diff --git a/startop/tools/view_compiler/Android.bp b/startop/tools/view_compiler/Android.bp
index c3e9184..3681529 100644
--- a/startop/tools/view_compiler/Android.bp
+++ b/startop/tools/view_compiler/Android.bp
@@ -14,19 +14,30 @@
 // limitations under the License.
 //
 
+cc_defaults {
+    name: "viewcompiler_defaults",
+    shared_libs: [
+        "libdexfile",
+        "slicer",
+    ],
+}
+
 cc_library_host_static {
     name: "libviewcompiler",
+    defaults: ["viewcompiler_defaults"],
     srcs: [
+        "dex_builder.cc",
         "java_lang_builder.cc",
         "util.cc",
     ],
     static_libs: [
-        "libbase"
-    ]
+        "libbase",
+    ],
 }
 
 cc_binary_host {
     name: "viewcompiler",
+    defaults: ["viewcompiler_defaults"],
     srcs: [
         "main.cc",
     ],
@@ -40,10 +51,12 @@
 
 cc_test_host {
     name: "view-compiler-tests",
+    defaults: ["viewcompiler_defaults"],
     srcs: [
+        "dex_builder_test.cc",
         "util_test.cc",
     ],
     static_libs: [
         "libviewcompiler",
-    ]
+    ],
 }
diff --git a/startop/tools/view_compiler/dex_builder.cc b/startop/tools/view_compiler/dex_builder.cc
new file mode 100644
index 0000000..7a9f41f
--- /dev/null
+++ b/startop/tools/view_compiler/dex_builder.cc
@@ -0,0 +1,214 @@
+/*
+ * Copyright (C) 2018 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 "dex_builder.h"
+
+#include "dex/descriptors_names.h"
+#include "dex/dex_instruction.h"
+
+#include <fstream>
+#include <memory>
+
+namespace startop {
+namespace dex {
+
+using std::shared_ptr;
+using std::string;
+
+using art::Instruction;
+using ::dex::kAccPublic;
+
+const TypeDescriptor TypeDescriptor::Int() { return TypeDescriptor{"I"}; };
+const TypeDescriptor TypeDescriptor::Void() { return TypeDescriptor{"V"}; };
+
+namespace {
+// From https://source.android.com/devices/tech/dalvik/dex-format#dex-file-magic
+constexpr uint8_t kDexFileMagic[]{0x64, 0x65, 0x78, 0x0a, 0x30, 0x33, 0x38, 0x00};
+
+// Strings lengths can be 32 bits long, but encoded as LEB128 this can take up to five bytes.
+constexpr size_t kMaxEncodedStringLength{5};
+
+}  // namespace
+
+void* TrackingAllocator::Allocate(size_t size) {
+  std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(size);
+  void* raw_buffer = buffer.get();
+  allocations_[raw_buffer] = std::move(buffer);
+  return raw_buffer;
+}
+
+void TrackingAllocator::Free(void* ptr) { allocations_.erase(allocations_.find(ptr)); }
+
+// Write out a DEX file that is basically:
+//
+// package dextest;
+// public class DexTest {
+//     public static int foo() { return 5; }
+// }
+void WriteTestDexFile(const string& filename) {
+  DexBuilder dex_file;
+
+  ClassBuilder cbuilder{dex_file.MakeClass("dextest.DexTest")};
+  cbuilder.set_source_file("dextest.java");
+
+  MethodBuilder method{cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Int()})};
+
+  MethodBuilder::Register r = method.MakeRegister();
+  method.BuildConst4(r, 5);
+  method.BuildReturn(r);
+
+  method.Encode();
+
+  slicer::MemView image{dex_file.CreateImage()};
+
+  std::ofstream out_file(filename);
+  out_file.write(image.ptr<const char>(), image.size());
+}
+
+DexBuilder::DexBuilder() : dex_file_{std::make_shared<ir::DexFile>()} {
+  dex_file_->magic = slicer::MemView{kDexFileMagic, sizeof(kDexFileMagic)};
+}
+
+slicer::MemView DexBuilder::CreateImage() {
+  ::dex::Writer writer(dex_file_);
+  size_t image_size{0};
+  ::dex::u1* image = writer.CreateImage(&allocator_, &image_size);
+  return slicer::MemView{image, image_size};
+}
+
+ir::String* DexBuilder::GetOrAddString(const std::string& string) {
+  ir::String*& entry = strings_[string];
+
+  if (entry == nullptr) {
+    // Need to encode the length and then write out the bytes, including 1 byte for null terminator
+    auto buffer = std::make_unique<uint8_t[]>(string.size() + kMaxEncodedStringLength + 1);
+    uint8_t* string_data_start = ::dex::WriteULeb128(buffer.get(), string.size());
+
+    size_t header_length =
+        reinterpret_cast<uintptr_t>(string_data_start) - reinterpret_cast<uintptr_t>(buffer.get());
