[Interpreter] Bytecodes for exchanging registers.

New bytecodes for making registers with indicies wider than 1-byte
accessible.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1555713002

Cr-Commit-Position: refs/heads/master@{#33091}

src/compiler/bytecode-graph-builder.cc

@@ -164,12 +164,23 @@ void BytecodeGraphBuilder::Environment::BindAccumulator(
   values()->at(accumulator_base_) = node;
 }
 
+
 void BytecodeGraphBuilder::Environment::RecordAfterState(
     Node* node, FrameStateBeforeAndAfter* states) {
   states->AddToNode(node, AccumulatorUpdateMode::kOutputIgnored);
 }
 
 
+void BytecodeGraphBuilder::Environment::ExchangeRegisters(
+    interpreter::Register reg0, interpreter::Register reg1) {
+  int reg0_index = RegisterToValuesIndex(reg0);
+  int reg1_index = RegisterToValuesIndex(reg1);
+  Node* saved_reg0_value = values()->at(reg0_index);
+  values()->at(reg0_index) = values()->at(reg1_index);
+  values()->at(reg1_index) = saved_reg0_value;
+}
+
+
 Node* BytecodeGraphBuilder::Environment::LookupAccumulator() const {
   return values()->at(accumulator_base_);
 }
@@ -561,6 +572,20 @@ void BytecodeGraphBuilder::VisitMov(
 }
 
 
+void BytecodeGraphBuilder::VisitExchange(
+    const interpreter::BytecodeArrayIterator& iterator) {
+  environment()->ExchangeRegisters(iterator.GetRegisterOperand(0),
+                                   iterator.GetRegisterOperand(1));
+}
+
+
+void BytecodeGraphBuilder::VisitExchangeWide(
+    const interpreter::BytecodeArrayIterator& iterator) {
+  environment()->ExchangeRegisters(iterator.GetRegisterOperand(0),
+                                   iterator.GetRegisterOperand(1));
+}
+
+
 void BytecodeGraphBuilder::BuildLoadGlobal(
     const interpreter::BytecodeArrayIterator& iterator,
     TypeofMode typeof_mode) {

src/compiler/bytecode-graph-builder.h

@@ -267,6 +267,8 @@ class BytecodeGraphBuilder::Environment : public ZoneObject {
 
   void BindRegister(interpreter::Register the_register, Node* node);
   Node* LookupRegister(interpreter::Register the_register) const;
+  void ExchangeRegisters(interpreter::Register reg0,
+                         interpreter::Register reg1);
 
   void BindAccumulator(Node* node, FrameStateBeforeAndAfter* states = nullptr);
   Node* LookupAccumulator() const;

src/compiler/interpreter-assembler.cc

@@ -209,6 +209,46 @@ Node* InterpreterAssembler::BytecodeOperandShort(int operand_index) {
 }
 
 
+Node* InterpreterAssembler::BytecodeOperandShortSignExtended(
+    int operand_index) {
+  DCHECK_LT(operand_index, interpreter::Bytecodes::NumberOfOperands(bytecode_));
+  DCHECK_EQ(interpreter::OperandSize::kShort,
+            interpreter::Bytecodes::GetOperandSize(bytecode_, operand_index));
+  int operand_offset =
+      interpreter::Bytecodes::GetOperandOffset(bytecode_, operand_index);
+  Node* load;
+  if (TargetSupportsUnalignedAccess()) {
+    load = raw_assembler_->Load(
+        MachineType::Int16(), BytecodeArrayTaggedPointer(),
+        IntPtrAdd(BytecodeOffset(), Int32Constant(operand_offset)));
+  } else {
+#if V8_TARGET_LITTLE_ENDIAN
+    Node* hi_byte_offset = Int32Constant(operand_offset + 1);
+    Node* lo_byte_offset = Int32Constant(operand_offset);
+#elif V8_TARGET_BIG_ENDIAN
+    Node* hi_byte_offset = Int32Constant(operand_offset);
+    Node* lo_byte_offset = Int32Constant(operand_offset + 1);
+#else
+#error "Unknown Architecture"
+#endif
+    Node* hi_byte =
+        raw_assembler_->Load(MachineType::Int8(), BytecodeArrayTaggedPointer(),
+                             IntPtrAdd(BytecodeOffset(), hi_byte_offset));
+    Node* lo_byte =
+        raw_assembler_->Load(MachineType::Uint8(), BytecodeArrayTaggedPointer(),
+                             IntPtrAdd(BytecodeOffset(), lo_byte_offset));
+    hi_byte = raw_assembler_->Word32Shl(hi_byte, Int32Constant(kBitsPerByte));
+    load = raw_assembler_->Word32Or(hi_byte, lo_byte);
+  }
+
+  // Ensure that we sign extend to full pointer size
+  if (kPointerSize == 8) {
+    load = raw_assembler_->ChangeInt32ToInt64(load);
+  }
+  return load;
+}
+
+
 Node* InterpreterAssembler::BytecodeOperandCount(int operand_index) {
   switch (interpreter::Bytecodes::GetOperandSize(bytecode_, operand_index)) {
     case interpreter::OperandSize::kByte:
@@ -255,13 +295,22 @@ Node* InterpreterAssembler::BytecodeOperandIdx(int operand_index) {
 
