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// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
// Declares a Simulator for ARM instructions if we are not generating a native
// ARM binary. This Simulator allows us to run and debug ARM code generation on
// regular desktop machines.
// Dart calls into generated code by "calling" the InvokeDartCode stub,
// which will start execution in the Simulator or forwards to the real entry
// on a ARM HW platform.
#error Do not include simulator_arm.h directly; use simulator.h.
#include "vm/constants_arm.h"
namespace dart {
class Isolate;
class Mutex;
class RawObject;
class SimulatorSetjmpBuffer;
class Thread;
#if !defined(SIMD_VALUE_T_)
typedef struct {
union {
uint32_t u;
float f;
} data_[4];
} simd_value_t;
class Simulator {
static const uword kSimulatorStackUnderflowSize = 64;
// The currently executing Simulator instance, which is associated to the
// current isolate
static Simulator* Current();
// Accessors for register state. Reading the pc value adheres to the ARM
// architecture specification and is off by 8 from the currently executing
// instruction.
void set_register(Register reg, int32_t value);
int32_t get_register(Register reg) 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;
// Accessors for VFP register state.
void set_sregister(SRegister reg, float value);
float get_sregister(SRegister reg) const;
void set_dregister(DRegister reg, double value);
double get_dregister(DRegister reg) const;
void set_qregister(QRegister reg, const simd_value_t& value);
void get_qregister(QRegister reg, simd_value_t* value) const;
// When moving integer (rather than floating point) values to/from
// the FPU registers, use the _bits calls to avoid gcc taking liberties with
// integers that map to such things as NaN floating point values.
void set_sregister_bits(SRegister reg, int32_t value);
int32_t get_sregister_bits(SRegister reg) const;
void set_dregister_bits(DRegister reg, int64_t value);
int64_t get_dregister_bits(DRegister reg) const;
// Accessors to the internal simulator stack base and top.
uword StackBase() const { return reinterpret_cast<uword>(stack_); }
uword StackTop() const;
// Accessor to the instruction counter.
uint64_t get_icount() const { return icount_; }
// The isolate's top_exit_frame_info refers to a Dart frame in the simulator
// stack. The simulator's top_exit_frame_info refers to a C++ frame in the
// native stack.
uword top_exit_frame_info() const { return top_exit_frame_info_; }
void set_top_exit_frame_info(uword value) { top_exit_frame_info_ = value; }
// Call on program start.
static void InitOnce();
// Dart generally calls into generated code with 4 parameters. This is a
// convenience function, which sets up the simulator state and grabs the
// result on return. When fp_return is true the return value is the D0
// floating point register. Otherwise, the return value is R1:R0.
// If fp_args is true, the parameters0-3 are placed in S0-3. Otherwise, they
// are placed in R0-3.
int64_t Call(int32_t entry,
int32_t parameter0,
int32_t parameter1,
int32_t parameter2,
int32_t parameter3,
bool fp_return = false,
bool fp_args = false);
// Implementation of atomic compare and exchange in the same synchronization
// domain as other synchronization primitive instructions (e.g. ldrex, strex).
static uword CompareExchange(uword* address,
uword compare_value,
uword new_value);
// Runtime and native call support.
enum CallKind {
static uword RedirectExternalReference(uword function,
CallKind call_kind,
int argument_count);
static uword FunctionForRedirect(uword redirect);
void Longjmp(uword pc,
uword sp,
uword fp,
RawObject* raw_exception,
RawObject* raw_stacktrace,
Thread* thread);
// Known bad pc value to ensure that the simulator does not execute
// without being properly setup.
static const uword kBadLR = -1;
// A pc value used to signal the simulator to stop execution. Generally
// the lr 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.
static const uword kEndSimulatingPC = -2;
// CPU state.
int32_t registers_[kNumberOfCpuRegisters];
bool n_flag_;
bool z_flag_;
bool c_flag_;
bool v_flag_;
// VFP state.
union { // S, D, and Q register banks are overlapping.
int32_t sregisters_[kNumberOfSRegisters];
int64_t dregisters_[kNumberOfDRegisters];
simd_value_t qregisters_[kNumberOfQRegisters];
bool fp_n_flag_;
bool fp_z_flag_;
bool fp_c_flag_;
bool fp_v_flag_;
// Simulator support.
char* stack_;
bool pc_modified_;
uint64_t icount_;
static int32_t flag_stop_sim_at_;
SimulatorSetjmpBuffer* last_setjmp_buffer_;
uword top_exit_frame_info_;
// Registered breakpoints.
