%
-% (c) The AQUA Project, Glasgow University, 1993-1995
+% (c) The AQUA Project, Glasgow University, 1993-1996
%
\section[SimplUtils]{The simplifier utilities}
module SimplUtils (
floatExposesHNF,
-
- mkCoTyLamTryingEta, mkCoLamTryingEta,
+
+ etaCoreExpr, mkRhsTyLam,
etaExpandCount,
-
+
mkIdentityAlts,
simplIdWantsToBeINLINEd,
- type_ok_for_let_to_case
+ singleConstructorType, typeOkForCase
) where
-IMPORT_Trace -- ToDo: rm (debugging)
-import Pretty
-
-import TaggedCore
-import PlainCore
-import SimplEnv
-import SimplMonad
+IMP_Ubiq(){-uitous-}
+IMPORT_DELOOPER(SmplLoop) -- paranoia checking
import BinderInfo
-
-import AbsPrel ( primOpIsCheap, realWorldStateTy, buildId
- IF_ATTACK_PRAGMAS(COMMA realWorldTy)
- IF_ATTACK_PRAGMAS(COMMA tagOf_PrimOp)
- IF_ATTACK_PRAGMAS(COMMA pprPrimOp)
+import CmdLineOpts ( opt_DoEtaReduction, SimplifierSwitch(..) )
+import CoreSyn
+import CoreUnfold ( SimpleUnfolding, mkFormSummary, exprIsTrivial, FormSummary(..) )
+import Id ( idType, isBottomingId, addInlinePragma, addIdDemandInfo,
+ idWantsToBeINLINEd, dataConArgTys, SYN_IE(Id),
+ getIdArity, GenId{-instance Eq-}
)
-import AbsUniType ( extractTyVarsFromTy, getTyVarMaybe, isPrimType,
- splitTypeWithDictsAsArgs, getUniDataTyCon_maybe,
- applyTy, isFunType, TyVar, TyVarTemplate
- IF_ATTACK_PRAGMAS(COMMA cmpTyVar COMMA cmpClass)
- )
-import Id ( getInstantiatedDataConSig, isDataCon, getIdUniType,
- getIdArity, isBottomingId, idWantsToBeINLINEd,
- DataCon(..), Id
+import IdInfo ( ArityInfo(..), DemandInfo )
+import Maybes ( maybeToBool )
+import PrelVals ( augmentId, buildId )
+import PrimOp ( primOpIsCheap )
+import SimplEnv
+import SimplMonad
+import Type ( tyVarsOfType, mkForAllTys, mkTyVarTys, isPrimType,
+ maybeAppDataTyConExpandingDicts, SYN_IE(Type)
)
-import IdInfo
-import CmdLineOpts ( SimplifierSwitch(..) )
-import Maybes ( maybeToBool, Maybe(..) )
-import Outputable -- isExported ...
-import Util
+import TysWiredIn ( realWorldStateTy )
+import TyVar ( elementOfTyVarSet,
+ GenTyVar{-instance Eq-} )
+import Util ( isIn, panic )
+
\end{code}
:: Bool -- Float let(rec)s out of rhs
-> Bool -- Float cheap primops out of rhs
-> Bool -- OK to duplicate code
- -> CoreExpr bdr Id
+ -> GenCoreExpr bdr Id tyvar uvar
-> Bool
floatExposesHNF float_lets float_primops ok_to_dup rhs
= try rhs
where
- try (CoCase (CoPrim _ _ _) (CoPrimAlts alts deflt) )
+ try (Case (Prim _ _) (PrimAlts alts deflt) )
| float_primops && (null alts || ok_to_dup)
= or (try_deflt deflt : map try_alt alts)
- try (CoLet bind body) | float_lets = try body
+ try (Let bind body) | float_lets = try body
-- `build g'
-- is like a HNF,
-- because it *will* become one.
- try (CoApp (CoTyApp (CoVar bld) _) _) | bld == buildId = True
+ -- likewise for `augment g h'
+ --
+ try (App (App (Var bld) _) _) | bld == buildId = True
+ try (App (App (App (Var aug) _) _) _) | aug == augmentId = True
- try other = manifestlyWHNF other
- {- but *not* necessarily "manifestlyBottom other"...
