X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=cd610a9865325f65bb7a0ebcc5f303d4f9f8dd5c;hb=f37e239fb5e81fc493e0ea1af98178bf1f7ceaba;hp=1e510421e72a1c94632f5c100e6faadc5557f97f;hpb=f2dcf256399e9a2de6343c625630b51f8abf4863;p=ghc-hetmet.git diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs index 1e51042..cd610a9 100644 --- a/compiler/simplCore/SimplUtils.lhs +++ b/compiler/simplCore/SimplUtils.lhs @@ -5,7 +5,7 @@ \begin{code} module SimplUtils ( - mkLam, mkCase, + mkLam, mkCase, -- Inlining, preInlineUnconditionally, postInlineUnconditionally, activeInline, activeRule, @@ -25,29 +25,35 @@ module SimplUtils ( import SimplEnv import DynFlags ( SimplifierSwitch(..), SimplifierMode(..), - DynFlag(..), dopt ) + DynFlags, DynFlag(..), dopt ) import StaticFlags ( opt_UF_UpdateInPlace, opt_SimplNoPreInlining, opt_RulesOff ) import CoreSyn import CoreFVs ( exprFreeVars ) import CoreUtils ( cheapEqExpr, exprType, exprIsTrivial, - etaExpand, exprEtaExpandArity, bindNonRec, mkCoerce2, - findDefault, exprOkForSpeculation, exprIsHNF, mergeAlts + etaExpand, exprEtaExpandArity, bindNonRec, mkCoerce, + findDefault, exprOkForSpeculation, exprIsHNF, mergeAlts, + applyTypeToArgs ) import Literal ( mkStringLit ) import CoreUnfold ( smallEnoughToInline ) -import MkId ( eRROR_ID ) +import MkId ( eRROR_ID, wrapNewTypeBody ) import Id ( Id, idType, isDataConWorkId, idOccInfo, isDictId, - isDeadBinder, idNewDemandInfo, isExportedId, + isDeadBinder, idNewDemandInfo, isExportedId, mkSysLocal, idUnfolding, idNewStrictness, idInlinePragma, idHasRules ) import NewDemand ( isStrictDmd, isBotRes, splitStrictSig ) import SimplMonad +import Var ( tyVarKind, mkTyVar ) +import Name ( mkSysTvName ) import Type ( Type, splitFunTys, dropForAlls, isStrictType, - splitTyConApp_maybe, tyConAppArgs + splitTyConApp_maybe, tyConAppArgs, mkTyVarTys ) +import Coercion ( isEqPredTy ) -import TyCon ( tyConDataCons_maybe ) -import DataCon ( dataConRepArity ) +import Coercion ( Coercion, mkUnsafeCoercion, coercionKind ) +import TyCon ( tyConDataCons_maybe, isClosedNewTyCon ) +import DataCon ( DataCon, dataConRepArity, dataConExTyVars, + dataConInstArgTys, dataConTyCon ) import VarSet import BasicTypes ( TopLevelFlag(..), isNotTopLevel, OccInfo(..), isLoopBreaker, isOneOcc, Activation, isAlwaysActive, isActive ) @@ -75,12 +81,14 @@ data SimplCont -- Strict contexts -- (b) This is an argument of a function that has RULES -- Inlining the call might allow the rule to fire - | CoerceIt OutType -- The To-type, simplified + | CoerceIt OutCoercion -- The coercion simplified SimplCont | ApplyTo DupFlag - InExpr SimplEnv -- The argument, as yet unsimplified, - SimplCont -- and its environment + CoreExpr -- The argument + (Maybe SimplEnv) -- (Just se) => the arg is un-simplified and this is its subst-env + -- Nothing => the arg is already simplified; don't repeatedly simplify it! + SimplCont -- and its environment | Select DupFlag InId [InAlt] SimplEnv -- The case binder, alts, and subst-env @@ -112,7 +120,7 @@ instance Outputable SimplCont where ppr (ArgOf _ _ _ _) = ptext SLIT("ArgOf...") ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$ (nest 4 (ppr alts)) $$ ppr cont - ppr (CoerceIt ty cont) = (ptext SLIT("CoerceIt") <+> ppr ty) $$ ppr cont + ppr (CoerceIt co cont) = (ptext SLIT("CoerceIt") <+> ppr co) $$ ppr cont data DupFlag = OkToDup | NoDup @@ -121,6 +129,7 @@ instance Outputable DupFlag where ppr NoDup = ptext SLIT("nodup") + ------------------- mkBoringStop :: OutType -> SimplCont mkBoringStop ty = Stop ty AnArg False @@ -154,13 +163,15 @@ discardableCont (Stop _ _ _) = False discardableCont (CoerceIt _ cont) = discardableCont cont discardableCont other = True -discardCont :: SimplCont -- A continuation, expecting +discardCont :: Type -- The type expected + -> SimplCont -- A continuation, expecting the previous type -> SimplCont -- Replace the continuation with a suitable coerce -discardCont cont = case cont of +discardCont from_ty cont = case cont of Stop to_ty is_rhs _ -> cont - other -> CoerceIt to_ty (mkBoringStop to_ty) + other -> CoerceIt co (mkBoringStop to_ty) where - to_ty = contResultType cont + co = mkUnsafeCoercion from_ty to_ty + to_ty = contResultType cont ------------------- contResultType :: SimplCont -> OutType @@ -181,18 +192,18 @@ countArgs (ApplyTo _ arg se cont) = 1 + countArgs cont countArgs other = 0 ------------------- -pushContArgs :: SimplEnv -> [OutArg] -> SimplCont -> SimplCont +pushContArgs ::[OutArg] -> SimplCont -> SimplCont -- Pushes args with the specified environment -pushContArgs env [] cont = cont -pushContArgs env (arg : args) cont = ApplyTo NoDup arg env (pushContArgs env args cont) +pushContArgs [] cont = cont +pushContArgs (arg : args) cont = ApplyTo NoDup arg Nothing (pushContArgs args cont) \end{code} \begin{code} getContArgs :: SwitchChecker -> OutId -> SimplCont - -> ([(InExpr, SimplEnv, Bool)], -- Arguments; the Bool is true for strict args - SimplCont) -- Remaining continuation + -> ([(InExpr, Maybe SimplEnv, Bool)], -- Arguments; the Bool is true for strict args + SimplCont) -- Remaining continuation -- getContArgs id k = (args, k', inl) -- args are the leading ApplyTo items in k -- (i.e. outermost comes first) @@ -228,17 +239,24 @@ getContArgs chkr fun orig_cont -- Then, especially in the first of these cases, we'd like to discard -- the continuation, leaving just the bottoming expression. But the -- type might not be right, so we may have to add a coerce. - go acc ss cont - | null ss && discardableCont cont = (reverse acc, discardCont cont) - | otherwise = (reverse acc, cont) + go acc ss cont + | null ss && discardableCont cont = (args, discardCont hole_ty cont) + | otherwise = (args, cont) + where + args = reverse acc + hole_ty = applyTypeToArgs (Var fun) (idType fun) + [substExpr_mb se arg | (arg,se,_) <- args] + substExpr_mb Nothing arg = arg + substExpr_mb (Just se) arg = substExpr se arg + ---------------------------- vanilla_stricts, computed_stricts :: [Bool] vanilla_stricts = repeat False computed_stricts = zipWith (||) fun_stricts arg_stricts ---------------------------- - (val_arg_tys, _) = splitFunTys (dropForAlls (idType fun)) + (val_arg_tys, res_ty) = splitFunTys (dropForAlls (idType fun)) arg_stricts = map isStrictType val_arg_tys ++ repeat False -- These argument types are used as a cheap and cheerful way to find -- unboxed arguments, which must be strict. But it's an InType @@ -374,12 +392,12 @@ interestingCallContext :: Bool -- False <=> no args at all interestingCallContext some_args some_val_args cont = interesting cont where - interesting (Select _ _ _ _ _) = some_args - interesting (ApplyTo _ _ _ _) = True -- Can happen if we have (coerce t (f x)) y + interesting (Select {}) = some_args + interesting (ApplyTo {}) = True -- Can happen if we have (coerce t (f x)) y -- Perhaps True is a bit over-keen, but I've -- seen (coerce f) x, where f has an INLINE prag, -- So we have to give some motivaiton for inlining it - interesting (ArgOf _ _ _ _) = some_val_args + interesting (ArgOf {}) = some_val_args