Wed, 29 Aug 2012 13:02:40 -0700
7160161: Missed safepoint in non-Counted loop
Summary: Do not remove safepoints during peeling optimization.
Reviewed-by: twisti
1 /*
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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"
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 }
54 //=============================================================================
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 }
66 //------------------------------compute_exact_trip_count-----------------------
67 // Compute loop exact trip count if possible. Do not recalculate trip count for
68 // split loops (pre-main-post) which have their limits and inits behind Opaque node.
69 void IdealLoopTree::compute_exact_trip_count( PhaseIdealLoop *phase ) {
70 if (!_head->as_Loop()->is_valid_counted_loop()) {
71 return;
72 }
73 CountedLoopNode* cl = _head->as_CountedLoop();
74 // Trip count may become nonexact for iteration split loops since
75 // RCE modifies limits. Note, _trip_count value is not reset since
76 // it is used to limit unrolling of main loop.
77 cl->set_nonexact_trip_count();
79 // Loop's test should be part of loop.
80 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
81 return; // Infinite loop
83 #ifdef ASSERT
84 BoolTest::mask bt = cl->loopexit()->test_trip();
85 assert(bt == BoolTest::lt || bt == BoolTest::gt ||
86 bt == BoolTest::ne, "canonical test is expected");
87 #endif
89 Node* init_n = cl->init_trip();
90 Node* limit_n = cl->limit();
91 if (init_n != NULL && init_n->is_Con() &&
92 limit_n != NULL && limit_n->is_Con()) {
93 // Use longs to avoid integer overflow.
94 int stride_con = cl->stride_con();
95 long init_con = cl->init_trip()->get_int();
96 long limit_con = cl->limit()->get_int();
97 int stride_m = stride_con - (stride_con > 0 ? 1 : -1);
98 long trip_count = (limit_con - init_con + stride_m)/stride_con;
99 if (trip_count > 0 && (julong)trip_count < (julong)max_juint) {
100 // Set exact trip count.
101 cl->set_exact_trip_count((uint)trip_count);
102 }
103 }
104 }
106 //------------------------------compute_profile_trip_cnt----------------------------
107 // Compute loop trip count from profile data as
108 // (backedge_count + loop_exit_count) / loop_exit_count
109 void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
110 if (!_head->is_CountedLoop()) {
111 return;
112 }
113 CountedLoopNode* head = _head->as_CountedLoop();
114 if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
115 return; // Already computed
116 }
117 float trip_cnt = (float)max_jint; // default is big
119 Node* back = head->in(LoopNode::LoopBackControl);
120 while (back != head) {
121 if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
122 back->in(0) &&
123 back->in(0)->is_If() &&
124 back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
125 back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
126 break;
127 }
128 back = phase->idom(back);
129 }
130 if (back != head) {
131 assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
132 back->in(0), "if-projection exists");
133 IfNode* back_if = back->in(0)->as_If();
134 float loop_back_cnt = back_if->_fcnt * back_if->_prob;
136 // Now compute a loop exit count
137 float loop_exit_cnt = 0.0f;
138 for( uint i = 0; i < _body.size(); i++ ) {
139 Node *n = _body[i];
140 if( n->is_If() ) {
141 IfNode *iff = n->as_If();
142 if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
143 Node *exit = is_loop_exit(iff);
144 if( exit ) {
145 float exit_prob = iff->_prob;
146 if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
147 if (exit_prob > PROB_MIN) {
148 float exit_cnt = iff->_fcnt * exit_prob;
149 loop_exit_cnt += exit_cnt;
150 }
151 }
152 }
153 }
154 }
155 if (loop_exit_cnt > 0.0f) {
156 trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
157 } else {
158 // No exit count so use
159 trip_cnt = loop_back_cnt;
160 }
161 }
162 #ifndef PRODUCT
163 if (TraceProfileTripCount) {
164 tty->print_cr("compute_profile_trip_cnt lp: %d cnt: %f\n", head->_idx, trip_cnt);
165 }
166 #endif
167 head->set_profile_trip_cnt(trip_cnt);
168 }
170 //---------------------is_invariant_addition-----------------------------
171 // Return nonzero index of invariant operand for an Add or Sub
172 // of (nonconstant) invariant and variant values. Helper for reassociate_invariants.
173 int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
174 int op = n->Opcode();
175 if (op == Op_AddI || op == Op_SubI) {
176 bool in1_invar = this->is_invariant(n->in(1));
177 bool in2_invar = this->is_invariant(n->in(2));
178 if (in1_invar && !in2_invar) return 1;
179 if (!in1_invar && in2_invar) return 2;
180 }
181 return 0;
182 }
184 //---------------------reassociate_add_sub-----------------------------
185 // Reassociate invariant add and subtract expressions:
186 //
187 // inv1 + (x + inv2) => ( inv1 + inv2) + x
188 // (x + inv2) + inv1 => ( inv1 + inv2) + x
189 // inv1 + (x - inv2) => ( inv1 - inv2) + x
190 // inv1 - (inv2 - x) => ( inv1 - inv2) + x
191 // (x + inv2) - inv1 => (-inv1 + inv2) + x
192 // (x - inv2) + inv1 => ( inv1 - inv2) + x
193 // (x - inv2) - inv1 => (-inv1 - inv2) + x
194 // inv1 + (inv2 - x) => ( inv1 + inv2) - x
195 // inv1 - (x - inv2) => ( inv1 + inv2) - x
196 // (inv2 - x) + inv1 => ( inv1 + inv2) - x
197 // (inv2 - x) - inv1 => (-inv1 + inv2) - x
198 // inv1 - (x + inv2) => ( inv1 - inv2) - x
199 //
200 Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
201 if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
202 if (is_invariant(n1)) return NULL;
203 int inv1_idx = is_invariant_addition(n1, phase);
204 if (!inv1_idx) return NULL;
205 // Don't mess with add of constant (igvn moves them to expression tree root.)
