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
21 * questions.
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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(Node* 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 }
570
571 //------------------------------up_one_dom-------------------------------------
572 // Walk up the dominator tree one step. Return null at root or true
573 // complex merges. Skips through small diamonds.
574 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
575 Node *dom = curr->in(0);
576 if( !dom ) // Found a Region degraded to a copy?
577 return curr->nonnull_req(); // Skip thru it
578
579 if( curr != dom ) // Normal walk up one step?
580 return dom;
581
582 // Use linear_only if we are still parsing, since we cannot
583 // trust the regions to be fully filled in.
584 if (linear_only)
585 return nullptr;
586
587 if( dom->is_Root() )
588 return nullptr;
589
590 // Else hit a Region. Check for a loop header
591 if( dom->is_Loop() )
592 return dom->in(1); // Skip up thru loops
593
594 // Check for small diamonds
595 Node *din1, *din2, *din3, *din4;
596 if( dom->req() == 3 && // 2-path merge point
597 (din1 = dom ->in(1)) && // Left path exists
598 (din2 = dom ->in(2)) && // Right path exists
599 (din3 = din1->in(0)) && // Left path up one
600 (din4 = din2->in(0)) ) { // Right path up one
601 if( din3->is_Call() && // Handle a slow-path call on either arm
602 (din3 = din3->in(0)) )
603 din3 = din3->in(0);
604 if( din4->is_Call() && // Handle a slow-path call on either arm
605 (din4 = din4->in(0)) )
606 din4 = din4->in(0);
607 if (din3 != nullptr && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
608 return din3; // Skip around diamonds
609 }
610
611 // Give up the search at true merges
612 return nullptr; // Dead loop? Or hit root?
613 }
614
615
616 //------------------------------filtered_int_type--------------------------------
617 // Return a possibly more restrictive type for val based on condition control flow for an if
618 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node* val, Node* if_proj) {
619 assert(if_proj &&
620 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
621 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
622 IfNode* iff = if_proj->in(0)->as_If();
623 if (iff->in(1) && iff->in(1)->is_Bool()) {
624 BoolNode* bol = iff->in(1)->as_Bool();
625 if (bol->in(1) && bol->in(1)->is_Cmp()) {
626 const CmpNode* cmp = bol->in(1)->as_Cmp();
627 if (cmp->in(1) == val) {
628 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
629 if (cmp2_t != nullptr) {
630 jint lo = cmp2_t->_lo;
631 jint hi = cmp2_t->_hi;
632 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
633 switch (msk) {
634 case BoolTest::ne: {
635 // If val is compared to its lower or upper bound, we can narrow the type
636 const TypeInt* val_t = gvn->type(val)->isa_int();
637 if (val_t != nullptr && !val_t->singleton() && cmp2_t->is_con()) {
638 if (val_t->_lo == lo) {
639 return TypeInt::make(val_t->_lo + 1, val_t->_hi, val_t->_widen);
640 } else if (val_t->_hi == hi) {
641 return TypeInt::make(val_t->_lo, val_t->_hi - 1, val_t->_widen);
642 }
643 }
644 // Can't refine type
645 return nullptr;
646 }
647 case BoolTest::eq:
648 return cmp2_t;
649 case BoolTest::lt:
650 lo = TypeInt::INT->_lo;
651 if (hi != min_jint) {
652 hi = hi - 1;
653 }
654 break;
655 case BoolTest::le:
656 lo = TypeInt::INT->_lo;
657 break;
658 case BoolTest::gt:
659 if (lo != max_jint) {
660 lo = lo + 1;
661 }
662 hi = TypeInt::INT->_hi;
663 break;
664 case BoolTest::ge:
665 // lo unchanged
666 hi = TypeInt::INT->_hi;
667 break;
668 default:
669 break;
670 }
671 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
672 return rtn_t;
673 }
674 }
675 }
676 }
677 }
678 return nullptr;
679 }
680
681 //------------------------------fold_compares----------------------------
682 // See if a pair of CmpIs can be converted into a CmpU. In some cases
683 // the direction of this if is determined by the preceding if so it
684 // can be eliminate entirely.
685 //
686 // Given an if testing (CmpI n v) check for an immediately control
687 // dependent if that is testing (CmpI n v2) and has one projection
688 // leading to this if and the other projection leading to a region
689 // that merges one of this ifs control projections.
690 //
691 // If
692 // / |
693 // / |
694 // / |
695 // If |
696 // /\ |
697 // / \ |
698 // / \ |
699 // / Region
700 //
701 // Or given an if testing (CmpI n v) check for a dominating if that is
702 // testing (CmpI n v2), both having one projection leading to an
703 // uncommon trap. Allow Another independent guard in between to cover
704 // an explicit range check:
705 // if (index < 0 || index >= array.length) {
706 // which may need a null check to guard the LoadRange
707 //
708 // If
709 // / \
710 // / \
711 // / \
712 // If unc
713 // /\
714 // / \
715 // / \
716 // / unc
717 //
718
719 // Is the comparison for this If suitable for folding?
720 bool IfNode::cmpi_folds(PhaseIterGVN* igvn, bool fold_ne) {
721 return in(1) != nullptr &&
722 in(1)->is_Bool() &&
723 in(1)->in(1) != nullptr &&
724 in(1)->in(1)->Opcode() == Op_CmpI &&
725 in(1)->in(1)->in(2) != nullptr &&
726 in(1)->in(1)->in(2) != igvn->C->top() &&
727 (in(1)->as_Bool()->_test.is_less() ||
728 in(1)->as_Bool()->_test.is_greater() ||
729 (fold_ne && in(1)->as_Bool()->_test._test == BoolTest::ne));
730 }
731
732 // Is a dominating control suitable for folding with this if?
733 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
734 return ctrl != nullptr &&
735 ctrl->is_Proj() &&
736 ctrl->in(0) != nullptr &&
737 ctrl->in(0)->Opcode() == Op_If &&
738 ctrl->in(0)->outcnt() == 2 &&
739 ctrl->in(0)->as_If()->cmpi_folds(igvn, true) &&
740 // Must compare same value
741 ctrl->in(0)->in(1)->in(1)->in(1) != nullptr &&
742 ctrl->in(0)->in(1)->in(1)->in(1) != igvn->C->top() &&
743 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
744 }
745
746 // Do this If and the dominating If share a region?
747 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
748 ProjNode* otherproj = proj->other_if_proj();
749 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out_or_null();
750 RegionNode* region = (otherproj_ctrl_use != nullptr && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : nullptr;
751 success = nullptr;
752 fail = nullptr;
753
754 if (otherproj->outcnt() == 1 && region != nullptr && !region->has_phi()) {
755 for (int i = 0; i < 2; i++) {
756 ProjNode* proj = proj_out(i);
757 if (success == nullptr && proj->outcnt() == 1 && proj->unique_out() == region) {
758 success = proj;
759 } else if (fail == nullptr) {
760 fail = proj;
761 } else {
762 success = fail = nullptr;
763 }
764 }
765 }
766 return success != nullptr && fail != nullptr;
767 }
768
769 bool IfNode::is_dominator_unc(CallStaticJavaNode* dom_unc, CallStaticJavaNode* unc) {
770 // Different methods and methods containing jsrs are not supported.
