1/*
2 * Copyright (c) 1998, 2019, 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 "gc/shared/barrierSet.hpp"
29#include "gc/shared/c2/barrierSetC2.hpp"
30#include "libadt/vectset.hpp"
31#include "memory/allocation.inline.hpp"
32#include "memory/resourceArea.hpp"
33#include "opto/addnode.hpp"
34#include "opto/callnode.hpp"
35#include "opto/connode.hpp"
36#include "opto/convertnode.hpp"
37#include "opto/divnode.hpp"
38#include "opto/idealGraphPrinter.hpp"
39#include "opto/loopnode.hpp"
40#include "opto/mulnode.hpp"
41#include "opto/rootnode.hpp"
42#include "opto/superword.hpp"
43
44//=============================================================================
45//--------------------------is_cloop_ind_var-----------------------------------
46// Determine if a node is a counted loop induction variable.
47// NOTE: The method is declared in "node.hpp".
48bool Node::is_cloop_ind_var() const {
49 return (is_Phi() && !as_Phi()->is_copy() &&
50 as_Phi()->region()->is_CountedLoop() &&
51 as_Phi()->region()->as_CountedLoop()->phi() == this);
52}
53
54//=============================================================================
55//------------------------------dump_spec--------------------------------------
56// Dump special per-node info
57#ifndef PRODUCT
58void LoopNode::dump_spec(outputStream *st) const {
59 if (is_inner_loop()) st->print( "inner " );
60 if (is_partial_peel_loop()) st->print( "partial_peel " );
61 if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
62}
63#endif
64
65//------------------------------is_valid_counted_loop-------------------------
66bool LoopNode::is_valid_counted_loop() const {
67 if (is_CountedLoop()) {
68 CountedLoopNode* l = as_CountedLoop();
69 CountedLoopEndNode* le = l->loopexit_or_null();
70 if (le != NULL &&
71 le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
72 Node* phi = l->phi();
73 Node* exit = le->proj_out_or_null(0 /* false */);
74 if (exit != NULL && exit->Opcode() == Op_IfFalse &&
75 phi != NULL && phi->is_Phi() &&
76 phi->in(LoopNode::LoopBackControl) == l->incr() &&
77 le->loopnode() == l && le->stride_is_con()) {
78 return true;
79 }
80 }
81 }
82 return false;
83}
84
85//------------------------------get_early_ctrl---------------------------------
86// Compute earliest legal control
87Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
88 assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
89 uint i;
90 Node *early;
91 if (n->in(0) && !n->is_expensive()) {
92 early = n->in(0);
93 if (!early->is_CFG()) // Might be a non-CFG multi-def
94 early = get_ctrl(early); // So treat input as a straight data input
95 i = 1;
96 } else {
97 early = get_ctrl(n->in(1));
98 i = 2;
99 }
100 uint e_d = dom_depth(early);
101 assert( early, "" );
102 for (; i < n->req(); i++) {
103 Node *cin = get_ctrl(n->in(i));
104 assert( cin, "" );
105 // Keep deepest dominator depth
106 uint c_d = dom_depth(cin);
107 if (c_d > e_d) { // Deeper guy?
108 early = cin; // Keep deepest found so far
109 e_d = c_d;
110 } else if (c_d == e_d && // Same depth?
111 early != cin) { // If not equal, must use slower algorithm
112 // If same depth but not equal, one _must_ dominate the other
113 // and we want the deeper (i.e., dominated) guy.
114 Node *n1 = early;
115 Node *n2 = cin;
116 while (1) {
117 n1 = idom(n1); // Walk up until break cycle
118 n2 = idom(n2);
119 if (n1 == cin || // Walked early up to cin
120 dom_depth(n2) < c_d)
121 break; // early is deeper; keep him
122 if (n2 == early || // Walked cin up to early
123 dom_depth(n1) < c_d) {
124 early = cin; // cin is deeper; keep him
125 break;
126 }
127 }
128 e_d = dom_depth(early); // Reset depth register cache
129 }
130 }
131
132 // Return earliest legal location
133 assert(early == find_non_split_ctrl(early), "unexpected early control");
134
135 if (n->is_expensive() && !_verify_only && !_verify_me) {
136 assert(n->in(0), "should have control input");
137 early = get_early_ctrl_for_expensive(n, early);
138 }
139
140 return early;
141}
142
143//------------------------------get_early_ctrl_for_expensive---------------------------------
144// Move node up the dominator tree as high as legal while still beneficial
145Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
146 assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
147 assert(OptimizeExpensiveOps, "optimization off?");
148
149 Node* ctl = n->in(0);
150 assert(ctl->is_CFG(), "expensive input 0 must be cfg");
151 uint min_dom_depth = dom_depth(earliest);
152#ifdef ASSERT
153 if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
154 dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
155 assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
156 }
157#endif
158 if (dom_depth(ctl) < min_dom_depth) {
159 return earliest;
160 }
161
162 while (1) {
163 Node *next = ctl;
164 // Moving the node out of a loop on the projection of a If
165 // confuses loop predication. So once we hit a Loop in a If branch
166 // that doesn't branch to an UNC, we stop. The code that process
167 // expensive nodes will notice the loop and skip over it to try to
168 // move the node further up.
169 if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
170 if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
171 break;
172 }
173 next = idom(ctl->in(1)->in(0));
174 } else if (ctl->is_Proj()) {
175 // We only move it up along a projection if the projection is
176 // the single control projection for its parent: same code path,
177 // if it's a If with UNC or fallthrough of a call.
178 Node* parent_ctl = ctl->in(0);
179 if (parent_ctl == NULL) {
180 break;
181 } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
182 next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
183 } else if (parent_ctl->is_If()) {
184 if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
185 break;
186 }
187 assert(idom(ctl) == parent_ctl, "strange");
188 next = idom(parent_ctl);
189 } else if (ctl->is_CatchProj()) {
190 if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
191 break;
192 }
193 assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
194 next = parent_ctl->in(0)->in(0)->in(0);
195 } else {
196 // Check if parent control has a single projection (this
197 // control is the only possible successor of the parent
198 // control). If so, we can try to move the node above the
199 // parent control.
200 int nb_ctl_proj = 0;
201 for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
202 Node *p = parent_ctl->fast_out(i);
203 if (p->is_Proj() && p->is_CFG()) {
204 nb_ctl_proj++;
205 if (nb_ctl_proj > 1) {
206 break;
207 }
208 }
209 }
210
211 if (nb_ctl_proj > 1) {
212 break;
213 }
214 assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
215 BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
216 assert(idom(ctl) == parent_ctl, "strange");
217 next = idom(parent_ctl);
218 }
219 } else {
220 next = idom(ctl);
221 }
222 if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
223 break;
224 }
225 ctl = next;
226 }
227
228 if (ctl != n->in(0)) {
229 _igvn.replace_input_of(n, 0, ctl);
230 _igvn.hash_insert(n);
231 }
232
233 return ctl;
234}
235
236
237//------------------------------set_early_ctrl---------------------------------
238// Set earliest legal control
239void PhaseIdealLoop::set_early_ctrl( Node *n ) {
240 Node *early = get_early_ctrl(n);
241
242 // Record earliest legal location
243 set_ctrl(n, early);
244}
245
246//------------------------------set_subtree_ctrl-------------------------------
247// set missing _ctrl entries on new nodes
248void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
249 // Already set? Get out.
250 if( _nodes[n->_idx] ) return;
251 // Recursively set _nodes array to indicate where the Node goes
252 uint i;
253 for( i = 0; i < n->req(); ++i ) {
254 Node *m = n->in(i);
255 if( m && m != C->root() )
256 set_subtree_ctrl( m );
257 }
258
259 // Fixup self
260 set_early_ctrl( n );
261}
262
263// Create a skeleton strip mined outer loop: a Loop head before the
264// inner strip mined loop, a safepoint and an exit condition guarded
265// by an opaque node after the inner strip mined loop with a backedge
266// to the loop head. The inner strip mined loop is left as it is. Only
267// once loop optimizations are over, do we adjust the inner loop exit
268// condition to limit its number of iterations, set the outer loop
269// exit condition and add Phis to the outer loop head. Some loop
270// optimizations that operate on the inner strip mined loop need to be
271// aware of the outer strip mined loop: loop unswitching needs to
272// clone the outer loop as well as the inner, unrolling needs to only
273// clone the inner loop etc. No optimizations need to change the outer
274// strip mined loop as it is only a skeleton.
275IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
276 IdealLoopTree* loop, float cl_prob, float le_fcnt,
277 Node*& entry_control, Node*& iffalse) {
278 Node* outer_test = _igvn.intcon(0);
279 set_ctrl(outer_test, C->root());
280 Node *orig = iffalse;
281 iffalse = iffalse->clone();
282 _igvn.register_new_node_with_optimizer(iffalse);
283 set_idom(iffalse, idom(orig), dom_depth(orig));
284
285 IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
286 Node *outer_ift = new IfTrueNode (outer_le);
287 Node* outer_iff = orig;
288 _igvn.replace_input_of(outer_iff, 0, outer_le);
289
290 LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
291 entry_control = outer_l;
292
293 IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
294 IdealLoopTree* parent = loop->_parent;
295 IdealLoopTree* sibling = parent->_child;
296 if (sibling == loop) {
297 parent->_child = outer_ilt;
298 } else {
299 while (sibling->_next != loop) {
300 sibling = sibling->_next;
301 }
302 sibling->_next = outer_ilt;
303 }
304 outer_ilt->_next = loop->_next;
305 outer_ilt->_parent = parent;
306 outer_ilt->_child = loop;
307 outer_ilt->_nest = loop->_nest;
308 loop->_parent = outer_ilt;
309 loop->_next = NULL;
310 loop->_nest++;
311
312 set_loop(iffalse, outer_ilt);
313 register_control(outer_le, outer_ilt, iffalse);
314 register_control(outer_ift, outer_ilt, outer_le);
315 set_idom(outer_iff, outer_le, dom_depth(outer_le));
316 _igvn.register_new_node_with_optimizer(outer_l);
317 set_loop(outer_l, outer_ilt);
318 set_idom(outer_l, init_control, dom_depth(init_control)+1);
319
320 return outer_ilt;
321}
322
323void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
324 Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
325 Deoptimization::Reason_loop_limit_check,
326 Op_If);
327 Node* iff = new_predicate_proj->in(0);
328 assert(iff->Opcode() == Op_If, "bad graph shape");
329 Node* conv = iff->in(1);
330 assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
331 Node* opaq = conv->in(1);
332 assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
333 cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
334 bol = _igvn.register_new_node_with_optimizer(bol);
335 set_subtree_ctrl(bol);
336 _igvn.replace_input_of(iff, 1, bol);
337
338#ifndef PRODUCT
339 // report that the loop predication has been actually performed
340 // for this loop
341 if (TraceLoopLimitCheck) {
342 tty->print_cr("Counted Loop Limit Check generated:");
343 debug_only( bol->dump(2); )
344 }
345#endif
346}
347
348//------------------------------is_counted_loop--------------------------------
349bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
350 PhaseGVN *gvn = &_igvn;
351
352 // Counted loop head must be a good RegionNode with only 3 not NULL
353 // control input edges: Self, Entry, LoopBack.
354 if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
355 return false;
356 }
357 Node *init_control = x->in(LoopNode::EntryControl);
358 Node *back_control = x->in(LoopNode::LoopBackControl);
359 if (init_control == NULL || back_control == NULL) // Partially dead
360 return false;
361 // Must also check for TOP when looking for a dead loop
362 if (init_control->is_top() || back_control->is_top())
363 return false;
364
365 // Allow funny placement of Safepoint
366 if (back_control->Opcode() == Op_SafePoint) {
367 if (LoopStripMiningIter != 0) {
368 // Leaving the safepoint on the backedge and creating a
369 // CountedLoop will confuse optimizations. We can't move the
370 // safepoint around because its jvm state wouldn't match a new
371 // location. Give up on that loop.
372 return false;
373 }
374 back_control = back_control->in(TypeFunc::Control);
375 }
376
377 // Controlling test for loop
378 Node *iftrue = back_control;
379 uint iftrue_op = iftrue->Opcode();
380 if (iftrue_op != Op_IfTrue &&
381 iftrue_op != Op_IfFalse)
382 // I have a weird back-control. Probably the loop-exit test is in
383 // the middle of the loop and I am looking at some trailing control-flow
384 // merge point. To fix this I would have to partially peel the loop.
385 return false; // Obscure back-control
386
387 // Get boolean guarding loop-back test
388 Node *iff = iftrue->in(0);
389 if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
390 return false;
391 BoolNode *test = iff->in(1)->as_Bool();
392 BoolTest::mask bt = test->_test._test;
393 float cl_prob = iff->as_If()->_prob;
394 if (iftrue_op == Op_IfFalse) {
395 bt = BoolTest(bt).negate();
396 cl_prob = 1.0 - cl_prob;
397 }
398 // Get backedge compare
399 Node *cmp = test->in(1);
400 int cmp_op = cmp->Opcode();
401 if (cmp_op != Op_CmpI)
402 return false; // Avoid pointer & float compares
403
404 // Find the trip-counter increment & limit. Limit must be loop invariant.
405 Node *incr = cmp->in(1);
406 Node *limit = cmp->in(2);
407
408 // ---------
409 // need 'loop()' test to tell if limit is loop invariant
410 // ---------
411
412 if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
413 Node *tmp = incr; // Then reverse order into the CmpI
414 incr = limit;
415 limit = tmp;
416 bt = BoolTest(bt).commute(); // And commute the exit test
417 }
418 if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
419 return false;
420 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
421 return false;
422
423 Node* phi_incr = NULL;
424 // Trip-counter increment must be commutative & associative.
425 if (incr->Opcode() == Op_CastII) {
426 incr = incr->in(1);
427 }
428 if (incr->is_Phi()) {
429 if (incr->as_Phi()->region() != x || incr->req() != 3)
430 return false; // Not simple trip counter expression
431 phi_incr = incr;
432 incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
433 if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
434 return false;
435 }
436
437 Node* trunc1 = NULL;
438 Node* trunc2 = NULL;
439 const TypeInt* iv_trunc_t = NULL;
440 Node* orig_incr = incr;
441 if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
442 return false; // Funny increment opcode
443 }
444 assert(incr->Opcode() == Op_AddI, "wrong increment code");
445
446 const TypeInt* limit_t = gvn->type(limit)->is_int();
447 if (trunc1 != NULL) {
448 // When there is a truncation, we must be sure that after the truncation
449 // the trip counter will end up higher than the limit, otherwise we are looking
450 // at an endless loop. Can happen with range checks.
451
452 // Example:
453 // int i = 0;
454 // while (true)
455 // sum + = array[i];
456 // i++;
457 // i = i && 0x7fff;
458 // }
459 //
460 // If the array is shorter than 0x8000 this exits through a AIOOB
461 // - Counted loop transformation is ok
462 // If the array is longer then this is an endless loop
463 // - No transformation can be done.
464
465 const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
466 if (limit_t->_hi > incr_t->_hi) {
467 // if the limit can have a higher value than the increment (before the phi)
468 return false;
469 }
470 }
471
472 // Get merge point
473 Node *xphi = incr->in(1);
474 Node *stride = incr->in(2);
475 if (!stride->is_Con()) { // Oops, swap these
476 if (!xphi->is_Con()) // Is the other guy a constant?
477 return false; // Nope, unknown stride, bail out
478 Node *tmp = xphi; // 'incr' is commutative, so ok to swap
479 xphi = stride;
480 stride = tmp;
481 }
482 if (xphi->Opcode() == Op_CastII) {
483 xphi = xphi->in(1);
484 }
485 // Stride must be constant
486 int stride_con = stride->get_int();
487 if (stride_con == 0)
488 return false; // missed some peephole opt
489
490 if (!xphi->is_Phi())
491 return false; // Too much math on the trip counter
492 if (phi_incr != NULL && phi_incr != xphi)
493 return false;
494 PhiNode *phi = xphi->as_Phi();
495
496 // Phi must be of loop header; backedge must wrap to increment
497 if (phi->region() != x)
498 return false;
499 if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
500 (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
501 return false;
502 }
503 Node *init_trip = phi->in(LoopNode::EntryControl);
504
505 // If iv trunc type is smaller than int, check for possible wrap.
506 if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
507 assert(trunc1 != NULL, "must have found some truncation");
508
509 // Get a better type for the phi (filtered thru if's)
510 const TypeInt* phi_ft = filtered_type(phi);
511
512 // Can iv take on a value that will wrap?
513 //
514 // Ensure iv's limit is not within "stride" of the wrap value.
515 //
516 // Example for "short" type
517 // Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
518 // If the stride is +10, then the last value of the induction
519 // variable before the increment (phi_ft->_hi) must be
520 // <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
521 // ensure no truncation occurs after the increment.
522
523 if (stride_con > 0) {
524 if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
525 iv_trunc_t->_lo > phi_ft->_lo) {
526 return false; // truncation may occur
527 }
528 } else if (stride_con < 0) {
529 if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
530 iv_trunc_t->_hi < phi_ft->_hi) {
531 return false; // truncation may occur
532 }
533 }
534 // No possibility of wrap so truncation can be discarded
535 // Promote iv type to Int
536 } else {
537 assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
538 }
539
540 // If the condition is inverted and we will be rolling
541 // through MININT to MAXINT, then bail out.
542 if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
543 // Odd stride
544 (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
545 // Count down loop rolls through MAXINT
546 ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
547 // Count up loop rolls through MININT
548 ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
549 return false; // Bail out
550 }
551
552 const TypeInt* init_t = gvn->type(init_trip)->is_int();
553
554 if (stride_con > 0) {
555 jlong init_p = (jlong)init_t->_lo + stride_con;
556 if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
557 return false; // cyclic loop or this loop trips only once
558 } else {
559 jlong init_p = (jlong)init_t->_hi + stride_con;
560 if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
561 return false; // cyclic loop or this loop trips only once
562 }
563
564 if (phi_incr != NULL && bt != BoolTest::ne) {
565 // check if there is a possiblity of IV overflowing after the first increment
566 if (stride_con > 0) {
567 if (init_t->_hi > max_jint - stride_con) {
568 return false;
569 }
570 } else {
571 if (init_t->_lo < min_jint - stride_con) {
572 return false;
573 }
574 }
575 }
576
577 // =================================================
578 // ---- SUCCESS! Found A Trip-Counted Loop! -----
579 //
580 assert(x->Opcode() == Op_Loop, "regular loops only");
581 C->print_method(PHASE_BEFORE_CLOOPS, 3);
582
583 Node *hook = new Node(6);
584
585 // ===================================================
586 // Generate loop limit check to avoid integer overflow
587 // in cases like next (cyclic loops):
588 //
589 // for (i=0; i <= max_jint; i++) {}
590 // for (i=0; i < max_jint; i+=2) {}
591 //
592 //
593 // Limit check predicate depends on the loop test:
594 //
595 // for(;i != limit; i++) --> limit <= (max_jint)
596 // for(;i < limit; i+=stride) --> limit <= (max_jint - stride + 1)
597 // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride )
598 //
599
600 // Check if limit is excluded to do more precise int overflow check.
601 bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
602 int stride_m = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
603
604 // If compare points directly to the phi we need to adjust
605 // the compare so that it points to the incr. Limit have
606 // to be adjusted to keep trip count the same and the
607 // adjusted limit should be checked for int overflow.
608 if (phi_incr != NULL) {
609 stride_m += stride_con;
610 }
611
612 if (limit->is_Con()) {
613 int limit_con = limit->get_int();
614 if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
615 (stride_con < 0 && limit_con < (min_jint - stride_m))) {
616 // Bailout: it could be integer overflow.
617 return false;
618 }
619 } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
620 (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
621 // Limit's type may satisfy the condition, for example,
622 // when it is an array length.
623 } else {
624 // Generate loop's limit check.
625 // Loop limit check predicate should be near the loop.
626 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
627 if (!limit_check_proj) {
628 // The limit check predicate is not generated if this method trapped here before.
629#ifdef ASSERT
630 if (TraceLoopLimitCheck) {
631 tty->print("missing loop limit check:");
632 loop->dump_head();
633 x->dump(1);
634 }
635#endif
636 return false;
637 }
638
639 IfNode* check_iff = limit_check_proj->in(0)->as_If();
640
641 if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
642 return false;
643 }
644
645 Node* cmp_limit;
646 Node* bol;
647
648 if (stride_con > 0) {
649 cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
650 bol = new BoolNode(cmp_limit, BoolTest::le);
651 } else {
652 cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
653 bol = new BoolNode(cmp_limit, BoolTest::ge);
654 }
655
656 insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
657 }
658
659 // Now we need to canonicalize loop condition.
