%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
%
-%************************************************************************
-%* *
-\section[CoreToStg]{Converting core syntax to STG syntax}
-%* *
-%************************************************************************
+\section[CoreToStg]{Converts Core to STG Syntax}
-Convert a @CoreSyntax@ program to a @StgSyntax@ program.
+And, as we have the info in hand, we may convert some lets to
+let-no-escapes.
\begin{code}
+module CoreToStg ( coreToStg, coreExprToStg ) where
+
#include "HsVersions.h"
-module CoreToStg ( topCoreBindsToStg ) where
-
-IMP_Ubiq(){-uitous-}
-IMPORT_1_3(Ratio(numerator,denominator))
-
-import CoreSyn -- input
-import StgSyn -- output
-
-import Bag ( emptyBag, unitBag, unionBags, unionManyBags, bagToList )
-import CoreUtils ( coreExprType )
-import CostCentre ( noCostCentre )
-import Id ( mkSysLocal, idType, isBottomingId,
- externallyVisibleId,
- nullIdEnv, addOneToIdEnv, lookupIdEnv,
- SYN_IE(IdEnv), GenId{-instance NamedThing-}
- )
-import Literal ( mkMachInt, Literal(..) )
-import PrelVals ( unpackCStringId, unpackCString2Id,
- integerZeroId, integerPlusOneId,
- integerPlusTwoId, integerMinusOneId
- )
-import PrimOp ( PrimOp(..) )
-import SpecUtils ( mkSpecialisedCon )
-import SrcLoc ( mkUnknownSrcLoc )
-import TyCon ( TyCon{-instance Uniquable-} )
-import Type ( maybeAppDataTyCon, getAppDataTyConExpandingDicts )
-import TysWiredIn ( stringTy )
-import Unique ( integerTyConKey, ratioTyConKey, Unique{-instance Eq-} )
-import UniqSupply -- all of it, really
-import Util ( panic, assertPanic, pprTrace{-ToDo:rm-} )
-import Pretty--ToDo:rm
-import PprStyle--ToDo:rm
-import PprType --ToDo:rm
-import Outputable--ToDo:rm
-import PprEnv--ToDo:rm
-
-isLeakFreeType x y = False -- safe option; ToDo
+import CoreSyn
+import CoreFVs
+import CoreUtils
+import SimplUtils
+import StgSyn
+
+import Type
+import TyCon ( isAlgTyCon )
+import Id
+import IdInfo
+import DataCon
+import CostCentre ( noCCS )
+import VarSet
+import VarEnv
+import DataCon ( dataConWrapId )
+import IdInfo ( OccInfo(..) )
+import PrimOp ( PrimOp(..), ccallMayGC )
+import TysPrim ( foreignObjPrimTyCon )
+import Maybes ( maybeToBool, orElse )
+import Name ( getOccName )
+import Module ( Module )
+import OccName ( occNameUserString )
+import BasicTypes ( TopLevelFlag(..), isNotTopLevel )
+import CmdLineOpts ( DynFlags )
+import Outputable
+import PprCore
+
+infixr 9 `thenLne`, `thenLne_`
\end{code}
+%************************************************************************
+%* *
+\subsection[live-vs-free-doc]{Documentation}
+%* *
+%************************************************************************
- *************** OVERVIEW *********************
-
-
-The business of this pass is to convert Core to Stg. On the way:
-
-* We discard type lambdas and applications. In so doing we discard
- "trivial" bindings such as
- x = y t1 t2
- where t1, t2 are types
-
-* We make the representation of NoRep literals explicit, and
- float their bindings to the top level
-
-* We do *not* pin on the correct free/live var info; that's done later.
- Instead we use bOGUS_LVS and _FVS as a placeholder.
-
-* We convert case x of {...; x' -> ...x'...}
- to
- case x of {...; _ -> ...x... }
-
- See notes in SimplCase.lhs, near simplDefault for the reasoning here.
-
+(There is other relevant documentation in codeGen/CgLetNoEscape.)
+
+The actual Stg datatype is decorated with {\em live variable}
+information, as well as {\em free variable} information. The two are
+{\em not} the same. Liveness is an operational property rather than a
+semantic one. A variable is live at a particular execution point if
+it can be referred to {\em directly} again. In particular, a dead
+variable's stack slot (if it has one):
+\begin{enumerate}
+\item
+should be stubbed to avoid space leaks, and
+\item
+may be reused for something else.
+\end{enumerate}
+
+There ought to be a better way to say this. Here are some examples:
+\begin{verbatim}
+ let v = [q] \[x] -> e
+ in
+ ...v... (but no q's)
+\end{verbatim}
+
+Just after the `in', v is live, but q is dead. If the whole of that
+let expression was enclosed in a case expression, thus:
+\begin{verbatim}
+ case (let v = [q] \[x] -> e in ...v...) of
+ alts[...q...]
+\end{verbatim}
+(ie @alts@ mention @q@), then @q@ is live even after the `in'; because
+we'll return later to the @alts@ and need it.
+
+Let-no-escapes make this a bit more interesting:
+\begin{verbatim}
+ let-no-escape v = [q] \ [x] -> e
+ in
+ ...v...
+\end{verbatim}
+Here, @q@ is still live at the `in', because @v@ is represented not by
+a closure but by the current stack state. In other words, if @v@ is
+live then so is @q@. Furthermore, if @e@ mentions an enclosing
+let-no-escaped variable, then {\em its} free variables are also live
+if @v@ is.
%************************************************************************
%* *
-\subsection[coreToStg-programs]{Converting a core program and core bindings}
+\subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
%* *
%************************************************************************
-Because we're going to come across ``boring'' bindings like
-\tr{let x = /\ tyvars -> y in ...}, we want to keep a small
-environment, so we can just replace all occurrences of \tr{x}
-with \tr{y}.
+\begin{code}
+coreToStg :: DynFlags -> Module -> [CoreBind] -> IO [StgBinding]
+coreToStg dflags this_mod pgm
+ = return (fst (initLne (coreTopBindsToStg pgm)))
+
+coreExprToStg :: CoreExpr -> StgExpr
+coreExprToStg expr
+ = new_expr where (new_expr,_,_) = initLne (coreToStgExpr expr)
+
+-- For top-level guys, we basically aren't worried about this
+-- live-variable stuff; we do need to keep adding to the environment
+-- as we step through the bindings (using @extendVarEnv@).
