X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=53c9149460d14838b5ddd534307d87bfac054137;hb=d95ce839533391e7118257537044f01cbb1d6694;hp=84506d85cdeade446579af1b0ccd5f6b6cced86a;hpb=2fb8e343ac2b9dcb5c2476648cf3e30ec6637afd;p=ghc-hetmet.git diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs index 84506d8..53c9149 100644 --- a/compiler/simplCore/SimplUtils.lhs +++ b/compiler/simplCore/SimplUtils.lhs @@ -10,12 +10,12 @@ module SimplUtils ( -- Inlining, preInlineUnconditionally, postInlineUnconditionally, - activeInline, activeRule, inlineMode, + activeInline, activeRule, -- The continuation type SimplCont(..), DupFlag(..), ArgInfo(..), contIsDupable, contResultType, contIsTrivial, contArgs, dropArgs, - countValArgs, countArgs, splitInlineCont, + countValArgs, countArgs, mkBoringStop, mkLazyArgStop, contIsRhsOrArg, interestingCallContext, interestingArgContext, @@ -214,24 +214,6 @@ 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 cont@(StrictArg {}) = Just (mkBoringStop, cont) -splitInlineCont _ = Nothing \end{code} @@ -308,17 +290,17 @@ 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 (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 @@ -359,7 +341,7 @@ mkArgInfo fun n_val_args call_cont 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 @@ -480,13 +462,7 @@ 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} - +We don't simplify inside InlineRules (which come from INLINE pragmas). It really is important to switch off inlinings inside such expressions. Consider the following example @@ -758,11 +734,11 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding -- 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 @@ -797,7 +773,7 @@ activeInline env 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 @@ -934,10 +910,16 @@ 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. @@ -950,6 +932,11 @@ There are some particularly delicate points here: 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. @@ -958,6 +945,8 @@ 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! @@ -971,11 +960,11 @@ 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 - | otherwise = panic "tryEtaReduce/ok_fun_id" + 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 @@ -1425,9 +1414,9 @@ prepareDefault _ _ case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rh _ -> return [(DEFAULT, [], deflt_rhs)] - | debugIsOn, isAlgTyCon tycon, [] <- tyConDataCons tycon + | 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) - -- This can legitimately happen for type families $ return [(DEFAULT, [], deflt_rhs)] --------- Catch-all cases -----------