660 if (bt == BoolTest::ne) {
661 assert(stride_con == 1 || stride_con == -1, "simple increment only");
662 if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
663 // 'ne' can be replaced with 'lt' only when init < limit.
664 bt = BoolTest::lt;
665 } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
666 // 'ne' can be replaced with 'gt' only when init > limit.
667 bt = BoolTest::gt;
668 } else {
669 ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
670 if (!limit_check_proj) {
671 // The limit check predicate is not generated if this method trapped here before.
672#ifdef ASSERT
673 if (TraceLoopLimitCheck) {
674 tty->print("missing loop limit check:");
675 loop->dump_head();
676 x->dump(1);
677 }
678#endif
679 return false;
680 }
681 IfNode* check_iff = limit_check_proj->in(0)->as_If();
682
683 if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
684 !is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
685 return false;
686 }
687
688 Node* cmp_limit;
689 Node* bol;
690
691 if (stride_con > 0) {
692 cmp_limit = new CmpINode(init_trip, limit);
693 bol = new BoolNode(cmp_limit, BoolTest::lt);
694 } else {
695 cmp_limit = new CmpINode(init_trip, limit);
696 bol = new BoolNode(cmp_limit, BoolTest::gt);
697 }
698
699 insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
700
701 if (stride_con > 0) {
702 // 'ne' can be replaced with 'lt' only when init < limit.
703 bt = BoolTest::lt;
704 } else if (stride_con < 0) {
705 // 'ne' can be replaced with 'gt' only when init > limit.
706 bt = BoolTest::gt;
707 }
708 }
709 }
710
711 if (phi_incr != NULL) {
712 // If compare points directly to the phi we need to adjust
713 // the compare so that it points to the incr. Limit have
714 // to be adjusted to keep trip count the same and we
715 // should avoid int overflow.
716 //
717 // i = init; do {} while(i++ < limit);
718 // is converted to
719 // i = init; do {} while(++i < limit+1);
720 //
721 limit = gvn->transform(new AddINode(limit, stride));
722 }
723
724 if (incl_limit) {
725 // The limit check guaranties that 'limit <= (max_jint - stride)' so
726 // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
727 //
728 Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
729 limit = gvn->transform(new AddINode(limit, one));
730 if (bt == BoolTest::le)
731 bt = BoolTest::lt;
732 else if (bt == BoolTest::ge)
733 bt = BoolTest::gt;
734 else
735 ShouldNotReachHere();
736 }
737 set_subtree_ctrl( limit );
738
739 if (LoopStripMiningIter == 0) {
740 // Check for SafePoint on backedge and remove
741 Node *sfpt = x->in(LoopNode::LoopBackControl);
742 if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
743 lazy_replace( sfpt, iftrue );
744 if (loop->_safepts != NULL) {
745 loop->_safepts->yank(sfpt);
746 }
747 loop->_tail = iftrue;
748 }
749 }
750
751 // Build a canonical trip test.
752 // Clone code, as old values may be in use.
753 incr = incr->clone();
754 incr->set_req(1,phi);
755 incr->set_req(2,stride);
756 incr = _igvn.register_new_node_with_optimizer(incr);
757 set_early_ctrl( incr );
758 _igvn.rehash_node_delayed(phi);
759 phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
760
761 // If phi type is more restrictive than Int, raise to
762 // Int to prevent (almost) infinite recursion in igvn
763 // which can only handle integer types for constants or minint..maxint.
764 if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
765 Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
766 nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
767 nphi = _igvn.register_new_node_with_optimizer(nphi);
768 set_ctrl(nphi, get_ctrl(phi));
769 _igvn.replace_node(phi, nphi);
770 phi = nphi->as_Phi();
771 }
772 cmp = cmp->clone();
773 cmp->set_req(1,incr);
774 cmp->set_req(2,limit);
775 cmp = _igvn.register_new_node_with_optimizer(cmp);
776 set_ctrl(cmp, iff->in(0));
777
778 test = test->clone()->as_Bool();
779 (*(BoolTest*)&test->_test)._test = bt;
780 test->set_req(1,cmp);
781 _igvn.register_new_node_with_optimizer(test);
782 set_ctrl(test, iff->in(0));
783
784 // Replace the old IfNode with a new LoopEndNode
785 Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
786 IfNode *le = lex->as_If();
787 uint dd = dom_depth(iff);
788 set_idom(le, le->in(0), dd); // Update dominance for loop exit
789 set_loop(le, loop);
790
791 // Get the loop-exit control
792 Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
793
794 // Need to swap loop-exit and loop-back control?
795 if (iftrue_op == Op_IfFalse) {
796 Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
797 Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
798
799 loop->_tail = back_control = ift2;
800 set_loop(ift2, loop);
801 set_loop(iff2, get_loop(iffalse));
802
803 // Lazy update of 'get_ctrl' mechanism.
804 lazy_replace(iffalse, iff2);
805 lazy_replace(iftrue, ift2);
806
807 // Swap names
808 iffalse = iff2;
809 iftrue = ift2;
810 } else {
811 _igvn.rehash_node_delayed(iffalse);
812 _igvn.rehash_node_delayed(iftrue);
813 iffalse->set_req_X( 0, le, &_igvn );
814 iftrue ->set_req_X( 0, le, &_igvn );
815 }
816
817 set_idom(iftrue, le, dd+1);
818 set_idom(iffalse, le, dd+1);
819 assert(iff->outcnt() == 0, "should be dead now");
820 lazy_replace( iff, le ); // fix 'get_ctrl'
821
822 Node *sfpt2 = le->in(0);
823
824 Node* entry_control = init_control;
825 bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
826 sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
827 IdealLoopTree* outer_ilt = NULL;
828 if (strip_mine_loop) {
829 outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
830 cl_prob, le->_fcnt, entry_control,
831 iffalse);
832 }
833
834 // Now setup a new CountedLoopNode to replace the existing LoopNode
835 CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
836 l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
837 // The following assert is approximately true, and defines the intention
838 // of can_be_counted_loop. It fails, however, because phase->type
839 // is not yet initialized for this loop and its parts.
840 //assert(l->can_be_counted_loop(this), "sanity");
841 _igvn.register_new_node_with_optimizer(l);
842 set_loop(l, loop);
843 loop->_head = l;
844 // Fix all data nodes placed at the old loop head.
845 // Uses the lazy-update mechanism of 'get_ctrl'.
846 lazy_replace( x, l );
847 set_idom(l, entry_control, dom_depth(entry_control) + 1);
848
849 if (LoopStripMiningIter == 0 || strip_mine_loop) {
850 // Check for immediately preceding SafePoint and remove
851 if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
852 if (strip_mine_loop) {
853 Node* outer_le = outer_ilt->_tail->in(0);
854 Node* sfpt = sfpt2->clone();
855 sfpt->set_req(0, iffalse);
856 outer_le->set_req(0, sfpt);
857 register_control(sfpt, outer_ilt, iffalse);
858 set_idom(outer_le, sfpt, dom_depth(sfpt));
859 }
860 lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
861 if (loop->_safepts != NULL) {
862 loop->_safepts->yank(sfpt2);
863 }
864 }
865 }
866
867 // Free up intermediate goo
868 _igvn.remove_dead_node(hook);
869
870#ifdef ASSERT
871 assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
872 assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
873#endif
874#ifndef PRODUCT
875 if (TraceLoopOpts) {
876 tty->print("Counted ");
877 loop->dump_head();
878 }
879#endif
880
881 C->print_method(PHASE_AFTER_CLOOPS, 3);
882
883 // Capture bounds of the loop in the induction variable Phi before
884 // subsequent transformation (iteration splitting) obscures the
885 // bounds
886 l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
887
888 if (strip_mine_loop) {
889 l->mark_strip_mined();
890 l->verify_strip_mined(1);
891 outer_ilt->_head->as_Loop()->verify_strip_mined(1);
892 loop = outer_ilt;
893 }
894
895 return true;
896}
897
898//----------------------exact_limit-------------------------------------------
899Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
900 assert(loop->_head->is_CountedLoop(), "");
901 CountedLoopNode *cl = loop->_head->as_CountedLoop();
902 assert(cl->is_valid_counted_loop(), "");
903
904 if (ABS(cl->stride_con()) == 1 ||
905 cl->limit()->Opcode() == Op_LoopLimit) {
906 // Old code has exact limit (it could be incorrect in case of int overflow).
907 // Loop limit is exact with stride == 1. And loop may already have exact limit.
908 return cl->limit();
909 }
910 Node *limit = NULL;
911#ifdef ASSERT
912 BoolTest::mask bt = cl->loopexit()->test_trip();
913 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
914#endif
915 if (cl->has_exact_trip_count()) {
916 // Simple case: loop has constant boundaries.
917 // Use jlongs to avoid integer overflow.
918 int stride_con = cl->stride_con();
919 jlong init_con = cl->init_trip()->get_int();
920 jlong limit_con = cl->limit()->get_int();
921 julong trip_cnt = cl->trip_count();
922 jlong final_con = init_con + trip_cnt*stride_con;
923 int final_int = (int)final_con;
924 // The final value should be in integer range since the loop
925 // is counted and the limit was checked for overflow.
926 assert(final_con == (jlong)final_int, "final value should be integer");
927 limit = _igvn.intcon(final_int);
928 } else {
929 // Create new LoopLimit node to get exact limit (final iv value).
930 limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
931 register_new_node(limit, cl->in(LoopNode::EntryControl));
932 }
933 assert(limit != NULL, "sanity");
934 return limit;
935}
936
937//------------------------------Ideal------------------------------------------
938// Return a node which is more "ideal" than the current node.
939// Attempt to convert into a counted-loop.
940Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
941 if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
942 phase->C->set_major_progress();
943 }
944 return RegionNode::Ideal(phase, can_reshape);
945}
946
947void LoopNode::verify_strip_mined(int expect_skeleton) const {
948#ifdef ASSERT
949 const OuterStripMinedLoopNode* outer = NULL;
950 const CountedLoopNode* inner = NULL;
951 if (is_strip_mined()) {
952 assert(is_CountedLoop(), "no Loop should be marked strip mined");
953 inner = as_CountedLoop();
954 outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
955 } else if (is_OuterStripMinedLoop()) {
956 outer = this->as_OuterStripMinedLoop();
957 inner = outer->unique_ctrl_out()->as_CountedLoop();
958 assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
959 }
960 if (inner != NULL || outer != NULL) {
961 assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
962 Node* outer_tail = outer->in(LoopNode::LoopBackControl);
963 Node* outer_le = outer_tail->in(0);
964 assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
965 Node* sfpt = outer_le->in(0);
966 assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
967 Node* inner_out = sfpt->in(0);
968 if (inner_out->outcnt() != 1) {
969 ResourceMark rm;
970 Unique_Node_List wq;
971
972 for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
973 Node* u = inner_out->fast_out(i);
974 if (u == sfpt) {
975 continue;
976 }
977 wq.clear();
978 wq.push(u);
979 bool found_sfpt = false;
980 for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
981 Node* n = wq.at(next);
982 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
983 Node* u = n->fast_out(i);
984 if (u == sfpt) {
985 found_sfpt = true;
986 }
987 if (!u->is_CFG()) {
988 wq.push(u);
989 }
990 }
991 }
992 assert(found_sfpt, "no node in loop that's not input to safepoint");
993 }
994 }
995
996 if (UseZGC && !inner_out->in(0)->is_CountedLoopEnd()) {
997 // In some very special cases there can be a load that has no other uses than the
998 // counted loop safepoint. Then its loadbarrier will be placed between the inner
999 // loop exit and the safepoint. This is very rare
1000
1001 Node* ifnode = inner_out->in(1)->in(0);
1002 // Region->IfTrue->If == Region->Iffalse->If
1003 if (ifnode == inner_out->in(2)->in(0)) {
1004 inner_out = ifnode->in(0);
1005 }
1006 }
1007
1008 CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
1009 assert(cle == inner->loopexit_or_null(), "mismatch");
1010 bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
1011 if (has_skeleton) {
1012 assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1013 assert(outer->outcnt() == 2, "only phis");
1014 } else {
1015 assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1016 uint phis = 0;
1017 for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1018 Node* u = inner->fast_out(i);
1019 if (u->is_Phi()) {
1020 phis++;
1021 }
1022 }
1023 for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1024 Node* u = outer->fast_out(i);
1025 assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1026 }
1027 uint stores = 0;
1028 for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1029 Node* u = inner_out->fast_out(i);
1030 if (u->is_Store()) {
1031 stores++;
1032 }
1033 }
1034 assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1035 }
1036 assert(sfpt->outcnt() == 1, "no data node");
1037 assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1038 }
1039#endif
1040}
1041
1042//=============================================================================
1043//------------------------------Ideal------------------------------------------
1044// Return a node which is more "ideal" than the current node.
1045// Attempt to convert into a counted-loop.
1046Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1047 return RegionNode::Ideal(phase, can_reshape);
1048}
1049
1050//------------------------------dump_spec--------------------------------------
1051// Dump special per-node info
1052#ifndef PRODUCT
1053void CountedLoopNode::dump_spec(outputStream *st) const {
1054 LoopNode::dump_spec(st);
1055 if (stride_is_con()) {
1056 st->print("stride: %d ",stride_con());
1057 }
1058 if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1059 if (is_main_loop()) st->print("main of N%d", _idx);
1060 if (is_post_loop()) st->print("post of N%d", _main_idx);
1061 if (is_strip_mined()) st->print(" strip mined");
1062}
1063#endif
1064
1065//=============================================================================
1066int CountedLoopEndNode::stride_con() const {
1067 return stride()->bottom_type()->is_int()->get_con();
1068}
1069
1070//=============================================================================
1071//------------------------------Value-----------------------------------------
1072const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1073 const Type* init_t = phase->type(in(Init));
1074 const Type* limit_t = phase->type(in(Limit));
1075 const Type* stride_t = phase->type(in(Stride));
1076 // Either input is TOP ==> the result is TOP
1077 if (init_t == Type::TOP) return Type::TOP;
1078 if (limit_t == Type::TOP) return Type::TOP;
1079 if (stride_t == Type::TOP) return Type::TOP;
1080
1081 int stride_con = stride_t->is_int()->get_con();
1082 if (stride_con == 1)
1083 return NULL; // Identity
1084
1085 if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1086 // Use jlongs to avoid integer overflow.
1087 jlong init_con = init_t->is_int()->get_con();
1088 jlong limit_con = limit_t->is_int()->get_con();
1089 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
1090 jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1091 jlong final_con = init_con + stride_con*trip_count;
1092 int final_int = (int)final_con;
1093 // The final value should be in integer range since the loop
1094 // is counted and the limit was checked for overflow.
1095 assert(final_con == (jlong)final_int, "final value should be integer");
1096 return TypeInt::make(final_int);
1097 }
1098
1099 return bottom_type(); // TypeInt::INT
1100}
1101
1102//------------------------------Ideal------------------------------------------
1103// Return a node which is more "ideal" than the current node.
1104Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1105 if (phase->type(in(Init)) == Type::TOP ||
1106 phase->type(in(Limit)) == Type::TOP ||
1107 phase->type(in(Stride)) == Type::TOP)
1108 return NULL; // Dead
1109
1110 int stride_con = phase->type(in(Stride))->is_int()->get_con();
1111 if (stride_con == 1)
1112 return NULL; // Identity
1113
1114 if (in(Init)->is_Con() && in(Limit)->is_Con())
1115 return NULL; // Value
1116
1117 // Delay following optimizations until all loop optimizations
1118 // done to keep Ideal graph simple.
1119 if (!can_reshape || phase->C->major_progress())
1120 return NULL;
1121
1122 const TypeInt* init_t = phase->type(in(Init) )->is_int();
1123 const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1124 int stride_p;
1125 jlong lim, ini;
1126 julong max;
1127 if (stride_con > 0) {
1128 stride_p = stride_con;
1129 lim = limit_t->_hi;
1130 ini = init_t->_lo;
1131 max = (julong)max_jint;
1132 } else {
1133 stride_p = -stride_con;
1134 lim = init_t->_hi;
1135 ini = limit_t->_lo;
1136 max = (julong)min_jint;
1137 }
1138 julong range = lim - ini + stride_p;
1139 if (range <= max) {
1140 // Convert to integer expression if it is not overflow.
1141 Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1142 Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1143 Node *bias = phase->transform(new AddINode(range, stride_m));
1144 Node *trip = phase->transform(new DivINode(0, bias, in(Stride)));
1145 Node *span = phase->transform(new MulINode(trip, in(Stride)));
1146 return new AddINode(span, in(Init)); // exact limit
1147 }
1148
1149 if (is_power_of_2(stride_p) || // divisor is 2^n
1150 !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1151 // Convert to long expression to avoid integer overflow
1152 // and let igvn optimizer convert this division.
1153 //
1154 Node* init = phase->transform( new ConvI2LNode(in(Init)));
1155 Node* limit = phase->transform( new ConvI2LNode(in(Limit)));
1156 Node* stride = phase->longcon(stride_con);
1157 Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1158
1159 Node *range = phase->transform(new SubLNode(limit, init));
1160 Node *bias = phase->transform(new AddLNode(range, stride_m));
1161 Node *span;
1162 if (stride_con > 0 && is_power_of_2(stride_p)) {
1163 // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1164 // and avoid generating rounding for division. Zero trip guard should
1165 // guarantee that init < limit but sometimes the guard is missing and
1166 // we can get situation when init > limit. Note, for the empty loop
1167 // optimization zero trip guard is generated explicitly which leaves
1168 // only RCE predicate where exact limit is used and the predicate
1169 // will simply fail forcing recompilation.
1170 Node* neg_stride = phase->longcon(-stride_con);
1171 span = phase->transform(new AndLNode(bias, neg_stride));
1172 } else {
1173 Node *trip = phase->transform(new DivLNode(0, bias, stride));
1174 span = phase->transform(new MulLNode(trip, stride));
1175 }
1176 // Convert back to int
1177 Node *span_int = phase->transform(new ConvL2INode(span));
1178 return new AddINode(span_int, in(Init)); // exact limit
1179 }
1180
1181 return NULL; // No progress
1182}
1183
1184//------------------------------Identity---------------------------------------
1185// If stride == 1 return limit node.
1186Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1187 int stride_con = phase->type(in(Stride))->is_int()->get_con();
1188 if (stride_con == 1 || stride_con == -1)
1189 return in(Limit);
1190 return this;
1191}
1192
1193//=============================================================================
1194//----------------------match_incr_with_optional_truncation--------------------
1195// Match increment with optional truncation:
1196// CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1197// Return NULL for failure. Success returns the increment node.
1198Node* CountedLoopNode::match_incr_with_optional_truncation(
1199 Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1200 // Quick cutouts:
1201 if (expr == NULL || expr->req() != 3) return NULL;
1202
1203 Node *t1 = NULL;
1204 Node *t2 = NULL;
1205 const TypeInt* trunc_t = TypeInt::INT;
1206 Node* n1 = expr;
1207 int n1op = n1->Opcode();
1208
1209 // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1210 if (n1op == Op_AndI &&
1211 n1->in(2)->is_Con() &&
1212 n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1213 // %%% This check should match any mask of 2**K-1.
1214 t1 = n1;
1215 n1 = t1->in(1);
1216 n1op = n1->Opcode();
1217 trunc_t = TypeInt::CHAR;
1218 } else if (n1op == Op_RShiftI &&
1219 n1->in(1) != NULL &&
1220 n1->in(1)->Opcode() == Op_LShiftI &&
1221 n1->in(2) == n1->in(1)->in(2) &&
1222 n1->in(2)->is_Con()) {
1223 jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1224 // %%% This check should match any shift in [1..31].
