#ifndef SHARE_VM_INTERPRETER_INVOCATIONCOUNTER_HPP

#define SHARE_VM_INTERPRETER_INVOCATIONCOUNTER_HPP

#include "memory/allocation.hpp"

#include "runtime/handles.hpp"

#include "utilities/exceptions.hpp"

class InvocationCounter VALUE_OBJ_CLASS_SPEC {

friend class VMStructs;

private: // bit no: |31 3| 2 | 1 0 |

unsigned int _counter; // format: [count|carry|state]

enum PrivateConstants {

number_of_state_bits = 2,

number_of_carry_bits = 1,

number_of_noncount_bits = number_of_state_bits + number_of_carry_bits,

number_of_count_bits = BitsPerInt - number_of_noncount_bits,

state_limit = nth_bit(number_of_state_bits),

count_grain = nth_bit(number_of_state_bits + number_of_carry_bits),

carry_mask = right_n_bits(number_of_carry_bits) << number_of_state_bits,

state_mask = right_n_bits(number_of_state_bits),

status_mask = right_n_bits(number_of_state_bits + number_of_carry_bits),

count_mask = ((int)(-1) ^ status_mask)

};

public:

static int InterpreterInvocationLimit; // CompileThreshold scaled for interpreter use

static int InterpreterBackwardBranchLimit; // A separate threshold for on stack replacement

static int InterpreterProfileLimit; // Profiling threshold scaled for interpreter use

typedef address (*Action)(methodHandle method, TRAPS);

enum PublicConstants {

count_increment = count_grain, // use this value to increment the 32bit _counter word

count_mask_value = count_mask, // use this value to mask the backedge counter

count_shift = number_of_noncount_bits,

count_limit = nth_bit(number_of_count_bits - 1)

};

enum State {

wait_for_nothing, // do nothing when count() > limit()

wait_for_compile, // introduce nmethod when count() > limit()

number_of_states // must be <= state_limit

};

// Manipulation

void reset(); // sets state to wait state

void init(); // sets state into original state

void set_state(State state); // sets state and initializes counter correspondingly

inline void set(State state, int count); // sets state and counter

inline void decay(); // decay counter (divide by two)

void set_carry(); // set the sticky carry bit

void set_carry_flag() { _counter |= carry_mask; }

// Accessors

State state() const { return (State)(_counter & state_mask); }

bool carry() const { return (_counter & carry_mask) != 0; }

int limit() const { return CompileThreshold; }

Action action() const { return _action[state()]; }

int count() const { return _counter >> number_of_noncount_bits; }

int get_InvocationLimit() const { return InterpreterInvocationLimit >> number_of_noncount_bits; }

int get_BackwardBranchLimit() const { return InterpreterBackwardBranchLimit >> number_of_noncount_bits; }

int get_ProfileLimit() const { return InterpreterProfileLimit >> number_of_noncount_bits; }

// Test counter using scaled limits like the asm interpreter would do rather than doing

// the shifts to normalize the counter.

bool reached_InvocationLimit() const { return _counter >= (unsigned int) InterpreterInvocationLimit; }

bool reached_BackwardBranchLimit() const { return _counter >= (unsigned int) InterpreterBackwardBranchLimit; }

// Do this just like asm interpreter does for max speed

bool reached_ProfileLimit(InvocationCounter *back_edge_count) const {

return (_counter && count_mask) + back_edge_count->_counter >= (unsigned int) InterpreterProfileLimit;

}

void increment() { _counter += count_increment; }

// Printing

void print();

void print_short();

// Miscellaneous

static ByteSize counter_offset() { return byte_offset_of(InvocationCounter, _counter); }

static void reinitialize(bool delay_overflow);

private:

static int _init [number_of_states]; // the counter limits

static Action _action[number_of_states]; // the actions

static void def(State state, int init, Action action);

static const char* state_as_string(State state);

static const char* state_as_short_string(State state);

};

inline void InvocationCounter::set(State state, int count) {

assert(0 <= state && state < number_of_states, "illegal state");

int carry = (_counter & carry_mask); // the carry bit is sticky

_counter = (count << number_of_noncount_bits) | carry | state;

}

inline void InvocationCounter::decay() {

int c = count();

int new_count = c >> 1;

// prevent from going to zero, to distinguish from never-executed methods

if (c > 0 && new_count == 0) new_count = 1;

set(state(), new_count);

}

#endif // SHARE_VM_INTERPRETER_INVOCATIONCOUNTER_HPP