The way reloc entries are visited by the ObjectVisitor is architecture...

src/x64/assembler-x64-inl.h

Index: src/x64/assembler-x64-inl.h
===================================================================
--- src/x64/assembler-x64-inl.h	(revision 4713)
+++ src/x64/assembler-x64-inl.h	(working copy)
@@ -29,6 +29,7 @@
 #define V8_X64_ASSEMBLER_X64_INL_H_
 
 #include "cpu.h"
+#include "debug.h"
 #include "memory.h"
 
 namespace v8 {
@@ -229,6 +230,15 @@
 }
 
 
+int RelocInfo::target_address_size() {
+  if (IsCodedSpecially()) {
+    return Assembler::kCallTargetSize;
+  } else {
+    return Assembler::kExternalTargetSize;
+  }
+}
+
+
 void RelocInfo::set_target_address(Address target) {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == RUNTIME_ENTRY);
   if (IsCodeTarget(rmode_)) {
@@ -320,6 +330,27 @@
       pc_ + Assembler::kPatchReturnSequenceAddressOffset);
 }
 
+
+void RelocInfo::Visit(ObjectVisitor* visitor) {
+  RelocInfo::Mode mode = rmode();
+  if (mode == RelocInfo::EMBEDDED_OBJECT) {
+    visitor->VisitPointer(target_object_address());
+  } else if (RelocInfo::IsCodeTarget(mode)) {
+    visitor->VisitCodeTarget(this);
+ } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
+    visitor->VisitExternalReference(target_reference_address());
+#ifdef ENABLE_DEBUGGER_SUPPORT
+  } else if (Debug::has_break_points() &&
+             RelocInfo::IsJSReturn(mode) &&
+             IsPatchedReturnSequence()) {
+    visitor->VisitDebugTarget(this);
+#endif
+  } else if (mode == RelocInfo::RUNTIME_ENTRY) {
+    visitor->VisitRuntimeEntry(this);
+  }
+}
+
+
 // -----------------------------------------------------------------------------
 // Implementation of Operand