 
 Node* InterpreterAssembler::BytecodeOperandReg(int operand_index) {
-#ifdef DEBUG
-  interpreter::OperandType operand_type =
-      interpreter::Bytecodes::GetOperandType(bytecode_, operand_index);
-  DCHECK(operand_type == interpreter::OperandType::kReg8 ||
-         operand_type == interpreter::OperandType::kMaybeReg8);
-#endif
+  switch (interpreter::Bytecodes::GetOperandType(bytecode_, operand_index)) {
+    case interpreter::OperandType::kReg8:
+    case interpreter::OperandType::kMaybeReg8:
+      DCHECK_EQ(
+          interpreter::OperandSize::kByte,
+          interpreter::Bytecodes::GetOperandSize(bytecode_, operand_index));
       return BytecodeOperandSignExtended(operand_index);
+    case interpreter::OperandType::kReg16:
+      DCHECK_EQ(
+          interpreter::OperandSize::kShort,
+          interpreter::Bytecodes::GetOperandSize(bytecode_, operand_index));
+      return BytecodeOperandShortSignExtended(operand_index);
+    default:
+      UNREACHABLE();
+      return nullptr;
+  }
 }
 
 

src/compiler/interpreter-assembler.h

@@ -181,6 +181,7 @@ class InterpreterAssembler {
   Node* BytecodeOperand(int operand_index);
   Node* BytecodeOperandSignExtended(int operand_index);
   Node* BytecodeOperandShort(int operand_index);
+  Node* BytecodeOperandShortSignExtended(int operand_index);
 
   Node* CallN(CallDescriptor* descriptor, Node* code_target, Node** args);
   Node* CallIC(CallInterfaceDescriptor descriptor, Node* target, Node** args);

src/interpreter/bytecode-array-builder.cc

@@ -379,6 +379,20 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::MoveRegister(Register from,
 }
 
 
+BytecodeArrayBuilder& BytecodeArrayBuilder::ExchangeRegisters(Register reg0,
+                                                              Register reg1) {
+  DCHECK(reg0 != reg1);
+  if (FitsInReg8Operand(reg0)) {
+    Output(Bytecode::kExchange, reg0.ToOperand(), reg1.ToWideOperand());
+  } else if (FitsInReg8Operand(reg1)) {
+    Output(Bytecode::kExchange, reg1.ToOperand(), reg0.ToWideOperand());
+  } else {
+    Output(Bytecode::kExchangeWide, reg0.ToWideOperand(), reg1.ToWideOperand());
+  }
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::LoadGlobal(
     const Handle<String> name, int feedback_slot, LanguageMode language_mode,
     TypeofMode typeof_mode) {
@@ -1163,6 +1177,24 @@ bool BytecodeArrayBuilder::OperandIsValid(Bytecode bytecode, int operand_index,
         return TemporaryRegisterIsLive(reg);
       }
     }
+    case OperandType::kReg16: {
+      if (bytecode != Bytecode::kExchange &&
+          bytecode != Bytecode::kExchangeWide) {
+        return false;
+      }
+      Register reg =
+          Register::FromWideOperand(static_cast<uint16_t>(operand_value));
+      if (reg.is_function_context() || reg.is_function_closure() ||
+          reg.is_new_target()) {
+        return false;
+      } else if (reg.is_parameter()) {
+        return false;
+      } else if (reg.index() < fixed_register_count()) {
+        return true;
+      } else {
+        return TemporaryRegisterIsLive(reg);
+      }
+    }
   }
   UNREACHABLE();
   return false;
@@ -1468,7 +1500,7 @@ bool BytecodeArrayBuilder::FitsInIdx8Operand(size_t value) {
 
 // static
 bool BytecodeArrayBuilder::FitsInImm8Operand(int value) {
-  return kMinInt8 <= value && value < kMaxInt8;
+  return kMinInt8 <= value && value <= kMaxInt8;
 }
 
 
@@ -1484,6 +1516,18 @@ bool BytecodeArrayBuilder::FitsInIdx16Operand(size_t value) {
 }
 
 
+// static
+bool BytecodeArrayBuilder::FitsInReg8Operand(Register value) {
+  return kMinInt8 <= value.index() && value.index() <= kMaxInt8;
+}
+
+
+// static
+bool BytecodeArrayBuilder::FitsInReg16Operand(Register value) {
+  return kMinInt16 <= value.index() && value.index() <= kMaxInt16;
+}
+
+
 TemporaryRegisterScope::TemporaryRegisterScope(BytecodeArrayBuilder* builder)
     : builder_(builder),
       allocated_(builder->zone()),

src/interpreter/bytecode-array-builder.h

@@ -100,6 +100,7 @@ class BytecodeArrayBuilder final {
 
   // Register-register transfer.
   BytecodeArrayBuilder& MoveRegister(Register from, Register to);
+  BytecodeArrayBuilder& ExchangeRegisters(Register reg0, Register reg1);
 
   // Named load property.
   BytecodeArrayBuilder& LoadNamedProperty(Register object,
@@ -249,12 +250,17 @@ class BytecodeArrayBuilder final {
   static bool FitsInImm8Operand(int value);
   static bool FitsInIdx16Operand(int value);
   static bool FitsInIdx16Operand(size_t value);
+  static bool FitsInReg8Operand(Register value);
+  static bool FitsInReg16Operand(Register value);
 
   static Bytecode GetJumpWithConstantOperand(Bytecode jump_with_smi8_operand);
   static Bytecode GetJumpWithToBoolean(Bytecode jump);
 
+  Register MapRegister(Register reg);
+  Register MapRegisters(Register reg, Register args_base, int args_length = 1);
+
   template <size_t N>
-  INLINE(void Output(Bytecode bytecode, uint32_t(&oprands)[N]));
+  INLINE(void Output(Bytecode bytecode, uint32_t(&operands)[N]));
   void Output(Bytecode bytecode, uint32_t operand0, uint32_t operand1,
               uint32_t operand2, uint32_t operand3);
   void Output(Bytecode bytecode, uint32_t operand0, uint32_t operand1,

src/interpreter/bytecode-array-iterator.cc

@@ -75,11 +75,11 @@ int BytecodeArrayIterator::GetCountOperand(int operand_index) const {
 
 
 int BytecodeArrayIterator::GetIndexOperand(int operand_index) const {
-  OperandSize size =
-      Bytecodes::GetOperandSize(current_bytecode(), operand_index);
-  OperandType type =
-      (size == OperandSize::kByte) ? OperandType::kIdx8 : OperandType::kIdx16;
-  uint32_t operand = GetRawOperand(operand_index, type);
+  OperandType operand_type =
+      Bytecodes::GetOperandType(current_bytecode(), operand_index);
+  DCHECK(operand_type == OperandType::kIdx8 ||
+         operand_type == OperandType::kIdx16);
+  uint32_t operand = GetRawOperand(operand_index, operand_type);
   return static_cast<int>(operand);
 }
 
