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

runtime/vm/compiler.cc

 // Copyright (c) 2012, 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/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/block_scheduler.h"
@@ skipping 24 matching lines @@
 #include "vm/scanner.h"
 #include "vm/symbols.h"
 #include "vm/tags.h"
 #include "vm/thread_registry.h"
 #include "vm/timer.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, allocation_sinking, true,
     "Attempt to sink temporary allocations to side exits");
+DEFINE_FLAG(bool, always_clone_ic_descriptor, false, "Testing flag");

[zra, 2015/12/21 19:31:47]

Did you mean to leave this in? If so, is it possible to include a bit more about
what the flag does?

[srdjan, 2015/12/21 20:22:49]

Removing it, once all platforms pass.

 DEFINE_FLAG(bool, common_subexpression_elimination, true,
     "Do common subexpression elimination.");
 DEFINE_FLAG(bool, constant_propagation, true,
     "Do conditional constant propagation/unreachable code elimination.");
 DEFINE_FLAG(int, deoptimization_counter_threshold, 16,
     "How many times we allow deoptimization before we disallow optimization.");
 DEFINE_FLAG(bool, disassemble, false, "Disassemble dart code.");
 DEFINE_FLAG(bool, disassemble_optimized, false, "Disassemble optimized code.");
 DEFINE_FLAG(bool, loop_invariant_code_motion, true,
     "Do loop invariant code motion.");
@@ skipping 399 matching lines @@
         ZoneGrowableArray<const ICData*>* ic_data_array =
             new(zone) ZoneGrowableArray<const ICData*>();
         if (optimized) {
           // Extract type feedback before the graph is built, as the graph
           // builder uses it to attach it to nodes.
           ASSERT(function.deoptimization_counter() <
                  FLAG_deoptimization_counter_threshold);
 
           // 'Freeze' ICData in background compilation so that it does not
           // change while compiling.
-          const bool clone_descriptors = Compiler::IsBackgroundCompilation();
+          const bool clone_descriptors = FLAG_always_clone_ic_descriptor ||
+              Compiler::IsBackgroundCompilation();
           function.RestoreICDataMap(ic_data_array, clone_descriptors);
 
           if (FLAG_print_ic_data_map) {
             for (intptr_t i = 0; i < ic_data_array->length(); i++) {
               if ((*ic_data_array)[i] != NULL) {
                 THR_Print("%" Pd " ", i);
                 FlowGraphPrinter::PrintICData(*(*ic_data_array)[i]);
               }
             }
           }
@@ skipping 1502 matching lines @@
 }
 
 
 void BackgroundCompiler::EnsureInit(Thread* thread) {
   UNREACHABLE();
 }
 
 #endif  // DART_PRECOMPILED
 
 }  // namespace dart