1/*
2 * Copyright (c) 2005, 2019, 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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24
25#ifndef SHARE_OPTO_ESCAPE_HPP
26#define SHARE_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
113class Compile;
114class Node;
115class CallNode;
116class PhiNode;
117class PhaseTransform;
118class PointsToNode;
119class Type;
120class TypePtr;
121class VectorSet;
122
123class JavaObjectNode;
124class LocalVarNode;
125class FieldNode;
126class ArraycopyNode;
127
128class ConnectionGraph;
129
130// ConnectionGraph nodes
131class PointsToNode : public ResourceObj {
132 GrowableArray<PointsToNode*> _edges; // List of nodes this node points to
133 GrowableArray<PointsToNode*> _uses; // List of nodes which point to this node
134
135 const u1 _type; // NodeType
136 u1 _flags; // NodeFlags
137 u1 _escape; // EscapeState of object
138 u1 _fields_escape; // EscapeState of object's fields
139
140 Node* const _node; // Ideal node corresponding to this PointsTo node.
141 const int _idx; // Cached ideal node's _idx
142 const uint _pidx; // Index of this node
143
144public:
145 typedef enum {
146 UnknownType = 0,
147 JavaObject = 1,
148 LocalVar = 2,
149 Field = 3,
150 Arraycopy = 4
151 } NodeType;
152
153 typedef enum {
154 UnknownEscape = 0,
155 NoEscape = 1, // An object does not escape method or thread and it is
156 // not passed to call. It could be replaced with scalar.
157 ArgEscape = 2, // An object does not escape method or thread but it is
158 // passed as argument to call or referenced by argument
159 // and it does not escape during call.
160 GlobalEscape = 3 // An object escapes the method or thread.
161 } EscapeState;
162
163 typedef enum {
164 ScalarReplaceable = 1, // Not escaped object could be replaced with scalar
165 PointsToUnknown = 2, // Has edge to phantom_object
166 ArraycopySrc = 4, // Has edge from Arraycopy node
167 ArraycopyDst = 8 // Has edge to Arraycopy node
168 } NodeFlags;
169
170
171 inline PointsToNode(ConnectionGraph* CG, Node* n, EscapeState es, NodeType type);
172
173 uint pidx() const { return _pidx; }
174
175 Node* ideal_node() const { return _node; }
176 int idx() const { return _idx; }
177
178 bool is_JavaObject() const { return _type == (u1)JavaObject; }
179 bool is_LocalVar() const { return _type == (u1)LocalVar; }
180 bool is_Field() const { return _type == (u1)Field; }
181 bool is_Arraycopy() const { return _type == (u1)Arraycopy; }
182
183 JavaObjectNode* as_JavaObject() { assert(is_JavaObject(),""); return (JavaObjectNode*)this; }
184 LocalVarNode* as_LocalVar() { assert(is_LocalVar(),""); return (LocalVarNode*)this; }
185 FieldNode* as_Field() { assert(is_Field(),""); return (FieldNode*)this; }
186 ArraycopyNode* as_Arraycopy() { assert(is_Arraycopy(),""); return (ArraycopyNode*)this; }
187
188 EscapeState escape_state() const { return (EscapeState)_escape; }
189 void set_escape_state(EscapeState state) { _escape = (u1)state; }
190
191 EscapeState fields_escape_state() const { return (EscapeState)_fields_escape; }
192 void set_fields_escape_state(EscapeState state) { _fields_escape = (u1)state; }
193
194 bool has_unknown_ptr() const { return (_flags & PointsToUnknown) != 0; }
195 void set_has_unknown_ptr() { _flags |= PointsToUnknown; }
196
197 bool arraycopy_src() const { return (_flags & ArraycopySrc) != 0; }
198 void set_arraycopy_src() { _flags |= ArraycopySrc; }
199 bool arraycopy_dst() const { return (_flags & ArraycopyDst) != 0; }
200 void set_arraycopy_dst() { _flags |= ArraycopyDst; }
201
202 bool scalar_replaceable() const { return (_flags & ScalarReplaceable) != 0;}
203 void set_scalar_replaceable(bool v) {
204 if (v)
205 _flags |= ScalarReplaceable;
206 else
207 _flags &= ~ScalarReplaceable;
208 }
209
210 int edge_count() const { return _edges.length(); }
211 PointsToNode* edge(int e) const { return _edges.at(e); }
212 bool add_edge(PointsToNode* edge) { return _edges.append_if_missing(edge); }
213
214 int use_count() const { return _uses.length(); }
215 PointsToNode* use(int e) const { return _uses.at(e); }
216 bool add_use(PointsToNode* use) { return _uses.append_if_missing(use); }
217
218 // Mark base edge use to distinguish from stored value edge.
