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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 //
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26 // Adaptation for C2 of the escape analysis algorithm described in:
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27 //
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28 // [Choi99] Jong-Deok Shoi, Manish Gupta, Mauricio Seffano,
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29 // Vugranam C. Sreedhar, Sam Midkiff,
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30 // "Escape Analysis for Java", Procedings of ACM SIGPLAN
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31 // OOPSLA Conference, November 1, 1999
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32 //
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33 // The flow-insensitive analysis described in the paper has been implemented.
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34 //
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35 // The analysis requires construction of a "connection graph" (CG) for
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36 // the method being analyzed. The nodes of the connection graph are:
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37 //
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38 // - Java objects (JO)
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39 // - Local variables (LV)
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40 // - Fields of an object (OF), these also include array elements
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41 //
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42 // The CG contains 3 types of edges:
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43 //
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44 // - PointsTo (-P>) {LV, OF} to JO
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45 // - Deferred (-D>) from {LV, OF} to {LV, OF}
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46 // - Field (-F>) from JO to OF
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47 //
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48 // The following utility functions is used by the algorithm:
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49 //
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50 // PointsTo(n) - n is any CG node, it returns the set of JO that n could
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51 // point to.
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52 //
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53 // The algorithm describes how to construct the connection graph
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54 // in the following 4 cases:
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55 //
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56 // Case Edges Created
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57 //
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58 // (1) p = new T() LV -P> JO
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59 // (2) p = q LV -D> LV
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60 // (3) p.f = q JO -F> OF, OF -D> LV
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61 // (4) p = q.f JO -F> OF, LV -D> OF
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62 //
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63 // In all these cases, p and q are local variables. For static field
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64 // references, we can construct a local variable containing a reference
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65 // to the static memory.
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66 //
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67 // C2 does not have local variables. However for the purposes of constructing
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68 // the connection graph, the following IR nodes are treated as local variables:
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69 // Phi (pointer values)
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70 // LoadP
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71 // Proj#5 (value returned from callnodes including allocations)
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72 // CheckCastPP, CastPP
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73 //
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74 // The LoadP, Proj and CheckCastPP behave like variables assigned to only once.
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75 // Only a Phi can have multiple assignments. Each input to a Phi is treated
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76 // as an assignment to it.
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77 //
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78 // The following node types are JavaObject:
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79 //
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80 // top()
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81 // Allocate
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82 // AllocateArray
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83 // Parm (for incoming arguments)
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84 // CastX2P ("unsafe" operations)
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85 // CreateEx
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86 // ConP
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87 // LoadKlass
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88 // ThreadLocal
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89 //
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90 // AddP nodes are fields.
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91 //
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92 // After building the graph, a pass is made over the nodes, deleting deferred
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93 // nodes and copying the edges from the target of the deferred edge to the
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94 // source. This results in a graph with no deferred edges, only:
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95 //
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96 // LV -P> JO
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97 // OF -P> JO (the object whose oop is stored in the field)
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98 // JO -F> OF
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99 //
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100 // Then, for each node which is GlobalEscape, anything it could point to
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101 // is marked GlobalEscape. Finally, for any node marked ArgEscape, anything
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102 // it could point to is marked ArgEscape.
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103 //
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104
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105 class Compile;
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106 class Node;
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107 class CallNode;
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108 class PhiNode;
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109 class PhaseTransform;
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110 class Type;
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111 class TypePtr;
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112 class VectorSet;
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113
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114 class PointsToNode {
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115 friend class ConnectionGraph;
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116 public:
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117 typedef enum {
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118 UnknownType = 0,
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119 JavaObject = 1,
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120 LocalVar = 2,
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121 Field = 3
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122 } NodeType;
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123
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124 typedef enum {
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125 UnknownEscape = 0,
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126 NoEscape = 1, // A scalar replaceable object with unique type.
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127 ArgEscape = 2, // An object passed as argument or referenced by
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128 // argument (and not globally escape during call).
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129 GlobalEscape = 3 // An object escapes the method and thread.
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130 } EscapeState;
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131
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132 typedef enum {
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133 UnknownEdge = 0,
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134 PointsToEdge = 1,
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135 DeferredEdge = 2,
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136 FieldEdge = 3
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137 } EdgeType;
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138
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139 private:
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140 enum {
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141 EdgeMask = 3,
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142 EdgeShift = 2,
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143
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144 INITIAL_EDGE_COUNT = 4
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145 };
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146
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147 NodeType _type;
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148 EscapeState _escape;
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149 GrowableArray<uint>* _edges; // outgoing edges
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150
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151 public:
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152 Node* _node; // Ideal node corresponding to this PointsTo node.
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153 int _offset; // Object fields offsets.
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154 bool _scalar_replaceable;// Not escaped object could be replaced with scalar
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155 bool _hidden_alias; // This node is an argument to a function.
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156 // which may return it creating a hidden alias.
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157
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158 PointsToNode():
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159 _type(UnknownType),
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160 _escape(UnknownEscape),
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161 _edges(NULL),
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162 _node(NULL),
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163 _offset(-1),
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164 _scalar_replaceable(true),
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165 _hidden_alias(false) {}
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166
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167
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168 EscapeState escape_state() const { return _escape; }
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169 NodeType node_type() const { return _type;}
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170 int offset() { return _offset;}
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171
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172 void set_offset(int offs) { _offset = offs;}
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173 void set_escape_state(EscapeState state) { _escape = state; }
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174 void set_node_type(NodeType ntype) {
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175 assert(_type == UnknownType || _type == ntype, "Can't change node type");
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176 _type = ntype;
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177 }
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178
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179 // count of outgoing edges
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180 uint edge_count() const { return (_edges == NULL) ? 0 : _edges->length(); }
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181 // node index of target of outgoing edge "e"
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182 uint edge_target(uint e) const;
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183 // type of outgoing edge "e"
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184 EdgeType edge_type(uint e) const;
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185 // add a edge of the specified type pointing to the specified target
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186 void add_edge(uint targIdx, EdgeType et);
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187 // remove an edge of the specified type pointing to the specified target
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188 void remove_edge(uint targIdx, EdgeType et);
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189 #ifndef PRODUCT
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190 void dump() const;
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191 #endif
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192
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193 };
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194
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195 class ConnectionGraph: public ResourceObj {
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196 private:
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197 GrowableArray<PointsToNode>* _nodes; // Connection graph nodes indexed
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198 // by ideal node index.
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199
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200 Unique_Node_List _delayed_worklist; // Nodes to be processed before
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201 // the call build_connection_graph().
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202
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203 VectorSet _processed; // Records which nodes have been
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204 // processed.
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205
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206 bool _collecting; // Indicates whether escape information
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207 // is still being collected. If false,
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208 // no new nodes will be processed.
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209
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210 bool _has_allocations; // Indicates whether method has any
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211 // non-escaping allocations.
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212
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213 uint _phantom_object; // Index of globally escaping object
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214 // that pointer values loaded from
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215 // a field which has not been set
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216 // are assumed to point to.
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217
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218 Compile * _compile; // Compile object for current compilation
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219
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220 // address of an element in _nodes. Used when the element is to be modified
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221 PointsToNode *ptnode_adr(uint idx) {
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222 if ((uint)_nodes->length() <= idx) {
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223 // expand _nodes array
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224 PointsToNode dummy = _nodes->at_grow(idx);
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225 }
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226 return _nodes->adr_at(idx);
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227 }
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228
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229 // Add node to ConnectionGraph.
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230 void add_node(Node *n, PointsToNode::NodeType nt, PointsToNode::EscapeState es, bool done);
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231
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232 // offset of a field reference
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233 int address_offset(Node* adr, PhaseTransform *phase);
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234
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235 // compute the escape state for arguments to a call
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236 void process_call_arguments(CallNode *call, PhaseTransform *phase);
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237
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238 // compute the escape state for the return value of a call
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239 void process_call_result(ProjNode *resproj, PhaseTransform *phase);
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240
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241 // Populate Connection Graph with Ideal nodes.
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242 void record_for_escape_analysis(Node *n, PhaseTransform *phase);
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243
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244 // Build Connection Graph and set nodes escape state.
