X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=c2128932150b992105119de922aed63979d97ca5;hp=6d2250550ebf376ce0e142124d613791afc7955c;hb=4bc25e8c30559b7a6a87b39afcc79340ae778788;hpb=30c122df62ec75f9ed7f392f24c2925675bf1d06 diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs index 6d22505..c212893 100644 --- a/compiler/simplCore/SimplUtils.lhs +++ b/compiler/simplCore/SimplUtils.lhs @@ -4,13 +4,6 @@ \section[SimplUtils]{The simplifier utilities} \begin{code} -{-# OPTIONS -w #-} --- The above warning supression flag is a temporary kludge. --- While working on this module you are encouraged to remove it and fix --- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings --- for details - module SimplUtils ( -- Rebuilding mkLam, mkCase, prepareAlts, bindCaseBndr, @@ -23,7 +16,7 @@ module SimplUtils ( SimplCont(..), DupFlag(..), ArgInfo(..), contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, countValArgs, countArgs, splitInlineCont, - mkBoringStop, mkLazyArgStop, mkRhsStop, contIsRhsOrArg, + mkBoringStop, mkLazyArgStop, contIsRhsOrArg, interestingCallContext, interestingArgContext, interestingArg, mkArgInfo, @@ -41,17 +34,16 @@ import qualified CoreSubst import PprCore import CoreFVs import CoreUtils -import Literal +import CoreArity ( etaExpand, exprEtaExpandArity ) import CoreUnfold -import MkId import Name import Id import Var ( isCoVar ) import NewDemand import SimplMonad import Type hiding( substTy ) +import Coercion ( coercionKind ) import TyCon -import DataCon import Unify ( dataConCannotMatch ) import VarSet import BasicTypes @@ -93,7 +85,6 @@ Key points: \begin{code} data SimplCont = Stop -- An empty context, or hole, [] - OutType -- Type of the result CallCtxt -- True <=> There is something interesting about -- the context, and hence the inliner -- should be a bit keener (see interestingCallContext) @@ -122,7 +113,7 @@ data SimplCont SimplCont | StrictArg -- e C - OutExpr OutType -- e and its type + OutExpr -- e CallCtxt -- Whether *this* argument position is interesting ArgInfo -- Whether the function at the head of e has rules, etc SimplCont -- plus strictness flags for *further* args @@ -140,72 +131,78 @@ data ArgInfo } instance Outputable SimplCont where - ppr (Stop ty _) = ptext SLIT("Stop") <+> ppr ty - ppr (ApplyTo dup arg se cont) = ((ptext SLIT("ApplyTo") <+> ppr dup <+> pprParendExpr arg) + ppr (Stop interesting) = ptext (sLit "Stop") <> brackets (ppr interesting) + ppr (ApplyTo dup arg _ cont) = ((ptext (sLit "ApplyTo") <+> ppr dup <+> pprParendExpr arg) {- $$ nest 2 (pprSimplEnv se) -}) $$ ppr cont - ppr (StrictBind b _ _ _ cont) = (ptext SLIT("StrictBind") <+> ppr b) $$ ppr cont - ppr (StrictArg f _ _ _ cont) = (ptext SLIT("StrictArg") <+> ppr f) $$ ppr cont - ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$ + ppr (StrictBind b _ _ _ cont) = (ptext (sLit "StrictBind") <+> ppr b) $$ ppr cont + ppr (StrictArg f _ _ cont) = (ptext (sLit "StrictArg") <+> ppr f) $$ ppr cont + ppr (Select dup bndr alts _ cont) = (ptext (sLit "Select") <+> ppr dup <+> ppr bndr) $$ (nest 4 (ppr alts)) $$ ppr cont - ppr (CoerceIt co cont) = (ptext SLIT("CoerceIt") <+> ppr co) $$ ppr cont + ppr (CoerceIt co cont) = (ptext (sLit "CoerceIt") <+> ppr co) $$ ppr cont data DupFlag = OkToDup | NoDup instance Outputable DupFlag where - ppr OkToDup = ptext SLIT("ok") - ppr NoDup = ptext SLIT("nodup") + ppr OkToDup = ptext (sLit "ok") + ppr NoDup = ptext (sLit "nodup") ------------------- -mkBoringStop :: OutType -> SimplCont -mkBoringStop ty = Stop ty BoringCtxt - -mkLazyArgStop :: OutType -> CallCtxt -> SimplCont -mkLazyArgStop ty cci = Stop ty cci +mkBoringStop :: SimplCont +mkBoringStop = Stop BoringCtxt -mkRhsStop :: OutType -> SimplCont -mkRhsStop ty = Stop ty