1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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, LoadN
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 // phantom_object (general globally escaped object)
88 // Allocate
89 // AllocateArray
90 // Parm (for incoming arguments)
91 // CastX2P ("unsafe" operations)
92 // CreateEx
93 // ConP
94 // LoadKlass
95 // ThreadLocal
96 // CallStaticJava (which returns Object)
97 //
98 // AddP nodes are fields.
99 //
100 // After building the graph, a pass is made over the nodes, deleting deferred
101 // nodes and copying the edges from the target of the deferred edge to the
102 // source. This results in a graph with no deferred edges, only:
103 //
104 // LV -P> JO
105 // OF -P> JO (the object whose oop is stored in the field)
106 // JO -F> OF
107 //
108 // Then, for each node which is GlobalEscape, anything it could point to
109 // is marked GlobalEscape. Finally, for any node marked ArgEscape, anything
110 // it could point to is marked ArgEscape.
111 //
112
113 class Compile;
114 class Node;
115 class CallNode;
116 class PhiNode;
117 class PhaseTransform;
118 class Type;
119 class TypePtr;
120 class VectorSet;
121
122 class PointsToNode {
123 friend class ConnectionGraph;
124 public:
125 typedef enum {
126 UnknownType = 0,
127 JavaObject = 1,
128 LocalVar = 2,
129 Field = 3
130 } NodeType;
131
132 typedef enum {
133 UnknownEscape = 0,
134 NoEscape = 1, // A scalar replaceable object with unique type.
135 ControlEscape = 2, // Complex control flow or some limitations do not
136 // allow scalar replacement of not escaping object.
137 ArgEscape = 3, // An object passed as argument or referenced by
138 // argument (and not globally escape during call).
139 GlobalEscape = 4 // An object escapes the method and thread.
140 } EscapeState;
141
142 typedef enum {
143 UnknownEdge = 0,
144 PointsToEdge = 1,
145 DeferredEdge = 2,
146 FieldEdge = 3
147 } EdgeType;
148
149 private:
150 enum {
151 EdgeMask = 3,
152 EdgeShift = 2,
153
154 INITIAL_EDGE_COUNT = 4
155 };
156
157 NodeType _type;
158 EscapeState _escape;
159 GrowableArray<uint>* _edges; // outgoing edges
160 Node* _node; // Ideal node corresponding to this PointsTo node.
161 int _offset; // Object fields offsets.
162
163 public:
164 PointsToNode():
165 _type(UnknownType),
166 _escape(UnknownEscape),
167 _edges(NULL),
168 _node(NULL),
169 _offset(-1) {}
170
171
172 EscapeState escape_state() const { return _escape; }
173 NodeType node_type() const { return _type;}
174 int offset() { return _offset;}
175
176 void set_offset(int offs) { _offset = offs;}
177 void set_escape_state(EscapeState state) { _escape = state; }
178 void set_node_type(NodeType ntype) {
179 assert(_type == UnknownType || _type == ntype, "Can't change node type");
180 _type = ntype;
181 }
182
183 // count of outgoing edges
184 uint edge_count() const { return (_edges == NULL) ? 0 : _edges->length(); }
185
186 // node index of target of outgoing edge "e"
187 uint edge_target(uint e) const {
188 assert(_edges != NULL, "valid edge index");
189 return (_edges->at(e) >> EdgeShift);
190 }
191 // type of outgoing edge "e"
192 EdgeType edge_type(uint e) const {
193 assert(_edges != NULL, "valid edge index");
194 return (EdgeType) (_edges->at(e) & EdgeMask);
195 }
196
197 // add a edge of the specified type pointing to the specified target
198 void add_edge(uint targIdx, EdgeType et);
199
200 // remove an edge of the specified type pointing to the specified target
201 void remove_edge(uint targIdx, EdgeType et);
202
203 #ifndef PRODUCT
204 void dump(bool print_state=true) const;
205 #endif
206
207 };
208
209 class ConnectionGraph: public ResourceObj {
210 private:
211 GrowableArray<PointsToNode> _nodes; // Connection graph nodes indexed
212 // by ideal node index.
213
214 Unique_Node_List _delayed_worklist; // Nodes to be processed before
215 // the call build_connection_graph().
216
217 GrowableArray<MergeMemNode *> _mergemem_worklist; // List of all MergeMem nodes
218
219 VectorSet _processed; // Records which nodes have been
220 // processed.
221
222 bool _collecting; // Indicates whether escape information
223 // is still being collected. If false,
224 // no new nodes will be processed.