+
+    auto end = std::copy(string.begin(), string.end(), string_data_start);
+    *end = '\0';
+
+    entry = Alloc<ir::String>();
+    // +1 for null terminator
+    entry->data = slicer::MemView{buffer.get(), header_length + string.size() + 1};
+    string_data_.push_back(std::move(buffer));
+  }
+  return entry;
+}
+
+ClassBuilder DexBuilder::MakeClass(const std::string& name) {
+  auto* class_def = Alloc<ir::Class>();
+  ir::Type* type_def = GetOrAddType(art::DotToDescriptor(name.c_str()));
+  type_def->class_def = class_def;
+
+  class_def->type = type_def;
+  class_def->super_class = GetOrAddType(art::DotToDescriptor("java.lang.Object"));
+  class_def->access_flags = kAccPublic;
+  return ClassBuilder{this, class_def};
+}
+
+// TODO(eholk): we probably want GetOrAddString() also
+ir::Type* DexBuilder::GetOrAddType(const std::string& descriptor) {
+  if (types_by_descriptor_.find(descriptor) != types_by_descriptor_.end()) {
+    return types_by_descriptor_[descriptor];
+  }
+
+  ir::Type* type = Alloc<ir::Type>();
+  type->descriptor = GetOrAddString(descriptor);
+  types_by_descriptor_[descriptor] = type;
+  return type;
+}
+
+ir::Proto* Prototype::Encode(DexBuilder* dex) const {
+  auto* proto = dex->Alloc<ir::Proto>();
+  proto->shorty = dex->GetOrAddString(Shorty());
+  proto->return_type = dex->GetOrAddType(return_type_.descriptor());
+  if (param_types_.size() > 0) {
+    proto->param_types = dex->Alloc<ir::TypeList>();
+    for (const auto& param_type : param_types_) {
+      proto->param_types->types.push_back(dex->GetOrAddType(param_type.descriptor()));
+    }
+  } else {
+    proto->param_types = nullptr;
+  }
+  return proto;
+}
+
+std::string Prototype::Shorty() const {
+  std::string shorty;
+  shorty.append(return_type_.short_descriptor());
+  for (const auto& type_descriptor : param_types_) {
+    shorty.append(type_descriptor.short_descriptor());
+  }
+  return shorty;
+}
+
+ClassBuilder::ClassBuilder(DexBuilder* parent, ir::Class* class_def)
+    : parent_(parent), class_(class_def) {}
+
+MethodBuilder ClassBuilder::CreateMethod(const std::string& name, Prototype prototype) {
+  ir::String* dex_name{parent_->GetOrAddString(name)};
+
+  auto* decl = parent_->Alloc<ir::MethodDecl>();
+  decl->name = dex_name;
+  decl->parent = class_->type;
+  decl->prototype = prototype.Encode(parent_);
+
+  return MethodBuilder{parent_, class_, decl};
+}
+
+void ClassBuilder::set_source_file(const string& source) {
+  class_->source_file = parent_->GetOrAddString(source);
+}
+
+MethodBuilder::MethodBuilder(DexBuilder* dex, ir::Class* class_def, ir::MethodDecl* decl)
+    : dex_{dex}, class_{class_def}, decl_{decl} {}
+
+ir::EncodedMethod* MethodBuilder::Encode() {
+  auto* method = dex_->Alloc<ir::EncodedMethod>();
+  method->decl = decl_;
+
+  // TODO: make access flags configurable
+  method->access_flags = kAccPublic | ::dex::kAccStatic;
+
+  auto* code = dex_->Alloc<ir::Code>();
+  code->registers = num_registers_;
+  // TODO: support ins and outs
+  code->instructions = slicer::ArrayView<const ::dex::u2>(buffer_.data(), buffer_.size());
+  method->code = code;
+
+  class_->direct_methods.push_back(method);
+
+  return method;
+}
+
+MethodBuilder::Register MethodBuilder::MakeRegister() { return num_registers_++; }
+
+void MethodBuilder::BuildReturn() { buffer_.push_back(Instruction::RETURN_VOID); }
+
+void MethodBuilder::BuildReturn(Register src) { buffer_.push_back(Instruction::RETURN | src << 8); }
+
+void MethodBuilder::BuildConst4(Register target, int value) {
+  DCHECK_LT(value, 16);
+  // TODO: support more registers
+  DCHECK_LT(target, 16);
+  buffer_.push_back(Instruction::CONST_4 | (value << 12) | (target << 8));
+}
+
+}  // namespace dex
+}  // namespace startop
diff --git a/startop/tools/view_compiler/dex_builder.h b/startop/tools/view_compiler/dex_builder.h
new file mode 100644
index 0000000..d280abc
--- /dev/null
+++ b/startop/tools/view_compiler/dex_builder.h
@@ -0,0 +1,189 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+#ifndef DEX_BUILDER_H_
