1 /*
2 * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciTypeFlow.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/castnode.hpp"
30 #include "opto/cfgnode.hpp"
31 #include "opto/connode.hpp"
32 #include "opto/loopnode.hpp"
33 #include "opto/phaseX.hpp"
34 #include "opto/runtime.hpp"
35 #include "opto/rootnode.hpp"
36 #include "opto/subnode.hpp"
37
38 // Portions of code courtesy of Clifford Click
39
40 // Optimization - Graph Style
41
42
43 extern int explicit_null_checks_elided;
44
45 //=============================================================================
46 //------------------------------Value------------------------------------------
47 // Return a tuple for whichever arm of the IF is reachable
48 const Type* IfNode::Value(PhaseGVN* phase) const {
49 if( !in(0) ) return Type::TOP;
50 if( phase->type(in(0)) == Type::TOP )
51 return Type::TOP;
52 const Type *t = phase->type(in(1));
53 if( t == Type::TOP ) // data is undefined
54 return TypeTuple::IFNEITHER; // unreachable altogether
55 if( t == TypeInt::ZERO ) // zero, or false
56 return TypeTuple::IFFALSE; // only false branch is reachable
57 if( t == TypeInt::ONE ) // 1, or true
58 return TypeTuple::IFTRUE; // only true branch is reachable
59 assert( t == TypeInt::BOOL, "expected boolean type" );
60
61 return TypeTuple::IFBOTH; // No progress
62 }
63
64 const RegMask &IfNode::out_RegMask() const {
65 return RegMask::Empty;
66 }
67
68 //------------------------------split_if---------------------------------------
69 // Look for places where we merge constants, then test on the merged value.
70 // If the IF test will be constant folded on the path with the constant, we
71 // win by splitting the IF to before the merge point.
72 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
73 // I could be a lot more general here, but I'm trying to squeeze this
74 // in before the Christmas '98 break so I'm gonna be kinda restrictive
75 // on the patterns I accept. CNC
76
77 // Look for a compare of a constant and a merged value
78 Node *i1 = iff->in(1);
79 if( !i1->is_Bool() ) return NULL;
80 BoolNode *b = i1->as_Bool();
81 Node *cmp = b->in(1);
82 if( !cmp->is_Cmp() ) return NULL;
83 i1 = cmp->in(1);
84 if( i1 == NULL || !i1->is_Phi() ) return NULL;
85 PhiNode *phi = i1->as_Phi();
86 if( phi->is_copy() ) return NULL;
87 Node *con2 = cmp->in(2);
88 if( !con2->is_Con() ) return NULL;
89 // See that the merge point contains some constants
90 Node *con1=NULL;
91 uint i4;
92 for( i4 = 1; i4 < phi->req(); i4++ ) {
93 con1 = phi->in(i4);
94 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
95 if( con1->is_Con() ) break; // Found a constant
96 // Also allow null-vs-not-null checks
97 const TypePtr *tp = igvn->type(con1)->isa_ptr();
98 if( tp && tp->_ptr == TypePtr::NotNull )
99 break;
100 }
101 if( i4 >= phi->req() ) return NULL; // Found no constants
102
103 igvn->C->set_has_split_ifs(true); // Has chance for split-if
104
105 // Make sure that the compare can be constant folded away
106 Node *cmp2 = cmp->clone();
107 cmp2->set_req(1,con1);
108 cmp2->set_req(2,con2);
109 const Type *t = cmp2->Value(igvn);
110 // This compare is dead, so whack it!
111 igvn->remove_dead_node(cmp2);
112 if( !t->singleton() ) return NULL;
113
114 // No intervening control, like a simple Call
115 Node *r = iff->in(0);
116 if( !r->is_Region() ) return NULL;
117 if( phi->region() != r ) return NULL;
118 // No other users of the cmp/bool
119 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
120 //tty->print_cr("many users of cmp/bool");
121 return NULL;
122 }
123
124 // Make sure we can determine where all the uses of merged values go
125 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
126 Node* u = r->fast_out(j);
127 if( u == r ) continue;
128 if( u == iff ) continue;
129 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
130 if( !u->is_Phi() ) {
131 /*
132 if( u->is_Start() ) {
133 tty->print_cr("Region has inlined start use");
134 } else {
135 tty->print_cr("Region has odd use");
136 u->dump(2);
137 }*/
138 return NULL;
139 }
140 if( u != phi ) {
141 // CNC - do not allow any other merged value
142 //tty->print_cr("Merging another value");
143 //u->dump(2);
144 return NULL;
145 }
146 // Make sure we can account for all Phi uses
147 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
148 Node* v = u->fast_out(k); // User of the phi
149 // CNC - Allow only really simple patterns.
150 // In particular I disallow AddP of the Phi, a fairly common pattern
151 if (v == cmp) continue; // The compare is OK
152 if (v->is_ConstraintCast()) {
153 // If the cast is derived from data flow edges, it may not have a control edge.
154 // If so, it should be safe to split. But follow-up code can not deal with
155 // this (l. 359). So skip.
156 if (v->in(0) == NULL) {
157 return NULL;
158 }
159 if (v->in(0)->in(0) == iff) {
160 continue; // CastPP/II of the IfNode is OK
161 }
162 }
163 // Disabled following code because I cannot tell if exactly one
164 // path dominates without a real dominator check. CNC 9/9/1999
165 //uint vop = v->Opcode();
166 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
167 // Node *r = v->in(0); // Get controlling point
168 // if( !r ) return NULL; // Degraded to a copy
169 // // Find exactly one path in (either True or False doms, but not IFF)
170 // int cnt = 0;
171 // for( uint i = 1; i < r->req(); i++ )
172 // if( r->in(i) && r->in(i)->in(0) == iff )
173 // cnt++;
174 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
175 //}
176 if( !v->is_Call() ) {
177 /*
178 if( v->Opcode() == Op_AddP ) {
179 tty->print_cr("Phi has AddP use");
180 } else if( v->Opcode() == Op_CastPP ) {
181 tty->print_cr("Phi has CastPP use");
182 } else if( v->Opcode() == Op_CastII ) {
183 tty->print_cr("Phi has CastII use");
184 } else {
185 tty->print_cr("Phi has use I cant be bothered with");
186 }
187 */
188 }
189 return NULL;
190
191 /* CNC - Cut out all the fancy acceptance tests
192 // Can we clone this use when doing the transformation?
193 // If all uses are from Phis at this merge or constants, then YES.
194 if( !v->in(0) && v != cmp ) {
195 tty->print_cr("Phi has free-floating use");
196 v->dump(2);
197 return NULL;
198 }
199 for( uint l = 1; l < v->req(); l++ ) {
200 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
201 !v->in(l)->is_Con() ) {
202 tty->print_cr("Phi has use");
203 v->dump(2);
204 return NULL;
205 } // End of if Phi-use input is neither Phi nor Constant
206 } // End of for all inputs to Phi-use
207 */
208 } // End of for all uses of Phi
209 } // End of for all uses of Region
210
211 // Only do this if the IF node is in a sane state
212 if (iff->outcnt() != 2)
213 return NULL;
214
215 // Got a hit! Do the Mondo Hack!
216 //
217 //ABC a1c def ghi B 1 e h A C a c d f g i
218 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
219 // cmp - 2 cmp - 2 cmp - 2
220 // bool bool_c bool_x
221 // if if_c if_x
222 // T F T F T F
223 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
224 //
225 // Split the paths coming into the merge point into 2 separate groups of
226 // merges. On the left will be all the paths feeding constants into the
227 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
228 // will fold up into a constant; this will let the Cmp fold up as well as
229 // all the control flow. Below the original IF we have 2 control
230 // dependent regions, 's' and 't'. Now we will merge the two paths
231 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
232 // likely 2 or more) will promptly constant fold away.
233 PhaseGVN *phase = igvn;
234
235 // Make a region merging constants and a region merging the rest
236 uint req_c = 0;
237 Node* predicate_proj = NULL;
238 int nb_predicate_proj = 0;
239 for (uint ii = 1; ii < r->req(); ii++) {
240 if (phi->in(ii) == con1) {
241 req_c++;
242 }
243 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
244 if (proj != NULL) {
245 nb_predicate_proj++;
246 predicate_proj = proj;
247 }
248 }
249 if (nb_predicate_proj > 1) {
250 // Can happen in case of loop unswitching and when the loop is
251 // optimized out: it's not a loop anymore so we don't care about
252 // predicates.
253 assert(!r->is_Loop(), "this must not be a loop anymore");
254 predicate_proj = NULL;
255 }
256 Node* predicate_c = NULL;
257 Node* predicate_x = NULL;
258 bool counted_loop = r->is_CountedLoop();
259
260 Node *region_c = new RegionNode(req_c + 1);
261 Node *phi_c = con1;
262 uint len = r->req();
263 Node *region_x = new RegionNode(len - req_c);
264 Node *phi_x = PhiNode::make_blank(region_x, phi);
265 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
266 if (phi->in(i) == con1) {
267 region_c->init_req( i_c++, r ->in(i) );
268 if (r->in(i) == predicate_proj)
269 predicate_c = predicate_proj;
270 } else {
271 region_x->init_req( i_x, r ->in(i) );
272 phi_x ->init_req( i_x++, phi->in(i) );
273 if (r->in(i) == predicate_proj)
274 predicate_x = predicate_proj;
275 }
276 }
277 if (predicate_c != NULL && (req_c > 1)) {
278 assert(predicate_x == NULL, "only one predicate entry expected");
279 predicate_c = NULL; // Do not clone predicate below merge point
280 }
281 if (predicate_x != NULL && ((len - req_c) > 2)) {
282 assert(predicate_c == NULL, "only one predicate entry expected");
283 predicate_x = NULL; // Do not clone predicate below merge point
284 }
285
286 // Register the new RegionNodes but do not transform them. Cannot
287 // transform until the entire Region/Phi conglomerate has been hacked
288 // as a single huge transform.
289 igvn->register_new_node_with_optimizer( region_c );
290 igvn->register_new_node_with_optimizer( region_x );
291 // Prevent the untimely death of phi_x. Currently he has no uses. He is
292 // about to get one. If this only use goes away, then phi_x will look dead.
293 // However, he will be picking up some more uses down below.
294 Node *hook = new Node(4);
295 hook->init_req(0, phi_x);
296 hook->init_req(1, phi_c);
297 phi_x = phase->transform( phi_x );
298
299 // Make the compare
300 Node *cmp_c = phase->makecon(t);
301 Node *cmp_x = cmp->clone();
302 cmp_x->set_req(1,phi_x);
303 cmp_x->set_req(2,con2);
304 cmp_x = phase->transform(cmp_x);
305 // Make the bool
306 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
307 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
308 // Make the IfNode
309 IfNode* iff_c = iff->clone()->as_If();
310 iff_c->set_req(0, region_c);
311 iff_c->set_req(1, b_c);
312 igvn->set_type_bottom(iff_c);
313 igvn->_worklist.push(iff_c);
314 hook->init_req(2, iff_c);
315
316 IfNode* iff_x = iff->clone()->as_If();
317 iff_x->set_req(0, region_x);
318 iff_x->set_req(1, b_x);
319 igvn->set_type_bottom(iff_x);
320 igvn->_worklist.push(iff_x);
321 hook->init_req(3, iff_x);
322
323 // Make the true/false arms
324 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
325 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
326 if (predicate_c != NULL) {
327 assert(predicate_x == NULL, "only one predicate entry expected");
328 // Clone loop predicates to each path
329 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
330 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
331 }
332 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
333 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
334 if (predicate_x != NULL) {
335 assert(predicate_c == NULL, "only one predicate entry expected");
336 // Clone loop predicates to each path
337 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
338 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
339 }
340
341 // Merge the TRUE paths
342 Node *region_s = new RegionNode(3);
343 igvn->_worklist.push(region_s);
344 region_s->init_req(1, iff_c_t);
345 region_s->init_req(2, iff_x_t);
346 igvn->register_new_node_with_optimizer( region_s );
347
348 // Merge the FALSE paths
349 Node *region_f = new RegionNode(3);
350 igvn->_worklist.push(region_f);
351 region_f->init_req(1, iff_c_f);
352 region_f->init_req(2, iff_x_f);
353 igvn->register_new_node_with_optimizer( region_f );
354
355 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
356 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
357 cmp->set_req(2,NULL);
358 // Check for all uses of the Phi and give them a new home.
359 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
360 Node *phi_s = NULL; // do not construct unless needed
361 Node *phi_f = NULL; // do not construct unless needed
362 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
363 Node* v = phi->last_out(i2);// User of the phi
364 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
365 uint vop = v->Opcode();
366 Node *proj = NULL;
367 if( vop == Op_Phi ) { // Remote merge point
368 Node *r = v->in(0);
369 for (uint i3 = 1; i3 < r->req(); i3++)
370 if (r->in(i3) && r->in(i3)->in(0) == iff) {
371 proj = r->in(i3);
372 break;
373 }
374 } else if( v->is_ConstraintCast() ) {
375 proj = v->in(0); // Controlling projection
376 } else {
377 assert( 0, "do not know how to handle this guy" );
378 }
379
380 Node *proj_path_data, *proj_path_ctrl;
381 if( proj->Opcode() == Op_IfTrue ) {
382 if( phi_s == NULL ) {
383 // Only construct phi_s if needed, otherwise provides
384 // interfering use.
385 phi_s = PhiNode::make_blank(region_s,phi);
386 phi_s->init_req( 1, phi_c );
387 phi_s->init_req( 2, phi_x );
388 hook->add_req(phi_s);
389 phi_s = phase->transform(phi_s);
390 }
391 proj_path_data = phi_s;
392 proj_path_ctrl = region_s;
393 } else {
394 if( phi_f == NULL ) {
395 // Only construct phi_f if needed, otherwise provides
396 // interfering use.
397 phi_f = PhiNode::make_blank(region_f,phi);
398 phi_f->init_req( 1, phi_c );
399 phi_f->init_req( 2, phi_x );
400 hook->add_req(phi_f);
401 phi_f = phase->transform(phi_f);
402 }
403 proj_path_data = phi_f;
404 proj_path_ctrl = region_f;
405 }
406
407 // Fixup 'v' for for the split
408 if( vop == Op_Phi ) { // Remote merge point
409 uint i;
410 for( i = 1; i < v->req(); i++ )
411 if( v->in(i) == phi )
412 break;
413 v->set_req(i, proj_path_data );
414 } else if( v->is_ConstraintCast() ) {
415 v->set_req(0, proj_path_ctrl );
416 v->set_req(1, proj_path_data );
417 } else
418 ShouldNotReachHere();
419 }
420
421 // Now replace the original iff's True/False with region_s/region_t.
422 // This makes the original iff go dead.
