1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciTypeFlow.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "opto/addnode.hpp"
30 #include "opto/castnode.hpp"
31 #include "opto/cfgnode.hpp"
32 #include "opto/connode.hpp"
33 #include "opto/loopnode.hpp"
34 #include "opto/phaseX.hpp"
35 #include "opto/runtime.hpp"
36 #include "opto/rootnode.hpp"
37 #include "opto/subnode.hpp"
38
39 // Portions of code courtesy of Clifford Click
40
41 // Optimization - Graph Style
42
43
44 #ifndef PRODUCT
45 extern int explicit_null_checks_elided;
46 #endif
47
48 //=============================================================================
49 //------------------------------Value------------------------------------------
50 // Return a tuple for whichever arm of the IF is reachable
51 const Type* IfNode::Value(PhaseGVN* phase) const {
52 if( !in(0) ) return Type::TOP;
53 if( phase->type(in(0)) == Type::TOP )
54 return Type::TOP;
55 const Type *t = phase->type(in(1));
56 if( t == Type::TOP ) // data is undefined
57 return TypeTuple::IFNEITHER; // unreachable altogether
58 if( t == TypeInt::ZERO ) // zero, or false
59 return TypeTuple::IFFALSE; // only false branch is reachable
60 if( t == TypeInt::ONE ) // 1, or true
61 return TypeTuple::IFTRUE; // only true branch is reachable
62 assert( t == TypeInt::BOOL, "expected boolean type" );
63
64 return TypeTuple::IFBOTH; // No progress
65 }
66
67 const RegMask &IfNode::out_RegMask() const {
68 return RegMask::Empty;
69 }
70
71 //------------------------------split_if---------------------------------------
72 // Look for places where we merge constants, then test on the merged value.
73 // If the IF test will be constant folded on the path with the constant, we
74 // win by splitting the IF to before the merge point.
75 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
76 // I could be a lot more general here, but I'm trying to squeeze this
77 // in before the Christmas '98 break so I'm gonna be kinda restrictive
78 // on the patterns I accept. CNC
79
80 // Look for a compare of a constant and a merged value
81 Node *i1 = iff->in(1);
82 if( !i1->is_Bool() ) return NULL;
83 BoolNode *b = i1->as_Bool();
84 Node *cmp = b->in(1);
85 if( !cmp->is_Cmp() ) return NULL;
86 i1 = cmp->in(1);
87 if( i1 == NULL || !i1->is_Phi() ) return NULL;
88 PhiNode *phi = i1->as_Phi();
89 if( phi->is_copy() ) return NULL;
90 Node *con2 = cmp->in(2);
91 if( !con2->is_Con() ) return NULL;
92 // See that the merge point contains some constants
93 Node *con1=NULL;
94 uint i4;
95 for( i4 = 1; i4 < phi->req(); i4++ ) {
96 con1 = phi->in(i4);
97 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
98 if( con1->is_Con() ) break; // Found a constant
99 // Also allow null-vs-not-null checks
100 const TypePtr *tp = igvn->type(con1)->isa_ptr();
101 if( tp && tp->_ptr == TypePtr::NotNull )
102 break;
103 }
104 if( i4 >= phi->req() ) return NULL; // Found no constants
105
106 igvn->C->set_has_split_ifs(true); // Has chance for split-if
107
108 // Make sure that the compare can be constant folded away
109 Node *cmp2 = cmp->clone();
110 cmp2->set_req(1,con1);
111 cmp2->set_req(2,con2);
112 const Type *t = cmp2->Value(igvn);
113 // This compare is dead, so whack it!
114 igvn->remove_dead_node(cmp2);
115 if( !t->singleton() ) return NULL;
116
117 // No intervening control, like a simple Call
118 Node *r = iff->in(0);
119 if( !r->is_Region() ) return NULL;
120 if( phi->region() != r ) return NULL;
121 // No other users of the cmp/bool
122 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
123 //tty->print_cr("many users of cmp/bool");
124 return NULL;
125 }
126
127 // Make sure we can determine where all the uses of merged values go
128 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
129 Node* u = r->fast_out(j);
130 if( u == r ) continue;
131 if( u == iff ) continue;
132 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
133 if( !u->is_Phi() ) {
134 /*
135 if( u->is_Start() ) {
136 tty->print_cr("Region has inlined start use");
137 } else {
138 tty->print_cr("Region has odd use");
139 u->dump(2);
140 }*/
141 return NULL;
142 }
143 if( u != phi ) {
144 // CNC - do not allow any other merged value
145 //tty->print_cr("Merging another value");
146 //u->dump(2);
147 return NULL;
148 }
149 // Make sure we can account for all Phi uses
150 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
151 Node* v = u->fast_out(k); // User of the phi
152 // CNC - Allow only really simple patterns.
153 // In particular I disallow AddP of the Phi, a fairly common pattern
154 if (v == cmp) continue; // The compare is OK
155 if (v->is_ConstraintCast()) {
156 // If the cast is derived from data flow edges, it may not have a control edge.
157 // If so, it should be safe to split. But follow-up code can not deal with
158 // this (l. 359). So skip.
159 if (v->in(0) == NULL) {
160 return NULL;
161 }
162 if (v->in(0)->in(0) == iff) {
163 continue; // CastPP/II of the IfNode is OK
164 }
165 }
166 // Disabled following code because I cannot tell if exactly one
167 // path dominates without a real dominator check. CNC 9/9/1999
168 //uint vop = v->Opcode();
169 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
170 // Node *r = v->in(0); // Get controlling point
171 // if( !r ) return NULL; // Degraded to a copy
172 // // Find exactly one path in (either True or False doms, but not IFF)
173 // int cnt = 0;
174 // for( uint i = 1; i < r->req(); i++ )
175 // if( r->in(i) && r->in(i)->in(0) == iff )
176 // cnt++;
177 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
178 //}
179 if( !v->is_Call() ) {
180 /*
181 if( v->Opcode() == Op_AddP ) {
182 tty->print_cr("Phi has AddP use");
183 } else if( v->Opcode() == Op_CastPP ) {
184 tty->print_cr("Phi has CastPP use");
185 } else if( v->Opcode() == Op_CastII ) {
186 tty->print_cr("Phi has CastII use");
187 } else {
188 tty->print_cr("Phi has use I cant be bothered with");
189 }
190 */
191 }
192 return NULL;
193
194 /* CNC - Cut out all the fancy acceptance tests
195 // Can we clone this use when doing the transformation?
196 // If all uses are from Phis at this merge or constants, then YES.
197 if( !v->in(0) && v != cmp ) {
198 tty->print_cr("Phi has free-floating use");
199 v->dump(2);
200 return NULL;
201 }
202 for( uint l = 1; l < v->req(); l++ ) {
203 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
204 !v->in(l)->is_Con() ) {
205 tty->print_cr("Phi has use");
206 v->dump(2);
207 return NULL;
208 } // End of if Phi-use input is neither Phi nor Constant
209 } // End of for all inputs to Phi-use
210 */
211 } // End of for all uses of Phi
212 } // End of for all uses of Region
213
214 // Only do this if the IF node is in a sane state
215 if (iff->outcnt() != 2)
216 return NULL;
217
218 // Got a hit! Do the Mondo Hack!
