%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section{SetLevels}
#include "HsVersions.h"
-import AnnCoreSyn
import CoreSyn
-import CoreUtils ( coreExprType, idSpecVars )
-import CoreUnfold ( FormSummary, whnfOrBottom, mkFormSummary )
-import FreeVars -- all of it
-import MkId ( mkSysLocal )
-import Id ( idType,
- nullIdEnv, addOneToIdEnv, growIdEnvList,
- unionManyIdSets, unionIdSets, minusIdSet, mkIdSet,
- idSetToList, Id,
- lookupIdEnv, IdEnv
- )
-import SrcLoc ( noSrcLoc )
-import Type ( isUnpointedType, mkTyVarTys, mkForAllTys, tyVarsOfTypes, Type )
-import TyVar ( emptyTyVarEnv, addToTyVarEnv,
- growTyVarEnvList, lookupTyVarEnv,
- tyVarSetToList,
- TyVarEnv, TyVar,
- unionManyTyVarSets, unionTyVarSets
- )
-import UniqSupply ( thenUs, returnUs, mapUs, mapAndUnzipUs,
- mapAndUnzip3Us, getUnique, UniqSM,
- UniqSupply
+import CoreUtils ( coreExprType, exprIsTrivial, idFreeVars, exprIsBottom
)
-import BasicTypes ( Unused )
-import Maybes ( maybeToBool )
-import Util ( mapAccumL, zipWithEqual, zipEqual, panic, assertPanic )
+import FreeVars -- all of it
+import Id ( Id, idType, mkUserLocal )
+import Name ( varOcc )
+import Var ( IdOrTyVar )
+import VarEnv
+import VarSet
+import Type ( isUnLiftedType, mkTyVarTys, mkForAllTys, Type )
+import VarSet
+import VarEnv
+import UniqSupply ( initUs, thenUs, returnUs, mapUs, mapAndUnzipUs, getUniqueUs,
+ mapAndUnzip3Us, UniqSM, UniqSupply )
+import Maybes ( maybeToBool )
+import Util ( zipWithEqual, zipEqual, panic, assertPanic )
import Outputable
isLeakFreeType x y = False -- safe option; ToDo
\begin{code}
data Level
- = Top -- Means *really* the top level.
+ = Top -- Means *really* the top level; short for (Level 0 0).
| Level Int -- Level number of enclosing lambdas
Int -- Number of big-lambda and/or case expressions between
-- here and the nearest enclosing lambda
\end{code}
The {\em level number} on a (type-)lambda-bound variable is the
-nesting depth of the (type-)lambda which binds it. On an expression,
-it's the maximum level number of its free (type-)variables. On a
-let(rec)-bound variable, it's the level of its RHS. On a case-bound
-variable, it's the number of enclosing lambdas.
+nesting depth of the (type-)lambda which binds it. The outermost lambda
+has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
+
+On an expression, it's the maximum level number of its free
+(type-)variables. On a let(rec)-bound variable, it's the level of its
+RHS. On a case-bound variable, it's the number of enclosing lambdas.
Top-level variables: level~0. Those bound on the RHS of a top-level
definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
at @Level 0 0@; it is never @Top@.
