1 /*
2 * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciTypeFlow.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "opto/addnode.hpp"
30 #include "opto/castnode.hpp"
31 #include "opto/cfgnode.hpp"
32 #include "opto/connode.hpp"
33 #include "opto/loopnode.hpp"
34 #include "opto/phaseX.hpp"
35 #include "opto/runtime.hpp"
36 #include "opto/rootnode.hpp"
37 #include "opto/subnode.hpp"
38
39 // Portions of code courtesy of Clifford Click
40
41 // Optimization - Graph Style
42
43
44 #ifndef PRODUCT
45 extern int explicit_null_checks_elided;
46 #endif
47
48 //=============================================================================
49 //------------------------------Value------------------------------------------
50 // Return a tuple for whichever arm of the IF is reachable
51 const Type* IfNode::Value(PhaseGVN* phase) const {
52 if( !in(0) ) return Type::TOP;
53 if( phase->type(in(0)) == Type::TOP )
54 return Type::TOP;
55 const Type *t = phase->type(in(1));
56 if( t == Type::TOP ) // data is undefined
57 return TypeTuple::IFNEITHER; // unreachable altogether
58 if( t == TypeInt::ZERO ) // zero, or false
59 return TypeTuple::IFFALSE; // only false branch is reachable
60 if( t == TypeInt::ONE ) // 1, or true
61 return TypeTuple::IFTRUE; // only true branch is reachable
62 assert( t == TypeInt::BOOL, "expected boolean type" );
63
64 return TypeTuple::IFBOTH; // No progress
65 }
66
67 const RegMask &IfNode::out_RegMask() const {
68 return RegMask::Empty;
69 }
70
71 //------------------------------split_if---------------------------------------
72 // Look for places where we merge constants, then test on the merged value.
73 // If the IF test will be constant folded on the path with the constant, we
74 // win by splitting the IF to before the merge point.
75 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
76 // I could be a lot more general here, but I'm trying to squeeze this
77 // in before the Christmas '98 break so I'm gonna be kinda restrictive
78 // on the patterns I accept. CNC
79
80 // Look for a compare of a constant and a merged value
81 Node *i1 = iff->in(1);
82 if( !i1->is_Bool() ) return NULL;
83 BoolNode *b = i1->as_Bool();
84 Node *cmp = b->in(1);
85 if( !cmp->is_Cmp() ) return NULL;
86 i1 = cmp->in(1);
87 if( i1 == NULL || !i1->is_Phi() ) return NULL;
88 PhiNode *phi = i1->as_Phi();
89 if( phi->is_copy() ) return NULL;
90 Node *con2 = cmp->in(2);
91 if( !con2->is_Con() ) return NULL;
92 // See that the merge point contains some constants
93 Node *con1=NULL;
94 uint i4;
95 for( i4 = 1; i4 < phi->req(); i4++ ) {
96 con1 = phi->in(i4);
97 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
98 if( con1->is_Con() ) break; // Found a constant
99 // Also allow null-vs-not-null checks
100 const TypePtr *tp = igvn->type(con1)->isa_ptr();
101 if( tp && tp->_ptr == TypePtr::NotNull )
102 break;
103 }
104 if( i4 >= phi->req() ) return NULL; // Found no constants
105
106 igvn->C->set_has_split_ifs(true); // Has chance for split-if
107
108 // Make sure that the compare can be constant folded away
109 Node *cmp2 = cmp->clone();
110 cmp2->set_req(1,con1);
111 cmp2->set_req(2,con2);
112 const Type *t = cmp2->Value(igvn);
113 // This compare is dead, so whack it!
114 igvn->remove_dead_node(cmp2);
115 if( !t->singleton() ) return NULL;
116
117 // No intervening control, like a simple Call
118 Node *r = iff->in(0);
119 if( !r->is_Region() ) return NULL;
120 if (r->is_Loop() && r->in(LoopNode::LoopBackControl)->is_top()) return NULL; // going away anyway
121 if( phi->region() != r ) return NULL;
122 // No other users of the cmp/bool
123 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
124 //tty->print_cr("many users of cmp/bool");
125 return NULL;
126 }
127
128 // Make sure we can determine where all the uses of merged values go
129 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
130 Node* u = r->fast_out(j);
131 if( u == r ) continue;
132 if( u == iff ) continue;
133 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
134 if( !u->is_Phi() ) {
135 /*
136 if( u->is_Start() ) {
137 tty->print_cr("Region has inlined start use");
138 } else {
139 tty->print_cr("Region has odd use");
140 u->dump(2);
141 }*/
142 return NULL;
143 }
144 if( u != phi ) {
145 // CNC - do not allow any other merged value
146 //tty->print_cr("Merging another value");
147 //u->dump(2);
148 return NULL;
149 }
150 // Make sure we can account for all Phi uses
151 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
152 Node* v = u->fast_out(k); // User of the phi
153 // CNC - Allow only really simple patterns.
154 // In particular I disallow AddP of the Phi, a fairly common pattern
155 if (v == cmp) continue; // The compare is OK
156 if (v->is_ConstraintCast()) {
157 // If the cast is derived from data flow edges, it may not have a control edge.
158 // If so, it should be safe to split. But follow-up code can not deal with
159 // this (l. 359). So skip.
160 if (v->in(0) == NULL) {
161 return NULL;
162 }
163 if (v->in(0)->in(0) == iff) {
164 continue; // CastPP/II of the IfNode is OK
165 }
166 }
167 // Disabled following code because I cannot tell if exactly one
168 // path dominates without a real dominator check. CNC 9/9/1999
169 //uint vop = v->Opcode();
170 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
171 // Node *r = v->in(0); // Get controlling point
172 // if( !r ) return NULL; // Degraded to a copy
173 // // Find exactly one path in (either True or False doms, but not IFF)
174 // int cnt = 0;
175 // for( uint i = 1; i < r->req(); i++ )
176 // if( r->in(i) && r->in(i)->in(0) == iff )
177 // cnt++;
178 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
179 //}
180 if( !v->is_Call() ) {
181 /*
182 if( v->Opcode() == Op_AddP ) {
183 tty->print_cr("Phi has AddP use");
184 } else if( v->Opcode() == Op_CastPP ) {
185 tty->print_cr("Phi has CastPP use");
186 } else if( v->Opcode() == Op_CastII ) {
187 tty->print_cr("Phi has CastII use");
188 } else {
189 tty->print_cr("Phi has use I cant be bothered with");
190 }
191 */
192 }
193 return NULL;
194
195 /* CNC - Cut out all the fancy acceptance tests
196 // Can we clone this use when doing the transformation?
197 // If all uses are from Phis at this merge or constants, then YES.
198 if( !v->in(0) && v != cmp ) {
199 tty->print_cr("Phi has free-floating use");
200 v->dump(2);
201 return NULL;
202 }
203 for( uint l = 1; l < v->req(); l++ ) {
204 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
205 !v->in(l)->is_Con() ) {
206 tty->print_cr("Phi has use");
207 v->dump(2);
208 return NULL;
209 } // End of if Phi-use input is neither Phi nor Constant
210 } // End of for all inputs to Phi-use
211 */
212 } // End of for all uses of Phi
213 } // End of for all uses of Region
214
215 // Only do this if the IF node is in a sane state
216 if (iff->outcnt() != 2)
217 return NULL;
218
219 // Got a hit! Do the Mondo Hack!