225
226 bool _progress; // Indicates whether new Graph's edges
227 // were created.
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)->_idx
234 uint _noop_null; // ConN(#NULL)->_idx
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 VectorSet* PointsTo(Node * n);
269
270 // Reused structures for PointsTo().
271 VectorSet pt_ptset;
272 VectorSet pt_visited;
273 GrowableArray<uint> pt_worklist;
274
275 // Edge manipulation. The "from_i" and "to_i" arguments are the
276 // node indices of the source and destination of the edge
277 void add_pointsto_edge(uint from_i, uint to_i);
278 void add_deferred_edge(uint from_i, uint to_i);
279 void add_field_edge(uint from_i, uint to_i, int offs);
280
281 // Add an edge of the specified type pointing to the specified target.
282 // Set _progress if new edge is added.
283 void add_edge(PointsToNode *f, uint to_i, PointsToNode::EdgeType et) {
284 uint e_cnt = f->edge_count();
285 f->add_edge(to_i, et);
286 _progress |= (f->edge_count() != e_cnt);
287 }
288
289 // Add an edge to node given by "to_i" from any field of adr_i whose offset
290 // matches "offset" A deferred edge is added if to_i is a LocalVar, and
291 // a pointsto edge is added if it is a JavaObject
292 void add_edge_from_fields(uint adr, uint to_i, int offs);
293
294 // Add a deferred edge from node given by "from_i" to any field
295 // of adr_i whose offset matches "offset"
296 void add_deferred_edge_to_fields(uint from_i, uint adr, int offs);
297
298
299 // Remove outgoing deferred edges from the node referenced by "ni".
300 // Any outgoing edges from the target of the deferred edge are copied
301 // to "ni".
302 void remove_deferred(uint ni, GrowableArray<uint>* deferred_edges, VectorSet* visited);
303
304 Node_Array _node_map; // used for bookeeping during type splitting
305 // Used for the following purposes:
306 // Memory Phi - most recent unique Phi split out
307 // from this Phi
308 // MemNode - new memory input for this node
309 // ChecCastPP - allocation that this is a cast of
310 // allocation - CheckCastPP of the allocation
311 bool split_AddP(Node *addp, Node *base, PhaseGVN *igvn);
312 PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn, bool &new_created);
313 PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
314 void move_inst_mem(Node* n, GrowableArray<PhiNode *> &orig_phis, PhaseGVN *igvn);
315 Node *find_inst_mem(Node *mem, int alias_idx,GrowableArray<PhiNode *> &orig_phi_worklist, PhaseGVN *igvn);
316
317 // Propagate unique types created for unescaped allocated objects
318 // through the graph
319 void split_unique_types(GrowableArray<Node *> &alloc_worklist);
320
321 // manage entries in _node_map
322 void set_map(int idx, Node *n) { _node_map.map(idx, n); }
323 Node *get_map(int idx) { return _node_map[idx]; }
324 PhiNode *get_map_phi(int idx) {
325 Node *phi = _node_map[idx];
326 return (phi == NULL) ? NULL : phi->as_Phi();
327 }
328
329 // Notify optimizer that a node has been modified
330 // Node: This assumes that escape analysis is run before
331 // PhaseIterGVN creation
332 void record_for_optimizer(Node *n) {
333 _igvn->_worklist.push(n);
334 }
335
336 // Set the escape state of a node
337 void set_escape_state(uint ni, PointsToNode::EscapeState es);
338
339 // Find fields initializing values for allocations.
340 void find_init_values(Node* n, VectorSet* visited, PhaseTransform* phase);
341
342 // Adjust escape state after Connection Graph is built.
343 void adjust_escape_state(Node* n);
344
345 // Propagate escape states to referenced nodes.
346 bool propagate_escape_state(GrowableArray<int>* cg_worklist,
347 GrowableArray<uint>* worklist,
348 PointsToNode::EscapeState esc_state);
349
350 // Compute the escape information
351 bool compute_escape();
352
353 public:
354 ConnectionGraph(Compile *C, PhaseIterGVN *igvn);
355
356 // Check for non-escaping candidates
357 static bool has_candidates(Compile *C);
358
359 // Perform escape analysis
360 static void do_analysis(Compile *C, PhaseIterGVN *igvn);
361
362 // escape state of a node
363 PointsToNode::EscapeState escape_state(Node *n);
364
365 #ifndef PRODUCT
366 void dump();
367 #endif
368 };
369
370 #endif // SHARE_VM_OPTO_ESCAPE_HPP