1225 if (shift == 16 || shift == 8) {
1226 t1 = n1;
1227 t2 = t1->in(1);
1228 n1 = t2->in(1);
1229 n1op = n1->Opcode();
1230 if (shift == 16) {
1231 trunc_t = TypeInt::SHORT;
1232 } else if (shift == 8) {
1233 trunc_t = TypeInt::BYTE;
1234 }
1235 }
1236 }
1237
1238 // If (maybe after stripping) it is an AddI, we won:
1239 if (n1op == Op_AddI) {
1240 *trunc1 = t1;
1241 *trunc2 = t2;
1242 *trunc_type = trunc_t;
1243 return n1;
1244 }
1245
1246 // failed
1247 return NULL;
1248}
1249
1250LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1251 if (is_strip_mined()) {
1252 verify_strip_mined(expect_skeleton);
1253 return in(EntryControl)->as_Loop();
1254 }
1255 return this;
1256}
1257
1258OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1259 assert(is_strip_mined(), "not a strip mined loop");
1260 Node* c = in(EntryControl);
1261 if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1262 return NULL;
1263 }
1264 return c->as_OuterStripMinedLoop();
1265}
1266
1267IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1268 Node* c = in(LoopBackControl);
1269 if (c == NULL || c->is_top()) {
1270 return NULL;
1271 }
1272 return c->as_IfTrue();
1273}
1274
1275IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1276 LoopNode* l = outer_loop();
1277 if (l == NULL) {
1278 return NULL;
1279 }
1280 return l->outer_loop_tail();
1281}
1282
1283OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1284 IfTrueNode* proj = outer_loop_tail();
1285 if (proj == NULL) {
1286 return NULL;
1287 }
1288 Node* c = proj->in(0);
1289 if (c == NULL || c->is_top() || c->outcnt() != 2) {
1290 return NULL;
1291 }
1292 return c->as_OuterStripMinedLoopEnd();
1293}
1294
1295OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1296 LoopNode* l = outer_loop();
1297 if (l == NULL) {
1298 return NULL;
1299 }
1300 return l->outer_loop_end();
1301}
1302
1303IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1304 IfNode* le = outer_loop_end();
1305 if (le == NULL) {
1306 return NULL;
1307 }
1308 Node* c = le->proj_out_or_null(false);
1309 if (c == NULL) {
1310 return NULL;
1311 }
1312 return c->as_IfFalse();
1313}
1314
1315IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1316 LoopNode* l = outer_loop();
1317 if (l == NULL) {
1318 return NULL;
1319 }
1320 return l->outer_loop_exit();
1321}
1322
1323SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1324 IfNode* le = outer_loop_end();
1325 if (le == NULL) {
1326 return NULL;
1327 }
1328 Node* c = le->in(0);
1329 if (c == NULL || c->is_top()) {
1330 return NULL;
1331 }
1332 assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1333 return c->as_SafePoint();
1334}
1335
1336SafePointNode* CountedLoopNode::outer_safepoint() const {
1337 LoopNode* l = outer_loop();
1338 if (l == NULL) {
1339 return NULL;
1340 }
1341 return l->outer_safepoint();
1342}
1343
1344Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1345 while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1346 ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1347 ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1348 ctrl = ctrl->in(0)->in(0);
1349 }
1350
1351 return ctrl;
1352 }
1353
1354Node* CountedLoopNode::skip_predicates() {
1355 if (is_main_loop()) {
1356 Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1357
1358 return skip_predicates_from_entry(ctrl);
1359 }
1360 return in(LoopNode::EntryControl);
1361}
1362
1363void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1364 // Look for the outer & inner strip mined loop, reduce number of
1365 // iterations of the inner loop, set exit condition of outer loop,
1366 // construct required phi nodes for outer loop.
1367 CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1368 assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1369 Node* inner_iv_phi = inner_cl->phi();
1370 if (inner_iv_phi == NULL) {
1371 IfNode* outer_le = outer_loop_end();
1372 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1373 igvn->replace_node(outer_le, iff);
1374 inner_cl->clear_strip_mined();
1375 return;
1376 }
1377 CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1378
1379 int stride = inner_cl->stride_con();
1380 jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1381 int scaled_iters = (int)scaled_iters_long;
1382 int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1383 const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1384 jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1385 assert(iter_estimate > 0, "broken");
1386 if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1387 // Remove outer loop and safepoint (too few iterations)
1388 Node* outer_sfpt = outer_safepoint();
1389 Node* outer_out = outer_loop_exit();
1390 igvn->replace_node(outer_out, outer_sfpt->in(0));
1391 igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1392 inner_cl->clear_strip_mined();
1393 return;
1394 }
1395 if (iter_estimate <= scaled_iters_long) {
1396 // We would only go through one iteration of
1397 // the outer loop: drop the outer loop but
1398 // keep the safepoint so we don't run for
1399 // too long without a safepoint
1400 IfNode* outer_le = outer_loop_end();
1401 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1402 igvn->replace_node(outer_le, iff);
1403 inner_cl->clear_strip_mined();
1404 return;
1405 }
1406
1407 Node* cle_tail = inner_cle->proj_out(true);
1408 ResourceMark rm;
1409 Node_List old_new;
1410 if (cle_tail->outcnt() > 1) {
1411 // Look for nodes on backedge of inner loop and clone them
1412 Unique_Node_List backedge_nodes;
1413 for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1414 Node* u = cle_tail->fast_out(i);
1415 if (u != inner_cl) {
1416 assert(!u->is_CFG(), "control flow on the backedge?");
1417 backedge_nodes.push(u);
1418 }
1419 }
1420 uint last = igvn->C->unique();
1421 for (uint next = 0; next < backedge_nodes.size(); next++) {
1422 Node* n = backedge_nodes.at(next);
1423 old_new.map(n->_idx, n->clone());
1424 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1425 Node* u = n->fast_out(i);
1426 assert(!u->is_CFG(), "broken");
1427 if (u->_idx >= last) {
1428 continue;
1429 }
1430 if (!u->is_Phi()) {
1431 backedge_nodes.push(u);
1432 } else {
1433 assert(u->in(0) == inner_cl, "strange phi on the backedge");
1434 }
1435 }
1436 }
1437 // Put the clones on the outer loop backedge
1438 Node* le_tail = outer_loop_tail();
1439 for (uint next = 0; next < backedge_nodes.size(); next++) {
1440 Node *n = old_new[backedge_nodes.at(next)->_idx];
1441 for (uint i = 1; i < n->req(); i++) {
1442 if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1443 n->set_req(i, old_new[n->in(i)->_idx]);
1444 }
1445 }
1446 if (n->in(0) != NULL && n->in(0) == cle_tail) {
1447 n->set_req(0, le_tail);
1448 }
1449 igvn->register_new_node_with_optimizer(n);
1450 }
1451 }
1452
1453 Node* iv_phi = NULL;
1454 // Make a clone of each phi in the inner loop
1455 // for the outer loop
1456 for (uint i = 0; i < inner_cl->outcnt(); i++) {
1457 Node* u = inner_cl->raw_out(i);
1458 if (u->is_Phi()) {
1459 assert(u->in(0) == inner_cl, "inconsistent");
1460 Node* phi = u->clone();
1461 phi->set_req(0, this);
1462 Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1463 if (be != NULL) {
1464 phi->set_req(LoopNode::LoopBackControl, be);
1465 }
1466 phi = igvn->transform(phi);
1467 igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1468 if (u == inner_iv_phi) {
1469 iv_phi = phi;
1470 }
1471 }
1472 }
1473 Node* cle_out = inner_cle->proj_out(false);
1474 if (cle_out->outcnt() > 1) {
1475 // Look for chains of stores that were sunk
1476 // out of the inner loop and are in the outer loop
1477 for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1478 Node* u = cle_out->fast_out(i);
1479 if (u->is_Store()) {
1480 Node* first = u;
1481 for(;;) {
1482 Node* next = first->in(MemNode::Memory);
1483 if (!next->is_Store() || next->in(0) != cle_out) {
1484 break;
1485 }
1486 first = next;
1487 }
1488 Node* last = u;
1489 for(;;) {
1490 Node* next = NULL;
1491 for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1492 Node* uu = last->fast_out(j);
1493 if (uu->is_Store() && uu->in(0) == cle_out) {
1494 assert(next == NULL, "only one in the outer loop");
1495 next = uu;
1496 }
1497 }
1498 if (next == NULL) {
1499 break;
1500 }
1501 last = next;
1502 }
1503 Node* phi = NULL;
1504 for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1505 Node* uu = fast_out(j);
1506 if (uu->is_Phi()) {
1507 Node* be = uu->in(LoopNode::LoopBackControl);
1508 if (be->is_Store() && old_new[be->_idx] != NULL) {
1509 assert(false, "store on the backedge + sunk stores: unsupported");
1510 // drop outer loop
1511 IfNode* outer_le = outer_loop_end();
1512 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1513 igvn->replace_node(outer_le, iff);
1514 inner_cl->clear_strip_mined();
1515 return;
1516 }
1517 if (be == last || be == first->in(MemNode::Memory)) {
1518 assert(phi == NULL, "only one phi");
1519 phi = uu;
1520 }
1521 }
1522 }
1523#ifdef ASSERT
1524 for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1525 Node* uu = fast_out(j);
1526 if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1527 if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1528 assert(phi == uu, "what's that phi?");
1529 } else if (uu->adr_type() == TypePtr::BOTTOM) {
1530 Node* n = uu->in(LoopNode::LoopBackControl);
1531 uint limit = igvn->C->live_nodes();
1532 uint i = 0;
1533 while (n != uu) {
1534 i++;
1535 assert(i < limit, "infinite loop");
1536 if (n->is_Proj()) {
1537 n = n->in(0);
1538 } else if (n->is_SafePoint() || n->is_MemBar()) {
1539 n = n->in(TypeFunc::Memory);
1540 } else if (n->is_Phi()) {
1541 n = n->in(1);
1542 } else if (n->is_MergeMem()) {
1543 n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1544 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1545 n = n->in(MemNode::Memory);
1546 } else {
1547 n->dump();
1548 ShouldNotReachHere();
1549 }
1550 }
1551 }
1552 }
1553 }
1554#endif
1555 if (phi == NULL) {
1556 // If the an entire chains was sunk, the
1557 // inner loop has no phi for that memory
1558 // slice, create one for the outer loop
1559 phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1560 igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1561 phi->set_req(LoopNode::LoopBackControl, last);
1562 phi = igvn->transform(phi);
1563 igvn->replace_input_of(first, MemNode::Memory, phi);
1564 } else {
1565 // Or fix the outer loop fix to include
1566 // that chain of stores.
1567 Node* be = phi->in(LoopNode::LoopBackControl);
1568 assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1569 if (be == first->in(MemNode::Memory)) {
1570 if (be == phi->in(LoopNode::LoopBackControl)) {
1571 igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1572 } else {
1573 igvn->replace_input_of(be, MemNode::Memory, last);
1574 }
1575 } else {
1576#ifdef ASSERT
1577 if (be == phi->in(LoopNode::LoopBackControl)) {
1578 assert(phi->in(LoopNode::LoopBackControl) == last, "");
1579 } else {
1580 assert(be->in(MemNode::Memory) == last, "");
1581 }
1582#endif
1583 }
1584 }
1585 }
1586 }
1587 }
1588
1589 if (iv_phi != NULL) {
1590 // Now adjust the inner loop's exit condition
1591 Node* limit = inner_cl->limit();
1592 Node* sub = NULL;
1593 if (stride > 0) {
1594 sub = igvn->transform(new SubINode(limit, iv_phi));
1595 } else {
1596 sub = igvn->transform(new SubINode(iv_phi, limit));
1597 }
1598 Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters)));
1599 Node* new_limit = NULL;
1600 if (stride > 0) {
1601 new_limit = igvn->transform(new AddINode(min, iv_phi));
1602 } else {
1603 new_limit = igvn->transform(new SubINode(iv_phi, min));
1604 }
1605 Node* inner_cmp = inner_cle->cmp_node();
1606 Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1607 Node* outer_bol = inner_bol;
1608 // cmp node for inner loop may be shared
1609 inner_cmp = inner_cmp->clone();
1610 inner_cmp->set_req(2, new_limit);
1611 inner_bol = inner_bol->clone();
1612 inner_bol->set_req(1, igvn->transform(inner_cmp));
1613 igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1614 // Set the outer loop's exit condition too
1615 igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1616 } else {
1617 assert(false, "should be able to adjust outer loop");
1618 IfNode* outer_le = outer_loop_end();
1619 Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1620 igvn->replace_node(outer_le, iff);
1621 inner_cl->clear_strip_mined();
1622 }
1623}
1624
1625const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1626 if (!in(0)) return Type::TOP;
1627 if (phase->type(in(0)) == Type::TOP)
1628 return Type::TOP;
1629
1630 return TypeTuple::IFBOTH;
1631}
1632
1633Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1634 if (remove_dead_region(phase, can_reshape)) return this;
1635
1636 return NULL;
1637}
1638
1639//------------------------------filtered_type--------------------------------
1640// Return a type based on condition control flow
1641// A successful return will be a type that is restricted due
1642// to a series of dominating if-tests, such as:
1643// if (i < 10) {
1644// if (i > 0) {
1645// here: "i" type is [1..10)
1646// }
1647// }
1648// or a control flow merge
1649// if (i < 10) {
1650// do {
1651// phi( , ) -- at top of loop type is [min_int..10)
1652// i = ?
1653// } while ( i < 10)
1654//
1655const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1656 assert(n && n->bottom_type()->is_int(), "must be int");
1657 const TypeInt* filtered_t = NULL;
1658 if (!n->is_Phi()) {
1659 assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1660 filtered_t = filtered_type_from_dominators(n, n_ctrl);
1661
1662 } else {
1663 Node* phi = n->as_Phi();
1664 Node* region = phi->in(0);
1665 assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1666 if (region && region != C->top()) {
1667 for (uint i = 1; i < phi->req(); i++) {
1668 Node* val = phi->in(i);
1669 Node* use_c = region->in(i);
1670 const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1671 if (val_t != NULL) {
1672 if (filtered_t == NULL) {
1673 filtered_t = val_t;
1674 } else {
1675 filtered_t = filtered_t->meet(val_t)->is_int();
1676 }
1677 }
1678 }
1679 }
1680 }
1681 const TypeInt* n_t = _igvn.type(n)->is_int();
1682 if (filtered_t != NULL) {
1683 n_t = n_t->join(filtered_t)->is_int();
1684 }
1685 return n_t;
1686}
1687
1688
1689//------------------------------filtered_type_from_dominators--------------------------------
1690// Return a possibly more restrictive type for val based on condition control flow of dominators
1691const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1692 if (val->is_Con()) {
1693 return val->bottom_type()->is_int();
1694 }
1695 uint if_limit = 10; // Max number of dominating if's visited
1696 const TypeInt* rtn_t = NULL;
1697
1698 if (use_ctrl && use_ctrl != C->top()) {
1699 Node* val_ctrl = get_ctrl(val);
1700 uint val_dom_depth = dom_depth(val_ctrl);
1701 Node* pred = use_ctrl;
1702 uint if_cnt = 0;
1703 while (if_cnt < if_limit) {
1704 if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1705 if_cnt++;
1706 const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1707 if (if_t != NULL) {
1708 if (rtn_t == NULL) {
1709 rtn_t = if_t;
1710 } else {
1711 rtn_t = rtn_t->join(if_t)->is_int();
1712 }
1713 }
1714 }
1715 pred = idom(pred);
1716 if (pred == NULL || pred == C->top()) {
1717 break;
1718 }
1719 // Stop if going beyond definition block of val
1720 if (dom_depth(pred) < val_dom_depth) {
1721 break;
1722 }
1723 }
1724 }
1725 return rtn_t;
1726}
1727
1728
1729//------------------------------dump_spec--------------------------------------
1730// Dump special per-node info
1731#ifndef PRODUCT
1732void CountedLoopEndNode::dump_spec(outputStream *st) const {
1733 if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1734 BoolTest bt( test_trip()); // Added this for g++.
1735
1736 st->print("[");
1737 bt.dump_on(st);
1738 st->print("]");
1739 }
1740 st->print(" ");
1741 IfNode::dump_spec(st);
1742}
1743#endif
1744
1745//=============================================================================
1746//------------------------------is_member--------------------------------------
1747// Is 'l' a member of 'this'?
1748bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1749 while( l->_nest > _nest ) l = l->_parent;
1750 return l == this;
1751}
1752
1753//------------------------------set_nest---------------------------------------
1754// Set loop tree nesting depth. Accumulate _has_call bits.
1755int IdealLoopTree::set_nest( uint depth ) {
1756 _nest = depth;
1757 int bits = _has_call;
1758 if( _child ) bits |= _child->set_nest(depth+1);
1759 if( bits ) _has_call = 1;
1760 if( _next ) bits |= _next ->set_nest(depth );
1761 return bits;
1762}
1763
1764//------------------------------split_fall_in----------------------------------
1765// Split out multiple fall-in edges from the loop header. Move them to a
1766// private RegionNode before the loop. This becomes the loop landing pad.
1767void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1768 PhaseIterGVN &igvn = phase->_igvn;
1769 uint i;
1770
1771 // Make a new RegionNode to be the landing pad.
1772 Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1773 phase->set_loop(landing_pad,_parent);
1774 // Gather all the fall-in control paths into the landing pad
1775 uint icnt = fall_in_cnt;
1776 uint oreq = _head->req();
1777 for( i = oreq-1; i>0; i-- )
1778 if( !phase->is_member( this, _head->in(i) ) )
1779 landing_pad->set_req(icnt--,_head->in(i));
1780
1781 // Peel off PhiNode edges as well
1782 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1783 Node *oj = _head->fast_out(j);
1784 if( oj->is_Phi() ) {
1785 PhiNode* old_phi = oj->as_Phi();
1786 assert( old_phi->region() == _head, "" );
1787 igvn.hash_delete(old_phi); // Yank from hash before hacking edges
1788 Node *p = PhiNode::make_blank(landing_pad, old_phi);
1789 uint icnt = fall_in_cnt;
1790 for( i = oreq-1; i>0; i-- ) {
1791 if( !phase->is_member( this, _head->in(i) ) ) {
1792 p->init_req(icnt--, old_phi->in(i));
1793 // Go ahead and clean out old edges from old phi
1794 old_phi->del_req(i);
1795 }
1796 }
1797 // Search for CSE's here, because ZKM.jar does a lot of
1798 // loop hackery and we need to be a little incremental
1799 // with the CSE to avoid O(N^2) node blow-up.
1800 Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1801 if( p2 ) { // Found CSE
1802 p->destruct(); // Recover useless new node
1803 p = p2; // Use old node
1804 } else {
1805 igvn.register_new_node_with_optimizer(p, old_phi);
1806 }
1807 // Make old Phi refer to new Phi.
1808 old_phi->add_req(p);
1809 // Check for the special case of making the old phi useless and
1810 // disappear it. In JavaGrande I have a case where this useless
1811 // Phi is the loop limit and prevents recognizing a CountedLoop
1812 // which in turn prevents removing an empty loop.
1813 Node *id_old_phi = igvn.apply_identity(old_phi);
1814 if( id_old_phi != old_phi ) { // Found a simple identity?
1815 // Note that I cannot call 'replace_node' here, because
1816 // that will yank the edge from old_phi to the Region and
1817 // I'm mid-iteration over the Region's uses.
1818 for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1819 Node* use = old_phi->last_out(i);
1820 igvn.rehash_node_delayed(use);
1821 uint uses_found = 0;
1822 for (uint j = 0; j < use->len(); j++) {
1823 if (use->in(j) == old_phi) {
1824 if (j < use->req()) use->set_req (j, id_old_phi);
1825 else use->set_prec(j, id_old_phi);
1826 uses_found++;
1827 }
1828 }
1829 i -= uses_found; // we deleted 1 or more copies of this edge
1830 }
1831 }
1832 igvn._worklist.push(old_phi);
1833 }
1834 }
1835 // Finally clean out the fall-in edges from the RegionNode
1836 for( i = oreq-1; i>0; i-- ) {
1837 if( !phase->is_member( this, _head->in(i) ) ) {
1838 _head->del_req(i);
1839 }
1840 }
1841 igvn.rehash_node_delayed(_head);
1842 // Transform landing pad
1843 igvn.register_new_node_with_optimizer(landing_pad, _head);
1844 // Insert landing pad into the header
1845 _head->add_req(landing_pad);
1846}
1847
1848//------------------------------split_outer_loop-------------------------------
1849// Split out the outermost loop from this shared header.
1850void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1851 PhaseIterGVN &igvn = phase->_igvn;
1852
1853 // Find index of outermost loop; it should also be my tail.
1854 uint outer_idx = 1;
1855 while( _head->in(outer_idx) != _tail ) outer_idx++;
1856
1857 // Make a LoopNode for the outermost loop.
