1 /*
   2  * Copyright (c) 1997, 2017, 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   MEMFLAGS _flags;
  50 
  51  public:
  52   CHeapBitMapAllocator(MEMFLAGS flags) : _flags(flags) {}
  53   bm_word_t* allocate(size_t size_in_words) const {
  54     return ArrayAllocator<bm_word_t>::allocate(size_in_words, _flags);
  55   }
  56   void free(bm_word_t* map, idx_t size_in_words) const {
  57     ArrayAllocator<bm_word_t>::free(map, size_in_words);
  58   }
  59 };
  60 
  61 class ArenaBitMapAllocator : StackObj {
  62   Arena* _arena;
  63 
  64  public:
  65   ArenaBitMapAllocator(Arena* arena) : _arena(arena) {}
  66   bm_word_t* allocate(idx_t size_in_words) const {
  67     return (bm_word_t*)_arena->Amalloc(size_in_words * BytesPerWord);
  68   }
  69   void free(bm_word_t* map, idx_t size_in_words) const {
  70     // ArenaBitMaps currently don't free memory.
  71   }
  72 };
  73 
  74 template <class Allocator>
  75 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) {
  76   size_t old_size_in_words = calc_size_in_words(old_size_in_bits);
  77   size_t new_size_in_words = calc_size_in_words(new_size_in_bits);
  78 
  79   bm_word_t* map = NULL;
  80 
  81   if (new_size_in_words > 0) {
  82     map = allocator.allocate(new_size_in_words);
  83 
  84     Copy::disjoint_words((HeapWord*)old_map, (HeapWord*) map,
  85                          MIN2(old_size_in_words, new_size_in_words));
  86 
  87     if (new_size_in_words > old_size_in_words) {
  88       clear_range_of_words(map, old_size_in_words, new_size_in_words);
  89     }
  90   }
  91 
  92   if (old_map != NULL) {
  93     allocator.free(old_map, old_size_in_words);
  94   }
  95 
  96   return map;
  97 }
  98 
  99 template <class Allocator>
 100 bm_word_t* BitMap::allocate(const Allocator& allocator, idx_t size_in_bits) {
 101   // Reuse reallocate to ensure that the new memory is cleared.
 102   return reallocate(allocator, NULL, 0, size_in_bits);
 103 }
 104 
 105 template <class Allocator>
 106 void BitMap::free(const Allocator& allocator, bm_word_t* map, idx_t  size_in_bits) {
 107   bm_word_t* ret = reallocate(allocator, map, size_in_bits, 0);
 108   assert(ret == NULL, "Reallocate shouldn't have allocated");
 109 }
 110 
 111 template <class Allocator>
 112 void BitMap::resize(const Allocator& allocator, idx_t new_size_in_bits) {
 113   bm_word_t* new_map = reallocate(allocator, map(), size(), new_size_in_bits);
 114 
 115   update(new_map, new_size_in_bits);
 116 }
 117 
 118 template <class Allocator>
 119 void BitMap::initialize(const Allocator& allocator, idx_t size_in_bits) {
 120   assert(map() == NULL, "precondition");
 121   assert(size() == 0,   "precondition");
 122 
 123   resize(allocator, size_in_bits);
 124 }
 125 
 126 template <class Allocator>
 127 void BitMap::reinitialize(const Allocator& allocator, idx_t new_size_in_bits) {
 128   // Remove previous bits.
 129   resize(allocator, 0);
 130 
 131   initialize(allocator, new_size_in_bits);
 132 }
 133 
 134 ResourceBitMap::ResourceBitMap(idx_t size_in_bits)
 135     : BitMap(allocate(ResourceBitMapAllocator(), size_in_bits), size_in_bits) {
 136 }
 137 
 138 void ResourceBitMap::resize(idx_t new_size_in_bits) {
 139   BitMap::resize(ResourceBitMapAllocator(), new_size_in_bits);
 140 }
 141 
 142 void ResourceBitMap::initialize(idx_t size_in_bits) {
 143   BitMap::initialize(ResourceBitMapAllocator(), size_in_bits);
 144 }
 145 
 146 void ResourceBitMap::reinitialize(idx_t size_in_bits) {
 147   BitMap::reinitialize(ResourceBitMapAllocator(), size_in_bits);
 148 }
 149 
 150 ArenaBitMap::ArenaBitMap(Arena* arena, idx_t size_in_bits)
 151     : BitMap(allocate(ArenaBitMapAllocator(arena), size_in_bits), size_in_bits) {
 152 }
 153 
 154 CHeapBitMap::CHeapBitMap(idx_t size_in_bits, MEMFLAGS flags)
 155     : BitMap(allocate(CHeapBitMapAllocator(flags), size_in_bits), size_in_bits), _flags(flags) {
 156 }
 157 
 158 CHeapBitMap::~CHeapBitMap() {
 159   free(CHeapBitMapAllocator(_flags), map(), size());
 160 }
 161 
 162 void CHeapBitMap::resize(idx_t new_size_in_bits) {
 163   BitMap::resize(CHeapBitMapAllocator(_flags), new_size_in_bits);
 164 }
 165 
 166 void CHeapBitMap::initialize(idx_t size_in_bits) {
 167   BitMap::initialize(CHeapBitMapAllocator(_flags), size_in_bits);
 168 }
 169 
 170 void CHeapBitMap::reinitialize(idx_t size_in_bits) {
 171   BitMap::reinitialize(CHeapBitMapAllocator(_flags), size_in_bits);
 172 }
 173 
 174 #ifdef ASSERT
 175 void BitMap::verify_index(idx_t index) const {
 176   assert(index < _size, "BitMap index out of bounds");
 177 }
 178 
 179 void BitMap::verify_range(idx_t beg_index, idx_t end_index) const {
 180   assert(beg_index <= end_index, "BitMap range error");
 181   // Note that [0,0) and [size,size) are both valid ranges.
 182   if (end_index != _size) verify_index(end_index);
 183 }
 184 #endif // #ifdef ASSERT
 185 
 186 void BitMap::pretouch() {
 187   os::pretouch_memory(word_addr(0), word_addr(size()));
 188 }
 189 
 190 void BitMap::set_range_within_word(idx_t beg, idx_t end) {
 191   // With a valid range (beg <= end), this test ensures that end != 0, as
 192   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 193   if (beg != end) {
 194     bm_word_t mask = inverted_bit_mask_for_range(beg, end);
 195     *word_addr(beg) |= ~mask;
 196   }
 197 }
 198 
 199 void BitMap::clear_range_within_word(idx_t beg, idx_t end) {
 200   // With a valid range (beg <= end), this test ensures that end != 0, as
 201   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 202   if (beg != end) {
 203     bm_word_t mask = inverted_bit_mask_for_range(beg, end);
 204     *word_addr(beg) &= mask;
 205   }
 206 }
 207 
 208 void BitMap::par_put_range_within_word(idx_t beg, idx_t end, bool value) {
 209   assert(value == 0 || value == 1, "0 for clear, 1 for set");
 210   // With a valid range (beg <= end), this test ensures that end != 0, as
 211   // required by inverted_bit_mask_for_range.  Also avoids an unnecessary write.
 212   if (beg != end) {
 213     bm_word_t* pw = word_addr(beg);
 214     bm_word_t  w  = *pw;
 215     bm_word_t  mr = inverted_bit_mask_for_range(beg, end);
 216     bm_word_t  nw = value ? (w | ~mr) : (w & mr);
 217     while (true) {
 218       bm_word_t res = Atomic::cmpxchg(nw, pw, w);
 219       if (res == w) break;
 220       w  = res;
 221       nw = value ? (w | ~mr) : (w & mr);
 222     }
 223   }
 224 }
 225 
 226 void BitMap::set_range(idx_t beg, idx_t end) {
 227   verify_range(beg, end);
 228 
 229   idx_t beg_full_word = word_index_round_up(beg);
 230   idx_t end_full_word = word_index(end);
 231 
 232   if (beg_full_word < end_full_word) {
 233     // The range includes at least one full word.
 234     set_range_within_word(beg, bit_index(beg_full_word));
 235     set_range_of_words(beg_full_word, end_full_word);
 236     set_range_within_word(bit_index(end_full_word), end);
 237   } else {
 238     // The range spans at most 2 partial words.
