1 /*
2 * Copyright (c) 1997, 2015, 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
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7 * published by the Free Software Foundation.
8 *
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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).
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
24
25 #ifndef SHARE_VM_OPTO_CFGNODE_HPP
26 #define SHARE_VM_OPTO_CFGNODE_HPP
27
28 #include "opto/multnode.hpp"
29 #include "opto/node.hpp"
30 #include "opto/opcodes.hpp"
31 #include "opto/type.hpp"
32
33 // Portions of code courtesy of Clifford Click
34
35 // Optimization - Graph Style
36
37 class Matcher;
38 class Node;
39 class RegionNode;
40 class TypeNode;
41 class PhiNode;
42 class GotoNode;
43 class MultiNode;
44 class MultiBranchNode;
45 class IfNode;
46 class PCTableNode;
47 class JumpNode;
48 class CatchNode;
49 class NeverBranchNode;
50 class ProjNode;
51 class CProjNode;
52 class IfTrueNode;
53 class IfFalseNode;
54 class CatchProjNode;
55 class JProjNode;
56 class JumpProjNode;
57 class SCMemProjNode;
58 class PhaseIdealLoop;
59
60 //------------------------------RegionNode-------------------------------------
61 // The class of RegionNodes, which can be mapped to basic blocks in the
62 // program. Their inputs point to Control sources. PhiNodes (described
63 // below) have an input point to a RegionNode. Merged data inputs to PhiNodes
64 // correspond 1-to-1 with RegionNode inputs. The zero input of a PhiNode is
65 // the RegionNode, and the zero input of the RegionNode is itself.
66 class RegionNode : public Node {
67 public:
68 // Node layout (parallels PhiNode):
69 enum { Region, // Generally points to self.
70 Control // Control arcs are [1..len)
71 };
72
73 RegionNode( uint required ) : Node(required) {
74 init_class_id(Class_Region);
75 init_req(0,this);
76 }
77
78 Node* is_copy() const {
79 const Node* r = _in[Region];
80 if (r == NULL)
81 return nonnull_req();
82 return NULL; // not a copy!
83 }
84 PhiNode* has_phi() const; // returns an arbitrary phi user, or NULL
85 PhiNode* has_unique_phi() const; // returns the unique phi user, or NULL
86 // Is this region node unreachable from root?
87 bool is_unreachable_region(PhaseGVN *phase) const;
88 virtual int Opcode() const;
89 virtual bool pinned() const { return (const Node *)in(0) == this; }
90 virtual bool is_CFG () const { return true; }
91 virtual uint hash() const { return NO_HASH; } // CFG nodes do not hash
92 virtual bool depends_only_on_test() const { return false; }
93 virtual const Type *bottom_type() const { return Type::CONTROL; }
94 virtual const Type *Value( PhaseTransform *phase ) const;
95 virtual Node *Identity( PhaseTransform *phase );
96 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
97 virtual const RegMask &out_RegMask() const;
98 bool try_clean_mem_phi(PhaseGVN *phase);
99 };
100
101 //------------------------------JProjNode--------------------------------------
102 // jump projection for node that produces multiple control-flow paths
103 class JProjNode : public ProjNode {
104 public:
105 JProjNode( Node* ctrl, uint idx ) : ProjNode(ctrl,idx) {}
106 virtual int Opcode() const;
107 virtual bool is_CFG() const { return true; }
108 virtual uint hash() const { return NO_HASH; } // CFG nodes do not hash
109 virtual const Node* is_block_proj() const { return in(0); }
110 virtual const RegMask& out_RegMask() const;
111 virtual uint ideal_reg() const { return 0; }
112 };
113
114 //------------------------------PhiNode----------------------------------------
115 // PhiNodes merge values from different Control paths. Slot 0 points to the
116 // controlling RegionNode. Other slots map 1-for-1 with incoming control flow
117 // paths to the RegionNode. For speed reasons (to avoid another pass) we
118 // can turn PhiNodes into copys in-place by NULL'ing out their RegionNode
119 // input in slot 0.
120 class PhiNode : public TypeNode {
121 const TypePtr* const _adr_type; // non-null only for Type::MEMORY nodes.
122 const int _inst_id; // Instance id of the memory slice.
123 const int _inst_index; // Alias index of the instance memory slice.
124 // Array elements references have the same alias_idx but different offset.
125 const int _inst_offset; // Offset of the instance memory slice.
126 // Size is bigger to hold the _adr_type field.
127 virtual uint hash() const; // Check the type
128 virtual uint cmp( const Node &n ) const;
129 virtual uint size_of() const { return sizeof(*this); }
130
131 // Determine if CMoveNode::is_cmove_id can be used at this join point.
132 Node* is_cmove_id(PhaseTransform* phase, int true_path);
133
134 public:
135 // Node layout (parallels RegionNode):
136 enum { Region, // Control input is the Phi's region.
137 Input // Input values are [1..len)
138 };
139
140 PhiNode( Node *r, const Type *t, const TypePtr* at = NULL,
141 const int iid = TypeOopPtr::InstanceTop,
142 const int iidx = Compile::AliasIdxTop,
143 const int ioffs = Type::OffsetTop )
144 : TypeNode(t,r->req()),
145 _adr_type(at),
146 _inst_id(iid),
147 _inst_index(iidx),
148 _inst_offset(ioffs)
149 {
150 init_class_id(Class_Phi);
151 init_req(0, r);
152 verify_adr_type();
153 }
154 // create a new phi with in edges matching r and set (initially) to x
155 static PhiNode* make( Node* r, Node* x );
156 // extra type arguments override the new phi's bottom_type and adr_type
157 static PhiNode* make( Node* r, Node* x, const Type *t, const TypePtr* at = NULL );
158 // create a new phi with narrowed memory type
159 PhiNode* slice_memory(const TypePtr* adr_type) const;
160 PhiNode* split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const;
161 // like make(r, x), but does not initialize the in edges to x
162 static PhiNode* make_blank( Node* r, Node* x );
163
164 // Accessors
165 RegionNode* region() const { Node* r = in(Region); assert(!r || r->is_Region(), ""); return (RegionNode*)r; }
166
167 Node* is_copy() const {
168 // The node is a real phi if _in[0] is a Region node.
169 DEBUG_ONLY(const Node* r = _in[Region];)
170 assert(r != NULL && r->is_Region(), "Not valid control");
171 return NULL; // not a copy!
172 }
173
174 bool is_tripcount() const;
175
176 // Determine a unique non-trivial input, if any.
177 // Ignore casts if it helps. Return NULL on failure.
178 Node* unique_input(PhaseTransform *phase);
179
180 // Check for a simple dead loop.
181 enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
182 LoopSafety simple_data_loop_check(Node *in) const;
183 // Is it unsafe data loop? It becomes a dead loop if this phi node removed.
184 bool is_unsafe_data_reference(Node *in) const;
185 int is_diamond_phi(bool check_control_only = false) const;
186 virtual int Opcode() const;
187 virtual bool pinned() const { return in(0) != 0; }
188 virtual const TypePtr *adr_type() const { verify_adr_type(true); return _adr_type; }
189
190 const int inst_id() const { return _inst_id; }
191 const int inst_index() const { return _inst_index; }
192 const int inst_offset() const { return _inst_offset; }
193 bool is_same_inst_field(const Type* tp, int id, int index, int offset) {
194 return type()->basic_type() == tp->basic_type() &&
195 inst_id() == id &&
196 inst_index() == index &&
197 inst_offset() == offset &&
198 type()->higher_equal(tp);
199 }
200
201 virtual const Type *Value( PhaseTransform *phase ) const;
202 virtual Node *Identity( PhaseTransform *phase );
203 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
204 virtual const RegMask &out_RegMask() const;
205 virtual const RegMask &in_RegMask(uint) const;
206 #ifndef PRODUCT
207 virtual void related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const;
208 virtual void dump_spec(outputStream *st) const;
209 #endif
210 #ifdef ASSERT
211 void verify_adr_type(VectorSet& visited, const TypePtr* at) const;
212 void verify_adr_type(bool recursive = false) const;
213 #else //ASSERT
214 void verify_adr_type(bool recursive = false) const {}
215 #endif //ASSERT
216 };
217
218 //------------------------------GotoNode---------------------------------------
219 // GotoNodes perform direct branches.
220 class GotoNode : public Node {
221 public:
222 GotoNode( Node *control ) : Node(control) {}
223 virtual int Opcode() const;
224 virtual bool pinned() const { return true; }
225 virtual bool is_CFG() const { return true; }
226 virtual uint hash() const { return NO_HASH; } // CFG nodes do not hash
227 virtual const Node *is_block_proj() const { return this; }
228 virtual bool depends_only_on_test() const { return false; }
229 virtual const Type *bottom_type() const { return Type::CONTROL; }
230 virtual const Type *Value( PhaseTransform *phase ) const;
231 virtual Node *Identity( PhaseTransform *phase );
232 virtual const RegMask &out_RegMask() const;
233
234 #ifndef PRODUCT
235 virtual void related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const;
236 #endif
237 };
238
239 //------------------------------CProjNode--------------------------------------
240 // control projection for node that produces multiple control-flow paths
241 class CProjNode : public ProjNode {
242 public:
243 CProjNode( Node *ctrl, uint idx ) : ProjNode(ctrl,idx) {}
244 virtual int Opcode() const;
245 virtual bool is_CFG() const { return true; }
246 virtual uint hash() const { return NO_HASH; } // CFG nodes do not hash
247 virtual const Node *is_block_proj() const { return in(0); }
248 virtual const RegMask &out_RegMask() const;
249 virtual uint ideal_reg() const { return 0; }
250 };
251
252 //---------------------------MultiBranchNode-----------------------------------
253 // This class defines a MultiBranchNode, a MultiNode which yields multiple
254 // control values. These are distinguished from other types of MultiNodes
255 // which yield multiple values, but control is always and only projection #0.
256 class MultiBranchNode : public MultiNode {
257 public:
258 MultiBranchNode( uint required ) : MultiNode(required) {
259 init_class_id(Class_MultiBranch);
260 }
261 // returns required number of users to be well formed.
262 virtual int required_outcnt() const = 0;
263 };
264
265 //------------------------------IfNode-----------------------------------------
266 // Output selected Control, based on a boolean test
267 class IfNode : public MultiBranchNode {
268 // Size is bigger to hold the probability field. However, _prob does not
269 // change the semantics so it does not appear in the hash & cmp functions.
270 virtual uint size_of() const { return sizeof(*this); }
271
272 private:
273 ProjNode* range_check_trap_proj(int& flip, Node*& l, Node*& r);
274 ProjNode* range_check_trap_proj() {
275 int flip_test = 0;
276 Node* l = NULL;
277 Node* r = NULL;
278 return range_check_trap_proj(flip_test, l, r);
279 }
280
281 // Helper methods for fold_compares
282 bool cmpi_folds(PhaseIterGVN* igvn);
283 bool is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn);
284 bool has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail);
285 bool has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn);
286 static void merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn);
287 static void improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn);
288 bool is_cmp_with_loadrange(ProjNode* proj);
289 bool is_null_check(ProjNode* proj, PhaseIterGVN* igvn);
290 bool is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn);
291 void reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn);
292 ProjNode* uncommon_trap_proj(CallStaticJavaNode*& call) const;
293 bool fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn);
294
295 public:
296
297 // Degrees of branch prediction probability by order of magnitude:
298 // PROB_UNLIKELY_1e(N) is a 1 in 1eN chance.
