diff --git a/ivl.def b/ivl.def
index d4a3a199c..764976cd1 100644
--- a/ivl.def
+++ b/ivl.def
@@ -1,5 +1,6 @@
 EXPORTS
 
+ivl_branch_island
 ivl_branch_terminal
 
 ivl_design_const
diff --git a/ivl_target.h b/ivl_target.h
index a18163c2f..3171472e6 100644
--- a/ivl_target.h
+++ b/ivl_target.h
@@ -422,11 +422,17 @@ typedef const struct ivl_attribute_s*ivl_attribute_t;
 
 /* BRANCH
  * Branches are analog constructs, a pair of terminals that is used in
- * branch access functions. Terminal-1 is the reference node for the
- * purposes of the access function that accesses it.
+ * branch access functions. Terminal-1 is the reference node (The
+ * "ground") for the purposes of the access function that accesses it.
+ *
+ * SEMANTIC NOTES
+ * All the branches in an island are connected by terminals or by
+ * expressions. The island is the connection of branches that must be
+ * solved together.
  */
   /* extern ivl_scope_t ivl_branch_scope(ivl_branch_t obj); */
 extern ivl_nexus_t ivl_branch_terminal(ivl_branch_t obj, int idx);
+extern ivl_island_t ivl_branch_island(ivl_branch_t obj);
 
 /* DELAYPATH
  * Delaypath objects represent delay paths called out by a specify
diff --git a/ivl_target_priv.h b/ivl_target_priv.h
index fd5c1338f..67f4b9800 100644
--- a/ivl_target_priv.h
+++ b/ivl_target_priv.h
@@ -64,6 +64,7 @@ struct ivl_design_s {
  */
 struct ivl_branch_s {
       ivl_nexus_t pins[2];
+      ivl_island_t island;
 };
 
 /*
diff --git a/t-dll-api.cc b/t-dll-api.cc
index 802584fc8..60ece7ebf 100644
--- a/t-dll-api.cc
+++ b/t-dll-api.cc
@@ -31,6 +31,11 @@ static StringHeap api_strings;
 
 /* THE FOLLOWING ARE FUNCTIONS THAT ARE CALLED FROM THE TARGET. */
 
+extern "C" ivl_island_t ivl_branch_island(ivl_branch_t net)
+{
+      return net->island;
+}
+
 extern "C" ivl_nexus_t ivl_branch_terminal(ivl_branch_t net, int idx)
 {
       assert(idx >= 0);
diff --git a/t-dll.cc b/t-dll.cc
index f81f48fe4..9b343778d 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -798,6 +798,8 @@ bool dll_target::branch(const NetBranch*net)
       obj->pins[1] = net->pin(1).nexus()->t_cookie();
       nexus_bra_add(obj->pins[1], obj, 1);
 
+      obj->island = net->get_island();
+
       return true;
 }