1 /*
2 * Copyright (c) 2000, 2009, 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 // Portions of code courtesy of Clifford Click
26
27 // Optimization - Graph Style
28
29 #include "incls/_precompiled.incl"
30 #include "incls/_ifnode.cpp.incl"
31
32
33 extern int explicit_null_checks_elided;
34
35 //=============================================================================
36 //------------------------------Value------------------------------------------
37 // Return a tuple for whichever arm of the IF is reachable
38 const Type *IfNode::Value( PhaseTransform *phase ) const {
39 if( !in(0) ) return Type::TOP;
40 if( phase->type(in(0)) == Type::TOP )
41 return Type::TOP;
42 const Type *t = phase->type(in(1));
43 if( t == Type::TOP ) // data is undefined
44 return TypeTuple::IFNEITHER; // unreachable altogether
45 if( t == TypeInt::ZERO ) // zero, or false
46 return TypeTuple::IFFALSE; // only false branch is reachable
47 if( t == TypeInt::ONE ) // 1, or true
48 return TypeTuple::IFTRUE; // only true branch is reachable
49 assert( t == TypeInt::BOOL, "expected boolean type" );
50
51 return TypeTuple::IFBOTH; // No progress
52 }
53
54 const RegMask &IfNode::out_RegMask() const {
55 return RegMask::Empty;
56 }
57
58 //------------------------------split_if---------------------------------------
59 // Look for places where we merge constants, then test on the merged value.
60 // If the IF test will be constant folded on the path with the constant, we
61 // win by splitting the IF to before the merge point.
62 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
63 // I could be a lot more general here, but I'm trying to squeeze this
64 // in before the Christmas '98 break so I'm gonna be kinda restrictive
65 // on the patterns I accept. CNC
66
67 // Look for a compare of a constant and a merged value
68 Node *i1 = iff->in(1);
69 if( !i1->is_Bool() ) return NULL;
70 BoolNode *b = i1->as_Bool();
71 Node *cmp = b->in(1);
72 if( !cmp->is_Cmp() ) return NULL;
73 i1 = cmp->in(1);
74 if( i1 == NULL || !i1->is_Phi() ) return NULL;
75 PhiNode *phi = i1->as_Phi();
76 if( phi->is_copy() ) return NULL;
77 Node *con2 = cmp->in(2);
78 if( !con2->is_Con() ) return NULL;
79 // See that the merge point contains some constants
80 Node *con1=NULL;
81 uint i4;
82 for( i4 = 1; i4 < phi->req(); i4++ ) {
83 con1 = phi->in(i4);
84 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
85 if( con1->is_Con() ) break; // Found a constant
86 // Also allow null-vs-not-null checks
87 const TypePtr *tp = igvn->type(con1)->isa_ptr();
88 if( tp && tp->_ptr == TypePtr::NotNull )
89 break;
90 }
91 if( i4 >= phi->req() ) return NULL; // Found no constants
92
93 igvn->C->set_has_split_ifs(true); // Has chance for split-if
94
95 // Make sure that the compare can be constant folded away
96 Node *cmp2 = cmp->clone();
97 cmp2->set_req(1,con1);
98 cmp2->set_req(2,con2);
99 const Type *t = cmp2->Value(igvn);
100 // This compare is dead, so whack it!
101 igvn->remove_dead_node(cmp2);
102 if( !t->singleton() ) return NULL;
103
104 // No intervening control, like a simple Call
105 Node *r = iff->in(0);
106 if( !r->is_Region() ) return NULL;
107 if( phi->region() != r ) return NULL;
108 // No other users of the cmp/bool
109 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
110 //tty->print_cr("many users of cmp/bool");
111 return NULL;
112 }
113
114 // Make sure we can determine where all the uses of merged values go
115 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
116 Node* u = r->fast_out(j);
117 if( u == r ) continue;
118 if( u == iff ) continue;
119 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
120 if( !u->is_Phi() ) {
121 /*
122 if( u->is_Start() ) {
123 tty->print_cr("Region has inlined start use");
124 } else {
125 tty->print_cr("Region has odd use");
126 u->dump(2);
127 }*/
128 return NULL;
129 }
130 if( u != phi ) {
131 // CNC - do not allow any other merged value
132 //tty->print_cr("Merging another value");
133 //u->dump(2);
134 return NULL;
135 }
136 // Make sure we can account for all Phi uses
137 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
138 Node* v = u->fast_out(k); // User of the phi
139 // CNC - Allow only really simple patterns.
