1 /*
2 * Copyright (c) 2000, 2023, 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/predicates.hpp"
36 #include "opto/runtime.hpp"
37 #include "opto/rootnode.hpp"
38 #include "opto/subnode.hpp"
39 #include "opto/subtypenode.hpp"
40
41 // Portions of code courtesy of Clifford Click
42
43 // Optimization - Graph Style
44
45
46 #ifndef PRODUCT
47 extern uint explicit_null_checks_elided;
48 #endif
49
50 //=============================================================================
51 //------------------------------Value------------------------------------------
52 // Return a tuple for whichever arm of the IF is reachable
53 const Type* IfNode::Value(PhaseGVN* phase) const {
54 if( !in(0) ) return Type::TOP;
55 if( phase->type(in(0)) == Type::TOP )
56 return Type::TOP;
57 const Type *t = phase->type(in(1));
58 if( t == Type::TOP ) // data is undefined
59 return TypeTuple::IFNEITHER; // unreachable altogether
60 if( t == TypeInt::ZERO ) // zero, or false
61 return TypeTuple::IFFALSE; // only false branch is reachable
62 if( t == TypeInt::ONE ) // 1, or true
63 return TypeTuple::IFTRUE; // only true branch is reachable
64 assert( t == TypeInt::BOOL, "expected boolean type" );
65
66 return TypeTuple::IFBOTH; // No progress
67 }
68
69 const RegMask &IfNode::out_RegMask() const {
70 return RegMask::Empty;
71 }
72
73 //------------------------------split_if---------------------------------------
74 // Look for places where we merge constants, then test on the merged value.
75 // If the IF test will be constant folded on the path with the constant, we
76 // win by splitting the IF to before the merge point.
77 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
78 // I could be a lot more general here, but I'm trying to squeeze this
79 // in before the Christmas '98 break so I'm gonna be kinda restrictive
80 // on the patterns I accept. CNC
81
82 // Look for a compare of a constant and a merged value
83 Node *i1 = iff->in(1);
84 if( !i1->is_Bool() ) return nullptr;
85 BoolNode *b = i1->as_Bool();
86 Node *cmp = b->in(1);
87 if( !cmp->is_Cmp() ) return nullptr;
88 i1 = cmp->in(1);
89 if( i1 == nullptr || !i1->is_Phi() ) return nullptr;
90 PhiNode *phi = i1->as_Phi();
91 Node *con2 = cmp->in(2);
92 if( !con2->is_Con() ) return nullptr;
93 // See that the merge point contains some constants
94 Node *con1=nullptr;
95 uint i4;
96 RegionNode* phi_region = phi->region();
97 for (i4 = 1; i4 < phi->req(); i4++ ) {
98 con1 = phi->in(i4);
99 // Do not optimize partially collapsed merges
100 if (con1 == nullptr || phi_region->in(i4) == nullptr || igvn->type(phi_region->in(i4)) == Type::TOP) {
101 igvn->_worklist.push(iff);
102 return nullptr;
103 }
104 if( con1->is_Con() ) break; // Found a constant
105 // Also allow null-vs-not-null checks
106 const TypePtr *tp = igvn->type(con1)->isa_ptr();
107 if( tp && tp->_ptr == TypePtr::NotNull )
108 break;
109 }
110 if( i4 >= phi->req() ) return nullptr; // Found no constants
111
112 igvn->C->set_has_split_ifs(true); // Has chance for split-if
113
114 // Make sure that the compare can be constant folded away
115 Node *cmp2 = cmp->clone();
116 cmp2->set_req(1,con1);
117 cmp2->set_req(2,con2);
118 const Type *t = cmp2->Value(igvn);
119 // This compare is dead, so whack it!
120 igvn->remove_dead_node(cmp2);
121 if( !t->singleton() ) return nullptr;
122
123 // No intervening control, like a simple Call
124 Node* r = iff->in(0);
125 if (!r->is_Region() || r->is_Loop() || phi_region != r || r->as_Region()->is_copy()) {
126 return nullptr;
127 }
128
129 // No other users of the cmp/bool
130 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
131 //tty->print_cr("many users of cmp/bool");
132 return nullptr;
133 }
134
135 // Make sure we can determine where all the uses of merged values go
136 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
137 Node* u = r->fast_out(j);
138 if( u == r ) continue;
139 if( u == iff ) continue;
140 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
141 if( !u->is_Phi() ) {
142 /*
143 if( u->is_Start() ) {
144 tty->print_cr("Region has inlined start use");
145 } else {
146 tty->print_cr("Region has odd use");
147 u->dump(2);
148 }*/
149 return nullptr;
150 }
151 if( u != phi ) {
152 // CNC - do not allow any other merged value
153 //tty->print_cr("Merging another value");
154 //u->dump(2);
155 return nullptr;
156 }
157 // Make sure we can account for all Phi uses
158 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
159 Node* v = u->fast_out(k); // User of the phi
160 // CNC - Allow only really simple patterns.
161 // In particular I disallow AddP of the Phi, a fairly common pattern
162 if (v == cmp) continue; // The compare is OK
163 if (v->is_ConstraintCast()) {
164 // If the cast is derived from data flow edges, it may not have a control edge.
165 // If so, it should be safe to split. But follow-up code can not deal with
166 // this (l. 359). So skip.
167 if (v->in(0) == nullptr) {
168 return nullptr;
169 }
170 if (v->in(0)->in(0) == iff) {
171 continue; // CastPP/II of the IfNode is OK
172 }
173 }
174 // Disabled following code because I cannot tell if exactly one
175 // path dominates without a real dominator check. CNC 9/9/1999
176 //uint vop = v->Opcode();
177 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
178 // Node *r = v->in(0); // Get controlling point
179 // if( !r ) return nullptr; // Degraded to a copy
180 // // Find exactly one path in (either True or False doms, but not IFF)
181 // int cnt = 0;
182 // for( uint i = 1; i < r->req(); i++ )
183 // if( r->in(i) && r->in(i)->in(0) == iff )
184 // cnt++;
185 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
186 //}
187 if( !v->is_Call() ) {
188 /*
189 if( v->Opcode() == Op_AddP ) {
190 tty->print_cr("Phi has AddP use");
191 } else if( v->Opcode() == Op_CastPP ) {
192 tty->print_cr("Phi has CastPP use");
193 } else if( v->Opcode() == Op_CastII ) {
194 tty->print_cr("Phi has CastII use");
195 } else {
196 tty->print_cr("Phi has use I can't be bothered with");
197 }
198 */
199 }
200 return nullptr;
201
202 /* CNC - Cut out all the fancy acceptance tests
203 // Can we clone this use when doing the transformation?
204 // If all uses are from Phis at this merge or constants, then YES.
205 if( !v->in(0) && v != cmp ) {
206 tty->print_cr("Phi has free-floating use");
207 v->dump(2);
208 return nullptr;
209 }
210 for( uint l = 1; l < v->req(); l++ ) {
211 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
212 !v->in(l)->is_Con() ) {
213 tty->print_cr("Phi has use");
214 v->dump(2);
215 return nullptr;
216 } // End of if Phi-use input is neither Phi nor Constant
217 } // End of for all inputs to Phi-use
218 */
219 } // End of for all uses of Phi
220 } // End of for all uses of Region
221
222 // Only do this if the IF node is in a sane state
223 if (iff->outcnt() != 2)
224 return nullptr;
225
226 // Got a hit! Do the Mondo Hack!
227 //
228 //ABC a1c def ghi B 1 e h A C a c d f g i
229 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
230 // cmp - 2 cmp - 2 cmp - 2
231 // bool bool_c bool_x
232 // if if_c if_x
233 // T F T F T F
234 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
235 //
236 // Split the paths coming into the merge point into 2 separate groups of
237 // merges. On the left will be all the paths feeding constants into the
238 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
239 // will fold up into a constant; this will let the Cmp fold up as well as
240 // all the control flow. Below the original IF we have 2 control
241 // dependent regions, 's' and 't'. Now we will merge the two paths
242 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
243 // likely 2 or more) will promptly constant fold away.
244 PhaseGVN *phase = igvn;
245
246 // Make a region merging constants and a region merging the rest
247 uint req_c = 0;
248 for (uint ii = 1; ii < r->req(); ii++) {
249 if (phi->in(ii) == con1) {
250 req_c++;
251 }
252 if (Node::may_be_loop_entry(r->in(ii))) {
253 // Bail out if splitting through a region with a Parse Predicate input (could
254 // also be a loop header before loop opts creates a LoopNode for it).
255 return nullptr;
256 }
257 }
258
259 // If all the defs of the phi are the same constant, we already have the desired end state.
260 // Skip the split that would create empty phi and region nodes.
261 if ((r->req() - req_c) == 1) {
262 return nullptr;
263 }
264
265 // At this point we know that we can apply the split if optimization. If the region is still on the worklist,
266 // we should wait until it is processed. The region might be removed which makes this optimization redundant.
267 // This also avoids the creation of dead data loops when rewiring data nodes below when a region is dying.
268 if (igvn->_worklist.member(r)) {
269 igvn->_worklist.push(iff); // retry split if later again
270 return nullptr;
271 }
272
273 Node *region_c = new RegionNode(req_c + 1);
274 Node *phi_c = con1;
275 uint len = r->req();
276 Node *region_x = new RegionNode(len - req_c);
277 Node *phi_x = PhiNode::make_blank(region_x, phi);
278 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
279 if (phi->in(i) == con1) {
280 region_c->init_req( i_c++, r ->in(i) );
281 } else {
282 region_x->init_req( i_x, r ->in(i) );
283 phi_x ->init_req( i_x++, phi->in(i) );
284 }
285 }
286
287 // Register the new RegionNodes but do not transform them. Cannot
288 // transform until the entire Region/Phi conglomerate has been hacked
289 // as a single huge transform.
290 igvn->register_new_node_with_optimizer( region_c );
291 igvn->register_new_node_with_optimizer( region_x );
292 // Prevent the untimely death of phi_x. Currently he has no uses. He is
293 // about to get one. If this only use goes away, then phi_x will look dead.
