src/mips/simulator-mips.h

// Copyright 2010 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
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//       with the distribution.
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// Declares a Simulator for MIPS instructions if we are not generating a native
// MIPS binary. This Simulator allows us to run and debug MIPS code generation
// on regular desktop machines.
// V8 calls into generated code by "calling" the CALL_GENERATED_CODE macro,
// which will start execution in the Simulator or forwards to the real entry
// on a MIPS HW platform.

#ifndef V8_MIPS_SIMULATOR_MIPS_H_
#define V8_MIPS_SIMULATOR_MIPS_H_

#include "allocation.h"

#if defined(__mips) && !defined(USE_SIMULATOR)

// When running without a simulator we call the entry directly.
#define CALL_GENERATED_CODE(entry, p0, p1, p2, p3, p4) \
  entry(p0, p1, p2, p3, p4);

// The stack limit beyond which we will throw stack overflow errors in
// generated code. Because generated code on mips uses the C stack, we
// just use the C stack limit.
class SimulatorStack : public v8::internal::AllStatic {
 public:
  static inline uintptr_t JsLimitFromCLimit(uintptr_t c_limit) {
    return c_limit;
  }

  static inline uintptr_t RegisterCTryCatch(uintptr_t try_catch_address) {
    return try_catch_address;
  }

  static inline void UnregisterCTryCatch() { }
};

// Calculated the stack limit beyond which we will throw stack overflow errors.
// This macro must be called from a C++ method. It relies on being able to take
// the address of "this" to get a value on the current execution stack and then
// calculates the stack limit based on that value.
// NOTE: The check for overflow is not safe as there is no guarantee that the
// running thread has its stack in all memory up to address 0x00000000.
#define GENERATED_CODE_STACK_LIMIT(limit) \
  (reinterpret_cast<uintptr_t>(this) >= limit ? \
      reinterpret_cast<uintptr_t>(this) - limit : 0)

// Call the generated regexp code directly. The entry function pointer should
// expect seven int/pointer sized arguments and return an int.
#define CALL_GENERATED_REGEXP_CODE(entry, p0, p1, p2, p3, p4, p5, p6) \
  entry(p0, p1, p2, p3, p4, p5, p6)

#define TRY_CATCH_FROM_ADDRESS(try_catch_address) \
  reinterpret_cast<TryCatch*>(try_catch_address)


#else  // #if !defined(__mips) || defined(USE_SIMULATOR)

// When running with the simulator transition into simulated execution at this
// point.
#define CALL_GENERATED_CODE(entry, p0, p1, p2, p3, p4) \
  reinterpret_cast<Object*>(\
      assembler::mips::Simulator::current()->Call(FUNCTION_ADDR(entry), 5, \
                                                  p0, p1, p2, p3, p4))

#define CALL_GENERATED_REGEXP_CODE(entry, p0, p1, p2, p3, p4, p5, p6) \
  assembler::mips::Simulator::current()->Call(\
    FUNCTION_ADDR(entry), 7, p0, p1, p2, p3, p4, p5, p6)

#define TRY_CATCH_FROM_ADDRESS(try_catch_address) \
  try_catch_address == NULL ? \
      NULL : *(reinterpret_cast<TryCatch**>(try_catch_address))


namespace assembler {
namespace mips {

class Simulator {
 public:
  friend class Debugger;

  // Registers are declared in order. See SMRL chapter 2.
  enum Register {
    no_reg = -1,
    zero_reg = 0,
    at,
    v0, v1,
    a0, a1, a2, a3,
    t0, t1, t2, t3, t4, t5, t6, t7,
    s0, s1, s2, s3, s4, s5, s6, s7,
    t8, t9,
    k0, k1,
    gp,
    sp,
    s8,
    ra,
    // LO, HI, and pc
    LO,
    HI,
    pc,   // pc must be the last register.
    kNumSimuRegisters,
    // aliases
    fp = s8
  };

  // Coprocessor registers.
  // Generated code will always use doubles. So we will only use even registers.
  enum FPURegister {
    f0, f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11,
    f12, f13, f14, f15,   // f12 and f14 are arguments FPURegisters
    f16, f17, f18, f19, f20, f21, f22, f23, f24, f25,
    f26, f27, f28, f29, f30, f31,
    kNumFPURegisters
  };

  Simulator();
  ~Simulator();

  // The currently executing Simulator instance. Potentially there can be one
  // for each native thread.
  static Simulator* current();

  // Accessors for register state. Reading the pc value adheres to the MIPS
  // architecture specification and is off by a 8 from the currently executing
  // instruction.
  void set_register(int reg, int32_t value);
  int32_t get_register(int reg) const;
  // Same for FPURegisters
  void set_fpu_register(int fpureg, int32_t value);
  void set_fpu_register_double(int fpureg, double value);
  int32_t get_fpu_register(int fpureg) const;
  double get_fpu_register_double(int fpureg) const;

  // Special case of set_register and get_register to access the raw PC value.
  void set_pc(int32_t value);
  int32_t get_pc() const;

