1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)loopnode.hpp 1.146 07/10/23 13:12:55 JVM"
3 #endif
4 /*
5 * Copyright 1998-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 class CmpNode;
29 class CountedLoopEndNode;
30 class CountedLoopNode;
31 class IdealLoopTree;
32 class LoopNode;
33 class Node;
34 class PhaseIdealLoop;
35 class VectorSet;
36 struct small_cache;
37
38 //
39 // I D E A L I Z E D L O O P S
40 //
41 // Idealized loops are the set of loops I perform more interesting
42 // transformations on, beyond simple hoisting.
43
44 //------------------------------LoopNode---------------------------------------
45 // Simple loop header. Fall in path on left, loop-back path on right.
46 class LoopNode : public RegionNode {
47 // Size is bigger to hold the flags. However, the flags do not change
48 // the semantics so it does not appear in the hash & cmp functions.
49 virtual uint size_of() const { return sizeof(*this); }
50 protected:
51 short _loop_flags;
52 // Names for flag bitfields
53 enum { pre_post_main=0, inner_loop=8, partial_peel_loop=16, partial_peel_failed=32 };
54 char _unswitch_count;
55 enum { _unswitch_max=3 };
56
57 public:
58 // Names for edge indices
59 enum { Self=0, EntryControl, LoopBackControl };
60
61 int is_inner_loop() const { return _loop_flags & inner_loop; }
62 void set_inner_loop() { _loop_flags |= inner_loop; }
63
64 int is_partial_peel_loop() const { return _loop_flags & partial_peel_loop; }
65 void set_partial_peel_loop() { _loop_flags |= partial_peel_loop; }
66 int partial_peel_has_failed() const { return _loop_flags & partial_peel_failed; }
67 void mark_partial_peel_failed() { _loop_flags |= partial_peel_failed; }
68
69 int unswitch_max() { return _unswitch_max; }
70 int unswitch_count() { return _unswitch_count; }
71 void set_unswitch_count(int val) {
72 assert (val <= unswitch_max(), "too many unswitches");
73 _unswitch_count = val;
74 }
75
76 LoopNode( Node *entry, Node *backedge ) : RegionNode(3), _loop_flags(0), _unswitch_count(0) {
77 init_class_id(Class_Loop);
78 init_req(EntryControl, entry);
79 init_req(LoopBackControl, backedge);
80 }
81
82 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
83 virtual int Opcode() const;
84 bool can_be_counted_loop(PhaseTransform* phase) const {
85 return req() == 3 && in(0) != NULL &&
86 in(1) != NULL && phase->type(in(1)) != Type::TOP &&
87 in(2) != NULL && phase->type(in(2)) != Type::TOP;
88 }
89 #ifndef PRODUCT
90 virtual void dump_spec(outputStream *st) const;
91 #endif
92 };
93
94 //------------------------------Counted Loops----------------------------------
95 // Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
96 // path (and maybe some other exit paths). The trip-counter exit is always
97 // last in the loop. The trip-counter does not have to stride by a constant,
98 // but it does have to stride by a loop-invariant amount; the exit value is
99 // also loop invariant.
100
101 // CountedLoopNodes and CountedLoopEndNodes come in matched pairs. The
102 // CountedLoopNode has the incoming loop control and the loop-back-control
103 // which is always the IfTrue before the matching CountedLoopEndNode. The
104 // CountedLoopEndNode has an incoming control (possibly not the
105 // CountedLoopNode if there is control flow in the loop), the post-increment
106 // trip-counter value, and the limit. The trip-counter value is always of
107 // the form (Op old-trip-counter stride). The old-trip-counter is produced
108 // by a Phi connected to the CountedLoopNode. The stride is loop invariant.
109 // The Op is any commutable opcode, including Add, Mul, Xor. The
110 // CountedLoopEndNode also takes in the loop-invariant limit value.
111
112 // From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
113 // loop-back control. From CountedLoopEndNodes I can reach CountedLoopNodes
114 // via the old-trip-counter from the Op node.
115
116 //------------------------------CountedLoopNode--------------------------------
117 // CountedLoopNodes head simple counted loops. CountedLoopNodes have as
118 // inputs the incoming loop-start control and the loop-back control, so they
119 // act like RegionNodes. They also take in the initial trip counter, the
120 // loop-invariant stride and the loop-invariant limit value. CountedLoopNodes
121 // produce a loop-body control and the trip counter value. Since
122 // CountedLoopNodes behave like RegionNodes I still have a standard CFG model.
