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 /*

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  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

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  * 2 along with this work; if not, write to the Free Software Foundation,

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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