\begin{code}
-type LevelledExpr = GenCoreExpr (Id, Level) Id Unused
-type LevelledArg = GenCoreArg Id Unused
-type LevelledBind = GenCoreBinding (Id, Level) Id Unused
-
-type LevelEnvs = (IdEnv Level, -- bind Ids to levels
- TyVarEnv Level) -- bind type variables to levels
+type LevelledExpr = TaggedExpr Level
+type LevelledArg = TaggedArg Level
+type LevelledBind = TaggedBind Level
tOP_LEVEL = Top
isTopMajLvl Top = True
isTopMajLvl (Level maj _) = maj == 0
-unTopify :: Level -> Level
-unTopify Top = Level 0 0
-unTopify lvl = lvl
-
instance Outputable Level where
ppr Top = ptext SLIT("<Top>")
ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
\end{code}
+\begin{code}
+type LevelEnv = VarEnv Level
+
+varLevel :: LevelEnv -> IdOrTyVar -> Level
+varLevel env v
+ = case lookupVarEnv env v of
+ Just level -> level
+ Nothing -> tOP_LEVEL
+
+maxIdLvl :: LevelEnv -> IdOrTyVar -> Level -> Level
+maxIdLvl env var lvl | isTyVar var = lvl
+ | otherwise = case lookupVarEnv env var of
+ Just lvl' -> maxLvl lvl' lvl
+ Nothing -> lvl
+
+maxTyVarLvl :: LevelEnv -> IdOrTyVar -> Level -> Level
+maxTyVarLvl env var lvl | isId var = lvl
+ | otherwise = case lookupVarEnv env var of
+ Just lvl' -> maxLvl lvl' lvl
+ Nothing -> lvl
+\end{code}
+
%************************************************************************
%* *
\subsection{Main level-setting code}
%************************************************************************
\begin{code}
-setLevels :: [CoreBinding]
+setLevels :: [CoreBind]
-> UniqSupply
-> [LevelledBind]
setLevels binds us
- = do_them binds us
+ = initLvl us (do_them binds)
where
-- "do_them"'s main business is to thread the monad along
-- It gives each top binding the same empty envt, because
-- things unbound in the envt have level number zero implicitly
- do_them :: [CoreBinding] -> LvlM [LevelledBind]
+ do_them :: [CoreBind] -> LvlM [LevelledBind]
do_them [] = returnLvl []
do_them (b:bs)
= lvlTopBind b `thenLvl` \ (lvld_bind, _) ->
- do_them bs `thenLvl` \ lvld_binds ->
+ do_them bs `thenLvl` \ lvld_binds ->
returnLvl (lvld_bind ++ lvld_binds)
-initial_envs = (nullIdEnv, emptyTyVarEnv)
+initialEnv = emptyVarEnv
lvlTopBind (NonRec binder rhs)
- = lvlBind (Level 0 0) initial_envs (AnnNonRec binder (freeVars rhs))
+ = lvlBind Top initialEnv (AnnNonRec binder (freeVars rhs))
-- Rhs can have no free vars!
lvlTopBind (Rec pairs)
- = lvlBind (Level 0 0) initial_envs (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
+ = lvlBind Top initialEnv (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
\end{code}
%************************************************************************
The binding stuff works for top level too.
\begin{code}
-type CoreBindingWithFVs = AnnCoreBinding Id Id Unused FVInfo
-
lvlBind :: Level
- -> LevelEnvs
- -> CoreBindingWithFVs
- -> LvlM ([LevelledBind], LevelEnvs)
+ -> LevelEnv
+ -> CoreBindWithFVs
+ -> LvlM ([LevelledBind], LevelEnv)
-lvlBind ctxt_lvl envs@(venv, tenv) (AnnNonRec name rhs)
- = setFloatLevel (Just name) {- Already let-bound -}
- ctxt_lvl envs rhs ty `thenLvl` \ (final_lvl, rhs') ->
+lvlBind ctxt_lvl env (AnnNonRec name rhs)
+ = setFloatLevel (Just name) ctxt_lvl env rhs ty `thenLvl` \ (final_lvl, rhs') ->
let
- new_envs = (addOneToIdEnv venv name final_lvl, tenv)
+ new_env = extendVarEnv env name final_lvl
in
- returnLvl ([NonRec (name, final_lvl) rhs'], new_envs)
+ returnLvl ([NonRec (name, final_lvl) rhs'], new_env)
where
ty = idType name
-lvlBind ctxt_lvl envs@(venv, tenv) (AnnRec pairs)
- = decideRecFloatLevel ctxt_lvl envs binders rhss
- `thenLvl` \ (final_lvl, extra_binds, rhss') ->
+lvlBind ctxt_lvl env (AnnRec pairs)
+ = decideRecFloatLevel ctxt_lvl env binders rhss `thenLvl` \ (final_lvl, extra_binds, rhss') ->
let
binders_w_lvls = binders `zip` repeat final_lvl
- new_envs = (growIdEnvList venv binders_w_lvls, tenv)
+ new_env = extendVarEnvList env binders_w_lvls
in
- returnLvl (extra_binds ++ [Rec (zipEqual "lvlBind" binders_w_lvls rhss')], new_envs)
+ returnLvl (extra_binds ++ [Rec (zipEqual "lvlBind" binders_w_lvls rhss')], new_env)
where
(binders,rhss) = unzip pairs
\end{code}
\begin{code}
lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
- -> LevelEnvs -- Level of in-scope names/tyvars
+ -> LevelEnv -- Level of in-scope names/tyvars
-> CoreExprWithFVs -- input expression
-> LvlM LevelledExpr -- Result expression
\end{code}
If there were another lambda in @r@'s rhs, it would get level-2 as well.