294 // However, he will be picking up some more uses down below.
295 Node *hook = new Node(4);
296 hook->init_req(0, phi_x);
297 hook->init_req(1, phi_c);
298 phi_x = phase->transform( phi_x );
299
300 // Make the compare
301 Node *cmp_c = phase->makecon(t);
302 Node *cmp_x = cmp->clone();
303 cmp_x->set_req(1,phi_x);
304 cmp_x->set_req(2,con2);
305 cmp_x = phase->transform(cmp_x);
306 // Make the bool
307 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
308 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
309 // Make the IfNode
310 IfNode* iff_c = iff->clone()->as_If();
311 iff_c->set_req(0, region_c);
312 iff_c->set_req(1, b_c);
313 igvn->set_type_bottom(iff_c);
314 igvn->_worklist.push(iff_c);
315 hook->init_req(2, iff_c);
316
317 IfNode* iff_x = iff->clone()->as_If();
318 iff_x->set_req(0, region_x);
319 iff_x->set_req(1, b_x);
320 igvn->set_type_bottom(iff_x);
321 igvn->_worklist.push(iff_x);
322 hook->init_req(3, iff_x);
323
324 // Make the true/false arms
325 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
326 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
327 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
328 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
329
330 // Merge the TRUE paths
331 Node *region_s = new RegionNode(3);
332 igvn->_worklist.push(region_s);
333 region_s->init_req(1, iff_c_t);
334 region_s->init_req(2, iff_x_t);
335 igvn->register_new_node_with_optimizer( region_s );
336
337 // Merge the FALSE paths
338 Node *region_f = new RegionNode(3);
339 igvn->_worklist.push(region_f);
340 region_f->init_req(1, iff_c_f);
341 region_f->init_req(2, iff_x_f);
342 igvn->register_new_node_with_optimizer( region_f );
343
344 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
345 cmp->set_req(1,nullptr); // Whack the inputs to cmp because it will be dead
346 cmp->set_req(2,nullptr);
347 // Check for all uses of the Phi and give them a new home.
348 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
349 Node *phi_s = nullptr; // do not construct unless needed
350 Node *phi_f = nullptr; // do not construct unless needed
351 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
352 Node* v = phi->last_out(i2);// User of the phi
353 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
354 uint vop = v->Opcode();
355 Node *proj = nullptr;
356 if( vop == Op_Phi ) { // Remote merge point
357 Node *r = v->in(0);
358 for (uint i3 = 1; i3 < r->req(); i3++)
359 if (r->in(i3) && r->in(i3)->in(0) == iff) {
360 proj = r->in(i3);
361 break;
362 }
363 } else if( v->is_ConstraintCast() ) {
364 proj = v->in(0); // Controlling projection
365 } else {
366 assert( 0, "do not know how to handle this guy" );
367 }
368 guarantee(proj != nullptr, "sanity");
369
370 Node *proj_path_data, *proj_path_ctrl;
371 if( proj->Opcode() == Op_IfTrue ) {
372 if( phi_s == nullptr ) {
373 // Only construct phi_s if needed, otherwise provides
374 // interfering use.
375 phi_s = PhiNode::make_blank(region_s,phi);
376 phi_s->init_req( 1, phi_c );
377 phi_s->init_req( 2, phi_x );
378 hook->add_req(phi_s);
379 phi_s = phase->transform(phi_s);
380 }
381 proj_path_data = phi_s;
382 proj_path_ctrl = region_s;
383 } else {
384 if( phi_f == nullptr ) {
385 // Only construct phi_f if needed, otherwise provides
386 // interfering use.
387 phi_f = PhiNode::make_blank(region_f,phi);
388 phi_f->init_req( 1, phi_c );
389 phi_f->init_req( 2, phi_x );
390 hook->add_req(phi_f);
391 phi_f = phase->transform(phi_f);
392 }
393 proj_path_data = phi_f;
394 proj_path_ctrl = region_f;
395 }
396
397 // Fixup 'v' for for the split
398 if( vop == Op_Phi ) { // Remote merge point
399 uint i;
400 for( i = 1; i < v->req(); i++ )
401 if( v->in(i) == phi )
402 break;
403 v->set_req(i, proj_path_data );
404 } else if( v->is_ConstraintCast() ) {
405 v->set_req(0, proj_path_ctrl );
406 v->set_req(1, proj_path_data );
407 } else
408 ShouldNotReachHere();
409 }
410
411 // Now replace the original iff's True/False with region_s/region_t.
412 // This makes the original iff go dead.
413 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
414 Node* p = iff->last_out(i3);
415 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
416 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
417 // Replace p with u
418 igvn->add_users_to_worklist(p);
419 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
420 Node* x = p->last_out(l);
421 igvn->hash_delete(x);
422 uint uses_found = 0;
423 for( uint j = 0; j < x->req(); j++ ) {
424 if( x->in(j) == p ) {
425 x->set_req(j, u);
426 uses_found++;
427 }
428 }
429 l -= uses_found; // we deleted 1 or more copies of this edge
430 }
431 igvn->remove_dead_node(p);
432 }
433
434 // Force the original merge dead
435 igvn->hash_delete(r);
436 // First, remove region's dead users.
437 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
438 Node* u = r->last_out(l);
439 if( u == r ) {
440 r->set_req(0, nullptr);
441 } else {
442 assert(u->outcnt() == 0, "only dead users");
443 igvn->remove_dead_node(u);
444 }
445 l -= 1;
446 }
447 igvn->remove_dead_node(r);
448
449 // Now remove the bogus extra edges used to keep things alive
450 igvn->remove_dead_node( hook );
451
452 // Must return either the original node (now dead) or a new node
453 // (Do not return a top here, since that would break the uniqueness of top.)
454 return new ConINode(TypeInt::ZERO);
455 }
456
457 // if this IfNode follows a range check pattern return the projection
458 // for the failed path
459 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
460 if (outcnt() != 2) {
461 return nullptr;
462 }
463 Node* b = in(1);
464 if (b == nullptr || !b->is_Bool()) return nullptr;
465 BoolNode* bn = b->as_Bool();
466 Node* cmp = bn->in(1);
467 if (cmp == nullptr) return nullptr;
468 if (cmp->Opcode() != Op_CmpU) return nullptr;
469
470 l = cmp->in(1);
471 r = cmp->in(2);
472 flip_test = 1;
473 if (bn->_test._test == BoolTest::le) {
474 l = cmp->in(2);
475 r = cmp->in(1);
476 flip_test = 2;
477 } else if (bn->_test._test != BoolTest::lt) {
478 return nullptr;
479 }
480 if (l->is_top()) return nullptr; // Top input means dead test
481 if (r->Opcode() != Op_LoadRange && !is_RangeCheck()) return nullptr;
482
483 // We have recognized one of these forms:
484 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
485 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
486
487 ProjNode* iftrap = proj_out_or_null(flip_test == 2 ? true : false);
488 return iftrap;
489 }
490
491
492 //------------------------------is_range_check---------------------------------
493 // Return 0 if not a range check. Return 1 if a range check and set index and
494 // offset. Return 2 if we had to negate the test. Index is null if the check
495 // is versus a constant.
496 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
497 int flip_test = 0;
498 Node* l = nullptr;
499 Node* r = nullptr;
500 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
501
502 if (iftrap == nullptr) {
503 return 0;
504 }
505
506 // Make sure it's a real range check by requiring an uncommon trap
507 // along the OOB path. Otherwise, it's possible that the user wrote
508 // something which optimized to look like a range check but behaves
509 // in some other way.
510 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == nullptr) {
511 return 0;
512 }
513
514 // Look for index+offset form
515 Node* ind = l;
516 jint off = 0;
517 if (l->is_top()) {
518 return 0;
519 } else if (l->Opcode() == Op_AddI) {
520 if ((off = l->in(1)->find_int_con(0)) != 0) {
521 ind = l->in(2)->uncast();
522 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
523 ind = l->in(1)->uncast();
524 }
525 } else if ((off = l->find_int_con(-1)) >= 0) {
526 // constant offset with no variable index
527 ind = nullptr;
528 } else {
529 // variable index with no constant offset (or dead negative index)
530 off = 0;
531 }
532
533 // Return all the values:
534 index = ind;
535 offset = off;
536 range = r;
537 return flip_test;
538 }
539
540 //------------------------------adjust_check-----------------------------------
541 // Adjust (widen) a prior range check
542 static void adjust_check(IfProjNode* proj, Node* range, Node* index,
543 int flip, jint off_lo, PhaseIterGVN* igvn) {
544 PhaseGVN *gvn = igvn;
545 // Break apart the old check
546 Node *iff = proj->in(0);
547 Node *bol = iff->in(1);
548 if( bol->is_top() ) return; // In case a partially dead range check appears
549 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
550 DEBUG_ONLY( if (!bol->is_Bool()) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
551 if (!bol->is_Bool()) return;
552
553 Node *cmp = bol->in(1);
554 // Compute a new check
555 Node *new_add = gvn->intcon(off_lo);
556 if (index) {
557 new_add = off_lo ? gvn->transform(new AddINode(index, new_add)) : index;
558 }
559 Node *new_cmp = (flip == 1)
560 ? new CmpUNode(new_add, range)
561 : new CmpUNode(range, new_add);
562 new_cmp = gvn->transform(new_cmp);
563 // See if no need to adjust the existing check
564 if (new_cmp == cmp) return;
565 // Else, adjust existing check
566 Node* new_bol = gvn->transform(new BoolNode(new_cmp, bol->as_Bool()->_test._test));
567 igvn->rehash_node_delayed(iff);
568 iff->set_req_X(1, new_bol, igvn);
569 // As part of range check smearing, this range check is widened. Loads and range check Cast nodes that are control
570 // dependent on this range check now depend on multiple dominating range checks. These control dependent nodes end up
571 // at the lowest/nearest dominating check in the graph. To ensure that these Loads/Casts do not float above any of the
572 // dominating checks (even when the lowest dominating check is later replaced by yet another dominating check), we
573 // need to pin them at the lowest dominating check.
