Mercurial > hg > truffle
comparison src/share/vm/opto/ifnode.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | ff5961f4c095 |
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1 /* | |
2 * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any 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 collaped 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 seperate 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 conglerate 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 phi_x = phase->transform( phi_x ); | |
244 // Prevent the untimely death of phi_x. Currently he has no uses. He is | |
245 // about to get one. If this only use goes away, then phi_x will look dead. | |
246 // However, he will be picking up some more uses down below. | |
247 Node *hook = new (igvn->C, 4) Node(4); | |
248 hook->init_req(0, phi_x); | |
249 hook->init_req(1, phi_c); | |
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 phi_s = phase->transform(phi_s); | |
326 } | |
327 proj_path_data = phi_s; | |
328 proj_path_ctrl = region_s; | |
329 } else { | |
330 if( phi_f == NULL ) { | |
331 // Only construct phi_f if needed, otherwise provides | |
332 // interfering use. | |
333 phi_f = PhiNode::make_blank(region_f,phi); | |
334 phi_f->init_req( 1, phi_c ); | |
335 phi_f->init_req( 2, phi_x ); | |
336 phi_f = phase->transform(phi_f); | |
337 } | |
338 proj_path_data = phi_f; | |
339 proj_path_ctrl = region_f; | |
340 } | |
341 | |
342 // Fixup 'v' for for the split | |
343 if( vop == Op_Phi ) { // Remote merge point | |
344 uint i; | |
345 for( i = 1; i < v->req(); i++ ) | |
346 if( v->in(i) == phi ) | |
347 break; | |
348 v->set_req(i, proj_path_data ); | |
349 } else if( v->is_ConstraintCast() ) { | |
350 v->set_req(0, proj_path_ctrl ); | |
351 v->set_req(1, proj_path_data ); | |
352 } else | |
353 ShouldNotReachHere(); | |
354 } | |
355 | |
356 // Now replace the original iff's True/False with region_s/region_t. | |
357 // This makes the original iff go dead. | |
358 for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) { | |
359 Node* p = iff->last_out(i3); | |
360 assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" ); | |
361 Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f; | |
362 // Replace p with u | |
363 igvn->add_users_to_worklist(p); | |
364 for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) { | |
365 Node* x = p->last_out(l); | |
366 igvn->hash_delete(x); | |
367 uint uses_found = 0; | |
368 for( uint j = 0; j < x->req(); j++ ) { | |
369 if( x->in(j) == p ) { | |
370 x->set_req(j, u); | |
371 uses_found++; | |
372 } | |
373 } | |
374 l -= uses_found; // we deleted 1 or more copies of this edge | |
375 } | |
376 igvn->remove_dead_node(p); | |
377 } | |
378 | |
379 // Force the original merge dead | |
380 igvn->hash_delete(r); | |
381 r->set_req_X(0,NULL,igvn); | |
382 | |
383 // Now remove the bogus extra edges used to keep things alive | |
384 igvn->remove_dead_node( hook ); | |
385 | |
386 // Must return either the original node (now dead) or a new node | |
387 // (Do not return a top here, since that would break the uniqueness of top.) | |
388 return new (igvn->C, 1) ConINode(TypeInt::ZERO); | |
389 } | |
390 | |
391 //------------------------------is_range_check--------------------------------- | |
392 // Return 0 if not a range check. Return 1 if a range check and set index and | |
393 // offset. Return 2 if we had to negate the test. Index is NULL if the check | |
394 // is versus a constant. | |
395 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) { | |