@@ -88,7 +88,8 @@ Register BytecodeArrayIterator::GetRegisterOperand(int operand_index) const {
   OperandType operand_type =
       Bytecodes::GetOperandType(current_bytecode(), operand_index);
   DCHECK(operand_type == OperandType::kReg8 ||
-         operand_type == OperandType::kMaybeReg8);
+         operand_type == OperandType::kMaybeReg8 ||
+         operand_type == OperandType::kReg16);
   uint32_t operand = GetRawOperand(operand_index, operand_type);
   return Register::FromOperand(operand);
 }

src/interpreter/bytecodes.cc

@@ -273,6 +273,18 @@ std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
         }
         break;
       }
+      case interpreter::OperandType::kReg16: {
+        Register reg =
+            Register::FromWideOperand(ReadUnalignedUInt16(operand_start));
+        if (reg.is_parameter()) {
+          int parameter_index = reg.ToParameterIndex(parameter_count);
+          DCHECK_NE(parameter_index, 0);
+          os << "a" << parameter_index - 1;
+        } else {
+          os << "r" << reg.index();
+        }
+        break;
+      }
       case interpreter::OperandType::kNone:
         UNREACHABLE();
         break;
@@ -322,7 +334,7 @@ Register Register::FromParameterIndex(int index, int parameter_count) {
   DCHECK_LE(parameter_count, kMaxParameterIndex + 1);
   int register_index = kLastParamRegisterIndex - parameter_count + index + 1;
   DCHECK_LT(register_index, 0);
-  DCHECK_GE(register_index, Register::kMinRegisterIndex);
+  DCHECK_GE(register_index, kMinInt8);
   return Register(register_index);
 }
 
@@ -364,7 +376,11 @@ bool Register::is_new_target() const {
 int Register::MaxParameterIndex() { return kMaxParameterIndex; }
 
 
-uint8_t Register::ToOperand() const { return static_cast<uint8_t>(-index_); }
+uint8_t Register::ToOperand() const {
+  DCHECK_GE(index_, kMinInt8);
+  DCHECK_LE(index_, kMaxInt8);
+  return static_cast<uint8_t>(-index_);
+}
 
 
 Register Register::FromOperand(uint8_t operand) {
@@ -372,6 +388,18 @@ Register Register::FromOperand(uint8_t operand) {
 }
 
 
+uint16_t Register::ToWideOperand() const {
+  DCHECK_GE(index_, kMinInt16);
+  DCHECK_LE(index_, kMaxInt16);
+  return static_cast<uint16_t>(-index_);
+}
+
+
+Register Register::FromWideOperand(uint16_t operand) {
+  return Register(-static_cast<int16_t>(operand));
+}
+
+
 bool Register::AreContiguous(Register reg1, Register reg2, Register reg3,
                              Register reg4, Register reg5) {
   if (reg1.index() + 1 != reg2.index()) {

src/interpreter/bytecodes.h

@@ -25,12 +25,13 @@ namespace interpreter {
   V(Count8, OperandSize::kByte)    \
   V(Imm8, OperandSize::kByte)      \
   V(Idx8, OperandSize::kByte)      \
-  V(Reg8, OperandSize::kByte)      \
   V(MaybeReg8, OperandSize::kByte) \
+  V(Reg8, OperandSize::kByte)      \
                                    \
   /* Short operands. */            \
   V(Count16, OperandSize::kShort)  \
-  V(Idx16, OperandSize::kShort)
+  V(Idx16, OperandSize::kShort)    \
+  V(Reg16, OperandSize::kShort)
 
 // The list of bytecodes which are interpreted by the interpreter.
 #define BYTECODE_LIST(V)                                                       \
@@ -78,6 +79,8 @@ namespace interpreter {
                                                                                \
   /* Register-register transfers */                                            \
   V(Mov, OperandType::kReg8, OperandType::kReg8)                               \
+  V(Exchange, OperandType::kReg8, OperandType::kReg16)                         \
+  V(ExchangeWide, OperandType::kReg16, OperandType::kReg16)                    \
                                                                                \
   /* LoadIC operations */                                                      \
   V(LoadICSloppy, OperandType::kReg8, OperandType::kIdx8, OperandType::kIdx8)  \
@@ -249,15 +252,9 @@ enum class Bytecode : uint8_t {
 // in its stack-frame. Register hold parameters, this, and expression values.
 class Register {
  public:
-  static const int kMaxRegisterIndex = 127;
-  static const int kMinRegisterIndex = -128;
-
   Register() : index_(kIllegalIndex) {}
 
-  explicit Register(int index) : index_(index) {
-    DCHECK_LE(index_, kMaxRegisterIndex);
-    DCHECK_GE(index_, kMinRegisterIndex);
-  }
+  explicit Register(int index) : index_(index) {}
 
   int index() const {
     DCHECK(index_ != kIllegalIndex);
@@ -285,6 +282,9 @@ class Register {
   static Register FromOperand(uint8_t operand);
   uint8_t ToOperand() const;
 
