X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FCorePrep.lhs;h=e5165f0ebe98ed34e3aa052a04f5b7d167d58c65;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=5a4b636896ee5cb501e9f411ebd5c4224258cc01;hpb=3d5a3720e58efcacc7bb9c746f04cb97eabf49a3;p=ghc-hetmet.git diff --git a/ghc/compiler/coreSyn/CorePrep.lhs b/ghc/compiler/coreSyn/CorePrep.lhs index 5a4b636..e5165f0 100644 --- a/ghc/compiler/coreSyn/CorePrep.lhs +++ b/ghc/compiler/coreSyn/CorePrep.lhs @@ -10,28 +10,33 @@ module CorePrep ( #include "HsVersions.h" -import CoreUtils( exprIsAtom, exprType, exprIsValue, etaExpand, exprArity, exprOkForSpeculation ) +import CoreUtils( exprType, exprIsHNF, etaExpand, exprArity, exprOkForSpeculation ) import CoreFVs ( exprFreeVars ) import CoreLint ( endPass ) import CoreSyn -import Type ( Type, applyTy, splitFunTy_maybe, isTyVarTy, - isUnLiftedType, isUnboxedTupleType, repType, - uaUTy, usOnce, usMany, eqUsage, seqType ) +import Type ( Type, applyTy, splitFunTy_maybe, + isUnLiftedType, isUnboxedTupleType, seqType ) +import TyCon ( TyCon, tyConDataCons ) import NewDemand ( Demand, isStrictDmd, lazyDmd, StrictSig(..), DmdType(..) ) -import PrimOp ( PrimOp(..) ) import Var ( Var, Id, setVarUnique ) import VarSet import VarEnv -import Id ( mkSysLocal, idType, idNewDemandInfo, idArity, - setIdType, isPrimOpId_maybe, isFCallId, isLocalId, - hasNoBinding, idNewStrictness +import Id ( mkSysLocal, idType, idNewDemandInfo, idArity, setIdUnfolding, setIdType, + isFCallId, isGlobalId, + isLocalId, hasNoBinding, idNewStrictness, + isPrimOpId_maybe ) -import HscTypes ( ModDetails(..) ) +import DataCon ( isVanillaDataCon, dataConWorkId ) +import PrimOp ( PrimOp( DataToTagOp ) ) +import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel, + RecFlag(..), isNonRec + ) import UniqSupply import Maybes import OrdList import ErrUtils -import CmdLineOpts +import DynFlags +import Util ( listLengthCmp ) import Outputable \end{code} @@ -60,44 +65,96 @@ The goal of this pass is to prepare for code generation. 4. Ensure that lambdas only occur as the RHS of a binding (The code generator can't deal with anything else.) -5. Do the seq/par munging. See notes with mkCase below. +5. [Not any more; nuked Jun 2002] Do the seq/par munging. + +6. Clone all local Ids. + This means that all such Ids are unique, rather than the + weaker guarantee of no clashes which the simplifier provides. + And that is what the code generator needs. + + We don't clone TyVars. The code gen doesn't need that, + and doing so would be tiresome because then we'd need + to substitute in types. -6. Clone all local Ids. This means that Tidy Core has the property - that all Ids are unique, rather than the weaker guarantee of - no clashes which the simplifier provides. 7. Give each dynamic CCall occurrence a fresh unique; this is rather like the cloning step above. +8. Inject bindings for the "implicit" Ids: + * Constructor wrappers + * Constructor workers + * Record selectors + We want curried definitions for all of these in case they + aren't inlined by some caller. + This is all done modulo type applications and abstractions, so that when type erasure is done for conversion to STG, we don't end up with any trivial or useless bindings. - -- ----------------------------------------------------------------------------- -- Top level stuff -- ----------------------------------------------------------------------------- \begin{code} -corePrepPgm :: DynFlags -> ModDetails -> IO ModDetails -corePrepPgm dflags mod_details +corePrepPgm :: DynFlags -> [CoreBind] -> [TyCon] -> IO [CoreBind] +corePrepPgm dflags binds data_tycons = do showPass dflags "CorePrep" us <- mkSplitUniqSupply 's' - let new_binds = initUs_ us (corePrepTopBinds emptyVarEnv (md_binds mod_details)) - endPass dflags "CorePrep" Opt_D_dump_sat new_binds - return (mod_details { md_binds = new_binds }) + + let implicit_binds = mkDataConWorkers data_tycons + -- NB: we must feed mkImplicitBinds through corePrep too + -- so that they are suitably cloned and eta-expanded + + binds_out = initUs_ us ( + corePrepTopBinds binds `thenUs` \ floats1 -> + corePrepTopBinds implicit_binds `thenUs` \ floats2 -> + returnUs (deFloatTop (floats1 `appendFloats` floats2)) + ) + + endPass dflags "CorePrep" Opt_D_dump_prep binds_out + return binds_out corePrepExpr :: DynFlags -> CoreExpr -> IO CoreExpr corePrepExpr dflags expr = do showPass dflags "CorePrep" us <- mkSplitUniqSupply 's' - let new_expr = initUs_ us (corePrepAnExpr emptyVarEnv expr) - dumpIfSet_dyn dflags Opt_D_dump_sat "CorePrep" + let new_expr = initUs_ us (corePrepAnExpr emptyCorePrepEnv expr) + dumpIfSet_dyn dflags Opt_D_dump_prep "CorePrep" (ppr new_expr) return new_expr +\end{code} + +-- ----------------------------------------------------------------------------- +-- Implicit