Mercurial > hg > graal-jvmci-8
annotate src/share/vm/opto/loopnode.hpp @ 368:36ccc817fca4
6747051: Improve code and implicit null check generation for compressed oops
Summary: Push DecodeN node below the Null check to the non-null path to use the mach node without 0 test.
Reviewed-by: rasbold, never
author | kvn |
---|---|
date | Tue, 23 Sep 2008 12:29:06 -0700 |
parents | 194b8e3a2fc4 |
children | ee8f06bfb27c |
rev | line source |
---|---|
0 | 1 /* |
196 | 2 * Copyright 1998-2008 Sun Microsystems, Inc. All Rights Reserved. |
0 | 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 class CmpNode; | |
26 class CountedLoopEndNode; | |
27 class CountedLoopNode; | |
28 class IdealLoopTree; | |
29 class LoopNode; | |
30 class Node; | |
31 class PhaseIdealLoop; | |
32 class VectorSet; | |
33 struct small_cache; | |
34 | |
35 // | |
36 // I D E A L I Z E D L O O P S | |
37 // | |
38 // Idealized loops are the set of loops I perform more interesting | |
39 // transformations on, beyond simple hoisting. | |
40 | |
41 //------------------------------LoopNode--------------------------------------- | |
42 // Simple loop header. Fall in path on left, loop-back path on right. | |
43 class LoopNode : public RegionNode { | |
44 // Size is bigger to hold the flags. However, the flags do not change | |
45 // the semantics so it does not appear in the hash & cmp functions. | |
46 virtual uint size_of() const { return sizeof(*this); } | |
47 protected: | |
48 short _loop_flags; | |
49 // Names for flag bitfields | |
50 enum { pre_post_main=0, inner_loop=8, partial_peel_loop=16, partial_peel_failed=32 }; | |
51 char _unswitch_count; | |
52 enum { _unswitch_max=3 }; | |
53 | |
54 public: | |
55 // Names for edge indices | |
56 enum { Self=0, EntryControl, LoopBackControl }; | |
57 | |
58 int is_inner_loop() const { return _loop_flags & inner_loop; } | |
59 void set_inner_loop() { _loop_flags |= inner_loop; } | |
60 | |
61 int is_partial_peel_loop() const { return _loop_flags & partial_peel_loop; } | |
62 void set_partial_peel_loop() { _loop_flags |= partial_peel_loop; } | |
63 int partial_peel_has_failed() const { return _loop_flags & partial_peel_failed; } | |
64 void mark_partial_peel_failed() { _loop_flags |= partial_peel_failed; } | |
65 | |
66 int unswitch_max() { return _unswitch_max; } | |
67 int unswitch_count() { return _unswitch_count; } | |
68 void set_unswitch_count(int val) { | |
69 assert (val <= unswitch_max(), "too many unswitches"); | |
70 _unswitch_count = val; | |
71 } | |
72 | |
73 LoopNode( Node *entry, Node *backedge ) : RegionNode(3), _loop_flags(0), _unswitch_count(0) { | |
74 init_class_id(Class_Loop); | |
75 init_req(EntryControl, entry); | |
76 init_req(LoopBackControl, backedge); | |
77 } | |
78 | |
79 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape); | |
80 virtual int Opcode() const; | |
81 bool can_be_counted_loop(PhaseTransform* phase) const { | |
82 return req() == 3 && in(0) != NULL && | |
83 in(1) != NULL && phase->type(in(1)) != Type::TOP && | |
84 in(2) != NULL && phase->type(in(2)) != Type::TOP; | |
85 } | |
86 #ifndef PRODUCT | |
87 virtual void dump_spec(outputStream *st) const; | |
88 #endif | |
89 }; | |
90 | |
91 //------------------------------Counted Loops---------------------------------- | |
92 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit | |
93 // path (and maybe some other exit paths). The trip-counter exit is always | |
94 // last in the loop. The trip-counter does not have to stride by a constant, | |
95 // but it does have to stride by a loop-invariant amount; the exit value is | |
96 // also loop invariant. | |
97 | |
98 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs. The | |
99 // CountedLoopNode has the incoming loop control and the loop-back-control | |
100 // which is always the IfTrue before the matching CountedLoopEndNode. The | |
101 // CountedLoopEndNode has an incoming control (possibly not the | |
102 // CountedLoopNode if there is control flow in the loop), the post-increment | |
103 // trip-counter value, and the limit. The trip-counter value is always of | |
104 // the form (Op old-trip-counter stride). The old-trip-counter is produced | |
105 // by a Phi connected to the CountedLoopNode. The stride is loop invariant. | |
106 // The Op is any commutable opcode, including Add, Mul, Xor. The | |
107 // CountedLoopEndNode also takes in the loop-invariant limit value. | |
108 | |
109 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the | |
110 // loop-back control. From CountedLoopEndNodes I can reach CountedLoopNodes | |
111 // via the old-trip-counter from the Op node. | |
112 | |
113 //------------------------------CountedLoopNode-------------------------------- | |
114 // CountedLoopNodes head simple counted loops. CountedLoopNodes have as | |
115 // inputs the incoming loop-start control and the loop-back control, so they | |
116 // act like RegionNodes. They also take in the initial trip counter, the | |
117 // loop-invariant stride and the loop-invariant limit value. CountedLoopNodes | |
118 // produce a loop-body control and the trip counter value. Since | |
119 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model. | |
120 | |
121 class CountedLoopNode : public LoopNode { | |
122 // Size is bigger to hold _main_idx. However, _main_idx does not change | |
