--- old/src/hotspot/share/code/codeCache.cpp	2019-03-11 22:56:10.442510045 +0100
+++ new/src/hotspot/share/code/codeCache.cpp	2019-03-11 22:56:09.874500836 +0100
@@ -145,7 +145,6 @@
 address CodeCache::_low_bound = 0;
 address CodeCache::_high_bound = 0;
 int CodeCache::_number_of_nmethods_with_dependencies = 0;
-nmethod* CodeCache::_scavenge_root_nmethods = NULL;
 ExceptionCache* volatile CodeCache::_exception_cache_purge_list = NULL;
 
 // Initialize arrays of CodeHeap subsets
@@ -711,167 +710,6 @@
   }
 }
 
-// Walk the list of methods which might contain oops to the java heap.
-void CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure* f) {
-  assert_locked_or_safepoint(CodeCache_lock);
-
-  const bool fix_relocations = f->fix_relocations();
-  debug_only(mark_scavenge_root_nmethods());
-
-  nmethod* prev = NULL;
-  nmethod* cur = scavenge_root_nmethods();
-  while (cur != NULL) {
-    debug_only(cur->clear_scavenge_root_marked());
-    assert(cur->scavenge_root_not_marked(), "");
-    assert(cur->on_scavenge_root_list(), "else shouldn't be on this list");
-
-    bool is_live = (!cur->is_zombie() && !cur->is_unloaded());
-    LogTarget(Trace, gc, nmethod) lt;
-    if (lt.is_enabled()) {
-      LogStream ls(lt);
-      CompileTask::print(&ls, cur,
-        is_live ? "scavenge root " : "dead scavenge root", /*short_form:*/ true);
-    }
-    if (is_live) {
-      // Perform cur->oops_do(f), maybe just once per nmethod.
-      f->do_code_blob(cur);
-    }
-    nmethod* const next = cur->scavenge_root_link();
-    // The scavengable nmethod list must contain all methods with scavengable
-    // oops. It is safe to include more nmethod on the list, but we do not
-    // expect any live non-scavengable nmethods on the list.
-    if (fix_relocations) {
-      if (!is_live || !cur->detect_scavenge_root_oops()) {
-        unlink_scavenge_root_nmethod(cur, prev);
-      } else {
-        prev = cur;
-      }
-    }
-    cur = next;
-  }
-
-  // Check for stray marks.
-  debug_only(verify_perm_nmethods(NULL));
-}
-
-void CodeCache::register_scavenge_root_nmethod(nmethod* nm) {
-  assert_locked_or_safepoint(CodeCache_lock);
-  if (!nm->on_scavenge_root_list() && nm->detect_scavenge_root_oops()) {
-    add_scavenge_root_nmethod(nm);
-  }
-}
-
-void CodeCache::verify_scavenge_root_nmethod(nmethod* nm) {
-  nm->verify_scavenge_root_oops();
-}
-
-void CodeCache::add_scavenge_root_nmethod(nmethod* nm) {
-  assert_locked_or_safepoint(CodeCache_lock);
-
-  nm->set_on_scavenge_root_list();
-  nm->set_scavenge_root_link(_scavenge_root_nmethods);
-  set_scavenge_root_nmethods(nm);
-  print_trace("add_scavenge_root", nm);
-}
-
-void CodeCache::unlink_scavenge_root_nmethod(nmethod* nm, nmethod* prev) {
-  assert_locked_or_safepoint(CodeCache_lock);
-
-  assert((prev == NULL && scavenge_root_nmethods() == nm) ||
-         (prev != NULL && prev->scavenge_root_link() == nm), "precondition");
-
-  print_trace("unlink_scavenge_root", nm);
-  if (prev == NULL) {
-    set_scavenge_root_nmethods(nm->scavenge_root_link());
-  } else {
-    prev->set_scavenge_root_link(nm->scavenge_root_link());
-  }
-  nm->set_scavenge_root_link(NULL);
-  nm->clear_on_scavenge_root_list();
-}
-
-void CodeCache::drop_scavenge_root_nmethod(nmethod* nm) {
-  assert_locked_or_safepoint(CodeCache_lock);
-
-  print_trace("drop_scavenge_root", nm);
-  nmethod* prev = NULL;
-  for (nmethod* cur = scavenge_root_nmethods(); cur != NULL; cur = cur->scavenge_root_link()) {
-    if (cur == nm) {
-      unlink_scavenge_root_nmethod(cur, prev);
-      return;
-    }
-    prev = cur;
-  }
-  assert(false, "should have been on list");
-}
-
-void CodeCache::prune_scavenge_root_nmethods() {
-  assert_locked_or_safepoint(CodeCache_lock);
-
-  debug_only(mark_scavenge_root_nmethods());
-
-  nmethod* last = NULL;
-  nmethod* cur = scavenge_root_nmethods();
-  while (cur != NULL) {
-    nmethod* next = cur->scavenge_root_link();
-    debug_only(cur->clear_scavenge_root_marked());
-    assert(cur->scavenge_root_not_marked(), "");
-    assert(cur->on_scavenge_root_list(), "else shouldn't be on this list");
-
-    if (!cur->is_zombie() && !cur->is_unloaded()
-        && cur->detect_scavenge_root_oops()) {
-      // Keep it.  Advance 'last' to prevent deletion.
-      last = cur;
-    } else {
-      // Prune it from the list, so we don't have to look at it any more.
-      print_trace("prune_scavenge_root", cur);
-      unlink_scavenge_root_nmethod(cur, last);
-    }
-    cur = next;
-  }
-
-  // Check for stray marks.
-  debug_only(verify_perm_nmethods(NULL));
-}
-
-#ifndef PRODUCT
-void CodeCache::asserted_non_scavengable_nmethods_do(CodeBlobClosure* f) {
-  // While we are here, verify the integrity of the list.
-  mark_scavenge_root_nmethods();
-  for (nmethod* cur = scavenge_root_nmethods(); cur != NULL; cur = cur->scavenge_root_link()) {
-    assert(cur->on_scavenge_root_list(), "else shouldn't be on this list");
-    cur->clear_scavenge_root_marked();
-  }
-  verify_perm_nmethods(f);
-}
-
-// Temporarily mark nmethods that are claimed to be on the scavenge list.
-void CodeCache::mark_scavenge_root_nmethods() {
-  NMethodIterator iter(NMethodIterator::only_alive);
-  while(iter.next()) {
-    nmethod* nm = iter.method();
-    assert(nm->scavenge_root_not_marked(), "clean state");
-    if (nm->on_scavenge_root_list())
-      nm->set_scavenge_root_marked();
-  }
-}
-
-// If the closure is given, run it on the unlisted nmethods.
-// Also make sure that the effects of mark_scavenge_root_nmethods is gone.
-void CodeCache::verify_perm_nmethods(CodeBlobClosure* f_or_null) {
-  NMethodIterator iter(NMethodIterator::only_alive);
-  while(iter.next()) {
-    nmethod* nm = iter.method();
-    bool call_f = (f_or_null != NULL);
-    assert(nm->scavenge_root_not_marked(), "must be already processed");
-    if (nm->on_scavenge_root_list())
-      call_f = false;  // don't show this one to the client
-    Universe::heap()->verify_nmethod(nm);
-    if (call_f)  f_or_null->do_code_blob(nm);
-  }
-}
-#endif //PRODUCT
-
 void CodeCache::verify_clean_inline_caches() {
 #ifdef ASSERT
   NMethodIterator iter(NMethodIterator::only_alive_and_not_unloading);
@@ -929,12 +767,6 @@
   _exception_cache_purge_list = NULL;
 }
 