206 if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
207 Node* inv1 = n1->in(inv1_idx);
208 Node* n2 = n1->in(3 - inv1_idx);
209 int inv2_idx = is_invariant_addition(n2, phase);
210 if (!inv2_idx) return NULL;
211 Node* x = n2->in(3 - inv2_idx);
212 Node* inv2 = n2->in(inv2_idx);
214 bool neg_x = n2->is_Sub() && inv2_idx == 1;
215 bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
216 bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
217 if (n1->is_Sub() && inv1_idx == 1) {
218 neg_x = !neg_x;
219 neg_inv2 = !neg_inv2;
220 }
221 Node* inv1_c = phase->get_ctrl(inv1);
222 Node* inv2_c = phase->get_ctrl(inv2);
223 Node* n_inv1;
224 if (neg_inv1) {
225 Node *zero = phase->_igvn.intcon(0);
226 phase->set_ctrl(zero, phase->C->root());
227 n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
228 phase->register_new_node(n_inv1, inv1_c);
229 } else {
230 n_inv1 = inv1;
231 }
232 Node* inv;
233 if (neg_inv2) {
234 inv = new (phase->C, 3) SubINode(n_inv1, inv2);
235 } else {
236 inv = new (phase->C, 3) AddINode(n_inv1, inv2);
237 }
238 phase->register_new_node(inv, phase->get_early_ctrl(inv));
240 Node* addx;
241 if (neg_x) {
242 addx = new (phase->C, 3) SubINode(inv, x);
243 } else {
244 addx = new (phase->C, 3) AddINode(x, inv);
245 }
246 phase->register_new_node(addx, phase->get_ctrl(x));
247 phase->_igvn.replace_node(n1, addx);
248 assert(phase->get_loop(phase->get_ctrl(n1)) == this, "");
249 _body.yank(n1);
250 return addx;
251 }
253 //---------------------reassociate_invariants-----------------------------
254 // Reassociate invariant expressions:
255 void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
256 for (int i = _body.size() - 1; i >= 0; i--) {
257 Node *n = _body.at(i);
258 for (int j = 0; j < 5; j++) {
259 Node* nn = reassociate_add_sub(n, phase);
260 if (nn == NULL) break;
261 n = nn; // again
262 };
263 }
264 }
266 //------------------------------policy_peeling---------------------------------
267 // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
268 // make some loop-invariant test (usually a null-check) happen before the loop.
269 bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
270 Node *test = ((IdealLoopTree*)this)->tail();
271 int body_size = ((IdealLoopTree*)this)->_body.size();
272 int uniq = phase->C->unique();
273 // Peeling does loop cloning which can result in O(N^2) node construction
274 if( body_size > 255 /* Prevent overflow for large body_size */
275 || (body_size * body_size + uniq > MaxNodeLimit) ) {
276 return false; // too large to safely clone
277 }
278 while( test != _head ) { // Scan till run off top of loop
279 if( test->is_If() ) { // Test?
280 Node *ctrl = phase->get_ctrl(test->in(1));
281 if (ctrl->is_top())
282 return false; // Found dead test on live IF? No peeling!
283 // Standard IF only has one input value to check for loop invariance
284 assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
285 // Condition is not a member of this loop?
286 if( !is_member(phase->get_loop(ctrl)) &&
287 is_loop_exit(test) )
288 return true; // Found reason to peel!
289 }
290 // Walk up dominators to loop _head looking for test which is
291 // executed on every path thru loop.
292 test = phase->idom(test);
293 }
294 return false;
295 }
297 //------------------------------peeled_dom_test_elim---------------------------
298 // If we got the effect of peeling, either by actually peeling or by making
299 // a pre-loop which must execute at least once, we can remove all
300 // loop-invariant dominated tests in the main body.
301 void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
302 bool progress = true;
303 while( progress ) {
304 progress = false; // Reset for next iteration
305 Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
306 Node *test = prev->in(0);
307 while( test != loop->_head ) { // Scan till run off top of loop
309 int p_op = prev->Opcode();
310 if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
311 test->is_If() && // Test?
312 !test->in(1)->is_Con() && // And not already obvious?
313 // Condition is not a member of this loop?
314 !loop->is_member(get_loop(get_ctrl(test->in(1))))){
315 // Walk loop body looking for instances of this test
316 for( uint i = 0; i < loop->_body.size(); i++ ) {
317 Node *n = loop->_body.at(i);
318 if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
319 // IfNode was dominated by version in peeled loop body
320 progress = true;
321 dominated_by( old_new[prev->_idx], n );
322 }
323 }
324 }
325 prev = test;
326 test = idom(test);
327 } // End of scan tests in loop
329 } // End of while( progress )
330 }
332 //------------------------------do_peeling-------------------------------------
333 // Peel the first iteration of the given loop.
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 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
337 // Do this by making the old-loop fall-in edges act as if they came
338 // around the loopback from the prior iteration (follow the old-loop
339 // backedges) and then map to the new peeled iteration. This leaves
340 // the pre-loop with only 1 user (the new peeled iteration), but the
341 // peeled-loop backedge has 2 users.
342 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
343 // extra backedge user.
344 //
345 // orig
346 //
347 // stmt1
348 // |
349 // v
350 // loop predicate
351 // |
352 // v
353 // loop<----+
354 // | |
355 // stmt2 |
356 // | |
357 // v |
358 // if ^
359 // / \ |
360 // / \ |
361 // v v |
362 // false true |
363 // / \ |
364 // / ----+
365 // |
366 // v
367 // exit
368 //
369 //
370 // after clone loop
371 //
372 // stmt1
373 // |
374 // v
375 // loop predicate
376 // / \
377 // clone / \ orig
378 // / \
379 // / \
380 // v v
381 // +---->loop clone loop<----+
382 // | | | |
383 // | stmt2 clone stmt2 |
384 // | | | |
385 // | v v |
386 // ^ if clone If ^
387 // | / \ / \ |
388 // | / \ / \ |
389 // | v v v v |
390 // | true false false true |
391 // | / \ / \ |
392 // +---- \ / ----+
393 // \ /
394 // 1v v2
395 // region
396 // |
397 // v
398 // exit
399 //
400 //
401 // after peel and predicate move
402 //
403 // stmt1
404 // /
405 // /
406 // clone / orig
407 // /
408 // / +----------+
409 // / | |
410 // / loop predicate |
411 // / | |
412 // v v |
413 // TOP-->loop clone loop<----+ |
414 // | | | |
415 // stmt2 clone stmt2 | |
416 // | | | ^
417 // v v | |
418 // if clone If ^ |
419 // / \ / \ | |
420 // / \ / \ | |
421 // v v v v | |
422 // true false false true | |
423 // | \ / \ | |
424 // | \ / ----+ ^
425 // | \ / |
426 // | 1v v2 |
427 // v region |
428 // | | |
429 // | v |
430 // | exit |
431 // | |
432 // +--------------->-----------------+
433 //
434 //
435 // final graph
436 //
437 // stmt1
438 // |
439 // v
440 // stmt2 clone
441 // |
442 // v
443 // if clone
444 // / |
445 // / |
446 // v v
447 // false true
448 // | |
449 // | v
450 // | loop predicate
451 // | |
452 // | v
453 // | loop<----+
454 // | | |
455 // | stmt2 |
456 // | | |
457 // | v |
458 // v if ^
459 // | / \ |
460 // | / \ |
461 // | v v |
462 // | false true |
463 // | | \ |
464 // v v --+
465 // region
466 // |
467 // v
468 // exit
469 //
470 void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
472 C->set_major_progress();
473 // Peeling a 'main' loop in a pre/main/post situation obfuscates the
474 // 'pre' loop from the main and the 'pre' can no longer have it's
475 // iterations adjusted. Therefore, we need to declare this loop as
476 // no longer a 'main' loop; it will need new pre and post loops before
477 // we can do further RCE.
