1 /*
2 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 #ifndef SHARE_VM_OPTO_ESCAPE_HPP
26 #define SHARE_VM_OPTO_ESCAPE_HPP
27
28 #include "opto/addnode.hpp"
29 #include "opto/node.hpp"
30 #include "utilities/growableArray.hpp"
31
32 //
33 // Adaptation for C2 of the escape analysis algorithm described in:
34 //
35 // [Choi99] Jong-Deok Shoi, Manish Gupta, Mauricio Seffano,
36 // Vugranam C. Sreedhar, Sam Midkiff,
37 // "Escape Analysis for Java", Procedings of ACM SIGPLAN
38 // OOPSLA Conference, November 1, 1999
39 //
40 // The flow-insensitive analysis described in the paper has been implemented.
41 //
42 // The analysis requires construction of a "connection graph" (CG) for
43 // the method being analyzed. The nodes of the connection graph are:
44 //
45 // - Java objects (JO)
46 // - Local variables (LV)
47 // - Fields of an object (OF), these also include array elements
48 //
49 // The CG contains 3 types of edges:
50 //
51 // - PointsTo (-P>) {LV, OF} to JO
52 // - Deferred (-D>) from {LV, OF} to {LV, OF}
53 // - Field (-F>) from JO to OF
54 //
55 // The following utility functions is used by the algorithm:
56 //
57 // PointsTo(n) - n is any CG node, it returns the set of JO that n could
58 // point to.
59 //
60 // The algorithm describes how to construct the connection graph
61 // in the following 4 cases:
62 //
63 // Case Edges Created
64 //
65 // (1) p = new T() LV -P> JO
66 // (2) p = q LV -D> LV
67 // (3) p.f = q JO -F> OF, OF -D> LV
68 // (4) p = q.f JO -F> OF, LV -D> OF
69 //
70 // In all these cases, p and q are local variables. For static field
71 // references, we can construct a local variable containing a reference
72 // to the static memory.
73 //
74 // C2 does not have local variables. However for the purposes of constructing
75 // the connection graph, the following IR nodes are treated as local variables:
76 // Phi (pointer values)
77 // LoadP
78 // Proj#5 (value returned from callnodes including allocations)
79 // CheckCastPP, CastPP
80 //
81 // The LoadP, Proj and CheckCastPP behave like variables assigned to only once.
82 // Only a Phi can have multiple assignments. Each input to a Phi is treated
83 // as an assignment to it.
84 //
85 // The following node types are JavaObject:
86 //
87 // top()
88 // Allocate
89 // AllocateArray
90 // Parm (for incoming arguments)
91 // CastX2P ("unsafe" operations)
92 // CreateEx
93 // ConP
94 // LoadKlass
95 // ThreadLocal
96 //
97 // AddP nodes are fields.
98 //
99 // After building the graph, a pass is made over the nodes, deleting deferred
100 // nodes and copying the edges from the target of the deferred edge to the
101 // source. This results in a graph with no deferred edges, only:
102 //
103 // LV -P> JO
104 // OF -P> JO (the object whose oop is stored in the field)
105 // JO -F> OF
106 //
107 // Then, for each node which is GlobalEscape, anything it could point to
108 // is marked GlobalEscape. Finally, for any node marked ArgEscape, anything
109 // it could point to is marked ArgEscape.
110 //
111
112 class Compile;
113 class Node;
114 class CallNode;
115 class PhiNode;
116 class PhaseTransform;
117 class Type;
118 class TypePtr;
119 class VectorSet;
120
121 class PointsToNode {
122 friend class ConnectionGraph;
123 public:
124 typedef enum {
125 UnknownType = 0,
126 JavaObject = 1,
127 LocalVar = 2,
128 Field = 3
129 } NodeType;
130
131 typedef enum {
132 UnknownEscape = 0,
133 NoEscape = 1, // A scalar replaceable object with unique type.
134 ArgEscape = 2, // An object passed as argument or referenced by
135 // argument (and not globally escape during call).
