src/share/vm/opto/gcm.cpp

*** 1736,1745 ****
--- 1736,1768 ----
      ch->compute_loop_depth(depth + 1);
      ch = ch->_sibling;
    }
  }
  
+ Block *CFGLoop::backedge_block() {
+   Block* hd = head();
+   Block* back_edge = NULL;
+   assert(_members.length() > 0, "no empty loops");
+   for (int i = 0; i < _members.length(); i++) {
+     CFGElement* s = _members.at(i);
+     if (s->is_block()) {
+       Block* b = s->as_Block();
+       if (b == hd) continue;
+       for (uint j = 0; j < b->_num_succs; j++) {
+         Block* sb = b->_succs[j];
+         if (sb == hd) {
+           back_edge = b;
+           break;
+         }
+       }
+     }
+     if (back_edge) break;
+   }
+ 
+   return back_edge;
+ }
+ 
  //------------------------------compute_freq-----------------------------------
  // Compute the frequency of each block and loop, relative to a single entry
  // into the dominating loop head.
  void CFGLoop::compute_freq() {
    // Bottom up traversal of loop tree (visit inner loops first.)