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1 /* |
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2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #ifndef SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP |
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26 #define SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP |
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27 |
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28 #include "oops/generateOopMap.hpp" |
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29 #include "runtime/mutex.hpp" |
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30 |
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31 // A Cache for storing (method, bci) -> oopMap. |
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32 // The memory management system uses the cache when locating object |
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33 // references in an interpreted frame. |
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34 // |
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35 // OopMapCache's are allocated lazily per InstanceKlass. |
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36 |
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37 // The oopMap (InterpreterOopMap) is stored as a bit mask. If the |
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38 // bit_mask can fit into two words it is stored in |
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39 // the _bit_mask array, otherwise it is allocated on the heap. |
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40 // For OopMapCacheEntry the bit_mask is allocated in the C heap |
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41 // because these entries persist between garbage collections. |
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42 // For InterpreterOopMap the bit_mask is allocated in |
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43 // a resource area for better performance. InterpreterOopMap |
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44 // should only be created and deleted during same garbage collection. |
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45 // |
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46 // If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used |
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47 // per entry instead of one. In all cases, |
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48 // the first bit is set to indicate oops as opposed to other |
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49 // values. If the second bit is available, |
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50 // it is set for dead values. We get the following encoding: |
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51 // |
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52 // 00 live value |
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53 // 01 live oop |
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54 // 10 dead value |
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55 // 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator) |
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56 |
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57 |
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58 class OffsetClosure { |
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59 public: |
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60 virtual void offset_do(int offset) = 0; |
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61 }; |
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62 |
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63 |
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64 class InterpreterOopMap: ResourceObj { |
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65 friend class OopMapCache; |
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66 |
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67 public: |
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68 enum { |
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69 N = 4, // the number of words reserved |
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70 // for inlined mask storage |
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71 small_mask_limit = N * BitsPerWord, // the maximum number of bits |
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72 // available for small masks, |
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73 // small_mask_limit can be set to 0 |
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74 // for testing bit_mask allocation |
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75 |
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76 bits_per_entry = 2, |
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77 dead_bit_number = 1, |
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78 oop_bit_number = 0 |
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79 }; |
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80 |
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81 private: |
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82 Method* _method; // the method for which the mask is valid |
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83 unsigned short _bci; // the bci for which the mask is valid |
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84 int _mask_size; // the mask size in bits |
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85 int _expression_stack_size; // the size of the expression stack in slots |
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86 |
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87 protected: |
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88 intptr_t _bit_mask[N]; // the bit mask if |
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89 // mask_size <= small_mask_limit, |
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90 // ptr to bit mask otherwise |
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91 // "protected" so that sub classes can |
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92 // access it without using trickery in |
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93 // methd bit_mask(). |
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94 #ifdef ASSERT |
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95 bool _resource_allocate_bit_mask; |
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96 #endif |
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97 |
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98 // access methods |
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99 Method* method() const { return _method; } |
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100 void set_method(Method* v) { _method = v; } |
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101 int bci() const { return _bci; } |
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102 void set_bci(int v) { _bci = v; } |
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103 int mask_size() const { return _mask_size; } |
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104 void set_mask_size(int v) { _mask_size = v; } |
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105 // Test bit mask size and return either the in-line bit mask or allocated |
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106 // bit mask. |
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107 uintptr_t* bit_mask() const { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); } |
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108 |
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109 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT |
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110 size_t mask_word_size() const { |
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111 return (mask_size() + BitsPerWord - 1) / BitsPerWord; |
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112 } |
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113 |
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114 uintptr_t entry_at(int offset) const { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); } |
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115 |
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116 void set_expression_stack_size(int sz) { _expression_stack_size = sz; } |
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117 |
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118 // Lookup |
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119 bool match(const methodHandle& method, int bci) const { return _method == method() && _bci == bci; } |
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120 bool is_empty() const; |
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121 |
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122 // Initialization |
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123 void initialize(); |
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124 |
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125 public: |
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126 InterpreterOopMap(); |
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127 ~InterpreterOopMap(); |
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128 |
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129 // Copy the OopMapCacheEntry in parameter "from" into this |
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130 // InterpreterOopMap. If the _bit_mask[0] in "from" points to |
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131 // allocated space (i.e., the bit mask was to large to hold |
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132 // in-line), allocate the space from a Resource area. |
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133 void resource_copy(OopMapCacheEntry* from); |
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134 |
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135 void iterate_oop(OffsetClosure* oop_closure) const; |
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136 void print() const; |
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137 |
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138 int number_of_entries() const { return mask_size() / bits_per_entry; } |
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139 bool is_dead(int offset) const { return (entry_at(offset) & (1 << dead_bit_number)) != 0; } |
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140 bool is_oop (int offset) const { return (entry_at(offset) & (1 << oop_bit_number )) != 0; } |
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141 |
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142 int expression_stack_size() const { return _expression_stack_size; } |
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143 |
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144 }; |
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145 |
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146 class OopMapCache : public CHeapObj<mtClass> { |
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147 static OopMapCacheEntry* volatile _old_entries; |
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148 private: |
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149 enum { _size = 32, // Use fixed size for now |
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150 _probe_depth = 3 // probe depth in case of collisions |
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151 }; |
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152 |
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153 OopMapCacheEntry* volatile * _array; |
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154 |
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155 unsigned int hash_value_for(const methodHandle& method, int bci) const; |
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156 OopMapCacheEntry* entry_at(int i) const; |
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157 bool put_at(int i, OopMapCacheEntry* entry, OopMapCacheEntry* old); |
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158 |
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159 static void enqueue_for_cleanup(OopMapCacheEntry* entry); |
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160 |
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161 void flush(); |
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162 |
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163 public: |
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164 OopMapCache(); |
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165 ~OopMapCache(); // free up memory |
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166 |
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167 // flush cache entry is occupied by an obsolete method |
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168 void flush_obsolete_entries(); |
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169 |
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170 // Returns the oopMap for (method, bci) in parameter "entry". |
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171 // Returns false if an oop map was not found. |
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172 void lookup(const methodHandle& method, int bci, InterpreterOopMap* entry); |
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173 |
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174 // Compute an oop map without updating the cache or grabbing any locks (for debugging) |
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175 static void compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry); |
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176 static void cleanup_old_entries(); |
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177 }; |
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178 |
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179 #endif // SHARE_VM_INTERPRETER_OOPMAPCACHE_HPP |