Await always waits

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
===================================================================
--- runtime/vm/flow_graph_builder.cc	(revision 40777)
+++ runtime/vm/flow_graph_builder.cc	(working copy)
@@ -1093,8 +1093,17 @@
     UnchainContexts(current_context_level);
   }
 
-
-  AddReturnExit(node->token_pos(), return_value);
+  if (function.is_async_closure() &&
+      (node->return_type() == ReturnNode::kContinuation)) {
+    // This return instruction may be followed by instructions
+    // that get called when the async closure is resumed, so
+    // do not add an exit and close the fragment.
+    ReturnInstr* return_instr =
+        new(I) ReturnInstr(node->token_pos(), return_value);
+    AddInstruction(return_instr);
+  } else {
+    AddReturnExit(node->token_pos(), return_value);
+  }

[Florian Schneider, 2014/10/06 17:32:54]

I'd imagine this looking like this:

AddReturnExit(node->token_pos(), return_value);

if (function.is_async_closure() &&
    (node->return_type() == ReturnNode::kContinuation)) {
  JoinEntryInstr* join = new(I) JoinEntryInstr(
      owner()->AllocateBlockId(), owner()->try_index());
  owner()->AddAwaitJoin(join);
  exit_ = join;
}

where AddAwaitJoin is like AddCatchEntry and the await-joins blocks are added to
the successors of GraphEntryInstr like catch-blocks.

 }