140 // In particular I disallow AddP of the Phi, a fairly common pattern
141 if( v == cmp ) continue; // The compare is OK
142 if( (v->is_ConstraintCast()) &&
143 v->in(0)->in(0) == iff )
144 continue; // CastPP/II of the IfNode is OK
145 // Disabled following code because I cannot tell if exactly one
146 // path dominates without a real dominator check. CNC 9/9/1999
147 //uint vop = v->Opcode();
148 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
149 // Node *r = v->in(0); // Get controlling point
150 // if( !r ) return NULL; // Degraded to a copy
151 // // Find exactly one path in (either True or False doms, but not IFF)
152 // int cnt = 0;
153 // for( uint i = 1; i < r->req(); i++ )
154 // if( r->in(i) && r->in(i)->in(0) == iff )
155 // cnt++;
156 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
157 //}
158 if( !v->is_Call() ) {
159 /*
160 if( v->Opcode() == Op_AddP ) {
161 tty->print_cr("Phi has AddP use");
162 } else if( v->Opcode() == Op_CastPP ) {
163 tty->print_cr("Phi has CastPP use");
164 } else if( v->Opcode() == Op_CastII ) {
165 tty->print_cr("Phi has CastII use");
166 } else {
167 tty->print_cr("Phi has use I cant be bothered with");
168 }
169 */
170 }
171 return NULL;
172
173 /* CNC - Cut out all the fancy acceptance tests
174 // Can we clone this use when doing the transformation?
175 // If all uses are from Phis at this merge or constants, then YES.
176 if( !v->in(0) && v != cmp ) {
177 tty->print_cr("Phi has free-floating use");
178 v->dump(2);
179 return NULL;
180 }
181 for( uint l = 1; l < v->req(); l++ ) {
182 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
183 !v->in(l)->is_Con() ) {
184 tty->print_cr("Phi has use");
185 v->dump(2);
186 return NULL;
187 } // End of if Phi-use input is neither Phi nor Constant
188 } // End of for all inputs to Phi-use
189 */
190 } // End of for all uses of Phi
191 } // End of for all uses of Region
192
193 // Only do this if the IF node is in a sane state
194 if (iff->outcnt() != 2)
195 return NULL;
196
197 // Got a hit! Do the Mondo Hack!
198 //
199 //ABC a1c def ghi B 1 e h A C a c d f g i
200 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
201 // cmp - 2 cmp - 2 cmp - 2
202 // bool bool_c bool_x
203 // if if_c if_x
204 // T F T F T F
205 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
206 //
207 // Split the paths coming into the merge point into 2 separate groups of
208 // merges. On the left will be all the paths feeding constants into the
209 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
210 // will fold up into a constant; this will let the Cmp fold up as well as
211 // all the control flow. Below the original IF we have 2 control
212 // dependent regions, 's' and 't'. Now we will merge the two paths
213 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
214 // likely 2 or more) will promptly constant fold away.
215 PhaseGVN *phase = igvn;
216
217 // Make a region merging constants and a region merging the rest
218 uint req_c = 0;
219 for (uint ii = 1; ii < r->req(); ii++) {
220 if( phi->in(ii) == con1 ) {
221 req_c++;
222 }
223 }
224 Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1);
225 Node *phi_c = con1;
226 uint len = r->req();
227 Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1);
228 Node *phi_x = PhiNode::make_blank(region_x, phi);
229 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
230 if( phi->in(i) == con1 ) {
231 region_c->init_req( i_c++, r ->in(i) );
232 } else {
233 region_x->init_req( i_x, r ->in(i) );
234 phi_x ->init_req( i_x++, phi->in(i) );
235 }
236 }
237
238 // Register the new RegionNodes but do not transform them. Cannot
239 // transform until the entire Region/Phi conglomerate has been hacked
240 // as a single huge transform.
241 igvn->register_new_node_with_optimizer( region_c );
242 igvn->register_new_node_with_optimizer( region_x );
243 // Prevent the untimely death of phi_x. Currently he has no uses. He is
244 // about to get one. If this only use goes away, then phi_x will look dead.
245 // However, he will be picking up some more uses down below.
246 Node *hook = new (igvn->C, 4) Node(4);
247 hook->init_req(0, phi_x);
248 hook->init_req(1, phi_c);
249 phi_x = phase->transform( phi_x );
250
251 // Make the compare
252 Node *cmp_c = phase->makecon(t);
253 Node *cmp_x = cmp->clone();
254 cmp_x->set_req(1,phi_x);
255 cmp_x->set_req(2,con2);
256 cmp_x = phase->transform(cmp_x);
257 // Make the bool
258 Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test));
259 Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test));
260 // Make the IfNode
261 IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
262 igvn->set_type_bottom(iff_c);
263 igvn->_worklist.push(iff_c);
264 hook->init_req(2, iff_c);
265
266 IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
267 igvn->set_type_bottom(iff_x);
268 igvn->_worklist.push(iff_x);
269 hook->init_req(3, iff_x);
270
271 // Make the true/false arms
272 Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c));
273 Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c));
274 Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x));
275 Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x));
276
277 // Merge the TRUE paths
278 Node *region_s = new (igvn->C, 3) RegionNode(3);
279 igvn->_worklist.push(region_s);
280 region_s->init_req(1, iff_c_t);
281 region_s->init_req(2, iff_x_t);
282 igvn->register_new_node_with_optimizer( region_s );
283
284 // Merge the FALSE paths
285 Node *region_f = new (igvn->C, 3) RegionNode(3);
286 igvn->_worklist.push(region_f);
287 region_f->init_req(1, iff_c_f);
288 region_f->init_req(2, iff_x_f);
289 igvn->register_new_node_with_optimizer( region_f );
290
291 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
292 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
293 cmp->set_req(2,NULL);
294 // Check for all uses of the Phi and give them a new home.
295 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
296 Node *phi_s = NULL; // do not construct unless needed
297 Node *phi_f = NULL; // do not construct unless needed
298 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
299 Node* v = phi->last_out(i2);// User of the phi
300 igvn->hash_delete(v); // Have to fixup other Phi users
301 igvn->_worklist.push(v);
302 uint vop = v->Opcode();
303 Node *proj = NULL;
304 if( vop == Op_Phi ) { // Remote merge point
305 Node *r = v->in(0);
306 for (uint i3 = 1; i3 < r->req(); i3++)
307 if (r->in(i3) && r->in(i3)->in(0) == iff) {
308 proj = r->in(i3);
309 break;
310 }
311 } else if( v->is_ConstraintCast() ) {
312 proj = v->in(0); // Controlling projection
313 } else {
314 assert( 0, "do not know how to handle this guy" );
315 }
316
317 Node *proj_path_data, *proj_path_ctrl;
318 if( proj->Opcode() == Op_IfTrue ) {
319 if( phi_s == NULL ) {
320 // Only construct phi_s if needed, otherwise provides
321 // interfering use.
322 phi_s = PhiNode::make_blank(region_s,phi);
323 phi_s->init_req( 1, phi_c );
324 phi_s->init_req( 2, phi_x );
325 hook->add_req(phi_s);
326 phi_s = phase->transform(phi_s);
327 }
328 proj_path_data = phi_s;
329 proj_path_ctrl = region_s;
330 } else {
331 if( phi_f == NULL ) {
332 // Only construct phi_f if needed, otherwise provides
333 // interfering use.
334 phi_f = PhiNode::make_blank(region_f,phi);
335 phi_f->init_req( 1, phi_c );
336 phi_f->init_req( 2, phi_x );
337 hook->add_req(phi_f);
338 phi_f = phase->transform(phi_f);
339 }
340 proj_path_data = phi_f;
341 proj_path_ctrl = region_f;
342 }
343
344 // Fixup 'v' for for the split
345 if( vop == Op_Phi ) { // Remote merge point
346 uint i;
347 for( i = 1; i < v->req(); i++ )
348 if( v->in(i) == phi )
349 break;
350 v->set_req(i, proj_path_data );
351 } else if( v->is_ConstraintCast() ) {
352 v->set_req(0, proj_path_ctrl );
353 v->set_req(1, proj_path_data );
354 } else
355 ShouldNotReachHere();
356 }
357
358 // Now replace the original iff's True/False with region_s/region_t.
359 // This makes the original iff go dead.
360 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
361 Node* p = iff->last_out(i3);
362 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
363 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
364 // Replace p with u
365 igvn->add_users_to_worklist(p);
366 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
367 Node* x = p->last_out(l);
368 igvn->hash_delete(x);
369 uint uses_found = 0;
370 for( uint j = 0; j < x->req(); j++ ) {
371 if( x->in(j) == p ) {
372 x->set_req(j, u);
373 uses_found++;
374 }
375 }
376 l -= uses_found; // we deleted 1 or more copies of this edge
377 }
378 igvn->remove_dead_node(p);
379 }
380
381 // Force the original merge dead
382 igvn->hash_delete(r);
383 // First, remove region's dead users.
384 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
385 Node* u = r->last_out(l);
386 if( u == r ) {
387 r->set_req(0, NULL);
388 } else {
389 assert(u->outcnt() == 0, "only dead users");
390 igvn->remove_dead_node(u);
391 }
392 l -= 1;
393 }
394 igvn->remove_dead_node(r);
395
396 // Now remove the bogus extra edges used to keep things alive
397 igvn->remove_dead_node( hook );
398
399 // Must return either the original node (now dead) or a new node
400 // (Do not return a top here, since that would break the uniqueness of top.)
401 return new (igvn->C, 1) ConINode(TypeInt::ZERO);
402 }
403
404 //------------------------------is_range_check---------------------------------
405 // Return 0 if not a range check. Return 1 if a range check and set index and
406 // offset. Return 2 if we had to negate the test. Index is NULL if the check
407 // is versus a constant.