+
+coreTopBindsToStg :: [CoreBind] -> LneM ([StgBinding], FreeVarsInfo)
+
+coreTopBindsToStg [] = returnLne ([], emptyFVInfo)
+coreTopBindsToStg (bind:binds)
+ = let
+ binders = bindersOf bind
+ env_extension = binders `zip` repeat how_bound
+ how_bound = LetrecBound True {- top level -}
+ emptyVarSet
+ in
+
+ extendVarEnvLne env_extension (
+ coreTopBindsToStg binds `thenLne` \ (binds', fv_binds) ->
+ coreTopBindToStg binders fv_binds bind `thenLne` \ (bind', fv_bind) ->
+ returnLne (
+ (bind' : binds'),
+ (fv_binds `unionFVInfo` fv_bind) `minusFVBinders` binders
+ )
+ )
+
+
+coreTopBindToStg
+ :: [Id] -- New binders (with correct arity)
+ -> FreeVarsInfo -- Info about the body
+ -> CoreBind
+ -> LneM (StgBinding, FreeVarsInfo)
+
+coreTopBindToStg [binder] body_fvs (NonRec _ rhs)
+ = coreToStgRhs body_fvs TopLevel (binder,rhs) `thenLne` \ (rhs2, fvs, _) ->
+ returnLne (StgNonRec binder rhs2, fvs)
+
+coreTopBindToStg binders body_fvs (Rec pairs)
+ = fixLne (\ ~(_, rec_rhs_fvs) ->
+ let scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
+ in
+ mapAndUnzip3Lne (coreToStgRhs scope_fvs TopLevel) pairs
+ `thenLne` \ (rhss2, fvss, _) ->
+ let fvs = unionFVInfos fvss
+ in
+ returnLne (StgRec (binders `zip` rhss2), fvs)
+ )
+\end{code}
\begin{code}
-type StgEnv = IdEnv StgArg
+coreToStgRhs
+ :: FreeVarsInfo -- Free var info for the scope of the binding
+ -> TopLevelFlag
+ -> (Id,CoreExpr)
+ -> LneM (StgRhs, FreeVarsInfo, EscVarsSet)
+
+coreToStgRhs scope_fv_info top (binder, rhs)
+ = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
+ case new_rhs of
+
+ StgLam _ bndrs body
+ -> let binder_info = lookupFVInfo scope_fv_info binder
+ in returnLne (StgRhsClosure noCCS
+ binder_info
+ noSRT
+ (getFVs rhs_fvs)
+ ReEntrant
+ bndrs
+ body,
+ rhs_fvs, rhs_escs)
+
+ StgConApp con args
+ | isNotTopLevel top || not (isDllConApp con args)
+ -> returnLne (StgRhsCon noCCS con args, rhs_fvs, rhs_escs)
+
+ _other_expr
+ -> let binder_info = lookupFVInfo scope_fv_info binder
+ in returnLne (StgRhsClosure noCCS
+ binder_info
+ noSRT
+ (getFVs rhs_fvs)
+ (updatable [] new_rhs)
+ []
+ new_rhs,
+ rhs_fvs, rhs_escs
+ )
+
+updatable args body | null args && isPAP body = ReEntrant
+ | otherwise = Updatable
+{- ToDo:
+ upd = if isOnceDem dem
+ then (if isNotTop toplev
+ then SingleEntry -- HA! Paydirt for "dem"
+ else
+#ifdef DEBUG
+ trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
+#endif
+ Updatable)
+ else Updatable
+ -- For now we forbid SingleEntry CAFs; they tickle the
+ -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
+ -- and I don't understand why. There's only one SE_CAF (well,
+ -- only one that tickled a great gaping bug in an earlier attempt
+ -- at ClosureInfo.getEntryConvention) in the whole of nofib,
+ -- specifically Main.lvl6 in spectral/cryptarithm2.
+ -- So no great loss. KSW 2000-07.
+-}
\end{code}
-No free/live variable information is pinned on in this pass; it's added
-later. For this pass
-we use @bOGUS_LVs@ and @bOGUS_FVs@ as placeholders.
+Detect thunks which will reduce immediately to PAPs, and make them
+non-updatable. This has several advantages:
-\begin{code}
-bOGUS_LVs :: StgLiveVars
-bOGUS_LVs = panic "bOGUS_LVs" -- emptyUniqSet (used when pprTracing)
+ - the non-updatable thunk behaves exactly like the PAP,
-bOGUS_FVs :: [Id]
-bOGUS_FVs = panic "bOGUS_FVs" -- [] (ditto)
-\end{code}
+ - the thunk is more efficient to enter, because it is
+ specialised to the task.
-\begin{code}
-topCoreBindsToStg :: UniqSupply -- name supply
- -> [CoreBinding] -- input
- -> [StgBinding] -- output
+ - we save one update frame, one stg_update_PAP, one update
+ and lots of PAP_enters.
+
+ - in the case where the thunk is top-level, we save building
+ a black hole and futhermore the thunk isn't considered to
+ be a CAF any more, so it doesn't appear in any SRTs.
-topCoreBindsToStg us core_binds
- = case (initUs us (binds_to_stg nullIdEnv core_binds)) of
- (_, stuff) -> stuff
+We do it here, because the arity information is accurate, and we need
+to do it before the SRT pass to save the SRT entries associated with
+any top-level PAPs.
+
+\begin{code}
+isPAP (StgApp f args) = idArity f > length args
+isPAP _ = False
+
+-- ---------------------------------------------------------------------------
+-- Atoms
+-- ---------------------------------------------------------------------------
+
+coreToStgAtoms :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
+coreToStgAtoms atoms
+ = let val_atoms = filter isValArg atoms in
+ mapAndUnzipLne coreToStgAtom val_atoms `thenLne` \ (args', fvs_lists) ->
+ returnLne (args', unionFVInfos fvs_lists)
where
- binds_to_stg :: StgEnv -> [CoreBinding] -> UniqSM [StgBinding]
-
- binds_to_stg env [] = returnUs []
- binds_to_stg env (b:bs)
- = do_top_bind env b `thenUs` \ (new_b, new_env, float_binds) ->
- binds_to_stg new_env bs `thenUs` \ new_bs ->
- returnUs (bagToList float_binds ++ -- Literals
- new_b ++
- new_bs)
-
- do_top_bind env bind@(Rec pairs)
- = coreBindToStg env bind
-
- do_top_bind env bind@(NonRec var rhs)
- = coreBindToStg env bind `thenUs` \ (stg_binds, new_env, float_binds) ->
-{- TESTING:
- let
- ppr_blah xs = ppInterleave ppComma (map pp_x xs)
- pp_x (u,x) = ppBesides [pprUnique u, ppStr ": ", ppr PprDebug x]
- in
- pprTrace "do_top_bind:" (ppAbove (ppr PprDebug stg_binds) (ppr_blah (ufmToList new_env))) $
+ coreToStgAtom e
+ = coreToStgExpr e `thenLne` \ (expr, fvs, escs) ->
+ case expr of
+ StgApp v [] -> returnLne (StgVarArg v, fvs)
+ StgConApp con [] -> returnLne (StgVarArg (dataConWrapId con), fvs)
+ StgLit lit -> returnLne (StgLitArg lit, fvs)
+ _ -> pprPanic "coreToStgAtom" (ppr expr)
+
+-- ---------------------------------------------------------------------------
+-- Expressions
+-- ---------------------------------------------------------------------------
+
+{-
+@varsExpr@ carries in a monad-ised environment, which binds each
+let(rec) variable (ie non top level, not imported, not lambda bound,
+not case-alternative bound) to:
+ - its STG arity, and
+ - its set of live vars.
+For normal variables the set of live vars is just the variable
+itself. For let-no-escaped variables, the set of live vars is the set
+live at the moment the variable is entered. The set is guaranteed to
+have no further let-no-escaped vars in it.
-}
- case stg_binds of
- [StgNonRec var (StgRhsClosure cc bi fvs u [] rhs_body)] ->
- -- Mega-special case; there's still a binding there
- -- no fvs (of course), *no args*, "let" rhs
- let
- (extra_float_binds, rhs_body') = seek_liftable [] rhs_body
- in
- returnUs (extra_float_binds ++
- [StgNonRec var (StgRhsClosure cc bi fvs u [] rhs_body')],
- new_env,
- float_binds)
-
- other -> returnUs (stg_binds, new_env, float_binds)
-
- --------------------
- -- HACK: look for very simple, obviously-liftable bindings
- -- that can come up to the top level; those that couldn't
- -- 'cause they were big-lambda constrained in the Core world.