219 //
220 //ABC a1c def ghi B 1 e h A C a c d f g i
221 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
222 // cmp - 2 cmp - 2 cmp - 2
223 // bool bool_c bool_x
224 // if if_c if_x
225 // T F T F T F
226 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
227 //
228 // Split the paths coming into the merge point into 2 separate groups of
229 // merges. On the left will be all the paths feeding constants into the
230 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
231 // will fold up into a constant; this will let the Cmp fold up as well as
232 // all the control flow. Below the original IF we have 2 control
233 // dependent regions, 's' and 't'. Now we will merge the two paths
234 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
235 // likely 2 or more) will promptly constant fold away.
236 PhaseGVN *phase = igvn;
237
238 // Make a region merging constants and a region merging the rest
239 uint req_c = 0;
240 Node* predicate_proj = NULL;
241 int nb_predicate_proj = 0;
242 for (uint ii = 1; ii < r->req(); ii++) {
243 if (phi->in(ii) == con1) {
244 req_c++;
245 }
246 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
247 if (proj != NULL) {
248 nb_predicate_proj++;
249 predicate_proj = proj;
250 }
251 }
252 if (nb_predicate_proj > 1) {
253 // Can happen in case of loop unswitching and when the loop is
254 // optimized out: it's not a loop anymore so we don't care about
255 // predicates.
256 assert(!r->is_Loop(), "this must not be a loop anymore");
257 predicate_proj = NULL;
258 }
259 Node* predicate_c = NULL;
260 Node* predicate_x = NULL;
261 bool counted_loop = r->is_CountedLoop();
262
263 Node *region_c = new RegionNode(req_c + 1);
264 Node *phi_c = con1;
265 uint len = r->req();
266 Node *region_x = new RegionNode(len - req_c);
267 Node *phi_x = PhiNode::make_blank(region_x, phi);
268 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
269 if (phi->in(i) == con1) {
270 region_c->init_req( i_c++, r ->in(i) );
271 if (r->in(i) == predicate_proj)
272 predicate_c = predicate_proj;
273 } else {
274 region_x->init_req( i_x, r ->in(i) );
275 phi_x ->init_req( i_x++, phi->in(i) );
276 if (r->in(i) == predicate_proj)
277 predicate_x = predicate_proj;
278 }
279 }
280 if (predicate_c != NULL && (req_c > 1)) {
281 assert(predicate_x == NULL, "only one predicate entry expected");
282 predicate_c = NULL; // Do not clone predicate below merge point
283 }
284 if (predicate_x != NULL && ((len - req_c) > 2)) {
285 assert(predicate_c == NULL, "only one predicate entry expected");
286 predicate_x = NULL; // Do not clone predicate below merge point
287 }
288
289 // Register the new RegionNodes but do not transform them. Cannot
290 // transform until the entire Region/Phi conglomerate has been hacked
291 // as a single huge transform.
292 igvn->register_new_node_with_optimizer( region_c );
293 igvn->register_new_node_with_optimizer( region_x );
294 // Prevent the untimely death of phi_x. Currently he has no uses. He is
295 // about to get one. If this only use goes away, then phi_x will look dead.
296 // However, he will be picking up some more uses down below.
297 Node *hook = new Node(4);
298 hook->init_req(0, phi_x);
299 hook->init_req(1, phi_c);
300 phi_x = phase->transform( phi_x );
301
302 // Make the compare
303 Node *cmp_c = phase->makecon(t);
304 Node *cmp_x = cmp->clone();
305 cmp_x->set_req(1,phi_x);
306 cmp_x->set_req(2,con2);
307 cmp_x = phase->transform(cmp_x);
308 // Make the bool
309 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
310 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
311 // Make the IfNode
312 IfNode* iff_c = iff->clone()->as_If();
313 iff_c->set_req(0, region_c);
314 iff_c->set_req(1, b_c);
315 igvn->set_type_bottom(iff_c);
316 igvn->_worklist.push(iff_c);
317 hook->init_req(2, iff_c);
318
319 IfNode* iff_x = iff->clone()->as_If();
320 iff_x->set_req(0, region_x);
321 iff_x->set_req(1, b_x);
322 igvn->set_type_bottom(iff_x);
323 igvn->_worklist.push(iff_x);
324 hook->init_req(3, iff_x);
325
326 // Make the true/false arms
327 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
328 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
329 if (predicate_c != NULL) {
330 assert(predicate_x == NULL, "only one predicate entry expected");
331 // Clone loop predicates to each path
332 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
333 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
334 }
335 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
336 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
337 if (predicate_x != NULL) {
338 assert(predicate_c == NULL, "only one predicate entry expected");
339 // Clone loop predicates to each path
340 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
341 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
342 }
343
344 // Merge the TRUE paths
345 Node *region_s = new RegionNode(3);
346 igvn->_worklist.push(region_s);
347 region_s->init_req(1, iff_c_t);
348 region_s->init_req(2, iff_x_t);
349 igvn->register_new_node_with_optimizer( region_s );
350
351 // Merge the FALSE paths
352 Node *region_f = new RegionNode(3);
353 igvn->_worklist.push(region_f);
354 region_f->init_req(1, iff_c_f);
355 region_f->init_req(2, iff_x_f);
356 igvn->register_new_node_with_optimizer( region_f );
357
358 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
359 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
360 cmp->set_req(2,NULL);
361 // Check for all uses of the Phi and give them a new home.
362 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
363 Node *phi_s = NULL; // do not construct unless needed
364 Node *phi_f = NULL; // do not construct unless needed
365 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
366 Node* v = phi->last_out(i2);// User of the phi
367 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
368 uint vop = v->Opcode();
369 Node *proj = NULL;
370 if( vop == Op_Phi ) { // Remote merge point
371 Node *r = v->in(0);
372 for (uint i3 = 1; i3 < r->req(); i3++)
373 if (r->in(i3) && r->in(i3)->in(0) == iff) {
374 proj = r->in(i3);
375 break;
376 }
377 } else if( v->is_ConstraintCast() ) {
378 proj = v->in(0); // Controlling projection
379 } else {
380 assert( 0, "do not know how to handle this guy" );
381 }
382
383 Node *proj_path_data, *proj_path_ctrl;
384 if( proj->Opcode() == Op_IfTrue ) {
385 if( phi_s == NULL ) {
386 // Only construct phi_s if needed, otherwise provides
387 // interfering use.
388 phi_s = PhiNode::make_blank(region_s,phi);
389 phi_s->init_req( 1, phi_c );
390 phi_s->init_req( 2, phi_x );
391 hook->add_req(phi_s);
392 phi_s = phase->transform(phi_s);
393 }
394 proj_path_data = phi_s;
395 proj_path_ctrl = region_s;
396 } else {
397 if( phi_f == NULL ) {
398 // Only construct phi_f if needed, otherwise provides
399 // interfering use.
400 phi_f = PhiNode::make_blank(region_f,phi);
401 phi_f->init_req( 1, phi_c );
402 phi_f->init_req( 2, phi_x );
403 hook->add_req(phi_f);
404 phi_f = phase->transform(phi_f);
405 }
406 proj_path_data = phi_f;
407 proj_path_ctrl = region_f;
408 }
409
410 // Fixup 'v' for for the split
411 if( vop == Op_Phi ) { // Remote merge point
412 uint i;
413 for( i = 1; i < v->req(); i++ )
414 if( v->in(i) == phi )
415 break;
416 v->set_req(i, proj_path_data );
417 } else if( v->is_ConstraintCast() ) {
418 v->set_req(0, proj_path_ctrl );
419 v->set_req(1, proj_path_data );
420 } else
421 ShouldNotReachHere();
422 }
423
424 // Now replace the original iff's True/False with region_s/region_t.
425 // This makes the original iff go dead.
