compiler/oat_writer.cc

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "oat_writer.h"

#include <zlib.h>

#include "base/allocator.h"
#include "base/bit_vector.h"
#include "base/stl_util.h"
#include "base/unix_file/fd_file.h"
#include "class_linker.h"
#include "compiled_class.h"
#include "dex_file-inl.h"
#include "dex/verification_results.h"
#include "gc/space/space.h"
#include "image_writer.h"
#include "mirror/art_method-inl.h"
#include "mirror/array.h"
#include "mirror/class_loader.h"
#include "mirror/object-inl.h"
#include "os.h"
#include "output_stream.h"
#include "safe_map.h"
#include "scoped_thread_state_change.h"
#include "handle_scope-inl.h"
#include "utils/arm/assembler_thumb2.h"
#include "utils/arm64/assembler_arm64.h"
#include "verifier/method_verifier.h"

namespace art {

class OatWriter::RelativeCallPatcher {
 public:
  virtual ~RelativeCallPatcher() { }

  // Reserve space for relative call thunks if needed, return adjusted offset.
  // After all methods have been processed it's call one last time with compiled_method == nullptr.
  virtual uint32_t ReserveSpace(uint32_t offset, const CompiledMethod* compiled_method) = 0;

  // Write relative call thunks if needed, return adjusted offset.
  virtual uint32_t WriteThunks(OutputStream* out, uint32_t offset) = 0;

  // Patch method code. The input displacement is relative to the patched location,
  // the patcher may need to adjust it if the correct base is different.
  virtual void Patch(std::vector<uint8_t>* code, uint32_t literal_offset, uint32_t patch_offset,
                     uint32_t target_offset) = 0;

 protected:
  RelativeCallPatcher() { }

 private:
  DISALLOW_COPY_AND_ASSIGN(RelativeCallPatcher);
};

class OatWriter::NoRelativeCallPatcher FINAL : public RelativeCallPatcher {
 public:
  NoRelativeCallPatcher() { }

  uint32_t ReserveSpace(uint32_t offset,
                        const CompiledMethod* compiled_method ATTRIBUTE_UNUSED) OVERRIDE {
    return offset;  // No space reserved; no patches expected.
  }

  uint32_t WriteThunks(OutputStream* out ATTRIBUTE_UNUSED, uint32_t offset) OVERRIDE {
    return offset;  // No thunks added; no patches expected.
  }

  void Patch(std::vector<uint8_t>* code ATTRIBUTE_UNUSED, uint32_t literal_offset ATTRIBUTE_UNUSED,
             uint32_t patch_offset ATTRIBUTE_UNUSED,
             uint32_t target_offset ATTRIBUTE_UNUSED) OVERRIDE {
    LOG(FATAL) << "Unexpected relative patch.";
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(NoRelativeCallPatcher);
};

class OatWriter::X86RelativeCallPatcher FINAL : public RelativeCallPatcher {
 public:
  X86RelativeCallPatcher() { }

  uint32_t ReserveSpace(uint32_t offset,
                        const CompiledMethod* compiled_method ATTRIBUTE_UNUSED) OVERRIDE {
    return offset;  // No space reserved; no limit on relative call distance.
  }

  uint32_t WriteThunks(OutputStream* out ATTRIBUTE_UNUSED, uint32_t offset) OVERRIDE {
    return offset;  // No thunks added; no limit on relative call distance.
  }

  void Patch(std::vector<uint8_t>* code, uint32_t literal_offset, uint32_t patch_offset,
             uint32_t target_offset) OVERRIDE {
    DCHECK_LE(literal_offset + 4u, code->size());
    // Unsigned arithmetic with its well-defined overflow behavior is just fine here.
    uint32_t displacement = target_offset - patch_offset;
    displacement -= kPcDisplacement;  // The base PC is at the end of the 4-byte patch.

    typedef __attribute__((__aligned__(1))) int32_t unaligned_int32_t;
    reinterpret_cast<unaligned_int32_t*>(&(*code)[literal_offset])[0] = displacement;
  }

 private:
  // PC displacement from patch location; x86 PC for relative calls points to the next
  // instruction and the patch location is 4 bytes earlier.
  static constexpr int32_t kPcDisplacement = 4;

  DISALLOW_COPY_AND_ASSIGN(X86RelativeCallPatcher);
};

class OatWriter::ArmBaseRelativeCallPatcher : public RelativeCallPatcher {
 public:
  ArmBaseRelativeCallPatcher(OatWriter* writer,
                             InstructionSet instruction_set, std::vector<uint8_t> thunk_code,
                             uint32_t max_positive_displacement, uint32_t max_negative_displacement)
      : writer_(writer), instruction_set_(instruction_set), thunk_code_(thunk_code),
        max_positive_displacement_(max_positive_displacement),
        max_negative_displacement_(max_negative_displacement),
        thunk_locations_(), current_thunk_to_write_(0u), unprocessed_patches_() {
  }

  uint32_t ReserveSpace(uint32_t offset, const CompiledMethod* compiled_method) OVERRIDE {
    // NOTE: The final thunk can be reserved from InitCodeMethodVisitor::EndClass() while it
    // may be written early by WriteCodeMethodVisitor::VisitMethod() for a deduplicated chunk
    // of code. To avoid any alignment discrepancies for the final chunk, we always align the
    // offset after reserving of writing any chunk.
    if (UNLIKELY(compiled_method == nullptr)) {
      uint32_t aligned_offset = CompiledMethod::AlignCode(offset, instruction_set_);
      bool needs_thunk = ReserveSpaceProcessPatches(aligned_offset);
      if (needs_thunk) {
        thunk_locations_.push_back(aligned_offset);
        offset = CompiledMethod::AlignCode(aligned_offset + thunk_code_.size(), instruction_set_);
      }
      return offset;
    }
    DCHECK(compiled_method->GetQuickCode() != nullptr);
    uint32_t quick_code_size = compiled_method->GetQuickCode()->size();
    uint32_t quick_code_offset = compiled_method->AlignCode(offset) + sizeof(OatQuickMethodHeader);
    uint32_t next_aligned_offset = compiled_method->AlignCode(quick_code_offset + quick_code_size);
    if (!unprocessed_patches_.empty() &&
        next_aligned_offset - unprocessed_patches_.front().second > max_positive_displacement_) {
      bool needs_thunk = ReserveSpaceProcessPatches(next_aligned_offset);
      if (needs_thunk) {
        // A single thunk will cover all pending patches.
        unprocessed_patches_.clear();
        uint32_t thunk_location = compiled_method->AlignCode(offset);
        thunk_locations_.push_back(thunk_location);
        offset = CompiledMethod::AlignCode(thunk_location + thunk_code_.size(), instruction_set_);
      }
    }
    for (const LinkerPatch& patch : compiled_method->GetPatches()) {
      if (patch.Type() == kLinkerPatchCallRelative) {
        unprocessed_patches_.emplace_back(patch.TargetMethod(),
                                          quick_code_offset + patch.LiteralOffset());
      }
    }
    return offset;
  }

  uint32_t WriteThunks(OutputStream* out, uint32_t offset) OVERRIDE {
    if (current_thunk_to_write_ == thunk_locations_.size()) {
      return offset;
    }
    uint32_t aligned_offset = CompiledMethod::AlignCode(offset, instruction_set_);
    if (UNLIKELY(aligned_offset == thunk_locations_[current_thunk_to_write_])) {
      ++current_thunk_to_write_;
      uint32_t aligned_code_delta = aligned_offset - offset;
      if (aligned_code_delta != 0u && !writer_->WriteCodeAlignment(out, aligned_code_delta)) {
        return 0u;
      }
      if (!out->WriteFully(thunk_code_.data(), thunk_code_.size())) {
        return 0u;
      }
      writer_->size_relative_call_thunks_ += thunk_code_.size();
      uint32_t thunk_end_offset = aligned_offset + thunk_code_.size();
      // Align after writing chunk, see the ReserveSpace() above.
      offset = CompiledMethod::AlignCode(thunk_end_offset, instruction_set_);
      aligned_code_delta = offset - thunk_end_offset;
      if (aligned_code_delta != 0u && !writer_->WriteCodeAlignment(out, aligned_code_delta)) {
        return 0u;
      }
    }
    return offset;
  }

 protected:
  uint32_t CalculateDisplacement(uint32_t patch_offset, uint32_t target_offset) {
    // Unsigned arithmetic with its well-defined overflow behavior is just fine here.
    uint32_t displacement = target_offset - patch_offset;
    // NOTE: With unsigned arithmetic we do mean to use && rather than || below.
    if (displacement > max_positive_displacement_ && displacement < -max_negative_displacement_) {
      // Unwritten thunks have higher offsets, check if it's within range.
      DCHECK(current_thunk_to_write_ == thunk_locations_.size() ||
             thunk_locations_[current_thunk_to_write_] > patch_offset);
      if (current_thunk_to_write_ != thunk_locations_.size() &&
          thunk_locations_[current_thunk_to_write_] - patch_offset < max_positive_displacement_) {
        displacement = thunk_locations_[current_thunk_to_write_] - patch_offset;
      } else {
        // We must have a previous thunk then.
        DCHECK_NE(current_thunk_to_write_, 0u);
        DCHECK_LT(thunk_locations_[current_thunk_to_write_ - 1], patch_offset);
        displacement = thunk_locations_[current_thunk_to_write_ - 1] - patch_offset;
        DCHECK(displacement >= -max_negative_displacement_);
      }
    }
    return displacement;
  }

 private:
  bool ReserveSpaceProcessPatches(uint32_t next_aligned_offset) {
    // Process as many patches as possible, stop only on unresolved targets or calls too far back.
    while (!unprocessed_patches_.empty()) {
      uint32_t patch_offset = unprocessed_patches_.front().second;
      auto it = writer_->method_offset_map_.find(unprocessed_patches_.front().first);
      if (it == writer_->method_offset_map_.end()) {
        // If still unresolved, check if we have a thunk within range.
        DCHECK(thunk_locations_.empty() || thunk_locations_.back() <= patch_offset);
        if (thunk_locations_.empty() ||
            patch_offset - thunk_locations_.back() > max_negative_displacement_) {
          return next_aligned_offset - patch_offset > max_positive_displacement_;
        }
      } else if (it->second >= patch_offset) {
        DCHECK_LE(it->second - patch_offset, max_positive_displacement_);
      } else {
        // When calling back, check if we have a thunk that's closer than the actual target.
        uint32_t target_offset = (thunk_locations_.empty() || it->second > thunk_locations_.back())
            ? it->second
            : thunk_locations_.back();
        DCHECK_GT(patch_offset, target_offset);
        if (patch_offset - target_offset > max_negative_displacement_) {
          return true;
        }
      }
      unprocessed_patches_.pop_front();
    }
    return false;
  }