771 ciMethod* method = unc->jvms()->method();
772 ciMethod* dom_method = dom_unc->jvms()->method();
773 if (method != dom_method || method->has_jsrs()) {
774 return false;
775 }
776 // Check that both traps are in the same activation of the method (instead
777 // of two activations being inlined through different call sites) by verifying
778 // that the call stacks are equal for both JVMStates.
779 JVMState* dom_caller = dom_unc->jvms()->caller();
780 JVMState* caller = unc->jvms()->caller();
781 if ((dom_caller == nullptr) != (caller == nullptr)) {
782 // The current method must either be inlined into both dom_caller and
783 // caller or must not be inlined at all (top method). Bail out otherwise.
784 return false;
785 } else if (dom_caller != nullptr && !dom_caller->same_calls_as(caller)) {
786 return false;
787 }
788 // Check that the bci of the dominating uncommon trap dominates the bci
789 // of the dominated uncommon trap. Otherwise we may not re-execute
790 // the dominated check after deoptimization from the merged uncommon trap.
791 ciTypeFlow* flow = dom_method->get_flow_analysis();
792 int bci = unc->jvms()->bci();
793 int dom_bci = dom_unc->jvms()->bci();
794 if (!flow->is_dominated_by(bci, dom_bci)) {
795 return false;
796 }
797
798 return true;
799 }
800
801 // Return projection that leads to an uncommon trap if any
802 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
803 for (int i = 0; i < 2; i++) {
804 call = proj_out(i)->is_uncommon_trap_proj();
805 if (call != nullptr) {
806 return proj_out(i);
807 }
808 }
809 return nullptr;
810 }
811
812 // Do this If and the dominating If both branch out to an uncommon trap
813 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
814 ProjNode* otherproj = proj->other_if_proj();
815 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
816
817 if (otherproj->outcnt() == 1 && dom_unc != nullptr) {
818 // We need to re-execute the folded Ifs after deoptimization from the merged traps
819 if (!dom_unc->jvms()->should_reexecute()) {
820 return false;
821 }
822
823 CallStaticJavaNode* unc = nullptr;
824 ProjNode* unc_proj = uncommon_trap_proj(unc);
825 if (unc_proj != nullptr && unc_proj->outcnt() == 1) {
826 if (dom_unc == unc) {
827 // Allow the uncommon trap to be shared through a region
828 RegionNode* r = unc->in(0)->as_Region();
829 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
830 return false;
831 }
832 assert(r->has_phi() == nullptr, "simple region shouldn't have a phi");
833 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
834 return false;
835 }
836
837 if (!is_dominator_unc(dom_unc, unc)) {
838 return false;
839 }
840
841 // See merge_uncommon_traps: the reason of the uncommon trap
842 // will be changed and the state of the dominating If will be
843 // used. Checked that we didn't apply this transformation in a
844 // previous compilation and it didn't cause too many traps
845 ciMethod* dom_method = dom_unc->jvms()->method();
846 int dom_bci = dom_unc->jvms()->bci();
847 if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
848 !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check) &&
849 // Return true if c2 manages to reconcile with UnstableIf optimization. See the comments for it.
850 igvn->C->remove_unstable_if_trap(dom_unc, true/*yield*/)) {
851 success = unc_proj;
852 fail = unc_proj->other_if_proj();
853 return true;
854 }
855 }
856 }
857 return false;
858 }
859
860 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
861 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
862 Node* this_cmp = in(1)->in(1);
863 BoolNode* this_bool = in(1)->as_Bool();
864 IfNode* dom_iff = proj->in(0)->as_If();
865 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
866 Node* lo = dom_iff->in(1)->in(1)->in(2);
867 Node* hi = this_cmp->in(2);
868 Node* n = this_cmp->in(1);
869 ProjNode* otherproj = proj->other_if_proj();
870
871 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
872 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
873
874 BoolTest::mask lo_test = dom_bool->_test._test;
875 BoolTest::mask hi_test = this_bool->_test._test;
876 BoolTest::mask cond = hi_test;
877
878 // convert:
879 //
880 // dom_bool = x {<,<=,>,>=} a
881 // / \
882 // proj = {True,False} / \ otherproj = {False,True}
883 // /
884 // this_bool = x {<,<=} b
885 // / \
886 // fail = {True,False} / \ success = {False,True}
887 // /
888 //
889 // (Second test guaranteed canonicalized, first one may not have
890 // been canonicalized yet)
891 //
892 // into:
893 //
894 // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
895 // / \
896 // fail / \ success
897 // /
898 //
899
900 // Figure out which of the two tests sets the upper bound and which
901 // sets the lower bound if any.