220 //
221 //ABC a1c def ghi B 1 e h A C a c d f g i
222 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
223 // cmp - 2 cmp - 2 cmp - 2
224 // bool bool_c bool_x
225 // if if_c if_x
226 // T F T F T F
227 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
228 //
229 // Split the paths coming into the merge point into 2 separate groups of
230 // merges. On the left will be all the paths feeding constants into the
231 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
232 // will fold up into a constant; this will let the Cmp fold up as well as
233 // all the control flow. Below the original IF we have 2 control
234 // dependent regions, 's' and 't'. Now we will merge the two paths
235 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
236 // likely 2 or more) will promptly constant fold away.
237 PhaseGVN *phase = igvn;
238
239 // Make a region merging constants and a region merging the rest
240 uint req_c = 0;
241 Node* predicate_proj = NULL;
242 int nb_predicate_proj = 0;
243 for (uint ii = 1; ii < r->req(); ii++) {
244 if (phi->in(ii) == con1) {
245 req_c++;
246 }
247 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
248 if (proj != NULL) {
249 nb_predicate_proj++;
250 predicate_proj = proj;
251 }
252 }
253
254 // If all the defs of the phi are the same constant, we already have the desired end state.
255 // Skip the split that would create empty phi and region nodes.
256 if((r->req() - req_c) == 1) {
257 return NULL;
258 }
259
260 if (nb_predicate_proj > 1) {
261 // Can happen in case of loop unswitching and when the loop is
262 // optimized out: it's not a loop anymore so we don't care about
263 // predicates.
264 assert(!r->is_Loop(), "this must not be a loop anymore");
265 predicate_proj = NULL;
266 }
267 Node* predicate_c = NULL;
268 Node* predicate_x = NULL;
269 bool counted_loop = r->is_CountedLoop();
270
271 Node *region_c = new RegionNode(req_c + 1);
272 Node *phi_c = con1;
273 uint len = r->req();
274 Node *region_x = new RegionNode(len - req_c);
275 Node *phi_x = PhiNode::make_blank(region_x, phi);
276 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
277 if (phi->in(i) == con1) {
278 region_c->init_req( i_c++, r ->in(i) );
279 if (r->in(i) == predicate_proj)
280 predicate_c = predicate_proj;
281 } else {
282 region_x->init_req( i_x, r ->in(i) );
283 phi_x ->init_req( i_x++, phi->in(i) );
284 if (r->in(i) == predicate_proj)
285 predicate_x = predicate_proj;
286 }
287 }
288 if (predicate_c != NULL && (req_c > 1)) {
289 assert(predicate_x == NULL, "only one predicate entry expected");
290 predicate_c = NULL; // Do not clone predicate below merge point
291 }
292 if (predicate_x != NULL && ((len - req_c) > 2)) {
293 assert(predicate_c == NULL, "only one predicate entry expected");
294 predicate_x = NULL; // Do not clone predicate below merge point
295 }
296
297 // Register the new RegionNodes but do not transform them. Cannot
298 // transform until the entire Region/Phi conglomerate has been hacked
299 // as a single huge transform.
300 igvn->register_new_node_with_optimizer( region_c );
301 igvn->register_new_node_with_optimizer( region_x );
302 // Prevent the untimely death of phi_x. Currently he has no uses. He is
303 // about to get one. If this only use goes away, then phi_x will look dead.
304 // However, he will be picking up some more uses down below.
305 Node *hook = new Node(4);
306 hook->init_req(0, phi_x);
307 hook->init_req(1, phi_c);
308 phi_x = phase->transform( phi_x );
309
310 // Make the compare
311 Node *cmp_c = phase->makecon(t);
312 Node *cmp_x = cmp->clone();
313 cmp_x->set_req(1,phi_x);
314 cmp_x->set_req(2,con2);
315 cmp_x = phase->transform(cmp_x);
316 // Make the bool
317 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
318 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
319 // Make the IfNode
320 IfNode* iff_c = iff->clone()->as_If();
321 iff_c->set_req(0, region_c);
322 iff_c->set_req(1, b_c);
323 igvn->set_type_bottom(iff_c);
324 igvn->_worklist.push(iff_c);
325 hook->init_req(2, iff_c);
326
327 IfNode* iff_x = iff->clone()->as_If();
328 iff_x->set_req(0, region_x);
329 iff_x->set_req(1, b_x);
330 igvn->set_type_bottom(iff_x);
331 igvn->_worklist.push(iff_x);
332 hook->init_req(3, iff_x);
333
334 // Make the true/false arms
335 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
336 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
337 if (predicate_c != NULL) {
338 assert(predicate_x == NULL, "only one predicate entry expected");
339 // Clone loop predicates to each path
340 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
341 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
342 }
343 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
344 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
345 if (predicate_x != NULL) {
346 assert(predicate_c == NULL, "only one predicate entry expected");
347 // Clone loop predicates to each path
348 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
349 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
350 }
351
352 // Merge the TRUE paths
353 Node *region_s = new RegionNode(3);
354 igvn->_worklist.push(region_s);
355 region_s->init_req(1, iff_c_t);
356 region_s->init_req(2, iff_x_t);
357 igvn->register_new_node_with_optimizer( region_s );
358
359 // Merge the FALSE paths
360 Node *region_f = new RegionNode(3);
361 igvn->_worklist.push(region_f);
362 region_f->init_req(1, iff_c_f);
363 region_f->init_req(2, iff_x_f);
364 igvn->register_new_node_with_optimizer( region_f );
365
366 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
367 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
368 cmp->set_req(2,NULL);
369 // Check for all uses of the Phi and give them a new home.
370 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
371 Node *phi_s = NULL; // do not construct unless needed
372 Node *phi_f = NULL; // do not construct unless needed
373 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
374 Node* v = phi->last_out(i2);// User of the phi
375 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
376 uint vop = v->Opcode();
377 Node *proj = NULL;
378 if( vop == Op_Phi ) { // Remote merge point
379 Node *r = v->in(0);
380 for (uint i3 = 1; i3 < r->req(); i3++)
381 if (r->in(i3) && r->in(i3)->in(0) == iff) {
382 proj = r->in(i3);
383 break;
384 }
385 } else if( v->is_ConstraintCast() ) {
386 proj = v->in(0); // Controlling projection
387 } else {
388 assert( 0, "do not know how to handle this guy" );
389 }
390
391 Node *proj_path_data, *proj_path_ctrl;
392 if( proj->Opcode() == Op_IfTrue ) {
393 if( phi_s == NULL ) {
394 // Only construct phi_s if needed, otherwise provides
395 // interfering use.
396 phi_s = PhiNode::make_blank(region_s,phi);
397 phi_s->init_req( 1, phi_c );
398 phi_s->init_req( 2, phi_x );
399 hook->add_req(phi_s);
400 phi_s = phase->transform(phi_s);
401 }
402 proj_path_data = phi_s;
403 proj_path_ctrl = region_s;
404 } else {
405 if( phi_f == NULL ) {
406 // Only construct phi_f if needed, otherwise provides
407 // interfering use.
408 phi_f = PhiNode::make_blank(region_f,phi);
409 phi_f->init_req( 1, phi_c );
410 phi_f->init_req( 2, phi_x );
411 hook->add_req(phi_f);
412 phi_f = phase->transform(phi_f);
413 }
414 proj_path_data = phi_f;
415 proj_path_ctrl = region_f;
416 }
417
418 // Fixup 'v' for for the split
419 if( vop == Op_Phi ) { // Remote merge point
420 uint i;
421 for( i = 1; i < v->req(); i++ )
422 if( v->in(i) == phi )
423 break;
424 v->set_req(i, proj_path_data );
425 } else if( v->is_ConstraintCast() ) {
426 v->set_req(0, proj_path_ctrl );
427 v->set_req(1, proj_path_data );
428 } else
429 ShouldNotReachHere();
430 }
431
432 // Now replace the original iff's True/False with region_s/region_t.
