Mercurial > hg > truffle
annotate src/share/vm/opto/loopTransform.cpp @ 420:a1980da045cc
6462850: generate biased locking code in C2 ideal graph
Summary: Inline biased locking code in C2 ideal graph during macro nodes expansion
Reviewed-by: never
author | kvn |
---|---|
date | Fri, 07 Nov 2008 09:29:38 -0800 |
parents | ee8f06bfb27c |
children | 98cb887364d3 |
rev | line source |
---|---|
0 | 1 /* |
196 | 2 * Copyright 2000-2008 Sun Microsystems, Inc. All Rights Reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 #include "incls/_precompiled.incl" | |
26 #include "incls/_loopTransform.cpp.incl" | |
27 | |
28 //------------------------------is_loop_exit----------------------------------- | |
29 // Given an IfNode, return the loop-exiting projection or NULL if both | |
30 // arms remain in the loop. | |
31 Node *IdealLoopTree::is_loop_exit(Node *iff) const { | |
32 if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests | |
33 PhaseIdealLoop *phase = _phase; | |
34 // Test is an IfNode, has 2 projections. If BOTH are in the loop | |
35 // we need loop unswitching instead of peeling. | |
36 if( !is_member(phase->get_loop( iff->raw_out(0) )) ) | |
37 return iff->raw_out(0); | |
38 if( !is_member(phase->get_loop( iff->raw_out(1) )) ) | |
39 return iff->raw_out(1); | |
40 return NULL; | |
41 } | |
42 | |
43 | |
44 //============================================================================= | |
45 | |
46 | |
47 //------------------------------record_for_igvn---------------------------- | |
48 // Put loop body on igvn work list | |
49 void IdealLoopTree::record_for_igvn() { | |
50 for( uint i = 0; i < _body.size(); i++ ) { | |
51 Node *n = _body.at(i); | |
52 _phase->_igvn._worklist.push(n); | |
53 } | |
54 } | |
55 | |
56 //------------------------------compute_profile_trip_cnt---------------------------- | |
57 // Compute loop trip count from profile data as | |
58 // (backedge_count + loop_exit_count) / loop_exit_count | |
59 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) { | |
60 if (!_head->is_CountedLoop()) { | |
61 return; | |
62 } | |
63 CountedLoopNode* head = _head->as_CountedLoop(); | |
64 if (head->profile_trip_cnt() != COUNT_UNKNOWN) { | |
65 return; // Already computed | |
66 } | |
67 float trip_cnt = (float)max_jint; // default is big | |
68 | |
69 Node* back = head->in(LoopNode::LoopBackControl); | |
70 while (back != head) { | |
71 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && | |
72 back->in(0) && | |
73 back->in(0)->is_If() && | |
74 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN && | |
75 back->in(0)->as_If()->_prob != PROB_UNKNOWN) { | |
76 break; | |
77 } | |
78 back = phase->idom(back); | |
79 } | |
80 if (back != head) { | |
81 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) && | |
82 back->in(0), "if-projection exists"); | |
83 IfNode* back_if = back->in(0)->as_If(); | |
84 float loop_back_cnt = back_if->_fcnt * back_if->_prob; | |
85 | |
86 // Now compute a loop exit count | |
87 float loop_exit_cnt = 0.0f; | |
88 for( uint i = 0; i < _body.size(); i++ ) { | |
89 Node *n = _body[i]; | |
90 if( n->is_If() ) { | |
91 IfNode *iff = n->as_If(); | |
92 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) { | |
93 Node *exit = is_loop_exit(iff); | |
94 if( exit ) { | |
95 float exit_prob = iff->_prob; | |
96 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob; | |
97 if (exit_prob > PROB_MIN) { | |
98 float exit_cnt = iff->_fcnt * exit_prob; | |
99 loop_exit_cnt += exit_cnt; | |
100 } | |
101 } | |
102 } | |
103 } | |
104 } | |
105 if (loop_exit_cnt > 0.0f) { | |
106 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt; | |
107 } else { | |
108 // No exit count so use | |
109 trip_cnt = loop_back_cnt; | |
110 } | |
111 } | |
112 #ifndef PRODUCT | |
113 if (TraceProfileTripCount) { | |
114 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt); | |
115 } | |
116 #endif | |
117 head->set_profile_trip_cnt(trip_cnt); | |
118 } | |
119 | |
120 //---------------------is_invariant_addition----------------------------- | |
121 // Return nonzero index of invariant operand for an Add or Sub | |
122 // of (nonconstant) invariant and variant values. Helper for reassoicate_invariants. | |
123 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) { | |
124 int op = n->Opcode(); | |
125 if (op == Op_AddI || op == Op_SubI) { | |
126 bool in1_invar = this->is_invariant(n->in(1)); | |
127 bool in2_invar = this->is_invariant(n->in(2)); | |
128 if (in1_invar && !in2_invar) return 1; | |
129 if (!in1_invar && in2_invar) return 2; | |
130 } | |
131 return 0; | |
132 } | |
133 | |
134 //---------------------reassociate_add_sub----------------------------- | |
135 // Reassociate invariant add and subtract expressions: | |
136 // | |
137 // inv1 + (x + inv2) => ( inv1 + inv2) + x | |
138 // (x + inv2) + inv1 => ( inv1 + inv2) + x | |
139 // inv1 + (x - inv2) => ( inv1 - inv2) + x | |
140 // inv1 - (inv2 - x) => ( inv1 - inv2) + x | |
141 // (x + inv2) - inv1 => (-inv1 + inv2) + x | |
142 // (x - inv2) + inv1 => ( inv1 - inv2) + x | |
143 // (x - inv2) - inv1 => (-inv1 - inv2) + x | |
144 // inv1 + (inv2 - x) => ( inv1 + inv2) - x | |
145 // inv1 - (x - inv2) => ( inv1 + inv2) - x | |
146 // (inv2 - x) + inv1 => ( inv1 + inv2) - x | |
147 // (inv2 - x) - inv1 => (-inv1 + inv2) - x | |
148 // inv1 - (x + inv2) => ( inv1 - inv2) - x | |
149 // | |
150 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) { | |
151 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL; | |
152 if (is_invariant(n1)) return NULL; | |
153 int inv1_idx = is_invariant_addition(n1, phase); | |
154 if (!inv1_idx) return NULL; | |
155 // Don't mess with add of constant (igvn moves them to expression tree root.) | |
156 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL; | |
157 Node* inv1 = n1->in(inv1_idx); | |
158 Node* n2 = n1->in(3 - inv1_idx); | |
159 int inv2_idx = is_invariant_addition(n2, phase); | |
160 if (!inv2_idx) return NULL; | |
161 Node* x = n2->in(3 - inv2_idx); | |
162 Node* inv2 = n2->in(inv2_idx); | |
163 | |
164 bool neg_x = n2->is_Sub() && inv2_idx == 1; | |
165 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2; | |
166 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2; | |
167 if (n1->is_Sub() && inv1_idx == 1) { | |
168 neg_x = !neg_x; | |
169 neg_inv2 = !neg_inv2; | |
170 } | |
171 Node* inv1_c = phase->get_ctrl(inv1); | |
172 Node* inv2_c = phase->get_ctrl(inv2); | |
173 Node* n_inv1; | |
174 if (neg_inv1) { | |
175 Node *zero = phase->_igvn.intcon(0); | |
176 phase->set_ctrl(zero, phase->C->root()); | |
177 n_inv1 = new (phase->C, 3) SubINode(zero, inv1); | |
178 phase->register_new_node(n_inv1, inv1_c); | |
179 } else { | |
180 n_inv1 = inv1; | |
181 } | |
182 Node* inv; | |
183 if (neg_inv2) { | |
184 inv = new (phase->C, 3) SubINode(n_inv1, inv2); | |
185 } else { | |
186 inv = new (phase->C, 3) AddINode(n_inv1, inv2); | |
187 } | |
188 phase->register_new_node(inv, phase->get_early_ctrl(inv)); | |
189 | |
190 Node* addx; | |
191 if (neg_x) { | |
192 addx = new (phase->C, 3) SubINode(inv, x); | |
193 } else { | |
194 addx = new (phase->C, 3) AddINode(x, inv); | |
195 } | |
196 phase->register_new_node(addx, phase->get_ctrl(x)); | |
197 phase->_igvn.hash_delete(n1); | |
198 phase->_igvn.subsume_node(n1, addx); | |
199 return addx; | |
200 } | |
201 | |
202 //---------------------reassociate_invariants----------------------------- | |
203 // Reassociate invariant expressions: | |
204 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) { | |
205 for (int i = _body.size() - 1; i >= 0; i--) { | |
206 Node *n = _body.at(i); | |
207 for (int j = 0; j < 5; j++) { | |
208 Node* nn = reassociate_add_sub(n, phase); | |
209 if (nn == NULL) break; | |
210 n = nn; // again | |
211 }; | |
212 } | |
213 } | |
214 | |
215 //------------------------------policy_peeling--------------------------------- | |
216 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can | |
217 // make some loop-invariant test (usually a null-check) happen before the loop. | |
218 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const { | |
219 Node *test = ((IdealLoopTree*)this)->tail(); | |
220 int body_size = ((IdealLoopTree*)this)->_body.size(); | |
221 int uniq = phase->C->unique(); | |
222 // Peeling does loop cloning which can result in O(N^2) node construction | |
223 if( body_size > 255 /* Prevent overflow for large body_size */ | |
224 || (body_size * body_size + uniq > MaxNodeLimit) ) { | |
225 return false; // too large to safely clone | |
226 } | |
227 while( test != _head ) { // Scan till run off top of loop | |
228 if( test->is_If() ) { // Test? | |
229 Node *ctrl = phase->get_ctrl(test->in(1)); | |
230 if (ctrl->is_top()) | |
231 return false; // Found dead test on live IF? No peeling! | |
232 // Standard IF only has one input value to check for loop invariance | |
233 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added"); | |
234 // Condition is not a member of this loop? | |
235 if( !is_member(phase->get_loop(ctrl)) && | |
236 is_loop_exit(test) ) | |
237 return true; // Found reason to peel! | |
238 } | |
239 // Walk up dominators to loop _head looking for test which is | |
240 // executed on every path thru loop. | |
241 test = phase->idom(test); | |
242 } | |
243 return false; | |
244 } | |
245 | |
246 //------------------------------peeled_dom_test_elim--------------------------- | |
247 // If we got the effect of peeling, either by actually peeling or by making | |
248 // a pre-loop which must execute at least once, we can remove all | |
