1 /*
2 * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciMethodData.hpp"
27 #include "compiler/compileLog.hpp"
28 #include "libadt/vectset.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "opto/addnode.hpp"
31 #include "opto/callnode.hpp"
32 #include "opto/connode.hpp"
33 #include "opto/convertnode.hpp"
34 #include "opto/divnode.hpp"
35 #include "opto/idealGraphPrinter.hpp"
36 #include "opto/loopnode.hpp"
37 #include "opto/mulnode.hpp"
38 #include "opto/rootnode.hpp"
39 #include "opto/superword.hpp"
40
41 //=============================================================================
42 //------------------------------is_loop_iv-------------------------------------
43 // Determine if a node is Counted loop induction variable.
44 // The method is declared in node.hpp.
45 const Node* Node::is_loop_iv() const {
46 if (this->is_Phi() && !this->as_Phi()->is_copy() &&
47 this->as_Phi()->region()->is_CountedLoop() &&
48 this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
49 return this;
50 } else {
51 return NULL;
52 }
53 }
54
55 //=============================================================================
56 //------------------------------dump_spec--------------------------------------
57 // Dump special per-node info
58 #ifndef PRODUCT
59 void LoopNode::dump_spec(outputStream *st) const {
60 if (is_inner_loop()) st->print( "inner " );
61 if (is_partial_peel_loop()) st->print( "partial_peel " );
62 if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
63 }
64 #endif
65
66 //------------------------------is_valid_counted_loop-------------------------
67 bool LoopNode::is_valid_counted_loop() const {
68 if (is_CountedLoop()) {
69 CountedLoopNode* l = as_CountedLoop();
70 CountedLoopEndNode* le = l->loopexit();
71 if (le != NULL &&
72 le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
73 Node* phi = l->phi();
74 Node* exit = le->proj_out(0 /* false */);
75 if (exit != NULL && exit->Opcode() == Op_IfFalse &&
76 phi != NULL && phi->is_Phi() &&
77 phi->in(LoopNode::LoopBackControl) == l->incr() &&
78 le->loopnode() == l && le->stride_is_con()) {
79 return true;
80 }
81 }
82 }
83 return false;
84 }
85
86 //------------------------------get_early_ctrl---------------------------------
87 // Compute earliest legal control
88 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
89 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
90 uint i;
91 Node *early;
92 if (n->in(0) && !n->is_expensive()) {
93 early = n->in(0);
94 if (!early->is_CFG()) // Might be a non-CFG multi-def
95 early = get_ctrl(early); // So treat input as a straight data input
96 i = 1;
97 } else {
98 early = get_ctrl(n->in(1));
99 i = 2;
100 }
101 uint e_d = dom_depth(early);
102 assert( early, "" );
103 for (; i < n->req(); i++) {
104 Node *cin = get_ctrl(n->in(i));
105 assert( cin, "" );
106 // Keep deepest dominator depth
107 uint c_d = dom_depth(cin);
108 if (c_d > e_d) { // Deeper guy?
109 early = cin; // Keep deepest found so far
110 e_d = c_d;
111 } else if (c_d == e_d && // Same depth?
112 early != cin) { // If not equal, must use slower algorithm
113 // If same depth but not equal, one _must_ dominate the other
114 // and we want the deeper (i.e., dominated) guy.
115 Node *n1 = early;
116 Node *n2 = cin;
117 while (1) {
118 n1 = idom(n1); // Walk up until break cycle
119 n2 = idom(n2);
120 if (n1 == cin || // Walked early up to cin
121 dom_depth(n2) < c_d)
122 break; // early is deeper; keep him
123 if (n2 == early || // Walked cin up to early
124 dom_depth(n1) < c_d) {
125 early = cin; // cin is deeper; keep him
126 break;
127 }
128 }
129 e_d = dom_depth(early); // Reset depth register cache
130 }
131 }
132
133 // Return earliest legal location
134 assert(early == find_non_split_ctrl(early), "unexpected early control");
135
136 if (n->is_expensive() && !_verify_only && !_verify_me) {
137 assert(n->in(0), "should have control input");
138 early = get_early_ctrl_for_expensive(n, early);
139 }
140
141 return early;
142 }
143
144 //------------------------------get_early_ctrl_for_expensive---------------------------------
145 // Move node up the dominator tree as high as legal while still beneficial
146 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
147 assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
148 assert(OptimizeExpensiveOps, "optimization off?");
149
150 Node* ctl = n->in(0);
151 assert(ctl->is_CFG(), "expensive input 0 must be cfg");
152 uint min_dom_depth = dom_depth(earliest);
153 #ifdef ASSERT
154 if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
155 dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
156 assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
157 }
158 #endif
159 if (dom_depth(ctl) < min_dom_depth) {
160 return earliest;
161 }
162
163 while (1) {
164 Node *next = ctl;
165 // Moving the node out of a loop on the projection of a If
166 // confuses loop predication. So once we hit a Loop in a If branch
167 // that doesn't branch to an UNC, we stop. The code that process
168 // expensive nodes will notice the loop and skip over it to try to
169 // move the node further up.
170 if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
171 if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
172 break;
173 }
174 next = idom(ctl->in(1)->in(0));
175 } else if (ctl->is_Proj()) {
176 // We only move it up along a projection if the projection is
177 // the single control projection for its parent: same code path,
178 // if it's a If with UNC or fallthrough of a call.
179 Node* parent_ctl = ctl->in(0);
180 if (parent_ctl == NULL) {
181 break;
182 } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
183 next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
184 } else if (parent_ctl->is_If()) {
185 if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
186 break;
187 }
188 assert(idom(ctl) == parent_ctl, "strange");
189 next = idom(parent_ctl);
190 } else if (ctl->is_CatchProj()) {
191 if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
192 break;
193 }
194 assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
195 next = parent_ctl->in(0)->in(0)->in(0);
196 } else {
197 // Check if parent control has a single projection (this
198 // control is the only possible successor of the parent
199 // control). If so, we can try to move the node above the
200 // parent control.
201 int nb_ctl_proj = 0;
202 for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
203 Node *p = parent_ctl->fast_out(i);
204 if (p->is_Proj() && p->is_CFG()) {
205 nb_ctl_proj++;
206 if (nb_ctl_proj > 1) {
207 break;
208 }
209 }
210 }
211
212 if (nb_ctl_proj > 1) {
213 break;
214 }
215 assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
216 assert(idom(ctl) == parent_ctl, "strange");
217 next = idom(parent_ctl);
218 }
219 } else {
220 next = idom(ctl);
221 }
222 if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
223 break;
224 }
225 ctl = next;
226 }
227
228 if (ctl != n->in(0)) {
229 _igvn.replace_input_of(n, 0, ctl);
230 _igvn.hash_insert(n);
231 }
232
233 return ctl;
234 }
235
236
237 //------------------------------set_early_ctrl---------------------------------
238 // Set earliest legal control
239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
240 Node *early = get_early_ctrl(n);
241
242 // Record earliest legal location
243 set_ctrl(n, early);
244 }
245
246 //------------------------------set_subtree_ctrl-------------------------------
247 // set missing _ctrl entries on new nodes
248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
249 // Already set? Get out.
250 if( _nodes[n->_idx] ) return;
251 // Recursively set _nodes array to indicate where the Node goes
252 uint i;
253 for( i = 0; i < n->req(); ++i ) {
254 Node *m = n->in(i);
255 if( m && m != C->root() )
256 set_subtree_ctrl( m );
257 }
258
259 // Fixup self
260 set_early_ctrl( n );
261 }
262
263 //------------------------------is_counted_loop--------------------------------
264 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
265 PhaseGVN *gvn = &_igvn;
266
267 // Counted loop head must be a good RegionNode with only 3 not NULL
268 // control input edges: Self, Entry, LoopBack.
269 if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
270 return false;
271 }
272 Node *init_control = x->in(LoopNode::EntryControl);
273 Node *back_control = x->in(LoopNode::LoopBackControl);
274 if (init_control == NULL || back_control == NULL) // Partially dead
275 return false;
276 // Must also check for TOP when looking for a dead loop
277 if (init_control->is_top() || back_control->is_top())
278 return false;
279
280 // Allow funny placement of Safepoint
281 if (back_control->Opcode() == Op_SafePoint)
282 back_control = back_control->in(TypeFunc::Control);
283
284 // Controlling test for loop
285 Node *iftrue = back_control;
286 uint iftrue_op = iftrue->Opcode();
287 if (iftrue_op != Op_IfTrue &&
288 iftrue_op != Op_IfFalse)
289 // I have a weird back-control. Probably the loop-exit test is in
290 // the middle of the loop and I am looking at some trailing control-flow
291 // merge point. To fix this I would have to partially peel the loop.
292 return false; // Obscure back-control
293
294 // Get boolean guarding loop-back test
295 Node *iff = iftrue->in(0);
296 if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
297 return false;
298 BoolNode *test = iff->in(1)->as_Bool();
299 BoolTest::mask bt = test->_test._test;
300 float cl_prob = iff->as_If()->_prob;
301 if (iftrue_op == Op_IfFalse) {
302 bt = BoolTest(bt).negate();
303 cl_prob = 1.0 - cl_prob;
304 }
305 // Get backedge compare
306 Node *cmp = test->in(1);
307 int cmp_op = cmp->Opcode();
308 if (cmp_op != Op_CmpI)
309 return false; // Avoid pointer & float compares
310
311 // Find the trip-counter increment & limit. Limit must be loop invariant.
312 Node *incr = cmp->in(1);
313 Node *limit = cmp->in(2);
314
315 // ---------
316 // need 'loop()' test to tell if limit is loop invariant
317 // ---------
318
319 if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
320 Node *tmp = incr; // Then reverse order into the CmpI
321 incr = limit;
322 limit = tmp;
323 bt = BoolTest(bt).commute(); // And commute the exit test
324 }
325 if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
326 return false;
327 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
328 return false;
329
330 Node* phi_incr = NULL;
331 // Trip-counter increment must be commutative & associative.
332 if (incr->Opcode() == Op_CastII) {
333 incr = incr->in(1);
334 }
335 if (incr->is_Phi()) {
336 if (incr->as_Phi()->region() != x || incr->req() != 3)
337 return false; // Not simple trip counter expression
338 phi_incr = incr;
339 incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
340 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
341 return false;
342 }
343
344 Node* trunc1 = NULL;
345 Node* trunc2 = NULL;
346 const TypeInt* iv_trunc_t = NULL;
347 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
348 return false; // Funny increment opcode
349 }
350 assert(incr->Opcode() == Op_AddI, "wrong increment code");
351
352 // Get merge point
353 Node *xphi = incr->in(1);
354 Node *stride = incr->in(2);
355 if (!stride->is_Con()) { // Oops, swap these
356 if (!xphi->is_Con()) // Is the other guy a constant?
357 return false; // Nope, unknown stride, bail out
358 Node *tmp = xphi; // 'incr' is commutative, so ok to swap
359 xphi = stride;
360 stride = tmp;
361 }
362 if (xphi->Opcode() == Op_CastII) {
363 xphi = xphi->in(1);
364 }
365 // Stride must be constant
366 int stride_con = stride->get_int();
367 if (stride_con == 0)
368 return false; // missed some peephole opt
369
370 if (!xphi->is_Phi())
371 return false; // Too much math on the trip counter
372 if (phi_incr != NULL && phi_incr != xphi)
373 return false;
374 PhiNode *phi = xphi->as_Phi();
375
376 // Phi must be of loop header; backedge must wrap to increment
377 if (phi->region() != x)
378 return false;
379 if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
380 trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
381 return false;
382 }
383 Node *init_trip = phi->in(LoopNode::EntryControl);
384
385 // If iv trunc type is smaller than int, check for possible wrap.
386 if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
387 assert(trunc1 != NULL, "must have found some truncation");
388
389 // Get a better type for the phi (filtered thru if's)
390 const TypeInt* phi_ft = filtered_type(phi);
391
392 // Can iv take on a value that will wrap?
393 //
394 // Ensure iv's limit is not within "stride" of the wrap value.
395 //
396 // Example for "short" type
397 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
398 // If the stride is +10, then the last value of the induction
399 // variable before the increment (phi_ft->_hi) must be
400 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
401 // ensure no truncation occurs after the increment.
402
403 if (stride_con > 0) {
404 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
405 iv_trunc_t->_lo > phi_ft->_lo) {
406 return false; // truncation may occur
407 }
408 } else if (stride_con < 0) {
409 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
410 iv_trunc_t->_hi < phi_ft->_hi) {
411 return false; // truncation may occur
412 }
413 }
414 // No possibility of wrap so truncation can be discarded
415 // Promote iv type to Int
416 } else {
417 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
418 }
419
420 // If the condition is inverted and we will be rolling
421 // through MININT to MAXINT, then bail out.
422 if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
423 // Odd stride
424 bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
425 // Count down loop rolls through MAXINT
426 (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
427 // Count up loop rolls through MININT
428 (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
429 return false; // Bail out
430 }
431
432 const TypeInt* init_t = gvn->type(init_trip)->is_int();
433 const TypeInt* limit_t = gvn->type(limit)->is_int();
434
435 if (stride_con > 0) {
436 jlong init_p = (jlong)init_t->_lo + stride_con;
437 if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
438 return false; // cyclic loop or this loop trips only once
439 } else {
440 jlong init_p = (jlong)init_t->_hi + stride_con;
441 if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
442 return false; // cyclic loop or this loop trips only once
443 }
444
445 if (phi_incr != NULL) {
446 // check if there is a possiblity of IV overflowing after the first increment
447 if (stride_con > 0) {
448 if (init_t->_hi > max_jint - stride_con) {
449 return false;
450 }
451 } else {
452 if (init_t->_lo < min_jint - stride_con) {
453 return false;
454 }
455 }
456 }
457
458 // =================================================
459 // ---- SUCCESS! Found A Trip-Counted Loop! -----
460 //
461 assert(x->Opcode() == Op_Loop, "regular loops only");
462 C->print_method(PHASE_BEFORE_CLOOPS, 3);
463
464 Node *hook = new Node(6);
465
466 if (LoopLimitCheck) {
467
468 // ===================================================
469 // Generate loop limit check to avoid integer overflow
470 // in cases like next (cyclic loops):
471 //
472 // for (i=0; i <= max_jint; i++) {}
473 // for (i=0; i < max_jint; i+=2) {}
474 //
475 //
476 // Limit check predicate depends on the loop test:
477 //
478 // for(;i != limit; i++) --> limit <= (max_jint)
479 // for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1)
480 // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride )
481 //
482
483 // Check if limit is excluded to do more precise int overflow check.
484 bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
485 int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
486
487 // If compare points directly to the phi we need to adjust
488 // the compare so that it points to the incr. Limit have
489 // to be adjusted to keep trip count the same and the
490 // adjusted limit should be checked for int overflow.
491 if (phi_incr != NULL) {
492 stride_m += stride_con;
493 }
494
495 if (limit->is_Con()) {
496 int limit_con = limit->get_int();
497 if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
498 (stride_con < 0 && limit_con < (min_jint - stride_m))) {
499 // Bailout: it could be integer overflow.
500 return false;
501 }
502 } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
503 (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
504 // Limit's type may satisfy the condition, for example,
505 // when it is an array length.
506 } else {
507 // Generate loop's limit check.
508 // Loop limit check predicate should be near the loop.
509 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
510 if (!limit_check_proj) {
511 // The limit check predicate is not generated if this method trapped here before.
512 #ifdef ASSERT
513 if (TraceLoopLimitCheck) {
514 tty->print("missing loop limit check:");
515 loop->dump_head();
516 x->dump(1);
517 }
518 #endif
519 return false;
520 }
521
522 IfNode* check_iff = limit_check_proj->in(0)->as_If();
523 Node* cmp_limit;
524 Node* bol;
525
526 if (stride_con > 0) {
527 cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
528 bol = new BoolNode(cmp_limit, BoolTest::le);
529 } else {
530 cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
531 bol = new BoolNode(cmp_limit, BoolTest::ge);
532 }
533 cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
534 bol = _igvn.register_new_node_with_optimizer(bol);
535 set_subtree_ctrl(bol);
536
537 // Replace condition in original predicate but preserve Opaque node
538 // so that previous predicates could be found.
539 assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
540 check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
541 Node* opq = check_iff->in(1)->in(1);
542 _igvn.replace_input_of(opq, 1, bol);
543 // Update ctrl.
544 set_ctrl(opq, check_iff->in(0));
545 set_ctrl(check_iff->in(1), check_iff->in(0));
546
547 #ifndef PRODUCT
548 // report that the loop predication has been actually performed
549 // for this loop
550 if (TraceLoopLimitCheck) {
551 tty->print_cr("Counted Loop Limit Check generated:");
552 debug_only( bol->dump(2); )
553 }
554 #endif
555 }
556
557 if (phi_incr != NULL) {
558 // If compare points directly to the phi we need to adjust
559 // the compare so that it points to the incr. Limit have
560 // to be adjusted to keep trip count the same and we
561 // should avoid int overflow.
