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/castnode.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/rootnode.hpp"
35 #include "opto/subnode.hpp"
36
37 // Portions of code courtesy of Clifford Click
38
39 // Optimization - Graph Style
40
41
42 extern int explicit_null_checks_elided;
43
44 //=============================================================================
45 //------------------------------Value------------------------------------------
46 // Return a tuple for whichever arm of the IF is reachable
47 const Type *IfNode::Value( PhaseTransform *phase ) const {
48 if( !in(0) ) return Type::TOP;
49 if( phase->type(in(0)) == Type::TOP )
50 return Type::TOP;
51 const Type *t = phase->type(in(1));
52 if( t == Type::TOP ) // data is undefined
53 return TypeTuple::IFNEITHER; // unreachable altogether
54 if( t == TypeInt::ZERO ) // zero, or false
55 return TypeTuple::IFFALSE; // only false branch is reachable
56 if( t == TypeInt::ONE ) // 1, or true
57 return TypeTuple::IFTRUE; // only true branch is reachable
58 assert( t == TypeInt::BOOL, "expected boolean type" );
59
60 return TypeTuple::IFBOTH; // No progress
61 }
62
63 const RegMask &IfNode::out_RegMask() const {
64 return RegMask::Empty;
65 }
66
67 //------------------------------split_if---------------------------------------
68 // Look for places where we merge constants, then test on the merged value.
69 // If the IF test will be constant folded on the path with the constant, we
70 // win by splitting the IF to before the merge point.
71 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
72 // I could be a lot more general here, but I'm trying to squeeze this
73 // in before the Christmas '98 break so I'm gonna be kinda restrictive
74 // on the patterns I accept. CNC
75
76 // Look for a compare of a constant and a merged value
77 Node *i1 = iff->in(1);
78 if( !i1->is_Bool() ) return NULL;
79 BoolNode *b = i1->as_Bool();
80 Node *cmp = b->in(1);
81 if( !cmp->is_Cmp() ) return NULL;
82 i1 = cmp->in(1);
83 if( i1 == NULL || !i1->is_Phi() ) return NULL;
84 PhiNode *phi = i1->as_Phi();
85 if( phi->is_copy() ) return NULL;
86 Node *con2 = cmp->in(2);
87 if( !con2->is_Con() ) return NULL;
88 // See that the merge point contains some constants
89 Node *con1=NULL;
90 uint i4;
91 for( i4 = 1; i4 < phi->req(); i4++ ) {
92 con1 = phi->in(i4);
93 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
94 if( con1->is_Con() ) break; // Found a constant
95 // Also allow null-vs-not-null checks
96 const TypePtr *tp = igvn->type(con1)->isa_ptr();
97 if( tp && tp->_ptr == TypePtr::NotNull )
98 break;
99 }
100 if( i4 >= phi->req() ) return NULL; // Found no constants
101
102 igvn->C->set_has_split_ifs(true); // Has chance for split-if
103
104 // Make sure that the compare can be constant folded away
105 Node *cmp2 = cmp->clone();
106 cmp2->set_req(1,con1);
107 cmp2->set_req(2,con2);
108 const Type *t = cmp2->Value(igvn);
109 // This compare is dead, so whack it!
110 igvn->remove_dead_node(cmp2);
111 if( !t->singleton() ) return NULL;
112
113 // No intervening control, like a simple Call
114 Node *r = iff->in(0);
115 if( !r->is_Region() ) return NULL;
116 if( phi->region() != r ) return NULL;
117 // No other users of the cmp/bool
118 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
119 //tty->print_cr("many users of cmp/bool");
120 return NULL;
121 }
122
123 // Make sure we can determine where all the uses of merged values go
124 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
125 Node* u = r->fast_out(j);
126 if( u == r ) continue;
127 if( u == iff ) continue;
128 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
129 if( !u->is_Phi() ) {
130 /*
131 if( u->is_Start() ) {
132 tty->print_cr("Region has inlined start use");
133 } else {
134 tty->print_cr("Region has odd use");
135 u->dump(2);
136 }*/
137 return NULL;
138 }
139 if( u != phi ) {
140 // CNC - do not allow any other merged value
141 //tty->print_cr("Merging another value");
142 //u->dump(2);
143 return NULL;
144 }
145 // Make sure we can account for all Phi uses
146 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
147 Node* v = u->fast_out(k); // User of the phi
148 // CNC - Allow only really simple patterns.
149 // In particular I disallow AddP of the Phi, a fairly common pattern
150 if (v == cmp) continue; // The compare is OK
151 if (v->is_ConstraintCast()) {
152 // If the cast is derived from data flow edges, it may not have a control edge.
153 // If so, it should be safe to split. But follow-up code can not deal with
154 // this (l. 359). So skip.
155 if (v->in(0) == NULL) {
156 return NULL;
157 }
158 if (v->in(0)->in(0) == iff) {
159 continue; // CastPP/II of the IfNode is OK
160 }
161 }
162 // Disabled following code because I cannot tell if exactly one
163 // path dominates without a real dominator check. CNC 9/9/1999
164 //uint vop = v->Opcode();
165 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
166 // Node *r = v->in(0); // Get controlling point
167 // if( !r ) return NULL; // Degraded to a copy
168 // // Find exactly one path in (either True or False doms, but not IFF)
169 // int cnt = 0;
170 // for( uint i = 1; i < r->req(); i++ )
171 // if( r->in(i) && r->in(i)->in(0) == iff )
172 // cnt++;
173 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
174 //}
175 if( !v->is_Call() ) {
176 /*
177 if( v->Opcode() == Op_AddP ) {
178 tty->print_cr("Phi has AddP use");
179 } else if( v->Opcode() == Op_CastPP ) {
180 tty->print_cr("Phi has CastPP use");
181 } else if( v->Opcode() == Op_CastII ) {
182 tty->print_cr("Phi has CastII use");
183 } else {
184 tty->print_cr("Phi has use I cant be bothered with");
185 }
186 */
187 }
188 return NULL;
189
190 /* CNC - Cut out all the fancy acceptance tests
191 // Can we clone this use when doing the transformation?
192 // If all uses are from Phis at this merge or constants, then YES.
193 if( !v->in(0) && v != cmp ) {
194 tty->print_cr("Phi has free-floating use");
195 v->dump(2);
196 return NULL;
197 }
198 for( uint l = 1; l < v->req(); l++ ) {
199 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
200 !v->in(l)->is_Con() ) {
201 tty->print_cr("Phi has use");
202 v->dump(2);
203 return NULL;
204 } // End of if Phi-use input is neither Phi nor Constant
205 } // End of for all inputs to Phi-use
206 */
207 } // End of for all uses of Phi
208 } // End of for all uses of Region
209
210 // Only do this if the IF node is in a sane state
211 if (iff->outcnt() != 2)
212 return NULL;
213
214 // Got a hit! Do the Mondo Hack!
