jdk-24/hotspot/src/share/vm/oops/instanceRefKlass.cpp

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 * 2 along with this work; if not, write to the Free Software Foundation,
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#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/systemDictionary.hpp"
#include "oops/instanceRefKlass.inline.hpp"
#include "oops/oop.inline.hpp"

void InstanceRefKlass::update_nonstatic_oop_maps(Klass* k) {
  // Clear the nonstatic oop-map entries corresponding to referent
  // and nextPending field.  They are treated specially by the
  // garbage collector.
  // The discovered field is used only by the garbage collector
  // and is also treated specially.
  InstanceKlass* ik = InstanceKlass::cast(k);

  // Check that we have the right class
  debug_only(static bool first_time = true);
  assert(k == SystemDictionary::Reference_klass() && first_time,
         "Invalid update of maps");
  debug_only(first_time = false);
  assert(ik->nonstatic_oop_map_count() == 1, "just checking");

  OopMapBlock* map = ik->start_of_nonstatic_oop_maps();

  // Check that the current map is (2,4) - currently points at field with
  // offset 2 (words) and has 4 map entries.
  debug_only(int offset = java_lang_ref_Reference::referent_offset);
  debug_only(unsigned int count = ((java_lang_ref_Reference::discovered_offset -
    java_lang_ref_Reference::referent_offset)/heapOopSize) + 1);

  if (UseSharedSpaces) {
    assert(map->offset() == java_lang_ref_Reference::queue_offset &&
           map->count() == 1, "just checking");
  } else {
    assert(map->offset() == offset && map->count() == count,
           "just checking");

    // Update map to (3,1) - point to offset of 3 (words) with 1 map entry.
    map->set_offset(java_lang_ref_Reference::queue_offset);
    map->set_count(1);
  }
}


// Verification

void InstanceRefKlass::oop_verify_on(oop obj, outputStream* st) {
  InstanceKlass::oop_verify_on(obj, st);
  // Verify referent field
  oop referent = java_lang_ref_Reference::referent(obj);
  if (referent != NULL) {
    guarantee(referent->is_oop(), "referent field heap failed");
  }
  // Verify next field
  oop next = java_lang_ref_Reference::next(obj);
  if (next != NULL) {
    guarantee(next->is_oop(), "next field should be an oop");
    guarantee(next->is_instance(), "next field should be an instance");
    guarantee(InstanceKlass::cast(next->klass())->is_reference_instance_klass(), "next field verify failed");
  }
}