1 /*
2 * Copyright (c) 1998, 2018, 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.
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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_LOOPNODE_HPP
26 #define SHARE_VM_OPTO_LOOPNODE_HPP
27
28 #include "opto/cfgnode.hpp"
29 #include "opto/multnode.hpp"
30 #include "opto/phaseX.hpp"
31 #include "opto/subnode.hpp"
32 #include "opto/type.hpp"
33
34 class CmpNode;
35 class CountedLoopEndNode;
36 class CountedLoopNode;
37 class IdealLoopTree;
38 class LoopNode;
39 class Node;
40 class OuterStripMinedLoopEndNode;
41 class PathFrequency;
42 class PhaseIdealLoop;
43 class CountedLoopReserveKit;
44 class VectorSet;
45 class Invariance;
46 struct small_cache;
47
48 //
49 // I D E A L I Z E D L O O P S
50 //
51 // Idealized loops are the set of loops I perform more interesting
52 // transformations on, beyond simple hoisting.
53
54 //------------------------------LoopNode---------------------------------------
55 // Simple loop header. Fall in path on left, loop-back path on right.
56 class LoopNode : public RegionNode {
57 // Size is bigger to hold the flags. However, the flags do not change
58 // the semantics so it does not appear in the hash & cmp functions.
59 virtual uint size_of() const { return sizeof(*this); }
60 protected:
61 uint _loop_flags;
62 // Names for flag bitfields
63 enum { Normal=0, Pre=1, Main=2, Post=3, PreMainPostFlagsMask=3,
64 MainHasNoPreLoop=4,
65 HasExactTripCount=8,
66 InnerLoop=16,
67 PartialPeelLoop=32,
68 PartialPeelFailed=64,
69 HasReductions=128,
70 WasSlpAnalyzed=256,
71 PassedSlpAnalysis=512,
72 DoUnrollOnly=1024,
73 VectorizedLoop=2048,
74 HasAtomicPostLoop=4096,
75 HasRangeChecks=8192,
76 IsMultiversioned=16384,
77 StripMined=32768,
78 ProfileTripFailed=65536};
79 char _unswitch_count;
80 enum { _unswitch_max=3 };
81 char _postloop_flags;
82 enum { LoopNotRCEChecked = 0, LoopRCEChecked = 1, RCEPostLoop = 2 };
83
84 // Expected trip count from profile data
85 float _profile_trip_cnt;
86
87 public:
88 // Names for edge indices
89 enum { Self=0, EntryControl, LoopBackControl };
90
91 uint is_inner_loop() const { return _loop_flags & InnerLoop; }
92 void set_inner_loop() { _loop_flags |= InnerLoop; }
93
94 uint range_checks_present() const { return _loop_flags & HasRangeChecks; }
95 uint is_multiversioned() const { return _loop_flags & IsMultiversioned; }
96 uint is_vectorized_loop() const { return _loop_flags & VectorizedLoop; }
97 uint is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
98 void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
99 uint partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
100 uint is_strip_mined() const { return _loop_flags & StripMined; }
101 uint is_profile_trip_failed() const { return _loop_flags & ProfileTripFailed; }
102
103 void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
104 void mark_has_reductions() { _loop_flags |= HasReductions; }
105 void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
106 void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
107 void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
108 void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
109 void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
110 void mark_has_range_checks() { _loop_flags |= HasRangeChecks; }
111 void mark_is_multiversioned() { _loop_flags |= IsMultiversioned; }
112 void mark_strip_mined() { _loop_flags |= StripMined; }
113 void clear_strip_mined() { _loop_flags &= ~StripMined; }
114 void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
115
116 int unswitch_max() { return _unswitch_max; }
117 int unswitch_count() { return _unswitch_count; }
118
119 int has_been_range_checked() const { return _postloop_flags & LoopRCEChecked; }
120 void set_has_been_range_checked() { _postloop_flags |= LoopRCEChecked; }
121 int is_rce_post_loop() const { return _postloop_flags & RCEPostLoop; }
122 void set_is_rce_post_loop() { _postloop_flags |= RCEPostLoop; }
123
124 void set_unswitch_count(int val) {
125 assert (val <= unswitch_max(), "too many unswitches");
126 _unswitch_count = val;
127 }
128
129 void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
130 float profile_trip_cnt() { return _profile_trip_cnt; }
131
132 LoopNode(Node *entry, Node *backedge)
133 : RegionNode(3), _loop_flags(0), _unswitch_count(0),
134 _postloop_flags(0), _profile_trip_cnt(COUNT_UNKNOWN) {
135 init_class_id(Class_Loop);
136 init_req(EntryControl, entry);
137 init_req(LoopBackControl, backedge);
138 }
139
140 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
141 virtual int Opcode() const;
142 bool can_be_counted_loop(PhaseTransform* phase) const {
143 return req() == 3 && in(0) != NULL &&
144 in(1) != NULL && phase->type(in(1)) != Type::TOP &&
145 in(2) != NULL && phase->type(in(2)) != Type::TOP;
146 }
147 bool is_valid_counted_loop() const;
148 #ifndef PRODUCT
149 virtual void dump_spec(outputStream *st) const;
150 #endif
151
152 void verify_strip_mined(int expect_skeleton) const;
153 virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
154 virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return NULL; }
155 virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return NULL; }
156 virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return NULL; }
157 virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return NULL; }
158 };
159
160 //------------------------------Counted Loops----------------------------------
161 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
162 // path (and maybe some other exit paths). The trip-counter exit is always
163 // last in the loop. The trip-counter have to stride by a constant;
164 // the exit value is also loop invariant.
165
166 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs. The
167 // CountedLoopNode has the incoming loop control and the loop-back-control
168 // which is always the IfTrue before the matching CountedLoopEndNode. The
169 // CountedLoopEndNode has an incoming control (possibly not the
170 // CountedLoopNode if there is control flow in the loop), the post-increment
171 // trip-counter value, and the limit. The trip-counter value is always of
172 // the form (Op old-trip-counter stride). The old-trip-counter is produced
173 // by a Phi connected to the CountedLoopNode. The stride is constant.
174 // The Op is any commutable opcode, including Add, Mul, Xor. The
175 // CountedLoopEndNode also takes in the loop-invariant limit value.
176
177 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
178 // loop-back control. From CountedLoopEndNodes I can reach CountedLoopNodes
179 // via the old-trip-counter from the Op node.
