src/share/vm/opto/cfgnode.cpp

*** 1529,1538 ****
--- 1529,1540 ----
    // This means we have to use type_or_null to defend against untyped regions.
    if( phase->type_or_null(r) == Type::TOP ) // Dead code?
      return NULL;                // No change
  
    Node *top = phase->C->top();
+   bool new_phi = (outcnt() == 0); // transforming new Phi
+   assert(!can_reshape || !new_phi, "for igvn new phi should be hooked");
  
    // The are 2 situations when only one valid phi's input is left
    // (in addition to Region input).
    // One: region is not loop - replace phi with this input.
    // Two: region is loop - replace phi with top since this data path is dead
*** 1548,1557 ****
--- 1550,1565 ----
          progress = this;        // Record progress
        }
      }
    }
  
+   if (can_reshape && outcnt() == 0) {
+     // set_req() above may kill outputs if Phi is referenced
+     // only by itself on the dead (top) control path.
+     return top;
+   }
+ 
    Node* uin = unique_input(phase);
    if (uin == top) {             // Simplest case: no alive inputs.
      if (can_reshape)            // IGVN transformation
        return top;
      else
*** 1682,1693 ****
              // compress paths and change unreachable cycles to TOP
              // If not, we can update the input infinitely along a MergeMem cycle
              // Equivalent code is in MemNode::Ideal_common
              Node *m  = phase->transform(n);
              if (outcnt() == 0) {  // Above transform() may kill us!
!               progress = phase->C->top();
!               break;
              }
              // If transformed to a MergeMem, get the desired slice
              // Otherwise the returned node represents memory for every slice
              Node *new_mem = (m->is_MergeMem()) ?
                               m->as_MergeMem()->memory_at(alias_idx) : m;
--- 1690,1700 ----
              // compress paths and change unreachable cycles to TOP
              // If not, we can update the input infinitely along a MergeMem cycle
              // Equivalent code is in MemNode::Ideal_common
              Node *m  = phase->transform(n);
              if (outcnt() == 0) {  // Above transform() may kill us!
!               return top;
              }
              // If transformed to a MergeMem, get the desired slice
              // Otherwise the returned node represents memory for every slice
              Node *new_mem = (m->is_MergeMem()) ?
                               m->as_MergeMem()->memory_at(alias_idx) : m;