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
238 // If all the defs of the phi are the same constant, we already have the desired end state.
239 // Skip the split that would create empty phi and region nodes.
240 if((r->req() - req_c) == 1) {
241 return NULL;
242 }
243
244 Node* predicate_c = NULL;
245 Node* predicate_x = NULL;
246 bool counted_loop = r->is_CountedLoop();
247
248 Node *region_c = new (igvn->C) RegionNode(req_c + 1);
249 Node *phi_c = con1;
250 uint len = r->req();
251 Node *region_x = new (igvn->C) RegionNode(len - req_c);
252 Node *phi_x = PhiNode::make_blank(region_x, phi);
253 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
254 if (phi->in(i) == con1) {
255 region_c->init_req( i_c++, r ->in(i) );
256 if (r->in(i) == predicate_proj)
257 predicate_c = predicate_proj;
258 } else {
259 region_x->init_req( i_x, r ->in(i) );
260 phi_x ->init_req( i_x++, phi->in(i) );
261 if (r->in(i) == predicate_proj)
262 predicate_x = predicate_proj;
263 }
264 }
265 if (predicate_c != NULL && (req_c > 1)) {
266 assert(predicate_x == NULL, "only one predicate entry expected");
267 predicate_c = NULL; // Do not clone predicate below merge point
268 }
269 if (predicate_x != NULL && ((len - req_c) > 2)) {
270 assert(predicate_c == NULL, "only one predicate entry expected");
271 predicate_x = NULL; // Do not clone predicate below merge point
272 }
273
274 // Register the new RegionNodes but do not transform them. Cannot
275 // transform until the entire Region/Phi conglomerate has been hacked
276 // as a single huge transform.
277 igvn->register_new_node_with_optimizer( region_c );
278 igvn->register_new_node_with_optimizer( region_x );
279 // Prevent the untimely death of phi_x. Currently he has no uses. He is
280 // about to get one. If this only use goes away, then phi_x will look dead.
281 // However, he will be picking up some more uses down below.
282 Node *hook = new (igvn->C) Node(4);
283 hook->init_req(0, phi_x);
284 hook->init_req(1, phi_c);
285 phi_x = phase->transform( phi_x );
286
287 // Make the compare
288 Node *cmp_c = phase->makecon(t);
289 Node *cmp_x = cmp->clone();
290 cmp_x->set_req(1,phi_x);
291 cmp_x->set_req(2,con2);
292 cmp_x = phase->transform(cmp_x);
293 // Make the bool
294 Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test));
295 Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test));
296 // Make the IfNode
297 IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
298 igvn->set_type_bottom(iff_c);
299 igvn->_worklist.push(iff_c);
300 hook->init_req(2, iff_c);
301
302 IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
303 igvn->set_type_bottom(iff_x);
304 igvn->_worklist.push(iff_x);
305 hook->init_req(3, iff_x);
306
307 // Make the true/false arms
308 Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c));
309 Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c));
310 if (predicate_c != NULL) {
311 assert(predicate_x == NULL, "only one predicate entry expected");
312 // Clone loop predicates to each path
313 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
314 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
315 }
316 Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x));
317 Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x));
318 if (predicate_x != NULL) {
319 assert(predicate_c == NULL, "only one predicate entry expected");
320 // Clone loop predicates to each path
321 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
322 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
323 }
324
325 // Merge the TRUE paths
326 Node *region_s = new (igvn->C) RegionNode(3);
327 igvn->_worklist.push(region_s);
328 region_s->init_req(1, iff_c_t);
329 region_s->init_req(2, iff_x_t);
330 igvn->register_new_node_with_optimizer( region_s );
331
332 // Merge the FALSE paths
333 Node *region_f = new (igvn->C) RegionNode(3);
334 igvn->_worklist.push(region_f);
335 region_f->init_req(1, iff_c_f);
336 region_f->init_req(2, iff_x_f);
337 igvn->register_new_node_with_optimizer( region_f );
338
339 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
340 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
341 cmp->set_req(2,NULL);
342 // Check for all uses of the Phi and give them a new home.
