This module exports some utility functions of no great interest.
\begin{code}
-
+-- | Utility functions for constructing Core syntax, principally for desugaring
module DsUtils (
EquationInfo(..),
firstPat, shiftEqns,
-
- mkDsLet, mkDsLets, mkDsApp, mkDsApps,
MatchResult(..), CanItFail(..),
cantFailMatchResult, alwaysFailMatchResult,
mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult,
wrapBind, wrapBinds,
- mkErrorAppDs, mkNilExpr, mkConsExpr, mkListExpr,
- mkIntExpr, mkCharExpr,
- mkStringExpr, mkStringExprFS, mkIntegerExpr,
- mkBuildExpr, mkFoldrExpr,
-
- seqVar,
-
- -- Core tuples
- mkCoreVarTup, mkCoreTup, mkCoreVarTupTy, mkCoreTupTy,
- mkBigCoreVarTup, mkBigCoreTup, mkBigCoreVarTupTy, mkBigCoreTupTy,
-
- -- LHs tuples
- mkLHsVarTup, mkLHsTup, mkLHsVarPatTup, mkLHsPatTup,
- mkBigLHsVarTup, mkBigLHsTup, mkBigLHsVarPatTup, mkBigLHsPatTup,
-
- -- Tuple bindings
- mkSelectorBinds, mkTupleSelector,
- mkSmallTupleCase, mkTupleCase,
-
- dsSyntaxTable, lookupEvidence,
+ mkErrorAppDs, mkCoreAppDs, mkCoreAppsDs,
+
+ seqVar,
+
+ -- LHs tuples
+ mkLHsVarPatTup, mkLHsPatTup, mkVanillaTuplePat,
+ mkBigLHsVarTup, mkBigLHsTup, mkBigLHsVarPatTup, mkBigLHsPatTup,
+
+ mkSelectorBinds,
+
+ dsSyntaxTable, lookupEvidence,
selectSimpleMatchVarL, selectMatchVars, selectMatchVar,
mkTickBox, mkOptTickBox, mkBinaryTickBox
import HsSyn
import TcHsSyn
+import TcType( tcSplitTyConApp )
import CoreSyn
-import Constants
import DsMonad
import CoreUtils
+import MkCore
import MkId
import Id
import Var
import ListSetOps
import FastString
import StaticFlags
-
-import Data.Char
-
-infixl 4 `mkDsApp`, `mkDsApps`
\end{code}
lookupEvidence prs std_name
= assocDefault (mk_panic std_name) prs std_name
where
- mk_panic std_name = pprPanic "dsSyntaxTable" (ptext SLIT("Not found:") <+> ppr std_name)
-\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 -- See Note [CoreSyn let/app invariant]
- | isUnLiftedType (idType bndr) && not (exprOkForSpeculation rhs)
- = Case rhs bndr (exprType body) [(DEFAULT,[],body)]
-mkDsLet bind body
- = Let bind body
-
-mkDsLets :: [CoreBind] -> CoreExpr -> CoreExpr
-mkDsLets binds body = foldr mkDsLet body binds
-
------------
-mkDsApp :: CoreExpr -> CoreExpr -> CoreExpr
--- Check the invariant that the arg of an App is ok-for-speculation if unlifted
--- See CoreSyn Note [CoreSyn let/app invariant]
-mkDsApp fun (Type ty) = App fun (Type ty)
-mkDsApp fun arg = mk_val_app fun arg arg_ty res_ty
- where
- (arg_ty, res_ty) = splitFunTy (exprType fun)
-
------------
-mkDsApps :: CoreExpr -> [CoreExpr] -> CoreExpr
--- Slightly more efficient version of (foldl mkDsApp)
-mkDsApps fun args
- = go fun (exprType fun) args
- where
- go fun _ [] = fun
- go fun fun_ty (Type ty : args) = go (App fun (Type ty)) (applyTy fun_ty ty) args
- go fun fun_ty (arg : args) = go (mk_val_app fun arg arg_ty res_ty) res_ty args
- where
- (arg_ty, res_ty) = splitFunTy fun_ty
------------
-mk_val_app :: CoreExpr -> CoreExpr -> Type -> Type -> CoreExpr
-mk_val_app fun arg arg_ty _ -- See Note [CoreSyn let/app invariant]
- | not (isUnLiftedType arg_ty) || exprOkForSpeculation arg
- = App fun arg -- The vastly common case
-
-mk_val_app (Var f `App` Type ty1 `App` Type _ `App` arg1) arg2 _ res_ty
- | f == seqId -- Note [Desugaring seq]
- = Case arg1 (mkWildId ty1) res_ty [(DEFAULT,[],arg2)]
-
-mk_val_app fun arg arg_ty res_ty
- = Case arg (mkWildId arg_ty) res_ty [(DEFAULT,[],App fun (Var arg_id))]
- where
- arg_id = mkWildId arg_ty -- Lots of shadowing, but it doesn't matter,
