X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FCSE.lhs;h=4eb977d5bb42e417a99925e77e394bbd8d0560f5;hb=5f087cf4add4e140e7df05d896ee6b271133f822;hp=66038f394c45cb74414927c577319173590ada53;hpb=d364541154457a49e3c35d671d7a1b57c9c4cca3;p=ghc-hetmet.git

diff --git a/ghc/compiler/simplCore/CSE.lhs b/ghc/compiler/simplCore/CSE.lhs
index 66038f3..4eb977d 100644
--- a/ghc/compiler/simplCore/CSE.lhs
+++ b/ghc/compiler/simplCore/CSE.lhs
@@ -10,7 +10,7 @@ module CSE (
 
 #include "HsVersions.h"
 
-import CmdLineOpts	( DynFlag(..), DynFlags, dopt )
+import CmdLineOpts	( DynFlag(..), DynFlags )
 import Id		( Id, idType )
 import CoreUtils	( hashExpr, cheapEqExpr, exprIsBig, mkAltExpr )
 import DataCon		( isUnboxedTupleCon )
@@ -21,7 +21,7 @@ import CoreSyn
 import VarEnv	
 import CoreLint		( showPass, endPass )
 import Outputable
-import Util		( mapAccumL )
+import Util		( mapAccumL, lengthExceeds )
 import UniqFM
 \end{code}
 
@@ -220,12 +220,14 @@ lookup_list ((x,e):es) expr | cheapEqExpr e expr = Just x
 
 addCSEnvItem env id expr | exprIsBig expr = env
 			 | otherwise      = extendCSEnv env id expr
+   -- We don't try to CSE big expressions, because they are expensive to compare
+   -- (and are unlikely to be the same anyway)
 
 extendCSEnv (CS cs in_scope sub) id expr
   = CS (addToUFM_C combine cs hash [(id, expr)]) in_scope sub
   where
     hash   = hashExpr expr
-    combine old new = WARN( length result > 4, text "extendCSEnv: long list:" <+> ppr result )
+    combine old new = WARN( result `lengthExceeds` 4, text "extendCSEnv: long list:" <+> ppr result )
 		      result
 		    where
 		      result = new ++ old