X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=a2fe28d602b8923d890dec080765dad5bd5bc2ff;hb=29c2794f358b1175f5402d81bb84fd26a4d39019;hp=d1c5cefce147e6934c3338c39214f026592a53f6;hpb=d2ce0f52d42edf32bb9f13796e6ba6edba8bd516;p=ghc-hetmet.git diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs index d1c5cef..a2fe28d 100644 --- a/compiler/simplCore/SimplUtils.lhs +++ b/compiler/simplCore/SimplUtils.lhs @@ -6,17 +6,19 @@ \begin{code} module SimplUtils ( -- Rebuilding - mkLam, mkCase, prepareAlts, + mkLam, mkCase, prepareAlts, tryEtaExpand, -- Inlining, preInlineUnconditionally, postInlineUnconditionally, - activeUnfolding, activeUnfInRule, activeRule, - simplEnvForGHCi, simplEnvForRules, updModeForInlineRules, + activeUnfolding, activeRule, + getUnfoldingInRuleMatch, + simplEnvForGHCi, updModeForInlineRules, -- The continuation type SimplCont(..), DupFlag(..), ArgInfo(..), + isSimplified, contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, - pushArgs, countValArgs, countArgs, addArgTo, + pushSimplifiedArgs, countValArgs, countArgs, addArgTo, mkBoringStop, mkRhsStop, mkLazyArgStop, contIsRhsOrArg, interestingCallContext, @@ -28,7 +30,7 @@ module SimplUtils ( #include "HsVersions.h" import SimplEnv -import CoreMonad ( SimplifierMode(..), Tick(..) ) +import CoreMonad ( SimplifierMode(..), Tick(..) ) import DynFlags import StaticFlags import CoreSyn @@ -40,7 +42,7 @@ import CoreArity import CoreUnfold import Name import Id -import Var ( isCoVar ) +import Var import Demand import SimplMonad import Type hiding( substTy ) @@ -99,12 +101,12 @@ data SimplCont SimplCont | ApplyTo -- C arg - DupFlag - InExpr StaticEnv -- The argument and its static env + DupFlag -- See Note [DupFlag invariants] + InExpr StaticEnv -- The argument and its static env SimplCont | Select -- case C of alts - DupFlag + DupFlag -- See Note [DupFlag invariants] InId [InAlt] StaticEnv -- The case binder, alts, and subst-env SimplCont @@ -151,14 +153,31 @@ instance Outputable SimplCont where (nest 2 $ vcat [ppr (seTvSubst se), ppr alts]) $$ ppr cont ppr (CoerceIt co cont) = (ptext (sLit "CoerceIt") <+> ppr co) $$ ppr cont -data DupFlag = OkToDup | NoDup +data DupFlag = NoDup -- Unsimplified, might be big + | Simplified -- Simplified + | OkToDup -- Simplified and small + +isSimplified :: DupFlag -> Bool +isSimplified NoDup = False +isSimplified _ = True -- Invariant: the subst-env is empty instance Outputable DupFlag where - ppr OkToDup = ptext (sLit "ok") - ppr NoDup = ptext (sLit "nodup") + ppr OkToDup = ptext (sLit "ok") + ppr NoDup = ptext (sLit "nodup") + ppr Simplified = ptext (sLit "simpl") +\end{code} +Note [DupFlag invariants] +~~~~~~~~~~~~~~~~~~~~~~~~~ +In both (ApplyTo dup _ env k) + and (Select dup _ _ env k) +the following invariants hold + (a) if dup = OkToDup, then continuation k is also ok-to-dup + (b) if dup = OkToDup or Simplified, the subst-env is empty + (and and hence no need to re-simplify) +\begin{code} ------------------- mkBoringStop :: SimplCont mkBoringStop = Stop BoringCtxt @@ -179,8 +198,8 @@ contIsRhsOrArg _ = False ------------------- contIsDupable :: SimplCont -> Bool contIsDupable (Stop {}) = True -contIsDupable (ApplyTo OkToDup _ _ _) = True -contIsDupable (Select OkToDup _ _ _ _) = True +contIsDupable (ApplyTo OkToDup _ _ _) = True -- See Note [DupFlag invariants] +contIsDupable (Select OkToDup _ _ _ _) = True -- ...ditto... contIsDupable (CoerceIt _ cont) = contIsDupable cont contIsDupable _ = False @@ -238,9 +257,10 @@ contArgs cont@(ApplyTo {}) contArgs cont = (True, [], cont) -pushArgs :: SimplEnv -> [CoreExpr] -> SimplCont -> SimplCont -pushArgs _env [] cont = cont -pushArgs env (arg:args) cont = ApplyTo NoDup arg env (pushArgs env args cont) +pushSimplifiedArgs :: SimplEnv -> [CoreExpr] -> SimplCont -> SimplCont +pushSimplifiedArgs _env [] cont = cont +pushSimplifiedArgs env (arg:args) cont = ApplyTo Simplified arg env (pushSimplifiedArgs env args cont) + -- The env has an empty SubstEnv dropArgs :: Int -> SimplCont -> SimplCont dropArgs 0 cont = cont @@ -433,33 +453,49 @@ interestingArgContext rules call_cont \end{code} - %************************************************************************ %* * -\subsection{Decisions about inlining} + SimplifierMode %* * %************************************************************************ -Inlining is controlled partly by the SimplifierMode switch. This has two -settings - - SimplGently (a) Simplifying before specialiser/full laziness - (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 - -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 +The SimplifierMode controls several switches; see its definition in +CoreMonad + sm_rules :: Bool -- Whether RULES are enabled + sm_inline :: Bool -- Whether inlining is enabled + sm_case_case :: Bool -- Whether case-of-case is enabled + sm_eta_expand :: Bool -- Whether eta-expansion is enabled + +\begin{code} +simplEnvForGHCi :: SimplEnv +simplEnvForGHCi = mkSimplEnv $ + SimplMode { sm_names = ["GHCi"] + , sm_phase = InitialPhase + , sm_rules = True, sm_inline = False + , sm_eta_expand = False, sm_case_case = True } + -- Do not do any inlining, in case we expose some unboxed + -- tuple stuff that confuses the bytecode interpreter +updModeForInlineRules :: Activation -> SimplifierMode -> SimplifierMode +-- See Note [Simplifying inside InlineRules] +updModeForInlineRules inline_rule_act current_mode + = current_mode { sm_phase = phaseFromActivation inline_rule_act + , sm_rules = True + , sm_inline = True + , sm_eta_expand = False } + where + phaseFromActivation (ActiveAfter n) = Phase n + phaseFromActivation _ = InitialPhase +\end{code} + +Note [Inlining in gentle mode] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Something is inlined if + (i) the sm_inline flag is on, AND + (ii) the thing has an INLINE pragma, AND + (iii) the thing is inlinable in the earliest phase. + +Example of why (iii) is important: {-# INLINE [~1] g #-} g = ... @@ -489,22 +525,6 @@ 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. -Note [RULEs enabled in SimplGently] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -RULES are enabled when doing "gentle" simplification. Two reasons: - - * We really want the class-op cancellation to happen: - op (df d1 d2) --> $cop3 d1 d2 - because this breaks the mutual recursion between 'op' and 'df' - - * I wanted the RULE - lift String ===> ... - to work in Template Haskell when simplifying - splices, so we get simpler code for literal strings - -But watch out: list fusion can prevent floating. So use phase control -to switch off those rules until after floating. - Note [Simplifying inside InlineRules] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We must take care with simplification inside InlineRules (which come from @@ -523,8 +543,9 @@ one; see OccurAnal.addRuleUsage. Second, we do want *do* to some modest rules/inlining stuff in InlineRules, partly to eliminate senseless crap, and partly to break the recursive knots -generated by instance declarations. To keep things simple, we always set -the phase to 'gentle' when processing InlineRules. OK, so suppose we have +generated by instance declarations. + +However, suppose we have {-# INLINE f #-} f = meaning "inline f in phases p where activation (p) holds". @@ -534,12 +555,8 @@ f when it is inlined. So our conservative plan (implemented by updModeForInlineRules) is this: ------------------------------------------------------------- - When simplifying the RHS of an InlineRule, - If the InlineRule becomes active in phase p, then - if the current phase is *earlier than* p, - make no inlinings or rules active when simplifying the RHS - otherwise - set the phase to p when simplifying the RHS + When simplifying the RHS of an InlineRule, set the phase to the + phase in which the InlineRule first becomes active ------------------------------------------------------------- That ensures that @@ -553,13 +570,13 @@ That ensures that inlining the *original* rhs in phase p. For example, - {-# INLINE f #-} - f x = ...g... + {-# INLINE f #-} + f x = ...g... - {-# NOINLINE [1] g #-} - g y = ... + {-# NOINLINE [1] g #-} + g