249 // loop-invariant dominated tests in the main body. | |
250 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) { | |
251 bool progress = true; | |
252 while( progress ) { | |
253 progress = false; // Reset for next iteration | |
254 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail(); | |
255 Node *test = prev->in(0); | |
256 while( test != loop->_head ) { // Scan till run off top of loop | |
257 | |
258 int p_op = prev->Opcode(); | |
259 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) && | |
260 test->is_If() && // Test? | |
261 !test->in(1)->is_Con() && // And not already obvious? | |
262 // Condition is not a member of this loop? | |
263 !loop->is_member(get_loop(get_ctrl(test->in(1))))){ | |
264 // Walk loop body looking for instances of this test | |
265 for( uint i = 0; i < loop->_body.size(); i++ ) { | |
266 Node *n = loop->_body.at(i); | |
267 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) { | |
268 // IfNode was dominated by version in peeled loop body | |
269 progress = true; | |
270 dominated_by( old_new[prev->_idx], n ); | |
271 } | |
272 } | |
273 } | |
274 prev = test; | |
275 test = idom(test); | |
276 } // End of scan tests in loop | |
277 | |
278 } // End of while( progress ) | |
279 } | |
280 | |
281 //------------------------------do_peeling------------------------------------- | |
282 // Peel the first iteration of the given loop. | |
283 // Step 1: Clone the loop body. The clone becomes the peeled iteration. | |
284 // The pre-loop illegally has 2 control users (old & new loops). | |
285 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. | |
286 // Do this by making the old-loop fall-in edges act as if they came | |
287 // around the loopback from the prior iteration (follow the old-loop | |
288 // backedges) and then map to the new peeled iteration. This leaves | |
289 // the pre-loop with only 1 user (the new peeled iteration), but the | |
290 // peeled-loop backedge has 2 users. | |
291 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the | |
292 // extra backedge user. | |
293 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) { | |
294 | |
295 C->set_major_progress(); | |
296 // Peeling a 'main' loop in a pre/main/post situation obfuscates the | |
297 // 'pre' loop from the main and the 'pre' can no longer have it's | |
298 // iterations adjusted. Therefore, we need to declare this loop as | |
299 // no longer a 'main' loop; it will need new pre and post loops before | |
300 // we can do further RCE. | |
301 Node *h = loop->_head; | |
302 if( h->is_CountedLoop() ) { | |
303 CountedLoopNode *cl = h->as_CountedLoop(); | |
304 assert(cl->trip_count() > 0, "peeling a fully unrolled loop"); | |
305 cl->set_trip_count(cl->trip_count() - 1); | |
306 if( cl->is_main_loop() ) { | |
307 cl->set_normal_loop(); | |
308 #ifndef PRODUCT | |
309 if( PrintOpto && VerifyLoopOptimizations ) { | |
310 tty->print("Peeling a 'main' loop; resetting to 'normal' "); | |
311 loop->dump_head(); | |
312 } | |
313 #endif | |
314 } | |
315 } | |
316 | |
317 // Step 1: Clone the loop body. The clone becomes the peeled iteration. | |
318 // The pre-loop illegally has 2 control users (old & new loops). | |
319 clone_loop( loop, old_new, dom_depth(loop->_head) ); | |
320 | |
321 | |
322 // Step 2: Make the old-loop fall-in edges point to the peeled iteration. | |
323 // Do this by making the old-loop fall-in edges act as if they came | |
324 // around the loopback from the prior iteration (follow the old-loop | |
325 // backedges) and then map to the new peeled iteration. This leaves | |
326 // the pre-loop with only 1 user (the new peeled iteration), but the | |
327 // peeled-loop backedge has 2 users. | |
328 for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) { | |
329 Node* old = loop->_head->fast_out(j); | |
330 if( old->in(0) == loop->_head && old->req() == 3 && | |
331 (old->is_Loop() || old->is_Phi()) ) { | |
332 Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx]; | |
333 if( !new_exit_value ) // Backedge value is ALSO loop invariant? | |
334 // Then loop body backedge value remains the same. | |
335 new_exit_value = old->in(LoopNode::LoopBackControl); | |
336 _igvn.hash_delete(old); | |
337 old->set_req(LoopNode::EntryControl, new_exit_value); | |
338 } | |
339 } | |
340 | |
341 | |
342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the | |
343 // extra backedge user. | |
344 Node *nnn = old_new[loop->_head->_idx]; | |
345 _igvn.hash_delete(nnn); | |
346 nnn->set_req(LoopNode::LoopBackControl, C->top()); | |
347 for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) { | |
348 Node* use = nnn->fast_out(j2); | |
349 if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) { | |
350 _igvn.hash_delete(use); | |
351 use->set_req(LoopNode::LoopBackControl, C->top()); | |
352 } | |
353 } | |
354 | |
355 | |
356 // Step 4: Correct dom-depth info. Set to loop-head depth. | |
357 int dd = dom_depth(loop->_head); | |
358 set_idom(loop->_head, loop->_head->in(1), dd); | |
359 for (uint j3 = 0; j3 < loop->_body.size(); j3++) { | |
360 Node *old = loop->_body.at(j3); | |
361 Node *nnn = old_new[old->_idx]; | |
362 if (!has_ctrl(nnn)) | |
363 set_idom(nnn, idom(nnn), dd-1); | |
364 // While we're at it, remove any SafePoints from the peeled code | |
365 if( old->Opcode() == Op_SafePoint ) { | |
366 Node *nnn = old_new[old->_idx]; | |
367 lazy_replace(nnn,nnn->in(TypeFunc::Control)); | |
368 } | |
369 } | |
370 | |
371 // Now force out all loop-invariant dominating tests. The optimizer | |
372 // finds some, but we _know_ they are all useless. | |
373 peeled_dom_test_elim(loop,old_new); | |
374 | |
375 loop->record_for_igvn(); | |
376 } | |
377 | |
378 //------------------------------policy_maximally_unroll------------------------ | |
379 // Return exact loop trip count, or 0 if not maximally unrolling | |
380 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const { | |
381 CountedLoopNode *cl = _head->as_CountedLoop(); | |
382 assert( cl->is_normal_loop(), "" ); | |
383 | |
384 Node *init_n = cl->init_trip(); | |
385 Node *limit_n = cl->limit(); | |
386 | |
387 // Non-constant bounds | |
388 if( init_n == NULL || !init_n->is_Con() || | |
389 limit_n == NULL || !limit_n->is_Con() || | |
390 // protect against stride not being a constant | |
391 !cl->stride_is_con() ) { | |
392 return false; | |
393 } | |
394 int init = init_n->get_int(); | |
395 int limit = limit_n->get_int(); | |
396 int span = limit - init; | |
397 int stride = cl->stride_con(); | |
398 | |
399 if (init >= limit || stride > span) { | |
400 // return a false (no maximally unroll) and the regular unroll/peel | |
401 // route will make a small mess which CCP will fold away. | |
402 return false; | |
403 } | |
404 uint trip_count = span/stride; // trip_count can be greater than 2 Gig. | |
405 assert( (int)trip_count*stride == span, "must divide evenly" ); | |
406 | |
407 // Real policy: if we maximally unroll, does it get too big? | |
408 // Allow the unrolled mess to get larger than standard loop | |
409 // size. After all, it will no longer be a loop. | |
410 uint body_size = _body.size(); | |
411 uint unroll_limit = (uint)LoopUnrollLimit * 4; | |
412 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits"); | |
413 cl->set_trip_count(trip_count); | |
414 if( trip_count <= unroll_limit && body_size <= unroll_limit ) { | |
415 uint new_body_size = body_size * trip_count; | |
416 if (new_body_size <= unroll_limit && | |
417 body_size == new_body_size / trip_count && | |
418 // Unrolling can result in a large amount of node construction | |
419 new_body_size < MaxNodeLimit - phase->C->unique()) { | |
420 return true; // maximally unroll | |
421 } | |
422 } | |
423 | |
424 return false; // Do not maximally unroll | |
425 } | |
426 | |
427 | |
428 //------------------------------policy_unroll---------------------------------- | |
429 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if | |
430 // the loop is a CountedLoop and the body is small enough. | |
431 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const { | |
432 | |
433 CountedLoopNode *cl = _head->as_CountedLoop(); | |
434 assert( cl->is_normal_loop() || cl->is_main_loop(), "" ); | |
435 | |
436 // protect against stride not being a constant | |
437 if( !cl->stride_is_con() ) return false; | |
438 | |
439 // protect against over-unrolling | |
440 if( cl->trip_count() <= 1 ) return false; | |
441 | |
442 int future_unroll_ct = cl->unrolled_count() * 2; | |
443 | |
444 // Don't unroll if the next round of unrolling would push us | |
445 // over the expected trip count of the loop. One is subtracted | |
446 // from the expected trip count because the pre-loop normally | |
447 // executes 1 iteration. | |
448 if (UnrollLimitForProfileCheck > 0 && | |
449 cl->profile_trip_cnt() != COUNT_UNKNOWN && | |
450 future_unroll_ct > UnrollLimitForProfileCheck && | |
451 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) { | |
452 return false; | |
453 } | |
454 | |
455 // When unroll count is greater than LoopUnrollMin, don't unroll if: | |
456 // the residual iterations are more than 10% of the trip count | |
457 // and rounds of "unroll,optimize" are not making significant progress | |
458 // Progress defined as current size less than 20% larger than previous size. | |
459 if (UseSuperWord && cl->node_count_before_unroll() > 0 && | |
460 future_unroll_ct > LoopUnrollMin && | |
461 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() && | |
