DBC: Adds UnarySmiOp instruction, etc.

runtime/vm/flow_graph_compiler_dbc.cc

Index: runtime/vm/flow_graph_compiler_dbc.cc
diff --git a/runtime/vm/flow_graph_compiler_dbc.cc b/runtime/vm/flow_graph_compiler_dbc.cc
index af756db0895dcdf660228ed3c401865d6fc9ce0c..e83b4049039c2dc701817a630e24d1cbe1b3c99b 100644
--- a/runtime/vm/flow_graph_compiler_dbc.cc
+++ b/runtime/vm/flow_graph_compiler_dbc.cc
@@ -239,7 +239,9 @@ void FlowGraphCompiler::GenerateAssertAssignable(TokenPosition token_pos,
     // Assert assignable keeps the instance on the stack as the result,
     // all other arguments are popped.
     ASSERT(locs->out(0).reg() == locs->in(0).reg());
-    __ Drop1();
+    // TODO(zra): __ Drop1() should be sufficient here, but it creates
+    // flakes in checked-mode tests. Need to investigate.
+    __ PopLocal(locs->out(0).reg());

[zra, 2016/06/16 21:38:02]

I guess this might just be masking the underlying problem. I need to get some
other (non-DBC) things started, but I'll return to investigate this after this
CL. If you have time to provide assistance here that would also be appreciated.

[Vyacheslav Egorov (Google), 2016/06/17 08:12:43]

I am looking into this now.

For me flakes seem to occur even with this change, though much more rarely.

[Vyacheslav Egorov (Google), 2016/06/17 11:01:07]

I fixed it see a CL I have sent to you. 

You can revert this part.

[zra, 2016/06/21 20:24:08]

Done.

   }
 }