--- old/src/hotspot/share/utilities/bitMap.hpp	2019-06-10 20:16:26.223680331 -0400
+++ new/src/hotspot/share/utilities/bitMap.hpp	2019-06-10 20:16:25.635648899 -0400
@@ -48,8 +48,10 @@
 
  public:
   typedef size_t idx_t;         // Type used for bit and word indices.
-  typedef uintptr_t bm_word_t;  // Element type of array that represents
-                                // the bitmap.  BitsPerWord bits per element.
+  typedef uintptr_t bm_word_t;  // Element type of array that represents the
+                                // bitmap, with BitsPerWord bits per element.
+  // If this were to fail, there are lots of places that would need repair.
+  STATIC_ASSERT((sizeof(bm_word_t) * BitsPerByte) == BitsPerWord);
 
   // Hints for range sizes.
   typedef enum {
@@ -60,10 +62,14 @@
   bm_word_t* _map;     // First word in bitmap
   idx_t      _size;    // Size of bitmap (in bits)
 
-  // Limit max_size_in_bits so roundup in calc_size_in_words can't overflow.
+  // Limit max_size_in_bits so aligning up to a word never overflows.
   static idx_t max_size_in_words() { return word_index(~idx_t(0)); }
   static idx_t max_size_in_bits() { return max_size_in_words() * BitsPerWord; }
 
+  // bit must be the begin/end of a validated range.
+  static inline idx_t range_begin_align_up(idx_t bit);
+  static inline idx_t range_end_align_down(idx_t bit);
+
   // Helper for get_next_{zero,one}_bit variants.
   // - flip designates whether searching for 1s or 0s.  Must be one of
   //   find_{zeros,ones}_flip.
@@ -79,6 +85,9 @@
   // operation was requested. Measured in words.
   static const size_t small_range_words = 32;
 
+  // beg/end_aligned must be from range_begin/end aligners.
+  static bool is_small_aligned_range(idx_t beg_aligned, idx_t end_aligned);
+
  protected:
   // Return the position of bit within the word that contains it (e.g., if
   // bitmap words are 32 bits, return a number 0 <= n <= 31).
@@ -124,14 +133,13 @@
 
   static void clear_range_of_words(bm_word_t* map, idx_t beg, idx_t end);
 
-  static bool is_small_range_of_words(idx_t beg_full_word, idx_t end_full_word);
-
-  // The index of the first full word in a range.
-  idx_t word_index_round_up(idx_t bit) const;
-
   // Verification.
-  static void verify_max_size_limited(idx_t bit) NOT_DEBUG_RETURN;
+
+  // Verify size_in_bits does not exceed maximum size.
+  static void verify_valid_size(idx_t size_in_bits) NOT_DEBUG_RETURN;
+  // Verify index is less than size.
   void verify_index(idx_t index) const NOT_DEBUG_RETURN;
+  // Verify [beg,end) is a valid range.
   void verify_range(idx_t beg_index, idx_t end_index) const NOT_DEBUG_RETURN;
 
   // Statistics.
@@ -191,7 +199,7 @@
   void pretouch();
 
   static idx_t calc_size_in_words(idx_t size_in_bits) {
-    verify_max_size_limited(size_in_bits);
+    verify_valid_size(size_in_bits);
     return word_index(size_in_bits + (BitsPerWord - 1));
   }