+ try other = case mkFormSummary other of
+ VarForm -> True
+ ValueForm -> True
+ other -> False
+ {- but *not* necessarily "BottomForm"...
We may want to float a let out of a let to expose WHNFs,
but to do that to expose a "bottom" is a Bad Idea:
to allocate it eagerly as that's a waste.
-}
- try_alt (lit,rhs) = try rhs
+ try_alt (lit,rhs) = try rhs
- try_deflt CoNoDefault = False
- try_deflt (CoBindDefault _ rhs) = try rhs
+ try_deflt NoDefault = False
+ try_deflt (BindDefault _ rhs) = try rhs
\end{code}
-Eta reduction on ordinary lambdas
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-We have a go at doing
+Local tyvar-lifting
+~~~~~~~~~~~~~~~~~~~
+mkRhsTyLam tries this transformation, when the big lambda appears as
+the RHS of a let(rec) binding:
+
+ /\abc -> let(rec) x = e in b
+ ==>
+ let(rec) x' = /\abc -> let x = x' a b c in e
+ in
+ /\abc -> let x = x' a b c in b
+
+This is good because it can turn things like:
+
+ let f = /\a -> letrec g = ... g ... in g
+into
+ letrec g' = /\a -> ... g' a ...
+ in
+ let f = /\ a -> f a
+
+which is better. In effect, it means that big lambdas don't impede
+let-floating.
- \ x y -> f x y ===> f
+This optimisation is CRUCIAL in eliminating the junk introduced by
+desugaring mutually recursive definitions. Don't eliminate it lightly!
+
+So far as the implemtation is concerned:
+
+ Invariant: go F e = /\tvs -> F e
+
+ Equalities:
+ go F (Let x=e in b)
+ = Let x' = /\tvs -> F e
+ in
+ go G b
+ where
+ G = F . Let x = x' tvs
+
+ go F (Letrec xi=ei in b)
+ = Letrec {xi' = /\tvs -> G ei}
+ in
+ go G b
+ where
+ G = F . Let {xi = xi' tvs}
+
+\begin{code}
+mkRhsTyLam [] body = returnSmpl body
+
+mkRhsTyLam tyvars body
+ = go (\x -> x) body
+ where
+ tyvar_tys = mkTyVarTys tyvars
+
+ go fn (Let bind@(NonRec var rhs) body) | exprIsTrivial rhs
+ = go (fn . Let bind) body
+
+ go fn (Let bind@(NonRec var rhs) body)
+ = mk_poly var `thenSmpl` \ (var', rhs') ->
+ go (fn . Let (mk_silly_bind var rhs')) body `thenSmpl` \ body' ->
+ returnSmpl (Let (NonRec var' (mkTyLam tyvars (fn rhs))) body')
+
+ go fn (Let (Rec prs) body)
+ = mapAndUnzipSmpl mk_poly vars `thenSmpl` \ (vars', rhss') ->
+ let
+ gn body = fn $ foldr Let body (zipWith mk_silly_bind vars rhss')
+ in
+ go gn body `thenSmpl` \ body' ->
+ returnSmpl (Let (Rec (vars' `zip` [mkTyLam tyvars (gn rhs) | rhs <- rhss])) body')
+ where
+ (vars,rhss) = unzip prs
+
+ go fn body = returnSmpl (mkTyLam tyvars (fn body))
+
+ mk_poly var
+ = newId (mkForAllTys tyvars (idType var)) `thenSmpl` \ poly_id ->
+ returnSmpl (poly_id, mkTyApp (Var poly_id) tyvar_tys)
+
+ mk_silly_bind var rhs = NonRec (addInlinePragma var) rhs
+ -- The addInlinePragma is really important! If we don't say
+ -- INLINE on these silly little bindings then look what happens!