\begin{code}
-lvlExpr _ _ (_, AnnVar v) = returnLvl (Var v)
-lvlExpr _ _ (_, AnnLit l) = returnLvl (Lit l)
-lvlExpr _ _ (_, AnnCon con args) = returnLvl (Con con args)
-lvlExpr _ _ (_, AnnPrim op args) = returnLvl (Prim op args)
+lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
+lvlExpr _ _ (_, AnnVar v) = returnLvl (Var v)
-lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnApp fun arg)
- = lvlExpr ctxt_lvl envs fun `thenLvl` \ fun' ->
- returnLvl (App fun' arg)
+lvlExpr ctxt_lvl env (_, AnnCon con args)
+ = mapLvl (lvlExpr ctxt_lvl env) args `thenLvl` \ args' ->
+ returnLvl (Con con args')
-lvlExpr ctxt_lvl envs (_, AnnNote note expr)
- = lvlExpr ctxt_lvl envs expr `thenLvl` \ expr' ->
+lvlExpr ctxt_lvl env (_, AnnApp fun arg)
+ = lvlExpr ctxt_lvl env fun `thenLvl` \ fun' ->
+ lvlMFE ctxt_lvl env arg `thenLvl` \ arg' ->
+ returnLvl (App fun' arg')
+
+lvlExpr ctxt_lvl env (_, AnnNote note expr)
+ = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
returnLvl (Note note expr')
-- We don't split adjacent lambdas. That is, given
-- Why not? Because partial applications are fairly rare, and splitting
-- lambdas makes them more expensive.
-lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnLam (ValBinder arg) rhs)
- = lvlMFE incd_lvl (new_venv, tenv) body `thenLvl` \ body' ->
- returnLvl (foldr (Lam . ValBinder) body' lvld_args)
+lvlExpr ctxt_lvl env (_, AnnLam bndr rhs)
+ = lvlMFE incd_lvl new_env body `thenLvl` \ body' ->
+ returnLvl (mkLams lvld_bndrs body')
where
- incd_lvl = incMajorLvl ctxt_lvl
- (args, body) = annCollectValBinders rhs
- lvld_args = [(a,incd_lvl) | a <- (arg:args)]
- new_venv = growIdEnvList venv lvld_args
-
--- We don't need to play such tricks for type lambdas, because
--- they don't get annotated
-
-lvlExpr ctxt_lvl (venv, tenv) (_, AnnLam (TyBinder tyvar) body)
- = lvlExpr incd_lvl (venv, new_tenv) body `thenLvl` \ body' ->
- returnLvl (Lam (TyBinder tyvar) body')
+ bndr_is_id = isId bndr
+ bndr_is_tyvar = isTyVar bndr
+ (bndrs, body) = go rhs
+
+ incd_lvl | bndr_is_id = incMajorLvl ctxt_lvl
+ | otherwise = incMinorLvl ctxt_lvl
+ lvld_bndrs = [(b,incd_lvl) | b <- (bndr:bndrs)]
+ new_env = extendVarEnvList env lvld_bndrs
+
+ go (_, AnnLam bndr rhs) | bndr_is_id && isId bndr
+ || bndr_is_tyvar && isTyVar bndr
+ = case go rhs of { (bndrs, body) -> (bndr:bndrs, body) }
+ go body = ([], body)
+
+lvlExpr ctxt_lvl env (_, AnnLet bind body)
+ = lvlBind ctxt_lvl env bind `thenLvl` \ (binds', new_env) ->
+ lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
+ returnLvl (mkLets binds' body')
+
+lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
+ = lvlMFE ctxt_lvl env expr `thenLvl` \ expr' ->
+ mapLvl lvl_alt alts `thenLvl` \ alts' ->
+ returnLvl (Case expr' (case_bndr, incd_lvl) alts')
where
- incd_lvl = incMinorLvl ctxt_lvl
- new_tenv = addToTyVarEnv tenv tyvar incd_lvl
-
-lvlExpr ctxt_lvl envs (_, AnnLet bind body)
- = lvlBind ctxt_lvl envs bind `thenLvl` \ (binds', new_envs) ->
- lvlExpr ctxt_lvl new_envs body `thenLvl` \ body' ->
- returnLvl (foldr Let body' binds') -- mkCoLet* requires Core...
