1 /*
2 * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_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 PhaseIdealLoop;
41 class CountedLoopReserveKit;
42 class VectorSet;
43 class Invariance;
44 struct small_cache;
45
46 //
47 // I D E A L I Z E D L O O P S
48 //
49 // Idealized loops are the set of loops I perform more interesting
50 // transformations on, beyond simple hoisting.
51
52 //------------------------------LoopNode---------------------------------------
53 // Simple loop header. Fall in path on left, loop-back path on right.
54 class LoopNode : public RegionNode {
55 // Size is bigger to hold the flags. However, the flags do not change
56 // the semantics so it does not appear in the hash & cmp functions.
57 virtual uint size_of() const { return sizeof(*this); }
58 protected:
59 short _loop_flags;
60 // Names for flag bitfields
61 enum { Normal=0, Pre=1, Main=2, Post=3, PreMainPostFlagsMask=3,
62 MainHasNoPreLoop=4,
63 HasExactTripCount=8,
64 InnerLoop=16,
65 PartialPeelLoop=32,
66 PartialPeelFailed=64,
67 HasReductions=128,
68 WasSlpAnalyzed=256,
69 PassedSlpAnalysis=512,
70 DoUnrollOnly=1024,
71 VectorizedLoop=2048,
72 HasAtomicPostLoop=4096 };
73 char _unswitch_count;
74 enum { _unswitch_max=3 };
75
76 public:
77 // Names for edge indices
78 enum { Self=0, EntryControl, LoopBackControl };
79
80 int is_inner_loop() const { return _loop_flags & InnerLoop; }
81 void set_inner_loop() { _loop_flags |= InnerLoop; }
82
83 int is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
84 void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
85 int partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
86 void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
87 void mark_has_reductions() { _loop_flags |= HasReductions; }
88 void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
89 void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
90 void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
91 void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
92 void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
93
94 int unswitch_max() { return _unswitch_max; }
95 int unswitch_count() { return _unswitch_count; }
96 void set_unswitch_count(int val) {
97 assert (val <= unswitch_max(), "too many unswitches");
98 _unswitch_count = val;
99 }
100
101 LoopNode( Node *entry, Node *backedge ) : RegionNode(3), _loop_flags(0), _unswitch_count(0) {
102 init_class_id(Class_Loop);
103 init_req(EntryControl, entry);
104 init_req(LoopBackControl, backedge);
105 }
106
107 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
108 virtual int Opcode() const;
109 bool can_be_counted_loop(PhaseTransform* phase) const {
110 return req() == 3 && in(0) != NULL &&
111 in(1) != NULL && phase->type(in(1)) != Type::TOP &&
112 in(2) != NULL && phase->type(in(2)) != Type::TOP;
113 }
114 bool is_valid_counted_loop() const;
115 #ifndef PRODUCT
116 virtual void dump_spec(outputStream *st) const;
117 #endif
118 };
119
120 //------------------------------Counted Loops----------------------------------
121 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
122 // path (and maybe some other exit paths). The trip-counter exit is always
123 // last in the loop. The trip-counter have to stride by a constant;
124 // the exit value is also loop invariant.
125
126 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs. The
127 // CountedLoopNode has the incoming loop control and the loop-back-control
128 // which is always the IfTrue before the matching CountedLoopEndNode. The
129 // CountedLoopEndNode has an incoming control (possibly not the
130 // CountedLoopNode if there is control flow in the loop), the post-increment
131 // trip-counter value, and the limit. The trip-counter value is always of
132 // the form (Op old-trip-counter stride). The old-trip-counter is produced
133 // by a Phi connected to the CountedLoopNode. The stride is constant.
134 // The Op is any commutable opcode, including Add, Mul, Xor. The
135 // CountedLoopEndNode also takes in the loop-invariant limit value.
136
137 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
138 // loop-back control. From CountedLoopEndNodes I can reach CountedLoopNodes
139 // via the old-trip-counter from the Op node.
140
141 //------------------------------CountedLoopNode--------------------------------
142 // CountedLoopNodes head simple counted loops. CountedLoopNodes have as
143 // inputs the incoming loop-start control and the loop-back control, so they
144 // act like RegionNodes. They also take in the initial trip counter, the
145 // loop-invariant stride and the loop-invariant limit value. CountedLoopNodes
146 // produce a loop-body control and the trip counter value. Since
147 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
148
149 class CountedLoopNode : public LoopNode {
150 // Size is bigger to hold _main_idx. However, _main_idx does not change
151 // the semantics so it does not appear in the hash & cmp functions.
152 virtual uint size_of() const { return sizeof(*this); }
153
154 // For Pre- and Post-loops during debugging ONLY, this holds the index of
155 // the Main CountedLoop. Used to assert that we understand the graph shape.
156 node_idx_t _main_idx;
157
158 // Known trip count calculated by compute_exact_trip_count()
159 uint _trip_count;
160
161 // Expected trip count from profile data
162 float _profile_trip_cnt;
163
164 // Log2 of original loop bodies in unrolled loop
165 int _unrolled_count_log2;
166
167 // Node count prior to last unrolling - used to decide if
168 // unroll,optimize,unroll,optimize,... is making progress
169 int _node_count_before_unroll;
170
171 // If slp analysis is performed we record the maximum
172 // vector mapped unroll factor here
173 int _slp_maximum_unroll_factor;
174
175 public:
176 CountedLoopNode( Node *entry, Node *backedge )
177 : LoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
178 _profile_trip_cnt(COUNT_UNKNOWN), _unrolled_count_log2(0),
179 _node_count_before_unroll(0), _slp_maximum_unroll_factor(0) {
180 init_class_id(Class_CountedLoop);
181 // Initialize _trip_count to the largest possible value.
182 // Will be reset (lower) if the loop's trip count is known.
