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1 /*
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2 * Copyright 2005-2006 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 //** Dependencies represent assertions (approximate invariants) within
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26 // the class hierarchy. An example is an assertion that a given
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27 // method is not overridden; another example is that a type has only
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28 // one concrete subtype. Compiled code which relies on such
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29 // assertions must be discarded if they are overturned by changes in
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30 // the class hierarchy. We can think of these assertions as
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31 // approximate invariants, because we expect them to be overturned
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32 // very infrequently. We are willing to perform expensive recovery
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33 // operations when they are overturned. The benefit, of course, is
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34 // performing optimistic optimizations (!) on the object code.
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35 //
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36 // Changes in the class hierarchy due to dynamic linking or
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37 // class evolution can violate dependencies. There is enough
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38 // indexing between classes and nmethods to make dependency
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39 // checking reasonably efficient.
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40
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41 class ciEnv;
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42 class nmethod;
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43 class OopRecorder;
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44 class xmlStream;
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45 class CompileLog;
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46 class DepChange;
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47 class No_Safepoint_Verifier;
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48
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49 class Dependencies: public ResourceObj {
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50 public:
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51 // Note: In the comments on dependency types, most uses of the terms
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52 // subtype and supertype are used in a "non-strict" or "inclusive"
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53 // sense, and are starred to remind the reader of this fact.
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54 // Strict uses of the terms use the word "proper".
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55 //
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56 // Specifically, every class is its own subtype* and supertype*.
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57 // (This trick is easier than continually saying things like "Y is a
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58 // subtype of X or X itself".)
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59 //
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60 // Sometimes we write X > Y to mean X is a proper supertype of Y.
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61 // The notation X > {Y, Z} means X has proper subtypes Y, Z.
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62 // The notation X.m > Y means that Y inherits m from X, while
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63 // X.m > Y.m means Y overrides X.m. A star denotes abstractness,
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64 // as *I > A, meaning (abstract) interface I is a super type of A,
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65 // or A.*m > B.m, meaning B.m implements abstract method A.m.
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66 //
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67 // In this module, the terms "subtype" and "supertype" refer to
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68 // Java-level reference type conversions, as detected by
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69 // "instanceof" and performed by "checkcast" operations. The method
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70 // Klass::is_subtype_of tests these relations. Note that "subtype"
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71 // is richer than "subclass" (as tested by Klass::is_subclass_of),
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72 // since it takes account of relations involving interface and array
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73 // types.
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74 //
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75 // To avoid needless complexity, dependencies involving array types
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76 // are not accepted. If you need to make an assertion about an
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77 // array type, make the assertion about its corresponding element
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78 // types. Any assertion that might change about an array type can
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79 // be converted to an assertion about its element type.
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80 //
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81 // Most dependencies are evaluated over a "context type" CX, which
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82 // stands for the set Subtypes(CX) of every Java type that is a subtype*
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83 // of CX. When the system loads a new class or interface N, it is
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84 // responsible for re-evaluating changed dependencies whose context
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85 // type now includes N, that is, all super types of N.
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86 //
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87 enum DepType {
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88 end_marker = 0,
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89
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90 // An 'evol' dependency simply notes that the contents of the
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91 // method were used. If it evolves (is replaced), the nmethod
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92 // must be recompiled. No other dependencies are implied.
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93 evol_method,
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94 FIRST_TYPE = evol_method,
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95
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96 // A context type CX is a leaf it if has no proper subtype.
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97 leaf_type,
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98
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99 // An abstract class CX has exactly one concrete subtype CC.
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100 abstract_with_unique_concrete_subtype,
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101
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102 // The type CX is purely abstract, with no concrete subtype* at all.
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103 abstract_with_no_concrete_subtype,
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104
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105 // The concrete CX is free of concrete proper subtypes.
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106 concrete_with_no_concrete_subtype,
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107
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108 // Given a method M1 and a context class CX, the set MM(CX, M1) of
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109 // "concrete matching methods" in CX of M1 is the set of every
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110 // concrete M2 for which it is possible to create an invokevirtual
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111 // or invokeinterface call site that can reach either M1 or M2.
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112 // That is, M1 and M2 share a name, signature, and vtable index.