  OatWriter* const writer_;
  const InstructionSet instruction_set_;
  const std::vector<uint8_t> thunk_code_;
  const uint32_t max_positive_displacement_;
  const uint32_t max_negative_displacement_;
  std::vector<uint32_t> thunk_locations_;
  size_t current_thunk_to_write_;

  // ReserveSpace() tracks unprocessed patches.
  typedef std::pair<MethodReference, uint32_t> UnprocessedPatch;
  std::deque<UnprocessedPatch> unprocessed_patches_;

  DISALLOW_COPY_AND_ASSIGN(ArmBaseRelativeCallPatcher);
};

class OatWriter::Thumb2RelativeCallPatcher FINAL : public ArmBaseRelativeCallPatcher {
 public:
  explicit Thumb2RelativeCallPatcher(OatWriter* writer)
      : ArmBaseRelativeCallPatcher(writer, kThumb2, CompileThunkCode(),
                                   kMaxPositiveDisplacement, kMaxNegativeDisplacement) {
  }

  void Patch(std::vector<uint8_t>* code, uint32_t literal_offset, uint32_t patch_offset,
             uint32_t target_offset) OVERRIDE {
    DCHECK_LE(literal_offset + 4u, code->size());
    DCHECK_EQ(literal_offset & 1u, 0u);
    DCHECK_EQ(patch_offset & 1u, 0u);
    DCHECK_EQ(target_offset & 1u, 1u);  // Thumb2 mode bit.
    uint32_t displacement = CalculateDisplacement(patch_offset, target_offset & ~1u);
    displacement -= kPcDisplacement;  // The base PC is at the end of the 4-byte patch.
    DCHECK_EQ(displacement & 1u, 0u);
    DCHECK((displacement >> 24) == 0u || (displacement >> 24) == 255u);  // 25-bit signed.
    uint32_t signbit = (displacement >> 31) & 0x1;
    uint32_t i1 = (displacement >> 23) & 0x1;
    uint32_t i2 = (displacement >> 22) & 0x1;
    uint32_t imm10 = (displacement >> 12) & 0x03ff;
    uint32_t imm11 = (displacement >> 1) & 0x07ff;
    uint32_t j1 = i1 ^ (signbit ^ 1);
    uint32_t j2 = i2 ^ (signbit ^ 1);
    uint32_t value = (signbit << 26) | (j1 << 13) | (j2 << 11) | (imm10 << 16) | imm11;
    value |= 0xf000d000;  // BL

    uint8_t* addr = &(*code)[literal_offset];
    // Check that we're just overwriting an existing BL.
    DCHECK_EQ(addr[1] & 0xf8, 0xf0);
    DCHECK_EQ(addr[3] & 0xd0, 0xd0);
    // Write the new BL.
    addr[0] = (value >> 16) & 0xff;
    addr[1] = (value >> 24) & 0xff;
    addr[2] = (value >> 0) & 0xff;
    addr[3] = (value >> 8) & 0xff;
  }

 private:
  static std::vector<uint8_t> CompileThunkCode() {
    // The thunk just uses the entry point in the ArtMethod. This works even for calls
    // to the generic JNI and interpreter trampolines.
    arm::Thumb2Assembler assembler;
    assembler.LoadFromOffset(
        arm::kLoadWord, arm::PC, arm::R0,
        mirror::ArtMethod::EntryPointFromQuickCompiledCodeOffset(kArmPointerSize).Int32Value());
    assembler.bkpt(0);
    std::vector<uint8_t> thunk_code(assembler.CodeSize());
    MemoryRegion code(thunk_code.data(), thunk_code.size());
    assembler.FinalizeInstructions(code);
    return thunk_code;
  }

  // PC displacement from patch location; Thumb2 PC is always at instruction address + 4.
  static constexpr int32_t kPcDisplacement = 4;

  // Maximum positive and negative displacement measured from the patch location.
  // (Signed 25 bit displacement with the last bit 0 has range [-2^24, 2^24-2] measured from
  // the Thumb2 PC pointing right after the BL, i.e. 4 bytes later than the patch location.)
  static constexpr uint32_t kMaxPositiveDisplacement = (1u << 24) - 2 + kPcDisplacement;
  static constexpr uint32_t kMaxNegativeDisplacement = (1u << 24) - kPcDisplacement;

  DISALLOW_COPY_AND_ASSIGN(Thumb2RelativeCallPatcher);
};

class OatWriter::Arm64RelativeCallPatcher FINAL : public ArmBaseRelativeCallPatcher {
 public:
  explicit Arm64RelativeCallPatcher(OatWriter* writer)
      : ArmBaseRelativeCallPatcher(writer, kArm64, CompileThunkCode(),
                                   kMaxPositiveDisplacement, kMaxNegativeDisplacement) {
  }

  void Patch(std::vector<uint8_t>* code, uint32_t literal_offset, uint32_t patch_offset,
             uint32_t target_offset) OVERRIDE {
    DCHECK_LE(literal_offset + 4u, code->size());
    DCHECK_EQ(literal_offset & 3u, 0u);
    DCHECK_EQ(patch_offset & 3u, 0u);
    DCHECK_EQ(target_offset & 3u, 0u);
    uint32_t displacement = CalculateDisplacement(patch_offset, target_offset & ~1u);
    DCHECK_EQ(displacement & 3u, 0u);
    DCHECK((displacement >> 27) == 0u || (displacement >> 27) == 31u);  // 28-bit signed.
    uint32_t value = (displacement & 0x0fffffffu) >> 2;
    value |= 0x94000000;  // BL

    uint8_t* addr = &(*code)[literal_offset];
    // Check that we're just overwriting an existing BL.
    DCHECK_EQ(addr[3] & 0xfc, 0x94);
    // Write the new BL.
    addr[0] = (value >> 0) & 0xff;
    addr[1] = (value >> 8) & 0xff;
    addr[2] = (value >> 16) & 0xff;
    addr[3] = (value >> 24) & 0xff;
  }

 private:
  static std::vector<uint8_t> CompileThunkCode() {
    // The thunk just uses the entry point in the ArtMethod. This works even for calls
    // to the generic JNI and interpreter trampolines.
    arm64::Arm64Assembler assembler;
    Offset offset(mirror::ArtMethod::EntryPointFromQuickCompiledCodeOffset(
        kArm64PointerSize).Int32Value());
    assembler.JumpTo(ManagedRegister(arm64::X0), offset, ManagedRegister(arm64::IP0));
    // Ensure we emit the literal pool.
    assembler.EmitSlowPaths();
    std::vector<uint8_t> thunk_code(assembler.CodeSize());
    MemoryRegion code(thunk_code.data(), thunk_code.size());
    assembler.FinalizeInstructions(code);
    return thunk_code;
  }

  // Maximum positive and negative displacement measured from the patch location.
  // (Signed 28 bit displacement with the last bit 0 has range [-2^27, 2^27-4] measured from
  // the ARM64 PC pointing to the BL.)
  static constexpr uint32_t kMaxPositiveDisplacement = (1u << 27) - 4u;
  static constexpr uint32_t kMaxNegativeDisplacement = (1u << 27);

  DISALLOW_COPY_AND_ASSIGN(Arm64RelativeCallPatcher);
};

#define DCHECK_OFFSET() \
  DCHECK_EQ(static_cast<off_t>(file_offset + relative_offset), out->Seek(0, kSeekCurrent)) \
    << "file_offset=" << file_offset << " relative_offset=" << relative_offset

#define DCHECK_OFFSET_() \
  DCHECK_EQ(static_cast<off_t>(file_offset + offset_), out->Seek(0, kSeekCurrent)) \
    << "file_offset=" << file_offset << " offset_=" << offset_

