X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=dfe9e836c96b0e2450656088c763acc0b7e462d6;hb=d7bc4e06c0b16d242f1f26100f4146f40f5de5a8;hp=88abf4ad81dcd5f92512d0f406fce0508f7dc132;hpb=62eeda5aed31173b234b2965ccf4bd6979ffd9a4;p=ghc-hetmet.git diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs index 88abf4a..dfe9e83 100644 --- a/compiler/simplCore/SimplUtils.lhs +++ b/compiler/simplCore/SimplUtils.lhs @@ -10,14 +10,15 @@ module SimplUtils ( -- Inlining, preInlineUnconditionally, postInlineUnconditionally, - activeInline, activeRule, inlineMode, + activeInline, activeRule, + simplEnvForGHCi, simplEnvForRules, simplGentlyForInlineRules, -- The continuation type SimplCont(..), DupFlag(..), ArgInfo(..), contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, - countValArgs, countArgs, splitInlineCont, - mkBoringStop, mkLazyArgStop, contIsRhsOrArg, - interestingCallContext, interestingArgContext, + countValArgs, countArgs, + mkBoringStop, mkRhsStop, mkLazyArgStop, contIsRhsOrArg, + interestingCallContext, interestingArg, mkArgInfo, @@ -52,7 +53,7 @@ import MonadUtils import Outputable import FastString -import List( nub ) +import Data.List \end{code} @@ -113,7 +114,7 @@ data SimplCont SimplCont | StrictArg -- e C - OutExpr -- e + OutExpr -- e; *always* of form (Var v `App1` e1 .. `App` en) 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 @@ -152,6 +153,9 @@ instance Outputable DupFlag where mkBoringStop :: SimplCont mkBoringStop = Stop BoringCtxt +mkRhsStop :: SimplCont -- See Note [RHS of lets] in CoreUnfold +mkRhsStop = Stop (ArgCtxt False) + mkLazyArgStop :: CallCtxt -> SimplCont mkLazyArgStop cci = Stop cci @@ -215,73 +219,11 @@ dropArgs :: Int -> SimplCont -> SimplCont dropArgs 0 cont = cont dropArgs n (ApplyTo _ _ _ cont) = dropArgs (n-1) cont dropArgs n other = pprPanic "dropArgs" (ppr n <+> ppr other) - --------------------- -splitInlineCont :: SimplCont -> Maybe (SimplCont, SimplCont) --- Returns Nothing if the continuation should dissolve an InlineMe Note --- Return Just (c1,c2) otherwise, --- where c1 is the continuation to put inside the InlineMe --- and c2 outside - --- Example: (__inline_me__ (/\a. e)) ty --- Here we want to do the beta-redex without dissolving the InlineMe --- 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 {}) = 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} - - -\begin{code} -interestingArg :: OutExpr -> Bool - -- An argument is interesting if it has *some* structure - -- We are here trying to avoid unfolding a function that - -- is applied only to variables that have no unfolding - -- (i.e. they are probably lambda bound): f x y z - -- There is little point in inlining f here. -interestingArg (Var v) = hasSomeUnfolding (idUnfolding v) - -- Was: isValueUnfolding (idUnfolding v') - -- But that seems over-pessimistic - || isDataConWorkId v - -- This accounts for an argument like - -- () or [], which is definitely interesting -interestingArg (Type _) = False -interestingArg (App fn (Type _)) = interestingArg fn -interestingArg (Note _ a) = interestingArg a - --- Idea (from Sam B); I'm not sure if it's a good idea, so commented out for now --- interestingArg expr | isUnLiftedType (exprType expr) --- -- Unlifted args are only ever interesting if we know what they are --- = case expr of --- Lit lit -> True --- _ -> False - -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. - -- But consider also (\x. f x y) y - -- The substitution will contain (x -> ContEx y), and we want to say - -- that x is not interesting (assuming y has no unfolding) \end{code} -Comment about interestingCallContext -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Note [Interesting call context] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We want to avoid inlining an expression where there can't possibly be any gain, such as in an argument position. Hence, if the continuation is interesting (eg. a case scrutinee, application etc.) then we @@ -316,13 +258,15 @@ default case. \begin{code} interestingCallContext :: SimplCont -> CallCtxt +-- See Note [Interesting call context] interestingCallContext cont = interesting cont where interesting (Select _ bndr _ _ _) | isDeadBinder bndr = CaseCtxt - | otherwise = ArgCtxt False 2 -- If the binder is used, this + | otherwise = ArgCtxt False -- If the binder is used, this -- is like a strict let + -- See Note [RHS of lets] in CoreUnfold interesting (ApplyTo _ arg _ cont) | isTypeArg arg = interesting cont @@ -353,24 +297,25 @@ interestingCallContext cont ------------------- mkArgInfo :: Id + -> [CoreRule] -- Rules for function -> Int -- Number of value args - -> SimplCont -- Context of the cal + -> SimplCont -- Context of the call -> ArgInfo -mkArgInfo fun n_val_args call_cont +mkArgInfo fun rules 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 + = ArgInfo { ai_rules = interestingArgContext rules call_cont , 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 {uf_guidance = UnfoldIfGoodArgs {ug_args = discounts}} -> discounts ++ vanilla_discounts _ -> vanilla_discounts @@ -424,7 +369,7 @@ 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 +interestingArgContext :: [CoreRule] -> SimplCont -> Bool -- If the argument has form (f x y), where x,y are boring, -- and f is marked INLINE, then we don't want to inline f. -- But if the context of the argument is @@ -435,16 +380,18 @@ interestingArgContext :: Id -> SimplCont -> Bool -- where h has rules, then we do want to inline f; hence the -- call_cont argument to interestingArgContext -- --- The interesting_arg_ctxt flag makes this happen; if it's +-- The ai-rules flag makes this happen; if it's -- set, the inliner gets just enough keener to inline f -- regardless of how boring f's arguments are, if it's marked INLINE -- -- The alternative would be to *always* inline an INLINE function, -- regardless of how boring its context is; but that seems overkill -- For example, it'd mean that wrapper functions were always inlined -interestingArgContext fn call_cont - = idHasRules fn || go call_cont +interestingArgContext rules call_cont + = notNull rules || enclosing_fn_has_rules where + enclosing_fn_has_rules = go call_cont + go (Select {}) = False go (ApplyTo {}) = False go (StrictArg _ cci _ _) = interesting cci @@ -452,8 +399,8 @@ interestingArgContext fn call_cont go (CoerceIt _ c) = go c go (Stop cci) = interesting cci - interesting (ArgCtxt rules _) = rules - interesting _ = False + interesting (ArgCtxt rules) = rules + interesting _ = False \end{code} @@ -464,18 +411,58 @@ interestingArgContext fn call_cont %* * %************************************************************************ -Inlining is controlled partly by the SimplifierMode switch. This has two -settings: +\begin{code} +simplEnvForGHCi :: SimplEnv +simplEnvForGHCi = mkSimplEnv allOffSwitchChecker $ + SimplGently { sm_rules = False, sm_inline = False } + -- Do not do any inlining, in case we expose some unboxed + -- tuple stuff that confuses the bytecode interpreter + +simplEnvForRules :: SimplEnv +simplEnvForRules = mkSimplEnv allOffSwitchChecker $ + SimplGently { sm_rules = True, sm_inline = False } + +simplGentlyForInlineRules :: SimplifierMode +simplGentlyForInlineRules = SimplGently { sm_rules = True, sm_inline = True } + -- Simplify as much as possible, subject to the usual "gentle" rules +\end{code} +Inlining is controlled partly by the SimplifierMode switch. This has two +settings + SimplGently (a) Simplifying before specialiser/full laziness - (b) Simplifiying inside INLINE pragma + (b) Simplifiying inside InlineRules (c) Simplifying the LHS of a rule (d) Simplifying a GHCi expression or Template Haskell splice SimplPhase n _ Used at all other times -The key thing about SimplGently is that it does no call-site inlining. +Note [Gentle mode] +~~~~~~~~~~~~~~~~~~ +Gentle mode has a separate boolean flag to control + a) inlining (sm_inline flag) + b) rules (sm_rules flag) +A key invariant about Gentle mode is that it is treated as the EARLIEST +phase. Something is inlined if the sm_inline flag is on AND the thing +is inlinable in the earliest phase. This is important. Example + + {-# INLINE [~1] g #-} + g = ... + + {-# INLINE f #-} + f x = g (g x) + +If we were to inline g into f's inlining, then an importing module would +never be able to do + f e --> g (g e) ---> RULE fires +because the InlineRule for f has had g inlined into it. + +On the other hand, it is bad not to do ANY inlining into an +InlineRule, because then recursive knots in instance declarations +don't get unravelled. + +However, *sometimes* SimplGently must do no call-site inlining at all. Before full laziness we must be careful not to inline wrappers, because doing so inhibits floating e.g. ...(case f x of ...)... @@ -489,17 +476,11 @@ running it, we don't want to use -O2. Indeed, we don't want to inline anything, because the byte-code interpreter might get confused about unboxed tuples and suchlike. -INLINE pragmas -~~~~~~~~~~~~~~ -SimplGently is also used as the mode to simplify inside an InlineMe note. - -\begin{code} -inlineMode :: SimplifierMode -inlineMode = SimplGently -\end{code} - -It really is important to switch off inlinings inside such -expressions. Consider the following example +Note [Simplifying gently inside InlineRules] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We don't do much simplification inside InlineRules (which come from +INLINE pragmas). It really is important to switch off inlinings +inside such expressions. Consider the following example let f = \pq -> BIG in @@ -508,16 +489,14 @@ expressions. Consider the following example in ...g...g...g...g...g... Now, if that's the ONLY occurrence of f, it will be inlined inside g, -and thence copied multiple times when g is inlined. - +and thence copied multiple times when g is inlined. -This function may be inlinined in other modules, so we -don't want to remove (by inlining) calls to functions that have -specialisations, or that may have transformation rules in an importing -scope. +This function may be inlinined in other modules, so we don't want to +remove (by inlining) calls to functions that have specialisations, or +that may have transformation rules in an importing scope. E.g. {-# INLINE f #-} - f x = ...g... + f x = ...g... and suppose that g is strict *and* has specialisations. If we inline g's wrapper, we deny f the chance of getting the specialised version @@ -535,15 +514,14 @@ continuation. That's why the keep_inline predicate returns True for ArgOf continuations. It shouldn't do any harm not to dissolve the inline-me note under these circumstances. -Note that the result is that we do very little simplification -inside an InlineMe. +Although we do very little simplification inside an InlineRule, +the RHS is simplified as normal. For example: all xs = foldr (&&) True xs any p = all . map p {-# INLINE any #-} -Problem: any won't get deforested, and so if it's exported and the -importer doesn't use the inlining, (eg passes it as an arg) then we -won't get deforestation at all. We havn't solved this problem yet! +The RHS of 'any' will get optimised and deforested; but the InlineRule +will still mention the original RHS. preInlineUnconditionally @@ -610,6 +588,18 @@ seems a bit fragile. Conclusion: inline top level things gaily until Phase 0 (the last phase), at which point don't. +Note [pre/postInlineUnconditionally in gentle mode] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Even in gentle mode we want to do preInlineUnconditionally. 