1 /*
2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/addnode.hpp"
28 #include "opto/cfgnode.hpp"
29 #include "opto/connode.hpp"
30 #include "opto/phaseX.hpp"
31 #include "opto/runtime.hpp"
32 #include "opto/subnode.hpp"
33
34 // Portions of code courtesy of Clifford Click
35
36 // Optimization - Graph Style
37
38
39 extern int explicit_null_checks_elided;
40
41 //=============================================================================
42 //------------------------------Value------------------------------------------
43 // Return a tuple for whichever arm of the IF is reachable
44 const Type *IfNode::Value( PhaseTransform *phase ) const {
45 if( !in(0) ) return Type::TOP;
46 if( phase->type(in(0)) == Type::TOP )
47 return Type::TOP;
48 const Type *t = phase->type(in(1));
49 if( t == Type::TOP ) // data is undefined
50 return TypeTuple::IFNEITHER; // unreachable altogether
51 if( t == TypeInt::ZERO ) // zero, or false
52 return TypeTuple::IFFALSE; // only false branch is reachable
53 if( t == TypeInt::ONE ) // 1, or true
54 return TypeTuple::IFTRUE; // only true branch is reachable
55 assert( t == TypeInt::BOOL, "expected boolean type" );
56
57 return TypeTuple::IFBOTH; // No progress
58 }
59
60 const RegMask &IfNode::out_RegMask() const {
61 return RegMask::Empty;
62 }
63
64 //------------------------------split_if---------------------------------------
65 // Look for places where we merge constants, then test on the merged value.
66 // If the IF test will be constant folded on the path with the constant, we
67 // win by splitting the IF to before the merge point.
68 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
69 // I could be a lot more general here, but I'm trying to squeeze this
70 // in before the Christmas '98 break so I'm gonna be kinda restrictive
71 // on the patterns I accept. CNC
72
73 // Look for a compare of a constant and a merged value
74 Node *i1 = iff->in(1);
75 if( !i1->is_Bool() ) return NULL;
76 BoolNode *b = i1->as_Bool();
77 Node *cmp = b->in(1);
78 if( !cmp->is_Cmp() ) return NULL;
79 i1 = cmp->in(1);
80 if( i1 == NULL || !i1->is_Phi() ) return NULL;
81 PhiNode *phi = i1->as_Phi();
82 if( phi->is_copy() ) return NULL;
83 Node *con2 = cmp->in(2);
84 if( !con2->is_Con() ) return NULL;
85 // See that the merge point contains some constants
86 Node *con1=NULL;
87 uint i4;
88 for( i4 = 1; i4 < phi->req(); i4++ ) {
89 con1 = phi->in(i4);
90 if( !con1 ) return NULL; // Do not optimize partially collapsed merges
91 if( con1->is_Con() ) break; // Found a constant
92 // Also allow null-vs-not-null checks
93 const TypePtr *tp = igvn->type(con1)->isa_ptr();
94 if( tp && tp->_ptr == TypePtr::NotNull )
95 break;
96 }
97 if( i4 >= phi->req() ) return NULL; // Found no constants
98
99 igvn->C->set_has_split_ifs(true); // Has chance for split-if
100
101 // Make sure that the compare can be constant folded away
102 Node *cmp2 = cmp->clone();
103 cmp2->set_req(1,con1);
104 cmp2->set_req(2,con2);
105 const Type *t = cmp2->Value(igvn);
106 // This compare is dead, so whack it!
107 igvn->remove_dead_node(cmp2);
108 if( !t->singleton() ) return NULL;
109
110 // No intervening control, like a simple Call
111 Node *r = iff->in(0);
112 if( !r->is_Region() ) return NULL;
113 if( phi->region() != r ) return NULL;
114 // No other users of the cmp/bool
115 if (b->outcnt() != 1 || cmp->outcnt() != 1) {
116 //tty->print_cr("many users of cmp/bool");
117 return NULL;
118 }
119
120 // Make sure we can determine where all the uses of merged values go
121 for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
122 Node* u = r->fast_out(j);
123 if( u == r ) continue;
124 if( u == iff ) continue;
125 if( u->outcnt() == 0 ) continue; // use is dead & ignorable
126 if( !u->is_Phi() ) {
127 /*
128 if( u->is_Start() ) {
129 tty->print_cr("Region has inlined start use");
130 } else {
131 tty->print_cr("Region has odd use");
132 u->dump(2);
133 }*/
134 return NULL;
135 }
136 if( u != phi ) {
137 // CNC - do not allow any other merged value
138 //tty->print_cr("Merging another value");
139 //u->dump(2);
140 return NULL;
141 }
142 // Make sure we can account for all Phi uses
143 for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
144 Node* v = u->fast_out(k); // User of the phi
145 // CNC - Allow only really simple patterns.
146 // In particular I disallow AddP of the Phi, a fairly common pattern
147 if( v == cmp ) continue; // The compare is OK
148 if( (v->is_ConstraintCast()) &&
149 v->in(0)->in(0) == iff )
150 continue; // CastPP/II of the IfNode is OK
151 // Disabled following code because I cannot tell if exactly one
152 // path dominates without a real dominator check. CNC 9/9/1999
153 //uint vop = v->Opcode();
154 //if( vop == Op_Phi ) { // Phi from another merge point might be OK
155 // Node *r = v->in(0); // Get controlling point
156 // if( !r ) return NULL; // Degraded to a copy
157 // // Find exactly one path in (either True or False doms, but not IFF)
158 // int cnt = 0;
159 // for( uint i = 1; i < r->req(); i++ )
160 // if( r->in(i) && r->in(i)->in(0) == iff )
161 // cnt++;
162 // if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
163 //}
164 if( !v->is_Call() ) {
165 /*
166 if( v->Opcode() == Op_AddP ) {
167 tty->print_cr("Phi has AddP use");
168 } else if( v->Opcode() == Op_CastPP ) {
169 tty->print_cr("Phi has CastPP use");
170 } else if( v->Opcode() == Op_CastII ) {
171 tty->print_cr("Phi has CastII use");
172 } else {
173 tty->print_cr("Phi has use I cant be bothered with");
174 }
175 */
176 }
177 return NULL;
178
179 /* CNC - Cut out all the fancy acceptance tests
180 // Can we clone this use when doing the transformation?
181 // If all uses are from Phis at this merge or constants, then YES.
182 if( !v->in(0) && v != cmp ) {
183 tty->print_cr("Phi has free-floating use");
184 v->dump(2);
185 return NULL;
186 }
187 for( uint l = 1; l < v->req(); l++ ) {
188 if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
189 !v->in(l)->is_Con() ) {
190 tty->print_cr("Phi has use");
191 v->dump(2);
192 return NULL;
193 } // End of if Phi-use input is neither Phi nor Constant
194 } // End of for all inputs to Phi-use
195 */
196 } // End of for all uses of Phi
197 } // End of for all uses of Region
198
199 // Only do this if the IF node is in a sane state
200 if (iff->outcnt() != 2)
201 return NULL;
202
203 // Got a hit! Do the Mondo Hack!
204 //
205 //ABC a1c def ghi B 1 e h A C a c d f g i
206 // R - Phi - Phi - Phi Rc - Phi - Phi - Phi Rx - Phi - Phi - Phi
207 // cmp - 2 cmp - 2 cmp - 2
208 // bool bool_c bool_x
209 // if if_c if_x
210 // T F T F T F
211 // ..s.. ..t .. ..s.. ..t.. ..s.. ..t..
212 //
213 // Split the paths coming into the merge point into 2 separate groups of
214 // merges. On the left will be all the paths feeding constants into the
215 // Cmp's Phi. On the right will be the remaining paths. The Cmp's Phi
216 // will fold up into a constant; this will let the Cmp fold up as well as
217 // all the control flow. Below the original IF we have 2 control
218 // dependent regions, 's' and 't'. Now we will merge the two paths
219 // just prior to 's' and 't' from the two IFs. At least 1 path (and quite
220 // likely 2 or more) will promptly constant fold away.
221 PhaseGVN *phase = igvn;
222
223 // Make a region merging constants and a region merging the rest
224 uint req_c = 0;
225 for (uint ii = 1; ii < r->req(); ii++) {
226 if( phi->in(ii) == con1 ) {
227 req_c++;
228 }
229 }
230 Node *region_c = new (igvn->C, req_c + 1) RegionNode(req_c + 1);
231 Node *phi_c = con1;
232 uint len = r->req();
233 Node *region_x = new (igvn->C, len - req_c + 1) RegionNode(len - req_c + 1);
234 Node *phi_x = PhiNode::make_blank(region_x, phi);
235 for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
236 if( phi->in(i) == con1 ) {
237 region_c->init_req( i_c++, r ->in(i) );
238 } else {
239 region_x->init_req( i_x, r ->in(i) );
240 phi_x ->init_req( i_x++, phi->in(i) );
241 }
242 }
243
244 // Register the new RegionNodes but do not transform them. Cannot
245 // transform until the entire Region/Phi conglomerate has been hacked
246 // as a single huge transform.
247 igvn->register_new_node_with_optimizer( region_c );
248 igvn->register_new_node_with_optimizer( region_x );
249 // Prevent the untimely death of phi_x. Currently he has no uses. He is
250 // about to get one. If this only use goes away, then phi_x will look dead.
251 // However, he will be picking up some more uses down below.