478 #ifndef PRODUCT
479 if (TraceLoopOpts) {
480 tty->print("Peel ");
481 loop->dump_head();
482 }
483 #endif
484 Node* head = loop->_head;
485 bool counted_loop = head->is_CountedLoop();
486 if (counted_loop) {
487 CountedLoopNode *cl = head->as_CountedLoop();
488 assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
489 cl->set_trip_count(cl->trip_count() - 1);
490 if (cl->is_main_loop()) {
491 cl->set_normal_loop();
492 #ifndef PRODUCT
493 if (PrintOpto && VerifyLoopOptimizations) {
494 tty->print("Peeling a 'main' loop; resetting to 'normal' ");
495 loop->dump_head();
496 }
497 #endif
498 }
499 }
500 Node* entry = head->in(LoopNode::EntryControl);
502 // Step 1: Clone the loop body. The clone becomes the peeled iteration.
503 // The pre-loop illegally has 2 control users (old & new loops).
504 clone_loop( loop, old_new, dom_depth(head) );
506 // Step 2: Make the old-loop fall-in edges point to the peeled iteration.
507 // Do this by making the old-loop fall-in edges act as if they came
508 // around the loopback from the prior iteration (follow the old-loop
509 // backedges) and then map to the new peeled iteration. This leaves
510 // the pre-loop with only 1 user (the new peeled iteration), but the
511 // peeled-loop backedge has 2 users.
512 Node* new_entry = old_new[head->in(LoopNode::LoopBackControl)->_idx];
513 _igvn.hash_delete(head);
514 head->set_req(LoopNode::EntryControl, new_entry);
515 for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
516 Node* old = head->fast_out(j);
517 if (old->in(0) == loop->_head && old->req() == 3 && old->is_Phi()) {
518 Node* new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
519 if (!new_exit_value ) // Backedge value is ALSO loop invariant?
520 // Then loop body backedge value remains the same.
521 new_exit_value = old->in(LoopNode::LoopBackControl);
522 _igvn.hash_delete(old);
523 old->set_req(LoopNode::EntryControl, new_exit_value);
524 }
525 }
528 // Step 3: Cut the backedge on the clone (so its not a loop) and remove the
529 // extra backedge user.
530 Node* new_head = old_new[head->_idx];
531 _igvn.hash_delete(new_head);
532 new_head->set_req(LoopNode::LoopBackControl, C->top());
533 for (DUIterator_Fast j2max, j2 = new_head->fast_outs(j2max); j2 < j2max; j2++) {
534 Node* use = new_head->fast_out(j2);
535 if (use->in(0) == new_head && use->req() == 3 && use->is_Phi()) {
536 _igvn.hash_delete(use);
537 use->set_req(LoopNode::LoopBackControl, C->top());
538 }
539 }
542 // Step 4: Correct dom-depth info. Set to loop-head depth.
543 int dd = dom_depth(head);
544 set_idom(head, head->in(1), dd);
545 for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
546 Node *old = loop->_body.at(j3);
547 Node *nnn = old_new[old->_idx];
548 if (!has_ctrl(nnn))
549 set_idom(nnn, idom(nnn), dd-1);
550 }
552 // Now force out all loop-invariant dominating tests. The optimizer
553 // finds some, but we _know_ they are all useless.
554 peeled_dom_test_elim(loop,old_new);
556 loop->record_for_igvn();
557 }
559 #define EMPTY_LOOP_SIZE 7 // number of nodes in an empty loop
561 //------------------------------policy_maximally_unroll------------------------
562 // Calculate exact loop trip count and return true if loop can be maximally
563 // unrolled.
564 bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
565 CountedLoopNode *cl = _head->as_CountedLoop();
566 assert(cl->is_normal_loop(), "");
567 if (!cl->is_valid_counted_loop())
568 return false; // Malformed counted loop
570 if (!cl->has_exact_trip_count()) {
571 // Trip count is not exact.
572 return false;
573 }
575 uint trip_count = cl->trip_count();
576 // Note, max_juint is used to indicate unknown trip count.
577 assert(trip_count > 1, "one iteration loop should be optimized out already");
578 assert(trip_count < max_juint, "exact trip_count should be less than max_uint.");
580 // Real policy: if we maximally unroll, does it get too big?
581 // Allow the unrolled mess to get larger than standard loop
582 // size. After all, it will no longer be a loop.
583 uint body_size = _body.size();
584 uint unroll_limit = (uint)LoopUnrollLimit * 4;
585 assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
586 if (trip_count > unroll_limit || body_size > unroll_limit) {
587 return false;
588 }
590 // Fully unroll a loop with few iterations regardless next
591 // conditions since following loop optimizations will split
592 // such loop anyway (pre-main-post).
593 if (trip_count <= 3)
594 return true;
596 // Take into account that after unroll conjoined heads and tails will fold,
597 // otherwise policy_unroll() may allow more unrolling than max unrolling.
598 uint new_body_size = EMPTY_LOOP_SIZE + (body_size - EMPTY_LOOP_SIZE) * trip_count;
599 uint tst_body_size = (new_body_size - EMPTY_LOOP_SIZE) / trip_count + EMPTY_LOOP_SIZE;
600 if (body_size != tst_body_size) // Check for int overflow
601 return false;
602 if (new_body_size > unroll_limit ||
603 // Unrolling can result in a large amount of node construction
604 new_body_size >= MaxNodeLimit - phase->C->unique()) {
605 return false;
606 }
608 // Do not unroll a loop with String intrinsics code.
609 // String intrinsics are large and have loops.
610 for (uint k = 0; k < _body.size(); k++) {
611 Node* n = _body.at(k);
612 switch (n->Opcode()) {
613 case Op_StrComp:
614 case Op_StrEquals:
615 case Op_StrIndexOf:
616 case Op_AryEq: {
617 return false;
618 }
619 } // switch
620 }
622 return true; // Do maximally unroll
623 }
626 #define MAX_UNROLL 16 // maximum number of unrolls for main loop
628 //------------------------------policy_unroll----------------------------------
629 // Return TRUE or FALSE if the loop should be unrolled or not. Unroll if
630 // the loop is a CountedLoop and the body is small enough.
631 bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
633 CountedLoopNode *cl = _head->as_CountedLoop();
634 assert(cl->is_normal_loop() || cl->is_main_loop(), "");
636 if (!cl->is_valid_counted_loop())
637 return false; // Malformed counted loop
639 // Protect against over-unrolling.
640 // After split at least one iteration will be executed in pre-loop.