123 // the semantics so it does not appear in the hash & cmp functions. | |
124 virtual uint size_of() const { return sizeof(*this); } | |
125 | |
126 // For Pre- and Post-loops during debugging ONLY, this holds the index of | |
127 // the Main CountedLoop. Used to assert that we understand the graph shape. | |
128 node_idx_t _main_idx; | |
129 | |
130 // Known trip count calculated by policy_maximally_unroll | |
131 int _trip_count; | |
132 | |
133 // Expected trip count from profile data | |
134 float _profile_trip_cnt; | |
135 | |
136 // Log2 of original loop bodies in unrolled loop | |
137 int _unrolled_count_log2; | |
138 | |
139 // Node count prior to last unrolling - used to decide if | |
140 // unroll,optimize,unroll,optimize,... is making progress | |
141 int _node_count_before_unroll; | |
142 | |
143 public: | |
144 CountedLoopNode( Node *entry, Node *backedge ) | |
145 : LoopNode(entry, backedge), _trip_count(max_jint), | |
146 _profile_trip_cnt(COUNT_UNKNOWN), _unrolled_count_log2(0), | |
147 _node_count_before_unroll(0) { | |
148 init_class_id(Class_CountedLoop); | |
149 // Initialize _trip_count to the largest possible value. | |
150 // Will be reset (lower) if the loop's trip count is known. | |
151 } | |
152 | |
153 virtual int Opcode() const; | |
154 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape); | |
155 | |
156 Node *init_control() const { return in(EntryControl); } | |
157 Node *back_control() const { return in(LoopBackControl); } | |
158 CountedLoopEndNode *loopexit() const; | |
159 Node *init_trip() const; | |
160 Node *stride() const; | |
161 int stride_con() const; | |
162 bool stride_is_con() const; | |
163 Node *limit() const; | |
164 Node *incr() const; | |
165 Node *phi() const; | |
166 | |
167 // Match increment with optional truncation | |
168 static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type); | |
169 | |
170 // A 'main' loop has a pre-loop and a post-loop. The 'main' loop | |
171 // can run short a few iterations and may start a few iterations in. | |
172 // It will be RCE'd and unrolled and aligned. | |
173 | |
174 // A following 'post' loop will run any remaining iterations. Used | |
175 // during Range Check Elimination, the 'post' loop will do any final | |
176 // iterations with full checks. Also used by Loop Unrolling, where | |
177 // the 'post' loop will do any epilog iterations needed. Basically, | |
178 // a 'post' loop can not profitably be further unrolled or RCE'd. | |
179 | |
180 // A preceding 'pre' loop will run at least 1 iteration (to do peeling), | |
181 // it may do under-flow checks for RCE and may do alignment iterations | |
182 // so the following main loop 'knows' that it is striding down cache | |
183 // lines. | |
184 | |
185 // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or | |
186 // Aligned, may be missing it's pre-loop. | |
187 enum { Normal=0, Pre=1, Main=2, Post=3, PrePostFlagsMask=3, Main_Has_No_Pre_Loop=4 }; | |
188 int is_normal_loop() const { return (_loop_flags&PrePostFlagsMask) == Normal; } | |
189 int is_pre_loop () const { return (_loop_flags&PrePostFlagsMask) == Pre; } | |
190 int is_main_loop () const { return (_loop_flags&PrePostFlagsMask) == Main; } | |
191 int is_post_loop () const { return (_loop_flags&PrePostFlagsMask) == Post; } | |
192 int is_main_no_pre_loop() const { return _loop_flags & Main_Has_No_Pre_Loop; } | |
193 void set_main_no_pre_loop() { _loop_flags |= Main_Has_No_Pre_Loop; } | |
194 | |
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195 int main_idx() const { return _main_idx; } |
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196 |
0 | 197 |
198 void set_pre_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; } | |
199 void set_main_loop ( ) { assert(is_normal_loop(),""); _loop_flags |= Main; } | |
200 void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; } | |
201 void set_normal_loop( ) { _loop_flags &= ~PrePostFlagsMask; } | |
202 | |
203 void set_trip_count(int tc) { _trip_count = tc; } | |
204 int trip_count() { return _trip_count; } | |
205 | |
206 void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; } | |
207 float profile_trip_cnt() { return _profile_trip_cnt; } | |
208 | |
209 void double_unrolled_count() { _unrolled_count_log2++; } | |
210 int unrolled_count() { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); } | |
211 | |
212 void set_node_count_before_unroll(int ct) { _node_count_before_unroll = ct; } | |
213 int node_count_before_unroll() { return _node_count_before_unroll; } | |
214 | |
215 #ifndef PRODUCT | |
216 virtual void dump_spec(outputStream *st) const; | |
217 #endif | |
218 }; | |
219 | |
220 //------------------------------CountedLoopEndNode----------------------------- | |
221 // CountedLoopEndNodes end simple trip counted loops. They act much like | |
222 // IfNodes. | |
223 class CountedLoopEndNode : public IfNode { | |
224 public: | |
225 enum { TestControl, TestValue }; | |
226 | |
227 CountedLoopEndNode( Node *control, Node *test, float prob, float cnt ) | |
228 : IfNode( control, test, prob, cnt) { | |
229 init_class_id(Class_CountedLoopEnd); | |
230 } | |
231 virtual int Opcode() const; | |
232 | |
233 Node *cmp_node() const { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; } | |
234 Node *incr() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } | |
235 Node *limit() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; } | |
236 Node *stride() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; } | |
237 Node *phi() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } | |
238 Node *init_trip() const { Node *tmp = phi (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; } | |
239 int stride_con() const; | |
240 bool stride_is_con() const { Node *tmp = stride (); return (tmp != NULL && tmp->is_Con()); } | |
241 BoolTest::mask test_trip() const { return in(TestValue)->as_Bool()->_test._test; } | |
242 CountedLoopNode *loopnode() const { | |
243 Node *ln = phi()->in(0); | |
244 assert( ln->Opcode() == Op_CountedLoop, "malformed loop" ); | |
245 return (CountedLoopNode*)ln; } | |
246 | |
247 #ifndef PRODUCT | |
248 virtual void dump_spec(outputStream *st) const; | |
249 #endif | |
250 }; | |
251 | |
252 | |
253 inline CountedLoopEndNode *CountedLoopNode::loopexit() const { | |
254 Node *bc = back_control(); | |
255 if( bc == NULL ) return NULL; | |
256 Node *le = bc->in(0); | |
257 if( le->Opcode() != Op_CountedLoopEnd ) | |
258 return NULL; | |
259 return (CountedLoopEndNode*)le; | |
260 } | |
261 inline Node *CountedLoopNode::init_trip() const { return loopexit() ? loopexit()->init_trip() : NULL; } | |
262 inline Node *CountedLoopNode::stride() const { return loopexit() ? loopexit()->stride() : NULL; } | |
263 inline int CountedLoopNode::stride_con() const { return loopexit() ? loopexit()->stride_con() : 0; } | |
264 inline bool CountedLoopNode::stride_is_con() const { return loopexit() && loopexit()->stride_is_con(); } | |
265 inline Node *CountedLoopNode::limit() const { return loopexit() ? loopexit()->limit() : NULL; } | |
266 inline Node *CountedLoopNode::incr() const { return loopexit() ? loopexit()->incr() : NULL; } | |
267 inline Node *CountedLoopNode::phi() const { return loopexit() ? loopexit()->phi() : NULL; } | |
268 | |
269 | |
270 // -----------------------------IdealLoopTree---------------------------------- | |
271 class IdealLoopTree : public ResourceObj { | |
272 public: | |
273 IdealLoopTree *_parent; // Parent in loop tree | |
274 IdealLoopTree *_next; // Next sibling in loop tree | |
275 IdealLoopTree *_child; // First child in loop tree | |
276 | |
277 // The head-tail backedge defines the loop. | |
278 // If tail is NULL then this loop has multiple backedges as part of the | |
279 // same loop. During cleanup I'll peel off the multiple backedges; merge | |
280 // them at the loop bottom and flow 1 real backedge into the loop. | |
281 Node *_head; // Head of loop | |
282 Node *_tail; // Tail of loop | |
283 inline Node *tail(); // Handle lazy update of _tail field | |
284 PhaseIdealLoop* _phase; | |
285 | |
286 Node_List _body; // Loop body for inner loops | |
287 | |
288 uint8 _nest; // Nesting depth | |
289 uint8 _irreducible:1, // True if irreducible | |
290 _has_call:1, // True if has call safepoint | |
291 _has_sfpt:1, // True if has non-call safepoint | |
292 _rce_candidate:1; // True if candidate for range check elimination | |
293 | |
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294 Node_List* _required_safept; // A inner loop cannot delete these safepts; |
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295 bool _allow_optimizations; // Allow loop optimizations |
0 | 296 |
297 IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail ) | |
298 : _parent(0), _next(0), _child(0), | |
299 _head(head), _tail(tail), | |
300 _phase(phase), | |
301 _required_safept(NULL), | |
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302 _allow_optimizations(true), |
0 | 303 _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0) |
304 { } | |
305 | |
306 // Is 'l' a member of 'this'? | |
307 int is_member( const IdealLoopTree *l ) const; // Test for nested membership | |
308 | |
309 // Set loop nesting depth. Accumulate has_call bits. | |
310 int set_nest( uint depth ); | |
311 | |
312 // Split out multiple fall-in edges from the loop header. Move them to a | |
313 // private RegionNode before the loop. This becomes the loop landing pad. | |
314 void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ); | |
315 | |
316 // Split out the outermost loop from this shared header. | |
317 void split_outer_loop( PhaseIdealLoop *phase ); | |
318 | |
319 // Merge all the backedges from the shared header into a private Region. | |
320 // Feed that region as the one backedge to this loop. | |
321 void merge_many_backedges( PhaseIdealLoop *phase ); | |
322 | |
323 // Split shared headers and insert loop landing pads. | |
324 // Insert a LoopNode to replace the RegionNode. | |
325 // Returns TRUE if loop tree is structurally changed. | |
326 bool beautify_loops( PhaseIdealLoop *phase ); | |
327 | |
328 // Perform iteration-splitting on inner loops. Split iterations to avoid | |
329 // range checks or one-shot null checks. | |
330 void iteration_split( PhaseIdealLoop *phase, Node_List &old_new ); | |
331 | |
332 // Driver for various flavors of iteration splitting | |
333 void iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ); | |
334 | |
335 // Given dominators, try to find loops with calls that must always be | |
336 // executed (call dominates loop tail). These loops do not need non-call | |
337 // safepoints (ncsfpt). | |
338 void check_safepts(VectorSet &visited, Node_List &stack); | |
339 | |