252 Node *hook = new (igvn->C, 4) Node(4);
253 hook->init_req(0, phi_x);
254 hook->init_req(1, phi_c);
255 phi_x = phase->transform( phi_x );
256
257 // Make the compare
258 Node *cmp_c = phase->makecon(t);
259 Node *cmp_x = cmp->clone();
260 cmp_x->set_req(1,phi_x);
261 cmp_x->set_req(2,con2);
262 cmp_x = phase->transform(cmp_x);
263 // Make the bool
264 Node *b_c = phase->transform(new (igvn->C, 2) BoolNode(cmp_c,b->_test._test));
265 Node *b_x = phase->transform(new (igvn->C, 2) BoolNode(cmp_x,b->_test._test));
266 // Make the IfNode
267 IfNode *iff_c = new (igvn->C, 2) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
268 igvn->set_type_bottom(iff_c);
269 igvn->_worklist.push(iff_c);
270 hook->init_req(2, iff_c);
271
272 IfNode *iff_x = new (igvn->C, 2) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
273 igvn->set_type_bottom(iff_x);
274 igvn->_worklist.push(iff_x);
275 hook->init_req(3, iff_x);
276
277 // Make the true/false arms
278 Node *iff_c_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_c));
279 Node *iff_c_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_c));
280 Node *iff_x_t = phase->transform(new (igvn->C, 1) IfTrueNode (iff_x));
281 Node *iff_x_f = phase->transform(new (igvn->C, 1) IfFalseNode(iff_x));
282
283 // Merge the TRUE paths
284 Node *region_s = new (igvn->C, 3) RegionNode(3);
285 igvn->_worklist.push(region_s);
286 region_s->init_req(1, iff_c_t);
287 region_s->init_req(2, iff_x_t);
288 igvn->register_new_node_with_optimizer( region_s );
289
290 // Merge the FALSE paths
291 Node *region_f = new (igvn->C, 3) RegionNode(3);
292 igvn->_worklist.push(region_f);
293 region_f->init_req(1, iff_c_f);
294 region_f->init_req(2, iff_x_f);
295 igvn->register_new_node_with_optimizer( region_f );
296
297 igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
298 cmp->set_req(1,NULL); // Whack the inputs to cmp because it will be dead
299 cmp->set_req(2,NULL);
300 // Check for all uses of the Phi and give them a new home.
301 // The 'cmp' got cloned, but CastPP/IIs need to be moved.
302 Node *phi_s = NULL; // do not construct unless needed
303 Node *phi_f = NULL; // do not construct unless needed
304 for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
305 Node* v = phi->last_out(i2);// User of the phi
306 igvn->hash_delete(v); // Have to fixup other Phi users
307 igvn->_worklist.push(v);
308 uint vop = v->Opcode();
309 Node *proj = NULL;
310 if( vop == Op_Phi ) { // Remote merge point
311 Node *r = v->in(0);
312 for (uint i3 = 1; i3 < r->req(); i3++)
313 if (r->in(i3) && r->in(i3)->in(0) == iff) {
314 proj = r->in(i3);
315 break;
316 }
317 } else if( v->is_ConstraintCast() ) {
318 proj = v->in(0); // Controlling projection
319 } else {
320 assert( 0, "do not know how to handle this guy" );
321 }
322
323 Node *proj_path_data, *proj_path_ctrl;
324 if( proj->Opcode() == Op_IfTrue ) {
325 if( phi_s == NULL ) {
326 // Only construct phi_s if needed, otherwise provides
327 // interfering use.
328 phi_s = PhiNode::make_blank(region_s,phi);
329 phi_s->init_req( 1, phi_c );
330 phi_s->init_req( 2, phi_x );
331 hook->add_req(phi_s);
332 phi_s = phase->transform(phi_s);
333 }
334 proj_path_data = phi_s;
335 proj_path_ctrl = region_s;
336 } else {
337 if( phi_f == NULL ) {
338 // Only construct phi_f if needed, otherwise provides
339 // interfering use.
340 phi_f = PhiNode::make_blank(region_f,phi);
341 phi_f->init_req( 1, phi_c );
342 phi_f->init_req( 2, phi_x );
343 hook->add_req(phi_f);
344 phi_f = phase->transform(phi_f);
345 }
346 proj_path_data = phi_f;
347 proj_path_ctrl = region_f;
348 }
349
350 // Fixup 'v' for for the split
351 if( vop == Op_Phi ) { // Remote merge point
352 uint i;
353 for( i = 1; i < v->req(); i++ )
354 if( v->in(i) == phi )
355 break;
356 v->set_req(i, proj_path_data );
357 } else if( v->is_ConstraintCast() ) {
358 v->set_req(0, proj_path_ctrl );
359 v->set_req(1, proj_path_data );
360 } else
361 ShouldNotReachHere();
362 }
363
364 // Now replace the original iff's True/False with region_s/region_t.
365 // This makes the original iff go dead.
366 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
367 Node* p = iff->last_out(i3);
368 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
369 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
370 // Replace p with u
371 igvn->add_users_to_worklist(p);
372 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
373 Node* x = p->last_out(l);
374 igvn->hash_delete(x);
375 uint uses_found = 0;
376 for( uint j = 0; j < x->req(); j++ ) {
377 if( x->in(j) == p ) {
378 x->set_req(j, u);
379 uses_found++;
380 }
381 }
382 l -= uses_found; // we deleted 1 or more copies of this edge
383 }
384 igvn->remove_dead_node(p);
385 }
386
387 // Force the original merge dead
388 igvn->hash_delete(r);
389 // First, remove region's dead users.