902 Node* adjusted_lim = nullptr;
903 if (lo_type != nullptr && hi_type != nullptr && hi_type->_lo > lo_type->_hi &&
904 hi_type->_hi == max_jint && lo_type->_lo == min_jint && lo_test != BoolTest::ne) {
905 assert((dom_bool->_test.is_less() && !proj->_con) ||
906 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
907
908 // this_bool = <
909 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
910 // x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
911 // lo = a, hi = b, adjusted_lim = b-a, cond = <u
912 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
913 // x in ]a, b[ on the fail (= True) projection, b > a:
914 // lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
915 // this_bool = <=
916 // dom_bool = >= (proj = True) or dom_bool = < (proj = False)
917 // x in [a, b] on the fail (= True) projection, b+1 > a-1:
918 // lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
919 // lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
920 // dom_bool = > (proj = True) or dom_bool = <= (proj = False)
921 // x in ]a, b] on the fail (= True) projection b+1 > a:
922 // lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
923 // 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
924
925 if (hi_test == BoolTest::lt) {
926 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
927 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
928 }
929 } else if (hi_test == BoolTest::le) {
930 if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
931 adjusted_lim = igvn->transform(new SubINode(hi, lo));
932 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
933 cond = BoolTest::lt;
934 } else if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
935 adjusted_lim = igvn->transform(new SubINode(hi, lo));
936 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
937 cond = BoolTest::lt;
938 } else {
939 assert(false, "unhandled lo_test: %d", lo_test);
940 return false;
941 }
942 } else {
943 assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled hi_test: %d", hi_test);
944 return false;
945 }
946 // this test was canonicalized
947 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
948 } else if (lo_type != nullptr && hi_type != nullptr && lo_type->_lo > hi_type->_hi &&
949 lo_type->_hi == max_jint && hi_type->_lo == min_jint && lo_test != BoolTest::ne) {
950
951 // this_bool = <
952 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
953 // x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
954 // lo = b, hi = a, adjusted_lim = a-b, cond = >=u
955 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
956 // x in [b, a] on the fail (= False) projection, a+1 > b-1:
957 // lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
958 // lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
959 // this_bool = <=
960 // dom_bool = < (proj = True) or dom_bool = >= (proj = False)
961 // x in ]b, a[ on the fail (= False) projection, a > b:
962 // lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
963 // dom_bool = <= (proj = True) or dom_bool = > (proj = False)
964 // x in ]b, a] on the fail (= False) projection, a+1 > b:
965 // lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
966 // 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
967
968 swap(lo, hi);
969 swap(lo_type, hi_type);
970 swap(lo_test, hi_test);
971
972 assert((dom_bool->_test.is_less() && proj->_con) ||
973 (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
974
975 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
976
977 if (lo_test == BoolTest::lt) {
978 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
979 cond = BoolTest::ge;
980 } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
981 adjusted_lim = igvn->transform(new SubINode(hi, lo));
982 adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
983 cond = BoolTest::ge;
984 } else {
985 assert(false, "unhandled hi_test: %d", hi_test);
986 return false;
987 }
988 } else if (lo_test == BoolTest::le) {
989 if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
990 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
991 cond = BoolTest::ge;
992 } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
993 adjusted_lim = igvn->transform(new SubINode(hi, lo));
994 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
995 cond = BoolTest::ge;
996 } else {
997 assert(false, "unhandled hi_test: %d", hi_test);
998 return false;
999 }
1000 } else {
1001 assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled lo_test: %d", lo_test);
1002 return false;
1003 }
1004 // this test was canonicalized
1005 assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
1006 } else {
1007 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
1008 if (failtype != nullptr) {
1009 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
1010 if (type2 != nullptr) {
1011 failtype = failtype->join(type2)->is_int();
1012 if (failtype->_lo > failtype->_hi) {
1013 // previous if determines the result of this if so
1014 // replace Bool with constant
1015 igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
1016 return true;
1017 }
1018 }
1019 }
1020 lo = nullptr;
1021 hi = nullptr;
1022 }
1023
1024 if (lo && hi) {
1025 Node* hook = new Node(1);
1026 hook->init_req(0, lo); // Add a use to lo to prevent him from dying
1027 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1028 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
1029 if (adjusted_lim == nullptr) {
1030 adjusted_lim = igvn->transform(new SubINode(hi, lo));
1031 }
1032 hook->destruct(igvn);
1033
1034 int lo = igvn->type(adjusted_lim)->is_int()->_lo;
1035 if (lo < 0) {
1036 // If range check elimination applies to this comparison, it includes code to protect from overflows that may
1037 // cause the main loop to be skipped entirely. Delay this transformation.
1038 // Example:
1039 // for (int i = 0; i < limit; i++) {
1040 // if (i < max_jint && i > min_jint) {...
1041 // }
1042 // Comparisons folded as:
1043 // i - min_jint - 1 <u -2
1044 // when RC applies, main loop limit becomes:
1045 // min(limit, max(-2 + min_jint + 1, min_jint))
1046 // = min(limit, min_jint)
1047 // = min_jint
1048 if (!igvn->C->post_loop_opts_phase()) {
1049 if (adjusted_val->outcnt() == 0) {
1050 igvn->remove_dead_node(adjusted_val);
1051 }
1052 if (adjusted_lim->outcnt() == 0) {
1053 igvn->remove_dead_node(adjusted_lim);
1054 }
1055 igvn->C->record_for_post_loop_opts_igvn(this);
1056 return false;
1057 }
1058 }
1059
1060 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1061 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1062
1063 igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1064 igvn->replace_input_of(this, 1, newbool);
1065
1066 return true;
1067 }
1068 return false;
1069 }
1070
1071 // Merge the branches that trap for this If and the dominating If into
1072 // a single region that branches to the uncommon trap for the
1073 // dominating If
1074 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1075 Node* res = this;
1076 assert(success->in(0) == this, "bad projection");
1077
1078 ProjNode* otherproj = proj->other_if_proj();
1079
1080 CallStaticJavaNode* unc = success->is_uncommon_trap_proj();
1081 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
1082
1083 if (unc != dom_unc) {
1084 Node* r = new RegionNode(3);
1085
1086 r->set_req(1, otherproj);
1087 r->set_req(2, success);
1088 r = igvn->transform(r);
1089 assert(r->is_Region(), "can't go away");
1090
1091 // Make both If trap at the state of the first If: once the CmpI
1092 // nodes are merged, if we trap we don't know which of the CmpI
1093 // nodes would have caused the trap so we have to restart
1094 // execution at the first one
1095 igvn->replace_input_of(dom_unc, 0, r);
1096 igvn->replace_input_of(unc, 0, igvn->C->top());
1097 }
1098 int trap_request = dom_unc->uncommon_trap_request();
1099 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1100 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1101
1102 int flip_test = 0;
1103 Node* l = nullptr;
1104 Node* r = nullptr;
1105
1106 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != nullptr) {
1107 // If this looks like a range check, change the trap to
1108 // Reason_range_check so the compiler recognizes it as a range
1109 // check and applies the corresponding optimizations
1110 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1111
1112 improve_address_types(l, r, fail, igvn);
1113
1114 res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1115 } else if (unc != dom_unc) {
1116 // If we trap we won't know what CmpI would have caused the trap
1117 // so use a special trap reason to mark this pair of CmpI nodes as
1118 // bad candidate for folding. On recompilation we won't fold them
1119 // and we may trap again but this time we'll know what branch
1120 // traps
1121 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1122 }
1123 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1124 return res;
1125 }
1126
1127 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1128 // of a rangecheck on index i, on 64 bit the compares may be followed