641 if (cl->trip_count() <= (uint)(cl->is_normal_loop() ? 2 : 1)) return false;
643 int future_unroll_ct = cl->unrolled_count() * 2;
644 if (future_unroll_ct > MAX_UNROLL) return false;
646 // Check for initial stride being a small enough constant
647 if (abs(cl->stride_con()) > (1<<2)*future_unroll_ct) return false;
649 // Don't unroll if the next round of unrolling would push us
650 // over the expected trip count of the loop. One is subtracted
651 // from the expected trip count because the pre-loop normally
652 // executes 1 iteration.
653 if (UnrollLimitForProfileCheck > 0 &&
654 cl->profile_trip_cnt() != COUNT_UNKNOWN &&
655 future_unroll_ct > UnrollLimitForProfileCheck &&
656 (float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
657 return false;
658 }
660 // When unroll count is greater than LoopUnrollMin, don't unroll if:
661 // the residual iterations are more than 10% of the trip count
662 // and rounds of "unroll,optimize" are not making significant progress
663 // Progress defined as current size less than 20% larger than previous size.
664 if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
665 future_unroll_ct > LoopUnrollMin &&
666 (future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
667 1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
668 return false;
669 }
671 Node *init_n = cl->init_trip();
672 Node *limit_n = cl->limit();
673 int stride_con = cl->stride_con();
674 // Non-constant bounds.
675 // Protect against over-unrolling when init or/and limit are not constant
676 // (so that trip_count's init value is maxint) but iv range is known.
677 if (init_n == NULL || !init_n->is_Con() ||
678 limit_n == NULL || !limit_n->is_Con()) {
679 Node* phi = cl->phi();
680 if (phi != NULL) {
681 assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
682 const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
683 int next_stride = stride_con * 2; // stride after this unroll
684 if (next_stride > 0) {
685 if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
686 iv_type->_lo + next_stride > iv_type->_hi) {
687 return false; // over-unrolling
688 }
689 } else if (next_stride < 0) {
690 if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
691 iv_type->_hi + next_stride < iv_type->_lo) {
692 return false; // over-unrolling
693 }
694 }
695 }
696 }
698 // After unroll limit will be adjusted: new_limit = limit-stride.
699 // Bailout if adjustment overflow.
700 const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
701 if (stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi) ||
702 stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo))
703 return false; // overflow
705 // Adjust body_size to determine if we unroll or not
706 uint body_size = _body.size();
707 // Key test to unroll loop in CRC32 java code
708 int xors_in_loop = 0;
709 // Also count ModL, DivL and MulL which expand mightly
710 for (uint k = 0; k < _body.size(); k++) {
711 Node* n = _body.at(k);
712 switch (n->Opcode()) {
713 case Op_XorI: xors_in_loop++; break; // CRC32 java code
714 case Op_ModL: body_size += 30; break;
715 case Op_DivL: body_size += 30; break;
716 case Op_MulL: body_size += 10; break;
717 case Op_StrComp:
718 case Op_StrEquals:
719 case Op_StrIndexOf:
720 case Op_AryEq: {
721 // Do not unroll a loop with String intrinsics code.
722 // String intrinsics are large and have loops.
723 return false;
724 }
725 } // switch
726 }
728 // Check for being too big
729 if (body_size > (uint)LoopUnrollLimit) {
730 if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
731 // Normal case: loop too big
732 return false;
733 }
735 // Unroll once! (Each trip will soon do double iterations)
736 return true;
737 }
739 //------------------------------policy_align-----------------------------------
740 // Return TRUE or FALSE if the loop should be cache-line aligned. Gather the
741 // expression that does the alignment. Note that only one array base can be
742 // aligned in a loop (unless the VM guarantees mutual alignment). Note that
743 // if we vectorize short memory ops into longer memory ops, we may want to
744 // increase alignment.
745 bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
746 return false;
747 }
749 //------------------------------policy_range_check-----------------------------
750 // Return TRUE or FALSE if the loop should be range-check-eliminated.
751 // Actually we do iteration-splitting, a more powerful form of RCE.
752 bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
753 if (!RangeCheckElimination) return false;
755 CountedLoopNode *cl = _head->as_CountedLoop();
756 // If we unrolled with no intention of doing RCE and we later
757 // changed our minds, we got no pre-loop. Either we need to
758 // make a new pre-loop, or we gotta disallow RCE.
759 if (cl->is_main_no_pre_loop()) return false; // Disallowed for now.
760 Node *trip_counter = cl->phi();
762 // Check loop body for tests of trip-counter plus loop-invariant vs
763 // loop-invariant.
764 for (uint i = 0; i < _body.size(); i++) {
765 Node *iff = _body[i];
766 if (iff->Opcode() == Op_If) { // Test?
768 // Comparing trip+off vs limit
769 Node *bol = iff->in(1);
770 if (bol->req() != 2) continue; // dead constant test
771 if (!bol->is_Bool()) {
772 assert(UseLoopPredicate && bol->Opcode() == Op_Conv2B, "predicate check only");
773 continue;
774 }
775 if (bol->as_Bool()->_test._test == BoolTest::ne)
776 continue; // not RC
778 Node *cmp = bol->in(1);
780 Node *rc_exp = cmp->in(1);
781 Node *limit = cmp->in(2);
783 Node *limit_c = phase->get_ctrl(limit);
784 if( limit_c == phase->C->top() )
785 return false; // Found dead test on live IF? No RCE!
786 if( is_member(phase->get_loop(limit_c) ) ) {
787 // Compare might have operands swapped; commute them
788 rc_exp = cmp->in(2);
789 limit = cmp->in(1);
790 limit_c = phase->get_ctrl(limit);
791 if( is_member(phase->get_loop(limit_c) ) )
792 continue; // Both inputs are loop varying; cannot RCE
793 }
795 if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
796 continue;
797 }
798 // Yeah! Found a test like 'trip+off vs limit'
799 // Test is an IfNode, has 2 projections. If BOTH are in the loop
800 // we need loop unswitching instead of iteration splitting.
801 if( is_loop_exit(iff) )
802 return true; // Found reason to split iterations
803 } // End of is IF
804 }
806 return false;
807 }
809 //------------------------------policy_peel_only-------------------------------
810 // Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned. Useful
811 // for unrolling loops with NO array accesses.
812 bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
814 for( uint i = 0; i < _body.size(); i++ )
815 if( _body[i]->is_Mem() )
816 return false;
818 // No memory accesses at all!
819 return true;
820 }
822 //------------------------------clone_up_backedge_goo--------------------------
823 // If Node n lives in the back_ctrl block and cannot float, we clone a private
824 // version of n in preheader_ctrl block and return that, otherwise return n.
