Collect type feedback for fields.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index bc4444030a93d7b96b96c1b496a5f026b73960fc..0d5790063a044225a883bba9ce0f9408016d1196 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -167,6 +167,8 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
       FlowGraphPrinter::PrintGraph("Before Optimizations", flow_graph);
     }
 
+    const ZoneGrowableArray<Field*>* guarded_fields = NULL;
+
     if (optimized) {
       TimerScope timer(FLAG_compiler_stats,
                        &CompilerStats::graphoptimizer_timer,
@@ -193,6 +195,8 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
       }
 
+      guarded_fields = &flow_graph->FieldDependencies();
+
       // Propagate types and eliminate more type tests.
       if (FLAG_propagate_types) {
         FlowGraphTypePropagator propagator(flow_graph);
@@ -221,6 +225,8 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
 
       // Propagate types and eliminate even more type tests.
       if (FLAG_propagate_types) {
+        // Recompute types after constant propagation to infer more precise
+        // types for uses that were previously reached by now eliminated phis.
         FlowGraphTypePropagator propagator(flow_graph);
         propagator.Propagate();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
@@ -259,6 +265,14 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
       }
 
       // The final canonicalization pass before the code generation.
+      if (FLAG_propagate_types) {
+        // Propagate types one more time after code movement phases.
+        // This recomputes types of values that became dominated by
+        // hoisted checks.
+        FlowGraphTypePropagator propagator(flow_graph);
+        propagator.Propagate();
+        DEBUG_ASSERT(flow_graph->VerifyUseLists());
+      }
       optimizer.Canonicalize();
       DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
@@ -296,6 +310,7 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
       graph_compiler.FinalizeExceptionHandlers(code);
       graph_compiler.FinalizeComments(code);
       graph_compiler.FinalizeStaticCallTargetsTable(code);
+
       if (optimized) {
         CodePatcher::PatchEntry(Code::Handle(function.CurrentCode()));
         function.SetCode(code);
@@ -303,6 +318,11 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
           OS::Print("--> patching entry %#"Px"\n",
                     Code::Handle(function.unoptimized_code()).EntryPoint());
         }
+
+        for (intptr_t i = 0; i < guarded_fields->length(); i++) {
+          const Field& field = *(*guarded_fields)[i];
+          field.RegisterDependentCode(code);
+        }
       } else {
         function.set_unoptimized_code(code);
         function.SetCode(code);