562 //
563 // i = init; do {} while(i++ < limit);
564 // is converted to
565 // i = init; do {} while(++i < limit+1);
566 //
567 limit = gvn->transform(new AddINode(limit, stride));
568 }
569
570 // Now we need to canonicalize loop condition.
571 if (bt == BoolTest::ne) {
572 assert(stride_con == 1 || stride_con == -1, "simple increment only");
573 // 'ne' can be replaced with 'lt' only when init < limit.
574 if (stride_con > 0 && init_t->_hi < limit_t->_lo)
575 bt = BoolTest::lt;
576 // 'ne' can be replaced with 'gt' only when init > limit.
577 if (stride_con < 0 && init_t->_lo > limit_t->_hi)
578 bt = BoolTest::gt;
579 }
580
581 if (incl_limit) {
582 // The limit check guaranties that 'limit <= (max_jint - stride)' so
583 // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
584 //
585 Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
586 limit = gvn->transform(new AddINode(limit, one));
587 if (bt == BoolTest::le)
588 bt = BoolTest::lt;
589 else if (bt == BoolTest::ge)
590 bt = BoolTest::gt;
591 else
592 ShouldNotReachHere();
593 }
594 set_subtree_ctrl( limit );
595
596 } else { // LoopLimitCheck
597
598 // If compare points to incr, we are ok. Otherwise the compare
599 // can directly point to the phi; in this case adjust the compare so that
600 // it points to the incr by adjusting the limit.
601 if (cmp->in(1) == phi || cmp->in(2) == phi)
602 limit = gvn->transform(new AddINode(limit,stride));
603
604 // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
605 // Final value for iterator should be: trip_count * stride + init_trip.
606 Node *one_p = gvn->intcon( 1);
607 Node *one_m = gvn->intcon(-1);
608
609 Node *trip_count = NULL;
610 switch( bt ) {
611 case BoolTest::eq:
612 ShouldNotReachHere();
613 case BoolTest::ne: // Ahh, the case we desire
614 if (stride_con == 1)
615 trip_count = gvn->transform(new SubINode(limit,init_trip));
616 else if (stride_con == -1)
617 trip_count = gvn->transform(new SubINode(init_trip,limit));
618 else
619 ShouldNotReachHere();
620 set_subtree_ctrl(trip_count);
621 //_loop.map(trip_count->_idx,loop(limit));
622 break;
623 case BoolTest::le: // Maybe convert to '<' case
624 limit = gvn->transform(new AddINode(limit,one_p));
625 set_subtree_ctrl( limit );
626 hook->init_req(4, limit);
627
628 bt = BoolTest::lt;
629 // Make the new limit be in the same loop nest as the old limit
630 //_loop.map(limit->_idx,limit_loop);
631 // Fall into next case
632 case BoolTest::lt: { // Maybe convert to '!=' case
633 if (stride_con < 0) // Count down loop rolls through MAXINT
634 ShouldNotReachHere();
635 Node *range = gvn->transform(new SubINode(limit,init_trip));
636 set_subtree_ctrl( range );
637 hook->init_req(0, range);
638
639 Node *bias = gvn->transform(new AddINode(range,stride));
640 set_subtree_ctrl( bias );
641 hook->init_req(1, bias);
642
643 Node *bias1 = gvn->transform(new AddINode(bias,one_m));
644 set_subtree_ctrl( bias1 );
645 hook->init_req(2, bias1);
646
647 trip_count = gvn->transform(new DivINode(0,bias1,stride));
648 set_subtree_ctrl( trip_count );
649 hook->init_req(3, trip_count);
650 break;
651 }
652
653 case BoolTest::ge: // Maybe convert to '>' case
654 limit = gvn->transform(new AddINode(limit,one_m));
655 set_subtree_ctrl( limit );
656 hook->init_req(4 ,limit);
657
658 bt = BoolTest::gt;
659 // Make the new limit be in the same loop nest as the old limit
660 //_loop.map(limit->_idx,limit_loop);
661 // Fall into next case
662 case BoolTest::gt: { // Maybe convert to '!=' case
663 if (stride_con > 0) // count up loop rolls through MININT
664 ShouldNotReachHere();
665 Node *range = gvn->transform(new SubINode(limit,init_trip));
666 set_subtree_ctrl( range );
667 hook->init_req(0, range);
668
669 Node *bias = gvn->transform(new AddINode(range,stride));
670 set_subtree_ctrl( bias );
671 hook->init_req(1, bias);
672
673 Node *bias1 = gvn->transform(new AddINode(bias,one_p));
674 set_subtree_ctrl( bias1 );
675 hook->init_req(2, bias1);
676
677 trip_count = gvn->transform(new DivINode(0,bias1,stride));
678 set_subtree_ctrl( trip_count );
679 hook->init_req(3, trip_count);
680 break;
681 }
682 } // switch( bt )
683
684 Node *span = gvn->transform(new MulINode(trip_count,stride));
685 set_subtree_ctrl( span );
686 hook->init_req(5, span);
687
688 limit = gvn->transform(new AddINode(span,init_trip));
689 set_subtree_ctrl( limit );
690
691 } // LoopLimitCheck
692
693 if (!UseCountedLoopSafepoints) {
694 // Check for SafePoint on backedge and remove
695 Node *sfpt = x->in(LoopNode::LoopBackControl);
696 if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
697 lazy_replace( sfpt, iftrue );
698 if (loop->_safepts != NULL) {
699 loop->_safepts->yank(sfpt);
700 }
701 loop->_tail = iftrue;
702 }
703 }
704
705 // Build a canonical trip test.
706 // Clone code, as old values may be in use.
707 incr = incr->clone();
708 incr->set_req(1,phi);
709 incr->set_req(2,stride);
710 incr = _igvn.register_new_node_with_optimizer(incr);
711 set_early_ctrl( incr );
712 _igvn.rehash_node_delayed(phi);
713 phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
714
715 // If phi type is more restrictive than Int, raise to
716 // Int to prevent (almost) infinite recursion in igvn
717 // which can only handle integer types for constants or minint..maxint.
718 if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
719 Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
720 nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
721 nphi = _igvn.register_new_node_with_optimizer(nphi);
722 set_ctrl(nphi, get_ctrl(phi));
723 _igvn.replace_node(phi, nphi);
724 phi = nphi->as_Phi();
725 }
726 cmp = cmp->clone();
727 cmp->set_req(1,incr);
728 cmp->set_req(2,limit);
729 cmp = _igvn.register_new_node_with_optimizer(cmp);
730 set_ctrl(cmp, iff->in(0));
731
732 test = test->clone()->as_Bool();
733 (*(BoolTest*)&test->_test)._test = bt;
734 test->set_req(1,cmp);
735 _igvn.register_new_node_with_optimizer(test);
736 set_ctrl(test, iff->in(0));
737
738 // Replace the old IfNode with a new LoopEndNode
739 Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
740 IfNode *le = lex->as_If();
741 uint dd = dom_depth(iff);
742 set_idom(le, le->in(0), dd); // Update dominance for loop exit
743 set_loop(le, loop);
744
745 // Get the loop-exit control
746 Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
747
748 // Need to swap loop-exit and loop-back control?
749 if (iftrue_op == Op_IfFalse) {
750 Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
751 Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
752
753 loop->_tail = back_control = ift2;
754 set_loop(ift2, loop);
755 set_loop(iff2, get_loop(iffalse));
756
757 // Lazy update of 'get_ctrl' mechanism.
758 lazy_replace_proj( iffalse, iff2 );
759 lazy_replace_proj( iftrue, ift2 );
760
761 // Swap names
762 iffalse = iff2;
763 iftrue = ift2;
764 } else {
765 _igvn.rehash_node_delayed(iffalse);
766 _igvn.rehash_node_delayed(iftrue);
767 iffalse->set_req_X( 0, le, &_igvn );
768 iftrue ->set_req_X( 0, le, &_igvn );
769 }
770
771 set_idom(iftrue, le, dd+1);
772 set_idom(iffalse, le, dd+1);
773 assert(iff->outcnt() == 0, "should be dead now");
774 lazy_replace( iff, le ); // fix 'get_ctrl'
775
776 // Now setup a new CountedLoopNode to replace the existing LoopNode
777 CountedLoopNode *l = new CountedLoopNode(init_control, back_control);
778 l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
779 // The following assert is approximately true, and defines the intention
780 // of can_be_counted_loop. It fails, however, because phase->type
781 // is not yet initialized for this loop and its parts.
782 //assert(l->can_be_counted_loop(this), "sanity");
783 _igvn.register_new_node_with_optimizer(l);
784 set_loop(l, loop);
785 loop->_head = l;
786 // Fix all data nodes placed at the old loop head.
787 // Uses the lazy-update mechanism of 'get_ctrl'.
788 lazy_replace( x, l );
789 set_idom(l, init_control, dom_depth(x));
790
791 if (!UseCountedLoopSafepoints) {
792 // Check for immediately preceding SafePoint and remove
793 Node *sfpt2 = le->in(0);
794 if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
795 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
796 if (loop->_safepts != NULL) {
797 loop->_safepts->yank(sfpt2);
798 }
799 }
800 }
801
802 // Free up intermediate goo
803 _igvn.remove_dead_node(hook);
804
805 #ifdef ASSERT
806 assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
807 assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
808 #endif
809 #ifndef PRODUCT
810 if (TraceLoopOpts) {
811 tty->print("Counted ");
812 loop->dump_head();
813 }
814 #endif
815
816 C->print_method(PHASE_AFTER_CLOOPS, 3);
817
818 return true;
819 }
820
821 //----------------------exact_limit-------------------------------------------
822 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
823 assert(loop->_head->is_CountedLoop(), "");
824 CountedLoopNode *cl = loop->_head->as_CountedLoop();
825 assert(cl->is_valid_counted_loop(), "");
826
827 if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
828 cl->limit()->Opcode() == Op_LoopLimit) {
829 // Old code has exact limit (it could be incorrect in case of int overflow).
830 // Loop limit is exact with stride == 1. And loop may already have exact limit.
831 return cl->limit();
832 }
833 Node *limit = NULL;
834 #ifdef ASSERT
835 BoolTest::mask bt = cl->loopexit()->test_trip();
836 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
837 #endif
838 if (cl->has_exact_trip_count()) {
839 // Simple case: loop has constant boundaries.
840 // Use jlongs to avoid integer overflow.
841 int stride_con = cl->stride_con();
842 jlong init_con = cl->init_trip()->get_int();
843 jlong limit_con = cl->limit()->get_int();
844 julong trip_cnt = cl->trip_count();
845 jlong final_con = init_con + trip_cnt*stride_con;
846 int final_int = (int)final_con;
847 // The final value should be in integer range since the loop
848 // is counted and the limit was checked for overflow.
849 assert(final_con == (jlong)final_int, "final value should be integer");
850 limit = _igvn.intcon(final_int);
851 } else {
852 // Create new LoopLimit node to get exact limit (final iv value).
853 limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
854 register_new_node(limit, cl->in(LoopNode::EntryControl));
855 }
856 assert(limit != NULL, "sanity");
857 return limit;
858 }
859
860 //------------------------------Ideal------------------------------------------
861 // Return a node which is more "ideal" than the current node.
862 // Attempt to convert into a counted-loop.
863 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
864 if (!can_be_counted_loop(phase)) {
865 phase->C->set_major_progress();
866 }
867 return RegionNode::Ideal(phase, can_reshape);
868 }
869
870
871 //=============================================================================
872 //------------------------------Ideal------------------------------------------
873 // Return a node which is more "ideal" than the current node.
874 // Attempt to convert into a counted-loop.
875 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
876 return RegionNode::Ideal(phase, can_reshape);
877 }
878
879 //------------------------------dump_spec--------------------------------------
880 // Dump special per-node info
881 #ifndef PRODUCT
882 void CountedLoopNode::dump_spec(outputStream *st) const {
883 LoopNode::dump_spec(st);
884 if (stride_is_con()) {
885 st->print("stride: %d ",stride_con());
886 }
887 if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
888 if (is_main_loop()) st->print("main of N%d", _idx);
889 if (is_post_loop()) st->print("post of N%d", _main_idx);
890 }
891 #endif
892
893 //=============================================================================
894 int CountedLoopEndNode::stride_con() const {
895 return stride()->bottom_type()->is_int()->get_con();
896 }
897
898 //=============================================================================
899 //------------------------------Value-----------------------------------------
900 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
901 const Type* init_t = phase->type(in(Init));
902 const Type* limit_t = phase->type(in(Limit));
903 const Type* stride_t = phase->type(in(Stride));
904 // Either input is TOP ==> the result is TOP
905 if (init_t == Type::TOP) return Type::TOP;
906 if (limit_t == Type::TOP) return Type::TOP;
907 if (stride_t == Type::TOP) return Type::TOP;
908
909 int stride_con = stride_t->is_int()->get_con();
910 if (stride_con == 1)
911 return NULL; // Identity
912
913 if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
914 // Use jlongs to avoid integer overflow.
915 jlong init_con = init_t->is_int()->get_con();
916 jlong limit_con = limit_t->is_int()->get_con();
917 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
918 jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
919 jlong final_con = init_con + stride_con*trip_count;
920 int final_int = (int)final_con;
921 // The final value should be in integer range since the loop
922 // is counted and the limit was checked for overflow.
923 assert(final_con == (jlong)final_int, "final value should be integer");
924 return TypeInt::make(final_int);
925 }
926
927 return bottom_type(); // TypeInt::INT
928 }
929
930 //------------------------------Ideal------------------------------------------
931 // Return a node which is more "ideal" than the current node.
932 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
933 if (phase->type(in(Init)) == Type::TOP ||
934 phase->type(in(Limit)) == Type::TOP ||
935 phase->type(in(Stride)) == Type::TOP)
936 return NULL; // Dead
937
938 int stride_con = phase->type(in(Stride))->is_int()->get_con();
939 if (stride_con == 1)
940 return NULL; // Identity
941
942 if (in(Init)->is_Con() && in(Limit)->is_Con())
943 return NULL; // Value
944
945 // Delay following optimizations until all loop optimizations
946 // done to keep Ideal graph simple.
947 if (!can_reshape || phase->C->major_progress())
948 return NULL;
949
950 const TypeInt* init_t = phase->type(in(Init) )->is_int();
951 const TypeInt* limit_t = phase->type(in(Limit))->is_int();
952 int stride_p;
953 jlong lim, ini;
954 julong max;
955 if (stride_con > 0) {
956 stride_p = stride_con;
957 lim = limit_t->_hi;
958 ini = init_t->_lo;
959 max = (julong)max_jint;
960 } else {
961 stride_p = -stride_con;
962 lim = init_t->_hi;
963 ini = limit_t->_lo;
964 max = (julong)min_jint;
965 }
966 julong range = lim - ini + stride_p;
967 if (range <= max) {
968 // Convert to integer expression if it is not overflow.
969 Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
970 Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
971 Node *bias = phase->transform(new AddINode(range, stride_m));
972 Node *trip = phase->transform(new DivINode(0, bias, in(Stride)));
973 Node *span = phase->transform(new MulINode(trip, in(Stride)));
974 return new AddINode(span, in(Init)); // exact limit
975 }
976
977 if (is_power_of_2(stride_p) || // divisor is 2^n
978 !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
979 // Convert to long expression to avoid integer overflow
980 // and let igvn optimizer convert this division.
981 //
982 Node* init = phase->transform( new ConvI2LNode(in(Init)));
983 Node* limit = phase->transform( new ConvI2LNode(in(Limit)));
984 Node* stride = phase->longcon(stride_con);
985 Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
986
987 Node *range = phase->transform(new SubLNode(limit, init));
988 Node *bias = phase->transform(new AddLNode(range, stride_m));
989 Node *span;
990 if (stride_con > 0 && is_power_of_2(stride_p)) {
991 // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
992 // and avoid generating rounding for division. Zero trip guard should
993 // guarantee that init < limit but sometimes the guard is missing and
994 // we can get situation when init > limit. Note, for the empty loop
995 // optimization zero trip guard is generated explicitly which leaves
996 // only RCE predicate where exact limit is used and the predicate
997 // will simply fail forcing recompilation.
998 Node* neg_stride = phase->longcon(-stride_con);
999 span = phase->transform(new AndLNode(bias, neg_stride));
1000 } else {
1001 Node *trip = phase->transform(new DivLNode(0, bias, stride));
1002 span = phase->transform(new MulLNode(trip, stride));
1003 }
1004 // Convert back to int
1005 Node *span_int = phase->transform(new ConvL2INode(span));
1006 return new AddINode(span_int, in(Init)); // exact limit
1007 }
1008
1009 return NULL; // No progress
1010 }
1011
1012 //------------------------------Identity---------------------------------------
1013 // If stride == 1 return limit node.
1014 Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
1015 int stride_con = phase->type(in(Stride))->is_int()->get_con();
1016 if (stride_con == 1 || stride_con == -1)
1017 return in(Limit);
1018 return this;
1019 }
1020
1021 //=============================================================================
1022 //----------------------match_incr_with_optional_truncation--------------------
1023 // Match increment with optional truncation:
1024 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1025 // Return NULL for failure. Success returns the increment node.