408 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
409 Node* b = in(1);
410 if (b == NULL || !b->is_Bool()) return 0;
411 BoolNode* bn = b->as_Bool();
412 Node* cmp = bn->in(1);
413 if (cmp == NULL) return 0;
414 if (cmp->Opcode() != Op_CmpU) return 0;
415
416 Node* l = cmp->in(1);
417 Node* r = cmp->in(2);
418 int flip_test = 1;
419 if (bn->_test._test == BoolTest::le) {
420 l = cmp->in(2);
421 r = cmp->in(1);
422 flip_test = 2;
423 } else if (bn->_test._test != BoolTest::lt) {
424 return 0;
425 }
426 if (l->is_top()) return 0; // Top input means dead test
427 if (r->Opcode() != Op_LoadRange) return 0;
428
429 // We have recognized one of these forms:
430 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
431 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
432
433 // Make sure it's a real range check by requiring an uncommon trap
434 // along the OOB path. Otherwise, it's possible that the user wrote
435 // something which optimized to look like a range check but behaves
436 // in some other way.
437 Node* iftrap = proj_out(flip_test == 2 ? true : false);
438 bool found_trap = false;
439 if (iftrap != NULL) {
440 Node* u = iftrap->unique_ctrl_out();
441 if (u != NULL) {
442 // It could be a merge point (Region) for uncommon trap.
443 if (u->is_Region()) {
444 Node* c = u->unique_ctrl_out();
445 if (c != NULL) {
446 iftrap = u;
447 u = c;
448 }
449 }
450 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
451 int req = u->as_CallStaticJava()->uncommon_trap_request();
452 if (Deoptimization::trap_request_reason(req) ==
453 Deoptimization::Reason_range_check) {
454 found_trap = true;
455 }
456 }
457 }
458 }
459 if (!found_trap) return 0; // sorry, no cigar
460
461 // Look for index+offset form
462 Node* ind = l;
463 jint off = 0;
464 if (l->is_top()) {
465 return 0;
466 } else if (l->is_Add()) {
467 if ((off = l->in(1)->find_int_con(0)) != 0) {
468 ind = l->in(2);
469 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
470 ind = l->in(1);
471 }
472 } else if ((off = l->find_int_con(-1)) >= 0) {
473 // constant offset with no variable index
474 ind = NULL;
475 } else {
476 // variable index with no constant offset (or dead negative index)
477 off = 0;
478 }
479
480 // Return all the values:
481 index = ind;
482 offset = off;
483 range = r;
484 return flip_test;
485 }
486
487 //------------------------------adjust_check-----------------------------------
488 // Adjust (widen) a prior range check
489 static void adjust_check(Node* proj, Node* range, Node* index,
490 int flip, jint off_lo, PhaseIterGVN* igvn) {
491 PhaseGVN *gvn = igvn;
492 // Break apart the old check
493 Node *iff = proj->in(0);
494 Node *bol = iff->in(1);
495 if( bol->is_top() ) return; // In case a partially dead range check appears
496 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
497 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
498 if( !bol->is_Bool() ) return;
499
500 Node *cmp = bol->in(1);
501 // Compute a new check
502 Node *new_add = gvn->intcon(off_lo);
503 if( index ) {
504 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index;
505 }
506 Node *new_cmp = (flip == 1)
507 ? new (gvn->C, 3) CmpUNode( new_add, range )
508 : new (gvn->C, 3) CmpUNode( range, new_add );
509 new_cmp = gvn->transform(new_cmp);
510 // See if no need to adjust the existing check
511 if( new_cmp == cmp ) return;
512 // Else, adjust existing check
513 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
514 igvn->hash_delete( iff );
515 iff->set_req_X( 1, new_bol, igvn );
516 }
517
518 //------------------------------up_one_dom-------------------------------------
519 // Walk up the dominator tree one step. Return NULL at root or true
520 // complex merges. Skips through small diamonds.
521 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
522 Node *dom = curr->in(0);
523 if( !dom ) // Found a Region degraded to a copy?
524 return curr->nonnull_req(); // Skip thru it
525
526 if( curr != dom ) // Normal walk up one step?
527 return dom;
528
529 // Use linear_only if we are still parsing, since we cannot
530 // trust the regions to be fully filled in.