+#define DEX_BUILDER_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "slicer/dex_ir.h"
+#include "slicer/writer.h"
+
+namespace startop {
+namespace dex {
+
+// TODO: remove this once the dex generation code is complete.
+void WriteTestDexFile(const std::string& filename);
+
+//////////////////////////
+// Forward declarations //
+//////////////////////////
+class DexBuilder;
+
+// Our custom allocator for dex::Writer
+//
+// This keeps track of all allocations and ensures they are freed when
+// TrackingAllocator is destroyed. Pointers to memory allocated by this
+// allocator must not outlive the allocator.
+class TrackingAllocator : public ::dex::Writer::Allocator {
+ public:
+  virtual void* Allocate(size_t size);
+  virtual void Free(void* ptr);
+
+ private:
+  std::map<void*, std::unique_ptr<uint8_t[]>> allocations_;
+};
+
+// Represents a DEX type descriptor.
+//
+// TODO: add a way to create a descriptor for a reference of a class type.
+class TypeDescriptor {
+ public:
+  // Named constructors for base type descriptors.
+  static const TypeDescriptor Int();
+  static const TypeDescriptor Void();
+
+  // Return the full descriptor, such as I or Ljava/lang/Object
+  const std::string& descriptor() const { return descriptor_; }
+  // Return the shorty descriptor, such as I or L
+  std::string short_descriptor() const { return descriptor().substr(0, 1); }
+
+ private:
+  TypeDescriptor(std::string descriptor) : descriptor_{descriptor} {}
+
+  const std::string descriptor_;
+};
+
+// Defines a function signature. For example, Prototype{TypeDescriptor::VOID, TypeDescriptor::Int}
+// represents the function type (Int) -> Void.
+class Prototype {
+ public:
+  template <typename... TypeDescriptors>
+  Prototype(TypeDescriptor return_type, TypeDescriptors... param_types)
+      : return_type_{return_type}, param_types_{param_types...} {}
+
+  // Encode this prototype into the dex file.
+  ir::Proto* Encode(DexBuilder* dex) const;
+
+  // Get the shorty descriptor, such as VII for (Int, Int) -> Void
+  std::string Shorty() const;
+
+ private:
+  const TypeDescriptor return_type_;
+  const std::vector<TypeDescriptor> param_types_;
+};
+
+// Tools to help build methods and their bodies.
+class MethodBuilder {
+ public:
+  MethodBuilder(DexBuilder* dex, ir::Class* class_def, ir::MethodDecl* decl);
+
+  // Encode the method into DEX format.
+  ir::EncodedMethod* Encode();
+
+  // Registers are just represented by their number.
+  using Register = size_t;
+
+  // Create a new register to be used to storing values. Note that these are not SSA registers, like
+  // might be expected in similar code generators. This does no liveness tracking or anything, so
+  // it's up to the caller to reuse registers as appropriate.
+  Register MakeRegister();
+
+  /////////////////////////////////
+  // Instruction builder methods //
+  /////////////////////////////////
+
+  // return-void
+  void BuildReturn();
+  void BuildReturn(Register src);
+  // const/4
+  void BuildConst4(Register target, int value);
+
+  // TODO: add builders for more instructions
+
+ private:
+  DexBuilder* dex_;
+  ir::Class* class_;
+  ir::MethodDecl* decl_;
+
+  // A buffer to hold instructions we are generating.
+  std::vector<::dex::u2> buffer_;
+
+  // How many registers we've allocated
+  size_t num_registers_;
+};
+
+// A helper to build class definitions.
+class ClassBuilder {
+ public:
+  ClassBuilder(DexBuilder* parent, ir::Class* class_def);
+
+  void set_source_file(const std::string& source);
+
+  // Create a method with the given name and prototype. The returned MethodBuilder can be used to
+  // fill in the method body.
+  MethodBuilder CreateMethod(const std::string& name, Prototype prototype);
+
+ private:
+  DexBuilder* parent_;
+  ir::Class* class_;
+};
+
+// Builds Dex files from scratch.
+class DexBuilder {
+ public:
+  DexBuilder();
+
+  // Create an in-memory image of the DEX file that can either be loaded directly or written to a
+  // file.
+  slicer::MemView CreateImage();
+
+  template <typename T>
+  T* Alloc() {