299 // PROB_LIKELY_1e(N) is a 1 - PROB_UNLIKELY_1e(N)
300 #define PROB_UNLIKELY_MAG(N) (1e- ## N ## f)
301 #define PROB_LIKELY_MAG(N) (1.0f-PROB_UNLIKELY_MAG(N))
302
303 // Maximum and minimum branch prediction probabilties
304 // 1 in 1,000,000 (magnitude 6)
305 //
306 // Although PROB_NEVER == PROB_MIN and PROB_ALWAYS == PROB_MAX
307 // they are used to distinguish different situations:
308 //
309 // The name PROB_MAX (PROB_MIN) is for probabilities which correspond to
310 // very likely (unlikely) but with a concrete possibility of a rare
311 // contrary case. These constants would be used for pinning
312 // measurements, and as measures for assertions that have high
313 // confidence, but some evidence of occasional failure.
314 //
315 // The name PROB_ALWAYS (PROB_NEVER) is to stand for situations for which
316 // there is no evidence at all that the contrary case has ever occurred.
317
318 #define PROB_NEVER PROB_UNLIKELY_MAG(6)
319 #define PROB_ALWAYS PROB_LIKELY_MAG(6)
320
321 #define PROB_MIN PROB_UNLIKELY_MAG(6)
322 #define PROB_MAX PROB_LIKELY_MAG(6)
323
324 // Static branch prediction probabilities
325 // 1 in 10 (magnitude 1)
326 #define PROB_STATIC_INFREQUENT PROB_UNLIKELY_MAG(1)
327 #define PROB_STATIC_FREQUENT PROB_LIKELY_MAG(1)
328
329 // Fair probability 50/50
330 #define PROB_FAIR (0.5f)
331
332 // Unknown probability sentinel
333 #define PROB_UNKNOWN (-1.0f)
334
335 // Probability "constructors", to distinguish as a probability any manifest
336 // constant without a names
337 #define PROB_LIKELY(x) ((float) (x))
338 #define PROB_UNLIKELY(x) (1.0f - (float)(x))
339
340 // Other probabilities in use, but without a unique name, are documented
341 // here for lack of a better place:
342 //
343 // 1 in 1000 probabilities (magnitude 3):
344 // threshold for converting to conditional move
345 // likelihood of null check failure if a null HAS been seen before
346 // likelihood of slow path taken in library calls
347 //
348 // 1 in 10,000 probabilities (magnitude 4):
349 // threshold for making an uncommon trap probability more extreme
350 // threshold for for making a null check implicit
351 // likelihood of needing a gc if eden top moves during an allocation
352 // likelihood of a predicted call failure
353 //
354 // 1 in 100,000 probabilities (magnitude 5):
355 // threshold for ignoring counts when estimating path frequency
356 // likelihood of FP clipping failure
357 // likelihood of catching an exception from a try block
358 // likelihood of null check failure if a null has NOT been seen before
359 //
360 // Magic manifest probabilities such as 0.83, 0.7, ... can be found in
361 // gen_subtype_check() and catch_inline_exceptions().
362
363 float _prob; // Probability of true path being taken.
364 float _fcnt; // Frequency counter
365 IfNode( Node *control, Node *b, float p, float fcnt )
366 : MultiBranchNode(2), _prob(p), _fcnt(fcnt) {
367 init_class_id(Class_If);
368 init_req(0,control);
369 init_req(1,b);
370 }
371 virtual int Opcode() const;
372 virtual bool pinned() const { return true; }
373 virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
374 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
375 virtual const Type *Value( PhaseTransform *phase ) const;
376 virtual int required_outcnt() const { return 2; }
377 virtual const RegMask &out_RegMask() const;
378 void dominated_by(Node* prev_dom, PhaseIterGVN* igvn);
379 int is_range_check(Node* &range, Node* &index, jint &offset);
380 Node* fold_compares(PhaseIterGVN* phase);
381 static Node* up_one_dom(Node* curr, bool linear_only = false);
382
383 // Takes the type of val and filters it through the test represented
384 // by if_proj and returns a more refined type if one is produced.
385 // Returns NULL is it couldn't improve the type.
