src/hotspot/share/compiler/oopMap.cpp

/*
 * Copyright (c) 1998, 2025, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "code/codeBlob.hpp"
#include "code/codeCache.hpp"
#include "code/nmethod.hpp"
#include "code/scopeDesc.hpp"
#include "compiler/oopMap.inline.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/iterator.hpp"
#include "memory/resourceArea.hpp"
#include "oops/compressedOops.hpp"
#include "runtime/atomic.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/signature.hpp"
#include "runtime/stackWatermarkSet.inline.hpp"
#include "utilities/align.hpp"
#include "utilities/lockFreeStack.hpp"
#ifdef COMPILER1
#include "c1/c1_Defs.hpp"
#endif
#ifdef COMPILER2
#include "opto/optoreg.hpp"
#endif
#if INCLUDE_JVMCI
#include "jvmci/jvmci_globals.hpp"
#endif

static_assert(sizeof(oop) == sizeof(intptr_t), "Derived pointer sanity check");

static inline intptr_t derived_pointer_value(derived_pointer p) {
  return static_cast<intptr_t>(p);
}

static inline derived_pointer to_derived_pointer(intptr_t obj) {
  return static_cast<derived_pointer>(obj);
}

static inline intptr_t operator-(derived_pointer p, derived_pointer p1) {
  return derived_pointer_value(p) - derived_pointer_value(p1);
}

static inline derived_pointer operator+(derived_pointer p, intptr_t offset) {
  return static_cast<derived_pointer>(derived_pointer_value(p) + offset);
}

// OopMapStream

OopMapStream::OopMapStream(const OopMap* oop_map)
  : _stream(oop_map->write_stream()->buffer()) {
  _size = oop_map->omv_count();
  _position = 0;
  _valid_omv = false;
}

OopMapStream::OopMapStream(const ImmutableOopMap* oop_map)
  : _stream(oop_map->data_addr()) {
  _size = oop_map->count();
  _position = 0;
  _valid_omv = false;
}

void OopMapStream::find_next() {
  if (_position++ < _size) {
    _omv.read_from(&_stream);
    _valid_omv = true;
    return;
  }
  _valid_omv = false;
}


// OopMap

// frame_size units are stack-slots (4 bytes) NOT intptr_t; we can name odd
// slots to hold 4-byte values like ints and floats in the LP64 build.
OopMap::OopMap(int frame_size, int arg_count) {
  // OopMaps are usually quite so small, so pick a small initial size
  set_write_stream(new CompressedWriteStream(32));
  set_omv_count(0);
  _num_oops = 0;
  _has_derived_oops = false;
  _index = -1;

#ifdef ASSERT
  _locs_length = VMRegImpl::stack2reg(0)->value() + frame_size + arg_count;
  _locs_used   = NEW_RESOURCE_ARRAY(OopMapValue::oop_types, _locs_length);
  for(int i = 0; i < _locs_length; i++) _locs_used[i] = OopMapValue::unused_value;
#endif
}


OopMap::OopMap(OopMap::DeepCopyToken, OopMap* source) {
  // This constructor does a deep copy
  // of the source OopMap.
  set_write_stream(new CompressedWriteStream(source->omv_count() * 2));
  set_omv_count(0);
  set_offset(source->offset());
  _num_oops = source->num_oops();
  _has_derived_oops = source->has_derived_oops();
  _index = -1;

#ifdef ASSERT
  _locs_length = source->_locs_length;
  _locs_used = NEW_RESOURCE_ARRAY(OopMapValue::oop_types, _locs_length);
  for(int i = 0; i < _locs_length; i++) _locs_used[i] = OopMapValue::unused_value;
#endif

  // We need to copy the entries too.
  for (OopMapStream oms(source); !oms.is_done(); oms.next()) {
    OopMapValue omv = oms.current();
    omv.write_on(write_stream());
    increment_count();
  }
}


OopMap* OopMap::deep_copy() {
  return new OopMap(_deep_copy_token, this);
}

void OopMap::copy_data_to(address addr) const {
  memcpy(addr, write_stream()->buffer(), write_stream()->position());
}

class OopMapSort {
private:
  const OopMap* _map;
  OopMapValue* _values;
  int _count;

public:
  OopMapSort(const OopMap* map) : _map(map), _count(0) {
    _values = NEW_RESOURCE_ARRAY(OopMapValue, _map->omv_count());
  }

  void sort();

  void print();

  void write(CompressedWriteStream* stream) {
    for (int i = 0; i < _count; ++i) {
      _values[i].write_on(stream);
    }
  }

private:
  int find_derived_position(OopMapValue omv, int start) {
    assert(omv.type() == OopMapValue::derived_oop_value, "");

