jdk/src/hotspot/share/code/debugInfo.cpp

/*
 * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
 * 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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 */

#include "code/debugInfo.hpp"
#include "code/debugInfoRec.hpp"
#include "code/nmethod.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "memory/universe.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/jniHandles.inline.hpp"
#include "runtime/stackValue.hpp"

// Constructors

DebugInfoWriteStream::DebugInfoWriteStream(DebugInformationRecorder* recorder, int initial_size)
: CompressedWriteStream(initial_size) {
  _recorder = recorder;
}

// Serializing oops

void DebugInfoWriteStream::write_handle(jobject h) {
  write_int(recorder()->oop_recorder()->find_index(h));
}

void DebugInfoWriteStream::write_metadata(Metadata* h) {
  write_int(recorder()->oop_recorder()->find_index(h));
}

oop DebugInfoReadStream::read_oop() {
  // Despite these oops being found inside nmethods that are on-stack,
  // they are not kept alive by all GCs (e.g. G1 and Shenandoah).
  oop o = code()->oop_at_phantom(read_int());
  assert(oopDesc::is_oop_or_null(o), "oop only");
  return o;
}

ScopeValue* DebugInfoReadStream::read_object_value(bool is_auto_box) {
  int id = read_int();
#ifdef ASSERT
  assert(_obj_pool != nullptr, "object pool does not exist");
  for (int i = _obj_pool->length() - 1; i >= 0; i--) {
    assert(_obj_pool->at(i)->as_ObjectValue()->id() != id, "should not be read twice");
  }
#endif
  ObjectValue* result = is_auto_box ? new AutoBoxObjectValue(id) : new ObjectValue(id);
  // Cache the object since an object field could reference it.
  _obj_pool->push(result);
  result->read_object(this);
  return result;
}

ScopeValue* DebugInfoReadStream::read_object_merge_value() {
  int id = read_int();
#ifdef ASSERT
  assert(_obj_pool != nullptr, "object pool does not exist");
  for (int i = _obj_pool->length() - 1; i >= 0; i--) {
    assert(_obj_pool->at(i)->as_ObjectValue()->id() != id, "should not be read twice");
  }
#endif
  ObjectMergeValue* result = new ObjectMergeValue(id);
  _obj_pool->push(result);
  result->read_object(this);
  return result;
}

ScopeValue* DebugInfoReadStream::get_cached_object() {
  int id = read_int();
  assert(_obj_pool != nullptr, "object pool does not exist");
  for (int i = _obj_pool->length() - 1; i >= 0; i--) {
    ObjectValue* ov = _obj_pool->at(i)->as_ObjectValue();
    if (ov->id() == id) {
      return ov;
    }
  }
  ShouldNotReachHere();
  return nullptr;
}

// Serializing scope values

enum { LOCATION_CODE = 0, CONSTANT_INT_CODE = 1,  CONSTANT_OOP_CODE = 2,
                          CONSTANT_LONG_CODE = 3, CONSTANT_DOUBLE_CODE = 4,
                          OBJECT_CODE = 5,        OBJECT_ID_CODE = 6,
                          AUTO_BOX_OBJECT_CODE = 7, MARKER_CODE = 8,
                          OBJECT_MERGE_CODE = 9 };

ScopeValue* ScopeValue::read_from(DebugInfoReadStream* stream) {
  ScopeValue* result = nullptr;
  switch(stream->read_int()) {
   case LOCATION_CODE:        result = new LocationValue(stream);                        break;
   case CONSTANT_INT_CODE:    result = new ConstantIntValue(stream);                     break;
   case CONSTANT_OOP_CODE:    result = new ConstantOopReadValue(stream);                 break;
   case CONSTANT_LONG_CODE:   result = new ConstantLongValue(stream);                    break;
   case CONSTANT_DOUBLE_CODE: result = new ConstantDoubleValue(stream);                  break;
   case OBJECT_CODE:          result = stream->read_object_value(false /*is_auto_box*/); break;
   case AUTO_BOX_OBJECT_CODE: result = stream->read_object_value(true /*is_auto_box*/);  break;
   case OBJECT_MERGE_CODE:    result = stream->read_object_merge_value();                break;
   case OBJECT_ID_CODE:       result = stream->get_cached_object();                      break;
   case MARKER_CODE:          result = new MarkerValue();                                break;
   default: ShouldNotReachHere();
  }
  return result;
}

// LocationValue

LocationValue::LocationValue(DebugInfoReadStream* stream) {
  _location = Location(stream);
}

void LocationValue::write_on(DebugInfoWriteStream* stream) {
  stream->write_int(LOCATION_CODE);
  location().write_on(stream);
}

void LocationValue::print_on(outputStream* st) const {
  location().print_on(st);
}

// MarkerValue

void MarkerValue::write_on(DebugInfoWriteStream* stream) {
  stream->write_int(MARKER_CODE);
}

void MarkerValue::print_on(outputStream* st) const {
    st->print("marker");
}

// ObjectValue

void ObjectValue::set_value(oop value) {
  _value = Handle(Thread::current(), value);
}

void ObjectValue::read_object(DebugInfoReadStream* stream) {
  _is_root = stream->read_bool();
  _klass = read_from(stream);
  assert(_klass->is_constant_oop(), "should be constant java mirror oop");
  int length = stream->read_int();
  for (int i = 0; i < length; i++) {
    ScopeValue* val = read_from(stream);
    _field_values.append(val);
  }
}

void ObjectValue::write_on(DebugInfoWriteStream* stream) {
  if (is_visited()) {
    stream->write_int(OBJECT_ID_CODE);
    stream->write_int(_id);
  } else {
    set_visited(true);
    stream->write_int(is_auto_box() ? AUTO_BOX_OBJECT_CODE : OBJECT_CODE);
    stream->write_int(_id);
    stream->write_bool(_is_root);
    _klass->write_on(stream);
    int length = _field_values.length();
    stream->write_int(length);
    for (int i = 0; i < length; i++) {
      _field_values.at(i)->write_on(stream);
    }
  }
}

void ObjectValue::print_on(outputStream* st) const {
  st->print("%s[%d]", is_auto_box() ? "box_obj" : is_object_merge() ? "merge_obj" : "obj", _id);
}

void ObjectValue::print_fields_on(outputStream* st) const {
#ifndef PRODUCT
  if (is_object_merge()) {
    ObjectMergeValue* omv = (ObjectMergeValue*)this;
    st->print("selector=\"");
    omv->selector()->print_on(st);
    st->print("\"");
    ScopeValue* merge_pointer = omv->merge_pointer();
    if (!(merge_pointer->is_object() && merge_pointer->as_ObjectValue()->value()() == nullptr) &&
        !(merge_pointer->is_constant_oop() && merge_pointer->as_ConstantOopReadValue()->value()() == nullptr)) {
      st->print(", merge_pointer=\"");
      merge_pointer->print_on(st);
      st->print("\"");
    }
    GrowableArray<ScopeValue*>* possible_objects = omv->possible_objects();
    st->print(", candidate_objs=[%d", possible_objects->at(0)->as_ObjectValue()->id());
    int ncandidates = possible_objects->length();
    for (int i = 1; i < ncandidates; i++) {
      st->print(", %d", possible_objects->at(i)->as_ObjectValue()->id());
    }
    st->print("]");
  } else {
    st->print("\n        Fields: ");
    if (_field_values.length() > 0) {
      _field_values.at(0)->print_on(st);
    }
    for (int i = 1; i < _field_values.length(); i++) {
      st->print(", ");
      _field_values.at(i)->print_on(st);
    }
  }
#endif
}


// ObjectMergeValue

// Returns the ObjectValue that should be used for the local that this
// ObjectMergeValue represents. ObjectMergeValue represents allocation
// merges in C2. This method will select which path the allocation merge
// took during execution of the Trap that triggered the rematerialization
// of the object.
ObjectValue* ObjectMergeValue::select(frame& fr, RegisterMap& reg_map) {
  StackValue* sv_selector = StackValue::create_stack_value(&fr, &reg_map, _selector);
  jint selector = sv_selector->get_jint();

  // If the selector is '-1' it means that execution followed the path
  // where no scalar replacement happened.
  // Otherwise, it is the index in _possible_objects array that holds
  // the description of the scalar replaced object.
  if (selector == -1) {
    StackValue* sv_merge_pointer = StackValue::create_stack_value(&fr, &reg_map, _merge_pointer);
    _selected = new ObjectValue(id(), nullptr, false);

    // Retrieve the pointer to the real object and use it as if we had
    // allocated it during the deoptimization
    _selected->set_value(sv_merge_pointer->get_obj()());

    return _selected;
  } else {
    assert(selector < _possible_objects.length(), "sanity");
    _selected = (ObjectValue*) _possible_objects.at(selector);
    return _selected;
  }
}