-
- seek_liftable :: [StgBinding] -- accumulator...
- -> StgExpr -- look for top-lev liftables
- -> ([StgBinding], StgExpr) -- result
-
- seek_liftable acc expr@(StgLet inner_bind body)
- | is_liftable inner_bind
- = seek_liftable (inner_bind : acc) body
-
- seek_liftable acc other_expr = (reverse acc, other_expr) -- Finished
-
- --------------------
- is_liftable (StgNonRec binder (StgRhsClosure _ _ _ _ args body))
- = not (null args) -- it's manifestly a function...
- || isLeakFreeType [] (idType binder)
- || is_whnf body
- -- ToDo: use a decent manifestlyWHNF function for STG?
- where
- is_whnf (StgCon _ _ _) = True
- is_whnf (StgApp (StgVarArg v) _ _) = isBottomingId v
- is_whnf other = False
- is_liftable (StgRec [(_, StgRhsClosure _ _ _ _ args body)])
- = not (null args) -- it's manifestly a (recursive) function...
-
- is_liftable anything_else = False
+coreToStgExpr
+ :: CoreExpr
+ -> LneM (StgExpr, -- Decorated STG expr
+ FreeVarsInfo, -- Its free vars (NB free, not live)
+ EscVarsSet) -- Its escapees, a subset of its free vars;
+ -- also a subset of the domain of the envt
+ -- because we are only interested in the escapees
+ -- for vars which might be turned into
+ -- let-no-escaped ones.
\end{code}
-%************************************************************************
-%* *
-\subsection[coreToStg-binds]{Converting bindings}
-%* *
-%************************************************************************
+The second and third components can be derived in a simple bottom up pass, not
+dependent on any decisions about which variables will be let-no-escaped or
+not. The first component, that is, the decorated expression, may then depend
+on these components, but it in turn is not scrutinised as the basis for any
+decisions. Hence no black holes.
\begin{code}
-coreBindToStg :: StgEnv
- -> CoreBinding
- -> UniqSM ([StgBinding], -- Empty or singleton
- StgEnv, -- New envt
- Bag StgBinding) -- Floats
+coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
-coreBindToStg env (NonRec binder rhs)
- = coreRhsToStg env rhs `thenUs` \ (stg_rhs, rhs_binds) ->
+coreToStgExpr (Var v)
+ = coreToStgApp Nothing v []
- let
- -- Binds to return if RHS is trivial
- triv_binds = if externallyVisibleId binder then
- -- pprTrace "coreBindToStg:keeping:" (ppCat [ppr PprDebug binder, ppr PprDebug (externallyVisibleId binder)]) $
- [StgNonRec binder stg_rhs] -- Retain it
- else
- -- pprTrace "coreBindToStg:tossing:" (ppCat [ppr PprDebug binder, ppr PprDebug (externallyVisibleId binder)]) $
- [] -- Discard it
- in
- case stg_rhs of
- StgRhsClosure cc bi fvs upd [] (StgApp atom [] lvs) ->
- -- Trivial RHS, so augment envt, and ditch the binding
- returnUs (triv_binds, new_env, rhs_binds)
- where
- new_env = addOneToIdEnv env binder atom
-
- StgRhsCon cc con_id [] ->
- -- Trivial RHS, so augment envt, and ditch the binding
- returnUs (triv_binds, new_env, rhs_binds)
- where
- new_env = addOneToIdEnv env binder (StgVarArg con_id)
-
- other -> -- Non-trivial RHS, so don't augment envt
- returnUs ([StgNonRec binder stg_rhs], env, rhs_binds)
-
-coreBindToStg env (Rec pairs)
- = -- NB: *** WE DO NOT CHECK FOR TRIV_BINDS in REC BIND ****
- -- (possibly ToDo)
- let
- (binders, rhss) = unzip pairs
+coreToStgExpr expr@(App _ _)
+ = let (f, args) = myCollectArgs expr
in
- mapAndUnzipUs (coreRhsToStg env) rhss `thenUs` \ (stg_rhss, rhs_binds) ->
- returnUs ([StgRec (binders `zip` stg_rhss)], env, unionManyBags rhs_binds)
-\end{code}
-
+ coreToStgApp Nothing (shouldBeVar f) args
-%************************************************************************
-%* *
-\subsection[coreToStg-rhss]{Converting right hand sides}
-%* *
-%************************************************************************
-
-\begin{code}
-coreRhsToStg :: StgEnv -> CoreExpr -> UniqSM (StgRhs, Bag StgBinding)
-
-coreRhsToStg env core_rhs
- = coreExprToStg env core_rhs `thenUs` \ (stg_expr, stg_binds) ->
-
- let stg_rhs = case stg_expr of
- StgLet (StgNonRec var1 rhs) (StgApp (StgVarArg var2) [] _)
- | var1 == var2 -> rhs
- -- This curious stuff is to unravel what a lambda turns into
- -- We have to do it this way, rather than spot a lambda in the
- -- incoming rhs
-
- StgCon con args _ -> StgRhsCon noCostCentre con args
-
- other -> StgRhsClosure noCostCentre -- No cost centre (ToDo?)
- stgArgOcc -- safe
- bOGUS_FVs
- Updatable -- Be pessimistic
- []
- stg_expr
+coreToStgExpr expr@(Lam _ _)
+ = let (args, body) = myCollectBinders expr
+ args' = filter isId args
in
- returnUs (stg_rhs, stg_binds)
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[coreToStg-lits]{Converting literals}
-%* *
-%************************************************************************
+ extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
+ coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
+ let
+ set_of_args = mkVarSet args'
+ fvs = body_fvs `minusFVBinders` args'
+ escs = body_escs `minusVarSet` set_of_args
+ in
+ if null args'
+ then returnLne (body, fvs, escs)
+ else returnLne (StgLam (exprType expr) args' body, fvs, escs)
-Literals: the NoRep kind need to be de-no-rep'd.
-We always replace them with a simple variable, and float a suitable
-binding out to the top level.
+coreToStgExpr (Note (SCC cc) expr)
+ = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
+ returnLne (StgSCC cc expr2, fvs, escs) )
-If an Integer is small enough (Haskell implementations must support
-Ints in the range $[-2^29+1, 2^29-1]$), wrap it up in @int2Integer@;
-otherwise, wrap with @litString2Integer@.
+coreToStgExpr (Note other_note expr)
+ = coreToStgExpr expr
-\begin{code}
-tARGET_MIN_INT, tARGET_MAX_INT :: Integer
-tARGET_MIN_INT = -536870912
-tARGET_MAX_INT = 536870912
-litToStgArg :: Literal -> UniqSM (StgArg, Bag StgBinding)
+-- Cases require a little more real work.
-litToStgArg (NoRepStr s)
- = newStgVar stringTy `thenUs` \ var ->
+coreToStgExpr (Case scrut bndr alts)
+ = getVarsLiveInCont `thenLne` \ live_in_cont ->
+ extendVarEnvLne [(bndr, CaseBound)] $
+ vars_alts (findDefault alts) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
+ lookupLiveVarsForSet alts_fvs `thenLne` \ alts_lvs ->
let
- rhs = StgRhsClosure noCostCentre -- No cost centre (ToDo?)
- stgArgOcc -- safe
- bOGUS_FVs
- Updatable -- WAS: ReEntrant (see note below)
- [] -- No arguments
- val
-
--- We used not to update strings, so that they wouldn't clog up the heap,
--- but instead be unpacked each time. But on some programs that costs a lot
--- [eg hpg], so now we update them.
