[project @ 2001-12-14 17:24:03 by simonpj]

[ghc-hetmet.git] / ghc / compiler / simplCore / CSE.lhs

diff --git a/ghc/compiler/simplCore/CSE.lhs b/ghc/compiler/simplCore/CSE.lhs
index b2e124a..4eb977d 100644 (file)
--- a/ghc/compiler/simplCore/CSE.lhs
+++ b/ghc/compiler/simplCore/CSE.lhs
@@ -10,18 +10,18 @@ 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 )
-import Type            ( splitTyConApp_maybe )
+import Type            ( tyConAppArgs )
 import Subst           ( InScopeSet, uniqAway, emptyInScopeSet, 
                          extendInScopeSet, elemInScopeSet )
 import CoreSyn
 import VarEnv  
-import CoreLint                ( beginPass, endPass )
+import CoreLint                ( showPass, endPass )
 import Outputable
-import Util            ( mapAccumL )
+import Util            ( mapAccumL, lengthExceeds )
 import UniqFM
 \end{code}
 
@@ -107,11 +107,9 @@ cseProgram :: DynFlags -> [CoreBind] -> IO [CoreBind]
 
 cseProgram dflags binds
   = do {
-       beginPass dflags "Common sub-expression";
+       showPass dflags "Common sub-expression";
        let { binds' = cseBinds emptyCSEnv binds };
-       endPass dflags "Common sub-expression" 
-               (dopt Opt_D_dump_cse dflags || dopt Opt_D_verbose_core2core dflags)
-               binds'  
+       endPass dflags "Common sub-expression"  Opt_D_dump_cse binds'   
     }
 
 cseBinds :: CSEnv -> [CoreBind] -> [CoreBind]
@@ -170,9 +168,7 @@ cseAlts env scrut' bndr bndr' alts
                other ->  (bndr', extendCSEnv env bndr' scrut') -- See "yet another wrinkle"
                                                                -- map: scrut' -> bndr'
 
-    arg_tys = case splitTyConApp_maybe (idType bndr) of
-               Just (_, arg_tys) -> arg_tys
-               other             -> pprPanic "cseAlts" (ppr bndr)
+    arg_tys = tyConAppArgs (idType bndr)
 
     cse_alt (DataAlt con, args, rhs)
        | not (null args || isUnboxedTupleCon con)
@@ -224,12 +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