Revert "Revert "Add support for LZ4 compressed image files""

Needed to call compiler_driver_->SetSupportBootImageFixup(false).

Bug: 22858531

This reverts commit 83d4d72aa0e4170209ab50c67ba22e46b71352c1.

Change-Id: Iaed6a810a0c088f1f2c57cf2f12087f3978a3de1

15 files changed, 287 insertions, 76 deletions

diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index a93d8a882a..43e1457a50 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -206,6 +206,7 @@ ART_CPP_EXTENSION := .cc
 ART_C_INCLUDES := \
   external/gtest/include \
   external/icu/icu4c/source/common \
+  external/lz4/lib \
   external/valgrind/include \
   external/valgrind \
   external/vixl/src \
diff --git a/compiler/Android.mk b/compiler/Android.mk
index 348eabdde5..bdd9a84433 100644
--- a/compiler/Android.mk
+++ b/compiler/Android.mk
@@ -258,9 +258,9 @@ define build-libart-compiler
   ifeq ($$(art_ndebug_or_debug),ndebug)
     LOCAL_MODULE := libart-compiler
     ifeq ($$(art_static_or_shared), static)
-      LOCAL_STATIC_LIBRARIES += libart
+      LOCAL_STATIC_LIBRARIES += libart liblz4
     else
-      LOCAL_SHARED_LIBRARIES += libart
+      LOCAL_SHARED_LIBRARIES += libart liblz4
     endif
     ifeq ($$(art_target_or_host),target)
       LOCAL_FDO_SUPPORT := true
@@ -268,9 +268,9 @@ define build-libart-compiler
   else # debug
     LOCAL_MODULE := libartd-compiler
     ifeq ($$(art_static_or_shared), static)
-      LOCAL_STATIC_LIBRARIES += libartd
+      LOCAL_STATIC_LIBRARIES += libartd liblz4
     else
-      LOCAL_SHARED_LIBRARIES += libartd
+      LOCAL_SHARED_LIBRARIES += libartd liblz4
     endif
   endif
 
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index e6cc50cc5e..638b897eea 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -189,17 +189,29 @@ void CommonCompilerTest::SetUp() {
     }
 
     timer_.reset(new CumulativeLogger("Compilation times"));
-    compiler_driver_.reset(new CompilerDriver(compiler_options_.get(),
-                                              verification_results_.get(),
-                                              method_inliner_map_.get(),
-                                              compiler_kind_, instruction_set,
-                                              instruction_set_features_.get(),
-                                              true,
-                                              GetImageClasses(),
-                                              GetCompiledClasses(),
-                                              GetCompiledMethods(),
-                                              2, true, true, "", false, timer_.get(), -1, ""));
+    CreateCompilerDriver(compiler_kind_, instruction_set);
   }
+}
+
+void CommonCompilerTest::CreateCompilerDriver(Compiler::Kind kind, InstructionSet isa) {
+  compiler_driver_.reset(new CompilerDriver(compiler_options_.get(),
+                                            verification_results_.get(),
+                                            method_inliner_map_.get(),
+                                            kind,
+                                            isa,
+                                            instruction_set_features_.get(),
+                                            true,
+                                            GetImageClasses(),
+                                            GetCompiledClasses(),
+                                            GetCompiledMethods(),
+                                            2,
+                                            true,
+                                            true,
+                                            "",
+                                            false,
+                                            timer_.get(),
+                                            -1,
+                                            ""));
   // We typically don't generate an image in unit tests, disable this optimization by default.
   compiler_driver_->SetSupportBootImageFixup(false);
 }
diff --git a/compiler/common_compiler_test.h b/compiler/common_compiler_test.h
index 1b57b7d1d2..b491946dc3 100644
--- a/compiler/common_compiler_test.h
+++ b/compiler/common_compiler_test.h
@@ -90,6 +90,8 @@ class CommonCompilerTest : public CommonRuntimeTest {
                             const char* method_name, const char* signature)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
+  void CreateCompilerDriver(Compiler::Kind kind, InstructionSet isa);
+
   void ReserveImageSpace();
 
   void UnreserveImageSpace();
diff --git a/compiler/image_test.cc b/compiler/image_test.cc
index cda6240bd4..b596ba66a5 100644
--- a/compiler/image_test.cc
+++ b/compiler/image_test.cc
@@ -43,10 +43,17 @@ class ImageTest : public CommonCompilerTest {
     ReserveImageSpace();
     CommonCompilerTest::SetUp();
   }
+  void TestWriteRead(ImageHeader::StorageMode storage_mode);
 };
 