-void CodeCache::gc_prologue() { }
-
-void CodeCache::gc_epilogue() {
-  prune_scavenge_root_nmethods();
-}
-
 uint8_t CodeCache::_unloading_cycle = 1;
 
 void CodeCache::increment_unloading_cycle() {
--- old/src/hotspot/share/code/codeCache.hpp	2019-03-11 22:56:11.150521524 +0100
+++ new/src/hotspot/share/code/codeCache.hpp	2019-03-11 22:56:10.606512704 +0100
@@ -94,14 +94,10 @@
   static address _low_bound;                            // Lower bound of CodeHeap addresses
   static address _high_bound;                           // Upper bound of CodeHeap addresses
   static int _number_of_nmethods_with_dependencies;     // Total number of nmethods with dependencies
-  static nmethod* _scavenge_root_nmethods;              // linked via nm->scavenge_root_link()
   static uint8_t _unloading_cycle;                      // Global state for recognizing old nmethods that need to be unloaded
 
   static ExceptionCache* volatile _exception_cache_purge_list;
 
-  static void mark_scavenge_root_nmethods() PRODUCT_RETURN;
-  static void verify_perm_nmethods(CodeBlobClosure* f_or_null) PRODUCT_RETURN;
-
   // CodeHeap management
   static void initialize_heaps();                             // Initializes the CodeHeaps
   // Check the code heap sizes set by the user via command line
@@ -124,10 +120,6 @@
   static int    allocated_segments();
   static size_t freelists_length();
 
-  static void set_scavenge_root_nmethods(nmethod* nm) { _scavenge_root_nmethods = nm; }
-  static void prune_scavenge_root_nmethods();
-  static void unlink_scavenge_root_nmethod(nmethod* nm, nmethod* prev);
-
   // Make private to prevent unsafe calls.  Not all CodeBlob*'s are embedded in a CodeHeap.
   static bool contains(CodeBlob *p) { fatal("don't call me!"); return false; }
 
@@ -171,8 +163,6 @@
   static int       nmethod_count(int code_blob_type);
 
   // GC support
-  static void gc_epilogue();
-  static void gc_prologue();
   static void verify_oops();
   // If any oops are not marked this method unloads (i.e., breaks root links
   // to) any unmarked codeBlobs in the cache.  Sets "marked_for_unloading"
@@ -189,25 +179,9 @@
   static void do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred);
   static uint8_t unloading_cycle() { return _unloading_cycle; }
   static void increment_unloading_cycle();
-  static void asserted_non_scavengable_nmethods_do(CodeBlobClosure* f = NULL) PRODUCT_RETURN;
   static void release_exception_cache(ExceptionCache* entry);
   static void purge_exception_caches();
 
-  // Apply f to every live code blob in scavengable nmethods. Prune nmethods
-  // from the list of scavengable nmethods if f->fix_relocations() and a nmethod
-  // no longer has scavengable oops.  If f->fix_relocations(), then f must copy
-  // objects to their new location immediately to avoid fixing nmethods on the
-  // basis of the old object locations.
-  static void scavenge_root_nmethods_do(CodeBlobToOopClosure* f);
-
-  static nmethod* scavenge_root_nmethods()            { return _scavenge_root_nmethods; }
-  // register_scavenge_root_nmethod() conditionally adds the nmethod to the list
-  // if it is not already on the list and has a scavengeable root
-  static void register_scavenge_root_nmethod(nmethod* nm);
-  static void verify_scavenge_root_nmethod(nmethod* nm);
-  static void add_scavenge_root_nmethod(nmethod* nm);
-  static void drop_scavenge_root_nmethod(nmethod* nm);
-
   // Printing/debugging
   static void print();                           // prints summary
   static void print_internals();
--- old/src/hotspot/share/code/compiledMethod.hpp	2019-03-11 22:56:11.830532549 +0100
+++ new/src/hotspot/share/code/compiledMethod.hpp	2019-03-11 22:56:11.294523860 +0100
@@ -408,10 +408,6 @@
   PcDesc* find_pc_desc(address pc, bool approximate) {
     return _pc_desc_container.find_pc_desc(pc, approximate, PcDescSearch(code_begin(), scopes_pcs_begin(), scopes_pcs_end()));
   }
-
-protected:
-  // Used by some GCs to chain nmethods.
-  nmethod* _scavenge_root_link; // from CodeCache::scavenge_root_nmethods
 };
 
 #endif // SHARE_CODE_COMPILEDMETHOD_HPP
--- old/src/hotspot/share/code/nmethod.cpp	2019-03-11 22:56:12.554544288 +0100
+++ new/src/hotspot/share/code/nmethod.cpp	2019-03-11 22:56:11.966534755 +0100
@@ -423,8 +423,6 @@
   _oops_do_mark_link       = NULL;
   _jmethod_id              = NULL;
   _osr_link                = NULL;
-  _scavenge_root_link      = NULL;
-  _scavenge_root_state     = 0;
 #if INCLUDE_RTM_OPT
   _rtm_state               = NoRTM;
 #endif
@@ -1360,10 +1358,6 @@
     ec = next;
   }
 
-  if (on_scavenge_root_list()) {
-    CodeCache::drop_scavenge_root_nmethod(this);
-  }
-
 #if INCLUDE_JVMCI
   assert(_jvmci_installed_code == NULL, "should have been nulled out when transitioned to zombie");
   assert(_speculation_log == NULL, "should have been nulled out when transitioned to zombie");
@@ -1777,44 +1771,6 @@
   log_trace(gc, nmethod)("oops_do_marking_epilogue");
 }
 
-class DetectScavengeRoot: public OopClosure {
-  bool     _detected_scavenge_root;
-  nmethod* _print_nm;
-public:
-  DetectScavengeRoot(nmethod* nm) : _detected_scavenge_root(false), _print_nm(nm) {}
-
-  bool detected_scavenge_root() { return _detected_scavenge_root; }
-  virtual void do_oop(oop* p) {
-    if ((*p) != NULL && Universe::heap()->is_scavengable(*p)) {
-      NOT_PRODUCT(maybe_print(p));
-      _detected_scavenge_root = true;
-    }
-  }
-  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
-
-#ifndef PRODUCT
-  void maybe_print(oop* p) {
-    LogTarget(Trace, gc, nmethod) lt;
-    if (lt.is_enabled()) {
-      LogStream ls(lt);
-      if (!_detected_scavenge_root) {
-        CompileTask::print(&ls, _print_nm, "new scavenge root", /*short_form:*/ true);
-      }
-      ls.print("" PTR_FORMAT "[offset=%d] detected scavengable oop " PTR_FORMAT " (found at " PTR_FORMAT ") ",
-               p2i(_print_nm), (int)((intptr_t)p - (intptr_t)_print_nm),
-               p2i(*p), p2i(p));
-      ls.cr();
-    }
-  }
-#endif //PRODUCT
-};
-
-bool nmethod::detect_scavenge_root_oops() {
-  DetectScavengeRoot detect_scavenge_root(this);
-  oops_do(&detect_scavenge_root);
-  return detect_scavenge_root.detected_scavenge_root();
-}
-
 inline bool includes(void* p, void* from, void* to) {
   return from <= p && p < to;
 }
@@ -2266,41 +2222,6 @@
 
