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/*
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* Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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// InvocationCounters are used to trigger actions when a limit (threshold) is reached.
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// For different states, different limits and actions can be defined in the initialization
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// routine of InvocationCounters.
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//
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// Implementation notes: For space reasons, state & counter are both encoded in one word,
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// The state is encoded using some of the least significant bits, the counter is using the
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// more significant bits. The counter is incremented before a method is activated and an
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// action is triggered when when count() > limit().
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class InvocationCounter VALUE_OBJ_CLASS_SPEC {
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friend class VMStructs;
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private: // bit no: |31 3| 2 | 1 0 |
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unsigned int _counter; // format: [count|carry|state]
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enum PrivateConstants {
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number_of_state_bits = 2,
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number_of_carry_bits = 1,
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number_of_noncount_bits = number_of_state_bits + number_of_carry_bits,
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number_of_count_bits = BitsPerInt - number_of_noncount_bits,
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state_limit = nth_bit(number_of_state_bits),
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count_grain = nth_bit(number_of_state_bits + number_of_carry_bits),
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count_limit = nth_bit(number_of_count_bits - 1),
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carry_mask = right_n_bits(number_of_carry_bits) << number_of_state_bits,
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state_mask = right_n_bits(number_of_state_bits),
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status_mask = right_n_bits(number_of_state_bits + number_of_carry_bits),
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count_mask = ((int)(-1) ^ status_mask)
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};
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public:
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static int InterpreterInvocationLimit; // CompileThreshold scaled for interpreter use
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static int Tier1InvocationLimit; // CompileThreshold scaled for tier1 use
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static int Tier1BackEdgeLimit; // BackEdgeThreshold scaled for tier1 use
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static int InterpreterBackwardBranchLimit; // A separate threshold for on stack replacement
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static int InterpreterProfileLimit; // Profiling threshold scaled for interpreter use
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typedef address (*Action)(methodHandle method, TRAPS);
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enum PublicConstants {
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count_increment = count_grain, // use this value to increment the 32bit _counter word
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count_mask_value = count_mask // use this value to mask the backedge counter
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};
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enum State {
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wait_for_nothing, // do nothing when count() > limit()
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wait_for_compile, // introduce nmethod when count() > limit()
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number_of_states // must be <= state_limit
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};
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// Manipulation
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void reset(); // sets state to wait state
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void init(); // sets state into original state
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void set_state(State state); // sets state and initializes counter correspondingly
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inline void set(State state, int count); // sets state and counter
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inline void decay(); // decay counter (divide by two)
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void set_carry(); // set the sticky carry bit
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// Accessors
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State state() const { return (State)(_counter & state_mask); }
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bool carry() const { return (_counter & carry_mask) != 0; }
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int limit() const { return CompileThreshold; }
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Action action() const { return _action[state()]; }
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int count() const { return _counter >> number_of_noncount_bits; }
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int get_InvocationLimit() const { return InterpreterInvocationLimit >> number_of_noncount_bits; }
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int get_BackwardBranchLimit() const { return InterpreterBackwardBranchLimit >> number_of_noncount_bits; }
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int get_ProfileLimit() const { return InterpreterProfileLimit >> number_of_noncount_bits; }
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// Test counter using scaled limits like the asm interpreter would do rather than doing
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// the shifts to normalize the counter.
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bool reached_InvocationLimit() const { return _counter >= (unsigned int) InterpreterInvocationLimit; }
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bool reached_BackwardBranchLimit() const { return _counter >= (unsigned int) InterpreterBackwardBranchLimit; }
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// Do this just like asm interpreter does for max speed
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bool reached_ProfileLimit(InvocationCounter *back_edge_count) const {
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return (_counter && count_mask) + back_edge_count->_counter >= (unsigned int) InterpreterProfileLimit;
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}
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void increment() { _counter += count_increment; }
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// Printing
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void print();
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void print_short();
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// Miscellaneous
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static ByteSize counter_offset() { return byte_offset_of(InvocationCounter, _counter); }
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static void reinitialize(bool delay_overflow);
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private:
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static int _init [number_of_states]; // the counter limits
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static Action _action[number_of_states]; // the actions
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static void def(State state, int init, Action action);
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static const char* state_as_string(State state);
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static const char* state_as_short_string(State state);
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};
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inline void InvocationCounter::set(State state, int count) {
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assert(0 <= state && state < number_of_states, "illegal state");
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int carry = (_counter & carry_mask); // the carry bit is sticky
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_counter = (count << number_of_noncount_bits) | carry | state;
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}
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inline void InvocationCounter::decay() {
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int c = count();
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int new_count = c >> 1;
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// prevent from going to zero, to distinguish from never-executed methods
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if (c > 0 && new_count == 0) new_count = 1;
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set(state(), new_count);
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}
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