-TEST_F(ImageTest, WriteRead) {
-  TEST_DISABLED_FOR_NON_PIC_COMPILING_WITH_OPTIMIZING();
+void ImageTest::TestWriteRead(ImageHeader::StorageMode storage_mode) {
+  // TODO: Test does not currently work with optimizing.
+  CreateCompilerDriver(Compiler::kQuick, kRuntimeISA);
+  ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
+  // Enable write for dex2dex.
+  for (const DexFile* dex_file : class_linker->GetBootClassPath()) {
+    dex_file->EnableWrite();
+  }
   // Create a generic location tmp file, to be the base of the .art and .oat temporary files.
   ScratchFile location;
   ScratchFile image_location(location, ".art");
@@ -68,17 +75,14 @@ TEST_F(ImageTest, WriteRead) {
   std::unique_ptr<ImageWriter> writer(new ImageWriter(*compiler_driver_,
                                                       requested_image_base,
                                                       /*compile_pic*/false,
-                                                      /*compile_app_image*/false));
+                                                      /*compile_app_image*/false,
+                                                      storage_mode));
   // TODO: compile_pic should be a test argument.
   {
     {
       jobject class_loader = nullptr;
-      ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
       TimingLogger timings("ImageTest::WriteRead", false, false);
       TimingLogger::ScopedTiming t("CompileAll", &timings);
-      for (const DexFile* dex_file : class_linker->GetBootClassPath()) {
-        dex_file->EnableWrite();
-      }
       compiler_driver_->SetDexFilesForOatFile(class_linker->GetBootClassPath());
       compiler_driver_->CompileAll(class_loader, class_linker->GetBootClassPath(), &timings);
 
@@ -209,7 +213,13 @@ TEST_F(ImageTest, WriteRead) {
 
   gc::space::ImageSpace* image_space = heap->GetBootImageSpace();
   ASSERT_TRUE(image_space != nullptr);
-  ASSERT_LE(image_space->Size(), image_file_size);
+  if (storage_mode == ImageHeader::kStorageModeUncompressed) {
+    // Uncompressed, image should be smaller than file.
+    ASSERT_LE(image_space->Size(), image_file_size);
+  } else {
+    // Compressed, file should be smaller than image.
+    ASSERT_LE(image_file_size, image_space->Size());
+  }
 
   image_space->VerifyImageAllocations();
   uint8_t* image_begin = image_space->Begin();
@@ -237,6 +247,14 @@ TEST_F(ImageTest, WriteRead) {
   CHECK_EQ(0, rmdir_result);
 }
 
+TEST_F(ImageTest, WriteReadUncompressed) {
+  TestWriteRead(ImageHeader::kStorageModeUncompressed);
+}
+
+TEST_F(ImageTest, WriteReadLZ4) {
+  TestWriteRead(ImageHeader::kStorageModeLZ4);
+}
+
 TEST_F(ImageTest, ImageHeaderIsValid) {
     uint32_t image_begin = ART_BASE_ADDRESS;
     uint32_t image_size_ = 16 * KB;
@@ -257,7 +275,9 @@ TEST_F(ImageTest, ImageHeaderIsValid) {
                              oat_data_end,
                              oat_file_end,
                              sizeof(void*),
-                             /*compile_pic*/false);
+                             /*compile_pic*/false,
+                             ImageHeader::kDefaultStorageMode,
+                             /*data_size*/0u);
     ASSERT_TRUE(image_header.IsValid());
 
     char* magic = const_cast<char*>(image_header.GetMagic());
diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index bf1fcdd5f5..f9f0eb8154 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -17,6 +17,7 @@
 #include "image_writer.h"
 
 #include <sys/stat.h>
+#include <lz4.h>
 
 #include <memory>
 #include <numeric>
@@ -225,27 +226,72 @@ bool ImageWriter::Write(int image_fd,
     return EXIT_FAILURE;
   }
 
-  // Write out the image + fields + methods.
+  std::unique_ptr<char[]> compressed_data;
+  // Image data size excludes the bitmap and the header.
   ImageHeader* const image_header = reinterpret_cast<ImageHeader*>(image_->Begin());
-  const auto write_count = image_header->GetImageSize();
-  if (!image_file->WriteFully(image_->Begin(), write_count)) {
-    PLOG(ERROR) << "Failed to write image file " << image_filename;
+  const size_t image_data_size = image_header->GetImageSize() - sizeof(ImageHeader);
+  char* image_data = reinterpret_cast<char*>(image_->Begin()) + sizeof(ImageHeader);
+  size_t data_size;
+  const char* image_data_to_write;
+
+  CHECK_EQ(image_header->storage_mode_, image_storage_mode_);
+  switch (image_storage_mode_) {
+    case ImageHeader::kStorageModeLZ4: {
+      size_t compressed_max_size = LZ4_compressBound(image_data_size);
+      compressed_data.reset(new char[compressed_max_size]);
+      data_size = LZ4_compress(
+          reinterpret_cast<char*>(image_->Begin()) + sizeof(ImageHeader),
+          &compressed_data[0],
+          image_data_size);
+      image_data_to_write = &compressed_data[0];
+      VLOG(compiler) << "Compressed from " << image_data_size << " to " << data_size;
+      break;
+    }
+    case ImageHeader::kStorageModeUncompressed: {
+      data_size = image_data_size;
+      image_data_to_write = image_data;
+      break;
+    }
+    default: {
+      LOG(FATAL) << "Unsupported";
+      UNREACHABLE();
+    }
+  }
+
+  // Write header first, as uncompressed.
+  image_header->data_size_ = data_size;
+  if (!image_file->WriteFully(image_->Begin(), sizeof(ImageHeader))) {
+    PLOG(ERROR) << "Failed to write image file header " << image_filename;
+    image_file->Erase();
+    return false;
+  }
+
+  // Write out the image + fields + methods.
+  const bool is_compressed = compressed_data != nullptr;
+  if (!image_file->WriteFully(image_data_to_write, data_size)) {
+    PLOG(ERROR) << "Failed to write image file data " << image_filename;
     image_file->Erase();
     return false;
   }
 
-  // Write out the image bitmap at the page aligned start of the image end.
+  // Write out the image bitmap at the page aligned start of the image end, also uncompressed for
+  // convenience.
   const ImageSection& bitmap_section = image_header->GetImageSection(
       ImageHeader::kSectionImageBitmap);
-  CHECK_ALIGNED(bitmap_section.Offset(), kPageSize);
+  // Align up since data size may be unaligned if the image is compressed.
+  size_t bitmap_position_in_file = RoundUp(sizeof(ImageHeader) + data_size, kPageSize);
+  if (!is_compressed) {
+    CHECK_EQ(bitmap_position_in_file, bitmap_section.Offset());
+  }
   if (!image_file->Write(reinterpret_cast<char*>(image_bitmap_->Begin()),
-                         bitmap_section.Size(), bitmap_section.Offset())) {
+                         bitmap_section.Size(),
+                         bitmap_position_in_file)) {
     PLOG(ERROR) << "Failed to write image file " << image_filename;
     image_file->Erase();
     return false;
   }
-
-  CHECK_EQ(bitmap_section.End(), static_cast<size_t>(image_file->GetLength()));
+  CHECK_EQ(bitmap_position_in_file + bitmap_section.Size(),
+           static_cast<size_t>(image_file->GetLength()));
   if (image_file->FlushCloseOrErase() != 0) {
     PLOG(ERROR) << "Failed to flush and close image file " << image_filename;
     return false;
@@ -1247,7 +1293,8 @@ void ImageWriter::CreateHeader(size_t oat_loaded_size, size_t oat_data_offset) {
   }
   CHECK_EQ(AlignUp(image_begin_ + image_end, kPageSize), oat_file_begin) <<
       "Oat file should be right after the image.";
-  // Create the header.
+  // Create the header, leave 0 for data size since we will fill this in as we are writing the
+  // image.
   new (image_->Begin()) ImageHeader(PointerToLowMemUInt32(image_begin_),
                                                           image_end,
                                                           sections,
@@ -1258,7 +1305,9 @@ void ImageWriter::CreateHeader(size_t oat_loaded_size, size_t oat_data_offset) {
                                                           PointerToLowMemUInt32(oat_data_end),
                                                           PointerToLowMemUInt32(oat_file_end),
                                                           target_ptr_size_,
-                                                          compile_pic_);
+                                                          compile_pic_,
+                                                          image_storage_mode_,
+                                                          /*data_size*/0u);
 }
 