462 1.2 * cl->node_count_before_unroll() < (double)_body.size()) { | |
463 return false; | |
464 } | |
465 | |
466 Node *init_n = cl->init_trip(); | |
467 Node *limit_n = cl->limit(); | |
468 // Non-constant bounds. | |
469 // Protect against over-unrolling when init or/and limit are not constant | |
470 // (so that trip_count's init value is maxint) but iv range is known. | |
471 if( init_n == NULL || !init_n->is_Con() || | |
472 limit_n == NULL || !limit_n->is_Con() ) { | |
473 Node* phi = cl->phi(); | |
474 if( phi != NULL ) { | |
475 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi."); | |
476 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int(); | |
477 int next_stride = cl->stride_con() * 2; // stride after this unroll | |
478 if( next_stride > 0 ) { | |
479 if( iv_type->_lo + next_stride <= iv_type->_lo || // overflow | |
480 iv_type->_lo + next_stride > iv_type->_hi ) { | |
481 return false; // over-unrolling | |
482 } | |
483 } else if( next_stride < 0 ) { | |
484 if( iv_type->_hi + next_stride >= iv_type->_hi || // overflow | |
485 iv_type->_hi + next_stride < iv_type->_lo ) { | |
486 return false; // over-unrolling | |
487 } | |
488 } | |
489 } | |
490 } | |
491 | |
492 // Adjust body_size to determine if we unroll or not | |
493 uint body_size = _body.size(); | |
494 // Key test to unroll CaffeineMark's Logic test | |
495 int xors_in_loop = 0; | |
496 // Also count ModL, DivL and MulL which expand mightly | |
497 for( uint k = 0; k < _body.size(); k++ ) { | |
498 switch( _body.at(k)->Opcode() ) { | |
499 case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test | |
500 case Op_ModL: body_size += 30; break; | |
501 case Op_DivL: body_size += 30; break; | |
502 case Op_MulL: body_size += 10; break; | |
503 } | |
504 } | |
505 | |
506 // Check for being too big | |
507 if( body_size > (uint)LoopUnrollLimit ) { | |
508 if( xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true; | |
509 // Normal case: loop too big | |
510 return false; | |
511 } | |
512 | |
513 // Check for stride being a small enough constant | |
514 if( abs(cl->stride_con()) > (1<<3) ) return false; | |
515 | |
516 // Unroll once! (Each trip will soon do double iterations) | |
517 return true; | |
518 } | |
519 | |
520 //------------------------------policy_align----------------------------------- | |
521 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the | |
522 // expression that does the alignment. Note that only one array base can be | |
523 // aligned in a loop (unless the VM guarentees mutual alignment). Note that | |
524 // if we vectorize short memory ops into longer memory ops, we may want to | |
525 // increase alignment. | |
526 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const { | |
527 return false; | |
528 } | |
529 | |
530 //------------------------------policy_range_check----------------------------- | |
531 // Return TRUE or FALSE if the loop should be range-check-eliminated. | |
532 // Actually we do iteration-splitting, a more powerful form of RCE. | |
533 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const { | |
534 if( !RangeCheckElimination ) return false; | |
535 | |
536 CountedLoopNode *cl = _head->as_CountedLoop(); | |
537 // If we unrolled with no intention of doing RCE and we later | |
538 // changed our minds, we got no pre-loop. Either we need to | |
539 // make a new pre-loop, or we gotta disallow RCE. | |
540 if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now. | |
541 Node *trip_counter = cl->phi(); | |
542 | |
543 // Check loop body for tests of trip-counter plus loop-invariant vs | |
544 // loop-invariant. | |
545 for( uint i = 0; i < _body.size(); i++ ) { | |
546 Node *iff = _body[i]; | |
547 if( iff->Opcode() == Op_If ) { // Test? | |
548 | |
549 // Comparing trip+off vs limit | |
550 Node *bol = iff->in(1); | |
551 if( bol->req() != 2 ) continue; // dead constant test | |
552 Node *cmp = bol->in(1); | |
553 | |
554 Node *rc_exp = cmp->in(1); | |
555 Node *limit = cmp->in(2); | |
556 | |
557 Node *limit_c = phase->get_ctrl(limit); | |
558 if( limit_c == phase->C->top() ) | |
559 return false; // Found dead test on live IF? No RCE! | |
560 if( is_member(phase->get_loop(limit_c) ) ) { | |
561 // Compare might have operands swapped; commute them | |
562 rc_exp = cmp->in(2); | |
563 limit = cmp->in(1); | |
564 limit_c = phase->get_ctrl(limit); | |
565 if( is_member(phase->get_loop(limit_c) ) ) | |
566 continue; // Both inputs are loop varying; cannot RCE | |
567 } | |
568 | |
569 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) { | |
570 continue; | |
571 } | |
572 // Yeah! Found a test like 'trip+off vs limit' | |
573 // Test is an IfNode, has 2 projections. If BOTH are in the loop | |
574 // we need loop unswitching instead of iteration splitting. | |
575 if( is_loop_exit(iff) ) | |
576 return true; // Found reason to split iterations | |
577 } // End of is IF | |
578 } | |
579 | |
580 return false; | |
581 } | |
582 | |
583 //------------------------------policy_peel_only------------------------------- | |
584 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful | |
585 // for unrolling loops with NO array accesses. | |
586 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const { | |
587 | |
588 for( uint i = 0; i < _body.size(); i++ ) | |
589 if( _body[i]->is_Mem() ) | |
590 return false; | |
591 | |
592 // No memory accesses at all! | |
593 return true; | |
594 } | |
595 | |
596 //------------------------------clone_up_backedge_goo-------------------------- | |
597 // If Node n lives in the back_ctrl block and cannot float, we clone a private | |
598 // version of n in preheader_ctrl block and return that, otherwise return n. | |
599 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) { | |
600 if( get_ctrl(n) != back_ctrl ) return n; | |
601 | |
602 Node *x = NULL; // If required, a clone of 'n' | |
603 // Check for 'n' being pinned in the backedge. | |
604 if( n->in(0) && n->in(0) == back_ctrl ) { | |
605 x = n->clone(); // Clone a copy of 'n' to preheader | |
606 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader | |
607 } | |
608 | |
609 // Recursive fixup any other input edges into x. | |
610 // If there are no changes we can just return 'n', otherwise | |
611 // we need to clone a private copy and change it. | |
612 for( uint i = 1; i < n->req(); i++ ) { | |
613 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) ); | |
614 if( g != n->in(i) ) { | |
615 if( !x ) | |
616 x = n->clone(); | |
617 x->set_req(i, g); | |
618 } | |
619 } | |
620 if( x ) { // x can legally float to pre-header location | |
621 register_new_node( x, preheader_ctrl ); | |
622 return x; | |
623 } else { // raise n to cover LCA of uses | |
624 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) ); | |
625 } | |
626 return n; | |
627 } | |
628 | |
629 //------------------------------insert_pre_post_loops-------------------------- | |
630 // Insert pre and post loops. If peel_only is set, the pre-loop can not have | |
631 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no | |
632 // alignment. Useful to unroll loops that do no array accesses. | |
633 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) { | |
634 | |
635 C->set_major_progress(); | |
636 | |
637 // Find common pieces of the loop being guarded with pre & post loops | |
638 CountedLoopNode *main_head = loop->_head->as_CountedLoop(); | |
639 assert( main_head->is_normal_loop(), "" ); | |
640 CountedLoopEndNode *main_end = main_head->loopexit(); | |
641 assert( main_end->outcnt() == 2, "1 true, 1 false path only" ); | |
642 uint dd_main_head = dom_depth(main_head); | |
643 uint max = main_head->outcnt(); | |
644 | |
645 Node *pre_header= main_head->in(LoopNode::EntryControl); | |
646 Node *init = main_head->init_trip(); | |
647 Node *incr = main_end ->incr(); | |
648 Node *limit = main_end ->limit(); | |
649 Node *stride = main_end ->stride(); | |
650 Node *cmp = main_end ->cmp_node(); | |
651 BoolTest::mask b_test = main_end->test_trip(); | |
652 | |
653 // Need only 1 user of 'bol' because I will be hacking the loop bounds. | |
654 Node *bol = main_end->in(CountedLoopEndNode::TestValue); | |
655 if( bol->outcnt() != 1 ) { | |
656 bol = bol->clone(); | |
657 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl)); | |
658 _igvn.hash_delete(main_end); | |
659 main_end->set_req(CountedLoopEndNode::TestValue, bol); | |
660 } | |
661 // Need only 1 user of 'cmp' because I will be hacking the loop bounds. | |
662 if( cmp->outcnt() != 1 ) { | |
663 cmp = cmp->clone(); | |
664 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl)); | |
665 _igvn.hash_delete(bol); | |
666 bol->set_req(1, cmp); | |
667 } | |
668 | |
669 //------------------------------ | |
670 // Step A: Create Post-Loop. | |
671 Node* main_exit = main_end->proj_out(false); | |
672 assert( main_exit->Opcode() == Op_IfFalse, "" ); | |
673 int dd_main_exit = dom_depth(main_exit); | |
674 | |
675 // Step A1: Clone the loop body. The clone becomes the post-loop. The main | |
676 // loop pre-header illegally has 2 control users (old & new loops). | |
677 clone_loop( loop, old_new, dd_main_exit ); | |
678 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" ); | |
679 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop(); | |
680 post_head->set_post_loop(main_head); | |
681 | |
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682 // Reduce the post-loop trip count. |
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683 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); |
