1 /*
   2  * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "memory/allocation.inline.hpp"
  27 #include "memory/resourceArea.hpp"
  28 #include "runtime/atomic.hpp"
  29 #include "utilities/bitMap.inline.hpp"
  30 #include "utilities/copy.hpp"
  31 #include "utilities/debug.hpp"
  32 
  33 STATIC_ASSERT(sizeof(BitMap::bm_word_t) == BytesPerWord); // "Implementation assumption."
  34 
  35 typedef BitMap::bm_word_t bm_word_t;
  36 typedef BitMap::idx_t     idx_t;
  37 
  38 class ResourceBitMapAllocator : StackObj {
  39  public:
  40   bm_word_t* allocate(idx_t size_in_words) const {
  41     return NEW_RESOURCE_ARRAY(bm_word_t, size_in_words);
  42   }
  43   void free(bm_word_t* map, idx_t size_in_words) const {
  44     // Don't free resource allocated arrays.
  45   }
  46 };
  47 
  48 class CHeapBitMapAllocator : StackObj {
  49  public:
  50   bm_word_t* allocate(size_t size_in_words) const {
  51     return ArrayAllocator<bm_word_t, mtInternal>::allocate(size_in_words);
  52   }
  53   void free(bm_word_t* map, idx_t size_in_words) const {
  54     ArrayAllocator<bm_word_t, mtInternal>::free(map, size_in_words);
  55   }
  56 };
  57 
  58 class ArenaBitMapAllocator : StackObj {
  59   Arena* _arena;
  60 
  61  public:
  62   ArenaBitMapAllocator(Arena* arena) : _arena(arena) {}
  63   bm_word_t* allocate(idx_t size_in_words) const {
  64     return (bm_word_t*)_arena->Amalloc(size_in_words * BytesPerWord);
  65   }
  66   void free(bm_word_t* map, idx_t size_in_words) const {
  67     // ArenaBitMaps currently don't free memory.
  68   }
  69 };
  70 
  71 template <class Allocator>
  72 BitMap::bm_word_t* BitMap::reallocate(const Allocator& allocator, bm_word_t* old_map, idx_t old_size_in_bits, idx_t new_size_in_bits) {
  73   size_t old_size_in_words = calc_size_in_words(old_size_in_bits);
  74   size_t new_size_in_words = calc_size_in_words(new_size_in_bits);
  75 
  76   bm_word_t* map = NULL;
  77 
  78   if (new_size_in_words > 0) {
  79     map = allocator.allocate(new_size_in_words);
  80 
  81     Copy::disjoint_words((HeapWord*)old_map, (HeapWord*) map,
  82                          MIN2(old_size_in_words, new_size_in_words));
  83 
  84     if (new_size_in_words > old_size_in_words) {
  85       clear_range_of_words(map, old_size_in_words, new_size_in_words);
  86     }
  87   }
  88 
  89   if (old_map != NULL) {
  90     allocator.free(old_map, old_size_in_words);
  91   }
  92 
  93   return map;
  94 }
  95 
  96 template <class Allocator>
  97 bm_word_t* BitMap::allocate(const Allocator& allocator, idx_t size_in_bits) {
  98   // Reuse reallocate to ensure that the new memory is cleared.
  99   return reallocate(allocator, NULL, 0, size_in_bits);
 100 }
 101 
 102 template <class Allocator>
 103 void BitMap::free(const Allocator& allocator, bm_word_t* map, idx_t  size_in_bits) {
 104   bm_word_t* ret = reallocate(allocator, map, size_in_bits, 0);
 105   assert(ret == NULL, "Reallocate shouldn't have allocated");
 106 }
 107 
 108 template <class Allocator>
 109 void BitMap::resize(const Allocator& allocator, idx_t new_size_in_bits) {
 110   bm_word_t* new_map = reallocate(allocator, map(), size(), new_size_in_bits);
 111 
 112   update(new_map, new_size_in_bits);
 113 }
 114 
 115 template <class Allocator>
 116 void BitMap::initialize(const Allocator& allocator, idx_t size_in_bits) {
 117   assert(map() == NULL, "precondition");
 118   assert(size() == 0,   "precondition");
 119 
 120   resize(allocator, size_in_bits);
 121 }
 122 
 123 template <class Allocator>
 124 void BitMap::reinitialize(const Allocator& allocator, idx_t new_size_in_bits) {
 125   // Remove previous bits.
