1 /*
2 * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "opto/loopnode.hpp"
27 #include "opto/addnode.hpp"
28 #include "opto/callnode.hpp"
29 #include "opto/connode.hpp"
30 #include "opto/loopnode.hpp"
31 #include "opto/mulnode.hpp"
32 #include "opto/rootnode.hpp"
33 #include "opto/subnode.hpp"
34
35 /*
36 * The general idea of Loop Predication is to insert a predicate on the entry
37 * path to a loop, and raise a uncommon trap if the check of the condition fails.
38 * The condition checks are promoted from inside the loop body, and thus
39 * the checks inside the loop could be eliminated. Currently, loop predication
40 * optimization has been applied to remove array range check and loop invariant
41 * checks (such as null checks).
42 */
43
44 //-------------------------------register_control-------------------------
45 void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
46 assert(n->is_CFG(), "must be control node");
47 _igvn.register_new_node_with_optimizer(n);
48 loop->_body.push(n);
49 set_loop(n, loop);
50 // When called from beautify_loops() idom is not constructed yet.
51 if (_idom != NULL) {
52 set_idom(n, pred, dom_depth(pred));
53 }
54 }
55
56 //------------------------------create_new_if_for_predicate------------------------
57 // create a new if above the uct_if_pattern for the predicate to be promoted.
58 //
59 // before after
60 // ---------- ----------
61 // ctrl ctrl
62 // | |
63 // | |
64 // v v
65 // iff new_iff
66 // / \ / \
67 // / \ / \
68 // v v v v
69 // uncommon_proj cont_proj if_uct if_cont
70 // \ | | | |
71 // \ | | | |
72 // v v v | v
73 // rgn loop | iff
74 // | | / \
75 // | | / \
76 // v | v v
77 // uncommon_trap | uncommon_proj cont_proj
78 // \ \ | |
79 // \ \ | |
80 // v v v v
81 // rgn loop
82 // |
83 // |
84 // v
85 // uncommon_trap
86 //
87 //
88 // We will create a region to guard the uct call if there is no one there.
89 // The true projecttion (if_cont) of the new_iff is returned.
90 // This code is also used to clone predicates to clonned loops.
91 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
92 Deoptimization::DeoptReason reason) {
93 assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
94 IfNode* iff = cont_proj->in(0)->as_If();
95
96 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
97 Node *rgn = uncommon_proj->unique_ctrl_out();
98 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
99
100 uint proj_index = 1; // region's edge corresponding to uncommon_proj
101 if (!rgn->is_Region()) { // create a region to guard the call
102 assert(rgn->is_Call(), "must be call uct");
103 CallNode* call = rgn->as_Call();
104 IdealLoopTree* loop = get_loop(call);
105 rgn = new (C) RegionNode(1);
106 rgn->add_req(uncommon_proj);
107 register_control(rgn, loop, uncommon_proj);
108 _igvn.hash_delete(call);
109 call->set_req(0, rgn);
110 // When called from beautify_loops() idom is not constructed yet.
111 if (_idom != NULL) {
112 set_idom(call, rgn, dom_depth(rgn));
113 }
114 } else {
115 // Find region's edge corresponding to uncommon_proj
116 for (; proj_index < rgn->req(); proj_index++)
117 if (rgn->in(proj_index) == uncommon_proj) break;
118 assert(proj_index < rgn->req(), "sanity");
119 }
120
121 Node* entry = iff->in(0);
122 if (new_entry != NULL) {
123 // Clonning the predicate to new location.
124 entry = new_entry;
125 }
126 // Create new_iff
127 IdealLoopTree* lp = get_loop(entry);
128 IfNode *new_iff = iff->clone()->as_If();
129 new_iff->set_req(0, entry);
130 register_control(new_iff, lp, entry);
131 Node *if_cont = new (C) IfTrueNode(new_iff);
132 Node *if_uct = new (C) IfFalseNode(new_iff);
133 if (cont_proj->is_IfFalse()) {
134 // Swap
135 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
136 }
137 register_control(if_cont, lp, new_iff);
138 register_control(if_uct, get_loop(rgn), new_iff);
139
140 // if_uct to rgn
141 _igvn.hash_delete(rgn);
142 rgn->add_req(if_uct);
143 // When called from beautify_loops() idom is not constructed yet.