180
181 //------------------------------CountedLoopNode--------------------------------
182 // CountedLoopNodes head simple counted loops. CountedLoopNodes have as
183 // inputs the incoming loop-start control and the loop-back control, so they
184 // act like RegionNodes. They also take in the initial trip counter, the
185 // loop-invariant stride and the loop-invariant limit value. CountedLoopNodes
186 // produce a loop-body control and the trip counter value. Since
187 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
188
189 class CountedLoopNode : public LoopNode {
190 // Size is bigger to hold _main_idx. However, _main_idx does not change
191 // the semantics so it does not appear in the hash & cmp functions.
192 virtual uint size_of() const { return sizeof(*this); }
193
194 // For Pre- and Post-loops during debugging ONLY, this holds the index of
195 // the Main CountedLoop. Used to assert that we understand the graph shape.
196 node_idx_t _main_idx;
197
198 // Known trip count calculated by compute_exact_trip_count()
199 uint _trip_count;
200
201 // Log2 of original loop bodies in unrolled loop
202 int _unrolled_count_log2;
203
204 // Node count prior to last unrolling - used to decide if
205 // unroll,optimize,unroll,optimize,... is making progress
206 int _node_count_before_unroll;
207
208 // If slp analysis is performed we record the maximum
209 // vector mapped unroll factor here
210 int _slp_maximum_unroll_factor;
211
212 public:
213 CountedLoopNode( Node *entry, Node *backedge )
214 : LoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
215 _unrolled_count_log2(0), _node_count_before_unroll(0),
216 _slp_maximum_unroll_factor(0) {
217 init_class_id(Class_CountedLoop);
218 // Initialize _trip_count to the largest possible value.
219 // Will be reset (lower) if the loop's trip count is known.
220 }
221
222 virtual int Opcode() const;
223 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
224
225 Node *init_control() const { return in(EntryControl); }
226 Node *back_control() const { return in(LoopBackControl); }
227 CountedLoopEndNode *loopexit_or_null() const;
228 CountedLoopEndNode *loopexit() const;
229 Node *init_trip() const;
230 Node *stride() const;
231 int stride_con() const;
232 bool stride_is_con() const;
233 Node *limit() const;
234 Node *incr() const;
235 Node *phi() const;
236
237 // Match increment with optional truncation
238 static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
239
240 // A 'main' loop has a pre-loop and a post-loop. The 'main' loop
241 // can run short a few iterations and may start a few iterations in.
242 // It will be RCE'd and unrolled and aligned.
243
244 // A following 'post' loop will run any remaining iterations. Used
245 // during Range Check Elimination, the 'post' loop will do any final
246 // iterations with full checks. Also used by Loop Unrolling, where
247 // the 'post' loop will do any epilog iterations needed. Basically,
248 // a 'post' loop can not profitably be further unrolled or RCE'd.
249
250 // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
251 // it may do under-flow checks for RCE and may do alignment iterations
252 // so the following main loop 'knows' that it is striding down cache
253 // lines.
254
255 // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
256 // Aligned, may be missing it's pre-loop.
257 uint is_normal_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
258 uint is_pre_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Pre; }
259 uint is_main_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Main; }
260 uint is_post_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Post; }
261 uint is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
262 uint was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
263 uint has_passed_slp () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
264 uint do_unroll_only () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
265 uint is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
266 uint has_atomic_post_loop () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
267 void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
268
269 int main_idx() const { return _main_idx; }
270
271
272 void set_pre_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
273 void set_main_loop ( ) { assert(is_normal_loop(),""); _loop_flags |= Main; }
274 void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
275 void set_normal_loop( ) { _loop_flags &= ~PreMainPostFlagsMask; }
276
277 void set_trip_count(uint tc) { _trip_count = tc; }
278 uint trip_count() { return _trip_count; }
279
280 bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
281 void set_exact_trip_count(uint tc) {
282 _trip_count = tc;
283 _loop_flags |= HasExactTripCount;
284 }
285 void set_nonexact_trip_count() {
286 _loop_flags &= ~HasExactTripCount;
287 }
288 void set_notpassed_slp() {
289 _loop_flags &= ~PassedSlpAnalysis;
290 }
291
292 void double_unrolled_count() { _unrolled_count_log2++; }
293 int unrolled_count() { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
294
295 void set_node_count_before_unroll(int ct) { _node_count_before_unroll = ct; }
296 int node_count_before_unroll() { return _node_count_before_unroll; }
297 void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
298 int slp_max_unroll() const { return _slp_maximum_unroll_factor; }
299
300 virtual LoopNode* skip_strip_mined(int expect_opaq = 1);
301 OuterStripMinedLoopNode* outer_loop() const;
302 virtual IfTrueNode* outer_loop_tail() const;
303 virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
304 virtual IfFalseNode* outer_loop_exit() const;
305 virtual SafePointNode* outer_safepoint() const;
306
307 // If this is a main loop in a pre/main/post loop nest, walk over
308 // the predicates that were inserted by
309 // duplicate_predicates()/add_range_check_predicate()
310 static Node* skip_predicates_from_entry(Node* ctrl);
311 Node* skip_predicates();
312
313 #ifndef PRODUCT
314 virtual void dump_spec(outputStream *st) const;
315 #endif
316 };
317
318 //------------------------------CountedLoopEndNode-----------------------------
319 // CountedLoopEndNodes end simple trip counted loops. They act much like
320 // IfNodes.
