1/*
2 * Copyright (c) 2000, 2018, 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.
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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
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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
45extern int explicit_null_checks_elided;
46#endif
47
48//=============================================================================
49//------------------------------Value------------------------------------------
50// Return a tuple for whichever arm of the IF is reachable
51const 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
67const 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.
75static 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 if (counted_loop) {
271 // Ignore counted loops for now because the split-if logic does not work
272 // in all the cases (for example, with strip mined loops). Also, above
273 // checks only pass for already degraded loops without a tripcount phi
274 // and these are essentially dead and will go away during igvn.
275 return NULL;
276 }
277
278 Node *region_c = new RegionNode(req_c + 1);
279 Node *phi_c = con1;
280 uint len = r->req();
281 Node *region_x = new RegionNode(len - req_c);
282 Node *phi_x = PhiNode::make_blank(region_x, phi);
283 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
284 if (phi->in(i) == con1) {
285 region_c->init_req( i_c++, r ->in(i) );
286 if (r->in(i) == predicate_proj)
287 predicate_c = predicate_proj;
288 } else {
289 region_x->init_req( i_x, r ->in(i) );
290 phi_x ->init_req( i_x++, phi->in(i) );
291 if (r->in(i) == predicate_proj)
292 predicate_x = predicate_proj;
293 }
294 }
295 if (predicate_c != NULL && (req_c > 1)) {
296 assert(predicate_x == NULL, "only one predicate entry expected");
297 predicate_c = NULL; // Do not clone predicate below merge point
298 }
299 if (predicate_x != NULL && ((len - req_c) > 2)) {
300 assert(predicate_c == NULL, "only one predicate entry expected");
301 predicate_x = NULL; // Do not clone predicate below merge point
302 }
303
304 // Register the new RegionNodes but do not transform them. Cannot
305 // transform until the entire Region/Phi conglomerate has been hacked
306 // as a single huge transform.
307 igvn->register_new_node_with_optimizer( region_c );
308 igvn->register_new_node_with_optimizer( region_x );
309 // Prevent the untimely death of phi_x. Currently he has no uses. He is
310 // about to get one. If this only use goes away, then phi_x will look dead.
311 // However, he will be picking up some more uses down below.
312 Node *hook = new Node(4);
313 hook->init_req(0, phi_x);
314 hook->init_req(1, phi_c);
315 phi_x = phase->transform( phi_x );
316
317 // Make the compare
318 Node *cmp_c = phase->makecon(t);
319 Node *cmp_x = cmp->clone();
320 cmp_x->set_req(1,phi_x);
321 cmp_x->set_req(2,con2);
322 cmp_x = phase->transform(cmp_x);
323 // Make the bool
324 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
325 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
326 // Make the IfNode
327 IfNode* iff_c = iff->clone()->as_If();
328 iff_c->set_req(0, region_c);
329 iff_c->set_req(1, b_c);
330 igvn->set_type_bottom(iff_c);
331 igvn->_worklist.push(iff_c);
332 hook->init_req(2, iff_c);
333
334 IfNode* iff_x = iff->clone()->as_If();
335 iff_x->set_req(0, region_x);
336 iff_x->set_req(1, b_x);
337 igvn->set_type_bottom(iff_x);
338 igvn->_worklist.push(iff_x);
339 hook->init_req(3, iff_x);
340
341 // Make the true/false arms
342 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
343 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
344 if (predicate_c != NULL) {
345 assert(predicate_x == NULL, "only one predicate entry expected");
346 // Clone loop predicates to each path
347 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
348 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
349 }
350 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
351 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
352 if (predicate_x != NULL) {
353 assert(predicate_c == NULL, "only one predicate entry expected");
354 // Clone loop predicates to each path
355 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
356 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
357 }
358
359 // Merge the TRUE paths
360 Node *region_s = new RegionNode(3);
361 igvn->_worklist.push(region_s);
362 region_s->init_req(1, iff_c_t);
363 region_s->init_req(2, iff_x_t);
364 igvn->register_new_node_with_optimizer( region_s );
365
366 // Merge the FALSE paths
367 Node *region_f = new RegionNode(3);
368 igvn->_worklist.push(region_f);
369 region_f->init_req(1, iff_c_f);
370 region_f->init_req(2, iff_x_f);
371 igvn->register_new_node_with_optimizer( region_f );
372
373 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
374 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
375 cmp->set_req(2,NULL);
376 // Check for all uses of the Phi and give them a new home.
377 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
378 Node *phi_s = NULL; // do not construct unless needed
379 Node *phi_f = NULL; // do not construct unless needed
380 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
381 Node* v = phi->last_out(i2);// User of the phi
382 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
383 uint vop = v->Opcode();
384 Node *proj = NULL;
385 if( vop == Op_Phi ) { // Remote merge point
386 Node *r = v->in(0);
387 for (uint i3 = 1; i3 < r->req(); i3++)
388 if (r->in(i3) && r->in(i3)->in(0) == iff) {
389 proj = r->in(i3);
390 break;
391 }
392 } else if( v->is_ConstraintCast() ) {
393 proj = v->in(0); // Controlling projection
394 } else {
395 assert( 0, "do not know how to handle this guy" );
396 }
397 guarantee(proj != NULL, "sanity");
398
399 Node *proj_path_data, *proj_path_ctrl;
400 if( proj->Opcode() == Op_IfTrue ) {
401 if( phi_s == NULL ) {
402 // Only construct phi_s if needed, otherwise provides
403 // interfering use.
404 phi_s = PhiNode::make_blank(region_s,phi);
405 phi_s->init_req( 1, phi_c );
406 phi_s->init_req( 2, phi_x );
407 hook->add_req(phi_s);
408 phi_s = phase->transform(phi_s);
409 }
410 proj_path_data = phi_s;
411 proj_path_ctrl = region_s;
412 } else {
413 if( phi_f == NULL ) {
414 // Only construct phi_f if needed, otherwise provides
415 // interfering use.
416 phi_f = PhiNode::make_blank(region_f,phi);
417 phi_f->init_req( 1, phi_c );
418 phi_f->init_req( 2, phi_x );
419 hook->add_req(phi_f);
420 phi_f = phase->transform(phi_f);
421 }
422 proj_path_data = phi_f;
423 proj_path_ctrl = region_f;
424 }
425
426 // Fixup 'v' for for the split
427 if( vop == Op_Phi ) { // Remote merge point
428 uint i;
429 for( i = 1; i < v->req(); i++ )
430 if( v->in(i) == phi )
431 break;
432 v->set_req(i, proj_path_data );
433 } else if( v->is_ConstraintCast() ) {
434 v->set_req(0, proj_path_ctrl );
435 v->set_req(1, proj_path_data );
436 } else
437 ShouldNotReachHere();
438 }
439
440 // Now replace the original iff's True/False with region_s/region_t.
