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src/share/vm/opto/loopPredicate.cpp@69ea58782b1a
src/share/vm/opto/loopPredicate.cpp
Thu, 31 Jul 2014 19:59:36 +0200
- author
- roland
- date
- Thu, 31 Jul 2014 19:59:36 +0200
- changeset 7003
- 69ea58782b1a
- parent 6680
- 78bbf4d43a14
- child 6876
- 710a3c8b516e
- child 7859
- c1c199dde5c9
- permissions
- -rw-r--r--
8054054: 8040121 is broken
Summary: C++ code pattern from 8040121 is incorrect
Reviewed-by: kvn
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 */
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"
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 */
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 }
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();
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");
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 }
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);
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 }
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");
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 }
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();
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");
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 }
204 // Create new_iff in new location.
205 IfNode *new_iff = iff->clone()->as_If();
206 new_iff->set_req(0, new_entry);
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);
218 // if_uct to rgn
219 hash_delete(rgn);
220 rgn->add_req(if_uct);
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");
236 return if_cont->as_Proj();
237 }
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);
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);
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 }
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 }
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 }
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 }
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 }
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 }
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 }
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;
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 }
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 _invariant.set(n->_idx); // I am a invariant too
442 }
443 } else { // process next input
444 _stack.set_index(idx + 1);
445 Node* m = n->in(idx);
446 if (m != NULL && !_visited.test_set(m->_idx)) {
447 visit(n, m);
448 }
449 }
450 }
451 }
453 // Helper function to set up _old_new map for clone_nodes.
454 // If n is a known invariant, set up directly ("clone" of n == n).
455 // Otherwise, push n onto the stack for real cloning.
456 void clone_visit(Node* n) {
457 assert(_invariant.test(n->_idx), "must be invariant");
458 if (_lpt->is_invariant(n)) { // known invariant
459 _old_new.map(n->_idx, n);
460 } else { // to be cloned
461 assert(!n->is_CFG(), "should not see CFG here");
462 _stack.push(n, n->in(0) == NULL ? 1 : 0);
463 }
464 }
466 // Clone "n" and (possibly) all its inputs recursively
467 void clone_nodes(Node* n, Node* ctrl) {
468 clone_visit(n);
469 while (_stack.is_nonempty()) {
470 Node* n = _stack.node();
471 uint idx = _stack.index();
472 if (idx == n->req()) { // all inputs processed, clone n!
473 _stack.pop();
474 // clone invariant node
475 Node* n_cl = n->clone();
476 _old_new.map(n->_idx, n_cl);
477 _phase->register_new_node(n_cl, ctrl);
478 for (uint i = 0; i < n->req(); i++) {
479 Node* in = n_cl->in(i);
480 if (in == NULL) continue;
481 n_cl->set_req(i, _old_new[in->_idx]);
482 }
483 } else { // process next input
484 _stack.set_index(idx + 1);
485 Node* m = n->in(idx);
486 if (m != NULL && !_clone_visited.test_set(m->_idx)) {
487 clone_visit(m); // visit the input
488 }
489 }
490 }
491 }
493 public:
494 Invariance(Arena* area, IdealLoopTree* lpt) :
495 _lpt(lpt), _phase(lpt->_phase),
496 _visited(area), _invariant(area), _stack(area, 10 /* guess */),
497 _clone_visited(area), _old_new(area)
498 {}
500 // Map old to n for invariance computation and clone
501 void map_ctrl(Node* old, Node* n) {
502 assert(old->is_CFG() && n->is_CFG(), "must be");
503 _old_new.map(old->_idx, n); // "clone" of old is n
504 _invariant.set(old->_idx); // old is invariant
505 _clone_visited.set(old->_idx);
506 }
508 // Driver function to compute invariance
509 bool is_invariant(Node* n) {
510 if (!_visited.test_set(n->_idx))
511 compute_invariance(n);
512 return (_invariant.test(n->_idx) != 0);
513 }
515 // Driver function to clone invariant
516 Node* clone(Node* n, Node* ctrl) {
517 assert(ctrl->is_CFG(), "must be");
518 assert(_invariant.test(n->_idx), "must be an invariant");
519 if (!_clone_visited.test(n->_idx))
520 clone_nodes(n, ctrl);
521 return _old_new[n->_idx];
522 }
523 };
525 //------------------------------is_range_check_if -----------------------------------
526 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
527 // Note: this function is particularly designed for loop predication. We require load_range
528 // and offset to be loop invariant computed on the fly by "invar"
529 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
530 if (!is_loop_exit(iff)) {
531 return false;
532 }
533 if (!iff->in(1)->is_Bool()) {
534 return false;
535 }
536 const BoolNode *bol = iff->in(1)->as_Bool();
537 if (bol->_test._test != BoolTest::lt) {
538 return false;
539 }
540 if (!bol->in(1)->is_Cmp()) {
541 return false;
542 }
543 const CmpNode *cmp = bol->in(1)->as_Cmp();
544 if (cmp->Opcode() != Op_CmpU) {
545 return false;
546 }
547 Node* range = cmp->in(2);
548 if (range->Opcode() != Op_LoadRange) {
549 const TypeInt* tint = phase->_igvn.type(range)->isa_int();
550 if (tint == NULL || tint->empty() || tint->_lo < 0) {
551 // Allow predication on positive values that aren't LoadRanges.
552 // This allows optimization of loops where the length of the
553 // array is a known value and doesn't need to be loaded back
554 // from the array.
555 return false;
556 }
557 }
558 if (!invar.is_invariant(range)) {
559 return false;
560 }
561 Node *iv = _head->as_CountedLoop()->phi();
562 int scale = 0;
563 Node *offset = NULL;
564 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
565 return false;
566 }
567 if (offset && !invar.is_invariant(offset)) { // offset must be invariant
568 return false;
569 }
570 return true;
571 }
573 //------------------------------rc_predicate-----------------------------------
574 // Create a range check predicate
575 //
576 // for (i = init; i < limit; i += stride) {
577 // a[scale*i+offset]
578 // }
579 //
580 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
581 // as "max(scale*i + offset) u< a.length".
582 //
583 // There are two cases for max(scale*i + offset):
584 // (1) stride*scale > 0
585 // max(scale*i + offset) = scale*(limit-stride) + offset
586 // (2) stride*scale < 0
587 // max(scale*i + offset) = scale*init + offset
588 BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
589 int scale, Node* offset,
590 Node* init, Node* limit, Node* stride,
591 Node* range, bool upper) {
592 stringStream* predString = NULL;
593 if (TraceLoopPredicate) {
594 predString = new stringStream();
595 predString->print("rc_predicate ");
596 }
598 Node* max_idx_expr = init;
599 int stride_con = stride->get_int();
600 if ((stride_con > 0) == (scale > 0) == upper) {
601 if (LoopLimitCheck) {
602 // With LoopLimitCheck limit is not exact.
603 // Calculate exact limit here.
604 // Note, counted loop's test is '<' or '>'.
605 limit = exact_limit(loop);
606 max_idx_expr = new (C) SubINode(limit, stride);
607 register_new_node(max_idx_expr, ctrl);
608 if (TraceLoopPredicate) predString->print("(limit - stride) ");
609 } else {
610 max_idx_expr = new (C) SubINode(limit, stride);
611 register_new_node(max_idx_expr, ctrl);
612 if (TraceLoopPredicate) predString->print("(limit - stride) ");
613 }
614 } else {
615 if (TraceLoopPredicate) predString->print("init ");
616 }
618 if (scale != 1) {
619 ConNode* con_scale = _igvn.intcon(scale);
620 max_idx_expr = new (C) MulINode(max_idx_expr, con_scale);
621 register_new_node(max_idx_expr, ctrl);
622 if (TraceLoopPredicate) predString->print("* %d ", scale);
623 }
625 if (offset && (!offset->is_Con() || offset->get_int() != 0)){
626 max_idx_expr = new (C) AddINode(max_idx_expr, offset);
627 register_new_node(max_idx_expr, ctrl);
628 if (TraceLoopPredicate)
629 if (offset->is_Con()) predString->print("+ %d ", offset->get_int());
630 else predString->print("+ offset ");
631 }
633 CmpUNode* cmp = new (C) CmpUNode(max_idx_expr, range);
634 register_new_node(cmp, ctrl);
635 BoolNode* bol = new (C) BoolNode(cmp, BoolTest::lt);
636 register_new_node(bol, ctrl);
638 if (TraceLoopPredicate) {
639 predString->print_cr("<u range");
640 tty->print("%s", predString->as_string());
641 }
642 return bol;
643 }
645 //------------------------------ loop_predication_impl--------------------------
646 // Insert loop predicates for null checks and range checks
647 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
648 if (!UseLoopPredicate) return false;
650 if (!loop->_head->is_Loop()) {
651 // Could be a simple region when irreducible loops are present.