219 bool add_base_use(FieldNode* use) { return _uses.append_if_missing((PointsToNode*)((intptr_t)use + 1)); }
220 static bool is_base_use(PointsToNode* use) { return (((intptr_t)use) & 1); }
221 static PointsToNode* get_use_node(PointsToNode* use) { return (PointsToNode*)(((intptr_t)use) & ~1); }
222
223 // Return true if this node points to specified node or nodes it points to.
224 bool points_to(JavaObjectNode* ptn) const;
225
226 // Return true if this node points only to non-escaping allocations.
227 bool non_escaping_allocation();
228
229 // Return true if one node points to an other.
230 bool meet(PointsToNode* ptn);
231
232#ifndef PRODUCT
233 NodeType node_type() const { return (NodeType)_type;}
234 void dump(bool print_state=true) const;
235#endif
236
237};
238
239class LocalVarNode: public PointsToNode {
240public:
241 LocalVarNode(ConnectionGraph *CG, Node* n, EscapeState es):
242 PointsToNode(CG, n, es, LocalVar) {}
243};
244
245class JavaObjectNode: public PointsToNode {
246public:
247 JavaObjectNode(ConnectionGraph *CG, Node* n, EscapeState es):
248 PointsToNode(CG, n, es, JavaObject) {
249 if (es > NoEscape)
250 set_scalar_replaceable(false);
251 }
252};
253
254class FieldNode: public PointsToNode {
255 GrowableArray<PointsToNode*> _bases; // List of JavaObject nodes which point to this node
256 const int _offset; // Field's offset.
257 const bool _is_oop; // Field points to object
258 bool _has_unknown_base; // Has phantom_object base
259public:
260 FieldNode(ConnectionGraph *CG, Node* n, EscapeState es, int offs, bool is_oop):
261 PointsToNode(CG, n, es, Field),
262 _offset(offs), _is_oop(is_oop),
263 _has_unknown_base(false) {}
264
265 int offset() const { return _offset;}
266 bool is_oop() const { return _is_oop;}
267 bool has_unknown_base() const { return _has_unknown_base; }
268 void set_has_unknown_base() { _has_unknown_base = true; }
269
270 int base_count() const { return _bases.length(); }
271 PointsToNode* base(int e) const { return _bases.at(e); }
272 bool add_base(PointsToNode* base) { return _bases.append_if_missing(base); }
273#ifdef ASSERT
274 // Return true if bases points to this java object.
275 bool has_base(JavaObjectNode* ptn) const;
276#endif
277
278};
279
280class ArraycopyNode: public PointsToNode {
281public:
282 ArraycopyNode(ConnectionGraph *CG, Node* n, EscapeState es):
283 PointsToNode(CG, n, es, Arraycopy) {}
284};
285
286// Iterators for PointsTo node's edges:
287// for (EdgeIterator i(n); i.has_next(); i.next()) {
288// PointsToNode* u = i.get();
289class PointsToIterator: public StackObj {
290protected:
291 const PointsToNode* node;
292 const int cnt;
293 int i;
294public:
295 inline PointsToIterator(const PointsToNode* n, int cnt) : node(n), cnt(cnt), i(0) { }
296 inline bool has_next() const { return i < cnt; }
297 inline void next() { i++; }
298 PointsToNode* get() const { ShouldNotCallThis(); return NULL; }
299};
300
301class EdgeIterator: public PointsToIterator {
302public:
303 inline EdgeIterator(const PointsToNode* n) : PointsToIterator(n, n->edge_count()) { }
304 inline PointsToNode* get() const { return node->edge(i); }
305};
306
307class UseIterator: public PointsToIterator {
308public:
309 inline UseIterator(const PointsToNode* n) : PointsToIterator(n, n->use_count()) { }
310 inline PointsToNode* get() const { return node->use(i); }
311};
312
313class BaseIterator: public PointsToIterator {
314public:
315 inline BaseIterator(const FieldNode* n) : PointsToIterator(n, n->base_count()) { }
316 inline PointsToNode* get() const { return ((PointsToNode*)node)->as_Field()->base(i); }
317};
318
319
320class ConnectionGraph: public ResourceObj {
321 friend class PointsToNode;
322private:
323 GrowableArray<PointsToNode*> _nodes; // Map from ideal nodes to
324 // ConnectionGraph nodes.
325
326 GrowableArray<PointsToNode*> _worklist; // Nodes to be processed
327 VectorSet _in_worklist;
328 uint _next_pidx;
329
330 bool _collecting; // Indicates whether escape information
331 // is still being collected. If false,
332 // no new nodes will be processed.