215 //
216 //ABC a1c def ghi B 1 e h A C a c d f g i
217 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
218 // cmp - 2 cmp - 2 cmp - 2
219 // bool bool_c bool_x
220 // if if_c if_x
221 // T F T F T F
222 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
223 //
224 // Split the paths coming into the merge point into 2 separate groups of
225 // merges. On the left will be all the paths feeding constants into the
226 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
227 // will fold up into a constant; this will let the Cmp fold up as well as
228 // all the control flow. Below the original IF we have 2 control
229 // dependent regions, 's' and 't'. Now we will merge the two paths
230 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
231 // likely 2 or more) will promptly constant fold away.
232 PhaseGVN *phase = igvn;
233
234 // Make a region merging constants and a region merging the rest
235 uint req_c = 0;
236 Node* predicate_proj = NULL;
237 int nb_predicate_proj = 0;
238 for (uint ii = 1; ii < r->req(); ii++) {
239 if (phi->in(ii) == con1) {
240 req_c++;
241 }
242 Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
243 if (proj != NULL) {
244 nb_predicate_proj++;
245 predicate_proj = proj;
246 }
247 }
248 if (nb_predicate_proj > 1) {
249 // Can happen in case of loop unswitching and when the loop is
250 // optimized out: it's not a loop anymore so we don't care about
251 // predicates.
252 assert(!r->is_Loop(), "this must not be a loop anymore");
253 predicate_proj = NULL;
254 }
255 Node* predicate_c = NULL;
256 Node* predicate_x = NULL;
257 bool counted_loop = r->is_CountedLoop();
258
259 Node *region_c = new RegionNode(req_c + 1);
260 Node *phi_c = con1;
261 uint len = r->req();
262 Node *region_x = new RegionNode(len - req_c);
263 Node *phi_x = PhiNode::make_blank(region_x, phi);
264 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
265 if (phi->in(i) == con1) {
266 region_c->init_req( i_c++, r ->in(i) );
267 if (r->in(i) == predicate_proj)
268 predicate_c = predicate_proj;
269 } else {
270 region_x->init_req( i_x, r ->in(i) );
271 phi_x ->init_req( i_x++, phi->in(i) );
272 if (r->in(i) == predicate_proj)
273 predicate_x = predicate_proj;
274 }
275 }
276 if (predicate_c != NULL && (req_c > 1)) {
277 assert(predicate_x == NULL, "only one predicate entry expected");
278 predicate_c = NULL; // Do not clone predicate below merge point
279 }
280 if (predicate_x != NULL && ((len - req_c) > 2)) {
281 assert(predicate_c == NULL, "only one predicate entry expected");
282 predicate_x = NULL; // Do not clone predicate below merge point
283 }
284
285 // Register the new RegionNodes but do not transform them. Cannot
286 // transform until the entire Region/Phi conglomerate has been hacked
287 // as a single huge transform.
288 igvn->register_new_node_with_optimizer( region_c );
289 igvn->register_new_node_with_optimizer( region_x );
290 // Prevent the untimely death of phi_x. Currently he has no uses. He is
291 // about to get one. If this only use goes away, then phi_x will look dead.
292 // However, he will be picking up some more uses down below.
293 Node *hook = new Node(4);
294 hook->init_req(0, phi_x);
295 hook->init_req(1, phi_c);
296 phi_x = phase->transform( phi_x );
297
298 // Make the compare
299 Node *cmp_c = phase->makecon(t);
300 Node *cmp_x = cmp->clone();
301 cmp_x->set_req(1,phi_x);
302 cmp_x->set_req(2,con2);
303 cmp_x = phase->transform(cmp_x);
304 // Make the bool
305 Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
306 Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
307 // Make the IfNode
308 IfNode *iff_c = new IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
309 igvn->set_type_bottom(iff_c);
310 igvn->_worklist.push(iff_c);
311 hook->init_req(2, iff_c);
312
313 IfNode *iff_x = new IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
314 igvn->set_type_bottom(iff_x);
315 igvn->_worklist.push(iff_x);
316 hook->init_req(3, iff_x);
317
318 // Make the true/false arms
319 Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
320 Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
321 if (predicate_c != NULL) {
322 assert(predicate_x == NULL, "only one predicate entry expected");
323 // Clone loop predicates to each path
324 iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
325 iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
326 }
327 Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
328 Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
329 if (predicate_x != NULL) {
330 assert(predicate_c == NULL, "only one predicate entry expected");
331 // Clone loop predicates to each path
332 iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
333 iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
334 }
335
336 // Merge the TRUE paths
337 Node *region_s = new RegionNode(3);
338 igvn->_worklist.push(region_s);
339 region_s->init_req(1, iff_c_t);
340 region_s->init_req(2, iff_x_t);
341 igvn->register_new_node_with_optimizer( region_s );
342
343 // Merge the FALSE paths
344 Node *region_f = new RegionNode(3);
345 igvn->_worklist.push(region_f);
346 region_f->init_req(1, iff_c_f);
347 region_f->init_req(2, iff_x_f);
348 igvn->register_new_node_with_optimizer( region_f );
349
350 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
351 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
352 cmp->set_req(2,NULL);
353 // Check for all uses of the Phi and give them a new home.
354 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
355 Node *phi_s = NULL; // do not construct unless needed
356 Node *phi_f = NULL; // do not construct unless needed
357 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
358 Node* v = phi->last_out(i2);// User of the phi
359 igvn->rehash_node_delayed(v); // Have to fixup other Phi users
360 uint vop = v->Opcode();
361 Node *proj = NULL;
362 if( vop == Op_Phi ) { // Remote merge point
363 Node *r = v->in(0);
364 for (uint i3 = 1; i3 < r->req(); i3++)
365 if (r->in(i3) && r->in(i3)->in(0) == iff) {
366 proj = r->in(i3);
367 break;
368 }
369 } else if( v->is_ConstraintCast() ) {
370 proj = v->in(0); // Controlling projection
371 } else {
372 assert( 0, "do not know how to handle this guy" );
373 }
374
375 Node *proj_path_data, *proj_path_ctrl;
376 if( proj->Opcode() == Op_IfTrue ) {
377 if( phi_s == NULL ) {
378 // Only construct phi_s if needed, otherwise provides
379 // interfering use.
380 phi_s = PhiNode::make_blank(region_s,phi);
381 phi_s->init_req( 1, phi_c );
382 phi_s->init_req( 2, phi_x );
383 hook->add_req(phi_s);
384 phi_s = phase->transform(phi_s);
385 }
386 proj_path_data = phi_s;
387 proj_path_ctrl = region_s;
388 } else {
389 if( phi_f == NULL ) {
390 // Only construct phi_f if needed, otherwise provides
391 // interfering use.
392 phi_f = PhiNode::make_blank(region_f,phi);
393 phi_f->init_req( 1, phi_c );
394 phi_f->init_req( 2, phi_x );
395 hook->add_req(phi_f);
396 phi_f = phase->transform(phi_f);
397 }
398 proj_path_data = phi_f;
399 proj_path_ctrl = region_f;
400 }
401
402 // Fixup 'v' for for the split
403 if( vop == Op_Phi ) { // Remote merge point
404 uint i;
405 for( i = 1; i < v->req(); i++ )
406 if( v->in(i) == phi )
407 break;
408 v->set_req(i, proj_path_data );
409 } else if( v->is_ConstraintCast() ) {
410 v->set_req(0, proj_path_ctrl );
411 v->set_req(1, proj_path_data );
412 } else
413 ShouldNotReachHere();
414 }
415
416 // Now replace the original iff's True/False with region_s/region_t.
