diff --git a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
index f4453a7ba0bb4..e081b3da7ee10 100644
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp
@@ -86,6 +86,7 @@
 #include "gc/shared/oopStorageParState.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
 #include "gc/shared/referenceProcessor.inline.hpp"
+#include "gc/shared/slidingForwarding.hpp"
 #include "gc/shared/suspendibleThreadSet.hpp"
 #include "gc/shared/taskqueue.inline.hpp"
 #include "gc/shared/taskTerminator.hpp"
@@ -1440,6 +1441,8 @@ jint G1CollectedHeap::initialize() {
 
   G1InitLogger::print();
 
+  SlidingForwarding::initialize(heap_rs.region(), HeapRegion::GrainWords);
+
   return JNI_OK;
 }
 
diff --git a/src/hotspot/share/gc/g1/g1FullCollector.cpp b/src/hotspot/share/gc/g1/g1FullCollector.cpp
index 430d6f327886b..1a87120b82998 100644
--- a/src/hotspot/share/gc/g1/g1FullCollector.cpp
+++ b/src/hotspot/share/gc/g1/g1FullCollector.cpp
@@ -40,6 +40,7 @@
 #include "gc/shared/preservedMarks.inline.hpp"
 #include "gc/shared/classUnloadingContext.hpp"
 #include "gc/shared/referenceProcessor.hpp"
+#include "gc/shared/slidingForwarding.hpp"
 #include "gc/shared/verifyOption.hpp"
 #include "gc/shared/weakProcessor.inline.hpp"
 #include "gc/shared/workerPolicy.hpp"
@@ -212,6 +213,8 @@ void G1FullCollector::collect() {
   // Don't add any more derived pointers during later phases
   deactivate_derived_pointers();
 
+  SlidingForwarding::begin();
+
   phase2_prepare_compaction();
 
   if (has_compaction_targets()) {
@@ -224,6 +227,8 @@ void G1FullCollector::collect() {
     log_info(gc, phases) ("No Regions selected for compaction. Skipping Phase 3: Adjust pointers and Phase 4: Compact heap");
   }
 
+  SlidingForwarding::end();
+
   phase5_reset_metadata();
 
   G1CollectedHeap::finish_codecache_marking_cycle();
diff --git a/src/hotspot/share/gc/g1/g1FullGCCompactTask.cpp b/src/hotspot/share/gc/g1/g1FullGCCompactTask.cpp
index 2ed6ccd4735fb..cfb16e59bc20e 100644
--- a/src/hotspot/share/gc/g1/g1FullGCCompactTask.cpp
+++ b/src/hotspot/share/gc/g1/g1FullGCCompactTask.cpp
@@ -30,6 +30,7 @@
 #include "gc/g1/g1FullGCCompactTask.hpp"
 #include "gc/g1/heapRegion.inline.hpp"
 #include "gc/shared/gcTraceTime.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "logging/log.hpp"
 #include "oops/oop.inline.hpp"
 #include "utilities/ticks.hpp"
@@ -41,7 +42,7 @@ void G1FullGCCompactTask::G1CompactRegionClosure::clear_in_bitmap(oop obj) {
 
 size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
   size_t size = obj->size();
-  if (obj->is_forwarded()) {
+  if (SlidingForwarding::is_forwarded(obj)) {
     G1FullGCCompactTask::copy_object_to_new_location(obj);
   }
 
@@ -52,13 +53,13 @@ size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
 }
 
 void G1FullGCCompactTask::copy_object_to_new_location(oop obj) {
-  assert(obj->is_forwarded(), "Sanity!");
-  assert(obj->forwardee() != obj, "Object must have a new location");
+  assert(SlidingForwarding::is_forwarded(obj), "Sanity!");
+  assert(SlidingForwarding::forwardee(obj) != obj, "Object must have a new location");
 
   size_t size = obj->size();
   // Copy object and reinit its mark.
   HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
-  HeapWord* destination = cast_from_oop<HeapWord*>(obj->forwardee());
+  HeapWord* destination = cast_from_oop<HeapWord*>(SlidingForwarding::forwardee(obj));
   Copy::aligned_conjoint_words(obj_addr, destination, size);
 
   // There is no need to transform stack chunks - marking already did that.
@@ -121,7 +122,7 @@ void G1FullGCCompactTask::compact_humongous_obj(HeapRegion* src_hr) {
   size_t word_size = obj->size();
 
   uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(word_size);
-  HeapWord* destination = cast_from_oop<HeapWord*>(obj->forwardee());
+  HeapWord* destination = cast_from_oop<HeapWord*>(SlidingForwarding::forwardee(obj));
 
   assert(collector()->mark_bitmap()->is_marked(obj), "Should only compact marked objects");
   collector()->mark_bitmap()->clear(obj);
diff --git a/src/hotspot/share/gc/g1/g1FullGCCompactionPoint.cpp b/src/hotspot/share/gc/g1/g1FullGCCompactionPoint.cpp
index a1db2aa87ba2e..573d10368453f 100644
--- a/src/hotspot/share/gc/g1/g1FullGCCompactionPoint.cpp
+++ b/src/hotspot/share/gc/g1/g1FullGCCompactionPoint.cpp
@@ -27,6 +27,7 @@
 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 #include "gc/g1/heapRegion.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "oops/oop.inline.hpp"
 #include "utilities/debug.hpp"
 
@@ -106,10 +107,10 @@ void G1FullGCCompactionPoint::forward(oop object, size_t size) {
     if (!object->is_forwarded()) {
       preserved_stack()->push_if_necessary(object, object->mark());
     }
-    object->forward_to(cast_to_oop(_compaction_top));
-    assert(object->is_forwarded(), "must be forwarded");
+    SlidingForwarding::forward_to(object, cast_to_oop(_compaction_top));
+    assert(SlidingForwarding::is_forwarded(object), "must be forwarded");
   } else {
-    assert(!object->is_forwarded(), "must not be forwarded");
+    assert(SlidingForwarding::is_not_forwarded(object), "must not be forwarded");
   }
 
   // Update compaction values.
@@ -172,8 +173,8 @@ void G1FullGCCompactionPoint::forward_humongous(HeapRegion* hr) {
   preserved_stack()->push_if_necessary(obj, obj->mark());
 
   HeapRegion* dest_hr = _compaction_regions->at(range_begin);
-  obj->forward_to(cast_to_oop(dest_hr->bottom()));
-  assert(obj->is_forwarded(), "Object must be forwarded!");
+  SlidingForwarding::forward_to(obj, cast_to_oop(dest_hr->bottom()));
+  assert(SlidingForwarding::is_forwarded(obj), "Object must be forwarded!");
 