333
334 bool _verify; // verify graph
335
336 JavaObjectNode* phantom_obj; // Unknown object
337 JavaObjectNode* null_obj;
338 Node* _pcmp_neq; // ConI(#CC_GT)
339 Node* _pcmp_eq; // ConI(#CC_EQ)
340
341 Compile* _compile; // Compile object for current compilation
342 PhaseIterGVN* _igvn; // Value numbering
343
344 Unique_Node_List ideal_nodes; // Used by CG construction and types splitting.
345
346 // Address of an element in _nodes. Used when the element is to be modified
347 PointsToNode* ptnode_adr(int idx) const {
348 // There should be no new ideal nodes during ConnectionGraph build,
349 // growableArray::at() will throw assert otherwise.
350 return _nodes.at(idx);
351 }
352 uint nodes_size() const { return _nodes.length(); }
353
354 uint next_pidx() { return _next_pidx++; }
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 inline void add_to_worklist(PointsToNode* pt) {
398 PointsToNode* ptf = pt;
399 uint pidx_bias = 0;
400 if (PointsToNode::is_base_use(pt)) {
401 // Create a separate entry in _in_worklist for a marked base edge
402 // because _worklist may have an entry for a normal edge pointing
403 // to the same node. To separate them use _next_pidx as bias.
404 ptf = PointsToNode::get_use_node(pt)->as_Field();
405 pidx_bias = _next_pidx;
406 }
407 if (!_in_worklist.test_set(ptf->pidx() + pidx_bias)) {
408 _worklist.append(pt);
409 }
410 }
411
412 // Put on worklist all uses of this node.
413 inline void add_uses_to_worklist(PointsToNode* pt) {
414 for (UseIterator i(pt); i.has_next(); i.next()) {
415 add_to_worklist(i.get());
416 }
417 }
418
419 // Put on worklist all field's uses and related field nodes.
420 void add_field_uses_to_worklist(FieldNode* field);
421
422 // Put on worklist all related field nodes.
423 void add_fields_to_worklist(FieldNode* field, PointsToNode* base);
424
425 // Find fields which have unknown value.
426 int find_field_value(FieldNode* field);
427
428 // Find fields initializing values for allocations.
429 int find_init_values(JavaObjectNode* ptn, PointsToNode* init_val, PhaseTransform* phase);
430
431 // Set the escape state of an object and its fields.
432 void set_escape_state(PointsToNode* ptn, PointsToNode::EscapeState esc) {
433 // Don't change non-escaping state of NULL pointer.
434 if (ptn != null_obj) {
435 if (ptn->escape_state() < esc)
436 ptn->set_escape_state(esc);
437 if (ptn->fields_escape_state() < esc)
438 ptn->set_fields_escape_state(esc);
439 }
440 }
441 void set_fields_escape_state(PointsToNode* ptn, PointsToNode::EscapeState esc) {
442 // Don't change non-escaping state of NULL pointer.
443 if (ptn != null_obj) {
444 if (ptn->fields_escape_state() < esc)
445 ptn->set_fields_escape_state(esc);
446 }
447 }
448
449 // Propagate GlobalEscape and ArgEscape escape states to all nodes
450 // and check that we still have non-escaping java objects.
451 bool find_non_escaped_objects(GrowableArray<PointsToNode*>& ptnodes_worklist,
452 GrowableArray<JavaObjectNode*>& non_escaped_worklist);
453
454 // Adjust scalar_replaceable state after Connection Graph is built.
455 void adjust_scalar_replaceable_state(JavaObjectNode* jobj);
456
457 // Optimize ideal graph.
458 void optimize_ideal_graph(GrowableArray<Node*>& ptr_cmp_worklist,
459 GrowableArray<Node*>& storestore_worklist);
460 // Optimize objects compare.
461 Node* optimize_ptr_compare(Node* n);
462
463 // Returns unique corresponding java object or NULL.
464 JavaObjectNode* unique_java_object(Node *n);
465
466 // Add an edge of the specified type pointing to the specified target.
467 bool add_edge(PointsToNode* from, PointsToNode* to) {
468 assert(!from->is_Field() || from->as_Field()->is_oop(), "sanity");
469
470 if (to == phantom_obj) {
471 if (from->has_unknown_ptr()) {
472 return false; // already points to phantom_obj
473 }
474 from->set_has_unknown_ptr();
475 }
476
477 bool is_new = from->add_edge(to);
478 assert(to != phantom_obj || is_new, "sanity");
479 if (is_new) { // New edge?
480 assert(!_verify, "graph is incomplete");
481 is_new = to->add_use(from);
482 assert(is_new, "use should be also new");
483 }
484 return is_new;
485 }
486
487 // Add an edge from Field node to its base and back.
488 bool add_base(FieldNode* from, PointsToNode* to) {
489 assert(!to->is_Arraycopy(), "sanity");
490 if (to == phantom_obj) {
491 if (from->has_unknown_base()) {
492 return false; // already has phantom_obj base
493 }
494 from->set_has_unknown_base();
495 }
496 bool is_new = from->add_base(to);
497 assert(to != phantom_obj || is_new, "sanity");
498 if (is_new) { // New edge?