340 // Allpaths backwards scan from loop tail, terminating each path at first safepoint | |
341 // encountered. | |
342 void allpaths_check_safepts(VectorSet &visited, Node_List &stack); | |
343 | |
344 // Convert to counted loops where possible | |
345 void counted_loop( PhaseIdealLoop *phase ); | |
346 | |
347 // Check for Node being a loop-breaking test | |
348 Node *is_loop_exit(Node *iff) const; | |
349 | |
350 // Returns true if ctrl is executed on every complete iteration | |
351 bool dominates_backedge(Node* ctrl); | |
352 | |
353 // Remove simplistic dead code from loop body | |
354 void DCE_loop_body(); | |
355 | |
356 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. | |
357 // Replace with a 1-in-10 exit guess. | |
358 void adjust_loop_exit_prob( PhaseIdealLoop *phase ); | |
359 | |
360 // Return TRUE or FALSE if the loop should never be RCE'd or aligned. | |
361 // Useful for unrolling loops with NO array accesses. | |
362 bool policy_peel_only( PhaseIdealLoop *phase ) const; | |
363 | |
364 // Return TRUE or FALSE if the loop should be unswitched -- clone | |
365 // loop with an invariant test | |
366 bool policy_unswitching( PhaseIdealLoop *phase ) const; | |
367 | |
368 // Micro-benchmark spamming. Remove empty loops. | |
369 bool policy_do_remove_empty_loop( PhaseIdealLoop *phase ); | |
370 | |
371 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can | |
372 // make some loop-invariant test (usually a null-check) happen before the | |
373 // loop. | |
374 bool policy_peeling( PhaseIdealLoop *phase ) const; | |
375 | |
376 // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any | |
377 // known trip count in the counted loop node. | |
378 bool policy_maximally_unroll( PhaseIdealLoop *phase ) const; | |
379 | |
380 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if | |
381 // the loop is a CountedLoop and the body is small enough. | |
382 bool policy_unroll( PhaseIdealLoop *phase ) const; | |
383 | |
384 // Return TRUE or FALSE if the loop should be range-check-eliminated. | |
385 // Gather a list of IF tests that are dominated by iteration splitting; | |
386 // also gather the end of the first split and the start of the 2nd split. | |
387 bool policy_range_check( PhaseIdealLoop *phase ) const; | |
388 | |
389 // Return TRUE or FALSE if the loop should be cache-line aligned. | |
390 // Gather the expression that does the alignment. Note that only | |
391 // one array base can be aligned in a loop (unless the VM guarentees | |
392 // mutual alignment). Note that if we vectorize short memory ops | |
393 // into longer memory ops, we may want to increase alignment. | |
394 bool policy_align( PhaseIdealLoop *phase ) const; | |
395 | |
396 // Compute loop trip count from profile data | |
397 void compute_profile_trip_cnt( PhaseIdealLoop *phase ); | |
398 | |
399 // Reassociate invariant expressions. | |
400 void reassociate_invariants(PhaseIdealLoop *phase); | |
401 // Reassociate invariant add and subtract expressions. | |
402 Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase); | |
403 // Return nonzero index of invariant operand if invariant and variant | |
404 // are combined with an Add or Sub. Helper for reassoicate_invariants. | |
405 int is_invariant_addition(Node* n, PhaseIdealLoop *phase); | |
406 | |
407 // Return true if n is invariant | |
408 bool is_invariant(Node* n) const; | |
409 | |
410 // Put loop body on igvn work list | |
411 void record_for_igvn(); | |
412 | |
413 bool is_loop() { return !_irreducible && _tail && !_tail->is_top(); } | |
414 bool is_inner() { return is_loop() && _child == NULL; } | |
415 bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); } | |
416 | |
417 #ifndef PRODUCT | |
418 void dump_head( ) const; // Dump loop head only | |
419 void dump() const; // Dump this loop recursively | |
420 void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const; | |
421 #endif | |
422 | |
423 }; | |
424 | |
425 // -----------------------------PhaseIdealLoop--------------------------------- | |
426 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees into a | |
427 // loop tree. Drives the loop-based transformations on the ideal graph. | |
428 class PhaseIdealLoop : public PhaseTransform { | |
429 friend class IdealLoopTree; | |
430 friend class SuperWord; | |
431 // Pre-computed def-use info | |
432 PhaseIterGVN &_igvn; | |
433 | |
434 // Head of loop tree | |
435 IdealLoopTree *_ltree_root; | |
436 | |
437 // Array of pre-order numbers, plus post-visited bit. | |
438 // ZERO for not pre-visited. EVEN for pre-visited but not post-visited. | |
439 // ODD for post-visited. Other bits are the pre-order number. | |
440 uint *_preorders; | |
441 uint _max_preorder; | |
442 | |
443 // Allocate _preorders[] array | |
444 void allocate_preorders() { | |
445 _max_preorder = C->unique()+8; | |
446 _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder); | |
447 memset(_preorders, 0, sizeof(uint) * _max_preorder); | |
448 } | |
449 | |
450 // Allocate _preorders[] array | |
451 void reallocate_preorders() { | |
452 if ( _max_preorder < C->unique() ) { | |
453 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique()); | |
454 _max_preorder = C->unique(); | |
455 } | |
456 memset(_preorders, 0, sizeof(uint) * _max_preorder); | |
457 } | |
458 | |
459 // Check to grow _preorders[] array for the case when build_loop_tree_impl() | |