183 }
184
185 virtual int Opcode() const;
186 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
187
188 Node *init_control() const { return in(EntryControl); }
189 Node *back_control() const { return in(LoopBackControl); }
190 CountedLoopEndNode *loopexit() const;
191 Node *init_trip() const;
192 Node *stride() const;
193 int stride_con() const;
194 bool stride_is_con() const;
195 Node *limit() const;
196 Node *incr() const;
197 Node *phi() const;
198
199 // Match increment with optional truncation
200 static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
201
202 // A 'main' loop has a pre-loop and a post-loop. The 'main' loop
203 // can run short a few iterations and may start a few iterations in.
204 // It will be RCE'd and unrolled and aligned.
205
206 // A following 'post' loop will run any remaining iterations. Used
207 // during Range Check Elimination, the 'post' loop will do any final
208 // iterations with full checks. Also used by Loop Unrolling, where
209 // the 'post' loop will do any epilog iterations needed. Basically,
210 // a 'post' loop can not profitably be further unrolled or RCE'd.
211
212 // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
213 // it may do under-flow checks for RCE and may do alignment iterations
214 // so the following main loop 'knows' that it is striding down cache
215 // lines.
216
217 // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
218 // Aligned, may be missing it's pre-loop.
219 int is_normal_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
220 int is_pre_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Pre; }
221 int is_main_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Main; }
222 int is_post_loop () const { return (_loop_flags&PreMainPostFlagsMask) == Post; }
223 int is_reduction_loop() const { return (_loop_flags&HasReductions) == HasReductions; }
224 int was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
225 int has_passed_slp () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
226 int do_unroll_only () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
227 int is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
228 int is_vectorized_loop () const { return (_loop_flags & VectorizedLoop) == VectorizedLoop; }
229 int has_atomic_post_loop () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
230 void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }
231
232 int main_idx() const { return _main_idx; }
233
234
235 void set_pre_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
236 void set_main_loop ( ) { assert(is_normal_loop(),""); _loop_flags |= Main; }
237 void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
238 void set_normal_loop( ) { _loop_flags &= ~PreMainPostFlagsMask; }
239
240 void set_trip_count(uint tc) { _trip_count = tc; }
241 uint trip_count() { return _trip_count; }
242
243 bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
244 void set_exact_trip_count(uint tc) {
245 _trip_count = tc;
246 _loop_flags |= HasExactTripCount;
247 }
248 void set_nonexact_trip_count() {
249 _loop_flags &= ~HasExactTripCount;
250 }
251 void set_notpassed_slp() {
252 _loop_flags &= ~PassedSlpAnalysis;
253 }
254
255 void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
256 float profile_trip_cnt() { return _profile_trip_cnt; }
257
258 void double_unrolled_count() { _unrolled_count_log2++; }
259 int unrolled_count() { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
260
261 void set_node_count_before_unroll(int ct) { _node_count_before_unroll = ct; }
262 int node_count_before_unroll() { return _node_count_before_unroll; }
263 void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
264 int slp_max_unroll() const { return _slp_maximum_unroll_factor; }
265
266 #ifndef PRODUCT
267 virtual void dump_spec(outputStream *st) const;
268 #endif
269 };
270
271 //------------------------------CountedLoopEndNode-----------------------------
272 // CountedLoopEndNodes end simple trip counted loops. They act much like
273 // IfNodes.
274 class CountedLoopEndNode : public IfNode {
275 public:
276 enum { TestControl, TestValue };
277
278 CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
279 : IfNode( control, test, prob, cnt) {
280 init_class_id(Class_CountedLoopEnd);
281 }
282 virtual int Opcode() const;
283
284 Node *cmp_node() const { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
285 Node *incr() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
286 Node *limit() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
287 Node *stride() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
288 Node *phi() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
289 Node *init_trip() const { Node *tmp = phi (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
290 int stride_con() const;
291 bool stride_is_con() const { Node *tmp = stride (); return (tmp != NULL && tmp->is_Con()); }
292 BoolTest::mask test_trip() const { return in(TestValue)->as_Bool()->_test._test; }
293 CountedLoopNode *loopnode() const {
294 // The CountedLoopNode that goes with this CountedLoopEndNode may
295 // have been optimized out by the IGVN so be cautious with the
296 // pattern matching on the graph
297 if (phi() == NULL) {
298 return NULL;
299 }
300 assert(phi()->is_Phi(), "should be PhiNode");
301 Node *ln = phi()->in(0);
302 if (ln->is_CountedLoop() && ln->as_CountedLoop()->loopexit() == this) {
303 return (CountedLoopNode*)ln;
304 }
305 return NULL;
306 }
307
308 #ifndef PRODUCT
309 virtual void dump_spec(outputStream *st) const;
310 #endif
311 };
312
313
314 inline CountedLoopEndNode *CountedLoopNode::loopexit() const {
315 Node *bc = back_control();
316 if( bc == NULL ) return NULL;
317 Node *le = bc->in(0);
318 if( le->Opcode() != Op_CountedLoopEnd )
319 return NULL;
320 return (CountedLoopEndNode*)le;
321 }
322 inline Node *CountedLoopNode::init_trip() const { return loopexit() ? loopexit()->init_trip() : NULL; }
323 inline Node *CountedLoopNode::stride() const { return loopexit() ? loopexit()->stride() : NULL; }
324 inline int CountedLoopNode::stride_con() const { return loopexit() ? loopexit()->stride_con() : 0; }
325 inline bool CountedLoopNode::stride_is_con() const { return loopexit() && loopexit()->stride_is_con(); }
326 inline Node *CountedLoopNode::limit() const { return loopexit() ? loopexit()->limit() : NULL; }
327 inline Node *CountedLoopNode::incr() const { return loopexit() ? loopexit()->incr() : NULL; }
328 inline Node *CountedLoopNode::phi() const { return loopexit() ? loopexit()->phi() : NULL; }
329
330 //------------------------------LoopLimitNode-----------------------------
331 // Counted Loop limit node which represents exact final iterator value:
332 // trip_count = (limit - init_trip + stride - 1)/stride
333 // final_value= trip_count * stride + init_trip.
