From: simonpj <unknown>
Date: Tue, 19 Nov 2002 15:51:17 +0000 (+0000)
Subject: [project @ 2002-11-19 15:51:16 by simonpj]
X-Git-Tag: Approx_11550_changesets_converted~1429
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=821d799485702aa76b393cecf3e2eb32381eb5df;p=ghc-hetmet.git

[project @ 2002-11-19 15:51:16 by simonpj]
Comments
---

diff --git a/ghc/compiler/stranal/DmdAnal.lhs b/ghc/compiler/stranal/DmdAnal.lhs
index 063a288..e02bf5e 100644
--- a/ghc/compiler/stranal/DmdAnal.lhs
+++ b/ghc/compiler/stranal/DmdAnal.lhs
@@ -487,11 +487,10 @@ We can't start with 'not-demanded' because then consider
 
 In the first iteration we'd have no demand info for x, so assume
 not-demanded; then we'd get TopRes for f's CPR info.  Next iteration
-we'd see that t was demanded, and so give it the CPR property, but
-by now f has TopRes, so it will stay TopRes.  
-ever_in
-Instead, with the Nothing setting the first time round, we say
-'yes t is demanded' the first time.  
+we'd see that t was demanded, and so give it the CPR property, but by
+now f has TopRes, so it will stay TopRes.  Instead, with the Nothing
+setting the first time round, we say 'yes t is demanded' the first
+time.
 
 However, this does mean that for non-recursive bindings we must
 iterate twice to be sure of not getting over-optimistic CPR info,
@@ -729,10 +728,15 @@ extendSigEnvList = extendVarEnvList
 
 extendSigsWithLam :: SigEnv -> Id -> SigEnv
 -- Extend the SigEnv when we meet a lambda binder
---  If the binder is marked demanded with a product demand, then give it a CPR 
+-- If the binder is marked demanded with a product demand, then give it a CPR 
 -- signature, because in the likely event that this is a lambda on a fn defn 
 -- [we only use this when the lambda is being consumed with a call demand],
--- it'll be w/w'd and so it will be CPR-ish.
+-- it'll be w/w'd and so it will be CPR-ish.  E.g.
+--	f = \x::(Int,Int).  if ...strict in x... then
+--				x
+--			    else
+--				(a,b)
+-- We want f to have the CPR property because x does, by the time f has been w/w'd
 --
 -- 	NOTE: see notes [CPR-AND-STRICTNESS]
 --
diff --git a/ghc/compiler/stranal/WwLib.lhs b/ghc/compiler/stranal/WwLib.lhs
index 58060b0..49571f3 100644
--- a/ghc/compiler/stranal/WwLib.lhs
+++ b/ghc/compiler/stranal/WwLib.lhs
@@ -420,6 +420,9 @@ mkWWcpr body_ty RetCPR
 
     | n_con_args == 1 && isUnLiftedType con_arg_ty1
 	-- Special case when there is a single result of unlifted type
+	--
+	-- Wrapper:	case (..call worker..) of x -> C x
+	-- Worker:	case (   ..body..    ) of C x -> x
     = getUniquesUs 			`thenUs` \ (work_uniq : arg_uniq : _) ->
       let
 	work_wild = mk_ww_local work_uniq body_ty
@@ -431,6 +434,8 @@ mkWWcpr body_ty RetCPR
 		con_arg_ty1)
 
     | otherwise		-- The general case
+	-- Wrapper: case (..call worker..) of (# a, b #) -> C a b
+	-- Worker:  case (   ...body...  ) of C a b -> (# a, b #)     
     = getUniquesUs 	  	`thenUs` \ uniqs ->
       let
         (wrap_wild : work_wild : args) = zipWith mk_ww_local uniqs (ubx_tup_ty : body_ty : con_arg_tys)
@@ -440,7 +445,7 @@ mkWWcpr body_ty RetCPR
 	ubx_tup_app		       = mkConApp ubx_tup_con (map Type con_arg_tys   ++ arg_vars)
         con_app			       = mkConApp data_con    (map Type tycon_arg_tys ++ arg_vars)
       in
-      returnUs (\ wkr_call -> Case wkr_call wrap_wild [(DataAlt ubx_tup_con, args, con_app)],
+      returnUs (\ wkr_call -> Case wkr_call wrap_wild   [(DataAlt ubx_tup_con, args, con_app)],
 		\ body     -> workerCase body work_wild [(DataAlt data_con,    args, ubx_tup_app)],
 		ubx_tup_ty)
     where