-- 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,
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}
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
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
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
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.
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.
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!
&& (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
_ -> 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 -----------