interesting (Stop ty _ interesting) = some_val_args && interesting interesting (CoerceIt _ cont) = interesting cont -- If this call is the arg of a strict function, the context @@ -695,7 +713,13 @@ our new view that inlining is like a RULE, so I'm sticking to the 'active' story for now. \begin{code} -postInlineUnconditionally :: SimplEnv -> TopLevelFlag -> OutId -> OccInfo -> OutExpr -> Unfolding -> Bool +postInlineUnconditionally + :: SimplEnv -> TopLevelFlag + -> InId -- The binder (an OutId would be fine too) + -> OccInfo -- From the InId + -> OutExpr + -> Unfolding + -> Bool postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding | not active = False | isLoopBreaker occ_info = False @@ -703,19 +727,28 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding | exprIsTrivial rhs = True | otherwise = case occ_info of - OneOcc in_lam one_br int_cxt - -> (one_br || smallEnoughToInline unfolding) -- Small enough to dup + -- The point of examining occ_info here is that for *non-values* + -- that occur outside a lambda, the call-site inliner won't have + -- a chance (becuase it doesn't know that the thing + -- only occurs once). The pre-inliner won't have gotten + -- it either, if the thing occurs in more than one branch + -- So the main target is things like + -- let x = f y in + -- case v of + -- True -> case x of ... + -- False -> case x of ... + -- I'm not sure how important this is in practice + OneOcc in_lam one_br int_cxt -- OneOcc => no work-duplication issue + -> smallEnoughToInline unfolding -- Small enough to dup -- ToDo: consider discount on smallEnoughToInline if int_cxt is true -- - -- NB: Do we want to inline arbitrarily big things becuase - -- one_br is True? that can lead to inline cascades. But - -- preInlineUnconditionlly has dealt with all the common cases - -- so perhaps it's worth the risk. Here's an example - -- let f = if b then Left (\x.BIG) else Right (\y.BIG) - -- in \y. ....f.... - -- We can't preInlineUnconditionally because that woud invalidate - -- the occ info for b. Yet f is used just once, and duplicating - -- the case work is fine (exprIsCheap). + -- NB: Do NOT inline arbitrarily big things, even if one_br is True + -- Reason: doing so risks exponential behaviour. We simplify a big + -- expression, inline it, and simplify it again. But if the + -- very same thing happens in the big expression, we get + -- exponential cost! + -- PRINCIPLE: when we've already simplified an expression once, + -- make sure that we only inline it if it's reasonably small. && ((isNotTopLevel top_lvl && not in_lam) || -- But outside a lambda, we want to be reasonably aggressive @@ -731,18 +764,25 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding -- int_cxt to prevent us inlining inside a lambda without some -- good reason. See the notes on int_cxt in preInlineUnconditionally + IAmDead -> True -- This happens; for example, the case_bndr during case of + -- known constructor: case (a,b) of x { (p,q) -> ... } + -- Here x isn't mentioned in the RHS, so we don't want to + -- create the (dead) let-binding let x = (a,b) in ... + other -> False - -- The point here is that for *non-values* that occur - -- outside a lambda, the call-site inliner won't have - -- a chance (becuase it doesn't know that the thing - -- only occurs once). The pre-inliner won't have gotten - -- it either, if the thing occurs in more than one branch - -- So the main target is things like - -- let x = f y in - -- case v of - -- True -> case x of ... - -- False -> case x of ... - -- I'm not sure how important this is in practice + +-- Here's an example that we don't handle well: +-- let f = if b then Left (\x.BIG) else Right (\y.BIG) +-- in \y. ....case f of {...