- -- because 'fun ' should not have a free wild-id
+ mk_panic std_name = pprPanic "dsSyntaxTable" (ptext (sLit "Not found:") <+> ppr std_name)
\end{code}
-Note [Desugaring seq] cf Trac #1031
-~~~~~~~~~~~~~~~~~~~~~
- f x y = x `seq` (y `seq` (# x,y #))
-
-The [CoreSyn let/app invariant] means that, other things being equal, because
-the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:
-
- f x y = case (y `seq` (# x,y #)) of v -> x `seq` v
-
-But that is bad for two reasons:
- (a) we now evaluate y before x, and
- (b) we can't bind v to an unboxed pair
-
-Seq is very, very special! So we recognise it right here, and desugar to
- case x of _ -> case y of _ -> (# x,y #)
-
-The special case would be valid for all calls to 'seq', but it's only *necessary*
-for ones whose second argument has an unlifted type. So we only catch the latter
-case here, to avoid unnecessary tests.
-
-
%************************************************************************
%* *
\subsection{ Selecting match variables}
selectMatchVars ps = mapM selectMatchVar ps
selectMatchVar :: Pat Id -> DsM Id
-selectMatchVar (BangPat pat) = selectMatchVar (unLoc pat)
-selectMatchVar (LazyPat pat) = selectMatchVar (unLoc pat)
-selectMatchVar (ParPat pat) = selectMatchVar (unLoc pat)
-selectMatchVar (VarPat var) = return var
+selectMatchVar (BangPat pat) = selectMatchVar (unLoc pat)
+selectMatchVar (LazyPat pat) = selectMatchVar (unLoc pat)
+selectMatchVar (ParPat pat) = selectMatchVar (unLoc pat)
+selectMatchVar (VarPat var) = return (localiseId var) -- Note [Localise pattern binders]
selectMatchVar (AsPat var _) = return (unLoc var)
-selectMatchVar other_pat = newSysLocalDs (hsPatType other_pat)
+selectMatchVar other_pat = newSysLocalDs (hsPatType other_pat)
-- OK, better make up one...
\end{code}
+Note [Localise pattern binders]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider module M where
+ [Just a] = e
+After renaming it looks like
+ module M where
+ [Just M.a] = e
+
+We don't generalise, since it's a pattern binding, monomorphic, etc,
+so after desugaring we may get something like
+ M.a = case e of (v:_) ->
+ case v of Just M.a -> M.a
+Notice the "M.a" in the pattern; after all, it was in the original
+pattern. However, after optimisation those pattern binders can become
+let-binders, and then end up floated to top level. They have a
+different *unique* by then (the simplifier is good about maintaining
+proper scoping), but it's BAD to have two top-level bindings with the
+External Name M.a, because that turns into two linker symbols for M.a.
+It's quite rare for this to actually *happen* -- the only case I know
+of is tc003 compiled with the 'hpc' way -- but that only makes it
+all the more annoying.
+
+To avoid this, we craftily call 'localiseId' in the desugarer, which
+simply turns the External Name for the Id into an Internal one, but
+doesn't change the unique. So the desugarer produces this:
+ M.a{r8} = case e of (v:_) ->
+ case v of Just a{r8} -> M.a{r8}
+The unique is still 'r8', but the binding site in the pattern
+is now an Internal Name. Now the simplifier's usual mechanisms
+will propagate that Name to all the occurrence sites, as well as
+un-shadowing it, so we'll get
+ M.a{r8} = case e of (v:_) ->
+ case v of Just a{s77} -> a{s77}
+In fact, even CoreSubst.simplOptExpr will do this, and simpleOptExpr
+runs on the output of the desugarer, so all is well by the end of
+the desugaring pass.