+  static Register FromWideOperand(uint16_t operand);
+  uint16_t ToWideOperand() const;
+
   static bool AreContiguous(Register reg1, Register reg2,
                             Register reg3 = Register(),
                             Register reg4 = Register(),

src/interpreter/interpreter.cc

@@ -201,6 +201,28 @@ void Interpreter::DoStar(compiler::InterpreterAssembler* assembler) {
 }
 
 
+// Exchange <reg8> <reg16>
+//
+// Exchange two registers.
+void Interpreter::DoExchange(compiler::InterpreterAssembler* assembler) {
+  Node* reg0_index = __ BytecodeOperandReg(0);
+  Node* reg1_index = __ BytecodeOperandReg(1);
+  Node* reg0_value = __ LoadRegister(reg0_index);
+  Node* reg1_value = __ LoadRegister(reg1_index);
+  __ StoreRegister(reg1_value, reg0_index);
+  __ StoreRegister(reg0_value, reg1_index);
+  __ Dispatch();
+}
+
+
+// ExchangeWide <reg16> <reg16>
+//
+// Exchange two registers.
+void Interpreter::DoExchangeWide(compiler::InterpreterAssembler* assembler) {
+  return DoExchange(assembler);
+}
+
+
 // Mov <src> <dst>
 //
 // Stores the value of register <src> to register <dst>.

test/cctest/interpreter/test-interpreter.cc

@@ -340,7 +340,7 @@ TEST(InterpreterLoadLiteral) {
 TEST(InterpreterLoadStoreRegisters) {
   HandleAndZoneScope handles;
   Handle<Object> true_value = handles.main_isolate()->factory()->true_value();
-  for (int i = 0; i <= Register::kMaxRegisterIndex; i++) {
+  for (int i = 0; i <= kMaxInt8; i++) {
     BytecodeArrayBuilder builder(handles.main_isolate(), handles.main_zone());
     builder.set_locals_count(i + 1);
     builder.set_context_count(0);
@@ -361,6 +361,117 @@ TEST(InterpreterLoadStoreRegisters) {
 }
 
