--- /dev/null	2019-02-14 11:31:37.500399000 +0100
+++ new/src/hotspot/share/gc/shared/scavengableNMethods.cpp	2019-03-11 14:43:09.851835732 +0100
@@ -0,0 +1,303 @@
+/*
+ * 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();
+    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