[view-compiler] Support method declaration and invocation in Dex builder

The Dex builder can now generate calls to methods (although not in all forms
yet). To help do this, we add a new virtual Instruction and Value class. This is
needed to generate code with values that are not known until the entire method
has been generated. In particular, we can now refer to function parameters.

The test method now accepts a String and returns the the length of the string.

Bug: 111895153
Change-Id: I11d52b083ae51d8151fccb1a65e45d40ff05fd81

5 files changed, 390 insertions, 51 deletions

diff --git a/startop/view_compiler/Android.bp b/startop/view_compiler/Android.bp
index 3681529643bc..c39688cb8f2d 100644
--- a/startop/view_compiler/Android.bp
+++ b/startop/view_compiler/Android.bp
@@ -16,10 +16,15 @@
 
 cc_defaults {
     name: "viewcompiler_defaults",
+    header_libs: [
+        "libbase_headers",
+    ],
     shared_libs: [
+        "libbase",
         "libdexfile",
         "slicer",
     ],
+    cppflags: ["-std=c++17"],
 }
 
 cc_library_host_static {
@@ -30,9 +35,6 @@ cc_library_host_static {
         "java_lang_builder.cc",
         "util.cc",
     ],
-    static_libs: [
-        "libbase",
-    ],
 }
 
 cc_binary_host {
@@ -42,7 +44,6 @@ cc_binary_host {
         "main.cc",
     ],
     static_libs: [
-        "libbase",
         "libtinyxml2",
         "libgflags",
         "libviewcompiler",
@@ -59,4 +60,5 @@ cc_test_host {
     static_libs: [
         "libviewcompiler",
     ],
+    test_suites: ["general-tests"],
 }
diff --git a/startop/view_compiler/TEST_MAPPING b/startop/view_compiler/TEST_MAPPING
deleted file mode 100644
index cc4b17a7a65a..000000000000
--- a/startop/view_compiler/TEST_MAPPING
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "presubmit": [
-    {
-      "name": "view-compiler-tests"
-    }
-  ]
-}
diff --git a/startop/view_compiler/dex_builder.cc b/startop/view_compiler/dex_builder.cc
index 7a9f41fd8f38..13e7f73e6713 100644
--- a/startop/view_compiler/dex_builder.cc
+++ b/startop/view_compiler/dex_builder.cc
@@ -22,14 +22,16 @@
 #include <fstream>
 #include <memory>
 
+#define DCHECK_NOT_NULL(p) DCHECK((p) != nullptr)
+
 namespace startop {
 namespace dex {
 
 using std::shared_ptr;
 using std::string;
 
-using art::Instruction;
 using ::dex::kAccPublic;
+using Op = Instruction::Op;
 
 const TypeDescriptor TypeDescriptor::Int() { return TypeDescriptor{"I"}; };
 const TypeDescriptor TypeDescriptor::Void() { return TypeDescriptor{"V"}; };
@@ -43,6 +45,20 @@ constexpr size_t kMaxEncodedStringLength{5};
 
 }  // namespace
 
+std::ostream& operator<<(std::ostream& out, const Instruction::Op& opcode) {
+  switch (opcode) {
+    case Instruction::Op::kReturn:
+      out << "kReturn";
+      return out;
+    case Instruction::Op::kMove:
+      out << "kMove";
+      return out;
+    case Instruction::Op::kInvokeVirtual:
+      out << "kInvokeVirtual";
+      return out;
+  }
+}
+
 void* TrackingAllocator::Allocate(size_t size) {
   std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(size);
   void* raw_buffer = buffer.get();
@@ -56,7 +72,7 @@ void TrackingAllocator::Free(void* ptr) { allocations_.erase(allocations_.find(p
 //
 // package dextest;
 // public class DexTest {
-//     public static int foo() { return 5; }
+//     public static int foo(String s) { return s.length(); }
 // }
 void WriteTestDexFile(const string& filename) {
   DexBuilder dex_file;
@@ -64,11 +80,17 @@ void WriteTestDexFile(const string& filename) {
   ClassBuilder cbuilder{dex_file.MakeClass("dextest.DexTest")};
   cbuilder.set_source_file("dextest.java");
 
