--- /dev/null	2020-02-06 11:34:07.664987501 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahCodeRoots.hpp	2020-02-06 19:19:34.676542338 +0100
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2017, 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_VM_GC_SHENANDOAH_SHENANDOAHCODEROOTS_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHCODEROOTS_HPP
+
+#include "code/codeCache.hpp"
+#include "gc/shenandoah/shenandoahSharedVariables.hpp"
+#include "gc/shenandoah/shenandoahLock.hpp"
+#include "memory/allocation.hpp"
+#include "memory/iterator.hpp"
+
+class ShenandoahHeap;
+class ShenandoahHeapRegion;
+
+class ShenandoahParallelCodeHeapIterator {
+  friend class CodeCache;
+private:
+  CodeHeap*     _heap;
+  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int));
+  volatile int  _claimed_idx;
+  volatile bool _finished;
+  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
+public:
+  ShenandoahParallelCodeHeapIterator(CodeHeap* heap);
+  void parallel_blobs_do(CodeBlobClosure* f);
+};
+
+class ShenandoahParallelCodeCacheIterator {
+  friend class CodeCache;
+private:
+  ShenandoahParallelCodeHeapIterator* _iters;
+  int                       _length;
+
+private:
+  // Noncopyable.
+  ShenandoahParallelCodeCacheIterator(const ShenandoahParallelCodeCacheIterator& o);
+  ShenandoahParallelCodeCacheIterator& operator=(const ShenandoahParallelCodeCacheIterator& o);
+public:
+  ShenandoahParallelCodeCacheIterator(const GrowableArray<CodeHeap*>* heaps);
+  ~ShenandoahParallelCodeCacheIterator();
+  void parallel_blobs_do(CodeBlobClosure* f);
+};
+
+// ShenandoahNMethod tuple records the internal locations of oop slots within 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* _nm;
+  oop**    _oops;
+  int      _oops_count;
+
+public:
+  ShenandoahNMethod(nmethod *nm, GrowableArray<oop*>* oops);
+  ~ShenandoahNMethod();
+
+  nmethod* nm() {
+    return _nm;
+  }
+
+  bool has_cset_oops(ShenandoahHeap* heap);
+
+  void assert_alive_and_correct() NOT_DEBUG_RETURN;
+  void assert_same_oops(GrowableArray<oop*>* oops) NOT_DEBUG_RETURN;
+
+  static bool find_with_nmethod(void* nm, ShenandoahNMethod* other) {
+    return other->_nm == nm;
+  }
+};
+
+class ShenandoahCodeRootsIterator {
+  friend class ShenandoahCodeRoots;
+protected:
+  ShenandoahHeap* _heap;
+  ShenandoahParallelCodeCacheIterator _par_iterator;
+  ShenandoahSharedFlag _seq_claimed;
+  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);
+protected:
+  ShenandoahCodeRootsIterator();
+  ~ShenandoahCodeRootsIterator();
+
+  template<bool CSET_FILTER>
+  void dispatch_parallel_blobs_do(CodeBlobClosure *f);
+
+  template<bool CSET_FILTER>
+  void fast_parallel_blobs_do(CodeBlobClosure *f);
+};
+
+class ShenandoahAllCodeRootsIterator : public ShenandoahCodeRootsIterator {
+public:
+  ShenandoahAllCodeRootsIterator() : ShenandoahCodeRootsIterator() {};
+  void possibly_parallel_blobs_do(CodeBlobClosure *f);
+};
+
+class ShenandoahCsetCodeRootsIterator : public ShenandoahCodeRootsIterator {
+public:
+  ShenandoahCsetCodeRootsIterator() : ShenandoahCodeRootsIterator() {};
+  void possibly_parallel_blobs_do(CodeBlobClosure* f);
+};
+
+class ShenandoahCodeRoots : public AllStatic {
+  friend class ShenandoahHeap;
+  friend class ShenandoahCodeRootsIterator;
+
+public:
+  static void initialize();
+  static void add_nmethod(nmethod* nm);
+  static void remove_nmethod(nmethod* nm);
+
+private:
+  static GrowableArray<ShenandoahNMethod*>* _recorded_nms;
+  static ShenandoahLock                     _recorded_nms_lock;
+};
+
+#endif //SHARE_VM_GC_SHENANDOAH_SHENANDOAHCODEROOTS_HPP