144 if (_idom != NULL) {
145 Node* ridom = idom(rgn);
146 Node* nrdom = dom_lca(ridom, new_iff);
147 set_idom(rgn, nrdom, dom_depth(rgn));
148 }
149
150 // If rgn has phis add new edges which has the same
151 // value as on original uncommon_proj pass.
152 assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
153 bool has_phi = false;
154 for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
155 Node* use = rgn->fast_out(i);
156 if (use->is_Phi() && use->outcnt() > 0) {
157 assert(use->in(0) == rgn, "");
158 _igvn.rehash_node_delayed(use);
159 use->add_req(use->in(proj_index));
160 has_phi = true;
161 }
162 }
163 assert(!has_phi || rgn->req() > 3, "no phis when region is created");
164
165 if (new_entry == NULL) {
166 // Attach if_cont to iff
167 _igvn.hash_delete(iff);
168 iff->set_req(0, if_cont);
169 if (_idom != NULL) {
170 set_idom(iff, if_cont, dom_depth(iff));
171 }
172 }
173 return if_cont->as_Proj();
174 }
175
176 //------------------------------create_new_if_for_predicate------------------------
177 // Create a new if below new_entry for the predicate to be cloned (IGVN optimization)
178 ProjNode* PhaseIterGVN::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
179 Deoptimization::DeoptReason reason) {
180 assert(new_entry != 0, "only used for clone predicate");
181 assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
182 IfNode* iff = cont_proj->in(0)->as_If();
183
184 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
185 Node *rgn = uncommon_proj->unique_ctrl_out();
186 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
187
188 uint proj_index = 1; // region's edge corresponding to uncommon_proj
189 if (!rgn->is_Region()) { // create a region to guard the call
190 assert(rgn->is_Call(), "must be call uct");
191 CallNode* call = rgn->as_Call();
192 rgn = new (C) RegionNode(1);
193 register_new_node_with_optimizer(rgn);
194 rgn->add_req(uncommon_proj);
195 hash_delete(call);
196 call->set_req(0, rgn);
197 } else {
198 // Find region's edge corresponding to uncommon_proj
199 for (; proj_index < rgn->req(); proj_index++)
200 if (rgn->in(proj_index) == uncommon_proj) break;
201 assert(proj_index < rgn->req(), "sanity");
202 }
203
204 // Create new_iff in new location.
205 IfNode *new_iff = iff->clone()->as_If();
206 new_iff->set_req(0, new_entry);
207
208 register_new_node_with_optimizer(new_iff);
209 Node *if_cont = new (C) IfTrueNode(new_iff);
210 Node *if_uct = new (C) IfFalseNode(new_iff);
211 if (cont_proj->is_IfFalse()) {
212 // Swap
213 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
214 }
215 register_new_node_with_optimizer(if_cont);
216 register_new_node_with_optimizer(if_uct);
217
218 // if_uct to rgn
219 hash_delete(rgn);
220 rgn->add_req(if_uct);
221
222 // If rgn has phis add corresponding new edges which has the same
223 // value as on original uncommon_proj pass.