321 class CountedLoopEndNode : public IfNode {
322 public:
323 enum { TestControl, TestValue };
324
325 CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
326 : IfNode( control, test, prob, cnt) {
327 init_class_id(Class_CountedLoopEnd);
328 }
329 virtual int Opcode() const;
330
331 Node *cmp_node() const { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
332 Node *incr() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
333 Node *limit() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
334 Node *stride() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
335 Node *init_trip() const { Node *tmp = phi (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
336 int stride_con() const;
337 bool stride_is_con() const { Node *tmp = stride (); return (tmp != NULL && tmp->is_Con()); }
338 BoolTest::mask test_trip() const { return in(TestValue)->as_Bool()->_test._test; }
339 PhiNode *phi() const {
340 Node *tmp = incr();
341 if (tmp && tmp->req() == 3) {
342 Node* phi = tmp->in(1);
343 if (phi->is_Phi()) {
344 return phi->as_Phi();
345 }
346 }
347 return NULL;
348 }
349 CountedLoopNode *loopnode() const {
350 // The CountedLoopNode that goes with this CountedLoopEndNode may
351 // have been optimized out by the IGVN so be cautious with the
352 // pattern matching on the graph
353 PhiNode* iv_phi = phi();
354 if (iv_phi == NULL) {
355 return NULL;
356 }
357 Node *ln = iv_phi->in(0);
358 if (ln->is_CountedLoop() && ln->as_CountedLoop()->loopexit_or_null() == this) {
359 return (CountedLoopNode*)ln;
360 }
361 return NULL;
362 }
363
364 #ifndef PRODUCT
365 virtual void dump_spec(outputStream *st) const;
366 #endif
367 };
368
369
370 inline CountedLoopEndNode *CountedLoopNode::loopexit_or_null() const {
371 Node *bc = back_control();
372 if( bc == NULL ) return NULL;
373 Node *le = bc->in(0);
374 if( le->Opcode() != Op_CountedLoopEnd )
375 return NULL;
376 return (CountedLoopEndNode*)le;
377 }
378 inline CountedLoopEndNode *CountedLoopNode::loopexit() const {
379 CountedLoopEndNode* cle = loopexit_or_null();
380 assert(cle != NULL, "loopexit is NULL");
381 return cle;
382 }
383 inline Node *CountedLoopNode::init_trip() const { return loopexit_or_null() ? loopexit()->init_trip() : NULL; }
384 inline Node *CountedLoopNode::stride() const { return loopexit_or_null() ? loopexit()->stride() : NULL; }
385 inline int CountedLoopNode::stride_con() const { return loopexit_or_null() ? loopexit()->stride_con() : 0; }
386 inline bool CountedLoopNode::stride_is_con() const { return loopexit_or_null() && loopexit()->stride_is_con(); }
387 inline Node *CountedLoopNode::limit() const { return loopexit_or_null() ? loopexit()->limit() : NULL; }
388 inline Node *CountedLoopNode::incr() const { return loopexit_or_null() ? loopexit()->incr() : NULL; }
389 inline Node *CountedLoopNode::phi() const { return loopexit_or_null() ? loopexit()->phi() : NULL; }
390
391 //------------------------------LoopLimitNode-----------------------------
392 // Counted Loop limit node which represents exact final iterator value:
393 // trip_count = (limit - init_trip + stride - 1)/stride
394 // final_value= trip_count * stride + init_trip.
395 // Use HW instructions to calculate it when it can overflow in integer.
396 // Note, final_value should fit into integer since counted loop has
397 // limit check: limit <= max_int-stride.
398 class LoopLimitNode : public Node {
399 enum { Init=1, Limit=2, Stride=3 };
400 public:
401 LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
402 // Put it on the Macro nodes list to optimize during macro nodes expansion.
403 init_flags(Flag_is_macro);
404 C->add_macro_node(this);
405 }
406 virtual int Opcode() const;
407 virtual const Type *bottom_type() const { return TypeInt::INT; }
408 virtual uint ideal_reg() const { return Op_RegI; }
409 virtual const Type* Value(PhaseGVN* phase) const;
410 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
411 virtual Node* Identity(PhaseGVN* phase);
412 };
413
414 // Support for strip mining
415 class OuterStripMinedLoopNode : public LoopNode {
416 private:
417 CountedLoopNode* inner_loop() const;
418 public:
419 OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
420 : LoopNode(entry, backedge) {
421 init_class_id(Class_OuterStripMinedLoop);
422 init_flags(Flag_is_macro);
423 C->add_macro_node(this);
424 }
425
426 virtual int Opcode() const;
427
428 virtual IfTrueNode* outer_loop_tail() const;
429 virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
430 virtual IfFalseNode* outer_loop_exit() const;
431 virtual SafePointNode* outer_safepoint() const;
432 void adjust_strip_mined_loop(PhaseIterGVN* igvn);
433 };
434
435 class OuterStripMinedLoopEndNode : public IfNode {
436 public:
437 OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
438 : IfNode(control, test, prob, cnt) {
439 init_class_id(Class_OuterStripMinedLoopEnd);
440 }
441
442 virtual int Opcode() const;
443
444 virtual const Type* Value(PhaseGVN* phase) const;
445 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
446 };
447
448 // -----------------------------IdealLoopTree----------------------------------
449 class IdealLoopTree : public ResourceObj {
450 public:
451 IdealLoopTree *_parent; // Parent in loop tree
452 IdealLoopTree *_next; // Next sibling in loop tree
453 IdealLoopTree *_child; // First child in loop tree
454
455 // The head-tail backedge defines the loop.
456 // If tail is NULL then this loop has multiple backedges as part of the
457 // same loop. During cleanup I'll peel off the multiple backedges; merge
458 // them at the loop bottom and flow 1 real backedge into the loop.
459 Node *_head; // Head of loop
460 Node *_tail; // Tail of loop
461 inline Node *tail(); // Handle lazy update of _tail field
462 PhaseIdealLoop* _phase;
463 int _local_loop_unroll_limit;
464 int _local_loop_unroll_factor;
465
466 Node_List _body; // Loop body for inner loops
467
468 uint8_t _nest; // Nesting depth
469 uint8_t _irreducible:1, // True if irreducible
470 _has_call:1, // True if has call safepoint
471 _has_sfpt:1, // True if has non-call safepoint
472 _rce_candidate:1; // True if candidate for range check elimination
473
474 Node_List* _safepts; // List of safepoints in this loop
475 Node_List* _required_safept; // A inner loop cannot delete these safepts;
476 bool _allow_optimizations; // Allow loop optimizations
477
478 IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
479 : _parent(0), _next(0), _child(0),
480 _head(head), _tail(tail),
481 _phase(phase),
482 _safepts(NULL),
483 _required_safept(NULL),
484 _allow_optimizations(true),
485 _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
486 _local_loop_unroll_limit(0), _local_loop_unroll_factor(0)
487 { }
488
489 // Is 'l' a member of 'this'?
490 bool is_member(const IdealLoopTree *l) const; // Test for nested membership
491
492 // Set loop nesting depth. Accumulate has_call bits.
493 int set_nest( uint depth );
494
495 // Split out multiple fall-in edges from the loop header. Move them to a
496 // private RegionNode before the loop. This becomes the loop landing pad.
497 void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
498
499 // Split out the outermost loop from this shared header.
500 void split_outer_loop( PhaseIdealLoop *phase );
501
502 // Merge all the backedges from the shared header into a private Region.
503 // Feed that region as the one backedge to this loop.
504 void merge_many_backedges( PhaseIdealLoop *phase );
505
506 // Split shared headers and insert loop landing pads.
507 // Insert a LoopNode to replace the RegionNode.
508 // Returns TRUE if loop tree is structurally changed.
509 bool beautify_loops( PhaseIdealLoop *phase );
510
511 // Perform optimization to use the loop predicates for null checks and range checks.
512 // Applies to any loop level (not just the innermost one)
513 bool loop_predication( PhaseIdealLoop *phase);
514
515 // Perform iteration-splitting on inner loops. Split iterations to
516 // avoid range checks or one-shot null checks. Returns false if the
517 // current round of loop opts should stop.