396 Node* b = in(1); | |
397 if (b == NULL || !b->is_Bool()) return 0; | |
398 BoolNode* bn = b->as_Bool(); | |
399 Node* cmp = bn->in(1); | |
400 if (cmp == NULL) return 0; | |
401 if (cmp->Opcode() != Op_CmpU) return 0; | |
402 | |
403 Node* l = cmp->in(1); | |
404 Node* r = cmp->in(2); | |
405 int flip_test = 1; | |
406 if (bn->_test._test == BoolTest::le) { | |
407 l = cmp->in(2); | |
408 r = cmp->in(1); | |
409 flip_test = 2; | |
410 } else if (bn->_test._test != BoolTest::lt) { | |
411 return 0; | |
412 } | |
413 if (l->is_top()) return 0; // Top input means dead test | |
414 if (r->Opcode() != Op_LoadRange) return 0; | |
415 | |
416 // We have recognized one of these forms: | |
417 // Flip 1: If (Bool[<] CmpU(l, LoadRange)) ... | |
418 // Flip 2: If (Bool[<=] CmpU(LoadRange, l)) ... | |
419 | |
420 // Make sure it's a real range check by requiring an uncommon trap | |
421 // along the OOB path. Otherwise, it's possible that the user wrote | |
422 // something which optimized to look like a range check but behaves | |
423 // in some other way. | |
424 Node* iftrap = proj_out(flip_test == 2 ? true : false); | |
425 bool found_trap = false; | |
426 if (iftrap != NULL) { | |
427 Node* u = iftrap->unique_ctrl_out(); | |
428 if (u != NULL) { | |
429 // It could be a merge point (Region) for uncommon trap. | |
430 if (u->is_Region()) { | |
431 Node* c = u->unique_ctrl_out(); | |
432 if (c != NULL) { | |
433 iftrap = u; | |
434 u = c; | |
435 } | |
436 } | |
437 if (u->in(0) == iftrap && u->is_CallStaticJava()) { | |
438 int req = u->as_CallStaticJava()->uncommon_trap_request(); | |
439 if (Deoptimization::trap_request_reason(req) == | |
440 Deoptimization::Reason_range_check) { | |
441 found_trap = true; | |
442 } | |
443 } | |
444 } | |
445 } | |
446 if (!found_trap) return 0; // sorry, no cigar | |
447 | |
448 // Look for index+offset form | |
449 Node* ind = l; | |
450 jint off = 0; | |
451 if (l->is_top()) { | |
452 return 0; | |
453 } else if (l->is_Add()) { | |
454 if ((off = l->in(1)->find_int_con(0)) != 0) { | |
455 ind = l->in(2); | |
456 } else if ((off = l->in(2)->find_int_con(0)) != 0) { | |
457 ind = l->in(1); | |
458 } | |
459 } else if ((off = l->find_int_con(-1)) >= 0) { | |
460 // constant offset with no variable index | |
461 ind = NULL; | |
462 } else { | |
463 // variable index with no constant offset (or dead negative index) | |
464 off = 0; | |
465 } | |
466 | |
467 // Return all the values: | |
468 index = ind; | |
469 offset = off; | |
470 range = r; | |
471 return flip_test; | |
472 } | |
473 | |
474 //------------------------------adjust_check----------------------------------- | |
475 // Adjust (widen) a prior range check | |
476 static void adjust_check(Node* proj, Node* range, Node* index, | |
477 int flip, jint off_lo, PhaseIterGVN* igvn) { | |
478 PhaseGVN *gvn = igvn; | |
479 // Break apart the old check | |
480 Node *iff = proj->in(0); | |
481 Node *bol = iff->in(1); | |
482 if( bol->is_top() ) return; // In case a partially dead range check appears | |
483 // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode | |
484 DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } ) | |
485 if( !bol->is_Bool() ) return; | |
486 | |
487 Node *cmp = bol->in(1); | |
488 // Compute a new check | |
489 Node *new_add = gvn->intcon(off_lo); | |
490 if( index ) { | |
491 new_add = off_lo ? gvn->transform(new (gvn->C, 3) AddINode( index, new_add )) : index; | |
492 } | |
493 Node *new_cmp = (flip == 1) | |
494 ? new (gvn->C, 3) CmpUNode( new_add, range ) | |
