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:

*** 101,121 ****
  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,
--- 101,110 ----