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// Copyright 2012 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.
// 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.
// 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 ARM HW platform.
#include "src/allocation.h"
#if !defined(USE_SIMULATOR)
// Running without a simulator on a native arm platform.
namespace v8 {
namespace internal {
// 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))
typedef int (*arm_regexp_matcher)(String*, int, const byte*, const byte*,
void*, int*, int, Address, int, Isolate*);
// Call the generated regexp code directly. The code at the entry address
// should act as a function matching the type arm_regexp_matcher.
// The fifth argument is a dummy that reserves the space used for
// the return address added by the ExitFrame in native calls.
#define CALL_GENERATED_REGEXP_CODE(entry, p0, p1, p2, p3, p4, p5, p6, p7, p8) \
(FUNCTION_CAST<arm_regexp_matcher>(entry)( \
p0, p1, p2, p3, NULL, p4, p5, p6, p7, p8))
// The stack limit beyond which we will throw stack overflow errors in
// generated code. Because generated code on arm uses the C stack, we
// just use the C stack limit.
class SimulatorStack : public v8::internal::AllStatic {
static inline uintptr_t JsLimitFromCLimit(v8::internal::Isolate* isolate,
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() { }
} } // namespace v8::internal
#else // !defined(USE_SIMULATOR)
// Running with a simulator.
#include "src/arm/constants-arm.h"
#include "src/assembler.h"
#include "src/hashmap.h"
namespace v8 {
namespace internal {
class CachePage {
static const int LINE_VALID = 0;
static const int LINE_INVALID = 1;
static const int kPageShift = 12;
static const int kPageSize = 1 << kPageShift;
static const int kPageMask = kPageSize - 1;
static const int kLineShift = 2; // The cache line is only 4 bytes right now.
static const int kLineLength = 1 << kLineShift;
static const int kLineMask = kLineLength - 1;
CachePage() {
memset(&validity_map_, LINE_INVALID, sizeof(validity_map_));
char* ValidityByte(int offset) {
return &validity_map_[offset >> kLineShift];
char* CachedData(int offset) {
return &data_[offset];
char data_[kPageSize]; // The cached data.
static const int kValidityMapSize = kPageSize >> kLineShift;
char validity_map_[kValidityMapSize]; // One byte per line.
class Simulator {
friend class ArmDebugger;
enum Register {
no_reg = -1,
r0 = 0, r1, r2, r3, r4, r5, r6, r7,
r8, r9, r10, r11, r12, r13, r14, r15,
sp = 13,
lr = 14,
pc = 15,
s0 = 0, s1, s2, s3, s4, s5, s6, s7,
s8, s9, s10, s11, s12, s13, s14, s15,
s16, s17, s18, s19, s20, s21, s22, s23,
s24, s25, s26, s27, s28, s29, s30, s31,
num_s_registers = 32,
d0 = 0, d1, d2, d3, d4, d5, d6, d7,
d8, d9, d10, d11, d12, d13, d14, d15,
d16, d17, d18, d19, d20, d21, d22, d23,
d24, d25, d26, d27, d28, d29, d30, d31,
num_d_registers = 32,
q0 = 0, q1, q2, q3, q4, q5, q6, q7,
q8, q9, q10, q11, q12, q13, q14, q15,
num_q_registers = 16
explicit Simulator(Isolate* isolate);
// The currently executing Simulator instance. Potentially there can be one
// for each native thread.
static Simulator* current(v8::internal::Isolate* isolate);
// Accessors for register state. Reading the pc value adheres to the ARM
// 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;
double get_double_from_register_pair(int reg);
void set_register_pair_from_double(int reg, double* value);
void set_dw_register(int dreg, const int* dbl);
// Support for VFP.
