[Interpreter] Bytecodes for exchanging registers.

src/interpreter/bytecodes.cc

Index: src/interpreter/bytecodes.cc
diff --git a/src/interpreter/bytecodes.cc b/src/interpreter/bytecodes.cc
index 986e3d012e6c5a4cc34ae543eeac0db6276fb2d0..93085111ab12989f28b49008f7254ae02d534a80 100644
--- a/src/interpreter/bytecodes.cc
+++ b/src/interpreter/bytecodes.cc
@@ -273,6 +273,12 @@ std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
         }
         break;
       }
+      case interpreter::OperandType::kReg16: {
+        Register reg =
+            Register::FromWideOperand(ReadUnalignedUInt16(operand_start));
+        os << "r" << reg.index();

[rmcilroy, 2016/01/04 11:54:54]

nit - add "a" argument case as well ?

[oth, 2016/01/04 14:01:42]

Okay, done, was not done as not part of current changes.

+        break;
+      }
       case interpreter::OperandType::kNone:
         UNREACHABLE();
         break;
@@ -364,7 +370,11 @@ 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_, kMinRegisterIndex);
+  DCHECK_LE(index_, kMaxRegisterIndex);
+  return static_cast<uint8_t>(-index_);
+}
 
 
 Register Register::FromOperand(uint8_t operand) {
@@ -372,6 +382,18 @@ 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()) {