From d7cbeba731716f176f4c116cfe92f3ec246e1396 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Tue, 21 Dec 2010 15:58:17 -0800
Subject: [PATCH] rustboot: Only bottom out at opaque IL types after finding
 two cycles. DON'T ASK ME WHY THIS WORKS.

---
 src/boot/me/semant.ml   | 2 +-
 src/boot/util/common.ml | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/boot/me/semant.ml b/src/boot/me/semant.ml
index cea0b479b13..019cd13ea12 100644
--- a/src/boot/me/semant.ml
+++ b/src/boot/me/semant.ml
@@ -2425,7 +2425,7 @@ and referent_type
                 Some parent_tags
                   when boxed
                     && parent_tags <> []
-                    && List.mem ttag parent_tags
+                    && (list_count ttag parent_tags) > 1
                     && is_back_edge ttag (List.hd parent_tags) ->
                   Il.StructTy [| word; Il.OpaqueTy |]
               | _ -> tag ttag
diff --git a/src/boot/util/common.ml b/src/boot/util/common.ml
index 7a95573cd4e..f9b18246c79 100644
--- a/src/boot/util/common.ml
+++ b/src/boot/util/common.ml
@@ -380,6 +380,13 @@ let rec list_drop n ls =
   else list_drop (n-1) (List.tl ls)
 ;;
 
+let rec list_count elem lst =
+  match lst with
+      [] -> 0
+    | h::t when h = elem -> 1 + (list_count elem t)
+    | _::t -> list_count elem t
+;;
+
 
 (*
  * Auxiliary pair functions.