src/hotspot/share/memory/iterator.inline.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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#ifndef SHARE_VM_MEMORY_ITERATOR_INLINE_HPP
#define SHARE_VM_MEMORY_ITERATOR_INLINE_HPP

#include "classfile/classLoaderData.hpp"
#include "memory/iterator.hpp"
#include "oops/access.inline.hpp"
#include "oops/compressedOops.inline.hpp"
#include "oops/klass.hpp"
#include "oops/instanceKlass.inline.hpp"
#include "oops/instanceMirrorKlass.inline.hpp"
#include "oops/instanceClassLoaderKlass.inline.hpp"
#include "oops/instanceRefKlass.inline.hpp"
#include "oops/objArrayKlass.inline.hpp"
#include "oops/typeArrayKlass.inline.hpp"
#include "utilities/debug.hpp"

inline void MetadataVisitingOopIterateClosure::do_cld(ClassLoaderData* cld) {
  bool claim = true;  // Must claim the class loader data before processing.
  cld->oops_do(this, claim);
}

inline void MetadataVisitingOopIterateClosure::do_klass(Klass* k) {
  ClassLoaderData* cld = k->class_loader_data();
  MetadataVisitingOopIterateClosure::do_cld(cld);
}

#ifdef ASSERT
// This verification is applied to all visited oops.
// The closures can turn is off by overriding should_verify_oops().
template <typename T>
void OopIterateClosure::verify(T* p) {
  if (should_verify_oops()) {
    T heap_oop = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(heap_oop)) {
      oop o = CompressedOops::decode_not_null(heap_oop);
      assert(Universe::heap()->is_in_closed_subset(o),
             "should be in closed *p " PTR_FORMAT " " PTR_FORMAT, p2i(p), p2i(o));
    }
  }
}
#endif

// Implementation of the non-virtual do_oop dispatch.
//
// The same implementation is used for do_metadata, do_klass, and do_cld.
//
// Preconditions:
//  - Base has a pure virtual do_oop
//  - Only one of the classes in the inheritance chain from OopClosureType to
//    Base implements do_oop.
//
// Given the preconditions:
//  - If &OopClosureType::do_oop is resolved to &Base::do_oop, then there is no
//    implementation of do_oop between Base and OopClosureType. However, there
//    must be one implementation in one of the subclasses of OopClosureType.
//    In this case we take the virtual call.
//
//  - Conversely, if &OopClosureType::do_oop is not resolved to &Base::do_oop,
//    then we've found the one and only concrete implementation. In this case we
//    take a non-virtual call.
//
// Because of this it's clear when we should call the virtual call and
//   when the non-virtual call should be made.
//
// The way we find if &OopClosureType::do_oop is resolved to &Base::do_oop is to
//   check if the resulting type of the class of a member-function pointer to
//   &OopClosureType::do_oop is equal to the type of the class of a
//   &Base::do_oop member-function pointer. Template parameter deduction is used
//   to find these types, and then the IsSame trait is used to check if they are
//   equal. Finally, SFINAE is used to select the appropriate implementation.
//
// Template parameters:
//   T              - narrowOop or oop
//   Receiver       - the resolved type of the class of the
//                    &OopClosureType::do_oop member-function pointer. That is,
//                    the klass with the do_oop member function.
//   Base           - klass with the pure virtual do_oop member function.
//   OopClosureType - The dynamic closure type
//
// Parameters:
//   closure - The closure to call
//   p       - The oop (or narrowOop) field to pass to the closure

template <typename T, typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<IsSame<Receiver, Base>::value, void>::type
call_do_oop(void (Receiver::*)(T*), void (Base::*)(T*), OopClosureType* closure, T* p) {
  closure->do_oop(p);
}

template <typename T, typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<!IsSame<Receiver, Base>::value, void>::type
call_do_oop(void (Receiver::*)(T*), void (Base::*)(T*), OopClosureType* closure, T* p) {
  // Sanity check
  STATIC_ASSERT((!IsSame<OopClosureType, OopIterateClosure>::value));
  closure->OopClosureType::do_oop(p);
}

template <typename OopClosureType, typename T>
inline void Devirtualizer::do_oop_no_verify(OopClosureType* closure, T* p) {
  call_do_oop<T>(&OopClosureType::do_oop, &OopClosure::do_oop, closure, p);
}

template <typename OopClosureType, typename T>
inline void Devirtualizer::do_oop(OopClosureType* closure, T* p) {
  debug_only(closure->verify(p));

  do_oop_no_verify(closure, p);
}

// Implementation of the non-virtual do_metadata dispatch.

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<IsSame<Receiver, Base>::value, bool>::type
call_do_metadata(bool (Receiver::*)(), bool (Base::*)(), OopClosureType* closure) {
  return closure->do_metadata();
}

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<!IsSame<Receiver, Base>::value, bool>::type
call_do_metadata(bool (Receiver::*)(), bool (Base::*)(), OopClosureType* closure) {
  return closure->OopClosureType::do_metadata();
}

template <typename OopClosureType>
inline bool Devirtualizer::do_metadata(OopClosureType* closure) {
  return call_do_metadata(&OopClosureType::do_metadata, &OopIterateClosure::do_metadata, closure);
}

// Implementation of the non-virtual do_klass dispatch.