   // Add the humongous object regions to the compaction point.
   add_humongous(hr);
diff --git a/src/hotspot/share/gc/g1/g1FullGCOopClosures.inline.hpp b/src/hotspot/share/gc/g1/g1FullGCOopClosures.inline.hpp
index aa194d16203b7..4df6d866811c8 100644
--- a/src/hotspot/share/gc/g1/g1FullGCOopClosures.inline.hpp
+++ b/src/hotspot/share/gc/g1/g1FullGCOopClosures.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2023, 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
@@ -32,6 +32,7 @@
 #include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
 #include "gc/g1/g1FullGCMarker.inline.hpp"
 #include "gc/g1/heapRegionRemSet.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "memory/iterator.inline.hpp"
 #include "memory/universe.hpp"
 #include "oops/access.inline.hpp"
@@ -65,8 +66,8 @@ template <class T> inline void G1AdjustClosure::adjust_pointer(T* p) {
     return;
   }
 
-  if (obj->is_forwarded()) {
-    oop forwardee = obj->forwardee();
+  if (SlidingForwarding::is_forwarded(obj)) {
+    oop forwardee = SlidingForwarding::forwardee(obj);
     // Forwarded, just update.
     assert(G1CollectedHeap::heap()->is_in_reserved(forwardee), "should be in object space");
     RawAccess<IS_NOT_NULL>::oop_store(p, forwardee);
diff --git a/src/hotspot/share/gc/g1/g1FullGCPrepareTask.inline.hpp b/src/hotspot/share/gc/g1/g1FullGCPrepareTask.inline.hpp
index 2a2add76f48c6..7a26b2c9ea0aa 100644
--- a/src/hotspot/share/gc/g1/g1FullGCPrepareTask.inline.hpp
+++ b/src/hotspot/share/gc/g1/g1FullGCPrepareTask.inline.hpp
@@ -32,6 +32,7 @@
 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 #include "gc/g1/g1FullGCScope.hpp"
 #include "gc/g1/heapRegion.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 
 void G1DetermineCompactionQueueClosure::free_empty_humongous_region(HeapRegion* hr) {
   _g1h->free_humongous_region(hr, nullptr);
@@ -114,10 +115,10 @@ inline bool G1DetermineCompactionQueueClosure::do_heap_region(HeapRegion* hr) {
 }
 
 inline size_t G1SerialRePrepareClosure::apply(oop obj) {
-  if (obj->is_forwarded()) {
+  if (SlidingForwarding::is_forwarded(obj)) {
     // We skip objects compiled into the first region or
     // into regions not part of the serial compaction point.
-    if (cast_from_oop<HeapWord*>(obj->forwardee()) < _dense_prefix_top) {
+    if (cast_from_oop<HeapWord*>(SlidingForwarding::forwardee(obj)) < _dense_prefix_top) {
       return obj->size();
     }
   }
diff --git a/src/hotspot/share/gc/serial/genMarkSweep.cpp b/src/hotspot/share/gc/serial/genMarkSweep.cpp
index d0594a3a50037..d9bb3c2b901ae 100644
--- a/src/hotspot/share/gc/serial/genMarkSweep.cpp
+++ b/src/hotspot/share/gc/serial/genMarkSweep.cpp
@@ -48,6 +48,7 @@
 #include "gc/shared/preservedMarks.inline.hpp"
 #include "gc/shared/referencePolicy.hpp"
 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "gc/shared/space.inline.hpp"
 #include "gc/shared/strongRootsScope.hpp"
 #include "gc/shared/weakProcessor.hpp"
@@ -198,7 +199,7 @@ class Compacter {
   static void forward_obj(oop obj, HeapWord* new_addr) {
     prefetch_write_scan(obj);
     if (cast_from_oop<HeapWord*>(obj) != new_addr) {
-      obj->forward_to(cast_to_oop(new_addr));
+      SlidingForwarding::forward_to(obj, cast_to_oop(new_addr));
     } else {
       assert(obj->is_gc_marked(), "inv");
       // This obj will stay in-place. Fix the markword.
@@ -223,7 +224,7 @@ class Compacter {
     prefetch_read_scan(addr);
 
     oop obj = cast_to_oop(addr);
-    oop new_obj = obj->forwardee();
+    oop new_obj = SlidingForwarding::forwardee(obj);
     HeapWord* new_addr = cast_from_oop<HeapWord*>(new_obj);
     assert(addr != new_addr, "inv");
     prefetch_write_copy(new_addr);
@@ -319,13 +320,13 @@ class Compacter {
       HeapWord* top = space->top();
 
       // Check if the first obj inside this space is forwarded.
-      if (!cast_to_oop(cur_addr)->is_forwarded()) {
+      if (SlidingForwarding::is_not_forwarded(cast_to_oop(cur_addr))) {
         // Jump over consecutive (in-place) live-objs-chunk
         cur_addr = get_first_dead(i);
       }
 
       while (cur_addr < top) {
-        if (!cast_to_oop(cur_addr)->is_forwarded()) {
+        if (SlidingForwarding::is_not_forwarded(cast_to_oop(cur_addr))) {
           cur_addr = *(HeapWord**) cur_addr;
           continue;
         }
@@ -448,6 +449,8 @@ void GenMarkSweep::invoke_at_safepoint(bool clear_all_softrefs) {
 
   phase1_mark(clear_all_softrefs);
 
+  SlidingForwarding::begin();
+
   Compacter compacter{gch};
 
   {
@@ -495,6 +498,8 @@ void GenMarkSweep::invoke_at_safepoint(bool clear_all_softrefs) {
   // (Should this be in general part?)
   gch->save_marks();
 
+  SlidingForwarding::end();
+
   deallocate_stacks();
 
   MarkSweep::_string_dedup_requests->flush();
diff --git a/src/hotspot/share/gc/serial/markSweep.inline.hpp b/src/hotspot/share/gc/serial/markSweep.inline.hpp
index 97283e987466f..41833fb5a5f40 100644
--- a/src/hotspot/share/gc/serial/markSweep.inline.hpp
+++ b/src/hotspot/share/gc/serial/markSweep.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2023, 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
@@ -31,6 +31,7 @@
 #include "classfile/javaClasses.inline.hpp"
 #include "gc/shared/continuationGCSupport.inline.hpp"
 #include "gc/serial/serialStringDedup.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "memory/universe.hpp"
 #include "oops/markWord.hpp"
 #include "oops/access.inline.hpp"
@@ -45,8 +46,8 @@ template <class T> inline void MarkSweep::adjust_pointer(T* p) {
     oop obj = CompressedOops::decode_not_null(heap_oop);
     assert(Universe::heap()->is_in(obj), "should be in heap");
 