1858 Node *ctl = _head->in(LoopNode::EntryControl);
1859 Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1860 outer = igvn.register_new_node_with_optimizer(outer, _head);
1861 phase->set_created_loop_node();
1862
1863 // Outermost loop falls into '_head' loop
1864 _head->set_req(LoopNode::EntryControl, outer);
1865 _head->del_req(outer_idx);
1866 // Split all the Phis up between '_head' loop and 'outer' loop.
1867 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1868 Node *out = _head->fast_out(j);
1869 if( out->is_Phi() ) {
1870 PhiNode *old_phi = out->as_Phi();
1871 assert( old_phi->region() == _head, "" );
1872 Node *phi = PhiNode::make_blank(outer, old_phi);
1873 phi->init_req(LoopNode::EntryControl, old_phi->in(LoopNode::EntryControl));
1874 phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1875 phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1876 // Make old Phi point to new Phi on the fall-in path
1877 igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1878 old_phi->del_req(outer_idx);
1879 }
1880 }
1881
1882 // Use the new loop head instead of the old shared one
1883 _head = outer;
1884 phase->set_loop(_head, this);
1885}
1886
1887//------------------------------fix_parent-------------------------------------
1888static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1889 loop->_parent = parent;
1890 if( loop->_child ) fix_parent( loop->_child, loop );
1891 if( loop->_next ) fix_parent( loop->_next , parent );
1892}
1893
1894//------------------------------estimate_path_freq-----------------------------
1895static float estimate_path_freq( Node *n ) {
1896 // Try to extract some path frequency info
1897 IfNode *iff;
1898 for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1899 uint nop = n->Opcode();
1900 if( nop == Op_SafePoint ) { // Skip any safepoint
1901 n = n->in(0);
1902 continue;
1903 }
1904 if( nop == Op_CatchProj ) { // Get count from a prior call
1905 // Assume call does not always throw exceptions: means the call-site
1906 // count is also the frequency of the fall-through path.
1907 assert( n->is_CatchProj(), "" );
1908 if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1909 return 0.0f; // Assume call exception path is rare
1910 Node *call = n->in(0)->in(0)->in(0);
1911 assert( call->is_Call(), "expect a call here" );
1912 const JVMState *jvms = ((CallNode*)call)->jvms();
1913 ciMethodData* methodData = jvms->method()->method_data();
1914 if (!methodData->is_mature()) return 0.0f; // No call-site data
1915 ciProfileData* data = methodData->bci_to_data(jvms->bci());
1916 if ((data == NULL) || !data->is_CounterData()) {
1917 // no call profile available, try call's control input
1918 n = n->in(0);
1919 continue;
1920 }
1921 return data->as_CounterData()->count()/FreqCountInvocations;
1922 }
1923 // See if there's a gating IF test
1924 Node *n_c = n->in(0);
1925 if( !n_c->is_If() ) break; // No estimate available
1926 iff = n_c->as_If();
1927 if( iff->_fcnt != COUNT_UNKNOWN ) // Have a valid count?
1928 // Compute how much count comes on this path
1929 return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1930 // Have no count info. Skip dull uncommon-trap like branches.
1931 if( (nop == Op_IfTrue && iff->_prob < PROB_LIKELY_MAG(5)) ||
1932 (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1933 break;
1934 // Skip through never-taken branch; look for a real loop exit.
1935 n = iff->in(0);
1936 }
1937 return 0.0f; // No estimate available
1938}
1939
1940//------------------------------merge_many_backedges---------------------------
1941// Merge all the backedges from the shared header into a private Region.
1942// Feed that region as the one backedge to this loop.
1943void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1944 uint i;
1945
1946 // Scan for the top 2 hottest backedges
1947 float hotcnt = 0.0f;
1948 float warmcnt = 0.0f;
1949 uint hot_idx = 0;
1950 // Loop starts at 2 because slot 1 is the fall-in path
1951 for( i = 2; i < _head->req(); i++ ) {
1952 float cnt = estimate_path_freq(_head->in(i));
1953 if( cnt > hotcnt ) { // Grab hottest path
1954 warmcnt = hotcnt;
1955 hotcnt = cnt;
1956 hot_idx = i;
1957 } else if( cnt > warmcnt ) { // And 2nd hottest path
1958 warmcnt = cnt;
1959 }
1960 }
1961
1962 // See if the hottest backedge is worthy of being an inner loop
1963 // by being much hotter than the next hottest backedge.
1964 if( hotcnt <= 0.0001 ||
1965 hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1966
1967 // Peel out the backedges into a private merge point; peel
1968 // them all except optionally hot_idx.
1969 PhaseIterGVN &igvn = phase->_igvn;
1970
1971 Node *hot_tail = NULL;
1972 // Make a Region for the merge point
1973 Node *r = new RegionNode(1);
1974 for( i = 2; i < _head->req(); i++ ) {
1975 if( i != hot_idx )
1976 r->add_req( _head->in(i) );
1977 else hot_tail = _head->in(i);
1978 }
1979 igvn.register_new_node_with_optimizer(r, _head);
1980 // Plug region into end of loop _head, followed by hot_tail
1981 while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1982 igvn.replace_input_of(_head, 2, r);
1983 if( hot_idx ) _head->add_req(hot_tail);
1984
1985 // Split all the Phis up between '_head' loop and the Region 'r'
1986 for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1987 Node *out = _head->fast_out(j);
1988 if( out->is_Phi() ) {
1989 PhiNode* n = out->as_Phi();
1990 igvn.hash_delete(n); // Delete from hash before hacking edges
1991 Node *hot_phi = NULL;
1992 Node *phi = new PhiNode(r, n->type(), n->adr_type());
1993 // Check all inputs for the ones to peel out
1994 uint j = 1;
1995 for( uint i = 2; i < n->req(); i++ ) {
1996 if( i != hot_idx )
1997 phi->set_req( j++, n->in(i) );
1998 else hot_phi = n->in(i);
1999 }
2000 // Register the phi but do not transform until whole place transforms
2001 igvn.register_new_node_with_optimizer(phi, n);
2002 // Add the merge phi to the old Phi
2003 while( n->req() > 3 ) n->del_req( n->req()-1 );
2004 igvn.replace_input_of(n, 2, phi);
2005 if( hot_idx ) n->add_req(hot_phi);
2006 }
2007 }
2008
2009
2010 // Insert a new IdealLoopTree inserted below me. Turn it into a clone
2011 // of self loop tree. Turn self into a loop headed by _head and with
2012 // tail being the new merge point.
2013 IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2014 phase->set_loop(_tail,ilt); // Adjust tail
2015 _tail = r; // Self's tail is new merge point
2016 phase->set_loop(r,this);
2017 ilt->_child = _child; // New guy has my children
2018 _child = ilt; // Self has new guy as only child
2019 ilt->_parent = this; // new guy has self for parent
2020 ilt->_nest = _nest; // Same nesting depth (for now)
2021
2022 // Starting with 'ilt', look for child loop trees using the same shared
2023 // header. Flatten these out; they will no longer be loops in the end.
2024 IdealLoopTree **pilt = &_child;
2025 while( ilt ) {
2026 if( ilt->_head == _head ) {
2027 uint i;
2028 for( i = 2; i < _head->req(); i++ )
2029 if( _head->in(i) == ilt->_tail )
2030 break; // Still a loop
2031 if( i == _head->req() ) { // No longer a loop
2032 // Flatten ilt. Hang ilt's "_next" list from the end of
2033 // ilt's '_child' list. Move the ilt's _child up to replace ilt.
2034 IdealLoopTree **cp = &ilt->_child;
2035 while( *cp ) cp = &(*cp)->_next; // Find end of child list
2036 *cp = ilt->_next; // Hang next list at end of child list
2037 *pilt = ilt->_child; // Move child up to replace ilt
2038 ilt->_head = NULL; // Flag as a loop UNIONED into parent
2039 ilt = ilt->_child; // Repeat using new ilt
2040 continue; // do not advance over ilt->_child
2041 }
2042 assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2043 phase->set_loop(_head,ilt);
2044 }
2045 pilt = &ilt->_child; // Advance to next
2046 ilt = *pilt;
2047 }
2048
2049 if( _child ) fix_parent( _child, this );
2050}
2051
2052//------------------------------beautify_loops---------------------------------
2053// Split shared headers and insert loop landing pads.
2054// Insert a LoopNode to replace the RegionNode.
2055// Return TRUE if loop tree is structurally changed.
2056bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2057 bool result = false;
2058 // Cache parts in locals for easy
2059 PhaseIterGVN &igvn = phase->_igvn;
2060
2061 igvn.hash_delete(_head); // Yank from hash before hacking edges
2062
2063 // Check for multiple fall-in paths. Peel off a landing pad if need be.
2064 int fall_in_cnt = 0;
2065 for( uint i = 1; i < _head->req(); i++ )
2066 if( !phase->is_member( this, _head->in(i) ) )
2067 fall_in_cnt++;
2068 assert( fall_in_cnt, "at least 1 fall-in path" );
2069 if( fall_in_cnt > 1 ) // Need a loop landing pad to merge fall-ins
2070 split_fall_in( phase, fall_in_cnt );
2071
2072 // Swap inputs to the _head and all Phis to move the fall-in edge to
2073 // the left.
2074 fall_in_cnt = 1;
2075 while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2076 fall_in_cnt++;
2077 if( fall_in_cnt > 1 ) {
2078 // Since I am just swapping inputs I do not need to update def-use info
2079 Node *tmp = _head->in(1);
2080 igvn.rehash_node_delayed(_head);
2081 _head->set_req( 1, _head->in(fall_in_cnt) );
2082 _head->set_req( fall_in_cnt, tmp );
2083 // Swap also all Phis
2084 for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2085 Node* phi = _head->fast_out(i);
2086 if( phi->is_Phi() ) {
2087 igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2088 tmp = phi->in(1);
2089 phi->set_req( 1, phi->in(fall_in_cnt) );
2090 phi->set_req( fall_in_cnt, tmp );
2091 }
2092 }
2093 }
2094 assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2095 assert( phase->is_member( this, _head->in(2) ), "right edge is loop" );
2096
2097 // If I am a shared header (multiple backedges), peel off the many
2098 // backedges into a private merge point and use the merge point as
2099 // the one true backedge.
2100 if( _head->req() > 3 ) {
2101 // Merge the many backedges into a single backedge but leave
2102 // the hottest backedge as separate edge for the following peel.
2103 merge_many_backedges( phase );
2104 result = true;
2105 }
2106
2107 // If I have one hot backedge, peel off myself loop.
2108 // I better be the outermost loop.
2109 if (_head->req() > 3 && !_irreducible) {
2110 split_outer_loop( phase );
2111 result = true;
2112
2113 } else if (!_head->is_Loop() && !_irreducible) {
2114 // Make a new LoopNode to replace the old loop head
2115 Node *l = new LoopNode( _head->in(1), _head->in(2) );
2116 l = igvn.register_new_node_with_optimizer(l, _head);
2117 phase->set_created_loop_node();
2118 // Go ahead and replace _head
2119 phase->_igvn.replace_node( _head, l );
2120 _head = l;
2121 phase->set_loop(_head, this);
2122 }
2123
2124 // Now recursively beautify nested loops
2125 if( _child ) result |= _child->beautify_loops( phase );
2126 if( _next ) result |= _next ->beautify_loops( phase );
2127 return result;
2128}
2129
2130//------------------------------allpaths_check_safepts----------------------------
2131// Allpaths backwards scan from loop tail, terminating each path at first safepoint
2132// encountered. Helper for check_safepts.
2133void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2134 assert(stack.size() == 0, "empty stack");
2135 stack.push(_tail);
2136 visited.Clear();
2137 visited.set(_tail->_idx);
2138 while (stack.size() > 0) {
2139 Node* n = stack.pop();
2140 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2141 // Terminate this path
2142 } else if (n->Opcode() == Op_SafePoint) {
2143 if (_phase->get_loop(n) != this) {
2144 if (_required_safept == NULL) _required_safept = new Node_List();
2145 _required_safept->push(n); // save the one closest to the tail
2146 }
2147 // Terminate this path
2148 } else {
2149 uint start = n->is_Region() ? 1 : 0;
2150 uint end = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2151 for (uint i = start; i < end; i++) {
2152 Node* in = n->in(i);
2153 assert(in->is_CFG(), "must be");
2154 if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2155 stack.push(in);
2156 }
2157 }
2158 }
2159 }
2160}
2161
2162//------------------------------check_safepts----------------------------
2163// Given dominators, try to find loops with calls that must always be
2164// executed (call dominates loop tail). These loops do not need non-call
2165// safepoints (ncsfpt).
2166//
2167// A complication is that a safepoint in a inner loop may be needed
2168// by an outer loop. In the following, the inner loop sees it has a
2169// call (block 3) on every path from the head (block 2) to the
2170// backedge (arc 3->2). So it deletes the ncsfpt (non-call safepoint)
2171// in block 2, _but_ this leaves the outer loop without a safepoint.
2172//
2173// entry 0
2174// |
2175// v
2176// outer 1,2 +->1
2177// | |
2178// | v
2179// | 2<---+ ncsfpt in 2
2180// |_/|\ |
2181// | v |
2182// inner 2,3 / 3 | call in 3
2183// / | |
2184// v +--+
2185// exit 4
2186//
2187//
2188// This method creates a list (_required_safept) of ncsfpt nodes that must
2189// be protected is created for each loop. When a ncsfpt maybe deleted, it
2190// is first looked for in the lists for the outer loops of the current loop.
2191//
2192// The insights into the problem:
2193// A) counted loops are okay
2194// B) innermost loops are okay (only an inner loop can delete
2195// a ncsfpt needed by an outer loop)
2196// C) a loop is immune from an inner loop deleting a safepoint
2197// if the loop has a call on the idom-path
2198// D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2199// idom-path that is not in a nested loop
2200// E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2201// loop needs to be prevented from deletion by an inner loop
2202//
2203// There are two analyses:
2204// 1) The first, and cheaper one, scans the loop body from
2205// tail to head following the idom (immediate dominator)
2206// chain, looking for the cases (C,D,E) above.
2207// Since inner loops are scanned before outer loops, there is summary
2208// information about inner loops. Inner loops can be skipped over
2209// when the tail of an inner loop is encountered.
2210//
2211// 2) The second, invoked if the first fails to find a call or ncsfpt on
2212// the idom path (which is rare), scans all predecessor control paths
2213// from the tail to the head, terminating a path when a call or sfpt
2214// is encountered, to find the ncsfpt's that are closest to the tail.
2215//
2216void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2217 // Bottom up traversal
2218 IdealLoopTree* ch = _child;
2219 if (_child) _child->check_safepts(visited, stack);
2220 if (_next) _next ->check_safepts(visited, stack);
2221
2222 if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2223 bool has_call = false; // call on dom-path
2224 bool has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2225 Node* nonlocal_ncsfpt = NULL; // ncsfpt on dom-path at a deeper depth
2226 // Scan the dom-path nodes from tail to head
2227 for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2228 if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2229 has_call = true;
2230 _has_sfpt = 1; // Then no need for a safept!
2231 break;
2232 } else if (n->Opcode() == Op_SafePoint) {
2233 if (_phase->get_loop(n) == this) {
2234 has_local_ncsfpt = true;
2235 break;
2236 }
2237 if (nonlocal_ncsfpt == NULL) {
2238 nonlocal_ncsfpt = n; // save the one closest to the tail
2239 }
2240 } else {
2241 IdealLoopTree* nlpt = _phase->get_loop(n);
2242 if (this != nlpt) {
2243 // If at an inner loop tail, see if the inner loop has already
2244 // recorded seeing a call on the dom-path (and stop.) If not,
2245 // jump to the head of the inner loop.
2246 assert(is_member(nlpt), "nested loop");
2247 Node* tail = nlpt->_tail;
2248 if (tail->in(0)->is_If()) tail = tail->in(0);
2249 if (n == tail) {
2250 // If inner loop has call on dom-path, so does outer loop
2251 if (nlpt->_has_sfpt) {
2252 has_call = true;
2253 _has_sfpt = 1;
2254 break;
2255 }
2256 // Skip to head of inner loop
2257 assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2258 n = nlpt->_head;
2259 }
2260 }
2261 }
2262 }
2263 // Record safept's that this loop needs preserved when an
2264 // inner loop attempts to delete it's safepoints.
2265 if (_child != NULL && !has_call && !has_local_ncsfpt) {
2266 if (nonlocal_ncsfpt != NULL) {
2267 if (_required_safept == NULL) _required_safept = new Node_List();
2268 _required_safept->push(nonlocal_ncsfpt);
2269 } else {
2270 // Failed to find a suitable safept on the dom-path. Now use
2271 // an all paths walk from tail to head, looking for safepoints to preserve.
2272 allpaths_check_safepts(visited, stack);
2273 }
2274 }
2275 }
2276}
2277
2278//---------------------------is_deleteable_safept----------------------------
2279// Is safept not required by an outer loop?
2280bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2281 assert(sfpt->Opcode() == Op_SafePoint, "");
2282 IdealLoopTree* lp = get_loop(sfpt)->_parent;
2283 while (lp != NULL) {
2284 Node_List* sfpts = lp->_required_safept;
2285 if (sfpts != NULL) {
2286 for (uint i = 0; i < sfpts->size(); i++) {
2287 if (sfpt == sfpts->at(i))
2288 return false;
2289 }
2290 }
2291 lp = lp->_parent;
2292 }
2293 return true;
2294}
2295
2296//---------------------------replace_parallel_iv-------------------------------
2297// Replace parallel induction variable (parallel to trip counter)
2298void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2299 assert(loop->_head->is_CountedLoop(), "");
2300 CountedLoopNode *cl = loop->_head->as_CountedLoop();
2301 if (!cl->is_valid_counted_loop())
2302 return; // skip malformed counted loop
2303 Node *incr = cl->incr();
2304 if (incr == NULL)
2305 return; // Dead loop?
2306 Node *init = cl->init_trip();
2307 Node *phi = cl->phi();
2308 int stride_con = cl->stride_con();
2309
2310 // Visit all children, looking for Phis
2311 for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2312 Node *out = cl->out(i);
2313 // Look for other phis (secondary IVs). Skip dead ones
2314 if (!out->is_Phi() || out == phi || !has_node(out))
2315 continue;
2316 PhiNode* phi2 = out->as_Phi();
2317 Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2318 // Look for induction variables of the form: X += constant
2319 if (phi2->region() != loop->_head ||
2320 incr2->req() != 3 ||
2321 incr2->in(1) != phi2 ||
2322 incr2 == incr ||
2323 incr2->Opcode() != Op_AddI ||
2324 !incr2->in(2)->is_Con())
2325 continue;
2326
2327 // Check for parallel induction variable (parallel to trip counter)
2328 // via an affine function. In particular, count-down loops with
2329 // count-up array indices are common. We only RCE references off
2330 // the trip-counter, so we need to convert all these to trip-counter
2331 // expressions.
2332 Node *init2 = phi2->in( LoopNode::EntryControl );
2333 int stride_con2 = incr2->in(2)->get_int();
2334
2335 // The ratio of the two strides cannot be represented as an int
2336 // if stride_con2 is min_int and stride_con is -1.
2337 if (stride_con2 == min_jint && stride_con == -1) {
2338 continue;
2339 }
2340
2341 // The general case here gets a little tricky. We want to find the
2342 // GCD of all possible parallel IV's and make a new IV using this
2343 // GCD for the loop. Then all possible IVs are simple multiples of
2344 // the GCD. In practice, this will cover very few extra loops.
2345 // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2346 // where +/-1 is the common case, but other integer multiples are
2347 // also easy to handle.
2348 int ratio_con = stride_con2/stride_con;
2349
2350 if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2351#ifndef PRODUCT
2352 if (TraceLoopOpts) {
2353 tty->print("Parallel IV: %d ", phi2->_idx);
2354 loop->dump_head();
2355 }
2356#endif
2357 // Convert to using the trip counter. The parallel induction
2358 // variable differs from the trip counter by a loop-invariant
2359 // amount, the difference between their respective initial values.
2360 // It is scaled by the 'ratio_con'.