 
+TEST(InterpreterExchangeRegisters) {
+  for (int locals_count = 2; locals_count < 300; locals_count += 126) {
+    HandleAndZoneScope handles;
+    for (int exchanges = 1; exchanges < 4; exchanges++) {
+      BytecodeArrayBuilder builder(handles.main_isolate(), handles.main_zone());
+      builder.set_locals_count(locals_count);
+      builder.set_context_count(0);
+      builder.set_parameter_count(0);
+
+      Register r0(0);
+      Register r1(locals_count - 1);
+      builder.LoadTrue();
+      builder.StoreAccumulatorInRegister(r0);
+      builder.ExchangeRegisters(r0, r1);
+      builder.LoadFalse();
+      builder.StoreAccumulatorInRegister(r0);
+
+      bool expected = false;
+      for (int i = 0; i < exchanges; i++) {
+        builder.ExchangeRegisters(r0, r1);
+        expected = !expected;
+      }
+      builder.LoadAccumulatorWithRegister(r0);
+      builder.Return();
+      Handle<BytecodeArray> bytecode_array = builder.ToBytecodeArray();
+      InterpreterTester tester(handles.main_isolate(), bytecode_array);
+      auto callable = tester.GetCallable<>();
+      Handle<Object> return_val = callable().ToHandleChecked();
+      Handle<Object> expected_val =
+          handles.main_isolate()->factory()->ToBoolean(expected);
+      CHECK(return_val.is_identical_to(expected_val));
+    }
+  }
+}
+
+
+TEST(InterpreterExchangeRegistersWithParameter) {
+  for (int locals_count = 2; locals_count < 300; locals_count += 126) {
+    HandleAndZoneScope handles;
+    for (int exchanges = 1; exchanges < 4; exchanges++) {
+      BytecodeArrayBuilder builder(handles.main_isolate(), handles.main_zone());
+      builder.set_locals_count(locals_count);
+      builder.set_context_count(0);
+      builder.set_parameter_count(3);
+
+      Register r0 = Register::FromParameterIndex(2, 3);
+      Register r1(locals_count - 1);
+      builder.LoadTrue();
+      builder.StoreAccumulatorInRegister(r0);
+      builder.ExchangeRegisters(r0, r1);
+      builder.LoadFalse();
+      builder.StoreAccumulatorInRegister(r0);
+
+      bool expected = false;
+      for (int i = 0; i < exchanges; i++) {
+        builder.ExchangeRegisters(r0, r1);
+        expected = !expected;
+      }
+      builder.LoadAccumulatorWithRegister(r0);
+      builder.Return();
+      Handle<BytecodeArray> bytecode_array = builder.ToBytecodeArray();
+      InterpreterTester tester(handles.main_isolate(), bytecode_array);
+      auto callable = tester.GetCallable<>();
+      Handle<Object> return_val = callable().ToHandleChecked();
+      Handle<Object> expected_val =
+          handles.main_isolate()->factory()->ToBoolean(expected);
+      CHECK(return_val.is_identical_to(expected_val));
+    }
+  }
+}
+
+
+TEST(InterpreterExchangeWideRegisters) {
+  for (int locals_count = 3; locals_count < 300; locals_count += 126) {
+    HandleAndZoneScope handles;
+    for (int exchanges = 0; exchanges < 7; exchanges++) {
+      BytecodeArrayBuilder builder(handles.main_isolate(), handles.main_zone());
+      builder.set_locals_count(locals_count);
+      builder.set_context_count(0);
+      builder.set_parameter_count(0);
+
+      Register r0(0);
+      Register r1(locals_count - 1);
+      Register r2(locals_count - 2);
+      builder.LoadLiteral(Smi::FromInt(200));
+      builder.StoreAccumulatorInRegister(r0);
+      builder.ExchangeRegisters(r0, r1);
+      builder.LoadLiteral(Smi::FromInt(100));
+      builder.StoreAccumulatorInRegister(r0);
+      builder.ExchangeRegisters(r0, r2);
+      builder.LoadLiteral(Smi::FromInt(0));
+      builder.StoreAccumulatorInRegister(r0);
+      for (int i = 0; i < exchanges; i++) {
+        builder.ExchangeRegisters(r1, r2);
+        builder.ExchangeRegisters(r0, r1);
+      }
+      builder.LoadAccumulatorWithRegister(r0);
+      builder.Return();
+      Handle<BytecodeArray> bytecode_array = builder.ToBytecodeArray();
+      InterpreterTester tester(handles.main_isolate(), bytecode_array);
+      auto callable = tester.GetCallable<>();
+      Handle<Object> return_val = callable().ToHandleChecked();
+      Handle<Object> expected_val =
+          handles.main_isolate()->factory()->NewNumberFromInt(100 *
+                                                              (exchanges % 3));
+      CHECK(return_val.is_identical_to(expected_val));
+    }
+  }
+}
+
+
 static const Token::Value kShiftOperators[] = {
     Token::Value::SHL, Token::Value::SAR, Token::Value::SHR};
 

test/unittests/compiler/interpreter-assembler-unittest.cc

@@ -140,6 +140,47 @@ InterpreterAssemblerTest::InterpreterAssemblerForTest::IsBytecodeOperandShort(
 }
 
