1 /*
2 * Copyright (c) 2005, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
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 PointsToNode;
119 class Type;
120 class TypePtr;
121 class VectorSet;
122
123 class JavaObjectNode;
124 class LocalVarNode;
125 class FieldNode;
126 class ArraycopyNode;
127
128 // ConnectionGraph nodes
129 class PointsToNode : public ResourceObj {
130 GrowableArray<PointsToNode*> _edges; // List of nodes this node points to
131 GrowableArray<PointsToNode*> _uses; // List of nodes which point to this node
132
133 const u1 _type; // NodeType
134 u1 _flags; // NodeFlags
135 u1 _escape; // EscapeState of object
136 u1 _fields_escape; // EscapeState of object's fields
137
138 Node* const _node; // Ideal node corresponding to this PointsTo node.
139 const int _idx; // Cached ideal node's _idx
140
141 public:
142 typedef enum {
143 UnknownType = 0,
144 JavaObject = 1,
145 LocalVar = 2,
146 Field = 3,
147 Arraycopy = 4
148 } NodeType;
149
150 typedef enum {
151 UnknownEscape = 0,
152 NoEscape = 1, // An object does not escape method or thread and it is
153 // not passed to call. It could be replaced with scalar.
154 ArgEscape = 2, // An object does not escape method or thread but it is
155 // passed as argument to call or referenced by argument
156 // and it does not escape during call.
157 GlobalEscape = 3 // An object escapes the method or thread.
158 } EscapeState;
159
160 typedef enum {
161 ScalarReplaceable = 1, // Not escaped object could be replaced with scalar
162 PointsToUnknown = 2, // Has edge to phantom_object
163 ArraycopySrc = 4, // Has edge from Arraycopy node
164 ArraycopyDst = 8 // Has edge to Arraycopy node
165 } NodeFlags;
166
167
168 PointsToNode(Compile *C, Node* n, EscapeState es, NodeType type):
169 _edges(C->comp_arena(), 2, 0, NULL),
170 _uses (C->comp_arena(), 2, 0, NULL),
171 _node(n),
172 _idx(n->_idx),
173 _type((u1)type),
174 _escape((u1)es),
175 _fields_escape((u1)es),
176 _flags(ScalarReplaceable) {
177 assert(n != NULL && es != UnknownEscape, "sanity");
178 }
179
180 Node* ideal_node() const { return _node; }
181 int idx() const { return _idx; }
182
183 bool is_JavaObject() const { return _type == (u1)JavaObject; }
184 bool is_LocalVar() const { return _type == (u1)LocalVar; }
185 bool is_Field() const { return _type == (u1)Field; }
186 bool is_Arraycopy() const { return _type == (u1)Arraycopy; }
187
188 JavaObjectNode* as_JavaObject() { assert(is_JavaObject(),""); return (JavaObjectNode*)this; }
189 LocalVarNode* as_LocalVar() { assert(is_LocalVar(),""); return (LocalVarNode*)this; }
190 FieldNode* as_Field() { assert(is_Field(),""); return (FieldNode*)this; }
191 ArraycopyNode* as_Arraycopy() { assert(is_Arraycopy(),""); return (ArraycopyNode*)this; }
192
193 EscapeState escape_state() const { return (EscapeState)_escape; }
194 void set_escape_state(EscapeState state) { _escape = (u1)state; }
195
196 EscapeState fields_escape_state() const { return (EscapeState)_fields_escape; }
197 void set_fields_escape_state(EscapeState state) { _fields_escape = (u1)state; }
198
199 bool has_unknown_ptr() const { return (_flags & PointsToUnknown) != 0; }
200 void set_has_unknown_ptr() { _flags |= PointsToUnknown; }
201
202 bool arraycopy_src() const { return (_flags & ArraycopySrc) != 0; }
203 void set_arraycopy_src() { _flags |= ArraycopySrc; }
204 bool arraycopy_dst() const { return (_flags & ArraycopyDst) != 0; }
205 void set_arraycopy_dst() { _flags |= ArraycopyDst; }
206
207 bool scalar_replaceable() const { return (_flags & ScalarReplaceable) != 0;}
208 void set_scalar_replaceable(bool v) {
209 if (v)
210 _flags |= ScalarReplaceable;
211 else
212 _flags &= ~ScalarReplaceable;
213 }
214
215 int edge_count() const { return _edges.length(); }
216 PointsToNode* edge(int e) const { return _edges.at(e); }
217 bool add_edge(PointsToNode* edge) { return _edges.append_if_missing(edge); }
218
219 int use_count() const { return _uses.length(); }
220 PointsToNode* use(int e) const { return _uses.at(e); }
221 bool add_use(PointsToNode* use) { return _uses.append_if_missing(use); }
222
223 // Mark base edge use to distinguish from stored value edge.