2361 Node* ratio = _igvn.intcon(ratio_con);
2362 set_ctrl(ratio, C->root());
2363 Node* ratio_init = new MulINode(init, ratio);
2364 _igvn.register_new_node_with_optimizer(ratio_init, init);
2365 set_early_ctrl(ratio_init);
2366 Node* diff = new SubINode(init2, ratio_init);
2367 _igvn.register_new_node_with_optimizer(diff, init2);
2368 set_early_ctrl(diff);
2369 Node* ratio_idx = new MulINode(phi, ratio);
2370 _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2371 set_ctrl(ratio_idx, cl);
2372 Node* add = new AddINode(ratio_idx, diff);
2373 _igvn.register_new_node_with_optimizer(add);
2374 set_ctrl(add, cl);
2375 _igvn.replace_node( phi2, add );
2376 // Sometimes an induction variable is unused
2377 if (add->outcnt() == 0) {
2378 _igvn.remove_dead_node(add);
2379 }
2380 --i; // deleted this phi; rescan starting with next position
2381 continue;
2382 }
2383 }
2384}
2385
2386void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2387 Node* keep = NULL;
2388 if (keep_one) {
2389 // Look for a safepoint on the idom-path.
2390 for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2391 if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2392 keep = i;
2393 break; // Found one
2394 }
2395 }
2396 }
2397
2398 // Don't remove any safepoints if it is requested to keep a single safepoint and
2399 // no safepoint was found on idom-path. It is not safe to remove any safepoint
2400 // in this case since there's no safepoint dominating all paths in the loop body.
2401 bool prune = !keep_one || keep != NULL;
2402
2403 // Delete other safepoints in this loop.
2404 Node_List* sfpts = _safepts;
2405 if (prune && sfpts != NULL) {
2406 assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2407 for (uint i = 0; i < sfpts->size(); i++) {
2408 Node* n = sfpts->at(i);
2409 assert(phase->get_loop(n) == this, "");
2410 if (n != keep && phase->is_deleteable_safept(n)) {
2411 phase->lazy_replace(n, n->in(TypeFunc::Control));
2412 }
2413 }
2414 }
2415}
2416
2417//------------------------------counted_loop-----------------------------------
2418// Convert to counted loops where possible
2419void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2420
2421 // For grins, set the inner-loop flag here
2422 if (!_child) {
2423 if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2424 }
2425
2426 IdealLoopTree* loop = this;
2427 if (_head->is_CountedLoop() ||
2428 phase->is_counted_loop(_head, loop)) {
2429
2430 if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2431 // Indicate we do not need a safepoint here
2432 _has_sfpt = 1;
2433 }
2434
2435 // Remove safepoints
2436 bool keep_one_sfpt = !(_has_call || _has_sfpt);
2437 remove_safepoints(phase, keep_one_sfpt);
2438
2439 // Look for induction variables
2440 phase->replace_parallel_iv(this);
2441
2442 } else if (_parent != NULL && !_irreducible) {
2443 // Not a counted loop. Keep one safepoint.
2444 bool keep_one_sfpt = true;
2445 remove_safepoints(phase, keep_one_sfpt);
2446 }
2447
2448 // Recursively
2449 assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2450 assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2451 if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2452 if (loop->_next) loop->_next ->counted_loop(phase);
2453}
2454
2455
2456// The Estimated Loop Clone Size:
2457// CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
2458// where BC and CC are totally ad-hoc/magic "body" and "clone" constants,
2459// respectively, used to ensure that the node usage estimates made are on the
2460// safe side, for the most part. The FanOutTerm is an attempt to estimate the
2461// possible additional/excessive nodes generated due to data and control flow
2462// merging, for edges reaching outside the loop.
2463uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
2464
2465 precond(0 < factor && factor < 16);
2466
2467 uint const bc = 13;
2468 uint const cc = 17;
2469 uint const sz = _body.size() + (_body.size() + 7) / 8;
2470 uint estimate = factor * (sz + bc) + cc;
2471
2472 assert((estimate - cc) / factor == sz + bc, "overflow");
2473
2474 uint ctrl_edge_out_cnt = 0;
2475 uint data_edge_out_cnt = 0;
2476
2477 for (uint i = 0; i < _body.size(); i++) {
2478 Node* node = _body.at(i);
2479 uint outcnt = node->outcnt();
2480
2481 for (uint k = 0; k < outcnt; k++) {
2482 Node* out = node->raw_out(k);
2483
2484 if (out->is_CFG()) {
2485 if (!is_member(_phase->get_loop(out))) {
2486 ctrl_edge_out_cnt++;
2487 }
2488 } else {
2489 Node* ctrl = _phase->get_ctrl(out);
2490 assert(ctrl->is_CFG(), "must be");
2491 if (!is_member(_phase->get_loop(ctrl))) {
2492 data_edge_out_cnt++;
2493 }
2494 }
2495 }
2496 }
2497 // Add data and control count (x2.0) to estimate iff both are > 0. This is
2498 // a rather pessimistic estimate for the most part, in particular for some
2499 // complex loops, but still not enough to capture all loops.
2500 if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
2501 estimate += 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
2502 }
2503
2504 return estimate;
2505}
2506
2507#ifndef PRODUCT
2508//------------------------------dump_head--------------------------------------
2509// Dump 1 liner for loop header info
2510void IdealLoopTree::dump_head() const {
2511 for (uint i = 0; i < _nest; i++) {
2512 tty->print(" ");
2513 }
2514 tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
2515 if (_irreducible) tty->print(" IRREDUCIBLE");
2516 Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2517 Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2518 if (predicate != NULL ) {
2519 tty->print(" limit_check");
2520 entry = PhaseIdealLoop::skip_loop_predicates(entry);
2521 }
2522 if (UseLoopPredicate) {
2523 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2524 if (entry != NULL) {
2525 tty->print(" predicated");
2526 entry = PhaseIdealLoop::skip_loop_predicates(entry);
2527 }
2528 }
2529 if (UseProfiledLoopPredicate) {
2530 entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2531 if (entry != NULL) {
2532 tty->print(" profile_predicated");
2533 }
2534 }
2535 if (_head->is_CountedLoop()) {
2536 CountedLoopNode *cl = _head->as_CountedLoop();
2537 tty->print(" counted");
2538
2539 Node* init_n = cl->init_trip();
2540 if (init_n != NULL && init_n->is_Con())
2541 tty->print(" [%d,", cl->init_trip()->get_int());
2542 else
2543 tty->print(" [int,");
2544 Node* limit_n = cl->limit();
2545 if (limit_n != NULL && limit_n->is_Con())
2546 tty->print("%d),", cl->limit()->get_int());
2547 else
2548 tty->print("int),");
2549 int stride_con = cl->stride_con();
2550 if (stride_con > 0) tty->print("+");
2551 tty->print("%d", stride_con);
2552
2553 tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2554
2555 if (cl->is_pre_loop ()) tty->print(" pre" );
2556 if (cl->is_main_loop()) tty->print(" main");
2557 if (cl->is_post_loop()) tty->print(" post");
2558 if (cl->is_vectorized_loop()) tty->print(" vector");
2559 if (cl->range_checks_present()) tty->print(" rc ");
2560 if (cl->is_multiversioned()) tty->print(" multi ");
2561 }
2562 if (_has_call) tty->print(" has_call");
2563 if (_has_sfpt) tty->print(" has_sfpt");
2564 if (_rce_candidate) tty->print(" rce");
2565 if (_safepts != NULL && _safepts->size() > 0) {
2566 tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2567 }
2568 if (_required_safept != NULL && _required_safept->size() > 0) {
2569 tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2570 }
2571 if (Verbose) {
2572 tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2573 }
2574 if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2575 tty->print(" strip_mined");
2576 }
2577 tty->cr();
2578}
2579
2580//------------------------------dump-------------------------------------------
2581// Dump loops by loop tree
2582void IdealLoopTree::dump() const {
2583 dump_head();
2584 if (_child) _child->dump();
2585 if (_next) _next ->dump();
2586}
2587
2588#endif
2589
2590static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2591 if (loop == root) {
2592 if (loop->_child != NULL) {
2593 log->begin_head("loop_tree");
2594 log->end_head();
2595 if( loop->_child ) log_loop_tree(root, loop->_child, log);
2596 log->tail("loop_tree");
2597 assert(loop->_next == NULL, "what?");
2598 }
2599 } else {
2600 Node* head = loop->_head;
2601 log->begin_head("loop");
2602 log->print(" idx='%d' ", head->_idx);
2603 if (loop->_irreducible) log->print("irreducible='1' ");
2604 if (head->is_Loop()) {
2605 if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2606 if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2607 }
2608 if (head->is_CountedLoop()) {
2609 CountedLoopNode* cl = head->as_CountedLoop();
2610 if (cl->is_pre_loop()) log->print("pre_loop='%d' ", cl->main_idx());
2611 if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2612 if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
2613 }
2614 log->end_head();
2615 if( loop->_child ) log_loop_tree(root, loop->_child, log);
2616 log->tail("loop");
2617 if( loop->_next ) log_loop_tree(root, loop->_next, log);
2618 }
2619}
2620
2621//---------------------collect_potentially_useful_predicates-----------------------
2622// Helper function to collect potentially useful predicates to prevent them from
2623// being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2624void PhaseIdealLoop::collect_potentially_useful_predicates(
2625 IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2626 if (loop->_child) { // child
2627 collect_potentially_useful_predicates(loop->_child, useful_predicates);
2628 }
2629
2630 // self (only loops that we can apply loop predication may use their predicates)
2631 if (loop->_head->is_Loop() &&
2632 !loop->_irreducible &&
2633 !loop->tail()->is_top()) {
2634 LoopNode* lpn = loop->_head->as_Loop();
2635 Node* entry = lpn->in(LoopNode::EntryControl);
2636 Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2637 if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2638 assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2639 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2640 entry = skip_loop_predicates(entry);
2641 }
2642 predicate_proj = find_predicate(entry); // Predicate
2643 if (predicate_proj != NULL ) {
2644 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2645 entry = skip_loop_predicates(entry);
2646 }
2647 if (UseProfiledLoopPredicate) {
2648 predicate_proj = find_predicate(entry); // Predicate
2649 if (predicate_proj != NULL ) {
2650 useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2651 }
2652 }
2653 }
2654
2655 if (loop->_next) { // sibling
2656 collect_potentially_useful_predicates(loop->_next, useful_predicates);
2657 }
2658}
2659
2660//------------------------eliminate_useless_predicates-----------------------------
2661// Eliminate all inserted predicates if they could not be used by loop predication.
2662// Note: it will also eliminates loop limits check predicate since it also uses
2663// Opaque1 node (see Parse::add_predicate()).
2664void PhaseIdealLoop::eliminate_useless_predicates() {
2665 if (C->predicate_count() == 0)
2666 return; // no predicate left
2667
2668 Unique_Node_List useful_predicates; // to store useful predicates
2669 if (C->has_loops()) {
2670 collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2671 }
2672
2673 for (int i = C->predicate_count(); i > 0; i--) {
2674 Node * n = C->predicate_opaque1_node(i-1);
2675 assert(n->Opcode() == Op_Opaque1, "must be");
2676 if (!useful_predicates.member(n)) { // not in the useful list
2677 _igvn.replace_node(n, n->in(1));
2678 }
2679 }
2680}
2681
2682//------------------------process_expensive_nodes-----------------------------
2683// Expensive nodes have their control input set to prevent the GVN
2684// from commoning them and as a result forcing the resulting node to
2685// be in a more frequent path. Use CFG information here, to change the
2686// control inputs so that some expensive nodes can be commoned while
2687// not executed more frequently.
2688bool PhaseIdealLoop::process_expensive_nodes() {
2689 assert(OptimizeExpensiveOps, "optimization off?");
2690
2691 // Sort nodes to bring similar nodes together
2692 C->sort_expensive_nodes();
2693
2694 bool progress = false;
2695
2696 for (int i = 0; i < C->expensive_count(); ) {
2697 Node* n = C->expensive_node(i);
2698 int start = i;
2699 // Find nodes similar to n
2700 i++;
2701 for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2702 int end = i;
2703 // And compare them two by two
2704 for (int j = start; j < end; j++) {
2705 Node* n1 = C->expensive_node(j);
2706 if (is_node_unreachable(n1)) {
2707 continue;
2708 }
2709 for (int k = j+1; k < end; k++) {
2710 Node* n2 = C->expensive_node(k);
2711 if (is_node_unreachable(n2)) {
2712 continue;
2713 }
2714
2715 assert(n1 != n2, "should be pair of nodes");
2716
2717 Node* c1 = n1->in(0);
2718 Node* c2 = n2->in(0);
2719
2720 Node* parent_c1 = c1;
2721 Node* parent_c2 = c2;
2722
2723 // The call to get_early_ctrl_for_expensive() moves the
2724 // expensive nodes up but stops at loops that are in a if
2725 // branch. See whether we can exit the loop and move above the
2726 // If.
2727 if (c1->is_Loop()) {
2728 parent_c1 = c1->in(1);
2729 }
2730 if (c2->is_Loop()) {
2731 parent_c2 = c2->in(1);
2732 }
2733
2734 if (parent_c1 == parent_c2) {
2735 _igvn._worklist.push(n1);
2736 _igvn._worklist.push(n2);
2737 continue;
2738 }
2739
2740 // Look for identical expensive node up the dominator chain.
2741 if (is_dominator(c1, c2)) {
2742 c2 = c1;
2743 } else if (is_dominator(c2, c1)) {
2744 c1 = c2;
2745 } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2746 parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2747 // Both branches have the same expensive node so move it up
2748 // before the if.
2749 c1 = c2 = idom(parent_c1->in(0));
2750 }
2751 // Do the actual moves
2752 if (n1->in(0) != c1) {
2753 _igvn.hash_delete(n1);
2754 n1->set_req(0, c1);
2755 _igvn.hash_insert(n1);
2756 _igvn._worklist.push(n1);
2757 progress = true;
2758 }
2759 if (n2->in(0) != c2) {
2760 _igvn.hash_delete(n2);
2761 n2->set_req(0, c2);
2762 _igvn.hash_insert(n2);
2763 _igvn._worklist.push(n2);
2764 progress = true;
2765 }
2766 }
2767 }
2768 }
2769
2770 return progress;
2771}
2772
2773
2774//=============================================================================
2775//----------------------------build_and_optimize-------------------------------
2776// Create a PhaseLoop. Build the ideal Loop tree. Map each Ideal Node to
2777// its corresponding LoopNode. If 'optimize' is true, do some loop cleanups.
2778void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2779 bool do_split_ifs = (mode == LoopOptsDefault);
2780 bool skip_loop_opts = (mode == LoopOptsNone);
2781
2782 int old_progress = C->major_progress();
2783 uint orig_worklist_size = _igvn._worklist.size();
2784
2785 // Reset major-progress flag for the driver's heuristics
2786 C->clear_major_progress();
2787
2788#ifndef PRODUCT
2789 // Capture for later assert
2790 uint unique = C->unique();
2791 _loop_invokes++;
2792 _loop_work += unique;
2793#endif
2794
2795 // True if the method has at least 1 irreducible loop
2796 _has_irreducible_loops = false;
2797
2798 _created_loop_node = false;
2799
2800 Arena *a = Thread::current()->resource_area();
2801 VectorSet visited(a);
2802 // Pre-grow the mapping from Nodes to IdealLoopTrees.
2803 _nodes.map(C->unique(), NULL);
2804 memset(_nodes.adr(), 0, wordSize * C->unique());
2805
2806 // Pre-build the top-level outermost loop tree entry
2807 _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2808 // Do not need a safepoint at the top level
2809 _ltree_root->_has_sfpt = 1;
2810
2811 // Initialize Dominators.
2812 // Checked in clone_loop_predicate() during beautify_loops().
2813 _idom_size = 0;
2814 _idom = NULL;
2815 _dom_depth = NULL;
2816 _dom_stk = NULL;
2817
2818 // Empty pre-order array
2819 allocate_preorders();
2820
2821 // Build a loop tree on the fly. Build a mapping from CFG nodes to
2822 // IdealLoopTree entries. Data nodes are NOT walked.
2823 build_loop_tree();
2824 // Check for bailout, and return
2825 if (C->failing()) {
2826 return;
2827 }
2828
2829 // No loops after all
2830 if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2831
2832 // There should always be an outer loop containing the Root and Return nodes.
2833 // If not, we have a degenerate empty program. Bail out in this case.
2834 if (!has_node(C->root())) {
2835 if (!_verify_only) {
2836 C->clear_major_progress();
2837 C->record_method_not_compilable("empty program detected during loop optimization");
2838 }
2839 return;
2840 }
2841
2842 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2843 // Nothing to do, so get out
2844 bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only &&
2845 !bs->is_gc_specific_loop_opts_pass(mode);
2846 bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2847 bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode);
2848 if (stop_early && !do_expensive_nodes) {
2849 _igvn.optimize(); // Cleanup NeverBranches
2850 return;
2851 }
2852
2853 // Set loop nesting depth
2854 _ltree_root->set_nest( 0 );
2855
2856 // Split shared headers and insert loop landing pads.
2857 // Do not bother doing this on the Root loop of course.
2858 if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2859 C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2860 if( _ltree_root->_child->beautify_loops( this ) ) {
2861 // Re-build loop tree!
2862 _ltree_root->_child = NULL;
2863 _nodes.clear();
2864 reallocate_preorders();
2865 build_loop_tree();
2866 // Check for bailout, and return
2867 if (C->failing()) {
2868 return;
2869 }
2870 // Reset loop nesting depth
2871 _ltree_root->set_nest( 0 );
2872
2873 C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2874 }
2875 }
2876
2877 // Build Dominators for elision of NULL checks & loop finding.
2878 // Since nodes do not have a slot for immediate dominator, make
2879 // a persistent side array for that info indexed on node->_idx.
2880 _idom_size = C->unique();
2881 _idom = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2882 _dom_depth = NEW_RESOURCE_ARRAY( uint, _idom_size );
2883 _dom_stk = NULL; // Allocated on demand in recompute_dom_depth
2884 memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2885
2886 Dominators();
2887
2888 if (!_verify_only) {
2889 // As a side effect, Dominators removed any unreachable CFG paths
2890 // into RegionNodes. It doesn't do this test against Root, so
2891 // we do it here.
2892 for( uint i = 1; i < C->root()->req(); i++ ) {
2893 if( !_nodes[C->root()->in(i)->_idx] ) { // Dead path into Root?
2894 _igvn.delete_input_of(C->root(), i);
2895 i--; // Rerun same iteration on compressed edges
2896 }
2897 }
2898
2899 // Given dominators, try to find inner loops with calls that must
2900 // always be executed (call dominates loop tail). These loops do
2901 // not need a separate safepoint.
2902 Node_List cisstack(a);
2903 _ltree_root->check_safepts(visited, cisstack);
2904 }
2905
2906 // Walk the DATA nodes and place into loops. Find earliest control
2907 // node. For CFG nodes, the _nodes array starts out and remains
2908 // holding the associated IdealLoopTree pointer. For DATA nodes, the
2909 // _nodes array holds the earliest legal controlling CFG node.
2910
2911 // Allocate stack with enough space to avoid frequent realloc
2912 int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2913 Node_Stack nstack( a, stack_size );
2914
2915 visited.Clear();
2916 Node_List worklist(a);
2917 // Don't need C->root() on worklist since
2918 // it will be processed among C->top() inputs
2919 worklist.push( C->top() );
2920 visited.set( C->top()->_idx ); // Set C->top() as visited now
2921 build_loop_early( visited, worklist, nstack );
2922
2923 // Given early legal placement, try finding counted loops. This placement
2924 // is good enough to discover most loop invariants.
2925 if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
2926 _ltree_root->counted_loop( this );
2927 }
2928
2929 // Find latest loop placement. Find ideal loop placement.
2930 visited.Clear();
2931 init_dom_lca_tags();
2932 // Need C->root() on worklist when processing outs
2933 worklist.push( C->root() );
2934 NOT_PRODUCT( C->verify_graph_edges(); )
2935 worklist.push( C->top() );
2936 build_loop_late( visited, worklist, nstack );
2937
2938 if (_verify_only) {
2939 C->restore_major_progress(old_progress);
2940 assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2941 assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2942 return;
2943 }
2944
2945 // clear out the dead code after build_loop_late
2946 while (_deadlist.size()) {
2947 _igvn.remove_globally_dead_node(_deadlist.pop());
2948 }
2949
2950 if (stop_early) {
2951 assert(do_expensive_nodes, "why are we here?");
2952 if (process_expensive_nodes()) {
2953 // If we made some progress when processing expensive nodes then
2954 // the IGVN may modify the graph in a way that will allow us to
2955 // make some more progress: we need to try processing expensive
2956 // nodes again.