    VMReg base = omv.content_reg();
    int i = start;

    for (; i < _count; ++i) {
      if (base == _values[i].reg()) {

        for (int n = i + 1; n < _count; ++n) {
          if (_values[i].type() != OopMapValue::derived_oop_value || _values[i].content_reg() != base) {
            return n;
          }

          if (derived_cost(_values[i]) > derived_cost(omv)) {
            return n;
          }
        }
        return _count;
      }
    }

    assert(false, "failed to find base");
    return -1;
  }

  int find_position(OopMapValue omv, int start) {
    assert(omv.type() != OopMapValue::derived_oop_value, "");

    int i = start;
    for (; i < _count; ++i) {
      if (omv_cost(_values[i]) > omv_cost(omv)) {
        return i;
      }
    }
    assert(i < _map->omv_count(), "bounds check");
    return i;
  }

  void insert(OopMapValue value, int pos) {
    assert(pos >= 0 && pos < _map->omv_count(), "bounds check");
    assert(pos <= _count, "sanity");

    if (pos < _count) {
      OopMapValue prev = _values[pos];

      for (int i = pos; i < _count; ++i) {
        OopMapValue tmp = _values[i+1];
        _values[i+1] = prev;
        prev = tmp;
      }
    }
    _values[pos] = value;

    ++_count;
  }

  int omv_cost(OopMapValue omv) {
    assert(omv.type() == OopMapValue::oop_value || omv.type() == OopMapValue::narrowoop_value, "");
    return reg_cost(omv.reg());
  }

  int reg_cost(VMReg reg) {
    if (reg->is_reg()) {
      return 0;
    }
    return reg->reg2stack() * VMRegImpl::stack_slot_size;
  }

  int derived_cost(OopMapValue omv) {
    return reg_cost(omv.reg());
  }
};

void OopMapSort::sort() {
#ifdef ASSERT
  for (OopMapStream oms(_map); !oms.is_done(); oms.next()) {
    OopMapValue omv = oms.current();
    assert(omv.type() == OopMapValue::oop_value || omv.type() == OopMapValue::narrowoop_value ||
           omv.type() == OopMapValue::derived_oop_value || omv.type() == OopMapValue::callee_saved_value, "");
  }
#endif

  for (OopMapStream oms(_map); !oms.is_done(); oms.next()) {
    if (oms.current().type() == OopMapValue::callee_saved_value) {
      insert(oms.current(), _count);
    }
  }

  int start = _count;
  for (OopMapStream oms(_map); !oms.is_done(); oms.next()) {
    OopMapValue omv = oms.current();
    if (omv.type() == OopMapValue::oop_value || omv.type() == OopMapValue::narrowoop_value) {
      int pos = find_position(omv, start);
      insert(omv, pos);
    }
  }

  for (OopMapStream oms(_map); !oms.is_done(); oms.next()) {
    OopMapValue omv = oms.current();
    if (omv.type() == OopMapValue::derived_oop_value) {
      int pos = find_derived_position(omv, start);
      assert(pos > 0, "");
      insert(omv, pos);
    }
  }
}

void OopMapSort::print() {
  for (int i = 0; i < _count; ++i) {
    OopMapValue omv = _values[i];
    if (omv.type() == OopMapValue::oop_value || omv.type() == OopMapValue::narrowoop_value) {
      if (omv.reg()->is_reg()) {
        tty->print_cr("[%c][%d] -> reg (%d)", omv.type() == OopMapValue::narrowoop_value ? 'n' : 'o', i, omv.reg()->value());
      } else {
        tty->print_cr("[%c][%d] -> stack (%d)", omv.type() == OopMapValue::narrowoop_value ? 'n' : 'o', i, omv.reg()->reg2stack() * VMRegImpl::stack_slot_size);
      }
    } else {
      if (omv.content_reg()->is_reg()) {
        tty->print_cr("[d][%d] -> reg (%d) stack (%d)", i, omv.content_reg()->value(), omv.reg()->reg2stack() * VMRegImpl::stack_slot_size);
      } else if (omv.reg()->is_reg()) {
        tty->print_cr("[d][%d] -> stack (%d) reg (%d)", i, omv.content_reg()->reg2stack() * VMRegImpl::stack_slot_size, omv.reg()->value());
      } else {
        int derived_offset = omv.reg()->reg2stack() * VMRegImpl::stack_slot_size;
        int base_offset = omv.content_reg()->reg2stack() * VMRegImpl::stack_slot_size;
        tty->print_cr("[d][%d] -> stack (%x) stack (%x)", i, base_offset, derived_offset);
      }
    }
  }
}