495 : new (gvn->C, 3) CmpUNode( range, new_add ); | |
496 new_cmp = gvn->transform(new_cmp); | |
497 // See if no need to adjust the existing check | |
498 if( new_cmp == cmp ) return; | |
499 // Else, adjust existing check | |
500 Node *new_bol = gvn->transform( new (gvn->C, 2) BoolNode( new_cmp, bol->as_Bool()->_test._test ) ); | |
501 igvn->hash_delete( iff ); | |
502 iff->set_req_X( 1, new_bol, igvn ); | |
503 } | |
504 | |
505 //------------------------------up_one_dom------------------------------------- | |
506 // Walk up the dominator tree one step. Return NULL at root or true | |
507 // complex merges. Skips through small diamonds. | |
508 Node* IfNode::up_one_dom(Node *curr, bool linear_only) { | |
509 Node *dom = curr->in(0); | |
510 if( !dom ) // Found a Region degraded to a copy? | |
511 return curr->nonnull_req(); // Skip thru it | |
512 | |
513 if( curr != dom ) // Normal walk up one step? | |
514 return dom; | |
515 | |
516 // Use linear_only if we are still parsing, since we cannot | |
517 // trust the regions to be fully filled in. | |
518 if (linear_only) | |
519 return NULL; | |
520 | |
521 // Else hit a Region. Check for a loop header | |
522 if( dom->is_Loop() ) | |
523 return dom->in(1); // Skip up thru loops | |
524 | |
525 // Check for small diamonds | |
526 Node *din1, *din2, *din3, *din4; | |
527 if( dom->req() == 3 && // 2-path merge point | |
528 (din1 = dom ->in(1)) && // Left path exists | |
529 (din2 = dom ->in(2)) && // Right path exists | |
530 (din3 = din1->in(0)) && // Left path up one | |
531 (din4 = din2->in(0)) ) { // Right path up one | |
532 if( din3->is_Call() && // Handle a slow-path call on either arm | |
533 (din3 = din3->in(0)) ) | |
534 din3 = din3->in(0); | |
535 if( din4->is_Call() && // Handle a slow-path call on either arm | |
536 (din4 = din4->in(0)) ) | |
537 din4 = din4->in(0); | |
538 if( din3 == din4 && din3->is_If() ) | |
539 return din3; // Skip around diamonds | |
540 } | |
541 | |
542 // Give up the search at true merges | |
543 return NULL; // Dead loop? Or hit root? | |
544 } | |
545 | |
546 //------------------------------remove_useless_bool---------------------------- | |
547 // Check for people making a useless boolean: things like | |
548 // if( (x < y ? true : false) ) { ... } | |
549 // Replace with if( x < y ) { ... } | |
550 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) { | |
551 Node *i1 = iff->in(1); | |
552 if( !i1->is_Bool() ) return NULL; | |
553 BoolNode *bol = i1->as_Bool(); | |
554 | |
555 Node *cmp = bol->in(1); | |
556 if( cmp->Opcode() != Op_CmpI ) return NULL; | |
557 | |
558 // Must be comparing against a bool | |
559 const Type *cmp2_t = phase->type( cmp->in(2) ); | |
560 if( cmp2_t != TypeInt::ZERO && | |
561 cmp2_t != TypeInt::ONE ) | |
562 return NULL; | |
563 | |
564 // Find a prior merge point merging the boolean | |
565 i1 = cmp->in(1); | |
566 if( !i1->is_Phi() ) return NULL; | |
567 PhiNode *phi = i1->as_Phi(); | |
568 if( phase->type( phi ) != TypeInt::BOOL ) | |
569 return NULL; | |
570 | |
571 // Check for diamond pattern | |
572 int true_path = phi->is_diamond_phi(); | |
573 if( true_path == 0 ) return NULL; | |
574 | |
575 // phi->region->if_proj->ifnode->bool->cmp | |
576 BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool(); | |
577 | |
578 // Now get the 'sense' of the test correct so we can plug in | |
579 // either iff2->in(1) or its complement. | |
580 int flip = 0; | |
581 if( bol->_test._test == BoolTest::ne ) flip = 1-flip; | |
582 else if( bol->_test._test != BoolTest::eq ) return NULL; | |