426 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
427 Node* p = iff->last_out(i3);
428 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
429 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
430 // Replace p with u
431 igvn->add_users_to_worklist(p);
432 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
433 Node* x = p->last_out(l);
434 igvn->hash_delete(x);
435 uint uses_found = 0;
436 for( uint j = 0; j < x->req(); j++ ) {
437 if( x->in(j) == p ) {
438 x->set_req(j, u);
439 uses_found++;
440 }
441 }
442 l -= uses_found; // we deleted 1 or more copies of this edge
443 }
444 igvn->remove_dead_node(p);
445 }
446
447 // Force the original merge dead
448 igvn->hash_delete(r);
449 // First, remove region's dead users.
450 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
451 Node* u = r->last_out(l);
452 if( u == r ) {
453 r->set_req(0, NULL);
454 } else {
455 assert(u->outcnt() == 0, "only dead users");
456 igvn->remove_dead_node(u);
457 }
458 l -= 1;
459 }
460 igvn->remove_dead_node(r);
461
462 // Now remove the bogus extra edges used to keep things alive
463 igvn->remove_dead_node( hook );
464
465 // Must return either the original node (now dead) or a new node
466 // (Do not return a top here, since that would break the uniqueness of top.)
467 return new ConINode(TypeInt::ZERO);
468 }
469
470 // if this IfNode follows a range check pattern return the projection
471 // for the failed path
472 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
473 Node* b = in(1);
474 if (b == NULL || !b->is_Bool()) return NULL;
475 BoolNode* bn = b->as_Bool();
476 Node* cmp = bn->in(1);
477 if (cmp == NULL) return NULL;
478 if (cmp->Opcode() != Op_CmpU) return NULL;
479
480 l = cmp->in(1);
481 r = cmp->in(2);
482 flip_test = 1;
483 if (bn->_test._test == BoolTest::le) {
484 l = cmp->in(2);
485 r = cmp->in(1);
486 flip_test = 2;
487 } else if (bn->_test._test != BoolTest::lt) {
488 return NULL;
489 }
490 if (l->is_top()) return NULL; // Top input means dead test
491 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return NULL;
492
493 // We have recognized one of these forms:
494 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
495 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
496
497 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
498 return iftrap;
499 }
500
501
502 //------------------------------is_range_check---------------------------------
503 // Return 0 if not a range check. Return 1 if a range check and set index and
504 // offset. Return 2 if we had to negate the test. Index is NULL if the check
505 // is versus a constant.
506 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
507 int flip_test = 0;
508 Node* l = NULL;
509 Node* r = NULL;
510 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
511
512 if (iftrap == NULL) {
513 return 0;
514 }
515
516 // Make sure it's a real range check by requiring an uncommon trap
517 // along the OOB path. Otherwise, it's possible that the user wrote
518 // something which optimized to look like a range check but behaves
519 // in some other way.
520 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
521 return 0;
522 }
523
524 // Look for index+offset form
525 Node* ind = l;
526 jint off = 0;
527 if (l->is_top()) {
528 return 0;
529 } else if (l->Opcode() == Op_AddI) {
530 if ((off = l->in(1)->find_int_con(0)) != 0) {
531 ind = l->in(2)->uncast();
532 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
533 ind = l->in(1)->uncast();
534 }
535 } else if ((off = l->find_int_con(-1)) >= 0) {
536 // constant offset with no variable index
537 ind = NULL;
538 } else {
539 // variable index with no constant offset (or dead negative index)
540 off = 0;
541 }
542
543 // Return all the values:
544 index = ind;
545 offset = off;
546 range = r;
547 return flip_test;
548 }
549
550 //------------------------------adjust_check-----------------------------------
551 // Adjust (widen) a prior range check
552 static void adjust_check(Node* proj, Node* range, Node* index,
553 int flip, jint off_lo, PhaseIterGVN* igvn) {
554 PhaseGVN *gvn = igvn;
555 // Break apart the old check
556 Node *iff = proj->in(0);
557 Node *bol = iff->in(1);
558 if( bol->is_top() ) return; // In case a partially dead range check appears
559 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
560 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
561 if( !bol->is_Bool() ) return;
562
563 Node *cmp = bol->in(1);
564 // Compute a new check
565 Node *new_add = gvn->intcon(off_lo);
566 if( index ) {
567 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
568 }
569 Node *new_cmp = (flip == 1)
570 ? new CmpUNode( new_add, range )
571 : new CmpUNode( range, new_add );
572 new_cmp = gvn->transform(new_cmp);
573 // See if no need to adjust the existing check
574 if( new_cmp == cmp ) return;
575 // Else, adjust existing check
576 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
577 igvn->rehash_node_delayed( iff );
578 iff->set_req_X( 1, new_bol, igvn );
579 }
580
581 //------------------------------up_one_dom-------------------------------------
582 // Walk up the dominator tree one step. Return NULL at root or true
583 // complex merges. Skips through small diamonds.
584 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
585 Node *dom = curr->in(0);
586 if( !dom ) // Found a Region degraded to a copy?
587 return curr->nonnull_req(); // Skip thru it
588
589 if( curr != dom ) // Normal walk up one step?
590 return dom;
591
592 // Use linear_only if we are still parsing, since we cannot
593 // trust the regions to be fully filled in.
594 if (linear_only)
595 return NULL;
596
597 if( dom->is_Root() )
598 return NULL;
599
600 // Else hit a Region. Check for a loop header
601 if( dom->is_Loop() )
602 return dom->in(1); // Skip up thru loops
603
604 // Check for small diamonds
605 Node *din1, *din2, *din3, *din4;
606 if( dom->req() == 3 && // 2-path merge point
607 (din1 = dom ->in(1)) && // Left path exists
608 (din2 = dom ->in(2)) && // Right path exists
609 (din3 = din1->in(0)) && // Left path up one
610 (din4 = din2->in(0)) ) { // Right path up one
611 if( din3->is_Call() && // Handle a slow-path call on either arm
612 (din3 = din3->in(0)) )
613 din3 = din3->in(0);
614 if( din4->is_Call() && // Handle a slow-path call on either arm
615 (din4 = din4->in(0)) )
616 din4 = din4->in(0);
617 if( din3 == din4 && din3->is_If() )
618 return din3; // Skip around diamonds
619 }
620
621 // Give up the search at true merges
622 return NULL; // Dead loop? Or hit root?
623 }
624
625
626 //------------------------------filtered_int_type--------------------------------
627 // Return a possibly more restrictive type for val based on condition control flow for an if
628 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
629 assert(if_proj &&
630 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
631 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
632 IfNode* iff = if_proj->in(0)->as_If();
633 if (iff->in(1) && iff->in(1)->is_Bool()) {
634 BoolNode* bol = iff->in(1)->as_Bool();
635 if (bol->in(1) && bol->in(1)->is_Cmp()) {
636 const CmpNode* cmp = bol->in(1)->as_Cmp();
637 if (cmp->in(1) == val) {
638 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
639 if (cmp2_t != NULL) {
640 jint lo = cmp2_t->_lo;
641 jint hi = cmp2_t->_hi;
642 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
643 switch (msk) {
644 case BoolTest::ne:
645 // Can't refine type
646 return NULL;
647 case BoolTest::eq:
648 return cmp2_t;
649 case BoolTest::lt:
650 lo = TypeInt::INT->_lo;
651 if (hi - 1 < hi) {
652 hi = hi - 1;
653 }
654 break;
655 case BoolTest::le:
656 lo = TypeInt::INT->_lo;
657 break;
658 case BoolTest::gt:
659 if (lo + 1 > lo) {
660 lo = lo + 1;
661 }
662 hi = TypeInt::INT->_hi;
663 break;
664 case BoolTest::ge:
665 // lo unchanged
666 hi = TypeInt::INT->_hi;
667 break;
668 }
669 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
670 return rtn_t;
671 }
672 }
673 }
674 }
675 }
676 return NULL;
677 }
678
679 //------------------------------fold_compares----------------------------
680 // See if a pair of CmpIs can be converted into a CmpU. In some cases
681 // the direction of this if is determined by the preceding if so it
682 // can be eliminate entirely.
683 //
684 // Given an if testing (CmpI n v) check for an immediately control
685 // dependent if that is testing (CmpI n v2) and has one projection
686 // leading to this if and the other projection leading to a region
687 // that merges one of this ifs control projections.
688 //
689 // If
690 // / |
691 // / |
692 // / |
693 // If |
694 // /\ |
695 // / \ |
696 // / \ |
697 // / Region
698 //
699 // Or given an if testing (CmpI n v) check for a dominating if that is
700 // testing (CmpI n v2), both having one projection leading to an
701 // uncommon trap. Allow Another independent guard in between to cover
702 // an explicit range check:
703 // if (index < 0 || index >= array.length) {
704 // which may need a null check to guard the LoadRange
705 //
706 // If
707 // / \
708 // / \
709 // / \
710 // If unc
711 // /\
712 // / \
713 // / \
714 // / unc
715 //
716
717 // Is the comparison for this If suitable for folding?
718 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
719 return in(1) != NULL &&
720 in(1)->is_Bool() &&
721 in(1)->in(1) != NULL &&
722 in(1)->in(1)->Opcode() == Op_CmpI &&
723 in(1)->in(1)->in(2) != NULL &&
724 in(1)->in(1)->in(2) != igvn->C->top() &&
725 (in(1)->as_Bool()->_test.is_less() ||
726 in(1)->as_Bool()->_test.is_greater());
727 }
728
729 // Is a dominating control suitable for folding with this if?
730 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
731 return ctrl != NULL &&
732 ctrl->is_Proj() &&
733 ctrl->in(0) != NULL &&
734 ctrl->in(0)->Opcode() == Op_If &&
735 ctrl->in(0)->outcnt() == 2 &&
736 ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
737 // Must compare same value
738 ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
739 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
740 }
741
742 // Do this If and the dominating If share a region?
743 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
744 ProjNode* otherproj = proj->other_if_proj();
745 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
746 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
747 success = NULL;
748 fail = NULL;
749
750 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
751 for (int i = 0; i < 2; i++) {
752 ProjNode* proj = proj_out(i);
753 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
754 success = proj;
755 } else if (fail == NULL) {
756 fail = proj;
757 } else {
758 success = fail = NULL;
759 }
760 }
761 }
762 return success != NULL && fail != NULL;
763 }
764
765 // Return projection that leads to an uncommon trap if any
766 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
767 for (int i = 0; i < 2; i++) {
768 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
769 if (call != NULL) {
770 return proj_out(i);
771 }
772 }
773 return NULL;
774 }
775
776 // Do this If and the dominating If both branch out to an uncommon trap
777 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
778 ProjNode* otherproj = proj->other_if_proj();
779 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
780
781 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
782 // We need to re-execute the folded Ifs after deoptimization from the merged traps
783 if (!dom_unc->jvms()->should_reexecute()) {
784 return false;
785 }
786
787 CallStaticJavaNode* unc = NULL;
788 ProjNode* unc_proj = uncommon_trap_proj(unc);
789 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
790 if (dom_unc == unc) {
791 // Allow the uncommon trap to be shared through a region
792 RegionNode* r = unc->in(0)->as_Region();
793 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
794 return false;
795 }
796 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
797 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
798 return false;
799 }
800
801 // Different methods and methods containing jsrs are not supported.
802 ciMethod* method = unc->jvms()->method();
803 ciMethod* dom_method = dom_unc->jvms()->method();
804 if (method != dom_method || method->has_jsrs()) {
805 return false;
806 }
807 // Check that both traps are in the same activation of the method (instead
808 // of two activations being inlined through different call sites) by verifying
809 // that the call stacks are equal for both JVMStates.
810 JVMState* dom_caller = dom_unc->jvms()->caller();
811 JVMState* caller = unc->jvms()->caller();
812 if ((dom_caller == NULL) != (caller == NULL)) {
813 // The current method must either be inlined into both dom_caller and
814 // caller or must not be inlined at all (top method). Bail out otherwise.
815 return false;
816 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
817 return false;
818 }
819 // Check that the bci of the dominating uncommon trap dominates the bci
820 // of the dominated uncommon trap. Otherwise we may not re-execute
821 // the dominated check after deoptimization from the merged uncommon trap.
822 ciTypeFlow* flow = dom_method->get_flow_analysis();
823 int bci = unc->jvms()->bci();
824 int dom_bci = dom_unc->jvms()->bci();
825 if (!flow->is_dominated_by(bci, dom_bci)) {
826 return false;
827 }
828
829 // See merge_uncommon_traps: the reason of the uncommon trap
830 // will be changed and the state of the dominating If will be
831 // used. Checked that we didn't apply this transformation in a
832 // previous compilation and it didn't cause too many traps
833 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
834 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
835 success = unc_proj;
836 fail = unc_proj->other_if_proj();
837 return true;
838 }
839 }
840 }
841 return false;
842 }
843
844 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
845 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
846 Node* this_cmp = in(1)->in(1);
847 BoolNode* this_bool = in(1)->as_Bool();
848 IfNode* dom_iff = proj->in(0)->as_If();
849 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
850 Node* lo = dom_iff->in(1)->in(1)->in(2);
851 Node* hi = this_cmp->in(2);
852 Node* n = this_cmp->in(1);
853 ProjNode* otherproj = proj->other_if_proj();
854
855 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
856 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
857
858 BoolTest::mask lo_test = dom_bool->_test._test;
859 BoolTest::mask hi_test = this_bool->_test._test;
860 BoolTest::mask cond = hi_test;
861
862 // convert:
863 //
864 // dom_bool = x {<,<=,>,>=} a
865 // / \
866 // proj = {True,False} / \ otherproj = {False,True}
867 // /
868 // this_bool = x {<,<=} b
869 // / \
870 // fail = {True,False} / \ success = {False,True}
871 // /
872 //
873 // (Second test guaranteed canonicalized, first one may not have
874 // been canonicalized yet)
875 //
876 // into:
877 //
878 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
879 // / \
880 // fail / \ success
881 // /
882 //
883
884 // Figure out which of the two tests sets the upper bound and which
885 // sets the lower bound if any.
886 Node* adjusted_lim = NULL;
887 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
888 assert((dom_bool->_test.is_less() && !proj->_con) ||
889 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
890 // this test was canonicalized
891 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
892
893 // this_bool = <
894 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
895 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
896 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
897 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
898 // x in ]a, b[ on the fail (= True) projection, b > a:
899 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
900 // this_bool = <=
901 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
902 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
903 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
904 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
905 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
906 // x in ]a, b] on the fail (= True) projection b+1 > a:
907 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
908 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1
909
910 if (hi_test == BoolTest::lt) {
911 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
912 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
913 }
914 } else {
915 assert(hi_test == BoolTest::le, "bad test");
916 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
917 adjusted_lim = igvn->transform(new SubINode(hi, lo));
918 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
919 cond = BoolTest::lt;
920 } else {
921 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
922 adjusted_lim = igvn->transform(new SubINode(hi, lo));
923 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
924 cond = BoolTest::lt;
925 }
926 }
927 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
928
929 // this_bool = <
930 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
931 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
932 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
933 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
934 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
935 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
936 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
937 // this_bool = <=
938 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
939 // x in ]b, a[ on the fail (= False) projection, a > b:
940 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
941 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
942 // x in ]b, a] on the fail (= False) projection, a+1 > b:
943 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
944 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >u doesn't work because a = b is possible, then b-a-1 = -1
945
946 swap(lo, hi);
947 swap(lo_type, hi_type);
948 swap(lo_test, hi_test);
949
950 assert((dom_bool->_test.is_less() && proj->_con) ||
951 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
952 // this test was canonicalized
953 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
954
955 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
956
957 if (lo_test == BoolTest::lt) {
958 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
959 cond = BoolTest::ge;
960 } else {
961 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
962 adjusted_lim = igvn->transform(new SubINode(hi, lo));
963 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
964 cond = BoolTest::ge;
965 }
966 } else if (lo_test == BoolTest::le) {
967 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
968 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
969 cond = BoolTest::ge;
970 } else {
971 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
972 adjusted_lim = igvn->transform(new SubINode(hi, lo));
973 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
974 cond = BoolTest::ge;
975 }
976 }
977 } else {
978 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
979 if (failtype != NULL) {
980 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
981 if (type2 != NULL) {
982 failtype = failtype->join(type2)->is_int();
983 if (failtype->_lo > failtype->_hi) {
984 // previous if determines the result of this if so
985 // replace Bool with constant
986 igvn->_worklist.push(in(1));
987 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
988 return true;
989 }
990 }
991 }
992 lo = NULL;
993 hi = NULL;
994 }
995
996 if (lo && hi) {
997 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
998 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
999 if (adjusted_lim == NULL) {
1000 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1001 }
1002 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1003 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1004
1005 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1006 igvn->_worklist.push(in(1));
1007 igvn->replace_input_of(this, 1, newbool);
1008
1009 return true;
1010 }
1011 return false;
1012 }
1013
1014 // Merge the branches that trap for this If and the dominating If into
1015 // a single region that branches to the uncommon trap for the
1016 // dominating If
1017 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1018 Node* res = this;
1019 assert(success->in(0) == this, "bad projection");
1020
1021 ProjNode* otherproj = proj->other_if_proj();
1022
1023 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1024 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1025
1026 if (unc != dom_unc) {
1027 Node* r = new RegionNode(3);
1028
1029 r->set_req(1, otherproj);
1030 r->set_req(2, success);
1031 r = igvn->transform(r);
1032 assert(r->is_Region(), "can't go away");
1033
1034 // Make both If trap at the state of the first If: once the CmpI
1035 // nodes are merged, if we trap we don't know which of the CmpI
1036 // nodes would have caused the trap so we have to restart
1037 // execution at the first one
1038 igvn->replace_input_of(dom_unc, 0, r);
1039 igvn->replace_input_of(unc, 0, igvn->C->top());
1040 }
1041 int trap_request = dom_unc->uncommon_trap_request();
1042 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1043 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1044
1045 int flip_test = 0;
1046 Node* l = NULL;
1047 Node* r = NULL;
1048
1049 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1050 // If this looks like a range check, change the trap to
1051 // Reason_range_check so the compiler recognizes it as a range
1052 // check and applies the corresponding optimizations
1053 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1054
1055 improve_address_types(l, r, fail, igvn);
1056
1057 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1058 } else if (unc != dom_unc) {
1059 // If we trap we won't know what CmpI would have caused the trap
1060 // so use a special trap reason to mark this pair of CmpI nodes as
1061 // bad candidate for folding. On recompilation we won't fold them
1062 // and we may trap again but this time we'll know what branch
1063 // traps
1064 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1065 }
1066 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1067 return res;
1068 }
1069
1070 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1071 // of a rangecheck on index i, on 64 bit the compares may be followed
1072 // by memory accesses using i as index. In that case, the CmpU tells
1073 // us something about the values taken by i that can help the compiler
1074 // (see Compile::conv_I2X_index())
1075 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1076 #ifdef _LP64
1077 ResourceMark rm;
1078 Node_Stack stack(2);
1079
1080 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1081 const TypeInt* array_size = igvn->type(r)->is_int();
1082
1083 stack.push(l, 0);
1084
1085 while(stack.size() > 0) {
1086 Node* n = stack.node();
1087 uint start = stack.index();
1088
1089 uint i = start;
1090 for (; i < n->outcnt(); i++) {
1091 Node* use = n->raw_out(i);
1092 if (stack.size() == 1) {
1093 if (use->Opcode() == Op_ConvI2L) {
1094 const TypeLong* bounds = use->as_Type()->type()->is_long();
1095 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1096 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1097 stack.set_index(i+1);
1098 stack.push(use, 0);
1099 break;
1100 }
1101 }
1102 } else if (use->is_Mem()) {
1103 Node* ctrl = use->in(0);
1104 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1105 ctrl = up_one_dom(ctrl);
1106 }
1107 if (ctrl == fail) {
1108 Node* init_n = stack.node_at(1);
1109 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1110 // Create a new narrow ConvI2L node that is dependent on the range check
1111 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1112
1113 // The type of the ConvI2L may be widen and so the new
1114 // ConvI2L may not be better than an existing ConvI2L
1115 if (new_n != init_n) {
1116 for (uint j = 2; j < stack.size(); j++) {
1117 Node* n = stack.node_at(j);
1118 Node* clone = n->clone();
1119 int rep = clone->replace_edge(init_n, new_n);
1120 assert(rep > 0, "can't find expected node?");
1121 clone = igvn->transform(clone);
1122 init_n = n;
1123 new_n = clone;
1124 }
1125 igvn->hash_delete(use);
1126 int rep = use->replace_edge(init_n, new_n);
1127 assert(rep > 0, "can't find expected node?");
1128 igvn->transform(use);
1129 if (init_n->outcnt() == 0) {
1130 igvn->_worklist.push(init_n);
1131 }
1132 }
1133 }
1134 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1135 igvn->type(use)->isa_ptr())) {
1136 stack.set_index(i+1);
1137 stack.push(use, 0);
1138 break;
1139 }
1140 }
1141 if (i == n->outcnt()) {
1142 stack.pop();
1143 }
1144 }
1145 #endif
1146 }
1147
1148 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1149 if (in(1) != NULL &&
1150 in(1)->in(1) != NULL &&
1151 in(1)->in(1)->in(2) != NULL) {
1152 Node* other = in(1)->in(1)->in(2);
1153 if (other->Opcode() == Op_LoadRange &&
1154 ((other->in(0) != NULL && other->in(0) == proj) ||
1155 (other->in(0) == NULL &&
1156 other->in(2) != NULL &&
1157 other->in(2)->is_AddP() &&
1158 other->in(2)->in(1) != NULL &&
1159 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1160 other->in(2)->in(1)->in(0) == proj))) {
1161 return true;
1162 }
1163 }
1164 return false;
1165 }
1166
1167 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1168 Node* other = in(1)->in(1)->in(2);
1169 if (other->in(MemNode::Address) != NULL &&
1170 proj->in(0)->in(1) != NULL &&
1171 proj->in(0)->in(1)->is_Bool() &&
1172 proj->in(0)->in(1)->in(1) != NULL &&
1173 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1174 proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1175 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1176 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1177 return true;
1178 }
1179 return false;
1180 }
1181
1182 // Check that the If that is in between the 2 integer comparisons has
1183 // no side effect
1184 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1185 if (proj != NULL &&
1186 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1187 proj->outcnt() <= 2) {
1188 if (proj->outcnt() == 1 ||
1189 // Allow simple null check from LoadRange
1190 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1191 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1192 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1193
1194 // reroute_side_effect_free_unc changes the state of this
1195 // uncommon trap to restart execution at the previous
1196 // CmpI. Check that this change in a previous compilation didn't
1197 // cause too many traps.