-    if (obj->is_forwarded()) {
-      oop new_obj = obj->forwardee();
+    if (SlidingForwarding::is_forwarded(obj)) {
+      oop new_obj = SlidingForwarding::forwardee(obj);
       assert(is_object_aligned(new_obj), "oop must be aligned");
       RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
     }
diff --git a/src/hotspot/share/gc/serial/serialHeap.cpp b/src/hotspot/share/gc/serial/serialHeap.cpp
index fe0ba9f3e8809..480f50fdd7470 100644
--- a/src/hotspot/share/gc/serial/serialHeap.cpp
+++ b/src/hotspot/share/gc/serial/serialHeap.cpp
@@ -55,6 +55,7 @@
 #include "gc/shared/oopStorageParState.inline.hpp"
 #include "gc/shared/oopStorageSet.inline.hpp"
 #include "gc/shared/scavengableNMethods.hpp"
+#include "gc/shared/slidingForwarding.hpp"
 #include "gc/shared/space.hpp"
 #include "gc/shared/strongRootsScope.hpp"
 #include "gc/shared/suspendibleThreadSet.hpp"
@@ -203,6 +204,8 @@ jint SerialHeap::initialize() {
 
   GCInitLogger::print();
 
+  SlidingForwarding::initialize(_reserved, SpaceAlignment / HeapWordSize);
+
   return JNI_OK;
 }
 
diff --git a/src/hotspot/share/gc/shared/preservedMarks.cpp b/src/hotspot/share/gc/shared/preservedMarks.cpp
index 9889dbc369018..d3c97e4fd82b2 100644
--- a/src/hotspot/share/gc/shared/preservedMarks.cpp
+++ b/src/hotspot/share/gc/shared/preservedMarks.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2023, 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
@@ -24,6 +24,7 @@
 
 #include "precompiled.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "gc/shared/workerThread.hpp"
 #include "gc/shared/workerUtils.hpp"
 #include "memory/allocation.inline.hpp"
@@ -43,7 +44,7 @@ void PreservedMarks::restore() {
 void PreservedMarks::adjust_preserved_mark(PreservedMark* elem) {
   oop obj = elem->get_oop();
   if (obj->is_forwarded()) {
-    elem->set_oop(obj->forwardee());
+    elem->set_oop(SlidingForwarding::forwardee(obj));
   }
 }
 
