[commit: ghc] master: no functional changes (acdebbb)

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/acdebbbad25f6d9c5c11550cc8998db10b8b8a48

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

commit acdebbbad25f6d9c5c11550cc8998db10b8b8a48
Author: Simon Marlow <[email protected]>
Date:   Fri Sep 21 11:05:53 2012 +0100

    no functional changes

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

 compiler/cmm/CmmSink.hs |   23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/compiler/cmm/CmmSink.hs b/compiler/cmm/CmmSink.hs
index 8c5c99d..28e3b77 100644
--- a/compiler/cmm/CmmSink.hs
+++ b/compiler/cmm/CmmSink.hs
@@ -155,7 +155,7 @@ cmmSink dflags graph = ofBlockList (g_entry graph) $ sink mapEmpty $ blocks
       drop_if a@(r,rhs,_) live_sets = (should_drop, live_sets')
           where
             should_drop =  conflicts dflags a final_last
-                        || {- not (isTiny rhs) && -} live_in_multi live_sets r
+                        || {- not (isSmall rhs) && -} live_in_multi live_sets r
                         || r `Set.member` live_in_joins
 
             live_sets' | should_drop = live_sets
@@ -172,12 +172,21 @@ cmmSink dflags graph = ofBlockList (g_entry graph) $ sink mapEmpty $ blocks
                  mapFromList [ (l, filterAssignments dflags (getLive l) assigs'')
                              | l <- succs ]
 
-{-
--- tiny: an expression we don't mind duplicating
-isTiny :: CmmExpr -> Bool
-isTiny (CmmReg _) = True
-isTiny (CmmLit _) = True
-isTiny _other     = False
+{- TODO: enable this later, when we have some good tests in place to
+   measure the effect and tune it.
+
+-- small: an expression we don't mind duplicating
+isSmall :: CmmExpr -> Bool
+isSmall (CmmReg (CmmLocal _)) = True  -- not globals, we want to coalesce them instead
+isSmall (CmmLit _) = True
+isSmall (CmmMachOp (MO_Add _) [x,y]) = isTrivial x && isTrivial y
+isSmall (CmmRegOff (CmmLocal _) _) = True
+isSmall _ = False
+
+isTrivial :: CmmExpr -> Bool
+isTrivial (CmmReg (CmmLocal _)) = True
+isTrivial (CmmLit _) = True
+isTrivial _ = False
 -}
 
 --