--- a/hotspot/src/share/vm/oops/objArrayKlass.cpp	Fri Jul 10 16:01:20 2009 -0700
+++ b/hotspot/src/share/vm/oops/objArrayKlass.cpp	Tue Jul 14 15:40:39 2009 -0700
@@ -84,8 +84,6 @@
 template <class T> void objArrayKlass::do_copy(arrayOop s, T* src,
                                arrayOop d, T* dst, int length, TRAPS) {
 
-  const size_t word_len = objArrayOopDesc::array_size(length);
-
   BarrierSet* bs = Universe::heap()->barrier_set();
   // For performance reasons, we assume we are that the write barrier we
   // are using has optimized modes for arrays of references.  At least one
@@ -93,11 +91,10 @@
   assert(bs->has_write_ref_array_opt(), "Barrier set must have ref array opt");
   assert(bs->has_write_ref_array_pre_opt(), "For pre-barrier as well.");
 
-  MemRegion dst_mr = MemRegion((HeapWord*)dst, word_len);
   if (s == d) {
     // since source and destination are equal we do not need conversion checks.
     assert(length > 0, "sanity check");
-    bs->write_ref_array_pre(dst_mr);
+    bs->write_ref_array_pre(dst, length);
     Copy::conjoint_oops_atomic(src, dst, length);
   } else {
     // We have to make sure all elements conform to the destination array
@@ -105,7 +102,7 @@
     klassOop stype = objArrayKlass::cast(s->klass())->element_klass();
     if (stype == bound || Klass::cast(stype)->is_subtype_of(bound)) {
       // elements are guaranteed to be subtypes, so no check necessary
-      bs->write_ref_array_pre(dst_mr);
+      bs->write_ref_array_pre(dst, length);
       Copy::conjoint_oops_atomic(src, dst, length);
     } else {
       // slow case: need individual subtype checks
@@ -137,6 +134,7 @@
       }
     }
   }
+  const size_t word_len = objArrayOopDesc::array_size(length);
   bs->write_ref_array(MemRegion((HeapWord*)dst, word_len));
 }