1026 Node* CountedLoopNode::match_incr_with_optional_truncation(
1027 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1028 // Quick cutouts:
1029 if (expr == NULL || expr->req() != 3) return NULL;
1030
1031 Node *t1 = NULL;
1032 Node *t2 = NULL;
1033 const TypeInt* trunc_t = TypeInt::INT;
1034 Node* n1 = expr;
1035 int n1op = n1->Opcode();
1036
1037 // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1038 if (n1op == Op_AndI &&
1039 n1->in(2)->is_Con() &&
1040 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1041 // %%% This check should match any mask of 2**K-1.
1042 t1 = n1;
1043 n1 = t1->in(1);
1044 n1op = n1->Opcode();
1045 trunc_t = TypeInt::CHAR;
1046 } else if (n1op == Op_RShiftI &&
1047 n1->in(1) != NULL &&
1048 n1->in(1)->Opcode() == Op_LShiftI &&
1049 n1->in(2) == n1->in(1)->in(2) &&
1050 n1->in(2)->is_Con()) {
1051 jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1052 // %%% This check should match any shift in [1..31].
1053 if (shift == 16 || shift == 8) {
1054 t1 = n1;
1055 t2 = t1->in(1);
1056 n1 = t2->in(1);
1057 n1op = n1->Opcode();
1058 if (shift == 16) {
1059 trunc_t = TypeInt::SHORT;
1060 } else if (shift == 8) {
1061 trunc_t = TypeInt::BYTE;
1062 }
1063 }
1064 }
1065
1066 // If (maybe after stripping) it is an AddI, we won:
1067 if (n1op == Op_AddI) {
1068 *trunc1 = t1;
1069 *trunc2 = t2;
1070 *trunc_type = trunc_t;
1071 return n1;
1072 }
1073
1074 // failed
1075 return NULL;
1076 }
1077
1078
1079 //------------------------------filtered_type--------------------------------
1080 // Return a type based on condition control flow
1081 // A successful return will be a type that is restricted due
1082 // to a series of dominating if-tests, such as:
1083 // if (i < 10) {
1084 // if (i > 0) {
1085 // here: "i" type is [1..10)
1086 // }
1087 // }
1088 // or a control flow merge
1089 // if (i < 10) {
1090 // do {
1091 // phi( , ) -- at top of loop type is [min_int..10)
1092 // i = ?
1093 // } while ( i < 10)
1094 //
1095 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1096 assert(n && n->bottom_type()->is_int(), "must be int");
1097 const TypeInt* filtered_t = NULL;
1098 if (!n->is_Phi()) {
1099 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1100 filtered_t = filtered_type_from_dominators(n, n_ctrl);
1101
1102 } else {
1103 Node* phi = n->as_Phi();
1104 Node* region = phi->in(0);
1105 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1106 if (region && region != C->top()) {
1107 for (uint i = 1; i < phi->req(); i++) {
1108 Node* val = phi->in(i);
1109 Node* use_c = region->in(i);
1110 const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1111 if (val_t != NULL) {
1112 if (filtered_t == NULL) {
1113 filtered_t = val_t;
1114 } else {
1115 filtered_t = filtered_t->meet(val_t)->is_int();
1116 }
1117 }
1118 }
1119 }
1120 }
1121 const TypeInt* n_t = _igvn.type(n)->is_int();
1122 if (filtered_t != NULL) {
1123 n_t = n_t->join(filtered_t)->is_int();
1124 }
1125 return n_t;
1126 }
1127
1128
1129 //------------------------------filtered_type_from_dominators--------------------------------
1130 // Return a possibly more restrictive type for val based on condition control flow of dominators
1131 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1132 if (val->is_Con()) {
1133 return val->bottom_type()->is_int();
1134 }
1135 uint if_limit = 10; // Max number of dominating if's visited
1136 const TypeInt* rtn_t = NULL;
1137
1138 if (use_ctrl && use_ctrl != C->top()) {
1139 Node* val_ctrl = get_ctrl(val);
1140 uint val_dom_depth = dom_depth(val_ctrl);
1141 Node* pred = use_ctrl;
1142 uint if_cnt = 0;
1143 while (if_cnt < if_limit) {
1144 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1145 if_cnt++;
1146 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1147 if (if_t != NULL) {
1148 if (rtn_t == NULL) {
1149 rtn_t = if_t;
1150 } else {
1151 rtn_t = rtn_t->join(if_t)->is_int();
1152 }
1153 }
1154 }
1155 pred = idom(pred);
1156 if (pred == NULL || pred == C->top()) {
1157 break;
1158 }
1159 // Stop if going beyond definition block of val
1160 if (dom_depth(pred) < val_dom_depth) {
1161 break;
1162 }
1163 }
1164 }
1165 return rtn_t;
1166 }
1167
1168
1169 //------------------------------dump_spec--------------------------------------
1170 // Dump special per-node info
1171 #ifndef PRODUCT
1172 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1173 if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1174 BoolTest bt( test_trip()); // Added this for g++.
1175
1176 st->print("[");
1177 bt.dump_on(st);
1178 st->print("]");
1179 }
1180 st->print(" ");
1181 IfNode::dump_spec(st);
1182 }
1183 #endif
1184
1185 //=============================================================================
1186 //------------------------------is_member--------------------------------------
1187 // Is 'l' a member of 'this'?
1188 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1189 while( l->_nest > _nest ) l = l->_parent;
1190 return l == this;
1191 }
1192
1193 //------------------------------set_nest---------------------------------------
1194 // Set loop tree nesting depth. Accumulate _has_call bits.
1195 int IdealLoopTree::set_nest( uint depth ) {
1196 _nest = depth;
1197 int bits = _has_call;
1198 if( _child ) bits |= _child->set_nest(depth+1);
1199 if( bits ) _has_call = 1;
1200 if( _next ) bits |= _next ->set_nest(depth );
1201 return bits;
1202 }
1203
1204 //------------------------------split_fall_in----------------------------------
1205 // Split out multiple fall-in edges from the loop header. Move them to a
1206 // private RegionNode before the loop. This becomes the loop landing pad.
1207 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1208 PhaseIterGVN &igvn = phase->_igvn;
1209 uint i;
1210
1211 // Make a new RegionNode to be the landing pad.
1212 Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1213 phase->set_loop(landing_pad,_parent);
1214 // Gather all the fall-in control paths into the landing pad
1215 uint icnt = fall_in_cnt;
1216 uint oreq = _head->req();
1217 for( i = oreq-1; i>0; i-- )
1218 if( !phase->is_member( this, _head->in(i) ) )
1219 landing_pad->set_req(icnt--,_head->in(i));
1220
1221 // Peel off PhiNode edges as well
1222 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1223 Node *oj = _head->fast_out(j);
1224 if( oj->is_Phi() ) {
1225 PhiNode* old_phi = oj->as_Phi();
1226 assert( old_phi->region() == _head, "" );
1227 igvn.hash_delete(old_phi); // Yank from hash before hacking edges
1228 Node *p = PhiNode::make_blank(landing_pad, old_phi);
1229 uint icnt = fall_in_cnt;
1230 for( i = oreq-1; i>0; i-- ) {
1231 if( !phase->is_member( this, _head->in(i) ) ) {
1232 p->init_req(icnt--, old_phi->in(i));
1233 // Go ahead and clean out old edges from old phi
1234 old_phi->del_req(i);
1235 }
1236 }
1237 // Search for CSE's here, because ZKM.jar does a lot of
1238 // loop hackery and we need to be a little incremental
1239 // with the CSE to avoid O(N^2) node blow-up.
1240 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1241 if( p2 ) { // Found CSE
1242 p->destruct(); // Recover useless new node
1243 p = p2; // Use old node
1244 } else {
1245 igvn.register_new_node_with_optimizer(p, old_phi);
1246 }
1247 // Make old Phi refer to new Phi.
1248 old_phi->add_req(p);
1249 // Check for the special case of making the old phi useless and
1250 // disappear it. In JavaGrande I have a case where this useless
1251 // Phi is the loop limit and prevents recognizing a CountedLoop
1252 // which in turn prevents removing an empty loop.
1253 Node *id_old_phi = old_phi->Identity( &igvn );
1254 if( id_old_phi != old_phi ) { // Found a simple identity?
1255 // Note that I cannot call 'replace_node' here, because
1256 // that will yank the edge from old_phi to the Region and
1257 // I'm mid-iteration over the Region's uses.
1258 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1259 Node* use = old_phi->last_out(i);
1260 igvn.rehash_node_delayed(use);
1261 uint uses_found = 0;
1262 for (uint j = 0; j < use->len(); j++) {
1263 if (use->in(j) == old_phi) {
1264 if (j < use->req()) use->set_req (j, id_old_phi);
1265 else use->set_prec(j, id_old_phi);
1266 uses_found++;
1267 }
1268 }
1269 i -= uses_found; // we deleted 1 or more copies of this edge
1270 }
1271 }
1272 igvn._worklist.push(old_phi);
1273 }
1274 }
1275 // Finally clean out the fall-in edges from the RegionNode
1276 for( i = oreq-1; i>0; i-- ) {
1277 if( !phase->is_member( this, _head->in(i) ) ) {
1278 _head->del_req(i);
1279 }
1280 }
1281 igvn.rehash_node_delayed(_head);
1282 // Transform landing pad
1283 igvn.register_new_node_with_optimizer(landing_pad, _head);
1284 // Insert landing pad into the header
1285 _head->add_req(landing_pad);
1286 }
1287
1288 //------------------------------split_outer_loop-------------------------------
1289 // Split out the outermost loop from this shared header.
1290 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1291 PhaseIterGVN &igvn = phase->_igvn;
1292
1293 // Find index of outermost loop; it should also be my tail.
1294 uint outer_idx = 1;
1295 while( _head->in(outer_idx) != _tail ) outer_idx++;
1296
1297 // Make a LoopNode for the outermost loop.
1298 Node *ctl = _head->in(LoopNode::EntryControl);
1299 Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1300 outer = igvn.register_new_node_with_optimizer(outer, _head);
1301 phase->set_created_loop_node();
1302
1303 // Outermost loop falls into '_head' loop
1304 _head->set_req(LoopNode::EntryControl, outer);
1305 _head->del_req(outer_idx);
1306 // Split all the Phis up between '_head' loop and 'outer' loop.
1307 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1308 Node *out = _head->fast_out(j);
1309 if( out->is_Phi() ) {
1310 PhiNode *old_phi = out->as_Phi();
1311 assert( old_phi->region() == _head, "" );
1312 Node *phi = PhiNode::make_blank(outer, old_phi);
1313 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl));
1314 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1315 phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1316 // Make old Phi point to new Phi on the fall-in path
1317 igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1318 old_phi->del_req(outer_idx);
1319 }
1320 }
1321
1322 // Use the new loop head instead of the old shared one
1323 _head = outer;
1324 phase->set_loop(_head, this);
1325 }
1326
1327 //------------------------------fix_parent-------------------------------------
1328 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1329 loop->_parent = parent;
1330 if( loop->_child ) fix_parent( loop->_child, loop );
1331 if( loop->_next ) fix_parent( loop->_next , parent );
1332 }
1333
1334 //------------------------------estimate_path_freq-----------------------------
1335 static float estimate_path_freq( Node *n ) {
1336 // Try to extract some path frequency info
1337 IfNode *iff;
1338 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1339 uint nop = n->Opcode();
1340 if( nop == Op_SafePoint ) { // Skip any safepoint
1341 n = n->in(0);
1342 continue;
1343 }
1344 if( nop == Op_CatchProj ) { // Get count from a prior call
1345 // Assume call does not always throw exceptions: means the call-site
1346 // count is also the frequency of the fall-through path.
1347 assert( n->is_CatchProj(), "" );
1348 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1349 return 0.0f; // Assume call exception path is rare
1350 Node *call = n->in(0)->in(0)->in(0);
1351 assert( call->is_Call(), "expect a call here" );
1352 const JVMState *jvms = ((CallNode*)call)->jvms();
1353 ciMethodData* methodData = jvms->method()->method_data();
1354 if (!methodData->is_mature()) return 0.0f; // No call-site data
1355 ciProfileData* data = methodData->bci_to_data(jvms->bci());
1356 if ((data == NULL) || !data->is_CounterData()) {
1357 // no call profile available, try call's control input
1358 n = n->in(0);
1359 continue;
1360 }
1361 return data->as_CounterData()->count()/FreqCountInvocations;
1362 }
1363 // See if there's a gating IF test
1364 Node *n_c = n->in(0);
1365 if( !n_c->is_If() ) break; // No estimate available
1366 iff = n_c->as_If();
1367 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count?
1368 // Compute how much count comes on this path
1369 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1370 // Have no count info. Skip dull uncommon-trap like branches.
1371 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) ||
1372 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1373 break;
1374 // Skip through never-taken branch; look for a real loop exit.
1375 n = iff->in(0);
1376 }
1377 return 0.0f; // No estimate available
1378 }
1379
1380 //------------------------------merge_many_backedges---------------------------
1381 // Merge all the backedges from the shared header into a private Region.
1382 // Feed that region as the one backedge to this loop.
1383 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1384 uint i;
1385
1386 // Scan for the top 2 hottest backedges
1387 float hotcnt = 0.0f;
1388 float warmcnt = 0.0f;
1389 uint hot_idx = 0;
1390 // Loop starts at 2 because slot 1 is the fall-in path
1391 for( i = 2; i < _head->req(); i++ ) {
1392 float cnt = estimate_path_freq(_head->in(i));
1393 if( cnt > hotcnt ) { // Grab hottest path
1394 warmcnt = hotcnt;
1395 hotcnt = cnt;
1396 hot_idx = i;
1397 } else if( cnt > warmcnt ) { // And 2nd hottest path
1398 warmcnt = cnt;
1399 }
1400 }
1401
1402 // See if the hottest backedge is worthy of being an inner loop
1403 // by being much hotter than the next hottest backedge.
1404 if( hotcnt <= 0.0001 ||
1405 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1406
1407 // Peel out the backedges into a private merge point; peel
1408 // them all except optionally hot_idx.
1409 PhaseIterGVN &igvn = phase->_igvn;
1410
1411 Node *hot_tail = NULL;
1412 // Make a Region for the merge point
1413 Node *r = new RegionNode(1);
1414 for( i = 2; i < _head->req(); i++ ) {
1415 if( i != hot_idx )
1416 r->add_req( _head->in(i) );
1417 else hot_tail = _head->in(i);
1418 }
1419 igvn.register_new_node_with_optimizer(r, _head);
1420 // Plug region into end of loop _head, followed by hot_tail
1421 while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1422 igvn.replace_input_of(_head, 2, r);
1423 if( hot_idx ) _head->add_req(hot_tail);
1424
1425 // Split all the Phis up between '_head' loop and the Region 'r'
1426 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1427 Node *out = _head->fast_out(j);
1428 if( out->is_Phi() ) {
1429 PhiNode* n = out->as_Phi();
1430 igvn.hash_delete(n); // Delete from hash before hacking edges
1431 Node *hot_phi = NULL;
1432 Node *phi = new PhiNode(r, n->type(), n->adr_type());
1433 // Check all inputs for the ones to peel out
1434 uint j = 1;
1435 for( uint i = 2; i < n->req(); i++ ) {
1436 if( i != hot_idx )
1437 phi->set_req( j++, n->in(i) );
1438 else hot_phi = n->in(i);
1439 }
1440 // Register the phi but do not transform until whole place transforms
1441 igvn.register_new_node_with_optimizer(phi, n);
1442 // Add the merge phi to the old Phi
1443 while( n->req() > 3 ) n->del_req( n->req()-1 );
1444 igvn.replace_input_of(n, 2, phi);
1445 if( hot_idx ) n->add_req(hot_phi);
1446 }
1447 }
1448
1449
1450 // Insert a new IdealLoopTree inserted below me. Turn it into a clone
1451 // of self loop tree. Turn self into a loop headed by _head and with
1452 // tail being the new merge point.
1453 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1454 phase->set_loop(_tail,ilt); // Adjust tail
1455 _tail = r; // Self's tail is new merge point
1456 phase->set_loop(r,this);
1457 ilt->_child = _child; // New guy has my children
1458 _child = ilt; // Self has new guy as only child
1459 ilt->_parent = this; // new guy has self for parent
1460 ilt->_nest = _nest; // Same nesting depth (for now)
1461
1462 // Starting with 'ilt', look for child loop trees using the same shared
1463 // header. Flatten these out; they will no longer be loops in the end.
1464 IdealLoopTree **pilt = &_child;
1465 while( ilt ) {
1466 if( ilt->_head == _head ) {
1467 uint i;
1468 for( i = 2; i < _head->req(); i++ )
1469 if( _head->in(i) == ilt->_tail )
1470 break; // Still a loop
1471 if( i == _head->req() ) { // No longer a loop
1472 // Flatten ilt. Hang ilt's "_next" list from the end of
1473 // ilt's '_child' list. Move the ilt's _child up to replace ilt.