 
 // -----------------------------------------------------------------------------
-// Non-product code
-#ifndef PRODUCT
-
-class DebugScavengeRoot: public OopClosure {
-  nmethod* _nm;
-  bool     _ok;
-public:
-  DebugScavengeRoot(nmethod* nm) : _nm(nm), _ok(true) { }
-  bool ok() { return _ok; }
-  virtual void do_oop(oop* p) {
-    if ((*p) == NULL || !Universe::heap()->is_scavengable(*p))  return;
-    if (_ok) {
-      _nm->print_nmethod(true);
-      _ok = false;
-    }
-    tty->print_cr("*** scavengable oop " PTR_FORMAT " found at " PTR_FORMAT " (offset %d)",
-                  p2i(*p), p2i(p), (int)((intptr_t)p - (intptr_t)_nm));
-    (*p)->print();
-  }
-  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
-};
-
-void nmethod::verify_scavenge_root_oops() {
-  if (!on_scavenge_root_list()) {
-    // Actually look inside, to verify the claim that it's clean.
-    DebugScavengeRoot debug_scavenge_root(this);
-    oops_do(&debug_scavenge_root);
-    if (!debug_scavenge_root.ok())
-      fatal("found an unadvertised bad scavengable oop in the code cache");
-  }
-  assert(scavenge_root_not_marked(), "");
-}
-
-#endif // PRODUCT
-
 // Printing operations
 
 void nmethod::print() const {
@@ -2326,7 +2247,6 @@
     tty->print(" for method " INTPTR_FORMAT , p2i(method()));
     tty->print(" { ");
     tty->print_cr("%s ", state());
-    if (on_scavenge_root_list())  tty->print("scavenge_root ");
     tty->print_cr("}:");
   }
   if (size              () > 0) tty->print_cr(" total in heap  [" INTPTR_FORMAT "," INTPTR_FORMAT "] = %d",
--- old/src/hotspot/share/code/nmethod.hpp	2019-03-11 22:56:13.270555897 +0100
+++ new/src/hotspot/share/code/nmethod.hpp	2019-03-11 22:56:12.730547142 +0100
@@ -131,8 +131,6 @@
   bool _oops_are_stale;  // indicates that it's no longer safe to access oops section
 #endif
 
-  jbyte _scavenge_root_state;
-
 #if INCLUDE_RTM_OPT
   // RTM state at compile time. Used during deoptimization to decide
   // whether to restart collecting RTM locking abort statistic again.
@@ -410,24 +408,6 @@
   void fix_oop_relocations(address begin, address end) { fix_oop_relocations(begin, end, false); }
   void fix_oop_relocations()                           { fix_oop_relocations(NULL, NULL, false); }
 
-  // Scavengable oop support
-  bool  on_scavenge_root_list() const                  { return (_scavenge_root_state & 1) != 0; }
- protected:
-  enum { sl_on_list = 0x01, sl_marked = 0x10 };
-  void  set_on_scavenge_root_list()                    { _scavenge_root_state = sl_on_list; }
-  void  clear_on_scavenge_root_list()                  { _scavenge_root_state = 0; }
-  // assertion-checking and pruning logic uses the bits of _scavenge_root_state
-#ifndef PRODUCT
-  void  set_scavenge_root_marked()                     { _scavenge_root_state |= sl_marked; }
-  void  clear_scavenge_root_marked()                   { _scavenge_root_state &= ~sl_marked; }
-  bool  scavenge_root_not_marked()                     { return (_scavenge_root_state &~ sl_on_list) == 0; }
-  // N.B. there is no positive marked query, and we only use the not_marked query for asserts.
-#endif //PRODUCT
-  nmethod* scavenge_root_link() const                  { return _scavenge_root_link; }
-  void     set_scavenge_root_link(nmethod *n)          { _scavenge_root_link = n; }
-
- public:
-
   // Sweeper support
   long  stack_traversal_mark()                    { return _stack_traversal_mark; }
   void  set_stack_traversal_mark(long l)          { _stack_traversal_mark = l; }
@@ -504,8 +484,6 @@
  public:
   void oops_do(OopClosure* f) { oops_do(f, false); }
   void oops_do(OopClosure* f, bool allow_zombie);
-  bool detect_scavenge_root_oops();
-  void verify_scavenge_root_oops() PRODUCT_RETURN;
 
   bool test_set_oops_do_mark();
   static void oops_do_marking_prologue();
--- old/src/hotspot/share/gc/cms/concurrentMarkSweepGeneration.cpp	2019-03-11 22:56:13.954566987 +0100
+++ new/src/hotspot/share/gc/cms/concurrentMarkSweepGeneration.cpp	2019-03-11 22:56:13.410558167 +0100
@@ -4194,9 +4194,6 @@
 
   CMSHeap* heap = CMSHeap::heap();
 
-  if (should_unload_classes()) {
-    CodeCache::gc_prologue();
-  }
   assert(haveFreelistLocks(), "must have free list locks");
   assert_lock_strong(bitMapLock());
 
@@ -4252,7 +4249,7 @@
   verify_overflow_empty();
 
   if (should_unload_classes()) {
-    CodeCache::gc_epilogue();
+    heap->prune_nmethods();
   }
   JvmtiExport::gc_epilogue();
 
--- old/src/hotspot/share/gc/epsilon/epsilonHeap.hpp	2019-03-11 22:56:14.722579439 +0100
+++ new/src/hotspot/share/gc/epsilon/epsilonHeap.hpp	2019-03-11 22:56:14.182570684 +0100
@@ -88,11 +88,6 @@
     return _space->is_in(p);
   }
 
-  virtual bool is_scavengable(oop obj) {
-    // No GC is going to happen, therefore no objects ever move.
-    return false;
-  }
-
   virtual bool is_maximal_no_gc() const {
     // No GC is going to happen. Return "we are at max", when we are about to fail.
     return used() == capacity();
--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2019-03-11 22:56:15.446591178 +0100
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2019-03-11 22:56:14.842581385 +0100
@@ -4798,13 +4798,6 @@
   void do_oop(narrowOop* p) { do_oop_work(p); }
 };
 
