
- DataCon, Id, GenId )
-import Literal ( Literal(..) )
-import PrimOp ( PrimOp )
+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 Type ( mkRhoTy, mkFunTy,
- isUnpointedType, mkTyConApp, splitAlgTyConApp,
- Type
- )
-import BasicTypes ( Unused )
-import TysPrim ( voidTy )
-import TysWiredIn ( unitDataCon, tupleCon, stringTy )
-import UniqSet ( mkUniqSet, minusUniqSet, uniqSetToList, UniqSet )
-import Unique ( Unique )
+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, smallIntegerDataCon,
+ floatDataCon,
+ doubleDataCon,
+ stringTy, isPArrFakeCon )
+import BasicTypes ( Boxity(..) )
+import UniqSet ( mkUniqSet, minusUniqSet, isEmptyUniqSet, UniqSet )
+import UniqSupply ( splitUniqSupply, uniqFromSupply )
+import PrelNames ( unpackCStringName, unpackCStringUtf8Name,
+ plusIntegerName, timesIntegerName,
+ lengthPName, indexPName )
import Outputable
+import UnicodeUtil ( intsToUtf8, stringToUtf8 )
+import Util ( isSingleton, notNull, zipEqual )
+import ListSetOps ( assocDefault )
+import FastString
\end{code}
+
%************************************************************************
%* *
-%* Selecting match variables
+ 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, HsVar id) = return ([], (std_name, id))
+ mk_bind (std_name, expr) = dsExpr 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 -> TypecheckedPat -> TypecheckedPat
+tidyLitPat (HsChar c) pat = mkCharLitPat c
+tidyLitPat lit pat = pat
+
+tidyNPat :: HsLit -> Type -> TypecheckedPat -> TypecheckedPat
+tidyNPat (HsString s) _ pat
+ | lengthFS s <= 1 -- Short string literals only
+ = foldr (\c pat -> mkPrefixConPat consDataCon [mkCharLitPat c,pat] stringTy)
+ (mkNilPat stringTy) (unpackIntFS 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 [LitPat (mk_int lit)] lit_ty
+ | isFloatTy lit_ty = mkPrefixConPat floatDataCon [LitPat (mk_float lit)] lit_ty
+ | isDoubleTy lit_ty = mkPrefixConPat doubleDataCon [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}
+
+
+%************************************************************************
+%* *
+\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}
%* *
%************************************************************************
otherwise, make one up.
\begin{code}
-selectMatchVars :: [TypecheckedPat] -> DsM [Id]
-selectMatchVars pats
- = mapDs var_from_pat_maybe pats
- where
- var_from_pat_maybe (VarPat var) = returnDs var
- var_from_pat_maybe (AsPat var pat) = returnDs var
- var_from_pat_maybe (LazyPat pat) = var_from_pat_maybe pat
- var_from_pat_maybe other_pat
- = newSysLocalDs (outPatType other_pat) -- OK, better make up one...
+selectMatchVar :: TypecheckedPat -> DsM Id
+selectMatchVar (VarPat var) = returnDs var
+selectMatchVar (AsPat var pat) = returnDs var
+selectMatchVar (LazyPat pat) = selectMatchVar pat
+selectMatchVar other_pat = newSysLocalDs (hsPatType other_pat) -- OK, better make up one...
\end{code}
data EquationInfo
= EqnInfo
- EqnNo -- The number of the equation
+ EqnNo -- The number of the equation
+
DsMatchContext -- The context info is used when producing warnings
-- about shadowed patterns. It's the context
-- of the *first* thing matched in this group.
-- Should perhaps be a list of them all!
- [TypecheckedPat] -- the patterns for an eqn
+
+ [TypecheckedPat] -- The patterns for an eqn
+
MatchResult -- Encapsulates the guards and bindings
\end{code}
\begin{code}
data MatchResult
= MatchResult
- CanItFail
- Type -- Type of argument expression
-
- (CoreExpr -> CoreExpr)
+ CanItFail -- Tells whether the failure expression is used
+ (CoreExpr -> DsM CoreExpr)
-- Takes a expression to plug in at the
-- failure point(s). The expression should
-- be duplicatable!
orFail CantFail CantFail = CantFail
orFail _ _ = CanFail
+\end{code}
+
+Functions on MatchResults
+\begin{code}
+cantFailMatchResult :: CoreExpr -> MatchResult
+cantFailMatchResult expr = MatchResult CantFail (\ ignore -> returnDs expr)
-mkCoLetsMatchResult :: [CoreBinding] -> MatchResult -> MatchResult
-mkCoLetsMatchResult binds (MatchResult can_it_fail ty body_fn)
- = MatchResult can_it_fail ty (\body -> mkCoLetsAny binds (body_fn body))
+extractMatchResult :: MatchResult -> CoreExpr -> DsM CoreExpr
+extractMatchResult (MatchResult CantFail match_fn) fail_expr
+ = match_fn (error "It can't fail!")
