Use load_acquire

Author: stefank

src/hotspot/share/oops/oop.hpp

@@ -90,6 +90,7 @@ class oopDesc {
 
   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
   inline narrowKlass narrow_klass() const;
+  inline narrowKlass narrow_klass_acquire() const;
   inline void set_klass(Klass* k);
   static inline void release_set_klass(HeapWord* mem, Klass* k);
 

src/hotspot/share/oops/oop.inline.hpp

@@ -39,7 +39,6 @@
 #include "oops/oopsHierarchy.hpp"
 #include "runtime/atomicAccess.hpp"
 #include "runtime/globals.hpp"
-#include "runtime/orderAccess.hpp"
 #include "utilities/align.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/globalDefinitions.hpp"
@@ -104,9 +103,7 @@ Klass* oopDesc::klass_or_null() const {
 }
 
 Klass* oopDesc::klass_or_null_acquire() const {
-  narrowKlass nk = narrow_klass();
-  OrderAccess::acquire();
-  return CompressedKlassPointers::decode(nk);
+  return CompressedKlassPointers::decode(narrow_klass_acquire());
 }
 
 Klass* oopDesc::klass_without_asserts() const {
@@ -124,6 +121,17 @@ narrowKlass oopDesc::narrow_klass() const {
   }
 }
 
+narrowKlass oopDesc::narrow_klass_acquire() const {
+  switch (ObjLayout::klass_mode()) {
+    case ObjLayout::Compact:
+      return mark_acquire().narrow_klass();
+    case ObjLayout::Compressed:
+      return AtomicAccess::load_acquire(&_compressed_klass);
+    default:
+      ShouldNotReachHere();
+  }
+}
+
 void oopDesc::set_klass(Klass* k) {
   assert(Universe::is_bootstrapping() || (k != nullptr && k->is_klass()), "incorrect Klass");
   assert(!UseCompactObjectHeaders, "don't set Klass* with compact headers");