123
124 class CountedLoopNode : public LoopNode {
125 // Size is bigger to hold _main_idx. However, _main_idx does not change
126 // the semantics so it does not appear in the hash & cmp functions.
127 virtual uint size_of() const { return sizeof(*this); }
128
129 // For Pre- and Post-loops during debugging ONLY, this holds the index of
130 // the Main CountedLoop. Used to assert that we understand the graph shape.
131 node_idx_t _main_idx;
132
133 // Known trip count calculated by policy_maximally_unroll
134 int _trip_count;
135
136 // Expected trip count from profile data
137 float _profile_trip_cnt;
138
139 // Log2 of original loop bodies in unrolled loop
140 int _unrolled_count_log2;
141
142 // Node count prior to last unrolling - used to decide if
143 // unroll,optimize,unroll,optimize,... is making progress
144 int _node_count_before_unroll;
145
146 public:
147 CountedLoopNode( Node *entry, Node *backedge )
148 : LoopNode(entry, backedge), _trip_count(max_jint),
149 _profile_trip_cnt(COUNT_UNKNOWN), _unrolled_count_log2(0),
150 _node_count_before_unroll(0) {
151 init_class_id(Class_CountedLoop);
152 // Initialize _trip_count to the largest possible value.
153 // Will be reset (lower) if the loop's trip count is known.
154 }
155
156 virtual int Opcode() const;
157 virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
158
159 Node *init_control() const { return in(EntryControl); }
160 Node *back_control() const { return in(LoopBackControl); }
161 CountedLoopEndNode *loopexit() const;
162 Node *init_trip() const;
163 Node *stride() const;
164 int stride_con() const;
165 bool stride_is_con() const;
166 Node *limit() const;
167 Node *incr() const;
168 Node *phi() const;
169
170 // Match increment with optional truncation
171 static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
172
173 // A 'main' loop has a pre-loop and a post-loop. The 'main' loop
174 // can run short a few iterations and may start a few iterations in.
175 // It will be RCE'd and unrolled and aligned.
176
177 // A following 'post' loop will run any remaining iterations. Used
178 // during Range Check Elimination, the 'post' loop will do any final
179 // iterations with full checks. Also used by Loop Unrolling, where
180 // the 'post' loop will do any epilog iterations needed. Basically,
181 // a 'post' loop can not profitably be further unrolled or RCE'd.
182
183 // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
184 // it may do under-flow checks for RCE and may do alignment iterations
185 // so the following main loop 'knows' that it is striding down cache
186 // lines.
187
188 // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
189 // Aligned, may be missing it's pre-loop.
190 enum { Normal=0, Pre=1, Main=2, Post=3, PrePostFlagsMask=3, Main_Has_No_Pre_Loop=4 };
191 int is_normal_loop() const { return (_loop_flags&PrePostFlagsMask) == Normal; }
192 int is_pre_loop () const { return (_loop_flags&PrePostFlagsMask) == Pre; }
193 int is_main_loop () const { return (_loop_flags&PrePostFlagsMask) == Main; }
194 int is_post_loop () const { return (_loop_flags&PrePostFlagsMask) == Post; }
195 int is_main_no_pre_loop() const { return _loop_flags & Main_Has_No_Pre_Loop; }
196 void set_main_no_pre_loop() { _loop_flags |= Main_Has_No_Pre_Loop; }
197
198 int main_idx() const { return _main_idx; }
199
200
201 void set_pre_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
202 void set_main_loop ( ) { assert(is_normal_loop(),""); _loop_flags |= Main; }
203 void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
204 void set_normal_loop( ) { _loop_flags &= ~PrePostFlagsMask; }
205
206 void set_trip_count(int tc) { _trip_count = tc; }
207 int trip_count() { return _trip_count; }
208
209 void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
210 float profile_trip_cnt() { return _profile_trip_cnt; }
211
212 void double_unrolled_count() { _unrolled_count_log2++; }
213 int unrolled_count() { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }
214
215 void set_node_count_before_unroll(int ct) { _node_count_before_unroll = ct; }
216 int node_count_before_unroll() { return _node_count_before_unroll; }
217
218 #ifndef PRODUCT
219 virtual void dump_spec(outputStream *st) const;
220 #endif
221 };
222
223 //------------------------------CountedLoopEndNode-----------------------------
224 // CountedLoopEndNodes end simple trip counted loops. They act much like
225 // IfNodes.