334 // Use HW instructions to calculate it when it can overflow in integer.
335 // Note, final_value should fit into integer since counted loop has
336 // limit check: limit <= max_int-stride.
337 class LoopLimitNode : public Node {
338 enum { Init=1, Limit=2, Stride=3 };
339 public:
340 LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(0,init,limit,stride) {
341 // Put it on the Macro nodes list to optimize during macro nodes expansion.
342 init_flags(Flag_is_macro);
343 C->add_macro_node(this);
344 }
345 virtual int Opcode() const;
346 virtual const Type *bottom_type() const { return TypeInt::INT; }
347 virtual uint ideal_reg() const { return Op_RegI; }
348 virtual const Type* Value(PhaseGVN* phase) const;
349 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
350 virtual Node* Identity(PhaseGVN* phase);
351 };
352
353 // -----------------------------IdealLoopTree----------------------------------
354 class IdealLoopTree : public ResourceObj {
355 public:
356 IdealLoopTree *_parent; // Parent in loop tree
357 IdealLoopTree *_next; // Next sibling in loop tree
358 IdealLoopTree *_child; // First child in loop tree
359
360 // The head-tail backedge defines the loop.
361 // If tail is NULL then this loop has multiple backedges as part of the
362 // same loop. During cleanup I'll peel off the multiple backedges; merge
363 // them at the loop bottom and flow 1 real backedge into the loop.
364 Node *_head; // Head of loop
365 Node *_tail; // Tail of loop
366 inline Node *tail(); // Handle lazy update of _tail field
367 PhaseIdealLoop* _phase;
368 int _local_loop_unroll_limit;
369 int _local_loop_unroll_factor;
370
371 Node_List _body; // Loop body for inner loops
372
373 uint8_t _nest; // Nesting depth
374 uint8_t _irreducible:1, // True if irreducible
375 _has_call:1, // True if has call safepoint
376 _has_sfpt:1, // True if has non-call safepoint
377 _rce_candidate:1; // True if candidate for range check elimination
378
379 Node_List* _safepts; // List of safepoints in this loop
380 Node_List* _required_safept; // A inner loop cannot delete these safepts;
381 bool _allow_optimizations; // Allow loop optimizations
382
383 IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
384 : _parent(0), _next(0), _child(0),
385 _head(head), _tail(tail),
386 _phase(phase),
387 _safepts(NULL),
388 _required_safept(NULL),
389 _allow_optimizations(true),
390 _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
391 _local_loop_unroll_limit(0), _local_loop_unroll_factor(0)
392 { }
393
394 // Is 'l' a member of 'this'?
395 bool is_member(const IdealLoopTree *l) const; // Test for nested membership
396
397 // Set loop nesting depth. Accumulate has_call bits.
398 int set_nest( uint depth );
399
400 // Split out multiple fall-in edges from the loop header. Move them to a
401 // private RegionNode before the loop. This becomes the loop landing pad.
402 void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
403
404 // Split out the outermost loop from this shared header.
405 void split_outer_loop( PhaseIdealLoop *phase );
406
407 // Merge all the backedges from the shared header into a private Region.
408 // Feed that region as the one backedge to this loop.
409 void merge_many_backedges( PhaseIdealLoop *phase );
410
411 // Split shared headers and insert loop landing pads.
412 // Insert a LoopNode to replace the RegionNode.
413 // Returns TRUE if loop tree is structurally changed.
414 bool beautify_loops( PhaseIdealLoop *phase );
415
416 // Perform optimization to use the loop predicates for null checks and range checks.
417 // Applies to any loop level (not just the innermost one)
418 bool loop_predication( PhaseIdealLoop *phase);
419
420 // Perform iteration-splitting on inner loops. Split iterations to
421 // avoid range checks or one-shot null checks. Returns false if the
422 // current round of loop opts should stop.
423 bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
424
425 // Driver for various flavors of iteration splitting. Returns false
426 // if the current round of loop opts should stop.
427 bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
428
429 // Given dominators, try to find loops with calls that must always be
430 // executed (call dominates loop tail). These loops do not need non-call
431 // safepoints (ncsfpt).
432 void check_safepts(VectorSet &visited, Node_List &stack);
433
434 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
435 // encountered.
436 void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
437
438 // Remove safepoints from loop. Optionally keeping one.
439 void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);
440
441 // Convert to counted loops where possible
442 void counted_loop( PhaseIdealLoop *phase );
443
444 // Check for Node being a loop-breaking test
445 Node *is_loop_exit(Node *iff) const;
446
447 // Returns true if ctrl is executed on every complete iteration
448 bool dominates_backedge(Node* ctrl);
449
450 // Remove simplistic dead code from loop body
451 void DCE_loop_body();
452
453 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
454 // Replace with a 1-in-10 exit guess.
455 void adjust_loop_exit_prob( PhaseIdealLoop *phase );
456
457 // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
458 // Useful for unrolling loops with NO array accesses.
459 bool policy_peel_only( PhaseIdealLoop *phase ) const;
460
461 // Return TRUE or FALSE if the loop should be unswitched -- clone
462 // loop with an invariant test
463 bool policy_unswitching( PhaseIdealLoop *phase ) const;
464
465 // Micro-benchmark spamming. Remove empty loops.
466 bool policy_do_remove_empty_loop( PhaseIdealLoop *phase );
467
468 // Convert one iteration loop into normal code.
469 bool policy_do_one_iteration_loop( PhaseIdealLoop *phase );
470
471 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
472 // make some loop-invariant test (usually a null-check) happen before the
473 // loop.