-// Returns true if the reference points to an object that
-// can move in an incremental collection.
-bool G1CollectedHeap::is_scavengable(oop obj) {
-  HeapRegion* hr = heap_region_containing(obj);
-  return !hr->is_pinned();
-}
-
 void G1CollectedHeap::register_nmethod(nmethod* nm) {
   guarantee(nm != NULL, "sanity");
   RegisterNMethodOopClosure reg_cl(this, nm);
--- old/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2019-03-11 22:56:16.250604213 +0100
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2019-03-11 22:56:15.638594291 +0100
@@ -1312,9 +1312,6 @@
 
   // Optimized nmethod scanning support routines
 
-  // Is an oop scavengeable
-  virtual bool is_scavengable(oop obj);
-
   // Register the given nmethod with the G1 heap.
   virtual void register_nmethod(nmethod* nm);
 
--- old/src/hotspot/share/gc/g1/g1FullCollector.cpp	2019-03-11 22:56:16.930615239 +0100
+++ new/src/hotspot/share/gc/g1/g1FullCollector.cpp	2019-03-11 22:56:16.394606548 +0100
@@ -152,10 +152,6 @@
   reference_processor()->enable_discovery();
   reference_processor()->setup_policy(scope()->should_clear_soft_refs());
 
-  // When collecting the permanent generation Method*s may be moving,
-  // so we either have to flush all bcp data or convert it into bci.
-  CodeCache::gc_prologue();
-
   // We should save the marks of the currently locked biased monitors.
   // The marking doesn't preserve the marks of biased objects.
   BiasedLocking::preserve_marks();
@@ -187,7 +183,6 @@
   update_derived_pointers();
 
   BiasedLocking::restore_marks();
-  CodeCache::gc_epilogue();
   JvmtiExport::gc_epilogue();
 
   _heap->prepare_heap_for_mutators();
--- old/src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp	2019-03-11 22:56:17.630626589 +0100
+++ new/src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp	2019-03-11 22:56:17.054617249 +0100
@@ -41,6 +41,7 @@
 #include "gc/shared/gcHeapSummary.hpp"
 #include "gc/shared/gcLocker.hpp"
 #include "gc/shared/gcWhen.hpp"
+#include "gc/shared/scavengableNMethods.hpp"
 #include "logging/log.hpp"
 #include "memory/metaspaceCounters.hpp"
 #include "oops/oop.inline.hpp"
@@ -150,6 +151,17 @@
 
 }
 
+namespace {
+  class PSIsScavengable : public BoolObjectClosure {
+    bool do_object_b(oop obj) {
+      return ParallelScavengeHeap::heap()->is_in_young(obj);
+    }
+  };
+
+  PSIsScavengable _is_scavengable;
+}
+
+
 void ParallelScavengeHeap::post_initialize() {
   CollectedHeap::post_initialize();
   // Need to init the tenuring threshold
@@ -160,6 +172,8 @@
     PSMarkSweepProxy::initialize();
   }
   PSPromotionManager::initialize();
+
+  ScavengableNMethods::initialize(&_is_scavengable);
 }
 
 void ParallelScavengeHeap::update_counters() {
@@ -697,16 +711,24 @@
 }
 #endif
 
-bool ParallelScavengeHeap::is_scavengable(oop obj) {
-  return is_in_young(obj);
+void ParallelScavengeHeap::register_nmethod(nmethod* nm) {
+  ScavengableNMethods::register_nmethod(nm);
 }
 
-void ParallelScavengeHeap::register_nmethod(nmethod* nm) {
-  CodeCache::register_scavenge_root_nmethod(nm);
+void ParallelScavengeHeap::unregister_nmethod(nmethod* nm) {
+  ScavengableNMethods::unregister_nmethod(nm);
 }
 
 void ParallelScavengeHeap::verify_nmethod(nmethod* nm) {
-  CodeCache::verify_scavenge_root_nmethod(nm);
+  ScavengableNMethods::verify_nmethod(nm);
+}
+
+void ParallelScavengeHeap::flush_nmethod(nmethod* nm) {
+  ScavengableNMethods::flush_nmethod(nm);
+}
+
+void ParallelScavengeHeap::prune_nmethods() {
+  ScavengableNMethods::prune_nmethods();
 }
 
 GrowableArray<GCMemoryManager*> ParallelScavengeHeap::memory_managers() {
--- old/src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp	2019-03-11 22:56:18.326637873 +0100
+++ new/src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp	2019-03-11 22:56:17.782629053 +0100
@@ -157,13 +157,12 @@
   // collection.
   virtual bool is_maximal_no_gc() const;
 
-  // Return true if the reference points to an object that
-  // can be moved in a partial collection.  For currently implemented
-  // generational collectors that means during a collection of
-  // the young gen.
-  virtual bool is_scavengable(oop obj);
   virtual void register_nmethod(nmethod* nm);
-  virtual void verify_nmethod(nmethod* nmethod);
+  virtual void unregister_nmethod(nmethod* nm);
+  virtual void verify_nmethod(nmethod* nm);
+  virtual void flush_nmethod(nmethod* nm);
+
+  void prune_nmethods();
 
   size_t max_capacity() const;
 
--- old/src/hotspot/share/gc/parallel/pcTasks.cpp	2019-03-11 22:56:19.058649742 +0100
+++ new/src/hotspot/share/gc/parallel/pcTasks.cpp	2019-03-11 22:56:18.462640078 +0100
@@ -117,7 +117,7 @@
 
     case code_cache:
       // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
-      //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
+      //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
       AOTLoader::oops_do(&mark_and_push_closure);
       break;
 
--- old/src/hotspot/share/gc/parallel/psMarkSweep.cpp	2019-03-11 22:56:19.782661481 +0100
+++ new/src/hotspot/share/gc/parallel/psMarkSweep.cpp	2019-03-11 22:56:19.182651752 +0100
@@ -187,7 +187,6 @@
     // Let the size policy know we're starting
     size_policy->major_collection_begin();
 
-    CodeCache::gc_prologue();
     BiasedLocking::preserve_marks();
 
     // Capture metadata size before collection for sizing.
@@ -255,7 +254,7 @@
     MetaspaceUtils::verify_metrics();
 
     BiasedLocking::restore_marks();
-    CodeCache::gc_epilogue();
+    heap->prune_nmethods();
     JvmtiExport::gc_epilogue();
 
 #if COMPILER2_OR_JVMCI
@@ -525,7 +524,7 @@
     SystemDictionary::oops_do(mark_and_push_closure());
     ClassLoaderDataGraph::always_strong_cld_do(follow_cld_closure());
     // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
-    //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
+    //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
     AOTLoader::oops_do(mark_and_push_closure());
   }
 
--- old/src/hotspot/share/gc/parallel/psParallelCompact.cpp	2019-03-11 22:56:20.514673349 +0100
+++ new/src/hotspot/share/gc/parallel/psParallelCompact.cpp	2019-03-11 22:56:19.926663815 +0100
@@ -1061,7 +1061,6 @@
   ClassLoaderDataGraph::purge();
   MetaspaceUtils::verify_metrics();
 
-  CodeCache::gc_epilogue();
   JvmtiExport::gc_epilogue();
 
 #if COMPILER2_OR_JVMCI
@@ -1807,7 +1806,7 @@
     // Let the size policy know we're starting
     size_policy->major_collection_begin();
 