226 class CountedLoopEndNode : public IfNode {
227 public:
228 enum { TestControl, TestValue };
229
230 CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
231 : IfNode( control, test, prob, cnt) {
232 init_class_id(Class_CountedLoopEnd);
233 }
234 virtual int Opcode() const;
235
236 Node *cmp_node() const { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
237 Node *incr() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
238 Node *limit() const { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
239 Node *stride() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
240 Node *phi() const { Node *tmp = incr (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
241 Node *init_trip() const { Node *tmp = phi (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
242 int stride_con() const;
243 bool stride_is_con() const { Node *tmp = stride (); return (tmp != NULL && tmp->is_Con()); }
244 BoolTest::mask test_trip() const { return in(TestValue)->as_Bool()->_test._test; }
245 CountedLoopNode *loopnode() const {
246 Node *ln = phi()->in(0);
247 assert( ln->Opcode() == Op_CountedLoop, "malformed loop" );
248 return (CountedLoopNode*)ln; }
249
250 #ifndef PRODUCT
251 virtual void dump_spec(outputStream *st) const;
252 #endif
253 };
254
255
256 inline CountedLoopEndNode *CountedLoopNode::loopexit() const {
257 Node *bc = back_control();
258 if( bc == NULL ) return NULL;
259 Node *le = bc->in(0);
260 if( le->Opcode() != Op_CountedLoopEnd )
261 return NULL;
262 return (CountedLoopEndNode*)le;
263 }
264 inline Node *CountedLoopNode::init_trip() const { return loopexit() ? loopexit()->init_trip() : NULL; }
265 inline Node *CountedLoopNode::stride() const { return loopexit() ? loopexit()->stride() : NULL; }
266 inline int CountedLoopNode::stride_con() const { return loopexit() ? loopexit()->stride_con() : 0; }
267 inline bool CountedLoopNode::stride_is_con() const { return loopexit() && loopexit()->stride_is_con(); }
268 inline Node *CountedLoopNode::limit() const { return loopexit() ? loopexit()->limit() : NULL; }
269 inline Node *CountedLoopNode::incr() const { return loopexit() ? loopexit()->incr() : NULL; }
270 inline Node *CountedLoopNode::phi() const { return loopexit() ? loopexit()->phi() : NULL; }
271
272
273 // -----------------------------IdealLoopTree----------------------------------
274 class IdealLoopTree : public ResourceObj {
275 public:
276 IdealLoopTree *_parent; // Parent in loop tree
277 IdealLoopTree *_next; // Next sibling in loop tree
278 IdealLoopTree *_child; // First child in loop tree
279
280 // The head-tail backedge defines the loop.
281 // If tail is NULL then this loop has multiple backedges as part of the
282 // same loop. During cleanup I'll peel off the multiple backedges; merge
283 // them at the loop bottom and flow 1 real backedge into the loop.
284 Node *_head; // Head of loop
285 Node *_tail; // Tail of loop
286 inline Node *tail(); // Handle lazy update of _tail field
287 PhaseIdealLoop* _phase;
288
289 Node_List _body; // Loop body for inner loops
290
291 uint8 _nest; // Nesting depth
292 uint8 _irreducible:1, // True if irreducible
293 _has_call:1, // True if has call safepoint
294 _has_sfpt:1, // True if has non-call safepoint
295 _rce_candidate:1; // True if candidate for range check elimination
296
297 Node_List* _required_safept; // A inner loop cannot delete these safepts;
298 bool _allow_optimizations; // Allow loop optimizations
299
300 IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
301 : _parent(0), _next(0), _child(0),
302 _head(head), _tail(tail),
303 _phase(phase),
304 _required_safept(NULL),
305 _allow_optimizations(true),
306 _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0)
307 { }
308
309 // Is 'l' a member of 'this'?
310 int is_member( const IdealLoopTree *l ) const; // Test for nested membership
311
312 // Set loop nesting depth. Accumulate has_call bits.
313 int set_nest( uint depth );
314
315 // Split out multiple fall-in edges from the loop header. Move them to a
316 // private RegionNode before the loop. This becomes the loop landing pad.
317 void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );
318
319 // Split out the outermost loop from this shared header.
320 void split_outer_loop( PhaseIdealLoop *phase );
321
322 // Merge all the backedges from the shared header into a private Region.
323 // Feed that region as the one backedge to this loop.
324 void merge_many_backedges( PhaseIdealLoop *phase );
325
326 // Split shared headers and insert loop landing pads.
327 // Insert a LoopNode to replace the RegionNode.
328 // Returns TRUE if loop tree is structurally changed.
329 bool beautify_loops( PhaseIdealLoop *phase );
330
331 // Perform iteration-splitting on inner loops. Split iterations to
332 // avoid range checks or one-shot null checks. Returns false if the
333 // current round of loop opts should stop.
