1 /*
2 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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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/connode.hpp"
31 #include "opto/divnode.hpp"
32 #include "opto/loopnode.hpp"
33 #include "opto/mulnode.hpp"
34 #include "opto/rootnode.hpp"
35 #include "opto/runtime.hpp"
36 #include "opto/subnode.hpp"
37
38 //------------------------------is_loop_exit-----------------------------------
39 // Given an IfNode, return the loop-exiting projection or NULL if both
40 // arms remain in the loop.
41 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
42 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
43 PhaseIdealLoop *phase = _phase;
44 // Test is an IfNode, has 2 projections. If BOTH are in the loop
45 // we need loop unswitching instead of peeling.
46 if( !is_member(phase->get_loop( iff->raw_out(0) )) )
47 return iff->raw_out(0);
48 if( !is_member(phase->get_loop( iff->raw_out(1) )) )
49 return iff->raw_out(1);
50 return NULL;
51 }
52
53
54 //=============================================================================
55
56
57 //------------------------------record_for_igvn----------------------------
58 // Put loop body on igvn work list
59 void IdealLoopTree::record_for_igvn() {
60 for( uint i = 0; i < _body.size(); i++ ) {
61 Node *n = _body.at(i);
62 _phase->_igvn._worklist.push(n);
63 }
64 }
65
66 //------------------------------compute_exact_trip_count-----------------------
67 // Compute loop exact trip count if possible. Do not recalculate trip count for
68 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
70 if (!_head->as_Loop()->is_valid_counted_loop()) {
71 return;
72 }
73 CountedLoopNode* cl = _head->as_CountedLoop();
74 // Trip count may become nonexact for iteration split loops since
75 // RCE modifies limits. Note, _trip_count value is not reset since
76 // it is used to limit unrolling of main loop.
77 cl->set_nonexact_trip_count();
78
79 // Loop's test should be part of loop.
80 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
81 return; // Infinite loop
82
83 #ifdef ASSERT
84 BoolTest::mask bt = cl->loopexit()->test_trip();
85 assert(bt == BoolTest::lt || bt == BoolTest::gt ||
86 (bt == BoolTest::ne && !LoopLimitCheck), "canonical test is expected");
87 #endif
88
89 Node* init_n = cl->init_trip();
90 Node* limit_n = cl->limit();
91 if (init_n != NULL && init_n->is_Con() &&
92 limit_n != NULL && limit_n->is_Con()) {
93 // Use longs to avoid integer overflow.
94 int stride_con = cl->stride_con();
95 long init_con = cl->init_trip()->get_int();
96 long limit_con = cl->limit()->get_int();
97 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
98 long trip_count = (limit_con - init_con + stride_m)/stride_con;
99 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
100 // Set exact trip count.
101 cl->set_exact_trip_count((uint)trip_count);
102 }
103 }
104 }
105
106 //------------------------------compute_profile_trip_cnt----------------------------
107 // Compute loop trip count from profile data as
108 // (backedge_count + loop_exit_count) / loop_exit_count
109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
110 if (!_head->is_CountedLoop()) {
111 return;
112 }
113 CountedLoopNode* head = _head->as_CountedLoop();
114 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
115 return; // Already computed
116 }
117 float trip_cnt = (float)max_jint; // default is big
118
119 Node* back = head->in(LoopNode::LoopBackControl);
120 while (back != head) {
121 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
122 back->in(0) &&
123 back->in(0)->is_If() &&
124 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
125 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
126 break;
127 }
128 back = phase->idom(back);
129 }
130 if (back != head) {
131 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
132 back->in(0), "if-projection exists");
133 IfNode* back_if = back->in(0)->as_If();
134 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
135
136 // Now compute a loop exit count
137 float loop_exit_cnt = 0.0f;
138 for( uint i = 0; i < _body.size(); i++ ) {
139 Node *n = _body[i];
140 if( n->is_If() ) {
141 IfNode *iff = n->as_If();
142 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
143 Node *exit = is_loop_exit(iff);
144 if( exit ) {
145 float exit_prob = iff->_prob;
146 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
147 if (exit_prob > PROB_MIN) {
148 float exit_cnt = iff->_fcnt * exit_prob;
149 loop_exit_cnt += exit_cnt;
150 }
151 }
152 }
153 }
154 }
155 if (loop_exit_cnt > 0.0f) {
156 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
157 } else {
158 // No exit count so use
159 trip_cnt = loop_back_cnt;
160 }
161 }
162 #ifndef PRODUCT
163 if (TraceProfileTripCount) {
164 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
165 }
166 #endif
167 head->set_profile_trip_cnt(trip_cnt);
168 }
169
170 //---------------------is_invariant_addition-----------------------------
171 // Return nonzero index of invariant operand for an Add or Sub
172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
174 int op = n->Opcode();
175 if (op == Op_AddI || op == Op_SubI) {
176 bool in1_invar = this->is_invariant(n->in(1));
177 bool in2_invar = this->is_invariant(n->in(2));
178 if (in1_invar && !in2_invar) return 1;
179 if (!in1_invar && in2_invar) return 2;
180 }
181 return 0;
182 }
183
184 //---------------------reassociate_add_sub-----------------------------
185 // Reassociate invariant add and subtract expressions:
186 //
187 // inv1 + (x + inv2) => ( inv1 + inv2) + x
188 // (x + inv2) + inv1 => ( inv1 + inv2) + x
189 // inv1 + (x - inv2) => ( inv1 - inv2) + x
190 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
191 // (x + inv2) - inv1 => (-inv1 + inv2) + x
192 // (x - inv2) + inv1 => ( inv1 - inv2) + x
193 // (x - inv2) - inv1 => (-inv1 - inv2) + x
194 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
195 // inv1 - (x - inv2) => ( inv1 + inv2) - x
196 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
197 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
198 // inv1 - (x + inv2) => ( inv1 - inv2) - x
199 //
200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
201 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
202 if (is_invariant(n1)) return NULL;
203 int inv1_idx = is_invariant_addition(n1, phase);
204 if (!inv1_idx) return NULL;
205 // Don't mess with add of constant (igvn moves them to expression tree root.)
206 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
207 Node* inv1 = n1->in(inv1_idx);
208 Node* n2 = n1->in(3 - inv1_idx);
209 int inv2_idx = is_invariant_addition(n2, phase);
210 if (!inv2_idx) return NULL;
211 Node* x = n2->in(3 - inv2_idx);
212 Node* inv2 = n2->in(inv2_idx);
213
214 bool neg_x = n2->is_Sub() && inv2_idx == 1;
215 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
216 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
217 if (n1->is_Sub() && inv1_idx == 1) {
218 neg_x = !neg_x;
219 neg_inv2 = !neg_inv2;
220 }
221 Node* inv1_c = phase->get_ctrl(inv1);
222 Node* inv2_c = phase->get_ctrl(inv2);
223 Node* n_inv1;
224 if (neg_inv1) {
225 Node *zero = phase->_igvn.intcon(0);
226 phase->set_ctrl(zero, phase->C->root());
227 n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
228 phase->register_new_node(n_inv1, inv1_c);
229 } else {
230 n_inv1 = inv1;
231 }
232 Node* inv;
233 if (neg_inv2) {
234 inv = new (phase->C, 3) SubINode(n_inv1, inv2);
235 } else {
236 inv = new (phase->C, 3) AddINode(n_inv1, inv2);
237 }
238 phase->register_new_node(inv, phase->get_early_ctrl(inv));
239
240 Node* addx;
241 if (neg_x) {
242 addx = new (phase->C, 3) SubINode(inv, x);
243 } else {
244 addx = new (phase->C, 3) AddINode(x, inv);
245 }
246 phase->register_new_node(addx, phase->get_ctrl(x));
247 phase->_igvn.replace_node(n1, addx);
248 assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
249 _body.yank(n1);
250 return addx;
251 }
252
253 //---------------------reassociate_invariants-----------------------------
254 // Reassociate invariant expressions:
255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
256 for (int i = _body.size() - 1; i >= 0; i--) {
257 Node *n = _body.at(i);
258 for (int j = 0; j < 5; j++) {
259 Node* nn = reassociate_add_sub(n, phase);
260 if (nn == NULL) break;
261 n = nn; // again
262 };
263 }
264 }
265
266 //------------------------------policy_peeling---------------------------------
267 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
268 // make some loop-invariant test (usually a null-check) happen before the loop.
269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
270 Node *test = ((IdealLoopTree*)this)->tail();
271 int body_size = ((IdealLoopTree*)this)->_body.size();
272 int uniq = phase->C->unique();
273 // Peeling does loop cloning which can result in O(N^2) node construction
274 if( body_size > 255 /* Prevent overflow for large body_size */
275 || (body_size * body_size + uniq > MaxNodeLimit) ) {
276 return false; // too large to safely clone
277 }
278 while( test != _head ) { // Scan till run off top of loop
279 if( test->is_If() ) { // Test?
280 Node *ctrl = phase->get_ctrl(test->in(1));
281 if (ctrl->is_top())
282 return false; // Found dead test on live IF? No peeling!
283 // Standard IF only has one input value to check for loop invariance
284 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
285 // Condition is not a member of this loop?
286 if( !is_member(phase->get_loop(ctrl)) &&
287 is_loop_exit(test) )
288 return true; // Found reason to peel!
289 }
290 // Walk up dominators to loop _head looking for test which is
291 // executed on every path thru loop.
292 test = phase->idom(test);
293 }
294 return false;
295 }
296
297 //------------------------------peeled_dom_test_elim---------------------------
298 // If we got the effect of peeling, either by actually peeling or by making
299 // a pre-loop which must execute at least once, we can remove all
300 // loop-invariant dominated tests in the main body.
301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
302 bool progress = true;
303 while( progress ) {
304 progress = false; // Reset for next iteration
305 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
306 Node *test = prev->in(0);
307 while( test != loop->_head ) { // Scan till run off top of loop
308
309 int p_op = prev->Opcode();
310 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
311 test->is_If() && // Test?
312 !test->in(1)->is_Con() && // And not already obvious?
313 // Condition is not a member of this loop?
314 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
315 // Walk loop body looking for instances of this test
316 for( uint i = 0; i < loop->_body.size(); i++ ) {
317 Node *n = loop->_body.at(i);
318 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
319 // IfNode was dominated by version in peeled loop body
320 progress = true;
321 dominated_by( old_new[prev->_idx], n );
322 }
323 }
324 }
325 prev = test;
326 test = idom(test);
327 } // End of scan tests in loop
328
329 } // End of while( progress )
330 }
331
332 //------------------------------do_peeling-------------------------------------
333 // Peel the first iteration of the given loop.
334 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
335 // The pre-loop illegally has 2 control users (old & new loops).
336 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
337 // Do this by making the old-loop fall-in edges act as if they came
338 // around the loopback from the prior iteration (follow the old-loop
339 // backedges) and then map to the new peeled iteration. This leaves
340 // the pre-loop with only 1 user (the new peeled iteration), but the
341 // peeled-loop backedge has 2 users.
342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
343 // extra backedge user.