y = ... - {-# RULE h g = ... #-} + {-# RULE h g = ... #-} Here we must not inline g into f's RHS, even when we get to phase 0, because when f is later inlined into some other module we want the rule for h to fire. @@ -588,42 +605,75 @@ mark it 'demanded', so when the RHS is simplified, it'll get an ArgOf continuation. \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 } +activeUnfolding :: SimplEnv -> Id -> Bool +activeUnfolding env + | not (sm_inline mode) = active_unfolding_minimal + | otherwise = case sm_phase mode of + InitialPhase -> active_unfolding_gentle + Phase n -> active_unfolding n + where + mode = getMode env -updModeForInlineRules :: Activation -> SimplifierMode -> SimplifierMode --- See Note [Simplifying inside InlineRules] --- Treat Gentle as phase "infinity" --- If current_phase `earlier than` inline_rule_start_phase --- then no_op --- else --- if current_phase `same phase` inline_rule_start_phase --- then current_phase (keep gentle flags) --- else inline_rule_start_phase -updModeForInlineRules inline_rule_act current_mode - = case inline_rule_act of - NeverActive -> no_op - AlwaysActive -> mk_gentle current_mode - ActiveBefore {} -> mk_gentle current_mode - ActiveAfter n -> mk_phase n current_mode +getUnfoldingInRuleMatch :: SimplEnv -> IdUnfoldingFun +-- When matching in RULE, we want to "look through" an unfolding +-- (to see a constructor) if *rules* are on, even if *inlinings* +-- are not. A notable example is DFuns, which really we want to +-- match in rules like (op dfun) in gentle mode. Another example +-- is 'otherwise' which we want exprIsConApp_maybe to be able to +-- see very early on +getUnfoldingInRuleMatch env id + | unf_is_active = idUnfolding id + | otherwise = NoUnfolding where - no_op = SimplGently { sm_rules = False, sm_inline = False } + mode = getMode env + unf_is_active + | not (sm_rules mode) = active_unfolding_minimal id + | otherwise = isActive (sm_phase mode) (idInlineActivation id) - mk_gentle (SimplGently {}) = current_mode - mk_gentle _ = SimplGently { sm_rules = True, sm_inline = True } +active_unfolding_minimal :: Id -> Bool +-- Compuslory unfoldings only +-- Ignore SimplGently, because we want to inline regardless; +-- the Id has no top-level binding at all +-- +-- NB: we used to have a second exception, for data con wrappers. +-- On the grounds that we use gentle mode for rule LHSs, and +-- they match better when data con wrappers are inlined. +-- But that only really applies to the trivial wrappers (like (:)), +-- and they are now constructed as Compulsory unfoldings (in MkId) +-- so they'll happen anyway. +active_unfolding_minimal id = isCompulsoryUnfolding (realIdUnfolding id) + +active_unfolding :: PhaseNum -> Id -> Bool +active_unfolding n id = isActiveIn n (idInlineActivation id) - mk_phase n (SimplPhase _ ss) = SimplPhase n ss - mk_phase n (SimplGently {}) = SimplPhase n ["gentle-rules"] +active_unfolding_gentle :: Id -> Bool +-- Anything that is early-active +-- See Note [Gentle mode] +active_unfolding_gentle id + = isInlinePragma prag + && isEarlyActive (inlinePragmaActivation prag) + -- NB: wrappers are not early-active + where + prag = idInlinePragma id + +---------------------- +activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool) +-- Nothing => No rules at all +activeRule _dflags env + | not (sm_rules mode) = Nothing -- Rewriting is off + | otherwise = Just (isActive (sm_phase mode)) + where + mode = getMode env \end{code} + +%************************************************************************ +%* * + preInlineUnconditionally +%* * +%************************************************************************ + preInlineUnconditionally ~~~~~~~~~~~~~~~~~~~~~~~~ @preInlineUnconditionally@ examines a bndr to see if it is used just @@ -739,11 +789,9 @@ preInlineUnconditionally env top_lvl bndr rhs OneOcc in_lam True int_cxt -> try_once in_lam int_cxt _ -> False where - phase = getMode env - active = case phase of - SimplGently {} -> isEarlyActive act - -- See Note [pre/postInlineUnconditionally in gentle mode] - SimplPhase