Fixup redefinitions before doing code motion

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
diff --git a/runtime/vm/flow_graph_type_propagator.cc b/runtime/vm/flow_graph_type_propagator.cc
index 782ea05234f7166d6e33c85c06cf6d12c7456799..d3cdc8418fb36da18f6e90f63ddd8fb341df80a6 100644
--- a/runtime/vm/flow_graph_type_propagator.cc
+++ b/runtime/vm/flow_graph_type_propagator.cc
@@ -232,8 +232,17 @@ void FlowGraphTypePropagator::VisitCheckClass(CheckClassInstr* check) {
 
 
 void FlowGraphTypePropagator::VisitCheckClassId(CheckClassIdInstr* check) {
-  // Can't propagate the type/cid because it may cause illegal code motion and
-  // we don't track dependencies in all places via redefinitions.
+  if (!check->Dependencies().IsNone()) {
+    // TODO(vegorov): If check is affected by side-effect we can still propagate
+    // the type further but not the cid.
+    return;
+  }
+
+  LoadClassIdInstr* load_cid =
+      check->value()->definition()->OriginalDefinition()->AsLoadClassId();
+  if (load_cid != NULL) {
+    SetCid(load_cid->object()->definition(), check->cid());
+  }
 }