499 assert(!_verify, "graph is incomplete");
500 if (to == null_obj)
501 return is_new; // Don't add fields to NULL pointer.
502 if (to->is_JavaObject()) {
503 is_new = to->add_edge(from);
504 } else {
505 is_new = to->add_base_use(from);
506 }
507 assert(is_new, "use should be also new");
508 }
509 return is_new;
510 }
511
512 // Helper functions
513 bool is_oop_field(Node* n, int offset, bool* unsafe);
514 static Node* find_second_addp(Node* addp, Node* n);
515 // offset of a field reference
516 int address_offset(Node* adr, PhaseTransform *phase);
517
518
519 // Propagate unique types created for unescaped allocated objects
520 // through the graph
521 void split_unique_types(GrowableArray<Node *> &alloc_worklist, GrowableArray<ArrayCopyNode*> &arraycopy_worklist);
522
523 // Helper methods for unique types split.
524 bool split_AddP(Node *addp, Node *base);
525
526 PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist, bool &new_created);
527 PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *> &orig_phi_worklist);
528
529 void move_inst_mem(Node* n, GrowableArray<PhiNode *> &orig_phis);
530 Node* find_inst_mem(Node* mem, int alias_idx,GrowableArray<PhiNode *> &orig_phi_worklist);
531 Node* step_through_mergemem(MergeMemNode *mmem, int alias_idx, const TypeOopPtr *toop);
532
533
534 GrowableArray<MergeMemNode*> _mergemem_worklist; // List of all MergeMem nodes
535
536 Node_Array _node_map; // used for bookeeping during type splitting
537 // Used for the following purposes:
538 // Memory Phi - most recent unique Phi split out
539 // from this Phi
540 // MemNode - new memory input for this node
541 // ChecCastPP - allocation that this is a cast of
542 // allocation - CheckCastPP of the allocation
543
544 // manage entries in _node_map
545
546 void set_map(Node* from, Node* to) {
547 ideal_nodes.push(from);
548 _node_map.map(from->_idx, to);
549 }
550
551 Node* get_map(int idx) { return _node_map[idx]; }
552
553 PhiNode* get_map_phi(int idx) {
554 Node* phi = _node_map[idx];
555 return (phi == NULL) ? NULL : phi->as_Phi();
556 }
557
558 // Notify optimizer that a node has been modified
559 void record_for_optimizer(Node *n);
560
561 // Compute the escape information
562 bool compute_escape();
563
564public:
565 ConnectionGraph(Compile *C, PhaseIterGVN *igvn);
566
567 // Check for non-escaping candidates
568 static bool has_candidates(Compile *C);
569
570 // Perform escape analysis
571 static void do_analysis(Compile *C, PhaseIterGVN *igvn);
572
573 bool not_global_escape(Node *n);
574
575 // To be used by, e.g., BarrierSetC2 impls
576 Node* get_addp_base(Node* addp);
577
578 // Utility function for nodes that load an object
579 void add_objload_to_connection_graph(Node* n, Unique_Node_List* delayed_worklist);
580
581 // Add LocalVar node and edge if possible
582 void add_local_var_and_edge(Node* n, PointsToNode::EscapeState es, Node* to,
583 Unique_Node_List *delayed_worklist) {
584 PointsToNode* ptn = ptnode_adr(to->_idx);
585 if (delayed_worklist != NULL) { // First iteration of CG construction
586 add_local_var(n, es);
587 if (ptn == NULL) {
588 delayed_worklist->push(n);
589 return; // Process it later.
590 }
591 } else {
592 assert(ptn != NULL, "node should be registered");
593 }
594 add_edge(ptnode_adr(n->_idx), ptn);
595 }
596
597 void add_to_congraph_unsafe_access(Node* n, uint opcode, Unique_Node_List* delayed_worklist);
598 bool add_final_edges_unsafe_access(Node* n, uint opcode);
599
600#ifndef PRODUCT
601 void dump(GrowableArray<PointsToNode*>& ptnodes_worklist);
602#endif
603};
604
605inline PointsToNode::PointsToNode(ConnectionGraph *CG, Node* n, EscapeState es, NodeType type):
606 _edges(CG->_compile->comp_arena(), 2, 0, NULL),
607 _uses (CG->_compile->comp_arena(), 2, 0, NULL),
608 _type((u1)type),
609 _flags(ScalarReplaceable),
610 _escape((u1)es),
611 _fields_escape((u1)es),
612 _node(n),
613 _idx(n->_idx),
614 _pidx(CG->next_pidx()) {
615 assert(n != NULL && es != UnknownEscape, "sanity");
616}
617
618#endif // SHARE_OPTO_ESCAPE_HPP
619