474 bool policy_peeling( PhaseIdealLoop *phase ) const;
475
476 // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
477 // known trip count in the counted loop node.
478 bool policy_maximally_unroll( PhaseIdealLoop *phase ) const;
479
480 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
481 // the loop is a CountedLoop and the body is small enough.
482 bool policy_unroll(PhaseIdealLoop *phase);
483
484 // Loop analyses to map to a maximal superword unrolling for vectorization.
485 void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);
486
487 // Return TRUE or FALSE if the loop should be range-check-eliminated.
488 // Gather a list of IF tests that are dominated by iteration splitting;
489 // also gather the end of the first split and the start of the 2nd split.
490 bool policy_range_check( PhaseIdealLoop *phase ) const;
491
492 // Return TRUE or FALSE if the loop should be cache-line aligned.
493 // Gather the expression that does the alignment. Note that only
494 // one array base can be aligned in a loop (unless the VM guarantees
495 // mutual alignment). Note that if we vectorize short memory ops
496 // into longer memory ops, we may want to increase alignment.
497 bool policy_align( PhaseIdealLoop *phase ) const;
498
499 // Return TRUE if "iff" is a range check.
500 bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const;
501
502 // Compute loop exact trip count if possible
503 void compute_exact_trip_count( PhaseIdealLoop *phase );
504
505 // Compute loop trip count from profile data
506 void compute_profile_trip_cnt( PhaseIdealLoop *phase );
507
508 // Reassociate invariant expressions.
509 void reassociate_invariants(PhaseIdealLoop *phase);
510 // Reassociate invariant add and subtract expressions.
511 Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
512 // Return nonzero index of invariant operand if invariant and variant
513 // are combined with an Add or Sub. Helper for reassociate_invariants.
514 int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
515
516 // Return true if n is invariant
517 bool is_invariant(Node* n) const;
518
519 // Put loop body on igvn work list
520 void record_for_igvn();
521
522 bool is_loop() { return !_irreducible && _tail && !_tail->is_top(); }
523 bool is_inner() { return is_loop() && _child == NULL; }
524 bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); }
525
526 void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);
527
528 #ifndef PRODUCT
529 void dump_head( ) const; // Dump loop head only
530 void dump() const; // Dump this loop recursively
531 void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
532 #endif
533
534 };
535
536 // -----------------------------PhaseIdealLoop---------------------------------
537 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees into a
538 // loop tree. Drives the loop-based transformations on the ideal graph.
539 class PhaseIdealLoop : public PhaseTransform {
540 friend class IdealLoopTree;
541 friend class SuperWord;
542 friend class CountedLoopReserveKit;
543
544 // Pre-computed def-use info
545 PhaseIterGVN &_igvn;
546
547 // Head of loop tree
548 IdealLoopTree *_ltree_root;
549
550 // Array of pre-order numbers, plus post-visited bit.
551 // ZERO for not pre-visited. EVEN for pre-visited but not post-visited.
552 // ODD for post-visited. Other bits are the pre-order number.
553 uint *_preorders;
554 uint _max_preorder;
555
556 const PhaseIdealLoop* _verify_me;
557 bool _verify_only;
558
559 // Allocate _preorders[] array
560 void allocate_preorders() {
561 _max_preorder = C->unique()+8;
562 _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
563 memset(_preorders, 0, sizeof(uint) * _max_preorder);
564 }
565
566 // Allocate _preorders[] array
567 void reallocate_preorders() {
568 if ( _max_preorder < C->unique() ) {
569 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
570 _max_preorder = C->unique();
571 }
572 memset(_preorders, 0, sizeof(uint) * _max_preorder);
573 }
574
575 // Check to grow _preorders[] array for the case when build_loop_tree_impl()
576 // adds new nodes.
577 void check_grow_preorders( ) {
578 if ( _max_preorder < C->unique() ) {
579 uint newsize = _max_preorder<<1; // double size of array
580 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
581 memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
582 _max_preorder = newsize;
583 }
584 }
585 // Check for pre-visited. Zero for NOT visited; non-zero for visited.
586 int is_visited( Node *n ) const { return _preorders[n->_idx]; }
587 // Pre-order numbers are written to the Nodes array as low-bit-set values.
588 void set_preorder_visited( Node *n, int pre_order ) {
589 assert( !is_visited( n ), "already set" );
590 _preorders[n->_idx] = (pre_order<<1);
591 };
592 // Return pre-order number.
593 int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
594
595 // Check for being post-visited.
596 // Should be previsited already (checked with assert(is_visited(n))).
597 int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
598
599 // Mark as post visited
600 void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
601
602 // Set/get control node out. Set lower bit to distinguish from IdealLoopTree
603 // Returns true if "n" is a data node, false if it's a control node.
604 bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
605
606 // clear out dead code after build_loop_late
607 Node_List _deadlist;
608
609 // Support for faster execution of get_late_ctrl()/dom_lca()
610 // when a node has many uses and dominator depth is deep.
611 Node_Array _dom_lca_tags;
612 void init_dom_lca_tags();
613 void clear_dom_lca_tags();
614
615 // Helper for debugging bad dominance relationships
616 bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);
617
618 Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);
619
620 // Inline wrapper for frequent cases:
621 // 1) only one use
622 // 2) a use is the same as the current LCA passed as 'n1'
623 Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
624 assert( n->is_CFG(), "" );
625 // Fast-path NULL lca
626 if( lca != NULL && lca != n ) {
627 assert( lca->is_CFG(), "" );
628 // find LCA of all uses
629 n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
630 }
631 return find_non_split_ctrl(n);
632 }
633 Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
634
635 // Helper function for directing control inputs away from CFG split
636 // points.
