1 /*
2 * Copyright (c) 1998, 2017, 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 "ci/ciMethodData.hpp"
27 #include "compiler/compileLog.hpp"
28 #include "libadt/vectset.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "opto/addnode.hpp"
31 #include "opto/callnode.hpp"
32 #include "opto/connode.hpp"
33 #include "opto/divnode.hpp"
34 #include "opto/idealGraphPrinter.hpp"
35 #include "opto/loopnode.hpp"
36 #include "opto/mulnode.hpp"
37 #include "opto/rootnode.hpp"
38 #include "opto/superword.hpp"
39
40 //=============================================================================
41 //------------------------------is_loop_iv-------------------------------------
42 // Determine if a node is Counted loop induction variable.
43 // The method is declared in node.hpp.
44 const Node* Node::is_loop_iv() const {
45 if (this->is_Phi() && !this->as_Phi()->is_copy() &&
46 this->as_Phi()->region()->is_CountedLoop() &&
47 this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
48 return this;
49 } else {
50 return NULL;
51 }
52 }
53
54 //=============================================================================
55 //------------------------------dump_spec--------------------------------------
56 // Dump special per-node info
57 #ifndef PRODUCT
58 void LoopNode::dump_spec(outputStream *st) const {
59 if (is_inner_loop()) st->print( "inner " );
60 if (is_partial_peel_loop()) st->print( "partial_peel " );
61 if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
62 }
63 #endif
64
65 //------------------------------is_valid_counted_loop-------------------------
66 bool LoopNode::is_valid_counted_loop() const {
67 if (is_CountedLoop()) {
68 CountedLoopNode* l = as_CountedLoop();
69 CountedLoopEndNode* le = l->loopexit();
70 if (le != NULL &&
71 le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
72 Node* phi = l->phi();
73 Node* exit = le->proj_out(0 /* false */);
74 if (exit != NULL && exit->Opcode() == Op_IfFalse &&
75 phi != NULL && phi->is_Phi() &&
76 phi->in(LoopNode::LoopBackControl) == l->incr() &&
77 le->loopnode() == l && le->stride_is_con()) {
78 return true;
79 }
80 }
81 }
82 return false;
83 }
84
85 //------------------------------get_early_ctrl---------------------------------
86 // Compute earliest legal control
87 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
88 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
89 uint i;
90 Node *early;
91 if (n->in(0) && !n->is_expensive()) {
92 early = n->in(0);
93 if (!early->is_CFG()) // Might be a non-CFG multi-def
94 early = get_ctrl(early); // So treat input as a straight data input
95 i = 1;
96 } else {
97 early = get_ctrl(n->in(1));
98 i = 2;
99 }
100 uint e_d = dom_depth(early);
101 assert( early, "" );
102 for (; i < n->req(); i++) {
103 Node *cin = get_ctrl(n->in(i));
104 assert( cin, "" );
105 // Keep deepest dominator depth
106 uint c_d = dom_depth(cin);
107 if (c_d > e_d) { // Deeper guy?
108 early = cin; // Keep deepest found so far
109 e_d = c_d;
110 } else if (c_d == e_d && // Same depth?
111 early != cin) { // If not equal, must use slower algorithm
112 // If same depth but not equal, one _must_ dominate the other
113 // and we want the deeper (i.e., dominated) guy.
114 Node *n1 = early;
115 Node *n2 = cin;
116 while (1) {
117 n1 = idom(n1); // Walk up until break cycle
118 n2 = idom(n2);
119 if (n1 == cin || // Walked early up to cin
120 dom_depth(n2) < c_d)
121 break; // early is deeper; keep him
122 if (n2 == early || // Walked cin up to early
123 dom_depth(n1) < c_d) {
124 early = cin; // cin is deeper; keep him
125 break;
126 }
127 }
128 e_d = dom_depth(early); // Reset depth register cache
129 }
130 }
131
132 // Return earliest legal location
133 assert(early == find_non_split_ctrl(early), "unexpected early control");
134
135 if (n->is_expensive()) {
136 assert(n->in(0), "should have control input");
137 early = get_early_ctrl_for_expensive(n, early);
138 }
139
140 return early;
141 }
142
143 //------------------------------get_early_ctrl_for_expensive---------------------------------
144 // Move node up the dominator tree as high as legal while still beneficial
145 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
146 assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
147 assert(OptimizeExpensiveOps, "optimization off?");
148
149 Node* ctl = n->in(0);
150 assert(ctl->is_CFG(), "expensive input 0 must be cfg");
151 uint min_dom_depth = dom_depth(earliest);
152 #ifdef ASSERT
153 if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
154 dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
155 assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
156 }
157 #endif
158 if (dom_depth(ctl) < min_dom_depth) {
159 return earliest;
160 }
161
162 while (1) {
163 Node *next = ctl;
164 // Moving the node out of a loop on the projection of a If
165 // confuses loop predication. So once we hit a Loop in a If branch
166 // that doesn't branch to an UNC, we stop. The code that process
167 // expensive nodes will notice the loop and skip over it to try to
168 // move the node further up.
169 if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
170 if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
171 break;
172 }
173 next = idom(ctl->in(1)->in(0));
174 } else if (ctl->is_Proj()) {
175 // We only move it up along a projection if the projection is
176 // the single control projection for its parent: same code path,
177 // if it's a If with UNC or fallthrough of a call.
178 Node* parent_ctl = ctl->in(0);
179 if (parent_ctl == NULL) {
180 break;
181 } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
182 next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
183 } else if (parent_ctl->is_If()) {
184 if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
185 break;
186 }
187 assert(idom(ctl) == parent_ctl, "strange");
188 next = idom(parent_ctl);
189 } else if (ctl->is_CatchProj()) {
190 if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
191 break;
192 }
193 assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
194 next = parent_ctl->in(0)->in(0)->in(0);
195 } else {
196 // Check if parent control has a single projection (this
197 // control is the only possible successor of the parent
198 // control). If so, we can try to move the node above the
199 // parent control.
200 int nb_ctl_proj = 0;
201 for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
202 Node *p = parent_ctl->fast_out(i);
203 if (p->is_Proj() && p->is_CFG()) {
204 nb_ctl_proj++;
205 if (nb_ctl_proj > 1) {
206 break;
207 }
208 }
209 }
210
211 if (nb_ctl_proj > 1) {
212 break;
213 }
214 assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
215 assert(idom(ctl) == parent_ctl, "strange");
216 next = idom(parent_ctl);
217 }
218 } else {
219 next = idom(ctl);
220 }
221 if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
222 break;
223 }
224 ctl = next;
225 }
226
227 if (ctl != n->in(0)) {
228 _igvn.hash_delete(n);
229 n->set_req(0, ctl);
230 _igvn.hash_insert(n);
231 }
232
233 return ctl;
234 }
235
236
237 //------------------------------set_early_ctrl---------------------------------
238 // Set earliest legal control
239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
240 Node *early = get_early_ctrl(n);
241
242 // Record earliest legal location
243 set_ctrl(n, early);
244 }
245
246 //------------------------------set_subtree_ctrl-------------------------------
247 // set missing _ctrl entries on new nodes
248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
249 // Already set? Get out.
250 if( _nodes[n->_idx] ) return;
251 // Recursively set _nodes array to indicate where the Node goes
252 uint i;
253 for( i = 0; i < n->req(); ++i ) {
254 Node *m = n->in(i);
255 if( m && m != C->root() )
256 set_subtree_ctrl( m );
257 }
258
259 // Fixup self
260 set_early_ctrl( n );
261 }
262
263 //------------------------------is_counted_loop--------------------------------
264 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
265 PhaseGVN *gvn = &_igvn;
266
267 // Counted loop head must be a good RegionNode with only 3 not NULL
268 // control input edges: Self, Entry, LoopBack.
269 if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
270 return false;
271 }
272 Node *init_control = x->in(LoopNode::EntryControl);
273 Node *back_control = x->in(LoopNode::LoopBackControl);
274 if (init_control == NULL || back_control == NULL) // Partially dead
275 return false;
276 // Must also check for TOP when looking for a dead loop
277 if (init_control->is_top() || back_control->is_top())
278 return false;
279
280 // Allow funny placement of Safepoint
281 if (back_control->Opcode() == Op_SafePoint) {
282 if (UseCountedLoopSafepoints) {
283 // Leaving the safepoint on the backedge and creating a
284 // CountedLoop will confuse optimizations. We can't move the
285 // safepoint around because its jvm state wouldn't match a new
286 // location. Give up on that loop.
287 return false;
288 }
289 back_control = back_control->in(TypeFunc::Control);
290 }
291
292 // Controlling test for loop
293 Node *iftrue = back_control;
294 uint iftrue_op = iftrue->Opcode();
295 if (iftrue_op != Op_IfTrue &&
296 iftrue_op != Op_IfFalse)
297 // I have a weird back-control. Probably the loop-exit test is in
298 // the middle of the loop and I am looking at some trailing control-flow
299 // merge point. To fix this I would have to partially peel the loop.
300 return false; // Obscure back-control
301
302 // Get boolean guarding loop-back test
303 Node *iff = iftrue->in(0);
304 if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
305 return false;
306 BoolNode *test = iff->in(1)->as_Bool();
307 BoolTest::mask bt = test->_test._test;
308 float cl_prob = iff->as_If()->_prob;
309 if (iftrue_op == Op_IfFalse) {
310 bt = BoolTest(bt).negate();
311 cl_prob = 1.0 - cl_prob;
312 }
313 // Get backedge compare
314 Node *cmp = test->in(1);
315 int cmp_op = cmp->Opcode();
316 if (cmp_op != Op_CmpI)
317 return false; // Avoid pointer & float compares
318
319 // Find the trip-counter increment & limit. Limit must be loop invariant.
320 Node *incr = cmp->in(1);
321 Node *limit = cmp->in(2);
322
323 // ---------
324 // need 'loop()' test to tell if limit is loop invariant
325 // ---------
326
327 if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
328 Node *tmp = incr; // Then reverse order into the CmpI
329 incr = limit;
330 limit = tmp;
331 bt = BoolTest(bt).commute(); // And commute the exit test
332 }
333 if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
334 return false;
335 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
336 return false;
337
338 Node* phi_incr = NULL;
339 // Trip-counter increment must be commutative & associative.
340 if (incr->is_Phi()) {
341 if (incr->as_Phi()->region() != x || incr->req() != 3)
342 return false; // Not simple trip counter expression
343 phi_incr = incr;
344 incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
345 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
346 return false;
347 }
348
349 Node* trunc1 = NULL;
350 Node* trunc2 = NULL;
351 const TypeInt* iv_trunc_t = NULL;
352 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
353 return false; // Funny increment opcode
354 }
355 assert(incr->Opcode() == Op_AddI, "wrong increment code");
356
357 // Get merge point
358 Node *xphi = incr->in(1);
359 Node *stride = incr->in(2);
360 if (!stride->is_Con()) { // Oops, swap these
361 if (!xphi->is_Con()) // Is the other guy a constant?
362 return false; // Nope, unknown stride, bail out
363 Node *tmp = xphi; // 'incr' is commutative, so ok to swap
364 xphi = stride;
365 stride = tmp;
366 }
367 // Stride must be constant
368 int stride_con = stride->get_int();
369 if (stride_con == 0)
370 return false; // missed some peephole opt
371
372 if (!xphi->is_Phi())
373 return false; // Too much math on the trip counter
374 if (phi_incr != NULL && phi_incr != xphi)
375 return false;
376 PhiNode *phi = xphi->as_Phi();
377
378 // Phi must be of loop header; backedge must wrap to increment
379 if (phi->region() != x)
380 return false;
381 if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
382 trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
383 return false;
384 }
385 Node *init_trip = phi->in(LoopNode::EntryControl);
386
387 // If iv trunc type is smaller than int, check for possible wrap.
388 if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
389 assert(trunc1 != NULL, "must have found some truncation");
390
391 // Get a better type for the phi (filtered thru if's)
392 const TypeInt* phi_ft = filtered_type(phi);
393
394 // Can iv take on a value that will wrap?
395 //
396 // Ensure iv's limit is not within "stride" of the wrap value.
397 //
398 // Example for "short" type
399 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
400 // If the stride is +10, then the last value of the induction
401 // variable before the increment (phi_ft->_hi) must be
402 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
403 // ensure no truncation occurs after the increment.
404
405 if (stride_con > 0) {
406 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
407 iv_trunc_t->_lo > phi_ft->_lo) {
408 return false; // truncation may occur
409 }
410 } else if (stride_con < 0) {
411 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
412 iv_trunc_t->_hi < phi_ft->_hi) {
413 return false; // truncation may occur
414 }
415 }
416 // No possibility of wrap so truncation can be discarded
417 // Promote iv type to Int
418 } else {
419 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
420 }
421
422 // If the condition is inverted and we will be rolling
423 // through MININT to MAXINT, then bail out.
424 if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
425 // Odd stride
426 bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
427 // Count down loop rolls through MAXINT
428 (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
429 // Count up loop rolls through MININT
430 (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
431 return false; // Bail out
432 }
433
434 const TypeInt* init_t = gvn->type(init_trip)->is_int();
435 const TypeInt* limit_t = gvn->type(limit)->is_int();
436
437 if (stride_con > 0) {
438 jlong init_p = (jlong)init_t->_lo + stride_con;
439 if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
440 return false; // cyclic loop or this loop trips only once
441 } else {
442 jlong init_p = (jlong)init_t->_hi + stride_con;
443 if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
444 return false; // cyclic loop or this loop trips only once
445 }
446
447 if (phi_incr != NULL) {
448 // check if there is a possiblity of IV overflowing after the first increment
449 if (stride_con > 0) {
450 if (init_t->_hi > max_jint - stride_con) {
451 return false;
452 }
453 } else {
454 if (init_t->_lo < min_jint - stride_con) {
455 return false;
456 }
457 }
458 }
459
460 // =================================================
461 // ---- SUCCESS! Found A Trip-Counted Loop! -----
462 //
463 assert(x->Opcode() == Op_Loop, "regular loops only");
464 C->print_method(PHASE_BEFORE_CLOOPS, 3);
465
466 Node *hook = new (C) Node(6);
467
468 if (LoopLimitCheck) {
469
470 // ===================================================
471 // Generate loop limit check to avoid integer overflow
472 // in cases like next (cyclic loops):
473 //
474 // for (i=0; i <= max_jint; i++) {}
475 // for (i=0; i < max_jint; i+=2) {}
476 //
477 //
478 // Limit check predicate depends on the loop test:
479 //
480 // for(;i != limit; i++) --> limit <= (max_jint)
481 // for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1)
482 // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride )
483 //
484
485 // Check if limit is excluded to do more precise int overflow check.
486 bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
487 int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
488
489 // If compare points directly to the phi we need to adjust
490 // the compare so that it points to the incr. Limit have
491 // to be adjusted to keep trip count the same and the
492 // adjusted limit should be checked for int overflow.
493 if (phi_incr != NULL) {
494 stride_m += stride_con;
495 }
496
497 if (limit->is_Con()) {
498 int limit_con = limit->get_int();
499 if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
500 (stride_con < 0 && limit_con < (min_jint - stride_m))) {
501 // Bailout: it could be integer overflow.
502 return false;
503 }
504 } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
505 (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
506 // Limit's type may satisfy the condition, for example,
507 // when it is an array length.
508 } else {
509 // Generate loop's limit check.
510 // Loop limit check predicate should be near the loop.
511 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
512 if (!limit_check_proj) {
513 // The limit check predicate is not generated if this method trapped here before.
514 #ifdef ASSERT
515 if (TraceLoopLimitCheck) {
516 tty->print("missing loop limit check:");
517 loop->dump_head();
518 x->dump(1);
519 }
520 #endif
521 return false;
522 }
523
524 IfNode* check_iff = limit_check_proj->in(0)->as_If();
525 Node* cmp_limit;
526 Node* bol;
527
528 if (stride_con > 0) {
529 cmp_limit = new (C) CmpINode(limit, _igvn.intcon(max_jint - stride_m));
530 bol = new (C) BoolNode(cmp_limit, BoolTest::le);
531 } else {
532 cmp_limit = new (C) CmpINode(limit, _igvn.intcon(min_jint - stride_m));
533 bol = new (C) BoolNode(cmp_limit, BoolTest::ge);
534 }
535 cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
536 bol = _igvn.register_new_node_with_optimizer(bol);
537 set_subtree_ctrl(bol);
538
539 // Replace condition in original predicate but preserve Opaque node
540 // so that previous predicates could be found.
541 assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
542 check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
543 Node* opq = check_iff->in(1)->in(1);
544 _igvn.hash_delete(opq);
545 opq->set_req(1, bol);
546 // Update ctrl.
547 set_ctrl(opq, check_iff->in(0));
548 set_ctrl(check_iff->in(1), check_iff->in(0));
549
550 #ifndef PRODUCT
551 // report that the loop predication has been actually performed
552 // for this loop
553 if (TraceLoopLimitCheck) {
554 tty->print_cr("Counted Loop Limit Check generated:");
555 debug_only( bol->dump(2); )
556 }
557 #endif
558 }
559
560 if (phi_incr != NULL) {
561 // If compare points directly to the phi we need to adjust
562 // the compare so that it points to the incr. Limit have
563 // to be adjusted to keep trip count the same and we
564 // should avoid int overflow.
565 //
566 // i = init; do {} while(i++ < limit);
567 // is converted to
568 // i = init; do {} while(++i < limit+1);
569 //
570 limit = gvn->transform(new (C) AddINode(limit, stride));
571 }
572
573 // Now we need to canonicalize loop condition.
