Introduce SynchronizedScope to allow heap access from compiler thread.

src/execution.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 485 matching lines @@
 void StackGuard::RequestInstallCode() {
   ExecutionAccess access(isolate_);
   thread_local_.interrupt_flags_ |= INSTALL_CODE;
   if (thread_local_.postpone_interrupts_nesting_ == 0) {
     thread_local_.jslimit_ = thread_local_.climit_ = kInterruptLimit;
     isolate_->heap()->SetStackLimits();
   }
 }
 
 
+bool StackGuard::IsCompilerSyncRequest() {
+  ExecutionAccess access(isolate_);
+  return (thread_local_.interrupt_flags_ & COMPILER_SYNC) != 0;
+}
+
+
+void StackGuard::RequestCompilerSync() {
+  ExecutionAccess access(isolate_);
+  thread_local_.interrupt_flags_ |= COMPILER_SYNC;
+  if (thread_local_.postpone_interrupts_nesting_ == 0) {
+    thread_local_.jslimit_ = thread_local_.climit_ = kInterruptLimit;
+    isolate_->heap()->SetStackLimits();
+  }
+}
+
+
 bool StackGuard::IsFullDeopt() {
   ExecutionAccess access(isolate_);
   return (thread_local_.interrupt_flags_ & FULL_DEOPT) != 0;
 }
 
 
 void StackGuard::FullDeopt() {
   ExecutionAccess access(isolate_);
   thread_local_.interrupt_flags_ |= FULL_DEOPT;
   set_interrupt_limits(access);
@@ skipping 526 matching lines @@
   }
   if (stack_guard->IsDeoptMarkedAllocationSites()) {
     stack_guard->Continue(DEOPT_MARKED_ALLOCATION_SITES);
     isolate->heap()->DeoptMarkedAllocationSites();
   }
   if (stack_guard->IsInstallCodeRequest()) {
     ASSERT(isolate->concurrent_recompilation_enabled());
     stack_guard->Continue(INSTALL_CODE);
     isolate->optimizing_compiler_thread()->InstallOptimizedFunctions();
   }
-  isolate->runtime_profiler()->OptimizeNow();
+  if (stack_guard->IsCompilerSyncRequest()) {
+    ASSERT(isolate->concurrent_recompilation_enabled());
+    stack_guard->Continue(COMPILER_SYNC);
+    isolate->optimizing_compiler_thread()->YieldToCompilerThread();
+  } else {
+    isolate->runtime_profiler()->OptimizeNow();
+  }
   return isolate->heap()->undefined_value();
 }
 
 
 } }  // namespace v8::internal