1198 int trap_request = unc->uncommon_trap_request();
1199 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1200
1201 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1202 return false;
1203 }
1204
1205 return true;
1206 }
1207 }
1208 return false;
1209 }
1210
1211 // Make the If between the 2 integer comparisons trap at the state of
1212 // the first If: the last CmpI is the one replaced by a CmpU and the
1213 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1214 // won't be guarded by the first CmpI anymore. It can trap in cases
1215 // where the first CmpI would have prevented it from executing: on a
1216 // trap, we need to restart execution at the state of the first CmpI
1217 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1218 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1219 ProjNode* otherproj = proj->other_if_proj();
1220 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1221 Node* call_proj = dom_unc->unique_ctrl_out();
1222 Node* halt = call_proj->unique_ctrl_out();
1223
1224 Node* new_unc = dom_unc->clone();
1225 call_proj = call_proj->clone();
1226 halt = halt->clone();
1227 Node* c = otherproj->clone();
1228
1229 c = igvn->transform(c);
1230 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1231 new_unc->set_req(0, c);
1232 new_unc = igvn->transform(new_unc);
1233 call_proj->set_req(0, new_unc);
1234 call_proj = igvn->transform(call_proj);
1235 halt->set_req(0, call_proj);
1236 halt = igvn->transform(halt);
1237
1238 igvn->replace_node(otherproj, igvn->C->top());
1239 igvn->C->root()->add_req(halt);
1240 }
1241
1242 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1243 if (Opcode() != Op_If) return NULL;
1244
1245 if (cmpi_folds(igvn)) {
1246 Node* ctrl = in(0);
1247 if (is_ctrl_folds(ctrl, igvn) &&
1248 ctrl->outcnt() == 1) {
1249 // A integer comparison immediately dominated by another integer
1250 // comparison
1251 ProjNode* success = NULL;
1252 ProjNode* fail = NULL;
1253 ProjNode* dom_cmp = ctrl->as_Proj();
1254 if (has_shared_region(dom_cmp, success, fail) &&
1255 // Next call modifies graph so must be last
1256 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1257 return this;
1258 }
1259 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1260 // Next call modifies graph so must be last
1261 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1262 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1263 }
1264 return NULL;
1265 } else if (ctrl->in(0) != NULL &&
1266 ctrl->in(0)->in(0) != NULL) {
1267 ProjNode* success = NULL;
1268 ProjNode* fail = NULL;
1269 Node* dom = ctrl->in(0)->in(0);
1270 ProjNode* dom_cmp = dom->isa_Proj();
1271 ProjNode* other_cmp = ctrl->isa_Proj();
1272
1273 // Check if it's an integer comparison dominated by another
1274 // integer comparison with another test in between
1275 if (is_ctrl_folds(dom, igvn) &&
1276 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1277 is_side_effect_free_test(other_cmp, igvn) &&
1278 // Next call modifies graph so must be last
1279 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1280 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1281 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1282 }
1283 }
1284 }
1285 return NULL;
1286 }
1287
1288 //------------------------------remove_useless_bool----------------------------
1289 // Check for people making a useless boolean: things like
1290 // if( (x < y ? true : false) ) { ... }
1291 // Replace with if( x < y ) { ... }
1292 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1293 Node *i1 = iff->in(1);
1294 if( !i1->is_Bool() ) return NULL;
1295 BoolNode *bol = i1->as_Bool();
1296
1297 Node *cmp = bol->in(1);
1298 if( cmp->Opcode() != Op_CmpI ) return NULL;
1299
1300 // Must be comparing against a bool
1301 const Type *cmp2_t = phase->type( cmp->in(2) );
1302 if( cmp2_t != TypeInt::ZERO &&
1303 cmp2_t != TypeInt::ONE )
1304 return NULL;
1305
1306 // Find a prior merge point merging the boolean
1307 i1 = cmp->in(1);
1308 if( !i1->is_Phi() ) return NULL;
1309 PhiNode *phi = i1->as_Phi();
1310 if( phase->type( phi ) != TypeInt::BOOL )
1311 return NULL;
1312
1313 // Check for diamond pattern
1314 int true_path = phi->is_diamond_phi();
1315 if( true_path == 0 ) return NULL;
1316
1317 // Make sure that iff and the control of the phi are different. This
1318 // should really only happen for dead control flow since it requires
1319 // an illegal cycle.
1320 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1321
1322 // phi->region->if_proj->ifnode->bool->cmp
1323 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1324
1325 // Now get the 'sense' of the test correct so we can plug in
1326 // either iff2->in(1) or its complement.
1327 int flip = 0;
1328 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1329 else if( bol->_test._test != BoolTest::eq ) return NULL;
1330 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1331
1332 const Type *phi1_t = phase->type( phi->in(1) );
1333 const Type *phi2_t = phase->type( phi->in(2) );
1334 // Check for Phi(0,1) and flip
1335 if( phi1_t == TypeInt::ZERO ) {
1336 if( phi2_t != TypeInt::ONE ) return NULL;
1337 flip = 1-flip;
1338 } else {
1339 // Check for Phi(1,0)
1340 if( phi1_t != TypeInt::ONE ) return NULL;
1341 if( phi2_t != TypeInt::ZERO ) return NULL;
1342 }
1343 if( true_path == 2 ) {
1344 flip = 1-flip;
1345 }
1346
1347 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1348 assert(new_bol != iff->in(1), "must make progress");
1349 iff->set_req(1, new_bol);
1350 // Intervening diamond probably goes dead
1351 phase->C->set_major_progress();
1352 return iff;
1353 }
1354
1355 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1356
1357 struct RangeCheck {
1358 Node* ctl;
1359 jint off;
1360 };
1361
1362 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1363 if (remove_dead_region(phase, can_reshape)) return this;
1364 // No Def-Use info?
1365 if (!can_reshape) return NULL;
1366
1367 // Don't bother trying to transform a dead if
1368 if (in(0)->is_top()) return NULL;
1369 // Don't bother trying to transform an if with a dead test
1370 if (in(1)->is_top()) return NULL;
1371 // Another variation of a dead test
1372 if (in(1)->is_Con()) return NULL;
1373 // Another variation of a dead if
1374 if (outcnt() < 2) return NULL;
1375
1376 // Canonicalize the test.
1377 Node* idt_if = idealize_test(phase, this);
1378 if (idt_if != NULL) return idt_if;
1379
1380 // Try to split the IF
1381 PhaseIterGVN *igvn = phase->is_IterGVN();
1382 Node *s = split_if(this, igvn);
1383 if (s != NULL) return s;
1384
1385 return NodeSentinel;
1386 }
1387
1388 //------------------------------Ideal------------------------------------------
1389 // Return a node which is more "ideal" than the current node. Strip out
1390 // control copies
1391 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1392 Node* res = Ideal_common(phase, can_reshape);
1393 if (res != NodeSentinel) {
1394 return res;
1395 }
1396
1397 // Check for people making a useless boolean: things like
1398 // if( (x < y ? true : false) ) { ... }
1399 // Replace with if( x < y ) { ... }
1400 Node *bol2 = remove_useless_bool(this, phase);
1401 if( bol2 ) return bol2;
1402
1403 if (in(0) == NULL) return NULL; // Dead loop?