OatWriter::OatWriter(const std::vector<const DexFile*>& dex_files,
                     uint32_t image_file_location_oat_checksum,
                     uintptr_t image_file_location_oat_begin,
                     int32_t image_patch_delta,
                     const CompilerDriver* compiler,
                     ImageWriter* image_writer,
                     TimingLogger* timings,
                     SafeMap<std::string, std::string>* key_value_store)
  : compiler_driver_(compiler),
    image_writer_(image_writer),
    dex_files_(&dex_files),
    size_(0u),
    oat_data_offset_(0u),
    image_file_location_oat_checksum_(image_file_location_oat_checksum),
    image_file_location_oat_begin_(image_file_location_oat_begin),
    image_patch_delta_(image_patch_delta),
    key_value_store_(key_value_store),
    oat_header_(NULL),
    size_dex_file_alignment_(0),
    size_executable_offset_alignment_(0),
    size_oat_header_(0),
    size_oat_header_key_value_store_(0),
    size_dex_file_(0),
    size_interpreter_to_interpreter_bridge_(0),
    size_interpreter_to_compiled_code_bridge_(0),
    size_jni_dlsym_lookup_(0),
    size_quick_generic_jni_trampoline_(0),
    size_quick_imt_conflict_trampoline_(0),
    size_quick_resolution_trampoline_(0),
    size_quick_to_interpreter_bridge_(0),
    size_trampoline_alignment_(0),
    size_method_header_(0),
    size_code_(0),
    size_code_alignment_(0),
    size_relative_call_thunks_(0),
    size_mapping_table_(0),
    size_vmap_table_(0),
    size_gc_map_(0),
    size_oat_dex_file_location_size_(0),
    size_oat_dex_file_location_data_(0),
    size_oat_dex_file_location_checksum_(0),
    size_oat_dex_file_offset_(0),
    size_oat_dex_file_methods_offsets_(0),
    size_oat_class_type_(0),
    size_oat_class_status_(0),
    size_oat_class_method_bitmaps_(0),
    size_oat_class_method_offsets_(0),
    method_offset_map_() {
  CHECK(key_value_store != nullptr);

  switch (compiler_driver_->GetInstructionSet()) {
    case kX86:
    case kX86_64:
      relative_call_patcher_.reset(new X86RelativeCallPatcher);
      break;
    case kArm:
      // Fall through: we generate Thumb2 code for "arm".
    case kThumb2:
      relative_call_patcher_.reset(new Thumb2RelativeCallPatcher(this));
      break;
    case kArm64:
      relative_call_patcher_.reset(new Arm64RelativeCallPatcher(this));
      break;
    default:
      relative_call_patcher_.reset(new NoRelativeCallPatcher);
      break;
  }

  size_t offset;
  {
    TimingLogger::ScopedTiming split("InitOatHeader", timings);
    offset = InitOatHeader();
  }
  {
    TimingLogger::ScopedTiming split("InitOatDexFiles", timings);
    offset = InitOatDexFiles(offset);
  }
  {
    TimingLogger::ScopedTiming split("InitDexFiles", timings);
    offset = InitDexFiles(offset);
  }
  {
    TimingLogger::ScopedTiming split("InitOatClasses", timings);
    offset = InitOatClasses(offset);
  }
  {
    TimingLogger::ScopedTiming split("InitOatMaps", timings);
    offset = InitOatMaps(offset);
  }
  {
    TimingLogger::ScopedTiming split("InitOatCode", timings);
    offset = InitOatCode(offset);
  }
  {
    TimingLogger::ScopedTiming split("InitOatCodeDexFiles", timings);
    offset = InitOatCodeDexFiles(offset);
  }
  size_ = offset;

  CHECK_EQ(dex_files_->size(), oat_dex_files_.size());
  CHECK_EQ(compiler->IsImage(), image_writer_ != nullptr);
  CHECK_EQ(compiler->IsImage(),
           key_value_store_->find(OatHeader::kImageLocationKey) == key_value_store_->end());
  CHECK_ALIGNED(image_patch_delta_, kPageSize);
}

OatWriter::~OatWriter() {
  delete oat_header_;
  STLDeleteElements(&oat_dex_files_);
  STLDeleteElements(&oat_classes_);
}

struct OatWriter::GcMapDataAccess {
  static const std::vector<uint8_t>* GetData(const CompiledMethod* compiled_method) ALWAYS_INLINE {
    return compiled_method->GetGcMap();
  }

  static uint32_t GetOffset(OatClass* oat_class, size_t method_offsets_index) ALWAYS_INLINE {
    uint32_t offset = oat_class->method_headers_[method_offsets_index].gc_map_offset_;
    return offset == 0u ? 0u :
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static void SetOffset(OatClass* oat_class, size_t method_offsets_index, uint32_t offset)
      ALWAYS_INLINE {
    oat_class->method_headers_[method_offsets_index].gc_map_offset_ =
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static const char* Name() {
    return "GC map";
  }
};

struct OatWriter::MappingTableDataAccess {
  static const std::vector<uint8_t>* GetData(const CompiledMethod* compiled_method) ALWAYS_INLINE {
    return compiled_method->GetMappingTable();
  }

  static uint32_t GetOffset(OatClass* oat_class, size_t method_offsets_index) ALWAYS_INLINE {
    uint32_t offset = oat_class->method_headers_[method_offsets_index].mapping_table_offset_;
    return offset == 0u ? 0u :
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static void SetOffset(OatClass* oat_class, size_t method_offsets_index, uint32_t offset)
      ALWAYS_INLINE {
    oat_class->method_headers_[method_offsets_index].mapping_table_offset_ =
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static const char* Name() {
    return "mapping table";
  }
};

struct OatWriter::VmapTableDataAccess {
  static const std::vector<uint8_t>* GetData(const CompiledMethod* compiled_method) ALWAYS_INLINE {
    return &compiled_method->GetVmapTable();
  }

  static uint32_t GetOffset(OatClass* oat_class, size_t method_offsets_index) ALWAYS_INLINE {
    uint32_t offset = oat_class->method_headers_[method_offsets_index].vmap_table_offset_;
    return offset == 0u ? 0u :
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static void SetOffset(OatClass* oat_class, size_t method_offsets_index, uint32_t offset)
      ALWAYS_INLINE {
    oat_class->method_headers_[method_offsets_index].vmap_table_offset_ =
        (oat_class->method_offsets_[method_offsets_index].code_offset_ & ~1) - offset;
  }

  static const char* Name() {
    return "vmap table";
  }
};

class OatWriter::DexMethodVisitor {
 public:
  DexMethodVisitor(OatWriter* writer, size_t offset)
    : writer_(writer),
      offset_(offset),
      dex_file_(nullptr),
      class_def_index_(DexFile::kDexNoIndex) {
  }

  virtual bool StartClass(const DexFile* dex_file, size_t class_def_index) {
    DCHECK(dex_file_ == nullptr);
    DCHECK_EQ(class_def_index_, DexFile::kDexNoIndex);
    dex_file_ = dex_file;
    class_def_index_ = class_def_index;
    return true;
  }

  virtual bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it) = 0;

  virtual bool EndClass() {
    if (kIsDebugBuild) {
      dex_file_ = nullptr;
      class_def_index_ = DexFile::kDexNoIndex;
    }
    return true;
  }

  size_t GetOffset() const {
    return offset_;
  }

 protected:
  virtual ~DexMethodVisitor() { }

  OatWriter* const writer_;

  // The offset is usually advanced for each visited method by the derived class.
  size_t offset_;

  // The dex file and class def index are set in StartClass().
  const DexFile* dex_file_;
  size_t class_def_index_;
};

class OatWriter::OatDexMethodVisitor : public DexMethodVisitor {
 public:
  OatDexMethodVisitor(OatWriter* writer, size_t offset)
    : DexMethodVisitor(writer, offset),
      oat_class_index_(0u),
      method_offsets_index_(0u) {
  }

  bool StartClass(const DexFile* dex_file, size_t class_def_index) {
    DexMethodVisitor::StartClass(dex_file, class_def_index);
    DCHECK_LT(oat_class_index_, writer_->oat_classes_.size());
    method_offsets_index_ = 0u;
    return true;
  }

  bool EndClass() {
    ++oat_class_index_;
    return DexMethodVisitor::EndClass();
  }

 protected:
  size_t oat_class_index_;
  size_t method_offsets_index_;
};

class OatWriter::InitOatClassesMethodVisitor : public DexMethodVisitor {
 public:
  InitOatClassesMethodVisitor(OatWriter* writer, size_t offset)
    : DexMethodVisitor(writer, offset),
      compiled_methods_(),
      num_non_null_compiled_methods_(0u) {
    compiled_methods_.reserve(256u);
  }

  bool StartClass(const DexFile* dex_file, size_t class_def_index) {
    DexMethodVisitor::StartClass(dex_file, class_def_index);
    compiled_methods_.clear();
    num_non_null_compiled_methods_ = 0u;
    return true;
  }

  bool VisitMethod(size_t class_def_method_index ATTRIBUTE_UNUSED, const ClassDataItemIterator& it) {
    // Fill in the compiled_methods_ array for methods that have a
    // CompiledMethod. We track the number of non-null entries in
    // num_non_null_compiled_methods_ since we only want to allocate
    // OatMethodOffsets for the compiled methods.
    uint32_t method_idx = it.GetMemberIndex();
    CompiledMethod* compiled_method =
        writer_->compiler_driver_->GetCompiledMethod(MethodReference(dex_file_, method_idx));
    compiled_methods_.push_back(compiled_method);
    if (compiled_method != nullptr) {
        ++num_non_null_compiled_methods_;
    }
    return true;
  }

  bool EndClass() {
    ClassReference class_ref(dex_file_, class_def_index_);
    CompiledClass* compiled_class = writer_->compiler_driver_->GetCompiledClass(class_ref);
    mirror::Class::Status status;
    if (compiled_class != NULL) {
      status = compiled_class->GetStatus();
    } else if (writer_->compiler_driver_->GetVerificationResults()->IsClassRejected(class_ref)) {
      status = mirror::Class::kStatusError;
    } else {
      status = mirror::Class::kStatusNotReady;
    }