518 bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
519
520 // Driver for various flavors of iteration splitting. Returns false
521 // if the current round of loop opts should stop.
522 bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
523
524 // Given dominators, try to find loops with calls that must always be
525 // executed (call dominates loop tail). These loops do not need non-call
526 // safepoints (ncsfpt).
527 void check_safepts(VectorSet &visited, Node_List &stack);
528
529 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
530 // encountered.
531 void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
532
533 // Remove safepoints from loop. Optionally keeping one.
534 void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
535
536 // Convert to counted loops where possible
537 void counted_loop( PhaseIdealLoop *phase );
538
539 // Check for Node being a loop-breaking test
540 Node *is_loop_exit(Node *iff) const;
541
542 // Remove simplistic dead code from loop body
543 void DCE_loop_body();
544
545 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
546 // Replace with a 1-in-10 exit guess.
547 void adjust_loop_exit_prob( PhaseIdealLoop *phase );
548
549 // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
550 // Useful for unrolling loops with NO array accesses.
551 bool policy_peel_only( PhaseIdealLoop *phase ) const;
552
553 // Return TRUE or FALSE if the loop should be unswitched -- clone
554 // loop with an invariant test
555 bool policy_unswitching( PhaseIdealLoop *phase ) const;
556
557 // Micro-benchmark spamming. Remove empty loops.
558 bool policy_do_remove_empty_loop( PhaseIdealLoop *phase );
559
560 // Convert one iteration loop into normal code.
561 bool policy_do_one_iteration_loop( PhaseIdealLoop *phase );
562
563 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
564 // make some loop-invariant test (usually a null-check) happen before the
565 // loop.
566 bool policy_peeling( PhaseIdealLoop *phase ) const;
567
568 // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
569 // known trip count in the counted loop node.
570 bool policy_maximally_unroll( PhaseIdealLoop *phase ) const;
571
572 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
573 // the loop is a CountedLoop and the body is small enough.
574 bool policy_unroll(PhaseIdealLoop *phase);
575
576 // Loop analyses to map to a maximal superword unrolling for vectorization.
577 void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
578
579 // Return TRUE or FALSE if the loop should be range-check-eliminated.
580 // Gather a list of IF tests that are dominated by iteration splitting;
581 // also gather the end of the first split and the start of the 2nd split.
582 bool policy_range_check( PhaseIdealLoop *phase ) const;
583
584 // Return TRUE or FALSE if the loop should be cache-line aligned.
585 // Gather the expression that does the alignment. Note that only
586 // one array base can be aligned in a loop (unless the VM guarantees
587 // mutual alignment). Note that if we vectorize short memory ops
588 // into longer memory ops, we may want to increase alignment.
589 bool policy_align( PhaseIdealLoop *phase ) const;
590
591 // Return TRUE if "iff" is a range check.
592 bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const;
593
594 // Compute loop trip count if possible
595 void compute_trip_count(PhaseIdealLoop* phase);
596
597 // Compute loop trip count from profile data
598 float compute_profile_trip_cnt_helper(Node* n);
599 void compute_profile_trip_cnt( PhaseIdealLoop *phase );
600
601 // Reassociate invariant expressions.
602 void reassociate_invariants(PhaseIdealLoop *phase);
603 // Reassociate invariant add and subtract expressions.
604 Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
605 // Return nonzero index of invariant operand if invariant and variant
606 // are combined with an Add or Sub. Helper for reassociate_invariants.
607 int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
608
609 // Return true if n is invariant
610 bool is_invariant(Node* n) const;
611
612 // Put loop body on igvn work list
613 void record_for_igvn();
614
615 bool is_loop() { return !_irreducible && _tail && !_tail->is_top(); }
616 bool is_inner() { return is_loop() && _child == NULL; }
617 bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); }
618
619 void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
620
621 #ifndef PRODUCT
622 void dump_head( ) const; // Dump loop head only
623 void dump() const; // Dump this loop recursively
624 void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
625 #endif
626
627 };
628
629 // -----------------------------PhaseIdealLoop---------------------------------
630 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees into a
631 // loop tree. Drives the loop-based transformations on the ideal graph.
632 class PhaseIdealLoop : public PhaseTransform {
633 friend class IdealLoopTree;
634 friend class SuperWord;
635 friend class CountedLoopReserveKit;
636
637 // Pre-computed def-use info
638 PhaseIterGVN &_igvn;
639
640 // Head of loop tree
641 IdealLoopTree *_ltree_root;
642
643 // Array of pre-order numbers, plus post-visited bit.
644 // ZERO for not pre-visited. EVEN for pre-visited but not post-visited.
645 // ODD for post-visited. Other bits are the pre-order number.
646 uint *_preorders;
647 uint _max_preorder;
648
649 const PhaseIdealLoop* _verify_me;
650 bool _verify_only;
651
652 // Allocate _preorders[] array
653 void allocate_preorders() {
654 _max_preorder = C->unique()+8;
655 _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
656 memset(_preorders, 0, sizeof(uint) * _max_preorder);
657 }
658
659 // Allocate _preorders[] array
660 void reallocate_preorders() {
661 if ( _max_preorder < C->unique() ) {
662 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
663 _max_preorder = C->unique();
664 }
665 memset(_preorders, 0, sizeof(uint) * _max_preorder);
666 }
667
668 // Check to grow _preorders[] array for the case when build_loop_tree_impl()
669 // adds new nodes.
670 void check_grow_preorders( ) {
671 if ( _max_preorder < C->unique() ) {
672 uint newsize = _max_preorder<<1; // double size of array
673 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
674 memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
675 _max_preorder = newsize;
676 }
677 }
678 // Check for pre-visited. Zero for NOT visited; non-zero for visited.
679 int is_visited( Node *n ) const { return _preorders[n->_idx]; }
680 // Pre-order numbers are written to the Nodes array as low-bit-set values.
681 void set_preorder_visited( Node *n, int pre_order ) {
682 assert( !is_visited( n ), "already set" );
683 _preorders[n->_idx] = (pre_order<<1);
684 };
685 // Return pre-order number.
686 int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
687
688 // Check for being post-visited.
689 // Should be previsited already (checked with assert(is_visited(n))).
690 int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
691
692 // Mark as post visited
693 void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
694
695 // Set/get control node out. Set lower bit to distinguish from IdealLoopTree
696 // Returns true if "n" is a data node, false if it's a control node.
697 bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
698
699 // clear out dead code after build_loop_late
700 Node_List _deadlist;
701
702 // Support for faster execution of get_late_ctrl()/dom_lca()
703 // when a node has many uses and dominator depth is deep.
