[Interpreter] Add support for short (16 bit) operands.

src/interpreter/bytecode-traits.h

Index: src/interpreter/bytecode-traits.h
diff --git a/src/interpreter/bytecode-traits.h b/src/interpreter/bytecode-traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..cd7fb4732fe0eb718091b14d218842b247f2d5b1
--- /dev/null
+++ b/src/interpreter/bytecode-traits.h
@@ -0,0 +1,142 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_INTERPRETER_BYTECODE_TRAITS_H_
+#define V8_INTERPRETER_BYTECODE_TRAITS_H_
+
+#include "src/interpreter/bytecodes.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+namespace internal {
+
+// Template helpers to deduce the number of operands each bytecode has.
+#define OPERAND_TERM OperandType::kNone, OperandType::kNone, OperandType::kNone
+
+template <OperandType>
+struct OperandTraits {};
+
+#define DECLARE_OPERAND_SIZE(Name, Size)             \
+  template <>                                        \
+  struct OperandTraits<OperandType::k##Name> {       \
+    static const int kSize = static_cast<int>(Size); \
+  };
+OPERAND_TYPE_LIST(DECLARE_OPERAND_SIZE)
+#undef DECLARE_OPERAND_SIZE
+
+
+template <OperandType... Args>
+struct BytecodeTraits {};
+
+template <OperandType operand_0, OperandType operand_1, OperandType operand_2,
+          OperandType operand_3>
+struct BytecodeTraits<operand_0, operand_1, operand_2, operand_3,
+                      OPERAND_TERM> {
+  static OperandType GetOperandType(int i) {
+    DCHECK(0 <= i && i < kOperandCount);
+    const OperandType kOperands[] = {operand_0, operand_1, operand_2,
+                                     operand_3};
+    return kOperands[i];
+  }
+
+  static inline int GetOperandOffset(int i) {
+    DCHECK(0 <= i && i < kOperandCount);
+    const int kOffset0 = 1;
+    const int kOffset1 = kOffset0 + OperandTraits<operand_0>::kSize;
+    const int kOffset2 = kOffset1 + OperandTraits<operand_1>::kSize;
+    const int kOffset3 = kOffset2 + OperandTraits<operand_2>::kSize;
+    const int kOperandOffsets[] = {kOffset0, kOffset1, kOffset2, kOffset3};
+    return kOperandOffsets[i];
+  }
+
+  static const int kOperandCount = 4;
+  static const int kSize =
+      1 + OperandTraits<operand_0>::kSize + OperandTraits<operand_1>::kSize +
+      OperandTraits<operand_2>::kSize + OperandTraits<operand_3>::kSize;
+};
+
+
+template <OperandType operand_0, OperandType operand_1, OperandType operand_2>
+struct BytecodeTraits<operand_0, operand_1, operand_2, OPERAND_TERM> {
+  static inline OperandType GetOperandType(int i) {
+    DCHECK(0 <= i && i <= 2);
+    const OperandType kOperands[] = {operand_0, operand_1, operand_2};
+    return kOperands[i];
+  }
+
+  static inline int GetOperandOffset(int i) {
+    DCHECK(0 <= i && i < kOperandCount);
+    const int kOffset0 = 1;
+    const int kOffset1 = kOffset0 + OperandTraits<operand_0>::kSize;
+    const int kOffset2 = kOffset1 + OperandTraits<operand_1>::kSize;
+    const int kOperandOffsets[] = {kOffset0, kOffset1, kOffset2};
+    return kOperandOffsets[i];
+  }
+
+  static const int kOperandCount = 3;
+  static const int kSize =
+      1 + OperandTraits<operand_0>::kSize + OperandTraits<operand_1>::kSize +
+      OperandTraits<operand_2>::kSize;
+};
+
+template <OperandType operand_0, OperandType operand_1>
+struct BytecodeTraits<operand_0, operand_1, OPERAND_TERM> {
+  static inline OperandType GetOperandType(int i) {
+    DCHECK(0 <= i && i < kOperandCount);
+    const OperandType kOperands[] = {operand_0, operand_1};
+    return kOperands[i];
+  }
+
+  static inline int GetOperandOffset(int i) {
+    DCHECK(0 <= i && i < kOperandCount);
+    const int kOffset0 = 1;
+    const int kOffset1 = kOffset0 + OperandTraits<operand_0>::kSize;
+    const int kOperandOffsets[] = {kOffset0, kOffset1};
+    return kOperandOffsets[i];
+  }
+
+  static const int kOperandCount = 2;
+  static const int kSize =
+      1 + OperandTraits<operand_0>::kSize + OperandTraits<operand_1>::kSize;
+};
+
+template <OperandType operand_0>
+struct BytecodeTraits<operand_0, OPERAND_TERM> {
+  static inline OperandType GetOperandType(int i) {
+    DCHECK(i == 0);
+    return operand_0;
+  }
+
+  static inline int GetOperandOffset(int i) {
+    DCHECK(i == 0);
+    return 1;
+  }
+
+  static const int kOperandCount = 1;
+  static const int kSize = 1 + OperandTraits<operand_0>::kSize;
+};
+
+template <>
+struct BytecodeTraits<OperandType::kNone, OPERAND_TERM> {
+  static inline OperandType GetOperandType(int i) {
+    UNREACHABLE();
+    return OperandType::kNone;
+  }
+
+  static inline int GetOperandOffset(int i) {
+    UNREACHABLE();
+    return 1;
+  }
+
+  static const int kOperandCount = 0;
+  static const int kSize = 1 + OperandTraits<OperandType::kNone>::kSize;
+};
+
+}  // namespace internal
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_INTERPRETER_BYTECODE_TRAITS_H_