    OatClass* oat_class = new OatClass(offset_, compiled_methods_,
                                       num_non_null_compiled_methods_, status);
    writer_->oat_classes_.push_back(oat_class);
    oat_class->UpdateChecksum(writer_->oat_header_);
    offset_ += oat_class->SizeOf();
    return DexMethodVisitor::EndClass();
  }

 private:
  std::vector<CompiledMethod*> compiled_methods_;
  size_t num_non_null_compiled_methods_;
};

class OatWriter::InitCodeMethodVisitor : public OatDexMethodVisitor {
 public:
  InitCodeMethodVisitor(OatWriter* writer, size_t offset)
    : OatDexMethodVisitor(writer, offset) {
    writer_->absolute_patch_locations_.reserve(
        writer_->compiler_driver_->GetNonRelativeLinkerPatchCount());
  }

  bool EndClass() {
    OatDexMethodVisitor::EndClass();
    if (oat_class_index_ == writer_->oat_classes_.size()) {
      offset_ = writer_->relative_call_patcher_->ReserveSpace(offset_, nullptr);
    }
    return true;
  }

  bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    OatClass* oat_class = writer_->oat_classes_[oat_class_index_];
    CompiledMethod* compiled_method = oat_class->GetCompiledMethod(class_def_method_index);

    if (compiled_method != nullptr) {
      // Derived from CompiledMethod.
      uint32_t quick_code_offset = 0;

      const std::vector<uint8_t>* quick_code = compiled_method->GetQuickCode();
      CHECK(quick_code != nullptr);
      offset_ = writer_->relative_call_patcher_->ReserveSpace(offset_, compiled_method);
      offset_ = compiled_method->AlignCode(offset_);
      DCHECK_ALIGNED_PARAM(offset_,
                           GetInstructionSetAlignment(compiled_method->GetInstructionSet()));
      uint32_t code_size = quick_code->size() * sizeof(uint8_t);
      CHECK_NE(code_size, 0U);
      uint32_t thumb_offset = compiled_method->CodeDelta();
      quick_code_offset = offset_ + sizeof(OatQuickMethodHeader) + thumb_offset;

      bool deduped = false;

      // Deduplicate code arrays.
      auto lb = dedupe_map_.lower_bound(compiled_method);
      if (lb != dedupe_map_.end() && !dedupe_map_.key_comp()(compiled_method, lb->first)) {
        quick_code_offset = lb->second;
        deduped = true;
      } else {
        dedupe_map_.PutBefore(lb, compiled_method, quick_code_offset);
      }

      MethodReference method_ref(dex_file_, it.GetMemberIndex());
      auto method_lb = writer_->method_offset_map_.lower_bound(method_ref);
      if (method_lb != writer_->method_offset_map_.end() &&
          !writer_->method_offset_map_.key_comp()(method_ref, method_lb->first)) {
        // TODO: Should this be a hard failure?
        LOG(WARNING) << "Multiple definitions of "
            << PrettyMethod(method_ref.dex_method_index, *method_ref.dex_file)
            << ((method_lb->second != quick_code_offset) ? "; OFFSET MISMATCH" : "");
      } else {
        writer_->method_offset_map_.PutBefore(method_lb, method_ref, quick_code_offset);
      }

      // Update quick method header.
      DCHECK_LT(method_offsets_index_, oat_class->method_headers_.size());
      OatQuickMethodHeader* method_header = &oat_class->method_headers_[method_offsets_index_];
      uint32_t mapping_table_offset = method_header->mapping_table_offset_;
      uint32_t vmap_table_offset = method_header->vmap_table_offset_;
      uint32_t gc_map_offset = method_header->gc_map_offset_;
      // The code offset was 0 when the mapping/vmap table offset was set, so it's set
      // to 0-offset and we need to adjust it by code_offset.
      uint32_t code_offset = quick_code_offset - thumb_offset;
      if (mapping_table_offset != 0u) {
        mapping_table_offset += code_offset;
        DCHECK_LT(mapping_table_offset, code_offset);
      }
      if (vmap_table_offset != 0u) {
        vmap_table_offset += code_offset;
        DCHECK_LT(vmap_table_offset, code_offset);
      }
      if (gc_map_offset != 0u) {
        gc_map_offset += code_offset;
        DCHECK_LT(gc_map_offset, code_offset);
      }
      uint32_t frame_size_in_bytes = compiled_method->GetFrameSizeInBytes();
      uint32_t core_spill_mask = compiled_method->GetCoreSpillMask();
      uint32_t fp_spill_mask = compiled_method->GetFpSpillMask();
      *method_header = OatQuickMethodHeader(mapping_table_offset, vmap_table_offset,
                                            gc_map_offset, frame_size_in_bytes, core_spill_mask,
                                            fp_spill_mask, code_size);

      if (!deduped) {
        // Update offsets. (Checksum is updated when writing.)
        offset_ += sizeof(*method_header);  // Method header is prepended before code.
        offset_ += code_size;
        // Record absolute patch locations.
        if (!compiled_method->GetPatches().empty()) {
          uintptr_t base_loc = offset_ - code_size - writer_->oat_header_->GetExecutableOffset();
          for (const LinkerPatch& patch : compiled_method->GetPatches()) {
            if (patch.Type() != kLinkerPatchCallRelative) {
              writer_->absolute_patch_locations_.push_back(base_loc + patch.LiteralOffset());
            }
          }
        }
      }

      if (writer_->compiler_driver_->GetCompilerOptions().GetIncludeDebugSymbols()) {
        // Record debug information for this function if we are doing that.

        std::string name = PrettyMethod(it.GetMemberIndex(), *dex_file_, true);
        if (deduped) {
          // TODO We should place the DEDUPED tag on the first instance of a deduplicated symbol
          // so that it will show up in a debuggerd crash report.
          name += " [ DEDUPED ]";
        }

        const uint32_t quick_code_start = quick_code_offset -
            writer_->oat_header_->GetExecutableOffset();
        const DexFile::CodeItem *code_item = it.GetMethodCodeItem();
        writer_->method_info_.push_back(DebugInfo(name,
              dex_file_->GetSourceFile(dex_file_->GetClassDef(class_def_index_)),
              quick_code_start, quick_code_start + code_size,
              code_item == nullptr ? nullptr : dex_file_->GetDebugInfoStream(code_item),
              compiled_method));
      }

      if (kIsDebugBuild) {
        // We expect GC maps except when the class hasn't been verified or the method is native.
        const CompilerDriver* compiler_driver = writer_->compiler_driver_;
        ClassReference class_ref(dex_file_, class_def_index_);
        CompiledClass* compiled_class = compiler_driver->GetCompiledClass(class_ref);
        mirror::Class::Status status;
        if (compiled_class != NULL) {
          status = compiled_class->GetStatus();
        } else if (compiler_driver->GetVerificationResults()->IsClassRejected(class_ref)) {
          status = mirror::Class::kStatusError;
        } else {
          status = mirror::Class::kStatusNotReady;
        }
        std::vector<uint8_t> const * gc_map = compiled_method->GetGcMap();
        if (gc_map != nullptr) {
          size_t gc_map_size = gc_map->size() * sizeof(gc_map[0]);
          bool is_native = it.MemberIsNative();
          CHECK(gc_map_size != 0 || is_native || status < mirror::Class::kStatusVerified)
              << gc_map << " " << gc_map_size << " " << (is_native ? "true" : "false") << " "
              << (status < mirror::Class::kStatusVerified) << " " << status << " "
              << PrettyMethod(it.GetMemberIndex(), *dex_file_);
        }
      }

      DCHECK_LT(method_offsets_index_, oat_class->method_offsets_.size());
      OatMethodOffsets* offsets = &oat_class->method_offsets_[method_offsets_index_];
      offsets->code_offset_ = quick_code_offset;
      ++method_offsets_index_;
    }

    return true;
  }

 private:
  // Deduplication is already done on a pointer basis by the compiler driver,
  // so we can simply compare the pointers to find out if things are duplicated.
  SafeMap<const CompiledMethod*, uint32_t, CodeOffsetsKeyComparator> dedupe_map_;
};

template <typename DataAccess>
class OatWriter::InitMapMethodVisitor : public OatDexMethodVisitor {
 public:
  InitMapMethodVisitor(OatWriter* writer, size_t offset)
    : OatDexMethodVisitor(writer, offset) {
  }

  bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it ATTRIBUTE_UNUSED)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    OatClass* oat_class = writer_->oat_classes_[oat_class_index_];
    CompiledMethod* compiled_method = oat_class->GetCompiledMethod(class_def_method_index);

    if (compiled_method != nullptr) {
      DCHECK_LT(method_offsets_index_, oat_class->method_offsets_.size());
      DCHECK_EQ(DataAccess::GetOffset(oat_class, method_offsets_index_), 0u);

      const std::vector<uint8_t>* map = DataAccess::GetData(compiled_method);
      uint32_t map_size = map == nullptr ? 0 : map->size() * sizeof((*map)[0]);
      if (map_size != 0u) {
        auto lb = dedupe_map_.lower_bound(map);
        if (lb != dedupe_map_.end() && !dedupe_map_.key_comp()(map, lb->first)) {
          DataAccess::SetOffset(oat_class, method_offsets_index_, lb->second);
        } else {
          DataAccess::SetOffset(oat_class, method_offsets_index_, offset_);
          dedupe_map_.PutBefore(lb, map, offset_);
          offset_ += map_size;
          writer_->oat_header_->UpdateChecksum(&(*map)[0], map_size);
        }
      }
      ++method_offsets_index_;
    }

    return true;
  }

 private:
  // Deduplication is already done on a pointer basis by the compiler driver,
  // so we can simply compare the pointers to find out if things are duplicated.
  SafeMap<const std::vector<uint8_t>*, uint32_t> dedupe_map_;
};

class OatWriter::InitImageMethodVisitor : public OatDexMethodVisitor {
 public:
  InitImageMethodVisitor(OatWriter* writer, size_t offset)
    : OatDexMethodVisitor(writer, offset) {
  }

  bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    OatClass* oat_class = writer_->oat_classes_[oat_class_index_];
    CompiledMethod* compiled_method = oat_class->GetCompiledMethod(class_def_method_index);

    OatMethodOffsets offsets(0u);
    if (compiled_method != nullptr) {
      DCHECK_LT(method_offsets_index_, oat_class->method_offsets_.size());
      offsets = oat_class->method_offsets_[method_offsets_index_];
      ++method_offsets_index_;
    }

