2 % (c) The GRASP/AQUA Project, Glasgow University, 1998
4 \section[UsageSPUtils]{UsageSP Utilities}
6 This code is (based on) PhD work of Keith Wansbrough <kw217@cl.cam.ac.uk>,
7 September 1998 .. May 1999.
9 Keith Wansbrough 1998-09-04..1999-05-07
12 module UsageSPUtils ( AnnotM(AnnotM), initAnnotM,
14 MungeFlags(isSigma,isLocal,isExp,hasUsg,mfLoc),
16 doAnnotBinds, doUnAnnotBinds,
17 annotMany, annotManyN, unannotTy, freshannotTy,
20 UniqSMM, usToUniqSMM, uniqSMMToUs,
25 #include "HsVersions.h"
28 import Const ( Con(..), Literal(..) )
29 import Var ( IdOrTyVar, varName, varType, setVarType, mkUVar )
30 import Id ( idMustBeINLINEd, isExportedId )
31 import Name ( isLocallyDefined )
32 import Type ( Type(..), TyNote(..), UsageAnn(..), isUsgTy, splitFunTys )
33 import Subst ( substTy, mkTyVarSubst )
34 import TyCon ( isAlgTyCon, isPrimTyCon, isSynTyCon, isFunTyCon )
36 import PrimOp ( PrimOp, primOpUsg )
37 import Maybes ( expectJust )
38 import UniqSupply ( UniqSupply, UniqSM, initUs, getUniqueUs, thenUs, returnUs )
40 import PprCore ( ) -- instances only
43 ======================================================================
45 Walking over (and altering) types
46 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
48 We often need to fiddle with (i.e., add or remove) usage annotations
49 on a type. We define here a general framework to do this. Usage
50 annotations come from any monad with a function @getAnnM@ which yields
51 a new annotation. We use two mutually recursive functions, one for
52 sigma types and one for tau types.
55 genAnnotTy :: Monad m =>
56 (m UsageAnn) -- get new annotation
60 genAnnotTy getAnnM ty = do { u <- getAnnM
61 ; ty' <- genAnnotTyN getAnnM ty
62 ; return (NoteTy (UsgNote u) ty')
65 genAnnotTyN :: Monad m =>
71 (NoteTy (UsgNote _) ty) = panic "genAnnotTyN: unexpected UsgNote"
73 (NoteTy (SynNote sty) ty) = do { sty' <- genAnnotTyN getAnnM sty
74 -- is this right? shouldn't there be some
75 -- correlation between sty' and ty'?
76 -- But sty is a TyConApp; does this make it safer?
77 ; ty' <- genAnnotTyN getAnnM ty
78 ; return (NoteTy (SynNote sty') ty')
81 (NoteTy fvn@(FTVNote _) ty) = do { ty' <- genAnnotTyN getAnnM ty
82 ; return (NoteTy fvn ty')
86 ty0@(TyVarTy _) = do { return ty0 }
89 (AppTy ty1 ty2) = do { ty1' <- genAnnotTyN getAnnM ty1
90 ; ty2' <- genAnnotTyN getAnnM ty2
91 ; return (AppTy ty1' ty2')
95 (TyConApp tc tys) = ASSERT( isFunTyCon tc || isAlgTyCon tc || isPrimTyCon tc || isSynTyCon tc )
96 do { let gAT = if isFunTyCon tc
97 then genAnnotTy -- sigma for partial apps of (->)
98 else genAnnotTyN -- tau otherwise
99 ; tys' <- mapM (gAT getAnnM) tys
100 ; return (TyConApp tc tys')
104 (FunTy ty1 ty2) = do { ty1' <- genAnnotTy getAnnM ty1
105 ; ty2' <- genAnnotTy getAnnM ty2
106 ; return (FunTy ty1' ty2')
110 (ForAllTy v ty) = do { ty' <- genAnnotTyN getAnnM ty
111 ; return (ForAllTy v ty')
117 Walking over (and retyping) terms
118 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
120 We also often need to play with the types in a term. This is slightly
121 tricky because of redundancy: we want to change binder types, and keep
122 the bound types matching these; then there's a special case also with
123 non-locally-defined bound variables. We generalise over all this
126 The name `annot' is a bit of a misnomer, as the code is parameterised
127 over exactly what it does to the types (and certain terms). Notice
128 also that it is possible for this parameter to use
129 monadically-threaded state: here called `flexi'. For genuine
130 annotation, this state will be a UniqSupply.