-
- val = if (any is_NUL (_UNPK_ s)) then -- must cater for NULs in literal string
- StgApp (StgVarArg unpackCString2Id)
- [StgLitArg (MachStr s),
- StgLitArg (mkMachInt (toInteger (_LENGTH_ s)))]
- bOGUS_LVs
- else
- StgApp (StgVarArg unpackCStringId)
- [StgLitArg (MachStr s)]
- bOGUS_LVs
+ -- determine whether the default binder is dead or not
+ bndr'= if (bndr `elementOfFVInfo` alts_fvs)
+ then bndr `setIdOccInfo` NoOccInfo
+ else bndr `setIdOccInfo` IAmDead
+
+ -- for a _ccall_GC_, some of the *arguments* need to live across the
+ -- call (see findLiveArgs comments.), so we annotate them as being live
+ -- in the alts to achieve the desired effect.
+ mb_live_across_case =
+ case scrut of
+ -- ToDo: Notes?
+ e@(App _ _) | (Var v, args) <- myCollectArgs e,
+ PrimOpId (CCallOp ccall) <- idFlavour v,
+ ccallMayGC ccall
+ -> Just (filterVarSet isForeignObjArg (exprFreeVars e))
+ _ -> Nothing
+
+ -- Don't consider the default binder as being 'live in alts',
+ -- since this is from the point of view of the case expr, where
+ -- the default binder is not free.
+ live_in_alts = orElse (FMAP unionVarSet mb_live_across_case) id $
+ live_in_cont `unionVarSet`
+ (alts_lvs `minusVarSet` unitVarSet bndr)
in
- returnUs (StgVarArg var, unitBag (StgNonRec var rhs))
- where
- is_NUL c = c == '\0'
-
-litToStgArg (NoRepInteger i integer_ty)
- -- extremely convenient to look out for a few very common
- -- Integer literals!
- | i == 0 = returnUs (StgVarArg integerZeroId, emptyBag)
- | i == 1 = returnUs (StgVarArg integerPlusOneId, emptyBag)
- | i == 2 = returnUs (StgVarArg integerPlusTwoId, emptyBag)
- | i == (-1) = returnUs (StgVarArg integerMinusOneId, emptyBag)
-
- | otherwise
- = newStgVar integer_ty `thenUs` \ var ->
- let
- rhs = StgRhsClosure noCostCentre -- No cost centre (ToDo?)
- stgArgOcc -- safe
- bOGUS_FVs
- Updatable -- Update an integer
- [] -- No arguments
- val
-
- val
- | i > tARGET_MIN_INT && i < tARGET_MAX_INT
- = -- Start from an Int
- StgPrim Int2IntegerOp [StgLitArg (mkMachInt i)] bOGUS_LVs
-
- | otherwise
- = -- Start from a string
- StgPrim Addr2IntegerOp [StgLitArg (MachStr (_PK_ (show i)))] bOGUS_LVs
- in
- returnUs (StgVarArg var, unitBag (StgNonRec var rhs))
-
-litToStgArg (NoRepRational r rational_ty)
- = --ASSERT(is_rational_ty)
- (if is_rational_ty then \x->x else pprTrace "litToStgArg:not rational?" (pprType PprDebug rational_ty)) $
- litToStgArg (NoRepInteger (numerator r) integer_ty) `thenUs` \ (num_atom, binds1) ->
- litToStgArg (NoRepInteger (denominator r) integer_ty) `thenUs` \ (denom_atom, binds2) ->
- newStgVar rational_ty `thenUs` \ var ->
+ -- we tell the scrutinee that everything live in the alts
+ -- is live in it, too.
+ setVarsLiveInCont live_in_alts (
+ coreToStgExpr scrut
+ ) `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
+
+ lookupLiveVarsForSet scrut_fvs `thenLne` \ scrut_lvs ->
let
- rhs = StgRhsCon noCostCentre -- No cost centre (ToDo?)
- ratio_data_con -- Constructor
- [num_atom, denom_atom]
+ live_in_whole_case = live_in_alts `unionVarSet` scrut_lvs
in
- returnUs (StgVarArg var, binds1 `unionBags`
- binds2 `unionBags`
- unitBag (StgNonRec var rhs))
+ returnLne (
+ mkStgCase scrut2 live_in_whole_case live_in_alts bndr' noSRT alts2,
+ (scrut_fvs `unionFVInfo` alts_fvs) `minusFVBinders` [bndr],
+ (alts_escs `minusVarSet` unitVarSet bndr) `unionVarSet` getFVSet scrut_fvs
+ -- You might think we should have scrut_escs, not (getFVSet scrut_fvs),
+ -- but actually we can't call, and then return from, a let-no-escape thing.
+ )
where
- (is_rational_ty, ratio_data_con, integer_ty)
- = case (maybeAppDataTyCon rational_ty) of
- Just (tycon, [i_ty], [con])
- -> ASSERT(is_integer_ty i_ty)
- (uniqueOf tycon == ratioTyConKey, con, i_ty)
+ scrut_ty = idType bndr
+ prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
+
+ vars_alts (alts,deflt)
+ | prim_case
+ = mapAndUnzip3Lne vars_prim_alt alts
+ `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
+ let
+ alts_fvs = unionFVInfos alts_fvs_list
+ alts_escs = unionVarSets alts_escs_list
+ in
+ vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
+ returnLne (
+ mkStgPrimAlts scrut_ty alts2 deflt2,
+ alts_fvs `unionFVInfo` deflt_fvs,
+ alts_escs `unionVarSet` deflt_escs
+ )
+
+ | otherwise
+ = mapAndUnzip3Lne vars_alg_alt alts
+ `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
+ let
+ alts_fvs = unionFVInfos alts_fvs_list
+ alts_escs = unionVarSets alts_escs_list
+ in
+ vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
+ returnLne (
+ mkStgAlgAlts scrut_ty alts2 deflt2,
+ alts_fvs `unionFVInfo` deflt_fvs,
+ alts_escs `unionVarSet` deflt_escs
+ )
- _ -> (False, panic "ratio_data_con", panic "integer_ty")
-
- is_integer_ty ty
- = case (maybeAppDataTyCon ty) of
- Just (tycon, [], _) -> uniqueOf tycon == integerTyConKey
- _ -> False
+ where
+ vars_prim_alt (LitAlt lit, _, rhs)
+ = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
+ returnLne ((lit, rhs2), rhs_fvs, rhs_escs)
+
+ vars_alg_alt (DataAlt con, binders, rhs)
+ = let
+ -- remove type variables
+ binders' = filter isId binders
+ in
+ extendVarEnvLne [(b, CaseBound) | b <- binders'] $
+ coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
+ let
+ good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
+ -- records whether each param is used in the RHS
+ in
+ returnLne (
+ (con, binders', good_use_mask, rhs2),
+ rhs_fvs `minusFVBinders` binders',
+ rhs_escs `minusVarSet` mkVarSet binders'
+ -- ToDo: remove the minusVarSet;
+ -- since escs won't include any of these binders
+ )
+
+ vars_deflt Nothing
+ = returnLne (StgNoDefault, emptyFVInfo, emptyVarSet)
+
+ vars_deflt (Just rhs)
+ = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
+ returnLne (StgBindDefault rhs2, rhs_fvs, rhs_escs)
-litToStgArg other_lit = returnUs (StgLitArg other_lit, emptyBag)
\end{code}
+Lets not only take quite a bit of work, but this is where we convert
+then to let-no-escapes, if we wish.