+
%************************************************************************
%* *
extractMatchResult (MatchResult CanFail match_fn) fail_expr = do
(fail_bind, if_it_fails) <- mkFailurePair fail_expr
body <- match_fn if_it_fails
- return (mkDsLet fail_bind body)
+ return (mkCoreLet fail_bind body)
combineMatchResults :: MatchResult -> MatchResult -> MatchResult
wrapBinds ((new,old):prs) e = wrapBind new old (wrapBinds prs e)
wrapBind :: Var -> Var -> CoreExpr -> CoreExpr
-wrapBind new old body
+wrapBind new old body -- Can deal with term variables *or* type variables
| new==old = body
- | isTyVar new = App (Lam new body) (Type (mkTyVarTy old))
- | otherwise = Let (NonRec new (Var old)) body
+ | isTyCoVar new = Let (mkTyBind new (mkTyVarTy old)) body
+ | otherwise = Let (NonRec new (Var old)) body
seqVar :: Var -> CoreExpr -> CoreExpr
seqVar var body = Case (Var var) var (exprType body)
[(DEFAULT, [], body)]
mkCoLetMatchResult :: CoreBind -> MatchResult -> MatchResult
-mkCoLetMatchResult bind = adjustMatchResult (mkDsLet bind)
+mkCoLetMatchResult bind = adjustMatchResult (mkCoreLet bind)
-- (mkViewMatchResult var' viewExpr var mr) makes the expression
-- let var' = viewExpr var in mr
mkViewMatchResult :: Id -> CoreExpr -> Id -> MatchResult -> MatchResult
mkViewMatchResult var' viewExpr var =
- adjustMatchResult (mkDsLet (NonRec var' (mkDsApp viewExpr (Var var))))
+ adjustMatchResult (mkCoreLet (NonRec var' (mkCoreAppDs viewExpr (Var var))))
mkEvalMatchResult :: Id -> Type -> MatchResult -> MatchResult
mkEvalMatchResult var ty
(con1, arg_ids1, match_result1) = ASSERT( notNull match_alts ) head match_alts
arg_id1 = ASSERT( notNull arg_ids1 ) head arg_ids1
var_ty = idType var
- (tc, ty_args) = splitNewTyConApp var_ty
+ (tc, ty_args) = tcSplitTyConApp var_ty -- Don't look through newtypes
+ -- (not that splitTyConApp does, these days)
newtype_rhs = unwrapNewTypeBody tc ty_args (Var var)
-- Stuff for data types
| otherwise
= CanFail
- wild_var = mkWildId (idType var)
sorted_alts = sortWith get_tag match_alts
get_tag (con, _, _) = dataConTag con
mk_case fail = do alts <- mapM (mk_alt fail) sorted_alts
- return (Case (Var var) wild_var ty (mk_default fail ++ alts))
+ return (mkWildCase (Var var) (idType var) ty (mk_default fail ++ alts))
mk_alt fail (con, args, MatchResult _ body_fn) = do
body <- body_fn fail
isPArrFakeAlts [] = panic "DsUtils: unexpectedly found an empty list of PArr fake alternatives"
--
mk_parrCase fail = do
- lengthP <- dsLookupGlobalId lengthPName
+ lengthP <- dsLookupDPHId lengthPName
alt <- unboxAlt
- return (Case (len lengthP) (mkWildId intTy) ty [alt])
+ return (mkWildCase (len lengthP) intTy ty [alt])
where
elemTy = case splitTyConApp (idType var) of
(_, [elemTy]) -> elemTy
--
unboxAlt = do
l <- newSysLocalDs intPrimTy
- indexP <- dsLookupGlobalId indexPName
+ indexP <- dsLookupDPHId indexPName
alts <- mapM (mkAlt indexP) sorted_alts
- return (DataAlt intDataCon, [l], (Case (Var l) wild ty (dft : alts)))
+ return (DataAlt intDataCon, [l], mkWildCase (Var l) intPrimTy ty (dft : alts))
where
- wild = mkWildId intPrimTy
dft = (DEFAULT, [], fail)
--
-- each alternative matches one array length (corresponding to one
--
mkAlt indexP (con, args, MatchResult _ bodyFun) = do
body <- bodyFun fail
- return (LitAlt lit, [], mkDsLets binds body)
+ return (LitAlt lit, [], mkCoreLets 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}
\begin{code}
mkErrorAppDs :: Id -- The error function
-> Type -- Type to which it should be applied
- -> String -- The error message string to pass
+ -> SDoc -- The error message string to pass
-> DsM CoreExpr
mkErrorAppDs err_id ty msg = do
src_loc <- getSrcSpanDs
let
- full_msg = showSDoc (hcat [ppr src_loc, text "|", text msg])
- core_msg = Lit (mkStringLit full_msg)
- -- mkStringLit returns a result of type String#
+ full_msg = showSDoc (hcat [ppr src_loc, text "|", msg])
+ core_msg = Lit (mkMachString full_msg)
+ -- mkMachString returns a result of type String#
return (mkApps (Var err_id) [Type ty, core_msg])
\end{code}
+'mkCoreAppDs' and 'mkCoreAppsDs' hand the special-case desugaring of 'seq'.