+    return dex_file_->Alloc<T>();
+  }
+
+  // Find the ir::String that matches the given string, creating it if it does not exist.
+  ir::String* GetOrAddString(const std::string& string);
+  // Create a new class of the given name.
+  ClassBuilder MakeClass(const std::string& name);
+
+  // Add a type for the given descriptor, or return the existing one if it already exists.
+  // See the TypeDescriptor class for help generating these.
+  ir::Type* GetOrAddType(const std::string& descriptor);
+
+ private:
+  std::shared_ptr<ir::DexFile> dex_file_;
+
+  // allocator_ is needed to be able to encode the image.
+  TrackingAllocator allocator_;
+
+  // We'll need to allocate buffers for all of the encoded strings we create. This is where we store
+  // all of them.
+  std::vector<std::unique_ptr<uint8_t[]>> string_data_;
+
+  // Keep track of what types we've defined so we can look them up later.
+  std::map<std::string, ir::Type*> types_by_descriptor_;
+
+  // Keep track of what strings we've defined so we can look them up later.
+  std::map<std::string, ir::String*> strings_;
+};
+
+}  // namespace dex
+}  // namespace startop
+
+#endif  // DEX_BUILDER_H_
diff --git a/startop/tools/view_compiler/dex_builder_test.cc b/startop/tools/view_compiler/dex_builder_test.cc
new file mode 100644
index 0000000..0d8b854
--- /dev/null
+++ b/startop/tools/view_compiler/dex_builder_test.cc
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2018 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 "dex_builder.h"
+
+#include "dex/art_dex_file_loader.h"
+#include "dex/dex_file.h"
+#include "gtest/gtest.h"
+
+using namespace startop::dex;
+
+// Takes a DexBuilder, encodes it into an in-memory DEX file, verifies the resulting DEX file and
+// returns whether the verification was successful.
+bool EncodeAndVerify(DexBuilder* dex_file) {
+  slicer::MemView image{dex_file->CreateImage()};
+
+  art::ArtDexFileLoader loader;
+  std::string error_msg;
+  std::unique_ptr<const art::DexFile> loaded_dex_file{loader.Open(image.ptr<const uint8_t>(),
+                                                                  image.size(),
+                                                                  /*location=*/"",
+                                                                  /*location_checksum=*/0,
+                                                                  /*oat_dex_file=*/nullptr,
+                                                                  /*verify=*/true,
+                                                                  /*verify_checksum=*/false,
+                                                                  &error_msg)};
+  return loaded_dex_file != nullptr;
+}
+
+TEST(DexBuilderTest, VerifyDexWithClassMethod) {
+  DexBuilder dex_file;
+
+  auto cbuilder{dex_file.MakeClass("dextest.DexTest")};
+
+  auto method{cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Void()})};
+  method.BuildReturn();
+  method.Encode();
+
+  EXPECT_TRUE(EncodeAndVerify(&dex_file));
+}
+
+// Makes sure a bad DEX class fails to verify.
+TEST(DexBuilderTest, VerifyBadDexWithClassMethod) {
+  DexBuilder dex_file;
+
+  auto cbuilder{dex_file.MakeClass("dextest.DexTest")};
+
+  // This method has the error, because methods cannot take Void() as a parameter.
+  auto method{
+      cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Void(), TypeDescriptor::Void()})};
+  method.BuildReturn();
+  method.Encode();
+
+  EXPECT_FALSE(EncodeAndVerify(&dex_file));
+}
+
+TEST(DexBuilderTest, VerifyDexReturn5) {
+  DexBuilder dex_file;
+
+  auto cbuilder{dex_file.MakeClass("dextest.DexTest")};
+
+  auto method{cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Int()})};
+  auto r = method.MakeRegister();
+  method.BuildConst4(r, 5);
+  method.BuildReturn(r);
+  method.Encode();
+
+  EXPECT_TRUE(EncodeAndVerify(&dex_file));
+}
diff --git a/startop/tools/view_compiler/main.cc b/startop/tools/view_compiler/main.cc
index 0ad7e24..7d791c2 100644
--- a/startop/tools/view_compiler/main.cc
+++ b/startop/tools/view_compiler/main.cc
@@ -16,6 +16,7 @@
 