343 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
344 Node *phi_s = NULL; // do not construct unless needed
345 Node *phi_f = NULL; // do not construct unless needed
346 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
347 Node* v = phi->last_out(i2);// User of the phi
348 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
349 uint vop = v->Opcode();
350 Node *proj = NULL;
351 if( vop == Op_Phi ) { // Remote merge point
352 Node *r = v->in(0);
353 for (uint i3 = 1; i3 < r->req(); i3++)
354 if (r->in(i3) && r->in(i3)->in(0) == iff) {
355 proj = r->in(i3);
356 break;
357 }
358 } else if( v->is_ConstraintCast() ) {
359 proj = v->in(0); // Controlling projection
360 } else {
361 assert( 0, "do not know how to handle this guy" );
362 }
363
364 Node *proj_path_data, *proj_path_ctrl;
365 if( proj->Opcode() == Op_IfTrue ) {
366 if( phi_s == NULL ) {
367 // Only construct phi_s if needed, otherwise provides
368 // interfering use.
369 phi_s = PhiNode::make_blank(region_s,phi);
370 phi_s->init_req( 1, phi_c );
371 phi_s->init_req( 2, phi_x );
372 hook->add_req(phi_s);
373 phi_s = phase->transform(phi_s);
374 }
375 proj_path_data = phi_s;
376 proj_path_ctrl = region_s;
377 } else {
378 if( phi_f == NULL ) {
379 // Only construct phi_f if needed, otherwise provides
380 // interfering use.
381 phi_f = PhiNode::make_blank(region_f,phi);
382 phi_f->init_req( 1, phi_c );
383 phi_f->init_req( 2, phi_x );
384 hook->add_req(phi_f);
385 phi_f = phase->transform(phi_f);
386 }
387 proj_path_data = phi_f;
388 proj_path_ctrl = region_f;
389 }
390
391 // Fixup 'v' for for the split
392 if( vop == Op_Phi ) { // Remote merge point
393 uint i;
394 for( i = 1; i < v->req(); i++ )
395 if( v->in(i) == phi )
396 break;
397 v->set_req(i, proj_path_data );
398 } else if( v->is_ConstraintCast() ) {
399 v->set_req(0, proj_path_ctrl );
400 v->set_req(1, proj_path_data );
401 } else
402 ShouldNotReachHere();
403 }
404
405 // Now replace the original iff's True/False with region_s/region_t.
406 // This makes the original iff go dead.
407 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
408 Node* p = iff->last_out(i3);
409 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
410 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
411 // Replace p with u
412 igvn->add_users_to_worklist(p);
413 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
414 Node* x = p->last_out(l);
415 igvn->hash_delete(x);
416 uint uses_found = 0;
417 for( uint j = 0; j < x->req(); j++ ) {
418 if( x->in(j) == p ) {
419 x->set_req(j, u);
420 uses_found++;
421 }
422 }
423 l -= uses_found; // we deleted 1 or more copies of this edge
424 }
425 igvn->remove_dead_node(p);
426 }
427
428 // Force the original merge dead
429 igvn->hash_delete(r);
430 // First, remove region's dead users.
431 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
432 Node* u = r->last_out(l);
433 if( u == r ) {
434 r->set_req(0, NULL);
435 } else {
436 assert(u->outcnt() == 0, "only dead users");
437 igvn->remove_dead_node(u);
438 }
439 l -= 1;
440 }
441 igvn->remove_dead_node(r);
442
443 // Now remove the bogus extra edges used to keep things alive
444 igvn->remove_dead_node( hook );
445
446 // Must return either the original node (now dead) or a new node
447 // (Do not return a top here, since that would break the uniqueness of top.)
448 return new (igvn->C) ConINode(TypeInt::ZERO);
449 }
450
451 //------------------------------is_range_check---------------------------------
452 // Return 0 if not a range check. Return 1 if a range check and set index and
453 // offset. Return 2 if we had to negate the test. Index is NULL if the check
454 // is versus a constant.
455 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
456 if (outcnt() != 2) {
457 return 0;
458 }
459 Node* b = in(1);
460 if (b == NULL || !b->is_Bool()) return 0;
461 BoolNode* bn = b->as_Bool();
462 Node* cmp = bn->in(1);
463 if (cmp == NULL) return 0;
464 if (cmp->Opcode() != Op_CmpU) return 0;
465
466 Node* l = cmp->in(1);
467 Node* r = cmp->in(2);
468 int flip_test = 1;
469 if (bn->_test._test == BoolTest::le) {
470 l = cmp->in(2);
471 r = cmp->in(1);
472 flip_test = 2;
473 } else if (bn->_test._test != BoolTest::lt) {
474 return 0;
475 }
476 if (l->is_top()) return 0; // Top input means dead test
477 if (r->Opcode() != Op_LoadRange) return 0;
478
479 // We have recognized one of these forms:
480 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
481 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
482
483 // Make sure it's a real range check by requiring an uncommon trap
484 // along the OOB path. Otherwise, it's possible that the user wrote
485 // something which optimized to look like a range check but behaves
486 // in some other way.
487 Node* iftrap = proj_out(flip_test == 2 ? true : false);
488 bool found_trap = false;
489 if (iftrap != NULL) {
490 Node* u = iftrap->unique_ctrl_out();
491 if (u != NULL) {
492 // It could be a merge point (Region) for uncommon trap.
493 if (u->is_Region()) {
494 Node* c = u->unique_ctrl_out();
495 if (c != NULL) {
496 iftrap = u;
497 u = c;
498 }
499 }
500 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
501 int req = u->as_CallStaticJava()->uncommon_trap_request();
502 if (Deoptimization::trap_request_reason(req) ==
503 Deoptimization::Reason_range_check) {
504 found_trap = true;
505 }
506 }
507 }
508 }
509 if (!found_trap) return 0; // sorry, no cigar
510
511 // Look for index+offset form
512 Node* ind = l;
513 jint off = 0;
514 if (l->is_top()) {
515 return 0;
516 } else if (l->Opcode() == Op_AddI) {
517 if ((off = l->in(1)->find_int_con(0)) != 0) {
518 ind = l->in(2);
519 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
520 ind = l->in(1);
521 }
522 } else if ((off = l->find_int_con(-1)) >= 0) {
523 // constant offset with no variable index
524 ind = NULL;
525 } else {
526 // variable index with no constant offset (or dead negative index)
527 off = 0;
528 }
529
530 // Return all the values:
531 index = ind;
532 offset = off;
533 range = r;
534 return flip_test;
535 }
536
537 //------------------------------adjust_check-----------------------------------
538 // Adjust (widen) a prior range check
539 static void adjust_check(Node* proj, Node* range, Node* index,
540 int flip, jint off_lo, PhaseIterGVN* igvn) {
541 PhaseGVN *gvn = igvn;
542 // Break apart the old check
543 Node *iff = proj->in(0);
544 Node *bol = iff->in(1);
545 if( bol->is_top() ) return; // In case a partially dead range check appears
546 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
547 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
548 if( !bol->is_Bool() ) return;
549
550 Node *cmp = bol->in(1);
551 // Compute a new check
552 Node *new_add = gvn->intcon(off_lo);
553 if( index ) {
554 new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index;
555 }
556 Node *new_cmp = (flip == 1)
557 ? new (gvn->C) CmpUNode( new_add, range )
558 : new (gvn->C) CmpUNode( range, new_add );
559 new_cmp = gvn->transform(new_cmp);
560 // See if no need to adjust the existing check
561 if( new_cmp == cmp ) return;
562 // Else, adjust existing check
563 Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
564 igvn->rehash_node_delayed( iff );
565 iff->set_req_X( 1, new_bol, igvn );
566 }
567
568 //------------------------------up_one_dom-------------------------------------
569 // Walk up the dominator tree one step. Return NULL at root or true
570 // complex merges. Skips through small diamonds.
571 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
572 Node *dom = curr->in(0);
573 if( !dom ) // Found a Region degraded to a copy?
574 return curr->nonnull_req(); // Skip thru it
575
576 if( curr != dom ) // Normal walk up one step?
577 return dom;
578
579 // Use linear_only if we are still parsing, since we cannot
580 // trust the regions to be fully filled in.
581 if (linear_only)
582 return NULL;
583
584 if( dom->is_Root() )
585 return NULL;
586
587 // Else hit a Region. Check for a loop header
588 if( dom->is_Loop() )
589 return dom->in(1); // Skip up thru loops
590
591 // Check for small diamonds
592 Node *din1, *din2, *din3, *din4;
593 if( dom->req() == 3 && // 2-path merge point
594 (din1 = dom ->in(1)) && // Left path exists
595 (din2 = dom ->in(2)) && // Right path exists
596 (din3 = din1->in(0)) && // Left path up one
597 (din4 = din2->in(0)) ) { // Right path up one
598 if( din3->is_Call() && // Handle a slow-path call on either arm
599 (din3 = din3->in(0)) )
600 din3 = din3->in(0);
601 if( din4->is_Call() && // Handle a slow-path call on either arm
602 (din4 = din4->in(0)) )
603 din4 = din4->in(0);
604 if (din3 != NULL && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
605 return din3; // Skip around diamonds
606 }
607
608 // Give up the search at true merges
609 return NULL; // Dead loop? Or hit root?
610 }
611
612
613 //------------------------------filtered_int_type--------------------------------
614 // Return a possibly more restrictive type for val based on condition control flow for an if
615 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
616 assert(if_proj &&
617 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
618 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
619 IfNode* iff = if_proj->in(0)->as_If();
620 if (iff->in(1) && iff->in(1)->is_Bool()) {
621 BoolNode* bol = iff->in(1)->as_Bool();
622 if (bol->in(1) && bol->in(1)->is_Cmp()) {
623 const CmpNode* cmp = bol->in(1)->as_Cmp();
624 if (cmp->in(1) == val) {
625 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
626 if (cmp2_t != NULL) {
627 jint lo = cmp2_t->_lo;
628 jint hi = cmp2_t->_hi;
629 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
630 switch (msk) {
631 case BoolTest::ne:
632 // Can't refine type
633 return NULL;
634 case BoolTest::eq:
635 return cmp2_t;
636 case BoolTest::lt:
637 lo = TypeInt::INT->_lo;
638 if (hi - 1 < hi) {
639 hi = hi - 1;
640 }
641 break;
642 case BoolTest::le:
643 lo = TypeInt::INT->_lo;
644 break;
645 case BoolTest::gt:
646 if (lo + 1 > lo) {
647 lo = lo + 1;
648 }
649 hi = TypeInt::INT->_hi;
650 break;
651 case BoolTest::ge:
652 // lo unchanged
653 hi = TypeInt::INT->_hi;
654 break;
655 }
656 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
657 return rtn_t;
658 }
659 }
660 }
661 }
662 }
663 return NULL;
664 }
665
666 //------------------------------fold_compares----------------------------
667 // See if a pair of CmpIs can be converted into a CmpU. In some cases
668 // the direction of this if is determined by the preceding if so it
669 // can be eliminate entirely. Given an if testing (CmpI n c) check
670 // for an immediately control dependent if that is testing (CmpI n c2)
671 // and has one projection leading to this if and the other projection
672 // leading to a region that merges one of this ifs control
673 // projections.
674 //
675 // If
676 // / |
677 // / |
678 // / |
679 // If |
680 // /\ |
681 // / \ |
682 // / \ |
683 // / Region
684 //
685 Node* IfNode::fold_compares(PhaseGVN* phase) {
686 if (Opcode() != Op_If) return NULL;
687
688 Node* this_cmp = in(1)->in(1);
689 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
690 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
691 Node* ctrl = in(0);
692 BoolNode* this_bool = in(1)->as_Bool();
693 Node* n = this_cmp->in(1);
694 int hi = this_cmp->in(2)->get_int();
695 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
696 ctrl->in(0)->is_If() &&
697 ctrl->in(0)->outcnt() == 2 &&
698 ctrl->in(0)->in(1)->is_Bool() &&
699 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
700 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
701 ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
702 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
703 IfNode* dom_iff = ctrl->in(0)->as_If();
704 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
705 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
706 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
707 // Identify which proj goes to the region and which continues on
708 RegionNode* region = otherproj->unique_out()->as_Region();
709 Node* success = NULL;
710 Node* fail = NULL;
711 for (int i = 0; i < 2; i++) {
712 Node* proj = proj_out(i);
713 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
714 success = proj;
715 } else if (fail == NULL) {
716 fail = proj;
717 } else {
718 success = fail = NULL;
719 }
720 }
721 if (success != NULL && fail != NULL && !region->has_phi()) {
722 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
723 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
724 Node* dom_cmp = dom_bool->in(1);
725 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
726 if (failtype != NULL) {
727 const TypeInt* type2 = filtered_int_type(phase, n, fail);
728 if (type2 != NULL) {
729 failtype = failtype->join(type2)->is_int();
730 } else {
731 failtype = NULL;
732 }
733 }
734
735 if (failtype != NULL &&
736 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
737 int bound = failtype->_hi - failtype->_lo + 1;
738 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
739 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
740 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
741 Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo)));
742 Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound)));
743 Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond));
744 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
745 phase->hash_delete(this);
746 set_req(1, newbool);
747 return this;
748 }
749 if (failtype->_lo > failtype->_hi) {
750 // previous if determines the result of this if so
751 // replace Bool with constant
752 phase->hash_delete(this);
753 set_req(1, phase->intcon(success->as_Proj()->_con));
754 return this;
755 }
756 }
757 }
758 }
759 }
760 }
761 return NULL;
762 }
763
764 //------------------------------remove_useless_bool----------------------------
765 // Check for people making a useless boolean: things like
766 // if( (x < y ? true : false) ) { ... }
767 // Replace with if( x < y ) { ... }
768 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
769 Node *i1 = iff->in(1);
770 if( !i1->is_Bool() ) return NULL;
771 BoolNode *bol = i1->as_Bool();
772
773 Node *cmp = bol->in(1);
774 if( cmp->Opcode() != Op_CmpI ) return NULL;
775
776 // Must be comparing against a bool
777 const Type *cmp2_t = phase->type( cmp->in(2) );
778 if( cmp2_t != TypeInt::ZERO &&
779 cmp2_t != TypeInt::ONE )
780 return NULL;
781
782 // Find a prior merge point merging the boolean
783 i1 = cmp->in(1);
784 if( !i1->is_Phi() ) return NULL;
785 PhiNode *phi = i1->as_Phi();
786 if( phase->type( phi ) != TypeInt::BOOL )
787 return NULL;
788
789 // Check for diamond pattern
790 int true_path = phi->is_diamond_phi();
791 if( true_path == 0 ) return NULL;
792
793 // Make sure that iff and the control of the phi are different. This
794 // should really only happen for dead control flow since it requires
795 // an illegal cycle.
796 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
797
798 // phi->region->if_proj->ifnode->bool->cmp
799 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
800
801 // Now get the 'sense' of the test correct so we can plug in
802 // either iff2->in(1) or its complement.
803 int flip = 0;
804 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
805 else if( bol->_test._test != BoolTest::eq ) return NULL;
806 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
807
808 const Type *phi1_t = phase->type( phi->in(1) );
809 const Type *phi2_t = phase->type( phi->in(2) );
810 // Check for Phi(0,1) and flip
811 if( phi1_t == TypeInt::ZERO ) {
812 if( phi2_t != TypeInt::ONE ) return NULL;
813 flip = 1-flip;
814 } else {
815 // Check for Phi(1,0)
816 if( phi1_t != TypeInt::ONE ) return NULL;
817 if( phi2_t != TypeInt::ZERO ) return NULL;
818 }
819 if( true_path == 2 ) {
820 flip = 1-flip;
821 }
822
823 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
824 assert(new_bol != iff->in(1), "must make progress");
825 iff->set_req(1, new_bol);
826 // Intervening diamond probably goes dead
827 phase->C->set_major_progress();
828 return iff;
829 }
830
831 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
832
833 struct RangeCheck {
834 Node* ctl;
835 jint off;
836 };
837
838 //------------------------------Ideal------------------------------------------
839 // Return a node which is more "ideal" than the current node. Strip out
840 // control copies
841 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
842 if (remove_dead_region(phase, can_reshape)) return this;
843 // No Def-Use info?
844 if (!can_reshape) return NULL;
845 PhaseIterGVN *igvn = phase->is_IterGVN();
846
847 // Don't bother trying to transform a dead if
848 if (in(0)->is_top()) return NULL;
849 // Don't bother trying to transform an if with a dead test
850 if (in(1)->is_top()) return NULL;
851 // Another variation of a dead test
852 if (in(1)->is_Con()) return NULL;
853 // Another variation of a dead if
854 if (outcnt() < 2) return NULL;
855
856 // Canonicalize the test.
857 Node* idt_if = idealize_test(phase, this);
858 if (idt_if != NULL) return idt_if;
859
860 // Try to split the IF
861 Node *s = split_if(this, igvn);
862 if (s != NULL) return s;
863
864 // Check for people making a useless boolean: things like
865 // if( (x < y ? true : false) ) { ... }
866 // Replace with if( x < y ) { ... }
867 Node *bol2 = remove_useless_bool(this, phase);
868 if( bol2 ) return bol2;
869
870 // Setup to scan up the CFG looking for a dominating test
871 Node *dom = in(0);
872 Node *prev_dom = this;
873
874 // Check for range-check vs other kinds of tests
875 Node *index1, *range1;
876 jint offset1;
877 int flip1 = is_range_check(range1, index1, offset1);
878 if( flip1 ) {
879 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
880 // so all checks we inspect post-dominate the top-most check we find.
881 // If we are going to fail the current check and we reach the top check
882 // then we are guaranteed to fail, so just start interpreting there.
883 // We 'expand' the top 3 range checks to include all post-dominating
884 // checks.
885
886 // The top 3 range checks seen
887 const int NRC =3;
888 RangeCheck prev_checks[NRC];
889 int nb_checks = 0;
890
891 // Low and high offsets seen so far
892 jint off_lo = offset1;
893 jint off_hi = offset1;
894
895 bool found_immediate_dominator = false;
896
897 // Scan for the top checks and collect range of offsets
898 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
899 if (dom->Opcode() == Op_If && // Not same opcode?
900 prev_dom->in(0) == dom) { // One path of test does dominate?
901 if (dom == this) return NULL; // dead loop
902 // See if this is a range check
903 Node *index2, *range2;
904 jint offset2;
905 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
906 // See if this is a _matching_ range check, checking against
907 // the same array bounds.
908 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
909 dom->outcnt() == 2) {
910 if (nb_checks == 0 && dom->in(1) == in(1)) {
911 // Found an immediately dominating test at the same offset.
912 // This kind of back-to-back test can be eliminated locally,
913 // and there is no need to search further for dominating tests.
914 assert(offset2 == offset1, "Same test but different offsets");
915 found_immediate_dominator = true;
916 break;
917 }
918 // Gather expanded bounds
919 off_lo = MIN2(off_lo,offset2);
920 off_hi = MAX2(off_hi,offset2);
921 // Record top NRC range checks
922 prev_checks[nb_checks%NRC].ctl = prev_dom;
923 prev_checks[nb_checks%NRC].off = offset2;
924 nb_checks++;
925 }
926 }
927 prev_dom = dom;
928 dom = up_one_dom(dom);
929 if (!dom) break;
930 }
931
932 if (!found_immediate_dominator) {
933 // Attempt to widen the dominating range check to cover some later
934 // ones. Since range checks "fail" by uncommon-trapping to the
935 // interpreter, widening a check can make us speculatively enter
936 // the interpreter. If we see range-check deopt's, do not widen!
937 if (!phase->C->allow_range_check_smearing()) return NULL;
938
939 // Didn't find prior covering check, so cannot remove anything.
940 if (nb_checks == 0) {
941 return NULL;
942 }
943 // Constant indices only need to check the upper bound.
944 // Non-constant indices must check both low and high.
945 int chk0 = (nb_checks - 1) % NRC;
946 if (index1) {
947 if (nb_checks == 1) {
948 return NULL;
949 } else {
950 // If the top range check's constant is the min or max of
951 // all constants we widen the next one to cover the whole
952 // range of constants.
953 RangeCheck rc0 = prev_checks[chk0];
954 int chk1 = (nb_checks - 2) % NRC;
955 RangeCheck rc1 = prev_checks[chk1];
956 if (rc0.off == off_lo) {
957 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
958 prev_dom = rc1.ctl;
959 } else if (rc0.off == off_hi) {
960 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
961 prev_dom = rc1.ctl;
962 } else {
963 // If the top test's constant is not the min or max of all
964 // constants, we need 3 range checks. We must leave the
965 // top test unchanged because widening it would allow the
966 // accesses it protects to successfully read/write out of
967 // bounds.
968 if (nb_checks == 2) {
969 return NULL;
970 }
971 int chk2 = (nb_checks - 3) % NRC;
972 RangeCheck rc2 = prev_checks[chk2];
973 // The top range check a+i covers interval: -a <= i < length-a
974 // The second range check b+i covers interval: -b <= i < length-b
975 if (rc1.off <= rc0.off) {
976 // if b <= a, we change the second range check to:
977 // -min_of_all_constants <= i < length-min_of_all_constants
978 // Together top and second range checks now cover:
979 // -min_of_all_constants <= i < length-a
980 // which is more restrictive than -b <= i < length-b:
981 // -b <= -min_of_all_constants <= i < length-a <= length-b
982 // The third check is then changed to:
983 // -max_of_all_constants <= i < length-max_of_all_constants
984 // so 2nd and 3rd checks restrict allowed values of i to:
985 // -min_of_all_constants <= i < length-max_of_all_constants
986 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
987 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
988 } else {
989 // if b > a, we change the second range check to:
990 // -max_of_all_constants <= i < length-max_of_all_constants
991 // Together top and second range checks now cover:
992 // -a <= i < length-max_of_all_constants
993 // which is more restrictive than -b <= i < length-b:
994 // -b < -a <= i < length-max_of_all_constants <= length-b
995 // The third check is then changed to:
996 // -max_of_all_constants <= i < length-max_of_all_constants
997 // so 2nd and 3rd checks restrict allowed values of i to:
998 // -min_of_all_constants <= i < length-max_of_all_constants
999 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1000 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1001 }
1002 prev_dom = rc2.ctl;
1003 }
1004 }
1005 } else {
1006 RangeCheck rc0 = prev_checks[chk0];
1007 // 'Widen' the offset of the 1st and only covering check
1008 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1009 // Test is now covered by prior checks, dominate it out
1010 prev_dom = rc0.ctl;
1011 }
1012 }
1013
1014 } else { // Scan for an equivalent test
1015
1016 Node *cmp;
1017 int dist = 0; // Cutoff limit for search
1018 int op = Opcode();
1019 if( op == Op_If &&
1020 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1021 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1022 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1023 dist = 64; // Limit for null-pointer scans
1024 } else {
1025 dist = 4; // Do not bother for random pointer tests
1026 }
1027 } else {
1028 dist = 4; // Limit for random junky scans
1029 }
1030
1031 // Normal equivalent-test check.
1032 if( !dom ) return NULL; // Dead loop?
1033
1034 Node* result = fold_compares(phase);
1035 if (result != NULL) {
1036 return result;
1037 }
1038
1039 // Search up the dominator tree for an If with an identical test
1040 while( dom->Opcode() != op || // Not same opcode?
1041 dom->in(1) != in(1) || // Not same input 1?
1042 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1043 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1044 if( dist < 0 ) return NULL;
1045
1046 dist--;
1047 prev_dom = dom;
1048 dom = up_one_dom( dom );
1049 if( !dom ) return NULL;
1050 }
1051
1052 // Check that we did not follow a loop back to ourselves
1053 if( this == dom )
1054 return NULL;
1055
1056 if( dist > 2 ) // Add to count of NULL checks elided
1057 explicit_null_checks_elided++;
1058
1059 } // End of Else scan for an equivalent test
1060
1061 // Hit! Remove this IF
1062 #ifndef PRODUCT
1063 if( TraceIterativeGVN ) {
1064 tty->print(" Removing IfNode: "); this->dump();
1065 }
1066 if( VerifyOpto && !phase->allow_progress() ) {
1067 // Found an equivalent dominating test,
1068 // we can not guarantee reaching a fix-point for these during iterativeGVN
1069 // since intervening nodes may not change.
1070 return NULL;
1071 }
1072 #endif
1073
1074 // Replace dominated IfNode
1075 dominated_by( prev_dom, igvn );
1076
1077 // Must return either the original node (now dead) or a new node
1078 // (Do not return a top here, since that would break the uniqueness of top.)
1079 return new (phase->C) ConINode(TypeInt::ZERO);
1080 }
1081
1082 //------------------------------dominated_by-----------------------------------
1083 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1084 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1085 Node *idom = in(0);
1086 // Need opcode to decide which way 'this' test goes
1087 int prev_op = prev_dom->Opcode();
1088 Node *top = igvn->C->top(); // Shortcut to top
1089
1090 // Loop predicates may have depending checks which should not
1091 // be skipped. For example, range check predicate has two checks
1092 // for lower and upper bounds.
1093 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1094 if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))) {
1095 prev_dom = idom;
1096 }
1097
1098 // Now walk the current IfNode's projections.
1099 // Loop ends when 'this' has no more uses.
1100 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1101 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1102 igvn->add_users_to_worklist(ifp);
1103 // Check which projection it is and set target.
1104 // Data-target is either the dominating projection of the same type
1105 // or TOP if the dominating projection is of opposite type.
1106 // Data-target will be used as the new control edge for the non-CFG
1107 // nodes like Casts and Loads.
1108 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1109 // Control-target is just the If's immediate dominator or TOP.
1110 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1111
1112 // For each child of an IfTrue/IfFalse projection, reroute.
1113 // Loop ends when projection has no more uses.
1114 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1115 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1116 if( !s->depends_only_on_test() ) {
1117 // Find the control input matching this def-use edge.
1118 // For Regions it may not be in slot 0.
1119 uint l;
1120 for( l = 0; s->in(l) != ifp; l++ ) { }
1121 igvn->replace_input_of(s, l, ctrl_target);
1122 } else { // Else, for control producers,
1123 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1124 }
1125 } // End for each child of a projection
1126
1127 igvn->remove_dead_node(ifp);
1128 } // End for each IfTrue/IfFalse child of If
1129
1130 // Kill the IfNode
1131 igvn->remove_dead_node(this);
1132 }
1133
1134 //------------------------------Identity---------------------------------------
1135 // If the test is constant & we match, then we are the input Control
1136 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1137 // Can only optimize if cannot go the other way
1138 const TypeTuple *t = phase->type(in(0))->is_tuple();
1139 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1140 ? in(0)->in(0) // IfNode control
1141 : this; // no progress
1142 }
1143
1144 //------------------------------dump_spec--------------------------------------
1145 #ifndef PRODUCT
1146 void IfNode::dump_spec(outputStream *st) const {
1147 st->print("P=%f, C=%f",_prob,_fcnt);
1148 }
1149 #endif
1150
1151 //------------------------------idealize_test----------------------------------
1152 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1153 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1154 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1155 // needed.
1156 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1157 assert(iff->in(0) != NULL, "If must be live");
1158
1159 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1160 Node* old_if_f = iff->proj_out(false);
1161 Node* old_if_t = iff->proj_out(true);
1162
1163 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1164 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1165 // happens in count-down loops
1166 if (iff->is_CountedLoopEnd()) return NULL;
1167 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1168 BoolNode *b = iff->in(1)->as_Bool();
1169 BoolTest bt = b->_test;
1170 // Test already in good order?
1171 if( bt.is_canonical() )
1172 return NULL;
1173
1174 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1175 // cloning the IfNode.
1176 Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) );
1177 if( !new_b->is_Bool() ) return NULL;
1178 b = new_b->as_Bool();
1179
1180 PhaseIterGVN *igvn = phase->is_IterGVN();
1181 assert( igvn, "Test is not canonical in parser?" );
1182
1183 // The IF node never really changes, but it needs to be cloned
1184 iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1185
1186 Node *prior = igvn->hash_find_insert(iff);
1187 if( prior ) {
1188 igvn->remove_dead_node(iff);
1189 iff = (IfNode*)prior;
1190 } else {
1191 // Cannot call transform on it just yet
1192 igvn->set_type_bottom(iff);
1193 }
1194 igvn->_worklist.push(iff);
1195
1196 // Now handle projections. Cloning not required.
1197 Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff ));
1198 Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff ));
1199
1200 igvn->register_new_node_with_optimizer(new_if_f);
1201 igvn->register_new_node_with_optimizer(new_if_t);
1202 // Flip test, so flip trailing control
1203 igvn->replace_node(old_if_f, new_if_t);
1204 igvn->replace_node(old_if_t, new_if_f);
1205
1206 // Progress
1207 return iff;
1208 }
1209
1210 //------------------------------Identity---------------------------------------
1211 // If the test is constant & we match, then we are the input Control
1212 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1213 // Can only optimize if cannot go the other way
1214 const TypeTuple *t = phase->type(in(0))->is_tuple();
1215 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1216 ? in(0)->in(0) // IfNode control
1217 : this; // no progress
1218 }