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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "compiler/compileLog.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "opto/addnode.hpp"
29 #include "opto/callnode.hpp"
30 #include "opto/connode.hpp"
31 #include "opto/divnode.hpp"
32 #include "opto/loopnode.hpp"
33 #include "opto/mulnode.hpp"
34 #include "opto/rootnode.hpp"
35 #include "opto/runtime.hpp"
36 #include "opto/subnode.hpp"
37
38 //------------------------------is_loop_exit-----------------------------------
39 // Given an IfNode, return the loop-exiting projection or NULL if both
40 // arms remain in the loop.
41 Node *IdealLoopTree::is_loop_exit(Node *iff) const {
42 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
43 PhaseIdealLoop *phase = _phase;
44 // Test is an IfNode, has 2 projections. If BOTH are in the loop
45 // we need loop unswitching instead of peeling.
46 if( !is_member(phase->get_loop( iff->raw_out(0) )) )
47 return iff->raw_out(0);
48 if( !is_member(phase->get_loop( iff->raw_out(1) )) )
49 return iff->raw_out(1);
50 return NULL;
51 }
52
53
54 //=============================================================================
55
56
57 //------------------------------record_for_igvn----------------------------
58 // Put loop body on igvn work list
59 void IdealLoopTree::record_for_igvn() {
60 for( uint i = 0; i < _body.size(); i++ ) {
61 Node *n = _body.at(i);
62 _phase->_igvn._worklist.push(n);
63 }
64 }
65
66 //------------------------------compute_profile_trip_cnt----------------------------
67 // Compute loop trip count from profile data as
68 // (backedge_count + loop_exit_count) / loop_exit_count
69 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
70 if (!_head->is_CountedLoop()) {
71 return;
72 }
73 CountedLoopNode* head = _head->as_CountedLoop();
74 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
75 return; // Already computed
76 }
77 float trip_cnt = (float)max_jint; // default is big
78
79 Node* back = head->in(LoopNode::LoopBackControl);
80 while (back != head) {
81 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
82 back->in(0) &&
83 back->in(0)->is_If() &&
84 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
85 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
86 break;
87 }
88 back = phase->idom(back);
89 }
90 if (back != head) {
91 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
92 back->in(0), "if-projection exists");
93 IfNode* back_if = back->in(0)->as_If();
94 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
95
96 // Now compute a loop exit count
97 float loop_exit_cnt = 0.0f;
98 for( uint i = 0; i < _body.size(); i++ ) {
99 Node *n = _body[i];
100 if( n->is_If() ) {
101 IfNode *iff = n->as_If();
102 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
103 Node *exit = is_loop_exit(iff);
104 if( exit ) {
105 float exit_prob = iff->_prob;
106 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
107 if (exit_prob > PROB_MIN) {
108 float exit_cnt = iff->_fcnt * exit_prob;
109 loop_exit_cnt += exit_cnt;
110 }
111 }
112 }
113 }
114 }
115 if (loop_exit_cnt > 0.0f) {
116 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
117 } else {
118 // No exit count so use
119 trip_cnt = loop_back_cnt;
120 }
121 }
122 #ifndef PRODUCT
123 if (TraceProfileTripCount) {
124 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
125 }
126 #endif
127 head->set_profile_trip_cnt(trip_cnt);
128 }
129
130 //---------------------is_invariant_addition-----------------------------
131 // Return nonzero index of invariant operand for an Add or Sub
132 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
133 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
134 int op = n->Opcode();
135 if (op == Op_AddI || op == Op_SubI) {
136 bool in1_invar = this->is_invariant(n->in(1));
137 bool in2_invar = this->is_invariant(n->in(2));
138 if (in1_invar && !in2_invar) return 1;
139 if (!in1_invar && in2_invar) return 2;
140 }
141 return 0;
142 }
143
144 //---------------------reassociate_add_sub-----------------------------
145 // Reassociate invariant add and subtract expressions:
146 //
147 // inv1 + (x + inv2) => ( inv1 + inv2) + x
148 // (x + inv2) + inv1 => ( inv1 + inv2) + x
149 // inv1 + (x - inv2) => ( inv1 - inv2) + x
150 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
151 // (x + inv2) - inv1 => (-inv1 + inv2) + x
152 // (x - inv2) + inv1 => ( inv1 - inv2) + x
153 // (x - inv2) - inv1 => (-inv1 - inv2) + x
154 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
155 // inv1 - (x - inv2) => ( inv1 + inv2) - x
156 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
157 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
158 // inv1 - (x + inv2) => ( inv1 - inv2) - x
159 //
160 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
161 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
162 if (is_invariant(n1)) return NULL;
163 int inv1_idx = is_invariant_addition(n1, phase);
164 if (!inv1_idx) return NULL;
165 // Don't mess with add of constant (igvn moves them to expression tree root.)
166 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
167 Node* inv1 = n1->in(inv1_idx);
168 Node* n2 = n1->in(3 - inv1_idx);
169 int inv2_idx = is_invariant_addition(n2, phase);
170 if (!inv2_idx) return NULL;
171 Node* x = n2->in(3 - inv2_idx);
172 Node* inv2 = n2->in(inv2_idx);
173
174 bool neg_x = n2->is_Sub() && inv2_idx == 1;
175 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
176 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
177 if (n1->is_Sub() && inv1_idx == 1) {
178 neg_x = !neg_x;
179 neg_inv2 = !neg_inv2;
180 }
181 Node* inv1_c = phase->get_ctrl(inv1);
182 Node* inv2_c = phase->get_ctrl(inv2);
183 Node* n_inv1;
184 if (neg_inv1) {
185 Node *zero = phase->_igvn.intcon(0);
186 phase->set_ctrl(zero, phase->C->root());
187 n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
188 phase->register_new_node(n_inv1, inv1_c);
189 } else {
190 n_inv1 = inv1;
191 }
192 Node* inv;
193 if (neg_inv2) {
194 inv = new (phase->C, 3) SubINode(n_inv1, inv2);
195 } else {
196 inv = new (phase->C, 3) AddINode(n_inv1, inv2);
197 }
198 phase->register_new_node(inv, phase->get_early_ctrl(inv));
199
200 Node* addx;
201 if (neg_x) {
202 addx = new (phase->C, 3) SubINode(inv, x);
203 } else {
204 addx = new (phase->C, 3) AddINode(x, inv);
205 }
206 phase->register_new_node(addx, phase->get_ctrl(x));
207 phase->_igvn.replace_node(n1, addx);
208 assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
209 _body.yank(n1);
210 return addx;
211 }
212
213 //---------------------reassociate_invariants-----------------------------
214 // Reassociate invariant expressions:
215 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
216 for (int i = _body.size() - 1; i >= 0; i--) {
217 Node *n = _body.at(i);
218 for (int j = 0; j < 5; j++) {
219 Node* nn = reassociate_add_sub(n, phase);
220 if (nn == NULL) break;
221 n = nn; // again
222 };
223 }
224 }
225
226 //------------------------------policy_peeling---------------------------------
227 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
228 // make some loop-invariant test (usually a null-check) happen before the loop.
229 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
230 Node *test = ((IdealLoopTree*)this)->tail();
231 int body_size = ((IdealLoopTree*)this)->_body.size();
232 int uniq = phase->C->unique();
233 // Peeling does loop cloning which can result in O(N^2) node construction
234 if( body_size > 255 /* Prevent overflow for large body_size */
235 || (body_size * body_size + uniq > MaxNodeLimit) ) {
236 return false; // too large to safely clone
237 }
238 while( test != _head ) { // Scan till run off top of loop
239 if( test->is_If() ) { // Test?
240 Node *ctrl = phase->get_ctrl(test->in(1));
241 if (ctrl->is_top())
242 return false; // Found dead test on live IF? No peeling!
243 // Standard IF only has one input value to check for loop invariance
244 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
245 // Condition is not a member of this loop?
246 if( !is_member(phase->get_loop(ctrl)) &&
247 is_loop_exit(test) )
248 return true; // Found reason to peel!
249 }
250 // Walk up dominators to loop _head looking for test which is
251 // executed on every path thru loop.
252 test = phase->idom(test);
253 }
254 return false;
255 }
256
257 //------------------------------peeled_dom_test_elim---------------------------
258 // If we got the effect of peeling, either by actually peeling or by making
259 // a pre-loop which must execute at least once, we can remove all
260 // loop-invariant dominated tests in the main body.
261 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
262 bool progress = true;
263 while( progress ) {
264 progress = false; // Reset for next iteration
265 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
266 Node *test = prev->in(0);
267 while( test != loop->_head ) { // Scan till run off top of loop
268
269 int p_op = prev->Opcode();
270 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
271 test->is_If() && // Test?
272 !test->in(1)->is_Con() && // And not already obvious?
273 // Condition is not a member of this loop?
274 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
275 // Walk loop body looking for instances of this test
276 for( uint i = 0; i < loop->_body.size(); i++ ) {
277 Node *n = loop->_body.at(i);
278 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
279 // IfNode was dominated by version in peeled loop body
280 progress = true;
281 dominated_by( old_new[prev->_idx], n );
282 }
283 }
284 }
285 prev = test;
286 test = idom(test);
287 } // End of scan tests in loop
288
289 } // End of while( progress )
290 }
291
292 //------------------------------do_peeling-------------------------------------
293 // Peel the first iteration of the given loop.
294 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
295 // The pre-loop illegally has 2 control users (old & new loops).
296 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
297 // Do this by making the old-loop fall-in edges act as if they came
298 // around the loopback from the prior iteration (follow the old-loop
299 // backedges) and then map to the new peeled iteration. This leaves
300 // the pre-loop with only 1 user (the new peeled iteration), but the
301 // peeled-loop backedge has 2 users.
302 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
303 // extra backedge user.
304 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
305
306 C->set_major_progress();
307 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
308 // 'pre' loop from the main and the 'pre' can no longer have it's
309 // iterations adjusted. Therefore, we need to declare this loop as
310 // no longer a 'main' loop; it will need new pre and post loops before
311 // we can do further RCE.
312 #ifndef PRODUCT
313 if (TraceLoopOpts) {
314 tty->print("Peel ");
315 loop->dump_head();
316 }
317 #endif
318 Node *h = loop->_head;
319 if (h->is_CountedLoop()) {
320 CountedLoopNode *cl = h->as_CountedLoop();
321 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
322 cl->set_trip_count(cl->trip_count() - 1);
323 if (cl->is_main_loop()) {
324 cl->set_normal_loop();
325 #ifndef PRODUCT
326 if (PrintOpto && VerifyLoopOptimizations) {
327 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
328 loop->dump_head();
329 }
330 #endif
331 }
332 }
333
334 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
335 // The pre-loop illegally has 2 control users (old & new loops).
336 clone_loop( loop, old_new, dom_depth(loop->_head) );
337
338
339 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
340 // Do this by making the old-loop fall-in edges act as if they came
341 // around the loopback from the prior iteration (follow the old-loop
342 // backedges) and then map to the new peeled iteration. This leaves
343 // the pre-loop with only 1 user (the new peeled iteration), but the
344 // peeled-loop backedge has 2 users.
345 for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) {
346 Node* old = loop->_head->fast_out(j);
347 if( old->in(0) == loop->_head && old->req() == 3 &&
348 (old->is_Loop() || old->is_Phi()) ) {
349 Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
350 if( !new_exit_value ) // Backedge value is ALSO loop invariant?
351 // Then loop body backedge value remains the same.
352 new_exit_value = old->in(LoopNode::LoopBackControl);
353 _igvn.hash_delete(old);
354 old->set_req(LoopNode::EntryControl, new_exit_value);
355 }
356 }
357
358
359 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
360 // extra backedge user.
361 Node *nnn = old_new[loop->_head->_idx];
362 _igvn.hash_delete(nnn);
363 nnn->set_req(LoopNode::LoopBackControl, C->top());
364 for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) {
365 Node* use = nnn->fast_out(j2);
366 if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) {
367 _igvn.hash_delete(use);
368 use->set_req(LoopNode::LoopBackControl, C->top());
369 }
370 }
371
372
373 // Step 4: Correct dom-depth info. Set to loop-head depth.
374 int dd = dom_depth(loop->_head);
375 set_idom(loop->_head, loop->_head->in(1), dd);
376 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
377 Node *old = loop->_body.at(j3);
378 Node *nnn = old_new[old->_idx];
379 if (!has_ctrl(nnn))
380 set_idom(nnn, idom(nnn), dd-1);
381 // While we're at it, remove any SafePoints from the peeled code
382 if( old->Opcode() == Op_SafePoint ) {
383 Node *nnn = old_new[old->_idx];
384 lazy_replace(nnn,nnn->in(TypeFunc::Control));
385 }
386 }
387
388 // Now force out all loop-invariant dominating tests. The optimizer
389 // finds some, but we _know_ they are all useless.