417 // This makes the original iff go dead.
418 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
419 Node* p = iff->last_out(i3);
420 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
421 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
422 // Replace p with u
423 igvn->add_users_to_worklist(p);
424 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
425 Node* x = p->last_out(l);
426 igvn->hash_delete(x);
427 uint uses_found = 0;
428 for( uint j = 0; j < x->req(); j++ ) {
429 if( x->in(j) == p ) {
430 x->set_req(j, u);
431 uses_found++;
432 }
433 }
434 l -= uses_found; // we deleted 1 or more copies of this edge
435 }
436 igvn->remove_dead_node(p);
437 }
438
439 // Force the original merge dead
440 igvn->hash_delete(r);
441 // First, remove region's dead users.
442 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
443 Node* u = r->last_out(l);
444 if( u == r ) {
445 r->set_req(0, NULL);
446 } else {
447 assert(u->outcnt() == 0, "only dead users");
448 igvn->remove_dead_node(u);
449 }
450 l -= 1;
451 }
452 igvn->remove_dead_node(r);
453
454 // Now remove the bogus extra edges used to keep things alive
455 igvn->remove_dead_node( hook );
456
457 // Must return either the original node (now dead) or a new node
458 // (Do not return a top here, since that would break the uniqueness of top.)
459 return new ConINode(TypeInt::ZERO);
460 }
461
462 // if this IfNode follows a range check pattern return the projection
463 // for the failed path
464 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
465 Node* b = in(1);
466 if (b == NULL || !b->is_Bool()) return NULL;
467 BoolNode* bn = b->as_Bool();
468 Node* cmp = bn->in(1);
469 if (cmp == NULL) return NULL;
470 if (cmp->Opcode() != Op_CmpU) return NULL;
471
472 l = cmp->in(1);
473 r = cmp->in(2);
474 flip_test = 1;
475 if (bn->_test._test == BoolTest::le) {
476 l = cmp->in(2);
477 r = cmp->in(1);
478 flip_test = 2;
479 } else if (bn->_test._test != BoolTest::lt) {
480 return NULL;
481 }
482 if (l->is_top()) return NULL; // Top input means dead test
483 if (r->Opcode() != Op_LoadRange) return NULL;
484
485 // We have recognized one of these forms:
486 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
487 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
488
489 ProjNode* iftrap = proj_out(flip_test == 2 ? true : false);
490 return iftrap;
491 }
492
493
494 //------------------------------is_range_check---------------------------------
495 // Return 0 if not a range check. Return 1 if a range check and set index and
496 // offset. Return 2 if we had to negate the test. Index is NULL if the check
497 // is versus a constant.
498 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
499 int flip_test = 0;
500 Node* l = NULL;
501 Node* r = NULL;
502 ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
503
504 if (iftrap == NULL) {
505 return 0;
506 }
507
508 // Make sure it's a real range check by requiring an uncommon trap
509 // along the OOB path. Otherwise, it's possible that the user wrote
510 // something which optimized to look like a range check but behaves
511 // in some other way.
512 if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == NULL) {
513 return 0;
514 }
515
516 // Look for index+offset form
517 Node* ind = l;
518 jint off = 0;
519 if (l->is_top()) {
520 return 0;
521 } else if (l->Opcode() == Op_AddI) {
522 if ((off = l->in(1)->find_int_con(0)) != 0) {
523 ind = l->in(2);
524 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
525 ind = l->in(1);
526 }
527 } else if ((off = l->find_int_con(-1)) >= 0) {
528 // constant offset with no variable index
529 ind = NULL;
530 } else {
531 // variable index with no constant offset (or dead negative index)
532 off = 0;
533 }
534
535 // Return all the values:
536 index = ind;
537 offset = off;
538 range = r;
539 return flip_test;
540 }
541
542 //------------------------------adjust_check-----------------------------------
543 // Adjust (widen) a prior range check
544 static void adjust_check(Node* proj, Node* range, Node* index,
545 int flip, jint off_lo, PhaseIterGVN* igvn) {
546 PhaseGVN *gvn = igvn;
547 // Break apart the old check
548 Node *iff = proj->in(0);
549 Node *bol = iff->in(1);
550 if( bol->is_top() ) return; // In case a partially dead range check appears
551 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
552 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
553 if( !bol->is_Bool() ) return;
554
555 Node *cmp = bol->in(1);
556 // Compute a new check
557 Node *new_add = gvn->intcon(off_lo);
558 if( index ) {
559 new_add = off_lo ? gvn->transform(new AddINode( index, new_add )) : index;
560 }
561 Node *new_cmp = (flip == 1)
562 ? new CmpUNode( new_add, range )
563 : new CmpUNode( range, new_add );
564 new_cmp = gvn->transform(new_cmp);
565 // See if no need to adjust the existing check
566 if( new_cmp == cmp ) return;
567 // Else, adjust existing check
568 Node *new_bol = gvn->transform( new BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
569 igvn->rehash_node_delayed( iff );
570 iff->set_req_X( 1, new_bol, igvn );
571 }
572
573 //------------------------------up_one_dom-------------------------------------
574 // Walk up the dominator tree one step. Return NULL at root or true
575 // complex merges. Skips through small diamonds.
576 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
577 Node *dom = curr->in(0);
578 if( !dom ) // Found a Region degraded to a copy?
579 return curr->nonnull_req(); // Skip thru it
580
581 if( curr != dom ) // Normal walk up one step?
582 return dom;
583
584 // Use linear_only if we are still parsing, since we cannot
585 // trust the regions to be fully filled in.
586 if (linear_only)
587 return NULL;
588
589 if( dom->is_Root() )
590 return NULL;
591
592 // Else hit a Region. Check for a loop header
593 if( dom->is_Loop() )
594 return dom->in(1); // Skip up thru loops
595
596 // Check for small diamonds
597 Node *din1, *din2, *din3, *din4;
598 if( dom->req() == 3 && // 2-path merge point
599 (din1 = dom ->in(1)) && // Left path exists
600 (din2 = dom ->in(2)) && // Right path exists
601 (din3 = din1->in(0)) && // Left path up one
602 (din4 = din2->in(0)) ) { // Right path up one
603 if( din3->is_Call() && // Handle a slow-path call on either arm
604 (din3 = din3->in(0)) )
605 din3 = din3->in(0);
606 if( din4->is_Call() && // Handle a slow-path call on either arm
607 (din4 = din4->in(0)) )
608 din4 = din4->in(0);
609 if( din3 == din4 && din3->is_If() )
610 return din3; // Skip around diamonds
611 }
612
613 // Give up the search at true merges
614 return NULL; // Dead loop? Or hit root?