334 bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );
335
336 // Driver for various flavors of iteration splitting. Returns false
337 // if the current round of loop opts should stop.
338 bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );
339
340 // Given dominators, try to find loops with calls that must always be
341 // executed (call dominates loop tail). These loops do not need non-call
342 // safepoints (ncsfpt).
343 void check_safepts(VectorSet &visited, Node_List &stack);
344
345 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
346 // encountered.
347 void allpaths_check_safepts(VectorSet &visited, Node_List &stack);
348
349 // Convert to counted loops where possible
350 void counted_loop( PhaseIdealLoop *phase );
351
352 // Check for Node being a loop-breaking test
353 Node *is_loop_exit(Node *iff) const;
354
355 // Returns true if ctrl is executed on every complete iteration
356 bool dominates_backedge(Node* ctrl);
357
358 // Remove simplistic dead code from loop body
359 void DCE_loop_body();
360
361 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
362 // Replace with a 1-in-10 exit guess.
363 void adjust_loop_exit_prob( PhaseIdealLoop *phase );
364
365 // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
366 // Useful for unrolling loops with NO array accesses.
367 bool policy_peel_only( PhaseIdealLoop *phase ) const;
368
369 // Return TRUE or FALSE if the loop should be unswitched -- clone
370 // loop with an invariant test
371 bool policy_unswitching( PhaseIdealLoop *phase ) const;
372
373 // Micro-benchmark spamming. Remove empty loops.
374 bool policy_do_remove_empty_loop( PhaseIdealLoop *phase );
375
376 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
377 // make some loop-invariant test (usually a null-check) happen before the
378 // loop.
379 bool policy_peeling( PhaseIdealLoop *phase ) const;
380
381 // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
382 // known trip count in the counted loop node.
383 bool policy_maximally_unroll( PhaseIdealLoop *phase ) const;
384
385 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
386 // the loop is a CountedLoop and the body is small enough.
387 bool policy_unroll( PhaseIdealLoop *phase ) const;
388
389 // Return TRUE or FALSE if the loop should be range-check-eliminated.
390 // Gather a list of IF tests that are dominated by iteration splitting;
391 // also gather the end of the first split and the start of the 2nd split.
392 bool policy_range_check( PhaseIdealLoop *phase ) const;
393
394 // Return TRUE or FALSE if the loop should be cache-line aligned.
395 // Gather the expression that does the alignment. Note that only
396 // one array base can be aligned in a loop (unless the VM guarentees
397 // mutual alignment). Note that if we vectorize short memory ops
398 // into longer memory ops, we may want to increase alignment.
399 bool policy_align( PhaseIdealLoop *phase ) const;
400
401 // Compute loop trip count from profile data
402 void compute_profile_trip_cnt( PhaseIdealLoop *phase );
403
404 // Reassociate invariant expressions.
405 void reassociate_invariants(PhaseIdealLoop *phase);
406 // Reassociate invariant add and subtract expressions.
407 Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
408 // Return nonzero index of invariant operand if invariant and variant
409 // are combined with an Add or Sub. Helper for reassoicate_invariants.
410 int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
411
412 // Return true if n is invariant
413 bool is_invariant(Node* n) const;
414
415 // Put loop body on igvn work list
416 void record_for_igvn();
417
418 bool is_loop() { return !_irreducible && _tail && !_tail->is_top(); }
419 bool is_inner() { return is_loop() && _child == NULL; }
420 bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); }
421
422 #ifndef PRODUCT
423 void dump_head( ) const; // Dump loop head only
424 void dump() const; // Dump this loop recursively
425 void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
426 #endif
427
428 };
429
430 // -----------------------------PhaseIdealLoop---------------------------------
431 // Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees into a
432 // loop tree. Drives the loop-based transformations on the ideal graph.
433 class PhaseIdealLoop : public PhaseTransform {
434 friend class IdealLoopTree;
435 friend class SuperWord;
436 // Pre-computed def-use info
437 PhaseIterGVN &_igvn;
438
439 // Head of loop tree
440 IdealLoopTree *_ltree_root;
441
442 // Array of pre-order numbers, plus post-visited bit.
443 // ZERO for not pre-visited. EVEN for pre-visited but not post-visited.
444 // ODD for post-visited. Other bits are the pre-order number.
445 uint *_preorders;
446 uint _max_preorder;
447
448 // Allocate _preorders[] array
449 void allocate_preorders() {
450 _max_preorder = C->unique()+8;
451 _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
452 memset(_preorders, 0, sizeof(uint) * _max_preorder);
453 }
454
455 // Allocate _preorders[] array
456 void reallocate_preorders() {
457 if ( _max_preorder < C->unique() ) {
458 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
459 _max_preorder = C->unique();
460 }
461 memset(_preorders, 0, sizeof(uint) * _max_preorder);
462 }
463
464 // Check to grow _preorders[] array for the case when build_loop_tree_impl()
465 // adds new nodes.