433 // This makes the original iff go dead.
434 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
435 Node* p = iff->last_out(i3);
436 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
437 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
438 // Replace p with u
439 igvn->add_users_to_worklist(p);
440 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
441 Node* x = p->last_out(l);
442 igvn->hash_delete(x);
443 uint uses_found = 0;
444 for( uint j = 0; j < x->req(); j++ ) {
445 if( x->in(j) == p ) {
446 x->set_req(j, u);
447 uses_found++;
448 }
449 }
450 l -= uses_found; // we deleted 1 or more copies of this edge
451 }
452 igvn->remove_dead_node(p);
453 }
454
455 // Force the original merge dead
456 igvn->hash_delete(r);
457 // First, remove region's dead users.
458 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
459 Node* u = r->last_out(l);
460 if( u == r ) {
461 r->set_req(0, NULL);
462 } else {
463 assert(u->outcnt() == 0, "only dead users");
464 igvn->remove_dead_node(u);
465 }
466 l -= 1;
467 }
468 igvn->remove_dead_node(r);
469
470 // Now remove the bogus extra edges used to keep things alive
471 igvn->remove_dead_node( hook );
472
473 // Must return either the original node (now dead) or a new node
474 // (Do not return a top here, since that would break the uniqueness of top.)
475 return new ConINode(TypeInt::ZERO);
476 }
477
478 // if this IfNode follows a range check pattern return the projection
479 // for the failed path
480 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
481 Node* b = in(1);
482 if (b == NULL || !b->is_Bool()) return NULL;
483 BoolNode* bn = b->as_Bool();
484 Node* cmp = bn->in(1);
485 if (cmp == NULL) return NULL;
486 if (cmp->Opcode() != Op_CmpU) return NULL;
487
488 l = cmp->in(1);
489 r = cmp->in(2);
490 flip_test = 1;
491 if (bn->_test._test == BoolTest::le) {
492 l = cmp->in(2);
493 r = cmp->in(1);
494 flip_test = 2;
495 } else if (bn->_test._test != BoolTest::lt) {
496 return NULL;
497 }
498 if (l->is_top()) return NULL; // Top input means dead test
499 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return NULL;
500
501 // We have recognized one of these forms:
502 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
503 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
504
505 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
506 return iftrap;
507 }
508
509
510 //------------------------------is_range_check---------------------------------
511 // Return 0 if not a range check. Return 1 if a range check and set index and
512 // offset. Return 2 if we had to negate the test. Index is NULL if the check
513 // is versus a constant.
514 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
515 int flip_test = 0;
516 Node* l = NULL;
517 Node* r = NULL;
518 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
519
520 if (iftrap == NULL) {
521 return 0;
522 }
523
524 // Make sure it's a real range check by requiring an uncommon trap
525 // along the OOB path. Otherwise, it's possible that the user wrote
526 // something which optimized to look like a range check but behaves
527 // in some other way.
528 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
529 return 0;
530 }
531
532 // Look for index+offset form
533 Node* ind = l;
534 jint off = 0;
535 if (l->is_top()) {
536 return 0;
537 } else if (l->Opcode() == Op_AddI) {
538 if ((off = l->in(1)->find_int_con(0)) != 0) {
539 ind = l->in(2)->uncast();
540 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
541 ind = l->in(1)->uncast();
542 }
543 } else if ((off = l->find_int_con(-1)) >= 0) {
544 // constant offset with no variable index
545 ind = NULL;
546 } else {
547 // variable index with no constant offset (or dead negative index)
548 off = 0;
549 }
550
551 // Return all the values:
552 index = ind;
553 offset = off;
554 range = r;
555 return flip_test;
556 }
557
558 //------------------------------adjust_check-----------------------------------
559 // Adjust (widen) a prior range check
560 static void adjust_check(Node* proj, Node* range, Node* index,
561 int flip, jint off_lo, PhaseIterGVN* igvn) {
562 PhaseGVN *gvn = igvn;
563 // Break apart the old check
564 Node *iff = proj->in(0);
565 Node *bol = iff->in(1);
566 if( bol->is_top() ) return; // In case a partially dead range check appears
567 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
568 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
569 if( !bol->is_Bool() ) return;
570
571 Node *cmp = bol->in(1);
572 // Compute a new check
573 Node *new_add = gvn->intcon(off_lo);
574 if( index ) {
575 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
576 }
577 Node *new_cmp = (flip == 1)
578 ? new CmpUNode( new_add, range )
579 : new CmpUNode( range, new_add );
580 new_cmp = gvn->transform(new_cmp);
581 // See if no need to adjust the existing check
582 if( new_cmp == cmp ) return;
583 // Else, adjust existing check
584 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
585 igvn->rehash_node_delayed( iff );
586 iff->set_req_X( 1, new_bol, igvn );
587 }
588
589 //------------------------------up_one_dom-------------------------------------
590 // Walk up the dominator tree one step. Return NULL at root or true
591 // complex merges. Skips through small diamonds.
592 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
593 Node *dom = curr->in(0);
594 if( !dom ) // Found a Region degraded to a copy?
595 return curr->nonnull_req(); // Skip thru it
596
597 if( curr != dom ) // Normal walk up one step?
598 return dom;
599
600 // Use linear_only if we are still parsing, since we cannot
601 // trust the regions to be fully filled in.
602 if (linear_only)
603 return NULL;
604
605 if( dom->is_Root() )
606 return NULL;
607
608 // Else hit a Region. Check for a loop header
609 if( dom->is_Loop() )
610 return dom->in(1); // Skip up thru loops
611
612 // Check for small diamonds
613 Node *din1, *din2, *din3, *din4;
614 if( dom->req() == 3 && // 2-path merge point
615 (din1 = dom ->in(1)) && // Left path exists
616 (din2 = dom ->in(2)) && // Right path exists
617 (din3 = din1->in(0)) && // Left path up one
618 (din4 = din2->in(0)) ) { // Right path up one
619 if( din3->is_Call() && // Handle a slow-path call on either arm
620 (din3 = din3->in(0)) )
621 din3 = din3->in(0);
622 if( din4->is_Call() && // Handle a slow-path call on either arm
623 (din4 = din4->in(0)) )
624 din4 = din4->in(0);
625 if( din3 == din4 && din3->is_If() )
626 return din3; // Skip around diamonds
627 }
628
629 // Give up the search at true merges
630 return NULL; // Dead loop? Or hit root?
631 }
632
633
634 //------------------------------filtered_int_type--------------------------------
635 // Return a possibly more restrictive type for val based on condition control flow for an if
636 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
637 assert(if_proj &&
638 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
639 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
640 IfNode* iff = if_proj->in(0)->as_If();
641 if (iff->in(1) && iff->in(1)->is_Bool()) {
642 BoolNode* bol = iff->in(1)->as_Bool();
643 if (bol->in(1) && bol->in(1)->is_Cmp()) {
644 const CmpNode* cmp = bol->in(1)->as_Cmp();
645 if (cmp->in(1) == val) {
646 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
647 if (cmp2_t != NULL) {
648 jint lo = cmp2_t->_lo;
649 jint hi = cmp2_t->_hi;
650 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
651 switch (msk) {
652 case BoolTest::ne:
653 // Can't refine type
654 return NULL;
655 case BoolTest::eq:
656 return cmp2_t;
657 case BoolTest::lt:
658 lo = TypeInt::INT->_lo;
659 if (hi - 1 < hi) {
660 hi = hi - 1;
661 }
662 break;
663 case BoolTest::le:
664 lo = TypeInt::INT->_lo;
665 break;
666 case BoolTest::gt:
667 if (lo + 1 > lo) {
668 lo = lo + 1;
669 }
670 hi = TypeInt::INT->_hi;
671 break;
672 case BoolTest::ge:
673 // lo unchanged
674 hi = TypeInt::INT->_hi;
675 break;
676 default:
677 break;
678 }
679 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
680 return rtn_t;
681 }
682 }
683 }
684 }
685 }
686 return NULL;
687 }
688
689 //------------------------------fold_compares----------------------------
690 // See if a pair of CmpIs can be converted into a CmpU. In some cases
691 // the direction of this if is determined by the preceding if so it
692 // can be eliminate entirely.
693 //
694 // Given an if testing (CmpI n v) check for an immediately control
695 // dependent if that is testing (CmpI n v2) and has one projection
696 // leading to this if and the other projection leading to a region
697 // that merges one of this ifs control projections.
698 //
699 // If
700 // / |
701 // / |
702 // / |
703 // If |
704 // /\ |
705 // / \ |
706 // / \ |
707 // / Region
708 //
709 // Or given an if testing (CmpI n v) check for a dominating if that is
710 // testing (CmpI n v2), both having one projection leading to an
711 // uncommon trap. Allow Another independent guard in between to cover
712 // an explicit range check:
713 // if (index < 0 || index >= array.length) {
714 // which may need a null check to guard the LoadRange
715 //
716 // If
717 // / \
718 // / \
719 // / \
720 // If unc
721 // /\
722 // / \
723 // / \
724 // / unc
725 //
726
727 // Is the comparison for this If suitable for folding?
728 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
729 return in(1) != NULL &&
730 in(1)->is_Bool() &&
731 in(1)->in(1) != NULL &&
732 in(1)->in(1)->Opcode() == Op_CmpI &&
733 in(1)->in(1)->in(2) != NULL &&
734 in(1)->in(1)->in(2) != igvn->C->top() &&
735 (in(1)->as_Bool()->_test.is_less() ||
736 in(1)->as_Bool()->_test.is_greater());
737 }
738
739 // Is a dominating control suitable for folding with this if?
740 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
741 return ctrl != NULL &&
742 ctrl->is_Proj() &&
743 ctrl->in(0) != NULL &&
744 ctrl->in(0)->Opcode() == Op_If &&
745 ctrl->in(0)->outcnt() == 2 &&
746 ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
747 // Must compare same value
748 ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
749 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
750 }
751
752 // Do this If and the dominating If share a region?
753 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
754 ProjNode* otherproj = proj->other_if_proj();
755 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
756 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
757 success = NULL;
758 fail = NULL;
759
760 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
761 for (int i = 0; i < 2; i++) {
762 ProjNode* proj = proj_out(i);
763 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
764 success = proj;
765 } else if (fail == NULL) {
766 fail = proj;
767 } else {
768 success = fail = NULL;
769 }
770 }
771 }
772 return success != NULL && fail != NULL;
773 }
774
775 // Return projection that leads to an uncommon trap if any
776 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
777 for (int i = 0; i < 2; i++) {
778 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
779 if (call != NULL) {
780 return proj_out(i);
781 }
782 }
783 return NULL;
784 }
785
786 // Do this If and the dominating If both branch out to an uncommon trap
787 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
788 ProjNode* otherproj = proj->other_if_proj();
789 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
790
791 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
792 // We need to re-execute the folded Ifs after deoptimization from the merged traps
793 if (!dom_unc->jvms()->should_reexecute()) {
794 return false;
795 }
796
797 CallStaticJavaNode* unc = NULL;
798 ProjNode* unc_proj = uncommon_trap_proj(unc);
799 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
800 if (dom_unc == unc) {
801 // Allow the uncommon trap to be shared through a region
802 RegionNode* r = unc->in(0)->as_Region();
803 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
804 return false;
805 }
806 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
807 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
808 return false;
809 }
810
811 // Different methods and methods containing jsrs are not supported.
812 ciMethod* method = unc->jvms()->method();
813 ciMethod* dom_method = dom_unc->jvms()->method();
814 if (method != dom_method || method->has_jsrs()) {
815 return false;
816 }
817 // Check that both traps are in the same activation of the method (instead
818 // of two activations being inlined through different call sites) by verifying
819 // that the call stacks are equal for both JVMStates.
820 JVMState* dom_caller = dom_unc->jvms()->caller();
821 JVMState* caller = unc->jvms()->caller();
822 if ((dom_caller == NULL) != (caller == NULL)) {
823 // The current method must either be inlined into both dom_caller and
824 // caller or must not be inlined at all (top method). Bail out otherwise.
825 return false;
826 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
827 return false;
828 }
829 // Check that the bci of the dominating uncommon trap dominates the bci
830 // of the dominated uncommon trap. Otherwise we may not re-execute
831 // the dominated check after deoptimization from the merged uncommon trap.
832 ciTypeFlow* flow = dom_method->get_flow_analysis();
833 int bci = unc->jvms()->bci();
834 int dom_bci = dom_unc->jvms()->bci();
835 if (!flow->is_dominated_by(bci, dom_bci)) {
836 return false;
837 }
838
839 // See merge_uncommon_traps: the reason of the uncommon trap
840 // will be changed and the state of the dominating If will be
841 // used. Checked that we didn't apply this transformation in a
842 // previous compilation and it didn't cause too many traps
843 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
844 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
845 success = unc_proj;
846 fail = unc_proj->other_if_proj();
847 return true;
848 }
849 }
850 }
851 return false;
852 }
853
854 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
855 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
856 Node* this_cmp = in(1)->in(1);
857 BoolNode* this_bool = in(1)->as_Bool();
858 IfNode* dom_iff = proj->in(0)->as_If();
859 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
860 Node* lo = dom_iff->in(1)->in(1)->in(2);
861 Node* hi = this_cmp->in(2);
862 Node* n = this_cmp->in(1);
863 ProjNode* otherproj = proj->other_if_proj();
864
865 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
866 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
867
868 BoolTest::mask lo_test = dom_bool->_test._test;
869 BoolTest::mask hi_test = this_bool->_test._test;
870 BoolTest::mask cond = hi_test;
871
872 // convert:
873 //
874 // dom_bool = x {<,<=,>,>=} a
875 // / \
876 // proj = {True,False} / \ otherproj = {False,True}
877 // /
878 // this_bool = x {<,<=} b
879 // / \
880 // fail = {True,False} / \ success = {False,True}
881 // /
882 //
883 // (Second test guaranteed canonicalized, first one may not have
884 // been canonicalized yet)
885 //
886 // into:
887 //
888 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
889 // / \
890 // fail / \ success
891 // /
892 //
893
894 // Figure out which of the two tests sets the upper bound and which
895 // sets the lower bound if any.