2957 C->set_major_progress();
2958 }
2959 _igvn.optimize();
2960 return;
2961 }
2962
2963 // Some parser-inserted loop predicates could never be used by loop
2964 // predication or they were moved away from loop during some optimizations.
2965 // For example, peeling. Eliminate them before next loop optimizations.
2966 eliminate_useless_predicates();
2967
2968#ifndef PRODUCT
2969 C->verify_graph_edges();
2970 if (_verify_me) { // Nested verify pass?
2971 // Check to see if the verify mode is broken
2972 assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2973 return;
2974 }
2975 if (VerifyLoopOptimizations) verify();
2976 if (TraceLoopOpts && C->has_loops()) {
2977 _ltree_root->dump();
2978 }
2979#endif
2980
2981 if (skip_loop_opts) {
2982 // restore major progress flag
2983 C->restore_major_progress(old_progress);
2984
2985 // Cleanup any modified bits
2986 _igvn.optimize();
2987
2988 if (C->log() != NULL) {
2989 log_loop_tree(_ltree_root, _ltree_root, C->log());
2990 }
2991 return;
2992 }
2993
2994 if (bs->optimize_loops(this, mode, visited, nstack, worklist)) {
2995 _igvn.optimize();
2996 if (C->log() != NULL) {
2997 log_loop_tree(_ltree_root, _ltree_root, C->log());
2998 }
2999 return;
3000 }
3001
3002 if (ReassociateInvariants) {
3003 // Reassociate invariants and prep for split_thru_phi
3004 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3005 IdealLoopTree* lpt = iter.current();
3006 bool is_counted = lpt->is_counted();
3007 if (!is_counted || !lpt->is_innermost()) continue;
3008
3009 // check for vectorized loops, any reassociation of invariants was already done
3010 if (is_counted && lpt->_head->as_CountedLoop()->is_unroll_only()) {
3011 continue;
3012 } else {
3013 AutoNodeBudget node_budget(this);
3014 lpt->reassociate_invariants(this);
3015 }
3016 // Because RCE opportunities can be masked by split_thru_phi,
3017 // look for RCE candidates and inhibit split_thru_phi
3018 // on just their loop-phi's for this pass of loop opts
3019 if (SplitIfBlocks && do_split_ifs) {
3020 AutoNodeBudget node_budget(this, AutoNodeBudget::NO_BUDGET_CHECK);
3021 if (lpt->policy_range_check(this)) {
3022 lpt->_rce_candidate = 1; // = true
3023 }
3024 }
3025 }
3026 }
3027
3028 // Check for aggressive application of split-if and other transforms
3029 // that require basic-block info (like cloning through Phi's)
3030 if( SplitIfBlocks && do_split_ifs ) {
3031 visited.Clear();
3032 split_if_with_blocks( visited, nstack);
3033 NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
3034 }
3035
3036 if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
3037 C->set_major_progress();
3038 }
3039
3040 // Perform loop predication before iteration splitting
3041 if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
3042 _ltree_root->_child->loop_predication(this);
3043 }
3044
3045 if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
3046 if (do_intrinsify_fill()) {
3047 C->set_major_progress();
3048 }
3049 }
3050
3051 // Perform iteration-splitting on inner loops. Split iterations to avoid
3052 // range checks or one-shot null checks.
3053
3054 // If split-if's didn't hack the graph too bad (no CFG changes)
3055 // then do loop opts.
3056 if (C->has_loops() && !C->major_progress()) {
3057 memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3058 _ltree_root->_child->iteration_split( this, worklist );
3059 // No verify after peeling! GCM has hoisted code out of the loop.
3060 // After peeling, the hoisted code could sink inside the peeled area.
3061 // The peeling code does not try to recompute the best location for
3062 // all the code before the peeled area, so the verify pass will always
3063 // complain about it.
3064 }
3065 // Do verify graph edges in any case
3066 NOT_PRODUCT( C->verify_graph_edges(); );
3067
3068 if (!do_split_ifs) {
3069 // We saw major progress in Split-If to get here. We forced a
3070 // pass with unrolling and not split-if, however more split-if's
3071 // might make progress. If the unrolling didn't make progress
3072 // then the major-progress flag got cleared and we won't try
3073 // another round of Split-If. In particular the ever-common
3074 // instance-of/check-cast pattern requires at least 2 rounds of
3075 // Split-If to clear out.
3076 C->set_major_progress();
3077 }
3078
3079 // Repeat loop optimizations if new loops were seen
3080 if (created_loop_node()) {
3081 C->set_major_progress();
3082 }
3083
3084 // Keep loop predicates and perform optimizations with them
3085 // until no more loop optimizations could be done.
3086 // After that switch predicates off and do more loop optimizations.
3087 if (!C->major_progress() && (C->predicate_count() > 0)) {
3088 C->cleanup_loop_predicates(_igvn);
3089 if (TraceLoopOpts) {
3090 tty->print_cr("PredicatesOff");
3091 }
3092 C->set_major_progress();
3093 }
3094
3095 // Convert scalar to superword operations at the end of all loop opts.
3096 if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3097 // SuperWord transform
3098 SuperWord sw(this);
3099 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3100 IdealLoopTree* lpt = iter.current();
3101 if (lpt->is_counted()) {
3102 CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3103
3104 if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3105 // Check that the rce'd post loop is encountered first, multiversion after all
3106 // major main loop optimization are concluded
3107 if (!C->major_progress()) {
3108 IdealLoopTree *lpt_next = lpt->_next;
3109 if (lpt_next && lpt_next->is_counted()) {
3110 CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3111 has_range_checks(lpt_next);
3112 if (cl->is_post_loop() && cl->range_checks_present()) {
3113 if (!cl->is_multiversioned()) {
3114 if (multi_version_post_loops(lpt, lpt_next) == false) {
3115 // Cause the rce loop to be optimized away if we fail
3116 cl->mark_is_multiversioned();
3117 cl->set_slp_max_unroll(0);
3118 poison_rce_post_loop(lpt);
3119 }
3120 }
3121 }
3122 }
3123 sw.transform_loop(lpt, true);
3124 }
3125 } else if (cl->is_main_loop()) {
3126 sw.transform_loop(lpt, true);
3127 }
3128 }
3129 }
3130 }
3131
3132 // Cleanup any modified bits
3133 _igvn.optimize();
3134
3135 // disable assert until issue with split_flow_path is resolved (6742111)
3136 // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3137 // "shouldn't introduce irreducible loops");
3138
3139 if (C->log() != NULL) {
3140 log_loop_tree(_ltree_root, _ltree_root, C->log());
3141 }
3142}
3143
3144#ifndef PRODUCT
3145//------------------------------print_statistics-------------------------------
3146int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3147int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3148void PhaseIdealLoop::print_statistics() {
3149 tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3150}
3151
3152//------------------------------verify-----------------------------------------
3153// Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3154static int fail; // debug only, so its multi-thread dont care
3155void PhaseIdealLoop::verify() const {
3156 int old_progress = C->major_progress();
3157 ResourceMark rm;
3158 PhaseIdealLoop loop_verify( _igvn, this );
3159 VectorSet visited(Thread::current()->resource_area());
3160
3161 fail = 0;
3162 verify_compare( C->root(), &loop_verify, visited );
3163 assert( fail == 0, "verify loops failed" );
3164 // Verify loop structure is the same
3165 _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3166 // Reset major-progress. It was cleared by creating a verify version of
3167 // PhaseIdealLoop.
3168 C->restore_major_progress(old_progress);
3169}
3170
3171//------------------------------verify_compare---------------------------------
3172// Make sure me and the given PhaseIdealLoop agree on key data structures
3173void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3174 if( !n ) return;
3175 if( visited.test_set( n->_idx ) ) return;
3176 if( !_nodes[n->_idx] ) { // Unreachable
3177 assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3178 return;
3179 }
3180
3181 uint i;
3182 for( i = 0; i < n->req(); i++ )
3183 verify_compare( n->in(i), loop_verify, visited );
3184
3185 // Check the '_nodes' block/loop structure
3186 i = n->_idx;
3187 if( has_ctrl(n) ) { // We have control; verify has loop or ctrl
3188 if( _nodes[i] != loop_verify->_nodes[i] &&
3189 get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3190 tty->print("Mismatched control setting for: ");
3191 n->dump();
3192 if( fail++ > 10 ) return;
3193 Node *c = get_ctrl_no_update(n);
3194 tty->print("We have it as: ");
3195 if( c->in(0) ) c->dump();
3196 else tty->print_cr("N%d",c->_idx);
3197 tty->print("Verify thinks: ");
3198 if( loop_verify->has_ctrl(n) )
3199 loop_verify->get_ctrl_no_update(n)->dump();
3200 else
3201 loop_verify->get_loop_idx(n)->dump();
3202 tty->cr();
3203 }
3204 } else { // We have a loop
3205 IdealLoopTree *us = get_loop_idx(n);
3206 if( loop_verify->has_ctrl(n) ) {
3207 tty->print("Mismatched loop setting for: ");
3208 n->dump();
3209 if( fail++ > 10 ) return;
3210 tty->print("We have it as: ");
3211 us->dump();
3212 tty->print("Verify thinks: ");
3213 loop_verify->get_ctrl_no_update(n)->dump();
3214 tty->cr();
3215 } else if (!C->major_progress()) {
3216 // Loop selection can be messed up if we did a major progress
3217 // operation, like split-if. Do not verify in that case.
3218 IdealLoopTree *them = loop_verify->get_loop_idx(n);
3219 if( us->_head != them->_head || us->_tail != them->_tail ) {
3220 tty->print("Unequals loops for: ");
3221 n->dump();
3222 if( fail++ > 10 ) return;
3223 tty->print("We have it as: ");
3224 us->dump();
3225 tty->print("Verify thinks: ");
3226 them->dump();
3227 tty->cr();
3228 }
3229 }
3230 }
3231
3232 // Check for immediate dominators being equal
3233 if( i >= _idom_size ) {
3234 if( !n->is_CFG() ) return;
3235 tty->print("CFG Node with no idom: ");
3236 n->dump();
3237 return;
3238 }
3239 if( !n->is_CFG() ) return;
3240 if( n == C->root() ) return; // No IDOM here
3241
3242 assert(n->_idx == i, "sanity");
3243 Node *id = idom_no_update(n);
3244 if( id != loop_verify->idom_no_update(n) ) {
3245 tty->print("Unequals idoms for: ");
3246 n->dump();
3247 if( fail++ > 10 ) return;
3248 tty->print("We have it as: ");
3249 id->dump();
3250 tty->print("Verify thinks: ");
3251 loop_verify->idom_no_update(n)->dump();
3252 tty->cr();
3253 }
3254
3255}
3256
3257//------------------------------verify_tree------------------------------------
3258// Verify that tree structures match. Because the CFG can change, siblings
3259// within the loop tree can be reordered. We attempt to deal with that by
3260// reordering the verify's loop tree if possible.
3261void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3262 assert( _parent == parent, "Badly formed loop tree" );
3263
3264 // Siblings not in same order? Attempt to re-order.
3265 if( _head != loop->_head ) {
3266 // Find _next pointer to update
3267 IdealLoopTree **pp = &loop->_parent->_child;
3268 while( *pp != loop )
3269 pp = &((*pp)->_next);
3270 // Find proper sibling to be next
3271 IdealLoopTree **nn = &loop->_next;
3272 while( (*nn) && (*nn)->_head != _head )
3273 nn = &((*nn)->_next);
3274
3275 // Check for no match.
3276 if( !(*nn) ) {
3277 // Annoyingly, irreducible loops can pick different headers
3278 // after a major_progress operation, so the rest of the loop
3279 // tree cannot be matched.
3280 if (_irreducible && Compile::current()->major_progress()) return;
3281 assert( 0, "failed to match loop tree" );
3282 }
3283
3284 // Move (*nn) to (*pp)
3285 IdealLoopTree *hit = *nn;
3286 *nn = hit->_next;
3287 hit->_next = loop;
3288 *pp = loop;
3289 loop = hit;
3290 // Now try again to verify
3291 }
3292
3293 assert( _head == loop->_head , "mismatched loop head" );
3294 Node *tail = _tail; // Inline a non-updating version of
3295 while( !tail->in(0) ) // the 'tail()' call.
3296 tail = tail->in(1);
3297 assert( tail == loop->_tail, "mismatched loop tail" );
3298
3299 // Counted loops that are guarded should be able to find their guards
3300 if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3301 CountedLoopNode *cl = _head->as_CountedLoop();
3302 Node *init = cl->init_trip();
3303 Node *ctrl = cl->in(LoopNode::EntryControl);
3304 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3305 Node *iff = ctrl->in(0);
3306 assert( iff->Opcode() == Op_If, "" );
3307 Node *bol = iff->in(1);
3308 assert( bol->Opcode() == Op_Bool, "" );
3309 Node *cmp = bol->in(1);
3310 assert( cmp->Opcode() == Op_CmpI, "" );
3311 Node *add = cmp->in(1);
3312 Node *opaq;
3313 if( add->Opcode() == Op_Opaque1 ) {
3314 opaq = add;
3315 } else {
3316 assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3317 assert( add == init, "" );
3318 opaq = cmp->in(2);
3319 }
3320 assert( opaq->Opcode() == Op_Opaque1, "" );
3321
3322 }
3323
3324 if (_child != NULL) _child->verify_tree(loop->_child, this);
3325 if (_next != NULL) _next ->verify_tree(loop->_next, parent);
3326 // Innermost loops need to verify loop bodies,
3327 // but only if no 'major_progress'
3328 int fail = 0;
3329 if (!Compile::current()->major_progress() && _child == NULL) {
3330 for( uint i = 0; i < _body.size(); i++ ) {
3331 Node *n = _body.at(i);
3332 if (n->outcnt() == 0) continue; // Ignore dead
3333 uint j;
3334 for( j = 0; j < loop->_body.size(); j++ )
3335 if( loop->_body.at(j) == n )
3336 break;
3337 if( j == loop->_body.size() ) { // Not found in loop body
3338 // Last ditch effort to avoid assertion: Its possible that we
3339 // have some users (so outcnt not zero) but are still dead.
3340 // Try to find from root.
3341 if (Compile::current()->root()->find(n->_idx)) {
3342 fail++;
3343 tty->print("We have that verify does not: ");
3344 n->dump();
3345 }
3346 }
3347 }
3348 for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3349 Node *n = loop->_body.at(i2);
3350 if (n->outcnt() == 0) continue; // Ignore dead
3351 uint j;
3352 for( j = 0; j < _body.size(); j++ )
3353 if( _body.at(j) == n )
3354 break;
3355 if( j == _body.size() ) { // Not found in loop body
3356 // Last ditch effort to avoid assertion: Its possible that we
3357 // have some users (so outcnt not zero) but are still dead.
3358 // Try to find from root.
3359 if (Compile::current()->root()->find(n->_idx)) {
3360 fail++;
3361 tty->print("Verify has that we do not: ");
3362 n->dump();
3363 }
3364 }
3365 }
3366 assert( !fail, "loop body mismatch" );
3367 }
3368}
3369
3370#endif
3371
3372//------------------------------set_idom---------------------------------------
3373void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3374 uint idx = d->_idx;
3375 if (idx >= _idom_size) {
3376 uint newsize = _idom_size<<1;
3377 while( idx >= newsize ) {
3378 newsize <<= 1;
3379 }
3380 _idom = REALLOC_RESOURCE_ARRAY( Node*, _idom,_idom_size,newsize);
3381 _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3382 memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3383 _idom_size = newsize;
3384 }
3385 _idom[idx] = n;
3386 _dom_depth[idx] = dom_depth;
3387}
3388
3389//------------------------------recompute_dom_depth---------------------------------------
3390// The dominator tree is constructed with only parent pointers.
3391// This recomputes the depth in the tree by first tagging all
3392// nodes as "no depth yet" marker. The next pass then runs up
3393// the dom tree from each node marked "no depth yet", and computes
3394// the depth on the way back down.
3395void PhaseIdealLoop::recompute_dom_depth() {
3396 uint no_depth_marker = C->unique();
3397 uint i;
3398 // Initialize depth to "no depth yet" and realize all lazy updates
3399 for (i = 0; i < _idom_size; i++) {
3400 // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3401 if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3402 _dom_depth[i] = no_depth_marker;
3403
3404 // heal _idom if it has a fwd mapping in _nodes
3405 if (_idom[i]->in(0) == NULL) {
3406 idom(i);
3407 }
3408 }
3409 }
3410 if (_dom_stk == NULL) {
3411 uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3412 if (init_size < 10) init_size = 10;
3413 _dom_stk = new GrowableArray<uint>(init_size);
3414 }
3415 // Compute new depth for each node.
3416 for (i = 0; i < _idom_size; i++) {
3417 uint j = i;
3418 // Run up the dom tree to find a node with a depth
3419 while (_dom_depth[j] == no_depth_marker) {
3420 _dom_stk->push(j);
3421 j = _idom[j]->_idx;
3422 }
3423 // Compute the depth on the way back down this tree branch
3424 uint dd = _dom_depth[j] + 1;
3425 while (_dom_stk->length() > 0) {
3426 uint j = _dom_stk->pop();
3427 _dom_depth[j] = dd;
3428 dd++;
3429 }
3430 }
3431}
3432
3433//------------------------------sort-------------------------------------------
3434// Insert 'loop' into the existing loop tree. 'innermost' is a leaf of the
3435// loop tree, not the root.
3436IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3437 if( !innermost ) return loop; // New innermost loop
3438
3439 int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3440 assert( loop_preorder, "not yet post-walked loop" );
3441 IdealLoopTree **pp = &innermost; // Pointer to previous next-pointer
3442 IdealLoopTree *l = *pp; // Do I go before or after 'l'?
3443
3444 // Insert at start of list
3445 while( l ) { // Insertion sort based on pre-order
3446 if( l == loop ) return innermost; // Already on list!
3447 int l_preorder = get_preorder(l->_head); // Cache pre-order number
3448 assert( l_preorder, "not yet post-walked l" );
3449 // Check header pre-order number to figure proper nesting
3450 if( loop_preorder > l_preorder )
3451 break; // End of insertion
3452 // If headers tie (e.g., shared headers) check tail pre-order numbers.
3453 // Since I split shared headers, you'd think this could not happen.
3454 // BUT: I must first do the preorder numbering before I can discover I
3455 // have shared headers, so the split headers all get the same preorder
3456 // number as the RegionNode they split from.
3457 if( loop_preorder == l_preorder &&
3458 get_preorder(loop->_tail) < get_preorder(l->_tail) )
3459 break; // Also check for shared headers (same pre#)
3460 pp = &l->_parent; // Chain up list
3461 l = *pp;
3462 }
3463 // Link into list
3464 // Point predecessor to me
3465 *pp = loop;
3466 // Point me to successor
3467 IdealLoopTree *p = loop->_parent;
3468 loop->_parent = l; // Point me to successor
3469 if( p ) sort( p, innermost ); // Insert my parents into list as well
3470 return innermost;
3471}
3472
3473//------------------------------build_loop_tree--------------------------------
3474// I use a modified Vick/Tarjan algorithm. I need pre- and a post- visit
3475// bits. The _nodes[] array is mapped by Node index and holds a NULL for
3476// not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3477// tightest enclosing IdealLoopTree for post-walked.
3478//
3479// During my forward walk I do a short 1-layer lookahead to see if I can find
3480// a loop backedge with that doesn't have any work on the backedge. This
3481// helps me construct nested loops with shared headers better.
3482//
3483// Once I've done the forward recursion, I do the post-work. For each child
3484// I check to see if there is a backedge. Backedges define a loop! I
3485// insert an IdealLoopTree at the target of the backedge.
3486//
3487// During the post-work I also check to see if I have several children
3488// belonging to different loops. If so, then this Node is a decision point
3489// where control flow can choose to change loop nests. It is at this
3490// decision point where I can figure out how loops are nested. At this
3491// time I can properly order the different loop nests from my children.
3492// Note that there may not be any backedges at the decision point!
3493//
3494// Since the decision point can be far removed from the backedges, I can't
3495// order my loops at the time I discover them. Thus at the decision point
3496// I need to inspect loop header pre-order numbers to properly nest my
3497// loops. This means I need to sort my childrens' loops by pre-order.
