1 /*
2 * Copyright (c) 2000, 2015, 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 "compiler/compileLog.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/callnode.hpp"
30 #include "opto/castnode.hpp"
31 #include "opto/connode.hpp"
32 #include "opto/convertnode.hpp"
33 #include "opto/divnode.hpp"
34 #include "opto/loopnode.hpp"
35 #include "opto/mulnode.hpp"
36 #include "opto/movenode.hpp"
37 #include "opto/opaquenode.hpp"
38 #include "opto/rootnode.hpp"
39 #include "opto/runtime.hpp"
40 #include "opto/subnode.hpp"
41 #include "opto/superword.hpp"
42 #include "opto/vectornode.hpp"
43
44 //------------------------------is_loop_exit-----------------------------------
45 // Given an IfNode, return the loop-exiting projection or NULL if both
46 // arms remain in the loop.
47 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
48 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
49 PhaseIdealLoop *phase = _phase;
50 // Test is an IfNode, has 2 projections. If BOTH are in the loop
51 // we need loop unswitching instead of peeling.
52 if( !is_member(phase->get_loop( iff->raw_out(0) )) )
53 return iff->raw_out(0);
54 if( !is_member(phase->get_loop( iff->raw_out(1) )) )
55 return iff->raw_out(1);
56 return NULL;
57 }
58
59
60 //=============================================================================
61
62
63 //------------------------------record_for_igvn----------------------------
64 // Put loop body on igvn work list
65 void IdealLoopTree::record_for_igvn() {
66 for( uint i = 0; i < _body.size(); i++ ) {
67 Node *n = _body.at(i);
68 _phase->_igvn._worklist.push(n);
69 }
70 }
71
72 //------------------------------compute_exact_trip_count-----------------------
73 // Compute loop exact trip count if possible. Do not recalculate trip count for
74 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
75 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
76 if (!_head->as_Loop()->is_valid_counted_loop()) {
77 return;
78 }
79 CountedLoopNode* cl = _head->as_CountedLoop();
80 // Trip count may become nonexact for iteration split loops since
81 // RCE modifies limits. Note, _trip_count value is not reset since
82 // it is used to limit unrolling of main loop.
83 cl->set_nonexact_trip_count();
84
85 // Loop's test should be part of loop.
86 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
87 return; // Infinite loop
88
89 #ifdef ASSERT
90 BoolTest::mask bt = cl->loopexit()->test_trip();
91 assert(bt == BoolTest::lt || bt == BoolTest::gt ||
92 bt == BoolTest::ne, "canonical test is expected");
93 #endif
94
95 Node* init_n = cl->init_trip();
96 Node* limit_n = cl->limit();
97 if (init_n != NULL && init_n->is_Con() &&
98 limit_n != NULL && limit_n->is_Con()) {
99 // Use longs to avoid integer overflow.
100 int stride_con = cl->stride_con();
101 jlong init_con = cl->init_trip()->get_int();
102 jlong limit_con = cl->limit()->get_int();
103 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
104 jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
105 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
106 // Set exact trip count.
107 cl->set_exact_trip_count((uint)trip_count);
108 }
109 }
110 }
111
112 //------------------------------compute_profile_trip_cnt----------------------------
113 // Compute loop trip count from profile data as
114 // (backedge_count + loop_exit_count) / loop_exit_count
115 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
116 if (!_head->is_CountedLoop()) {
117 return;
118 }
119 CountedLoopNode* head = _head->as_CountedLoop();
120 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
121 return; // Already computed
122 }
123 float trip_cnt = (float)max_jint; // default is big
124
125 Node* back = head->in(LoopNode::LoopBackControl);
126 while (back != head) {
127 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
128 back->in(0) &&
129 back->in(0)->is_If() &&
130 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
131 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
132 break;
133 }
134 back = phase->idom(back);
135 }
136 if (back != head) {
137 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
138 back->in(0), "if-projection exists");
139 IfNode* back_if = back->in(0)->as_If();
140 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
141
142 // Now compute a loop exit count
143 float loop_exit_cnt = 0.0f;
144 for( uint i = 0; i < _body.size(); i++ ) {
145 Node *n = _body[i];
146 if( n->is_If() ) {
147 IfNode *iff = n->as_If();
148 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
149 Node *exit = is_loop_exit(iff);
150 if( exit ) {
151 float exit_prob = iff->_prob;
152 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
153 if (exit_prob > PROB_MIN) {
154 float exit_cnt = iff->_fcnt * exit_prob;
155 loop_exit_cnt += exit_cnt;
156 }
157 }
158 }
159 }
160 }
161 if (loop_exit_cnt > 0.0f) {
162 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
163 } else {
164 // No exit count so use
165 trip_cnt = loop_back_cnt;
166 }
167 }
168 #ifndef PRODUCT
169 if (TraceProfileTripCount) {
170 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
171 }
172 #endif
173 head->set_profile_trip_cnt(trip_cnt);
174 }
175
176 //---------------------is_invariant_addition-----------------------------
177 // Return nonzero index of invariant operand for an Add or Sub
178 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
179 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
180 int op = n->Opcode();
181 if (op == Op_AddI || op == Op_SubI) {
182 bool in1_invar = this->is_invariant(n->in(1));
183 bool in2_invar = this->is_invariant(n->in(2));
184 if (in1_invar && !in2_invar) return 1;
185 if (!in1_invar && in2_invar) return 2;
186 }
187 return 0;
188 }
189
190 //---------------------reassociate_add_sub-----------------------------
191 // Reassociate invariant add and subtract expressions:
192 //
193 // inv1 + (x + inv2) => ( inv1 + inv2) + x
194 // (x + inv2) + inv1 => ( inv1 + inv2) + x
195 // inv1 + (x - inv2) => ( inv1 - inv2) + x
196 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
197 // (x + inv2) - inv1 => (-inv1 + inv2) + x
198 // (x - inv2) + inv1 => ( inv1 - inv2) + x
199 // (x - inv2) - inv1 => (-inv1 - inv2) + x
200 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
201 // inv1 - (x - inv2) => ( inv1 + inv2) - x
202 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
203 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
204 // inv1 - (x + inv2) => ( inv1 - inv2) - x
205 //
206 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
207 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
208 if (is_invariant(n1)) return NULL;
209 int inv1_idx = is_invariant_addition(n1, phase);
210 if (!inv1_idx) return NULL;
211 // Don't mess with add of constant (igvn moves them to expression tree root.)
212 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
213 Node* inv1 = n1->in(inv1_idx);
214 Node* n2 = n1->in(3 - inv1_idx);
215 int inv2_idx = is_invariant_addition(n2, phase);
216 if (!inv2_idx) return NULL;
217 Node* x = n2->in(3 - inv2_idx);
218 Node* inv2 = n2->in(inv2_idx);
219
220 bool neg_x = n2->is_Sub() && inv2_idx == 1;
221 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
222 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
223 if (n1->is_Sub() && inv1_idx == 1) {
224 neg_x = !neg_x;
225 neg_inv2 = !neg_inv2;
226 }
227 Node* inv1_c = phase->get_ctrl(inv1);
228 Node* inv2_c = phase->get_ctrl(inv2);
229 Node* n_inv1;
230 if (neg_inv1) {
231 Node *zero = phase->_igvn.intcon(0);
232 phase->set_ctrl(zero, phase->C->root());
233 n_inv1 = new SubINode(zero, inv1);
234 phase->register_new_node(n_inv1, inv1_c);
235 } else {
236 n_inv1 = inv1;
237 }
238 Node* inv;
239 if (neg_inv2) {
240 inv = new SubINode(n_inv1, inv2);
241 } else {
242 inv = new AddINode(n_inv1, inv2);
243 }
244 phase->register_new_node(inv, phase->get_early_ctrl(inv));
245
246 Node* addx;
247 if (neg_x) {
248 addx = new SubINode(inv, x);
249 } else {
250 addx = new AddINode(x, inv);
251 }
252 phase->register_new_node(addx, phase->get_ctrl(x));
253 phase->_igvn.replace_node(n1, addx);
254 assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
255 _body.yank(n1);
256 return addx;
257 }
258
259 //---------------------reassociate_invariants-----------------------------
260 // Reassociate invariant expressions:
261 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
262 for (int i = _body.size() - 1; i >= 0; i--) {
263 Node *n = _body.at(i);
264 for (int j = 0; j < 5; j++) {
265 Node* nn = reassociate_add_sub(n, phase);
266 if (nn == NULL) break;
267 n = nn; // again
268 };
269 }
270 }
271
272 //------------------------------policy_peeling---------------------------------
273 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
274 // make some loop-invariant test (usually a null-check) happen before the loop.
275 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
276 Node *test = ((IdealLoopTree*)this)->tail();
277 int body_size = ((IdealLoopTree*)this)->_body.size();
278 // Peeling does loop cloning which can result in O(N^2) node construction
279 if( body_size > 255 /* Prevent overflow for large body_size */
280 || (body_size * body_size + phase->C->live_nodes()) > phase->C->max_node_limit() ) {
281 return false; // too large to safely clone
282 }
283
284 // check for vectorized loops, any peeling done was already applied
285 if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
286
287 while( test != _head ) { // Scan till run off top of loop
288 if( test->is_If() ) { // Test?
289 Node *ctrl = phase->get_ctrl(test->in(1));
290 if (ctrl->is_top())
291 return false; // Found dead test on live IF? No peeling!
292 // Standard IF only has one input value to check for loop invariance
293 assert(test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd || test->Opcode() == Op_RangeCheck, "Check this code when new subtype is added");
294 // Condition is not a member of this loop?
295 if( !is_member(phase->get_loop(ctrl)) &&
296 is_loop_exit(test) )
297 return true; // Found reason to peel!
298 }
299 // Walk up dominators to loop _head looking for test which is
300 // executed on every path thru loop.
301 test = phase->idom(test);
302 }
303 return false;
304 }
305
306 //------------------------------peeled_dom_test_elim---------------------------
307 // If we got the effect of peeling, either by actually peeling or by making
308 // a pre-loop which must execute at least once, we can remove all
309 // loop-invariant dominated tests in the main body.
310 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
311 bool progress = true;
312 while( progress ) {
313 progress = false; // Reset for next iteration
314 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
315 Node *test = prev->in(0);
316 while( test != loop->_head ) { // Scan till run off top of loop
317
318 int p_op = prev->Opcode();
319 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
320 test->is_If() && // Test?
321 !test->in(1)->is_Con() && // And not already obvious?
322 // Condition is not a member of this loop?
323 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
324 // Walk loop body looking for instances of this test
325 for( uint i = 0; i < loop->_body.size(); i++ ) {
326 Node *n = loop->_body.at(i);
327 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
328 // IfNode was dominated by version in peeled loop body
329 progress = true;
330 dominated_by( old_new[prev->_idx], n );
331 }
332 }
333 }
334 prev = test;
335 test = idom(test);
336 } // End of scan tests in loop
337
338 } // End of while( progress )
339 }
340
341 //------------------------------do_peeling-------------------------------------
342 // Peel the first iteration of the given loop.
343 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
344 // The pre-loop illegally has 2 control users (old & new loops).
345 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
346 // Do this by making the old-loop fall-in edges act as if they came
347 // around the loopback from the prior iteration (follow the old-loop
348 // backedges) and then map to the new peeled iteration. This leaves
349 // the pre-loop with only 1 user (the new peeled iteration), but the
350 // peeled-loop backedge has 2 users.
351 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
352 // extra backedge user.
353 //
354 // orig
355 //
356 // stmt1
357 // |
358 // v
359 // loop predicate
360 // |
361 // v
362 // loop<----+
363 // | |
364 // stmt2 |
365 // | |
366 // v |
367 // if ^
368 // / \ |
369 // / \ |
370 // v v |
371 // false true |
372 // / \ |
373 // / ----+
374 // |
375 // v
376 // exit
377 //
378 //
379 // after clone loop
380 //
381 // stmt1
382 // |
383 // v
384 // loop predicate
385 // / \
386 // clone / \ orig
387 // / \
388 // / \
389 // v v
390 // +---->loop clone loop<----+
391 // | | | |
392 // | stmt2 clone stmt2 |
393 // | | | |
394 // | v v |
395 // ^ if clone If ^
396 // | / \ / \ |
397 // | / \ / \ |
398 // | v v v v |
399 // | true false false true |
400 // | / \ / \ |
401 // +---- \ / ----+
402 // \ /
403 // 1v v2
404 // region
405 // |
406 // v
407 // exit
408 //
409 //
410 // after peel and predicate move
411 //
412 // stmt1
413 // /
414 // /
415 // clone / orig
416 // /
417 // / +----------+
418 // / | |
419 // / loop predicate |
420 // / | |
421 // v v |
422 // TOP-->loop clone loop<----+ |
423 // | | | |
424 // stmt2 clone stmt2 | |
425 // | | | ^
426 // v v | |
427 // if clone If ^ |
428 // / \ / \ | |
429 // / \ / \ | |
430 // v v v v | |
431 // true false false true | |
432 // | \ / \ | |
433 // | \ / ----+ ^
434 // | \ / |
435 // | 1v v2 |
436 // v region |
437 // | | |
438 // | v |
439 // | exit |
440 // | |
441 // +--------------->-----------------+
442 //
443 //
444 // final graph
445 //
446 // stmt1
447 // |
448 // v
449 // stmt2 clone
450 // |
451 // v
452 // if clone
453 // / |
454 // / |
455 // v v
456 // false true
457 // | |
458 // | v
459 // | loop predicate
460 // | |
461 // | v
462 // | loop<----+
463 // | | |
464 // | stmt2 |
465 // | | |
466 // | v |
467 // v if ^
468 // | / \ |
469 // | / \ |
470 // | v v |
471 // | false true |
472 // | | \ |
473 // v v --+
474 // region
475 // |
476 // v
477 // exit
478 //
479 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
480
481 C->set_major_progress();
482 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
483 // 'pre' loop from the main and the 'pre' can no longer have its
484 // iterations adjusted. Therefore, we need to declare this loop as
485 // no longer a 'main' loop; it will need new pre and post loops before
486 // we can do further RCE.
487 #ifndef PRODUCT
488 if (TraceLoopOpts) {
489 tty->print("Peel ");
490 loop->dump_head();
491 }
492 #endif
493 Node* head = loop->_head;
494 bool counted_loop = head->is_CountedLoop();
495 if (counted_loop) {
496 CountedLoopNode *cl = head->as_CountedLoop();
497 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
498 cl->set_trip_count(cl->trip_count() - 1);
499 if (cl->is_main_loop()) {
500 cl->set_normal_loop();
501 #ifndef PRODUCT
502 if (PrintOpto && VerifyLoopOptimizations) {
503 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
504 loop->dump_head();
505 }
506 #endif
507 }
508 }
509 Node* entry = head->in(LoopNode::EntryControl);
510
511 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
512 // The pre-loop illegally has 2 control users (old & new loops).
513 clone_loop( loop, old_new, dom_depth(head) );
514
515 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
516 // Do this by making the old-loop fall-in edges act as if they came
517 // around the loopback from the prior iteration (follow the old-loop
518 // backedges) and then map to the new peeled iteration. This leaves
519 // the pre-loop with only 1 user (the new peeled iteration), but the
520 // peeled-loop backedge has 2 users.
521 Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
522 _igvn.hash_delete(head);
523 head->set_req(LoopNode::EntryControl, new_entry);
524 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
525 Node* old = head->fast_out(j);
526 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
527 Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
528 if (!new_exit_value ) // Backedge value is ALSO loop invariant?
529 // Then loop body backedge value remains the same.
530 new_exit_value = old->in(LoopNode::LoopBackControl);
531 _igvn.hash_delete(old);
532 old->set_req(LoopNode::EntryControl, new_exit_value);
533 }
534 }
535
536
537 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
538 // extra backedge user.
539 Node* new_head = old_new[head->_idx];
540 _igvn.hash_delete(new_head);
541 new_head->set_req(LoopNode::LoopBackControl, C->top());
542 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
543 Node* use = new_head->fast_out(j2);
544 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
545 _igvn.hash_delete(use);
546 use->set_req(LoopNode::LoopBackControl, C->top());
547 }
548 }
549
550
551 // Step 4: Correct dom-depth info. Set to loop-head depth.
552 int dd = dom_depth(head);
553 set_idom(head, head->in(1), dd);
554 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
555 Node *old = loop->_body.at(j3);
556 Node *nnn = old_new[old->_idx];
557 if (!has_ctrl(nnn))
558 set_idom(nnn, idom(nnn), dd-1);
559 }
560
561 // Now force out all loop-invariant dominating tests. The optimizer
562 // finds some, but we _know_ they are all useless.
563 peeled_dom_test_elim(loop,old_new);
564
565 loop->record_for_igvn();
566 }
567
568 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
569
570 //------------------------------policy_maximally_unroll------------------------
571 // Calculate exact loop trip count and return true if loop can be maximally
572 // unrolled.
573 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
574 CountedLoopNode *cl = _head->as_CountedLoop();
575 assert(cl->is_normal_loop(), "");
576 if (!cl->is_valid_counted_loop())
577 return false; // Malformed counted loop
578
579 if (!cl->has_exact_trip_count()) {
580 // Trip count is not exact.
581 return false;
582 }
583
584 uint trip_count = cl->trip_count();
585 // Note, max_juint is used to indicate unknown trip count.
586 assert(trip_count > 1, "one iteration loop should be optimized out already");
587 assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
588
589 // Real policy: if we maximally unroll, does it get too big?
590 // Allow the unrolled mess to get larger than standard loop
591 // size. After all, it will no longer be a loop.
592 uint body_size = _body.size();
593 uint unroll_limit = (uint)LoopUnrollLimit * 4;
594 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
595 if (trip_count > unroll_limit || body_size > unroll_limit) {
596 return false;
597 }
598
599 // Fully unroll a loop with few iterations regardless next
600 // conditions since following loop optimizations will split
601 // such loop anyway (pre-main-post).
602 if (trip_count <= 3)
603 return true;
604
605 // Take into account that after unroll conjoined heads and tails will fold,
606 // otherwise policy_unroll() may allow more unrolling than max unrolling.
607 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
608 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
609 if (body_size != tst_body_size) // Check for int overflow
610 return false;
611 if (new_body_size > unroll_limit ||
612 // Unrolling can result in a large amount of node construction
613 new_body_size >= phase->C->max_node_limit() - phase->C->live_nodes()) {
614 return false;
615 }
616
617 // Do not unroll a loop with String intrinsics code.
618 // String intrinsics are large and have loops.
619 for (uint k = 0; k < _body.size(); k++) {
620 Node* n = _body.at(k);
621 switch (n->Opcode()) {
622 case Op_StrComp:
623 case Op_StrEquals:
624 case Op_StrIndexOf:
625 case Op_StrIndexOfChar:
626 case Op_EncodeISOArray:
627 case Op_AryEq:
628 case Op_HasNegatives: {
629 return false;
630 }
631 #if INCLUDE_RTM_OPT
632 case Op_FastLock:
633 case Op_FastUnlock: {
634 // Don't unroll RTM locking code because it is large.
635 if (UseRTMLocking) {
636 return false;
637 }
638 }
639 #endif
640 } // switch
641 }
642
643 return true; // Do maximally unroll
644 }
645
646
647 //------------------------------policy_unroll----------------------------------
648 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
649 // the loop is a CountedLoop and the body is small enough.
650 bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
651
652 CountedLoopNode *cl = _head->as_CountedLoop();
653 assert(cl->is_normal_loop() || cl->is_main_loop(), "");
654
655 if (!cl->is_valid_counted_loop())
656 return false; // Malformed counted loop
657
658 // Protect against over-unrolling.
659 // After split at least one iteration will be executed in pre-loop.
660 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
661
662 _local_loop_unroll_limit = LoopUnrollLimit;
663 _local_loop_unroll_factor = 4;
664 int future_unroll_ct = cl->unrolled_count() * 2;
665 if (!cl->do_unroll_only()) {
666 if (future_unroll_ct > LoopMaxUnroll) return false;
667 } else {
668 // obey user constraints on vector mapped loops with additional unrolling applied
669 int unroll_constraint = (cl->slp_max_unroll()) ? cl->slp_max_unroll() : 1;
670 if ((future_unroll_ct / unroll_constraint) > LoopMaxUnroll) return false;
671 }
672
673 // Check for initial stride being a small enough constant
674 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
675
676 // Don't unroll if the next round of unrolling would push us
677 // over the expected trip count of the loop. One is subtracted
678 // from the expected trip count because the pre-loop normally
679 // executes 1 iteration.
680 if (UnrollLimitForProfileCheck > 0 &&
681 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
682 future_unroll_ct > UnrollLimitForProfileCheck &&
683 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
684 return false;
685 }
686
687 // When unroll count is greater than LoopUnrollMin, don't unroll if:
688 // the residual iterations are more than 10% of the trip count
689 // and rounds of "unroll,optimize" are not making significant progress
690 // Progress defined as current size less than 20% larger than previous size.
691 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
692 future_unroll_ct > LoopUnrollMin &&
693 (future_unroll_ct - 1) * (100 / LoopPercentProfileLimit) > cl->profile_trip_cnt() &&
694 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
695 return false;
696 }
697
698 Node *init_n = cl->init_trip();
699 Node *limit_n = cl->limit();
700 int stride_con = cl->stride_con();
701 // Non-constant bounds.
702 // Protect against over-unrolling when init or/and limit are not constant
703 // (so that trip_count's init value is maxint) but iv range is known.
704 if (init_n == NULL || !init_n->is_Con() ||
705 limit_n == NULL || !limit_n->is_Con()) {
706 Node* phi = cl->phi();
707 if (phi != NULL) {
708 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
709 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
710 int next_stride = stride_con * 2; // stride after this unroll
711 if (next_stride > 0) {
712 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
713 iv_type->_lo + next_stride > iv_type->_hi) {
714 return false; // over-unrolling
715 }
716 } else if (next_stride < 0) {
717 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
718 iv_type->_hi + next_stride < iv_type->_lo) {
719 return false; // over-unrolling
720 }
721 }
722 }
723 }
724
725 // After unroll limit will be adjusted: new_limit = limit-stride.
726 // Bailout if adjustment overflow.
727 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
728 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
729 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
730 return false; // overflow
731
732 // Adjust body_size to determine if we unroll or not
733 uint body_size = _body.size();
734 // Key test to unroll loop in CRC32 java code
735 int xors_in_loop = 0;
736 // Also count ModL, DivL and MulL which expand mightly
737 for (uint k = 0; k < _body.size(); k++) {
738 Node* n = _body.at(k);
739 switch (n->Opcode()) {
740 case Op_XorI: xors_in_loop++; break; // CRC32 java code
741 case Op_ModL: body_size += 30; break;
742 case Op_DivL: body_size += 30; break;
743 case Op_MulL: body_size += 10; break;
744 case Op_StrComp:
745 case Op_StrEquals:
746 case Op_StrIndexOf:
747 case Op_StrIndexOfChar:
748 case Op_EncodeISOArray:
749 case Op_AryEq:
750 case Op_HasNegatives: {
751 // Do not unroll a loop with String intrinsics code.
752 // String intrinsics are large and have loops.
753 return false;
754 }
755 #if INCLUDE_RTM_OPT
756 case Op_FastLock:
757 case Op_FastUnlock: {
758 // Don't unroll RTM locking code because it is large.
759 if (UseRTMLocking) {
760 return false;
761 }
762 }
763 #endif
764 } // switch
765 }
766
767 if (UseSuperWord) {
768 if (!cl->is_reduction_loop()) {
769 phase->mark_reductions(this);
770 }
771
772 // Only attempt slp analysis when user controls do not prohibit it
773 if (LoopMaxUnroll > _local_loop_unroll_factor) {
774 // Once policy_slp_analysis succeeds, mark the loop with the
775 // maximal unroll factor so that we minimize analysis passes
776 if (future_unroll_ct >= _local_loop_unroll_factor) {
777 policy_unroll_slp_analysis(cl, phase, future_unroll_ct);
778 }
779 }
780 }
781
782 int slp_max_unroll_factor = cl->slp_max_unroll();
783 if (cl->has_passed_slp()) {
784 if (slp_max_unroll_factor >= future_unroll_ct) return true;
785 // Normal case: loop too big
786 return false;
787 }
788
789 // Check for being too big
790 if (body_size > (uint)_local_loop_unroll_limit) {
791 if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
792 // Normal case: loop too big
793 return false;
794 }
795
796 if (cl->do_unroll_only()) {
797 if (TraceSuperWordLoopUnrollAnalysis) {
798 tty->print_cr("policy_unroll passed vector loop(vlen=%d,factor = %d)\n", slp_max_unroll_factor, future_unroll_ct);
799 }
800 }
801
802 // Unroll once! (Each trip will soon do double iterations)
803 return true;
804 }
805
806 void IdealLoopTree::policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct) {
807 // Enable this functionality target by target as needed
808 if (SuperWordLoopUnrollAnalysis) {
809 if (!cl->was_slp_analyzed()) {
810 SuperWord sw(phase);
811 sw.transform_loop(this, false);
812
813 // If the loop is slp canonical analyze it
814 if (sw.early_return() == false) {
815 sw.unrolling_analysis(_local_loop_unroll_factor);
816 }
817 }
818
819 if (cl->has_passed_slp()) {
820 int slp_max_unroll_factor = cl->slp_max_unroll();
821 if (slp_max_unroll_factor >= future_unroll_ct) {
822 int new_limit = cl->node_count_before_unroll() * slp_max_unroll_factor;
823 if (new_limit > LoopUnrollLimit) {
824 if (TraceSuperWordLoopUnrollAnalysis) {
825 tty->print_cr("slp analysis unroll=%d, default limit=%d\n", new_limit, _local_loop_unroll_limit);
826 }
827 _local_loop_unroll_limit = new_limit;
828 }
829 }
830 }
831 }
832 }
833
834 //------------------------------policy_align-----------------------------------
835 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
836 // expression that does the alignment. Note that only one array base can be
837 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
838 // if we vectorize short memory ops into longer memory ops, we may want to
839 // increase alignment.
840 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
841 return false;
842 }
843
844 //------------------------------policy_range_check-----------------------------
845 // Return TRUE or FALSE if the loop should be range-check-eliminated.
846 // Actually we do iteration-splitting, a more powerful form of RCE.
847 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
848 if (!RangeCheckElimination) return false;
849
850 CountedLoopNode *cl = _head->as_CountedLoop();
851 // If we unrolled with no intention of doing RCE and we later
852 // changed our minds, we got no pre-loop. Either we need to
853 // make a new pre-loop, or we gotta disallow RCE.
854 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
855 Node *trip_counter = cl->phi();
856
857 // check for vectorized loops, some opts are no longer needed
858 if (cl->do_unroll_only()) return false;
859
860 // Check loop body for tests of trip-counter plus loop-invariant vs
861 // loop-invariant.
862 for (uint i = 0; i < _body.size(); i++) {
863 Node *iff = _body[i];
864 if (iff->Opcode() == Op_If ||
865 iff->Opcode() == Op_RangeCheck) { // Test?
866
867 // Comparing trip+off vs limit
868 Node *bol = iff->in(1);
869 if (bol->req() != 2) continue; // dead constant test
870 if (!bol->is_Bool()) {
871 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
872 continue;
873 }
874 if (bol->as_Bool()->_test._test == BoolTest::ne)
875 continue; // not RC
876
877 Node *cmp = bol->in(1);
878 Node *rc_exp = cmp->in(1);
879 Node *limit = cmp->in(2);
880
881 Node *limit_c = phase->get_ctrl(limit);
882 if( limit_c == phase->C->top() )
883 return false; // Found dead test on live IF? No RCE!
884 if( is_member(phase->get_loop(limit_c) ) ) {
885 // Compare might have operands swapped; commute them
886 rc_exp = cmp->in(2);
887 limit = cmp->in(1);
888 limit_c = phase->get_ctrl(limit);
889 if( is_member(phase->get_loop(limit_c) ) )
890 continue; // Both inputs are loop varying; cannot RCE
891 }
892
893 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
894 continue;
895 }
896 // Yeah! Found a test like 'trip+off vs limit'
897 // Test is an IfNode, has 2 projections. If BOTH are in the loop
898 // we need loop unswitching instead of iteration splitting.
899 if( is_loop_exit(iff) )
900 return true; // Found reason to split iterations
901 } // End of is IF
902 }
903
904 return false;
905 }
906
907 //------------------------------policy_peel_only-------------------------------
908 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
909 // for unrolling loops with NO array accesses.
910 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
911 // check for vectorized loops, any peeling done was already applied
912 if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) return false;
913
914 for( uint i = 0; i < _body.size(); i++ )
915 if( _body[i]->is_Mem() )
916 return false;
917
918 // No memory accesses at all!
919 return true;
920 }
921
922 //------------------------------clone_up_backedge_goo--------------------------
923 // If Node n lives in the back_ctrl block and cannot float, we clone a private
924 // version of n in preheader_ctrl block and return that, otherwise return n.
925 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
926 if( get_ctrl(n) != back_ctrl ) return n;
927
928 // Only visit once
929 if (visited.test_set(n->_idx)) {
930 Node *x = clones.find(n->_idx);
931 if (x != NULL)
932 return x;
933 return n;
934 }
935
936 Node *x = NULL; // If required, a clone of 'n'
937 // Check for 'n' being pinned in the backedge.
938 if( n->in(0) && n->in(0) == back_ctrl ) {
939 assert(clones.find(n->_idx) == NULL, "dead loop");
940 x = n->clone(); // Clone a copy of 'n' to preheader
941 clones.push(x, n->_idx);
942 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
943 }
944
945 // Recursive fixup any other input edges into x.
946 // If there are no changes we can just return 'n', otherwise
947 // we need to clone a private copy and change it.
948 for( uint i = 1; i < n->req(); i++ ) {
949 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
950 if( g != n->in(i) ) {
951 if( !x ) {
952 assert(clones.find(n->_idx) == NULL, "dead loop");
953 x = n->clone();
954 clones.push(x, n->_idx);
955 }
956 x->set_req(i, g);
957 }
958 }
959 if( x ) { // x can legally float to pre-header location
960 register_new_node( x, preheader_ctrl );
961 return x;
962 } else { // raise n to cover LCA of uses
963 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
964 }
965 return n;
966 }
967
968 bool PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
969 Node* castii = new CastIINode(incr, TypeInt::INT, true);
970 castii->set_req(0, ctrl);
971 register_new_node(castii, ctrl);
972 for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
973 Node* n = incr->fast_out(i);
974 if (n->is_Phi() && n->in(0) == loop) {
975 int nrep = n->replace_edge(incr, castii);
976 return true;
977 }
978 }
979 return false;
980 }
981
982 //------------------------------insert_pre_post_loops--------------------------
983 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
984 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
985 // alignment. Useful to unroll loops that do no array accesses.