-  MethodBuilder method{cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Int()})};
+  TypeDescriptor string_type = TypeDescriptor::FromClassname("java.lang.String");
+
+  MethodBuilder method{cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Int(), string_type})};
+
+  Value result = method.MakeRegister();
 
-  MethodBuilder::Register r = method.MakeRegister();
-  method.BuildConst4(r, 5);
-  method.BuildReturn(r);
+  MethodDeclData string_length =
+      dex_file.GetOrDeclareMethod(string_type, "length", Prototype{TypeDescriptor::Int()});
+
+  method.AddInstruction(Instruction::InvokeVirtual(string_length.id, result, Value::Parameter(0)));
+  method.BuildReturn(result);
 
   method.Encode();
 
@@ -78,6 +100,10 @@ void WriteTestDexFile(const string& filename) {
   out_file.write(image.ptr<const char>(), image.size());
 }
 
+TypeDescriptor TypeDescriptor::FromClassname(const std::string& name) {
+  return TypeDescriptor{art::DotToDescriptor(name.c_str())};
+}
+
 DexBuilder::DexBuilder() : dex_file_{std::make_shared<ir::DexFile>()} {
   dex_file_->magic = slicer::MemView{kDexFileMagic, sizeof(kDexFileMagic)};
 }
@@ -119,10 +145,9 @@ ClassBuilder DexBuilder::MakeClass(const std::string& name) {
   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};
+  return ClassBuilder{this, name, 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];
@@ -158,16 +183,11 @@ std::string Prototype::Shorty() const {
   return shorty;
 }
 
-ClassBuilder::ClassBuilder(DexBuilder* parent, ir::Class* class_def)
-    : parent_(parent), class_(class_def) {}
+ClassBuilder::ClassBuilder(DexBuilder* parent, const std::string& name, ir::Class* class_def)
+    : parent_(parent), type_descriptor_{TypeDescriptor::FromClassname(name)}, 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_);
+  ir::MethodDecl* decl = parent_->GetOrDeclareMethod(type_descriptor_, name, prototype).decl;
 
   return MethodBuilder{parent_, class_, decl};
 }
@@ -187,8 +207,13 @@ ir::EncodedMethod* MethodBuilder::Encode() {
   method->access_flags = kAccPublic | ::dex::kAccStatic;
 
   auto* code = dex_->Alloc<ir::Code>();
-  code->registers = num_registers_;
-  // TODO: support ins and outs
+  DCHECK_NOT_NULL(decl_->prototype);
+  size_t const num_args =
+      decl_->prototype->param_types != nullptr ? decl_->prototype->param_types->types.size() : 0;
+  code->registers = num_registers_ + num_args;
+  code->ins_count = num_args;
+  code->outs_count = decl_->prototype->return_type == dex_->GetOrAddType("V") ? 0 : 1;
+  EncodeInstructions();
   code->instructions = slicer::ArrayView<const ::dex::u2>(buffer_.data(), buffer_.size());
   method->code = code;
 
@@ -197,17 +222,135 @@ ir::EncodedMethod* MethodBuilder::Encode() {
   return method;
 }
 
-MethodBuilder::Register MethodBuilder::MakeRegister() { return num_registers_++; }
+Value MethodBuilder::MakeRegister() { return Value::Local(num_registers_++); }
+
+void MethodBuilder::AddInstruction(Instruction instruction) {
+  instructions_.push_back(instruction);
+}
 
-void MethodBuilder::BuildReturn() { buffer_.push_back(Instruction::RETURN_VOID); }
+void MethodBuilder::BuildReturn() { AddInstruction(Instruction::OpNoArgs(Op::kReturn)); }
 
-void MethodBuilder::BuildReturn(Register src) { buffer_.push_back(Instruction::RETURN | src << 8); }
+void MethodBuilder::BuildReturn(Value src) {
+  AddInstruction(Instruction::OpWithArgs(Op::kReturn, /*destination=*/{}, src));
+}
 