3498// The sort is of size number-of-control-children, which generally limits
3499// it to size 2 (i.e., I just choose between my 2 target loops).
3500void PhaseIdealLoop::build_loop_tree() {
3501 // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3502 GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3503 Node *n = C->root();
3504 bltstack.push(n);
3505 int pre_order = 1;
3506 int stack_size;
3507
3508 while ( ( stack_size = bltstack.length() ) != 0 ) {
3509 n = bltstack.top(); // Leave node on stack
3510 if ( !is_visited(n) ) {
3511 // ---- Pre-pass Work ----
3512 // Pre-walked but not post-walked nodes need a pre_order number.
3513
3514 set_preorder_visited( n, pre_order ); // set as visited
3515
3516 // ---- Scan over children ----
3517 // Scan first over control projections that lead to loop headers.
3518 // This helps us find inner-to-outer loops with shared headers better.
3519
3520 // Scan children's children for loop headers.
3521 for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3522 Node* m = n->raw_out(i); // Child
3523 if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3524 // Scan over children's children to find loop
3525 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3526 Node* l = m->fast_out(j);
3527 if( is_visited(l) && // Been visited?
3528 !is_postvisited(l) && // But not post-visited
3529 get_preorder(l) < pre_order ) { // And smaller pre-order
3530 // Found! Scan the DFS down this path before doing other paths
3531 bltstack.push(m);
3532 break;
3533 }
3534 }
3535 }
3536 }
3537 pre_order++;
3538 }
3539 else if ( !is_postvisited(n) ) {
3540 // Note: build_loop_tree_impl() adds out edges on rare occasions,
3541 // such as com.sun.rsasign.am::a.
3542 // For non-recursive version, first, process current children.
3543 // On next iteration, check if additional children were added.
3544 for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3545 Node* u = n->raw_out(k);
3546 if ( u->is_CFG() && !is_visited(u) ) {
3547 bltstack.push(u);
3548 }
3549 }
3550 if ( bltstack.length() == stack_size ) {
3551 // There were no additional children, post visit node now
3552 (void)bltstack.pop(); // Remove node from stack
3553 pre_order = build_loop_tree_impl( n, pre_order );
3554 // Check for bailout
3555 if (C->failing()) {
3556 return;
3557 }
3558 // Check to grow _preorders[] array for the case when
3559 // build_loop_tree_impl() adds new nodes.
3560 check_grow_preorders();
3561 }
3562 }
3563 else {
3564 (void)bltstack.pop(); // Remove post-visited node from stack
3565 }
3566 }
3567}
3568
3569//------------------------------build_loop_tree_impl---------------------------
3570int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3571 // ---- Post-pass Work ----
3572 // Pre-walked but not post-walked nodes need a pre_order number.
3573
3574 // Tightest enclosing loop for this Node
3575 IdealLoopTree *innermost = NULL;
3576
3577 // For all children, see if any edge is a backedge. If so, make a loop
3578 // for it. Then find the tightest enclosing loop for the self Node.
3579 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3580 Node* m = n->fast_out(i); // Child
3581 if( n == m ) continue; // Ignore control self-cycles
3582 if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3583
3584 IdealLoopTree *l; // Child's loop
3585 if( !is_postvisited(m) ) { // Child visited but not post-visited?
3586 // Found a backedge
3587 assert( get_preorder(m) < pre_order, "should be backedge" );
3588 // Check for the RootNode, which is already a LoopNode and is allowed
3589 // to have multiple "backedges".
3590 if( m == C->root()) { // Found the root?
3591 l = _ltree_root; // Root is the outermost LoopNode
3592 } else { // Else found a nested loop
3593 // Insert a LoopNode to mark this loop.
3594 l = new IdealLoopTree(this, m, n);
3595 } // End of Else found a nested loop
3596 if( !has_loop(m) ) // If 'm' does not already have a loop set
3597 set_loop(m, l); // Set loop header to loop now
3598
3599 } else { // Else not a nested loop
3600 if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3601 l = get_loop(m); // Get previously determined loop
3602 // If successor is header of a loop (nest), move up-loop till it
3603 // is a member of some outer enclosing loop. Since there are no
3604 // shared headers (I've split them already) I only need to go up
3605 // at most 1 level.
3606 while( l && l->_head == m ) // Successor heads loop?
3607 l = l->_parent; // Move up 1 for me
3608 // If this loop is not properly parented, then this loop
3609 // has no exit path out, i.e. its an infinite loop.
3610 if( !l ) {
3611 // Make loop "reachable" from root so the CFG is reachable. Basically
3612 // insert a bogus loop exit that is never taken. 'm', the loop head,
3613 // points to 'n', one (of possibly many) fall-in paths. There may be
3614 // many backedges as well.
3615
3616 // Here I set the loop to be the root loop. I could have, after
3617 // inserting a bogus loop exit, restarted the recursion and found my
3618 // new loop exit. This would make the infinite loop a first-class
3619 // loop and it would then get properly optimized. What's the use of
3620 // optimizing an infinite loop?
3621 l = _ltree_root; // Oops, found infinite loop
3622
3623 if (!_verify_only) {
3624 // Insert the NeverBranch between 'm' and it's control user.
3625 NeverBranchNode *iff = new NeverBranchNode( m );
3626 _igvn.register_new_node_with_optimizer(iff);
3627 set_loop(iff, l);
3628 Node *if_t = new CProjNode( iff, 0 );
3629 _igvn.register_new_node_with_optimizer(if_t);
3630 set_loop(if_t, l);
3631
3632 Node* cfg = NULL; // Find the One True Control User of m
3633 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3634 Node* x = m->fast_out(j);
3635 if (x->is_CFG() && x != m && x != iff)
3636 { cfg = x; break; }
3637 }
3638 assert(cfg != NULL, "must find the control user of m");
3639 uint k = 0; // Probably cfg->in(0)
3640 while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3641 cfg->set_req( k, if_t ); // Now point to NeverBranch
3642 _igvn._worklist.push(cfg);
3643
3644 // Now create the never-taken loop exit
3645 Node *if_f = new CProjNode( iff, 1 );
3646 _igvn.register_new_node_with_optimizer(if_f);
3647 set_loop(if_f, l);
3648 // Find frame ptr for Halt. Relies on the optimizer
3649 // V-N'ing. Easier and quicker than searching through
3650 // the program structure.
3651 Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3652 _igvn.register_new_node_with_optimizer(frame);
3653 // Halt & Catch Fire
3654 Node *halt = new HaltNode( if_f, frame );
3655 _igvn.register_new_node_with_optimizer(halt);
3656 set_loop(halt, l);
3657 C->root()->add_req(halt);
3658 }
3659 set_loop(C->root(), _ltree_root);
3660 }
3661 }
3662 // Weeny check for irreducible. This child was already visited (this
3663 // IS the post-work phase). Is this child's loop header post-visited
3664 // as well? If so, then I found another entry into the loop.
3665 if (!_verify_only) {
3666 while( is_postvisited(l->_head) ) {
3667 // found irreducible
3668 l->_irreducible = 1; // = true
3669 l = l->_parent;
3670 _has_irreducible_loops = true;
3671 // Check for bad CFG here to prevent crash, and bailout of compile
3672 if (l == NULL) {
3673 C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3674 return pre_order;
3675 }
3676 }
3677 C->set_has_irreducible_loop(_has_irreducible_loops);
3678 }
3679
3680 // This Node might be a decision point for loops. It is only if
3681 // it's children belong to several different loops. The sort call
3682 // does a trivial amount of work if there is only 1 child or all
3683 // children belong to the same loop. If however, the children
3684 // belong to different loops, the sort call will properly set the
3685 // _parent pointers to show how the loops nest.
3686 //
3687 // In any case, it returns the tightest enclosing loop.
3688 innermost = sort( l, innermost );
3689 }
3690
3691 // Def-use info will have some dead stuff; dead stuff will have no
3692 // loop decided on.
3693
3694 // Am I a loop header? If so fix up my parent's child and next ptrs.
3695 if( innermost && innermost->_head == n ) {
3696 assert( get_loop(n) == innermost, "" );
3697 IdealLoopTree *p = innermost->_parent;
3698 IdealLoopTree *l = innermost;
3699 while( p && l->_head == n ) {
3700 l->_next = p->_child; // Put self on parents 'next child'
3701 p->_child = l; // Make self as first child of parent
3702 l = p; // Now walk up the parent chain
3703 p = l->_parent;
3704 }
3705 } else {
3706 // Note that it is possible for a LoopNode to reach here, if the
3707 // backedge has been made unreachable (hence the LoopNode no longer
3708 // denotes a Loop, and will eventually be removed).
3709
3710 // Record tightest enclosing loop for self. Mark as post-visited.
3711 set_loop(n, innermost);
3712 // Also record has_call flag early on
3713 if( innermost ) {
3714 if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3715 // Do not count uncommon calls
3716 if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3717 Node *iff = n->in(0)->in(0);
3718 // No any calls for vectorized loops.
3719 if( UseSuperWord || !iff->is_If() ||
3720 (n->in(0)->Opcode() == Op_IfFalse &&
3721 (1.0 - iff->as_If()->_prob) >= 0.01) ||
3722 (iff->as_If()->_prob >= 0.01) )
3723 innermost->_has_call = 1;
3724 }
3725 } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3726 // Disable loop optimizations if the loop has a scalar replaceable
3727 // allocation. This disabling may cause a potential performance lost
3728 // if the allocation is not eliminated for some reason.
3729 innermost->_allow_optimizations = false;
3730 innermost->_has_call = 1; // = true
3731 } else if (n->Opcode() == Op_SafePoint) {
3732 // Record all safepoints in this loop.
3733 if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3734 innermost->_safepts->push(n);
3735 }
3736 }
3737 }
3738
3739 // Flag as post-visited now
3740 set_postvisited(n);
3741 return pre_order;
3742}
3743
3744
3745//------------------------------build_loop_early-------------------------------
3746// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3747// First pass computes the earliest controlling node possible. This is the
3748// controlling input with the deepest dominating depth.
3749void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3750 while (worklist.size() != 0) {
3751 // Use local variables nstack_top_n & nstack_top_i to cache values
3752 // on nstack's top.
3753 Node *nstack_top_n = worklist.pop();
3754 uint nstack_top_i = 0;
3755//while_nstack_nonempty:
3756 while (true) {
3757 // Get parent node and next input's index from stack's top.
3758 Node *n = nstack_top_n;
3759 uint i = nstack_top_i;
3760 uint cnt = n->req(); // Count of inputs
3761 if (i == 0) { // Pre-process the node.
3762 if( has_node(n) && // Have either loop or control already?
3763 !has_ctrl(n) ) { // Have loop picked out already?
3764 // During "merge_many_backedges" we fold up several nested loops
3765 // into a single loop. This makes the members of the original
3766 // loop bodies pointing to dead loops; they need to move up
3767 // to the new UNION'd larger loop. I set the _head field of these
3768 // dead loops to NULL and the _parent field points to the owning
3769 // loop. Shades of UNION-FIND algorithm.
3770 IdealLoopTree *ilt;
3771 while( !(ilt = get_loop(n))->_head ) {
3772 // Normally I would use a set_loop here. But in this one special
3773 // case, it is legal (and expected) to change what loop a Node
3774 // belongs to.
3775 _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3776 }
3777 // Remove safepoints ONLY if I've already seen I don't need one.
3778 // (the old code here would yank a 2nd safepoint after seeing a
3779 // first one, even though the 1st did not dominate in the loop body
3780 // and thus could be avoided indefinitely)
3781 if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3782 is_deleteable_safept(n)) {
3783 Node *in = n->in(TypeFunc::Control);
3784 lazy_replace(n,in); // Pull safepoint now
3785 if (ilt->_safepts != NULL) {
3786 ilt->_safepts->yank(n);
3787 }
3788 // Carry on with the recursion "as if" we are walking
3789 // only the control input
3790 if( !visited.test_set( in->_idx ) ) {
3791 worklist.push(in); // Visit this guy later, using worklist
3792 }
3793 // Get next node from nstack:
3794 // - skip n's inputs processing by setting i > cnt;
3795 // - we also will not call set_early_ctrl(n) since
3796 // has_node(n) == true (see the condition above).
3797 i = cnt + 1;
3798 }
3799 }
3800 } // if (i == 0)
3801
3802 // Visit all inputs
3803 bool done = true; // Assume all n's inputs will be processed
3804 while (i < cnt) {
3805 Node *in = n->in(i);
3806 ++i;
3807 if (in == NULL) continue;
3808 if (in->pinned() && !in->is_CFG())
3809 set_ctrl(in, in->in(0));
3810 int is_visited = visited.test_set( in->_idx );
3811 if (!has_node(in)) { // No controlling input yet?
3812 assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3813 assert( !is_visited, "visit only once" );
3814 nstack.push(n, i); // Save parent node and next input's index.
3815 nstack_top_n = in; // Process current input now.
3816 nstack_top_i = 0;
3817 done = false; // Not all n's inputs processed.
3818 break; // continue while_nstack_nonempty;
3819 } else if (!is_visited) {
3820 // This guy has a location picked out for him, but has not yet
3821 // been visited. Happens to all CFG nodes, for instance.
3822 // Visit him using the worklist instead of recursion, to break
3823 // cycles. Since he has a location already we do not need to
3824 // find his location before proceeding with the current Node.
3825 worklist.push(in); // Visit this guy later, using worklist
3826 }
3827 }
3828 if (done) {
3829 // All of n's inputs have been processed, complete post-processing.
3830
3831 // Compute earliest point this Node can go.
3832 // CFG, Phi, pinned nodes already know their controlling input.
3833 if (!has_node(n)) {
3834 // Record earliest legal location
3835 set_early_ctrl( n );
3836 }
3837 if (nstack.is_empty()) {
3838 // Finished all nodes on stack.
3839 // Process next node on the worklist.
3840 break;
3841 }
3842 // Get saved parent node and next input's index.
3843 nstack_top_n = nstack.node();
3844 nstack_top_i = nstack.index();
3845 nstack.pop();
3846 }
3847 } // while (true)
3848 }
3849}
3850
3851//------------------------------dom_lca_internal--------------------------------
3852// Pair-wise LCA
3853Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3854 if( !n1 ) return n2; // Handle NULL original LCA
3855 assert( n1->is_CFG(), "" );
3856 assert( n2->is_CFG(), "" );
3857 // find LCA of all uses
3858 uint d1 = dom_depth(n1);
3859 uint d2 = dom_depth(n2);
3860 while (n1 != n2) {
3861 if (d1 > d2) {
3862 n1 = idom(n1);
3863 d1 = dom_depth(n1);
3864 } else if (d1 < d2) {
3865 n2 = idom(n2);
3866 d2 = dom_depth(n2);
3867 } else {
3868 // Here d1 == d2. Due to edits of the dominator-tree, sections
3869 // of the tree might have the same depth. These sections have
3870 // to be searched more carefully.
3871
3872 // Scan up all the n1's with equal depth, looking for n2.
3873 Node *t1 = idom(n1);
3874 while (dom_depth(t1) == d1) {
3875 if (t1 == n2) return n2;
3876 t1 = idom(t1);
3877 }
3878 // Scan up all the n2's with equal depth, looking for n1.
3879 Node *t2 = idom(n2);
3880 while (dom_depth(t2) == d2) {
3881 if (t2 == n1) return n1;
3882 t2 = idom(t2);
3883 }
3884 // Move up to a new dominator-depth value as well as up the dom-tree.
3885 n1 = t1;
3886 n2 = t2;
3887 d1 = dom_depth(n1);
3888 d2 = dom_depth(n2);
3889 }
3890 }
3891 return n1;
3892}
3893
3894//------------------------------compute_idom-----------------------------------
3895// Locally compute IDOM using dom_lca call. Correct only if the incoming
3896// IDOMs are correct.
3897Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3898 assert( region->is_Region(), "" );
3899 Node *LCA = NULL;
3900 for( uint i = 1; i < region->req(); i++ ) {
3901 if( region->in(i) != C->top() )
3902 LCA = dom_lca( LCA, region->in(i) );
3903 }
3904 return LCA;
3905}
3906
3907bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3908 bool had_error = false;
3909#ifdef ASSERT
3910 if (early != C->root()) {
3911 // Make sure that there's a dominance path from LCA to early
3912 Node* d = LCA;
3913 while (d != early) {
3914 if (d == C->root()) {
3915 dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3916 tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3917 had_error = true;
3918 break;
3919 }
3920 d = idom(d);
3921 }
3922 }
3923#endif
3924 return had_error;
3925}
3926
3927
3928Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3929 // Compute LCA over list of uses
3930 bool had_error = false;
3931 Node *LCA = NULL;
3932 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3933 Node* c = n->fast_out(i);
3934 if (_nodes[c->_idx] == NULL)
3935 continue; // Skip the occasional dead node
3936 if( c->is_Phi() ) { // For Phis, we must land above on the path
3937 for( uint j=1; j<c->req(); j++ ) {// For all inputs
3938 if( c->in(j) == n ) { // Found matching input?
3939 Node *use = c->in(0)->in(j);
3940 if (_verify_only && use->is_top()) continue;
3941 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3942 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3943 }
3944 }
3945 } else {
3946 // For CFG data-users, use is in the block just prior
3947 Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3948 LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3949 if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3950 }
3951 }
3952 assert(!had_error, "bad dominance");
3953 return LCA;
3954}
3955
3956// Check the shape of the graph at the loop entry. In some cases,
3957// the shape of the graph does not match the shape outlined below.
3958// That is caused by the Opaque1 node "protecting" the shape of
3959// the graph being removed by, for example, the IGVN performed
3960// in PhaseIdealLoop::build_and_optimize().
3961//
3962// After the Opaque1 node has been removed, optimizations (e.g., split-if,
3963// loop unswitching, and IGVN, or a combination of them) can freely change
3964// the graph's shape. As a result, the graph shape outlined below cannot
3965// be guaranteed anymore.
3966bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
3967 if (!cl->is_main_loop() && !cl->is_post_loop()) {
3968 return false;
3969 }
3970 Node* ctrl = cl->skip_predicates();
3971
3972 if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
3973 return false;
3974 }
3975 Node* iffm = ctrl->in(0);
3976 if (iffm == NULL || !iffm->is_If()) {
3977 return false;
3978 }
3979 Node* bolzm = iffm->in(1);
3980 if (bolzm == NULL || !bolzm->is_Bool()) {
3981 return false;
3982 }
3983 Node* cmpzm = bolzm->in(1);
3984 if (cmpzm == NULL || !cmpzm->is_Cmp()) {
3985 return false;
3986 }
3987 // compares can get conditionally flipped
3988 bool found_opaque = false;
3989 for (uint i = 1; i < cmpzm->req(); i++) {
3990 Node* opnd = cmpzm->in(i);
3991 if (opnd && opnd->Opcode() == Op_Opaque1) {
3992 found_opaque = true;
3993 break;
3994 }
3995 }
3996 if (!found_opaque) {
3997 return false;
3998 }
3999 return true;
4000}
4001
4002//------------------------------get_late_ctrl----------------------------------
4003// Compute latest legal control.
4004Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
4005 assert(early != NULL, "early control should not be NULL");
4006
4007 Node* LCA = compute_lca_of_uses(n, early);
4008#ifdef ASSERT
4009 if (LCA == C->root() && LCA != early) {
4010 // def doesn't dominate uses so print some useful debugging output
4011 compute_lca_of_uses(n, early, true);
4012 }
4013#endif
4014
4015 // if this is a load, check for anti-dependent stores
4016 // We use a conservative algorithm to identify potential interfering
4017 // instructions and for rescheduling the load. The users of the memory
4018 // input of this load are examined. Any use which is not a load and is
4019 // dominated by early is considered a potentially interfering store.
4020 // This can produce false positives.