 126   resize(allocator, 0);
 127 
 128   initialize(allocator, new_size_in_bits);
 129 }
 130 
 131 ResourceBitMap::ResourceBitMap(idx_t size_in_bits)
 132     : BitMap(allocate(ResourceBitMapAllocator(), size_in_bits), size_in_bits) {
 133 }
 134 
 135 void ResourceBitMap::resize(idx_t new_size_in_bits) {
 136   BitMap::resize(ResourceBitMapAllocator(), new_size_in_bits);
 137 }
 138 
 139 void ResourceBitMap::initialize(idx_t size_in_bits) {
 140   BitMap::initialize(ResourceBitMapAllocator(), size_in_bits);
 141 }
 142 
 143 void ResourceBitMap::reinitialize(idx_t size_in_bits) {
 144   BitMap::reinitialize(ResourceBitMapAllocator(), size_in_bits);
 145 }
 146 
 147 ArenaBitMap::ArenaBitMap(Arena* arena, idx_t size_in_bits)
 148     : BitMap(allocate(ArenaBitMapAllocator(arena), size_in_bits), size_in_bits) {
 149 }
 150 
 151 CHeapBitMap::CHeapBitMap(idx_t size_in_bits)
 152     : BitMap(allocate(CHeapBitMapAllocator(), size_in_bits), size_in_bits) {
 153 }
 154 
 155 CHeapBitMap::~CHeapBitMap() {
 156   free(CHeapBitMapAllocator(), map(), size());
 157 }
 158 
 159 void CHeapBitMap::resize(idx_t new_size_in_bits) {
 160   BitMap::resize(CHeapBitMapAllocator(), new_size_in_bits);
 161 }
 162 
 163 void CHeapBitMap::initialize(idx_t size_in_bits) {
 164   BitMap::initialize(CHeapBitMapAllocator(), size_in_bits);
 165 }
 166 
 167 void CHeapBitMap::reinitialize(idx_t size_in_bits) {
 168   BitMap::reinitialize(CHeapBitMapAllocator(), size_in_bits);
 169 }
 170 
 171 #ifdef ASSERT
 172 void BitMap::verify_index(idx_t index) const {
 173   assert(index < _size, "BitMap index out of bounds");
 174 }
 175 
 176 void BitMap::verify_range(idx_t beg_index, idx_t end_index) const {
 177   assert(beg_index <= end_index, "BitMap range error");
 178   // Note that [0,0) and [size,size) are both valid ranges.
 179   if (end_index != _size) verify_index(end_index);
 180 }
 181 #endif // #ifdef ASSERT
 182 
 183 void BitMap::pretouch() {
 184   os::pretouch_memory(word_addr(0), word_addr(size()));
 185 }
 186 
 187 void BitMap::set_range_within_word(idx_t beg, idx_t end) {
 188   // With a valid range (beg <= end), this test ensures that end != 0, as
 189   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 190   if (beg != end) {
 191     bm_word_t mask = inverted_bit_mask_for_range(beg, end);
 192     *word_addr(beg) |= ~mask;
 193   }
 194 }
 195 
 196 void BitMap::clear_range_within_word(idx_t beg, idx_t end) {
 197   // With a valid range (beg <= end), this test ensures that end != 0, as
 198   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 199   if (beg != end) {
 200     bm_word_t mask = inverted_bit_mask_for_range(beg, end);
 201     *word_addr(beg) &= mask;
 202   }
 203 }
 204 
 205 void BitMap::par_put_range_within_word(idx_t beg, idx_t end, bool value) {
 206   assert(value == 0 || value == 1, "0 for clear, 1 for set");
 207   // With a valid range (beg <= end), this test ensures that end != 0, as
 208   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 209   if (beg != end) {
 210     intptr_t* pw  = (intptr_t*)word_addr(beg);
 211     intptr_t  w   = *pw;
 212     intptr_t  mr  = (intptr_t)inverted_bit_mask_for_range(beg, end);
 213     intptr_t  nw  = value ? (w | ~mr) : (w & mr);
 214     while (true) {
 215       intptr_t res = Atomic::cmpxchg_ptr(nw, pw, w);
 216       if (res == w) break;
 217       w  = res;
 218       nw = value ? (w | ~mr) : (w & mr);
 219     }
 220   }
 221 }
 222 
 223 void BitMap::set_range(idx_t beg, idx_t end) {
 224   verify_range(beg, end);
 225 
 226   idx_t beg_full_word = word_index_round_up(beg);
 227   idx_t end_full_word = word_index(end);
 228 
 229   if (beg_full_word < end_full_word) {
 230     // The range includes at least one full word.
