import CoreSyn
import Demand ( isStrictDmd )
import PprCore ( pprParendExpr, pprCoreExpr )
-import CoreUnfold ( mkUnfolding, mkCoreUnfolding
- , mkInlineUnfolding, mkSimpleUnfolding
- , exprIsConApp_maybe, callSiteInline, CallCtxt(..) )
+import CoreUnfold
import CoreUtils
import qualified CoreSubst
import CoreArity
; (new_arity, final_rhs) <- tryEtaExpand env new_bndr new_rhs
-- Simplify the unfolding
- ; new_unfolding <- simplUnfolding env top_lvl old_bndr occ_info final_rhs old_unf
+ ; new_unfolding <- simplUnfolding env top_lvl old_bndr final_rhs old_unf
; if postInlineUnconditionally env top_lvl new_bndr occ_info final_rhs new_unfolding
-- Inline and discard the binding
-- opportunity to inline 'y' too.
addPolyBind top_lvl env (NonRec poly_id rhs)
- = do { unfolding <- simplUnfolding env top_lvl poly_id NoOccInfo rhs noUnfolding
+ = do { unfolding <- simplUnfolding env top_lvl poly_id rhs noUnfolding
-- Assumes that poly_id did not have an INLINE prag
-- which is perhaps wrong. ToDo: think about this
; let final_id = setIdInfo poly_id $
------------------------------
simplUnfolding :: SimplEnv-> TopLevelFlag
- -> Id
- -> OccInfo -> OutExpr
+ -> InId
+ -> OutExpr
-> Unfolding -> SimplM Unfolding
-- Note [Setting the new unfolding]
-simplUnfolding env _ _ _ _ (DFunUnfolding ar con ops)
+simplUnfolding env _ _ _ (DFunUnfolding ar con ops)
= return (DFunUnfolding ar con ops')
where
ops' = map (fmap (substExpr (text "simplUnfolding") env)) ops
-simplUnfolding env top_lvl id _ _
+simplUnfolding env top_lvl id _
(CoreUnfolding { uf_tmpl = expr, uf_arity = arity
, uf_src = src, uf_guidance = guide })
| isStableSource src
; let src' = CoreSubst.substUnfoldingSource (mkCoreSubst (text "inline-unf") env) src
is_top_lvl = isTopLevel top_lvl
; case guide of
- UnfIfGoodArgs{} ->
- -- We need to force bottoming, or the new unfolding holds
- -- on to the old unfolding (which is part of the id).
- let bottoming = isBottomingId id
- in bottoming `seq` return (mkUnfolding src' is_top_lvl bottoming expr')
+ UnfWhen sat_ok _ -- Happens for INLINE things
+ -> let guide' = UnfWhen sat_ok (inlineBoringOk expr')
+ -- Refresh the boring-ok flag, in case expr'
+ -- has got small. This happens, notably in the inlinings
+ -- for dfuns for single-method classes; see
+ -- Note [Single-method classes] in TcInstDcls.
+ -- A test case is Trac #4138
+ in return (mkCoreUnfolding src' is_top_lvl expr' arity guide')
+ -- See Note [Top-level flag on inline rules] in CoreUnfold
+
+ _other -- Happens for INLINABLE things
+ -> let bottoming = isBottomingId id
+ in bottoming `seq` -- See Note [Force bottoming field]
+ return (mkUnfolding src' is_top_lvl bottoming expr')
-- If the guidance is UnfIfGoodArgs, this is an INLINABLE
-- unfolding, and we need to make sure the guidance is kept up
-- to date with respect to any changes in the unfolding.
- _other ->
- return (mkCoreUnfolding src' is_top_lvl expr' arity guide)
- -- See Note [Top-level flag on inline rules] in CoreUnfold
}
where
act = idInlineActivation id
rule_env = updMode (updModeForInlineRules act) env
-- See Note [Simplifying inside InlineRules] in SimplUtils
-simplUnfolding _ top_lvl id _occ_info new_rhs _
- = -- We need to force bottoming, or the new unfolding holds
- -- on to the old unfolding (which is part of the id).
- let bottoming = isBottomingId id
- in bottoming `seq` return (mkUnfolding InlineRhs (isTopLevel top_lvl) bottoming new_rhs)
- -- We make an unfolding *even for loop-breakers*.
- -- Reason: (a) It might be useful to know that they are WHNF
- -- (b) In TidyPgm we currently assume that, if we want to
- -- expose the unfolding then indeed we *have* an unfolding
- -- to expose. (We could instead use the RHS, but currently
- -- we don't.) The simple thing is always to have one.
+simplUnfolding _ top_lvl id new_rhs _
+ = let bottoming = isBottomingId id
+ in bottoming `seq` -- See Note [Force bottoming field]
+ return (mkUnfolding InlineRhs (isTopLevel top_lvl) bottoming new_rhs)
+ -- We make an unfolding *even for loop-breakers*.
+ -- Reason: (a) It might be useful to know that they are WHNF
+ -- (b) In TidyPgm we currently assume that, if we want to
+ -- expose the unfolding then indeed we *have* an unfolding
+ -- to expose. (We could instead use the RHS, but currently
+ -- we don't.) The simple thing is always to have one.
\end{code}
+Note [Force bottoming field]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We need to force bottoming, or the new unfolding holds
+on to the old unfolding (which is part of the id).
+
Note [Arity decrease]
~~~~~~~~~~~~~~~~~~~~~
Generally speaking the arity of a binding should not decrease. But it *can*
%* *
%************************************************************************
+Note [Zap unfolding when beta-reducing]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Lambda-bound variables can have stable unfoldings, such as
+ $j = \x. \b{Unf=Just x}. e
+See Note [Case binders and join points] below; the unfolding for lets
+us optimise e better. However when we beta-reduce it we want to
+revert to using the actual value, otherwise we can end up in the
+stupid situation of
+ let x = blah in
+ let b{Unf=Just x} = y
+ in ...b...
+Here it'd be far better to drop the unfolding and use the actual RHS.
+
\begin{code}
simplLam :: SimplEnv -> [InId] -> InExpr -> SimplCont
-> SimplM (SimplEnv, OutExpr)
-- Beta reduction
simplLam env (bndr:bndrs) body (ApplyTo _ arg arg_se cont)
= do { tick (BetaReduction bndr)
- ; simplNonRecE env bndr (arg, arg_se) (bndrs, body) cont }
+ ; simplNonRecE env (zap_unfolding bndr) (arg, arg_se) (bndrs, body) cont }
+ where
+ zap_unfolding bndr -- See Note [Zap unfolding when beta-reducing]
+ | isId bndr, isStableUnfolding (realIdUnfolding bndr)
+ = setIdUnfolding bndr NoUnfolding
+ | otherwise = bndr
-- Not enough args, so there are real lambdas left to put in the result
simplLam env bndrs body cont
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