-void MethodBuilder::BuildConst4(Register target, int value) {
+void MethodBuilder::BuildConst4(Value 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));
+  AddInstruction(Instruction::OpWithArgs(Op::kMove, target, Value::Immediate(value)));
+}
+
+void MethodBuilder::EncodeInstructions() {
+  buffer_.clear();
+  for (const auto& instruction : instructions_) {
+    EncodeInstruction(instruction);
+  }
+}
+
+void MethodBuilder::EncodeInstruction(const Instruction& instruction) {
+  switch (instruction.opcode()) {
+    case Instruction::Op::kReturn:
+      return EncodeReturn(instruction);
+    case Instruction::Op::kMove:
+      return EncodeMove(instruction);
+    case Instruction::Op::kInvokeVirtual:
+      return EncodeInvokeVirtual(instruction);
+  }
+}
+
+void MethodBuilder::EncodeReturn(const Instruction& instruction) {
+  DCHECK_EQ(Instruction::Op::kReturn, instruction.opcode());
+  DCHECK(!instruction.dest().has_value());
+  if (instruction.args().size() == 0) {
+    buffer_.push_back(art::Instruction::RETURN_VOID);
+  } else {
+    DCHECK(instruction.args().size() == 1);
+    size_t source = RegisterValue(instruction.args()[0]);
+    buffer_.push_back(art::Instruction::RETURN | source << 8);
+  }
+}
+
+void MethodBuilder::EncodeMove(const Instruction& instruction) {
+  DCHECK_EQ(Instruction::Op::kMove, instruction.opcode());
+  DCHECK(instruction.dest().has_value());
+  DCHECK(instruction.dest()->is_register() || instruction.dest()->is_parameter());
+  DCHECK_EQ(1, instruction.args().size());
+
+  const Value& source = instruction.args()[0];
+
+  if (source.is_immediate()) {
+    // TODO: support more registers
+    DCHECK_LT(RegisterValue(*instruction.dest()), 16);
+    DCHECK_LT(source.value(), 16);
+    buffer_.push_back(art::Instruction::CONST_4 | (source.value() << 12) |
+                      (RegisterValue(*instruction.dest()) << 8));
+  } else {
+    UNIMPLEMENTED(FATAL);
+  }
+}
+
+void MethodBuilder::EncodeInvokeVirtual(const Instruction& instruction) {
+  DCHECK_EQ(Instruction::Op::kInvokeVirtual, instruction.opcode());
+
+  // TODO: support more than one argument (i.e. the this argument) and change this to DCHECK_GE
+  DCHECK_EQ(1, instruction.args().size());
+
+  const Value& this_arg = instruction.args()[0];
+
+  size_t real_reg = RegisterValue(this_arg) & 0xf;
+  buffer_.push_back(1 << 12 | art::Instruction::INVOKE_VIRTUAL);
+  buffer_.push_back(instruction.method_id());
+  buffer_.push_back(real_reg);
+
+  if (instruction.dest().has_value()) {
+    real_reg = RegisterValue(*instruction.dest());
+    buffer_.push_back(real_reg << 8 | art::Instruction::MOVE_RESULT);
+  }
+}
+
+size_t MethodBuilder::RegisterValue(Value value) const {
+  if (value.is_register()) {
+    return value.value();
+  } else if (value.is_parameter()) {
+    return value.value() + num_registers_;
+  }
+  DCHECK(false && "Must be either a parameter or a register");
+  return 0;
+}
+
+const MethodDeclData& DexBuilder::GetOrDeclareMethod(TypeDescriptor type, const std::string& name,
+                                                     Prototype prototype) {
+  MethodDeclData& entry = method_id_map_[{type, name, prototype}];
+
+  if (entry.decl == nullptr) {
+    // This method has not already been declared, so declare it.
+    ir::MethodDecl* decl = dex_file_->Alloc<ir::MethodDecl>();
+    // The method id is the last added method.
+    size_t id = dex_file_->methods.size() - 1;
+
+    ir::String* dex_name{GetOrAddString(name)};
+    decl->name = dex_name;
+    decl->parent = GetOrAddType(type.descriptor());
+    decl->prototype = GetOrEncodeProto(prototype);
+
+    // update the index -> ir node map (see tools/dexter/slicer/dex_ir_builder.cc)
+    auto new_index = dex_file_->methods_indexes.AllocateIndex();
+    auto& ir_node = dex_file_->methods_map[new_index];
+    SLICER_CHECK(ir_node == nullptr);
+    ir_node = decl;
+    decl->orig_index = new_index;
+
+    entry = {id, decl};
+  }
+
+  return entry;
+}
+
+ir::Proto* DexBuilder::GetOrEncodeProto(Prototype prototype) {
+  ir::Proto*& ir_proto = proto_map_[prototype];
+  if (ir_proto == nullptr) {
+    ir_proto = prototype.Encode(this);
+  }
+  return ir_proto;
 }
 