583 if( cmp2_t == TypeInt::ZERO ) flip = 1-flip; | |
584 | |
585 const Type *phi1_t = phase->type( phi->in(1) ); | |
586 const Type *phi2_t = phase->type( phi->in(2) ); | |
587 // Check for Phi(0,1) and flip | |
588 if( phi1_t == TypeInt::ZERO ) { | |
589 if( phi2_t != TypeInt::ONE ) return NULL; | |
590 flip = 1-flip; | |
591 } else { | |
592 // Check for Phi(1,0) | |
593 if( phi1_t != TypeInt::ONE ) return NULL; | |
594 if( phi2_t != TypeInt::ZERO ) return NULL; | |
595 } | |
596 if( true_path == 2 ) { | |
597 flip = 1-flip; | |
598 } | |
599 | |
600 Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2); | |
601 iff->set_req(1, new_bol); | |
602 // Intervening diamond probably goes dead | |
603 phase->C->set_major_progress(); | |
604 return iff; | |
605 } | |
606 | |
607 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff); | |
608 | |
609 //------------------------------Ideal------------------------------------------ | |
610 // Return a node which is more "ideal" than the current node. Strip out | |
611 // control copies | |
612 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) { | |
613 if (remove_dead_region(phase, can_reshape)) return this; | |
614 // No Def-Use info? | |
615 if (!can_reshape) return NULL; | |
616 PhaseIterGVN *igvn = phase->is_IterGVN(); | |
617 | |
618 // Don't bother trying to transform a dead if | |
619 if (in(0)->is_top()) return NULL; | |
620 // Don't bother trying to transform an if with a dead test | |
621 if (in(1)->is_top()) return NULL; | |
622 // Another variation of a dead test | |
623 if (in(1)->is_Con()) return NULL; | |
624 // Another variation of a dead if | |
625 if (outcnt() < 2) return NULL; | |
626 | |
627 // Canonicalize the test. | |
628 Node* idt_if = idealize_test(phase, this); | |
629 if (idt_if != NULL) return idt_if; | |
630 | |
631 // Try to split the IF | |
632 Node *s = split_if(this, igvn); | |
633 if (s != NULL) return s; | |
634 | |
635 // Check for people making a useless boolean: things like | |
636 // if( (x < y ? true : false) ) { ... } | |
637 // Replace with if( x < y ) { ... } | |
638 Node *bol2 = remove_useless_bool(this, phase); | |
639 if( bol2 ) return bol2; | |
640 | |
641 // Setup to scan up the CFG looking for a dominating test | |
642 Node *dom = in(0); | |
643 Node *prev_dom = this; | |
644 | |
645 // Check for range-check vs other kinds of tests | |
646 Node *index1, *range1; | |
647 jint offset1; | |
648 int flip1 = is_range_check(range1, index1, offset1); | |
649 if( flip1 ) { | |
650 Node *first_prev_dom = NULL; | |
651 | |
652 // Try to remove extra range checks. All 'up_one_dom' gives up at merges | |
653 // so all checks we inspect post-dominate the top-most check we find. | |
654 // If we are going to fail the current check and we reach the top check | |
655 // then we are guarenteed to fail, so just start interpreting there. | |
656 // We 'expand' the top 2 range checks to include all post-dominating | |
657 // checks. | |
658 | |
659 // The top 2 range checks seen | |
660 Node *prev_chk1 = NULL; | |
661 Node *prev_chk2 = NULL; | |
662 // Low and high offsets seen so far | |
663 jint off_lo = offset1; | |
664 jint off_hi = offset1; | |
665 | |
666 // Scan for the top 2 checks and collect range of offsets | |
667 for( int dist = 0; dist < 999; dist++ ) { // Range-Check scan limit | |
668 if( dom->Opcode() == Op_If && // Not same opcode? | |
669 prev_dom->in(0) == dom ) { // One path of test does dominate? | |
670 if( dom == this ) return NULL; // dead loop | |
671 // See if this is a range check | |
672 Node *index2, *range2; | |