132 We may add annotations to the outside of a (term, not type) lambda; a
133 function passed to @genAnnotBinds@ does this, taking the lambda and
134 returning the annotated lambda. It is inside the @AnnotM@ monad.
135 This term-munging function is applied when we see either a term lambda
136 or a usage annotation; *IMPORTANT:* it is applied *before* we recurse
137 down into the term, and it is expected to work only at the top level.
138 Recursion will subsequently be done by genAnnotBinds. It may
139 optionally remove a Note TermUsg, or optionally add one if it is not
140 already present, but it may perform NO OTHER MODIFICATIONS to the
141 structure of the term.
143 We do different things to types of variables bound locally and of
144 variables bound in other modules, in certain cases: the former get
145 uvars and the latter keep their existing annotations when we annotate,
146 for example. To control this, @MungeFlags@ describes what kind of a
147 type this is that we're about to munge.
150 data MungeFlags = MungeFlags { isSigma :: Bool, -- want annotated on top (sigma type)
151 isLocal :: Bool, -- is locally-defined type
152 hasUsg :: Bool, -- has fixed usage info, don't touch
153 isExp :: Bool, -- is exported (and must be pessimised)
154 mfLoc :: SDoc -- location info
157 tauTyMF loc = MungeFlags { isSigma = False, isLocal = True,
158 hasUsg = False, isExp = False, mfLoc = loc }
159 sigVarTyMF v = MungeFlags { isSigma = True, isLocal = hasLocalDef v,
160 hasUsg = hasUsgInfo v, isExp = isExportedId v,
161 mfLoc = ptext SLIT("type of binder") <+> ppr v }
164 The helper functions @tauTyMF@ and @sigVarTyMF@ create @MungeFlags@
165 for us. @sigVarTyMF@ checks the variable to see how to set the flags.
167 @hasLocalDef@ tells us if the given variable has an actual local
168 definition that we can play with. This is not quite the same as
169 @isLocallyDefined@, since @IMustBeINLINEd@ things (usually) don't have
170 a local definition - the simplifier will inline whatever their
171 unfolding is anyway. We treat these as if they were externally
172 defined, since we don't have access to their definition (at least not
173 easily). This doesn't hurt much, since after the simplifier has run
174 the unfolding will have been inlined and we can access the unfolding
177 @hasUsgInfo@, on the other hand, says if the variable already has
178 usage info in its type that must at all costs be preserved. This is
179 assumed true (exactly) of all imported ids.
182 hasLocalDef :: IdOrTyVar -> Bool
183 hasLocalDef var = isLocallyDefined var
184 && not (idMustBeINLINEd var)
186 hasUsgInfo :: IdOrTyVar -> Bool
187 hasUsgInfo var = (not . isLocallyDefined) var
190 Here's the walk itself.
193 genAnnotBinds :: (MungeFlags -> Type -> AnnotM flexi Type)
194 -> (CoreExpr -> AnnotM flexi CoreExpr) -- see caveats above
196 -> AnnotM flexi [CoreBind]
198 genAnnotBinds _ _ [] = return []
200 genAnnotBinds f g (b:bs) = do { (b',vs,vs') <- genAnnotBind f g b
201 ; bs' <- withAnnVars vs vs' $
206 genAnnotBind :: (MungeFlags -> Type -> AnnotM flexi Type) -- type-altering function
207 -> (CoreExpr -> AnnotM flexi CoreExpr) -- term-altering function
208 -> CoreBind -- original CoreBind
210 (CoreBind, -- annotated CoreBind
211 [IdOrTyVar], -- old variables, to be mapped to...