 }  // namespace dex
diff --git a/startop/view_compiler/dex_builder.h b/startop/view_compiler/dex_builder.h
index d280abce21f5..e46655e0d429 100644
--- a/startop/view_compiler/dex_builder.h
+++ b/startop/view_compiler/dex_builder.h
@@ -17,7 +17,9 @@
 #define DEX_BUILDER_H_
 
 #include <map>
+#include <optional>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include "slicer/dex_ir.h"
@@ -45,7 +47,7 @@ class TrackingAllocator : public ::dex::Writer::Allocator {
   virtual void Free(void* ptr);
 
  private:
-  std::map<void*, std::unique_ptr<uint8_t[]>> allocations_;
+  std::unordered_map<void*, std::unique_ptr<uint8_t[]>> allocations_;
 };
 
 // Represents a DEX type descriptor.
@@ -57,11 +59,17 @@ class TypeDescriptor {
   static const TypeDescriptor Int();
   static const TypeDescriptor Void();
 
+  // Creates a type descriptor from a fully-qualified class name. For example, it turns the class
+  // name java.lang.Object into the descriptor Ljava/lang/Object.
+  static TypeDescriptor FromClassname(const std::string& name);
+
   // 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); }
 
+  bool operator<(const TypeDescriptor& rhs) const { return descriptor_ < rhs.descriptor_; }
+
  private:
   TypeDescriptor(std::string descriptor) : descriptor_{descriptor} {}
 
@@ -82,11 +90,98 @@ class Prototype {
   // Get the shorty descriptor, such as VII for (Int, Int) -> Void
   std::string Shorty() const;
 
+  bool operator<(const Prototype& rhs) const {
+    return std::make_tuple(return_type_, param_types_) <
+           std::make_tuple(rhs.return_type_, rhs.param_types_);
+  }
+
  private:
   const TypeDescriptor return_type_;
   const std::vector<TypeDescriptor> param_types_;
 };
 
+// Represents a DEX register or constant. We separate regular registers and parameters
+// because we will not know the real parameter id until after all instructions
+// have been generated.
+class Value {
+ public:
+  static constexpr Value Local(size_t id) { return Value{id, Kind::kLocalRegister}; }
+  static constexpr Value Parameter(size_t id) { return Value{id, Kind::kParameter}; }
+  static constexpr Value Immediate(size_t value) { return Value{value, Kind::kImmediate}; }
+
+  bool is_register() const { return kind_ == Kind::kLocalRegister; }
+  bool is_parameter() const { return kind_ == Kind::kParameter; }
+  bool is_immediate() const { return kind_ == Kind::kImmediate; }
+
+  size_t value() const { return value_; }
+
+ private:
+  enum class Kind { kLocalRegister, kParameter, kImmediate };
+
+  const size_t value_;
+  const Kind kind_;
+
+  constexpr Value(size_t value, Kind kind) : value_{value}, kind_{kind} {}
+};
+
+// A virtual instruction. We convert these to real instructions in MethodBuilder::Encode.
+// Virtual instructions are needed to keep track of information that is not known until all of the
+// code is generated. This information includes things like how many local registers are created and
+// branch target locations.
+class Instruction {
+ public:
+  // The operation performed by this instruction. These are virtual instructions that do not
+  // correspond exactly to DEX instructions.
+  enum class Op { kReturn, kMove, kInvokeVirtual };
+
+  ////////////////////////
+  // Named Constructors //
+  ////////////////////////
+
+  // For instructions with no return value and no arguments.
+  static inline Instruction OpNoArgs(Op opcode) {
+    return Instruction{opcode, /*method_id*/ 0, /*dest*/ {}};
+  }
+  // For most instructions, which take some number of arguments and have an optional return value.
+  template <typename... T>
+  static inline Instruction OpWithArgs(Op opcode, std::optional<const Value> dest, T... args) {
+    return Instruction{opcode, /*method_id*/ 0, dest, args...};
+  }
+  // For method calls.
+  template <typename... T>
+  static inline Instruction InvokeVirtual(size_t method_id, std::optional<const Value> dest,
+                                          Value this_arg, T... args) {
+    return Instruction{Op::kInvokeVirtual, method_id, dest, this_arg, args...};
+  }
+
+  ///////////////
+  // Accessors //
+  ///////////////
+
+  Op opcode() const { return opcode_; }
+  size_t method_id() const { return method_id_; }
+  const std::optional<const Value>& dest() const { return dest_; }
+  const std::vector<const Value>& args() const { return args_; }
+
+ private:
+  inline Instruction(Op opcode, size_t method_id, std::optional<const Value> dest)
+      : opcode_{opcode}, method_id_{method_id}, dest_{dest}, args_{} {}
+
+  template <typename... T>
+  inline constexpr Instruction(Op opcode, size_t method_id, std::optional<const Value> dest,
+                               T... args)
+      : opcode_{opcode}, method_id_{method_id}, dest_{dest}, args_{args...} {}
+
+  const Op opcode_;
+  // The index of the method to invoke, for kInvokeVirtual and similar opcodes.
+  const size_t method_id_{0};
+  const std::optional<const Value> dest_;
+  const std::vector<const Value> args_;
+};
+
+// Needed for CHECK_EQ, DCHECK_EQ, etc.
+std::ostream& operator<<(std::ostream& out, const Instruction::Op& opcode);
+
 // Tools to help build methods and their bodies.
 class MethodBuilder {
  public:
@@ -95,42 +190,53 @@ class MethodBuilder {
   // 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();
+  Value MakeRegister();
 