704 Node_Array _dom_lca_tags;
705 void init_dom_lca_tags();
706 void clear_dom_lca_tags();
707
708 // Helper for debugging bad dominance relationships
709 bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
710
711 Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
712
713 // Inline wrapper for frequent cases:
714 // 1) only one use
715 // 2) a use is the same as the current LCA passed as 'n1'
716 Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
717 assert( n->is_CFG(), "" );
718 // Fast-path NULL lca
719 if( lca != NULL && lca != n ) {
720 assert( lca->is_CFG(), "" );
721 // find LCA of all uses
722 n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
723 }
724 return find_non_split_ctrl(n);
725 }
726 Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
727
728 // Helper function for directing control inputs away from CFG split
729 // points.
730 Node *find_non_split_ctrl( Node *ctrl ) const {
731 if (ctrl != NULL) {
732 if (ctrl->is_MultiBranch()) {
733 ctrl = ctrl->in(0);
734 }
735 assert(ctrl->is_CFG(), "CFG");
736 }
737 return ctrl;
738 }
739
740 Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
741 void duplicate_predicates_helper(Node* predicate, Node* castii, IdealLoopTree* outer_loop,
742 LoopNode* outer_main_head, uint dd_main_head);
743 void duplicate_predicates(CountedLoopNode* pre_head, Node* castii, IdealLoopTree* outer_loop,
744 LoopNode* outer_main_head, uint dd_main_head);
745
746 public:
747
748 static bool is_canonical_loop_entry(CountedLoopNode* cl);
749
750 bool has_node( Node* n ) const {
751 guarantee(n != NULL, "No Node.");
752 return _nodes[n->_idx] != NULL;
753 }
754 // check if transform created new nodes that need _ctrl recorded
755 Node *get_late_ctrl( Node *n, Node *early );
756 Node *get_early_ctrl( Node *n );
757 Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
758 void set_early_ctrl( Node *n );
759 void set_subtree_ctrl( Node *root );
760 void set_ctrl( Node *n, Node *ctrl ) {
761 assert( !has_node(n) || has_ctrl(n), "" );
762 assert( ctrl->in(0), "cannot set dead control node" );
763 assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
764 _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
765 }
766 // Set control and update loop membership
767 void set_ctrl_and_loop(Node* n, Node* ctrl) {
768 IdealLoopTree* old_loop = get_loop(get_ctrl(n));
769 IdealLoopTree* new_loop = get_loop(ctrl);
770 if (old_loop != new_loop) {
771 if (old_loop->_child == NULL) old_loop->_body.yank(n);
772 if (new_loop->_child == NULL) new_loop->_body.push(n);
773 }
774 set_ctrl(n, ctrl);
775 }
776 // Control nodes can be replaced or subsumed. During this pass they
777 // get their replacement Node in slot 1. Instead of updating the block
778 // location of all Nodes in the subsumed block, we lazily do it. As we
779 // pull such a subsumed block out of the array, we write back the final
780 // correct block.
781 Node *get_ctrl( Node *i ) {
782 assert(has_node(i), "");
783 Node *n = get_ctrl_no_update(i);
784 _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
785 assert(has_node(i) && has_ctrl(i), "");
786 assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
787 return n;
788 }
789 // true if CFG node d dominates CFG node n
790 bool is_dominator(Node *d, Node *n);
791 // return get_ctrl for a data node and self(n) for a CFG node
792 Node* ctrl_or_self(Node* n) {
793 if (has_ctrl(n))
794 return get_ctrl(n);
795 else {
796 assert (n->is_CFG(), "must be a CFG node");
797 return n;
798 }
799 }
800
801 private:
802 Node *get_ctrl_no_update_helper(Node *i) const {
803 assert(has_ctrl(i), "should be control, not loop");
804 return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
805 }
806
807 Node *get_ctrl_no_update(Node *i) const {
808 assert( has_ctrl(i), "" );
809 Node *n = get_ctrl_no_update_helper(i);
810 if (!n->in(0)) {
811 // Skip dead CFG nodes
812 do {
813 n = get_ctrl_no_update_helper(n);
814 } while (!n->in(0));
815 n = find_non_split_ctrl(n);
816 }
817 return n;
818 }
819
820 // Check for loop being set
821 // "n" must be a control node. Returns true if "n" is known to be in a loop.
822 bool has_loop( Node *n ) const {
823 assert(!has_node(n) || !has_ctrl(n), "");
824 return has_node(n);
825 }
826 // Set loop
827 void set_loop( Node *n, IdealLoopTree *loop ) {
828 _nodes.map(n->_idx, (Node*)loop);
829 }
830 // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms. Replace
831 // the 'old_node' with 'new_node'. Kill old-node. Add a reference
832 // from old_node to new_node to support the lazy update. Reference
833 // replaces loop reference, since that is not needed for dead node.
834 public:
835 void lazy_update(Node *old_node, Node *new_node) {
836 assert(old_node != new_node, "no cycles please");
837 // Re-use the side array slot for this node to provide the
838 // forwarding pointer.
839 _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
840 }
841 void lazy_replace(Node *old_node, Node *new_node) {
842 _igvn.replace_node(old_node, new_node);
843 lazy_update(old_node, new_node);
844 }
845
846 private:
847
848 // Place 'n' in some loop nest, where 'n' is a CFG node
849 void build_loop_tree();
850 int build_loop_tree_impl( Node *n, int pre_order );
851 // Insert loop into the existing loop tree. 'innermost' is a leaf of the
852 // loop tree, not the root.
853 IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
854
855 // Place Data nodes in some loop nest
856 void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
857 void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
858 void build_loop_late_post ( Node* n );
859 void verify_strip_mined_scheduling(Node *n, Node* least);
860
861 // Array of immediate dominance info for each CFG node indexed by node idx
862 private:
863 uint _idom_size;
864 Node **_idom; // Array of immediate dominators
865 uint *_dom_depth; // Used for fast LCA test
866 GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
867
868 Node* idom_no_update(Node* d) const {
869 assert(d->_idx < _idom_size, "oob");
870 Node* n = _idom[d->_idx];
871 assert(n != NULL,"Bad immediate dominator info.");
872 while (n->in(0) == NULL) { // Skip dead CFG nodes
873 //n = n->in(1);
874 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
875 assert(n != NULL,"Bad immediate dominator info.");
876 }
877 return n;
878 }
879 Node *idom(Node* d) const {
880 uint didx = d->_idx;
881 Node *n = idom_no_update(d);
882 _idom[didx] = n; // Lazily remove dead CFG nodes from table.