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684 post_end->_prob = PROB_FAIR; |
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685 |
0 | 686 // Build the main-loop normal exit. |
687 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end); | |
688 _igvn.register_new_node_with_optimizer( new_main_exit ); | |
689 set_idom(new_main_exit, main_end, dd_main_exit ); | |
690 set_loop(new_main_exit, loop->_parent); | |
691 | |
692 // Step A2: Build a zero-trip guard for the post-loop. After leaving the | |
693 // main-loop, the post-loop may not execute at all. We 'opaque' the incr | |
694 // (the main-loop trip-counter exit value) because we will be changing | |
695 // the exit value (via unrolling) so we cannot constant-fold away the zero | |
696 // trip guard until all unrolling is done. | |
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697 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr); |
0 | 698 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit ); |
699 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test ); | |
700 register_new_node( zer_opaq, new_main_exit ); | |
701 register_new_node( zer_cmp , new_main_exit ); | |
702 register_new_node( zer_bol , new_main_exit ); | |
703 | |
704 // Build the IfNode | |
705 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN ); | |
706 _igvn.register_new_node_with_optimizer( zer_iff ); | |
707 set_idom(zer_iff, new_main_exit, dd_main_exit); | |
708 set_loop(zer_iff, loop->_parent); | |
709 | |
710 // Plug in the false-path, taken if we need to skip post-loop | |
711 _igvn.hash_delete( main_exit ); | |
712 main_exit->set_req(0, zer_iff); | |
713 _igvn._worklist.push(main_exit); | |
714 set_idom(main_exit, zer_iff, dd_main_exit); | |
715 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit); | |
716 // Make the true-path, must enter the post loop | |
717 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff ); | |
718 _igvn.register_new_node_with_optimizer( zer_taken ); | |
719 set_idom(zer_taken, zer_iff, dd_main_exit); | |
720 set_loop(zer_taken, loop->_parent); | |
721 // Plug in the true path | |
722 _igvn.hash_delete( post_head ); | |
723 post_head->set_req(LoopNode::EntryControl, zer_taken); | |
724 set_idom(post_head, zer_taken, dd_main_exit); | |
725 | |
726 // Step A3: Make the fall-in values to the post-loop come from the | |
727 // fall-out values of the main-loop. | |
728 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) { | |
729 Node* main_phi = main_head->fast_out(i); | |
730 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) { | |
731 Node *post_phi = old_new[main_phi->_idx]; | |
732 Node *fallmain = clone_up_backedge_goo(main_head->back_control(), | |
733 post_head->init_control(), | |
734 main_phi->in(LoopNode::LoopBackControl)); | |
735 _igvn.hash_delete(post_phi); | |
736 post_phi->set_req( LoopNode::EntryControl, fallmain ); | |
737 } | |
738 } | |
739 | |
740 // Update local caches for next stanza | |
741 main_exit = new_main_exit; | |
742 | |
743 | |
744 //------------------------------ | |
745 // Step B: Create Pre-Loop. | |
746 | |
747 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main | |
748 // loop pre-header illegally has 2 control users (old & new loops). | |
749 clone_loop( loop, old_new, dd_main_head ); | |
750 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop(); | |
751 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); | |
752 pre_head->set_pre_loop(main_head); | |
753 Node *pre_incr = old_new[incr->_idx]; | |
754 | |
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755 // Reduce the pre-loop trip count. |
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756 pre_end->_prob = PROB_FAIR; |
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757 |
0 | 758 // Find the pre-loop normal exit. |
759 Node* pre_exit = pre_end->proj_out(false); | |
760 assert( pre_exit->Opcode() == Op_IfFalse, "" ); | |
761 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end); | |
762 _igvn.register_new_node_with_optimizer( new_pre_exit ); | |
763 set_idom(new_pre_exit, pre_end, dd_main_head); | |
764 set_loop(new_pre_exit, loop->_parent); | |
765 | |
766 // Step B2: Build a zero-trip guard for the main-loop. After leaving the | |
767 // pre-loop, the main-loop may not execute at all. Later in life this | |
768 // zero-trip guard will become the minimum-trip guard when we unroll | |
769 // the main-loop. | |
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770 Node *min_opaq = new (C, 2) Opaque1Node(C, limit); |
0 | 771 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq ); |
772 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test ); | |
773 register_new_node( min_opaq, new_pre_exit ); | |
774 register_new_node( min_cmp , new_pre_exit ); | |
775 register_new_node( min_bol , new_pre_exit ); | |
776 | |
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777 // Build the IfNode (assume the main-loop is executed always). |
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778 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN ); |
0 | 779 _igvn.register_new_node_with_optimizer( min_iff ); |
780 set_idom(min_iff, new_pre_exit, dd_main_head); | |
781 set_loop(min_iff, loop->_parent); | |
782 | |
783 // Plug in the false-path, taken if we need to skip main-loop | |
784 _igvn.hash_delete( pre_exit ); | |
785 pre_exit->set_req(0, min_iff); | |
786 set_idom(pre_exit, min_iff, dd_main_head); | |
787 set_idom(pre_exit->unique_out(), min_iff, dd_main_head); | |
788 // Make the true-path, must enter the main loop | |
789 Node *min_taken = new (C, 1) IfTrueNode( min_iff ); | |
790 _igvn.register_new_node_with_optimizer( min_taken ); | |
791 set_idom(min_taken, min_iff, dd_main_head); | |
792 set_loop(min_taken, loop->_parent); | |
793 // Plug in the true path | |
794 _igvn.hash_delete( main_head ); | |
795 main_head->set_req(LoopNode::EntryControl, min_taken); | |
796 set_idom(main_head, min_taken, dd_main_head); | |
797 | |
798 // Step B3: Make the fall-in values to the main-loop come from the | |
799 // fall-out values of the pre-loop. | |
800 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) { | |
801 Node* main_phi = main_head->fast_out(i2); | |
802 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) { | |
803 Node *pre_phi = old_new[main_phi->_idx]; | |
804 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(), | |
805 main_head->init_control(), | |
806 pre_phi->in(LoopNode::LoopBackControl)); | |
807 _igvn.hash_delete(main_phi); | |
808 main_phi->set_req( LoopNode::EntryControl, fallpre ); | |
809 } | |
810 } | |
811 | |
812 // Step B4: Shorten the pre-loop to run only 1 iteration (for now). | |
813 // RCE and alignment may change this later. | |
814 Node *cmp_end = pre_end->cmp_node(); | |
815 assert( cmp_end->in(2) == limit, "" ); | |
816 Node *pre_limit = new (C, 3) AddINode( init, stride ); | |
817 | |
818 // Save the original loop limit in this Opaque1 node for | |
819 // use by range check elimination. | |
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820 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit); |
0 | 821 |
822 register_new_node( pre_limit, pre_head->in(0) ); | |
823 register_new_node( pre_opaq , pre_head->in(0) ); | |
824 | |
825 // Since no other users of pre-loop compare, I can hack limit directly | |
826 assert( cmp_end->outcnt() == 1, "no other users" ); | |
827 _igvn.hash_delete(cmp_end); | |
828 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq); | |
829 | |
830 // Special case for not-equal loop bounds: | |
831 // Change pre loop test, main loop test, and the | |
832 // main loop guard test to use lt or gt depending on stride | |
833 // direction: | |
834 // positive stride use < | |
835 // negative stride use > | |
836 | |
837 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) { | |
838 | |
839 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt; | |
840 // Modify pre loop end condition | |
841 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool(); | |
842 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test); | |
843 register_new_node( new_bol0, pre_head->in(0) ); | |
844 _igvn.hash_delete(pre_end); | |
845 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0); | |
846 // Modify main loop guard condition | |
847 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay"); | |
848 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test); | |
849 register_new_node( new_bol1, new_pre_exit ); | |
850 _igvn.hash_delete(min_iff); | |
851 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1); | |
852 // Modify main loop end condition | |
853 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool(); | |
854 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test); | |
855 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) ); | |
856 _igvn.hash_delete(main_end); | |
857 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2); | |
858 } | |
859 | |
860 // Flag main loop | |
861 main_head->set_main_loop(); | |
862 if( peel_only ) main_head->set_main_no_pre_loop(); | |
863 | |
864 // It's difficult to be precise about the trip-counts | |
865 // for the pre/post loops. They are usually very short, | |
866 // so guess that 4 trips is a reasonable value. | |
867 post_head->set_profile_trip_cnt(4.0); | |
868 pre_head->set_profile_trip_cnt(4.0); | |
869 | |
870 // Now force out all loop-invariant dominating tests. The optimizer | |
871 // finds some, but we _know_ they are all useless. | |
872 peeled_dom_test_elim(loop,old_new); | |