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<IsSame<Receiver, Base>::value, void>::type
call_do_klass(void (Receiver::*)(Klass*), void (Base::*)(Klass*), OopClosureType* closure, Klass* k) {
  closure->do_klass(k);
}

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<!IsSame<Receiver, Base>::value, void>::type
call_do_klass(void (Receiver::*)(Klass*), void (Base::*)(Klass*), OopClosureType* closure, Klass* k) {
  closure->OopClosureType::do_klass(k);
}

template <typename OopClosureType>
inline void Devirtualizer::do_klass(OopClosureType* closure, Klass* k) {
  call_do_klass(&OopClosureType::do_klass, &OopIterateClosure::do_klass, closure, k);
}

// Implementation of the non-virtual do_cld dispatch.

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<IsSame<Receiver, Base>::value, void>::type
call_do_cld(void (Receiver::*)(ClassLoaderData*), void (Base::*)(ClassLoaderData*), OopClosureType* closure, ClassLoaderData* cld) {
  closure->do_cld(cld);
}

template <typename Receiver, typename Base, typename OopClosureType>
static typename EnableIf<!IsSame<Receiver, Base>::value, void>::type
call_do_cld(void (Receiver::*)(ClassLoaderData*), void (Base::*)(ClassLoaderData*), OopClosureType* closure, ClassLoaderData* cld) {
  closure->OopClosureType::do_cld(cld);
}

template <typename OopClosureType>
void Devirtualizer::do_cld(OopClosureType* closure, ClassLoaderData* cld) {
  call_do_cld(&OopClosureType::do_cld, &OopIterateClosure::do_cld, closure, cld);
}

// Dispatch table implementation for *Klass::oop_oop_iterate
//
// It allows for a single call to do a multi-dispatch to an optimized version
//   of oop_oop_iterate that statically know all these types:
//   - OopClosureType    : static type give at call site
//   - Klass*            : dynamic to static type through Klass::id() -> table index
//   - UseCompressedOops : dynamic to static value determined once
//
// when users call obj->oop_iterate(&cl).
//
// oopDesc::oop_iterate() calls OopOopIterateDispatch::function(klass)(cl, obj, klass),
//   which dispatches to an optimized version of
//   [Instance, ObjArry, etc]Klass::oop_oop_iterate(oop, OopClosureType)
//
// OopClosureType :
//   If OopClosureType has an implementation of do_oop (and do_metadata et.al.),
//   then the static type of OopClosureType will be used to allow inlining of
//   do_oop (even though do_oop is virtual). Otherwise, a virtual call will be
//   used when calling do_oop.
//
// Klass* :
//   A table mapping from *Klass::ID to function is setup. This happens once
//   when the program starts, when the static _table instance is initialized for
//   the OopOopIterateDispatch specialized with the OopClosureType.
//
// UseCompressedOops :
//   Initially the table is populated with an init function, and not the actual
//   oop_oop_iterate function. This is done, so that the first time we dispatch
//   through the init function we check what the value of UseCompressedOops
//   became, and use that to determine if we should install an optimized
//   narrowOop version or optimized oop version of oop_oop_iterate. The appropriate
//   oop_oop_iterate function replaces the init function in the table, and
//   succeeding calls will jump directly to oop_oop_iterate.


template <typename OopClosureType>
class OopOopIterateDispatch : public AllStatic {
private:
  class Table {
  private:
    template <typename KlassType, typename T>
    static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* k) {
      ((KlassType*)k)->KlassType::template oop_oop_iterate<T>(obj, cl);
    }

    template <typename KlassType>
    static void init(OopClosureType* cl, oop obj, Klass* k) {
      OopOopIterateDispatch<OopClosureType>::_table.set_resolve_function_and_execute<KlassType>(cl, obj, k);
    }

    template <typename KlassType>
    void set_init_function() {
      _function[KlassType::ID] = &init<KlassType>;
    }

    template <typename KlassType>
    void set_resolve_function() {
      // Size requirement to prevent word tearing
      // when functions pointers are updated.
      STATIC_ASSERT(sizeof(_function[0]) == sizeof(void*));
      if (UseCompressedOops) {
        _function[KlassType::ID] = &oop_oop_iterate<KlassType, narrowOop>;
      } else {
        _function[KlassType::ID] = &oop_oop_iterate<KlassType, oop>;
      }
    }

    template <typename KlassType>
    void set_resolve_function_and_execute(OopClosureType* cl, oop obj, Klass* k) {
      set_resolve_function<KlassType>();
      _function[KlassType::ID](cl, obj, k);
    }

  public:
    void (*_function[KLASS_ID_COUNT])(OopClosureType*, oop, Klass*);

