text: /*
   * Copyright (c) 2015, 2020, Red Hat, Inc. 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_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
  #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
  
  #include "gc/shenandoah/shenandoahHeap.hpp"
  
  #include "classfile/javaClasses.inline.hpp"
  #include "gc/shared/markBitMap.inline.hpp"
  #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
  #include "gc/shared/suspendibleThreadSet.hpp"
  #include "gc/shared/tlab_globals.hpp"
  #include "gc/shenandoah/shenandoahAsserts.hpp"
  #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
  #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
  #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
  #include "gc/shenandoah/shenandoahWorkGroup.hpp"
  #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
  #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
  #include "gc/shenandoah/shenandoahControlThread.hpp"
  #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
  #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
  #include "oops/compressedOops.inline.hpp"
  #include "oops/oop.inline.hpp"
  #include "runtime/atomic.hpp"
  #include "runtime/prefetch.inline.hpp"
  #include "runtime/thread.hpp"
  #include "utilities/copy.hpp"
  #include "utilities/globalDefinitions.hpp"
  
  inline ShenandoahHeap* ShenandoahHeap::heap() {
    return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
  }
  
  inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
    size_t new_index = Atomic::add(&_index, (size_t) 1, memory_order_relaxed);
    // get_region() provides the bounds-check and returns NULL on OOB.
    return _heap->get_region(new_index - 1);
  }
  
  inline bool ShenandoahHeap::has_forwarded_objects() const {
    return _gc_state.is_set(HAS_FORWARDED);
  }
  
  inline WorkGang* ShenandoahHeap::workers() const {
    return _workers;
  }
  
  inline WorkGang* ShenandoahHeap::safepoint_workers() {
    return _safepoint_workers;
  }
  
  inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
    uintptr_t region_start = ((uintptr_t) addr);
    uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
    assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
    return index;
  }
  
  inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
    size_t index = heap_region_index_containing(addr);
    ShenandoahHeapRegion* const result = get_region(index);
    assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
    return result;
  }
  
  inline void ShenandoahHeap::enter_evacuation(Thread* t) {
    _oom_evac_handler.enter_evacuation(t);
  }
  
  inline void ShenandoahHeap::leave_evacuation(Thread* t) {
    _oom_evac_handler.leave_evacuation(t);
  }
  
  template <class T>
  inline void ShenandoahHeap::update_with_forwarded(T* p) {
    T o = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(o)) {
      oop obj = CompressedOops::decode_not_null(o);
      if (in_collection_set(obj)) {
        // Corner case: when evacuation fails, there are objects in collection
        // set that are not really forwarded. We can still go and try and update them
        // (uselessly) to simplify the common path.
        shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
        oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
        shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
  
        // Unconditionally store the update: no concurrent updates expected.
        RawAccess<IS_NOT_NULL>::oop_store(p, fwd);
      }
    }
  }
  
  template <class T>
  inline void ShenandoahHeap::conc_update_with_forwarded(T* p) {
    T o = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(o)) {
      oop obj = CompressedOops::decode_not_null(o);
      if (in_collection_set(obj)) {
        // Corner case: when evacuation fails, there are objects in collection
        // set that are not really forwarded. We can still go and try CAS-update them
        // (uselessly) to simplify the common path.
        shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
        oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
        shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
  
        // Sanity check: we should not be updating the cset regions themselves,
        // unless we are recovering from the evacuation failure.
        shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || cancelled_gc());
  
        // Either we succeed in updating the reference, or something else gets in our way.
        // We don't care if that is another concurrent GC update, or another mutator update.
        atomic_update_oop(fwd, p, obj);
      }
    }
  }
  