diff --git a/src/hotspot/share/gc/shared/slidingForwarding.cpp b/src/hotspot/share/gc/shared/slidingForwarding.cpp
new file mode 100644
index 0000000000000..0ca378f433668
--- /dev/null
+++ b/src/hotspot/share/gc/shared/slidingForwarding.cpp
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. 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 "gc/shared/gc_globals.hpp"
+#include "gc/shared/slidingForwarding.hpp"
+#include "utilities/ostream.hpp"
+#include "utilities/powerOfTwo.hpp"
+
+// We cannot use 0, because that may already be a valid base address in zero-based heaps.
+// 0x1 is safe because heap base addresses must be aligned by much larger alignment
+HeapWord* const SlidingForwarding::UNUSED_BASE = reinterpret_cast<HeapWord*>(0x1);
+
+HeapWord* SlidingForwarding::_heap_start = nullptr;
+size_t SlidingForwarding::_region_size_words = 0;
+size_t SlidingForwarding::_heap_start_region_bias = 0;
+size_t SlidingForwarding::_num_regions = 0;
+uint SlidingForwarding::_region_size_bytes_shift = 0;
+uintptr_t SlidingForwarding::_region_mask = 0;
+HeapWord** SlidingForwarding::_biased_bases[SlidingForwarding::NUM_TARGET_REGIONS] = { nullptr, nullptr };
+HeapWord** SlidingForwarding::_bases_table = nullptr;
+SlidingForwarding::FallbackTable* SlidingForwarding::_fallback_table = nullptr;
+
+void SlidingForwarding::initialize(MemRegion heap, size_t region_size_words) {
+#ifdef _LP64
+  _heap_start = heap.start();
+
+  // If the heap is small enough to fit directly into the available offset bits,
+  // and we are running Serial GC, we can treat the whole heap as a single region
+  // if it happens to be aligned to allow biasing.
+  size_t rounded_heap_size = round_up_power_of_2(heap.byte_size());
+
+  if (UseSerialGC && (heap.word_size() <= (1 << NUM_OFFSET_BITS)) &&
+      is_aligned((uintptr_t)_heap_start, rounded_heap_size)) {
+    _num_regions = 1;
+    _region_size_words = heap.word_size();
+    _region_size_bytes_shift = log2i_exact(rounded_heap_size);
+  } else {
+    _num_regions = align_up(pointer_delta(heap.end(), heap.start()), region_size_words) / region_size_words;
+    _region_size_words = region_size_words;
+    _region_size_bytes_shift = log2i_exact(_region_size_words) + LogHeapWordSize;
+  }
+  _heap_start_region_bias = (uintptr_t)_heap_start >> _region_size_bytes_shift;
+  _region_mask = ~((uintptr_t(1) << _region_size_bytes_shift) - 1);
+
+  guarantee((_heap_start_region_bias << _region_size_bytes_shift) == (uintptr_t)_heap_start, "must be aligned: _heap_start_region_bias: " SIZE_FORMAT ", _region_size_byte_shift: %u, _heap_start: " PTR_FORMAT, _heap_start_region_bias, _region_size_bytes_shift, p2i(_heap_start));
+
+  assert(_region_size_words >= 1, "regions must be at least a word large");
+  assert(_bases_table == nullptr, "should not be initialized yet");
+  assert(_fallback_table == nullptr, "should not be initialized yet");
+#endif
+}
+
+void SlidingForwarding::begin() {
+#ifdef _LP64
+  assert(_bases_table == nullptr, "should not be initialized yet");
+  assert(_fallback_table == nullptr, "should not be initialized yet");
+
+  size_t max = _num_regions * NUM_TARGET_REGIONS;
+  _bases_table = NEW_C_HEAP_ARRAY(HeapWord*, max, mtGC);
+  HeapWord** biased_start = _bases_table - _heap_start_region_bias;
+  _biased_bases[0] = biased_start;
+  _biased_bases[1] = biased_start + _num_regions;
+  for (size_t i = 0; i < max; i++) {
+    _bases_table[i] = UNUSED_BASE;
+  }
+#endif
+}
+
+void SlidingForwarding::end() {
+#ifdef _LP64
+  assert(_bases_table != nullptr, "should be initialized");
+  FREE_C_HEAP_ARRAY(HeapWord*, _bases_table);
+  _bases_table = nullptr;
+  delete _fallback_table;
+  _fallback_table = nullptr;
+#endif
+}
+
+void SlidingForwarding::fallback_forward_to(HeapWord* from, HeapWord* to) {
+  if (_fallback_table == nullptr) {
+    _fallback_table = new (mtGC) FallbackTable();
+  }
+  _fallback_table->put_when_absent(from, to);
+}
+
+HeapWord* SlidingForwarding::fallback_forwardee(HeapWord* from) {
+  assert(_fallback_table != nullptr, "fallback table must be present");
+  HeapWord** found = _fallback_table->get(from);
+  if (found != nullptr) {
+    return *found;
+  } else {
+    return nullptr;
+  }
+}
diff --git a/src/hotspot/share/gc/shared/slidingForwarding.hpp b/src/hotspot/share/gc/shared/slidingForwarding.hpp
new file mode 100644
index 0000000000000..851d863aa8d2d
--- /dev/null
+++ b/src/hotspot/share/gc/shared/slidingForwarding.hpp
@@ -0,0 +1,179 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. 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_SLIDINGFORWARDING_HPP
+#define SHARE_GC_SHARED_SLIDINGFORWARDING_HPP
+
+#include "memory/allocation.hpp"
+#include "memory/memRegion.hpp"
+#include "oops/markWord.hpp"
+#include "oops/oopsHierarchy.hpp"
+#include "utilities/fastHash.hpp"
+#include "utilities/resourceHash.hpp"
+
+/**
+ * SlidingForwarding is a method to store forwarding information in a compressed form into the object header,
+ * that has been specifically designed for sliding compaction GCs and compact object headers. With compact object
+ * headers, we store the compressed class pointer in the header, which would be overwritten by full forwarding
+ * pointer, if we allow the legacy forwarding code to act. This would lose the class information for the object,
+ * which is required later in GC cycle to iterate the reference fields and get the object size for copying.
+ *
+ * SlidingForwarding requires only small side tables and guarantees constant-time access and modification.
+ *
+ * The idea is to use a pointer compression scheme very similar to the one that is used for compressed oops.
+ * We divide the heap into number of logical regions. Each region spans maximum of 2^NUM_OFFSET_BITS words.
+ *
+ * The key advantage of sliding compaction for encoding efficiency: it can forward objects from one region to a
+ * maximum of two regions. This is an intuitive property: when we slide the compact region full of data, it can
+ * only span two adjacent regions. This property allows us to use the off-side table to record the addresses of
+ * two target regions. The table holds N*2 entries for N logical regions. For each region, it gives the base
+ * address of the two target regions, or a special placeholder if not used. A single bit in forwarding would
+ * indicate to which of the two "to" regions the object is forwarded into.
+ *
+ * This encoding efficiency allows to store the forwarding information in the object header _together_ with the
+ * compressed class pointer.
+ *
+ * When recording the sliding forwarding, the mark word would look roughly like this:
+ *
+ *   64                              32                                0
+ *    [................................OOOOOOOOOOOOOOOOOOOOOOOOOOOOAFTT]
+ *                                                                    ^----- normal lock bits, would record "object is forwarded"
+ *                                                                  ^------- fallback bit (explained below)
+ *                                                                 ^-------- alternate region select
+ *                                     ^------------------------------------ in-region offset
+ *     ^-------------------------------------------------------------------- protected area, *not touched* by this code, useful for
+ *                                                                           compressed class pointer with compact object headers
+ *
+ * Adding a forwarding then generally works as follows:
+ *   1. Compute the "to" offset in the "to" region, this gives "offset".
+ *   2. Check if the primary "from" offset at base table contains "to" region base, use it.
+ *      If not usable, continue to next step. If usable, set "alternate" = "false" and jump to (4).
+ *   3. Check if the alternate "from" offset at base table contains "to" region base, use it.
+ *      This gives us "alternate" = "true". This should always complete for sliding forwarding.
+ *   4. Compute the mark word from "offset" and "alternate", write it out
+ *
+ * Similarly, looking up the target address, given an original object address generally works as follows:
+ *   1. Load the mark from object, and decode "offset" and "alternate" from there
+ *   2. Compute the "from" base offset from the object
+ *   3. Look up "to" region base from the base table either at primary or alternate indices, using "alternate" flag
+ *   4. Compute the "to" address from "to" region base and "offset"
+ *
+ * This algorithm is broken by G1 last-ditch serial compaction: there, object from a single region can be
+ * forwarded to multiple, more than two regions. To deal with that, we initialize a fallback-hashtable for
+ * storing those extra forwardings, and set another bit in the header to indicate that the forwardee is not
+ * encoded but should be looked-up in the hashtable. G1 serial compaction is not very common - it is the
+ * last-last-ditch GC that is used when the JVM is scrambling to squeeze more space out of the heap, and at
+ * that point, ultimate performance is no longer the main concern.
+ */
+class SlidingForwarding : public AllStatic {
+private:
+
+  /*
+   * A simple hash-table that acts as fallback for the sliding forwarding.
+   * This is used in the case of G1 serial compaction, which violates the
+   * assumption of sliding forwarding that each object of any region is only
+   * ever forwarded to one of two target regions. At this point, the GC is
+   * scrambling to free up more Java heap memory, and therefore performance