-    CodeCache::gc_prologue();
+    heap->prune_nmethods();
 
 #if COMPILER2_OR_JVMCI
     DerivedPointerTable::clear();
--- old/src/hotspot/share/gc/parallel/psTasks.cpp	2019-03-11 22:56:21.274685672 +0100
+++ new/src/hotspot/share/gc/parallel/psTasks.cpp	2019-03-11 22:56:20.694676267 +0100
@@ -28,12 +28,14 @@
 #include "classfile/systemDictionary.hpp"
 #include "code/codeCache.hpp"
 #include "gc/parallel/gcTaskManager.hpp"
+#include "gc/parallel/parallelScavengeHeap.inline.hpp"
 #include "gc/parallel/psCardTable.hpp"
 #include "gc/parallel/psClosure.inline.hpp"
 #include "gc/parallel/psPromotionManager.hpp"
 #include "gc/parallel/psPromotionManager.inline.hpp"
 #include "gc/parallel/psScavenge.inline.hpp"
 #include "gc/parallel/psTasks.hpp"
+#include "gc/shared/scavengableNMethods.hpp"
 #include "gc/shared/taskqueue.inline.hpp"
 #include "memory/iterator.hpp"
 #include "memory/resourceArea.hpp"
@@ -97,7 +99,7 @@
     case code_cache:
       {
         MarkingCodeBlobClosure each_scavengable_code_blob(&roots_to_old_closure, CodeBlobToOopClosure::FixRelocations);
-        CodeCache::scavenge_root_nmethods_do(&each_scavengable_code_blob);
+        ScavengableNMethods::scavengable_nmethods_do(&each_scavengable_code_blob);
         AOTLoader::oops_do(&roots_closure);
       }
       break;
--- old/src/hotspot/share/gc/serial/genMarkSweep.cpp	2019-03-11 22:56:21.946696567 +0100
+++ new/src/hotspot/share/gc/serial/genMarkSweep.cpp	2019-03-11 22:56:21.402687747 +0100
@@ -75,10 +75,6 @@
 
   gch->trace_heap_before_gc(_gc_tracer);
 
-  // When collecting the permanent generation Method*s may be moving,
-  // so we either have to flush all bcp data or convert it into bci.
-  CodeCache::gc_prologue();
-
   // Increment the invocation count
   _total_invocations++;
 
@@ -128,7 +124,7 @@
     rs->invalidate_or_clear(old_gen);
   }
 
-  CodeCache::gc_epilogue();
+  gch->prune_nmethods();
   JvmtiExport::gc_epilogue();
 
   // refs processing: clean slate
--- old/src/hotspot/share/gc/shared/collectedHeap.hpp	2019-03-11 22:56:22.666708241 +0100
+++ new/src/hotspot/share/gc/shared/collectedHeap.hpp	2019-03-11 22:56:22.070698577 +0100
@@ -514,9 +514,6 @@
   void print_heap_before_gc();
   void print_heap_after_gc();
 
-  // An object is scavengable if its location may move during a scavenge.
-  // (A scavenge is a GC which is not a full GC.)
-  virtual bool is_scavengable(oop obj) = 0;
   // Registering and unregistering an nmethod (compiled code) with the heap.
   // Override with specific mechanism for each specialized heap type.
   virtual void register_nmethod(nmethod* nm) {}
--- old/src/hotspot/share/gc/shared/genCollectedHeap.cpp	2019-03-11 22:56:23.342719201 +0100
+++ new/src/hotspot/share/gc/shared/genCollectedHeap.cpp	2019-03-11 22:56:22.802710446 +0100
@@ -47,6 +47,7 @@
 #include "gc/shared/genOopClosures.inline.hpp"
 #include "gc/shared/generationSpec.hpp"
 #include "gc/shared/oopStorageParState.inline.hpp"
+#include "gc/shared/scavengableNMethods.hpp"
 #include "gc/shared/space.hpp"
 #include "gc/shared/strongRootsScope.hpp"
 #include "gc/shared/weakProcessor.hpp"
@@ -175,6 +176,17 @@
   return heap_rs->base();
 }
 
+namespace {
+  class GenIsScavengable : public BoolObjectClosure {
+  public:
+    bool do_object_b(oop obj) {
+      return GenCollectedHeap::heap()->is_in_young(obj);
+    }
+  };
+
+  GenIsScavengable _is_scavengable;
+}
+
 void GenCollectedHeap::post_initialize() {
   CollectedHeap::post_initialize();
   ref_processing_init();
@@ -186,6 +198,8 @@
                          def_new_gen->from()->capacity());
 
   MarkSweep::initialize();
+
+  ScavengableNMethods::initialize(&_is_scavengable);
 }
 
 void GenCollectedHeap::ref_processing_init() {
@@ -685,11 +699,23 @@
 }
 
 void GenCollectedHeap::register_nmethod(nmethod* nm) {
-  CodeCache::register_scavenge_root_nmethod(nm);
+  ScavengableNMethods::register_nmethod(nm);
+}
+
+void GenCollectedHeap::unregister_nmethod(nmethod* nm) {
+  ScavengableNMethods::unregister_nmethod(nm);
 }
 
 void GenCollectedHeap::verify_nmethod(nmethod* nm) {
-  CodeCache::verify_scavenge_root_nmethod(nm);
+  ScavengableNMethods::verify_nmethod(nm);
+}
+
+void GenCollectedHeap::flush_nmethod(nmethod* nm) {
+  ScavengableNMethods::flush_nmethod(nm);
+}
+
+void GenCollectedHeap::prune_nmethods() {
+  ScavengableNMethods::prune_nmethods();
 }
 
 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
@@ -833,7 +859,7 @@
       assert(code_roots != NULL, "must supply closure for code cache");
 
       // We only visit parts of the CodeCache when scavenging.
-      CodeCache::scavenge_root_nmethods_do(code_roots);
+      ScavengableNMethods::scavengable_nmethods_do(code_roots);
     }
     if (so & SO_AllCodeCache) {
       assert(code_roots != NULL, "must supply closure for code cache");
@@ -845,7 +871,7 @@
     // Verify that the code cache contents are not subject to
     // movement by a scavenging collection.
     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
-    DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
+    DEBUG_ONLY(ScavengableNMethods::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
   }
 }
 
--- old/src/hotspot/share/gc/shared/genCollectedHeap.hpp	2019-03-11 22:56:24.102731524 +0100
+++ new/src/hotspot/share/gc/shared/genCollectedHeap.hpp	2019-03-11 22:56:23.498721731 +0100
@@ -249,13 +249,13 @@
   bool is_in_partial_collection(const void* p);
 #endif
 
-  virtual bool is_scavengable(oop obj) {
-    return is_in_young(obj);
-  }
-
   // Optimized nmethod scanning support routines
   virtual void register_nmethod(nmethod* nm);
-  virtual void verify_nmethod(nmethod* nmethod);
+  virtual void unregister_nmethod(nmethod* nm);
+  virtual void verify_nmethod(nmethod* nm);
+  virtual void flush_nmethod(nmethod* nm);
+
+  void prune_nmethods();
 