825 Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones ) {
826 if( get_ctrl(n) != back_ctrl ) return n;
828 // Only visit once
829 if (visited.test_set(n->_idx)) {
830 Node *x = clones.find(n->_idx);
831 if (x != NULL)
832 return x;
833 return n;
834 }
836 Node *x = NULL; // If required, a clone of 'n'
837 // Check for 'n' being pinned in the backedge.
838 if( n->in(0) && n->in(0) == back_ctrl ) {
839 assert(clones.find(n->_idx) == NULL, "dead loop");
840 x = n->clone(); // Clone a copy of 'n' to preheader
841 clones.push(x, n->_idx);
842 x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
843 }
845 // Recursive fixup any other input edges into x.
846 // If there are no changes we can just return 'n', otherwise
847 // we need to clone a private copy and change it.
848 for( uint i = 1; i < n->req(); i++ ) {
849 Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i), visited, clones );
850 if( g != n->in(i) ) {
851 if( !x ) {
852 assert(clones.find(n->_idx) == NULL, "dead loop");
853 x = n->clone();
854 clones.push(x, n->_idx);
855 }
856 x->set_req(i, g);
857 }
858 }
859 if( x ) { // x can legally float to pre-header location
860 register_new_node( x, preheader_ctrl );
861 return x;
862 } else { // raise n to cover LCA of uses
863 set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
864 }
865 return n;
866 }
868 //------------------------------insert_pre_post_loops--------------------------
869 // Insert pre and post loops. If peel_only is set, the pre-loop can not have
870 // more iterations added. It acts as a 'peel' only, no lower-bound RCE, no
871 // alignment. Useful to unroll loops that do no array accesses.
872 void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
874 #ifndef PRODUCT
875 if (TraceLoopOpts) {
876 if (peel_only)
877 tty->print("PeelMainPost ");
878 else
879 tty->print("PreMainPost ");
880 loop->dump_head();
881 }
882 #endif
883 C->set_major_progress();
885 // Find common pieces of the loop being guarded with pre & post loops
886 CountedLoopNode *main_head = loop->_head->as_CountedLoop();
887 assert( main_head->is_normal_loop(), "" );
888 CountedLoopEndNode *main_end = main_head->loopexit();
889 assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
890 uint dd_main_head = dom_depth(main_head);
891 uint max = main_head->outcnt();
893 Node *pre_header= main_head->in(LoopNode::EntryControl);
894 Node *init = main_head->init_trip();
895 Node *incr = main_end ->incr();
896 Node *limit = main_end ->limit();
897 Node *stride = main_end ->stride();
898 Node *cmp = main_end ->cmp_node();
899 BoolTest::mask b_test = main_end->test_trip();
901 // Need only 1 user of 'bol' because I will be hacking the loop bounds.
902 Node *bol = main_end->in(CountedLoopEndNode::TestValue);
903 if( bol->outcnt() != 1 ) {
904 bol = bol->clone();
905 register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
906 _igvn.hash_delete(main_end);
907 main_end->set_req(CountedLoopEndNode::TestValue, bol);
908 }
909 // Need only 1 user of 'cmp' because I will be hacking the loop bounds.
910 if( cmp->outcnt() != 1 ) {
911 cmp = cmp->clone();
912 register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
913 _igvn.hash_delete(bol);
914 bol->set_req(1, cmp);
915 }
917 //------------------------------
918 // Step A: Create Post-Loop.
919 Node* main_exit = main_end->proj_out(false);
920 assert( main_exit->Opcode() == Op_IfFalse, "" );
921 int dd_main_exit = dom_depth(main_exit);
923 // Step A1: Clone the loop body. The clone becomes the post-loop. The main
924 // loop pre-header illegally has 2 control users (old & new loops).
925 clone_loop( loop, old_new, dd_main_exit );
926 assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
927 CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
928 post_head->set_post_loop(main_head);
930 // Reduce the post-loop trip count.
931 CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
932 post_end->_prob = PROB_FAIR;
934 // Build the main-loop normal exit.
935 IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
936 _igvn.register_new_node_with_optimizer( new_main_exit );
937 set_idom(new_main_exit, main_end, dd_main_exit );
938 set_loop(new_main_exit, loop->_parent);
940 // Step A2: Build a zero-trip guard for the post-loop. After leaving the
941 // main-loop, the post-loop may not execute at all. We 'opaque' the incr
942 // (the main-loop trip-counter exit value) because we will be changing
943 // the exit value (via unrolling) so we cannot constant-fold away the zero
944 // trip guard until all unrolling is done.
945 Node *zer_opaq = new (C, 2) Opaque1Node(C, incr);
946 Node *zer_cmp = new (C, 3) CmpINode( zer_opaq, limit );
947 Node *zer_bol = new (C, 2) BoolNode( zer_cmp, b_test );
948 register_new_node( zer_opaq, new_main_exit );
949 register_new_node( zer_cmp , new_main_exit );
950 register_new_node( zer_bol , new_main_exit );
952 // Build the IfNode
953 IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
954 _igvn.register_new_node_with_optimizer( zer_iff );
955 set_idom(zer_iff, new_main_exit, dd_main_exit);
956 set_loop(zer_iff, loop->_parent);
958 // Plug in the false-path, taken if we need to skip post-loop
959 _igvn.replace_input_of(main_exit, 0, zer_iff);
960 set_idom(main_exit, zer_iff, dd_main_exit);
961 set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
962 // Make the true-path, must enter the post loop
963 Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
964 _igvn.register_new_node_with_optimizer( zer_taken );
965 set_idom(zer_taken, zer_iff, dd_main_exit);
966 set_loop(zer_taken, loop->_parent);
967 // Plug in the true path
968 _igvn.hash_delete( post_head );
969 post_head->set_req(LoopNode::EntryControl, zer_taken);
970 set_idom(post_head, zer_taken, dd_main_exit);
972 Arena *a = Thread::current()->resource_area();
973 VectorSet visited(a);
974 Node_Stack clones(a, main_head->back_control()->outcnt());
975 // Step A3: Make the fall-in values to the post-loop come from the
976 // fall-out values of the main-loop.
977 for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
978 Node* main_phi = main_head->fast_out(i);
979 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
980 Node *post_phi = old_new[main_phi->_idx];
981 Node *fallmain = clone_up_backedge_goo(main_head->back_control(),
982 post_head->init_control(),
983 main_phi->in(LoopNode::LoopBackControl),
984 visited, clones);
985 _igvn.hash_delete(post_phi);
986 post_phi->set_req( LoopNode::EntryControl, fallmain );
987 }
988 }
990 // Update local caches for next stanza
991 main_exit = new_main_exit;
994 //------------------------------
995 // Step B: Create Pre-Loop.
997 // Step B1: Clone the loop body. The clone becomes the pre-loop. The main
998 // loop pre-header illegally has 2 control users (old & new loops).
