--- old/src/hotspot/share/utilities/bitMap.cpp	2019-11-26 19:23:24.890720664 -0500
+++ new/src/hotspot/share/utilities/bitMap.cpp	2019-11-26 19:23:24.618706085 -0500
@@ -174,14 +174,27 @@
 }
 
 #ifdef ASSERT
-void BitMap::verify_index(idx_t index) const {
-  assert(index < _size, "BitMap index out of bounds");
+void BitMap::verify_size(idx_t size_in_bits) {
+  assert(size_in_bits <= max_size_in_bits(),
+         "out of bounds: " SIZE_FORMAT, size_in_bits);
 }
 
-void BitMap::verify_range(idx_t beg_index, idx_t end_index) const {
-  assert(beg_index <= end_index, "BitMap range error");
-  // Note that [0,0) and [size,size) are both valid ranges.
-  if (end_index != _size) verify_index(end_index);
+void BitMap::verify_index(idx_t bit) const {
+  assert(bit < _size,
+         "BitMap index out of bounds: " SIZE_FORMAT " >= " SIZE_FORMAT,
+         bit, _size);
+}
+
+void BitMap::verify_limit(idx_t bit) const {
+  assert(bit <= _size,
+         "BitMap limit out of bounds: " SIZE_FORMAT " > " SIZE_FORMAT,
+         bit, _size);
+}
+
+void BitMap::verify_range(idx_t beg, idx_t end) const {
+  assert(beg <= end,
+         "BitMap range error: " SIZE_FORMAT " > " SIZE_FORMAT, beg, end);
+  verify_limit(end);
 }
 #endif // #ifdef ASSERT
 
@@ -228,8 +241,8 @@
 void BitMap::set_range(idx_t beg, idx_t end) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (beg_full_word < end_full_word) {
     // The range includes at least one full word.
@@ -247,8 +260,8 @@
 void BitMap::clear_range(idx_t beg, idx_t end) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (beg_full_word < end_full_word) {
     // The range includes at least one full word.
@@ -265,17 +278,19 @@
 
 bool BitMap::is_small_range_of_words(idx_t beg_full_word, idx_t end_full_word) {
   // There is little point to call large version on small ranges.
-  // Need to check carefully, keeping potential idx_t underflow in mind.
+  // Need to check carefully, keeping potential idx_t over/underflow in mind,
+  // because beg_full_word > end_full_word can occur when beg and end are in
+  // the same word.
   // The threshold should be at least one word.
   STATIC_ASSERT(small_range_words >= 1);
-  return (beg_full_word + small_range_words >= end_full_word);
+  return beg_full_word + small_range_words >= end_full_word;
 }
 
 void BitMap::set_large_range(idx_t beg, idx_t end) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (is_small_range_of_words(beg_full_word, end_full_word)) {
     set_range(beg, end);
@@ -291,8 +306,8 @@
 void BitMap::clear_large_range(idx_t beg, idx_t end) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (is_small_range_of_words(beg_full_word, end_full_word)) {
     clear_range(beg, end);
@@ -343,8 +358,8 @@
 void BitMap::par_at_put_range(idx_t beg, idx_t end, bool value) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (beg_full_word < end_full_word) {
     // The range includes at least one full word.
@@ -375,8 +390,8 @@
 void BitMap::par_at_put_large_range(idx_t beg, idx_t end, bool value) {
   verify_range(beg, end);
 
-  idx_t beg_full_word = word_index_round_up(beg);
-  idx_t end_full_word = word_index(end);
+  idx_t beg_full_word = to_words_align_up(beg);
+  idx_t end_full_word = to_words_align_down(end);
 
   if (is_small_range_of_words(beg_full_word, end_full_word)) {
     par_at_put_range(beg, end, value);
@@ -420,7 +435,7 @@
   assert(size() == other.size(), "must have same size");
   const bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     // false if other bitmap has bits set which are clear in this bitmap.
     if ((~dest_map[index] & other_map[index]) != 0) return false;
@@ -435,7 +450,7 @@
   assert(size() == other.size(), "must have same size");
   const bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     if ((dest_map[index] & other_map[index]) != 0) return true;
   }
@@ -448,7 +463,7 @@
   assert(size() == other.size(), "must have same size");
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     dest_map[index] |= other_map[index];
   }
@@ -463,7 +478,7 @@
   assert(size() == other.size(), "must have same size");
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     dest_map[index] &= ~other_map[index];
   }
@@ -478,7 +493,7 @@
   assert(size() == other.size(), "must have same size");
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     dest_map[index] &= other_map[index];
   }
@@ -494,7 +509,7 @@
   bool changed = false;
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     bm_word_t orig = dest_map[index];
     bm_word_t temp = orig | other_map[index];
@@ -516,7 +531,7 @@
   bool changed = false;
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     bm_word_t orig = dest_map[index];
     bm_word_t temp = orig & ~other_map[index];
@@ -538,7 +553,7 @@
   bool changed = false;
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     bm_word_t orig = dest_map[index];
     bm_word_t temp = orig & other_map[index];
@@ -559,7 +574,7 @@
   assert(size() == other.size(), "must have same size");
   bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t copy_words = word_index(size());
+  idx_t copy_words = to_words_align_down(size());
   Copy::disjoint_words((HeapWord*)other_map, (HeapWord*)dest_map, copy_words);
   idx_t rest = bit_in_word(size());
   if (rest > 0) {
@@ -573,7 +588,7 @@
   assert(size() == other.size(), "must have same size");
   const bm_word_t* dest_map = map();
   const bm_word_t* other_map = other.map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     if (dest_map[index] != other_map[index]) return false;
   }
@@ -583,7 +598,7 @@
 
 bool BitMap::is_full() const {
   const bm_word_t* words = map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     if (~words[index] != 0) return false;
   }
@@ -593,7 +608,7 @@
 
 bool BitMap::is_empty() const {
   const bm_word_t* words = map();
-  idx_t limit = word_index(size());
+  idx_t limit = to_words_align_down(size());
   for (idx_t index = 0; index < limit; ++index) {
     if (words[index] != 0) return false;
   }
@@ -612,8 +627,8 @@
 bool BitMap::iterate(BitMapClosure* blk, idx_t leftOffset, idx_t rightOffset) {
   verify_range(leftOffset, rightOffset);
 
-  idx_t startIndex = word_index(leftOffset);
-  idx_t endIndex   = MIN2(word_index(rightOffset) + 1, size_in_words());
+  idx_t startIndex = to_words_align_down(leftOffset);
+  idx_t endIndex   = to_words_align_up(rightOffset);
   for (idx_t index = startIndex, offset = leftOffset;
        offset < rightOffset && index < endIndex;
        offset = (++index) << LogBitsPerWord) {