    ClassLinker* linker = Runtime::Current()->GetClassLinker();
    InvokeType invoke_type = it.GetMethodInvokeType(dex_file_->GetClassDef(class_def_index_));
    // Unchecked as we hold mutator_lock_ on entry.
    ScopedObjectAccessUnchecked soa(Thread::Current());
    StackHandleScope<1> hs(soa.Self());
    Handle<mirror::DexCache> dex_cache(hs.NewHandle(linker->FindDexCache(*dex_file_)));
    mirror::ArtMethod* method = linker->ResolveMethod(*dex_file_, it.GetMemberIndex(), dex_cache,
                                                      NullHandle<mirror::ClassLoader>(),
                                                      NullHandle<mirror::ArtMethod>(),
                                                      invoke_type);
    if (method == nullptr) {
      LOG(ERROR) << "Unexpected failure to resolve a method: "
                 << PrettyMethod(it.GetMemberIndex(), *dex_file_, true);
      soa.Self()->AssertPendingException();
      mirror::Throwable* exc = soa.Self()->GetException(nullptr);
      std::string dump = exc->Dump();
      LOG(FATAL) << dump;
    }
    method->SetQuickOatCodeOffset(offsets.code_offset_);

    return true;
  }
};

class OatWriter::WriteCodeMethodVisitor : public OatDexMethodVisitor {
 public:
  WriteCodeMethodVisitor(OatWriter* writer, OutputStream* out, const size_t file_offset,
                         size_t relative_offset) SHARED_LOCK_FUNCTION(Locks::mutator_lock_)
    : OatDexMethodVisitor(writer, relative_offset),
      out_(out),
      file_offset_(file_offset),
      soa_(Thread::Current()),
      no_thread_suspension_(soa_.Self(), "OatWriter patching"),
      class_linker_(Runtime::Current()->GetClassLinker()),
      dex_cache_(nullptr) {
    if (writer_->image_writer_ != nullptr) {
      // If we're creating the image, the address space must be ready so that we can apply patches.
      CHECK(writer_->image_writer_->IsImageAddressSpaceReady());
      patched_code_.reserve(16 * KB);
    }
  }

  ~WriteCodeMethodVisitor() UNLOCK_FUNCTION(Locks::mutator_lock_) {
  }

  bool StartClass(const DexFile* dex_file, size_t class_def_index)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    OatDexMethodVisitor::StartClass(dex_file, class_def_index);
    if (dex_cache_ == nullptr || dex_cache_->GetDexFile() != dex_file) {
      dex_cache_ = class_linker_->FindDexCache(*dex_file);
    }
    return true;
  }

  bool EndClass() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    bool result = OatDexMethodVisitor::EndClass();
    if (oat_class_index_ == writer_->oat_classes_.size()) {
      DCHECK(result);  // OatDexMethodVisitor::EndClass() never fails.
      offset_ = writer_->relative_call_patcher_->WriteThunks(out_, offset_);
      if (UNLIKELY(offset_ == 0u)) {
        PLOG(ERROR) << "Failed to write final relative call thunks";
        result = false;
      }
    }
    return result;
  }

  bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    OatClass* oat_class = writer_->oat_classes_[oat_class_index_];
    const CompiledMethod* compiled_method = oat_class->GetCompiledMethod(class_def_method_index);

    if (compiled_method != NULL) {  // ie. not an abstract method
      size_t file_offset = file_offset_;
      OutputStream* out = out_;

      const std::vector<uint8_t>* quick_code = compiled_method->GetQuickCode();
      if (quick_code != nullptr) {
        offset_ = writer_->relative_call_patcher_->WriteThunks(out, offset_);
        if (offset_ == 0u) {
          ReportWriteFailure("relative call thunk", it);
          return false;
        }
        uint32_t aligned_offset = compiled_method->AlignCode(offset_);
        uint32_t aligned_code_delta = aligned_offset - offset_;
        if (aligned_code_delta != 0) {
          if (!writer_->WriteCodeAlignment(out, aligned_code_delta)) {
            ReportWriteFailure("code alignment padding", it);
            return false;
          }
          offset_ += aligned_code_delta;
          DCHECK_OFFSET_();
        }
        DCHECK_ALIGNED_PARAM(offset_,
                             GetInstructionSetAlignment(compiled_method->GetInstructionSet()));
        uint32_t code_size = quick_code->size() * sizeof(uint8_t);
        CHECK_NE(code_size, 0U);

        // Deduplicate code arrays.
        const OatMethodOffsets& method_offsets = oat_class->method_offsets_[method_offsets_index_];
        DCHECK(method_offsets.code_offset_ < offset_ || method_offsets.code_offset_ ==
                   offset_ + sizeof(OatQuickMethodHeader) + compiled_method->CodeDelta())
            << PrettyMethod(it.GetMemberIndex(), *dex_file_);
        if (method_offsets.code_offset_ >= offset_) {
          const OatQuickMethodHeader& method_header =
              oat_class->method_headers_[method_offsets_index_];
          writer_->oat_header_->UpdateChecksum(&method_header, sizeof(method_header));
          if (!out->WriteFully(&method_header, sizeof(method_header))) {
            ReportWriteFailure("method header", it);
            return false;
          }
          writer_->size_method_header_ += sizeof(method_header);
          offset_ += sizeof(method_header);
          DCHECK_OFFSET_();

          if (!compiled_method->GetPatches().empty()) {
            patched_code_ =  *quick_code;
            quick_code = &patched_code_;
            for (const LinkerPatch& patch : compiled_method->GetPatches()) {
              if (patch.Type() == kLinkerPatchCallRelative) {
                // NOTE: Relative calls across oat files are not supported.
                uint32_t target_offset = GetTargetOffset(patch);
                uint32_t literal_offset = patch.LiteralOffset();
                writer_->relative_call_patcher_->Patch(&patched_code_, literal_offset,
                                                       offset_ + literal_offset, target_offset);
              } else if (patch.Type() == kLinkerPatchCall) {
                uint32_t target_offset = GetTargetOffset(patch);
                PatchCodeAddress(&patched_code_, patch.LiteralOffset(), target_offset);
              } else if (patch.Type() == kLinkerPatchMethod) {
                mirror::ArtMethod* method = GetTargetMethod(patch);
                PatchObjectAddress(&patched_code_, patch.LiteralOffset(), method);
              } else if (patch.Type() == kLinkerPatchType) {
                mirror::Class* type = GetTargetType(patch);
                PatchObjectAddress(&patched_code_, patch.LiteralOffset(), type);
              }
            }
          }

          writer_->oat_header_->UpdateChecksum(&(*quick_code)[0], code_size);
          if (!out->WriteFully(&(*quick_code)[0], code_size)) {
            ReportWriteFailure("method code", it);
            return false;
          }
          writer_->size_code_ += code_size;
          offset_ += code_size;
        }
        DCHECK_OFFSET_();
      }
      ++method_offsets_index_;
    }

    return true;
  }

 private:
  OutputStream* const out_;
  const size_t file_offset_;
  const ScopedObjectAccess soa_;
  const ScopedAssertNoThreadSuspension no_thread_suspension_;
  ClassLinker* const class_linker_;
  mirror::DexCache* dex_cache_;
  std::vector<uint8_t> patched_code_;

  void ReportWriteFailure(const char* what, const ClassDataItemIterator& it) {
    PLOG(ERROR) << "Failed to write " << what << " for "
        << PrettyMethod(it.GetMemberIndex(), *dex_file_) << " to " << out_->GetLocation();
  }

  mirror::ArtMethod* GetTargetMethod(const LinkerPatch& patch)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    MethodReference ref = patch.TargetMethod();
    mirror::DexCache* dex_cache =
        (dex_file_ == ref.dex_file) ? dex_cache_ : class_linker_->FindDexCache(*ref.dex_file);
    mirror::ArtMethod* method = dex_cache->GetResolvedMethod(ref.dex_method_index);
    CHECK(method != nullptr);
    return method;
  }

  uint32_t GetTargetOffset(const LinkerPatch& patch) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    auto target_it = writer_->method_offset_map_.find(patch.TargetMethod());
    uint32_t target_offset =
        (target_it != writer_->method_offset_map_.end()) ? target_it->second : 0u;
    // If there's no compiled code, point to the correct trampoline.
    if (UNLIKELY(target_offset == 0)) {
      mirror::ArtMethod* target = GetTargetMethod(patch);
      DCHECK(target != nullptr);
      DCHECK_EQ(target->GetQuickOatCodeOffset(), 0u);
      target_offset = target->IsNative()
          ? writer_->oat_header_->GetQuickGenericJniTrampolineOffset()
          : writer_->oat_header_->GetQuickToInterpreterBridgeOffset();
    }
    return target_offset;
  }

  mirror::Class* GetTargetType(const LinkerPatch& patch)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    mirror::DexCache* dex_cache = (dex_file_ == patch.TargetTypeDexFile())
        ? dex_cache_ : class_linker_->FindDexCache(*patch.TargetTypeDexFile());
    mirror::Class* type = dex_cache->GetResolvedType(patch.TargetTypeIndex());
    CHECK(type != nullptr);
    return type;
  }

  void PatchObjectAddress(std::vector<uint8_t>* code, uint32_t offset, mirror::Object* object)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    // NOTE: Direct method pointers across oat files don't use linker patches. However, direct
    // type pointers across oat files do. (TODO: Investigate why.)
    if (writer_->image_writer_ != nullptr) {
      object = writer_->image_writer_->GetImageAddress(object);
    }
    uint32_t address = PointerToLowMemUInt32(object);
    DCHECK_LE(offset + 4, code->size());
    uint8_t* data = &(*code)[offset];
    data[0] = address & 0xffu;
    data[1] = (address >> 8) & 0xffu;
    data[2] = (address >> 16) & 0xffu;
    data[3] = (address >> 24) & 0xffu;
  }