999 clone_loop( loop, old_new, dd_main_head );
1000 CountedLoopNode* pre_head = old_new[main_head->_idx]->as_CountedLoop();
1001 CountedLoopEndNode* pre_end = old_new[main_end ->_idx]->as_CountedLoopEnd();
1002 pre_head->set_pre_loop(main_head);
1003 Node *pre_incr = old_new[incr->_idx];
1005 // Reduce the pre-loop trip count.
1006 pre_end->_prob = PROB_FAIR;
1008 // Find the pre-loop normal exit.
1009 Node* pre_exit = pre_end->proj_out(false);
1010 assert( pre_exit->Opcode() == Op_IfFalse, "" );
1011 IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
1012 _igvn.register_new_node_with_optimizer( new_pre_exit );
1013 set_idom(new_pre_exit, pre_end, dd_main_head);
1014 set_loop(new_pre_exit, loop->_parent);
1016 // Step B2: Build a zero-trip guard for the main-loop. After leaving the
1017 // pre-loop, the main-loop may not execute at all. Later in life this
1018 // zero-trip guard will become the minimum-trip guard when we unroll
1019 // the main-loop.
1020 Node *min_opaq = new (C, 2) Opaque1Node(C, limit);
1021 Node *min_cmp = new (C, 3) CmpINode( pre_incr, min_opaq );
1022 Node *min_bol = new (C, 2) BoolNode( min_cmp, b_test );
1023 register_new_node( min_opaq, new_pre_exit );
1024 register_new_node( min_cmp , new_pre_exit );
1025 register_new_node( min_bol , new_pre_exit );
1027 // Build the IfNode (assume the main-loop is executed always).
1028 IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, COUNT_UNKNOWN );
1029 _igvn.register_new_node_with_optimizer( min_iff );
1030 set_idom(min_iff, new_pre_exit, dd_main_head);
1031 set_loop(min_iff, loop->_parent);
1033 // Plug in the false-path, taken if we need to skip main-loop
1034 _igvn.hash_delete( pre_exit );
1035 pre_exit->set_req(0, min_iff);
1036 set_idom(pre_exit, min_iff, dd_main_head);
1037 set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
1038 // Make the true-path, must enter the main loop
1039 Node *min_taken = new (C, 1) IfTrueNode( min_iff );
1040 _igvn.register_new_node_with_optimizer( min_taken );
1041 set_idom(min_taken, min_iff, dd_main_head);
1042 set_loop(min_taken, loop->_parent);
1043 // Plug in the true path
1044 _igvn.hash_delete( main_head );
1045 main_head->set_req(LoopNode::EntryControl, min_taken);
1046 set_idom(main_head, min_taken, dd_main_head);
1048 visited.Clear();
1049 clones.clear();
1050 // Step B3: Make the fall-in values to the main-loop come from the
1051 // fall-out values of the pre-loop.
1052 for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
1053 Node* main_phi = main_head->fast_out(i2);
1054 if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
1055 Node *pre_phi = old_new[main_phi->_idx];
1056 Node *fallpre = clone_up_backedge_goo(pre_head->back_control(),
1057 main_head->init_control(),
1058 pre_phi->in(LoopNode::LoopBackControl),
1059 visited, clones);
1060 _igvn.hash_delete(main_phi);
1061 main_phi->set_req( LoopNode::EntryControl, fallpre );
1062 }
1063 }
1065 // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
1066 // RCE and alignment may change this later.
1067 Node *cmp_end = pre_end->cmp_node();
1068 assert( cmp_end->in(2) == limit, "" );
1069 Node *pre_limit = new (C, 3) AddINode( init, stride );
1071 // Save the original loop limit in this Opaque1 node for
1072 // use by range check elimination.
1073 Node *pre_opaq = new (C, 3) Opaque1Node(C, pre_limit, limit);
1075 register_new_node( pre_limit, pre_head->in(0) );
1076 register_new_node( pre_opaq , pre_head->in(0) );
1078 // Since no other users of pre-loop compare, I can hack limit directly
1079 assert( cmp_end->outcnt() == 1, "no other users" );
1080 _igvn.hash_delete(cmp_end);
1081 cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
1083 // Special case for not-equal loop bounds:
1084 // Change pre loop test, main loop test, and the
1085 // main loop guard test to use lt or gt depending on stride
1086 // direction:
1087 // positive stride use <
1088 // negative stride use >
1089 //
1090 // not-equal test is kept for post loop to handle case
1091 // when init > limit when stride > 0 (and reverse).
1093 if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
1095 BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
1096 // Modify pre loop end condition
1097 Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1098 BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
1099 register_new_node( new_bol0, pre_head->in(0) );
1100 _igvn.hash_delete(pre_end);
1101 pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
1102 // Modify main loop guard condition
1103 assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
1104 BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
1105 register_new_node( new_bol1, new_pre_exit );
1106 _igvn.hash_delete(min_iff);
1107 min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
1108 // Modify main loop end condition
1109 BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
1110 BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
1111 register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
1112 _igvn.hash_delete(main_end);
1113 main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
1114 }
1116 // Flag main loop
1117 main_head->set_main_loop();
1118 if( peel_only ) main_head->set_main_no_pre_loop();
1120 // Subtract a trip count for the pre-loop.
1121 main_head->set_trip_count(main_head->trip_count() - 1);
1123 // It's difficult to be precise about the trip-counts
1124 // for the pre/post loops. They are usually very short,
1125 // so guess that 4 trips is a reasonable value.
1126 post_head->set_profile_trip_cnt(4.0);
1127 pre_head->set_profile_trip_cnt(4.0);
1129 // Now force out all loop-invariant dominating tests. The optimizer
1130 // finds some, but we _know_ they are all useless.
1131 peeled_dom_test_elim(loop,old_new);
1132 }
1134 //------------------------------is_invariant-----------------------------
1135 // Return true if n is invariant
1136 bool IdealLoopTree::is_invariant(Node* n) const {
1137 Node *n_c = _phase->has_ctrl(n) ? _phase->get_ctrl(n) : n;
1138 if (n_c->is_top()) return false;
1139 return !is_member(_phase->get_loop(n_c));
1140 }
1143 //------------------------------do_unroll--------------------------------------
1144 // Unroll the loop body one step - make each trip do 2 iterations.