673 jint offset2; | |
674 int flip2 = dom->as_If()->is_range_check(range2, index2, offset2); | |
675 // See if this is a _matching_ range check, checking against | |
676 // the same array bounds. | |
677 if( flip2 == flip1 && range2 == range1 && index2 == index1 && | |
678 dom->outcnt() == 2 ) { | |
679 // Gather expanded bounds | |
680 off_lo = MIN2(off_lo,offset2); | |
681 off_hi = MAX2(off_hi,offset2); | |
682 // Record top 2 range checks | |
683 prev_chk2 = prev_chk1; | |
684 prev_chk1 = prev_dom; | |
685 // If we match the test exactly, then the top test covers | |
686 // both our lower and upper bounds. | |
687 if( dom->in(1) == in(1) ) | |
688 prev_chk2 = prev_chk1; | |
689 } | |
690 } | |
691 prev_dom = dom; | |
692 dom = up_one_dom( dom ); | |
693 if( !dom ) break; | |
694 } | |
695 | |
696 | |
697 // Attempt to widen the dominating range check to cover some later | |
698 // ones. Since range checks "fail" by uncommon-trapping to the | |
699 // interpreter, widening a check can make us speculative enter the | |
700 // interpreter. If we see range-check deopt's, do not widen! | |
701 if (!phase->C->allow_range_check_smearing()) return NULL; | |
702 | |
703 // Constant indices only need to check the upper bound. | |
704 // Non-constance indices must check both low and high. | |
705 if( index1 ) { | |
706 // Didn't find 2 prior covering checks, so cannot remove anything. | |
707 if( !prev_chk2 ) return NULL; | |
708 // 'Widen' the offsets of the 1st and 2nd covering check | |
709 adjust_check( prev_chk1, range1, index1, flip1, off_lo, igvn ); | |
710 // Do not call adjust_check twice on the same projection | |
711 // as the first call may have transformed the BoolNode to a ConI | |
712 if( prev_chk1 != prev_chk2 ) { | |
713 adjust_check( prev_chk2, range1, index1, flip1, off_hi, igvn ); | |
714 } | |
715 // Test is now covered by prior checks, dominate it out | |
716 prev_dom = prev_chk2; | |
717 } else { | |
718 // Didn't find prior covering check, so cannot remove anything. | |
719 if( !prev_chk1 ) return NULL; | |
720 // 'Widen' the offset of the 1st and only covering check | |
721 adjust_check( prev_chk1, range1, index1, flip1, off_hi, igvn ); | |
722 // Test is now covered by prior checks, dominate it out | |
723 prev_dom = prev_chk1; | |
724 } | |
725 | |
726 | |
727 } else { // Scan for an equivalent test | |
728 | |
729 Node *cmp; | |
730 int dist = 0; // Cutoff limit for search | |
731 int op = Opcode(); | |
732 if( op == Op_If && | |
733 (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) { | |
734 if( cmp->in(2) != NULL && // make sure cmp is not already dead | |
735 cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) { | |
736 dist = 64; // Limit for null-pointer scans | |
737 } else { | |
738 dist = 4; // Do not bother for random pointer tests | |
739 } | |
740 } else { | |
741 dist = 4; // Limit for random junky scans | |
742 } | |
743 | |
744 // Normal equivalent-test check. | |
745 if( !dom ) return NULL; // Dead loop? | |
746 | |
747 // Search up the dominator tree for an If with an identical test | |
748 while( dom->Opcode() != op || // Not same opcode? | |
749 dom->in(1) != in(1) || // Not same input 1? | |
750 (req() == 3 && dom->in(2) != in(2)) || // Not same input 2? | |
751 prev_dom->in(0) != dom ) { // One path of test does not dominate? | |
752 if( dist < 0 ) return NULL; | |
753 | |
754 dist--; | |
755 prev_dom = dom; | |
756 dom = up_one_dom( dom ); | |
757 if( !dom ) return NULL; | |
758 } | |
759 | |
760 // Check that we did not follow a loop back to ourselves | |
