[commit: stm] master: add some UNPACKs to improve performance a bit (9703c74)

[Simon Marlow]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/stm

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/9703c744181a6f71c4a6c836ac3b5be897da8b11

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

commit 9703c744181a6f71c4a6c836ac3b5be897da8b11
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Tue Jun 12 10:56:43 2012 +0100

    add some UNPACKs to improve performance a bit

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

 Control/Concurrent/STM/TChan.hs |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Control/Concurrent/STM/TChan.hs b/Control/Concurrent/STM/TChan.hs
index aea5176..713624e 100644
--- a/Control/Concurrent/STM/TChan.hs
+++ b/Control/Concurrent/STM/TChan.hs
@@ -43,11 +43,15 @@ import GHC.Conc
 
 import Data.Typeable (Typeable)
 
+#define _UPK_(x) {-# UNPACK #-} !(x)
+
 -- | 'TChan' is an abstract type representing an unbounded FIFO channel.
-data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a)) deriving Typeable
+data TChan a = TChan _UPK_(TVar (TVarList a))
+                     _UPK_(TVar (TVarList a))
+  deriving Typeable
 
 type TVarList a = TVar (TList a)
-data TList a = TNil | TCons a (TVarList a)
+data TList a = TNil | TCons a _UPK_(TVarList a)
 
 -- |Build and returns a new instance of 'TChan'
 newTChan :: STM (TChan a)