-
-lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnCase expr alts)
- = lvlMFE ctxt_lvl envs expr `thenLvl` \ expr' ->
- lvl_alts alts `thenLvl` \ alts' ->
- returnLvl (Case expr' alts')
- where
expr_type = coreExprType (deAnnotate expr)
incd_lvl = incMinorLvl ctxt_lvl
-
- lvl_alts (AnnAlgAlts alts deflt)
- = mapLvl lvl_alt alts `thenLvl` \ alts' ->
- lvl_deflt deflt `thenLvl` \ deflt' ->
- returnLvl (AlgAlts alts' deflt')
- where
- lvl_alt (con, bs, e)
- = let
- bs' = [ (b, incd_lvl) | b <- bs ]
- new_envs = (growIdEnvList venv bs', tenv)
- in
- lvlMFE incd_lvl new_envs e `thenLvl` \ e' ->
- returnLvl (con, bs', e')
-
- lvl_alts (AnnPrimAlts alts deflt)
- = mapLvl lvl_alt alts `thenLvl` \ alts' ->
- lvl_deflt deflt `thenLvl` \ deflt' ->
- returnLvl (PrimAlts alts' deflt')
- where
- lvl_alt (lit, e)
- = lvlMFE incd_lvl envs e `thenLvl` \ e' ->
- returnLvl (lit, e')
-
- lvl_deflt AnnNoDefault = returnLvl NoDefault
-
- lvl_deflt (AnnBindDefault b expr)
- = let
- new_envs = (addOneToIdEnv venv b incd_lvl, tenv)
- in
- lvlMFE incd_lvl new_envs expr `thenLvl` \ expr' ->
- returnLvl (BindDefault (b, incd_lvl) expr')
+ alts_env = extendVarEnv env case_bndr incd_lvl
+
+ lvl_alt (con, bs, rhs)
+ = let
+ bs' = [ (b, incd_lvl) | b <- bs ]
+ new_env = extendVarEnvList alts_env bs'
+ in
+ lvlMFE incd_lvl new_env rhs `thenLvl` \ rhs' ->
+ returnLvl (con, bs', rhs')
\end{code}
@lvlMFE@ is just like @lvlExpr@, except that it might let-bind
\begin{code}
lvlMFE :: Level -- Level of innermost enclosing lambda/tylam
- -> LevelEnvs -- Level of in-scope names/tyvars
+ -> LevelEnv -- Level of in-scope names/tyvars
-> CoreExprWithFVs -- input expression
-> LvlM LevelledExpr -- Result expression
-lvlMFE ctxt_lvl envs@(venv,_) ann_expr
- | isUnpointedType ty -- Can't let-bind it
- = lvlExpr ctxt_lvl envs ann_expr
+lvlMFE ctxt_lvl env (_, AnnType ty)
+ = returnLvl (Type ty)
+
+lvlMFE ctxt_lvl env ann_expr
+ | isUnLiftedType ty -- Can't let-bind it
+ = lvlExpr ctxt_lvl env ann_expr
| otherwise -- Not primitive type so could be let-bound
= setFloatLevel Nothing {- Not already let-bound -}
- ctxt_lvl envs ann_expr ty `thenLvl` \ (final_lvl, expr') ->
+ ctxt_lvl env ann_expr ty `thenLvl` \ (final_lvl, expr') ->
returnLvl expr'
where
ty = coreExprType (deAnnotate ann_expr)
setFloatLevel :: Maybe Id -- Just id <=> the expression is already let-bound to id
-- Nothing <=> it's a possible MFE
-> Level -- of context
- -> LevelEnvs
+ -> LevelEnv
-> CoreExprWithFVs -- Original rhs
- -> Type -- Type of rhs
+ -> Type -- Type of rhs
-> LvlM (Level, -- Level to attribute to this let-binding
LevelledExpr) -- Final rhs
-setFloatLevel maybe_let_bound ctxt_lvl envs@(venv, tenv)
- expr@(FVInfo fvs tfvs might_leak, _) ty
--- Invariant: ctxt_lvl is never = Top
--- Beautiful ASSERT, dudes (WDP 95/04)...