761 if( this == dom ) | |
762 return NULL; | |
763 | |
764 if( dist > 2 ) // Add to count of NULL checks elided | |
765 explicit_null_checks_elided++; | |
766 | |
767 } // End of Else scan for an equivalent test | |
768 | |
769 // Hit! Remove this IF | |
770 #ifndef PRODUCT | |
771 if( TraceIterativeGVN ) { | |
772 tty->print(" Removing IfNode: "); this->dump(); | |
773 } | |
774 if( VerifyOpto && !phase->allow_progress() ) { | |
775 // Found an equivalent dominating test, | |
776 // we can not guarantee reaching a fix-point for these during iterativeGVN | |
777 // since intervening nodes may not change. | |
778 return NULL; | |
779 } | |
780 #endif | |
781 | |
782 // Replace dominated IfNode | |
783 dominated_by( prev_dom, igvn ); | |
784 | |
785 // Must return either the original node (now dead) or a new node | |
786 // (Do not return a top here, since that would break the uniqueness of top.) | |
787 return new (phase->C, 1) ConINode(TypeInt::ZERO); | |
788 } | |
789 | |
790 //------------------------------dominated_by----------------------------------- | |
791 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) { | |
792 igvn->hash_delete(this); // Remove self to prevent spurious V-N | |
793 Node *idom = in(0); | |
794 // Need opcode to decide which way 'this' test goes | |
795 int prev_op = prev_dom->Opcode(); | |
796 Node *top = igvn->C->top(); // Shortcut to top | |
797 | |
798 // Now walk the current IfNode's projections. | |
799 // Loop ends when 'this' has no more uses. | |
800 for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) { | |
801 Node *ifp = last_out(i); // Get IfTrue/IfFalse | |
802 igvn->add_users_to_worklist(ifp); | |
803 // Check which projection it is and set target. | |
804 // Data-target is either the dominating projection of the same type | |
805 // or TOP if the dominating projection is of opposite type. | |
806 // Data-target will be used as the new control edge for the non-CFG | |
807 // nodes like Casts and Loads. | |
808 Node *data_target = (ifp->Opcode() == prev_op ) ? prev_dom : top; | |
809 // Control-target is just the If's immediate dominator or TOP. | |
810 Node *ctrl_target = (ifp->Opcode() == prev_op ) ? idom : top; | |
811 | |
812 // For each child of an IfTrue/IfFalse projection, reroute. | |
813 // Loop ends when projection has no more uses. | |
814 for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) { | |
815 Node* s = ifp->last_out(j); // Get child of IfTrue/IfFalse | |
816 igvn->hash_delete(s); // Yank from hash table before edge hacking | |
817 if( !s->depends_only_on_test() ) { | |
818 // Find the control input matching this def-use edge. | |
819 // For Regions it may not be in slot 0. | |
820 uint l; | |
821 for( l = 0; s->in(l) != ifp; l++ ) { } | |
822 s->set_req(l, ctrl_target); | |
823 } else { // Else, for control producers, | |
824 s->set_req(0, data_target); // Move child to data-target | |
825 } | |
826 igvn->_worklist.push(s); // Revisit collapsed Phis | |
827 } // End for each child of a projection | |
828 | |
829 igvn->remove_dead_node(ifp); | |
830 } // End for each IfTrue/IfFalse child of If | |
831 | |
832 // Kill the IfNode | |
833 igvn->remove_dead_node(this); | |
834 } | |
835 | |
836 //------------------------------Identity--------------------------------------- | |
837 // If the test is constant & we match, then we are the input Control | |
838 Node *IfTrueNode::Identity( PhaseTransform *phase ) { | |
839 // Can only optimize if cannot go the other way | |
840 const TypeTuple *t = phase->type(in(0))->is_tuple(); | |