+   * is not the major concern.
+   *
+   * The implementation is a straightforward open hashtable.
+   * It is a single-threaded (not thread-safe) implementation, and that
+   * is sufficient because G1 serial compaction is single-threaded.
+   */
+  inline static unsigned hash(HeapWord* const& from) {
+    uint64_t val = reinterpret_cast<uint64_t>(from);
+    uint64_t hash = FastHash::get_hash64(val, UCONST64(0xAAAAAAAAAAAAAAAA));
+    return checked_cast<unsigned>(hash >> 32);
+  }
+  inline static bool equals(HeapWord* const& lhs, HeapWord* const& rhs) {
+    return lhs == rhs;
+  }
+  typedef ResourceHashtable<HeapWord* /* key-type */, HeapWord* /* value-type */,
+                            1024 /* size */, AnyObj::C_HEAP /* alloc-type */, mtGC,
+                            SlidingForwarding::hash, SlidingForwarding::equals> FallbackTable;
+
+  static const uintptr_t MARK_LOWER_HALF_MASK = right_n_bits(32);
+
+  // We need the lowest two bits to indicate a forwarded object.
+  // The next bit indicates that the forwardee should be looked-up in a fallback-table.
+  static const int FALLBACK_SHIFT = markWord::lock_bits;
+  static const int FALLBACK_BITS = 1;
+  static const int FALLBACK_MASK = right_n_bits(FALLBACK_BITS) << FALLBACK_SHIFT;
+
+  // Next bit selects the target region
+  static const int ALT_REGION_SHIFT = FALLBACK_SHIFT + FALLBACK_BITS;
+  static const int ALT_REGION_BITS = 1;
+  // This will be "2" always, but expose it as named constant for clarity
+  static const size_t NUM_TARGET_REGIONS = 1 << ALT_REGION_BITS;
+
+  // The offset bits start then
+  static const int OFFSET_BITS_SHIFT = ALT_REGION_SHIFT + ALT_REGION_BITS;
+
+  // How many bits we use for the offset
+  static const int NUM_OFFSET_BITS = 32 - OFFSET_BITS_SHIFT;
+
+  // Indicates an unused base address in the target base table.
+  static HeapWord* const UNUSED_BASE;
+
+  static HeapWord*      _heap_start;
+  static size_t         _region_size_words;
+
+  static size_t         _heap_start_region_bias;
+  static size_t         _num_regions;
+  static uint           _region_size_bytes_shift;
+  static uintptr_t      _region_mask;
+
+  // The target base table memory.
+  static HeapWord**     _bases_table;
+  // Entries into the target base tables, biased to the start of the heap.
+  static HeapWord**     _biased_bases[NUM_TARGET_REGIONS];
+
+  static FallbackTable* _fallback_table;
+
+  static inline size_t biased_region_index_containing(HeapWord* addr);
+
+  static inline uintptr_t encode_forwarding(HeapWord* from, HeapWord* to);
+  static inline HeapWord* decode_forwarding(HeapWord* from, uintptr_t encoded);
+
+  static void fallback_forward_to(HeapWord* from, HeapWord* to);
+  static HeapWord* fallback_forwardee(HeapWord* from);
+
+  static inline void forward_to_impl(oop from, oop to);
+  static inline oop forwardee_impl(oop from);
+
+public:
+  static void initialize(MemRegion heap, size_t region_size_words);
+
+  static void begin();
+  static void end();
+
+  static inline bool is_forwarded(oop obj);
+  static inline bool is_not_forwarded(oop obj);
+
+  static inline void forward_to(oop from, oop to);
+  static inline oop forwardee(oop from);
+};
+
+#endif // SHARE_GC_SHARED_SLIDINGFORWARDING_HPP
diff --git a/src/hotspot/share/gc/shared/slidingForwarding.inline.hpp b/src/hotspot/share/gc/shared/slidingForwarding.inline.hpp
new file mode 100644
index 0000000000000..8f314b11b0f47
--- /dev/null
+++ b/src/hotspot/share/gc/shared/slidingForwarding.inline.hpp
@@ -0,0 +1,163 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. 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_SLIDINGFORWARDING_INLINE_HPP
+#define SHARE_GC_SHARED_SLIDINGFORWARDING_INLINE_HPP
+
+#include "gc/shared/gc_globals.hpp"
+#include "gc/shared/slidingForwarding.hpp"
+#include "oops/markWord.hpp"
+#include "oops/oop.inline.hpp"
+#include "utilities/macros.hpp"
+
+inline bool SlidingForwarding::is_forwarded(oop obj) {
+  return obj->is_forwarded();
+}
+
+inline bool SlidingForwarding::is_not_forwarded(oop obj) {
+  return !obj->is_forwarded();
+}
+
+size_t SlidingForwarding::biased_region_index_containing(HeapWord* addr) {
+  return (uintptr_t)addr >> _region_size_bytes_shift;
+}
+
+uintptr_t SlidingForwarding::encode_forwarding(HeapWord* from, HeapWord* to) {
+  static_assert(NUM_TARGET_REGIONS == 2, "Only implemented for this amount");
+
+  size_t from_reg_idx = biased_region_index_containing(from);
+  HeapWord* to_region_base = (HeapWord*)((uintptr_t)to & _region_mask);
+
+  HeapWord** base = &_biased_bases[0][from_reg_idx];
+  uintptr_t alternate = 0;
+  if (*base == to_region_base) {
+    // Primary is good
+  } else if (*base == UNUSED_BASE) {
+    // Primary is free
+    *base = to_region_base;
+  } else {
+    base = &_biased_bases[1][from_reg_idx];
+    if (*base == to_region_base) {
+      // Alternate is good
+    } else if (*base == UNUSED_BASE) {
+      // Alternate is free
+      *base = to_region_base;
+    } else {
+      // Both primary and alternate are not fitting
+      // This happens only in the following rare situations:
+      // - In Serial GC, sometimes when compact-top switches spaces, because the
+      //   region boudaries are virtual and objects can cross regions
+      // - In G1 serial compaction, because tails of various compaction chains
+      //   are distributed across the remainders of already compacted regions.
+      return (1 << FALLBACK_SHIFT) | markWord::marked_value;
+    }
+    alternate = 1;
+  }
+
+  size_t offset = pointer_delta(to, to_region_base);
+  assert(offset < _region_size_words, "Offset should be within the region. from: " PTR_FORMAT
+         ", to: " PTR_FORMAT ", to_region_base: " PTR_FORMAT ", offset: " SIZE_FORMAT,
+         p2i(from), p2i(to), p2i(to_region_base), offset);
+
+  uintptr_t encoded = (offset << OFFSET_BITS_SHIFT) |
+                      (alternate << ALT_REGION_SHIFT) |
+                      markWord::marked_value;
+
+  assert(to == decode_forwarding(from, encoded), "must be reversible");
+  assert((encoded & ~MARK_LOWER_HALF_MASK) == 0, "must encode to lowest 32 bits");
+  return encoded;
+}
+
+HeapWord* SlidingForwarding::decode_forwarding(HeapWord* from, uintptr_t encoded) {
+  assert((encoded & markWord::lock_mask_in_place) == markWord::marked_value, "must be marked as forwarded");
+  assert((encoded & FALLBACK_MASK) == 0, "must not be fallback-forwarded");
+  assert((encoded & ~MARK_LOWER_HALF_MASK) == 0, "must decode from lowest 32 bits");
+  size_t alternate = (encoded >> ALT_REGION_SHIFT) & right_n_bits(ALT_REGION_BITS);
+  assert(alternate < NUM_TARGET_REGIONS, "Sanity");
+  uintptr_t offset = (encoded >> OFFSET_BITS_SHIFT);
+
+  size_t from_idx = biased_region_index_containing(from);
+  HeapWord* base = _biased_bases[alternate][from_idx];
+  assert(base != UNUSED_BASE, "must not be unused base: encoded: " INTPTR_FORMAT, encoded);
+  HeapWord* decoded = base + offset;
+  assert(decoded >= _heap_start,
+         "Address must be above heap start. encoded: " INTPTR_FORMAT ", alt_region: " SIZE_FORMAT ", base: " PTR_FORMAT,
+         encoded, alternate, p2i(base));
+
+  return decoded;
+}
+
+inline void SlidingForwarding::forward_to_impl(oop from, oop to) {
+  assert(_bases_table != nullptr, "call begin() before forwarding");
+
+  markWord from_header = from->mark();
+  if (from_header.has_displaced_mark_helper()) {
+    from_header = from_header.displaced_mark_helper();
+  }
+
+  HeapWord* from_hw = cast_from_oop<HeapWord*>(from);
+  HeapWord* to_hw   = cast_from_oop<HeapWord*>(to);
+  uintptr_t encoded = encode_forwarding(from_hw, to_hw);
+  markWord new_header = markWord((from_header.value() & ~MARK_LOWER_HALF_MASK) | encoded);
+  from->set_mark(new_header);
+
+  if ((encoded & FALLBACK_MASK) != 0) {
+    fallback_forward_to(from_hw, to_hw);
+  }
+}
+
+inline void SlidingForwarding::forward_to(oop obj, oop fwd) {
+#ifdef _LP64
+  assert(_bases_table != nullptr, "expect sliding forwarding initialized");
+  forward_to_impl(obj, fwd);
+  assert(forwardee(obj) == fwd, "must be forwarded to correct forwardee");
+#else
+  obj->forward_to(fwd);
+#endif
+}
+
+inline oop SlidingForwarding::forwardee_impl(oop from) {
+  assert(_bases_table != nullptr, "call begin() before asking for forwarding");
+
+  markWord header = from->mark();
+  HeapWord* from_hw = cast_from_oop<HeapWord*>(from);
+  if ((header.value() & FALLBACK_MASK) != 0) {
+    HeapWord* to = fallback_forwardee(from_hw);
+    return cast_to_oop(to);
+  }
+  uintptr_t encoded = header.value() & MARK_LOWER_HALF_MASK;
+  HeapWord* to = decode_forwarding(from_hw, encoded);
+  return cast_to_oop(to);
+}
+
+inline oop SlidingForwarding::forwardee(oop obj) {
+#ifdef _LP64
+  assert(_bases_table != nullptr, "expect sliding forwarding initialized");
+  return forwardee_impl(obj);
+#else
+  return obj->forwardee();
+#endif
+}
+
+#endif // SHARE_GC_SHARED_SLIDINGFORWARDING_INLINE_HPP
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp b/src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp
index 3552669abb661..a4ee7f2e7dc68 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp
@@ -28,6 +28,7 @@
 #include "gc/shared/continuationGCSupport.hpp"
 #include "gc/shared/gcTraceTime.inline.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "gc/shared/tlab_globals.hpp"
 #include "gc/shared/workerThread.hpp"
 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
@@ -228,6 +229,8 @@ void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
     // until all phases run together.
     ShenandoahHeapLocker lock(heap->lock());
 