441 // This makes the original iff go dead.
442 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
443 Node* p = iff->last_out(i3);
444 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
445 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
446 // Replace p with u
447 igvn->add_users_to_worklist(p);
448 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
449 Node* x = p->last_out(l);
450 igvn->hash_delete(x);
451 uint uses_found = 0;
452 for( uint j = 0; j < x->req(); j++ ) {
453 if( x->in(j) == p ) {
454 x->set_req(j, u);
455 uses_found++;
456 }
457 }
458 l -= uses_found; // we deleted 1 or more copies of this edge
459 }
460 igvn->remove_dead_node(p);
461 }
462
463 // Force the original merge dead
464 igvn->hash_delete(r);
465 // First, remove region's dead users.
466 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
467 Node* u = r->last_out(l);
468 if( u == r ) {
469 r->set_req(0, NULL);
470 } else {
471 assert(u->outcnt() == 0, "only dead users");
472 igvn->remove_dead_node(u);
473 }
474 l -= 1;
475 }
476 igvn->remove_dead_node(r);
477
478 // Now remove the bogus extra edges used to keep things alive
479 igvn->remove_dead_node( hook );
480
481 // Must return either the original node (now dead) or a new node
482 // (Do not return a top here, since that would break the uniqueness of top.)
483 return new ConINode(TypeInt::ZERO);
484}
485
486// if this IfNode follows a range check pattern return the projection
487// for the failed path
488ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
489 if (outcnt() != 2) {
490 return NULL;
491 }
492 Node* b = in(1);
493 if (b == NULL || !b->is_Bool()) return NULL;
494 BoolNode* bn = b->as_Bool();
495 Node* cmp = bn->in(1);
496 if (cmp == NULL) return NULL;
497 if (cmp->Opcode() != Op_CmpU) return NULL;
498
499 l = cmp->in(1);
500 r = cmp->in(2);
501 flip_test = 1;
502 if (bn->_test._test == BoolTest::le) {
503 l = cmp->in(2);
504 r = cmp->in(1);
505 flip_test = 2;
506 } else if (bn->_test._test != BoolTest::lt) {
507 return NULL;
508 }
509 if (l->is_top()) return NULL; // Top input means dead test
510 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return NULL;
511
512 // We have recognized one of these forms:
513 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
514 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
515
516 ProjNode* iftrap = proj_out_or_null(flip_test == 2 ? true : false);
517 return iftrap;
518}
519
520
521//------------------------------is_range_check---------------------------------
522// Return 0 if not a range check. Return 1 if a range check and set index and
523// offset. Return 2 if we had to negate the test. Index is NULL if the check
524// is versus a constant.
525int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
526 int flip_test = 0;
527 Node* l = NULL;
528 Node* r = NULL;
529 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
530
531 if (iftrap == NULL) {
532 return 0;
533 }
534
535 // Make sure it's a real range check by requiring an uncommon trap
536 // along the OOB path. Otherwise, it's possible that the user wrote
537 // something which optimized to look like a range check but behaves
538 // in some other way.
539 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
540 return 0;
541 }
542
543 // Look for index+offset form
544 Node* ind = l;
545 jint off = 0;
546 if (l->is_top()) {
547 return 0;
548 } else if (l->Opcode() == Op_AddI) {
549 if ((off = l->in(1)->find_int_con(0)) != 0) {
550 ind = l->in(2)->uncast();
551 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
552 ind = l->in(1)->uncast();
553 }
554 } else if ((off = l->find_int_con(-1)) >= 0) {
555 // constant offset with no variable index
556 ind = NULL;
557 } else {
558 // variable index with no constant offset (or dead negative index)
559 off = 0;
560 }
561
562 // Return all the values:
563 index = ind;
564 offset = off;
565 range = r;
566 return flip_test;
567}
568
569//------------------------------adjust_check-----------------------------------
570// Adjust (widen) a prior range check
571static void adjust_check(Node* proj, Node* range, Node* index,
572 int flip, jint off_lo, PhaseIterGVN* igvn) {
573 PhaseGVN *gvn = igvn;
574 // Break apart the old check
575 Node *iff = proj->in(0);
576 Node *bol = iff->in(1);
577 if( bol->is_top() ) return; // In case a partially dead range check appears
578 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
579 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
580 if( !bol->is_Bool() ) return;
581
582 Node *cmp = bol->in(1);
583 // Compute a new check
584 Node *new_add = gvn->intcon(off_lo);
585 if( index ) {
586 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
587 }
588 Node *new_cmp = (flip == 1)
589 ? new CmpUNode( new_add, range )
590 : new CmpUNode( range, new_add );
591 new_cmp = gvn->transform(new_cmp);
592 // See if no need to adjust the existing check
593 if( new_cmp == cmp ) return;
594 // Else, adjust existing check
595 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
596 igvn->rehash_node_delayed( iff );
597 iff->set_req_X( 1, new_bol, igvn );
598}
599
600//------------------------------up_one_dom-------------------------------------
601// Walk up the dominator tree one step. Return NULL at root or true
602// complex merges. Skips through small diamonds.
603Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
604 Node *dom = curr->in(0);
605 if( !dom ) // Found a Region degraded to a copy?
606 return curr->nonnull_req(); // Skip thru it
607
608 if( curr != dom ) // Normal walk up one step?
609 return dom;
610
611 // Use linear_only if we are still parsing, since we cannot
612 // trust the regions to be fully filled in.
613 if (linear_only)
614 return NULL;
615
616 if( dom->is_Root() )
617 return NULL;
618
619 // Else hit a Region. Check for a loop header
620 if( dom->is_Loop() )
621 return dom->in(1); // Skip up thru loops
622
623 // Check for small diamonds
624 Node *din1, *din2, *din3, *din4;
625 if( dom->req() == 3 && // 2-path merge point
626 (din1 = dom ->in(1)) && // Left path exists
627 (din2 = dom ->in(2)) && // Right path exists
628 (din3 = din1->in(0)) && // Left path up one
629 (din4 = din2->in(0)) ) { // Right path up one
630 if( din3->is_Call() && // Handle a slow-path call on either arm
631 (din3 = din3->in(0)) )
632 din3 = din3->in(0);
633 if( din4->is_Call() && // Handle a slow-path call on either arm
634 (din4 = din4->in(0)) )
635 din4 = din4->in(0);
636 if (din3 != NULL && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
637 return din3; // Skip around diamonds
638 }
639
640 // Give up the search at true merges
641 return NULL; // Dead loop? Or hit root?