void OopMap::copy_and_sort_data_to(address addr) const {
  OopMapSort sort(this);
  sort.sort();
  CompressedWriteStream* stream = new CompressedWriteStream(_write_stream->position());
  sort.write(stream);

  assert(stream->position() == write_stream()->position(), "");
  memcpy(addr, stream->buffer(), stream->position());
}

int OopMap::heap_size() const {
  int size = sizeof(OopMap);
  int align = sizeof(void *) - 1;
  size += write_stream()->position();
  // Align to a reasonable ending point
  size = ((size+align) & ~align);
  return size;
}

// frame_size units are stack-slots (4 bytes) NOT intptr_t; we can name odd
// slots to hold 4-byte values like ints and floats in the LP64 build.
void OopMap::set_xxx(VMReg reg, OopMapValue::oop_types x, VMReg optional) {

  assert(reg->value() < _locs_length, "too big reg value for stack size");
  assert( _locs_used[reg->value()] == OopMapValue::unused_value, "cannot insert twice" );
  DEBUG_ONLY( _locs_used[reg->value()] = x; )

  OopMapValue o(reg, x, optional);
  o.write_on(write_stream());
  increment_count();
  if (x == OopMapValue::oop_value || x == OopMapValue::narrowoop_value) {
    increment_num_oops();
  } else if (x == OopMapValue::derived_oop_value) {
    set_has_derived_oops(true);
  }
}


void OopMap::set_oop(VMReg reg) {
  set_xxx(reg, OopMapValue::oop_value, VMRegImpl::Bad());
}


void OopMap::set_narrowoop(VMReg reg) {
  set_xxx(reg, OopMapValue::narrowoop_value, VMRegImpl::Bad());
}


void OopMap::set_callee_saved(VMReg reg, VMReg caller_machine_register ) {
  set_xxx(reg, OopMapValue::callee_saved_value, caller_machine_register);
}


void OopMap::set_derived_oop(VMReg reg, VMReg derived_from_local_register ) {
  if( reg == derived_from_local_register ) {
    // Actually an oop, derived shares storage with base,
    set_oop(reg);
  } else {
    set_xxx(reg, OopMapValue::derived_oop_value, derived_from_local_register);
  }
}

// OopMapSet

OopMapSet::OopMapSet() : _list(MinOopMapAllocation) {}

int OopMapSet::add_gc_map(int pc_offset, OopMap *map ) {
  map->set_offset(pc_offset);

#ifdef ASSERT
  if(_list.length() > 0) {
    OopMap* last = _list.last();
    if (last->offset() == map->offset() ) {
      fatal("OopMap inserted twice");
    }
    if (last->offset() > map->offset()) {
      tty->print_cr( "WARNING, maps not sorted: pc[%d]=%d, pc[%d]=%d",
                      _list.length(),last->offset(),_list.length()+1,map->offset());
    }
  }
#endif // ASSERT

  int index = add(map);
  map->_index = index;
  return index;
}

class AddDerivedOop : public DerivedOopClosure {
 public:
  enum {
    SkipNull = true, NeedsLock = true
  };

  virtual void do_derived_oop(derived_base* base, derived_pointer* derived) {
#if COMPILER2_OR_JVMCI
    DerivedPointerTable::add(derived, base);
#endif // COMPILER2_OR_JVMCI
  }
};

class ProcessDerivedOop : public DerivedOopClosure {
  OopClosure* _oop_cl;

public:
  ProcessDerivedOop(OopClosure* oop_cl) :
      _oop_cl(oop_cl) {}

  enum {
    SkipNull = true, NeedsLock = true
  };