 ArtMethod* ImageWriter::GetImageMethodAddress(ArtMethod* method) {
diff --git a/compiler/image_writer.h b/compiler/image_writer.h
index 386838fde0..c20d83639a 100644
--- a/compiler/image_writer.h
+++ b/compiler/image_writer.h
@@ -30,6 +30,7 @@
 #include "base/macros.h"
 #include "driver/compiler_driver.h"
 #include "gc/space/space.h"
+#include "image.h"
 #include "length_prefixed_array.h"
 #include "lock_word.h"
 #include "mem_map.h"
@@ -54,7 +55,8 @@ class ImageWriter FINAL {
   ImageWriter(const CompilerDriver& compiler_driver,
               uintptr_t image_begin,
               bool compile_pic,
-              bool compile_app_image)
+              bool compile_app_image,
+              ImageHeader::StorageMode image_storage_mode)
       : compiler_driver_(compiler_driver),
         image_begin_(reinterpret_cast<uint8_t*>(image_begin)),
         image_end_(0),
@@ -73,7 +75,8 @@ class ImageWriter FINAL {
         image_method_array_(ImageHeader::kImageMethodsCount),
         dirty_methods_(0u),
         clean_methods_(0u),
-        class_table_bytes_(0u) {
+        class_table_bytes_(0u),
+        image_storage_mode_(image_storage_mode) {
     CHECK_NE(image_begin, 0U);
     std::fill_n(image_methods_, arraysize(image_methods_), nullptr);
     std::fill_n(oat_address_offsets_, arraysize(oat_address_offsets_), 0);
@@ -460,6 +463,9 @@ class ImageWriter FINAL {
   // Number of image class table bytes.
   size_t class_table_bytes_;
 
+  // Which mode the image is stored as, see image.h
+  const ImageHeader::StorageMode image_storage_mode_;
+
   friend class ContainsBootClassLoaderNonImageClassVisitor;
   friend class FixupClassVisitor;
   friend class FixupRootVisitor;
diff --git a/dex2oat/Android.mk b/dex2oat/Android.mk
index f10acf9d7b..77f8d6cd9f 100644
--- a/dex2oat/Android.mk
+++ b/dex2oat/Android.mk
@@ -57,18 +57,18 @@ endif
 
 # We always build dex2oat and dependencies, even if the host build is otherwise disabled, since they are used to cross compile for the target.
 ifeq ($(ART_BUILD_HOST_NDEBUG),true)
-  $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libcutils libart-compiler libsigchain libziparchive-host,art/compiler,host,ndebug,$(dex2oat_host_arch)))
+  $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libcutils libart-compiler libsigchain libziparchive-host liblz4,art/compiler,host,ndebug,$(dex2oat_host_arch)))
   ifeq ($(ART_BUILD_HOST_STATIC),true)
     $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libart libart-compiler libart libziparchive-host libnativehelper libnativebridge libsigchain_dummy libvixl liblog libz \
-        libbacktrace libLLVMObject libLLVMBitReader libLLVMMC libLLVMMCParser libLLVMCore libLLVMSupport libcutils libunwindbacktrace libutils libbase,art/compiler,host,ndebug,$(dex2oat_host_arch),static))
+        libbacktrace libLLVMObject libLLVMBitReader libLLVMMC libLLVMMCParser libLLVMCore libLLVMSupport libcutils libunwindbacktrace libutils libbase liblz4,art/compiler,host,ndebug,$(dex2oat_host_arch),static))
   endif
 endif
 
 ifeq ($(ART_BUILD_HOST_DEBUG),true)
-  $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libcutils libartd-compiler libsigchain libziparchive-host,art/compiler,host,debug,$(dex2oat_host_arch)))
+  $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libcutils libartd-compiler libsigchain libziparchive-host liblz4,art/compiler,host,debug,$(dex2oat_host_arch)))
   ifeq ($(ART_BUILD_HOST_STATIC),true)
     $(eval $(call build-art-executable,dex2oat,$(DEX2OAT_SRC_FILES),libartd libartd-compiler libartd libziparchive-host libnativehelper libnativebridge libsigchain_dummy libvixld liblog libz \
-        libbacktrace libLLVMObject libLLVMBitReader libLLVMMC libLLVMMCParser libLLVMCore libLLVMSupport libcutils libunwindbacktrace libutils libbase,art/compiler,host,debug,$(dex2oat_host_arch),static))
+        libbacktrace libLLVMObject libLLVMBitReader libLLVMMC libLLVMMCParser libLLVMCore libLLVMSupport libcutils libunwindbacktrace libutils libbase liblz4,art/compiler,host,debug,$(dex2oat_host_arch),static))
   endif
 endif
 