344 //
345 // orig
346 //
347 // stmt1
348 // |
349 // v
350 // loop predicate
351 // |
352 // v
353 // loop<----+
354 // | |
355 // stmt2 |
356 // | |
357 // v |
358 // if ^
359 // / \ |
360 // / \ |
361 // v v |
362 // false true |
363 // / \ |
364 // / ----+
365 // |
366 // v
367 // exit
368 //
369 //
370 // after clone loop
371 //
372 // stmt1
373 // |
374 // v
375 // loop predicate
376 // / \
377 // clone / \ orig
378 // / \
379 // / \
380 // v v
381 // +---->loop clone loop<----+
382 // | | | |
383 // | stmt2 clone stmt2 |
384 // | | | |
385 // | v v |
386 // ^ if clone If ^
387 // | / \ / \ |
388 // | / \ / \ |
389 // | v v v v |
390 // | true false false true |
391 // | / \ / \ |
392 // +---- \ / ----+
393 // \ /
394 // 1v v2
395 // region
396 // |
397 // v
398 // exit
399 //
400 //
401 // after peel and predicate move
402 //
403 // stmt1
404 // /
405 // /
406 // clone / orig
407 // /
408 // / +----------+
409 // / | |
410 // / loop predicate |
411 // / | |
412 // v v |
413 // TOP-->loop clone loop<----+ |
414 // | | | |
415 // stmt2 clone stmt2 | |
416 // | | | ^
417 // v v | |
418 // if clone If ^ |
419 // / \ / \ | |
420 // / \ / \ | |
421 // v v v v | |
422 // true false false true | |
423 // | \ / \ | |
424 // | \ / ----+ ^
425 // | \ / |
426 // | 1v v2 |
427 // v region |
428 // | | |
429 // | v |
430 // | exit |
431 // | |
432 // +--------------->-----------------+
433 //
434 //
435 // final graph
436 //
437 // stmt1
438 // |
439 // v
440 // stmt2 clone
441 // |
442 // v
443 // if clone
444 // / |
445 // / |
446 // v v
447 // false true
448 // | |
449 // | v
450 // | loop predicate
451 // | |
452 // | v
453 // | loop<----+
454 // | | |
455 // | stmt2 |
456 // | | |
457 // | v |
458 // v if ^
459 // | / \ |
460 // | / \ |
461 // | v v |
462 // | false true |
463 // | | \ |
464 // v v --+
465 // region
466 // |
467 // v
468 // exit
469 //
470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
471
472 C->set_major_progress();
473 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
474 // 'pre' loop from the main and the 'pre' can no longer have it's
475 // iterations adjusted. Therefore, we need to declare this loop as
476 // no longer a 'main' loop; it will need new pre and post loops before
477 // we can do further RCE.
478 #ifndef PRODUCT
479 if (TraceLoopOpts) {
480 tty->print("Peel ");
481 loop->dump_head();
482 }
483 #endif
484 Node* head = loop->_head;
485 bool counted_loop = head->is_CountedLoop();
486 if (counted_loop) {
487 CountedLoopNode *cl = head->as_CountedLoop();
488 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
489 cl->set_trip_count(cl->trip_count() - 1);
490 if (cl->is_main_loop()) {
491 cl->set_normal_loop();
492 #ifndef PRODUCT
493 if (PrintOpto && VerifyLoopOptimizations) {
494 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
495 loop->dump_head();
496 }
497 #endif
498 }
499 }
500 Node* entry = head->in(LoopNode::EntryControl);
501
502 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
503 // The pre-loop illegally has 2 control users (old & new loops).
504 clone_loop( loop, old_new, dom_depth(head) );
505
506 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
507 // Do this by making the old-loop fall-in edges act as if they came
508 // around the loopback from the prior iteration (follow the old-loop
509 // backedges) and then map to the new peeled iteration. This leaves
510 // the pre-loop with only 1 user (the new peeled iteration), but the
511 // peeled-loop backedge has 2 users.
512 Node* new_exit_value = old_new[head->in(LoopNode::LoopBackControl)->_idx];
513 new_exit_value = move_loop_predicates(entry, new_exit_value, !counted_loop);
514 _igvn.hash_delete(head);
515 head->set_req(LoopNode::EntryControl, new_exit_value);
516 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
517 Node* old = head->fast_out(j);
518 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
519 new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
520 if (!new_exit_value ) // Backedge value is ALSO loop invariant?
521 // Then loop body backedge value remains the same.
522 new_exit_value = old->in(LoopNode::LoopBackControl);
523 _igvn.hash_delete(old);
524 old->set_req(LoopNode::EntryControl, new_exit_value);
525 }
526 }
527
528
529 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
530 // extra backedge user.
531 Node* new_head = old_new[head->_idx];
532 _igvn.hash_delete(new_head);
533 new_head->set_req(LoopNode::LoopBackControl, C->top());
534 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
535 Node* use = new_head->fast_out(j2);
536 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
537 _igvn.hash_delete(use);
538 use->set_req(LoopNode::LoopBackControl, C->top());
539 }
540 }
541
542
543 // Step 4: Correct dom-depth info. Set to loop-head depth.
544 int dd = dom_depth(head);
545 set_idom(head, head->in(1), dd);
546 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
547 Node *old = loop->_body.at(j3);
548 Node *nnn = old_new[old->_idx];
549 if (!has_ctrl(nnn))
550 set_idom(nnn, idom(nnn), dd-1);
551 // While we're at it, remove any SafePoints from the peeled code
552 if (old->Opcode() == Op_SafePoint) {
553 Node *nnn = old_new[old->_idx];
554 lazy_replace(nnn,nnn->in(TypeFunc::Control));
555 }
556 }
557
558 // Now force out all loop-invariant dominating tests. The optimizer
559 // finds some, but we _know_ they are all useless.
560 peeled_dom_test_elim(loop,old_new);
561
562 loop->record_for_igvn();
563 }
564
565 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
566
567 //------------------------------policy_maximally_unroll------------------------
568 // Calculate exact loop trip count and return true if loop can be maximally
569 // unrolled.
570 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
571 CountedLoopNode *cl = _head->as_CountedLoop();
572 assert(cl->is_normal_loop(), "");
573 if (!cl->is_valid_counted_loop())
574 return false; // Malformed counted loop
575
576 if (!cl->has_exact_trip_count()) {
577 // Trip count is not exact.
578 return false;
579 }
580
581 uint trip_count = cl->trip_count();
582 // Note, max_juint is used to indicate unknown trip count.
583 assert(trip_count > 1, "one iteration loop should be optimized out already");
584 assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
585
586 // Real policy: if we maximally unroll, does it get too big?
587 // Allow the unrolled mess to get larger than standard loop
588 // size. After all, it will no longer be a loop.
589 uint body_size = _body.size();
590 uint unroll_limit = (uint)LoopUnrollLimit * 4;
591 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
592 if (trip_count > unroll_limit || body_size > unroll_limit) {
593 return false;
594 }
595
596 // Fully unroll a loop with few iterations regardless next
597 // conditions since following loop optimizations will split
598 // such loop anyway (pre-main-post).
599 if (trip_count <= 3)
600 return true;
601
602 // Take into account that after unroll conjoined heads and tails will fold,
603 // otherwise policy_unroll() may allow more unrolling than max unrolling.
604 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
605 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
606 if (body_size != tst_body_size) // Check for int overflow
607 return false;
608 if (new_body_size > unroll_limit ||
609 // Unrolling can result in a large amount of node construction
610 new_body_size >= MaxNodeLimit - phase->C->unique()) {
611 return false;
612 }
613
614 // Do not unroll a loop with String intrinsics code.
615 // String intrinsics are large and have loops.
616 for (uint k = 0; k < _body.size(); k++) {
617 Node* n = _body.at(k);
618 switch (n->Opcode()) {
619 case Op_StrComp:
620 case Op_StrEquals:
621 case Op_StrIndexOf:
622 case Op_AryEq: {
623 return false;
624 }
625 } // switch
626 }
627
628 return true; // Do maximally unroll
629 }
630
631
632 #define MAX_UNROLL 16 // maximum number of unrolls for main loop
633
634 //------------------------------policy_unroll----------------------------------
635 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
636 // the loop is a CountedLoop and the body is small enough.
637 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
638
639 CountedLoopNode *cl = _head->as_CountedLoop();
640 assert(cl->is_normal_loop() || cl->is_main_loop(), "");
641
642 if (!cl->is_valid_counted_loop())
643 return false; // Malformed counted loop
644
645 // Protect against over-unrolling.
646 // After split at least one iteration will be executed in pre-loop.
647 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
648
649 int future_unroll_ct = cl->unrolled_count() * 2;
650 if (future_unroll_ct > MAX_UNROLL) return false;
651
652 // Check for initial stride being a small enough constant
653 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
654
655 // Don't unroll if the next round of unrolling would push us
656 // over the expected trip count of the loop. One is subtracted
657 // from the expected trip count because the pre-loop normally
658 // executes 1 iteration.
659 if (UnrollLimitForProfileCheck > 0 &&
660 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
661 future_unroll_ct > UnrollLimitForProfileCheck &&
662 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
663 return false;
664 }
665
666 // When unroll count is greater than LoopUnrollMin, don't unroll if:
667 // the residual iterations are more than 10% of the trip count
668 // and rounds of "unroll,optimize" are not making significant progress
669 // Progress defined as current size less than 20% larger than previous size.
670 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
671 future_unroll_ct > LoopUnrollMin &&
672 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
673 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
674 return false;
675 }
676
677 Node *init_n = cl->init_trip();
678 Node *limit_n = cl->limit();
679 int stride_con = cl->stride_con();
680 // Non-constant bounds.
681 // Protect against over-unrolling when init or/and limit are not constant
682 // (so that trip_count's init value is maxint) but iv range is known.
683 if (init_n == NULL || !init_n->is_Con() ||
684 limit_n == NULL || !limit_n->is_Con()) {
685 Node* phi = cl->phi();
686 if (phi != NULL) {
687 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
688 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
689 int next_stride = stride_con * 2; // stride after this unroll
690 if (next_stride > 0) {
691 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
692 iv_type->_lo + next_stride > iv_type->_hi) {
693 return false; // over-unrolling
694 }
695 } else if (next_stride < 0) {
696 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
697 iv_type->_hi + next_stride < iv_type->_lo) {
698 return false; // over-unrolling
699 }
700 }
701 }
702 }
703
704 // After unroll limit will be adjusted: new_limit = limit-stride.
705 // Bailout if adjustment overflow.
706 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
707 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
708 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
709 return false; // overflow
710
711 // Adjust body_size to determine if we unroll or not
712 uint body_size = _body.size();
713 // Also count ModL, DivL and MulL which expand mightly
714 for (uint k = 0; k < _body.size(); k++) {
715 Node* n = _body.at(k);
716 switch (n->Opcode()) {
717 case Op_ModL: body_size += 30; break;
718 case Op_DivL: body_size += 30; break;
719 case Op_MulL: body_size += 10; break;
720 case Op_StrComp:
721 case Op_StrEquals:
722 case Op_StrIndexOf:
723 case Op_AryEq: {
724 // Do not unroll a loop with String intrinsics code.
725 // String intrinsics are large and have loops.
726 return false;
727 }
728 } // switch
729 }
730
731 // Check for being too big
732 if (body_size > (uint)LoopUnrollLimit) {
733 // Normal case: loop too big
734 return false;
735 }
736
737 // Unroll once! (Each trip will soon do double iterations)
738 return true;
739 }
740
741 //------------------------------policy_align-----------------------------------
742 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
743 // expression that does the alignment. Note that only one array base can be
744 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
745 // if we vectorize short memory ops into longer memory ops, we may want to
746 // increase alignment.
747 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
748 return false;
749 }
750
751 //------------------------------policy_range_check-----------------------------
752 // Return TRUE or FALSE if the loop should be range-check-eliminated.
753 // Actually we do iteration-splitting, a more powerful form of RCE.
754 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
755 if (!RangeCheckElimination) return false;
756
757 CountedLoopNode *cl = _head->as_CountedLoop();
758 // If we unrolled with no intention of doing RCE and we later
759 // changed our minds, we got no pre-loop. Either we need to
760 // make a new pre-loop, or we gotta disallow RCE.
761 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
762 Node *trip_counter = cl->phi();
763
764 // Check loop body for tests of trip-counter plus loop-invariant vs
765 // loop-invariant.
766 for (uint i = 0; i < _body.size(); i++) {
767 Node *iff = _body[i];
768 if (iff->Opcode() == Op_If) { // Test?
769
770 // Comparing trip+off vs limit
771 Node *bol = iff->in(1);
772 if (bol->req() != 2) continue; // dead constant test
773 if (!bol->is_Bool()) {
774 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
775 continue;
776 }
777 if (bol->as_Bool()->_test._test == BoolTest::ne)
778 continue; // not RC
779
780 Node *cmp = bol->in(1);
781
782 Node *rc_exp = cmp->in(1);
783 Node *limit = cmp->in(2);
784
785 Node *limit_c = phase->get_ctrl(limit);
786 if( limit_c == phase->C->top() )
787 return false; // Found dead test on live IF? No RCE!