224 bool add_base_use(FieldNode* use) { return _uses.append_if_missing((PointsToNode*)((intptr_t)use + 1)); }
225 static bool is_base_use(PointsToNode* use) { return (((intptr_t)use) & 1); }
226 static PointsToNode* get_use_node(PointsToNode* use) { return (PointsToNode*)(((intptr_t)use) & ~1); }
227
228 // Return true if this node points to specified node or nodes it points to.
229 bool points_to(JavaObjectNode* ptn) const;
230
231 // Return true if this node points only to non-escaping allocations.
232 bool non_escaping_allocation();
233
234 // Return true if one node points to an other.
235 bool meet(PointsToNode* ptn);
236
237 #ifndef PRODUCT
238 NodeType node_type() const { return (NodeType)_type;}
239 void dump(bool print_state=true) const;
240 #endif
241
242 };
243
244 class LocalVarNode: public PointsToNode {
245 public:
246 LocalVarNode(Compile *C, Node* n, EscapeState es):
247 PointsToNode(C, n, es, LocalVar) {}
248 };
249
250 class JavaObjectNode: public PointsToNode {
251 public:
252 JavaObjectNode(Compile *C, Node* n, EscapeState es):
253 PointsToNode(C, n, es, JavaObject) {
254 if (es > NoEscape)
255 set_scalar_replaceable(false);
256 }
257 };
258
259 class FieldNode: public PointsToNode {
260 GrowableArray<PointsToNode*> _bases; // List of JavaObject nodes which point to this node
261 const int _offset; // Field's offset.
262 const bool _is_oop; // Field points to object
263 bool _has_unknown_base; // Has phantom_object base
264 public:
265 FieldNode(Compile *C, Node* n, EscapeState es, int offs, bool is_oop):
266 PointsToNode(C, n, es, Field),
267 _offset(offs), _is_oop(is_oop),
268 _has_unknown_base(false) {}
269
270 int offset() const { return _offset;}
271 bool is_oop() const { return _is_oop;}
272 bool has_unknown_base() const { return _has_unknown_base; }
273 void set_has_unknown_base() { _has_unknown_base = true; }
274
275 int base_count() const { return _bases.length(); }
276 PointsToNode* base(int e) const { return _bases.at(e); }
277 bool add_base(PointsToNode* base) { return _bases.append_if_missing(base); }
278 #ifdef ASSERT
279 // Return true if bases points to this java object.
