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 // If the cast is derived from data flow edges, it may not have a control.
151 // If so, it should be save to split. But follow-up code can not deal with
152 // this (l. 359). So skip.
153 if (v->in(0) == NULL) {
154 return NULL;
155 }
156 if (v->in(0)->in(0) == iff) {
157 continue; // CastPP/II of the IfNode is OK
158 }
159 }
160 // Disabled following code because I cannot tell if exactly one
161 // path dominates without a real dominator check. CNC 9/9/1999
162 //uint vop = v->Opcode();
163 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
164 // Node *r = v->in(0); // Get controlling point
165 // if( !r ) return NULL; // Degraded to a copy
166 // // Find exactly one path in (either True or False doms, but not IFF)
167 // int cnt = 0;
168 // for( uint i = 1; i < r->req(); i++ )
169 // if( r->in(i) && r->in(i)->in(0) == iff )
170 // cnt++;
171 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
172 //}
173 if( !v->is_Call() ) {
174 /*
175 if( v->Opcode() == Op_AddP ) {
176 tty->print_cr("Phi has AddP use");
177 } else if( v->Opcode() == Op_CastPP ) {
178 tty->print_cr("Phi has CastPP use");
179 } else if( v->Opcode() == Op_CastII ) {
180 tty->print_cr("Phi has CastII use");
181 } else {
182 tty->print_cr("Phi has use I cant be bothered with");
183 }
184 */
185 }
186 return NULL;
187
188 /* CNC - Cut out all the fancy acceptance tests
189 // Can we clone this use when doing the transformation?
190 // If all uses are from Phis at this merge or constants, then YES.
191 if( !v->in(0) && v != cmp ) {
192 tty->print_cr("Phi has free-floating use");
193 v->dump(2);
194 return NULL;
195 }
196 for( uint l = 1; l < v->req(); l++ ) {
197 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
198 !v->in(l)->is_Con() ) {
199 tty->print_cr("Phi has use");
200 v->dump(2);
201 return NULL;
202 } // End of if Phi-use input is neither Phi nor Constant
203 } // End of for all inputs to Phi-use
204 */
205 } // End of for all uses of Phi
206 } // End of for all uses of Region
207
208 // Only do this if the IF node is in a sane state
209 if (iff->outcnt() != 2)
210 return NULL;
211
212 // Got a hit! Do the Mondo Hack!
213 //
214 //ABC a1c def ghi B 1 e h A C a c d f g i
215 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
216 // cmp - 2 cmp - 2 cmp - 2
217 // bool bool_c bool_x
218 // if if_c if_x
219 // T F T F T F
220 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
221 //
222 // Split the paths coming into the merge point into 2 separate groups of
223 // merges. On the left will be all the paths feeding constants into the
224 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
225 // will fold up into a constant; this will let the Cmp fold up as well as
226 // all the control flow. Below the original IF we have 2 control
227 // dependent regions, 's' and 't'. Now we will merge the two paths
228 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
229 // likely 2 or more) will promptly constant fold away.
230 PhaseGVN *phase = igvn;
231
232 // Make a region merging constants and a region merging the rest
233 uint req_c = 0;
234 Node* predicate_proj = NULL;
235 for (uint ii = 1; ii < r->req(); ii++) {
236 if (phi->in(ii) == con1) {
237 req_c++;
238 }
239 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
240 if (proj != NULL) {
241 assert(predicate_proj == NULL, "only one predicate entry expected");
242 predicate_proj = proj;
243 }
244 }
245 Node* predicate_c = NULL;
246 Node* predicate_x = NULL;
247 bool counted_loop = r->is_CountedLoop();
248
249 Node *region_c = new RegionNode(req_c + 1);
250 Node *phi_c = con1;
251 uint len = r->req();
252 Node *region_x = new RegionNode(len - req_c);
253 Node *phi_x = PhiNode::make_blank(region_x, phi);
254 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
255 if (phi->in(i) == con1) {
256 region_c->init_req( i_c++, r ->in(i) );
257 if (r->in(i) == predicate_proj)
258 predicate_c = predicate_proj;
259 } else {
260 region_x->init_req( i_x, r ->in(i) );
261 phi_x ->init_req( i_x++, phi->in(i) );
262 if (r->in(i) == predicate_proj)
263 predicate_x = predicate_proj;
264 }
265 }
266 if (predicate_c != NULL && (req_c > 1)) {
267 assert(predicate_x == NULL, "only one predicate entry expected");
268 predicate_c = NULL; // Do not clone predicate below merge point
269 }
270 if (predicate_x != NULL && ((len - req_c) > 2)) {
271 assert(predicate_c == NULL, "only one predicate entry expected");
272 predicate_x = NULL; // Do not clone predicate below merge point
273 }
274
275 // Register the new RegionNodes but do not transform them. Cannot
276 // transform until the entire Region/Phi conglomerate has been hacked
277 // as a single huge transform.