BoringCtxt +mkLazyArgStop :: CallCtxt -> SimplCont +mkLazyArgStop cci = Stop cci ------------------- -contIsRhsOrArg (Stop {}) = True -contIsRhsOrArg (StrictBind {}) = True -contIsRhsOrArg (StrictArg {}) = True -contIsRhsOrArg other = False +contIsRhsOrArg :: SimplCont -> Bool +contIsRhsOrArg (Stop {}) = True +contIsRhsOrArg (StrictBind {}) = True +contIsRhsOrArg (StrictArg {}) = True +contIsRhsOrArg _ = False ------------------- contIsDupable :: SimplCont -> Bool -contIsDupable (Stop {}) = True +contIsDupable (Stop {}) = True contIsDupable (ApplyTo OkToDup _ _ _) = True contIsDupable (Select OkToDup _ _ _ _) = True contIsDupable (CoerceIt _ cont) = contIsDupable cont -contIsDupable other = False +contIsDupable _ = False ------------------- contIsTrivial :: SimplCont -> Bool -contIsTrivial (Stop {}) = True +contIsTrivial (Stop {}) = True contIsTrivial (ApplyTo _ (Type _) _ cont) = contIsTrivial cont -contIsTrivial (CoerceIt _ cont) = contIsTrivial cont -contIsTrivial other = False +contIsTrivial (CoerceIt _ cont) = contIsTrivial cont +contIsTrivial _ = False ------------------- -contResultType :: SimplCont -> OutType -contResultType (Stop to_ty _) = to_ty -contResultType (StrictArg _ _ _ _ cont) = contResultType cont -contResultType (StrictBind _ _ _ _ cont) = contResultType cont -contResultType (ApplyTo _ _ _ cont) = contResultType cont -contResultType (CoerceIt _ cont) = contResultType cont -contResultType (Select _ _ _ _ cont) = contResultType cont +contResultType :: SimplEnv -> OutType -> SimplCont -> OutType +contResultType env ty cont + = go cont ty + where + subst_ty se ty = substTy (se `setInScope` env) ty + + go (Stop {}) ty = ty + go (CoerceIt co cont) _ = go cont (snd (coercionKind co)) + go (StrictBind _ bs body se cont) _ = go cont (subst_ty se (exprType (mkLams bs body))) + go (StrictArg fn _ _ cont) _ = go cont (funResultTy (exprType fn)) + go (Select _ _ alts se cont) _ = go cont (subst_ty se (coreAltsType alts)) + go (ApplyTo _ arg se cont) ty = go cont (apply_to_arg ty arg se) + + apply_to_arg ty (Type ty_arg) se = applyTy ty (subst_ty se ty_arg) + apply_to_arg ty _ _ = funResultTy ty ------------------- countValArgs :: SimplCont -> Int -countValArgs (ApplyTo _ (Type ty) se cont) = countValArgs cont -countValArgs (ApplyTo _ val_arg se cont) = 1 + countValArgs cont -countValArgs other = 0 +countValArgs (ApplyTo _ (Type _) _ cont) = countValArgs cont +countValArgs (ApplyTo _ _ _ cont) = 1 + countValArgs cont +countValArgs _ = 0 countArgs :: SimplCont -> Int -countArgs (ApplyTo _ arg se cont) = 1 + countArgs cont -countArgs other = 0 +countArgs (ApplyTo _ _ _ cont) = 1 + countArgs cont +countArgs _ = 0 contArgs :: SimplCont -> ([OutExpr], SimplCont) -- Uses substitution to turn each arg into an OutExpr @@ -231,13 +228,21 @@ splitInlineCont :: SimplCont -> Maybe (SimplCont, SimplCont) -- See test simpl017 (and Trac #1627) for a good example of why this is important splitInlineCont (ApplyTo dup (Type ty) se c) - | Just (c1, c2) <- splitInlineCont c = Just (ApplyTo dup (Type ty) se c1, c2) -splitInlineCont cont@(Stop ty _) = Just (mkBoringStop ty, cont) -splitInlineCont cont@(StrictBind bndr _ _ se _) = Just (mkBoringStop (substTy se (idType bndr)), cont) -splitInlineCont cont@(StrictArg _ fun_ty _ _ _) = Just (mkBoringStop (funArgTy fun_ty), cont) -splitInlineCont other = Nothing - -- NB: the calculation of the type for mkBoringStop is an annoying - -- duplication of the same calucation in mkDupableCont + | Just (c1, c2) <- splitInlineCont c = Just (ApplyTo dup (Type ty) se c1, c2) +splitInlineCont cont@(Stop {}) = Just (mkBoringStop, cont) +splitInlineCont cont@(StrictBind {}) = Just (mkBoringStop, cont) +splitInlineCont _ = Nothing + -- NB: we dissolve an InlineMe in any