-*************************************************************
-%* *
-\subsection{Making literals}
-%* *
-%************************************************************************
+Note [Desugaring seq (1)] cf Trac #1031
+~~~~~~~~~~~~~~~~~~~~~~~~~
+ f x y = x `seq` (y `seq` (# x,y #))
-\begin{code}
-mkCharExpr :: Char -> CoreExpr -- Returns C# c :: Int
-mkIntExpr :: Integer -> CoreExpr -- Returns I# i :: Int
-mkIntegerExpr :: Integer -> DsM CoreExpr -- Result :: Integer
-mkStringExpr :: String -> DsM CoreExpr -- Result :: String
-mkStringExprFS :: 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
- = do integer_id <- dsLookupGlobalId smallIntegerName
- return (mkSmallIntegerLit integer_id 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 = do -- Big, so start from a string
- plus_id <- dsLookupGlobalId plusIntegerName
- times_id <- dsLookupGlobalId timesIntegerName
- integer_id <- dsLookupGlobalId smallIntegerName
- let
- lit i = mkSmallIntegerLit integer_id 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
-
- return (horner tARGET_MAX_INT i)
-
-mkSmallIntegerLit :: Id -> Integer -> CoreExpr
-mkSmallIntegerLit small_integer i = mkApps (Var small_integer) [mkIntLit i]
-
-mkStringExpr str = mkStringExprFS (mkFastString str)
-
-mkStringExprFS str
- | nullFS str
- = return (mkNilExpr charTy)
-
- | lengthFS str == 1
- = do let the_char = mkCharExpr (headFS str)
- return (mkConsExpr charTy the_char (mkNilExpr charTy))
-
- | all safeChar chars
- = do unpack_id <- dsLookupGlobalId unpackCStringName
- return (App (Var unpack_id) (Lit (MachStr str)))
-
- | otherwise
- = do unpack_id <- dsLookupGlobalId unpackCStringUtf8Name
- return (App (Var unpack_id) (Lit (MachStr str)))
+The [CoreSyn let/app invariant] means that, other things being equal, because
+the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:
+
+ f x y = case (y `seq` (# x,y #)) of v -> x `seq` v
+
+But that is bad for two reasons:
+ (a) we now evaluate y before x, and
+ (b) we can't bind v to an unboxed pair
+
+Seq is very, very special! So we recognise it right here, and desugar to
+ case x of _ -> case y of _ -> (# x,y #)
+
+Note [Desugaring seq (2)] cf Trac #2273
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ let chp = case b of { True -> fst x; False -> 0 }
+ in chp `seq` ...chp...
+Here the seq is designed to plug the space leak of retaining (snd x)
+for too long.
+
+If we rely on the ordinary inlining of seq, we'll get
+ let chp = case b of { True -> fst x; False -> 0 }
+ case chp of _ { I# -> ...chp... }
+
+But since chp is cheap, and the case is an alluring contet, we'll
+inline chp into the case scrutinee. Now there is only one use of chp,
+so we'll inline a second copy. Alas, we've now ruined the purpose of
+the seq, by re-introducing the space leak:
+ case (case b of {True -> fst x; False -> 0}) of
+ I# _ -> ...case b of {True -> fst x; False -> 0}...