278 igvn->register_new_node_with_optimizer( region_c );
279 igvn->register_new_node_with_optimizer( region_x );
280 // Prevent the untimely death of phi_x. Currently he has no uses. He is
281 // about to get one. If this only use goes away, then phi_x will look dead.
282 // However, he will be picking up some more uses down below.
283 Node *hook = new Node(4);
284 hook->init_req(0, phi_x);
285 hook->init_req(1, phi_c);
286 phi_x = phase->transform( phi_x );
287
288 // Make the compare
289 Node *cmp_c = phase->makecon(t);
290 Node *cmp_x = cmp->clone();
291 cmp_x->set_req(1,phi_x);
292 cmp_x->set_req(2,con2);
293 cmp_x = phase->transform(cmp_x);
294 // Make the bool
295 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
296 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
297 // Make the IfNode
298 IfNode *iff_c = new IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
299 igvn->set_type_bottom(iff_c);
300 igvn->_worklist.push(iff_c);
301 hook->init_req(2, iff_c);
302
303 IfNode *iff_x = new IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
304 igvn->set_type_bottom(iff_x);
305 igvn->_worklist.push(iff_x);
306 hook->init_req(3, iff_x);
307
308 // Make the true/false arms
309 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
310 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
311 if (predicate_c != NULL) {
312 assert(predicate_x == NULL, "only one predicate entry expected");
313 // Clone loop predicates to each path
314 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
315 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
316 }
317 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
318 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
319 if (predicate_x != NULL) {
320 assert(predicate_c == NULL, "only one predicate entry expected");
321 // Clone loop predicates to each path
322 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
323 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
324 }
325
326 // Merge the TRUE paths
327 Node *region_s = new RegionNode(3);
328 igvn->_worklist.push(region_s);
329 region_s->init_req(1, iff_c_t);
330 region_s->init_req(2, iff_x_t);
331 igvn->register_new_node_with_optimizer( region_s );
332
333 // Merge the FALSE paths
334 Node *region_f = new RegionNode(3);
335 igvn->_worklist.push(region_f);
336 region_f->init_req(1, iff_c_f);
337 region_f->init_req(2, iff_x_f);
338 igvn->register_new_node_with_optimizer( region_f );
339
340 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
341 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
342 cmp->set_req(2,NULL);
343 // Check for all uses of the Phi and give them a new home.
344 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
345 Node *phi_s = NULL; // do not construct unless needed
346 Node *phi_f = NULL; // do not construct unless needed
347 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
348 Node* v = phi->last_out(i2);// User of the phi
349 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
350 uint vop = v->Opcode();
351 Node *proj = NULL;
352 if( vop == Op_Phi ) { // Remote merge point
353 Node *r = v->in(0);
354 for (uint i3 = 1; i3 < r->req(); i3++)
355 if (r->in(i3) && r->in(i3)->in(0) == iff) {
356 proj = r->in(i3);
357 break;
358 }
359 } else if( v->is_ConstraintCast() ) {
360 proj = v->in(0); // Controlling projection
361 } else {
362 assert( 0, "do not know how to handle this guy" );
363 }
364
365 Node *proj_path_data, *proj_path_ctrl;
366 if( proj->Opcode() == Op_IfTrue ) {
367 if( phi_s == NULL ) {
368 // Only construct phi_s if needed, otherwise provides
369 // interfering use.
370 phi_s = PhiNode::make_blank(region_s,phi);
371 phi_s->init_req( 1, phi_c );
372 phi_s->init_req( 2, phi_x );
373 hook->add_req(phi_s);
374 phi_s = phase->transform(phi_s);
375 }
376 proj_path_data = phi_s;
377 proj_path_ctrl = region_s;
378 } else {
379 if( phi_f == NULL ) {
380 // Only construct phi_f if needed, otherwise provides
381 // interfering use.
382 phi_f = PhiNode::make_blank(region_f,phi);
383 phi_f->init_req( 1, phi_c );
384 phi_f->init_req( 2, phi_x );
385 hook->add_req(phi_f);
386 phi_f = phase->transform(phi_f);
387 }
388 proj_path_data = phi_f;
389 proj_path_ctrl = region_f;
390 }
391
392 // Fixup 'v' for for the split
393 if( vop == Op_Phi ) { // Remote merge point
394 uint i;
395 for( i = 1; i < v->req(); i++ )
396 if( v->in(i) == phi )
397 break;
398 v->set_req(i, proj_path_data );
399 } else if( v->is_ConstraintCast() ) {
400 v->set_req(0, proj_path_ctrl );
401 v->set_req(1, proj_path_data );
402 } else
403 ShouldNotReachHere();
404 }
405
406 // Now replace the original iff's True/False with region_s/region_t.