4021 if (n->is_Load() && LCA != early) {
4022 Node_List worklist;
4023
4024 Node *mem = n->in(MemNode::Memory);
4025 for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
4026 Node* s = mem->fast_out(i);
4027 worklist.push(s);
4028 }
4029 while(worklist.size() != 0 && LCA != early) {
4030 Node* s = worklist.pop();
4031 if (s->is_Load() || s->Opcode() == Op_SafePoint ||
4032 (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
4033 continue;
4034 } else if (s->is_MergeMem()) {
4035 for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
4036 Node* s1 = s->fast_out(i);
4037 worklist.push(s1);
4038 }
4039 } else {
4040 Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
4041 assert(sctrl != NULL || s->outcnt() == 0, "must have control");
4042 if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
4043 LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
4044 }
4045 }
4046 }
4047 }
4048
4049 assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4050 return LCA;
4051}
4052
4053// true if CFG node d dominates CFG node n
4054bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4055 if (d == n)
4056 return true;
4057 assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4058 uint dd = dom_depth(d);
4059 while (dom_depth(n) >= dd) {
4060 if (n == d)
4061 return true;
4062 n = idom(n);
4063 }
4064 return false;
4065}
4066
4067//------------------------------dom_lca_for_get_late_ctrl_internal-------------
4068// Pair-wise LCA with tags.
4069// Tag each index with the node 'tag' currently being processed
4070// before advancing up the dominator chain using idom().
4071// Later calls that find a match to 'tag' know that this path has already
4072// been considered in the current LCA (which is input 'n1' by convention).
4073// Since get_late_ctrl() is only called once for each node, the tag array
4074// does not need to be cleared between calls to get_late_ctrl().
4075// Algorithm trades a larger constant factor for better asymptotic behavior
4076//
4077Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4078 uint d1 = dom_depth(n1);
4079 uint d2 = dom_depth(n2);
4080
4081 do {
4082 if (d1 > d2) {
4083 // current lca is deeper than n2
4084 _dom_lca_tags.map(n1->_idx, tag);
4085 n1 = idom(n1);
4086 d1 = dom_depth(n1);
4087 } else if (d1 < d2) {
4088 // n2 is deeper than current lca
4089 Node *memo = _dom_lca_tags[n2->_idx];
4090 if( memo == tag ) {
4091 return n1; // Return the current LCA
4092 }
4093 _dom_lca_tags.map(n2->_idx, tag);
4094 n2 = idom(n2);
4095 d2 = dom_depth(n2);
4096 } else {
4097 // Here d1 == d2. Due to edits of the dominator-tree, sections
4098 // of the tree might have the same depth. These sections have
4099 // to be searched more carefully.
4100
4101 // Scan up all the n1's with equal depth, looking for n2.
4102 _dom_lca_tags.map(n1->_idx, tag);
4103 Node *t1 = idom(n1);
4104 while (dom_depth(t1) == d1) {
4105 if (t1 == n2) return n2;
4106 _dom_lca_tags.map(t1->_idx, tag);
4107 t1 = idom(t1);
4108 }
4109 // Scan up all the n2's with equal depth, looking for n1.
4110 _dom_lca_tags.map(n2->_idx, tag);
4111 Node *t2 = idom(n2);
4112 while (dom_depth(t2) == d2) {
4113 if (t2 == n1) return n1;
4114 _dom_lca_tags.map(t2->_idx, tag);
4115 t2 = idom(t2);
4116 }
4117 // Move up to a new dominator-depth value as well as up the dom-tree.
4118 n1 = t1;
4119 n2 = t2;
4120 d1 = dom_depth(n1);
4121 d2 = dom_depth(n2);
4122 }
4123 } while (n1 != n2);
4124 return n1;
4125}
4126
4127//------------------------------init_dom_lca_tags------------------------------
4128// Tag could be a node's integer index, 32bits instead of 64bits in some cases
4129// Intended use does not involve any growth for the array, so it could
4130// be of fixed size.
4131void PhaseIdealLoop::init_dom_lca_tags() {
4132 uint limit = C->unique() + 1;
4133 _dom_lca_tags.map( limit, NULL );
4134#ifdef ASSERT
4135 for( uint i = 0; i < limit; ++i ) {
4136 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4137 }
4138#endif // ASSERT
4139}
4140
4141//------------------------------clear_dom_lca_tags------------------------------
4142// Tag could be a node's integer index, 32bits instead of 64bits in some cases
4143// Intended use does not involve any growth for the array, so it could
4144// be of fixed size.
4145void PhaseIdealLoop::clear_dom_lca_tags() {
4146 uint limit = C->unique() + 1;
4147 _dom_lca_tags.map( limit, NULL );
4148 _dom_lca_tags.clear();
4149#ifdef ASSERT
4150 for( uint i = 0; i < limit; ++i ) {
4151 assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4152 }
4153#endif // ASSERT
4154}
4155
4156//------------------------------build_loop_late--------------------------------
4157// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4158// Second pass finds latest legal placement, and ideal loop placement.
4159void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
4160 while (worklist.size() != 0) {
4161 Node *n = worklist.pop();
4162 // Only visit once
4163 if (visited.test_set(n->_idx)) continue;
4164 uint cnt = n->outcnt();
4165 uint i = 0;
4166 while (true) {
4167 assert( _nodes[n->_idx], "no dead nodes" );
4168 // Visit all children
4169 if (i < cnt) {
4170 Node* use = n->raw_out(i);
4171 ++i;
4172 // Check for dead uses. Aggressively prune such junk. It might be
4173 // dead in the global sense, but still have local uses so I cannot
4174 // easily call 'remove_dead_node'.
4175 if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4176 // Due to cycles, we might not hit the same fixed point in the verify
4177 // pass as we do in the regular pass. Instead, visit such phis as
4178 // simple uses of the loop head.
4179 if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4180 if( !visited.test(use->_idx) )
4181 worklist.push(use);
4182 } else if( !visited.test_set(use->_idx) ) {
4183 nstack.push(n, i); // Save parent and next use's index.
4184 n = use; // Process all children of current use.
4185 cnt = use->outcnt();
4186 i = 0;
4187 }
4188 } else {
4189 // Do not visit around the backedge of loops via data edges.
4190 // push dead code onto a worklist
4191 _deadlist.push(use);
4192 }
4193 } else {
4194 // All of n's children have been processed, complete post-processing.
4195 build_loop_late_post(n);
4196 if (nstack.is_empty()) {
4197 // Finished all nodes on stack.
4198 // Process next node on the worklist.
4199 break;
4200 }
4201 // Get saved parent node and next use's index. Visit the rest of uses.
4202 n = nstack.node();
4203 cnt = n->outcnt();
4204 i = nstack.index();
4205 nstack.pop();
4206 }
4207 }
4208 }
4209}
4210
4211// Verify that no data node is scheduled in the outer loop of a strip
4212// mined loop.
4213void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4214#ifdef ASSERT
4215 if (get_loop(least)->_nest == 0) {
4216 return;
4217 }
4218 IdealLoopTree* loop = get_loop(least);
4219 Node* head = loop->_head;
4220 if (head->is_OuterStripMinedLoop() &&
4221 // Verification can't be applied to fully built strip mined loops
4222 head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
4223 Node* sfpt = head->as_Loop()->outer_safepoint();
4224 ResourceMark rm;
4225 Unique_Node_List wq;
4226 wq.push(sfpt);
4227 for (uint i = 0; i < wq.size(); i++) {
4228 Node *m = wq.at(i);
4229 for (uint i = 1; i < m->req(); i++) {
4230 Node* nn = m->in(i);
4231 if (nn == n) {
4232 return;
4233 }
4234 if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4235 wq.push(nn);
4236 }
4237 }
4238 }
4239 ShouldNotReachHere();
4240 }
4241#endif
4242}
4243
4244
4245//------------------------------build_loop_late_post---------------------------
4246// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4247// Second pass finds latest legal placement, and ideal loop placement.
4248void PhaseIdealLoop::build_loop_late_post(Node *n) {
4249 BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4250
4251 if (bs->build_loop_late_post(this, n)) {
4252 return;
4253 }
4254
4255 build_loop_late_post_work(n, true);
4256}
4257
4258void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
4259
4260 if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4261 _igvn._worklist.push(n); // Maybe we'll normalize it, if no more loops.
4262 }
4263
4264#ifdef ASSERT
4265 if (_verify_only && !n->is_CFG()) {
4266 // Check def-use domination.
4267 compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4268 }
4269#endif
4270
4271 // CFG and pinned nodes already handled
4272 if( n->in(0) ) {
4273 if( n->in(0)->is_top() ) return; // Dead?
4274
4275 // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4276 // _must_ be pinned (they have to observe their control edge of course).
4277 // Unlike Stores (which modify an unallocable resource, the memory
4278 // state), Mods/Loads can float around. So free them up.
4279 switch( n->Opcode() ) {
4280 case Op_DivI:
4281 case Op_DivF:
4282 case Op_DivD:
4283 case Op_ModI:
4284 case Op_ModF:
4285 case Op_ModD:
4286 case Op_LoadB: // Same with Loads; they can sink
4287 case Op_LoadUB: // during loop optimizations.
4288 case Op_LoadUS:
4289 case Op_LoadD:
4290 case Op_LoadF:
4291 case Op_LoadI:
4292 case Op_LoadKlass:
4293 case Op_LoadNKlass:
4294 case Op_LoadL:
4295 case Op_LoadS:
4296 case Op_LoadP:
4297 case Op_LoadN:
4298 case Op_LoadRange:
4299 case Op_LoadD_unaligned:
4300 case Op_LoadL_unaligned:
4301 case Op_StrComp: // Does a bunch of load-like effects
4302 case Op_StrEquals:
4303 case Op_StrIndexOf:
4304 case Op_StrIndexOfChar:
4305 case Op_AryEq:
4306 case Op_HasNegatives:
4307 pinned = false;
4308 }
4309 if( pinned ) {
4310 IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4311 if( !chosen_loop->_child ) // Inner loop?
4312 chosen_loop->_body.push(n); // Collect inner loops
4313 return;
4314 }
4315 } else { // No slot zero
4316 if( n->is_CFG() ) { // CFG with no slot 0 is dead
4317 _nodes.map(n->_idx,0); // No block setting, it's globally dead
4318 return;
4319 }
4320 assert(!n->is_CFG() || n->outcnt() == 0, "");
4321 }
4322
4323 // Do I have a "safe range" I can select over?
4324 Node *early = get_ctrl(n);// Early location already computed
4325
4326 // Compute latest point this Node can go
4327 Node *LCA = get_late_ctrl( n, early );
4328 // LCA is NULL due to uses being dead
4329 if( LCA == NULL ) {
4330#ifdef ASSERT
4331 for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4332 assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4333 }
4334#endif
4335 _nodes.map(n->_idx, 0); // This node is useless
4336 _deadlist.push(n);
4337 return;
4338 }
4339 assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4340
4341 Node *legal = LCA; // Walk 'legal' up the IDOM chain
4342 Node *least = legal; // Best legal position so far
4343 while( early != legal ) { // While not at earliest legal
4344#ifdef ASSERT
4345 if (legal->is_Start() && !early->is_Root()) {
4346 // Bad graph. Print idom path and fail.
4347 dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4348 assert(false, "Bad graph detected in build_loop_late");
4349 }
4350#endif
4351 // Find least loop nesting depth
4352 legal = idom(legal); // Bump up the IDOM tree
4353 // Check for lower nesting depth
4354 if( get_loop(legal)->_nest < get_loop(least)->_nest )
4355 least = legal;
4356 }
4357 assert(early == legal || legal != C->root(), "bad dominance of inputs");
4358
4359 // Try not to place code on a loop entry projection
4360 // which can inhibit range check elimination.
4361 if (least != early) {
4362 Node* ctrl_out = least->unique_ctrl_out();
4363 if (ctrl_out && ctrl_out->is_Loop() &&
4364 least == ctrl_out->in(LoopNode::EntryControl)) {
4365 // Move the node above predicates as far up as possible so a
4366 // following pass of loop predication doesn't hoist a predicate
4367 // that depends on it above that node.
4368 Node* new_ctrl = least;
4369 for (;;) {
4370 if (!new_ctrl->is_Proj()) {
4371 break;
4372 }
4373 CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4374 if (call == NULL) {
4375 break;
4376 }
4377 int req = call->uncommon_trap_request();
4378 Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4379 if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4380 trap_reason != Deoptimization::Reason_predicate &&
4381 trap_reason != Deoptimization::Reason_profile_predicate) {
4382 break;
4383 }
4384 Node* c = new_ctrl->in(0)->in(0);
4385 if (is_dominator(c, early) && c != early) {
4386 break;
4387 }
4388 new_ctrl = c;
4389 }
4390 least = new_ctrl;
4391 }
4392 }
4393
4394#ifdef ASSERT
4395 // If verifying, verify that 'verify_me' has a legal location
4396 // and choose it as our location.
4397 if( _verify_me ) {
4398 Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4399 Node *legal = LCA;
4400 while( early != legal ) { // While not at earliest legal
4401 if( legal == v_ctrl ) break; // Check for prior good location
4402 legal = idom(legal) ;// Bump up the IDOM tree
4403 }
4404 // Check for prior good location
4405 if( legal == v_ctrl ) least = legal; // Keep prior if found
4406 }
4407#endif
4408
4409 // Assign discovered "here or above" point
4410 least = find_non_split_ctrl(least);
4411 verify_strip_mined_scheduling(n, least);
4412 set_ctrl(n, least);
4413
4414 // Collect inner loop bodies
4415 IdealLoopTree *chosen_loop = get_loop(least);
4416 if( !chosen_loop->_child ) // Inner loop?
4417 chosen_loop->_body.push(n);// Collect inner loops
4418}
4419
4420#ifdef ASSERT
4421void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4422 tty->print_cr("%s", msg);
4423 tty->print("n: "); n->dump();
4424 tty->print("early(n): "); early->dump();
4425 if (n->in(0) != NULL && !n->in(0)->is_top() &&
4426 n->in(0) != early && !n->in(0)->is_Root()) {
4427 tty->print("n->in(0): "); n->in(0)->dump();
4428 }
4429 for (uint i = 1; i < n->req(); i++) {
4430 Node* in1 = n->in(i);
4431 if (in1 != NULL && in1 != n && !in1->is_top()) {
4432 tty->print("n->in(%d): ", i); in1->dump();
4433 Node* in1_early = get_ctrl(in1);
4434 tty->print("early(n->in(%d)): ", i); in1_early->dump();
4435 if (in1->in(0) != NULL && !in1->in(0)->is_top() &&
4436 in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4437 tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4438 }
4439 for (uint j = 1; j < in1->req(); j++) {
4440 Node* in2 = in1->in(j);
4441 if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4442 tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4443 Node* in2_early = get_ctrl(in2);
4444 tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4445 if (in2->in(0) != NULL && !in2->in(0)->is_top() &&
4446 in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4447 tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4448 }
4449 }
4450 }
4451 }
4452 }
4453 tty->cr();
4454 tty->print("LCA(n): "); LCA->dump();
4455 for (uint i = 0; i < n->outcnt(); i++) {
4456 Node* u1 = n->raw_out(i);
4457 if (u1 == n)
4458 continue;
4459 tty->print("n->out(%d): ", i); u1->dump();
4460 if (u1->is_CFG()) {
4461 for (uint j = 0; j < u1->outcnt(); j++) {
4462 Node* u2 = u1->raw_out(j);
4463 if (u2 != u1 && u2 != n && u2->is_CFG()) {
4464 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4465 }
4466 }
4467 } else {
4468 Node* u1_later = get_ctrl(u1);
4469 tty->print("later(n->out(%d)): ", i); u1_later->dump();
4470 if (u1->in(0) != NULL && !u1->in(0)->is_top() &&
4471 u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4472 tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4473 }
4474 for (uint j = 0; j < u1->outcnt(); j++) {
4475 Node* u2 = u1->raw_out(j);
4476 if (u2 == n || u2 == u1)
4477 continue;
4478 tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4479 if (!u2->is_CFG()) {
4480 Node* u2_later = get_ctrl(u2);
4481 tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4482 if (u2->in(0) != NULL && !u2->in(0)->is_top() &&
4483 u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4484 tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4485 }
4486 }
4487 }
4488 }
4489 }
4490 tty->cr();
4491 int ct = 0;
4492 Node *dbg_legal = LCA;
4493 while(!dbg_legal->is_Start() && ct < 100) {
4494 tty->print("idom[%d] ",ct); dbg_legal->dump();
4495 ct++;
4496 dbg_legal = idom(dbg_legal);
4497 }
4498 tty->cr();
4499}
4500#endif
4501
4502#ifndef PRODUCT
4503//------------------------------dump-------------------------------------------
4504void PhaseIdealLoop::dump( ) const {
4505 ResourceMark rm;
4506 Arena* arena = Thread::current()->resource_area();
4507 Node_Stack stack(arena, C->live_nodes() >> 2);
4508 Node_List rpo_list;
4509 VectorSet visited(arena);
4510 visited.set(C->top()->_idx);
4511 rpo( C->root(), stack, visited, rpo_list );
4512 // Dump root loop indexed by last element in PO order
4513 dump( _ltree_root, rpo_list.size(), rpo_list );
4514}
4515
4516void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
4517 loop->dump_head();
4518
4519 // Now scan for CFG nodes in the same loop
4520 for( uint j=idx; j > 0; j-- ) {
4521 Node *n = rpo_list[j-1];
4522 if( !_nodes[n->_idx] ) // Skip dead nodes
4523 continue;
4524 if( get_loop(n) != loop ) { // Wrong loop nest
4525 if( get_loop(n)->_head == n && // Found nested loop?
4526 get_loop(n)->_parent == loop )
4527 dump(get_loop(n),rpo_list.size(),rpo_list); // Print it nested-ly
4528 continue;
4529 }
4530
4531 // Dump controlling node
4532 for( uint x = 0; x < loop->_nest; x++ )
4533 tty->print(" ");
4534 tty->print("C");
4535 if( n == C->root() ) {
4536 n->dump();
4537 } else {
4538 Node* cached_idom = idom_no_update(n);
4539 Node *computed_idom = n->in(0);
4540 if( n->is_Region() ) {
4541 computed_idom = compute_idom(n);
4542 // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4543 // any MultiBranch ctrl node), so apply a similar transform to
4544 // the cached idom returned from idom_no_update.
4545 cached_idom = find_non_split_ctrl(cached_idom);
4546 }
4547 tty->print(" ID:%d",computed_idom->_idx);
4548 n->dump();
4549 if( cached_idom != computed_idom ) {
4550 tty->print_cr("*** BROKEN IDOM! Computed as: %d, cached as: %d",
4551 computed_idom->_idx, cached_idom->_idx);
4552 }
4553 }
4554 // Dump nodes it controls
4555 for( uint k = 0; k < _nodes.Size(); k++ ) {
4556 // (k < C->unique() && get_ctrl(find(k)) == n)
4557 if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4558 Node *m = C->root()->find(k);
4559 if( m && m->outcnt() > 0 ) {
4560 if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4561 tty->print_cr("*** BROKEN CTRL ACCESSOR! _nodes[k] is %p, ctrl is %p",
4562 _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4563 }
4564 for( uint j = 0; j < loop->_nest; j++ )
4565 tty->print(" ");
4566 tty->print(" ");
4567 m->dump();
4568 }
4569 }
4570 }
4571 }
4572}
4573#endif
4574
4575// Collect a R-P-O for the whole CFG.
4576// Result list is in post-order (scan backwards for RPO)
4577void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
4578 stk.push(start, 0);
4579 visited.set(start->_idx);
4580
4581 while (stk.is_nonempty()) {
4582 Node* m = stk.node();
4583 uint idx = stk.index();
4584 if (idx < m->outcnt()) {
4585 stk.set_index(idx + 1);
4586 Node* n = m->raw_out(idx);
4587 if (n->is_CFG() && !visited.test_set(n->_idx)) {
4588 stk.push(n, 0);
4589 }
4590 } else {
4591 rpo_list.push(m);
4592 stk.pop();
4593 }
4594 }
4595}
4596
4597
4598//=============================================================================
4599//------------------------------LoopTreeIterator-----------------------------------
4600
4601// Advance to next loop tree using a preorder, left-to-right traversal.
4602void LoopTreeIterator::next() {
4603 assert(!done(), "must not be done.");
4604 if (_curnt->_child != NULL) {
4605 _curnt = _curnt->_child;
4606 } else if (_curnt->_next != NULL) {
4607 _curnt = _curnt->_next;
4608 } else {
4609 while (_curnt != _root && _curnt->_next == NULL) {
4610 _curnt = _curnt->_parent;
4611 }
4612 if (_curnt == _root) {
4613 _curnt = NULL;
4614 assert(done(), "must be done.");
4615 } else {
4616 assert(_curnt->_next != NULL, "must be more to do");
4617 _curnt = _curnt->_next;
4618 }
4619 }
4620}
4621