615 }
616
617
618 //------------------------------filtered_int_type--------------------------------
619 // Return a possibly more restrictive type for val based on condition control flow for an if
620 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
621 assert(if_proj &&
622 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
623 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
624 IfNode* iff = if_proj->in(0)->as_If();
625 if (iff->in(1) && iff->in(1)->is_Bool()) {
626 BoolNode* bol = iff->in(1)->as_Bool();
627 if (bol->in(1) && bol->in(1)->is_Cmp()) {
628 const CmpNode* cmp = bol->in(1)->as_Cmp();
629 if (cmp->in(1) == val) {
630 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
631 if (cmp2_t != NULL) {
632 jint lo = cmp2_t->_lo;
633 jint hi = cmp2_t->_hi;
634 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
635 switch (msk) {
636 case BoolTest::ne:
637 // Can't refine type
638 return NULL;
639 case BoolTest::eq:
640 return cmp2_t;
641 case BoolTest::lt:
642 lo = TypeInt::INT->_lo;
643 if (hi - 1 < hi) {
644 hi = hi - 1;
645 }
646 break;
647 case BoolTest::le:
648 lo = TypeInt::INT->_lo;
649 break;
650 case BoolTest::gt:
651 if (lo + 1 > lo) {
652 lo = lo + 1;
653 }
654 hi = TypeInt::INT->_hi;
655 break;
656 case BoolTest::ge:
657 // lo unchanged
658 hi = TypeInt::INT->_hi;
659 break;
660 }
661 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
662 return rtn_t;
663 }
664 }
665 }
666 }
667 }
668 return NULL;
669 }
670
671 //------------------------------fold_compares----------------------------
672 // See if a pair of CmpIs can be converted into a CmpU. In some cases
673 // the direction of this if is determined by the preceding if so it
674 // can be eliminate entirely.
675 //
676 // Given an if testing (CmpI n v) check for an immediately control
677 // dependent if that is testing (CmpI n v2) and has one projection
678 // leading to this if and the other projection leading to a region
679 // that merges one of this ifs control projections.
680 //
681 // If
682 // / |
683 // / |
684 // / |
685 // If |
686 // /\ |
687 // / \ |
688 // / \ |
689 // / Region
690 //
691 // Or given an if testing (CmpI n v) check for a dominating if that is
692 // testing (CmpI n v2), both having one projection leading to an
693 // uncommon trap. Allow Another independent guard in between to cover
694 // an explicit range check:
695 // if (index < 0 || index >= array.length) {
696 // which may need a null check to guard the LoadRange
697 //
698 // If
699 // / \
700 // / \
701 // / \
702 // If unc
703 // /\
704 // / \
705 // / \
706 // / unc
707 //
708
709 // Is the comparison for this If suitable for folding?
710 bool IfNode::cmpi_folds(PhaseIterGVN* igvn) {
711 return in(1) != NULL &&
712 in(1)->is_Bool() &&
713 in(1)->in(1) != NULL &&
714 in(1)->in(1)->Opcode() == Op_CmpI &&
715 in(1)->in(1)->in(2) != NULL &&
716 in(1)->in(1)->in(2) != igvn->C->top() &&
717 (in(1)->as_Bool()->_test.is_less() ||
718 in(1)->as_Bool()->_test.is_greater());
719 }
720
721 // Is a dominating control suitable for folding with this if?
722 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
723 return ctrl != NULL &&
724 ctrl->is_Proj() &&
725 ctrl->in(0) != NULL &&
726 ctrl->in(0)->is_If() &&
727 ctrl->in(0)->outcnt() == 2 &&
728 ctrl->in(0)->as_If()->cmpi_folds(igvn) &&
729 // Must compare same value
730 ctrl->in(0)->in(1)->in(1)->in(1) != NULL &&
731 ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
732 }
733
734 // Do this If and the dominating If share a region?
735 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
736 ProjNode* otherproj = proj->other_if_proj();
737 Node* otherproj_ctrl_use = otherproj->unique_ctrl_out();
738 RegionNode* region = (otherproj_ctrl_use != NULL && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : NULL;
739 success = NULL;
740 fail = NULL;
741
742 if (otherproj->outcnt() == 1 && region != NULL && !region->has_phi()) {
743 for (int i = 0; i < 2; i++) {
744 ProjNode* proj = proj_out(i);
745 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
746 success = proj;
747 } else if (fail == NULL) {
748 fail = proj;
749 } else {
750 success = fail = NULL;
751 }
752 }
753 }
754 return success != NULL && fail != NULL;
755 }
756
757 // Return projection that leads to an uncommon trap if any
758 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call) const {
759 for (int i = 0; i < 2; i++) {
760 call = proj_out(i)->is_uncommon_trap_proj(Deoptimization::Reason_none);
761 if (call != NULL) {
762 return proj_out(i);
763 }
764 }
765 return NULL;
766 }
767
768 // Do this If and the dominating If both branch out to an uncommon trap
769 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
770 ProjNode* otherproj = proj->other_if_proj();
771 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
772
773 if (otherproj->outcnt() == 1 && dom_unc != NULL) {
774 CallStaticJavaNode* unc = NULL;
775 ProjNode* unc_proj = uncommon_trap_proj(unc);
776 if (unc_proj != NULL && unc_proj->outcnt() == 1) {
777 if (dom_unc == unc) {
778 // Allow the uncommon trap to be shared through a region
779 RegionNode* r = unc->in(0)->as_Region();
780 if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
781 return false;
782 }
783 assert(r->has_phi() == NULL, "simple region shouldn't have a phi");
784 } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
785 return false;
786 }
787 // See merge_uncommon_traps: the reason of the uncommon trap
788 // will be changed and the state of the dominating If will be
789 // used. Checked that we didn't apply this transformation in a
790 // previous compilation and it didn't cause too many traps
791 if (!igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_unstable_fused_if) &&
792 !igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), Deoptimization::Reason_range_check)) {
793 success = unc_proj;
794 fail = unc_proj->other_if_proj();
795 return true;
796 }
797 }
798 }
799 return false;
800 }
801
802 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
803 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
804 Node* this_cmp = in(1)->in(1);
805 BoolNode* this_bool = in(1)->as_Bool();
806 IfNode* dom_iff = proj->in(0)->as_If();
807 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
808 Node* lo = dom_iff->in(1)->in(1)->in(2);
809 Node* hi = this_cmp->in(2);
810 Node* n = this_cmp->in(1);
811 ProjNode* otherproj = proj->other_if_proj();
812
813 const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
814 const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
815
816 BoolTest::mask lo_test = dom_bool->_test._test;
817 BoolTest::mask hi_test = this_bool->_test._test;
818 BoolTest::mask cond = hi_test;
819
820 // Figure out which of the two tests sets the upper bound and which
821 // sets the lower bound if any.
