Optimize functions on a second thread.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 765081a9ca874d035478c80a7ee85dadf3d6eea4..5f6ec663e247a39278f254ff0b4494520aa809fe 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -155,7 +155,8 @@ Heap::Heap()
       scavenges_since_last_idle_round_(kIdleScavengeThreshold),
       promotion_queue_(this),
       configured_(false),
-      chunks_queued_for_free_(NULL) {
+      chunks_queued_for_free_(NULL),
+      relocation_mutex_(NULL) {
   // Allow build-time customization of the max semispace size. Building
   // V8 with snapshots and a non-default max semispace size is much
   // easier if you can define it as part of the build environment.
@@ -1199,6 +1200,7 @@ class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
 
 
 void Heap::Scavenge() {
+  RelocationLock relocation_lock(this);
 #ifdef DEBUG
   if (FLAG_verify_heap) VerifyNonPointerSpacePointers();
 #endif
@@ -6156,6 +6158,8 @@ bool Heap::SetUp(bool create_heap_objects) {
 
   store_buffer()->SetUp();
 
+  if (FLAG_parallel_recompilation) relocation_mutex_ = OS::CreateMutex();
+
   return true;
 }
 
@@ -6241,6 +6245,8 @@ void Heap::TearDown() {
 
   isolate_->memory_allocator()->TearDown();
 
+  delete relocation_mutex_;
+
 #ifdef DEBUG
   delete debug_utils_;
   debug_utils_ = NULL;