386 static const TypeInt* filtered_int_type(PhaseGVN* phase, Node* val, Node* if_proj);
387
388 #ifndef PRODUCT
389 virtual void dump_spec(outputStream *st) const;
390 virtual void related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const;
391 #endif
392 };
393
394 class IfProjNode : public CProjNode {
395 public:
396 IfProjNode(IfNode *ifnode, uint idx) : CProjNode(ifnode,idx) {}
397 virtual Node *Identity(PhaseTransform *phase);
398
399 protected:
400 // Type of If input when this branch is always taken
401 virtual bool always_taken(const TypeTuple* t) const = 0;
402
403 #ifndef PRODUCT
404 public:
405 virtual void related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const;
406 #endif
407 };
408
409 class IfTrueNode : public IfProjNode {
410 public:
411 IfTrueNode( IfNode *ifnode ) : IfProjNode(ifnode,1) {
412 init_class_id(Class_IfTrue);
413 }
414 virtual int Opcode() const;
415
416 protected:
417 virtual bool always_taken(const TypeTuple* t) const { return t == TypeTuple::IFTRUE; }
418 };
419
420 class IfFalseNode : public IfProjNode {
421 public:
422 IfFalseNode( IfNode *ifnode ) : IfProjNode(ifnode,0) {
423 init_class_id(Class_IfFalse);
424 }
425 virtual int Opcode() const;
426
427 protected:
428 virtual bool always_taken(const TypeTuple* t) const { return t == TypeTuple::IFFALSE; }
429 };
430
431
432 //------------------------------PCTableNode------------------------------------
433 // Build an indirect branch table. Given a control and a table index,
434 // control is passed to the Projection matching the table index. Used to
435 // implement switch statements and exception-handling capabilities.
436 // Undefined behavior if passed-in index is not inside the table.
437 class PCTableNode : public MultiBranchNode {
438 virtual uint hash() const; // Target count; table size
439 virtual uint cmp( const Node &n ) const;
440 virtual uint size_of() const { return sizeof(*this); }
441
442 public:
443 const uint _size; // Number of targets
444
445 PCTableNode( Node *ctrl, Node *idx, uint size ) : MultiBranchNode(2), _size(size) {
446 init_class_id(Class_PCTable);
447 init_req(0, ctrl);
448 init_req(1, idx);
449 }
450 virtual int Opcode() const;
451 virtual const Type *Value( PhaseTransform *phase ) const;
452 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
453 virtual const Type *bottom_type() const;
454 virtual bool pinned() const { return true; }
455 virtual int required_outcnt() const { return _size; }
456 };
457
458 //------------------------------JumpNode---------------------------------------
459 // Indirect branch. Uses PCTable above to implement a switch statement.
460 // It emits as a table load and local branch.
461 class JumpNode : public PCTableNode {
462 public:
463 JumpNode( Node* control, Node* switch_val, uint size) : PCTableNode(control, switch_val, size) {
464 init_class_id(Class_Jump);
465 }
466 virtual int Opcode() const;
467 virtual const RegMask& out_RegMask() const;
468 virtual const Node* is_block_proj() const { return this; }
469 #ifndef PRODUCT
470 virtual void related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const;
471 #endif
472 };
473
474 class JumpProjNode : public JProjNode {
475 virtual uint hash() const;
476 virtual uint cmp( const Node &n ) const;
477 virtual uint size_of() const { return sizeof(*this); }
478
479 private:
480 const int _dest_bci;
481 const uint _proj_no;
482 const int _switch_val;
483 public:
484 JumpProjNode(Node* jumpnode, uint proj_no, int dest_bci, int switch_val)
485 : JProjNode(jumpnode, proj_no), _dest_bci(dest_bci), _proj_no(proj_no), _switch_val(switch_val) {
486 init_class_id(Class_JumpProj);
487 }
488
489 virtual int Opcode() const;
490 virtual const Type* bottom_type() const { return Type::CONTROL; }
491 int dest_bci() const { return _dest_bci; }
492 int switch_val() const { return _switch_val; }
493 uint proj_no() const { return _proj_no; }
494 #ifndef PRODUCT
495 virtual void dump_spec(outputStream *st) const;
496 virtual void dump_compact_spec(outputStream *st) const;
497 virtual void related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const;
498 #endif
499 };
500
501 //------------------------------CatchNode--------------------------------------
502 // Helper node to fork exceptions. "Catch" catches any exceptions thrown by
503 // a just-prior call. Looks like a PCTableNode but emits no code - just the
504 // table. The table lookup and branch is implemented by RethrowNode.