822 if (hi_type->_lo > lo_type->_hi && hi_type->_hi == max_jint && lo_type->_lo == min_jint) {
823
824 assert((dom_bool->_test.is_less() && !proj->_con) ||
825 (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
826 // this test was canonicalized
827 assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
828
829 if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
830 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
831 }
832 } else if (lo_type->_lo > hi_type->_hi && lo_type->_hi == max_jint && hi_type->_lo == min_jint) {
833 swap(lo, hi);
834 swap(lo_type, hi_type);
835 swap(lo_test, hi_test);
836
837 assert((this_bool->_test.is_less() && proj->_con) ||
838 (this_bool->_test.is_greater() && !proj->_con), "incorrect test");
839 // this test was canonicalized
840 assert(dom_bool->_test.is_less() && !fail->_con, "incorrect test");
841
842 cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
843
844 if (lo_test == BoolTest::le) {
845 lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
846 }
847
848 } else {
849 const TypeInt* failtype = filtered_int_type(igvn, n, proj);
850 if (failtype != NULL) {
851 const TypeInt* type2 = filtered_int_type(igvn, n, fail);
852 if (type2 != NULL) {
853 failtype = failtype->join(type2)->is_int();
854 if (failtype->_lo > failtype->_hi) {
855 // previous if determines the result of this if so
856 // replace Bool with constant
857 igvn->hash_delete(this);
858 set_req(1, igvn->intcon(success->_con));
859 return true;
860 }
861 }
862 }
863
864 lo = NULL;
865 hi = NULL;
866 }
867
868 if (lo && hi) {
869 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
870 Node* adjusted_val = igvn->transform(new SubINode(n, lo));
871 Node* adjusted_lim = igvn->transform(new SubINode(hi, lo));
872 Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
873 Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
874
875 igvn->is_IterGVN()->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
876 igvn->hash_delete(this);
877 set_req(1, newbool);
878
879 return true;
880 }
881 return false;
882 }
883
884 // Merge the branches that trap for this If and the dominating If into
885 // a single region that branches to the uncommon trap for the
886 // dominating If
887 void IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
888 ProjNode* otherproj = proj->other_if_proj();
889
890 CallStaticJavaNode* unc = success->is_uncommon_trap_proj(Deoptimization::Reason_none);
891 CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj(Deoptimization::Reason_none);
892
893 if (unc != dom_unc) {
894 Node* r = new RegionNode(3);
895
896 r->set_req(1, otherproj);
897 r->set_req(2, success);
898 r = igvn->transform(r);
899 assert(r->is_Region(), "can't go away");
900
901 // Make both If trap at the state of the first If: once the CmpI
902 // nodes are merged, if we trap we don't know which of the CmpI
903 // nodes would have caused the trap so we have to restart
904 // execution at the first one
905 igvn->replace_input_of(dom_unc, 0, r);
906 igvn->replace_input_of(unc, 0, igvn->C->top());
907 }
908 int trap_request = dom_unc->uncommon_trap_request();
909 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
910 Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
911
912 int flip_test = 0;
913 Node* l = NULL;
914 Node* r = NULL;
915
916 if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != NULL) {
917 // If this looks like a range check, change the trap to
918 // Reason_range_check so the compiler recognizes it as a range
919 // check and applies the corresponding optimizations
920 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
921
922 improve_address_types(l, r, fail, igvn);
923 } else if (unc != dom_unc) {
924 // If we trap we won't know what CmpI would have caused the trap
925 // so use a special trap reason to mark this pair of CmpI nodes as
926 // bad candidate for folding. On recompilation we won't fold them
927 // and we may trap again but this time we'll know what branch
928 // traps
929 trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
930 }
931 igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
932 }
933
934 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
935 // of a rangecheck on index i, on 64 bit the compares may be followed
936 // by memory accesses using i as index. In that case, the CmpU tells
937 // us something about the values taken by i that can help the compiler
938 // (see Compile::conv_I2X_index())
939 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
940 #ifdef _LP64
941 ResourceMark rm;
942 Node_Stack stack(2);
943
944 assert(r->Opcode() == Op_LoadRange, "unexpected range check");
945 const TypeInt* array_size = igvn->type(r)->is_int();
946
947 stack.push(l, 0);
948
949 while(stack.size() > 0) {
950 Node* n = stack.node();
951 uint start = stack.index();
952
953 uint i = start;
954 for (; i < n->outcnt(); i++) {
955 Node* use = n->raw_out(i);
956 if (stack.size() == 1) {
957 if (use->Opcode() == Op_ConvI2L) {
958 const TypeLong* bounds = use->as_Type()->type()->is_long();
959 if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
960 (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
961 stack.set_index(i+1);
962 stack.push(use, 0);
963 break;
964 }
965 }
966 } else if (use->is_Mem()) {
967 Node* ctrl = use->in(0);
968 for (int i = 0; i < 10 && ctrl != NULL && ctrl != fail; i++) {
969 ctrl = up_one_dom(ctrl);
970 }
971 if (ctrl == fail) {
972 Node* init_n = stack.node_at(1);
973 assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
974 Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size);
975
976 for (uint j = 2; j < stack.size(); j++) {
977 Node* n = stack.node_at(j);
978 Node* clone = n->clone();
979 int rep = clone->replace_edge(init_n, new_n);
980 assert(rep > 0, "can't find expected node?");
981 clone = igvn->transform(clone);
982 init_n = n;
983 new_n = clone;
984 }
985 igvn->hash_delete(use);
986 int rep = use->replace_edge(init_n, new_n);
987 assert(rep > 0, "can't find expected node?");
988 igvn->transform(use);
989 if (init_n->outcnt() == 0) {
990 igvn->_worklist.push(init_n);
991 }
992 }
993 } else if (use->in(0) == NULL && (igvn->type(use)->isa_long() ||
994 igvn->type(use)->isa_ptr())) {
995 stack.set_index(i+1);
996 stack.push(use, 0);
997 break;
998 }
999 }
1000 if (i == n->outcnt()) {
1001 stack.pop();
1002 }
1003 }
1004 #endif
1005 }
1006
1007 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1008 if (in(1) != NULL &&
1009 in(1)->in(1) != NULL &&
1010 in(1)->in(1)->in(2) != NULL) {
1011 Node* other = in(1)->in(1)->in(2);
1012 if (other->Opcode() == Op_LoadRange &&
1013 ((other->in(0) != NULL && other->in(0) == proj) ||
1014 (other->in(0) == NULL &&
1015 other->in(2) != NULL &&
1016 other->in(2)->is_AddP() &&
1017 other->in(2)->in(1) != NULL &&
1018 other->in(2)->in(1)->Opcode() == Op_CastPP &&
1019 other->in(2)->in(1)->in(0) == proj))) {
1020 return true;
1021 }
1022 }
1023 return false;
1024 }
1025
1026 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1027 Node* other = in(1)->in(1)->in(2);
1028 if (other->in(MemNode::Address) != NULL &&
1029 proj->in(0)->in(1) != NULL &&
1030 proj->in(0)->in(1)->is_Bool() &&
1031 proj->in(0)->in(1)->in(1) != NULL &&
1032 proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1033 proj->in(0)->in(1)->in(1)->in(2) != NULL &&
1034 proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1035 igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1036 return true;
1037 }
1038 return false;
1039 }
1040
1041 // Check that the If that is in between the 2 integer comparisons has
1042 // no side effect
1043 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1044 if (proj != NULL &&
1045 proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1046 proj->outcnt() <= 2) {
1047 if (proj->outcnt() == 1 ||
1048 // Allow simple null check from LoadRange
1049 (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1050 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1051 CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1052
1053 // reroute_side_effect_free_unc changes the state of this
1054 // uncommon trap to restart execution at the previous
1055 // CmpI. Check that this change in a previous compilation didn't
1056 // cause too many traps.