-mkGuardedMatchResult :: CoreExpr -> MatchResult -> DsM MatchResult
-mkGuardedMatchResult pred_expr (MatchResult can_it_fail ty body_fn)
- = returnDs (MatchResult CanFail
- ty
- (\fail -> mkCoreIfThenElse pred_expr (body_fn fail) fail)
- )
+extractMatchResult (MatchResult CanFail match_fn) fail_expr
+ = mkFailurePair fail_expr `thenDs` \ (fail_bind, if_it_fails) ->
+ match_fn if_it_fails `thenDs` \ body ->
+ returnDs (mkDsLet fail_bind body)
-mkCoPrimCaseMatchResult :: Id -- Scrutinee
- -> [(Literal, MatchResult)] -- Alternatives
- -> DsM MatchResult
-mkCoPrimCaseMatchResult var alts
- = newSysLocalDs (idType var) `thenDs` \ wild ->
- returnDs (MatchResult CanFail
- ty1
- (mk_case alts wild))
+
+combineMatchResults :: MatchResult -> MatchResult -> MatchResult
+combineMatchResults (MatchResult CanFail body_fn1)
+ (MatchResult can_it_fail2 body_fn2)
+ = MatchResult can_it_fail2 body_fn
where
- ((_,MatchResult _ ty1 _) : _) = alts
+ body_fn fail = body_fn2 fail `thenDs` \ body2 ->
+ mkFailurePair body2 `thenDs` \ (fail_bind, duplicatable_expr) ->
+ body_fn1 duplicatable_expr `thenDs` \ body1 ->
+ returnDs (Let fail_bind body1)
- mk_case alts wild fail_expr
- = Case (Var var) (PrimAlts final_alts (BindDefault wild fail_expr))
- where
- final_alts = [ (lit, body_fn fail_expr)
- | (lit, MatchResult _ _ body_fn) <- alts
- ]
-
-
-mkCoAlgCaseMatchResult :: Id -- Scrutinee
- -> [(DataCon, [Id], MatchResult)] -- Alternatives
- -> DsM MatchResult
-
-mkCoAlgCaseMatchResult var alts
- | isNewTyCon tycon -- newtype case; use a let
- = ASSERT( newtype_sanity )
- returnDs (mkCoLetsMatchResult [coercion_bind] match_result)
-
- | otherwise -- datatype case
- = -- Find all the constructors in the type which aren't
- -- explicitly mentioned in the alternatives:
- case un_mentioned_constructors of
- [] -> -- All constructors mentioned, so no default needed
- returnDs (MatchResult can_any_alt_fail
- ty1
- (mk_case alts (\ignore -> NoDefault)))
-
- [con] -> -- Just one constructor missing, so add a case for it
- -- We need to build new locals for the args of the constructor,
- -- and figuring out their types is somewhat tiresome.
- let
- arg_tys = dataConArgTys con tycon_arg_tys
- in
- newSysLocalsDs arg_tys `thenDs` \ arg_ids ->
-
- -- Now we are ready to construct the new alternative
- let
- new_alt = (con, arg_ids, MatchResult CanFail ty1 id)
- in
- returnDs (MatchResult CanFail
- ty1
- (mk_case (new_alt:alts) (\ignore -> NoDefault)))
-
- other -> -- Many constructors missing, so use a default case
- newSysLocalDs scrut_ty `thenDs` \ wild ->
- returnDs (MatchResult CanFail
- ty1
- (mk_case alts (\fail_expr -> BindDefault wild fail_expr)))
+combineMatchResults match_result1@(MatchResult CantFail body_fn1) match_result2
+ = match_result1
+
+
+adjustMatchResult :: (CoreExpr -> CoreExpr) -> MatchResult -> MatchResult
+adjustMatchResult encl_fn (MatchResult can_it_fail body_fn)
+ = MatchResult can_it_fail (\fail -> body_fn fail `thenDs` \ body ->
+ returnDs (encl_fn body))
+
+adjustMatchResultDs :: (CoreExpr -> DsM CoreExpr) -> MatchResult -> MatchResult
+adjustMatchResultDs encl_fn (MatchResult can_it_fail body_fn)
+ = MatchResult can_it_fail (\fail -> body_fn fail `thenDs` \ body ->
+ encl_fn body)
+
+
+mkCoLetsMatchResult :: [CoreBind] -> MatchResult -> MatchResult
+mkCoLetsMatchResult binds match_result
+ = adjustMatchResult (mkDsLets binds) match_result
+
+
+mkGuardedMatchResult :: CoreExpr -> MatchResult -> MatchResult
+mkGuardedMatchResult pred_expr (MatchResult can_it_fail body_fn)
+ = MatchResult CanFail (\fail -> body_fn fail `thenDs` \ body ->
+ returnDs (mkIfThenElse pred_expr body fail))
+
+mkCoPrimCaseMatchResult :: Id -- Scrutinee
+ -> [(Literal, MatchResult)] -- Alternatives
