1019 

  1020 //--------------------------find_exact_control---------------------------------

  1021 // Skip Proj and CatchProj nodes chains. Check for Null and Top.

  1022 Node* Node::find_exact_control(Node* ctrl) {

  1023   if (ctrl == NULL && this->is_Region())

  1024     ctrl = this->as_Region()->is_copy();

  1025 

  1026   if (ctrl != NULL && ctrl->is_CatchProj()) {

  1027     if (ctrl->as_CatchProj()->_con == CatchProjNode::fall_through_index)

  1028       ctrl = ctrl->in(0);

  1029     if (ctrl != NULL && !ctrl->is_top())

  1030       ctrl = ctrl->in(0);

  1031   }

  1032 

  1033   if (ctrl != NULL && ctrl->is_Proj())

  1034     ctrl = ctrl->in(0);

  1035 

  1036   return ctrl;

  1037 }

  1038 

  1039 //--------------------------dominates------------------------------------------

  1040 // Helper function for MemNode::all_controls_dominate().

  1041 // Check if 'this' control node dominates or equal to 'sub' control node.

  1042 bool Node::dominates(Node* sub, Node_List &nlist) {

  1043   assert(this->is_CFG(), "expecting control");

  1044   assert(sub != NULL && sub->is_CFG(), "expecting control");

  1045 

  1046   Node* orig_sub = sub;

  1047   nlist.clear();

  1048   bool this_dominates = false;

  1049   uint region_input = 0;

  1050   while (sub != NULL) {        // walk 'sub' up the chain to 'this'

  1051     if (sub == this) {

  1052       if (nlist.size() == 0) {

  1053         // No Region nodes except loops were visited before and the EntryControl

  1054         // path was taken for loops: it did not walk in a cycle.

  1055         return true;

  1056       } else if (!this_dominates) {

  1057         // Region nodes were visited. Continue walk up to Start or Root

  1058         // to make sure that it did not walk in a cycle.

  1059         this_dominates = true; // first time meet

  1060       } else {

  1061         return false;          // already met before: walk in a cycle

  1062       }

  1063     }

  1064     if (sub->is_Start() || sub->is_Root())

  1065       return this_dominates;

  1066 

  1067     Node* up = sub->find_exact_control(sub->in(0));

  1068     if (up == NULL || up->is_top())

  1069       return false; // Conservative answer for dead code

  1070 

  1071     if (sub == up && sub->is_Loop()) {

  1072       up = sub->in(0); // in(LoopNode::EntryControl);

  1073     } else if (sub == up && sub->is_Region()) {

  1074       uint i = 1;

  1075       if (nlist.size() == 0) {

  1076         // No Region nodes (except Loops) were visited before.

  1077         // Take first valid path on the way up to 'this'.

  1078       } else if (nlist.at(nlist.size() - 1) == sub) {

  1079         // This Region node was just visited. Take other path.

  1080         i = region_input + 1;

  1081         nlist.pop();

  1082       } else {

  1083         // Was this Region node visited before?

  1084         uint size = nlist.size();

  1085         for (uint j = 0; j < size; j++) {

  1086           if (nlist.at(j) == sub) {

  1087             return false; // The Region node was visited before. Give up.

  1088           }

  1089         }

  1090         // The Region node was not visited before.

  1091         // Take first valid path on the way up to 'this'.

  1092       }

  1093       for (; i < sub->req(); i++) {

  1094         Node* in = sub->in(i);

  1095         if (in != NULL && !in->is_top() && in != sub) {

  1096           break;

  1097         }

  1098       }

  1099       if (i < sub->req()) {

  1100         nlist.push(sub);

  1101         up = sub->in(i);

  1102         region_input = i;

  1103       }

  1104     }

  1105     if (sub == up)

  1106       return false;    // some kind of tight cycle

  1107     if (orig_sub == up)

  1108       return false;    // walk in a cycle

  1109 

  1110     sub = up;

  1111   }

  1112   return false;

  1113 }