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1 /*
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2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // A Cache for storing (method, bci) -> oopMap.
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26 // The memory management system uses the cache when locating object
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27 // references in an interpreted frame.
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28 //
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29 // OopMapCache's are allocated lazily per instanceKlass.
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30
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31 // The oopMap (InterpreterOopMap) is stored as a bit mask. If the
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32 // bit_mask can fit into two words it is stored in
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33 // the _bit_mask array, otherwise it is allocated on the heap.
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34 // For OopMapCacheEntry the bit_mask is allocated in the C heap
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35 // because these entries persist between garbage collections.
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36 // For InterpreterOopMap the bit_mask is allocated in
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37 // a resource area for better performance. InterpreterOopMap
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38 // should only be created and deleted during same garbage collection.
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39 //
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40 // If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
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41 // per entry instead of one. In all cases,
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42 // the first bit is set to indicate oops as opposed to other
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43 // values. If the second bit is available,
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44 // it is set for dead values. We get the following encoding:
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45 //
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46 // 00 live value
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47 // 01 live oop
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48 // 10 dead value
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49 // 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator)
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50
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51
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52 class OffsetClosure {
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53 public:
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54 virtual void offset_do(int offset) = 0;
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55 };
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56
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57
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58 class InterpreterOopMap: ResourceObj {
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59 friend class OopMapCache;
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60
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61 public:
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62 enum {
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63 N = 2, // the number of words reserved
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64 // for inlined mask storage
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65 small_mask_limit = N * BitsPerWord, // the maximum number of bits
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66 // available for small masks,
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67 // small_mask_limit can be set to 0
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68 // for testing bit_mask allocation
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69
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70 #ifdef ENABLE_ZAP_DEAD_LOCALS
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71 bits_per_entry = 2,
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72 dead_bit_number = 1,
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73 #else
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74 bits_per_entry = 1,
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75 #endif
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76 oop_bit_number = 0
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77 };
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78
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79 private:
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80 methodOop _method; // the method for which the mask is valid
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81 unsigned short _bci; // the bci for which the mask is valid
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82 int _mask_size; // the mask size in bits
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83 int _expression_stack_size; // the size of the expression stack in slots
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84
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85 protected:
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86 intptr_t _bit_mask[N]; // the bit mask if
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87 // mask_size <= small_mask_limit,
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88 // ptr to bit mask otherwise
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89 // "protected" so that sub classes can
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90 // access it without using trickery in
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91 // methd bit_mask().
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92 #ifdef ASSERT
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93 bool _resource_allocate_bit_mask;
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94 #endif
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95
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96 // access methods
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97 methodOop method() const { return _method; }
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98 void set_method(methodOop v) { _method = v; }
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99 int bci() const { return _bci; }
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100 void set_bci(int v) { _bci = v; }
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101 int mask_size() const { return _mask_size; }
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102 void set_mask_size(int v) { _mask_size = v; }
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103 int number_of_entries() const { return mask_size() / bits_per_entry; }
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104 // Test bit mask size and return either the in-line bit mask or allocated
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105 // bit mask.
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106 uintptr_t* bit_mask() { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }
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107
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108 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT
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109 size_t mask_word_size() {
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110 return (mask_size() + BitsPerWord - 1) / BitsPerWord;
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111 }
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112
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113 uintptr_t entry_at(int offset) { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }
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114
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115 void set_expression_stack_size(int sz) { _expression_stack_size = sz; }
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116
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117 #ifdef ENABLE_ZAP_DEAD_LOCALS
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118 bool is_dead(int offset) { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
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119 #endif
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120
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121 // Lookup
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122 bool match(methodHandle method, int bci) { return _method == method() && _bci == bci; }
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123 bool is_empty();
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124
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125 // Initialization
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126 void initialize();
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127
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128 public:
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129 InterpreterOopMap();
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130 ~InterpreterOopMap();
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131
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132 // Copy the OopMapCacheEntry in parameter "from" into this
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133 // InterpreterOopMap. If the _bit_mask[0] in "from" points to
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134 // allocated space (i.e., the bit mask was to large to hold
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135 // in-line), allocate the space from a Resource area.
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136 void resource_copy(OopMapCacheEntry* from);
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137
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138 void iterate_oop(OffsetClosure* oop_closure);
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139 void oop_iterate(OopClosure * blk);
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140 void oop_iterate(OopClosure * blk, MemRegion mr);
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141 void verify();
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142 void print();
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143
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144 bool is_oop (int offset) { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
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145
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146 int expression_stack_size() { return _expression_stack_size; }
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147
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148 #ifdef ENABLE_ZAP_DEAD_LOCALS
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149 void iterate_all(OffsetClosure* oop_closure, OffsetClosure* value_closure, OffsetClosure* dead_closure);
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150 #endif
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151 };
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152
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153 class OopMapCache : public CHeapObj {
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154 private:
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155 enum { _size = 32, // Use fixed size for now
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156 _probe_depth = 3 // probe depth in case of collisions
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157 };
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158
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159 OopMapCacheEntry* _array;
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160
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161 unsigned int hash_value_for(methodHandle method, int bci);
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162 OopMapCacheEntry* entry_at(int i) const;
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163
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164 Mutex _mut;
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165
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166 void flush();
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167
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168 public:
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169 OopMapCache();
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170 ~OopMapCache(); // free up memory
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171
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172 // flush cache entry is occupied by an obsolete method
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173 void flush_obsolete_entries();
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174
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175 // Returns the oopMap for (method, bci) in parameter "entry".
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176 // Returns false if an oop map was not found.
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177 void lookup(methodHandle method, int bci, InterpreterOopMap* entry);
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178
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179 // Compute an oop map without updating the cache or grabbing any locks (for debugging)
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180 static void compute_one_oop_map(methodHandle method, int bci, InterpreterOopMap* entry);
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181
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182 // Helpers
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183 // Iterate over the entries in the cached OopMapCacheEntry's
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184 void oop_iterate(OopClosure *blk);
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185 void oop_iterate(OopClosure *blk, MemRegion mr);
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186 void verify();
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187
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188 // Returns total no. of bytes allocated as part of OopMapCache's
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189 static long memory_usage() PRODUCT_RETURN0;
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190 };
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