1145 void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
1146 assert(LoopUnrollLimit, "");
1147 CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
1148 CountedLoopEndNode *loop_end = loop_head->loopexit();
1149 assert(loop_end, "");
1150 #ifndef PRODUCT
1151 if (PrintOpto && VerifyLoopOptimizations) {
1152 tty->print("Unrolling ");
1153 loop->dump_head();
1154 } else if (TraceLoopOpts) {
1155 if (loop_head->trip_count() < (uint)LoopUnrollLimit) {
1156 tty->print("Unroll %d(%2d) ", loop_head->unrolled_count()*2, loop_head->trip_count());
1157 } else {
1158 tty->print("Unroll %d ", loop_head->unrolled_count()*2);
1159 }
1160 loop->dump_head();
1161 }
1162 #endif
1164 // Remember loop node count before unrolling to detect
1165 // if rounds of unroll,optimize are making progress
1166 loop_head->set_node_count_before_unroll(loop->_body.size());
1168 Node *ctrl = loop_head->in(LoopNode::EntryControl);
1169 Node *limit = loop_head->limit();
1170 Node *init = loop_head->init_trip();
1171 Node *stride = loop_head->stride();
1173 Node *opaq = NULL;
1174 if (adjust_min_trip) { // If not maximally unrolling, need adjustment
1175 // Search for zero-trip guard.
1176 assert( loop_head->is_main_loop(), "" );
1177 assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
1178 Node *iff = ctrl->in(0);
1179 assert( iff->Opcode() == Op_If, "" );
1180 Node *bol = iff->in(1);
1181 assert( bol->Opcode() == Op_Bool, "" );
1182 Node *cmp = bol->in(1);
1183 assert( cmp->Opcode() == Op_CmpI, "" );
1184 opaq = cmp->in(2);
1185 // Occasionally it's possible for a zero-trip guard Opaque1 node to be
1186 // optimized away and then another round of loop opts attempted.
1187 // We can not optimize this particular loop in that case.
1188 if (opaq->Opcode() != Op_Opaque1)
1189 return; // Cannot find zero-trip guard! Bail out!
1190 // Zero-trip test uses an 'opaque' node which is not shared.
1191 assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
1192 }
1194 C->set_major_progress();
1196 Node* new_limit = NULL;
1197 if (UnrollLimitCheck) {
1198 int stride_con = stride->get_int();
1199 int stride_p = (stride_con > 0) ? stride_con : -stride_con;
1200 uint old_trip_count = loop_head->trip_count();
1201 // Verify that unroll policy result is still valid.
1202 assert(old_trip_count > 1 &&
1203 (!adjust_min_trip || stride_p <= (1<<3)*loop_head->unrolled_count()), "sanity");
1205 // Adjust loop limit to keep valid iterations number after unroll.
1206 // Use (limit - stride) instead of (((limit - init)/stride) & (-2))*stride
1207 // which may overflow.
1208 if (!adjust_min_trip) {
1209 assert(old_trip_count > 1 && (old_trip_count & 1) == 0,
1210 "odd trip count for maximally unroll");
1211 // Don't need to adjust limit for maximally unroll since trip count is even.
1212 } else if (loop_head->has_exact_trip_count() && init->is_Con()) {
1213 // Loop's limit is constant. Loop's init could be constant when pre-loop
1214 // become peeled iteration.
1215 long init_con = init->get_int();
1216 // We can keep old loop limit if iterations count stays the same:
1217 // old_trip_count == new_trip_count * 2
1218 // Note: since old_trip_count >= 2 then new_trip_count >= 1
1219 // so we also don't need to adjust zero trip test.
1220 long limit_con = limit->get_int();
1221 // (stride_con*2) not overflow since stride_con <= 8.
1222 int new_stride_con = stride_con * 2;
1223 int stride_m = new_stride_con - (stride_con > 0 ? 1 : -1);
1224 long trip_count = (limit_con - init_con + stride_m)/new_stride_con;
1225 // New trip count should satisfy next conditions.
1226 assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
1227 uint new_trip_count = (uint)trip_count;
1228 adjust_min_trip = (old_trip_count != new_trip_count*2);
1229 }
1231 if (adjust_min_trip) {
1232 // Step 2: Adjust the trip limit if it is called for.
1233 // The adjustment amount is -stride. Need to make sure if the
1234 // adjustment underflows or overflows, then the main loop is skipped.
1235 Node* cmp = loop_end->cmp_node();
1236 assert(cmp->in(2) == limit, "sanity");
1237 assert(opaq != NULL && opaq->in(1) == limit, "sanity");
1239 // Verify that policy_unroll result is still valid.
1240 const TypeInt* limit_type = _igvn.type(limit)->is_int();
1241 assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) ||
1242 stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), "sanity");
1244 if (limit->is_Con()) {
1245 // The check in policy_unroll and the assert above guarantee
1246 // no underflow if limit is constant.
1247 new_limit = _igvn.intcon(limit->get_int() - stride_con);
1248 set_ctrl(new_limit, C->root());
1249 } else {
1250 // Limit is not constant.
1251 if (loop_head->unrolled_count() == 1) { // only for first unroll
1252 // Separate limit by Opaque node in case it is an incremented
1253 // variable from previous loop to avoid using pre-incremented
1254 // value which could increase register pressure.
1255 // Otherwise reorg_offsets() optimization will create a separate
1256 // Opaque node for each use of trip-counter and as result
1257 // zero trip guard limit will be different from loop limit.
1258 assert(has_ctrl(opaq), "should have it");
1259 Node* opaq_ctrl = get_ctrl(opaq);
1260 limit = new (C, 2) Opaque2Node( C, limit );
1261 register_new_node( limit, opaq_ctrl );
1262 }
1263 if (stride_con > 0 && ((limit_type->_lo - stride_con) < limit_type->_lo) ||
1264 stride_con < 0 && ((limit_type->_hi - stride_con) > limit_type->_hi)) {
1265 // No underflow.
1266 new_limit = new (C, 3) SubINode(limit, stride);
1267 } else {
1268 // (limit - stride) may underflow.
1269 // Clamp the adjustment value with MININT or MAXINT:
1270 //
1271 // new_limit = limit-stride
1272 // if (stride > 0)
1273 // new_limit = (limit < new_limit) ? MININT : new_limit;
1274 // else
1275 // new_limit = (limit > new_limit) ? MAXINT : new_limit;
1276 //
1277 BoolTest::mask bt = loop_end->test_trip();
1278 assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
1279 Node* adj_max = _igvn.intcon((stride_con > 0) ? min_jint : max_jint);
1280 set_ctrl(adj_max, C->root());
1281 Node* old_limit = NULL;
1282 Node* adj_limit = NULL;
1283 Node* bol = limit->is_CMove() ? limit->in(CMoveNode::Condition) : NULL;
1284 if (loop_head->unrolled_count() > 1 &&
1285 limit->is_CMove() && limit->Opcode() == Op_CMoveI &&
1286 limit->in(CMoveNode::IfTrue) == adj_max &&
1287 bol->as_Bool()->_test._test == bt &&
1288 bol->in(1)->Opcode() == Op_CmpI &&
1289 bol->in(1)->in(2) == limit->in(CMoveNode::IfFalse)) {
1290 // Loop was unrolled before.