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index 2aa4085fb1..87d5a78454 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -208,6 +208,11 @@ NO_RETURN static void Usage(const char* fmt, ...) {
   UsageError("  --image=<file.art>: specifies the output image filename.");
   UsageError("      Example: --image=/system/framework/boot.art");
   UsageError("");
+  UsageError("  --image-format=(uncompressed|lz4):");
+  UsageError("      Which format to store the image.");
+  UsageError("      Example: --image-format=lz4");
+  UsageError("      Default: uncompressed");
+  UsageError("");
   UsageError("  --image-classes=<classname-file>: specifies classes to include in an image.");
   UsageError("      Example: --image=frameworks/base/preloaded-classes");
   UsageError("");
@@ -490,6 +495,7 @@ class Dex2Oat FINAL {
       image_base_(0U),
       image_classes_zip_filename_(nullptr),
       image_classes_filename_(nullptr),
+      image_storage_mode_(ImageHeader::kStorageModeUncompressed),
       compiled_classes_zip_filename_(nullptr),
       compiled_classes_filename_(nullptr),
       compiled_methods_zip_filename_(nullptr),
@@ -621,6 +627,19 @@ class Dex2Oat FINAL {
     }
   }
 
+  void ParseImageFormat(const StringPiece& option) {
+    const StringPiece substr("--image-format=");
+    DCHECK(option.starts_with(substr));
+    const StringPiece format_str = option.substr(substr.length());
+    if (format_str == "lz4") {
+      image_storage_mode_ = ImageHeader::kStorageModeLZ4;
+    } else if (format_str == "uncompressed") {
+      image_storage_mode_ = ImageHeader::kStorageModeUncompressed;
+    } else {
+      Usage("Unknown image format: %s", format_str.data());
+    }
+  }
+
   void ProcessOptions(ParserOptions* parser_options) {
     boot_image_ = !image_filename_.empty();
     app_image_ = app_image_fd_ != -1 || !app_image_file_name_.empty();
@@ -877,6 +896,8 @@ class Dex2Oat FINAL {
         image_classes_filename_ = option.substr(strlen("--image-classes=")).data();
       } else if (option.starts_with("--image-classes-zip=")) {
         image_classes_zip_filename_ = option.substr(strlen("--image-classes-zip=")).data();
+      } else if (option.starts_with("--image-format=")) {
+        ParseImageFormat(option);
       } else if (option.starts_with("--compiled-classes=")) {
         compiled_classes_filename_ = option.substr(strlen("--compiled-classes=")).data();
       } else if (option.starts_with("--compiled-classes-zip=")) {
@@ -1643,7 +1664,8 @@ class Dex2Oat FINAL {
     image_writer_.reset(new ImageWriter(*driver_,
                                         image_base,
                                         compiler_options_->GetCompilePic(),
-                                        IsAppImage()));
+                                        IsAppImage(),
+                                        image_storage_mode_));
   }
 
   // Let the ImageWriter write the image file. If we do not compile PIC, also fix up the oat file.
@@ -1818,6 +1840,7 @@ class Dex2Oat FINAL {
   uintptr_t image_base_;
   const char* image_classes_zip_filename_;
   const char* image_classes_filename_;
+  ImageHeader::StorageMode image_storage_mode_;
   const char* compiled_classes_zip_filename_;
   const char* compiled_classes_filename_;
   const char* compiled_methods_zip_filename_;
diff --git a/patchoat/patchoat.cc b/patchoat/patchoat.cc
index 723bb1762d..46ab34bea3 100644
--- a/patchoat/patchoat.cc
+++ b/patchoat/patchoat.cc
@@ -153,6 +153,12 @@ bool PatchOat::Patch(const std::string& image_location, off_t delta,
     return false;
   }
 
+  if (image_header.GetStorageMode() != ImageHeader::kStorageModeUncompressed) {
+    LOG(ERROR) << "Patchoat is not supported with compressed image files "
+               << input_image->GetPath();
+    return false;
+  }
+
   /*bool is_image_pic = */IsImagePic(image_header, input_image->GetPath());
   // Nothing special to do right now since the image always needs to get patched.
   // Perhaps in some far-off future we may have images with relative addresses that are true-PIC.
diff --git a/runtime/Android.mk b/runtime/Android.mk
index 74cc89911d..36c81fb078 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -491,9 +491,9 @@ $$(ENUM_OPERATOR_OUT_GEN): $$(GENERATED_SRC_DIR)/%_operator_out.cc : $(LOCAL_PAT
   LOCAL_C_INCLUDES += art
 
   ifeq ($$(art_static_or_shared),static)
-    LOCAL_STATIC_LIBRARIES := libnativehelper libnativebridge libsigchain_dummy libbacktrace
+    LOCAL_STATIC_LIBRARIES := libnativehelper libnativebridge libsigchain_dummy libbacktrace liblz4
   else
-    LOCAL_SHARED_LIBRARIES := libnativehelper libnativebridge libsigchain libbacktrace
+    LOCAL_SHARED_LIBRARIES := libnativehelper libnativebridge libsigchain libbacktrace liblz4
   endif
 