 231     set_range_within_word(beg, bit_index(beg_full_word));
 232     set_range_of_words(beg_full_word, end_full_word);
 233     set_range_within_word(bit_index(end_full_word), end);
 234   } else {
 235     // The range spans at most 2 partial words.
 236     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 237     set_range_within_word(beg, boundary);
 238     set_range_within_word(boundary, end);
 239   }
 240 }
 241 
 242 void BitMap::clear_range(idx_t beg, idx_t end) {
 243   verify_range(beg, end);
 244 
 245   idx_t beg_full_word = word_index_round_up(beg);
 246   idx_t end_full_word = word_index(end);
 247 
 248   if (beg_full_word < end_full_word) {
 249     // The range includes at least one full word.
 250     clear_range_within_word(beg, bit_index(beg_full_word));
 251     clear_range_of_words(beg_full_word, end_full_word);
 252     clear_range_within_word(bit_index(end_full_word), end);
 253   } else {
 254     // The range spans at most 2 partial words.
 255     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 256     clear_range_within_word(beg, boundary);
 257     clear_range_within_word(boundary, end);
 258   }
 259 }
 260 
 261 void BitMap::set_large_range(idx_t beg, idx_t end) {
 262   verify_range(beg, end);
 263 
 264   idx_t beg_full_word = word_index_round_up(beg);
 265   idx_t end_full_word = word_index(end);
 266 
 267   assert(end_full_word - beg_full_word >= 32,
 268          "the range must include at least 32 bytes");
 269 
 270   // The range includes at least one full word.
 271   set_range_within_word(beg, bit_index(beg_full_word));
 272   set_large_range_of_words(beg_full_word, end_full_word);
 273   set_range_within_word(bit_index(end_full_word), end);
 274 }
 275 
 276 void BitMap::clear_large_range(idx_t beg, idx_t end) {
 277   verify_range(beg, end);
 278 
 279   idx_t beg_full_word = word_index_round_up(beg);
 280   idx_t end_full_word = word_index(end);
 281 
 282   if (end_full_word - beg_full_word < 32) {
 283     clear_range(beg, end);
 284     return;
 285   }
 286 
 287   // The range includes at least one full word.
 288   clear_range_within_word(beg, bit_index(beg_full_word));
 289   clear_large_range_of_words(beg_full_word, end_full_word);
 290   clear_range_within_word(bit_index(end_full_word), end);
 291 }
 292 
 293 void BitMap::at_put(idx_t offset, bool value) {
 294   if (value) {
 295     set_bit(offset);
 296   } else {
 297     clear_bit(offset);
 298   }
 299 }
 300 
 301 // Return true to indicate that this thread changed
 302 // the bit, false to indicate that someone else did.
 303 // In either case, the requested bit is in the
 304 // requested state some time during the period that
 305 // this thread is executing this call. More importantly,
 306 // if no other thread is executing an action to
 307 // change the requested bit to a state other than
 308 // the one that this thread is trying to set it to,
 309 // then the the bit is in the expected state
 310 // at exit from this method. However, rather than
 311 // make such a strong assertion here, based on
 312 // assuming such constrained use (which though true
 313 // today, could change in the future to service some
 314 // funky parallel algorithm), we encourage callers
 315 // to do such verification, as and when appropriate.
