1 /*
2 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/addnode.hpp"
28 #include "opto/cfgnode.hpp"
29 #include "opto/connode.hpp"
30 #include "opto/loopnode.hpp"
31 #include "opto/phaseX.hpp"
32 #include "opto/runtime.hpp"
33 #include "opto/rootnode.hpp"
34 #include "opto/subnode.hpp"
35
36 // Portions of code courtesy of Clifford Click
37
38 // Optimization - Graph Style
39
40
41 extern int explicit_null_checks_elided;
42
43 //=============================================================================
44 //------------------------------Value------------------------------------------
45 // Return a tuple for whichever arm of the IF is reachable
46 const Type *IfNode::Value( PhaseTransform *phase ) const {
47 if( !in(0) ) return Type::TOP;
48 if( phase->type(in(0)) == Type::TOP )
49 return Type::TOP;
50 const Type *t = phase->type(in(1));
51 if( t == Type::TOP ) // data is undefined
52 return TypeTuple::IFNEITHER; // unreachable altogether
53 if( t == TypeInt::ZERO ) // zero, or false
54 return TypeTuple::IFFALSE; // only false branch is reachable
55 if( t == TypeInt::ONE ) // 1, or true
56 return TypeTuple::IFTRUE; // only true branch is reachable
57 assert( t == TypeInt::BOOL, "expected boolean type" );
58
59 return TypeTuple::IFBOTH; // No progress
60 }
61
62 const RegMask &IfNode::out_RegMask() const {
63 return RegMask::Empty;
64 }
65
66 //------------------------------split_if---------------------------------------
67 // Look for places where we merge constants, then test on the merged value.
68 // If the IF test will be constant folded on the path with the constant, we
69 // win by splitting the IF to before the merge point.
70 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
71 // I could be a lot more general here, but I'm trying to squeeze this
72 // in before the Christmas '98 break so I'm gonna be kinda restrictive
73 // on the patterns I accept. CNC
74
75 // Look for a compare of a constant and a merged value
76 Node *i1 = iff->in(1);
77 if( !i1->is_Bool() ) return NULL;
78 BoolNode *b = i1->as_Bool();
79 Node *cmp = b->in(1);
80 if( !cmp->is_Cmp() ) return NULL;
81 i1 = cmp->in(1);
82 if( i1 == NULL || !i1->is_Phi() ) return NULL;
83 PhiNode *phi = i1->as_Phi();
84 if( phi->is_copy() ) return NULL;
85 Node *con2 = cmp->in(2);
86 if( !con2->is_Con() ) return NULL;
87 // See that the merge point contains some constants
88 Node *con1=NULL;
89 uint i4;
90 for( i4 = 1; i4 < phi->req(); i4++ ) {
91 con1 = phi->in(i4);
92 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
93 if( con1->is_Con() ) break; // Found a constant
94 // Also allow null-vs-not-null checks
95 const TypePtr *tp = igvn->type(con1)->isa_ptr();
96 if( tp && tp->_ptr == TypePtr::NotNull )
97 break;
98 }
99 if( i4 >= phi->req() ) return NULL; // Found no constants
100
101 igvn->C->set_has_split_ifs(true); // Has chance for split-if
102
103 // Make sure that the compare can be constant folded away
104 Node *cmp2 = cmp->clone();
105 cmp2->set_req(1,con1);
106 cmp2->set_req(2,con2);
107 const Type *t = cmp2->Value(igvn);
108 // This compare is dead, so whack it!
109 igvn->remove_dead_node(cmp2);
110 if( !t->singleton() ) return NULL;
111
112 // No intervening control, like a simple Call
113 Node *r = iff->in(0);
114 if( !r->is_Region() ) return NULL;
115 if( phi->region() != r ) return NULL;
116 // No other users of the cmp/bool
117 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
118 //tty->print_cr("many users of cmp/bool");
119 return NULL;
120 }
121
122 // Make sure we can determine where all the uses of merged values go
123 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
124 Node* u = r->fast_out(j);
125 if( u == r ) continue;
126 if( u == iff ) continue;
127 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
128 if( !u->is_Phi() ) {
129 /*
130 if( u->is_Start() ) {
131 tty->print_cr("Region has inlined start use");
132 } else {
133 tty->print_cr("Region has odd use");
134 u->dump(2);
135 }*/
136 return NULL;
137 }
138 if( u != phi ) {
139 // CNC - do not allow any other merged value
140 //tty->print_cr("Merging another value");
141 //u->dump(2);
142 return NULL;
143 }
144 // Make sure we can account for all Phi uses
145 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
146 Node* v = u->fast_out(k); // User of the phi
147 // CNC - Allow only really simple patterns.
148 // In particular I disallow AddP of the Phi, a fairly common pattern
149 if (v == cmp) continue; // The compare is OK
150 if (v->is_ConstraintCast()) {
151 // If the cast is derived from data flow edges, it may not have a control edge.
152 // If so, it should be safe to split. But follow-up code can not deal with
153 // this (l. 359). So skip.
154 if (v->in(0) == NULL) {
155 return NULL;
156 }
157 if (v->in(0)->in(0) == iff) {
158 continue; // CastPP/II of the IfNode is OK
159 }
160 }
161 // Disabled following code because I cannot tell if exactly one
162 // path dominates without a real dominator check. CNC 9/9/1999
163 //uint vop = v->Opcode();
164 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
165 // Node *r = v->in(0); // Get controlling point
166 // if( !r ) return NULL; // Degraded to a copy
167 // // Find exactly one path in (either True or False doms, but not IFF)
168 // int cnt = 0;
169 // for( uint i = 1; i < r->req(); i++ )
170 // if( r->in(i) && r->in(i)->in(0) == iff )
171 // cnt++;
172 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
173 //}
174 if( !v->is_Call() ) {
175 /*
176 if( v->Opcode() == Op_AddP ) {
177 tty->print_cr("Phi has AddP use");
178 } else if( v->Opcode() == Op_CastPP ) {
179 tty->print_cr("Phi has CastPP use");
180 } else if( v->Opcode() == Op_CastII ) {
181 tty->print_cr("Phi has CastII use");
182 } else {
183 tty->print_cr("Phi has use I cant be bothered with");
184 }
185 */
186 }
187 return NULL;
188
189 /* CNC - Cut out all the fancy acceptance tests
190 // Can we clone this use when doing the transformation?
191 // If all uses are from Phis at this merge or constants, then YES.