+    SlidingForwarding::begin();
+
     phase2_calculate_target_addresses(worker_slices);
 
     OrderAccess::fence();
@@ -241,6 +244,7 @@ void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
     // Epilogue
     _preserved_marks->restore(heap->workers());
     _preserved_marks->reclaim();
+    SlidingForwarding::end();
   }
 
   // Resize metaspace
@@ -370,7 +374,7 @@ class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
     assert(_compact_point + obj_size <= _to_region->end(), "must fit");
     shenandoah_assert_not_forwarded(nullptr, p);
     _preserved_marks->push_if_necessary(p, p->mark());
-    p->forward_to(cast_to_oop(_compact_point));
+    SlidingForwarding::forward_to(p, cast_to_oop(_compact_point));
     _compact_point += obj_size;
   }
 };
@@ -478,7 +482,7 @@ void ShenandoahFullGC::calculate_target_humongous_objects() {
       if (start >= to_begin && start != r->index()) {
         // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
         _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
-        old_obj->forward_to(cast_to_oop(heap->get_region(start)->bottom()));
+        SlidingForwarding::forward_to(old_obj, cast_to_oop(heap->get_region(start)->bottom()));
         to_end = start;
         continue;
       }
@@ -738,8 +742,8 @@ class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure
     if (!CompressedOops::is_null(o)) {
       oop obj = CompressedOops::decode_not_null(o);
       assert(_ctx->is_marked(obj), "must be marked");
-      if (obj->is_forwarded()) {
-        oop forw = obj->forwardee();
+      if (SlidingForwarding::is_forwarded(obj)) {
+        oop forw = SlidingForwarding::forwardee(obj);
         RawAccess<IS_NOT_NULL>::oop_store(p, forw);
       }
     }
@@ -849,9 +853,9 @@ class ShenandoahCompactObjectsClosure : public ObjectClosure {
   void do_object(oop p) {
     assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
     size_t size = p->size();
-    if (p->is_forwarded()) {
+    if (SlidingForwarding::is_forwarded(p)) {
       HeapWord* compact_from = cast_from_oop<HeapWord*>(p);
-      HeapWord* compact_to = cast_from_oop<HeapWord*>(p->forwardee());
+      HeapWord* compact_to = cast_from_oop<HeapWord*>(SlidingForwarding::forwardee(p));
       Copy::aligned_conjoint_words(compact_from, compact_to, size);
       oop new_obj = cast_to_oop(compact_to);
 
@@ -956,7 +960,7 @@ void ShenandoahFullGC::compact_humongous_objects() {
     ShenandoahHeapRegion* r = heap->get_region(c - 1);
     if (r->is_humongous_start()) {
       oop old_obj = cast_to_oop(r->bottom());
-      if (!old_obj->is_forwarded()) {
+      if (SlidingForwarding::is_not_forwarded(old_obj)) {
         // No need to move the object, it stays at the same slot
         continue;
       }
@@ -965,7 +969,7 @@ void ShenandoahFullGC::compact_humongous_objects() {
 
       size_t old_start = r->index();
       size_t old_end   = old_start + num_regions - 1;
-      size_t new_start = heap->heap_region_index_containing(old_obj->forwardee());
+      size_t new_start = heap->heap_region_index_containing(SlidingForwarding::forwardee(old_obj));
       size_t new_end   = new_start + num_regions - 1;
       assert(old_start != new_start, "must be real move");
       assert(r->is_stw_move_allowed(), "Region " SIZE_FORMAT " should be movable", r->index());
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
index de55dde8aca96..75fc1a6642d30 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
@@ -34,6 +34,7 @@
 #include "gc/shared/locationPrinter.inline.hpp"
 #include "gc/shared/memAllocator.hpp"
 #include "gc/shared/plab.hpp"
+#include "gc/shared/slidingForwarding.hpp"
 #include "gc/shared/tlab_globals.hpp"
 
 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
@@ -438,6 +439,8 @@ jint ShenandoahHeap::initialize() {
 
   ShenandoahInitLogger::print();
 