423 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
424 Node* p = iff->last_out(i3);
425 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
426 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
427 // Replace p with u
428 igvn->add_users_to_worklist(p);
429 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
430 Node* x = p->last_out(l);
431 igvn->hash_delete(x);
432 uint uses_found = 0;
433 for( uint j = 0; j < x->req(); j++ ) {
434 if( x->in(j) == p ) {
435 x->set_req(j, u);
436 uses_found++;
437 }
438 }
439 l -= uses_found; // we deleted 1 or more copies of this edge
440 }
441 igvn->remove_dead_node(p);
442 }
443
444 // Force the original merge dead
445 igvn->hash_delete(r);
446 // First, remove region's dead users.
447 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
448 Node* u = r->last_out(l);
449 if( u == r ) {
450 r->set_req(0, NULL);
451 } else {
452 assert(u->outcnt() == 0, "only dead users");
453 igvn->remove_dead_node(u);
454 }
455 l -= 1;
456 }
457 igvn->remove_dead_node(r);
458
459 // Now remove the bogus extra edges used to keep things alive
460 igvn->remove_dead_node( hook );
461
462 // Must return either the original node (now dead) or a new node
463 // (Do not return a top here, since that would break the uniqueness of top.)
464 return new ConINode(TypeInt::ZERO);
465 }
466
467 // if this IfNode follows a range check pattern return the projection
468 // for the failed path
469 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
470 Node* b = in(1);
471 if (b == NULL || !b->is_Bool()) return NULL;
472 BoolNode* bn = b->as_Bool();
473 Node* cmp = bn->in(1);
474 if (cmp == NULL) return NULL;
475 if (cmp->Opcode() != Op_CmpU) return NULL;
476
477 l = cmp->in(1);
478 r = cmp->in(2);
479 flip_test = 1;
480 if (bn->_test._test == BoolTest::le) {
481 l = cmp->in(2);
482 r = cmp->in(1);
483 flip_test = 2;
484 } else if (bn->_test._test != BoolTest::lt) {
485 return NULL;
486 }
487 if (l->is_top()) return NULL; // Top input means dead test
488 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return NULL;
489
490 // We have recognized one of these forms:
491 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
492 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
493
494 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
495 return iftrap;
496 }
497
498
499 //------------------------------is_range_check---------------------------------
500 // Return 0 if not a range check. Return 1 if a range check and set index and
501 // offset. Return 2 if we had to negate the test. Index is NULL if the check
502 // is versus a constant.
503 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
504 int flip_test = 0;
505 Node* l = NULL;
506 Node* r = NULL;
507 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
508
509 if (iftrap == NULL) {
510 return 0;
511 }
512
513 // Make sure it's a real range check by requiring an uncommon trap
514 // along the OOB path. Otherwise, it's possible that the user wrote
515 // something which optimized to look like a range check but behaves
516 // in some other way.
517 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
518 return 0;
519 }
520
521 // Look for index+offset form
522 Node* ind = l;
523 jint off = 0;
524 if (l->is_top()) {
525 return 0;
526 } else if (l->Opcode() == Op_AddI) {
527 if ((off = l->in(1)->find_int_con(0)) != 0) {
528 ind = l->in(2)->uncast();
529 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
530 ind = l->in(1)->uncast();
531 }
532 } else if ((off = l->find_int_con(-1)) >= 0) {
533 // constant offset with no variable index
534 ind = NULL;
535 } else {
536 // variable index with no constant offset (or dead negative index)
537 off = 0;
538 }
539
540 // Return all the values:
541 index = ind;
542 offset = off;
543 range = r;
544 return flip_test;
545 }
546
547 //------------------------------adjust_check-----------------------------------
548 // Adjust (widen) a prior range check
549 static void adjust_check(Node* proj, Node* range, Node* index,
550 int flip, jint off_lo, PhaseIterGVN* igvn) {
551 PhaseGVN *gvn = igvn;
552 // Break apart the old check
553 Node *iff = proj->in(0);
554 Node *bol = iff->in(1);
555 if( bol->is_top() ) return; // In case a partially dead range check appears
556 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
557 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
558 if( !bol->is_Bool() ) return;
559
560 Node *cmp = bol->in(1);
561 // Compute a new check
562 Node *new_add = gvn->intcon(off_lo);
563 if( index ) {
564 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
565 }
566 Node *new_cmp = (flip == 1)
567 ? new CmpUNode( new_add, range )
568 : new CmpUNode( range, new_add );
569 new_cmp = gvn->transform(new_cmp);
570 // See if no need to adjust the existing check
571 if( new_cmp == cmp ) return;
572 // Else, adjust existing check
573 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
574 igvn->rehash_node_delayed( iff );
575 iff->set_req_X( 1, new_bol, igvn );
576 }
577
578 //------------------------------up_one_dom-------------------------------------
579 // Walk up the dominator tree one step. Return NULL at root or true
580 // complex merges. Skips through small diamonds.
581 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
582 Node *dom = curr->in(0);
583 if( !dom ) // Found a Region degraded to a copy?
584 return curr->nonnull_req(); // Skip thru it
585
586 if( curr != dom ) // Normal walk up one step?
587 return dom;
588
589 // Use linear_only if we are still parsing, since we cannot
590 // trust the regions to be fully filled in.
591 if (linear_only)
592 return NULL;
593
594 if( dom->is_Root() )
595 return NULL;
596
597 // Else hit a Region. Check for a loop header
598 if( dom->is_Loop() )
599 return dom->in(1); // Skip up thru loops
600
601 // Check for small diamonds
602 Node *din1, *din2, *din3, *din4;
603 if( dom->req() == 3 && // 2-path merge point
604 (din1 = dom ->in(1)) && // Left path exists
605 (din2 = dom ->in(2)) && // Right path exists
606 (din3 = din1->in(0)) && // Left path up one
607 (din4 = din2->in(0)) ) { // Right path up one
608 if( din3->is_Call() && // Handle a slow-path call on either arm
609 (din3 = din3->in(0)) )
610 din3 = din3->in(0);
611 if( din4->is_Call() && // Handle a slow-path call on either arm
612 (din4 = din4->in(0)) )
613 din4 = din4->in(0);
614 if( din3 == din4 && din3->is_If() )
615 return din3; // Skip around diamonds
616 }
617
618 // Give up the search at true merges
619 return NULL; // Dead loop? Or hit root?
620 }
621
622
623 //------------------------------filtered_int_type--------------------------------
624 // Return a possibly more restrictive type for val based on condition control flow for an if
625 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
626 assert(if_proj &&
627 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
628 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
629 IfNode* iff = if_proj->in(0)->as_If();
630 if (iff->in(1) && iff->in(1)->is_Bool()) {
631 BoolNode* bol = iff->in(1)->as_Bool();
632 if (bol->in(1) && bol->in(1)->is_Cmp()) {
633 const CmpNode* cmp = bol->in(1)->as_Cmp();
634 if (cmp->in(1) == val) {
635 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
636 if (cmp2_t != NULL) {
637 jint lo = cmp2_t->_lo;
638 jint hi = cmp2_t->_hi;
639 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
640 switch (msk) {
641 case BoolTest::ne:
642 // Can't refine type
643 return NULL;
644 case BoolTest::eq:
645 return cmp2_t;
646 case BoolTest::lt:
647 lo = TypeInt::INT->_lo;
648 if (hi - 1 < hi) {
649 hi = hi - 1;
650 }
651 break;
652 case BoolTest::le:
653 lo = TypeInt::INT->_lo;
654 break;
655 case BoolTest::gt:
656 if (lo + 1 > lo) {
657 lo = lo + 1;
658 }
659 hi = TypeInt::INT->_hi;
660 break;
661 case BoolTest::ge:
662 // lo unchanged
663 hi = TypeInt::INT->_hi;
664 break;
665 }
666 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
667 return rtn_t;
668 }
669 }
670 }
671 }
672 }
673 return NULL;
674 }
675
676 //------------------------------fold_compares----------------------------
677 // See if a pair of CmpIs can be converted into a CmpU. In some cases
678 // the direction of this if is determined by the preceding if so it
679 // can be eliminate entirely.
