[Interpreter] Add option to trace bytecode execution.

src/interpreter/bytecode-array-iterator.cc

 // 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.
 
 #include "src/interpreter/bytecode-array-iterator.h"
 
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 82 matching lines @@
     case OperandSize::kByte:
       return Register::FromOperand(static_cast<uint8_t>(operand));
     case OperandSize::kShort:
       return Register::FromWideOperand(static_cast<uint16_t>(operand));
     case OperandSize::kNone:
       UNREACHABLE();
   }
   return Register();
 }
 
+int BytecodeArrayIterator::GetRegisterOperandRange(int operand_index) const {
+  interpreter::OperandType operand_type =
+      Bytecodes::GetOperandType(current_bytecode(), operand_index);
+  DCHECK(Bytecodes::IsRegisterOperandType(operand_type));
+  switch (operand_type) {
+    case OperandType::kRegPair8:
+    case OperandType::kRegPair16:
+    case OperandType::kRegOutPair8:
+    case OperandType::kRegOutPair16:
+      return 2;
+    case OperandType::kRegOutTriple8:
+    case OperandType::kRegOutTriple16:
+      return 3;
+    default: {
+      if (operand_index + 1 !=
+          Bytecodes::NumberOfOperands(current_bytecode())) {
+        OperandType next_operand_type =

[oth, 2016/01/27 15:10:09]

Can you add a TODO(oth) here to update bytecodes so that the kCount8/kCount16
operands have the same semantics for all bytecodes?
ie Call/CallJSRuntime the count argument is for registers 1 after the receiver,
for CallRuntime/New the count argument covers the last register operand.

[rmcilroy, 2016/01/28 16:39:51]

Done.

+            Bytecodes::GetOperandType(current_bytecode(), operand_index + 1);
+        if (next_operand_type == OperandType::kRegCount8 ||
+            next_operand_type == OperandType::kRegCount16) {
+          return GetCountOperand(operand_index + 1);
+        }
+      }
+      return 1;
+    }
+  }
+}
 
 Handle<Object> BytecodeArrayIterator::GetConstantForIndexOperand(
     int operand_index) const {
   Handle<FixedArray> constants = handle(bytecode_array()->constant_pool());
   return FixedArray::get(constants, GetIndexOperand(operand_index));
 }
 
 
 int BytecodeArrayIterator::GetJumpTargetOffset() const {
   Bytecode bytecode = current_bytecode();
   if (interpreter::Bytecodes::IsJumpImmediate(bytecode)) {
     int relative_offset = GetImmediateOperand(0);
     return current_offset() + relative_offset;
   } else if (interpreter::Bytecodes::IsJumpConstant(bytecode) ||
              interpreter::Bytecodes::IsJumpConstantWide(bytecode)) {
     Smi* smi = Smi::cast(*GetConstantForIndexOperand(0));
     return current_offset() + smi->value();
   } else {
     UNREACHABLE();
     return kMinInt;
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8