src/share/vm/opto/node.cpp

*** 1015,1024 ****
--- 1015,1119 ----
      return n->Opcode() == op && n->in(2) == this;
    }
    return false;
  };
  
+ //--------------------------find_exact_control---------------------------------
+ // Skip Proj and CatchProj nodes chains. Check for Null and Top.
+ Node* Node::find_exact_control(Node* ctrl) {
+   if (ctrl == NULL && this->is_Region())
+     ctrl = this->as_Region()->is_copy();
+ 
+   if (ctrl != NULL && ctrl->is_CatchProj()) {
+     if (ctrl->as_CatchProj()->_con == CatchProjNode::fall_through_index)
+       ctrl = ctrl->in(0);
+     if (ctrl != NULL && !ctrl->is_top())
+       ctrl = ctrl->in(0);
+   }
+ 
+   if (ctrl != NULL && ctrl->is_Proj())
+     ctrl = ctrl->in(0);
+ 
+   return ctrl;
+ }
+ 
+ //--------------------------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");
+ 
+   Node* orig_sub = sub;
+   nlist.clear();
+   bool this_dominates = false;
+   uint region_input = 0;
+   while (sub != NULL) {        // walk 'sub' up the chain to 'this'
+     if (sub == this) {
+       if (nlist.size() == 0) {
+         // No Region nodes except loops were visited before and the EntryControl
+         // path was taken for loops: it did not walk in a cycle.
+         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
+       } else {
+         return false;          // already met before: walk in a cycle
+       }
+     }
+     if (sub->is_Start() || sub->is_Root())
+       return this_dominates;
+ 
+     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.
+           }
+         }
+         // The Region node was not visited before.
+         // Take first valid path on the way up to 'this'.
+       }
+       for (; i < sub->req(); i++) {
+         Node* in = sub->in(i);
+         if (in != NULL && !in->is_top() && in != sub) {
+           break;
+         }
+       }
+       if (i < sub->req()) {
+         nlist.push(sub);
+         up = sub->in(i);
+         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;
+ }
+ 
  //------------------------------remove_dead_region-----------------------------
  // This control node is dead.  Follow the subgraph below it making everything
  // using it dead as well.  This will happen normally via the usual IterGVN
  // worklist but this call is more efficient.  Do not update use-def info
  // inside the dead region, just at the borders.