bindings +-- ----------------------------------------------------------------------------- + +Create any necessary "implicit" bindings for data con workers. We +create the rather strange (non-recursive!) binding + + $wC = \x y -> $wC x y + +i.e. a curried constructor that allocates. This means that we can +treat the worker for a constructor like any other function in the rest +of the compiler. The point here is that CoreToStg will generate a +StgConApp for the RHS, rather than a call to the worker (which would +give a loop). As Lennart says: the ice is thin here, but it works. + +Hmm. Should we create bindings for dictionary constructors? They are +always fully applied, and the bindings are just there to support +partial applications. But it's easier to let them through. + +\begin{code} +mkDataConWorkers data_tycons + = [ NonRec id (Var id) -- The ice is thin here, but it works + | tycon <- data_tycons, -- CorePrep will eta-expand it + data_con <- tyConDataCons tycon, + let id = dataConWorkId data_con ] +\end{code} + +\begin{code} -- --------------------------------------------------------------------------- -- Dealing with bindings -- --------------------------------------------------------------------------- @@ -106,113 +163,176 @@ data FloatingBind = FloatLet CoreBind | FloatCase Id CoreExpr Bool -- The bool indicates "ok-for-speculation" -instance Outputable FloatingBind where - ppr (FloatLet bind) = text "FloatLet" <+> ppr bind - ppr (FloatCase b rhs spec) = text "FloatCase" <+> ppr b <+> ppr spec <+> equals <+> ppr rhs +data Floats = Floats OkToSpec (OrdList FloatingBind) -type CloneEnv = IdEnv Id -- Clone local Ids +-- Can we float these binds out of the rhs of a let? We cache this decision +-- to avoid having to recompute it in a non-linear way when there are +-- deeply nested lets. +data OkToSpec + = NotOkToSpec -- definitely not + | OkToSpec -- yes + | IfUnboxedOk -- only if floating an unboxed binding is ok -allLazy :: OrdList FloatingBind -> Bool -allLazy floats - = foldrOL check True floats +emptyFloats :: Floats +emptyFloats = Floats OkToSpec nilOL + +addFloat :: Floats -> FloatingBind -> Floats +addFloat (Floats ok_to_spec floats) new_float + = Floats (combine ok_to_spec (check new_float)) (floats `snocOL` new_float) where - check (FloatLet _) y = y - check (FloatCase _ _ ok_for_spec) y = ok_for_spec && y + check (FloatLet _) = OkToSpec + check (FloatCase _ _ ok_for_spec) + | ok_for_spec = IfUnboxedOk + | otherwise = NotOkToSpec -- The ok-for-speculation flag says that it's safe to -- float this Case out of a let, and thereby do it more eagerly -- We need the top-level flag because it's never ok to float -- an unboxed binding to the top level --- --------------------------------------------------------------------------- --- Bindings --- --------------------------------------------------------------------------- +unitFloat :: FloatingBind -> Floats +unitFloat = addFloat emptyFloats -corePrepTopBinds :: CloneEnv -> [CoreBind] -> UniqSM [CoreBind] -corePrepTopBinds env [] = returnUs [] +appendFloats :: Floats -> Floats -> Floats +appendFloats (Floats spec1 floats1) (Floats spec2 floats2) + = Floats (combine spec1 spec2) (floats1 `appOL` floats2) -corePrepTopBinds env (bind : binds) - = corePrepTopBind env bind `thenUs` \ (env', bind') -> - corePrepTopBinds env' binds `thenUs` \ binds' -> - returnUs (bind' : binds') +concatFloats :: [Floats] -> Floats +concatFloats = foldr appendFloats emptyFloats --- From top level bindings we don't get any floats --- (a) it isn't necessary because the mkAtomicArgs in Simplify --- has already done all the floating necessary --- (b) floating would give rise to top-level LocaIds, generated --- by CorePrep.newVar. That breaks the invariant that --- after CorePrep all top-level vars are GlobalIds +combine NotOkToSpec _ = NotOkToSpec +combine _ NotOkToSpec = NotOkToSpec +combine IfUnboxedOk _ = IfUnboxedOk +combine _ IfUnboxedOk = IfUnboxedOk +combine _ _ = OkToSpec + +instance Outputable FloatingBind where + ppr (FloatLet bind) = text "FloatLet" <+> ppr bind + ppr (FloatCase b rhs spec) = text "FloatCase" <+> ppr b <+> ppr spec <+> equals <+> ppr rhs -corePrepTopBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, CoreBind) -corePrepTopBind env (NonRec bndr rhs) - = corePrepRhs env (bndr, rhs) `thenUs` \ rhs' -> - cloneBndr env bndr `thenUs` \ (env', bndr') -> - returnUs (env', NonRec bndr' rhs') +deFloatTop :: Floats -> [CoreBind] +-- For top level only; we don't expect any FloatCases +deFloatTop (Floats _ floats) + = foldrOL get [] floats + where + get (FloatLet b) bs = b:bs + get b bs = pprPanic "corePrepPgm" (ppr b) -corePrepTopBind env (Rec pairs) - = corePrepRecPairs