1 /*
2 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "compiler/compileLog.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/callnode.hpp"
30 #include "opto/connode.hpp"
31 #include "opto/convertnode.hpp"
32 #include "opto/divnode.hpp"
33 #include "opto/loopnode.hpp"
34 #include "opto/mulnode.hpp"
35 #include "opto/movenode.hpp"
36 #include "opto/opaquenode.hpp"
37 #include "opto/rootnode.hpp"
38 #include "opto/runtime.hpp"
39 #include "opto/subnode.hpp"
40
41 //------------------------------is_loop_exit-----------------------------------
42 // Given an IfNode, return the loop-exiting projection or NULL if both
43 // arms remain in the loop.
44 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
45 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
46 PhaseIdealLoop *phase = _phase;
47 // Test is an IfNode, has 2 projections. If BOTH are in the loop
48 // we need loop unswitching instead of peeling.
49 if( !is_member(phase->get_loop( iff->raw_out(0) )) )
50 return iff->raw_out(0);
51 if( !is_member(phase->get_loop( iff->raw_out(1) )) )
52 return iff->raw_out(1);
53 return NULL;
54 }
55
56
57 //=============================================================================
58
59
60 //------------------------------record_for_igvn----------------------------
61 // Put loop body on igvn work list
62 void IdealLoopTree::record_for_igvn() {
63 for( uint i = 0; i < _body.size(); i++ ) {
64 Node *n = _body.at(i);
65 _phase->_igvn._worklist.push(n);
66 }
67 }
68
69 //------------------------------compute_exact_trip_count-----------------------
70 // Compute loop exact trip count if possible. Do not recalculate trip count for
71 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
72 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
73 if (!_head->as_Loop()->is_valid_counted_loop()) {
74 return;
75 }
76 CountedLoopNode* cl = _head->as_CountedLoop();
77 // Trip count may become nonexact for iteration split loops since
78 // RCE modifies limits. Note, _trip_count value is not reset since
79 // it is used to limit unrolling of main loop.
80 cl->set_nonexact_trip_count();
81
82 // Loop's test should be part of loop.
83 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
84 return; // Infinite loop
85
86 #ifdef ASSERT
87 BoolTest::mask bt = cl->loopexit()->test_trip();
88 assert(bt == BoolTest::lt || bt == BoolTest::gt ||
89 bt == BoolTest::ne, "canonical test is expected");
90 #endif
91
92 Node* init_n = cl->init_trip();
93 Node* limit_n = cl->limit();
94 if (init_n != NULL && init_n->is_Con() &&
95 limit_n != NULL && limit_n->is_Con()) {
96 // Use longs to avoid integer overflow.
97 int stride_con = cl->stride_con();
98 jlong init_con = cl->init_trip()->get_int();
99 jlong limit_con = cl->limit()->get_int();
100 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
101 jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
102 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
103 // Set exact trip count.
104 cl->set_exact_trip_count((uint)trip_count);
105 }
106 }
107 }
108
109 //------------------------------compute_profile_trip_cnt----------------------------
110 // Compute loop trip count from profile data as
111 // (backedge_count + loop_exit_count) / loop_exit_count
112 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
113 if (!_head->is_CountedLoop()) {
114 return;
115 }
116 CountedLoopNode* head = _head->as_CountedLoop();
117 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
118 return; // Already computed
119 }
120 float trip_cnt = (float)max_jint; // default is big
121
122 Node* back = head->in(LoopNode::LoopBackControl);
123 while (back != head) {
124 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
125 back->in(0) &&
126 back->in(0)->is_If() &&
127 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
128 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
129 break;
130 }
131 back = phase->idom(back);
132 }
133 if (back != head) {
134 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
135 back->in(0), "if-projection exists");
136 IfNode* back_if = back->in(0)->as_If();
137 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
138
139 // Now compute a loop exit count
140 float loop_exit_cnt = 0.0f;
141 for( uint i = 0; i < _body.size(); i++ ) {
142 Node *n = _body[i];
143 if( n->is_If() ) {
144 IfNode *iff = n->as_If();
145 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
146 Node *exit = is_loop_exit(iff);
147 if( exit ) {
148 float exit_prob = iff->_prob;
149 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
150 if (exit_prob > PROB_MIN) {
151 float exit_cnt = iff->_fcnt * exit_prob;
152 loop_exit_cnt += exit_cnt;
153 }
154 }
155 }
156 }
157 }
158 if (loop_exit_cnt > 0.0f) {
159 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
160 } else {
161 // No exit count so use
162 trip_cnt = loop_back_cnt;
163 }
164 }
165 #ifndef PRODUCT
166 if (TraceProfileTripCount) {
167 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
168 }
169 #endif
170 head->set_profile_trip_cnt(trip_cnt);
171 }
172
173 //---------------------is_invariant_addition-----------------------------
174 // Return nonzero index of invariant operand for an Add or Sub
175 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
176 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
177 int op = n->Opcode();
178 if (op == Op_AddI || op == Op_SubI) {
179 bool in1_invar = this->is_invariant(n->in(1));
180 bool in2_invar = this->is_invariant(n->in(2));
181 if (in1_invar && !in2_invar) return 1;
182 if (!in1_invar && in2_invar) return 2;
183 }
184 return 0;
185 }
186
187 //---------------------reassociate_add_sub-----------------------------
188 // Reassociate invariant add and subtract expressions:
189 //
190 // inv1 + (x + inv2) => ( inv1 + inv2) + x
191 // (x + inv2) + inv1 => ( inv1 + inv2) + x
192 // inv1 + (x - inv2) => ( inv1 - inv2) + x
193 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
194 // (x + inv2) - inv1 => (-inv1 + inv2) + x
195 // (x - inv2) + inv1 => ( inv1 - inv2) + x
196 // (x - inv2) - inv1 => (-inv1 - inv2) + x
197 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
198 // inv1 - (x - inv2) => ( inv1 + inv2) - x
199 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
200 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
201 // inv1 - (x + inv2) => ( inv1 - inv2) - x
202 //
203 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
204 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
205 if (is_invariant(n1)) return NULL;
206 int inv1_idx = is_invariant_addition(n1, phase);
207 if (!inv1_idx) return NULL;
208 // Don't mess with add of constant (igvn moves them to expression tree root.)
209 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
210 Node* inv1 = n1->in(inv1_idx);
211 Node* n2 = n1->in(3 - inv1_idx);
212 int inv2_idx = is_invariant_addition(n2, phase);
213 if (!inv2_idx) return NULL;
214 Node* x = n2->in(3 - inv2_idx);
215 Node* inv2 = n2->in(inv2_idx);
216
217 bool neg_x = n2->is_Sub() && inv2_idx == 1;
218 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
219 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
220 if (n1->is_Sub() && inv1_idx == 1) {
221 neg_x = !neg_x;
222 neg_inv2 = !neg_inv2;
223 }
224 Node* inv1_c = phase->get_ctrl(inv1);
225 Node* inv2_c = phase->get_ctrl(inv2);
226 Node* n_inv1;
227 if (neg_inv1) {
228 Node *zero = phase->_igvn.intcon(0);
229 phase->set_ctrl(zero, phase->C->root());
230 n_inv1 = new SubINode(zero, inv1);
231 phase->register_new_node(n_inv1, inv1_c);
232 } else {
233 n_inv1 = inv1;
234 }
235 Node* inv;
236 if (neg_inv2) {
237 inv = new SubINode(n_inv1, inv2);
238 } else {
239 inv = new AddINode(n_inv1, inv2);
240 }
241 phase->register_new_node(inv, phase->get_early_ctrl(inv));
242
243 Node* addx;
244 if (neg_x) {
245 addx = new SubINode(inv, x);
246 } else {
247 addx = new AddINode(x, inv);
248 }
249 phase->register_new_node(addx, phase->get_ctrl(x));
250 phase->_igvn.replace_node(n1, addx);
251 assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
252 _body.yank(n1);
253 return addx;
254 }
255
256 //---------------------reassociate_invariants-----------------------------
257 // Reassociate invariant expressions:
258 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
259 for (int i = _body.size() - 1; i >= 0; i--) {
260 Node *n = _body.at(i);
261 for (int j = 0; j < 5; j++) {
262 Node* nn = reassociate_add_sub(n, phase);
263 if (nn == NULL) break;
264 n = nn; // again
265 };
266 }
267 }
268
269 //------------------------------policy_peeling---------------------------------
270 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
271 // make some loop-invariant test (usually a null-check) happen before the loop.
272 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
273 Node *test = ((IdealLoopTree*)this)->tail();
274 int body_size = ((IdealLoopTree*)this)->_body.size();
275 int live_node_count = phase->C->live_nodes();
276 // Peeling does loop cloning which can result in O(N^2) node construction
277 if( body_size > 255 /* Prevent overflow for large body_size */
278 || (body_size * body_size + live_node_count > MaxNodeLimit) ) {
279 return false; // too large to safely clone
280 }
281 while( test != _head ) { // Scan till run off top of loop
282 if( test->is_If() ) { // Test?
283 Node *ctrl = phase->get_ctrl(test->in(1));
284 if (ctrl->is_top())
285 return false; // Found dead test on live IF? No peeling!
286 // Standard IF only has one input value to check for loop invariance
287 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
288 // Condition is not a member of this loop?
289 if( !is_member(phase->get_loop(ctrl)) &&
290 is_loop_exit(test) )
291 return true; // Found reason to peel!
292 }
293 // Walk up dominators to loop _head looking for test which is
294 // executed on every path thru loop.
295 test = phase->idom(test);
296 }
297 return false;
298 }
299
300 //------------------------------peeled_dom_test_elim---------------------------
301 // If we got the effect of peeling, either by actually peeling or by making
302 // a pre-loop which must execute at least once, we can remove all
303 // loop-invariant dominated tests in the main body.
304 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
305 bool progress = true;
306 while( progress ) {
307 progress = false; // Reset for next iteration
308 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
309 Node *test = prev->in(0);
310 while( test != loop->_head ) { // Scan till run off top of loop
311
312 int p_op = prev->Opcode();
313 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
314 test->is_If() && // Test?
315 !test->in(1)->is_Con() && // And not already obvious?
316 // Condition is not a member of this loop?
317 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
318 // Walk loop body looking for instances of this test
319 for( uint i = 0; i < loop->_body.size(); i++ ) {
320 Node *n = loop->_body.at(i);
321 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
322 // IfNode was dominated by version in peeled loop body
323 progress = true;
324 dominated_by( old_new[prev->_idx], n );
325 }
326 }
327 }
328 prev = test;
329 test = idom(test);
330 } // End of scan tests in loop
331
332 } // End of while( progress )
333 }
334
335 //------------------------------do_peeling-------------------------------------
336 // Peel the first iteration of the given loop.
337 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
338 // The pre-loop illegally has 2 control users (old & new loops).
339 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
340 // Do this by making the old-loop fall-in edges act as if they came
341 // around the loopback from the prior iteration (follow the old-loop
342 // backedges) and then map to the new peeled iteration. This leaves
343 // the pre-loop with only 1 user (the new peeled iteration), but the
344 // peeled-loop backedge has 2 users.
345 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
346 // extra backedge user.