  // Atomic updates of heap location. This is only expected to work with updating the same
  // logical object with its forwardee. The reason why we need stronger-than-relaxed memory
  // ordering has to do with coordination with GC barriers and mutator accesses.
  //
  // In essence, stronger CAS access is required to maintain the transitive chains that mutator
  // accesses build by themselves. To illustrate this point, consider the following example.
  //
  // Suppose "o" is the object that has a field "x" and the reference to "o" is stored
  // to field at "addr", which happens to be Java volatile field. Normally, the accesses to volatile
  // field at "addr" would be matched with release/acquire barriers. This changes when GC moves
  // the object under mutator feet.
  //
  // Thread 1 (Java)
  //         // --- previous access starts here
  //         ...
  //   T1.1: store(&o.x, 1, mo_relaxed)
  //   T1.2: store(&addr, o, mo_release) // volatile store
  //
  //         // --- new access starts here
  //         // LRB: copy and install the new copy to fwdptr
  //   T1.3: var copy = copy(o)
  //   T1.4: cas(&fwd, t, copy, mo_release) // pointer-mediated publication
  //         <access continues>
  //
  // Thread 2 (GC updater)
  //   T2.1: var f = load(&fwd, mo_{consume|acquire}) // pointer-mediated acquisition
  //   T2.2: cas(&addr, o, f, mo_release) // this method
  //
  // Thread 3 (Java)
  //   T3.1: var o = load(&addr, mo_acquire) // volatile read
  //   T3.2: if (o != null)
  //   T3.3:   var r = load(&o.x, mo_relaxed)
  //
  // r is guaranteed to contain "1".
  //
  // Without GC involvement, there is synchronizes-with edge from T1.2 to T3.1,
  // which guarantees this. With GC involvement, when LRB copies the object and
  // another thread updates the reference to it, we need to have the transitive edge
  // from T1.4 to T2.1 (that one is guaranteed by forwarding accesses), plus the edge
  // from T2.2 to T3.1 (which is brought by this CAS).
  //
  // Note that we do not need to "acquire" in these methods, because we do not read the
  // failure witnesses contents on any path, and "release" is enough.
  //
  
  inline void ShenandoahHeap::atomic_update_oop(oop update, oop* addr, oop compare) {
    assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    Atomic::cmpxchg(addr, compare, update, memory_order_release);
  }
  
  inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, narrowOop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    narrowOop u = CompressedOops::encode(update);
    Atomic::cmpxchg(addr, compare, u, memory_order_release);
  }
  
  inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, oop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    narrowOop c = CompressedOops::encode(compare);
    narrowOop u = CompressedOops::encode(update);
    Atomic::cmpxchg(addr, c, u, memory_order_release);
  }
  
  inline bool ShenandoahHeap::atomic_update_oop_check(oop update, oop* addr, oop compare) {
    assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    return (oop) Atomic::cmpxchg(addr, compare, update, memory_order_release) == compare;
  }
  
  inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    narrowOop u = CompressedOops::encode(update);
    return (narrowOop) Atomic::cmpxchg(addr, compare, u, memory_order_release) == compare;
  }
  
  inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, oop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    narrowOop c = CompressedOops::encode(compare);
    narrowOop u = CompressedOops::encode(update);
    return CompressedOops::decode(Atomic::cmpxchg(addr, c, u, memory_order_release)) == compare;
  }
  
  // The memory ordering discussion above does not apply for methods that store NULLs:
  // then, there is no transitive reads in mutator (as we see NULLs), and we can do
  // relaxed memory ordering there.
  
  inline void ShenandoahHeap::atomic_clear_oop(oop* addr, oop compare) {
    assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    Atomic::cmpxchg(addr, compare, oop(), memory_order_relaxed);
  }
  
  inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, oop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    narrowOop cmp = CompressedOops::encode(compare);
    Atomic::cmpxchg(addr, cmp, narrowOop(), memory_order_relaxed);
  }
  
  inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, narrowOop compare) {
    assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
    Atomic::cmpxchg(addr, compare, narrowOop(), memory_order_relaxed);
  }
  
  inline bool ShenandoahHeap::cancelled_gc() const {
    return _cancelled_gc.get() == CANCELLED;
  }
  
  inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
    if (! (sts_active && ShenandoahSuspendibleWorkers)) {
      return cancelled_gc();
    }
  
    jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
    if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
      if (SuspendibleThreadSet::should_yield()) {
        SuspendibleThreadSet::yield();
      }
  
      // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
      // to restore to CANCELLABLE.
      if (prev == CANCELLABLE) {
        _cancelled_gc.set(CANCELLABLE);
      }
      return false;
    } else {
      return true;
    }
  }
  
  inline void ShenandoahHeap::clear_cancelled_gc() {
    _cancelled_gc.set(CANCELLABLE);
    _oom_evac_handler.clear();
  }
  
  inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
    assert(UseTLAB, "TLABs should be enabled");
  
    PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
    if (gclab == NULL) {
      assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
             "Performance: thread should have GCLAB: %s", thread->name());
      // No GCLABs in this thread, fallback to shared allocation
      return NULL;
    }
    HeapWord* obj = gclab->allocate(size);
    if (obj != NULL) {
      return obj;
    }
    // Otherwise...
    return allocate_from_gclab_slow(thread, size);
  }
  
  inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
    if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
      // This thread went through the OOM during evac protocol and it is safe to return
      // the forward pointer. It must not attempt to evacuate any more.
      return ShenandoahBarrierSet::resolve_forwarded(p);
    }
  
    assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
  
    size_t size = p->size();
  
    assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
  
    bool alloc_from_gclab = true;
    HeapWord* copy = NULL;
  
  #ifdef ASSERT
    if (ShenandoahOOMDuringEvacALot &&
        (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
          copy = NULL;
    } else {
  #endif
      if (UseTLAB) {
        copy = allocate_from_gclab(thread, size);
      }
      if (copy == NULL) {
        ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
        copy = allocate_memory(req);
        alloc_from_gclab = false;
      }
  #ifdef ASSERT
    }
  #endif
  
    if (copy == NULL) {
      control_thread()->handle_alloc_failure_evac(size);
  
      _oom_evac_handler.handle_out_of_memory_during_evacuation();
  
      return ShenandoahBarrierSet::resolve_forwarded(p);
    }
  
    // Copy the object:
    Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
  
    // Try to install the new forwarding pointer.
    oop copy_val = cast_to_oop(copy);
    oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
    if (result == copy_val) {
      // Successfully evacuated. Our copy is now the public one!
      shenandoah_assert_correct(NULL, copy_val);
      return copy_val;
    }  else {
      // Failed to evacuate. We need to deal with the object that is left behind. Since this
      // new allocation is certainly after TAMS, it will be considered live in the next cycle.
      // But if it happens to contain references to evacuated regions, those references would
      // not get updated for this stale copy during this cycle, and we will crash while scanning
      // it the next cycle.
      //
      // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
      // object will overwrite this stale copy, or the filler object on LAB retirement will
      // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
      // have to explicitly overwrite the copy with the filler object. With that overwrite,
      // we have to keep the fwdptr initialized and pointing to our (stale) copy.
      if (alloc_from_gclab) {
        ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
      } else {
        fill_with_object(copy, size);
        shenandoah_assert_correct(NULL, copy_val);
      }
      shenandoah_assert_correct(NULL, result);
      return result;
    }
  }
  
  inline bool ShenandoahHeap::requires_marking(const void* entry) const {
    oop obj = cast_to_oop(entry);
    return !_marking_context->is_marked_strong(obj);
  }
  
  inline bool ShenandoahHeap::in_collection_set(oop p) const {
    assert(collection_set() != NULL, "Sanity");
    return collection_set()->is_in(p);
  }
  
  inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
    assert(collection_set() != NULL, "Sanity");
    return collection_set()->is_in_loc(p);
  }
  
  inline bool ShenandoahHeap::is_stable() const {
    return _gc_state.is_clear();
  }
  
  inline bool ShenandoahHeap::is_idle() const {
    return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
  }
  
  inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
    return _gc_state.is_set(MARKING);
  }
  
  inline bool ShenandoahHeap::is_evacuation_in_progress() const {
    return _gc_state.is_set(EVACUATION);
  }
  
  inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
    return _gc_state.is_set(mask);
  }
  
  inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
    return _degenerated_gc_in_progress.is_set();
  }
  
  inline bool ShenandoahHeap::is_full_gc_in_progress() const {
    return _full_gc_in_progress.is_set();
  }
  
  inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
    return _full_gc_move_in_progress.is_set();
  }
  
  inline bool ShenandoahHeap::is_update_refs_in_progress() const {
    return _gc_state.is_set(UPDATEREFS);
  }
  
  inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
    return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
  }
  
  inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
    return _concurrent_strong_root_in_progress.is_set();
  }
  
  inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
    return _gc_state.is_set(WEAK_ROOTS);
  }
  
  template<class T>
  inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
    marked_object_iterate(region, cl, region->top());
  }
  
  template<class T>
  inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
    assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
  
    ShenandoahMarkingContext* const ctx = complete_marking_context();
    assert(ctx->is_complete(), "sanity");
  