+ -- Suppose we start with:
+ --
+ -- x = let g = /\a -> \x -> f x x
+ -- in
+ -- /\ b -> let g* = g b in E
+ --
+ -- Then: * the binding for g gets floated out
+ -- * but then it gets inlined into the rhs of g*
+ -- * then the binding for g* is floated out of the /\b
+ -- * so we're back to square one
+ -- The silly binding for g* must be INLINE, so that no inlining
+ -- will happen in its RHS.
+\end{code}
+
+Eta reduction
+~~~~~~~~~~~~~
+@etaCoreExpr@ trys an eta reduction at the top level of a Core Expr.
+
+e.g. \ x y -> f x y ===> f
+
+It is used
+ a) Before constructing an Unfolding, to
+ try to make the unfolding smaller;
+ b) In tidyCoreExpr, which is done just before converting to STG.
But we only do this if it gets rid of a whole lambda, not part.
-The idea is that lambdas are often quite helpful: they indicate
+The idea is that lambdas are often quite helpful: they indicate
head normal forms, so we don't want to chuck them away lightly.
But if they expose a simple variable then we definitely win. Even
if they expose a type application we win. So we check for this special
gives rise to a recursive function for the list comprehension, and
f turns out to be just a single call to this recursive function.
+Doing eta on type lambdas is useful too:
+
+ /\a -> <expr> a ===> <expr>
+
+where <expr> doesn't mention a.
+This is sometimes quite useful, because we can get the sequence:
+
+ f ab d = let d1 = ...d... in
+ letrec f' b x = ...d...(f' b)... in
+ f' b
+specialise ==>
+
+ f.Int b = letrec f' b x = ...dInt...(f' b)... in
+ f' b
+
+float ==>
+
+ f' b x = ...dInt...(f' b)...
+ f.Int b = f' b
+
+Now we really want to simplify to
+
+ f.Int = f'
+
+and then replace all the f's with f.Ints.
+
+N.B. We are careful not to partially eta-reduce a sequence of type
+applications since this breaks the specialiser:
+
+ /\ a -> f Char# a =NO=> f Char#
+
\begin{code}
-mkCoLamTryingEta :: [Id] -- Args to the lambda
- -> PlainCoreExpr -- Lambda body
- -> PlainCoreExpr
+etaCoreExpr :: CoreExpr -> CoreExpr
-mkCoLamTryingEta [] body = body
-mkCoLamTryingEta orig_ids body
- = reduce_it (reverse orig_ids) body
+etaCoreExpr expr@(Lam bndr body)
+ | opt_DoEtaReduction
+ = case etaCoreExpr body of
+ App fun arg | eta_match bndr arg &&
+ residual_ok fun
+ -> fun -- Eta
+ other -> expr -- Can't eliminate it, so do nothing at all
where
- bale_out = mkCoLam orig_ids body
-
- reduce_it [] residual
- | residual_ok residual = residual
- | otherwise = bale_out
-
- reduce_it (id:ids) (CoApp fun (CoVarAtom arg))
- | id == arg
- && getIdUniType id /= realWorldStateTy
- -- *never* eta-reduce away a PrimIO state token! (WDP 94/11)
- = reduce_it ids fun
-
- reduce_it ids other = bale_out
-
- is_elem = isIn "mkCoLamTryingEta"
-
- -----------
- residual_ok :: PlainCoreExpr -> Bool -- Checks for type application
- -- and function not one of the
- -- bound vars
- residual_ok (CoTyApp fun ty) = residual_ok fun
- residual_ok (CoVar v) = not (v `is_elem` orig_ids) -- Fun mustn't be one of
- -- the bound ids
- residual_ok other = False
+ eta_match (ValBinder v) (VarArg v') = v == v'
+ eta_match (TyBinder tv) (TyArg ty) = tv `elementOfTyVarSet` tyVarsOfType ty
+ eta_match bndr arg = False
+
+ residual_ok :: CoreExpr -> Bool -- Checks for type application
+ -- and function not one of the
+ -- bound vars
+
+ residual_ok (Var v)
+ = not (eta_match bndr (VarArg v))
+ residual_ok (App fun arg)
+ | eta_match bndr arg = False
+ | otherwise = residual_ok fun
+ residual_ok (Coerce coercion ty body)
+ | eta_match bndr (TyArg ty) = False
+ | otherwise = residual_ok body
+
+ residual_ok other = False -- Safe answer
+ -- This last clause may seem conservative, but consider:
+ -- primops, constructors, and literals, are impossible here
+ -- let and case are unlikely (the argument would have been floated inside)
+ -- SCCs we probably want to be conservative about (not sure, but it's safe to be)
+
+etaCoreExpr expr = expr -- The common case
\end{code}
+
Eta expansion
~~~~~~~~~~~~~
E ===> (\x1::t1 x1::t2 ... xn::tn -> E x1 x2 ... xn)
-is a safe transformation. In particular, the transformation should not
-cause work to be duplicated, unless it is ``cheap'' (see @manifestlyCheap@ below).
