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comparison: src/share/vm/opto/ifnode.cpp

src/share/vm/opto/ifnode.cpp

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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/subnode.hpp"
34
35 // Portions of code courtesy of Clifford Click
36
37 // Optimization - Graph Style
38
39
40 extern int explicit_null_checks_elided;
41
42 //=============================================================================
43 //------------------------------Value------------------------------------------
44 // Return a tuple for whichever arm of the IF is reachable
45 const Type *IfNode::Value( PhaseTransform *phase ) const {
46 if( !in(0) ) return Type::TOP;
47 if( phase->type(in(0)) == Type::TOP )
48 return Type::TOP;
49 const Type *t = phase->type(in(1));
50 if( t == Type::TOP ) // data is undefined
51 return TypeTuple::IFNEITHER; // unreachable altogether
52 if( t == TypeInt::ZERO ) // zero, or false
53 return TypeTuple::IFFALSE; // only false branch is reachable
54 if( t == TypeInt::ONE ) // 1, or true
55 return TypeTuple::IFTRUE; // only true branch is reachable
56 assert( t == TypeInt::BOOL, "expected boolean type" );
57
58 return TypeTuple::IFBOTH; // No progress
59 }
60
61 const RegMask &IfNode::out_RegMask() const {
62 return RegMask::Empty;
63 }
64
65 //------------------------------split_if---------------------------------------
66 // Look for places where we merge constants, then test on the merged value.
67 // If the IF test will be constant folded on the path with the constant, we
68 // win by splitting the IF to before the merge point.
69 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
70 // I could be a lot more general here, but I'm trying to squeeze this
71 // in before the Christmas '98 break so I'm gonna be kinda restrictive
72 // on the patterns I accept. CNC
73
74 // Look for a compare of a constant and a merged value
75 Node *i1 = iff->in(1);
76 if( !i1->is_Bool() ) return NULL;
77 BoolNode *b = i1->as_Bool();
78 Node *cmp = b->in(1);
79 if( !cmp->is_Cmp() ) return NULL;
80 i1 = cmp->in(1);
81 if( i1 == NULL || !i1->is_Phi() ) return NULL;
82 PhiNode *phi = i1->as_Phi();
83 if( phi->is_copy() ) return NULL;
84 Node *con2 = cmp->in(2);
85 if( !con2->is_Con() ) return NULL;
86 // See that the merge point contains some constants
87 Node *con1=NULL;
88 uint i4;
89 for( i4 = 1; i4 < phi->req(); i4++ ) {
90 con1 = phi->in(i4);
91 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
92 if( con1->is_Con() ) break; // Found a constant
93 // Also allow null-vs-not-null checks
94 const TypePtr *tp = igvn->type(con1)->isa_ptr();
95 if( tp && tp->_ptr == TypePtr::NotNull )
96 break;
97 }
98 if( i4 >= phi->req() ) return NULL; // Found no constants
99
100 igvn->C->set_has_split_ifs(true); // Has chance for split-if
101
102 // Make sure that the compare can be constant folded away
103 Node *cmp2 = cmp->clone();
104 cmp2->set_req(1,con1);
105 cmp2->set_req(2,con2);
106 const Type *t = cmp2->Value(igvn);
107 // This compare is dead, so whack it!
108 igvn->remove_dead_node(cmp2);
109 if( !t->singleton() ) return NULL;
110
111 // No intervening control, like a simple Call
112 Node *r = iff->in(0);
113 if( !r->is_Region() ) return NULL;
114 if( phi->region() != r ) return NULL;
115 // No other users of the cmp/bool
116 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
117 //tty->print_cr("many users of cmp/bool");
118 return NULL;
119 }
120
121 // Make sure we can determine where all the uses of merged values go
122 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
123 Node* u = r->fast_out(j);
124 if( u == r ) continue;
125 if( u == iff ) continue;
126 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
127 if( !u->is_Phi() ) {
128 /*
129 if( u->is_Start() ) {
130 tty->print_cr("Region has inlined start use");
131 } else {
132 tty->print_cr("Region has odd use");
133 u->dump(2);
134 }*/
135 return NULL;
136 }
137 if( u != phi ) {
138 // CNC - do not allow any other merged value
139 //tty->print_cr("Merging another value");
140 //u->dump(2);
141 return NULL;
142 }
143 // Make sure we can account for all Phi uses
144 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
145 Node* v = u->fast_out(k); // User of the phi
146 // CNC - Allow only really simple patterns.