1474 IdealLoopTree **cp = &ilt->_child;
1475 while( *cp ) cp = &(*cp)->_next; // Find end of child list
1476 *cp = ilt->_next; // Hang next list at end of child list
1477 *pilt = ilt->_child; // Move child up to replace ilt
1478 ilt->_head = NULL; // Flag as a loop UNIONED into parent
1479 ilt = ilt->_child; // Repeat using new ilt
1480 continue; // do not advance over ilt->_child
1481 }
1482 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1483 phase->set_loop(_head,ilt);
1484 }
1485 pilt = &ilt->_child; // Advance to next
1486 ilt = *pilt;
1487 }
1488
1489 if( _child ) fix_parent( _child, this );
1490 }
1491
1492 //------------------------------beautify_loops---------------------------------
1493 // Split shared headers and insert loop landing pads.
1494 // Insert a LoopNode to replace the RegionNode.
1495 // Return TRUE if loop tree is structurally changed.
1496 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1497 bool result = false;
1498 // Cache parts in locals for easy
1499 PhaseIterGVN &igvn = phase->_igvn;
1500
1501 igvn.hash_delete(_head); // Yank from hash before hacking edges
1502
1503 // Check for multiple fall-in paths. Peel off a landing pad if need be.
1504 int fall_in_cnt = 0;
1505 for( uint i = 1; i < _head->req(); i++ )
1506 if( !phase->is_member( this, _head->in(i) ) )
1507 fall_in_cnt++;
1508 assert( fall_in_cnt, "at least 1 fall-in path" );
1509 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins
1510 split_fall_in( phase, fall_in_cnt );
1511
1512 // Swap inputs to the _head and all Phis to move the fall-in edge to
1513 // the left.
1514 fall_in_cnt = 1;
1515 while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1516 fall_in_cnt++;
1517 if( fall_in_cnt > 1 ) {
1518 // Since I am just swapping inputs I do not need to update def-use info
1519 Node *tmp = _head->in(1);
1520 igvn.rehash_node_delayed(_head);
1521 _head->set_req( 1, _head->in(fall_in_cnt) );
1522 _head->set_req( fall_in_cnt, tmp );
1523 // Swap also all Phis
1524 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1525 Node* phi = _head->fast_out(i);
1526 if( phi->is_Phi() ) {
1527 igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
1528 tmp = phi->in(1);
1529 phi->set_req( 1, phi->in(fall_in_cnt) );
1530 phi->set_req( fall_in_cnt, tmp );
1531 }
1532 }
1533 }
1534 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1535 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" );
1536
1537 // If I am a shared header (multiple backedges), peel off the many
1538 // backedges into a private merge point and use the merge point as
1539 // the one true backedge.
1540 if( _head->req() > 3 ) {
1541 // Merge the many backedges into a single backedge but leave
1542 // the hottest backedge as separate edge for the following peel.
1543 merge_many_backedges( phase );
1544 result = true;
1545 }
1546
1547 // If I have one hot backedge, peel off myself loop.
1548 // I better be the outermost loop.
1549 if (_head->req() > 3 && !_irreducible) {
1550 split_outer_loop( phase );
1551 result = true;
1552
1553 } else if (!_head->is_Loop() && !_irreducible) {
1554 // Make a new LoopNode to replace the old loop head
1555 Node *l = new LoopNode( _head->in(1), _head->in(2) );
1556 l = igvn.register_new_node_with_optimizer(l, _head);
1557 phase->set_created_loop_node();
1558 // Go ahead and replace _head
1559 phase->_igvn.replace_node( _head, l );
1560 _head = l;
1561 phase->set_loop(_head, this);
1562 }
1563
1564 // Now recursively beautify nested loops
1565 if( _child ) result |= _child->beautify_loops( phase );
1566 if( _next ) result |= _next ->beautify_loops( phase );
1567 return result;
1568 }
1569
1570 //------------------------------allpaths_check_safepts----------------------------
1571 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1572 // encountered. Helper for check_safepts.
1573 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1574 assert(stack.size() == 0, "empty stack");
1575 stack.push(_tail);
1576 visited.Clear();
1577 visited.set(_tail->_idx);
1578 while (stack.size() > 0) {
1579 Node* n = stack.pop();
1580 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1581 // Terminate this path
1582 } else if (n->Opcode() == Op_SafePoint) {
1583 if (_phase->get_loop(n) != this) {
1584 if (_required_safept == NULL) _required_safept = new Node_List();
1585 _required_safept->push(n); // save the one closest to the tail
1586 }
1587 // Terminate this path
1588 } else {
1589 uint start = n->is_Region() ? 1 : 0;
1590 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1591 for (uint i = start; i < end; i++) {
1592 Node* in = n->in(i);
1593 assert(in->is_CFG(), "must be");
1594 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1595 stack.push(in);
1596 }
1597 }
1598 }
1599 }
1600 }
1601
1602 //------------------------------check_safepts----------------------------
1603 // Given dominators, try to find loops with calls that must always be
1604 // executed (call dominates loop tail). These loops do not need non-call
1605 // safepoints (ncsfpt).
1606 //
1607 // A complication is that a safepoint in a inner loop may be needed
1608 // by an outer loop. In the following, the inner loop sees it has a
1609 // call (block 3) on every path from the head (block 2) to the
1610 // backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint)
1611 // in block 2, _but_ this leaves the outer loop without a safepoint.
1612 //
1613 // entry 0
1614 // |
1615 // v
1616 // outer 1,2 +->1
1617 // | |
1618 // | v
1619 // | 2<---+ ncsfpt in 2
1620 // |_/|\ |
1621 // | v |
1622 // inner 2,3 / 3 | call in 3
1623 // / | |
1624 // v +--+
1625 // exit 4
1626 //
1627 //
1628 // This method creates a list (_required_safept) of ncsfpt nodes that must
1629 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1630 // is first looked for in the lists for the outer loops of the current loop.
1631 //
1632 // The insights into the problem:
1633 // A) counted loops are okay
1634 // B) innermost loops are okay (only an inner loop can delete
1635 // a ncsfpt needed by an outer loop)
1636 // C) a loop is immune from an inner loop deleting a safepoint
1637 // if the loop has a call on the idom-path
1638 // D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1639 // idom-path that is not in a nested loop
1640 // E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1641 // loop needs to be prevented from deletion by an inner loop
1642 //
1643 // There are two analyses:
1644 // 1) The first, and cheaper one, scans the loop body from
1645 // tail to head following the idom (immediate dominator)
1646 // chain, looking for the cases (C,D,E) above.
1647 // Since inner loops are scanned before outer loops, there is summary
1648 // information about inner loops. Inner loops can be skipped over
1649 // when the tail of an inner loop is encountered.
1650 //
1651 // 2) The second, invoked if the first fails to find a call or ncsfpt on
1652 // the idom path (which is rare), scans all predecessor control paths
1653 // from the tail to the head, terminating a path when a call or sfpt
1654 // is encountered, to find the ncsfpt's that are closest to the tail.
1655 //
1656 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1657 // Bottom up traversal
1658 IdealLoopTree* ch = _child;
1659 if (_child) _child->check_safepts(visited, stack);
1660 if (_next) _next ->check_safepts(visited, stack);
1661
1662 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1663 bool has_call = false; // call on dom-path
1664 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1665 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth
1666 // Scan the dom-path nodes from tail to head
1667 for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1668 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1669 has_call = true;
1670 _has_sfpt = 1; // Then no need for a safept!
1671 break;
1672 } else if (n->Opcode() == Op_SafePoint) {
1673 if (_phase->get_loop(n) == this) {
1674 has_local_ncsfpt = true;
1675 break;
1676 }
1677 if (nonlocal_ncsfpt == NULL) {
1678 nonlocal_ncsfpt = n; // save the one closest to the tail
1679 }
1680 } else {
1681 IdealLoopTree* nlpt = _phase->get_loop(n);
1682 if (this != nlpt) {
1683 // If at an inner loop tail, see if the inner loop has already
1684 // recorded seeing a call on the dom-path (and stop.) If not,
1685 // jump to the head of the inner loop.
1686 assert(is_member(nlpt), "nested loop");
1687 Node* tail = nlpt->_tail;
1688 if (tail->in(0)->is_If()) tail = tail->in(0);
1689 if (n == tail) {
1690 // If inner loop has call on dom-path, so does outer loop
1691 if (nlpt->_has_sfpt) {
1692 has_call = true;
1693 _has_sfpt = 1;
1694 break;
1695 }
1696 // Skip to head of inner loop
1697 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1698 n = nlpt->_head;
1699 }
1700 }
1701 }
1702 }
1703 // Record safept's that this loop needs preserved when an
1704 // inner loop attempts to delete it's safepoints.
1705 if (_child != NULL && !has_call && !has_local_ncsfpt) {
1706 if (nonlocal_ncsfpt != NULL) {
1707 if (_required_safept == NULL) _required_safept = new Node_List();
1708 _required_safept->push(nonlocal_ncsfpt);
1709 } else {
1710 // Failed to find a suitable safept on the dom-path. Now use
1711 // an all paths walk from tail to head, looking for safepoints to preserve.
1712 allpaths_check_safepts(visited, stack);
1713 }
1714 }
1715 }
1716 }
1717
1718 //---------------------------is_deleteable_safept----------------------------
1719 // Is safept not required by an outer loop?
1720 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1721 assert(sfpt->Opcode() == Op_SafePoint, "");
1722 IdealLoopTree* lp = get_loop(sfpt)->_parent;
1723 while (lp != NULL) {
1724 Node_List* sfpts = lp->_required_safept;
1725 if (sfpts != NULL) {
1726 for (uint i = 0; i < sfpts->size(); i++) {
1727 if (sfpt == sfpts->at(i))
1728 return false;
1729 }
1730 }
1731 lp = lp->_parent;
1732 }
1733 return true;
1734 }
1735
1736 //---------------------------replace_parallel_iv-------------------------------
1737 // Replace parallel induction variable (parallel to trip counter)
1738 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1739 assert(loop->_head->is_CountedLoop(), "");
1740 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1741 if (!cl->is_valid_counted_loop())
1742 return; // skip malformed counted loop
1743 Node *incr = cl->incr();
1744 if (incr == NULL)
1745 return; // Dead loop?
1746 Node *init = cl->init_trip();
1747 Node *phi = cl->phi();
1748 int stride_con = cl->stride_con();
1749
1750 // Visit all children, looking for Phis
1751 for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1752 Node *out = cl->out(i);
1753 // Look for other phis (secondary IVs). Skip dead ones
1754 if (!out->is_Phi() || out == phi || !has_node(out))
1755 continue;
1756 PhiNode* phi2 = out->as_Phi();
1757 Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1758 // Look for induction variables of the form: X += constant
1759 if (phi2->region() != loop->_head ||
1760 incr2->req() != 3 ||
1761 incr2->in(1) != phi2 ||
1762 incr2 == incr ||
1763 incr2->Opcode() != Op_AddI ||
1764 !incr2->in(2)->is_Con())
1765 continue;
1766
1767 // Check for parallel induction variable (parallel to trip counter)
1768 // via an affine function. In particular, count-down loops with
1769 // count-up array indices are common. We only RCE references off
1770 // the trip-counter, so we need to convert all these to trip-counter
1771 // expressions.
1772 Node *init2 = phi2->in( LoopNode::EntryControl );
1773 int stride_con2 = incr2->in(2)->get_int();
1774
1775 // The general case here gets a little tricky. We want to find the
1776 // GCD of all possible parallel IV's and make a new IV using this
1777 // GCD for the loop. Then all possible IVs are simple multiples of
1778 // the GCD. In practice, this will cover very few extra loops.
1779 // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1780 // where +/-1 is the common case, but other integer multiples are
1781 // also easy to handle.
1782 int ratio_con = stride_con2/stride_con;
1783
1784 if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1785 #ifndef PRODUCT
1786 if (TraceLoopOpts) {
1787 tty->print("Parallel IV: %d ", phi2->_idx);
1788 loop->dump_head();
1789 }
1790 #endif
1791 // Convert to using the trip counter. The parallel induction
1792 // variable differs from the trip counter by a loop-invariant
1793 // amount, the difference between their respective initial values.
1794 // It is scaled by the 'ratio_con'.
1795 Node* ratio = _igvn.intcon(ratio_con);
1796 set_ctrl(ratio, C->root());
1797 Node* ratio_init = new MulINode(init, ratio);
1798 _igvn.register_new_node_with_optimizer(ratio_init, init);
1799 set_early_ctrl(ratio_init);
1800 Node* diff = new SubINode(init2, ratio_init);
1801 _igvn.register_new_node_with_optimizer(diff, init2);
1802 set_early_ctrl(diff);
1803 Node* ratio_idx = new MulINode(phi, ratio);
1804 _igvn.register_new_node_with_optimizer(ratio_idx, phi);
1805 set_ctrl(ratio_idx, cl);
1806 Node* add = new AddINode(ratio_idx, diff);
1807 _igvn.register_new_node_with_optimizer(add);
1808 set_ctrl(add, cl);
1809 _igvn.replace_node( phi2, add );
1810 // Sometimes an induction variable is unused
1811 if (add->outcnt() == 0) {
1812 _igvn.remove_dead_node(add);
1813 }
1814 --i; // deleted this phi; rescan starting with next position
1815 continue;
1816 }
1817 }
1818 }
1819
1820 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
1821 Node* keep = NULL;
1822 if (keep_one) {
1823 // Look for a safepoint on the idom-path.
1824 for (Node* i = tail(); i != _head; i = phase->idom(i)) {
1825 if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
1826 keep = i;
1827 break; // Found one
1828 }
1829 }
1830 }
1831
1832 // Don't remove any safepoints if it is requested to keep a single safepoint and
1833 // no safepoint was found on idom-path. It is not safe to remove any safepoint
1834 // in this case since there's no safepoint dominating all paths in the loop body.
1835 bool prune = !keep_one || keep != NULL;
1836
1837 // Delete other safepoints in this loop.
1838 Node_List* sfpts = _safepts;
1839 if (prune && sfpts != NULL) {
1840 assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
1841 for (uint i = 0; i < sfpts->size(); i++) {
1842 Node* n = sfpts->at(i);
1843 assert(phase->get_loop(n) == this, "");
1844 if (n != keep && phase->is_deleteable_safept(n)) {
1845 phase->lazy_replace(n, n->in(TypeFunc::Control));
1846 }
1847 }
1848 }
1849 }
1850
1851 //------------------------------counted_loop-----------------------------------
1852 // Convert to counted loops where possible
1853 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1854
1855 // For grins, set the inner-loop flag here
1856 if (!_child) {
1857 if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1858 }
1859
1860 if (_head->is_CountedLoop() ||
1861 phase->is_counted_loop(_head, this)) {
1862
1863 if (!UseCountedLoopSafepoints) {
1864 // Indicate we do not need a safepoint here
1865 _has_sfpt = 1;
1866 }
1867
1868 // Remove safepoints
1869 bool keep_one_sfpt = !(_has_call || _has_sfpt);
1870 remove_safepoints(phase, keep_one_sfpt);
1871
1872 // Look for induction variables
1873 phase->replace_parallel_iv(this);
1874
1875 } else if (_parent != NULL && !_irreducible) {
1876 // Not a counted loop. Keep one safepoint.
1877 bool keep_one_sfpt = true;
1878 remove_safepoints(phase, keep_one_sfpt);
1879 }
1880
1881 // Recursively
1882 if (_child) _child->counted_loop( phase );
1883 if (_next) _next ->counted_loop( phase );
1884 }
1885
1886 #ifndef PRODUCT
1887 //------------------------------dump_head--------------------------------------
1888 // Dump 1 liner for loop header info
1889 void IdealLoopTree::dump_head( ) const {
1890 for (uint i=0; i<_nest; i++)
1891 tty->print(" ");
1892 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1893 if (_irreducible) tty->print(" IRREDUCIBLE");
1894 Node* entry = _head->in(LoopNode::EntryControl);
1895 if (LoopLimitCheck) {
1896 Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1897 if (predicate != NULL ) {
1898 tty->print(" limit_check");
1899 entry = entry->in(0)->in(0);
1900 }
1901 }
1902 if (UseLoopPredicate) {
1903 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1904 if (entry != NULL) {
1905 tty->print(" predicated");
1906 }
1907 }
1908 if (_head->is_CountedLoop()) {
1909 CountedLoopNode *cl = _head->as_CountedLoop();
1910 tty->print(" counted");
1911
1912 Node* init_n = cl->init_trip();
1913 if (init_n != NULL && init_n->is_Con())
1914 tty->print(" [%d,", cl->init_trip()->get_int());
1915 else
1916 tty->print(" [int,");
1917 Node* limit_n = cl->limit();
1918 if (limit_n != NULL && limit_n->is_Con())
1919 tty->print("%d),", cl->limit()->get_int());
1920 else
1921 tty->print("int),");
1922 int stride_con = cl->stride_con();
1923 if (stride_con > 0) tty->print("+");
1924 tty->print("%d", stride_con);
1925
1926 tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
1927
1928 if (cl->is_pre_loop ()) tty->print(" pre" );
1929 if (cl->is_main_loop()) tty->print(" main");
1930 if (cl->is_post_loop()) tty->print(" post");
1931 }
1932 if (_has_call) tty->print(" has_call");
1933 if (_has_sfpt) tty->print(" has_sfpt");
1934 if (_rce_candidate) tty->print(" rce");
1935 if (_safepts != NULL && _safepts->size() > 0) {
1936 tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
1937 }
1938 if (_required_safept != NULL && _required_safept->size() > 0) {
1939 tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
1940 }
1941 tty->cr();
1942 }
1943
1944 //------------------------------dump-------------------------------------------
1945 // Dump loops by loop tree
1946 void IdealLoopTree::dump( ) const {
1947 dump_head();
1948 if (_child) _child->dump();
1949 if (_next) _next ->dump();
1950 }
1951
1952 #endif
1953
1954 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1955 if (loop == root) {
1956 if (loop->_child != NULL) {
1957 log->begin_head("loop_tree");
1958 log->end_head();
1959 if( loop->_child ) log_loop_tree(root, loop->_child, log);
1960 log->tail("loop_tree");
1961 assert(loop->_next == NULL, "what?");
1962 }
1963 } else {
1964 Node* head = loop->_head;
1965 log->begin_head("loop");
1966 log->print(" idx='%d' ", head->_idx);
1967 if (loop->_irreducible) log->print("irreducible='1' ");
1968 if (head->is_Loop()) {
1969 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1970 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1971 }
1972 if (head->is_CountedLoop()) {
1973 CountedLoopNode* cl = head->as_CountedLoop();
1974 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx());
1975 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1976 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
1977 }
1978 log->end_head();
1979 if( loop->_child ) log_loop_tree(root, loop->_child, log);
1980 log->tail("loop");
1981 if( loop->_next ) log_loop_tree(root, loop->_next, log);
1982 }
1983 }
1984
1985 //---------------------collect_potentially_useful_predicates-----------------------
1986 // Helper function to collect potentially useful predicates to prevent them from
1987 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1988 void PhaseIdealLoop::collect_potentially_useful_predicates(
1989 IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1990 if (loop->_child) { // child
1991 collect_potentially_useful_predicates(loop->_child, useful_predicates);
1992 }
1993
1994 // self (only loops that we can apply loop predication may use their predicates)
1995 if (loop->_head->is_Loop() &&
1996 !loop->_irreducible &&
1997 !loop->tail()->is_top()) {
1998 LoopNode* lpn = loop->_head->as_Loop();
1999 Node* entry = lpn->in(LoopNode::EntryControl);
2000 Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2001 if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2002 assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2003 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2004 entry = entry->in(0)->in(0);
2005 }
2006 predicate_proj = find_predicate(entry); // Predicate
2007 if (predicate_proj != NULL ) {
2008 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2009 }
2010 }
2011
2012 if (loop->_next) { // sibling
2013 collect_potentially_useful_predicates(loop->_next, useful_predicates);
2014 }
2015 }
2016
2017 //------------------------eliminate_useless_predicates-----------------------------
2018 // Eliminate all inserted predicates if they could not be used by loop predication.
2019 // Note: it will also eliminates loop limits check predicate since it also uses
2020 // Opaque1 node (see Parse::add_predicate()).
2021 void PhaseIdealLoop::eliminate_useless_predicates() {
2022 if (C->predicate_count() == 0)
2023 return; // no predicate left
2024
2025 Unique_Node_List useful_predicates; // to store useful predicates
2026 if (C->has_loops()) {
2027 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2028 }
2029
2030 for (int i = C->predicate_count(); i > 0; i--) {
2031 Node * n = C->predicate_opaque1_node(i-1);
2032 assert(n->Opcode() == Op_Opaque1, "must be");
2033 if (!useful_predicates.member(n)) { // not in the useful list
2034 _igvn.replace_node(n, n->in(1));
2035 }
2036 }
2037 }
2038
2039 //------------------------process_expensive_nodes-----------------------------
2040 // Expensive nodes have their control input set to prevent the GVN
2041 // from commoning them and as a result forcing the resulting node to
2042 // be in a more frequent path. Use CFG information here, to change the
2043 // control inputs so that some expensive nodes can be commoned while
2044 // not executed more frequently.
2045 bool PhaseIdealLoop::process_expensive_nodes() {
2046 assert(OptimizeExpensiveOps, "optimization off?");
2047
2048 // Sort nodes to bring similar nodes together
2049 C->sort_expensive_nodes();
2050
2051 bool progress = false;
2052
2053 for (int i = 0; i < C->expensive_count(); ) {
2054 Node* n = C->expensive_node(i);
2055 int start = i;
2056 // Find nodes similar to n
2057 i++;
2058 for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2059 int end = i;
2060 // And compare them two by two
2061 for (int j = start; j < end; j++) {
2062 Node* n1 = C->expensive_node(j);
2063 if (is_node_unreachable(n1)) {
2064 continue;
2065 }
2066 for (int k = j+1; k < end; k++) {
2067 Node* n2 = C->expensive_node(k);
2068 if (is_node_unreachable(n2)) {
2069 continue;
2070 }
2071
2072 assert(n1 != n2, "should be pair of nodes");
2073
2074 Node* c1 = n1->in(0);
2075 Node* c2 = n2->in(0);
2076
2077 Node* parent_c1 = c1;
2078 Node* parent_c2 = c2;
2079
2080 // The call to get_early_ctrl_for_expensive() moves the
2081 // expensive nodes up but stops at loops that are in a if
2082 // branch. See whether we can exit the loop and move above the
2083 // If.
2084 if (c1->is_Loop()) {
2085 parent_c1 = c1->in(1);
2086 }
2087 if (c2->is_Loop()) {
2088 parent_c2 = c2->in(1);
2089 }
2090
2091 if (parent_c1 == parent_c2) {
2092 _igvn._worklist.push(n1);
2093 _igvn._worklist.push(n2);
2094 continue;
2095 }
2096
2097 // Look for identical expensive node up the dominator chain.
2098 if (is_dominator(c1, c2)) {
2099 c2 = c1;
2100 } else if (is_dominator(c2, c1)) {
2101 c1 = c2;
2102 } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2103 parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2104 // Both branches have the same expensive node so move it up
2105 // before the if.
2106 c1 = c2 = idom(parent_c1->in(0));
2107 }
2108 // Do the actual moves
2109 if (n1->in(0) != c1) {
2110 _igvn.hash_delete(n1);
2111 n1->set_req(0, c1);
2112 _igvn.hash_insert(n1);
2113 _igvn._worklist.push(n1);
2114 progress = true;
2115 }
2116 if (n2->in(0) != c2) {
2117 _igvn.hash_delete(n2);
2118 n2->set_req(0, c2);
2119 _igvn.hash_insert(n2);
2120 _igvn._worklist.push(n2);
2121 progress = true;
2122 }
2123 }
2124 }
2125 }
2126
2127 return progress;
2128 }
2129
2130
2131 //=============================================================================
2132 //----------------------------build_and_optimize-------------------------------
2133 // Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to
2134 // its corresponding LoopNode. If 'optimize' is true, do some loop cleanups.
2135 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
2136 ResourceMark rm;
2137
2138 int old_progress = C->major_progress();
2139 uint orig_worklist_size = _igvn._worklist.size();
2140
2141 // Reset major-progress flag for the driver's heuristics
2142 C->clear_major_progress();
2143
2144 #ifndef PRODUCT
2145 // Capture for later assert
2146 uint unique = C->unique();
2147 _loop_invokes++;
2148 _loop_work += unique;
2149 #endif
2150
2151 // True if the method has at least 1 irreducible loop
2152 _has_irreducible_loops = false;
2153
2154 _created_loop_node = false;
2155
2156 Arena *a = Thread::current()->resource_area();
2157 VectorSet visited(a);
2158 // Pre-grow the mapping from Nodes to IdealLoopTrees.
2159 _nodes.map(C->unique(), NULL);
2160 memset(_nodes.adr(), 0, wordSize * C->unique());
2161
2162 // Pre-build the top-level outermost loop tree entry
2163 _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2164 // Do not need a safepoint at the top level
2165 _ltree_root->_has_sfpt = 1;
2166
2167 // Initialize Dominators.
2168 // Checked in clone_loop_predicate() during beautify_loops().
2169 _idom_size = 0;
2170 _idom = NULL;
2171 _dom_depth = NULL;
2172 _dom_stk = NULL;
2173
2174 // Empty pre-order array
2175 allocate_preorders();
2176
2177 // Build a loop tree on the fly. Build a mapping from CFG nodes to
2178 // IdealLoopTree entries. Data nodes are NOT walked.
2179 build_loop_tree();
2180 // Check for bailout, and return
2181 if (C->failing()) {
2182 return;
2183 }
2184
2185 // No loops after all
2186 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2187
2188 // There should always be an outer loop containing the Root and Return nodes.
2189 // If not, we have a degenerate empty program. Bail out in this case.
2190 if (!has_node(C->root())) {
2191 if (!_verify_only) {
2192 C->clear_major_progress();
2193 C->record_method_not_compilable("empty program detected during loop optimization");
2194 }
2195 return;
2196 }
2197
2198 // Nothing to do, so get out
2199 bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
2200 bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2201 if (stop_early && !do_expensive_nodes) {
2202 _igvn.optimize(); // Cleanup NeverBranches
2203 return;
2204 }
2205
2206 // Set loop nesting depth
2207 _ltree_root->set_nest( 0 );
2208
2209 // Split shared headers and insert loop landing pads.
2210 // Do not bother doing this on the Root loop of course.
2211 if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2212 C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2213 if( _ltree_root->_child->beautify_loops( this ) ) {
2214 // Re-build loop tree!
2215 _ltree_root->_child = NULL;
2216 _nodes.clear();
2217 reallocate_preorders();
2218 build_loop_tree();
2219 // Check for bailout, and return
2220 if (C->failing()) {
2221 return;
2222 }
2223 // Reset loop nesting depth
2224 _ltree_root->set_nest( 0 );
2225
2226 C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2227 }
2228 }
2229
2230 // Build Dominators for elision of NULL checks & loop finding.
2231 // Since nodes do not have a slot for immediate dominator, make
2232 // a persistent side array for that info indexed on node->_idx.
2233 _idom_size = C->unique();
2234 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2235 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size );
2236 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth
2237 memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2238
2239 Dominators();
2240
2241 if (!_verify_only) {
2242 // As a side effect, Dominators removed any unreachable CFG paths
2243 // into RegionNodes. It doesn't do this test against Root, so
2244 // we do it here.
2245 for( uint i = 1; i < C->root()->req(); i++ ) {
2246 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root?
2247 _igvn.delete_input_of(C->root(), i);
2248 i--; // Rerun same iteration on compressed edges
2249 }
2250 }
2251
2252 // Given dominators, try to find inner loops with calls that must
2253 // always be executed (call dominates loop tail). These loops do
2254 // not need a separate safepoint.
2255 Node_List cisstack(a);
2256 _ltree_root->check_safepts(visited, cisstack);
2257 }
2258
2259 // Walk the DATA nodes and place into loops. Find earliest control
2260 // node. For CFG nodes, the _nodes array starts out and remains
2261 // holding the associated IdealLoopTree pointer. For DATA nodes, the
2262 // _nodes array holds the earliest legal controlling CFG node.
2263
2264 // Allocate stack with enough space to avoid frequent realloc
2265 int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2266 Node_Stack nstack( a, stack_size );
2267
2268 visited.Clear();
2269 Node_List worklist(a);
2270 // Don't need C->root() on worklist since
2271 // it will be processed among C->top() inputs
2272 worklist.push( C->top() );
2273 visited.set( C->top()->_idx ); // Set C->top() as visited now
2274 build_loop_early( visited, worklist, nstack );
2275
2276 // Given early legal placement, try finding counted loops. This placement
2277 // is good enough to discover most loop invariants.
2278 if( !_verify_me && !_verify_only )
2279 _ltree_root->counted_loop( this );
2280
2281 // Find latest loop placement. Find ideal loop placement.
2282 visited.Clear();
2283 init_dom_lca_tags();
2284 // Need C->root() on worklist when processing outs
2285 worklist.push( C->root() );
2286 NOT_PRODUCT( C->verify_graph_edges(); )
2287 worklist.push( C->top() );
2288 build_loop_late( visited, worklist, nstack );
2289
2290 if (_verify_only) {
2291 // restore major progress flag
2292 for (int i = 0; i < old_progress; i++)
2293 C->set_major_progress();
2294 assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2295 assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2296 return;
2297 }
2298
2299 // clear out the dead code after build_loop_late
2300 while (_deadlist.size()) {
2301 _igvn.remove_globally_dead_node(_deadlist.pop());
2302 }
2303
2304 if (stop_early) {
2305 assert(do_expensive_nodes, "why are we here?");
2306 if (process_expensive_nodes()) {
2307 // If we made some progress when processing expensive nodes then
2308 // the IGVN may modify the graph in a way that will allow us to
2309 // make some more progress: we need to try processing expensive
2310 // nodes again.
2311 C->set_major_progress();
2312 }
2313 _igvn.optimize();
2314 return;
2315 }
2316
2317 // Some parser-inserted loop predicates could never be used by loop
2318 // predication or they were moved away from loop during some optimizations.
2319 // For example, peeling. Eliminate them before next loop optimizations.
2320 if (UseLoopPredicate || LoopLimitCheck) {
2321 eliminate_useless_predicates();
2322 }
2323
2324 #ifndef PRODUCT
2325 C->verify_graph_edges();
2326 if (_verify_me) { // Nested verify pass?
2327 // Check to see if the verify mode is broken
2328 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2329 return;
2330 }
2331 if(VerifyLoopOptimizations) verify();
2332 if(TraceLoopOpts && C->has_loops()) {
2333 _ltree_root->dump();
2334 }
2335 #endif
2336
2337 if (skip_loop_opts) {
2338 // Cleanup any modified bits
2339 _igvn.optimize();
2340
2341 if (C->log() != NULL) {
2342 log_loop_tree(_ltree_root, _ltree_root, C->log());
2343 }
2344 return;
2345 }
2346
2347 if (ReassociateInvariants) {
2348 // Reassociate invariants and prep for split_thru_phi
2349 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2350 IdealLoopTree* lpt = iter.current();
2351 bool is_counted = lpt->is_counted();
2352 if (!is_counted || !lpt->is_inner()) continue;
2353
2354 // check for vectorized loops, any reassociation of invariants was already done
2355 if (is_counted && lpt->_head->as_CountedLoop()->do_unroll_only()) continue;
2356
2357 lpt->reassociate_invariants(this);
2358
2359 // Because RCE opportunities can be masked by split_thru_phi,
2360 // look for RCE candidates and inhibit split_thru_phi
2361 // on just their loop-phi's for this pass of loop opts
2362 if (SplitIfBlocks && do_split_ifs) {
2363 if (lpt->policy_range_check(this)) {
2364 lpt->_rce_candidate = 1; // = true
2365 }
2366 }
2367 }
2368 }
2369
2370 // Check for aggressive application of split-if and other transforms
2371 // that require basic-block info (like cloning through Phi's)
2372 if( SplitIfBlocks && do_split_ifs ) {
2373 visited.Clear();
2374 split_if_with_blocks( visited, nstack );
2375 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2376 }
2377
2378 if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2379 C->set_major_progress();
2380 }
2381
2382 // Perform loop predication before iteration splitting
2383 if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2384 _ltree_root->_child->loop_predication(this);
2385 }
2386
2387 if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2388 if (do_intrinsify_fill()) {
2389 C->set_major_progress();
2390 }
2391 }
2392
2393 // Perform iteration-splitting on inner loops. Split iterations to avoid
2394 // range checks or one-shot null checks.
2395
2396 // If split-if's didn't hack the graph too bad (no CFG changes)
2397 // then do loop opts.
2398 if (C->has_loops() && !C->major_progress()) {
2399 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2400 _ltree_root->_child->iteration_split( this, worklist );
2401 // No verify after peeling! GCM has hoisted code out of the loop.
2402 // After peeling, the hoisted code could sink inside the peeled area.
2403 // The peeling code does not try to recompute the best location for
2404 // all the code before the peeled area, so the verify pass will always
2405 // complain about it.
2406 }
2407 // Do verify graph edges in any case
2408 NOT_PRODUCT( C->verify_graph_edges(); );
2409
2410 if (!do_split_ifs) {
2411 // We saw major progress in Split-If to get here. We forced a
2412 // pass with unrolling and not split-if, however more split-if's
2413 // might make progress. If the unrolling didn't make progress
2414 // then the major-progress flag got cleared and we won't try
2415 // another round of Split-If. In particular the ever-common
2416 // instance-of/check-cast pattern requires at least 2 rounds of
2417 // Split-If to clear out.
2418 C->set_major_progress();
2419 }
2420
2421 // Repeat loop optimizations if new loops were seen
2422 if (created_loop_node()) {
2423 C->set_major_progress();
2424 }
2425
2426 // Keep loop predicates and perform optimizations with them
2427 // until no more loop optimizations could be done.
2428 // After that switch predicates off and do more loop optimizations.
2429 if (!C->major_progress() && (C->predicate_count() > 0)) {
2430 C->cleanup_loop_predicates(_igvn);
2431 if (TraceLoopOpts) {
2432 tty->print_cr("PredicatesOff");
2433 }
2434 C->set_major_progress();
2435 }
2436
2437 // Convert scalar to superword operations at the end of all loop opts.
2438 if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2439 // SuperWord transform
2440 SuperWord sw(this);
2441 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2442 IdealLoopTree* lpt = iter.current();
2443 if (lpt->is_counted()) {
2444 sw.transform_loop(lpt, true);
2445 }
2446 }
2447 }
2448
2449 // Cleanup any modified bits
2450 _igvn.optimize();
2451
2452 // disable assert until issue with split_flow_path is resolved (6742111)
2453 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2454 // "shouldn't introduce irreducible loops");
2455
2456 if (C->log() != NULL) {
2457 log_loop_tree(_ltree_root, _ltree_root, C->log());
2458 }
2459 }
2460
2461 #ifndef PRODUCT
2462 //------------------------------print_statistics-------------------------------
2463 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2464 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2465 void PhaseIdealLoop::print_statistics() {
2466 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2467 }
2468
2469 //------------------------------verify-----------------------------------------
2470 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2471 static int fail; // debug only, so its multi-thread dont care
2472 void PhaseIdealLoop::verify() const {
2473 int old_progress = C->major_progress();
2474 ResourceMark rm;
2475 PhaseIdealLoop loop_verify( _igvn, this );
2476 VectorSet visited(Thread::current()->resource_area());
2477
2478 fail = 0;
2479 verify_compare( C->root(), &loop_verify, visited );
2480 assert( fail == 0, "verify loops failed" );
2481 // Verify loop structure is the same
2482 _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2483 // Reset major-progress. It was cleared by creating a verify version of
2484 // PhaseIdealLoop.
2485 for( int i=0; i<old_progress; i++ )
2486 C->set_major_progress();
2487 }
2488
2489 //------------------------------verify_compare---------------------------------
2490 // Make sure me and the given PhaseIdealLoop agree on key data structures
2491 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2492 if( !n ) return;
2493 if( visited.test_set( n->_idx ) ) return;
2494 if( !_nodes[n->_idx] ) { // Unreachable
2495 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2496 return;
2497 }
2498
2499 uint i;
2500 for( i = 0; i < n->req(); i++ )
2501 verify_compare( n->in(i), loop_verify, visited );
2502
2503 // Check the '_nodes' block/loop structure
2504 i = n->_idx;
2505 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl
2506 if( _nodes[i] != loop_verify->_nodes[i] &&
2507 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2508 tty->print("Mismatched control setting for: ");
2509 n->dump();
2510 if( fail++ > 10 ) return;
2511 Node *c = get_ctrl_no_update(n);
2512 tty->print("We have it as: ");
2513 if( c->in(0) ) c->dump();
2514 else tty->print_cr("N%d",c->_idx);
2515 tty->print("Verify thinks: ");
2516 if( loop_verify->has_ctrl(n) )
2517 loop_verify->get_ctrl_no_update(n)->dump();
2518 else
2519 loop_verify->get_loop_idx(n)->dump();
2520 tty->cr();
2521 }
2522 } else { // We have a loop
2523 IdealLoopTree *us = get_loop_idx(n);
2524 if( loop_verify->has_ctrl(n) ) {
2525 tty->print("Mismatched loop setting for: ");
2526 n->dump();
2527 if( fail++ > 10 ) return;
2528 tty->print("We have it as: ");
2529 us->dump();
2530 tty->print("Verify thinks: ");
2531 loop_verify->get_ctrl_no_update(n)->dump();
2532 tty->cr();
2533 } else if (!C->major_progress()) {
2534 // Loop selection can be messed up if we did a major progress
2535 // operation, like split-if. Do not verify in that case.
2536 IdealLoopTree *them = loop_verify->get_loop_idx(n);
2537 if( us->_head != them->_head || us->_tail != them->_tail ) {
2538 tty->print("Unequals loops for: ");
2539 n->dump();
2540 if( fail++ > 10 ) return;
2541 tty->print("We have it as: ");
2542 us->dump();
2543 tty->print("Verify thinks: ");
2544 them->dump();
2545 tty->cr();
2546 }
2547 }
2548 }
2549
2550 // Check for immediate dominators being equal
2551 if( i >= _idom_size ) {
2552 if( !n->is_CFG() ) return;
2553 tty->print("CFG Node with no idom: ");
2554 n->dump();
2555 return;
2556 }
2557 if( !n->is_CFG() ) return;
2558 if( n == C->root() ) return; // No IDOM here
2559
2560 assert(n->_idx == i, "sanity");
2561 Node *id = idom_no_update(n);
2562 if( id != loop_verify->idom_no_update(n) ) {
2563 tty->print("Unequals idoms for: ");
2564 n->dump();
2565 if( fail++ > 10 ) return;
2566 tty->print("We have it as: ");
2567 id->dump();
2568 tty->print("Verify thinks: ");
2569 loop_verify->idom_no_update(n)->dump();
2570 tty->cr();
2571 }
2572
2573 }
2574
2575 //------------------------------verify_tree------------------------------------
2576 // Verify that tree structures match. Because the CFG can change, siblings
2577 // within the loop tree can be reordered. We attempt to deal with that by
2578 // reordering the verify's loop tree if possible.
2579 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2580 assert( _parent == parent, "Badly formed loop tree" );
2581
2582 // Siblings not in same order? Attempt to re-order.
2583 if( _head != loop->_head ) {
2584 // Find _next pointer to update
2585 IdealLoopTree **pp = &loop->_parent->_child;
2586 while( *pp != loop )
2587 pp = &((*pp)->_next);
2588 // Find proper sibling to be next
2589 IdealLoopTree **nn = &loop->_next;
2590 while( (*nn) && (*nn)->_head != _head )
2591 nn = &((*nn)->_next);
2592
2593 // Check for no match.
2594 if( !(*nn) ) {
2595 // Annoyingly, irreducible loops can pick different headers
2596 // after a major_progress operation, so the rest of the loop
2597 // tree cannot be matched.
2598 if (_irreducible && Compile::current()->major_progress()) return;
2599 assert( 0, "failed to match loop tree" );
2600 }
2601
2602 // Move (*nn) to (*pp)
2603 IdealLoopTree *hit = *nn;
2604 *nn = hit->_next;
2605 hit->_next = loop;
2606 *pp = loop;
2607 loop = hit;
2608 // Now try again to verify
2609 }
2610
2611 assert( _head == loop->_head , "mismatched loop head" );
2612 Node *tail = _tail; // Inline a non-updating version of
2613 while( !tail->in(0) ) // the 'tail()' call.
2614 tail = tail->in(1);
2615 assert( tail == loop->_tail, "mismatched loop tail" );
2616
2617 // Counted loops that are guarded should be able to find their guards
2618 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2619 CountedLoopNode *cl = _head->as_CountedLoop();
2620 Node *init = cl->init_trip();
2621 Node *ctrl = cl->in(LoopNode::EntryControl);
2622 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2623 Node *iff = ctrl->in(0);
2624 assert( iff->Opcode() == Op_If, "" );
2625 Node *bol = iff->in(1);
2626 assert( bol->Opcode() == Op_Bool, "" );
2627 Node *cmp = bol->in(1);
2628 assert( cmp->Opcode() == Op_CmpI, "" );
2629 Node *add = cmp->in(1);
2630 Node *opaq;
2631 if( add->Opcode() == Op_Opaque1 ) {
2632 opaq = add;
2633 } else {
2634 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2635 assert( add == init, "" );
2636 opaq = cmp->in(2);
2637 }
2638 assert( opaq->Opcode() == Op_Opaque1, "" );
2639
2640 }
2641
2642 if (_child != NULL) _child->verify_tree(loop->_child, this);
2643 if (_next != NULL) _next ->verify_tree(loop->_next, parent);
2644 // Innermost loops need to verify loop bodies,
2645 // but only if no 'major_progress'
2646 int fail = 0;
2647 if (!Compile::current()->major_progress() && _child == NULL) {
2648 for( uint i = 0; i < _body.size(); i++ ) {
2649 Node *n = _body.at(i);
2650 if (n->outcnt() == 0) continue; // Ignore dead
2651 uint j;
2652 for( j = 0; j < loop->_body.size(); j++ )
2653 if( loop->_body.at(j) == n )
2654 break;
2655 if( j == loop->_body.size() ) { // Not found in loop body
2656 // Last ditch effort to avoid assertion: Its possible that we
2657 // have some users (so outcnt not zero) but are still dead.
2658 // Try to find from root.
2659 if (Compile::current()->root()->find(n->_idx)) {
2660 fail++;
2661 tty->print("We have that verify does not: ");
2662 n->dump();
2663 }
2664 }
2665 }
2666 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2667 Node *n = loop->_body.at(i2);
2668 if (n->outcnt() == 0) continue; // Ignore dead
2669 uint j;
2670 for( j = 0; j < _body.size(); j++ )
2671 if( _body.at(j) == n )
2672 break;
2673 if( j == _body.size() ) { // Not found in loop body
2674 // Last ditch effort to avoid assertion: Its possible that we
2675 // have some users (so outcnt not zero) but are still dead.
2676 // Try to find from root.
2677 if (Compile::current()->root()->find(n->_idx)) {
2678 fail++;
2679 tty->print("Verify has that we do not: ");
2680 n->dump();
2681 }
2682 }
2683 }
2684 assert( !fail, "loop body mismatch" );
2685 }
2686 }
2687
2688 #endif
2689
2690 //------------------------------set_idom---------------------------------------
2691 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2692 uint idx = d->_idx;
2693 if (idx >= _idom_size) {
2694 uint newsize = _idom_size<<1;
2695 while( idx >= newsize ) {
2696 newsize <<= 1;
2697 }
2698 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize);
2699 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2700 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2701 _idom_size = newsize;
2702 }
2703 _idom[idx] = n;
2704 _dom_depth[idx] = dom_depth;
2705 }
2706
2707 //------------------------------recompute_dom_depth---------------------------------------
2708 // The dominator tree is constructed with only parent pointers.
2709 // This recomputes the depth in the tree by first tagging all
2710 // nodes as "no depth yet" marker. The next pass then runs up
2711 // the dom tree from each node marked "no depth yet", and computes
2712 // the depth on the way back down.
2713 void PhaseIdealLoop::recompute_dom_depth() {
2714 uint no_depth_marker = C->unique();
2715 uint i;
2716 // Initialize depth to "no depth yet"
2717 for (i = 0; i < _idom_size; i++) {
2718 if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2719 _dom_depth[i] = no_depth_marker;
2720 }
2721 }
2722 if (_dom_stk == NULL) {
2723 uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
2724 if (init_size < 10) init_size = 10;
2725 _dom_stk = new GrowableArray<uint>(init_size);
2726 }
2727 // Compute new depth for each node.
2728 for (i = 0; i < _idom_size; i++) {
2729 uint j = i;
2730 // Run up the dom tree to find a node with a depth
2731 while (_dom_depth[j] == no_depth_marker) {
2732 _dom_stk->push(j);
2733 j = _idom[j]->_idx;
2734 }
2735 // Compute the depth on the way back down this tree branch
2736 uint dd = _dom_depth[j] + 1;
2737 while (_dom_stk->length() > 0) {
2738 uint j = _dom_stk->pop();
2739 _dom_depth[j] = dd;
2740 dd++;
2741 }
2742 }
2743 }
2744
2745 //------------------------------sort-------------------------------------------
2746 // Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the
2747 // loop tree, not the root.
2748 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2749 if( !innermost ) return loop; // New innermost loop
2750
2751 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2752 assert( loop_preorder, "not yet post-walked loop" );
2753 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer
2754 IdealLoopTree *l = *pp; // Do I go before or after 'l'?
2755
2756 // Insert at start of list
2757 while( l ) { // Insertion sort based on pre-order
2758 if( l == loop ) return innermost; // Already on list!
2759 int l_preorder = get_preorder(l->_head); // Cache pre-order number
2760 assert( l_preorder, "not yet post-walked l" );
2761 // Check header pre-order number to figure proper nesting
2762 if( loop_preorder > l_preorder )
2763 break; // End of insertion
2764 // If headers tie (e.g., shared headers) check tail pre-order numbers.
2765 // Since I split shared headers, you'd think this could not happen.
2766 // BUT: I must first do the preorder numbering before I can discover I
2767 // have shared headers, so the split headers all get the same preorder
2768 // number as the RegionNode they split from.
2769 if( loop_preorder == l_preorder &&
2770 get_preorder(loop->_tail) < get_preorder(l->_tail) )
2771 break; // Also check for shared headers (same pre#)
2772 pp = &l->_parent; // Chain up list
2773 l = *pp;
2774 }
2775 // Link into list
2776 // Point predecessor to me
2777 *pp = loop;
2778 // Point me to successor
2779 IdealLoopTree *p = loop->_parent;
2780 loop->_parent = l; // Point me to successor
2781 if( p ) sort( p, innermost ); // Insert my parents into list as well
2782 return innermost;
2783 }
2784
2785 //------------------------------build_loop_tree--------------------------------
2786 // I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit
2787 // bits. The _nodes[] array is mapped by Node index and holds a NULL for
2788 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2789 // tightest enclosing IdealLoopTree for post-walked.
2790 //
2791 // During my forward walk I do a short 1-layer lookahead to see if I can find
2792 // a loop backedge with that doesn't have any work on the backedge. This
2793 // helps me construct nested loops with shared headers better.
2794 //
2795 // Once I've done the forward recursion, I do the post-work. For each child
2796 // I check to see if there is a backedge. Backedges define a loop! I
2797 // insert an IdealLoopTree at the target of the backedge.
2798 //
2799 // During the post-work I also check to see if I have several children
2800 // belonging to different loops. If so, then this Node is a decision point
2801 // where control flow can choose to change loop nests. It is at this
2802 // decision point where I can figure out how loops are nested. At this
2803 // time I can properly order the different loop nests from my children.
2804 // Note that there may not be any backedges at the decision point!
2805 //
2806 // Since the decision point can be far removed from the backedges, I can't
2807 // order my loops at the time I discover them. Thus at the decision point
2808 // I need to inspect loop header pre-order numbers to properly nest my
2809 // loops. This means I need to sort my childrens' loops by pre-order.
2810 // The sort is of size number-of-control-children, which generally limits
2811 // it to size 2 (i.e., I just choose between my 2 target loops).
2812 void PhaseIdealLoop::build_loop_tree() {
2813 // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
2814 GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
2815 Node *n = C->root();
2816 bltstack.push(n);
2817 int pre_order = 1;
2818 int stack_size;
2819
2820 while ( ( stack_size = bltstack.length() ) != 0 ) {
2821 n = bltstack.top(); // Leave node on stack
2822 if ( !is_visited(n) ) {
2823 // ---- Pre-pass Work ----
2824 // Pre-walked but not post-walked nodes need a pre_order number.
2825
2826 set_preorder_visited( n, pre_order ); // set as visited
2827
2828 // ---- Scan over children ----
2829 // Scan first over control projections that lead to loop headers.
2830 // This helps us find inner-to-outer loops with shared headers better.
2831
2832 // Scan children's children for loop headers.
2833 for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2834 Node* m = n->raw_out(i); // Child
2835 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2836 // Scan over children's children to find loop
2837 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2838 Node* l = m->fast_out(j);
2839 if( is_visited(l) && // Been visited?
2840 !is_postvisited(l) && // But not post-visited
2841 get_preorder(l) < pre_order ) { // And smaller pre-order
2842 // Found! Scan the DFS down this path before doing other paths
2843 bltstack.push(m);
2844 break;
2845 }
2846 }
2847 }
2848 }
2849 pre_order++;
2850 }
2851 else if ( !is_postvisited(n) ) {
2852 // Note: build_loop_tree_impl() adds out edges on rare occasions,
2853 // such as com.sun.rsasign.am::a.
2854 // For non-recursive version, first, process current children.
2855 // On next iteration, check if additional children were added.
2856 for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2857 Node* u = n->raw_out(k);
2858 if ( u->is_CFG() && !is_visited(u) ) {
2859 bltstack.push(u);
2860 }
2861 }
2862 if ( bltstack.length() == stack_size ) {
2863 // There were no additional children, post visit node now
2864 (void)bltstack.pop(); // Remove node from stack
2865 pre_order = build_loop_tree_impl( n, pre_order );
2866 // Check for bailout
2867 if (C->failing()) {
2868 return;
2869 }
2870 // Check to grow _preorders[] array for the case when
2871 // build_loop_tree_impl() adds new nodes.
2872 check_grow_preorders();
2873 }
2874 }
2875 else {
2876 (void)bltstack.pop(); // Remove post-visited node from stack
2877 }
2878 }
2879 }
2880
2881 //------------------------------build_loop_tree_impl---------------------------
2882 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2883 // ---- Post-pass Work ----
2884 // Pre-walked but not post-walked nodes need a pre_order number.
2885
2886 // Tightest enclosing loop for this Node
2887 IdealLoopTree *innermost = NULL;
2888
2889 // For all children, see if any edge is a backedge. If so, make a loop
2890 // for it. Then find the tightest enclosing loop for the self Node.
2891 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2892 Node* m = n->fast_out(i); // Child
2893 if( n == m ) continue; // Ignore control self-cycles
2894 if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2895
2896 IdealLoopTree *l; // Child's loop
2897 if( !is_postvisited(m) ) { // Child visited but not post-visited?
2898 // Found a backedge
2899 assert( get_preorder(m) < pre_order, "should be backedge" );
2900 // Check for the RootNode, which is already a LoopNode and is allowed
2901 // to have multiple "backedges".
2902 if( m == C->root()) { // Found the root?
2903 l = _ltree_root; // Root is the outermost LoopNode
2904 } else { // Else found a nested loop
2905 // Insert a LoopNode to mark this loop.
2906 l = new IdealLoopTree(this, m, n);
2907 } // End of Else found a nested loop
2908 if( !has_loop(m) ) // If 'm' does not already have a loop set
2909 set_loop(m, l); // Set loop header to loop now
2910
2911 } else { // Else not a nested loop
2912 if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2913 l = get_loop(m); // Get previously determined loop
2914 // If successor is header of a loop (nest), move up-loop till it
2915 // is a member of some outer enclosing loop. Since there are no
2916 // shared headers (I've split them already) I only need to go up
2917 // at most 1 level.
2918 while( l && l->_head == m ) // Successor heads loop?
2919 l = l->_parent; // Move up 1 for me
2920 // If this loop is not properly parented, then this loop
2921 // has no exit path out, i.e. its an infinite loop.
2922 if( !l ) {
2923 // Make loop "reachable" from root so the CFG is reachable. Basically
2924 // insert a bogus loop exit that is never taken. 'm', the loop head,
2925 // points to 'n', one (of possibly many) fall-in paths. There may be
2926 // many backedges as well.
2927
2928 // Here I set the loop to be the root loop. I could have, after
2929 // inserting a bogus loop exit, restarted the recursion and found my
2930 // new loop exit. This would make the infinite loop a first-class
2931 // loop and it would then get properly optimized. What's the use of
2932 // optimizing an infinite loop?
2933 l = _ltree_root; // Oops, found infinite loop
2934
2935 if (!_verify_only) {
2936 // Insert the NeverBranch between 'm' and it's control user.
2937 NeverBranchNode *iff = new NeverBranchNode( m );
2938 _igvn.register_new_node_with_optimizer(iff);
2939 set_loop(iff, l);
2940 Node *if_t = new CProjNode( iff, 0 );
2941 _igvn.register_new_node_with_optimizer(if_t);
2942 set_loop(if_t, l);
2943
2944 Node* cfg = NULL; // Find the One True Control User of m
2945 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2946 Node* x = m->fast_out(j);
2947 if (x->is_CFG() && x != m && x != iff)
2948 { cfg = x; break; }
2949 }
2950 assert(cfg != NULL, "must find the control user of m");
2951 uint k = 0; // Probably cfg->in(0)
2952 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2953 cfg->set_req( k, if_t ); // Now point to NeverBranch
2954 _igvn._worklist.push(cfg);
2955
2956 // Now create the never-taken loop exit
2957 Node *if_f = new CProjNode( iff, 1 );
2958 _igvn.register_new_node_with_optimizer(if_f);
2959 set_loop(if_f, l);
2960 // Find frame ptr for Halt. Relies on the optimizer
2961 // V-N'ing. Easier and quicker than searching through
2962 // the program structure.
2963 Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
2964 _igvn.register_new_node_with_optimizer(frame);
2965 // Halt & Catch Fire
2966 Node *halt = new HaltNode( if_f, frame );
2967 _igvn.register_new_node_with_optimizer(halt);
2968 set_loop(halt, l);
2969 C->root()->add_req(halt);
2970 }
2971 set_loop(C->root(), _ltree_root);
2972 }
2973 }
2974 // Weeny check for irreducible. This child was already visited (this
2975 // IS the post-work phase). Is this child's loop header post-visited
2976 // as well? If so, then I found another entry into the loop.
2977 if (!_verify_only) {
2978 while( is_postvisited(l->_head) ) {
2979 // found irreducible
2980 l->_irreducible = 1; // = true
2981 l = l->_parent;
2982 _has_irreducible_loops = true;
2983 // Check for bad CFG here to prevent crash, and bailout of compile
2984 if (l == NULL) {
2985 C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2986 return pre_order;
2987 }
2988 }
2989 C->set_has_irreducible_loop(_has_irreducible_loops);
2990 }
2991
2992 // This Node might be a decision point for loops. It is only if
2993 // it's children belong to several different loops. The sort call
2994 // does a trivial amount of work if there is only 1 child or all
2995 // children belong to the same loop. If however, the children
2996 // belong to different loops, the sort call will properly set the
2997 // _parent pointers to show how the loops nest.
2998 //
2999 // In any case, it returns the tightest enclosing loop.
3000 innermost = sort( l, innermost );
3001 }
3002
3003 // Def-use info will have some dead stuff; dead stuff will have no
3004 // loop decided on.
3005
3006 // Am I a loop header? If so fix up my parent's child and next ptrs.
3007 if( innermost && innermost->_head == n ) {
3008 assert( get_loop(n) == innermost, "" );
3009 IdealLoopTree *p = innermost->_parent;
3010 IdealLoopTree *l = innermost;
3011 while( p && l->_head == n ) {
3012 l->_next = p->_child; // Put self on parents 'next child'
3013 p->_child = l; // Make self as first child of parent
3014 l = p; // Now walk up the parent chain
3015 p = l->_parent;
3016 }
3017 } else {
3018 // Note that it is possible for a LoopNode to reach here, if the
3019 // backedge has been made unreachable (hence the LoopNode no longer
3020 // denotes a Loop, and will eventually be removed).
3021
3022 // Record tightest enclosing loop for self. Mark as post-visited.
3023 set_loop(n, innermost);
3024 // Also record has_call flag early on
3025 if( innermost ) {
3026 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3027 // Do not count uncommon calls
3028 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3029 Node *iff = n->in(0)->in(0);
3030 // No any calls for vectorized loops.
3031 if( UseSuperWord || !iff->is_If() ||
3032 (n->in(0)->Opcode() == Op_IfFalse &&
3033 (1.0 - iff->as_If()->_prob) >= 0.01) ||
3034 (iff->as_If()->_prob >= 0.01) )
3035 innermost->_has_call = 1;
3036 }
3037 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3038 // Disable loop optimizations if the loop has a scalar replaceable
3039 // allocation. This disabling may cause a potential performance lost
3040 // if the allocation is not eliminated for some reason.
3041 innermost->_allow_optimizations = false;
3042 innermost->_has_call = 1; // = true
3043 } else if (n->Opcode() == Op_SafePoint) {
3044 // Record all safepoints in this loop.
3045 if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3046 innermost->_safepts->push(n);
3047 }
3048 }
3049 }
3050
3051 // Flag as post-visited now
3052 set_postvisited(n);
3053 return pre_order;
3054 }
3055
3056
3057 //------------------------------build_loop_early-------------------------------
3058 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3059 // First pass computes the earliest controlling node possible. This is the
3060 // controlling input with the deepest dominating depth.
3061 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3062 while (worklist.size() != 0) {
3063 // Use local variables nstack_top_n & nstack_top_i to cache values
3064 // on nstack's top.
3065 Node *nstack_top_n = worklist.pop();
3066 uint nstack_top_i = 0;
3067 //while_nstack_nonempty:
3068 while (true) {
3069 // Get parent node and next input's index from stack's top.
3070 Node *n = nstack_top_n;
3071 uint i = nstack_top_i;
3072 uint cnt = n->req(); // Count of inputs
3073 if (i == 0) { // Pre-process the node.
3074 if( has_node(n) && // Have either loop or control already?
3075 !has_ctrl(n) ) { // Have loop picked out already?
3076 // During "merge_many_backedges" we fold up several nested loops
3077 // into a single loop. This makes the members of the original
3078 // loop bodies pointing to dead loops; they need to move up
3079 // to the new UNION'd larger loop. I set the _head field of these
3080 // dead loops to NULL and the _parent field points to the owning
3081 // loop. Shades of UNION-FIND algorithm.
3082 IdealLoopTree *ilt;
3083 while( !(ilt = get_loop(n))->_head ) {
3084 // Normally I would use a set_loop here. But in this one special
3085 // case, it is legal (and expected) to change what loop a Node
3086 // belongs to.
3087 _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3088 }
3089 // Remove safepoints ONLY if I've already seen I don't need one.
3090 // (the old code here would yank a 2nd safepoint after seeing a
3091 // first one, even though the 1st did not dominate in the loop body
3092 // and thus could be avoided indefinitely)
3093 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3094 is_deleteable_safept(n)) {
3095 Node *in = n->in(TypeFunc::Control);
3096 lazy_replace(n,in); // Pull safepoint now
3097 if (ilt->_safepts != NULL) {
3098 ilt->_safepts->yank(n);
3099 }
3100 // Carry on with the recursion "as if" we are walking
3101 // only the control input
3102 if( !visited.test_set( in->_idx ) ) {
3103 worklist.push(in); // Visit this guy later, using worklist
3104 }
3105 // Get next node from nstack:
3106 // - skip n's inputs processing by setting i > cnt;
3107 // - we also will not call set_early_ctrl(n) since
3108 // has_node(n) == true (see the condition above).
3109 i = cnt + 1;
3110 }
3111 }
3112 } // if (i == 0)
3113
3114 // Visit all inputs
3115 bool done = true; // Assume all n's inputs will be processed
3116 while (i < cnt) {
3117 Node *in = n->in(i);
3118 ++i;
3119 if (in == NULL) continue;
3120 if (in->pinned() && !in->is_CFG())
3121 set_ctrl(in, in->in(0));
3122 int is_visited = visited.test_set( in->_idx );
3123 if (!has_node(in)) { // No controlling input yet?
3124 assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3125 assert( !is_visited, "visit only once" );
3126 nstack.push(n, i); // Save parent node and next input's index.
3127 nstack_top_n = in; // Process current input now.
3128 nstack_top_i = 0;
3129 done = false; // Not all n's inputs processed.
3130 break; // continue while_nstack_nonempty;
3131 } else if (!is_visited) {
3132 // This guy has a location picked out for him, but has not yet
3133 // been visited. Happens to all CFG nodes, for instance.
3134 // Visit him using the worklist instead of recursion, to break
3135 // cycles. Since he has a location already we do not need to
3136 // find his location before proceeding with the current Node.
3137 worklist.push(in); // Visit this guy later, using worklist
3138 }
3139 }
3140 if (done) {
3141 // All of n's inputs have been processed, complete post-processing.
3142
3143 // Compute earliest point this Node can go.
3144 // CFG, Phi, pinned nodes already know their controlling input.
3145 if (!has_node(n)) {
3146 // Record earliest legal location
3147 set_early_ctrl( n );
3148 }
3149 if (nstack.is_empty()) {
3150 // Finished all nodes on stack.
3151 // Process next node on the worklist.
3152 break;
3153 }
3154 // Get saved parent node and next input's index.
3155 nstack_top_n = nstack.node();
3156 nstack_top_i = nstack.index();
3157 nstack.pop();
3158 }
3159 } // while (true)
3160 }
3161 }
3162
3163 //------------------------------dom_lca_internal--------------------------------
3164 // Pair-wise LCA
3165 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3166 if( !n1 ) return n2; // Handle NULL original LCA
3167 assert( n1->is_CFG(), "" );
3168 assert( n2->is_CFG(), "" );
3169 // find LCA of all uses
3170 uint d1 = dom_depth(n1);
3171 uint d2 = dom_depth(n2);
3172 while (n1 != n2) {
3173 if (d1 > d2) {
3174 n1 = idom(n1);
3175 d1 = dom_depth(n1);
3176 } else if (d1 < d2) {
3177 n2 = idom(n2);
3178 d2 = dom_depth(n2);
3179 } else {
3180 // Here d1 == d2. Due to edits of the dominator-tree, sections
3181 // of the tree might have the same depth. These sections have
3182 // to be searched more carefully.
3183
3184 // Scan up all the n1's with equal depth, looking for n2.
3185 Node *t1 = idom(n1);
3186 while (dom_depth(t1) == d1) {
3187 if (t1 == n2) return n2;
3188 t1 = idom(t1);
3189 }
3190 // Scan up all the n2's with equal depth, looking for n1.
3191 Node *t2 = idom(n2);
3192 while (dom_depth(t2) == d2) {
3193 if (t2 == n1) return n1;
3194 t2 = idom(t2);
3195 }
3196 // Move up to a new dominator-depth value as well as up the dom-tree.
3197 n1 = t1;
3198 n2 = t2;
3199 d1 = dom_depth(n1);
3200 d2 = dom_depth(n2);
3201 }
3202 }
3203 return n1;
3204 }
3205
3206 //------------------------------compute_idom-----------------------------------
3207 // Locally compute IDOM using dom_lca call. Correct only if the incoming
3208 // IDOMs are correct.
3209 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3210 assert( region->is_Region(), "" );
3211 Node *LCA = NULL;
3212 for( uint i = 1; i < region->req(); i++ ) {
3213 if( region->in(i) != C->top() )
3214 LCA = dom_lca( LCA, region->in(i) );
3215 }
3216 return LCA;
3217 }
3218
3219 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3220 bool had_error = false;
3221 #ifdef ASSERT
3222 if (early != C->root()) {
3223 // Make sure that there's a dominance path from LCA to early
3224 Node* d = LCA;
3225 while (d != early) {
3226 if (d == C->root()) {
3227 dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3228 tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3229 had_error = true;
3230 break;
3231 }
3232 d = idom(d);
3233 }
3234 }
3235 #endif
3236 return had_error;
3237 }
3238
3239
3240 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3241 // Compute LCA over list of uses
3242 bool had_error = false;
3243 Node *LCA = NULL;
3244 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3245 Node* c = n->fast_out(i);
3246 if (_nodes[c->_idx] == NULL)
3247 continue; // Skip the occasional dead node
3248 if( c->is_Phi() ) { // For Phis, we must land above on the path
3249 for( uint j=1; j<c->req(); j++ ) {// For all inputs
3250 if( c->in(j) == n ) { // Found matching input?
3251 Node *use = c->in(0)->in(j);
3252 if (_verify_only && use->is_top()) continue;
3253 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3254 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3255 }
3256 }
3257 } else {
3258 // For CFG data-users, use is in the block just prior
3259 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3260 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3261 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3262 }
3263 }
3264 assert(!had_error, "bad dominance");
3265 return LCA;
3266 }
3267
3268 //------------------------------get_late_ctrl----------------------------------
3269 // Compute latest legal control.
3270 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3271 assert(early != NULL, "early control should not be NULL");
3272
3273 Node* LCA = compute_lca_of_uses(n, early);
3274 #ifdef ASSERT
3275 if (LCA == C->root() && LCA != early) {
3276 // def doesn't dominate uses so print some useful debugging output
3277 compute_lca_of_uses(n, early, true);
3278 }
3279 #endif
3280
3281 // if this is a load, check for anti-dependent stores
3282 // We use a conservative algorithm to identify potential interfering
3283 // instructions and for rescheduling the load. The users of the memory
3284 // input of this load are examined. Any use which is not a load and is
3285 // dominated by early is considered a potentially interfering store.
3286 // This can produce false positives.
3287 if (n->is_Load() && LCA != early) {
3288 Node_List worklist;
3289
3290 Node *mem = n->in(MemNode::Memory);
3291 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3292 Node* s = mem->fast_out(i);
3293 worklist.push(s);
3294 }
3295 while(worklist.size() != 0 && LCA != early) {
3296 Node* s = worklist.pop();
3297 if (s->is_Load()) {
3298 continue;
3299 } else if (s->is_MergeMem()) {
3300 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3301 Node* s1 = s->fast_out(i);
3302 worklist.push(s1);
3303 }
3304 } else {
3305 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3306 assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3307 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3308 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3309 }
3310 }
3311 }
3312 }
3313
3314 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3315 return LCA;
3316 }
3317
3318 // true if CFG node d dominates CFG node n
3319 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3320 if (d == n)
3321 return true;
3322 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3323 uint dd = dom_depth(d);
3324 while (dom_depth(n) >= dd) {
3325 if (n == d)
3326 return true;
3327 n = idom(n);
3328 }
3329 return false;
3330 }
3331
3332 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3333 // Pair-wise LCA with tags.
3334 // Tag each index with the node 'tag' currently being processed
3335 // before advancing up the dominator chain using idom().
3336 // Later calls that find a match to 'tag' know that this path has already
3337 // been considered in the current LCA (which is input 'n1' by convention).
3338 // Since get_late_ctrl() is only called once for each node, the tag array
3339 // does not need to be cleared between calls to get_late_ctrl().
3340 // Algorithm trades a larger constant factor for better asymptotic behavior
3341 //
3342 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3343 uint d1 = dom_depth(n1);
3344 uint d2 = dom_depth(n2);
3345
3346 do {
3347 if (d1 > d2) {
3348 // current lca is deeper than n2
3349 _dom_lca_tags.map(n1->_idx, tag);
3350 n1 = idom(n1);
3351 d1 = dom_depth(n1);
3352 } else if (d1 < d2) {
3353 // n2 is deeper than current lca
3354 Node *memo = _dom_lca_tags[n2->_idx];
3355 if( memo == tag ) {
3356 return n1; // Return the current LCA
3357 }
3358 _dom_lca_tags.map(n2->_idx, tag);
3359 n2 = idom(n2);
3360 d2 = dom_depth(n2);
3361 } else {
3362 // Here d1 == d2. Due to edits of the dominator-tree, sections
3363 // of the tree might have the same depth. These sections have
3364 // to be searched more carefully.
3365
3366 // Scan up all the n1's with equal depth, looking for n2.
3367 _dom_lca_tags.map(n1->_idx, tag);
3368 Node *t1 = idom(n1);
3369 while (dom_depth(t1) == d1) {
3370 if (t1 == n2) return n2;
3371 _dom_lca_tags.map(t1->_idx, tag);
3372 t1 = idom(t1);
3373 }
3374 // Scan up all the n2's with equal depth, looking for n1.
3375 _dom_lca_tags.map(n2->_idx, tag);
3376 Node *t2 = idom(n2);
3377 while (dom_depth(t2) == d2) {
3378 if (t2 == n1) return n1;
3379 _dom_lca_tags.map(t2->_idx, tag);
3380 t2 = idom(t2);
3381 }
3382 // Move up to a new dominator-depth value as well as up the dom-tree.
3383 n1 = t1;
3384 n2 = t2;
3385 d1 = dom_depth(n1);
3386 d2 = dom_depth(n2);
3387 }
3388 } while (n1 != n2);
3389 return n1;
3390 }
3391
3392 //------------------------------init_dom_lca_tags------------------------------
3393 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3394 // Intended use does not involve any growth for the array, so it could
3395 // be of fixed size.
3396 void PhaseIdealLoop::init_dom_lca_tags() {
3397 uint limit = C->unique() + 1;
3398 _dom_lca_tags.map( limit, NULL );
3399 #ifdef ASSERT
3400 for( uint i = 0; i < limit; ++i ) {
3401 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3402 }
3403 #endif // ASSERT
3404 }
3405
3406 //------------------------------clear_dom_lca_tags------------------------------
3407 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3408 // Intended use does not involve any growth for the array, so it could
3409 // be of fixed size.
3410 void PhaseIdealLoop::clear_dom_lca_tags() {
3411 uint limit = C->unique() + 1;
3412 _dom_lca_tags.map( limit, NULL );
3413 _dom_lca_tags.clear();
3414 #ifdef ASSERT
3415 for( uint i = 0; i < limit; ++i ) {
3416 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3417 }
3418 #endif // ASSERT
3419 }
3420
3421 //------------------------------build_loop_late--------------------------------
3422 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3423 // Second pass finds latest legal placement, and ideal loop placement.
3424 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3425 while (worklist.size() != 0) {
3426 Node *n = worklist.pop();
3427 // Only visit once
3428 if (visited.test_set(n->_idx)) continue;
3429 uint cnt = n->outcnt();
3430 uint i = 0;
3431 while (true) {
3432 assert( _nodes[n->_idx], "no dead nodes" );
3433 // Visit all children
3434 if (i < cnt) {
3435 Node* use = n->raw_out(i);
3436 ++i;
3437 // Check for dead uses. Aggressively prune such junk. It might be
3438 // dead in the global sense, but still have local uses so I cannot
3439 // easily call 'remove_dead_node'.
3440 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3441 // Due to cycles, we might not hit the same fixed point in the verify
3442 // pass as we do in the regular pass. Instead, visit such phis as
3443 // simple uses of the loop head.
3444 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3445 if( !visited.test(use->_idx) )
3446 worklist.push(use);
3447 } else if( !visited.test_set(use->_idx) ) {
3448 nstack.push(n, i); // Save parent and next use's index.
3449 n = use; // Process all children of current use.
3450 cnt = use->outcnt();
3451 i = 0;
3452 }
3453 } else {
3454 // Do not visit around the backedge of loops via data edges.
3455 // push dead code onto a worklist
3456 _deadlist.push(use);
3457 }
3458 } else {
3459 // All of n's children have been processed, complete post-processing.
3460 build_loop_late_post(n);
3461 if (nstack.is_empty()) {
3462 // Finished all nodes on stack.
3463 // Process next node on the worklist.
3464 break;
3465 }
3466 // Get saved parent node and next use's index. Visit the rest of uses.
3467 n = nstack.node();
3468 cnt = n->outcnt();
3469 i = nstack.index();
3470 nstack.pop();
3471 }
3472 }
3473 }
3474 }
3475
3476 //------------------------------build_loop_late_post---------------------------
3477 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3478 // Second pass finds latest legal placement, and ideal loop placement.
3479 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3480
3481 if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3482 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops.
3483 }
3484
3485 #ifdef ASSERT
3486 if (_verify_only && !n->is_CFG()) {
3487 // Check def-use domination.
3488 compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
3489 }
3490 #endif
3491
3492 // CFG and pinned nodes already handled
3493 if( n->in(0) ) {
3494 if( n->in(0)->is_top() ) return; // Dead?
3495
3496 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3497 // _must_ be pinned (they have to observe their control edge of course).
3498 // Unlike Stores (which modify an unallocable resource, the memory
3499 // state), Mods/Loads can float around. So free them up.
3500 bool pinned = true;
3501 switch( n->Opcode() ) {
3502 case Op_DivI:
3503 case Op_DivF:
3504 case Op_DivD:
3505 case Op_ModI:
3506 case Op_ModF:
3507 case Op_ModD:
3508 case Op_LoadB: // Same with Loads; they can sink
3509 case Op_LoadUB: // during loop optimizations.
3510 case Op_LoadUS:
3511 case Op_LoadD:
3512 case Op_LoadF:
3513 case Op_LoadI:
3514 case Op_LoadKlass:
3515 case Op_LoadNKlass:
3516 case Op_LoadL:
3517 case Op_LoadS:
3518 case Op_LoadP:
3519 case Op_LoadN:
3520 case Op_LoadRange:
3521 case Op_LoadD_unaligned:
3522 case Op_LoadL_unaligned:
3523 case Op_StrComp: // Does a bunch of load-like effects
3524 case Op_StrEquals:
3525 case Op_StrIndexOf:
3526 case Op_StrIndexOfChar:
3527 case Op_AryEq:
3528 case Op_HasNegatives:
3529 pinned = false;
3530 }
3531 if( pinned ) {
3532 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3533 if( !chosen_loop->_child ) // Inner loop?
3534 chosen_loop->_body.push(n); // Collect inner loops
3535 return;
3536 }
3537 } else { // No slot zero
3538 if( n->is_CFG() ) { // CFG with no slot 0 is dead
3539 _nodes.map(n->_idx,0); // No block setting, it's globally dead
3540 return;
3541 }
3542 assert(!n->is_CFG() || n->outcnt() == 0, "");
3543 }
3544
3545 // Do I have a "safe range" I can select over?
3546 Node *early = get_ctrl(n);// Early location already computed
3547
3548 // Compute latest point this Node can go
3549 Node *LCA = get_late_ctrl( n, early );
3550 // LCA is NULL due to uses being dead
3551 if( LCA == NULL ) {
3552 #ifdef ASSERT
3553 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3554 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3555 }
3556 #endif
3557 _nodes.map(n->_idx, 0); // This node is useless
3558 _deadlist.push(n);
3559 return;
3560 }
3561 assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3562
3563 Node *legal = LCA; // Walk 'legal' up the IDOM chain
3564 Node *least = legal; // Best legal position so far
3565 while( early != legal ) { // While not at earliest legal
3566 #ifdef ASSERT
3567 if (legal->is_Start() && !early->is_Root()) {
3568 // Bad graph. Print idom path and fail.
3569 dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
3570 assert(false, "Bad graph detected in build_loop_late");
3571 }
3572 #endif
3573 // Find least loop nesting depth
3574 legal = idom(legal); // Bump up the IDOM tree
3575 // Check for lower nesting depth
3576 if( get_loop(legal)->_nest < get_loop(least)->_nest )
3577 least = legal;
3578 }
3579 assert(early == legal || legal != C->root(), "bad dominance of inputs");
3580
3581 // Try not to place code on a loop entry projection
3582 // which can inhibit range check elimination.
3583 if (least != early) {
3584 Node* ctrl_out = least->unique_ctrl_out();
3585 if (ctrl_out && ctrl_out->is_CountedLoop() &&
3586 least == ctrl_out->in(LoopNode::EntryControl)) {
3587 Node* least_dom = idom(least);
3588 if (get_loop(least_dom)->is_member(get_loop(least))) {
3589 least = least_dom;
3590 }
3591 }
3592 }
3593
3594 #ifdef ASSERT
3595 // If verifying, verify that 'verify_me' has a legal location
3596 // and choose it as our location.
3597 if( _verify_me ) {
3598 Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3599 Node *legal = LCA;
3600 while( early != legal ) { // While not at earliest legal
3601 if( legal == v_ctrl ) break; // Check for prior good location
3602 legal = idom(legal) ;// Bump up the IDOM tree
3603 }
3604 // Check for prior good location
3605 if( legal == v_ctrl ) least = legal; // Keep prior if found
3606 }
3607 #endif
3608
3609 // Assign discovered "here or above" point
3610 least = find_non_split_ctrl(least);
3611 set_ctrl(n, least);
3612
3613 // Collect inner loop bodies
3614 IdealLoopTree *chosen_loop = get_loop(least);
3615 if( !chosen_loop->_child ) // Inner loop?
3616 chosen_loop->_body.push(n);// Collect inner loops
3617 }
3618
3619 #ifdef ASSERT
3620 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
3621 tty->print_cr("%s", msg);
3622 tty->print("n: "); n->dump();
3623 tty->print("early(n): "); early->dump();
3624 if (n->in(0) != NULL && !n->in(0)->is_top() &&
3625 n->in(0) != early && !n->in(0)->is_Root()) {
3626 tty->print("n->in(0): "); n->in(0)->dump();
3627 }
3628 for (uint i = 1; i < n->req(); i++) {
3629 Node* in1 = n->in(i);
3630 if (in1 != NULL && in1 != n && !in1->is_top()) {
3631 tty->print("n->in(%d): ", i); in1->dump();
3632 Node* in1_early = get_ctrl(in1);
3633 tty->print("early(n->in(%d)): ", i); in1_early->dump();
3634 if (in1->in(0) != NULL && !in1->in(0)->is_top() &&
3635 in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
3636 tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
3637 }
3638 for (uint j = 1; j < in1->req(); j++) {
3639 Node* in2 = in1->in(j);
3640 if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
3641 tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
3642 Node* in2_early = get_ctrl(in2);
3643 tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
3644 if (in2->in(0) != NULL && !in2->in(0)->is_top() &&
3645 in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
3646 tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
3647 }
3648 }
3649 }
3650 }
3651 }
3652 tty->cr();
3653 tty->print("LCA(n): "); LCA->dump();
3654 for (uint i = 0; i < n->outcnt(); i++) {
3655 Node* u1 = n->raw_out(i);
3656 if (u1 == n)
3657 continue;
3658 tty->print("n->out(%d): ", i); u1->dump();
3659 if (u1->is_CFG()) {
3660 for (uint j = 0; j < u1->outcnt(); j++) {
3661 Node* u2 = u1->raw_out(j);
3662 if (u2 != u1 && u2 != n && u2->is_CFG()) {
3663 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3664 }
3665 }
3666 } else {
3667 Node* u1_later = get_ctrl(u1);
3668 tty->print("later(n->out(%d)): ", i); u1_later->dump();
3669 if (u1->in(0) != NULL && !u1->in(0)->is_top() &&
3670 u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
3671 tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
3672 }
3673 for (uint j = 0; j < u1->outcnt(); j++) {
3674 Node* u2 = u1->raw_out(j);
3675 if (u2 == n || u2 == u1)
3676 continue;
3677 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3678 if (!u2->is_CFG()) {
3679 Node* u2_later = get_ctrl(u2);
3680 tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
3681 if (u2->in(0) != NULL && !u2->in(0)->is_top() &&
3682 u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
3683 tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
3684 }
3685 }
3686 }
3687 }
3688 }
3689 tty->cr();
3690 int ct = 0;
3691 Node *dbg_legal = LCA;
3692 while(!dbg_legal->is_Start() && ct < 100) {
3693 tty->print("idom[%d] ",ct); dbg_legal->dump();
3694 ct++;
3695 dbg_legal = idom(dbg_legal);
3696 }
3697 tty->cr();
3698 }
3699 #endif
3700
3701 #ifndef PRODUCT
3702 //------------------------------dump-------------------------------------------
3703 void PhaseIdealLoop::dump( ) const {
3704 ResourceMark rm;
3705 Arena* arena = Thread::current()->resource_area();
3706 Node_Stack stack(arena, C->live_nodes() >> 2);
3707 Node_List rpo_list;
3708 VectorSet visited(arena);
3709 visited.set(C->top()->_idx);
3710 rpo( C->root(), stack, visited, rpo_list );
3711 // Dump root loop indexed by last element in PO order
3712 dump( _ltree_root, rpo_list.size(), rpo_list );
3713 }
3714
3715 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3716 loop->dump_head();
3717
3718 // Now scan for CFG nodes in the same loop
3719 for( uint j=idx; j > 0; j-- ) {
3720 Node *n = rpo_list[j-1];
3721 if( !_nodes[n->_idx] ) // Skip dead nodes
3722 continue;
3723 if( get_loop(n) != loop ) { // Wrong loop nest
3724 if( get_loop(n)->_head == n && // Found nested loop?
3725 get_loop(n)->_parent == loop )
3726 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly
3727 continue;
3728 }
3729
3730 // Dump controlling node
3731 for( uint x = 0; x < loop->_nest; x++ )
3732 tty->print(" ");
3733 tty->print("C");
3734 if( n == C->root() ) {
3735 n->dump();
3736 } else {
3737 Node* cached_idom = idom_no_update(n);
3738 Node *computed_idom = n->in(0);
3739 if( n->is_Region() ) {
3740 computed_idom = compute_idom(n);
3741 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3742 // any MultiBranch ctrl node), so apply a similar transform to
3743 // the cached idom returned from idom_no_update.
3744 cached_idom = find_non_split_ctrl(cached_idom);
3745 }
3746 tty->print(" ID:%d",computed_idom->_idx);
3747 n->dump();
3748 if( cached_idom != computed_idom ) {
3749 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d",
3750 computed_idom->_idx, cached_idom->_idx);
3751 }
3752 }
3753 // Dump nodes it controls
3754 for( uint k = 0; k < _nodes.Size(); k++ ) {
3755 // (k < C->unique() && get_ctrl(find(k)) == n)
3756 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3757 Node *m = C->root()->find(k);
3758 if( m && m->outcnt() > 0 ) {
3759 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3760 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p",
3761 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3762 }
3763 for( uint j = 0; j < loop->_nest; j++ )
3764 tty->print(" ");
3765 tty->print(" ");
3766 m->dump();
3767 }
3768 }
3769 }
3770 }
3771 }
3772
3773 // Collect a R-P-O for the whole CFG.
3774 // Result list is in post-order (scan backwards for RPO)
3775 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3776 stk.push(start, 0);
3777 visited.set(start->_idx);
3778
3779 while (stk.is_nonempty()) {
3780 Node* m = stk.node();
3781 uint idx = stk.index();
3782 if (idx < m->outcnt()) {
3783 stk.set_index(idx + 1);
3784 Node* n = m->raw_out(idx);
3785 if (n->is_CFG() && !visited.test_set(n->_idx)) {
3786 stk.push(n, 0);
3787 }
3788 } else {
3789 rpo_list.push(m);
3790 stk.pop();
3791 }
3792 }
3793 }
3794 #endif
3795
3796
3797 //=============================================================================
3798 //------------------------------LoopTreeIterator-----------------------------------
3799
3800 // Advance to next loop tree using a preorder, left-to-right traversal.
3801 void LoopTreeIterator::next() {
3802 assert(!done(), "must not be done.");
3803 if (_curnt->_child != NULL) {
3804 _curnt = _curnt->_child;
3805 } else if (_curnt->_next != NULL) {
3806 _curnt = _curnt->_next;
3807 } else {
3808 while (_curnt != _root && _curnt->_next == NULL) {
3809 _curnt = _curnt->_parent;
3810 }
3811 if (_curnt == _root) {
3812 _curnt = NULL;
3813 assert(done(), "must be done.");
3814 } else {
3815 assert(_curnt->_next != NULL, "must be more to do");
3816 _curnt = _curnt->_next;
3817 }
3818 }
3819 }