+is a safe transformation. In particular, the transformation should
+not cause work to be duplicated, unless it is ``cheap'' (see
+@manifestlyCheap@ below).
-@etaExpandCount@ errs on the conservative side. It is always safe to return 0.
+@etaExpandCount@ errs on the conservative side. It is always safe to
+return 0.
An application of @error@ is special, because it can absorb as many
-arguments as you care to give it. For this special case we return 100,
-to represent "infinity", which is a bit of a hack.
+arguments as you care to give it. For this special case we return
+100, to represent "infinity", which is a bit of a hack.
\begin{code}
-etaExpandCount :: CoreExpr bdr Id
- -> Int -- Number of extra args you can safely abstract
+etaExpandCount :: GenCoreExpr bdr Id tyvar uvar
+ -> Int -- Number of extra args you can safely abstract
-etaExpandCount (CoLam ids body)
- = length ids + etaExpandCount body
+etaExpandCount (Lam (ValBinder _) body)
+ = 1 + etaExpandCount body
-etaExpandCount (CoLet bind body)
- | all manifestlyCheap (rhssOfBind bind)
+etaExpandCount (Let bind body)
+ | all manifestlyCheap (rhssOfBind bind)
= etaExpandCount body
-
-etaExpandCount (CoCase scrut alts)
- | manifestlyCheap scrut
- = minimum [etaExpandCount rhs | rhs <- rhssOfAlts alts]
-etaExpandCount (CoApp fun _) = case etaExpandCount fun of
- 0 -> 0
- n -> n-1 -- Knock off one
+etaExpandCount (Case scrut alts)
+ | manifestlyCheap scrut
+ = minimum [etaExpandCount rhs | rhs <- rhssOfAlts alts]
-etaExpandCount fun@(CoTyApp _ _) = eta_fun fun
-etaExpandCount fun@(CoVar _) = eta_fun fun
+etaExpandCount fun@(Var _) = eta_fun fun
+etaExpandCount (App fun arg)
+ | notValArg arg = eta_fun fun
+ | otherwise = case etaExpandCount fun of
+ 0 -> 0
+ n -> n-1 -- Knock off one
-etaExpandCount other = 0 -- Give up
- -- CoLit, CoCon, CoPrim,
- -- CoTyLam,
- -- CoScc (pessimistic; ToDo),
- -- CoLet with non-whnf rhs(s),
- -- CoCase with non-whnf scrutinee
+etaExpandCount other = 0 -- Give up
+ -- Lit, Con, Prim,
+ -- non-val Lam,
+ -- Scc (pessimistic; ToDo),
+ -- Let with non-whnf rhs(s),
+ -- Case with non-whnf scrutinee
-eta_fun :: CoreExpr bdr Id -- The function
- -> Int -- How many args it can safely be applied to
+-----------------------------
+eta_fun :: GenCoreExpr bdr Id tv uv -- The function
+ -> Int -- How many args it can safely be applied to
-eta_fun (CoTyApp fun ty) = eta_fun fun
+eta_fun (App fun arg) | notValArg arg = eta_fun fun
-eta_fun expr@(CoVar v)
- | isBottomingId v -- Bottoming ids have "infinite arity"
- = 10000 -- Blargh. Infinite enough!