466 void check_grow_preorders( ) {
467 if ( _max_preorder < C->unique() ) {
468 uint newsize = _max_preorder<<1; // double size of array
469 _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
470 memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
471 _max_preorder = newsize;
472 }
473 }
474 // Check for pre-visited. Zero for NOT visited; non-zero for visited.
475 int is_visited( Node *n ) const { return _preorders[n->_idx]; }
476 // Pre-order numbers are written to the Nodes array as low-bit-set values.
477 void set_preorder_visited( Node *n, int pre_order ) {
478 assert( !is_visited( n ), "already set" );
479 _preorders[n->_idx] = (pre_order<<1);
480 };
481 // Return pre-order number.
482 int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }
483
484 // Check for being post-visited.
485 // Should be previsited already (checked with assert(is_visited(n))).
486 int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }
487
488 // Mark as post visited
489 void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }
490
491 // Set/get control node out. Set lower bit to distinguish from IdealLoopTree
492 // Returns true if "n" is a data node, false if it's a control node.
493 bool has_ctrl( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
494
495 // clear out dead code after build_loop_late
496 Node_List _deadlist;
497
498 // Support for faster execution of get_late_ctrl()/dom_lca()
499 // when a node has many uses and dominator depth is deep.
500 Node_Array _dom_lca_tags;
501 void init_dom_lca_tags();
502 void clear_dom_lca_tags();
503 // Inline wrapper for frequent cases:
504 // 1) only one use
505 // 2) a use is the same as the current LCA passed as 'n1'
506 Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
507 assert( n->is_CFG(), "" );
508 // Fast-path NULL lca
509 if( lca != NULL && lca != n ) {
510 assert( lca->is_CFG(), "" );
511 // find LCA of all uses
512 n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
513 }
514 return find_non_split_ctrl(n);
515 }
516 Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );
517 // true if CFG node d dominates CFG node n
518 bool is_dominator(Node *d, Node *n);
519
520 // Helper function for directing control inputs away from CFG split
521 // points.
522 Node *find_non_split_ctrl( Node *ctrl ) const {
523 if (ctrl != NULL) {
524 if (ctrl->is_MultiBranch()) {
525 ctrl = ctrl->in(0);
526 }
527 assert(ctrl->is_CFG(), "CFG");
528 }
529 return ctrl;
530 }
531
532 public:
533 bool has_node( Node* n ) const { return _nodes[n->_idx] != NULL; }
534 // check if transform created new nodes that need _ctrl recorded
535 Node *get_late_ctrl( Node *n, Node *early );
536 Node *get_early_ctrl( Node *n );
537 void set_early_ctrl( Node *n );
538 void set_subtree_ctrl( Node *root );
539 void set_ctrl( Node *n, Node *ctrl ) {
540 assert( !has_node(n) || has_ctrl(n), "" );
541 assert( ctrl->in(0), "cannot set dead control node" );
542 assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
543 _nodes.map( n->_idx, (Node*)((intptr_t)ctrl + 1) );
544 }
545 // Set control and update loop membership
546 void set_ctrl_and_loop(Node* n, Node* ctrl) {
547 IdealLoopTree* old_loop = get_loop(get_ctrl(n));
548 IdealLoopTree* new_loop = get_loop(ctrl);
549 if (old_loop != new_loop) {
550 if (old_loop->_child == NULL) old_loop->_body.yank(n);
551 if (new_loop->_child == NULL) new_loop->_body.push(n);
552 }
553 set_ctrl(n, ctrl);
554 }
555 // Control nodes can be replaced or subsumed. During this pass they
556 // get their replacement Node in slot 1. Instead of updating the block
557 // location of all Nodes in the subsumed block, we lazily do it. As we
558 // pull such a subsumed block out of the array, we write back the final
559 // correct block.
560 Node *get_ctrl( Node *i ) {
561 assert(has_node(i), "");
562 Node *n = get_ctrl_no_update(i);
563 _nodes.map( i->_idx, (Node*)((intptr_t)n + 1) );
564 assert(has_node(i) && has_ctrl(i), "");
565 assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
566 return n;
567 }
568
569 private:
570 Node *get_ctrl_no_update( Node *i ) const {
571 assert( has_ctrl(i), "" );
572 Node *n = (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
573 if (!n->in(0)) {
574 // Skip dead CFG nodes
575 do {
576 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
577 } while (!n->in(0));
578 n = find_non_split_ctrl(n);
579 }
580 return n;
581 }
582
583 // Check for loop being set
584 // "n" must be a control node. Returns true if "n" is known to be in a loop.