strict context, + -- not just function aplication. + -- E.g. foldr k z (__inline_me (case x of p -> build ...)) + -- Here we want to get rid of the __inline_me__ so we + -- can float the case, and see foldr/build + -- + -- However *not* in a strict RHS, else we get + -- let f = __inline_me__ (\x. e) in ...f... + -- Now if f is guaranteed to be called, hence a strict binding + -- we don't thereby want to dissolve the __inline_me__; for + -- example, 'f' might be a wrapper, so we'd inline the worker \end{code} @@ -265,7 +270,7 @@ interestingArg (Note _ a) = interestingArg a -- Lit lit -> True -- _ -> False -interestingArg other = True +interestingArg _ = True -- Consider let x = 3 in f x -- The substitution will contain (x -> ContEx 3), and we want to -- to say that x is an interesting argument. @@ -314,21 +319,21 @@ interestingCallContext :: SimplCont -> CallCtxt interestingCallContext cont = interesting cont where - interestingCtxt = ArgCtxt False 2 -- Give *some* incentive! - interesting (Select _ bndr _ _ _) - | isDeadBinder bndr = CaseCtxt - | otherwise = interestingCtxt + | isDeadBinder bndr = CaseCtxt + | otherwise = ArgCtxt False 2 -- If the binder is used, this + -- is like a strict let - interesting (ApplyTo {}) = interestingCtxt - -- Can happen if we have (coerce t (f x)) y - -- Perhaps interestingCtxt is a bit over-keen, but I've - -- seen (coerce f) x, where f has an INLINE prag, - -- So we have to give some motivation for inlining it - - interesting (StrictArg _ _ cci _ _) = cci + interesting (ApplyTo _ arg _ cont) + | isTypeArg arg = interesting cont + | otherwise = ValAppCtxt -- Can happen if we have (f Int |> co) y + -- If f has an INLINE prag we need to give it some + -- motivation to inline. See Note [Cast then apply] + -- in CoreUnfold + + interesting (StrictArg _ cci _ _) = cci interesting (StrictBind {}) = BoringCtxt - interesting (Stop ty cci) = cci + interesting (Stop cci) = cci interesting (CoerceIt _ cont) = interesting cont -- If this call is the arg of a strict function, the context -- is a bit interesting. If we inline here, we may get useful @@ -353,16 +358,21 @@ mkArgInfo :: Id -> ArgInfo mkArgInfo fun n_val_args call_cont + | n_val_args < idArity fun -- Note [Unsaturated functions] + = ArgInfo { ai_rules = False + , ai_strs = vanilla_stricts + , ai_discs = vanilla_discounts } + | otherwise = ArgInfo { ai_rules = interestingArgContext fun call_cont - , ai_strs = arg_stricts + , ai_strs = add_type_str (idType fun) arg_stricts , ai_discs = arg_discounts } where vanilla_discounts, arg_discounts :: [Int] vanilla_discounts = repeat 0 arg_discounts = case idUnfolding fun of - CoreUnfolding _ _ _ _ (UnfoldIfGoodArgs _ discounts _ _) + CoreUnfolding _ _ _ _ _ (UnfoldIfGoodArgs _ discounts _ _) -> discounts ++ vanilla_discounts - other -> vanilla_discounts + _ -> vanilla_discounts vanilla_stricts, arg_stricts :: [Bool] vanilla_stricts = repeat False @@ -382,8 +392,37 @@ mkArgInfo fun n_val_args call_cont map isStrictDmd demands -- Finite => result is bottom else map isStrictDmd demands ++ vanilla_stricts - - other -> vanilla_stricts -- Not enough args, or no strictness + | otherwise + -> WARN( True, text "More demands than arity" <+> ppr fun <+> ppr (idArity fun) + <+> ppr n_val_args <+> ppr demands ) + vanilla_stricts -- Not enough args, or no strictness + + add_type_str :: Type -> [Bool] -> [Bool] + -- If the function arg types are strict, record that in the 'strictness bits' + -- No need to instantiate because unboxed types (which dominate the strict + -- types) can't instantiate type variables. + -- add_type_str is done repeatedly (for each call); might be better + -- once-for-all in the function + -- But beware primops/datacons with no strictness + add_type_str _ [] = [] + add_type_str fun_ty strs -- Look through foralls + | Just (_, fun_ty') <- splitForAllTy_maybe fun_ty -- Includes coercions + = add_type_str fun_ty' strs + add_type_str fun_ty (str:strs) -- Add strict-type info + | Just (arg_ty, fun_ty') <- splitFunTy_maybe fun_ty + = (str || isStrictType arg_ty) : add_type_str fun_ty' strs + add_type_str _ strs + = strs + +{- Note [Unsaturated functions] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider (test eyeball/inline4) + x = a:as + y = f x +where f has arity 2. Then we do not want to inline 'x', because +it'll just be floated out again. Even if f has lots of discounts +on its first argument -- it must be saturated for these to kick in +-} interestingArgContext :: Id -> SimplCont -> Bool -- If the argument has form (f x y), where x,y are boring, @@ -406,15 +445,15 @@ interestingArgContext :: Id -> SimplCont -> Bool interestingArgContext fn call_cont = idHasRules fn || go call_cont where - go (Select {}) = False - go (ApplyTo {}) = False - go (StrictArg _ _ cci _ _) = interesting cci - go (StrictBind {}) = False -- ?? - go (CoerceIt _ c) = go c - go (Stop _ cci) = interesting cci + go (Select {}) = False + go (ApplyTo {}) = False + go (StrictArg _ cci _ _) = interesting cci + go (StrictBind {}) = False -- ?? + go (CoerceIt _ c) = go c + go (Stop cci) = interesting cci interesting (ArgCtxt rules _) = rules - interesting other = False + interesting _ = False \end{code} @@ -579,13 +618,13 @@ preInlineUnconditionally env top_lvl bndr rhs | otherwise = case idOccInfo bndr of IAmDead -> True -- Happens in ((\x.1) v) OneOcc in_lam True int_cxt -> try_once in_lam int_cxt - other -> False + _ -> False where phase = getMode env active = case phase of - SimplGently -> isAlwaysActive prag - SimplPhase n _ -> isActive n prag - prag = idInlinePragma bndr + SimplGently -> isAlwaysActive act + SimplPhase n _ -> isActive n act + act = idInlineActivation bndr try_once in_lam int_cxt -- There's one textual occurrence | not in_lam = isNotTopLevel top_lvl || early_phase @@ -612,14 +651,14 @@ preInlineUnconditionally env top_lvl bndr rhs -- canInlineInLam => free vars of rhs are (Once in_lam) or Many, -- so substituting rhs inside a lambda doesn't change the occ info. -- Sadly, not quite the same as exprIsHNF. - canInlineInLam (Lit l) = True + canInlineInLam (Lit _) = True canInlineInLam (Lam b e) = isRuntimeVar b || canInlineInLam e canInlineInLam (Note _ e) = canInlineInLam e canInlineInLam _ = False early_phase = case phase of SimplPhase 0 _ -> False - other -> True + _ -> True -- If we don't have this early_phase test, consider -- x = length [1,2,3] -- The full laziness pass carefully floats all the cons cells to @@ -675,7 +714,7 @@ postInlineUnconditionally -> Bool postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding | not active = False - | isLoopBreaker occ_info = False -- If it's a loop-breaker of any kind, dont' inline + | isLoopBreaker occ_info = False -- If it's a loop-breaker of any kind, don't inline -- because it might be referred to "earlier" | isExportedId bndr = False | exprIsTrivial rhs = True @@ -692,7 +731,7 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding -- 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 code-duplication issue + OneOcc in_lam _one_br int_cxt -- OneOcc => no code-duplication issue -> smallEnoughToInline unfolding -- Small enough to dup -- ToDo: consider discount on smallEnoughToInline if int_cxt is true -- @@ -723,32 +762,32 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding -- 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 + _ -> False -- 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 +-- - 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 - SimplPhase