8294569: Remove CardTable::_last_valid_index

Reviewed-by: tschatzl, kbarrett

Author: albertnetymk

src/hotspot/share/gc/g1/g1CardTable.cpp

@@ -53,7 +53,6 @@ void G1CardTable::initialize(G1RegionToSpaceMapper* mapper) {
   _byte_map_size = mapper->reserved().byte_size();
 
   size_t num_cards = cards_required(_whole_heap.word_size());
-  _last_valid_index = num_cards - 1;
 
   HeapWord* low_bound  = _whole_heap.start();
   HeapWord* high_bound = _whole_heap.end();
@@ -64,11 +63,11 @@ void G1CardTable::initialize(G1RegionToSpaceMapper* mapper) {
   _byte_map = (CardValue*) mapper->reserved().start();
   _byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift);
   assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
-  assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
+  assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map");
 
   log_trace(gc, barrier)("G1CardTable::G1CardTable: ");
-  log_trace(gc, barrier)("    &_byte_map[0]: " PTR_FORMAT "  &_byte_map[_last_valid_index]: " PTR_FORMAT,
-                         p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
+  log_trace(gc, barrier)("    &_byte_map[0]: " PTR_FORMAT "  &_byte_map[last_valid_index()]: " PTR_FORMAT,
+                         p2i(&_byte_map[0]), p2i(&_byte_map[last_valid_index()]));
   log_trace(gc, barrier)("    _byte_map_base: " PTR_FORMAT,  p2i(_byte_map_base));
 }
 

src/hotspot/share/gc/shared/cardTable.cpp

@@ -69,7 +69,6 @@ size_t CardTable::compute_byte_map_size(size_t num_bytes) {
 
 CardTable::CardTable(MemRegion whole_heap) :
   _whole_heap(whole_heap),
-  _last_valid_index(0),
   _page_size(os::vm_page_size()),
   _byte_map_size(0),
   _byte_map(NULL),
@@ -90,7 +89,6 @@ CardTable::~CardTable() {
 
 void CardTable::initialize() {
   size_t num_cards = cards_required(_whole_heap.word_size());
-  _last_valid_index = num_cards - 1;
 
   // each card takes 1 byte; + 1 for the guard card
   size_t num_bytes = num_cards + 1;
@@ -121,15 +119,15 @@ void CardTable::initialize() {
   _byte_map = (CardValue*) heap_rs.base();
   _byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift);
   assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
-  assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
+  assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map");
 
   CardValue* guard_card = &_byte_map[num_cards];
   assert(is_aligned(guard_card, _page_size), "must be on its own OS page");
   _guard_region = MemRegion((HeapWord*)guard_card, _page_size);
 
   log_trace(gc, barrier)("CardTable::CardTable: ");
-  log_trace(gc, barrier)("    &_byte_map[0]: " PTR_FORMAT "  &_byte_map[_last_valid_index]: " PTR_FORMAT,
-                  p2i(&_byte_map[0]), p2i(&_byte_map[_last_valid_index]));
+  log_trace(gc, barrier)("    &_byte_map[0]: " PTR_FORMAT "  &_byte_map[last_valid_index()]: " PTR_FORMAT,
+                  p2i(&_byte_map[0]), p2i(&_byte_map[last_valid_index()]));
   log_trace(gc, barrier)("    _byte_map_base: " PTR_FORMAT, p2i(_byte_map_base));
 }
 
@@ -295,7 +293,7 @@ void CardTable::resize_covered_region(MemRegion new_region) {
     } else {
       entry = byte_after(old_region.last());
     }
-    assert(index_for(new_region.last()) <=  _last_valid_index,
+    assert(index_for(new_region.last()) <=  last_valid_index(),
       "The guard card will be overwritten");
     // This line commented out cleans the newly expanded region and
     // not the aligned up expanded region.

src/hotspot/share/gc/shared/cardTable.hpp

@@ -44,7 +44,6 @@ class CardTable: public CHeapObj<mtGC> {
   // The declaration order of these const fields is important; see the
   // constructor before changing.
   const MemRegion _whole_heap;       // the region covered by the card table
-  size_t          _last_valid_index; // index of the last valid element
   const size_t    _page_size;        // page size used when mapping _byte_map
   size_t          _byte_map_size;    // in bytes
   CardValue*      _byte_map;         // the card marking array
@@ -107,6 +106,9 @@ class CardTable: public CHeapObj<mtGC> {
   static uint _card_size;
   static uint _card_size_in_words;
 
+  size_t last_valid_index() const {
+    return cards_required(_whole_heap.word_size()) - 1;
+  }
 public:
   CardTable(MemRegion whole_heap);
   virtual ~CardTable();
@@ -127,7 +129,7 @@ class CardTable: public CHeapObj<mtGC> {
 
   // Initialization utilities; covered_words is the size of the covered region
   // in, um, words.
-  inline size_t cards_required(size_t covered_words) {
+  inline size_t cards_required(size_t covered_words) const {
     assert(is_aligned(covered_words, _card_size_in_words), "precondition");
     return covered_words / _card_size_in_words;
   }

src/hotspot/share/gc/shared/vmStructs_gc.hpp

@@ -88,7 +88,6 @@
   nonstatic_field(BarrierSet::FakeRtti,        _concrete_tag,                                 BarrierSet::Name)                      \
                                                                                                                                      \
   nonstatic_field(CardTable,                   _whole_heap,                                   const MemRegion)                       \
-  nonstatic_field(CardTable,                   _last_valid_index,                             const size_t)                          \
   nonstatic_field(CardTable,                   _page_size,                                    const size_t)                          \
   nonstatic_field(CardTable,                   _byte_map_size,                                const size_t)                          \
   nonstatic_field(CardTable,                   _byte_map,                                     CardTable::CardValue*)                                \