For background compilation we copy ICData so that it is immutable during comnpilation. However, we …

runtime/vm/flow_graph_compiler.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/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
@@ skipping 1100 matching lines @@
   assembler()->Bind(&intrinsic_slow_path_label_);
   return false;
 }
 
 
 void FlowGraphCompiler::GenerateInstanceCall(
     intptr_t deopt_id,
     intptr_t token_pos,
     intptr_t argument_count,
     LocationSummary* locs,
-    const ICData& ic_data) {
+    const ICData& ic_data_in) {
+  const ICData& ic_data = ICData::ZoneHandle(ic_data_in.Original());
   if (Compiler::always_optimize()) {
     EmitSwitchableInstanceCall(ic_data, argument_count,
                                deopt_id, token_pos, locs);
     return;
   }
   if (FLAG_always_megamorphic_calls) {
     EmitMegamorphicInstanceCall(ic_data, argument_count,
                                 deopt_id, token_pos, locs);
     return;
   }
@@ skipping 46 matching lines @@
   }
 }
 
 
 void FlowGraphCompiler::GenerateStaticCall(intptr_t deopt_id,
                                            intptr_t token_pos,
                                            const Function& function,
                                            intptr_t argument_count,
                                            const Array& argument_names,
                                            LocationSummary* locs,
-                                           const ICData& ic_data) {
+                                           const ICData& ic_data_in) {
+  const ICData& ic_data = ICData::ZoneHandle(ic_data_in.Original());
   const Array& arguments_descriptor = Array::ZoneHandle(
       ic_data.IsNull() ? ArgumentsDescriptor::New(argument_count,
                                                   argument_names)
                        : ic_data.arguments_descriptor());
   // Proper reporting of Javascript incompatibilities requires icdata and
   // may therefore prevent the optimization of some static calls.
   if (is_optimizing() &&
       !(FLAG_warn_on_javascript_compatibility &&
         (MethodRecognizer::RecognizeKind(function) ==
          MethodRecognizer::kObjectIdentical))) {
@@ skipping 657 matching lines @@
 
 
 void FlowGraphCompiler::FrameStateClear() {
   ASSERT(!is_optimizing());
   frame_state_.TruncateTo(0);
 }
 #endif
 
 
 }  // namespace dart