1404
1405 PhaseIterGVN *igvn = phase->is_IterGVN();
1406 Node* result = fold_compares(igvn);
1407 if (result != NULL) {
1408 return result;
1409 }
1410
1411 // Scan for an equivalent test
1412 Node *cmp;
1413 int dist = 0; // Cutoff limit for search
1414 int op = Opcode();
1415 if( op == Op_If &&
1416 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1417 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1418 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1419 dist = 64; // Limit for null-pointer scans
1420 } else {
1421 dist = 4; // Do not bother for random pointer tests
1422 }
1423 } else {
1424 dist = 4; // Limit for random junky scans
1425 }
1426
1427 Node* prev_dom = search_identical(dist);
1428
1429 if (prev_dom == NULL) {
1430 return NULL;
1431 }
1432
1433 // Replace dominated IfNode
1434 return dominated_by(prev_dom, igvn);
1435 }
1436
1437 //------------------------------dominated_by-----------------------------------
1438 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1439 #ifndef PRODUCT
1440 if (TraceIterativeGVN) {
1441 tty->print(" Removing IfNode: "); this->dump();
1442 }
1443 if (VerifyOpto && !igvn->allow_progress()) {
1444 // Found an equivalent dominating test,
1445 // we can not guarantee reaching a fix-point for these during iterativeGVN
1446 // since intervening nodes may not change.
1447 return NULL;
1448 }
1449 #endif
1450
1451 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1452 Node *idom = in(0);
1453 // Need opcode to decide which way 'this' test goes
1454 int prev_op = prev_dom->Opcode();
1455 Node *top = igvn->C->top(); // Shortcut to top
1456
1457 // Loop predicates may have depending checks which should not
1458 // be skipped. For example, range check predicate has two checks
1459 // for lower and upper bounds.
1460 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1461 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1462 prev_dom = idom;
1463
1464 // Now walk the current IfNode's projections.
1465 // Loop ends when 'this' has no more uses.
1466 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1467 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1468 igvn->add_users_to_worklist(ifp);
1469 // Check which projection it is and set target.
1470 // Data-target is either the dominating projection of the same type
1471 // or TOP if the dominating projection is of opposite type.
1472 // Data-target will be used as the new control edge for the non-CFG
1473 // nodes like Casts and Loads.
1474 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1475 // Control-target is just the If's immediate dominator or TOP.
1476 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1477
1478 // For each child of an IfTrue/IfFalse projection, reroute.
1479 // Loop ends when projection has no more uses.
1480 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1481 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1482 if( !s->depends_only_on_test() ) {
1483 // Find the control input matching this def-use edge.
1484 // For Regions it may not be in slot 0.
1485 uint l;
1486 for( l = 0; s->in(l) != ifp; l++ ) { }
1487 igvn->replace_input_of(s, l, ctrl_target);
1488 } else { // Else, for control producers,
1489 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1490 }
1491 } // End for each child of a projection
1492
1493 igvn->remove_dead_node(ifp);
1494 } // End for each IfTrue/IfFalse child of If
1495
1496 // Kill the IfNode
1497 igvn->remove_dead_node(this);
1498
1499 // Must return either the original node (now dead) or a new node
1500 // (Do not return a top here, since that would break the uniqueness of top.)
1501 return new ConINode(TypeInt::ZERO);
1502 }
1503
1504 Node* IfNode::search_identical(int dist) {
1505 // Setup to scan up the CFG looking for a dominating test
1506 Node* dom = in(0);
1507 Node* prev_dom = this;
1508 int op = Opcode();
1509 // Search up the dominator tree for an If with an identical test
1510 while (dom->Opcode() != op || // Not same opcode?
1511 dom->in(1) != in(1) || // Not same input 1?
1512 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1513 prev_dom->in(0) != dom) { // One path of test does not dominate?
1514 if (dist < 0) return NULL;
1515
1516 dist--;
1517 prev_dom = dom;
1518 dom = up_one_dom(dom);
1519 if (!dom) return NULL;
1520 }
1521
1522 // Check that we did not follow a loop back to ourselves
1523 if (this == dom) {
1524 return NULL;
1525 }
1526
1527 #ifndef PRODUCT
1528 if (dist > 2) { // Add to count of NULL checks elided
1529 explicit_null_checks_elided++;
1530 }
1531 #endif
1532
1533 return prev_dom;
1534 }
1535
1536 //------------------------------Identity---------------------------------------
1537 // If the test is constant & we match, then we are the input Control
1538 Node* IfProjNode::Identity(PhaseGVN* phase) {
1539 // Can only optimize if cannot go the other way
1540 const TypeTuple *t = phase->type(in(0))->is_tuple();
1541 if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1542 // During parsing (GVN) we don't remove dead code aggressively.
1543 // Cut off dead branch and let PhaseRemoveUseless take care of it.
1544 (!phase->is_IterGVN() ||
1545 // During IGVN, first wait for the dead branch to be killed.
1546 // Otherwise, the IfNode's control will have two control uses (the IfNode
1547 // that doesn't go away because it still has uses and this branch of the
1548 // If) which breaks other optimizations. Node::has_special_unique_user()
1549 // will cause this node to be reprocessed once the dead branch is killed.
1550 in(0)->outcnt() == 1))) {
1551 // IfNode control
1552 return in(0)->in(0);
1553 }
1554 // no progress
1555 return this;
1556 }
1557
1558 #ifndef PRODUCT
1559 //-------------------------------related---------------------------------------
1560 // An IfProjNode's related node set consists of its input (an IfNode) including
1561 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1562 // the restrictions for IfNode apply (see IfNode::rel).
1563 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1564 Node* ifNode = this->in(0);
1565 in_rel->append(ifNode);
1566 if (compact) {
1567 ifNode->collect_nodes(in_rel, 3, false, true);
1568 } else {
1569 ifNode->collect_nodes_in_all_data(in_rel, false);
1570 }
1571 this->collect_nodes(out_rel, -1, false, false);
1572 }
1573
1574 //------------------------------dump_spec--------------------------------------
1575 void IfNode::dump_spec(outputStream *st) const {
1576 st->print("P=%f, C=%f",_prob,_fcnt);
1577 }
1578
1579 //-------------------------------related---------------------------------------
1580 // For an IfNode, the set of related output nodes is just the output nodes till
1581 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1582 // The related input nodes contain no control nodes, but all data nodes
1583 // pertaining to the condition. In compact mode, the input nodes are collected
1584 // up to a depth of 3.
1585 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1586 if (compact) {
1587 this->collect_nodes(in_rel, 3, false, true);
1588 } else {
1589 this->collect_nodes_in_all_data(in_rel, false);
1590 }
1591 this->collect_nodes(out_rel, -2, false, false);
1592 }
1593 #endif
1594
1595 //------------------------------idealize_test----------------------------------
1596 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1597 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1598 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1599 // needed.
1600 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1601 assert(iff->in(0) != NULL, "If must be live");
1602
1603 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1604 Node* old_if_f = iff->proj_out(false);
1605 Node* old_if_t = iff->proj_out(true);
1606
1607 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1608 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1609 // happens in count-down loops
1610 if (iff->is_CountedLoopEnd()) return NULL;
1611 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1612 BoolNode *b = iff->in(1)->as_Bool();
1613 BoolTest bt = b->_test;
1614 // Test already in good order?
1615 if( bt.is_canonical() )
1616 return NULL;
1617
1618 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1619 // cloning the IfNode.