390 peeled_dom_test_elim(loop,old_new);
391
392 loop->record_for_igvn();
393 }
394
395 //------------------------------policy_maximally_unroll------------------------
396 // Return exact loop trip count, or 0 if not maximally unrolling
397 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
398 CountedLoopNode *cl = _head->as_CountedLoop();
399 assert(cl->is_normal_loop(), "");
400
401 Node *init_n = cl->init_trip();
402 Node *limit_n = cl->limit();
403
404 // Non-constant bounds
405 if (init_n == NULL || !init_n->is_Con() ||
406 limit_n == NULL || !limit_n->is_Con() ||
407 // protect against stride not being a constant
408 !cl->stride_is_con()) {
409 return false;
410 }
411 int init = init_n->get_int();
412 int limit = limit_n->get_int();
413 int span = limit - init;
414 int stride = cl->stride_con();
415
416 if (init >= limit || stride > span) {
417 // return a false (no maximally unroll) and the regular unroll/peel
418 // route will make a small mess which CCP will fold away.
419 return false;
420 }
421 uint trip_count = span/stride; // trip_count can be greater than 2 Gig.
422 assert( (int)trip_count*stride == span, "must divide evenly" );
423
424 // Real policy: if we maximally unroll, does it get too big?
425 // Allow the unrolled mess to get larger than standard loop
426 // size. After all, it will no longer be a loop.
427 uint body_size = _body.size();
428 uint unroll_limit = (uint)LoopUnrollLimit * 4;
429 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
430 cl->set_trip_count(trip_count);
431 if (trip_count > unroll_limit || body_size > unroll_limit) {
432 return false;
433 }
434
435 // Do not unroll a loop with String intrinsics code.
436 // String intrinsics are large and have loops.
437 for (uint k = 0; k < _body.size(); k++) {
438 Node* n = _body.at(k);
439 switch (n->Opcode()) {
440 case Op_StrComp:
441 case Op_StrEquals:
442 case Op_StrIndexOf:
443 case Op_AryEq: {
444 return false;
445 }
446 } // switch
447 }
448
449 if (body_size <= unroll_limit) {
450 uint new_body_size = body_size * trip_count;
451 if (new_body_size <= unroll_limit &&
452 body_size == new_body_size / trip_count &&
453 // Unrolling can result in a large amount of node construction
454 new_body_size < MaxNodeLimit - phase->C->unique()) {
455 return true; // maximally unroll
456 }
457 }
458
459 return false; // Do not maximally unroll
460 }
461
462
463 //------------------------------policy_unroll----------------------------------
464 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
465 // the loop is a CountedLoop and the body is small enough.
466 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
467
468 CountedLoopNode *cl = _head->as_CountedLoop();
469 assert(cl->is_normal_loop() || cl->is_main_loop(), "");
470
471 // protect against stride not being a constant
472 if (!cl->stride_is_con()) return false;
473
474 // protect against over-unrolling
475 if (cl->trip_count() <= 1) return false;
476
477 int future_unroll_ct = cl->unrolled_count() * 2;
478
479 // Don't unroll if the next round of unrolling would push us
480 // over the expected trip count of the loop. One is subtracted
481 // from the expected trip count because the pre-loop normally
482 // executes 1 iteration.
483 if (UnrollLimitForProfileCheck > 0 &&
484 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
485 future_unroll_ct > UnrollLimitForProfileCheck &&
486 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
487 return false;
488 }
489
490 // When unroll count is greater than LoopUnrollMin, don't unroll if:
491 // the residual iterations are more than 10% of the trip count
492 // and rounds of "unroll,optimize" are not making significant progress
493 // Progress defined as current size less than 20% larger than previous size.
494 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
495 future_unroll_ct > LoopUnrollMin &&
496 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
497 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
498 return false;
499 }
500
501 Node *init_n = cl->init_trip();
502 Node *limit_n = cl->limit();
503 // Non-constant bounds.
504 // Protect against over-unrolling when init or/and limit are not constant
505 // (so that trip_count's init value is maxint) but iv range is known.
506 if (init_n == NULL || !init_n->is_Con() ||
507 limit_n == NULL || !limit_n->is_Con()) {
508 Node* phi = cl->phi();
509 if (phi != NULL) {
510 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
511 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
512 int next_stride = cl->stride_con() * 2; // stride after this unroll
513 if (next_stride > 0) {
514 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
515 iv_type->_lo + next_stride > iv_type->_hi) {
516 return false; // over-unrolling
517 }
518 } else if (next_stride < 0) {
519 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
520 iv_type->_hi + next_stride < iv_type->_lo) {
521 return false; // over-unrolling
522 }
523 }
524 }
525 }
526
527 // Adjust body_size to determine if we unroll or not
528 uint body_size = _body.size();
529 // Key test to unroll CaffeineMark's Logic test
530 int xors_in_loop = 0;
531 // Also count ModL, DivL and MulL which expand mightly
532 for (uint k = 0; k < _body.size(); k++) {
533 Node* n = _body.at(k);
534 switch (n->Opcode()) {
535 case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test
536 case Op_ModL: body_size += 30; break;
537 case Op_DivL: body_size += 30; break;
538 case Op_MulL: body_size += 10; break;
539 case Op_StrComp:
540 case Op_StrEquals:
541 case Op_StrIndexOf:
542 case Op_AryEq: {
543 // Do not unroll a loop with String intrinsics code.
544 // String intrinsics are large and have loops.
545 return false;
546 }
547 } // switch
548 }
549
550 // Check for being too big
551 if (body_size > (uint)LoopUnrollLimit) {
552 if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
553 // Normal case: loop too big
554 return false;
555 }
556
557 // Check for stride being a small enough constant
558 if (abs(cl->stride_con()) > (1<<3)) return false;
559
560 // Unroll once! (Each trip will soon do double iterations)
561 return true;
562 }
563
564 //------------------------------policy_align-----------------------------------
565 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
566 // expression that does the alignment. Note that only one array base can be
567 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
568 // if we vectorize short memory ops into longer memory ops, we may want to
569 // increase alignment.
570 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
571 return false;
572 }
573
574 //------------------------------policy_range_check-----------------------------
575 // Return TRUE or FALSE if the loop should be range-check-eliminated.
576 // Actually we do iteration-splitting, a more powerful form of RCE.
577 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
578 if( !RangeCheckElimination ) return false;
579
580 CountedLoopNode *cl = _head->as_CountedLoop();
581 // If we unrolled with no intention of doing RCE and we later
582 // changed our minds, we got no pre-loop. Either we need to
583 // make a new pre-loop, or we gotta disallow RCE.
584 if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now.
585 Node *trip_counter = cl->phi();
586
587 // Check loop body for tests of trip-counter plus loop-invariant vs
588 // loop-invariant.
589 for( uint i = 0; i < _body.size(); i++ ) {
590 Node *iff = _body[i];
591 if( iff->Opcode() == Op_If ) { // Test?
592
593 // Comparing trip+off vs limit
594 Node *bol = iff->in(1);
595 if( bol->req() != 2 ) continue; // dead constant test
596 if (!bol->is_Bool()) {
597 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
598 continue;
599 }
600 Node *cmp = bol->in(1);
601
602 Node *rc_exp = cmp->in(1);
603 Node *limit = cmp->in(2);
604
605 Node *limit_c = phase->get_ctrl(limit);
606 if( limit_c == phase->C->top() )
607 return false; // Found dead test on live IF? No RCE!
608 if( is_member(phase->get_loop(limit_c) ) ) {
609 // Compare might have operands swapped; commute them
610 rc_exp = cmp->in(2);
611 limit = cmp->in(1);
612 limit_c = phase->get_ctrl(limit);
613 if( is_member(phase->get_loop(limit_c) ) )
614 continue; // Both inputs are loop varying; cannot RCE
615 }
616
617 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
618 continue;
619 }
620 // Yeah! Found a test like 'trip+off vs limit'
621 // Test is an IfNode, has 2 projections. If BOTH are in the loop
622 // we need loop unswitching instead of iteration splitting.
623 if( is_loop_exit(iff) )
624 return true; // Found reason to split iterations
625 } // End of is IF
626 }
627
628 return false;
629 }
630
631 //------------------------------policy_peel_only-------------------------------
632 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
633 // for unrolling loops with NO array accesses.
634 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
635
636 for( uint i = 0; i < _body.size(); i++ )
637 if( _body[i]->is_Mem() )
638 return false;
639
640 // No memory accesses at all!
641 return true;
642 }
643
644 //------------------------------clone_up_backedge_goo--------------------------
645 // If Node n lives in the back_ctrl block and cannot float, we clone a private
646 // version of n in preheader_ctrl block and return that, otherwise return n.
647 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
648 if( get_ctrl(n) != back_ctrl ) return n;
649
650 Node *x = NULL; // If required, a clone of 'n'
651 // Check for 'n' being pinned in the backedge.
652 if( n->in(0) && n->in(0) == back_ctrl ) {
653 x = n->clone(); // Clone a copy of 'n' to preheader
654 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
655 }
656
657 // Recursive fixup any other input edges into x.
658 // If there are no changes we can just return 'n', otherwise
659 // we need to clone a private copy and change it.
660 for( uint i = 1; i < n->req(); i++ ) {
661 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
662 if( g != n->in(i) ) {
663 if( !x )
664 x = n->clone();
665 x->set_req(i, g);
666 }
667 }
668 if( x ) { // x can legally float to pre-header location
669 register_new_node( x, preheader_ctrl );
670 return x;
671 } else { // raise n to cover LCA of uses
672 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
673 }
674 return n;
675 }
676
677 //------------------------------insert_pre_post_loops--------------------------
678 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
679 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
680 // alignment. Useful to unroll loops that do no array accesses.
681 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
682
683 #ifndef PRODUCT
684 if (TraceLoopOpts) {
685 if (peel_only)
686 tty->print("PeelMainPost ");
687 else
688 tty->print("PreMainPost ");
689 loop->dump_head();
690 }
691 #endif
692 C->set_major_progress();
693
694 // Find common pieces of the loop being guarded with pre & post loops
695 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
696 assert( main_head->is_normal_loop(), "" );
697 CountedLoopEndNode *main_end = main_head->loopexit();
698 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
699 uint dd_main_head = dom_depth(main_head);
700 uint max = main_head->outcnt();
701
702 Node *pre_header= main_head->in(LoopNode::EntryControl);
703 Node *init = main_head->init_trip();
704 Node *incr = main_end ->incr();
705 Node *limit = main_end ->limit();
706 Node *stride = main_end ->stride();
707 Node *cmp = main_end ->cmp_node();
708 BoolTest::mask b_test = main_end->test_trip();
709
710 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
711 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
712 if( bol->outcnt() != 1 ) {
713 bol = bol->clone();
714 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
715 _igvn.hash_delete(main_end);
716 main_end->set_req(CountedLoopEndNode::TestValue, bol);
717 }
718 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
719 if( cmp->outcnt() != 1 ) {
720 cmp = cmp->clone();
721 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
722 _igvn.hash_delete(bol);
723 bol->set_req(1, cmp);
724 }
725
726 //------------------------------
727 // Step A: Create Post-Loop.
728 Node* main_exit = main_end->proj_out(false);
729 assert( main_exit->Opcode() == Op_IfFalse, "" );
730 int dd_main_exit = dom_depth(main_exit);
731
732 // Step A1: Clone the loop body. The clone becomes the post-loop. The main
733 // loop pre-header illegally has 2 control users (old & new loops).
734 clone_loop( loop, old_new, dd_main_exit );
735 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
736 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
737 post_head->set_post_loop(main_head);
738
739 // Reduce the post-loop trip count.
740 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
741 post_end->_prob = PROB_FAIR;
742
743 // Build the main-loop normal exit.
744 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
745 _igvn.register_new_node_with_optimizer( new_main_exit );
746 set_idom(new_main_exit, main_end, dd_main_exit );
747 set_loop(new_main_exit, loop->_parent);
748
749 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
750 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
751 // (the main-loop trip-counter exit value) because we will be changing
752 // the exit value (via unrolling) so we cannot constant-fold away the zero
753 // trip guard until all unrolling is done.
754 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr);
755 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit );
756 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test );
757 register_new_node( zer_opaq, new_main_exit );
758 register_new_node( zer_cmp , new_main_exit );
759 register_new_node( zer_bol , new_main_exit );
760
761 // Build the IfNode
762 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
763 _igvn.register_new_node_with_optimizer( zer_iff );
764 set_idom(zer_iff, new_main_exit, dd_main_exit);
765 set_loop(zer_iff, loop->_parent);
766
767 // Plug in the false-path, taken if we need to skip post-loop
768 _igvn.hash_delete( main_exit );
769 main_exit->set_req(0, zer_iff);
770 _igvn._worklist.push(main_exit);
771 set_idom(main_exit, zer_iff, dd_main_exit);
772 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
773 // Make the true-path, must enter the post loop
774 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
775 _igvn.register_new_node_with_optimizer( zer_taken );
776 set_idom(zer_taken, zer_iff, dd_main_exit);
777 set_loop(zer_taken, loop->_parent);
778 // Plug in the true path
779 _igvn.hash_delete( post_head );
780 post_head->set_req(LoopNode::EntryControl, zer_taken);
781 set_idom(post_head, zer_taken, dd_main_exit);
782
783 // Step A3: Make the fall-in values to the post-loop come from the
784 // fall-out values of the main-loop.