883 return n;
884 }
885 uint dom_depth(Node* d) const {
886 guarantee(d != NULL, "Null dominator info.");
887 guarantee(d->_idx < _idom_size, "");
888 return _dom_depth[d->_idx];
889 }
890 void set_idom(Node* d, Node* n, uint dom_depth);
891 // Locally compute IDOM using dom_lca call
892 Node *compute_idom( Node *region ) const;
893 // Recompute dom_depth
894 void recompute_dom_depth();
895
896 // Is safept not required by an outer loop?
897 bool is_deleteable_safept(Node* sfpt);
898
899 // Replace parallel induction variable (parallel to trip counter)
900 void replace_parallel_iv(IdealLoopTree *loop);
901
902 // Perform verification that the graph is valid.
903 PhaseIdealLoop( PhaseIterGVN &igvn) :
904 PhaseTransform(Ideal_Loop),
905 _igvn(igvn),
906 _dom_lca_tags(arena()), // Thread::resource_area
907 _verify_me(NULL),
908 _verify_only(true) {
909 build_and_optimize(false, false);
910 }
911
912 // build the loop tree and perform any requested optimizations
913 void build_and_optimize(bool do_split_if, bool skip_loop_opts);
914
915 public:
916 // Dominators for the sea of nodes
917 void Dominators();
918 Node *dom_lca( Node *n1, Node *n2 ) const {
919 return find_non_split_ctrl(dom_lca_internal(n1, n2));
920 }
921 Node *dom_lca_internal( Node *n1, Node *n2 ) const;
922
923 // Compute the Ideal Node to Loop mapping
924 PhaseIdealLoop( PhaseIterGVN &igvn, bool do_split_ifs, bool skip_loop_opts = false) :
925 PhaseTransform(Ideal_Loop),
926 _igvn(igvn),
927 _dom_lca_tags(arena()), // Thread::resource_area
928 _verify_me(NULL),
929 _verify_only(false) {
930 build_and_optimize(do_split_ifs, skip_loop_opts);
931 }
932
933 // Verify that verify_me made the same decisions as a fresh run.
934 PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) :
935 PhaseTransform(Ideal_Loop),
936 _igvn(igvn),
937 _dom_lca_tags(arena()), // Thread::resource_area
938 _verify_me(verify_me),
939 _verify_only(false) {
940 build_and_optimize(false, false);
941 }
942
943 // Build and verify the loop tree without modifying the graph. This
944 // is useful to verify that all inputs properly dominate their uses.
945 static void verify(PhaseIterGVN& igvn) {
946 #ifdef ASSERT
947 PhaseIdealLoop v(igvn);
948 #endif
949 }
950
951 // True if the method has at least 1 irreducible loop
952 bool _has_irreducible_loops;
953
954 // Per-Node transform
955 virtual Node *transform( Node *a_node ) { return 0; }
956
957 bool is_counted_loop(Node* x, IdealLoopTree*& loop);
958 IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
959 IdealLoopTree* loop, float cl_prob, float le_fcnt,
960 Node*& entry_control, Node*& iffalse);
961
962 Node* exact_limit( IdealLoopTree *loop );
963
964 // Return a post-walked LoopNode
965 IdealLoopTree *get_loop( Node *n ) const {
966 // Dead nodes have no loop, so return the top level loop instead
967 if (!has_node(n)) return _ltree_root;
968 assert(!has_ctrl(n), "");
969 return (IdealLoopTree*)_nodes[n->_idx];
970 }
971
972 // Is 'n' a (nested) member of 'loop'?
973 int is_member( const IdealLoopTree *loop, Node *n ) const {
974 return loop->is_member(get_loop(n)); }
975
976 // This is the basic building block of the loop optimizations. It clones an
977 // entire loop body. It makes an old_new loop body mapping; with this
978 // mapping you can find the new-loop equivalent to an old-loop node. All
979 // new-loop nodes are exactly equal to their old-loop counterparts, all
980 // edges are the same. All exits from the old-loop now have a RegionNode
981 // that merges the equivalent new-loop path. This is true even for the
982 // normal "loop-exit" condition. All uses of loop-invariant old-loop values
983 // now come from (one or more) Phis that merge their new-loop equivalents.
984 // Parameter side_by_side_idom:
985 // When side_by_size_idom is NULL, the dominator tree is constructed for
986 // the clone loop to dominate the original. Used in construction of
987 // pre-main-post loop sequence.
988 // When nonnull, the clone and original are side-by-side, both are
989 // dominated by the passed in side_by_side_idom node. Used in
990 // construction of unswitched loops.
991 enum CloneLoopMode {
992 IgnoreStripMined = 0, // Only clone inner strip mined loop
993 CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
994 ControlAroundStripMined = 2 // Only clone inner strip mined loop,
995 // result control flow branches
996 // either to inner clone or outer
997 // strip mined loop.
998 };
999 void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
1000 CloneLoopMode mode, Node* side_by_side_idom = NULL);
1001 void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
1002 IdealLoopTree* loop, IdealLoopTree* companion_loop,
1003 Node_List*& split_if_set, Node_List*& split_bool_set,
1004 Node_List*& split_cex_set, Node_List& worklist,
1005 uint new_counter, CloneLoopMode mode);
1006 void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
1007 IdealLoopTree* outer_loop, int dd, Node_List &old_new,
1008 Node_List& extra_data_nodes);
1009
1010 // If we got the effect of peeling, either by actually peeling or by
1011 // making a pre-loop which must execute at least once, we can remove
1012 // all loop-invariant dominated tests in the main body.
1013 void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
1014
1015 // Generate code to do a loop peel for the given loop (and body).
1016 // old_new is a temp array.
1017 void do_peeling( IdealLoopTree *loop, Node_List &old_new );
1018
1019 // Add pre and post loops around the given loop. These loops are used
1020 // during RCE, unrolling and aligning loops.
1021 void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
1022
1023 // Add post loop after the given loop.
1024 Node *insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1025 CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1026 Node *incr, Node *limit, CountedLoopNode *&post_head);
1027
1028 // Add an RCE'd post loop which we will multi-version adapt for run time test path usage
1029 void insert_scalar_rced_post_loop( IdealLoopTree *loop, Node_List &old_new );
1030
1031 // Add a vector post loop between a vector main loop and the current post loop
1032 void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
1033 // If Node n lives in the back_ctrl block, we clone a private version of n
1034 // in preheader_ctrl block and return that, otherwise return n.
1035 Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
1036
1037 // Take steps to maximally unroll the loop. Peel any odd iterations, then
1038 // unroll to do double iterations. The next round of major loop transforms
1039 // will repeat till the doubled loop body does all remaining iterations in 1
1040 // pass.