986 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
987
988 #ifndef PRODUCT
989 if (TraceLoopOpts) {
990 if (peel_only)
991 tty->print("PeelMainPost ");
992 else
993 tty->print("PreMainPost ");
994 loop->dump_head();
995 }
996 #endif
997 C->set_major_progress();
998
999 // Find common pieces of the loop being guarded with pre & post loops
1000 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1001 assert( main_head->is_normal_loop(), "" );
1002 CountedLoopEndNode *main_end = main_head->loopexit();
1003 guarantee(main_end != NULL, "no loop exit node");
1004 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
1005 uint dd_main_head = dom_depth(main_head);
1006 uint max = main_head->outcnt();
1007
1008 Node *pre_header= main_head->in(LoopNode::EntryControl);
1009 Node *init = main_head->init_trip();
1010 Node *incr = main_end ->incr();
1011 Node *limit = main_end ->limit();
1012 Node *stride = main_end ->stride();
1013 Node *cmp = main_end ->cmp_node();
1014 BoolTest::mask b_test = main_end->test_trip();
1015
1016 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
1017 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
1018 if( bol->outcnt() != 1 ) {
1019 bol = bol->clone();
1020 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
1021 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
1022 }
1023 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
1024 if( cmp->outcnt() != 1 ) {
1025 cmp = cmp->clone();
1026 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
1027 _igvn.replace_input_of(bol, 1, cmp);
1028 }
1029
1030 // Add the post loop
1031 PostLoopInfo post_loop_info;
1032 insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_loop_info);
1033
1034 // Update local caches for next stanza
1035 Node *main_exit = post_loop_info.new_main_exit;
1036
1037
1038 //------------------------------
1039 // Step B: Create Pre-Loop.
1040
1041 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
1042 // loop pre-header illegally has 2 control users (old & new loops).
1043 clone_loop( loop, old_new, dd_main_head );
1044 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
1045 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
1046 pre_head->set_pre_loop(main_head);
1047 Node *pre_incr = old_new[incr->_idx];
1048
1049 // Reduce the pre-loop trip count.
1050 pre_end->_prob = PROB_FAIR;
1051
1052 // Find the pre-loop normal exit.
1053 Node* pre_exit = pre_end->proj_out(false);
1054 assert( pre_exit->Opcode() == Op_IfFalse, "" );
1055 IfFalseNode *new_pre_exit = new IfFalseNode(pre_end);
1056 _igvn.register_new_node_with_optimizer( new_pre_exit );
1057 set_idom(new_pre_exit, pre_end, dd_main_head);
1058 set_loop(new_pre_exit, loop->_parent);
1059
1060 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
1061 // pre-loop, the main-loop may not execute at all. Later in life this
1062 // zero-trip guard will become the minimum-trip guard when we unroll
1063 // the main-loop.
1064 Node *min_opaq = new Opaque1Node(C, limit);
1065 Node *min_cmp = new CmpINode( pre_incr, min_opaq );
1066 Node *min_bol = new BoolNode( min_cmp, b_test );
1067 register_new_node( min_opaq, new_pre_exit );
1068 register_new_node( min_cmp , new_pre_exit );
1069 register_new_node( min_bol , new_pre_exit );
1070
1071 // Build the IfNode (assume the main-loop is executed always).
1072 IfNode *min_iff = new IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1073 _igvn.register_new_node_with_optimizer( min_iff );
1074 set_idom(min_iff, new_pre_exit, dd_main_head);
1075 set_loop(min_iff, loop->_parent);
1076
1077 // Plug in the false-path, taken if we need to skip main-loop
1078 _igvn.hash_delete( pre_exit );
1079 pre_exit->set_req(0, min_iff);
1080 set_idom(pre_exit, min_iff, dd_main_head);
1081 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1082 // Make the true-path, must enter the main loop
1083 Node *min_taken = new IfTrueNode( min_iff );
1084 _igvn.register_new_node_with_optimizer( min_taken );
1085 set_idom(min_taken, min_iff, dd_main_head);
1086 set_loop(min_taken, loop->_parent);
1087 // Plug in the true path
1088 _igvn.hash_delete( main_head );
1089 main_head->set_req(LoopNode::EntryControl, min_taken);
1090 set_idom(main_head, min_taken, dd_main_head);
1091
1092 Arena *a = Thread::current()->resource_area();
1093 VectorSet visited(a);
1094 Node_Stack clones(a, main_head->back_control()->outcnt());
1095 // Step B3: Make the fall-in values to the main-loop come from the
1096 // fall-out values of the pre-loop.
1097 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1098 Node* main_phi = main_head->fast_out(i2);
1099 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1100 Node *pre_phi = old_new[main_phi->_idx];
1101 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
1102 main_head->init_control(),
1103 pre_phi->in(LoopNode::LoopBackControl),
1104 visited, clones);
1105 _igvn.hash_delete(main_phi);
1106 main_phi->set_req( LoopNode::EntryControl, fallpre );
1107 }
1108 }
1109
1110 // Nodes inside the loop may be control dependent on a predicate
1111 // that was moved before the preloop. If the back branch of the main
1112 // or post loops becomes dead, those nodes won't be dependent on the
1113 // test that guards that loop nest anymore which could lead to an
1114 // incorrect array access because it executes independently of the
1115 // test that was guarding the loop nest. We add a special CastII on
1116 // the if branch that enters the loop, between the input induction
1117 // variable value and the induction variable Phi to preserve correct
1118 // dependencies.
1119
1120 // CastII for the main loop:
1121 bool inserted = cast_incr_before_loop( pre_incr, min_taken, main_head );
1122 assert(inserted, "no castII inserted");
1123
1124 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1125 // RCE and alignment may change this later.
1126 Node *cmp_end = pre_end->cmp_node();
1127 assert( cmp_end->in(2) == limit, "" );
1128 Node *pre_limit = new AddINode( init, stride );
1129
1130 // Save the original loop limit in this Opaque1 node for
1131 // use by range check elimination.
1132 Node *pre_opaq = new Opaque1Node(C, pre_limit, limit);
1133
1134 register_new_node( pre_limit, pre_head->in(0) );
1135 register_new_node( pre_opaq , pre_head->in(0) );
1136
1137 // Since no other users of pre-loop compare, I can hack limit directly
1138 assert( cmp_end->outcnt() == 1, "no other users" );
1139 _igvn.hash_delete(cmp_end);
1140 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1141
1142 // Special case for not-equal loop bounds:
1143 // Change pre loop test, main loop test, and the
1144 // main loop guard test to use lt or gt depending on stride
1145 // direction:
1146 // positive stride use <
1147 // negative stride use >
1148 //
1149 // not-equal test is kept for post loop to handle case
1150 // when init > limit when stride > 0 (and reverse).
1151
1152 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1153
1154 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1155 // Modify pre loop end condition
1156 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1157 BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test);
1158 register_new_node( new_bol0, pre_head->in(0) );
1159 _igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0);
1160 // Modify main loop guard condition
1161 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1162 BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test);
1163 register_new_node( new_bol1, new_pre_exit );
1164 _igvn.hash_delete(min_iff);
1165 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1166 // Modify main loop end condition
1167 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1168 BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test);
1169 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1170 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2);
1171 }
1172
1173 // Flag main loop
1174 main_head->set_main_loop();
1175 if( peel_only ) main_head->set_main_no_pre_loop();
1176
1177 // Subtract a trip count for the pre-loop.
1178 main_head->set_trip_count(main_head->trip_count() - 1);
1179
1180 // It's difficult to be precise about the trip-counts
1181 // for the pre/post loops. They are usually very short,
1182 // so guess that 4 trips is a reasonable value.
1183 post_loop_info.post_head->set_profile_trip_cnt(4.0);
1184 pre_head->set_profile_trip_cnt(4.0);
1185
1186 // Now force out all loop-invariant dominating tests. The optimizer
1187 // finds some, but we _know_ they are all useless.
1188 peeled_dom_test_elim(loop,old_new);
1189 loop->record_for_igvn();
1190 }
1191
1192 //------------------------------insert_vector_post_loop------------------------
1193 // Insert a copy of the atomic unrolled vectorized main loop as a post loop,
1194 // unroll_policy has already informed us that more unrolling is about to happen to
1195 // the main loop. The resultant post loop will serve as a vectorized drain loop.
1196 void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new) {
1197 if (!loop->_head->is_CountedLoop()) return;
1198
1199 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1200
1201 // only process vectorized main loops
1202 if (!cl->is_vectorized_loop() || !cl->is_main_loop()) return;
1203
1204 int slp_max_unroll_factor = cl->slp_max_unroll();
1205 int cur_unroll = cl->unrolled_count();
1206
1207 if (slp_max_unroll_factor == 0) return;
1208
1209 // only process atomic unroll vector loops (not super unrolled after vectorization)
1210 if (cur_unroll != slp_max_unroll_factor) return;
1211
1212 // we only ever process this one time
1213 if (cl->has_atomic_post_loop()) return;
1214
1215 #ifndef PRODUCT
1216 if (TraceLoopOpts) {
1217 tty->print("PostVector ");
1218 loop->dump_head();
1219 }
1220 #endif
1221 C->set_major_progress();
1222
1223 // Find common pieces of the loop being guarded with pre & post loops
1224 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1225 CountedLoopEndNode *main_end = main_head->loopexit();
1226 guarantee(main_end != NULL, "no loop exit node");
1227 // diagnostic to show loop end is not properly formed
1228 assert(main_end->outcnt() == 2, "1 true, 1 false path only");
1229
1230 // mark this loop as processed
1231 main_head->mark_has_atomic_post_loop();
1232
1233 Node *incr = main_end->incr();
1234 Node *limit = main_end->limit();
1235
1236 // In this case we throw away the result as we are not using it to connect anything else.
1237 PostLoopInfo post_loop_info;
1238 insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_loop_info);
1239
1240 // It's difficult to be precise about the trip-counts
1241 // for post loops. They are usually very short,
1242 // so guess that unit vector trips is a reasonable value.
1243 post_loop_info.post_head->set_profile_trip_cnt(cur_unroll);
1244
1245 // Now force out all loop-invariant dominating tests. The optimizer
1246 // finds some, but we _know_ they are all useless.
1247 peeled_dom_test_elim(loop, old_new);
1248 loop->record_for_igvn();
1249 }
1250
1251
1252 //-------------------------insert_scalar_rced_post_loop------------------------
1253 // Insert a copy of the rce'd main loop as a post loop,
1254 // We have not unrolled the main loop, so this is the right time to inject this.
1255 // Later we will examine the partner of this post loop pair which still has range checks
1256 // to see inject code which tests at runtime if the range checks are applicable.
1257 void PhaseIdealLoop::insert_scalar_rced_post_loop(IdealLoopTree *loop, Node_List &old_new) {
1258 if (!loop->_head->is_CountedLoop()) return;
1259
1260 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1261
1262 // only process RCE'd main loops
1263 if (cl->has_range_checks() || !cl->is_main_loop()) return;
1264
1265 #ifndef PRODUCT
1266 if (TraceLoopOpts) {
1267 tty->print("PostScalarRce ");
1268 loop->dump_head();
1269 }
1270 #endif
1271 C->set_major_progress();
1272
1273 // Find common pieces of the loop being guarded with pre & post loops
1274 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
1275 CountedLoopEndNode *main_end = main_head->loopexit();
1276 guarantee(main_end != NULL, "no loop exit node");
1277 // diagnostic to show loop end is not properly formed
1278 assert(main_end->outcnt() == 2, "1 true, 1 false path only");
1279
1280 Node *incr = main_end->incr();
1281 Node *limit = main_end->limit();
1282
1283 // In this case we throw away the result as we are not using it to connect anything else.
1284 PostLoopInfo post_loop_info;
1285 insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_loop_info);
1286
1287 // It's difficult to be precise about the trip-counts
1288 // for post loops. They are usually very short,
1289 // so guess that unit vector trips is a reasonable value.
1290 post_loop_info.post_head->set_profile_trip_cnt(4.0);
1291
1292 // Now force out all loop-invariant dominating tests. The optimizer
1293 // finds some, but we _know_ they are all useless.
1294 peeled_dom_test_elim(loop, old_new);
1295 loop->record_for_igvn();
1296 }
1297
1298
1299 //------------------------------insert_post_loop-------------------------------
1300 // Insert post loops. Add a post loop to the given loop passed.
1301 void PhaseIdealLoop::insert_post_loop(IdealLoopTree *loop, Node_List &old_new,
1302 CountedLoopNode *main_head, CountedLoopEndNode *main_end,
1303 Node *incr, Node *limit, PostLoopInfo &post_loop_info) {
1304
1305 //------------------------------
1306 // Step A: Create a new post-Loop.
1307 Node* main_exit = main_end->proj_out(false);
1308 assert(main_exit->Opcode() == Op_IfFalse, "");
1309 int dd_main_exit = dom_depth(main_exit);
1310
1311 // Step A1: Clone the loop body of main. The clone becomes the vector post-loop.
1312 // The main loop pre-header illegally has 2 control users (old & new loops).
1313 clone_loop(loop, old_new, dd_main_exit);
1314 assert(old_new[main_end->_idx]->Opcode() == Op_CountedLoopEnd, "");
1315 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
1316 post_head->set_normal_loop();
1317 post_head->set_post_loop(main_head);
1318 post_loop_info.post_head = post_head;
1319
1320 // Reduce the post-loop trip count.
1321 CountedLoopEndNode* post_end = old_new[main_end->_idx]->as_CountedLoopEnd();
1322 post_end->_prob = PROB_FAIR;
1323
1324 // Build the main-loop normal exit.
1325 IfFalseNode *new_main_exit = new IfFalseNode(main_end);
1326 _igvn.register_new_node_with_optimizer(new_main_exit);
1327 set_idom(new_main_exit, main_end, dd_main_exit);
1328 set_loop(new_main_exit, loop->_parent);
1329
1330 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
1331 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
1332 // (the previous loop trip-counter exit value) because we will be changing
1333 // the exit value (via additional unrolling) so we cannot constant-fold away the zero
1334 // trip guard until all unrolling is done.
1335 Node *zer_opaq = new Opaque1Node(C, incr);
1336 Node *zer_cmp = new CmpINode(zer_opaq, limit);
1337 Node *zer_bol = new BoolNode(zer_cmp, main_end->test_trip());
1338 register_new_node(zer_opaq, new_main_exit);
1339 register_new_node(zer_cmp, new_main_exit);
1340 register_new_node(zer_bol, new_main_exit);
1341
1342 // Build the IfNode
1343 IfNode *zer_iff = new IfNode(new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN);
1344 _igvn.register_new_node_with_optimizer(zer_iff);
1345 set_idom(zer_iff, new_main_exit, dd_main_exit);
1346 set_loop(zer_iff, loop->_parent);
1347
1348 // Plug in the false-path, taken if we need to skip this post-loop
1349 _igvn.replace_input_of(main_exit, 0, zer_iff);
1350 set_idom(main_exit, zer_iff, dd_main_exit);
1351 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
1352 // Make the true-path, must enter this post loop
1353 Node *zer_taken = new IfTrueNode(zer_iff);
1354 _igvn.register_new_node_with_optimizer(zer_taken);
1355 set_idom(zer_taken, zer_iff, dd_main_exit);
1356 set_loop(zer_taken, loop->_parent);
1357 // Plug in the true path
1358 _igvn.hash_delete(post_head);
1359 post_head->set_req(LoopNode::EntryControl, zer_taken);
1360 set_idom(post_head, zer_taken, dd_main_exit);
1361
1362 Arena *a = Thread::current()->resource_area();
1363 VectorSet visited(a);
1364 Node_Stack clones(a, main_head->back_control()->outcnt());
1365 // Step A3: Make the fall-in values to the post-loop come from the
1366 // fall-out values of the main-loop.