147 // In particular I disallow AddP of the Phi, a fairly common pattern
148 if( v == cmp ) continue; // The compare is OK
149 if( (v->is_ConstraintCast()) &&
150 v->in(0)->in(0) == iff )
151 continue; // CastPP/II of the IfNode is OK
152 // Disabled following code because I cannot tell if exactly one
153 // path dominates without a real dominator check. CNC 9/9/1999
154 //uint vop = v->Opcode();
155 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
156 // Node *r = v->in(0); // Get controlling point
157 // if( !r ) return NULL; // Degraded to a copy
158 // // Find exactly one path in (either True or False doms, but not IFF)
159 // int cnt = 0;
160 // for( uint i = 1; i < r->req(); i++ )
161 // if( r->in(i) && r->in(i)->in(0) == iff )
162 // cnt++;
163 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
164 //}
165 if( !v->is_Call() ) {
166 /*
167 if( v->Opcode() == Op_AddP ) {
168 tty->print_cr("Phi has AddP use");
169 } else if( v->Opcode() == Op_CastPP ) {
170 tty->print_cr("Phi has CastPP use");
171 } else if( v->Opcode() == Op_CastII ) {
172 tty->print_cr("Phi has CastII use");
173 } else {
174 tty->print_cr("Phi has use I cant be bothered with");
175 }
176 */
177 }
178 return NULL;
179
180 /* CNC - Cut out all the fancy acceptance tests
181 // Can we clone this use when doing the transformation?
182 // If all uses are from Phis at this merge or constants, then YES.
183 if( !v->in(0) && v != cmp ) {
184 tty->print_cr("Phi has free-floating use");
185 v->dump(2);
186 return NULL;
187 }
188 for( uint l = 1; l < v->req(); l++ ) {
189 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
190 !v->in(l)->is_Con() ) {
191 tty->print_cr("Phi has use");
192 v->dump(2);
193 return NULL;
194 } // End of if Phi-use input is neither Phi nor Constant
195 } // End of for all inputs to Phi-use
196 */
197 } // End of for all uses of Phi
198 } // End of for all uses of Region
199
200 // Only do this if the IF node is in a sane state
201 if (iff->outcnt() != 2)
202 return NULL;
203
204 // Got a hit! Do the Mondo Hack!
205 //
206 //ABC a1c def ghi B 1 e h A C a c d f g i
207 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
208 // cmp - 2 cmp - 2 cmp - 2
209 // bool bool_c bool_x
210 // if if_c if_x
211 // T F T F T F
212 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
213 //
214 // Split the paths coming into the merge point into 2 separate groups of
215 // merges. On the left will be all the paths feeding constants into the
216 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
217 // will fold up into a constant; this will let the Cmp fold up as well as
218 // all the control flow. Below the original IF we have 2 control
219 // dependent regions, 's' and 't'. Now we will merge the two paths
220 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
221 // likely 2 or more) will promptly constant fold away.
222 PhaseGVN *phase = igvn;
223
224 // Make a region merging constants and a region merging the rest
225 uint req_c = 0;
226 Node* predicate_proj = NULL;
227 for (uint ii = 1; ii < r->req(); ii++) {
228 if (phi->in(ii) == con1) {
229 req_c++;
230 }
231 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
232 if (proj != NULL) {
233 assert(predicate_proj == NULL, "only one predicate entry expected");
234 predicate_proj = proj;
235 }
236 }
237 Node* predicate_c = NULL;
238 Node* predicate_x = NULL;
239 bool counted_loop = r->is_CountedLoop();
240
241 Node *region_c = new (igvn->C) RegionNode(req_c + 1);
242 Node *phi_c = con1;
243 uint len = r->req();
244 Node *region_x = new (igvn->C) RegionNode(len - req_c);
245 Node *phi_x = PhiNode::make_blank(region_x, phi);
246 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
247 if (phi->in(i) == con1) {
248 region_c->init_req( i_c++, r ->in(i) );
249 if (r->in(i) == predicate_proj)
250 predicate_c = predicate_proj;
251 } else {
252 region_x->init_req( i_x, r ->in(i) );
253 phi_x ->init_req( i_x++, phi->in(i) );
254 if (r->in(i) == predicate_proj)
255 predicate_x = predicate_proj;
256 }
257 }
258 if (predicate_c != NULL && (req_c > 1)) {
259 assert(predicate_x == NULL, "only one predicate entry expected");
260 predicate_c = NULL; // Do not clone predicate below merge point
261 }
262 if (predicate_x != NULL && ((len - req_c) > 2)) {
263 assert(predicate_c == NULL, "only one predicate entry expected");
264 predicate_x = NULL; // Do not clone predicate below merge point
265 }
266
267 // Register the new RegionNodes but do not transform them. Cannot
268 // transform until the entire Region/Phi conglomerate has been hacked
269 // as a single huge transform.
270 igvn->register_new_node_with_optimizer( region_c );
271 igvn->register_new_node_with_optimizer( region_x );
272 // Prevent the untimely death of phi_x. Currently he has no uses. He is
273 // about to get one. If this only use goes away, then phi_x will look dead.
274 // However, he will be picking up some more uses down below.