+eta_fun expr@(Var v)
+ | isBottomingId v -- Bottoming ids have "infinite arity"
+ = 10000 -- Blargh. Infinite enough!
-eta_fun expr@(CoVar v)
- | maybeToBool arity_maybe -- We know the arity
- = arity
- where
- arity_maybe = arityMaybe (getIdArity v)
- arity = case arity_maybe of { Just arity -> arity }
+eta_fun expr@(Var v) = idMinArity v
-eta_fun other = 0 -- Give up
+eta_fun other = 0 -- Give up
\end{code}
@manifestlyCheap@ looks at a Core expression and returns \tr{True} if
to bring a couple of lambdas together. The main examples of things
which aren't WHNF but are ``cheap'' are:
- * case e of
+ * case e of
pi -> ei
where e, and all the ei are cheap; and
where op is a cheap primitive operator
\begin{code}
-manifestlyCheap :: CoreExpr bndr Id -> Bool
+manifestlyCheap :: GenCoreExpr bndr Id tv uv -> Bool
-manifestlyCheap (CoVar _) = True
-manifestlyCheap (CoLit _) = True
-manifestlyCheap (CoCon _ _ _) = True
-manifestlyCheap (CoLam _ _) = True
-manifestlyCheap (CoTyLam _ e) = manifestlyCheap e
-manifestlyCheap (CoSCC _ e) = manifestlyCheap e
+manifestlyCheap (Var _) = True
+manifestlyCheap (Lit _) = True
+manifestlyCheap (Con _ _) = True
+manifestlyCheap (SCC _ e) = manifestlyCheap e
+manifestlyCheap (Coerce _ _ e) = manifestlyCheap e
+manifestlyCheap (Lam x e) = if isValBinder x then True else manifestlyCheap e
+manifestlyCheap (Prim op _) = primOpIsCheap op
-manifestlyCheap (CoPrim op _ _) = primOpIsCheap op
-
-manifestlyCheap (CoLet bind body)
+manifestlyCheap (Let bind body)
= manifestlyCheap body && all manifestlyCheap (rhssOfBind bind)
-manifestlyCheap (CoCase scrut alts)
+manifestlyCheap (Case scrut alts)
= manifestlyCheap scrut && all manifestlyCheap (rhssOfAlts alts)
manifestlyCheap other_expr -- look for manifest partial application
- = case (collectArgs other_expr) of { (fun, args) ->
+ = case (collectArgs other_expr) of { (fun, _, _, vargs) ->
case fun of
- CoVar f | isBottomingId f -> True -- Application of a function which
- -- always gives bottom; we treat this as
- -- a WHNF, because it certainly doesn't
- -- need to be shared!
-
- CoVar f -> let
- num_val_args = length [ a | (ValArg a) <- args ]
- in
- num_val_args == 0 || -- Just a type application of
- -- a variable (f t1 t2 t3)
- -- counts as WHNF
- case (arityMaybe (getIdArity f)) of
- Nothing -> False
- Just arity -> num_val_args < arity
+ Var f | isBottomingId f -> True -- Application of a function which
+ -- always gives bottom; we treat this as
+ -- a WHNF, because it certainly doesn't
+ -- need to be shared!
+
+ Var f -> let
+ num_val_args = length vargs
+ in
+ num_val_args == 0 || -- Just a type application of
+ -- a variable (f t1 t2 t3)
+ -- counts as WHNF
+ num_val_args < idMinArity f
_ -> False
}
-
--- ToDo: Move to CoreFuns
-
-rhssOfBind :: CoreBinding bndr bdee -> [CoreExpr bndr bdee]
-
-rhssOfBind (CoNonRec _ rhs) = [rhs]
-rhssOfBind (CoRec pairs) = [rhs | (_,rhs) <- pairs]
-
-rhssOfAlts :: CoreCaseAlternatives bndr bdee -> [CoreExpr bndr bdee]
-
-rhssOfAlts (CoAlgAlts alts deflt) = rhssOfDeflt deflt ++
- [rhs | (_,_,rhs) <- alts]
-rhssOfAlts (CoPrimAlts alts deflt) = rhssOfDeflt deflt ++
- [rhs | (_,rhs) <- alts]
-rhssOfDeflt CoNoDefault = []
-rhssOfDeflt (CoBindDefault _ rhs) = [rhs]
\end{code}
-Eta reduction on type lambdas
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-We have a go at doing
-
- /\a -> <expr> a ===> <expr>
-
-where <expr> doesn't mention a.
