Bailout if field state changed during background compilation.

runtime/vm/block_scheduler.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/block_scheduler.h"
 
 #include "vm/allocation.h"
 #include "vm/code_patcher.h"
+#include "vm/compiler.h"
 #include "vm/flow_graph.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, emit_edge_counters, true, "Emit edge counters at targets.");
 
 static intptr_t GetEdgeCount(const Array& edge_counters, intptr_t edge_id) {
   if (!FLAG_emit_edge_counters) {
     // Assume everything was visited once.
     return 1;
@@ skipping 34 matching lines @@
 }
 
 
 void BlockScheduler::AssignEdgeWeights() const {
   if (!FLAG_emit_edge_counters) {
     return;
   }
 
   const Array& ic_data_array = Array::Handle(flow_graph()->zone(),
       flow_graph()->parsed_function().function().ic_data_array());
+  if (Compiler::IsBackgroundCompilation() && ic_data_array.IsNull()) {
+    // Deferred loading cleared ic_data_array.
+    Compiler::AbortBackgroundCompilation(Thread::kNoDeoptId);
+  }
+  ASSERT(!ic_data_array.IsNull());
   Array& edge_counters = Array::Handle();
   edge_counters ^= ic_data_array.At(0);
 
   intptr_t entry_count = GetEdgeCount(
       edge_counters,
       flow_graph()->graph_entry()->normal_entry()->preorder_number());
   flow_graph()->graph_entry()->set_entry_count(entry_count);
 
   for (BlockIterator it = flow_graph()->reverse_postorder_iterator();
        !it.Done();
@@ skipping 131 matching lines @@
   for (intptr_t i = block_count - 1; i >= 0; --i) {
     if (chains[i]->first->block == flow_graph()->postorder()[i]) {
       for (Link* link = chains[i]->first; link != NULL; link = link->next) {
         flow_graph()->CodegenBlockOrder(true)->Add(link->block);
       }
     }
   }
 }
 
 }  // namespace dart