390 for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
391 Node* u = r->last_out(l);
392 if( u == r ) {
393 r->set_req(0, NULL);
394 } else {
395 assert(u->outcnt() == 0, "only dead users");
396 igvn->remove_dead_node(u);
397 }
398 l -= 1;
399 }
400 igvn->remove_dead_node(r);
401
402 // Now remove the bogus extra edges used to keep things alive
403 igvn->remove_dead_node( hook );
404
405 // Must return either the original node (now dead) or a new node
406 // (Do not return a top here, since that would break the uniqueness of top.)
407 return new (igvn->C, 1) ConINode(TypeInt::ZERO);
408 }
409
410 //------------------------------is_range_check---------------------------------
411 // Return 0 if not a range check. Return 1 if a range check and set index and
412 // offset. Return 2 if we had to negate the test. Index is NULL if the check
413 // is versus a constant.
414 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
415 Node* b = in(1);
416 if (b == NULL || !b->is_Bool()) return 0;
417 BoolNode* bn = b->as_Bool();
418 Node* cmp = bn->in(1);
419 if (cmp == NULL) return 0;
420 if (cmp->Opcode() != Op_CmpU) return 0;
421
422 Node* l = cmp->in(1);
423 Node* r = cmp->in(2);
424 int flip_test = 1;
425 if (bn->_test._test == BoolTest::le) {
426 l = cmp->in(2);
427 r = cmp->in(1);
428 flip_test = 2;
429 } else if (bn->_test._test != BoolTest::lt) {
430 return 0;
431 }
432 if (l->is_top()) return 0; // Top input means dead test
433 if (r->Opcode() != Op_LoadRange) return 0;
434
435 // We have recognized one of these forms:
436 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ...
437 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ...
438
439 // Make sure it's a real range check by requiring an uncommon trap
440 // along the OOB path. Otherwise, it's possible that the user wrote
441 // something which optimized to look like a range check but behaves
442 // in some other way.
443 Node* iftrap = proj_out(flip_test == 2 ? true : false);
444 bool found_trap = false;
445 if (iftrap != NULL) {
446 Node* u = iftrap->unique_ctrl_out();
447 if (u != NULL) {
448 // It could be a merge point (Region) for uncommon trap.
449 if (u->is_Region()) {
450 Node* c = u->unique_ctrl_out();
451 if (c != NULL) {
452 iftrap = u;
453 u = c;
454 }
455 }
456 if (u->in(0) == iftrap && u->is_CallStaticJava()) {
457 int req = u->as_CallStaticJava()->uncommon_trap_request();
458 if (Deoptimization::trap_request_reason(req) ==
459 Deoptimization::Reason_range_check) {
460 found_trap = true;
461 }
462 }
463 }
464 }
465 if (!found_trap) return 0; // sorry, no cigar
466
467 // Look for index+offset form
468 Node* ind = l;
469 jint off = 0;
470 if (l->is_top()) {
471 return 0;
472 } else if (l->is_Add()) {
473 if ((off = l->in(1)->find_int_con(0)) != 0) {
474 ind = l->in(2);
475 } else if ((off = l->in(2)->find_int_con(0)) != 0) {
476 ind = l->in(1);
477 }
478 } else if ((off = l->find_int_con(-1)) >= 0) {
479 // constant offset with no variable index
480 ind = NULL;
481 } else {
482 // variable index with no constant offset (or dead negative index)
483 off = 0;
484 }
485
486 // Return all the values:
487 index = ind;
488 offset = off;
489 range = r;
490 return flip_test;
491 }
492
493 //------------------------------adjust_check-----------------------------------
494 // Adjust (widen) a prior range check
495 static void adjust_check(Node* proj, Node* range, Node* index,
496 int flip, jint off_lo, PhaseIterGVN* igvn) {
497 PhaseGVN *gvn = igvn;
498 // Break apart the old check
499 Node *iff = proj->in(0);
500 Node *bol = iff->in(1);
501 if( bol->is_top() ) return; // In case a partially dead range check appears
502 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
503 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
504 if( !bol->is_Bool() ) return;
505
506 Node *cmp = bol->in(1);
507 // Compute a new check
508 Node *new_add = gvn->intcon(off_lo);
509 if( index ) {
510 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index;
511 }
512 Node *new_cmp = (flip == 1)
513 ? new (gvn->C, 3) CmpUNode( new_add, range )
514 : new (gvn->C, 3) CmpUNode( range, new_add );
515 new_cmp = gvn->transform(new_cmp);
516 // See if no need to adjust the existing check
517 if( new_cmp == cmp ) return;
518 // Else, adjust existing check
519 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
520 igvn->hash_delete( iff );
521 iff->set_req_X( 1, new_bol, igvn );
522 }
523
524 //------------------------------up_one_dom-------------------------------------
525 // Walk up the dominator tree one step. Return NULL at root or true
526 // complex merges. Skips through small diamonds.
527 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
528 Node *dom = curr->in(0);
529 if( !dom ) // Found a Region degraded to a copy?
530 return curr->nonnull_req(); // Skip thru it
531
532 if( curr != dom ) // Normal walk up one step?
533 return dom;
534
535 // Use linear_only if we are still parsing, since we cannot
536 // trust the regions to be fully filled in.