  virtual void do_derived_oop(derived_base* base, derived_pointer* derived) {
    // All derived pointers must be processed before the base pointer of any derived pointer is processed.
    // Otherwise, if two derived pointers use the same base, the second derived pointer will get an obscured
    // offset, if the base pointer is processed in the first derived pointer.
  derived_pointer derived_base = to_derived_pointer(*reinterpret_cast<intptr_t*>(base));
    intptr_t offset = *derived - derived_base;
    *derived = derived_base;
    _oop_cl->do_oop((oop*)derived);
    *derived = *derived + offset;
  }
};

class IgnoreDerivedOop : public DerivedOopClosure {
  OopClosure* _oop_cl;

public:
  enum {
    SkipNull = true, NeedsLock = true
  };

  virtual void do_derived_oop(derived_base* base, derived_pointer* derived) {}
};

void OopMapSet::oops_do(const frame* fr, const RegisterMap* reg_map, OopClosure* f, DerivedPointerIterationMode mode) {
  find_map(fr)->oops_do(fr, reg_map, f, mode);
}

void OopMapSet::oops_do(const frame *fr, const RegisterMap* reg_map, OopClosure* f, DerivedOopClosure* df) {
  find_map(fr)->oops_do(fr, reg_map, f, df);
}

void ImmutableOopMap::oops_do(const frame *fr, const RegisterMap *reg_map,
                              OopClosure* oop_fn, DerivedOopClosure* derived_oop_fn) const {
  assert(derived_oop_fn != nullptr, "sanity");
  OopMapDo<OopClosure, DerivedOopClosure, SkipNullValue> visitor(oop_fn, derived_oop_fn);
  visitor.oops_do(fr, reg_map, this);
}

void ImmutableOopMap::oops_do(const frame *fr, const RegisterMap *reg_map,
                              OopClosure* oop_fn, DerivedPointerIterationMode derived_mode) const {
  ProcessDerivedOop process_cl(oop_fn);
  AddDerivedOop add_cl;
  IgnoreDerivedOop ignore_cl;
  DerivedOopClosure* derived_cl;
  switch (derived_mode) {
  case DerivedPointerIterationMode::_directly:
    derived_cl = &process_cl;
    break;
  case DerivedPointerIterationMode::_with_table:
    derived_cl = &add_cl;
    break;
  case DerivedPointerIterationMode::_ignore:
    derived_cl = &ignore_cl;
    break;
  default:
    guarantee (false, "unreachable");
  }
  OopMapDo<OopClosure, DerivedOopClosure, SkipNullValue> visitor(oop_fn, derived_cl);
  visitor.oops_do(fr, reg_map, this);
}

void ImmutableOopMap::all_type_do(const frame *fr, OopMapClosure* fn) const {
  OopMapValue omv;
  for (OopMapStream oms(this); !oms.is_done(); oms.next()) {
    omv = oms.current();
    if (fn->handle_type(omv.type())) {
      fn->do_value(omv.reg(), omv.type());
    }
  }
}

void ImmutableOopMap::all_type_do(const frame *fr, OopMapValue::oop_types type, OopMapClosure* fn) const {
  OopMapValue omv;
  for (OopMapStream oms(this); !oms.is_done(); oms.next()) {
    omv = oms.current();
    if (omv.type() == type) {
      fn->do_value(omv.reg(), omv.type());
    }
  }
}

static void update_register_map1(const ImmutableOopMap* oopmap, const frame* fr, RegisterMap* reg_map) {
  for (OopMapStream oms(oopmap); !oms.is_done(); oms.next()) {
    OopMapValue omv = oms.current();
    if (omv.type() == OopMapValue::callee_saved_value) {
      VMReg reg = omv.content_reg();
      address loc = fr->oopmapreg_to_location(omv.reg(), reg_map);
      reg_map->set_location(reg, loc);
    }
  }
}

// Update callee-saved register info for the following frame
void ImmutableOopMap::update_register_map(const frame *fr, RegisterMap *reg_map) const {
  CodeBlob* cb = fr->cb();
  assert(cb != nullptr, "no codeblob");
  // Any reg might be saved by a safepoint handler (see generate_handler_blob).
  assert( reg_map->_update_for_id == nullptr || fr->is_older(reg_map->_update_for_id),
         "already updated this map; do not 'update' it twice!" );
  DEBUG_ONLY(reg_map->_update_for_id = fr->id());