 239     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 240     set_range_within_word(beg, boundary);
 241     set_range_within_word(boundary, end);
 242   }
 243 }
 244 
 245 void BitMap::clear_range(idx_t beg, idx_t end) {
 246   verify_range(beg, end);
 247 
 248   idx_t beg_full_word = word_index_round_up(beg);
 249   idx_t end_full_word = word_index(end);
 250 
 251   if (beg_full_word < end_full_word) {
 252     // The range includes at least one full word.
 253     clear_range_within_word(beg, bit_index(beg_full_word));
 254     clear_range_of_words(beg_full_word, end_full_word);
 255     clear_range_within_word(bit_index(end_full_word), end);
 256   } else {
 257     // The range spans at most 2 partial words.
 258     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 259     clear_range_within_word(beg, boundary);
 260     clear_range_within_word(boundary, end);
 261   }
 262 }
 263 
 264 void BitMap::set_large_range(idx_t beg, idx_t end) {
 265   verify_range(beg, end);
 266 
 267   idx_t beg_full_word = word_index_round_up(beg);
 268   idx_t end_full_word = word_index(end);
 269 
 270   assert(end_full_word - beg_full_word >= 32,
 271          "the range must include at least 32 bytes");
 272 
 273   // The range includes at least one full word.
 274   set_range_within_word(beg, bit_index(beg_full_word));
 275   set_large_range_of_words(beg_full_word, end_full_word);
 276   set_range_within_word(bit_index(end_full_word), end);
 277 }
 278 
 279 void BitMap::clear_large_range(idx_t beg, idx_t end) {
 280   verify_range(beg, end);
 281 
 282   idx_t beg_full_word = word_index_round_up(beg);
 283   idx_t end_full_word = word_index(end);
 284 
 285   if (end_full_word - beg_full_word < 32) {
 286     clear_range(beg, end);
 287     return;
 288   }
 289 
 290   // The range includes at least one full word.
 291   clear_range_within_word(beg, bit_index(beg_full_word));
 292   clear_large_range_of_words(beg_full_word, end_full_word);
 293   clear_range_within_word(bit_index(end_full_word), end);
 294 }
 295 
 296 void BitMap::at_put(idx_t offset, bool value) {
 297   if (value) {
 298     set_bit(offset);
 299   } else {
 300     clear_bit(offset);
 301   }
 302 }
 303 
 304 // Return true to indicate that this thread changed
 305 // the bit, false to indicate that someone else did.
 306 // In either case, the requested bit is in the
 307 // requested state some time during the period that
 308 // this thread is executing this call. More importantly,
 309 // if no other thread is executing an action to
 310 // change the requested bit to a state other than
 311 // the one that this thread is trying to set it to,
 312 // then the the bit is in the expected state
 313 // at exit from this method. However, rather than
 314 // make such a strong assertion here, based on
 315 // assuming such constrained use (which though true
 316 // today, could change in the future to service some
 317 // funky parallel algorithm), we encourage callers
 318 // to do such verification, as and when appropriate.
 319 bool BitMap::par_at_put(idx_t bit, bool value) {
 320   return value ? par_set_bit(bit) : par_clear_bit(bit);
 321 }
 322 
 323 void BitMap::at_put_range(idx_t start_offset, idx_t end_offset, bool value) {
 324   if (value) {
 325     set_range(start_offset, end_offset);
 326   } else {
 327     clear_range(start_offset, end_offset);
 328   }
 329 }
 330 
 331 void BitMap::par_at_put_range(idx_t beg, idx_t end, bool value) {
 332   verify_range(beg, end);
 333 
 334   idx_t beg_full_word = word_index_round_up(beg);
 335   idx_t end_full_word = word_index(end);
 336 
 337   if (beg_full_word < end_full_word) {
 338     // The range includes at least one full word.
 339     par_put_range_within_word(beg, bit_index(beg_full_word), value);
 340     if (value) {
 341       set_range_of_words(beg_full_word, end_full_word);
 342     } else {
 343       clear_range_of_words(beg_full_word, end_full_word);
 344     }
 345     par_put_range_within_word(bit_index(end_full_word), end, value);
 346   } else {
 347     // The range spans at most 2 partial words.