537 if (linear_only)
538 return NULL;
539
540 if( dom->is_Root() )
541 return NULL;
542
543 // Else hit a Region. Check for a loop header
544 if( dom->is_Loop() )
545 return dom->in(1); // Skip up thru loops
546
547 // Check for small diamonds
548 Node *din1, *din2, *din3, *din4;
549 if( dom->req() == 3 && // 2-path merge point
550 (din1 = dom ->in(1)) && // Left path exists
551 (din2 = dom ->in(2)) && // Right path exists
552 (din3 = din1->in(0)) && // Left path up one
553 (din4 = din2->in(0)) ) { // Right path up one
554 if( din3->is_Call() && // Handle a slow-path call on either arm
555 (din3 = din3->in(0)) )
556 din3 = din3->in(0);
557 if( din4->is_Call() && // Handle a slow-path call on either arm
558 (din4 = din4->in(0)) )
559 din4 = din4->in(0);
560 if( din3 == din4 && din3->is_If() )
561 return din3; // Skip around diamonds
562 }
563
564 // Give up the search at true merges
565 return NULL; // Dead loop? Or hit root?
566 }
567
568
569 //------------------------------filtered_int_type--------------------------------
570 // Return a possibly more restrictive type for val based on condition control flow for an if
571 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
572 assert(if_proj &&
573 (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
574 if (if_proj->in(0) && if_proj->in(0)->is_If()) {
575 IfNode* iff = if_proj->in(0)->as_If();
576 if (iff->in(1) && iff->in(1)->is_Bool()) {
577 BoolNode* bol = iff->in(1)->as_Bool();
578 if (bol->in(1) && bol->in(1)->is_Cmp()) {
579 const CmpNode* cmp = bol->in(1)->as_Cmp();
580 if (cmp->in(1) == val) {
581 const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
582 if (cmp2_t != NULL) {
583 jint lo = cmp2_t->_lo;
584 jint hi = cmp2_t->_hi;
585 BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
586 switch (msk) {
587 case BoolTest::ne:
588 // Can't refine type
589 return NULL;
590 case BoolTest::eq:
591 return cmp2_t;
592 case BoolTest::lt:
593 lo = TypeInt::INT->_lo;
594 if (hi - 1 < hi) {
595 hi = hi - 1;
596 }
597 break;
598 case BoolTest::le:
599 lo = TypeInt::INT->_lo;
600 break;
601 case BoolTest::gt:
602 if (lo + 1 > lo) {
603 lo = lo + 1;
604 }
605 hi = TypeInt::INT->_hi;
606 break;
607 case BoolTest::ge:
608 // lo unchanged
609 hi = TypeInt::INT->_hi;
610 break;
611 }
612 const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
613 return rtn_t;
614 }
615 }
616 }
617 }
618 }
619 return NULL;
620 }
621
622 //------------------------------fold_compares----------------------------
623 // See if a pair of CmpIs can be converted into a CmpU. In some cases
624 // the direction of this if is determined by the preceding if so it
625 // can be eliminate entirely. Given an if testing (CmpI n c) check
626 // for an immediately control dependent if that is testing (CmpI n c2)
627 // and has one projection leading to this if and the other projection
628 // leading to a region that merges one of this ifs control
629 // projections.
630 //
631 // If
632 // / |
633 // / |
634 // / |
635 // If |
636 // /\ |
637 // / \ |
638 // / \ |
639 // / Region
640 //
641 Node* IfNode::fold_compares(PhaseGVN* phase) {
642 if (!EliminateAutoBox || Opcode() != Op_If) return NULL;
643
644 Node* this_cmp = in(1)->in(1);
645 if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
646 this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
647 Node* ctrl = in(0);
648 BoolNode* this_bool = in(1)->as_Bool();
649 Node* n = this_cmp->in(1);
650 int hi = this_cmp->in(2)->get_int();
651 if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
652 ctrl->in(0)->is_If() &&
653 ctrl->in(0)->outcnt() == 2 &&
654 ctrl->in(0)->in(1)->is_Bool() &&
655 ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
656 ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
657 ctrl->in(0)->in(1)->in(1)->in(1) == n) {
658 IfNode* dom_iff = ctrl->in(0)->as_If();
659 Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
660 if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
661 this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
662 // Identify which proj goes to the region and which continues on
663 RegionNode* region = otherproj->unique_out()->as_Region();
664 Node* success = NULL;
665 Node* fail = NULL;
666 for (int i = 0; i < 2; i++) {
667 Node* proj = proj_out(i);
668 if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
669 success = proj;
670 } else if (fail == NULL) {
671 fail = proj;
672 } else {
673 success = fail = NULL;
674 }
675 }
676 if (success != NULL && fail != NULL && !region->has_phi()) {
677 int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
678 BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
679 Node* dom_cmp = dom_bool->in(1);
680 const TypeInt* failtype = filtered_int_type(phase, n, ctrl);
681 if (failtype != NULL) {
682 const TypeInt* type2 = filtered_int_type(phase, n, fail);
683 if (type2 != NULL) {
684 failtype = failtype->join(type2)->is_int();
685 } else {
686 failtype = NULL;
687 }
688 }
689
690 if (failtype != NULL &&
691 dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