 316 bool BitMap::par_at_put(idx_t bit, bool value) {
 317   return value ? par_set_bit(bit) : par_clear_bit(bit);
 318 }
 319 
 320 void BitMap::at_put_range(idx_t start_offset, idx_t end_offset, bool value) {
 321   if (value) {
 322     set_range(start_offset, end_offset);
 323   } else {
 324     clear_range(start_offset, end_offset);
 325   }
 326 }
 327 
 328 void BitMap::par_at_put_range(idx_t beg, idx_t end, bool value) {
 329   verify_range(beg, end);
 330 
 331   idx_t beg_full_word = word_index_round_up(beg);
 332   idx_t end_full_word = word_index(end);
 333 
 334   if (beg_full_word < end_full_word) {
 335     // The range includes at least one full word.
 336     par_put_range_within_word(beg, bit_index(beg_full_word), value);
 337     if (value) {
 338       set_range_of_words(beg_full_word, end_full_word);
 339     } else {
 340       clear_range_of_words(beg_full_word, end_full_word);
 341     }
 342     par_put_range_within_word(bit_index(end_full_word), end, value);
 343   } else {
 344     // The range spans at most 2 partial words.
 345     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 346     par_put_range_within_word(beg, boundary, value);
 347     par_put_range_within_word(boundary, end, value);
 348   }
 349 
 350 }
 351 
 352 void BitMap::at_put_large_range(idx_t beg, idx_t end, bool value) {
 353   if (value) {
 354     set_large_range(beg, end);
 355   } else {
 356     clear_large_range(beg, end);
 357   }
 358 }
 359 
 360 void BitMap::par_at_put_large_range(idx_t beg, idx_t end, bool value) {
 361   verify_range(beg, end);
 362 
 363   idx_t beg_full_word = word_index_round_up(beg);
 364   idx_t end_full_word = word_index(end);
 365 
 366   assert(end_full_word - beg_full_word >= 32,
 367          "the range must include at least 32 bytes");
 368 
 369   // The range includes at least one full word.
 370   par_put_range_within_word(beg, bit_index(beg_full_word), value);
 371   if (value) {
 372     set_large_range_of_words(beg_full_word, end_full_word);
 373   } else {
 374     clear_large_range_of_words(beg_full_word, end_full_word);
 375   }
 376   par_put_range_within_word(bit_index(end_full_word), end, value);
 377 }
 378 
 379 inline bm_word_t tail_mask(idx_t tail_bits) {
 380   assert(tail_bits != 0, "precondition"); // Works, but shouldn't be called.
 381   assert(tail_bits < (idx_t)BitsPerWord, "precondition");
 382   return (bm_word_t(1) << tail_bits) - 1;
 383 }
 384 
 385 // Get the low tail_bits of value, which is the last partial word of a map.
 386 inline bm_word_t tail_of_map(bm_word_t value, idx_t tail_bits) {
 387   return value & tail_mask(tail_bits);
 388 }
 389 
 390 // Compute the new last word of a map with a non-aligned length.
 391 // new_value has the new trailing bits of the map in the low tail_bits.
 392 // old_value is the last word of the map, including bits beyond the end.
 393 // Returns old_value with the low tail_bits replaced by the corresponding
 394 // bits in new_value.
 395 inline bm_word_t merge_tail_of_map(bm_word_t new_value,
 396                                    bm_word_t old_value,
 397                                    idx_t tail_bits) {
 398   bm_word_t mask = tail_mask(tail_bits);
 399   return (new_value & mask) | (old_value & ~mask);
 400 }
 401 
 402 bool BitMap::contains(const BitMap& other) const {
 403   assert(size() == other.size(), "must have same size");
 404   const bm_word_t* dest_map = map();
 405   const bm_word_t* other_map = other.map();
 406   idx_t limit = word_index(size());
 407   for (idx_t index = 0; index < limit; ++index) {
 408     // false if other bitmap has bits set which are clear in this bitmap.