 348     idx_t boundary = MIN2(bit_index(beg_full_word), end);
 349     par_put_range_within_word(beg, boundary, value);
 350     par_put_range_within_word(boundary, end, value);
 351   }
 352 
 353 }
 354 
 355 void BitMap::at_put_large_range(idx_t beg, idx_t end, bool value) {
 356   if (value) {
 357     set_large_range(beg, end);
 358   } else {
 359     clear_large_range(beg, end);
 360   }
 361 }
 362 
 363 void BitMap::par_at_put_large_range(idx_t beg, idx_t end, bool value) {
 364   verify_range(beg, end);
 365 
 366   idx_t beg_full_word = word_index_round_up(beg);
 367   idx_t end_full_word = word_index(end);
 368 
 369   assert(end_full_word - beg_full_word >= 32,
 370          "the range must include at least 32 bytes");
 371 
 372   // The range includes at least one full word.
 373   par_put_range_within_word(beg, bit_index(beg_full_word), value);
 374   if (value) {
 375     set_large_range_of_words(beg_full_word, end_full_word);
 376   } else {
 377     clear_large_range_of_words(beg_full_word, end_full_word);
 378   }
 379   par_put_range_within_word(bit_index(end_full_word), end, value);
 380 }
 381 
 382 inline bm_word_t tail_mask(idx_t tail_bits) {
 383   assert(tail_bits != 0, "precondition"); // Works, but shouldn't be called.
 384   assert(tail_bits < (idx_t)BitsPerWord, "precondition");
 385   return (bm_word_t(1) << tail_bits) - 1;
 386 }
 387 
 388 // Get the low tail_bits of value, which is the last partial word of a map.
 389 inline bm_word_t tail_of_map(bm_word_t value, idx_t tail_bits) {
 390   return value & tail_mask(tail_bits);
 391 }
 392 
 393 // Compute the new last word of a map with a non-aligned length.
 394 // new_value has the new trailing bits of the map in the low tail_bits.
 395 // old_value is the last word of the map, including bits beyond the end.
 396 // Returns old_value with the low tail_bits replaced by the corresponding
 397 // bits in new_value.
 398 inline bm_word_t merge_tail_of_map(bm_word_t new_value,
 399                                    bm_word_t old_value,
 400                                    idx_t tail_bits) {
 401   bm_word_t mask = tail_mask(tail_bits);
 402   return (new_value & mask) | (old_value & ~mask);
 403 }
 404 
 405 bool BitMap::contains(const BitMap& other) const {
 406   assert(size() == other.size(), "must have same size");
 407   const bm_word_t* dest_map = map();
 408   const bm_word_t* other_map = other.map();
 409   idx_t limit = word_index(size());
 410   for (idx_t index = 0; index < limit; ++index) {
 411     // false if other bitmap has bits set which are clear in this bitmap.
 412     if ((~dest_map[index] & other_map[index]) != 0) return false;
 413   }
 414   idx_t rest = bit_in_word(size());
 415   // true unless there is a partial-word tail in which the other
 416   // bitmap has bits set which are clear in this bitmap.
 417   return (rest == 0) || tail_of_map(~dest_map[limit] & other_map[limit], rest) == 0;
 418 }
 419 
 420 bool BitMap::intersects(const BitMap& other) const {
 421   assert(size() == other.size(), "must have same size");
 422   const bm_word_t* dest_map = map();
 423   const bm_word_t* other_map = other.map();
 424   idx_t limit = word_index(size());
 425   for (idx_t index = 0; index < limit; ++index) {
 426     if ((dest_map[index] & other_map[index]) != 0) return true;
 427   }
 428   idx_t rest = bit_in_word(size());
 429   // false unless there is a partial-word tail with non-empty intersection.
 430   return (rest > 0) && tail_of_map(dest_map[limit] & other_map[limit], rest) != 0;
 431 }
 432 
 433 void BitMap::set_union(const BitMap& other) {
 434   assert(size() == other.size(), "must have same size");
 435   bm_word_t* dest_map = map();
 436   const bm_word_t* other_map = other.map();
 437   idx_t limit = word_index(size());
 438   for (idx_t index = 0; index < limit; ++index) {
 439     dest_map[index] |= other_map[index];
 440   }
 441   idx_t rest = bit_in_word(size());
 442   if (rest > 0) {
 443     bm_word_t orig = dest_map[limit];
 444     dest_map[limit] = merge_tail_of_map(orig | other_map[limit], orig, rest);
 445   }
 446 }
 447 
 448 void BitMap::set_difference(const BitMap& other) {
 449   assert(size() == other.size(), "must have same size");
 450   bm_word_t* dest_map = map();
 451   const bm_word_t* other_map = other.map();
 452   idx_t limit = word_index(size());
 453   for (idx_t index = 0; index < limit; ++index) {
 454     dest_map[index] &= ~other_map[index];
 455   }
 456   idx_t rest = bit_in_word(size());
 457   if (rest > 0) {
 458     bm_word_t orig = dest_map[limit];
 459     dest_map[limit] = merge_tail_of_map(orig & ~other_map[limit], orig, rest);
 460   }
 461 }
 462 
 463 void BitMap::set_intersection(const BitMap& other) {
 464   assert(size() == other.size(), "must have same size");
 465   bm_word_t* dest_map = map();
 466   const bm_word_t* other_map = other.map();
 467   idx_t limit = word_index(size());
 468   for (idx_t index = 0; index < limit; ++index) {
 469     dest_map[index] &= other_map[index];
 470   }
 471   idx_t rest = bit_in_word(size());
 472   if (rest > 0) {
 473     bm_word_t orig = dest_map[limit];
 474     dest_map[limit] = merge_tail_of_map(orig & other_map[limit], orig, rest);
 475   }
 476 }
 477 
 478 bool BitMap::set_union_with_result(const BitMap& other) {
 479   assert(size() == other.size(), "must have same size");
 480   bool changed = false;
 481   bm_word_t* dest_map = map();
 482   const bm_word_t* other_map = other.map();
 483   idx_t limit = word_index(size());
 484   for (idx_t index = 0; index < limit; ++index) {
 485     bm_word_t orig = dest_map[index];
 486     bm_word_t temp = orig | other_map[index];
 487     changed = changed || (temp != orig);
 488     dest_map[index] = temp;
 489   }
 490   idx_t rest = bit_in_word(size());
 491   if (rest > 0) {
 492     bm_word_t orig = dest_map[limit];
 493     bm_word_t temp = merge_tail_of_map(orig | other_map[limit], orig, rest);
 494     changed = changed || (temp != orig);
 495     dest_map[limit] = temp;
 496   }
 497   return changed;
 498 }
 499 
 500 bool BitMap::set_difference_with_result(const BitMap& other) {
 501   assert(size() == other.size(), "must have same size");
 502   bool changed = false;
 503   bm_word_t* dest_map = map();
 504   const bm_word_t* other_map = other.map();
 505   idx_t limit = word_index(size());
 506   for (idx_t index = 0; index < limit; ++index) {
 507     bm_word_t orig = dest_map[index];
 508     bm_word_t temp = orig & ~other_map[index];
 509     changed = changed || (temp != orig);
 510     dest_map[index] = temp;
 511   }
 512   idx_t rest = bit_in_word(size());
 513   if (rest > 0) {
 514     bm_word_t orig = dest_map[limit];
 515     bm_word_t temp = merge_tail_of_map(orig & ~other_map[limit], orig, rest);
 516     changed = changed || (temp != orig);
 517     dest_map[limit] = temp;
 518   }
 519   return changed;
 520 }
 521 
 522 bool BitMap::set_intersection_with_result(const BitMap& other) {
 523   assert(size() == other.size(), "must have same size");
 524   bool changed = false;
 525   bm_word_t* dest_map = map();
 526   const bm_word_t* other_map = other.map();
 527   idx_t limit = word_index(size());
 528   for (idx_t index = 0; index < limit; ++index) {
 529     bm_word_t orig = dest_map[index];
 530     bm_word_t temp = orig & other_map[index];
 531     changed = changed || (temp != orig);