+
+We can try to avoid doing this by ensuring that the binder-swap in the
+case happens, so we get his at an early stage:
+ case chp of chp2 { I# -> ...chp2... }
+But this is fragile. The real culprit is the source program. Perhaps we
+should have said explicitly
+ let !chp2 = chp in ...chp2...
+
+But that's painful. So the code here does a little hack to make seq
+more robust: a saturated application of 'seq' is turned *directly* into
+the case expression, thus:
+ x `seq` e2 ==> case x of x -> e2 -- Note shadowing!
+ e1 `seq` e2 ==> case x of _ -> e2
+
+So we desugar our example to:
+ let chp = case b of { True -> fst x; False -> 0 }
+ case chp of chp { I# -> ...chp... }
+And now all is well.
+
+The reason it's a hack is because if you define mySeq=seq, the hack
+won't work on mySeq.
+
+Note [Desugaring seq (3)] cf Trac #2409
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The isLocalId ensures that we don't turn
+ True `seq` e
+into
+ case True of True { ... }
+which stupidly tries to bind the datacon 'True'.
+\begin{code}
+mkCoreAppDs :: CoreExpr -> CoreExpr -> CoreExpr
+mkCoreAppDs (Var f `App` Type ty1 `App` Type ty2 `App` arg1) arg2
+ | f `hasKey` seqIdKey -- Note [Desugaring seq (1), (2)]
+ = Case arg1 case_bndr ty2 [(DEFAULT,[],arg2)]
where
- chars = unpackFS str
- safeChar c = ord c >= 1 && ord c <= 0x7F
+ case_bndr = case arg1 of
+ Var v1 | isLocalId v1 -> v1 -- Note [Desugaring seq (2) and (3)]
+ _ -> mkWildValBinder ty1
+
+mkCoreAppDs fun arg = mkCoreApp fun arg -- The rest is done in MkCore
+
+mkCoreAppsDs :: CoreExpr -> [CoreExpr] -> CoreExpr
+mkCoreAppsDs fun args = foldl mkCoreAppDs fun args
\end{code}
-- 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
- err_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID unitTy (showSDoc (ppr pat))
+ err_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID unitTy (ppr pat)
err_var <- newSysLocalDs unitTy
binds <- mapM (mk_bind val_var err_var) binders
return ( (val_var, val_expr) :
| otherwise = do
- error_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (showSDoc (ppr pat))
+ error_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (ppr pat)
tuple_expr <- matchSimply val_expr PatBindRhs pat local_tuple error_expr
tuple_var <- newSysLocalDs tuple_ty
- let
- mk_tup_bind binder
- = (binder, mkTupleSelector binders binder tuple_var (Var tuple_var))
+ let mk_tup_bind binder
+ = (binder, mkTupleSelector local_binders binder tuple_var (Var tuple_var))
return ( (tuple_var, tuple_expr) : map mk_tup_bind binders )
where
- binders = collectPatBinders pat
- local_tuple = mkBigCoreVarTup binders
- tuple_ty = exprType local_tuple
+ binders = collectPatBinders pat
+ local_binders = map localiseId binders -- See Note [Localise pattern binders]
+ local_tuple = mkBigCoreVarTup binders
+ tuple_ty = exprType local_tuple
mk_bind scrut_var err_var bndr_var = do
-- (mk_bind sv err_var) generates
is_triv_pat (WildPat _) = True
is_triv_pat (ParPat p) = is_triv_lpat p
is_triv_pat _ = False
-\end{code}
-
-
-%************************************************************************
-%* *
- Big 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}
-
-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}
-
-Creating tuples and their types for Core expressions
-
-@mkBigCoreVarTup@ 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.