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113 // We wish to notice when the set MM(CX, M1) is just {M1}, or
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114 // perhaps a set of two {M1,M2}, and issue dependencies on this.
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115
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116 // The set MM(CX, M1) can be computed by starting with any matching
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117 // concrete M2 that is inherited into CX, and then walking the
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118 // subtypes* of CX looking for concrete definitions.
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119
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120 // The parameters to this dependency are the method M1 and the
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121 // context class CX. M1 must be either inherited in CX or defined
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122 // in a subtype* of CX. It asserts that MM(CX, M1) is no greater
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123 // than {M1}.
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124 unique_concrete_method, // one unique concrete method under CX
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125
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126 // An "exclusive" assertion concerns two methods or subtypes, and
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127 // declares that there are at most two (or perhaps later N>2)
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128 // specific items that jointly satisfy the restriction.
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129 // We list all items explicitly rather than just giving their
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130 // count, for robustness in the face of complex schema changes.
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131
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132 // A context class CX (which may be either abstract or concrete)
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133 // has two exclusive concrete subtypes* C1, C2 if every concrete
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134 // subtype* of CX is either C1 or C2. Note that if neither C1 or C2
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135 // are equal to CX, then CX itself must be abstract. But it is
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136 // also possible (for example) that C1 is CX (a concrete class)
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137 // and C2 is a proper subtype of C1.
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138 abstract_with_exclusive_concrete_subtypes_2,
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139
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140 // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
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141 exclusive_concrete_methods_2,
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142
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143 // This dependency asserts that no instances of class or it's
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144 // subclasses require finalization registration.
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145 no_finalizable_subclasses,
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146
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147 TYPE_LIMIT
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148 };
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149 enum {
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150 LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
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151
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152 // handy categorizations of dependency types:
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153 all_types = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE),
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154 non_ctxk_types = (1<<evol_method),
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155 ctxk_types = all_types & ~non_ctxk_types,
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156
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157 max_arg_count = 3, // current maximum number of arguments (incl. ctxk)
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158
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159 // A "context type" is a class or interface that
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160 // provides context for evaluating a dependency.
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161 // When present, it is one of the arguments (dep_context_arg).
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162 //
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163 // If a dependency does not have a context type, there is a
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164 // default context, depending on the type of the dependency.
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165 // This bit signals that a default context has been compressed away.
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166 default_context_type_bit = (1<<LG2_TYPE_LIMIT)
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167 };
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168
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169 static const char* dep_name(DepType dept);
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170 static int dep_args(DepType dept);
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171 static int dep_context_arg(DepType dept) {
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172 return dept_in_mask(dept, ctxk_types)? 0: -1;
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173 }
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174
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175 private:
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176 // State for writing a new set of dependencies:
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177 GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept))
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178 GrowableArray<ciObject*>* _deps[TYPE_LIMIT];
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179
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180 static const char* _dep_name[TYPE_LIMIT];
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181 static int _dep_args[TYPE_LIMIT];
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182
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183 static bool dept_in_mask(DepType dept, int mask) {
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184 return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
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185 }
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186
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187 bool note_dep_seen(int dept, ciObject* x) {
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188 assert(dept < BitsPerInt, "oob");
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189 int x_id = x->ident();
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190 assert(_dep_seen != NULL, "deps must be writable");
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191 int seen = _dep_seen->at_grow(x_id, 0);
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192 _dep_seen->at_put(x_id, seen | (1<<dept));
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193 // return true if we've already seen dept/x
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194 return (seen & (1<<dept)) != 0;
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195 }
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196
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197 bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
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198 int ctxk_i, ciKlass* ctxk);
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199
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200 void sort_all_deps();
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201 size_t estimate_size_in_bytes();
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202
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203 // Initialize _deps, etc.
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204 void initialize(ciEnv* env);
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205
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206 // State for making a new set of dependencies:
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207 OopRecorder* _oop_recorder;
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208
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209 // Logging support
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210 CompileLog* _log;
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211
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212 address _content_bytes; // everything but the oop references, encoded
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213 size_t _size_in_bytes;
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214
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215 public:
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216 // Make a new empty dependencies set.