574 proj->pin_array_access_nodes(igvn);
575 }
576
577 //------------------------------up_one_dom-------------------------------------
578 // Walk up the dominator tree one step. Return null at root or true
579 // complex merges. Skips through small diamonds.
580 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
581 Node *dom = curr->in(0);
582 if( !dom ) // Found a Region degraded to a copy?
583 return curr->nonnull_req(); // Skip thru it
584
585 if( curr != dom ) // Normal walk up one step?
586 return dom;
587
588 // Use linear_only if we are still parsing, since we cannot
589 // trust the regions to be fully filled in.
590 if (linear_only)
591 return nullptr;
592
593 if( dom->is_Root() )
594 return nullptr;
595
596 // Else hit a Region. Check for a loop header
597 if( dom->is_Loop() )
598 return dom->in(1); // Skip up thru loops
599
600 // Check for small diamonds
601 Node *din1, *din2, *din3, *din4;
602 if( dom->req() == 3 && // 2-path merge point
603 (din1 = dom ->in(1)) && // Left path exists
604 (din2 = dom ->in(2)) && // Right path exists
605 (din3 = din1->in(0)) && // Left path up one
606 (din4 = din2->in(0)) ) { // Right path up one
607 if( din3->is_Call() && // Handle a slow-path call on either arm
608 (din3 = din3->in(0)) )
609 din3 = din3->in(0);
610 if( din4->is_Call() && // Handle a slow-path call on either arm
611 (din4 = din4->in(0)) )
612 din4 = din4->in(0);
613 if (din3 != nullptr && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
614 return din3; // Skip around diamonds
615 }
616
617 // Give up the search at true merges
618 return nullptr; // Dead loop? Or hit root?
619 }
620
621
622 //------------------------------filtered_int_type--------------------------------
623 // Return a possibly more restrictive type for val based on condition control flow for an if
624 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node* val, Node* if_proj) {
625 assert(if_proj &&
626 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
627 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
628 IfNode* iff = if_proj->in(0)->as_If();
629 if (iff->in(1) && iff->in(1)->is_Bool()) {
630 BoolNode* bol = iff->in(1)->as_Bool();
631 if (bol->in(1) && bol->in(1)->is_Cmp()) {
632 const CmpNode* cmp = bol->in(1)->as_Cmp();
633 if (cmp->in(1) == val) {
634 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
635 if (cmp2_t != nullptr) {
636 jint lo = cmp2_t->_lo;
637 jint hi = cmp2_t->_hi;
638 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
639 switch (msk) {
640 case BoolTest::ne: {
641 // If val is compared to its lower or upper bound, we can narrow the type
642 const TypeInt* val_t = gvn->type(val)->isa_int();
643 if (val_t != nullptr && !val_t->singleton() && cmp2_t->is_con()) {
644 if (val_t->_lo == lo) {
645 return TypeInt::make(val_t->_lo + 1, val_t->_hi, val_t->_widen);
646 } else if (val_t->_hi == hi) {
647 return TypeInt::make(val_t->_lo, val_t->_hi - 1, val_t->_widen);
648 }
649 }
650 // Can't refine type
651 return nullptr;
652 }
653 case BoolTest::eq:
654 return cmp2_t;
655 case BoolTest::lt:
656 lo = TypeInt::INT->_lo;
657 if (hi != min_jint) {
658 hi = hi - 1;
659 }
660 break;
661 case BoolTest::le:
662 lo = TypeInt::INT->_lo;
663 break;
664 case BoolTest::gt:
665 if (lo != max_jint) {
666 lo = lo + 1;
667 }
668 hi = TypeInt::INT->_hi;
669 break;
670 case BoolTest::ge:
671 // lo unchanged
672 hi = TypeInt::INT->_hi;
673 break;
674 default:
675 break;
676 }
677 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
678 return rtn_t;
679 }
680 }
681 }
682 }
683 }
684 return nullptr;
685 }
686
687 //------------------------------fold_compares----------------------------
688 // See if a pair of CmpIs can be converted into a CmpU. In some cases
689 // the direction of this if is determined by the preceding if so it
690 // can be eliminate entirely.
691 //
692 // Given an if testing (CmpI n v) check for an immediately control
693 // dependent if that is testing (CmpI n v2) and has one projection
694 // leading to this if and the other projection leading to a region
695 // that merges one of this ifs control projections.
696 //
697 // If
698 // / |
699 // / |
700 // / |
701 // If |
702 // /\ |
703 // / \ |
704 // / \ |
705 // / Region
706 //
707 // Or given an if testing (CmpI n v) check for a dominating if that is
708 // testing (CmpI n v2), both having one projection leading to an
709 // uncommon trap. Allow Another independent guard in between to cover
710 // an explicit range check:
711 // if (index < 0 || index >= array.length) {
712 // which may need a null check to guard the LoadRange
713 //
714 // If
715 // / \
716 // / \
717 // / \
718 // If unc
719 // /\
720 // / \
721 // / \
722 // / unc
723 //
724
725 // Is the comparison for this If suitable for folding?
726 bool IfNode::cmpi_folds(PhaseIterGVN* igvn, bool fold_ne) {
727 return in(1) != nullptr &&
728 in(1)->is_Bool() &&
729 in(1)->in(1) != nullptr &&
730 in(1)->in(1)->Opcode() == Op_CmpI &&
731 in(1)->in(1)->in(2) != nullptr &&
732 in(1)->in(1)->in(2) != igvn->C->top() &&
733 (in(1)->as_Bool()->_test.is_less() ||
734 in(1)->as_Bool()->_test.is_greater() ||
735 (fold_ne && in(1)->as_Bool()->_test._test == BoolTest::ne));
736 }
737
738 // Is a dominating control suitable for folding with this if?
739 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
740 return ctrl != nullptr &&
741 ctrl->is_Proj() &&
742 ctrl->in(0) != nullptr &&
743 ctrl->in(0)->Opcode() == Op_If &&
744 ctrl->in(0)->outcnt() == 2 &&
745 ctrl->in(0)->as_If()->cmpi_folds(igvn, true) &&
746 // Must compare same value
747 ctrl->in(0)->in(1)->in(1)->in(1) != nullptr &&
748 ctrl->in(0)->in(1)->in(1)->in(1) != igvn->C->top() &&
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_or_null();
756 RegionNode* region = (otherproj_ctrl_use != nullptr && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : nullptr;
757 success = nullptr;
758 fail = nullptr;
759
760 if (otherproj->outcnt() == 1 && region != nullptr && !region->has_phi()) {
761 for (int i = 0; i < 2; i++) {
762 ProjNode* proj = proj_out(i);
763 if (success == nullptr && proj->outcnt() == 1 && proj->unique_out() == region) {
764 success = proj;
765 } else if (fail == nullptr) {
766 fail = proj;
767 } else {
768 success = fail = nullptr;
769 }
770 }
771 }
772 return success != nullptr && fail != nullptr;
773 }
774
775 bool IfNode::is_dominator_unc(CallStaticJavaNode* dom_unc, CallStaticJavaNode* unc) {
776 // Different methods and methods containing jsrs are not supported.
777 ciMethod* method = unc->jvms()->method();
778 ciMethod* dom_method = dom_unc->jvms()->method();
779 if (method != dom_method || method->has_jsrs()) {
780 return false;
781 }
782 // Check that both traps are in the same activation of the method (instead
783 // of two activations being inlined through different call sites) by verifying
784 // that the call stacks are equal for both JVMStates.
785 JVMState* dom_caller = dom_unc->jvms()->caller();
786 JVMState* caller = unc->jvms()->caller();
787 if ((dom_caller == nullptr) != (caller == nullptr)) {
788 // The current method must either be inlined into both dom_caller and
789 // caller or must not be inlined at all (top method). Bail out otherwise.
790 return false;
791 } else if (dom_caller != nullptr && !dom_caller->same_calls_as(caller)) {
792 return false;
793 }
794 // Check that the bci of the dominating uncommon trap dominates the bci
795 // of the dominated uncommon trap. Otherwise we may not re-execute
796 // the dominated check after deoptimization from the merged uncommon trap.
797 ciTypeFlow* flow = dom_method->get_flow_analysis();
798 int bci = unc->jvms()->bci();
799 int dom_bci = dom_unc->jvms()->bci();
800 if (!flow->is_dominated_by(bci, dom_bci)) {
801 return false;
802 }
803
804 return true;
805 }
806
807 // Return projection that leads to an uncommon trap if any
808 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
809 for (int i = 0; i < 2; i++) {
810 call = proj_out(i)->is_uncommon_trap_proj();
811 if (call != nullptr) {
812 return proj_out(i);
813 }
814 }
815 return nullptr;
816 }
817
818 // Do this If and the dominating If both branch out to an uncommon trap
819 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
820 ProjNode* otherproj = proj->other_if_proj();
821 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
822
823 if (otherproj->outcnt() == 1 && dom_unc != nullptr) {
824 // We need to re-execute the folded Ifs after deoptimization from the merged traps
825 if (!dom_unc->jvms()->should_reexecute()) {
826 return false;
827 }
828
829 CallStaticJavaNode* unc = nullptr;
830 ProjNode* unc_proj = uncommon_trap_proj(unc);
831 if (unc_proj != nullptr && unc_proj->outcnt() == 1) {
832 if (dom_unc == unc) {
833 // Allow the uncommon trap to be shared through a region
834 RegionNode* r = unc->in(0)->as_Region();
835 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
836 return false;
837 }
838 assert(r->has_phi() == nullptr, "simple region shouldn't have a phi");
839 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
840 return false;
841 }
842
843 if (!is_dominator_unc(dom_unc, unc)) {
844 return false;
845 }
846
847 // See merge_uncommon_traps: the reason of the uncommon trap
848 // will be changed and the state of the dominating If will be
849 // used. Checked that we didn't apply this transformation in a
850 // previous compilation and it didn't cause too many traps
851 ciMethod* dom_method = dom_unc->jvms()->method();
852 int dom_bci = dom_unc->jvms()->bci();
853 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
854 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check) &&
855 // Return true if c2 manages to reconcile with UnstableIf optimization. See the comments for it.