873 } | |
874 | |
875 //------------------------------is_invariant----------------------------- | |
876 // Return true if n is invariant | |
877 bool IdealLoopTree::is_invariant(Node* n) const { | |
878 Node *n_c = _phase->get_ctrl(n); | |
879 if (n_c->is_top()) return false; | |
880 return !is_member(_phase->get_loop(n_c)); | |
881 } | |
882 | |
883 | |
884 //------------------------------do_unroll-------------------------------------- | |
885 // Unroll the loop body one step - make each trip do 2 iterations. | |
886 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) { | |
887 assert( LoopUnrollLimit, "" ); | |
888 #ifndef PRODUCT | |
889 if( PrintOpto && VerifyLoopOptimizations ) { | |
890 tty->print("Unrolling "); | |
891 loop->dump_head(); | |
892 } | |
893 #endif | |
894 CountedLoopNode *loop_head = loop->_head->as_CountedLoop(); | |
895 CountedLoopEndNode *loop_end = loop_head->loopexit(); | |
896 assert( loop_end, "" ); | |
897 | |
898 // Remember loop node count before unrolling to detect | |
899 // if rounds of unroll,optimize are making progress | |
900 loop_head->set_node_count_before_unroll(loop->_body.size()); | |
901 | |
902 Node *ctrl = loop_head->in(LoopNode::EntryControl); | |
903 Node *limit = loop_head->limit(); | |
904 Node *init = loop_head->init_trip(); | |
905 Node *strid = loop_head->stride(); | |
906 | |
907 Node *opaq = NULL; | |
908 if( adjust_min_trip ) { // If not maximally unrolling, need adjustment | |
909 assert( loop_head->is_main_loop(), "" ); | |
910 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); | |
911 Node *iff = ctrl->in(0); | |
912 assert( iff->Opcode() == Op_If, "" ); | |
913 Node *bol = iff->in(1); | |
914 assert( bol->Opcode() == Op_Bool, "" ); | |
915 Node *cmp = bol->in(1); | |
916 assert( cmp->Opcode() == Op_CmpI, "" ); | |
917 opaq = cmp->in(2); | |
918 // Occasionally it's possible for a pre-loop Opaque1 node to be | |
919 // optimized away and then another round of loop opts attempted. | |
920 // We can not optimize this particular loop in that case. | |
921 if( opaq->Opcode() != Op_Opaque1 ) | |
922 return; // Cannot find pre-loop! Bail out! | |
923 } | |
924 | |
925 C->set_major_progress(); | |
926 | |
927 // Adjust max trip count. The trip count is intentionally rounded | |
928 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll, | |
929 // the main, unrolled, part of the loop will never execute as it is protected | |
930 // by the min-trip test. See bug 4834191 for a case where we over-unrolled | |
931 // and later determined that part of the unrolled loop was dead. | |
932 loop_head->set_trip_count(loop_head->trip_count() / 2); | |
933 | |
934 // Double the count of original iterations in the unrolled loop body. | |
935 loop_head->double_unrolled_count(); | |
936 | |
937 // ----------- | |
938 // Step 2: Cut back the trip counter for an unroll amount of 2. | |
939 // Loop will normally trip (limit - init)/stride_con. Since it's a | |
940 // CountedLoop this is exact (stride divides limit-init exactly). | |
941 // We are going to double the loop body, so we want to knock off any | |
942 // odd iteration: (trip_cnt & ~1). Then back compute a new limit. | |
943 Node *span = new (C, 3) SubINode( limit, init ); | |
944 register_new_node( span, ctrl ); | |
945 Node *trip = new (C, 3) DivINode( 0, span, strid ); | |
946 register_new_node( trip, ctrl ); | |
947 Node *mtwo = _igvn.intcon(-2); | |
948 set_ctrl(mtwo, C->root()); | |
949 Node *rond = new (C, 3) AndINode( trip, mtwo ); | |
950 register_new_node( rond, ctrl ); | |
951 Node *spn2 = new (C, 3) MulINode( rond, strid ); | |
952 register_new_node( spn2, ctrl ); | |
953 Node *lim2 = new (C, 3) AddINode( spn2, init ); | |
954 register_new_node( lim2, ctrl ); | |
955 | |
956 // Hammer in the new limit | |
957 Node *ctrl2 = loop_end->in(0); | |
958 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 ); | |
959 register_new_node( cmp2, ctrl2 ); | |
960 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() ); | |
961 register_new_node( bol2, ctrl2 ); | |
962 _igvn.hash_delete(loop_end); | |
963 loop_end->set_req(CountedLoopEndNode::TestValue, bol2); | |
964 | |
965 // Step 3: Find the min-trip test guaranteed before a 'main' loop. | |
966 // Make it a 1-trip test (means at least 2 trips). | |
967 if( adjust_min_trip ) { | |
968 // Guard test uses an 'opaque' node which is not shared. Hence I | |
969 // can edit it's inputs directly. Hammer in the new limit for the | |
970 // minimum-trip guard. | |
971 assert( opaq->outcnt() == 1, "" ); | |
972 _igvn.hash_delete(opaq); | |
973 opaq->set_req(1, lim2); | |
974 } | |
975 | |
976 // --------- | |
977 // Step 4: Clone the loop body. Move it inside the loop. This loop body | |
978 // represents the odd iterations; since the loop trips an even number of | |
979 // times its backedge is never taken. Kill the backedge. | |
980 uint dd = dom_depth(loop_head); | |
981 clone_loop( loop, old_new, dd ); | |
982 | |
983 // Make backedges of the clone equal to backedges of the original. | |
984 // Make the fall-in from the original come from the fall-out of the clone. | |
985 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) { | |
986 Node* phi = loop_head->fast_out(j); | |
987 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) { | |
988 Node *newphi = old_new[phi->_idx]; | |
989 _igvn.hash_delete( phi ); | |
990 _igvn.hash_delete( newphi ); | |
991 | |
992 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl)); | |
993 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl)); | |
994 phi ->set_req(LoopNode::LoopBackControl, C->top()); | |
995 } | |
996 } | |
997 Node *clone_head = old_new[loop_head->_idx]; | |
998 _igvn.hash_delete( clone_head ); | |
999 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl)); | |
1000 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl)); | |
1001 loop_head ->set_req(LoopNode::LoopBackControl, C->top()); | |
1002 loop->_head = clone_head; // New loop header | |
1003 | |
1004 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd); | |
1005 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd); | |
1006 | |
1007 // Kill the clone's backedge | |
1008 Node *newcle = old_new[loop_end->_idx]; | |
1009 _igvn.hash_delete( newcle ); | |
1010 Node *one = _igvn.intcon(1); | |
1011 set_ctrl(one, C->root()); | |
1012 newcle->set_req(1, one); | |
1013 // Force clone into same loop body | |
1014 uint max = loop->_body.size(); | |
1015 for( uint k = 0; k < max; k++ ) { | |
1016 Node *old = loop->_body.at(k); | |
1017 Node *nnn = old_new[old->_idx]; | |
1018 loop->_body.push(nnn); | |
1019 if (!has_ctrl(old)) | |
1020 set_loop(nnn, loop); | |
1021 } | |
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1023 loop->record_for_igvn(); |
0 | 1024 } |
1025 | |
1026 //------------------------------do_maximally_unroll---------------------------- | |
1027 | |
1028 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) { | |
1029 CountedLoopNode *cl = loop->_head->as_CountedLoop(); | |
1030 assert( cl->trip_count() > 0, ""); | |
1031 | |
1032 // If loop is tripping an odd number of times, peel odd iteration | |
1033 if( (cl->trip_count() & 1) == 1 ) { | |
1034 do_peeling( loop, old_new ); | |
1035 } | |
1036 | |
1037 // Now its tripping an even number of times remaining. Double loop body. | |
1038 // Do not adjust pre-guards; they are not needed and do not exist. | |
1039 if( cl->trip_count() > 0 ) { | |
1040 do_unroll( loop, old_new, false ); | |
1041 } | |
1042 } | |
1043 | |
1044 //------------------------------dominates_backedge--------------------------------- | |
1045 // Returns true if ctrl is executed on every complete iteration | |
1046 bool IdealLoopTree::dominates_backedge(Node* ctrl) { | |
1047 assert(ctrl->is_CFG(), "must be control"); | |
1048 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl); | |
1049 return _phase->dom_lca_internal(ctrl, backedge) == ctrl; | |
1050 } | |
1051 | |
1052 //------------------------------add_constraint--------------------------------- | |
1053 // Constrain the main loop iterations so the condition: | |
1054 // scale_con * I + offset < limit | |
1055 // always holds true. That is, either increase the number of iterations in | |
1056 // the pre-loop or the post-loop until the condition holds true in the main | |
1057 // loop. Stride, scale, offset and limit are all loop invariant. Further, | |
1058 // stride and scale are constants (offset and limit often are). | |
1059 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) { | |
1060 | |
1061 // Compute "I :: (limit-offset)/scale_con" | |
1062 Node *con = new (C, 3) SubINode( limit, offset ); | |
1063 register_new_node( con, pre_ctrl ); | |
1064 Node *scale = _igvn.intcon(scale_con); | |
1065 set_ctrl(scale, C->root()); | |
1066 Node *X = new (C, 3) DivINode( 0, con, scale ); | |
1067 register_new_node( X, pre_ctrl ); | |
1068 | |
1069 // For positive stride, the pre-loop limit always uses a MAX function | |
1070 // and the main loop a MIN function. For negative stride these are | |
1071 // reversed. | |
1072 | |
1073 // Also for positive stride*scale the affine function is increasing, so the | |
1074 // pre-loop must check for underflow and the post-loop for overflow. | |
1075 // Negative stride*scale reverses this; pre-loop checks for overflow and | |
1076 // post-loop for underflow. | |
1077 if( stride_con*scale_con > 0 ) { | |
1078 // Compute I < (limit-offset)/scale_con | |
1079 // Adjust main-loop last iteration to be MIN/MAX(main_loop,X) | |
1080 *main_limit = (stride_con > 0) | |