+  SlidingForwarding::initialize(_heap_region, ShenandoahHeapRegion::region_size_words());
+
   return JNI_OK;
 }
 
diff --git a/src/hotspot/share/utilities/fastHash.hpp b/src/hotspot/share/utilities/fastHash.hpp
new file mode 100644
index 0000000000000..86b1dcf2b5ee4
--- /dev/null
+++ b/src/hotspot/share/utilities/fastHash.hpp
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2023, 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_UTILITIES_FASTHASH_HPP
+#define SHARE_UTILITIES_FASTHASH_HPP
+
+#include "memory/allStatic.hpp"
+
+class FastHash : public AllStatic {
+private:
+  static void fullmul64(uint64_t& hi, uint64_t& lo, uint64_t op1, uint64_t op2) {
+#if defined(__SIZEOF_INT128__)
+    __uint128_t prod = static_cast<__uint128_t>(op1) * static_cast<__uint128_t>(op2);
+    hi = static_cast<uint64_t>(prod >> 64);
+    lo = static_cast<uint64_t>(prod >>  0);
+#else
+    /* First calculate all of the cross products. */
+    uint64_t lo_lo = (op1 & 0xFFFFFFFF) * (op2 & 0xFFFFFFFF);
+    uint64_t hi_lo = (op1 >> 32)        * (op2 & 0xFFFFFFFF);
+    uint64_t lo_hi = (op1 & 0xFFFFFFFF) * (op2 >> 32);
+    uint64_t hi_hi = (op1 >> 32)        * (op2 >> 32);
+
+    /* Now add the products together. These will never overflow. */
+    uint64_t cross = (lo_lo >> 32) + (hi_lo & 0xFFFFFFFF) + lo_hi;
+    uint64_t upper = (hi_lo >> 32) + (cross >> 32)        + hi_hi;
+    hi = upper;
+    lo = (cross << 32) | (lo_lo & 0xFFFFFFFF);
+#endif
+  }
+
+  static void fullmul32(uint32_t& hi, uint32_t& lo, uint32_t op1, uint32_t op2) {
+    uint64_t x64 = op1, y64 = op2, xy64 = x64 * y64;
+    hi = (uint32_t)(xy64 >> 32);
+    lo = (uint32_t)(xy64 >>  0);
+  }
+
+  static uint64_t ror(uint64_t x, uint64_t distance) {
+    distance = distance & 0x3F;
+    return (x >> distance) | (x << (64 - distance));
+  }
+
+public:
+  static uint64_t get_hash64(uint64_t x, uint64_t y) {
+    const uint64_t M  = 0x8ADAE89C337954D5;
+    const uint64_t A  = 0xAAAAAAAAAAAAAAAA; // REPAA
+    const uint64_t H0 = (x ^ y), L0 = (x ^ A);
+
+    uint64_t U0, V0; fullmul64(U0, V0, L0, M);
+    const uint64_t Q0 = (H0 * M);
+    const uint64_t L1 = (Q0 ^ U0);
+
+    uint64_t U1, V1; fullmul64(U1, V1, L1, M);
+    const uint64_t P1 = (V0 ^ M);
+    const uint64_t Q1 = ror(P1, L1);
+    const uint64_t L2 = (Q1 ^ U1);
+    return V1 ^ L2;
+  }
+
+  static uint32_t get_hash32(uint32_t x, uint32_t y) {
+    const uint32_t M  = 0x337954D5;
+    const uint32_t A  = 0xAAAAAAAA; // REPAA
+    const uint32_t H0 = (x ^ y), L0 = (x ^ A);
+
+    uint32_t U0, V0; fullmul32(U0, V0, L0, M);
+    const uint32_t Q0 = (H0 * M);
+    const uint32_t L1 = (Q0 ^ U0);
+
+    uint32_t U1, V1; fullmul32(U1, V1, L1, M);
+    const uint32_t P1 = (V0 ^ M);
+    const uint32_t Q1 = ror(P1, L1);
+    const uint32_t L2 = (Q1 ^ U1);
+    return V1 ^ L2;
+  }
+};
+
+#endif// SHARE_UTILITIES_FASTHASH_HPP
diff --git a/test/hotspot/gtest/gc/shared/test_preservedMarks.cpp b/test/hotspot/gtest/gc/shared/test_preservedMarks.cpp
index 5f9a361105ec7..fa8d246415a45 100644
--- a/test/hotspot/gtest/gc/shared/test_preservedMarks.cpp
+++ b/test/hotspot/gtest/gc/shared/test_preservedMarks.cpp
@@ -23,59 +23,50 @@
 
 #include "precompiled.hpp"
 #include "gc/shared/preservedMarks.inline.hpp"
+#include "gc/shared/slidingForwarding.inline.hpp"
 #include "oops/oop.inline.hpp"
 #include "unittest.hpp"
 
-// Class to create a "fake" oop with a mark that will
-// return true for calls to must_be_preserved().
-class FakeOop {
-  oopDesc _oop;
-
-public:
-  FakeOop() : _oop() { _oop.set_mark(originalMark()); }
-
-  oop get_oop() { return &_oop; }
-  markWord mark() { return _oop.mark(); }
-  void set_mark(markWord m) { _oop.set_mark(m); }
-  void forward_to(oop obj) {
-    markWord m = markWord::encode_pointer_as_mark(obj);
-    _oop.set_mark(m);
-  }
-
-  static markWord originalMark() { return markWord(markWord::lock_mask_in_place); }
-  static markWord changedMark()  { return markWord(0x4711); }
-};
+static markWord originalMark() { return markWord(markWord::lock_mask_in_place); }
+static markWord changedMark()  { return markWord(0x4711); }
 
 #define ASSERT_MARK_WORD_EQ(a, b) ASSERT_EQ((a).value(), (b).value())
 
 TEST_VM(PreservedMarks, iterate_and_restore) {
   PreservedMarks pm;
-  FakeOop o1;
-  FakeOop o2;
-  FakeOop o3;
-  FakeOop o4;
+
+  HeapWord fakeheap[32] = { nullptr };
+  HeapWord* heap = align_up(fakeheap, 8 * sizeof(HeapWord));
+  SlidingForwarding::initialize(MemRegion(&heap[0], &heap[16]), 8);
+
+  oop o1 = cast_to_oop(&heap[0]); o1->set_mark(originalMark());
+  oop o2 = cast_to_oop(&heap[2]); o2->set_mark(originalMark());
+  oop o3 = cast_to_oop(&heap[4]); o3->set_mark(originalMark());
+  oop o4 = cast_to_oop(&heap[6]); o4->set_mark(originalMark());
 
   // Make sure initial marks are correct.
-  ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::originalMark());
-  ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::originalMark());
-  ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::originalMark());
-  ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::originalMark());
+  ASSERT_MARK_WORD_EQ(o1->mark(), originalMark());
+  ASSERT_MARK_WORD_EQ(o2->mark(), originalMark());
+  ASSERT_MARK_WORD_EQ(o3->mark(), originalMark());
+  ASSERT_MARK_WORD_EQ(o4->mark(), originalMark());
 
   // Change the marks and verify change.
-  o1.set_mark(FakeOop::changedMark());
-  o2.set_mark(FakeOop::changedMark());
-  ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::changedMark());
-  ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::changedMark());
+  o1->set_mark(changedMark());
+  o2->set_mark(changedMark());
+  ASSERT_MARK_WORD_EQ(o1->mark(), changedMark());
+  ASSERT_MARK_WORD_EQ(o2->mark(), changedMark());
+
+  SlidingForwarding::begin();
 
   // Push o1 and o2 to have their marks preserved.
-  pm.push_if_necessary(o1.get_oop(), o1.mark());
-  pm.push_if_necessary(o2.get_oop(), o2.mark());
+  pm.push_if_necessary(o1, o1->mark());
+  pm.push_if_necessary(o2, o2->mark());
 
