src/share/vm/opto/ifnode.cpp

*** 1528,1551 ****
  //------------------------------Identity---------------------------------------
  // If the test is constant & we match, then we are the input Control
  Node *IfProjNode::Identity(PhaseTransform *phase) {
    // Can only optimize if cannot go the other way
    const TypeTuple *t = phase->type(in(0))->is_tuple();
!   if (t == TypeTuple::IFNEITHER ||
!       // kill dead branch first otherwise the IfNode's control will
!       // have 2 control uses (the IfNode that doesn't go away because
!       // it still has uses and this branch of the
!       // If). Node::has_special_unique_user() will cause this node to
!       // be reprocessed once the dead branch is killed.
!       (always_taken(t) && in(0)->outcnt() == 1)) {
      // IfNode control
      return in(0)->in(0);
    }
    // no progress
    return this;
  }
  
  #ifndef PRODUCT
  //-------------------------------related---------------------------------------
  // An IfProjNode's related node set consists of its input (an IfNode) including
  // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
  // the restrictions for IfNode apply (see IfNode::rel).
--- 1528,1556 ----
  //------------------------------Identity---------------------------------------
  // If the test is constant & we match, then we are the input Control
  Node *IfProjNode::Identity(PhaseTransform *phase) {
    // Can only optimize if cannot go the other way
    const TypeTuple *t = phase->type(in(0))->is_tuple();
!   if (t == TypeTuple::IFNEITHER || always_taken(t)) {
      // IfNode control
      return in(0)->in(0);
    }
    // no progress
    return this;
  }
  
+ Node* IfProjNode::Ideal(PhaseGVN* phase, bool can_reshape) {
+   const Type* t = phase->type(in(0));
+   if (can_reshape && in(0)->outcnt() == 2 && t != Type::TOP && always_taken(t->is_tuple())) {
+     // Cut off dead branch if this branch is always taken
+     Node* other = in(0)->as_If()->proj_out(!is_IfTrue());
+     other->set_req(0, phase->C->top());
+     return this;
+   }
+   return NULL;
+ }
+ 
  #ifndef PRODUCT
  //-------------------------------related---------------------------------------
  // An IfProjNode's related node set consists of its input (an IfNode) including
  // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
  // the restrictions for IfNode apply (see IfNode::rel).