788 if( is_member(phase->get_loop(limit_c) ) ) {
789 // Compare might have operands swapped; commute them
790 rc_exp = cmp->in(2);
791 limit = cmp->in(1);
792 limit_c = phase->get_ctrl(limit);
793 if( is_member(phase->get_loop(limit_c) ) )
794 continue; // Both inputs are loop varying; cannot RCE
795 }
796
797 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
798 continue;
799 }
800 // Yeah! Found a test like 'trip+off vs limit'
801 // Test is an IfNode, has 2 projections. If BOTH are in the loop
802 // we need loop unswitching instead of iteration splitting.
803 if( is_loop_exit(iff) )
804 return true; // Found reason to split iterations
805 } // End of is IF
806 }
807
808 return false;
809 }
810
811 //------------------------------policy_peel_only-------------------------------
812 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
813 // for unrolling loops with NO array accesses.
814 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
815
816 for( uint i = 0; i < _body.size(); i++ )
817 if( _body[i]->is_Mem() )
818 return false;
819
820 // No memory accesses at all!
821 return true;
822 }
823
824 //------------------------------clone_up_backedge_goo--------------------------
825 // If Node n lives in the back_ctrl block and cannot float, we clone a private
826 // version of n in preheader_ctrl block and return that, otherwise return n.
827 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
828 if( get_ctrl(n) != back_ctrl ) return n;
829
830 Node *x = NULL; // If required, a clone of 'n'
831 // Check for 'n' being pinned in the backedge.
832 if( n->in(0) && n->in(0) == back_ctrl ) {
833 x = n->clone(); // Clone a copy of 'n' to preheader
834 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
835 }
836
837 // Recursive fixup any other input edges into x.
838 // If there are no changes we can just return 'n', otherwise
839 // we need to clone a private copy and change it.
840 for( uint i = 1; i < n->req(); i++ ) {
841 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
842 if( g != n->in(i) ) {
843 if( !x )
844 x = n->clone();
845 x->set_req(i, g);
846 }
847 }
848 if( x ) { // x can legally float to pre-header location
849 register_new_node( x, preheader_ctrl );
850 return x;
851 } else { // raise n to cover LCA of uses
852 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
853 }
854 return n;
855 }
856
857 //------------------------------insert_pre_post_loops--------------------------
858 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
859 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
860 // alignment. Useful to unroll loops that do no array accesses.
861 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
862
863 #ifndef PRODUCT
864 if (TraceLoopOpts) {
865 if (peel_only)
866 tty->print("PeelMainPost ");
867 else
868 tty->print("PreMainPost ");
869 loop->dump_head();
870 }
871 #endif
872 C->set_major_progress();
873
874 // Find common pieces of the loop being guarded with pre & post loops
875 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
876 assert( main_head->is_normal_loop(), "" );
877 CountedLoopEndNode *main_end = main_head->loopexit();
878 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
879 uint dd_main_head = dom_depth(main_head);
880 uint max = main_head->outcnt();
881
882 Node *pre_header= main_head->in(LoopNode::EntryControl);
883 Node *init = main_head->init_trip();
884 Node *incr = main_end ->incr();
885 Node *limit = main_end ->limit();
886 Node *stride = main_end ->stride();
887 Node *cmp = main_end ->cmp_node();
888 BoolTest::mask b_test = main_end->test_trip();
889
890 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
891 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
892 if( bol->outcnt() != 1 ) {
893 bol = bol->clone();
894 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
895 _igvn.hash_delete(main_end);
896 main_end->set_req(CountedLoopEndNode::TestValue, bol);
897 }
898 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
899 if( cmp->outcnt() != 1 ) {
900 cmp = cmp->clone();
901 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
902 _igvn.hash_delete(bol);
903 bol->set_req(1, cmp);
904 }
905
906 //------------------------------
907 // Step A: Create Post-Loop.
908 Node* main_exit = main_end->proj_out(false);
909 assert( main_exit->Opcode() == Op_IfFalse, "" );
910 int dd_main_exit = dom_depth(main_exit);
911
912 // Step A1: Clone the loop body. The clone becomes the post-loop. The main
913 // loop pre-header illegally has 2 control users (old & new loops).
914 clone_loop( loop, old_new, dd_main_exit );
915 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
916 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
917 post_head->set_post_loop(main_head);
918
919 // Reduce the post-loop trip count.
920 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
921 post_end->_prob = PROB_FAIR;
922
923 // Build the main-loop normal exit.
924 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
925 _igvn.register_new_node_with_optimizer( new_main_exit );
926 set_idom(new_main_exit, main_end, dd_main_exit );
927 set_loop(new_main_exit, loop->_parent);
928
929 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
930 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
931 // (the main-loop trip-counter exit value) because we will be changing
932 // the exit value (via unrolling) so we cannot constant-fold away the zero
933 // trip guard until all unrolling is done.
934 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr);
935 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit );
936 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test );
937 register_new_node( zer_opaq, new_main_exit );
938 register_new_node( zer_cmp , new_main_exit );
939 register_new_node( zer_bol , new_main_exit );
940
941 // Build the IfNode
942 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
943 _igvn.register_new_node_with_optimizer( zer_iff );
944 set_idom(zer_iff, new_main_exit, dd_main_exit);
945 set_loop(zer_iff, loop->_parent);
946
947 // Plug in the false-path, taken if we need to skip post-loop
948 _igvn.hash_delete( main_exit );
949 main_exit->set_req(0, zer_iff);
950 _igvn._worklist.push(main_exit);
951 set_idom(main_exit, zer_iff, dd_main_exit);
952 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
953 // Make the true-path, must enter the post loop
954 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
955 _igvn.register_new_node_with_optimizer( zer_taken );
956 set_idom(zer_taken, zer_iff, dd_main_exit);
957 set_loop(zer_taken, loop->_parent);
958 // Plug in the true path
959 _igvn.hash_delete( post_head );
960 post_head->set_req(LoopNode::EntryControl, zer_taken);
961 set_idom(post_head, zer_taken, dd_main_exit);
962
963 // Step A3: Make the fall-in values to the post-loop come from the
964 // fall-out values of the main-loop.
965 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
966 Node* main_phi = main_head->fast_out(i);
967 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
968 Node *post_phi = old_new[main_phi->_idx];
969 Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
970 post_head->init_control(),
971 main_phi->in(LoopNode::LoopBackControl));
972 _igvn.hash_delete(post_phi);
973 post_phi->set_req( LoopNode::EntryControl, fallmain );
974 }
975 }
976
977 // Update local caches for next stanza
978 main_exit = new_main_exit;
979
980
981 //------------------------------
982 // Step B: Create Pre-Loop.
983
984 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
985 // loop pre-header illegally has 2 control users (old & new loops).
986 clone_loop( loop, old_new, dd_main_head );
987 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
988 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
989 pre_head->set_pre_loop(main_head);
990 Node *pre_incr = old_new[incr->_idx];
991
992 // Reduce the pre-loop trip count.
993 pre_end->_prob = PROB_FAIR;
994
995 // Find the pre-loop normal exit.
996 Node* pre_exit = pre_end->proj_out(false);
997 assert( pre_exit->Opcode() == Op_IfFalse, "" );
998 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
999 _igvn.register_new_node_with_optimizer( new_pre_exit );
1000 set_idom(new_pre_exit, pre_end, dd_main_head);
1001 set_loop(new_pre_exit, loop->_parent);
1002
1003 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
1004 // pre-loop, the main-loop may not execute at all. Later in life this
1005 // zero-trip guard will become the minimum-trip guard when we unroll
1006 // the main-loop.
1007 Node *min_opaq = new (C, 2) Opaque1Node(C, limit);
1008 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq );
1009 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test );
1010 register_new_node( min_opaq, new_pre_exit );
1011 register_new_node( min_cmp , new_pre_exit );
1012 register_new_node( min_bol , new_pre_exit );
1013
1014 // Build the IfNode (assume the main-loop is executed always).
1015 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1016 _igvn.register_new_node_with_optimizer( min_iff );
1017 set_idom(min_iff, new_pre_exit, dd_main_head);
1018 set_loop(min_iff, loop->_parent);
1019
1020 // Plug in the false-path, taken if we need to skip main-loop
1021 _igvn.hash_delete( pre_exit );
1022 pre_exit->set_req(0, min_iff);
1023 set_idom(pre_exit, min_iff, dd_main_head);
1024 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1025 // Make the true-path, must enter the main loop
1026 Node *min_taken = new (C, 1) IfTrueNode( min_iff );
1027 _igvn.register_new_node_with_optimizer( min_taken );
1028 set_idom(min_taken, min_iff, dd_main_head);
1029 set_loop(min_taken, loop->_parent);
1030 // Plug in the true path
1031 _igvn.hash_delete( main_head );
1032 main_head->set_req(LoopNode::EntryControl, min_taken);
1033 set_idom(main_head, min_taken, dd_main_head);
1034
1035 // Step B3: Make the fall-in values to the main-loop come from the
1036 // fall-out values of the pre-loop.
1037 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1038 Node* main_phi = main_head->fast_out(i2);
1039 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1040 Node *pre_phi = old_new[main_phi->_idx];
1041 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
1042 main_head->init_control(),
1043 pre_phi->in(LoopNode::LoopBackControl));
1044 _igvn.hash_delete(main_phi);
1045 main_phi->set_req( LoopNode::EntryControl, fallpre );
1046 }
1047 }
1048
1049 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1050 // RCE and alignment may change this later.
1051 Node *cmp_end = pre_end->cmp_node();
1052 assert( cmp_end->in(2) == limit, "" );
1053 Node *pre_limit = new (C, 3) AddINode( init, stride );
1054
1055 // Save the original loop limit in this Opaque1 node for
1056 // use by range check elimination.
1057 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit);
1058
1059 register_new_node( pre_limit, pre_head->in(0) );
1060 register_new_node( pre_opaq , pre_head->in(0) );
1061
1062 // Since no other users of pre-loop compare, I can hack limit directly
1063 assert( cmp_end->outcnt() == 1, "no other users" );
1064 _igvn.hash_delete(cmp_end);
1065 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1066
1067 // Special case for not-equal loop bounds:
1068 // Change pre loop test, main loop test, and the
1069 // main loop guard test to use lt or gt depending on stride
1070 // direction:
1071 // positive stride use <
1072 // negative stride use >
1073
1074 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1075 assert(!LoopLimitCheck, "only canonical tests (lt or gt) are expected");
1076
1077 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1078 // Modify pre loop end condition
1079 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1080 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
1081 register_new_node( new_bol0, pre_head->in(0) );
1082 _igvn.hash_delete(pre_end);
1083 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
1084 // Modify main loop guard condition
1085 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1086 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
1087 register_new_node( new_bol1, new_pre_exit );
1088 _igvn.hash_delete(min_iff);
1089 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1090 // Modify main loop end condition
1091 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1092 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
1093 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1094 _igvn.hash_delete(main_end);
1095 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
1096 }
1097
1098 // Flag main loop
1099 main_head->set_main_loop();
1100 if( peel_only ) main_head->set_main_no_pre_loop();
1101
1102 // Subtract a trip count for the pre-loop.
1103 main_head->set_trip_count(main_head->trip_count() - 1);
1104
1105 // It's difficult to be precise about the trip-counts
1106 // for the pre/post loops. They are usually very short,
1107 // so guess that 4 trips is a reasonable value.
1108 post_head->set_profile_trip_cnt(4.0);
1109 pre_head->set_profile_trip_cnt(4.0);
1110
1111 // Now force out all loop-invariant dominating tests. The optimizer
1112 // finds some, but we _know_ they are all useless.
1113 peeled_dom_test_elim(loop,old_new);
1114 }
1115
1116 //------------------------------is_invariant-----------------------------
1117 // Return true if n is invariant
1118 bool IdealLoopTree::is_invariant(Node* n) const {
1119 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1120 if (n_c->is_top()) return false;
1121 return !is_member(_phase->get_loop(n_c));
1122 }
1123
1124
1125 //------------------------------do_unroll--------------------------------------
1126 // Unroll the loop body one step - make each trip do 2 iterations.
1127 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1128 assert(LoopUnrollLimit, "");
1129 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1130 CountedLoopEndNode *loop_end = loop_head->loopexit();
1131 assert(loop_end, "");
1132 #ifndef PRODUCT
1133 if (PrintOpto && VerifyLoopOptimizations) {
1134 tty->print("Unrolling ");
1135 loop->dump_head();
1136 } else if (TraceLoopOpts) {
1137 if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1138 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1139 } else {
1140 tty->print("Unroll %d ", loop_head->unrolled_count()*2);
1141 }
1142 loop->dump_head();
1143 }
1144 #endif
1145
1146 // Remember loop node count before unrolling to detect
1147 // if rounds of unroll,optimize are making progress
1148 loop_head->set_node_count_before_unroll(loop->_body.size());
1149
1150 Node *ctrl = loop_head->in(LoopNode::EntryControl);
1151 Node *limit = loop_head->limit();
1152 Node *init = loop_head->init_trip();
1153 Node *stride = loop_head->stride();
1154
1155 Node *opaq = NULL;
1156 if (adjust_min_trip) { // If not maximally unrolling, need adjustment
1157 // Search for zero-trip guard.
1158 assert( loop_head->is_main_loop(), "" );
1159 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1160 Node *iff = ctrl->in(0);
1161 assert( iff->Opcode() == Op_If, "" );
1162 Node *bol = iff->in(1);
1163 assert( bol->Opcode() == Op_Bool, "" );
1164 Node *cmp = bol->in(1);
1165 assert( cmp->Opcode() == Op_CmpI, "" );
1166 opaq = cmp->in(2);
1167 // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1168 // optimized away and then another round of loop opts attempted.
1169 // We can not optimize this particular loop in that case.
1170 if (opaq->Opcode() != Op_Opaque1)
1171 return; // Cannot find zero-trip guard! Bail out!
1172 // Zero-trip test uses an 'opaque' node which is not shared.
1173 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1174 }
1175
1176 C->set_major_progress();
1177
1178 Node* new_limit = NULL;
1179 if (UnrollLimitCheck) {
1180 int stride_con = stride->get_int();
1181 int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1182 uint old_trip_count = loop_head->trip_count();
1183 // Verify that unroll policy result is still valid.
1184 assert(old_trip_count > 1 &&
1185 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1186
1187 // Adjust loop limit to keep valid iterations number after unroll.
1188 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1189 // which may overflow.
1190 if (!adjust_min_trip) {
1191 assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1192 "odd trip count for maximally unroll");
1193 // Don't need to adjust limit for maximally unroll since trip count is even.
1194 } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1195 // Loop's limit is constant. Loop's init could be constant when pre-loop
1196 // become peeled iteration.
1197 long init_con = init->get_int();
1198 // We can keep old loop limit if iterations count stays the same:
1199 // old_trip_count == new_trip_count * 2
1200 // Note: since old_trip_count >= 2 then new_trip_count >= 1
1201 // so we also don't need to adjust zero trip test.
1202 long limit_con = limit->get_int();
1203 // (stride_con*2) not overflow since stride_con <= 8.
1204 int new_stride_con = stride_con * 2;
1205 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1);
1206 long trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1207 // New trip count should satisfy next conditions.
1208 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1209 uint new_trip_count = (uint)trip_count;
1210 adjust_min_trip = (old_trip_count != new_trip_count*2);
1211 }
1212
1213 if (adjust_min_trip) {
1214 // Step 2: Adjust the trip limit if it is called for.
1215 // The adjustment amount is -stride. Need to make sure if the
1216 // adjustment underflows or overflows, then the main loop is skipped.
1217 Node* cmp = loop_end->cmp_node();
1218 assert(cmp->in(2) == limit, "sanity");
1219 assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1220
1221 // Verify that policy_unroll result is still valid.
1222 const TypeInt* limit_type = _igvn.type(limit)->is_int();
1223 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1224 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1225
1226 if (limit->is_Con()) {
1227 // The check in policy_unroll and the assert above guarantee
1228 // no underflow if limit is constant.
1229 new_limit = _igvn.intcon(limit->get_int() - stride_con);
1230 set_ctrl(new_limit, C->root());
1231 } else {
1232 // Limit is not constant.
1233 if (loop_head->unrolled_count() == 1) { // only for first unroll
1234 // Separate limit by Opaque node in case it is an incremented
1235 // variable from previous loop to avoid using pre-incremented
1236 // value which could increase register pressure.
1237 // Otherwise reorg_offsets() optimization will create a separate
1238 // Opaque node for each use of trip-counter and as result
1239 // zero trip guard limit will be different from loop limit.
1240 assert(has_ctrl(opaq), "should have it");
1241 Node* opaq_ctrl = get_ctrl(opaq);
1242 limit = new (C, 2) Opaque2Node( C, limit );
1243 register_new_node( limit, opaq_ctrl );
1244 }
1245 if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1246 stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1247 // No underflow.
1248 new_limit = new (C, 3) SubINode(limit, stride);
1249 } else {
1250 // (limit - stride) may underflow.
1251 // Clamp the adjustment value with MININT or MAXINT:
1252 //
1253 // new_limit = limit-stride
1254 // if (stride > 0)
1255 // new_limit = (limit < new_limit) ? MININT : new_limit;
1256 // else
1257 // new_limit = (limit > new_limit) ? MAXINT : new_limit;
1258 //
1259 BoolTest::mask bt = loop_end->test_trip();
1260 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1261 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1262 set_ctrl(adj_max, C->root());
1263 Node* old_limit = NULL;
1264 Node* adj_limit = NULL;
1265 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1266 if (loop_head->unrolled_count() > 1 &&
1267 limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1268 limit->in(CMoveNode::IfTrue) == adj_max &&
1269 bol->as_Bool()->_test._test == bt &&
1270 bol->in(1)->Opcode() == Op_CmpI &&
1271 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1272 // Loop was unrolled before.
1273 // Optimize the limit to avoid nested CMove:
1274 // use original limit as old limit.
1275 old_limit = bol->in(1)->in(1);
1276 // Adjust previous adjusted limit.
1277 adj_limit = limit->in(CMoveNode::IfFalse);
1278 adj_limit = new (C, 3) SubINode(adj_limit, stride);
1279 } else {
1280 old_limit = limit;
1281 adj_limit = new (C, 3) SubINode(limit, stride);
1282 }
1283 assert(old_limit != NULL && adj_limit != NULL, "");
1284 register_new_node( adj_limit, ctrl ); // adjust amount
1285 Node* adj_cmp = new (C, 3) CmpINode(old_limit, adj_limit);
1286 register_new_node( adj_cmp, ctrl );
1287 Node* adj_bool = new (C, 2) BoolNode(adj_cmp, bt);
1288 register_new_node( adj_bool, ctrl );
1289 new_limit = new (C, 4) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1290 }
1291 register_new_node(new_limit, ctrl);
1292 }
1293 assert(new_limit != NULL, "");
1294 // Replace in loop test.
1295 assert(loop_end->in(1)->in(1) == cmp, "sanity");
1296 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1297 // Don't need to create new test since only one user.
1298 _igvn.hash_delete(cmp);
1299 cmp->set_req(2, new_limit);
1300 } else {
1301 // Create new test since it is shared.
1302 Node* ctrl2 = loop_end->in(0);
1303 Node* cmp2 = cmp->clone();
1304 cmp2->set_req(2, new_limit);
1305 register_new_node(cmp2, ctrl2);
1306 Node* bol2 = loop_end->in(1)->clone();
1307 bol2->set_req(1, cmp2);
1308 register_new_node(bol2, ctrl2);
1309 _igvn.hash_delete(loop_end);
1310 loop_end->set_req(1, bol2);
1311 }
1312 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1313 // Make it a 1-trip test (means at least 2 trips).
1314
1315 // Guard test uses an 'opaque' node which is not shared. Hence I
1316 // can edit it's inputs directly. Hammer in the new limit for the
1317 // minimum-trip guard.
1318 assert(opaq->outcnt() == 1, "");
1319 _igvn.hash_delete(opaq);
1320 opaq->set_req(1, new_limit);
1321 }
1322
1323 // Adjust max trip count. The trip count is intentionally rounded
1324 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1325 // the main, unrolled, part of the loop will never execute as it is protected
1326 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1327 // and later determined that part of the unrolled loop was dead.
1328 loop_head->set_trip_count(old_trip_count / 2);
1329
1330 // Double the count of original iterations in the unrolled loop body.
1331 loop_head->double_unrolled_count();
1332
1333 } else { // LoopLimitCheck
1334
1335 // Adjust max trip count. The trip count is intentionally rounded
1336 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1337 // the main, unrolled, part of the loop will never execute as it is protected
1338 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1339 // and later determined that part of the unrolled loop was dead.
1340 loop_head->set_trip_count(loop_head->trip_count() / 2);
1341
1342 // Double the count of original iterations in the unrolled loop body.
1343 loop_head->double_unrolled_count();
1344
1345 // -----------
1346 // Step 2: Cut back the trip counter for an unroll amount of 2.
1347 // Loop will normally trip (limit - init)/stride_con. Since it's a
1348 // CountedLoop this is exact (stride divides limit-init exactly).
1349 // We are going to double the loop body, so we want to knock off any
1350 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
1351 Node *span = new (C, 3) SubINode( limit, init );
1352 register_new_node( span, ctrl );
1353 Node *trip = new (C, 3) DivINode( 0, span, stride );
1354 register_new_node( trip, ctrl );
1355 Node *mtwo = _igvn.intcon(-2);
1356 set_ctrl(mtwo, C->root());
1357 Node *rond = new (C, 3) AndINode( trip, mtwo );
1358 register_new_node( rond, ctrl );
1359 Node *spn2 = new (C, 3) MulINode( rond, stride );
1360 register_new_node( spn2, ctrl );
1361 new_limit = new (C, 3) AddINode( spn2, init );
1362 register_new_node( new_limit, ctrl );
1363
1364 // Hammer in the new limit
1365 Node *ctrl2 = loop_end->in(0);
1366 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), new_limit );
1367 register_new_node( cmp2, ctrl2 );
1368 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
1369 register_new_node( bol2, ctrl2 );
1370 _igvn.hash_delete(loop_end);
1371 loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1372
1373 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1374 // Make it a 1-trip test (means at least 2 trips).
1375 if( adjust_min_trip ) {
1376 assert( new_limit != NULL, "" );
1377 // Guard test uses an 'opaque' node which is not shared. Hence I
1378 // can edit it's inputs directly. Hammer in the new limit for the
1379 // minimum-trip guard.
1380 assert( opaq->outcnt() == 1, "" );
1381 _igvn.hash_delete(opaq);
1382 opaq->set_req(1, new_limit);
1383 }
1384 } // LoopLimitCheck
1385
1386 // ---------
1387 // Step 4: Clone the loop body. Move it inside the loop. This loop body
1388 // represents the odd iterations; since the loop trips an even number of
1389 // times its backedge is never taken. Kill the backedge.
1390 uint dd = dom_depth(loop_head);
1391 clone_loop( loop, old_new, dd );
1392
1393 // Make backedges of the clone equal to backedges of the original.
1394 // Make the fall-in from the original come from the fall-out of the clone.
1395 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1396 Node* phi = loop_head->fast_out(j);
1397 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1398 Node *newphi = old_new[phi->_idx];
1399 _igvn.hash_delete( phi );
1400 _igvn.hash_delete( newphi );
1401
1402 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1403 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1404 phi ->set_req(LoopNode::LoopBackControl, C->top());
1405 }
1406 }
1407 Node *clone_head = old_new[loop_head->_idx];
1408 _igvn.hash_delete( clone_head );
1409 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1410 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1411 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1412 loop->_head = clone_head; // New loop header
1413
1414 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1415 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1416
1417 // Kill the clone's backedge
1418 Node *newcle = old_new[loop_end->_idx];
1419 _igvn.hash_delete( newcle );
1420 Node *one = _igvn.intcon(1);
1421 set_ctrl(one, C->root());
1422 newcle->set_req(1, one);
1423 // Force clone into same loop body
1424 uint max = loop->_body.size();
1425 for( uint k = 0; k < max; k++ ) {
1426 Node *old = loop->_body.at(k);
1427 Node *nnn = old_new[old->_idx];
1428 loop->_body.push(nnn);
1429 if (!has_ctrl(old))
1430 set_loop(nnn, loop);
1431 }
1432
1433 loop->record_for_igvn();
1434 }
1435
1436 //------------------------------do_maximally_unroll----------------------------
1437
1438 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1439 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1440 assert(cl->has_exact_trip_count(), "trip count is not exact");
1441 assert(cl->trip_count() > 0, "");
1442 #ifndef PRODUCT
1443 if (TraceLoopOpts) {
1444 tty->print("MaxUnroll %d ", cl->trip_count());
1445 loop->dump_head();
1446 }
1447 #endif
1448
1449 // If loop is tripping an odd number of times, peel odd iteration
1450 if ((cl->trip_count() & 1) == 1) {
1451 do_peeling(loop, old_new);
1452 }
1453
1454 // Now its tripping an even number of times remaining. Double loop body.
1455 // Do not adjust pre-guards; they are not needed and do not exist.
1456 if (cl->trip_count() > 0) {
1457 assert((cl->trip_count() & 1) == 0, "missed peeling");
1458 do_unroll(loop, old_new, false);
1459 }
1460 }
1461
1462 //------------------------------dominates_backedge---------------------------------
1463 // Returns true if ctrl is executed on every complete iteration
1464 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1465 assert(ctrl->is_CFG(), "must be control");
1466 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1467 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1468 }
1469
1470 //------------------------------adjust_limit-----------------------------------
1471 // Helper function for add_constraint().
1472 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1473 // Compute "I :: (limit-offset)/scale"
1474 Node *con = new (C, 3) SubINode(rc_limit, offset);
1475 register_new_node(con, pre_ctrl);
1476 Node *X = new (C, 3) DivINode(0, con, scale);
1477 register_new_node(X, pre_ctrl);
1478
1479 // Adjust loop limit
1480 loop_limit = (stride_con > 0)
1481 ? (Node*)(new (C, 3) MinINode(loop_limit, X))
1482 : (Node*)(new (C, 3) MaxINode(loop_limit, X));
1483 register_new_node(loop_limit, pre_ctrl);
1484 return loop_limit;
1485 }
1486
1487 //------------------------------add_constraint---------------------------------
1488 // Constrain the main loop iterations so the conditions:
1489 // low_limit <= scale_con * I + offset < upper_limit
1490 // always holds true. That is, either increase the number of iterations in
1491 // the pre-loop or the post-loop until the condition holds true in the main
1492 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1493 // stride and scale are constants (offset and limit often are).
1494 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 ) {
1495 // For positive stride, the pre-loop limit always uses a MAX function
1496 // and the main loop a MIN function. For negative stride these are
1497 // reversed.
1498
1499 // Also for positive stride*scale the affine function is increasing, so the
1500 // pre-loop must check for underflow and the post-loop for overflow.
1501 // Negative stride*scale reverses this; pre-loop checks for overflow and
1502 // post-loop for underflow.
1503
1504 Node *scale = _igvn.intcon(scale_con);
1505 set_ctrl(scale, C->root());
1506
1507 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1508 // The overflow limit: scale*I+offset < upper_limit
1509 // For main-loop compute
1510 // ( if (scale > 0) /* and stride > 0 */
1511 // I < (upper_limit-offset)/scale
1512 // else /* scale < 0 and stride < 0 */
1513 // I > (upper_limit-offset)/scale
1514 // )
1515 //
1516 // (upper_limit-offset) may overflow or underflow.
1517 // But it is fine since main loop will either have
1518 // less iterations or will be skipped in such case.
1519 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1520
1521 // The underflow limit: low_limit <= scale*I+offset.
1522 // For pre-loop compute
1523 // NOT(scale*I+offset >= low_limit)
1524 // scale*I+offset < low_limit
1525 // ( if (scale > 0) /* and stride > 0 */
1526 // I < (low_limit-offset)/scale
1527 // else /* scale < 0 and stride < 0 */
1528 // I > (low_limit-offset)/scale
1529 // )
1530
1531 if (low_limit->get_int() == -max_jint) {
1532 if (!RangeLimitCheck) return;
1533 // We need this guard when scale*pre_limit+offset >= limit
1534 // due to underflow. So we need execute pre-loop until
1535 // scale*I+offset >= min_int. But (min_int-offset) will
1536 // underflow when offset > 0 and X will be > original_limit
1537 // when stride > 0. To avoid it we replace positive offset with 0.
1538 //
1539 // Also (min_int+1 == -max_int) is used instead of min_int here
1540 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1541 Node* shift = _igvn.intcon(31);
1542 set_ctrl(shift, C->root());
1543 Node* sign = new (C, 3) RShiftINode(offset, shift);
1544 register_new_node(sign, pre_ctrl);
1545 offset = new (C, 3) AndINode(offset, sign);
1546 register_new_node(offset, pre_ctrl);
1547 } else {
1548 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1549 // The only problem we have here when offset == min_int
1550 // since (0-min_int) == min_int. It may be fine for stride > 0
1551 // but for stride < 0 X will be < original_limit. To avoid it
1552 // max(pre_limit, original_limit) is used in do_range_check().
1553 }
1554 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1555 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1556
1557 } else { // stride_con*scale_con < 0
1558 // For negative stride*scale pre-loop checks for overflow and
1559 // post-loop for underflow.
1560 //
1561 // The overflow limit: scale*I+offset < upper_limit
1562 // For pre-loop compute
1563 // NOT(scale*I+offset < upper_limit)
1564 // scale*I+offset >= upper_limit
1565 // scale*I+offset+1 > upper_limit
1566 // ( if (scale < 0) /* and stride > 0 */
1567 // I < (upper_limit-(offset+1))/scale
1568 // else /* scale > 0 and stride < 0 */
1569 // I > (upper_limit-(offset+1))/scale
1570 // )
1571 //
1572 // (upper_limit-offset-1) may underflow or overflow.
1573 // To avoid it min(pre_limit, original_limit) is used
1574 // in do_range_check() for stride > 0 and max() for < 0.
1575 Node *one = _igvn.intcon(1);
1576 set_ctrl(one, C->root());
1577
1578 Node *plus_one = new (C, 3) AddINode(offset, one);
1579 register_new_node( plus_one, pre_ctrl );
1580 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1581 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1582
1583 if (low_limit->get_int() == -max_jint) {
1584 if (!RangeLimitCheck) return;
1585 // We need this guard when scale*main_limit+offset >= limit
1586 // due to underflow. So we need execute main-loop while
1587 // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1588 // underflow when (offset+1) > 0 and X will be < main_limit
1589 // when scale < 0 (and stride > 0). To avoid it we replace
1590 // positive (offset+1) with 0.
1591 //
1592 // Also (min_int+1 == -max_int) is used instead of min_int here
1593 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1594 Node* shift = _igvn.intcon(31);
1595 set_ctrl(shift, C->root());
1596 Node* sign = new (C, 3) RShiftINode(plus_one, shift);
1597 register_new_node(sign, pre_ctrl);
1598 plus_one = new (C, 3) AndINode(plus_one, sign);
1599 register_new_node(plus_one, pre_ctrl);
1600 } else {
1601 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1602 // The only problem we have here when offset == max_int
1603 // since (max_int+1) == min_int and (0-min_int) == min_int.
1604 // But it is fine since main loop will either have
1605 // less iterations or will be skipped in such case.
1606 }
1607 // The underflow limit: low_limit <= scale*I+offset.
1608 // For main-loop compute
1609 // scale*I+offset+1 > low_limit
1610 // ( if (scale < 0) /* and stride > 0 */
1611 // I < (low_limit-(offset+1))/scale
1612 // else /* scale > 0 and stride < 0 */
1613 // I > (low_limit-(offset+1))/scale
1614 // )
1615
1616 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1617 }
1618 }
1619
1620
1621 //------------------------------is_scaled_iv---------------------------------
1622 // Return true if exp is a constant times an induction var
1623 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1624 if (exp == iv) {
1625 if (p_scale != NULL) {
1626 *p_scale = 1;
1627 }
1628 return true;
1629 }
1630 int opc = exp->Opcode();
1631 if (opc == Op_MulI) {
1632 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1633 if (p_scale != NULL) {
1634 *p_scale = exp->in(2)->get_int();
1635 }
1636 return true;
1637 }
1638 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1639 if (p_scale != NULL) {
1640 *p_scale = exp->in(1)->get_int();
1641 }
1642 return true;
1643 }
1644 } else if (opc == Op_LShiftI) {
1645 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1646 if (p_scale != NULL) {
1647 *p_scale = 1 << exp->in(2)->get_int();
1648 }
1649 return true;
1650 }
1651 }
1652 return false;
1653 }
1654
1655 //-----------------------------is_scaled_iv_plus_offset------------------------------
1656 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1657 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1658 if (is_scaled_iv(exp, iv, p_scale)) {
1659 if (p_offset != NULL) {
1660 Node *zero = _igvn.intcon(0);
1661 set_ctrl(zero, C->root());
1662 *p_offset = zero;
1663 }
1664 return true;
1665 }
1666 int opc = exp->Opcode();
1667 if (opc == Op_AddI) {
1668 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1669 if (p_offset != NULL) {
1670 *p_offset = exp->in(2);
1671 }
1672 return true;
1673 }
1674 if (exp->in(2)->is_Con()) {
1675 Node* offset2 = NULL;
1676 if (depth < 2 &&
1677 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1678 p_offset != NULL ? &offset2 : NULL, depth+1)) {
1679 if (p_offset != NULL) {
1680 Node *ctrl_off2 = get_ctrl(offset2);
1681 Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
1682 register_new_node(offset, ctrl_off2);
1683 *p_offset = offset;
1684 }
1685 return true;
1686 }
1687 }
1688 } else if (opc == Op_SubI) {
1689 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1690 if (p_offset != NULL) {
1691 Node *zero = _igvn.intcon(0);
1692 set_ctrl(zero, C->root());
1693 Node *ctrl_off = get_ctrl(exp->in(2));
1694 Node* offset = new (C, 3) SubINode(zero, exp->in(2));
1695 register_new_node(offset, ctrl_off);
1696 *p_offset = offset;
1697 }
1698 return true;
1699 }
1700 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1701 if (p_offset != NULL) {
1702 *p_scale *= -1;
1703 *p_offset = exp->in(1);
1704 }
1705 return true;
1706 }
1707 }
1708 return false;
1709 }
1710
1711 //------------------------------do_range_check---------------------------------
1712 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1713 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1714 #ifndef PRODUCT
1715 if (PrintOpto && VerifyLoopOptimizations) {
1716 tty->print("Range Check Elimination ");
1717 loop->dump_head();
1718 } else if (TraceLoopOpts) {
1719 tty->print("RangeCheck ");
1720 loop->dump_head();
1721 }
1722 #endif
1723 assert(RangeCheckElimination, "");
1724 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1725 assert(cl->is_main_loop(), "");
1726
1727 // protect against stride not being a constant
1728 if (!cl->stride_is_con())
1729 return;
1730
1731 // Find the trip counter; we are iteration splitting based on it
1732 Node *trip_counter = cl->phi();
1733 // Find the main loop limit; we will trim it's iterations
1734 // to not ever trip end tests
1735 Node *main_limit = cl->limit();
1736
1737 // Need to find the main-loop zero-trip guard
1738 Node *ctrl = cl->in(LoopNode::EntryControl);
1739 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1740 Node *iffm = ctrl->in(0);
1741 assert(iffm->Opcode() == Op_If, "");
1742 Node *bolzm = iffm->in(1);
1743 assert(bolzm->Opcode() == Op_Bool, "");
1744 Node *cmpzm = bolzm->in(1);
1745 assert(cmpzm->is_Cmp(), "");
1746 Node *opqzm = cmpzm->in(2);
1747 // Can not optimize a loop if zero-trip Opaque1 node is optimized
1748 // away and then another round of loop opts attempted.
1749 if (opqzm->Opcode() != Op_Opaque1)
1750 return;
1751 assert(opqzm->in(1) == main_limit, "do not understand situation");
1752
1753 // Find the pre-loop limit; we will expand it's iterations to
1754 // not ever trip low tests.
1755 Node *p_f = iffm->in(0);
1756 assert(p_f->Opcode() == Op_IfFalse, "");
1757 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1758 assert(pre_end->loopnode()->is_pre_loop(), "");
1759 Node *pre_opaq1 = pre_end->limit();
1760 // Occasionally it's possible for a pre-loop Opaque1 node to be
1761 // optimized away and then another round of loop opts attempted.
1762 // We can not optimize this particular loop in that case.
1763 if (pre_opaq1->Opcode() != Op_Opaque1)
1764 return;
1765 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1766 Node *pre_limit = pre_opaq->in(1);
1767
1768 // Where do we put new limit calculations
1769 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1770
1771 // Ensure the original loop limit is available from the
1772 // pre-loop Opaque1 node.
1773 Node *orig_limit = pre_opaq->original_loop_limit();
1774 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1775 return;
1776
1777 // Must know if its a count-up or count-down loop
1778
1779 int stride_con = cl->stride_con();
1780 Node *zero = _igvn.intcon(0);
1781 Node *one = _igvn.intcon(1);
1782 // Use symmetrical int range [-max_jint,max_jint]
1783 Node *mini = _igvn.intcon(-max_jint);
1784 set_ctrl(zero, C->root());
1785 set_ctrl(one, C->root());
1786 set_ctrl(mini, C->root());
1787
1788 // Range checks that do not dominate the loop backedge (ie.
1789 // conditionally executed) can lengthen the pre loop limit beyond
1790 // the original loop limit. To prevent this, the pre limit is
1791 // (for stride > 0) MINed with the original loop limit (MAXed
1792 // stride < 0) when some range_check (rc) is conditionally
1793 // executed.
1794 bool conditional_rc = false;
1795
1796 // Check loop body for tests of trip-counter plus loop-invariant vs
1797 // loop-invariant.
1798 for( uint i = 0; i < loop->_body.size(); i++ ) {
1799 Node *iff = loop->_body[i];
1800 if( iff->Opcode() == Op_If ) { // Test?
1801
1802 // Test is an IfNode, has 2 projections. If BOTH are in the loop
1803 // we need loop unswitching instead of iteration splitting.
1804 Node *exit = loop->is_loop_exit(iff);
1805 if( !exit ) continue;
1806 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1807
1808 // Get boolean condition to test
1809 Node *i1 = iff->in(1);
1810 if( !i1->is_Bool() ) continue;
1811 BoolNode *bol = i1->as_Bool();
1812 BoolTest b_test = bol->_test;
1813 // Flip sense of test if exit condition is flipped
1814 if( flip )
1815 b_test = b_test.negate();
1816
1817 // Get compare
1818 Node *cmp = bol->in(1);
1819
1820 // Look for trip_counter + offset vs limit
1821 Node *rc_exp = cmp->in(1);
1822 Node *limit = cmp->in(2);
1823 jint scale_con= 1; // Assume trip counter not scaled
1824
1825 Node *limit_c = get_ctrl(limit);
1826 if( loop->is_member(get_loop(limit_c) ) ) {
1827 // Compare might have operands swapped; commute them
1828 b_test = b_test.commute();
1829 rc_exp = cmp->in(2);
1830 limit = cmp->in(1);
1831 limit_c = get_ctrl(limit);
1832 if( loop->is_member(get_loop(limit_c) ) )
1833 continue; // Both inputs are loop varying; cannot RCE
1834 }
1835 // Here we know 'limit' is loop invariant
1836
1837 // 'limit' maybe pinned below the zero trip test (probably from a
1838 // previous round of rce), in which case, it can't be used in the
1839 // zero trip test expression which must occur before the zero test's if.
1840 if( limit_c == ctrl ) {
1841 continue; // Don't rce this check but continue looking for other candidates.
1842 }
1843
1844 // Check for scaled induction variable plus an offset
1845 Node *offset = NULL;
1846
1847 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1848 continue;
1849 }
1850
1851 Node *offset_c = get_ctrl(offset);
1852 if( loop->is_member( get_loop(offset_c) ) )
1853 continue; // Offset is not really loop invariant
1854 // Here we know 'offset' is loop invariant.
1855
1856 // As above for the 'limit', the 'offset' maybe pinned below the
1857 // zero trip test.
1858 if( offset_c == ctrl ) {
1859 continue; // Don't rce this check but continue looking for other candidates.
1860 }
1861 #ifdef ASSERT
1862 if (TraceRangeLimitCheck) {
1863 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1864 bol->dump(2);
1865 }
1866 #endif
1867 // At this point we have the expression as:
1868 // scale_con * trip_counter + offset :: limit
1869 // where scale_con, offset and limit are loop invariant. Trip_counter
1870 // monotonically increases by stride_con, a constant. Both (or either)
1871 // stride_con and scale_con can be negative which will flip about the
1872 // sense of the test.
1873
1874 // Adjust pre and main loop limits to guard the correct iteration set
1875 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1876 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1877 // The underflow and overflow limits: 0 <= scale*I+offset < limit
1878 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1879 if (!conditional_rc) {
1880 // (0-offset)/scale could be outside of loop iterations range.
1881 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1882 }
1883 } else {
1884 #ifndef PRODUCT
1885 if( PrintOpto )
1886 tty->print_cr("missed RCE opportunity");
1887 #endif
1888 continue; // In release mode, ignore it
1889 }
1890 } else { // Otherwise work on normal compares
1891 switch( b_test._test ) {
1892 case BoolTest::gt:
1893 // Fall into GE case
1894 case BoolTest::ge:
1895 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1896 scale_con = -scale_con;
1897 offset = new (C, 3) SubINode( zero, offset );
1898 register_new_node( offset, pre_ctrl );
1899 limit = new (C, 3) SubINode( zero, limit );
1900 register_new_node( limit, pre_ctrl );
1901 // Fall into LE case
1902 case BoolTest::le:
1903 if (b_test._test != BoolTest::gt) {
1904 // Convert X <= Y to X < Y+1
1905 limit = new (C, 3) AddINode( limit, one );
1906 register_new_node( limit, pre_ctrl );
1907 }
1908 // Fall into LT case
1909 case BoolTest::lt:
1910 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1911 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1912 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1913 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1914 if (!conditional_rc) {
1915 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1916 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1917 // still be outside of loop range.
1918 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1919 }
1920 break;
1921 default:
1922 #ifndef PRODUCT
1923 if( PrintOpto )
1924 tty->print_cr("missed RCE opportunity");
1925 #endif
1926 continue; // Unhandled case
1927 }
1928 }
1929
1930 // Kill the eliminated test
1931 C->set_major_progress();
1932 Node *kill_con = _igvn.intcon( 1-flip );
1933 set_ctrl(kill_con, C->root());
1934 _igvn.hash_delete(iff);
1935 iff->set_req(1, kill_con);
1936 _igvn._worklist.push(iff);
1937 // Find surviving projection
1938 assert(iff->is_If(), "");
1939 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1940 // Find loads off the surviving projection; remove their control edge
1941 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1942 Node* cd = dp->fast_out(i); // Control-dependent node
1943 if( cd->is_Load() ) { // Loads can now float around in the loop
1944 _igvn.hash_delete(cd);
1945 // Allow the load to float around in the loop, or before it
1946 // but NOT before the pre-loop.
1947 cd->set_req(0, ctrl); // ctrl, not NULL
1948 _igvn._worklist.push(cd);
1949 --i;
1950 --imax;
1951 }
1952 }
1953
1954 } // End of is IF
1955
1956 }
1957
1958 // Update loop limits
1959 if (conditional_rc) {
1960 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
1961 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
1962 register_new_node(pre_limit, pre_ctrl);
1963 }
1964 _igvn.hash_delete(pre_opaq);
1965 pre_opaq->set_req(1, pre_limit);
1966
1967 // Note:: we are making the main loop limit no longer precise;
1968 // need to round up based on stride.
1969 cl->set_nonexact_trip_count();
1970 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
1971 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
1972 // Hopefully, compiler will optimize for powers of 2.
1973 Node *ctrl = get_ctrl(main_limit);
1974 Node *stride = cl->stride();
1975 Node *init = cl->init_trip();
1976 Node *span = new (C, 3) SubINode(main_limit,init);
1977 register_new_node(span,ctrl);
1978 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1979 Node *add = new (C, 3) AddINode(span,rndup);
1980 register_new_node(add,ctrl);
1981 Node *div = new (C, 3) DivINode(0,add,stride);
1982 register_new_node(div,ctrl);
1983 Node *mul = new (C, 3) MulINode(div,stride);
1984 register_new_node(mul,ctrl);
1985 Node *newlim = new (C, 3) AddINode(mul,init);
1986 register_new_node(newlim,ctrl);
1987 main_limit = newlim;
1988 }
1989
1990 Node *main_cle = cl->loopexit();
1991 Node *main_bol = main_cle->in(1);
1992 // Hacking loop bounds; need private copies of exit test
1993 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
1994 _igvn.hash_delete(main_cle);
1995 main_bol = main_bol->clone();// Clone a private BoolNode
1996 register_new_node( main_bol, main_cle->in(0) );
1997 main_cle->set_req(1,main_bol);
1998 }
1999 Node *main_cmp = main_bol->in(1);
2000 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2001 _igvn.hash_delete(main_bol);
2002 main_cmp = main_cmp->clone();// Clone a private CmpNode
2003 register_new_node( main_cmp, main_cle->in(0) );
2004 main_bol->set_req(1,main_cmp);
2005 }
2006 // Hack the now-private loop bounds
2007 _igvn.hash_delete(main_cmp);
2008 main_cmp->set_req(2, main_limit);
2009 _igvn._worklist.push(main_cmp);
2010 // The OpaqueNode is unshared by design
2011 _igvn.hash_delete(opqzm);
2012 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2013 opqzm->set_req(1,main_limit);
2014 _igvn._worklist.push(opqzm);
2015 }
2016
2017 //------------------------------DCE_loop_body----------------------------------
2018 // Remove simplistic dead code from loop body
2019 void IdealLoopTree::DCE_loop_body() {
2020 for( uint i = 0; i < _body.size(); i++ )
2021 if( _body.at(i)->outcnt() == 0 )
2022 _body.map( i--, _body.pop() );
2023 }
2024
2025
2026 //------------------------------adjust_loop_exit_prob--------------------------
2027 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2028 // Replace with a 1-in-10 exit guess.
2029 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2030 Node *test = tail();
2031 while( test != _head ) {
2032 uint top = test->Opcode();
2033 if( top == Op_IfTrue || top == Op_IfFalse ) {
2034 int test_con = ((ProjNode*)test)->_con;
2035 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2036 IfNode *iff = test->in(0)->as_If();
2037 if( iff->outcnt() == 2 ) { // Ignore dead tests
2038 Node *bol = iff->in(1);
2039 if( bol && bol->req() > 1 && bol->in(1) &&
2040 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2041 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2042 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2043 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2044 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2045 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2046 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2047 return; // Allocation loops RARELY take backedge
2048 // Find the OTHER exit path from the IF
2049 Node* ex = iff->proj_out(1-test_con);
2050 float p = iff->_prob;
2051 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2052 if( top == Op_IfTrue ) {
2053 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2054 iff->_prob = PROB_STATIC_FREQUENT;
2055 }
2056 } else {
2057 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2058 iff->_prob = PROB_STATIC_INFREQUENT;
2059 }
2060 }
2061 }
2062 }
2063 }
2064 test = phase->idom(test);
2065 }
2066 }
2067
2068
2069 //------------------------------policy_do_remove_empty_loop--------------------
2070 // Micro-benchmark spamming. Policy is to always remove empty loops.
2071 // The 'DO' part is to replace the trip counter with the value it will
2072 // have on the last iteration. This will break the loop.
2073 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2074 // Minimum size must be empty loop
2075 if (_body.size() > EMPTY_LOOP_SIZE)
2076 return false;
2077
2078 if (!_head->is_CountedLoop())
2079 return false; // Dead loop
2080 CountedLoopNode *cl = _head->as_CountedLoop();
2081 if (!cl->loopexit())
2082 return false; // Malformed loop
2083 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2084 return false; // Infinite loop
2085
2086 #ifdef ASSERT
2087 // Ensure only one phi which is the iv.
2088 Node* iv = NULL;
2089 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2090 Node* n = cl->fast_out(i);
2091 if (n->Opcode() == Op_Phi) {
2092 assert(iv == NULL, "Too many phis" );
2093 iv = n;
2094 }
2095 }
2096 assert(iv == cl->phi(), "Wrong phi" );
2097 #endif
2098
2099 // main and post loops have explicitly created zero trip guard
2100 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2101 if (needs_guard) {
2102 // Skip guard if values not overlap.
2103 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2104 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2105 int stride_con = cl->stride_con();
2106 if (stride_con > 0) {
2107 needs_guard = (init_t->_hi >= limit_t->_lo);
2108 } else {
2109 needs_guard = (init_t->_lo <= limit_t->_hi);
2110 }
2111 }
2112 if (needs_guard) {
2113 // Check for an obvious zero trip guard.
2114 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2115 if (inctrl->Opcode() == Op_IfTrue) {
2116 // The test should look like just the backedge of a CountedLoop
2117 Node* iff = inctrl->in(0);
2118 if (iff->is_If()) {
2119 Node* bol = iff->in(1);
2120 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2121 Node* cmp = bol->in(1);
2122 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2123 needs_guard = false;
2124 }
2125 }
2126 }
2127 }
2128 }
2129
2130 #ifndef PRODUCT
2131 if (PrintOpto) {
2132 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2133 this->dump_head();
2134 } else if (TraceLoopOpts) {
2135 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
2136 this->dump_head();
2137 }
2138 #endif
2139
2140 if (needs_guard) {
2141 // Peel the loop to ensure there's a zero trip guard
2142 Node_List old_new;
2143 phase->do_peeling(this, old_new);
2144 }
2145
2146 // Replace the phi at loop head with the final value of the last
2147 // iteration. Then the CountedLoopEnd will collapse (backedge never
2148 // taken) and all loop-invariant uses of the exit values will be correct.
2149 Node *phi = cl->phi();
2150 Node *exact_limit = phase->exact_limit(this);
2151 if (exact_limit != cl->limit()) {
2152 // We also need to replace the original limit to collapse loop exit.
2153 Node* cmp = cl->loopexit()->cmp_node();
2154 assert(cl->limit() == cmp->in(2), "sanity");
2155 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2156 phase->_igvn.hash_delete(cmp);
2157 cmp->set_req(2, exact_limit);
2158 phase->_igvn._worklist.push(cmp); // put cmp on worklist
2159 }
2160 // Note: the final value after increment should not overflow since
2161 // counted loop has limit check predicate.
2162 Node *final = new (phase->C, 3) SubINode( exact_limit, cl->stride() );
2163 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2164 phase->_igvn.replace_node(phi,final);
2165 phase->C->set_major_progress();
2166 return true;
2167 }
2168
2169 //------------------------------policy_do_one_iteration_loop-------------------
2170 // Convert one iteration loop into normal code.
2171 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2172 if (!_head->as_Loop()->is_valid_counted_loop())
2173 return false; // Only for counted loop
2174
2175 CountedLoopNode *cl = _head->as_CountedLoop();
2176 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2177 return false;
2178 }
2179
2180 #ifndef PRODUCT
2181 if(TraceLoopOpts) {
2182 tty->print("OneIteration ");
2183 this->dump_head();
2184 }
2185 #endif
2186
2187 Node *init_n = cl->init_trip();
2188 #ifdef ASSERT
2189 // Loop boundaries should be constant since trip count is exact.
2190 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2191 #endif
2192 // Replace the phi at loop head with the value of the init_trip.
2193 // Then the CountedLoopEnd will collapse (backedge will not be taken)
2194 // and all loop-invariant uses of the exit values will be correct.
2195 phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2196 phase->C->set_major_progress();
2197 return true;
2198 }
2199
2200 //=============================================================================
2201 //------------------------------iteration_split_impl---------------------------
2202 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2203 // Compute exact loop trip count if possible.
2204 compute_exact_trip_count(phase);
2205
2206 // Convert one iteration loop into normal code.
2207 if (policy_do_one_iteration_loop(phase))
2208 return true;
2209
2210 // Check and remove empty loops (spam micro-benchmarks)
2211 if (policy_do_remove_empty_loop(phase))
2212 return true; // Here we removed an empty loop
2213
2214 bool should_peel = policy_peeling(phase); // Should we peel?
2215
2216 bool should_unswitch = policy_unswitching(phase);
2217
2218 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2219 // This removes loop-invariant tests (usually null checks).
2220 if (!_head->is_CountedLoop()) { // Non-counted loop
2221 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2222 // Partial peel succeeded so terminate this round of loop opts
2223 return false;
2224 }
2225 if (should_peel) { // Should we peel?
2226 #ifndef PRODUCT
2227 if (PrintOpto) tty->print_cr("should_peel");
2228 #endif
2229 phase->do_peeling(this,old_new);
2230 } else if (should_unswitch) {
2231 phase->do_unswitching(this, old_new);
2232 }
2233 return true;
2234 }
2235 CountedLoopNode *cl = _head->as_CountedLoop();
2236
2237 if (!cl->loopexit()) return true; // Ignore various kinds of broken loops
2238
2239 // Do nothing special to pre- and post- loops
2240 if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2241
2242 // Compute loop trip count from profile data
2243 compute_profile_trip_cnt(phase);
2244
2245 // Before attempting fancy unrolling, RCE or alignment, see if we want
2246 // to completely unroll this loop or do loop unswitching.
2247 if (cl->is_normal_loop()) {
2248 if (should_unswitch) {
2249 phase->do_unswitching(this, old_new);
2250 return true;
2251 }
2252 bool should_maximally_unroll = policy_maximally_unroll(phase);
2253 if (should_maximally_unroll) {
2254 // Here we did some unrolling and peeling. Eventually we will
2255 // completely unroll this loop and it will no longer be a loop.
2256 phase->do_maximally_unroll(this,old_new);
2257 return true;
2258 }
2259 }
2260
2261 // Skip next optimizations if running low on nodes. Note that
2262 // policy_unswitching and policy_maximally_unroll have this check.
2263 uint nodes_left = MaxNodeLimit - phase->C->unique();
2264 if ((2 * _body.size()) > nodes_left) {
2265 return true;
2266 }
2267
2268 // Counted loops may be peeled, may need some iterations run up
2269 // front for RCE, and may want to align loop refs to a cache
2270 // line. Thus we clone a full loop up front whose trip count is
2271 // at least 1 (if peeling), but may be several more.
2272
2273 // The main loop will start cache-line aligned with at least 1
2274 // iteration of the unrolled body (zero-trip test required) and
2275 // will have some range checks removed.
2276
2277 // A post-loop will finish any odd iterations (leftover after
2278 // unrolling), plus any needed for RCE purposes.
2279
2280 bool should_unroll = policy_unroll(phase);
2281
2282 bool should_rce = policy_range_check(phase);
2283
2284 bool should_align = policy_align(phase);
2285
2286 // If not RCE'ing (iteration splitting) or Aligning, then we do not
2287 // need a pre-loop. We may still need to peel an initial iteration but
2288 // we will not be needing an unknown number of pre-iterations.
2289 //
2290 // Basically, if may_rce_align reports FALSE first time through,
2291 // we will not be able to later do RCE or Aligning on this loop.
2292 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2293
2294 // If we have any of these conditions (RCE, alignment, unrolling) met, then
2295 // we switch to the pre-/main-/post-loop model. This model also covers
2296 // peeling.
2297 if (should_rce || should_align || should_unroll) {
2298 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops
2299 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2300
2301 // Adjust the pre- and main-loop limits to let the pre and post loops run
2302 // with full checks, but the main-loop with no checks. Remove said
2303 // checks from the main body.
2304 if (should_rce)
2305 phase->do_range_check(this,old_new);
2306
2307 // Double loop body for unrolling. Adjust the minimum-trip test (will do
2308 // twice as many iterations as before) and the main body limit (only do
2309 // an even number of trips). If we are peeling, we might enable some RCE
2310 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2311 // peeling.
2312 if (should_unroll && !should_peel)
2313 phase->do_unroll(this,old_new, true);
2314
2315 // Adjust the pre-loop limits to align the main body
2316 // iterations.
2317 if (should_align)
2318 Unimplemented();
2319
2320 } else { // Else we have an unchanged counted loop
2321 if (should_peel) // Might want to peel but do nothing else
2322 phase->do_peeling(this,old_new);
2323 }
2324 return true;
2325 }
2326
2327
2328 //=============================================================================
2329 //------------------------------iteration_split--------------------------------
2330 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2331 // Recursively iteration split nested loops
2332 if (_child && !_child->iteration_split(phase, old_new))
2333 return false;
2334
2335 // Clean out prior deadwood
2336 DCE_loop_body();
2337
2338
2339 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2340 // Replace with a 1-in-10 exit guess.
2341 if (_parent /*not the root loop*/ &&
2342 !_irreducible &&
2343 // Also ignore the occasional dead backedge
2344 !tail()->is_top()) {
2345 adjust_loop_exit_prob(phase);
2346 }
2347
2348 // Gate unrolling, RCE and peeling efforts.
2349 if (!_child && // If not an inner loop, do not split
2350 !_irreducible &&
2351 _allow_optimizations &&
2352 !tail()->is_top()) { // Also ignore the occasional dead backedge
2353 if (!_has_call) {
2354 if (!iteration_split_impl(phase, old_new)) {
2355 return false;
2356 }
2357 } else if (policy_unswitching(phase)) {
2358 phase->do_unswitching(this, old_new);
2359 }
2360 }
2361
2362 // Minor offset re-organization to remove loop-fallout uses of
2363 // trip counter when there was no major reshaping.
2364 phase->reorg_offsets(this);
2365
2366 if (_next && !_next->iteration_split(phase, old_new))
2367 return false;
2368 return true;
2369 }
2370
2371
2372 //=============================================================================
2373 // Process all the loops in the loop tree and replace any fill
2374 // patterns with an intrisc version.
2375 bool PhaseIdealLoop::do_intrinsify_fill() {
2376 bool changed = false;
2377 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2378 IdealLoopTree* lpt = iter.current();
2379 changed |= intrinsify_fill(lpt);
2380 }
2381 return changed;
2382 }
2383
2384
2385 // Examine an inner loop looking for a a single store of an invariant
2386 // value in a unit stride loop,
2387 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2388 Node*& shift, Node*& con) {
2389 const char* msg = NULL;
2390 Node* msg_node = NULL;
2391
2392 store_value = NULL;
2393 con = NULL;
2394 shift = NULL;
2395
2396 // Process the loop looking for stores. If there are multiple
2397 // stores or extra control flow give at this point.
2398 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2399 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2400 Node* n = lpt->_body.at(i);
2401 if (n->outcnt() == 0) continue; // Ignore dead
2402 if (n->is_Store()) {
2403 if (store != NULL) {
2404 msg = "multiple stores";
2405 break;
2406 }
2407 int opc = n->Opcode();
2408 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreCM) {
2409 msg = "oop fills not handled";
2410 break;
2411 }
2412 Node* value = n->in(MemNode::ValueIn);
2413 if (!lpt->is_invariant(value)) {
2414 msg = "variant store value";
2415 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2416 msg = "not array address";
2417 }
2418 store = n;
2419 store_value = value;
2420 } else if (n->is_If() && n != head->loopexit()) {
2421 msg = "extra control flow";
2422 msg_node = n;
2423 }
2424 }
2425
2426 if (store == NULL) {
2427 // No store in loop
2428 return false;
2429 }
2430
2431 if (msg == NULL && head->stride_con() != 1) {
2432 // could handle negative strides too
2433 if (head->stride_con() < 0) {
2434 msg = "negative stride";
2435 } else {
2436 msg = "non-unit stride";
2437 }
2438 }
2439
2440 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2441 msg = "can't handle store address";
2442 msg_node = store->in(MemNode::Address);
2443 }
2444
2445 if (msg == NULL &&
2446 (!store->in(MemNode::Memory)->is_Phi() ||
2447 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2448 msg = "store memory isn't proper phi";
2449 msg_node = store->in(MemNode::Memory);
2450 }
2451
2452 // Make sure there is an appropriate fill routine
2453 BasicType t = store->as_Mem()->memory_type();
2454 const char* fill_name;
2455 if (msg == NULL &&
2456 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2457 msg = "unsupported store";
2458 msg_node = store;
2459 }
2460
2461 if (msg != NULL) {
2462 #ifndef PRODUCT
2463 if (TraceOptimizeFill) {
2464 tty->print_cr("not fill intrinsic candidate: %s", msg);
2465 if (msg_node != NULL) msg_node->dump();
2466 }
2467 #endif
2468 return false;
2469 }
2470
2471 // Make sure the address expression can be handled. It should be
2472 // head->phi * elsize + con. head->phi might have a ConvI2L.
2473 Node* elements[4];
2474 Node* conv = NULL;
2475 bool found_index = false;
2476 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2477 for (int e = 0; e < count; e++) {
2478 Node* n = elements[e];
2479 if (n->is_Con() && con == NULL) {
2480 con = n;
2481 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2482 Node* value = n->in(1);
2483 #ifdef _LP64
2484 if (value->Opcode() == Op_ConvI2L) {
2485 conv = value;
2486 value = value->in(1);
2487 }
2488 #endif
2489 if (value != head->phi()) {
2490 msg = "unhandled shift in address";
2491 } else {
2492 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2493 msg = "scale doesn't match";
2494 } else {
2495 found_index = true;
2496 shift = n;
2497 }
2498 }
2499 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2500 if (n->in(1) == head->phi()) {
2501 found_index = true;
2502 conv = n;
2503 } else {
2504 msg = "unhandled input to ConvI2L";
2505 }
2506 } else if (n == head->phi()) {
2507 // no shift, check below for allowed cases
2508 found_index = true;
2509 } else {
2510 msg = "unhandled node in address";
2511 msg_node = n;
2512 }
2513 }
2514
2515 if (count == -1) {
2516 msg = "malformed address expression";
2517 msg_node = store;
2518 }
2519
2520 if (!found_index) {
2521 msg = "missing use of index";
2522 }
2523
2524 // byte sized items won't have a shift
2525 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2526 msg = "can't find shift";
2527 msg_node = store;
2528 }
2529
2530 if (msg != NULL) {
2531 #ifndef PRODUCT
2532 if (TraceOptimizeFill) {
2533 tty->print_cr("not fill intrinsic: %s", msg);
2534 if (msg_node != NULL) msg_node->dump();
2535 }
2536 #endif
2537 return false;
2538 }
2539
2540 // No make sure all the other nodes in the loop can be handled
2541 VectorSet ok(Thread::current()->resource_area());
2542
2543 // store related values are ok
2544 ok.set(store->_idx);
2545 ok.set(store->in(MemNode::Memory)->_idx);
2546
2547 // Loop structure is ok
2548 ok.set(head->_idx);
2549 ok.set(head->loopexit()->_idx);
2550 ok.set(head->phi()->_idx);
2551 ok.set(head->incr()->_idx);
2552 ok.set(head->loopexit()->cmp_node()->_idx);
2553 ok.set(head->loopexit()->in(1)->_idx);
2554
2555 // Address elements are ok
2556 if (con) ok.set(con->_idx);
2557 if (shift) ok.set(shift->_idx);
2558 if (conv) ok.set(conv->_idx);
2559
2560 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2561 Node* n = lpt->_body.at(i);
2562 if (n->outcnt() == 0) continue; // Ignore dead
2563 if (ok.test(n->_idx)) continue;
2564 // Backedge projection is ok
2565 if (n->is_IfTrue() && n->in(0) == head->loopexit()) continue;
2566 if (!n->is_AddP()) {
2567 msg = "unhandled node";
2568 msg_node = n;
2569 break;
2570 }
2571 }
2572
2573 // Make sure no unexpected values are used outside the loop
2574 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2575 Node* n = lpt->_body.at(i);
2576 // These values can be replaced with other nodes if they are used
2577 // outside the loop.
2578 if (n == store || n == head->loopexit() || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2579 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2580 Node* use = iter.get();
2581 if (!lpt->_body.contains(use)) {
2582 msg = "node is used outside loop";
2583 // lpt->_body.dump();
2584 msg_node = n;
2585 break;
2586 }
2587 }
2588 }
2589
2590 #ifdef ASSERT
2591 if (TraceOptimizeFill) {
2592 if (msg != NULL) {
2593 tty->print_cr("no fill intrinsic: %s", msg);
2594 if (msg_node != NULL) msg_node->dump();
2595 } else {
2596 tty->print_cr("fill intrinsic for:");
2597 }
2598 store->dump();
2599 if (Verbose) {
2600 lpt->_body.dump();
2601 }
2602 }
2603 #endif
2604
2605 return msg == NULL;
2606 }
2607
2608
2609
2610 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2611 // Only for counted inner loops
2612 if (!lpt->is_counted() || !lpt->is_inner()) {
2613 return false;
2614 }
2615
2616 // Must have constant stride
2617 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2618 if (!head->stride_is_con() || !head->is_normal_loop()) {
2619 return false;
2620 }
2621
2622 // Check that the body only contains a store of a loop invariant
2623 // value that is indexed by the loop phi.
2624 Node* store = NULL;
2625 Node* store_value = NULL;
2626 Node* shift = NULL;
2627 Node* offset = NULL;
2628 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2629 return false;
2630 }
2631
2632 #ifndef PRODUCT
2633 if (TraceLoopOpts) {
2634 tty->print("ArrayFill ");
2635 lpt->dump_head();
2636 }
2637 #endif
2638
2639 // Now replace the whole loop body by a call to a fill routine that
2640 // covers the same region as the loop.
2641 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2642
2643 // Build an expression for the beginning of the copy region
2644 Node* index = head->init_trip();
2645 #ifdef _LP64
2646 index = new (C, 2) ConvI2LNode(index);
2647 _igvn.register_new_node_with_optimizer(index);
2648 #endif
2649 if (shift != NULL) {
2650 // byte arrays don't require a shift but others do.
2651 index = new (C, 3) LShiftXNode(index, shift->in(2));
2652 _igvn.register_new_node_with_optimizer(index);
2653 }
2654 index = new (C, 4) AddPNode(base, base, index);
2655 _igvn.register_new_node_with_optimizer(index);
2656 Node* from = new (C, 4) AddPNode(base, index, offset);
2657 _igvn.register_new_node_with_optimizer(from);
2658 // Compute the number of elements to copy
2659 Node* len = new (C, 3) SubINode(head->limit(), head->init_trip());
2660 _igvn.register_new_node_with_optimizer(len);
2661
2662 BasicType t = store->as_Mem()->memory_type();
2663 bool aligned = false;
2664 if (offset != NULL && head->init_trip()->is_Con()) {
2665 int element_size = type2aelembytes(t);
2666 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2667 }
2668
2669 // Build a call to the fill routine
2670 const char* fill_name;
2671 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2672 assert(fill != NULL, "what?");
2673
2674 // Convert float/double to int/long for fill routines
2675 if (t == T_FLOAT) {
2676 store_value = new (C, 2) MoveF2INode(store_value);
2677 _igvn.register_new_node_with_optimizer(store_value);
2678 } else if (t == T_DOUBLE) {
2679 store_value = new (C, 2) MoveD2LNode(store_value);
2680 _igvn.register_new_node_with_optimizer(store_value);
2681 }
2682
2683 Node* mem_phi = store->in(MemNode::Memory);
2684 Node* result_ctrl;
2685 Node* result_mem;
2686 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2687 int size = call_type->domain()->cnt();
2688 CallLeafNode *call = new (C, size) CallLeafNoFPNode(call_type, fill,
2689 fill_name, TypeAryPtr::get_array_body_type(t));
2690 call->init_req(TypeFunc::Parms+0, from);
2691 call->init_req(TypeFunc::Parms+1, store_value);
2692 #ifdef _LP64
2693 len = new (C, 2) ConvI2LNode(len);
2694 _igvn.register_new_node_with_optimizer(len);
2695 #endif
2696 call->init_req(TypeFunc::Parms+2, len);
2697 #ifdef _LP64
2698 call->init_req(TypeFunc::Parms+3, C->top());
2699 #endif
2700 call->init_req( TypeFunc::Control, head->init_control());
2701 call->init_req( TypeFunc::I_O , C->top() ) ; // does no i/o
2702 call->init_req( TypeFunc::Memory , mem_phi->in(LoopNode::EntryControl) );
2703 call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) );
2704 call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) );
2705 _igvn.register_new_node_with_optimizer(call);
2706 result_ctrl = new (C, 1) ProjNode(call,TypeFunc::Control);
2707 _igvn.register_new_node_with_optimizer(result_ctrl);
2708 result_mem = new (C, 1) ProjNode(call,TypeFunc::Memory);
2709 _igvn.register_new_node_with_optimizer(result_mem);
2710
2711 // If this fill is tightly coupled to an allocation and overwrites
2712 // the whole body, allow it to take over the zeroing.
2713 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2714 if (alloc != NULL && alloc->is_AllocateArray()) {
2715 Node* length = alloc->as_AllocateArray()->Ideal_length();
2716 if (head->limit() == length &&
2717 head->init_trip() == _igvn.intcon(0)) {
2718 if (TraceOptimizeFill) {
2719 tty->print_cr("Eliminated zeroing in allocation");
2720 }
2721 alloc->maybe_set_complete(&_igvn);
2722 } else {
2723 #ifdef ASSERT
2724 if (TraceOptimizeFill) {
2725 tty->print_cr("filling array but bounds don't match");
2726 alloc->dump();
2727 head->init_trip()->dump();
2728 head->limit()->dump();
2729 length->dump();
2730 }
2731 #endif
2732 }
2733 }
2734
2735 // Redirect the old control and memory edges that are outside the loop.
2736 Node* exit = head->loopexit()->proj_out(0);
2737 // Sometimes the memory phi of the head is used as the outgoing
2738 // state of the loop. It's safe in this case to replace it with the
2739 // result_mem.
2740 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2741 _igvn.replace_node(exit, result_ctrl);
2742 _igvn.replace_node(store, result_mem);
2743 // Any uses the increment outside of the loop become the loop limit.
2744 _igvn.replace_node(head->incr(), head->limit());
2745
2746 // Disconnect the head from the loop.
2747 for (uint i = 0; i < lpt->_body.size(); i++) {
2748 Node* n = lpt->_body.at(i);
2749 _igvn.replace_node(n, C->top());
2750 }
2751
2752 return true;
2753 }