   ifeq ($$(art_target_or_host),target)
diff --git a/runtime/gc/collector/immune_spaces_test.cc b/runtime/gc/collector/immune_spaces_test.cc
index f741117bc1..4884e668c2 100644
--- a/runtime/gc/collector/immune_spaces_test.cc
+++ b/runtime/gc/collector/immune_spaces_test.cc
@@ -113,7 +113,9 @@ class DummyImageSpace : public space::ImageSpace {
         /*oat_data_end*/PointerToLowMemUInt32(map->End() + oat_size),
         /*oat_file_end*/PointerToLowMemUInt32(map->End() + oat_size),
         /*pointer_size*/sizeof(void*),
-        /*compile_pic*/false);
+        /*compile_pic*/false,
+        ImageHeader::kStorageModeUncompressed,
+        /*storage_size*/0u);
     return new DummyImageSpace(map.release(), live_bitmap.release());
   }
 };
diff --git a/runtime/gc/space/image_space.cc b/runtime/gc/space/image_space.cc
index e2b2431054..8f67c213a6 100644
--- a/runtime/gc/space/image_space.cc
+++ b/runtime/gc/space/image_space.cc
@@ -17,12 +17,12 @@
 #include "image_space.h"
 
 #include <dirent.h>
+#include <lz4.h>
+#include <random>
 #include <sys/statvfs.h>
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <random>
-
 #include "art_method.h"
 #include "base/macros.h"
 #include "base/stl_util.h"
@@ -677,11 +677,12 @@ ImageSpace* ImageSpace::Init(const char* image_filename, const char* image_locat
     *error_msg = StringPrintf("Invalid image header in '%s'", image_filename);
     return nullptr;
   }
-  // Check that the file is large enough.
-  uint64_t image_file_size = static_cast<uint64_t>(file->GetLength());
-  if (image_header.GetImageSize() > image_file_size) {
-    *error_msg = StringPrintf("Image file too small for image heap: %" PRIu64 " vs. %zu.",
-                              image_file_size, image_header.GetImageSize());
+  // Check that the file is larger or equal to the header size + data size.
+  const uint64_t image_file_size = static_cast<uint64_t>(file->GetLength());
+  if (image_file_size < sizeof(ImageHeader) + image_header.GetDataSize()) {
+    *error_msg = StringPrintf("Image file truncated: %" PRIu64 " vs. %" PRIu64 ".",
+                              image_file_size,
+                              image_header.GetDataSize());
     return nullptr;
   }
 
@@ -697,7 +698,11 @@ ImageSpace* ImageSpace::Init(const char* image_filename, const char* image_locat
   }
 
   const auto& bitmap_section = image_header.GetImageSection(ImageHeader::kSectionImageBitmap);
-  auto end_of_bitmap = static_cast<size_t>(bitmap_section.End());
+  // The location we want to map from is the first aligned page after the end of the stored
+  // (possibly compressed) data.
+  const size_t image_bitmap_offset = RoundUp(sizeof(image_header) + image_header.GetDataSize(),
+                                             kPageSize);
+  const size_t end_of_bitmap = image_bitmap_offset + bitmap_section.Size();
   if (end_of_bitmap != image_file_size) {
     *error_msg = StringPrintf(
         "Image file size does not equal end of bitmap: size=%" PRIu64 " vs. %zu.", image_file_size,
@@ -706,16 +711,60 @@ ImageSpace* ImageSpace::Init(const char* image_filename, const char* image_locat
   }
 