void get_d_register(int dreg, uint64_t* value);
void set_d_register(int dreg, const uint64_t* value);
void get_d_register(int dreg, uint32_t* value);
void set_d_register(int dreg, const uint32_t* value);
void get_q_register(int qreg, uint64_t* value);
void set_q_register(int qreg, const uint64_t* value);
void get_q_register(int qreg, uint32_t* value);
void set_q_register(int qreg, const uint32_t* value);
void set_s_register(int reg, unsigned int value);
unsigned int get_s_register(int reg) const;
void set_d_register_from_double(int dreg, const double& dbl) {
SetVFPRegister<double, 2>(dreg, dbl);
double get_double_from_d_register(int dreg) {
return GetFromVFPRegister<double, 2>(dreg);
void set_s_register_from_float(int sreg, const float flt) {
SetVFPRegister<float, 1>(sreg, flt);
float get_float_from_s_register(int sreg) {
return GetFromVFPRegister<float, 1>(sreg);
void set_s_register_from_sinteger(int sreg, const int sint) {
SetVFPRegister<int, 1>(sreg, sint);
int get_sinteger_from_s_register(int sreg) {
return GetFromVFPRegister<int, 1>(sreg);
// 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;
Address get_sp() {
return reinterpret_cast<Address>(static_cast<intptr_t>(get_register(sp)));
// Accessor to the internal simulator stack area.
uintptr_t StackLimit() const;
// Executes ARM instructions until the PC reaches end_sim_pc.
void Execute();
// Call on program start.
static void Initialize(Isolate* isolate);
// 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, ...);
// Alternative: call a 2-argument double function.
void CallFP(byte* entry, double d0, double d1);
int32_t CallFPReturnsInt(byte* entry, double d0, double d1);
double CallFPReturnsDouble(byte* entry, double d0, double d1);
// Push an address onto the JS stack.
uintptr_t PushAddress(uintptr_t address);
// Pop an address from the JS stack.
uintptr_t PopAddress();
// Debugger input.
void set_last_debugger_input(char* input);
char* last_debugger_input() { return last_debugger_input_; }
// ICache checking.
static void FlushICache(v8::internal::HashMap* i_cache, void* start,
size_t size);
// Returns true if pc register contains one of the 'special_values' defined
// below (bad_lr, end_sim_pc).
bool has_bad_pc() const;
// EABI variant for double arguments in use.
bool use_eabi_hardfloat() {
return true;
return false;
enum special_values {
// Known bad pc value to ensure that the simulator does not execute
// without being properly setup.
bad_lr = -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.
end_sim_pc = -2
// Unsupported instructions use Format to print an error and stop execution.
void Format(Instruction* instr, const char* format);
// Checks if the current instruction should be executed based on its
// condition bits.
inline bool ConditionallyExecute(Instruction* 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 = 0);
bool BorrowFrom(int32_t left, int32_t right);
bool OverflowFrom(int32_t alu_out,
int32_t left,
int32_t right,
bool addition);
inline int GetCarry() {
return c_flag_ ? 1 : 0;
// Support for VFP.
void Compute_FPSCR_Flags(double val1, double val2);
void Copy_FPSCR_to_APSR();
inline double canonicalizeNaN(double value);
// Helper functions to decode common "addressing" modes
int32_t GetShiftRm(Instruction* instr, bool* carry_out);
int32_t GetImm(Instruction* instr, bool* carry_out);
int32_t ProcessPU(Instruction* instr,
int num_regs,
int operand_size,
intptr_t* start_address,
intptr_t* end_address);
void HandleRList(Instruction* instr, bool load);
void HandleVList(Instruction* inst);
void SoftwareInterrupt(Instruction* instr);
// Stop helper functions.
inline bool isStopInstruction(Instruction* instr);
inline bool isWatchedStop(uint32_t bkpt_code);
inline bool isEnabledStop(uint32_t bkpt_code);
inline void EnableStop(uint32_t bkpt_code);
inline void DisableStop(uint32_t bkpt_code);
inline void IncreaseStopCounter(uint32_t bkpt_code);
void PrintStopInfo(uint32_t code);
// Read and write memory.
inline uint8_t ReadBU(int32_t addr);
inline int8_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);
int32_t* ReadDW(int32_t addr);
void WriteDW(int32_t addr, int32_t value1, int32_t value2);
// Executing is handled based on the instruction type.