1129 // by memory accesses using i as index. In that case, the CmpU tells
1130 // us something about the values taken by i that can help the compiler
1131 // (see Compile::conv_I2X_index())
1132 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1133 #ifdef _LP64
1134 ResourceMark rm;
1135 Node_Stack stack(2);
1136
1137 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1138 const TypeInt* array_size = igvn->type(r)->is_int();
1139
1140 stack.push(l, 0);
1141
1142 while(stack.size() > 0) {
1143 Node* n = stack.node();
1144 uint start = stack.index();
1145
1146 uint i = start;
1147 for (; i < n->outcnt(); i++) {
1148 Node* use = n->raw_out(i);
1149 if (stack.size() == 1) {
1150 if (use->Opcode() == Op_ConvI2L) {
1151 const TypeLong* bounds = use->as_Type()->type()->is_long();
1152 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1153 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1154 stack.set_index(i+1);
1155 stack.push(use, 0);
1156 break;
1157 }
1158 }
1159 } else if (use->is_Mem()) {
1160 Node* ctrl = use->in(0);
1161 for (int i = 0; i < 10 && ctrl != nullptr && ctrl != fail; i++) {
1162 ctrl = up_one_dom(ctrl);
1163 }
1164 if (ctrl == fail) {
1165 Node* init_n = stack.node_at(1);
1166 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1167 // Create a new narrow ConvI2L node that is dependent on the range check
1168 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1169
1170 // The type of the ConvI2L may be widen and so the new
1171 // ConvI2L may not be better than an existing ConvI2L
1172 if (new_n != init_n) {
1173 for (uint j = 2; j < stack.size(); j++) {
1174 Node* n = stack.node_at(j);
1175 Node* clone = n->clone();
1176 int rep = clone->replace_edge(init_n, new_n, igvn);
1177 assert(rep > 0, "can't find expected node?");
1178 clone = igvn->transform(clone);
1179 init_n = n;
1180 new_n = clone;
1181 }
1182 igvn->hash_delete(use);
1183 int rep = use->replace_edge(init_n, new_n, igvn);
1184 assert(rep > 0, "can't find expected node?");
1185 igvn->transform(use);
1186 if (init_n->outcnt() == 0) {
1187 igvn->_worklist.push(init_n);
1188 }
1189 }
1190 }
1191 } else if (use->in(0) == nullptr && (igvn->type(use)->isa_long() ||
1192 igvn->type(use)->isa_ptr())) {
1193 stack.set_index(i+1);
1194 stack.push(use, 0);
1195 break;
1196 }
1197 }
1198 if (i == n->outcnt()) {
1199 stack.pop();
1200 }
1201 }
1202 #endif
1203 }
1204
1205 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1206 if (in(1) != nullptr &&
1207 in(1)->in(1) != nullptr &&
1208 in(1)->in(1)->in(2) != nullptr) {
1209 Node* other = in(1)->in(1)->in(2);
1210 if (other->Opcode() == Op_LoadRange &&
1211 ((other->in(0) != nullptr && other->in(0) == proj) ||
1212 (other->in(0) == nullptr &&
1213 other->in(2) != nullptr &&
1214 other->in(2)->is_AddP() &&
1215 other->in(2)->in(1) != nullptr &&
1216 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1217 other->in(2)->in(1)->in(0) == proj))) {
1218 return true;
1219 }
1220 }
1221 return false;
1222 }
1223
1224 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1225 Node* other = in(1)->in(1)->in(2);
1226 if (other->in(MemNode::Address) != nullptr &&
1227 proj->in(0)->in(1) != nullptr &&
1228 proj->in(0)->in(1)->is_Bool() &&
1229 proj->in(0)->in(1)->in(1) != nullptr &&
1230 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1231 proj->in(0)->in(1)->in(1)->in(2) != nullptr &&
1232 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1233 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1234 return true;
1235 }
1236 return false;
1237 }
1238
1239 // Check that the If that is in between the 2 integer comparisons has
1240 // no side effect
1241 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1242 if (proj == nullptr) {
1243 return false;
1244 }
1245 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1246 if (unc != nullptr && proj->outcnt() <= 2) {
1247 if (proj->outcnt() == 1 ||
1248 // Allow simple null check from LoadRange
1249 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1250 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1251 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern();
1252 assert(dom_unc != nullptr, "is_uncommon_trap_if_pattern returned null");
1253
1254 // reroute_side_effect_free_unc changes the state of this
1255 // uncommon trap to restart execution at the previous
1256 // CmpI. Check that this change in a previous compilation didn't
1257 // cause too many traps.
1258 int trap_request = unc->uncommon_trap_request();
1259 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1260
1261 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1262 return false;
1263 }
1264
1265 if (!is_dominator_unc(dom_unc, unc)) {
1266 return false;
1267 }
1268
1269 return true;
1270 }
1271 }
1272 return false;
1273 }
1274
1275 // Make the If between the 2 integer comparisons trap at the state of
1276 // the first If: the last CmpI is the one replaced by a CmpU and the
1277 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1278 // won't be guarded by the first CmpI anymore. It can trap in cases
1279 // where the first CmpI would have prevented it from executing: on a
1280 // trap, we need to restart execution at the state of the first CmpI
1281 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1282 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern();
1283 ProjNode* otherproj = proj->other_if_proj();
1284 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1285 Node* call_proj = dom_unc->unique_ctrl_out();
1286 Node* halt = call_proj->unique_ctrl_out();
1287
1288 Node* new_unc = dom_unc->clone();
1289 call_proj = call_proj->clone();
1290 halt = halt->clone();
1291 Node* c = otherproj->clone();
1292
1293 c = igvn->transform(c);
1294 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1295 new_unc->set_req(0, c);
1296 new_unc = igvn->transform(new_unc);
1297 call_proj->set_req(0, new_unc);
1298 call_proj = igvn->transform(call_proj);
1299 halt->set_req(0, call_proj);
1300 halt = igvn->transform(halt);
1301
1302 igvn->replace_node(otherproj, igvn->C->top());
1303 igvn->C->root()->add_req(halt);
1304 }
1305
1306 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1307 if (Opcode() != Op_If) return nullptr;
1308
1309 if (cmpi_folds(igvn)) {
1310 Node* ctrl = in(0);
1311 if (is_ctrl_folds(ctrl, igvn) && ctrl->outcnt() == 1) {
1312 // A integer comparison immediately dominated by another integer
1313 // comparison
1314 ProjNode* success = nullptr;
1315 ProjNode* fail = nullptr;
1316 ProjNode* dom_cmp = ctrl->as_Proj();
1317 if (has_shared_region(dom_cmp, success, fail) &&
1318 // Next call modifies graph so must be last
1319 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1320 return this;
1321 }
1322 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1323 // Next call modifies graph so must be last
1324 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1325 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1326 }
1327 return nullptr;
1328 } else if (ctrl->in(0) != nullptr &&
1329 ctrl->in(0)->in(0) != nullptr) {
1330 ProjNode* success = nullptr;
1331 ProjNode* fail = nullptr;
1332 Node* dom = ctrl->in(0)->in(0);
1333 ProjNode* dom_cmp = dom->isa_Proj();
1334 ProjNode* other_cmp = ctrl->isa_Proj();
1335
1336 // Check if it's an integer comparison dominated by another
1337 // integer comparison with another test in between
1338 if (is_ctrl_folds(dom, igvn) &&
1339 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1340 is_side_effect_free_test(other_cmp, igvn) &&
1341 // Next call modifies graph so must be last
1342 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1343 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1344 return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1345 }
1346 }
1347 }
1348 return nullptr;
1349 }
1350
1351 //------------------------------remove_useless_bool----------------------------
1352 // Check for people making a useless boolean: things like
1353 // if( (x < y ? true : false) ) { ... }
1354 // Replace with if( x < y ) { ... }
1355 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1356 Node *i1 = iff->in(1);
1357 if( !i1->is_Bool() ) return nullptr;
1358 BoolNode *bol = i1->as_Bool();
1359
1360 Node *cmp = bol->in(1);
1361 if( cmp->Opcode() != Op_CmpI ) return nullptr;
1362
1363 // Must be comparing against a bool
1364 const Type *cmp2_t = phase->type( cmp->in(2) );
1365 if( cmp2_t != TypeInt::ZERO &&
1366 cmp2_t != TypeInt::ONE )
1367 return nullptr;
1368
1369 // Find a prior merge point merging the boolean
1370 i1 = cmp->in(1);
1371 if( !i1->is_Phi() ) return nullptr;
1372 PhiNode *phi = i1->as_Phi();
1373 if( phase->type( phi ) != TypeInt::BOOL )
1374 return nullptr;
1375
1376 // Check for diamond pattern
1377 int true_path = phi->is_diamond_phi();
1378 if( true_path == 0 ) return nullptr;
1379
1380 // Make sure that iff and the control of the phi are different. This
1381 // should really only happen for dead control flow since it requires
1382 // an illegal cycle.
