X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FstgSyn%2FCoreToStg.lhs;h=15e9fc3cd65015eda357ce509949fe69b17a60ae;hb=1cfc9faaa059b9b090971399e4eb8ae9d364335c;hp=c3bd393c518026a860b8ecd6e09a9ccbb1245dc0;hpb=7b0181919416d8f04324575b7e17031ca692f5b0;p=ghc-hetmet.git diff --git a/ghc/compiler/stgSyn/CoreToStg.lhs b/ghc/compiler/stgSyn/CoreToStg.lhs index c3bd393..15e9fc3 100644 --- a/ghc/compiler/stgSyn/CoreToStg.lhs +++ b/ghc/compiler/stgSyn/CoreToStg.lhs @@ -1,643 +1,1111 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998 % +\section[CoreToStg]{Converts Core to STG Syntax} + +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" + +import CoreSyn +import CoreUtils ( rhsIsStatic, manifestArity, exprType ) +import StgSyn + +import Type +import TyCon ( isAlgTyCon ) +import Literal +import Id +import Var ( Var, globalIdDetails, varType ) +#ifdef ILX +import MkId ( unsafeCoerceId ) +#endif +import IdInfo +import DataCon +import CostCentre ( noCCS ) +import VarSet +import VarEnv +import Maybes ( maybeToBool ) +import Name ( getOccName, isExternalName, nameOccName ) +import OccName ( occNameUserString, occNameFS ) +import BasicTypes ( Arity ) +import CmdLineOpts ( DynFlags, opt_RuntimeTypes ) +import Outputable + +infixr 9 `thenLne` +\end{code} + %************************************************************************ %* * -\section[CoreToStg]{Converting core syntax to STG syntax} +\subsection[live-vs-free-doc]{Documentation} %* * %************************************************************************ -Convert a @CoreSyntax@ program to a @StgSyntax@ program. +(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[caf-info]{Collecting live CAF info} +%* * +%************************************************************************ +In this pass we also collect information on which CAFs are live for +constructing SRTs (see SRT.lhs). -\begin{code} -#include "HsVersions.h" +A top-level Id has CafInfo, which is -module CoreToStg ( topCoreBindsToStg ) where - -import Ubiq{-uitous-} - -import CoreSyn -- input -import StgSyn -- output - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, bagToList ) -import CoreUtils ( coreExprType ) -import CostCentre ( noCostCentre ) -import Id ( mkSysLocal, idType, isBottomingId, - nullIdEnv, addOneToIdEnv, lookupIdEnv, - IdEnv(..), GenId{-instance NamedThing-} - ) -import Literal ( mkMachInt, Literal(..) ) -import Name ( isExported ) -import PrelInfo ( unpackCStringId, unpackCString2Id, stringTy, - integerTy, rationalTy, ratioDataCon, - integerZeroId, integerPlusOneId, - integerPlusTwoId, integerMinusOneId - ) -import PrimOp ( PrimOp(..) ) -import SpecUtils ( mkSpecialisedCon ) -import SrcLoc ( mkUnknownSrcLoc ) -import Type ( getAppDataTyCon ) -import UniqSupply -- all of it, really -import Util ( panic ) - -isLeakFreeType = panic "CoreToStg.isLeakFreeType (ToDo)" -\end{code} + - MayHaveCafRefs, if it may refer indirectly to + one or more CAFs, or + - NoCafRefs if it definitely doesn't +The CafInfo has already been calculated during the CoreTidy pass. - *************** OVERVIEW ********************* +During CoreToStg, we then pin onto each binding and case expression, a +list of Ids which represents the "live" CAFs at that point. The meaning +of "live" here is the same as for live variables, see above (which is +why it's convenient to collect CAF information here rather than elsewhere). +The later SRT pass takes these lists of Ids and uses them to construct +the actual nested SRTs, and replaces the lists of Ids with (offset,length) +pairs. -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 +Interaction of let-no-escape with SRTs [Sept 01] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider -* We make the representation of NoRep literals explicit, and - float their bindings to the top level + let-no-escape x = ...caf1...caf2... + in + ...x...x...x... -* 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. +where caf1,caf2 are CAFs. Since x doesn't have a closure, we +build SRTs just as if x's defn was inlined at each call site, and +that means that x's CAF refs get duplicated in the overall SRT. -* We convert case x of {...; x' -> ...x'...