1 /*
2 * Copyright (c) 1997, 2006, 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.
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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 // A Cache for storing (method, bci) -> oopMap.
26 // The memory management system uses the cache when locating object
27 // references in an interpreted frame.
28 //
29 // OopMapCache's are allocated lazily per instanceKlass.
30
31 // The oopMap (InterpreterOopMap) is stored as a bit mask. If the
32 // bit_mask can fit into two words it is stored in
33 // the _bit_mask array, otherwise it is allocated on the heap.
34 // For OopMapCacheEntry the bit_mask is allocated in the C heap
35 // because these entries persist between garbage collections.
36 // For InterpreterOopMap the bit_mask is allocated in
37 // a resource area for better performance. InterpreterOopMap
38 // should only be created and deleted during same garbage collection.
39 //
40 // If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
41 // per entry instead of one. In all cases,
42 // the first bit is set to indicate oops as opposed to other
43 // values. If the second bit is available,
44 // it is set for dead values. We get the following encoding:
45 //
46 // 00 live value
47 // 01 live oop
48 // 10 dead value
49 // 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator)
50
51
52 class OffsetClosure {
53 public:
54 virtual void offset_do(int offset) = 0;
55 };
56
57
58 class InterpreterOopMap: ResourceObj {
59 friend class OopMapCache;
60
61 public:
62 enum {
63 N = 2, // the number of words reserved
64 // for inlined mask storage
65 small_mask_limit = N * BitsPerWord, // the maximum number of bits
66 // available for small masks,
67 // small_mask_limit can be set to 0
68 // for testing bit_mask allocation
69
70 #ifdef ENABLE_ZAP_DEAD_LOCALS
71 bits_per_entry = 2,
72 dead_bit_number = 1,
73 #else
74 bits_per_entry = 1,
75 #endif
76 oop_bit_number = 0
77 };
78
79 private:
80 methodOop _method; // the method for which the mask is valid
81 unsigned short _bci; // the bci for which the mask is valid
82 int _mask_size; // the mask size in bits
83 int _expression_stack_size; // the size of the expression stack in slots
84
85 protected:
86 intptr_t _bit_mask[N]; // the bit mask if
87 // mask_size <= small_mask_limit,
88 // ptr to bit mask otherwise
89 // "protected" so that sub classes can
90 // access it without using trickery in
91 // methd bit_mask().
92 #ifdef ASSERT
93 bool _resource_allocate_bit_mask;
94 #endif
95
96 // access methods
97 methodOop method() const { return _method; }
98 void set_method(methodOop v) { _method = v; }
99 int bci() const { return _bci; }
100 void set_bci(int v) { _bci = v; }
101 int mask_size() const { return _mask_size; }
102 void set_mask_size(int v) { _mask_size = v; }
103 int number_of_entries() const { return mask_size() / bits_per_entry; }
104 // Test bit mask size and return either the in-line bit mask or allocated
105 // bit mask.
106 uintptr_t* bit_mask() { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }
107
108 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT
109 size_t mask_word_size() {
110 return (mask_size() + BitsPerWord - 1) / BitsPerWord;
111 }
112
113 uintptr_t entry_at(int offset) { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }
114
115 void set_expression_stack_size(int sz) { _expression_stack_size = sz; }
116
117 #ifdef ENABLE_ZAP_DEAD_LOCALS
118 bool is_dead(int offset) { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
119 #endif
120
121 // Lookup
122 bool match(methodHandle method, int bci) { return _method == method() && _bci == bci; }
123 bool is_empty();
124
125 // Initialization
126 void initialize();
127
128 public:
129 InterpreterOopMap();
130 ~InterpreterOopMap();
131
132 // Copy the OopMapCacheEntry in parameter "from" into this
133 // InterpreterOopMap. If the _bit_mask[0] in "from" points to
134 // allocated space (i.e., the bit mask was to large to hold
135 // in-line), allocate the space from a Resource area.
136 void resource_copy(OopMapCacheEntry* from);
137
138 void iterate_oop(OffsetClosure* oop_closure);
139 void oop_iterate(OopClosure * blk);
140 void oop_iterate(OopClosure * blk, MemRegion mr);
141 void verify();
142 void print();
143
144 bool is_oop (int offset) { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
145
146 int expression_stack_size() { return _expression_stack_size; }
147
148 #ifdef ENABLE_ZAP_DEAD_LOCALS
149 void iterate_all(OffsetClosure* oop_closure, OffsetClosure* value_closure, OffsetClosure* dead_closure);
150 #endif
151 };
152
153 class OopMapCache : public CHeapObj {
154 private:
155 enum { _size = 32, // Use fixed size for now
156 _probe_depth = 3 // probe depth in case of collisions
157 };
158
159 OopMapCacheEntry* _array;
160
161 unsigned int hash_value_for(methodHandle method, int bci);
162 OopMapCacheEntry* entry_at(int i) const;
163
164 Mutex _mut;
165
166 void flush();
167
168 public:
169 OopMapCache();
170 ~OopMapCache(); // free up memory
171
172 // flush cache entry is occupied by an obsolete method
173 void flush_obsolete_entries();
174
175 // Returns the oopMap for (method, bci) in parameter "entry".
176 // Returns false if an oop map was not found.
177 void lookup(methodHandle method, int bci, InterpreterOopMap* entry);
178
179 // Compute an oop map without updating the cache or grabbing any locks (for debugging)
180 static void compute_one_oop_map(methodHandle method, int bci, InterpreterOopMap* entry);
181
182 // Helpers
183 // Iterate over the entries in the cached OopMapCacheEntry's
184 void oop_iterate(OopClosure *blk);
185 void oop_iterate(OopClosure *blk, MemRegion mr);
186 void verify();
187
188 // Returns total no. of bytes allocated as part of OopMapCache's
189 static long memory_usage() PRODUCT_RETURN0;
190 };