+setFloatLevel maybe_let_bound ctxt_lvl env expr@(expr_fvs, _) ty
-- Now deal with (by not floating) trivial non-let-bound expressions
-- which just aren't worth let-binding in order to float. We always
-- for top level.
| not alreadyLetBound
- && (manifestly_whnf || not will_float_past_lambda)
- = -- Pin whnf non-let-bound expressions,
+ && (expr_is_trivial || expr_is_bottom || not will_float_past_lambda)
+ = -- Pin trivial non-let-bound expressions,
-- or ones which aren't going anywhere useful
- lvlExpr ctxt_lvl envs expr `thenLvl` \ expr' ->
+ lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
returnLvl (ctxt_lvl, expr')
+{- SDM 7/98
+The above case used to read (whnf_or_bottom || not will_float_past_lambda).
+It was changed because we really do want to float out constructors if possible:
+this can save a great deal of needless allocation inside a loop. On the other
+hand, there's no point floating out nullary constructors and literals, hence
+the expr_is_trivial condition.
+-}
+
| alreadyLetBound && not worth_type_abstraction
= -- Process the expression with a new ctxt_lvl, obtained from
-- the free vars of the expression itself
- lvlExpr (unTopify expr_lvl) envs expr `thenLvl` \ expr' ->
- returnLvl (maybe_unTopify expr_lvl, expr')
+ lvlExpr expr_lvl env expr `thenLvl` \ expr' ->
+ returnLvl (expr_lvl, expr')
| otherwise -- This will create a let anyway, even if there is no
-- type variable to abstract, so we try to abstract anyway
- = abstractWrtTyVars offending_tyvars ty envs lvl_after_ty_abstr expr
+ = abstractWrtTyVars offending_tyvars ty env lvl_after_ty_abstr expr
`thenLvl` \ final_expr ->
returnLvl (expr_lvl, final_expr)
-- OLD LIE: The body of the let, just a type application, isn't worth floating
-- something non-trivial which depends on it.
where
alreadyLetBound = maybeToBool maybe_let_bound
-
-
-
- real_fvs = case maybe_let_bound of
- Nothing -> fvs -- Just the expr fvs
- Just id -> fvs `unionIdSets` mkIdSet (idSpecVars id)
- -- Tiresome! Add the specVars
-
- fv_list = idSetToList real_fvs
- tv_list = tyVarSetToList tfvs
- expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
- ids_only_lvl = foldr (maxLvl . idLevel venv) tOP_LEVEL fv_list
- tyvars_only_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL tv_list
+
+ fvs = case maybe_let_bound of
+ Nothing -> expr_fvs
+ Just id -> expr_fvs `unionVarSet` idFreeVars id
+
+ ids_only_lvl = foldVarSet (maxIdLvl env) tOP_LEVEL fvs
+ tyvars_only_lvl = foldVarSet (maxTyVarLvl env) tOP_LEVEL fvs
+ expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
lvl_after_ty_abstr = ids_only_lvl --`maxLvl` non_offending_tyvars_lvl
- will_float_past_lambda = -- Will escape lambda if let-bound
- ids_only_lvl `ltMajLvl` ctxt_lvl
-
- worth_type_abstraction = -- Will escape (more) lambda(s)/type lambda(s)
- -- if type abstracted
- (ids_only_lvl `ltLvl` tyvars_only_lvl)
- && not (is_trivial de_ann_expr) -- avoids abstracting trivial type applications
-
- de_ann_expr = deAnnotate expr
-
- is_trivial (App e a)
- | notValArg a = is_trivial e
- is_trivial (Var _) = True
- is_trivial _ = False
-
- offending_tyvars = filter offending tv_list
- --non_offending_tyvars = filter (not . offending) tv_list
- --non_offending_tyvars_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL non_offending_tyvars
-
- offending tyvar = ids_only_lvl `ltLvl` tyvarLevel tenv tyvar
-
- manifestly_whnf = whnfOrBottom (mkFormSummary de_ann_expr)
-
- maybe_unTopify Top | not (canFloatToTop (ty, expr)) = Level 0 0
- maybe_unTopify lvl = lvl
- {- ToDo [Andre]: the line above (maybe) should be Level 1 0,
- -- so that the let will not go past the *last* lambda if it can
- -- generate a space leak. If it is already in major level 0
- -- It won't do any harm to give it a Level 1 0.