1081 ? (Node*)(new (C, 3) MinINode( *main_limit, X )) | |
1082 : (Node*)(new (C, 3) MaxINode( *main_limit, X )); | |
1083 register_new_node( *main_limit, pre_ctrl ); | |
1084 | |
1085 } else { | |
1086 // Compute (limit-offset)/scale_con + SGN(-scale_con) <= I | |
1087 // Add the negation of the main-loop constraint to the pre-loop. | |
1088 // See footnote [++] below for a derivation of the limit expression. | |
1089 Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1); | |
1090 set_ctrl(incr, C->root()); | |
1091 Node *adj = new (C, 3) AddINode( X, incr ); | |
1092 register_new_node( adj, pre_ctrl ); | |
1093 *pre_limit = (scale_con > 0) | |
1094 ? (Node*)new (C, 3) MinINode( *pre_limit, adj ) | |
1095 : (Node*)new (C, 3) MaxINode( *pre_limit, adj ); | |
1096 register_new_node( *pre_limit, pre_ctrl ); | |
1097 | |
1098 // [++] Here's the algebra that justifies the pre-loop limit expression: | |
1099 // | |
1100 // NOT( scale_con * I + offset < limit ) | |
1101 // == | |
1102 // scale_con * I + offset >= limit | |
1103 // == | |
1104 // SGN(scale_con) * I >= (limit-offset)/|scale_con| | |
1105 // == | |
1106 // (limit-offset)/|scale_con| <= I * SGN(scale_con) | |
1107 // == | |
1108 // (limit-offset)/|scale_con|-1 < I * SGN(scale_con) | |
1109 // == | |
1110 // ( if (scale_con > 0) /*common case*/ | |
1111 // (limit-offset)/scale_con - 1 < I | |
1112 // else | |
1113 // (limit-offset)/scale_con + 1 > I | |
1114 // ) | |
1115 // ( if (scale_con > 0) /*common case*/ | |
1116 // (limit-offset)/scale_con + SGN(-scale_con) < I | |
1117 // else | |
1118 // (limit-offset)/scale_con + SGN(-scale_con) > I | |
1119 } | |
1120 } | |
1121 | |
1122 | |
1123 //------------------------------is_scaled_iv--------------------------------- | |
1124 // Return true if exp is a constant times an induction var | |
1125 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) { | |
1126 if (exp == iv) { | |
1127 if (p_scale != NULL) { | |
1128 *p_scale = 1; | |
1129 } | |
1130 return true; | |
1131 } | |
1132 int opc = exp->Opcode(); | |
1133 if (opc == Op_MulI) { | |
1134 if (exp->in(1) == iv && exp->in(2)->is_Con()) { | |
1135 if (p_scale != NULL) { | |
1136 *p_scale = exp->in(2)->get_int(); | |
1137 } | |
1138 return true; | |
1139 } | |
1140 if (exp->in(2) == iv && exp->in(1)->is_Con()) { | |
1141 if (p_scale != NULL) { | |
1142 *p_scale = exp->in(1)->get_int(); | |
1143 } | |
1144 return true; | |
1145 } | |
1146 } else if (opc == Op_LShiftI) { | |
1147 if (exp->in(1) == iv && exp->in(2)->is_Con()) { | |
1148 if (p_scale != NULL) { | |
1149 *p_scale = 1 << exp->in(2)->get_int(); | |
1150 } | |
1151 return true; | |
1152 } | |
1153 } | |
1154 return false; | |
1155 } | |
1156 | |
1157 //-----------------------------is_scaled_iv_plus_offset------------------------------ | |
1158 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2) | |
1159 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) { | |
1160 if (is_scaled_iv(exp, iv, p_scale)) { | |
1161 if (p_offset != NULL) { | |
1162 Node *zero = _igvn.intcon(0); | |
1163 set_ctrl(zero, C->root()); | |
1164 *p_offset = zero; | |
1165 } | |
1166 return true; | |
1167 } | |
1168 int opc = exp->Opcode(); | |
1169 if (opc == Op_AddI) { | |
1170 if (is_scaled_iv(exp->in(1), iv, p_scale)) { | |
1171 if (p_offset != NULL) { | |
1172 *p_offset = exp->in(2); | |
1173 } | |
1174 return true; | |
1175 } | |
1176 if (exp->in(2)->is_Con()) { | |
1177 Node* offset2 = NULL; | |
1178 if (depth < 2 && | |
1179 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale, | |
1180 p_offset != NULL ? &offset2 : NULL, depth+1)) { | |
1181 if (p_offset != NULL) { | |
1182 Node *ctrl_off2 = get_ctrl(offset2); | |
1183 Node* offset = new (C, 3) AddINode(offset2, exp->in(2)); | |
1184 register_new_node(offset, ctrl_off2); | |
1185 *p_offset = offset; | |
1186 } | |
1187 return true; | |
1188 } | |
1189 } | |
1190 } else if (opc == Op_SubI) { | |
1191 if (is_scaled_iv(exp->in(1), iv, p_scale)) { | |
1192 if (p_offset != NULL) { | |
1193 Node *zero = _igvn.intcon(0); | |
1194 set_ctrl(zero, C->root()); | |
1195 Node *ctrl_off = get_ctrl(exp->in(2)); | |
1196 Node* offset = new (C, 3) SubINode(zero, exp->in(2)); | |
1197 register_new_node(offset, ctrl_off); | |
1198 *p_offset = offset; | |
1199 } | |
1200 return true; | |
1201 } | |
1202 if (is_scaled_iv(exp->in(2), iv, p_scale)) { | |
1203 if (p_offset != NULL) { | |
1204 *p_scale *= -1; | |
1205 *p_offset = exp->in(1); | |
1206 } | |
1207 return true; | |
1208 } | |
1209 } | |
1210 return false; | |
1211 } | |
1212 | |
1213 //------------------------------do_range_check--------------------------------- | |
1214 // Eliminate range-checks and other trip-counter vs loop-invariant tests. | |
1215 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) { | |
1216 #ifndef PRODUCT | |
1217 if( PrintOpto && VerifyLoopOptimizations ) { | |
1218 tty->print("Range Check Elimination "); | |
1219 loop->dump_head(); | |
1220 } | |
1221 #endif | |
1222 assert( RangeCheckElimination, "" ); | |
1223 CountedLoopNode *cl = loop->_head->as_CountedLoop(); | |
1224 assert( cl->is_main_loop(), "" ); | |
1225 | |
1226 // Find the trip counter; we are iteration splitting based on it | |
1227 Node *trip_counter = cl->phi(); | |
1228 // Find the main loop limit; we will trim it's iterations | |
1229 // to not ever trip end tests | |
1230 Node *main_limit = cl->limit(); | |
1231 // Find the pre-loop limit; we will expand it's iterations to | |
1232 // not ever trip low tests. | |
1233 Node *ctrl = cl->in(LoopNode::EntryControl); | |
1234 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" ); | |
1235 Node *iffm = ctrl->in(0); | |
1236 assert( iffm->Opcode() == Op_If, "" ); | |
1237 Node *p_f = iffm->in(0); | |
1238 assert( p_f->Opcode() == Op_IfFalse, "" ); | |
1239 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd(); | |
1240 assert( pre_end->loopnode()->is_pre_loop(), "" ); | |
1241 Node *pre_opaq1 = pre_end->limit(); | |
1242 // Occasionally it's possible for a pre-loop Opaque1 node to be | |
1243 // optimized away and then another round of loop opts attempted. | |
1244 // We can not optimize this particular loop in that case. | |
1245 if( pre_opaq1->Opcode() != Op_Opaque1 ) | |
1246 return; | |
1247 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1; | |
1248 Node *pre_limit = pre_opaq->in(1); | |
1249 | |
1250 // Where do we put new limit calculations | |
1251 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl); | |
1252 | |
1253 // Ensure the original loop limit is available from the | |
1254 // pre-loop Opaque1 node. | |
1255 Node *orig_limit = pre_opaq->original_loop_limit(); | |
1256 if( orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP ) | |
1257 return; | |
1258 | |
1259 // Need to find the main-loop zero-trip guard | |
1260 Node *bolzm = iffm->in(1); | |
1261 assert( bolzm->Opcode() == Op_Bool, "" ); | |
1262 Node *cmpzm = bolzm->in(1); | |
1263 assert( cmpzm->is_Cmp(), "" ); | |
1264 Node *opqzm = cmpzm->in(2); | |
1265 if( opqzm->Opcode() != Op_Opaque1 ) | |
1266 return; | |
1267 assert( opqzm->in(1) == main_limit, "do not understand situation" ); | |
1268 | |
1269 // Must know if its a count-up or count-down loop | |
1270 | |
1271 // protect against stride not being a constant | |
1272 if ( !cl->stride_is_con() ) { | |
1273 return; | |
1274 } | |
1275 int stride_con = cl->stride_con(); | |
1276 Node *zero = _igvn.intcon(0); | |
1277 Node *one = _igvn.intcon(1); | |
1278 set_ctrl(zero, C->root()); | |
1279 set_ctrl(one, C->root()); | |
1280 | |
1281 // Range checks that do not dominate the loop backedge (ie. | |
1282 // conditionally executed) can lengthen the pre loop limit beyond | |
1283 // the original loop limit. To prevent this, the pre limit is | |
1284 // (for stride > 0) MINed with the original loop limit (MAXed | |
1285 // stride < 0) when some range_check (rc) is conditionally | |
1286 // executed. | |
1287 bool conditional_rc = false; | |
1288 | |
1289 // Check loop body for tests of trip-counter plus loop-invariant vs | |
1290 // loop-invariant. | |
1291 for( uint i = 0; i < loop->_body.size(); i++ ) { | |
1292 Node *iff = loop->_body[i]; | |
1293 if( iff->Opcode() == Op_If ) { // Test? | |
1294 | |
1295 // Test is an IfNode, has 2 projections. If BOTH are in the loop | |
1296 // we need loop unswitching instead of iteration splitting. | |
1297 Node *exit = loop->is_loop_exit(iff); | |
1298 if( !exit ) continue; | |
1299 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0; | |
1300 | |
1301 // Get boolean condition to test | |
1302 Node *i1 = iff->in(1); | |
1303 if( !i1->is_Bool() ) continue; | |
1304 BoolNode *bol = i1->as_Bool(); | |
1305 BoolTest b_test = bol->_test; | |
1306 // Flip sense of test if exit condition is flipped | |
1307 if( flip ) | |
1308 b_test = b_test.negate(); | |
1309 | |
1310 // Get compare | |
1311 Node *cmp = bol->in(1); | |
1312 | |
1313 // Look for trip_counter + offset vs limit | |
1314 Node *rc_exp = cmp->in(1); | |
1315 Node *limit = cmp->in(2); | |
1316 jint scale_con= 1; // Assume trip counter not scaled | |
1317 | |
1318 Node *limit_c = get_ctrl(limit); | |
1319 if( loop->is_member(get_loop(limit_c) ) ) { | |
1320 // Compare might have operands swapped; commute them | |
1321 b_test = b_test.commute(); | |
1322 rc_exp = cmp->in(2); | |
1323 limit = cmp->in(1); | |
1324 limit_c = get_ctrl(limit); | |
1325 if( loop->is_member(get_loop(limit_c) ) ) | |
1326 continue; // Both inputs are loop varying; cannot RCE | |
1327 } | |