347 //
348 // orig
349 //
350 // stmt1
351 // |
352 // v
353 // loop predicate
354 // |
355 // v
356 // loop<----+
357 // | |
358 // stmt2 |
359 // | |
360 // v |
361 // if ^
362 // / \ |
363 // / \ |
364 // v v |
365 // false true |
366 // / \ |
367 // / ----+
368 // |
369 // v
370 // exit
371 //
372 //
373 // after clone loop
374 //
375 // stmt1
376 // |
377 // v
378 // loop predicate
379 // / \
380 // clone / \ orig
381 // / \
382 // / \
383 // v v
384 // +---->loop clone loop<----+
385 // | | | |
386 // | stmt2 clone stmt2 |
387 // | | | |
388 // | v v |
389 // ^ if clone If ^
390 // | / \ / \ |
391 // | / \ / \ |
392 // | v v v v |
393 // | true false false true |
394 // | / \ / \ |
395 // +---- \ / ----+
396 // \ /
397 // 1v v2
398 // region
399 // |
400 // v
401 // exit
402 //
403 //
404 // after peel and predicate move
405 //
406 // stmt1
407 // /
408 // /
409 // clone / orig
410 // /
411 // / +----------+
412 // / | |
413 // / loop predicate |
414 // / | |
415 // v v |
416 // TOP-->loop clone loop<----+ |
417 // | | | |
418 // stmt2 clone stmt2 | |
419 // | | | ^
420 // v v | |
421 // if clone If ^ |
422 // / \ / \ | |
423 // / \ / \ | |
424 // v v v v | |
425 // true false false true | |
426 // | \ / \ | |
427 // | \ / ----+ ^
428 // | \ / |
429 // | 1v v2 |
430 // v region |
431 // | | |
432 // | v |
433 // | exit |
434 // | |
435 // +--------------->-----------------+
436 //
437 //
438 // final graph
439 //
440 // stmt1
441 // |
442 // v
443 // stmt2 clone
444 // |
445 // v
446 // if clone
447 // / |
448 // / |
449 // v v
450 // false true
451 // | |
452 // | v
453 // | loop predicate
454 // | |
455 // | v
456 // | loop<----+
457 // | | |
458 // | stmt2 |
459 // | | |
460 // | v |
461 // v if ^
462 // | / \ |
463 // | / \ |
464 // | v v |
465 // | false true |
466 // | | \ |
467 // v v --+
468 // region
469 // |
470 // v
471 // exit
472 //
473 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
474
475 C->set_major_progress();
476 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
477 // 'pre' loop from the main and the 'pre' can no longer have it's
478 // iterations adjusted. Therefore, we need to declare this loop as
479 // no longer a 'main' loop; it will need new pre and post loops before
480 // we can do further RCE.
481 #ifndef PRODUCT
482 if (TraceLoopOpts) {
483 tty->print("Peel ");
484 loop->dump_head();
485 }
486 #endif
487 Node* head = loop->_head;
488 bool counted_loop = head->is_CountedLoop();
489 if (counted_loop) {
490 CountedLoopNode *cl = head->as_CountedLoop();
491 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
492 cl->set_trip_count(cl->trip_count() - 1);
493 if (cl->is_main_loop()) {
494 cl->set_normal_loop();
495 #ifndef PRODUCT
496 if (PrintOpto && VerifyLoopOptimizations) {
497 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
498 loop->dump_head();
499 }
500 #endif
501 }
502 }
503 Node* entry = head->in(LoopNode::EntryControl);
504
505 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
506 // The pre-loop illegally has 2 control users (old & new loops).
507 clone_loop( loop, old_new, dom_depth(head) );
508
509 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
510 // Do this by making the old-loop fall-in edges act as if they came
511 // around the loopback from the prior iteration (follow the old-loop
512 // backedges) and then map to the new peeled iteration. This leaves
513 // the pre-loop with only 1 user (the new peeled iteration), but the
514 // peeled-loop backedge has 2 users.
515 Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
516 _igvn.hash_delete(head);
517 head->set_req(LoopNode::EntryControl, new_entry);
518 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
519 Node* old = head->fast_out(j);
520 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
521 Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
522 if (!new_exit_value ) // Backedge value is ALSO loop invariant?
523 // Then loop body backedge value remains the same.
524 new_exit_value = old->in(LoopNode::LoopBackControl);
525 _igvn.hash_delete(old);
526 old->set_req(LoopNode::EntryControl, new_exit_value);
527 }
528 }
529
530
531 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
532 // extra backedge user.
533 Node* new_head = old_new[head->_idx];
534 _igvn.hash_delete(new_head);
535 new_head->set_req(LoopNode::LoopBackControl, C->top());
536 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
537 Node* use = new_head->fast_out(j2);
538 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
539 _igvn.hash_delete(use);
540 use->set_req(LoopNode::LoopBackControl, C->top());
541 }
542 }
543
544
545 // Step 4: Correct dom-depth info. Set to loop-head depth.
546 int dd = dom_depth(head);
547 set_idom(head, head->in(1), dd);
548 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
549 Node *old = loop->_body.at(j3);
550 Node *nnn = old_new[old->_idx];
551 if (!has_ctrl(nnn))
552 set_idom(nnn, idom(nnn), dd-1);
553 }
554
555 // Now force out all loop-invariant dominating tests. The optimizer
556 // finds some, but we _know_ they are all useless.
557 peeled_dom_test_elim(loop,old_new);
558
559 loop->record_for_igvn();
560 }
561
562 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
563
564 //------------------------------policy_maximally_unroll------------------------
565 // Calculate exact loop trip count and return true if loop can be maximally
566 // unrolled.
567 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
568 CountedLoopNode *cl = _head->as_CountedLoop();
569 assert(cl->is_normal_loop(), "");
570 if (!cl->is_valid_counted_loop())
571 return false; // Malformed counted loop
572
573 if (!cl->has_exact_trip_count()) {
574 // Trip count is not exact.
575 return false;
576 }
577
578 uint trip_count = cl->trip_count();
579 // Note, max_juint is used to indicate unknown trip count.
580 assert(trip_count > 1, "one iteration loop should be optimized out already");
581 assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
582
583 // Real policy: if we maximally unroll, does it get too big?
584 // Allow the unrolled mess to get larger than standard loop
585 // size. After all, it will no longer be a loop.
586 uint body_size = _body.size();
587 uint unroll_limit = (uint)LoopUnrollLimit * 4;
588 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
589 if (trip_count > unroll_limit || body_size > unroll_limit) {
590 return false;
591 }
592
593 // Fully unroll a loop with few iterations regardless next
594 // conditions since following loop optimizations will split
595 // such loop anyway (pre-main-post).
596 if (trip_count <= 3)
597 return true;
598
599 // Take into account that after unroll conjoined heads and tails will fold,
600 // otherwise policy_unroll() may allow more unrolling than max unrolling.
601 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
602 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
603 if (body_size != tst_body_size) // Check for int overflow
604 return false;
605 if (new_body_size > unroll_limit ||
606 // Unrolling can result in a large amount of node construction
607 new_body_size >= MaxNodeLimit - (uint) phase->C->live_nodes()) {
608 return false;
609 }
610
611 // Do not unroll a loop with String intrinsics code.
612 // String intrinsics are large and have loops.
613 for (uint k = 0; k < _body.size(); k++) {
614 Node* n = _body.at(k);
615 switch (n->Opcode()) {
616 case Op_StrComp:
617 case Op_StrEquals:
618 case Op_StrIndexOf:
619 case Op_EncodeISOArray:
620 case Op_AryEq: {
621 return false;
622 }
623 #if INCLUDE_RTM_OPT
624 case Op_FastLock:
625 case Op_FastUnlock: {
626 // Don't unroll RTM locking code because it is large.
627 if (UseRTMLocking) {
628 return false;
629 }
630 }
631 #endif
632 } // switch
633 }
634
635 return true; // Do maximally unroll
636 }
637
638
639 //------------------------------policy_unroll----------------------------------
640 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
641 // the loop is a CountedLoop and the body is small enough.
642 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
643
644 CountedLoopNode *cl = _head->as_CountedLoop();
645 assert(cl->is_normal_loop() || cl->is_main_loop(), "");
646
647 if (!cl->is_valid_counted_loop())
648 return false; // Malformed counted loop
649
650 // Protect against over-unrolling.
651 // After split at least one iteration will be executed in pre-loop.
652 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
653
654 int future_unroll_ct = cl->unrolled_count() * 2;
655 if (future_unroll_ct > LoopMaxUnroll) return false;
656
657 // Check for initial stride being a small enough constant
658 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
659
660 // Don't unroll if the next round of unrolling would push us
661 // over the expected trip count of the loop. One is subtracted
662 // from the expected trip count because the pre-loop normally
663 // executes 1 iteration.
664 if (UnrollLimitForProfileCheck > 0 &&
665 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
666 future_unroll_ct > UnrollLimitForProfileCheck &&
667 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
668 return false;
669 }
670
671 // When unroll count is greater than LoopUnrollMin, don't unroll if:
672 // the residual iterations are more than 10% of the trip count
673 // and rounds of "unroll,optimize" are not making significant progress
674 // Progress defined as current size less than 20% larger than previous size.
675 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
676 future_unroll_ct > LoopUnrollMin &&
677 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
678 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
679 return false;
680 }
681
682 Node *init_n = cl->init_trip();
683 Node *limit_n = cl->limit();
684 int stride_con = cl->stride_con();
685 // Non-constant bounds.
686 // Protect against over-unrolling when init or/and limit are not constant
687 // (so that trip_count's init value is maxint) but iv range is known.
688 if (init_n == NULL || !init_n->is_Con() ||
689 limit_n == NULL || !limit_n->is_Con()) {
690 Node* phi = cl->phi();
691 if (phi != NULL) {
692 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
693 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
694 int next_stride = stride_con * 2; // stride after this unroll
695 if (next_stride > 0) {
696 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
697 iv_type->_lo + next_stride > iv_type->_hi) {
698 return false; // over-unrolling
699 }
700 } else if (next_stride < 0) {
701 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
702 iv_type->_hi + next_stride < iv_type->_lo) {
703 return false; // over-unrolling
704 }
705 }
706 }
707 }
708
709 // After unroll limit will be adjusted: new_limit = limit-stride.
710 // Bailout if adjustment overflow.
711 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
712 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
713 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
714 return false; // overflow
715
716 // Adjust body_size to determine if we unroll or not
717 uint body_size = _body.size();
718 // Key test to unroll loop in CRC32 java code
719 int xors_in_loop = 0;
720 // Also count ModL, DivL and MulL which expand mightly
721 for (uint k = 0; k < _body.size(); k++) {
722 Node* n = _body.at(k);
723 switch (n->Opcode()) {
724 case Op_XorI: xors_in_loop++; break; // CRC32 java code
725 case Op_ModL: body_size += 30; break;
726 case Op_DivL: body_size += 30; break;
727 case Op_MulL: body_size += 10; break;
728 case Op_StrComp:
729 case Op_StrEquals:
730 case Op_StrIndexOf:
731 case Op_EncodeISOArray:
732 case Op_AryEq: {
733 // Do not unroll a loop with String intrinsics code.
734 // String intrinsics are large and have loops.
735 return false;
736 }
737 #if INCLUDE_RTM_OPT
738 case Op_FastLock:
739 case Op_FastUnlock: {
740 // Don't unroll RTM locking code because it is large.
741 if (UseRTMLocking) {
742 return false;
743 }
744 }
745 #endif
746 } // switch
747 }
748
749 // Check for being too big
750 if (body_size > (uint)LoopUnrollLimit) {
751 if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
752 // Normal case: loop too big
753 return false;
754 }
755
756 // Unroll once! (Each trip will soon do double iterations)
757 return true;
758 }
759
760 //------------------------------policy_align-----------------------------------
761 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
762 // expression that does the alignment. Note that only one array base can be
763 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
764 // if we vectorize short memory ops into longer memory ops, we may want to
765 // increase alignment.
766 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
767 return false;
768 }
769
770 //------------------------------policy_range_check-----------------------------
771 // Return TRUE or FALSE if the loop should be range-check-eliminated.
772 // Actually we do iteration-splitting, a more powerful form of RCE.
773 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
774 if (!RangeCheckElimination) return false;
775
776 CountedLoopNode *cl = _head->as_CountedLoop();
777 // If we unrolled with no intention of doing RCE and we later
778 // changed our minds, we got no pre-loop. Either we need to
779 // make a new pre-loop, or we gotta disallow RCE.
780 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
781 Node *trip_counter = cl->phi();
782
783 // Check loop body for tests of trip-counter plus loop-invariant vs
784 // loop-invariant.
785 for (uint i = 0; i < _body.size(); i++) {
786 Node *iff = _body[i];
787 if (iff->Opcode() == Op_If) { // Test?
788
789 // Comparing trip+off vs limit
790 Node *bol = iff->in(1);
791 if (bol->req() != 2) continue; // dead constant test
792 if (!bol->is_Bool()) {
793 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
794 continue;
795 }
796 if (bol->as_Bool()->_test._test == BoolTest::ne)
797 continue; // not RC
798
799 Node *cmp = bol->in(1);
800 Node *rc_exp = cmp->in(1);
801 Node *limit = cmp->in(2);
802
803 Node *limit_c = phase->get_ctrl(limit);
804 if( limit_c == phase->C->top() )
805 return false; // Found dead test on live IF? No RCE!