env pairs `thenUs` \ (env', pairs') -> - returnUs (env, Rec pairs') +allLazy :: TopLevelFlag -> RecFlag -> Floats -> Bool +allLazy top_lvl is_rec (Floats ok_to_spec _) + = case ok_to_spec of + OkToSpec -> True + NotOkToSpec -> False + IfUnboxedOk -> isNotTopLevel top_lvl && isNonRec is_rec -corePrepRecPairs env pairs - = cloneBndrs env bndrs `thenUs` \ (env', bndrs') -> - mapUs (corePrepRhs env') pairs `thenUs` \ rhss' -> - returnUs (env', bndrs' `zip` rhss') - where - bndrs = map fst pairs - -corePrepRhs :: CloneEnv -> (Id, CoreExpr) -> UniqSM CoreExpr - -- Used for top-level bindings, and local recursive bindings - -- c.f. mkLocalNonRec, which does the other case - -- No nonsense about floating. - -- Prepare the RHS and eta expand it. -corePrepRhs env (bndr, rhs) - = corePrepAnExpr env rhs `thenUs` \ rhs' -> - getUniquesUs `thenUs` \ us -> - returnUs (etaExpand (exprArity rhs') us rhs' (idType bndr)) +-- --------------------------------------------------------------------------- +-- Bindings +-- --------------------------------------------------------------------------- +corePrepTopBinds :: [CoreBind] -> UniqSM Floats +corePrepTopBinds binds + = go emptyCorePrepEnv binds + where + go env [] = returnUs emptyFloats + go env (bind : binds) = corePrepTopBind env bind `thenUs` \ (env', bind') -> + go env' binds `thenUs` \ binds' -> + returnUs (bind' `appendFloats` binds') + +-- NB: we do need to float out of top-level bindings +-- Consider x = length [True,False] +-- We want to get +-- s1 = False : [] +-- s2 = True : s1 +-- x = length s2 -corePrepBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, OrdList FloatingBind) --- This one is used for *local* bindings -- We return a *list* of bindings, because we may start with -- x* = f (g y) -- where x is demanded, in which case we want to finish with -- a = g y -- x* = f a -- And then x will actually end up case-bound +-- +-- What happens to the CafInfo on the floated bindings? By +-- default, all the CafInfos will be set to MayHaveCafRefs, +-- which is safe. +-- +-- This might be pessimistic, because eg. s1 & s2 +-- might not refer to any CAFs and the GC will end up doing +-- more traversal than is necessary, but it's still better +-- than not floating the bindings at all, because then +-- the GC would have to traverse the structure in the heap +-- instead. Given this, we decided not to try to get +-- the CafInfo on the floated bindings correct, because +-- it looks difficult. + +-------------------------------- +corePrepTopBind :: CorePrepEnv -> CoreBind -> UniqSM (CorePrepEnv, Floats) +corePrepTopBind env (NonRec bndr rhs) + = cloneBndr env bndr `thenUs` \ (env', bndr') -> + corePrepRhs TopLevel NonRecursive env (bndr, rhs) `thenUs` \ (floats, rhs') -> + returnUs (env', addFloat floats (FloatLet (NonRec bndr' rhs'))) + +corePrepTopBind env (Rec pairs) = corePrepRecPairs TopLevel env pairs +-------------------------------- +corePrepBind :: CorePrepEnv -> CoreBind -> UniqSM (CorePrepEnv, Floats) + -- This one is used for *local* bindings corePrepBind env (NonRec bndr rhs) - = corePrepExprFloat env rhs `thenUs` \ (floats, rhs') -> - cloneBndr env bndr `thenUs` \ (env', bndr') -> - mkLocalNonRec bndr' (bdrDem bndr') floats rhs' `thenUs` \ floats' -> - returnUs (env', floats') + = etaExpandRhs bndr rhs `thenUs` \ rhs1 -> + corePrepExprFloat env rhs1 `thenUs` \ (floats, rhs2) -> + cloneBndr env bndr `thenUs` \ (_, bndr') -> + mkLocalNonRec bndr' (bdrDem bndr) floats rhs2 `thenUs` \ (floats', bndr'') -> + -- We want bndr'' in the envt, because it records + -- the evaluated-ness of the binder + returnUs (extendCorePrepEnv env bndr bndr'', floats') + +corePrepBind env (Rec pairs) = corePrepRecPairs NotTopLevel env pairs + +-------------------------------- +corePrepRecPairs :: TopLevelFlag -> CorePrepEnv + -> [(Id,CoreExpr)] -- Recursive bindings + -> UniqSM (CorePrepEnv, Floats) +-- Used for all recursive bindings, top level and otherwise +corePrepRecPairs lvl env pairs + = cloneBndrs env (map fst pairs) `thenUs` \ (env', bndrs') -> + mapAndUnzipUs (corePrepRhs lvl Recursive env') pairs `thenUs` \ (floats_s, rhss') -> + returnUs (env', unitFloat (FloatLet (Rec (flatten (concatFloats floats_s) bndrs' rhss')))) + where + -- Flatten all the floats, and the currrent + -- group into a single giant Rec + flatten (Floats _ floats) bndrs rhss = foldrOL get (bndrs `zip` rhss) floats + + get (FloatLet (NonRec b r)) prs2 = (b,r) : prs2 + get (FloatLet (Rec prs1)) prs2 = prs1 ++ prs2 + get b prs2 = pprPanic "corePrepRecPairs" (ppr b) + +-------------------------------- +corePrepRhs :: TopLevelFlag -> RecFlag + -> CorePrepEnv -> (Id, CoreExpr) + -> UniqSM (Floats, CoreExpr) +-- Used for top-level bindings, and local recursive bindings +corePrepRhs