src/share/vm/opto/node.cpp

*** 1034,1050 ****
--- 1034,1055 ----
      ctrl = ctrl->in(0);
  
    return ctrl;
  }
  
+ #define ITERATIONS_LIMIT 1000
+ 
  //--------------------------dominates------------------------------------------
  // Helper function for MemNode::all_controls_dominate().
  // Check if 'this' control node dominates or equal to 'sub' control node.
  bool Node::dominates(Node* sub, Node_List &nlist) {
    assert(this->is_CFG(), "expecting control");
    assert(sub != NULL && sub->is_CFG(), "expecting control");
  
+   // detect dead cycle without regions
+   int iterations_without_region_limit = ITERATIONS_LIMIT;
+ 
    Node* orig_sub = sub;
    nlist.clear();
    bool this_dominates = false;
    uint region_input = 0;
    while (sub != NULL) {        // walk 'sub' up the chain to 'this'
*** 1055,1064 ****
--- 1060,1070 ----
          return true;
        } else if (!this_dominates) {
          // Region nodes were visited. Continue walk up to Start or Root
          // to make sure that it did not walk in a cycle.
          this_dominates = true; // first time meet
+         iterations_without_region_limit = ITERATIONS_LIMIT; // Reset
        } else {
          return false;          // already met before: walk in a cycle
        }
      }
      if (sub->is_Start() || sub->is_Root())
*** 1067,1089 ****
      Node* up = sub->find_exact_control(sub->in(0));
      if (up == NULL || up->is_top())
        return false; // Conservative answer for dead code
  
      if (sub == up && sub->is_Loop()) {
!       up = sub->in(0); // in(LoopNode::EntryControl);
!     } else if (sub == up && sub->is_Region()) {
        uint i = 1;
!       if (nlist.size() == 0) {
          // No Region nodes (except Loops) were visited before.
          // Take first valid path on the way up to 'this'.
!       } else if (nlist.at(nlist.size() - 1) == sub) {
          // This Region node was just visited. Take other path.
          i = region_input + 1;
          nlist.pop();
        } else {
          // Was this Region node visited before?
-         uint size = nlist.size();
          for (uint j = 0; j < size; j++) {
            if (nlist.at(j) == sub) {
              return false; // The Region node was visited before. Give up.
            }
          }
--- 1073,1096 ----
      Node* up = sub->find_exact_control(sub->in(0));
      if (up == NULL || up->is_top())
        return false; // Conservative answer for dead code
  
      if (sub == up && sub->is_Loop()) {
!       up = sub->in(1); // in(LoopNode::EntryControl);
!     } else if (sub == up && sub->is_Region() && sub->req() == 3) {
!       iterations_without_region_limit = ITERATIONS_LIMIT; // Reset
        uint i = 1;
!       uint size = nlist.size();
!       if (size == 0) {
          // No Region nodes (except Loops) were visited before.
          // Take first valid path on the way up to 'this'.
!       } else if (nlist.at(size - 1) == sub) {
          // This Region node was just visited. Take other path.
          i = region_input + 1;
          nlist.pop();
        } else {
          // Was this Region node visited before?
          for (uint j = 0; j < size; j++) {
            if (nlist.at(j) == sub) {
              return false; // The Region node was visited before. Give up.
            }
          }
*** 1102,1114 ****
          region_input = i;
        }
      }
      if (sub == up)
        return false;    // some kind of tight cycle
-     if (orig_sub == up)
-       return false;    // walk in a cycle
  
      sub = up;
    }
    return false;
  }
  
--- 1109,1122 ----
          region_input = i;
        }
      }
      if (sub == up)
        return false;    // some kind of tight cycle
  
+     if (--iterations_without_region_limit < 0)
+       return false;    // dead cycle
+ 
      sub = up;
    }
    return false;
  }