136 GlobalEscape = 3 // An object escapes the method and thread.
137 } EscapeState;
138
139 typedef enum {
140 UnknownEdge = 0,
141 PointsToEdge = 1,
142 DeferredEdge = 2,
143 FieldEdge = 3
144 } EdgeType;
145
146 private:
147 enum {
148 EdgeMask = 3,
149 EdgeShift = 2,
150
151 INITIAL_EDGE_COUNT = 4
152 };
153
154 NodeType _type;
155 EscapeState _escape;
156 GrowableArray<uint>* _edges; // outgoing edges
157
158 public:
159 Node* _node; // Ideal node corresponding to this PointsTo node.
160 int _offset; // Object fields offsets.
161 bool _scalar_replaceable;// Not escaped object could be replaced with scalar
162 bool _hidden_alias; // This node is an argument to a function.
163 // which may return it creating a hidden alias.
164
165 PointsToNode():
166 _type(UnknownType),
167 _escape(UnknownEscape),
168 _edges(NULL),
169 _node(NULL),
170 _offset(-1),
171 _scalar_replaceable(true),
172 _hidden_alias(false) {}
173
174
175 EscapeState escape_state() const { return _escape; }
176 NodeType node_type() const { return _type;}
177 int offset() { return _offset;}
178
179 void set_offset(int offs) { _offset = offs;}
180 void set_escape_state(EscapeState state) { _escape = state; }
181 void set_node_type(NodeType ntype) {
182 assert(_type == UnknownType || _type == ntype, "Can't change node type");
183 _type = ntype;
184 }
185
186 // count of outgoing edges
187 uint edge_count() const { return (_edges == NULL) ? 0 : _edges->length(); }
188
189 // node index of target of outgoing edge "e"
190 uint edge_target(uint e) const {
191 assert(_edges != NULL, "valid edge index");
192 return (_edges->at(e) >> EdgeShift);
193 }
194 // type of outgoing edge "e"
195 EdgeType edge_type(uint e) const {
196 assert(_edges != NULL, "valid edge index");
197 return (EdgeType) (_edges->at(e) & EdgeMask);
198 }
199
200 // add a edge of the specified type pointing to the specified target
201 void add_edge(uint targIdx, EdgeType et);
202
203 // remove an edge of the specified type pointing to the specified target
204 void remove_edge(uint targIdx, EdgeType et);
205
206 #ifndef PRODUCT
207 void dump(bool print_state=true) const;
208 #endif
209
210 };
211
212 class ConnectionGraph: public ResourceObj {
213 private:
214 GrowableArray<PointsToNode> _nodes; // Connection graph nodes indexed
215 // by ideal node index.
216
217 Unique_Node_List _delayed_worklist; // Nodes to be processed before
218 // the call build_connection_graph().
219
220 GrowableArray<MergeMemNode *> _mergemem_worklist; // List of all MergeMem nodes
221
222 VectorSet _processed; // Records which nodes have been
223 // processed.
224
225 bool _collecting; // Indicates whether escape information
226 // is still being collected. If false,
227 // no new nodes will be processed.
228
229 uint _phantom_object; // Index of globally escaping object
230 // that pointer values loaded from
231 // a field which has not been set
232 // are assumed to point to.
233 uint _oop_null; // ConP(#NULL)
234 uint _noop_null; // ConN(#NULL)
235
236 Compile * _compile; // Compile object for current compilation
237 PhaseIterGVN * _igvn; // Value numbering
238
239 // Address of an element in _nodes. Used when the element is to be modified
240 PointsToNode *ptnode_adr(uint idx) const {
241 // There should be no new ideal nodes during ConnectionGraph build,
242 // growableArray::adr_at() will throw assert otherwise.
243 return _nodes.adr_at(idx);
244 }
245 uint nodes_size() const { return _nodes.length(); }
246
247 // Add node to ConnectionGraph.
248 void add_node(Node *n, PointsToNode::NodeType nt, PointsToNode::EscapeState es, bool done);
249
250 // offset of a field reference
251 int address_offset(Node* adr, PhaseTransform *phase);
252
253 // compute the escape state for arguments to a call
254 void process_call_arguments(CallNode *call, PhaseTransform *phase);
255
256 // compute the escape state for the return value of a call
257 void process_call_result(ProjNode *resproj, PhaseTransform *phase);
258
259 // Populate Connection Graph with Ideal nodes.
260 void record_for_escape_analysis(Node *n, PhaseTransform *phase);
261
262 // Build Connection Graph and set nodes escape state.