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. Example in +spectral/mandel/Mandel.hs, where the mandelset function gets a useful +let-float if you inline windowToViewport + +However, as usual for Gentle mode, do not inline things that are +inactive in the intial stages. See Note [Gentle mode]. + \begin{code} preInlineUnconditionally :: SimplEnv -> TopLevelFlag -> InId -> InExpr -> Bool preInlineUnconditionally env top_lvl bndr rhs @@ -622,9 +612,10 @@ preInlineUnconditionally env top_lvl bndr rhs where phase = getMode env active = case phase of - SimplGently -> isAlwaysActive prag - SimplPhase n _ -> isActive n prag - prag = idInlinePragma bndr + SimplGently {} -> isEarlyActive act + -- See Note [pre/postInlineUnconditionally in gentle mode] + 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 @@ -707,7 +698,7 @@ story for now. \begin{code} postInlineUnconditionally :: SimplEnv -> TopLevelFlag - -> InId -- The binder (an OutId would be fine too) + -> OutId -- The binder (an InId would be fine too) -> OccInfo -- From the InId -> OutExpr -> Unfolding @@ -717,6 +708,7 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding | 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 + | isInlineRule unfolding = False -- Note [InlineRule and postInlineUnconditionally] | exprIsTrivial rhs = True | otherwise = case occ_info of @@ -778,21 +770,17 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding where active = case getMode env of - SimplGently -> isAlwaysActive prag - SimplPhase n _ -> isActive n prag - prag = idInlinePragma bndr + SimplGently {} -> isEarlyActive act + -- See Note [pre/postInlineUnconditionally in gentle mode] + 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 (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. - -- Example in spectral/mandel/Mandel.hs, where the mandelset - -- function gets a useful let-float if you inline windowToViewport + SimplGently { sm_inline = inlining_on } + -> inlining_on && isEarlyActive act + -- See Note [Gentle mode] -- NB: we used to have a second exception, for data con wrappers. -- On the grounds that we use gentle mode for rule LHSs, and @@ -801,9 +789,9 @@ 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 @@ -812,15 +800,34 @@ activeRule dflags env = Nothing -- Rewriting is off | otherwise = case getMode env of - SimplGently -> Just isAlwaysActive + SimplGently { sm_rules = rules_on } + | rules_on -> Just isEarlyActive + | otherwise -> Nothing -- Used to be Nothing (no rules in gentle mode) -- Main motivation for changing is that I wanted -- lift String ===> ... -- to work in Template Haskell when simplifying -- splices, so we get simpler code for literal strings - SimplPhase n _ -> Just (isActive n) + SimplPhase n _ -> Just (isActive n) \end{code} +Note [InlineRule and postInlineUnconditionally] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Do not do postInlineUnconditionally if the Id has an InlineRule, otherwise +we lose the unfolding. Example + + -- f has InlineRule with rhs (e |> co) + -- where 'e' is big + f = e |> co + +Then there's a danger we'll optimise to + + f' = e + f = f' |> co + +and now postInlineUnconditionally, losing the InlineRule on f. Now f' +won't inline because 'e' is too big. + %************************************************************************ %* * @@ -836,7 +843,7 @@ mkLam :: SimplEnv -> [OutBndr] -> OutExpr -> SimplM OutExpr mkLam _b [] body = return body -mkLam _env bndrs body +mkLam env bndrs body = do { dflags <- getDOptsSmpl ; mkLam' dflags bndrs body } where @@ -857,7 +864,9 @@ mkLam _env bndrs body ; return etad_lam } | dopt Opt_DoLambdaEtaExpansion dflags, - any isRuntimeVar bndrs + not (inGentleMode env), -- In gentle mode don't eta-expansion + any isRuntimeVar bndrs -- because it can clutter up the code + -- with casts etc that may not be removed = do { let body' = tryEtaExpansion dflags body ; return (mkLams bndrs body') } @@ -1199,7 +1208,7 @@ 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 = transferPolyIdInfo var $ -- Note [transferPolyIdInfo] in Id.lhs + 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,