Instr* break_pc_;
int32_t break_instr_;
// Illegal memory access support.
static bool IsIllegalAddress(uword addr) {
return addr < 64*1024;
void HandleIllegalAccess(uword addr, Instr* instr);
// Handles a legal instruction that the simulator does not implement.
void UnimplementedInstruction(Instr* instr);
// Unsupported instructions use Format to print an error and stop execution.
void Format(Instr* instr, const char* format);
// Checks if the current instruction should be executed based on its
// condition bits.
bool ConditionallyExecute(Instr* instr);
// Helper functions to set the conditional flags in the architecture state.
void SetNZFlags(int32_t val);
void SetCFlag(bool val);
void SetVFlag(bool val);
bool CarryFrom(int32_t left, int32_t right, int32_t carry);
bool OverflowFrom(int32_t left, int32_t right, int32_t carry);
// Helper functions to decode common "addressing" modes.
int32_t GetShiftRm(Instr* instr, bool* carry_out);
int32_t GetImm(Instr* instr, bool* carry_out);
void HandleRList(Instr* instr, bool load);
void SupervisorCall(Instr* instr);
// Read and write memory.
void UnalignedAccess(const char* msg, uword addr, Instr* instr);
// Perform a division.
void DoDivision(Instr* instr);
inline uint8_t ReadBU(uword addr);
inline int8_t ReadB(uword addr);
inline void WriteB(uword addr, uint8_t value);
inline uint16_t ReadHU(uword addr, Instr* instr);
inline int16_t ReadH(uword addr, Instr* instr);
inline void WriteH(uword addr, uint16_t value, Instr* instr);
inline intptr_t ReadW(uword addr, Instr* instr);
inline void WriteW(uword addr, intptr_t value, Instr* instr);
// Synchronization primitives support.
void ClearExclusive();
intptr_t ReadExclusiveW(uword addr, Instr* instr);
intptr_t WriteExclusiveW(uword addr, intptr_t value, Instr* instr);
// We keep track of 16 exclusive access address tags across all threads.
// Since we cannot simulate a native context switch, which clears
// the exclusive access state of the local monitor (using the CLREX
// instruction), we associate the thread requesting exclusive access to the
// address tag. Multiple threads requesting exclusive access (using the LDREX
// instruction) to the same address will result in multiple address tags being
// created for the same address, one per thread.
// At any given time, each thread is associated to at most one address tag.
static Mutex* exclusive_access_lock_;
static const int kNumAddressTags = 16;
static struct AddressTag {
Thread* thread;
uword addr;
} exclusive_access_state_[kNumAddressTags];
static int next_address_tag_;
// Set access to given address to 'exclusive state' for current thread.
static void SetExclusiveAccess(uword addr);
// Returns true if the current thread has exclusive access to given address,
// returns false otherwise. In either case, set access to given address to
// 'open state' for all threads.
// If given addr is NULL, set access to 'open state' for current
// thread (CLREX).
static bool HasExclusiveAccessAndOpen(uword addr);
// Executing is handled based on the instruction type.
void DecodeType01(Instr* instr); // Both type 0 and type 1 rolled into one.
void DecodeType2(Instr* instr);
void DecodeType3(Instr* instr);
void DecodeType4(Instr* instr);
void DecodeType5(Instr* instr);
void DecodeType6(Instr* instr);
void DecodeType7(Instr* instr);
void DecodeSIMDDataProcessing(Instr* instr);
// Executes one instruction.
void InstructionDecode(Instr* instr);
// Executes ARM instructions until the PC reaches kEndSimulatingPC.
void Execute();
// Returns true if tracing of executed instructions is enabled.
bool IsTracingExecution() const;
// Longjmp support for exceptions.
SimulatorSetjmpBuffer* last_setjmp_buffer() {
return last_setjmp_buffer_;
void set_last_setjmp_buffer(SimulatorSetjmpBuffer* buffer) {
last_setjmp_buffer_ = buffer;
friend class SimulatorDebugger;
friend class SimulatorSetjmpBuffer;
} // namespace dart