280 bool has_base(JavaObjectNode* ptn) const;
281 #endif
282
283 };
284
285 class ArraycopyNode: public PointsToNode {
286 public:
287 ArraycopyNode(Compile *C, Node* n, EscapeState es):
288 PointsToNode(C, n, es, Arraycopy) {}
289 };
290
291 // Iterators for PointsTo node's edges:
292 // for (EdgeIterator i(n); i.has_next(); i.next()) {
293 // PointsToNode* u = i.get();
294 class PointsToIterator: public StackObj {
295 protected:
296 const PointsToNode* node;
297 const int cnt;
298 int i;
299 public:
300 inline PointsToIterator(const PointsToNode* n, int cnt) : node(n), cnt(cnt), i(0) { }
301 inline bool has_next() const { return i < cnt; }
302 inline void next() { i++; }
303 PointsToNode* get() const { ShouldNotCallThis(); return NULL; }
304 };
305
306 class EdgeIterator: public PointsToIterator {
307 public:
308 inline EdgeIterator(const PointsToNode* n) : PointsToIterator(n, n->edge_count()) { }
309 inline PointsToNode* get() const { return node->edge(i); }
310 };
311
312 class UseIterator: public PointsToIterator {
313 public:
314 inline UseIterator(const PointsToNode* n) : PointsToIterator(n, n->use_count()) { }
315 inline PointsToNode* get() const { return node->use(i); }
316 };
317
318 class BaseIterator: public PointsToIterator {
319 public:
320 inline BaseIterator(const FieldNode* n) : PointsToIterator(n, n->base_count()) { }
321 inline PointsToNode* get() const { return ((PointsToNode*)node)->as_Field()->base(i); }
322 };
323
324
325 class ConnectionGraph: public ResourceObj {
326 private:
327 GrowableArray<PointsToNode*> _nodes; // Map from ideal nodes to
328 // ConnectionGraph nodes.
329
330 GrowableArray<PointsToNode*> _worklist; // Nodes to be processed
331
332 bool _collecting; // Indicates whether escape information
333 // is still being collected. If false,
334 // no new nodes will be processed.
335
336 bool _verify; // verify graph
337
338 JavaObjectNode* phantom_obj; // Unknown object
339 JavaObjectNode* null_obj;
340 Node* _pcmp_neq; // ConI(#CC_GT)
341 Node* _pcmp_eq; // ConI(#CC_EQ)
342
343 Compile* _compile; // Compile object for current compilation
344 PhaseIterGVN* _igvn; // Value numbering
345
346 Unique_Node_List ideal_nodes; // Used by CG construction and types splitting.
347
348 // Address of an element in _nodes. Used when the element is to be modified
349 PointsToNode* ptnode_adr(int idx) const {
350 // There should be no new ideal nodes during ConnectionGraph build,
351 // growableArray::at() will throw assert otherwise.
352 return _nodes.at(idx);
353 }
354 uint nodes_size() const { return _nodes.length(); }
355
356 // Add nodes to ConnectionGraph.
357 void add_local_var(Node* n, PointsToNode::EscapeState es);
358 void add_java_object(Node* n, PointsToNode::EscapeState es);
359 void add_field(Node* n, PointsToNode::EscapeState es, int offset);
360 void add_arraycopy(Node* n, PointsToNode::EscapeState es, PointsToNode* src, PointsToNode* dst);
361
362 // Compute the escape state for arguments to a call.
363 void process_call_arguments(CallNode *call);
364
365 // Add PointsToNode node corresponding to a call
366 void add_call_node(CallNode* call);
367
368 // Map ideal node to existing PointsTo node (usually phantom_object).
369 void map_ideal_node(Node *n, PointsToNode* ptn) {
370 assert(ptn != NULL, "only existing PointsTo node");
371 _nodes.at_put(n->_idx, ptn);
372 }
373
374 // Create PointsToNode node and add it to Connection Graph.
375 void add_node_to_connection_graph(Node *n, Unique_Node_List *delayed_worklist);
376
377 // Add final simple edges to graph.
378 void add_final_edges(Node *n);
379
380 // Finish Graph construction.
381 bool complete_connection_graph(GrowableArray<PointsToNode*>& ptnodes_worklist,
382 GrowableArray<JavaObjectNode*>& non_escaped_worklist,
383 GrowableArray<JavaObjectNode*>& java_objects_worklist,
384 GrowableArray<FieldNode*>& oop_fields_worklist);
385
386 #ifdef ASSERT
387 void verify_connection_graph(GrowableArray<PointsToNode*>& ptnodes_worklist,
388 GrowableArray<JavaObjectNode*>& non_escaped_worklist,
389 GrowableArray<JavaObjectNode*>& java_objects_worklist,
390 GrowableArray<Node*>& addp_worklist);
391 #endif
392
393 // Add all references to this JavaObject node.