} - to - case x of {...; _ -> ...x... } +This is unlike ordinary lets, in which the CAF refs are not duplicated. - See notes in SimplCase.lhs, near simplDefault for the reasoning here. +We could fix this loss of (static) sharing by making a sort of pseudo-closure +for x, solely to put in the SRTs lower down. %************************************************************************ %* * -\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} -type StgEnv = IdEnv StgArg -\end{code} +coreToStg :: DynFlags -> [CoreBind] -> IO [StgBinding] +coreToStg dflags pgm + = return pgm' + where (_, _, pgm') = coreTopBindsToStg emptyVarEnv pgm -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. +coreExprToStg :: CoreExpr -> StgExpr +coreExprToStg expr + = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr) -\begin{code} -bOGUS_LVs :: StgLiveVars -bOGUS_LVs = panic "bOGUS_LVs" -- emptyUniqSet (used when pprTracing) -bOGUS_FVs :: [Id] -bOGUS_FVs = panic "bOGUS_FVs" -- [] (ditto) +coreTopBindsToStg + :: IdEnv HowBound -- environment for the bindings + -> [CoreBind] + -> (IdEnv HowBound, FreeVarsInfo, [StgBinding]) + +coreTopBindsToStg env [] = (env, emptyFVInfo, []) +coreTopBindsToStg env (b:bs) + = (env2, fvs2, b':bs') + where + -- env accumulates down the list of binds, fvs accumulates upwards + (env1, fvs2, b' ) = coreTopBindToStg env fvs1 b + (env2, fvs1, bs') = coreTopBindsToStg env1 bs + + +coreTopBindToStg + :: IdEnv HowBound + -> FreeVarsInfo -- Info about the body + -> CoreBind + -> (IdEnv HowBound, FreeVarsInfo, StgBinding) + +coreTopBindToStg env body_fvs (NonRec id rhs) + = let + env' = extendVarEnv env id how_bound + how_bound = LetBound TopLet (manifestArity rhs) + + (stg_rhs, fvs') = + initLne env ( + coreToTopStgRhs body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') -> + returnLne (stg_rhs, fvs') + ) + + bind = StgNonRec id stg_rhs + in + ASSERT2(manifestArity rhs == stgRhsArity stg_rhs, ppr id) + ASSERT2(consistentCafInfo id bind, ppr id) +-- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info) + (env', fvs' `unionFVInfo` body_fvs, bind) + +coreTopBindToStg env body_fvs (Rec pairs) + = let + (binders, rhss) = unzip pairs + + extra_env' = [ (b, LetBound TopLet (manifestArity rhs)) + | (b, rhs) <- pairs ] + env' = extendVarEnvList env extra_env' + + (stg_rhss, fvs') + = initLne env' ( + mapAndUnzipLne (coreToTopStgRhs body_fvs) pairs + `thenLne` \ (stg_rhss, fvss') -> + let fvs' = unionFVInfos fvss' in + returnLne (stg_rhss, fvs') + ) + + bind = StgRec (zip binders stg_rhss) + in + ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders) + ASSERT2(consistentCafInfo (head binders) bind, ppr binders) + (env', fvs' `unionFVInfo` body_fvs, bind) + +#ifdef DEBUG +-- Assertion helper: this checks that the CafInfo on the Id matches +-- what CoreToStg has figured out about the binding's SRT. The +-- CafInfo will be exact in all cases except when CorePrep has +-- floated out a binding, in which case it will be approximate. +consistentCafInfo id bind + | occNameFS (nameOccName (idName id)) == FSLIT("sat") + = safe + | otherwise + = WARN (not exact, ppr id) safe + where + safe = id_marked_caffy || not binding_is_caffy + exact = id_marked_caffy == binding_is_caffy + id_marked_caffy = mayHaveCafRefs (idCafInfo id) + binding_is_caffy = stgBindHasCafRefs bind +#endif \end{code} \begin{code} -topCoreBindsToStg :: UniqSupply -- name supply - -> [CoreBinding] -- input - -> [StgBinding] -- output - -topCoreBindsToStg us core_binds - = case (initUs us (binds_to_stg nullIdEnv core_binds)) of - (_, stuff) -> stuff +coreToTopStgRhs + :: FreeVarsInfo -- Free var info for the scope of the binding + -> (Id,CoreExpr) + -> LneM (StgRhs, FreeVarsInfo) + +coreToTopStgRhs scope_fv_info (bndr, rhs) + = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) -> + freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info -> + returnLne (mkTopStgRhs is_static rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs) 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))) $ --} - 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 + bndr_info = lookupFVInfo scope_fv_info bndr + is_static = rhsIsStatic rhs + +mkTopStgRhs :: Bool -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr + -> StgRhs + +mkTopStgRhs is_static rhs_fvs srt binder_info (StgLam _ bndrs body) + = ASSERT( is_static ) + StgRhsClosure noCCS binder_info + (getFVs rhs_fvs) + ReEntrant + srt + bndrs body + +mkTopStgRhs is_static rhs_fvs srt binder_info (StgConApp con args) + | is_static -- StgConApps can be updatable (see isCrossDllConApp) + = StgRhsCon noCCS con args + +mkTopStgRhs is_static rhs_fvs srt binder_info rhs + = ASSERT( not is_static ) + StgRhsClosure noCCS binder_info + (getFVs rhs_fvs) + Updatable + srt + [] rhs \end{code} -%************************************************************************ -%* * -\subsection[coreToStg-binds]{Converting bindings} -%* * -%************************************************************************ + +-- --------------------------------------------------------------------------- +-- Expressions +-- --------------------------------------------------------------------------- \begin{code} -coreBindToStg :: StgEnv - -> CoreBinding - -> UniqSM ([StgBinding], -- Empty or singleton - StgEnv, -- New envt - Bag StgBinding) -- Floats +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} + +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. -coreBindToStg env (NonRec binder rhs) - = coreRhsToStg env rhs `thenUs` \ (stg_rhs, rhs_binds) -> +\begin{code} +coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet) +coreToStgExpr (Var v) = coreToStgApp Nothing v [] + +coreToStgExpr expr@(App _ _) + = coreToStgApp Nothing f args + where + (f, args) = myCollectArgs expr +coreToStgExpr expr@(Lam _ _) + = let + (args, body) = myCollectBinders expr + args' = filterStgBinders args + in + extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $ + coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) -> let - -- Binds to return if RHS is trivial - triv_binds = if isExported binder then - [StgNonRec binder stg_rhs] -- Retain it - else - [] -- Discard it + fvs = args' `minusFVBinders` body_fvs + escs = body_escs `delVarSetList` args' + result_expr | null args' = body + | otherwise = StgLam (exprType expr) args' body 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) + returnLne (result_expr, fvs, escs) + +coreToStgExpr (Note (SCC cc) expr) + = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) -> + returnLne (StgSCC cc expr2, fvs, escs) ) + +#ifdef ILX +-- For ILX, convert (__coerce__ to_ty from_ty e) +-- into (coerce to_ty from_ty e) +-- where coerce is real function +coreToStgExpr (Note (Coerce to_ty from_ty) expr) + = coreToStgExpr (mkApps (Var unsafeCoerceId) + [Type from_ty, Type to_ty, expr]) +#endif + +coreToStgExpr (Note other_note expr) + = coreToStgExpr expr + +-- Cases require a little more real work. + +coreToStgExpr (Case scrut bndr alts) + = extendVarEnvLne [(bndr, LambdaBound)] ( + mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) -> + returnLne ( mkStgAlts (idType bndr) alts2, + unionFVInfos fvs_s, + unionVarSets escs_s ) + ) `thenLne` \ (alts2, alts_fvs, alts_escs) -> let - (binders, rhss) = unzip pairs + -- Determine whether the default binder is dead or not + -- This helps the code generator to avoid generating an assignment + -- for the case binder (is extremely rare cases) ToDo: remove. + bndr' | bndr `elementOfFVInfo` alts_fvs = bndr + | otherwise = bndr `setIdOccInfo` IAmDead + + -- 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. + alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs + alts_escs_wo_bndr = alts_escs `delVarSet` bndr in - mapAndUnzipUs (coreRhsToStg env) rhss `thenUs` \ (stg_rhss, rhs_binds) -> - returnUs ([StgRec (binders `zip` stg_rhss)], env, unionManyBags rhs_binds) -\end{code} + freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info -> + + -- We tell the scrutinee that everything + -- live in the alts is live in it, too. + setVarsLiveInCont alts_lv_info ( + coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) -> + freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info -> + returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) + ) + `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) -> + + returnLne ( + StgCase scrut2 (getLiveVars scrut_lv_info) + (getLiveVars alts_lv_info) + bndr' + (mkSRT alts_lv_info) + alts2, + scrut_fvs `unionFVInfo` alts_fvs_wo_bndr, + alts_escs_wo_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 + vars_alt (con, binders, rhs) + = let -- Remove type variables + binders' = filterStgBinders binders + in + extendVarEnvLne [(b, LambdaBound) | b <- binders'] $ + coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) -> + let + -- Records whether each param is used in the RHS + good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ] + in + returnLne ( (con, binders', good_use_mask, rhs2), + binders' `minusFVBinders` rhs_fvs, + rhs_escs `delVarSetList` binders' ) + -- ToDo: remove the delVarSet; + -- since escs won't include any of these binders +\end{code} -%************************************************************************ -%* * -\subsection[coreToStg-rhss]{Converting right hand sides} -%* * -%************************************************************************ +Lets not only take quite a bit of work, but this is where we convert +then to let-no-escapes, if we wish. +(Meanwhile, we don't expect to see let-no-escapes...) \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 - in - returnUs (stg_rhs, stg_binds) +coreToStgExpr (Let bind body) + = fixLne (\ ~(_, _, _, no_binder_escapes) -> + coreToStgLet no_binder_escapes bind body + ) `thenLne` \ (new_let, fvs, escs, _) -> + + returnLne (new_let, fvs, escs) \end{code} +\begin{code} +mkStgAlts scrut_ty orig_alts + | is_prim_case = StgPrimAlts (tyConAppTyCon scrut_ty) prim_alts deflt + | otherwise = StgAlgAlts maybe_tycon alg_alts deflt + where + is_prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty) -%************************************************************************ -%* * -\subsection[coreToStg-lits]{Converting literals} -%* * -%************************************************************************ + prim_alts = [(lit, rhs) | (LitAlt lit, _, _, rhs) <- other_alts] + alg_alts = [(con, bndrs, use, rhs) | (DataAlt con, bndrs, use, rhs) <- other_alts] -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. + (other_alts, deflt) + = case orig_alts of -- DEFAULT is always first if it's there at all + (DEFAULT, _, _, rhs) : other_alts -> (other_alts, StgBindDefault rhs) + other -> (orig_alts, StgNoDefault) -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@. + maybe_tycon = case alg_alts of + -- Get the tycon from the data con + (dc, _, _, _) : _rest -> Just (dataConTyCon dc) + + -- Otherwise just do your best + [] -> case splitTyConApp_maybe (repType scrut_ty) of + Just (tc,_) | isAlgTyCon tc -> Just tc + _other -> Nothing +\end{code} -\begin{code} -tARGET_MIN_INT, tARGET_MAX_INT :: Integer -tARGET_MIN_INT = -536870912 -tARGET_MAX_INT = 536870912 -litToStgArg :: Literal -> UniqSM (StgArg, Bag StgBinding) +-- --------------------------------------------------------------------------- +-- 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 + = coreToStgArgs args `thenLne` \ (args', args_fvs) -> + lookupVarLne f `thenLne` \ how_bound -> -litToStgArg (NoRepStr s) - = newStgVar stringTy `thenUs` \ var -> 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 + n_val_args = valArgCount args + not_letrec_bound = not (isLetBound how_bound) + fun_fvs + = let fvs = singletonFVInfo f how_bound fun_occ in + -- e.g. (f :: a -> int) (x :: a) + -- Here the free variables are "f", "x" AND the type variable "a" + -- coreToStgArgs will deal with the arguments recursively + if opt_RuntimeTypes then + fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (varType f)) + else fvs + + -- Mostly, the arity info of a function is in the fn's IdInfo + -- But new bindings introduced by CoreSat may not have no + -- arity info; it would do us no good anyway. For example: + -- let f = \ab -> e in f + -- No point in having correct arity info for f! + -- Hence the hasArity stuff below. + -- NB: f_arity is only consulted for LetBound things + f_arity = stgArity f how_bound + saturated = f_arity <= n_val_args + + fun_occ + | not_letrec_bound = noBinderInfo -- Uninteresting variable + | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call + | otherwise = stgUnsatOcc -- Unsaturated function or thunk + + fun_escs + | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting + | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly + -- saturated call doesn't escape + -- (let-no-escape applies to 'thunks' too) + + | otherwise = unitVarSet f -- 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. + + res_ty = exprType (mkApps (Var f) args) + app = case globalIdDetails f of + DataConWorkId dc | saturated -> StgConApp dc args' + PrimOpId op -> ASSERT( saturated ) + StgOpApp (StgPrimOp op) args' res_ty + FCallId call -> ASSERT( saturated ) + StgOpApp (StgFCallOp call (idUnique f)) args' res_ty + _other -> StgApp f args' + in - returnUs (StgVarArg var, unitBag (StgNonRec var rhs)) - where - is_NUL c = c == '\0' + 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. + ) -litToStgArg (NoRepInteger i) - -- 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 integerTy `thenUs` \ var -> + +-- --------------------------------------------------------------------------- +-- Argument lists +-- This is the guy that turns applications into A-normal form +-- --------------------------------------------------------------------------- + +coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo) +coreToStgArgs [] + = returnLne ([], emptyFVInfo) + +coreToStgArgs (Type ty : args) -- Type argument + = coreToStgArgs args `thenLne` \ (args', fvs) -> + if opt_RuntimeTypes then + returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty)) + else + returnLne (args', fvs) + +coreToStgArgs (arg : args) -- Non-type argument + = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) -> + coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) -> 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 + fvs = args_fvs `unionFVInfo` arg_fvs + stg_arg = case arg' of + StgApp v [] -> StgVarArg v + StgConApp con [] -> StgVarArg (dataConWorkId con) + StgLit lit -> StgLitArg lit + _ -> pprPanic "coreToStgArgs" (ppr arg) in - returnUs (StgVarArg var, unitBag (StgNonRec var rhs)) - -litToStgArg (NoRepRational r) - = litToStgArg (NoRepInteger (numerator r)) `thenUs` \ (num_atom, binds1) -> - litToStgArg (NoRepInteger (denominator r)) `thenUs` \ (denom_atom, binds2) -> - newStgVar rationalTy `thenUs` \ var -> - let - rhs = StgRhsCon noCostCentre -- No cost centre (ToDo?) - ratioDataCon -- Constructor - [num_atom, denom_atom] - in - returnUs (StgVarArg var, binds1 `unionBags` - binds2 `unionBags` - unitBag (StgNonRec var rhs)) - -litToStgArg other_lit = returnUs (StgLitArg other_lit, emptyBag) -\end{code} + returnLne (stg_arg : stg_args, fvs) -%************************************************************************ -%* * -\subsection[coreToStg-atoms{Converting atoms} -%* * -%************************************************************************ +-- --------------------------------------------------------------------------- +-- The magic for lets: +-- --------------------------------------------------------------------------- -\begin{code} -coreArgsToStg :: StgEnv -> [CoreArg] -> UniqSM ([Type], [StgArg], Bag StgBinding) +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_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 emptyLiveInfo) + (vars_bind rec_body_fvs bind) + `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) -> + + -- Do the body + extendVarEnvLne env_ext ( + coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) -> + freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info -> + + returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info, + body2, body_fvs, body_escs, getLiveVars body_lv_info) + ) -coreArgsToStg env [] = returnUs ([], [], emptyBag) -coreArgsToStg env (a:as) - = coreArgsToStg env as `thenUs` \ (tys, args, binds) -> - do_arg a tys args binds + ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs, + body2, body_fvs, body_escs, body_lvs) -> + + + -- 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 + = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs) + + live_in_whole_let + = bind_lvs `unionVarSet` (body_lvs `delVarSetList` 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) `delVarSetList` 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 - 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) + set_of_binders = mkVarSet binders + binders = bindersOf bind + + mk_binding bind_lv_info binder rhs + = (binder, LetBound (NestedLet live_vars) (manifestArity rhs)) + where + live_vars | let_no_escape = addLiveVar bind_lv_info binder + | otherwise = unitLiveVar binder + -- c.f. the invariant on NestedLet + + vars_bind :: FreeVarsInfo -- Free var info for body of binding + -> CoreBind + -> LneM (StgBinding, + FreeVarsInfo, + EscVarsSet, -- free vars; escapee vars + LiveInfo, -- Vars and CAFs live in binding + [(Id, HowBound)]) -- extension to environment + + + vars_bind body_fvs (NonRec binder rhs) + = coreToStgRhs body_fvs [] (binder,rhs) + `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) -> + let + env_ext_item = mk_binding bind_lv_info binder rhs + in + returnLne (StgNonRec binder rhs2, + bind_fvs, escs, bind_lv_info, [env_ext_item]) + + + vars_bind body_fvs (Rec pairs) + = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) -> + let + rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs + binders = map fst pairs + env_ext = [ mk_binding bind_lv_info b rhs + | (b,rhs) <- pairs ] + in + extendVarEnvLne env_ext ( + mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs + `thenLne` \ (rhss2, fvss, lv_infos, escss) -> + let + bind_fvs = unionFVInfos fvss + bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos + escs = unionVarSets escss + in + returnLne (StgRec (binders `zip` rhss2), + bind_fvs, escs, bind_lv_info, 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} -There's not anything interesting we can ASSERT about \tr{var} if it -isn't in the StgEnv. (WDP 94/06) \begin{code} -stgLookup :: StgEnv -> Id -> StgArg - -stgLookup env var = case (lookupIdEnv env var) of - Nothing -> StgVarArg var - Just atom -> atom +coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding + -> [Id] + -> (Id,CoreExpr) + -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet) + +coreToStgRhs scope_fv_info binders (bndr, rhs) + = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) -> + getEnvLne `thenLne` \ env -> + freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info -> + returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs, + rhs_fvs, lv_info, rhs_escs) + where + bndr_info = lookupFVInfo scope_fv_info bndr + +mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs + +mkStgRhs rhs_fvs srt binder_info (StgConApp con args) + = StgRhsCon noCCS con args + +mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body) + = StgRhsClosure noCCS binder_info + (getFVs rhs_fvs) + ReEntrant + srt bndrs body + +mkStgRhs rhs_fvs srt binder_info rhs + = StgRhsClosure noCCS binder_info + (getFVs rhs_fvs) + upd_flag srt [] rhs + where + upd_flag = Updatable + {- + SDM: disabled. Eval/Apply can't handle functions with arity zero very + well; and making these into simple non-updatable thunks breaks other + assumptions (namely that they will be entered only once). + + upd_flag | isPAP env rhs = 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} +Detect thunks which will reduce immediately to PAPs, and make them +non-updatable. This has several advantages: + + - the non-updatable thunk behaves exactly like the PAP, + + - the thunk is more efficient to enter, because it is + specialised to the task. + + - 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. + +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. + +isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args + where + arity = stgArity f (lookupBinding env f) +isPAP env _ = False + + %************************************************************************ %* * -\subsection[coreToStg-exprs]{Converting core expressions} +\subsection[LNE-monad]{A little monad for this let-no-escaping pass} %* * %************************************************************************ -\begin{code} -coreExprToStg :: StgEnv - -> CoreExpr - -> UniqSM (StgExpr, -- Result - Bag StgBinding) -- Float these to top level -\end{code} +There's a lot of stuff to pass around, so we use this @LneM@ monad to +help. All the stuff here is only passed *down*. \begin{code} -coreExprToStg env (Lit lit) - = litToStgArg lit `thenUs` \ (atom, binds) -> - returnUs (StgApp atom [] bOGUS_LVs, binds) +type LneM a = IdEnv HowBound + -> LiveInfo -- Vars and CAFs live in continuation + -> a -coreExprToStg env (Var var) - = returnUs (StgApp (stgLookup env var) [] bOGUS_LVs, emptyBag) +type LiveInfo = (StgLiveVars, -- Dynamic live variables; + -- i.e. ones with a nested (non-top-level) binding + CafSet) -- Static live variables; + -- i.e. top-level variables that are CAFs or refer to them -coreExprToStg env (Con con args) - = coreArgsToStg env args `thenUs` \ (types, stg_atoms, stg_binds) -> - let - spec_con = mkSpecialisedCon con types - in - returnUs (StgCon spec_con stg_atoms bOGUS_LVs, stg_binds) +type EscVarsSet = IdSet +type CafSet = IdSet + +data HowBound + = ImportBound -- Used only as a response to lookupBinding; never + -- exists in the range of the (IdEnv HowBound) -coreExprToStg env (Prim op args) - = coreArgsToStg env args `thenUs` \ (_, stg_atoms, stg_binds) -> - returnUs (StgPrim op stg_atoms bOGUS_LVs, stg_binds) + | LetBound -- A let(rec) in this module + LetInfo -- Whether top level or nested + Arity -- Its arity (local Ids don't have arity info at this point) + + | LambdaBound -- Used for both lambda and case + +data LetInfo + = TopLet -- top level things + | NestedLet LiveInfo -- For nested things, what is live if this + -- thing is live? Invariant: the binder + -- itself is always a member of + -- the dynamic set of its own LiveInfo + +isLetBound (LetBound _ _) = True +isLetBound other = False + +topLevelBound ImportBound = True +topLevelBound (LetBound TopLet _) = True +topLevelBound other = False \end{code} -%************************************************************************ -%* * -\subsubsection[coreToStg-lambdas]{Lambda abstractions} -%* * -%************************************************************************ +For a let(rec)-bound variable, x, we record LiveInfo, the set of +variables that are live if x is live. This LiveInfo comprises + (a) dynamic live variables (ones with a non-top-level binding) + (b) static live variabes (CAFs or things that refer to CAFs) + +For "normal" variables (a) 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 +LetBound constructor; x itself *is* included. + +The set of dynamic live variables is guaranteed ot have no further let-no-escaped +variables in it. \begin{code} -coreExprToStg env expr@(Lam _ _) - = let - (_,_, binders, body) = collectBinders expr - in - coreExprToStg env body `thenUs` \ (stg_body, binds) -> - 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) +emptyLiveInfo :: LiveInfo +emptyLiveInfo = (emptyVarSet,emptyVarSet) + +unitLiveVar :: Id -> LiveInfo +unitLiveVar lv = (unitVarSet lv, emptyVarSet) + +unitLiveCaf :: Id -> LiveInfo +unitLiveCaf caf = (emptyVarSet, unitVarSet caf) + +addLiveVar :: LiveInfo -> Id -> LiveInfo +addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs) + +unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo +unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2) + +mkSRT :: LiveInfo -> SRT +mkSRT (_, cafs) = SRTEntries cafs + +getLiveVars :: LiveInfo -> StgLiveVars +getLiveVars (lvs, _) = lvs \end{code} -%************************************************************************ -%* * -\subsubsection[coreToStg-applications]{Applications} -%* * -%************************************************************************ +The std monad functions: \begin{code} -coreExprToStg env expr@(App _ _) - = let - (fun, _, _, args) = collectArgs expr - in - -- Deal with the arguments - coreArgsToStg env args `thenUs` \ (_, stg_args, arg_binds) -> - - -- Now deal with the function - case fun of - Var fun_id -> returnUs (StgApp (stgLookup env fun_id) stg_args bOGUS_LVs, arg_binds) - - 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) -> - let - fun_rhs = StgRhsClosure noCostCentre -- No cost centre (ToDo?) - stgArgOcc - bOGUS_FVs - SingleEntry -- Only entered once - [] - stg_fun - in - returnUs (StgLet (StgNonRec fun_id fun_rhs) - (StgApp (StgVarArg fun_id) stg_args bOGUS_LVs), - arg_binds `unionBags` fun_binds) -\end{code} +initLne :: IdEnv HowBound -> LneM a -> a +initLne env m = m env emptyLiveInfo -%************************************************************************ -%* * -\subsubsection[coreToStg-cases]{Case expressions} -%* * -%************************************************************************ -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# +{-# INLINE thenLne #-} +{-# INLINE returnLne #-} -to +returnLne :: a -> LneM a +returnLne e env lvs_cont = e - case par# e of - _ -> rhs +thenLne :: LneM a -> (a -> LneM b) -> LneM b +thenLne m k env lvs_cont + = k (m env lvs_cont) env lvs_cont -\begin{code} +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) -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 +mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c]) - discrim_ty = coreExprType discrim +mapAndUnzipLne f [] = returnLne ([],[]) +mapAndUnzipLne f (x:xs) + = f x `thenLne` \ (r1, r2) -> + mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) -> + returnLne (r1:rs1, r2:rs2) - 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 - ) +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) + +mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e]) + +mapAndUnzip4Lne f [] = returnLne ([],[],[],[]) +mapAndUnzip4Lne f (x:xs) + = f x `thenLne` \ (r1, r2, r3, r4) -> + mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) -> + returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4) + +fixLne :: (a -> LneM a) -> LneM a +fixLne expr env lvs_cont + = result where - discrim_ty = coreExprType discrim - (_, discrim_ty_args, _) = getAppDataTyCon 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) -\end{code} +getVarsLiveInCont :: LneM LiveInfo +getVarsLiveInCont env lvs_cont = lvs_cont + +setVarsLiveInCont :: LiveInfo -> 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 (lookupBinding env v) env lvs_cont + +getEnvLne :: LneM (IdEnv HowBound) +getEnvLne env lvs_cont = returnLne env env lvs_cont +lookupBinding :: IdEnv HowBound -> Id -> HowBound +lookupBinding env v = case lookupVarEnv env v of + Just xx -> xx + Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound + + +-- 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. + +freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo +freeVarsToLiveVars fvs env live_in_cont + = returnLne live_info env live_in_cont + where + live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs + lvs_from_fvs = map do_one (allFreeIds fvs) + + do_one (v, how_bound) + = case how_bound of + ImportBound -> unitLiveCaf v -- Only CAF imports are + -- recorded in fvs + LetBound TopLet _ + | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v + | otherwise -> emptyLiveInfo + + LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v + -- (see the invariant on NestedLet) + + _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case +\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 = VarEnv (Var, HowBound, StgBinderInfo) + -- The Var is so we can gather up the free variables + -- as a set. + -- + -- The HowBound info just saves repeated lookups; + -- we look up just once when we encounter the occurrence. + -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids + -- Imported Ids without CAF refs are simply + -- not put in the FreeVarsInfo for an expression. + -- See