+ -> MatchResult
+mkCoPrimCaseMatchResult var match_alts
+ = MatchResult CanFail mk_case
where
- -- Common stuff
- scrut_ty = idType var
- (tycon, tycon_arg_tys, _) = splitAlgTyConApp scrut_ty
+ mk_case fail
+ = mapDs (mk_alt fail) match_alts `thenDs` \ alts ->
+ returnDs (Case (Var var) var ((DEFAULT, [], fail) : alts))
- -- Stuff for newtype
- (con_id, arg_ids, match_result) = head alts
- arg_id = head arg_ids
- coercion_bind = NonRec arg_id (Coerce (CoerceOut con_id)
- (idType arg_id)
- (Var var))
- newtype_sanity = null (tail alts) && null (tail arg_ids)
+ mk_alt fail (lit, MatchResult _ body_fn) = body_fn fail `thenDs` \ body ->
+ returnDs (LitAlt lit, [], body)
- -- Stuff for data types
- data_cons = tyConDataCons tycon
- un_mentioned_constructors
- = uniqSetToList (mkUniqSet data_cons `minusUniqSet` mkUniqSet [ con | (con, _, _) <- alts] )
+mkCoAlgCaseMatchResult :: Id -- Scrutinee
+ -> [(DataCon, [CoreBndr], MatchResult)] -- Alternatives
+ -> MatchResult
- match_results = [match_result | (_,_,match_result) <- alts]
- (MatchResult _ ty1 _ : _) = match_results
- can_any_alt_fail = foldr1 orFail [can_it_fail | MatchResult can_it_fail _ _ <- match_results]
+mkCoAlgCaseMatchResult var match_alts
+ | isNewTyCon tycon -- Newtype case; use a let
+ = ASSERT( null (tail match_alts) && null (tail arg_ids) )
+ mkCoLetsMatchResult [NonRec arg_id newtype_rhs] match_result
- mk_case alts deflt_fn fail_expr
- = Case (Var var) (AlgAlts final_alts (deflt_fn fail_expr))
- where
- final_alts = [ (con, args, body_fn fail_expr)
- | (con, args, MatchResult _ _ body_fn) <- alts
- ]
+ | 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 = tcTyConAppTyCon scrut_ty -- Newtypes must be opaque here
+ -- Stuff for newtype
+ (_, 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]
-combineMatchResults :: MatchResult -> MatchResult -> DsM MatchResult
-combineMatchResults (MatchResult CanFail ty1 body_fn1)
- (MatchResult can_it_fail2 ty2 body_fn2)
- = mkFailurePair ty1 `thenDs` \ (bind_fn, duplicatable_expr) ->
- let
- new_body_fn1 = \body1 -> Let (bind_fn body1) (body_fn1 duplicatable_expr)
- new_body_fn2 = \body2 -> new_body_fn1 (body_fn2 body2)
- in
- returnDs (MatchResult can_it_fail2 ty1 new_body_fn2)
+ fail_flag | exhaustive_case
+ = foldr1 orFail [can_it_fail | MatchResult can_it_fail _ <- match_results]
+ | otherwise
+ = CanFail
-combineMatchResults match_result1@(MatchResult CantFail ty body_fn1)
- match_result2
- = returnDs match_result1
+ wild_var = mkWildId (idType var)
+ mk_case fail = mapDs (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 ->
+ getUniquesDs `thenDs` \ us ->
+ returnDs (mkReboxingAlt us con args body)
--- The difference in combineGRHSMatchResults is that there is no
--- need to let-bind to avoid code duplication
-combineGRHSMatchResults :: MatchResult -> MatchResult -> DsM MatchResult
-combineGRHSMatchResults (MatchResult CanFail ty1 body_fn1)
- (MatchResult can_it_fail ty2 body_fn2)
- = returnDs (MatchResult can_it_fail ty1 (\ body -> body_fn1 (body_fn2 body)))
+ mk_default fail | exhaustive_case = []
+ | otherwise = [(DEFAULT, [], fail)]
-combineGRHSMatchResults match_result1 match_result2
- = -- Delegate to avoid duplication of code
- combineMatchResults match_result1 match_result2
+ un_mentioned_constructors
+ = 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 ->
+ mapDs (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[dsExprToAtom]{Take an expression and produce an atom}
+\subsection{Desugarer's versions of some Core functions}
%* *
%************************************************************************
\begin{code}
-dsArgToAtom :: DsCoreArg -- The argument expression
- -> (CoreArg -> DsM CoreExpr) -- Something taking the argument *atom*,