  // Check if caller must update oop argument
  assert((reg_map->include_argument_oops() ||
          !cb->caller_must_gc_arguments(reg_map->thread())),
         "include_argument_oops should already be set");

  // Scan through oopmap and find location of all callee-saved registers
  // (we do not do update in place, since info could be overwritten)

  update_register_map1(this, fr, reg_map);
}

const ImmutableOopMap* OopMapSet::find_map(const frame *fr) {
  return find_map(fr->cb(), fr->pc());
}

const ImmutableOopMap* OopMapSet::find_map(const CodeBlob* cb, address pc) {
  assert(cb != nullptr, "no codeblob");
  const ImmutableOopMap* map = cb->oop_map_for_return_address(pc);
  assert(map != nullptr, "no ptr map found");
  return map;
}

// Update callee-saved register info for the following frame
void OopMapSet::update_register_map(const frame *fr, RegisterMap *reg_map) {
  find_map(fr)->update_register_map(fr, reg_map);
}

//=============================================================================
// Non-Product code

#ifndef PRODUCT
void OopMapSet::trace_codeblob_maps(const frame *fr, const RegisterMap *reg_map) {
  // Print oopmap and regmap
  tty->print_cr("------ ");
  CodeBlob* cb = fr->cb();
  const ImmutableOopMapSet* maps = cb->oop_maps();
  const ImmutableOopMap* map = cb->oop_map_for_return_address(fr->pc());
  map->print();
  if( cb->is_nmethod() ) {
    nmethod* nm = (nmethod*)cb;
    // native wrappers have no scope data, it is implied
    if (nm->is_native_method()) {
      tty->print("bci: 0 (native)");
    } else {
      ScopeDesc* scope  = nm->scope_desc_at(fr->pc());
      tty->print("bci: %d ",scope->bci());
    }
  }
  tty->cr();
  fr->print_on(tty);
  tty->print("     ");
  cb->print_value_on(tty);  tty->cr();
  if (reg_map != nullptr) {
    reg_map->print();
  }
  tty->print_cr("------ ");

}
#endif // PRODUCT

// Printing code is present in product build for -XX:+PrintAssembly.

static
void print_register_type(OopMapValue::oop_types x, VMReg optional,
                         outputStream* st) {
  switch( x ) {
  case OopMapValue::oop_value:
    st->print("Oop");
    break;
  case OopMapValue::narrowoop_value:
    st->print("NarrowOop");
    break;
  case OopMapValue::callee_saved_value:
    st->print("Callers_");
    optional->print_on(st);
    break;
  case OopMapValue::derived_oop_value:
    st->print("Derived_oop_");
    optional->print_on(st);
    break;
  default:
    ShouldNotReachHere();
  }
}

void OopMapValue::print_on(outputStream* st) const {
  reg()->print_on(st);
  st->print("=");
  print_register_type(type(),content_reg(),st);
  st->print(" ");
}

void OopMapValue::print() const { print_on(tty); }

void ImmutableOopMap::print_on(outputStream* st) const {
  OopMapValue omv;
  st->print("ImmutableOopMap {");
  for(OopMapStream oms(this); !oms.is_done(); oms.next()) {
    omv = oms.current();
    omv.print_on(st);
  }
  st->print("}");
}

void ImmutableOopMap::print() const { print_on(tty); }

void OopMap::print_on(outputStream* st) const {
  OopMapValue omv;
  st->print("OopMap {");
  for(OopMapStream oms((OopMap*)this); !oms.is_done(); oms.next()) {
    omv = oms.current();
    omv.print_on(st);
  }
  // Print hex offset in addition.
  st->print("off=%d/0x%x}", (int) offset(), (int) offset());
}

void OopMap::print() const { print_on(tty); }

void ImmutableOopMapSet::print_on(outputStream* st) const {
  const ImmutableOopMap* last = nullptr;
  const int len = count();

  st->print_cr("ImmutableOopMapSet contains %d OopMaps", len);

  for (int i = 0; i < len; i++) {
    const ImmutableOopMapPair* pair = pair_at(i);
    const ImmutableOopMap* map = pair->get_from(this);
    if (map != last) {
      st->cr();
      map->print_on(st);
      st->print(" pc offsets: ");
    }
    last = map;
    st->print("%d ", pair->pc_offset());
  }
  st->cr();
}