856 igvn->C->remove_unstable_if_trap(dom_unc, true/*yield*/)) {
857 success = unc_proj;
858 fail = unc_proj->other_if_proj();
859 return true;
860 }
861 }
862 }
863 return false;
864 }
865
866 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
867 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
868 Node* this_cmp = in(1)->in(1);
869 BoolNode* this_bool = in(1)->as_Bool();
870 IfNode* dom_iff = proj->in(0)->as_If();
871 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
872 Node* lo = dom_iff->in(1)->in(1)->in(2);
873 Node* hi = this_cmp->in(2);
874 Node* n = this_cmp->in(1);
875 ProjNode* otherproj = proj->other_if_proj();
876
877 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
878 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
879
880 BoolTest::mask lo_test = dom_bool->_test._test;
881 BoolTest::mask hi_test = this_bool->_test._test;
882 BoolTest::mask cond = hi_test;
883
884 // convert:
885 //
886 // dom_bool = x {<,<=,>,>=} a
887 // / \
888 // proj = {True,False} / \ otherproj = {False,True}
889 // /
890 // this_bool = x {<,<=} b
891 // / \
892 // fail = {True,False} / \ success = {False,True}
893 // /
894 //
895 // (Second test guaranteed canonicalized, first one may not have
896 // been canonicalized yet)
897 //
898 // into:
899 //
900 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
901 // / \
902 // fail / \ success
903 // /
904 //
905
906 // Figure out which of the two tests sets the upper bound and which
907 // sets the lower bound if any.
908 Node* adjusted_lim = nullptr;
909 if (lo_type != nullptr && hi_type != nullptr && hi_type->_lo > lo_type->_hi &&
910 hi_type->_hi == max_jint && lo_type->_lo == min_jint && lo_test != BoolTest::ne) {
911 assert((dom_bool->_test.is_less() && !proj->_con) ||
912 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
913
914 // this_bool = <
915 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
916 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
917 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
918 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
919 // x in ]a, b[ on the fail (= True) projection, b > a:
920 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
921 // this_bool = <=
922 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
923 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
924 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
925 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
926 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
927 // x in ]a, b] on the fail (= True) projection b+1 > a:
928 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
929 // 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
930
931 if (hi_test == BoolTest::lt) {
932 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
933 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
934 }
935 } else if (hi_test == BoolTest::le) {
936 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
937 adjusted_lim = igvn->transform(new SubINode(hi, lo));
938 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
939 cond = BoolTest::lt;
940 } else if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
941 adjusted_lim = igvn->transform(new SubINode(hi, lo));
942 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
943 cond = BoolTest::lt;
944 } else {
945 assert(false, "unhandled lo_test: %d", lo_test);
946 return false;
947 }
948 } else {
949 assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled hi_test: %d", hi_test);
950 return false;
951 }
952 // this test was canonicalized
953 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
954 } else if (lo_type != nullptr && hi_type != nullptr && lo_type->_lo > hi_type->_hi &&
955 lo_type->_hi == max_jint && hi_type->_lo == min_jint && lo_test != BoolTest::ne) {
956
957 // this_bool = <
958 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
959 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
960 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
961 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
962 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
963 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
964 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
965 // this_bool = <=
966 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
967 // x in ]b, a[ on the fail (= False) projection, a > b:
968 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
969 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
970 // x in ]b, a] on the fail (= False) projection, a+1 > b:
971 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
972 // 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
973
974 swap(lo, hi);
975 swap(lo_type, hi_type);
976 swap(lo_test, hi_test);
977
978 assert((dom_bool->_test.is_less() && proj->_con) ||
979 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
980
981 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
982
983 if (lo_test == BoolTest::lt) {
984 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
985 cond = BoolTest::ge;
986 } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
987 adjusted_lim = igvn->transform(new SubINode(hi, lo));
988 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
989 cond = BoolTest::ge;
990 } else {
991 assert(false, "unhandled hi_test: %d", hi_test);
992 return false;
993 }
994 } else if (lo_test == BoolTest::le) {
995 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
996 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
997 cond = BoolTest::ge;
998 } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
999 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1000 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
1001 cond = BoolTest::ge;
1002 } else {
1003 assert(false, "unhandled hi_test: %d", hi_test);
1004 return false;
1005 }
1006 } else {
1007 assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled lo_test: %d", lo_test);
1008 return false;
1009 }
1010 // this test was canonicalized
1011 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
1012 } else {
1013 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
1014 if (failtype != nullptr) {
1015 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
1016 if (type2 != nullptr) {
1017 failtype = failtype->join(type2)->is_int();
1018 if (failtype->_lo > failtype->_hi) {
1019 // previous if determines the result of this if so
1020 // replace Bool with constant
1021 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
1022 return true;
1023 }
1024 }
1025 }
1026 lo = nullptr;
1027 hi = nullptr;
1028 }
1029
1030 if (lo && hi) {
1031 Node* hook = new Node(1);
1032 hook->init_req(0, lo); // Add a use to lo to prevent him from dying
1033 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1034 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
1035 if (adjusted_lim == nullptr) {
1036 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1037 }
1038 hook->destruct(igvn);
1039
1040 int lo = igvn->type(adjusted_lim)->is_int()->_lo;
1041 if (lo < 0) {
1042 // If range check elimination applies to this comparison, it includes code to protect from overflows that may
1043 // cause the main loop to be skipped entirely. Delay this transformation.
1044 // Example:
1045 // for (int i = 0; i < limit; i++) {
1046 // if (i < max_jint && i > min_jint) {...
1047 // }
1048 // Comparisons folded as:
1049 // i - min_jint - 1 <u -2
1050 // when RC applies, main loop limit becomes:
1051 // min(limit, max(-2 + min_jint + 1, min_jint))
1052 // = min(limit, min_jint)
1053 // = min_jint
1054 if (!igvn->C->post_loop_opts_phase()) {
1055 if (adjusted_val->outcnt() == 0) {
1056 igvn->remove_dead_node(adjusted_val);
1057 }
1058 if (adjusted_lim->outcnt() == 0) {
1059 igvn->remove_dead_node(adjusted_lim);
1060 }
1061 igvn->C->record_for_post_loop_opts_igvn(this);
1062 return false;
1063 }
1064 }
1065
1066 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1067 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1068
1069 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1070 igvn->replace_input_of(this, 1, newbool);
1071
1072 return true;
1073 }
1074 return false;
1075 }
1076
1077 // Merge the branches that trap for this If and the dominating If into
1078 // a single region that branches to the uncommon trap for the
1079 // dominating If
1080 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1081 Node* res = this;
1082 assert(success->in(0) == this, "bad projection");
1083
1084 ProjNode* otherproj = proj->other_if_proj();
1085
1086 CallStaticJavaNode* unc = success->is_uncommon_trap_proj();
1087 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
1088
1089 if (unc != dom_unc) {
1090 Node* r = new RegionNode(3);
1091
1092 r->set_req(1, otherproj);
1093 r->set_req(2, success);
1094 r = igvn->transform(r);
1095 assert(r->is_Region(), "can't go away");
1096
1097 // Make both If trap at the state of the first If: once the CmpI
1098 // nodes are merged, if we trap we don't know which of the CmpI
1099 // nodes would have caused the trap so we have to restart
1100 // execution at the first one
1101 igvn->replace_input_of(dom_unc, 0, r);
1102 igvn->replace_input_of(unc, 0, igvn->C->top());
1103 }
1104 int trap_request = dom_unc->uncommon_trap_request();
1105 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1106 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1107
1108 int flip_test = 0;
1109 Node* l = nullptr;
1110 Node* r = nullptr;
1111
1112 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != nullptr) {
1113 // If this looks like a range check, change the trap to
1114 // Reason_range_check so the compiler recognizes it as a range
1115 // check and applies the corresponding optimizations
1116 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1117
1118 improve_address_types(l, r, fail, igvn);
1119
1120 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1121 } else if (unc != dom_unc) {
1122 // If we trap we won't know what CmpI would have caused the trap
1123 // so use a special trap reason to mark this pair of CmpI nodes as
1124 // bad candidate for folding. On recompilation we won't fold them
1125 // and we may trap again but this time we'll know what branch
1126 // traps
1127 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1128 }
1129 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1130 return res;
1131 }
1132
1133 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1134 // of a rangecheck on index i, on 64 bit the compares may be followed
1135 // by memory accesses using i as index. In that case, the CmpU tells
1136 // us something about the values taken by i that can help the compiler
1137 // (see Compile::conv_I2X_index())
