\begin{code}
module SimplUtils (
- mkLam, prepareAlts, mkCase,
+ mkLam, mkCase,
-- Inlining,
preInlineUnconditionally, postInlineUnconditionally, activeInline, activeRule,
SimplCont(..), DupFlag(..), LetRhsFlag(..),
contIsDupable, contResultType,
countValArgs, countArgs, pushContArgs,
- mkBoringStop, mkRhsStop, contIsRhs, contIsRhsOrArg,
- getContArgs, interestingCallContext, interestingArg, isStrictType
+ mkBoringStop, mkLazyArgStop, mkRhsStop, contIsRhs, contIsRhsOrArg,
+ getContArgs, interestingCallContext, interestingArgContext,
+ interestingArg, isStrictType
) where
opt_RulesOff )
import CoreSyn
import CoreFVs ( exprFreeVars )
-import CoreUtils ( cheapEqExpr, exprType, exprIsTrivial, exprIsCheap,
+import CoreUtils ( cheapEqExpr, exprType, exprIsTrivial,
etaExpand, exprEtaExpandArity, bindNonRec, mkCoerce2,
- findDefault, exprOkForSpeculation, exprIsHNF
+ findDefault, exprOkForSpeculation, exprIsHNF, mergeAlts
)
import Literal ( mkStringLit )
import CoreUnfold ( smallEnoughToInline )
import MkId ( eRROR_ID )
-import Id ( idType, isDataConWorkId, idOccInfo, isDictId,
- mkSysLocal, isDeadBinder, idNewDemandInfo, isExportedId,
- idUnfolding, idNewStrictness, idInlinePragma,
+import Id ( Id, idType, isDataConWorkId, idOccInfo, isDictId,
+ isDeadBinder, idNewDemandInfo, isExportedId,
+ idUnfolding, idNewStrictness, idInlinePragma, idHasRules
)
import NewDemand ( isStrictDmd, isBotRes, splitStrictSig )
import SimplMonad
import Type ( Type, splitFunTys, dropForAlls, isStrictType,
- splitTyConApp_maybe, tyConAppArgs, mkTyVarTys
+ splitTyConApp_maybe, tyConAppArgs
)
-import Name ( mkSysTvName )
-import TyCon ( tyConDataCons_maybe, isAlgTyCon, isNewTyCon )
-import DataCon ( dataConRepArity, dataConTyVars, dataConInstArgTys, isVanillaDataCon )
-import Var ( tyVarKind, mkTyVar )
+import TyCon ( tyConDataCons_maybe )
+import DataCon ( dataConRepArity )
import VarSet
import BasicTypes ( TopLevelFlag(..), isNotTopLevel, OccInfo(..), isLoopBreaker, isOneOcc,
Activation, isAlwaysActive, isActive )
\begin{code}
data SimplCont -- Strict contexts
- = Stop OutType -- Type of the result
+ = Stop OutType -- Type of the result
LetRhsFlag
- Bool -- True <=> This is the RHS of a thunk whose type suggests
- -- that update-in-place would be possible
- -- (This makes the inliner a little keener.)