785 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
786 Node* main_phi = main_head->fast_out(i);
787 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
788 Node *post_phi = old_new[main_phi->_idx];
789 Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
790 post_head->init_control(),
791 main_phi->in(LoopNode::LoopBackControl));
792 _igvn.hash_delete(post_phi);
793 post_phi->set_req( LoopNode::EntryControl, fallmain );
794 }
795 }
796
797 // Update local caches for next stanza
798 main_exit = new_main_exit;
799
800
801 //------------------------------
802 // Step B: Create Pre-Loop.
803
804 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
805 // loop pre-header illegally has 2 control users (old & new loops).
806 clone_loop( loop, old_new, dd_main_head );
807 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
808 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
809 pre_head->set_pre_loop(main_head);
810 Node *pre_incr = old_new[incr->_idx];
811
812 // Reduce the pre-loop trip count.
813 pre_end->_prob = PROB_FAIR;
814
815 // Find the pre-loop normal exit.
816 Node* pre_exit = pre_end->proj_out(false);
817 assert( pre_exit->Opcode() == Op_IfFalse, "" );
818 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
819 _igvn.register_new_node_with_optimizer( new_pre_exit );
820 set_idom(new_pre_exit, pre_end, dd_main_head);
821 set_loop(new_pre_exit, loop->_parent);
822
823 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
824 // pre-loop, the main-loop may not execute at all. Later in life this
825 // zero-trip guard will become the minimum-trip guard when we unroll
826 // the main-loop.
827 Node *min_opaq = new (C, 2) Opaque1Node(C, limit);
828 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq );
829 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test );
830 register_new_node( min_opaq, new_pre_exit );
831 register_new_node( min_cmp , new_pre_exit );
832 register_new_node( min_bol , new_pre_exit );
833
834 // Build the IfNode (assume the main-loop is executed always).
835 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
836 _igvn.register_new_node_with_optimizer( min_iff );
837 set_idom(min_iff, new_pre_exit, dd_main_head);
838 set_loop(min_iff, loop->_parent);
839
840 // Plug in the false-path, taken if we need to skip main-loop
841 _igvn.hash_delete( pre_exit );
842 pre_exit->set_req(0, min_iff);
843 set_idom(pre_exit, min_iff, dd_main_head);
844 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
845 // Make the true-path, must enter the main loop
846 Node *min_taken = new (C, 1) IfTrueNode( min_iff );
847 _igvn.register_new_node_with_optimizer( min_taken );
848 set_idom(min_taken, min_iff, dd_main_head);
849 set_loop(min_taken, loop->_parent);
850 // Plug in the true path
851 _igvn.hash_delete( main_head );
852 main_head->set_req(LoopNode::EntryControl, min_taken);
853 set_idom(main_head, min_taken, dd_main_head);
854
855 // Step B3: Make the fall-in values to the main-loop come from the
856 // fall-out values of the pre-loop.
857 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
858 Node* main_phi = main_head->fast_out(i2);
859 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
860 Node *pre_phi = old_new[main_phi->_idx];
861 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
862 main_head->init_control(),
863 pre_phi->in(LoopNode::LoopBackControl));
864 _igvn.hash_delete(main_phi);
865 main_phi->set_req( LoopNode::EntryControl, fallpre );
866 }
867 }
868
869 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
870 // RCE and alignment may change this later.
871 Node *cmp_end = pre_end->cmp_node();
872 assert( cmp_end->in(2) == limit, "" );
873 Node *pre_limit = new (C, 3) AddINode( init, stride );
874
875 // Save the original loop limit in this Opaque1 node for
876 // use by range check elimination.
877 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit);
878
879 register_new_node( pre_limit, pre_head->in(0) );
880 register_new_node( pre_opaq , pre_head->in(0) );
881
882 // Since no other users of pre-loop compare, I can hack limit directly
883 assert( cmp_end->outcnt() == 1, "no other users" );
884 _igvn.hash_delete(cmp_end);
885 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
886
887 // Special case for not-equal loop bounds:
888 // Change pre loop test, main loop test, and the
889 // main loop guard test to use lt or gt depending on stride
890 // direction:
891 // positive stride use <
892 // negative stride use >
893
894 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
895
896 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
897 // Modify pre loop end condition
898 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
899 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
900 register_new_node( new_bol0, pre_head->in(0) );
901 _igvn.hash_delete(pre_end);
902 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
903 // Modify main loop guard condition
904 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
905 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
906 register_new_node( new_bol1, new_pre_exit );
907 _igvn.hash_delete(min_iff);
908 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
909 // Modify main loop end condition
910 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
911 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
912 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
913 _igvn.hash_delete(main_end);
914 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
915 }
916
917 // Flag main loop
918 main_head->set_main_loop();
919 if( peel_only ) main_head->set_main_no_pre_loop();
920
921 // It's difficult to be precise about the trip-counts
922 // for the pre/post loops. They are usually very short,
923 // so guess that 4 trips is a reasonable value.
924 post_head->set_profile_trip_cnt(4.0);
925 pre_head->set_profile_trip_cnt(4.0);
926
927 // Now force out all loop-invariant dominating tests. The optimizer
928 // finds some, but we _know_ they are all useless.
929 peeled_dom_test_elim(loop,old_new);
930 }
931
932 //------------------------------is_invariant-----------------------------
933 // Return true if n is invariant
934 bool IdealLoopTree::is_invariant(Node* n) const {
935 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
936 if (n_c->is_top()) return false;
937 return !is_member(_phase->get_loop(n_c));
938 }
939
940
941 //------------------------------do_unroll--------------------------------------
942 // Unroll the loop body one step - make each trip do 2 iterations.
943 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
944 assert(LoopUnrollLimit, "");
945 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
946 CountedLoopEndNode *loop_end = loop_head->loopexit();
947 assert(loop_end, "");
948 #ifndef PRODUCT
949 if (PrintOpto && VerifyLoopOptimizations) {
950 tty->print("Unrolling ");
951 loop->dump_head();
952 } else if (TraceLoopOpts) {
953 tty->print("Unroll %d ", loop_head->unrolled_count()*2);
954 loop->dump_head();
955 }
956 #endif
957
958 // Remember loop node count before unrolling to detect
959 // if rounds of unroll,optimize are making progress
960 loop_head->set_node_count_before_unroll(loop->_body.size());
961
962 Node *ctrl = loop_head->in(LoopNode::EntryControl);
963 Node *limit = loop_head->limit();
964 Node *init = loop_head->init_trip();
965 Node *stride = loop_head->stride();
966
967 Node *opaq = NULL;
968 if( adjust_min_trip ) { // If not maximally unrolling, need adjustment
969 assert( loop_head->is_main_loop(), "" );
970 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
971 Node *iff = ctrl->in(0);
972 assert( iff->Opcode() == Op_If, "" );
973 Node *bol = iff->in(1);
974 assert( bol->Opcode() == Op_Bool, "" );
975 Node *cmp = bol->in(1);
976 assert( cmp->Opcode() == Op_CmpI, "" );
977 opaq = cmp->in(2);
978 // Occasionally it's possible for a pre-loop Opaque1 node to be
979 // optimized away and then another round of loop opts attempted.
980 // We can not optimize this particular loop in that case.
981 if( opaq->Opcode() != Op_Opaque1 )
982 return; // Cannot find pre-loop! Bail out!
983 }
984
985 C->set_major_progress();
986
987 // Adjust max trip count. The trip count is intentionally rounded
988 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
989 // the main, unrolled, part of the loop will never execute as it is protected
990 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
991 // and later determined that part of the unrolled loop was dead.
992 loop_head->set_trip_count(loop_head->trip_count() / 2);
993
994 // Double the count of original iterations in the unrolled loop body.
995 loop_head->double_unrolled_count();
996
997 // -----------
998 // Step 2: Cut back the trip counter for an unroll amount of 2.
999 // Loop will normally trip (limit - init)/stride_con. Since it's a
1000 // CountedLoop this is exact (stride divides limit-init exactly).
1001 // We are going to double the loop body, so we want to knock off any
1002 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
1003 Node *span = new (C, 3) SubINode( limit, init );
1004 register_new_node( span, ctrl );
1005 Node *trip = new (C, 3) DivINode( 0, span, stride );
1006 register_new_node( trip, ctrl );
1007 Node *mtwo = _igvn.intcon(-2);
1008 set_ctrl(mtwo, C->root());
1009 Node *rond = new (C, 3) AndINode( trip, mtwo );
1010 register_new_node( rond, ctrl );
1011 Node *spn2 = new (C, 3) MulINode( rond, stride );
1012 register_new_node( spn2, ctrl );
1013 Node *lim2 = new (C, 3) AddINode( spn2, init );
1014 register_new_node( lim2, ctrl );
1015
1016 // Hammer in the new limit
1017 Node *ctrl2 = loop_end->in(0);
1018 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 );
1019 register_new_node( cmp2, ctrl2 );
1020 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
1021 register_new_node( bol2, ctrl2 );
1022 _igvn.hash_delete(loop_end);
1023 loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1024
1025 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1026 // Make it a 1-trip test (means at least 2 trips).
1027 if( adjust_min_trip ) {
1028 // Guard test uses an 'opaque' node which is not shared. Hence I
1029 // can edit it's inputs directly. Hammer in the new limit for the
1030 // minimum-trip guard.
1031 assert( opaq->outcnt() == 1, "" );
1032 _igvn.hash_delete(opaq);
1033 opaq->set_req(1, lim2);
1034 }
1035
1036 // ---------
1037 // Step 4: Clone the loop body. Move it inside the loop. This loop body
1038 // represents the odd iterations; since the loop trips an even number of
1039 // times its backedge is never taken. Kill the backedge.
1040 uint dd = dom_depth(loop_head);
1041 clone_loop( loop, old_new, dd );
1042
1043 // Make backedges of the clone equal to backedges of the original.
1044 // Make the fall-in from the original come from the fall-out of the clone.
1045 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1046 Node* phi = loop_head->fast_out(j);
1047 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1048 Node *newphi = old_new[phi->_idx];
1049 _igvn.hash_delete( phi );
1050 _igvn.hash_delete( newphi );
1051
1052 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1053 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1054 phi ->set_req(LoopNode::LoopBackControl, C->top());
1055 }
1056 }
1057 Node *clone_head = old_new[loop_head->_idx];
1058 _igvn.hash_delete( clone_head );
1059 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1060 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1061 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1062 loop->_head = clone_head; // New loop header
1063
1064 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1065 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1066
1067 // Kill the clone's backedge
1068 Node *newcle = old_new[loop_end->_idx];
1069 _igvn.hash_delete( newcle );
1070 Node *one = _igvn.intcon(1);
1071 set_ctrl(one, C->root());
1072 newcle->set_req(1, one);
1073 // Force clone into same loop body
1074 uint max = loop->_body.size();
1075 for( uint k = 0; k < max; k++ ) {
1076 Node *old = loop->_body.at(k);
1077 Node *nnn = old_new[old->_idx];
1078 loop->_body.push(nnn);
1079 if (!has_ctrl(old))
1080 set_loop(nnn, loop);
1081 }
1082
1083 loop->record_for_igvn();
1084 }
1085
1086 //------------------------------do_maximally_unroll----------------------------
1087
1088 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1089 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1090 assert(cl->trip_count() > 0, "");
1091 #ifndef PRODUCT
1092 if (TraceLoopOpts) {
1093 tty->print("MaxUnroll %d ", cl->trip_count());
1094 loop->dump_head();
1095 }
1096 #endif
1097
1098 // If loop is tripping an odd number of times, peel odd iteration
1099 if ((cl->trip_count() & 1) == 1) {
1100 do_peeling(loop, old_new);
1101 }
1102
1103 // Now its tripping an even number of times remaining. Double loop body.
1104 // Do not adjust pre-guards; they are not needed and do not exist.
1105 if (cl->trip_count() > 0) {
1106 do_unroll(loop, old_new, false);
1107 }
1108 }
1109
1110 //------------------------------dominates_backedge---------------------------------
1111 // Returns true if ctrl is executed on every complete iteration
1112 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1113 assert(ctrl->is_CFG(), "must be control");
1114 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1115 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1116 }
1117
1118 //------------------------------add_constraint---------------------------------
1119 // Constrain the main loop iterations so the condition:
1120 // scale_con * I + offset < limit
1121 // always holds true. That is, either increase the number of iterations in
1122 // the pre-loop or the post-loop until the condition holds true in the main
1123 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1124 // stride and scale are constants (offset and limit often are).