531 if (linear_only)
532 return NULL;
533
534 if( dom->is_Root() )
535 return NULL;
536
537 // Else hit a Region. Check for a loop header
538 if( dom->is_Loop() )
539 return dom->in(1); // Skip up thru loops
540
541 // Check for small diamonds
542 Node *din1, *din2, *din3, *din4;
543 if( dom->req() == 3 && // 2-path merge point
544 (din1 = dom ->in(1)) && // Left path exists
545 (din2 = dom ->in(2)) && // Right path exists
546 (din3 = din1->in(0)) && // Left path up one
547 (din4 = din2->in(0)) ) { // Right path up one
548 if( din3->is_Call() && // Handle a slow-path call on either arm
549 (din3 = din3->in(0)) )
550 din3 = din3->in(0);
551 if( din4->is_Call() && // Handle a slow-path call on either arm
552 (din4 = din4->in(0)) )
553 din4 = din4->in(0);
554 if( din3 == din4 && din3->is_If() )
555 return din3; // Skip around diamonds
556 }
557
558 // Give up the search at true merges
559 return NULL; // Dead loop? Or hit root?
560 }
561
562
563 //------------------------------filtered_int_type--------------------------------
564 // Return a possibly more restrictive type for val based on condition control flow for an if
565 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
566 assert(if_proj &&
567 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
568 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
569 IfNode* iff = if_proj->in(0)->as_If();
570 if (iff->in(1) && iff->in(1)->is_Bool()) {
571 BoolNode* bol = iff->in(1)->as_Bool();
572 if (bol->in(1) && bol->in(1)->is_Cmp()) {
573 const CmpNode* cmp = bol->in(1)->as_Cmp();
574 if (cmp->in(1) == val) {
575 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
576 if (cmp2_t != NULL) {
577 jint lo = cmp2_t->_lo;
578 jint hi = cmp2_t->_hi;
579 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
580 switch (msk) {
581 case BoolTest::ne:
582 // Can't refine type
583 return NULL;
584 case BoolTest::eq:
585 return cmp2_t;
586 case BoolTest::lt:
587 lo = TypeInt::INT->_lo;
588 if (hi - 1 < hi) {
589 hi = hi - 1;
590 }
591 break;
592 case BoolTest::le:
593 lo = TypeInt::INT->_lo;
594 break;
595 case BoolTest::gt:
596 if (lo + 1 > lo) {
597 lo = lo + 1;
598 }
599 hi = TypeInt::INT->_hi;
600 break;
601 case BoolTest::ge:
602 // lo unchanged
603 hi = TypeInt::INT->_hi;
604 break;
605 }
606 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
607 return rtn_t;
608 }
609 }
610 }
611 }
612 }
613 return NULL;
614 }
615
616 //------------------------------fold_compares----------------------------
617 // See if a pair of CmpIs can be converted into a CmpU. In some cases
618 // the direction of this if is determined by the preceding if so it
619 // can be eliminate entirely. Given an if testing (CmpI n c) check
620 // for an immediately control dependent if that is testing (CmpI n c2)
621 // and has one projection leading to this if and the other projection
622 // leading to a region that merges one of this ifs control
623 // projections.
624 //
625 // If
626 // / |
627 // / |
628 // / |
629 // If |
630 // /\ |
631 // / \ |
632 // / \ |
633 // / Region
634 //
635 Node* IfNode::fold_compares(PhaseGVN* phase) {
636 if (!EliminateAutoBox || Opcode() != Op_If) return NULL;
637
638 Node* this_cmp = in(1)->in(1);
639 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
640 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
641 Node* ctrl = in(0);
642 BoolNode* this_bool = in(1)->as_Bool();
643 Node* n = this_cmp->in(1);
644 int hi = this_cmp->in(2)->get_int();
645 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
646 ctrl->in(0)->is_If() &&
647 ctrl->in(0)->outcnt() == 2 &&
648 ctrl->in(0)->in(1)->is_Bool() &&
649 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
650 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
651 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
652 IfNode* dom_iff = ctrl->in(0)->as_If();
653 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
654 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
655 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
656 // Identify which proj goes to the region and which continues on
657 RegionNode* region = otherproj->unique_out()->as_Region();
658 Node* success = NULL;
659 Node* fail = NULL;
660 for (int i = 0; i < 2; i++) {
661 Node* proj = proj_out(i);
662 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
663 success = proj;
664 } else if (fail == NULL) {
665 fail = proj;
666 } else {
667 success = fail = NULL;
668 }
669 }
670 if (success != NULL && fail != NULL && !region->has_phi()) {
671 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
672 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
673 Node* dom_cmp = dom_bool->in(1);
674 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
675 if (failtype != NULL) {
676 const TypeInt* type2 = filtered_int_type(phase, n, fail);
677 if (type2 != NULL) {
678 failtype = failtype->join(type2)->is_int();
679 } else {
680 failtype = NULL;
681 }
682 }
683
684 if (failtype != NULL &&
685 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