407 // This makes the original iff go dead.
408 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
409 Node* p = iff->last_out(i3);
410 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
411 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
412 // Replace p with u
413 igvn->add_users_to_worklist(p);
414 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
415 Node* x = p->last_out(l);
416 igvn->hash_delete(x);
417 uint uses_found = 0;
418 for( uint j = 0; j < x->req(); j++ ) {
419 if( x->in(j) == p ) {
420 x->set_req(j, u);
421 uses_found++;
422 }
423 }
424 l -= uses_found; // we deleted 1 or more copies of this edge
425 }
426 igvn->remove_dead_node(p);
427 }
428
429 // Force the original merge dead
430 igvn->hash_delete(r);
431 // First, remove region's dead users.
432 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
433 Node* u = r->last_out(l);
434 if( u == r ) {
435 r->set_req(0, NULL);
436 } else {
437 assert(u->outcnt() == 0, "only dead users");
438 igvn->remove_dead_node(u);
439 }
440 l -= 1;
441 }
442 igvn->remove_dead_node(r);
443
444 // Now remove the bogus extra edges used to keep things alive
445 igvn->remove_dead_node( hook );
446
447 // Must return either the original node (now dead) or a new node
448 // (Do not return a top here, since that would break the uniqueness of top.)
449 return new ConINode(TypeInt::ZERO);
450 }
451
452 //------------------------------is_range_check---------------------------------
453 // Return 0 if not a range check. Return 1 if a range check and set index and
454 // offset. Return 2 if we had to negate the test. Index is NULL if the check
455 // is versus a constant.
456 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
457 Node* b = in(1);
458 if (b == NULL || !b->is_Bool()) return 0;
459 BoolNode* bn = b->as_Bool();
460 Node* cmp = bn->in(1);
461 if (cmp == NULL) return 0;
462 if (cmp->Opcode() != Op_CmpU) return 0;
463
464 Node* l = cmp->in(1);
465 Node* r = cmp->in(2);
466 int flip_test = 1;
467 if (bn->_test._test == BoolTest::le) {
468 l = cmp->in(2);
469 r = cmp->in(1);
470 flip_test = 2;
471 } else if (bn->_test._test != BoolTest::lt) {
472 return 0;
473 }
474 if (l->is_top()) return 0; // Top input means dead test
475 if (r->Opcode() != Op_LoadRange) return 0;
476
477 // We have recognized one of these forms:
478 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
479 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
480
481 // Make sure it's a real range check by requiring an uncommon trap
482 // along the OOB path. Otherwise, it's possible that the user wrote
483 // something which optimized to look like a range check but behaves
484 // in some other way.
485 Node* iftrap = proj_out(flip_test == 2 ? true : false);
486 bool found_trap = false;
487 if (iftrap != NULL) {
488 Node* u = iftrap->unique_ctrl_out();
489 if (u != NULL) {
490 // It could be a merge point (Region) for uncommon trap.
491 if (u->is_Region()) {
492 Node* c = u->unique_ctrl_out();
493 if (c != NULL) {
494 iftrap = u;
495 u = c;
496 }
497 }
498 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
499 int req = u->as_CallStaticJava()->uncommon_trap_request();
500 if (Deoptimization::trap_request_reason(req) ==
501 Deoptimization::Reason_range_check) {
502 found_trap = true;
503 }
504 }
505 }
506 }
507 if (!found_trap) return 0; // sorry, no cigar
508
509 // Look for index+offset form
510 Node* ind = l;
511 jint off = 0;
512 if (l->is_top()) {
513 return 0;
514 } else if (l->Opcode() == Op_AddI) {
515 if ((off = l->in(1)->find_int_con(0)) != 0) {
516 ind = l->in(2);
517 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
518 ind = l->in(1);
519 }
520 } else if ((off = l->find_int_con(-1)) >= 0) {
521 // constant offset with no variable index
522 ind = NULL;
523 } else {
524 // variable index with no constant offset (or dead negative index)
525 off = 0;
526 }
527
528 // Return all the values:
529 index = ind;
530 offset = off;
531 range = r;
532 return flip_test;
533 }
534
535 //------------------------------adjust_check-----------------------------------
536 // Adjust (widen) a prior range check
537 static void adjust_check(Node* proj, Node* range, Node* index,
538 int flip, jint off_lo, PhaseIterGVN* igvn) {
539 PhaseGVN *gvn = igvn;
540 // Break apart the old check
541 Node *iff = proj->in(0);
542 Node *bol = iff->in(1);
543 if( bol->is_top() ) return; // In case a partially dead range check appears
544 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
545 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
546 if( !bol->is_Bool() ) return;
547
548 Node *cmp = bol->in(1);
549 // Compute a new check
550 Node *new_add = gvn->intcon(off_lo);
551 if( index ) {
552 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
553 }
554 Node *new_cmp = (flip == 1)
555 ? new CmpUNode( new_add, range )
556 : new CmpUNode( range, new_add );
557 new_cmp = gvn->transform(new_cmp);
558 // See if no need to adjust the existing check
559 if( new_cmp == cmp ) return;
560 // Else, adjust existing check
561 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
562 igvn->rehash_node_delayed( iff );
563 iff->set_req_X( 1, new_bol, igvn );
564 }
565
566 //------------------------------up_one_dom-------------------------------------
567 // Walk up the dominator tree one step. Return NULL at root or true
568 // complex merges. Skips through small diamonds.