224 assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
225 bool has_phi = false;
226 for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
227 Node* use = rgn->fast_out(i);
228 if (use->is_Phi() && use->outcnt() > 0) {
229 rehash_node_delayed(use);
230 use->add_req(use->in(proj_index));
231 has_phi = true;
232 }
233 }
234 assert(!has_phi || rgn->req() > 3, "no phis when region is created");
235
236 return if_cont->as_Proj();
237 }
238
239 //--------------------------clone_predicate-----------------------
240 ProjNode* PhaseIdealLoop::clone_predicate(ProjNode* predicate_proj, Node* new_entry,
241 Deoptimization::DeoptReason reason,
242 PhaseIdealLoop* loop_phase,
243 PhaseIterGVN* igvn) {
244 ProjNode* new_predicate_proj;
245 if (loop_phase != NULL) {
246 new_predicate_proj = loop_phase->create_new_if_for_predicate(predicate_proj, new_entry, reason);
247 } else {
248 new_predicate_proj = igvn->create_new_if_for_predicate(predicate_proj, new_entry, reason);
249 }
250 IfNode* iff = new_predicate_proj->in(0)->as_If();
251 Node* ctrl = iff->in(0);
252
253 // Match original condition since predicate's projections could be swapped.
254 assert(predicate_proj->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
255 Node* opq = new (igvn->C) Opaque1Node(igvn->C, predicate_proj->in(0)->in(1)->in(1)->in(1));
256 igvn->C->add_predicate_opaq(opq);
257
258 Node* bol = new (igvn->C) Conv2BNode(opq);
259 if (loop_phase != NULL) {
260 loop_phase->register_new_node(opq, ctrl);
261 loop_phase->register_new_node(bol, ctrl);
262 } else {
263 igvn->register_new_node_with_optimizer(opq);
264 igvn->register_new_node_with_optimizer(bol);
265 }
266 igvn->hash_delete(iff);
267 iff->set_req(1, bol);
268 return new_predicate_proj;
269 }
270
271
272 //--------------------------clone_loop_predicates-----------------------
273 // Interface from IGVN
274 Node* PhaseIterGVN::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
275 return PhaseIdealLoop::clone_loop_predicates(old_entry, new_entry, clone_limit_check, NULL, this);
276 }
277
278 // Interface from PhaseIdealLoop
279 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
280 return clone_loop_predicates(old_entry, new_entry, clone_limit_check, this, &this->_igvn);
281 }
282
283 // Clone loop predicates to cloned loops (peeled, unswitched, split_if).
284 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry,
285 bool clone_limit_check,
286 PhaseIdealLoop* loop_phase,
287 PhaseIterGVN* igvn) {
288 #ifdef ASSERT
289 if (new_entry == NULL || !(new_entry->is_Proj() || new_entry->is_Region() || new_entry->is_SafePoint())) {
290 if (new_entry != NULL)
291 new_entry->dump();
292 assert(false, "not IfTrue, IfFalse, Region or SafePoint");
293 }
294 #endif
295 // Search original predicates
296 Node* entry = old_entry;
297 ProjNode* limit_check_proj = NULL;
298 if (LoopLimitCheck) {
299 limit_check_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
300 if (limit_check_proj != NULL) {
301 entry = entry->in(0)->in(0);
302 }
303 }
304 if (UseLoopPredicate) {
305 ProjNode* predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
306 if (predicate_proj != NULL) { // right pattern that can be used by loop predication
307 // clone predicate
308 new_entry = clone_predicate(predicate_proj, new_entry,
309 Deoptimization::Reason_predicate,
310 loop_phase, igvn);
311 assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
312 if (TraceLoopPredicate) {
313 tty->print("Loop Predicate cloned: ");
314 debug_only( new_entry->in(0)->dump(); )
315 }
316 }
317 }
318 if (limit_check_proj != NULL && clone_limit_check) {
319 // Clone loop limit check last to insert it before loop.
320 // Don't clone a limit check which was already finalized
321 // for this counted loop (only one limit check is needed).
322 new_entry = clone_predicate(limit_check_proj, new_entry,
323 Deoptimization::Reason_loop_limit_check,
324 loop_phase, igvn);
325 assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone limit check");
326 if (TraceLoopLimitCheck) {
327 tty->print("Loop Limit Check cloned: ");
328 debug_only( new_entry->in(0)->dump(); )
329 }
330 }
331 return new_entry;
332 }
333
334 //--------------------------skip_loop_predicates------------------------------
335 // Skip related predicates.
336 Node* PhaseIdealLoop::skip_loop_predicates(Node* entry) {
337 Node* predicate = NULL;
338 if (LoopLimitCheck) {
339 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
340 if (predicate != NULL) {
341 entry = entry->in(0)->in(0);
342 }
343 }
344 if (UseLoopPredicate) {
345 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
346 if (predicate != NULL) { // right pattern that can be used by loop predication
347 IfNode* iff = entry->in(0)->as_If();
348 ProjNode* uncommon_proj = iff->proj_out(1 - entry->as_Proj()->_con);
349 Node* rgn = uncommon_proj->unique_ctrl_out();
350 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
351 entry = entry->in(0)->in(0);
352 while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
353 uncommon_proj = entry->in(0)->as_If()->proj_out(1 - entry->as_Proj()->_con);
354 if (uncommon_proj->unique_ctrl_out() != rgn)
355 break;
356 entry = entry->in(0)->in(0);
357 }
358 }
359 }
360 return entry;
361 }
362
363 //--------------------------find_predicate_insertion_point-------------------
364 // Find a good location to insert a predicate
365 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
366 if (start_c == NULL || !start_c->is_Proj())
367 return NULL;
368 if (start_c->as_Proj()->is_uncommon_trap_if_pattern(reason)) {
369 return start_c->as_Proj();
370 }
371 return NULL;
372 }
373
374 //--------------------------find_predicate------------------------------------
375 // Find a predicate
376 Node* PhaseIdealLoop::find_predicate(Node* entry) {
377 Node* predicate = NULL;
378 if (LoopLimitCheck) {
379 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
380 if (predicate != NULL) { // right pattern that can be used by loop predication
381 return entry;
382 }
383 }
384 if (UseLoopPredicate) {
385 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
386 if (predicate != NULL) { // right pattern that can be used by loop predication
387 return entry;
388 }
389 }
390 return NULL;
391 }
392
393 //------------------------------Invariance-----------------------------------
394 // Helper class for loop_predication_impl to compute invariance on the fly and
395 // clone invariants.
396 class Invariance : public StackObj {
397 VectorSet _visited, _invariant;
398 Node_Stack _stack;
399 VectorSet _clone_visited;
400 Node_List _old_new; // map of old to new (clone)
401 IdealLoopTree* _lpt;
402 PhaseIdealLoop* _phase;
403
404 // Helper function to set up the invariance for invariance computation
405 // If n is a known invariant, set up directly. Otherwise, look up the
406 // the possibility to push n onto the stack for further processing.
407 void visit(Node* use, Node* n) {
408 if (_lpt->is_invariant(n)) { // known invariant
409 _invariant.set(n->_idx);
410 } else if (!n->is_CFG()) {
411 Node *n_ctrl = _phase->ctrl_or_self(n);
412 Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
413 if (_phase->is_dominator(n_ctrl, u_ctrl)) {
414 _stack.push(n, n->in(0) == NULL ? 1 : 0);
415 }
416 }
417 }
418
419 // Compute invariance for "the_node" and (possibly) all its inputs recursively
420 // on the fly
421 void compute_invariance(Node* n) {
422 assert(_visited.test(n->_idx), "must be");
423 visit(n, n);
424 while (_stack.is_nonempty()) {
425 Node* n = _stack.node();
426 uint idx = _stack.index();
427 if (idx == n->req()) { // all inputs are processed
428 _stack.pop();
429 // n is invariant if it's inputs are all invariant
430 bool all_inputs_invariant = true;
431 for (uint i = 0; i < n->req(); i++) {
432 Node* in = n->in(i);
433 if (in == NULL) continue;
434 assert(_visited.test(in->_idx), "must have visited input");
435 if (!_invariant.test(in->_idx)) { // bad guy
436 all_inputs_invariant = false;
437 break;
438 }
439 }
440 if (all_inputs_invariant) {
441 // If n's control is a predicate that was moved out of the
442 // loop, it was marked invariant but n is only invariant if
443 // it depends only on that test. Otherwise, unless that test
444 // is out of the loop, it's not invariant.
445 if (n->is_CFG() || n->depends_only_on_test() || n->in(0) == NULL || !_phase->is_member(_lpt, n->in(0))) {
446 _invariant.set(n->_idx); // I am a invariant too
447 }
448 }
449 } else { // process next input
450 _stack.set_index(idx + 1);
451 Node* m = n->in(idx);
452 if (m != NULL && !_visited.test_set(m->_idx)) {
453 visit(n, m);
454 }
455 }
456 }
457 }
458
459 // Helper function to set up _old_new map for clone_nodes.
460 // If n is a known invariant, set up directly ("clone" of n == n).
461 // Otherwise, push n onto the stack for real cloning.
462 void clone_visit(Node* n) {
463 assert(_invariant.test(n->_idx), "must be invariant");
464 if (_lpt->is_invariant(n)) { // known invariant
465 _old_new.map(n->_idx, n);
466 } else { // to be cloned
467 assert(!n->is_CFG(), "should not see CFG here");
468 _stack.push(n, n->in(0) == NULL ? 1 : 0);
469 }
470 }
471
472 // Clone "n" and (possibly) all its inputs recursively
473 void clone_nodes(Node* n, Node* ctrl) {
474 clone_visit(n);
475 while (_stack.is_nonempty()) {
476 Node* n = _stack.node();
477 uint idx = _stack.index();
478 if (idx == n->req()) { // all inputs processed, clone n!
479 _stack.pop();
480 // clone invariant node
481 Node* n_cl = n->clone();
482 _old_new.map(n->_idx, n_cl);
483 _phase->register_new_node(n_cl, ctrl);
484 for (uint i = 0; i < n->req(); i++) {
485 Node* in = n_cl->in(i);
486 if (in == NULL) continue;
487 n_cl->set_req(i, _old_new[in->_idx]);
488 }
489 } else { // process next input
490 _stack.set_index(idx + 1);
491 Node* m = n->in(idx);
492 if (m != NULL && !_clone_visited.test_set(m->_idx)) {
493 clone_visit(m); // visit the input
494 }
495 }
496 }
497 }
498
499 public:
500 Invariance(Arena* area, IdealLoopTree* lpt) :
501 _lpt(lpt), _phase(lpt->_phase),
502 _visited(area), _invariant(area), _stack(area, 10 /* guess */),
503 _clone_visited(area), _old_new(area)
504 {}
505
506 // Map old to n for invariance computation and clone
507 void map_ctrl(Node* old, Node* n) {
508 assert(old->is_CFG() && n->is_CFG(), "must be");
509 _old_new.map(old->_idx, n); // "clone" of old is n
510 _invariant.set(old->_idx); // old is invariant
511 _clone_visited.set(old->_idx);
512 }
513
514 // Driver function to compute invariance
515 bool is_invariant(Node* n) {
516 if (!_visited.test_set(n->_idx))
517 compute_invariance(n);
518 return (_invariant.test(n->_idx) != 0);
519 }
520
521 // Driver function to clone invariant
522 Node* clone(Node* n, Node* ctrl) {
523 assert(ctrl->is_CFG(), "must be");
524 assert(_invariant.test(n->_idx), "must be an invariant");
525 if (!_clone_visited.test(n->_idx))
526 clone_nodes(n, ctrl);
527 return _old_new[n->_idx];
528 }
529 };
530
531 //------------------------------is_range_check_if -----------------------------------
532 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
533 // Note: this function is particularly designed for loop predication. We require load_range
534 // and offset to be loop invariant computed on the fly by "invar"
535 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
536 if (!is_loop_exit(iff)) {
537 return false;
538 }
539 if (!iff->in(1)->is_Bool()) {
540 return false;
541 }
542 const BoolNode *bol = iff->in(1)->as_Bool();
543 if (bol->_test._test != BoolTest::lt) {
544 return false;
545 }
546 if (!bol->in(1)->is_Cmp()) {
547 return false;
548 }
549 const CmpNode *cmp = bol->in(1)->as_Cmp();
550 if (cmp->Opcode() != Op_CmpU) {
551 return false;
552 }
553 Node* range = cmp->in(2);
554 if (range->Opcode() != Op_LoadRange) {
555 const TypeInt* tint = phase->_igvn.type(range)->isa_int();
556 if (tint == NULL || tint->empty() || tint->_lo < 0) {
557 // Allow predication on positive values that aren't LoadRanges.
558 // This allows optimization of loops where the length of the
559 // array is a known value and doesn't need to be loaded back
560 // from the array.
561 return false;
562 }
563 }
564 if (!invar.is_invariant(range)) {
565 return false;
566 }
567 Node *iv = _head->as_CountedLoop()->phi();
568 int scale = 0;
569 Node *offset = NULL;
570 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
571 return false;
572 }
573 if (offset && !invar.is_invariant(offset)) { // offset must be invariant
574 return false;
575 }
576 return true;
577 }
578
579 //------------------------------rc_predicate-----------------------------------
580 // Create a range check predicate
581 //
582 // for (i = init; i < limit; i += stride) {
583 // a[scale*i+offset]
584 // }
585 //
586 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
587 // as "max(scale*i + offset) u< a.length".
588 //
589 // There are two cases for max(scale*i + offset):
590 // (1) stride*scale > 0
591 // max(scale*i + offset) = scale*(limit-stride) + offset
592 // (2) stride*scale < 0
593 // max(scale*i + offset) = scale*init + offset
594 BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
595 int scale, Node* offset,
596 Node* init, Node* limit, Node* stride,
597 Node* range, bool upper) {
598 stringStream* predString = NULL;
599 if (TraceLoopPredicate) {
600 predString = new stringStream();
601 predString->print("rc_predicate ");
602 }
603
604 Node* max_idx_expr = init;
605 int stride_con = stride->get_int();
606 if ((stride_con > 0) == (scale > 0) == upper) {
607 if (LoopLimitCheck) {
608 // With LoopLimitCheck limit is not exact.
609 // Calculate exact limit here.
610 // Note, counted loop's test is '<' or '>'.
611 limit = exact_limit(loop);
612 max_idx_expr = new (C) SubINode(limit, stride);
613 register_new_node(max_idx_expr, ctrl);
614 if (TraceLoopPredicate) predString->print("(limit - stride) ");
615 } else {
616 max_idx_expr = new (C) SubINode(limit, stride);
617 register_new_node(max_idx_expr, ctrl);
618 if (TraceLoopPredicate) predString->print("(limit - stride) ");
619 }
620 } else {
621 if (TraceLoopPredicate) predString->print("init ");
622 }
623
624 if (scale != 1) {
625 ConNode* con_scale = _igvn.intcon(scale);
626 max_idx_expr = new (C) MulINode(max_idx_expr, con_scale);
627 register_new_node(max_idx_expr, ctrl);
628 if (TraceLoopPredicate) predString->print("* %d ", scale);
629 }
630
631 if (offset && (!offset->is_Con() || offset->get_int() != 0)){
632 max_idx_expr = new (C) AddINode(max_idx_expr, offset);
633 register_new_node(max_idx_expr, ctrl);
634 if (TraceLoopPredicate)
635 if (offset->is_Con()) predString->print("+ %d ", offset->get_int());
636 else predString->print("+ offset ");
637 }
638
639 CmpUNode* cmp = new (C) CmpUNode(max_idx_expr, range);
640 register_new_node(cmp, ctrl);
641 BoolNode* bol = new (C) BoolNode(cmp, BoolTest::lt);
642 register_new_node(bol, ctrl);
643
644 if (TraceLoopPredicate) {
645 predString->print_cr("<u range");
646 tty->print("%s", predString->as_string());
647 }
648 return bol;
649 }
650
651 //------------------------------ loop_predication_impl--------------------------
652 // Insert loop predicates for null checks and range checks
653 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
654 if (!UseLoopPredicate) return false;
655
656 if (!loop->_head->is_Loop()) {
657 // Could be a simple region when irreducible loops are present.