n _ -> isActive n prag - prag = idInlinePragma bndr + SimplGently -> isAlwaysActive act + SimplPhase n _ -> isActive n act + act = idInlineActivation bndr activeInline :: SimplEnv -> OutId -> Bool activeInline env id = case getMode env of SimplGently -> False -- No inlining at all when doing gentle stuff, - -- except for local things that occur once + -- except for local things that occur once (pre/postInlineUnconditionally) -- The reason is that too little clean-up happens if you -- don't inline use-once things. Also a bit of inlining is *good* for -- full laziness; it can expose constant sub-expressions. @@ -762,14 +801,14 @@ activeInline env id -- and they are now constructed as Compulsory unfoldings (in MkId) -- so they'll happen anyway. - SimplPhase n _ -> isActive n prag + SimplPhase n _ -> isActive n act where - prag = idInlinePragma id + act = idInlineActivation id activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool) -- Nothing => No rules at all activeRule dflags env - | not (dopt Opt_RewriteRules dflags) + | not (dopt Opt_EnableRewriteRules dflags) = Nothing -- Rewriting is off | otherwise = case getMode env of @@ -790,14 +829,14 @@ activeRule dflags env %************************************************************************ \begin{code} -mkLam :: [OutBndr] -> OutExpr -> SimplM OutExpr +mkLam :: SimplEnv -> [OutBndr] -> OutExpr -> SimplM OutExpr -- mkLam tries three things -- a) eta reduction, if that gives a trivial expression -- b) eta expansion [only if there are some value lambdas] -mkLam [] body +mkLam _b [] body = return body -mkLam bndrs body +mkLam _env bndrs body = do { dflags <- getDOptsSmpl ; mkLam' dflags bndrs body } where @@ -819,7 +858,7 @@ mkLam bndrs body | dopt Opt_DoLambdaEtaExpansion dflags, any isRuntimeVar bndrs - = do { body' <- tryEtaExpansion dflags body + = do { let body' = tryEtaExpansion dflags body ; return (mkLams bndrs body') } | otherwise @@ -906,22 +945,33 @@ There are some particularly delicate points here: So it's important to to the right thing. -* We need to be careful if we just look at f's arity. Currently (Dec07), - f's arity is visible in its own RHS (see Note [Arity robustness] in - SimplEnv) so we must *not* trust the arity when checking that 'f' is - a value. Instead, look at the unfolding. +* Note [Arity care]: we need to be careful if we just look at f's + arity. Currently (Dec07), f's arity is visible in its own RHS (see + Note [Arity robustness] in SimplEnv) so we must *not* trust the + arity when checking that 'f' is a value. Otherwise we will + eta-reduce + f = \x. f x + to + f = f + Which might change a terminiating program (think (f `seq` e)) to a + non-terminating one. So we check for being a loop breaker first. However for GlobalIds we can look at the arity; and for primops we must, since they have no unfolding. -* Regardless of whether 'f' is a vlaue, we always want to +* Regardless of whether 'f' is a value, we always want to reduce (/\a -> f a) to f This came up in a RULE: foldr (build (/\a -> g a)) - did not match foldr (build (/\b -> ...something complex...)) + did not match foldr (build (/\b -> ...something complex...)) The type checker can insert these eta-expanded versions, with both type and dictionary lambdas; hence the slightly ad-hoc isDictId +* Never *reduce* arity. For example + f = \xy. g x y + Then if h has arity 1 we don't want to eta-reduce because then + f's arity would decrease, and that is bad + These delicacies are why we don't use exprIsTrivial and exprIsHNF here. Alas. @@ -930,6 +980,8 @@ tryEtaReduce :: [OutBndr] -> OutExpr -> Maybe OutExpr tryEtaReduce bndrs body = go (reverse bndrs) body where + incoming_arity = count isId bndrs + go (b : bs) (App fun arg) | ok_arg b arg = go