   // Iteration functions.
   void oop_iterate(OopIterateClosure* cl);
--- old/src/hotspot/share/gc/shared/parallelCleaning.cpp	2019-03-11 22:56:24.774742419 +0100
+++ new/src/hotspot/share/gc/shared/parallelCleaning.cpp	2019-03-11 22:56:24.234733664 +0100
@@ -70,9 +70,6 @@
 
 CodeCacheUnloadingTask::~CodeCacheUnloadingTask() {
   CodeCache::verify_clean_inline_caches();
-
-  guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
-
   CodeCache::verify_icholder_relocations();
 }
 
--- old/src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp	2019-03-11 22:56:25.494754094 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp	2019-03-11 22:56:24.906744560 +0100
@@ -557,9 +557,6 @@
   size_t obj_size(oop obj) const;
   virtual ptrdiff_t cell_header_size() const;
 
-  // All objects can potentially move
-  bool is_scavengable(oop obj) { return true; };
-
   void collect(GCCause::Cause cause);
   void do_full_collection(bool clear_all_soft_refs);
 
--- old/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp	2019-03-11 22:56:26.226765962 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp	2019-03-11 22:56:25.630756299 +0100
@@ -123,8 +123,6 @@
 
   heap->make_parsable(true);
 
-  CodeCache::gc_prologue();
-
   OrderAccess::fence();
 
   phase1_mark_heap();
@@ -168,7 +166,6 @@
   }
   FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
 
-  CodeCache::gc_epilogue();
   JvmtiExport::gc_epilogue();
 
   heap->set_full_gc_move_in_progress(false);
--- old/src/hotspot/share/gc/z/zCollectedHeap.cpp	2019-03-11 22:56:26.894776793 +0100
+++ new/src/hotspot/share/gc/z/zCollectedHeap.cpp	2019-03-11 22:56:26.354768038 +0100
@@ -106,10 +106,6 @@
   return false;
 }
 
-bool ZCollectedHeap::is_scavengable(oop obj) {
-  return false;
-}
-
 bool ZCollectedHeap::is_in(const void* p) const {
   return is_in_reserved(p) && _heap.is_in((uintptr_t)p);
 }
--- old/src/hotspot/share/gc/z/zCollectedHeap.hpp	2019-03-11 22:56:27.626788662 +0100
+++ new/src/hotspot/share/gc/z/zCollectedHeap.hpp	2019-03-11 22:56:27.026778933 +0100
@@ -71,7 +71,6 @@
   virtual size_t used() const;
 
   virtual bool is_maximal_no_gc() const;
-  virtual bool is_scavengable(oop obj);
   virtual bool is_in(const void* p) const;
   virtual bool is_in_closed_subset(const void* p) const;
 
--- old/src/hotspot/share/runtime/vmStructs.cpp	2019-03-11 22:56:28.358800531 +0100
+++ new/src/hotspot/share/runtime/vmStructs.cpp	2019-03-11 22:56:27.758790802 +0100
@@ -539,7 +539,6 @@
      static_field(CodeCache,                   _heaps,                                        GrowableArray<CodeHeap*>*)             \
      static_field(CodeCache,                   _low_bound,                                    address)                               \
      static_field(CodeCache,                   _high_bound,                                   address)                               \
-     static_field(CodeCache,                   _scavenge_root_nmethods,                       nmethod*)                              \
                                                                                                                                      \
   /*******************************/                                                                                                  \
   /* CodeHeap (NOTE: incomplete) */                                                                                                  \
@@ -681,8 +680,6 @@
                                                                                                                                      \
   nonstatic_field(nmethod,                     _entry_bci,                                    int)                                   \
   nonstatic_field(nmethod,                     _osr_link,                                     nmethod*)                              \
-  nonstatic_field(nmethod,                     _scavenge_root_link,                           nmethod*)                              \
-  nonstatic_field(nmethod,                     _scavenge_root_state,                          jbyte)                                 \
   nonstatic_field(nmethod,                     _state,                                        volatile signed char)                  \
   nonstatic_field(nmethod,                     _exception_offset,                             int)                                   \
   nonstatic_field(nmethod,                     _orig_pc_offset,                               int)                                   \
--- old/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/code/CodeCache.java	2019-03-11 22:56:29.182813891 +0100
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/code/CodeCache.java	2019-03-11 22:56:28.562803838 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -33,7 +33,6 @@
 
 public class CodeCache {
   private static GrowableArray<CodeHeap> heapArray;
-  private static AddressField scavengeRootNMethodsField;
   private static VirtualConstructor virtualConstructor;
 
   static {
@@ -56,8 +55,6 @@
     AddressField heapsField = type.getAddressField("_heaps");
     heapArray = GrowableArray.create(heapsField.getValue(), heapConstructor);
 
-    scavengeRootNMethodsField = type.getAddressField("_scavenge_root_nmethods");
-
     virtualConstructor = new VirtualConstructor(db);
     // Add mappings for all possible CodeBlob subclasses
     virtualConstructor.addMapping("BufferBlob", BufferBlob.class);
@@ -73,10 +70,6 @@
     }
   }
 
-  public NMethod scavengeRootMethods() {
-    return (NMethod) VMObjectFactory.newObject(NMethod.class, scavengeRootNMethodsField.getValue());
-  }
-
   public boolean contains(Address p) {
     for (int i = 0; i < heapArray.length(); ++i) {
       if (heapArray.at(i).contains(p)) {
--- old/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/code/NMethod.java	2019-03-11 22:56:29.902825564 +0100
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/code/NMethod.java	2019-03-11 22:56:29.314816031 +0100
@@ -38,8 +38,6 @@
   private static CIntegerField entryBCIField;
   /** To support simple linked-list chaining of nmethods */
   private static AddressField  osrLinkField;
-  private static AddressField  scavengeRootLinkField;
-  private static JByteField    scavengeRootStateField;
 
   /** Offsets for different nmethod parts */
   private static CIntegerField exceptionOffsetField;
@@ -88,8 +86,6 @@
 
     entryBCIField               = type.getCIntegerField("_entry_bci");
     osrLinkField                = type.getAddressField("_osr_link");
-    scavengeRootLinkField       = type.getAddressField("_scavenge_root_link");
-    scavengeRootStateField      = type.getJByteField("_scavenge_root_state");
 
     exceptionOffsetField        = type.getCIntegerField("_exception_offset");
     origPCOffsetField           = type.getCIntegerField("_orig_pc_offset");
@@ -251,14 +247,6 @@
     return (NMethod) VMObjectFactory.newObject(NMethod.class, osrLinkField.getValue(addr));
   }
 