1057 int trap_request = unc->uncommon_trap_request();
1058 Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1059
1060 if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1061 return false;
1062 }
1063
1064 return true;
1065 }
1066 }
1067 return false;
1068 }
1069
1070 // Make the If between the 2 integer comparisons trap at the state of
1071 // the first If: the last CmpI is the one replaced by a CmpU and the
1072 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1073 // won't be guarded by the first CmpI anymore. It can trap in cases
1074 // where the first CmpI would have prevented it from executing: on a
1075 // trap, we need to restart execution at the state of the first CmpI
1076 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1077 CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1078 ProjNode* otherproj = proj->other_if_proj();
1079 CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1080 Node* call_proj = dom_unc->unique_ctrl_out();
1081 Node* halt = call_proj->unique_ctrl_out();
1082
1083 Node* new_unc = dom_unc->clone();
1084 call_proj = call_proj->clone();
1085 halt = halt->clone();
1086 Node* c = otherproj->clone();
1087
1088 c = igvn->transform(c);
1089 new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1090 new_unc->set_req(0, c);
1091 new_unc = igvn->transform(new_unc);
1092 call_proj->set_req(0, new_unc);
1093 call_proj = igvn->transform(call_proj);
1094 halt->set_req(0, call_proj);
1095 halt = igvn->transform(halt);
1096
1097 igvn->replace_node(otherproj, igvn->C->top());
1098 igvn->C->root()->add_req(halt);
1099 }
1100
1101 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1102 if (Opcode() != Op_If) return NULL;
1103
1104 if (cmpi_folds(igvn)) {
1105 Node* ctrl = in(0);
1106 if (is_ctrl_folds(ctrl, igvn) &&
1107 ctrl->outcnt() == 1) {
1108 // A integer comparison immediately dominated by another integer
1109 // comparison
1110 ProjNode* success = NULL;
1111 ProjNode* fail = NULL;
1112 ProjNode* dom_cmp = ctrl->as_Proj();
1113 if (has_shared_region(dom_cmp, success, fail) &&
1114 // Next call modifies graph so must be last
1115 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1116 return this;
1117 }
1118 if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1119 // Next call modifies graph so must be last
1120 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1121 merge_uncommon_traps(dom_cmp, success, fail, igvn);
1122 return this;
1123 }
1124 return NULL;
1125 } else if (ctrl->in(0) != NULL &&
1126 ctrl->in(0)->in(0) != NULL) {
1127 ProjNode* success = NULL;
1128 ProjNode* fail = NULL;
1129 Node* dom = ctrl->in(0)->in(0);
1130 ProjNode* dom_cmp = dom->isa_Proj();
1131 ProjNode* other_cmp = ctrl->isa_Proj();
1132
1133 // Check if it's an integer comparison dominated by another
1134 // integer comparison with another test in between
1135 if (is_ctrl_folds(dom, igvn) &&
1136 has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1137 is_side_effect_free_test(other_cmp, igvn) &&
1138 // Next call modifies graph so must be last
1139 fold_compares_helper(dom_cmp, success, fail, igvn)) {
1140 reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1141 merge_uncommon_traps(dom_cmp, success, fail, igvn);
1142 return this;
1143 }
1144 }
1145 }
1146 return NULL;
1147 }
1148
1149 //------------------------------remove_useless_bool----------------------------
1150 // Check for people making a useless boolean: things like
1151 // if( (x < y ? true : false) ) { ... }
1152 // Replace with if( x < y ) { ... }
1153 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1154 Node *i1 = iff->in(1);
1155 if( !i1->is_Bool() ) return NULL;
1156 BoolNode *bol = i1->as_Bool();
1157
1158 Node *cmp = bol->in(1);
1159 if( cmp->Opcode() != Op_CmpI ) return NULL;
1160
1161 // Must be comparing against a bool
1162 const Type *cmp2_t = phase->type( cmp->in(2) );
1163 if( cmp2_t != TypeInt::ZERO &&
1164 cmp2_t != TypeInt::ONE )
1165 return NULL;
1166
1167 // Find a prior merge point merging the boolean
1168 i1 = cmp->in(1);
1169 if( !i1->is_Phi() ) return NULL;
1170 PhiNode *phi = i1->as_Phi();
1171 if( phase->type( phi ) != TypeInt::BOOL )
1172 return NULL;
1173
1174 // Check for diamond pattern
1175 int true_path = phi->is_diamond_phi();
1176 if( true_path == 0 ) return NULL;
1177
1178 // Make sure that iff and the control of the phi are different. This
1179 // should really only happen for dead control flow since it requires
1180 // an illegal cycle.
1181 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
1182
1183 // phi->region->if_proj->ifnode->bool->cmp
1184 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1185
1186 // Now get the 'sense' of the test correct so we can plug in
1187 // either iff2->in(1) or its complement.
1188 int flip = 0;
1189 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1190 else if( bol->_test._test != BoolTest::eq ) return NULL;
1191 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1192
1193 const Type *phi1_t = phase->type( phi->in(1) );
1194 const Type *phi2_t = phase->type( phi->in(2) );
1195 // Check for Phi(0,1) and flip
1196 if( phi1_t == TypeInt::ZERO ) {
1197 if( phi2_t != TypeInt::ONE ) return NULL;
1198 flip = 1-flip;
1199 } else {
1200 // Check for Phi(1,0)
1201 if( phi1_t != TypeInt::ONE ) return NULL;
1202 if( phi2_t != TypeInt::ZERO ) return NULL;
1203 }
1204 if( true_path == 2 ) {
1205 flip = 1-flip;
1206 }
1207
1208 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1209 assert(new_bol != iff->in(1), "must make progress");
1210 iff->set_req(1, new_bol);
1211 // Intervening diamond probably goes dead
1212 phase->C->set_major_progress();
1213 return iff;
1214 }
1215
1216 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1217
1218 struct RangeCheck {
1219 Node* ctl;
1220 jint off;
1221 };
1222
1223 //------------------------------Ideal------------------------------------------
1224 // Return a node which is more "ideal" than the current node. Strip out
1225 // control copies
1226 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1227 if (remove_dead_region(phase, can_reshape)) return this;
1228 // No Def-Use info?