569 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
570 Node *dom = curr->in(0);
571 if( !dom ) // Found a Region degraded to a copy?
572 return curr->nonnull_req(); // Skip thru it
573
574 if( curr != dom ) // Normal walk up one step?
575 return dom;
576
577 // Use linear_only if we are still parsing, since we cannot
578 // trust the regions to be fully filled in.
579 if (linear_only)
580 return NULL;
581
582 if( dom->is_Root() )
583 return NULL;
584
585 // Else hit a Region. Check for a loop header
586 if( dom->is_Loop() )
587 return dom->in(1); // Skip up thru loops
588
589 // Check for small diamonds
590 Node *din1, *din2, *din3, *din4;
591 if( dom->req() == 3 && // 2-path merge point
592 (din1 = dom ->in(1)) && // Left path exists
593 (din2 = dom ->in(2)) && // Right path exists
594 (din3 = din1->in(0)) && // Left path up one
595 (din4 = din2->in(0)) ) { // Right path up one
596 if( din3->is_Call() && // Handle a slow-path call on either arm
597 (din3 = din3->in(0)) )
598 din3 = din3->in(0);
599 if( din4->is_Call() && // Handle a slow-path call on either arm
600 (din4 = din4->in(0)) )
601 din4 = din4->in(0);
602 if( din3 == din4 && din3->is_If() )
603 return din3; // Skip around diamonds
604 }
605
606 // Give up the search at true merges
607 return NULL; // Dead loop? Or hit root?
608 }
609
610
611 //------------------------------filtered_int_type--------------------------------
612 // Return a possibly more restrictive type for val based on condition control flow for an if
613 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
614 assert(if_proj &&
615 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
616 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
617 IfNode* iff = if_proj->in(0)->as_If();
618 if (iff->in(1) && iff->in(1)->is_Bool()) {
619 BoolNode* bol = iff->in(1)->as_Bool();
620 if (bol->in(1) && bol->in(1)->is_Cmp()) {
621 const CmpNode* cmp = bol->in(1)->as_Cmp();
622 if (cmp->in(1) == val) {
623 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
624 if (cmp2_t != NULL) {
625 jint lo = cmp2_t->_lo;
626 jint hi = cmp2_t->_hi;
627 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
628 switch (msk) {
629 case BoolTest::ne:
630 // Can't refine type
631 return NULL;
632 case BoolTest::eq:
633 return cmp2_t;
634 case BoolTest::lt:
635 lo = TypeInt::INT->_lo;
636 if (hi - 1 < hi) {
637 hi = hi - 1;
638 }
639 break;
640 case BoolTest::le:
641 lo = TypeInt::INT->_lo;
642 break;
643 case BoolTest::gt:
644 if (lo + 1 > lo) {
645 lo = lo + 1;
646 }
647 hi = TypeInt::INT->_hi;
648 break;
649 case BoolTest::ge:
650 // lo unchanged
651 hi = TypeInt::INT->_hi;
652 break;
653 }
654 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
655 return rtn_t;
656 }
657 }
658 }
659 }
660 }
661 return NULL;
662 }
663
664 //------------------------------fold_compares----------------------------
665 // See if a pair of CmpIs can be converted into a CmpU. In some cases
666 // the direction of this if is determined by the preceding if so it
667 // can be eliminate entirely. Given an if testing (CmpI n c) check
668 // for an immediately control dependent if that is testing (CmpI n c2)
669 // and has one projection leading to this if and the other projection
670 // leading to a region that merges one of this ifs control
671 // projections.