-
-\begin{code}
-
--- Small tuples: build exactly the specified tuple
-mkCoreVarTup :: [Id] -> CoreExpr
-mkCoreVarTup ids = mkCoreTup (map Var ids)
-
-mkCoreVarTupTy :: [Id] -> Type
-mkCoreVarTupTy ids = mkCoreTupTy (map idType ids)
-
-
-mkCoreTup :: [CoreExpr] -> CoreExpr
-mkCoreTup [] = Var unitDataConId
-mkCoreTup [c] = c
-mkCoreTup cs = mkConApp (tupleCon Boxed (length cs))
- (map (Type . exprType) cs ++ cs)
-
-mkCoreTupTy :: [Type] -> Type
-mkCoreTupTy [ty] = ty
-mkCoreTupTy tys = mkTupleTy Boxed (length tys) tys
-
-
-
--- Big tuples
-mkBigCoreVarTup :: [Id] -> CoreExpr
-mkBigCoreVarTup ids = mkBigCoreTup (map Var ids)
-
-mkBigCoreVarTupTy :: [Id] -> Type
-mkBigCoreVarTupTy ids = mkBigCoreTupTy (map idType ids)
-
-
-mkBigCoreTup :: [CoreExpr] -> CoreExpr
-mkBigCoreTup = mkBigTuple mkCoreTup
-
-mkBigCoreTupTy :: [Type] -> Type
-mkBigCoreTupTy = mkBigTuple mkCoreTupTy
\end{code}
-Creating tuples and their types for full Haskell expressions
+Creating big tuples and their types for full Haskell expressions.
+They work over *Ids*, and create tuples replete with their types,
+which is whey they are not in HsUtils.
\begin{code}
+mkLHsPatTup :: [LPat Id] -> LPat Id
+mkLHsPatTup [] = noLoc $ mkVanillaTuplePat [] Boxed
+mkLHsPatTup [lpat] = lpat
+mkLHsPatTup lpats = L (getLoc (head lpats)) $
+ mkVanillaTuplePat lpats Boxed
--- Smart constructors for source tuple expressions
-mkLHsVarTup :: [Id] -> LHsExpr Id
-mkLHsVarTup ids = mkLHsTup (map nlHsVar ids)
-
-mkLHsTup :: [LHsExpr Id] -> LHsExpr Id
-mkLHsTup [] = nlHsVar unitDataConId
-mkLHsTup [lexp] = lexp
-mkLHsTup lexps = noLoc $ ExplicitTuple lexps Boxed
-
-
--- Smart constructors for source tuple patterns
mkLHsVarPatTup :: [Id] -> LPat Id
mkLHsVarPatTup bs = mkLHsPatTup (map nlVarPat bs)
-mkLHsPatTup :: [LPat Id] -> LPat Id
-mkLHsPatTup [lpat] = lpat
-mkLHsPatTup lpats = noLoc $ mkVanillaTuplePat lpats Boxed -- Handles the case where lpats = [] gracefully
-
+mkVanillaTuplePat :: [OutPat Id] -> Boxity -> Pat Id
+-- A vanilla tuple pattern simply gets its type from its sub-patterns
+mkVanillaTuplePat pats box
+ = TuplePat pats box (mkTupleTy box (map hsLPatType pats))
-- The Big equivalents for the source tuple expressions
mkBigLHsVarTup :: [Id] -> LHsExpr Id
mkBigLHsVarTup ids = mkBigLHsTup (map nlHsVar ids)
mkBigLHsTup :: [LHsExpr Id] -> LHsExpr Id
-mkBigLHsTup = mkBigTuple mkLHsTup
-
+mkBigLHsTup = mkChunkified mkLHsTupleExpr
-- The Big equivalents for the source tuple patterns
mkBigLHsVarPatTup :: [Id] -> LPat Id
mkBigLHsVarPatTup bs = mkBigLHsPatTup (map nlVarPat bs)
mkBigLHsPatTup :: [LPat Id] -> LPat Id
-mkBigLHsPatTup = mkBigTuple mkLHsPatTup
-
-\end{code}
-
-
-@mkTupleSelector@ builds a selector which scrutises the given
-expression and extracts the one name from the list given.
-If you want the no-shadowing rule to apply, the caller
-is responsible for making sure that none of these names
-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
- -> CoreExpr
-
-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
- -- This is the case where don't need any nesting
- mk_tuple_case _ [vars] body
- = mkSmallTupleCase vars body scrut_var scrut
-
- -- This is the case where we must make nest tuples at least once
- 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
--- One branch no refinement?