1138 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1139 #ifdef _LP64
1140 ResourceMark rm;
1141 Node_Stack stack(2);
1142
1143 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1144 const TypeInt* array_size = igvn->type(r)->is_int();
1145
1146 stack.push(l, 0);
1147
1148 while(stack.size() > 0) {
1149 Node* n = stack.node();
1150 uint start = stack.index();
1151
1152 uint i = start;
1153 for (; i < n->outcnt(); i++) {
1154 Node* use = n->raw_out(i);
1155 if (stack.size() == 1) {
1156 if (use->Opcode() == Op_ConvI2L) {
1157 const TypeLong* bounds = use->as_Type()->type()->is_long();
1158 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1159 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1160 stack.set_index(i+1);
1161 stack.push(use, 0);
1162 break;
1163 }
1164 }
1165 } else if (use->is_Mem()) {
1166 Node* ctrl = use->in(0);
1167 for (int i = 0; i < 10 && ctrl != nullptr && ctrl != fail; i++) {
1168 ctrl = up_one_dom(ctrl);
1169 }
1170 if (ctrl == fail) {
1171 Node* init_n = stack.node_at(1);
1172 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1173 // Create a new narrow ConvI2L node that is dependent on the range check
1174 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1175
1176 // The type of the ConvI2L may be widen and so the new
1177 // ConvI2L may not be better than an existing ConvI2L
1178 if (new_n != init_n) {
1179 for (uint j = 2; j < stack.size(); j++) {
1180 Node* n = stack.node_at(j);
1181 Node* clone = n->clone();
1182 int rep = clone->replace_edge(init_n, new_n, igvn);
1183 assert(rep > 0, "can't find expected node?");
1184 clone = igvn->transform(clone);
1185 init_n = n;
1186 new_n = clone;
1187 }
1188 igvn->hash_delete(use);
1189 int rep = use->replace_edge(init_n, new_n, igvn);
1190 assert(rep > 0, "can't find expected node?");
1191 igvn->transform(use);
1192 if (init_n->outcnt() == 0) {
1193 igvn->_worklist.push(init_n);
1194 }
1195 }
1196 }
1197 } else if (use->in(0) == nullptr && (igvn->type(use)->isa_long() ||
1198 igvn->type(use)->isa_ptr())) {
1199 stack.set_index(i+1);
1200 stack.push(use, 0);
1201 break;
1202 }
1203 }
1204 if (i == n->outcnt()) {
1205 stack.pop();
1206 }
1207 }
1208 #endif
1209 }
1210
1211 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1212 if (in(1) != nullptr &&
1213 in(1)->in(1) != nullptr &&
1214 in(1)->in(1)->in(2) != nullptr) {
1215 Node* other = in(1)->in(1)->in(2);
1216 if (other->Opcode() == Op_LoadRange &&
1217 ((other->in(0) != nullptr && other->in(0) == proj) ||
1218 (other->in(0) == nullptr &&
1219 other->in(2) != nullptr &&
1220 other->in(2)->is_AddP() &&
1221 other->in(2)->in(1) != nullptr &&
1222 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1223 other->in(2)->in(1)->in(0) == proj))) {
1224 return true;
1225 }
1226 }
1227 return false;
1228 }
1229
1230 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1231 Node* other = in(1)->in(1)->in(2);
1232 if (other->in(MemNode::Address) != nullptr &&
1233 proj->in(0)->in(1) != nullptr &&
1234 proj->in(0)->in(1)->is_Bool() &&
1235 proj->in(0)->in(1)->in(1) != nullptr &&
1236 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1237 proj->in(0)->in(1)->in(1)->in(2) != nullptr &&
1238 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1239 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1240 return true;
1241 }
1242 return false;
1243 }
1244
1245 // Check that the If that is in between the 2 integer comparisons has
1246 // no side effect
1247 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1248 if (proj == nullptr) {
1249 return false;
1250 }
1251 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1252 if (unc != nullptr && proj->outcnt() <= 2) {
1253 if (proj->outcnt() == 1 ||
1254 // Allow simple null check from LoadRange
1255 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1256 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1257 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern();
1258 assert(dom_unc != nullptr, "is_uncommon_trap_if_pattern returned null");
1259
1260 // reroute_side_effect_free_unc changes the state of this
1261 // uncommon trap to restart execution at the previous
1262 // CmpI. Check that this change in a previous compilation didn't
1263 // cause too many traps.
1264 int trap_request = unc->uncommon_trap_request();
1265 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1266
1267 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1268 return false;
1269 }
1270
1271 if (!is_dominator_unc(dom_unc, unc)) {
1272 return false;
1273 }
1274
1275 return true;
1276 }
1277 }
1278 return false;
1279 }
1280
1281 // Make the If between the 2 integer comparisons trap at the state of
1282 // the first If: the last CmpI is the one replaced by a CmpU and the
1283 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1284 // won't be guarded by the first CmpI anymore. It can trap in cases
1285 // where the first CmpI would have prevented it from executing: on a
1286 // trap, we need to restart execution at the state of the first CmpI
1287 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1288 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern();
1289 ProjNode* otherproj = proj->other_if_proj();
1290 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1291 Node* call_proj = dom_unc->unique_ctrl_out();
1292 Node* halt = call_proj->unique_ctrl_out();
1293
1294 Node* new_unc = dom_unc->clone();
1295 call_proj = call_proj->clone();
1296 halt = halt->clone();
1297 Node* c = otherproj->clone();
1298
1299 c = igvn->transform(c);
1300 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1301 new_unc->set_req(0, c);
1302 new_unc = igvn->transform(new_unc);
1303 call_proj->set_req(0, new_unc);
1304 call_proj = igvn->transform(call_proj);
1305 halt->set_req(0, call_proj);
1306 halt = igvn->transform(halt);
1307
1308 igvn->replace_node(otherproj, igvn->C->top());
1309 igvn->C->root()->add_req(halt);
1310 }
1311
1312 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1313 if (Opcode() != Op_If) return nullptr;
1314
1315 if (cmpi_folds(igvn)) {
1316 Node* ctrl = in(0);
1317 if (is_ctrl_folds(ctrl, igvn) && ctrl->outcnt() == 1) {
1318 // A integer comparison immediately dominated by another integer
1319 // comparison
1320 ProjNode* success = nullptr;
1321 ProjNode* fail = nullptr;
1322 ProjNode* dom_cmp = ctrl->as_Proj();
1323 if (has_shared_region(dom_cmp, success, fail) &&
1324 // Next call modifies graph so must be last
1325 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1326 return this;
1327 }
1328 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1329 // Next call modifies graph so must be last
1330 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1331 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1332 }
1333 return nullptr;
1334 } else if (ctrl->in(0) != nullptr &&
1335 ctrl->in(0)->in(0) != nullptr) {
1336 ProjNode* success = nullptr;
1337 ProjNode* fail = nullptr;
1338 Node* dom = ctrl->in(0)->in(0);
1339 ProjNode* dom_cmp = dom->isa_Proj();
1340 ProjNode* other_cmp = ctrl->isa_Proj();
1341
1342 // Check if it's an integer comparison dominated by another
1343 // integer comparison with another test in between
1344 if (is_ctrl_folds(dom, igvn) &&
1345 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1346 is_side_effect_free_test(other_cmp, igvn) &&
1347 // Next call modifies graph so must be last
1348 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1349 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1350 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1351 }
1352 }
1353 }
1354 return nullptr;
1355 }
1356
1357 //------------------------------remove_useless_bool----------------------------
1358 // Check for people making a useless boolean: things like
1359 // if( (x < y ? true : false) ) { ... }
1360 // Replace with if( x < y ) { ... }
1361 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1362 Node *i1 = iff->in(1);
1363 if( !i1->is_Bool() ) return nullptr;
1364 BoolNode *bol = i1->as_Bool();
1365
1366 Node *cmp = bol->in(1);
1367 if( cmp->Opcode() != Op_CmpI ) return nullptr;
1368
1369 // Must be comparing against a bool
1370 const Type *cmp2_t = phase->type( cmp->in(2) );
1371 if( cmp2_t != TypeInt::ZERO &&
1372 cmp2_t != TypeInt::ONE )
1373 return nullptr;
1374
1375 // Find a prior merge point merging the boolean
1376 i1 = cmp->in(1);
1377 if( !i1->is_Phi() ) return nullptr;
1378 PhiNode *phi = i1->as_Phi();
1379 if( phase->type( phi ) != TypeInt::BOOL )
1380 return nullptr;
1381
1382 // Check for diamond pattern
1383 int true_path = phi->is_diamond_phi();
1384 if( true_path == 0 ) return nullptr;
1385
1386 // Make sure that iff and the control of the phi are different. This
1387 // should really only happen for dead control flow since it requires
1388 // an illegal cycle.
1389 if (phi->in(0)->in(1)->in(0) == iff) return nullptr;
1390
1391 // phi->region->if_proj->ifnode->bool->cmp
1392 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1393
1394 // Now get the 'sense' of the test correct so we can plug in
1395 // either iff2->in(1) or its complement.
1396 int flip = 0;
1397 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1398 else if( bol->_test._test != BoolTest::eq ) return nullptr;
1399 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1400
1401 const Type *phi1_t = phase->type( phi->in(1) );
1402 const Type *phi2_t = phase->type( phi->in(2) );
1403 // Check for Phi(0,1) and flip
1404 if( phi1_t == TypeInt::ZERO ) {
1405 if( phi2_t != TypeInt::ONE ) return nullptr;
1406 flip = 1-flip;
1407 } else {
1408 // Check for Phi(1,0)
1409 if( phi1_t != TypeInt::ONE ) return nullptr;
1410 if( phi2_t != TypeInt::ZERO ) return nullptr;
1411 }
1412 if( true_path == 2 ) {
1413 flip = 1-flip;
1414 }
1415
1416 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1417 assert(new_bol != iff->in(1), "must make progress");
1418 iff->set_req_X(1, new_bol, phase);
1419 // Intervening diamond probably goes dead
1420 phase->C->set_major_progress();
1421 return iff;
1422 }
1423
1424 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1425
1426 struct RangeCheck {
1427 IfProjNode* ctl;
1428 jint off;
1429 };
1430
1431 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1432 if (remove_dead_region(phase, can_reshape)) return this;
1433 // No Def-Use info?
1434 if (!can_reshape) return nullptr;
1435
1436 // Don't bother trying to transform a dead if
1437 if (in(0)->is_top()) return nullptr;
1438 // Don't bother trying to transform an if with a dead test
1439 if (in(1)->is_top()) return nullptr;
1440 // Another variation of a dead test
1441 if (in(1)->is_Con()) return nullptr;
1442 // Another variation of a dead if
1443 if (outcnt() < 2) return nullptr;
1444
1445 // Canonicalize the test.
1446 Node* idt_if = idealize_test(phase, this);
1447 if (idt_if != nullptr) return idt_if;
1448
1449 // Try to split the IF
1450 PhaseIterGVN *igvn = phase->is_IterGVN();
1451 Node *s = split_if(this, igvn);
1452 if (s != nullptr) return s;
1453
1454 return NodeSentinel;
1455 }
1456
1457 //------------------------------Ideal------------------------------------------
1458 // Return a node which is more "ideal" than the current node. Strip out
1459 // control copies
1460 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1461 Node* res = Ideal_common(phase, can_reshape);
1462 if (res != NodeSentinel) {
1463 return res;
1464 }
1465
1466 // Check for people making a useless boolean: things like
1467 // if( (x < y ? true : false) ) { ... }
1468 // Replace with if( x < y ) { ... }
1469 Node* bol2 = remove_useless_bool(this, phase);
1470 if (bol2) return bol2;
1471
1472 if (in(0) == nullptr) return nullptr; // Dead loop?
1473
1474 PhaseIterGVN* igvn = phase->is_IterGVN();
1475 Node* result = fold_compares(igvn);
1476 if (result != nullptr) {
1477 return result;
1478 }
1479
1480 // Scan for an equivalent test
1481 int dist = 4; // Cutoff limit for search
1482 if (is_If() && in(1)->is_Bool()) {
1483 Node* cmp = in(1)->in(1);
1484 if (cmp->Opcode() == Op_CmpP &&
1485 cmp->in(2) != nullptr && // make sure cmp is not already dead
1486 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR) {
1487 dist = 64; // Limit for null-pointer scans
1488 }
1489 }
1490
1491 Node* prev_dom = search_identical(dist, igvn);
1492
1493 if (prev_dom != nullptr) {
1494 // Replace dominated IfNode
1495 return dominated_by(prev_dom, igvn, false);
1496 }
1497
1498 return simple_subsuming(igvn);
1499 }
1500
1501 //------------------------------dominated_by-----------------------------------
1502 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN* igvn, bool pin_array_access_nodes) {
1503 #ifndef PRODUCT
1504 if (TraceIterativeGVN) {
1505 tty->print(" Removing IfNode: "); this->dump();
1506 }
1507 #endif
1508
1509 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1510 Node *idom = in(0);
1511 // Need opcode to decide which way 'this' test goes
1512 int prev_op = prev_dom->Opcode();
1513 Node *top = igvn->C->top(); // Shortcut to top
1514
1515 // Now walk the current IfNode's projections.
1516 // Loop ends when 'this' has no more uses.
1517 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1518 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1519 igvn->add_users_to_worklist(ifp);
1520 // Check which projection it is and set target.
1521 // Data-target is either the dominating projection of the same type
1522 // or TOP if the dominating projection is of opposite type.
1523 // Data-target will be used as the new control edge for the non-CFG
1524 // nodes like Casts and Loads.
1525 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1526 // Control-target is just the If's immediate dominator or TOP.
1527 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1528
1529 // For each child of an IfTrue/IfFalse projection, reroute.
1530 // Loop ends when projection has no more uses.
1531 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1532 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1533 if (s->depends_only_on_test() && igvn->no_dependent_zero_check(s)) {
1534 // For control producers.
1535 // Do not rewire Div and Mod nodes which could have a zero divisor to avoid skipping their zero check.
1536 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1537 if (pin_array_access_nodes && data_target != top) {
1538 // As a result of range check smearing, Loads and range check Cast nodes that are control dependent on this
1539 // range check (that is about to be removed) now depend on multiple dominating range checks. After the removal
1540 // of this range check, these control dependent nodes end up at the lowest/nearest dominating check in the
1541 // graph. To ensure that these Loads/Casts do not float above any of the dominating checks (even when the
1542 // lowest dominating check is later replaced by yet another dominating check), we need to pin them at the
1543 // lowest dominating check.
1544 Node* clone = s->pin_array_access_node();
1545 if (clone != nullptr) {
1546 clone = igvn->transform(clone);
1547 igvn->replace_node(s, clone);
1548 }
1549 }
1550 } else {
1551 // Find the control input matching this def-use edge.
1552 // For Regions it may not be in slot 0.
1553 uint l;
1554 for (l = 0; s->in(l) != ifp; l++) { }
1555 igvn->replace_input_of(s, l, ctrl_target);
1556 }
1557 } // End for each child of a projection
1558
1559 igvn->remove_dead_node(ifp);
1560 } // End for each IfTrue/IfFalse child of If
1561
1562 // Kill the IfNode
1563 igvn->remove_dead_node(this);
1564
1565 // Must return either the original node (now dead) or a new node
1566 // (Do not return a top here, since that would break the uniqueness of top.)
1567 return new ConINode(TypeInt::ZERO);
1568 }
1569
1570 Node* IfNode::search_identical(int dist, PhaseIterGVN* igvn) {
1571 // Setup to scan up the CFG looking for a dominating test
1572 Node* dom = in(0);
1573 Node* prev_dom = this;
1574 int op = Opcode();
1575 // Search up the dominator tree for an If with an identical test
1576 while (dom->Opcode() != op || // Not same opcode?
1577 !same_condition(dom, igvn) || // Not same input 1?
1578 prev_dom->in(0) != dom) { // One path of test does not dominate?
1579 if (dist < 0) return nullptr;
1580
1581 dist--;
1582 prev_dom = dom;
1583 dom = up_one_dom(dom);
1584 if (!dom) return nullptr;
1585 }
1586
1587 // Check that we did not follow a loop back to ourselves
1588 if (this == dom) {
1589 return nullptr;
1590 }
1591
1592 #ifndef PRODUCT
1593 if (dist > 2) { // Add to count of null checks elided
1594 explicit_null_checks_elided++;
1595 }
1596 #endif
1597
1598 return prev_dom;
1599 }
1600
1601 bool IfNode::same_condition(const Node* dom, PhaseIterGVN* igvn) const {
1602 Node* dom_bool = dom->in(1);
1603 Node* this_bool = in(1);
1604 if (dom_bool == this_bool) {
1605 return true;
1606 }
1607
1608 if (dom_bool == nullptr || !dom_bool->is_Bool() ||
1609 this_bool == nullptr || !this_bool->is_Bool()) {
1610 return false;
1611 }
1612 Node* dom_cmp = dom_bool->in(1);
1613 Node* this_cmp = this_bool->in(1);
1614
1615 // If the comparison is a subtype check, then SubTypeCheck nodes may have profile data attached to them and may be
1616 // different nodes even-though they perform the same subtype check
1617 if (dom_cmp == nullptr || !dom_cmp->is_SubTypeCheck() ||
1618 this_cmp == nullptr || !this_cmp->is_SubTypeCheck()) {
1619 return false;
1620 }
1621
1622 if (dom_cmp->in(1) != this_cmp->in(1) ||
1623 dom_cmp->in(2) != this_cmp->in(2) ||
1624 dom_bool->as_Bool()->_test._test != this_bool->as_Bool()->_test._test) {
1625 return false;
1626 }
1627
1628 return true;
1629 }
1630
1631
1632 static int subsuming_bool_test_encode(Node*);
1633
1634 // Check if dominating test is subsuming 'this' one.
1635 //
1636 // cmp
1637 // / \
1638 // (r1) bool \
1639 // / bool (r2)
1640 // (dom) if \
1641 // \ )
1642 // (pre) if[TF] /
1643 // \ /
1644 // if (this)
1645 // \r1
1646 // r2\ eqT eqF neT neF ltT ltF leT leF gtT gtF geT geF
1647 // eq t f f t f - - f f - - f
1648 // ne f t t f t - - t t - - t
1649 // lt f - - f t f - f f - f t
1650 // le t - - t t - t f f t - t
1651 // gt f - - f f - f t t f - f
1652 // ge t - - t f t - t t - t f
1653 //
1654 Node* IfNode::simple_subsuming(PhaseIterGVN* igvn) {
1655 // Table encoding: N/A (na), True-branch (tb), False-branch (fb).
1656 static enum { na, tb, fb } s_short_circuit_map[6][12] = {
1657 /*rel: eq+T eq+F ne+T ne+F lt+T lt+F le+T le+F gt+T gt+F ge+T ge+F*/
1658 /*eq*/{ tb, fb, fb, tb, fb, na, na, fb, fb, na, na, fb },
1659 /*ne*/{ fb, tb, tb, fb, tb, na, na, tb, tb, na, na, tb },
1660 /*lt*/{ fb, na, na, fb, tb, fb, na, fb, fb, na, fb, tb },
1661 /*le*/{ tb, na, na, tb, tb, na, tb, fb, fb, tb, na, tb },
1662 /*gt*/{ fb, na, na, fb, fb, na, fb, tb, tb, fb, na, fb },
1663 /*ge*/{ tb, na, na, tb, fb, tb, na, tb, tb, na, tb, fb }};
1664
1665 Node* pre = in(0);
1666 if (!pre->is_IfTrue() && !pre->is_IfFalse()) {
1667 return nullptr;
1668 }
1669 Node* dom = pre->in(0);
1670 if (!dom->is_If()) {
1671 return nullptr;
1672 }
1673 Node* bol = in(1);
1674 if (!bol->is_Bool()) {
1675 return nullptr;
1676 }
1677 Node* cmp = in(1)->in(1);
1678 if (!cmp->is_Cmp()) {
1679 return nullptr;
1680 }
1681
1682 if (!dom->in(1)->is_Bool()) {
1683 return nullptr;
1684 }
1685 if (dom->in(1)->in(1) != cmp) { // Not same cond?
1686 return nullptr;
1687 }
1688
1689 int drel = subsuming_bool_test_encode(dom->in(1));
1690 int trel = subsuming_bool_test_encode(bol);
1691 int bout = pre->is_IfFalse() ? 1 : 0;
1692
1693 if (drel < 0 || trel < 0) {
1694 return nullptr;
1695 }
1696 int br = s_short_circuit_map[trel][2*drel+bout];
1697 if (br == na) {
1698 return nullptr;
1699 }
1700 #ifndef PRODUCT
1701 if (TraceIterativeGVN) {
1702 tty->print(" Subsumed IfNode: "); dump();
1703 }
1704 #endif
1705 // Replace condition with constant True(1)/False(0).