   // Fake a move from o1->o3 and o2->o4.
-  o1.forward_to(o3.get_oop());
-  o2.forward_to(o4.get_oop());
-  ASSERT_EQ(o1.get_oop()->forwardee(), o3.get_oop());
-  ASSERT_EQ(o2.get_oop()->forwardee(), o4.get_oop());
+  SlidingForwarding::forward_to(o1, o3);
+  SlidingForwarding::forward_to(o2, o4);
+  ASSERT_EQ(SlidingForwarding::forwardee(o1), o3);
+  ASSERT_EQ(SlidingForwarding::forwardee(o2), o4);
   // Adjust will update the PreservedMarks stack to
   // make sure the mark is updated at the new location.
   pm.adjust_during_full_gc();
@@ -83,6 +74,7 @@ TEST_VM(PreservedMarks, iterate_and_restore) {
   // Restore all preserved and verify that the changed
   // mark is now present at o3 and o4.
   pm.restore();
-  ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::changedMark());
-  ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::changedMark());
+  ASSERT_MARK_WORD_EQ(o3->mark(), changedMark());
+  ASSERT_MARK_WORD_EQ(o4->mark(), changedMark());
+  SlidingForwarding::end();
 }
diff --git a/test/hotspot/gtest/gc/shared/test_slidingForwarding.cpp b/test/hotspot/gtest/gc/shared/test_slidingForwarding.cpp
new file mode 100644
index 0000000000000..68960f49145ef
--- /dev/null
+++ b/test/hotspot/gtest/gc/shared/test_slidingForwarding.cpp
@@ -0,0 +1,120 @@
+/*
+ * Copyright Amazon.com Inc. 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 "gc/shared/slidingForwarding.inline.hpp"
+#include "oops/markWord.hpp"
+#include "oops/oop.inline.hpp"
+#include "utilities/align.hpp"
+#include "unittest.hpp"
+
+#ifdef _LP64
+#ifndef PRODUCT
+
+static uintptr_t make_mark(uintptr_t target_region, uintptr_t offset) {
+  return (target_region) << 3 | (offset << 4) | 3 /* forwarded */;
+}
+
+static uintptr_t make_fallback() {
+  return ((uintptr_t(1) << 2) /* fallback */ | 3 /* forwarded */);
+}
+
+// Test simple forwarding within the same region.
+TEST_VM(SlidingForwarding, simple) {
+  HeapWord fakeheap[32] = { nullptr };
+  HeapWord* heap = align_up(fakeheap, 8 * sizeof(HeapWord));
+  oop obj1 = cast_to_oop(&heap[2]);
+  oop obj2 = cast_to_oop(&heap[0]);
+  SlidingForwarding::initialize(MemRegion(&heap[0], &heap[16]), 8);
+  obj1->set_mark(markWord::prototype());
+  SlidingForwarding::begin();
+
+  SlidingForwarding::forward_to(obj1, obj2);
+  ASSERT_EQ(obj1->mark().value(), make_mark(0 /* target_region */, 0 /* offset */));
+  ASSERT_EQ(SlidingForwarding::forwardee(obj1), obj2);
+
+  SlidingForwarding::end();
+}
+
+// Test forwardings crossing 2 regions.
+TEST_VM(SlidingForwarding, tworegions) {
+  HeapWord fakeheap[32] = { nullptr };
+  HeapWord* heap = align_up(fakeheap, 8 * sizeof(HeapWord));
+  oop obj1 = cast_to_oop(&heap[14]);
+  oop obj2 = cast_to_oop(&heap[2]);
+  oop obj3 = cast_to_oop(&heap[10]);
+  SlidingForwarding::initialize(MemRegion(&heap[0], &heap[16]), 8);
+  obj1->set_mark(markWord::prototype());
+  SlidingForwarding::begin();
+
+  SlidingForwarding::forward_to(obj1, obj2);
+  ASSERT_EQ(obj1->mark().value(), make_mark(0 /* target_region */, 2 /* offset */));
+  ASSERT_EQ(SlidingForwarding::forwardee(obj1), obj2);
+
+  SlidingForwarding::forward_to(obj1, obj3);
+  ASSERT_EQ(obj1->mark().value(), make_mark(1 /* target_region */, 2 /* offset */));
+  ASSERT_EQ(SlidingForwarding::forwardee(obj1), obj3);
+
+  SlidingForwarding::end();
+}
+
+// Test fallback forwardings crossing 4 regions.
+TEST_VM(SlidingForwarding, fallback) {
+  HeapWord fakeheap[32] = { nullptr };
+  HeapWord* heap = align_up(fakeheap, 8 * sizeof(HeapWord));
+  oop s_obj1 = cast_to_oop(&heap[12]);
+  oop s_obj2 = cast_to_oop(&heap[13]);
+  oop s_obj3 = cast_to_oop(&heap[14]);
+  oop s_obj4 = cast_to_oop(&heap[15]);
+  oop t_obj1 = cast_to_oop(&heap[2]);
+  oop t_obj2 = cast_to_oop(&heap[4]);
+  oop t_obj3 = cast_to_oop(&heap[10]);
+  oop t_obj4 = cast_to_oop(&heap[12]);
+  SlidingForwarding::initialize(MemRegion(&heap[0], &heap[16]), 4);
+  s_obj1->set_mark(markWord::prototype());
+  s_obj2->set_mark(markWord::prototype());
+  s_obj3->set_mark(markWord::prototype());
+  s_obj4->set_mark(markWord::prototype());
+  SlidingForwarding::begin();
+
+  SlidingForwarding::forward_to(s_obj1, t_obj1);
+  ASSERT_EQ(s_obj1->mark().value(), make_mark(0 /* target_region */, 2 /* offset */));
+  ASSERT_EQ(SlidingForwarding::forwardee(s_obj1), t_obj1);
+
+  SlidingForwarding::forward_to(s_obj2, t_obj2);
+  ASSERT_EQ(s_obj2->mark().value(), make_mark(1 /* target_region */, 0 /* offset */));
+  ASSERT_EQ(SlidingForwarding::forwardee(s_obj2), t_obj2);
+
+  SlidingForwarding::forward_to(s_obj3, t_obj3);
+  ASSERT_EQ(s_obj3->mark().value(), make_fallback());
+  ASSERT_EQ(SlidingForwarding::forwardee(s_obj3), t_obj3);
+
+  SlidingForwarding::forward_to(s_obj4, t_obj4);
+  ASSERT_EQ(s_obj4->mark().value(), make_fallback());
+  ASSERT_EQ(SlidingForwarding::forwardee(s_obj4), t_obj4);
+
+  SlidingForwarding::end();
+}
+
+#endif // PRODUCT
+#endif // _LP64