  void PatchCodeAddress(std::vector<uint8_t>* code, uint32_t offset, uint32_t target_offset)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    // NOTE: Direct calls across oat files don't use linker patches.
    DCHECK(writer_->image_writer_ != nullptr);
    uint32_t address = PointerToLowMemUInt32(writer_->image_writer_->GetOatFileBegin() +
                                             writer_->oat_data_offset_ + target_offset);
    DCHECK_LE(offset + 4, code->size());
    uint8_t* data = &(*code)[offset];
    data[0] = address & 0xffu;
    data[1] = (address >> 8) & 0xffu;
    data[2] = (address >> 16) & 0xffu;
    data[3] = (address >> 24) & 0xffu;
  }
};

template <typename DataAccess>
class OatWriter::WriteMapMethodVisitor : public OatDexMethodVisitor {
 public:
  WriteMapMethodVisitor(OatWriter* writer, OutputStream* out, const size_t file_offset,
                        size_t relative_offset)
    : OatDexMethodVisitor(writer, relative_offset),
      out_(out),
      file_offset_(file_offset) {
  }

  bool VisitMethod(size_t class_def_method_index, const ClassDataItemIterator& it) {
    OatClass* oat_class = writer_->oat_classes_[oat_class_index_];
    const CompiledMethod* compiled_method = oat_class->GetCompiledMethod(class_def_method_index);

    if (compiled_method != NULL) {  // ie. not an abstract method
      size_t file_offset = file_offset_;
      OutputStream* out = out_;

      uint32_t map_offset = DataAccess::GetOffset(oat_class, method_offsets_index_);
      ++method_offsets_index_;

      // Write deduplicated map.
      const std::vector<uint8_t>* map = DataAccess::GetData(compiled_method);
      size_t map_size = map == nullptr ? 0 : map->size() * sizeof((*map)[0]);
      DCHECK((map_size == 0u && map_offset == 0u) ||
            (map_size != 0u && map_offset != 0u && map_offset <= offset_))
          << map_size << " " << map_offset << " " << offset_ << " "
          << PrettyMethod(it.GetMemberIndex(), *dex_file_) << " for " << DataAccess::Name();
      if (map_size != 0u && map_offset == offset_) {
        if (UNLIKELY(!out->WriteFully(&(*map)[0], map_size))) {
          ReportWriteFailure(it);
          return false;
        }
        offset_ += map_size;
      }
      DCHECK_OFFSET_();
    }

    return true;
  }

 private:
  OutputStream* const out_;
  size_t const file_offset_;

  void ReportWriteFailure(const ClassDataItemIterator& it) {
    PLOG(ERROR) << "Failed to write " << DataAccess::Name() << " for "
        << PrettyMethod(it.GetMemberIndex(), *dex_file_) << " to " << out_->GetLocation();
  }
};

// Visit all methods from all classes in all dex files with the specified visitor.
bool OatWriter::VisitDexMethods(DexMethodVisitor* visitor) {
  for (const DexFile* dex_file : *dex_files_) {
    const size_t class_def_count = dex_file->NumClassDefs();
    for (size_t class_def_index = 0; class_def_index != class_def_count; ++class_def_index) {
      if (UNLIKELY(!visitor->StartClass(dex_file, class_def_index))) {
        return false;
      }
      const DexFile::ClassDef& class_def = dex_file->GetClassDef(class_def_index);
      const uint8_t* class_data = dex_file->GetClassData(class_def);
      if (class_data != NULL) {  // ie not an empty class, such as a marker interface
        ClassDataItemIterator it(*dex_file, class_data);
        while (it.HasNextStaticField()) {
          it.Next();
        }
        while (it.HasNextInstanceField()) {
          it.Next();
        }
        size_t class_def_method_index = 0u;
        while (it.HasNextDirectMethod()) {
          if (!visitor->VisitMethod(class_def_method_index, it)) {
            return false;
          }
          ++class_def_method_index;
          it.Next();
        }
        while (it.HasNextVirtualMethod()) {
          if (UNLIKELY(!visitor->VisitMethod(class_def_method_index, it))) {
            return false;
          }
          ++class_def_method_index;
          it.Next();
        }
      }
      if (UNLIKELY(!visitor->EndClass())) {
        return false;
      }
    }
  }
  return true;
}

size_t OatWriter::InitOatHeader() {
  oat_header_ = OatHeader::Create(compiler_driver_->GetInstructionSet(),
                                  compiler_driver_->GetInstructionSetFeatures(),
                                  dex_files_,
                                  image_file_location_oat_checksum_,
                                  image_file_location_oat_begin_,
                                  key_value_store_);

  return oat_header_->GetHeaderSize();
}

size_t OatWriter::InitOatDexFiles(size_t offset) {
  // create the OatDexFiles
  for (size_t i = 0; i != dex_files_->size(); ++i) {
    const DexFile* dex_file = (*dex_files_)[i];
    CHECK(dex_file != NULL);
    OatDexFile* oat_dex_file = new OatDexFile(offset, *dex_file);
    oat_dex_files_.push_back(oat_dex_file);
    offset += oat_dex_file->SizeOf();
  }
  return offset;
}

size_t OatWriter::InitDexFiles(size_t offset) {
  // calculate the offsets within OatDexFiles to the DexFiles
  for (size_t i = 0; i != dex_files_->size(); ++i) {
    // dex files are required to be 4 byte aligned
    size_t original_offset = offset;
    offset = RoundUp(offset, 4);
    size_dex_file_alignment_ += offset - original_offset;

    // set offset in OatDexFile to DexFile
    oat_dex_files_[i]->dex_file_offset_ = offset;

    const DexFile* dex_file = (*dex_files_)[i];
    offset += dex_file->GetHeader().file_size_;
  }
  return offset;
}

size_t OatWriter::InitOatClasses(size_t offset) {
  // calculate the offsets within OatDexFiles to OatClasses
  InitOatClassesMethodVisitor visitor(this, offset);
  bool success = VisitDexMethods(&visitor);
  CHECK(success);
  offset = visitor.GetOffset();

  // Update oat_dex_files_.
  auto oat_class_it = oat_classes_.begin();
  for (OatDexFile* oat_dex_file : oat_dex_files_) {
    for (uint32_t& method_offset : oat_dex_file->methods_offsets_) {
      DCHECK(oat_class_it != oat_classes_.end());
      method_offset = (*oat_class_it)->offset_;
      ++oat_class_it;
    }
    oat_dex_file->UpdateChecksum(oat_header_);
  }
  CHECK(oat_class_it == oat_classes_.end());

  return offset;
}

size_t OatWriter::InitOatMaps(size_t offset) {
  #define VISIT(VisitorType)                          \
    do {                                              \
      VisitorType visitor(this, offset);              \
      bool success = VisitDexMethods(&visitor);       \
      DCHECK(success);                                \
      offset = visitor.GetOffset();                   \
    } while (false)

  VISIT(InitMapMethodVisitor<GcMapDataAccess>);
  VISIT(InitMapMethodVisitor<MappingTableDataAccess>);
  VISIT(InitMapMethodVisitor<VmapTableDataAccess>);

  #undef VISIT

  return offset;
}

size_t OatWriter::InitOatCode(size_t offset) {
  // calculate the offsets within OatHeader to executable code
  size_t old_offset = offset;
  size_t adjusted_offset = offset;
  // required to be on a new page boundary
  offset = RoundUp(offset, kPageSize);
  oat_header_->SetExecutableOffset(offset);
  size_executable_offset_alignment_ = offset - old_offset;
  if (compiler_driver_->IsImage()) {
    CHECK_EQ(image_patch_delta_, 0);
    InstructionSet instruction_set = compiler_driver_->GetInstructionSet();

    #define DO_TRAMPOLINE(field, fn_name) \
      offset = CompiledCode::AlignCode(offset, instruction_set); \
      adjusted_offset = offset + CompiledCode::CodeDelta(instruction_set); \
      oat_header_->Set ## fn_name ## Offset(adjusted_offset); \
      field.reset(compiler_driver_->Create ## fn_name()); \
      offset += field->size();

    DO_TRAMPOLINE(interpreter_to_interpreter_bridge_, InterpreterToInterpreterBridge);
    DO_TRAMPOLINE(interpreter_to_compiled_code_bridge_, InterpreterToCompiledCodeBridge);
    DO_TRAMPOLINE(jni_dlsym_lookup_, JniDlsymLookup);
    DO_TRAMPOLINE(quick_generic_jni_trampoline_, QuickGenericJniTrampoline);
    DO_TRAMPOLINE(quick_imt_conflict_trampoline_, QuickImtConflictTrampoline);
    DO_TRAMPOLINE(quick_resolution_trampoline_, QuickResolutionTrampoline);
    DO_TRAMPOLINE(quick_to_interpreter_bridge_, QuickToInterpreterBridge);

    #undef DO_TRAMPOLINE
  } else {
    oat_header_->SetInterpreterToInterpreterBridgeOffset(0);
    oat_header_->SetInterpreterToCompiledCodeBridgeOffset(0);
    oat_header_->SetJniDlsymLookupOffset(0);
    oat_header_->SetQuickGenericJniTrampolineOffset(0);
    oat_header_->SetQuickImtConflictTrampolineOffset(0);
    oat_header_->SetQuickResolutionTrampolineOffset(0);
    oat_header_->SetQuickToInterpreterBridgeOffset(0);
    oat_header_->SetImagePatchDelta(image_patch_delta_);
  }
  return offset;
}

size_t OatWriter::InitOatCodeDexFiles(size_t offset) {
  #define VISIT(VisitorType)                          \
    do {                                              \
      VisitorType visitor(this, offset);              \
      bool success = VisitDexMethods(&visitor);       \
      DCHECK(success);                                \
      offset = visitor.GetOffset();                   \
    } while (false)

  VISIT(InitCodeMethodVisitor);
  if (compiler_driver_->IsImage()) {
    VISIT(InitImageMethodVisitor);
  }