 #include "gflags/gflags.h"
 
+#include "dex_builder.h"
 #include "java_lang_builder.h"
 #include "util.h"
 
@@ -27,15 +28,17 @@
 #include <string>
 #include <vector>
 
+namespace {
+
 using namespace tinyxml2;
 using std::string;
 
 constexpr char kStdoutFilename[]{"stdout"};
 
-DEFINE_string(package, "", "The package name for the generated class (required)");
+DEFINE_bool(dex, false, "Generate a DEX file instead of Java");
 DEFINE_string(out, kStdoutFilename, "Where to write the generated class");
+DEFINE_string(package, "", "The package name for the generated class (required)");
 
-namespace {
 class ViewCompilerXmlVisitor : public XMLVisitor {
  public:
   ViewCompilerXmlVisitor(JavaLangViewBuilder* builder) : builder_(builder) {}
@@ -63,6 +66,7 @@
  private:
   JavaLangViewBuilder* builder_;
 };
+
 }  // end namespace
 
 int main(int argc, char** argv) {
@@ -82,6 +86,11 @@
     return 1;
   }
 
+  if (FLAGS_dex) {
+    startop::dex::WriteTestDexFile("test.dex");
+    return 0;
+  }
+
   const char* const filename = argv[kFileNameParam];
   const string layout_name = FindLayoutNameFromFilename(filename);
 
@@ -102,4 +111,4 @@
   xml.Accept(&visitor);
 
   return 0;
-}
\ No newline at end of file
+}