1328 // Here we know 'limit' is loop invariant | |
1329 | |
1330 // 'limit' maybe pinned below the zero trip test (probably from a | |
1331 // previous round of rce), in which case, it can't be used in the | |
1332 // zero trip test expression which must occur before the zero test's if. | |
1333 if( limit_c == ctrl ) { | |
1334 continue; // Don't rce this check but continue looking for other candidates. | |
1335 } | |
1336 | |
1337 // Check for scaled induction variable plus an offset | |
1338 Node *offset = NULL; | |
1339 | |
1340 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) { | |
1341 continue; | |
1342 } | |
1343 | |
1344 Node *offset_c = get_ctrl(offset); | |
1345 if( loop->is_member( get_loop(offset_c) ) ) | |
1346 continue; // Offset is not really loop invariant | |
1347 // Here we know 'offset' is loop invariant. | |
1348 | |
1349 // As above for the 'limit', the 'offset' maybe pinned below the | |
1350 // zero trip test. | |
1351 if( offset_c == ctrl ) { | |
1352 continue; // Don't rce this check but continue looking for other candidates. | |
1353 } | |
1354 | |
1355 // At this point we have the expression as: | |
1356 // scale_con * trip_counter + offset :: limit | |
1357 // where scale_con, offset and limit are loop invariant. Trip_counter | |
1358 // monotonically increases by stride_con, a constant. Both (or either) | |
1359 // stride_con and scale_con can be negative which will flip about the | |
1360 // sense of the test. | |
1361 | |
1362 // Adjust pre and main loop limits to guard the correct iteration set | |
1363 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests | |
1364 if( b_test._test == BoolTest::lt ) { // Range checks always use lt | |
1365 // The overflow limit: scale*I+offset < limit | |
1366 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit ); | |
1367 // The underflow limit: 0 <= scale*I+offset. | |
1368 // Some math yields: -scale*I-(offset+1) < 0 | |
1369 Node *plus_one = new (C, 3) AddINode( offset, one ); | |
1370 register_new_node( plus_one, pre_ctrl ); | |
1371 Node *neg_offset = new (C, 3) SubINode( zero, plus_one ); | |
1372 register_new_node( neg_offset, pre_ctrl ); | |
1373 add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit ); | |
1374 if (!conditional_rc) { | |
1375 conditional_rc = !loop->dominates_backedge(iff); | |
1376 } | |
1377 } else { | |
1378 #ifndef PRODUCT | |
1379 if( PrintOpto ) | |
1380 tty->print_cr("missed RCE opportunity"); | |
1381 #endif | |
1382 continue; // In release mode, ignore it | |
1383 } | |
1384 } else { // Otherwise work on normal compares | |
1385 switch( b_test._test ) { | |
1386 case BoolTest::ge: // Convert X >= Y to -X <= -Y | |
1387 scale_con = -scale_con; | |
1388 offset = new (C, 3) SubINode( zero, offset ); | |
1389 register_new_node( offset, pre_ctrl ); | |
1390 limit = new (C, 3) SubINode( zero, limit ); | |
1391 register_new_node( limit, pre_ctrl ); | |
1392 // Fall into LE case | |
1393 case BoolTest::le: // Convert X <= Y to X < Y+1 | |
1394 limit = new (C, 3) AddINode( limit, one ); | |
1395 register_new_node( limit, pre_ctrl ); | |
1396 // Fall into LT case | |
1397 case BoolTest::lt: | |
1398 add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit ); | |
1399 if (!conditional_rc) { | |
1400 conditional_rc = !loop->dominates_backedge(iff); | |
1401 } | |
1402 break; | |
1403 default: | |
1404 #ifndef PRODUCT | |
1405 if( PrintOpto ) | |
1406 tty->print_cr("missed RCE opportunity"); | |
1407 #endif | |
1408 continue; // Unhandled case | |
1409 } | |
1410 } | |
1411 | |
1412 // Kill the eliminated test | |
1413 C->set_major_progress(); | |
1414 Node *kill_con = _igvn.intcon( 1-flip ); | |
1415 set_ctrl(kill_con, C->root()); | |
1416 _igvn.hash_delete(iff); | |
1417 iff->set_req(1, kill_con); | |
1418 _igvn._worklist.push(iff); | |
1419 // Find surviving projection | |
1420 assert(iff->is_If(), ""); | |
1421 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip); | |
1422 // Find loads off the surviving projection; remove their control edge | |
1423 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) { | |
1424 Node* cd = dp->fast_out(i); // Control-dependent node | |
1425 if( cd->is_Load() ) { // Loads can now float around in the loop | |
1426 _igvn.hash_delete(cd); | |
1427 // Allow the load to float around in the loop, or before it | |
1428 // but NOT before the pre-loop. | |
1429 cd->set_req(0, ctrl); // ctrl, not NULL | |
1430 _igvn._worklist.push(cd); | |
1431 --i; | |
1432 --imax; | |
1433 } | |
1434 } | |
1435 | |
1436 } // End of is IF | |
1437 | |
1438 } | |
1439 | |
1440 // Update loop limits | |
1441 if (conditional_rc) { | |
1442 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit) | |
1443 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit); | |
1444 register_new_node(pre_limit, pre_ctrl); | |
1445 } | |
1446 _igvn.hash_delete(pre_opaq); | |
1447 pre_opaq->set_req(1, pre_limit); | |
1448 | |
1449 // Note:: we are making the main loop limit no longer precise; | |
1450 // need to round up based on stride. | |
1451 if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case | |
1452 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init | |
1453 // Hopefully, compiler will optimize for powers of 2. | |
1454 Node *ctrl = get_ctrl(main_limit); | |
1455 Node *stride = cl->stride(); | |
1456 Node *init = cl->init_trip(); | |
1457 Node *span = new (C, 3) SubINode(main_limit,init); | |
1458 register_new_node(span,ctrl); | |
1459 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1)); | |
1460 Node *add = new (C, 3) AddINode(span,rndup); | |
1461 register_new_node(add,ctrl); | |
1462 Node *div = new (C, 3) DivINode(0,add,stride); | |
1463 register_new_node(div,ctrl); | |
1464 Node *mul = new (C, 3) MulINode(div,stride); | |
1465 register_new_node(mul,ctrl); | |
1466 Node *newlim = new (C, 3) AddINode(mul,init); | |
1467 register_new_node(newlim,ctrl); | |
1468 main_limit = newlim; | |
1469 } | |
1470 | |
1471 Node *main_cle = cl->loopexit(); | |
1472 Node *main_bol = main_cle->in(1); | |
1473 // Hacking loop bounds; need private copies of exit test | |
1474 if( main_bol->outcnt() > 1 ) {// BoolNode shared? | |
1475 _igvn.hash_delete(main_cle); | |
1476 main_bol = main_bol->clone();// Clone a private BoolNode | |
1477 register_new_node( main_bol, main_cle->in(0) ); | |
1478 main_cle->set_req(1,main_bol); | |
1479 } | |
1480 Node *main_cmp = main_bol->in(1); | |
1481 if( main_cmp->outcnt() > 1 ) { // CmpNode shared? | |
1482 _igvn.hash_delete(main_bol); | |
1483 main_cmp = main_cmp->clone();// Clone a private CmpNode | |
1484 register_new_node( main_cmp, main_cle->in(0) ); | |
1485 main_bol->set_req(1,main_cmp); | |
1486 } | |
1487 // Hack the now-private loop bounds | |
1488 _igvn.hash_delete(main_cmp); | |
1489 main_cmp->set_req(2, main_limit); | |
1490 _igvn._worklist.push(main_cmp); | |
1491 // The OpaqueNode is unshared by design | |
1492 _igvn.hash_delete(opqzm); | |
1493 assert( opqzm->outcnt() == 1, "cannot hack shared node" ); | |
1494 opqzm->set_req(1,main_limit); | |
1495 _igvn._worklist.push(opqzm); | |
1496 } | |
1497 | |
1498 //------------------------------DCE_loop_body---------------------------------- | |
1499 // Remove simplistic dead code from loop body | |
1500 void IdealLoopTree::DCE_loop_body() { | |
1501 for( uint i = 0; i < _body.size(); i++ ) | |
1502 if( _body.at(i)->outcnt() == 0 ) | |
1503 _body.map( i--, _body.pop() ); | |
1504 } | |
1505 | |
1506 | |
1507 //------------------------------adjust_loop_exit_prob-------------------------- | |
1508 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage. | |
1509 // Replace with a 1-in-10 exit guess. | |
1510 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) { | |
1511 Node *test = tail(); | |
1512 while( test != _head ) { | |
1513 uint top = test->Opcode(); | |
1514 if( top == Op_IfTrue || top == Op_IfFalse ) { | |
1515 int test_con = ((ProjNode*)test)->_con; | |
1516 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity"); | |
1517 IfNode *iff = test->in(0)->as_If(); | |
1518 if( iff->outcnt() == 2 ) { // Ignore dead tests | |
1519 Node *bol = iff->in(1); | |
1520 if( bol && bol->req() > 1 && bol->in(1) && | |
1521 ((bol->in(1)->Opcode() == Op_StorePConditional ) || | |
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1522 (bol->in(1)->Opcode() == Op_StoreIConditional ) || |
0 | 1523 (bol->in(1)->Opcode() == Op_StoreLConditional ) || |
1524 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || | |
1525 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || | |
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1526 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || |
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1527 (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) |
0 | 1528 return; // Allocation loops RARELY take backedge |
1529 // Find the OTHER exit path from the IF | |
1530 Node* ex = iff->proj_out(1-test_con); | |
1531 float p = iff->_prob; | |
1532 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) { | |
1533 if( top == Op_IfTrue ) { | |
1534 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) { | |
1535 iff->_prob = PROB_STATIC_FREQUENT; | |
1536 } | |
1537 } else { | |
1538 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) { | |
1539 iff->_prob = PROB_STATIC_INFREQUENT; | |
1540 } | |
1541 } | |
1542 } | |
1543 } | |
1544 } | |
1545 test = phase->idom(test); | |
1546 } | |
1547 } | |
1548 | |
1549 | |
1550 //------------------------------policy_do_remove_empty_loop-------------------- | |