  #undef VISIT

  return offset;
}

bool OatWriter::Write(OutputStream* out) {
  const off_t raw_file_offset = out->Seek(0, kSeekCurrent);
  if (raw_file_offset == (off_t) -1) {
    LOG(ERROR) << "Failed to get file offset in " << out->GetLocation();
    return false;
  }
  const size_t file_offset = static_cast<size_t>(raw_file_offset);

  // Reserve space for header. It will be written last - after updating the checksum.
  size_t header_size = oat_header_->GetHeaderSize();
  if (out->Seek(header_size, kSeekCurrent) == (off_t) -1) {
    PLOG(ERROR) << "Failed to reserve space for oat header in " << out->GetLocation();
    return false;
  }
  size_oat_header_ += sizeof(OatHeader);
  size_oat_header_key_value_store_ += oat_header_->GetHeaderSize() - sizeof(OatHeader);

  if (!WriteTables(out, file_offset)) {
    LOG(ERROR) << "Failed to write oat tables to " << out->GetLocation();
    return false;
  }

  off_t tables_end_offset = out->Seek(0, kSeekCurrent);
  if (tables_end_offset == (off_t) -1) {
    LOG(ERROR) << "Failed to seek to oat code position in " << out->GetLocation();
    return false;
  }
  size_t relative_offset = static_cast<size_t>(tables_end_offset) - file_offset;
  relative_offset = WriteMaps(out, file_offset, relative_offset);
  if (relative_offset == 0) {
    LOG(ERROR) << "Failed to write oat code to " << out->GetLocation();
    return false;
  }

  relative_offset = WriteCode(out, file_offset, relative_offset);
  if (relative_offset == 0) {
    LOG(ERROR) << "Failed to write oat code to " << out->GetLocation();
    return false;
  }

  relative_offset = WriteCodeDexFiles(out, file_offset, relative_offset);
  if (relative_offset == 0) {
    LOG(ERROR) << "Failed to write oat code for dex files to " << out->GetLocation();
    return false;
  }

  const off_t oat_end_file_offset = out->Seek(0, kSeekCurrent);
  if (oat_end_file_offset == (off_t) -1) {
    LOG(ERROR) << "Failed to get oat end file offset in " << out->GetLocation();
    return false;
  }

  if (kIsDebugBuild) {
    uint32_t size_total = 0;
    #define DO_STAT(x) \
      VLOG(compiler) << #x "=" << PrettySize(x) << " (" << x << "B)"; \
      size_total += x;

    DO_STAT(size_dex_file_alignment_);
    DO_STAT(size_executable_offset_alignment_);
    DO_STAT(size_oat_header_);
    DO_STAT(size_oat_header_key_value_store_);
    DO_STAT(size_dex_file_);
    DO_STAT(size_interpreter_to_interpreter_bridge_);
    DO_STAT(size_interpreter_to_compiled_code_bridge_);
    DO_STAT(size_jni_dlsym_lookup_);
    DO_STAT(size_quick_generic_jni_trampoline_);
    DO_STAT(size_quick_imt_conflict_trampoline_);
    DO_STAT(size_quick_resolution_trampoline_);
    DO_STAT(size_quick_to_interpreter_bridge_);
    DO_STAT(size_trampoline_alignment_);
    DO_STAT(size_method_header_);
    DO_STAT(size_code_);
    DO_STAT(size_code_alignment_);
    DO_STAT(size_relative_call_thunks_);
    DO_STAT(size_mapping_table_);
    DO_STAT(size_vmap_table_);
    DO_STAT(size_gc_map_);
    DO_STAT(size_oat_dex_file_location_size_);
    DO_STAT(size_oat_dex_file_location_data_);
    DO_STAT(size_oat_dex_file_location_checksum_);
    DO_STAT(size_oat_dex_file_offset_);
    DO_STAT(size_oat_dex_file_methods_offsets_);
    DO_STAT(size_oat_class_type_);
    DO_STAT(size_oat_class_status_);
    DO_STAT(size_oat_class_method_bitmaps_);
    DO_STAT(size_oat_class_method_offsets_);
    #undef DO_STAT

    VLOG(compiler) << "size_total=" << PrettySize(size_total) << " (" << size_total << "B)"; \
    CHECK_EQ(file_offset + size_total, static_cast<size_t>(oat_end_file_offset));
    CHECK_EQ(size_, size_total);
  }

  CHECK_EQ(file_offset + size_, static_cast<size_t>(oat_end_file_offset));
  CHECK_EQ(size_, relative_offset);

  // Write the header now that the checksum is final.
  if (out->Seek(file_offset, kSeekSet) == (off_t) -1) {
    PLOG(ERROR) << "Failed to seek to oat header position in " << out->GetLocation();
    return false;
  }
  DCHECK_EQ(raw_file_offset, out->Seek(0, kSeekCurrent));
  if (!out->WriteFully(oat_header_, header_size)) {
    PLOG(ERROR) << "Failed to write oat header to " << out->GetLocation();
    return false;
  }
  if (out->Seek(oat_end_file_offset, kSeekSet) == (off_t) -1) {
    PLOG(ERROR) << "Failed to seek to end after writing oat header to " << out->GetLocation();
    return false;
  }
  DCHECK_EQ(oat_end_file_offset, out->Seek(0, kSeekCurrent));

  return true;
}

bool OatWriter::WriteTables(OutputStream* out, const size_t file_offset) {
  for (size_t i = 0; i != oat_dex_files_.size(); ++i) {
    if (!oat_dex_files_[i]->Write(this, out, file_offset)) {
      PLOG(ERROR) << "Failed to write oat dex information to " << out->GetLocation();
      return false;
    }
  }
  for (size_t i = 0; i != oat_dex_files_.size(); ++i) {
    uint32_t expected_offset = file_offset + oat_dex_files_[i]->dex_file_offset_;
    off_t actual_offset = out->Seek(expected_offset, kSeekSet);
    if (static_cast<uint32_t>(actual_offset) != expected_offset) {
      const DexFile* dex_file = (*dex_files_)[i];
      PLOG(ERROR) << "Failed to seek to dex file section. Actual: " << actual_offset
                  << " Expected: " << expected_offset << " File: " << dex_file->GetLocation();
      return false;
    }
    const DexFile* dex_file = (*dex_files_)[i];
    if (!out->WriteFully(&dex_file->GetHeader(), dex_file->GetHeader().file_size_)) {
      PLOG(ERROR) << "Failed to write dex file " << dex_file->GetLocation()
                  << " to " << out->GetLocation();
      return false;
    }
    size_dex_file_ += dex_file->GetHeader().file_size_;
  }
  for (size_t i = 0; i != oat_classes_.size(); ++i) {
    if (!oat_classes_[i]->Write(this, out, file_offset)) {
      PLOG(ERROR) << "Failed to write oat methods information to " << out->GetLocation();
      return false;
    }
  }
  return true;
}

size_t OatWriter::WriteMaps(OutputStream* out, const size_t file_offset, size_t relative_offset) {
  #define VISIT(VisitorType)                                              \
    do {                                                                  \
      VisitorType visitor(this, out, file_offset, relative_offset);       \
      if (UNLIKELY(!VisitDexMethods(&visitor))) {                         \
        return 0;                                                         \
      }                                                                   \
      relative_offset = visitor.GetOffset();                              \
    } while (false)

  size_t gc_maps_offset = relative_offset;
  VISIT(WriteMapMethodVisitor<GcMapDataAccess>);
  size_gc_map_ = relative_offset - gc_maps_offset;

  size_t mapping_tables_offset = relative_offset;
  VISIT(WriteMapMethodVisitor<MappingTableDataAccess>);
  size_mapping_table_ = relative_offset - mapping_tables_offset;

  size_t vmap_tables_offset = relative_offset;
  VISIT(WriteMapMethodVisitor<VmapTableDataAccess>);
  size_vmap_table_ = relative_offset - vmap_tables_offset;

  #undef VISIT

  return relative_offset;
}

size_t OatWriter::WriteCode(OutputStream* out, const size_t file_offset, size_t relative_offset) {
  off_t new_offset = out->Seek(size_executable_offset_alignment_, kSeekCurrent);
  relative_offset += size_executable_offset_alignment_;
  DCHECK_EQ(relative_offset, oat_header_->GetExecutableOffset());
  size_t expected_file_offset = file_offset + relative_offset;
  if (static_cast<uint32_t>(new_offset) != expected_file_offset) {
    PLOG(ERROR) << "Failed to seek to oat code section. Actual: " << new_offset
                << " Expected: " << expected_file_offset << " File: " << out->GetLocation();
    return 0;
  }
  DCHECK_OFFSET();
  if (compiler_driver_->IsImage()) {
    InstructionSet instruction_set = compiler_driver_->GetInstructionSet();

    #define DO_TRAMPOLINE(field) \
      do { \
        uint32_t aligned_offset = CompiledCode::AlignCode(relative_offset, instruction_set); \
        uint32_t alignment_padding = aligned_offset - relative_offset; \
        out->Seek(alignment_padding, kSeekCurrent); \
        size_trampoline_alignment_ += alignment_padding; \
        if (!out->WriteFully(&(*field)[0], field->size())) { \
          PLOG(ERROR) << "Failed to write " # field " to " << out->GetLocation(); \
          return false; \
        } \
        size_ ## field += field->size(); \
        relative_offset += alignment_padding + field->size(); \
        DCHECK_OFFSET(); \
      } while (false)