394 int add_java_object_edges(JavaObjectNode* jobj, bool populate_worklist);
395
396 // Put node on worklist if it is (or was) not there.
397 void add_to_worklist(PointsToNode* pt) {
398 _worklist.push(pt);
399 return;
400 }
401
402 // Put on worklist all uses of this node.
403 void add_uses_to_worklist(PointsToNode* pt) {
404 for (UseIterator i(pt); i.has_next(); i.next())
405 _worklist.push(i.get());
406 }
407
408 // Put on worklist all field's uses and related field nodes.
409 void add_field_uses_to_worklist(FieldNode* field);
410
411 // Put on worklist all related field nodes.
412 void add_fields_to_worklist(FieldNode* field, PointsToNode* base);
413
414 // Find fields which have unknown value.
415 int find_field_value(FieldNode* field);
416
417 // Find fields initializing values for allocations.
418 int find_init_values(JavaObjectNode* ptn, PointsToNode* init_val, PhaseTransform* phase);
419
420 // Set the escape state of an object and its fields.
421 void set_escape_state(PointsToNode* ptn, PointsToNode::EscapeState esc) {
422 // Don't change non-escaping state of NULL pointer.
423 if (ptn != null_obj) {
424 if (ptn->escape_state() < esc)
425 ptn->set_escape_state(esc);
426 if (ptn->fields_escape_state() < esc)
427 ptn->set_fields_escape_state(esc);
428 }
429 }
430 void set_fields_escape_state(PointsToNode* ptn, PointsToNode::EscapeState esc) {
431 // Don't change non-escaping state of NULL pointer.
432 if (ptn != null_obj) {
433 if (ptn->fields_escape_state() < esc)
434 ptn->set_fields_escape_state(esc);
435 }
436 }
437
438 // Propagate GlobalEscape and ArgEscape escape states to all nodes
439 // and check that we still have non-escaping java objects.
440 bool find_non_escaped_objects(GrowableArray<PointsToNode*>& ptnodes_worklist,
441 GrowableArray<JavaObjectNode*>& non_escaped_worklist);
442
443 // Adjust scalar_replaceable state after Connection Graph is built.
444 void adjust_scalar_replaceable_state(JavaObjectNode* jobj);
445
446 // Optimize ideal graph.
447 void optimize_ideal_graph(GrowableArray<Node*>& ptr_cmp_worklist,
448 GrowableArray<Node*>& storestore_worklist);
449 // Optimize objects compare.
450 Node* optimize_ptr_compare(Node* n);
451
452 // Returns unique corresponding java object or NULL.
453 JavaObjectNode* unique_java_object(Node *n);
454
455 // Add an edge of the specified type pointing to the specified target.
456 bool add_edge(PointsToNode* from, PointsToNode* to) {
457 assert(!from->is_Field() || from->as_Field()->is_oop(), "sanity");
458
459 if (to == phantom_obj) {
460 if (from->has_unknown_ptr()) {
461 return false; // already points to phantom_obj
462 }
463 from->set_has_unknown_ptr();
464 }
465
466 bool is_new = from->add_edge(to);
467 assert(to != phantom_obj || is_new, "sanity");
468 if (is_new) { // New edge?
469 assert(!_verify, "graph is incomplete");
470 is_new = to->add_use(from);
471 assert(is_new, "use should be also new");
472 }
473 return is_new;
474 }
475
476 // Add an edge from Field node to its base and back.