top_lvl is_rec env (bndr, rhs) + = etaExpandRhs bndr rhs `thenUs` \ rhs' -> + corePrepExprFloat env rhs' `thenUs` \ floats_w_rhs -> + floatRhs top_lvl is_rec bndr floats_w_rhs -corePrepBind env (Rec pairs) - -- Don't bother to try to float bindings out of RHSs - -- (compare mkNonRec, which does try) - = corePrepRecPairs env pairs `thenUs` \ (env', pairs') -> - returnUs (env', unitOL (FloatLet (Rec pairs'))) -- --------------------------------------------------------------------------- -- Making arguments atomic (function args & constructor args) -- --------------------------------------------------------------------------- -- This is where we arrange that a non-trivial argument is let-bound -corePrepArg :: CloneEnv -> CoreArg -> RhsDemand - -> UniqSM (OrdList FloatingBind, CoreArg) +corePrepArg :: CorePrepEnv -> CoreArg -> RhsDemand + -> UniqSM (Floats, CoreArg) corePrepArg env arg dem = corePrepExprFloat env arg `thenUs` \ (floats, arg') -> - if needs_binding arg' - then returnUs (floats, arg') - else newVar (exprType arg') `thenUs` \ v -> - mkLocalNonRec v dem floats arg' `thenUs` \ floats' -> - returnUs (floats', Var v) - -needs_binding | opt_RuntimeTypes = exprIsAtom - | otherwise = exprIsTrivial + if exprIsTrivial arg' + then returnUs (floats, arg') + else newVar (exprType arg') `thenUs` \ v -> + mkLocalNonRec v dem floats arg' `thenUs` \ (floats', v') -> + returnUs (floats', Var v') -- version that doesn't consider an scc annotation to be trivial. -exprIsTrivial (Var v) - | hasNoBinding v = idArity v == 0 - | otherwise = True +exprIsTrivial (Var v) = True exprIsTrivial (Type _) = True exprIsTrivial (Lit lit) = True exprIsTrivial (App e arg) = isTypeArg arg && exprIsTrivial e @@ -225,13 +345,13 @@ exprIsTrivial other = False -- Dealing with expressions -- --------------------------------------------------------------------------- -corePrepAnExpr :: CloneEnv -> CoreExpr -> UniqSM CoreExpr +corePrepAnExpr :: CorePrepEnv -> CoreExpr -> UniqSM CoreExpr corePrepAnExpr env expr = corePrepExprFloat env expr `thenUs` \ (floats, expr) -> mkBinds floats expr -corePrepExprFloat :: CloneEnv -> CoreExpr -> UniqSM (OrdList FloatingBind, CoreExpr) +corePrepExprFloat :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CoreExpr) -- If -- e ===> (bs, e') -- then @@ -242,45 +362,55 @@ corePrepExprFloat :: CloneEnv -> CoreExpr -> UniqSM (OrdList FloatingBind, CoreE corePrepExprFloat env (Var v) = fiddleCCall v `thenUs` \ v1 -> - let v2 = lookupVarEnv env v1 `orElse` v1 in - maybeSaturate v2 (Var v2) 0 (idType v2) `thenUs` \ app -> - returnUs (nilOL, app) + let + v2 = lookupCorePrepEnv env v1 + in + maybeSaturate v2 (Var v2) 0 emptyFloats (idType v2) corePrepExprFloat env expr@(Type _) - = returnUs (nilOL, expr) + = returnUs (emptyFloats, expr) corePrepExprFloat env expr@(Lit lit) - = returnUs (nilOL, expr) + = returnUs (emptyFloats, expr) corePrepExprFloat env (Let bind body) = corePrepBind env bind `thenUs` \ (env', new_binds) -> corePrepExprFloat env' body `thenUs` \ (floats, new_body) -> - returnUs (new_binds `appOL` floats, new_body) + returnUs (new_binds `appendFloats` floats, new_body) corePrepExprFloat env (Note n@(SCC _) expr) = corePrepAnExpr env expr `thenUs` \ expr1 -> - deLam expr1 `thenUs` \ expr2 -> - returnUs (nilOL, Note n expr2) + deLamFloat expr1 `thenUs` \ (floats, expr2) -> + returnUs (floats, Note n expr2) corePrepExprFloat env (Note other_note expr) = corePrepExprFloat env expr `thenUs` \ (floats, expr') -> returnUs (floats, Note other_note expr') corePrepExprFloat env expr@(Lam _ _) - = corePrepAnExpr env body `thenUs` \ body' -> - returnUs (nilOL, mkLams bndrs body') + = cloneBndrs env bndrs `thenUs` \ (env', bndrs') -> + corePrepAnExpr env' body `thenUs` \ body' -> + returnUs (emptyFloats, mkLams bndrs' body') where (bndrs,body) = collectBinders expr -corePrepExprFloat env (Case scrut bndr alts) - = corePrepExprFloat env scrut `thenUs` \ (floats, scrut') -> - cloneBndr env bndr `thenUs` \ (env', bndr') -> +corePrepExprFloat env (Case scrut bndr ty alts) + = corePrepExprFloat env scrut `thenUs` \ (floats1, scrut1) -> + deLamFloat scrut1 `thenUs` \ (floats2, scrut2) -> + let + bndr1 = bndr `setIdUnfolding` evaldUnfolding + -- Record that the case binder is evaluated in the alternatives + in + cloneBndr env bndr1 `thenUs` \ (env', bndr2) -> mapUs (sat_alt env') alts `thenUs` \ alts' -> - returnUs (floats, mkCase scrut' bndr' alts') + returnUs (floats1 `appendFloats` floats2 , Case scrut2 bndr2 ty alts') where sat_alt env (con, bs, rhs) - = cloneBndrs env bs `thenUs` \ (env', bs') -> - corePrepAnExpr env' rhs `thenUs` \ rhs1 -> + = let + env1 = setGadt env con + in + cloneBndrs env1 bs `thenUs` \ (env2, bs') -> + corePrepAnExpr env2 rhs `thenUs` \ rhs1 -> deLam rhs1 `thenUs` \ rhs2 -> returnUs (con, bs', rhs2) @@ -290,9 +420,7 @@ corePrepExprFloat env expr@(App _ _) -- Now deal with the function case head of - Var fn_id -> maybeSaturate fn_id app depth ty `thenUs` \ app' -> - returnUs (floats, app') - + Var fn_id -> maybeSaturate fn_id app depth floats ty _other -> returnUs (floats, app) where @@ -310,7 +438,7 @@ corePrepExprFloat env expr@(App _ _) (CoreExpr,Int), -- the head of the application, -- and no. of args it was applied to Type, -- type of the whole expr - OrdList FloatingBind, -- any floats we pulled out + Floats, -- any floats we pulled out [Demand]) -- remaining argument demands collect_args (App fun arg@(Type arg_ty)) depth @@ -327,17 +455,20 @@ corePrepExprFloat env expr@(App _ _) splitFunTy_maybe fun_ty in corePrepArg env arg (mkDemTy ss1 arg_ty) `thenUs` \ (fs, arg') -> - returnUs (App fun' arg', hd, res_ty, fs `appOL` floats, ss_rest) + returnUs (App fun' arg', hd, res_ty, fs `appendFloats` floats, ss_rest) collect_args (Var v) depth = fiddleCCall v `thenUs` \ v1 -> - let v2 = lookupVarEnv env v1 `orElse` v1 in - returnUs (Var v2, (Var v2, depth), idType v2, nilOL, stricts) + let + v2 = lookupCorePrepEnv env v1 + in + returnUs (Var v2, (Var v2, depth), idType v2, emptyFloats, stricts) where stricts = case idNewStrictness v of StrictSig (DmdType _ demands _) - | depth >= length demands -> demands - | otherwise -> [] + | listLengthCmp demands depth /= GT -> demands + -- length demands <= depth + | otherwise -> [] -- If depth < length demands, then we have too few args to -- satisfy strictness info so we have to ignore all the -- strictness info, e.g. + (error "urk") @@ -350,23 +481,27 @@ corePrepExprFloat env expr@(App _ _) returnUs (Note (Coerce ty1 ty2) fun', hd, ty1, floats, ss) collect_args (Note note fun) depth - | ignore_note note + | ignore_note note -- Drop these notes altogether + -- They aren't used by the code generator = collect_args fun depth `thenUs` \ (fun', hd, fun_ty, floats, ss) -> - returnUs (Note note fun', hd, fun_ty, floats, ss) + returnUs (fun', hd, fun_ty, floats, ss) - -- non-variable fun, better let-bind it + -- N-variable fun, better let-bind it + -- ToDo: perhaps we can case-bind rather than let-bind this closure, + -- since it is sure to be evaluated. collect_args fun depth - = corePrepExprFloat env fun `thenUs` \ (fun_floats, fun) -> + = corePrepExprFloat env fun `thenUs` \ (fun_floats, fun') -> newVar ty `thenUs` \ fn_id -> - mkLocalNonRec fn_id onceDem fun_floats fun `thenUs` \ floats -> - returnUs (Var fn_id, (Var fn_id, depth), ty, floats, []) + mkLocalNonRec fn_id onceDem fun_floats fun' `thenUs` \ (floats, fn_id') -> + returnUs (Var fn_id', (Var fn_id', depth), ty, floats, []) where ty = exprType fun - ignore_note InlineCall = True - ignore_note InlineMe = True - ignore_note _other = False - -- we don't ignore SCCs, since they require some code generation + ignore_note (CoreNote _) = True + ignore_note InlineCall = True + ignore_note InlineMe = True + ignore_note _other = False + -- We don't ignore SCCs, since they require some code generation ------------------------------------------------------------------------------ -- Building the saturated syntax @@ -374,109 +509,195 @@ corePrepExprFloat env expr@(App _ _) -- maybeSaturate deals with saturating primops and constructors -- The type is the type of the entire application -maybeSaturate :: Id -> CoreExpr -> Int -> Type -> UniqSM CoreExpr -maybeSaturate fn expr n_args ty - | hasNoBinding fn = saturate_it - | otherwise = returnUs expr +maybeSaturate :: Id -> CoreExpr -> Int -> Floats -> Type -> UniqSM (Floats, CoreExpr) +maybeSaturate fn expr n_args floats ty + | Just DataToTagOp <- isPrimOpId_maybe fn -- DataToTag must have an evaluated arg + -- A gruesome special case + = saturate_it `thenUs` \ sat_expr -> + + -- OK, now ensure that the arg is evaluated. + -- But (sigh) take into account the lambdas we've now introduced + let + (eta_bndrs, eta_body) = collectBinders sat_expr + in + eval_data2tag_arg eta_body `thenUs` \ (eta_floats, eta_body') -> + if null eta_bndrs then + returnUs (floats `appendFloats` eta_floats, eta_body') + else + mkBinds eta_floats eta_body' `thenUs` \ eta_body'' -> + returnUs (floats, mkLams eta_bndrs eta_body'') + + | hasNoBinding fn = saturate_it `thenUs` \ sat_expr -> + returnUs (floats, sat_expr) + + | otherwise = returnUs (floats, expr) + where fn_arity = idArity fn excess_arity = fn_arity - n_args - saturate_it = getUniquesUs `thenUs` \ us -> - returnUs (etaExpand excess_arity us expr ty) + + saturate_it :: UniqSM CoreExpr + saturate_it | excess_arity == 0 = returnUs expr + | otherwise = getUniquesUs `thenUs` \ us -> + returnUs (etaExpand excess_arity us expr ty) + + -- Ensure that the