680 //
681 // Given an if testing (CmpI n v) check for an immediately control
682 // dependent if that is testing (CmpI n v2) and has one projection
683 // leading to this if and the other projection leading to a region
684 // that merges one of this ifs control projections.
685 //
686 // If
687 // / |
688 // / |
689 // / |
690 // If |
691 // /\ |
692 // / \ |
693 // / \ |
694 // / Region
695 //
696 // Or given an if testing (CmpI n v) check for a dominating if that is
697 // testing (CmpI n v2), both having one projection leading to an
698 // uncommon trap. Allow Another independent guard in between to cover
699 // an explicit range check:
700 // if (index < 0 || index >= array.length) {
701 // which may need a null check to guard the LoadRange
702 //
703 // If
704 // / \
705 // / \
706 // / \
707 // If unc
708 // /\
709 // / \
710 // / \
711 // / unc
712 //
713
714 // Is the comparison for this If suitable for folding?
715 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
716 return in(1) != NULL &&
717 in(1)->is_Bool() &&
718 in(1)->in(1) != NULL &&
719 in(1)->in(1)->Opcode() == Op_CmpI &&
720 in(1)->in(1)->in(2) != NULL &&
721 in(1)->in(1)->in(2) != igvn->C->top() &&
722 (in(1)->as_Bool()->_test.is_less() ||
723 in(1)->as_Bool()->_test.is_greater());
724 }
725
726 // Is a dominating control suitable for folding with this if?
727 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
728 return ctrl != NULL &&
729 ctrl->is_Proj() &&
730 ctrl->in(0) != NULL &&
731 ctrl->in(0)->Opcode() == Op_If &&
732 ctrl->in(0)->outcnt() == 2 &&
733 ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
734 // Must compare same value
735 ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
736 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
737 }
738
739 // Do this If and the dominating If share a region?
740 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
741 ProjNode* otherproj = proj->other_if_proj();
742 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
743 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
744 success = NULL;
745 fail = NULL;
746
747 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
748 for (int i = 0; i < 2; i++) {
749 ProjNode* proj = proj_out(i);
750 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
751 success = proj;
752 } else if (fail == NULL) {
753 fail = proj;
754 } else {
755 success = fail = NULL;
756 }
757 }
758 }
759 return success != NULL && fail != NULL;
760 }
761
762 // Return projection that leads to an uncommon trap if any
763 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
764 for (int i = 0; i < 2; i++) {
765 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
766 if (call != NULL) {
767 return proj_out(i);
768 }
769 }
770 return NULL;
771 }
772
773 // Do this If and the dominating If both branch out to an uncommon trap
774 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
775 ProjNode* otherproj = proj->other_if_proj();
776 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
777
778 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
779 // We need to re-execute the folded Ifs after deoptimization from the merged traps
780 if (!dom_unc->jvms()->should_reexecute()) {
781 return false;
782 }
783
784 CallStaticJavaNode* unc = NULL;
785 ProjNode* unc_proj = uncommon_trap_proj(unc);
786 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
787 if (dom_unc == unc) {
788 // Allow the uncommon trap to be shared through a region
789 RegionNode* r = unc->in(0)->as_Region();
790 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
791 return false;
792 }
793 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
794 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
795 return false;
796 }
797
798 // Different methods and methods containing jsrs are not supported.
799 ciMethod* method = unc->jvms()->method();
800 ciMethod* dom_method = dom_unc->jvms()->method();
801 if (method != dom_method || method->has_jsrs()) {
802 return false;
803 }
804 // Check that both traps are in the same activation of the method (instead
805 // of two activations being inlined through different call sites) by verifying
806 // that the call stacks are equal for both JVMStates.
807 JVMState* dom_caller = dom_unc->jvms()->caller();
808 JVMState* caller = unc->jvms()->caller();
809 if ((dom_caller == NULL) != (caller == NULL)) {
810 // The current method must either be inlined into both dom_caller and
811 // caller or must not be inlined at all (top method). Bail out otherwise.
812 return false;
813 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
814 return false;
815 }
816 // Check that the bci of the dominating uncommon trap dominates the bci
817 // of the dominated uncommon trap. Otherwise we may not re-execute
818 // the dominated check after deoptimization from the merged uncommon trap.
819 ciTypeFlow* flow = dom_method->get_flow_analysis();
820 int bci = unc->jvms()->bci();
821 int dom_bci = dom_unc->jvms()->bci();
822 if (!flow->is_dominated_by(bci, dom_bci)) {
823 return false;
824 }
825
826 // See merge_uncommon_traps: the reason of the uncommon trap
827 // will be changed and the state of the dominating If will be
828 // used. Checked that we didn't apply this transformation in a
829 // previous compilation and it didn't cause too many traps
830 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
831 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
832 success = unc_proj;
833 fail = unc_proj->other_if_proj();
834 return true;
835 }
836 }
837 }
838 return false;
839 }
840
841 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
842 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
843 Node* this_cmp = in(1)->in(1);
844 BoolNode* this_bool = in(1)->as_Bool();
845 IfNode* dom_iff = proj->in(0)->as_If();
846 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
847 Node* lo = dom_iff->in(1)->in(1)->in(2);
848 Node* hi = this_cmp->in(2);
849 Node* n = this_cmp->in(1);
850 ProjNode* otherproj = proj->other_if_proj();
851
852 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
853 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
854
855 BoolTest::mask lo_test = dom_bool->_test._test;
856 BoolTest::mask hi_test = this_bool->_test._test;
857 BoolTest::mask cond = hi_test;
858
859 // convert:
860 //
861 // dom_bool = x {<,<=,>,>=} a
862 // / \
863 // proj = {True,False} / \ otherproj = {False,True}
864 // /
865 // this_bool = x {<,<=} b
866 // / \
867 // fail = {True,False} / \ success = {False,True}
868 // /
869 //
870 // (Second test guaranteed canonicalized, first one may not have
871 // been canonicalized yet)
872 //
873 // into:
874 //
875 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
876 // / \
877 // fail / \ success
878 // /
879 //
880
881 // Figure out which of the two tests sets the upper bound and which
882 // sets the lower bound if any.
