Log moving-space end of previous compaction when corruption detected

If an object's class is found to be null past this pointer then the
corruption must have happened elsewhere.

Test: ATP test-infra
Change-Id: I9e8819ceaf99f3d6117115ddf7ef0aed0b774b0d

runtime/gc/collector/mark_compact.cc

diff --git a/runtime/gc/collector/mark_compact.cc b/runtime/gc/collector/mark_compact.cc
index 021d8ba..9e98d7e 100644
--- a/runtime/gc/collector/mark_compact.cc
+++ b/runtime/gc/collector/mark_compact.cc
@@ -500,7 +500,8 @@
       uffd_(kFdUnused),
       marking_done_(false),
       uffd_initialized_(false),
-      clamp_info_map_status_(ClampInfoStatus::kClampInfoNotDone) {
+      clamp_info_map_status_(ClampInfoStatus::kClampInfoNotDone),
+      prev_moving_space_end_at_compaction_(moving_space_begin_) {
   if (kIsDebugBuild) {
     updated_roots_.reset(new std::unordered_set<void*>());
   }
@@ -2985,6 +2986,7 @@
   bump_pointer_space_->SetBlockSizes(thread_running_gc_,
                                      post_compact_end_ - begin,
                                      consumed_blocks_count);
+  prev_moving_space_end_at_compaction_ = static_cast<void*>(bump_pointer_space_->End());
   if (kIsDebugBuild) {
     size_t moving_space_size = bump_pointer_space_->Size();
     size_t los_size = 0;
@@ -4724,6 +4726,8 @@
                                << " prev_post_compact_end: " << prev_post_compact_end_
                                << " prev_black_allocations_begin: " << prev_black_allocations_begin_
                                << " prev_black_dense_end: " << prev_black_dense_end_
+                               << " prev_moving_space_end_at_compaction: "
+                               << prev_moving_space_end_at_compaction_
                                << " prev_gc_young: " << prev_gc_young_
                                << " prev_gc_performed_compaction: "
                                << prev_gc_performed_compaction_;

runtime/gc/collector/mark_compact.h

diff --git a/runtime/gc/collector/mark_compact.h b/runtime/gc/collector/mark_compact.h
index 24f2b8f..717ac5f 100644
--- a/runtime/gc/collector/mark_compact.h
+++ b/runtime/gc/collector/mark_compact.h
@@ -958,6 +958,7 @@
   void* prev_post_compact_end_;
   void* prev_black_dense_end_;
   void* prev_black_allocations_begin_;
+  void* prev_moving_space_end_at_compaction_;
   bool prev_gc_young_;
   bool prev_gc_performed_compaction_;
   // Timestamp when the read-barrier is enabled