686 int bound = failtype->_hi - failtype->_lo + 1;
687 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
688 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
689 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
690 Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo)));
691 Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound)));
692 Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond));
693 phase->hash_delete(dom_iff);
694 dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con));
695 phase->is_IterGVN()->_worklist.push(dom_iff);
696 phase->hash_delete(this);
697 set_req(1, newbool);
698 return this;
699 }
700 if (failtype->_lo > failtype->_hi) {
701 // previous if determines the result of this if so
702 // replace Bool with constant
703 phase->hash_delete(this);
704 set_req(1, phase->intcon(success->as_Proj()->_con));
705 return this;
706 }
707 }
708 }
709 }
710 }
711 }
712 return NULL;
713 }
714
715 //------------------------------remove_useless_bool----------------------------
716 // Check for people making a useless boolean: things like
717 // if( (x < y ? true : false) ) { ... }
718 // Replace with if( x < y ) { ... }
719 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
720 Node *i1 = iff->in(1);
721 if( !i1->is_Bool() ) return NULL;
722 BoolNode *bol = i1->as_Bool();
723
724 Node *cmp = bol->in(1);
725 if( cmp->Opcode() != Op_CmpI ) return NULL;
726
727 // Must be comparing against a bool
728 const Type *cmp2_t = phase->type( cmp->in(2) );
729 if( cmp2_t != TypeInt::ZERO &&
730 cmp2_t != TypeInt::ONE )
731 return NULL;
732
733 // Find a prior merge point merging the boolean
734 i1 = cmp->in(1);
735 if( !i1->is_Phi() ) return NULL;
736 PhiNode *phi = i1->as_Phi();
737 if( phase->type( phi ) != TypeInt::BOOL )
738 return NULL;
739
740 // Check for diamond pattern
741 int true_path = phi->is_diamond_phi();
742 if( true_path == 0 ) return NULL;
743
744 // Make sure that iff and the control of the phi are different. This
745 // should really only happen for dead control flow since it requires
746 // an illegal cycle.
747 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
748
749 // phi->region->if_proj->ifnode->bool->cmp
750 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
751
752 // Now get the 'sense' of the test correct so we can plug in
753 // either iff2->in(1) or its complement.
754 int flip = 0;
755 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
756 else if( bol->_test._test != BoolTest::eq ) return NULL;
757 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
758
759 const Type *phi1_t = phase->type( phi->in(1) );
760 const Type *phi2_t = phase->type( phi->in(2) );
761 // Check for Phi(0,1) and flip
762 if( phi1_t == TypeInt::ZERO ) {
763 if( phi2_t != TypeInt::ONE ) return NULL;
764 flip = 1-flip;
765 } else {
766 // Check for Phi(1,0)
767 if( phi1_t != TypeInt::ONE ) return NULL;
768 if( phi2_t != TypeInt::ZERO ) return NULL;
769 }
770 if( true_path == 2 ) {
771 flip = 1-flip;
772 }
773
774 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
775 assert(new_bol != iff->in(1), "must make progress");
776 iff->set_req(1, new_bol);
777 // Intervening diamond probably goes dead
778 phase->C->set_major_progress();
779 return iff;
780 }
781
782 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
783
784 //------------------------------Ideal------------------------------------------
785 // Return a node which is more "ideal" than the current node. Strip out
786 // control copies
787 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
788 if (remove_dead_region(phase, can_reshape)) return this;
789 // No Def-Use info?
790 if (!can_reshape) return NULL;
791 PhaseIterGVN *igvn = phase->is_IterGVN();
792
793 // Don't bother trying to transform a dead if
794 if (in(0)->is_top()) return NULL;
795 // Don't bother trying to transform an if with a dead test
796 if (in(1)->is_top()) return NULL;
797 // Another variation of a dead test
798 if (in(1)->is_Con()) return NULL;
799 // Another variation of a dead if
800 if (outcnt() < 2) return NULL;
801
802 // Canonicalize the test.
803 Node* idt_if = idealize_test(phase, this);
804 if (idt_if != NULL) return idt_if;
805
806 // Try to split the IF
807 Node *s = split_if(this, igvn);
808 if (s != NULL) return s;
809
810 // Check for people making a useless boolean: things like
811 // if( (x < y ? true : false) ) { ... }
812 // Replace with if( x < y ) { ... }
813 Node *bol2 = remove_useless_bool(this, phase);
814 if( bol2 ) return bol2;
815
816 // Setup to scan up the CFG looking for a dominating test
817 Node *dom = in(0);
818 Node *prev_dom = this;
819
820 // Check for range-check vs other kinds of tests
821 Node *index1, *range1;
822 jint offset1;
823 int flip1 = is_range_check(range1, index1, offset1);
824 if( flip1 ) {
825 Node *first_prev_dom = NULL;
826
827 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
828 // so all checks we inspect post-dominate the top-most check we find.