+ Bool -- True <=> There is something interesting about
+ -- the context, and hence the inliner
+ -- should be a bit keener (see interestingCallContext)
+ -- Two cases:
+ -- (a) This is the RHS of a thunk whose type suggests
+ -- that update-in-place would be possible
+ -- (b) This is an argument of a function that has RULES
+ -- Inlining the call might allow the rule to fire
| CoerceIt OutType -- The To-type, simplified
SimplCont
- | InlinePlease -- This continuation makes a function very
- SimplCont -- keen to inline itelf
-
| ApplyTo DupFlag
InExpr SimplEnv -- The argument, as yet unsimplified,
SimplCont -- and its environment
| ArgOf LetRhsFlag -- An arbitrary strict context: the argument
-- of a strict function, or a primitive-arg fn
-- or a PrimOp
- -- No DupFlag because we never duplicate it
+ -- No DupFlag, because we never duplicate it
OutType -- arg_ty: type of the argument itself
OutType -- cont_ty: the type of the expression being sought by the context
-- f (error "foo") ==> coerce t (error "foo")
ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$
(nest 4 (ppr alts)) $$ ppr cont
ppr (CoerceIt ty cont) = (ptext SLIT("CoerceIt") <+> ppr ty) $$ ppr cont
- ppr (InlinePlease cont) = ptext SLIT("InlinePlease") $$ ppr cont
data DupFlag = OkToDup | NoDup
-------------------
-mkBoringStop, mkRhsStop :: OutType -> SimplCont
-mkBoringStop ty = Stop ty AnArg (canUpdateInPlace ty)
-mkRhsStop ty = Stop ty AnRhs (canUpdateInPlace ty)
+mkBoringStop :: OutType -> SimplCont
+mkBoringStop ty = Stop ty AnArg False
+
+mkLazyArgStop :: OutType -> Bool -> SimplCont
+mkLazyArgStop ty has_rules = Stop ty AnArg (canUpdateInPlace ty || has_rules)
+
+mkRhsStop :: OutType -> SimplCont
+mkRhsStop ty = Stop ty AnRhs (canUpdateInPlace ty)
contIsRhs :: SimplCont -> Bool
contIsRhs (Stop _ AnRhs _) = True
contIsDupable (ApplyTo OkToDup _ _ _) = True
contIsDupable (Select OkToDup _ _ _ _) = True
contIsDupable (CoerceIt _ cont) = contIsDupable cont
-contIsDupable (InlinePlease cont) = contIsDupable cont
contIsDupable other = False
-------------------
discardableCont :: SimplCont -> Bool
discardableCont (Stop _ _ _) = False
discardableCont (CoerceIt _ cont) = discardableCont cont
-discardableCont (InlinePlease cont) = discardableCont cont
discardableCont other = True
discardCont :: SimplCont -- A continuation, expecting
contResultType (ArgOf _ _ to_ty _) = to_ty
contResultType (ApplyTo _ _ _ cont) = contResultType cont
contResultType (CoerceIt _ cont) = contResultType cont
-contResultType (InlinePlease cont) = contResultType cont
contResultType (Select _ _ _ _ cont) = contResultType cont
-------------------
getContArgs :: SwitchChecker
-> OutId -> SimplCont
-> ([(InExpr, SimplEnv, Bool)], -- Arguments; the Bool is true for strict args
- SimplCont, -- Remaining continuation
- Bool) -- Whether we came across an InlineCall
+ SimplCont) -- Remaining continuation
-- getContArgs id k = (args, k', inl)
-- args are the leading ApplyTo items in k
-- (i.e. outermost comes first)
stricts | switchIsOn chkr NoCaseOfCase = vanilla_stricts
| otherwise = computed_stricts
in
- go [] stricts False orig_cont
+ go [] stricts orig_cont
where
----------------------------
-- Type argument
- go acc ss inl (ApplyTo _ arg@(Type _) se cont)
- = go ((arg,se,False) : acc) ss inl cont
+ go acc ss (ApplyTo _ arg@(Type _) se cont)
+ = go ((arg,se,False) : acc) ss cont
-- NB: don't bother to instantiate the function type
-- Value argument
- go acc (s:ss) inl (ApplyTo _ arg se cont)
- = go ((arg,se,s) : acc) ss inl cont
-
- -- An Inline continuation
- go acc ss inl (InlinePlease cont)
- = go acc ss True cont
+ go acc (s:ss) (ApplyTo _ arg se cont)
+ = go ((arg,se,s) : acc) ss cont
-- We're run out of arguments, or else we've run out of demands
-- The latter only happens if the result is guaranteed bottom
-- Then, especially in the first of these cases, we'd like to discard
-- the continuation, leaving just the bottoming expression. But the
-- type might not be right, so we may have to add a coerce.
- go acc ss inl cont
- | null ss && discardableCont cont = (reverse acc, discardCont cont, inl)
- | otherwise = (reverse acc, cont, inl)
+ go acc ss cont
+ | null ss && discardableCont cont = (reverse acc, discardCont cont)
+ | otherwise = (reverse acc, cont)
----------------------------
vanilla_stricts, computed_stricts :: [Bool]
interestingCallContext some_args some_val_args cont
= interesting cont
where
- interesting (InlinePlease _) = True
interesting (Select _ _ _ _ _) = some_args
interesting (ApplyTo _ _ _ _) = True -- Can happen if we have (coerce t (f x)) y
-- Perhaps True is a bit over-keen, but I've
-- seen (coerce f) x, where f has an INLINE prag,
-- So we have to give some motivaiton for inlining it
interesting (ArgOf _ _ _ _) = some_val_args
- interesting (Stop ty _ upd_in_place) = some_val_args && upd_in_place
+ interesting (Stop ty _ interesting) = some_val_args && interesting
interesting (CoerceIt _ cont) = interesting cont
-- If this call is the arg of a strict function, the context
-- is a bit interesting. If we inline here, we may get useful
-------------------
+interestingArgContext :: Id -> SimplCont -> Bool
+-- If the argument has form (f x y), where x,y are boring,
+-- and f is marked INLINE, then we don't want to inline f.