void ImmutableOopMapSet::print() const { print_on(tty); }

void OopMapSet::print_on(outputStream* st) const {
  const int len = _list.length();

  st->print_cr("OopMapSet contains %d OopMaps", len);

  for( int i = 0; i < len; i++) {
    OopMap* m = at(i);
    st->print_cr("#%d ",i);
    m->print_on(st);
    st->cr();
  }
  st->cr();
}

void OopMapSet::print() const { print_on(tty); }

bool OopMap::equals(const OopMap* other) const {
  if (other->_omv_count != _omv_count) {
    return false;
  }
  if (other->write_stream()->position() != write_stream()->position()) {
    return false;
  }
  if (memcmp(other->write_stream()->buffer(), write_stream()->buffer(), write_stream()->position()) != 0) {
    return false;
  }
  return true;
}

int ImmutableOopMapSet::find_slot_for_offset(int pc_offset) const {
  // we might not have an oopmap at asynchronous (non-safepoint) stackwalks
  ImmutableOopMapPair* pairs = get_pairs();
  for (int i = 0; i < _count; ++i) {
    if (pairs[i].pc_offset() >= pc_offset) {
      ImmutableOopMapPair* last = &pairs[i];
      return last->pc_offset() == pc_offset ? i : -1;
    }
  }
  return -1;
}

const ImmutableOopMap* ImmutableOopMapSet::find_map_at_offset(int pc_offset) const {
  ImmutableOopMapPair* pairs = get_pairs();
  ImmutableOopMapPair* last  = nullptr;

  for (int i = 0; i < _count; ++i) {
    if (pairs[i].pc_offset() >= pc_offset) {
      last = &pairs[i];
      break;
    }
  }

  // Heal Coverity issue: potential index out of bounds access.
  guarantee(last != nullptr, "last may not be null");
  assert(last->pc_offset() == pc_offset, "oopmap not found");
  return last->get_from(this);
}

ImmutableOopMap::ImmutableOopMap(const OopMap* oopmap)
  : _count(oopmap->count()), _num_oops(oopmap->num_oops()) {
  _num_oops = oopmap->num_oops();
  _has_derived_oops = oopmap->has_derived_oops();
  address addr = data_addr();
  oopmap->copy_and_sort_data_to(addr);
}

bool ImmutableOopMap::has_any(OopMapValue::oop_types type) const {
  for (OopMapStream oms(this); !oms.is_done(); oms.next()) {
    if (oms.current().type() == type) {
      return true;
    }
  }
  return false;
}

int ImmutableOopMap::nr_of_bytes() const {
  OopMapStream oms(this);

  while (!oms.is_done()) {
    oms.next();
  }
  return sizeof(ImmutableOopMap) + oms.stream_position();
}

ImmutableOopMapBuilder::ImmutableOopMapBuilder(const OopMapSet* set) : _set(set), _empty(nullptr), _last(nullptr), _empty_offset(-1), _last_offset(-1), _offset(0), _required(-1), _new_set(nullptr) {
  _mapping = NEW_RESOURCE_ARRAY(Mapping, _set->size());
}

int ImmutableOopMapBuilder::size_for(const OopMap* map) const {
  return align_up((int)sizeof(ImmutableOopMap) + map->data_size(), 8);
}

int ImmutableOopMapBuilder::heap_size() {
  int base = sizeof(ImmutableOopMapSet);
  base = align_up(base, 8);

  // all of ours pc / offset pairs
  int pairs = _set->size() * sizeof(ImmutableOopMapPair);
  pairs = align_up(pairs, 8);

  for (int i = 0; i < _set->size(); ++i) {
    int size = 0;
    OopMap* map = _set->at(i);

    if (is_empty(map)) {
      /* only keep a single empty map in the set */
      if (has_empty()) {
        _mapping[i].set(Mapping::OOPMAP_EMPTY, _empty_offset, 0, map, _empty);
      } else {
        _empty_offset = _offset;
        _empty = map;
        size = size_for(map);
        _mapping[i].set(Mapping::OOPMAP_NEW, _offset, size, map);
      }
    } else if (is_last_duplicate(map)) {
      /* if this entry is identical to the previous one, just point it there */
      _mapping[i].set(Mapping::OOPMAP_DUPLICATE, _last_offset, 0, map, _last);
    } else {
      /* not empty, not an identical copy of the previous entry */
      size = size_for(map);
      _mapping[i].set(Mapping::OOPMAP_NEW, _offset, size, map);
      _last_offset = _offset;
      _last = map;
    }