1125 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1126
1127 // Compute "I :: (limit-offset)/scale_con"
1128 Node *con = new (C, 3) SubINode( limit, offset );
1129 register_new_node( con, pre_ctrl );
1130 Node *scale = _igvn.intcon(scale_con);
1131 set_ctrl(scale, C->root());
1132 Node *X = new (C, 3) DivINode( 0, con, scale );
1133 register_new_node( X, pre_ctrl );
1134
1135 // For positive stride, the pre-loop limit always uses a MAX function
1136 // and the main loop a MIN function. For negative stride these are
1137 // reversed.
1138
1139 // Also for positive stride*scale the affine function is increasing, so the
1140 // pre-loop must check for underflow and the post-loop for overflow.
1141 // Negative stride*scale reverses this; pre-loop checks for overflow and
1142 // post-loop for underflow.
1143 if( stride_con*scale_con > 0 ) {
1144 // Compute I < (limit-offset)/scale_con
1145 // Adjust main-loop last iteration to be MIN/MAX(main_loop,X)
1146 *main_limit = (stride_con > 0)
1147 ? (Node*)(new (C, 3) MinINode( *main_limit, X ))
1148 : (Node*)(new (C, 3) MaxINode( *main_limit, X ));
1149 register_new_node( *main_limit, pre_ctrl );
1150
1151 } else {
1152 // Compute (limit-offset)/scale_con + SGN(-scale_con) <= I
1153 // Add the negation of the main-loop constraint to the pre-loop.
1154 // See footnote [++] below for a derivation of the limit expression.
1155 Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1);
1156 set_ctrl(incr, C->root());
1157 Node *adj = new (C, 3) AddINode( X, incr );
1158 register_new_node( adj, pre_ctrl );
1159 *pre_limit = (scale_con > 0)
1160 ? (Node*)new (C, 3) MinINode( *pre_limit, adj )
1161 : (Node*)new (C, 3) MaxINode( *pre_limit, adj );
1162 register_new_node( *pre_limit, pre_ctrl );
1163
1164 // [++] Here's the algebra that justifies the pre-loop limit expression:
1165 //
1166 // NOT( scale_con * I + offset < limit )
1167 // ==
1168 // scale_con * I + offset >= limit
1169 // ==
1170 // SGN(scale_con) * I >= (limit-offset)/|scale_con|
1171 // ==
1172 // (limit-offset)/|scale_con| <= I * SGN(scale_con)
1173 // ==
1174 // (limit-offset)/|scale_con|-1 < I * SGN(scale_con)
1175 // ==
1176 // ( if (scale_con > 0) /*common case*/
1177 // (limit-offset)/scale_con - 1 < I
1178 // else
1179 // (limit-offset)/scale_con + 1 > I
1180 // )
1181 // ( if (scale_con > 0) /*common case*/
1182 // (limit-offset)/scale_con + SGN(-scale_con) < I
1183 // else
1184 // (limit-offset)/scale_con + SGN(-scale_con) > I
1185 }
1186 }
1187
1188
1189 //------------------------------is_scaled_iv---------------------------------
1190 // Return true if exp is a constant times an induction var
1191 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1192 if (exp == iv) {
1193 if (p_scale != NULL) {
1194 *p_scale = 1;
1195 }
1196 return true;
1197 }
1198 int opc = exp->Opcode();
1199 if (opc == Op_MulI) {
1200 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1201 if (p_scale != NULL) {
1202 *p_scale = exp->in(2)->get_int();
1203 }
1204 return true;
1205 }
1206 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1207 if (p_scale != NULL) {
1208 *p_scale = exp->in(1)->get_int();
1209 }
1210 return true;
1211 }
1212 } else if (opc == Op_LShiftI) {
1213 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1214 if (p_scale != NULL) {
1215 *p_scale = 1 << exp->in(2)->get_int();
1216 }
1217 return true;
1218 }
1219 }
1220 return false;
1221 }
1222
1223 //-----------------------------is_scaled_iv_plus_offset------------------------------
1224 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1225 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1226 if (is_scaled_iv(exp, iv, p_scale)) {
1227 if (p_offset != NULL) {
1228 Node *zero = _igvn.intcon(0);
1229 set_ctrl(zero, C->root());
1230 *p_offset = zero;
1231 }
1232 return true;
1233 }
1234 int opc = exp->Opcode();
1235 if (opc == Op_AddI) {
1236 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1237 if (p_offset != NULL) {
1238 *p_offset = exp->in(2);
1239 }
1240 return true;
1241 }
1242 if (exp->in(2)->is_Con()) {
1243 Node* offset2 = NULL;
1244 if (depth < 2 &&
1245 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1246 p_offset != NULL ? &offset2 : NULL, depth+1)) {
1247 if (p_offset != NULL) {
1248 Node *ctrl_off2 = get_ctrl(offset2);
1249 Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
1250 register_new_node(offset, ctrl_off2);
1251 *p_offset = offset;
1252 }
1253 return true;
1254 }
1255 }
1256 } else if (opc == Op_SubI) {
1257 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1258 if (p_offset != NULL) {
1259 Node *zero = _igvn.intcon(0);
1260 set_ctrl(zero, C->root());
1261 Node *ctrl_off = get_ctrl(exp->in(2));
1262 Node* offset = new (C, 3) SubINode(zero, exp->in(2));
1263 register_new_node(offset, ctrl_off);
1264 *p_offset = offset;
1265 }
1266 return true;
1267 }
1268 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1269 if (p_offset != NULL) {
1270 *p_scale *= -1;
1271 *p_offset = exp->in(1);
1272 }
1273 return true;
1274 }
1275 }
1276 return false;
1277 }
1278
1279 //------------------------------do_range_check---------------------------------
1280 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1281 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1282 #ifndef PRODUCT
1283 if (PrintOpto && VerifyLoopOptimizations) {
1284 tty->print("Range Check Elimination ");
1285 loop->dump_head();
1286 } else if (TraceLoopOpts) {
1287 tty->print("RangeCheck ");
1288 loop->dump_head();
1289 }
1290 #endif
1291 assert(RangeCheckElimination, "");
1292 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1293 assert(cl->is_main_loop(), "");
1294
1295 // protect against stride not being a constant
1296 if (!cl->stride_is_con())
1297 return;
1298
1299 // Find the trip counter; we are iteration splitting based on it
1300 Node *trip_counter = cl->phi();
1301 // Find the main loop limit; we will trim it's iterations
1302 // to not ever trip end tests
1303 Node *main_limit = cl->limit();
1304
1305 // Need to find the main-loop zero-trip guard
1306 Node *ctrl = cl->in(LoopNode::EntryControl);
1307 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1308 Node *iffm = ctrl->in(0);
1309 assert(iffm->Opcode() == Op_If, "");
1310 Node *bolzm = iffm->in(1);
1311 assert(bolzm->Opcode() == Op_Bool, "");
1312 Node *cmpzm = bolzm->in(1);
1313 assert(cmpzm->is_Cmp(), "");
1314 Node *opqzm = cmpzm->in(2);
1315 // Can not optimize a loop if pre-loop Opaque1 node is optimized
1316 // away and then another round of loop opts attempted.
1317 if (opqzm->Opcode() != Op_Opaque1)
1318 return;
1319 assert(opqzm->in(1) == main_limit, "do not understand situation");
1320
1321 // Find the pre-loop limit; we will expand it's iterations to
1322 // not ever trip low tests.
1323 Node *p_f = iffm->in(0);
1324 assert(p_f->Opcode() == Op_IfFalse, "");
1325 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1326 assert(pre_end->loopnode()->is_pre_loop(), "");
1327 Node *pre_opaq1 = pre_end->limit();
1328 // Occasionally it's possible for a pre-loop Opaque1 node to be
1329 // optimized away and then another round of loop opts attempted.
1330 // We can not optimize this particular loop in that case.
1331 if (pre_opaq1->Opcode() != Op_Opaque1)
1332 return;
1333 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1334 Node *pre_limit = pre_opaq->in(1);
1335
1336 // Where do we put new limit calculations
1337 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1338
1339 // Ensure the original loop limit is available from the
1340 // pre-loop Opaque1 node.
1341 Node *orig_limit = pre_opaq->original_loop_limit();
1342 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1343 return;
1344
1345 // Must know if its a count-up or count-down loop
1346
1347 int stride_con = cl->stride_con();
1348 Node *zero = _igvn.intcon(0);
1349 Node *one = _igvn.intcon(1);
1350 set_ctrl(zero, C->root());
1351 set_ctrl(one, C->root());
1352
1353 // Range checks that do not dominate the loop backedge (ie.
1354 // conditionally executed) can lengthen the pre loop limit beyond
1355 // the original loop limit. To prevent this, the pre limit is
1356 // (for stride > 0) MINed with the original loop limit (MAXed
1357 // stride < 0) when some range_check (rc) is conditionally
1358 // executed.
1359 bool conditional_rc = false;
1360
1361 // Check loop body for tests of trip-counter plus loop-invariant vs
1362 // loop-invariant.
1363 for( uint i = 0; i < loop->_body.size(); i++ ) {
1364 Node *iff = loop->_body[i];
1365 if( iff->Opcode() == Op_If ) { // Test?
1366
1367 // Test is an IfNode, has 2 projections. If BOTH are in the loop
1368 // we need loop unswitching instead of iteration splitting.
1369 Node *exit = loop->is_loop_exit(iff);
1370 if( !exit ) continue;
1371 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1372
1373 // Get boolean condition to test
1374 Node *i1 = iff->in(1);
1375 if( !i1->is_Bool() ) continue;
1376 BoolNode *bol = i1->as_Bool();
1377 BoolTest b_test = bol->_test;
1378 // Flip sense of test if exit condition is flipped
1379 if( flip )
1380 b_test = b_test.negate();
1381
1382 // Get compare
1383 Node *cmp = bol->in(1);
1384
1385 // Look for trip_counter + offset vs limit
1386 Node *rc_exp = cmp->in(1);
1387 Node *limit = cmp->in(2);
1388 jint scale_con= 1; // Assume trip counter not scaled
1389
1390 Node *limit_c = get_ctrl(limit);
1391 if( loop->is_member(get_loop(limit_c) ) ) {
1392 // Compare might have operands swapped; commute them
1393 b_test = b_test.commute();
1394 rc_exp = cmp->in(2);
1395 limit = cmp->in(1);
1396 limit_c = get_ctrl(limit);
1397 if( loop->is_member(get_loop(limit_c) ) )
1398 continue; // Both inputs are loop varying; cannot RCE
1399 }
1400 // Here we know 'limit' is loop invariant
1401
1402 // 'limit' maybe pinned below the zero trip test (probably from a
1403 // previous round of rce), in which case, it can't be used in the
1404 // zero trip test expression which must occur before the zero test's if.
1405 if( limit_c == ctrl ) {
1406 continue; // Don't rce this check but continue looking for other candidates.
1407 }
1408
1409 // Check for scaled induction variable plus an offset
1410 Node *offset = NULL;
1411
1412 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1413 continue;
1414 }
1415
1416 Node *offset_c = get_ctrl(offset);
1417 if( loop->is_member( get_loop(offset_c) ) )
1418 continue; // Offset is not really loop invariant
1419 // Here we know 'offset' is loop invariant.
1420
1421 // As above for the 'limit', the 'offset' maybe pinned below the
1422 // zero trip test.
1423 if( offset_c == ctrl ) {
1424 continue; // Don't rce this check but continue looking for other candidates.
1425 }
1426
1427 // At this point we have the expression as:
1428 // scale_con * trip_counter + offset :: limit
1429 // where scale_con, offset and limit are loop invariant. Trip_counter
1430 // monotonically increases by stride_con, a constant. Both (or either)
1431 // stride_con and scale_con can be negative which will flip about the
1432 // sense of the test.
1433
1434 // Adjust pre and main loop limits to guard the correct iteration set
1435 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1436 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1437 // The overflow limit: scale*I+offset < limit
1438 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1439 // The underflow limit: 0 <= scale*I+offset.
