1 /*
2 * Copyright (c) 1997, 2015, 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
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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 #include "runtime/mutex.hpp"
30
31 // A Cache for storing (method, bci) -> oopMap.
32 // The memory management system uses the cache when locating object
33 // references in an interpreted frame.
34 //
35 // OopMapCache's are allocated lazily per InstanceKlass.
36
37 // The oopMap (InterpreterOopMap) is stored as a bit mask. If the
38 // bit_mask can fit into two words it is stored in
39 // the _bit_mask array, otherwise it is allocated on the heap.
40 // For OopMapCacheEntry the bit_mask is allocated in the C heap
41 // because these entries persist between garbage collections.
42 // For InterpreterOopMap the bit_mask is allocated in
43 // a resource area for better performance. InterpreterOopMap
44 // should only be created and deleted during same garbage collection.
45 //
46 // If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
47 // per entry instead of one. In all cases,
48 // the first bit is set to indicate oops as opposed to other
49 // values. If the second bit is available,
50 // it is set for dead values. We get the following encoding:
51 //
52 // 00 live value
53 // 01 live oop
54 // 10 dead value
55 // 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator)
56
57
58 class OffsetClosure {
59 public:
60 virtual void offset_do(int offset) = 0;
61 };
62
63
64 class InterpreterOopMap: ResourceObj {
65 friend class OopMapCache;
66
67 public:
68 enum {
69 N = 4, // the number of words reserved
70 // for inlined mask storage
71 small_mask_limit = N * BitsPerWord, // the maximum number of bits
72 // available for small masks,
73 // small_mask_limit can be set to 0
74 // for testing bit_mask allocation
75
76 bits_per_entry = 2,
77 dead_bit_number = 1,
78 oop_bit_number = 0
79 };
80
81 private:
82 Method* _method; // the method for which the mask is valid
83 unsigned short _bci; // the bci for which the mask is valid
84 int _mask_size; // the mask size in bits
85 int _expression_stack_size; // the size of the expression stack in slots
86
87 protected:
88 intptr_t _bit_mask[N]; // the bit mask if
89 // mask_size <= small_mask_limit,
90 // ptr to bit mask otherwise
91 // "protected" so that sub classes can
92 // access it without using trickery in
93 // methd bit_mask().
94 #ifdef ASSERT
95 bool _resource_allocate_bit_mask;
96 #endif
97
98 // access methods
99 Method* method() const { return _method; }
100 void set_method(Method* v) { _method = v; }
101 int bci() const { return _bci; }
102 void set_bci(int v) { _bci = v; }
103 int mask_size() const { return _mask_size; }
104 void set_mask_size(int v) { _mask_size = v; }
105 // Test bit mask size and return either the in-line bit mask or allocated
106 // bit mask.
107 uintptr_t* bit_mask() const { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }
108
109 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT
110 size_t mask_word_size() const {
111 return (mask_size() + BitsPerWord - 1) / BitsPerWord;
112 }
113
114 uintptr_t entry_at(int offset) const { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }
115
116 void set_expression_stack_size(int sz) { _expression_stack_size = sz; }
117
118 // Lookup
119 bool match(const methodHandle& method, int bci) const { return _method == method() && _bci == bci; }
120 bool is_empty() const;
121
122 // Initialization
123 void initialize();
124
125 public:
126 InterpreterOopMap();
127 ~InterpreterOopMap();
128
129 // Copy the OopMapCacheEntry in parameter "from" into this
130 // InterpreterOopMap. If the _bit_mask[0] in "from" points to
131 // allocated space (i.e., the bit mask was to large to hold
132 // in-line), allocate the space from a Resource area.
133 void resource_copy(OopMapCacheEntry* from);
134
135 void iterate_oop(OffsetClosure* oop_closure) const;
136 void print() const;
137
138 int number_of_entries() const { return mask_size() / bits_per_entry; }
139 bool is_dead(int offset) const { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
140 bool is_oop (int offset) const { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
141
142 int expression_stack_size() const { return _expression_stack_size; }
143
144 };
145
146 class OopMapCache : public CHeapObj<mtClass> {
147 private:
148 enum { _size = 32, // Use fixed size for now
149 _probe_depth = 3 // probe depth in case of collisions
150 };
151
152 OopMapCacheEntry* _array;
153
154 unsigned int hash_value_for(const methodHandle& method, int bci) const;
155 OopMapCacheEntry* entry_at(int i) const;
156
157 mutable Mutex _mut;
158
159 void flush();
160
161 public:
162 OopMapCache();
163 ~OopMapCache(); // free up memory
164
165 // flush cache entry is occupied by an obsolete method
166 void flush_obsolete_entries();
167
168 // Returns the oopMap for (method, bci) in parameter "entry".
169 // Returns false if an oop map was not found.
170 void lookup(const methodHandle& method, int bci, InterpreterOopMap* entry) const;
171
172 // Compute an oop map without updating the cache or grabbing any locks (for debugging)
173 static void compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry);
174
175 // Returns total no. of bytes allocated as part of OopMapCache's
176 static long memory_usage() PRODUCT_RETURN0;
177 };
178
179 #endif // SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP