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src/share/vm/opto/loopPredicate.cpp@1bd45abaa507
src/share/vm/opto/loopPredicate.cpp
Wed, 16 Nov 2011 09:13:57 -0800
- author
- kvn
- date
- Wed, 16 Nov 2011 09:13:57 -0800
- changeset 3311
- 1bd45abaa507
- parent 3048
- 6987871cfb9b
- child 3847
- 5e990493719e
- permissions
- -rw-r--r--
6890673: Eliminate allocations immediately after EA
Summary: Try to eliminate allocations and related locks immediately after escape analysis.
Reviewed-by: never
1 /*
2 * Copyright (c) 2011, 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 //-------------------------------is_uncommon_trap_proj----------------------------
45 // Return true if proj is the form of "proj->[region->..]call_uct"
46 bool PhaseIdealLoop::is_uncommon_trap_proj(ProjNode* proj, Deoptimization::DeoptReason reason) {
47 int path_limit = 10;
48 assert(proj, "invalid argument");
49 Node* out = proj;
50 for (int ct = 0; ct < path_limit; ct++) {
51 out = out->unique_ctrl_out();
52 if (out == NULL)
53 return false;
54 if (out->is_CallStaticJava()) {
55 int req = out->as_CallStaticJava()->uncommon_trap_request();
56 if (req != 0) {
57 Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
58 if (trap_reason == reason || reason == Deoptimization::Reason_none) {
59 return true;
60 }
61 }
62 return false; // don't do further after call
63 }
64 if (out->Opcode() != Op_Region)
65 return false;
66 }
67 return false;
68 }
70 //-------------------------------is_uncommon_trap_if_pattern-------------------------
71 // Return true for "if(test)-> proj -> ...
72 // |
73 // V
74 // other_proj->[region->..]call_uct"
75 //
76 // "must_reason_predicate" means the uct reason must be Reason_predicate
77 bool PhaseIdealLoop::is_uncommon_trap_if_pattern(ProjNode *proj, Deoptimization::DeoptReason reason) {
78 Node *in0 = proj->in(0);
79 if (!in0->is_If()) return false;
80 // Variation of a dead If node.
81 if (in0->outcnt() < 2) return false;
82 IfNode* iff = in0->as_If();
84 // we need "If(Conv2B(Opaque1(...)))" pattern for reason_predicate
85 if (reason != Deoptimization::Reason_none) {
86 if (iff->in(1)->Opcode() != Op_Conv2B ||
87 iff->in(1)->in(1)->Opcode() != Op_Opaque1) {
88 return false;
89 }
90 }
92 ProjNode* other_proj = iff->proj_out(1-proj->_con)->as_Proj();
93 if (is_uncommon_trap_proj(other_proj, reason)) {
94 assert(reason == Deoptimization::Reason_none ||
95 Compile::current()->is_predicate_opaq(iff->in(1)->in(1)), "should be on the list");
96 return true;
97 }
98 return false;
99 }
101 //-------------------------------register_control-------------------------
102 void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
103 assert(n->is_CFG(), "must be control node");
104 _igvn.register_new_node_with_optimizer(n);
105 loop->_body.push(n);
106 set_loop(n, loop);
107 // When called from beautify_loops() idom is not constructed yet.
108 if (_idom != NULL) {
109 set_idom(n, pred, dom_depth(pred));
110 }
111 }
113 //------------------------------create_new_if_for_predicate------------------------
114 // create a new if above the uct_if_pattern for the predicate to be promoted.
115 //
116 // before after
117 // ---------- ----------
118 // ctrl ctrl
119 // | |
120 // | |
121 // v v
122 // iff new_iff
123 // / \ / \
124 // / \ / \
125 // v v v v
126 // uncommon_proj cont_proj if_uct if_cont
127 // \ | | | |
128 // \ | | | |
129 // v v v | v
130 // rgn loop | iff
131 // | | / \
132 // | | / \
133 // v | v v
134 // uncommon_trap | uncommon_proj cont_proj
135 // \ \ | |
136 // \ \ | |
137 // v v v v
138 // rgn loop
139 // |
140 // |
141 // v
142 // uncommon_trap
143 //
144 //
145 // We will create a region to guard the uct call if there is no one there.
146 // The true projecttion (if_cont) of the new_iff is returned.
147 // This code is also used to clone predicates to clonned loops.
148 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
149 Deoptimization::DeoptReason reason) {
150 assert(is_uncommon_trap_if_pattern(cont_proj, reason), "must be a uct if pattern!");
151 IfNode* iff = cont_proj->in(0)->as_If();
153 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
154 Node *rgn = uncommon_proj->unique_ctrl_out();
155 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
157 uint proj_index = 1; // region's edge corresponding to uncommon_proj
158 if (!rgn->is_Region()) { // create a region to guard the call
159 assert(rgn->is_Call(), "must be call uct");
160 CallNode* call = rgn->as_Call();
161 IdealLoopTree* loop = get_loop(call);
162 rgn = new (C, 1) RegionNode(1);
163 rgn->add_req(uncommon_proj);
164 register_control(rgn, loop, uncommon_proj);
165 _igvn.hash_delete(call);
166 call->set_req(0, rgn);
167 // When called from beautify_loops() idom is not constructed yet.
168 if (_idom != NULL) {
169 set_idom(call, rgn, dom_depth(rgn));
170 }
171 } else {
172 // Find region's edge corresponding to uncommon_proj
173 for (; proj_index < rgn->req(); proj_index++)
174 if (rgn->in(proj_index) == uncommon_proj) break;
175 assert(proj_index < rgn->req(), "sanity");
176 }
178 Node* entry = iff->in(0);
179 if (new_entry != NULL) {
180 // Clonning the predicate to new location.
181 entry = new_entry;
182 }
183 // Create new_iff
184 IdealLoopTree* lp = get_loop(entry);
185 IfNode *new_iff = iff->clone()->as_If();
186 new_iff->set_req(0, entry);
187 register_control(new_iff, lp, entry);
188 Node *if_cont = new (C, 1) IfTrueNode(new_iff);
189 Node *if_uct = new (C, 1) IfFalseNode(new_iff);
190 if (cont_proj->is_IfFalse()) {
191 // Swap
192 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
193 }
194 register_control(if_cont, lp, new_iff);
195 register_control(if_uct, get_loop(rgn), new_iff);
197 // if_uct to rgn
198 _igvn.hash_delete(rgn);
199 rgn->add_req(if_uct);
200 // When called from beautify_loops() idom is not constructed yet.
201 if (_idom != NULL) {
202 Node* ridom = idom(rgn);
203 Node* nrdom = dom_lca(ridom, new_iff);
204 set_idom(rgn, nrdom, dom_depth(rgn));
205 }
207 // If rgn has phis add new edges which has the same
208 // value as on original uncommon_proj pass.
209 assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
210 bool has_phi = false;
211 for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
212 Node* use = rgn->fast_out(i);
213 if (use->is_Phi() && use->outcnt() > 0) {
214 assert(use->in(0) == rgn, "");
215 _igvn.hash_delete(use);
216 use->add_req(use->in(proj_index));
217 _igvn._worklist.push(use);
218 has_phi = true;
219 }
220 }
221 assert(!has_phi || rgn->req() > 3, "no phis when region is created");
223 if (new_entry == NULL) {
224 // Attach if_cont to iff
225 _igvn.hash_delete(iff);
226 iff->set_req(0, if_cont);
227 if (_idom != NULL) {
228 set_idom(iff, if_cont, dom_depth(iff));
229 }
230 }
231 return if_cont->as_Proj();
232 }
234 //------------------------------create_new_if_for_predicate------------------------
235 // Create a new if below new_entry for the predicate to be cloned (IGVN optimization)
236 ProjNode* PhaseIterGVN::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
237 Deoptimization::DeoptReason reason) {
238 assert(new_entry != 0, "only used for clone predicate");
239 assert(PhaseIdealLoop::is_uncommon_trap_if_pattern(cont_proj, reason), "must be a uct if pattern!");
240 IfNode* iff = cont_proj->in(0)->as_If();
242 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
243 Node *rgn = uncommon_proj->unique_ctrl_out();
244 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
246 uint proj_index = 1; // region's edge corresponding to uncommon_proj
247 if (!rgn->is_Region()) { // create a region to guard the call
248 assert(rgn->is_Call(), "must be call uct");
249 CallNode* call = rgn->as_Call();
250 rgn = new (C, 1) RegionNode(1);
251 register_new_node_with_optimizer(rgn);
252 rgn->add_req(uncommon_proj);
253 hash_delete(call);
254 call->set_req(0, rgn);
255 } else {
256 // Find region's edge corresponding to uncommon_proj
257 for (; proj_index < rgn->req(); proj_index++)
258 if (rgn->in(proj_index) == uncommon_proj) break;
259 assert(proj_index < rgn->req(), "sanity");
260 }
262 // Create new_iff in new location.
263 IfNode *new_iff = iff->clone()->as_If();
264 new_iff->set_req(0, new_entry);
266 register_new_node_with_optimizer(new_iff);
267 Node *if_cont = new (C, 1) IfTrueNode(new_iff);
268 Node *if_uct = new (C, 1) IfFalseNode(new_iff);
269 if (cont_proj->is_IfFalse()) {
270 // Swap
271 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
272 }
273 register_new_node_with_optimizer(if_cont);
274 register_new_node_with_optimizer(if_uct);
276 // if_uct to rgn
277 hash_delete(rgn);
278 rgn->add_req(if_uct);
280 // If rgn has phis add corresponding new edges which has the same
281 // value as on original uncommon_proj pass.
282 assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
283 bool has_phi = false;
284 for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
285 Node* use = rgn->fast_out(i);
286 if (use->is_Phi() && use->outcnt() > 0) {
287 hash_delete(use);
288 use->add_req(use->in(proj_index));
289 _worklist.push(use);
290 has_phi = true;
291 }
292 }
293 assert(!has_phi || rgn->req() > 3, "no phis when region is created");
295 return if_cont->as_Proj();
296 }
298 //--------------------------clone_predicate-----------------------
299 ProjNode* PhaseIdealLoop::clone_predicate(ProjNode* predicate_proj, Node* new_entry,
300 Deoptimization::DeoptReason reason,
301 PhaseIdealLoop* loop_phase,
302 PhaseIterGVN* igvn) {
303 ProjNode* new_predicate_proj;
304 if (loop_phase != NULL) {
305 new_predicate_proj = loop_phase->create_new_if_for_predicate(predicate_proj, new_entry, reason);
306 } else {
307 new_predicate_proj = igvn->create_new_if_for_predicate(predicate_proj, new_entry, reason);
308 }
309 IfNode* iff = new_predicate_proj->in(0)->as_If();
310 Node* ctrl = iff->in(0);
312 // Match original condition since predicate's projections could be swapped.
313 assert(predicate_proj->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
314 Node* opq = new (igvn->C, 2) Opaque1Node(igvn->C, predicate_proj->in(0)->in(1)->in(1)->in(1));
315 igvn->C->add_predicate_opaq(opq);
317 Node* bol = new (igvn->C, 2) Conv2BNode(opq);
318 if (loop_phase != NULL) {
319 loop_phase->register_new_node(opq, ctrl);
320 loop_phase->register_new_node(bol, ctrl);
321 } else {
322 igvn->register_new_node_with_optimizer(opq);
323 igvn->register_new_node_with_optimizer(bol);
324 }
325 igvn->hash_delete(iff);
326 iff->set_req(1, bol);
327 return new_predicate_proj;
328 }
331 //--------------------------clone_loop_predicates-----------------------
332 // Interface from IGVN
333 Node* PhaseIterGVN::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
334 return PhaseIdealLoop::clone_loop_predicates(old_entry, new_entry, clone_limit_check, NULL, this);
335 }
337 // Interface from PhaseIdealLoop
338 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
339 return clone_loop_predicates(old_entry, new_entry, clone_limit_check, this, &this->_igvn);
340 }
342 // Clone loop predicates to cloned loops (peeled, unswitched, split_if).
343 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry,
344 bool clone_limit_check,
345 PhaseIdealLoop* loop_phase,
346 PhaseIterGVN* igvn) {
347 #ifdef ASSERT
348 if (new_entry == NULL || !(new_entry->is_Proj() || new_entry->is_Region() || new_entry->is_SafePoint())) {
349 if (new_entry != NULL)
350 new_entry->dump();
351 assert(false, "not IfTrue, IfFalse, Region or SafePoint");
352 }
353 #endif
354 // Search original predicates
355 Node* entry = old_entry;
356 ProjNode* limit_check_proj = NULL;
357 if (LoopLimitCheck) {
358 limit_check_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
359 if (limit_check_proj != NULL) {
360 entry = entry->in(0)->in(0);
361 }
362 }
363 if (UseLoopPredicate) {
364 ProjNode* predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
365 if (predicate_proj != NULL) { // right pattern that can be used by loop predication
366 // clone predicate
367 new_entry = clone_predicate(predicate_proj, new_entry,
368 Deoptimization::Reason_predicate,
369 loop_phase, igvn);
370 assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
371 if (TraceLoopPredicate) {
372 tty->print("Loop Predicate cloned: ");
373 debug_only( new_entry->in(0)->dump(); )
374 }
375 }
376 }
377 if (limit_check_proj != NULL && clone_limit_check) {
378 // Clone loop limit check last to insert it before loop.
379 // Don't clone a limit check which was already finalized
380 // for this counted loop (only one limit check is needed).
381 new_entry = clone_predicate(limit_check_proj, new_entry,
382 Deoptimization::Reason_loop_limit_check,
383 loop_phase, igvn);
384 assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone limit check");
385 if (TraceLoopLimitCheck) {
386 tty->print("Loop Limit Check cloned: ");
387 debug_only( new_entry->in(0)->dump(); )
388 }
389 }
390 return new_entry;
391 }
393 //--------------------------skip_loop_predicates------------------------------
394 // Skip related predicates.
395 Node* PhaseIdealLoop::skip_loop_predicates(Node* entry) {
396 Node* predicate = NULL;
397 if (LoopLimitCheck) {
398 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
399 if (predicate != NULL) {
400 entry = entry->in(0)->in(0);
401 }
402 }
403 if (UseLoopPredicate) {
404 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
405 if (predicate != NULL) { // right pattern that can be used by loop predication
406 IfNode* iff = entry->in(0)->as_If();
407 ProjNode* uncommon_proj = iff->proj_out(1 - entry->as_Proj()->_con);
408 Node* rgn = uncommon_proj->unique_ctrl_out();
409 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
410 entry = entry->in(0)->in(0);
411 while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
412 uncommon_proj = entry->in(0)->as_If()->proj_out(1 - entry->as_Proj()->_con);
413 if (uncommon_proj->unique_ctrl_out() != rgn)
414 break;
415 entry = entry->in(0)->in(0);
416 }
417 }
418 }
419 return entry;
420 }
422 //--------------------------find_predicate_insertion_point-------------------
423 // Find a good location to insert a predicate
424 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
425 if (start_c == NULL || !start_c->is_Proj())
426 return NULL;
427 if (is_uncommon_trap_if_pattern(start_c->as_Proj(), reason)) {
428 return start_c->as_Proj();
429 }
430 return NULL;
431 }
433 //--------------------------find_predicate------------------------------------
434 // Find a predicate
435 Node* PhaseIdealLoop::find_predicate(Node* entry) {
436 Node* predicate = NULL;
437 if (LoopLimitCheck) {
438 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
439 if (predicate != NULL) { // right pattern that can be used by loop predication
440 return entry;
441 }
442 }
443 if (UseLoopPredicate) {
444 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
445 if (predicate != NULL) { // right pattern that can be used by loop predication
446 return entry;
447 }
448 }
449 return NULL;
450 }
452 //------------------------------Invariance-----------------------------------
453 // Helper class for loop_predication_impl to compute invariance on the fly and
454 // clone invariants.
455 class Invariance : public StackObj {
456 VectorSet _visited, _invariant;
457 Node_Stack _stack;
458 VectorSet _clone_visited;
459 Node_List _old_new; // map of old to new (clone)
460 IdealLoopTree* _lpt;
461 PhaseIdealLoop* _phase;
463 // Helper function to set up the invariance for invariance computation
464 // If n is a known invariant, set up directly. Otherwise, look up the
465 // the possibility to push n onto the stack for further processing.
466 void visit(Node* use, Node* n) {
467 if (_lpt->is_invariant(n)) { // known invariant
468 _invariant.set(n->_idx);
469 } else if (!n->is_CFG()) {
470 Node *n_ctrl = _phase->ctrl_or_self(n);
471 Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
472 if (_phase->is_dominator(n_ctrl, u_ctrl)) {
473 _stack.push(n, n->in(0) == NULL ? 1 : 0);
474 }
475 }
476 }
478 // Compute invariance for "the_node" and (possibly) all its inputs recursively
479 // on the fly
480 void compute_invariance(Node* n) {
481 assert(_visited.test(n->_idx), "must be");
482 visit(n, n);
483 while (_stack.is_nonempty()) {
484 Node* n = _stack.node();
485 uint idx = _stack.index();
486 if (idx == n->req()) { // all inputs are processed
487 _stack.pop();
488 // n is invariant if it's inputs are all invariant
489 bool all_inputs_invariant = true;
490 for (uint i = 0; i < n->req(); i++) {
491 Node* in = n->in(i);
492 if (in == NULL) continue;
493 assert(_visited.test(in->_idx), "must have visited input");
494 if (!_invariant.test(in->_idx)) { // bad guy
495 all_inputs_invariant = false;
496 break;
497 }
498 }
499 if (all_inputs_invariant) {
500 _invariant.set(n->_idx); // I am a invariant too
501 }
502 } else { // process next input
503 _stack.set_index(idx + 1);
504 Node* m = n->in(idx);
505 if (m != NULL && !_visited.test_set(m->_idx)) {
506 visit(n, m);
507 }
508 }
509 }
510 }
512 // Helper function to set up _old_new map for clone_nodes.
513 // If n is a known invariant, set up directly ("clone" of n == n).
514 // Otherwise, push n onto the stack for real cloning.
515 void clone_visit(Node* n) {
516 assert(_invariant.test(n->_idx), "must be invariant");
517 if (_lpt->is_invariant(n)) { // known invariant
518 _old_new.map(n->_idx, n);
519 } else { // to be cloned
520 assert(!n->is_CFG(), "should not see CFG here");
521 _stack.push(n, n->in(0) == NULL ? 1 : 0);
522 }
523 }
525 // Clone "n" and (possibly) all its inputs recursively
526 void clone_nodes(Node* n, Node* ctrl) {
527 clone_visit(n);
528 while (_stack.is_nonempty()) {
529 Node* n = _stack.node();
530 uint idx = _stack.index();
531 if (idx == n->req()) { // all inputs processed, clone n!
532 _stack.pop();
533 // clone invariant node
534 Node* n_cl = n->clone();
535 _old_new.map(n->_idx, n_cl);
536 _phase->register_new_node(n_cl, ctrl);
537 for (uint i = 0; i < n->req(); i++) {
538 Node* in = n_cl->in(i);
539 if (in == NULL) continue;
540 n_cl->set_req(i, _old_new[in->_idx]);
541 }
542 } else { // process next input
543 _stack.set_index(idx + 1);
544 Node* m = n->in(idx);
545 if (m != NULL && !_clone_visited.test_set(m->_idx)) {
546 clone_visit(m); // visit the input
547 }
548 }
549 }
550 }
552 public:
553 Invariance(Arena* area, IdealLoopTree* lpt) :
554 _lpt(lpt), _phase(lpt->_phase),
555 _visited(area), _invariant(area), _stack(area, 10 /* guess */),
556 _clone_visited(area), _old_new(area)
557 {}
559 // Map old to n for invariance computation and clone
560 void map_ctrl(Node* old, Node* n) {
561 assert(old->is_CFG() && n->is_CFG(), "must be");
562 _old_new.map(old->_idx, n); // "clone" of old is n
563 _invariant.set(old->_idx); // old is invariant
564 _clone_visited.set(old->_idx);
565 }
567 // Driver function to compute invariance
568 bool is_invariant(Node* n) {
569 if (!_visited.test_set(n->_idx))
570 compute_invariance(n);
571 return (_invariant.test(n->_idx) != 0);
572 }
574 // Driver function to clone invariant
575 Node* clone(Node* n, Node* ctrl) {
576 assert(ctrl->is_CFG(), "must be");
577 assert(_invariant.test(n->_idx), "must be an invariant");
578 if (!_clone_visited.test(n->_idx))
579 clone_nodes(n, ctrl);
580 return _old_new[n->_idx];
581 }
582 };
584 //------------------------------is_range_check_if -----------------------------------
585 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
586 // Note: this function is particularly designed for loop predication. We require load_range
587 // and offset to be loop invariant computed on the fly by "invar"
588 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