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245 void build_connection_graph(Node *n, PhaseTransform *phase);
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246
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247 // walk the connection graph starting at the node corresponding to "n" and
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248 // add the index of everything it could point to, to "ptset". This may cause
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249 // Phi's encountered to get (re)processed (which requires "phase".)
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250 void PointsTo(VectorSet &ptset, Node * n, PhaseTransform *phase);
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251
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252 // Edge manipulation. The "from_i" and "to_i" arguments are the
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253 // node indices of the source and destination of the edge
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254 void add_pointsto_edge(uint from_i, uint to_i);
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255 void add_deferred_edge(uint from_i, uint to_i);
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256 void add_field_edge(uint from_i, uint to_i, int offs);
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257
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258
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259 // Add an edge to node given by "to_i" from any field of adr_i whose offset
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260 // matches "offset" A deferred edge is added if to_i is a LocalVar, and
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261 // a pointsto edge is added if it is a JavaObject
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262 void add_edge_from_fields(uint adr, uint to_i, int offs);
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263
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264 // Add a deferred edge from node given by "from_i" to any field
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265 // of adr_i whose offset matches "offset"
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266 void add_deferred_edge_to_fields(uint from_i, uint adr, int offs);
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267
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268
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269 // Remove outgoing deferred edges from the node referenced by "ni".
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270 // Any outgoing edges from the target of the deferred edge are copied
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271 // to "ni".
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272 void remove_deferred(uint ni);
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273
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274 Node_Array _node_map; // used for bookeeping during type splitting
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275 // Used for the following purposes:
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276 // Memory Phi - most recent unique Phi split out
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277 // from this Phi
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278 // MemNode - new memory input for this node
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279 // ChecCastPP - allocation that this is a cast of
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280 // allocation - CheckCastPP of the allocation
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281 void split_AddP(Node *addp, Node *base, PhaseGVN *igvn);
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282 PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn, bool &new_created);
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283 PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
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284 Node *find_mem(Node *mem, int alias_idx, PhaseGVN *igvn);
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285 Node *find_inst_mem(Node *mem, int alias_idx,GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
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286
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287 // Propagate unique types created for unescaped allocated objects
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288 // through the graph
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289 void split_unique_types(GrowableArray<Node *> &alloc_worklist);
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290
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291 // manage entries in _node_map
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292 void set_map(int idx, Node *n) { _node_map.map(idx, n); }
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293 void set_map_phi(int idx, PhiNode *p) { _node_map.map(idx, (Node *) p); }
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294 Node *get_map(int idx) { return _node_map[idx]; }
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295 PhiNode *get_map_phi(int idx) {
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296 Node *phi = _node_map[idx];
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297 return (phi == NULL) ? NULL : phi->as_Phi();
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298 }
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299
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300 // Notify optimizer that a node has been modified
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301 // Node: This assumes that escape analysis is run before
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302 // PhaseIterGVN creation
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303 void record_for_optimizer(Node *n) {
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304 _compile->record_for_igvn(n);
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305 }
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306
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307 // Set the escape state of a node
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308 void set_escape_state(uint ni, PointsToNode::EscapeState es);
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309
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310 // Get Compile object for current compilation.
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311 Compile *C() const { return _compile; }
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312
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313 public:
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314 ConnectionGraph(Compile *C);
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315
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316 // Compute the escape information
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317 void compute_escape();
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318
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319 // escape state of a node
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320 PointsToNode::EscapeState escape_state(Node *n, PhaseTransform *phase);
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321 // other information we have collected
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322 bool is_scalar_replaceable(Node *n) {
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323 if (_collecting)
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324 return false;
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325 PointsToNode ptn = _nodes->at_grow(n->_idx);
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326 return ptn.escape_state() == PointsToNode::NoEscape && ptn._scalar_replaceable;
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327 }
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328
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329 bool hidden_alias(Node *n) {
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330 if (_collecting)
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331 return true;
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332 PointsToNode ptn = _nodes->at_grow(n->_idx);
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333 return (ptn.escape_state() != PointsToNode::NoEscape) || ptn._hidden_alias;
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334 }
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335
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336 #ifndef PRODUCT
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337 void dump();
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338 #endif
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339 };
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