672 //
673 // If
674 // / |
675 // / |
676 // / |
677 // If |
678 // /\ |
679 // / \ |
680 // / \ |
681 // / Region
682 //
683 Node* IfNode::fold_compares(PhaseGVN* phase) {
684 if (Opcode() != Op_If) return NULL;
685
686 Node* this_cmp = in(1)->in(1);
687 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
688 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
689 Node* ctrl = in(0);
690 BoolNode* this_bool = in(1)->as_Bool();
691 Node* n = this_cmp->in(1);
692 int hi = this_cmp->in(2)->get_int();
693 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
694 ctrl->in(0)->is_If() &&
695 ctrl->in(0)->outcnt() == 2 &&
696 ctrl->in(0)->in(1)->is_Bool() &&
697 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
698 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
699 ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
700 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
701 IfNode* dom_iff = ctrl->in(0)->as_If();
702 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
703 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
704 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
705 // Identify which proj goes to the region and which continues on
706 RegionNode* region = otherproj->unique_out()->as_Region();
707 Node* success = NULL;
708 Node* fail = NULL;
709 for (int i = 0; i < 2; i++) {
710 Node* proj = proj_out(i);
711 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
712 success = proj;
713 } else if (fail == NULL) {
714 fail = proj;
715 } else {
716 success = fail = NULL;
717 }
718 }
719 if (success != NULL && fail != NULL && !region->has_phi()) {
720 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
721 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
722 Node* dom_cmp = dom_bool->in(1);
723 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
724 if (failtype != NULL) {
725 const TypeInt* type2 = filtered_int_type(phase, n, fail);
726 if (type2 != NULL) {
727 failtype = failtype->join(type2)->is_int();
728 } else {
729 failtype = NULL;
730 }
731 }
732
733 if (failtype != NULL &&
734 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
735 int bound = failtype->_hi - failtype->_lo + 1;
736 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
737 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
738 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
739 Node* adjusted = phase->transform(new SubINode(n, phase->intcon(failtype->_lo)));
740 Node* newcmp = phase->transform(new CmpUNode(adjusted, phase->intcon(bound)));
741 Node* newbool = phase->transform(new BoolNode(newcmp, cond));
742 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
743 phase->hash_delete(this);
744 set_req(1, newbool);
745 return this;
746 }
747 if (failtype->_lo > failtype->_hi) {
748 // previous if determines the result of this if so
749 // replace Bool with constant
750 phase->hash_delete(this);
751 set_req(1, phase->intcon(success->as_Proj()->_con));
752 return this;
753 }
754 }
755 }
756 }
757 }
758 }
759 return NULL;
760 }
761
762 //------------------------------remove_useless_bool----------------------------
763 // Check for people making a useless boolean: things like
764 // if( (x < y ? true : false) ) { ... }
765 // Replace with if( x < y ) { ... }
766 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
767 Node *i1 = iff->in(1);
768 if( !i1->is_Bool() ) return NULL;
769 BoolNode *bol = i1->as_Bool();
770
771 Node *cmp = bol->in(1);
772 if( cmp->Opcode() != Op_CmpI ) return NULL;
773
774 // Must be comparing against a bool
775 const Type *cmp2_t = phase->type( cmp->in(2) );
776 if( cmp2_t != TypeInt::ZERO &&
777 cmp2_t != TypeInt::ONE )
778 return NULL;
779
780 // Find a prior merge point merging the boolean
781 i1 = cmp->in(1);
782 if( !i1->is_Phi() ) return NULL;
783 PhiNode *phi = i1->as_Phi();
784 if( phase->type( phi ) != TypeInt::BOOL )
785 return NULL;
786
787 // Check for diamond pattern
788 int true_path = phi->is_diamond_phi();
789 if( true_path == 0 ) return NULL;
790
791 // Make sure that iff and the control of the phi are different. This
792 // should really only happen for dead control flow since it requires
793 // an illegal cycle.
794 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
795
796 // phi->region->if_proj->ifnode->bool->cmp
797 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
798
799 // Now get the 'sense' of the test correct so we can plug in
800 // either iff2->in(1) or its complement.
801 int flip = 0;
802 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
803 else if( bol->_test._test != BoolTest::eq ) return NULL;
804 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
805
806 const Type *phi1_t = phase->type( phi->in(1) );
807 const Type *phi2_t = phase->type( phi->in(2) );
808 // Check for Phi(0,1) and flip
809 if( phi1_t == TypeInt::ZERO ) {
810 if( phi2_t != TypeInt::ONE ) return NULL;
811 flip = 1-flip;
812 } else {
813 // Check for Phi(1,0)
814 if( phi1_t != TypeInt::ONE ) return NULL;
815 if( phi2_t != TypeInt::ZERO ) return NULL;
816 }
817 if( true_path == 2 ) {
818 flip = 1-flip;
819 }
820
821 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
822 assert(new_bol != iff->in(1), "must make progress");
823 iff->set_req(1, new_bol);
824 // Intervening diamond probably goes dead
825 phase->C->set_major_progress();
826 return iff;
827 }
828
829 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
830
831 struct RangeCheck {
832 Node* ctl;
833 jint off;
834 };
835
836 //------------------------------Ideal------------------------------------------
837 // Return a node which is more "ideal" than the current node. Strip out
838 // control copies
839 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
840 if (remove_dead_region(phase, can_reshape)) return this;
841 // No Def-Use info?
842 if (!can_reshape) return NULL;
843 PhaseIterGVN *igvn = phase->is_IterGVN();
844
845 // Don't bother trying to transform a dead if
846 if (in(0)->is_top()) return NULL;
847 // Don't bother trying to transform an if with a dead test
848 if (in(1)->is_top()) return NULL;
849 // Another variation of a dead test
850 if (in(1)->is_Con()) return NULL;
851 // Another variation of a dead if
852 if (outcnt() < 2) return NULL;
853
854 // Canonicalize the test.
855 Node* idt_if = idealize_test(phase, this);
856 if (idt_if != NULL) return idt_if;
857
858 // Try to split the IF
859 Node *s = split_if(this, igvn);
860 if (s != NULL) return s;
861
862 // Check for people making a useless boolean: things like
863 // if( (x < y ? true : false) ) { ... }
864 // Replace with if( x < y ) { ... }
865 Node *bol2 = remove_useless_bool(this, phase);
866 if( bol2 ) return bol2;
867
868 // Setup to scan up the CFG looking for a dominating test
869 Node *dom = in(0);
870 Node *prev_dom = this;
871
872 // Check for range-check vs other kinds of tests
873 Node *index1, *range1;
874 jint offset1;
875 int flip1 = is_range_check(range1, index1, offset1);
876 if( flip1 ) {
877 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
878 // so all checks we inspect post-dominate the top-most check we find.
879 // If we are going to fail the current check and we reach the top check
880 // then we are guaranteed to fail, so just start interpreting there.
881 // We 'expand' the top 3 range checks to include all post-dominating
882 // checks.
883
884 // The top 3 range checks seen
885 const int NRC =3;
886 RangeCheck prev_checks[NRC];
887 int nb_checks = 0;
888
889 // Low and high offsets seen so far
890 jint off_lo = offset1;
891 jint off_hi = offset1;
892
893 bool found_immediate_dominator = false;
894
895 // Scan for the top checks and collect range of offsets
896 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
897 if (dom->Opcode() == Op_If && // Not same opcode?
898 prev_dom->in(0) == dom) { // One path of test does dominate?
899 if (dom == this) return NULL; // dead loop
900 // See if this is a range check
901 Node *index2, *range2;
902 jint offset2;
903 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
904 // See if this is a _matching_ range check, checking against
905 // the same array bounds.
906 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
907 dom->outcnt() == 2) {
908 if (nb_checks == 0 && dom->in(1) == in(1)) {
909 // Found an immediately dominating test at the same offset.
910 // This kind of back-to-back test can be eliminated locally,
911 // and there is no need to search further for dominating tests.
912 assert(offset2 == offset1, "Same test but different offsets");
913 found_immediate_dominator = true;
914 break;
915 }
916 // Gather expanded bounds
917 off_lo = MIN2(off_lo,offset2);
918 off_hi = MAX2(off_hi,offset2);
919 // Record top NRC range checks
920 prev_checks[nb_checks%NRC].ctl = prev_dom;
921 prev_checks[nb_checks%NRC].off = offset2;
922 nb_checks++;
923 }
924 }
925 prev_dom = dom;
926 dom = up_one_dom(dom);
927 if (!dom) break;
928 }
929
930 if (!found_immediate_dominator) {
931 // Attempt to widen the dominating range check to cover some later
932 // ones. Since range checks "fail" by uncommon-trapping to the
933 // interpreter, widening a check can make us speculatively enter
934 // the interpreter. If we see range-check deopt's, do not widen!
935 if (!phase->C->allow_range_check_smearing()) return NULL;
936
937 // Didn't find prior covering check, so cannot remove anything.
938 if (nb_checks == 0) {
939 return NULL;
940 }
941 // Constant indices only need to check the upper bound.
942 // Non-constant indices must check both low and high.
943 int chk0 = (nb_checks - 1) % NRC;
944 if (index1) {
945 if (nb_checks == 1) {
946 return NULL;
947 } else {
948 // If the top range check's constant is the min or max of
949 // all constants we widen the next one to cover the whole
950 // range of constants.