+-- But if the context of the argument is
+-- g (f x y)
+-- where g has rules, then we *do* want to inline f, in case it
+-- exposes a rule that might fire. Similarly, if the context is
+-- h (g (f x x))
+-- where h has rules, then we do want to inline f.
+-- The interesting_arg_ctxt flag makes this happen; if it's
+-- set, the inliner gets just enough keener to inline f
+-- regardless of how boring f's arguments are, if it's marked INLINE
+--
+-- The alternative would be to *always* inline an INLINE function,
+-- regardless of how boring its context is; but that seems overkill
+-- For example, it'd mean that wrapper functions were always inlined
+interestingArgContext fn cont
+ = idHasRules fn || go cont
+ where
+ go (Select {}) = False
+ go (ApplyTo {}) = False
+ go (ArgOf {}) = True
+ go (CoerceIt _ c) = go c
+ go (Stop _ _ interesting) = interesting
+
+-------------------
canUpdateInPlace :: Type -> Bool
-- Consider let x = <wurble> in ...
-- If <wurble> returns an explicit constructor, we might be able
==> ...(case x of I# x# -> case fw x# of ...)...
and now the redex (f x) isn't floatable any more.
-The no-inling thing is also important for Template Haskell. You might be
+The no-inlining thing is also important for Template Haskell. You might be
compiling in one-shot mode with -O2; but when TH compiles a splice before
running it, we don't want to use -O2. Indeed, we don't want to inline
anything, because the byte-code interpreter might get confused about
%************************************************************************
%* *
-\subsection{Case alternative filtering
-%* *
-%************************************************************************
-
-prepareAlts does two things:
-
-1. Eliminate alternatives that cannot match, including the
- DEFAULT alternative.
-
-2. If the DEFAULT alternative can match only one possible constructor,
- then make that constructor explicit.
- e.g.
- case e of x { DEFAULT -> rhs }
- ===>
- case e of x { (a,b) -> rhs }
- where the type is a single constructor type. This gives better code
- when rhs also scrutinises x or e.
-
-It's a good idea do do this stuff before simplifying the alternatives, to
-avoid simplifying alternatives we know can't happen, and to come up with
-the list of constructors that are handled, to put into the IdInfo of the
-case binder, for use when simplifying the alternatives.
-
-Eliminating the default alternative in (1) isn't so obvious, but it can
-happen:
-
-data Colour = Red | Green | Blue
-
-f x = case x of
- Red -> ..
- Green -> ..
- DEFAULT -> h x
-
-h y = case y of
- Blue -> ..
- DEFAULT -> [ case y of ... ]
-
-If we inline h into f, the default case of the inlined h can't happen.
-If we don't notice this, we may end up filtering out *all* the cases
-of the inner case y, which give us nowhere to go!
-
-
-\begin{code}
-prepareAlts :: OutExpr -- Scrutinee
- -> InId -- Case binder (passed only to use in statistics)
- -> [InAlt] -- Increasing order
- -> SimplM ([InAlt], -- Better alternatives, still incresaing order
- [AltCon]) -- These cases are handled
-
-prepareAlts scrut case_bndr alts
- = let
- (alts_wo_default, maybe_deflt) = findDefault alts
-
- impossible_cons = case scrut of
- Var v -> otherCons (idUnfolding v)
- other -> []
-
- -- Filter out alternatives that can't possibly match
- better_alts | null impossible_cons = alts_wo_default
- | otherwise = [alt | alt@(con,_,_) <- alts_wo_default,
- not (con `elem` impossible_cons)]
-
- -- "handled_cons" are handled either by the context,
- -- or by a branch in this case expression
- -- (Don't add DEFAULT to the handled_cons!!)