singletonFVInfo and freeVarsToLiveVars + -- + -- StgBinderInfo records how it occurs; notably, we + -- are interested in whether it only occurs in saturated + -- applications, because then we don't need to build a + -- curried version. + -- If f is mapped to noBinderInfo, that means + -- that f *is* mentioned (else it wouldn't be in the + -- IdEnv at all), but perhaps in an unsaturated applications. + -- + -- All case/lambda-bound things are also mapped to + -- noBinderInfo, since we aren't interested in their + -- occurence info. + -- + -- For ILX we track free var info for type variables too; + -- hence VarEnv not IdEnv \end{code} +\begin{code} +emptyFVInfo :: FreeVarsInfo +emptyFVInfo = emptyVarEnv + +singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo +-- Don't record non-CAF imports at all, to keep free-var sets small +singletonFVInfo id ImportBound info + | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info) + | otherwise = emptyVarEnv +singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info) + +tyvarFVInfo :: TyVarSet -> FreeVarsInfo +tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs + where + add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo) + -- Type variables must be lambda-bound + +unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo +unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2 + +unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo +unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs + +minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo +minusFVBinders vs fv = foldr minusFVBinder fv vs + +minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo +minusFVBinder v fv | isId v && opt_RuntimeTypes + = (fv `delVarEnv` v) `unionFVInfo` + tyvarFVInfo (tyVarsOfType (idType v)) + | otherwise = fv `delVarEnv` v + -- When removing a binder, remember to add its type variables + -- c.f. CoreFVs.delBinderFV + +elementOfFVInfo :: Id -> FreeVarsInfo -> Bool +elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id) + +lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo +-- Find how the given Id is used. +-- Externally visible things may be used any old how +lookupFVInfo fvs id + | isExternalName (idName id) = noBinderInfo + | otherwise = case lookupVarEnv fvs id of + Nothing -> noBinderInfo + Just (_,_,info) -> info + +allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids +allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- rngVarEnv fvs, isId id] + +-- Non-top-level things only, both type variables and ids +-- (type variables only if opt_RuntimeTypes) +getFVs :: FreeVarsInfo -> [Var] +getFVs fvs = [id | (id, how_bound, _) <- rngVarEnv fvs, + not (topLevelBound how_bound) ] + +getFVSet :: FreeVarsInfo -> VarSet +getFVSet fvs = mkVarSet (getFVs fvs) + +plusFVInfo (id1,hb1,info1) (id2,hb2,info2) + = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2) + (id1, hb1, combineStgBinderInfo info1 info2) + +#ifdef DEBUG +-- The HowBound info for a variable in the FVInfo should be consistent +check_eq_how_bound ImportBound ImportBound = True +check_eq_how_bound LambdaBound LambdaBound = True +check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2 +check_eq_how_bound hb1 hb2 = False + +check_eq_li (NestedLet _) (NestedLet _) = True +check_eq_li TopLet TopLet = True +check_eq_li li1 li2 = False +#endif +\end{code} -%************************************************************************ -%* * -\subsection[coreToStg-misc]{Miscellaneous helping functions} -%* * -%************************************************************************ +Misc. +\begin{code} +filterStgBinders :: [Var] -> [Var] +filterStgBinders bndrs + | opt_RuntimeTypes = bndrs + | otherwise = filter isId bndrs +\end{code} -Utilities. -Invent a fresh @Id@: \begin{code} -newStgVar :: Type -> UniqSM Id -newStgVar ty - = getUnique `thenUs` \ uniq -> - returnUs (mkSysLocal SLIT("stg") uniq ty mkUnknownSrcLoc) + -- 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 :: CoreExpr -> (Id, [CoreArg]) + -- We assume that we only have variables + -- in the function position by now +myCollectArgs expr + = go expr [] + where + go (Var v) as = (v, as) + go (App f a) as = go f (a:as) + go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr) + go (Note n e) as = go e as + go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr) \end{code} \begin{code} -mkStgLets :: [StgBinding] - -> StgExpr -- body of let - -> StgExpr - -mkStgLets binds body = foldr StgLet body binds +stgArity :: Id -> HowBound -> Arity +stgArity f (LetBound _ arity) = arity +stgArity f ImportBound = idArity f +stgArity f LambdaBound = 0 \end{code}