    assert(_mapping[i]._map == map, "check");
    _offset += size;
  }

  int total = base + pairs + _offset;
  DEBUG_ONLY(total += 8);
  _required = total;
  return total;
}

void ImmutableOopMapBuilder::fill_pair(ImmutableOopMapPair* pair, const OopMap* map, int offset, const ImmutableOopMapSet* set) {
  assert(offset < set->nr_of_bytes(), "check");
  new ((address) pair) ImmutableOopMapPair(map->offset(), offset);
}

int ImmutableOopMapBuilder::fill_map(ImmutableOopMapPair* pair, const OopMap* map, int offset, const ImmutableOopMapSet* set) {
  fill_pair(pair, map, offset, set);
  address addr = (address) pair->get_from(_new_set); // location of the ImmutableOopMap

  new (addr) ImmutableOopMap(map);
  return size_for(map);
}

void ImmutableOopMapBuilder::fill(ImmutableOopMapSet* set, int sz) {
  ImmutableOopMapPair* pairs = set->get_pairs();

  for (int i = 0; i < set->count(); ++i) {
    const OopMap* map = _mapping[i]._map;
    ImmutableOopMapPair* pair = nullptr;
    int size = 0;

    if (_mapping[i]._kind == Mapping::OOPMAP_NEW) {
      size = fill_map(&pairs[i], map, _mapping[i]._offset, set);
    } else if (_mapping[i]._kind == Mapping::OOPMAP_DUPLICATE || _mapping[i]._kind == Mapping::OOPMAP_EMPTY) {
      fill_pair(&pairs[i], map, _mapping[i]._offset, set);
    }

    //const ImmutableOopMap* nv = set->find_map_at_offset(map->offset());
    //assert(memcmp(map->data(), nv->data_addr(), map->data_size()) == 0, "check identity");
  }
}

#ifdef ASSERT
void ImmutableOopMapBuilder::verify(address buffer, int size, const ImmutableOopMapSet* set) {
  for (int i = 0; i < 8; ++i) {
    assert(buffer[size - 8 + i] == (unsigned char) 0xff, "overwritten memory check");
  }

  for (int i = 0; i < set->count(); ++i) {
    const ImmutableOopMapPair* pair = set->pair_at(i);
    assert(pair->oopmap_offset() < set->nr_of_bytes(), "check size");
    const ImmutableOopMap* map = pair->get_from(set);
    int nr_of_bytes = map->nr_of_bytes();
    assert(pair->oopmap_offset() + nr_of_bytes <= set->nr_of_bytes(), "check size + size");
  }
}
#endif

ImmutableOopMapSet* ImmutableOopMapBuilder::generate_into(address buffer) {
  DEBUG_ONLY(memset(&buffer[_required-8], 0xff, 8));

  _new_set = new (buffer) ImmutableOopMapSet(_set, _required);
  fill(_new_set, _required);

  DEBUG_ONLY(verify(buffer, _required, _new_set));

  return _new_set;
}

ImmutableOopMapSet* ImmutableOopMapBuilder::build() {
  _required = heap_size();

  // We need to allocate a chunk big enough to hold the ImmutableOopMapSet and all of its ImmutableOopMaps
  address buffer = NEW_C_HEAP_ARRAY(unsigned char, _required, mtCode);
  return generate_into(buffer);
}

ImmutableOopMapSet* ImmutableOopMapSet::build_from(const OopMapSet* oopmap_set) {
  ResourceMark mark;
  ImmutableOopMapBuilder builder(oopmap_set);
  return builder.build();
}

void ImmutableOopMapSet::operator delete(void* p) {
  FREE_C_HEAP_ARRAY(unsigned char, p);
}