192 if( !v->in(0) && v != cmp ) {
193 tty->print_cr("Phi has free-floating use");
194 v->dump(2);
195 return NULL;
196 }
197 for( uint l = 1; l < v->req(); l++ ) {
198 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
199 !v->in(l)->is_Con() ) {
200 tty->print_cr("Phi has use");
201 v->dump(2);
202 return NULL;
203 } // End of if Phi-use input is neither Phi nor Constant
204 } // End of for all inputs to Phi-use
205 */
206 } // End of for all uses of Phi
207 } // End of for all uses of Region
208
209 // Only do this if the IF node is in a sane state
210 if (iff->outcnt() != 2)
211 return NULL;
212
213 // Got a hit! Do the Mondo Hack!
214 //
215 //ABC a1c def ghi B 1 e h A C a c d f g i
216 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
217 // cmp - 2 cmp - 2 cmp - 2
218 // bool bool_c bool_x
219 // if if_c if_x
220 // T F T F T F
221 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
222 //
223 // Split the paths coming into the merge point into 2 separate groups of
224 // merges. On the left will be all the paths feeding constants into the
225 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
226 // will fold up into a constant; this will let the Cmp fold up as well as
227 // all the control flow. Below the original IF we have 2 control
228 // dependent regions, 's' and 't'. Now we will merge the two paths
229 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
230 // likely 2 or more) will promptly constant fold away.
231 PhaseGVN *phase = igvn;
232
233 // Make a region merging constants and a region merging the rest
234 uint req_c = 0;
235 Node* predicate_proj = NULL;
236 for (uint ii = 1; ii < r->req(); ii++) {
237 if (phi->in(ii) == con1) {
238 req_c++;
239 }
240 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
241 if (proj != NULL) {
242 assert(predicate_proj == NULL, "only one predicate entry expected");
243 predicate_proj = proj;
244 }
245 }
246 Node* predicate_c = NULL;
247 Node* predicate_x = NULL;
248 bool counted_loop = r->is_CountedLoop();
249
250 Node *region_c = new RegionNode(req_c + 1);
251 Node *phi_c = con1;
252 uint len = r->req();
253 Node *region_x = new RegionNode(len - req_c);
254 Node *phi_x = PhiNode::make_blank(region_x, phi);
255 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
256 if (phi->in(i) == con1) {
257 region_c->init_req( i_c++, r ->in(i) );
258 if (r->in(i) == predicate_proj)
259 predicate_c = predicate_proj;
260 } else {
261 region_x->init_req( i_x, r ->in(i) );
262 phi_x ->init_req( i_x++, phi->in(i) );
263 if (r->in(i) == predicate_proj)
264 predicate_x = predicate_proj;
265 }
266 }
267 if (predicate_c != NULL && (req_c > 1)) {
268 assert(predicate_x == NULL, "only one predicate entry expected");
269 predicate_c = NULL; // Do not clone predicate below merge point
270 }
271 if (predicate_x != NULL && ((len - req_c) > 2)) {
272 assert(predicate_c == NULL, "only one predicate entry expected");
273 predicate_x = NULL; // Do not clone predicate below merge point
274 }
275
276 // Register the new RegionNodes but do not transform them. Cannot
277 // transform until the entire Region/Phi conglomerate has been hacked
278 // as a single huge transform.
279 igvn->register_new_node_with_optimizer( region_c );
280 igvn->register_new_node_with_optimizer( region_x );
281 // Prevent the untimely death of phi_x. Currently he has no uses. He is
282 // about to get one. If this only use goes away, then phi_x will look dead.
283 // However, he will be picking up some more uses down below.
284 Node *hook = new Node(4);
285 hook->init_req(0, phi_x);
286 hook->init_req(1, phi_c);
287 phi_x = phase->transform( phi_x );
288
289 // Make the compare
290 Node *cmp_c = phase->makecon(t);
291 Node *cmp_x = cmp->clone();
292 cmp_x->set_req(1,phi_x);
293 cmp_x->set_req(2,con2);
294 cmp_x = phase->transform(cmp_x);
295 // Make the bool
296 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
297 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
298 // Make the IfNode
299 IfNode *iff_c = new IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
300 igvn->set_type_bottom(iff_c);
301 igvn->_worklist.push(iff_c);
302 hook->init_req(2, iff_c);
303
304 IfNode *iff_x = new IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
305 igvn->set_type_bottom(iff_x);
306 igvn->_worklist.push(iff_x);
307 hook->init_req(3, iff_x);
308
309 // Make the true/false arms
310 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
311 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
312 if (predicate_c != NULL) {
313 assert(predicate_x == NULL, "only one predicate entry expected");
314 // Clone loop predicates to each path
315 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
316 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
317 }
318 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
319 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
320 if (predicate_x != NULL) {
321 assert(predicate_c == NULL, "only one predicate entry expected");
322 // Clone loop predicates to each path
323 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
324 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
325 }
326
327 // Merge the TRUE paths
328 Node *region_s = new RegionNode(3);
329 igvn->_worklist.push(region_s);
330 region_s->init_req(1, iff_c_t);
331 region_s->init_req(2, iff_x_t);
332 igvn->register_new_node_with_optimizer( region_s );
333
334 // Merge the FALSE paths
335 Node *region_f = new RegionNode(3);
336 igvn->_worklist.push(region_f);
337 region_f->init_req(1, iff_c_f);
338 region_f->init_req(2, iff_x_f);
339 igvn->register_new_node_with_optimizer( region_f );
340
341 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
342 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
343 cmp->set_req(2,NULL);
344 // Check for all uses of the Phi and give them a new home.
345 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
346 Node *phi_s = NULL; // do not construct unless needed
347 Node *phi_f = NULL; // do not construct unless needed
348 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
349 Node* v = phi->last_out(i2);// User of the phi
350 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
351 uint vop = v->Opcode();
352 Node *proj = NULL;
353 if( vop == Op_Phi ) { // Remote merge point
354 Node *r = v->in(0);
355 for (uint i3 = 1; i3 < r->req(); i3++)
356 if (r->in(i3) && r->in(i3)->in(0) == iff) {
357 proj = r->in(i3);
358 break;
359 }
360 } else if( v->is_ConstraintCast() ) {
361 proj = v->in(0); // Controlling projection
362 } else {
363 assert( 0, "do not know how to handle this guy" );
364 }
365
366 Node *proj_path_data, *proj_path_ctrl;
367 if( proj->Opcode() == Op_IfTrue ) {
368 if( phi_s == NULL ) {
369 // Only construct phi_s if needed, otherwise provides
370 // interfering use.
