1 /*
2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 // InvocationCounters are used to trigger actions when a limit (threshold) is reached.
26 // For different states, different limits and actions can be defined in the initialization
27 // routine of InvocationCounters.
28 //
29 // Implementation notes: For space reasons, state & counter are both encoded in one word,
30 // The state is encoded using some of the least significant bits, the counter is using the
31 // more significant bits. The counter is incremented before a method is activated and an
32 // action is triggered when when count() > limit().
33
34 class InvocationCounter VALUE_OBJ_CLASS_SPEC {
35 friend class VMStructs;
36 private: // bit no: |31 3| 2 | 1 0 |
37 unsigned int _counter; // format: [count|carry|state]
38
39 enum PrivateConstants {
40 number_of_state_bits = 2,
41 number_of_carry_bits = 1,
42 number_of_noncount_bits = number_of_state_bits + number_of_carry_bits,
43 number_of_count_bits = BitsPerInt - number_of_noncount_bits,
44 state_limit = nth_bit(number_of_state_bits),
45 count_grain = nth_bit(number_of_state_bits + number_of_carry_bits),
46 carry_mask = right_n_bits(number_of_carry_bits) << number_of_state_bits,
47 state_mask = right_n_bits(number_of_state_bits),
48 status_mask = right_n_bits(number_of_state_bits + number_of_carry_bits),
49 count_mask = ((int)(-1) ^ status_mask)
50 };
51
52 public:
53 static int InterpreterInvocationLimit; // CompileThreshold scaled for interpreter use
54 static int InterpreterBackwardBranchLimit; // A separate threshold for on stack replacement
55 static int InterpreterProfileLimit; // Profiling threshold scaled for interpreter use
56
57 typedef address (*Action)(methodHandle method, TRAPS);
58
59 enum PublicConstants {
60 count_increment = count_grain, // use this value to increment the 32bit _counter word
61 count_mask_value = count_mask, // use this value to mask the backedge counter
62 count_shift = number_of_noncount_bits,
63 count_limit = nth_bit(number_of_count_bits - 1)
64 };
65
66 enum State {
67 wait_for_nothing, // do nothing when count() > limit()
68 wait_for_compile, // introduce nmethod when count() > limit()
69 number_of_states // must be <= state_limit
70 };
71
72 // Manipulation
73 void reset(); // sets state to wait state
74 void init(); // sets state into original state
75 void set_state(State state); // sets state and initializes counter correspondingly
76 inline void set(State state, int count); // sets state and counter
77 inline void decay(); // decay counter (divide by two)
78 void set_carry(); // set the sticky carry bit
79 void set_carry_flag() { _counter |= carry_mask; }
80
81 // Accessors
82 State state() const { return (State)(_counter & state_mask); }
83 bool carry() const { return (_counter & carry_mask) != 0; }
84 int limit() const { return CompileThreshold; }
85 Action action() const { return _action[state()]; }
86 int count() const { return _counter >> number_of_noncount_bits; }
87
88 int get_InvocationLimit() const { return InterpreterInvocationLimit >> number_of_noncount_bits; }
89 int get_BackwardBranchLimit() const { return InterpreterBackwardBranchLimit >> number_of_noncount_bits; }
90 int get_ProfileLimit() const { return InterpreterProfileLimit >> number_of_noncount_bits; }
91
92 // Test counter using scaled limits like the asm interpreter would do rather than doing
93 // the shifts to normalize the counter.
94
95 bool reached_InvocationLimit() const { return _counter >= (unsigned int) InterpreterInvocationLimit; }
96 bool reached_BackwardBranchLimit() const { return _counter >= (unsigned int) InterpreterBackwardBranchLimit; }
97
98 // Do this just like asm interpreter does for max speed
99 bool reached_ProfileLimit(InvocationCounter *back_edge_count) const {
100 return (_counter && count_mask) + back_edge_count->_counter >= (unsigned int) InterpreterProfileLimit;
101 }
102
103 void increment() { _counter += count_increment; }
104
105
106 // Printing
107 void print();
108 void print_short();
109
110 // Miscellaneous
111 static ByteSize counter_offset() { return byte_offset_of(InvocationCounter, _counter); }
112 static void reinitialize(bool delay_overflow);
113
114 private:
115 static int _init [number_of_states]; // the counter limits
116 static Action _action[number_of_states]; // the actions
117
118 static void def(State state, int init, Action action);
119 static const char* state_as_string(State state);
120 static const char* state_as_short_string(State state);
121 };
122
123 inline void InvocationCounter::set(State state, int count) {
124 assert(0 <= state && state < number_of_states, "illegal state");
125 int carry = (_counter & carry_mask); // the carry bit is sticky
126 _counter = (count << number_of_noncount_bits) | carry | state;
127 }
128
129 inline void InvocationCounter::decay() {
130 int c = count();
131 int new_count = c >> 1;
132 // prevent from going to zero, to distinguish from never-executed methods
133 if (c > 0 && new_count == 0) new_count = 1;
134 set(state(), new_count);
135 }
136