212 [IdOrTyVar]) -- ... new variables
214 genAnnotBind f g (NonRec v1 e1) = do { v1' <- genAnnotVar f v1
215 ; e1' <- genAnnotCE f g e1
216 ; return (NonRec v1' e1', [v1], [v1'])
219 genAnnotBind f g (Rec ves) = do { let (vs,es) = unzip ves
220 ; vs' <- mapM (genAnnotVar f) vs
221 ; es' <- withAnnVars vs vs' $
222 mapM (genAnnotCE f g) es
223 ; return (Rec (zip vs' es'), vs, vs')
226 genAnnotCE :: (MungeFlags -> Type -> AnnotM flexi Type) -- type-altering function
227 -> (CoreExpr -> AnnotM flexi CoreExpr) -- term-altering function
228 -> CoreExpr -- original expression
229 -> AnnotM flexi CoreExpr -- yields new expression
231 genAnnotCE mungeType mungeTerm = go
232 where go e0@(Var v) | isTyVar v = return e0 -- arises, e.g., as tyargs of Con
233 -- (no it doesn't: (Type (TyVar tyvar))
234 | otherwise = do { mv' <- lookupAnnVar v
236 Just var -> return var
237 Nothing -> fixedVar v
241 go (Con c args) = -- we know it's saturated
242 do { args' <- mapM go args
243 ; return (Con c args')
246 go (App e arg) = do { e' <- go e
248 ; return (App e' arg')
251 go e0@(Lam v0 _) = do { e1 <- (if isTyVar v0 then return else mungeTerm) e0
253 = case e1 of -- munge may have added note
254 Note tu@(TermUsg _) (Lam v e2)
256 Lam v e2 -> (v,e2,id)
257 ; v' <- genAnnotVar mungeType v
258 ; e' <- withAnnVar v v' $ go e2
259 ; return (wrap (Lam v' e'))
262 go (Let bind e) = do { (bind',vs,vs') <- genAnnotBind mungeType mungeTerm bind
263 ; e' <- withAnnVars vs vs' $ go e
264 ; return (Let bind' e')
267 go (Case e v alts) = do { e' <- go e
268 ; v' <- genAnnotVar mungeType v
269 ; alts' <- withAnnVar v v' $ mapM genAnnotAlt alts
270 ; return (Case e' v' alts')
273 go (Note scc@(SCC _) e) = do { e' <- go e
274 ; return (Note scc e')
276 go e0@(Note (Coerce ty1 ty0)
277 e) = do { ty1' <- mungeType
278 (tauTyMF (ptext SLIT("coercer of")
281 (tauTyMF (ptext SLIT("coercee of")
283 -- (Better to specify ty0'
284 -- identical to the type of e, including
285 -- annotations, right at the beginning, but
286 -- not possible at this point.)
288 ; return (Note (Coerce ty1' ty0') e')
290 go (Note InlineCall e) = do { e' <- go e
291 ; return (Note InlineCall e')
293 go e0@(Note (TermUsg _) _) = do { e1 <- mungeTerm e0
294 ; case e1 of -- munge may have removed note
295 Note tu@(TermUsg _) e2 -> do { e3 <- go e2
296 ; return (Note tu e3)
301 go e0@(Type ty) = -- should only occur at toplevel of Arg,
303 do { ty' <- mungeType
304 (tauTyMF (ptext SLIT("tyarg")
309 fixedVar v = ASSERT2( not (hasLocalDef v), text "genAnnotCE: locally defined var" <+> ppr v <+> text "not in varenv" )
310 genAnnotVar mungeType v
312 genAnnotAlt (c,vs,e) = do { vs' <- mapM (genAnnotVar mungeType) vs
313 ; e' <- withAnnVars vs vs' $ go e
314 ; return (c, vs', e')
318 genAnnotVar :: (MungeFlags -> Type -> AnnotM flexi Type)
320 -> AnnotM flexi IdOrTyVar
322 genAnnotVar mungeType v | isTyVar v = return v
323 | otherwise = do { vty' <- mungeType (sigVarTyMF v) (varType v)
324 ; return (setVarType v vty')
328 pprTrace "genAnnotVar" (ppr (tyUsg vty') <+> ppr v) $
334 ======================================================================
336 Some specific things to do to types inside terms
337 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
339 @annotTyM@ annotates a type with fresh uvars everywhere the inference
340 is allowed to go, and leaves alone annotations where it may not go.