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217 Dependencies(ciEnv* env) {
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218 initialize(env);
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219 }
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220
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221 private:
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222 // Check for a valid context type.
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223 // Enforce the restriction against array types.
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224 static void check_ctxk(ciKlass* ctxk) {
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225 assert(ctxk->is_instance_klass(), "java types only");
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226 }
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227 static void check_ctxk_concrete(ciKlass* ctxk) {
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228 assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
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229 }
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230 static void check_ctxk_abstract(ciKlass* ctxk) {
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231 check_ctxk(ctxk);
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232 assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
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233 }
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234
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235 void assert_common_1(DepType dept, ciObject* x);
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236 void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x);
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237 void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2);
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238
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239 public:
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240 // Adding assertions to a new dependency set at compile time:
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241 void assert_evol_method(ciMethod* m);
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242 void assert_leaf_type(ciKlass* ctxk);
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243 void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
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244 void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
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245 void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
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246 void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
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247 void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
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248 void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
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249 void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
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250
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251 // Define whether a given method or type is concrete.
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252 // These methods define the term "concrete" as used in this module.
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253 // For this module, an "abstract" class is one which is non-concrete.
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254 //
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255 // Future optimizations may allow some classes to remain
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256 // non-concrete until their first instantiation, and allow some
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257 // methods to remain non-concrete until their first invocation.
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258 // In that case, there would be a middle ground between concrete
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259 // and abstract (as defined by the Java language and VM).
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260 static bool is_concrete_klass(klassOop k); // k is instantiable
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261 static bool is_concrete_method(methodOop m); // m is invocable
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262 static Klass* find_finalizable_subclass(Klass* k);
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263
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264 // These versions of the concreteness queries work through the CI.
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265 // The CI versions are allowed to skew sometimes from the VM
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266 // (oop-based) versions. The cost of such a difference is a
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267 // (safely) aborted compilation, or a deoptimization, or a missed
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268 // optimization opportunity.
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269 //
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270 // In order to prevent spurious assertions, query results must
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271 // remain stable within any single ciEnv instance. (I.e., they must
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272 // not go back into the VM to get their value; they must cache the
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273 // bit in the CI, either eagerly or lazily.)
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274 static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
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275 static bool is_concrete_method(ciMethod* m); // m appears invocable
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276 static bool has_finalizable_subclass(ciInstanceKlass* k);
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277
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278 // As a general rule, it is OK to compile under the assumption that
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279 // a given type or method is concrete, even if it at some future
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280 // point becomes abstract. So dependency checking is one-sided, in
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281 // that it permits supposedly concrete classes or methods to turn up
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282 // as really abstract. (This shouldn't happen, except during class
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283 // evolution, but that's the logic of the checking.) However, if a
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284 // supposedly abstract class or method suddenly becomes concrete, a
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285 // dependency on it must fail.
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286
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287 // Checking old assertions at run-time (in the VM only):
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288 static klassOop check_evol_method(methodOop m);
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289 static klassOop check_leaf_type(klassOop ctxk);
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290 static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck,
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291 DepChange* changes = NULL);
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292 static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk,
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293 DepChange* changes = NULL);
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294 static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk,
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295 DepChange* changes = NULL);
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296 static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
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297 DepChange* changes = NULL);
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298 static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2,
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299 DepChange* changes = NULL);
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300 static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2,
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301 DepChange* changes = NULL);
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302 static klassOop check_has_no_finalizable_subclasses(klassOop ctxk,
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303 DepChange* changes = NULL);
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304 // A returned klassOop is NULL if the dependency assertion is still
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305 // valid. A non-NULL klassOop is a 'witness' to the assertion
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306 // failure, a point in the class hierarchy where the assertion has
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307 // been proven false. For example, if check_leaf_type returns
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308 // non-NULL, the value is a subtype of the supposed leaf type. This
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309 // witness value may be useful for logging the dependency failure.
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310 // Note that, when a dependency fails, there may be several possible
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311 // witnesses to the failure. The value returned from the check_foo
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312 // method is chosen arbitrarily.
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313
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314 // The 'changes' value, if non-null, requests a limited spot-check
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315 // near the indicated recent changes in the class hierarchy.
