DBC: Adds BinarySmiOp instruction

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 eae97e28972bb29ceacca4dd182ffd970cd70563..5a60cb7d9b5a86c7e4056462ccfb305fdfbc53f7 100644
--- a/runtime/vm/flow_graph_compiler_dbc.cc
+++ b/runtime/vm/flow_graph_compiler_dbc.cc
@@ -237,11 +237,9 @@ void FlowGraphCompiler::GenerateAssertAssignable(TokenPosition token_pos,
   AddCurrentDescriptor(RawPcDescriptors::kOther, deopt_id, token_pos);
   if (is_optimizing()) {
     // Assert assignable keeps the instance on the stack as the result,
-    // all other arguments are popped.
-    // In optimized code we need to drop it because optimized code
-    // expects the result in the register and it is already there
-    // because locs()->in(0).reg() == locs()->out(0).reg().
-    __ Drop1();
+    // all other arguments are popped. Since there may have been a GC during
+    // the runtime call, we have to reload the instance.
+    __ PopLocal(locs->out(0).reg());

[Vyacheslav Egorov (Google), 2016/06/16 08:31:53]

I don't get this comment. GC can't have anything to do with this reload because
all live registers must be scanned. If in(0) is not scanned - it's a bug in
stack maps and it needs to be fixed.

   }
 }