src/share/vm/gc_implementation/g1/concurrentMark.cpp

rev 2896 : 7121547: G1: High number mispredicted branches while iterating over the marking bitmap
Summary: There is a high number of mispredicted branches associated with calling BitMap::iteratate() from within CMBitMapRO::iterate(). Implement a version of CMBitMapRO::iterate() directly using inline-able routines.
Reviewed-by:

@@ -101,21 +101,10 @@
 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
   assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
   return (int) (diff >> _shifter);
 }
 
-bool CMBitMapRO::iterate(BitMapClosure* cl, MemRegion mr) {
-  HeapWord* left  = MAX2(_bmStartWord, mr.start());
-  HeapWord* right = MIN2(_bmStartWord + _bmWordSize, mr.end());
-  if (right > left) {
-    // Right-open interval [leftOffset, rightOffset).
-    return _bm.iterate(cl, heapWordToOffset(left), heapWordToOffset(right));
-  } else {
-    return true;
-  }
-}
-
 void CMBitMapRO::mostly_disjoint_range_union(BitMap*   from_bitmap,
                                              size_t    from_start_index,
                                              HeapWord* to_start_word,
                                              size_t    word_num) {
   _bm.mostly_disjoint_range_union(from_bitmap,