589 if (!is_loop_exit(iff)) {
590 return false;
591 }
592 if (!iff->in(1)->is_Bool()) {
593 return false;
594 }
595 const BoolNode *bol = iff->in(1)->as_Bool();
596 if (bol->_test._test != BoolTest::lt) {
597 return false;
598 }
599 if (!bol->in(1)->is_Cmp()) {
600 return false;
601 }
602 const CmpNode *cmp = bol->in(1)->as_Cmp();
603 if (cmp->Opcode() != Op_CmpU) {
604 return false;
605 }
606 Node* range = cmp->in(2);
607 if (range->Opcode() != Op_LoadRange) {
608 const TypeInt* tint = phase->_igvn.type(range)->isa_int();
609 if (tint == NULL || tint->empty() || tint->_lo < 0) {
610 // Allow predication on positive values that aren't LoadRanges.
611 // This allows optimization of loops where the length of the
612 // array is a known value and doesn't need to be loaded back
613 // from the array.
614 return false;
615 }
616 }
617 if (!invar.is_invariant(range)) {
618 return false;
619 }
620 Node *iv = _head->as_CountedLoop()->phi();
621 int scale = 0;
622 Node *offset = NULL;
623 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
624 return false;
625 }
626 if (offset && !invar.is_invariant(offset)) { // offset must be invariant
627 return false;
628 }
629 return true;
630 }
632 //------------------------------rc_predicate-----------------------------------
633 // Create a range check predicate
634 //
635 // for (i = init; i < limit; i += stride) {
636 // a[scale*i+offset]
637 // }
638 //
639 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
640 // as "max(scale*i + offset) u< a.length".
641 //
642 // There are two cases for max(scale*i + offset):
643 // (1) stride*scale > 0
644 // max(scale*i + offset) = scale*(limit-stride) + offset
645 // (2) stride*scale < 0
646 // max(scale*i + offset) = scale*init + offset
647 BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
648 int scale, Node* offset,
649 Node* init, Node* limit, Node* stride,
650 Node* range, bool upper) {
651 stringStream* predString = NULL;
652 if (TraceLoopPredicate) {
653 predString = new stringStream();
654 predString->print("rc_predicate ");
655 }
657 Node* max_idx_expr = init;
658 int stride_con = stride->get_int();
659 if ((stride_con > 0) == (scale > 0) == upper) {
660 if (LoopLimitCheck) {
661 // With LoopLimitCheck limit is not exact.
662 // Calculate exact limit here.
663 // Note, counted loop's test is '<' or '>'.
664 limit = exact_limit(loop);
665 max_idx_expr = new (C, 3) SubINode(limit, stride);
666 register_new_node(max_idx_expr, ctrl);
667 if (TraceLoopPredicate) predString->print("(limit - stride) ");
668 } else {
669 max_idx_expr = new (C, 3) SubINode(limit, stride);
670 register_new_node(max_idx_expr, ctrl);
671 if (TraceLoopPredicate) predString->print("(limit - stride) ");
672 }
673 } else {
674 if (TraceLoopPredicate) predString->print("init ");
675 }
677 if (scale != 1) {
678 ConNode* con_scale = _igvn.intcon(scale);
679 max_idx_expr = new (C, 3) MulINode(max_idx_expr, con_scale);
680 register_new_node(max_idx_expr, ctrl);
681 if (TraceLoopPredicate) predString->print("* %d ", scale);
682 }
684 if (offset && (!offset->is_Con() || offset->get_int() != 0)){
685 max_idx_expr = new (C, 3) AddINode(max_idx_expr, offset);
686 register_new_node(max_idx_expr, ctrl);
687 if (TraceLoopPredicate)
688 if (offset->is_Con()) predString->print("+ %d ", offset->get_int());
689 else predString->print("+ offset ");
690 }
692 CmpUNode* cmp = new (C, 3) CmpUNode(max_idx_expr, range);
693 register_new_node(cmp, ctrl);
694 BoolNode* bol = new (C, 2) BoolNode(cmp, BoolTest::lt);
695 register_new_node(bol, ctrl);
697 if (TraceLoopPredicate) {
698 predString->print_cr("<u range");
699 tty->print(predString->as_string());
700 }
701 return bol;
702 }
704 //------------------------------ loop_predication_impl--------------------------
705 // Insert loop predicates for null checks and range checks
706 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
707 if (!UseLoopPredicate) return false;
709 if (!loop->_head->is_Loop()) {
710 // Could be a simple region when irreducible loops are present.
