src/share/vm/opto/callnode.cpp

rev 9640 : 8144993: Elide redundant memory barrier after AllocationNode
Summary: Elide memory barrier for AllocationNode when it doesn't escape in initializer and has an MemBarRelease node at exit of initializer method.
Reviewed-by: duke

@@ -1331,10 +1331,11 @@
 {
   init_class_id(Class_Allocate);
   init_flags(Flag_is_macro);
   _is_scalar_replaceable = false;
   _is_non_escaping = false;
+  _is_allocation_MemBar_redundant = false;
   Node *topnode = C->top();
 
   init_req( TypeFunc::Control  , ctrl );
   init_req( TypeFunc::I_O      , abio );
   init_req( TypeFunc::Memory   , mem );

@@ -1345,10 +1346,27 @@
   init_req( InitialTest        , initial_test);
   init_req( ALength            , topnode);
   C->add_macro_node(this);
 }
 
+void AllocateNode::compute_MemBar_redundancy(ciMethod* initializer)
+{
+  assert(initializer != NULL &&
+         initializer->is_initializer() &&
+         !initializer->is_static(),
+             "unexpected initializer method");
+  BCEscapeAnalyzer* analyzer = initializer->get_bcea();
+  if (analyzer == NULL) {
+    return;
+  }
+
+  // Allocation node is first parameter in its initializer
+  if (analyzer->is_arg_stack(0) || analyzer->is_arg_local(0)) {
+    _is_allocation_MemBar_redundant = true;
+  }
+}
+
 //=============================================================================
 Node* AllocateArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   if (remove_dead_region(phase, can_reshape))  return this;
   // Don't bother trying to transform a dead node
   if (in(0) && in(0)->is_top())  return NULL;