 532     dest_map[index] = temp;
 533   }
 534   idx_t rest = bit_in_word(size());
 535   if (rest > 0) {
 536     bm_word_t orig = dest_map[limit];
 537     bm_word_t temp = merge_tail_of_map(orig & other_map[limit], orig, rest);
 538     changed = changed || (temp != orig);
 539     dest_map[limit] = temp;
 540   }
 541   return changed;
 542 }
 543 
 544 void BitMap::set_from(const BitMap& other) {
 545   assert(size() == other.size(), "must have same size");
 546   bm_word_t* dest_map = map();
 547   const bm_word_t* other_map = other.map();
 548   idx_t copy_words = word_index(size());
 549   Copy::disjoint_words((HeapWord*)other_map, (HeapWord*)dest_map, copy_words);
 550   idx_t rest = bit_in_word(size());
 551   if (rest > 0) {
 552     dest_map[copy_words] = merge_tail_of_map(other_map[copy_words],
 553                                              dest_map[copy_words],
 554                                              rest);
 555   }
 556 }
 557 
 558 bool BitMap::is_same(const BitMap& other) const {
 559   assert(size() == other.size(), "must have same size");
 560   const bm_word_t* dest_map = map();
 561   const bm_word_t* other_map = other.map();
 562   idx_t limit = word_index(size());
 563   for (idx_t index = 0; index < limit; ++index) {
 564     if (dest_map[index] != other_map[index]) return false;
 565   }
 566   idx_t rest = bit_in_word(size());
 567   return (rest == 0) || (tail_of_map(dest_map[limit] ^ other_map[limit], rest) == 0);
 568 }
 569 
 570 bool BitMap::is_full() const {
 571   const bm_word_t* words = map();
 572   idx_t limit = word_index(size());
 573   for (idx_t index = 0; index < limit; ++index) {
 574     if (~words[index] != 0) return false;
 575   }
 576   idx_t rest = bit_in_word(size());
 577   return (rest == 0) || (tail_of_map(~words[limit], rest) == 0);
 578 }
 579 
 580 bool BitMap::is_empty() const {
 581   const bm_word_t* words = map();
 582   idx_t limit = word_index(size());
 583   for (idx_t index = 0; index < limit; ++index) {
 584     if (words[index] != 0) return false;
 585   }
 586   idx_t rest = bit_in_word(size());
 587   return (rest == 0) || (tail_of_map(words[limit], rest) == 0);
 588 }
 589 
 590 void BitMap::clear_large() {
 591   clear_large_range_of_words(0, size_in_words());
 592 }
 593 
 594 // Note that if the closure itself modifies the bitmap
 595 // then modifications in and to the left of the _bit_ being
 596 // currently sampled will not be seen. Note also that the
 597 // interval [leftOffset, rightOffset) is right open.
 598 bool BitMap::iterate(BitMapClosure* blk, idx_t leftOffset, idx_t rightOffset) {
 599   verify_range(leftOffset, rightOffset);
 600 
 601   idx_t startIndex = word_index(leftOffset);
 602   idx_t endIndex   = MIN2(word_index(rightOffset) + 1, size_in_words());
 603   for (idx_t index = startIndex, offset = leftOffset;
 604        offset < rightOffset && index < endIndex;
 605        offset = (++index) << LogBitsPerWord) {
 606     idx_t rest = map(index) >> (offset & (BitsPerWord - 1));
 607     for (; offset < rightOffset && rest != 0; offset++) {
 608       if (rest & 1) {
 609         if (!blk->do_bit(offset)) return false;
 610         //  resample at each closure application
 611         // (see, for instance, CMS bug 4525989)
 612         rest = map(index) >> (offset & (BitsPerWord -1));
 613       }
 614       rest = rest >> 1;
 615     }
 616   }
 617   return true;
 618 }
 619 
 620 BitMap::idx_t* BitMap::_pop_count_table = NULL;
 621 
 622 void BitMap::init_pop_count_table() {
 623   if (_pop_count_table == NULL) {
 624     BitMap::idx_t *table = NEW_C_HEAP_ARRAY(idx_t, 256, mtInternal);
 625     for (uint i = 0; i < 256; i++) {
 626       table[i] = num_set_bits(i);
 627     }
 628 
 629     if (!Atomic::conditional_store_ptr(table, &_pop_count_table)) {
 630       guarantee(_pop_count_table != NULL, "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