711 return false;
712 }
713 LoopNode* head = loop->_head->as_Loop();
715 if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
716 // do nothing for infinite loops
717 return false;
718 }
720 CountedLoopNode *cl = NULL;
721 if (head->is_valid_counted_loop()) {
722 cl = head->as_CountedLoop();
723 // do nothing for iteration-splitted loops
724 if (!cl->is_normal_loop()) return false;
725 // Avoid RCE if Counted loop's test is '!='.
726 BoolTest::mask bt = cl->loopexit()->test_trip();
727 if (bt != BoolTest::lt && bt != BoolTest::gt)
728 cl = NULL;
729 }
731 Node* entry = head->in(LoopNode::EntryControl);
732 ProjNode *predicate_proj = NULL;
733 // Loop limit check predicate should be near the loop.
734 if (LoopLimitCheck) {
735 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
736 if (predicate_proj != NULL)
737 entry = predicate_proj->in(0)->in(0);
738 }
740 predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
741 if (!predicate_proj) {
742 #ifndef PRODUCT
743 if (TraceLoopPredicate) {
744 tty->print("missing predicate:");
745 loop->dump_head();
746 head->dump(1);
747 }
748 #endif
749 return false;
750 }
751 ConNode* zero = _igvn.intcon(0);
752 set_ctrl(zero, C->root());
754 ResourceArea *area = Thread::current()->resource_area();
755 Invariance invar(area, loop);
757 // Create list of if-projs such that a newer proj dominates all older
758 // projs in the list, and they all dominate loop->tail()
759 Node_List if_proj_list(area);
760 Node *current_proj = loop->tail(); //start from tail
761 while (current_proj != head) {
762 if (loop == get_loop(current_proj) && // still in the loop ?
763 current_proj->is_Proj() && // is a projection ?
764 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
765 if_proj_list.push(current_proj);
766 }
767 current_proj = idom(current_proj);
768 }
770 bool hoisted = false; // true if at least one proj is promoted
771 while (if_proj_list.size() > 0) {
772 // Following are changed to nonnull when a predicate can be hoisted
773 ProjNode* new_predicate_proj = NULL;
775 ProjNode* proj = if_proj_list.pop()->as_Proj();
776 IfNode* iff = proj->in(0)->as_If();
778 if (!is_uncommon_trap_if_pattern(proj, Deoptimization::Reason_none)) {
779 if (loop->is_loop_exit(iff)) {
780 // stop processing the remaining projs in the list because the execution of them
781 // depends on the condition of "iff" (iff->in(1)).
782 break;
783 } else {
784 // Both arms are inside the loop. There are two cases:
785 // (1) there is one backward branch. In this case, any remaining proj
786 // in the if_proj list post-dominates "iff". So, the condition of "iff"
787 // does not determine the execution the remining projs directly, and we
788 // can safely continue.
789 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
790 // does not dominate loop->tail(), so it can not be in the if_proj list.
791 continue;
792 }
793 }
795 Node* test = iff->in(1);
796 if (!test->is_Bool()){ //Conv2B, ...