- handled_cons = impossible_cons ++ [con | (con,_,_) <- better_alts]
- in
- -- Filter out the default, if it can't happen,
- -- or replace it with "proper" alternative if there
- -- is only one constructor left
- prepareDefault scrut case_bndr handled_cons maybe_deflt `thenSmpl` \ deflt_alt ->
-
- returnSmpl (mergeAlts better_alts deflt_alt, handled_cons)
- -- We need the mergeAlts in case the new default_alt
- -- has turned into a constructor alternative.
-
-prepareDefault scrut case_bndr handled_cons (Just rhs)
- | Just (tycon, inst_tys) <- splitTyConApp_maybe (exprType scrut),
- -- Use exprType scrut here, rather than idType case_bndr, because
- -- case_bndr is an InId, so exprType scrut may have more information
- -- Test simpl013 is an example
- isAlgTyCon tycon, -- It's a data type, tuple, or unboxed tuples.
- not (isNewTyCon tycon), -- We can have a newtype, if we are just doing an eval:
- -- case x of { DEFAULT -> e }
- -- and we don't want to fill in a default for them!
- Just all_cons <- tyConDataCons_maybe tycon,
- not (null all_cons), -- This is a tricky corner case. If the data type has no constructors,
- -- which GHC allows, then the case expression will have at most a default
- -- alternative. We don't want to eliminate that alternative, because the
- -- invariant is that there's always one alternative. It's more convenient
- -- to leave
- -- case x of { DEFAULT -> e }
- -- as it is, rather than transform it to
- -- error "case cant match"
- -- which would be quite legitmate. But it's a really obscure corner, and
- -- not worth wasting code on.
- let handled_data_cons = [data_con | DataAlt data_con <- handled_cons],
- let missing_cons = [con | con <- all_cons,
- not (con `elem` handled_data_cons)]
- = case missing_cons of
- [] -> returnSmpl [] -- Eliminate the default alternative
- -- if it can't match
-
- [con] -> -- It matches exactly one constructor, so fill it in
- tick (FillInCaseDefault case_bndr) `thenSmpl_`
- mk_args con inst_tys `thenSmpl` \ args ->
- returnSmpl [(DataAlt con, args, rhs)]
-
- two_or_more -> returnSmpl [(DEFAULT, [], rhs)]
-
- | otherwise
- = returnSmpl [(DEFAULT, [], rhs)]
-
-prepareDefault scrut case_bndr handled_cons Nothing
- = returnSmpl []
-
-mk_args missing_con inst_tys
- = mk_tv_bndrs missing_con inst_tys `thenSmpl` \ (tv_bndrs, inst_tys') ->
- getUniquesSmpl `thenSmpl` \ id_uniqs ->
- let arg_tys = dataConInstArgTys missing_con inst_tys'
- arg_ids = zipWith (mkSysLocal FSLIT("a")) id_uniqs arg_tys
- in
- returnSmpl (tv_bndrs ++ arg_ids)
-
-mk_tv_bndrs missing_con inst_tys
- | isVanillaDataCon missing_con
- = returnSmpl ([], inst_tys)
- | otherwise
- = getUniquesSmpl `thenSmpl` \ tv_uniqs ->
- let new_tvs = zipWith mk tv_uniqs (dataConTyVars missing_con)
- mk uniq tv = mkTyVar (mkSysTvName uniq FSLIT("t")) (tyVarKind tv)
- in
- returnSmpl (new_tvs, mkTyVarTys new_tvs)
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Case absorption and identity-case elimination}
%* *
%************************************************************************
------------------------------------------------
mkAlts dflags scrut case_bndr other_alts = returnSmpl other_alts
-
-
----------------------------------
-mergeAlts :: [OutAlt] -> [OutAlt] -> [OutAlt]
--- Merge preserving order; alternatives in the first arg
--- shadow ones in the second
-mergeAlts [] as2 = as2
-mergeAlts as1 [] = as1
-mergeAlts (a1:as1) (a2:as2)
- = case a1 `cmpAlt` a2 of
- LT -> a1 : mergeAlts as1 (a2:as2)
- EQ -> a1 : mergeAlts as1 as2 -- Discard a2
- GT -> a2 : mergeAlts (a1:as1) as2
\end{code}
projects / ghc-hetmet.git / blobdiff