[commit: ghc] master: Extra comment about the fix to Trac #5113 (33683ba)

[Simon Peyton Jones]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/33683ba9367e03b6b051f1c0c694fd8bf244a759

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

commit 33683ba9367e03b6b051f1c0c694fd8bf244a759
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Mon Feb 11 08:38:12 2013 +0000

    Extra comment about the fix to Trac #5113

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

 compiler/specialise/Specialise.lhs |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/compiler/specialise/Specialise.lhs b/compiler/specialise/Specialise.lhs
index 61f134e..e6e4c48 100644
--- a/compiler/specialise/Specialise.lhs
+++ b/compiler/specialise/Specialise.lhs
@@ -1641,6 +1641,12 @@ variables?
    We have to take care to put any new interesting dictionary 
    bindings in the set.
 
+We accidentally lost accurate tracking of local variables for a long
+time, because cloned variables don't have unfoldings. But makes a 
+massive difference in a few cases, eg Trac #5113. For nofib as a 
+whole it's only a small win: 2.2% improvement in allocation for ansi,
+1.2% for bspt, but mostly 0.0!  Average 0.1% increase in binary size.
+
 
 \begin{code}
 interestingDict :: SpecEnv -> CoreExpr -> Bool