Avoid unnecessary code target changes during code compaction.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/11198032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12754 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -2315,8 +2315,13 @@ class PointersUpdatingVisitor: public ObjectVisitor {
   void VisitEmbeddedPointer(RelocInfo* rinfo) {
     ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
     Object* target = rinfo->target_object();
+    Object* old_target = target;
     VisitPointer(&target);
-    rinfo->set_target_object(target);
+    // Avoid unnecessary changes that might unnecessary flush the instruction
+    // cache.
+    if (target != old_target) {
+      rinfo->set_target_object(target);
+    }
   }
 
   void VisitCodeTarget(RelocInfo* rinfo) {