585 bool has_loop( Node *n ) const {
586 assert(!has_node(n) || !has_ctrl(n), "");
587 return has_node(n);
588 }
589 // Set loop
590 void set_loop( Node *n, IdealLoopTree *loop ) {
591 _nodes.map(n->_idx, (Node*)loop);
592 }
593 // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms. Replace
594 // the 'old_node' with 'new_node'. Kill old-node. Add a reference
595 // from old_node to new_node to support the lazy update. Reference
596 // replaces loop reference, since that is not neede for dead node.
597 public:
598 void lazy_update( Node *old_node, Node *new_node ) {
599 assert( old_node != new_node, "no cycles please" );
600 //old_node->set_req( 1, new_node /*NO DU INFO*/ );
601 // Nodes always have DU info now, so re-use the side array slot
602 // for this node to provide the forwarding pointer.
603 _nodes.map( old_node->_idx, (Node*)((intptr_t)new_node + 1) );
604 }
605 void lazy_replace( Node *old_node, Node *new_node ) {
606 _igvn.hash_delete(old_node);
607 _igvn.subsume_node( old_node, new_node );
608 lazy_update( old_node, new_node );
609 }
610 void lazy_replace_proj( Node *old_node, Node *new_node ) {
611 assert( old_node->req() == 1, "use this for Projs" );
612 _igvn.hash_delete(old_node); // Must hash-delete before hacking edges
613 old_node->add_req( NULL );
614 lazy_replace( old_node, new_node );
615 }
616
617 private:
618
619 // Place 'n' in some loop nest, where 'n' is a CFG node
620 void build_loop_tree();
621 int build_loop_tree_impl( Node *n, int pre_order );
622 // Insert loop into the existing loop tree. 'innermost' is a leaf of the
623 // loop tree, not the root.
624 IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );
625
626 // Place Data nodes in some loop nest
627 void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me );
628 void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me );
629 void build_loop_late_post ( Node* n, const PhaseIdealLoop *verify_me );
630
631 // Array of immediate dominance info for each CFG node indexed by node idx
632 private:
633 uint _idom_size;
634 Node **_idom; // Array of immediate dominators
635 uint *_dom_depth; // Used for fast LCA test
636 GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
637
638 Node* idom_no_update(Node* d) const {
639 assert(d->_idx < _idom_size, "oob");
640 Node* n = _idom[d->_idx];
641 assert(n != NULL,"Bad immediate dominator info.");
642 while (n->in(0) == NULL) { // Skip dead CFG nodes
643 //n = n->in(1);
644 n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
645 assert(n != NULL,"Bad immediate dominator info.");
646 }
647 return n;
648 }
649 Node *idom(Node* d) const {
650 uint didx = d->_idx;
651 Node *n = idom_no_update(d);
652 _idom[didx] = n; // Lazily remove dead CFG nodes from table.
653 return n;
654 }
655 uint dom_depth(Node* d) const {
656 assert(d->_idx < _idom_size, "");
657 return _dom_depth[d->_idx];
658 }
659 void set_idom(Node* d, Node* n, uint dom_depth);
660 // Locally compute IDOM using dom_lca call
661 Node *compute_idom( Node *region ) const;
662 // Recompute dom_depth
663 void recompute_dom_depth();
664
665 // Is safept not required by an outer loop?
666 bool is_deleteable_safept(Node* sfpt);
667
668 public:
669 // Dominators for the sea of nodes
670 void Dominators();
671 Node *dom_lca( Node *n1, Node *n2 ) const {
672 return find_non_split_ctrl(dom_lca_internal(n1, n2));
673 }
674 Node *dom_lca_internal( Node *n1, Node *n2 ) const;
675
676 // Compute the Ideal Node to Loop mapping
677 PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me, bool do_split_ifs );
678
679 // True if the method has at least 1 irreducible loop
680 bool _has_irreducible_loops;
681
682 // Per-Node transform
683 virtual Node *transform( Node *a_node ) { return 0; }
684
685 Node *is_counted_loop( Node *x, IdealLoopTree *loop );
686
687 // Return a post-walked LoopNode
688 IdealLoopTree *get_loop( Node *n ) const {
689 // Dead nodes have no loop, so return the top level loop instead
690 if (!has_node(n)) return _ltree_root;
691 assert(!has_ctrl(n), "");
692 return (IdealLoopTree*)_nodes[n->_idx];
693 }
694
695 // Is 'n' a (nested) member of 'loop'?