692 int bound = failtype->_hi - failtype->_lo + 1;
693 if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
694 // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) hi)
695 BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
696 Node* adjusted = phase->transform(new (phase->C, 3) SubINode(n, phase->intcon(failtype->_lo)));
697 Node* newcmp = phase->transform(new (phase->C, 3) CmpUNode(adjusted, phase->intcon(bound)));
698 Node* newbool = phase->transform(new (phase->C, 2) BoolNode(newcmp, cond));
699 phase->hash_delete(dom_iff);
700 dom_iff->set_req(1, phase->intcon(ctrl->as_Proj()->_con));
701 phase->is_IterGVN()->_worklist.push(dom_iff);
702 phase->hash_delete(this);
703 set_req(1, newbool);
704 return this;
705 }
706 if (failtype->_lo > failtype->_hi) {
707 // previous if determines the result of this if so
708 // replace Bool with constant
709 phase->hash_delete(this);
710 set_req(1, phase->intcon(success->as_Proj()->_con));
711 return this;
712 }
713 }
714 }
715 }
716 }
717 }
718 return NULL;
719 }
720
721 //------------------------------remove_useless_bool----------------------------
722 // Check for people making a useless boolean: things like
723 // if( (x < y ? true : false) ) { ... }
724 // Replace with if( x < y ) { ... }
725 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
726 Node *i1 = iff->in(1);
727 if( !i1->is_Bool() ) return NULL;
728 BoolNode *bol = i1->as_Bool();
729
730 Node *cmp = bol->in(1);
731 if( cmp->Opcode() != Op_CmpI ) return NULL;
732
733 // Must be comparing against a bool
734 const Type *cmp2_t = phase->type( cmp->in(2) );
735 if( cmp2_t != TypeInt::ZERO &&
736 cmp2_t != TypeInt::ONE )
737 return NULL;
738
739 // Find a prior merge point merging the boolean
740 i1 = cmp->in(1);
741 if( !i1->is_Phi() ) return NULL;
742 PhiNode *phi = i1->as_Phi();
743 if( phase->type( phi ) != TypeInt::BOOL )
744 return NULL;
745
746 // Check for diamond pattern
747 int true_path = phi->is_diamond_phi();
748 if( true_path == 0 ) return NULL;
749
750 // Make sure that iff and the control of the phi are different. This
751 // should really only happen for dead control flow since it requires
752 // an illegal cycle.
753 if (phi->in(0)->in(1)->in(0) == iff) return NULL;
754
755 // phi->region->if_proj->ifnode->bool->cmp
756 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
757
758 // Now get the 'sense' of the test correct so we can plug in
759 // either iff2->in(1) or its complement.
760 int flip = 0;
761 if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
762 else if( bol->_test._test != BoolTest::eq ) return NULL;
763 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
764
765 const Type *phi1_t = phase->type( phi->in(1) );
766 const Type *phi2_t = phase->type( phi->in(2) );
767 // Check for Phi(0,1) and flip
768 if( phi1_t == TypeInt::ZERO ) {
769 if( phi2_t != TypeInt::ONE ) return NULL;
770 flip = 1-flip;
771 } else {
772 // Check for Phi(1,0)
773 if( phi1_t != TypeInt::ONE ) return NULL;
774 if( phi2_t != TypeInt::ZERO ) return NULL;
775 }
776 if( true_path == 2 ) {
777 flip = 1-flip;
778 }
779
780 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
781 assert(new_bol != iff->in(1), "must make progress");
782 iff->set_req(1, new_bol);
783 // Intervening diamond probably goes dead
784 phase->C->set_major_progress();
785 return iff;
786 }
787
788 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
789
790 //------------------------------Ideal------------------------------------------
791 // Return a node which is more "ideal" than the current node. Strip out
792 // control copies
793 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
794 if (remove_dead_region(phase, can_reshape)) return this;
795 // No Def-Use info?
796 if (!can_reshape) return NULL;
797 PhaseIterGVN *igvn = phase->is_IterGVN();
798
799 // Don't bother trying to transform a dead if
800 if (in(0)->is_top()) return NULL;
801 // Don't bother trying to transform an if with a dead test
802 if (in(1)->is_top()) return NULL;
803 // Another variation of a dead test
804 if (in(1)->is_Con()) return NULL;
805 // Another variation of a dead if
806 if (outcnt() < 2) return NULL;
807
808 // Canonicalize the test.
809 Node* idt_if = idealize_test(phase, this);
810 if (idt_if != NULL) return idt_if;
811
812 // Try to split the IF
813 Node *s = split_if(this, igvn);
814 if (s != NULL) return s;
815
816 // Check for people making a useless boolean: things like
817 // if( (x < y ? true : false) ) { ... }
818 // Replace with if( x < y ) { ... }
819 Node *bol2 = remove_useless_bool(this, phase);
820 if( bol2 ) return bol2;
821
822 // Setup to scan up the CFG looking for a dominating test
823 Node *dom = in(0);
824 Node *prev_dom = this;
825
826 // Check for range-check vs other kinds of tests
827 Node *index1, *range1;
828 jint offset1;
829 int flip1 = is_range_check(range1, index1, offset1);
830 if( flip1 ) {
831 Node *first_prev_dom = NULL;
832
833 // Try to remove extra range checks. All 'up_one_dom' gives up at merges
834 // so all checks we inspect post-dominate the top-most check we find.