-%************************************************************************
-%* *
-\subsection[coreToStg-atoms{Converting atoms}
-%* *
-%************************************************************************
-
+(Meanwhile, we don't expect to see let-no-escapes...)
\begin{code}
-coreArgsToStg :: StgEnv -> [CoreArg] -> UniqSM ([Type], [StgArg], Bag StgBinding)
+coreToStgExpr (Let bind body)
+ = fixLne (\ ~(_, _, _, no_binder_escapes) ->
+ coreToStgLet no_binder_escapes bind body
+ ) `thenLne` \ (new_let, fvs, escs, _) ->
-coreArgsToStg env [] = returnUs ([], [], emptyBag)
-coreArgsToStg env (a:as)
- = coreArgsToStg env as `thenUs` \ (tys, args, binds) ->
- do_arg a tys args binds
- where
- do_arg a trest vrest binds
- = case a of
- TyArg t -> returnUs (t:trest, vrest, binds)
- UsageArg u -> returnUs (trest, vrest, binds)
- VarArg v -> returnUs (trest, stgLookup env v : vrest, binds)
- LitArg i -> litToStgArg i `thenUs` \ (v, bs) ->
- returnUs (trest, v:vrest, bs `unionBags` binds)
+ returnLne (new_let, fvs, escs)
\end{code}
-There's not anything interesting we can ASSERT about \tr{var} if it
-isn't in the StgEnv. (WDP 94/06)
+If we've got a case containing a _ccall_GC_ primop, we need to
+ensure that the arguments are kept live for the duration of the
+call. This only an issue
+
\begin{code}
-stgLookup :: StgEnv -> Id -> StgArg
+isForeignObjArg :: Id -> Bool
+isForeignObjArg x = isId x && isForeignObjPrimTy (idType x)
-stgLookup env var = case (lookupIdEnv env var) of
- Nothing -> StgVarArg var
- Just atom -> atom
+isForeignObjPrimTy ty
+ = case splitTyConApp_maybe ty of
+ Just (tycon, _) -> tycon == foreignObjPrimTyCon
+ Nothing -> False
\end{code}
-%************************************************************************
-%* *
-\subsection[coreToStg-exprs]{Converting core expressions}
-%* *
-%************************************************************************
-
\begin{code}
-coreExprToStg :: StgEnv
- -> CoreExpr
- -> UniqSM (StgExpr, -- Result
- Bag StgBinding) -- Float these to top level
+mkStgCase scrut@(StgPrimApp ParOp _ _) lvs1 lvs2 bndr srt
+ (StgPrimAlts tycon _ deflt@(StgBindDefault _))
+ = StgCase scrut lvs1 lvs2 bndr srt (StgPrimAlts tycon [] deflt)
+
+mkStgCase (StgPrimApp SeqOp [scrut] _) lvs1 lvs2 bndr srt
+ (StgPrimAlts _ _ deflt@(StgBindDefault rhs))
+ = StgCase scrut_expr lvs1 lvs2 new_bndr srt new_alts
+ where
+ new_alts
+ | isUnLiftedType scrut_ty = WARN( True, text "mkStgCase" )
+ mkStgPrimAlts scrut_ty [] deflt
+ | otherwise = mkStgAlgAlts scrut_ty [] deflt
+
+ scrut_ty = stgArgType scrut
+ new_bndr = setIdType bndr scrut_ty
+ -- NB: SeqOp :: forall a. a -> Int#
+ -- So bndr has type Int#
+ -- But now we are going to scrutinise the SeqOp's argument directly,
+ -- so we must change the type of the case binder to match that
+ -- of the argument expression e.
+
+ scrut_expr = case scrut of
+ StgVarArg v -> StgApp v []
+ -- Others should not happen because
+ -- seq of a value should have disappeared
+ StgLitArg l -> WARN( True, text "seq on" <+> ppr l ) StgLit l
+
+mkStgCase scrut lvs1 lvs2 bndr srt alts
+ = StgCase scrut lvs1 lvs2 bndr srt alts
+
+
+mkStgAlgAlts ty alts deflt
+ = case alts of
+ -- Get the tycon from the data con
+ (dc, _, _, _) : _rest
+ -> StgAlgAlts (Just (dataConTyCon dc)) alts deflt
+
+ -- Otherwise just do your best
+ [] -> case splitTyConApp_maybe (repType ty) of
+ Just (tc,_) | isAlgTyCon tc
+ -> StgAlgAlts (Just tc) alts deflt
+ other
+ -> StgAlgAlts Nothing alts deflt
+
+mkStgPrimAlts ty alts deflt
+ = StgPrimAlts (tyConAppTyCon ty) alts deflt
\end{code}
-\begin{code}
-coreExprToStg env (Lit lit)
- = litToStgArg lit `thenUs` \ (atom, binds) ->
- returnUs (StgApp atom [] bOGUS_LVs, binds)
-coreExprToStg env (Var var)
- = returnUs (StgApp (stgLookup env var) [] bOGUS_LVs, emptyBag)
+Applications:
+\begin{code}
+coreToStgApp
+ :: Maybe UpdateFlag -- Just upd <=> this application is
+ -- the rhs of a thunk binding
+ -- x = [...] \upd [] -> the_app
+ -- with specified update flag
+ -> Id -- Function
+ -> [CoreArg] -- Arguments
+ -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
+
+coreToStgApp maybe_thunk_body f args
+ = getVarsLiveInCont `thenLne` \ live_in_cont ->
+ coreToStgAtoms args `thenLne` \ (args', args_fvs) ->
+ lookupVarLne f `thenLne` \ how_bound ->
-coreExprToStg env (Con con args)
- = coreArgsToStg env args `thenUs` \ (types, stg_atoms, stg_binds) ->
let
- spec_con = mkSpecialisedCon con types
+ n_args = length args
+ not_letrec_bound = not (isLetrecBound how_bound)
+ f_arity = idArity f
+ fun_fvs = singletonFVInfo f how_bound fun_occ
+
+ fun_occ
+ | not_letrec_bound = NoStgBinderInfo -- Uninteresting variable
+
+ -- Otherwise it is letrec bound; must have its arity
+ | n_args == 0 = stgFakeFunAppOcc -- Function Application
+ -- with no arguments.
+ -- used by the lambda lifter.
+ | f_arity > n_args = stgUnsatOcc -- Unsaturated
+
+ | f_arity == n_args &&
+ maybeToBool maybe_thunk_body -- Exactly saturated,
+ -- and rhs of thunk
+ = case maybe_thunk_body of
+ Just Updatable -> stgStdHeapOcc
+ Just SingleEntry -> stgNoUpdHeapOcc
+ other -> panic "coreToStgApp"
+
+ | otherwise = stgNormalOcc
+ -- Record only that it occurs free
+
+ myself = unitVarSet f
+
+ fun_escs | not_letrec_bound = emptyVarSet
+ -- Only letrec-bound escapees are interesting
+ | f_arity == n_args = emptyVarSet
+ -- Function doesn't escape
+ | otherwise = myself
+ -- Inexact application; it does escape
+
+ -- At the moment of the call:
+
+ -- either the function is *not* let-no-escaped, in which case
+ -- nothing is live except live_in_cont
+ -- or the function *is* let-no-escaped in which case the
+ -- variables it uses are live, but still the function
+ -- itself is not. PS. In this case, the function's
+ -- live vars should already include those of the
+ -- continuation, but it does no harm to just union the
+ -- two regardless.