658 return false;
659 }
660 LoopNode* head = loop->_head->as_Loop();
661
662 if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
663 // do nothing for infinite loops
664 return false;
665 }
666
667 CountedLoopNode *cl = NULL;
668 if (head->is_valid_counted_loop()) {
669 cl = head->as_CountedLoop();
670 // do nothing for iteration-splitted loops
671 if (!cl->is_normal_loop()) return false;
672 // Avoid RCE if Counted loop's test is '!='.
673 BoolTest::mask bt = cl->loopexit()->test_trip();
674 if (bt != BoolTest::lt && bt != BoolTest::gt)
675 cl = NULL;
676 }
677
678 Node* entry = head->in(LoopNode::EntryControl);
679 ProjNode *predicate_proj = NULL;
680 // Loop limit check predicate should be near the loop.
681 if (LoopLimitCheck) {
682 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
683 if (predicate_proj != NULL)
684 entry = predicate_proj->in(0)->in(0);
685 }
686
687 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
688 if (!predicate_proj) {
689 #ifndef PRODUCT
690 if (TraceLoopPredicate) {
691 tty->print("missing predicate:");
692 loop->dump_head();
693 head->dump(1);
694 }
695 #endif
696 return false;
697 }
698 ConNode* zero = _igvn.intcon(0);
699 set_ctrl(zero, C->root());
700
701 ResourceArea *area = Thread::current()->resource_area();
702 Invariance invar(area, loop);
703
704 // Create list of if-projs such that a newer proj dominates all older
705 // projs in the list, and they all dominate loop->tail()
706 Node_List if_proj_list(area);
707 Node *current_proj = loop->tail(); //start from tail
708 while (current_proj != head) {
709 if (loop == get_loop(current_proj) && // still in the loop ?
710 current_proj->is_Proj() && // is a projection ?
711 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
712 if_proj_list.push(current_proj);
713 }
714 current_proj = idom(current_proj);
715 }
716
717 bool hoisted = false; // true if at least one proj is promoted
718 while (if_proj_list.size() > 0) {
719 // Following are changed to nonnull when a predicate can be hoisted
720 ProjNode* new_predicate_proj = NULL;
721
722 ProjNode* proj = if_proj_list.pop()->as_Proj();
723 IfNode* iff = proj->in(0)->as_If();
724
725 if (!proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
726 if (loop->is_loop_exit(iff)) {
727 // stop processing the remaining projs in the list because the execution of them
728 // depends on the condition of "iff" (iff->in(1)).
729 break;
730 } else {
731 // Both arms are inside the loop. There are two cases:
732 // (1) there is one backward branch. In this case, any remaining proj
733 // in the if_proj list post-dominates "iff". So, the condition of "iff"
734 // does not determine the execution the remining projs directly, and we
735 // can safely continue.
736 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
737 // does not dominate loop->tail(), so it can not be in the if_proj list.
738 continue;
739 }
740 }
741
742 Node* test = iff->in(1);
743 if (!test->is_Bool()){ //Conv2B, ...
