Collect type feedback for fields.

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index fe14079dc1a7890a34bccecb53a4664db5f7f4af..9f8e9a5871e3256d83d0fe187e6e18babb04b53f 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -696,4 +696,39 @@ intptr_t FlowGraph::InstructionCount() const {
 }
 
 
+const ZoneGrowableArray<Field*>* FlowGraph::FieldDependencies() const {
+  ZoneGrowableArray<Field*>* result = new ZoneGrowableArray<Field*>(10);
+
+  for (intptr_t i = 1; i < reverse_postorder().length(); i++) {
+    BlockEntryInstr* entry = reverse_postorder()[i];
+    for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
+      LoadFieldInstr* load_field = it.Current()->AsLoadField();
+      if (load_field == NULL) {
+        continue;
+      }
+
+      Field* field = load_field->field();
+      if ((field == NULL) ||
+          (field->guarded_cid() == kDynamicCid) ||
+          (field->guarded_cid() == kIllegalCid)) {
+        continue;
+      }
+
+      bool found = false;
+      for (intptr_t j = 0; j < result->length(); j++) {
+        if ((*result)[j]->raw() == field->raw()) {
+          found = true;
+          break;
+        }
+      }
+
+      if (!found) {
+        result->Add(field);
+      }
+    }
+  }
+
+  return result;
+}
+
 }  // namespace dart