342 We assume there are no annotations already.
345 annotTyM :: MungeFlags -> Type -> AnnotM UniqSupply Type
347 annotTyM mf ty = uniqSMtoAnnotM . uniqSMMToUs $
348 case (hasUsg mf, isLocal mf, isSigma mf) of
349 (True ,_ ,_ ) -> ASSERT( isUsgTy ty )
351 (False,True ,True ) -> if isExp mf then
352 annotTyP (tag 'p') ty
355 (False,True ,False) -> annotTyN (tag 't') ty
356 (False,False,True ) -> return $ annotMany ty -- assume worst
357 (False,False,False) -> return $ annotManyN ty
358 where tag c = Right $ "annotTyM:" ++ [c] ++ ": " ++ showSDoc (ppr ty)
360 -- specific functions for annotating tau and sigma types
363 annotTy tag = genAnnotTy (newVarUSMM tag)
364 annotTyN tag = genAnnotTyN (newVarUSMM tag)
366 -- ...with uvars and pessimal Manys (for exported ids)
367 annotTyP tag ty = do { ty' <- annotTy tag ty ; return (pessimise True ty') }
370 annotMany, annotManyN :: Type -> Type
375 annotMany ty = unId (genAnnotTy (return UsMany) ty)
376 annotManyN ty = unId (genAnnotTyN (return UsMany) ty)
379 -- monad required for the above
380 newtype Id a = Id a ; unId (Id a) = a
381 instance Monad Id where { a >>= f = f (unId a) ; return a = Id a }
383 -- lambda-annotating function for use along with the above
384 annotLam e0@(Lam v e) = do { uv <- uniqSMtoAnnotM $ newVarUs (Left e0)
385 ; return (Note (TermUsg uv) (Lam v e))
387 annotLam (Note (TermUsg _) _) = panic "annotLam: unexpected term usage annot"
390 The above requires a `pessimising' translation. This is applied to
391 types of exported ids, and ensures that they have a fully general
392 type (since we don't know how they will be used in other modules).
395 pessimise :: Bool -> Type -> Type
398 pessimise co ty0@(NoteTy usg@(UsgNote u ) ty)
400 then case u of UsMany -> pty
401 UsVar _ -> pty -- force to UsMany
402 UsOnce -> pprPanic "pessimise:" (ppr ty0)
404 where pty = pessimiseN co ty
406 pessimise co ty0 = pessimiseN co ty0 -- assume UsMany
408 pessimise co ty0@(NoteTy usg@(UsgNote u ) ty)
410 then case u of UsMany -> NoteTy usg pty
411 UsVar _ -> NoteTy (UsgNote UsMany) pty
412 UsOnce -> pprPanic "pessimise:" (ppr ty0)
414 where pty = pessimiseN co ty
416 pessimise co ty0 = pprPanic "pessimise: missing usage note:" $
420 pessimiseN co ty0@(NoteTy usg@(UsgNote _ ) ty) = pprPanic "pessimiseN: unexpected usage note:" $
422 pessimiseN co (NoteTy (SynNote sty) ty) = NoteTy (SynNote (pessimiseN co sty))
424 pessimiseN co (NoteTy note@(FTVNote _ ) ty) = NoteTy note (pessimiseN co ty)
425 pessimiseN co ty0@(TyVarTy _) = ty0
426 pessimiseN co ty0@(AppTy _ _) = ty0
427 pessimiseN co ty0@(TyConApp tc tys) = ASSERT( not ((isFunTyCon tc) && (length tys > 1)) )
429 pessimiseN co (FunTy ty1 ty2) = FunTy (pessimise (not co) ty1)
431 pessimiseN co (ForAllTy tyv ty) = ForAllTy tyv (pessimiseN co ty)
435 @unAnnotTyM@ strips annotations (that the inference is allowed to
436 touch) from a term, and `fixes' those it isn't permitted to touch (by
437 putting @Many@ annotations where they are missing, but leaving
438 existing annotations in the type).
