diff -r 8b6cc0bb93d0 -r 9186be5c78ba src/hotspot/share/gc/shenandoah/shenandoahNMethod.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/shenandoahNMethod.hpp	Wed Nov 27 11:52:57 2019 -0500
@@ -0,0 +1,172 @@
+/*
+ * Copyright (c) 2019, Red Hat, Inc. All rights reserved.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHNMETHOD_HPP
+#define SHARE_GC_SHENANDOAH_SHENANDOAHNMETHOD_HPP
+
+#include "code/nmethod.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahLock.hpp"
+#include "memory/allocation.hpp"
+#include "utilities/growableArray.hpp"
+
+// ShenandoahNMethod tuple records the internal locations of oop slots within reclocation stream in
+// the nmethod. This allows us to quickly scan the oops without doing the nmethod-internal scans,
+// that sometimes involves parsing the machine code. Note it does not record the oops themselves,
+// because it would then require handling these tuples as the new class of roots.
+class ShenandoahNMethod : public CHeapObj<mtGC> {
+private:
+  nmethod* const          _nm;
+  oop**                   _oops;
+  int                     _oops_count;
+  bool                    _has_non_immed_oops;
+  bool                    _unregistered;
+  ShenandoahReentrantLock _lock;
+
+public:
+  ShenandoahNMethod(nmethod *nm, GrowableArray<oop*>& oops, bool has_non_immed_oops);
+  ~ShenandoahNMethod();
+
+  inline nmethod* nm() const;
+  inline ShenandoahReentrantLock* lock();
+  void oops_do(OopClosure* oops, bool fix_relocations = false);
+  // Update oops when the nmethod is re-registered
+  void update();
+
+  bool has_cset_oops(ShenandoahHeap* heap);
+
+  inline int oop_count() const;
+  inline bool has_oops() const;
+
+  inline void mark_unregistered();
+  inline bool is_unregistered() const;
+
+  static ShenandoahNMethod* for_nmethod(nmethod* nm);
+  static inline ShenandoahReentrantLock* lock_for_nmethod(nmethod* nm);
+
+  static void heal_nmethod(nmethod* nm);
+  static inline void disarm_nmethod(nmethod* nm);
+
+  static inline ShenandoahNMethod* gc_data(nmethod* nm);
+  static inline void attach_gc_data(nmethod* nm, ShenandoahNMethod* gc_data);
+
+  void assert_alive_and_correct() NOT_DEBUG_RETURN;
+  void assert_same_oops(bool allow_dead = false) NOT_DEBUG_RETURN;
+  static void assert_no_oops(nmethod* nm, bool allow_dea = false) NOT_DEBUG_RETURN;
+
+private:
+  bool has_non_immed_oops() const { return _has_non_immed_oops; }
+  static void detect_reloc_oops(nmethod* nm, GrowableArray<oop*>& oops, bool& _has_non_immed_oops);
+};
+
+class ShenandoahNMethodTable;
+
+// An opaque snapshot of current nmethod table for iteration
+class ShenandoahNMethodTableSnapshot : public CHeapObj<mtGC> {
+  friend class ShenandoahNMethodTable;
+private:
+  ShenandoahHeap* const       _heap;
+  ShenandoahNMethodTable*     _table;
+  ShenandoahNMethod** const   _array;
+  const int                   _length;
+
+  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
+  volatile size_t       _claimed;
+  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
+
+public:
+  ShenandoahNMethodTableSnapshot(ShenandoahNMethodTable* table);
+
+  template<bool CSET_FILTER>
+  void parallel_blobs_do(CodeBlobClosure *f);
+
+  void concurrent_nmethods_do(NMethodClosure* cl);
+};
+
+class ShenandoahNMethodTable : public CHeapObj<mtGC> {
+  friend class ShenandoahNMethodTableSnapshot;
+private:
+  enum {
+    minSize = 1024
+  };
+
+  ShenandoahHeap* const _heap;
+  ShenandoahNMethod**   _array;
+  int                   _size;
+  int                   _index;
+  ShenandoahLock        _lock;
+  bool                  _iteration_in_progress;
+
+public:
+  ShenandoahNMethodTable();
+  ~ShenandoahNMethodTable();
+
+  void register_nmethod(nmethod* nm);
+  void unregister_nmethod(nmethod* nm);
+  void flush_nmethod(nmethod* nm);
+
+  bool contain(nmethod* nm) const;
+  int length() const { return _index; }
+
+  // Table iteration support
+  ShenandoahNMethodTableSnapshot* snapshot_for_iteration();
+  void finish_iteration(ShenandoahNMethodTableSnapshot* snapshot);
+
+  void assert_nmethods_alive_and_correct() NOT_DEBUG_RETURN;
+private:
+  // Rebuild table and replace current one
+  void rebuild(int size);
+
+  bool is_full() const {
+    assert(_index <= _size, "Sanity");
+    return _index == _size;
+  }
+
+  ShenandoahNMethod* at(int index) const;
+  int  index_of(nmethod* nm) const;
+  void remove(int index);
+  void append(ShenandoahNMethod* snm);
+
+  inline bool iteration_in_progress() const;
+  void wait_until_concurrent_iteration_done();
+
+  // Logging support
+  void log_register_nmethod(nmethod* nm);
+  void log_unregister_nmethod(nmethod* nm);
+  void log_flush_nmethod(nmethod* nm);
+};
+
+class ShenandoahConcurrentNMethodIterator {
+private:
+  ShenandoahNMethodTable*         const _table;
+  ShenandoahNMethodTableSnapshot*       _table_snapshot;
+
+public:
+  ShenandoahConcurrentNMethodIterator(ShenandoahNMethodTable* table);
+
+  void nmethods_do_begin();
+  void nmethods_do(NMethodClosure* cl);
+  void nmethods_do_end();
+};
+
+#endif // SHARE_GC_SHENANDOAH_SHENANDOAHNMETHOD_HPP