1706 bool is_always_true = br == tb;
1707 set_req(1, igvn->intcon(is_always_true ? 1 : 0));
1708
1709 // Update any data dependencies to the directly dominating test. This subsumed test is not immediately removed by igvn
1710 // and therefore subsequent optimizations might miss these data dependencies otherwise. There might be a dead loop
1711 // ('always_taken_proj' == 'pre') that is cleaned up later. Skip this case to make the iterator work properly.
1712 Node* always_taken_proj = proj_out(is_always_true);
1713 if (always_taken_proj != pre) {
1714 for (DUIterator_Fast imax, i = always_taken_proj->fast_outs(imax); i < imax; i++) {
1715 Node* u = always_taken_proj->fast_out(i);
1716 if (!u->is_CFG()) {
1717 igvn->replace_input_of(u, 0, pre);
1718 --i;
1719 --imax;
1720 }
1721 }
1722 }
1723
1724 if (bol->outcnt() == 0) {
1725 igvn->remove_dead_node(bol); // Kill the BoolNode.
1726 }
1727 return this;
1728 }
1729
1730 // Map BoolTest to local table encoding. The BoolTest (e)numerals
1731 // { eq = 0, ne = 4, le = 5, ge = 7, lt = 3, gt = 1 }
1732 // are mapped to table indices, while the remaining (e)numerals in BoolTest
1733 // { overflow = 2, no_overflow = 6, never = 8, illegal = 9 }
1734 // are ignored (these are not modeled in the table).
1735 //
1736 static int subsuming_bool_test_encode(Node* node) {
1737 precond(node->is_Bool());
1738 BoolTest::mask x = node->as_Bool()->_test._test;
1739 switch (x) {
1740 case BoolTest::eq: return 0;
1741 case BoolTest::ne: return 1;
1742 case BoolTest::lt: return 2;
1743 case BoolTest::le: return 3;
1744 case BoolTest::gt: return 4;
1745 case BoolTest::ge: return 5;
1746 case BoolTest::overflow:
1747 case BoolTest::no_overflow:
1748 case BoolTest::never:
1749 case BoolTest::illegal:
1750 default:
1751 return -1;
1752 }
1753 }
1754
1755 //------------------------------Identity---------------------------------------
1756 // If the test is constant & we match, then we are the input Control
1757 Node* IfProjNode::Identity(PhaseGVN* phase) {
1758 // Can only optimize if cannot go the other way
1759 const TypeTuple *t = phase->type(in(0))->is_tuple();
1760 if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1761 // During parsing (GVN) we don't remove dead code aggressively.
1762 // Cut off dead branch and let PhaseRemoveUseless take care of it.
1763 (!phase->is_IterGVN() ||
1764 // During IGVN, first wait for the dead branch to be killed.
1765 // Otherwise, the IfNode's control will have two control uses (the IfNode
1766 // that doesn't go away because it still has uses and this branch of the
1767 // If) which breaks other optimizations. Node::has_special_unique_user()
1768 // will cause this node to be reprocessed once the dead branch is killed.
1769 in(0)->outcnt() == 1))) {
1770 // IfNode control
1771 if (in(0)->is_BaseCountedLoopEnd()) {
1772 // CountedLoopEndNode may be eliminated by if subsuming, replace CountedLoopNode with LoopNode to
1773 // avoid mismatching between CountedLoopNode and CountedLoopEndNode in the following optimization.
1774 Node* head = unique_ctrl_out_or_null();
1775 if (head != nullptr && head->is_BaseCountedLoop() && head->in(LoopNode::LoopBackControl) == this) {
1776 Node* new_head = new LoopNode(head->in(LoopNode::EntryControl), this);
1777 phase->is_IterGVN()->register_new_node_with_optimizer(new_head);
1778 phase->is_IterGVN()->replace_node(head, new_head);
1779 }
1780 }
1781 return in(0)->in(0);
1782 }
1783 // no progress
1784 return this;
1785 }
1786
1787 bool IfNode::is_zero_trip_guard() const {
1788 if (in(1)->is_Bool() && in(1)->in(1)->is_Cmp()) {
1789 return in(1)->in(1)->in(1)->Opcode() == Op_OpaqueZeroTripGuard;
1790 }
1791 return false;
1792 }
1793
1794 void IfProjNode::pin_array_access_nodes(PhaseIterGVN* igvn) {
1795 for (DUIterator i = outs(); has_out(i); i++) {
1796 Node* u = out(i);
1797 if (!u->depends_only_on_test()) {
1798 continue;
1799 }
1800 Node* clone = u->pin_array_access_node();
1801 if (clone != nullptr) {
1802 clone = igvn->transform(clone);
1803 assert(clone != u, "shouldn't common");
1804 igvn->replace_node(u, clone);
1805 --i;
1806 }
1807 }
1808 }
1809
1810 #ifndef PRODUCT
1811 //------------------------------dump_spec--------------------------------------
1812 void IfNode::dump_spec(outputStream *st) const {
1813 st->print("P=%f, C=%f",_prob,_fcnt);
1814 }
1815 #endif
1816
1817 //------------------------------idealize_test----------------------------------
1818 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1819 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1820 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1821 // needed.
1822 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1823 assert(iff->in(0) != nullptr, "If must be live");
1824
1825 if (iff->outcnt() != 2) return nullptr; // Malformed projections.
1826 Node* old_if_f = iff->proj_out(false);
1827 Node* old_if_t = iff->proj_out(true);
1828
1829 // CountedLoopEnds want the back-control test to be TRUE, regardless of
1830 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1831 // happens in count-down loops
1832 if (iff->is_BaseCountedLoopEnd()) return nullptr;
1833 if (!iff->in(1)->is_Bool()) return nullptr; // Happens for partially optimized IF tests
1834 BoolNode *b = iff->in(1)->as_Bool();
1835 BoolTest bt = b->_test;
1836 // Test already in good order?
1837 if( bt.is_canonical() )
1838 return nullptr;
1839
1840 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1841 // cloning the IfNode.
1842 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1843 if( !new_b->is_Bool() ) return nullptr;
1844 b = new_b->as_Bool();
1845
1846 PhaseIterGVN *igvn = phase->is_IterGVN();
1847 assert( igvn, "Test is not canonical in parser?" );
1848
1849 // The IF node never really changes, but it needs to be cloned
1850 iff = iff->clone()->as_If();
1851 iff->set_req(1, b);
1852 iff->_prob = 1.0-iff->_prob;
1853
1854 Node *prior = igvn->hash_find_insert(iff);
1855 if( prior ) {
1856 igvn->remove_dead_node(iff);
1857 iff = (IfNode*)prior;
1858 } else {
1859 // Cannot call transform on it just yet
1860 igvn->set_type_bottom(iff);
1861 }
1862 igvn->_worklist.push(iff);
1863
1864 // Now handle projections. Cloning not required.
1865 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1866 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1867
1868 igvn->register_new_node_with_optimizer(new_if_f);
1869 igvn->register_new_node_with_optimizer(new_if_t);
1870 // Flip test, so flip trailing control
1871 igvn->replace_node(old_if_f, new_if_t);
1872 igvn->replace_node(old_if_t, new_if_f);
1873
1874 // Progress
1875 return iff;
1876 }
1877
1878 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1879 Node* res = Ideal_common(phase, can_reshape);
1880 if (res != NodeSentinel) {
1881 return res;
1882 }
1883
1884 PhaseIterGVN *igvn = phase->is_IterGVN();
1885 // Setup to scan up the CFG looking for a dominating test
1886 Node* prev_dom = this;
1887
1888 // Check for range-check vs other kinds of tests
1889 Node* index1;
1890 Node* range1;
1891 jint offset1;
1892 int flip1 = is_range_check(range1, index1, offset1);
1893 if (flip1) {
1894 Node* dom = in(0);
1895 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1896 // so all checks we inspect post-dominate the top-most check we find.
1897 // If we are going to fail the current check and we reach the top check
1898 // then we are guaranteed to fail, so just start interpreting there.
1899 // We 'expand' the top 3 range checks to include all post-dominating
1900 // checks.
1901 //
1902 // Example:
1903 // a[i+x] // (1) 1 < x < 6
1904 // a[i+3] // (2)
1905 // a[i+4] // (3)
1906 // a[i+6] // max = max of all constants
1907 // a[i+2]
1908 // a[i+1] // min = min of all constants
1909 //
1910 // If x < 3:
1911 // (1) a[i+x]: Leave unchanged
1912 // (2) a[i+3]: Replace with a[i+max] = a[i+6]: i+x < i+3 <= i+6 -> (2) is covered
1913 // (3) a[i+4]: Replace with a[i+min] = a[i+1]: i+1 < i+4 <= i+6 -> (3) and all following checks are covered
1914 // Remove all other a[i+c] checks
1915 //
1916 // If x >= 3:
1917 // (1) a[i+x]: Leave unchanged
1918 // (2) a[i+3]: Replace with a[i+min] = a[i+1]: i+1 < i+3 <= i+x -> (2) is covered
1919 // (3) a[i+4]: Replace with a[i+max] = a[i+6]: i+1 < i+4 <= i+6 -> (3) and all following checks are covered
1920 // Remove all other a[i+c] checks
1921 //
1922 // We only need the top 2 range checks if x is the min or max of all constants.
1923 //
1924 // This, however, only works if the interval [i+min,i+max] is not larger than max_int (i.e. abs(max - min) < max_int):
1925 // The theoretical max size of an array is max_int with:
1926 // - Valid index space: [0,max_int-1]
1927 // - Invalid index space: [max_int,-1] // max_int, min_int, min_int - 1 ..., -1
1928 //
1929 // The size of the consecutive valid index space is smaller than the size of the consecutive invalid index space.
1930 // If we choose min and max in such a way that:
1931 // - abs(max - min) < max_int
1932 // - i+max and i+min are inside the valid index space
1933 // then all indices [i+min,i+max] must be in the valid index space. Otherwise, the invalid index space must be
1934 // smaller than the valid index space which is never the case for any array size.
1935 //
1936 // Choosing a smaller array size only makes the valid index space smaller and the invalid index space larger and
1937 // the argument above still holds.
1938 //
1939 // Note that the same optimization with the same maximal accepted interval size can also be found in C1.
1940 const jlong maximum_number_of_min_max_interval_indices = (jlong)max_jint;
1941
1942 // The top 3 range checks seen
1943 const int NRC = 3;
1944 RangeCheck prev_checks[NRC];
1945 int nb_checks = 0;
1946
1947 // Low and high offsets seen so far
1948 jint off_lo = offset1;
1949 jint off_hi = offset1;
1950
1951 bool found_immediate_dominator = false;
1952
1953 // Scan for the top checks and collect range of offsets
1954 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1955 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1956 prev_dom->in(0) == dom) { // One path of test does dominate?
1957 if (dom == this) return nullptr; // dead loop
1958 // See if this is a range check
1959 Node* index2;
1960 Node* range2;
1961 jint offset2;
1962 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1963 // See if this is a _matching_ range check, checking against
1964 // the same array bounds.
1965 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1966 dom->outcnt() == 2) {
1967 if (nb_checks == 0 && dom->in(1) == in(1)) {
1968 // Found an immediately dominating test at the same offset.
1969 // This kind of back-to-back test can be eliminated locally,
1970 // and there is no need to search further for dominating tests.
1971 assert(offset2 == offset1, "Same test but different offsets");
1972 found_immediate_dominator = true;
1973 break;
1974 }
1975
1976 // "x - y" -> must add one to the difference for number of elements in [x,y]
1977 const jlong diff = (jlong)MIN2(offset2, off_lo) - (jlong)MAX2(offset2, off_hi);
1978 if (ABS(diff) < maximum_number_of_min_max_interval_indices) {
1979 // Gather expanded bounds
1980 off_lo = MIN2(off_lo, offset2);
1981 off_hi = MAX2(off_hi, offset2);
1982 // Record top NRC range checks
1983 prev_checks[nb_checks % NRC].ctl = prev_dom->as_IfProj();
1984 prev_checks[nb_checks % NRC].off = offset2;
1985 nb_checks++;
1986 }
1987 }
1988 }
1989 prev_dom = dom;
1990 dom = up_one_dom(dom);
1991 if (!dom) break;
1992 }
1993
1994 if (!found_immediate_dominator) {
1995 // Attempt to widen the dominating range check to cover some later
1996 // ones. Since range checks "fail" by uncommon-trapping to the
1997 // interpreter, widening a check can make us speculatively enter
1998 // the interpreter. If we see range-check deopt's, do not widen!
1999 if (!phase->C->allow_range_check_smearing()) return nullptr;
2000
2001 if (can_reshape && !phase->C->post_loop_opts_phase()) {
2002 // We are about to perform range check smearing (i.e. remove this RangeCheck if it is dominated by
2003 // a series of RangeChecks which have a range that covers this RangeCheck). This can cause array access nodes to
2004 // be pinned. We want to avoid that and first allow range check elimination a chance to remove the RangeChecks
2005 // from loops. Hence, we delay range check smearing until after loop opts.
2006 phase->C->record_for_post_loop_opts_igvn(this);
2007 return nullptr;
2008 }
2009
2010 // Didn't find prior covering check, so cannot remove anything.
2011 if (nb_checks == 0) {
2012 return nullptr;
2013 }
2014 // Constant indices only need to check the upper bound.
2015 // Non-constant indices must check both low and high.
2016 int chk0 = (nb_checks - 1) % NRC;
2017 if (index1) {
2018 if (nb_checks == 1) {
2019 return nullptr;
2020 } else {
2021 // If the top range check's constant is the min or max of
2022 // all constants we widen the next one to cover the whole
2023 // range of constants.
2024 RangeCheck rc0 = prev_checks[chk0];
2025 int chk1 = (nb_checks - 2) % NRC;
2026 RangeCheck rc1 = prev_checks[chk1];
2027 if (rc0.off == off_lo) {
2028 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
2029 prev_dom = rc1.ctl;
2030 } else if (rc0.off == off_hi) {
2031 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
2032 prev_dom = rc1.ctl;
2033 } else {
2034 // If the top test's constant is not the min or max of all
2035 // constants, we need 3 range checks. We must leave the
2036 // top test unchanged because widening it would allow the
2037 // accesses it protects to successfully read/write out of
2038 // bounds.
2039 if (nb_checks == 2) {
2040 return nullptr;
2041 }
2042 int chk2 = (nb_checks - 3) % NRC;
2043 RangeCheck rc2 = prev_checks[chk2];
2044 // The top range check a+i covers interval: -a <= i < length-a
2045 // The second range check b+i covers interval: -b <= i < length-b
2046 if (rc1.off <= rc0.off) {
2047 // if b <= a, we change the second range check to:
2048 // -min_of_all_constants <= i < length-min_of_all_constants
2049 // Together top and second range checks now cover:
2050 // -min_of_all_constants <= i < length-a
2051 // which is more restrictive than -b <= i < length-b:
2052 // -b <= -min_of_all_constants <= i < length-a <= length-b
2053 // The third check is then changed to:
2054 // -max_of_all_constants <= i < length-max_of_all_constants
2055 // so 2nd and 3rd checks restrict allowed values of i to:
2056 // -min_of_all_constants <= i < length-max_of_all_constants
2057 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
2058 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
2059 } else {
2060 // if b > a, we change the second range check to:
2061 // -max_of_all_constants <= i < length-max_of_all_constants
2062 // Together top and second range checks now cover:
2063 // -a <= i < length-max_of_all_constants
2064 // which is more restrictive than -b <= i < length-b:
2065 // -b < -a <= i < length-max_of_all_constants <= length-b
2066 // The third check is then changed to:
2067 // -max_of_all_constants <= i < length-max_of_all_constants
2068 // so 2nd and 3rd checks restrict allowed values of i to:
2069 // -min_of_all_constants <= i < length-max_of_all_constants
2070 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
2071 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
2072 }
2073 prev_dom = rc2.ctl;
2074 }
2075 }
2076 } else {
2077 RangeCheck rc0 = prev_checks[chk0];
2078 // 'Widen' the offset of the 1st and only covering check
2079 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
2080 // Test is now covered by prior checks, dominate it out
2081 prev_dom = rc0.ctl;
2082 }
2083 // The last RangeCheck is found to be redundant with a sequence of n (n >= 2) preceding RangeChecks.
2084 // If an array load is control dependent on the eliminated range check, the array load nodes (CastII and Load)
2085 // become control dependent on the last range check of the sequence, but they are really dependent on the entire
2086 // sequence of RangeChecks. If RangeCheck#n is later replaced by a dominating identical check, the array load
2087 // nodes must not float above the n-1 other RangeCheck in the sequence. We pin the array load nodes here to
2088 // guarantee it doesn't happen.
2089 //
2090 // RangeCheck#1 RangeCheck#1
2091 // | \ | \
2092 // | uncommon trap | uncommon trap
2093 // .. ..
2094 // RangeCheck#n -> RangeCheck#n
2095 // | \ | \
2096 // | uncommon trap CastII uncommon trap
2097 // RangeCheck Load
2098 // | \
2099 // CastII uncommon trap
2100 // Load
2101
2102 return dominated_by(prev_dom, igvn, true);
2103 }
2104 } else {
2105 prev_dom = search_identical(4, igvn);
2106
2107 if (prev_dom == nullptr) {
2108 return nullptr;
2109 }
2110 }
2111
2112 // Replace dominated IfNode
2113 return dominated_by(prev_dom, igvn, false);
2114 }
2115
2116 ParsePredicateNode::ParsePredicateNode(Node* control, Deoptimization::DeoptReason deopt_reason, PhaseGVN* gvn)
2117 : IfNode(control, gvn->intcon(1), PROB_MAX, COUNT_UNKNOWN),
2118 _deopt_reason(deopt_reason),
2119 _useless(false) {
2120 init_class_id(Class_ParsePredicate);
2121 gvn->C->add_parse_predicate(this);
2122 gvn->C->record_for_post_loop_opts_igvn(this);
2123 #ifdef ASSERT
2124 switch (deopt_reason) {
2125 case Deoptimization::Reason_predicate:
2126 case Deoptimization::Reason_profile_predicate:
2127 case Deoptimization::Reason_loop_limit_check:
2128 break;
2129 default:
2130 assert(false, "unsupported deoptimization reason for Parse Predicate");
2131 }
2132 #endif // ASSERT
2133 }
2134
2135 Node* ParsePredicateNode::uncommon_trap() const {
2136 ParsePredicateUncommonProj* uncommon_proj = proj_out(0)->as_IfFalse();
2137 Node* uct_region_or_call = uncommon_proj->unique_ctrl_out();
2138 assert(uct_region_or_call->is_Region() || uct_region_or_call->is_Call(), "must be a region or call uct");
2139 return uct_region_or_call;
2140 }
2141
2142 // Fold this node away once it becomes useless or at latest in post loop opts IGVN.
2143 const Type* ParsePredicateNode::Value(PhaseGVN* phase) const {
2144 if (phase->type(in(0)) == Type::TOP) {
2145 return Type::TOP;
2146 }
2147 if (_useless || phase->C->post_loop_opts_phase()) {
2148 return TypeTuple::IFTRUE;
2149 } else {
2150 return bottom_type();
2151 }
2152 }
2153
2154 #ifndef PRODUCT
2155 void ParsePredicateNode::dump_spec(outputStream* st) const {
2156 st->print(" #");
2157 switch (_deopt_reason) {
2158 case Deoptimization::DeoptReason::Reason_predicate:
2159 st->print("Loop ");
2160 break;
2161 case Deoptimization::DeoptReason::Reason_profile_predicate:
2162 st->print("Profiled_Loop ");
2163 break;
2164 case Deoptimization::DeoptReason::Reason_loop_limit_check:
2165 st->print("Loop_Limit_Check ");
2166 break;
2167 default:
2168 fatal("unknown kind");
2169 }
2170 }
2171
2172 #endif // NOT PRODUCT