371 phi_s = PhiNode::make_blank(region_s,phi);
372 phi_s->init_req( 1, phi_c );
373 phi_s->init_req( 2, phi_x );
374 hook->add_req(phi_s);
375 phi_s = phase->transform(phi_s);
376 }
377 proj_path_data = phi_s;
378 proj_path_ctrl = region_s;
379 } else {
380 if( phi_f == NULL ) {
381 // Only construct phi_f if needed, otherwise provides
382 // interfering use.
383 phi_f = PhiNode::make_blank(region_f,phi);
384 phi_f->init_req( 1, phi_c );
385 phi_f->init_req( 2, phi_x );
386 hook->add_req(phi_f);
387 phi_f = phase->transform(phi_f);
388 }
389 proj_path_data = phi_f;
390 proj_path_ctrl = region_f;
391 }
392
393 // Fixup 'v' for for the split
394 if( vop == Op_Phi ) { // Remote merge point
395 uint i;
396 for( i = 1; i < v->req(); i++ )
397 if( v->in(i) == phi )
398 break;
399 v->set_req(i, proj_path_data );
400 } else if( v->is_ConstraintCast() ) {
401 v->set_req(0, proj_path_ctrl );
402 v->set_req(1, proj_path_data );
403 } else
404 ShouldNotReachHere();
405 }
406
407 // Now replace the original iff's True/False with region_s/region_t.
408 // This makes the original iff go dead.
409 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
410 Node* p = iff->last_out(i3);
411 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
412 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
413 // Replace p with u
414 igvn->add_users_to_worklist(p);
415 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
416 Node* x = p->last_out(l);
417 igvn->hash_delete(x);
418 uint uses_found = 0;
419 for( uint j = 0; j < x->req(); j++ ) {
420 if( x->in(j) == p ) {
421 x->set_req(j, u);
422 uses_found++;
423 }
424 }
425 l -= uses_found; // we deleted 1 or more copies of this edge
426 }
427 igvn->remove_dead_node(p);
428 }
429
430 // Force the original merge dead
431 igvn->hash_delete(r);
432 // First, remove region's dead users.
433 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
434 Node* u = r->last_out(l);
435 if( u == r ) {
436 r->set_req(0, NULL);
437 } else {
438 assert(u->outcnt() == 0, "only dead users");
439 igvn->remove_dead_node(u);
440 }
441 l -= 1;
442 }
443 igvn->remove_dead_node(r);
444
445 // Now remove the bogus extra edges used to keep things alive
446 igvn->remove_dead_node( hook );
447
448 // Must return either the original node (now dead) or a new node
449 // (Do not return a top here, since that would break the uniqueness of top.)
450 return new ConINode(TypeInt::ZERO);
451 }
452
453 // if this IfNode follows a range check pattern return the projection
454 // for the failed path
455 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
456 Node* b = in(1);
457 if (b == NULL || !b->is_Bool()) return NULL;
458 BoolNode* bn = b->as_Bool();
459 Node* cmp = bn->in(1);
460 if (cmp == NULL) return NULL;
461 if (cmp->Opcode() != Op_CmpU) return NULL;
462
463 l = cmp->in(1);
464 r = cmp->in(2);
465 flip_test = 1;
466 if (bn->_test._test == BoolTest::le) {
467 l = cmp->in(2);
468 r = cmp->in(1);
469 flip_test = 2;
470 } else if (bn->_test._test != BoolTest::lt) {
471 return NULL;
472 }
473 if (l->is_top()) return NULL; // Top input means dead test
474 if (r->Opcode() != Op_LoadRange) return NULL;
475
476 // We have recognized one of these forms:
477 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
478 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
479
480 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
481 return iftrap;
482 }
483
484
485 //------------------------------is_range_check---------------------------------
486 // Return 0 if not a range check. Return 1 if a range check and set index and
487 // offset. Return 2 if we had to negate the test. Index is NULL if the check
488 // is versus a constant.
489 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
490 int flip_test = 0;
491 Node* l = NULL;
492 Node* r = NULL;
493 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
494
495 if (iftrap == NULL) {
496 return 0;
497 }
498
499 // Make sure it's a real range check by requiring an uncommon trap
500 // along the OOB path. Otherwise, it's possible that the user wrote
501 // something which optimized to look like a range check but behaves
502 // in some other way.
503 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
504 return 0;
505 }
506
507 // Look for index+offset form
508 Node* ind = l;
509 jint off = 0;
510 if (l->is_top()) {
511 return 0;
512 } else if (l->Opcode() == Op_AddI) {
513 if ((off = l->in(1)->find_int_con(0)) != 0) {
514 ind = l->in(2);
515 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
516 ind = l->in(1);
517 }
518 } else if ((off = l->find_int_con(-1)) >= 0) {
519 // constant offset with no variable index
520 ind = NULL;
521 } else {
522 // variable index with no constant offset (or dead negative index)
523 off = 0;
524 }
525
526 // Return all the values:
527 index = ind;
528 offset = off;
529 range = r;
530 return flip_test;
531 }
532
533 //------------------------------adjust_check-----------------------------------
534 // Adjust (widen) a prior range check
535 static void adjust_check(Node* proj, Node* range, Node* index,
536 int flip, jint off_lo, PhaseIterGVN* igvn) {
537 PhaseGVN *gvn = igvn;
538 // Break apart the old check
539 Node *iff = proj->in(0);
540 Node *bol = iff->in(1);
541 if( bol->is_top() ) return; // In case a partially dead range check appears
542 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
543 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
544 if( !bol->is_Bool() ) return;
545
546 Node *cmp = bol->in(1);
547 // Compute a new check
548 Node *new_add = gvn->intcon(off_lo);
549 if( index ) {
550 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
551 }
552 Node *new_cmp = (flip == 1)
553 ? new CmpUNode( new_add, range )
554 : new CmpUNode( range, new_add );
555 new_cmp = gvn->transform(new_cmp);
556 // See if no need to adjust the existing check
557 if( new_cmp == cmp ) return;
558 // Else, adjust existing check
559 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
560 igvn->rehash_node_delayed( iff );
561 iff->set_req_X( 1, new_bol, igvn );
562 }
563
564 //------------------------------up_one_dom-------------------------------------
565 // Walk up the dominator tree one step. Return NULL at root or true
566 // complex merges. Skips through small diamonds.
567 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
568 Node *dom = curr->in(0);
569 if( !dom ) // Found a Region degraded to a copy?
570 return curr->nonnull_req(); // Skip thru it
571
572 if( curr != dom ) // Normal walk up one step?
573 return dom;
574
575 // Use linear_only if we are still parsing, since we cannot
576 // trust the regions to be fully filled in.
577 if (linear_only)
578 return NULL;
579
580 if( dom->is_Root() )
581 return NULL;
582
583 // Else hit a Region. Check for a loop header
584 if( dom->is_Loop() )
585 return dom->in(1); // Skip up thru loops
586
587 // Check for small diamonds
588 Node *din1, *din2, *din3, *din4;
589 if( dom->req() == 3 && // 2-path merge point
590 (din1 = dom ->in(1)) && // Left path exists
591 (din2 = dom ->in(2)) && // Right path exists
592 (din3 = din1->in(0)) && // Left path up one
593 (din4 = din2->in(0)) ) { // Right path up one
594 if( din3->is_Call() && // Handle a slow-path call on either arm
595 (din3 = din3->in(0)) )
596 din3 = din3->in(0);
597 if( din4->is_Call() && // Handle a slow-path call on either arm
598 (din4 = din4->in(0)) )
599 din4 = din4->in(0);
600 if( din3 == din4 && din3->is_If() )
601 return din3; // Skip around diamonds
602 }
603
604 // Give up the search at true merges
605 return NULL; // Dead loop? Or hit root?
606 }
607
608
609 //------------------------------filtered_int_type--------------------------------
610 // Return a possibly more restrictive type for val based on condition control flow for an if
611 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
612 assert(if_proj &&
613 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
614 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
615 IfNode* iff = if_proj->in(0)->as_If();
616 if (iff->in(1) && iff->in(1)->is_Bool()) {
617 BoolNode* bol = iff->in(1)->as_Bool();
618 if (bol->in(1) && bol->in(1)->is_Cmp()) {
619 const CmpNode* cmp = bol->in(1)->as_Cmp();
620 if (cmp->in(1) == val) {
621 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
622 if (cmp2_t != NULL) {
623 jint lo = cmp2_t->_lo;
624 jint hi = cmp2_t->_hi;
625 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
626 switch (msk) {
627 case BoolTest::ne:
628 // Can't refine type
629 return NULL;
630 case BoolTest::eq:
631 return cmp2_t;
632 case BoolTest::lt:
633 lo = TypeInt::INT->_lo;
634 if (hi - 1 < hi) {
635 hi = hi - 1;
636 }
637 break;
638 case BoolTest::le:
639 lo = TypeInt::INT->_lo;
640 break;
641 case BoolTest::gt:
642 if (lo + 1 > lo) {
643 lo = lo + 1;
644 }
645 hi = TypeInt::INT->_hi;
646 break;
647 case BoolTest::ge:
648 // lo unchanged
649 hi = TypeInt::INT->_hi;
650 break;
651 }
652 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
653 return rtn_t;
654 }
655 }
656 }
657 }
658 }
659 return NULL;
660 }
661
662 //------------------------------fold_compares----------------------------
663 // See if a pair of CmpIs can be converted into a CmpU. In some cases
664 // the direction of this if is determined by the preceding if so it
665 // can be eliminate entirely.
666 //
667 // Given an if testing (CmpI n v) check for an immediately control
668 // dependent if that is testing (CmpI n v2) and has one projection
669 // leading to this if and the other projection leading to a region
670 // that merges one of this ifs control projections.
671 //
672 // If
673 // / |
674 // / |
675 // / |
676 // If |
677 // /\ |
678 // / \ |
679 // / \ |
680 // / Region
681 //
682 // Or given an if testing (CmpI n v) check for a dominating if that is
683 // testing (CmpI n v2), both having one projection leading to an
684 // uncommon trap. Allow Another independent guard in between to cover
685 // an explicit range check:
686 // if (index < 0 || index >= array.length) {
687 // which may need a null check to guard the LoadRange
688 //
689 // If
690 // / \
691 // / \
692 // / \
693 // If unc
694 // /\
695 // / \
696 // / \
697 // / unc
698 //
699
700 // Is the comparison for this If suitable for folding?
701 bool IfNode::cmpi_if(PhaseIterGVN* igvn) {
702 return in(1)->is_Bool() &&
703 in(1)->in(1)->Opcode() == Op_CmpI &&
704 in(1)->in(1)->in(2) != igvn->C->top() &&
705 in(1)->as_Bool()->_test._test != BoolTest::ne &&
706 in(1)->as_Bool()->_test._test != BoolTest::eq;
707 }
708
709 // Is a dominating control suitable for folding with this if?
710 bool IfNode::proj_cmpi_with(Node* ctrl, PhaseIterGVN* igvn) {
711 return ctrl != NULL &&
712 ctrl->is_Proj() &&
713 ctrl->in(0)->is_If() &&
714 ctrl->in(0)->outcnt() == 2 &&
715 ctrl->in(0)->as_If()->cmpi_if(igvn) &&
716 // Must compare same value
717 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
718 }
719
720 // Do this If and the dominating If share a region?
721 bool IfNode::shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
722 ProjNode* otherproj = proj->other_if_proj();
723 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
724 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
725 success = NULL;
726 fail = NULL;
727
728 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
729 for (int i = 0; i < 2; i++) {
730 ProjNode* proj = proj_out(i);
731 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
732 success = proj;
733 } else if (fail == NULL) {
734 fail = proj;
735 } else {
736 success = fail = NULL;
737 }
738 }
739 }
740 return success != NULL && fail != NULL;
741 }
742
743 // Return projection that leads to an uncommon trap if any
744 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
745 for (int i = 0; i < 2; i++) {
746 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
747 if (call != NULL) {
748 return proj_out(i);
749 }
750 }
751 return NULL;
752 }
753
754 // Do this If and the dominating If both branch out to an uncommon trap
755 bool IfNode::uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
756 ProjNode* otherproj = proj->other_if_proj();
757 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
758
759 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
760 CallStaticJavaNode* unc = NULL;
761 ProjNode* unc_proj = uncommon_trap_proj(unc);
762 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
763 if (dom_unc == unc) {
764 // Allow the uncommon trap to be shared through a region
765 RegionNode* r = unc->in(0)->as_Region();
766 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
767 return false;
768 }
769 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
770 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
771 return false;
772 }
773 // See merge_uncommon_traps: the reason of the uncmmon trap will
774 // be changed and the state of the dominating If will be
775 // used. Checked that we didn't apply this transformation in a
776 // previous compilation and it didn't cause too many traps
777 if (!igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_unstable_fused_if) &&
778 !igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_range_check)) {
779 success = unc_proj;
780 fail = unc_proj->other_if_proj();
781 return true;
782 }
783 }
784 }
785 return false;
786 }
787
788 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
789 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
790 Node* this_cmp = in(1)->in(1);
791 BoolNode* this_bool = in(1)->as_Bool();
792 IfNode* dom_iff = proj->in(0)->as_If();
793 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
794 Node* lo = dom_iff->in(1)->in(1)->in(2);
795 Node* hi = this_cmp->in(2);
796 Node* n = this_cmp->in(1);
797 ProjNode* otherproj = proj->other_if_proj();
798
799 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
800 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
801
802 BoolTest::mask lo_test = dom_bool->_test._test;
803 BoolTest::mask hi_test = this_bool->_test._test;
804 BoolTest::mask cond = hi_test;
805
806 // Figure out which of the two tests sets the upper bound and which
807 // sets the lower bound if any.
808 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
809
810 assert(((lo_test == BoolTest::le || lo_test == BoolTest::lt) && !proj->_con) ||
811 ((lo_test == BoolTest::ge || lo_test == BoolTest::gt) && proj->_con), "incorrect test");
812 // this test was canonicalized
813 assert((hi_test == BoolTest::le || hi_test == BoolTest::lt) && fail->_con, "incorrect test");
814
815 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
816 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
817 }
818 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
819 swap(lo, hi);
820 swap(lo_type, hi_type);
821 swap(lo_test, hi_test);
822
823 assert(((hi_test == BoolTest::le || hi_test == BoolTest::lt) && proj->_con) ||
824 ((hi_test == BoolTest::ge || hi_test == BoolTest::gt) && !proj->_con), "incorrect test");
825 // this test was canonicalized
826 assert((lo_test == BoolTest::le || lo_test == BoolTest::lt) && !fail->_con, "incorrect test");
827
828 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
829
830 if (lo_test == BoolTest::le) {
831 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
832 }
833
834 } else {
835 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
836 if (failtype != NULL) {
837 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
838 if (type2 != NULL) {
839 failtype = failtype->join(type2)->is_int();
840 if (failtype->_lo > failtype->_hi) {
841 // previous if determines the result of this if so
842 // replace Bool with constant
843 igvn->hash_delete(this);
844 set_req(1, igvn->intcon(success->_con));
845 return true;
846 }
847 }
848 }
849
850 lo = NULL;
851 hi = NULL;
852 }
853
854 if (lo && hi) {
855 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
856 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
857 Node* adjusted_lim = igvn->transform(new SubINode(hi, lo));
858 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
859 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
860
861 igvn->is_IterGVN()->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
862 igvn->hash_delete(this);
863 set_req(1, newbool);
864
865 return true;
866 }
867 return false;
868 }
869
870 // Merge the branches that trap for this If and the dominating If into
871 // a single region that branches to the uncommon trap for the
872 // dominating If
873 void IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, PhaseIterGVN* igvn) {
874 ProjNode* otherproj = proj->other_if_proj();
875
876 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
877 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
878
879 if (unc != dom_unc) {
880 Node* r = new RegionNode(3);
881
882 r->set_req(1, otherproj);
883 r->set_req(2, success);
884 r = igvn->transform(r);
885 assert(r->is_Region(), "can't go away");
886
887 // Make both If trap at the state of the first If: once the CmpI
888 // nodes are merged, if we trap we don't know which of the CmpI
889 // nodes would have caused the trap so we have to restart
890 // execution at the first one
891 igvn->replace_input_of(dom_unc, 0, r);
892 igvn->replace_input_of(unc, 0, igvn->C->top());
893 }
894 int trap_request = dom_unc->uncommon_trap_request();
895 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
896 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
897 if (success->in(0)->as_If()->range_check_trap_proj() != NULL) {
898 // If this looks like a range check, change the trap to
899 // Reason_range_check so the compiler recognizes it as a range
900 // check and applies the corresponding optimizations
901 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
902 } else if (unc != dom_unc) {
903 // If we trap we won't know what CmpI would have caused the trap
904 // so use a special trap reason to mark this pair of CmpI nodes as
905 // bad candidate for folding. On recompilation we won't fold them
906 // and we may trap again but this time we'll know what branch
907 // traps
908 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
909 }
910 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
911 }
912
913 // Check that the If that is in between the 2 integer comparisons has
914 // no side effect
915 bool IfNode::side_effect_free(ProjNode* proj, PhaseIterGVN* igvn) {
916 if (proj != NULL &&
917 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
918 proj->outcnt() <= 2) {
919 Node* this_cmp = in(1)->in(1);
920 Node* other = this_cmp->in(2);
921 if (proj->outcnt() == 1 ||
922 // Allow simple null check from LoadRange
923 (other->Opcode() == Op_LoadRange &&
924 ((other->in(0) != NULL && other->in(0) == proj) ||
925 (other->in(0) == NULL && other->in(2)->is_AddP() && other->in(2)->in(1)->Opcode() == Op_CastPP && other->in(2)->in(1)->in(0) == proj)))) {
926 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
927 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
928
929 // reroute_side_effect_free_unc changes the state of this
930 // uncommon trap to restart execution at the previous
931 // CmpI. Check that this change in a previous compilation didn't
932 // cause too many traps.