1383 if (phi->in(0)->in(1)->in(0) == iff) return nullptr;
1384
1385 // phi->region->if_proj->ifnode->bool->cmp
1386 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1387
1388 // Now get the 'sense' of the test correct so we can plug in
1389 // either iff2->in(1) or its complement.
1390 int flip = 0;
1391 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1392 else if( bol->_test._test != BoolTest::eq ) return nullptr;
1393 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1394
1395 const Type *phi1_t = phase->type( phi->in(1) );
1396 const Type *phi2_t = phase->type( phi->in(2) );
1397 // Check for Phi(0,1) and flip
1398 if( phi1_t == TypeInt::ZERO ) {
1399 if( phi2_t != TypeInt::ONE ) return nullptr;
1400 flip = 1-flip;
1401 } else {
1402 // Check for Phi(1,0)
1403 if( phi1_t != TypeInt::ONE ) return nullptr;
1404 if( phi2_t != TypeInt::ZERO ) return nullptr;
1405 }
1406 if( true_path == 2 ) {
1407 flip = 1-flip;
1408 }
1409
1410 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1411 assert(new_bol != iff->in(1), "must make progress");
1412 iff->set_req_X(1, new_bol, phase);
1413 // Intervening diamond probably goes dead
1414 phase->C->set_major_progress();
1415 return iff;
1416 }
1417
1418 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1419
1420 struct RangeCheck {
1421 Node* ctl;
1422 jint off;
1423 };
1424
1425 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1426 if (remove_dead_region(phase, can_reshape)) return this;
1427 // No Def-Use info?
1428 if (!can_reshape) return nullptr;
1429
1430 // Don't bother trying to transform a dead if
1431 if (in(0)->is_top()) return nullptr;
1432 // Don't bother trying to transform an if with a dead test
1433 if (in(1)->is_top()) return nullptr;
1434 // Another variation of a dead test
1435 if (in(1)->is_Con()) return nullptr;
1436 // Another variation of a dead if
1437 if (outcnt() < 2) return nullptr;
1438
1439 // Canonicalize the test.
1440 Node* idt_if = idealize_test(phase, this);
1441 if (idt_if != nullptr) return idt_if;
1442
1443 // Try to split the IF
1444 PhaseIterGVN *igvn = phase->is_IterGVN();
1445 Node *s = split_if(this, igvn);
1446 if (s != nullptr) return s;
1447
1448 return NodeSentinel;
1449 }
1450
1451 //------------------------------Ideal------------------------------------------
1452 // Return a node which is more "ideal" than the current node. Strip out
1453 // control copies
1454 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1455 Node* res = Ideal_common(phase, can_reshape);
1456 if (res != NodeSentinel) {
1457 return res;
1458 }
1459
1460 // Check for people making a useless boolean: things like
1461 // if( (x < y ? true : false) ) { ... }
1462 // Replace with if( x < y ) { ... }
1463 Node* bol2 = remove_useless_bool(this, phase);
1464 if (bol2) return bol2;
1465
1466 if (in(0) == nullptr) return nullptr; // Dead loop?
1467
1468 PhaseIterGVN* igvn = phase->is_IterGVN();
1469 Node* result = fold_compares(igvn);
1470 if (result != nullptr) {
1471 return result;
1472 }
1473
1474 // Scan for an equivalent test
1475 int dist = 4; // Cutoff limit for search
1476 if (is_If() && in(1)->is_Bool()) {
1477 Node* cmp = in(1)->in(1);
1478 if (cmp->Opcode() == Op_CmpP &&
1479 cmp->in(2) != nullptr && // make sure cmp is not already dead
1480 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR) {
1481 dist = 64; // Limit for null-pointer scans
1482 }
1483 }
1484
1485 Node* prev_dom = search_identical(dist, igvn);
1486
1487 if (prev_dom != nullptr) {
1488 // Replace dominated IfNode
1489 return dominated_by(prev_dom, igvn);
1490 }
1491
1492 return simple_subsuming(igvn);
1493 }
1494
1495 //------------------------------dominated_by-----------------------------------
1496 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN *igvn) {
1497 #ifndef PRODUCT
1498 if (TraceIterativeGVN) {
1499 tty->print(" Removing IfNode: "); this->dump();
1500 }
1501 #endif
1502
1503 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1504 Node *idom = in(0);
1505 // Need opcode to decide which way 'this' test goes
1506 int prev_op = prev_dom->Opcode();
1507 Node *top = igvn->C->top(); // Shortcut to top
1508
1509 // Loop predicates may have depending checks which should not
1510 // be skipped. For example, range check predicate has two checks
1511 // for lower and upper bounds.
1512 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1513 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != nullptr ||
1514 unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_profile_predicate) != nullptr) {
1515 prev_dom = idom;
1516 }
1517
1518 // Now walk the current IfNode's projections.
1519 // Loop ends when 'this' has no more uses.
1520 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1521 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1522 igvn->add_users_to_worklist(ifp);
1523 // Check which projection it is and set target.
1524 // Data-target is either the dominating projection of the same type
1525 // or TOP if the dominating projection is of opposite type.
1526 // Data-target will be used as the new control edge for the non-CFG
1527 // nodes like Casts and Loads.
1528 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1529 // Control-target is just the If's immediate dominator or TOP.
1530 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1531
1532 // For each child of an IfTrue/IfFalse projection, reroute.
1533 // Loop ends when projection has no more uses.
1534 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1535 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1536 if (s->depends_only_on_test() && igvn->no_dependent_zero_check(s)) {
1537 // For control producers.
1538 // Do not rewire Div and Mod nodes which could have a zero divisor to avoid skipping their zero check.
1539 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1540 } else {
1541 // Find the control input matching this def-use edge.
1542 // For Regions it may not be in slot 0.
1543 uint l;
1544 for (l = 0; s->in(l) != ifp; l++) { }
1545 igvn->replace_input_of(s, l, ctrl_target);
1546 }
1547 } // End for each child of a projection
1548
1549 igvn->remove_dead_node(ifp);
1550 } // End for each IfTrue/IfFalse child of If
1551
1552 // Kill the IfNode
1553 igvn->remove_dead_node(this);
1554
1555 // Must return either the original node (now dead) or a new node
1556 // (Do not return a top here, since that would break the uniqueness of top.)
1557 return new ConINode(TypeInt::ZERO);
1558 }
1559
1560 Node* IfNode::search_identical(int dist, PhaseIterGVN* igvn) {
1561 // Setup to scan up the CFG looking for a dominating test
1562 Node* dom = in(0);
1563 Node* prev_dom = this;
1564 int op = Opcode();
1565 // Search up the dominator tree for an If with an identical test
1566 while (dom->Opcode() != op || // Not same opcode?
1567 !same_condition(dom, igvn) || // Not same input 1?
1568 prev_dom->in(0) != dom) { // One path of test does not dominate?
1569 if (dist < 0) return nullptr;
1570
1571 dist--;
1572 prev_dom = dom;
1573 dom = up_one_dom(dom);
1574 if (!dom) return nullptr;
1575 }
1576
1577 // Check that we did not follow a loop back to ourselves
1578 if (this == dom) {
1579 return nullptr;
1580 }
1581
1582 #ifndef PRODUCT
1583 if (dist > 2) { // Add to count of null checks elided
1584 explicit_null_checks_elided++;
1585 }
1586 #endif
1587
1588 return prev_dom;
1589 }
1590
1591 bool IfNode::same_condition(const Node* dom, PhaseIterGVN* igvn) const {
1592 Node* dom_bool = dom->in(1);
1593 Node* this_bool = in(1);
1594 if (dom_bool == this_bool) {
1595 return true;
1596 }
1597
1598 if (dom_bool == nullptr || !dom_bool->is_Bool() ||
1599 this_bool == nullptr || !this_bool->is_Bool()) {
1600 return false;
1601 }
1602 Node* dom_cmp = dom_bool->in(1);
1603 Node* this_cmp = this_bool->in(1);
1604
1605 // If the comparison is a subtype check, then SubTypeCheck nodes may have profile data attached to them and may be
1606 // different nodes even-though they perform the same subtype check
1607 if (dom_cmp == nullptr || !dom_cmp->is_SubTypeCheck() ||
1608 this_cmp == nullptr || !this_cmp->is_SubTypeCheck()) {
1609 return false;
1610 }
1611
1612 if (dom_cmp->in(1) != this_cmp->in(1) ||
1613 dom_cmp->in(2) != this_cmp->in(2) ||
1614 dom_bool->as_Bool()->_test._test != this_bool->as_Bool()->_test._test) {
1615 return false;
1616 }
1617
1618 return true;
1619 }
1620
1621
1622 static int subsuming_bool_test_encode(Node*);
1623
1624 // Check if dominating test is subsuming 'this' one.
1625 //
1626 // cmp
1627 // / \
1628 // (r1) bool \
1629 // / bool (r2)
1630 // (dom) if \
1631 // \ )
1632 // (pre) if[TF] /
1633 // \ /
1634 // if (this)
1635 // \r1
1636 // r2\ eqT eqF neT neF ltT ltF leT leF gtT gtF geT geF
1637 // eq t f f t f - - f f - - f
1638 // ne f t t f t - - t t - - t
1639 // lt f - - f t f - f f - f t
1640 // le t - - t t - t f f t - t
1641 // gt f - - f f - f t t f - f
1642 // ge t - - t f t - t t - t f
1643 //
1644 Node* IfNode::simple_subsuming(PhaseIterGVN* igvn) {
1645 // Table encoding: N/A (na), True-branch (tb), False-branch (fb).
1646 static enum { na, tb, fb } s_short_circuit_map[6][12] = {
1647 /*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*/
1648 /*eq*/{ tb, fb, fb, tb, fb, na, na, fb, fb, na, na, fb },
1649 /*ne*/{ fb, tb, tb, fb, tb, na, na, tb, tb, na, na, tb },
1650 /*lt*/{ fb, na, na, fb, tb, fb, na, fb, fb, na, fb, tb },
1651 /*le*/{ tb, na, na, tb, tb, na, tb, fb, fb, tb, na, tb },
1652 /*gt*/{ fb, na, na, fb, fb, na, fb, tb, tb, fb, na, fb },
1653 /*ge*/{ tb, na, na, tb, fb, tb, na, tb, tb, na, tb, fb }};
1654
1655 Node* pre = in(0);
1656 if (!pre->is_IfTrue() && !pre->is_IfFalse()) {
1657 return nullptr;
1658 }
1659 Node* dom = pre->in(0);
1660 if (!dom->is_If()) {
1661 return nullptr;
1662 }
1663 Node* bol = in(1);
1664 if (!bol->is_Bool()) {
1665 return nullptr;
1666 }
1667 Node* cmp = in(1)->in(1);
1668 if (!cmp->is_Cmp()) {
1669 return nullptr;
1670 }
1671
1672 if (!dom->in(1)->is_Bool()) {
1673 return nullptr;
1674 }
1675 if (dom->in(1)->in(1) != cmp) { // Not same cond?
1676 return nullptr;
1677 }
1678
1679 int drel = subsuming_bool_test_encode(dom->in(1));
1680 int trel = subsuming_bool_test_encode(bol);
1681 int bout = pre->is_IfFalse() ? 1 : 0;
1682
1683 if (drel < 0 || trel < 0) {
1684 return nullptr;
1685 }
1686 int br = s_short_circuit_map[trel][2*drel+bout];
1687 if (br == na) {
1688 return nullptr;
1689 }
1690 #ifndef PRODUCT
1691 if (TraceIterativeGVN) {
1692 tty->print(" Subsumed IfNode: "); dump();
1693 }
1694 #endif
1695 // Replace condition with constant True(1)/False(0).
1696 bool is_always_true = br == tb;
1697 set_req(1, igvn->intcon(is_always_true ? 1 : 0));
1698
1699 // Update any data dependencies to the directly dominating test. This subsumed test is not immediately removed by igvn
1700 // and therefore subsequent optimizations might miss these data dependencies otherwise. There might be a dead loop
1701 // ('always_taken_proj' == 'pre') that is cleaned up later. Skip this case to make the iterator work properly.
1702 Node* always_taken_proj = proj_out(is_always_true);
1703 if (always_taken_proj != pre) {
1704 for (DUIterator_Fast imax, i = always_taken_proj->fast_outs(imax); i < imax; i++) {
1705 Node* u = always_taken_proj->fast_out(i);
1706 if (!u->is_CFG()) {
1707 igvn->replace_input_of(u, 0, pre);
1708 --i;
1709 --imax;
1710 }
1711 }
1712 }
1713
1714 if (bol->outcnt() == 0) {
1715 igvn->remove_dead_node(bol); // Kill the BoolNode.
1716 }
1717 return this;
1718 }
1719
1720 // Map BoolTest to local table encoding. The BoolTest (e)numerals
1721 // { eq = 0, ne = 4, le = 5, ge = 7, lt = 3, gt = 1 }
1722 // are mapped to table indices, while the remaining (e)numerals in BoolTest
1723 // { overflow = 2, no_overflow = 6, never = 8, illegal = 9 }
1724 // are ignored (these are not modeled in the table).
1725 //
1726 static int subsuming_bool_test_encode(Node* node) {
1727 precond(node->is_Bool());
1728 BoolTest::mask x = node->as_Bool()->_test._test;
1729 switch (x) {
1730 case BoolTest::eq: return 0;
1731 case BoolTest::ne: return 1;
1732 case BoolTest::lt: return 2;
1733 case BoolTest::le: return 3;
1734 case BoolTest::gt: return 4;
1735 case BoolTest::ge: return 5;
1736 case BoolTest::overflow:
1737 case BoolTest::no_overflow:
1738 case BoolTest::never:
1739 case BoolTest::illegal:
1740 default:
1741 return -1;
1742 }
1743 }
1744
1745 //------------------------------Identity---------------------------------------
1746 // If the test is constant & we match, then we are the input Control
1747 Node* IfProjNode::Identity(PhaseGVN* phase) {
1748 // Can only optimize if cannot go the other way
1749 const TypeTuple *t = phase->type(in(0))->is_tuple();
1750 if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1751 // During parsing (GVN) we don't remove dead code aggressively.
1752 // Cut off dead branch and let PhaseRemoveUseless take care of it.
1753 (!phase->is_IterGVN() ||
1754 // During IGVN, first wait for the dead branch to be killed.
1755 // Otherwise, the IfNode's control will have two control uses (the IfNode
1756 // that doesn't go away because it still has uses and this branch of the
1757 // If) which breaks other optimizations. Node::has_special_unique_user()
1758 // will cause this node to be reprocessed once the dead branch is killed.
1759 in(0)->outcnt() == 1))) {
1760 // IfNode control
1761 if (in(0)->is_BaseCountedLoopEnd()) {
1762 // CountedLoopEndNode may be eliminated by if subsuming, replace CountedLoopNode with LoopNode to
1763 // avoid mismatching between CountedLoopNode and CountedLoopEndNode in the following optimization.
1764 Node* head = unique_ctrl_out_or_null();
1765 if (head != nullptr && head->is_BaseCountedLoop() && head->in(LoopNode::LoopBackControl) == this) {
1766 Node* new_head = new LoopNode(head->in(LoopNode::EntryControl), this);
1767 phase->is_IterGVN()->register_new_node_with_optimizer(new_head);
1768 phase->is_IterGVN()->replace_node(head, new_head);
1769 }
1770 }
1771 return in(0)->in(0);
1772 }
1773 // no progress
1774 return this;
1775 }
1776
1777 #ifndef PRODUCT
1778 //------------------------------dump_spec--------------------------------------
1779 void IfNode::dump_spec(outputStream *st) const {
1780 st->print("P=%f, C=%f",_prob,_fcnt);
1781 }
1782 #endif
1783
1784 //------------------------------idealize_test----------------------------------
1785 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1786 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1787 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1788 // needed.
1789 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1790 assert(iff->in(0) != nullptr, "If must be live");
1791
1792 if (iff->outcnt() != 2) return nullptr; // Malformed projections.
1793 Node* old_if_f = iff->proj_out(false);
1794 Node* old_if_t = iff->proj_out(true);
1795
1796 // CountedLoopEnds want the back-control test to be TRUE, regardless of
1797 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1798 // happens in count-down loops
1799 if (iff->is_BaseCountedLoopEnd()) return nullptr;
1800 if (!iff->in(1)->is_Bool()) return nullptr; // Happens for partially optimized IF tests
1801 BoolNode *b = iff->in(1)->as_Bool();
1802 BoolTest bt = b->_test;
1803 // Test already in good order?
1804 if( bt.is_canonical() )
1805 return nullptr;
1806
1807 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1808 // cloning the IfNode.
1809 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1810 if( !new_b->is_Bool() ) return nullptr;
1811 b = new_b->as_Bool();
1812
1813 PhaseIterGVN *igvn = phase->is_IterGVN();
1814 assert( igvn, "Test is not canonical in parser?" );
1815
1816 // The IF node never really changes, but it needs to be cloned
1817 iff = iff->clone()->as_If();
1818 iff->set_req(1, b);
1819 iff->_prob = 1.0-iff->_prob;
1820
1821 Node *prior = igvn->hash_find_insert(iff);
1822 if( prior ) {
1823 igvn->remove_dead_node(iff);
1824 iff = (IfNode*)prior;
1825 } else {
1826 // Cannot call transform on it just yet
1827 igvn->set_type_bottom(iff);
1828 }
1829 igvn->_worklist.push(iff);
1830
1831 // Now handle projections. Cloning not required.
1832 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1833 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1834
1835 igvn->register_new_node_with_optimizer(new_if_f);
1836 igvn->register_new_node_with_optimizer(new_if_t);
1837 // Flip test, so flip trailing control
1838 igvn->replace_node(old_if_f, new_if_t);
1839 igvn->replace_node(old_if_t, new_if_f);
1840
1841 // Progress
1842 return iff;
1843 }
1844
1845 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1846 Node* res = Ideal_common(phase, can_reshape);
1847 if (res != NodeSentinel) {
1848 return res;
1849 }
1850
1851 PhaseIterGVN *igvn = phase->is_IterGVN();
1852 // Setup to scan up the CFG looking for a dominating test
1853 Node* prev_dom = this;
1854
1855 // Check for range-check vs other kinds of tests
1856 Node* index1;
1857 Node* range1;
1858 jint offset1;
1859 int flip1 = is_range_check(range1, index1, offset1);
1860 if (flip1) {
1861 Node* dom = in(0);
1862 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1863 // so all checks we inspect post-dominate the top-most check we find.
1864 // If we are going to fail the current check and we reach the top check
1865 // then we are guaranteed to fail, so just start interpreting there.
1866 // We 'expand' the top 3 range checks to include all post-dominating
1867 // checks.
1868
1869 // The top 3 range checks seen
1870 const int NRC = 3;
1871 RangeCheck prev_checks[NRC];
1872 int nb_checks = 0;
1873
1874 // Low and high offsets seen so far
1875 jint off_lo = offset1;
1876 jint off_hi = offset1;
1877
1878 bool found_immediate_dominator = false;
1879
1880 // Scan for the top checks and collect range of offsets
1881 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1882 if (dom->Opcode() == Op_RangeCheck && // Not same opcode?
1883 prev_dom->in(0) == dom) { // One path of test does dominate?
1884 if (dom == this) return nullptr; // dead loop
1885 // See if this is a range check
1886 Node* index2;
1887 Node* range2;
1888 jint offset2;
1889 int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
1890 // See if this is a _matching_ range check, checking against
1891 // the same array bounds.
1892 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1893 dom->outcnt() == 2) {
1894 if (nb_checks == 0 && dom->in(1) == in(1)) {
1895 // Found an immediately dominating test at the same offset.
1896 // This kind of back-to-back test can be eliminated locally,
1897 // and there is no need to search further for dominating tests.
1898 assert(offset2 == offset1, "Same test but different offsets");
1899 found_immediate_dominator = true;
1900 break;
1901 }
1902 // Gather expanded bounds
1903 off_lo = MIN2(off_lo,offset2);
1904 off_hi = MAX2(off_hi,offset2);
1905 // Record top NRC range checks
1906 prev_checks[nb_checks%NRC].ctl = prev_dom;
1907 prev_checks[nb_checks%NRC].off = offset2;
1908 nb_checks++;
1909 }
1910 }
1911 prev_dom = dom;
1912 dom = up_one_dom(dom);
1913 if (!dom) break;
1914 }
1915
1916 if (!found_immediate_dominator) {
1917 // Attempt to widen the dominating range check to cover some later
1918 // ones. Since range checks "fail" by uncommon-trapping to the
1919 // interpreter, widening a check can make us speculatively enter
1920 // the interpreter. If we see range-check deopt's, do not widen!
1921 if (!phase->C->allow_range_check_smearing()) return nullptr;
1922
1923 // Didn't find prior covering check, so cannot remove anything.
1924 if (nb_checks == 0) {
1925 return nullptr;
1926 }
1927 // Constant indices only need to check the upper bound.
1928 // Non-constant indices must check both low and high.
1929 int chk0 = (nb_checks - 1) % NRC;
1930 if (index1) {
1931 if (nb_checks == 1) {
1932 return nullptr;
1933 } else {
1934 // If the top range check's constant is the min or max of
1935 // all constants we widen the next one to cover the whole
1936 // range of constants.
1937 RangeCheck rc0 = prev_checks[chk0];
1938 int chk1 = (nb_checks - 2) % NRC;
1939 RangeCheck rc1 = prev_checks[chk1];
1940 if (rc0.off == off_lo) {
1941 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1942 prev_dom = rc1.ctl;
1943 } else if (rc0.off == off_hi) {
1944 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1945 prev_dom = rc1.ctl;
1946 } else {
1947 // If the top test's constant is not the min or max of all
1948 // constants, we need 3 range checks. We must leave the
1949 // top test unchanged because widening it would allow the
1950 // accesses it protects to successfully read/write out of
1951 // bounds.
1952 if (nb_checks == 2) {
1953 return nullptr;
1954 }
1955 int chk2 = (nb_checks - 3) % NRC;
1956 RangeCheck rc2 = prev_checks[chk2];
1957 // The top range check a+i covers interval: -a <= i < length-a
1958 // The second range check b+i covers interval: -b <= i < length-b
1959 if (rc1.off <= rc0.off) {
1960 // if b <= a, we change the second range check to:
1961 // -min_of_all_constants <= i < length-min_of_all_constants
1962 // Together top and second range checks now cover:
1963 // -min_of_all_constants <= i < length-a
1964 // which is more restrictive than -b <= i < length-b:
1965 // -b <= -min_of_all_constants <= i < length-a <= length-b
1966 // The third check is then changed to:
1967 // -max_of_all_constants <= i < length-max_of_all_constants
1968 // so 2nd and 3rd checks restrict allowed values of i to:
1969 // -min_of_all_constants <= i < length-max_of_all_constants
1970 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1971 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1972 } else {
1973 // if b > a, we change the second range check to:
1974 // -max_of_all_constants <= i < length-max_of_all_constants
1975 // Together top and second range checks now cover:
1976 // -a <= i < length-max_of_all_constants
1977 // which is more restrictive than -b <= i < length-b:
1978 // -b < -a <= i < length-max_of_all_constants <= length-b
1979 // The third check is then changed to:
1980 // -max_of_all_constants <= i < length-max_of_all_constants
1981 // so 2nd and 3rd checks restrict allowed values of i to:
1982 // -min_of_all_constants <= i < length-max_of_all_constants
1983 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1984 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1985 }
1986 prev_dom = rc2.ctl;
1987 }
1988 }
1989 } else {
1990 RangeCheck rc0 = prev_checks[chk0];
1991 // 'Widen' the offset of the 1st and only covering check
1992 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1993 // Test is now covered by prior checks, dominate it out
1994 prev_dom = rc0.ctl;
1995 }
1996 }
1997 } else {
1998 prev_dom = search_identical(4, igvn);
1999
2000 if (prev_dom == nullptr) {
2001 return nullptr;
2002 }
2003 }
2004
2005 // Replace dominated IfNode
2006 return dominated_by(prev_dom, igvn);
2007 }
2008
2009 ParsePredicateNode::ParsePredicateNode(Node* control, Deoptimization::DeoptReason deopt_reason, PhaseGVN* gvn)
2010 : IfNode(control, gvn->intcon(1), PROB_MAX, COUNT_UNKNOWN),
2011 _deopt_reason(deopt_reason),
2012 _useless(false) {
2013 init_class_id(Class_ParsePredicate);
2014 gvn->C->add_parse_predicate(this);
2015 gvn->C->record_for_post_loop_opts_igvn(this);
2016 #ifdef ASSERT
2017 switch (deopt_reason) {
2018 case Deoptimization::Reason_predicate:
2019 case Deoptimization::Reason_profile_predicate:
2020 case Deoptimization::Reason_loop_limit_check:
2021 break;
2022 default:
2023 assert(false, "unsupported deoptimization reason for Parse Predicate");
2024 }
2025 #endif // ASSERT
2026 }
2027
2028 Node* ParsePredicateNode::uncommon_trap() const {
2029 ParsePredicateUncommonProj* uncommon_proj = proj_out(0)->as_IfFalse();
2030 Node* uct_region_or_call = uncommon_proj->unique_ctrl_out();
2031 assert(uct_region_or_call->is_Region() || uct_region_or_call->is_Call(), "must be a region or call uct");
2032 return uct_region_or_call;
2033 }
2034
2035 // Fold this node away once it becomes useless or at latest in post loop opts IGVN.
2036 const Type* ParsePredicateNode::Value(PhaseGVN* phase) const {
2037 if (phase->type(in(0)) == Type::TOP) {
2038 return Type::TOP;
2039 }
2040 if (_useless || phase->C->post_loop_opts_phase()) {
2041 return TypeTuple::IFTRUE;
2042 } else {
2043 return bottom_type();
2044 }
2045 }
2046
2047 #ifndef PRODUCT
2048 void ParsePredicateNode::dump_spec(outputStream* st) const {
2049 st->print(" #");
2050 switch (_deopt_reason) {
2051 case Deoptimization::DeoptReason::Reason_predicate:
2052 st->print("Loop ");
2053 break;
2054 case Deoptimization::DeoptReason::Reason_profile_predicate:
2055 st->print("Profiled_Loop ");
2056 break;
2057 case Deoptimization::DeoptReason::Reason_loop_limit_check:
2058 st->print("Loop_Limit_Check ");
2059 break;
2060 default:
2061 fatal("unknown kind");
2062 }
2063 }
2064
2065 #endif // NOT PRODUCT