    Table(){
      set_init_function<InstanceKlass>();
      set_init_function<InstanceRefKlass>();
      set_init_function<InstanceMirrorKlass>();
      set_init_function<InstanceClassLoaderKlass>();
      set_init_function<ObjArrayKlass>();
      set_init_function<TypeArrayKlass>();
    }
  };

  static Table _table;
public:

  static void (*function(Klass* klass))(OopClosureType*, oop, Klass*) {
    return _table._function[klass->id()];
  }
};

template <typename OopClosureType>
typename OopOopIterateDispatch<OopClosureType>::Table OopOopIterateDispatch<OopClosureType>::_table;


template <typename OopClosureType>
class OopOopIterateBoundedDispatch {
private:
  class Table {
  private:
    template <typename KlassType, typename T>
    static void oop_oop_iterate_bounded(OopClosureType* cl, oop obj, Klass* k, MemRegion mr) {
      ((KlassType*)k)->KlassType::template oop_oop_iterate_bounded<T>(obj, cl, mr);
    }

    template <typename KlassType>
    static void init(OopClosureType* cl, oop obj, Klass* k, MemRegion mr) {
      OopOopIterateBoundedDispatch<OopClosureType>::_table.set_resolve_function_and_execute<KlassType>(cl, obj, k, mr);
    }

    template <typename KlassType>
    void set_init_function() {
      _function[KlassType::ID] = &init<KlassType>;
    }

    template <typename KlassType>
    void set_resolve_function() {
      if (UseCompressedOops) {
        _function[KlassType::ID] = &oop_oop_iterate_bounded<KlassType, narrowOop>;
      } else {
        _function[KlassType::ID] = &oop_oop_iterate_bounded<KlassType, oop>;
      }
    }

    template <typename KlassType>
    void set_resolve_function_and_execute(OopClosureType* cl, oop obj, Klass* k, MemRegion mr) {
      set_resolve_function<KlassType>();
      _function[KlassType::ID](cl, obj, k, mr);
    }

  public:
    void (*_function[KLASS_ID_COUNT])(OopClosureType*, oop, Klass*, MemRegion);

    Table(){
      set_init_function<InstanceKlass>();
      set_init_function<InstanceRefKlass>();
      set_init_function<InstanceMirrorKlass>();
      set_init_function<InstanceClassLoaderKlass>();
      set_init_function<ObjArrayKlass>();
      set_init_function<TypeArrayKlass>();
    }
  };

  static Table _table;
public:

  static void (*function(Klass* klass))(OopClosureType*, oop, Klass*, MemRegion) {
    return _table._function[klass->id()];
  }
};

template <typename OopClosureType>
typename OopOopIterateBoundedDispatch<OopClosureType>::Table OopOopIterateBoundedDispatch<OopClosureType>::_table;


template <typename OopClosureType>
class OopOopIterateBackwardsDispatch {
private:
  class Table {
  private:
    template <typename KlassType, typename T>
    static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* k) {
      ((KlassType*)k)->KlassType::template oop_oop_iterate_reverse<T>(obj, cl);
    }

    template <typename KlassType>
    static void init(OopClosureType* cl, oop obj, Klass* k) {
      OopOopIterateBackwardsDispatch<OopClosureType>::_table.set_resolve_function_and_execute<KlassType>(cl, obj, k);
    }

    template <typename KlassType>
    void set_init_function() {
      _function[KlassType::ID] = &init<KlassType>;
    }

    template <typename KlassType>
    void set_resolve_function() {
      if (UseCompressedOops) {
        _function[KlassType::ID] = &oop_oop_iterate_backwards<KlassType, narrowOop>;
      } else {
        _function[KlassType::ID] = &oop_oop_iterate_backwards<KlassType, oop>;
      }
    }

    template <typename KlassType>
    void set_resolve_function_and_execute(OopClosureType* cl, oop obj, Klass* k) {
      set_resolve_function<KlassType>();
      _function[KlassType::ID](cl, obj, k);
    }

  public:
    void (*_function[KLASS_ID_COUNT])(OopClosureType*, oop, Klass*);

    Table(){
      set_init_function<InstanceKlass>();
      set_init_function<InstanceRefKlass>();
      set_init_function<InstanceMirrorKlass>();
      set_init_function<InstanceClassLoaderKlass>();
      set_init_function<ObjArrayKlass>();
      set_init_function<TypeArrayKlass>();
    }
  };

  static Table _table;
public:

  static void (*function(Klass* klass))(OopClosureType*, oop, Klass*) {
    return _table._function[klass->id()];
  }
};

template <typename OopClosureType>
typename OopOopIterateBackwardsDispatch<OopClosureType>::Table OopOopIterateBackwardsDispatch<OopClosureType>::_table;


template <typename OopClosureType>
void OopIteratorClosureDispatch::oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass) {
  OopOopIterateDispatch<OopClosureType>::function(klass)(cl, obj, klass);
}

template <typename OopClosureType>
void OopIteratorClosureDispatch::oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr) {
  OopOopIterateBoundedDispatch<OopClosureType>::function(klass)(cl, obj, klass, mr);
}

template <typename OopClosureType>
void OopIteratorClosureDispatch::oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass) {
  OopOopIterateBackwardsDispatch<OopClosureType>::function(klass)(cl, obj, klass);
}

#endif // SHARE_VM_MEMORY_ITERATOR_INLINE_HPP