  // Accessor to the internal simulator stack area.
  uintptr_t StackLimit() const;

  // Executes MIPS instructions until the PC reaches end_sim_pc.
  void Execute();

  // Call on program start.
  static void Initialize();

  // V8 generally calls into generated JS code with 5 parameters and into
  // generated RegExp code with 7 parameters. This is a convenience function,
  // which sets up the simulator state and grabs the result on return.
  int32_t Call(byte_* entry, int argument_count, ...);

  // Push an address onto the JS stack.
  uintptr_t PushAddress(uintptr_t address);

  // Pop an address from the JS stack.
  uintptr_t PopAddress();

 private:
  enum special_values {
    // Known bad pc value to ensure that the simulator does not execute
    // without being properly setup.
    bad_ra = -1,
    // A pc value used to signal the simulator to stop execution.  Generally
    // the ra is set to this value on transition from native C code to
    // simulated execution, so that the simulator can "return" to the native
    // C code.
    end_sim_pc = -2,
    // Unpredictable value.
    Unpredictable = 0xbadbeaf
  };

  // Unsupported instructions use Format to print an error and stop execution.
  void Format(Instruction* instr, const char* format);

  // Read and write memory.
  inline uint32_t ReadBU(int32_t addr);
  inline int32_t ReadB(int32_t addr);
  inline void WriteB(int32_t addr, uint8_t value);
  inline void WriteB(int32_t addr, int8_t value);

  inline uint16_t ReadHU(int32_t addr, Instruction* instr);
  inline int16_t ReadH(int32_t addr, Instruction* instr);
  // Note: Overloaded on the sign of the value.
  inline void WriteH(int32_t addr, uint16_t value, Instruction* instr);
  inline void WriteH(int32_t addr, int16_t value, Instruction* instr);

  inline int ReadW(int32_t addr, Instruction* instr);
  inline void WriteW(int32_t addr, int value, Instruction* instr);

  inline double ReadD(int32_t addr, Instruction* instr);
  inline void WriteD(int32_t addr, double value, Instruction* instr);

  // Operations depending on endianness.
  // Get Double Higher / Lower word.
  inline int32_t GetDoubleHIW(double* addr);
  inline int32_t GetDoubleLOW(double* addr);
  // Set Double Higher / Lower word.
  inline int32_t SetDoubleHIW(double* addr);
  inline int32_t SetDoubleLOW(double* addr);


  // Executing is handled based on the instruction type.
  void DecodeTypeRegister(Instruction* instr);
  void DecodeTypeImmediate(Instruction* instr);
  void DecodeTypeJump(Instruction* instr);

  // Used for breakpoints and traps.
  void SoftwareInterrupt(Instruction* instr);

  // Executes one instruction.
  void InstructionDecode(Instruction* instr);
  // Execute one instruction placed in a branch delay slot.
  void BranchDelayInstructionDecode(Instruction* instr) {
    if (instr->IsForbiddenInBranchDelay()) {
      V8_Fatal(__FILE__, __LINE__,
               "Eror:Unexpected %i opcode in a branch delay slot.",
               instr->OpcodeField());
    }
    InstructionDecode(instr);
  }

  enum Exception {
    none,
    kIntegerOverflow,
    kIntegerUnderflow,
    kDivideByZero,
    kNumExceptions
  };
  int16_t exceptions[kNumExceptions];

  // Exceptions.
  void SignalExceptions();

  // Runtime call support.
  static void* RedirectExternalReference(void* external_function,
                                         bool fp_return);

  // Used for real time calls that takes two double values as arguments and
  // returns a double.
  void SetFpResult(double result);

  // Architecture state.
  // Registers.
  int32_t registers_[kNumSimuRegisters];
  // Coprocessor Registers.
  int32_t FPUregisters_[kNumFPURegisters];

  // Simulator support.
  char* stack_;
  bool pc_modified_;
  int icount_;
  static bool initialized_;

  // Registered breakpoints.
  Instruction* break_pc_;
  Instr break_instr_;
};

} }   // namespace assembler::mips


// The simulator has its own stack. Thus it has a different stack limit from
// the C-based native code.  Setting the c_limit to indicate a very small
// stack cause stack overflow errors, since the simulator ignores the input.
// This is unlikely to be an issue in practice, though it might cause testing
// trouble down the line.
class SimulatorStack : public v8::internal::AllStatic {
 public:
  static inline uintptr_t JsLimitFromCLimit(uintptr_t c_limit) {
    return assembler::mips::Simulator::current()->StackLimit();
  }

  static inline uintptr_t RegisterCTryCatch(uintptr_t try_catch_address) {
    assembler::mips::Simulator* sim = assembler::mips::Simulator::current();
    return sim->PushAddress(try_catch_address);
  }

  static inline void UnregisterCTryCatch() {
    assembler::mips::Simulator::current()->PopAddress();
  }
};

#endif  // !defined(__mips) || defined(USE_SIMULATOR)

#endif  // V8_MIPS_SIMULATOR_MIPS_H_