1229 if (!can_reshape) return NULL;
1230 PhaseIterGVN *igvn = phase->is_IterGVN();
1231
1232 // Don't bother trying to transform a dead if
1233 if (in(0)->is_top()) return NULL;
1234 // Don't bother trying to transform an if with a dead test
1235 if (in(1)->is_top()) return NULL;
1236 // Another variation of a dead test
1237 if (in(1)->is_Con()) return NULL;
1238 // Another variation of a dead if
1239 if (outcnt() < 2) return NULL;
1240
1241 // Canonicalize the test.
1242 Node* idt_if = idealize_test(phase, this);
1243 if (idt_if != NULL) return idt_if;
1244
1245 // Try to split the IF
1246 Node *s = split_if(this, igvn);
1247 if (s != NULL) return s;
1248
1249 // Check for people making a useless boolean: things like
1250 // if( (x < y ? true : false) ) { ... }
1251 // Replace with if( x < y ) { ... }
1252 Node *bol2 = remove_useless_bool(this, phase);
1253 if( bol2 ) return bol2;
1254
1255 // Setup to scan up the CFG looking for a dominating test
1256 Node *dom = in(0);
1257 Node *prev_dom = this;
1258
1259 // Check for range-check vs other kinds of tests
1260 Node *index1, *range1;
1261 jint offset1;
1262 int flip1 = is_range_check(range1, index1, offset1);
1263 if( flip1 ) {
1264 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
1265 // so all checks we inspect post-dominate the top-most check we find.
1266 // If we are going to fail the current check and we reach the top check
1267 // then we are guaranteed to fail, so just start interpreting there.
1268 // We 'expand' the top 3 range checks to include all post-dominating
1269 // checks.
1270
1271 // The top 3 range checks seen
1272 const int NRC =3;
1273 RangeCheck prev_checks[NRC];
1274 int nb_checks = 0;
1275
1276 // Low and high offsets seen so far
1277 jint off_lo = offset1;
1278 jint off_hi = offset1;
1279
1280 bool found_immediate_dominator = false;
1281
1282 // Scan for the top checks and collect range of offsets
1283 for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
1284 if (dom->Opcode() == Op_If && // Not same opcode?
1285 prev_dom->in(0) == dom) { // One path of test does dominate?
1286 if (dom == this) return NULL; // dead loop
1287 // See if this is a range check
1288 Node *index2, *range2;
1289 jint offset2;
1290 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
1291 // See if this is a _matching_ range check, checking against
1292 // the same array bounds.
1293 if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
1294 dom->outcnt() == 2) {
1295 if (nb_checks == 0 && dom->in(1) == in(1)) {
1296 // Found an immediately dominating test at the same offset.
1297 // This kind of back-to-back test can be eliminated locally,
1298 // and there is no need to search further for dominating tests.
1299 assert(offset2 == offset1, "Same test but different offsets");
1300 found_immediate_dominator = true;
1301 break;
1302 }
1303 // Gather expanded bounds
1304 off_lo = MIN2(off_lo,offset2);
1305 off_hi = MAX2(off_hi,offset2);
1306 // Record top NRC range checks
1307 prev_checks[nb_checks%NRC].ctl = prev_dom;
1308 prev_checks[nb_checks%NRC].off = offset2;
1309 nb_checks++;
1310 }
1311 }
1312 prev_dom = dom;
1313 dom = up_one_dom(dom);
1314 if (!dom) break;
1315 }
1316
1317 if (!found_immediate_dominator) {
1318 // Attempt to widen the dominating range check to cover some later
1319 // ones. Since range checks "fail" by uncommon-trapping to the
1320 // interpreter, widening a check can make us speculatively enter
1321 // the interpreter. If we see range-check deopt's, do not widen!
1322 if (!phase->C->allow_range_check_smearing()) return NULL;
1323
1324 // Didn't find prior covering check, so cannot remove anything.
1325 if (nb_checks == 0) {
1326 return NULL;
1327 }
1328 // Constant indices only need to check the upper bound.
1329 // Non-constant indices must check both low and high.
1330 int chk0 = (nb_checks - 1) % NRC;
1331 if (index1) {
1332 if (nb_checks == 1) {
1333 return NULL;
1334 } else {
1335 // If the top range check's constant is the min or max of
1336 // all constants we widen the next one to cover the whole
1337 // range of constants.
1338 RangeCheck rc0 = prev_checks[chk0];
1339 int chk1 = (nb_checks - 2) % NRC;
1340 RangeCheck rc1 = prev_checks[chk1];
1341 if (rc0.off == off_lo) {
1342 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1343 prev_dom = rc1.ctl;
1344 } else if (rc0.off == off_hi) {
1345 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1346 prev_dom = rc1.ctl;
1347 } else {
1348 // If the top test's constant is not the min or max of all
1349 // constants, we need 3 range checks. We must leave the
1350 // top test unchanged because widening it would allow the
1351 // accesses it protects to successfully read/write out of
1352 // bounds.
1353 if (nb_checks == 2) {
1354 return NULL;
1355 }
1356 int chk2 = (nb_checks - 3) % NRC;
1357 RangeCheck rc2 = prev_checks[chk2];
1358 // The top range check a+i covers interval: -a <= i < length-a
1359 // The second range check b+i covers interval: -b <= i < length-b
1360 if (rc1.off <= rc0.off) {
1361 // if b <= a, we change the second range check to:
1362 // -min_of_all_constants <= i < length-min_of_all_constants
1363 // Together top and second range checks now cover:
1364 // -min_of_all_constants <= i < length-a
1365 // which is more restrictive than -b <= i < length-b:
1366 // -b <= -min_of_all_constants <= i < length-a <= length-b
1367 // The third check is then changed to:
1368 // -max_of_all_constants <= i < length-max_of_all_constants
1369 // so 2nd and 3rd checks restrict allowed values of i to:
1370 // -min_of_all_constants <= i < length-max_of_all_constants
1371 adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
1372 adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
1373 } else {
1374 // if b > a, we change the second range check to:
1375 // -max_of_all_constants <= i < length-max_of_all_constants
1376 // Together top and second range checks now cover:
1377 // -a <= i < length-max_of_all_constants
1378 // which is more restrictive than -b <= i < length-b:
1379 // -b < -a <= i < length-max_of_all_constants <= length-b
1380 // The third check is then changed to:
1381 // -max_of_all_constants <= i < length-max_of_all_constants
1382 // so 2nd and 3rd checks restrict allowed values of i to:
1383 // -min_of_all_constants <= i < length-max_of_all_constants
1384 adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
1385 adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
1386 }
1387 prev_dom = rc2.ctl;
1388 }
1389 }
1390 } else {
1391 RangeCheck rc0 = prev_checks[chk0];
1392 // 'Widen' the offset of the 1st and only covering check
1393 adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
1394 // Test is now covered by prior checks, dominate it out
1395 prev_dom = rc0.ctl;
1396 }
1397 }
1398
1399 } else { // Scan for an equivalent test
1400
1401 Node *cmp;
1402 int dist = 0; // Cutoff limit for search
1403 int op = Opcode();
1404 if( op == Op_If &&
1405 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
1406 if( cmp->in(2) != NULL && // make sure cmp is not already dead
1407 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
1408 dist = 64; // Limit for null-pointer scans
1409 } else {
1410 dist = 4; // Do not bother for random pointer tests
1411 }
1412 } else {
1413 dist = 4; // Limit for random junky scans
1414 }
1415
1416 // Normal equivalent-test check.