652 return false;
653 }
654 LoopNode* head = loop->_head->as_Loop();
656 if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
657 // do nothing for infinite loops
658 return false;
659 }
661 CountedLoopNode *cl = NULL;
662 if (head->is_valid_counted_loop()) {
663 cl = head->as_CountedLoop();
664 // do nothing for iteration-splitted loops
665 if (!cl->is_normal_loop()) return false;
666 // Avoid RCE if Counted loop's test is '!='.
667 BoolTest::mask bt = cl->loopexit()->test_trip();
668 if (bt != BoolTest::lt && bt != BoolTest::gt)
669 cl = NULL;
670 }
672 Node* entry = head->in(LoopNode::EntryControl);
673 ProjNode *predicate_proj = NULL;
674 // Loop limit check predicate should be near the loop.
675 if (LoopLimitCheck) {
676 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
677 if (predicate_proj != NULL)
678 entry = predicate_proj->in(0)->in(0);
679 }
681 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
682 if (!predicate_proj) {
683 #ifndef PRODUCT
684 if (TraceLoopPredicate) {
685 tty->print("missing predicate:");
686 loop->dump_head();
687 head->dump(1);
688 }
689 #endif
690 return false;
691 }
692 ConNode* zero = _igvn.intcon(0);
693 set_ctrl(zero, C->root());
695 ResourceArea *area = Thread::current()->resource_area();
696 Invariance invar(area, loop);
698 // Create list of if-projs such that a newer proj dominates all older
699 // projs in the list, and they all dominate loop->tail()
700 Node_List if_proj_list(area);
701 Node *current_proj = loop->tail(); //start from tail
702 while (current_proj != head) {
703 if (loop == get_loop(current_proj) && // still in the loop ?
704 current_proj->is_Proj() && // is a projection ?
705 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
706 if_proj_list.push(current_proj);
707 }
708 current_proj = idom(current_proj);
709 }
711 bool hoisted = false; // true if at least one proj is promoted
712 while (if_proj_list.size() > 0) {
713 // Following are changed to nonnull when a predicate can be hoisted
714 ProjNode* new_predicate_proj = NULL;
716 ProjNode* proj = if_proj_list.pop()->as_Proj();
717 IfNode* iff = proj->in(0)->as_If();
719 if (!proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
720 if (loop->is_loop_exit(iff)) {
721 // stop processing the remaining projs in the list because the execution of them
722 // depends on the condition of "iff" (iff->in(1)).
723 break;
724 } else {
725 // Both arms are inside the loop. There are two cases:
726 // (1) there is one backward branch. In this case, any remaining proj
727 // in the if_proj list post-dominates "iff". So, the condition of "iff"
728 // does not determine the execution the remining projs directly, and we
729 // can safely continue.
730 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
731 // does not dominate loop->tail(), so it can not be in the if_proj list.
732 continue;
733 }
734 }
736 Node* test = iff->in(1);
737 if (!test->is_Bool()){ //Conv2B, ...
