X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FsimplCore%2FCSE.lhs;h=5bec8f0c3d7705dbaf78cce28f9886013004477d;hp=8c386614c6e6f05a6da186a92a48e96b0040376d;hb=fdf8656855d26105ff36bdd24d41827b05037b91;hpb=72462499b891d5779c19f3bda03f96e24f9554ae

diff --git a/compiler/simplCore/CSE.lhs b/compiler/simplCore/CSE.lhs
index 8c38661..5bec8f0 100644
--- a/compiler/simplCore/CSE.lhs
+++ b/compiler/simplCore/CSE.lhs
@@ -11,7 +11,7 @@ module CSE (
 #include "HsVersions.h"
 
 import Id		( Id, idType, idInlineActivation, zapIdOccInfo )
-import CoreUtils	( hashExpr, cheapEqExpr, exprIsBig, mkAltExpr, exprIsCheap )
+import CoreUtils	( hashExpr, eqExpr, exprIsBig, mkAltExpr, exprIsCheap )
 import DataCon		( isUnboxedTupleCon )
 import Type		( tyConAppArgs )
 import CoreSyn
@@ -207,6 +207,7 @@ do_one env (id, rhs)
 
 tryForCSE :: CSEnv -> CoreExpr -> CoreExpr
 tryForCSE _   (Type t) = Type t
+tryForCSE _   (Coercion c) = Coercion c
 tryForCSE env expr     = case lookupCSEnv env expr' of
 			    Just smaller_expr -> smaller_expr
  			    Nothing  	      -> expr'
@@ -215,6 +216,7 @@ tryForCSE env expr     = case lookupCSEnv env expr' of
 
 cseExpr :: CSEnv -> CoreExpr -> CoreExpr
 cseExpr _   (Type t)               = Type t
+cseExpr _   (Coercion co)          = Coercion co
 cseExpr _   (Lit lit)              = Lit lit
 cseExpr env (Var v)		   = Var (lookupSubst env v)
 cseExpr env (App f a)        	   = App (cseExpr env f) (tryForCSE env a)
@@ -301,15 +303,19 @@ emptyCSEnv :: CSEnv
 emptyCSEnv = CS emptyUFM emptyInScopeSet emptyVarEnv
 
 lookupCSEnv :: CSEnv -> CoreExpr -> Maybe CoreExpr
-lookupCSEnv (CS cs _ _) expr
+lookupCSEnv (CS cs in_scope _) expr
   = case lookupUFM cs (hashExpr expr) of
 	Nothing -> Nothing
-	Just pairs -> lookup_list pairs expr
-
-lookup_list :: [(CoreExpr,CoreExpr)] -> CoreExpr -> Maybe CoreExpr
-lookup_list [] _ = Nothing
-lookup_list ((e,e'):es) expr | cheapEqExpr e expr = Just e'
-			     | otherwise	  = lookup_list es expr
+	Just pairs -> lookup_list pairs
+  where
+  -- In this lookup we use full expression equality
+  -- Reason: when expressions differ we generally find out quickly
+  --         but I found that cheapEqExpr was saying (\x.x) /= (\y.y),
+  -- 	     and this kind of thing happened in real programs
+    lookup_list :: [(CoreExpr,CoreExpr)] -> Maybe CoreExpr
+    lookup_list []                                   = Nothing
+    lookup_list ((e,e'):es) | eqExpr in_scope e expr = Just e'
+        		    | otherwise	             = lookup_list es
 
 addCSEnvItem :: CSEnv -> CoreExpr -> CoreExpr -> CSEnv
 addCSEnvItem env expr expr' | exprIsBig expr = env