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