 409     if ((~dest_map[index] & other_map[index]) != 0) return false;
 410   }
 411   idx_t rest = bit_in_word(size());
 412   // true unless there is a partial-word tail in which the other
 413   // bitmap has bits set which are clear in this bitmap.
 414   return (rest == 0) || tail_of_map(~dest_map[limit] & other_map[limit], rest) == 0;
 415 }
 416 
 417 bool BitMap::intersects(const BitMap& other) const {
 418   assert(size() == other.size(), "must have same size");
 419   const bm_word_t* dest_map = map();
 420   const bm_word_t* other_map = other.map();
 421   idx_t limit = word_index(size());
 422   for (idx_t index = 0; index < limit; ++index) {
 423     if ((dest_map[index] & other_map[index]) != 0) return true;
 424   }
 425   idx_t rest = bit_in_word(size());
 426   // false unless there is a partial-word tail with non-empty intersection.
 427   return (rest > 0) && tail_of_map(dest_map[limit] & other_map[limit], rest) != 0;
 428 }
 429 
 430 void BitMap::set_union(const BitMap& other) {
 431   assert(size() == other.size(), "must have same size");
 432   bm_word_t* dest_map = map();
 433   const bm_word_t* other_map = other.map();
 434   idx_t limit = word_index(size());
 435   for (idx_t index = 0; index < limit; ++index) {
 436     dest_map[index] |= other_map[index];
 437   }
 438   idx_t rest = bit_in_word(size());
 439   if (rest > 0) {
 440     bm_word_t orig = dest_map[limit];
 441     dest_map[limit] = merge_tail_of_map(orig | other_map[limit], orig, rest);
 442   }
 443 }
 444 
 445 void BitMap::set_difference(const BitMap& other) {
 446   assert(size() == other.size(), "must have same size");
 447   bm_word_t* dest_map = map();
 448   const bm_word_t* other_map = other.map();
 449   idx_t limit = word_index(size());
 450   for (idx_t index = 0; index < limit; ++index) {
 451     dest_map[index] &= ~other_map[index];
 452   }
 453   idx_t rest = bit_in_word(size());
 454   if (rest > 0) {
 455     bm_word_t orig = dest_map[limit];
 456     dest_map[limit] = merge_tail_of_map(orig & ~other_map[limit], orig, rest);
 457   }
 458 }
 459 
 460 void BitMap::set_intersection(const BitMap& other) {
 461   assert(size() == other.size(), "must have same size");
 462   bm_word_t* dest_map = map();
 463   const bm_word_t* other_map = other.map();
 464   idx_t limit = word_index(size());
 465   for (idx_t index = 0; index < limit; ++index) {
 466     dest_map[index] &= other_map[index];
 467   }
 468   idx_t rest = bit_in_word(size());
 469   if (rest > 0) {
 470     bm_word_t orig = dest_map[limit];
 471     dest_map[limit] = merge_tail_of_map(orig & other_map[limit], orig, rest);
 472   }
 473 }
 474 
 475 bool BitMap::set_union_with_result(const BitMap& other) {
 476   assert(size() == other.size(), "must have same size");
 477   bool changed = false;
 478   bm_word_t* dest_map = map();
 479   const bm_word_t* other_map = other.map();
 480   idx_t limit = word_index(size());
 481   for (idx_t index = 0; index < limit; ++index) {
 482     bm_word_t orig = dest_map[index];
 483     bm_word_t temp = orig | other_map[index];
 484     changed = changed || (temp != orig);
 485     dest_map[index] = temp;
 486   }
 487   idx_t rest = bit_in_word(size());
 488   if (rest > 0) {
 489     bm_word_t orig = dest_map[limit];
 490     bm_word_t temp = merge_tail_of_map(orig | other_map[limit], orig, rest);
 491     changed = changed || (temp != orig);
 492     dest_map[limit] = temp;
 493   }
 494   return changed;
 495 }
 496 
 497 bool BitMap::set_difference_with_result(const BitMap& other) {
 498   assert(size() == other.size(), "must have same size");
 499   bool changed = false;
 500   bm_word_t* dest_map = map();