1440 // Some math yields: -scale*I-(offset+1) < 0
1441 Node *plus_one = new (C, 3) AddINode( offset, one );
1442 register_new_node( plus_one, pre_ctrl );
1443 Node *neg_offset = new (C, 3) SubINode( zero, plus_one );
1444 register_new_node( neg_offset, pre_ctrl );
1445 add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit );
1446 if (!conditional_rc) {
1447 conditional_rc = !loop->dominates_backedge(iff);
1448 }
1449 } else {
1450 #ifndef PRODUCT
1451 if( PrintOpto )
1452 tty->print_cr("missed RCE opportunity");
1453 #endif
1454 continue; // In release mode, ignore it
1455 }
1456 } else { // Otherwise work on normal compares
1457 switch( b_test._test ) {
1458 case BoolTest::ge: // Convert X >= Y to -X <= -Y
1459 scale_con = -scale_con;
1460 offset = new (C, 3) SubINode( zero, offset );
1461 register_new_node( offset, pre_ctrl );
1462 limit = new (C, 3) SubINode( zero, limit );
1463 register_new_node( limit, pre_ctrl );
1464 // Fall into LE case
1465 case BoolTest::le: // Convert X <= Y to X < Y+1
1466 limit = new (C, 3) AddINode( limit, one );
1467 register_new_node( limit, pre_ctrl );
1468 // Fall into LT case
1469 case BoolTest::lt:
1470 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
1471 if (!conditional_rc) {
1472 conditional_rc = !loop->dominates_backedge(iff);
1473 }
1474 break;
1475 default:
1476 #ifndef PRODUCT
1477 if( PrintOpto )
1478 tty->print_cr("missed RCE opportunity");
1479 #endif
1480 continue; // Unhandled case
1481 }
1482 }
1483
1484 // Kill the eliminated test
1485 C->set_major_progress();
1486 Node *kill_con = _igvn.intcon( 1-flip );
1487 set_ctrl(kill_con, C->root());
1488 _igvn.hash_delete(iff);
1489 iff->set_req(1, kill_con);
1490 _igvn._worklist.push(iff);
1491 // Find surviving projection
1492 assert(iff->is_If(), "");
1493 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1494 // Find loads off the surviving projection; remove their control edge
1495 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1496 Node* cd = dp->fast_out(i); // Control-dependent node
1497 if( cd->is_Load() ) { // Loads can now float around in the loop
1498 _igvn.hash_delete(cd);
1499 // Allow the load to float around in the loop, or before it
1500 // but NOT before the pre-loop.
1501 cd->set_req(0, ctrl); // ctrl, not NULL
1502 _igvn._worklist.push(cd);
1503 --i;
1504 --imax;
1505 }
1506 }
1507
1508 } // End of is IF
1509
1510 }
1511
1512 // Update loop limits
1513 if (conditional_rc) {
1514 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
1515 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
1516 register_new_node(pre_limit, pre_ctrl);
1517 }
1518 _igvn.hash_delete(pre_opaq);
1519 pre_opaq->set_req(1, pre_limit);
1520
1521 // Note:: we are making the main loop limit no longer precise;
1522 // need to round up based on stride.
1523 if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case
1524 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
1525 // Hopefully, compiler will optimize for powers of 2.
1526 Node *ctrl = get_ctrl(main_limit);
1527 Node *stride = cl->stride();
1528 Node *init = cl->init_trip();
1529 Node *span = new (C, 3) SubINode(main_limit,init);
1530 register_new_node(span,ctrl);
1531 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1532 Node *add = new (C, 3) AddINode(span,rndup);
1533 register_new_node(add,ctrl);
1534 Node *div = new (C, 3) DivINode(0,add,stride);
1535 register_new_node(div,ctrl);
1536 Node *mul = new (C, 3) MulINode(div,stride);
1537 register_new_node(mul,ctrl);
1538 Node *newlim = new (C, 3) AddINode(mul,init);
1539 register_new_node(newlim,ctrl);
1540 main_limit = newlim;
1541 }
1542
1543 Node *main_cle = cl->loopexit();
1544 Node *main_bol = main_cle->in(1);
1545 // Hacking loop bounds; need private copies of exit test
1546 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
1547 _igvn.hash_delete(main_cle);
1548 main_bol = main_bol->clone();// Clone a private BoolNode
1549 register_new_node( main_bol, main_cle->in(0) );
1550 main_cle->set_req(1,main_bol);
1551 }
1552 Node *main_cmp = main_bol->in(1);
1553 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
1554 _igvn.hash_delete(main_bol);
1555 main_cmp = main_cmp->clone();// Clone a private CmpNode
1556 register_new_node( main_cmp, main_cle->in(0) );
1557 main_bol->set_req(1,main_cmp);
1558 }
1559 // Hack the now-private loop bounds
1560 _igvn.hash_delete(main_cmp);
1561 main_cmp->set_req(2, main_limit);
1562 _igvn._worklist.push(main_cmp);
1563 // The OpaqueNode is unshared by design
1564 _igvn.hash_delete(opqzm);
1565 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
1566 opqzm->set_req(1,main_limit);
1567 _igvn._worklist.push(opqzm);
1568 }
1569
1570 //------------------------------DCE_loop_body----------------------------------
1571 // Remove simplistic dead code from loop body
1572 void IdealLoopTree::DCE_loop_body() {
1573 for( uint i = 0; i < _body.size(); i++ )
1574 if( _body.at(i)->outcnt() == 0 )
1575 _body.map( i--, _body.pop() );
1576 }
1577
1578
1579 //------------------------------adjust_loop_exit_prob--------------------------
1580 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
1581 // Replace with a 1-in-10 exit guess.
1582 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
1583 Node *test = tail();
1584 while( test != _head ) {
1585 uint top = test->Opcode();
1586 if( top == Op_IfTrue || top == Op_IfFalse ) {
1587 int test_con = ((ProjNode*)test)->_con;
1588 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
1589 IfNode *iff = test->in(0)->as_If();
1590 if( iff->outcnt() == 2 ) { // Ignore dead tests
1591 Node *bol = iff->in(1);
1592 if( bol && bol->req() > 1 && bol->in(1) &&
1593 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
1594 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
1595 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
1596 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
1597 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
1598 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
1599 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
1600 return; // Allocation loops RARELY take backedge
1601 // Find the OTHER exit path from the IF
1602 Node* ex = iff->proj_out(1-test_con);
1603 float p = iff->_prob;
1604 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
1605 if( top == Op_IfTrue ) {
1606 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
1607 iff->_prob = PROB_STATIC_FREQUENT;
1608 }
1609 } else {
1610 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
1611 iff->_prob = PROB_STATIC_INFREQUENT;
1612 }
1613 }
1614 }
1615 }
1616 }
1617 test = phase->idom(test);
1618 }
1619 }
1620
1621
1622 //------------------------------policy_do_remove_empty_loop--------------------
1623 // Micro-benchmark spamming. Policy is to always remove empty loops.
1624 // The 'DO' part is to replace the trip counter with the value it will
1625 // have on the last iteration. This will break the loop.
1626 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
1627 // Minimum size must be empty loop
1628 if (_body.size() > 7/*number of nodes in an empty loop*/)
1629 return false;
1630
1631 if (!_head->is_CountedLoop())
1632 return false; // Dead loop
1633 CountedLoopNode *cl = _head->as_CountedLoop();
1634 if (!cl->loopexit())
1635 return false; // Malformed loop
1636 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
1637 return false; // Infinite loop
1638
1639 #ifdef ASSERT
1640 // Ensure only one phi which is the iv.
1641 Node* iv = NULL;
1642 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
1643 Node* n = cl->fast_out(i);
1644 if (n->Opcode() == Op_Phi) {
1645 assert(iv == NULL, "Too many phis" );
1646 iv = n;
1647 }
1648 }
1649 assert(iv == cl->phi(), "Wrong phi" );
1650 #endif
1651
1652 // main and post loops have explicitly created zero trip guard
1653 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
1654 if (needs_guard) {
1655 // Check for an obvious zero trip guard.
1656 Node* inctrl = cl->in(LoopNode::EntryControl);
1657 if (inctrl->Opcode() == Op_IfTrue) {
1658 // The test should look like just the backedge of a CountedLoop
1659 Node* iff = inctrl->in(0);
1660 if (iff->is_If()) {
1661 Node* bol = iff->in(1);
1662 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
1663 Node* cmp = bol->in(1);
1664 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
1665 needs_guard = false;
1666 }
1667 }
1668 }
1669 }
1670 }
1671
1672 #ifndef PRODUCT
1673 if (PrintOpto) {
1674 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
1675 this->dump_head();
1676 } else if (TraceLoopOpts) {
1677 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
1678 this->dump_head();
1679 }
1680 #endif
1681
1682 if (needs_guard) {
1683 // Peel the loop to ensure there's a zero trip guard
1684 Node_List old_new;
1685 phase->do_peeling(this, old_new);
1686 }
1687
1688 // Replace the phi at loop head with the final value of the last
1689 // iteration. Then the CountedLoopEnd will collapse (backedge never
1690 // taken) and all loop-invariant uses of the exit values will be correct.
1691 Node *phi = cl->phi();
1692 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
1693 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
1694 phase->_igvn.replace_node(phi,final);
1695 phase->C->set_major_progress();
1696 return true;
1697 }
1698
1699
1700 //=============================================================================
1701 //------------------------------iteration_split_impl---------------------------
1702 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
1703 // Check and remove empty loops (spam micro-benchmarks)
1704 if( policy_do_remove_empty_loop(phase) )
1705 return true; // Here we removed an empty loop
1706
1707 bool should_peel = policy_peeling(phase); // Should we peel?
1708
1709 bool should_unswitch = policy_unswitching(phase);
1710
1711 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
1712 // This removes loop-invariant tests (usually null checks).
1713 if( !_head->is_CountedLoop() ) { // Non-counted loop
1714 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
1715 // Partial peel succeeded so terminate this round of loop opts
1716 return false;
1717 }
1718 if( should_peel ) { // Should we peel?
1719 #ifndef PRODUCT
1720 if (PrintOpto) tty->print_cr("should_peel");
1721 #endif
1722 phase->do_peeling(this,old_new);
1723 } else if( should_unswitch ) {
1724 phase->do_unswitching(this, old_new);
1725 }
1726 return true;
1727 }
1728 CountedLoopNode *cl = _head->as_CountedLoop();
1729
1730 if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops
1731
1732 // Do nothing special to pre- and post- loops
1733 if( cl->is_pre_loop() || cl->is_post_loop() ) return true;
1734
1735 // Compute loop trip count from profile data
1736 compute_profile_trip_cnt(phase);
1737
1738 // Before attempting fancy unrolling, RCE or alignment, see if we want
1739 // to completely unroll this loop or do loop unswitching.
1740 if( cl->is_normal_loop() ) {
1741 if (should_unswitch) {
1742 phase->do_unswitching(this, old_new);
1743 return true;
1744 }
1745 bool should_maximally_unroll = policy_maximally_unroll(phase);
1746 if( should_maximally_unroll ) {
1747 // Here we did some unrolling and peeling. Eventually we will
1748 // completely unroll this loop and it will no longer be a loop.
1749 phase->do_maximally_unroll(this,old_new);
1750 return true;
1751 }
1752 }
1753
1754
1755 // Counted loops may be peeled, may need some iterations run up
1756 // front for RCE, and may want to align loop refs to a cache
1757 // line. Thus we clone a full loop up front whose trip count is
1758 // at least 1 (if peeling), but may be several more.
1759
1760 // The main loop will start cache-line aligned with at least 1
1761 // iteration of the unrolled body (zero-trip test required) and
1762 // will have some range checks removed.
1763
1764 // A post-loop will finish any odd iterations (leftover after
1765 // unrolling), plus any needed for RCE purposes.
1766
1767 bool should_unroll = policy_unroll(phase);
1768
1769 bool should_rce = policy_range_check(phase);
1770
1771 bool should_align = policy_align(phase);
1772
1773 // If not RCE'ing (iteration splitting) or Aligning, then we do not
1774 // need a pre-loop. We may still need to peel an initial iteration but
1775 // we will not be needing an unknown number of pre-iterations.
1776 //
1777 // Basically, if may_rce_align reports FALSE first time through,
1778 // we will not be able to later do RCE or Aligning on this loop.
1779 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
1780
1781 // If we have any of these conditions (RCE, alignment, unrolling) met, then
1782 // we switch to the pre-/main-/post-loop model. This model also covers
1783 // peeling.
1784 if( should_rce || should_align || should_unroll ) {
1785 if( cl->is_normal_loop() ) // Convert to 'pre/main/post' loops
1786 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
1787
1788 // Adjust the pre- and main-loop limits to let the pre and post loops run
1789 // with full checks, but the main-loop with no checks. Remove said
1790 // checks from the main body.
1791 if( should_rce )
1792 phase->do_range_check(this,old_new);
1793
1794 // Double loop body for unrolling. Adjust the minimum-trip test (will do
1795 // twice as many iterations as before) and the main body limit (only do
1796 // an even number of trips). If we are peeling, we might enable some RCE
1797 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
1798 // peeling.
1799 if( should_unroll && !should_peel )
1800 phase->do_unroll(this,old_new, true);
1801
1802 // Adjust the pre-loop limits to align the main body
1803 // iterations.
1804 if( should_align )
1805 Unimplemented();
1806
1807 } else { // Else we have an unchanged counted loop
1808 if( should_peel ) // Might want to peel but do nothing else
1809 phase->do_peeling(this,old_new);
1810 }
1811 return true;
1812 }
1813
1814
1815 //=============================================================================
1816 //------------------------------iteration_split--------------------------------
1817 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
1818 // Recursively iteration split nested loops
1819 if (_child && !_child->iteration_split(phase, old_new))
1820 return false;
1821
1822 // Clean out prior deadwood
1823 DCE_loop_body();
1824
1825
1826 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
1827 // Replace with a 1-in-10 exit guess.