argument of DataToTagOp is evaluated + eval_data2tag_arg :: CoreExpr -> UniqSM (Floats, CoreExpr) + eval_data2tag_arg app@(fun `App` arg) + | exprIsHNF arg -- Includes nullary constructors + = returnUs (emptyFloats, app) -- The arg is evaluated + | otherwise -- Arg not evaluated, so evaluate it + = newVar (exprType arg) `thenUs` \ arg_id -> + let + arg_id1 = setIdUnfolding arg_id evaldUnfolding + in + returnUs (unitFloat (FloatCase arg_id1 arg False ), + fun `App` Var arg_id1) + + eval_data2tag_arg (Note note app) -- Scc notes can appear + = eval_data2tag_arg app `thenUs` \ (floats, app') -> + returnUs (floats, Note note app') + + eval_data2tag_arg other -- Should not happen + = pprPanic "eval_data2tag" (ppr other) + -- --------------------------------------------------------------------------- -- Precipitating the floating bindings -- --------------------------------------------------------------------------- --- mkLocalNonRec is used only for local bindings -mkLocalNonRec :: Id -> RhsDemand -- Lhs: id with demand - -> OrdList FloatingBind -> CoreExpr -- Rhs: let binds in body - -> UniqSM (OrdList FloatingBind) +floatRhs :: TopLevelFlag -> RecFlag + -> Id + -> (Floats, CoreExpr) -- Rhs: let binds in body + -> UniqSM (Floats, -- Floats out of this bind + CoreExpr) -- Final Rhs -mkLocalNonRec bndr dem floats rhs - | exprIsValue rhs && allLazy floats -- Notably constructor applications - = -- Why the test for allLazy? You might think that the only - -- floats we can get out of a value are eta expansions - -- e.g. C $wJust ==> let s = \x -> $wJust x in C s - -- Here we want to float the s binding. - -- - -- But if the programmer writes this: - -- f x = case x of { (a,b) -> \y -> a } - -- then the strictness analyser may say that f has strictness "S" - -- Later the eta expander will transform to - -- f x y = case x of { (a,b) -> a } - -- So now f has arity 2. Now CorePrep may see - -- v = f E - -- so the E argument will turn into a FloatCase. - -- Indeed we should end up with - -- v = case E of { r -> f r } - -- That is, we should not float, even though (f r) is a value - -- - -- Similarly, given +floatRhs top_lvl is_rec bndr (floats, rhs) + | isTopLevel top_lvl || exprIsHNF rhs, -- Float to expose value or + allLazy top_lvl is_rec floats -- at top level + = -- Why the test for allLazy? -- v = f (x `divInt#` y) -- we don't want to float the case, even if f has arity 2, -- because floating the case would make it evaluated too early - -- - -- Finally, eta-expand the RHS, for the benefit of the code gen - -- This might not have happened already, because eta expansion - -- is done by the simplifier only when there at least one lambda already. - -- - -- NB: we could refrain when the RHS is trivial (which can happen - -- for exported things. This would reduce the amount of code - -- generated (a little) and make things a little words for - -- code compiled without -O. The case in point is data constructor - -- wrappers. - -- - getUniquesUs `thenUs` \ us -> + returnUs (floats, rhs) + + | otherwise + -- Don't float; the RHS isn't a value + = mkBinds floats rhs `thenUs` \ rhs' -> + returnUs (emptyFloats, rhs') + +-- mkLocalNonRec is used only for *nested*, *non-recursive* bindings +mkLocalNonRec :: Id -> RhsDemand -- Lhs: id with demand + -> Floats -> CoreExpr -- Rhs: let binds in body + -> UniqSM (Floats, Id) -- The new Id may have an evaldUnfolding, + -- to record that it's been evaluated + +mkLocalNonRec bndr dem floats rhs + | isUnLiftedType (idType bndr) + -- If this is an unlifted binding, we always make a case for it. + = ASSERT( not (isUnboxedTupleType (idType bndr)) ) let - rhs' = etaExpand (exprArity rhs) us rhs bndr_ty + float = FloatCase bndr rhs (exprOkForSpeculation rhs) in - returnUs (floats `snocOL` FloatLet (NonRec bndr rhs')) - - | isUnLiftedType bndr_rep_ty || isStrict dem - -- It's a strict let, or the binder is unlifted, - -- so we definitely float all the bindings - = ASSERT( not (isUnboxedTupleType bndr_rep_ty) ) - returnUs (floats `snocOL` FloatCase bndr rhs (exprOkForSpeculation rhs)) + returnUs (addFloat floats float, evald_bndr) + + | isStrict dem + -- It's a strict let so we definitely float all the bindings + = let -- Don't make a case for a value binding, + -- even if it's strict. Otherwise we get + -- case (\x -> e) of ...! + float | exprIsHNF rhs = FloatLet (NonRec bndr rhs) + | otherwise = FloatCase bndr rhs (exprOkForSpeculation rhs) + in + returnUs (addFloat floats float, evald_bndr) | otherwise - -- Don't float; the RHS isn't a value - = mkBinds floats rhs `thenUs` \ rhs' -> - returnUs (unitOL (FloatLet (NonRec bndr rhs'))) + = floatRhs NotTopLevel NonRecursive bndr (floats, rhs) `thenUs` \ (floats', rhs') -> + returnUs (addFloat floats' (FloatLet (NonRec bndr rhs')), + if exprIsHNF rhs' then evald_bndr else bndr) where - bndr_ty = idType bndr - bndr_rep_ty = repType bndr_ty + evald_bndr = bndr `setIdUnfolding` evaldUnfolding + -- Record if the binder is evaluated + -mkBinds :: OrdList FloatingBind -> CoreExpr -> UniqSM CoreExpr -mkBinds binds body +mkBinds :: Floats -> CoreExpr -> UniqSM CoreExpr +mkBinds (Floats _ binds) body | isNilOL binds = returnUs body | otherwise = deLam body `thenUs` \ body' -> + -- Lambdas are not allowed as the body of a 'let' returnUs (foldrOL mk_bind body' binds) where - mk_bind (FloatCase bndr rhs _) body = mkCase rhs bndr [(DEFAULT, [], body)] + mk_bind (FloatCase bndr rhs _) body = Case rhs bndr (exprType body) [(DEFAULT, [], body)] mk_bind (FloatLet bind) body = Let bind body +etaExpandRhs bndr rhs + = -- Eta expand to match the arity claimed by the binder + -- Remember, after CorePrep we must not change arity + -- + -- Eta expansion might not have happened already, + -- because it is done by the simplifier only when + -- there at least one lambda already. + -- + -- NB1:we could refrain when the RHS is trivial (which can happen + -- for exported things). This would reduce the amount of code + -- generated (a little) and make things a little words for + -- code compiled without -O. The case in point is data constructor + -- wrappers. + -- + -- NB2: we have to be careful that the result of etaExpand doesn't + -- invalidate any of the assumptions that CorePrep is attempting + -- to establish. One possible cause is eta expanding inside of + -- an SCC note - we're now careful in etaExpand to make sure the + -- SCC is pushed inside any new lambdas that are generated. + -- + -- NB3: It's important to do eta expansion, and *then* ANF-ising + -- f = /\a -> g (h 3) -- h has arity 2 + -- If we ANF first we get + -- f = /\a -> let s = h 3 in g s + -- and now eta expansion gives + -- f = /\a -> \ y -> (let s = h 3 in g s) y + -- which is horrible. + -- Eta expanding first gives + -- f = /\a -> \y -> let s = h 3 in g s y + -- + getUniquesUs `thenUs` \ us -> + returnUs (etaExpand arity us rhs (idType bndr)) + where + -- For a GlobalId, take the Arity from the Id. + -- It was set in CoreTidy and must not change + -- For all others, just expand at will + arity | isGlobalId bndr = idArity bndr + | otherwise = exprArity rhs + -- --------------------------------------------------------------------------- -- Eliminate Lam as a non-rhs (STG doesn't have such a thing) -- We arrange that they only show up as the RHS of a let(rec) -- --------------------------------------------------------------------------- -deLam :: CoreExpr -> UniqSM CoreExpr +deLam :: CoreExpr -> UniqSM CoreExpr +deLam expr = + deLamFloat expr `thenUs` \ (floats, expr) -> + mkBinds floats expr + + +deLamFloat :: CoreExpr -> UniqSM (Floats, CoreExpr) -- Remove top level lambdas by let-bindinig -deLam (Note n expr) +deLamFloat (Note n expr) = -- You can get things like -- case e of { p -> coerce t (\s -> ...) } - deLam expr `thenUs` \ expr' -> - returnUs (Note n expr') - -deLam expr - | null bndrs = returnUs expr - | otherwise = case tryEta bndrs body of - Just no_lam_result -> returnUs no_lam_result - Nothing -> newVar (exprType expr) `thenUs` \ fn -> - returnUs (Let (NonRec fn expr) (Var fn)) + deLamFloat expr `thenUs` \ (floats, expr') -> + returnUs (floats, Note n expr') + +deLamFloat expr + | null bndrs = returnUs (emptyFloats, expr) + | otherwise + = case tryEta bndrs body of + Just no_lam_result -> returnUs (emptyFloats, no_lam_result) + Nothing -> newVar (exprType expr) `thenUs` \ fn -> + returnUs (unitFloat (FloatLet (NonRec fn expr)), + Var fn) where (bndrs,body) = collectBinders expr @@ -499,7 +720,7 @@ tryEta bndrs expr@(App _ _) n_remaining = length args - length bndrs ok bndr (Var arg) = bndr == arg - ok bndr other = False + ok bndr other = False -- we can't eta reduce something which must be saturated. ok_to_eta_reduce (Var f) = not (hasNoBinding f) @@ -518,55 +739,6 @@ tryEta bndrs _ = Nothing -- ----------------------------------------------------------------------------- --- Do the seq and par transformation --- ----------------------------------------------------------------------------- - -Here we do two pre-codegen transformations: - -1. case seq# a of { - 0 -> seqError ... - DEFAULT -> rhs } - ==> - case a of { DEFAULT -> rhs } - - -2. case par# a of { - 0 -> parError ... - DEFAULT -> rhs } - ==> - case par# a of { - DEFAULT -> rhs } - -NB: seq# :: a -> Int# -- Evaluate value and return anything - par# :: a -> Int# -- Spark value and return anything - -These transformations can't be done earlier, or else we might -think that the expression was strict in the variables in which -rhs is strict --- but that would