1551 // Micro-benchmark spamming. Policy is to always remove empty loops. | |
1552 // The 'DO' part is to replace the trip counter with the value it will | |
1553 // have on the last iteration. This will break the loop. | |
1554 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) { | |
1555 // Minimum size must be empty loop | |
1556 if( _body.size() > 7/*number of nodes in an empty loop*/ ) return false; | |
1557 | |
1558 if( !_head->is_CountedLoop() ) return false; // Dead loop | |
1559 CountedLoopNode *cl = _head->as_CountedLoop(); | |
1560 if( !cl->loopexit() ) return false; // Malformed loop | |
1561 if( !phase->is_member(this,phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)) ) ) | |
1562 return false; // Infinite loop | |
1563 #ifndef PRODUCT | |
1564 if( PrintOpto ) | |
1565 tty->print_cr("Removing empty loop"); | |
1566 #endif | |
1567 #ifdef ASSERT | |
1568 // Ensure only one phi which is the iv. | |
1569 Node* iv = NULL; | |
1570 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) { | |
1571 Node* n = cl->fast_out(i); | |
1572 if (n->Opcode() == Op_Phi) { | |
1573 assert(iv == NULL, "Too many phis" ); | |
1574 iv = n; | |
1575 } | |
1576 } | |
1577 assert(iv == cl->phi(), "Wrong phi" ); | |
1578 #endif | |
1579 // Replace the phi at loop head with the final value of the last | |
1580 // iteration. Then the CountedLoopEnd will collapse (backedge never | |
1581 // taken) and all loop-invariant uses of the exit values will be correct. | |
1582 Node *phi = cl->phi(); | |
1583 Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() ); | |
1584 phase->register_new_node(final,cl->in(LoopNode::EntryControl)); | |
1585 phase->_igvn.hash_delete(phi); | |
1586 phase->_igvn.subsume_node(phi,final); | |
1587 phase->C->set_major_progress(); | |
1588 return true; | |
1589 } | |
1590 | |
1591 | |
1592 //============================================================================= | |
1593 //------------------------------iteration_split_impl--------------------------- | |
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1594 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) { |
0 | 1595 // Check and remove empty loops (spam micro-benchmarks) |
1596 if( policy_do_remove_empty_loop(phase) ) | |
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1597 return true; // Here we removed an empty loop |
0 | 1598 |
1599 bool should_peel = policy_peeling(phase); // Should we peel? | |
1600 | |
1601 bool should_unswitch = policy_unswitching(phase); | |
1602 | |
1603 // Non-counted loops may be peeled; exactly 1 iteration is peeled. | |
1604 // This removes loop-invariant tests (usually null checks). | |
1605 if( !_head->is_CountedLoop() ) { // Non-counted loop | |
1606 if (PartialPeelLoop && phase->partial_peel(this, old_new)) { | |
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1607 // Partial peel succeeded so terminate this round of loop opts |
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1608 return false; |
0 | 1609 } |
1610 if( should_peel ) { // Should we peel? | |
1611 #ifndef PRODUCT | |
1612 if (PrintOpto) tty->print_cr("should_peel"); | |
1613 #endif | |
1614 phase->do_peeling(this,old_new); | |
1615 } else if( should_unswitch ) { | |
1616 phase->do_unswitching(this, old_new); | |
1617 } | |
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1618 return true; |
0 | 1619 } |
1620 CountedLoopNode *cl = _head->as_CountedLoop(); | |
1621 | |
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1622 if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops |
0 | 1623 |
1624 // Do nothing special to pre- and post- loops | |
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1625 if( cl->is_pre_loop() || cl->is_post_loop() ) return true; |
0 | 1626 |
1627 // Compute loop trip count from profile data | |
1628 compute_profile_trip_cnt(phase); | |
1629 | |
1630 // Before attempting fancy unrolling, RCE or alignment, see if we want | |
1631 // to completely unroll this loop or do loop unswitching. | |
1632 if( cl->is_normal_loop() ) { | |
1633 bool should_maximally_unroll = policy_maximally_unroll(phase); | |
1634 if( should_maximally_unroll ) { | |
1635 // Here we did some unrolling and peeling. Eventually we will | |
1636 // completely unroll this loop and it will no longer be a loop. | |
1637 phase->do_maximally_unroll(this,old_new); | |
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1638 return true; |
0 | 1639 } |
1640 if (should_unswitch) { | |
1641 phase->do_unswitching(this, old_new); | |
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1642 return true; |
0 | 1643 } |
1644 } | |
1645 | |
1646 | |
1647 // Counted loops may be peeled, may need some iterations run up | |
1648 // front for RCE, and may want to align loop refs to a cache | |
1649 // line. Thus we clone a full loop up front whose trip count is | |
1650 // at least 1 (if peeling), but may be several more. | |
1651 | |
1652 // The main loop will start cache-line aligned with at least 1 | |
1653 // iteration of the unrolled body (zero-trip test required) and | |
1654 // will have some range checks removed. | |
1655 | |
1656 // A post-loop will finish any odd iterations (leftover after | |
1657 // unrolling), plus any needed for RCE purposes. | |
1658 | |
1659 bool should_unroll = policy_unroll(phase); | |
1660 | |
1661 bool should_rce = policy_range_check(phase); | |
1662 | |
1663 bool should_align = policy_align(phase); | |
1664 | |
1665 // If not RCE'ing (iteration splitting) or Aligning, then we do not | |
1666 // need a pre-loop. We may still need to peel an initial iteration but | |
1667 // we will not be needing an unknown number of pre-iterations. | |
1668 // | |
1669 // Basically, if may_rce_align reports FALSE first time through, | |
1670 // we will not be able to later do RCE or Aligning on this loop. | |
1671 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align; | |
1672 | |
1673 // If we have any of these conditions (RCE, alignment, unrolling) met, then | |
1674 // we switch to the pre-/main-/post-loop model. This model also covers | |
1675 // peeling. | |
1676 if( should_rce || should_align || should_unroll ) { | |
1677 if( cl->is_normal_loop() ) // Convert to 'pre/main/post' loops | |
1678 phase->insert_pre_post_loops(this,old_new, !may_rce_align); | |
1679 | |
1680 // Adjust the pre- and main-loop limits to let the pre and post loops run | |
1681 // with full checks, but the main-loop with no checks. Remove said | |
1682 // checks from the main body. | |
1683 if( should_rce ) | |
1684 phase->do_range_check(this,old_new); | |
1685 | |
1686 // Double loop body for unrolling. Adjust the minimum-trip test (will do | |
1687 // twice as many iterations as before) and the main body limit (only do | |
1688 // an even number of trips). If we are peeling, we might enable some RCE | |
1689 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if | |
1690 // peeling. | |
1691 if( should_unroll && !should_peel ) | |
1692 phase->do_unroll(this,old_new, true); | |
1693 | |
1694 // Adjust the pre-loop limits to align the main body | |
1695 // iterations. | |
1696 if( should_align ) | |
1697 Unimplemented(); | |
1698 | |
1699 } else { // Else we have an unchanged counted loop | |
1700 if( should_peel ) // Might want to peel but do nothing else | |
1701 phase->do_peeling(this,old_new); | |
1702 } | |
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1703 return true; |
0 | 1704 } |
1705 | |
1706 | |
1707 //============================================================================= | |
1708 //------------------------------iteration_split-------------------------------- | |
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1709 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { |
0 | 1710 // Recursively iteration split nested loops |
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1711 if( _child && !_child->iteration_split( phase, old_new )) |
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1712 return false; |
0 | 1713 |
1714 // Clean out prior deadwood | |
1715 DCE_loop_body(); | |
1716 | |
1717 | |
1718 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage. | |
1719 // Replace with a 1-in-10 exit guess. | |
1720 if( _parent /*not the root loop*/ && | |
1721 !_irreducible && | |
1722 // Also ignore the occasional dead backedge | |
1723 !tail()->is_top() ) { | |
1724 adjust_loop_exit_prob(phase); | |
1725 } | |
1726 | |
1727 | |
1728 // Gate unrolling, RCE and peeling efforts. | |
1729 if( !_child && // If not an inner loop, do not split | |
1730 !_irreducible && | |
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1731 _allow_optimizations && |
0 | 1732 !tail()->is_top() ) { // Also ignore the occasional dead backedge |
1733 if (!_has_call) { | |
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1734 if (!iteration_split_impl( phase, old_new )) { |
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1735 return false; |
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1736 } |
0 | 1737 } else if (policy_unswitching(phase)) { |
1738 phase->do_unswitching(this, old_new); | |
1739 } | |
1740 } | |
1741 | |
1742 // Minor offset re-organization to remove loop-fallout uses of | |
1743 // trip counter. | |
1744 if( _head->is_CountedLoop() ) phase->reorg_offsets( this ); | |
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1745 if( _next && !_next->iteration_split( phase, old_new )) |
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1746 return false; |
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1747 return true; |
0 | 1748 } |