574 if (bt == BoolTest::ne) {
575 assert(stride_con == 1 || stride_con == -1, "simple increment only");
576 // 'ne' can be replaced with 'lt' only when init < limit.
577 if (stride_con > 0 && init_t->_hi < limit_t->_lo)
578 bt = BoolTest::lt;
579 // 'ne' can be replaced with 'gt' only when init > limit.
580 if (stride_con < 0 && init_t->_lo > limit_t->_hi)
581 bt = BoolTest::gt;
582 }
583
584 if (incl_limit) {
585 // The limit check guaranties that 'limit <= (max_jint - stride)' so
586 // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
587 //
588 Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
589 limit = gvn->transform(new (C) AddINode(limit, one));
590 if (bt == BoolTest::le)
591 bt = BoolTest::lt;
592 else if (bt == BoolTest::ge)
593 bt = BoolTest::gt;
594 else
595 ShouldNotReachHere();
596 }
597 set_subtree_ctrl( limit );
598
599 } else { // LoopLimitCheck
600
601 // If compare points to incr, we are ok. Otherwise the compare
602 // can directly point to the phi; in this case adjust the compare so that
603 // it points to the incr by adjusting the limit.
604 if (cmp->in(1) == phi || cmp->in(2) == phi)
605 limit = gvn->transform(new (C) AddINode(limit,stride));
606
607 // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
608 // Final value for iterator should be: trip_count * stride + init_trip.
609 Node *one_p = gvn->intcon( 1);
610 Node *one_m = gvn->intcon(-1);
611
612 Node *trip_count = NULL;
613 switch( bt ) {
614 case BoolTest::eq:
615 ShouldNotReachHere();
616 case BoolTest::ne: // Ahh, the case we desire
617 if (stride_con == 1)
618 trip_count = gvn->transform(new (C) SubINode(limit,init_trip));
619 else if (stride_con == -1)
620 trip_count = gvn->transform(new (C) SubINode(init_trip,limit));
621 else
622 ShouldNotReachHere();
623 set_subtree_ctrl(trip_count);
624 //_loop.map(trip_count->_idx,loop(limit));
625 break;
626 case BoolTest::le: // Maybe convert to '<' case
627 limit = gvn->transform(new (C) AddINode(limit,one_p));
628 set_subtree_ctrl( limit );
629 hook->init_req(4, limit);
630
631 bt = BoolTest::lt;
632 // Make the new limit be in the same loop nest as the old limit
633 //_loop.map(limit->_idx,limit_loop);
634 // Fall into next case
635 case BoolTest::lt: { // Maybe convert to '!=' case
636 if (stride_con < 0) // Count down loop rolls through MAXINT
637 ShouldNotReachHere();
638 Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
639 set_subtree_ctrl( range );
640 hook->init_req(0, range);
641
642 Node *bias = gvn->transform(new (C) AddINode(range,stride));
643 set_subtree_ctrl( bias );
644 hook->init_req(1, bias);
645
646 Node *bias1 = gvn->transform(new (C) AddINode(bias,one_m));
647 set_subtree_ctrl( bias1 );
648 hook->init_req(2, bias1);
649
650 trip_count = gvn->transform(new (C) DivINode(0,bias1,stride));
651 set_subtree_ctrl( trip_count );
652 hook->init_req(3, trip_count);
653 break;
654 }
655
656 case BoolTest::ge: // Maybe convert to '>' case
657 limit = gvn->transform(new (C) AddINode(limit,one_m));
658 set_subtree_ctrl( limit );
659 hook->init_req(4 ,limit);
660
661 bt = BoolTest::gt;
662 // Make the new limit be in the same loop nest as the old limit
663 //_loop.map(limit->_idx,limit_loop);
664 // Fall into next case
665 case BoolTest::gt: { // Maybe convert to '!=' case
666 if (stride_con > 0) // count up loop rolls through MININT
667 ShouldNotReachHere();
668 Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
669 set_subtree_ctrl( range );
670 hook->init_req(0, range);
671
672 Node *bias = gvn->transform(new (C) AddINode(range,stride));
673 set_subtree_ctrl( bias );
674 hook->init_req(1, bias);
675
676 Node *bias1 = gvn->transform(new (C) AddINode(bias,one_p));
677 set_subtree_ctrl( bias1 );
678 hook->init_req(2, bias1);
679
680 trip_count = gvn->transform(new (C) DivINode(0,bias1,stride));
681 set_subtree_ctrl( trip_count );
682 hook->init_req(3, trip_count);
683 break;
684 }
685 } // switch( bt )
686
687 Node *span = gvn->transform(new (C) MulINode(trip_count,stride));
688 set_subtree_ctrl( span );
689 hook->init_req(5, span);
690
691 limit = gvn->transform(new (C) AddINode(span,init_trip));
692 set_subtree_ctrl( limit );
693
694 } // LoopLimitCheck
695
696 if (!UseCountedLoopSafepoints) {
697 // Check for SafePoint on backedge and remove
698 Node *sfpt = x->in(LoopNode::LoopBackControl);
699 if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
700 lazy_replace( sfpt, iftrue );
701 if (loop->_safepts != NULL) {
702 loop->_safepts->yank(sfpt);
703 }
704 loop->_tail = iftrue;
705 }
706 }
707
708 // Build a canonical trip test.
709 // Clone code, as old values may be in use.
710 incr = incr->clone();
711 incr->set_req(1,phi);
712 incr->set_req(2,stride);
713 incr = _igvn.register_new_node_with_optimizer(incr);
714 set_early_ctrl( incr );
715 _igvn.hash_delete(phi);
716 phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
717
718 // If phi type is more restrictive than Int, raise to
719 // Int to prevent (almost) infinite recursion in igvn
720 // which can only handle integer types for constants or minint..maxint.
721 if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
722 Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
723 nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
724 nphi = _igvn.register_new_node_with_optimizer(nphi);
725 set_ctrl(nphi, get_ctrl(phi));
726 _igvn.replace_node(phi, nphi);
727 phi = nphi->as_Phi();
728 }
729 cmp = cmp->clone();
730 cmp->set_req(1,incr);
731 cmp->set_req(2,limit);
732 cmp = _igvn.register_new_node_with_optimizer(cmp);
733 set_ctrl(cmp, iff->in(0));
734
735 test = test->clone()->as_Bool();
736 (*(BoolTest*)&test->_test)._test = bt;
737 test->set_req(1,cmp);
738 _igvn.register_new_node_with_optimizer(test);
739 set_ctrl(test, iff->in(0));
740
741 // Replace the old IfNode with a new LoopEndNode
742 Node *lex = _igvn.register_new_node_with_optimizer(new (C) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
743 IfNode *le = lex->as_If();
744 uint dd = dom_depth(iff);
745 set_idom(le, le->in(0), dd); // Update dominance for loop exit
746 set_loop(le, loop);
747
748 // Get the loop-exit control
749 Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
750
751 // Need to swap loop-exit and loop-back control?
752 if (iftrue_op == Op_IfFalse) {
753 Node *ift2=_igvn.register_new_node_with_optimizer(new (C) IfTrueNode (le));
754 Node *iff2=_igvn.register_new_node_with_optimizer(new (C) IfFalseNode(le));
755
756 loop->_tail = back_control = ift2;
757 set_loop(ift2, loop);
758 set_loop(iff2, get_loop(iffalse));
759
760 // Lazy update of 'get_ctrl' mechanism.
761 lazy_replace(iffalse, iff2);
762 lazy_replace(iftrue, ift2);
763
764 // Swap names
765 iffalse = iff2;
766 iftrue = ift2;
767 } else {
768 _igvn.hash_delete(iffalse);
769 _igvn.hash_delete(iftrue);
770 iffalse->set_req_X( 0, le, &_igvn );
771 iftrue ->set_req_X( 0, le, &_igvn );
772 }
773
774 set_idom(iftrue, le, dd+1);
775 set_idom(iffalse, le, dd+1);
776 assert(iff->outcnt() == 0, "should be dead now");
777 lazy_replace( iff, le ); // fix 'get_ctrl'
778
779 // Now setup a new CountedLoopNode to replace the existing LoopNode
780 CountedLoopNode *l = new (C) CountedLoopNode(init_control, back_control);
781 l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
782 // The following assert is approximately true, and defines the intention
783 // of can_be_counted_loop. It fails, however, because phase->type
784 // is not yet initialized for this loop and its parts.
785 //assert(l->can_be_counted_loop(this), "sanity");
786 _igvn.register_new_node_with_optimizer(l);
787 set_loop(l, loop);
788 loop->_head = l;
789 // Fix all data nodes placed at the old loop head.
790 // Uses the lazy-update mechanism of 'get_ctrl'.
791 lazy_replace( x, l );
792 set_idom(l, init_control, dom_depth(x));
793
794 if (!UseCountedLoopSafepoints) {
795 // Check for immediately preceding SafePoint and remove
796 Node *sfpt2 = le->in(0);
797 if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
798 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
799 if (loop->_safepts != NULL) {
800 loop->_safepts->yank(sfpt2);
801 }
802 }
803 }
804
805 // Free up intermediate goo
806 _igvn.remove_dead_node(hook);
807
808 #ifdef ASSERT
809 assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
810 assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
811 #endif
812 #ifndef PRODUCT
813 if (TraceLoopOpts) {
814 tty->print("Counted ");
815 loop->dump_head();
816 }
817 #endif
818
819 C->print_method(PHASE_AFTER_CLOOPS, 3);
820
821 return true;
822 }
823
824 //----------------------exact_limit-------------------------------------------
825 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
826 assert(loop->_head->is_CountedLoop(), "");
827 CountedLoopNode *cl = loop->_head->as_CountedLoop();
828 assert(cl->is_valid_counted_loop(), "");
829
830 if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
831 cl->limit()->Opcode() == Op_LoopLimit) {
832 // Old code has exact limit (it could be incorrect in case of int overflow).
833 // Loop limit is exact with stride == 1. And loop may already have exact limit.
834 return cl->limit();
835 }
836 Node *limit = NULL;
837 #ifdef ASSERT
838 BoolTest::mask bt = cl->loopexit()->test_trip();
839 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
840 #endif
841 if (cl->has_exact_trip_count()) {
842 // Simple case: loop has constant boundaries.
843 // Use jlongs to avoid integer overflow.
844 int stride_con = cl->stride_con();
845 jlong init_con = cl->init_trip()->get_int();
846 jlong limit_con = cl->limit()->get_int();
847 julong trip_cnt = cl->trip_count();
848 jlong final_con = init_con + trip_cnt*stride_con;
849 int final_int = (int)final_con;
850 // The final value should be in integer range since the loop
851 // is counted and the limit was checked for overflow.
852 assert(final_con == (jlong)final_int, "final value should be integer");
853 limit = _igvn.intcon(final_int);
854 } else {
855 // Create new LoopLimit node to get exact limit (final iv value).
856 limit = new (C) LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
857 register_new_node(limit, cl->in(LoopNode::EntryControl));
858 }
859 assert(limit != NULL, "sanity");
860 return limit;
861 }
862
863 //------------------------------Ideal------------------------------------------
864 // Return a node which is more "ideal" than the current node.
865 // Attempt to convert into a counted-loop.
866 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
867 if (!can_be_counted_loop(phase)) {
868 phase->C->set_major_progress();
869 }
870 return RegionNode::Ideal(phase, can_reshape);
871 }
872
873
874 //=============================================================================
875 //------------------------------Ideal------------------------------------------
876 // Return a node which is more "ideal" than the current node.
877 // Attempt to convert into a counted-loop.
878 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
879 return RegionNode::Ideal(phase, can_reshape);
880 }
881
882 //------------------------------dump_spec--------------------------------------
883 // Dump special per-node info
884 #ifndef PRODUCT
885 void CountedLoopNode::dump_spec(outputStream *st) const {
886 LoopNode::dump_spec(st);
887 if (stride_is_con()) {
888 st->print("stride: %d ",stride_con());
889 }
890 if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
891 if (is_main_loop()) st->print("main of N%d", _idx);
892 if (is_post_loop()) st->print("post of N%d", _main_idx);
893 }
894 #endif
895
896 //=============================================================================
897 int CountedLoopEndNode::stride_con() const {
898 return stride()->bottom_type()->is_int()->get_con();
899 }
900
901 //=============================================================================
902 //------------------------------Value-----------------------------------------
903 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
904 const Type* init_t = phase->type(in(Init));
905 const Type* limit_t = phase->type(in(Limit));
906 const Type* stride_t = phase->type(in(Stride));
907 // Either input is TOP ==> the result is TOP
908 if (init_t == Type::TOP) return Type::TOP;
909 if (limit_t == Type::TOP) return Type::TOP;
910 if (stride_t == Type::TOP) return Type::TOP;
911
912 int stride_con = stride_t->is_int()->get_con();
913 if (stride_con == 1)
914 return NULL; // Identity
915
916 if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
917 // Use jlongs to avoid integer overflow.
918 jlong init_con = init_t->is_int()->get_con();
919 jlong limit_con = limit_t->is_int()->get_con();
920 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
921 jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
922 jlong final_con = init_con + stride_con*trip_count;
923 int final_int = (int)final_con;
924 // The final value should be in integer range since the loop
925 // is counted and the limit was checked for overflow.
926 assert(final_con == (jlong)final_int, "final value should be integer");
927 return TypeInt::make(final_int);
928 }
929
930 return bottom_type(); // TypeInt::INT
931 }
932
933 //------------------------------Ideal------------------------------------------
934 // Return a node which is more "ideal" than the current node.
935 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
936 if (phase->type(in(Init)) == Type::TOP ||
937 phase->type(in(Limit)) == Type::TOP ||
938 phase->type(in(Stride)) == Type::TOP)
939 return NULL; // Dead
940
941 int stride_con = phase->type(in(Stride))->is_int()->get_con();
942 if (stride_con == 1)
943 return NULL; // Identity
944
945 if (in(Init)->is_Con() && in(Limit)->is_Con())
946 return NULL; // Value
947
948 // Delay following optimizations until all loop optimizations
949 // done to keep Ideal graph simple.
950 if (!can_reshape || phase->C->major_progress())
951 return NULL;
952
953 const TypeInt* init_t = phase->type(in(Init) )->is_int();
954 const TypeInt* limit_t = phase->type(in(Limit))->is_int();
955 int stride_p;
956 jlong lim, ini;
957 julong max;
958 if (stride_con > 0) {
959 stride_p = stride_con;
960 lim = limit_t->_hi;
961 ini = init_t->_lo;
962 max = (julong)max_jint;
963 } else {
964 stride_p = -stride_con;
965 lim = init_t->_hi;
966 ini = limit_t->_lo;
967 max = (julong)min_jint;
968 }
969 julong range = lim - ini + stride_p;
970 if (range <= max) {
971 // Convert to integer expression if it is not overflow.
972 Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
973 Node *range = phase->transform(new (phase->C) SubINode(in(Limit), in(Init)));
974 Node *bias = phase->transform(new (phase->C) AddINode(range, stride_m));
975 Node *trip = phase->transform(new (phase->C) DivINode(0, bias, in(Stride)));
976 Node *span = phase->transform(new (phase->C) MulINode(trip, in(Stride)));
977 return new (phase->C) AddINode(span, in(Init)); // exact limit
978 }
979
980 if (is_power_of_2(stride_p) || // divisor is 2^n
981 !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
982 // Convert to long expression to avoid integer overflow
983 // and let igvn optimizer convert this division.
984 //
985 Node* init = phase->transform( new (phase->C) ConvI2LNode(in(Init)));
986 Node* limit = phase->transform( new (phase->C) ConvI2LNode(in(Limit)));
987 Node* stride = phase->longcon(stride_con);
988 Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
989
990 Node *range = phase->transform(new (phase->C) SubLNode(limit, init));
991 Node *bias = phase->transform(new (phase->C) AddLNode(range, stride_m));
992 Node *span;
993 if (stride_con > 0 && is_power_of_2(stride_p)) {
994 // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
995 // and avoid generating rounding for division. Zero trip guard should
996 // guarantee that init < limit but sometimes the guard is missing and
997 // we can get situation when init > limit. Note, for the empty loop
998 // optimization zero trip guard is generated explicitly which leaves
999 // only RCE predicate where exact limit is used and the predicate
1000 // will simply fail forcing recompilation.
1001 Node* neg_stride = phase->longcon(-stride_con);
1002 span = phase->transform(new (phase->C) AndLNode(bias, neg_stride));
1003 } else {
1004 Node *trip = phase->transform(new (phase->C) DivLNode(0, bias, stride));
1005 span = phase->transform(new (phase->C) MulLNode(trip, stride));
1006 }
1007 // Convert back to int
1008 Node *span_int = phase->transform(new (phase->C) ConvL2INode(span));
1009 return new (phase->C) AddINode(span_int, in(Init)); // exact limit
1010 }
1011
1012 return NULL; // No progress
1013 }
1014
1015 //------------------------------Identity---------------------------------------
1016 // If stride == 1 return limit node.
1017 Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
1018 int stride_con = phase->type(in(Stride))->is_int()->get_con();
1019 if (stride_con == 1 || stride_con == -1)
1020 return in(Limit);
1021 return this;
1022 }
1023
1024 //=============================================================================
1025 //----------------------match_incr_with_optional_truncation--------------------
1026 // Match increment with optional truncation:
1027 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1028 // Return NULL for failure. Success returns the increment node.
