Don't look through SCC in exprIsConApp_maybe

By not taking account of SCC notes we were inadvertently
discarding some, which led to mis-counted entries with -O

Should fix (part of) Trac #4414

diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs
index e007682..e54acc0 100644 (file)
--- a/compiler/coreSyn/CoreUnfold.lhs
+++ b/compiler/coreSyn/CoreUnfold.lhs
@@ -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])
 
 -- 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
   = 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
        --      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
 
 exprIsConApp_maybe id_unf (Cast expr co)
   =     -- Here we do the KPush reduction rule as described in the FC paper