738 continue;
739 }
740 BoolNode* bol = test->as_Bool();
741 if (invar.is_invariant(bol)) {
742 // Invariant test
743 new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
744 Deoptimization::Reason_predicate);
745 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
746 BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
748 // Negate test if necessary
749 bool negated = false;
750 if (proj->_con != predicate_proj->_con) {
751 new_predicate_bol = new (C) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
752 register_new_node(new_predicate_bol, ctrl);
753 negated = true;
754 }
755 IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
756 _igvn.hash_delete(new_predicate_iff);
757 new_predicate_iff->set_req(1, new_predicate_bol);
758 #ifndef PRODUCT
759 if (TraceLoopPredicate) {
760 tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
761 loop->dump_head();
762 } else if (TraceLoopOpts) {
763 tty->print("Predicate IC ");
764 loop->dump_head();
765 }
766 #endif
767 } else if ((cl != NULL) && (proj->_con == predicate_proj->_con) &&
768 loop->is_range_check_if(iff, this, invar)) {
770 // Range check for counted loops
771 const Node* cmp = bol->in(1)->as_Cmp();
772 Node* idx = cmp->in(1);
773 assert(!invar.is_invariant(idx), "index is variant");
774 Node* rng = cmp->in(2);
775 assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() >= 0, "must be");
776 assert(invar.is_invariant(rng), "range must be invariant");
777 int scale = 1;
778 Node* offset = zero;
779 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
780 assert(ok, "must be index expression");
782 Node* init = cl->init_trip();
783 Node* limit = cl->limit();
784 Node* stride = cl->stride();
786 // Build if's for the upper and lower bound tests. The
787 // lower_bound test will dominate the upper bound test and all
788 // cloned or created nodes will use the lower bound test as
789 // their declared control.
790 ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
791 ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
792 assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
793 Node *ctrl = lower_bound_proj->in(0)->as_If()->in(0);
795 // Perform cloning to keep Invariance state correct since the
796 // late schedule will place invariant things in the loop.
797 rng = invar.clone(rng, ctrl);
798 if (offset && offset != zero) {
799 assert(invar.is_invariant(offset), "offset must be loop invariant");
800 offset = invar.clone(offset, ctrl);
801 }
803 // Test the lower bound
804 Node* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false);
805 IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
806 _igvn.hash_delete(lower_bound_iff);
807 lower_bound_iff->set_req(1, lower_bound_bol);
808 if (TraceLoopPredicate) tty->print_cr("lower bound check if: %d", lower_bound_iff->_idx);
810 // Test the upper bound
811 Node* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true);
812 IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
813 _igvn.hash_delete(upper_bound_iff);
814 upper_bound_iff->set_req(1, upper_bound_bol);
815 if (TraceLoopPredicate) tty->print_cr("upper bound check if: %d", lower_bound_iff->_idx);
817 // Fall through into rest of the clean up code which will move
818 // any dependent nodes onto the upper bound test.
819 new_predicate_proj = upper_bound_proj;
821 #ifndef PRODUCT
822 if (TraceLoopOpts && !TraceLoopPredicate) {
823 tty->print("Predicate RC ");
824 loop->dump_head();
825 }
826 #endif
827 } else {
828 // Loop variant check (for example, range check in non-counted loop)
829 // with uncommon trap.
830 continue;
831 }
832 assert(new_predicate_proj != NULL, "sanity");
833 // Success - attach condition (new_predicate_bol) to predicate if
834 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
836 // Eliminate the old If in the loop body
837 dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
839 hoisted = true;
840 C->set_major_progress();
841 } // end while
843 #ifndef PRODUCT
844 // report that the loop predication has been actually performed
845 // for this loop
846 if (TraceLoopPredicate && hoisted) {
847 tty->print("Loop Predication Performed:");
848 loop->dump_head();
849 }
850 #endif
852 return hoisted;
853 }
855 //------------------------------loop_predication--------------------------------
856 // driver routine for loop predication optimization
857 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
858 bool hoisted = false;
859 // Recursively promote predicates
860 if (_child) {
861 hoisted = _child->loop_predication( phase);
862 }
864 // self
865 if (!_irreducible && !tail()->is_top()) {
866 hoisted |= phase->loop_predication_impl(this);
867 }
869 if (_next) { //sibling
870 hoisted |= _next->loop_predication( phase);
871 }
873 return hoisted;
874 }