829 // If we are going to fail the current check and we reach the top check
830 // then we are guaranteed to fail, so just start interpreting there.
831 // We 'expand' the top 2 range checks to include all post-dominating
832 // checks.
833
834 // The top 2 range checks seen
835 Node *prev_chk1 = NULL;
836 Node *prev_chk2 = NULL;
837 // Low and high offsets seen so far
838 jint off_lo = offset1;
839 jint off_hi = offset1;
840
841 // Scan for the top 2 checks and collect range of offsets
842 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
843 if( dom->Opcode() == Op_If && // Not same opcode?
844 prev_dom->in(0) == dom ) { // One path of test does dominate?
845 if( dom == this ) return NULL; // dead loop
846 // See if this is a range check
847 Node *index2, *range2;
848 jint offset2;
849 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
850 // See if this is a _matching_ range check, checking against
851 // the same array bounds.
852 if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
853 dom->outcnt() == 2 ) {
854 // Gather expanded bounds
855 off_lo = MIN2(off_lo,offset2);
856 off_hi = MAX2(off_hi,offset2);
857 // Record top 2 range checks
858 prev_chk2 = prev_chk1;
859 prev_chk1 = prev_dom;
860 // If we match the test exactly, then the top test covers
861 // both our lower and upper bounds.
862 if( dom->in(1) == in(1) )
863 prev_chk2 = prev_chk1;
864 }
865 }
866 prev_dom = dom;
867 dom = up_one_dom( dom );
868 if( !dom ) break;
869 }
870
871
872 // Attempt to widen the dominating range check to cover some later
873 // ones. Since range checks "fail" by uncommon-trapping to the
874 // interpreter, widening a check can make us speculative enter the
875 // interpreter. If we see range-check deopt's, do not widen!
876 if (!phase->C->allow_range_check_smearing()) return NULL;
877
878 // Constant indices only need to check the upper bound.
879 // Non-constance indices must check both low and high.
880 if( index1 ) {
881 // Didn't find 2 prior covering checks, so cannot remove anything.
882 if( !prev_chk2 ) return NULL;
883 // 'Widen' the offsets of the 1st and 2nd covering check
884 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
885 // Do not call adjust_check twice on the same projection
886 // as the first call may have transformed the BoolNode to a ConI
887 if( prev_chk1 != prev_chk2 ) {
888 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
889 }
890 // Test is now covered by prior checks, dominate it out
891 prev_dom = prev_chk2;
892 } else {
893 // Didn't find prior covering check, so cannot remove anything.
894 if( !prev_chk1 ) return NULL;
895 // 'Widen' the offset of the 1st and only covering check
896 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
897 // Test is now covered by prior checks, dominate it out
898 prev_dom = prev_chk1;
899 }
900
901
902 } else { // Scan for an equivalent test
903
904 Node *cmp;
905 int dist = 0; // Cutoff limit for search
906 int op = Opcode();
907 if( op == Op_If &&
908 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
909 if( cmp->in(2) != NULL && // make sure cmp is not already dead
910 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
911 dist = 64; // Limit for null-pointer scans
912 } else {
913 dist = 4; // Do not bother for random pointer tests
914 }
915 } else {
916 dist = 4; // Limit for random junky scans
917 }
918
919 // Normal equivalent-test check.
920 if( !dom ) return NULL; // Dead loop?
921
922 Node* result = fold_compares(phase);
923 if (result != NULL) {
924 return result;
925 }
926
927 // Search up the dominator tree for an If with an identical test
928 while( dom->Opcode() != op || // Not same opcode?
929 dom->in(1) != in(1) || // Not same input 1?
930 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
931 prev_dom->in(0) != dom ) { // One path of test does not dominate?
932 if( dist < 0 ) return NULL;
933
934 dist--;
935 prev_dom = dom;
936 dom = up_one_dom( dom );
937 if( !dom ) return NULL;
938 }
939
940 // Check that we did not follow a loop back to ourselves
941 if( this == dom )
942 return NULL;
943
944 if( dist > 2 ) // Add to count of NULL checks elided
945 explicit_null_checks_elided++;
946
947 } // End of Else scan for an equivalent test
948
949 // Hit! Remove this IF
950 #ifndef PRODUCT
951 if( TraceIterativeGVN ) {
952 tty->print(" Removing IfNode: "); this->dump();
953 }
954 if( VerifyOpto && !phase->allow_progress() ) {
955 // Found an equivalent dominating test,
956 // we can not guarantee reaching a fix-point for these during iterativeGVN
957 // since intervening nodes may not change.
958 return NULL;
959 }
960 #endif
961
962 // Replace dominated IfNode
963 dominated_by( prev_dom, igvn );
964
965 // Must return either the original node (now dead) or a new node
966 // (Do not return a top here, since that would break the uniqueness of top.)