275 Node *hook = new (igvn->C) Node(4);
276 hook->init_req(0, phi_x);
277 hook->init_req(1, phi_c);
278 phi_x = phase->transform( phi_x );
279
280 // Make the compare
281 Node *cmp_c = phase->makecon(t);
282 Node *cmp_x = cmp->clone();
283 cmp_x->set_req(1,phi_x);
284 cmp_x->set_req(2,con2);
285 cmp_x = phase->transform(cmp_x);
286 // Make the bool
287 Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test));
288 Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test));
289 // Make the IfNode
290 IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
291 igvn->set_type_bottom(iff_c);
292 igvn->_worklist.push(iff_c);
293 hook->init_req(2, iff_c);
294
295 IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
296 igvn->set_type_bottom(iff_x);
297 igvn->_worklist.push(iff_x);
298 hook->init_req(3, iff_x);
299
300 // Make the true/false arms
301 Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c));
302 Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c));
303 if (predicate_c != NULL) {
304 assert(predicate_x == NULL, "only one predicate entry expected");
305 // Clone loop predicates to each path
306 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
307 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
308 }
309 Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x));
310 Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x));
311 if (predicate_x != NULL) {
312 assert(predicate_c == NULL, "only one predicate entry expected");
313 // Clone loop predicates to each path
314 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
315 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
316 }
317
318 // Merge the TRUE paths
319 Node *region_s = new (igvn->C) RegionNode(3);
320 igvn->_worklist.push(region_s);
321 region_s->init_req(1, iff_c_t);
322 region_s->init_req(2, iff_x_t);
323 igvn->register_new_node_with_optimizer( region_s );
324
325 // Merge the FALSE paths
326 Node *region_f = new (igvn->C) RegionNode(3);
327 igvn->_worklist.push(region_f);
328 region_f->init_req(1, iff_c_f);
329 region_f->init_req(2, iff_x_f);
330 igvn->register_new_node_with_optimizer( region_f );
331
332 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
333 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
334 cmp->set_req(2,NULL);
335 // Check for all uses of the Phi and give them a new home.
336 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
337 Node *phi_s = NULL; // do not construct unless needed
338 Node *phi_f = NULL; // do not construct unless needed
339 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
340 Node* v = phi->last_out(i2);// User of the phi
341 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
342 uint vop = v->Opcode();
343 Node *proj = NULL;
344 if( vop == Op_Phi ) { // Remote merge point
345 Node *r = v->in(0);
346 for (uint i3 = 1; i3 < r->req(); i3++)
347 if (r->in(i3) && r->in(i3)->in(0) == iff) {
348 proj = r->in(i3);
349 break;
350 }
351 } else if( v->is_ConstraintCast() ) {
352 proj = v->in(0); // Controlling projection
353 } else {
354 assert( 0, "do not know how to handle this guy" );
355 }
356
357 Node *proj_path_data, *proj_path_ctrl;
358 if( proj->Opcode() == Op_IfTrue ) {
359 if( phi_s == NULL ) {
360 // Only construct phi_s if needed, otherwise provides
361 // interfering use.
362 phi_s = PhiNode::make_blank(region_s,phi);
363 phi_s->init_req( 1, phi_c );
364 phi_s->init_req( 2, phi_x );
365 hook->add_req(phi_s);
366 phi_s = phase->transform(phi_s);
367 }
368 proj_path_data = phi_s;
369 proj_path_ctrl = region_s;
370 } else {
371 if( phi_f == NULL ) {
372 // Only construct phi_f if needed, otherwise provides
373 // interfering use.
374 phi_f = PhiNode::make_blank(region_f,phi);
375 phi_f->init_req( 1, phi_c );
376 phi_f->init_req( 2, phi_x );
377 hook->add_req(phi_f);
378 phi_f = phase->transform(phi_f);
379 }
380 proj_path_data = phi_f;
381 proj_path_ctrl = region_f;
382 }
383
384 // Fixup 'v' for for the split
385 if( vop == Op_Phi ) { // Remote merge point
386 uint i;
387 for( i = 1; i < v->req(); i++ )
388 if( v->in(i) == phi )
389 break;
390 v->set_req(i, proj_path_data );
391 } else if( v->is_ConstraintCast() ) {
392 v->set_req(0, proj_path_ctrl );
393 v->set_req(1, proj_path_data );
394 } else
395 ShouldNotReachHere();
396 }
397
398 // Now replace the original iff's True/False with region_s/region_t.
399 // This makes the original iff go dead.
400 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
401 Node* p = iff->last_out(i3);
402 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
403 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
404 // Replace p with u
405 igvn->add_users_to_worklist(p);
406 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
407 Node* x = p->last_out(l);
408 igvn->hash_delete(x);
409 uint uses_found = 0;
410 for( uint j = 0; j < x->req(); j++ ) {
411 if( x->in(j) == p ) {
412 x->set_req(j, u);
413 uses_found++;
414 }
415 }
416 l -= uses_found; // we deleted 1 or more copies of this edge
417 }
418 igvn->remove_dead_node(p);
419 }
420
421 // Force the original merge dead
422 igvn->hash_delete(r);
423 // First, remove region's dead users.