806 if( is_member(phase->get_loop(limit_c) ) ) {
807 // Compare might have operands swapped; commute them
808 rc_exp = cmp->in(2);
809 limit = cmp->in(1);
810 limit_c = phase->get_ctrl(limit);
811 if( is_member(phase->get_loop(limit_c) ) )
812 continue; // Both inputs are loop varying; cannot RCE
813 }
814
815 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
816 continue;
817 }
818 // Yeah! Found a test like 'trip+off vs limit'
819 // Test is an IfNode, has 2 projections. If BOTH are in the loop
820 // we need loop unswitching instead of iteration splitting.
821 if( is_loop_exit(iff) )
822 return true; // Found reason to split iterations
823 } // End of is IF
824 }
825
826 return false;
827 }
828
829 //------------------------------policy_peel_only-------------------------------
830 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
831 // for unrolling loops with NO array accesses.
832 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
833
834 for( uint i = 0; i < _body.size(); i++ )
835 if( _body[i]->is_Mem() )
836 return false;
837
838 // No memory accesses at all!
839 return true;
840 }
841
842 //------------------------------clone_up_backedge_goo--------------------------
843 // If Node n lives in the back_ctrl block and cannot float, we clone a private
844 // version of n in preheader_ctrl block and return that, otherwise return n.
845 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
846 if( get_ctrl(n) != back_ctrl ) return n;
847
848 // Only visit once
849 if (visited.test_set(n->_idx)) {
850 Node *x = clones.find(n->_idx);
851 if (x != NULL)
852 return x;
853 return n;
854 }
855
856 Node *x = NULL; // If required, a clone of 'n'
857 // Check for 'n' being pinned in the backedge.
858 if( n->in(0) && n->in(0) == back_ctrl ) {
859 assert(clones.find(n->_idx) == NULL, "dead loop");
860 x = n->clone(); // Clone a copy of 'n' to preheader
861 clones.push(x, n->_idx);
862 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
863 }
864
865 // Recursive fixup any other input edges into x.
866 // If there are no changes we can just return 'n', otherwise
867 // we need to clone a private copy and change it.
868 for( uint i = 1; i < n->req(); i++ ) {
869 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
870 if( g != n->in(i) ) {
871 if( !x ) {
872 assert(clones.find(n->_idx) == NULL, "dead loop");
873 x = n->clone();
874 clones.push(x, n->_idx);
875 }
876 x->set_req(i, g);
877 }
878 }
879 if( x ) { // x can legally float to pre-header location
880 register_new_node( x, preheader_ctrl );
881 return x;
882 } else { // raise n to cover LCA of uses
883 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
884 }
885 return n;
886 }
887
888 //------------------------------insert_pre_post_loops--------------------------
889 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
890 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
891 // alignment. Useful to unroll loops that do no array accesses.
892 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
893
894 #ifndef PRODUCT
895 if (TraceLoopOpts) {
896 if (peel_only)
897 tty->print("PeelMainPost ");
898 else
899 tty->print("PreMainPost ");
900 loop->dump_head();
901 }
902 #endif
903 C->set_major_progress();
904
905 // Find common pieces of the loop being guarded with pre & post loops
906 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
907 assert( main_head->is_normal_loop(), "" );
908 CountedLoopEndNode *main_end = main_head->loopexit();
909 guarantee(main_end != NULL, "no loop exit node");
910 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
911 uint dd_main_head = dom_depth(main_head);
912 uint max = main_head->outcnt();
913
914 Node *pre_header= main_head->in(LoopNode::EntryControl);
915 Node *init = main_head->init_trip();
916 Node *incr = main_end ->incr();
917 Node *limit = main_end ->limit();
918 Node *stride = main_end ->stride();
919 Node *cmp = main_end ->cmp_node();
920 BoolTest::mask b_test = main_end->test_trip();
921
922 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
923 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
924 if( bol->outcnt() != 1 ) {
925 bol = bol->clone();
926 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
927 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, bol);
928 }
929 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
930 if( cmp->outcnt() != 1 ) {
931 cmp = cmp->clone();
932 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
933 _igvn.replace_input_of(bol, 1, cmp);
934 }
935
936 //------------------------------
937 // Step A: Create Post-Loop.
938 Node* main_exit = main_end->proj_out(false);
939 assert( main_exit->Opcode() == Op_IfFalse, "" );
940 int dd_main_exit = dom_depth(main_exit);
941
942 // Step A1: Clone the loop body. The clone becomes the post-loop. The main
943 // loop pre-header illegally has 2 control users (old & new loops).
944 clone_loop( loop, old_new, dd_main_exit );
945 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
946 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
947 post_head->set_post_loop(main_head);
948
949 // Reduce the post-loop trip count.
950 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
951 post_end->_prob = PROB_FAIR;
952
953 // Build the main-loop normal exit.
954 IfFalseNode *new_main_exit = new IfFalseNode(main_end);
955 _igvn.register_new_node_with_optimizer( new_main_exit );
956 set_idom(new_main_exit, main_end, dd_main_exit );
957 set_loop(new_main_exit, loop->_parent);
958
959 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
960 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
961 // (the main-loop trip-counter exit value) because we will be changing
962 // the exit value (via unrolling) so we cannot constant-fold away the zero
963 // trip guard until all unrolling is done.
964 Node *zer_opaq = new Opaque1Node(C, incr);
965 Node *zer_cmp = new CmpINode( zer_opaq, limit );
966 Node *zer_bol = new BoolNode( zer_cmp, b_test );
967 register_new_node( zer_opaq, new_main_exit );
968 register_new_node( zer_cmp , new_main_exit );
969 register_new_node( zer_bol , new_main_exit );
970
971 // Build the IfNode
972 IfNode *zer_iff = new IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
973 _igvn.register_new_node_with_optimizer( zer_iff );
974 set_idom(zer_iff, new_main_exit, dd_main_exit);
975 set_loop(zer_iff, loop->_parent);
976
977 // Plug in the false-path, taken if we need to skip post-loop
978 _igvn.replace_input_of(main_exit, 0, zer_iff);
979 set_idom(main_exit, zer_iff, dd_main_exit);
980 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
981 // Make the true-path, must enter the post loop
982 Node *zer_taken = new IfTrueNode( zer_iff );
983 _igvn.register_new_node_with_optimizer( zer_taken );
984 set_idom(zer_taken, zer_iff, dd_main_exit);
985 set_loop(zer_taken, loop->_parent);
986 // Plug in the true path
987 _igvn.hash_delete( post_head );
988 post_head->set_req(LoopNode::EntryControl, zer_taken);
989 set_idom(post_head, zer_taken, dd_main_exit);
990
991 Arena *a = Thread::current()->resource_area();
992 VectorSet visited(a);
993 Node_Stack clones(a, main_head->back_control()->outcnt());
994 // Step A3: Make the fall-in values to the post-loop come from the
995 // fall-out values of the main-loop.
996 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
997 Node* main_phi = main_head->fast_out(i);
998 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
999 Node *post_phi = old_new[main_phi->_idx];
1000 Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
1001 post_head->init_control(),
1002 main_phi->in(LoopNode::LoopBackControl),
1003 visited, clones);
1004 _igvn.hash_delete(post_phi);
1005 post_phi->set_req( LoopNode::EntryControl, fallmain );
1006 }
1007 }
1008
1009 // Update local caches for next stanza
1010 main_exit = new_main_exit;
1011
1012
1013 //------------------------------
1014 // Step B: Create Pre-Loop.
1015
1016 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
1017 // loop pre-header illegally has 2 control users (old & new loops).
1018 clone_loop( loop, old_new, dd_main_head );
1019 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
1020 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
1021 pre_head->set_pre_loop(main_head);
1022 Node *pre_incr = old_new[incr->_idx];
1023
1024 // Reduce the pre-loop trip count.
1025 pre_end->_prob = PROB_FAIR;
1026
1027 // Find the pre-loop normal exit.
1028 Node* pre_exit = pre_end->proj_out(false);
1029 assert( pre_exit->Opcode() == Op_IfFalse, "" );
1030 IfFalseNode *new_pre_exit = new IfFalseNode(pre_end);
1031 _igvn.register_new_node_with_optimizer( new_pre_exit );
1032 set_idom(new_pre_exit, pre_end, dd_main_head);
1033 set_loop(new_pre_exit, loop->_parent);
1034
1035 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
1036 // pre-loop, the main-loop may not execute at all. Later in life this
1037 // zero-trip guard will become the minimum-trip guard when we unroll
1038 // the main-loop.
1039 Node *min_opaq = new Opaque1Node(C, limit);
1040 Node *min_cmp = new CmpINode( pre_incr, min_opaq );
1041 Node *min_bol = new BoolNode( min_cmp, b_test );
1042 register_new_node( min_opaq, new_pre_exit );
1043 register_new_node( min_cmp , new_pre_exit );
1044 register_new_node( min_bol , new_pre_exit );
1045
1046 // Build the IfNode (assume the main-loop is executed always).
1047 IfNode *min_iff = new IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1048 _igvn.register_new_node_with_optimizer( min_iff );
1049 set_idom(min_iff, new_pre_exit, dd_main_head);
1050 set_loop(min_iff, loop->_parent);
1051
1052 // Plug in the false-path, taken if we need to skip main-loop
1053 _igvn.hash_delete( pre_exit );
1054 pre_exit->set_req(0, min_iff);
1055 set_idom(pre_exit, min_iff, dd_main_head);
1056 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1057 // Make the true-path, must enter the main loop
1058 Node *min_taken = new IfTrueNode( min_iff );
1059 _igvn.register_new_node_with_optimizer( min_taken );
1060 set_idom(min_taken, min_iff, dd_main_head);
1061 set_loop(min_taken, loop->_parent);
1062 // Plug in the true path
1063 _igvn.hash_delete( main_head );
1064 main_head->set_req(LoopNode::EntryControl, min_taken);
1065 set_idom(main_head, min_taken, dd_main_head);
1066
1067 visited.Clear();
1068 clones.clear();
1069 // Step B3: Make the fall-in values to the main-loop come from the
1070 // fall-out values of the pre-loop.
1071 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1072 Node* main_phi = main_head->fast_out(i2);
1073 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1074 Node *pre_phi = old_new[main_phi->_idx];
1075 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
1076 main_head->init_control(),
1077 pre_phi->in(LoopNode::LoopBackControl),
1078 visited, clones);
1079 _igvn.hash_delete(main_phi);
1080 main_phi->set_req( LoopNode::EntryControl, fallpre );
1081 }
1082 }
1083
1084 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1085 // RCE and alignment may change this later.
1086 Node *cmp_end = pre_end->cmp_node();
1087 assert( cmp_end->in(2) == limit, "" );
1088 Node *pre_limit = new AddINode( init, stride );
1089
1090 // Save the original loop limit in this Opaque1 node for
1091 // use by range check elimination.
1092 Node *pre_opaq = new Opaque1Node(C, pre_limit, limit);
1093
1094 register_new_node( pre_limit, pre_head->in(0) );
1095 register_new_node( pre_opaq , pre_head->in(0) );
1096
1097 // Since no other users of pre-loop compare, I can hack limit directly
1098 assert( cmp_end->outcnt() == 1, "no other users" );
1099 _igvn.hash_delete(cmp_end);
1100 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1101
1102 // Special case for not-equal loop bounds:
1103 // Change pre loop test, main loop test, and the
1104 // main loop guard test to use lt or gt depending on stride
1105 // direction:
1106 // positive stride use <
1107 // negative stride use >
1108 //
1109 // not-equal test is kept for post loop to handle case
1110 // when init > limit when stride > 0 (and reverse).
1111
1112 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1113
1114 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1115 // Modify pre loop end condition
1116 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1117 BoolNode* new_bol0 = new BoolNode(pre_bol->in(1), new_test);
1118 register_new_node( new_bol0, pre_head->in(0) );
1119 _igvn.replace_input_of(pre_end, CountedLoopEndNode::TestValue, new_bol0);
1120 // Modify main loop guard condition
1121 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1122 BoolNode* new_bol1 = new BoolNode(min_bol->in(1), new_test);
1123 register_new_node( new_bol1, new_pre_exit );
1124 _igvn.hash_delete(min_iff);
1125 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1126 // Modify main loop end condition
1127 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1128 BoolNode* new_bol2 = new BoolNode(main_bol->in(1), new_test);
1129 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1130 _igvn.replace_input_of(main_end, CountedLoopEndNode::TestValue, new_bol2);
1131 }
1132
1133 // Flag main loop
1134 main_head->set_main_loop();
1135 if( peel_only ) main_head->set_main_no_pre_loop();
1136
1137 // Subtract a trip count for the pre-loop.
1138 main_head->set_trip_count(main_head->trip_count() - 1);
1139
1140 // It's difficult to be precise about the trip-counts
1141 // for the pre/post loops. They are usually very short,
1142 // so guess that 4 trips is a reasonable value.
1143 post_head->set_profile_trip_cnt(4.0);
1144 pre_head->set_profile_trip_cnt(4.0);
1145
1146 // Now force out all loop-invariant dominating tests. The optimizer
1147 // finds some, but we _know_ they are all useless.
1148 peeled_dom_test_elim(loop,old_new);
1149 loop->record_for_igvn();
1150 }
1151
1152 //------------------------------is_invariant-----------------------------
1153 // Return true if n is invariant
1154 bool IdealLoopTree::is_invariant(Node* n) const {
1155 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1156 if (n_c->is_top()) return false;
1157 return !is_member(_phase->get_loop(n_c));
1158 }
1159
1160
1161 //------------------------------do_unroll--------------------------------------
1162 // Unroll the loop body one step - make each trip do 2 iterations.
1163 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1164 assert(LoopUnrollLimit, "");
1165 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1166 CountedLoopEndNode *loop_end = loop_head->loopexit();
1167 assert(loop_end, "");
1168 #ifndef PRODUCT
1169 if (PrintOpto && VerifyLoopOptimizations) {
1170 tty->print("Unrolling ");
1171 loop->dump_head();
1172 } else if (TraceLoopOpts) {
1173 if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1174 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1175 } else {
1176 tty->print("Unroll %d ", loop_head->unrolled_count()*2);
1177 }
1178 loop->dump_head();
1179 }
1180 #endif
1181
1182 // Remember loop node count before unrolling to detect
1183 // if rounds of unroll,optimize are making progress
1184 loop_head->set_node_count_before_unroll(loop->_body.size());
1185
1186 Node *ctrl = loop_head->in(LoopNode::EntryControl);
1187 Node *limit = loop_head->limit();
1188 Node *init = loop_head->init_trip();
1189 Node *stride = loop_head->stride();
1190
1191 Node *opaq = NULL;
1192 if (adjust_min_trip) { // If not maximally unrolling, need adjustment
1193 // Search for zero-trip guard.
1194 assert( loop_head->is_main_loop(), "" );
1195 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1196 Node *iff = ctrl->in(0);
1197 assert( iff->Opcode() == Op_If, "" );
1198 Node *bol = iff->in(1);
1199 assert( bol->Opcode() == Op_Bool, "" );
1200 Node *cmp = bol->in(1);
1201 assert( cmp->Opcode() == Op_CmpI, "" );
1202 opaq = cmp->in(2);
1203 // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1204 // optimized away and then another round of loop opts attempted.
1205 // We can not optimize this particular loop in that case.
1206 if (opaq->Opcode() != Op_Opaque1)
1207 return; // Cannot find zero-trip guard! Bail out!
1208 // Zero-trip test uses an 'opaque' node which is not shared.
1209 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1210 }
1211
1212 C->set_major_progress();
1213
1214 Node* new_limit = NULL;
1215 if (UnrollLimitCheck) {
1216 int stride_con = stride->get_int();
1217 int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1218 uint old_trip_count = loop_head->trip_count();
1219 // Verify that unroll policy result is still valid.
1220 assert(old_trip_count > 1 &&
1221 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1222
1223 // Adjust loop limit to keep valid iterations number after unroll.
1224 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1225 // which may overflow.
1226 if (!adjust_min_trip) {
1227 assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1228 "odd trip count for maximally unroll");
1229 // Don't need to adjust limit for maximally unroll since trip count is even.
1230 } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1231 // Loop's limit is constant. Loop's init could be constant when pre-loop
1232 // become peeled iteration.
1233 jlong init_con = init->get_int();
1234 // We can keep old loop limit if iterations count stays the same:
1235 // old_trip_count == new_trip_count * 2
1236 // Note: since old_trip_count >= 2 then new_trip_count >= 1
1237 // so we also don't need to adjust zero trip test.
1238 jlong limit_con = limit->get_int();
1239 // (stride_con*2) not overflow since stride_con <= 8.
1240 int new_stride_con = stride_con * 2;
1241 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1);
1242 jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1243 // New trip count should satisfy next conditions.
1244 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1245 uint new_trip_count = (uint)trip_count;
1246 adjust_min_trip = (old_trip_count != new_trip_count*2);
1247 }
1248
1249 if (adjust_min_trip) {
1250 // Step 2: Adjust the trip limit if it is called for.
1251 // The adjustment amount is -stride. Need to make sure if the
1252 // adjustment underflows or overflows, then the main loop is skipped.
1253 Node* cmp = loop_end->cmp_node();
1254 assert(cmp->in(2) == limit, "sanity");
1255 assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1256
1257 // Verify that policy_unroll result is still valid.
1258 const TypeInt* limit_type = _igvn.type(limit)->is_int();
1259 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1260 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1261
1262 if (limit->is_Con()) {
1263 // The check in policy_unroll and the assert above guarantee
1264 // no underflow if limit is constant.
1265 new_limit = _igvn.intcon(limit->get_int() - stride_con);
1266 set_ctrl(new_limit, C->root());
1267 } else {
1268 // Limit is not constant.
1269 if (loop_head->unrolled_count() == 1) { // only for first unroll
1270 // Separate limit by Opaque node in case it is an incremented
1271 // variable from previous loop to avoid using pre-incremented
1272 // value which could increase register pressure.
1273 // Otherwise reorg_offsets() optimization will create a separate
1274 // Opaque node for each use of trip-counter and as result
1275 // zero trip guard limit will be different from loop limit.
1276 assert(has_ctrl(opaq), "should have it");
1277 Node* opaq_ctrl = get_ctrl(opaq);
1278 limit = new Opaque2Node( C, limit );
1279 register_new_node( limit, opaq_ctrl );
1280 }
1281 if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1282 stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1283 // No underflow.
1284 new_limit = new SubINode(limit, stride);
1285 } else {
1286 // (limit - stride) may underflow.
1287 // Clamp the adjustment value with MININT or MAXINT:
1288 //
1289 // new_limit = limit-stride
1290 // if (stride > 0)
1291 // new_limit = (limit < new_limit) ? MININT : new_limit;
1292 // else
1293 // new_limit = (limit > new_limit) ? MAXINT : new_limit;
1294 //
1295 BoolTest::mask bt = loop_end->test_trip();
1296 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1297 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1298 set_ctrl(adj_max, C->root());
1299 Node* old_limit = NULL;
1300 Node* adj_limit = NULL;
1301 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1302 if (loop_head->unrolled_count() > 1 &&
1303 limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1304 limit->in(CMoveNode::IfTrue) == adj_max &&
1305 bol->as_Bool()->_test._test == bt &&
1306 bol->in(1)->Opcode() == Op_CmpI &&
1307 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1308 // Loop was unrolled before.
1309 // Optimize the limit to avoid nested CMove:
1310 // use original limit as old limit.
1311 old_limit = bol->in(1)->in(1);
1312 // Adjust previous adjusted limit.
1313 adj_limit = limit->in(CMoveNode::IfFalse);
1314 adj_limit = new SubINode(adj_limit, stride);
1315 } else {
1316 old_limit = limit;
1317 adj_limit = new SubINode(limit, stride);
1318 }
1319 assert(old_limit != NULL && adj_limit != NULL, "");
1320 register_new_node( adj_limit, ctrl ); // adjust amount
1321 Node* adj_cmp = new CmpINode(old_limit, adj_limit);
1322 register_new_node( adj_cmp, ctrl );
1323 Node* adj_bool = new BoolNode(adj_cmp, bt);
1324 register_new_node( adj_bool, ctrl );
1325 new_limit = new CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1326 }
1327 register_new_node(new_limit, ctrl);
1328 }
1329 assert(new_limit != NULL, "");
1330 // Replace in loop test.
1331 assert(loop_end->in(1)->in(1) == cmp, "sanity");
1332 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1333 // Don't need to create new test since only one user.
1334 _igvn.hash_delete(cmp);
1335 cmp->set_req(2, new_limit);
1336 } else {
1337 // Create new test since it is shared.
1338 Node* ctrl2 = loop_end->in(0);
1339 Node* cmp2 = cmp->clone();
1340 cmp2->set_req(2, new_limit);
1341 register_new_node(cmp2, ctrl2);
1342 Node* bol2 = loop_end->in(1)->clone();
1343 bol2->set_req(1, cmp2);
1344 register_new_node(bol2, ctrl2);
1345 _igvn.replace_input_of(loop_end, 1, bol2);
1346 }
1347 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1348 // Make it a 1-trip test (means at least 2 trips).
1349
1350 // Guard test uses an 'opaque' node which is not shared. Hence I
1351 // can edit it's inputs directly. Hammer in the new limit for the
1352 // minimum-trip guard.
1353 assert(opaq->outcnt() == 1, "");
1354 _igvn.replace_input_of(opaq, 1, new_limit);
1355 }
1356
1357 // Adjust max trip count. The trip count is intentionally rounded
1358 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1359 // the main, unrolled, part of the loop will never execute as it is protected
1360 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1361 // and later determined that part of the unrolled loop was dead.
1362 loop_head->set_trip_count(old_trip_count / 2);
1363
1364 // Double the count of original iterations in the unrolled loop body.
1365 loop_head->double_unrolled_count();
1366
1367 } else { // LoopLimitCheck
1368
1369 // Adjust max trip count. The trip count is intentionally rounded
1370 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1371 // the main, unrolled, part of the loop will never execute as it is protected
1372 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1373 // and later determined that part of the unrolled loop was dead.
1374 loop_head->set_trip_count(loop_head->trip_count() / 2);
1375
1376 // Double the count of original iterations in the unrolled loop body.
1377 loop_head->double_unrolled_count();
1378
1379 // -----------
1380 // Step 2: Cut back the trip counter for an unroll amount of 2.
1381 // Loop will normally trip (limit - init)/stride_con. Since it's a
1382 // CountedLoop this is exact (stride divides limit-init exactly).
1383 // We are going to double the loop body, so we want to knock off any
1384 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
1385 Node *span = new SubINode( limit, init );
1386 register_new_node( span, ctrl );
1387 Node *trip = new DivINode( 0, span, stride );
1388 register_new_node( trip, ctrl );
1389 Node *mtwo = _igvn.intcon(-2);
1390 set_ctrl(mtwo, C->root());
1391 Node *rond = new AndINode( trip, mtwo );
1392 register_new_node( rond, ctrl );
1393 Node *spn2 = new MulINode( rond, stride );
1394 register_new_node( spn2, ctrl );
1395 new_limit = new AddINode( spn2, init );
1396 register_new_node( new_limit, ctrl );
1397
1398 // Hammer in the new limit
1399 Node *ctrl2 = loop_end->in(0);
1400 Node *cmp2 = new CmpINode( loop_head->incr(), new_limit );
1401 register_new_node( cmp2, ctrl2 );
1402 Node *bol2 = new BoolNode( cmp2, loop_end->test_trip() );
1403 register_new_node( bol2, ctrl2 );
1404 _igvn.replace_input_of(loop_end, CountedLoopEndNode::TestValue, bol2);
1405
1406 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1407 // Make it a 1-trip test (means at least 2 trips).
1408 if( adjust_min_trip ) {
1409 assert( new_limit != NULL, "" );
1410 // Guard test uses an 'opaque' node which is not shared. Hence I
1411 // can edit it's inputs directly. Hammer in the new limit for the
1412 // minimum-trip guard.
1413 assert( opaq->outcnt() == 1, "" );
1414 _igvn.hash_delete(opaq);
1415 opaq->set_req(1, new_limit);
1416 }
1417 } // LoopLimitCheck
1418
1419 // ---------
1420 // Step 4: Clone the loop body. Move it inside the loop. This loop body
1421 // represents the odd iterations; since the loop trips an even number of
1422 // times its backedge is never taken. Kill the backedge.
1423 uint dd = dom_depth(loop_head);
1424 clone_loop( loop, old_new, dd );
1425
1426 // Make backedges of the clone equal to backedges of the original.
1427 // Make the fall-in from the original come from the fall-out of the clone.
1428 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1429 Node* phi = loop_head->fast_out(j);
1430 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1431 Node *newphi = old_new[phi->_idx];
1432 _igvn.hash_delete( phi );
1433 _igvn.hash_delete( newphi );
1434
1435 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1436 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1437 phi ->set_req(LoopNode::LoopBackControl, C->top());
1438 }
1439 }
1440 Node *clone_head = old_new[loop_head->_idx];
1441 _igvn.hash_delete( clone_head );
1442 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1443 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1444 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1445 loop->_head = clone_head; // New loop header
1446
1447 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1448 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1449
1450 // Kill the clone's backedge
1451 Node *newcle = old_new[loop_end->_idx];
1452 _igvn.hash_delete( newcle );
1453 Node *one = _igvn.intcon(1);
1454 set_ctrl(one, C->root());
1455 newcle->set_req(1, one);
1456 // Force clone into same loop body
1457 uint max = loop->_body.size();
1458 for( uint k = 0; k < max; k++ ) {
1459 Node *old = loop->_body.at(k);
1460 Node *nnn = old_new[old->_idx];
1461 loop->_body.push(nnn);
1462 if (!has_ctrl(old))
1463 set_loop(nnn, loop);
1464 }
1465
1466 loop->record_for_igvn();
1467 }
1468
1469 //------------------------------do_maximally_unroll----------------------------
1470
1471 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1472 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1473 assert(cl->has_exact_trip_count(), "trip count is not exact");
1474 assert(cl->trip_count() > 0, "");
1475 #ifndef PRODUCT
1476 if (TraceLoopOpts) {
1477 tty->print("MaxUnroll %d ", cl->trip_count());
1478 loop->dump_head();
1479 }
1480 #endif
1481
1482 // If loop is tripping an odd number of times, peel odd iteration
1483 if ((cl->trip_count() & 1) == 1) {
1484 do_peeling(loop, old_new);
1485 }
1486
1487 // Now its tripping an even number of times remaining. Double loop body.
1488 // Do not adjust pre-guards; they are not needed and do not exist.
1489 if (cl->trip_count() > 0) {
1490 assert((cl->trip_count() & 1) == 0, "missed peeling");
1491 do_unroll(loop, old_new, false);
1492 }
1493 }
1494
1495 //------------------------------dominates_backedge---------------------------------
1496 // Returns true if ctrl is executed on every complete iteration
1497 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1498 assert(ctrl->is_CFG(), "must be control");
1499 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1500 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1501 }
1502
1503 //------------------------------adjust_limit-----------------------------------
1504 // Helper function for add_constraint().
1505 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1506 // Compute "I :: (limit-offset)/scale"
1507 Node *con = new SubINode(rc_limit, offset);
1508 register_new_node(con, pre_ctrl);
1509 Node *X = new DivINode(0, con, scale);
1510 register_new_node(X, pre_ctrl);
1511
1512 // Adjust loop limit
1513 loop_limit = (stride_con > 0)
1514 ? (Node*)(new MinINode(loop_limit, X))
1515 : (Node*)(new MaxINode(loop_limit, X));
1516 register_new_node(loop_limit, pre_ctrl);
1517 return loop_limit;
1518 }
1519
1520 //------------------------------add_constraint---------------------------------
1521 // Constrain the main loop iterations so the conditions:
1522 // low_limit <= scale_con * I + offset < upper_limit
1523 // always holds true. That is, either increase the number of iterations in
1524 // the pre-loop or the post-loop until the condition holds true in the main
1525 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1526 // stride and scale are constants (offset and limit often are).
1527 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 ) {
1528 // For positive stride, the pre-loop limit always uses a MAX function
1529 // and the main loop a MIN function. For negative stride these are
1530 // reversed.
1531
1532 // Also for positive stride*scale the affine function is increasing, so the
1533 // pre-loop must check for underflow and the post-loop for overflow.
1534 // Negative stride*scale reverses this; pre-loop checks for overflow and
1535 // post-loop for underflow.
1536
1537 Node *scale = _igvn.intcon(scale_con);
1538 set_ctrl(scale, C->root());
1539
1540 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1541 // The overflow limit: scale*I+offset < upper_limit
1542 // For main-loop compute
1543 // ( if (scale > 0) /* and stride > 0 */
1544 // I < (upper_limit-offset)/scale
1545 // else /* scale < 0 and stride < 0 */
1546 // I > (upper_limit-offset)/scale
1547 // )
1548 //
1549 // (upper_limit-offset) may overflow or underflow.
1550 // But it is fine since main loop will either have
1551 // less iterations or will be skipped in such case.
1552 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1553
1554 // The underflow limit: low_limit <= scale*I+offset.
1555 // For pre-loop compute
1556 // NOT(scale*I+offset >= low_limit)
1557 // scale*I+offset < low_limit
1558 // ( if (scale > 0) /* and stride > 0 */
1559 // I < (low_limit-offset)/scale
1560 // else /* scale < 0 and stride < 0 */
1561 // I > (low_limit-offset)/scale
1562 // )
1563
1564 if (low_limit->get_int() == -max_jint) {
1565 if (!RangeLimitCheck) return;
1566 // We need this guard when scale*pre_limit+offset >= limit
1567 // due to underflow. So we need execute pre-loop until
1568 // scale*I+offset >= min_int. But (min_int-offset) will
1569 // underflow when offset > 0 and X will be > original_limit
1570 // when stride > 0. To avoid it we replace positive offset with 0.
1571 //
1572 // Also (min_int+1 == -max_int) is used instead of min_int here
1573 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1574 Node* shift = _igvn.intcon(31);
1575 set_ctrl(shift, C->root());
1576 Node* sign = new RShiftINode(offset, shift);
1577 register_new_node(sign, pre_ctrl);
1578 offset = new AndINode(offset, sign);
1579 register_new_node(offset, pre_ctrl);
1580 } else {
1581 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1582 // The only problem we have here when offset == min_int
1583 // since (0-min_int) == min_int. It may be fine for stride > 0
1584 // but for stride < 0 X will be < original_limit. To avoid it
1585 // max(pre_limit, original_limit) is used in do_range_check().
1586 }
1587 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1588 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1589
1590 } else { // stride_con*scale_con < 0
1591 // For negative stride*scale pre-loop checks for overflow and
1592 // post-loop for underflow.
1593 //
1594 // The overflow limit: scale*I+offset < upper_limit
1595 // For pre-loop compute
1596 // NOT(scale*I+offset < upper_limit)
1597 // scale*I+offset >= upper_limit
1598 // scale*I+offset+1 > upper_limit
1599 // ( if (scale < 0) /* and stride > 0 */
1600 // I < (upper_limit-(offset+1))/scale
1601 // else /* scale > 0 and stride < 0 */
1602 // I > (upper_limit-(offset+1))/scale
1603 // )
1604 //
1605 // (upper_limit-offset-1) may underflow or overflow.
1606 // To avoid it min(pre_limit, original_limit) is used
1607 // in do_range_check() for stride > 0 and max() for < 0.
1608 Node *one = _igvn.intcon(1);
1609 set_ctrl(one, C->root());
1610
1611 Node *plus_one = new AddINode(offset, one);
1612 register_new_node( plus_one, pre_ctrl );
1613 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1614 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1615
1616 if (low_limit->get_int() == -max_jint) {
1617 if (!RangeLimitCheck) return;
1618 // We need this guard when scale*main_limit+offset >= limit
1619 // due to underflow. So we need execute main-loop while
1620 // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1621 // underflow when (offset+1) > 0 and X will be < main_limit
1622 // when scale < 0 (and stride > 0). To avoid it we replace
1623 // positive (offset+1) with 0.
1624 //
1625 // Also (min_int+1 == -max_int) is used instead of min_int here
1626 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1627 Node* shift = _igvn.intcon(31);
1628 set_ctrl(shift, C->root());
1629 Node* sign = new RShiftINode(plus_one, shift);
1630 register_new_node(sign, pre_ctrl);
1631 plus_one = new AndINode(plus_one, sign);
1632 register_new_node(plus_one, pre_ctrl);
1633 } else {
1634 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1635 // The only problem we have here when offset == max_int
1636 // since (max_int+1) == min_int and (0-min_int) == min_int.
1637 // But it is fine since main loop will either have
1638 // less iterations or will be skipped in such case.
1639 }
1640 // The underflow limit: low_limit <= scale*I+offset.
1641 // For main-loop compute
1642 // scale*I+offset+1 > low_limit
1643 // ( if (scale < 0) /* and stride > 0 */
1644 // I < (low_limit-(offset+1))/scale
1645 // else /* scale > 0 and stride < 0 */
1646 // I > (low_limit-(offset+1))/scale
1647 // )
1648
1649 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1650 }
1651 }
1652
1653
1654 //------------------------------is_scaled_iv---------------------------------
1655 // Return true if exp is a constant times an induction var
1656 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1657 if (exp == iv) {
1658 if (p_scale != NULL) {
1659 *p_scale = 1;
1660 }
1661 return true;
1662 }
1663 int opc = exp->Opcode();
1664 if (opc == Op_MulI) {
1665 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1666 if (p_scale != NULL) {
1667 *p_scale = exp->in(2)->get_int();
1668 }
1669 return true;
1670 }
1671 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1672 if (p_scale != NULL) {
1673 *p_scale = exp->in(1)->get_int();
1674 }
1675 return true;
1676 }
1677 } else if (opc == Op_LShiftI) {
1678 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1679 if (p_scale != NULL) {
1680 *p_scale = 1 << exp->in(2)->get_int();
1681 }
1682 return true;
1683 }
1684 }
1685 return false;
1686 }
1687
1688 //-----------------------------is_scaled_iv_plus_offset------------------------------
1689 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1690 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1691 if (is_scaled_iv(exp, iv, p_scale)) {
1692 if (p_offset != NULL) {
1693 Node *zero = _igvn.intcon(0);
1694 set_ctrl(zero, C->root());
1695 *p_offset = zero;
1696 }
1697 return true;
1698 }
1699 int opc = exp->Opcode();
1700 if (opc == Op_AddI) {
1701 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1702 if (p_offset != NULL) {
1703 *p_offset = exp->in(2);
1704 }
1705 return true;
1706 }
1707 if (exp->in(2)->is_Con()) {
1708 Node* offset2 = NULL;
1709 if (depth < 2 &&
1710 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1711 p_offset != NULL ? &offset2 : NULL, depth+1)) {
1712 if (p_offset != NULL) {
1713 Node *ctrl_off2 = get_ctrl(offset2);
1714 Node* offset = new AddINode(offset2, exp->in(2));
1715 register_new_node(offset, ctrl_off2);
1716 *p_offset = offset;
1717 }
1718 return true;
1719 }
1720 }
1721 } else if (opc == Op_SubI) {
1722 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1723 if (p_offset != NULL) {
1724 Node *zero = _igvn.intcon(0);
1725 set_ctrl(zero, C->root());
1726 Node *ctrl_off = get_ctrl(exp->in(2));
1727 Node* offset = new SubINode(zero, exp->in(2));
1728 register_new_node(offset, ctrl_off);
1729 *p_offset = offset;
1730 }
1731 return true;
1732 }
1733 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1734 if (p_offset != NULL) {
1735 *p_scale *= -1;
1736 *p_offset = exp->in(1);
1737 }
1738 return true;
1739 }
1740 }
1741 return false;
1742 }
1743
1744 //------------------------------do_range_check---------------------------------
1745 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1746 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1747 #ifndef PRODUCT
1748 if (PrintOpto && VerifyLoopOptimizations) {
1749 tty->print("Range Check Elimination ");
1750 loop->dump_head();
1751 } else if (TraceLoopOpts) {
1752 tty->print("RangeCheck ");
1753 loop->dump_head();
1754 }
1755 #endif
1756 assert(RangeCheckElimination, "");
1757 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1758 assert(cl->is_main_loop(), "");
1759
1760 // protect against stride not being a constant
1761 if (!cl->stride_is_con())
1762 return;
1763
1764 // Find the trip counter; we are iteration splitting based on it
1765 Node *trip_counter = cl->phi();
1766 // Find the main loop limit; we will trim it's iterations
1767 // to not ever trip end tests
1768 Node *main_limit = cl->limit();
1769
1770 // Need to find the main-loop zero-trip guard
1771 Node *ctrl = cl->in(LoopNode::EntryControl);
1772 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1773 Node *iffm = ctrl->in(0);
1774 assert(iffm->Opcode() == Op_If, "");
1775 Node *bolzm = iffm->in(1);
1776 assert(bolzm->Opcode() == Op_Bool, "");
1777 Node *cmpzm = bolzm->in(1);
1778 assert(cmpzm->is_Cmp(), "");
1779 Node *opqzm = cmpzm->in(2);
1780 // Can not optimize a loop if zero-trip Opaque1 node is optimized
1781 // away and then another round of loop opts attempted.
1782 if (opqzm->Opcode() != Op_Opaque1)
1783 return;
1784 assert(opqzm->in(1) == main_limit, "do not understand situation");
1785
1786 // Find the pre-loop limit; we will expand it's iterations to
1787 // not ever trip low tests.
1788 Node *p_f = iffm->in(0);
1789 assert(p_f->Opcode() == Op_IfFalse, "");
1790 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1791 assert(pre_end->loopnode()->is_pre_loop(), "");
1792 Node *pre_opaq1 = pre_end->limit();
1793 // Occasionally it's possible for a pre-loop Opaque1 node to be
1794 // optimized away and then another round of loop opts attempted.
1795 // We can not optimize this particular loop in that case.
1796 if (pre_opaq1->Opcode() != Op_Opaque1)
1797 return;
1798 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1799 Node *pre_limit = pre_opaq->in(1);
1800
1801 // Where do we put new limit calculations
1802 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1803
1804 // Ensure the original loop limit is available from the
1805 // pre-loop Opaque1 node.
1806 Node *orig_limit = pre_opaq->original_loop_limit();
1807 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1808 return;
1809
1810 // Must know if its a count-up or count-down loop
1811
1812 int stride_con = cl->stride_con();
1813 Node *zero = _igvn.intcon(0);
1814 Node *one = _igvn.intcon(1);
1815 // Use symmetrical int range [-max_jint,max_jint]
1816 Node *mini = _igvn.intcon(-max_jint);
1817 set_ctrl(zero, C->root());
1818 set_ctrl(one, C->root());
1819 set_ctrl(mini, C->root());
1820
1821 // Range checks that do not dominate the loop backedge (ie.
1822 // conditionally executed) can lengthen the pre loop limit beyond
1823 // the original loop limit. To prevent this, the pre limit is
1824 // (for stride > 0) MINed with the original loop limit (MAXed
1825 // stride < 0) when some range_check (rc) is conditionally
1826 // executed.
1827 bool conditional_rc = false;
1828
1829 // Check loop body for tests of trip-counter plus loop-invariant vs
1830 // loop-invariant.
1831 for( uint i = 0; i < loop->_body.size(); i++ ) {
1832 Node *iff = loop->_body[i];
1833 if( iff->Opcode() == Op_If ) { // Test?
1834
1835 // Test is an IfNode, has 2 projections. If BOTH are in the loop
1836 // we need loop unswitching instead of iteration splitting.
1837 Node *exit = loop->is_loop_exit(iff);
1838 if( !exit ) continue;
1839 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1840
1841 // Get boolean condition to test
1842 Node *i1 = iff->in(1);
1843 if( !i1->is_Bool() ) continue;
1844 BoolNode *bol = i1->as_Bool();
1845 BoolTest b_test = bol->_test;
1846 // Flip sense of test if exit condition is flipped
1847 if( flip )
1848 b_test = b_test.negate();
1849
1850 // Get compare
1851 Node *cmp = bol->in(1);
1852
1853 // Look for trip_counter + offset vs limit
1854 Node *rc_exp = cmp->in(1);
1855 Node *limit = cmp->in(2);
1856 jint scale_con= 1; // Assume trip counter not scaled
1857
1858 Node *limit_c = get_ctrl(limit);
1859 if( loop->is_member(get_loop(limit_c) ) ) {
1860 // Compare might have operands swapped; commute them
1861 b_test = b_test.commute();
1862 rc_exp = cmp->in(2);
1863 limit = cmp->in(1);
1864 limit_c = get_ctrl(limit);
1865 if( loop->is_member(get_loop(limit_c) ) )
1866 continue; // Both inputs are loop varying; cannot RCE
1867 }
1868 // Here we know 'limit' is loop invariant
1869
1870 // 'limit' maybe pinned below the zero trip test (probably from a
1871 // previous round of rce), in which case, it can't be used in the
1872 // zero trip test expression which must occur before the zero test's if.
1873 if( limit_c == ctrl ) {
1874 continue; // Don't rce this check but continue looking for other candidates.
1875 }
1876
1877 // Check for scaled induction variable plus an offset
1878 Node *offset = NULL;
1879
1880 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1881 continue;
1882 }
1883
1884 Node *offset_c = get_ctrl(offset);
1885 if( loop->is_member( get_loop(offset_c) ) )
1886 continue; // Offset is not really loop invariant
1887 // Here we know 'offset' is loop invariant.
1888
1889 // As above for the 'limit', the 'offset' maybe pinned below the
1890 // zero trip test.
1891 if( offset_c == ctrl ) {
1892 continue; // Don't rce this check but continue looking for other candidates.
1893 }
1894 #ifdef ASSERT
1895 if (TraceRangeLimitCheck) {
1896 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1897 bol->dump(2);
1898 }
1899 #endif
1900 // At this point we have the expression as:
1901 // scale_con * trip_counter + offset :: limit
1902 // where scale_con, offset and limit are loop invariant. Trip_counter
1903 // monotonically increases by stride_con, a constant. Both (or either)
1904 // stride_con and scale_con can be negative which will flip about the
1905 // sense of the test.
1906
1907 // Adjust pre and main loop limits to guard the correct iteration set
1908 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1909 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1910 // The underflow and overflow limits: 0 <= scale*I+offset < limit
1911 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1912 if (!conditional_rc) {
1913 // (0-offset)/scale could be outside of loop iterations range.
1914 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1915 }
1916 } else {
1917 #ifndef PRODUCT
1918 if( PrintOpto )
1919 tty->print_cr("missed RCE opportunity");
1920 #endif
1921 continue; // In release mode, ignore it
1922 }
1923 } else { // Otherwise work on normal compares
1924 switch( b_test._test ) {
1925 case BoolTest::gt:
1926 // Fall into GE case
1927 case BoolTest::ge:
1928 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1929 scale_con = -scale_con;
1930 offset = new SubINode( zero, offset );
1931 register_new_node( offset, pre_ctrl );
1932 limit = new SubINode( zero, limit );
1933 register_new_node( limit, pre_ctrl );
1934 // Fall into LE case
1935 case BoolTest::le:
1936 if (b_test._test != BoolTest::gt) {
1937 // Convert X <= Y to X < Y+1
1938 limit = new AddINode( limit, one );
1939 register_new_node( limit, pre_ctrl );
1940 }
1941 // Fall into LT case
1942 case BoolTest::lt:
1943 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1944 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1945 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1946 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1947 if (!conditional_rc) {
1948 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1949 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1950 // still be outside of loop range.
1951 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1952 }
1953 break;
1954 default:
1955 #ifndef PRODUCT
1956 if( PrintOpto )
1957 tty->print_cr("missed RCE opportunity");
1958 #endif
1959 continue; // Unhandled case
1960 }
1961 }
1962
1963 // Kill the eliminated test
1964 C->set_major_progress();
1965 Node *kill_con = _igvn.intcon( 1-flip );
1966 set_ctrl(kill_con, C->root());
1967 _igvn.replace_input_of(iff, 1, kill_con);
1968 // Find surviving projection
1969 assert(iff->is_If(), "");
1970 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1971 // Find loads off the surviving projection; remove their control edge
1972 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1973 Node* cd = dp->fast_out(i); // Control-dependent node
1974 if (cd->is_Load() && cd->depends_only_on_test()) { // Loads can now float around in the loop
1975 // Allow the load to float around in the loop, or before it
1976 // but NOT before the pre-loop.
1977 _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
1978 --i;
1979 --imax;
1980 }
1981 }
1982
1983 } // End of is IF
1984
1985 }
1986
1987 // Update loop limits
1988 if (conditional_rc) {
1989 pre_limit = (stride_con > 0) ? (Node*)new MinINode(pre_limit, orig_limit)
1990 : (Node*)new MaxINode(pre_limit, orig_limit);
1991 register_new_node(pre_limit, pre_ctrl);
1992 }
1993 _igvn.replace_input_of(pre_opaq, 1, pre_limit);
1994
1995 // Note:: we are making the main loop limit no longer precise;
1996 // need to round up based on stride.
1997 cl->set_nonexact_trip_count();
1998 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
1999 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
2000 // Hopefully, compiler will optimize for powers of 2.
2001 Node *ctrl = get_ctrl(main_limit);
2002 Node *stride = cl->stride();
2003 Node *init = cl->init_trip();
2004 Node *span = new SubINode(main_limit,init);
2005 register_new_node(span,ctrl);
2006 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
2007 Node *add = new AddINode(span,rndup);
2008 register_new_node(add,ctrl);
2009 Node *div = new DivINode(0,add,stride);
2010 register_new_node(div,ctrl);
2011 Node *mul = new MulINode(div,stride);
2012 register_new_node(mul,ctrl);
2013 Node *newlim = new AddINode(mul,init);
2014 register_new_node(newlim,ctrl);
2015 main_limit = newlim;
2016 }
2017
2018 Node *main_cle = cl->loopexit();
2019 Node *main_bol = main_cle->in(1);
2020 // Hacking loop bounds; need private copies of exit test
2021 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2022 main_bol = main_bol->clone();// Clone a private BoolNode
2023 register_new_node( main_bol, main_cle->in(0) );
2024 _igvn.replace_input_of(main_cle, 1, main_bol);
2025 }
2026 Node *main_cmp = main_bol->in(1);
2027 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2028 _igvn.hash_delete(main_bol);
2029 main_cmp = main_cmp->clone();// Clone a private CmpNode
2030 register_new_node( main_cmp, main_cle->in(0) );
2031 main_bol->set_req(1,main_cmp);
2032 }
2033 // Hack the now-private loop bounds
2034 _igvn.replace_input_of(main_cmp, 2, main_limit);
2035 // The OpaqueNode is unshared by design
2036 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2037 _igvn.replace_input_of(opqzm, 1, main_limit);
2038 }
2039
2040 //------------------------------DCE_loop_body----------------------------------
2041 // Remove simplistic dead code from loop body
2042 void IdealLoopTree::DCE_loop_body() {
2043 for( uint i = 0; i < _body.size(); i++ )
2044 if( _body.at(i)->outcnt() == 0 )
2045 _body.map( i--, _body.pop() );
2046 }
2047
2048
2049 //------------------------------adjust_loop_exit_prob--------------------------
2050 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2051 // Replace with a 1-in-10 exit guess.
2052 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2053 Node *test = tail();
2054 while( test != _head ) {
2055 uint top = test->Opcode();
2056 if( top == Op_IfTrue || top == Op_IfFalse ) {
2057 int test_con = ((ProjNode*)test)->_con;
2058 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2059 IfNode *iff = test->in(0)->as_If();
2060 if( iff->outcnt() == 2 ) { // Ignore dead tests
2061 Node *bol = iff->in(1);
2062 if( bol && bol->req() > 1 && bol->in(1) &&
2063 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2064 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2065 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2066 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2067 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2068 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2069 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2070 return; // Allocation loops RARELY take backedge
2071 // Find the OTHER exit path from the IF
2072 Node* ex = iff->proj_out(1-test_con);
2073 float p = iff->_prob;
2074 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2075 if( top == Op_IfTrue ) {
2076 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2077 iff->_prob = PROB_STATIC_FREQUENT;
2078 }
2079 } else {
2080 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2081 iff->_prob = PROB_STATIC_INFREQUENT;
2082 }
2083 }
2084 }
2085 }
2086 }
2087 test = phase->idom(test);
2088 }
2089 }
2090
2091
2092 //------------------------------policy_do_remove_empty_loop--------------------
2093 // Micro-benchmark spamming. Policy is to always remove empty loops.
2094 // The 'DO' part is to replace the trip counter with the value it will
2095 // have on the last iteration. This will break the loop.
2096 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2097 // Minimum size must be empty loop
2098 if (_body.size() > EMPTY_LOOP_SIZE)
2099 return false;
2100
2101 if (!_head->is_CountedLoop())
2102 return false; // Dead loop
2103 CountedLoopNode *cl = _head->as_CountedLoop();
2104 if (!cl->is_valid_counted_loop())
2105 return false; // Malformed loop
2106 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2107 return false; // Infinite loop
2108
2109 #ifdef ASSERT
2110 // Ensure only one phi which is the iv.
2111 Node* iv = NULL;
2112 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2113 Node* n = cl->fast_out(i);
2114 if (n->Opcode() == Op_Phi) {
2115 assert(iv == NULL, "Too many phis" );
2116 iv = n;
2117 }
2118 }
2119 assert(iv == cl->phi(), "Wrong phi" );
2120 #endif
2121
2122 // main and post loops have explicitly created zero trip guard
2123 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2124 if (needs_guard) {
2125 // Skip guard if values not overlap.
2126 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2127 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2128 int stride_con = cl->stride_con();
2129 if (stride_con > 0) {
2130 needs_guard = (init_t->_hi >= limit_t->_lo);
2131 } else {
2132 needs_guard = (init_t->_lo <= limit_t->_hi);
2133 }
2134 }
2135 if (needs_guard) {
2136 // Check for an obvious zero trip guard.
2137 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2138 if (inctrl->Opcode() == Op_IfTrue) {
2139 // The test should look like just the backedge of a CountedLoop
2140 Node* iff = inctrl->in(0);
2141 if (iff->is_If()) {
2142 Node* bol = iff->in(1);
2143 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2144 Node* cmp = bol->in(1);
2145 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2146 needs_guard = false;
2147 }
2148 }
2149 }
2150 }
2151 }
2152
2153 #ifndef PRODUCT
2154 if (PrintOpto) {
2155 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2156 this->dump_head();
2157 } else if (TraceLoopOpts) {
2158 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
2159 this->dump_head();
2160 }
2161 #endif
2162
2163 if (needs_guard) {
2164 // Peel the loop to ensure there's a zero trip guard
2165 Node_List old_new;
2166 phase->do_peeling(this, old_new);
2167 }
2168
2169 // Replace the phi at loop head with the final value of the last
2170 // iteration. Then the CountedLoopEnd will collapse (backedge never
2171 // taken) and all loop-invariant uses of the exit values will be correct.
2172 Node *phi = cl->phi();
2173 Node *exact_limit = phase->exact_limit(this);
2174 if (exact_limit != cl->limit()) {
2175 // We also need to replace the original limit to collapse loop exit.
2176 Node* cmp = cl->loopexit()->cmp_node();
2177 assert(cl->limit() == cmp->in(2), "sanity");
2178 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2179 phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2180 }
2181 // Note: the final value after increment should not overflow since
2182 // counted loop has limit check predicate.
2183 Node *final = new SubINode( exact_limit, cl->stride() );
2184 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2185 phase->_igvn.replace_node(phi,final);
2186 phase->C->set_major_progress();
2187 return true;
2188 }
2189
2190 //------------------------------policy_do_one_iteration_loop-------------------
2191 // Convert one iteration loop into normal code.
2192 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2193 if (!_head->as_Loop()->is_valid_counted_loop())
2194 return false; // Only for counted loop
2195
2196 CountedLoopNode *cl = _head->as_CountedLoop();
2197 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2198 return false;
2199 }
2200
2201 #ifndef PRODUCT
2202 if(TraceLoopOpts) {
2203 tty->print("OneIteration ");
2204 this->dump_head();
2205 }
2206 #endif
2207
2208 Node *init_n = cl->init_trip();
2209 #ifdef ASSERT
2210 // Loop boundaries should be constant since trip count is exact.
2211 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2212 #endif
2213 // Replace the phi at loop head with the value of the init_trip.
2214 // Then the CountedLoopEnd will collapse (backedge will not be taken)
2215 // and all loop-invariant uses of the exit values will be correct.
2216 phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2217 phase->C->set_major_progress();
2218 return true;
2219 }
2220
2221 //=============================================================================
2222 //------------------------------iteration_split_impl---------------------------
2223 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2224 // Compute exact loop trip count if possible.
2225 compute_exact_trip_count(phase);
2226
2227 // Convert one iteration loop into normal code.
2228 if (policy_do_one_iteration_loop(phase))
2229 return true;
2230
2231 // Check and remove empty loops (spam micro-benchmarks)
2232 if (policy_do_remove_empty_loop(phase))
2233 return true; // Here we removed an empty loop
2234
2235 bool should_peel = policy_peeling(phase); // Should we peel?
2236
2237 bool should_unswitch = policy_unswitching(phase);
2238
2239 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2240 // This removes loop-invariant tests (usually null checks).
2241 if (!_head->is_CountedLoop()) { // Non-counted loop
2242 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2243 // Partial peel succeeded so terminate this round of loop opts
2244 return false;
2245 }
2246 if (should_peel) { // Should we peel?
2247 #ifndef PRODUCT
2248 if (PrintOpto) tty->print_cr("should_peel");
2249 #endif
2250 phase->do_peeling(this,old_new);
2251 } else if (should_unswitch) {
2252 phase->do_unswitching(this, old_new);
2253 }
2254 return true;
2255 }
2256 CountedLoopNode *cl = _head->as_CountedLoop();
2257
2258 if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2259
2260 // Do nothing special to pre- and post- loops
2261 if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2262
2263 // Compute loop trip count from profile data
2264 compute_profile_trip_cnt(phase);
2265
2266 // Before attempting fancy unrolling, RCE or alignment, see if we want
2267 // to completely unroll this loop or do loop unswitching.
2268 if (cl->is_normal_loop()) {
2269 if (should_unswitch) {
2270 phase->do_unswitching(this, old_new);
2271 return true;
2272 }
2273 bool should_maximally_unroll = policy_maximally_unroll(phase);
2274 if (should_maximally_unroll) {
2275 // Here we did some unrolling and peeling. Eventually we will
2276 // completely unroll this loop and it will no longer be a loop.
2277 phase->do_maximally_unroll(this,old_new);
2278 return true;
2279 }
2280 }
2281
2282 // Skip next optimizations if running low on nodes. Note that
2283 // policy_unswitching and policy_maximally_unroll have this check.
2284 uint nodes_left = MaxNodeLimit - (uint) phase->C->live_nodes();
2285 if ((2 * _body.size()) > nodes_left) {
2286 return true;
2287 }
2288
2289 // Counted loops may be peeled, may need some iterations run up
2290 // front for RCE, and may want to align loop refs to a cache
2291 // line. Thus we clone a full loop up front whose trip count is
2292 // at least 1 (if peeling), but may be several more.
2293
2294 // The main loop will start cache-line aligned with at least 1
2295 // iteration of the unrolled body (zero-trip test required) and
2296 // will have some range checks removed.
2297
2298 // A post-loop will finish any odd iterations (leftover after
2299 // unrolling), plus any needed for RCE purposes.
2300
2301 bool should_unroll = policy_unroll(phase);
2302
2303 bool should_rce = policy_range_check(phase);
2304
2305 bool should_align = policy_align(phase);
2306
2307 // If not RCE'ing (iteration splitting) or Aligning, then we do not
2308 // need a pre-loop. We may still need to peel an initial iteration but
2309 // we will not be needing an unknown number of pre-iterations.
2310 //
2311 // Basically, if may_rce_align reports FALSE first time through,
2312 // we will not be able to later do RCE or Aligning on this loop.
2313 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2314
2315 // If we have any of these conditions (RCE, alignment, unrolling) met, then
2316 // we switch to the pre-/main-/post-loop model. This model also covers
2317 // peeling.
2318 if (should_rce || should_align || should_unroll) {
2319 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops
2320 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2321
2322 // Adjust the pre- and main-loop limits to let the pre and post loops run
2323 // with full checks, but the main-loop with no checks. Remove said
2324 // checks from the main body.
2325 if (should_rce)
2326 phase->do_range_check(this,old_new);
2327
2328 // Double loop body for unrolling. Adjust the minimum-trip test (will do
2329 // twice as many iterations as before) and the main body limit (only do
2330 // an even number of trips). If we are peeling, we might enable some RCE
2331 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2332 // peeling.
2333 if (should_unroll && !should_peel)
2334 phase->do_unroll(this,old_new, true);
2335
2336 // Adjust the pre-loop limits to align the main body
2337 // iterations.
2338 if (should_align)
2339 Unimplemented();
2340
2341 } else { // Else we have an unchanged counted loop
2342 if (should_peel) // Might want to peel but do nothing else
2343 phase->do_peeling(this,old_new);
2344 }
2345 return true;
2346 }
2347
2348
2349 //=============================================================================
2350 //------------------------------iteration_split--------------------------------
2351 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2352 // Recursively iteration split nested loops
2353 if (_child && !_child->iteration_split(phase, old_new))
2354 return false;
2355
2356 // Clean out prior deadwood
2357 DCE_loop_body();
2358
2359
2360 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2361 // Replace with a 1-in-10 exit guess.
2362 if (_parent /*not the root loop*/ &&
2363 !_irreducible &&
2364 // Also ignore the occasional dead backedge
2365 !tail()->is_top()) {
2366 adjust_loop_exit_prob(phase);
2367 }
2368
2369 // Gate unrolling, RCE and peeling efforts.
2370 if (!_child && // If not an inner loop, do not split
2371 !_irreducible &&
2372 _allow_optimizations &&
2373 !tail()->is_top()) { // Also ignore the occasional dead backedge
2374 if (!_has_call) {
2375 if (!iteration_split_impl(phase, old_new)) {
2376 return false;
2377 }
2378 } else if (policy_unswitching(phase)) {
2379 phase->do_unswitching(this, old_new);
2380 }
2381 }
2382
2383 // Minor offset re-organization to remove loop-fallout uses of
2384 // trip counter when there was no major reshaping.
2385 phase->reorg_offsets(this);
2386
2387 if (_next && !_next->iteration_split(phase, old_new))
2388 return false;
2389 return true;
2390 }
2391
2392
2393 //=============================================================================
2394 // Process all the loops in the loop tree and replace any fill
2395 // patterns with an intrisc version.
2396 bool PhaseIdealLoop::do_intrinsify_fill() {
2397 bool changed = false;
2398 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2399 IdealLoopTree* lpt = iter.current();
2400 changed |= intrinsify_fill(lpt);
2401 }
2402 return changed;
2403 }
2404
2405
2406 // Examine an inner loop looking for a a single store of an invariant
2407 // value in a unit stride loop,
2408 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2409 Node*& shift, Node*& con) {
2410 const char* msg = NULL;
2411 Node* msg_node = NULL;
2412
2413 store_value = NULL;
2414 con = NULL;
2415 shift = NULL;
2416
2417 // Process the loop looking for stores. If there are multiple
2418 // stores or extra control flow give at this point.
2419 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2420 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2421 Node* n = lpt->_body.at(i);
2422 if (n->outcnt() == 0) continue; // Ignore dead
2423 if (n->is_Store()) {
2424 if (store != NULL) {
2425 msg = "multiple stores";
2426 break;
2427 }
2428 int opc = n->Opcode();
2429 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreNKlass || opc == Op_StoreCM) {
2430 msg = "oop fills not handled";
2431 break;
2432 }
2433 Node* value = n->in(MemNode::ValueIn);
2434 if (!lpt->is_invariant(value)) {
2435 msg = "variant store value";
2436 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2437 msg = "not array address";
2438 }
2439 store = n;
2440 store_value = value;
2441 } else if (n->is_If() && n != head->loopexit()) {
2442 msg = "extra control flow";
2443 msg_node = n;
2444 }
2445 }
2446
2447 if (store == NULL) {
2448 // No store in loop
2449 return false;
2450 }
2451
2452 if (msg == NULL && head->stride_con() != 1) {
2453 // could handle negative strides too
2454 if (head->stride_con() < 0) {
2455 msg = "negative stride";
2456 } else {
2457 msg = "non-unit stride";
2458 }
2459 }
2460
2461 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2462 msg = "can't handle store address";
2463 msg_node = store->in(MemNode::Address);
2464 }
2465
2466 if (msg == NULL &&
2467 (!store->in(MemNode::Memory)->is_Phi() ||
2468 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2469 msg = "store memory isn't proper phi";
2470 msg_node = store->in(MemNode::Memory);
2471 }
2472
2473 // Make sure there is an appropriate fill routine
2474 BasicType t = store->as_Mem()->memory_type();
2475 const char* fill_name;
2476 if (msg == NULL &&
2477 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2478 msg = "unsupported store";
2479 msg_node = store;
2480 }
2481
2482 if (msg != NULL) {
2483 #ifndef PRODUCT
2484 if (TraceOptimizeFill) {
2485 tty->print_cr("not fill intrinsic candidate: %s", msg);
2486 if (msg_node != NULL) msg_node->dump();
2487 }
2488 #endif
2489 return false;
2490 }
2491
2492 // Make sure the address expression can be handled. It should be
2493 // head->phi * elsize + con. head->phi might have a ConvI2L.
2494 Node* elements[4];
2495 Node* conv = NULL;
2496 bool found_index = false;
2497 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2498 for (int e = 0; e < count; e++) {
2499 Node* n = elements[e];
2500 if (n->is_Con() && con == NULL) {
2501 con = n;
2502 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2503 Node* value = n->in(1);
2504 #ifdef _LP64
2505 if (value->Opcode() == Op_ConvI2L) {
2506 conv = value;
2507 value = value->in(1);
2508 }
2509 #endif
2510 if (value != head->phi()) {
2511 msg = "unhandled shift in address";
2512 } else {
2513 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2514 msg = "scale doesn't match";
2515 } else {
2516 found_index = true;
2517 shift = n;
2518 }
2519 }
2520 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2521 if (n->in(1) == head->phi()) {
2522 found_index = true;
2523 conv = n;
2524 } else {
2525 msg = "unhandled input to ConvI2L";
2526 }
2527 } else if (n == head->phi()) {
2528 // no shift, check below for allowed cases
2529 found_index = true;
2530 } else {
2531 msg = "unhandled node in address";
2532 msg_node = n;
2533 }
2534 }
2535
2536 if (count == -1) {
2537 msg = "malformed address expression";
2538 msg_node = store;
2539 }
2540
2541 if (!found_index) {
2542 msg = "missing use of index";
2543 }
2544
2545 // byte sized items won't have a shift
2546 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2547 msg = "can't find shift";
2548 msg_node = store;
2549 }
2550
2551 if (msg != NULL) {
2552 #ifndef PRODUCT
2553 if (TraceOptimizeFill) {
2554 tty->print_cr("not fill intrinsic: %s", msg);
2555 if (msg_node != NULL) msg_node->dump();
2556 }
2557 #endif
2558 return false;
2559 }
2560
2561 // No make sure all the other nodes in the loop can be handled
2562 VectorSet ok(Thread::current()->resource_area());
2563
2564 // store related values are ok
2565 ok.set(store->_idx);
2566 ok.set(store->in(MemNode::Memory)->_idx);
2567
2568 CountedLoopEndNode* loop_exit = head->loopexit();
2569 guarantee(loop_exit != NULL, "no loop exit node");
2570
2571 // Loop structure is ok
2572 ok.set(head->_idx);
2573 ok.set(loop_exit->_idx);
2574 ok.set(head->phi()->_idx);
2575 ok.set(head->incr()->_idx);
2576 ok.set(loop_exit->cmp_node()->_idx);
2577 ok.set(loop_exit->in(1)->_idx);
2578
2579 // Address elements are ok
2580 if (con) ok.set(con->_idx);
2581 if (shift) ok.set(shift->_idx);
2582 if (conv) ok.set(conv->_idx);
2583
2584 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2585 Node* n = lpt->_body.at(i);
2586 if (n->outcnt() == 0) continue; // Ignore dead
2587 if (ok.test(n->_idx)) continue;
2588 // Backedge projection is ok
2589 if (n->is_IfTrue() && n->in(0) == loop_exit) continue;
2590 if (!n->is_AddP()) {
2591 msg = "unhandled node";
2592 msg_node = n;
2593 break;
2594 }
2595 }
2596
2597 // Make sure no unexpected values are used outside the loop
2598 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2599 Node* n = lpt->_body.at(i);
2600 // These values can be replaced with other nodes if they are used
2601 // outside the loop.
2602 if (n == store || n == loop_exit || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2603 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2604 Node* use = iter.get();
2605 if (!lpt->_body.contains(use)) {
2606 msg = "node is used outside loop";
2607 // lpt->_body.dump();
2608 msg_node = n;
2609 break;
2610 }
2611 }
2612 }
2613
2614 #ifdef ASSERT
2615 if (TraceOptimizeFill) {
2616 if (msg != NULL) {
2617 tty->print_cr("no fill intrinsic: %s", msg);
2618 if (msg_node != NULL) msg_node->dump();
2619 } else {
2620 tty->print_cr("fill intrinsic for:");
2621 }
2622 store->dump();
2623 if (Verbose) {
2624 lpt->_body.dump();
2625 }
2626 }
2627 #endif
2628
2629 return msg == NULL;
2630 }
2631
2632
2633
2634 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2635 // Only for counted inner loops
2636 if (!lpt->is_counted() || !lpt->is_inner()) {
2637 return false;
2638 }
2639
2640 // Must have constant stride
2641 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2642 if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
2643 return false;
2644 }
2645
2646 // Check that the body only contains a store of a loop invariant
2647 // value that is indexed by the loop phi.
2648 Node* store = NULL;
2649 Node* store_value = NULL;
2650 Node* shift = NULL;
2651 Node* offset = NULL;
2652 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2653 return false;
2654 }
2655
2656 #ifndef PRODUCT
2657 if (TraceLoopOpts) {
2658 tty->print("ArrayFill ");
2659 lpt->dump_head();
2660 }
2661 #endif
2662
2663 // Now replace the whole loop body by a call to a fill routine that
2664 // covers the same region as the loop.
2665 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2666
2667 // Build an expression for the beginning of the copy region
2668 Node* index = head->init_trip();
2669 #ifdef _LP64
2670 index = new ConvI2LNode(index);
2671 _igvn.register_new_node_with_optimizer(index);
2672 #endif
2673 if (shift != NULL) {
2674 // byte arrays don't require a shift but others do.
2675 index = new LShiftXNode(index, shift->in(2));
2676 _igvn.register_new_node_with_optimizer(index);
2677 }
2678 index = new AddPNode(base, base, index);
2679 _igvn.register_new_node_with_optimizer(index);
2680 Node* from = new AddPNode(base, index, offset);
2681 _igvn.register_new_node_with_optimizer(from);
2682 // Compute the number of elements to copy
2683 Node* len = new SubINode(head->limit(), head->init_trip());
2684 _igvn.register_new_node_with_optimizer(len);
2685
2686 BasicType t = store->as_Mem()->memory_type();
2687 bool aligned = false;
2688 if (offset != NULL && head->init_trip()->is_Con()) {
2689 int element_size = type2aelembytes(t);
2690 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2691 }
2692
2693 // Build a call to the fill routine
2694 const char* fill_name;
2695 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2696 assert(fill != NULL, "what?");
2697
2698 // Convert float/double to int/long for fill routines
2699 if (t == T_FLOAT) {
2700 store_value = new MoveF2INode(store_value);
2701 _igvn.register_new_node_with_optimizer(store_value);
2702 } else if (t == T_DOUBLE) {
2703 store_value = new MoveD2LNode(store_value);
2704 _igvn.register_new_node_with_optimizer(store_value);
2705 }
2706
2707 if (CCallingConventionRequiresIntsAsLongs &&
2708 // See StubRoutines::select_fill_function for types. FLOAT has been converted to INT.
2709 (t == T_FLOAT || t == T_INT || is_subword_type(t))) {
2710 store_value = new ConvI2LNode(store_value);
2711 _igvn.register_new_node_with_optimizer(store_value);
2712 }
2713
2714 Node* mem_phi = store->in(MemNode::Memory);
2715 Node* result_ctrl;
2716 Node* result_mem;
2717 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2718 CallLeafNode *call = new CallLeafNoFPNode(call_type, fill,
2719 fill_name, TypeAryPtr::get_array_body_type(t));
2720 uint cnt = 0;
2721 call->init_req(TypeFunc::Parms + cnt++, from);
2722 call->init_req(TypeFunc::Parms + cnt++, store_value);
2723 if (CCallingConventionRequiresIntsAsLongs) {
2724 call->init_req(TypeFunc::Parms + cnt++, C->top());
2725 }
2726 #ifdef _LP64
2727 len = new ConvI2LNode(len);
2728 _igvn.register_new_node_with_optimizer(len);
2729 #endif
2730 call->init_req(TypeFunc::Parms + cnt++, len);
2731 #ifdef _LP64
2732 call->init_req(TypeFunc::Parms + cnt++, C->top());
2733 #endif
2734 call->init_req(TypeFunc::Control, head->init_control());
2735 call->init_req(TypeFunc::I_O, C->top()); // Does no I/O.
2736 call->init_req(TypeFunc::Memory, mem_phi->in(LoopNode::EntryControl));
2737 call->init_req(TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr));
2738 call->init_req(TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr));
2739 _igvn.register_new_node_with_optimizer(call);
2740 result_ctrl = new ProjNode(call,TypeFunc::Control);
2741 _igvn.register_new_node_with_optimizer(result_ctrl);
2742 result_mem = new ProjNode(call,TypeFunc::Memory);
2743 _igvn.register_new_node_with_optimizer(result_mem);
2744
2745 /* Disable following optimization until proper fix (add missing checks).
2746
2747 // If this fill is tightly coupled to an allocation and overwrites
2748 // the whole body, allow it to take over the zeroing.
2749 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2750 if (alloc != NULL && alloc->is_AllocateArray()) {
2751 Node* length = alloc->as_AllocateArray()->Ideal_length();
2752 if (head->limit() == length &&
2753 head->init_trip() == _igvn.intcon(0)) {
2754 if (TraceOptimizeFill) {
2755 tty->print_cr("Eliminated zeroing in allocation");
2756 }
2757 alloc->maybe_set_complete(&_igvn);
2758 } else {
2759 #ifdef ASSERT
2760 if (TraceOptimizeFill) {
2761 tty->print_cr("filling array but bounds don't match");
2762 alloc->dump();
2763 head->init_trip()->dump();
2764 head->limit()->dump();
2765 length->dump();
2766 }
2767 #endif
2768 }
2769 }
2770 */
2771
2772 // Redirect the old control and memory edges that are outside the loop.
2773 Node* exit = head->loopexit()->proj_out(0);
2774 // Sometimes the memory phi of the head is used as the outgoing
2775 // state of the loop. It's safe in this case to replace it with the
2776 // result_mem.
2777 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2778 _igvn.replace_node(exit, result_ctrl);
2779 _igvn.replace_node(store, result_mem);
2780 // Any uses the increment outside of the loop become the loop limit.
2781 _igvn.replace_node(head->incr(), head->limit());
2782
2783 // Disconnect the head from the loop.
2784 for (uint i = 0; i < lpt->_body.size(); i++) {
2785 Node* n = lpt->_body.at(i);
2786 _igvn.replace_node(n, C->top());
2787 }
2788
2789 return true;
2790 }