+
+ -- XXX not needed?
+ -- live_at_call
+ -- = live_in_cont `unionVarSet` case how_bound of
+ -- LetrecBound _ lvs -> lvs `minusVarSet` myself
+ -- other -> emptyVarSet
+
+ app = case idFlavour f of
+ DataConId dc -> StgConApp dc args'
+ PrimOpId op -> StgPrimApp op args' (exprType (mkApps (Var f) args))
+ _other -> StgApp f args'
+
in
- returnUs (StgCon spec_con stg_atoms bOGUS_LVs, stg_binds)
+ returnLne (
+ app,
+ fun_fvs `unionFVInfo` args_fvs,
+ fun_escs `unionVarSet` (getFVSet args_fvs)
+ -- All the free vars of the args are disqualified
+ -- from being let-no-escaped.
+ )
-coreExprToStg env (Prim op args)
- = coreArgsToStg env args `thenUs` \ (_, stg_atoms, stg_binds) ->
- returnUs (StgPrim op stg_atoms bOGUS_LVs, stg_binds)
-\end{code}
-%************************************************************************
-%* *
-\subsubsection[coreToStg-lambdas]{Lambda abstractions}
-%* *
-%************************************************************************
+-- ---------------------------------------------------------------------------
+-- The magic for lets:
+-- ---------------------------------------------------------------------------
+
+coreToStgLet
+ :: Bool -- True <=> yes, we are let-no-escaping this let
+ -> CoreBind -- bindings
+ -> CoreExpr -- body
+ -> LneM (StgExpr, -- new let
+ FreeVarsInfo, -- variables free in the whole let
+ EscVarsSet, -- variables that escape from the whole let
+ Bool) -- True <=> none of the binders in the bindings
+ -- is among the escaping vars
+
+coreToStgLet let_no_escape bind body
+ = fixLne (\ ~(_, _, _, rec_bind_lvs, _, rec_body_fvs, _, _) ->
+
+ -- Do the bindings, setting live_in_cont to empty if
+ -- we ain't in a let-no-escape world
+ getVarsLiveInCont `thenLne` \ live_in_cont ->
+ setVarsLiveInCont
+ (if let_no_escape then live_in_cont else emptyVarSet)
+ (vars_bind rec_bind_lvs rec_body_fvs bind)
+ `thenLne` \ (bind2, bind_fvs, bind_escs, env_ext) ->
+
+ -- The live variables of this binding are the ones which are live
+ -- by virtue of being accessible via the free vars of the binding (lvs_from_fvs)
+ -- together with the live_in_cont ones
+ lookupLiveVarsForSet (bind_fvs `minusFVBinders` binders)
+ `thenLne` \ lvs_from_fvs ->
+ let
+ bind_lvs = lvs_from_fvs `unionVarSet` live_in_cont
+ in
-\begin{code}
-coreExprToStg env expr@(Lam _ _)
- = let
- (_,_, binders, body) = collectBinders expr
- in
- coreExprToStg env body `thenUs` \ stuff@(stg_body, binds) ->
-
- if null binders then -- it was all type/usage binders; tossed
- returnUs stuff
- else
- newStgVar (coreExprType expr) `thenUs` \ var ->
- returnUs
- (StgLet (StgNonRec var (StgRhsClosure noCostCentre
- stgArgOcc
- bOGUS_FVs
- ReEntrant -- binders is non-empty
- binders
- stg_body))
- (StgApp (StgVarArg var) [] bOGUS_LVs),
- binds)
-\end{code}
+ -- bind_fvs and bind_escs still include the binders of the let(rec)
+ -- but bind_lvs does not
-%************************************************************************
-%* *
-\subsubsection[coreToStg-applications]{Applications}
-%* *
-%************************************************************************
+ -- Do the body
+ extendVarEnvLne env_ext (
+ coreToStgExpr body `thenLne` \ (body2, body_fvs, body_escs) ->
+ lookupLiveVarsForSet body_fvs `thenLne` \ body_lvs ->
-\begin{code}
-coreExprToStg env expr@(App _ _)
- = let
- (fun,args) = collect_args expr []
- in
- -- Deal with the arguments
- coreArgsToStg env args `thenUs` \ (_, stg_args, arg_binds) ->
+ returnLne (bind2, bind_fvs, bind_escs, bind_lvs,
+ body2, body_fvs, body_escs, body_lvs)
+
+ )) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
+ body2, body_fvs, body_escs, body_lvs) ->
- -- Now deal with the function
- case (fun, args) of
- (Var fun_id, _) -> -- A function Id, so do an StgApp; it's ok if
- -- there are no arguments.
- returnUs (StgApp (stgLookup env fun_id) stg_args bOGUS_LVs, arg_binds)
- (non_var_fun, []) -> -- No value args, so recurse into the function
- coreExprToStg env non_var_fun
+ -- Compute the new let-expression
+ let
+ new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
+ | otherwise = StgLet bind2 body2
+
+ free_in_whole_let
+ = (bind_fvs `unionFVInfo` body_fvs) `minusFVBinders` binders
+
+ live_in_whole_let
+ = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
+
+ real_bind_escs = if let_no_escape then
+ bind_escs
+ else
+ getFVSet bind_fvs
+ -- Everything escapes which is free in the bindings
+
+ let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
+
+ all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
+ -- this let(rec)
+
+ no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
+
+#ifdef DEBUG
+ -- Debugging code as requested by Andrew Kennedy
+ checked_no_binder_escapes
+ | not no_binder_escapes && any is_join_var binders
+ = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
+ False
+ | otherwise = no_binder_escapes
+#else
+ checked_no_binder_escapes = no_binder_escapes
+#endif
+
+ -- Mustn't depend on the passed-in let_no_escape flag, since
+ -- no_binder_escapes is used by the caller to derive the flag!
+ in
+ returnLne (
+ new_let,
+ free_in_whole_let,
+ let_escs,
+ checked_no_binder_escapes
+ ))
+ where
+ set_of_binders = mkVarSet binders
+ binders = case bind of
+ NonRec binder rhs -> [binder]
+ Rec pairs -> map fst pairs
+
+ mk_binding bind_lvs binder
+ = (binder, LetrecBound False -- Not top level
+ live_vars
+ )
+ where
+ live_vars = if let_no_escape then
+ extendVarSet bind_lvs binder
+ else
+ unitVarSet binder
+
+ vars_bind :: StgLiveVars
+ -> FreeVarsInfo -- Free var info for body of binding
+ -> CoreBind
+ -> LneM (StgBinding,
+ FreeVarsInfo, EscVarsSet, -- free vars; escapee vars
+ [(Id, HowBound)])
+ -- extension to environment
+
+ vars_bind rec_bind_lvs rec_body_fvs (NonRec binder rhs)
+ = coreToStgRhs rec_body_fvs NotTopLevel (binder,rhs)
+ `thenLne` \ (rhs2, fvs, escs) ->
+ let
+ env_ext_item@(binder', _) = mk_binding rec_bind_lvs binder
+ in
+ returnLne (StgNonRec binder' rhs2, fvs, escs, [env_ext_item])
- other -> -- A non-variable applied to things; better let-bind it.