- = Case scrut scrut_var (exprType body) [(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
-
-mkFoldrExpr :: PostTcType -> PostTcType -> CoreExpr -> CoreExpr -> CoreExpr -> DsM CoreExpr
-mkFoldrExpr elt_ty result_ty c n list = do
- foldr_id <- dsLookupGlobalId foldrName
- return (Var foldr_id `App` Type elt_ty
- `App` Type result_ty
- `App` c
- `App` n
- `App` list)
-
-mkBuildExpr :: Type -> ((Id, Type) -> (Id, Type) -> DsM CoreExpr) -> DsM CoreExpr
-mkBuildExpr elt_ty mk_build_inside = do
- [n_tyvar] <- newTyVarsDs [alphaTyVar]
- let n_ty = mkTyVarTy n_tyvar
- c_ty = mkFunTys [elt_ty, n_ty] n_ty
- [c, n] <- newSysLocalsDs [c_ty, n_ty]
-
- build_inside <- mk_build_inside (c, c_ty) (n, n_ty)
-
- build_id <- dsLookupGlobalId buildName
- return $ Var build_id `App` Type elt_ty `App` mkLams [n_tyvar, c, n] build_inside
-
-mkCoreSel :: [Id] -- The tuple args
- -> Id -- The selected one
- -> Id -- A variable of the same type as the scrutinee
- -> CoreExpr -- Scrutinee
- -> CoreExpr
-
--- mkCoreSel [x] x v e
--- ===> e
-mkCoreSel [var] should_be_the_same_var _ scrut
- = ASSERT(var == should_be_the_same_var)
- scrut
-
--- mkCoreSel [x,y,z] x v e
--- ===> case e of v { (x,y,z) -> x
-mkCoreSel vars the_var scrut_var scrut
- = ASSERT( notNull vars )
- Case scrut scrut_var (idType the_var)
- [(DataAlt (tupleCon Boxed (length vars)), vars, Var the_var)]
+mkBigLHsPatTup = mkChunkified mkLHsPatTup
\end{code}
%************************************************************************
\begin{code}
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
+ -- to \ _ -> expression
+ CoreExpr) -- Fail variable applied to realWorld#
+-- See Note [Failure thunks and CPR]
mkFailurePair expr
- | isUnLiftedType ty = do
- fail_fun_var <- newFailLocalDs (unitTy `mkFunTy` ty)
- fail_fun_arg <- newSysLocalDs unitTy
- return (NonRec fail_fun_var (Lam fail_fun_arg expr),
- App (Var fail_fun_var) (Var unitDataConId))
-
- | otherwise = do
- fail_var <- newFailLocalDs ty
- return (NonRec fail_var expr, Var fail_var)
+ = do { fail_fun_var <- newFailLocalDs (realWorldStatePrimTy `mkFunTy` ty)
+ ; fail_fun_arg <- newSysLocalDs realWorldStatePrimTy
+ ; return (NonRec fail_fun_var (Lam fail_fun_arg expr),
+ App (Var fail_fun_var) (Var realWorldPrimId)) }
where
ty = exprType expr
\end{code}
+Note [Failure thunks and CPR]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When we make a failure point we ensure that it
+does not look like a thunk. Example:
+
+ let fail = \rw -> error "urk"
+ in case x of
+ [] -> fail realWorld#
+ (y:ys) -> case ys of
+ [] -> fail realWorld#
+ (z:zs) -> (y,z)
+
+Reason: we know that a failure point is always a "join point" and is
+entered at most once. Adding a dummy 'realWorld' token argument makes
+it clear that sharing is not an issue. And that in turn makes it more
+CPR-friendly. This matters a lot: if you don't get it right, you lose
+the tail call property. For example, see Trac #3403.
+
\begin{code}
mkOptTickBox :: Maybe (Int,[Id]) -> CoreExpr -> DsM CoreExpr
mkOptTickBox Nothing e = return e
mkBinaryTickBox :: Int -> Int -> CoreExpr -> DsM CoreExpr
mkBinaryTickBox ixT ixF e = do
uq <- newUnique
- let bndr1 = mkSysLocal FSLIT("t1") uq boolTy
+ let bndr1 = mkSysLocal (fsLit "t1") uq boolTy
falseBox <- mkTickBox ixF [] $ Var falseDataConId
trueBox <- mkTickBox ixT [] $ Var trueDataConId
return $ Case e bndr1 boolTy
projects / ghc-hetmet.git / blobdiff