bs fun -- Loop round go [] fun | ok_fun fun = Just fun -- Success! go _ _ = Nothing -- Failure! @@ -943,10 +995,11 @@ tryEtaReduce bndrs body && (ok_fun_id fun_id || all ok_lam bndrs) ok_fun _fun = False - ok_fun_id fun - | isLocalId fun = isEvaldUnfolding (idUnfolding fun) - | isDataConWorkId fun = True - | isGlobalId fun = idArity fun > 0 + ok_fun_id fun = fun_arity fun >= incoming_arity + + fun_arity fun -- See Note [Arity care] + | isLocalId fun && isLoopBreaker (idOccInfo fun) = 0 + | otherwise = idArity fun ok_lam v = isTyVar v || isDictId v @@ -990,11 +1043,10 @@ when computing arity; and etaExpand adds the coerces as necessary when actually computing the expansion. \begin{code} -tryEtaExpansion :: DynFlags -> OutExpr -> SimplM OutExpr +tryEtaExpansion :: DynFlags -> OutExpr -> OutExpr -- There is at least one runtime binder in the binders -tryEtaExpansion dflags body = do - us <- getUniquesM - return (etaExpand fun_arity us body (exprType body)) +tryEtaExpansion dflags body + = etaExpand fun_arity body where fun_arity = exprEtaExpandArity dflags body \end{code} @@ -1013,7 +1065,7 @@ Consider this: We'd like to float this to y1 = /\a. e1 y2 = /\a. e2 - x = /\a. C (y1 a) (y2 a) + x = /\a. C (y1 a) (y2 a) for the usual reasons: we want to inline x rather vigorously. You may think that this kind of thing is rare. But in some programs it is @@ -1147,7 +1199,8 @@ abstractFloats main_tvs body_env body = do { uniq <- getUniqueM ; let poly_name = setNameUnique (idName var) uniq -- Keep same name poly_ty = mkForAllTys tvs_here (idType var) -- But new type of course - poly_id = mkLocalId poly_name poly_ty + poly_id = transferPolyIdInfo var tvs_here $ -- Note [transferPolyIdInfo] in Id.lhs + mkLocalId poly_name poly_ty ; return (poly_id, mkTyApps (Var poly_id) (mkTyVarTys tvs_here)) } -- In the olden days, it was crucial to copy the occInfo of the original var, -- because we were looking at occurrence-analysed but as yet unsimplified code! @@ -1289,12 +1342,12 @@ prepareAlts env scrut case_bndr' alts imposs_cons = case scrut of Var v -> otherCons (idUnfolding v) - other -> [] + _ -> [] impossible_alt :: CoreAlt -> Bool impossible_alt (con, _, _) | con `elem` imposs_cons = True impossible_alt (DataAlt con, _, _) = dataConCannotMatch inst_tys con - impossible_alt alt = False + impossible_alt _ = False -------------------------------------------------- @@ -1302,7 +1355,7 @@ prepareAlts env scrut case_bndr' alts -------------------------------------------------- combineIdenticalAlts :: OutId -> [InAlt] -> SimplM [InAlt] -combineIdenticalAlts case_bndr alts@((con1,bndrs1,rhs1) : con_alts) +combineIdenticalAlts case_bndr ((_con1,bndrs1,rhs1) : con_alts) | all isDeadBinder bndrs1, -- Remember the default length filtered_alts < length con_alts -- alternative comes first -- Also Note [Dead binders] @@ -1310,9 +1363,9 @@ combineIdenticalAlts case_bndr alts@((con1,bndrs1,rhs1) : con_alts) ; return ((DEFAULT, [], rhs1) : filtered_alts) } where filtered_alts = filter keep con_alts - keep (con,bndrs,rhs) = not (all isDeadBinder bndrs && rhs `cheapEqExpr` rhs1) + keep (_con,bndrs,rhs) = not (all isDeadBinder bndrs && rhs `cheapEqExpr` rhs1) -combineIdenticalAlts case_bndr alts = return alts +combineIdenticalAlts _ alts = return alts ------------------------------------------------------------------------- -- Prepare the default alternative @@ -1330,7 +1383,7 @@ prepareDefault :: DynFlags -- And becuase case-merging can cause many to show up ------- Merge nested cases ---------- -prepareDefault dflags env outer_bndr bndr_ty imposs_cons (Just deflt_rhs) +prepareDefault dflags env outer_bndr _bndr_ty imposs_cons (Just deflt_rhs) | dopt Opt_CaseMerge dflags , Case (Var inner_scrut_var) inner_bndr _ inner_alts <- deflt_rhs , DoneId inner_scrut_var' <- substId env inner_scrut_var @@ -1362,7 +1415,7 @@ prepareDefault dflags env outer_bndr bndr_ty imposs_cons (Just deflt_rhs) --------- Fill in known constructor ----------- -prepareDefault dflags env case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rhs) +prepareDefault _ _ case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rhs) | -- This branch handles the case where we are -- scrutinisng an algebraic data type isAlgTyCon tycon -- It's a data type, tuple, or unboxed tuples. @@ -1393,13 +1446,18 @@ prepareDefault dflags env case_bndr (Just (tycon, inst_tys)) imposs_cons (Just d dataConRepInstPat us con inst_tys ; return [(DataAlt con, ex_tvs ++ co_tvs ++ arg_ids, deflt_rhs)] } - two_or_more -> return [(DEFAULT, [], deflt_rhs)] + _ -> return [(DEFAULT, [], deflt_rhs)] + + | debugIsOn, isAlgTyCon tycon, not (isOpenTyCon tycon), null (tyConDataCons tycon) + -- This can legitimately happen for type families, so don't report that + = pprTrace "prepareDefault" (ppr case_bndr <+> ppr tycon) + $ return [(DEFAULT, [], deflt_rhs)] --------- Catch-all cases ----------- -prepareDefault dflags env case_bndr bndr_ty imposs_cons (Just deflt_rhs) +prepareDefault _dflags _env _case_bndr _bndr_ty _imposs_cons (Just deflt_rhs) = return [(DEFAULT, [], deflt_rhs)] -prepareDefault dflags env case_bndr bndr_ty imposs_cons Nothing +prepareDefault _dflags _env _case_bndr _bndr_ty _imposs_cons Nothing = return [] -- No default branch \end{code} @@ -1421,29 +1479,14 @@ mkCase tries these things \begin{code} -mkCase :: OutExpr -> OutId -> OutType - -> [OutAlt] -- Increasing order +mkCase :: OutExpr -> OutId -> [OutAlt] -- Increasing order -> SimplM OutExpr -------------------------------------------------- --- 1. Check for empty alternatives --------------------------------------------------- - --- This isn't strictly an error. It's possible that the simplifer might "see" --- that an inner case has no accessible alternatives before it "sees" that the --- entire branch of an outer case is inaccessible. So we simply --- put an error case here insteadd -mkCase scrut case_bndr ty [] - = pprTrace "mkCase: null alts" (ppr case_bndr <+> ppr scrut) $ - return (mkApps (Var rUNTIME_ERROR_ID) - [Type ty, Lit (mkStringLit "Impossible alternative")]) - - --------------------------------------------------- -- 2. Identity case -------------------------------------------------- -mkCase scrut case_bndr ty alts -- Identity case +mkCase scrut case_bndr alts -- Identity case | all identity_alt alts = do tick (CaseIdentity case_bndr) return (re_cast scrut) @@ -1454,7 +1497,7 @@ mkCase scrut case_bndr ty alts -- Identity case check_eq (LitAlt lit') _ (Lit lit) = lit == lit' check_eq (DataAlt con) args rhs = rhs `cheapEqExpr` mkConApp con (arg_tys ++ varsToCoreExprs args) || rhs `cheapEqExpr` Var case_bndr - check_eq con args rhs = False + check_eq _ _ _ = False arg_tys = map Type (tyConAppArgs (idType case_bndr)) @@ -1472,14 +1515,14 @@ mkCase scrut case_bndr ty alts -- Identity case re_cast scrut = case head alts of (_,_,Cast _ co) -> Cast scrut co - other -> scrut + _ -> scrut -------------------------------------------------- -- Catch-all -------------------------------------------------- -mkCase scrut bndr ty alts = return (Case scrut bndr ty alts) +mkCase scrut bndr alts = return (Case scrut bndr (coreAltsType alts) alts) \end{code} @@ -1488,7 +1531,8 @@ its dead, because it often is, and occasionally these mkCase transformations cascade rather nicely. \begin{code} +bindCaseBndr :: Id -> CoreExpr -> CoreExpr -> CoreExpr bindCaseBndr bndr rhs body | isDeadBinder bndr = body - | otherwise = bindNonRec bndr rhs body + | otherwise = bindNonRec bndr rhs body \end{code}