 501   const bm_word_t* other_map = other.map();
 502   idx_t limit = word_index(size());
 503   for (idx_t index = 0; index < limit; ++index) {
 504     bm_word_t orig = dest_map[index];
 505     bm_word_t temp = orig & ~other_map[index];
 506     changed = changed || (temp != orig);
 507     dest_map[index] = temp;
 508   }
 509   idx_t rest = bit_in_word(size());
 510   if (rest > 0) {
 511     bm_word_t orig = dest_map[limit];
 512     bm_word_t temp = merge_tail_of_map(orig & ~other_map[limit], orig, rest);
 513     changed = changed || (temp != orig);
 514     dest_map[limit] = temp;
 515   }
 516   return changed;
 517 }
 518 
 519 bool BitMap::set_intersection_with_result(const BitMap& other) {
 520   assert(size() == other.size(), "must have same size");
 521   bool changed = false;
 522   bm_word_t* dest_map = map();
 523   const bm_word_t* other_map = other.map();
 524   idx_t limit = word_index(size());
 525   for (idx_t index = 0; index < limit; ++index) {
 526     bm_word_t orig = dest_map[index];
 527     bm_word_t temp = orig & other_map[index];
 528     changed = changed || (temp != orig);
 529     dest_map[index] = temp;
 530   }
 531   idx_t rest = bit_in_word(size());
 532   if (rest > 0) {
 533     bm_word_t orig = dest_map[limit];
 534     bm_word_t temp = merge_tail_of_map(orig & other_map[limit], orig, rest);
 535     changed = changed || (temp != orig);
 536     dest_map[limit] = temp;
 537   }
 538   return changed;
 539 }
 540 
 541 void BitMap::set_from(const BitMap& other) {
 542   assert(size() == other.size(), "must have same size");
 543   bm_word_t* dest_map = map();
 544   const bm_word_t* other_map = other.map();
 545   idx_t copy_words = word_index(size());
 546   Copy::disjoint_words((HeapWord*)other_map, (HeapWord*)dest_map, copy_words);
 547   idx_t rest = bit_in_word(size());
 548   if (rest > 0) {
 549     dest_map[copy_words] = merge_tail_of_map(other_map[copy_words],
 550                                              dest_map[copy_words],
 551                                              rest);
 552   }
 553 }
 554 
 555 bool BitMap::is_same(const BitMap& other) const {
 556   assert(size() == other.size(), "must have same size");
 557   const bm_word_t* dest_map = map();
 558   const bm_word_t* other_map = other.map();
 559   idx_t limit = word_index(size());
 560   for (idx_t index = 0; index < limit; ++index) {
 561     if (dest_map[index] != other_map[index]) return false;
 562   }
 563   idx_t rest = bit_in_word(size());
 564   return (rest == 0) || (tail_of_map(dest_map[limit] ^ other_map[limit], rest) == 0);
 565 }
 566 
 567 bool BitMap::is_full() const {
 568   const bm_word_t* words = map();
 569   idx_t limit = word_index(size());
 570   for (idx_t index = 0; index < limit; ++index) {
 571     if (~words[index] != 0) return false;
 572   }
 573   idx_t rest = bit_in_word(size());
 574   return (rest == 0) || (tail_of_map(~words[limit], rest) == 0);
 575 }
 576 
 577 bool BitMap::is_empty() const {
 578   const bm_word_t* words = map();
 579   idx_t limit = word_index(size());
 580   for (idx_t index = 0; index < limit; ++index) {
 581     if (words[index] != 0) return false;
 582   }
 583   idx_t rest = bit_in_word(size());
 584   return (rest == 0) || (tail_of_map(words[limit], rest) == 0);
 585 }
 586 
 587 void BitMap::clear_large() {
 588   clear_large_range_of_words(0, size_in_words());
 589 }
 590 
 591 // Note that if the closure itself modifies the bitmap
 592 // then modifications in and to the left of the _bit_ being
 593 // currently sampled will not be seen. Note also that the
 594 // interval [leftOffset, rightOffset) is right open.
