[project @ 2005-07-28 14:45:55 by simonpj]

Restore costant folding

diff --git a/ghc/compiler/specialise/Rules.lhs b/ghc/compiler/specialise/Rules.lhs
index 9220604..702902f 100644 (file)
--- a/ghc/compiler/specialise/Rules.lhs
+++ b/ghc/compiler/specialise/Rules.lhs
@@ -39,10 +39,9 @@ import Name          ( Name, NamedThing(..), nameOccName )
 import NameEnv
 import Unify           ( tcMatchTyX, MatchEnv(..) )
 import BasicTypes      ( Activation, CompilerPhase, isActive )
-
 import Outputable
 import FastString
-import Maybe           ( isJust )
+import Maybes          ( isJust, orElse )
 import Bag
 import Util            ( singleton )
 import List            ( isPrefixOf )
@@ -198,10 +197,13 @@ lookupRule :: (Activation -> Bool) -> InScopeSet
 lookupRule is_active in_scope rule_base fn args
   = matchRules is_active in_scope fn args rules
   where
-    rules | isLocalId fn = idCoreRules fn
-         | otherwise    = case lookupNameEnv rule_base (idName fn) of
-                               Just rules -> rules
-                               Nothing    -> []
+       -- The rules for an Id come from two places:
+       --      (a) the ones it is born with (idCoreRules fn)
+       --      (b) rules added in subsequent modules (extra_rules)
+       -- PrimOps, for example, are born with a bunch of rules under (a)
+    rules = extra_rules ++ idCoreRules fn
+    extra_rules | isLocalId fn = []
+               | otherwise    = lookupNameEnv rule_base (idName fn) `orElse` []
 
 matchRules :: (Activation -> Bool) -> InScopeSet
           -> Id -> [CoreExpr]