460 // adds new nodes. | |
461 void check_grow_preorders( ) { | |
462 if ( _max_preorder < C->unique() ) { | |
463 uint newsize = _max_preorder<<1; // double size of array | |
464 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize); | |
465 memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder)); | |
466 _max_preorder = newsize; | |
467 } | |
468 } | |
469 // Check for pre-visited. Zero for NOT visited; non-zero for visited. | |
470 int is_visited( Node *n ) const { return _preorders[n->_idx]; } | |
471 // Pre-order numbers are written to the Nodes array as low-bit-set values. | |
472 void set_preorder_visited( Node *n, int pre_order ) { | |
473 assert( !is_visited( n ), "already set" ); | |
474 _preorders[n->_idx] = (pre_order<<1); | |
475 }; | |
476 // Return pre-order number. | |
477 int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; } | |
478 | |
479 // Check for being post-visited. | |
480 // Should be previsited already (checked with assert(is_visited(n))). | |
481 int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; } | |
482 | |
483 // Mark as post visited | |
484 void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; } | |
485 | |
486 // Set/get control node out. Set lower bit to distinguish from IdealLoopTree | |
487 // Returns true if "n" is a data node, false if it's a control node. | |
488 bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; } | |
489 | |
490 // clear out dead code after build_loop_late | |
491 Node_List _deadlist; | |
492 | |
493 // Support for faster execution of get_late_ctrl()/dom_lca() | |
494 // when a node has many uses and dominator depth is deep. | |
495 Node_Array _dom_lca_tags; | |
496 void init_dom_lca_tags(); | |
497 void clear_dom_lca_tags(); | |
498 // Inline wrapper for frequent cases: | |
499 // 1) only one use | |
500 // 2) a use is the same as the current LCA passed as 'n1' | |
501 Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) { | |
502 assert( n->is_CFG(), "" ); | |
503 // Fast-path NULL lca | |
504 if( lca != NULL && lca != n ) { | |
505 assert( lca->is_CFG(), "" ); | |
506 // find LCA of all uses | |
507 n = dom_lca_for_get_late_ctrl_internal( lca, n, tag ); | |
508 } | |
509 return find_non_split_ctrl(n); | |
510 } | |
511 Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag ); | |
512 // true if CFG node d dominates CFG node n | |
513 bool is_dominator(Node *d, Node *n); | |
514 | |
515 // Helper function for directing control inputs away from CFG split | |
516 // points. | |
517 Node *find_non_split_ctrl( Node *ctrl ) const { | |
518 if (ctrl != NULL) { | |
519 if (ctrl->is_MultiBranch()) { | |
520 ctrl = ctrl->in(0); | |
521 } | |
522 assert(ctrl->is_CFG(), "CFG"); | |
523 } | |
524 return ctrl; | |
525 } | |
526 | |
527 public: | |
528 bool has_node( Node* n ) const { return _nodes[n->_idx] != NULL; } | |
529 // check if transform created new nodes that need _ctrl recorded | |
530 Node *get_late_ctrl( Node *n, Node *early ); | |
531 Node *get_early_ctrl( Node *n ); | |
532 void set_early_ctrl( Node *n ); | |
533 void set_subtree_ctrl( Node *root ); | |
534 void set_ctrl( Node *n, Node *ctrl ) { | |
535 assert( !has_node(n) || has_ctrl(n), "" ); | |
536 assert( ctrl->in(0), "cannot set dead control node" ); | |
537 assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" ); | |
538 _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) ); | |
539 } | |
540 // Set control and update loop membership | |
541 void set_ctrl_and_loop(Node* n, Node* ctrl) { | |
542 IdealLoopTree* old_loop = get_loop(get_ctrl(n)); | |
543 IdealLoopTree* new_loop = get_loop(ctrl); | |
544 if (old_loop != new_loop) { | |
545 if (old_loop->_child == NULL) old_loop->_body.yank(n); | |
546 if (new_loop->_child == NULL) new_loop->_body.push(n); | |
547 } | |
548 set_ctrl(n, ctrl); | |
549 } | |
550 // Control nodes can be replaced or subsumed. During this pass they | |
551 // get their replacement Node in slot 1. Instead of updating the block | |
552 // location of all Nodes in the subsumed block, we lazily do it. As we | |
553 // pull such a subsumed block out of the array, we write back the final | |
554 // correct block. | |
555 Node *get_ctrl( Node *i ) { | |
556 assert(has_node(i), ""); | |
557 Node *n = get_ctrl_no_update(i); | |
558 _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) ); | |
559 assert(has_node(i) && has_ctrl(i), ""); | |
560 assert(n == find_non_split_ctrl(n), "must return legal ctrl" ); | |
561 return n; | |
562 } | |
563 | |
564 private: | |
565 Node *get_ctrl_no_update( Node *i ) const { | |
566 assert( has_ctrl(i), "" ); | |
567 Node *n = (Node*)(((intptr_t)_nodes[i->_idx]) & ~1); | |
568 if (!n->in(0)) { | |
569 // Skip dead CFG nodes | |
570 do { | |
571 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1); | |
572 } while (!n->in(0)); | |
573 n = find_non_split_ctrl(n); | |
574 } | |
575 return n; | |
576 } | |
577 | |
578 // Check for loop being set | |
579 // "n" must be a control node. Returns true if "n" is known to be in a loop. | |
580 bool has_loop( Node *n ) const { | |
581 assert(!has_node(n) || !has_ctrl(n), ""); | |
582 return has_node(n); | |
583 } | |
584 // Set loop | |
585 void set_loop( Node *n, IdealLoopTree *loop ) { | |
586 _nodes.map(n->_idx, (Node*)loop); | |
587 } | |