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316 // It is used by DepStream::spot_check_dependency_at.
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317
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318 // Detecting possible new assertions:
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319 static klassOop find_unique_concrete_subtype(klassOop ctxk);
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320 static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m);
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321 static int find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]);
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322 static int find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]);
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323
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324 // Create the encoding which will be stored in an nmethod.
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325 void encode_content_bytes();
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326
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327 address content_bytes() {
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328 assert(_content_bytes != NULL, "encode it first");
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329 return _content_bytes;
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330 }
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331 size_t size_in_bytes() {
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332 assert(_content_bytes != NULL, "encode it first");
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333 return _size_in_bytes;
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334 }
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335
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336 OopRecorder* oop_recorder() { return _oop_recorder; }
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337 CompileLog* log() { return _log; }
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338
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339 void copy_to(nmethod* nm);
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340
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341 void log_all_dependencies();
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342 void log_dependency(DepType dept, int nargs, ciObject* args[]) {
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343 write_dependency_to(log(), dept, nargs, args);
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344 }
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345 void log_dependency(DepType dept,
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346 ciObject* x0,
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347 ciObject* x1 = NULL,
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348 ciObject* x2 = NULL) {
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349 if (log() == NULL) return;
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350 ciObject* args[max_arg_count];
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351 args[0] = x0;
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352 args[1] = x1;
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353 args[2] = x2;
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354 assert(2 < max_arg_count, "");
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355 log_dependency(dept, dep_args(dept), args);
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356 }
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357
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358 static void write_dependency_to(CompileLog* log,
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359 DepType dept,
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360 int nargs, ciObject* args[],
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361 klassOop witness = NULL);
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362 static void write_dependency_to(CompileLog* log,
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363 DepType dept,
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364 int nargs, oop args[],
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365 klassOop witness = NULL);
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366 static void write_dependency_to(xmlStream* xtty,
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367 DepType dept,
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368 int nargs, oop args[],
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369 klassOop witness = NULL);
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370 static void print_dependency(DepType dept,
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371 int nargs, oop args[],
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372 klassOop witness = NULL);
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373
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374 private:
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375 // helper for encoding common context types as zero:
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376 static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x);
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377
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378 static klassOop ctxk_encoded_as_null(DepType dept, oop x);
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379
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380 public:
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381 // Use this to iterate over an nmethod's dependency set.
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382 // Works on new and old dependency sets.
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383 // Usage:
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384 //
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385 // ;
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386 // Dependencies::DepType dept;
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387 // for (Dependencies::DepStream deps(nm); deps.next(); ) {
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388 // ...
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389 // }
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390 //
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391 // The caller must be in the VM, since oops are not wrapped in handles.
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392 class DepStream {
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393 private:
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394 nmethod* _code; // null if in a compiler thread
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395 Dependencies* _deps; // null if not in a compiler thread
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396 CompressedReadStream _bytes;
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397 #ifdef ASSERT
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398 size_t _byte_limit;
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399 #endif
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400
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401 // iteration variables:
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402 DepType _type;
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403 int _xi[max_arg_count+1];
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404
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405 void initial_asserts(size_t byte_limit) NOT_DEBUG({});
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406
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407 inline oop recorded_oop_at(int i);
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408 // => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i)
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409
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410 klassOop check_dependency_impl(DepChange* changes);
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411
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412 public:
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413 DepStream(Dependencies* deps)
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414 : _deps(deps),
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415 _code(NULL),
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416 _bytes(deps->content_bytes())
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417 {
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418 initial_asserts(deps->size_in_bytes());
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419 }
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420 DepStream(nmethod* code)
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421 : _deps(NULL),
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422 _code(code),
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423 _bytes(code->dependencies_begin())
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424 {
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425 initial_asserts(code->dependencies_size());
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426 }
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427
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428 bool next();
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429
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430 DepType type() { return _type; }
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431 int argument_count() { return dep_args(type()); }
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432 int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob");
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433 return _xi[i]; }
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434 oop argument(int i); // => recorded_oop_at(argument_index(i))
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435 klassOop context_type();
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436
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437 methodOop method_argument(int i) {
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438 oop x = argument(i);
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439 assert(x->is_method(), "type");
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440 return (methodOop) x;
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441 }
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442 klassOop type_argument(int i) {
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443 oop x = argument(i);
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444 assert(x->is_klass(), "type");
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445 return (klassOop) x;
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446 }
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447
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448 // The point of the whole exercise: Is this dep is still OK?
