[commit: ghc] wip/nested-cpr: Apply state hack only to information about arguments (938cf3d)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/nested-cpr
Link       : http://ghc.haskell.org/trac/ghc/changeset/938cf3d4d6601ca2fce814b20eb75e03c514c341/ghc

>---------------------------------------------------------------

commit 938cf3d4d6601ca2fce814b20eb75e03c514c341
Author: Joachim Breitner <mail at joachim-breitner.de>
Date:   Thu Nov 28 10:29:47 2013 +0000

    Apply state hack only to information about arguments


>---------------------------------------------------------------

938cf3d4d6601ca2fce814b20eb75e03c514c341
 compiler/basicTypes/Demand.lhs |    8 ++++++++
 compiler/stranal/DmdAnal.lhs   |    4 +++-
 compiler/stranal/WwLib.lhs     |    2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/compiler/basicTypes/Demand.lhs b/compiler/basicTypes/Demand.lhs
index e3cd5d6..b3fe942 100644
--- a/compiler/basicTypes/Demand.lhs
+++ b/compiler/basicTypes/Demand.lhs
@@ -20,6 +20,7 @@ module Demand (
 
         DmdType(..), dmdTypeDepth, lubDmdType, bothDmdEnv, bothDmdType, bothDmdTypeCase,
         topDmdType, botDmdType, mkDmdType, mkTopDmdType, 
+        dmdTypeArgTop,
 
         DmdEnv, emptyDmdEnv,
 
@@ -1141,6 +1142,13 @@ splitDmdTy :: DmdType -> (Demand, DmdType)
 splitDmdTy (DmdType fv (dmd:dmds) res_ty) = (dmd, DmdType fv dmds res_ty)
 splitDmdTy ty@(DmdType _ [] res_ty)       = (resTypeArgDmd res_ty, ty)
 
+-- We want to forget what we know about the arguments, but keep the information
+-- of the result, see Note [IO State Hack]
+dmdTypeArgTop :: DmdType -> DmdType
+dmdTypeArgTop d@(DmdType _ _ res)
+  = let (DmdType env' ds' _) = d `lubDmdType` topDmdType
+    in   DmdType env' ds' res
+
 modifyEnv :: Bool                       -- No-op if False
           -> (Demand -> Demand)         -- The zapper
           -> DmdEnv -> DmdEnv           -- Env1 and Env2
diff --git a/compiler/stranal/DmdAnal.lhs b/compiler/stranal/DmdAnal.lhs
index 8da502c..67e5663 100644
--- a/compiler/stranal/DmdAnal.lhs
+++ b/compiler/stranal/DmdAnal.lhs
@@ -307,9 +307,11 @@ dmdAnalAlt env dmd (con,bndrs,rhs)
 	(rhs_ty, rhs')   = dmdAnal env dmd rhs
         rhs_ty'          = addDataConPatDmds con bndrs rhs_ty
 	(alt_ty, bndrs') = annotateBndrs env rhs_ty' bndrs
-	final_alt_ty | io_hack_reqd = alt_ty `lubDmdType` topDmdType
+	final_alt_ty | io_hack_reqd = dmdTypeArgTop alt_ty
 		     | otherwise    = alt_ty
 
+        -- Note [IO State Hack]
+        --
 	-- There's a hack here for I/O operations.  Consider
 	-- 	case foo x s of { (# s, r #) -> y }
 	-- Is this strict in 'y'.  Normally yes, but what if 'foo' is an I/O
diff --git a/compiler/stranal/WwLib.lhs b/compiler/stranal/WwLib.lhs
index 0b819dc..861a03b 100644
--- a/compiler/stranal/WwLib.lhs
+++ b/compiler/stranal/WwLib.lhs
@@ -503,7 +503,7 @@ deepSplitCprType_maybe :: ConTag -> Type -> Maybe (DataCon, [Type], [Type], Coer
 deepSplitCprType_maybe con_tag ty
   | let (co, ty1) = topNormaliseNewType_maybe ty `orElse` (mkReflCo Representational ty, ty)
   , Just (tc, tc_args) <- splitTyConApp_maybe ty1
-  , isDataTyCon tc
+  , isDataTyCon tc || isUnboxedTupleTyCon tc
   , let cons = tyConDataCons tc
         con = ASSERT( cons `lengthAtLeast` con_tag ) cons !! (con_tag - fIRST_TAG)
   = Just (con, tc_args, dataConInstArgTys con tc_args, co)