 595 bool BitMap::iterate(BitMapClosure* blk, idx_t leftOffset, idx_t rightOffset) {
 596   verify_range(leftOffset, rightOffset);
 597 
 598   idx_t startIndex = word_index(leftOffset);
 599   idx_t endIndex   = MIN2(word_index(rightOffset) + 1, size_in_words());
 600   for (idx_t index = startIndex, offset = leftOffset;
 601        offset < rightOffset && index < endIndex;
 602        offset = (++index) << LogBitsPerWord) {
 603     idx_t rest = map(index) >> (offset & (BitsPerWord - 1));
 604     for (; offset < rightOffset && rest != 0; offset++) {
 605       if (rest & 1) {
 606         if (!blk->do_bit(offset)) return false;
 607         //  resample at each closure application
 608         // (see, for instance, CMS bug 4525989)
 609         rest = map(index) >> (offset & (BitsPerWord -1));
 610       }
 611       rest = rest >> 1;
 612     }
 613   }
 614   return true;
 615 }
 616 
 617 BitMap::idx_t* BitMap::_pop_count_table = NULL;
 618 
 619 void BitMap::init_pop_count_table() {
 620   if (_pop_count_table == NULL) {
 621     BitMap::idx_t *table = NEW_C_HEAP_ARRAY(idx_t, 256, mtInternal);
 622     for (uint i = 0; i < 256; i++) {
 623       table[i] = num_set_bits(i);
 624     }
 625 
 626     intptr_t res = Atomic::cmpxchg_ptr((intptr_t)  table,
 627                                        (intptr_t*) &_pop_count_table,
 628                                        (intptr_t)  NULL_WORD);
 629     if (res != NULL_WORD) {
 630       guarantee( _pop_count_table == (void*) res, "invariant" );
 631       FREE_C_HEAP_ARRAY(idx_t, table);
 632     }
 633   }
 634 }
 635 
 636 BitMap::idx_t BitMap::num_set_bits(bm_word_t w) {
 637   idx_t bits = 0;
 638 
 639   while (w != 0) {
 640     while ((w & 1) == 0) {
 641       w >>= 1;
 642     }
 643     bits++;
 644     w >>= 1;
 645   }
 646   return bits;
 647 }
 648 
 649 BitMap::idx_t BitMap::num_set_bits_from_table(unsigned char c) {
 650   assert(_pop_count_table != NULL, "precondition");
 651   return _pop_count_table[c];
 652 }
 653 
 654 BitMap::idx_t BitMap::count_one_bits() const {
 655   init_pop_count_table(); // If necessary.
 656   idx_t sum = 0;
 657   typedef unsigned char uchar;
 658   for (idx_t i = 0; i < size_in_words(); i++) {
 659     bm_word_t w = map()[i];
 660     for (size_t j = 0; j < sizeof(bm_word_t); j++) {
 661       sum += num_set_bits_from_table(uchar(w & 255));
 662       w >>= 8;
 663     }
 664   }
 665   return sum;
 666 }
 667 
 668 void BitMap::print_on_error(outputStream* st, const char* prefix) const {
 669   st->print_cr("%s[" PTR_FORMAT ", " PTR_FORMAT ")",
 670       prefix, p2i(map()), p2i((char*)map() + (size() >> LogBitsPerByte)));
 671 }
 672 
 673 #ifndef PRODUCT
 674 
 675 void BitMap::print_on(outputStream* st) const {
 676   tty->print("Bitmap(" SIZE_FORMAT "):", size());
 677   for (idx_t index = 0; index < size(); index++) {
 678     tty->print("%c", at(index) ? '1' : '0');
 679   }
 680   tty->cr();
 681 }
 682 
 683 #endif