//------------------------------DerivedPointerTable---------------------------

#if COMPILER2_OR_JVMCI

class DerivedPointerTable::Entry : public CHeapObj<mtCompiler> {
  derived_pointer* _location; // Location of derived pointer, also pointing to base
  intptr_t         _offset;   // Offset from base pointer
  Entry* volatile  _next;

  static Entry* volatile* next_ptr(Entry& entry) { return &entry._next; }

public:
  Entry(derived_pointer* location, intptr_t offset) :
    _location(location), _offset(offset), _next(nullptr) {}

  derived_pointer* location() const { return _location; }
  intptr_t offset() const { return _offset; }
  Entry* next() const { return _next; }

  typedef LockFreeStack<Entry, &next_ptr> List;
  static List* _list;
};

DerivedPointerTable::Entry::List* DerivedPointerTable::Entry::_list = nullptr;
bool DerivedPointerTable::_active = false;

bool DerivedPointerTable::is_empty() {
  return Entry::_list == nullptr || Entry::_list->empty();
}

void DerivedPointerTable::clear() {
  // The first time, we create the list.  Otherwise it should be
  // empty.  If not, then we have probably forgotton to call
  // update_pointers after last GC/Scavenge.
  assert (!_active, "should not be active");
  assert(is_empty(), "table not empty");
  if (Entry::_list == nullptr) {
    void* mem = NEW_C_HEAP_OBJ(Entry::List, mtCompiler);
    Entry::_list = ::new (mem) Entry::List();
  }
  _active = true;
}

void DerivedPointerTable::add(derived_pointer* derived_loc, derived_base* base_loc) {
  assert(Universe::heap()->is_in_or_null((void*)*base_loc), "not an oop");
  assert(derived_loc != (void*)base_loc, "Base and derived in same location");
  derived_pointer base_loc_as_derived_pointer =
    static_cast<derived_pointer>(reinterpret_cast<intptr_t>(base_loc));
  assert(*derived_loc != base_loc_as_derived_pointer, "location already added");
  assert(Entry::_list != nullptr, "list must exist");
  assert(is_active(), "table must be active here");
  intptr_t offset = *derived_loc - to_derived_pointer(*reinterpret_cast<intptr_t*>(base_loc));
  // This assert is invalid because derived pointers can be
  // arbitrarily far away from their base.
  // assert(offset >= -1000000, "wrong derived pointer info");

  if (TraceDerivedPointers) {
    tty->print_cr(
      "Add derived pointer@" INTPTR_FORMAT
      " - Derived: " INTPTR_FORMAT
      " Base: " INTPTR_FORMAT " (@" INTPTR_FORMAT ") (Offset: %zd)",
      p2i(derived_loc), derived_pointer_value(*derived_loc), intptr_t(*base_loc), p2i(base_loc), offset
    );
  }
  // Set derived oop location to point to base.
  *derived_loc = base_loc_as_derived_pointer;
  Entry* entry = new Entry(derived_loc, offset);
  Entry::_list->push(*entry);
}

void DerivedPointerTable::update_pointers() {
  assert(Entry::_list != nullptr, "list must exist");
  Entry* entries = Entry::_list->pop_all();
  while (entries != nullptr) {
    Entry* entry = entries;
    entries = entry->next();
    derived_pointer* derived_loc = entry->location();
    intptr_t offset  = entry->offset();
    // The derived oop was setup to point to location of base
    oop base = **reinterpret_cast<oop**>(derived_loc);
    assert(Universe::heap()->is_in_or_null(base), "must be an oop");

    derived_pointer derived_base = to_derived_pointer(cast_from_oop<intptr_t>(base));
    *derived_loc = derived_base + offset;
    assert(*derived_loc - derived_base == offset, "sanity check");

    // assert(offset >= 0 && offset <= (intptr_t)(base->size() << LogHeapWordSize), "offset: %ld base->size: %zu relative: %d", offset, base->size() << LogHeapWordSize, *(intptr_t*)derived_loc <= 0);

    if (TraceDerivedPointers) {
      tty->print_cr("Updating derived pointer@" INTPTR_FORMAT
                    " - Derived: " INTPTR_FORMAT "  Base: " INTPTR_FORMAT " (Offset: %zd)",
                    p2i(derived_loc), derived_pointer_value(*derived_loc), p2i(base), offset);
    }

    // Delete entry
    delete entry;
  }
  assert(Entry::_list->empty(), "invariant");
  _active = false;
}

#endif // COMPILER2_OR_JVMCI