424 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
425 Node* u = r->last_out(l);
426 if( u == r ) {
427 r->set_req(0, NULL);
428 } else {
429 assert(u->outcnt() == 0, "only dead users");
430 igvn->remove_dead_node(u);
431 }
432 l -= 1;
433 }
434 igvn->remove_dead_node(r);
435
436 // Now remove the bogus extra edges used to keep things alive
437 igvn->remove_dead_node( hook );
438
439 // Must return either the original node (now dead) or a new node
440 // (Do not return a top here, since that would break the uniqueness of top.)
441 return new (igvn->C) ConINode(TypeInt::ZERO);
442 }
443
444 //------------------------------is_range_check---------------------------------
445 // Return 0 if not a range check. Return 1 if a range check and set index and
446 // offset. Return 2 if we had to negate the test. Index is NULL if the check
447 // is versus a constant.
448 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
449 Node* b = in(1);
450 if (b == NULL || !b->is_Bool()) return 0;
451 BoolNode* bn = b->as_Bool();
452 Node* cmp = bn->in(1);
453 if (cmp == NULL) return 0;
454 if (cmp->Opcode() != Op_CmpU) return 0;
455
456 Node* l = cmp->in(1);
457 Node* r = cmp->in(2);
458 int flip_test = 1;
459 if (bn->_test._test == BoolTest::le) {
460 l = cmp->in(2);
461 r = cmp->in(1);
462 flip_test = 2;
463 } else if (bn->_test._test != BoolTest::lt) {
464 return 0;
465 }
466 if (l->is_top()) return 0; // Top input means dead test
467 if (r->Opcode() != Op_LoadRange) return 0;
468
469 // We have recognized one of these forms:
470 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
471 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
472
473 // Make sure it's a real range check by requiring an uncommon trap
474 // along the OOB path. Otherwise, it's possible that the user wrote
475 // something which optimized to look like a range check but behaves
476 // in some other way.
477 Node* iftrap = proj_out(flip_test == 2 ? true : false);
478 bool found_trap = false;
479 if (iftrap != NULL) {
480 Node* u = iftrap->unique_ctrl_out();
481 if (u != NULL) {
482 // It could be a merge point (Region) for uncommon trap.
483 if (u->is_Region()) {
484 Node* c = u->unique_ctrl_out();
485 if (c != NULL) {
486 iftrap = u;
487 u = c;
488 }
489 }
490 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
491 int req = u->as_CallStaticJava()->uncommon_trap_request();
492 if (Deoptimization::trap_request_reason(req) ==
493 Deoptimization::Reason_range_check) {
494 found_trap = true;
495 }
496 }
497 }
498 }
499 if (!found_trap) return 0; // sorry, no cigar
500
501 // Look for index+offset form
502 Node* ind = l;
503 jint off = 0;
504 if (l->is_top()) {
505 return 0;
506 } else if (l->is_Add()) {
507 if ((off = l->in(1)->find_int_con(0)) != 0) {
508 ind = l->in(2);
509 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
510 ind = l->in(1);
511 }
512 } else if ((off = l->find_int_con(-1)) >= 0) {
513 // constant offset with no variable index
514 ind = NULL;
515 } else {
516 // variable index with no constant offset (or dead negative index)
517 off = 0;
518 }
519
520 // Return all the values:
521 index = ind;
522 offset = off;
523 range = r;
524 return flip_test;
525 }
526
527 //------------------------------adjust_check-----------------------------------
528 // Adjust (widen) a prior range check
529 static void adjust_check(Node* proj, Node* range, Node* index,
530 int flip, jint off_lo, PhaseIterGVN* igvn) {
531 PhaseGVN *gvn = igvn;
532 // Break apart the old check
533 Node *iff = proj->in(0);
534 Node *bol = iff->in(1);
535 if( bol->is_top() ) return; // In case a partially dead range check appears
536 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
537 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
538 if( !bol->is_Bool() ) return;
539
540 Node *cmp = bol->in(1);
541 // Compute a new check
542 Node *new_add = gvn->intcon(off_lo);
543 if( index ) {
544 new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index;
545 }
546 Node *new_cmp = (flip == 1)
547 ? new (gvn->C) CmpUNode( new_add, range )
548 : new (gvn->C) CmpUNode( range, new_add );
549 new_cmp = gvn->transform(new_cmp);
550 // See if no need to adjust the existing check
551 if( new_cmp == cmp ) return;
552 // Else, adjust existing check
553 Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
554 igvn->rehash_node_delayed( iff );
555 iff->set_req_X( 1, new_bol, igvn );
556 }
557
558 //------------------------------up_one_dom-------------------------------------
559 // Walk up the dominator tree one step. Return NULL at root or true
560 // complex merges. Skips through small diamonds.
561 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
562 Node *dom = curr->in(0);
563 if( !dom ) // Found a Region degraded to a copy?
564 return curr->nonnull_req(); // Skip thru it
565
566 if( curr != dom ) // Normal walk up one step?
567 return dom;
568
569 // Use linear_only if we are still parsing, since we cannot
570 // trust the regions to be fully filled in.
571 if (linear_only)
572 return NULL;
573
574 if( dom->is_Root() )
575 return NULL;
576
577 // Else hit a Region. Check for a loop header
578 if( dom->is_Loop() )
579 return dom->in(1); // Skip up thru loops
580
581 // Check for small diamonds
582 Node *din1, *din2, *din3, *din4;
583 if( dom->req() == 3 && // 2-path merge point
584 (din1 = dom ->in(1)) && // Left path exists
585 (din2 = dom ->in(2)) && // Right path exists
586 (din3 = din1->in(0)) && // Left path up one
587 (din4 = din2->in(0)) ) { // Right path up one
588 if( din3->is_Call() && // Handle a slow-path call on either arm
589 (din3 = din3->in(0)) )
590 din3 = din3->in(0);
591 if( din4->is_Call() && // Handle a slow-path call on either arm
592 (din4 = din4->in(0)) )
593 din4 = din4->in(0);
594 if( din3 == din4 && din3->is_If() )
595 return din3; // Skip around diamonds
596 }
597
598 // Give up the search at true merges
599 return NULL; // Dead loop? Or hit root?
600 }
601
602
603 //------------------------------filtered_int_type--------------------------------
604 // Return a possibly more restrictive type for val based on condition control flow for an if
605 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
606 assert(if_proj &&
607 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
608 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
609 IfNode* iff = if_proj->in(0)->as_If();
610 if (iff->in(1) && iff->in(1)->is_Bool()) {
611 BoolNode* bol = iff->in(1)->as_Bool();
612 if (bol->in(1) && bol->in(1)->is_Cmp()) {
613 const CmpNode* cmp = bol->in(1)->as_Cmp();
614 if (cmp->in(1) == val) {
615 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
616 if (cmp2_t != NULL) {
617 jint lo = cmp2_t->_lo;
618 jint hi = cmp2_t->_hi;
619 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
620 switch (msk) {
621 case BoolTest::ne:
622 // Can't refine type
623 return NULL;
624 case BoolTest::eq:
625 return cmp2_t;
626 case BoolTest::lt:
627 lo = TypeInt::INT->_lo;
628 if (hi - 1 < hi) {
629 hi = hi - 1;
630 }
631 break;
632 case BoolTest::le:
633 lo = TypeInt::INT->_lo;
634 break;
635 case BoolTest::gt:
636 if (lo + 1 > lo) {
637 lo = lo + 1;
638 }
639 hi = TypeInt::INT->_hi;
640 break;
641 case BoolTest::ge:
642 // lo unchanged
643 hi = TypeInt::INT->_hi;
644 break;
645 }
646 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
647 return rtn_t;
648 }
649 }
650 }
651 }
652 }
653 return NULL;
654 }
655
656 //------------------------------fold_compares----------------------------
657 // See if a pair of CmpIs can be converted into a CmpU. In some cases
658 // the direction of this if is determined by the preceding if so it
659 // can be eliminate entirely. Given an if testing (CmpI n c) check
660 // for an immediately control dependent if that is testing (CmpI n c2)
661 // and has one projection leading to this if and the other projection
662 // leading to a region that merges one of this ifs control
663 // projections.