1828 if (_parent /*not the root loop*/ &&
1829 !_irreducible &&
1830 // Also ignore the occasional dead backedge
1831 !tail()->is_top()) {
1832 adjust_loop_exit_prob(phase);
1833 }
1834
1835 // Gate unrolling, RCE and peeling efforts.
1836 if (!_child && // If not an inner loop, do not split
1837 !_irreducible &&
1838 _allow_optimizations &&
1839 !tail()->is_top()) { // Also ignore the occasional dead backedge
1840 if (!_has_call) {
1841 if (!iteration_split_impl(phase, old_new)) {
1842 return false;
1843 }
1844 } else if (policy_unswitching(phase)) {
1845 phase->do_unswitching(this, old_new);
1846 }
1847 }
1848
1849 // Minor offset re-organization to remove loop-fallout uses of
1850 // trip counter when there was no major reshaping.
1851 phase->reorg_offsets(this);
1852
1853 if (_next && !_next->iteration_split(phase, old_new))
1854 return false;
1855 return true;
1856 }
1857
1858 //-------------------------------is_uncommon_trap_proj----------------------------
1859 // Return true if proj is the form of "proj->[region->..]call_uct"
1860 bool PhaseIdealLoop::is_uncommon_trap_proj(ProjNode* proj, Deoptimization::DeoptReason reason) {
1861 int path_limit = 10;
1862 assert(proj, "invalid argument");
1863 Node* out = proj;
1864 for (int ct = 0; ct < path_limit; ct++) {
1865 out = out->unique_ctrl_out();
1866 if (out == NULL || out->is_Root() || out->is_Start())
1867 return false;
1868 if (out->is_CallStaticJava()) {
1869 int req = out->as_CallStaticJava()->uncommon_trap_request();
1870 if (req != 0) {
1871 Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
1872 if (trap_reason == reason || reason == Deoptimization::Reason_none) {
1873 return true;
1874 }
1875 }
1876 return false; // don't do further after call
1877 }
1878 }
1879 return false;
1880 }
1881
1882 //-------------------------------is_uncommon_trap_if_pattern-------------------------
1883 // Return true for "if(test)-> proj -> ...
1884 // |
1885 // V
1886 // other_proj->[region->..]call_uct"
1887 //
1888 // "must_reason_predicate" means the uct reason must be Reason_predicate
1889 bool PhaseIdealLoop::is_uncommon_trap_if_pattern(ProjNode *proj, Deoptimization::DeoptReason reason) {
1890 Node *in0 = proj->in(0);
1891 if (!in0->is_If()) return false;
1892 // Variation of a dead If node.
1893 if (in0->outcnt() < 2) return false;
1894 IfNode* iff = in0->as_If();
1895
1896 // we need "If(Conv2B(Opaque1(...)))" pattern for reason_predicate
1897 if (reason != Deoptimization::Reason_none) {
1898 if (iff->in(1)->Opcode() != Op_Conv2B ||
1899 iff->in(1)->in(1)->Opcode() != Op_Opaque1) {
1900 return false;
1901 }
1902 }
1903
1904 ProjNode* other_proj = iff->proj_out(1-proj->_con)->as_Proj();
1905 return is_uncommon_trap_proj(other_proj, reason);
1906 }
1907
1908 //-------------------------------register_control-------------------------
1909 void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
1910 assert(n->is_CFG(), "must be control node");
1911 _igvn.register_new_node_with_optimizer(n);
1912 loop->_body.push(n);
1913 set_loop(n, loop);
1914 // When called from beautify_loops() idom is not constructed yet.
1915 if (_idom != NULL) {
1916 set_idom(n, pred, dom_depth(pred));
1917 }
1918 }
1919
1920 //------------------------------create_new_if_for_predicate------------------------
1921 // create a new if above the uct_if_pattern for the predicate to be promoted.
1922 //
1923 // before after
1924 // ---------- ----------
1925 // ctrl ctrl
1926 // | |
1927 // | |
1928 // v v
1929 // iff new_iff
1930 // / \ / \
1931 // / \ / \
1932 // v v v v
1933 // uncommon_proj cont_proj if_uct if_cont
1934 // \ | | | |
1935 // \ | | | |
1936 // v v v | v
1937 // rgn loop | iff
1938 // | | / \
1939 // | | / \
1940 // v | v v
1941 // uncommon_trap | uncommon_proj cont_proj
1942 // \ \ | |
1943 // \ \ | |
1944 // v v v v
1945 // rgn loop
1946 // |
1947 // |
1948 // v
1949 // uncommon_trap
1950 //
1951 //
1952 // We will create a region to guard the uct call if there is no one there.
1953 // The true projecttion (if_cont) of the new_iff is returned.
1954 // This code is also used to clone predicates to clonned loops.
1955 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
1956 Deoptimization::DeoptReason reason) {
1957 assert(is_uncommon_trap_if_pattern(cont_proj, reason), "must be a uct if pattern!");
1958 IfNode* iff = cont_proj->in(0)->as_If();
1959
1960 ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
1961 Node *rgn = uncommon_proj->unique_ctrl_out();
1962 assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
1963
1964 if (!rgn->is_Region()) { // create a region to guard the call
1965 assert(rgn->is_Call(), "must be call uct");
1966 CallNode* call = rgn->as_Call();
1967 IdealLoopTree* loop = get_loop(call);
1968 rgn = new (C, 1) RegionNode(1);
1969 rgn->add_req(uncommon_proj);
1970 register_control(rgn, loop, uncommon_proj);
1971 _igvn.hash_delete(call);
1972 call->set_req(0, rgn);
1973 // When called from beautify_loops() idom is not constructed yet.
1974 if (_idom != NULL) {
1975 set_idom(call, rgn, dom_depth(rgn));
1976 }
1977 }
1978
1979 Node* entry = iff->in(0);
1980 if (new_entry != NULL) {
1981 // Clonning the predicate to new location.
1982 entry = new_entry;
1983 }
1984 // Create new_iff
1985 IdealLoopTree* lp = get_loop(entry);
1986 IfNode *new_iff = new (C, 2) IfNode(entry, NULL, iff->_prob, iff->_fcnt);
1987 register_control(new_iff, lp, entry);
1988 Node *if_cont = new (C, 1) IfTrueNode(new_iff);
1989 Node *if_uct = new (C, 1) IfFalseNode(new_iff);
1990 if (cont_proj->is_IfFalse()) {
1991 // Swap
1992 Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
1993 }
1994 register_control(if_cont, lp, new_iff);
1995 register_control(if_uct, get_loop(rgn), new_iff);
1996
1997 // if_uct to rgn
1998 _igvn.hash_delete(rgn);
1999 rgn->add_req(if_uct);
2000 // When called from beautify_loops() idom is not constructed yet.
2001 if (_idom != NULL) {
2002 Node* ridom = idom(rgn);
2003 Node* nrdom = dom_lca(ridom, new_iff);
2004 set_idom(rgn, nrdom, dom_depth(rgn));
2005 }
2006 // rgn must have no phis
2007 assert(!rgn->as_Region()->has_phi(), "region must have no phis");
2008
2009 if (new_entry == NULL) {
2010 // Attach if_cont to iff
2011 _igvn.hash_delete(iff);
2012 iff->set_req(0, if_cont);
2013 if (_idom != NULL) {
2014 set_idom(iff, if_cont, dom_depth(iff));
2015 }
2016 }
2017 return if_cont->as_Proj();
2018 }
2019
2020 //--------------------------find_predicate_insertion_point-------------------
2021 // Find a good location to insert a predicate
2022 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
2023 if (start_c == NULL || !start_c->is_Proj())
2024 return NULL;
2025 if (is_uncommon_trap_if_pattern(start_c->as_Proj(), reason)) {
2026 return start_c->as_Proj();
2027 }
2028 return NULL;
2029 }
2030
2031 //--------------------------find_predicate------------------------------------
2032 // Find a predicate
2033 Node* PhaseIdealLoop::find_predicate(Node* entry) {
2034 Node* predicate = NULL;
2035 if (UseLoopPredicate) {
2036 predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2037 if (predicate != NULL) { // right pattern that can be used by loop predication
2038 assert(entry->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
2039 return entry;
2040 }
2041 }
2042 return NULL;
2043 }
2044
2045 //------------------------------Invariance-----------------------------------
2046 // Helper class for loop_predication_impl to compute invariance on the fly and
2047 // clone invariants.
2048 class Invariance : public StackObj {
2049 VectorSet _visited, _invariant;
2050 Node_Stack _stack;
2051 VectorSet _clone_visited;
2052 Node_List _old_new; // map of old to new (clone)
2053 IdealLoopTree* _lpt;
2054 PhaseIdealLoop* _phase;
2055
2056 // Helper function to set up the invariance for invariance computation
2057 // If n is a known invariant, set up directly. Otherwise, look up the
2058 // the possibility to push n onto the stack for further processing.
2059 void visit(Node* use, Node* n) {
2060 if (_lpt->is_invariant(n)) { // known invariant
2061 _invariant.set(n->_idx);
2062 } else if (!n->is_CFG()) {
2063 Node *n_ctrl = _phase->ctrl_or_self(n);
2064 Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
2065 if (_phase->is_dominator(n_ctrl, u_ctrl)) {
2066 _stack.push(n, n->in(0) == NULL ? 1 : 0);
2067 }
2068 }
2069 }
2070
2071 // Compute invariance for "the_node" and (possibly) all its inputs recursively
2072 // on the fly
2073 void compute_invariance(Node* n) {
2074 assert(_visited.test(n->_idx), "must be");
2075 visit(n, n);
2076 while (_stack.is_nonempty()) {
2077 Node* n = _stack.node();
2078 uint idx = _stack.index();
2079 if (idx == n->req()) { // all inputs are processed
2080 _stack.pop();
2081 // n is invariant if it's inputs are all invariant
2082 bool all_inputs_invariant = true;
2083 for (uint i = 0; i < n->req(); i++) {
2084 Node* in = n->in(i);
2085 if (in == NULL) continue;
2086 assert(_visited.test(in->_idx), "must have visited input");
2087 if (!_invariant.test(in->_idx)) { // bad guy
2088 all_inputs_invariant = false;
2089 break;
2090 }
2091 }
2092 if (all_inputs_invariant) {
2093 _invariant.set(n->_idx); // I am a invariant too
2094 }
2095 } else { // process next input
2096 _stack.set_index(idx + 1);
2097 Node* m = n->in(idx);
2098 if (m != NULL && !_visited.test_set(m->_idx)) {
2099 visit(n, m);
2100 }
2101 }
2102 }
2103 }
2104
2105 // Helper function to set up _old_new map for clone_nodes.
2106 // If n is a known invariant, set up directly ("clone" of n == n).
2107 // Otherwise, push n onto the stack for real cloning.
2108 void clone_visit(Node* n) {
2109 assert(_invariant.test(n->_idx), "must be invariant");
2110 if (_lpt->is_invariant(n)) { // known invariant
2111 _old_new.map(n->_idx, n);
2112 } else{ // to be cloned
2113 assert (!n->is_CFG(), "should not see CFG here");
2114 _stack.push(n, n->in(0) == NULL ? 1 : 0);
2115 }
2116 }
2117
2118 // Clone "n" and (possibly) all its inputs recursively
2119 void clone_nodes(Node* n, Node* ctrl) {
2120 clone_visit(n);
2121 while (_stack.is_nonempty()) {
2122 Node* n = _stack.node();
2123 uint idx = _stack.index();
2124 if (idx == n->req()) { // all inputs processed, clone n!