744 continue;
745 }
746 BoolNode* bol = test->as_Bool();
747 if (invar.is_invariant(bol)) {
748 // Invariant test
749 new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
750 Deoptimization::Reason_predicate);
751 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
752 BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
753
754 // Negate test if necessary
755 bool negated = false;
756 if (proj->_con != predicate_proj->_con) {
757 new_predicate_bol = new (C) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
758 register_new_node(new_predicate_bol, ctrl);
759 negated = true;
760 }
761 IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
762 _igvn.hash_delete(new_predicate_iff);
763 new_predicate_iff->set_req(1, new_predicate_bol);
764 #ifndef PRODUCT
765 if (TraceLoopPredicate) {
766 tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
767 loop->dump_head();
768 } else if (TraceLoopOpts) {
769 tty->print("Predicate IC ");
770 loop->dump_head();
771 }
772 #endif
773 } else if ((cl != NULL) && (proj->_con == predicate_proj->_con) &&
774 loop->is_range_check_if(iff, this, invar)) {
775
776 // Range check for counted loops
777 const Node* cmp = bol->in(1)->as_Cmp();
778 Node* idx = cmp->in(1);
779 assert(!invar.is_invariant(idx), "index is variant");
780 Node* rng = cmp->in(2);
781 assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() >= 0, "must be");
782 assert(invar.is_invariant(rng), "range must be invariant");
783 int scale = 1;
784 Node* offset = zero;
785 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
786 assert(ok, "must be index expression");
787
788 Node* init = cl->init_trip();
789 Node* limit = cl->limit();
790 Node* stride = cl->stride();
791
792 // Build if's for the upper and lower bound tests. The
793 // lower_bound test will dominate the upper bound test and all
794 // cloned or created nodes will use the lower bound test as
795 // their declared control.
796 ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
797 ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
798 assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
799 Node *ctrl = lower_bound_proj->in(0)->as_If()->in(0);
800
801 // Perform cloning to keep Invariance state correct since the
802 // late schedule will place invariant things in the loop.
803 rng = invar.clone(rng, ctrl);
804 if (offset && offset != zero) {
805 assert(invar.is_invariant(offset), "offset must be loop invariant");
806 offset = invar.clone(offset, ctrl);
807 }
808
809 // Test the lower bound
810 Node* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false);
811 IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
812 _igvn.hash_delete(lower_bound_iff);
813 lower_bound_iff->set_req(1, lower_bound_bol);
814 if (TraceLoopPredicate) tty->print_cr("lower bound check if: %d", lower_bound_iff->_idx);
815
816 // Test the upper bound
817 Node* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true);
818 IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
819 _igvn.hash_delete(upper_bound_iff);
820 upper_bound_iff->set_req(1, upper_bound_bol);
821 if (TraceLoopPredicate) tty->print_cr("upper bound check if: %d", lower_bound_iff->_idx);
822
823 // Fall through into rest of the clean up code which will move
824 // any dependent nodes onto the upper bound test.
825 new_predicate_proj = upper_bound_proj;
826
827 #ifndef PRODUCT
828 if (TraceLoopOpts && !TraceLoopPredicate) {
829 tty->print("Predicate RC ");
830 loop->dump_head();
831 }
832 #endif
833 } else {
834 // Loop variant check (for example, range check in non-counted loop)
835 // with uncommon trap.
836 continue;
837 }
838 assert(new_predicate_proj != NULL, "sanity");
839 // Success - attach condition (new_predicate_bol) to predicate if
840 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
841
842 // Eliminate the old If in the loop body
843 dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
844
845 hoisted = true;
846 C->set_major_progress();
847 } // end while
848
849 #ifndef PRODUCT
850 // report that the loop predication has been actually performed
851 // for this loop
852 if (TraceLoopPredicate && hoisted) {
853 tty->print("Loop Predication Performed:");
854 loop->dump_head();
855 }
856 #endif
857
858 return hoisted;
859 }
860
861 //------------------------------loop_predication--------------------------------
862 // driver routine for loop predication optimization
863 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
864 bool hoisted = false;
865 // Recursively promote predicates
866 if (_child) {
867 hoisted = _child->loop_predication( phase);
868 }
869
870 // self
871 if (!_irreducible && !tail()->is_top()) {
872 hoisted |= phase->loop_predication_impl(this);
873 }
874
875 if (_next) { //sibling
876 hoisted |= _next->loop_predication( phase);
877 }
878
879 return hoisted;
880 }