896 Node* adjusted_lim = NULL;
897 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
898 assert((dom_bool->_test.is_less() && !proj->_con) ||
899 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
900 // this test was canonicalized
901 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
902
903 // this_bool = <
904 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
905 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
906 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
907 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
908 // x in ]a, b[ on the fail (= True) projection, b > a:
909 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
910 // this_bool = <=
911 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
912 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
913 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
914 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
915 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
916 // x in ]a, b] on the fail (= True) projection b+1 > a:
917 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
918 // 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
919
920 if (hi_test == BoolTest::lt) {
921 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
922 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
923 }
924 } else {
925 assert(hi_test == BoolTest::le, "bad test");
926 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
927 adjusted_lim = igvn->transform(new SubINode(hi, lo));
928 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
929 cond = BoolTest::lt;
930 } else {
931 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
932 adjusted_lim = igvn->transform(new SubINode(hi, lo));
933 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
934 cond = BoolTest::lt;
935 }
936 }
937 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
938
939 // this_bool = <
940 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
941 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
942 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
943 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
944 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
945 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
946 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
947 // this_bool = <=
948 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
949 // x in ]b, a[ on the fail (= False) projection, a > b:
950 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
951 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
952 // x in ]b, a] on the fail (= False) projection, a+1 > b:
953 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
954 // 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
955
956 swap(lo, hi);
957 swap(lo_type, hi_type);
958 swap(lo_test, hi_test);
959
960 assert((dom_bool->_test.is_less() && proj->_con) ||
961 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
962 // this test was canonicalized
963 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
964
965 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
966
967 if (lo_test == BoolTest::lt) {
968 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
969 cond = BoolTest::ge;
970 } else {
971 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
972 adjusted_lim = igvn->transform(new SubINode(hi, lo));
973 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
974 cond = BoolTest::ge;
975 }
976 } else if (lo_test == BoolTest::le) {
977 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
978 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
979 cond = BoolTest::ge;
980 } else {
981 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
982 adjusted_lim = igvn->transform(new SubINode(hi, lo));
983 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
984 cond = BoolTest::ge;
985 }
986 }
987 } else {
988 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
989 if (failtype != NULL) {
990 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
991 if (type2 != NULL) {
992 failtype = failtype->join(type2)->is_int();
993 if (failtype->_lo > failtype->_hi) {
994 // previous if determines the result of this if so
995 // replace Bool with constant
996 igvn->_worklist.push(in(1));
997 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
998 return true;
999 }
1000 }
1001 }
1002 lo = NULL;
1003 hi = NULL;
1004 }
1005
1006 if (lo && hi) {
1007 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1008 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
1009 if (adjusted_lim == NULL) {
1010 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1011 }
1012 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1013 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1014
1015 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1016 igvn->_worklist.push(in(1));
1017 igvn->replace_input_of(this, 1, newbool);
1018
1019 return true;
1020 }
1021 return false;
1022 }
1023
1024 // Merge the branches that trap for this If and the dominating If into
1025 // a single region that branches to the uncommon trap for the
1026 // dominating If
1027 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1028 Node* res = this;
1029 assert(success->in(0) == this, "bad projection");
1030
1031 ProjNode* otherproj = proj->other_if_proj();
1032
1033 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1034 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1035
1036 if (unc != dom_unc) {
1037 Node* r = new RegionNode(3);
1038
1039 r->set_req(1, otherproj);
1040 r->set_req(2, success);
1041 r = igvn->transform(r);
1042 assert(r->is_Region(), "can't go away");
1043
1044 // Make both If trap at the state of the first If: once the CmpI
1045 // nodes are merged, if we trap we don't know which of the CmpI
1046 // nodes would have caused the trap so we have to restart
1047 // execution at the first one
1048 igvn->replace_input_of(dom_unc, 0, r);
1049 igvn->replace_input_of(unc, 0, igvn->C->top());
1050 }
1051 int trap_request = dom_unc->uncommon_trap_request();
1052 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1053 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1054
1055 int flip_test = 0;
1056 Node* l = NULL;
1057 Node* r = NULL;
1058
1059 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1060 // If this looks like a range check, change the trap to
1061 // Reason_range_check so the compiler recognizes it as a range
1062 // check and applies the corresponding optimizations
1063 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1064
1065 improve_address_types(l, r, fail, igvn);
1066
1067 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1068 } else if (unc != dom_unc) {
1069 // If we trap we won't know what CmpI would have caused the trap
1070 // so use a special trap reason to mark this pair of CmpI nodes as
1071 // bad candidate for folding. On recompilation we won't fold them
1072 // and we may trap again but this time we'll know what branch
1073 // traps
1074 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1075 }
1076 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1077 return res;
1078 }
1079
1080 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1081 // of a rangecheck on index i, on 64 bit the compares may be followed
1082 // by memory accesses using i as index. In that case, the CmpU tells
1083 // us something about the values taken by i that can help the compiler
1084 // (see Compile::conv_I2X_index())
1085 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1086 #ifdef _LP64
1087 ResourceMark rm;
1088 Node_Stack stack(2);
1089
1090 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1091 const TypeInt* array_size = igvn->type(r)->is_int();
1092
1093 stack.push(l, 0);
1094
1095 while(stack.size() > 0) {
1096 Node* n = stack.node();
1097 uint start = stack.index();
1098
1099 uint i = start;
1100 for (; i < n->outcnt(); i++) {
1101 Node* use = n->raw_out(i);
1102 if (stack.size() == 1) {
1103 if (use->Opcode() == Op_ConvI2L) {
1104 const TypeLong* bounds = use->as_Type()->type()->is_long();
1105 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1106 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1107 stack.set_index(i+1);
1108 stack.push(use, 0);
1109 break;
1110 }
1111 }
1112 } else if (use->is_Mem()) {
1113 Node* ctrl = use->in(0);
1114 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1115 ctrl = up_one_dom(ctrl);
1116 }
1117 if (ctrl == fail) {
1118 Node* init_n = stack.node_at(1);
1119 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1120 // Create a new narrow ConvI2L node that is dependent on the range check
1121 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1122
1123 // The type of the ConvI2L may be widen and so the new
1124 // ConvI2L may not be better than an existing ConvI2L
1125 if (new_n != init_n) {
1126 for (uint j = 2; j < stack.size(); j++) {
1127 Node* n = stack.node_at(j);
1128 Node* clone = n->clone();
1129 int rep = clone->replace_edge(init_n, new_n);
1130 assert(rep > 0, "can't find expected node?");
1131 clone = igvn->transform(clone);
1132 init_n = n;
1133 new_n = clone;
1134 }
1135 igvn->hash_delete(use);
1136 int rep = use->replace_edge(init_n, new_n);
1137 assert(rep > 0, "can't find expected node?");
1138 igvn->transform(use);
1139 if (init_n->outcnt() == 0) {
1140 igvn->_worklist.push(init_n);
1141 }
1142 }
1143 }
1144 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1145 igvn->type(use)->isa_ptr())) {
1146 stack.set_index(i+1);
1147 stack.push(use, 0);
1148 break;
1149 }
1150 }
1151 if (i == n->outcnt()) {
1152 stack.pop();
1153 }
1154 }
1155 #endif
1156 }
1157
1158 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1159 if (in(1) != NULL &&
1160 in(1)->in(1) != NULL &&
1161 in(1)->in(1)->in(2) != NULL) {
1162 Node* other = in(1)->in(1)->in(2);
1163 if (other->Opcode() == Op_LoadRange &&
1164 ((other->in(0) != NULL && other->in(0) == proj) ||
1165 (other->in(0) == NULL &&
1166 other->in(2) != NULL &&
1167 other->in(2)->is_AddP() &&
1168 other->in(2)->in(1) != NULL &&
1169 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1170 other->in(2)->in(1)->in(0) == proj))) {
1171 return true;
1172 }
1173 }
1174 return false;
1175 }
1176
1177 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1178 Node* other = in(1)->in(1)->in(2);
1179 if (other->in(MemNode::Address) != NULL &&
1180 proj->in(0)->in(1) != NULL &&
1181 proj->in(0)->in(1)->is_Bool() &&
1182 proj->in(0)->in(1)->in(1) != NULL &&
1183 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1184 proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1185 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1186 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1187 return true;
1188 }
1189 return false;
1190 }
1191
1192 // Check that the If that is in between the 2 integer comparisons has
1193 // no side effect
1194 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1195 if (proj != NULL &&
1196 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1197 proj->outcnt() <= 2) {
1198 if (proj->outcnt() == 1 ||
1199 // Allow simple null check from LoadRange
1200 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1201 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1202 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1203
1204 // reroute_side_effect_free_unc changes the state of this
1205 // uncommon trap to restart execution at the previous
1206 // CmpI. Check that this change in a previous compilation didn't
1207 // cause too many traps.
1208 int trap_request = unc->uncommon_trap_request();
1209 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1210
1211 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1212 return false;
1213 }
1214
1215 return true;
1216 }
1217 }
1218 return false;
1219 }
1220
1221 // Make the If between the 2 integer comparisons trap at the state of
1222 // the first If: the last CmpI is the one replaced by a CmpU and the
1223 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1224 // won't be guarded by the first CmpI anymore. It can trap in cases
1225 // where the first CmpI would have prevented it from executing: on a
1226 // trap, we need to restart execution at the state of the first CmpI
1227 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1228 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1229 ProjNode* otherproj = proj->other_if_proj();
1230 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1231 Node* call_proj = dom_unc->unique_ctrl_out();
1232 Node* halt = call_proj->unique_ctrl_out();
1233
1234 Node* new_unc = dom_unc->clone();
1235 call_proj = call_proj->clone();
1236 halt = halt->clone();
1237 Node* c = otherproj->clone();
1238
1239 c = igvn->transform(c);
1240 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1241 new_unc->set_req(0, c);
1242 new_unc = igvn->transform(new_unc);
1243 call_proj->set_req(0, new_unc);
1244 call_proj = igvn->transform(call_proj);
1245 halt->set_req(0, call_proj);
1246 halt = igvn->transform(halt);
1247
1248 igvn->replace_node(otherproj, igvn->C->top());
1249 igvn->C->root()->add_req(halt);
1250 }
1251
1252 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1253 if (Opcode() != Op_If) return NULL;
1254
1255 if (cmpi_folds(igvn)) {
1256 Node* ctrl = in(0);
1257 if (is_ctrl_folds(ctrl, igvn) &&
1258 ctrl->outcnt() == 1) {
1259 // A integer comparison immediately dominated by another integer
1260 // comparison
1261 ProjNode* success = NULL;
1262 ProjNode* fail = NULL;
1263 ProjNode* dom_cmp = ctrl->as_Proj();
1264 if (has_shared_region(dom_cmp, success, fail) &&
1265 // Next call modifies graph so must be last
1266 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1267 return this;
1268 }
1269 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1270 // Next call modifies graph so must be last
1271 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1272 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1273 }
1274 return NULL;
1275 } else if (ctrl->in(0) != NULL &&
1276 ctrl->in(0)->in(0) != NULL) {
1277 ProjNode* success = NULL;
1278 ProjNode* fail = NULL;
1279 Node* dom = ctrl->in(0)->in(0);
1280 ProjNode* dom_cmp = dom->isa_Proj();
1281 ProjNode* other_cmp = ctrl->isa_Proj();
1282
1283 // Check if it's an integer comparison dominated by another
1284 // integer comparison with another test in between
1285 if (is_ctrl_folds(dom, igvn) &&
1286 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1287 is_side_effect_free_test(other_cmp, igvn) &&
1288 // Next call modifies graph so must be last
1289 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1290 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1291 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1292 }
1293 }
1294 }
1295 return NULL;
1296 }
1297
1298 //------------------------------remove_useless_bool----------------------------
1299 // Check for people making a useless boolean: things like
1300 // if( (x < y ? true : false) ) { ... }
1301 // Replace with if( x < y ) { ... }
1302 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1303 Node *i1 = iff->in(1);
1304 if( !i1->is_Bool() ) return NULL;
1305 BoolNode *bol = i1->as_Bool();
1306
1307 Node *cmp = bol->in(1);
1308 if( cmp->Opcode() != Op_CmpI ) return NULL;
1309
1310 // Must be comparing against a bool
1311 const Type *cmp2_t = phase->type( cmp->in(2) );
1312 if( cmp2_t != TypeInt::ZERO &&
1313 cmp2_t != TypeInt::ONE )
1314 return NULL;
1315
1316 // Find a prior merge point merging the boolean
1317 i1 = cmp->in(1);
1318 if( !i1->is_Phi() ) return NULL;
1319 PhiNode *phi = i1->as_Phi();
1320 if( phase->type( phi ) != TypeInt::BOOL )
1321 return NULL;
1322
1323 // Check for diamond pattern
1324 int true_path = phi->is_diamond_phi();
1325 if( true_path == 0 ) return NULL;
1326
1327 // Make sure that iff and the control of the phi are different. This
1328 // should really only happen for dead control flow since it requires
1329 // an illegal cycle.
1330 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1331
1332 // phi->region->if_proj->ifnode->bool->cmp
1333 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1334
1335 // Now get the 'sense' of the test correct so we can plug in
1336 // either iff2->in(1) or its complement.
1337 int flip = 0;
1338 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1339 else if( bol->_test._test != BoolTest::eq ) return NULL;
1340 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1341
1342 const Type *phi1_t = phase->type( phi->in(1) );
1343 const Type *phi2_t = phase->type( phi->in(2) );
1344 // Check for Phi(0,1) and flip
1345 if( phi1_t == TypeInt::ZERO ) {
1346 if( phi2_t != TypeInt::ONE ) return NULL;
1347 flip = 1-flip;
1348 } else {
1349 // Check for Phi(1,0)
1350 if( phi1_t != TypeInt::ONE ) return NULL;
1351 if( phi2_t != TypeInt::ZERO ) return NULL;
1352 }
1353 if( true_path == 2 ) {
1354 flip = 1-flip;
1355 }
1356
1357 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1358 assert(new_bol != iff->in(1), "must make progress");
1359 iff->set_req(1, new_bol);
1360 // Intervening diamond probably goes dead
1361 phase->C->set_major_progress();
1362 return iff;
1363 }
1364
1365 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1366
1367 struct RangeCheck {
1368 Node* ctl;
1369 jint off;
1370 };
1371
1372 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1373 if (remove_dead_region(phase, can_reshape)) return this;
1374 // No Def-Use info?
1375 if (!can_reshape) return NULL;
1376
1377 // Don't bother trying to transform a dead if
1378 if (in(0)->is_top()) return NULL;
1379 // Don't bother trying to transform an if with a dead test
1380 if (in(1)->is_top()) return NULL;
1381 // Another variation of a dead test
1382 if (in(1)->is_Con()) return NULL;
1383 // Another variation of a dead if
1384 if (outcnt() < 2) return NULL;
1385
1386 // Canonicalize the test.
1387 Node* idt_if = idealize_test(phase, this);
1388 if (idt_if != NULL) return idt_if;
1389
1390 // Try to split the IF
1391 PhaseIterGVN *igvn = phase->is_IterGVN();
1392 Node *s = split_if(this, igvn);
1393 if (s != NULL) return s;
1394
1395 return NodeSentinel;
1396 }
1397
1398 //------------------------------Ideal------------------------------------------
1399 // Return a node which is more "ideal" than the current node. Strip out
1400 // control copies
1401 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1402 Node* res = Ideal_common(phase, can_reshape);
1403 if (res != NodeSentinel) {
1404 return res;
1405 }
1406
1407 // Check for people making a useless boolean: things like
1408 // if( (x < y ? true : false) ) { ... }
1409 // Replace with if( x < y ) { ... }
1410 Node *bol2 = remove_useless_bool(this, phase);
1411 if( bol2 ) return bol2;
1412
1413 if (in(0) == NULL) return NULL; // Dead loop?
1414
1415 PhaseIterGVN *igvn = phase->is_IterGVN();
1416 Node* result = fold_compares(igvn);
1417 if (result != NULL) {
1418 return result;
1419 }
1420
1421 // Scan for an equivalent test
1422 Node *cmp;
1423 int dist = 0; // Cutoff limit for search
1424 int op = Opcode();
1425 if( op == Op_If &&
1426 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1427 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1428 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1429 dist = 64; // Limit for null-pointer scans
1430 } else {
1431 dist = 4; // Do not bother for random pointer tests
1432 }
1433 } else {
1434 dist = 4; // Limit for random junky scans
1435 }
1436
1437 Node* prev_dom = search_identical(dist);
1438
1439 if (prev_dom == NULL) {
1440 return NULL;
1441 }
1442
1443 // Replace dominated IfNode
1444 return dominated_by(prev_dom, igvn);
1445 }
1446
1447 //------------------------------dominated_by-----------------------------------
1448 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1449 #ifndef PRODUCT
1450 if (TraceIterativeGVN) {
1451 tty->print(" Removing IfNode: "); this->dump();
1452 }
1453 if (VerifyOpto && !igvn->allow_progress()) {
1454 // Found an equivalent dominating test,
1455 // we can not guarantee reaching a fix-point for these during iterativeGVN
1456 // since intervening nodes may not change.
1457 return NULL;
1458 }
1459 #endif
1460
1461 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1462 Node *idom = in(0);
1463 // Need opcode to decide which way 'this' test goes
1464 int prev_op = prev_dom->Opcode();
1465 Node *top = igvn->C->top(); // Shortcut to top
1466
1467 // Loop predicates may have depending checks which should not
1468 // be skipped. For example, range check predicate has two checks
1469 // for lower and upper bounds.
1470 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1471 if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)) {
1472 prev_dom = idom;
1473 }
1474
1475 // Now walk the current IfNode's projections.
1476 // Loop ends when 'this' has no more uses.
1477 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1478 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1479 igvn->add_users_to_worklist(ifp);
1480 // Check which projection it is and set target.
1481 // Data-target is either the dominating projection of the same type
1482 // or TOP if the dominating projection is of opposite type.
1483 // Data-target will be used as the new control edge for the non-CFG
1484 // nodes like Casts and Loads.
1485 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1486 // Control-target is just the If's immediate dominator or TOP.
1487 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1488
1489 // For each child of an IfTrue/IfFalse projection, reroute.
1490 // Loop ends when projection has no more uses.
1491 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1492 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1493 if( !s->depends_only_on_test() ) {
1494 // Find the control input matching this def-use edge.
1495 // For Regions it may not be in slot 0.
1496 uint l;
1497 for( l = 0; s->in(l) != ifp; l++ ) { }
1498 igvn->replace_input_of(s, l, ctrl_target);
1499 } else { // Else, for control producers,
1500 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1501 }
1502 } // End for each child of a projection
1503
1504 igvn->remove_dead_node(ifp);
1505 } // End for each IfTrue/IfFalse child of If
1506
1507 // Kill the IfNode
1508 igvn->remove_dead_node(this);
1509
1510 // Must return either the original node (now dead) or a new node
1511 // (Do not return a top here, since that would break the uniqueness of top.)
1512 return new ConINode(TypeInt::ZERO);
1513 }
1514
1515 Node* IfNode::search_identical(int dist) {
1516 // Setup to scan up the CFG looking for a dominating test
1517 Node* dom = in(0);
1518 Node* prev_dom = this;
1519 int op = Opcode();
1520 // Search up the dominator tree for an If with an identical test
1521 while (dom->Opcode() != op || // Not same opcode?
1522 dom->in(1) != in(1) || // Not same input 1?
1523 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1524 prev_dom->in(0) != dom) { // One path of test does not dominate?
1525 if (dist < 0) return NULL;
1526
1527 dist--;
1528 prev_dom = dom;
1529 dom = up_one_dom(dom);
1530 if (!dom) return NULL;
1531 }
1532
1533 // Check that we did not follow a loop back to ourselves
1534 if (this == dom) {
1535 return NULL;
1536 }
1537
1538 #ifndef PRODUCT
1539 if (dist > 2) { // Add to count of NULL checks elided
1540 explicit_null_checks_elided++;
1541 }
1542 #endif
1543
1544 return prev_dom;
1545 }
1546
1547 //------------------------------Identity---------------------------------------
1548 // If the test is constant & we match, then we are the input Control
1549 Node* IfProjNode::Identity(PhaseGVN* phase) {
1550 // Can only optimize if cannot go the other way
1551 const TypeTuple *t = phase->type(in(0))->is_tuple();
1552 if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1553 // During parsing (GVN) we don't remove dead code aggressively.
1554 // Cut off dead branch and let PhaseRemoveUseless take care of it.
1555 (!phase->is_IterGVN() ||
1556 // During IGVN, first wait for the dead branch to be killed.
1557 // Otherwise, the IfNode's control will have two control uses (the IfNode
1558 // that doesn't go away because it still has uses and this branch of the
1559 // If) which breaks other optimizations. Node::has_special_unique_user()
1560 // will cause this node to be reprocessed once the dead branch is killed.
1561 in(0)->outcnt() == 1))) {
1562 // IfNode control
1563 return in(0)->in(0);
1564 }
1565 // no progress
1566 return this;
1567 }
1568
1569 #ifndef PRODUCT
1570 //-------------------------------related---------------------------------------
1571 // An IfProjNode's related node set consists of its input (an IfNode) including
1572 // the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1573 // the restrictions for IfNode apply (see IfNode::rel).
1574 void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1575 Node* ifNode = this->in(0);
1576 in_rel->append(ifNode);
1577 if (compact) {
1578 ifNode->collect_nodes(in_rel, 3, false, true);
1579 } else {
1580 ifNode->collect_nodes_in_all_data(in_rel, false);
1581 }
1582 this->collect_nodes(out_rel, -1, false, false);
1583 }
1584
1585 //------------------------------dump_spec--------------------------------------
1586 void IfNode::dump_spec(outputStream *st) const {
1587 st->print("P=%f, C=%f",_prob,_fcnt);
1588 }
1589
1590 //-------------------------------related---------------------------------------
1591 // For an IfNode, the set of related output nodes is just the output nodes till
1592 // depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1593 // The related input nodes contain no control nodes, but all data nodes
1594 // pertaining to the condition. In compact mode, the input nodes are collected
1595 // up to a depth of 3.
1596 void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1597 if (compact) {
1598 this->collect_nodes(in_rel, 3, false, true);
1599 } else {
1600 this->collect_nodes_in_all_data(in_rel, false);
1601 }
1602 this->collect_nodes(out_rel, -2, false, false);
1603 }
1604 #endif
1605
1606 //------------------------------idealize_test----------------------------------
1607 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1608 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1609 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1610 // needed.
1611 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1612 assert(iff->in(0) != NULL, "If must be live");
1613
1614 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1615 Node* old_if_f = iff->proj_out(false);
1616 Node* old_if_t = iff->proj_out(true);
1617
1618 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1619 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1620 // happens in count-down loops
1621 if (iff->is_CountedLoopEnd()) return NULL;
1622 Node* proj_true = iff->proj_out(true);
1623 if (proj_true->outcnt() == 1) {
1624 Node* c = proj_true->unique_out();
1625 // Leave test of outer strip mined loop alone
1626 if (c != NULL && c->is_Loop() &&
1627 c->in(LoopNode::LoopBackControl) == proj_true &&
1628 c->as_Loop()->is_strip_mined()) {
1629 return NULL;
1630 }
1631 }
1632 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1633 BoolNode *b = iff->in(1)->as_Bool();
1634 BoolTest bt = b->_test;
1635 // Test already in good order?
1636 if( bt.is_canonical() )
1637 return NULL;
1638
1639 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1640 // cloning the IfNode.
1641 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1642 if( !new_b->is_Bool() ) return NULL;
1643 b = new_b->as_Bool();
1644
1645 PhaseIterGVN *igvn = phase->is_IterGVN();
1646 assert( igvn, "Test is not canonical in parser?" );
1647
1648 // The IF node never really changes, but it needs to be cloned
1649 iff = iff->clone()->as_If();
1650 iff->set_req(1, b);
1651 iff->_prob = 1.0-iff->_prob;
1652
1653 Node *prior = igvn->hash_find_insert(iff);
1654 if( prior ) {
1655 igvn->remove_dead_node(iff);
1656 iff = (IfNode*)prior;
1657 } else {
1658 // Cannot call transform on it just yet
1659 igvn->set_type_bottom(iff);
1660 }
1661 igvn->_worklist.push(iff);
1662
1663 // Now handle projections. Cloning not required.
1664 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1665 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1666
1667 igvn->register_new_node_with_optimizer(new_if_f);
1668 igvn->register_new_node_with_optimizer(new_if_t);
1669 // Flip test, so flip trailing control
1670 igvn->replace_node(old_if_f, new_if_t);
1671 igvn->replace_node(old_if_t, new_if_f);
1672
1673 // Progress
1674 return iff;
1675 }
1676
1677 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1678 Node* res = Ideal_common(phase, can_reshape);
1679 if (res != NodeSentinel) {
1680 return res;
1681 }
1682
1683 PhaseIterGVN *igvn = phase->is_IterGVN();
1684 // Setup to scan up the CFG looking for a dominating test
1685 Node* prev_dom = this;
1686
1687 // Check for range-check vs other kinds of tests
1688 Node* index1;
1689 Node* range1;
1690 jint offset1;
1691 int flip1 = is_range_check(range1, index1, offset1);
1692 if (flip1) {
1693 Node* dom = in(0);
1694 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1695 // so all checks we inspect post-dominate the top-most check we find.
1696 // If we are going to fail the current check and we reach the top check
1697 // then we are guaranteed to fail, so just start interpreting there.
1698 // We 'expand' the top 3 range checks to include all post-dominating
1699 // checks.
1700
1701 // The top 3 range checks seen
1702 const int NRC =3;
1703 RangeCheck prev_checks[NRC];
1704 int nb_checks = 0;
1705
1706 // Low and high offsets seen so far
1707 jint off_lo = offset1;
1708 jint off_hi = offset1;
1709
1710 bool found_immediate_dominator = false;
1711
1712 // Scan for the top checks and collect range of offsets
1713 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1714 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1715 prev_dom->in(0) == dom) { // One path of test does dominate?
1716 if (dom == this) return NULL; // dead loop
1717 // See if this is a range check
1718 Node* index2;
1719 Node* range2;
1720 jint offset2;
1721 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1722 // See if this is a _matching_ range check, checking against
1723 // the same array bounds.
1724 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1725 dom->outcnt() == 2) {
1726 if (nb_checks == 0 && dom->in(1) == in(1)) {
1727 // Found an immediately dominating test at the same offset.
1728 // This kind of back-to-back test can be eliminated locally,
1729 // and there is no need to search further for dominating tests.
1730 assert(offset2 == offset1, "Same test but different offsets");
1731 found_immediate_dominator = true;
1732 break;
1733 }
1734 // Gather expanded bounds
1735 off_lo = MIN2(off_lo,offset2);
1736 off_hi = MAX2(off_hi,offset2);
1737 // Record top NRC range checks
1738 prev_checks[nb_checks%NRC].ctl = prev_dom;
1739 prev_checks[nb_checks%NRC].off = offset2;
1740 nb_checks++;
1741 }
1742 }
1743 prev_dom = dom;
1744 dom = up_one_dom(dom);
1745 if (!dom) break;
1746 }
1747
1748 if (!found_immediate_dominator) {
1749 // Attempt to widen the dominating range check to cover some later
1750 // ones. Since range checks "fail" by uncommon-trapping to the
1751 // interpreter, widening a check can make us speculatively enter
1752 // the interpreter. If we see range-check deopt's, do not widen!
1753 if (!phase->C->allow_range_check_smearing()) return NULL;
1754
1755 // Didn't find prior covering check, so cannot remove anything.
1756 if (nb_checks == 0) {
1757 return NULL;
1758 }
1759 // Constant indices only need to check the upper bound.
1760 // Non-constant indices must check both low and high.
1761 int chk0 = (nb_checks - 1) % NRC;
1762 if (index1) {
1763 if (nb_checks == 1) {
1764 return NULL;
1765 } else {
1766 // If the top range check's constant is the min or max of
1767 // all constants we widen the next one to cover the whole
1768 // range of constants.
1769 RangeCheck rc0 = prev_checks[chk0];
1770 int chk1 = (nb_checks - 2) % NRC;
1771 RangeCheck rc1 = prev_checks[chk1];
1772 if (rc0.off == off_lo) {
1773 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1774 prev_dom = rc1.ctl;
1775 } else if (rc0.off == off_hi) {
1776 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1777 prev_dom = rc1.ctl;
1778 } else {
1779 // If the top test's constant is not the min or max of all
1780 // constants, we need 3 range checks. We must leave the
1781 // top test unchanged because widening it would allow the
1782 // accesses it protects to successfully read/write out of
1783 // bounds.
1784 if (nb_checks == 2) {
1785 return NULL;
1786 }
1787 int chk2 = (nb_checks - 3) % NRC;
1788 RangeCheck rc2 = prev_checks[chk2];
1789 // The top range check a+i covers interval: -a <= i < length-a
1790 // The second range check b+i covers interval: -b <= i < length-b
1791 if (rc1.off <= rc0.off) {
1792 // if b <= a, we change the second range check to:
1793 // -min_of_all_constants <= i < length-min_of_all_constants
1794 // Together top and second range checks now cover:
1795 // -min_of_all_constants <= i < length-a
1796 // which is more restrictive than -b <= i < length-b:
1797 // -b <= -min_of_all_constants <= i < length-a <= length-b
1798 // The third check is then changed to:
1799 // -max_of_all_constants <= i < length-max_of_all_constants
1800 // so 2nd and 3rd checks restrict allowed values of i to:
1801 // -min_of_all_constants <= i < length-max_of_all_constants
1802 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1803 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1804 } else {
1805 // if b > a, we change the second range check to:
1806 // -max_of_all_constants <= i < length-max_of_all_constants
1807 // Together top and second range checks now cover:
1808 // -a <= i < length-max_of_all_constants
1809 // which is more restrictive than -b <= i < length-b:
1810 // -b < -a <= i < length-max_of_all_constants <= length-b
1811 // The third check is then changed to:
1812 // -max_of_all_constants <= i < length-max_of_all_constants
1813 // so 2nd and 3rd checks restrict allowed values of i to:
1814 // -min_of_all_constants <= i < length-max_of_all_constants
1815 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1816 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1817 }
1818 prev_dom = rc2.ctl;
1819 }
1820 }
1821 } else {
1822 RangeCheck rc0 = prev_checks[chk0];
1823 // 'Widen' the offset of the 1st and only covering check
1824 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1825 // Test is now covered by prior checks, dominate it out
1826 prev_dom = rc0.ctl;
1827 }
1828 }
1829 } else {
1830 prev_dom = search_identical(4);
1831
1832 if (prev_dom == NULL) {
1833 return NULL;
1834 }
1835 }
1836
1837 // Replace dominated IfNode
1838 return dominated_by(prev_dom, igvn);
1839 }