883 Node* adjusted_lim = NULL;
884 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
885 assert((dom_bool->_test.is_less() && !proj->_con) ||
886 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
887 // this test was canonicalized
888 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
889
890 // this_bool = <
891 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
892 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
893 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
894 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
895 // x in ]a, b[ on the fail (= True) projection, b > a:
896 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
897 // this_bool = <=
898 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
899 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
900 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
901 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
902 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
903 // x in ]a, b] on the fail (= True) projection b+1 > a:
904 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
905 // 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
906
907 if (hi_test == BoolTest::lt) {
908 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
909 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
910 }
911 } else {
912 assert(hi_test == BoolTest::le, "bad test");
913 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
914 adjusted_lim = igvn->transform(new SubINode(hi, lo));
915 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
916 cond = BoolTest::lt;
917 } else {
918 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
919 adjusted_lim = igvn->transform(new SubINode(hi, lo));
920 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
921 cond = BoolTest::lt;
922 }
923 }
924 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
925
926 // this_bool = <
927 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
928 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
929 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
930 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
931 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
932 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
933 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
934 // this_bool = <=
935 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
936 // x in ]b, a[ on the fail (= False) projection, a > b:
937 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
938 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
939 // x in ]b, a] on the fail (= False) projection, a+1 > b:
940 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
941 // 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
942
943 swap(lo, hi);
944 swap(lo_type, hi_type);
945 swap(lo_test, hi_test);
946
947 assert((dom_bool->_test.is_less() && proj->_con) ||
948 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
949 // this test was canonicalized
950 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
951
952 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
953
954 if (lo_test == BoolTest::lt) {
955 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
956 cond = BoolTest::ge;
957 } else {
958 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
959 adjusted_lim = igvn->transform(new SubINode(hi, lo));
960 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
961 cond = BoolTest::ge;
962 }
963 } else if (lo_test == BoolTest::le) {
964 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
965 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
966 cond = BoolTest::ge;
967 } else {
968 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
969 adjusted_lim = igvn->transform(new SubINode(hi, lo));
970 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
971 cond = BoolTest::ge;
972 }
973 }
974 } else {
975 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
976 if (failtype != NULL) {
977 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
978 if (type2 != NULL) {
979 failtype = failtype->join(type2)->is_int();
980 if (failtype->_lo > failtype->_hi) {
981 // previous if determines the result of this if so
982 // replace Bool with constant
983 igvn->_worklist.push(in(1));
984 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
985 return true;
986 }
987 }
988 }
989 lo = NULL;
990 hi = NULL;
991 }
992
993 if (lo && hi) {
994 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
995 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
996 if (adjusted_lim == NULL) {
997 adjusted_lim = igvn->transform(new SubINode(hi, lo));
998 }
999 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1000 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1001
1002 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1003 igvn->_worklist.push(in(1));
1004 igvn->replace_input_of(this, 1, newbool);
1005
1006 return true;
1007 }
1008 return false;
1009 }
1010
1011 // Merge the branches that trap for this If and the dominating If into
1012 // a single region that branches to the uncommon trap for the
1013 // dominating If
1014 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1015 Node* res = this;
1016 assert(success->in(0) == this, "bad projection");
1017
1018 ProjNode* otherproj = proj->other_if_proj();
1019
1020 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1021 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1022
1023 if (unc != dom_unc) {
1024 Node* r = new RegionNode(3);
1025
1026 r->set_req(1, otherproj);
1027 r->set_req(2, success);
1028 r = igvn->transform(r);
1029 assert(r->is_Region(), "can't go away");
1030
1031 // Make both If trap at the state of the first If: once the CmpI
1032 // nodes are merged, if we trap we don't know which of the CmpI
1033 // nodes would have caused the trap so we have to restart
1034 // execution at the first one
1035 igvn->replace_input_of(dom_unc, 0, r);
1036 igvn->replace_input_of(unc, 0, igvn->C->top());
1037 }
1038 int trap_request = dom_unc->uncommon_trap_request();
1039 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1040 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1041
1042 int flip_test = 0;
1043 Node* l = NULL;
1044 Node* r = NULL;
1045
1046 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1047 // If this looks like a range check, change the trap to
1048 // Reason_range_check so the compiler recognizes it as a range
1049 // check and applies the corresponding optimizations
1050 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1051
1052 improve_address_types(l, r, fail, igvn);
1053
1054 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1055 } else if (unc != dom_unc) {
1056 // If we trap we won't know what CmpI would have caused the trap
1057 // so use a special trap reason to mark this pair of CmpI nodes as
1058 // bad candidate for folding. On recompilation we won't fold them
1059 // and we may trap again but this time we'll know what branch
1060 // traps
1061 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1062 }
1063 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1064 return res;
1065 }
1066
1067 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1068 // of a rangecheck on index i, on 64 bit the compares may be followed
1069 // by memory accesses using i as index. In that case, the CmpU tells
1070 // us something about the values taken by i that can help the compiler
1071 // (see Compile::conv_I2X_index())
1072 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1073 #ifdef _LP64
1074 ResourceMark rm;
1075 Node_Stack stack(2);
1076
1077 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1078 const TypeInt* array_size = igvn->type(r)->is_int();
1079
1080 stack.push(l, 0);
1081
1082 while(stack.size() > 0) {
1083 Node* n = stack.node();
1084 uint start = stack.index();
1085
1086 uint i = start;
1087 for (; i < n->outcnt(); i++) {
1088 Node* use = n->raw_out(i);
1089 if (stack.size() == 1) {
1090 if (use->Opcode() == Op_ConvI2L) {
1091 const TypeLong* bounds = use->as_Type()->type()->is_long();
1092 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1093 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1094 stack.set_index(i+1);
1095 stack.push(use, 0);
1096 break;
1097 }
1098 }
1099 } else if (use->is_Mem()) {
1100 Node* ctrl = use->in(0);
1101 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1102 ctrl = up_one_dom(ctrl);
1103 }
1104 if (ctrl == fail) {
1105 Node* init_n = stack.node_at(1);
1106 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1107 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size);
1108
1109 // The type of the ConvI2L may be widen and so the new
1110 // ConvI2L may not be better than an existing ConvI2L
1111 if (new_n != init_n) {
1112 for (uint j = 2; j < stack.size(); j++) {
1113 Node* n = stack.node_at(j);
1114 Node* clone = n->clone();
1115 int rep = clone->replace_edge(init_n, new_n);
1116 assert(rep > 0, "can't find expected node?");
1117 clone = igvn->transform(clone);
1118 init_n = n;
1119 new_n = clone;
1120 }
1121 igvn->hash_delete(use);
1122 int rep = use->replace_edge(init_n, new_n);
1123 assert(rep > 0, "can't find expected node?");
1124 igvn->transform(use);
1125 if (init_n->outcnt() == 0) {
1126 igvn->_worklist.push(init_n);
1127 }
1128 }
1129 }
1130 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1131 igvn->type(use)->isa_ptr())) {
1132 stack.set_index(i+1);
1133 stack.push(use, 0);
1134 break;
1135 }
1136 }
1137 if (i == n->outcnt()) {
1138 stack.pop();
1139 }
1140 }
1141 #endif
1142 }
1143
1144 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1145 if (in(1) != NULL &&
1146 in(1)->in(1) != NULL &&
1147 in(1)->in(1)->in(2) != NULL) {
1148 Node* other = in(1)->in(1)->in(2);
1149 if (other->Opcode() == Op_LoadRange &&
1150 ((other->in(0) != NULL && other->in(0) == proj) ||
1151 (other->in(0) == NULL &&
1152 other->in(2) != NULL &&
1153 other->in(2)->is_AddP() &&
1154 other->in(2)->in(1) != NULL &&
1155 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1156 other->in(2)->in(1)->in(0) == proj))) {
1157 return true;
1158 }
1159 }
1160 return false;
1161 }
1162
1163 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1164 Node* other = in(1)->in(1)->in(2);
1165 if (other->in(MemNode::Address) != NULL &&
1166 proj->in(0)->in(1) != NULL &&
1167 proj->in(0)->in(1)->is_Bool() &&
1168 proj->in(0)->in(1)->in(1) != NULL &&
1169 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1170 proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1171 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1172 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1173 return true;
1174 }
1175 return false;
1176 }
1177
1178 // Check that the If that is in between the 2 integer comparisons has
1179 // no side effect
1180 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1181 if (proj != NULL &&
1182 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1183 proj->outcnt() <= 2) {
1184 if (proj->outcnt() == 1 ||
1185 // Allow simple null check from LoadRange
1186 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1187 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1188 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1189
1190 // reroute_side_effect_free_unc changes the state of this
1191 // uncommon trap to restart execution at the previous
1192 // CmpI. Check that this change in a previous compilation didn't
1193 // cause too many traps.