- -- and delivering an expression E
- -> DsM CoreExpr -- Either E or let x=arg-expr in E
-
-dsArgToAtom (TyArg t) continue_with = continue_with (TyArg t)
-dsArgToAtom (LitArg l) continue_with = continue_with (LitArg l)
-dsArgToAtom (VarArg arg) continue_with = dsExprToAtomGivenTy arg (coreExprType arg) continue_with
-
-dsExprToAtomGivenTy
- :: CoreExpr -- The argument expression
- -> Type -- Type of the argument
- -> (CoreArg -> DsM CoreExpr) -- Something taking the argument *atom*,
- -- and delivering an expression E
- -> DsM CoreExpr -- Either E or let x=arg-expr in E
-
-dsExprToAtomGivenTy (Var v) arg_ty continue_with = continue_with (VarArg v)
-dsExprToAtomGivenTy (Lit v) arg_ty continue_with = continue_with (LitArg v)
-dsExprToAtomGivenTy arg_expr arg_ty continue_with
- = newSysLocalDs arg_ty `thenDs` \ arg_id ->
- continue_with (VarArg arg_id) `thenDs` \ body ->
- returnDs (
- if isUnpointedType arg_ty
- then Case arg_expr (PrimAlts [] (BindDefault arg_id body))
- else Let (NonRec arg_id arg_expr) body
- )
-
-dsArgsToAtoms :: [DsCoreArg]
- -> ([CoreArg] -> DsM CoreExpr)
- -> DsM CoreExpr
-
-dsArgsToAtoms [] continue_with = continue_with []
-
-dsArgsToAtoms (arg:args) continue_with
- = dsArgToAtom arg $ \ arg_atom ->
- dsArgsToAtoms args $ \ arg_atoms ->
- continue_with (arg_atom:arg_atoms)
+mkErrorAppDs :: Id -- The error function
+ -> Type -- Type to which it should be applied
+ -> String -- The error message string to pass
+ -> DsM CoreExpr
+
+mkErrorAppDs err_id ty msg
+ = getSrcLocDs `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, core_msg])
\end{code}
-%************************************************************************
+
+*************************************************************
%* *
-\subsection{Desugarer's versions of some Core functions}
+\subsection{Making literals}
%* *
%************************************************************************
\begin{code}
-type DsCoreArg = GenCoreArg CoreExpr{-NB!-} Unused
+mkCharExpr :: Int -> 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
+ = returnDs (mkSmallIntegerLit 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 ->
+ let
+ 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 mkSmallIntegerLit i
+ else mkSmallIntegerLit r `plus` mkSmallIntegerLit (i-r)
+ | r == 0 = horner b q `times` mkSmallIntegerLit b
+ | otherwise = mkSmallIntegerLit r `plus` (horner b q `times` mkSmallIntegerLit b)
+ where
+ (q,r) = i `quotRem` b
-mkAppDs :: CoreExpr -> [DsCoreArg] -> DsM CoreExpr
-mkConDs :: Id -> [DsCoreArg] -> DsM CoreExpr
-mkPrimDs :: PrimOp -> [DsCoreArg] -> DsM CoreExpr
+ in
+ returnDs (horner tARGET_MAX_INT i)
-mkAppDs fun args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (mkGenApp fun atoms)
+mkSmallIntegerLit i = mkConApp smallIntegerDataCon [mkIntLit i]
-mkConDs con args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (Con con atoms)
+mkStringLit str = mkStringLitFS (mkFastString str)
-mkPrimDs op args
- = dsArgsToAtoms args $ \ atoms ->
- returnDs (Prim op atoms)
-\end{code}
+mkStringLitFS str
+ | nullFastString str
+ = returnDs (mkNilExpr charTy)
-\begin{code}
-showForErr :: Outputable a => a -> String -- Boring but useful
-showForErr thing = showSDoc (ppr thing)
+ | lengthFS str == 1
+ = let
+ the_char = mkCharExpr (headIntFS str)
+ in
+ returnDs (mkConsExpr charTy the_char (mkNilExpr charTy))
-mkErrorAppDs :: Id -- The error function
- -> Type -- Type to which it should be applied
- -> String -- The error message string to pass
- -> DsM CoreExpr
+ | all safeChar int_chars
+ = dsLookupGlobalId unpackCStringName `thenDs` \ unpack_id ->
+ returnDs (App (Var unpack_id) (Lit (MachStr str)))
-mkErrorAppDs err_id ty msg
- = getSrcLocDs `thenDs` \ src_loc ->
- let
