Don't look through SCC in exprIsConApp_maybe

[ghc-hetmet.git] / compiler / coreSyn / CoreUnfold.lhs

diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs
index 7ab0e23..e54acc0 100644 (file)
--- a/compiler/coreSyn/CoreUnfold.lhs
+++ b/compiler/coreSyn/CoreUnfold.lhs
@@ -871,7 +871,7 @@ But the defn of GHC.Classes.$dmmin is:
     {- Arity: 3, HasNoCafRefs, Strictness: SLL,
        Unfolding: (\ @ a $dOrd :: GHC.Classes.Ord a x :: a y :: a ->
                    case @ a GHC.Classes.<= @ a $dOrd x y of wild {
-                     GHC.Bool.False -> y GHC.Bool.True -> x }) -}
+                     GHC.Types.False -> y GHC.Types.True -> x }) -}
 
 We *really* want to inline $dmmin, even though it has arity 3, in
 order to unravel the recursion.
@@ -1163,13 +1163,14 @@ However e might not *look* as if
 -- where t1..tk are the *universally-qantified* type args of 'dc'
 exprIsConApp_maybe :: IdUnfoldingFun -> CoreExpr -> Maybe (DataCon, [Type], [CoreExpr])
 
-exprIsConApp_maybe id_unf (Note _ expr)
+exprIsConApp_maybe id_unf (Note note expr)
+  | notSccNote note
   = exprIsConApp_maybe id_unf expr
-       -- We ignore all notes.  For example,
+       -- We ignore all notes except SCCs.  For example,
        --      case _scc_ "foo" (C a b) of
        --                      C a b -> e
-       -- should be optimised away, but it will be only if we look
-       -- through the SCC note.
+       -- should not be optimised away, because we'll lose the
+       -- entry count on 'foo'; see Trac #4414
 
 exprIsConApp_maybe id_unf (Cast expr co)
   =     -- Here we do the KPush reduction rule as described in the FC paper