797 continue;
798 }
799 BoolNode* bol = test->as_Bool();
800 if (invar.is_invariant(bol)) {
801 // Invariant test
802 new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
803 Deoptimization::Reason_predicate);
804 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
805 BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
807 // Negate test if necessary
808 bool negated = false;
809 if (proj->_con != predicate_proj->_con) {
810 new_predicate_bol = new (C, 2) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
811 register_new_node(new_predicate_bol, ctrl);
812 negated = true;
813 }
814 IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
815 _igvn.hash_delete(new_predicate_iff);
816 new_predicate_iff->set_req(1, new_predicate_bol);
817 #ifndef PRODUCT
818 if (TraceLoopPredicate) {
819 tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
820 loop->dump_head();
821 } else if (TraceLoopOpts) {
822 tty->print("Predicate IC ");
823 loop->dump_head();
824 }
825 #endif
826 } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
827 assert(proj->_con == predicate_proj->_con, "must match");
829 // Range check for counted loops
830 const Node* cmp = bol->in(1)->as_Cmp();
831 Node* idx = cmp->in(1);
832 assert(!invar.is_invariant(idx), "index is variant");
833 Node* rng = cmp->in(2);
834 assert(rng->Opcode() == Op_LoadRange || _igvn.type(rng)->is_int() >= 0, "must be");
835 assert(invar.is_invariant(rng), "range must be invariant");
836 int scale = 1;
837 Node* offset = zero;
838 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
839 assert(ok, "must be index expression");
841 Node* init = cl->init_trip();
842 Node* limit = cl->limit();
843 Node* stride = cl->stride();
845 // Build if's for the upper and lower bound tests. The
846 // lower_bound test will dominate the upper bound test and all
847 // cloned or created nodes will use the lower bound test as
848 // their declared control.
849 ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
850 ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
851 assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
852 Node *ctrl = lower_bound_proj->in(0)->as_If()->in(0);
854 // Perform cloning to keep Invariance state correct since the
855 // late schedule will place invariant things in the loop.
856 rng = invar.clone(rng, ctrl);
857 if (offset && offset != zero) {
858 assert(invar.is_invariant(offset), "offset must be loop invariant");
859 offset = invar.clone(offset, ctrl);
860 }
862 // Test the lower bound
863 Node* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false);
864 IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
865 _igvn.hash_delete(lower_bound_iff);
866 lower_bound_iff->set_req(1, lower_bound_bol);
867 if (TraceLoopPredicate) tty->print_cr("lower bound check if: %d", lower_bound_iff->_idx);
869 // Test the upper bound
870 Node* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true);
871 IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
872 _igvn.hash_delete(upper_bound_iff);
873 upper_bound_iff->set_req(1, upper_bound_bol);
874 if (TraceLoopPredicate) tty->print_cr("upper bound check if: %d", lower_bound_iff->_idx);
876 // Fall through into rest of the clean up code which will move
877 // any dependent nodes onto the upper bound test.
878 new_predicate_proj = upper_bound_proj;
880 #ifndef PRODUCT
881 if (TraceLoopOpts && !TraceLoopPredicate) {
882 tty->print("Predicate RC ");
883 loop->dump_head();
884 }
885 #endif
886 } else {
887 // Loop variant check (for example, range check in non-counted loop)
888 // with uncommon trap.
889 continue;
890 }
891 assert(new_predicate_proj != NULL, "sanity");
892 // Success - attach condition (new_predicate_bol) to predicate if
893 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
895 // Eliminate the old If in the loop body
896 dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
898 hoisted = true;
899 C->set_major_progress();
900 } // end while
902 #ifndef PRODUCT
903 // report that the loop predication has been actually performed
904 // for this loop
905 if (TraceLoopPredicate && hoisted) {
906 tty->print("Loop Predication Performed:");
907 loop->dump_head();
908 }
909 #endif
911 return hoisted;
912 }
914 //------------------------------loop_predication--------------------------------
915 // driver routine for loop predication optimization
916 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
917 bool hoisted = false;
918 // Recursively promote predicates
919 if (_child) {
920 hoisted = _child->loop_predication( phase);
921 }
923 // self
924 if (!_irreducible && !tail()->is_top()) {
925 hoisted |= phase->loop_predication_impl(this);
926 }
928 if (_next) { //sibling
929 hoisted |= _next->loop_predication( phase);
930 }
932 return hoisted;
933 }