- -- we should do the same test not only for things with level Top,
- -- but also for anything that gets a major level 0.
- the problem is that
- f = \a -> let x = [1..1000]
- in zip a x
- ==>
- f = let x = [1..1000]
- in \a -> zip a x
- is just as bad as floating x to the top level.
- Notice it would be OK in cases like
- f = \a -> let x = [1..1000]
- y = length x
- in a + y
- ==>
- f = let x = [1..1000]
- y = length x
- in \a -> a + y
- as x will be gc'd after y is updated.
- [We did not hit any problems with the above (Level 0 0) code
- in nofib benchmark]
- -}
+ -- Will escape lambda if let-bound
+ will_float_past_lambda = ids_only_lvl `ltMajLvl` ctxt_lvl
+
+ -- Will escape (more) lambda(s)/type lambda(s) if type abstracted
+ worth_type_abstraction = (ids_only_lvl `ltLvl` tyvars_only_lvl)
+ && not expr_is_trivial -- Avoids abstracting trivial type applications
+
+ offending_tyvars = filter offending_tv (varSetElems fvs)
+ offending_tv var | isId var = False
+ | otherwise = ids_only_lvl `ltLvl` varLevel env var
+
+ expr_is_trivial = exprIsTrivial de_ann_expr
+ expr_is_bottom = exprIsBottom de_ann_expr
+ de_ann_expr = deAnnotate expr
\end{code}
Abstract wrt tyvars, by making it just as if we had seen
variables, then we just return E.
\begin{code}
-abstractWrtTyVars offending_tyvars ty (venv,tenv) lvl expr
- = lvlExpr incd_lvl new_envs expr `thenLvl` \ expr' ->
+abstractWrtTyVars offending_tyvars ty env lvl expr
+ = lvlExpr incd_lvl new_env expr `thenLvl` \ expr' ->
newLvlVar poly_ty `thenLvl` \ poly_var ->
let
- poly_var_rhs = mkTyLam offending_tyvars expr'
+ poly_var_rhs = mkLams tyvar_lvls expr'
poly_var_binding = NonRec (poly_var, lvl) poly_var_rhs
- poly_var_app = mkTyApp (Var poly_var) (mkTyVarTys offending_tyvars)
+ poly_var_app = mkTyApps (Var poly_var) (mkTyVarTys offending_tyvars)
final_expr = Let poly_var_binding poly_var_app -- mkCoLet* requires Core
in
returnLvl final_expr
poly_ty = mkForAllTys offending_tyvars ty
-- These defns are just like those in the TyLam case of lvlExpr
- (incd_lvl, tyvar_lvls) = mapAccumL next (unTopify lvl) offending_tyvars
-
- next lvl tyvar = (lvl1, (tyvar,lvl1))
- where lvl1 = incMinorLvl lvl
-
- new_tenv = growTyVarEnvList tenv tyvar_lvls
- new_envs = (venv, new_tenv)
+ incd_lvl = incMinorLvl lvl
+ tyvar_lvls = [(tv,incd_lvl) | tv <- offending_tyvars]
+ new_env = extendVarEnvList env tyvar_lvls
\end{code}
Recursive definitions. We want to transform
type lambdas.