- newStgVar (coreExprType fun) `thenUs` \ fun_id ->
- coreExprToStg env fun `thenUs` \ (stg_fun, fun_binds) ->
+ vars_bind rec_bind_lvs rec_body_fvs (Rec pairs)
+ = let
+ binders = map fst pairs
+ env_ext = map (mk_binding rec_bind_lvs) binders
+ in
+ extendVarEnvLne env_ext (
+ fixLne (\ ~(_, rec_rhs_fvs, _, _) ->
let
- fun_rhs = StgRhsClosure noCostCentre -- No cost centre (ToDo?)
- stgArgOcc
- bOGUS_FVs
- SingleEntry -- Only entered once
- []
- stg_fun
+ rec_scope_fvs = unionFVInfo rec_body_fvs rec_rhs_fvs
in
- returnUs (StgLet (StgNonRec fun_id fun_rhs)
- (StgApp (StgVarArg fun_id) stg_args bOGUS_LVs),
- arg_binds `unionBags` fun_binds)
- where
- -- Collect arguments, discarding type/usage applications
- collect_args (App e (TyArg _)) args = collect_args e args
- collect_args (App e (UsageArg _)) args = collect_args e args
- collect_args (App fun arg) args = collect_args fun (arg:args)
- collect_args fun args = (fun, args)
+ mapAndUnzip3Lne (coreToStgRhs rec_scope_fvs NotTopLevel) pairs
+ `thenLne` \ (rhss2, fvss, escss) ->
+ let
+ fvs = unionFVInfos fvss
+ escs = unionVarSets escss
+ in
+ returnLne (StgRec (binders `zip` rhss2), fvs, escs, env_ext)
+ ))
+
+is_join_var :: Id -> Bool
+-- A hack (used only for compiler debuggging) to tell if
+-- a variable started life as a join point ($j)
+is_join_var j = occNameUserString (getOccName j) == "$j"
\end{code}
%************************************************************************
%* *
-\subsubsection[coreToStg-cases]{Case expressions}
+\subsection[LNE-monad]{A little monad for this let-no-escaping pass}
%* *
%************************************************************************
-At this point, we *mangle* cases involving fork# and par# in the
-discriminant. The original templates for these primops (see
-@PrelVals.lhs@) constructed case expressions with boolean results
-solely to fool the strictness analyzer, the simplifier, and anyone
-else who might want to fool with the evaluation order. Now, we
-believe that once the translation to STG code is performed, our
-evaluation order is safe. Therefore, we convert expressions of the
-form:
-
- case par# e of
- True -> rhs
- False -> parError#
-
-to
-
- case par# e of
- _ -> rhs
+There's a lot of stuff to pass around, so we use this @LneM@ monad to
+help. All the stuff here is only passed {\em down}.
\begin{code}
+type LneM a = IdEnv HowBound
+ -> StgLiveVars -- vars live in continuation
+ -> a
+
+data HowBound
+ = ImportBound
+ | CaseBound
+ | LambdaBound
+ | LetrecBound
+ Bool -- True <=> bound at top level
+ StgLiveVars -- Live vars... see notes below
+
+isLetrecBound (LetrecBound _ _) = True
+isLetrecBound other = False
+\end{code}
-coreExprToStg env (Case discrim@(Prim op _) alts)
- | funnyParallelOp op
- = getUnique `thenUs` \ uniq ->
- coreExprToStg env discrim `thenUs` \ (stg_discrim, discrim_binds) ->
- alts_to_stg alts `thenUs` \ (stg_alts, alts_binds) ->
- returnUs (
- StgCase stg_discrim
- bOGUS_LVs
- bOGUS_LVs
- uniq
- stg_alts,
- discrim_binds `unionBags` alts_binds
- )
- where
- funnyParallelOp SeqOp = True
- funnyParallelOp ParOp = True
- funnyParallelOp ForkOp = True
- funnyParallelOp _ = False
-
- discrim_ty = coreExprType discrim
+For a let(rec)-bound variable, x, we record what varibles are live if
+x is live. For "normal" variables that is just x alone. If x is
+a let-no-escaped variable then x is represented by a code pointer and
+a stack pointer (well, one for each stack). So all of the variables
+needed in the execution of x are live if x is, and are therefore recorded
+in the LetrecBound constructor; x itself *is* included.
- alts_to_stg (PrimAlts _ (BindDefault binder rhs))
- = coreExprToStg env rhs `thenUs` \ (stg_rhs, rhs_binds) ->
- let
- stg_deflt = StgBindDefault binder False stg_rhs
- in
- returnUs (StgPrimAlts discrim_ty [] stg_deflt, rhs_binds)
-
--- OK, back to real life...
-
-coreExprToStg env (Case discrim alts)
- = coreExprToStg env discrim `thenUs` \ (stg_discrim, discrim_binds) ->
- alts_to_stg discrim alts `thenUs` \ (stg_alts, alts_binds) ->
- getUnique `thenUs` \ uniq ->
- returnUs (
- StgCase stg_discrim
- bOGUS_LVs
- bOGUS_LVs
- uniq
- stg_alts,
- discrim_binds `unionBags` alts_binds
- )
+The std monad functions:
+\begin{code}
+initLne :: LneM a -> a
+initLne m = m emptyVarEnv emptyVarSet
+
+{-# INLINE thenLne #-}
+{-# INLINE thenLne_ #-}
+{-# INLINE returnLne #-}
+
+returnLne :: a -> LneM a
+returnLne e env lvs_cont = e
+
+thenLne :: LneM a -> (a -> LneM b) -> LneM b
+thenLne m k env lvs_cont
+ = case (m env lvs_cont) of
+ m_result -> k m_result env lvs_cont
+
+thenLne_ :: LneM a -> LneM b -> LneM b
+thenLne_ m k env lvs_cont
+ = case (m env lvs_cont) of
+ _ -> k env lvs_cont
+
+mapLne :: (a -> LneM b) -> [a] -> LneM [b]
+mapLne f [] = returnLne []
+mapLne f (x:xs)
+ = f x `thenLne` \ r ->
+ mapLne f xs `thenLne` \ rs ->
+ returnLne (r:rs)
+
+mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
+
+mapAndUnzipLne f [] = returnLne ([],[])
+mapAndUnzipLne f (x:xs)
+ = f x `thenLne` \ (r1, r2) ->
+ mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
+ returnLne (r1:rs1, r2:rs2)
+
+mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
+
+mapAndUnzip3Lne f [] = returnLne ([],[],[])
+mapAndUnzip3Lne f (x:xs)
+ = f x `thenLne` \ (r1, r2, r3) ->
+ mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
+ returnLne (r1:rs1, r2:rs2, r3:rs3)
+
+fixLne :: (a -> LneM a) -> LneM a
+fixLne expr env lvs_cont = result
where
- discrim_ty = coreExprType discrim
- (_, discrim_ty_args, _) = getAppDataTyConExpandingDicts discrim_ty
-
- alts_to_stg discrim (AlgAlts alts deflt)
- = default_to_stg discrim deflt `thenUs` \ (stg_deflt, deflt_binds) ->
- mapAndUnzipUs boxed_alt_to_stg alts `thenUs` \ (stg_alts, alts_binds) ->
- returnUs (StgAlgAlts discrim_ty stg_alts stg_deflt,
- deflt_binds `unionBags` unionManyBags alts_binds)
- where
- boxed_alt_to_stg (con, bs, rhs)
- = coreExprToStg env rhs `thenUs` \ (stg_rhs, rhs_binds) ->
- returnUs ((spec_con, bs, [ True | b <- bs ]{-bogus use mask-}, stg_rhs),
- rhs_binds)
- where
- spec_con = mkSpecialisedCon con discrim_ty_args
-
- alts_to_stg discrim (PrimAlts alts deflt)
- = default_to_stg discrim deflt `thenUs` \ (stg_deflt,deflt_binds) ->
- mapAndUnzipUs unboxed_alt_to_stg alts `thenUs` \ (stg_alts, alts_binds) ->
- returnUs (StgPrimAlts discrim_ty stg_alts stg_deflt,
- deflt_binds `unionBags` unionManyBags alts_binds)
- where
- unboxed_alt_to_stg (lit, rhs)
- = coreExprToStg env rhs `thenUs` \ (stg_rhs, rhs_binds) ->
- returnUs ((lit, stg_rhs), rhs_binds)
-
- default_to_stg discrim NoDefault
- = returnUs (StgNoDefault, emptyBag)
-
- default_to_stg discrim (BindDefault binder rhs)
- = coreExprToStg new_env rhs `thenUs` \ (stg_rhs, rhs_binds) ->
- returnUs (StgBindDefault binder True{-used? no it is lying-} stg_rhs,
- rhs_binds)
- where
- --
- -- We convert case x of {...; x' -> ...x'...}
- -- to
- -- case x of {...; _ -> ...x... }
- --
- -- See notes in SimplCase.lhs, near simplDefault for the reasoning.