642}
643
644
645//------------------------------filtered_int_type--------------------------------
646// Return a possibly more restrictive type for val based on condition control flow for an if
647const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
648 assert(if_proj &&
649 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
650 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
651 IfNode* iff = if_proj->in(0)->as_If();
652 if (iff->in(1) && iff->in(1)->is_Bool()) {
653 BoolNode* bol = iff->in(1)->as_Bool();
654 if (bol->in(1) && bol->in(1)->is_Cmp()) {
655 const CmpNode* cmp = bol->in(1)->as_Cmp();
656 if (cmp->in(1) == val) {
657 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
658 if (cmp2_t != NULL) {
659 jint lo = cmp2_t->_lo;
660 jint hi = cmp2_t->_hi;
661 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
662 switch (msk) {
663 case BoolTest::ne:
664 // Can't refine type
665 return NULL;
666 case BoolTest::eq:
667 return cmp2_t;
668 case BoolTest::lt:
669 lo = TypeInt::INT->_lo;
670 if (hi - 1 < hi) {
671 hi = hi - 1;
672 }
673 break;
674 case BoolTest::le:
675 lo = TypeInt::INT->_lo;
676 break;
677 case BoolTest::gt:
678 if (lo + 1 > lo) {
679 lo = lo + 1;
680 }
681 hi = TypeInt::INT->_hi;
682 break;
683 case BoolTest::ge:
684 // lo unchanged
685 hi = TypeInt::INT->_hi;
686 break;
687 default:
688 break;
689 }
690 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
691 return rtn_t;
692 }
693 }
694 }
695 }
696 }
697 return NULL;
698}
699
700//------------------------------fold_compares----------------------------
701// See if a pair of CmpIs can be converted into a CmpU. In some cases
702// the direction of this if is determined by the preceding if so it
703// can be eliminate entirely.
704//
705// Given an if testing (CmpI n v) check for an immediately control
706// dependent if that is testing (CmpI n v2) and has one projection
707// leading to this if and the other projection leading to a region
708// that merges one of this ifs control projections.
709//
710// If
711// / |
712// / |
713// / |
714// If |
715// /\ |
716// / \ |
717// / \ |
718// / Region
719//
720// Or given an if testing (CmpI n v) check for a dominating if that is
721// testing (CmpI n v2), both having one projection leading to an
722// uncommon trap. Allow Another independent guard in between to cover
723// an explicit range check:
724// if (index < 0 || index >= array.length) {
725// which may need a null check to guard the LoadRange
726//
727// If
728// / \
729// / \
730// / \
731// If unc
732// /\
733// / \
734// / \
735// / unc
736//
737
738// Is the comparison for this If suitable for folding?
739bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
740 return in(1) != NULL &&
741 in(1)->is_Bool() &&
742 in(1)->in(1) != NULL &&
743 in(1)->in(1)->Opcode() == Op_CmpI &&
744 in(1)->in(1)->in(2) != NULL &&
745 in(1)->in(1)->in(2) != igvn->C->top() &&
746 (in(1)->as_Bool()->_test.is_less() ||
747 in(1)->as_Bool()->_test.is_greater());
748}
749
750// Is a dominating control suitable for folding with this if?
751bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
752 return ctrl != NULL &&
753 ctrl->is_Proj() &&
754 ctrl->in(0) != NULL &&
755 ctrl->in(0)->Opcode() == Op_If &&
756 ctrl->in(0)->outcnt() == 2 &&
757 ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
758 // Must compare same value
759 ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
760 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
761}
762
763// Do this If and the dominating If share a region?
764bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
765 ProjNode* otherproj = proj->other_if_proj();
766 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
767 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
768 success = NULL;
769 fail = NULL;
770
771 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
772 for (int i = 0; i < 2; i++) {
773 ProjNode* proj = proj_out(i);
774 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
775 success = proj;
776 } else if (fail == NULL) {
777 fail = proj;
778 } else {
779 success = fail = NULL;
780 }
781 }
782 }
783 return success != NULL && fail != NULL;
784}
785
786bool IfNode::is_dominator_unc(CallStaticJavaNode* dom_unc, CallStaticJavaNode* unc) {
787 // Different methods and methods containing jsrs are not supported.
788 ciMethod* method = unc->jvms()->method();
789 ciMethod* dom_method = dom_unc->jvms()->method();
790 if (method != dom_method || method->has_jsrs()) {
791 return false;
792 }
793 // Check that both traps are in the same activation of the method (instead
794 // of two activations being inlined through different call sites) by verifying
795 // that the call stacks are equal for both JVMStates.
796 JVMState* dom_caller = dom_unc->jvms()->caller();
797 JVMState* caller = unc->jvms()->caller();
798 if ((dom_caller == NULL) != (caller == NULL)) {
799 // The current method must either be inlined into both dom_caller and
800 // caller or must not be inlined at all (top method). Bail out otherwise.
801 return false;
802 } else if (dom_caller != NULL && !dom_caller->same_calls_as(caller)) {
803 return false;
804 }
805 // Check that the bci of the dominating uncommon trap dominates the bci
806 // of the dominated uncommon trap. Otherwise we may not re-execute
807 // the dominated check after deoptimization from the merged uncommon trap.
808 ciTypeFlow* flow = dom_method->get_flow_analysis();
809 int bci = unc->jvms()->bci();
810 int dom_bci = dom_unc->jvms()->bci();
811 if (!flow->is_dominated_by(bci, dom_bci)) {
812 return false;
813 }
814
815 return true;
816}
817
818// Return projection that leads to an uncommon trap if any
819ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
820 for (int i = 0; i < 2; i++) {
821 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
822 if (call != NULL) {
823 return proj_out(i);
824 }
825 }
826 return NULL;
827}
828
829// Do this If and the dominating If both branch out to an uncommon trap
830bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
831 ProjNode* otherproj = proj->other_if_proj();
832 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
833
834 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
835 // We need to re-execute the folded Ifs after deoptimization from the merged traps
836 if (!dom_unc->jvms()->should_reexecute()) {
837 return false;
838 }
839
840 CallStaticJavaNode* unc = NULL;
841 ProjNode* unc_proj = uncommon_trap_proj(unc);
842 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
843 if (dom_unc == unc) {
844 // Allow the uncommon trap to be shared through a region
845 RegionNode* r = unc->in(0)->as_Region();
846 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
847 return false;
848 }
849 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
850 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
851 return false;
852 }
853
854 if (!is_dominator_unc(dom_unc, unc)) {
855 return false;
856 }
857
858 // See merge_uncommon_traps: the reason of the uncommon trap
859 // will be changed and the state of the dominating If will be
860 // used. Checked that we didn't apply this transformation in a
861 // previous compilation and it didn't cause too many traps
862 ciMethod* dom_method = dom_unc->jvms()->method();
863 int dom_bci = dom_unc->jvms()->bci();
864 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
865 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check)) {
866 success = unc_proj;
867 fail = unc_proj->other_if_proj();
868 return true;
869 }
870 }
871 }
872 return false;
873}
874
875// Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
876bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
877 Node* this_cmp = in(1)->in(1);
878 BoolNode* this_bool = in(1)->as_Bool();
879 IfNode* dom_iff = proj->in(0)->as_If();
880 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
881 Node* lo = dom_iff->in(1)->in(1)->in(2);
882 Node* hi = this_cmp->in(2);
883 Node* n = this_cmp->in(1);
884 ProjNode* otherproj = proj->other_if_proj();
885
886 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
887 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
888
889 BoolTest::mask lo_test = dom_bool->_test._test;
890 BoolTest::mask hi_test = this_bool->_test._test;
891 BoolTest::mask cond = hi_test;
892
893 // convert:
894 //
895 // dom_bool = x {<,<=,>,>=} a
896 // / \
897 // proj = {True,False} / \ otherproj = {False,True}
898 // /
899 // this_bool = x {<,<=} b
900 // / \
901 // fail = {True,False} / \ success = {False,True}
902 // /
903 //
904 // (Second test guaranteed canonicalized, first one may not have
905 // been canonicalized yet)
906 //
907 // into:
908 //
909 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
910 // / \
911 // fail / \ success
912 // /
913 //
914
915 // Figure out which of the two tests sets the upper bound and which
916 // sets the lower bound if any.