637 Node *find_non_split_ctrl( Node *ctrl ) const {
638 if (ctrl != NULL) {
639 if (ctrl->is_MultiBranch()) {
640 ctrl = ctrl->in(0);
641 }
642 assert(ctrl->is_CFG(), "CFG");
643 }
644 return ctrl;
645 }
646
647 bool cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
648
649 public:
650 bool has_node( Node* n ) const {
651 guarantee(n != NULL, "No Node.");
652 return _nodes[n->_idx] != NULL;
653 }
654 // check if transform created new nodes that need _ctrl recorded
655 Node *get_late_ctrl( Node *n, Node *early );
656 Node *get_early_ctrl( Node *n );
657 Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
658 void set_early_ctrl( Node *n );
659 void set_subtree_ctrl( Node *root );
660 void set_ctrl( Node *n, Node *ctrl ) {
661 assert( !has_node(n) || has_ctrl(n), "" );
662 assert( ctrl->in(0), "cannot set dead control node" );
663 assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
664 _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
665 }
666 // Set control and update loop membership
667 void set_ctrl_and_loop(Node* n, Node* ctrl) {
668 IdealLoopTree* old_loop = get_loop(get_ctrl(n));
669 IdealLoopTree* new_loop = get_loop(ctrl);
670 if (old_loop != new_loop) {
671 if (old_loop->_child == NULL) old_loop->_body.yank(n);
672 if (new_loop->_child == NULL) new_loop->_body.push(n);
673 }
674 set_ctrl(n, ctrl);
675 }
676 // Control nodes can be replaced or subsumed. During this pass they
677 // get their replacement Node in slot 1. Instead of updating the block
678 // location of all Nodes in the subsumed block, we lazily do it. As we
679 // pull such a subsumed block out of the array, we write back the final
680 // correct block.
681 Node *get_ctrl( Node *i ) {
682 assert(has_node(i), "");
683 Node *n = get_ctrl_no_update(i);
684 _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
685 assert(has_node(i) && has_ctrl(i), "");
686 assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
687 return n;
688 }
689 // true if CFG node d dominates CFG node n
690 bool is_dominator(Node *d, Node *n);
691 // return get_ctrl for a data node and self(n) for a CFG node
692 Node* ctrl_or_self(Node* n) {
693 if (has_ctrl(n))
694 return get_ctrl(n);
695 else {
696 assert (n->is_CFG(), "must be a CFG node");
697 return n;
698 }
699 }
700
701 private:
702 Node *get_ctrl_no_update_helper(Node *i) const {
703 assert(has_ctrl(i), "should be control, not loop");
704 return (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
705 }
706
707 Node *get_ctrl_no_update(Node *i) const {
708 assert( has_ctrl(i), "" );
709 Node *n = get_ctrl_no_update_helper(i);
710 if (!n->in(0)) {
711 // Skip dead CFG nodes
712 do {
713 n = get_ctrl_no_update_helper(n);
714 } while (!n->in(0));
715 n = find_non_split_ctrl(n);
716 }
717 return n;
718 }
719
720 // Check for loop being set
721 // "n" must be a control node. Returns true if "n" is known to be in a loop.
722 bool has_loop( Node *n ) const {
723 assert(!has_node(n) || !has_ctrl(n), "");
724 return has_node(n);
725 }
726 // Set loop
727 void set_loop( Node *n, IdealLoopTree *loop ) {
728 _nodes.map(n->_idx, (Node*)loop);
729 }
730 // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms. Replace
731 // the 'old_node' with 'new_node'. Kill old-node. Add a reference
732 // from old_node to new_node to support the lazy update. Reference
733 // replaces loop reference, since that is not needed for dead node.
734 public:
735 void lazy_update(Node *old_node, Node *new_node) {
736 assert(old_node != new_node, "no cycles please");
737 // Re-use the side array slot for this node to provide the
738 // forwarding pointer.
739 _nodes.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
740 }
741 void lazy_replace(Node *old_node, Node *new_node) {
742 _igvn.replace_node(old_node, new_node);
743 lazy_update(old_node, new_node);
744 }
745
746 private:
747
748 // Place 'n' in some loop nest, where 'n' is a CFG node
749 void build_loop_tree();
750 int build_loop_tree_impl( Node *n, int pre_order );
751 // Insert loop into the existing loop tree. 'innermost' is a leaf of the
752 // loop tree, not the root.
753 IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
754
755 // Place Data nodes in some loop nest
756 void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
757 void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
758 void build_loop_late_post ( Node* n );
759
760 // Array of immediate dominance info for each CFG node indexed by node idx
761 private:
762 uint _idom_size;
763 Node **_idom; // Array of immediate dominators
764 uint *_dom_depth; // Used for fast LCA test
765 GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
766
767 Node* idom_no_update(Node* d) const {
768 assert(d->_idx < _idom_size, "oob");
769 Node* n = _idom[d->_idx];
770 assert(n != NULL,"Bad immediate dominator info.");
771 while (n->in(0) == NULL) { // Skip dead CFG nodes
772 //n = n->in(1);
773 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
774 assert(n != NULL,"Bad immediate dominator info.");
775 }
776 return n;
777 }
778 Node *idom(Node* d) const {
779 uint didx = d->_idx;
780 Node *n = idom_no_update(d);
781 _idom[didx] = n; // Lazily remove dead CFG nodes from table.
782 return n;
783 }
784 uint dom_depth(Node* d) const {
785 guarantee(d != NULL, "Null dominator info.");
786 guarantee(d->_idx < _idom_size, "");
787 return _dom_depth[d->_idx];
788 }
789 void set_idom(Node* d, Node* n, uint dom_depth);
790 // Locally compute IDOM using dom_lca call
791 Node *compute_idom( Node *region ) const;
792 // Recompute dom_depth
793 void recompute_dom_depth();
794
795 // Is safept not required by an outer loop?
796 bool is_deleteable_safept(Node* sfpt);
797
798 // Replace parallel induction variable (parallel to trip counter)
799 void replace_parallel_iv(IdealLoopTree *loop);
800
801 // Perform verification that the graph is valid.