-This is sometimes quite useful, because we can get the sequence:
-
- f ab d = let d1 = ...d... in
- letrec f' b x = ...d...(f' b)... in
- f' b
-specialise ==>
-
- f.Int b = letrec f' b x = ...dInt...(f' b)... in
- f' b
-
-float ==>
-
- f' b x = ...dInt...(f' b)...
- f.Int b = f' b
-
-Now we really want to simplify to
-
- f.Int = f'
-
-and then replace all the f's with f.Ints.
-
-N.B. We are careful not to partially eta-reduce a sequence of type
-applications since this breaks the specialiser:
-
- /\ a -> f Char# a =NO=> f Char#
-
-\begin{code}
-mkCoTyLamTryingEta :: [TyVar] -> PlainCoreExpr -> PlainCoreExpr
-
-mkCoTyLamTryingEta tyvars tylam_body
- = if
- tyvars == tyvar_args && -- Same args in same order
- check_fun fun -- Function left is ok
- then
- -- Eta reduction worked
- fun
- else
- -- The vastly common case
- mkCoTyLam tyvars tylam_body
- where
- (tyvar_args, fun) = strip_tyvar_args [] tylam_body
-
- strip_tyvar_args args_so_far tyapp@(CoTyApp fun ty)
- = case getTyVarMaybe ty of
- Just tyvar_arg -> strip_tyvar_args (tyvar_arg:args_so_far) fun
- Nothing -> (args_so_far, tyapp)
-
- strip_tyvar_args args_so_far fun
- = (args_so_far, fun)
-
- check_fun (CoVar f) = True -- Claim: tyvars not mentioned by type of f
- check_fun other = False
-
-{- OLD:
-mkCoTyLamTryingEta :: TyVar -> PlainCoreExpr -> PlainCoreExpr
-
-mkCoTyLamTryingEta tyvar body
- = case body of
- CoTyApp fun ty ->
- case getTyVarMaybe ty of
- Just tyvar' | tyvar == tyvar' &&
- ok fun -> fun
- -- Ha! So it's /\ a -> fun a, and fun is "ok"
-
- other -> CoTyLam tyvar body
- other -> CoTyLam tyvar body
- where
- is_elem = isIn "mkCoTyLamTryingEta"
-
- ok :: PlainCoreExpr -> Bool -- Returns True iff the expression doesn't
- -- mention tyvar
-
- ok (CoVar v) = True -- Claim: tyvar not mentioned by type of v
- ok (CoApp fun arg) = ok fun -- Claim: tyvar not mentioned by type of arg
- ok (CoTyApp fun ty) = not (tyvar `is_elem` extractTyVarsFromTy ty) &&
- ok fun
- ok other = False
--}
-\end{code}
Let to case
~~~~~~~~~~~
\begin{code}
mkIdentityAlts
- :: UniType -- type of RHS
+ :: Type -- type of RHS
+ -> DemandInfo -- Appropriate demand info
-> SmplM InAlts -- result
-mkIdentityAlts rhs_ty
- | isPrimType rhs_ty
- = newId rhs_ty `thenSmpl` \ binder ->
- returnSmpl (CoPrimAlts [] (CoBindDefault (binder, bad_occ_info) (CoVar binder)))
-
- | otherwise
- = case getUniDataTyCon_maybe rhs_ty of
+mkIdentityAlts rhs_ty demand_info
+ = case (maybeAppDataTyConExpandingDicts rhs_ty) of
Just (tycon, ty_args, [data_con]) -> -- algebraic type suitable for unpacking
let
- (_,inst_con_arg_tys,_) = getInstantiatedDataConSig data_con ty_args
+ inst_con_arg_tys = dataConArgTys data_con ty_args
in
newIds inst_con_arg_tys `thenSmpl` \ new_bindees ->
let
- new_binders = [ (b, bad_occ_info) | b <- new_bindees ]
+ new_binders = [ (b, bad_occ_info) | b <- new_bindees ]
in
returnSmpl (
- CoAlgAlts
- [(data_con, new_binders, CoCon data_con ty_args (map CoVarAtom new_bindees))]
- CoNoDefault
+ AlgAlts
+ [(data_con, new_binders, mkCon data_con [] ty_args (map VarArg new_bindees))]
+ NoDefault
)
- _ -> -- Multi-constructor or abstract algebraic type
- newId rhs_ty `thenSmpl` \ binder ->
- returnSmpl (CoAlgAlts [] (CoBindDefault (binder,bad_occ_info) (CoVar binder)))
+ _ -> panic "mkIdentityAlts" -- Should never happen; only called for single-constructor types
where
bad_occ_info = ManyOcc 0 -- Non-committal!