440 @unTermUsg@ removes from a term any term usage annotations it finds.
443 unAnnotTyM :: MungeFlags -> Type -> AnnotM a Type
445 unAnnotTyM mf ty = if hasUsg mf then
447 return (fixAnnotTy ty)
448 else return (unannotTy ty)
451 unTermUsg :: CoreExpr -> AnnotM a CoreExpr
452 -- strip all term annotations
453 unTermUsg e@(Lam _ _) = return e
454 unTermUsg (Note (TermUsg _) e) = return e
455 unTermUsg _ = panic "unTermUsg"
457 unannotTy :: Type -> Type
458 -- strip all annotations
459 unannotTy (NoteTy (UsgNote _ ) ty) = unannotTy ty
460 unannotTy (NoteTy (SynNote sty) ty) = NoteTy (SynNote (unannotTy sty)) (unannotTy ty)
461 unannotTy (NoteTy note@(FTVNote _ ) ty) = NoteTy note (unannotTy ty)
462 unannotTy ty@(TyVarTy _) = ty
463 unannotTy (AppTy ty1 ty2) = AppTy (unannotTy ty1) (unannotTy ty2)
464 unannotTy (TyConApp tc tys) = TyConApp tc (map unannotTy tys)
465 unannotTy (FunTy ty1 ty2) = FunTy (unannotTy ty1) (unannotTy ty2)
466 unannotTy (ForAllTy tyv ty) = ForAllTy tyv (unannotTy ty)
469 fixAnnotTy :: Type -> Type
470 -- put Manys where they are missing
474 fixAnnotTy (NoteTy note@(UsgNote _ ) ty) = NoteTy note (fixAnnotTyN ty)
475 fixAnnotTy ty0 = NoteTy (UsgNote UsMany) (fixAnnotTyN ty0)
477 fixAnnotTyN ty0@(NoteTy note@(UsgNote _ ) ty) = pprPanic "fixAnnotTyN: unexpected usage note:" $
479 fixAnnotTyN (NoteTy (SynNote sty) ty) = NoteTy (SynNote (fixAnnotTyN sty))
481 fixAnnotTyN (NoteTy note@(FTVNote _ ) ty) = NoteTy note (fixAnnotTyN ty)
482 fixAnnotTyN ty0@(TyVarTy _) = ty0
483 fixAnnotTyN (AppTy ty1 ty2) = AppTy (fixAnnotTyN ty1) (fixAnnotTyN ty2)
484 fixAnnotTyN (TyConApp tc tys) = ASSERT( isFunTyCon tc || isAlgTyCon tc || isPrimTyCon tc || isSynTyCon tc )
485 TyConApp tc (map (if isFunTyCon tc then
489 fixAnnotTyN (FunTy ty1 ty2) = FunTy (fixAnnotTy ty1) (fixAnnotTy ty2)
490 fixAnnotTyN (ForAllTy tyv ty) = ForAllTy tyv (fixAnnotTyN ty)
494 The composition (reannotating a type with fresh uvars but the same
495 structure) is useful elsewhere:
498 freshannotTy :: Type -> UniqSMM Type
499 freshannotTy = annotTy (Right "freshannotTy") . unannotTy
503 Wrappers apply these functions to sets of bindings.
506 doAnnotBinds :: UniqSupply
508 -> ([CoreBind],UniqSupply)
510 doAnnotBinds us binds = initAnnotM us (genAnnotBinds annotTyM annotLam binds)
513 doUnAnnotBinds :: [CoreBind]
516 doUnAnnotBinds binds = fst $ initAnnotM () $
517 genAnnotBinds unAnnotTyM unTermUsg binds
520 ======================================================================
525 The @UniqSM@ type is not an instance of @Monad@, and cannot be made so
526 since it is merely a synonym rather than a newtype. Here we define
527 @UniqSMM@, which *is* an instance of @Monad@.