\begin{code}
-decideRecFloatLevel ctxt_lvl envs@(venv, tenv) ids rhss
- | isTopMajLvl ids_only_lvl && -- Destination = top
- not (all canFloatToTop (zipEqual "decideRec" tys rhss)) -- Some can't float to top
- = -- Pin it here
- let
- ids_w_lvls = ids `zip` repeat ctxt_lvl
- new_envs = (growIdEnvList venv ids_w_lvls, tenv)
- in
- mapLvl (lvlExpr ctxt_lvl new_envs) rhss `thenLvl` \ rhss' ->
- returnLvl (ctxt_lvl, [], rhss')
-
-{- OMITTED; see comments above near isWorthFloatingExpr
-
- | not (any (isWorthFloating True . deAnnotate) rhss)
- = -- Pin it here
- mapLvl (lvlExpr ctxt_lvl envs) rhss `thenLvl` \ rhss' ->
- returnLvl (ctxt_lvl, [], rhss')
-
--}
-
+decideRecFloatLevel ctxt_lvl env ids rhss
| ids_only_lvl `ltLvl` tyvars_only_lvl
= -- Abstract wrt tyvars;
-- offending_tyvars is definitely non-empty
-- (I love the ASSERT to check this... WDP 95/02)
let
- -- These defns are just like those in the TyLam case of lvlExpr
- (incd_lvl, tyvar_lvls) = mapAccumL next (unTopify ids_only_lvl) offending_tyvars
-
- next lvl tyvar = (lvl1, (tyvar,lvl1))
- where lvl1 = incMinorLvl lvl
-
- ids_w_incd_lvl = [(id,incd_lvl) | id <- ids]
- new_tenv = growTyVarEnvList tenv tyvar_lvls
- new_venv = growIdEnvList venv ids_w_incd_lvl
- new_envs = (new_venv, new_tenv)
+ incd_lvl = incMinorLvl ids_only_lvl
+ tyvars_w_lvl = [(var,incd_lvl) | var <- offending_tyvars]
+ ids_w_lvl = [(var,incd_lvl) | var <- ids]
+ new_env = extendVarEnvList env (tyvars_w_lvl ++ ids_w_lvl)
in
- mapLvl (lvlExpr incd_lvl new_envs) rhss `thenLvl` \ rhss' ->
+ mapLvl (lvlExpr incd_lvl new_env) rhss `thenLvl` \ rhss' ->
mapLvl newLvlVar poly_tys `thenLvl` \ poly_vars ->
let
ids_w_poly_vars = zipEqual "decideRec2" ids poly_vars
-- The "d_rhss" are the right-hand sides of "D" and "D'"
-- in the documentation above
- d_rhss = [ mkTyApp (Var poly_var) offending_tyvar_tys | poly_var <- poly_vars]
+ d_rhss = [ mkTyApps (Var poly_var) offending_tyvar_tys | poly_var <- poly_vars]
-- "local_binds" are "D'" in the documentation above
- local_binds = zipWithEqual "SetLevels" NonRec ids_w_incd_lvl d_rhss
+ local_binds = zipWithEqual "SetLevels" NonRec ids_w_lvl d_rhss
- poly_var_rhss = [ mkTyLam offending_tyvars (foldr Let rhs' local_binds)
- | rhs' <- rhss' -- mkCoLet* requires Core...
+ poly_var_rhss = [ mkLams tyvars_w_lvl (mkLets local_binds rhs')
+ | rhs' <- rhss'
]
poly_binds = zipEqual "poly_binds" [(poly_var, ids_only_lvl) | poly_var <- poly_vars]
= -- Let it float freely
let
ids_w_lvls = ids `zip` repeat expr_lvl
- new_envs = (growIdEnvList venv ids_w_lvls, tenv)
+ new_env = extendVarEnvList env ids_w_lvls
in
- mapLvl (lvlExpr (unTopify expr_lvl) new_envs) rhss `thenLvl` \ rhss' ->
+ mapLvl (lvlExpr expr_lvl new_env) rhss `thenLvl` \ rhss' ->
returnLvl (expr_lvl, [], rhss')
where
- tys = map idType ids
-
- fvs = (unionManyIdSets [freeVarsOf rhs | rhs <- rhss] `unionIdSets`
- mkIdSet (concat (map idSpecVars ids)))
- `minusIdSet` mkIdSet ids
-
- tfvs = unionManyTyVarSets [freeTyVarsOf rhs | rhs <- rhss]
- `unionTyVarSets`
- tyVarsOfTypes tys
- -- Why the "tyVarsOfTypes" part? Consider this:
- -- /\a -> letrec x::a = x in E
- -- Now, there are no explicit free type variables in the RHS of x,
- -- but nevertheless "a" is free in its definition. So we add in
- -- the free tyvars of the types of the binders.
- -- This actually happened in the defn of errorIO in IOBase.lhs:
- -- errorIO (ST io) = case (errorIO# io) of
- -- _ -> bottom
- -- where
- -- bottom = bottom -- Never evaluated
- -- I don't think this can every happen for non-recursive bindings.