664 //
665 // If
666 // / |
667 // / |
668 // / |
669 // If |
670 // /\ |
671 // / \ |
672 // / \ |
673 // / Region
674 //
675 Node* IfNode::fold_compares(PhaseGVN* phase) {
676 if (Opcode() != Op_If) return NULL;
677
678 Node* this_cmp = in(1)->in(1);
679 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
680 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
681 Node* ctrl = in(0);
682 BoolNode* this_bool = in(1)->as_Bool();
683 Node* n = this_cmp->in(1);
684 int hi = this_cmp->in(2)->get_int();
685 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
686 ctrl->in(0)->is_If() &&
687 ctrl->in(0)->outcnt() == 2 &&
688 ctrl->in(0)->in(1)->is_Bool() &&
689 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
690 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
691 ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
692 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
693 IfNode* dom_iff = ctrl->in(0)->as_If();
694 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
695 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
696 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
697 // Identify which proj goes to the region and which continues on
698 RegionNode* region = otherproj->unique_out()->as_Region();
699 Node* success = NULL;
700 Node* fail = NULL;
701 for (int i = 0; i < 2; i++) {
702 Node* proj = proj_out(i);
703 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
704 success = proj;
705 } else if (fail == NULL) {
706 fail = proj;
707 } else {
708 success = fail = NULL;
709 }
710 }
711 if (success != NULL && fail != NULL && !region->has_phi()) {
712 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
713 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
714 Node* dom_cmp = dom_bool->in(1);
715 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
716 if (failtype != NULL) {
717 const TypeInt* type2 = filtered_int_type(phase, n, fail);
718 if (type2 != NULL) {
719 failtype = failtype->join(type2)->is_int();
720 } else {
721 failtype = NULL;
722 }
723 }
724
725 if (failtype != NULL &&
726 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
727 int bound = failtype->_hi - failtype->_lo + 1;
728 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
729 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
730 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
731 Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo)));
732 Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound)));
733 Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond));
734 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
735 phase->hash_delete(this);
736 set_req(1, newbool);
737 return this;
738 }
739 if (failtype->_lo > failtype->_hi) {
740 // previous if determines the result of this if so
741 // replace Bool with constant
742 phase->hash_delete(this);
743 set_req(1, phase->intcon(success->as_Proj()->_con));
744 return this;
745 }
746 }
747 }
748 }
749 }
750 }
751 return NULL;
752 }
753
754 //------------------------------remove_useless_bool----------------------------
755 // Check for people making a useless boolean: things like
756 // if( (x < y ? true : false) ) { ... }
757 // Replace with if( x < y ) { ... }
758 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
759 Node *i1 = iff->in(1);
760 if( !i1->is_Bool() ) return NULL;
761 BoolNode *bol = i1->as_Bool();
762
763 Node *cmp = bol->in(1);
764 if( cmp->Opcode() != Op_CmpI ) return NULL;
765
766 // Must be comparing against a bool
767 const Type *cmp2_t = phase->type( cmp->in(2) );
768 if( cmp2_t != TypeInt::ZERO &&
769 cmp2_t != TypeInt::ONE )
770 return NULL;
771
772 // Find a prior merge point merging the boolean
773 i1 = cmp->in(1);
774 if( !i1->is_Phi() ) return NULL;
775 PhiNode *phi = i1->as_Phi();
776 if( phase->type( phi ) != TypeInt::BOOL )
777 return NULL;
778
779 // Check for diamond pattern
780 int true_path = phi->is_diamond_phi();
781 if( true_path == 0 ) return NULL;
782
783 // Make sure that iff and the control of the phi are different. This
784 // should really only happen for dead control flow since it requires
785 // an illegal cycle.
786 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
787
788 // phi->region->if_proj->ifnode->bool->cmp
789 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
790
791 // Now get the 'sense' of the test correct so we can plug in
792 // either iff2->in(1) or its complement.
793 int flip = 0;
794 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
795 else if( bol->_test._test != BoolTest::eq ) return NULL;
796 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
797
798 const Type *phi1_t = phase->type( phi->in(1) );
799 const Type *phi2_t = phase->type( phi->in(2) );
800 // Check for Phi(0,1) and flip
801 if( phi1_t == TypeInt::ZERO ) {
802 if( phi2_t != TypeInt::ONE ) return NULL;
803 flip = 1-flip;
804 } else {
805 // Check for Phi(1,0)
806 if( phi1_t != TypeInt::ONE ) return NULL;
807 if( phi2_t != TypeInt::ZERO ) return NULL;
808 }
809 if( true_path == 2 ) {
810 flip = 1-flip;
811 }
812
813 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
814 assert(new_bol != iff->in(1), "must make progress");
815 iff->set_req(1, new_bol);
816 // Intervening diamond probably goes dead
817 phase->C->set_major_progress();
818 return iff;
819 }
820
821 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
822
823 //------------------------------Ideal------------------------------------------
824 // Return a node which is more "ideal" than the current node. Strip out
825 // control copies
826 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
827 if (remove_dead_region(phase, can_reshape)) return this;
828 // No Def-Use info?
829 if (!can_reshape) return NULL;
830 PhaseIterGVN *igvn = phase->is_IterGVN();
831
832 // Don't bother trying to transform a dead if
833 if (in(0)->is_top()) return NULL;
834 // Don't bother trying to transform an if with a dead test
835 if (in(1)->is_top()) return NULL;
836 // Another variation of a dead test
837 if (in(1)->is_Con()) return NULL;
838 // Another variation of a dead if
839 if (outcnt() < 2) return NULL;
840
841 // Canonicalize the test.
842 Node* idt_if = idealize_test(phase, this);
843 if (idt_if != NULL) return idt_if;
844
845 // Try to split the IF
846 Node *s = split_if(this, igvn);
847 if (s != NULL) return s;
848
849 // Check for people making a useless boolean: things like
850 // if( (x < y ? true : false) ) { ... }
851 // Replace with if( x < y ) { ... }
852 Node *bol2 = remove_useless_bool(this, phase);
853 if( bol2 ) return bol2;
854
855 // Setup to scan up the CFG looking for a dominating test
856 Node *dom = in(0);
857 Node *prev_dom = this;
858
859 // Check for range-check vs other kinds of tests
860 Node *index1, *range1;
861 jint offset1;
862 int flip1 = is_range_check(range1, index1, offset1);
863 if( flip1 ) {
864 Node *first_prev_dom = NULL;
865
866 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
867 // so all checks we inspect post-dominate the top-most check we find.
868 // If we are going to fail the current check and we reach the top check
869 // then we are guaranteed to fail, so just start interpreting there.
870 // We 'expand' the top 2 range checks to include all post-dominating
871 // checks.
872
873 // The top 2 range checks seen
874 Node *prev_chk1 = NULL;
875 Node *prev_chk2 = NULL;
876 // Low and high offsets seen so far
877 jint off_lo = offset1;
878 jint off_hi = offset1;
879
880 // Scan for the top 2 checks and collect range of offsets
881 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
882 if( dom->Opcode() == Op_If && // Not same opcode?
883 prev_dom->in(0) == dom ) { // One path of test does dominate?
884 if( dom == this ) return NULL; // dead loop
885 // See if this is a range check
886 Node *index2, *range2;
887 jint offset2;
888 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
889 // See if this is a _matching_ range check, checking against
890 // the same array bounds.
891 if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
892 dom->outcnt() == 2 ) {
893 // Gather expanded bounds
894 off_lo = MIN2(off_lo,offset2);
895 off_hi = MAX2(off_hi,offset2);
896 // Record top 2 range checks
897 prev_chk2 = prev_chk1;
898 prev_chk1 = prev_dom;
899 // If we match the test exactly, then the top test covers
900 // both our lower and upper bounds.
901 if( dom->in(1) == in(1) )
902 prev_chk2 = prev_chk1;
903 }
904 }
905 prev_dom = dom;
906 dom = up_one_dom( dom );
907 if( !dom ) break;
908 }
909
910
911 // Attempt to widen the dominating range check to cover some later
912 // ones. Since range checks "fail" by uncommon-trapping to the
913 // interpreter, widening a check can make us speculative enter the
914 // interpreter. If we see range-check deopt's, do not widen!
915 if (!phase->C->allow_range_check_smearing()) return NULL;
916
917 // Constant indices only need to check the upper bound.
918 // Non-constance indices must check both low and high.
919 if( index1 ) {
920 // Didn't find 2 prior covering checks, so cannot remove anything.
921 if( !prev_chk2 ) return NULL;
922 // 'Widen' the offsets of the 1st and 2nd covering check
923 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
924 // Do not call adjust_check twice on the same projection
925 // as the first call may have transformed the BoolNode to a ConI
926 if( prev_chk1 != prev_chk2 ) {
927 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
928 }
929 // Test is now covered by prior checks, dominate it out
930 prev_dom = prev_chk2;
931 } else {
932 // Didn't find prior covering check, so cannot remove anything.
933 if( !prev_chk1 ) return NULL;
934 // 'Widen' the offset of the 1st and only covering check
935 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
936 // Test is now covered by prior checks, dominate it out
937 prev_dom = prev_chk1;
938 }
939
940
941 } else { // Scan for an equivalent test
942
943 Node *cmp;
944 int dist = 0; // Cutoff limit for search
945 int op = Opcode();
946 if( op == Op_If &&
947 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
948 if( cmp->in(2) != NULL && // make sure cmp is not already dead
949 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
950 dist = 64; // Limit for null-pointer scans
951 } else {
952 dist = 4; // Do not bother for random pointer tests
953 }
954 } else {
955 dist = 4; // Limit for random junky scans
956 }
957
958 // Normal equivalent-test check.
959 if( !dom ) return NULL; // Dead loop?
960
961 Node* result = fold_compares(phase);
962 if (result != NULL) {
963 return result;
964 }
965
966 // Search up the dominator tree for an If with an identical test
967 while( dom->Opcode() != op || // Not same opcode?
968 dom->in(1) != in(1) || // Not same input 1?
969 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
970 prev_dom->in(0) != dom ) { // One path of test does not dominate?
971 if( dist < 0 ) return NULL;
972
973 dist--;
974 prev_dom = dom;
975 dom = up_one_dom( dom );
976 if( !dom ) return NULL;
977 }
978
979 // Check that we did not follow a loop back to ourselves
980 if( this == dom )
981 return NULL;
982
983 if( dist > 2 ) // Add to count of NULL checks elided
984 explicit_null_checks_elided++;
985
986 } // End of Else scan for an equivalent test
987
988 // Hit! Remove this IF
989 #ifndef PRODUCT
990 if( TraceIterativeGVN ) {
991 tty->print(" Removing IfNode: "); this->dump();
992 }
993 if( VerifyOpto && !phase->allow_progress() ) {
994 // Found an equivalent dominating test,
995 // we can not guarantee reaching a fix-point for these during iterativeGVN
996 // since intervening nodes may not change.
997 return NULL;
998 }
999 #endif
1000
1001 // Replace dominated IfNode
1002 dominated_by( prev_dom, igvn );
1003
1004 // Must return either the original node (now dead) or a new node
1005 // (Do not return a top here, since that would break the uniqueness of top.)
1006 return new (phase->C) ConINode(TypeInt::ZERO);
1007 }
1008
1009 //------------------------------dominated_by-----------------------------------
1010 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1011 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1012 Node *idom = in(0);
1013 // Need opcode to decide which way 'this' test goes
1014 int prev_op = prev_dom->Opcode();
1015 Node *top = igvn->C->top(); // Shortcut to top
1016
1017 // Loop predicates may have depending checks which should not
1018 // be skipped. For example, range check predicate has two checks
1019 // for lower and upper bounds.
1020 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1021 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))
1022 prev_dom = idom;
1023
1024 // Now walk the current IfNode's projections.
1025 // Loop ends when 'this' has no more uses.
1026 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1027 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1028 igvn->add_users_to_worklist(ifp);
1029 // Check which projection it is and set target.
1030 // Data-target is either the dominating projection of the same type
1031 // or TOP if the dominating projection is of opposite type.
1032 // Data-target will be used as the new control edge for the non-CFG
1033 // nodes like Casts and Loads.
1034 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1035 // Control-target is just the If's immediate dominator or TOP.
1036 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1037
1038 // For each child of an IfTrue/IfFalse projection, reroute.
1039 // Loop ends when projection has no more uses.
1040 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1041 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1042 if( !s->depends_only_on_test() ) {
1043 // Find the control input matching this def-use edge.
1044 // For Regions it may not be in slot 0.
1045 uint l;
1046 for( l = 0; s->in(l) != ifp; l++ ) { }
1047 igvn->replace_input_of(s, l, ctrl_target);
1048 } else { // Else, for control producers,
1049 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1050 }
1051 } // End for each child of a projection
1052
1053 igvn->remove_dead_node(ifp);
1054 } // End for each IfTrue/IfFalse child of If
1055
1056 // Kill the IfNode
1057 igvn->remove_dead_node(this);
1058 }
1059
1060 //------------------------------Identity---------------------------------------
1061 // If the test is constant & we match, then we are the input Control
1062 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1063 // Can only optimize if cannot go the other way
1064 const TypeTuple *t = phase->type(in(0))->is_tuple();
1065 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1066 ? in(0)->in(0) // IfNode control
1067 : this; // no progress
1068 }
1069
1070 //------------------------------dump_spec--------------------------------------
1071 #ifndef PRODUCT
1072 void IfNode::dump_spec(outputStream *st) const {
1073 st->print("P=%f, C=%f",_prob,_fcnt);
1074 }
1075 #endif
1076
1077 //------------------------------idealize_test----------------------------------
1078 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1079 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1080 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1081 // needed.
1082 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1083 assert(iff->in(0) != NULL, "If must be live");
1084
1085 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1086 Node* old_if_f = iff->proj_out(false);
1087 Node* old_if_t = iff->proj_out(true);
1088
1089 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1090 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1091 // happens in count-down loops
1092 if (iff->is_CountedLoopEnd()) return NULL;
1093 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1094 BoolNode *b = iff->in(1)->as_Bool();
1095 BoolTest bt = b->_test;
1096 // Test already in good order?
1097 if( bt.is_canonical() )
1098 return NULL;
1099
1100 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1101 // cloning the IfNode.
1102 Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) );
1103 if( !new_b->is_Bool() ) return NULL;
1104 b = new_b->as_Bool();
1105
1106 PhaseIterGVN *igvn = phase->is_IterGVN();
1107 assert( igvn, "Test is not canonical in parser?" );
1108
1109 // The IF node never really changes, but it needs to be cloned
1110 iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1111
1112 Node *prior = igvn->hash_find_insert(iff);
1113 if( prior ) {
1114 igvn->remove_dead_node(iff);
1115 iff = (IfNode*)prior;
1116 } else {
1117 // Cannot call transform on it just yet
1118 igvn->set_type_bottom(iff);
1119 }
1120 igvn->_worklist.push(iff);
1121
1122 // Now handle projections. Cloning not required.
1123 Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff ));
1124 Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff ));
1125
1126 igvn->register_new_node_with_optimizer(new_if_f);
1127 igvn->register_new_node_with_optimizer(new_if_t);
1128 // Flip test, so flip trailing control
1129 igvn->replace_node(old_if_f, new_if_t);
1130 igvn->replace_node(old_if_t, new_if_f);
1131
1132 // Progress
1133 return iff;
1134 }
1135
1136 //------------------------------Identity---------------------------------------
1137 // If the test is constant & we match, then we are the input Control
1138 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1139 // Can only optimize if cannot go the other way
1140 const TypeTuple *t = phase->type(in(0))->is_tuple();
1141 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1142 ? in(0)->in(0) // IfNode control
1143 : this; // no progress
1144 }

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