[commit: ghc] cardinality: defaulta demand for seq changed (c6c2149)

[Ilya Sergey]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : cardinality

http://hackage.haskell.org/trac/ghc/changeset/c6c2149e4d1552f0a9929eb22136eadd8d50deda

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

commit c6c2149e4d1552f0a9929eb22136eadd8d50deda
Author: Ilya Sergey <Ilya.Sergey at cs.kuleuven.be>
Date:   Wed Sep 26 19:45:08 2012 +0100

    defaulta demand for seq changed

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

 compiler/basicTypes/Demand.lhs  |   10 +++++++---
 compiler/prelude/primops.txt.pp |    2 +-
 compiler/stranal/DmdAnal.lhs    |    2 +-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/compiler/basicTypes/Demand.lhs b/compiler/basicTypes/Demand.lhs
index 8e27004..c56f0c6 100644
--- a/compiler/basicTypes/Demand.lhs
+++ b/compiler/basicTypes/Demand.lhs
@@ -24,7 +24,7 @@ module Demand (
        
         seqStrDmd, seqStrDmdList, seqAbsDmd, seqAbsDmdList,
         seqDemand, seqDemandList, seqDmdType, seqStrictSig, 
-        evalDmd, onceEvalDmd, mkRhsDmd, isStrictDmd, splitCallDmd, splitDmdTy,
+        evalDmd, headDmd, onceEvalDmd, mkRhsDmd, isStrictDmd, splitCallDmd, splitDmdTy,
         someCompUsed, isUsed, isUsedDmd,
         defer, use, deferType, deferEnv, modifyEnv,
         isProdDmd, isPolyDmd, replicateDmd, splitProdDmd, peelCallDmd, mkCallDmd,
@@ -489,10 +489,14 @@ someCompUsed (UProd _ _) = True
 someCompUsed _           = False
 
 -- Evaluation demands
-evalDmd :: JointDmd
+evalDmd :: Demand
 evalDmd = mkJointDmd strStr top
 
-onceEvalDmd :: JointDmd
+-- A special demand for `seq`
+headDmd :: Demand
+headDmd = mkJointDmd strStr (UHead One)
+
+onceEvalDmd :: Demand
 onceEvalDmd = mkJointDmd strStr (Used One)
 
 defer :: Demand -> Demand
diff --git a/compiler/prelude/primops.txt.pp b/compiler/prelude/primops.txt.pp
index 8446c20..8478177 100644
--- a/compiler/prelude/primops.txt.pp
+++ b/compiler/prelude/primops.txt.pp
@@ -2002,7 +2002,7 @@ section "Tag to enum stuff"
 primop  DataToTagOp "dataToTag#" GenPrimOp
    a -> Int#
    with
-   strictness  = { \ _arity -> mkStrictSig (mkTopDmdType [evalDmd] topRes) }
+   strictness  = { \ _arity -> mkStrictSig (mkTopDmdType [headDmd] topRes) }
 
 	-- dataToTag# must have an evaluated argument
 
diff --git a/compiler/stranal/DmdAnal.lhs b/compiler/stranal/DmdAnal.lhs
index 4dcf4ce..a237163 100644
--- a/compiler/stranal/DmdAnal.lhs
+++ b/compiler/stranal/DmdAnal.lhs
@@ -380,7 +380,7 @@ aggregating approach exhibits worse results because of the nature of
 |both| operation for strictness. Consider the example:
 
 f y c = 
-  let h x = y |seq| x
+  let h x = y `seq` x
    in case of 
         True  -> h True
         False -> y