defeat the purpose of seq and par. - - -\begin{code} -mkCase scrut@(Var fn `App` Type ty `App` arg) bndr alts@(deflt_alt@(DEFAULT,_,rhs) : con_alts) - -- DEFAULT alt is always first - = case isPrimOpId_maybe fn of - Just ParOp -> Case scrut bndr [deflt_alt] - Just SeqOp -> Case arg new_bndr [deflt_alt] - other -> Case scrut bndr alts - where - -- The binder shouldn't be used in the expression! - new_bndr = ASSERT2( not (bndr `elemVarSet` exprFreeVars rhs), ppr bndr ) - setIdType bndr (exprType arg) - -- 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. - -mkCase scrut bndr alts = Case scrut bndr alts -\end{code} - - --- ----------------------------------------------------------------------------- -- Demands -- ----------------------------------------------------------------------------- @@ -580,26 +752,17 @@ mkDem :: Demand -> Bool -> RhsDemand mkDem strict once = RhsDemand (isStrictDmd strict) once mkDemTy :: Demand -> Type -> RhsDemand -mkDemTy strict ty = RhsDemand (isStrictDmd strict) (isOnceTy ty) - -isOnceTy :: Type -> Bool -isOnceTy ty - = -#ifdef USMANY - opt_UsageSPOn && -- can't expect annotations if -fusagesp is off -#endif - once - where - u = uaUTy ty - once | u `eqUsage` usOnce = True - | u `eqUsage` usMany = False - | isTyVarTy u = False -- if unknown at compile-time, is Top ie usMany +mkDemTy strict ty = RhsDemand (isStrictDmd strict) + False {- For now -} bdrDem :: Id -> RhsDemand -bdrDem id = mkDem (idNewDemandInfo id) (isOnceTy (idType id)) +bdrDem id = mkDem (idNewDemandInfo id) + False {- For now -} + +-- safeDem :: RhsDemand +-- safeDem = RhsDemand False False -- always safe to use this -safeDem, onceDem :: RhsDemand -safeDem = RhsDemand False False -- always safe to use this +onceDem :: RhsDemand onceDem = RhsDemand False True -- used at most once \end{code} @@ -613,24 +776,65 @@ onceDem = RhsDemand False True -- used at most once %************************************************************************ \begin{code} +-- --------------------------------------------------------------------------- +-- The environment +-- --------------------------------------------------------------------------- + +data CorePrepEnv = CPE (IdEnv Id) -- Clone local Ids + Bool -- True <=> inside a GADT case; see Note [GADT] + +-- Note [GADT] +-- +-- Be careful with cloning inside GADTs. For example, +-- /\a. \f::a. \x::T a. case x of { T -> f True; ... } +-- The case on x may refine the type of f to be a function type. +-- Without this type refinement, exprType (f True) may simply fail, +-- which is bad. +-- +-- Solution: remember when we are inside a potentially-type-refining case, +-- and in that situation use the type from the old occurrence +-- when looking up occurrences + +emptyCorePrepEnv :: CorePrepEnv +emptyCorePrepEnv = CPE emptyVarEnv False + +extendCorePrepEnv :: CorePrepEnv -> Id -> Id -> CorePrepEnv +extendCorePrepEnv (CPE env gadt) id id' = CPE (extendVarEnv env id id') gadt + +lookupCorePrepEnv :: CorePrepEnv -> Id -> Id +-- See Note [GADT] above +lookupCorePrepEnv (CPE env gadt) id + = case lookupVarEnv env id of + Nothing -> id + Just id' | gadt -> setIdType id' (idType id) + | otherwise -> id' + +setGadt :: CorePrepEnv -> AltCon -> CorePrepEnv +setGadt env@(CPE id_env _) (DataAlt data_con) | not (isVanillaDataCon data_con) = CPE id_env True +setGadt env other = env + + ------------------------------------------------------------------------------ -- Cloning binders -- --------------------------------------------------------------------------- -cloneBndrs :: CloneEnv -> [Var] -> UniqSM (CloneEnv, [Var]) +cloneBndrs :: CorePrepEnv -> [Var] -> UniqSM (CorePrepEnv, [Var]) cloneBndrs env bs = mapAccumLUs cloneBndr env bs -cloneBndr :: CloneEnv -> Var -> UniqSM (CloneEnv, Var) +cloneBndr :: CorePrepEnv -> Var -> UniqSM (CorePrepEnv, Var) cloneBndr env bndr - | isId bndr && isLocalId bndr -- Top level things, which we don't want - -- to clone, have become GlobalIds by now + | isLocalId bndr = getUniqueUs `thenUs` \ uniq -> let bndr' = setVarUnique bndr uniq in - returnUs (extendVarEnv env bndr bndr', bndr') + returnUs (extendCorePrepEnv env bndr bndr', bndr') - | otherwise = returnUs (env, bndr) + | otherwise -- Top level things, which we don't want + -- to clone, have become GlobalIds by now + -- And we don't clone tyvars + = returnUs (env, bndr) + ------------------------------------------------------------------------------ -- Cloning ccall Ids; each must have a unique name, @@ -649,7 +853,7 @@ fiddleCCall id newVar :: Type -> UniqSM Id newVar ty - = getUniqueUs `thenUs` \ uniq -> - seqType ty `seq` - returnUs (mkSysLocal SLIT("sat") uniq ty) + = seqType ty `seq` + getUniqueUs `thenUs` \ uniq -> + returnUs (mkSysLocal FSLIT("sat") uniq ty) \end{code}