967 return new (phase->C, 1) ConINode(TypeInt::ZERO);
968 }
969
970 //------------------------------dominated_by-----------------------------------
971 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
972 igvn->hash_delete(this); // Remove self to prevent spurious V-N
973 Node *idom = in(0);
974 // Need opcode to decide which way 'this' test goes
975 int prev_op = prev_dom->Opcode();
976 Node *top = igvn->C->top(); // Shortcut to top
977
978 // Now walk the current IfNode's projections.
979 // Loop ends when 'this' has no more uses.
980 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
981 Node *ifp = last_out(i); // Get IfTrue/IfFalse
982 igvn->add_users_to_worklist(ifp);
983 // Check which projection it is and set target.
984 // Data-target is either the dominating projection of the same type
985 // or TOP if the dominating projection is of opposite type.
986 // Data-target will be used as the new control edge for the non-CFG
987 // nodes like Casts and Loads.
988 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top;
989 // Control-target is just the If's immediate dominator or TOP.
990 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top;
991
992 // For each child of an IfTrue/IfFalse projection, reroute.
993 // Loop ends when projection has no more uses.
994 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
995 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
996 igvn->hash_delete(s); // Yank from hash table before edge hacking
997 if( !s->depends_only_on_test() ) {
998 // Find the control input matching this def-use edge.
999 // For Regions it may not be in slot 0.
1000 uint l;
1001 for( l = 0; s->in(l) != ifp; l++ ) { }
1002 s->set_req(l, ctrl_target);
1003 } else { // Else, for control producers,
1004 s->set_req(0, data_target); // Move child to data-target
1005 }
1006 igvn->_worklist.push(s); // Revisit collapsed Phis
1007 } // End for each child of a projection
1008
1009 igvn->remove_dead_node(ifp);
1010 } // End for each IfTrue/IfFalse child of If
1011
1012 // Kill the IfNode
1013 igvn->remove_dead_node(this);
1014 }
1015
1016 //------------------------------Identity---------------------------------------
1017 // If the test is constant & we match, then we are the input Control
1018 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1019 // Can only optimize if cannot go the other way
1020 const TypeTuple *t = phase->type(in(0))->is_tuple();
1021 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1022 ? in(0)->in(0) // IfNode control
1023 : this; // no progress
1024 }
1025
1026 //------------------------------dump_spec--------------------------------------
1027 #ifndef PRODUCT
1028 void IfNode::dump_spec(outputStream *st) const {
1029 st->print("P=%f, C=%f",_prob,_fcnt);
1030 }
1031 #endif
1032
1033 //------------------------------idealize_test----------------------------------
1034 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1035 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1036 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1037 // needed.
1038 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1039 assert(iff->in(0) != NULL, "If must be live");
1040
1041 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1042 Node* old_if_f = iff->proj_out(false);
1043 Node* old_if_t = iff->proj_out(true);
1044
1045 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1046 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1047 // happens in count-down loops
1048 if (iff->is_CountedLoopEnd()) return NULL;
1049 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1050 BoolNode *b = iff->in(1)->as_Bool();
1051 BoolTest bt = b->_test;
1052 // Test already in good order?
1053 if( bt.is_canonical() )
1054 return NULL;
1055
1056 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1057 // cloning the IfNode.
1058 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) );
1059 if( !new_b->is_Bool() ) return NULL;
1060 b = new_b->as_Bool();
1061
1062 PhaseIterGVN *igvn = phase->is_IterGVN();
1063 assert( igvn, "Test is not canonical in parser?" );
1064
1065 // The IF node never really changes, but it needs to be cloned
1066 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1067
1068 Node *prior = igvn->hash_find_insert(iff);
1069 if( prior ) {
1070 igvn->remove_dead_node(iff);
1071 iff = (IfNode*)prior;
1072 } else {
1073 // Cannot call transform on it just yet
1074 igvn->set_type_bottom(iff);
1075 }
1076 igvn->_worklist.push(iff);
1077
1078 // Now handle projections. Cloning not required.
1079 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff ));
1080 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff ));
1081
1082 igvn->register_new_node_with_optimizer(new_if_f);
1083 igvn->register_new_node_with_optimizer(new_if_t);
1084 // Flip test, so flip trailing control
1085 igvn->replace_node(old_if_f, new_if_t);
1086 igvn->replace_node(old_if_t, new_if_f);
1087
1088 // Progress
1089 return iff;
1090 }
1091
1092 //------------------------------Identity---------------------------------------
1093 // If the test is constant & we match, then we are the input Control
1094 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1095 // Can only optimize if cannot go the other way
1096 const TypeTuple *t = phase->type(in(0))->is_tuple();
1097 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1098 ? in(0)->in(0) // IfNode control
1099 : this; // no progress
1100 }