1194 int trap_request = unc->uncommon_trap_request();
1195 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1196
1197 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1198 return false;
1199 }
1200
1201 return true;
1202 }
1203 }
1204 return false;
1205 }
1206
1207 // Make the If between the 2 integer comparisons trap at the state of
1208 // the first If: the last CmpI is the one replaced by a CmpU and the
1209 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1210 // won't be guarded by the first CmpI anymore. It can trap in cases
1211 // where the first CmpI would have prevented it from executing: on a
1212 // trap, we need to restart execution at the state of the first CmpI
1213 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1214 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1215 ProjNode* otherproj = proj->other_if_proj();
1216 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1217 Node* call_proj = dom_unc->unique_ctrl_out();
1218 Node* halt = call_proj->unique_ctrl_out();
1219
1220 Node* new_unc = dom_unc->clone();
1221 call_proj = call_proj->clone();
1222 halt = halt->clone();
1223 Node* c = otherproj->clone();
1224
1225 c = igvn->transform(c);
1226 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1227 new_unc->set_req(0, c);
1228 new_unc = igvn->transform(new_unc);
1229 call_proj->set_req(0, new_unc);
1230 call_proj = igvn->transform(call_proj);
1231 halt->set_req(0, call_proj);
1232 halt = igvn->transform(halt);
1233
1234 igvn->replace_node(otherproj, igvn->C->top());
1235 igvn->C->root()->add_req(halt);
1236 }
1237
1238 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1239 if (Opcode() != Op_If) return NULL;
1240
1241 if (cmpi_folds(igvn)) {
1242 Node* ctrl = in(0);
1243 if (is_ctrl_folds(ctrl, igvn) &&
1244 ctrl->outcnt() == 1) {
1245 // A integer comparison immediately dominated by another integer
1246 // comparison
1247 ProjNode* success = NULL;
1248 ProjNode* fail = NULL;
1249 ProjNode* dom_cmp = ctrl->as_Proj();
1250 if (has_shared_region(dom_cmp, success, fail) &&
1251 // Next call modifies graph so must be last
1252 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1253 return this;
1254 }
1255 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1256 // Next call modifies graph so must be last
1257 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1258 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1259 }
1260 return NULL;
1261 } else if (ctrl->in(0) != NULL &&
1262 ctrl->in(0)->in(0) != NULL) {
1263 ProjNode* success = NULL;
1264 ProjNode* fail = NULL;
1265 Node* dom = ctrl->in(0)->in(0);
1266 ProjNode* dom_cmp = dom->isa_Proj();
1267 ProjNode* other_cmp = ctrl->isa_Proj();
1268
1269 // Check if it's an integer comparison dominated by another
1270 // integer comparison with another test in between
1271 if (is_ctrl_folds(dom, igvn) &&
1272 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1273 is_side_effect_free_test(other_cmp, igvn) &&
1274 // Next call modifies graph so must be last
1275 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1276 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1277 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1278 }
1279 }
1280 }
1281 return NULL;
1282 }
1283
1284 //------------------------------remove_useless_bool----------------------------
1285 // Check for people making a useless boolean: things like
1286 // if( (x < y ? true : false) ) { ... }
1287 // Replace with if( x < y ) { ... }
1288 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1289 Node *i1 = iff->in(1);
1290 if( !i1->is_Bool() ) return NULL;
1291 BoolNode *bol = i1->as_Bool();
1292
1293 Node *cmp = bol->in(1);
1294 if( cmp->Opcode() != Op_CmpI ) return NULL;
1295
1296 // Must be comparing against a bool
1297 const Type *cmp2_t = phase->type( cmp->in(2) );
1298 if( cmp2_t != TypeInt::ZERO &&
1299 cmp2_t != TypeInt::ONE )
1300 return NULL;
1301
1302 // Find a prior merge point merging the boolean
1303 i1 = cmp->in(1);
1304 if( !i1->is_Phi() ) return NULL;
1305 PhiNode *phi = i1->as_Phi();
1306 if( phase->type( phi ) != TypeInt::BOOL )
1307 return NULL;
1308
1309 // Check for diamond pattern
1310 int true_path = phi->is_diamond_phi();
1311 if( true_path == 0 ) return NULL;
1312
1313 // Make sure that iff and the control of the phi are different. This
1314 // should really only happen for dead control flow since it requires
1315 // an illegal cycle.
1316 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1317
1318 // phi->region->if_proj->ifnode->bool->cmp
1319 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1320
1321 // Now get the 'sense' of the test correct so we can plug in
1322 // either iff2->in(1) or its complement.
1323 int flip = 0;
1324 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1325 else if( bol->_test._test != BoolTest::eq ) return NULL;
1326 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1327
1328 const Type *phi1_t = phase->type( phi->in(1) );
1329 const Type *phi2_t = phase->type( phi->in(2) );
1330 // Check for Phi(0,1) and flip
1331 if( phi1_t == TypeInt::ZERO ) {
1332 if( phi2_t != TypeInt::ONE ) return NULL;
1333 flip = 1-flip;
1334 } else {
1335 // Check for Phi(1,0)
1336 if( phi1_t != TypeInt::ONE ) return NULL;
1337 if( phi2_t != TypeInt::ZERO ) return NULL;
1338 }
1339 if( true_path == 2 ) {
1340 flip = 1-flip;
1341 }
1342
1343 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1344 assert(new_bol != iff->in(1), "must make progress");
1345 iff->set_req(1, new_bol);
1346 // Intervening diamond probably goes dead
1347 phase->C->set_major_progress();
1348 return iff;
1349 }
1350
1351 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1352
1353 struct RangeCheck {
1354 Node* ctl;
1355 jint off;
1356 };
1357
1358 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1359 if (remove_dead_region(phase, can_reshape)) return this;
1360 // No Def-Use info?
1361 if (!can_reshape) return NULL;
1362
1363 // Don't bother trying to transform a dead if
1364 if (in(0)->is_top()) return NULL;
1365 // Don't bother trying to transform an if with a dead test
1366 if (in(1)->is_top()) return NULL;
1367 // Another variation of a dead test
1368 if (in(1)->is_Con()) return NULL;
1369 // Another variation of a dead if
1370 if (outcnt() < 2) return NULL;
1371
1372 // Canonicalize the test.
1373 Node* idt_if = idealize_test(phase, this);
1374 if (idt_if != NULL) return idt_if;
1375
1376 // Try to split the IF
1377 PhaseIterGVN *igvn = phase->is_IterGVN();
1378 Node *s = split_if(this, igvn);
1379 if (s != NULL) return s;
1380
1381 return NodeSentinel;
1382 }
1383
1384 //------------------------------Ideal------------------------------------------
1385 // Return a node which is more "ideal" than the current node. Strip out
1386 // control copies
1387 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1388 Node* res = Ideal_common(phase, can_reshape);
1389 if (res != NodeSentinel) {
1390 return res;
1391 }
1392
1393 // Check for people making a useless boolean: things like
1394 // if( (x < y ? true : false) ) { ... }
1395 // Replace with if( x < y ) { ... }
1396 Node *bol2 = remove_useless_bool(this, phase);
1397 if( bol2 ) return bol2;
1398
1399 if (in(0) == NULL) return NULL; // Dead loop?
1400
1401 PhaseIterGVN *igvn = phase->is_IterGVN();
1402 Node* result = fold_compares(igvn);
1403 if (result != NULL) {
1404 return result;
1405 }
1406
1407 // Scan for an equivalent test
1408 Node *cmp;
1409 int dist = 0; // Cutoff limit for search
1410 int op = Opcode();
1411 if( op == Op_If &&
1412 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1413 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1414 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1415 dist = 64; // Limit for null-pointer scans
1416 } else {
1417 dist = 4; // Do not bother for random pointer tests
1418 }
1419 } else {
1420 dist = 4; // Limit for random junky scans
1421 }
1422
1423 Node* prev_dom = search_identical(dist);
1424
1425 if (prev_dom == NULL) {
1426 return NULL;
1427 }
1428
1429 // Replace dominated IfNode
1430 return dominated_by(prev_dom, igvn);
1431 }
1432
1433 //------------------------------dominated_by-----------------------------------
1434 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1435 #ifndef PRODUCT
1436 if (TraceIterativeGVN) {
1437 tty->print(" Removing IfNode: "); this->dump();
1438 }
1439 if (VerifyOpto && !igvn->allow_progress()) {
1440 // Found an equivalent dominating test,
1441 // we can not guarantee reaching a fix-point for these during iterativeGVN
1442 // since intervening nodes may not change.
1443 return NULL;
1444 }
1445 #endif
1446
1447 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1448 Node *idom = in(0);
1449 // Need opcode to decide which way 'this' test goes
1450 int prev_op = prev_dom->Opcode();
1451 Node *top = igvn->C->top(); // Shortcut to top
1452
1453 // Loop predicates may have depending checks which should not
1454 // be skipped. For example, range check predicate has two checks
1455 // for lower and upper bounds.
1456 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1457 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1458 prev_dom = idom;
1459
1460 // Now walk the current IfNode's projections.
1461 // Loop ends when 'this' has no more uses.
1462 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1463 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1464 igvn->add_users_to_worklist(ifp);
1465 // Check which projection it is and set target.
1466 // Data-target is either the dominating projection of the same type
1467 // or TOP if the dominating projection is of opposite type.
1468 // Data-target will be used as the new control edge for the non-CFG
1469 // nodes like Casts and Loads.
1470 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1471 // Control-target is just the If's immediate dominator or TOP.
1472 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1473
1474 // For each child of an IfTrue/IfFalse projection, reroute.
1475 // Loop ends when projection has no more uses.
1476 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1477 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1478 if( !s->depends_only_on_test() ) {
1479 // Find the control input matching this def-use edge.
1480 // For Regions it may not be in slot 0.
1481 uint l;
1482 for( l = 0; s->in(l) != ifp; l++ ) { }
1483 igvn->replace_input_of(s, l, ctrl_target);
1484 } else { // Else, for control producers,
1485 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1486 }
1487 } // End for each child of a projection
1488
1489 igvn->remove_dead_node(ifp);
1490 } // End for each IfTrue/IfFalse child of If
1491
1492 // Kill the IfNode
1493 igvn->remove_dead_node(this);
1494
1495 // Must return either the original node (now dead) or a new node
1496 // (Do not return a top here, since that would break the uniqueness of top.)
1497 return new ConINode(TypeInt::ZERO);
1498 }
1499
1500 Node* IfNode::search_identical(int dist) {
1501 // Setup to scan up the CFG looking for a dominating test
1502 Node* dom = in(0);
1503 Node* prev_dom = this;
1504 int op = Opcode();
1505 // Search up the dominator tree for an If with an identical test
1506 while( dom->Opcode() != op || // Not same opcode?
1507 dom->in(1) != in(1) || // Not same input 1?
1508 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1509 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1510 if( dist < 0 ) return NULL;
1511
1512 dist--;
1513 prev_dom = dom;
1514 dom = up_one_dom( dom );
1515 if( !dom ) return NULL;
1516 }
1517
1518 // Check that we did not follow a loop back to ourselves
1519 if( this == dom )
1520 return NULL;
1521
1522 if( dist > 2 ) // Add to count of NULL checks elided
1523 explicit_null_checks_elided++;
1524
1525 return prev_dom;
1526 }
1527
1528 //------------------------------Identity---------------------------------------
1529 // If the test is constant & we match, then we are the input Control
1530 Node* IfProjNode::Identity(PhaseGVN* phase) {
1531 // Can only optimize if cannot go the other way
1532 const TypeTuple *t = phase->type(in(0))->is_tuple();
1533 if (t == TypeTuple::IFNEITHER ||
1534 // kill dead branch first otherwise the IfNode's control will
1535 // have 2 control uses (the IfNode that doesn't go away because
1536 // it still has uses and this branch of the
1537 // If). Node::has_special_unique_user() will cause this node to
1538 // be reprocessed once the dead branch is killed.
1539 (always_taken(t) && in(0)->outcnt() == 1)) {
1540 // IfNode control
1541 return in(0)->in(0);
1542 }
1543 // no progress
1544 return this;
1545 }
1546
1547 #ifndef PRODUCT
1548 //-------------------------------related---------------------------------------
1549 // An IfProjNode's related node set consists of its input (an IfNode) including
1550 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1551 // the restrictions for IfNode apply (see IfNode::rel).
1552 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1553 Node* ifNode = this->in(0);
1554 in_rel->append(ifNode);
1555 if (compact) {
1556 ifNode->collect_nodes(in_rel, 3, false, true);
1557 } else {
1558 ifNode->collect_nodes_in_all_data(in_rel, false);
1559 }
1560 this->collect_nodes(out_rel, -1, false, false);
1561 }
1562
1563 //------------------------------dump_spec--------------------------------------
1564 void IfNode::dump_spec(outputStream *st) const {
1565 st->print("P=%f, C=%f",_prob,_fcnt);
1566 }
1567
1568 //-------------------------------related---------------------------------------
1569 // For an IfNode, the set of related output nodes is just the output nodes till
1570 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1571 // The related input nodes contain no control nodes, but all data nodes
1572 // pertaining to the condition. In compact mode, the input nodes are collected
1573 // up to a depth of 3.
1574 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1575 if (compact) {
1576 this->collect_nodes(in_rel, 3, false, true);
1577 } else {
1578 this->collect_nodes_in_all_data(in_rel, false);
1579 }
1580 this->collect_nodes(out_rel, -2, false, false);
1581 }
1582 #endif
1583
1584 //------------------------------idealize_test----------------------------------
1585 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1586 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1587 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1588 // needed.
1589 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1590 assert(iff->in(0) != NULL, "If must be live");
1591
1592 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1593 Node* old_if_f = iff->proj_out(false);
1594 Node* old_if_t = iff->proj_out(true);
1595
1596 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1597 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1598 // happens in count-down loops
1599 if (iff->is_CountedLoopEnd()) return NULL;
1600 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1601 BoolNode *b = iff->in(1)->as_Bool();
1602 BoolTest bt = b->_test;
1603 // Test already in good order?
1604 if( bt.is_canonical() )
1605 return NULL;
1606
1607 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1608 // cloning the IfNode.
