diff options
Diffstat (limited to 'compiler/basicTypes/MkId.hs')
| -rw-r--r-- | compiler/basicTypes/MkId.hs | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/compiler/basicTypes/MkId.hs b/compiler/basicTypes/MkId.hs index 616454ff7e..98ff0b0c3d 100644 --- a/compiler/basicTypes/MkId.hs +++ b/compiler/basicTypes/MkId.hs @@ -409,8 +409,8 @@ dictSelRule :: Int -> Arity -> RuleFun -- dictSelRule val_index n_ty_args _ id_unf _ args | (dict_arg : _) <- drop n_ty_args args - , Just (_, _, con_args) <- exprIsConApp_maybe id_unf dict_arg - = Just (getNth con_args val_index) + , Just (floats, _, _, con_args) <- exprIsConApp_maybe id_unf dict_arg + = Just (wrapFloats floats $ getNth con_args val_index) | otherwise = Nothing @@ -596,7 +596,7 @@ mkDataConRep dflags fam_envs wrap_name mb_bangs data_con | otherwise = topDmd wrap_prag = alwaysInlinePragma `setInlinePragmaActivation` - activeAfterInitial + activeDuringFinal -- See Note [Activation for data constructor wrappers] -- The wrapper will usually be inlined (see wrap_unf), so its @@ -706,16 +706,24 @@ mkDataConRep dflags fam_envs wrap_name mb_bangs data_con {- Note [Activation for data constructor wrappers] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The Activation on a data constructor wrapper allows it to inline in -Phase 2 and later (1, 0). But not in the InitialPhase. That gives -rewrite rules a chance to fire (in the InitialPhase) if they mention -a data constructor on the left +The Activation on a data constructor wrapper allows it to inline only in Phase +0. This way rules have a chance to fire if they mention a data constructor on +the left RULE "foo" f (K a b) = ... Since the LHS of rules are simplified with InitialPhase, we won't inline the wrapper on the LHS either. -People have asked for this before, but now that even the InitialPhase -does some inlining, it has become important. +On the other hand, this means that exprIsConApp_maybe must be able to deal +with wrappers so that case-of-constructor is not delayed; see +Note [exprIsConApp_maybe on data constructors with wrappers] for details. + +It used to activate in phases 2 (afterInitial) and later, but it makes it +awkward to write a RULE[1] with a constructor on the left: it would work if a +constructor has no wrapper, but whether a constructor has a wrapper depends, for +instance, on the order of type argument of that constructors. Therefore changing +the order of type argument could make previously working RULEs fail. + +See also https://ghc.haskell.org/trac/ghc/ticket/15840 . Note [Bangs on imported data constructors] |