   // Note: The image header is part of the image due to mmap page alignment required of offset.
-  std::unique_ptr<MemMap> map(MemMap::MapFileAtAddress(image_header.GetImageBegin(),
-                                                       image_header.GetImageSize(),
-                                                       PROT_READ | PROT_WRITE,
+  std::unique_ptr<MemMap> map;
+  if (image_header.GetStorageMode() == ImageHeader::kStorageModeUncompressed) {
+    map.reset(MemMap::MapFileAtAddress(image_header.GetImageBegin(),
+                                       image_header.GetImageSize(),
+                                       PROT_READ | PROT_WRITE,
+                                       MAP_PRIVATE,
+                                       file->Fd(),
+                                       0,
+                                       /*low_4gb*/false,
+                                       /*reuse*/false,
+                                       image_filename,
+                                       error_msg));
+  } else {
+    // Reserve output and decompress into it.
+    map.reset(MemMap::MapAnonymous(image_location,
+                                   image_header.GetImageBegin(),
+                                   image_header.GetImageSize(),
+                                   PROT_READ | PROT_WRITE,
+                                   /*low_4gb*/false,
+                                   /*reuse*/false,
+                                   error_msg));
+    if (map != nullptr) {
+      const size_t stored_size = image_header.GetDataSize();
+      const size_t write_offset = sizeof(image_header);  // Skip the header.
+      std::unique_ptr<MemMap> temp_map(MemMap::MapFile(sizeof(ImageHeader) + stored_size,
+                                                       PROT_READ,
                                                        MAP_PRIVATE,
                                                        file->Fd(),
-                                                       0,
+                                                       /*offset*/0,
                                                        /*low_4gb*/false,
-                                                       /*reuse*/false,
                                                        image_filename,
                                                        error_msg));
+      if (temp_map == nullptr) {
+        DCHECK(!error_msg->empty());
+        return nullptr;
+      }
+      memcpy(map->Begin(), &image_header, sizeof(image_header));
+      const uint64_t start = NanoTime();
+      const size_t decompressed_size = LZ4_decompress_safe(
+          reinterpret_cast<char*>(temp_map->Begin()) + sizeof(ImageHeader),
+          reinterpret_cast<char*>(map->Begin()) + write_offset,
+          stored_size,
+          map->Size());
+      // TODO: VLOG(image)
+      VLOG(class_linker) << "Decompressing image took " << PrettyDuration(NanoTime() - start);
+      if (decompressed_size + sizeof(ImageHeader) != image_header.GetImageSize()) {
+        *error_msg = StringPrintf("Decompressed size does not match expected image size %zu vs %zu",
+                                  decompressed_size + sizeof(ImageHeader),
+                                  image_header.GetImageSize());
+        return nullptr;
+      }
+    }
+  }
+
   if (map == nullptr) {
     DCHECK(!error_msg->empty());
     return nullptr;
@@ -723,16 +772,16 @@ ImageSpace* ImageSpace::Init(const char* image_filename, const char* image_locat
   CHECK_EQ(image_header.GetImageBegin(), map->Begin());
   DCHECK_EQ(0, memcmp(&image_header, map->Begin(), sizeof(ImageHeader)));
 
-  std::unique_ptr<MemMap> image_map(MemMap::MapFileAtAddress(nullptr,
-                                                             bitmap_section.Size(),
-                                                             PROT_READ, MAP_PRIVATE,
-                                                             file->Fd(),
-                                                             bitmap_section.Offset(),
-                                                             /*low_4gb*/false,
-                                                             /*reuse*/false,
-                                                             image_filename,
-                                                             error_msg));
-  if (image_map.get() == nullptr) {
+  std::unique_ptr<MemMap> image_bitmap_map(MemMap::MapFileAtAddress(nullptr,
+                                                                    bitmap_section.Size(),
+                                                                    PROT_READ, MAP_PRIVATE,
+                                                                    file->Fd(),
+                                                                    image_bitmap_offset,
+                                                                    /*low_4gb*/false,
+                                                                    /*reuse*/false,
+                                                                    image_filename,
+                                                                    error_msg));
+  if (image_bitmap_map == nullptr) {
     *error_msg = StringPrintf("Failed to map image bitmap: %s", error_msg->c_str());
     return nullptr;
   }
@@ -741,9 +790,11 @@ ImageSpace* ImageSpace::Init(const char* image_filename, const char* image_locat
                                        bitmap_index));
   std::unique_ptr<accounting::ContinuousSpaceBitmap> bitmap(
       accounting::ContinuousSpaceBitmap::CreateFromMemMap(
-          bitmap_name, image_map.release(), reinterpret_cast<uint8_t*>(map->Begin()),
+          bitmap_name,
+          image_bitmap_map.release(),
+          reinterpret_cast<uint8_t*>(map->Begin()),
           accounting::ContinuousSpaceBitmap::ComputeHeapSize(bitmap_section.Size())));
-  if (bitmap.get() == nullptr) {
+  if (bitmap == nullptr) {
     *error_msg = StringPrintf("Could not create bitmap '%s'", bitmap_name.c_str());
     return nullptr;
   }
diff --git a/runtime/image.cc b/runtime/image.cc
index 2eac3fb873..7d2ef75c06 100644
--- a/runtime/image.cc
+++ b/runtime/image.cc
@@ -24,7 +24,7 @@
 namespace art {
 
 const uint8_t ImageHeader::kImageMagic[] = { 'a', 'r', 't', '\n' };
-const uint8_t ImageHeader::kImageVersion[] = { '0', '2', '3', '\0' };
+const uint8_t ImageHeader::kImageVersion[] = { '0', '2', '4', '\0' };
 
