src/interpreter/bytecodes.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/bytecodes.h"

#include "src/frames.h"

namespace v8 {
namespace internal {
namespace interpreter {

// Maximum number of operands a bytecode may have.
static const int kMaxOperands = 3;

// kBytecodeTable relies on kNone being the same as zero to detect length.
STATIC_ASSERT(static_cast<int>(OperandType::kNone) == 0);

static const OperandType kBytecodeTable[][kMaxOperands] = {
#define DECLARE_OPERAND(_, ...) \
  { __VA_ARGS__ }               \
  ,
    BYTECODE_LIST(DECLARE_OPERAND)
#undef DECLARE_OPERAND
};


// static
const char* Bytecodes::ToString(Bytecode bytecode) {
  switch (bytecode) {
#define CASE(Name, ...)   \
  case Bytecode::k##Name: \
    return #Name;
    BYTECODE_LIST(CASE)
#undef CASE
  }
  UNREACHABLE();
  return "";
}


// static
const char* Bytecodes::OperandTypeToString(OperandType operand_type) {
  switch (operand_type) {
#define CASE(Name)           \
  case OperandType::k##Name: \
    return #Name;
    OPERAND_TYPE_LIST(CASE)
#undef CASE
  }
  UNREACHABLE();
  return "";
}


// static
uint8_t Bytecodes::ToByte(Bytecode bytecode) {
  return static_cast<uint8_t>(bytecode);
}


// static
Bytecode Bytecodes::FromByte(uint8_t value) {
  Bytecode bytecode = static_cast<Bytecode>(value);
  DCHECK(bytecode <= Bytecode::kLast);
  return bytecode;
}


// static
int Bytecodes::NumberOfOperands(Bytecode bytecode) {
  DCHECK(bytecode <= Bytecode::kLast);
  int count;
  uint8_t row = ToByte(bytecode);
  for (count = 0; count < kMaxOperands; count++) {
    if (kBytecodeTable[row][count] == OperandType::kNone) {
      break;
    }
  }
  return count;
}


// static
OperandType Bytecodes::GetOperandType(Bytecode bytecode, int i) {
  DCHECK(bytecode <= Bytecode::kLast && i < NumberOfOperands(bytecode));
  return kBytecodeTable[ToByte(bytecode)][i];
}


// static
int Bytecodes::Size(Bytecode bytecode) {
  return 1 + NumberOfOperands(bytecode);
}


// static
int Bytecodes::MaximumNumberOfOperands() { return kMaxOperands; }


// static
int Bytecodes::MaximumSize() { return 1 + kMaxOperands; }


// 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]);
  int bytecode_size = Bytecodes::Size(bytecode);

  for (int i = 0; i < bytecode_size; i++) {
    SNPrintF(buf, "%02x ", bytecode_start[i]);
    os << buf.start();
  }
  for (int i = bytecode_size; i < Bytecodes::MaximumSize(); i++) {
    os << "   ";
  }

  os << bytecode << " ";

  const uint8_t* operands_start = bytecode_start + 1;
  int operands_size = bytecode_size - 1;
  for (int i = 0; i < operands_size; i++) {
    OperandType op_type = GetOperandType(bytecode, i);
    uint8_t operand = operands_start[i];
    switch (op_type) {
      case interpreter::OperandType::kCount:
        os << "#" << static_cast<unsigned int>(operand);
        break;
      case interpreter::OperandType::kIdx:
        os << "[" << static_cast<unsigned int>(operand) << "]";
        break;
      case interpreter::OperandType::kImm8:
        os << "#" << static_cast<int>(operand);
        break;
      case interpreter::OperandType::kReg: {
        Register reg = Register::FromOperand(operand);
        if (reg.is_parameter()) {
          int parameter_index = reg.ToParameterIndex(parameter_count);
          if (parameter_index == 0) {
            os << "<this>";
          } else {
            os << "a" << parameter_index - 1;
          }
        } else {
          os << "r" << reg.index();
        }
        break;
      }
      case interpreter::OperandType::kNone:
        UNREACHABLE();
        break;
    }
    if (i != operands_size - 1) {
      os << ", ";
    }
  }
  return os;
}


std::ostream& operator<<(std::ostream& os, const Bytecode& bytecode) {
  return os << Bytecodes::ToString(bytecode);
}


std::ostream& operator<<(std::ostream& os, const OperandType& operand_type) {
  return os << Bytecodes::OperandTypeToString(operand_type);
}


static const int kLastParamRegisterIndex =
    -InterpreterFrameConstants::kLastParamFromRegisterPointer / kPointerSize;


// Registers occupy range 0-127 in 8-bit value leaving 128 unused values.
// Parameter indices are biased with the negative value kLastParamRegisterIndex
// for ease of access in the interpreter.
static const int kMaxParameterIndex = 128 + kLastParamRegisterIndex;


Register Register::FromParameterIndex(int index, int parameter_count) {
  DCHECK_GE(index, 0);
  DCHECK_LT(index, 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);
  return Register(register_index);
}


int Register::ToParameterIndex(int parameter_count) const {
  DCHECK(is_parameter());
  return index() - kLastParamRegisterIndex + parameter_count - 1;
}


int Register::MaxParameterIndex() { return kMaxParameterIndex; }


uint8_t Register::ToOperand() const { return static_cast<uint8_t>(-index_); }


Register Register::FromOperand(uint8_t operand) {
  return Register(-static_cast<int8_t>(operand));
}

}  // namespace interpreter
}  // namespace internal
}  // namespace v8