588 // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms. Replace | |
589 // the 'old_node' with 'new_node'. Kill old-node. Add a reference | |
590 // from old_node to new_node to support the lazy update. Reference | |
591 // replaces loop reference, since that is not neede for dead node. | |
592 public: | |
593 void lazy_update( Node *old_node, Node *new_node ) { | |
594 assert( old_node != new_node, "no cycles please" ); | |
595 //old_node->set_req( 1, new_node /*NO DU INFO*/ ); | |
596 // Nodes always have DU info now, so re-use the side array slot | |
597 // for this node to provide the forwarding pointer. | |
598 _nodes.map( old_node->_idx, (Node*)((intptr_t)new_node + 1) ); | |
599 } | |
600 void lazy_replace( Node *old_node, Node *new_node ) { | |
601 _igvn.hash_delete(old_node); | |
602 _igvn.subsume_node( old_node, new_node ); | |
603 lazy_update( old_node, new_node ); | |
604 } | |
605 void lazy_replace_proj( Node *old_node, Node *new_node ) { | |
606 assert( old_node->req() == 1, "use this for Projs" ); | |
607 _igvn.hash_delete(old_node); // Must hash-delete before hacking edges | |
608 old_node->add_req( NULL ); | |
609 lazy_replace( old_node, new_node ); | |
610 } | |
611 | |
612 private: | |
613 | |
614 // Place 'n' in some loop nest, where 'n' is a CFG node | |
615 void build_loop_tree(); | |
616 int build_loop_tree_impl( Node *n, int pre_order ); | |
617 // Insert loop into the existing loop tree. 'innermost' is a leaf of the | |
618 // loop tree, not the root. | |
619 IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost ); | |
620 | |
621 // Place Data nodes in some loop nest | |
622 void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ); | |
623 void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ); | |
624 void build_loop_late_post ( Node* n, const PhaseIdealLoop *verify_me ); | |
625 | |
626 // Array of immediate dominance info for each CFG node indexed by node idx | |
627 private: | |
628 uint _idom_size; | |
629 Node **_idom; // Array of immediate dominators | |
630 uint *_dom_depth; // Used for fast LCA test | |
631 GrowableArray<uint>* _dom_stk; // For recomputation of dom depth | |
632 | |
633 Node* idom_no_update(Node* d) const { | |
634 assert(d->_idx < _idom_size, "oob"); | |
635 Node* n = _idom[d->_idx]; | |
636 assert(n != NULL,"Bad immediate dominator info."); | |
637 while (n->in(0) == NULL) { // Skip dead CFG nodes | |
638 //n = n->in(1); | |
639 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1); | |
640 assert(n != NULL,"Bad immediate dominator info."); | |
641 } | |
642 return n; | |
643 } | |
644 Node *idom(Node* d) const { | |
645 uint didx = d->_idx; | |
646 Node *n = idom_no_update(d); | |
647 _idom[didx] = n; // Lazily remove dead CFG nodes from table. | |
648 return n; | |
649 } | |
650 uint dom_depth(Node* d) const { | |
651 assert(d->_idx < _idom_size, ""); | |
652 return _dom_depth[d->_idx]; | |
653 } | |
654 void set_idom(Node* d, Node* n, uint dom_depth); | |
655 // Locally compute IDOM using dom_lca call | |
656 Node *compute_idom( Node *region ) const; | |
657 // Recompute dom_depth | |
658 void recompute_dom_depth(); | |
659 | |
660 // Is safept not required by an outer loop? | |
661 bool is_deleteable_safept(Node* sfpt); | |
662 | |
663 public: | |
664 // Dominators for the sea of nodes | |
665 void Dominators(); | |
666 Node *dom_lca( Node *n1, Node *n2 ) const { | |
667 return find_non_split_ctrl(dom_lca_internal(n1, n2)); | |
668 } | |
669 Node *dom_lca_internal( Node *n1, Node *n2 ) const; | |
670 | |
671 // Compute the Ideal Node to Loop mapping | |
672 PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me, bool do_split_ifs ); | |
673 | |
674 // True if the method has at least 1 irreducible loop | |
675 bool _has_irreducible_loops; | |
676 | |
677 // Per-Node transform | |
678 virtual Node *transform( Node *a_node ) { return 0; } | |
679 | |
680 Node *is_counted_loop( Node *x, IdealLoopTree *loop ); | |
681 | |
682 // Return a post-walked LoopNode | |
683 IdealLoopTree *get_loop( Node *n ) const { | |
684 // Dead nodes have no loop, so return the top level loop instead | |
685 if (!has_node(n)) return _ltree_root; | |
686 assert(!has_ctrl(n), ""); | |
687 return (IdealLoopTree*)_nodes[n->_idx]; | |
688 } | |
689 | |
690 // Is 'n' a (nested) member of 'loop'? | |
691 int is_member( const IdealLoopTree *loop, Node *n ) const { | |
692 return loop->is_member(get_loop(n)); } | |
693 | |
694 // This is the basic building block of the loop optimizations. It clones an | |
695 // entire loop body. It makes an old_new loop body mapping; with this | |
696 // mapping you can find the new-loop equivalent to an old-loop node. All | |
697 // new-loop nodes are exactly equal to their old-loop counterparts, all | |
698 // edges are the same. All exits from the old-loop now have a RegionNode | |
699 // that merges the equivalent new-loop path. This is true even for the | |
700 // normal "loop-exit" condition. All uses of loop-invariant old-loop values | |
701 // now come from (one or more) Phis that merge their new-loop equivalents. | |
702 // Parameter side_by_side_idom: | |
703 // When side_by_size_idom is NULL, the dominator tree is constructed for | |
704 // the clone loop to dominate the original. Used in construction of | |
705 // pre-main-post loop sequence. | |
706 // When nonnull, the clone and original are side-by-side, both are | |