 ImageHeader::ImageHeader(uint32_t image_begin,
                          uint32_t image_size,
@@ -36,7 +36,9 @@ ImageHeader::ImageHeader(uint32_t image_begin,
                          uint32_t oat_data_end,
                          uint32_t oat_file_end,
                          uint32_t pointer_size,
-                         bool compile_pic)
+                         bool compile_pic,
+                         StorageMode storage_mode,
+                         size_t data_size)
   : image_begin_(image_begin),
     image_size_(image_size),
     oat_checksum_(oat_checksum),
@@ -47,7 +49,9 @@ ImageHeader::ImageHeader(uint32_t image_begin,
     patch_delta_(0),
     image_roots_(image_roots),
     pointer_size_(pointer_size),
-    compile_pic_(compile_pic) {
+    compile_pic_(compile_pic),
+    storage_mode_(storage_mode),
+    data_size_(data_size) {
   CHECK_EQ(image_begin, RoundUp(image_begin, kPageSize));
   CHECK_EQ(oat_file_begin, RoundUp(oat_file_begin, kPageSize));
   CHECK_EQ(oat_data_begin, RoundUp(oat_data_begin, kPageSize));
diff --git a/runtime/image.h b/runtime/image.h
index a16f3c98fb..3032bebc18 100644
--- a/runtime/image.h
+++ b/runtime/image.h
@@ -78,10 +78,27 @@ class PACKED(4) ImageSection {
 // header of image files written by ImageWriter, read and validated by Space.
 class PACKED(4) ImageHeader {
  public:
+  enum StorageMode : uint32_t {
+    kStorageModeUncompressed,
+    kStorageModeLZ4,
+    kStorageModeCount,  // Number of elements in enum.
+  };
+  static constexpr StorageMode kDefaultStorageMode = kStorageModeUncompressed;
+
   ImageHeader()
-      : image_begin_(0U), image_size_(0U), oat_checksum_(0U), oat_file_begin_(0U),
-        oat_data_begin_(0U), oat_data_end_(0U), oat_file_end_(0U), patch_delta_(0),
-        image_roots_(0U), pointer_size_(0U), compile_pic_(0) {}
+      : image_begin_(0U),
+        image_size_(0U),
+        oat_checksum_(0U),
+        oat_file_begin_(0U),
+        oat_data_begin_(0U),
+        oat_data_end_(0U),
+        oat_file_end_(0U),
+        patch_delta_(0),
+        image_roots_(0U),
+        pointer_size_(0U),
+        compile_pic_(0),
+        storage_mode_(kDefaultStorageMode),
+        data_size_(0) {}
 
   ImageHeader(uint32_t image_begin,
               uint32_t image_size,
@@ -93,7 +110,9 @@ class PACKED(4) ImageHeader {
               uint32_t oat_data_end,
               uint32_t oat_file_end,
               uint32_t pointer_size,
-              bool compile_pic);
+              bool compile_pic,
+              StorageMode storage_mode,
+              size_t data_size);
 
   bool IsValid() const;
   const char* GetMagic() const;
@@ -194,6 +213,14 @@ class PACKED(4) ImageHeader {
     return compile_pic_ != 0;
   }
 
+  StorageMode GetStorageMode() const {
+    return storage_mode_;
+  }
+
+  uint64_t GetDataSize() const {
+    return data_size_;
+  }
+
  private:
   static const uint8_t kImageMagic[4];
   static const uint8_t kImageVersion[4];
@@ -241,6 +268,13 @@ class PACKED(4) ImageHeader {
   // Image methods.
   uint64_t image_methods_[kImageMethodsCount];
 
+  // Storage method for the image, the image may be compressed.
+  StorageMode storage_mode_;
+
+  // Data size for the image data excluding the bitmap and the header. For compressed images, this
+  // is the compressed size in the file.
+  uint32_t data_size_;
+
   friend class ImageWriter;
 };
 
@@ -248,6 +282,7 @@ std::ostream& operator<<(std::ostream& os, const ImageHeader::ImageMethod& polic
 std::ostream& operator<<(std::ostream& os, const ImageHeader::ImageRoot& policy);
 std::ostream& operator<<(std::ostream& os, const ImageHeader::ImageSections& section);
 std::ostream& operator<<(std::ostream& os, const ImageSection& section);
+std::ostream& operator<<(std::ostream& os, const ImageHeader::StorageMode& mode);
 
 }  // namespace art