-  public NMethod getScavengeRootLink() {
-    return (NMethod) VMObjectFactory.newObject(NMethod.class, scavengeRootLinkField.getValue(addr));
-  }
-
-  public int getScavengeRootState() {
-    return (int) scavengeRootStateField.getValue(addr);
-  }
-
   // MethodHandle
   public boolean isMethodHandleReturn(Address returnPc) {
     // Hard to read a bit fields from Java and it's only there for performance
--- /dev/null	2019-02-14 11:31:37.500399000 +0100
+++ new/src/hotspot/share/gc/shared/scavengableNMethods.cpp	2019-03-11 22:56:30.046827899 +0100
@@ -0,0 +1,304 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "code/codeCache.hpp"
+#include "code/nmethod.hpp"
+#include "compiler/compileTask.hpp"
+#include "gc/shared/collectedHeap.hpp"
+#include "gc/shared/scavengableNMethods.hpp"
+#include "gc/shared/scavengableNMethodsData.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/universe.hpp"
+#include "utilities/debug.hpp"
+
+static ScavengableNMethodsData gc_data(nmethod* nm) {
+  return ScavengableNMethodsData(nm);
+}
+
+nmethod* ScavengableNMethods::_head = NULL;
+BoolObjectClosure* ScavengableNMethods::_is_scavengable = NULL;
+
+void ScavengableNMethods::initialize(BoolObjectClosure* is_scavengable) {
+  _is_scavengable = is_scavengable;
+}
+
+// Conditionally adds the nmethod to the list if it is
+// not already on the list and has a scavengeable root.
+void ScavengableNMethods::register_nmethod(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  ScavengableNMethodsData data = gc_data(nm);
+
+  if (data.on_list() || !has_scavengable_oops(nm)) {
+    return;
+  }
+
+  data.set_on_list();
+  data.set_next(_head);
+
+  _head = nm;
+
+  CodeCache::print_trace("register_nmethod", nm);
+}
+
+void ScavengableNMethods::unregister_nmethod(nmethod* nm) {
+  // Do nothing. Unlinking is currently delayed until the purge phase.
+}
+
+#ifndef PRODUCT
+
+class DebugScavengableOops: public OopClosure {
+  BoolObjectClosure* _is_scavengable;
+  nmethod*           _nm;
+  bool               _ok;
+public:
+  DebugScavengableOops(BoolObjectClosure* is_scavengable, nmethod* nm) :
+      _is_scavengable(is_scavengable),
+      _nm(nm),
+      _ok(true) { }
+
+  bool ok() { return _ok; }
+  virtual void do_oop(oop* p) {
+    if (*p == NULL || !_is_scavengable->do_object_b(*p)) {
+      return;
+    }
+
+    if (_ok) {
+      _nm->print_nmethod(true);
+      _ok = false;
+    }
+    tty->print_cr("*** scavengable oop " PTR_FORMAT " found at " PTR_FORMAT " (offset %d)",
+                  p2i(*p), p2i(p), (int)((intptr_t)p - (intptr_t)_nm));
+    (*p)->print();
+  }
+  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
+};
+
+#endif // PRODUCT
+
+void ScavengableNMethods::verify_nmethod(nmethod* nm) {
+#ifndef PRODUCT
+  if (!gc_data(nm).on_list()) {
+    // Actually look inside, to verify the claim that it's clean.
+    DebugScavengableOops cl(_is_scavengable, nm);
+    nm->oops_do(&cl);
+    if (!cl.ok())
+      fatal("found an unadvertised bad scavengable oop in the code cache");
+  }
+  assert(gc_data(nm).not_marked(), "");
+#endif // PRODUCT
+}
+
+void ScavengableNMethods::flush_nmethod(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  // TODO: Should be done in unregister_nmethod, during the "unlink" phase.
+  if (gc_data(nm).on_list()) {
+    CodeCache::print_trace("flush_nmethod", nm);
+    nmethod* prev = NULL;
+    for (nmethod* cur = _head; cur != NULL; cur = gc_data(cur).next()) {
+      if (cur == nm) {
+        unlist_nmethod(cur, prev);
+        return;
+      }
+      prev = cur;
+    }
+  }
+}
+
+class HasScavengableOops: public OopClosure {
+  BoolObjectClosure* _is_scavengable;
+  bool               _found;
+  nmethod*           _print_nm;
+public:
+  HasScavengableOops(BoolObjectClosure* is_scavengable, nmethod* nm) :
+      _is_scavengable(is_scavengable),
+      _found(false),
+      _print_nm(nm) {}
+
+  bool found() { return _found; }
+  virtual void do_oop(oop* p) {
+    if (*p != NULL && _is_scavengable->do_object_b(*p)) {
+      NOT_PRODUCT(maybe_print(p));
+      _found = true;
+    }
+  }
+  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
+
+#ifndef PRODUCT
+  void maybe_print(oop* p) {
+    LogTarget(Trace, gc, nmethod) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      if (!_found) {
+        CompileTask::print(&ls, _print_nm, "new scavengable oop", /*short_form:*/ true);
+      }
+      ls.print("" PTR_FORMAT "[offset=%d] found scavengable oop " PTR_FORMAT " (found at " PTR_FORMAT ") ",
+               p2i(_print_nm), (int)((intptr_t)p - (intptr_t)_print_nm),
+               p2i(*p), p2i(p));
+      ls.cr();
+    }
+  }
+#endif //PRODUCT
+};
+
+bool ScavengableNMethods::has_scavengable_oops(nmethod* nm) {
+  HasScavengableOops cl(_is_scavengable, nm);
+  nm->oops_do(&cl);
+  return cl.found();
+}
+
+// Walk the list of methods which might contain oops to the java heap.
+void ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure* f) {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  const bool fix_relocations = f->fix_relocations();
+  debug_only(mark_on_list_nmethods());
+
+  nmethod* prev = NULL;
+  nmethod* cur = _head;
+  while (cur != NULL) {
+    ScavengableNMethodsData data = gc_data(cur);
+    debug_only(data.clear_marked());
+    assert(data.not_marked(), "");
+    assert(data.on_list(), "else shouldn't be on this list");
+
+    bool is_live = (!cur->is_zombie() && !cur->is_unloaded());
+    LogTarget(Trace, gc, nmethod) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      CompileTask::print(&ls, cur,
+        is_live ? "scavengable root " : "dead scavengable root", /*short_form:*/ true);
+    }
+    if (is_live) {
+      // Perform cur->oops_do(f), maybe just once per nmethod.
+      f->do_code_blob(cur);
+    }
+    nmethod* const next = data.next();
+    // The scavengable nmethod list must contain all methods with scavengable
+    // oops. It is safe to include more nmethod on the list, but we do not
+    // expect any live non-scavengable nmethods on the list.
+    if (fix_relocations) {
+      if (!is_live || !has_scavengable_oops(cur)) {
+        unlist_nmethod(cur, prev);
+      } else {
+        prev = cur;
+      }
+    }
+    cur = next;
+  }
+
+  // Check for stray marks.
+  debug_only(verify_unlisted_nmethods(NULL));
+}
+
+#ifndef PRODUCT
+void ScavengableNMethods::asserted_non_scavengable_nmethods_do(CodeBlobClosure* f) {
+  // While we are here, verify the integrity of the list.
+  mark_on_list_nmethods();