1367 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
1368 Node* main_phi = main_head->fast_out(i);
1369 if (main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0) {
1370 Node *cur_phi = old_new[main_phi->_idx];
1371 Node *fallnew = clone_up_backedge_goo(main_head->back_control(),
1372 post_head->init_control(),
1373 main_phi->in(LoopNode::LoopBackControl),
1374 visited, clones);
1375 _igvn.hash_delete(cur_phi);
1376 cur_phi->set_req(LoopNode::EntryControl, fallnew);
1377 }
1378 }
1379
1380 // CastII for the new post loop:
1381 bool inserted = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
1382 assert(inserted, "no castII inserted");
1383
1384 post_loop_info.new_main_exit = new_main_exit;
1385 }
1386
1387 //------------------------------is_invariant-----------------------------
1388 // Return true if n is invariant
1389 bool IdealLoopTree::is_invariant(Node* n) const {
1390 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1391 if (n_c->is_top()) return false;
1392 return !is_member(_phase->get_loop(n_c));
1393 }
1394
1395
1396 //------------------------------do_unroll--------------------------------------
1397 // Unroll the loop body one step - make each trip do 2 iterations.
1398 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1399 assert(LoopUnrollLimit, "");
1400 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1401 CountedLoopEndNode *loop_end = loop_head->loopexit();
1402 assert(loop_end, "");
1403 #ifndef PRODUCT
1404 if (PrintOpto && VerifyLoopOptimizations) {
1405 tty->print("Unrolling ");
1406 loop->dump_head();
1407 } else if (TraceLoopOpts) {
1408 if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1409 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1410 } else {
1411 tty->print("Unroll %d ", loop_head->unrolled_count()*2);
1412 }
1413 loop->dump_head();
1414 }
1415
1416 if (C->do_vector_loop() && (PrintOpto && VerifyLoopOptimizations || TraceLoopOpts)) {
1417 Arena* arena = Thread::current()->resource_area();
1418 Node_Stack stack(arena, C->live_nodes() >> 2);
1419 Node_List rpo_list;
1420 VectorSet visited(arena);
1421 visited.set(loop_head->_idx);
1422 rpo( loop_head, stack, visited, rpo_list );
1423 dump(loop, rpo_list.size(), rpo_list );
1424 }
1425 #endif
1426
1427 // Remember loop node count before unrolling to detect
1428 // if rounds of unroll,optimize are making progress
1429 loop_head->set_node_count_before_unroll(loop->_body.size());
1430
1431 Node *ctrl = loop_head->in(LoopNode::EntryControl);
1432 Node *limit = loop_head->limit();
1433 Node *init = loop_head->init_trip();
1434 Node *stride = loop_head->stride();
1435
1436 Node *opaq = NULL;
1437 if (adjust_min_trip) { // If not maximally unrolling, need adjustment
1438 // Search for zero-trip guard.
1439 assert( loop_head->is_main_loop(), "" );
1440 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1441 Node *iff = ctrl->in(0);
1442 assert( iff->Opcode() == Op_If, "" );
1443 Node *bol = iff->in(1);
1444 assert( bol->Opcode() == Op_Bool, "" );
1445 Node *cmp = bol->in(1);
1446 assert( cmp->Opcode() == Op_CmpI, "" );
1447 opaq = cmp->in(2);
1448 // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1449 // optimized away and then another round of loop opts attempted.
1450 // We can not optimize this particular loop in that case.
1451 if (opaq->Opcode() != Op_Opaque1)
1452 return; // Cannot find zero-trip guard! Bail out!
1453 // Zero-trip test uses an 'opaque' node which is not shared.
1454 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1455 }
1456
1457 C->set_major_progress();
1458
1459 Node* new_limit = NULL;
1460 if (UnrollLimitCheck) {
1461 int stride_con = stride->get_int();
1462 int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1463 uint old_trip_count = loop_head->trip_count();
1464 // Verify that unroll policy result is still valid.
1465 assert(old_trip_count > 1 &&
1466 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1467
1468 // Adjust loop limit to keep valid iterations number after unroll.
1469 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1470 // which may overflow.
1471 if (!adjust_min_trip) {
1472 assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1473 "odd trip count for maximally unroll");
1474 // Don't need to adjust limit for maximally unroll since trip count is even.
1475 } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1476 // Loop's limit is constant. Loop's init could be constant when pre-loop
1477 // become peeled iteration.
1478 jlong init_con = init->get_int();
1479 // We can keep old loop limit if iterations count stays the same:
1480 // old_trip_count == new_trip_count * 2
1481 // Note: since old_trip_count >= 2 then new_trip_count >= 1
1482 // so we also don't need to adjust zero trip test.
1483 jlong limit_con = limit->get_int();
1484 // (stride_con*2) not overflow since stride_con <= 8.
1485 int new_stride_con = stride_con * 2;
1486 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1);
1487 jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1488 // New trip count should satisfy next conditions.
1489 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1490 uint new_trip_count = (uint)trip_count;
1491 adjust_min_trip = (old_trip_count != new_trip_count*2);
1492 }
1493
1494 if (adjust_min_trip) {
1495 // Step 2: Adjust the trip limit if it is called for.
1496 // The adjustment amount is -stride. Need to make sure if the
1497 // adjustment underflows or overflows, then the main loop is skipped.
1498 Node* cmp = loop_end->cmp_node();
1499 assert(cmp->in(2) == limit, "sanity");
1500 assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1501
1502 // Verify that policy_unroll result is still valid.
1503 const TypeInt* limit_type = _igvn.type(limit)->is_int();
1504 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1505 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1506
1507 if (limit->is_Con()) {
1508 // The check in policy_unroll and the assert above guarantee
1509 // no underflow if limit is constant.
1510 new_limit = _igvn.intcon(limit->get_int() - stride_con);
1511 set_ctrl(new_limit, C->root());
1512 } else {
1513 // Limit is not constant.
1514 if (loop_head->unrolled_count() == 1) { // only for first unroll
1515 // Separate limit by Opaque node in case it is an incremented
1516 // variable from previous loop to avoid using pre-incremented
1517 // value which could increase register pressure.
1518 // Otherwise reorg_offsets() optimization will create a separate
1519 // Opaque node for each use of trip-counter and as result
1520 // zero trip guard limit will be different from loop limit.
1521 assert(has_ctrl(opaq), "should have it");
1522 Node* opaq_ctrl = get_ctrl(opaq);
1523 limit = new Opaque2Node( C, limit );
1524 register_new_node( limit, opaq_ctrl );
1525 }
1526 if (stride_con > 0 && (java_subtract(limit_type->_lo, stride_con) < limit_type->_lo) ||
1527 stride_con < 0 && (java_subtract(limit_type->_hi, stride_con) > limit_type->_hi)) {
1528 // No underflow.
1529 new_limit = new SubINode(limit, stride);
1530 } else {
1531 // (limit - stride) may underflow.
1532 // Clamp the adjustment value with MININT or MAXINT:
1533 //
1534 // new_limit = limit-stride
1535 // if (stride > 0)
1536 // new_limit = (limit < new_limit) ? MININT : new_limit;
1537 // else
1538 // new_limit = (limit > new_limit) ? MAXINT : new_limit;
1539 //
1540 BoolTest::mask bt = loop_end->test_trip();
1541 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1542 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1543 set_ctrl(adj_max, C->root());
1544 Node* old_limit = NULL;
1545 Node* adj_limit = NULL;
1546 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1547 if (loop_head->unrolled_count() > 1 &&
1548 limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1549 limit->in(CMoveNode::IfTrue) == adj_max &&
1550 bol->as_Bool()->_test._test == bt &&
1551 bol->in(1)->Opcode() == Op_CmpI &&
1552 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1553 // Loop was unrolled before.
1554 // Optimize the limit to avoid nested CMove:
1555 // use original limit as old limit.
1556 old_limit = bol->in(1)->in(1);
1557 // Adjust previous adjusted limit.
1558 adj_limit = limit->in(CMoveNode::IfFalse);
1559 adj_limit = new SubINode(adj_limit, stride);
1560 } else {
1561 old_limit = limit;
1562 adj_limit = new SubINode(limit, stride);
1563 }
1564 assert(old_limit != NULL && adj_limit != NULL, "");
1565 register_new_node( adj_limit, ctrl ); // adjust amount
1566 Node* adj_cmp = new CmpINode(old_limit, adj_limit);
1567 register_new_node( adj_cmp, ctrl );
1568 Node* adj_bool = new BoolNode(adj_cmp, bt);
1569 register_new_node( adj_bool, ctrl );
1570 new_limit = new CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1571 }
1572 register_new_node(new_limit, ctrl);
1573 }
1574 assert(new_limit != NULL, "");
1575 // Replace in loop test.
1576 assert(loop_end->in(1)->in(1) == cmp, "sanity");
1577 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1578 // Don't need to create new test since only one user.
1579 _igvn.hash_delete(cmp);
1580 cmp->set_req(2, new_limit);
1581 } else {
1582 // Create new test since it is shared.
1583 Node* ctrl2 = loop_end->in(0);
1584 Node* cmp2 = cmp->clone();
1585 cmp2->set_req(2, new_limit);
1586 register_new_node(cmp2, ctrl2);
1587 Node* bol2 = loop_end->in(1)->clone();
1588 bol2->set_req(1, cmp2);
1589 register_new_node(bol2, ctrl2);
1590 _igvn.replace_input_of(loop_end, 1, bol2);
1591 }
1592 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1593 // Make it a 1-trip test (means at least 2 trips).
1594
1595 // Guard test uses an 'opaque' node which is not shared. Hence I
1596 // can edit it's inputs directly. Hammer in the new limit for the
1597 // minimum-trip guard.
1598 assert(opaq->outcnt() == 1, "");
1599 _igvn.replace_input_of(opaq, 1, new_limit);
1600 }
1601
1602 // Adjust max trip count. The trip count is intentionally rounded
1603 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1604 // the main, unrolled, part of the loop will never execute as it is protected
1605 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1606 // and later determined that part of the unrolled loop was dead.
1607 loop_head->set_trip_count(old_trip_count / 2);
1608
1609 // Double the count of original iterations in the unrolled loop body.
1610 loop_head->double_unrolled_count();
1611
1612 } else { // LoopLimitCheck
1613
1614 // Adjust max trip count. The trip count is intentionally rounded
1615 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1616 // the main, unrolled, part of the loop will never execute as it is protected
1617 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1618 // and later determined that part of the unrolled loop was dead.
1619 loop_head->set_trip_count(loop_head->trip_count() / 2);
1620
1621 // Double the count of original iterations in the unrolled loop body.
1622 loop_head->double_unrolled_count();
1623
1624 // -----------
1625 // Step 2: Cut back the trip counter for an unroll amount of 2.
1626 // Loop will normally trip (limit - init)/stride_con. Since it's a
1627 // CountedLoop this is exact (stride divides limit-init exactly).
1628 // We are going to double the loop body, so we want to knock off any
1629 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
1630 Node *span = new SubINode( limit, init );
1631 register_new_node( span, ctrl );
1632 Node *trip = new DivINode( 0, span, stride );
1633 register_new_node( trip, ctrl );
1634 Node *mtwo = _igvn.intcon(-2);
1635 set_ctrl(mtwo, C->root());
1636 Node *rond = new AndINode( trip, mtwo );
1637 register_new_node( rond, ctrl );
1638 Node *spn2 = new MulINode( rond, stride );
1639 register_new_node( spn2, ctrl );
1640 new_limit = new AddINode( spn2, init );
1641 register_new_node( new_limit, ctrl );
1642
1643 // Hammer in the new limit
1644 Node *ctrl2 = loop_end->in(0);
1645 Node *cmp2 = new CmpINode( loop_head->incr(), new_limit );
1646 register_new_node( cmp2, ctrl2 );
1647 Node *bol2 = new BoolNode( cmp2, loop_end->test_trip() );
1648 register_new_node( bol2, ctrl2 );
1649 _igvn.replace_input_of(loop_end, CountedLoopEndNode::TestValue, bol2);
1650
1651 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1652 // Make it a 1-trip test (means at least 2 trips).
1653 if( adjust_min_trip ) {
1654 assert( new_limit != NULL, "" );
1655 // Guard test uses an 'opaque' node which is not shared. Hence I
1656 // can edit it's inputs directly. Hammer in the new limit for the
1657 // minimum-trip guard.
1658 assert( opaq->outcnt() == 1, "" );
1659 _igvn.hash_delete(opaq);
1660 opaq->set_req(1, new_limit);
1661 }
1662 } // LoopLimitCheck
1663
1664 // ---------
1665 // Step 4: Clone the loop body. Move it inside the loop. This loop body
1666 // represents the odd iterations; since the loop trips an even number of
1667 // times its backedge is never taken. Kill the backedge.
1668 uint dd = dom_depth(loop_head);
1669 clone_loop( loop, old_new, dd );
1670
1671 // Make backedges of the clone equal to backedges of the original.
1672 // Make the fall-in from the original come from the fall-out of the clone.
1673 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1674 Node* phi = loop_head->fast_out(j);
1675 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1676 Node *newphi = old_new[phi->_idx];
1677 _igvn.hash_delete( phi );
1678 _igvn.hash_delete( newphi );
1679
1680 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1681 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1682 phi ->set_req(LoopNode::LoopBackControl, C->top());
1683 }
1684 }
1685 Node *clone_head = old_new[loop_head->_idx];
1686 _igvn.hash_delete( clone_head );
1687 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1688 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1689 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1690 loop->_head = clone_head; // New loop header
1691
1692 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1693 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1694
1695 // Kill the clone's backedge
1696 Node *newcle = old_new[loop_end->_idx];
1697 _igvn.hash_delete( newcle );
1698 Node *one = _igvn.intcon(1);
1699 set_ctrl(one, C->root());
1700 newcle->set_req(1, one);
1701 // Force clone into same loop body
1702 uint max = loop->_body.size();
1703 for( uint k = 0; k < max; k++ ) {
1704 Node *old = loop->_body.at(k);
1705 Node *nnn = old_new[old->_idx];
1706 loop->_body.push(nnn);
1707 if (!has_ctrl(old))
1708 set_loop(nnn, loop);
1709 }
1710
1711 loop->record_for_igvn();
1712
1713 #ifndef PRODUCT
1714 if (C->do_vector_loop() && (PrintOpto && VerifyLoopOptimizations || TraceLoopOpts)) {
1715 tty->print("\nnew loop after unroll\n"); loop->dump_head();
1716 for (uint i = 0; i < loop->_body.size(); i++) {
1717 loop->_body.at(i)->dump();
1718 }
1719 if(C->clone_map().is_debug()) {
1720 tty->print("\nCloneMap\n");
1721 Dict* dict = C->clone_map().dict();
1722 DictI i(dict);
1723 tty->print_cr("Dict@%p[%d] = ", dict, dict->Size());
1724 for (int ii = 0; i.test(); ++i, ++ii) {
1725 NodeCloneInfo cl((uint64_t)dict->operator[]((void*)i._key));
1726 tty->print("%d->%d:%d,", (int)(intptr_t)i._key, cl.idx(), cl.gen());
1727 if (ii % 10 == 9) {
1728 tty->print_cr(" ");
1729 }
1730 }
1731 tty->print_cr(" ");
1732 }
1733 }
1734 #endif
1735
1736 }
1737
1738 //------------------------------do_maximally_unroll----------------------------
1739
1740 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1741 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1742 assert(cl->has_exact_trip_count(), "trip count is not exact");
1743 assert(cl->trip_count() > 0, "");
1744 #ifndef PRODUCT
1745 if (TraceLoopOpts) {
1746 tty->print("MaxUnroll %d ", cl->trip_count());
1747 loop->dump_head();
1748 }
1749 #endif
1750
1751 // If loop is tripping an odd number of times, peel odd iteration
1752 if ((cl->trip_count() & 1) == 1) {
1753 do_peeling(loop, old_new);
1754 }
1755
1756 // Now its tripping an even number of times remaining. Double loop body.
1757 // Do not adjust pre-guards; they are not needed and do not exist.
1758 if (cl->trip_count() > 0) {
1759 assert((cl->trip_count() & 1) == 0, "missed peeling");
1760 do_unroll(loop, old_new, false);
1761 }
1762 }
1763
1764 void PhaseIdealLoop::mark_reductions(IdealLoopTree *loop) {
1765 if (SuperWordReductions == false) return;
1766
1767 CountedLoopNode* loop_head = loop->_head->as_CountedLoop();
1768 if (loop_head->unrolled_count() > 1) {
1769 return;
1770 }
1771
1772 Node* trip_phi = loop_head->phi();
1773 for (DUIterator_Fast imax, i = loop_head->fast_outs(imax); i < imax; i++) {
1774 Node* phi = loop_head->fast_out(i);
1775 if (phi->is_Phi() && phi->outcnt() > 0 && phi != trip_phi) {
1776 // For definitions which are loop inclusive and not tripcounts.
1777 Node* def_node = phi->in(LoopNode::LoopBackControl);
1778
1779 if (def_node != NULL) {
1780 Node* n_ctrl = get_ctrl(def_node);
1781 if (n_ctrl != NULL && loop->is_member(get_loop(n_ctrl))) {
1782 // Now test it to see if it fits the standard pattern for a reduction operator.
1783 int opc = def_node->Opcode();
1784 if (opc != ReductionNode::opcode(opc, def_node->bottom_type()->basic_type())) {
1785 if (!def_node->is_reduction()) { // Not marked yet
1786 // To be a reduction, the arithmetic node must have the phi as input and provide a def to it
1787 bool ok = false;
1788 for (unsigned j = 1; j < def_node->req(); j++) {
1789 Node* in = def_node->in(j);
1790 if (in == phi) {
1791 ok = true;
1792 break;
1793 }
1794 }
1795
1796 // do nothing if we did not match the initial criteria
1797 if (ok == false) {
1798 continue;
1799 }
1800
1801 // The result of the reduction must not be used in the loop
1802 for (DUIterator_Fast imax, i = def_node->fast_outs(imax); i < imax && ok; i++) {
1803 Node* u = def_node->fast_out(i);
1804 if (has_ctrl(u) && !loop->is_member(get_loop(get_ctrl(u)))) {
1805 continue;
1806 }
1807 if (u == phi) {
1808 continue;
1809 }
1810 ok = false;
1811 }
1812
1813 // iff the uses conform
1814 if (ok) {
1815 def_node->add_flag(Node::Flag_is_reduction);
1816 loop_head->mark_has_reductions();
1817 }
1818 }
1819 }
1820 }
1821 }
1822 }
1823 }
1824 }
1825
1826 //------------------------------dominates_backedge---------------------------------
1827 // Returns true if ctrl is executed on every complete iteration
1828 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1829 assert(ctrl->is_CFG(), "must be control");
1830 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1831 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1832 }
1833
1834 //------------------------------adjust_limit-----------------------------------
1835 // Helper function for add_constraint().
1836 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1837 // Compute "I :: (limit-offset)/scale"
1838 Node *con = new SubINode(rc_limit, offset);
1839 register_new_node(con, pre_ctrl);
1840 Node *X = new DivINode(0, con, scale);
1841 register_new_node(X, pre_ctrl);
1842
1843 // Adjust loop limit
1844 loop_limit = (stride_con > 0)
1845 ? (Node*)(new MinINode(loop_limit, X))
1846 : (Node*)(new MaxINode(loop_limit, X));
1847 register_new_node(loop_limit, pre_ctrl);
1848 return loop_limit;
1849 }
1850
1851 //------------------------------add_constraint---------------------------------
1852 // Constrain the main loop iterations so the conditions:
1853 // low_limit <= scale_con * I + offset < upper_limit
1854 // always holds true. That is, either increase the number of iterations in
1855 // the pre-loop or the post-loop until the condition holds true in the main
1856 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1857 // stride and scale are constants (offset and limit often are).
1858 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1859 // For positive stride, the pre-loop limit always uses a MAX function
1860 // and the main loop a MIN function. For negative stride these are
1861 // reversed.
1862
1863 // Also for positive stride*scale the affine function is increasing, so the
1864 // pre-loop must check for underflow and the post-loop for overflow.
1865 // Negative stride*scale reverses this; pre-loop checks for overflow and
1866 // post-loop for underflow.
1867
1868 Node *scale = _igvn.intcon(scale_con);
1869 set_ctrl(scale, C->root());
1870
1871 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1872 // The overflow limit: scale*I+offset < upper_limit
1873 // For main-loop compute
1874 // ( if (scale > 0) /* and stride > 0 */
1875 // I < (upper_limit-offset)/scale
1876 // else /* scale < 0 and stride < 0 */
1877 // I > (upper_limit-offset)/scale
1878 // )
1879 //
1880 // (upper_limit-offset) may overflow or underflow.
1881 // But it is fine since main loop will either have
1882 // less iterations or will be skipped in such case.
1883 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1884
1885 // The underflow limit: low_limit <= scale*I+offset.
1886 // For pre-loop compute
1887 // NOT(scale*I+offset >= low_limit)
1888 // scale*I+offset < low_limit
1889 // ( if (scale > 0) /* and stride > 0 */
1890 // I < (low_limit-offset)/scale
1891 // else /* scale < 0 and stride < 0 */
1892 // I > (low_limit-offset)/scale
1893 // )
1894
1895 if (low_limit->get_int() == -max_jint) {
1896 if (!RangeLimitCheck) return;
1897 // We need this guard when scale*pre_limit+offset >= limit
1898 // due to underflow. So we need execute pre-loop until
1899 // scale*I+offset >= min_int. But (min_int-offset) will
1900 // underflow when offset > 0 and X will be > original_limit
1901 // when stride > 0. To avoid it we replace positive offset with 0.
1902 //
1903 // Also (min_int+1 == -max_int) is used instead of min_int here
1904 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1905 Node* shift = _igvn.intcon(31);
1906 set_ctrl(shift, C->root());
1907 Node* sign = new RShiftINode(offset, shift);
1908 register_new_node(sign, pre_ctrl);
1909 offset = new AndINode(offset, sign);
1910 register_new_node(offset, pre_ctrl);
1911 } else {
1912 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1913 // The only problem we have here when offset == min_int
1914 // since (0-min_int) == min_int. It may be fine for stride > 0
1915 // but for stride < 0 X will be < original_limit. To avoid it
1916 // max(pre_limit, original_limit) is used in do_range_check().
1917 }
1918 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1919 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1920
1921 } else { // stride_con*scale_con < 0
1922 // For negative stride*scale pre-loop checks for overflow and
1923 // post-loop for underflow.
1924 //
1925 // The overflow limit: scale*I+offset < upper_limit
1926 // For pre-loop compute
1927 // NOT(scale*I+offset < upper_limit)
1928 // scale*I+offset >= upper_limit
1929 // scale*I+offset+1 > upper_limit
1930 // ( if (scale < 0) /* and stride > 0 */
1931 // I < (upper_limit-(offset+1))/scale
1932 // else /* scale > 0 and stride < 0 */
1933 // I > (upper_limit-(offset+1))/scale
1934 // )
1935 //
1936 // (upper_limit-offset-1) may underflow or overflow.
1937 // To avoid it min(pre_limit, original_limit) is used
1938 // in do_range_check() for stride > 0 and max() for < 0.
1939 Node *one = _igvn.intcon(1);
1940 set_ctrl(one, C->root());
1941
1942 Node *plus_one = new AddINode(offset, one);
1943 register_new_node( plus_one, pre_ctrl );
1944 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1945 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1946
1947 if (low_limit->get_int() == -max_jint) {
1948 if (!RangeLimitCheck) return;
1949 // We need this guard when scale*main_limit+offset >= limit
1950 // due to underflow. So we need execute main-loop while
1951 // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1952 // underflow when (offset+1) > 0 and X will be < main_limit
1953 // when scale < 0 (and stride > 0). To avoid it we replace
1954 // positive (offset+1) with 0.
1955 //
1956 // Also (min_int+1 == -max_int) is used instead of min_int here
1957 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1958 Node* shift = _igvn.intcon(31);
1959 set_ctrl(shift, C->root());
1960 Node* sign = new RShiftINode(plus_one, shift);
1961 register_new_node(sign, pre_ctrl);
1962 plus_one = new AndINode(plus_one, sign);
1963 register_new_node(plus_one, pre_ctrl);
1964 } else {
1965 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1966 // The only problem we have here when offset == max_int
1967 // since (max_int+1) == min_int and (0-min_int) == min_int.
1968 // But it is fine since main loop will either have
1969 // less iterations or will be skipped in such case.
1970 }
1971 // The underflow limit: low_limit <= scale*I+offset.
1972 // For main-loop compute
1973 // scale*I+offset+1 > low_limit
1974 // ( if (scale < 0) /* and stride > 0 */
1975 // I < (low_limit-(offset+1))/scale
1976 // else /* scale > 0 and stride < 0 */
1977 // I > (low_limit-(offset+1))/scale
1978 // )
1979
1980 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1981 }
1982 }
1983
1984
1985 //------------------------------is_scaled_iv---------------------------------
1986 // Return true if exp is a constant times an induction var
1987 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1988 if (exp == iv) {
1989 if (p_scale != NULL) {
1990 *p_scale = 1;
1991 }
1992 return true;
1993 }
1994 int opc = exp->Opcode();
1995 if (opc == Op_MulI) {
1996 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1997 if (p_scale != NULL) {
1998 *p_scale = exp->in(2)->get_int();
1999 }
2000 return true;
2001 }
2002 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
2003 if (p_scale != NULL) {
2004 *p_scale = exp->in(1)->get_int();
2005 }
2006 return true;
2007 }
2008 } else if (opc == Op_LShiftI) {
2009 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
2010 if (p_scale != NULL) {
2011 *p_scale = 1 << exp->in(2)->get_int();
2012 }
2013 return true;
2014 }
2015 }
2016 return false;
2017 }
2018
2019 //-----------------------------is_scaled_iv_plus_offset------------------------------
2020 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
2021 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
2022 if (is_scaled_iv(exp, iv, p_scale)) {
2023 if (p_offset != NULL) {
2024 Node *zero = _igvn.intcon(0);
2025 set_ctrl(zero, C->root());
2026 *p_offset = zero;
2027 }
2028 return true;
2029 }
2030 int opc = exp->Opcode();
2031 if (opc == Op_AddI) {
2032 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
2033 if (p_offset != NULL) {
2034 *p_offset = exp->in(2);
2035 }
2036 return true;
2037 }
2038 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
2039 if (p_offset != NULL) {
2040 *p_offset = exp->in(1);
2041 }
2042 return true;
2043 }
2044 if (exp->in(2)->is_Con()) {
2045 Node* offset2 = NULL;
2046 if (depth < 2 &&
2047 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
2048 p_offset != NULL ? &offset2 : NULL, depth+1)) {
2049 if (p_offset != NULL) {
2050 Node *ctrl_off2 = get_ctrl(offset2);
2051 Node* offset = new AddINode(offset2, exp->in(2));
2052 register_new_node(offset, ctrl_off2);
2053 *p_offset = offset;
2054 }
2055 return true;
2056 }
2057 }
2058 } else if (opc == Op_SubI) {
2059 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
2060 if (p_offset != NULL) {
2061 Node *zero = _igvn.intcon(0);
2062 set_ctrl(zero, C->root());
2063 Node *ctrl_off = get_ctrl(exp->in(2));
2064 Node* offset = new SubINode(zero, exp->in(2));
2065 register_new_node(offset, ctrl_off);
2066 *p_offset = offset;
2067 }
2068 return true;
2069 }
2070 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
2071 if (p_offset != NULL) {
2072 *p_scale *= -1;
2073 *p_offset = exp->in(1);
2074 }
2075 return true;
2076 }
2077 }
2078 return false;
2079 }
2080
2081 //------------------------------do_range_check---------------------------------
2082 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
2083 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
2084 #ifndef PRODUCT
2085 if (PrintOpto && VerifyLoopOptimizations) {
2086 tty->print("Range Check Elimination ");
2087 loop->dump_head();
2088 } else if (TraceLoopOpts) {
2089 tty->print("RangeCheck ");
2090 loop->dump_head();
2091 }
2092 #endif
2093 assert(RangeCheckElimination, "");
2094 CountedLoopNode *cl = loop->_head->as_CountedLoop();
2095 assert(cl->is_main_loop(), "");
2096
2097 // protect against stride not being a constant
2098 if (!cl->stride_is_con())
2099 return;
2100
2101 // Find the trip counter; we are iteration splitting based on it
2102 Node *trip_counter = cl->phi();
2103 // Find the main loop limit; we will trim it's iterations
2104 // to not ever trip end tests
2105 Node *main_limit = cl->limit();
2106
2107 // Need to find the main-loop zero-trip guard
2108 Node *ctrl = cl->in(LoopNode::EntryControl);
2109 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
2110 Node *iffm = ctrl->in(0);
2111 assert(iffm->Opcode() == Op_If, "");
2112 Node *bolzm = iffm->in(1);
2113 assert(bolzm->Opcode() == Op_Bool, "");
2114 Node *cmpzm = bolzm->in(1);
2115 assert(cmpzm->is_Cmp(), "");
2116 Node *opqzm = cmpzm->in(2);
2117 // Can not optimize a loop if zero-trip Opaque1 node is optimized
2118 // away and then another round of loop opts attempted.
2119 if (opqzm->Opcode() != Op_Opaque1)
2120 return;
2121 assert(opqzm->in(1) == main_limit, "do not understand situation");
2122
2123 // Find the pre-loop limit; we will expand its iterations to
2124 // not ever trip low tests.
2125 Node *p_f = iffm->in(0);
2126 // pre loop may have been optimized out
2127 if (p_f->Opcode() != Op_IfFalse) {
2128 return;
2129 }
2130 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2131 assert(pre_end->loopnode()->is_pre_loop(), "");
2132 Node *pre_opaq1 = pre_end->limit();
2133 // Occasionally it's possible for a pre-loop Opaque1 node to be
2134 // optimized away and then another round of loop opts attempted.
2135 // We can not optimize this particular loop in that case.
2136 if (pre_opaq1->Opcode() != Op_Opaque1)
2137 return;
2138 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
2139 Node *pre_limit = pre_opaq->in(1);
2140
2141 // Where do we put new limit calculations
2142 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
2143
2144 // Ensure the original loop limit is available from the
2145 // pre-loop Opaque1 node.
2146 Node *orig_limit = pre_opaq->original_loop_limit();
2147 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
2148 return;
2149
2150 // Must know if its a count-up or count-down loop
2151
2152 int stride_con = cl->stride_con();
2153 Node *zero = _igvn.intcon(0);
2154 Node *one = _igvn.intcon(1);
2155 // Use symmetrical int range [-max_jint,max_jint]
2156 Node *mini = _igvn.intcon(-max_jint);
2157 set_ctrl(zero, C->root());
2158 set_ctrl(one, C->root());
2159 set_ctrl(mini, C->root());
2160
2161 // Range checks that do not dominate the loop backedge (ie.
2162 // conditionally executed) can lengthen the pre loop limit beyond
2163 // the original loop limit. To prevent this, the pre limit is
2164 // (for stride > 0) MINed with the original loop limit (MAXed
2165 // stride < 0) when some range_check (rc) is conditionally
2166 // executed.
2167 bool conditional_rc = false;
2168
2169 // Check loop body for tests of trip-counter plus loop-invariant vs
2170 // loop-invariant.
2171 for( uint i = 0; i < loop->_body.size(); i++ ) {
2172 Node *iff = loop->_body[i];
2173 if (iff->Opcode() == Op_If ||
2174 iff->Opcode() == Op_RangeCheck) { // Test?
2175 // Test is an IfNode, has 2 projections. If BOTH are in the loop
2176 // we need loop unswitching instead of iteration splitting.
2177 old_new.push(iff);
2178 Node *exit = loop->is_loop_exit(iff);
2179 if( !exit ) continue;
2180 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
2181
2182 // Get boolean condition to test
2183 Node *i1 = iff->in(1);
2184 if( !i1->is_Bool() ) continue;
2185 BoolNode *bol = i1->as_Bool();
2186 BoolTest b_test = bol->_test;
2187 // Flip sense of test if exit condition is flipped
2188 if( flip )
2189 b_test = b_test.negate();
2190
2191 // Get compare
2192 Node *cmp = bol->in(1);
2193
2194 // Look for trip_counter + offset vs limit
2195 Node *rc_exp = cmp->in(1);
2196 Node *limit = cmp->in(2);
2197 jint scale_con= 1; // Assume trip counter not scaled
2198
2199 Node *limit_c = get_ctrl(limit);
2200 if( loop->is_member(get_loop(limit_c) ) ) {
2201 // Compare might have operands swapped; commute them
2202 b_test = b_test.commute();
2203 rc_exp = cmp->in(2);
2204 limit = cmp->in(1);
2205 limit_c = get_ctrl(limit);
2206 if( loop->is_member(get_loop(limit_c) ) )
2207 continue; // Both inputs are loop varying; cannot RCE
2208 }
2209 // Here we know 'limit' is loop invariant
2210
2211 // 'limit' maybe pinned below the zero trip test (probably from a
2212 // previous round of rce), in which case, it can't be used in the
2213 // zero trip test expression which must occur before the zero test's if.
2214 if( limit_c == ctrl ) {
2215 continue; // Don't rce this check but continue looking for other candidates.
2216 }
2217
2218 // Check for scaled induction variable plus an offset
2219 Node *offset = NULL;
2220
2221 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
2222 continue;
2223 }
2224
2225 Node *offset_c = get_ctrl(offset);
2226 if( loop->is_member( get_loop(offset_c) ) )
2227 continue; // Offset is not really loop invariant
2228 // Here we know 'offset' is loop invariant.
2229
2230 // As above for the 'limit', the 'offset' maybe pinned below the
2231 // zero trip test.
2232 if( offset_c == ctrl ) {
2233 continue; // Don't rce this check but continue looking for other candidates.
2234 }
2235 #ifdef ASSERT
2236 if (TraceRangeLimitCheck) {
2237 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
2238 bol->dump(2);
2239 }
2240 #endif
2241 // At this point we have the expression as:
2242 // scale_con * trip_counter + offset :: limit
2243 // where scale_con, offset and limit are loop invariant. Trip_counter
2244 // monotonically increases by stride_con, a constant. Both (or either)
2245 // stride_con and scale_con can be negative which will flip about the
2246 // sense of the test.
2247
2248 // Adjust pre and main loop limits to guard the correct iteration set
2249 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
2250 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
2251 // The underflow and overflow limits: 0 <= scale*I+offset < limit
2252 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
2253 if (!conditional_rc) {
2254 // (0-offset)/scale could be outside of loop iterations range.
2255 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
2256 }
2257 } else {
2258 if (PrintOpto) {
2259 tty->print_cr("missed RCE opportunity");
2260 }
2261 continue; // In release mode, ignore it
2262 }
2263 } else { // Otherwise work on normal compares
2264 switch( b_test._test ) {
2265 case BoolTest::gt:
2266 // Fall into GE case
2267 case BoolTest::ge:
2268 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
2269 scale_con = -scale_con;
2270 offset = new SubINode( zero, offset );
2271 register_new_node( offset, pre_ctrl );
2272 limit = new SubINode( zero, limit );
2273 register_new_node( limit, pre_ctrl );
2274 // Fall into LE case
2275 case BoolTest::le:
2276 if (b_test._test != BoolTest::gt) {
2277 // Convert X <= Y to X < Y+1
2278 limit = new AddINode( limit, one );
2279 register_new_node( limit, pre_ctrl );
2280 }
2281 // Fall into LT case
2282 case BoolTest::lt:
2283 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
2284 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
2285 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
2286 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
2287 if (!conditional_rc) {
2288 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
2289 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
2290 // still be outside of loop range.
2291 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
2292 }
2293 break;
2294 default:
2295 if (PrintOpto) {
2296 tty->print_cr("missed RCE opportunity");
2297 }
2298 continue; // Unhandled case
2299 }
2300 }
2301
2302 // Kill the eliminated test
2303 C->set_major_progress();
2304 Node *kill_con = _igvn.intcon( 1-flip );
2305 set_ctrl(kill_con, C->root());
2306 _igvn.replace_input_of(iff, 1, kill_con);
2307 // Find surviving projection
2308 assert(iff->is_If(), "");
2309 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
2310 // Find loads off the surviving projection; remove their control edge
2311 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
2312 Node* cd = dp->fast_out(i); // Control-dependent node
2313 if (cd->is_Load() && cd->depends_only_on_test()) { // Loads can now float around in the loop
2314 // Allow the load to float around in the loop, or before it
2315 // but NOT before the pre-loop.
2316 _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
2317 --i;
2318 --imax;
2319 }
2320 }
2321 if (limit->Opcode() == Op_LoadRange) {
2322 old_new.pop();
2323 }
2324
2325 } // End of is IF
2326
2327 }
2328
2329 // Update loop limits
2330 if (conditional_rc) {
2331 pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit)
2332 : (Node*)new MaxINode(pre_limit, orig_limit);
2333 register_new_node(pre_limit, pre_ctrl);
2334 }
2335 _igvn.replace_input_of(pre_opaq, 1, pre_limit);
2336
2337 // Note:: we are making the main loop limit no longer precise;
2338 // need to round up based on stride.
2339 cl->set_nonexact_trip_count();
2340 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
2341 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
2342 // Hopefully, compiler will optimize for powers of 2.
2343 Node *ctrl = get_ctrl(main_limit);
2344 Node *stride = cl->stride();
2345 Node *init = cl->init_trip()->uncast();
2346 Node *span = new SubINode(main_limit,init);
2347 register_new_node(span,ctrl);
2348 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
2349 Node *add = new AddINode(span,rndup);
2350 register_new_node(add,ctrl);
2351 Node *div = new DivINode(0,add,stride);
2352 register_new_node(div,ctrl);
2353 Node *mul = new MulINode(div,stride);
2354 register_new_node(mul,ctrl);
2355 Node *newlim = new AddINode(mul,init);
2356 register_new_node(newlim,ctrl);
2357 main_limit = newlim;
2358 }
2359
2360 Node *main_cle = cl->loopexit();
2361 Node *main_bol = main_cle->in(1);
2362 // Hacking loop bounds; need private copies of exit test
2363 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2364 main_bol = main_bol->clone();// Clone a private BoolNode
2365 register_new_node( main_bol, main_cle->in(0) );
2366 _igvn.replace_input_of(main_cle, 1, main_bol);
2367 }
2368 Node *main_cmp = main_bol->in(1);
2369 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2370 main_cmp = main_cmp->clone();// Clone a private CmpNode
2371 register_new_node( main_cmp, main_cle->in(0) );
2372 _igvn.replace_input_of(main_bol, 1, main_cmp);
2373 }
2374 // Hack the now-private loop bounds
2375 _igvn.replace_input_of(main_cmp, 2, main_limit);
2376 // The OpaqueNode is unshared by design
2377 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2378 _igvn.replace_input_of(opqzm, 1, main_limit);
2379 }
2380
2381 //------------------------------has_range_checks-------------------------------
2382 // Check to see if RCE cleaned the current loop of range-checks.
2383 void PhaseIdealLoop::has_range_checks(IdealLoopTree *loop) {
2384 assert(RangeCheckElimination, "");
2385
2386 // skip if not a counted loop
2387 if (!loop->is_counted()) return;
2388
2389 CountedLoopNode *cl = loop->_head->as_CountedLoop();
2390
2391 // skip this loop if it is already marked
2392 if (cl->has_range_checks()) return;
2393
2394 // Now check for existance of range checks
2395 for (uint i = 0; i < loop->_body.size(); i++) {
2396 Node *iff = loop->_body[i];
2397 if (iff->Opcode() == Op_If ||
2398 iff->Opcode() == Op_RangeCheck) {
2399 cl->mark_has_range_checks();
2400 break;
2401 }
2402 }
2403 }
2404
2405 //-------------------------multi_version_post_loops----------------------------
2406 // Check the range checks that remain, if simple, use the bounds to guard
2407 // which version to a post loop we execute, one with range checks or one without
2408 bool PhaseIdealLoop::multi_version_post_loops(IdealLoopTree *rce_loop, IdealLoopTree *legacy_loop) {
2409 bool multi_version_succeeded = false;
2410 assert(RangeCheckElimination, "");
2411 CountedLoopNode *legacy_cl = legacy_loop->_head->as_CountedLoop();
2412 assert(legacy_cl->is_post_loop(), "");
2413
2414 // Check for existance of range checks using the unique instance to make a guard with
2415 Unique_Node_List worklist;
2416 for (uint i = 0; i < legacy_loop->_body.size(); i++) {
2417 Node *iff = legacy_loop->_body[i];
2418 if (iff->Opcode() == Op_If || iff->Opcode() == Op_RangeCheck) {
2419 worklist.push(iff);
2420 }
2421 }
2422
2423 // Find RCE'd post loop so that we can stage its guard.
2424 Node* ctrl = legacy_cl->in(LoopNode::EntryControl);
2425 if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return multi_version_succeeded;
2426 Node* iffm = ctrl->in(0);
2427 if (!iffm->is_If()) return multi_version_succeeded;
2428 Node* cur_bool = iffm->in(1);
2429 if (!cur_bool->is_Bool()) return multi_version_succeeded;
2430 Node* cur_cmp = cur_bool->in(1);
2431 if (!cur_cmp->is_Cmp()) return multi_version_succeeded;
2432 Node* cur_opq = cur_cmp->in(1);
2433 // Can not optimize a loop if zero-trip Opaque1 node is optimized away.
2434 if (cur_opq->Opcode() != Op_Opaque1) return multi_version_succeeded;
2435
2436 // Now we test that both the post loops are connected
2437 Node* post_loop_region = iffm->in(0);
2438 if (post_loop_region == NULL) return multi_version_succeeded;
2439 if (!post_loop_region->is_Region()) return multi_version_succeeded;
2440 Node* covering_region = post_loop_region->in(RegionNode::Control+1);
2441 if (covering_region == NULL) return multi_version_succeeded;
2442 if (!covering_region->is_Region()) return multi_version_succeeded;
2443 Node* p_f = covering_region->in(RegionNode::Control);
2444 if (p_f == NULL) return multi_version_succeeded;
2445 if (!p_f->is_IfFalse()) return multi_version_succeeded;
2446 if (!p_f->in(0)->is_CountedLoopEnd()) return multi_version_succeeded;
2447 CountedLoopEndNode* rce_loop_end = p_f->in(0)->as_CountedLoopEnd();
2448 if (rce_loop_end == NULL) return multi_version_succeeded;
2449 CountedLoopNode* rce_cl = rce_loop_end->loopnode();
2450 if (rce_cl == NULL || !rce_cl->is_post_loop()) return multi_version_succeeded;
2451 CountedLoopNode *known_rce_cl = rce_loop->_head->as_CountedLoop();
2452 if (rce_cl != known_rce_cl) return multi_version_succeeded;
2453
2454 // Then we fetch the cover entry test
2455 ctrl = rce_cl->in(LoopNode::EntryControl);
2456 if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return multi_version_succeeded;
2457
2458 #ifndef PRODUCT
2459 if (TraceLoopOpts) {
2460 tty->print("PostMultiVersion\n");
2461 rce_loop->dump_head();
2462 legacy_loop->dump_head();
2463 }
2464 #endif
2465
2466 // Now fetch the limit we want to compare against
2467 Node *limit = rce_cl->limit();
2468 bool first_time = true;
2469
2470 // If we got this far, we identified the post loop which has been RCE'd and
2471 // we have a work list. Now we will try to transform the if guard to cause
2472 // the loop pair to be multi version executed with the determination left to runtime
2473 // or the optimizer if full information is known about the given arrays at compile time.
2474 Node *last_min = NULL;
2475 multi_version_succeeded = true;
2476 while (worklist.size()) {
2477 Node* rc_iffm = worklist.pop();
2478 if (rc_iffm->is_If()) {
2479 Node *rc_bolzm = rc_iffm->in(1);
2480 if (rc_bolzm->is_Bool()) {
2481 Node *rc_cmpzm = rc_bolzm->in(1);
2482 if (rc_cmpzm->is_Cmp()) {
2483 Node *rc_left = rc_cmpzm->in(2);
2484 if (rc_left->Opcode() != Op_LoadRange) {
2485 multi_version_succeeded = false;
2486 break;
2487 }
2488 if (first_time) {
2489 last_min = rc_left;
2490 first_time = false;
2491 } else {
2492 Node *cur_min = new MinINode(last_min, rc_left);
2493 last_min = cur_min;
2494 _igvn.register_new_node_with_optimizer(last_min);
2495 }
2496 }
2497 }
2498 }
2499 }
2500
2501 // All we have to do is update the limit of the rce loop
2502 // with the min of our expression and the current limit.
2503 // We will use this expression to replace the current limit.
2504 if (last_min && multi_version_succeeded) {
2505 Node *cur_min = new MinINode(last_min, limit);
2506 _igvn.register_new_node_with_optimizer(cur_min);
2507 Node *cmp_node = rce_loop_end->cmp_node();
2508 _igvn.replace_input_of(cmp_node, 2, cur_min);
2509 set_idom(cmp_node, cur_min, dom_depth(ctrl));
2510 set_ctrl(cur_min, ctrl);
2511 set_loop(cur_min, rce_loop->_parent);
2512
2513 legacy_cl->mark_is_multiversioned();
2514 rce_cl->mark_is_multiversioned();
2515 multi_version_succeeded = true;
2516
2517 C->set_major_progress();
2518 }
2519
2520 return multi_version_succeeded;
2521 }
2522
2523 //-------------------------poison_rce_post_loop--------------------------------
2524 // Causes the rce'd post loop to be optimized away if multiverioning fails
2525 void PhaseIdealLoop::poison_rce_post_loop(IdealLoopTree *rce_loop) {
2526 CountedLoopNode *rce_cl = rce_loop->_head->as_CountedLoop();
2527 Node* ctrl = rce_cl->in(LoopNode::EntryControl);
2528 if (ctrl->is_IfTrue() || ctrl->is_IfFalse()) {
2529 Node* iffm = ctrl->in(0);
2530 if (iffm->is_If()) {
2531 Node* cur_bool = iffm->in(1);
2532 if (cur_bool->is_Bool()) {
2533 Node* cur_cmp = cur_bool->in(1);
2534 if (cur_cmp->is_Cmp()) {
2535 BoolTest::mask new_test = BoolTest::gt;
2536 BoolNode *new_bool = new BoolNode(cur_cmp, new_test);
2537 _igvn.replace_node(cur_bool, new_bool);
2538 _igvn._worklist.push(new_bool);
2539 Node* left_op = cur_cmp->in(1);
2540 _igvn.replace_input_of(cur_cmp, 2, left_op);
2541 C->set_major_progress();
2542 }
2543 }
2544 }
2545 }
2546 }
2547
2548 //------------------------------DCE_loop_body----------------------------------
2549 // Remove simplistic dead code from loop body
2550 void IdealLoopTree::DCE_loop_body() {
2551 for( uint i = 0; i < _body.size(); i++ )
2552 if( _body.at(i)->outcnt() == 0 )
2553 _body.map( i--, _body.pop() );
2554 }
2555
2556
2557 //------------------------------adjust_loop_exit_prob--------------------------
2558 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2559 // Replace with a 1-in-10 exit guess.
2560 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2561 Node *test = tail();
2562 while( test != _head ) {
2563 uint top = test->Opcode();
2564 if( top == Op_IfTrue || top == Op_IfFalse ) {
2565 int test_con = ((ProjNode*)test)->_con;
2566 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2567 IfNode *iff = test->in(0)->as_If();
2568 if( iff->outcnt() == 2 ) { // Ignore dead tests
2569 Node *bol = iff->in(1);
2570 if( bol && bol->req() > 1 && bol->in(1) &&
2571 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2572 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2573 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2574 (bol->in(1)->Opcode() == Op_CompareAndExchangeI ) ||
2575 (bol->in(1)->Opcode() == Op_CompareAndExchangeL ) ||
2576 (bol->in(1)->Opcode() == Op_CompareAndExchangeP ) ||
2577 (bol->in(1)->Opcode() == Op_CompareAndExchangeN ) ||
2578 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapI ) ||
2579 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapL ) ||
2580 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapP ) ||
2581 (bol->in(1)->Opcode() == Op_WeakCompareAndSwapN ) ||
2582 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2583 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2584 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2585 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2586 return; // Allocation loops RARELY take backedge
2587 // Find the OTHER exit path from the IF
2588 Node* ex = iff->proj_out(1-test_con);
2589 float p = iff->_prob;
2590 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2591 if( top == Op_IfTrue ) {
2592 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2593 iff->_prob = PROB_STATIC_FREQUENT;
2594 }
2595 } else {
2596 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2597 iff->_prob = PROB_STATIC_INFREQUENT;
2598 }
2599 }
2600 }
2601 }
2602 }
2603 test = phase->idom(test);
2604 }
2605 }
2606
2607 #ifdef ASSERT
2608 static CountedLoopNode* locate_pre_from_main(CountedLoopNode *cl) {
2609 Node *ctrl = cl->in(LoopNode::EntryControl);
2610 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
2611 Node *iffm = ctrl->in(0);
2612 assert(iffm->Opcode() == Op_If, "");
2613 Node *p_f = iffm->in(0);
2614 assert(p_f->Opcode() == Op_IfFalse, "");
2615 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
2616 assert(pre_end->loopnode()->is_pre_loop(), "");
2617 return pre_end->loopnode();
2618 }
2619 #endif
2620
2621 // Remove the main and post loops and make the pre loop execute all
2622 // iterations. Useful when the pre loop is found empty.
2623 void IdealLoopTree::remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase) {
2624 CountedLoopEndNode* pre_end = cl->loopexit();
2625 Node* pre_cmp = pre_end->cmp_node();
2626 if (pre_cmp->in(2)->Opcode() != Op_Opaque1) {
2627 // Only safe to remove the main loop if the compiler optimized it
2628 // out based on an unknown number of iterations
2629 return;
2630 }
2631
2632 // Can we find the main loop?
2633 if (_next == NULL) {
2634 return;
2635 }
2636
2637 Node* next_head = _next->_head;
2638 if (!next_head->is_CountedLoop()) {
2639 return;
2640 }
2641
2642 CountedLoopNode* main_head = next_head->as_CountedLoop();
2643 if (!main_head->is_main_loop()) {
2644 return;
2645 }
2646
2647 assert(locate_pre_from_main(main_head) == cl, "bad main loop");
2648 Node* main_iff = main_head->in(LoopNode::EntryControl)->in(0);
2649
2650 // Remove the Opaque1Node of the pre loop and make it execute all iterations
2651 phase->_igvn.replace_input_of(pre_cmp, 2, pre_cmp->in(2)->in(2));
2652 // Remove the Opaque1Node of the main loop so it can be optimized out
2653 Node* main_cmp = main_iff->in(1)->in(1);
2654 assert(main_cmp->in(2)->Opcode() == Op_Opaque1, "main loop has no opaque node?");
2655 phase->_igvn.replace_input_of(main_cmp, 2, main_cmp->in(2)->in(1));
2656 }
2657
2658 //------------------------------policy_do_remove_empty_loop--------------------
2659 // Micro-benchmark spamming. Policy is to always remove empty loops.
2660 // The 'DO' part is to replace the trip counter with the value it will
2661 // have on the last iteration. This will break the loop.
2662 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2663 // Minimum size must be empty loop
2664 if (_body.size() > EMPTY_LOOP_SIZE)
2665 return false;
2666
2667 if (!_head->is_CountedLoop())
2668 return false; // Dead loop
2669 CountedLoopNode *cl = _head->as_CountedLoop();
2670 if (!cl->is_valid_counted_loop())
2671 return false; // Malformed loop
2672 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2673 return false; // Infinite loop
2674
2675 if (cl->is_pre_loop()) {
2676 // If the loop we are removing is a pre-loop then the main and
2677 // post loop can be removed as well
2678 remove_main_post_loops(cl, phase);
2679 }
2680
2681 #ifdef ASSERT
2682 // Ensure only one phi which is the iv.
2683 Node* iv = NULL;
2684 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2685 Node* n = cl->fast_out(i);
2686 if (n->Opcode() == Op_Phi) {
2687 assert(iv == NULL, "Too many phis" );
2688 iv = n;
2689 }
2690 }
2691 assert(iv == cl->phi(), "Wrong phi" );
2692 #endif
2693
2694 // main and post loops have explicitly created zero trip guard
2695 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2696 if (needs_guard) {
2697 // Skip guard if values not overlap.
2698 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2699 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2700 int stride_con = cl->stride_con();
2701 if (stride_con > 0) {
2702 needs_guard = (init_t->_hi >= limit_t->_lo);
2703 } else {
2704 needs_guard = (init_t->_lo <= limit_t->_hi);
2705 }
2706 }
2707 if (needs_guard) {
2708 // Check for an obvious zero trip guard.
2709 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2710 if (inctrl->Opcode() == Op_IfTrue || inctrl->Opcode() == Op_IfFalse) {
2711 bool maybe_swapped = (inctrl->Opcode() == Op_IfFalse);
2712 // The test should look like just the backedge of a CountedLoop
2713 Node* iff = inctrl->in(0);
2714 if (iff->is_If()) {
2715 Node* bol = iff->in(1);
2716 if (bol->is_Bool()) {
2717 BoolTest test = bol->as_Bool()->_test;
2718 if (maybe_swapped) {
2719 test._test = test.commute();
2720 test._test = test.negate();
2721 }
2722 if (test._test == cl->loopexit()->test_trip()) {
2723 Node* cmp = bol->in(1);
2724 int init_idx = maybe_swapped ? 2 : 1;
2725 int limit_idx = maybe_swapped ? 1 : 2;
2726 if (cmp->is_Cmp() && cmp->in(init_idx) == cl->init_trip() && cmp->in(limit_idx) == cl->limit()) {
2727 needs_guard = false;
2728 }
2729 }
2730 }
2731 }
2732 }
2733 }
2734
2735 #ifndef PRODUCT
2736 if (PrintOpto) {
2737 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2738 this->dump_head();
2739 } else if (TraceLoopOpts) {
2740 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
2741 this->dump_head();
2742 }
2743 #endif
2744
2745 if (needs_guard) {
2746 // Peel the loop to ensure there's a zero trip guard
2747 Node_List old_new;
2748 phase->do_peeling(this, old_new);
2749 }
2750
2751 // Replace the phi at loop head with the final value of the last
2752 // iteration. Then the CountedLoopEnd will collapse (backedge never
2753 // taken) and all loop-invariant uses of the exit values will be correct.
2754 Node *phi = cl->phi();
2755 Node *exact_limit = phase->exact_limit(this);
2756 if (exact_limit != cl->limit()) {
2757 // We also need to replace the original limit to collapse loop exit.
2758 Node* cmp = cl->loopexit()->cmp_node();
2759 assert(cl->limit() == cmp->in(2), "sanity");
2760 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2761 phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2762 }
2763 // Note: the final value after increment should not overflow since
2764 // counted loop has limit check predicate.
2765 Node *final = new SubINode( exact_limit, cl->stride() );
2766 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2767 phase->_igvn.replace_node(phi,final);
2768 phase->C->set_major_progress();
2769 return true;
2770 }
2771
2772 //------------------------------policy_do_one_iteration_loop-------------------
2773 // Convert one iteration loop into normal code.
2774 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2775 if (!_head->as_Loop()->is_valid_counted_loop())
2776 return false; // Only for counted loop
2777
2778 CountedLoopNode *cl = _head->as_CountedLoop();
2779 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2780 return false;
2781 }
2782
2783 #ifndef PRODUCT
2784 if(TraceLoopOpts) {
2785 tty->print("OneIteration ");
2786 this->dump_head();
2787 }
2788 #endif
2789
2790 Node *init_n = cl->init_trip();
2791 #ifdef ASSERT
2792 // Loop boundaries should be constant since trip count is exact.
2793 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2794 #endif
2795 // Replace the phi at loop head with the value of the init_trip.
2796 // Then the CountedLoopEnd will collapse (backedge will not be taken)
2797 // and all loop-invariant uses of the exit values will be correct.
2798 phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2799 phase->C->set_major_progress();
2800 return true;
2801 }
2802
2803 //=============================================================================
2804 //------------------------------iteration_split_impl---------------------------
2805 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2806 // Compute exact loop trip count if possible.
2807 compute_exact_trip_count(phase);
2808
2809 // Convert one iteration loop into normal code.
2810 if (policy_do_one_iteration_loop(phase))
2811 return true;
2812
2813 // Check and remove empty loops (spam micro-benchmarks)
2814 if (policy_do_remove_empty_loop(phase))
2815 return true; // Here we removed an empty loop
2816
2817 bool should_peel = policy_peeling(phase); // Should we peel?
2818
2819 bool should_unswitch = policy_unswitching(phase);
2820
2821 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2822 // This removes loop-invariant tests (usually null checks).
2823 if (!_head->is_CountedLoop()) { // Non-counted loop
2824 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2825 // Partial peel succeeded so terminate this round of loop opts
2826 return false;
2827 }
2828 if (should_peel) { // Should we peel?
2829 if (PrintOpto) { tty->print_cr("should_peel"); }
2830 phase->do_peeling(this,old_new);
2831 } else if (should_unswitch) {
2832 phase->do_unswitching(this, old_new);
2833 }
2834 return true;
2835 }
2836 CountedLoopNode *cl = _head->as_CountedLoop();
2837
2838 if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2839
2840 // Do nothing special to pre- and post- loops
2841 if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2842
2843 // Compute loop trip count from profile data
2844 compute_profile_trip_cnt(phase);
2845
2846 // Before attempting fancy unrolling, RCE or alignment, see if we want
2847 // to completely unroll this loop or do loop unswitching.
2848 if (cl->is_normal_loop()) {
2849 if (should_unswitch) {
2850 phase->do_unswitching(this, old_new);
2851 return true;
2852 }
2853 bool should_maximally_unroll = policy_maximally_unroll(phase);
2854 if (should_maximally_unroll) {
2855 // Here we did some unrolling and peeling. Eventually we will
2856 // completely unroll this loop and it will no longer be a loop.
2857 phase->do_maximally_unroll(this,old_new);
2858 return true;
2859 }
2860 }
2861
2862 // Skip next optimizations if running low on nodes. Note that
2863 // policy_unswitching and policy_maximally_unroll have this check.
2864 int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes();
2865 if ((int)(2 * _body.size()) > nodes_left) {
2866 return true;
2867 }
2868
2869 // Counted loops may be peeled, may need some iterations run up
2870 // front for RCE, and may want to align loop refs to a cache
2871 // line. Thus we clone a full loop up front whose trip count is
2872 // at least 1 (if peeling), but may be several more.
2873
2874 // The main loop will start cache-line aligned with at least 1
2875 // iteration of the unrolled body (zero-trip test required) and
2876 // will have some range checks removed.
2877
2878 // A post-loop will finish any odd iterations (leftover after
2879 // unrolling), plus any needed for RCE purposes.
2880
2881 bool should_unroll = policy_unroll(phase);
2882
2883 bool should_rce = policy_range_check(phase);
2884
2885 bool should_align = policy_align(phase);
2886
2887 // If not RCE'ing (iteration splitting) or Aligning, then we do not
2888 // need a pre-loop. We may still need to peel an initial iteration but
2889 // we will not be needing an unknown number of pre-iterations.
2890 //
2891 // Basically, if may_rce_align reports FALSE first time through,
2892 // we will not be able to later do RCE or Aligning on this loop.
2893 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2894
2895 // If we have any of these conditions (RCE, alignment, unrolling) met, then
2896 // we switch to the pre-/main-/post-loop model. This model also covers
2897 // peeling.
2898 if (should_rce || should_align || should_unroll) {
2899 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops
2900 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2901
2902 // Adjust the pre- and main-loop limits to let the pre and post loops run
2903 // with full checks, but the main-loop with no checks. Remove said
2904 // checks from the main body.
2905 if (should_rce) {
2906 old_new.clear();
2907 phase->do_range_check(this, old_new);
2908 if (old_new.size() > 0) {
2909 cl->mark_has_range_checks();
2910 old_new.clear();
2911 }
2912 }
2913
2914 if (should_rce && should_unroll && !should_peel && PostLoopMultiversioning) {
2915 // Try to setup multiversioning on main loops before they are unrolled
2916 if (cl->is_main_loop() && (cl->unrolled_count() == 1))
2917 phase->insert_scalar_rced_post_loop(this, old_new);
2918 }
2919
2920 // Double loop body for unrolling. Adjust the minimum-trip test (will do
2921 // twice as many iterations as before) and the main body limit (only do
2922 // an even number of trips). If we are peeling, we might enable some RCE
2923 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2924 // peeling.
2925 if (should_unroll && !should_peel) {
2926 if (SuperWordLoopUnrollAnalysis) {
2927 phase->insert_vector_post_loop(this, old_new);
2928 }
2929 phase->do_unroll(this, old_new, true);
2930 }
2931
2932 // Adjust the pre-loop limits to align the main body
2933 // iterations.
2934 if (should_align)
2935 Unimplemented();
2936
2937 } else { // Else we have an unchanged counted loop
2938 if (should_peel) // Might want to peel but do nothing else
2939 phase->do_peeling(this,old_new);
2940 }
2941 return true;
2942 }
2943
2944
2945 //=============================================================================
2946 //------------------------------iteration_split--------------------------------
2947 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2948 // Recursively iteration split nested loops
2949 if (_child && !_child->iteration_split(phase, old_new))
2950 return false;
2951
2952 // Clean out prior deadwood
2953 DCE_loop_body();
2954
2955
2956 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2957 // Replace with a 1-in-10 exit guess.
2958 if (_parent /*not the root loop*/ &&
2959 !_irreducible &&
2960 // Also ignore the occasional dead backedge
2961 !tail()->is_top()) {
2962 adjust_loop_exit_prob(phase);
2963 }
2964
2965 // Gate unrolling, RCE and peeling efforts.
2966 if (!_child && // If not an inner loop, do not split
2967 !_irreducible &&
2968 _allow_optimizations &&
2969 !tail()->is_top()) { // Also ignore the occasional dead backedge
2970 if (!_has_call) {
2971 if (!iteration_split_impl(phase, old_new)) {
2972 return false;
2973 }
2974 } else if (policy_unswitching(phase)) {
2975 phase->do_unswitching(this, old_new);
2976 }
2977 }
2978
2979 // Minor offset re-organization to remove loop-fallout uses of
2980 // trip counter when there was no major reshaping.
2981 phase->reorg_offsets(this);
2982
2983 if (_next && !_next->iteration_split(phase, old_new))
2984 return false;
2985 return true;
2986 }
2987
2988
2989 //=============================================================================
2990 // Process all the loops in the loop tree and replace any fill
2991 // patterns with an intrinsic version.
2992 bool PhaseIdealLoop::do_intrinsify_fill() {
2993 bool changed = false;
2994 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2995 IdealLoopTree* lpt = iter.current();
2996 changed |= intrinsify_fill(lpt);
2997 }
2998 return changed;
2999 }
3000
3001
3002 // Examine an inner loop looking for a a single store of an invariant
3003 // value in a unit stride loop,
3004 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
3005 Node*& shift, Node*& con) {
3006 const char* msg = NULL;
3007 Node* msg_node = NULL;
3008
3009 store_value = NULL;
3010 con = NULL;
3011 shift = NULL;
3012
3013 // Process the loop looking for stores. If there are multiple
3014 // stores or extra control flow give at this point.
3015 CountedLoopNode* head = lpt->_head->as_CountedLoop();
3016 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3017 Node* n = lpt->_body.at(i);
3018 if (n->outcnt() == 0) continue; // Ignore dead
3019 if (n->is_Store()) {
3020 if (store != NULL) {
3021 msg = "multiple stores";
3022 break;
3023 }
3024 int opc = n->Opcode();
3025 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
3026 msg = "oop fills not handled";
3027 break;
3028 }
3029 Node* value = n->in(MemNode::ValueIn);
3030 if (!lpt->is_invariant(value)) {
3031 msg = "variant store value";
3032 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
3033 msg = "not array address";
3034 }
3035 store = n;
3036 store_value = value;
3037 } else if (n->is_If() && n != head->loopexit()) {
3038 msg = "extra control flow";
3039 msg_node = n;
3040 }
3041 }
3042
3043 if (store == NULL) {
3044 // No store in loop
3045 return false;
3046 }
3047
3048 if (msg == NULL && head->stride_con() != 1) {
3049 // could handle negative strides too
3050 if (head->stride_con() < 0) {
3051 msg = "negative stride";
3052 } else {
3053 msg = "non-unit stride";
3054 }
3055 }
3056
3057 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
3058 msg = "can't handle store address";
3059 msg_node = store->in(MemNode::Address);
3060 }
3061
3062 if (msg == NULL &&
3063 (!store->in(MemNode::Memory)->is_Phi() ||
3064 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
3065 msg = "store memory isn't proper phi";
3066 msg_node = store->in(MemNode::Memory);
3067 }
3068
3069 // Make sure there is an appropriate fill routine
3070 BasicType t = store->as_Mem()->memory_type();
3071 const char* fill_name;
3072 if (msg == NULL &&
3073 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
3074 msg = "unsupported store";
3075 msg_node = store;
3076 }
3077
3078 if (msg != NULL) {
3079 #ifndef PRODUCT
3080 if (TraceOptimizeFill) {
3081 tty->print_cr("not fill intrinsic candidate: %s", msg);
3082 if (msg_node != NULL) msg_node->dump();
3083 }
3084 #endif
3085 return false;
3086 }
3087
3088 // Make sure the address expression can be handled. It should be
3089 // head->phi * elsize + con. head->phi might have a ConvI2L(CastII()).
3090 Node* elements[4];
3091 Node* cast = NULL;
3092 Node* conv = NULL;
3093 bool found_index = false;
3094 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
3095 for (int e = 0; e < count; e++) {
3096 Node* n = elements[e];
3097 if (n->is_Con() && con == NULL) {
3098 con = n;
3099 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
3100 Node* value = n->in(1);
3101 #ifdef _LP64
3102 if (value->Opcode() == Op_ConvI2L) {
3103 conv = value;
3104 value = value->in(1);
3105 }
3106 if (value->Opcode() == Op_CastII &&
3107 value->as_CastII()->has_range_check()) {
3108 // Skip range check dependent CastII nodes
3109 cast = value;
3110 value = value->in(1);
3111 }
3112 #endif
3113 if (value != head->phi()) {
3114 msg = "unhandled shift in address";
3115 } else {
3116 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
3117 msg = "scale doesn't match";
3118 } else {
3119 found_index = true;
3120 shift = n;
3121 }
3122 }
3123 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
3124 conv = n;
3125 n = n->in(1);
3126 if (n->Opcode() == Op_CastII &&
3127 n->as_CastII()->has_range_check()) {
3128 // Skip range check dependent CastII nodes
3129 cast = n;
3130 n = n->in(1);
3131 }
3132 if (n == head->phi()) {
3133 found_index = true;
3134 } else {
3135 msg = "unhandled input to ConvI2L";
3136 }
3137 } else if (n == head->phi()) {
3138 // no shift, check below for allowed cases
3139 found_index = true;
3140 } else {
3141 msg = "unhandled node in address";
3142 msg_node = n;
3143 }
3144 }
3145
3146 if (count == -1) {
3147 msg = "malformed address expression";
3148 msg_node = store;
3149 }
3150
3151 if (!found_index) {
3152 msg = "missing use of index";
3153 }
3154
3155 // byte sized items won't have a shift
3156 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
3157 msg = "can't find shift";
3158 msg_node = store;
3159 }
3160
3161 if (msg != NULL) {
3162 #ifndef PRODUCT
3163 if (TraceOptimizeFill) {
3164 tty->print_cr("not fill intrinsic: %s", msg);
3165 if (msg_node != NULL) msg_node->dump();
3166 }
3167 #endif
3168 return false;
3169 }
3170
3171 // No make sure all the other nodes in the loop can be handled
3172 VectorSet ok(Thread::current()->resource_area());
3173
3174 // store related values are ok
3175 ok.set(store->_idx);
3176 ok.set(store->in(MemNode::Memory)->_idx);
3177
3178 CountedLoopEndNode* loop_exit = head->loopexit();
3179 guarantee(loop_exit != NULL, "no loop exit node");
3180
3181 // Loop structure is ok
3182 ok.set(head->_idx);
3183 ok.set(loop_exit->_idx);
3184 ok.set(head->phi()->_idx);
3185 ok.set(head->incr()->_idx);
3186 ok.set(loop_exit->cmp_node()->_idx);
3187 ok.set(loop_exit->in(1)->_idx);
3188
3189 // Address elements are ok
3190 if (con) ok.set(con->_idx);
3191 if (shift) ok.set(shift->_idx);
3192 if (cast) ok.set(cast->_idx);
3193 if (conv) ok.set(conv->_idx);
3194
3195 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3196 Node* n = lpt->_body.at(i);
3197 if (n->outcnt() == 0) continue; // Ignore dead
3198 if (ok.test(n->_idx)) continue;
3199 // Backedge projection is ok
3200 if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
3201 if (!n->is_AddP()) {
3202 msg = "unhandled node";
3203 msg_node = n;
3204 break;
3205 }
3206 }
3207
3208 // Make sure no unexpected values are used outside the loop
3209 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
3210 Node* n = lpt->_body.at(i);
3211 // These values can be replaced with other nodes if they are used
3212 // outside the loop.
3213 if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
3214 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
3215 Node* use = iter.get();
3216 if (!lpt->_body.contains(use)) {
3217 msg = "node is used outside loop";
3218 // lpt->_body.dump();
3219 msg_node = n;
3220 break;
3221 }
3222 }
3223 }
3224
3225 #ifdef ASSERT
3226 if (TraceOptimizeFill) {
3227 if (msg != NULL) {
3228 tty->print_cr("no fill intrinsic: %s", msg);
3229 if (msg_node != NULL) msg_node->dump();
3230 } else {
3231 tty->print_cr("fill intrinsic for:");
3232 }
3233 store->dump();
3234 if (Verbose) {
3235 lpt->_body.dump();
3236 }
3237 }
3238 #endif
3239
3240 return msg == NULL;
3241 }
3242
3243
3244
3245 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
3246 // Only for counted inner loops
3247 if (!lpt->is_counted() || !lpt->is_inner()) {
3248 return false;
3249 }
3250
3251 // Must have constant stride
3252 CountedLoopNode* head = lpt->_head->as_CountedLoop();
3253 if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
3254 return false;
3255 }
3256
3257 // Check that the body only contains a store of a loop invariant
3258 // value that is indexed by the loop phi.
3259 Node* store = NULL;
3260 Node* store_value = NULL;
3261 Node* shift = NULL;
3262 Node* offset = NULL;
3263 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
3264 return false;
3265 }
3266
3267 #ifndef PRODUCT
3268 if (TraceLoopOpts) {
3269 tty->print("ArrayFill ");
3270 lpt->dump_head();
3271 }
3272 #endif
3273
3274 // Now replace the whole loop body by a call to a fill routine that
3275 // covers the same region as the loop.
3276 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
3277
3278 // Build an expression for the beginning of the copy region
3279 Node* index = head->init_trip();
3280 #ifdef _LP64
3281 index = new ConvI2LNode(index);
3282 _igvn.register_new_node_with_optimizer(index);
3283 #endif
3284 if (shift != NULL) {
3285 // byte arrays don't require a shift but others do.
3286 index = new LShiftXNode(index, shift->in(2));
3287 _igvn.register_new_node_with_optimizer(index);
3288 }
3289 index = new AddPNode(base, base, index);
3290 _igvn.register_new_node_with_optimizer(index);
3291 Node* from = new AddPNode(base, index, offset);
3292 _igvn.register_new_node_with_optimizer(from);
3293 // Compute the number of elements to copy
3294 Node* len = new SubINode(head->limit(), head->init_trip());
3295 _igvn.register_new_node_with_optimizer(len);
3296
3297 BasicType t = store->as_Mem()->memory_type();
3298 bool aligned = false;
3299 if (offset != NULL && head->init_trip()->is_Con()) {
3300 int element_size = type2aelembytes(t);
3301 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
3302 }
3303
3304 // Build a call to the fill routine
3305 const char* fill_name;
3306 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
3307 assert(fill != NULL, "what?");
3308
3309 // Convert float/double to int/long for fill routines
3310 if (t == T_FLOAT) {
3311 store_value = new MoveF2INode(store_value);
3312 _igvn.register_new_node_with_optimizer(store_value);
3313 } else if (t == T_DOUBLE) {
3314 store_value = new MoveD2LNode(store_value);
3315 _igvn.register_new_node_with_optimizer(store_value);
3316 }
3317
3318 Node* mem_phi = store->in(MemNode::Memory);
3319 Node* result_ctrl;
3320 Node* result_mem;
3321 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
3322 CallLeafNode *call = new CallLeafNoFPNode(call_type, fill,
3323 fill_name, TypeAryPtr::get_array_body_type(t));
3324 uint cnt = 0;
3325 call->init_req(TypeFunc::Parms + cnt++, from);
3326 call->init_req(TypeFunc::Parms + cnt++, store_value);
3327 #ifdef _LP64
3328 len = new ConvI2LNode(len);
3329 _igvn.register_new_node_with_optimizer(len);
3330 #endif
3331 call->init_req(TypeFunc::Parms + cnt++, len);
3332 #ifdef _LP64
3333 call->init_req(TypeFunc::Parms + cnt++, C->top());
3334 #endif
3335 call->init_req(TypeFunc::Control, head->init_control());
3336 call->init_req(TypeFunc::I_O, C->top()); // Does no I/O.
3337 call->init_req(TypeFunc::Memory, mem_phi->in(LoopNode::EntryControl));
3338 call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr));
3339 call->init_req(TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr));
3340 _igvn.register_new_node_with_optimizer(call);
3341 result_ctrl = new ProjNode(call,TypeFunc::Control);
3342 _igvn.register_new_node_with_optimizer(result_ctrl);
3343 result_mem = new ProjNode(call,TypeFunc::Memory);
3344 _igvn.register_new_node_with_optimizer(result_mem);
3345
3346 /* Disable following optimization until proper fix (add missing checks).
3347
3348 // If this fill is tightly coupled to an allocation and overwrites
3349 // the whole body, allow it to take over the zeroing.
3350 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
3351 if (alloc != NULL && alloc->is_AllocateArray()) {
3352 Node* length = alloc->as_AllocateArray()->Ideal_length();
3353 if (head->limit() == length &&
3354 head->init_trip() == _igvn.intcon(0)) {
3355 if (TraceOptimizeFill) {
3356 tty->print_cr("Eliminated zeroing in allocation");
3357 }
3358 alloc->maybe_set_complete(&_igvn);
3359 } else {
3360 #ifdef ASSERT
3361 if (TraceOptimizeFill) {
3362 tty->print_cr("filling array but bounds don't match");
3363 alloc->dump();
3364 head->init_trip()->dump();
3365 head->limit()->dump();
3366 length->dump();
3367 }
3368 #endif
3369 }
3370 }
3371 */
3372
3373 // Redirect the old control and memory edges that are outside the loop.
3374 Node* exit = head->loopexit()->proj_out(0);
3375 // Sometimes the memory phi of the head is used as the outgoing
3376 // state of the loop. It's safe in this case to replace it with the
3377 // result_mem.
3378 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
3379 lazy_replace(exit, result_ctrl);
3380 _igvn.replace_node(store, result_mem);
3381 // Any uses the increment outside of the loop become the loop limit.
3382 _igvn.replace_node(head->incr(), head->limit());
3383
3384 // Disconnect the head from the loop.
3385 for (uint i = 0; i < lpt->_body.size(); i++) {
3386 Node* n = lpt->_body.at(i);
3387 _igvn.replace_node(n, C->top());
3388 }
3389
3390 return true;
3391 }