707 // dominated by the passed in side_by_side_idom node. Used in | |
708 // construction of unswitched loops. | |
709 void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth, | |
710 Node* side_by_side_idom = NULL); | |
711 | |
712 // If we got the effect of peeling, either by actually peeling or by | |
713 // making a pre-loop which must execute at least once, we can remove | |
714 // all loop-invariant dominated tests in the main body. | |
715 void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ); | |
716 | |
717 // Generate code to do a loop peel for the given loop (and body). | |
718 // old_new is a temp array. | |
719 void do_peeling( IdealLoopTree *loop, Node_List &old_new ); | |
720 | |
721 // Add pre and post loops around the given loop. These loops are used | |
722 // during RCE, unrolling and aligning loops. | |
723 void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ); | |
724 // If Node n lives in the back_ctrl block, we clone a private version of n | |
725 // in preheader_ctrl block and return that, otherwise return n. | |
726 Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ); | |
727 | |
728 // Take steps to maximally unroll the loop. Peel any odd iterations, then | |
729 // unroll to do double iterations. The next round of major loop transforms | |
730 // will repeat till the doubled loop body does all remaining iterations in 1 | |
731 // pass. | |
732 void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ); | |
733 | |
734 // Unroll the loop body one step - make each trip do 2 iterations. | |
735 void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ); | |
736 | |
737 // Return true if exp is a constant times an induction var | |
738 bool is_scaled_iv(Node* exp, Node* iv, int* p_scale); | |
739 | |
740 // Return true if exp is a scaled induction var plus (or minus) constant | |
741 bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0); | |
742 | |
743 // Eliminate range-checks and other trip-counter vs loop-invariant tests. | |
744 void do_range_check( IdealLoopTree *loop, Node_List &old_new ); | |
745 | |
746 // Create a slow version of the loop by cloning the loop | |
747 // and inserting an if to select fast-slow versions. | |
748 ProjNode* create_slow_version_of_loop(IdealLoopTree *loop, | |
749 Node_List &old_new); | |
750 | |
751 // Clone loop with an invariant test (that does not exit) and | |
752 // insert a clone of the test that selects which version to | |
753 // execute. | |
754 void do_unswitching (IdealLoopTree *loop, Node_List &old_new); | |
755 | |
756 // Find candidate "if" for unswitching | |
757 IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const; | |
758 | |
759 // Range Check Elimination uses this function! | |
760 // Constrain the main loop iterations so the affine function: | |
761 // scale_con * I + offset < limit | |
762 // always holds true. That is, either increase the number of iterations in | |
763 // the pre-loop or the post-loop until the condition holds true in the main | |
764 // loop. Scale_con, offset and limit are all loop invariant. | |
765 void add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ); | |
766 | |
767 // Partially peel loop up through last_peel node. | |
768 bool partial_peel( IdealLoopTree *loop, Node_List &old_new ); | |
769 | |
770 // Create a scheduled list of nodes control dependent on ctrl set. | |
771 void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched ); | |
772 // Has a use in the vector set | |
773 bool has_use_in_set( Node* n, VectorSet& vset ); | |
774 // Has use internal to the vector set (ie. not in a phi at the loop head) | |
775 bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ); | |
776 // clone "n" for uses that are outside of loop | |
777 void clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ); | |
778 // clone "n" for special uses that are in the not_peeled region | |
779 void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n, | |
780 VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ); | |
781 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist | |
782 void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ); | |
783 #ifdef ASSERT | |
784 // Validate the loop partition sets: peel and not_peel | |
785 bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel ); | |
786 // Ensure that uses outside of loop are of the right form | |
787 bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list, | |
788 uint orig_exit_idx, uint clone_exit_idx); | |
789 bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx); | |
790 #endif | |
791 | |
792 // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.) | |
793 int stride_of_possible_iv( Node* iff ); | |
794 bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; } | |
795 // Return the (unique) control output node that's in the loop (if it exists.) | |
796 Node* stay_in_loop( Node* n, IdealLoopTree *loop); | |
797 // Insert a signed compare loop exit cloned from an unsigned compare. | |
798 IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop); | |
799 void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop); | |
800 // Utility to register node "n" with PhaseIdealLoop | |
801 void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth); | |
802 // Utility to create an if-projection | |
803 ProjNode* proj_clone(ProjNode* p, IfNode* iff); | |