933 int trap_request = unc->uncommon_trap_request();
934 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
935
936 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
937 return false;
938 }
939
940 return true;
941 }
942 }
943 return false;
944 }
945
946 // Make the If between the 2 integer comparisons trap at the state of
947 // the first If: the last CmpI is the one replaced by a CmpU and the
948 // first CmpI is eliminated, so the test between the 2 CmpI nodes
949 // won't be guarded by the first CmpI anymore. It can trap in cases
950 // where the first CmpI would have prevented it from executing: on a
951 // trap, we need to restart execution at the state of the first CmpI
952 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
953 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
954 ProjNode* otherproj = proj->other_if_proj();
955 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
956
957 CallStaticJavaNode* new_unc = dom_unc->clone()->as_CallStaticJava();
958 Node* call_proj = dom_unc->unique_ctrl_out();
959 Node* halt = call_proj->unique_ctrl_out();
960
961 call_proj = call_proj->clone();
962 halt = halt->clone();
963 Node* c = otherproj->clone();
964 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
965 new_unc->set_req(0, c);
966 call_proj->set_req(0, new_unc);
967 halt->set_req(0, call_proj);
968
969 igvn->replace_node(otherproj, igvn->C->top());
970
971 igvn->transform(c);
972 igvn->transform(new_unc);
973 igvn->transform(call_proj);
974 igvn->transform(halt);
975
976 igvn->C->root()->add_req(halt);
977 }
978
979 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
980 if (Opcode() != Op_If) return NULL;
981
982 if (cmpi_if(igvn)) {
983 Node* ctrl = in(0);
984 if (proj_cmpi_with(ctrl, igvn) &&
985 ctrl->outcnt() == 1) {
986 // A integer comparison immediately dominated by another integer
987 // comparison
988 ProjNode* success = NULL;
989 ProjNode* fail = NULL;
990 ProjNode* dom_cmp = ctrl->as_Proj();
991 if (shared_region(dom_cmp, success, fail) &&
992 // Next call modifies graph so must be last
993 fold_compares_helper(dom_cmp, success, fail, igvn)) {
994 return this;
995 }
996 if (uncommon_traps(dom_cmp, success, fail, igvn) &&
997 // Next call modifies graph so must be last
998 fold_compares_helper(dom_cmp, success, fail, igvn)) {
999 merge_uncommon_traps(dom_cmp, success, igvn);
1000 return this;
1001 }
1002 return NULL;
1003 } else {
1004 ProjNode* success = NULL;
1005 ProjNode* fail = NULL;
1006 Node* dom = ctrl->in(0)->in(0);
1007 ProjNode* dom_cmp = dom->isa_Proj();
1008 ProjNode* other_cmp = ctrl->isa_Proj();
1009
1010 // Check if it's an integer comparison dominated by another
1011 // integer comparison with another test in between
1012 if (proj_cmpi_with(dom, igvn) &&
1013 uncommon_traps(dom_cmp, success, fail, igvn) &&
1014 side_effect_free(other_cmp, igvn) &&
1015 // Next call modifies graph so must be last
1016 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1017 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1018 merge_uncommon_traps(dom_cmp, success, igvn);
1019 return this;
1020 }
1021 }
1022 }
1023 return NULL;
1024 }
1025
1026 //------------------------------remove_useless_bool----------------------------
1027 // Check for people making a useless boolean: things like
1028 // if( (x < y ? true : false) ) { ... }
1029 // Replace with if( x < y ) { ... }
1030 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1031 Node *i1 = iff->in(1);
1032 if( !i1->is_Bool() ) return NULL;
1033 BoolNode *bol = i1->as_Bool();
1034
1035 Node *cmp = bol->in(1);
1036 if( cmp->Opcode() != Op_CmpI ) return NULL;
1037
1038 // Must be comparing against a bool
1039 const Type *cmp2_t = phase->type( cmp->in(2) );
1040 if( cmp2_t != TypeInt::ZERO &&
1041 cmp2_t != TypeInt::ONE )
1042 return NULL;
1043
1044 // Find a prior merge point merging the boolean
1045 i1 = cmp->in(1);
1046 if( !i1->is_Phi() ) return NULL;
1047 PhiNode *phi = i1->as_Phi();
1048 if( phase->type( phi ) != TypeInt::BOOL )
1049 return NULL;
1050
1051 // Check for diamond pattern
1052 int true_path = phi->is_diamond_phi();
1053 if( true_path == 0 ) return NULL;
1054
1055 // Make sure that iff and the control of the phi are different. This
1056 // should really only happen for dead control flow since it requires
1057 // an illegal cycle.
1058 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1059
1060 // phi->region->if_proj->ifnode->bool->cmp
1061 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1062
1063 // Now get the 'sense' of the test correct so we can plug in
1064 // either iff2->in(1) or its complement.
1065 int flip = 0;
1066 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1067 else if( bol->_test._test != BoolTest::eq ) return NULL;
1068 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1069
1070 const Type *phi1_t = phase->type( phi->in(1) );
1071 const Type *phi2_t = phase->type( phi->in(2) );
1072 // Check for Phi(0,1) and flip
1073 if( phi1_t == TypeInt::ZERO ) {
1074 if( phi2_t != TypeInt::ONE ) return NULL;
1075 flip = 1-flip;
1076 } else {
1077 // Check for Phi(1,0)
1078 if( phi1_t != TypeInt::ONE ) return NULL;
1079 if( phi2_t != TypeInt::ZERO ) return NULL;
1080 }
1081 if( true_path == 2 ) {
1082 flip = 1-flip;
1083 }
1084
1085 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1086 assert(new_bol != iff->in(1), "must make progress");
1087 iff->set_req(1, new_bol);
1088 // Intervening diamond probably goes dead
1089 phase->C->set_major_progress();
1090 return iff;
1091 }
1092
1093 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1094
1095 struct RangeCheck {
1096 Node* ctl;
1097 jint off;
1098 };
1099
1100 //------------------------------Ideal------------------------------------------
1101 // Return a node which is more "ideal" than the current node. Strip out
1102 // control copies
1103 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1104 if (remove_dead_region(phase, can_reshape)) return this;
1105 // No Def-Use info?
1106 if (!can_reshape) return NULL;
1107 PhaseIterGVN *igvn = phase->is_IterGVN();
1108
1109 // Don't bother trying to transform a dead if
1110 if (in(0)->is_top()) return NULL;
1111 // Don't bother trying to transform an if with a dead test
1112 if (in(1)->is_top()) return NULL;
1113 // Another variation of a dead test
1114 if (in(1)->is_Con()) return NULL;
1115 // Another variation of a dead if
1116 if (outcnt() < 2) return NULL;
1117
1118 // Canonicalize the test.
1119 Node* idt_if = idealize_test(phase, this);
1120 if (idt_if != NULL) return idt_if;
1121
1122 // Try to split the IF
1123 Node *s = split_if(this, igvn);
1124 if (s != NULL) return s;
1125
1126 // Check for people making a useless boolean: things like
1127 // if( (x < y ? true : false) ) { ... }
1128 // Replace with if( x < y ) { ... }
1129 Node *bol2 = remove_useless_bool(this, phase);
1130 if( bol2 ) return bol2;
1131
1132 // Setup to scan up the CFG looking for a dominating test
1133 Node *dom = in(0);
1134 Node *prev_dom = this;
1135
1136 // Check for range-check vs other kinds of tests
1137 Node *index1, *range1;
1138 jint offset1;
1139 int flip1 = is_range_check(range1, index1, offset1);
1140 if( flip1 ) {
1141 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1142 // so all checks we inspect post-dominate the top-most check we find.
1143 // If we are going to fail the current check and we reach the top check
1144 // then we are guaranteed to fail, so just start interpreting there.
1145 // We 'expand' the top 3 range checks to include all post-dominating
1146 // checks.
1147
1148 // The top 3 range checks seen
1149 const int NRC =3;
1150 RangeCheck prev_checks[NRC];
1151 int nb_checks = 0;
1152
1153 // Low and high offsets seen so far
1154 jint off_lo = offset1;
1155 jint off_hi = offset1;
1156
1157 bool found_immediate_dominator = false;
1158
1159 // Scan for the top checks and collect range of offsets
1160 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1161 if (dom->Opcode() == Op_If && // Not same opcode?
1162 prev_dom->in(0) == dom) { // One path of test does dominate?
1163 if (dom == this) return NULL; // dead loop
1164 // See if this is a range check
1165 Node *index2, *range2;
1166 jint offset2;
1167 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
1168 // See if this is a _matching_ range check, checking against
1169 // the same array bounds.
1170 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1171 dom->outcnt() == 2) {
1172 if (nb_checks == 0 && dom->in(1) == in(1)) {
1173 // Found an immediately dominating test at the same offset.
1174 // This kind of back-to-back test can be eliminated locally,
1175 // and there is no need to search further for dominating tests.
1176 assert(offset2 == offset1, "Same test but different offsets");
1177 found_immediate_dominator = true;
1178 break;
1179 }
1180 // Gather expanded bounds
1181 off_lo = MIN2(off_lo,offset2);
1182 off_hi = MAX2(off_hi,offset2);
1183 // Record top NRC range checks
1184 prev_checks[nb_checks%NRC].ctl = prev_dom;
1185 prev_checks[nb_checks%NRC].off = offset2;
1186 nb_checks++;
1187 }
1188 }
1189 prev_dom = dom;
1190 dom = up_one_dom(dom);
1191 if (!dom) break;
1192 }
1193
1194 if (!found_immediate_dominator) {
1195 // Attempt to widen the dominating range check to cover some later
1196 // ones. Since range checks "fail" by uncommon-trapping to the
1197 // interpreter, widening a check can make us speculatively enter
1198 // the interpreter. If we see range-check deopt's, do not widen!
1199 if (!phase->C->allow_range_check_smearing()) return NULL;
1200
1201 // Didn't find prior covering check, so cannot remove anything.
1202 if (nb_checks == 0) {
1203 return NULL;
1204 }
1205 // Constant indices only need to check the upper bound.
1206 // Non-constant indices must check both low and high.
1207 int chk0 = (nb_checks - 1) % NRC;
1208 if (index1) {
1209 if (nb_checks == 1) {
1210 return NULL;
1211 } else {
1212 // If the top range check's constant is the min or max of
1213 // all constants we widen the next one to cover the whole
1214 // range of constants.
1215 RangeCheck rc0 = prev_checks[chk0];
1216 int chk1 = (nb_checks - 2) % NRC;
1217 RangeCheck rc1 = prev_checks[chk1];
1218 if (rc0.off == off_lo) {
1219 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1220 prev_dom = rc1.ctl;
1221 } else if (rc0.off == off_hi) {
1222 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1223 prev_dom = rc1.ctl;
1224 } else {
1225 // If the top test's constant is not the min or max of all
1226 // constants, we need 3 range checks. We must leave the
1227 // top test unchanged because widening it would allow the
1228 // accesses it protects to successfully read/write out of
1229 // bounds.
1230 if (nb_checks == 2) {
1231 return NULL;
1232 }
1233 int chk2 = (nb_checks - 3) % NRC;
1234 RangeCheck rc2 = prev_checks[chk2];
1235 // The top range check a+i covers interval: -a <= i < length-a
1236 // The second range check b+i covers interval: -b <= i < length-b
1237 if (rc1.off <= rc0.off) {
1238 // if b <= a, we change the second range check to:
1239 // -min_of_all_constants <= i < length-min_of_all_constants
1240 // Together top and second range checks now cover:
1241 // -min_of_all_constants <= i < length-a
1242 // which is more restrictive than -b <= i < length-b:
1243 // -b <= -min_of_all_constants <= i < length-a <= length-b
1244 // The third check is then changed to:
1245 // -max_of_all_constants <= i < length-max_of_all_constants
1246 // so 2nd and 3rd checks restrict allowed values of i to:
1247 // -min_of_all_constants <= i < length-max_of_all_constants
1248 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1249 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1250 } else {
1251 // if b > a, we change the second range check to:
1252 // -max_of_all_constants <= i < length-max_of_all_constants
1253 // Together top and second range checks now cover:
1254 // -a <= i < length-max_of_all_constants
1255 // which is more restrictive than -b <= i < length-b:
1256 // -b < -a <= i < length-max_of_all_constants <= length-b
1257 // The third check is then changed to:
1258 // -max_of_all_constants <= i < length-max_of_all_constants
1259 // so 2nd and 3rd checks restrict allowed values of i to:
1260 // -min_of_all_constants <= i < length-max_of_all_constants
1261 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1262 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1263 }
1264 prev_dom = rc2.ctl;
1265 }
1266 }
1267 } else {
1268 RangeCheck rc0 = prev_checks[chk0];
1269 // 'Widen' the offset of the 1st and only covering check
1270 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1271 // Test is now covered by prior checks, dominate it out
1272 prev_dom = rc0.ctl;
1273 }
1274 }
1275
1276 } else { // Scan for an equivalent test
1277
1278 Node *cmp;
1279 int dist = 0; // Cutoff limit for search
1280 int op = Opcode();
1281 if( op == Op_If &&
1282 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1283 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1284 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1285 dist = 64; // Limit for null-pointer scans
1286 } else {
1287 dist = 4; // Do not bother for random pointer tests
1288 }
1289 } else {
1290 dist = 4; // Limit for random junky scans
1291 }
1292
1293 // Normal equivalent-test check.
1294 if( !dom ) return NULL; // Dead loop?
1295
1296 Node* result = fold_compares(igvn);
1297 if (result != NULL) {
1298 return result;
1299 }
1300
1301 // Search up the dominator tree for an If with an identical test
1302 while( dom->Opcode() != op || // Not same opcode?
1303 dom->in(1) != in(1) || // Not same input 1?
1304 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1305 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1306 if( dist < 0 ) return NULL;
1307
1308 dist--;
1309 prev_dom = dom;
1310 dom = up_one_dom( dom );
1311 if( !dom ) return NULL;
1312 }
1313
1314 // Check that we did not follow a loop back to ourselves
1315 if( this == dom )
1316 return NULL;
1317
1318 if( dist > 2 ) // Add to count of NULL checks elided
1319 explicit_null_checks_elided++;
1320
1321 } // End of Else scan for an equivalent test
1322
1323 // Hit! Remove this IF
1324 #ifndef PRODUCT
1325 if( TraceIterativeGVN ) {
1326 tty->print(" Removing IfNode: "); this->dump();
1327 }
1328 if( VerifyOpto && !phase->allow_progress() ) {
1329 // Found an equivalent dominating test,
1330 // we can not guarantee reaching a fix-point for these during iterativeGVN
1331 // since intervening nodes may not change.
1332 return NULL;
1333 }
1334 #endif
1335
1336 // Replace dominated IfNode
1337 dominated_by( prev_dom, igvn );
1338
1339 // Must return either the original node (now dead) or a new node
1340 // (Do not return a top here, since that would break the uniqueness of top.)
1341 return new ConINode(TypeInt::ZERO);
1342 }
1343
1344 //------------------------------dominated_by-----------------------------------
1345 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1346 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1347 Node *idom = in(0);
1348 // Need opcode to decide which way 'this' test goes
1349 int prev_op = prev_dom->Opcode();
1350 Node *top = igvn->C->top(); // Shortcut to top
1351
1352 // Loop predicates may have depending checks which should not
1353 // be skipped. For example, range check predicate has two checks
1354 // for lower and upper bounds.
1355 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1356 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1357 prev_dom = idom;
1358
1359 // Now walk the current IfNode's projections.
1360 // Loop ends when 'this' has no more uses.
1361 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1362 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1363 igvn->add_users_to_worklist(ifp);
1364 // Check which projection it is and set target.
1365 // Data-target is either the dominating projection of the same type
1366 // or TOP if the dominating projection is of opposite type.
1367 // Data-target will be used as the new control edge for the non-CFG
1368 // nodes like Casts and Loads.
1369 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1370 // Control-target is just the If's immediate dominator or TOP.
1371 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1372
1373 // For each child of an IfTrue/IfFalse projection, reroute.
1374 // Loop ends when projection has no more uses.
1375 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1376 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1377 if( !s->depends_only_on_test() ) {
1378 // Find the control input matching this def-use edge.
1379 // For Regions it may not be in slot 0.
1380 uint l;
1381 for( l = 0; s->in(l) != ifp; l++ ) { }
1382 igvn->replace_input_of(s, l, ctrl_target);
1383 } else { // Else, for control producers,
1384 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1385 }
1386 } // End for each child of a projection
1387
1388 igvn->remove_dead_node(ifp);
1389 } // End for each IfTrue/IfFalse child of If
1390
1391 // Kill the IfNode
1392 igvn->remove_dead_node(this);
1393 }
1394
1395 //------------------------------Identity---------------------------------------
1396 // If the test is constant & we match, then we are the input Control
1397 Node *IfProjNode::Identity(PhaseTransform *phase) {
1398 // Can only optimize if cannot go the other way
1399 const TypeTuple *t = phase->type(in(0))->is_tuple();
1400 if (t == TypeTuple::IFNEITHER ||
1401 // kill dead branch first otherwise the IfNode's control will
1402 // have 2 control uses (the IfNode that doesn't go away because
1403 // it still has uses and this branch of the
1404 // If). Node::has_special_unique_user() will cause this node to
1405 // be reprocessed once the dead branch is killed.
1406 (always_taken(t) && in(0)->outcnt() == 1)) {
1407 // IfNode control
1408 return in(0)->in(0);
1409 }
1410 // no progress
1411 return this;
1412 }
1413
1414 //------------------------------dump_spec--------------------------------------
1415 #ifndef PRODUCT
1416 void IfNode::dump_spec(outputStream *st) const {
1417 st->print("P=%f, C=%f",_prob,_fcnt);
1418 }
1419 #endif
1420
1421 //------------------------------idealize_test----------------------------------
1422 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1423 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1424 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1425 // needed.
1426 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1427 assert(iff->in(0) != NULL, "If must be live");
1428
1429 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1430 Node* old_if_f = iff->proj_out(false);
1431 Node* old_if_t = iff->proj_out(true);
1432
1433 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1434 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1435 // happens in count-down loops
1436 if (iff->is_CountedLoopEnd()) return NULL;
1437 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1438 BoolNode *b = iff->in(1)->as_Bool();
1439 BoolTest bt = b->_test;
1440 // Test already in good order?
1441 if( bt.is_canonical() )
1442 return NULL;
1443
1444 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1445 // cloning the IfNode.
1446 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1447 if( !new_b->is_Bool() ) return NULL;
1448 b = new_b->as_Bool();
1449
1450 PhaseIterGVN *igvn = phase->is_IterGVN();
1451 assert( igvn, "Test is not canonical in parser?" );
1452
1453 // The IF node never really changes, but it needs to be cloned
1454 iff = new IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1455
1456 Node *prior = igvn->hash_find_insert(iff);
1457 if( prior ) {
1458 igvn->remove_dead_node(iff);
1459 iff = (IfNode*)prior;
1460 } else {
1461 // Cannot call transform on it just yet
1462 igvn->set_type_bottom(iff);
1463 }
1464 igvn->_worklist.push(iff);
1465
1466 // Now handle projections. Cloning not required.
1467 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1468 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1469
1470 igvn->register_new_node_with_optimizer(new_if_f);
1471 igvn->register_new_node_with_optimizer(new_if_t);
1472 // Flip test, so flip trailing control
1473 igvn->replace_node(old_if_f, new_if_t);
1474 igvn->replace_node(old_if_t, new_if_f);
1475
1476 // Progress
1477 return iff;
1478 }