835 // If we are going to fail the current check and we reach the top check
836 // then we are guaranteed to fail, so just start interpreting there.
837 // We 'expand' the top 2 range checks to include all post-dominating
838 // checks.
839
840 // The top 2 range checks seen
841 Node *prev_chk1 = NULL;
842 Node *prev_chk2 = NULL;
843 // Low and high offsets seen so far
844 jint off_lo = offset1;
845 jint off_hi = offset1;
846
847 // Scan for the top 2 checks and collect range of offsets
848 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit
849 if( dom->Opcode() == Op_If && // Not same opcode?
850 prev_dom->in(0) == dom ) { // One path of test does dominate?
851 if( dom == this ) return NULL; // dead loop
852 // See if this is a range check
853 Node *index2, *range2;
854 jint offset2;
855 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
856 // See if this is a _matching_ range check, checking against
857 // the same array bounds.
858 if( flip2 == flip1 && range2 == range1 && index2 == index1 &&
859 dom->outcnt() == 2 ) {
860 // Gather expanded bounds
861 off_lo = MIN2(off_lo,offset2);
862 off_hi = MAX2(off_hi,offset2);
863 // Record top 2 range checks
864 prev_chk2 = prev_chk1;
865 prev_chk1 = prev_dom;
866 // If we match the test exactly, then the top test covers
867 // both our lower and upper bounds.
868 if( dom->in(1) == in(1) )
869 prev_chk2 = prev_chk1;
870 }
871 }
872 prev_dom = dom;
873 dom = up_one_dom( dom );
874 if( !dom ) break;
875 }
876
877
878 // Attempt to widen the dominating range check to cover some later
879 // ones. Since range checks "fail" by uncommon-trapping to the
880 // interpreter, widening a check can make us speculative enter the
881 // interpreter. If we see range-check deopt's, do not widen!
882 if (!phase->C->allow_range_check_smearing()) return NULL;
883
884 // Constant indices only need to check the upper bound.
885 // Non-constance indices must check both low and high.
886 if( index1 ) {
887 // Didn't find 2 prior covering checks, so cannot remove anything.
888 if( !prev_chk2 ) return NULL;
889 // 'Widen' the offsets of the 1st and 2nd covering check
890 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn );
891 // Do not call adjust_check twice on the same projection
892 // as the first call may have transformed the BoolNode to a ConI
893 if( prev_chk1 != prev_chk2 ) {
894 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn );
895 }
896 // Test is now covered by prior checks, dominate it out
897 prev_dom = prev_chk2;
898 } else {
899 // Didn't find prior covering check, so cannot remove anything.
900 if( !prev_chk1 ) return NULL;
901 // 'Widen' the offset of the 1st and only covering check
902 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn );
903 // Test is now covered by prior checks, dominate it out
904 prev_dom = prev_chk1;
905 }
906
907
908 } else { // Scan for an equivalent test
909
910 Node *cmp;
911 int dist = 0; // Cutoff limit for search
912 int op = Opcode();
913 if( op == Op_If &&
914 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
915 if( cmp->in(2) != NULL && // make sure cmp is not already dead
916 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
917 dist = 64; // Limit for null-pointer scans
918 } else {
919 dist = 4; // Do not bother for random pointer tests
920 }
921 } else {
922 dist = 4; // Limit for random junky scans
923 }
924
925 // Normal equivalent-test check.
926 if( !dom ) return NULL; // Dead loop?
927
928 Node* result = fold_compares(phase);
929 if (result != NULL) {
930 return result;
931 }
932
933 // Search up the dominator tree for an If with an identical test
934 while( dom->Opcode() != op || // Not same opcode?
935 dom->in(1) != in(1) || // Not same input 1?
936 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
937 prev_dom->in(0) != dom ) { // One path of test does not dominate?
938 if( dist < 0 ) return NULL;
939
940 dist--;
941 prev_dom = dom;
942 dom = up_one_dom( dom );
943 if( !dom ) return NULL;
944 }
945
946 // Check that we did not follow a loop back to ourselves
947 if( this == dom )
948 return NULL;
949
950 if( dist > 2 ) // Add to count of NULL checks elided
951 explicit_null_checks_elided++;
952
953 } // End of Else scan for an equivalent test
954
955 // Hit! Remove this IF
956 #ifndef PRODUCT
957 if( TraceIterativeGVN ) {
958 tty->print(" Removing IfNode: "); this->dump();
959 }
960 if( VerifyOpto && !phase->allow_progress() ) {
961 // Found an equivalent dominating test,
962 // we can not guarantee reaching a fix-point for these during iterativeGVN
963 // since intervening nodes may not change.