1417 if( !dom ) return NULL; // Dead loop?
1418
1419 Node* result = fold_compares(igvn);
1420 if (result != NULL) {
1421 return result;
1422 }
1423
1424 // Search up the dominator tree for an If with an identical test
1425 while( dom->Opcode() != op || // Not same opcode?
1426 dom->in(1) != in(1) || // Not same input 1?
1427 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
1428 prev_dom->in(0) != dom ) { // One path of test does not dominate?
1429 if( dist < 0 ) return NULL;
1430
1431 dist--;
1432 prev_dom = dom;
1433 dom = up_one_dom( dom );
1434 if( !dom ) return NULL;
1435 }
1436
1437 // Check that we did not follow a loop back to ourselves
1438 if( this == dom )
1439 return NULL;
1440
1441 if( dist > 2 ) // Add to count of NULL checks elided
1442 explicit_null_checks_elided++;
1443
1444 } // End of Else scan for an equivalent test
1445
1446 // Hit! Remove this IF
1447 #ifndef PRODUCT
1448 if( TraceIterativeGVN ) {
1449 tty->print(" Removing IfNode: "); this->dump();
1450 }
1451 if( VerifyOpto && !phase->allow_progress() ) {
1452 // Found an equivalent dominating test,
1453 // we can not guarantee reaching a fix-point for these during iterativeGVN
1454 // since intervening nodes may not change.
1455 return NULL;
1456 }
1457 #endif
1458
1459 // Replace dominated IfNode
1460 dominated_by( prev_dom, igvn );
1461
1462 // Must return either the original node (now dead) or a new node
1463 // (Do not return a top here, since that would break the uniqueness of top.)
1464 return new ConINode(TypeInt::ZERO);
1465 }
1466
1467 //------------------------------dominated_by-----------------------------------
1468 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
1469 igvn->hash_delete(this); // Remove self to prevent spurious V-N
1470 Node *idom = in(0);
1471 // Need opcode to decide which way 'this' test goes
1472 int prev_op = prev_dom->Opcode();
1473 Node *top = igvn->C->top(); // Shortcut to top
1474
1475 // Loop predicates may have depending checks which should not
1476 // be skipped. For example, range check predicate has two checks
1477 // for lower and upper bounds.
1478 ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
1479 if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate) != NULL)
1480 prev_dom = idom;
1481
1482 // Now walk the current IfNode's projections.
1483 // Loop ends when 'this' has no more uses.
1484 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1485 Node *ifp = last_out(i); // Get IfTrue/IfFalse
1486 igvn->add_users_to_worklist(ifp);
1487 // Check which projection it is and set target.
1488 // Data-target is either the dominating projection of the same type
1489 // or TOP if the dominating projection is of opposite type.
1490 // Data-target will be used as the new control edge for the non-CFG
1491 // nodes like Casts and Loads.
1492 Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1493 // Control-target is just the If's immediate dominator or TOP.
1494 Node *ctrl_target = (ifp->Opcode() == prev_op) ? idom : top;
1495
1496 // For each child of an IfTrue/IfFalse projection, reroute.
1497 // Loop ends when projection has no more uses.
1498 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1499 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1500 if( !s->depends_only_on_test() ) {
1501 // Find the control input matching this def-use edge.
1502 // For Regions it may not be in slot 0.
1503 uint l;
1504 for( l = 0; s->in(l) != ifp; l++ ) { }
1505 igvn->replace_input_of(s, l, ctrl_target);
1506 } else { // Else, for control producers,
1507 igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1508 }
1509 } // End for each child of a projection
1510
1511 igvn->remove_dead_node(ifp);
1512 } // End for each IfTrue/IfFalse child of If
1513
1514 // Kill the IfNode
1515 igvn->remove_dead_node(this);
1516 }
1517
1518 //------------------------------Identity---------------------------------------
1519 // If the test is constant & we match, then we are the input Control
1520 Node *IfProjNode::Identity(PhaseTransform *phase) {
1521 // Can only optimize if cannot go the other way
1522 const TypeTuple *t = phase->type(in(0))->is_tuple();
1523 if (t == TypeTuple::IFNEITHER ||
1524 // kill dead branch first otherwise the IfNode's control will
1525 // have 2 control uses (the IfNode that doesn't go away because
1526 // it still has uses and this branch of the
1527 // If). Node::has_special_unique_user() will cause this node to
1528 // be reprocessed once the dead branch is killed.
1529 (always_taken(t) && in(0)->outcnt() == 1)) {
1530 // IfNode control
1531 return in(0)->in(0);
1532 }
1533 // no progress
1534 return this;
1535 }
1536
1537 //------------------------------dump_spec--------------------------------------
1538 #ifndef PRODUCT
1539 void IfNode::dump_spec(outputStream *st) const {
1540 st->print("P=%f, C=%f",_prob,_fcnt);
1541 }
1542 #endif
1543
1544 //------------------------------idealize_test----------------------------------
1545 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1546 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1547 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1548 // needed.
1549 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1550 assert(iff->in(0) != NULL, "If must be live");
1551
1552 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1553 Node* old_if_f = iff->proj_out(false);
1554 Node* old_if_t = iff->proj_out(true);
1555
1556 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1557 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1558 // happens in count-down loops
1559 if (iff->is_CountedLoopEnd()) return NULL;
1560 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1561 BoolNode *b = iff->in(1)->as_Bool();
1562 BoolTest bt = b->_test;
1563 // Test already in good order?
1564 if( bt.is_canonical() )
1565 return NULL;
1566
1567 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1568 // cloning the IfNode.
1569 Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1570 if( !new_b->is_Bool() ) return NULL;
1571 b = new_b->as_Bool();
1572
1573 PhaseIterGVN *igvn = phase->is_IterGVN();
1574 assert( igvn, "Test is not canonical in parser?" );
1575
1576 // The IF node never really changes, but it needs to be cloned
1577 iff = new IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1578
1579 Node *prior = igvn->hash_find_insert(iff);
1580 if( prior ) {
1581 igvn->remove_dead_node(iff);
1582 iff = (IfNode*)prior;
1583 } else {
1584 // Cannot call transform on it just yet
1585 igvn->set_type_bottom(iff);
1586 }
1587 igvn->_worklist.push(iff);
1588
1589 // Now handle projections. Cloning not required.
1590 Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1591 Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1592
1593 igvn->register_new_node_with_optimizer(new_if_f);
1594 igvn->register_new_node_with_optimizer(new_if_t);
1595 // Flip test, so flip trailing control
1596 igvn->replace_node(old_if_f, new_if_t);
1597 igvn->replace_node(old_if_t, new_if_f);
1598
1599 // Progress
1600 return iff;
1601 }