--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/code/dependencyContext.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2015, 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_VM_CODE_DEPENDENCYCONTEXT_HPP
+#define SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
+
+#include "memory/allocation.hpp"
+#include "oops/oop.hpp"
+#include "runtime/handles.hpp"
+#include "runtime/perfData.hpp"
+#include "runtime/safepoint.hpp"
+
+class nmethod;
+class DepChange;
+
+//
+// nmethodBucket is used to record dependent nmethods for
+// deoptimization.  nmethod dependencies are actually <klass, method>
+// pairs but we really only care about the klass part for purposes of
+// finding nmethods which might need to be deoptimized.  Instead of
+// recording the method, a count of how many times a particular nmethod
+// was recorded is kept.  This ensures that any recording errors are
+// noticed since an nmethod should be removed as many times are it's
+// added.
+//
+class nmethodBucket: public CHeapObj<mtClass> {
+  friend class VMStructs;
+ private:
+  nmethod*       _nmethod;
+  int            _count;
+  nmethodBucket* _next;
+
+ public:
+  nmethodBucket(nmethod* nmethod, nmethodBucket* next) :
+   _nmethod(nmethod), _next(next), _count(1) {}
+
+  int count()                             { return _count; }
+  int increment()                         { _count += 1; return _count; }
+  int decrement();
+  nmethodBucket* next()                   { return _next; }
+  void set_next(nmethodBucket* b)         { _next = b; }
+  nmethod* get_nmethod()                  { return _nmethod; }
+};
+
+//
+// Utility class to manipulate nmethod dependency context.
+// The context consists of nmethodBucket* (a head of a linked list)
+// and a boolean flag (does the list contains stale entries). The structure is
+// encoded as an intptr_t: lower bit is used for the flag. It is possible since
+// nmethodBucket* is aligned - the structure is malloc'ed in C heap.
+// Dependency context can be attached either to an InstanceKlass (_dep_context field)
+// or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp).
+// DependencyContext class operates on some location which holds a intptr_t value.
+//
+class DependencyContext : public StackObj {
+  friend class VMStructs;
+  friend class TestDependencyContext;
+ private:
+  enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 };
+
+  intptr_t* _dependency_context_addr;
+
+  void set_dependencies(nmethodBucket* b) {
+    assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned");
+    if (has_stale_entries()) {
+      *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask;
+    } else {
+      *_dependency_context_addr = intptr_t(b);
+    }
+  }
+
+  void set_has_stale_entries(bool x) {
+    if (x) {
+      *_dependency_context_addr |= _has_stale_entries_mask;
+    } else {
+      *_dependency_context_addr &= ~_has_stale_entries_mask;
+    }
+  }
+
+  nmethodBucket* dependencies() {
+    intptr_t value = *_dependency_context_addr;
+    return (nmethodBucket*) (value & ~_has_stale_entries_mask);
+  }
+
+  bool has_stale_entries() const {
+    intptr_t value = *_dependency_context_addr;
+    return (value & _has_stale_entries_mask) != 0;
+  }
+
+  static PerfCounter* _perf_total_buckets_allocated_count;
+  static PerfCounter* _perf_total_buckets_deallocated_count;
+  static PerfCounter* _perf_total_buckets_stale_count;
+  static PerfCounter* _perf_total_buckets_stale_acc_count;
+
+ public:
+#ifdef ASSERT
+  // Safepoints are forbidden during DC lifetime. GC can invalidate
+  // _dependency_context_addr if it relocates the holder
+  // (e.g. CallSiteContext Java object).
+  int _safepoint_counter;
+
+  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr),
+    _safepoint_counter(SafepointSynchronize::_safepoint_counter) {}
+
+  ~DependencyContext() {
+    assert(_safepoint_counter == SafepointSynchronize::_safepoint_counter, "safepoint happened");
+  }
+#else
+  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {}
+#endif // ASSERT
+
+  static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false
+
+  static void init();
+
+  int  mark_dependent_nmethods(DepChange& changes);
+  void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
+  void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
+  int  remove_all_dependents();
+
+  void expunge_stale_entries();
+
+  // Unsafe deallocation of nmethodBuckets. Used in IK::release_C_heap_structures
+  // to clean up the context possibly containing live entries pointing to unloaded nmethods.
+  void wipe();
+
+#ifndef PRODUCT
+  void print_dependent_nmethods(bool verbose);
+  bool is_dependent_nmethod(nmethod* nm);
+  bool find_stale_entries();
+#endif //PRODUCT
+};
+#endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP