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