802 PhaseIdealLoop( PhaseIterGVN &igvn) :
803 PhaseTransform(Ideal_Loop),
804 _igvn(igvn),
805 _dom_lca_tags(arena()), // Thread::resource_area
806 _verify_me(NULL),
807 _verify_only(true) {
808 build_and_optimize(false, false);
809 }
810
811 // build the loop tree and perform any requested optimizations
812 void build_and_optimize(bool do_split_if, bool skip_loop_opts);
813
814 public:
815 // Dominators for the sea of nodes
816 void Dominators();
817 Node *dom_lca( Node *n1, Node *n2 ) const {
818 return find_non_split_ctrl(dom_lca_internal(n1, n2));
819 }
820 Node *dom_lca_internal( Node *n1, Node *n2 ) const;
821
822 // Compute the Ideal Node to Loop mapping
823 PhaseIdealLoop( PhaseIterGVN &igvn, bool do_split_ifs, bool skip_loop_opts = false) :
824 PhaseTransform(Ideal_Loop),
825 _igvn(igvn),
826 _dom_lca_tags(arena()), // Thread::resource_area
827 _verify_me(NULL),
828 _verify_only(false) {
829 build_and_optimize(do_split_ifs, skip_loop_opts);
830 }
831
832 // Verify that verify_me made the same decisions as a fresh run.
833 PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) :
834 PhaseTransform(Ideal_Loop),
835 _igvn(igvn),
836 _dom_lca_tags(arena()), // Thread::resource_area
837 _verify_me(verify_me),
838 _verify_only(false) {
839 build_and_optimize(false, false);
840 }
841
842 // Build and verify the loop tree without modifying the graph. This
843 // is useful to verify that all inputs properly dominate their uses.
844 static void verify(PhaseIterGVN& igvn) {
845 #ifdef ASSERT
846 PhaseIdealLoop v(igvn);
847 #endif
848 }
849
850 // True if the method has at least 1 irreducible loop
851 bool _has_irreducible_loops;
852
853 // Per-Node transform
854 virtual Node *transform( Node *a_node ) { return 0; }
855
856 bool is_counted_loop( Node *x, IdealLoopTree *loop );
857
858 Node* exact_limit( IdealLoopTree *loop );
859
860 // Return a post-walked LoopNode
861 IdealLoopTree *get_loop( Node *n ) const {
862 // Dead nodes have no loop, so return the top level loop instead
863 if (!has_node(n)) return _ltree_root;
864 assert(!has_ctrl(n), "");
865 return (IdealLoopTree*)_nodes[n->_idx];
866 }
867
868 // Is 'n' a (nested) member of 'loop'?
869 int is_member( const IdealLoopTree *loop, Node *n ) const {
870 return loop->is_member(get_loop(n)); }
871
872 // This is the basic building block of the loop optimizations. It clones an
873 // entire loop body. It makes an old_new loop body mapping; with this
874 // mapping you can find the new-loop equivalent to an old-loop node. All
875 // new-loop nodes are exactly equal to their old-loop counterparts, all
876 // edges are the same. All exits from the old-loop now have a RegionNode
877 // that merges the equivalent new-loop path. This is true even for the
878 // normal "loop-exit" condition. All uses of loop-invariant old-loop values
879 // now come from (one or more) Phis that merge their new-loop equivalents.
880 // Parameter side_by_side_idom:
881 // When side_by_size_idom is NULL, the dominator tree is constructed for
882 // the clone loop to dominate the original. Used in construction of
883 // pre-main-post loop sequence.
884 // When nonnull, the clone and original are side-by-side, both are
885 // dominated by the passed in side_by_side_idom node. Used in
886 // construction of unswitched loops.
887 void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
888 Node* side_by_side_idom = NULL);
889
890 // If we got the effect of peeling, either by actually peeling or by
891 // making a pre-loop which must execute at least once, we can remove
892 // all loop-invariant dominated tests in the main body.
893 void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
894
895 // Generate code to do a loop peel for the given loop (and body).
896 // old_new is a temp array.
897 void do_peeling( IdealLoopTree *loop, Node_List &old_new );
898
899 // Add pre and post loops around the given loop. These loops are used
900 // during RCE, unrolling and aligning loops.
901 void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
902 // Add a vector post loop between a vector main loop and the current post loop
903 void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
904 // If Node n lives in the back_ctrl block, we clone a private version of n
905 // in preheader_ctrl block and return that, otherwise return n.
906 Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );
907
908 // Take steps to maximally unroll the loop. Peel any odd iterations, then
909 // unroll to do double iterations. The next round of major loop transforms
910 // will repeat till the doubled loop body does all remaining iterations in 1
911 // pass.
912 void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
913
914 // Unroll the loop body one step - make each trip do 2 iterations.
915 void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
916
917 // Mark vector reduction candidates before loop unrolling
918 void mark_reductions( IdealLoopTree *loop );
919
920 // Return true if exp is a constant times an induction var
921 bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
922
923 // Return true if exp is a scaled induction var plus (or minus) constant
924 bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
925
926 // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
927 ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
928 Deoptimization::DeoptReason reason,
929 int opcode);
930 void register_control(Node* n, IdealLoopTree *loop, Node* pred);
931
932 // Clone loop predicates to cloned loops (peeled, unswitched)
933 static ProjNode* clone_predicate(ProjNode* predicate_proj, Node* new_entry,
934 Deoptimization::DeoptReason reason,
935 PhaseIdealLoop* loop_phase,
936 PhaseIterGVN* igvn);
937
938 static Node* clone_loop_predicates(Node* old_entry, Node* new_entry,
939 bool clone_limit_check,
940 PhaseIdealLoop* loop_phase,
941 PhaseIterGVN* igvn);
942 Node* clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check);
943
944 static Node* skip_loop_predicates(Node* entry);
945
946 // Find a good location to insert a predicate
947 static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
948 // Find a predicate
949 static Node* find_predicate(Node* entry);
950 // Construct a range check for a predicate if
951 BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
952 int scale, Node* offset,
953 Node* init, Node* limit, Node* stride,
954 Node* range, bool upper);
955
956 // Implementation of the loop predication to promote checks outside the loop
957 bool loop_predication_impl(IdealLoopTree *loop);
958
959 // Helper function to collect predicate for eliminating the useless ones
960 void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
961 void eliminate_useless_predicates();
962
963 // Change the control input of expensive nodes to allow commoning by
964 // IGVN when it is guaranteed to not result in a more frequent
965 // execution of the expensive node. Return true if progress.