2125 _stack.pop();
2126 // clone invariant node
2127 Node* n_cl = n->clone();
2128 _old_new.map(n->_idx, n_cl);
2129 _phase->register_new_node(n_cl, ctrl);
2130 for (uint i = 0; i < n->req(); i++) {
2131 Node* in = n_cl->in(i);
2132 if (in == NULL) continue;
2133 n_cl->set_req(i, _old_new[in->_idx]);
2134 }
2135 } else { // process next input
2136 _stack.set_index(idx + 1);
2137 Node* m = n->in(idx);
2138 if (m != NULL && !_clone_visited.test_set(m->_idx)) {
2139 clone_visit(m); // visit the input
2140 }
2141 }
2142 }
2143 }
2144
2145 public:
2146 Invariance(Arena* area, IdealLoopTree* lpt) :
2147 _lpt(lpt), _phase(lpt->_phase),
2148 _visited(area), _invariant(area), _stack(area, 10 /* guess */),
2149 _clone_visited(area), _old_new(area)
2150 {}
2151
2152 // Map old to n for invariance computation and clone
2153 void map_ctrl(Node* old, Node* n) {
2154 assert(old->is_CFG() && n->is_CFG(), "must be");
2155 _old_new.map(old->_idx, n); // "clone" of old is n
2156 _invariant.set(old->_idx); // old is invariant
2157 _clone_visited.set(old->_idx);
2158 }
2159
2160 // Driver function to compute invariance
2161 bool is_invariant(Node* n) {
2162 if (!_visited.test_set(n->_idx))
2163 compute_invariance(n);
2164 return (_invariant.test(n->_idx) != 0);
2165 }
2166
2167 // Driver function to clone invariant
2168 Node* clone(Node* n, Node* ctrl) {
2169 assert(ctrl->is_CFG(), "must be");
2170 assert(_invariant.test(n->_idx), "must be an invariant");
2171 if (!_clone_visited.test(n->_idx))
2172 clone_nodes(n, ctrl);
2173 return _old_new[n->_idx];
2174 }
2175 };
2176
2177 //------------------------------is_range_check_if -----------------------------------
2178 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
2179 // Note: this function is particularly designed for loop predication. We require load_range
2180 // and offset to be loop invariant computed on the fly by "invar"
2181 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
2182 if (!is_loop_exit(iff)) {
2183 return false;
2184 }
2185 if (!iff->in(1)->is_Bool()) {
2186 return false;
2187 }
2188 const BoolNode *bol = iff->in(1)->as_Bool();
2189 if (bol->_test._test != BoolTest::lt) {
2190 return false;
2191 }
2192 if (!bol->in(1)->is_Cmp()) {
2193 return false;
2194 }
2195 const CmpNode *cmp = bol->in(1)->as_Cmp();
2196 if (cmp->Opcode() != Op_CmpU ) {
2197 return false;
2198 }
2199 Node* range = cmp->in(2);
2200 if (range->Opcode() != Op_LoadRange) {
2201 const TypeInt* tint = phase->_igvn.type(range)->isa_int();
2202 if (!OptimizeFill || tint == NULL || tint->empty() || tint->_lo < 0) {
2203 // Allow predication on positive values that aren't LoadRanges.
2204 // This allows optimization of loops where the length of the
2205 // array is a known value and doesn't need to be loaded back
2206 // from the array.
2207 return false;
2208 }
2209 }
2210 if (!invar.is_invariant(range)) {
2211 return false;
2212 }
2213 Node *iv = _head->as_CountedLoop()->phi();
2214 int scale = 0;
2215 Node *offset = NULL;
2216 if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
2217 return false;
2218 }
2219 if(offset && !invar.is_invariant(offset)) { // offset must be invariant
2220 return false;
2221 }
2222 return true;
2223 }
2224
2225 //------------------------------rc_predicate-----------------------------------
2226 // Create a range check predicate
2227 //
2228 // for (i = init; i < limit; i += stride) {
2229 // a[scale*i+offset]
2230 // }
2231 //
2232 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
2233 // as "max(scale*i + offset) u< a.length".
2234 //
2235 // There are two cases for max(scale*i + offset):
2236 // (1) stride*scale > 0
2237 // max(scale*i + offset) = scale*(limit-stride) + offset
2238 // (2) stride*scale < 0
2239 // max(scale*i + offset) = scale*init + offset
2240 BoolNode* PhaseIdealLoop::rc_predicate(Node* ctrl,
2241 int scale, Node* offset,
2242 Node* init, Node* limit, Node* stride,
2243 Node* range, bool upper) {
2244 DEBUG_ONLY(ttyLocker ttyl);
2245 if (TraceLoopPredicate) tty->print("rc_predicate ");
2246
2247 Node* max_idx_expr = init;
2248 int stride_con = stride->get_int();
2249 if ((stride_con > 0) == (scale > 0) == upper) {
2250 max_idx_expr = new (C, 3) SubINode(limit, stride);
2251 register_new_node(max_idx_expr, ctrl);
2252 if (TraceLoopPredicate) tty->print("(limit - stride) ");
2253 } else {
2254 if (TraceLoopPredicate) tty->print("init ");
2255 }
2256
2257 if (scale != 1) {
2258 ConNode* con_scale = _igvn.intcon(scale);
2259 max_idx_expr = new (C, 3) MulINode(max_idx_expr, con_scale);
2260 register_new_node(max_idx_expr, ctrl);
2261 if (TraceLoopPredicate) tty->print("* %d ", scale);
2262 }
2263
2264 if (offset && (!offset->is_Con() || offset->get_int() != 0)){
2265 max_idx_expr = new (C, 3) AddINode(max_idx_expr, offset);
2266 register_new_node(max_idx_expr, ctrl);
2267 if (TraceLoopPredicate)
2268 if (offset->is_Con()) tty->print("+ %d ", offset->get_int());
2269 else tty->print("+ offset ");
2270 }
2271
2272 CmpUNode* cmp = new (C, 3) CmpUNode(max_idx_expr, range);
2273 register_new_node(cmp, ctrl);
2274 BoolNode* bol = new (C, 2) BoolNode(cmp, BoolTest::lt);
2275 register_new_node(bol, ctrl);
2276
2277 if (TraceLoopPredicate) tty->print_cr("<u range");
2278 return bol;
2279 }
2280
2281 //------------------------------ loop_predication_impl--------------------------
2282 // Insert loop predicates for null checks and range checks
2283 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
2284 if (!UseLoopPredicate) return false;
2285
2286 if (!loop->_head->is_Loop()) {
2287 // Could be a simple region when irreducible loops are present.
2288 return false;
2289 }
2290
2291 if (loop->_head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
2292 // do nothing for infinite loops
2293 return false;
2294 }
2295
2296 CountedLoopNode *cl = NULL;
2297 if (loop->_head->is_CountedLoop()) {
2298 cl = loop->_head->as_CountedLoop();
2299 // do nothing for iteration-splitted loops
2300 if (!cl->is_normal_loop()) return false;
2301 }
2302
2303 LoopNode *lpn = loop->_head->as_Loop();
2304 Node* entry = lpn->in(LoopNode::EntryControl);
2305
2306 ProjNode *predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2307 if (!predicate_proj) {
2308 #ifndef PRODUCT
2309 if (TraceLoopPredicate) {
2310 tty->print("missing predicate:");
2311 loop->dump_head();
2312 lpn->dump(1);
2313 }
2314 #endif
2315 return false;
2316 }
2317 ConNode* zero = _igvn.intcon(0);
2318 set_ctrl(zero, C->root());
2319
2320 ResourceArea *area = Thread::current()->resource_area();
2321 Invariance invar(area, loop);
2322
2323 // Create list of if-projs such that a newer proj dominates all older
2324 // projs in the list, and they all dominate loop->tail()
2325 Node_List if_proj_list(area);
2326 LoopNode *head = loop->_head->as_Loop();
2327 Node *current_proj = loop->tail(); //start from tail
2328 while ( current_proj != head ) {
2329 if (loop == get_loop(current_proj) && // still in the loop ?
2330 current_proj->is_Proj() && // is a projection ?
2331 current_proj->in(0)->Opcode() == Op_If) { // is a if projection ?
2332 if_proj_list.push(current_proj);
2333 }
2334 current_proj = idom(current_proj);
2335 }
2336
2337 bool hoisted = false; // true if at least one proj is promoted
2338 while (if_proj_list.size() > 0) {
2339 // Following are changed to nonnull when a predicate can be hoisted
2340 ProjNode* new_predicate_proj = NULL;
2341
2342 ProjNode* proj = if_proj_list.pop()->as_Proj();
2343 IfNode* iff = proj->in(0)->as_If();
2344
2345 if (!is_uncommon_trap_if_pattern(proj, Deoptimization::Reason_none)) {
2346 if (loop->is_loop_exit(iff)) {
2347 // stop processing the remaining projs in the list because the execution of them
2348 // depends on the condition of "iff" (iff->in(1)).
2349 break;
2350 } else {
2351 // Both arms are inside the loop. There are two cases:
2352 // (1) there is one backward branch. In this case, any remaining proj
2353 // in the if_proj list post-dominates "iff". So, the condition of "iff"
2354 // does not determine the execution the remining projs directly, and we
2355 // can safely continue.
2356 // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
2357 // does not dominate loop->tail(), so it can not be in the if_proj list.
2358 continue;
2359 }
2360 }
2361
2362 Node* test = iff->in(1);
2363 if (!test->is_Bool()){ //Conv2B, ...
2364 continue;
2365 }
2366 BoolNode* bol = test->as_Bool();
2367 if (invar.is_invariant(bol)) {
2368 // Invariant test
2369 new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
2370 Deoptimization::Reason_predicate);
2371 Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
2372 BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
2373
2374 // Negate test if necessary
2375 bool negated = false;
2376 if (proj->_con != predicate_proj->_con) {
2377 new_predicate_bol = new (C, 2) BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
2378 register_new_node(new_predicate_bol, ctrl);
2379 negated = true;
2380 }
2381 IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
2382 _igvn.hash_delete(new_predicate_iff);
2383 new_predicate_iff->set_req(1, new_predicate_bol);
2384 #ifndef PRODUCT
2385 if (TraceLoopPredicate) {
2386 tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
2387 loop->dump_head();
2388 } else if (TraceLoopOpts) {
2389 tty->print("Predicate IC ");
2390 loop->dump_head();
2391 }
2392 #endif
2393 } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
2394 assert(proj->_con == predicate_proj->_con, "must match");
2395
2396 // Range check for counted loops
2397 const Node* cmp = bol->in(1)->as_Cmp();
2398 Node* idx = cmp->in(1);
2399 assert(!invar.is_invariant(idx), "index is variant");
2400 assert(cmp->in(2)->Opcode() == Op_LoadRange || OptimizeFill, "must be");
2401 Node* rng = cmp->in(2);
2402 assert(invar.is_invariant(rng), "range must be invariant");
2403 int scale = 1;
2404 Node* offset = zero;
2405 bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
2406 assert(ok, "must be index expression");
2407
2408 Node* init = cl->init_trip();
2409 Node* limit = cl->limit();
2410 Node* stride = cl->stride();
2411
2412 // Build if's for the upper and lower bound tests. The
2413 // lower_bound test will dominate the upper bound test and all
2414 // cloned or created nodes will use the lower bound test as
2415 // their declared control.
2416 ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
2417 ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, Deoptimization::Reason_predicate);
2418 assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
2419 Node *ctrl = lower_bound_proj->in(0)->as_If()->in(0);
2420
2421 // Perform cloning to keep Invariance state correct since the
2422 // late schedule will place invariant things in the loop.
2423 rng = invar.clone(rng, ctrl);
2424 if (offset && offset != zero) {
2425 assert(invar.is_invariant(offset), "offset must be loop invariant");
2426 offset = invar.clone(offset, ctrl);
2427 }
2428
2429 // Test the lower bound
2430 Node* lower_bound_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, rng, false);
2431 IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
2432 _igvn.hash_delete(lower_bound_iff);
2433 lower_bound_iff->set_req(1, lower_bound_bol);
2434 if (TraceLoopPredicate) tty->print_cr("lower bound check if: %d", lower_bound_iff->_idx);
2435
2436 // Test the upper bound
2437 Node* upper_bound_bol = rc_predicate(ctrl, scale, offset, init, limit, stride, rng, true);
2438 IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
2439 _igvn.hash_delete(upper_bound_iff);
2440 upper_bound_iff->set_req(1, upper_bound_bol);
2441 if (TraceLoopPredicate) tty->print_cr("upper bound check if: %d", lower_bound_iff->_idx);
2442
2443 // Fall through into rest of the clean up code which will move
2444 // any dependent nodes onto the upper bound test.
2445 new_predicate_proj = upper_bound_proj;
2446
2447 #ifndef PRODUCT
2448 if (TraceLoopOpts && !TraceLoopPredicate) {
2449 tty->print("Predicate RC ");
2450 loop->dump_head();
2451 }
2452 #endif
2453 } else {
2454 // Loop variant check (for example, range check in non-counted loop)
2455 // with uncommon trap.
2456 continue;
2457 }
2458 assert(new_predicate_proj != NULL, "sanity");
2459 // Success - attach condition (new_predicate_bol) to predicate if
2460 invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
2461
2462 // Eliminate the old If in the loop body
2463 dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
2464
2465 hoisted = true;
2466 C->set_major_progress();
2467 } // end while
2468
2469 #ifndef PRODUCT
2470 // report that the loop predication has been actually performed
2471 // for this loop
2472 if (TraceLoopPredicate && hoisted) {
2473 tty->print("Loop Predication Performed:");
2474 loop->dump_head();
2475 }
2476 #endif
2477
2478 return hoisted;
2479 }
2480
2481 //------------------------------loop_predication--------------------------------
2482 // driver routine for loop predication optimization
2483 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
2484 bool hoisted = false;
2485 // Recursively promote predicates
2486 if ( _child ) {
2487 hoisted = _child->loop_predication( phase);
2488 }
2489
2490 // self
2491 if (!_irreducible && !tail()->is_top()) {
2492 hoisted |= phase->loop_predication_impl(this);
2493 }
2494
2495 if ( _next ) { //sibling
2496 hoisted |= _next->loop_predication( phase);
2497 }
2498
2499 return hoisted;
2500 }
2501
2502
2503 // Process all the loops in the loop tree and replace any fill
2504 // patterns with an intrisc version.