696 int is_member( const IdealLoopTree *loop, Node *n ) const {
697 return loop->is_member(get_loop(n)); }
698
699 // This is the basic building block of the loop optimizations. It clones an
700 // entire loop body. It makes an old_new loop body mapping; with this
701 // mapping you can find the new-loop equivalent to an old-loop node. All
702 // new-loop nodes are exactly equal to their old-loop counterparts, all
703 // edges are the same. All exits from the old-loop now have a RegionNode
704 // that merges the equivalent new-loop path. This is true even for the
705 // normal "loop-exit" condition. All uses of loop-invariant old-loop values
706 // now come from (one or more) Phis that merge their new-loop equivalents.
707 // Parameter side_by_side_idom:
708 // When side_by_size_idom is NULL, the dominator tree is constructed for
709 // the clone loop to dominate the original. Used in construction of
710 // pre-main-post loop sequence.
711 // When nonnull, the clone and original are side-by-side, both are
712 // dominated by the passed in side_by_side_idom node. Used in
713 // construction of unswitched loops.
714 void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
715 Node* side_by_side_idom = NULL);
716
717 // If we got the effect of peeling, either by actually peeling or by
718 // making a pre-loop which must execute at least once, we can remove
719 // all loop-invariant dominated tests in the main body.
720 void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );
721
722 // Generate code to do a loop peel for the given loop (and body).
723 // old_new is a temp array.
724 void do_peeling( IdealLoopTree *loop, Node_List &old_new );
725
726 // Add pre and post loops around the given loop. These loops are used
727 // during RCE, unrolling and aligning loops.
728 void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );
729 // If Node n lives in the back_ctrl block, we clone a private version of n
730 // in preheader_ctrl block and return that, otherwise return n.
731 Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n );
732
733 // Take steps to maximally unroll the loop. Peel any odd iterations, then
734 // unroll to do double iterations. The next round of major loop transforms
735 // will repeat till the doubled loop body does all remaining iterations in 1
736 // pass.
737 void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );
738
739 // Unroll the loop body one step - make each trip do 2 iterations.
740 void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );
741
742 // Return true if exp is a constant times an induction var
743 bool is_scaled_iv(Node* exp, Node* iv, int* p_scale);
744
745 // Return true if exp is a scaled induction var plus (or minus) constant
746 bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
747
748 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
749 void do_range_check( IdealLoopTree *loop, Node_List &old_new );
750
751 // Create a slow version of the loop by cloning the loop
752 // and inserting an if to select fast-slow versions.
753 ProjNode* create_slow_version_of_loop(IdealLoopTree *loop,
754 Node_List &old_new);
755
756 // Clone loop with an invariant test (that does not exit) and
757 // insert a clone of the test that selects which version to
758 // execute.
759 void do_unswitching (IdealLoopTree *loop, Node_List &old_new);
760
761 // Find candidate "if" for unswitching
762 IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
763
764 // Range Check Elimination uses this function!
765 // Constrain the main loop iterations so the affine function:
766 // scale_con * I + offset < limit
767 // always holds true. That is, either increase the number of iterations in
768 // the pre-loop or the post-loop until the condition holds true in the main
769 // loop. Scale_con, offset and limit are all loop invariant.
770 void add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit );
771
772 // Partially peel loop up through last_peel node.
773 bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
774
775 // Create a scheduled list of nodes control dependent on ctrl set.
776 void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
777 // Has a use in the vector set
778 bool has_use_in_set( Node* n, VectorSet& vset );
779 // Has use internal to the vector set (ie. not in a phi at the loop head)
780 bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
781 // clone "n" for uses that are outside of loop
782 void clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
783 // clone "n" for special uses that are in the not_peeled region
784 void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
785 VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
786 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
787 void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
788 #ifdef ASSERT
789 // Validate the loop partition sets: peel and not_peel
790 bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
791 // Ensure that uses outside of loop are of the right form
792 bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
793 uint orig_exit_idx, uint clone_exit_idx);
794 bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
795 #endif
796
797 // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
798 int stride_of_possible_iv( Node* iff );
799 bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
800 // Return the (unique) control output node that's in the loop (if it exists.)
801 Node* stay_in_loop( Node* n, IdealLoopTree *loop);
802 // Insert a signed compare loop exit cloned from an unsigned compare.