   /////////////////////////////////
   // Instruction builder methods //
   /////////////////////////////////
 
+  void AddInstruction(Instruction instruction);
+
   // return-void
   void BuildReturn();
-  void BuildReturn(Register src);
+  void BuildReturn(Value src);
   // const/4
-  void BuildConst4(Register target, int value);
+  void BuildConst4(Value target, int value);
 
   // TODO: add builders for more instructions
 
  private:
+  void EncodeInstructions();
+  void EncodeInstruction(const Instruction& instruction);
+  void EncodeReturn(const Instruction& instruction);
+  void EncodeMove(const Instruction& instruction);
+  void EncodeInvokeVirtual(const Instruction& instruction);
+
+  // Converts a register or parameter to its DEX register number.
+  size_t RegisterValue(Value value) const;
+
   DexBuilder* dex_;
   ir::Class* class_;
   ir::MethodDecl* decl_;
 
-  // A buffer to hold instructions we are generating.
+  // A list of the instructions we will eventually encode.
+  std::vector<Instruction> instructions_;
+
+  // A buffer to hold instructions that have been encoded.
   std::vector<::dex::u2> buffer_;
 
   // How many registers we've allocated
-  size_t num_registers_;
+  size_t num_registers_{0};
 };
 
 // A helper to build class definitions.
 class ClassBuilder {
  public:
-  ClassBuilder(DexBuilder* parent, ir::Class* class_def);
+  ClassBuilder(DexBuilder* parent, const std::string& name, ir::Class* class_def);
 
   void set_source_file(const std::string& source);
 
@@ -139,8 +245,15 @@ class ClassBuilder {
   MethodBuilder CreateMethod(const std::string& name, Prototype prototype);
 
  private:
-  DexBuilder* parent_;
-  ir::Class* class_;
+  DexBuilder* const parent_;
+  const TypeDescriptor type_descriptor_;
+  ir::Class* const class_;
+};
+
+// Keeps track of information needed to manipulate or call a method.
+struct MethodDeclData {
+  size_t id;
+  ir::MethodDecl* decl;
 };
 
 // Builds Dex files from scratch.
@@ -163,10 +276,19 @@ class DexBuilder {
   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.
+  // See the TypeDescriptor class for help generating these. GetOrAddType can be used to declare
+  // imported classes.
   ir::Type* GetOrAddType(const std::string& descriptor);
 
+  // Returns the method id for the method, creating it if it has not been created yet.
+  const MethodDeclData& GetOrDeclareMethod(TypeDescriptor type, const std::string& name,
+                                           Prototype prototype);
+
  private:
+  // Looks up the ir::Proto* corresponding to this given prototype, or creates one if it does not
+  // exist.
+  ir::Proto* GetOrEncodeProto(Prototype prototype);
+
   std::shared_ptr<ir::DexFile> dex_file_;
 