1041 void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
1042
1043 // Unroll the loop body one step - make each trip do 2 iterations.
1044 void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
1045
1046 // Mark vector reduction candidates before loop unrolling
1047 void mark_reductions( IdealLoopTree *loop );
1048
1049 // Return true if exp is a constant times an induction var
1050 bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
1051
1052 // Return true if exp is a scaled induction var plus (or minus) constant
1053 bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
1054
1055 // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
1056 ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
1057 Deoptimization::DeoptReason reason,
1058 int opcode);
1059 void register_control(Node* n, IdealLoopTree *loop, Node* pred);
1060
1061 // Clone loop predicates to cloned loops (peeled, unswitched)
1062 static ProjNode* clone_predicate(ProjNode* predicate_proj, Node* new_entry,
1063 Deoptimization::DeoptReason reason,
1064 PhaseIdealLoop* loop_phase,
1065 PhaseIterGVN* igvn);
1066
1067 static Node* clone_loop_predicates(Node* old_entry, Node* new_entry,
1068 bool clone_limit_check,
1069 PhaseIdealLoop* loop_phase,
1070 PhaseIterGVN* igvn);
1071 Node* clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check);
1072
1073 static Node* skip_all_loop_predicates(Node* entry);
1074 static Node* skip_loop_predicates(Node* entry);
1075
1076 // Find a good location to insert a predicate
1077 static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
1078 // Find a predicate
1079 static Node* find_predicate(Node* entry);
1080 // Construct a range check for a predicate if
1081 BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
1082 int scale, Node* offset,
1083 Node* init, Node* limit, jint stride,
1084 Node* range, bool upper, bool &overflow);
1085
1086 // Implementation of the loop predication to promote checks outside the loop
1087 bool loop_predication_impl(IdealLoopTree *loop);
1088 bool loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1089 CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1090 Deoptimization::DeoptReason reason);
1091 bool loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt);
1092 void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
1093 PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1094 Node_List& if_proj_list);
1095 ProjNode* insert_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1096 ProjNode* proj, ProjNode *predicate_proj,
1097 ProjNode* upper_bound_proj,
1098 int scale, Node* offset,
1099 Node* init, Node* limit, jint stride,
1100 Node* rng, bool& overflow,
1101 Deoptimization::DeoptReason reason);
1102 Node* add_range_check_predicate(IdealLoopTree* loop, CountedLoopNode* cl,
1103 Node* predicate_proj, int scale_con, Node* offset,
1104 Node* limit, jint stride_con);
1105
1106 // Helper function to collect predicate for eliminating the useless ones
1107 void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
1108 void eliminate_useless_predicates();
1109
1110 // Change the control input of expensive nodes to allow commoning by
1111 // IGVN when it is guaranteed to not result in a more frequent
1112 // execution of the expensive node. Return true if progress.
1113 bool process_expensive_nodes();
1114
1115 // Check whether node has become unreachable
1116 bool is_node_unreachable(Node *n) const {
1117 return !has_node(n) || n->is_unreachable(_igvn);
1118 }
1119
1120 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1121 int do_range_check( IdealLoopTree *loop, Node_List &old_new );
1122
1123 // Check to see if do_range_check(...) cleaned the main loop of range-checks
1124 void has_range_checks(IdealLoopTree *loop);
1125
1126 // Process post loops which have range checks and try to build a multi-version
1127 // guard to safely determine if we can execute the post loop which was RCE'd.
1128 bool multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop);
1129
1130 // Cause the rce'd post loop to optimized away, this happens if we cannot complete multiverioning
1131 void poison_rce_post_loop(IdealLoopTree *rce_loop);
1132
1133 // Create a slow version of the loop by cloning the loop
1134 // and inserting an if to select fast-slow versions.
1135 ProjNode* create_slow_version_of_loop(IdealLoopTree *loop,
1136 Node_List &old_new,
1137 int opcode,
1138 CloneLoopMode mode);
1139
1140 // Clone a loop and return the clone head (clone_loop_head).
1141 // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
1142 // This routine was created for usage in CountedLoopReserveKit.
1143 //
1144 // int(1) -> If -> IfTrue -> original_loop_head
1145 // |
1146 // V
1147 // IfFalse -> clone_loop_head (returned by function pointer)
1148 //
1149 LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
1150 // Clone loop with an invariant test (that does not exit) and
1151 // insert a clone of the test that selects which version to
1152 // execute.
1153 void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
1154
1155 // Find candidate "if" for unswitching
1156 IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
1157
1158 // Range Check Elimination uses this function!
1159 // Constrain the main loop iterations so the affine function:
1160 // low_limit <= scale_con * I + offset < upper_limit
1161 // always holds true. That is, either increase the number of iterations in
1162 // the pre-loop or the post-loop until the condition holds true in the main
1163 // loop. Scale_con, offset and limit are all loop invariant.
1164 void add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit );
1165 // Helper function for add_constraint().
1166 Node* adjust_limit( int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl );
1167
1168 // Partially peel loop up through last_peel node.
1169 bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1170
1171 // Create a scheduled list of nodes control dependent on ctrl set.
1172 void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1173 // Has a use in the vector set
1174 bool has_use_in_set( Node* n, VectorSet& vset );
1175 // Has use internal to the vector set (ie. not in a phi at the loop head)
1176 bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1177 // clone "n" for uses that are outside of loop
1178 int clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1179 // clone "n" for special uses that are in the not_peeled region
1180 void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1181 VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1182 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1183 void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1184 #ifdef ASSERT
1185 // Validate the loop partition sets: peel and not_peel
1186 bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1187 // Ensure that uses outside of loop are of the right form
1188 bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1189 uint orig_exit_idx, uint clone_exit_idx);
1190 bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1191 #endif
1192
1193 // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1194 int stride_of_possible_iv( Node* iff );
1195 bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1196 // Return the (unique) control output node that's in the loop (if it exists.)
1197 Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1198 // Insert a signed compare loop exit cloned from an unsigned compare.
1199 IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1200 void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1201 // Utility to register node "n" with PhaseIdealLoop
1202 void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1203 // Utility to create an if-projection
1204 ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1205 // Force the iff control output to be the live_proj
1206 Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1207 // Insert a region before an if projection
1208 RegionNode* insert_region_before_proj(ProjNode* proj);
1209 // Insert a new if before an if projection
1210 ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1211
1212 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1213 // "Nearly" because all Nodes have been cloned from the original in the loop,
1214 // but the fall-in edges to the Cmp are different. Clone bool/Cmp pairs
1215 // through the Phi recursively, and return a Bool.
1216 Node *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1217 CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1218
1219
1220 // Rework addressing expressions to get the most loop-invariant stuff
1221 // moved out. We'd like to do all associative operators, but it's especially
1222 // important (common) to do address expressions.