803 IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
804 void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
805 // Utility to register node "n" with PhaseIdealLoop
806 void register_node(Node* n, IdealLoopTree *loop, Node* pred, int ddepth);
807 // Utility to create an if-projection
808 ProjNode* proj_clone(ProjNode* p, IfNode* iff);
809 // Force the iff control output to be the live_proj
810 Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
811 // Insert a region before an if projection
812 RegionNode* insert_region_before_proj(ProjNode* proj);
813 // Insert a new if before an if projection
814 ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);
815
816 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
817 // "Nearly" because all Nodes have been cloned from the original in the loop,
818 // but the fall-in edges to the Cmp are different. Clone bool/Cmp pairs
819 // through the Phi recursively, and return a Bool.
820 BoolNode *clone_iff( PhiNode *phi, IdealLoopTree *loop );
821 CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
822
823
824 // Rework addressing expressions to get the most loop-invariant stuff
825 // moved out. We'd like to do all associative operators, but it's especially
826 // important (common) to do address expressions.
827 Node *remix_address_expressions( Node *n );
828
829 // Attempt to use a conditional move instead of a phi/branch
830 Node *conditional_move( Node *n );
831
832 // Reorganize offset computations to lower register pressure.
833 // Mostly prevent loop-fallout uses of the pre-incremented trip counter
834 // (which are then alive with the post-incremented trip counter
835 // forcing an extra register move)
836 void reorg_offsets( IdealLoopTree *loop );
837
838 // Check for aggressive application of 'split-if' optimization,
839 // using basic block level info.
840 void split_if_with_blocks ( VectorSet &visited, Node_Stack &nstack );
841 Node *split_if_with_blocks_pre ( Node *n );
842 void split_if_with_blocks_post( Node *n );
843 Node *has_local_phi_input( Node *n );
844 // Mark an IfNode as being dominated by a prior test,
845 // without actually altering the CFG (and hence IDOM info).
846 void dominated_by( Node *prevdom, Node *iff );
847
848 // Split Node 'n' through merge point
849 Node *split_thru_region( Node *n, Node *region );
850 // Split Node 'n' through merge point if there is enough win.
851 Node *split_thru_phi( Node *n, Node *region, int policy );
852 // Found an If getting its condition-code input from a Phi in the
853 // same block. Split thru the Region.
854 void do_split_if( Node *iff );
855
856 private:
857 // Return a type based on condition control flow
858 const TypeInt* filtered_type( Node *n, Node* n_ctrl);
859 const TypeInt* filtered_type( Node *n ) { return filtered_type(n, NULL); }
860 // Helpers for filtered type
861 const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);
862
863 // Helper functions
864 void register_new_node( Node *n, Node *blk );
865 Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
866 Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
867 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 );
868 bool split_up( Node *n, Node *blk1, Node *blk2 );
869 void sink_use( Node *use, Node *post_loop );
870 Node *place_near_use( Node *useblock ) const;
871
872 bool _created_loop_node;
873 public:
874 void set_created_loop_node() { _created_loop_node = true; }
875 bool created_loop_node() { return _created_loop_node; }
876
877 #ifndef PRODUCT
878 void dump( ) const;
879 void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const;
880 void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const;
881 void verify() const; // Major slow :-)
882 void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const;
883 IdealLoopTree *get_loop_idx(Node* n) const {
884 // Dead nodes have no loop, so return the top level loop instead
885 return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[n->_idx] : _ltree_root;
886 }
887 // Print some stats
888 static void print_statistics();
889 static int _loop_invokes; // Count of PhaseIdealLoop invokes
890 static int _loop_work; // Sum of PhaseIdealLoop x _unique
891 #endif
892 };
893
894 inline Node* IdealLoopTree::tail() {
895 // Handle lazy update of _tail field
896 Node *n = _tail;
897 //while( !n->in(0) ) // Skip dead CFG nodes
898 //n = n->in(1);
899 if (n->in(0) == NULL)
900 n = _phase->get_ctrl(n);
901 _tail = n;
902 return n;
903 }
904
905
906 // Iterate over the loop tree using a preorder, left-to-right traversal.
907 //
908 // Example that visits all counted loops from within PhaseIdealLoop
909 //
910 // for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
911 // IdealLoopTree* lpt = iter.current();
912 // if (!lpt->is_counted()) continue;
913 // ...
914 class LoopTreeIterator : public StackObj {
915 private:
916 IdealLoopTree* _root;
917 IdealLoopTree* _curnt;
918
919 public:
920 LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}
921
922 bool done() { return _curnt == NULL; } // Finished iterating?
923
924 void next(); // Advance to next loop tree
925
926 IdealLoopTree* current() { return _curnt; } // Return current value of iterator.
927 };
928