477 bool add_base(FieldNode* from, PointsToNode* to) {
478 assert(!to->is_Arraycopy(), "sanity");
479 if (to == phantom_obj) {
480 if (from->has_unknown_base()) {
481 return false; // already has phantom_obj base
482 }
483 from->set_has_unknown_base();
484 }
485 bool is_new = from->add_base(to);
486 assert(to != phantom_obj || is_new, "sanity");
487 if (is_new) { // New edge?
488 assert(!_verify, "graph is incomplete");
489 if (to == null_obj)
490 return is_new; // Don't add fields to NULL pointer.
491 if (to->is_JavaObject()) {
492 is_new = to->add_edge(from);
493 } else {
494 is_new = to->add_base_use(from);
495 }
496 assert(is_new, "use should be also new");
497 }
498 return is_new;
499 }
500
501 // Add LocalVar node and edge if possible
502 void add_local_var_and_edge(Node* n, PointsToNode::EscapeState es, Node* to,
503 Unique_Node_List *delayed_worklist) {
504 PointsToNode* ptn = ptnode_adr(to->_idx);
505 if (delayed_worklist != NULL) { // First iteration of CG construction
506 add_local_var(n, es);
507 if (ptn == NULL) {
508 delayed_worklist->push(n);
509 return; // Process it later.
510 }
511 } else {
512 assert(ptn != NULL, "node should be registered");
513 }
514 add_edge(ptnode_adr(n->_idx), ptn);
515 }
516
517 // Helper functions
518 bool is_oop_field(Node* n, int offset);
519 static Node* get_addp_base(Node *addp);
520 static Node* find_second_addp(Node* addp, Node* n);
521
522 // offset of a field reference
523 int address_offset(Node* adr, PhaseTransform *phase);
524
525
526 // Propagate unique types created for unescaped allocated objects
527 // through the graph
528 void split_unique_types(GrowableArray<Node *> &alloc_worklist);
529
530 // Helper methods for unique types split.
531 bool split_AddP(Node *addp, Node *base);
532
533 PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, bool &new_created);
534 PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist);
535
536 void move_inst_mem(Node* n, GrowableArray<PhiNode *> &orig_phis);
537 Node* find_inst_mem(Node* mem, int alias_idx,GrowableArray<PhiNode *> &orig_phi_worklist);
538 Node* step_through_mergemem(MergeMemNode *mmem, int alias_idx, const TypeOopPtr *toop);
539
540
541 GrowableArray<MergeMemNode*> _mergemem_worklist; // List of all MergeMem nodes
542
543 Node_Array _node_map; // used for bookeeping during type splitting
544 // Used for the following purposes:
545 // Memory Phi - most recent unique Phi split out
546 // from this Phi
547 // MemNode - new memory input for this node
548 // ChecCastPP - allocation that this is a cast of
549 // allocation - CheckCastPP of the allocation
550
551 // manage entries in _node_map
552
553 void set_map(Node* from, Node* to) {
554 ideal_nodes.push(from);
555 _node_map.map(from->_idx, to);
556 }
557
558 Node* get_map(int idx) { return _node_map[idx]; }
559
560 PhiNode* get_map_phi(int idx) {
561 Node* phi = _node_map[idx];
562 return (phi == NULL) ? NULL : phi->as_Phi();
563 }
564
565 // Notify optimizer that a node has been modified
566 void record_for_optimizer(Node *n) {
567 _igvn->_worklist.push(n);
568 _igvn->add_users_to_worklist(n);
569 }
570
571 // Compute the escape information
572 bool compute_escape();
573
574 public:
575 ConnectionGraph(Compile *C, PhaseIterGVN *igvn);
576
577 // Check for non-escaping candidates
578 static bool has_candidates(Compile *C);
579
580 // Perform escape analysis
581 static void do_analysis(Compile *C, PhaseIterGVN *igvn);
582
583 bool not_global_escape(Node *n);
584
585 #ifndef PRODUCT
586 void dump(GrowableArray<PointsToNode*>& ptnodes_worklist);
587 #endif
588 };
589
590 #endif // SHARE_VM_OPTO_ESCAPE_HPP