    DO_TRAMPOLINE(interpreter_to_interpreter_bridge_);
    DO_TRAMPOLINE(interpreter_to_compiled_code_bridge_);
    DO_TRAMPOLINE(jni_dlsym_lookup_);
    DO_TRAMPOLINE(quick_generic_jni_trampoline_);
    DO_TRAMPOLINE(quick_imt_conflict_trampoline_);
    DO_TRAMPOLINE(quick_resolution_trampoline_);
    DO_TRAMPOLINE(quick_to_interpreter_bridge_);
    #undef DO_TRAMPOLINE
  }
  return relative_offset;
}

size_t OatWriter::WriteCodeDexFiles(OutputStream* out,
                                    const size_t file_offset,
                                    size_t relative_offset) {
  #define VISIT(VisitorType)                                              \
    do {                                                                  \
      VisitorType visitor(this, out, file_offset, relative_offset);       \
      if (UNLIKELY(!VisitDexMethods(&visitor))) {                         \
        return 0;                                                         \
      }                                                                   \
      relative_offset = visitor.GetOffset();                              \
    } while (false)

  VISIT(WriteCodeMethodVisitor);

  #undef VISIT

  return relative_offset;
}

bool OatWriter::WriteCodeAlignment(OutputStream* out, uint32_t aligned_code_delta) {
  static const uint8_t kPadding[] = {
      0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u
  };
  DCHECK_LE(aligned_code_delta, sizeof(kPadding));
  if (UNLIKELY(!out->WriteFully(kPadding, aligned_code_delta))) {
    return false;
  }
  size_code_alignment_ += aligned_code_delta;
  return true;
}

OatWriter::OatDexFile::OatDexFile(size_t offset, const DexFile& dex_file) {
  offset_ = offset;
  const std::string& location(dex_file.GetLocation());
  dex_file_location_size_ = location.size();
  dex_file_location_data_ = reinterpret_cast<const uint8_t*>(location.data());
  dex_file_location_checksum_ = dex_file.GetLocationChecksum();
  dex_file_offset_ = 0;
  methods_offsets_.resize(dex_file.NumClassDefs());
}

size_t OatWriter::OatDexFile::SizeOf() const {
  return sizeof(dex_file_location_size_)
          + dex_file_location_size_
          + sizeof(dex_file_location_checksum_)
          + sizeof(dex_file_offset_)
          + (sizeof(methods_offsets_[0]) * methods_offsets_.size());
}

void OatWriter::OatDexFile::UpdateChecksum(OatHeader* oat_header) const {
  oat_header->UpdateChecksum(&dex_file_location_size_, sizeof(dex_file_location_size_));
  oat_header->UpdateChecksum(dex_file_location_data_, dex_file_location_size_);
  oat_header->UpdateChecksum(&dex_file_location_checksum_, sizeof(dex_file_location_checksum_));
  oat_header->UpdateChecksum(&dex_file_offset_, sizeof(dex_file_offset_));
  oat_header->UpdateChecksum(&methods_offsets_[0],
                            sizeof(methods_offsets_[0]) * methods_offsets_.size());
}

bool OatWriter::OatDexFile::Write(OatWriter* oat_writer,
                                  OutputStream* out,
                                  const size_t file_offset) const {
  DCHECK_OFFSET_();
  if (!out->WriteFully(&dex_file_location_size_, sizeof(dex_file_location_size_))) {
    PLOG(ERROR) << "Failed to write dex file location length to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_dex_file_location_size_ += sizeof(dex_file_location_size_);
  if (!out->WriteFully(dex_file_location_data_, dex_file_location_size_)) {
    PLOG(ERROR) << "Failed to write dex file location data to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_dex_file_location_data_ += dex_file_location_size_;
  if (!out->WriteFully(&dex_file_location_checksum_, sizeof(dex_file_location_checksum_))) {
    PLOG(ERROR) << "Failed to write dex file location checksum to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_dex_file_location_checksum_ += sizeof(dex_file_location_checksum_);
  if (!out->WriteFully(&dex_file_offset_, sizeof(dex_file_offset_))) {
    PLOG(ERROR) << "Failed to write dex file offset to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_dex_file_offset_ += sizeof(dex_file_offset_);
  if (!out->WriteFully(&methods_offsets_[0],
                      sizeof(methods_offsets_[0]) * methods_offsets_.size())) {
    PLOG(ERROR) << "Failed to write methods offsets to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_dex_file_methods_offsets_ +=
      sizeof(methods_offsets_[0]) * methods_offsets_.size();
  return true;
}

OatWriter::OatClass::OatClass(size_t offset,
                              const std::vector<CompiledMethod*>& compiled_methods,
                              uint32_t num_non_null_compiled_methods,
                              mirror::Class::Status status)
    : compiled_methods_(compiled_methods) {
  uint32_t num_methods = compiled_methods.size();
  CHECK_LE(num_non_null_compiled_methods, num_methods);

  offset_ = offset;
  oat_method_offsets_offsets_from_oat_class_.resize(num_methods);

  // Since both kOatClassNoneCompiled and kOatClassAllCompiled could
  // apply when there are 0 methods, we just arbitrarily say that 0
  // methods means kOatClassNoneCompiled and that we won't use
  // kOatClassAllCompiled unless there is at least one compiled
  // method. This means in an interpretter only system, we can assert
  // that all classes are kOatClassNoneCompiled.
  if (num_non_null_compiled_methods == 0) {
    type_ = kOatClassNoneCompiled;
  } else if (num_non_null_compiled_methods == num_methods) {
    type_ = kOatClassAllCompiled;
  } else {
    type_ = kOatClassSomeCompiled;
  }

  status_ = status;
  method_offsets_.resize(num_non_null_compiled_methods);
  method_headers_.resize(num_non_null_compiled_methods);

  uint32_t oat_method_offsets_offset_from_oat_class = sizeof(type_) + sizeof(status_);
  if (type_ == kOatClassSomeCompiled) {
    method_bitmap_ = new BitVector(num_methods, false, Allocator::GetMallocAllocator());
    method_bitmap_size_ = method_bitmap_->GetSizeOf();
    oat_method_offsets_offset_from_oat_class += sizeof(method_bitmap_size_);
    oat_method_offsets_offset_from_oat_class += method_bitmap_size_;
  } else {
    method_bitmap_ = NULL;
    method_bitmap_size_ = 0;
  }

  for (size_t i = 0; i < num_methods; i++) {
    CompiledMethod* compiled_method = compiled_methods_[i];
    if (compiled_method == NULL) {
      oat_method_offsets_offsets_from_oat_class_[i] = 0;
    } else {
      oat_method_offsets_offsets_from_oat_class_[i] = oat_method_offsets_offset_from_oat_class;
      oat_method_offsets_offset_from_oat_class += sizeof(OatMethodOffsets);
      if (type_ == kOatClassSomeCompiled) {
        method_bitmap_->SetBit(i);
      }
    }
  }
}

OatWriter::OatClass::~OatClass() {
  delete method_bitmap_;
}

size_t OatWriter::OatClass::GetOatMethodOffsetsOffsetFromOatHeader(
    size_t class_def_method_index_) const {
  uint32_t method_offset = GetOatMethodOffsetsOffsetFromOatClass(class_def_method_index_);
  if (method_offset == 0) {
    return 0;
  }
  return offset_ + method_offset;
}

size_t OatWriter::OatClass::GetOatMethodOffsetsOffsetFromOatClass(
    size_t class_def_method_index_) const {
  return oat_method_offsets_offsets_from_oat_class_[class_def_method_index_];
}

size_t OatWriter::OatClass::SizeOf() const {
  return sizeof(status_)
          + sizeof(type_)
          + ((method_bitmap_size_ == 0) ? 0 : sizeof(method_bitmap_size_))
          + method_bitmap_size_
          + (sizeof(method_offsets_[0]) * method_offsets_.size());
}

void OatWriter::OatClass::UpdateChecksum(OatHeader* oat_header) const {
  oat_header->UpdateChecksum(&status_, sizeof(status_));
  oat_header->UpdateChecksum(&type_, sizeof(type_));
  if (method_bitmap_size_ != 0) {
    CHECK_EQ(kOatClassSomeCompiled, type_);
    oat_header->UpdateChecksum(&method_bitmap_size_, sizeof(method_bitmap_size_));
    oat_header->UpdateChecksum(method_bitmap_->GetRawStorage(), method_bitmap_size_);
  }
  oat_header->UpdateChecksum(&method_offsets_[0],
                             sizeof(method_offsets_[0]) * method_offsets_.size());
}

bool OatWriter::OatClass::Write(OatWriter* oat_writer,
                                OutputStream* out,
                                const size_t file_offset) const {
  DCHECK_OFFSET_();
  if (!out->WriteFully(&status_, sizeof(status_))) {
    PLOG(ERROR) << "Failed to write class status to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_class_status_ += sizeof(status_);
  if (!out->WriteFully(&type_, sizeof(type_))) {
    PLOG(ERROR) << "Failed to write oat class type to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_class_type_ += sizeof(type_);
  if (method_bitmap_size_ != 0) {
    CHECK_EQ(kOatClassSomeCompiled, type_);
    if (!out->WriteFully(&method_bitmap_size_, sizeof(method_bitmap_size_))) {
      PLOG(ERROR) << "Failed to write method bitmap size to " << out->GetLocation();
      return false;
    }
    oat_writer->size_oat_class_method_bitmaps_ += sizeof(method_bitmap_size_);
    if (!out->WriteFully(method_bitmap_->GetRawStorage(), method_bitmap_size_)) {
      PLOG(ERROR) << "Failed to write method bitmap to " << out->GetLocation();
      return false;
    }
    oat_writer->size_oat_class_method_bitmaps_ += method_bitmap_size_;
  }
  if (!out->WriteFully(&method_offsets_[0],
                      sizeof(method_offsets_[0]) * method_offsets_.size())) {
    PLOG(ERROR) << "Failed to write method offsets to " << out->GetLocation();
    return false;
  }
  oat_writer->size_oat_class_method_offsets_ += sizeof(method_offsets_[0]) * method_offsets_.size();
  return true;
}

}  // namespace art