- full_msg = showSDoc (hcat [ppr src_loc, text "|", text msg])
- msg_lit = NoRepStr (_PK_ full_msg)
- in
- returnDs (mkApp (Var err_id) [ty] [LitArg msg_lit])
+ | 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}
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
= 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])
- msg_lit = NoRepStr (_PK_ full_msg)
- in
- mapDs (mk_bind val_var msg_var) binders `thenDs` \ binds ->
+ | isSingleton binders || is_simple_pat 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 SourceType, 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 ->
+ mapDs (mk_bind val_var err_var) binders `thenDs` \ binds ->
returnDs ( (val_var, val_expr) :
- (msg_var, Lit msg_lit) :
+ (err_var, err_expr) :
binds )
| otherwise
- = mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (showSDoc (ppr pat)) `thenDs` \ error_expr ->
- matchSimply val_expr LetMatch pat tuple_ty local_tuple error_expr `thenDs` \ tuple_expr ->
- newSysLocalDs tuple_ty `thenDs` \ tuple_var ->
+ = 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 (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 binder_ty
+ = 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 = mkApp (Var iRREFUT_PAT_ERROR_ID) [binder_ty] [VarArg msg_var]
+ error_expr = mkCoerce (idType bndr_var) (Var err_var)
- is_simple_pat (TuplePat ps) = all is_triv_pat ps
- is_simple_pat (ConPat _ _ ps) = all is_triv_pat ps
- is_simple_pat (VarPat _) = True
- is_simple_pat (ConOpPat p1 _ p2 _) = is_triv_pat p1 && is_triv_pat p2
- is_simple_pat (RecPat _ _ ps) = and [is_triv_pat p | (_,p,_) <- ps]
- is_simple_pat other = False
+ is_simple_pat (TuplePat ps Boxed) = all is_triv_pat ps
+ is_simple_pat (ConPatOut _ ps _ _ _) = all is_triv_pat (hsConArgs ps)
+ is_simple_pat (VarPat _) = True
+ is_simple_pat (ParPat p) = is_simple_pat p
+ is_simple_pat other = False
is_triv_pat (VarPat v) = True
is_triv_pat (WildPat _) = True
+ is_triv_pat (ParPat p) = is_triv_pat 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 [] = Con unitDataCon []
-mkTupleExpr [id] = Var id
-mkTupleExpr ids = mkCon (tupleCon (length ids))
- (map idType ids)
- [ VarArg 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}
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
- -> 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
+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
- = ASSERT( not (null vars) )
- Case scrut (AlgAlts [(tupleCon (length vars), vars, Var the_var)] NoDefault)
+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}
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
\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
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 :: Type -- Result type of the whole case expression
- -> DsM (CoreExpr -> CoreBinding,
- -- Binds the newly-created fail variable
+mkFailurePair :: CoreExpr -- Result type of the whole case expression
+ -> DsM (CoreBind, -- Binds the newly-created fail variable
-- to either the expression or \ _ -> expression
CoreExpr) -- Either the fail variable, or fail variable
-- applied to unit tuple
-mkFailurePair ty
- | isUnpointedType ty
- = newFailLocalDs (voidTy `mkFunTy` ty) `thenDs` \ fail_fun_var ->
- newSysLocalDs voidTy `thenDs` \ fail_fun_arg ->
- returnDs (\ body ->
- NonRec fail_fun_var (Lam (ValBinder fail_fun_arg) body),
- App (Var fail_fun_var) (VarArg voidId))
+mkFailurePair expr
+ | isUnLiftedType ty
+ = 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) (Var unitDataConId))
| otherwise
= newFailLocalDs ty `thenDs` \ fail_var ->
- returnDs (\ body -> NonRec fail_var body, Var fail_var)
+ returnDs (NonRec fail_var expr, Var fail_var)
+ where
+ ty = exprType expr
\end{code}
-
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