+
+
+{- SHOULD NEVER HAPPEN
+ | isPrimType rhs_ty
+ = newId rhs_ty `thenSmpl` \ binder ->
+ let
+ binder_w_info = binder `addIdDemandInfo` demand_info
+ -- It's occasionally really worth adding the right demand info. Consider
+ -- let x = E in B
+ -- where x is sure to be demanded in B
+ -- We will transform to:
+ -- case E of x -> B
+ -- Now suppose that E simplifies to just y; we get
+ -- case y of x -> B
+ -- Because x is sure to be demanded, we can eliminate the case
+ -- even if pedantic-bottoms is on; but we need to have the right
+ -- demand-info on the default branch of the case. That's what
+ -- we are doing here.
+ in
+ returnSmpl (PrimAlts [] (BindDefault (binder, bad_occ_info) (Var binder)))
+-}
\end{code}
\begin{code}
simplIdWantsToBeINLINEd :: Id -> SimplEnv -> Bool
-simplIdWantsToBeINLINEd id env
- = if switchIsSet env IgnoreINLINEPragma
+simplIdWantsToBeINLINEd id env
+ = {- We used to arrange that in the final simplification pass we'd switch
+ off all INLINE pragmas, so that we'd inline workers back into the
+ body of their wrapper if the wrapper hadn't itself been inlined by then.
+ This occurred especially for methods in dictionaries.
+
+ We no longer do this:
+ a) there's a good chance that the exported wrapper will get
+ inlined in some importing scope, in which case we don't
+ want to lose the w/w idea.
+
+ b) The occurrence analyser must agree about what has an
+ INLINE pragma. Not hard, but delicate.
+
+ c) if the worker gets inlined we have to tell the wrapepr
+ that it's no longer a wrapper, else the interface file stuff
+ asks for a worker that no longer exists.
+
+ if switchIsSet env IgnoreINLINEPragma
then False
- else idWantsToBeINLINEd id
+ else
+ -}
+
+ idWantsToBeINLINEd id
+
+idMinArity id = case getIdArity id of
+ UnknownArity -> 0
+ ArityAtLeast n -> n
+ ArityExactly n -> n
-type_ok_for_let_to_case :: UniType -> Bool
+singleConstructorType :: Type -> Bool
+singleConstructorType ty
+ = case (maybeAppDataTyConExpandingDicts ty) of
+ Just (tycon, ty_args, [con]) -> True
+ other -> False
-type_ok_for_let_to_case ty
- = case getUniDataTyCon_maybe ty of
+typeOkForCase :: Type -> Bool
+typeOkForCase ty
+ = case (maybeAppDataTyConExpandingDicts ty) of
Nothing -> False
Just (tycon, ty_args, []) -> False
Just (tycon, ty_args, non_null_data_cons) -> True
- -- Null data cons => type is abstract
+ -- Null data cons => type is abstract, which code gen can't
+ -- currently handle. (ToDo: when return-in-heap is universal we
+ -- don't need to worry about this.)
\end{code}
projects / ghc-hetmet.git / blobdiff