// Both type 0 and type 1 rolled into one.
void DecodeType01(Instruction* instr);
void DecodeType2(Instruction* instr);
void DecodeType3(Instruction* instr);
void DecodeType4(Instruction* instr);
void DecodeType5(Instruction* instr);
void DecodeType6(Instruction* instr);
void DecodeType7(Instruction* instr);
// Support for VFP.
void DecodeTypeVFP(Instruction* instr);
void DecodeType6CoprocessorIns(Instruction* instr);
void DecodeSpecialCondition(Instruction* instr);
void DecodeVMOVBetweenCoreAndSinglePrecisionRegisters(Instruction* instr);
void DecodeVCMP(Instruction* instr);
void DecodeVCVTBetweenDoubleAndSingle(Instruction* instr);
void DecodeVCVTBetweenFloatingPointAndInteger(Instruction* instr);
// Executes one instruction.
void InstructionDecode(Instruction* instr);
// ICache.
static void CheckICache(v8::internal::HashMap* i_cache, Instruction* instr);
static void FlushOnePage(v8::internal::HashMap* i_cache, intptr_t start,
int size);
static CachePage* GetCachePage(v8::internal::HashMap* i_cache, void* page);
// Runtime call support.
static void* RedirectExternalReference(
void* external_function,
v8::internal::ExternalReference::Type type);
// Handle arguments and return value for runtime FP functions.
void GetFpArgs(double* x, double* y, int32_t* z);
void SetFpResult(const double& result);
void TrashCallerSaveRegisters();
template<class ReturnType, int register_size>
ReturnType GetFromVFPRegister(int reg_index);
template<class InputType, int register_size>
void SetVFPRegister(int reg_index, const InputType& value);
void CallInternal(byte* entry);
// Architecture state.
// Saturating instructions require a Q flag to indicate saturation.
// There is currently no way to read the CPSR directly, and thus read the Q
// flag, so this is left unimplemented.
int32_t registers_[16];
bool n_flag_;
bool z_flag_;
bool c_flag_;
bool v_flag_;
// VFP architecture state.
unsigned int vfp_registers_[num_d_registers * 2];
bool n_flag_FPSCR_;
bool z_flag_FPSCR_;
bool c_flag_FPSCR_;
bool v_flag_FPSCR_;
// VFP rounding mode. See ARM DDI 0406B Page A2-29.
VFPRoundingMode FPSCR_rounding_mode_;
bool FPSCR_default_NaN_mode_;
// VFP FP exception flags architecture state.
bool inv_op_vfp_flag_;
bool div_zero_vfp_flag_;
bool overflow_vfp_flag_;
bool underflow_vfp_flag_;
bool inexact_vfp_flag_;
// Simulator support.
char* stack_;
bool pc_modified_;
int icount_;
// Debugger input.
char* last_debugger_input_;
// Icache simulation
v8::internal::HashMap* i_cache_;
// Registered breakpoints.
Instruction* break_pc_;
Instr break_instr_;
v8::internal::Isolate* isolate_;
// A stop is watched if its code is less than kNumOfWatchedStops.
// Only watched stops support enabling/disabling and the counter feature.
static const uint32_t kNumOfWatchedStops = 256;
// Breakpoint is disabled if bit 31 is set.
static const uint32_t kStopDisabledBit = 1 << 31;
// A stop is enabled, meaning the simulator will stop when meeting the
// instruction, if bit 31 of watched_stops_[code].count is unset.
// The value watched_stops_[code].count & ~(1 << 31) indicates how many times
// the breakpoint was hit or gone through.
struct StopCountAndDesc {
uint32_t count;
char* desc;
StopCountAndDesc watched_stops_[kNumOfWatchedStops];
// 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*>(Simulator::current(Isolate::Current())->Call( \
FUNCTION_ADDR(entry), 5, p0, p1, p2, p3, p4))
#define CALL_GENERATED_FP_INT(entry, p0, p1) \
Simulator::current(Isolate::Current())->CallFPReturnsInt( \
FUNCTION_ADDR(entry), p0, p1)
#define CALL_GENERATED_REGEXP_CODE(entry, p0, p1, p2, p3, p4, p5, p6, p7, p8) \
Simulator::current(Isolate::Current())->Call( \
entry, 10, p0, p1, p2, p3, NULL, p4, p5, p6, p7, p8)
// 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 {
static inline uintptr_t JsLimitFromCLimit(v8::internal::Isolate* isolate,
uintptr_t c_limit) {
return Simulator::current(isolate)->StackLimit();
static inline uintptr_t RegisterCTryCatch(uintptr_t try_catch_address) {
Simulator* sim = Simulator::current(Isolate::Current());
return sim->PushAddress(try_catch_address);
static inline void UnregisterCTryCatch() {
} } // namespace v8::internal
#endif // !defined(USE_SIMULATOR)