} .... +-- Here f is used just once, and duplicating the case work is fine (exprIsCheap). +-- But +-- * We can't preInlineUnconditionally because that woud invalidate +-- the occ info for b. +-- * We can't postInlineUnconditionally because the RHS is big, and +-- that risks exponential behaviour +-- * We can't call-site inline, because the rhs is big +-- Alas! + where active = case getMode env of SimplGently -> isAlwaysActive prag @@ -818,7 +858,7 @@ mkLam env bndrs body cont | dopt Opt_DoLambdaEtaExpansion dflags, any isRuntimeVar bndrs - = tryEtaExpansion body `thenSmpl` \ body' -> + = tryEtaExpansion dflags body `thenSmpl` \ body' -> returnSmpl (emptyFloats env, mkLams bndrs body') {- Sept 01: I'm experimenting with getting the @@ -901,13 +941,13 @@ when computing arity; and etaExpand adds the coerces as necessary when actually computing the expansion. \begin{code} -tryEtaExpansion :: OutExpr -> SimplM OutExpr +tryEtaExpansion :: DynFlags -> OutExpr -> SimplM OutExpr -- There is at least one runtime binder in the binders -tryEtaExpansion body +tryEtaExpansion dflags body = getUniquesSmpl `thenSmpl` \ us -> returnSmpl (etaExpand fun_arity us body (exprType body)) where - fun_arity = exprEtaExpandArity body + fun_arity = exprEtaExpandArity dflags body \end{code} @@ -1099,6 +1139,7 @@ tryRhsTyLam env tyvars body -- Only does something if there's a let %* * %************************************************************************ + mkCase puts a case expression back together, trying various transformations first. \begin{code} @@ -1421,28 +1462,32 @@ mkCase1 scrut case_bndr ty [(con,bndrs,rhs)] mkCase1 scrut case_bndr ty alts -- Identity case | all identity_alt alts = tick (CaseIdentity case_bndr) `thenSmpl_` - returnSmpl (re_note scrut) + returnSmpl (re_cast scrut) where - identity_alt (con, args, rhs) = de_note rhs `cheapEqExpr` identity_rhs con args + identity_alt (con, args, rhs) = de_cast rhs `cheapEqExpr` mk_id_rhs con args - identity_rhs (DataAlt con) args = mkConApp con (arg_tys ++ map varToCoreExpr args) - identity_rhs (LitAlt lit) _ = Lit lit - identity_rhs DEFAULT _ = Var case_bndr + mk_id_rhs (DataAlt con) args = mkConApp con (arg_tys ++ varsToCoreExprs args) + mk_id_rhs (LitAlt lit) _ = Lit lit + mk_id_rhs DEFAULT _ = Var case_bndr arg_tys = map Type (tyConAppArgs (idType case_bndr)) -- We've seen this: - -- case coerce T e of x { _ -> coerce T' x } - -- And we definitely want to eliminate this case! - -- So we throw away notes from the RHS, and reconstruct - -- (at least an approximation) at the other end - de_note (Note _ e) = de_note e - de_note e = e - - -- re_note wraps a coerce if it might be necessary - re_note scrut = case head alts of - (_,_,rhs1@(Note _ _)) -> mkCoerce2 (exprType rhs1) (idType case_bndr) scrut - other -> scrut + -- case e of x { _ -> x `cast` c } + -- And we definitely want to eliminate this case, to give + -- e `cast` c + -- So we throw away the cast from the RHS, and reconstruct + -- it at the other end. All the RHS casts must be the same + -- if (all identity_alt alts) holds. + -- + -- Don't worry about nested casts, because the simplifier combines them + de_cast (Cast e _) = e + de_cast e = e + + re_cast scrut = case head alts of + (_,_,Cast _ co) -> Cast scrut co + other -> scrut + --------------------------------------------------