1620 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1621 if( !new_b->is_Bool() ) return NULL;
1622 b = new_b->as_Bool();
1623
1624 PhaseIterGVN *igvn = phase->is_IterGVN();
1625 assert( igvn, "Test is not canonical in parser?" );
1626
1627 // The IF node never really changes, but it needs to be cloned
1628 iff = iff->clone()->as_If();
1629 iff->set_req(1, b);
1630 iff->_prob = 1.0-iff->_prob;
1631
1632 Node *prior = igvn->hash_find_insert(iff);
1633 if( prior ) {
1634 igvn->remove_dead_node(iff);
1635 iff = (IfNode*)prior;
1636 } else {
1637 // Cannot call transform on it just yet
1638 igvn->set_type_bottom(iff);
1639 }
1640 igvn->_worklist.push(iff);
1641
1642 // Now handle projections. Cloning not required.
1643 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1644 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1645
1646 igvn->register_new_node_with_optimizer(new_if_f);
1647 igvn->register_new_node_with_optimizer(new_if_t);
1648 // Flip test, so flip trailing control
1649 igvn->replace_node(old_if_f, new_if_t);
1650 igvn->replace_node(old_if_t, new_if_f);
1651
1652 // Progress
1653 return iff;
1654 }
1655
1656 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1657 Node* res = Ideal_common(phase, can_reshape);
1658 if (res != NodeSentinel) {
1659 return res;
1660 }
1661
1662 PhaseIterGVN *igvn = phase->is_IterGVN();
1663 // Setup to scan up the CFG looking for a dominating test
1664 Node* prev_dom = this;
1665
1666 // Check for range-check vs other kinds of tests
1667 Node* index1;
1668 Node* range1;
1669 jint offset1;
1670 int flip1 = is_range_check(range1, index1, offset1);
1671 if (flip1) {
1672 Node* dom = in(0);
1673 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1674 // so all checks we inspect post-dominate the top-most check we find.
1675 // If we are going to fail the current check and we reach the top check
1676 // then we are guaranteed to fail, so just start interpreting there.
1677 // We 'expand' the top 3 range checks to include all post-dominating
1678 // checks.
1679
1680 // The top 3 range checks seen
1681 const int NRC =3;
1682 RangeCheck prev_checks[NRC];
1683 int nb_checks = 0;
1684
1685 // Low and high offsets seen so far
1686 jint off_lo = offset1;
1687 jint off_hi = offset1;
1688
1689 bool found_immediate_dominator = false;
1690
1691 // Scan for the top checks and collect range of offsets
1692 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1693 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1694 prev_dom->in(0) == dom) { // One path of test does dominate?
1695 if (dom == this) return NULL; // dead loop
1696 // See if this is a range check
1697 Node* index2;
1698 Node* range2;
1699 jint offset2;
1700 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1701 // See if this is a _matching_ range check, checking against
1702 // the same array bounds.
1703 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1704 dom->outcnt() == 2) {
1705 if (nb_checks == 0 && dom->in(1) == in(1)) {
1706 // Found an immediately dominating test at the same offset.
1707 // This kind of back-to-back test can be eliminated locally,
1708 // and there is no need to search further for dominating tests.
1709 assert(offset2 == offset1, "Same test but different offsets");
1710 found_immediate_dominator = true;
1711 break;
1712 }
1713 // Gather expanded bounds
1714 off_lo = MIN2(off_lo,offset2);
1715 off_hi = MAX2(off_hi,offset2);
1716 // Record top NRC range checks
1717 prev_checks[nb_checks%NRC].ctl = prev_dom;
1718 prev_checks[nb_checks%NRC].off = offset2;
1719 nb_checks++;
1720 }
1721 }
1722 prev_dom = dom;
1723 dom = up_one_dom(dom);
1724 if (!dom) break;
1725 }
1726
1727 if (!found_immediate_dominator) {
1728 // Attempt to widen the dominating range check to cover some later
1729 // ones. Since range checks "fail" by uncommon-trapping to the
1730 // interpreter, widening a check can make us speculatively enter
1731 // the interpreter. If we see range-check deopt's, do not widen!
1732 if (!phase->C->allow_range_check_smearing()) return NULL;
1733
1734 // Didn't find prior covering check, so cannot remove anything.
1735 if (nb_checks == 0) {
1736 return NULL;
1737 }
1738 // Constant indices only need to check the upper bound.
1739 // Non-constant indices must check both low and high.
1740 int chk0 = (nb_checks - 1) % NRC;
1741 if (index1) {
1742 if (nb_checks == 1) {
1743 return NULL;
1744 } else {
1745 // If the top range check's constant is the min or max of
1746 // all constants we widen the next one to cover the whole
1747 // range of constants.
1748 RangeCheck rc0 = prev_checks[chk0];
1749 int chk1 = (nb_checks - 2) % NRC;
1750 RangeCheck rc1 = prev_checks[chk1];
1751 if (rc0.off == off_lo) {
1752 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1753 prev_dom = rc1.ctl;
1754 } else if (rc0.off == off_hi) {
1755 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1756 prev_dom = rc1.ctl;
1757 } else {
1758 // If the top test's constant is not the min or max of all
1759 // constants, we need 3 range checks. We must leave the
1760 // top test unchanged because widening it would allow the
1761 // accesses it protects to successfully read/write out of
1762 // bounds.
1763 if (nb_checks == 2) {
1764 return NULL;
1765 }
1766 int chk2 = (nb_checks - 3) % NRC;
1767 RangeCheck rc2 = prev_checks[chk2];
1768 // The top range check a+i covers interval: -a <= i < length-a
1769 // The second range check b+i covers interval: -b <= i < length-b
1770 if (rc1.off <= rc0.off) {
1771 // if b <= a, we change the second range check to:
1772 // -min_of_all_constants <= i < length-min_of_all_constants
1773 // Together top and second range checks now cover:
1774 // -min_of_all_constants <= i < length-a
1775 // which is more restrictive than -b <= i < length-b:
1776 // -b <= -min_of_all_constants <= i < length-a <= length-b
1777 // The third check is then changed to:
1778 // -max_of_all_constants <= i < length-max_of_all_constants
1779 // so 2nd and 3rd checks restrict allowed values of i to:
1780 // -min_of_all_constants <= i < length-max_of_all_constants
1781 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1782 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1783 } else {
1784 // if b > a, we change the second range check to:
1785 // -max_of_all_constants <= i < length-max_of_all_constants
1786 // Together top and second range checks now cover:
1787 // -a <= i < length-max_of_all_constants
1788 // which is more restrictive than -b <= i < length-b:
1789 // -b < -a <= i < length-max_of_all_constants <= length-b
1790 // The third check is then changed to:
1791 // -max_of_all_constants <= i < length-max_of_all_constants
1792 // so 2nd and 3rd checks restrict allowed values of i to:
1793 // -min_of_all_constants <= i < length-max_of_all_constants
1794 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1795 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1796 }
1797 prev_dom = rc2.ctl;
1798 }
1799 }
1800 } else {
1801 RangeCheck rc0 = prev_checks[chk0];
1802 // 'Widen' the offset of the 1st and only covering check
1803 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1804 // Test is now covered by prior checks, dominate it out
1805 prev_dom = rc0.ctl;
1806 }
1807 }
1808 } else {
1809 prev_dom = search_identical(4);
1810
1811 if (prev_dom == NULL) {
1812 return NULL;
1813 }
1814 }
1815
1816 // Replace dominated IfNode
1817 return dominated_by(prev_dom, igvn);
1818 }