+  for (nmethod* cur = _head; cur != NULL; cur = gc_data(cur).next()) {
+    assert(gc_data(cur).on_list(), "else shouldn't be on this list");
+    gc_data(cur).clear_marked();
+  }
+  verify_unlisted_nmethods(f);
+}
+#endif // PRODUCT
+
+void ScavengableNMethods::unlist_nmethod(nmethod* nm, nmethod* prev) {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  assert((prev == NULL && _head == nm) ||
+         (prev != NULL && gc_data(prev).next() == nm), "precondition");
+
+  CodeCache::print_trace("unlist_nmethod", nm);
+
+  ScavengableNMethodsData data = gc_data(nm);
+
+  if (prev == NULL) {
+    _head = data.next();
+  } else {
+    gc_data(prev).set_next(data.next());
+  }
+  data.set_next(NULL);
+  data.clear_on_list();
+}
+
+void ScavengableNMethods::prune_nmethods() {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  debug_only(mark_on_list_nmethods());
+
+  nmethod* last = NULL;
+  nmethod* cur = _head;
+  while (cur != NULL) {
+    nmethod* next = gc_data(cur).next();
+    debug_only(gc_data(cur).clear_marked());
+    assert(gc_data(cur).on_list(), "else shouldn't be on this list");
+
+    if (!cur->is_zombie() && !cur->is_unloaded() && has_scavengable_oops(cur)) {
+      // Keep it.  Advance 'last' to prevent deletion.
+      last = cur;
+    } else {
+      // Prune it from the list, so we don't have to look at it any more.
+      CodeCache::print_trace("prune_nmethods", cur);
+      unlist_nmethod(cur, last);
+    }
+    cur = next;
+  }
+
+  // Check for stray marks.
+  debug_only(verify_unlisted_nmethods(NULL));
+}
+
+#ifndef PRODUCT
+// Temporarily mark nmethods that are claimed to be on the scavenge list.
+void ScavengableNMethods::mark_on_list_nmethods() {
+  NMethodIterator iter(NMethodIterator::only_alive);
+  while(iter.next()) {
+    nmethod* nm = iter.method();
+    ScavengableNMethodsData data = gc_data(nm);
+    assert(data.not_marked(), "clean state");
+    if (data.on_list())
+      data.set_marked();
+  }
+}
+
+// If the closure is given, run it on the unlisted nmethods.
+// Also make sure that the effects of mark_on_list_nmethods is gone.
+void ScavengableNMethods::verify_unlisted_nmethods(CodeBlobClosure* f_or_null) {
+  NMethodIterator iter(NMethodIterator::only_alive);
+  while(iter.next()) {
+    nmethod* nm = iter.method();
+
+    verify_nmethod(nm);
+
+    if (f_or_null != NULL && !gc_data(nm).on_list()) {
+      f_or_null->do_code_blob(nm);
+    }
+  }
+}
+
+#endif //PRODUCT
--- /dev/null	2019-02-14 11:31:37.500399000 +0100
+++ new/src/hotspot/share/gc/shared/scavengableNMethods.hpp	2019-03-11 22:56:30.774839703 +0100
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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_SHARED_SCAVENGABLENMETHODS_HPP
+#define SHARE_GC_SHARED_SCAVENGABLENMETHODS_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/macros.hpp"
+
+class BoolObjectClosure;
+class CodeBlobClosure;
+class CodeBlobToOopClosure;
+class nmethod;
+
+class ScavengableNMethods : public AllStatic {
+  friend class VMStructs;
+
+  static nmethod*           _head;
+  static BoolObjectClosure* _is_scavengable;
+
+public:
+  static void initialize(BoolObjectClosure* is_scavengable);
+
+  static void register_nmethod(nmethod* nm);
+  static void unregister_nmethod(nmethod* nm);
+  static void verify_nmethod(nmethod* nm);
+  static void flush_nmethod(nmethod* nm);
+
+  static void prune_nmethods();
+
+  // Apply f to every live code blob in scavengable nmethods. Prune nmethods
+  // from the list of scavengable nmethods if f->fix_relocations() and a nmethod
+  // no longer has scavengable oops.  If f->fix_relocations(), then f must copy
+  // objects to their new location immediately to avoid fixing nmethods on the
+  // basis of the old object locations.
+  static void scavengable_nmethods_do(CodeBlobToOopClosure* f);
+
+  static void asserted_non_scavengable_nmethods_do(CodeBlobClosure* f = NULL) PRODUCT_RETURN;
+
+private:
+  static void unlist_nmethod(nmethod* nm, nmethod* prev);
+
+  static bool has_scavengable_oops(nmethod* nm);
+
+  static void mark_on_list_nmethods() PRODUCT_RETURN;
+  static void verify_unlisted_nmethods(CodeBlobClosure* f_or_null) PRODUCT_RETURN;
+};
+
+#endif // SHARE_GC_SHARED_SCAVENGABLENMETHODS_HPP
--- /dev/null	2019-02-14 11:31:37.500399000 +0100
+++ new/src/hotspot/share/gc/shared/scavengableNMethodsData.hpp	2019-03-11 22:56:31.498851442 +0100
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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_SHARED_SCAVENGABLENMETHODDATAS_HPP
+#define SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+class nmethod;
+
+class ScavengableNMethodsData : public CHeapObj<mtGC> {
+  // State bits put into the two lower alignment bits.
+  static const uintptr_t state_bits = 2;
+  static const uintptr_t state_mask = (1 << state_bits) - 1;
+  static const uintptr_t state_on_list = 0x1;
+  static const uintptr_t state_marked  = 0x2;
+
+  // nmethod containing the GC data.
+  nmethod* const _nm;
+
+  // The data is stored as a bit pattern in a void* inside the nmethod.
+  uintptr_t data() const                    { return reinterpret_cast<uintptr_t>(_nm->gc_data<void>()); }
+  void set_data(uintptr_t data) const       { _nm->set_gc_data(reinterpret_cast<void*>(data)); }
+
+  jbyte state() const                       { return data() & state_mask; }
+  void set_state(jbyte state) const         { set_data((data() & ~state_mask) | state); }
+
+  uintptr_t from_nmethod(nmethod* nm) const { return reinterpret_cast<uintptr_t>(nm); }
+  nmethod* to_nmethod(uintptr_t data) const { return reinterpret_cast<nmethod*>(data); }
+
+public:
+  ScavengableNMethodsData(nmethod* nm) : _nm(nm) {
+    assert(is_aligned(nm, 4), "Must be aligned to fit state bits");
+  }
+
+  // Scavengable oop support
+  bool  on_list() const { return (state() & state_on_list) != 0; }
+  void  set_on_list()   { set_state(state_on_list); }
+  void  clear_on_list() { set_state(0); }
+
+#ifndef PRODUCT
+  void  set_marked()   { set_state(state() | state_marked); }
+  void  clear_marked() { set_state(state() & ~state_marked); }
+  bool  not_marked()   { return (state() & ~state_on_list) == 0; }
+  // N.B. there is no positive marked query, and we only use the not_marked query for asserts.
+#endif //PRODUCT
+
+  nmethod* next() const     { return to_nmethod(data() & ~state_mask); }
+  void set_next(nmethod *n) { set_data(from_nmethod(n) | state()); }
+};
+
+#endif // SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP