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 "gc_implementation/shenandoah/shenandoahHeap.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/cfgnode.hpp"
30 #include "opto/connode.hpp"
31 #include "opto/loopnode.hpp"
32 #include "opto/phaseX.hpp"
33 #include "opto/runtime.hpp"
34 #include "opto/subnode.hpp"
35
36 // Portions of code courtesy of Clifford Click
37
38 // Optimization - Graph Style
39
40
41 extern int explicit_null_checks_elided;
42
43 //=============================================================================
44 //------------------------------Value------------------------------------------
45 // Return a tuple for whichever arm of the IF is reachable
46 const Type *IfNode::Value( PhaseTransform *phase ) const {
47 if( !in(0) ) return Type::TOP;
48 if( phase->type(in(0)) == Type::TOP )
49 return Type::TOP;
50 const Type *t = phase->type(in(1));
51 if( t == Type::TOP ) // data is undefined
52 return TypeTuple::IFNEITHER; // unreachable altogether
53 if( t == TypeInt::ZERO ) // zero, or false
54 return TypeTuple::IFFALSE; // only false branch is reachable
55 if( t == TypeInt::ONE ) // 1, or true
56 return TypeTuple::IFTRUE; // only true branch is reachable
57 assert( t == TypeInt::BOOL, "expected boolean type" );
58
59 return TypeTuple::IFBOTH; // No progress
60 }
61
62 const RegMask &IfNode::out_RegMask() const {
63 return RegMask::Empty;
64 }
65
66 //------------------------------split_if---------------------------------------
67 // Look for places where we merge constants, then test on the merged value.
68 // If the IF test will be constant folded on the path with the constant, we
69 // win by splitting the IF to before the merge point.
70 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
71 // I could be a lot more general here, but I'm trying to squeeze this
72 // in before the Christmas '98 break so I'm gonna be kinda restrictive
73 // on the patterns I accept. CNC
74
75 // Look for a compare of a constant and a merged value
76 Node *i1 = iff->in(1);
77 if( !i1->is_Bool() ) return NULL;
78 BoolNode *b = i1->as_Bool();
79 Node *cmp = b->in(1);
80 if( !cmp->is_Cmp() ) return NULL;
81 i1 = cmp->in(1);
82 if( i1 == NULL || !i1->is_Phi() ) return NULL;
83 PhiNode *phi = i1->as_Phi();
84 if( phi->is_copy() ) return NULL;
85 Node *con2 = cmp->in(2);
86 if( !con2->is_Con() ) return NULL;
87 // See that the merge point contains some constants
88 Node *con1=NULL;
89 uint i4;
90 for( i4 = 1; i4 < phi->req(); i4++ ) {
91 con1 = phi->in(i4);
92 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
93 if( con1->is_Con() ) break; // Found a constant
94 // Also allow null-vs-not-null checks
95 const TypePtr *tp = igvn->type(con1)->isa_ptr();
96 if( tp && tp->_ptr == TypePtr::NotNull )
97 break;
98 }
99 if( i4 >= phi->req() ) return NULL; // Found no constants
100
101 igvn->C->set_has_split_ifs(true); // Has chance for split-if
102
103 // Make sure that the compare can be constant folded away
104 Node *cmp2 = cmp->clone();
105 cmp2->set_req(1,con1);
106 cmp2->set_req(2,con2);
107 const Type *t = cmp2->Value(igvn);
108 // This compare is dead, so whack it!
109 igvn->remove_dead_node(cmp2);
110 if( !t->singleton() ) return NULL;
111
112 // No intervening control, like a simple Call
113 Node *r = iff->in(0);
114 if( !r->is_Region() ) return NULL;
115 if( phi->region() != r ) return NULL;
116 // No other users of the cmp/bool
117 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
118 //tty->print_cr("many users of cmp/bool");
119 return NULL;
120 }
121
122 // Make sure we can determine where all the uses of merged values go
123 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
124 Node* u = r->fast_out(j);
125 if( u == r ) continue;
126 if( u == iff ) continue;
127 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
128 if( !u->is_Phi() ) {
129 /*
130 if( u->is_Start() ) {
131 tty->print_cr("Region has inlined start use");
132 } else {
133 tty->print_cr("Region has odd use");
134 u->dump(2);
135 }*/
136 return NULL;
137 }
138 if( u != phi ) {
139 // CNC - do not allow any other merged value
140 //tty->print_cr("Merging another value");
141 //u->dump(2);
142 return NULL;
143 }
144 // Make sure we can account for all Phi uses
145 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
146 Node* v = u->fast_out(k); // User of the phi
147 // CNC - Allow only really simple patterns.
148 // In particular I disallow AddP of the Phi, a fairly common pattern
149 if( v == cmp ) continue; // The compare is OK
150 if( (v->is_ConstraintCast()) &&
151 v->in(0)->in(0) == iff )
152 continue; // CastPP/II of the IfNode is OK
153 // Disabled following code because I cannot tell if exactly one
154 // path dominates without a real dominator check. CNC 9/9/1999
155 //uint vop = v->Opcode();
156 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
157 // Node *r = v->in(0); // Get controlling point
158 // if( !r ) return NULL; // Degraded to a copy
159 // // Find exactly one path in (either True or False doms, but not IFF)
160 // int cnt = 0;
161 // for( uint i = 1; i < r->req(); i++ )
162 // if( r->in(i) && r->in(i)->in(0) == iff )
163 // cnt++;
164 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
165 //}
166 if( !v->is_Call() ) {
167 /*
168 if( v->Opcode() == Op_AddP ) {
169 tty->print_cr("Phi has AddP use");
170 } else if( v->Opcode() == Op_CastPP ) {
171 tty->print_cr("Phi has CastPP use");
172 } else if( v->Opcode() == Op_CastII ) {
173 tty->print_cr("Phi has CastII use");
174 } else {
175 tty->print_cr("Phi has use I cant be bothered with");
176 }
177 */
178 }
179 return NULL;
180
181 /* CNC - Cut out all the fancy acceptance tests
182 // Can we clone this use when doing the transformation?
183 // If all uses are from Phis at this merge or constants, then YES.
184 if( !v->in(0) && v != cmp ) {
185 tty->print_cr("Phi has free-floating use");
186 v->dump(2);
187 return NULL;
188 }
189 for( uint l = 1; l < v->req(); l++ ) {
190 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
191 !v->in(l)->is_Con() ) {
192 tty->print_cr("Phi has use");
193 v->dump(2);
194 return NULL;
195 } // End of if Phi-use input is neither Phi nor Constant
196 } // End of for all inputs to Phi-use
197 */
198 } // End of for all uses of Phi
199 } // End of for all uses of Region
200
201 // Only do this if the IF node is in a sane state
202 if (iff->outcnt() != 2)
203 return NULL;
204
205 // Got a hit! Do the Mondo Hack!
206 //
207 //ABC a1c def ghi B 1 e h A C a c d f g i
208 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
209 // cmp - 2 cmp - 2 cmp - 2
210 // bool bool_c bool_x
211 // if if_c if_x
212 // T F T F T F
213 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
214 //
215 // Split the paths coming into the merge point into 2 separate groups of
216 // merges. On the left will be all the paths feeding constants into the
217 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
218 // will fold up into a constant; this will let the Cmp fold up as well as
219 // all the control flow. Below the original IF we have 2 control
220 // dependent regions, 's' and 't'. Now we will merge the two paths
221 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
222 // likely 2 or more) will promptly constant fold away.
223 PhaseGVN *phase = igvn;
224
225 // Make a region merging constants and a region merging the rest
226 uint req_c = 0;
227 Node* predicate_proj = NULL;
228 for (uint ii = 1; ii < r->req(); ii++) {
229 if (phi->in(ii) == con1) {
230 req_c++;
231 }
232 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
233 if (proj != NULL) {
234 assert(predicate_proj == NULL, "only one predicate entry expected");
235 predicate_proj = proj;
236 }
237 }
238
239 // If all the defs of the phi are the same constant, we already have the desired end state.
240 // Skip the split that would create empty phi and region nodes.
241 if((r->req() - req_c) == 1) {
242 return NULL;
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 (igvn->C) RegionNode(req_c + 1);
250 Node *phi_c = con1;
251 uint len = r->req();
252 Node *region_x = new (igvn->C) 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 (igvn->C) 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 (igvn->C) BoolNode(cmp_c,b->_test._test));
296 Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test));
297 // Make the IfNode
298 IfNode *iff_c = new (igvn->C) 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 (igvn->C) 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 (igvn->C) IfTrueNode (iff_c));
310 Node *iff_c_f = phase->transform(new (igvn->C) 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 (igvn->C) IfTrueNode (iff_x));
318 Node *iff_x_f = phase->transform(new (igvn->C) 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 (igvn->C) 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 (igvn->C) 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 (igvn->C) 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 if (outcnt() != 2) {
458 return 0;
459 }
460 Node* b = in(1);
461 if (b == NULL || !b->is_Bool()) return 0;
462 BoolNode* bn = b->as_Bool();
463 Node* cmp = bn->in(1);
464 if (cmp == NULL) return 0;
465 if (cmp->Opcode() != Op_CmpU) return 0;
466
467 Node* l = cmp->in(1);
468 Node* r = cmp->in(2);
469 int flip_test = 1;
470 if (bn->_test._test == BoolTest::le) {
471 l = cmp->in(2);
472 r = cmp->in(1);
473 flip_test = 2;
474 } else if (bn->_test._test != BoolTest::lt) {
475 return 0;
476 }
477 if (l->is_top()) return 0; // Top input means dead test
478 if (r->Opcode() != Op_LoadRange) return 0;
479
480 // We have recognized one of these forms:
481 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
482 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
483
484 // Make sure it's a real range check by requiring an uncommon trap
485 // along the OOB path. Otherwise, it's possible that the user wrote
486 // something which optimized to look like a range check but behaves
487 // in some other way.
488 Node* iftrap = proj_out(flip_test == 2 ? true : false);
489 bool found_trap = false;
490 if (iftrap != NULL) {
491 Node* u = iftrap->unique_ctrl_out();
492 if (u != NULL) {
493 // It could be a merge point (Region) for uncommon trap.
494 if (u->is_Region()) {
495 Node* c = u->unique_ctrl_out();
496 if (c != NULL) {
497 iftrap = u;
498 u = c;
499 }
500 }
501 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
502 int req = u->as_CallStaticJava()->uncommon_trap_request();
503 if (Deoptimization::trap_request_reason(req) ==
504 Deoptimization::Reason_range_check) {
505 found_trap = true;
506 }
507 }
508 }
509 }
510 if (!found_trap) return 0; // sorry, no cigar
511
512 // Look for index+offset form
513 Node* ind = l;
514 jint off = 0;
515 if (l->is_top()) {
516 return 0;
517 } else if (l->Opcode() == Op_AddI) {
518 if ((off = l->in(1)->find_int_con(0)) != 0) {
519 ind = l->in(2);
520 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
521 ind = l->in(1);
522 }
523 } else if ((off = l->find_int_con(-1)) >= 0) {
524 // constant offset with no variable index
525 ind = NULL;
526 } else {
527 // variable index with no constant offset (or dead negative index)
528 off = 0;
529 }
530
531 // Return all the values:
532 index = ind;
533 offset = off;
534 range = r;
535 return flip_test;
536 }
537
538 //------------------------------adjust_check-----------------------------------
539 // Adjust (widen) a prior range check
540 static void adjust_check(Node* proj, Node* range, Node* index,
541 int flip, jint off_lo, PhaseIterGVN* igvn) {
542 PhaseGVN *gvn = igvn;
543 // Break apart the old check
544 Node *iff = proj->in(0);
545 Node *bol = iff->in(1);
546 if( bol->is_top() ) return; // In case a partially dead range check appears
547 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
548 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
549 if( !bol->is_Bool() ) return;
550
551 Node *cmp = bol->in(1);
552 // Compute a new check
553 Node *new_add = gvn->intcon(off_lo);
554 if( index ) {
555 new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index;
556 }
557 Node *new_cmp = (flip == 1)
558 ? new (gvn->C) CmpUNode( new_add, range )
559 : new (gvn->C) CmpUNode( range, new_add );
560 new_cmp = gvn->transform(new_cmp);
561 // See if no need to adjust the existing check
562 if( new_cmp == cmp ) return;
563 // Else, adjust existing check
564 Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
565 igvn->rehash_node_delayed( iff );
566 iff->set_req_X( 1, new_bol, igvn );
567 }
568
569 //------------------------------up_one_dom-------------------------------------
570 // Walk up the dominator tree one step. Return NULL at root or true
571 // complex merges. Skips through small diamonds.
572 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
573 Node *dom = curr->in(0);
574 if( !dom ) // Found a Region degraded to a copy?
575 return curr->nonnull_req(); // Skip thru it
576
577 if( curr != dom ) // Normal walk up one step?
578 return dom;
579
580 // Use linear_only if we are still parsing, since we cannot
581 // trust the regions to be fully filled in.
582 if (linear_only)
583 return NULL;
584
585 if( dom->is_Root() )
586 return NULL;
587
588 // Else hit a Region. Check for a loop header
589 if( dom->is_Loop() )
590 return dom->in(1); // Skip up thru loops
591
592 // Check for small diamonds
593 Node *din1, *din2, *din3, *din4;
594 if( dom->req() == 3 && // 2-path merge point
595 (din1 = dom ->in(1)) && // Left path exists
596 (din2 = dom ->in(2)) && // Right path exists
597 (din3 = din1->in(0)) && // Left path up one
598 (din4 = din2->in(0)) ) { // Right path up one
599 if( din3->is_Call() && // Handle a slow-path call on either arm
600 (din3 = din3->in(0)) )
601 din3 = din3->in(0);
602 if( din4->is_Call() && // Handle a slow-path call on either arm
603 (din4 = din4->in(0)) )
604 din4 = din4->in(0);
605 if( din3 == din4 && din3->is_If() )
606 return din3; // Skip around diamonds
607 }
608
609 // Give up the search at true merges
610 return NULL; // Dead loop? Or hit root?
611 }
612
613 bool IfNode::is_shenandoah_marking_if(PhaseTransform *phase) const {
614 if (!UseShenandoahGC) {
615 return false;
616 }
617
618 if (Opcode() != Op_If) {
619 return false;
620 }
621
622 Node* bol = in(1);
623 assert(bol->is_Bool(), "");
624 Node* cmpx = bol->in(1);
625 if (bol->as_Bool()->_test._test == BoolTest::ne &&
626 cmpx->is_Cmp() && cmpx->in(2) == phase->intcon(0) &&
627 cmpx->in(1)->in(1)->is_shenandoah_state_load() &&
628 cmpx->in(1)->in(2)->is_Con() &&
629 cmpx->in(1)->in(2) == phase->intcon(ShenandoahHeap::MARKING)) {
630 return true;
631 }
632
633 return false;
634 }
635
636
637 //------------------------------filtered_int_type--------------------------------
638 // Return a possibly more restrictive type for val based on condition control flow for an if
639 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
640 assert(if_proj &&
641 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
642 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
643 IfNode* iff = if_proj->in(0)->as_If();
644 if (iff->in(1) && iff->in(1)->is_Bool()) {
645 BoolNode* bol = iff->in(1)->as_Bool();
646 if (bol->in(1) && bol->in(1)->is_Cmp()) {
647 const CmpNode* cmp = bol->in(1)->as_Cmp();
648 if (cmp->in(1) == val) {
649 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
650 if (cmp2_t != NULL) {
651 jint lo = cmp2_t->_lo;
652 jint hi = cmp2_t->_hi;
653 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
654 switch (msk) {
655 case BoolTest::ne:
656 // Can't refine type
657 return NULL;
658 case BoolTest::eq:
659 return cmp2_t;
660 case BoolTest::lt:
661 lo = TypeInt::INT->_lo;
662 if (hi - 1 < hi) {
663 hi = hi - 1;
664 }
665 break;
666 case BoolTest::le:
667 lo = TypeInt::INT->_lo;
668 break;
669 case BoolTest::gt:
670 if (lo + 1 > lo) {
671 lo = lo + 1;
672 }
673 hi = TypeInt::INT->_hi;
674 break;
675 case BoolTest::ge:
676 // lo unchanged
677 hi = TypeInt::INT->_hi;
678 break;
679 }
680 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
681 return rtn_t;
682 }
683 }
684 }
685 }
686 }
687 return NULL;
688 }
689
690 //------------------------------fold_compares----------------------------
691 // See if a pair of CmpIs can be converted into a CmpU. In some cases
692 // the direction of this if is determined by the preceding if so it
693 // can be eliminate entirely. Given an if testing (CmpI n c) check
694 // for an immediately control dependent if that is testing (CmpI n c2)
695 // and has one projection leading to this if and the other projection
696 // leading to a region that merges one of this ifs control
697 // projections.
698 //
699 // If
700 // / |
701 // / |
702 // / |
703 // If |
704 // /\ |
705 // / \ |
706 // / \ |
707 // / Region
708 //
709 Node* IfNode::fold_compares(PhaseGVN* phase) {
710 if (Opcode() != Op_If) return NULL;
711
712 Node* this_cmp = in(1)->in(1);
713 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
714 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
715 Node* ctrl = in(0);
716 BoolNode* this_bool = in(1)->as_Bool();
717 Node* n = this_cmp->in(1);
718 int hi = this_cmp->in(2)->get_int();
719 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
720 ctrl->in(0)->is_If() &&
721 ctrl->in(0)->outcnt() == 2 &&
722 ctrl->in(0)->in(1)->is_Bool() &&
723 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
724 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
725 ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
726 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
727 IfNode* dom_iff = ctrl->in(0)->as_If();
728 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
729 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
730 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
731 // Identify which proj goes to the region and which continues on
732 RegionNode* region = otherproj->unique_out()->as_Region();
733 Node* success = NULL;
734 Node* fail = NULL;
735 for (int i = 0; i < 2; i++) {
736 Node* proj = proj_out(i);
737 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
738 success = proj;
739 } else if (fail == NULL) {
740 fail = proj;
741 } else {
742 success = fail = NULL;
743 }
744 }
745 if (success != NULL && fail != NULL && !region->has_phi()) {
746 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
747 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
748 Node* dom_cmp = dom_bool->in(1);
749 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
750 if (failtype != NULL) {
751 const TypeInt* type2 = filtered_int_type(phase, n, fail);
752 if (type2 != NULL) {
753 failtype = failtype->join(type2)->is_int();
754 } else {
755 failtype = NULL;
756 }
757 }
758
759 if (failtype != NULL &&
760 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
761 int bound = failtype->_hi - failtype->_lo + 1;
762 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
763 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
764 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
765 Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo)));
766 Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound)));
767 Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond));
768 phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
769 phase->hash_delete(this);
770 set_req(1, newbool);
771 return this;
772 }
773 if (failtype->_lo > failtype->_hi) {
774 // previous if determines the result of this if so
775 // replace Bool with constant
776 phase->hash_delete(this);
777 set_req(1, phase->intcon(success->as_Proj()->_con));
778 return this;
779 }
780 }
781 }
782 }
783 }
784 }
785 return NULL;
786 }
787
788 //------------------------------remove_useless_bool----------------------------
789 // Check for people making a useless boolean: things like
790 // if( (x < y ? true : false) ) { ... }
791 // Replace with if( x < y ) { ... }
792 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
793 Node *i1 = iff->in(1);
794 if( !i1->is_Bool() ) return NULL;
795 BoolNode *bol = i1->as_Bool();
796
797 Node *cmp = bol->in(1);
798 if( cmp->Opcode() != Op_CmpI ) return NULL;
799
800 // Must be comparing against a bool
801 const Type *cmp2_t = phase->type( cmp->in(2) );
802 if( cmp2_t != TypeInt::ZERO &&
803 cmp2_t != TypeInt::ONE )
804 return NULL;
805
806 // Find a prior merge point merging the boolean
807 i1 = cmp->in(1);
808 if( !i1->is_Phi() ) return NULL;
809 PhiNode *phi = i1->as_Phi();
810 if( phase->type( phi ) != TypeInt::BOOL )
811 return NULL;
812
813 // Check for diamond pattern
814 int true_path = phi->is_diamond_phi();
815 if( true_path == 0 ) return NULL;
816
817 // Make sure that iff and the control of the phi are different. This
818 // should really only happen for dead control flow since it requires
819 // an illegal cycle.
820 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
821
822 // phi->region->if_proj->ifnode->bool->cmp
823 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
824
825 // Now get the 'sense' of the test correct so we can plug in
826 // either iff2->in(1) or its complement.
827 int flip = 0;
828 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
829 else if( bol->_test._test != BoolTest::eq ) return NULL;
830 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
831
832 const Type *phi1_t = phase->type( phi->in(1) );
833 const Type *phi2_t = phase->type( phi->in(2) );
834 // Check for Phi(0,1) and flip
835 if( phi1_t == TypeInt::ZERO ) {
836 if( phi2_t != TypeInt::ONE ) return NULL;
837 flip = 1-flip;
838 } else {
839 // Check for Phi(1,0)
840 if( phi1_t != TypeInt::ONE ) return NULL;
841 if( phi2_t != TypeInt::ZERO ) return NULL;
842 }
843 if( true_path == 2 ) {
844 flip = 1-flip;
845 }
846
847 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
848 assert(new_bol != iff->in(1), "must make progress");
849 iff->set_req(1, new_bol);
850 // Intervening diamond probably goes dead
851 phase->C->set_major_progress();
852 return iff;
853 }
854
855 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
856
857 struct RangeCheck {
858 Node* ctl;
859 jint off;
860 };
861
862 //------------------------------Ideal------------------------------------------
863 // Return a node which is more "ideal" than the current node. Strip out
864 // control copies
865 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
866 if (remove_dead_region(phase, can_reshape)) return this;
867 // No Def-Use info?
868 if (!can_reshape) return NULL;
869 PhaseIterGVN *igvn = phase->is_IterGVN();
870
871 // Don't bother trying to transform a dead if
872 if (in(0)->is_top()) return NULL;
873 // Don't bother trying to transform an if with a dead test
874 if (in(1)->is_top()) return NULL;
875 // Another variation of a dead test
876 if (in(1)->is_Con()) return NULL;
877 // Another variation of a dead if
878 if (outcnt() < 2) return NULL;
879
880 // Canonicalize the test.
881 Node* idt_if = idealize_test(phase, this);
882 if (idt_if != NULL) return idt_if;
883
884 // Try to split the IF
885 Node *s = split_if(this, igvn);
886 if (s != NULL) return s;
887
888 // Check for people making a useless boolean: things like
889 // if( (x < y ? true : false) ) { ... }
890 // Replace with if( x < y ) { ... }
891 Node *bol2 = remove_useless_bool(this, phase);
892 if( bol2 ) return bol2;
893
894 // Setup to scan up the CFG looking for a dominating test
895 Node *dom = in(0);
896 Node *prev_dom = this;
897
898 // Check for range-check vs other kinds of tests
899 Node *index1, *range1;
900 jint offset1;
901 int flip1 = is_range_check(range1, index1, offset1);
902 if( flip1 ) {
903 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
904 // so all checks we inspect post-dominate the top-most check we find.
905 // If we are going to fail the current check and we reach the top check
906 // then we are guaranteed to fail, so just start interpreting there.
907 // We 'expand' the top 3 range checks to include all post-dominating
908 // checks.
909
910 // The top 3 range checks seen
911 const int NRC =3;
912 RangeCheck prev_checks[NRC];
913 int nb_checks = 0;
914
915 // Low and high offsets seen so far
916 jint off_lo = offset1;
917 jint off_hi = offset1;
918
919 bool found_immediate_dominator = false;
920
921 // Scan for the top checks and collect range of offsets
922 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
923 if (dom->Opcode() == Op_If && // Not same opcode?
924 prev_dom->in(0) == dom) { // One path of test does dominate?
925 if (dom == this) return NULL; // dead loop
926 // See if this is a range check
927 Node *index2, *range2;
928 jint offset2;
929 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
930 // See if this is a _matching_ range check, checking against
931 // the same array bounds.
932 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
933 dom->outcnt() == 2) {
934 if (nb_checks == 0 && dom->in(1) == in(1)) {
935 // Found an immediately dominating test at the same offset.
936 // This kind of back-to-back test can be eliminated locally,
937 // and there is no need to search further for dominating tests.
938 assert(offset2 == offset1, "Same test but different offsets");
939 found_immediate_dominator = true;
940 break;
941 }
942 // Gather expanded bounds
943 off_lo = MIN2(off_lo,offset2);
944 off_hi = MAX2(off_hi,offset2);
945 // Record top NRC range checks
946 prev_checks[nb_checks%NRC].ctl = prev_dom;
947 prev_checks[nb_checks%NRC].off = offset2;
948 nb_checks++;
949 }
950 }
951 prev_dom = dom;
952 dom = up_one_dom(dom);
953 if (!dom) break;
954 }
955
956 if (!found_immediate_dominator) {
957 // Attempt to widen the dominating range check to cover some later
958 // ones. Since range checks "fail" by uncommon-trapping to the
959 // interpreter, widening a check can make us speculatively enter
960 // the interpreter. If we see range-check deopt's, do not widen!
961 if (!phase->C->allow_range_check_smearing()) return NULL;
962
963 // Didn't find prior covering check, so cannot remove anything.
964 if (nb_checks == 0) {
965 return NULL;
966 }
967 // Constant indices only need to check the upper bound.
968 // Non-constant indices must check both low and high.
969 int chk0 = (nb_checks - 1) % NRC;
970 if (index1) {
971 if (nb_checks == 1) {
972 return NULL;
973 } else {
974 // If the top range check's constant is the min or max of
975 // all constants we widen the next one to cover the whole
976 // range of constants.
977 RangeCheck rc0 = prev_checks[chk0];
978 int chk1 = (nb_checks - 2) % NRC;
979 RangeCheck rc1 = prev_checks[chk1];
980 if (rc0.off == off_lo) {
981 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
982 prev_dom = rc1.ctl;
983 } else if (rc0.off == off_hi) {
984 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
985 prev_dom = rc1.ctl;
986 } else {
987 // If the top test's constant is not the min or max of all
988 // constants, we need 3 range checks. We must leave the
989 // top test unchanged because widening it would allow the
990 // accesses it protects to successfully read/write out of
991 // bounds.
992 if (nb_checks == 2) {
993 return NULL;
994 }
995 int chk2 = (nb_checks - 3) % NRC;
996 RangeCheck rc2 = prev_checks[chk2];
997 // The top range check a+i covers interval: -a <= i < length-a
998 // The second range check b+i covers interval: -b <= i < length-b
999 if (rc1.off <= rc0.off) {
1000 // if b <= a, we change the second range check to:
1001 // -min_of_all_constants <= i < length-min_of_all_constants
1002 // Together top and second range checks now cover:
1003 // -min_of_all_constants <= i < length-a
1004 // which is more restrictive than -b <= i < length-b:
1005 // -b <= -min_of_all_constants <= i < length-a <= length-b
1006 // The third check is then changed to:
1007 // -max_of_all_constants <= i < length-max_of_all_constants
1008 // so 2nd and 3rd checks restrict allowed values of i to:
1009 // -min_of_all_constants <= i < length-max_of_all_constants
1010 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1011 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1012 } else {
1013 // if b > a, we change the second range check to:
1014 // -max_of_all_constants <= i < length-max_of_all_constants
1015 // Together top and second range checks now cover:
1016 // -a <= i < length-max_of_all_constants
1017 // which is more restrictive than -b <= i < length-b:
1018 // -b < -a <= i < length-max_of_all_constants <= length-b
1019 // The third check is then changed to:
1020 // -max_of_all_constants <= i < length-max_of_all_constants
1021 // so 2nd and 3rd checks restrict allowed values of i to:
1022 // -min_of_all_constants <= i < length-max_of_all_constants
1023 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1024 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1025 }
1026 prev_dom = rc2.ctl;
1027 }
1028 }
1029 } else {
1030 RangeCheck rc0 = prev_checks[chk0];
1031 // 'Widen' the offset of the 1st and only covering check
1032 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1033 // Test is now covered by prior checks, dominate it out
1034 prev_dom = rc0.ctl;
1035 }
1036 }
1037
1038 } else { // Scan for an equivalent test
1039
1040 Node *cmp;
1041 int dist = 0; // Cutoff limit for search
1042 int op = Opcode();
1043 if( op == Op_If &&
1044 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1045 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1046 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1047 dist = 64; // Limit for null-pointer scans
1048 } else {
1049 dist = 4; // Do not bother for random pointer tests
1050 }
1051 } else {
1052 dist = 4; // Limit for random junky scans
1053 }
1054
1055 // Normal equivalent-test check.
1056 if( !dom ) return NULL; // Dead loop?
1057
1058 Node* result = fold_compares(phase);
1059 if (result != NULL) {
1060 return result;
1061 }
1062
1063 // Search up the dominator tree for an If with an identical test
1064 while( dom->Opcode() != op || // Not same opcode?
1065 dom->in(1) != in(1) || // Not same input 1?
1066 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1067 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1068 if( dist < 0 ) return NULL;
1069
1070 dist--;
1071 prev_dom = dom;
1072 dom = up_one_dom( dom );
1073 if( !dom ) return NULL;
1074 }
1075
1076 // Check that we did not follow a loop back to ourselves
1077 if( this == dom )
1078 return NULL;
1079
1080 if( dist > 2 ) // Add to count of NULL checks elided
1081 explicit_null_checks_elided++;
1082
1083 } // End of Else scan for an equivalent test
1084
1085 // Hit! Remove this IF
1086 #ifndef PRODUCT
1087 if( TraceIterativeGVN ) {
1088 tty->print(" Removing IfNode: "); this->dump();
1089 }
1090 if( VerifyOpto && !phase->allow_progress() ) {
1091 // Found an equivalent dominating test,
1092 // we can not guarantee reaching a fix-point for these during iterativeGVN
1093 // since intervening nodes may not change.
1094 return NULL;
1095 }
1096 #endif
1097
1098 // Replace dominated IfNode
1099 dominated_by( prev_dom, igvn );
1100
1101 // Must return either the original node (now dead) or a new node
1102 // (Do not return a top here, since that would break the uniqueness of top.)
1103 return new (phase->C) ConINode(TypeInt::ZERO);
1104 }
1105
1106 //------------------------------dominated_by-----------------------------------
1107 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1108 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1109 Node *idom = in(0);
1110 // Need opcode to decide which way 'this' test goes
1111 int prev_op = prev_dom->Opcode();
1112 Node *top = igvn->C->top(); // Shortcut to top
1113
1114 // Loop predicates may have depending checks which should not
1115 // be skipped. For example, range check predicate has two checks
1116 // for lower and upper bounds.
1117 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1118 if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))) {
1119 prev_dom = idom;
1120 }
1121
1122 // Now walk the current IfNode's projections.
1123 // Loop ends when 'this' has no more uses.
1124 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1125 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1126 igvn->add_users_to_worklist(ifp);
1127 // Check which projection it is and set target.
1128 // Data-target is either the dominating projection of the same type
1129 // or TOP if the dominating projection is of opposite type.
1130 // Data-target will be used as the new control edge for the non-CFG
1131 // nodes like Casts and Loads.
1132 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1133 // Control-target is just the If's immediate dominator or TOP.
1134 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1135
1136 // For each child of an IfTrue/IfFalse projection, reroute.
1137 // Loop ends when projection has no more uses.
1138 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1139 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1140 if( !s->depends_only_on_test() ) {
1141 // Find the control input matching this def-use edge.
1142 // For Regions it may not be in slot 0.
1143 uint l;
1144 for( l = 0; s->in(l) != ifp; l++ ) { }
1145 igvn->replace_input_of(s, l, ctrl_target);
1146 } else { // Else, for control producers,
1147 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1148 }
1149 } // End for each child of a projection
1150
1151 igvn->remove_dead_node(ifp);
1152 } // End for each IfTrue/IfFalse child of If
1153
1154 // Kill the IfNode
1155 igvn->remove_dead_node(this);
1156 }
1157
1158 //------------------------------Identity---------------------------------------
1159 // If the test is constant & we match, then we are the input Control
1160 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1161 // Can only optimize if cannot go the other way
1162 const TypeTuple *t = phase->type(in(0))->is_tuple();
1163 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1164 ? in(0)->in(0) // IfNode control
1165 : this; // no progress
1166 }
1167
1168 //------------------------------dump_spec--------------------------------------
1169 #ifndef PRODUCT
1170 void IfNode::dump_spec(outputStream *st) const {
1171 st->print("P=%f, C=%f",_prob,_fcnt);
1172 }
1173 #endif
1174
1175 //------------------------------idealize_test----------------------------------
1176 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1177 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1178 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1179 // needed.
1180 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1181 assert(iff->in(0) != NULL, "If must be live");
1182
1183 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1184 Node* old_if_f = iff->proj_out(false);
1185 Node* old_if_t = iff->proj_out(true);
1186
1187 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1188 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1189 // happens in count-down loops
1190 if (iff->is_CountedLoopEnd()) return NULL;
1191 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1192 BoolNode *b = iff->in(1)->as_Bool();
1193 BoolTest bt = b->_test;
1194 // Test already in good order?
1195 if( bt.is_canonical() )
1196 return NULL;
1197
1198 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1199 // cloning the IfNode.
1200 Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) );
1201 if( !new_b->is_Bool() ) return NULL;
1202 b = new_b->as_Bool();
1203
1204 PhaseIterGVN *igvn = phase->is_IterGVN();
1205 assert( igvn, "Test is not canonical in parser?" );
1206
1207 // The IF node never really changes, but it needs to be cloned
1208 iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1209
1210 Node *prior = igvn->hash_find_insert(iff);
1211 if( prior ) {
1212 igvn->remove_dead_node(iff);
1213 iff = (IfNode*)prior;
1214 } else {
1215 // Cannot call transform on it just yet
1216 igvn->set_type_bottom(iff);
1217 }
1218 igvn->_worklist.push(iff);
1219
1220 // Now handle projections. Cloning not required.
1221 Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff ));
1222 Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff ));
1223
1224 igvn->register_new_node_with_optimizer(new_if_f);
1225 igvn->register_new_node_with_optimizer(new_if_t);
1226 // Flip test, so flip trailing control
1227 igvn->replace_node(old_if_f, new_if_t);
1228 igvn->replace_node(old_if_t, new_if_f);
1229
1230 // Progress
1231 return iff;
1232 }
1233
1234 //------------------------------Identity---------------------------------------
1235 // If the test is constant & we match, then we are the input Control
1236 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1237 // Can only optimize if cannot go the other way
1238 const TypeTuple *t = phase->type(in(0))->is_tuple();
1239 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1240 ? in(0)->in(0) // IfNode control
1241 : this; // no progress
1242 }