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.
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23 */
24
25 #ifndef SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP
26 #define SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP
27
28 #include "oops/generateOopMap.hpp"
29
30 // A Cache for storing (method, bci) -> oopMap.
31 // The memory management system uses the cache when locating object
32 // references in an interpreted frame.
33 //
34 // OopMapCache's are allocated lazily per instanceKlass.
35
36 // The oopMap (InterpreterOopMap) is stored as a bit mask. If the
37 // bit_mask can fit into two words it is stored in
38 // the _bit_mask array, otherwise it is allocated on the heap.
39 // For OopMapCacheEntry the bit_mask is allocated in the C heap
40 // because these entries persist between garbage collections.
41 // For InterpreterOopMap the bit_mask is allocated in
42 // a resource area for better performance. InterpreterOopMap
43 // should only be created and deleted during same garbage collection.
44 //
45 // If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
46 // per entry instead of one. In all cases,
47 // the first bit is set to indicate oops as opposed to other
48 // values. If the second bit is available,
49 // it is set for dead values. We get the following encoding:
50 //
51 // 00 live value
52 // 01 live oop
53 // 10 dead value
54 // 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator)
55
56
57 class OffsetClosure {
58 public:
59 virtual void offset_do(int offset) = 0;
60 };
61
62
63 class InterpreterOopMap: ResourceObj {
64 friend class OopMapCache;
65
66 public:
67 enum {
68 N = 2, // the number of words reserved
69 // for inlined mask storage
70 small_mask_limit = N * BitsPerWord, // the maximum number of bits
71 // available for small masks,
72 // small_mask_limit can be set to 0
73 // for testing bit_mask allocation
74
75 #ifdef ENABLE_ZAP_DEAD_LOCALS
76 bits_per_entry = 2,
77 dead_bit_number = 1,
78 #else
79 bits_per_entry = 1,
80 #endif
81 oop_bit_number = 0
82 };
83
84 private:
85 methodOop _method; // the method for which the mask is valid
86 unsigned short _bci; // the bci for which the mask is valid
87 int _mask_size; // the mask size in bits
88 int _expression_stack_size; // the size of the expression stack in slots
89
90 protected:
91 intptr_t _bit_mask[N]; // the bit mask if
92 // mask_size <= small_mask_limit,
93 // ptr to bit mask otherwise
94 // "protected" so that sub classes can
95 // access it without using trickery in
96 // methd bit_mask().
97 #ifdef ASSERT
98 bool _resource_allocate_bit_mask;
99 #endif
100
101 // access methods
102 methodOop method() const { return _method; }
103 void set_method(methodOop v) { _method = v; }
104 int bci() const { return _bci; }
105 void set_bci(int v) { _bci = v; }
106 int mask_size() const { return _mask_size; }
107 void set_mask_size(int v) { _mask_size = v; }
108 int number_of_entries() const { return mask_size() / bits_per_entry; }
109 // Test bit mask size and return either the in-line bit mask or allocated
110 // bit mask.
111 uintptr_t* bit_mask() { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }
112
113 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT
114 size_t mask_word_size() {
115 return (mask_size() + BitsPerWord - 1) / BitsPerWord;
116 }
117
118 uintptr_t entry_at(int offset) { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }
119
120 void set_expression_stack_size(int sz) { _expression_stack_size = sz; }
121
122 #ifdef ENABLE_ZAP_DEAD_LOCALS
123 bool is_dead(int offset) { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
124 #endif
125
126 // Lookup
127 bool match(methodHandle method, int bci) { return _method == method() && _bci == bci; }
128 bool is_empty();
129
130 // Initialization
131 void initialize();
132
133 public:
134 InterpreterOopMap();
135 ~InterpreterOopMap();
136
137 // Copy the OopMapCacheEntry in parameter "from" into this
138 // InterpreterOopMap. If the _bit_mask[0] in "from" points to
139 // allocated space (i.e., the bit mask was to large to hold
140 // in-line), allocate the space from a Resource area.
141 void resource_copy(OopMapCacheEntry* from);
142
143 void iterate_oop(OffsetClosure* oop_closure);
144 void oop_iterate(OopClosure * blk);
145 void oop_iterate(OopClosure * blk, MemRegion mr);
146 void verify();
147 void print();
148
149 bool is_oop (int offset) { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
150
151 int expression_stack_size() { return _expression_stack_size; }
152
153 #ifdef ENABLE_ZAP_DEAD_LOCALS
154 void iterate_all(OffsetClosure* oop_closure, OffsetClosure* value_closure, OffsetClosure* dead_closure);
155 #endif
156 };
157
158 class OopMapCache : public CHeapObj {
159 private:
160 enum { _size = 32, // Use fixed size for now
161 _probe_depth = 3 // probe depth in case of collisions
162 };
163
164 OopMapCacheEntry* _array;
165
166 unsigned int hash_value_for(methodHandle method, int bci);
167 OopMapCacheEntry* entry_at(int i) const;
168
169 Mutex _mut;
170
171 void flush();
172
173 public:
174 OopMapCache();
175 ~OopMapCache(); // free up memory
176
177 // flush cache entry is occupied by an obsolete method
178 void flush_obsolete_entries();
179
180 // Returns the oopMap for (method, bci) in parameter "entry".
181 // Returns false if an oop map was not found.
182 void lookup(methodHandle method, int bci, InterpreterOopMap* entry);
183
184 // Compute an oop map without updating the cache or grabbing any locks (for debugging)
185 static void compute_one_oop_map(methodHandle method, int bci, InterpreterOopMap* entry);
186
187 // Helpers
188 // Iterate over the entries in the cached OopMapCacheEntry's
189 void oop_iterate(OopClosure *blk);
190 void oop_iterate(OopClosure *blk, MemRegion mr);
191 void verify();
192
193 // Returns total no. of bytes allocated as part of OopMapCache's
194 static long memory_usage() PRODUCT_RETURN0;
195 };
196
197 #endif // SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP