src/share/vm/adlc/formssel.cpp

*** 418,427 ****
--- 418,434 ----
    if( _matrule == NULL ) return Form::none;
  
    return  _matrule->is_ideal_load();
  }
  
+ // Return 'true' if this instruction matches an ideal 'LoadKlass' node
+ bool InstructForm::skip_antidep_check() const {
+   if( _matrule == NULL ) return false;
+ 
+   return  _matrule->skip_antidep_check();
+ }
+ 
  // Return 'true' if this instruction matches an ideal 'Load?' node
  Form::DataType InstructForm::is_ideal_store() const {
    if( _matrule == NULL ) return Form::none;
  
    return  _matrule->is_ideal_store();
*** 565,574 ****
--- 572,583 ----
    return rematerialize;
  }
  
  // loads from memory, so must check for anti-dependence
  bool InstructForm::needs_anti_dependence_check(FormDict &globals) const {
+   if ( skip_antidep_check() ) return false;
+ 
    // Machine independent loads must be checked for anti-dependences
    if( is_ideal_load() != Form::none )  return true;
  
    // !!!!! !!!!! !!!!!
    // TEMPORARY
*** 3954,3963 ****
--- 3963,3994 ----
    }
  
    return ideal_load;
  }
  
+ 
+ bool MatchRule::skip_antidep_check() const {
+   // Some loads operate on what is effectively immutable memory so we
+   // should skip the anti dep computations.  For some of these nodes
+   // the rewritable field keeps the anti dep logic from triggering but
+   // for certain kinds of LoadKlass it does not since they are
+   // actually reading memory which could be rewritten by the runtime,
+   // though never by generated code.  This disables it uniformly for
+   // the nodes that behave like this: LoadKlass, LoadNKlass and
+   // LoadRange.
+   if ( _opType && (strcmp(_opType,"Set") == 0) && _rChild ) {
+     const char *opType = _rChild->_opType;
+     if (strcmp("LoadKlass", opType) == 0 ||
+         strcmp("LoadNKlass", opType) == 0 ||
+         strcmp("LoadRange", opType) == 0) {
+       return true;
+     }
+   }
+ 
+   return false;
+ }
+ 
  
  Form::DataType MatchRule::is_ideal_store() const {
    Form::DataType ideal_store = Form::none;
  
    if ( _opType && (strcmp(_opType,"Set") == 0) && _rChild ) {