1609 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1610 if( !new_b->is_Bool() ) return NULL;
1611 b = new_b->as_Bool();
1612
1613 PhaseIterGVN *igvn = phase->is_IterGVN();
1614 assert( igvn, "Test is not canonical in parser?" );
1615
1616 // The IF node never really changes, but it needs to be cloned
1617 iff = iff->clone()->as_If();
1618 iff->set_req(1, b);
1619 iff->_prob = 1.0-iff->_prob;
1620
1621 Node *prior = igvn->hash_find_insert(iff);
1622 if( prior ) {
1623 igvn->remove_dead_node(iff);
1624 iff = (IfNode*)prior;
1625 } else {
1626 // Cannot call transform on it just yet
1627 igvn->set_type_bottom(iff);
1628 }
1629 igvn->_worklist.push(iff);
1630
1631 // Now handle projections. Cloning not required.
1632 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1633 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1634
1635 igvn->register_new_node_with_optimizer(new_if_f);
1636 igvn->register_new_node_with_optimizer(new_if_t);
1637 // Flip test, so flip trailing control
1638 igvn->replace_node(old_if_f, new_if_t);
1639 igvn->replace_node(old_if_t, new_if_f);
1640
1641 // Progress
1642 return iff;
1643 }
1644
1645 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1646 Node* res = Ideal_common(phase, can_reshape);
1647 if (res != NodeSentinel) {
1648 return res;
1649 }
1650
1651 PhaseIterGVN *igvn = phase->is_IterGVN();
1652 // Setup to scan up the CFG looking for a dominating test
1653 Node* prev_dom = this;
1654
1655 // Check for range-check vs other kinds of tests
1656 Node* index1;
1657 Node* range1;
1658 jint offset1;
1659 int flip1 = is_range_check(range1, index1, offset1);
1660 if (flip1) {
1661 Node* dom = in(0);
1662 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1663 // so all checks we inspect post-dominate the top-most check we find.
1664 // If we are going to fail the current check and we reach the top check
1665 // then we are guaranteed to fail, so just start interpreting there.
1666 // We 'expand' the top 3 range checks to include all post-dominating
1667 // checks.
1668
1669 // The top 3 range checks seen
1670 const int NRC =3;
1671 RangeCheck prev_checks[NRC];
1672 int nb_checks = 0;
1673
1674 // Low and high offsets seen so far
1675 jint off_lo = offset1;
1676 jint off_hi = offset1;
1677
1678 bool found_immediate_dominator = false;
1679
1680 // Scan for the top checks and collect range of offsets
1681 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1682 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1683 prev_dom->in(0) == dom) { // One path of test does dominate?
1684 if (dom == this) return NULL; // dead loop
1685 // See if this is a range check
1686 Node* index2;
1687 Node* range2;
1688 jint offset2;
1689 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1690 // See if this is a _matching_ range check, checking against
1691 // the same array bounds.
1692 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1693 dom->outcnt() == 2) {
1694 if (nb_checks == 0 && dom->in(1) == in(1)) {
1695 // Found an immediately dominating test at the same offset.
1696 // This kind of back-to-back test can be eliminated locally,
1697 // and there is no need to search further for dominating tests.
1698 assert(offset2 == offset1, "Same test but different offsets");
1699 found_immediate_dominator = true;
1700 break;
1701 }
1702 // Gather expanded bounds
1703 off_lo = MIN2(off_lo,offset2);
1704 off_hi = MAX2(off_hi,offset2);
1705 // Record top NRC range checks
1706 prev_checks[nb_checks%NRC].ctl = prev_dom;
1707 prev_checks[nb_checks%NRC].off = offset2;
1708 nb_checks++;
1709 }
1710 }
1711 prev_dom = dom;
1712 dom = up_one_dom(dom);
1713 if (!dom) break;
1714 }
1715
1716 if (!found_immediate_dominator) {
1717 // Attempt to widen the dominating range check to cover some later
1718 // ones. Since range checks "fail" by uncommon-trapping to the
1719 // interpreter, widening a check can make us speculatively enter
1720 // the interpreter. If we see range-check deopt's, do not widen!
1721 if (!phase->C->allow_range_check_smearing()) return NULL;
1722
1723 // Didn't find prior covering check, so cannot remove anything.
1724 if (nb_checks == 0) {
1725 return NULL;
1726 }
1727 // Constant indices only need to check the upper bound.
1728 // Non-constant indices must check both low and high.
1729 int chk0 = (nb_checks - 1) % NRC;
1730 if (index1) {
1731 if (nb_checks == 1) {
1732 return NULL;
1733 } else {
1734 // If the top range check's constant is the min or max of
1735 // all constants we widen the next one to cover the whole
1736 // range of constants.
1737 RangeCheck rc0 = prev_checks[chk0];
1738 int chk1 = (nb_checks - 2) % NRC;
1739 RangeCheck rc1 = prev_checks[chk1];
1740 if (rc0.off == off_lo) {
1741 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1742 prev_dom = rc1.ctl;
1743 } else if (rc0.off == off_hi) {
1744 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1745 prev_dom = rc1.ctl;
1746 } else {
1747 // If the top test's constant is not the min or max of all
1748 // constants, we need 3 range checks. We must leave the
1749 // top test unchanged because widening it would allow the
1750 // accesses it protects to successfully read/write out of
1751 // bounds.
1752 if (nb_checks == 2) {
1753 return NULL;
1754 }
1755 int chk2 = (nb_checks - 3) % NRC;
1756 RangeCheck rc2 = prev_checks[chk2];
1757 // The top range check a+i covers interval: -a <= i < length-a
1758 // The second range check b+i covers interval: -b <= i < length-b
1759 if (rc1.off <= rc0.off) {
1760 // if b <= a, we change the second range check to:
1761 // -min_of_all_constants <= i < length-min_of_all_constants
1762 // Together top and second range checks now cover:
1763 // -min_of_all_constants <= i < length-a
1764 // which is more restrictive than -b <= i < length-b:
1765 // -b <= -min_of_all_constants <= i < length-a <= length-b
1766 // The third check is then changed to:
1767 // -max_of_all_constants <= i < length-max_of_all_constants
1768 // so 2nd and 3rd checks restrict allowed values of i to:
1769 // -min_of_all_constants <= i < length-max_of_all_constants
1770 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1771 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1772 } else {
1773 // if b > a, we change the second range check to:
1774 // -max_of_all_constants <= i < length-max_of_all_constants
1775 // Together top and second range checks now cover:
1776 // -a <= i < length-max_of_all_constants
1777 // which is more restrictive than -b <= i < length-b:
1778 // -b < -a <= i < length-max_of_all_constants <= length-b
1779 // The third check is then changed to:
1780 // -max_of_all_constants <= i < length-max_of_all_constants
1781 // so 2nd and 3rd checks restrict allowed values of i to:
1782 // -min_of_all_constants <= i < length-max_of_all_constants
1783 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1784 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1785 }
1786 prev_dom = rc2.ctl;
1787 }
1788 }
1789 } else {
1790 RangeCheck rc0 = prev_checks[chk0];
1791 // 'Widen' the offset of the 1st and only covering check
1792 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1793 // Test is now covered by prior checks, dominate it out
1794 prev_dom = rc0.ctl;
1795 }
1796 }
1797 } else {
1798 prev_dom = search_identical(4);
1799
1800 if (prev_dom == NULL) {
1801 return NULL;
1802 }
1803 }
1804
1805 // Replace dominated IfNode
1806 return dominated_by(prev_dom, igvn);
1807 }