1223 Node *remix_address_expressions( Node *n );
1224
1225 // Attempt to use a conditional move instead of a phi/branch
1226 Node *conditional_move( Node *n );
1227
1228 // Reorganize offset computations to lower register pressure.
1229 // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1230 // (which are then alive with the post-incremented trip counter
1231 // forcing an extra register move)
1232 void reorg_offsets( IdealLoopTree *loop );
1233
1234 // Check for aggressive application of 'split-if' optimization,
1235 // using basic block level info.
1236 void split_if_with_blocks ( VectorSet &visited, Node_Stack &nstack );
1237 Node *split_if_with_blocks_pre ( Node *n );
1238 void split_if_with_blocks_post( Node *n );
1239 Node *has_local_phi_input( Node *n );
1240 // Mark an IfNode as being dominated by a prior test,
1241 // without actually altering the CFG (and hence IDOM info).
1242 void dominated_by( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
1243
1244 // Split Node 'n' through merge point
1245 Node *split_thru_region( Node *n, Node *region );
1246 // Split Node 'n' through merge point if there is enough win.
1247 Node *split_thru_phi( Node *n, Node *region, int policy );
1248 // Found an If getting its condition-code input from a Phi in the
1249 // same block. Split thru the Region.
1250 void do_split_if( Node *iff );
1251
1252 // Conversion of fill/copy patterns into intrisic versions
1253 bool do_intrinsify_fill();
1254 bool intrinsify_fill(IdealLoopTree* lpt);
1255 bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1256 Node*& shift, Node*& offset);
1257
1258 private:
1259 // Return a type based on condition control flow
1260 const TypeInt* filtered_type( Node *n, Node* n_ctrl);
1261 const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1262 // Helpers for filtered type
1263 const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1264
1265 // Helper functions
1266 Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1267 Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1268 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 );
1269 bool split_up( Node *n, Node *blk1, Node *blk2 );
1270 void sink_use( Node *use, Node *post_loop );
1271 Node *place_near_use( Node *useblock ) const;
1272 Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1273 void try_move_store_after_loop(Node* n);
1274 bool identical_backtoback_ifs(Node *n);
1275 bool can_split_if(Node *n_ctrl);
1276
1277 bool _created_loop_node;
1278 public:
1279 void set_created_loop_node() { _created_loop_node = true; }
1280 bool created_loop_node() { return _created_loop_node; }
1281 void register_new_node( Node *n, Node *blk );
1282
1283 #ifdef ASSERT
1284 void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1285 #endif
1286
1287 #ifndef PRODUCT
1288 void dump( ) const;
1289 void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const;
1290 void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const;
1291 void verify() const; // Major slow :-)
1292 void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const;
1293 IdealLoopTree *get_loop_idx(Node* n) const {
1294 // Dead nodes have no loop, so return the top level loop instead
1295 return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1296 }
1297 // Print some stats
1298 static void print_statistics();
1299 static int _loop_invokes; // Count of PhaseIdealLoop invokes
1300 static int _loop_work; // Sum of PhaseIdealLoop x _unique
1301 #endif
1302 };
1303
1304 // This kit may be used for making of a reserved copy of a loop before this loop
1305 // goes under non-reversible changes.
1306 //
1307 // Function create_reserve() creates a reserved copy (clone) of the loop.
1308 // The reserved copy is created by calling
1309 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1310 // the original and reserved loops are connected in the outer graph.
1311 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1312 //
1313 // By default the reserved copy (clone) of the loop is created as dead code - it is
1314 // dominated in the outer loop by this node chain:
1315 // intcon(1)->If->IfFalse->reserved_copy.
1316 // The original loop is dominated by the the same node chain but IfTrue projection:
1317 // intcon(0)->If->IfTrue->original_loop.
1318 //
1319 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1320 // and the dtor, checks _use_new value.
1321 // If _use_new == false, it "switches" control to reserved copy of the loop
1322 // by simple replacing of node intcon(1) with node intcon(0).
1323 //
1324 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1325 //
1326 // void CountedLoopReserveKit_example()
1327 // {
1328 // CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1329 // if (DoReserveCopy && !lrk.has_reserved()) {
1330 // return; //failed to create reserved loop copy
1331 // }
1332 // ...
1333 // //something is wrong, switch to original loop
1334 /// if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1335 // ...
1336 // //everything worked ok, return with the newly modified loop
1337 // lrk.use_new();
1338 // return; // ~CountedLoopReserveKit does nothing once use_new() was called
1339 // }
1340 //
1341 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1342 // the dtor will "switch to the original" loop.
1343 // NOTE. You you modify outside of the original loop this class is no help.
1344 //
1345 class CountedLoopReserveKit {
1346 private:
1347 PhaseIdealLoop* _phase;
1348 IdealLoopTree* _lpt;
1349 LoopNode* _lp;
1350 IfNode* _iff;
1351 LoopNode* _lp_reserved;
1352 bool _has_reserved;
1353 bool _use_new;
1354 const bool _active; //may be set to false in ctor, then the object is dummy
1355
1356 public:
1357 CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1358 ~CountedLoopReserveKit();
1359 void use_new() {_use_new = true;}
1360 void set_iff(IfNode* x) {_iff = x;}
1361 bool has_reserved() const { return _active && _has_reserved;}
1362 private:
1363 bool create_reserve();
1364 };// class CountedLoopReserveKit
1365
1366 inline Node* IdealLoopTree::tail() {
1367 // Handle lazy update of _tail field
1368 Node *n = _tail;
1369 //while( !n->in(0) ) // Skip dead CFG nodes
1370 //n = n->in(1);
1371 if (n->in(0) == NULL)
1372 n = _phase->get_ctrl(n);
1373 _tail = n;
1374 return n;
1375 }
1376
1377
1378 // Iterate over the loop tree using a preorder, left-to-right traversal.
1379 //
1380 // Example that visits all counted loops from within PhaseIdealLoop
1381 //
1382 // for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1383 // IdealLoopTree* lpt = iter.current();
1384 // if (!lpt->is_counted()) continue;
1385 // ...
1386 class LoopTreeIterator : public StackObj {
1387 private:
1388 IdealLoopTree* _root;
1389 IdealLoopTree* _curnt;
1390
1391 public:
1392 LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1393
1394 bool done() { return _curnt == NULL; } // Finished iterating?
1395
1396 void next(); // Advance to next loop tree
1397
1398 IdealLoopTree* current() { return _curnt; } // Return current value of iterator.
1399 };
1400
1401 #endif // SHARE_VM_OPTO_LOOPNODE_HPP