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#ifndef SHARE_VM_INTERPRETER_INVOCATIONCOUNTER_HPP
#define SHARE_VM_INTERPRETER_INVOCATIONCOUNTER_HPP
#include "memory/allocation.hpp"
#include "runtime/handles.hpp"
#include "utilities/exceptions.hpp"
// InvocationCounters are used to trigger actions when a limit (threshold) is reached.
// For different states, different limits and actions can be defined in the initialization
// routine of InvocationCounters.
//
// Implementation notes: For space reasons, state & counter are both encoded in one word,
// The state is encoded using some of the least significant bits, the counter is using the
// more significant bits. The counter is incremented before a method is activated and an
// action is triggered when when count() > limit().
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