917 Node* adjusted_lim = NULL;
918 if (lo_type != NULL && hi_type != NULL && hi_type->_lo > lo_type->_hi &&
919 hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
920 assert((dom_bool->_test.is_less() && !proj->_con) ||
921 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
922 // this test was canonicalized
923 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
924
925 // this_bool = <
926 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
927 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
928 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
929 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
930 // x in ]a, b[ on the fail (= True) projection, b > a:
931 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
932 // this_bool = <=
933 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
934 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
935 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
936 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
937 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
938 // x in ]a, b] on the fail (= True) projection b+1 > a:
939 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
940 // 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
941
942 if (hi_test == BoolTest::lt) {
943 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
944 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
945 }
946 } else {
947 assert(hi_test == BoolTest::le, "bad test");
948 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
949 adjusted_lim = igvn->transform(new SubINode(hi, lo));
950 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
951 cond = BoolTest::lt;
952 } else {
953 assert(lo_test == BoolTest::gt || lo_test == BoolTest::le, "bad test");
954 adjusted_lim = igvn->transform(new SubINode(hi, lo));
955 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
956 cond = BoolTest::lt;
957 }
958 }
959 } else if (lo_type != NULL && hi_type != NULL && lo_type->_lo > hi_type->_hi &&
960 lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
961
962 // this_bool = <
963 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
964 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
965 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
966 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
967 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
968 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
969 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
970 // this_bool = <=
971 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
972 // x in ]b, a[ on the fail (= False) projection, a > b:
973 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
974 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
975 // x in ]b, a] on the fail (= False) projection, a+1 > b:
976 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
977 // 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
978
979 swap(lo, hi);
980 swap(lo_type, hi_type);
981 swap(lo_test, hi_test);
982
983 assert((dom_bool->_test.is_less() && proj->_con) ||
984 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
985 // this test was canonicalized
986 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
987
988 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
989
990 if (lo_test == BoolTest::lt) {
991 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
992 cond = BoolTest::ge;
993 } else {
994 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
995 adjusted_lim = igvn->transform(new SubINode(hi, lo));
996 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
997 cond = BoolTest::ge;
998 }
999 } else if (lo_test == BoolTest::le) {
1000 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
1001 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
1002 cond = BoolTest::ge;
1003 } else {
1004 assert(hi_test == BoolTest::le || hi_test == BoolTest::gt, "bad test");
1005 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1006 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
1007 cond = BoolTest::ge;
1008 }
1009 }
1010 } else {
1011 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
1012 if (failtype != NULL) {
1013 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
1014 if (type2 != NULL) {
1015 failtype = failtype->join(type2)->is_int();
1016 if (failtype->_lo > failtype->_hi) {
1017 // previous if determines the result of this if so
1018 // replace Bool with constant
1019 igvn->_worklist.push(in(1));
1020 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
1021 return true;
1022 }
1023 }
1024 }
1025 lo = NULL;
1026 hi = NULL;
1027 }
1028
1029 if (lo && hi) {
1030 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1031 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
1032 if (adjusted_lim == NULL) {
1033 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1034 }
1035 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1036 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1037
1038 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1039 igvn->_worklist.push(in(1));
1040 igvn->replace_input_of(this, 1, newbool);
1041
1042 return true;
1043 }
1044 return false;
1045}
1046
1047// Merge the branches that trap for this If and the dominating If into
1048// a single region that branches to the uncommon trap for the
1049// dominating If
1050Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1051 Node* res = this;
1052 assert(success->in(0) == this, "bad projection");
1053
1054 ProjNode* otherproj = proj->other_if_proj();
1055
1056 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
1057 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
1058
1059 if (unc != dom_unc) {
1060 Node* r = new RegionNode(3);
1061
1062 r->set_req(1, otherproj);
1063 r->set_req(2, success);
1064 r = igvn->transform(r);
1065 assert(r->is_Region(), "can't go away");
1066
1067 // Make both If trap at the state of the first If: once the CmpI
1068 // nodes are merged, if we trap we don't know which of the CmpI
1069 // nodes would have caused the trap so we have to restart
1070 // execution at the first one
1071 igvn->replace_input_of(dom_unc, 0, r);
1072 igvn->replace_input_of(unc, 0, igvn->C->top());
1073 }
1074 int trap_request = dom_unc->uncommon_trap_request();
1075 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1076 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1077
1078 int flip_test = 0;
1079 Node* l = NULL;
1080 Node* r = NULL;
1081
1082 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
1083 // If this looks like a range check, change the trap to
1084 // Reason_range_check so the compiler recognizes it as a range
1085 // check and applies the corresponding optimizations
1086 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1087
1088 improve_address_types(l, r, fail, igvn);
1089
1090 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1091 } else if (unc != dom_unc) {
1092 // If we trap we won't know what CmpI would have caused the trap
1093 // so use a special trap reason to mark this pair of CmpI nodes as
1094 // bad candidate for folding. On recompilation we won't fold them
1095 // and we may trap again but this time we'll know what branch
1096 // traps
1097 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1098 }
1099 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1100 return res;
1101}
1102
1103// If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1104// of a rangecheck on index i, on 64 bit the compares may be followed
1105// by memory accesses using i as index. In that case, the CmpU tells
1106// us something about the values taken by i that can help the compiler
1107// (see Compile::conv_I2X_index())
1108void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1109#ifdef _LP64
1110 ResourceMark rm;
1111 Node_Stack stack(2);
1112
1113 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1114 const TypeInt* array_size = igvn->type(r)->is_int();
1115
1116 stack.push(l, 0);
1117
1118 while(stack.size() > 0) {
1119 Node* n = stack.node();
1120 uint start = stack.index();
1121
1122 uint i = start;
1123 for (; i < n->outcnt(); i++) {
1124 Node* use = n->raw_out(i);
1125 if (stack.size() == 1) {
1126 if (use->Opcode() == Op_ConvI2L) {
1127 const TypeLong* bounds = use->as_Type()->type()->is_long();
1128 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1129 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1130 stack.set_index(i+1);
1131 stack.push(use, 0);
1132 break;
1133 }
1134 }
1135 } else if (use->is_Mem()) {
1136 Node* ctrl = use->in(0);
1137 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
1138 ctrl = up_one_dom(ctrl);
1139 }
1140 if (ctrl == fail) {
1141 Node* init_n = stack.node_at(1);
1142 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1143 // Create a new narrow ConvI2L node that is dependent on the range check
1144 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1145
1146 // The type of the ConvI2L may be widen and so the new
1147 // ConvI2L may not be better than an existing ConvI2L
1148 if (new_n != init_n) {
1149 for (uint j = 2; j < stack.size(); j++) {
1150 Node* n = stack.node_at(j);
1151 Node* clone = n->clone();
1152 int rep = clone->replace_edge(init_n, new_n);
1153 assert(rep > 0, "can't find expected node?");
1154 clone = igvn->transform(clone);
1155 init_n = n;
1156 new_n = clone;
1157 }
1158 igvn->hash_delete(use);
1159 int rep = use->replace_edge(init_n, new_n);
1160 assert(rep > 0, "can't find expected node?");
1161 igvn->transform(use);
1162 if (init_n->outcnt() == 0) {
1163 igvn->_worklist.push(init_n);
1164 }
1165 }
1166 }
1167 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
1168 igvn->type(use)->isa_ptr())) {
1169 stack.set_index(i+1);
1170 stack.push(use, 0);
1171 break;
1172 }
1173 }
1174 if (i == n->outcnt()) {
1175 stack.pop();
1176 }
1177 }
1178#endif
1179}
1180
1181bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1182 if (in(1) != NULL &&
1183 in(1)->in(1) != NULL &&
1184 in(1)->in(1)->in(2) != NULL) {
1185 Node* other = in(1)->in(1)->in(2);
1186 if (other->Opcode() == Op_LoadRange &&
1187 ((other->in(0) != NULL && other->in(0) == proj) ||
1188 (other->in(0) == NULL &&
1189 other->in(2) != NULL &&
1190 other->in(2)->is_AddP() &&
1191 other->in(2)->in(1) != NULL &&
1192 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1193 other->in(2)->in(1)->in(0) == proj))) {
1194 return true;
1195 }
1196 }
1197 return false;
1198}
1199
1200bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1201 Node* other = in(1)->in(1)->in(2);
1202 if (other->in(MemNode::Address) != NULL &&
1203 proj->in(0)->in(1) != NULL &&
1204 proj->in(0)->in(1)->is_Bool() &&
1205 proj->in(0)->in(1)->in(1) != NULL &&
1206 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1207 proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1208 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1209 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1210 return true;
1211 }
1212 return false;
1213}
1214
1215// Check that the If that is in between the 2 integer comparisons has
1216// no side effect
1217bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1218 if (proj == NULL) {
1219 return false;
1220 }
1221 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1222 if (unc != NULL && proj->outcnt() <= 2) {
1223 if (proj->outcnt() == 1 ||
1224 // Allow simple null check from LoadRange
1225 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1226 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1227 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1228 assert(dom_unc != NULL, "is_uncommon_trap_if_pattern returned NULL");
1229
1230 // reroute_side_effect_free_unc changes the state of this
1231 // uncommon trap to restart execution at the previous
1232 // CmpI. Check that this change in a previous compilation didn't
1233 // cause too many traps.
1234 int trap_request = unc->uncommon_trap_request();
1235 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1236
1237 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1238 return false;
1239 }
1240
1241 if (!is_dominator_unc(dom_unc, unc)) {
1242 return false;
1243 }
1244
1245 return true;
1246 }
1247 }
1248 return false;
1249}
1250
1251// Make the If between the 2 integer comparisons trap at the state of
1252// the first If: the last CmpI is the one replaced by a CmpU and the
1253// first CmpI is eliminated, so the test between the 2 CmpI nodes
1254// won't be guarded by the first CmpI anymore. It can trap in cases
1255// where the first CmpI would have prevented it from executing: on a
1256// trap, we need to restart execution at the state of the first CmpI
1257void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1258 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1259 ProjNode* otherproj = proj->other_if_proj();
1260 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1261 Node* call_proj = dom_unc->unique_ctrl_out();
1262 Node* halt = call_proj->unique_ctrl_out();
1263
1264 Node* new_unc = dom_unc->clone();
1265 call_proj = call_proj->clone();
1266 halt = halt->clone();
1267 Node* c = otherproj->clone();
1268
1269 c = igvn->transform(c);
1270 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1271 new_unc->set_req(0, c);
1272 new_unc = igvn->transform(new_unc);
1273 call_proj->set_req(0, new_unc);
1274 call_proj = igvn->transform(call_proj);
1275 halt->set_req(0, call_proj);
1276 halt = igvn->transform(halt);
1277
1278 igvn->replace_node(otherproj, igvn->C->top());
1279 igvn->C->root()->add_req(halt);
1280}
1281
1282Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1283 if (Opcode() != Op_If) return NULL;
1284
1285 if (cmpi_folds(igvn)) {
1286 Node* ctrl = in(0);
1287 if (is_ctrl_folds(ctrl, igvn) &&
1288 ctrl->outcnt() == 1) {
1289 // A integer comparison immediately dominated by another integer
1290 // comparison
1291 ProjNode* success = NULL;
1292 ProjNode* fail = NULL;
1293 ProjNode* dom_cmp = ctrl->as_Proj();
1294 if (has_shared_region(dom_cmp, success, fail) &&
1295 // Next call modifies graph so must be last
1296 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1297 return this;
1298 }
1299 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1300 // Next call modifies graph so must be last
1301 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1302 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1303 }
1304 return NULL;
1305 } else if (ctrl->in(0) != NULL &&
1306 ctrl->in(0)->in(0) != NULL) {
1307 ProjNode* success = NULL;
1308 ProjNode* fail = NULL;
1309 Node* dom = ctrl->in(0)->in(0);
1310 ProjNode* dom_cmp = dom->isa_Proj();
1311 ProjNode* other_cmp = ctrl->isa_Proj();
1312
1313 // Check if it's an integer comparison dominated by another
1314 // integer comparison with another test in between
1315 if (is_ctrl_folds(dom, igvn) &&
1316 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1317 is_side_effect_free_test(other_cmp, igvn) &&
1318 // Next call modifies graph so must be last
1319 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1320 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1321 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1322 }
1323 }
1324 }
1325 return NULL;
1326}
1327
1328//------------------------------remove_useless_bool----------------------------
1329// Check for people making a useless boolean: things like
1330// if( (x < y ? true : false) ) { ... }
1331// Replace with if( x < y ) { ... }
1332static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1333 Node *i1 = iff->in(1);
1334 if( !i1->is_Bool() ) return NULL;
1335 BoolNode *bol = i1->as_Bool();
1336
1337 Node *cmp = bol->in(1);
1338 if( cmp->Opcode() != Op_CmpI ) return NULL;
1339
1340 // Must be comparing against a bool
1341 const Type *cmp2_t = phase->type( cmp->in(2) );
1342 if( cmp2_t != TypeInt::ZERO &&
1343 cmp2_t != TypeInt::ONE )
1344 return NULL;
1345
1346 // Find a prior merge point merging the boolean
1347 i1 = cmp->in(1);
1348 if( !i1->is_Phi() ) return NULL;
1349 PhiNode *phi = i1->as_Phi();
1350 if( phase->type( phi ) != TypeInt::BOOL )
1351 return NULL;
1352
1353 // Check for diamond pattern
1354 int true_path = phi->is_diamond_phi();
1355 if( true_path == 0 ) return NULL;
1356
1357 // Make sure that iff and the control of the phi are different. This
1358 // should really only happen for dead control flow since it requires
1359 // an illegal cycle.
