# HG changeset patch
# User kbarrett
# Date 1474305146 14400
# Node ID db3b97029d3ddd4c9c56e674f902864f22751e43
# Parent  c80a6fd21394340e17d3c966eaf57881dacdd0e2
8258079: Eliminate ParNew's use of klass_or_null()
Summary: Use list_ptr_from_klass instead of klass_or_null.
Reviewed-by: mgerdin, jmasa

diff -r c80a6fd21394 -r db3b97029d3d src/share/vm/gc_implementation/parNew/parNewGeneration.cpp
--- a/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp	Mon May 05 20:17:19 2014 +0200
+++ b/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp	Mon Sep 19 13:12:26 2016 -0400
@@ -1544,22 +1544,25 @@
      return false;
   }
   assert(prefix != NULL && prefix != BUSY, "Error");
-  size_t i = 1;
   oop cur = prefix;
-  while (i < objsFromOverflow && cur->klass_or_null() != NULL) {
-    i++; cur = cur->list_ptr_from_klass();
+  for (size_t i = 1; i < objsFromOverflow; ++i) {
+    oop next = cur->list_ptr_from_klass();
+    if (next == NULL) break;
+    cur = next;
   }
+  assert(cur != NULL, "Loop postcondition");
 
   // Reattach remaining (suffix) to overflow list
-  if (cur->klass_or_null() == NULL) {
+  oop suffix = cur->list_ptr_from_klass();
+  if (suffix == NULL) {
     // Write back the NULL in lieu of the BUSY we wrote
     // above and it is still the same value.
     if (_overflow_list == BUSY) {
       (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY);
     }
   } else {
-    assert(cur->klass_or_null() != (Klass*)(address)BUSY, "Error");
-    oop suffix = cur->list_ptr_from_klass();       // suffix will be put back on global list
+    assert(suffix != BUSY, "Error");
+    // suffix will be put back on global list
     cur->set_klass_to_list_ptr(NULL);     // break off suffix
     // It's possible that the list is still in the empty(busy) state
     // we left it in a short while ago; in that case we may be
@@ -1579,8 +1582,10 @@
       // Too bad, someone else got in in between; we'll need to do a splice.
       // Find the last item of suffix list
       oop last = suffix;
-      while (last->klass_or_null() != NULL) {
-        last = last->list_ptr_from_klass();
+      while (true) {
+        oop next = last->list_ptr_from_klass();
+        if (next == NULL) break;
+        last = next;
       }
       // Atomically prepend suffix to current overflow list
       observed_overflow_list = _overflow_list;