n _ -> isActive n act + mode = getMode env + active = isActive (sm_phase mode) act + -- See Note [pre/postInlineUnconditionally in gentle mode] act = idInlineActivation bndr try_once in_lam int_cxt -- There's one textual occurrence | not in_lam = isNotTopLevel top_lvl || early_phase @@ -775,9 +823,9 @@ preInlineUnconditionally env top_lvl bndr rhs canInlineInLam (Note _ e) = canInlineInLam e canInlineInLam _ = False - early_phase = case phase of - SimplPhase 0 _ -> False - _ -> True + early_phase = case sm_phase mode of + Phase 0 -> False + _ -> 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 @@ -795,6 +843,12 @@ preInlineUnconditionally env top_lvl bndr rhs \end{code} +%************************************************************************ +%* * + postInlineUnconditionally +%* * +%************************************************************************ + postInlineUnconditionally ~~~~~~~~~~~~~~~~~~~~~~~~~ @postInlineUnconditionally@ decides whether to unconditionally inline @@ -899,74 +953,8 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding -- Alas! where - active = case getMode env of - SimplGently {} -> isEarlyActive act - -- See Note [pre/postInlineUnconditionally in gentle mode] - SimplPhase n _ -> isActive n act - act = idInlineActivation bndr - -activeUnfolding :: SimplEnv -> IdUnfoldingFun -activeUnfolding env - = case getMode env of - SimplGently { sm_inline = False } -> active_unfolding_minimal - SimplGently { sm_inline = True } -> active_unfolding_gentle - SimplPhase n _ -> active_unfolding n - -activeUnfInRule :: SimplEnv -> IdUnfoldingFun --- When matching in RULE, we want to "look through" an unfolding --- if *rules* are on, even if *inlinings* are not. A notable example --- is DFuns, which really we want to match in rules like (op dfun) --- in gentle mode. -activeUnfInRule env - = case getMode env of - SimplGently { sm_rules = False } -> active_unfolding_minimal - SimplGently { sm_rules = True } -> active_unfolding_gentle - SimplPhase n _ -> active_unfolding n - -active_unfolding_minimal :: IdUnfoldingFun --- Compuslory unfoldings only --- Ignore SimplGently, because we want to inline regardless; --- the Id has no top-level binding at all --- --- NB: we used to have a second exception, for data con wrappers. --- On the grounds that we use gentle mode for rule LHSs, and --- they match better when data con wrappers are inlined. --- But that only really applies to the trivial wrappers (like (:)), --- and they are now constructed as Compulsory unfoldings (in MkId) --- so they'll happen anyway. -active_unfolding_minimal id - | isCompulsoryUnfolding unf = unf - | otherwise = NoUnfolding - where - unf = realIdUnfolding id -- Never a loop breaker - -active_unfolding_gentle :: IdUnfoldingFun --- Anything that is early-active --- See Note [Gentle mode] -active_unfolding_gentle id - | isEarlyActive (idInlineActivation id) = idUnfolding id - | otherwise = NoUnfolding - -- idUnfolding checks for loop-breakers - -- Things with an INLINE pragma may have - -- an unfolding *and* be a loop breaker - -- (maybe the knot is not yet untied) - -active_unfolding :: CompilerPhase -> IdUnfoldingFun -active_unfolding n id - | isActive n (idInlineActivation id) = idUnfolding id - | otherwise = NoUnfolding - -activeRule :: DynFlags -> SimplEnv -> Maybe (Activation -> Bool) --- Nothing => No rules at all -activeRule dflags env - | not (dopt Opt_EnableRewriteRules dflags) - = Nothing -- Rewriting is off - | otherwise - = case getMode env of - SimplGently { sm_rules = rules_on } - | rules_on -> Just isEarlyActive -- Note [RULEs enabled in SimplGently] - | otherwise -> Nothing - SimplPhase n _ -> Just (isActive n) + active = isActive (sm_phase (getMode env)) (idInlineActivation bndr) + -- See Note [pre/postInlineUnconditionally in gentle mode] \end{code} Note [Top level and postInlineUnconditionally] @@ -1033,20 +1021,16 @@ mkLam _env bndrs body (bndrs1, body1) = collectBinders body mkLam' dflags bndrs body - | dopt Opt_DoEtaReduction dflags, - Just etad_lam <- tryEtaReduce bndrs body + | dopt