1029 Node* CountedLoopNode::match_incr_with_optional_truncation(
1030 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1031 // Quick cutouts:
1032 if (expr == NULL || expr->req() != 3) return NULL;
1033
1034 Node *t1 = NULL;
1035 Node *t2 = NULL;
1036 const TypeInt* trunc_t = TypeInt::INT;
1037 Node* n1 = expr;
1038 int n1op = n1->Opcode();
1039
1040 // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1041 if (n1op == Op_AndI &&
1042 n1->in(2)->is_Con() &&
1043 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1044 // %%% This check should match any mask of 2**K-1.
1045 t1 = n1;
1046 n1 = t1->in(1);
1047 n1op = n1->Opcode();
1048 trunc_t = TypeInt::CHAR;
1049 } else if (n1op == Op_RShiftI &&
1050 n1->in(1) != NULL &&
1051 n1->in(1)->Opcode() == Op_LShiftI &&
1052 n1->in(2) == n1->in(1)->in(2) &&
1053 n1->in(2)->is_Con()) {
1054 jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1055 // %%% This check should match any shift in [1..31].
1056 if (shift == 16 || shift == 8) {
1057 t1 = n1;
1058 t2 = t1->in(1);
1059 n1 = t2->in(1);
1060 n1op = n1->Opcode();
1061 if (shift == 16) {
1062 trunc_t = TypeInt::SHORT;
1063 } else if (shift == 8) {
1064 trunc_t = TypeInt::BYTE;
1065 }
1066 }
1067 }
1068
1069 // If (maybe after stripping) it is an AddI, we won:
1070 if (n1op == Op_AddI) {
1071 *trunc1 = t1;
1072 *trunc2 = t2;
1073 *trunc_type = trunc_t;
1074 return n1;
1075 }
1076
1077 // failed
1078 return NULL;
1079 }
1080
1081
1082 //------------------------------filtered_type--------------------------------
1083 // Return a type based on condition control flow
1084 // A successful return will be a type that is restricted due
1085 // to a series of dominating if-tests, such as:
1086 // if (i < 10) {
1087 // if (i > 0) {
1088 // here: "i" type is [1..10)
1089 // }
1090 // }
1091 // or a control flow merge
1092 // if (i < 10) {
1093 // do {
1094 // phi( , ) -- at top of loop type is [min_int..10)
1095 // i = ?
1096 // } while ( i < 10)
1097 //
1098 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1099 assert(n && n->bottom_type()->is_int(), "must be int");
1100 const TypeInt* filtered_t = NULL;
1101 if (!n->is_Phi()) {
1102 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1103 filtered_t = filtered_type_from_dominators(n, n_ctrl);
1104
1105 } else {
1106 Node* phi = n->as_Phi();
1107 Node* region = phi->in(0);
1108 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1109 if (region && region != C->top()) {
1110 for (uint i = 1; i < phi->req(); i++) {
1111 Node* val = phi->in(i);
1112 Node* use_c = region->in(i);
1113 const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1114 if (val_t != NULL) {
1115 if (filtered_t == NULL) {
1116 filtered_t = val_t;
1117 } else {
1118 filtered_t = filtered_t->meet(val_t)->is_int();
1119 }
1120 }
1121 }
1122 }
1123 }
1124 const TypeInt* n_t = _igvn.type(n)->is_int();
1125 if (filtered_t != NULL) {
1126 n_t = n_t->join(filtered_t)->is_int();
1127 }
1128 return n_t;
1129 }
1130
1131
1132 //------------------------------filtered_type_from_dominators--------------------------------
1133 // Return a possibly more restrictive type for val based on condition control flow of dominators
1134 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1135 if (val->is_Con()) {
1136 return val->bottom_type()->is_int();
1137 }
1138 uint if_limit = 10; // Max number of dominating if's visited
1139 const TypeInt* rtn_t = NULL;
1140
1141 if (use_ctrl && use_ctrl != C->top()) {
1142 Node* val_ctrl = get_ctrl(val);
1143 uint val_dom_depth = dom_depth(val_ctrl);
1144 Node* pred = use_ctrl;
1145 uint if_cnt = 0;
1146 while (if_cnt < if_limit) {
1147 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1148 if_cnt++;
1149 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1150 if (if_t != NULL) {
1151 if (rtn_t == NULL) {
1152 rtn_t = if_t;
1153 } else {
1154 rtn_t = rtn_t->join(if_t)->is_int();
1155 }
1156 }
1157 }
1158 pred = idom(pred);
1159 if (pred == NULL || pred == C->top()) {
1160 break;
1161 }
1162 // Stop if going beyond definition block of val
1163 if (dom_depth(pred) < val_dom_depth) {
1164 break;
1165 }
1166 }
1167 }
1168 return rtn_t;
1169 }
1170
1171
1172 //------------------------------dump_spec--------------------------------------
1173 // Dump special per-node info
1174 #ifndef PRODUCT
1175 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1176 if( in(TestValue)->is_Bool() ) {
1177 BoolTest bt( test_trip()); // Added this for g++.
1178
1179 st->print("[");
1180 bt.dump_on(st);
1181 st->print("]");
1182 }
1183 st->print(" ");
1184 IfNode::dump_spec(st);
1185 }
1186 #endif
1187
1188 //=============================================================================
1189 //------------------------------is_member--------------------------------------
1190 // Is 'l' a member of 'this'?
1191 int IdealLoopTree::is_member( const IdealLoopTree *l ) const {
1192 while( l->_nest > _nest ) l = l->_parent;
1193 return l == this;
1194 }
1195
1196 //------------------------------set_nest---------------------------------------
1197 // Set loop tree nesting depth. Accumulate _has_call bits.
1198 int IdealLoopTree::set_nest( uint depth ) {
1199 _nest = depth;
1200 int bits = _has_call;
1201 if( _child ) bits |= _child->set_nest(depth+1);
1202 if( bits ) _has_call = 1;
1203 if( _next ) bits |= _next ->set_nest(depth );
1204 return bits;
1205 }
1206
1207 //------------------------------split_fall_in----------------------------------
1208 // Split out multiple fall-in edges from the loop header. Move them to a
1209 // private RegionNode before the loop. This becomes the loop landing pad.
1210 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1211 PhaseIterGVN &igvn = phase->_igvn;
1212 uint i;
1213
1214 // Make a new RegionNode to be the landing pad.
1215 Node *landing_pad = new (phase->C) RegionNode( fall_in_cnt+1 );
1216 phase->set_loop(landing_pad,_parent);
1217 // Gather all the fall-in control paths into the landing pad
1218 uint icnt = fall_in_cnt;
1219 uint oreq = _head->req();
1220 for( i = oreq-1; i>0; i-- )
1221 if( !phase->is_member( this, _head->in(i) ) )
1222 landing_pad->set_req(icnt--,_head->in(i));
1223
1224 // Peel off PhiNode edges as well
1225 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1226 Node *oj = _head->fast_out(j);
1227 if( oj->is_Phi() ) {
1228 PhiNode* old_phi = oj->as_Phi();
1229 assert( old_phi->region() == _head, "" );
1230 igvn.hash_delete(old_phi); // Yank from hash before hacking edges
1231 Node *p = PhiNode::make_blank(landing_pad, old_phi);
1232 uint icnt = fall_in_cnt;
1233 for( i = oreq-1; i>0; i-- ) {
1234 if( !phase->is_member( this, _head->in(i) ) ) {
1235 p->init_req(icnt--, old_phi->in(i));
1236 // Go ahead and clean out old edges from old phi
1237 old_phi->del_req(i);
1238 }
1239 }
1240 // Search for CSE's here, because ZKM.jar does a lot of
1241 // loop hackery and we need to be a little incremental
1242 // with the CSE to avoid O(N^2) node blow-up.
1243 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1244 if( p2 ) { // Found CSE
1245 p->destruct(); // Recover useless new node
1246 p = p2; // Use old node
1247 } else {
1248 igvn.register_new_node_with_optimizer(p, old_phi);
1249 }
1250 // Make old Phi refer to new Phi.
1251 old_phi->add_req(p);
1252 // Check for the special case of making the old phi useless and
1253 // disappear it. In JavaGrande I have a case where this useless
1254 // Phi is the loop limit and prevents recognizing a CountedLoop
1255 // which in turn prevents removing an empty loop.
1256 Node *id_old_phi = old_phi->Identity( &igvn );
1257 if( id_old_phi != old_phi ) { // Found a simple identity?
1258 // Note that I cannot call 'replace_node' here, because
1259 // that will yank the edge from old_phi to the Region and
1260 // I'm mid-iteration over the Region's uses.
1261 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1262 Node* use = old_phi->last_out(i);
1263 igvn.rehash_node_delayed(use);
1264 uint uses_found = 0;
1265 for (uint j = 0; j < use->len(); j++) {
1266 if (use->in(j) == old_phi) {
1267 if (j < use->req()) use->set_req (j, id_old_phi);
1268 else use->set_prec(j, id_old_phi);
1269 uses_found++;
1270 }
1271 }
1272 i -= uses_found; // we deleted 1 or more copies of this edge
1273 }
1274 }
1275 igvn._worklist.push(old_phi);
1276 }
1277 }
1278 // Finally clean out the fall-in edges from the RegionNode
1279 for( i = oreq-1; i>0; i-- ) {
1280 if( !phase->is_member( this, _head->in(i) ) ) {
1281 _head->del_req(i);
1282 }
1283 }
1284 // Transform landing pad
1285 igvn.register_new_node_with_optimizer(landing_pad, _head);
1286 // Insert landing pad into the header
1287 _head->add_req(landing_pad);
1288 }
1289
1290 //------------------------------split_outer_loop-------------------------------
1291 // Split out the outermost loop from this shared header.
1292 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1293 PhaseIterGVN &igvn = phase->_igvn;
1294
1295 // Find index of outermost loop; it should also be my tail.
1296 uint outer_idx = 1;
1297 while( _head->in(outer_idx) != _tail ) outer_idx++;
1298
1299 // Make a LoopNode for the outermost loop.
1300 Node *ctl = _head->in(LoopNode::EntryControl);
1301 Node *outer = new (phase->C) LoopNode( ctl, _head->in(outer_idx) );
1302 outer = igvn.register_new_node_with_optimizer(outer, _head);
1303 phase->set_created_loop_node();
1304
1305 // Outermost loop falls into '_head' loop
1306 _head->set_req(LoopNode::EntryControl, outer);
1307 _head->del_req(outer_idx);
1308 // Split all the Phis up between '_head' loop and 'outer' loop.
1309 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1310 Node *out = _head->fast_out(j);
1311 if( out->is_Phi() ) {
1312 PhiNode *old_phi = out->as_Phi();
1313 assert( old_phi->region() == _head, "" );
1314 Node *phi = PhiNode::make_blank(outer, old_phi);
1315 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl));
1316 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1317 phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1318 // Make old Phi point to new Phi on the fall-in path
1319 igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1320 old_phi->del_req(outer_idx);
1321 }
1322 }
1323
1324 // Use the new loop head instead of the old shared one
1325 _head = outer;
1326 phase->set_loop(_head, this);
1327 }
1328
1329 //------------------------------fix_parent-------------------------------------
1330 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1331 loop->_parent = parent;
1332 if( loop->_child ) fix_parent( loop->_child, loop );
1333 if( loop->_next ) fix_parent( loop->_next , parent );
1334 }
1335
1336 //------------------------------estimate_path_freq-----------------------------
1337 static float estimate_path_freq( Node *n ) {
1338 // Try to extract some path frequency info
1339 IfNode *iff;
1340 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1341 uint nop = n->Opcode();
1342 if( nop == Op_SafePoint ) { // Skip any safepoint
1343 n = n->in(0);
1344 continue;
1345 }
1346 if( nop == Op_CatchProj ) { // Get count from a prior call
1347 // Assume call does not always throw exceptions: means the call-site
1348 // count is also the frequency of the fall-through path.
1349 assert( n->is_CatchProj(), "" );
1350 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1351 return 0.0f; // Assume call exception path is rare
1352 Node *call = n->in(0)->in(0)->in(0);
1353 assert( call->is_Call(), "expect a call here" );
1354 const JVMState *jvms = ((CallNode*)call)->jvms();
1355 ciMethodData* methodData = jvms->method()->method_data();
1356 if (!methodData->is_mature()) return 0.0f; // No call-site data
1357 ciProfileData* data = methodData->bci_to_data(jvms->bci());
1358 if ((data == NULL) || !data->is_CounterData()) {
1359 // no call profile available, try call's control input
1360 n = n->in(0);
1361 continue;
1362 }
1363 return data->as_CounterData()->count()/FreqCountInvocations;
1364 }
1365 // See if there's a gating IF test
1366 Node *n_c = n->in(0);
1367 if( !n_c->is_If() ) break; // No estimate available
1368 iff = n_c->as_If();
1369 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count?
1370 // Compute how much count comes on this path
1371 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1372 // Have no count info. Skip dull uncommon-trap like branches.
1373 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) ||
1374 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1375 break;
1376 // Skip through never-taken branch; look for a real loop exit.
1377 n = iff->in(0);
1378 }
1379 return 0.0f; // No estimate available
1380 }
1381
1382 //------------------------------merge_many_backedges---------------------------
1383 // Merge all the backedges from the shared header into a private Region.
1384 // Feed that region as the one backedge to this loop.
1385 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1386 uint i;
1387
1388 // Scan for the top 2 hottest backedges
1389 float hotcnt = 0.0f;
1390 float warmcnt = 0.0f;
1391 uint hot_idx = 0;
1392 // Loop starts at 2 because slot 1 is the fall-in path
1393 for( i = 2; i < _head->req(); i++ ) {
1394 float cnt = estimate_path_freq(_head->in(i));
1395 if( cnt > hotcnt ) { // Grab hottest path
1396 warmcnt = hotcnt;
1397 hotcnt = cnt;
1398 hot_idx = i;
1399 } else if( cnt > warmcnt ) { // And 2nd hottest path
1400 warmcnt = cnt;
1401 }
1402 }
1403
1404 // See if the hottest backedge is worthy of being an inner loop
1405 // by being much hotter than the next hottest backedge.
1406 if( hotcnt <= 0.0001 ||
1407 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1408
1409 // Peel out the backedges into a private merge point; peel
1410 // them all except optionally hot_idx.
1411 PhaseIterGVN &igvn = phase->_igvn;
1412
1413 Node *hot_tail = NULL;
1414 // Make a Region for the merge point
1415 Node *r = new (phase->C) RegionNode(1);
1416 for( i = 2; i < _head->req(); i++ ) {
1417 if( i != hot_idx )
1418 r->add_req( _head->in(i) );
1419 else hot_tail = _head->in(i);
1420 }
1421 igvn.register_new_node_with_optimizer(r, _head);
1422 // Plug region into end of loop _head, followed by hot_tail
1423 while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1424 _head->set_req(2, r);
1425 if( hot_idx ) _head->add_req(hot_tail);
1426
1427 // Split all the Phis up between '_head' loop and the Region 'r'
1428 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1429 Node *out = _head->fast_out(j);
1430 if( out->is_Phi() ) {
1431 PhiNode* n = out->as_Phi();
1432 igvn.hash_delete(n); // Delete from hash before hacking edges
1433 Node *hot_phi = NULL;
1434 Node *phi = new (phase->C) PhiNode(r, n->type(), n->adr_type());
1435 // Check all inputs for the ones to peel out
1436 uint j = 1;
1437 for( uint i = 2; i < n->req(); i++ ) {
1438 if( i != hot_idx )
1439 phi->set_req( j++, n->in(i) );
1440 else hot_phi = n->in(i);
1441 }
1442 // Register the phi but do not transform until whole place transforms
1443 igvn.register_new_node_with_optimizer(phi, n);
1444 // Add the merge phi to the old Phi
1445 while( n->req() > 3 ) n->del_req( n->req()-1 );
1446 n->set_req(2, phi);
1447 if( hot_idx ) n->add_req(hot_phi);
1448 }
1449 }
1450
1451
1452 // Insert a new IdealLoopTree inserted below me. Turn it into a clone
1453 // of self loop tree. Turn self into a loop headed by _head and with
1454 // tail being the new merge point.
1455 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1456 phase->set_loop(_tail,ilt); // Adjust tail
1457 _tail = r; // Self's tail is new merge point
1458 phase->set_loop(r,this);
1459 ilt->_child = _child; // New guy has my children
1460 _child = ilt; // Self has new guy as only child
1461 ilt->_parent = this; // new guy has self for parent
1462 ilt->_nest = _nest; // Same nesting depth (for now)
1463
1464 // Starting with 'ilt', look for child loop trees using the same shared
1465 // header. Flatten these out; they will no longer be loops in the end.
1466 IdealLoopTree **pilt = &_child;
1467 while( ilt ) {
1468 if( ilt->_head == _head ) {
1469 uint i;
1470 for( i = 2; i < _head->req(); i++ )
1471 if( _head->in(i) == ilt->_tail )
1472 break; // Still a loop
1473 if( i == _head->req() ) { // No longer a loop
1474 // Flatten ilt. Hang ilt's "_next" list from the end of
1475 // ilt's '_child' list. Move the ilt's _child up to replace ilt.
1476 IdealLoopTree **cp = &ilt->_child;
1477 while( *cp ) cp = &(*cp)->_next; // Find end of child list
1478 *cp = ilt->_next; // Hang next list at end of child list
1479 *pilt = ilt->_child; // Move child up to replace ilt
1480 ilt->_head = NULL; // Flag as a loop UNIONED into parent
1481 ilt = ilt->_child; // Repeat using new ilt
1482 continue; // do not advance over ilt->_child
1483 }
1484 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1485 phase->set_loop(_head,ilt);
1486 }
1487 pilt = &ilt->_child; // Advance to next
1488 ilt = *pilt;
1489 }
1490
1491 if( _child ) fix_parent( _child, this );
1492 }
1493
1494 //------------------------------beautify_loops---------------------------------
1495 // Split shared headers and insert loop landing pads.
1496 // Insert a LoopNode to replace the RegionNode.
1497 // Return TRUE if loop tree is structurally changed.
1498 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1499 bool result = false;
1500 // Cache parts in locals for easy
1501 PhaseIterGVN &igvn = phase->_igvn;
1502
1503 igvn.hash_delete(_head); // Yank from hash before hacking edges
1504
1505 // Check for multiple fall-in paths. Peel off a landing pad if need be.
1506 int fall_in_cnt = 0;
1507 for( uint i = 1; i < _head->req(); i++ )
1508 if( !phase->is_member( this, _head->in(i) ) )
1509 fall_in_cnt++;
1510 assert( fall_in_cnt, "at least 1 fall-in path" );
1511 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins
1512 split_fall_in( phase, fall_in_cnt );
1513
1514 // Swap inputs to the _head and all Phis to move the fall-in edge to
1515 // the left.
1516 fall_in_cnt = 1;
1517 while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1518 fall_in_cnt++;
1519 if( fall_in_cnt > 1 ) {
1520 // Since I am just swapping inputs I do not need to update def-use info
1521 Node *tmp = _head->in(1);
1522 _head->set_req( 1, _head->in(fall_in_cnt) );
1523 _head->set_req( fall_in_cnt, tmp );
1524 // Swap also all Phis
1525 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1526 Node* phi = _head->fast_out(i);
1527 if( phi->is_Phi() ) {
1528 igvn.hash_delete(phi); // Yank from hash before hacking edges
1529 tmp = phi->in(1);
1530 phi->set_req( 1, phi->in(fall_in_cnt) );
1531 phi->set_req( fall_in_cnt, tmp );
1532 }
1533 }
1534 }
1535 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1536 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" );
1537
1538 // If I am a shared header (multiple backedges), peel off the many
1539 // backedges into a private merge point and use the merge point as
1540 // the one true backedge.
1541 if( _head->req() > 3 ) {
1542 // Merge the many backedges into a single backedge but leave
1543 // the hottest backedge as separate edge for the following peel.
1544 merge_many_backedges( phase );
1545 result = true;
1546 }
1547
1548 // If I have one hot backedge, peel off myself loop.
1549 // I better be the outermost loop.
1550 if (_head->req() > 3 && !_irreducible) {
1551 split_outer_loop( phase );
1552 result = true;
1553
1554 } else if (!_head->is_Loop() && !_irreducible) {
1555 // Make a new LoopNode to replace the old loop head
1556 Node *l = new (phase->C) LoopNode( _head->in(1), _head->in(2) );
1557 l = igvn.register_new_node_with_optimizer(l, _head);
1558 phase->set_created_loop_node();
1559 // Go ahead and replace _head
1560 phase->_igvn.replace_node( _head, l );
1561 _head = l;
1562 phase->set_loop(_head, this);
1563 }
1564
1565 // Now recursively beautify nested loops
1566 if( _child ) result |= _child->beautify_loops( phase );
1567 if( _next ) result |= _next ->beautify_loops( phase );
1568 return result;
1569 }
1570
1571 //------------------------------allpaths_check_safepts----------------------------
1572 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1573 // encountered. Helper for check_safepts.
1574 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1575 assert(stack.size() == 0, "empty stack");
1576 stack.push(_tail);
1577 visited.Clear();
1578 visited.set(_tail->_idx);
1579 while (stack.size() > 0) {
1580 Node* n = stack.pop();
1581 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1582 // Terminate this path
1583 } else if (n->Opcode() == Op_SafePoint) {
1584 if (_phase->get_loop(n) != this) {
1585 if (_required_safept == NULL) _required_safept = new Node_List();
1586 _required_safept->push(n); // save the one closest to the tail
1587 }
1588 // Terminate this path
1589 } else {
1590 uint start = n->is_Region() ? 1 : 0;
1591 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1592 for (uint i = start; i < end; i++) {
1593 Node* in = n->in(i);
1594 assert(in->is_CFG(), "must be");
1595 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1596 stack.push(in);
1597 }
1598 }
1599 }
1600 }
1601 }
1602
1603 //------------------------------check_safepts----------------------------
1604 // Given dominators, try to find loops with calls that must always be
1605 // executed (call dominates loop tail). These loops do not need non-call
1606 // safepoints (ncsfpt).
1607 //
1608 // A complication is that a safepoint in a inner loop may be needed
1609 // by an outer loop. In the following, the inner loop sees it has a
1610 // call (block 3) on every path from the head (block 2) to the
1611 // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint)
1612 // in block 2, _but_ this leaves the outer loop without a safepoint.
1613 //
1614 // entry 0
1615 // |
1616 // v
1617 // outer 1,2 +->1
1618 // | |
1619 // | v
1620 // | 2<---+ ncsfpt in 2
1621 // |_/|\ |
1622 // | v |
1623 // inner 2,3 / 3 | call in 3
1624 // / | |
1625 // v +--+
1626 // exit 4
1627 //
1628 //
1629 // This method creates a list (_required_safept) of ncsfpt nodes that must
1630 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1631 // is first looked for in the lists for the outer loops of the current loop.
1632 //
1633 // The insights into the problem:
1634 // A) counted loops are okay
1635 // B) innermost loops are okay (only an inner loop can delete
1636 // a ncsfpt needed by an outer loop)
1637 // C) a loop is immune from an inner loop deleting a safepoint
1638 // if the loop has a call on the idom-path
1639 // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1640 // idom-path that is not in a nested loop
1641 // E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1642 // loop needs to be prevented from deletion by an inner loop
1643 //
1644 // There are two analyses:
1645 // 1) The first, and cheaper one, scans the loop body from
1646 // tail to head following the idom (immediate dominator)
1647 // chain, looking for the cases (C,D,E) above.
1648 // Since inner loops are scanned before outer loops, there is summary
1649 // information about inner loops. Inner loops can be skipped over
1650 // when the tail of an inner loop is encountered.
1651 //
1652 // 2) The second, invoked if the first fails to find a call or ncsfpt on
1653 // the idom path (which is rare), scans all predecessor control paths
1654 // from the tail to the head, terminating a path when a call or sfpt
1655 // is encountered, to find the ncsfpt's that are closest to the tail.
1656 //
1657 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1658 // Bottom up traversal
1659 IdealLoopTree* ch = _child;
1660 if (_child) _child->check_safepts(visited, stack);
1661 if (_next) _next ->check_safepts(visited, stack);
1662
1663 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1664 bool has_call = false; // call on dom-path
1665 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1666 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth
1667 // Scan the dom-path nodes from tail to head
1668 for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1669 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1670 has_call = true;
1671 _has_sfpt = 1; // Then no need for a safept!
1672 break;
1673 } else if (n->Opcode() == Op_SafePoint) {
1674 if (_phase->get_loop(n) == this) {
1675 has_local_ncsfpt = true;
1676 break;
1677 }
1678 if (nonlocal_ncsfpt == NULL) {
1679 nonlocal_ncsfpt = n; // save the one closest to the tail
1680 }
1681 } else {
1682 IdealLoopTree* nlpt = _phase->get_loop(n);
1683 if (this != nlpt) {
1684 // If at an inner loop tail, see if the inner loop has already
1685 // recorded seeing a call on the dom-path (and stop.) If not,
1686 // jump to the head of the inner loop.
1687 assert(is_member(nlpt), "nested loop");
1688 Node* tail = nlpt->_tail;
1689 if (tail->in(0)->is_If()) tail = tail->in(0);
1690 if (n == tail) {
1691 // If inner loop has call on dom-path, so does outer loop
1692 if (nlpt->_has_sfpt) {
1693 has_call = true;
1694 _has_sfpt = 1;
1695 break;
1696 }
1697 // Skip to head of inner loop
1698 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1699 n = nlpt->_head;
1700 }
1701 }
1702 }
1703 }
1704 // Record safept's that this loop needs preserved when an
1705 // inner loop attempts to delete it's safepoints.
1706 if (_child != NULL && !has_call && !has_local_ncsfpt) {
1707 if (nonlocal_ncsfpt != NULL) {
1708 if (_required_safept == NULL) _required_safept = new Node_List();
1709 _required_safept->push(nonlocal_ncsfpt);
1710 } else {
1711 // Failed to find a suitable safept on the dom-path. Now use
1712 // an all paths walk from tail to head, looking for safepoints to preserve.
1713 allpaths_check_safepts(visited, stack);
1714 }
1715 }
1716 }
1717 }
1718
1719 //---------------------------is_deleteable_safept----------------------------
1720 // Is safept not required by an outer loop?
1721 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1722 assert(sfpt->Opcode() == Op_SafePoint, "");
1723 IdealLoopTree* lp = get_loop(sfpt)->_parent;
1724 while (lp != NULL) {
1725 Node_List* sfpts = lp->_required_safept;
1726 if (sfpts != NULL) {
1727 for (uint i = 0; i < sfpts->size(); i++) {
1728 if (sfpt == sfpts->at(i))
1729 return false;
1730 }
1731 }
1732 lp = lp->_parent;
1733 }
1734 return true;
1735 }
1736
1737 //---------------------------replace_parallel_iv-------------------------------
1738 // Replace parallel induction variable (parallel to trip counter)
1739 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1740 assert(loop->_head->is_CountedLoop(), "");
1741 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1742 if (!cl->is_valid_counted_loop())
1743 return; // skip malformed counted loop
1744 Node *incr = cl->incr();
1745 if (incr == NULL)
1746 return; // Dead loop?
1747 Node *init = cl->init_trip();
1748 Node *phi = cl->phi();
1749 int stride_con = cl->stride_con();
1750
1751 // Visit all children, looking for Phis
1752 for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1753 Node *out = cl->out(i);
1754 // Look for other phis (secondary IVs). Skip dead ones
1755 if (!out->is_Phi() || out == phi || !has_node(out))
1756 continue;
1757 PhiNode* phi2 = out->as_Phi();
1758 Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1759 // Look for induction variables of the form: X += constant
1760 if (phi2->region() != loop->_head ||
1761 incr2->req() != 3 ||
1762 incr2->in(1) != phi2 ||
1763 incr2 == incr ||
1764 incr2->Opcode() != Op_AddI ||
1765 !incr2->in(2)->is_Con())
1766 continue;
1767
1768 // Check for parallel induction variable (parallel to trip counter)
1769 // via an affine function. In particular, count-down loops with
1770 // count-up array indices are common. We only RCE references off
1771 // the trip-counter, so we need to convert all these to trip-counter
1772 // expressions.
1773 Node *init2 = phi2->in( LoopNode::EntryControl );
1774 int stride_con2 = incr2->in(2)->get_int();
1775
1776 // The ratio of the two strides cannot be represented as an int
1777 // if stride_con2 is min_int and stride_con is -1.
1778 if (stride_con2 == min_jint && stride_con == -1) {
1779 continue;
1780 }
1781
1782 // The general case here gets a little tricky. We want to find the
1783 // GCD of all possible parallel IV's and make a new IV using this
1784 // GCD for the loop. Then all possible IVs are simple multiples of
1785 // the GCD. In practice, this will cover very few extra loops.
1786 // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1787 // where +/-1 is the common case, but other integer multiples are
1788 // also easy to handle.
1789 int ratio_con = stride_con2/stride_con;
1790
1791 if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1792 #ifndef PRODUCT
1793 if (TraceLoopOpts) {
1794 tty->print("Parallel IV: %d ", phi2->_idx);
1795 loop->dump_head();
1796 }
1797 #endif
1798 // Convert to using the trip counter. The parallel induction
1799 // variable differs from the trip counter by a loop-invariant
1800 // amount, the difference between their respective initial values.
1801 // It is scaled by the 'ratio_con'.
1802 Node* ratio = _igvn.intcon(ratio_con);
1803 set_ctrl(ratio, C->root());
1804 Node* ratio_init = new (C) MulINode(init, ratio);
1805 _igvn.register_new_node_with_optimizer(ratio_init, init);
1806 set_early_ctrl(ratio_init);
1807 Node* diff = new (C) SubINode(init2, ratio_init);
1808 _igvn.register_new_node_with_optimizer(diff, init2);
1809 set_early_ctrl(diff);
1810 Node* ratio_idx = new (C) MulINode(phi, ratio);
1811 _igvn.register_new_node_with_optimizer(ratio_idx, phi);
1812 set_ctrl(ratio_idx, cl);
1813 Node* add = new (C) AddINode(ratio_idx, diff);
1814 _igvn.register_new_node_with_optimizer(add);
1815 set_ctrl(add, cl);
1816 _igvn.replace_node( phi2, add );
1817 // Sometimes an induction variable is unused
1818 if (add->outcnt() == 0) {
1819 _igvn.remove_dead_node(add);
1820 }
1821 --i; // deleted this phi; rescan starting with next position
1822 continue;
1823 }
1824 }
1825 }
1826
1827 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
1828 Node* keep = NULL;
1829 if (keep_one) {
1830 // Look for a safepoint on the idom-path.
1831 for (Node* i = tail(); i != _head; i = phase->idom(i)) {
1832 if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
1833 keep = i;
1834 break; // Found one
1835 }
1836 }
1837 }
1838
1839 // Don't remove any safepoints if it is requested to keep a single safepoint and
1840 // no safepoint was found on idom-path. It is not safe to remove any safepoint
1841 // in this case since there's no safepoint dominating all paths in the loop body.
1842 bool prune = !keep_one || keep != NULL;
1843
1844 // Delete other safepoints in this loop.
1845 Node_List* sfpts = _safepts;
1846 if (prune && sfpts != NULL) {
1847 assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
1848 for (uint i = 0; i < sfpts->size(); i++) {
1849 Node* n = sfpts->at(i);
1850 assert(phase->get_loop(n) == this, "");
1851 if (n != keep && phase->is_deleteable_safept(n)) {
1852 phase->lazy_replace(n, n->in(TypeFunc::Control));
1853 }
1854 }
1855 }
1856 }
1857
1858 //------------------------------counted_loop-----------------------------------
1859 // Convert to counted loops where possible
1860 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1861
1862 // For grins, set the inner-loop flag here
1863 if (!_child) {
1864 if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1865 }
1866
1867 if (_head->is_CountedLoop() ||
1868 phase->is_counted_loop(_head, this)) {
1869
1870 if (!UseCountedLoopSafepoints) {
1871 // Indicate we do not need a safepoint here
1872 _has_sfpt = 1;
1873 }
1874
1875 // Remove safepoints
1876 bool keep_one_sfpt = !(_has_call || _has_sfpt);
1877 remove_safepoints(phase, keep_one_sfpt);
1878
1879 // Look for induction variables
1880 phase->replace_parallel_iv(this);
1881
1882 } else if (_parent != NULL && !_irreducible) {
1883 // Not a counted loop. Keep one safepoint.
1884 bool keep_one_sfpt = true;
1885 remove_safepoints(phase, keep_one_sfpt);
1886 }
1887
1888 // Recursively
1889 if (_child) _child->counted_loop( phase );
1890 if (_next) _next ->counted_loop( phase );
1891 }
1892
1893 #ifndef PRODUCT
1894 //------------------------------dump_head--------------------------------------
1895 // Dump 1 liner for loop header info
1896 void IdealLoopTree::dump_head( ) const {
1897 for (uint i=0; i<_nest; i++)
1898 tty->print(" ");
1899 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1900 if (_irreducible) tty->print(" IRREDUCIBLE");
1901 Node* entry = _head->in(LoopNode::EntryControl);
1902 if (LoopLimitCheck) {
1903 Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1904 if (predicate != NULL ) {
1905 tty->print(" limit_check");
1906 entry = entry->in(0)->in(0);
1907 }
1908 }
1909 if (UseLoopPredicate) {
1910 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1911 if (entry != NULL) {
1912 tty->print(" predicated");
1913 }
1914 }
1915 if (_head->is_CountedLoop()) {
1916 CountedLoopNode *cl = _head->as_CountedLoop();
1917 tty->print(" counted");
1918
1919 Node* init_n = cl->init_trip();
1920 if (init_n != NULL && init_n->is_Con())
1921 tty->print(" [%d,", cl->init_trip()->get_int());
1922 else
1923 tty->print(" [int,");
1924 Node* limit_n = cl->limit();
1925 if (limit_n != NULL && limit_n->is_Con())
1926 tty->print("%d),", cl->limit()->get_int());
1927 else
1928 tty->print("int),");
1929 int stride_con = cl->stride_con();
1930 if (stride_con > 0) tty->print("+");
1931 tty->print("%d", stride_con);
1932
1933 tty->print(" (%d iters) ", (int)cl->profile_trip_cnt());
1934
1935 if (cl->is_pre_loop ()) tty->print(" pre" );
1936 if (cl->is_main_loop()) tty->print(" main");
1937 if (cl->is_post_loop()) tty->print(" post");
1938 }
1939 if (_has_call) tty->print(" has_call");
1940 if (_has_sfpt) tty->print(" has_sfpt");
1941 if (_rce_candidate) tty->print(" rce");
1942 if (_safepts != NULL && _safepts->size() > 0) {
1943 tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
1944 }
1945 if (_required_safept != NULL && _required_safept->size() > 0) {
1946 tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
1947 }
1948 tty->cr();
1949 }
1950
1951 //------------------------------dump-------------------------------------------
1952 // Dump loops by loop tree
1953 void IdealLoopTree::dump( ) const {
1954 dump_head();
1955 if (_child) _child->dump();
1956 if (_next) _next ->dump();
1957 }
1958
1959 #endif
1960
1961 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1962 if (loop == root) {
1963 if (loop->_child != NULL) {
1964 log->begin_head("loop_tree");
1965 log->end_head();
1966 if( loop->_child ) log_loop_tree(root, loop->_child, log);
1967 log->tail("loop_tree");
1968 assert(loop->_next == NULL, "what?");
1969 }
1970 } else {
1971 Node* head = loop->_head;
1972 log->begin_head("loop");
1973 log->print(" idx='%d' ", head->_idx);
1974 if (loop->_irreducible) log->print("irreducible='1' ");
1975 if (head->is_Loop()) {
1976 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1977 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1978 }
1979 if (head->is_CountedLoop()) {
1980 CountedLoopNode* cl = head->as_CountedLoop();
1981 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx());
1982 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1983 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
1984 }
1985 log->end_head();
1986 if( loop->_child ) log_loop_tree(root, loop->_child, log);
1987 log->tail("loop");
1988 if( loop->_next ) log_loop_tree(root, loop->_next, log);
1989 }
1990 }
1991
1992 //---------------------collect_potentially_useful_predicates-----------------------
1993 // Helper function to collect potentially useful predicates to prevent them from
1994 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1995 void PhaseIdealLoop::collect_potentially_useful_predicates(
1996 IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1997 if (loop->_child) { // child
1998 collect_potentially_useful_predicates(loop->_child, useful_predicates);
1999 }
2000
2001 // self (only loops that we can apply loop predication may use their predicates)
2002 if (loop->_head->is_Loop() &&
2003 !loop->_irreducible &&
2004 !loop->tail()->is_top()) {
2005 LoopNode* lpn = loop->_head->as_Loop();
2006 Node* entry = lpn->in(LoopNode::EntryControl);
2007 Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2008 if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2009 assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2010 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2011 entry = entry->in(0)->in(0);
2012 }
2013 predicate_proj = find_predicate(entry); // Predicate
2014 if (predicate_proj != NULL ) {
2015 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2016 }
2017 }
2018
2019 if (loop->_next) { // sibling
2020 collect_potentially_useful_predicates(loop->_next, useful_predicates);
2021 }
2022 }
2023
2024 //------------------------eliminate_useless_predicates-----------------------------
2025 // Eliminate all inserted predicates if they could not be used by loop predication.
2026 // Note: it will also eliminates loop limits check predicate since it also uses
2027 // Opaque1 node (see Parse::add_predicate()).
2028 void PhaseIdealLoop::eliminate_useless_predicates() {
2029 if (C->predicate_count() == 0)
2030 return; // no predicate left
2031
2032 Unique_Node_List useful_predicates; // to store useful predicates
2033 if (C->has_loops()) {
2034 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2035 }
2036
2037 for (int i = C->predicate_count(); i > 0; i--) {
2038 Node * n = C->predicate_opaque1_node(i-1);
2039 assert(n->Opcode() == Op_Opaque1, "must be");
2040 if (!useful_predicates.member(n)) { // not in the useful list
2041 _igvn.replace_node(n, n->in(1));
2042 }
2043 }
2044 }
2045
2046 //------------------------process_expensive_nodes-----------------------------
2047 // Expensive nodes have their control input set to prevent the GVN
2048 // from commoning them and as a result forcing the resulting node to
2049 // be in a more frequent path. Use CFG information here, to change the
2050 // control inputs so that some expensive nodes can be commoned while
2051 // not executed more frequently.
2052 bool PhaseIdealLoop::process_expensive_nodes() {
2053 assert(OptimizeExpensiveOps, "optimization off?");
2054
2055 // Sort nodes to bring similar nodes together
2056 C->sort_expensive_nodes();
2057
2058 bool progress = false;
2059
2060 for (int i = 0; i < C->expensive_count(); ) {
2061 Node* n = C->expensive_node(i);
2062 int start = i;
2063 // Find nodes similar to n
2064 i++;
2065 for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2066 int end = i;
2067 // And compare them two by two
2068 for (int j = start; j < end; j++) {
2069 Node* n1 = C->expensive_node(j);
2070 if (is_node_unreachable(n1)) {
2071 continue;
2072 }
2073 for (int k = j+1; k < end; k++) {
2074 Node* n2 = C->expensive_node(k);
2075 if (is_node_unreachable(n2)) {
2076 continue;
2077 }
2078
2079 assert(n1 != n2, "should be pair of nodes");
2080
2081 Node* c1 = n1->in(0);
2082 Node* c2 = n2->in(0);
2083
2084 Node* parent_c1 = c1;
2085 Node* parent_c2 = c2;
2086
2087 // The call to get_early_ctrl_for_expensive() moves the
2088 // expensive nodes up but stops at loops that are in a if
2089 // branch. See whether we can exit the loop and move above the
2090 // If.
2091 if (c1->is_Loop()) {
2092 parent_c1 = c1->in(1);
2093 }
2094 if (c2->is_Loop()) {
2095 parent_c2 = c2->in(1);
2096 }
2097
2098 if (parent_c1 == parent_c2) {
2099 _igvn._worklist.push(n1);
2100 _igvn._worklist.push(n2);
2101 continue;
2102 }
2103
2104 // Look for identical expensive node up the dominator chain.
2105 if (is_dominator(c1, c2)) {
2106 c2 = c1;
2107 } else if (is_dominator(c2, c1)) {
2108 c1 = c2;
2109 } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2110 parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2111 // Both branches have the same expensive node so move it up
2112 // before the if.
2113 c1 = c2 = idom(parent_c1->in(0));
2114 }
2115 // Do the actual moves
2116 if (n1->in(0) != c1) {
2117 _igvn.hash_delete(n1);
2118 n1->set_req(0, c1);
2119 _igvn.hash_insert(n1);
2120 _igvn._worklist.push(n1);
2121 progress = true;
2122 }
2123 if (n2->in(0) != c2) {
2124 _igvn.hash_delete(n2);
2125 n2->set_req(0, c2);
2126 _igvn.hash_insert(n2);
2127 _igvn._worklist.push(n2);
2128 progress = true;
2129 }
2130 }
2131 }
2132 }
2133
2134 return progress;
2135 }
2136
2137
2138 //=============================================================================
2139 //----------------------------build_and_optimize-------------------------------
2140 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to
2141 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups.
2142 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
2143 ResourceMark rm;
2144
2145 int old_progress = C->major_progress();
2146 uint orig_worklist_size = _igvn._worklist.size();
2147
2148 // Reset major-progress flag for the driver's heuristics
2149 C->clear_major_progress();
2150
2151 #ifndef PRODUCT
2152 // Capture for later assert
2153 uint unique = C->unique();
2154 _loop_invokes++;
2155 _loop_work += unique;
2156 #endif
2157
2158 // True if the method has at least 1 irreducible loop
2159 _has_irreducible_loops = false;
2160
2161 _created_loop_node = false;
2162
2163 Arena *a = Thread::current()->resource_area();
2164 VectorSet visited(a);
2165 // Pre-grow the mapping from Nodes to IdealLoopTrees.
2166 _nodes.map(C->unique(), NULL);
2167 memset(_nodes.adr(), 0, wordSize * C->unique());
2168
2169 // Pre-build the top-level outermost loop tree entry
2170 _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2171 // Do not need a safepoint at the top level
2172 _ltree_root->_has_sfpt = 1;
2173
2174 // Initialize Dominators.
2175 // Checked in clone_loop_predicate() during beautify_loops().
2176 _idom_size = 0;
2177 _idom = NULL;
2178 _dom_depth = NULL;
2179 _dom_stk = NULL;
2180
2181 // Empty pre-order array
2182 allocate_preorders();
2183
2184 // Build a loop tree on the fly. Build a mapping from CFG nodes to
2185 // IdealLoopTree entries. Data nodes are NOT walked.
2186 build_loop_tree();
2187 // Check for bailout, and return
2188 if (C->failing()) {
2189 return;
2190 }
2191
2192 // No loops after all
2193 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2194
2195 // There should always be an outer loop containing the Root and Return nodes.
2196 // If not, we have a degenerate empty program. Bail out in this case.
2197 if (!has_node(C->root())) {
2198 if (!_verify_only) {
2199 C->clear_major_progress();
2200 C->record_method_not_compilable("empty program detected during loop optimization");
2201 }
2202 return;
2203 }
2204
2205 // Nothing to do, so get out
2206 bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
2207 bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2208 if (stop_early && !do_expensive_nodes) {
2209 _igvn.optimize(); // Cleanup NeverBranches
2210 return;
2211 }
2212
2213 // Set loop nesting depth
2214 _ltree_root->set_nest( 0 );
2215
2216 // Split shared headers and insert loop landing pads.
2217 // Do not bother doing this on the Root loop of course.
2218 if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2219 C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2220 if( _ltree_root->_child->beautify_loops( this ) ) {
2221 // Re-build loop tree!
2222 _ltree_root->_child = NULL;
2223 _nodes.clear();
2224 reallocate_preorders();
2225 build_loop_tree();
2226 // Check for bailout, and return
2227 if (C->failing()) {
2228 return;
2229 }
2230 // Reset loop nesting depth
2231 _ltree_root->set_nest( 0 );
2232
2233 C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2234 }
2235 }
2236
2237 // Build Dominators for elision of NULL checks & loop finding.
2238 // Since nodes do not have a slot for immediate dominator, make
2239 // a persistent side array for that info indexed on node->_idx.
2240 _idom_size = C->unique();
2241 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2242 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size );
2243 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth
2244 memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2245
2246 Dominators();
2247
2248 if (!_verify_only) {
2249 // As a side effect, Dominators removed any unreachable CFG paths
2250 // into RegionNodes. It doesn't do this test against Root, so
2251 // we do it here.
2252 for( uint i = 1; i < C->root()->req(); i++ ) {
2253 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root?
2254 _igvn.delete_input_of(C->root(), i);
2255 i--; // Rerun same iteration on compressed edges
2256 }
2257 }
2258
2259 // Given dominators, try to find inner loops with calls that must
2260 // always be executed (call dominates loop tail). These loops do
2261 // not need a separate safepoint.
2262 Node_List cisstack(a);
2263 _ltree_root->check_safepts(visited, cisstack);
2264 }
2265
2266 // Walk the DATA nodes and place into loops. Find earliest control
2267 // node. For CFG nodes, the _nodes array starts out and remains
2268 // holding the associated IdealLoopTree pointer. For DATA nodes, the
2269 // _nodes array holds the earliest legal controlling CFG node.
2270
2271 // Allocate stack with enough space to avoid frequent realloc
2272 int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2273 Node_Stack nstack( a, stack_size );
2274
2275 visited.Clear();
2276 Node_List worklist(a);
2277 // Don't need C->root() on worklist since
2278 // it will be processed among C->top() inputs
2279 worklist.push( C->top() );
2280 visited.set( C->top()->_idx ); // Set C->top() as visited now
2281 build_loop_early( visited, worklist, nstack );
2282
2283 // Given early legal placement, try finding counted loops. This placement
2284 // is good enough to discover most loop invariants.
2285 if( !_verify_me && !_verify_only )
2286 _ltree_root->counted_loop( this );
2287
2288 // Find latest loop placement. Find ideal loop placement.
2289 visited.Clear();
2290 init_dom_lca_tags();
2291 // Need C->root() on worklist when processing outs
2292 worklist.push( C->root() );
2293 NOT_PRODUCT( C->verify_graph_edges(); )
2294 worklist.push( C->top() );
2295 build_loop_late( visited, worklist, nstack );
2296
2297 if (_verify_only) {
2298 // restore major progress flag
2299 for (int i = 0; i < old_progress; i++)
2300 C->set_major_progress();
2301 assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2302 assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2303 return;
2304 }
2305
2306 // clear out the dead code after build_loop_late
2307 while (_deadlist.size()) {
2308 _igvn.remove_globally_dead_node(_deadlist.pop());
2309 }
2310
2311 if (stop_early) {
2312 assert(do_expensive_nodes, "why are we here?");
2313 if (process_expensive_nodes()) {
2314 // If we made some progress when processing expensive nodes then
2315 // the IGVN may modify the graph in a way that will allow us to
2316 // make some more progress: we need to try processing expensive
2317 // nodes again.
2318 C->set_major_progress();
2319 }
2320 _igvn.optimize();
2321 return;
2322 }
2323
2324 // Some parser-inserted loop predicates could never be used by loop
2325 // predication or they were moved away from loop during some optimizations.
2326 // For example, peeling. Eliminate them before next loop optimizations.
2327 if (UseLoopPredicate || LoopLimitCheck) {
2328 eliminate_useless_predicates();
2329 }
2330
2331 #ifndef PRODUCT
2332 C->verify_graph_edges();
2333 if (_verify_me) { // Nested verify pass?
2334 // Check to see if the verify mode is broken
2335 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2336 return;
2337 }
2338 if(VerifyLoopOptimizations) verify();
2339 if(TraceLoopOpts && C->has_loops()) {
2340 _ltree_root->dump();
2341 }
2342 #endif
2343
2344 if (skip_loop_opts) {
2345 // restore major progress flag
2346 for (int i = 0; i < old_progress; i++) {
2347 C->set_major_progress();
2348 }
2349
2350 if (UseShenandoahGC && !C->major_progress()) {
2351 shenandoah_pin_and_expand_barriers();
2352 }
2353
2354 // Cleanup any modified bits
2355 _igvn.optimize();
2356
2357 if (C->log() != NULL) {
2358 log_loop_tree(_ltree_root, _ltree_root, C->log());
2359 }
2360 return;
2361 }
2362
2363 if (ReassociateInvariants) {
2364 // Reassociate invariants and prep for split_thru_phi
2365 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2366 IdealLoopTree* lpt = iter.current();
2367 if (!lpt->is_counted() || !lpt->is_inner()) continue;
2368
2369 lpt->reassociate_invariants(this);
2370
2371 // Because RCE opportunities can be masked by split_thru_phi,
2372 // look for RCE candidates and inhibit split_thru_phi
2373 // on just their loop-phi's for this pass of loop opts
2374 if (SplitIfBlocks && do_split_ifs) {
2375 if (lpt->policy_range_check(this)) {
2376 lpt->_rce_candidate = 1; // = true
2377 }
2378 }
2379 }
2380 }
2381
2382 // Check for aggressive application of split-if and other transforms
2383 // that require basic-block info (like cloning through Phi's)
2384 if( SplitIfBlocks && do_split_ifs ) {
2385 visited.Clear();
2386 split_if_with_blocks( visited, nstack );
2387 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2388 }
2389
2390 if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2391 C->set_major_progress();
2392 }
2393
2394 // Perform loop predication before iteration splitting
2395 if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2396 _ltree_root->_child->loop_predication(this);
2397 }
2398
2399 if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2400 if (do_intrinsify_fill()) {
2401 C->set_major_progress();
2402 }
2403 }
2404
2405 // Perform iteration-splitting on inner loops. Split iterations to avoid
2406 // range checks or one-shot null checks.
2407
2408 // If split-if's didn't hack the graph too bad (no CFG changes)
2409 // then do loop opts.
2410 if (C->has_loops() && !C->major_progress()) {
2411 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2412 _ltree_root->_child->iteration_split( this, worklist );
2413 // No verify after peeling! GCM has hoisted code out of the loop.
2414 // After peeling, the hoisted code could sink inside the peeled area.
2415 // The peeling code does not try to recompute the best location for
2416 // all the code before the peeled area, so the verify pass will always
2417 // complain about it.
2418 }
2419 // Do verify graph edges in any case
2420 NOT_PRODUCT( C->verify_graph_edges(); );
2421
2422 if (!do_split_ifs) {
2423 // We saw major progress in Split-If to get here. We forced a
2424 // pass with unrolling and not split-if, however more split-if's
2425 // might make progress. If the unrolling didn't make progress
2426 // then the major-progress flag got cleared and we won't try
2427 // another round of Split-If. In particular the ever-common
2428 // instance-of/check-cast pattern requires at least 2 rounds of
2429 // Split-If to clear out.
2430 C->set_major_progress();
2431 }
2432
2433 // Repeat loop optimizations if new loops were seen
2434 if (created_loop_node()) {
2435 C->set_major_progress();
2436 }
2437
2438 // Keep loop predicates and perform optimizations with them
2439 // until no more loop optimizations could be done.
2440 // After that switch predicates off and do more loop optimizations.
2441 if (!C->major_progress() && (C->predicate_count() > 0)) {
2442 C->cleanup_loop_predicates(_igvn);
2443 #ifndef PRODUCT
2444 if (TraceLoopOpts) {
2445 tty->print_cr("PredicatesOff");
2446 }
2447 #endif
2448 C->set_major_progress();
2449 }
2450
2451 // Convert scalar to superword operations at the end of all loop opts.
2452 if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2453 // SuperWord transform
2454 SuperWord sw(this);
2455 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2456 IdealLoopTree* lpt = iter.current();
2457 if (lpt->is_counted()) {
2458 sw.transform_loop(lpt);
2459 }
2460 }
2461 }
2462
2463 // Cleanup any modified bits
2464 _igvn.optimize();
2465
2466 // disable assert until issue with split_flow_path is resolved (6742111)
2467 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2468 // "shouldn't introduce irreducible loops");
2469
2470 if (C->log() != NULL) {
2471 log_loop_tree(_ltree_root, _ltree_root, C->log());
2472 }
2473 }
2474
2475 #ifndef PRODUCT
2476 //------------------------------print_statistics-------------------------------
2477 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2478 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2479 void PhaseIdealLoop::print_statistics() {
2480 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2481 }
2482
2483 //------------------------------verify-----------------------------------------
2484 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2485 static int fail; // debug only, so its multi-thread dont care
2486 void PhaseIdealLoop::verify() const {
2487 int old_progress = C->major_progress();
2488 ResourceMark rm;
2489 PhaseIdealLoop loop_verify( _igvn, this );
2490 VectorSet visited(Thread::current()->resource_area());
2491
2492 fail = 0;
2493 verify_compare( C->root(), &loop_verify, visited );
2494 assert( fail == 0, "verify loops failed" );
2495 // Verify loop structure is the same
2496 _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2497 // Reset major-progress. It was cleared by creating a verify version of
2498 // PhaseIdealLoop.
2499 for( int i=0; i<old_progress; i++ )
2500 C->set_major_progress();
2501 }
2502
2503 //------------------------------verify_compare---------------------------------
2504 // Make sure me and the given PhaseIdealLoop agree on key data structures
2505 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2506 if( !n ) return;
2507 if( visited.test_set( n->_idx ) ) return;
2508 if( !_nodes[n->_idx] ) { // Unreachable
2509 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2510 return;
2511 }
2512
2513 uint i;
2514 for( i = 0; i < n->req(); i++ )
2515 verify_compare( n->in(i), loop_verify, visited );
2516
2517 // Check the '_nodes' block/loop structure
2518 i = n->_idx;
2519 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl
2520 if( _nodes[i] != loop_verify->_nodes[i] &&
2521 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2522 tty->print("Mismatched control setting for: ");
2523 n->dump();
2524 if( fail++ > 10 ) return;
2525 Node *c = get_ctrl_no_update(n);
2526 tty->print("We have it as: ");
2527 if( c->in(0) ) c->dump();
2528 else tty->print_cr("N%d",c->_idx);
2529 tty->print("Verify thinks: ");
2530 if( loop_verify->has_ctrl(n) )
2531 loop_verify->get_ctrl_no_update(n)->dump();
2532 else
2533 loop_verify->get_loop_idx(n)->dump();
2534 tty->cr();
2535 }
2536 } else { // We have a loop
2537 IdealLoopTree *us = get_loop_idx(n);
2538 if( loop_verify->has_ctrl(n) ) {
2539 tty->print("Mismatched loop setting for: ");
2540 n->dump();
2541 if( fail++ > 10 ) return;
2542 tty->print("We have it as: ");
2543 us->dump();
2544 tty->print("Verify thinks: ");
2545 loop_verify->get_ctrl_no_update(n)->dump();
2546 tty->cr();
2547 } else if (!C->major_progress()) {
2548 // Loop selection can be messed up if we did a major progress
2549 // operation, like split-if. Do not verify in that case.
2550 IdealLoopTree *them = loop_verify->get_loop_idx(n);
2551 if( us->_head != them->_head || us->_tail != them->_tail ) {
2552 tty->print("Unequals loops for: ");
2553 n->dump();
2554 if( fail++ > 10 ) return;
2555 tty->print("We have it as: ");
2556 us->dump();
2557 tty->print("Verify thinks: ");
2558 them->dump();
2559 tty->cr();
2560 }
2561 }
2562 }
2563
2564 // Check for immediate dominators being equal
2565 if( i >= _idom_size ) {
2566 if( !n->is_CFG() ) return;
2567 tty->print("CFG Node with no idom: ");
2568 n->dump();
2569 return;
2570 }
2571 if( !n->is_CFG() ) return;
2572 if( n == C->root() ) return; // No IDOM here
2573
2574 assert(n->_idx == i, "sanity");
2575 Node *id = idom_no_update(n);
2576 if( id != loop_verify->idom_no_update(n) ) {
2577 tty->print("Unequals idoms for: ");
2578 n->dump();
2579 if( fail++ > 10 ) return;
2580 tty->print("We have it as: ");
2581 id->dump();
2582 tty->print("Verify thinks: ");
2583 loop_verify->idom_no_update(n)->dump();
2584 tty->cr();
2585 }
2586
2587 }
2588
2589 //------------------------------verify_tree------------------------------------
2590 // Verify that tree structures match. Because the CFG can change, siblings
2591 // within the loop tree can be reordered. We attempt to deal with that by
2592 // reordering the verify's loop tree if possible.
2593 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2594 assert( _parent == parent, "Badly formed loop tree" );
2595
2596 // Siblings not in same order? Attempt to re-order.
2597 if( _head != loop->_head ) {
2598 // Find _next pointer to update
2599 IdealLoopTree **pp = &loop->_parent->_child;
2600 while( *pp != loop )
2601 pp = &((*pp)->_next);
2602 // Find proper sibling to be next
2603 IdealLoopTree **nn = &loop->_next;
2604 while( (*nn) && (*nn)->_head != _head )
2605 nn = &((*nn)->_next);
2606
2607 // Check for no match.
2608 if( !(*nn) ) {
2609 // Annoyingly, irreducible loops can pick different headers
2610 // after a major_progress operation, so the rest of the loop
2611 // tree cannot be matched.
2612 if (_irreducible && Compile::current()->major_progress()) return;
2613 assert( 0, "failed to match loop tree" );
2614 }
2615
2616 // Move (*nn) to (*pp)
2617 IdealLoopTree *hit = *nn;
2618 *nn = hit->_next;
2619 hit->_next = loop;
2620 *pp = loop;
2621 loop = hit;
2622 // Now try again to verify
2623 }
2624
2625 assert( _head == loop->_head , "mismatched loop head" );
2626 Node *tail = _tail; // Inline a non-updating version of
2627 while( !tail->in(0) ) // the 'tail()' call.
2628 tail = tail->in(1);
2629 assert( tail == loop->_tail, "mismatched loop tail" );
2630
2631 // Counted loops that are guarded should be able to find their guards
2632 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2633 CountedLoopNode *cl = _head->as_CountedLoop();
2634 Node *init = cl->init_trip();
2635 Node *ctrl = cl->in(LoopNode::EntryControl);
2636 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2637 Node *iff = ctrl->in(0);
2638 assert( iff->Opcode() == Op_If, "" );
2639 Node *bol = iff->in(1);
2640 assert( bol->Opcode() == Op_Bool, "" );
2641 Node *cmp = bol->in(1);
2642 assert( cmp->Opcode() == Op_CmpI, "" );
2643 Node *add = cmp->in(1);
2644 Node *opaq;
2645 if( add->Opcode() == Op_Opaque1 ) {
2646 opaq = add;
2647 } else {
2648 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2649 assert( add == init, "" );
2650 opaq = cmp->in(2);
2651 }
2652 assert( opaq->Opcode() == Op_Opaque1, "" );
2653
2654 }
2655
2656 if (_child != NULL) _child->verify_tree(loop->_child, this);
2657 if (_next != NULL) _next ->verify_tree(loop->_next, parent);
2658 // Innermost loops need to verify loop bodies,
2659 // but only if no 'major_progress'
2660 int fail = 0;
2661 if (!Compile::current()->major_progress() && _child == NULL) {
2662 for( uint i = 0; i < _body.size(); i++ ) {
2663 Node *n = _body.at(i);
2664 if (n->outcnt() == 0) continue; // Ignore dead
2665 uint j;
2666 for( j = 0; j < loop->_body.size(); j++ )
2667 if( loop->_body.at(j) == n )
2668 break;
2669 if( j == loop->_body.size() ) { // Not found in loop body
2670 // Last ditch effort to avoid assertion: Its possible that we
2671 // have some users (so outcnt not zero) but are still dead.
2672 // Try to find from root.
2673 if (Compile::current()->root()->find(n->_idx)) {
2674 fail++;
2675 tty->print("We have that verify does not: ");
2676 n->dump();
2677 }
2678 }
2679 }
2680 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2681 Node *n = loop->_body.at(i2);
2682 if (n->outcnt() == 0) continue; // Ignore dead
2683 uint j;
2684 for( j = 0; j < _body.size(); j++ )
2685 if( _body.at(j) == n )
2686 break;
2687 if( j == _body.size() ) { // Not found in loop body
2688 // Last ditch effort to avoid assertion: Its possible that we
2689 // have some users (so outcnt not zero) but are still dead.
2690 // Try to find from root.
2691 if (Compile::current()->root()->find(n->_idx)) {
2692 fail++;
2693 tty->print("Verify has that we do not: ");
2694 n->dump();
2695 }
2696 }
2697 }
2698 assert( !fail, "loop body mismatch" );
2699 }
2700 }
2701
2702 #endif
2703
2704 //------------------------------set_idom---------------------------------------
2705 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2706 uint idx = d->_idx;
2707 if (idx >= _idom_size) {
2708 uint newsize = _idom_size<<1;
2709 while( idx >= newsize ) {
2710 newsize <<= 1;
2711 }
2712 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize);
2713 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2714 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2715 _idom_size = newsize;
2716 }
2717 _idom[idx] = n;
2718 _dom_depth[idx] = dom_depth;
2719 }
2720
2721 //------------------------------recompute_dom_depth---------------------------------------
2722 // The dominator tree is constructed with only parent pointers.
2723 // This recomputes the depth in the tree by first tagging all
2724 // nodes as "no depth yet" marker. The next pass then runs up
2725 // the dom tree from each node marked "no depth yet", and computes
2726 // the depth on the way back down.
2727 void PhaseIdealLoop::recompute_dom_depth() {
2728 uint no_depth_marker = C->unique();
2729 uint i;
2730 // Initialize depth to "no depth yet"
2731 for (i = 0; i < _idom_size; i++) {
2732 if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2733 _dom_depth[i] = no_depth_marker;
2734 }
2735 }
2736 if (_dom_stk == NULL) {
2737 uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
2738 if (init_size < 10) init_size = 10;
2739 _dom_stk = new GrowableArray<uint>(init_size);
2740 }
2741 // Compute new depth for each node.
2742 for (i = 0; i < _idom_size; i++) {
2743 uint j = i;
2744 // Run up the dom tree to find a node with a depth
2745 while (_dom_depth[j] == no_depth_marker) {
2746 _dom_stk->push(j);
2747 j = _idom[j]->_idx;
2748 }
2749 // Compute the depth on the way back down this tree branch
2750 uint dd = _dom_depth[j] + 1;
2751 while (_dom_stk->length() > 0) {
2752 uint j = _dom_stk->pop();
2753 _dom_depth[j] = dd;
2754 dd++;
2755 }
2756 }
2757 }
2758
2759 //------------------------------sort-------------------------------------------
2760 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the
2761 // loop tree, not the root.
2762 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2763 if( !innermost ) return loop; // New innermost loop
2764
2765 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2766 assert( loop_preorder, "not yet post-walked loop" );
2767 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer
2768 IdealLoopTree *l = *pp; // Do I go before or after 'l'?
2769
2770 // Insert at start of list
2771 while( l ) { // Insertion sort based on pre-order
2772 if( l == loop ) return innermost; // Already on list!
2773 int l_preorder = get_preorder(l->_head); // Cache pre-order number
2774 assert( l_preorder, "not yet post-walked l" );
2775 // Check header pre-order number to figure proper nesting
2776 if( loop_preorder > l_preorder )
2777 break; // End of insertion
2778 // If headers tie (e.g., shared headers) check tail pre-order numbers.
2779 // Since I split shared headers, you'd think this could not happen.
2780 // BUT: I must first do the preorder numbering before I can discover I
2781 // have shared headers, so the split headers all get the same preorder
2782 // number as the RegionNode they split from.
2783 if( loop_preorder == l_preorder &&
2784 get_preorder(loop->_tail) < get_preorder(l->_tail) )
2785 break; // Also check for shared headers (same pre#)
2786 pp = &l->_parent; // Chain up list
2787 l = *pp;
2788 }
2789 // Link into list
2790 // Point predecessor to me
2791 *pp = loop;
2792 // Point me to successor
2793 IdealLoopTree *p = loop->_parent;
2794 loop->_parent = l; // Point me to successor
2795 if( p ) sort( p, innermost ); // Insert my parents into list as well
2796 return innermost;
2797 }
2798
2799 //------------------------------build_loop_tree--------------------------------
2800 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit
2801 // bits. The _nodes[] array is mapped by Node index and holds a NULL for
2802 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2803 // tightest enclosing IdealLoopTree for post-walked.
2804 //
2805 // During my forward walk I do a short 1-layer lookahead to see if I can find
2806 // a loop backedge with that doesn't have any work on the backedge. This
2807 // helps me construct nested loops with shared headers better.
2808 //
2809 // Once I've done the forward recursion, I do the post-work. For each child
2810 // I check to see if there is a backedge. Backedges define a loop! I
2811 // insert an IdealLoopTree at the target of the backedge.
2812 //
2813 // During the post-work I also check to see if I have several children
2814 // belonging to different loops. If so, then this Node is a decision point
2815 // where control flow can choose to change loop nests. It is at this
2816 // decision point where I can figure out how loops are nested. At this
2817 // time I can properly order the different loop nests from my children.
2818 // Note that there may not be any backedges at the decision point!
2819 //
2820 // Since the decision point can be far removed from the backedges, I can't
2821 // order my loops at the time I discover them. Thus at the decision point
2822 // I need to inspect loop header pre-order numbers to properly nest my
2823 // loops. This means I need to sort my childrens' loops by pre-order.
2824 // The sort is of size number-of-control-children, which generally limits
2825 // it to size 2 (i.e., I just choose between my 2 target loops).
2826 void PhaseIdealLoop::build_loop_tree() {
2827 // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
2828 GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
2829 Node *n = C->root();
2830 bltstack.push(n);
2831 int pre_order = 1;
2832 int stack_size;
2833
2834 while ( ( stack_size = bltstack.length() ) != 0 ) {
2835 n = bltstack.top(); // Leave node on stack
2836 if ( !is_visited(n) ) {
2837 // ---- Pre-pass Work ----
2838 // Pre-walked but not post-walked nodes need a pre_order number.
2839
2840 set_preorder_visited( n, pre_order ); // set as visited
2841
2842 // ---- Scan over children ----
2843 // Scan first over control projections that lead to loop headers.
2844 // This helps us find inner-to-outer loops with shared headers better.
2845
2846 // Scan children's children for loop headers.
2847 for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2848 Node* m = n->raw_out(i); // Child
2849 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2850 // Scan over children's children to find loop
2851 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2852 Node* l = m->fast_out(j);
2853 if( is_visited(l) && // Been visited?
2854 !is_postvisited(l) && // But not post-visited
2855 get_preorder(l) < pre_order ) { // And smaller pre-order
2856 // Found! Scan the DFS down this path before doing other paths
2857 bltstack.push(m);
2858 break;
2859 }
2860 }
2861 }
2862 }
2863 pre_order++;
2864 }
2865 else if ( !is_postvisited(n) ) {
2866 // Note: build_loop_tree_impl() adds out edges on rare occasions,
2867 // such as com.sun.rsasign.am::a.
2868 // For non-recursive version, first, process current children.
2869 // On next iteration, check if additional children were added.
2870 for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2871 Node* u = n->raw_out(k);
2872 if ( u->is_CFG() && !is_visited(u) ) {
2873 bltstack.push(u);
2874 }
2875 }
2876 if ( bltstack.length() == stack_size ) {
2877 // There were no additional children, post visit node now
2878 (void)bltstack.pop(); // Remove node from stack
2879 pre_order = build_loop_tree_impl( n, pre_order );
2880 // Check for bailout
2881 if (C->failing()) {
2882 return;
2883 }
2884 // Check to grow _preorders[] array for the case when
2885 // build_loop_tree_impl() adds new nodes.
2886 check_grow_preorders();
2887 }
2888 }
2889 else {
2890 (void)bltstack.pop(); // Remove post-visited node from stack
2891 }
2892 }
2893 }
2894
2895 //------------------------------build_loop_tree_impl---------------------------
2896 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2897 // ---- Post-pass Work ----
2898 // Pre-walked but not post-walked nodes need a pre_order number.
2899
2900 // Tightest enclosing loop for this Node
2901 IdealLoopTree *innermost = NULL;
2902
2903 // For all children, see if any edge is a backedge. If so, make a loop
2904 // for it. Then find the tightest enclosing loop for the self Node.
2905 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2906 Node* m = n->fast_out(i); // Child
2907 if( n == m ) continue; // Ignore control self-cycles
2908 if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2909
2910 IdealLoopTree *l; // Child's loop
2911 if( !is_postvisited(m) ) { // Child visited but not post-visited?
2912 // Found a backedge
2913 assert( get_preorder(m) < pre_order, "should be backedge" );
2914 // Check for the RootNode, which is already a LoopNode and is allowed
2915 // to have multiple "backedges".
2916 if( m == C->root()) { // Found the root?
2917 l = _ltree_root; // Root is the outermost LoopNode
2918 } else { // Else found a nested loop
2919 // Insert a LoopNode to mark this loop.
2920 l = new IdealLoopTree(this, m, n);
2921 } // End of Else found a nested loop
2922 if( !has_loop(m) ) // If 'm' does not already have a loop set
2923 set_loop(m, l); // Set loop header to loop now
2924
2925 } else { // Else not a nested loop
2926 if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2927 l = get_loop(m); // Get previously determined loop
2928 // If successor is header of a loop (nest), move up-loop till it
2929 // is a member of some outer enclosing loop. Since there are no
2930 // shared headers (I've split them already) I only need to go up
2931 // at most 1 level.
2932 while( l && l->_head == m ) // Successor heads loop?
2933 l = l->_parent; // Move up 1 for me
2934 // If this loop is not properly parented, then this loop
2935 // has no exit path out, i.e. its an infinite loop.
2936 if( !l ) {
2937 // Make loop "reachable" from root so the CFG is reachable. Basically
2938 // insert a bogus loop exit that is never taken. 'm', the loop head,
2939 // points to 'n', one (of possibly many) fall-in paths. There may be
2940 // many backedges as well.
2941
2942 // Here I set the loop to be the root loop. I could have, after
2943 // inserting a bogus loop exit, restarted the recursion and found my
2944 // new loop exit. This would make the infinite loop a first-class
2945 // loop and it would then get properly optimized. What's the use of
2946 // optimizing an infinite loop?
2947 l = _ltree_root; // Oops, found infinite loop
2948
2949 if (!_verify_only) {
2950 // Insert the NeverBranch between 'm' and it's control user.
2951 NeverBranchNode *iff = new (C) NeverBranchNode( m );
2952 _igvn.register_new_node_with_optimizer(iff);
2953 set_loop(iff, l);
2954 Node *if_t = new (C) CProjNode( iff, 0 );
2955 _igvn.register_new_node_with_optimizer(if_t);
2956 set_loop(if_t, l);
2957
2958 Node* cfg = NULL; // Find the One True Control User of m
2959 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2960 Node* x = m->fast_out(j);
2961 if (x->is_CFG() && x != m && x != iff)
2962 { cfg = x; break; }
2963 }
2964 assert(cfg != NULL, "must find the control user of m");
2965 uint k = 0; // Probably cfg->in(0)
2966 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2967 cfg->set_req( k, if_t ); // Now point to NeverBranch
2968
2969 // Now create the never-taken loop exit
2970 Node *if_f = new (C) CProjNode( iff, 1 );
2971 _igvn.register_new_node_with_optimizer(if_f);
2972 set_loop(if_f, l);
2973 // Find frame ptr for Halt. Relies on the optimizer
2974 // V-N'ing. Easier and quicker than searching through
2975 // the program structure.
2976 Node *frame = new (C) ParmNode( C->start(), TypeFunc::FramePtr );
2977 _igvn.register_new_node_with_optimizer(frame);
2978 // Halt & Catch Fire
2979 Node *halt = new (C) HaltNode( if_f, frame );
2980 _igvn.register_new_node_with_optimizer(halt);
2981 set_loop(halt, l);
2982 C->root()->add_req(halt);
2983 }
2984 set_loop(C->root(), _ltree_root);
2985 }
2986 }
2987 // Weeny check for irreducible. This child was already visited (this
2988 // IS the post-work phase). Is this child's loop header post-visited
2989 // as well? If so, then I found another entry into the loop.
2990 if (!_verify_only) {
2991 while( is_postvisited(l->_head) ) {
2992 // found irreducible
2993 l->_irreducible = 1; // = true
2994 l = l->_parent;
2995 _has_irreducible_loops = true;
2996 // Check for bad CFG here to prevent crash, and bailout of compile
2997 if (l == NULL) {
2998 C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2999 return pre_order;
3000 }
3001 }
3002 C->set_has_irreducible_loop(_has_irreducible_loops);
3003 }
3004
3005 // This Node might be a decision point for loops. It is only if
3006 // it's children belong to several different loops. The sort call
3007 // does a trivial amount of work if there is only 1 child or all
3008 // children belong to the same loop. If however, the children
3009 // belong to different loops, the sort call will properly set the
3010 // _parent pointers to show how the loops nest.
3011 //
3012 // In any case, it returns the tightest enclosing loop.
3013 innermost = sort( l, innermost );
3014 }
3015
3016 // Def-use info will have some dead stuff; dead stuff will have no
3017 // loop decided on.
3018
3019 // Am I a loop header? If so fix up my parent's child and next ptrs.
3020 if( innermost && innermost->_head == n ) {
3021 assert( get_loop(n) == innermost, "" );
3022 IdealLoopTree *p = innermost->_parent;
3023 IdealLoopTree *l = innermost;
3024 while( p && l->_head == n ) {
3025 l->_next = p->_child; // Put self on parents 'next child'
3026 p->_child = l; // Make self as first child of parent
3027 l = p; // Now walk up the parent chain
3028 p = l->_parent;
3029 }
3030 } else {
3031 // Note that it is possible for a LoopNode to reach here, if the
3032 // backedge has been made unreachable (hence the LoopNode no longer
3033 // denotes a Loop, and will eventually be removed).
3034
3035 // Record tightest enclosing loop for self. Mark as post-visited.
3036 set_loop(n, innermost);
3037 // Also record has_call flag early on
3038 if( innermost ) {
3039 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3040 // Do not count uncommon calls
3041 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3042 Node *iff = n->in(0)->in(0);
3043 // No any calls for vectorized loops.
3044 if( UseSuperWord || !iff->is_If() ||
3045 (n->in(0)->Opcode() == Op_IfFalse &&
3046 (1.0 - iff->as_If()->_prob) >= 0.01) ||
3047 (iff->as_If()->_prob >= 0.01) )
3048 innermost->_has_call = 1;
3049 }
3050 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3051 // Disable loop optimizations if the loop has a scalar replaceable
3052 // allocation. This disabling may cause a potential performance lost
3053 // if the allocation is not eliminated for some reason.
3054 innermost->_allow_optimizations = false;
3055 innermost->_has_call = 1; // = true
3056 } else if (n->Opcode() == Op_SafePoint) {
3057 // Record all safepoints in this loop.
3058 if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3059 innermost->_safepts->push(n);
3060 }
3061 }
3062 }
3063
3064 // Flag as post-visited now
3065 set_postvisited(n);
3066 return pre_order;
3067 }
3068
3069
3070 //------------------------------build_loop_early-------------------------------
3071 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3072 // First pass computes the earliest controlling node possible. This is the
3073 // controlling input with the deepest dominating depth.
3074 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3075 while (worklist.size() != 0) {
3076 // Use local variables nstack_top_n & nstack_top_i to cache values
3077 // on nstack's top.
3078 Node *nstack_top_n = worklist.pop();
3079 uint nstack_top_i = 0;
3080 //while_nstack_nonempty:
3081 while (true) {
3082 // Get parent node and next input's index from stack's top.
3083 Node *n = nstack_top_n;
3084 uint i = nstack_top_i;
3085 uint cnt = n->req(); // Count of inputs
3086 if (i == 0) { // Pre-process the node.
3087 if( has_node(n) && // Have either loop or control already?
3088 !has_ctrl(n) ) { // Have loop picked out already?
3089 // During "merge_many_backedges" we fold up several nested loops
3090 // into a single loop. This makes the members of the original
3091 // loop bodies pointing to dead loops; they need to move up
3092 // to the new UNION'd larger loop. I set the _head field of these
3093 // dead loops to NULL and the _parent field points to the owning
3094 // loop. Shades of UNION-FIND algorithm.
3095 IdealLoopTree *ilt;
3096 while( !(ilt = get_loop(n))->_head ) {
3097 // Normally I would use a set_loop here. But in this one special
3098 // case, it is legal (and expected) to change what loop a Node
3099 // belongs to.
3100 _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3101 }
3102 // Remove safepoints ONLY if I've already seen I don't need one.
3103 // (the old code here would yank a 2nd safepoint after seeing a
3104 // first one, even though the 1st did not dominate in the loop body
3105 // and thus could be avoided indefinitely)
3106 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3107 is_deleteable_safept(n)) {
3108 Node *in = n->in(TypeFunc::Control);
3109 lazy_replace(n,in); // Pull safepoint now
3110 if (ilt->_safepts != NULL) {
3111 ilt->_safepts->yank(n);
3112 }
3113 // Carry on with the recursion "as if" we are walking
3114 // only the control input
3115 if( !visited.test_set( in->_idx ) ) {
3116 worklist.push(in); // Visit this guy later, using worklist
3117 }
3118 // Get next node from nstack:
3119 // - skip n's inputs processing by setting i > cnt;
3120 // - we also will not call set_early_ctrl(n) since
3121 // has_node(n) == true (see the condition above).
3122 i = cnt + 1;
3123 }
3124 }
3125 } // if (i == 0)
3126
3127 // Visit all inputs
3128 bool done = true; // Assume all n's inputs will be processed
3129 while (i < cnt) {
3130 Node *in = n->in(i);
3131 ++i;
3132 if (in == NULL) continue;
3133 if (in->pinned() && !in->is_CFG())
3134 set_ctrl(in, in->in(0));
3135 int is_visited = visited.test_set( in->_idx );
3136 if (!has_node(in)) { // No controlling input yet?
3137 assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3138 assert( !is_visited, "visit only once" );
3139 nstack.push(n, i); // Save parent node and next input's index.
3140 nstack_top_n = in; // Process current input now.
3141 nstack_top_i = 0;
3142 done = false; // Not all n's inputs processed.
3143 break; // continue while_nstack_nonempty;
3144 } else if (!is_visited) {
3145 // This guy has a location picked out for him, but has not yet
3146 // been visited. Happens to all CFG nodes, for instance.
3147 // Visit him using the worklist instead of recursion, to break
3148 // cycles. Since he has a location already we do not need to
3149 // find his location before proceeding with the current Node.
3150 worklist.push(in); // Visit this guy later, using worklist
3151 }
3152 }
3153 if (done) {
3154 // All of n's inputs have been processed, complete post-processing.
3155
3156 // Compute earliest point this Node can go.
3157 // CFG, Phi, pinned nodes already know their controlling input.
3158 if (!has_node(n)) {
3159 // Record earliest legal location
3160 set_early_ctrl( n );
3161 }
3162 if (nstack.is_empty()) {
3163 // Finished all nodes on stack.
3164 // Process next node on the worklist.
3165 break;
3166 }
3167 // Get saved parent node and next input's index.
3168 nstack_top_n = nstack.node();
3169 nstack_top_i = nstack.index();
3170 nstack.pop();
3171 }
3172 } // while (true)
3173 }
3174 }
3175
3176 //------------------------------dom_lca_internal--------------------------------
3177 // Pair-wise LCA
3178 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3179 if( !n1 ) return n2; // Handle NULL original LCA
3180 assert( n1->is_CFG(), "" );
3181 assert( n2->is_CFG(), "" );
3182 // find LCA of all uses
3183 uint d1 = dom_depth(n1);
3184 uint d2 = dom_depth(n2);
3185 while (n1 != n2) {
3186 if (d1 > d2) {
3187 n1 = idom(n1);
3188 d1 = dom_depth(n1);
3189 } else if (d1 < d2) {
3190 n2 = idom(n2);
3191 d2 = dom_depth(n2);
3192 } else {
3193 // Here d1 == d2. Due to edits of the dominator-tree, sections
3194 // of the tree might have the same depth. These sections have
3195 // to be searched more carefully.
3196
3197 // Scan up all the n1's with equal depth, looking for n2.
3198 Node *t1 = idom(n1);
3199 while (dom_depth(t1) == d1) {
3200 if (t1 == n2) return n2;
3201 t1 = idom(t1);
3202 }
3203 // Scan up all the n2's with equal depth, looking for n1.
3204 Node *t2 = idom(n2);
3205 while (dom_depth(t2) == d2) {
3206 if (t2 == n1) return n1;
3207 t2 = idom(t2);
3208 }
3209 // Move up to a new dominator-depth value as well as up the dom-tree.
3210 n1 = t1;
3211 n2 = t2;
3212 d1 = dom_depth(n1);
3213 d2 = dom_depth(n2);
3214 }
3215 }
3216 return n1;
3217 }
3218
3219 //------------------------------compute_idom-----------------------------------
3220 // Locally compute IDOM using dom_lca call. Correct only if the incoming
3221 // IDOMs are correct.
3222 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3223 assert( region->is_Region(), "" );
3224 Node *LCA = NULL;
3225 for( uint i = 1; i < region->req(); i++ ) {
3226 if( region->in(i) != C->top() )
3227 LCA = dom_lca( LCA, region->in(i) );
3228 }
3229 return LCA;
3230 }
3231
3232 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3233 bool had_error = false;
3234 #ifdef ASSERT
3235 if (early != C->root()) {
3236 // Make sure that there's a dominance path from LCA to early
3237 Node* d = LCA;
3238 while (d != early) {
3239 if (d == C->root()) {
3240 dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3241 tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3242 had_error = true;
3243 break;
3244 }
3245 d = idom(d);
3246 }
3247 }
3248 #endif
3249 return had_error;
3250 }
3251
3252
3253 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3254 // Compute LCA over list of uses
3255 bool had_error = false;
3256 Node *LCA = NULL;
3257 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3258 Node* c = n->fast_out(i);
3259 if (_nodes[c->_idx] == NULL)
3260 continue; // Skip the occasional dead node
3261 if( c->is_Phi() ) { // For Phis, we must land above on the path
3262 for( uint j=1; j<c->req(); j++ ) {// For all inputs
3263 if( c->in(j) == n ) { // Found matching input?
3264 Node *use = c->in(0)->in(j);
3265 if (_verify_only && use->is_top()) continue;
3266 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3267 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3268 }
3269 }
3270 } else {
3271 // For CFG data-users, use is in the block just prior
3272 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3273 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3274 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3275 }
3276 }
3277 assert(!had_error, "bad dominance");
3278 return LCA;
3279 }
3280
3281 //------------------------------get_late_ctrl----------------------------------
3282 // Compute latest legal control.
3283 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3284 assert(early != NULL, "early control should not be NULL");
3285
3286 Node* LCA = compute_lca_of_uses(n, early);
3287 #ifdef ASSERT
3288 if (LCA == C->root() && LCA != early) {
3289 // def doesn't dominate uses so print some useful debugging output
3290 compute_lca_of_uses(n, early, true);
3291 }
3292 #endif
3293
3294 // if this is a load, check for anti-dependent stores
3295 // We use a conservative algorithm to identify potential interfering
3296 // instructions and for rescheduling the load. The users of the memory
3297 // input of this load are examined. Any use which is not a load and is
3298 // dominated by early is considered a potentially interfering store.
3299 // This can produce false positives.
3300 if (n->is_Load() && LCA != early) {
3301 Node_List worklist;
3302
3303 Node *mem = n->in(MemNode::Memory);
3304 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3305 Node* s = mem->fast_out(i);
3306 worklist.push(s);
3307 }
3308 while(worklist.size() != 0 && LCA != early) {
3309 Node* s = worklist.pop();
3310 if (s->is_Load() ||
3311 (UseShenandoahGC &&
3312 (s->is_ShenandoahBarrier() || s->Opcode() == Op_SafePoint ||
3313 (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)))) {
3314 continue;
3315 } else if (s->is_MergeMem()) {
3316 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3317 Node* s1 = s->fast_out(i);
3318 worklist.push(s1);
3319 }
3320 } else {
3321 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3322 assert(sctrl != NULL || s->outcnt() == 0 || s->is_ShenandoahBarrier(), "must have control");
3323 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3324 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3325 }
3326 }
3327 }
3328 }
3329
3330 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3331 return LCA;
3332 }
3333
3334 // true if CFG node d dominates CFG node n
3335 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3336 if (d == n)
3337 return true;
3338 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3339 uint dd = dom_depth(d);
3340 while (dom_depth(n) >= dd) {
3341 if (n == d)
3342 return true;
3343 n = idom(n);
3344 }
3345 return false;
3346 }
3347
3348 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3349 // Pair-wise LCA with tags.
3350 // Tag each index with the node 'tag' currently being processed
3351 // before advancing up the dominator chain using idom().
3352 // Later calls that find a match to 'tag' know that this path has already
3353 // been considered in the current LCA (which is input 'n1' by convention).
3354 // Since get_late_ctrl() is only called once for each node, the tag array
3355 // does not need to be cleared between calls to get_late_ctrl().
3356 // Algorithm trades a larger constant factor for better asymptotic behavior
3357 //
3358 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3359 uint d1 = dom_depth(n1);
3360 uint d2 = dom_depth(n2);
3361
3362 do {
3363 if (d1 > d2) {
3364 // current lca is deeper than n2
3365 _dom_lca_tags.map(n1->_idx, tag);
3366 n1 = idom(n1);
3367 d1 = dom_depth(n1);
3368 } else if (d1 < d2) {
3369 // n2 is deeper than current lca
3370 Node *memo = _dom_lca_tags[n2->_idx];
3371 if( memo == tag ) {
3372 return n1; // Return the current LCA
3373 }
3374 _dom_lca_tags.map(n2->_idx, tag);
3375 n2 = idom(n2);
3376 d2 = dom_depth(n2);
3377 } else {
3378 // Here d1 == d2. Due to edits of the dominator-tree, sections
3379 // of the tree might have the same depth. These sections have
3380 // to be searched more carefully.
3381
3382 // Scan up all the n1's with equal depth, looking for n2.
3383 _dom_lca_tags.map(n1->_idx, tag);
3384 Node *t1 = idom(n1);
3385 while (dom_depth(t1) == d1) {
3386 if (t1 == n2) return n2;
3387 _dom_lca_tags.map(t1->_idx, tag);
3388 t1 = idom(t1);
3389 }
3390 // Scan up all the n2's with equal depth, looking for n1.
3391 _dom_lca_tags.map(n2->_idx, tag);
3392 Node *t2 = idom(n2);
3393 while (dom_depth(t2) == d2) {
3394 if (t2 == n1) return n1;
3395 _dom_lca_tags.map(t2->_idx, tag);
3396 t2 = idom(t2);
3397 }
3398 // Move up to a new dominator-depth value as well as up the dom-tree.
3399 n1 = t1;
3400 n2 = t2;
3401 d1 = dom_depth(n1);
3402 d2 = dom_depth(n2);
3403 }
3404 } while (n1 != n2);
3405 return n1;
3406 }
3407
3408 //------------------------------init_dom_lca_tags------------------------------
3409 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3410 // Intended use does not involve any growth for the array, so it could
3411 // be of fixed size.
3412 void PhaseIdealLoop::init_dom_lca_tags() {
3413 uint limit = C->unique() + 1;
3414 _dom_lca_tags.map( limit, NULL );
3415 #ifdef ASSERT
3416 for( uint i = 0; i < limit; ++i ) {
3417 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3418 }
3419 #endif // ASSERT
3420 }
3421
3422 //------------------------------clear_dom_lca_tags------------------------------
3423 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3424 // Intended use does not involve any growth for the array, so it could
3425 // be of fixed size.
3426 void PhaseIdealLoop::clear_dom_lca_tags() {
3427 uint limit = C->unique() + 1;
3428 _dom_lca_tags.map( limit, NULL );
3429 _dom_lca_tags.clear();
3430 #ifdef ASSERT
3431 for( uint i = 0; i < limit; ++i ) {
3432 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3433 }
3434 #endif // ASSERT
3435 }
3436
3437 //------------------------------build_loop_late--------------------------------
3438 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3439 // Second pass finds latest legal placement, and ideal loop placement.
3440 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3441 while (worklist.size() != 0) {
3442 Node *n = worklist.pop();
3443 // Only visit once
3444 if (visited.test_set(n->_idx)) continue;
3445 uint cnt = n->outcnt();
3446 uint i = 0;
3447 while (true) {
3448 assert( _nodes[n->_idx], "no dead nodes" );
3449 // Visit all children
3450 if (i < cnt) {
3451 Node* use = n->raw_out(i);
3452 ++i;
3453 // Check for dead uses. Aggressively prune such junk. It might be
3454 // dead in the global sense, but still have local uses so I cannot
3455 // easily call 'remove_dead_node'.
3456 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3457 // Due to cycles, we might not hit the same fixed point in the verify
3458 // pass as we do in the regular pass. Instead, visit such phis as
3459 // simple uses of the loop head.
3460 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3461 if( !visited.test(use->_idx) )
3462 worklist.push(use);
3463 } else if( !visited.test_set(use->_idx) ) {
3464 nstack.push(n, i); // Save parent and next use's index.
3465 n = use; // Process all children of current use.
3466 cnt = use->outcnt();
3467 i = 0;
3468 }
3469 } else {
3470 // Do not visit around the backedge of loops via data edges.
3471 // push dead code onto a worklist
3472 _deadlist.push(use);
3473 }
3474 } else {
3475 // All of n's children have been processed, complete post-processing.
3476 build_loop_late_post(n);
3477 if (nstack.is_empty()) {
3478 // Finished all nodes on stack.
3479 // Process next node on the worklist.
3480 break;
3481 }
3482 // Get saved parent node and next use's index. Visit the rest of uses.
3483 n = nstack.node();
3484 cnt = n->outcnt();
3485 i = nstack.index();
3486 nstack.pop();
3487 }
3488 }
3489 }
3490 }
3491
3492 //------------------------------build_loop_late_post---------------------------
3493 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3494 // Second pass finds latest legal placement, and ideal loop placement.
3495 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3496
3497 if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3498 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops.
3499 }
3500
3501 #ifdef ASSERT
3502 if (_verify_only && !n->is_CFG()) {
3503 // Check def-use domination.
3504 compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
3505 }
3506 #endif
3507
3508 // CFG and pinned nodes already handled
3509 if( n->in(0) ) {
3510 if( n->in(0)->is_top() ) return; // Dead?
3511
3512 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3513 // _must_ be pinned (they have to observe their control edge of course).
3514 // Unlike Stores (which modify an unallocable resource, the memory
3515 // state), Mods/Loads can float around. So free them up.
3516 bool pinned = true;
3517 switch( n->Opcode() ) {
3518 case Op_DivI:
3519 case Op_DivF:
3520 case Op_DivD:
3521 case Op_ModI:
3522 case Op_ModF:
3523 case Op_ModD:
3524 case Op_LoadB: // Same with Loads; they can sink
3525 case Op_LoadUB: // during loop optimizations.
3526 case Op_LoadUS:
3527 case Op_LoadD:
3528 case Op_LoadF:
3529 case Op_LoadI:
3530 case Op_LoadKlass:
3531 case Op_LoadNKlass:
3532 case Op_LoadL:
3533 case Op_LoadS:
3534 case Op_LoadP:
3535 case Op_LoadN:
3536 case Op_LoadRange:
3537 case Op_LoadD_unaligned:
3538 case Op_LoadL_unaligned:
3539 case Op_StrComp: // Does a bunch of load-like effects
3540 case Op_StrEquals:
3541 case Op_StrIndexOf:
3542 case Op_AryEq:
3543 case Op_ShenandoahReadBarrier:
3544 case Op_ShenandoahWriteBarrier:
3545 case Op_ShenandoahWBMemProj:
3546 pinned = false;
3547 }
3548 if( pinned ) {
3549 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3550 if( !chosen_loop->_child ) // Inner loop?
3551 chosen_loop->_body.push(n); // Collect inner loops
3552 return;
3553 }
3554 } else { // No slot zero
3555 if( n->is_CFG() ) { // CFG with no slot 0 is dead
3556 _nodes.map(n->_idx,0); // No block setting, it's globally dead
3557 return;
3558 }
3559 assert(!n->is_CFG() || n->outcnt() == 0, "");
3560 }
3561
3562 // Do I have a "safe range" I can select over?
3563 Node *early = get_ctrl(n);// Early location already computed
3564
3565 // Compute latest point this Node can go
3566 Node *LCA = get_late_ctrl( n, early );
3567 // LCA is NULL due to uses being dead
3568 if( LCA == NULL ) {
3569 #ifdef ASSERT
3570 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3571 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3572 }
3573 #endif
3574 _nodes.map(n->_idx, 0); // This node is useless
3575 _deadlist.push(n);
3576 return;
3577 }
3578 assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3579
3580 Node *legal = LCA; // Walk 'legal' up the IDOM chain
3581 Node *least = legal; // Best legal position so far
3582 while( early != legal ) { // While not at earliest legal
3583 #ifdef ASSERT
3584 if (legal->is_Start() && !early->is_Root()) {
3585 // Bad graph. Print idom path and fail.
3586 dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
3587 assert(false, "Bad graph detected in build_loop_late");
3588 }
3589 #endif
3590 // Find least loop nesting depth
3591 legal = idom(legal); // Bump up the IDOM tree
3592 // Check for lower nesting depth
3593 if( get_loop(legal)->_nest < get_loop(least)->_nest )
3594 least = legal;
3595 }
3596 assert(early == legal || legal != C->root(), "bad dominance of inputs");
3597
3598 // Try not to place code on a loop entry projection
3599 // which can inhibit range check elimination.
3600 if (least != early) {
3601 Node* ctrl_out = least->unique_ctrl_out();
3602 if (UseShenandoahGC &&
3603 ctrl_out && ctrl_out->is_Loop() &&
3604 least == ctrl_out->in(LoopNode::EntryControl)) {
3605 Node* new_ctrl = least;
3606 if (find_predicate_insertion_point(new_ctrl, Deoptimization::Reason_loop_limit_check) != NULL) {
3607 new_ctrl = new_ctrl->in(0)->in(0);
3608 assert(is_dominator(early, new_ctrl), "least != early so we can move up the dominator tree");
3609 }
3610 if (find_predicate_insertion_point(new_ctrl, Deoptimization::Reason_predicate) != NULL) {
3611 Node* c = new_ctrl->in(0)->in(0);
3612 assert(is_dominator(early, c), "least != early so we can move up the dominator tree");
3613 new_ctrl = c;
3614 }
3615 if (new_ctrl != least) {
3616 least = new_ctrl;
3617 } else if (ctrl_out->is_CountedLoop()) {
3618 Node* least_dom = idom(least);
3619 if (get_loop(least_dom)->is_member(get_loop(least))) {
3620 least = least_dom;
3621 }
3622 }
3623 } else if (ctrl_out && ctrl_out->is_CountedLoop() &&
3624 least == ctrl_out->in(LoopNode::EntryControl)) {
3625 Node* least_dom = idom(least);
3626 if (get_loop(least_dom)->is_member(get_loop(least))) {
3627 least = least_dom;
3628 }
3629 }
3630 }
3631
3632 #ifdef ASSERT
3633 // If verifying, verify that 'verify_me' has a legal location
3634 // and choose it as our location.
3635 if( _verify_me ) {
3636 Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3637 Node *legal = LCA;
3638 while( early != legal ) { // While not at earliest legal
3639 if( legal == v_ctrl ) break; // Check for prior good location
3640 legal = idom(legal) ;// Bump up the IDOM tree
3641 }
3642 // Check for prior good location
3643 if( legal == v_ctrl ) least = legal; // Keep prior if found
3644 }
3645 #endif
3646
3647 // Assign discovered "here or above" point
3648 least = find_non_split_ctrl(least);
3649 set_ctrl(n, least);
3650
3651 // Collect inner loop bodies
3652 IdealLoopTree *chosen_loop = get_loop(least);
3653 if( !chosen_loop->_child ) // Inner loop?
3654 chosen_loop->_body.push(n);// Collect inner loops
3655
3656 if (n->Opcode() == Op_ShenandoahWriteBarrier) {
3657 // The write barrier and its memory proj must have the same
3658 // control otherwise some loop opts could put nodes (Phis) between
3659 // them
3660 Node* proj = n->find_out_with(Op_ShenandoahWBMemProj);
3661 if (proj != NULL) {
3662 set_ctrl_and_loop(proj, least);
3663 }
3664 }
3665 }
3666
3667 #ifdef ASSERT
3668 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
3669 tty->print_cr("%s", msg);
3670 tty->print("n: "); n->dump();
3671 tty->print("early(n): "); early->dump();
3672 if (n->in(0) != NULL && !n->in(0)->is_top() &&
3673 n->in(0) != early && !n->in(0)->is_Root()) {
3674 tty->print("n->in(0): "); n->in(0)->dump();
3675 }
3676 for (uint i = 1; i < n->req(); i++) {
3677 Node* in1 = n->in(i);
3678 if (in1 != NULL && in1 != n && !in1->is_top()) {
3679 tty->print("n->in(%d): ", i); in1->dump();
3680 Node* in1_early = get_ctrl(in1);
3681 tty->print("early(n->in(%d)): ", i); in1_early->dump();
3682 if (in1->in(0) != NULL && !in1->in(0)->is_top() &&
3683 in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
3684 tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
3685 }
3686 for (uint j = 1; j < in1->req(); j++) {
3687 Node* in2 = in1->in(j);
3688 if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
3689 tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
3690 Node* in2_early = get_ctrl(in2);
3691 tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
3692 if (in2->in(0) != NULL && !in2->in(0)->is_top() &&
3693 in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
3694 tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
3695 }
3696 }
3697 }
3698 }
3699 }
3700 tty->cr();
3701 tty->print("LCA(n): "); LCA->dump();
3702 for (uint i = 0; i < n->outcnt(); i++) {
3703 Node* u1 = n->raw_out(i);
3704 if (u1 == n)
3705 continue;
3706 tty->print("n->out(%d): ", i); u1->dump();
3707 if (u1->is_CFG()) {
3708 for (uint j = 0; j < u1->outcnt(); j++) {
3709 Node* u2 = u1->raw_out(j);
3710 if (u2 != u1 && u2 != n && u2->is_CFG()) {
3711 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3712 }
3713 }
3714 } else {
3715 Node* u1_later = get_ctrl(u1);
3716 tty->print("later(n->out(%d)): ", i); u1_later->dump();
3717 if (u1->in(0) != NULL && !u1->in(0)->is_top() &&
3718 u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
3719 tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
3720 }
3721 for (uint j = 0; j < u1->outcnt(); j++) {
3722 Node* u2 = u1->raw_out(j);
3723 if (u2 == n || u2 == u1)
3724 continue;
3725 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3726 if (!u2->is_CFG()) {
3727 Node* u2_later = get_ctrl(u2);
3728 tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
3729 if (u2->in(0) != NULL && !u2->in(0)->is_top() &&
3730 u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
3731 tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
3732 }
3733 }
3734 }
3735 }
3736 }
3737 tty->cr();
3738 int ct = 0;
3739 Node *dbg_legal = LCA;
3740 while(!dbg_legal->is_Start() && ct < 100) {
3741 tty->print("idom[%d] ",ct); dbg_legal->dump();
3742 ct++;
3743 dbg_legal = idom(dbg_legal);
3744 }
3745 tty->cr();
3746 }
3747 #endif
3748
3749 #ifndef PRODUCT
3750 //------------------------------dump-------------------------------------------
3751 void PhaseIdealLoop::dump( ) const {
3752 ResourceMark rm;
3753 Arena* arena = Thread::current()->resource_area();
3754 Node_Stack stack(arena, C->live_nodes() >> 2);
3755 Node_List rpo_list;
3756 VectorSet visited(arena);
3757 visited.set(C->top()->_idx);
3758 rpo( C->root(), stack, visited, rpo_list );
3759 // Dump root loop indexed by last element in PO order
3760 dump( _ltree_root, rpo_list.size(), rpo_list );
3761 }
3762
3763 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3764 loop->dump_head();
3765
3766 // Now scan for CFG nodes in the same loop
3767 for( uint j=idx; j > 0; j-- ) {
3768 Node *n = rpo_list[j-1];
3769 if( !_nodes[n->_idx] ) // Skip dead nodes
3770 continue;
3771 if( get_loop(n) != loop ) { // Wrong loop nest
3772 if( get_loop(n)->_head == n && // Found nested loop?
3773 get_loop(n)->_parent == loop )
3774 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly
3775 continue;
3776 }
3777
3778 // Dump controlling node
3779 for( uint x = 0; x < loop->_nest; x++ )
3780 tty->print(" ");
3781 tty->print("C");
3782 if( n == C->root() ) {
3783 n->dump();
3784 } else {
3785 Node* cached_idom = idom_no_update(n);
3786 Node *computed_idom = n->in(0);
3787 if( n->is_Region() ) {
3788 computed_idom = compute_idom(n);
3789 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3790 // any MultiBranch ctrl node), so apply a similar transform to
3791 // the cached idom returned from idom_no_update.
3792 cached_idom = find_non_split_ctrl(cached_idom);
3793 }
3794 tty->print(" ID:%d",computed_idom->_idx);
3795 n->dump();
3796 if( cached_idom != computed_idom ) {
3797 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d",
3798 computed_idom->_idx, cached_idom->_idx);
3799 }
3800 }
3801 // Dump nodes it controls
3802 for( uint k = 0; k < _nodes.Size(); k++ ) {
3803 // (k < C->unique() && get_ctrl(find(k)) == n)
3804 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3805 Node *m = C->root()->find(k);
3806 if( m && m->outcnt() > 0 ) {
3807 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3808 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p",
3809 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3810 }
3811 for( uint j = 0; j < loop->_nest; j++ )
3812 tty->print(" ");
3813 tty->print(" ");
3814 m->dump();
3815 }
3816 }
3817 }
3818 }
3819 }
3820 #endif
3821
3822 // Collect a R-P-O for the whole CFG.
3823 // Result list is in post-order (scan backwards for RPO)
3824 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3825 stk.push(start, 0);
3826 visited.set(start->_idx);
3827
3828 while (stk.is_nonempty()) {
3829 Node* m = stk.node();
3830 uint idx = stk.index();
3831 if (idx < m->outcnt()) {
3832 stk.set_index(idx + 1);
3833 Node* n = m->raw_out(idx);
3834 if (n->is_CFG() && !visited.test_set(n->_idx)) {
3835 stk.push(n, 0);
3836 }
3837 } else {
3838 rpo_list.push(m);
3839 stk.pop();
3840 }
3841 }
3842 }
3843
3844
3845 //=============================================================================
3846 //------------------------------LoopTreeIterator-----------------------------------
3847
3848 // Advance to next loop tree using a preorder, left-to-right traversal.
3849 void LoopTreeIterator::next() {
3850 assert(!done(), "must not be done.");
3851 if (_curnt->_child != NULL) {
3852 _curnt = _curnt->_child;
3853 } else if (_curnt->_next != NULL) {
3854 _curnt = _curnt->_next;
3855 } else {
3856 while (_curnt != _root && _curnt->_next == NULL) {
3857 _curnt = _curnt->_parent;
3858 }
3859 if (_curnt == _root) {
3860 _curnt = NULL;
3861 assert(done(), "must be done.");
3862 } else {
3863 assert(_curnt->_next != NULL, "must be more to do");
3864 _curnt = _curnt->_next;
3865 }
3866 }
3867 }