530 newtype UniqSMM a = UsToUniqSMM (UniqSM a)
531 uniqSMMToUs (UsToUniqSMM us) = us
532 usToUniqSMM = UsToUniqSMM
534 instance Monad UniqSMM where
535 m >>= f = UsToUniqSMM $ uniqSMMToUs m `thenUs` \ a ->
537 return = UsToUniqSMM . returnUs
541 For annotation, the monad @AnnotM@, we need to carry around our
542 variable mapping, along with some general state.
545 newtype AnnotM flexi a = AnnotM ( flexi -- UniqSupply etc
546 -> VarEnv IdOrTyVar -- unannotated to annotated variables
547 -> (a,flexi,VarEnv IdOrTyVar))
548 unAnnotM (AnnotM f) = f
550 instance Monad (AnnotM flexi) where
551 a >>= f = AnnotM (\ us ve -> let (r,us',ve') = unAnnotM a us ve
552 in unAnnotM (f r) us' ve')
553 return a = AnnotM (\ us ve -> (a,us,ve))
555 initAnnotM :: fl -> AnnotM fl a -> (a,fl)
556 initAnnotM fl m = case (unAnnotM m) fl emptyVarEnv of { (r,fl',_) -> (r,fl') }
558 withAnnVar :: IdOrTyVar -> IdOrTyVar -> AnnotM fl a -> AnnotM fl a
559 withAnnVar v v' m = AnnotM (\ us ve -> let ve' = extendVarEnv ve v v'
560 (r,us',_) = (unAnnotM m) us ve'
563 withAnnVars :: [IdOrTyVar] -> [IdOrTyVar] -> AnnotM fl a -> AnnotM fl a
564 withAnnVars vs vs' m = AnnotM (\ us ve -> let ve' = plusVarEnv ve (zipVarEnv vs vs')
565 (r,us',_) = (unAnnotM m) us ve'
568 lookupAnnVar :: IdOrTyVar -> AnnotM fl (Maybe IdOrTyVar)
569 lookupAnnVar var = AnnotM (\ us ve -> (lookupVarEnv ve var,
574 A useful helper allows us to turn a computation in the unique supply
575 monad into one in the annotation monad parameterised by a unique
579 uniqSMtoAnnotM :: UniqSM a -> AnnotM UniqSupply a
581 uniqSMtoAnnotM m = AnnotM (\ us ve -> let (r,us') = initUs us m
585 @newVarUs@ and @newVarUSMM@ generate a new usage variable. They take
586 an argument which is used for debugging only, describing what the
587 variable is to annotate.
590 newVarUs :: (Either CoreExpr String) -> UniqSM UsageAnn
591 -- the first arg is for debugging use only
592 newVarUs e = getUniqueUs `thenUs` \ u ->
597 Left (Con (Literal _) _) -> "literal"
598 Left (Con _ _) -> "primop"
599 Left (Lam v e) -> "lambda: " ++ showSDoc (ppr v)
602 in pprTrace "newVarUs:" (ppr uv <+> text src) $
606 newVarUSMM :: (Either CoreExpr String) -> UniqSMM UsageAnn
607 newVarUSMM = usToUniqSMM . newVarUs
610 ======================================================================
612 PrimOps and usage information.
614 Analagously to @DataCon.dataConArgTys@, we determine the argtys and
615 result ty of a primop, *after* substition (which may reveal more args,
616 notably for @CCall@s).
619 primOpUsgTys :: PrimOp -- this primop
620 -> [Type] -- instantiated at these (tau) types
621 -> ([Type],Type) -- requires args of these (sigma) types,
622 -- and returns this (sigma) type
624 primOpUsgTys p tys = let (tyvs,ty0us,rtyu) = primOpUsg p
625 s = mkTyVarSubst tyvs tys
626 (ty1us,rty1u) = splitFunTys (substTy s rtyu)
627 -- substitution may reveal more args
628 in ((map (substTy s) ty0us) ++ ty1us,
632 ======================================================================