Opt_DoEtaReduction dflags + , Just etad_lam <- tryEtaReduce bndrs body = do { tick (EtaReduction (head bndrs)) ; return etad_lam } - | dopt Opt_DoLambdaEtaExpansion dflags, - not (all isTyCoVar bndrs) -- Don't eta expand type abstractions - = do { let body' = tryEtaExpansion dflags body - ; return (mkLams bndrs body') } - | otherwise = return (mkLams bndrs body) \end{code} + Note [Casts and lambdas] ~~~~~~~~~~~~~~~~~~~~~~~~ Consider @@ -1079,66 +1063,63 @@ It does not make sense to transform /\g. e `cast` g ==> (/\g.e) `cast` (/\g.g) because the latter is not well-kinded. --- c) floating lets out through big lambdas --- [only if all tyvar lambdas, and only if this lambda --- is the RHS of a let] - -{- Sept 01: I'm experimenting with getting the - full laziness pass to float out past big lambdsa - | all isTyCoVar bndrs, -- Only for big lambdas - contIsRhs cont -- Only try the rhs type-lambda floating - -- if this is indeed a right-hand side; otherwise - -- we end up floating the thing out, only for float-in - -- to float it right back in again! - = do (floats, body') <- tryRhsTyLam env bndrs body - return (floats, mkLams bndrs body') --} - - %************************************************************************ %* * - Eta expansion + Eta expansion %* * %************************************************************************ - -We go for: - f = \x1..xn -> N ==> f = \x1..xn y1..ym -> N y1..ym - (n >= 0) - -where (in both cases) - - * The xi can include type variables - - * The yi are all value variables - - * N is a NORMAL FORM (i.e. no redexes anywhere) - wanting a suitable number of extra args. - -The biggest reason for doing this is for cases like - - f = \x -> case x of - True -> \y -> e1 - False -> \y -> e2 - -Here we want to get the lambdas together. A good exmaple is the nofib -program fibheaps, which gets 25% more allocation if you don't do this -eta-expansion. - -We may have to sandwich some coerces between the lambdas -to make the types work. exprEtaExpandArity looks through coerces -when computing arity; and etaExpand adds the coerces as necessary when -actually computing the expansion. - \begin{code} -tryEtaExpansion :: DynFlags -> OutExpr -> OutExpr --- There is at least one runtime binder in the binders -tryEtaExpansion dflags body - = etaExpand fun_arity body +tryEtaExpand :: SimplEnv -> OutId -> OutExpr -> SimplM (Arity, OutExpr) +-- See Note [Eta-expanding at let bindings] +tryEtaExpand env bndr rhs + = do { dflags <- getDOptsSmpl + ; (new_arity, new_rhs) <- try_expand dflags + + ; WARN( new_arity < old_arity || new_arity < _dmd_arity, + (ptext (sLit "Arity decrease:") <+> (ppr bndr <+> ppr old_arity + <+> ppr new_arity <+> ppr _dmd_arity) $$ ppr new_rhs) ) + -- Note [Arity decrease] + return (new_arity, new_rhs) } where - fun_arity = exprEtaExpandArity dflags body + try_expand dflags + | sm_eta_expand (getMode env) -- Provided eta-expansion is on + , not (exprIsTrivial rhs) + , let new_arity = exprEtaExpandArity dflags rhs + , new_arity > rhs_arity + = do { tick (EtaExpansion bndr) + ; return (new_arity, etaExpand new_arity rhs) } + | otherwise + = return (rhs_arity, rhs) + + rhs_arity = exprArity rhs + old_arity = idArity bndr + _dmd_arity = length $ fst $ splitStrictSig $ idStrictness bndr \end{code} +Note [Eta-expanding at let bindings] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We now eta expand at let-bindings, which is where the payoff +comes. + +One useful consequence is this example: + genMap :: C a => ... + {-# INLINE genMap #-} + genMap f xs = ... + + myMap :: D a => ... + {-# INLINE myMap #-} + myMap = genMap + +Notice that 'genMap' should only inline if applied to two arguments. +In the InlineRule for myMap we'll have the unfolding + (\d -> genMap Int (..d..)) +We do not want to eta-expand to + (\d f xs -> genMap Int (..d..) f xs) +because then 'genMap' will inline, and it really shouldn't: at least +as far as the programmer is concerned, it's not applied to two +arguments! + %************************************************************************ %* *