- -- It's quite easily done: simply extend the environment to bind the
- -- default binder to the scrutinee.
- --
- new_env = case discrim of
- Var v -> addOneToIdEnv env binder (stgLookup env v)
- other -> env
+ result = expr result env lvs_cont
+-- ^^^^^^ ------ ^^^^^^
\end{code}
-%************************************************************************
-%* *
-\subsubsection[coreToStg-let(rec)]{Let and letrec expressions}
-%* *
-%************************************************************************
-
+Functions specific to this monad:
\begin{code}
-coreExprToStg env (Let bind body)
- = coreBindToStg env bind `thenUs` \ (stg_binds, new_env, float_binds1) ->
- coreExprToStg new_env body `thenUs` \ (stg_body, float_binds2) ->
- returnUs (mkStgLets stg_binds stg_body, float_binds1 `unionBags` float_binds2)
+getVarsLiveInCont :: LneM StgLiveVars
+getVarsLiveInCont env lvs_cont = lvs_cont
+
+setVarsLiveInCont :: StgLiveVars -> LneM a -> LneM a
+setVarsLiveInCont new_lvs_cont expr env lvs_cont
+ = expr env new_lvs_cont
+
+extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
+extendVarEnvLne ids_w_howbound expr env lvs_cont
+ = expr (extendVarEnvList env ids_w_howbound) lvs_cont
+
+lookupVarLne :: Id -> LneM HowBound
+lookupVarLne v env lvs_cont
+ = returnLne (
+ case (lookupVarEnv env v) of
+ Just xx -> xx
+ Nothing -> ImportBound
+ ) env lvs_cont
+
+-- The result of lookupLiveVarsForSet, a set of live variables, is
+-- only ever tacked onto a decorated expression. It is never used as
+-- the basis of a control decision, which might give a black hole.
+
+lookupLiveVarsForSet :: FreeVarsInfo -> LneM StgLiveVars
+
+lookupLiveVarsForSet fvs env lvs_cont
+ = returnLne (unionVarSets (map do_one (getFVs fvs)))
+ env lvs_cont
+ where
+ do_one v
+ = if isLocalId v then
+ case (lookupVarEnv env v) of
+ Just (LetrecBound _ lvs) -> extendVarSet lvs v
+ Just _ -> unitVarSet v
+ Nothing -> pprPanic "lookupVarEnv/do_one:" (ppr v)
+ else
+ emptyVarSet
\end{code}
%************************************************************************
%* *
-\subsubsection[coreToStg-scc]{SCC expressions}
+\subsection[Free-var info]{Free variable information}
%* *
%************************************************************************
-Covert core @scc@ expression directly to STG @scc@ expression.
\begin{code}
-coreExprToStg env (SCC cc expr)
- = coreExprToStg env expr `thenUs` \ (stg_expr, binds) ->
- returnUs (StgSCC (coreExprType expr) cc stg_expr, binds)
+type FreeVarsInfo = IdEnv (Id, Bool, StgBinderInfo)
+ -- If f is mapped to NoStgBinderInfo, that means
+ -- that f *is* mentioned (else it wouldn't be in the
+ -- IdEnv at all), but only in a saturated applications.
+ --
+ -- All case/lambda-bound things are also mapped to
+ -- NoStgBinderInfo, since we aren't interested in their
+ -- occurence info.
+ --
+ -- The Bool is True <=> the Id is top level letrec bound
+
+type EscVarsSet = IdSet
\end{code}
\begin{code}
-coreExprToStg env (Coerce c ty expr) = coreExprToStg env expr
-\end{code}
+emptyFVInfo :: FreeVarsInfo
+emptyFVInfo = emptyVarEnv
+singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
+singletonFVInfo id ImportBound info = emptyVarEnv
+singletonFVInfo id (LetrecBound top_level _) info = unitVarEnv id (id, top_level, info)
+singletonFVInfo id other info = unitVarEnv id (id, False, info)
-%************************************************************************
-%* *
-\subsection[coreToStg-misc]{Miscellaneous helping functions}
-%* *
-%************************************************************************
+unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
+unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
-Utilities.
+unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
+unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
-Invent a fresh @Id@:
-\begin{code}
-newStgVar :: Type -> UniqSM Id
-newStgVar ty
- = getUnique `thenUs` \ uniq ->
- returnUs (mkSysLocal SLIT("stg") uniq ty mkUnknownSrcLoc)
+minusFVBinders :: FreeVarsInfo -> [Id] -> FreeVarsInfo
+minusFVBinders fv ids = fv `delVarEnvList` ids
+
+elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
+elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
+
+lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
+lookupFVInfo fvs id = case lookupVarEnv fvs id of
+ Nothing -> NoStgBinderInfo
+ Just (_,_,info) -> info
+
+getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
+getFVs fvs = [id | (id,False,_) <- rngVarEnv fvs]
+
+getFVSet :: FreeVarsInfo -> IdSet
+getFVSet fvs = mkVarSet (getFVs fvs)
+
+plusFVInfo (id1,top1,info1) (id2,top2,info2)
+ = ASSERT (id1 == id2 && top1 == top2)
+ (id1, top1, combineStgBinderInfo info1 info2)
\end{code}
+Misc.
+
\begin{code}
-mkStgLets :: [StgBinding]
- -> StgExpr -- body of let
- -> StgExpr
+shouldBeVar (Note _ e) = shouldBeVar e
+shouldBeVar (Var v) = v
+shouldBeVar e = pprPanic "shouldBeVar" (ppr e)
-mkStgLets binds body = foldr StgLet body binds
+-- ignore all notes except SCC
+myCollectBinders expr
+ = go [] expr
+ where
+ go bs (Lam b e) = go (b:bs) e
+ go bs e@(Note (SCC _) _) = (reverse bs, e)
+ go bs (Note _ e) = go bs e
+ go bs e = (reverse bs, e)
+
+myCollectArgs :: Expr b -> (Expr b, [Arg b])
+myCollectArgs expr
+ = go expr []
+ where
+ go (App f a) as = go f (a:as)
+ go (Note (SCC _) e) as = panic "CoreToStg.myCollectArgs"
+ go (Note n e) as = go e as
+ go e as = (e, as)
\end{code}
projects / ghc-hetmet.git / blobdiff