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449 klassOop check_dependency() {
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450 return check_dependency_impl(NULL);
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451 }
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452 // A lighter version: Checks only around recent changes in a class
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453 // hierarchy. (See Universe::flush_dependents_on.)
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454 klassOop spot_check_dependency_at(DepChange& changes);
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455
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456 // Log the current dependency to xtty or compilation log.
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457 void log_dependency(klassOop witness = NULL);
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458
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459 // Print the current dependency to tty.
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460 void print_dependency(klassOop witness = NULL, bool verbose = false);
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461 };
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462 friend class Dependencies::DepStream;
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463
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464 static void print_statistics() PRODUCT_RETURN;
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465 };
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466
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467 // A class hierarchy change coming through the VM (under the Compile_lock).
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468 // The change is structured as a single new type with any number of supers
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|
469 // and implemented interface types. Other than the new type, any of the
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|
470 // super types can be context types for a relevant dependency, which the
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|
471 // new type could invalidate.
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|
472 class DepChange : public StackObj {
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473 private:
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474 enum ChangeType {
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475 NO_CHANGE = 0, // an uninvolved klass
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476 Change_new_type, // a newly loaded type
|
|
477 Change_new_sub, // a super with a new subtype
|
|
478 Change_new_impl, // an interface with a new implementation
|
|
479 CHANGE_LIMIT,
|
|
480 Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream
|
|
481 };
|
|
482
|
|
483 // each change set is rooted in exactly one new type (at present):
|
|
484 KlassHandle _new_type;
|
|
485
|
|
486 void initialize();
|
|
487
|
|
488 public:
|
|
489 // notes the new type, marks it and all its super-types
|
|
490 DepChange(KlassHandle new_type)
|
|
491 : _new_type(new_type)
|
|
492 {
|
|
493 initialize();
|
|
494 }
|
|
495
|
|
496 // cleans up the marks
|
|
497 ~DepChange();
|
|
498
|
|
499 klassOop new_type() { return _new_type(); }
|
|
500
|
|
501 // involves_context(k) is true if k is new_type or any of the super types
|
|
502 bool involves_context(klassOop k);
|
|
503
|
|
504 // Usage:
|
|
505 // for (DepChange::ContextStream str(changes); str.next(); ) {
|
|
506 // klassOop k = str.klass();
|
|
507 // switch (str.change_type()) {
|
|
508 // ...
|
|
509 // }
|
|
510 // }
|
|
511 class ContextStream : public StackObj {
|
|
512 private:
|
|
513 DepChange& _changes;
|
|
514 friend class DepChange;
|
|
515
|
|
516 // iteration variables:
|
|
517 ChangeType _change_type;
|
|
518 klassOop _klass;
|
|
519 objArrayOop _ti_base; // i.e., transitive_interfaces
|
|
520 int _ti_index;
|
|
521 int _ti_limit;
|
|
522
|
|
523 // start at the beginning:
|
|
524 void start() {
|
|
525 klassOop new_type = _changes.new_type();
|
|
526 _change_type = (new_type == NULL ? NO_CHANGE: Start_Klass);
|
|
527 _klass = new_type;
|
|
528 _ti_base = NULL;
|
|
529 _ti_index = 0;
|
|
530 _ti_limit = 0;
|
|
531 }
|
|
532
|
|
533 ContextStream(DepChange& changes)
|
|
534 : _changes(changes)
|
|
535 { start(); }
|
|
536
|
|
537 public:
|
|
538 ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
|
|
539 : _changes(changes)
|
|
540 // the nsv argument makes it safe to hold oops like _klass
|
|
541 { start(); }
|
|
542
|
|
543 bool next();
|
|
544
|
|
545 klassOop klass() { return _klass; }
|
|
546 };
|
|
547 friend class DepChange::ContextStream;
|
|
548
|
|
549 void print();
|
|
550 };
|