2505 bool PhaseIdealLoop::do_intrinsify_fill() {
2506 bool changed = false;
2507 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2508 IdealLoopTree* lpt = iter.current();
2509 changed |= intrinsify_fill(lpt);
2510 }
2511 return changed;
2512 }
2513
2514
2515 // Examine an inner loop looking for a a single store of an invariant
2516 // value in a unit stride loop,
2517 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2518 Node*& shift, Node*& con) {
2519 const char* msg = NULL;
2520 Node* msg_node = NULL;
2521
2522 store_value = NULL;
2523 con = NULL;
2524 shift = NULL;
2525
2526 // Process the loop looking for stores. If there are multiple
2527 // stores or extra control flow give at this point.
2528 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2529 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2530 Node* n = lpt->_body.at(i);
2531 if (n->outcnt() == 0) continue; // Ignore dead
2532 if (n->is_Store()) {
2533 if (store != NULL) {
2534 msg = "multiple stores";
2535 break;
2536 }
2537 int opc = n->Opcode();
2538 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreCM) {
2539 msg = "oop fills not handled";
2540 break;
2541 }
2542 Node* value = n->in(MemNode::ValueIn);
2543 if (!lpt->is_invariant(value)) {
2544 msg = "variant store value";
2545 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2546 msg = "not array address";
2547 }
2548 store = n;
2549 store_value = value;
2550 } else if (n->is_If() && n != head->loopexit()) {
2551 msg = "extra control flow";
2552 msg_node = n;
2553 }
2554 }
2555
2556 if (store == NULL) {
2557 // No store in loop
2558 return false;
2559 }
2560
2561 if (msg == NULL && head->stride_con() != 1) {
2562 // could handle negative strides too
2563 if (head->stride_con() < 0) {
2564 msg = "negative stride";
2565 } else {
2566 msg = "non-unit stride";
2567 }
2568 }
2569
2570 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2571 msg = "can't handle store address";
2572 msg_node = store->in(MemNode::Address);
2573 }
2574
2575 if (msg == NULL &&
2576 (!store->in(MemNode::Memory)->is_Phi() ||
2577 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2578 msg = "store memory isn't proper phi";
2579 msg_node = store->in(MemNode::Memory);
2580 }
2581
2582 // Make sure there is an appropriate fill routine
2583 BasicType t = store->as_Mem()->memory_type();
2584 const char* fill_name;
2585 if (msg == NULL &&
2586 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2587 msg = "unsupported store";
2588 msg_node = store;
2589 }
2590
2591 if (msg != NULL) {
2592 #ifndef PRODUCT
2593 if (TraceOptimizeFill) {
2594 tty->print_cr("not fill intrinsic candidate: %s", msg);
2595 if (msg_node != NULL) msg_node->dump();
2596 }
2597 #endif
2598 return false;
2599 }
2600
2601 // Make sure the address expression can be handled. It should be
2602 // head->phi * elsize + con. head->phi might have a ConvI2L.
2603 Node* elements[4];
2604 Node* conv = NULL;
2605 bool found_index = false;
2606 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2607 for (int e = 0; e < count; e++) {
2608 Node* n = elements[e];
2609 if (n->is_Con() && con == NULL) {
2610 con = n;
2611 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2612 Node* value = n->in(1);
2613 #ifdef _LP64
2614 if (value->Opcode() == Op_ConvI2L) {
2615 conv = value;
2616 value = value->in(1);
2617 }
2618 #endif
2619 if (value != head->phi()) {
2620 msg = "unhandled shift in address";
2621 } else {
2622 found_index = true;
2623 shift = n;
2624 assert(type2aelembytes(store->as_Mem()->memory_type(), true) == 1 << shift->in(2)->get_int(), "scale should match");
2625 }
2626 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2627 if (n->in(1) == head->phi()) {
2628 found_index = true;
2629 conv = n;
2630 } else {
2631 msg = "unhandled input to ConvI2L";
2632 }
2633 } else if (n == head->phi()) {
2634 // no shift, check below for allowed cases
2635 found_index = true;
2636 } else {
2637 msg = "unhandled node in address";
2638 msg_node = n;
2639 }
2640 }
2641
2642 if (count == -1) {
2643 msg = "malformed address expression";
2644 msg_node = store;
2645 }
2646
2647 if (!found_index) {
2648 msg = "missing use of index";
2649 }
2650
2651 // byte sized items won't have a shift
2652 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2653 msg = "can't find shift";
2654 msg_node = store;
2655 }
2656
2657 if (msg != NULL) {
2658 #ifndef PRODUCT
2659 if (TraceOptimizeFill) {
2660 tty->print_cr("not fill intrinsic: %s", msg);
2661 if (msg_node != NULL) msg_node->dump();
2662 }
2663 #endif
2664 return false;
2665 }
2666
2667 // No make sure all the other nodes in the loop can be handled
2668 VectorSet ok(Thread::current()->resource_area());
2669
2670 // store related values are ok
2671 ok.set(store->_idx);
2672 ok.set(store->in(MemNode::Memory)->_idx);
2673
2674 // Loop structure is ok
2675 ok.set(head->_idx);
2676 ok.set(head->loopexit()->_idx);
2677 ok.set(head->phi()->_idx);
2678 ok.set(head->incr()->_idx);
2679 ok.set(head->loopexit()->cmp_node()->_idx);
2680 ok.set(head->loopexit()->in(1)->_idx);
2681
2682 // Address elements are ok
2683 if (con) ok.set(con->_idx);
2684 if (shift) ok.set(shift->_idx);
2685 if (conv) ok.set(conv->_idx);
2686
2687 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2688 Node* n = lpt->_body.at(i);
2689 if (n->outcnt() == 0) continue; // Ignore dead
2690 if (ok.test(n->_idx)) continue;
2691 // Backedge projection is ok
2692 if (n->is_IfTrue() && n->in(0) == head->loopexit()) continue;
2693 if (!n->is_AddP()) {
2694 msg = "unhandled node";
2695 msg_node = n;
2696 break;
2697 }
2698 }
2699
2700 // Make sure no unexpected values are used outside the loop
2701 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2702 Node* n = lpt->_body.at(i);
2703 // These values can be replaced with other nodes if they are used
2704 // outside the loop.
2705 if (n == store || n == head->loopexit() || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2706 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2707 Node* use = iter.get();
2708 if (!lpt->_body.contains(use)) {
2709 msg = "node is used outside loop";
2710 // lpt->_body.dump();
2711 msg_node = n;
2712 break;
2713 }
2714 }
2715 }
2716
2717 #ifdef ASSERT
2718 if (TraceOptimizeFill) {
2719 if (msg != NULL) {
2720 tty->print_cr("no fill intrinsic: %s", msg);
2721 if (msg_node != NULL) msg_node->dump();
2722 } else {
2723 tty->print_cr("fill intrinsic for:");
2724 }
2725 store->dump();
2726 if (Verbose) {
2727 lpt->_body.dump();
2728 }
2729 }
2730 #endif
2731
2732 return msg == NULL;
2733 }
2734
2735
2736
2737 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2738 // Only for counted inner loops
2739 if (!lpt->is_counted() || !lpt->is_inner()) {
2740 return false;
2741 }
2742
2743 // Must have constant stride
2744 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2745 if (!head->stride_is_con() || !head->is_normal_loop()) {
2746 return false;
2747 }
2748
2749 // Check that the body only contains a store of a loop invariant
2750 // value that is indexed by the loop phi.
2751 Node* store = NULL;
2752 Node* store_value = NULL;
2753 Node* shift = NULL;
2754 Node* offset = NULL;
2755 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2756 return false;
2757 }
2758
2759 // Now replace the whole loop body by a call to a fill routine that
2760 // covers the same region as the loop.
2761 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2762
2763 // Build an expression for the beginning of the copy region
2764 Node* index = head->init_trip();
2765 #ifdef _LP64
2766 index = new (C, 2) ConvI2LNode(index);
2767 _igvn.register_new_node_with_optimizer(index);
2768 #endif
2769 if (shift != NULL) {
2770 // byte arrays don't require a shift but others do.
2771 index = new (C, 3) LShiftXNode(index, shift->in(2));
2772 _igvn.register_new_node_with_optimizer(index);
2773 }
2774 index = new (C, 4) AddPNode(base, base, index);
2775 _igvn.register_new_node_with_optimizer(index);
2776 Node* from = new (C, 4) AddPNode(base, index, offset);
2777 _igvn.register_new_node_with_optimizer(from);
2778 // Compute the number of elements to copy
2779 Node* len = new (C, 3) SubINode(head->limit(), head->init_trip());
2780 _igvn.register_new_node_with_optimizer(len);
2781
2782 BasicType t = store->as_Mem()->memory_type();
2783 bool aligned = false;
2784 if (offset != NULL && head->init_trip()->is_Con()) {
2785 int element_size = type2aelembytes(t);
2786 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2787 }
2788
2789 // Build a call to the fill routine
2790 const char* fill_name;
2791 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2792 assert(fill != NULL, "what?");
2793
2794 // Convert float/double to int/long for fill routines
2795 if (t == T_FLOAT) {
2796 store_value = new (C, 2) MoveF2INode(store_value);
2797 _igvn.register_new_node_with_optimizer(store_value);
2798 } else if (t == T_DOUBLE) {
2799 store_value = new (C, 2) MoveD2LNode(store_value);
2800 _igvn.register_new_node_with_optimizer(store_value);
2801 }
2802
2803 Node* mem_phi = store->in(MemNode::Memory);
2804 Node* result_ctrl;
2805 Node* result_mem;
2806 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2807 int size = call_type->domain()->cnt();
2808 CallLeafNode *call = new (C, size) CallLeafNoFPNode(call_type, fill,
2809 fill_name, TypeAryPtr::get_array_body_type(t));
2810 call->init_req(TypeFunc::Parms+0, from);
2811 call->init_req(TypeFunc::Parms+1, store_value);
2812 #ifdef _LP64
2813 len = new (C, 2) ConvI2LNode(len);
2814 _igvn.register_new_node_with_optimizer(len);
2815 #endif
2816 call->init_req(TypeFunc::Parms+2, len);
2817 #ifdef _LP64
2818 call->init_req(TypeFunc::Parms+3, C->top());
2819 #endif
2820 call->init_req( TypeFunc::Control, head->init_control());
2821 call->init_req( TypeFunc::I_O , C->top() ) ; // does no i/o
2822 call->init_req( TypeFunc::Memory , mem_phi->in(LoopNode::EntryControl) );
2823 call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) );
2824 call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) );
2825 _igvn.register_new_node_with_optimizer(call);
2826 result_ctrl = new (C, 1) ProjNode(call,TypeFunc::Control);
2827 _igvn.register_new_node_with_optimizer(result_ctrl);
2828 result_mem = new (C, 1) ProjNode(call,TypeFunc::Memory);
2829 _igvn.register_new_node_with_optimizer(result_mem);
2830
2831 // If this fill is tightly coupled to an allocation and overwrites
2832 // the whole body, allow it to take over the zeroing.
2833 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2834 if (alloc != NULL && alloc->is_AllocateArray()) {
2835 Node* length = alloc->as_AllocateArray()->Ideal_length();
2836 if (head->limit() == length &&
2837 head->init_trip() == _igvn.intcon(0)) {
2838 if (TraceOptimizeFill) {
2839 tty->print_cr("Eliminated zeroing in allocation");
2840 }
2841 alloc->maybe_set_complete(&_igvn);
2842 } else {
2843 #ifdef ASSERT
2844 if (TraceOptimizeFill) {
2845 tty->print_cr("filling array but bounds don't match");
2846 alloc->dump();
2847 head->init_trip()->dump();
2848 head->limit()->dump();
2849 length->dump();
2850 }
2851 #endif
2852 }
2853 }
2854
2855 // Redirect the old control and memory edges that are outside the loop.
2856 Node* exit = head->loopexit()->proj_out(0);
2857 // Sometimes the memory phi of the head is used as the outgoing
2858 // state of the loop. It's safe in this case to replace it with the
2859 // result_mem.
2860 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2861 _igvn.replace_node(exit, result_ctrl);
2862 _igvn.replace_node(store, result_mem);
2863 // Any uses the increment outside of the loop become the loop limit.
2864 _igvn.replace_node(head->incr(), head->limit());
2865
2866 // Disconnect the head from the loop.
2867 for (uint i = 0; i < lpt->_body.size(); i++) {
2868 Node* n = lpt->_body.at(i);
2869 _igvn.replace_node(n, C->top());
2870 }
2871
2872 return true;
2873 }