Handle ObjectMergeValue::value() const {
  if (_selected != nullptr) {
    return _selected->value();
  } else {
    return Handle();
  }
}

void ObjectMergeValue::read_object(DebugInfoReadStream* stream) {
  _selector = read_from(stream);
  _merge_pointer = read_from(stream);
  int ncandidates = stream->read_int();
  for (int i = 0; i < ncandidates; i++) {
    ScopeValue* result = read_from(stream);
    assert(result->is_object(), "Candidate is not an object!");
    ObjectValue* obj = result->as_ObjectValue();
    _possible_objects.append(obj);
  }
}

void ObjectMergeValue::write_on(DebugInfoWriteStream* stream) {
  if (is_visited()) {
    stream->write_int(OBJECT_ID_CODE);
    stream->write_int(_id);
  } else {
    set_visited(true);
    stream->write_int(OBJECT_MERGE_CODE);
    stream->write_int(_id);
    _selector->write_on(stream);
    _merge_pointer->write_on(stream);
    int ncandidates = _possible_objects.length();
    stream->write_int(ncandidates);
    for (int i = 0; i < ncandidates; i++) {
      _possible_objects.at(i)->as_ObjectValue()->write_on(stream);
    }
  }
}

// ConstantIntValue

ConstantIntValue::ConstantIntValue(DebugInfoReadStream* stream) {
  _value = stream->read_signed_int();
}

void ConstantIntValue::write_on(DebugInfoWriteStream* stream) {
  stream->write_int(CONSTANT_INT_CODE);
  stream->write_signed_int(value());
}

void ConstantIntValue::print_on(outputStream* st) const {
  st->print("%d", value());
}

// ConstantLongValue

ConstantLongValue::ConstantLongValue(DebugInfoReadStream* stream) {
  _value = stream->read_long();
}

void ConstantLongValue::write_on(DebugInfoWriteStream* stream) {
  stream->write_int(CONSTANT_LONG_CODE);
  stream->write_long(value());
}

void ConstantLongValue::print_on(outputStream* st) const {
  st->print(JLONG_FORMAT, value());
}

// ConstantDoubleValue

ConstantDoubleValue::ConstantDoubleValue(DebugInfoReadStream* stream) {
  _value = stream->read_double();
}

void ConstantDoubleValue::write_on(DebugInfoWriteStream* stream) {
  stream->write_int(CONSTANT_DOUBLE_CODE);
  stream->write_double(value());
}

void ConstantDoubleValue::print_on(outputStream* st) const {
  st->print("%f", value());
}

// ConstantOopWriteValue

void ConstantOopWriteValue::write_on(DebugInfoWriteStream* stream) {
#ifdef ASSERT
  {
    ThreadInVMfromNative tiv(JavaThread::current());
    assert(JNIHandles::resolve(value()) == nullptr ||
           Universe::heap()->is_in(JNIHandles::resolve(value())),
           "Should be in heap");
 }
#endif
  stream->write_int(CONSTANT_OOP_CODE);
  stream->write_handle(value());
}

void ConstantOopWriteValue::print_on(outputStream* st) const {
  ThreadInVMfromNative tiv(JavaThread::current());
  JNIHandles::resolve(value())->print_value_on(st);
}


// ConstantOopReadValue

ConstantOopReadValue::ConstantOopReadValue(DebugInfoReadStream* stream) {
  _value = Handle(Thread::current(), stream->read_oop());
  assert(_value() == nullptr ||
         Universe::heap()->is_in(_value()), "Should be in heap");
}

void ConstantOopReadValue::write_on(DebugInfoWriteStream* stream) {
  ShouldNotReachHere();
}

void ConstantOopReadValue::print_on(outputStream* st) const {
  if (value()() != nullptr) {
    value()()->print_value_on(st);
  } else {
    st->print("null");
  }
}


// MonitorValue

MonitorValue::MonitorValue(ScopeValue* owner, Location basic_lock, bool eliminated) {
  _owner       = owner;
  _basic_lock  = basic_lock;
  _eliminated  = eliminated;
}

MonitorValue::MonitorValue(DebugInfoReadStream* stream) {
  _basic_lock  = Location(stream);
  _owner       = ScopeValue::read_from(stream);
  _eliminated  = (stream->read_bool() != 0);
}

void MonitorValue::write_on(DebugInfoWriteStream* stream) {
  _basic_lock.write_on(stream);
  _owner->write_on(stream);
  stream->write_bool(_eliminated);
}

#ifndef PRODUCT
void MonitorValue::print_on(outputStream* st) const {
  st->print("monitor{");
  owner()->print_on(st);
  st->print(",");
  basic_lock().print_on(st);
  st->print("}");
  if (_eliminated) {
    st->print(" (eliminated)");
  }
}
#endif