804 // Force the iff control output to be the live_proj | |
805 Node* short_circuit_if(IfNode* iff, ProjNode* live_proj); | |
806 // Insert a region before an if projection | |
807 RegionNode* insert_region_before_proj(ProjNode* proj); | |
808 // Insert a new if before an if projection | |
809 ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj); | |
810 | |
811 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps. | |
812 // "Nearly" because all Nodes have been cloned from the original in the loop, | |
813 // but the fall-in edges to the Cmp are different. Clone bool/Cmp pairs | |
814 // through the Phi recursively, and return a Bool. | |
815 BoolNode *clone_iff( PhiNode *phi, IdealLoopTree *loop ); | |
816 CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop ); | |
817 | |
818 | |
819 // Rework addressing expressions to get the most loop-invariant stuff | |
820 // moved out. We'd like to do all associative operators, but it's especially | |
821 // important (common) to do address expressions. | |
822 Node *remix_address_expressions( Node *n ); | |
823 | |
824 // Attempt to use a conditional move instead of a phi/branch | |
825 Node *conditional_move( Node *n ); | |
826 | |
827 // Reorganize offset computations to lower register pressure. | |
828 // Mostly prevent loop-fallout uses of the pre-incremented trip counter | |
829 // (which are then alive with the post-incremented trip counter | |
830 // forcing an extra register move) | |
831 void reorg_offsets( IdealLoopTree *loop ); | |
832 | |
833 // Check for aggressive application of 'split-if' optimization, | |
834 // using basic block level info. | |
835 void split_if_with_blocks ( VectorSet &visited, Node_Stack &nstack ); | |
836 Node *split_if_with_blocks_pre ( Node *n ); | |
837 void split_if_with_blocks_post( Node *n ); | |
838 Node *has_local_phi_input( Node *n ); | |
839 // Mark an IfNode as being dominated by a prior test, | |
840 // without actually altering the CFG (and hence IDOM info). | |
841 void dominated_by( Node *prevdom, Node *iff ); | |
842 | |
843 // Split Node 'n' through merge point | |
844 Node *split_thru_region( Node *n, Node *region ); | |
845 // Split Node 'n' through merge point if there is enough win. | |
846 Node *split_thru_phi( Node *n, Node *region, int policy ); | |
847 // Found an If getting its condition-code input from a Phi in the | |
848 // same block. Split thru the Region. | |
849 void do_split_if( Node *iff ); | |
850 | |
851 private: | |
852 // Return a type based on condition control flow | |
853 const TypeInt* filtered_type( Node *n, Node* n_ctrl); | |
854 const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); } | |
855 // Helpers for filtered type | |
856 const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl); | |
857 | |
858 // Helper functions | |
859 void register_new_node( Node *n, Node *blk ); | |
860 Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache ); | |
861 Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ); | |
862 void handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ); | |
863 bool split_up( Node *n, Node *blk1, Node *blk2 ); | |
864 void sink_use( Node *use, Node *post_loop ); | |
865 Node *place_near_use( Node *useblock ) const; | |
866 | |
867 bool _created_loop_node; | |
868 public: | |
869 void set_created_loop_node() { _created_loop_node = true; } | |
870 bool created_loop_node() { return _created_loop_node; } | |
871 | |
872 #ifndef PRODUCT | |
873 void dump( ) const; | |
874 void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const; | |
875 void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const; | |
876 void verify() const; // Major slow :-) | |
877 void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const; | |
878 IdealLoopTree *get_loop_idx(Node* n) const { | |
879 // Dead nodes have no loop, so return the top level loop instead | |
880 return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root; | |
881 } | |
882 // Print some stats | |
883 static void print_statistics(); | |
884 static int _loop_invokes; // Count of PhaseIdealLoop invokes | |
885 static int _loop_work; // Sum of PhaseIdealLoop x _unique | |
886 #endif | |
887 }; | |
888 | |
889 inline Node* IdealLoopTree::tail() { | |
890 // Handle lazy update of _tail field | |
891 Node *n = _tail; | |
892 //while( !n->in(0) ) // Skip dead CFG nodes | |
893 //n = n->in(1); | |
894 if (n->in(0) == NULL) | |
895 n = _phase->get_ctrl(n); | |
896 _tail = n; | |
897 return n; | |
898 } | |
899 | |
900 | |
901 // Iterate over the loop tree using a preorder, left-to-right traversal. | |
902 // | |
903 // Example that visits all counted loops from within PhaseIdealLoop | |
904 // | |
905 // for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) { | |
906 // IdealLoopTree* lpt = iter.current(); | |
907 // if (!lpt->is_counted()) continue; | |
908 // ... | |
909 class LoopTreeIterator : public StackObj { | |
910 private: | |
911 IdealLoopTree* _root; | |
912 IdealLoopTree* _curnt; | |
913 | |
914 public: | |
915 LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {} | |
916 | |
917 bool done() { return _curnt == NULL; } // Finished iterating? | |
918 | |
919 void next(); // Advance to next loop tree | |
920 | |
921 IdealLoopTree* current() { return _curnt; } // Return current value of iterator. | |
922 }; |