[Intepreter] Extend and move Register class.

src/interpreter/bytecodes.cc

Index: src/interpreter/bytecodes.cc
diff --git a/src/interpreter/bytecodes.cc b/src/interpreter/bytecodes.cc
index 5f334d1ff82ae844af75cfc528731fa89917e704..0ed7ae185016bf76a5aff4d22ef4cf5d513788c3 100644
--- a/src/interpreter/bytecodes.cc
+++ b/src/interpreter/bytecodes.cc
@@ -4,7 +4,7 @@
 
 #include "src/interpreter/bytecodes.h"
 
-#include "src/interpreter/bytecode-array-builder.h"
+#include "src/frames.h"
 
 namespace v8 {
 namespace internal {
@@ -103,8 +103,51 @@ int Bytecodes::MaximumSize() { return 1 + kMaxOperands; }
 
 
 // static
-std::ostream& Bytecodes::Decode(std::ostream& os,
-                                const uint8_t* bytecode_start) {
+uint8_t Bytecodes::RegisterIndexToOperand(int index) {
+  return static_cast<uint8_t>(-index);
+}
+
+
+// static
+int Bytecodes::RegisterIndexFromOperand(uint8_t operand) {
+  int8_t index = -static_cast<int8_t>(operand);
+  return index;
+}
+
+
+static const int kLastParamRegisterIndex =
+    -InterpreterFrameConstants::kLastParamFromRegisterPointer / kPointerSize;
+
+
+// static
+uint8_t Bytecodes::ParameterIndexToOperand(int index, int parameter_count) {

[rmcilroy, 2015/09/02 11:42:42]

Could we make this a Register::FromParameterIndex() instead (and then can use
Register::ToOperand if we need the operand)? This is assuming we can move
Register class over to bytecodes.h as in my earlier comment.

[oth, 2015/09/02 14:02:20]

Done.

+  // Parameters share the same space as registers
+  DCHECK_LE(parameter_count, MaximumNumberOfParameters());
+  DCHECK_GE(index, 0);

[rmcilroy, 2015/09/02 11:42:41]

nit - DCHECK_LT(index, parameter_count)

[oth, 2015/09/02 14:02:20]

Done.

+  int register_index = kLastParamRegisterIndex - parameter_count + index + 1;
+  DCHECK_LT(register_index, 0);
+  return RegisterIndexToOperand(register_index);
+}
+
+
+// static
+int Bytecodes::ParameterIndexFromOperand(uint8_t operand, int parameter_count) {
+  // Parameters share the same space as registers
+  DCHECK_LE(parameter_count, MaximumNumberOfParameters());
+  int register_index = RegisterIndexFromOperand(operand);
+  return register_index - kLastParamRegisterIndex + parameter_count - 1;
+}
+
+
+// static
+int Bytecodes::MaximumNumberOfParameters() {
+  return 128 + kLastParamRegisterIndex;

[rmcilroy, 2015/09/02 11:42:41]

This is a bit confusing. Could you use kMinRegisterIndex with the -1 adjustment
(from count to index) and mention that kLastParamRegisterIndex is negative.

[oth, 2015/09/02 14:02:20]

Comment added.

+}
+
+
+// static
+std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
+                                int parameter_count) {
   Vector<char> buf = Vector<char>::New(50);
 
   Bytecode bytecode = Bytecodes::FromByte(bytecode_start[0]);
@@ -132,9 +175,21 @@ std::ostream& Bytecodes::Decode(std::ostream& os,
       case interpreter::OperandType::kImm8:
         os << "#" << static_cast<int>(operand);
         break;
-      case interpreter::OperandType::kReg:
-        os << "r" << Register::FromOperand(operand).index();
+      case interpreter::OperandType::kReg: {
+        int register_index = RegisterIndexFromOperand(operand);
+        if (register_index >= 0) {
+          os << "r" << register_index;
+        } else {
+          int parameter_index =
+              ParameterIndexFromOperand(operand, parameter_count);
+          if (parameter_index == 0) {
+            os << "this";

[rmcilroy, 2015/09/02 11:42:42]

nit - could we make it "<this>" or "|this|" or something to make it clear this
is a parameter? Maybe do the same with "<a0>" or "|a0|"as well?

[oth, 2015/09/02 14:02:20]

Done <this>.

Prefer current consistency of r0, r1, r2, ...a0, a1, etc.

+          } else {
+            os << "a" << parameter_index - 1;
+          }
+        }
         break;
+      }
       case interpreter::OperandType::kNone:
         UNREACHABLE();
         break;