966 bool process_expensive_nodes();
967
968 // Check whether node has become unreachable
969 bool is_node_unreachable(Node *n) const {
970 return !has_node(n) || n->is_unreachable(_igvn);
971 }
972
973 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
974 void do_range_check( IdealLoopTree *loop, Node_List &old_new );
975
976 // Create a slow version of the loop by cloning the loop
977 // and inserting an if to select fast-slow versions.
978 ProjNode* create_slow_version_of_loop(IdealLoopTree *loop,
979 Node_List &old_new,
980 int opcode);
981
982 // Clone a loop and return the clone head (clone_loop_head).
983 // Added nodes include int(1), int(0) - disconnected, If, IfTrue, IfFalse,
984 // This routine was created for usage in CountedLoopReserveKit.
985 //
986 // int(1) -> If -> IfTrue -> original_loop_head
987 // |
988 // V
989 // IfFalse -> clone_loop_head (returned by function pointer)
990 //
991 LoopNode* create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk);
992 // Clone loop with an invariant test (that does not exit) and
993 // insert a clone of the test that selects which version to
994 // execute.
995 void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
996
997 // Find candidate "if" for unswitching
998 IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
999
1000 // Range Check Elimination uses this function!
1001 // Constrain the main loop iterations so the affine function:
1002 // low_limit <= scale_con * I + offset < upper_limit
1003 // always holds true. That is, either increase the number of iterations in
1004 // the pre-loop or the post-loop until the condition holds true in the main
1005 // loop. Scale_con, offset and limit are all loop invariant.
1006 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 );
1007 // Helper function for add_constraint().
1008 Node* adjust_limit( int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl );
1009
1010 // Partially peel loop up through last_peel node.
1011 bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
1012
1013 // Create a scheduled list of nodes control dependent on ctrl set.
1014 void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
1015 // Has a use in the vector set
1016 bool has_use_in_set( Node* n, VectorSet& vset );
1017 // Has use internal to the vector set (ie. not in a phi at the loop head)
1018 bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
1019 // clone "n" for uses that are outside of loop
1020 int clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
1021 // clone "n" for special uses that are in the not_peeled region
1022 void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
1023 VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
1024 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
1025 void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
1026 #ifdef ASSERT
1027 // Validate the loop partition sets: peel and not_peel
1028 bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
1029 // Ensure that uses outside of loop are of the right form
1030 bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
1031 uint orig_exit_idx, uint clone_exit_idx);
1032 bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
1033 #endif
1034
1035 // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
1036 int stride_of_possible_iv( Node* iff );
1037 bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
1038 // Return the (unique) control output node that's in the loop (if it exists.)
1039 Node* stay_in_loop( Node* n, IdealLoopTree *loop);
1040 // Insert a signed compare loop exit cloned from an unsigned compare.
1041 IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
1042 void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
1043 // Utility to register node "n" with PhaseIdealLoop
1044 void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
1045 // Utility to create an if-projection
1046 ProjNode* proj_clone(ProjNode* p, IfNode* iff);
1047 // Force the iff control output to be the live_proj
1048 Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
1049 // Insert a region before an if projection
1050 RegionNode* insert_region_before_proj(ProjNode* proj);
1051 // Insert a new if before an if projection
1052 ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
1053
1054 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
1055 // "Nearly" because all Nodes have been cloned from the original in the loop,
1056 // but the fall-in edges to the Cmp are different. Clone bool/Cmp pairs
1057 // through the Phi recursively, and return a Bool.
1058 BoolNode *clone_iff( PhiNode *phi, IdealLoopTree *loop );
1059 CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
1060
1061
1062 // Rework addressing expressions to get the most loop-invariant stuff
1063 // moved out. We'd like to do all associative operators, but it's especially
1064 // important (common) to do address expressions.
1065 Node *remix_address_expressions( Node *n );
1066
1067 // Attempt to use a conditional move instead of a phi/branch
1068 Node *conditional_move( Node *n );
1069
1070 // Reorganize offset computations to lower register pressure.
1071 // Mostly prevent loop-fallout uses of the pre-incremented trip counter
1072 // (which are then alive with the post-incremented trip counter
1073 // forcing an extra register move)
1074 void reorg_offsets( IdealLoopTree *loop );
1075
1076 // Check for aggressive application of 'split-if' optimization,
1077 // using basic block level info.
1078 void split_if_with_blocks ( VectorSet &visited, Node_Stack &nstack );
1079 Node *split_if_with_blocks_pre ( Node *n );
1080 void split_if_with_blocks_post( Node *n );
1081 Node *has_local_phi_input( Node *n );
1082 // Mark an IfNode as being dominated by a prior test,
1083 // without actually altering the CFG (and hence IDOM info).
1084 void dominated_by( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
1085
1086 // Split Node 'n' through merge point
1087 Node *split_thru_region( Node *n, Node *region );
1088 // Split Node 'n' through merge point if there is enough win.
1089 Node *split_thru_phi( Node *n, Node *region, int policy );
1090 // Found an If getting its condition-code input from a Phi in the
1091 // same block. Split thru the Region.