1360 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1361
1362 // phi->region->if_proj->ifnode->bool->cmp
1363 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1364
1365 // Now get the 'sense' of the test correct so we can plug in
1366 // either iff2->in(1) or its complement.
1367 int flip = 0;
1368 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1369 else if( bol->_test._test != BoolTest::eq ) return NULL;
1370 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1371
1372 const Type *phi1_t = phase->type( phi->in(1) );
1373 const Type *phi2_t = phase->type( phi->in(2) );
1374 // Check for Phi(0,1) and flip
1375 if( phi1_t == TypeInt::ZERO ) {
1376 if( phi2_t != TypeInt::ONE ) return NULL;
1377 flip = 1-flip;
1378 } else {
1379 // Check for Phi(1,0)
1380 if( phi1_t != TypeInt::ONE ) return NULL;
1381 if( phi2_t != TypeInt::ZERO ) return NULL;
1382 }
1383 if( true_path == 2 ) {
1384 flip = 1-flip;
1385 }
1386
1387 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1388 assert(new_bol != iff->in(1), "must make progress");
1389 iff->set_req(1, new_bol);
1390 // Intervening diamond probably goes dead
1391 phase->C->set_major_progress();
1392 return iff;
1393}
1394
1395static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1396
1397struct RangeCheck {
1398 Node* ctl;
1399 jint off;
1400};
1401
1402Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1403 if (remove_dead_region(phase, can_reshape)) return this;
1404 // No Def-Use info?
1405 if (!can_reshape) return NULL;
1406
1407 // Don't bother trying to transform a dead if
1408 if (in(0)->is_top()) return NULL;
1409 // Don't bother trying to transform an if with a dead test
1410 if (in(1)->is_top()) return NULL;
1411 // Another variation of a dead test
1412 if (in(1)->is_Con()) return NULL;
1413 // Another variation of a dead if
1414 if (outcnt() < 2) return NULL;
1415
1416 // Canonicalize the test.
1417 Node* idt_if = idealize_test(phase, this);
1418 if (idt_if != NULL) return idt_if;
1419
1420 // Try to split the IF
1421 PhaseIterGVN *igvn = phase->is_IterGVN();
1422 Node *s = split_if(this, igvn);
1423 if (s != NULL) return s;
1424
1425 return NodeSentinel;
1426}
1427
1428//------------------------------Ideal------------------------------------------
1429// Return a node which is more "ideal" than the current node. Strip out
1430// control copies
1431Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1432 Node* res = Ideal_common(phase, can_reshape);
1433 if (res != NodeSentinel) {
1434 return res;
1435 }
1436
1437 // Check for people making a useless boolean: things like
1438 // if( (x < y ? true : false) ) { ... }
1439 // Replace with if( x < y ) { ... }
1440 Node *bol2 = remove_useless_bool(this, phase);
1441 if( bol2 ) return bol2;
1442
1443 if (in(0) == NULL) return NULL; // Dead loop?
1444
1445 PhaseIterGVN *igvn = phase->is_IterGVN();
1446 Node* result = fold_compares(igvn);
1447 if (result != NULL) {
1448 return result;
1449 }
1450
1451 // Scan for an equivalent test
1452 Node *cmp;
1453 int dist = 0; // Cutoff limit for search
1454 int op = Opcode();
1455 if( op == Op_If &&
1456 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1457 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1458 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1459 dist = 64; // Limit for null-pointer scans
1460 } else {
1461 dist = 4; // Do not bother for random pointer tests
1462 }
1463 } else {
1464 dist = 4; // Limit for random junky scans
1465 }
1466
1467 Node* prev_dom = search_identical(dist);
1468
1469 if (prev_dom == NULL) {
1470 return NULL;
1471 }
1472
1473 // Replace dominated IfNode
1474 return dominated_by(prev_dom, igvn);
1475}
1476
1477//------------------------------dominated_by-----------------------------------
1478Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1479#ifndef PRODUCT
1480 if (TraceIterativeGVN) {
1481 tty->print(" Removing IfNode: "); this->dump();
1482 }
1483 if (VerifyOpto && !igvn->allow_progress()) {
1484 // Found an equivalent dominating test,
1485 // we can not guarantee reaching a fix-point for these during iterativeGVN
1486 // since intervening nodes may not change.
1487 return NULL;
1488 }
1489#endif
1490
1491 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1492 Node *idom = in(0);
1493 // Need opcode to decide which way 'this' test goes
1494 int prev_op = prev_dom->Opcode();
1495 Node *top = igvn->C->top(); // Shortcut to top
1496
1497 // Loop predicates may have depending checks which should not
1498 // be skipped. For example, range check predicate has two checks
1499 // for lower and upper bounds.
1500 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1501 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL ||
1502 unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_profile_predicate) != NULL) {
1503 prev_dom = idom;
1504 }
1505
1506 // Now walk the current IfNode's projections.
1507 // Loop ends when 'this' has no more uses.
1508 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1509 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1510 igvn->add_users_to_worklist(ifp);
1511 // Check which projection it is and set target.
1512 // Data-target is either the dominating projection of the same type
1513 // or TOP if the dominating projection is of opposite type.
1514 // Data-target will be used as the new control edge for the non-CFG
1515 // nodes like Casts and Loads.
1516 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1517 // Control-target is just the If's immediate dominator or TOP.
1518 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1519
1520 // For each child of an IfTrue/IfFalse projection, reroute.
1521 // Loop ends when projection has no more uses.
1522 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1523 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1524 if( !s->depends_only_on_test() ) {
1525 // Find the control input matching this def-use edge.
1526 // For Regions it may not be in slot 0.
1527 uint l;
1528 for( l = 0; s->in(l) != ifp; l++ ) { }
1529 igvn->replace_input_of(s, l, ctrl_target);
1530 } else { // Else, for control producers,
1531 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1532 }
1533 } // End for each child of a projection
1534
1535 igvn->remove_dead_node(ifp);
1536 } // End for each IfTrue/IfFalse child of If
1537
1538 // Kill the IfNode
1539 igvn->remove_dead_node(this);
1540
1541 // Must return either the original node (now dead) or a new node
1542 // (Do not return a top here, since that would break the uniqueness of top.)
1543 return new ConINode(TypeInt::ZERO);
1544}
1545
1546Node* IfNode::search_identical(int dist) {
1547 // Setup to scan up the CFG looking for a dominating test
1548 Node* dom = in(0);
1549 Node* prev_dom = this;
1550 int op = Opcode();
1551 // Search up the dominator tree for an If with an identical test
1552 while (dom->Opcode() != op || // Not same opcode?
1553 dom->in(1) != in(1) || // Not same input 1?
1554 prev_dom->in(0) != dom) { // One path of test does not dominate?
1555 if (dist < 0) return NULL;
1556
1557 dist--;
1558 prev_dom = dom;
1559 dom = up_one_dom(dom);
1560 if (!dom) return NULL;
1561 }
1562
1563 // Check that we did not follow a loop back to ourselves
1564 if (this == dom) {
1565 return NULL;
1566 }
1567
1568#ifndef PRODUCT
1569 if (dist > 2) { // Add to count of NULL checks elided
1570 explicit_null_checks_elided++;
1571 }
1572#endif
1573
1574 return prev_dom;
1575}
1576
1577//------------------------------Identity---------------------------------------
1578// If the test is constant & we match, then we are the input Control
1579Node* IfProjNode::Identity(PhaseGVN* phase) {
1580 // Can only optimize if cannot go the other way
1581 const TypeTuple *t = phase->type(in(0))->is_tuple();
1582 if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1583 // During parsing (GVN) we don't remove dead code aggressively.
1584 // Cut off dead branch and let PhaseRemoveUseless take care of it.
1585 (!phase->is_IterGVN() ||
1586 // During IGVN, first wait for the dead branch to be killed.
1587 // Otherwise, the IfNode's control will have two control uses (the IfNode
1588 // that doesn't go away because it still has uses and this branch of the
1589 // If) which breaks other optimizations. Node::has_special_unique_user()
1590 // will cause this node to be reprocessed once the dead branch is killed.
1591 in(0)->outcnt() == 1))) {
1592 // IfNode control
1593 return in(0)->in(0);
1594 }
1595 // no progress
1596 return this;
1597}
1598
1599#ifndef PRODUCT
1600//-------------------------------related---------------------------------------
1601// An IfProjNode's related node set consists of its input (an IfNode) including
1602// the IfNode's condition, plus all of its outputs at level 1. In compact mode,
1603// the restrictions for IfNode apply (see IfNode::rel).
1604void IfProjNode::related(GrowableArray<Node*> *in_rel, GrowableArray<Node*> *out_rel, bool compact) const {
1605 Node* ifNode = this->in(0);
1606 in_rel->append(ifNode);
1607 if (compact) {
1608 ifNode->collect_nodes(in_rel, 3, false, true);
1609 } else {
1610 ifNode->collect_nodes_in_all_data(in_rel, false);
1611 }
1612 this->collect_nodes(out_rel, -1, false, false);
1613}
1614
1615//------------------------------dump_spec--------------------------------------
1616void IfNode::dump_spec(outputStream *st) const {
1617 st->print("P=%f, C=%f",_prob,_fcnt);
1618}
1619
1620//-------------------------------related---------------------------------------
1621// For an IfNode, the set of related output nodes is just the output nodes till
1622// depth 2, i.e, the IfTrue/IfFalse projection nodes plus the nodes they refer.
1623// The related input nodes contain no control nodes, but all data nodes
1624// pertaining to the condition. In compact mode, the input nodes are collected
1625// up to a depth of 3.
1626void IfNode::related(GrowableArray <Node *> *in_rel, GrowableArray <Node *> *out_rel, bool compact) const {
1627 if (compact) {
1628 this->collect_nodes(in_rel, 3, false, true);
1629 } else {
1630 this->collect_nodes_in_all_data(in_rel, false);
1631 }
1632 this->collect_nodes(out_rel, -2, false, false);
1633}
1634#endif
1635
1636//------------------------------idealize_test----------------------------------
1637// Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1638// come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1639// converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1640// needed.
1641static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1642 assert(iff->in(0) != NULL, "If must be live");
1643
1644 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1645 Node* old_if_f = iff->proj_out(false);
1646 Node* old_if_t = iff->proj_out(true);
1647
1648 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1649 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1650 // happens in count-down loops
1651 if (iff->is_CountedLoopEnd()) return NULL;
1652 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1653 BoolNode *b = iff->in(1)->as_Bool();
1654 BoolTest bt = b->_test;
1655 // Test already in good order?
1656 if( bt.is_canonical() )
1657 return NULL;
1658
1659 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1660 // cloning the IfNode.
1661 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1662 if( !new_b->is_Bool() ) return NULL;
1663 b = new_b->as_Bool();
1664
1665 PhaseIterGVN *igvn = phase->is_IterGVN();
1666 assert( igvn, "Test is not canonical in parser?" );
1667
1668 // The IF node never really changes, but it needs to be cloned
1669 iff = iff->clone()->as_If();
1670 iff->set_req(1, b);
1671 iff->_prob = 1.0-iff->_prob;
1672
1673 Node *prior = igvn->hash_find_insert(iff);
1674 if( prior ) {
1675 igvn->remove_dead_node(iff);
1676 iff = (IfNode*)prior;
1677 } else {
1678 // Cannot call transform on it just yet
1679 igvn->set_type_bottom(iff);
1680 }
1681 igvn->_worklist.push(iff);
1682
1683 // Now handle projections. Cloning not required.
1684 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1685 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1686
1687 igvn->register_new_node_with_optimizer(new_if_f);
1688 igvn->register_new_node_with_optimizer(new_if_t);
1689 // Flip test, so flip trailing control
1690 igvn->replace_node(old_if_f, new_if_t);
1691 igvn->replace_node(old_if_t, new_if_f);
1692
1693 // Progress
1694 return iff;
1695}
1696
1697Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1698 Node* res = Ideal_common(phase, can_reshape);
1699 if (res != NodeSentinel) {
1700 return res;
1701 }
1702
1703 PhaseIterGVN *igvn = phase->is_IterGVN();
1704 // Setup to scan up the CFG looking for a dominating test
1705 Node* prev_dom = this;
1706
1707 // Check for range-check vs other kinds of tests
1708 Node* index1;
1709 Node* range1;
1710 jint offset1;
1711 int flip1 = is_range_check(range1, index1, offset1);
1712 if (flip1) {
1713 Node* dom = in(0);
1714 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1715 // so all checks we inspect post-dominate the top-most check we find.
1716 // If we are going to fail the current check and we reach the top check
1717 // then we are guaranteed to fail, so just start interpreting there.
1718 // We 'expand' the top 3 range checks to include all post-dominating
1719 // checks.
1720
1721 // The top 3 range checks seen
1722 const int NRC =3;
1723 RangeCheck prev_checks[NRC];
1724 int nb_checks = 0;
1725
1726 // Low and high offsets seen so far
1727 jint off_lo = offset1;
1728 jint off_hi = offset1;
1729
1730 bool found_immediate_dominator = false;
1731
1732 // Scan for the top checks and collect range of offsets
1733 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1734 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1735 prev_dom->in(0) == dom) { // One path of test does dominate?
1736 if (dom == this) return NULL; // dead loop
1737 // See if this is a range check
1738 Node* index2;
1739 Node* range2;
1740 jint offset2;
1741 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1742 // See if this is a _matching_ range check, checking against
1743 // the same array bounds.
1744 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1745 dom->outcnt() == 2) {
1746 if (nb_checks == 0 && dom->in(1) == in(1)) {
1747 // Found an immediately dominating test at the same offset.
1748 // This kind of back-to-back test can be eliminated locally,
1749 // and there is no need to search further for dominating tests.
1750 assert(offset2 == offset1, "Same test but different offsets");
1751 found_immediate_dominator = true;
1752 break;
1753 }
1754 // Gather expanded bounds
1755 off_lo = MIN2(off_lo,offset2);
1756 off_hi = MAX2(off_hi,offset2);
1757 // Record top NRC range checks
1758 prev_checks[nb_checks%NRC].ctl = prev_dom;
1759 prev_checks[nb_checks%NRC].off = offset2;
1760 nb_checks++;
1761 }
1762 }
1763 prev_dom = dom;
1764 dom = up_one_dom(dom);
1765 if (!dom) break;
1766 }
1767
1768 if (!found_immediate_dominator) {
1769 // Attempt to widen the dominating range check to cover some later
1770 // ones. Since range checks "fail" by uncommon-trapping to the
1771 // interpreter, widening a check can make us speculatively enter
1772 // the interpreter. If we see range-check deopt's, do not widen!
1773 if (!phase->C->allow_range_check_smearing()) return NULL;
1774
1775 // Didn't find prior covering check, so cannot remove anything.
1776 if (nb_checks == 0) {
1777 return NULL;
1778 }
1779 // Constant indices only need to check the upper bound.
1780 // Non-constant indices must check both low and high.
1781 int chk0 = (nb_checks - 1) % NRC;
1782 if (index1) {
1783 if (nb_checks == 1) {
1784 return NULL;
1785 } else {
1786 // If the top range check's constant is the min or max of
1787 // all constants we widen the next one to cover the whole
1788 // range of constants.
1789 RangeCheck rc0 = prev_checks[chk0];
1790 int chk1 = (nb_checks - 2) % NRC;
1791 RangeCheck rc1 = prev_checks[chk1];
1792 if (rc0.off == off_lo) {
1793 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1794 prev_dom = rc1.ctl;
1795 } else if (rc0.off == off_hi) {
1796 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1797 prev_dom = rc1.ctl;
1798 } else {
1799 // If the top test's constant is not the min or max of all
1800 // constants, we need 3 range checks. We must leave the
1801 // top test unchanged because widening it would allow the
1802 // accesses it protects to successfully read/write out of
1803 // bounds.
1804 if (nb_checks == 2) {
1805 return NULL;
1806 }
1807 int chk2 = (nb_checks - 3) % NRC;
1808 RangeCheck rc2 = prev_checks[chk2];
1809 // The top range check a+i covers interval: -a <= i < length-a
1810 // The second range check b+i covers interval: -b <= i < length-b
1811 if (rc1.off <= rc0.off) {
1812 // if b <= a, we change the second range check to:
1813 // -min_of_all_constants <= i < length-min_of_all_constants
1814 // Together top and second range checks now cover:
1815 // -min_of_all_constants <= i < length-a
1816 // which is more restrictive than -b <= i < length-b:
1817 // -b <= -min_of_all_constants <= i < length-a <= length-b
1818 // The third check is then changed to:
1819 // -max_of_all_constants <= i < length-max_of_all_constants
1820 // so 2nd and 3rd checks restrict allowed values of i to:
1821 // -min_of_all_constants <= i < length-max_of_all_constants
1822 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1823 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1824 } else {
1825 // if b > a, we change the second range check to:
1826 // -max_of_all_constants <= i < length-max_of_all_constants
1827 // Together top and second range checks now cover:
1828 // -a <= i < length-max_of_all_constants
1829 // which is more restrictive than -b <= i < length-b:
1830 // -b < -a <= i < length-max_of_all_constants <= length-b
1831 // The third check is then changed to:
1832 // -max_of_all_constants <= i < length-max_of_all_constants
1833 // so 2nd and 3rd checks restrict allowed values of i to:
1834 // -min_of_all_constants <= i < length-max_of_all_constants
1835 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1836 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1837 }
1838 prev_dom = rc2.ctl;
1839 }
1840 }
1841 } else {
1842 RangeCheck rc0 = prev_checks[chk0];
1843 // 'Widen' the offset of the 1st and only covering check
1844 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1845 // Test is now covered by prior checks, dominate it out
1846 prev_dom = rc0.ctl;
1847 }
1848 }
1849 } else {
1850 prev_dom = search_identical(4);
1851
1852 if (prev_dom == NULL) {
1853 return NULL;
1854 }
1855 }
1856
1857 // Replace dominated IfNode
1858 return dominated_by(prev_dom, igvn);
1859}
1860