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