-
- fv_list = idSetToList fvs
- tv_list = tyVarSetToList tfvs
-
- ids_only_lvl = foldr (maxLvl . idLevel venv) tOP_LEVEL fv_list
- tyvars_only_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL tv_list
- expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
+ -- Finding the free vars of the binding group is annoying
+ bind_fvs = (unionVarSets (map fst rhss) `unionVarSet` unionVarSets (map idFreeVars ids))
+ `minusVarSet`
+ mkVarSet ids
- offending_tyvars
- | ids_only_lvl `ltLvl` tyvars_only_lvl = filter offending tv_list
- | otherwise = []
+ ids_only_lvl = foldVarSet (maxIdLvl env) tOP_LEVEL bind_fvs
+ tyvars_only_lvl = foldVarSet (maxTyVarLvl env) tOP_LEVEL bind_fvs
+ expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
+ offending_tyvars = filter offending_tv (varSetElems bind_fvs)
+ offending_tv var | isId var = False
+ | otherwise = ids_only_lvl `ltLvl` varLevel env var
offending_tyvar_tys = mkTyVarTys offending_tyvars
- poly_tys = map (mkForAllTys offending_tyvars) tys
- offending tyvar = ids_only_lvl `ltLvl` tyvarLevel tenv tyvar
-\end{code}
-
-
-\begin{code}
-{- ******** OMITTED NOW
-
-isWorthFloating :: Bool -- True <=> already let-bound
- -> CoreExpr -- The expression
- -> Bool
-
-isWorthFloating alreadyLetBound expr
-
- | alreadyLetBound = isWorthFloatingExpr expr
-
- | otherwise = -- No point in adding a fresh let-binding for a WHNF, because
- -- floating it isn't beneficial enough.
- isWorthFloatingExpr expr &&
- not (whnfOrBottom expr)
-********** -}
-
-isWorthFloatingExpr :: CoreExpr -> Bool
-
-isWorthFloatingExpr (Var v) = False
-isWorthFloatingExpr (Lit lit) = False
-isWorthFloatingExpr (App e arg)
- | notValArg arg = isWorthFloatingExpr e
-isWorthFloatingExpr (Con con as)
- | all notValArg as = False -- Just a type application
-isWorthFloatingExpr _ = True
-
-canFloatToTop :: (Type, CoreExprWithFVs) -> Bool
-
-canFloatToTop (ty, (FVInfo _ _ (LeakFree _), expr)) = True
-canFloatToTop (ty, (FVInfo _ _ MightLeak, expr)) = isLeakFreeType [] ty
-
-valSuggestsLeakFree expr = whnfOrBottom expr
-\end{code}
-
-
-
-%************************************************************************
-%* *
-\subsection{Help functions}
-%* *
-%************************************************************************
-
-\begin{code}
-idLevel :: IdEnv Level -> Id -> Level
-idLevel venv v
- = case lookupIdEnv venv v of
- Just level -> level
- Nothing -> tOP_LEVEL
-
-tyvarLevel :: TyVarEnv Level -> TyVar -> Level
-tyvarLevel tenv tyvar
- = case lookupTyVarEnv tenv tyvar of
- Just level -> level
- Nothing -> tOP_LEVEL
-\end{code}
-
-\begin{code}
-annCollectValBinders (_, (AnnLam (ValBinder arg) rhs))
- = (arg:args, body)
- where
- (args, body) = annCollectValBinders rhs
-
-annCollectValBinders body
- = ([], body)
+ tys = map idType ids
+ poly_tys = map (mkForAllTys offending_tyvars) tys
\end{code}
%************************************************************************
\begin{code}
type LvlM result = UniqSM result
+initLvl = initUs
thenLvl = thenUs
returnLvl = returnUs
mapLvl = mapUs
\begin{code}
newLvlVar :: Type -> LvlM Id
-
-newLvlVar ty us
- = mkSysLocal SLIT("lvl") (getUnique us) ty noSrcLoc
+newLvlVar ty = getUniqueUs `thenLvl` \ uniq ->
+ returnUs (mkUserLocal (varOcc SLIT("lvl")) uniq ty)
\end{code}
projects / ghc-hetmet.git / blobdiff