    HeapWord* tams = ctx->top_at_mark_start(region);
  
    size_t skip_bitmap_delta = 1;
    HeapWord* start = region->bottom();
    HeapWord* end = MIN2(tams, region->end());
  
    // Step 1. Scan below the TAMS based on bitmap data.
    HeapWord* limit_bitmap = MIN2(limit, tams);
  
    // Try to scan the initial candidate. If the candidate is above the TAMS, it would
    // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
    HeapWord* cb = ctx->get_next_marked_addr(start, end);
  
    intx dist = ShenandoahMarkScanPrefetch;
    if (dist > 0) {
      // Batched scan that prefetches the oop data, anticipating the access to
      // either header, oop field, or forwarding pointer. Not that we cannot
      // touch anything in oop, while it still being prefetched to get enough
      // time for prefetch to work. This is why we try to scan the bitmap linearly,
      // disregarding the object size. However, since we know forwarding pointer
      // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
      // there is no point for prefetching the oop contents, as oop->size() will
      // touch it prematurely.
  
      // No variable-length arrays in standard C++, have enough slots to fit
      // the prefetch distance.
      static const int SLOT_COUNT = 256;
      guarantee(dist <= SLOT_COUNT, "adjust slot count");
      HeapWord* slots[SLOT_COUNT];
  
      int avail;
      do {
        avail = 0;
        for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
          Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
          slots[avail++] = cb;
          cb += skip_bitmap_delta;
          if (cb < limit_bitmap) {
            cb = ctx->get_next_marked_addr(cb, limit_bitmap);
          }
        }
  
        for (int c = 0; c < avail; c++) {
          assert (slots[c] < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
          assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
          oop obj = cast_to_oop(slots[c]);
          assert(oopDesc::is_oop(obj), "sanity");
          assert(ctx->is_marked(obj), "object expected to be marked");
          cl->do_object(obj);
        }
      } while (avail > 0);
    } else {
      while (cb < limit_bitmap) {
        assert (cb < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
        assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
        oop obj = cast_to_oop(cb);
        assert(oopDesc::is_oop(obj), "sanity");
        assert(ctx->is_marked(obj), "object expected to be marked");
        cl->do_object(obj);
        cb += skip_bitmap_delta;
        if (cb < limit_bitmap) {
          cb = ctx->get_next_marked_addr(cb, limit_bitmap);
        }
      }
    }
  
    // Step 2. Accurate size-based traversal, happens past the TAMS.
    // This restarts the scan at TAMS, which makes sure we traverse all objects,
    // regardless of what happened at Step 1.
    HeapWord* cs = tams;
    while (cs < limit) {
      assert (cs >= tams, "only objects past TAMS here: "   PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
      assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
      oop obj = cast_to_oop(cs);
      assert(oopDesc::is_oop(obj), "sanity");
      assert(ctx->is_marked(obj), "object expected to be marked");
      int size = obj->size();
      cl->do_object(obj);
      cs += size;
    }
  }
  
  template <class T>
  class ShenandoahObjectToOopClosure : public ObjectClosure {
    T* _cl;
  public:
    ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
  
    void do_object(oop obj) {
      obj->oop_iterate(_cl);
    }
  };
  
  template <class T>
  class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
    T* _cl;
    MemRegion _bounds;
  public:
    ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
      _cl(cl), _bounds(bottom, top) {}
  
    void do_object(oop obj) {
      obj->oop_iterate(_cl, _bounds);
    }
  };
  
  template<class T>
  inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
    if (region->is_humongous()) {
      HeapWord* bottom = region->bottom();
      if (top > bottom) {
        region = region->humongous_start_region();
        ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
        marked_object_iterate(region, &objs);
      }
    } else {
      ShenandoahObjectToOopClosure<T> objs(cl);
      marked_object_iterate(region, &objs, top);
    }
  }
  
  inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
    if (region_idx < _num_regions) {
      return _regions[region_idx];
    } else {
      return NULL;
    }
  }
  
  inline void ShenandoahHeap::mark_complete_marking_context() {
    _marking_context->mark_complete();
  }
  
  inline void ShenandoahHeap::mark_incomplete_marking_context() {
    _marking_context->mark_incomplete();
  }
  
  inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
    assert (_marking_context->is_complete()," sanity");
    return _marking_context;
  }
  
  inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
    return _marking_context;
  }
  
  #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
  