841 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE ) | |
842 ? in(0)->in(0) // IfNode control | |
843 : this; // no progress | |
844 } | |
845 | |
846 //------------------------------dump_spec-------------------------------------- | |
847 #ifndef PRODUCT | |
848 void IfNode::dump_spec(outputStream *st) const { | |
849 st->print("P=%f, C=%f",_prob,_fcnt); | |
850 } | |
851 #endif | |
852 | |
853 //------------------------------idealize_test---------------------------------- | |
854 // Try to canonicalize tests better. Peek at the Cmp/Bool/If sequence and | |
855 // come up with a canonical sequence. Bools getting 'eq', 'gt' and 'ge' forms | |
856 // converted to 'ne', 'le' and 'lt' forms. IfTrue/IfFalse get swapped as | |
857 // needed. | |
858 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) { | |
859 assert(iff->in(0) != NULL, "If must be live"); | |
860 | |
861 if (iff->outcnt() != 2) return NULL; // Malformed projections. | |
862 Node* old_if_f = iff->proj_out(false); | |
863 Node* old_if_t = iff->proj_out(true); | |
864 | |
865 // CountedLoopEnds want the back-control test to be TRUE, irregardless of | |
866 // whether they are testing a 'gt' or 'lt' condition. The 'gt' condition | |
867 // happens in count-down loops | |
868 if (iff->is_CountedLoopEnd()) return NULL; | |
869 if (!iff->in(1)->is_Bool()) return NULL; // Happens for partially optimized IF tests | |
870 BoolNode *b = iff->in(1)->as_Bool(); | |
871 BoolTest bt = b->_test; | |
872 // Test already in good order? | |
873 if( bt.is_canonical() ) | |
874 return NULL; | |
875 | |
876 // Flip test to be canonical. Requires flipping the IfFalse/IfTrue and | |
877 // cloning the IfNode. | |
878 Node* new_b = phase->transform( new (phase->C, 2) BoolNode(b->in(1), bt.negate()) ); | |
879 if( !new_b->is_Bool() ) return NULL; | |
880 b = new_b->as_Bool(); | |
881 | |
882 PhaseIterGVN *igvn = phase->is_IterGVN(); | |
883 assert( igvn, "Test is not canonical in parser?" ); | |
884 | |
885 // The IF node never really changes, but it needs to be cloned | |
886 iff = new (phase->C, 2) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt); | |
887 | |
888 Node *prior = igvn->hash_find_insert(iff); | |
889 if( prior ) { | |
890 igvn->remove_dead_node(iff); | |
891 iff = (IfNode*)prior; | |
892 } else { | |
893 // Cannot call transform on it just yet | |
894 igvn->set_type_bottom(iff); | |
895 } | |
896 igvn->_worklist.push(iff); | |
897 | |
898 // Now handle projections. Cloning not required. | |
899 Node* new_if_f = (Node*)(new (phase->C, 1) IfFalseNode( iff )); | |
900 Node* new_if_t = (Node*)(new (phase->C, 1) IfTrueNode ( iff )); | |
901 | |
902 igvn->register_new_node_with_optimizer(new_if_f); | |
903 igvn->register_new_node_with_optimizer(new_if_t); | |
904 igvn->hash_delete(old_if_f); | |
905 igvn->hash_delete(old_if_t); | |
906 // Flip test, so flip trailing control | |
907 igvn->subsume_node(old_if_f, new_if_t); | |
908 igvn->subsume_node(old_if_t, new_if_f); | |
909 | |
910 // Progress | |
911 return iff; | |
912 } | |
913 | |
914 //------------------------------Identity--------------------------------------- | |
915 // If the test is constant & we match, then we are the input Control | |
916 Node *IfFalseNode::Identity( PhaseTransform *phase ) { | |
917 // Can only optimize if cannot go the other way | |
918 const TypeTuple *t = phase->type(in(0))->is_tuple(); | |
919 return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE ) | |
920 ? in(0)->in(0) // IfNode control | |
921 : this; // no progress | |
922 } |