505 class CatchNode : public PCTableNode {
506 public:
507 CatchNode( Node *ctrl, Node *idx, uint size ) : PCTableNode(ctrl,idx,size){
508 init_class_id(Class_Catch);
509 }
510 virtual int Opcode() const;
511 virtual const Type *Value( PhaseTransform *phase ) const;
512 };
513
514 // CatchProjNode controls which exception handler is targetted after a call.
515 // It is passed in the bci of the target handler, or no_handler_bci in case
516 // the projection doesn't lead to an exception handler.
517 class CatchProjNode : public CProjNode {
518 virtual uint hash() const;
519 virtual uint cmp( const Node &n ) const;
520 virtual uint size_of() const { return sizeof(*this); }
521
522 private:
523 const int _handler_bci;
524
525 public:
526 enum {
527 fall_through_index = 0, // the fall through projection index
528 catch_all_index = 1, // the projection index for catch-alls
529 no_handler_bci = -1 // the bci for fall through or catch-all projs
530 };
531
532 CatchProjNode(Node* catchnode, uint proj_no, int handler_bci)
533 : CProjNode(catchnode, proj_no), _handler_bci(handler_bci) {
534 init_class_id(Class_CatchProj);
535 assert(proj_no != fall_through_index || handler_bci < 0, "fall through case must have bci < 0");
536 }
537
538 virtual int Opcode() const;
539 virtual Node *Identity( PhaseTransform *phase );
540 virtual const Type *bottom_type() const { return Type::CONTROL; }
541 int handler_bci() const { return _handler_bci; }
542 bool is_handler_proj() const { return _handler_bci >= 0; }
543 #ifndef PRODUCT
544 virtual void dump_spec(outputStream *st) const;
545 #endif
546 };
547
548
549 //---------------------------------CreateExNode--------------------------------
550 // Helper node to create the exception coming back from a call
551 class CreateExNode : public TypeNode {
552 public:
553 CreateExNode(const Type* t, Node* control, Node* i_o) : TypeNode(t, 2) {
554 init_req(0, control);
555 init_req(1, i_o);
556 }
557 virtual int Opcode() const;
558 virtual Node *Identity( PhaseTransform *phase );
559 virtual bool pinned() const { return true; }
560 uint match_edge(uint idx) const { return 0; }
561 virtual uint ideal_reg() const { return Op_RegP; }
562 };
563
564 //------------------------------NeverBranchNode-------------------------------
565 // The never-taken branch. Used to give the appearance of exiting infinite
566 // loops to those algorithms that like all paths to be reachable. Encodes
567 // empty.
568 class NeverBranchNode : public MultiBranchNode {
569 public:
570 NeverBranchNode( Node *ctrl ) : MultiBranchNode(1) { init_req(0,ctrl); }
571 virtual int Opcode() const;
572 virtual bool pinned() const { return true; };
573 virtual const Type *bottom_type() const { return TypeTuple::IFBOTH; }
574 virtual const Type *Value( PhaseTransform *phase ) const;
575 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
576 virtual int required_outcnt() const { return 2; }
577 virtual void emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const { }
578 virtual uint size(PhaseRegAlloc *ra_) const { return 0; }
579 #ifndef PRODUCT
580 virtual void format( PhaseRegAlloc *, outputStream *st ) const;
581 #endif
582 };
583
584 #endif // SHARE_VM_OPTO_CFGNODE_HPP