964 return NULL;
965 }
966 #endif
967
968 // Replace dominated IfNode
969 dominated_by( prev_dom, igvn );
970
971 // Must return either the original node (now dead) or a new node
972 // (Do not return a top here, since that would break the uniqueness of top.)
973 return new (phase->C, 1) ConINode(TypeInt::ZERO);
974 }
975
976 //------------------------------dominated_by-----------------------------------
977 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
978 igvn->hash_delete(this); // Remove self to prevent spurious V-N
979 Node *idom = in(0);
980 // Need opcode to decide which way 'this' test goes
981 int prev_op = prev_dom->Opcode();
982 Node *top = igvn->C->top(); // Shortcut to top
983
984 // Now walk the current IfNode's projections.
985 // Loop ends when 'this' has no more uses.
986 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
987 Node *ifp = last_out(i); // Get IfTrue/IfFalse
988 igvn->add_users_to_worklist(ifp);
989 // Check which projection it is and set target.
990 // Data-target is either the dominating projection of the same type
991 // or TOP if the dominating projection is of opposite type.
992 // Data-target will be used as the new control edge for the non-CFG
993 // nodes like Casts and Loads.
994 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top;
995 // Control-target is just the If's immediate dominator or TOP.
996 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top;
997
998 // For each child of an IfTrue/IfFalse projection, reroute.
999 // Loop ends when projection has no more uses.
1000 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1001 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse
1002 igvn->hash_delete(s); // Yank from hash table before edge hacking
1003 if( !s->depends_only_on_test() ) {
1004 // Find the control input matching this def-use edge.
1005 // For Regions it may not be in slot 0.
1006 uint l;
1007 for( l = 0; s->in(l) != ifp; l++ ) { }
1008 s->set_req(l, ctrl_target);
1009 } else { // Else, for control producers,
1010 s->set_req(0, data_target); // Move child to data-target
1011 }
1012 igvn->_worklist.push(s); // Revisit collapsed Phis
1013 } // End for each child of a projection
1014
1015 igvn->remove_dead_node(ifp);
1016 } // End for each IfTrue/IfFalse child of If
1017
1018 // Kill the IfNode
1019 igvn->remove_dead_node(this);
1020 }
1021
1022 //------------------------------Identity---------------------------------------
1023 // If the test is constant & we match, then we are the input Control
1024 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
1025 // Can only optimize if cannot go the other way
1026 const TypeTuple *t = phase->type(in(0))->is_tuple();
1027 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
1028 ? in(0)->in(0) // IfNode control
1029 : this; // no progress
1030 }
1031
1032 //------------------------------dump_spec--------------------------------------
1033 #ifndef PRODUCT
1034 void IfNode::dump_spec(outputStream *st) const {
1035 st->print("P=%f, C=%f",_prob,_fcnt);
1036 }
1037 #endif
1038
1039 //------------------------------idealize_test----------------------------------
1040 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and
1041 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms
1042 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as
1043 // needed.
1044 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1045 assert(iff->in(0) != NULL, "If must be live");
1046
1047 if (iff->outcnt() != 2) return NULL; // Malformed projections.
1048 Node* old_if_f = iff->proj_out(false);
1049 Node* old_if_t = iff->proj_out(true);
1050
1051 // CountedLoopEnds want the back-control test to be TRUE, irregardless of
1052 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition
1053 // happens in count-down loops
1054 if (iff->is_CountedLoopEnd()) return NULL;
1055 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests
1056 BoolNode *b = iff->in(1)->as_Bool();
1057 BoolTest bt = b->_test;
1058 // Test already in good order?
1059 if( bt.is_canonical() )
1060 return NULL;
1061
1062 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and
1063 // cloning the IfNode.
1064 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) );
1065 if( !new_b->is_Bool() ) return NULL;
1066 b = new_b->as_Bool();
1067
1068 PhaseIterGVN *igvn = phase->is_IterGVN();
1069 assert( igvn, "Test is not canonical in parser?" );
1070
1071 // The IF node never really changes, but it needs to be cloned
1072 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
1073
1074 Node *prior = igvn->hash_find_insert(iff);
1075 if( prior ) {
1076 igvn->remove_dead_node(iff);
1077 iff = (IfNode*)prior;
1078 } else {
1079 // Cannot call transform on it just yet
1080 igvn->set_type_bottom(iff);
1081 }
1082 igvn->_worklist.push(iff);
1083
1084 // Now handle projections. Cloning not required.
1085 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff ));
1086 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff ));
1087
1088 igvn->register_new_node_with_optimizer(new_if_f);
1089 igvn->register_new_node_with_optimizer(new_if_t);
1090 // Flip test, so flip trailing control
1091 igvn->replace_node(old_if_f, new_if_t);
1092 igvn->replace_node(old_if_t, new_if_f);
1093
1094 // Progress
1095 return iff;
1096 }
1097
1098 //------------------------------Identity---------------------------------------
1099 // If the test is constant & we match, then we are the input Control
1100 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
1101 // Can only optimize if cannot go the other way
1102 const TypeTuple *t = phase->type(in(0))->is_tuple();
1103 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
1104 ? in(0)->in(0) // IfNode control
1105 : this; // no progress
1106 }