   // allocator_ is needed to be able to encode the image.
@@ -177,10 +299,29 @@ class DexBuilder {
   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_;
+  std::unordered_map<std::string, ir::Type*> types_by_descriptor_;
+
+  struct MethodDescriptor {
+    TypeDescriptor type;
+    std::string name;
+    Prototype prototype;
+
+    inline bool operator<(const MethodDescriptor& rhs) const {
+      return std::make_tuple(type, name, prototype) <
+             std::make_tuple(rhs.type, rhs.name, rhs.prototype);
+    }
+  };
+
+  // Maps method declarations to their method index. This is needed to encode references to them.
+  // When we go to actually write the DEX file, slicer will re-assign these after correctly sorting
+  // the methods list.
+  std::map<MethodDescriptor, MethodDeclData> method_id_map_;
 
   // Keep track of what strings we've defined so we can look them up later.
-  std::map<std::string, ir::String*> strings_;
+  std::unordered_map<std::string, ir::String*> strings_;
+
+  // Keep track of already-encoded protos.
+  std::map<Prototype, ir::Proto*> proto_map_;
 };
 
 }  // namespace dex
diff --git a/startop/view_compiler/dex_builder_test.cc b/startop/view_compiler/dex_builder_test.cc
index 0d8b8541caeb..61c86b4091b3 100644
--- a/startop/view_compiler/dex_builder_test.cc
+++ b/startop/view_compiler/dex_builder_test.cc
@@ -40,6 +40,12 @@ bool EncodeAndVerify(DexBuilder* dex_file) {
   return loaded_dex_file != nullptr;
 }
 
+// Write out and verify a DEX file that corresponds to:
+//
+// package dextest;
+// public class DexTest {
+//     public static void foo() {}
+// }
 TEST(DexBuilderTest, VerifyDexWithClassMethod) {
   DexBuilder dex_file;
 
@@ -67,6 +73,12 @@ TEST(DexBuilderTest, VerifyBadDexWithClassMethod) {
   EXPECT_FALSE(EncodeAndVerify(&dex_file));
 }
 
+// Write out and verify a DEX file that corresponds to:
+//
+// package dextest;
+// public class DexTest {
+//     public static int foo() { return 5; }
+// }
 TEST(DexBuilderTest, VerifyDexReturn5) {
   DexBuilder dex_file;
 
@@ -80,3 +92,51 @@ TEST(DexBuilderTest, VerifyDexReturn5) {
 
   EXPECT_TRUE(EncodeAndVerify(&dex_file));
 }
+
+// Write out and verify a DEX file that corresponds to:
+//
+// package dextest;
+// public class DexTest {
+//     public static int foo(int x) { return x; }
+// }
+TEST(DexBuilderTest, VerifyDexReturnIntParam) {
+  DexBuilder dex_file;
+
+  auto cbuilder{dex_file.MakeClass("dextest.DexTest")};
+
+  auto method{
+      cbuilder.CreateMethod("foo", Prototype{TypeDescriptor::Int(), TypeDescriptor::Int()})};
+  method.BuildReturn(Value::Parameter(0));
+  method.Encode();
+
+  EXPECT_TRUE(EncodeAndVerify(&dex_file));
+}
+
+// Write out and verify a DEX file that corresponds to:
+//
+// package dextest;
+// public class DexTest {
+//     public static int foo(String s) { return s.length(); }
+// }
+TEST(DexBuilderTest, VerifyDexCallStringLength) {
+  DexBuilder dex_file;
+
+  auto cbuilder{dex_file.MakeClass("dextest.DexTest")};
+
+  MethodBuilder method{cbuilder.CreateMethod(
+      "foo", Prototype{TypeDescriptor::Int(), TypeDescriptor::FromClassname("java.lang.String")})};
+
+  Value result = method.MakeRegister();
+
+  MethodDeclData string_length =
+      dex_file.GetOrDeclareMethod(TypeDescriptor::FromClassname("java.lang.String"),
+                                  "length",
+                                  Prototype{TypeDescriptor::Int()});
+
+  method.AddInstruction(Instruction::InvokeVirtual(string_length.id, result, Value::Parameter(0)));
+  method.BuildReturn(result);
+
+  method.Encode();
+
+  EXPECT_TRUE(EncodeAndVerify(&dex_file));
+}