263 void build_connection_graph(Node *n, PhaseTransform *phase);
264
265 // walk the connection graph starting at the node corresponding to "n" and
266 // add the index of everything it could point to, to "ptset". This may cause
267 // Phi's encountered to get (re)processed (which requires "phase".)
268 void PointsTo(VectorSet &ptset, Node * n);
269
270 // Edge manipulation. The "from_i" and "to_i" arguments are the
271 // node indices of the source and destination of the edge
272 void add_pointsto_edge(uint from_i, uint to_i);
273 void add_deferred_edge(uint from_i, uint to_i);
274 void add_field_edge(uint from_i, uint to_i, int offs);
275
276
277 // Add an edge to node given by "to_i" from any field of adr_i whose offset
278 // matches "offset" A deferred edge is added if to_i is a LocalVar, and
279 // a pointsto edge is added if it is a JavaObject
280 void add_edge_from_fields(uint adr, uint to_i, int offs);
281
282 // Add a deferred edge from node given by "from_i" to any field
283 // of adr_i whose offset matches "offset"
284 void add_deferred_edge_to_fields(uint from_i, uint adr, int offs);
285
286
287 // Remove outgoing deferred edges from the node referenced by "ni".
288 // Any outgoing edges from the target of the deferred edge are copied
289 // to "ni".
290 void remove_deferred(uint ni, GrowableArray<uint>* deferred_edges, VectorSet* visited);
291
292 Node_Array _node_map; // used for bookeeping during type splitting
293 // Used for the following purposes:
294 // Memory Phi - most recent unique Phi split out
295 // from this Phi
296 // MemNode - new memory input for this node
297 // ChecCastPP - allocation that this is a cast of
298 // allocation - CheckCastPP of the allocation
299 bool split_AddP(Node *addp, Node *base, PhaseGVN *igvn);
300 PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn, bool &new_created);
301 PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
302 void move_inst_mem(Node* n, GrowableArray<PhiNode *> &orig_phis, PhaseGVN *igvn);
303 Node *find_inst_mem(Node *mem, int alias_idx,GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
304
305 // Propagate unique types created for unescaped allocated objects
306 // through the graph
307 void split_unique_types(GrowableArray<Node *> &alloc_worklist);
308
309 // manage entries in _node_map
310 void set_map(int idx, Node *n) { _node_map.map(idx, n); }
311 Node *get_map(int idx) { return _node_map[idx]; }
312 PhiNode *get_map_phi(int idx) {
313 Node *phi = _node_map[idx];
314 return (phi == NULL) ? NULL : phi->as_Phi();
315 }
316
317 // Notify optimizer that a node has been modified
318 // Node: This assumes that escape analysis is run before
319 // PhaseIterGVN creation
320 void record_for_optimizer(Node *n) {
321 _igvn->_worklist.push(n);
322 }
323
324 // Set the escape state of a node
325 void set_escape_state(uint ni, PointsToNode::EscapeState es);
326
327 // Search for objects which are not scalar replaceable.
328 void verify_escape_state(int nidx, VectorSet& ptset, PhaseTransform* phase);
329
330 public:
331 ConnectionGraph(Compile *C, PhaseIterGVN *igvn);
332
333 // Check for non-escaping candidates
334 static bool has_candidates(Compile *C);
335
336 // Perform escape analysis
337 static void do_analysis(Compile *C, PhaseIterGVN *igvn);
338
339 // Compute the escape information
340 bool compute_escape();
341
342 // escape state of a node
343 PointsToNode::EscapeState escape_state(Node *n);
344
345 // other information we have collected
346 bool is_scalar_replaceable(Node *n) {
347 if (_collecting || (n->_idx >= nodes_size()))
348 return false;
349 PointsToNode* ptn = ptnode_adr(n->_idx);
350 return ptn->escape_state() == PointsToNode::NoEscape && ptn->_scalar_replaceable;
351 }
352
353 bool hidden_alias(Node *n) {
354 if (_collecting || (n->_idx >= nodes_size()))
355 return true;
356 PointsToNode* ptn = ptnode_adr(n->_idx);
357 return (ptn->escape_state() != PointsToNode::NoEscape) || ptn->_hidden_alias;
358 }
359
360 #ifndef PRODUCT
361 void dump();
362 #endif
363 };
364
365 #endif // SHARE_VM_OPTO_ESCAPE_HPP