 
+Matcher<Node*> InterpreterAssemblerTest::InterpreterAssemblerForTest::
+    IsBytecodeOperandShortSignExtended(int offset) {
+  Matcher<Node*> load_matcher;
+  if (TargetSupportsUnalignedAccess()) {
+    load_matcher = IsLoad(
+        MachineType::Int16(),
+        IsParameter(Linkage::kInterpreterBytecodeArrayParameter),
+        IsIntPtrAdd(IsParameter(Linkage::kInterpreterBytecodeOffsetParameter),
+                    IsInt32Constant(offset)));
+  } else {
+#if V8_TARGET_LITTLE_ENDIAN
+    int hi_byte_offset = offset + 1;
+    int lo_byte_offset = offset;
+
+#elif V8_TARGET_BIG_ENDIAN
+    int hi_byte_offset = offset;
+    int lo_byte_offset = offset + 1;
+#else
+#error "Unknown Architecture"
+#endif
+    Matcher<Node*> hi_byte = IsLoad(
+        MachineType::Int8(),
+        IsParameter(Linkage::kInterpreterBytecodeArrayParameter),
+        IsIntPtrAdd(IsParameter(Linkage::kInterpreterBytecodeOffsetParameter),
+                    IsInt32Constant(hi_byte_offset)));
+    hi_byte = IsWord32Shl(hi_byte, IsInt32Constant(kBitsPerByte));
+    Matcher<Node*> lo_byte = IsLoad(
+        MachineType::Uint8(),
+        IsParameter(Linkage::kInterpreterBytecodeArrayParameter),
+        IsIntPtrAdd(IsParameter(Linkage::kInterpreterBytecodeOffsetParameter),
+                    IsInt32Constant(lo_byte_offset)));
+    load_matcher = IsWord32Or(hi_byte, lo_byte);
+  }
+
+  if (kPointerSize == 8) {
+    load_matcher = IsChangeInt32ToInt64(load_matcher);
+  }
+  return load_matcher;
+}
+
+
 TARGET_TEST_F(InterpreterAssemblerTest, Dispatch) {
   TRACED_FOREACH(interpreter::Bytecode, bytecode, kBytecodes) {
     InterpreterAssemblerForTest m(this, bytecode);
@@ -320,6 +361,10 @@ TARGET_TEST_F(InterpreterAssemblerTest, BytecodeOperand) {
           EXPECT_THAT(m.BytecodeOperandIdx(i),
                       m.IsBytecodeOperandShort(offset));
           break;
+        case interpreter::OperandType::kReg16:
+          EXPECT_THAT(m.BytecodeOperandReg(i),
+                      m.IsBytecodeOperandShortSignExtended(offset));
+          break;
         case interpreter::OperandType::kNone:
           UNREACHABLE();
           break;

test/unittests/compiler/interpreter-assembler-unittest.h

@@ -40,6 +40,7 @@ class InterpreterAssemblerTest : public TestWithIsolateAndZone {
     Matcher<Node*> IsBytecodeOperand(int offset);
     Matcher<Node*> IsBytecodeOperandSignExtended(int offset);
     Matcher<Node*> IsBytecodeOperandShort(int offset);
+    Matcher<Node*> IsBytecodeOperandShortSignExtended(int offset);
 
     using InterpreterAssembler::call_descriptor;
     using InterpreterAssembler::graph;

test/unittests/interpreter/bytecode-array-builder-unittest.cc

@@ -22,12 +22,12 @@ class BytecodeArrayBuilderTest : public TestWithIsolateAndZone {
 TEST_F(BytecodeArrayBuilderTest, AllBytecodesGenerated) {
   BytecodeArrayBuilder builder(isolate(), zone());
 
-  builder.set_locals_count(2);
+  builder.set_locals_count(200);
   builder.set_context_count(1);
   builder.set_parameter_count(0);
-  CHECK_EQ(builder.locals_count(), 2);
+  CHECK_EQ(builder.locals_count(), 200);
   CHECK_EQ(builder.context_count(), 1);
-  CHECK_EQ(builder.fixed_register_count(), 3);
+  CHECK_EQ(builder.fixed_register_count(), 201);
 
   // Emit constant loads.
   builder.LoadLiteral(Smi::FromInt(0))
@@ -50,6 +50,13 @@ TEST_F(BytecodeArrayBuilderTest, AllBytecodesGenerated) {
   Register other(1);
   builder.MoveRegister(reg, other);
 
+  // Emit register-register exchanges.
+  Register wide(150);
+  builder.ExchangeRegisters(reg, wide);
+  builder.ExchangeRegisters(wide, reg);
+  Register wider(151);
+  builder.ExchangeRegisters(wide, wider);
+
   // Emit global load / store operations.
   Factory* factory = isolate()->factory();
   Handle<String> name = factory->NewStringFromStaticChars("var_name");

test/unittests/interpreter/bytecodes-unittest.cc

@@ -42,7 +42,7 @@ TEST(OperandConversion, Parameters) {
 TEST(OperandConversion, RegistersParametersNoOverlap) {
   std::vector<uint8_t> operand_count(256);
 
-  for (int i = 0; i <= Register::kMaxRegisterIndex; i++) {
+  for (int i = 0; i <= kMaxInt8; i++) {
     Register r = Register(i);
     uint8_t operand = r.ToOperand();
     operand_count[operand] += 1;