1092 void do_split_if( Node *iff );
1093
1094 // Conversion of fill/copy patterns into intrisic versions
1095 bool do_intrinsify_fill();
1096 bool intrinsify_fill(IdealLoopTree* lpt);
1097 bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
1098 Node*& shift, Node*& offset);
1099
1100 private:
1101 // Return a type based on condition control flow
1102 const TypeInt* filtered_type( Node *n, Node* n_ctrl);
1103 const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
1104 // Helpers for filtered type
1105 const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
1106
1107 // Helper functions
1108 Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
1109 Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
1110 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 );
1111 bool split_up( Node *n, Node *blk1, Node *blk2 );
1112 void sink_use( Node *use, Node *post_loop );
1113 Node *place_near_use( Node *useblock ) const;
1114 Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
1115 void try_move_store_after_loop(Node* n);
1116
1117 bool _created_loop_node;
1118 public:
1119 void set_created_loop_node() { _created_loop_node = true; }
1120 bool created_loop_node() { return _created_loop_node; }
1121 void register_new_node( Node *n, Node *blk );
1122
1123 #ifdef ASSERT
1124 void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
1125 #endif
1126
1127 #ifndef PRODUCT
1128 void dump( ) const;
1129 void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const;
1130 void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const;
1131 void verify() const; // Major slow :-)
1132 void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const;
1133 IdealLoopTree *get_loop_idx(Node* n) const {
1134 // Dead nodes have no loop, so return the top level loop instead
1135 return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
1136 }
1137 // Print some stats
1138 static void print_statistics();
1139 static int _loop_invokes; // Count of PhaseIdealLoop invokes
1140 static int _loop_work; // Sum of PhaseIdealLoop x _unique
1141 #endif
1142 };
1143
1144 // This kit may be used for making of a reserved copy of a loop before this loop
1145 // goes under non-reversible changes.
1146 //
1147 // Function create_reserve() creates a reserved copy (clone) of the loop.
1148 // The reserved copy is created by calling
1149 // PhaseIdealLoop::create_reserve_version_of_loop - see there how
1150 // the original and reserved loops are connected in the outer graph.
1151 // If create_reserve succeeded, it returns 'true' and _has_reserved is set to 'true'.
1152 //
1153 // By default the reserved copy (clone) of the loop is created as dead code - it is
1154 // dominated in the outer loop by this node chain:
1155 // intcon(1)->If->IfFalse->reserved_copy.
1156 // The original loop is dominated by the the same node chain but IfTrue projection:
1157 // intcon(0)->If->IfTrue->original_loop.
1158 //
1159 // In this implementation of CountedLoopReserveKit the ctor includes create_reserve()
1160 // and the dtor, checks _use_new value.
1161 // If _use_new == false, it "switches" control to reserved copy of the loop
1162 // by simple replacing of node intcon(1) with node intcon(0).
1163 //
1164 // Here is a proposed example of usage (see also SuperWord::output in superword.cpp).
1165 //
1166 // void CountedLoopReserveKit_example()
1167 // {
1168 // CountedLoopReserveKit lrk((phase, lpt, DoReserveCopy = true); // create local object
1169 // if (DoReserveCopy && !lrk.has_reserved()) {
1170 // return; //failed to create reserved loop copy
1171 // }
1172 // ...
1173 // //something is wrong, switch to original loop
1174 /// if(something_is_wrong) return; // ~CountedLoopReserveKit makes the switch
1175 // ...
1176 // //everything worked ok, return with the newly modified loop
1177 // lrk.use_new();
1178 // return; // ~CountedLoopReserveKit does nothing once use_new() was called
1179 // }
1180 //
1181 // Keep in mind, that by default if create_reserve() is not followed by use_new()
1182 // the dtor will "switch to the original" loop.
1183 // NOTE. You you modify outside of the original loop this class is no help.
1184 //
1185 class CountedLoopReserveKit {
1186 private:
1187 PhaseIdealLoop* _phase;
1188 IdealLoopTree* _lpt;
1189 LoopNode* _lp;
1190 IfNode* _iff;
1191 LoopNode* _lp_reserved;
1192 bool _has_reserved;
1193 bool _use_new;
1194 const bool _active; //may be set to false in ctor, then the object is dummy
1195
1196 public:
1197 CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active);
1198 ~CountedLoopReserveKit();
1199 void use_new() {_use_new = true;}
1200 void set_iff(IfNode* x) {_iff = x;}
1201 bool has_reserved() const { return _active && _has_reserved;}
1202 private:
1203 bool create_reserve();
1204 };// class CountedLoopReserveKit
1205
1206 inline Node* IdealLoopTree::tail() {
1207 // Handle lazy update of _tail field
1208 Node *n = _tail;
1209 //while( !n->in(0) ) // Skip dead CFG nodes
1210 //n = n->in(1);
1211 if (n->in(0) == NULL)
1212 n = _phase->get_ctrl(n);
1213 _tail = n;
1214 return n;
1215 }
1216
1217
1218 // Iterate over the loop tree using a preorder, left-to-right traversal.
1219 //
1220 // Example that visits all counted loops from within PhaseIdealLoop
1221 //
1222 // for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
1223 // IdealLoopTree* lpt = iter.current();
1224 // if (!lpt->is_counted()) continue;
1225 // ...
1226 class LoopTreeIterator : public StackObj {
1227 private:
1228 IdealLoopTree* _root;
1229 IdealLoopTree* _curnt;
1230
1231 public:
1232 LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
1233
1234 bool done() { return _curnt == NULL; } // Finished iterating?
1235
1236 void next(); // Advance to next loop tree
1237
1238 IdealLoopTree* current() { return _curnt; } // Return current value of iterator.
1239 };
1240
1241 #endif // SHARE_VM_OPTO_LOOPNODE_HPP