951 RangeCheck rc0 = prev_checks[chk0];
952 int chk1 = (nb_checks - 2) % NRC;
953 RangeCheck rc1 = prev_checks[chk1];
954 if (rc0.off == off_lo) {
955 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
956 prev_dom = rc1.ctl;
957 } else if (rc0.off == off_hi) {
958 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
959 prev_dom = rc1.ctl;
960 } else {
961 // If the top test's constant is not the min or max of all
962 // constants, we need 3 range checks. We must leave the
963 // top test unchanged because widening it would allow the
964 // accesses it protects to successfully read/write out of
965 // bounds.
966 if (nb_checks == 2) {
967 return NULL;
968 }
969 int chk2 = (nb_checks - 3) % NRC;
970 RangeCheck rc2 = prev_checks[chk2];
971 // The top range check a+i covers interval: -a <= i < length-a
972 // The second range check b+i covers interval: -b <= i < length-b
973 if (rc1.off <= rc0.off) {
974 // if b <= a, we change the second range check to:
975 // -min_of_all_constants <= i < length-min_of_all_constants
976 // Together top and second range checks now cover:
977 // -min_of_all_constants <= i < length-a
978 // which is more restrictive than -b <= i < length-b:
979 // -b <= -min_of_all_constants <= i < length-a <= length-b
980 // The third check is then changed to:
981 // -max_of_all_constants <= i < length-max_of_all_constants
982 // so 2nd and 3rd checks restrict allowed values of i to:
983 // -min_of_all_constants <= i < length-max_of_all_constants
984 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
985 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
986 } else {
987 // if b > a, we change the second range check to:
988 // -max_of_all_constants <= i < length-max_of_all_constants
989 // Together top and second range checks now cover:
990 // -a <= i < length-max_of_all_constants
991 // which is more restrictive than -b <= i < length-b:
992 // -b < -a <= i < length-max_of_all_constants <= length-b
993 // The third check is then changed to:
994 // -max_of_all_constants <= i < length-max_of_all_constants
995 // so 2nd and 3rd checks restrict allowed values of i to:
996 // -min_of_all_constants <= i < length-max_of_all_constants
997 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
998 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
999 }
1000 prev_dom = rc2.ctl;
1001 }
1002 }
1003 } else {
1004 RangeCheck rc0 = prev_checks[chk0];
1005 // 'Widen' the offset of the 1st and only covering check
1006 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1007 // Test is now covered by prior checks, dominate it out
1008 prev_dom = rc0.ctl;
1009 }
1010 }
1011
1012 } else { // Scan for an equivalent test
1013
1014 Node *cmp;
1015 int dist = 0; // Cutoff limit for search
1016 int op = Opcode();
1017 if( op == Op_If &&
1018 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1019 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1020 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1021 dist = 64; // Limit for null-pointer scans
1022 } else {
1023 dist = 4; // Do not bother for random pointer tests
1024 }
1025 } else {
1026 dist = 4; // Limit for random junky scans
1027 }
1028
1029 // Normal equivalent-test check.
1030 if( !dom ) return NULL; // Dead loop?
1031
1032 Node* result = fold_compares(phase);
1033 if (result != NULL) {
1034 return result;
1035 }
1036
1037 // Search up the dominator tree for an If with an identical test
1038 while( dom->Opcode() != op || // Not same opcode?
1039 dom->in(1) != in(1) || // Not same input 1?
1040 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1041 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1042 if( dist < 0 ) return NULL;
1043
1044 dist--;
1045 prev_dom = dom;
1046 dom = up_one_dom( dom );
1047 if( !dom ) return NULL;
1048 }
1049
1050 // Check that we did not follow a loop back to ourselves
1051 if( this == dom )
1052 return NULL;
1053
1054 if( dist > 2 ) // Add to count of NULL checks elided
1055 explicit_null_checks_elided++;
1056
1057 } // End of Else scan for an equivalent test
1058
1059 // Hit! Remove this IF
1060 #ifndef PRODUCT
1061 if( TraceIterativeGVN ) {
1062 tty->print(" Removing IfNode: "); this->dump();
1063 }
1064 if( VerifyOpto && !phase->allow_progress() ) {
1065 // Found an equivalent dominating test,
1066 // we can not guarantee reaching a fix-point for these during iterativeGVN
1067 // since intervening nodes may not change.
1068 return NULL;
1069 }
1070 #endif
1071
1072 // Replace dominated IfNode
1073 dominated_by( prev_dom, igvn );
1074
1075 // Must return either the original node (now dead) or a new node
1076 // (Do not return a top here, since that would break the uniqueness of top.)
1077 return new ConINode(TypeInt::ZERO);
1078 }
1079
1080 //------------------------------dominated_by-----------------------------------
1081 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1082 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1083 Node *idom = in(0);
1084 // Need opcode to decide which way 'this' test goes
1085 int prev_op = prev_dom->Opcode();
1086 Node *top = igvn->C->top(); // Shortcut to top
1087
1088 // Loop predicates may have depending checks which should not
1089 // be skipped. For example, range check predicate has two checks
1090 // for lower and upper bounds.
1091 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1092 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))
1093 prev_dom = idom;
1094
1095 // Now walk the current IfNode's projections.
1096 // Loop ends when 'this' has no more uses.
1097 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1098 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1099 igvn->add_users_to_worklist(ifp);
1100 // Check which projection it is and set target.
1101 // Data-target is either the dominating projection of the same type
1102 // or TOP if the dominating projection is of opposite type.
1103 // Data-target will be used as the new control edge for the non-CFG
1104 // nodes like Casts and Loads.
1105 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1106 // Control-target is just the If's immediate dominator or TOP.
1107 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1108
1109 // For each child of an IfTrue/IfFalse projection, reroute.
1110 // Loop ends when projection has no more uses.
1111 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1112 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1113 if( !s->depends_only_on_test() ) {
1114 // Find the control input matching this def-use edge.
1115 // For Regions it may not be in slot 0.
1116 uint l;
1117 for( l = 0; s->in(l) != ifp; l++ ) { }
1118 igvn->replace_input_of(s, l, ctrl_target);
1119 } else { // Else, for control producers,
1120 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1121 }
1122 } // End for each child of a projection
1123
1124 igvn->remove_dead_node(ifp);
1125 } // End for each IfTrue/IfFalse child of If
1126
1127 // Kill the IfNode
1128 igvn->remove_dead_node(this);
1129 }
1130
1131 //------------------------------Identity---------------------------------------
1132 // If the test is constant & we match, then we are the input Control
1133 Node *IfProjNode::Identity(PhaseTransform *phase) {
1134 // Can only optimize if cannot go the other way
1135 const TypeTuple *t = phase->type(in(0))->is_tuple();
1136 if (t == TypeTuple::IFNEITHER ||
1137 // kill dead branch first otherwise the IfNode's control will
1138 // have 2 control uses (the IfNode that doesn't go away because
1139 // it still has uses and this branch of the
1140 // If). Node::has_special_unique_user() will cause this node to
1141 // be reprocessed once the dead branch is killed.
1142 (always_taken(t) && in(0)->outcnt() == 1)) {
1143 // IfNode control
1144 return in(0)->in(0);
1145 }
1146 // no progress
1147 return this;
1148 }
1149
1150 //------------------------------dump_spec--------------------------------------
1151 #ifndef PRODUCT
1152 void IfNode::dump_spec(outputStream *st) const {
1153 st->print("P=%f, C=%f",_prob,_fcnt);
1154 }
1155 #endif
1156
1157 //------------------------------idealize_test----------------------------------
1158 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1159 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1160 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1161 // needed.
1162 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1163 assert(iff->in(0) != NULL, "If must be live");
1164
1165 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1166 Node* old_if_f = iff->proj_out(false);
1167 Node* old_if_t = iff->proj_out(true);
1168
1169 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1170 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1171 // happens in count-down loops
1172 if (iff->is_CountedLoopEnd()) return NULL;
1173 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1174 BoolNode *b = iff->in(1)->as_Bool();
1175 BoolTest bt = b->_test;
1176 // Test already in good order?
1177 if( bt.is_canonical() )
1178 return NULL;
1179
1180 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1181 // cloning the IfNode.
1182 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1183 if( !new_b->is_Bool() ) return NULL;
1184 b = new_b->as_Bool();
1185
1186 PhaseIterGVN *igvn = phase->is_IterGVN();
1187 assert( igvn, "Test is not canonical in parser?" );
1188
1189 // The IF node never really changes, but it needs to be cloned
1190 iff = new IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1191
1192 Node *prior = igvn->hash_find_insert(iff);
1193 if( prior ) {
1194 igvn->remove_dead_node(iff);
1195 iff = (IfNode*)prior;
1196 } else {
1197 // Cannot call transform on it just yet
1198 igvn->set_type_bottom(iff);
1199 }
1200 igvn->_worklist.push(iff);
1201
1202 // Now handle projections. Cloning not required.
1203 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1204 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1205
1206 igvn->register_new_node_with_optimizer(new_if_f);
1207 igvn->register_new_node_with_optimizer(new_if_t);
1208 // Flip test, so flip trailing control
1209 igvn->replace_node(old_if_f, new_if_t);
1210 igvn->replace_node(old_if_t, new_if_f);
1211
1212 // Progress
1213 return iff;
1214 }