1291 // Optimize the limit to avoid nested CMove:
1292 // use original limit as old limit.
1293 old_limit = bol->in(1)->in(1);
1294 // Adjust previous adjusted limit.
1295 adj_limit = limit->in(CMoveNode::IfFalse);
1296 adj_limit = new (C, 3) SubINode(adj_limit, stride);
1297 } else {
1298 old_limit = limit;
1299 adj_limit = new (C, 3) SubINode(limit, stride);
1300 }
1301 assert(old_limit != NULL && adj_limit != NULL, "");
1302 register_new_node( adj_limit, ctrl ); // adjust amount
1303 Node* adj_cmp = new (C, 3) CmpINode(old_limit, adj_limit);
1304 register_new_node( adj_cmp, ctrl );
1305 Node* adj_bool = new (C, 2) BoolNode(adj_cmp, bt);
1306 register_new_node( adj_bool, ctrl );
1307 new_limit = new (C, 4) CMoveINode(adj_bool, adj_limit, adj_max, TypeInt::INT);
1308 }
1309 register_new_node(new_limit, ctrl);
1310 }
1311 assert(new_limit != NULL, "");
1312 // Replace in loop test.
1313 assert(loop_end->in(1)->in(1) == cmp, "sanity");
1314 if (cmp->outcnt() == 1 && loop_end->in(1)->outcnt() == 1) {
1315 // Don't need to create new test since only one user.
1316 _igvn.hash_delete(cmp);
1317 cmp->set_req(2, new_limit);
1318 } else {
1319 // Create new test since it is shared.
1320 Node* ctrl2 = loop_end->in(0);
1321 Node* cmp2 = cmp->clone();
1322 cmp2->set_req(2, new_limit);
1323 register_new_node(cmp2, ctrl2);
1324 Node* bol2 = loop_end->in(1)->clone();
1325 bol2->set_req(1, cmp2);
1326 register_new_node(bol2, ctrl2);
1327 _igvn.hash_delete(loop_end);
1328 loop_end->set_req(1, bol2);
1329 }
1330 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1331 // Make it a 1-trip test (means at least 2 trips).
1333 // Guard test uses an 'opaque' node which is not shared. Hence I
1334 // can edit it's inputs directly. Hammer in the new limit for the
1335 // minimum-trip guard.
1336 assert(opaq->outcnt() == 1, "");
1337 _igvn.hash_delete(opaq);
1338 opaq->set_req(1, new_limit);
1339 }
1341 // Adjust max trip count. The trip count is intentionally rounded
1342 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1343 // the main, unrolled, part of the loop will never execute as it is protected
1344 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1345 // and later determined that part of the unrolled loop was dead.
1346 loop_head->set_trip_count(old_trip_count / 2);
1348 // Double the count of original iterations in the unrolled loop body.
1349 loop_head->double_unrolled_count();
1351 } else { // LoopLimitCheck
1353 // Adjust max trip count. The trip count is intentionally rounded
1354 // down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
1355 // the main, unrolled, part of the loop will never execute as it is protected
1356 // by the min-trip test. See bug 4834191 for a case where we over-unrolled
1357 // and later determined that part of the unrolled loop was dead.
1358 loop_head->set_trip_count(loop_head->trip_count() / 2);
1360 // Double the count of original iterations in the unrolled loop body.
1361 loop_head->double_unrolled_count();
1363 // -----------
1364 // Step 2: Cut back the trip counter for an unroll amount of 2.
1365 // Loop will normally trip (limit - init)/stride_con. Since it's a
1366 // CountedLoop this is exact (stride divides limit-init exactly).
1367 // We are going to double the loop body, so we want to knock off any
1368 // odd iteration: (trip_cnt & ~1). Then back compute a new limit.
1369 Node *span = new (C, 3) SubINode( limit, init );
1370 register_new_node( span, ctrl );
1371 Node *trip = new (C, 3) DivINode( 0, span, stride );
1372 register_new_node( trip, ctrl );
1373 Node *mtwo = _igvn.intcon(-2);
1374 set_ctrl(mtwo, C->root());
1375 Node *rond = new (C, 3) AndINode( trip, mtwo );
1376 register_new_node( rond, ctrl );
1377 Node *spn2 = new (C, 3) MulINode( rond, stride );
1378 register_new_node( spn2, ctrl );
1379 new_limit = new (C, 3) AddINode( spn2, init );
1380 register_new_node( new_limit, ctrl );
1382 // Hammer in the new limit
1383 Node *ctrl2 = loop_end->in(0);
1384 Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), new_limit );
1385 register_new_node( cmp2, ctrl2 );
1386 Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
1387 register_new_node( bol2, ctrl2 );
1388 _igvn.hash_delete(loop_end);
1389 loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
1391 // Step 3: Find the min-trip test guaranteed before a 'main' loop.
1392 // Make it a 1-trip test (means at least 2 trips).
1393 if( adjust_min_trip ) {
1394 assert( new_limit != NULL, "" );
1395 // Guard test uses an 'opaque' node which is not shared. Hence I
1396 // can edit it's inputs directly. Hammer in the new limit for the
1397 // minimum-trip guard.
1398 assert( opaq->outcnt() == 1, "" );
1399 _igvn.hash_delete(opaq);
1400 opaq->set_req(1, new_limit);
1401 }
1402 } // LoopLimitCheck
1404 // ---------
1405 // Step 4: Clone the loop body. Move it inside the loop. This loop body
1406 // represents the odd iterations; since the loop trips an even number of
1407 // times its backedge is never taken. Kill the backedge.
1408 uint dd = dom_depth(loop_head);
1409 clone_loop( loop, old_new, dd );
1411 // Make backedges of the clone equal to backedges of the original.
1412 // Make the fall-in from the original come from the fall-out of the clone.
1413 for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
1414 Node* phi = loop_head->fast_out(j);
1415 if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
1416 Node *newphi = old_new[phi->_idx];
1417 _igvn.hash_delete( phi );
1418 _igvn.hash_delete( newphi );
1420 phi ->set_req(LoopNode:: EntryControl, newphi->in(LoopNode::LoopBackControl));
1421 newphi->set_req(LoopNode::LoopBackControl, phi ->in(LoopNode::LoopBackControl));
1422 phi ->set_req(LoopNode::LoopBackControl, C->top());
1423 }
1424 }
1425 Node *clone_head = old_new[loop_head->_idx];
1426 _igvn.hash_delete( clone_head );
1427 loop_head ->set_req(LoopNode:: EntryControl, clone_head->in(LoopNode::LoopBackControl));
1428 clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
1429 loop_head ->set_req(LoopNode::LoopBackControl, C->top());
1430 loop->_head = clone_head; // New loop header
1432 set_idom(loop_head, loop_head ->in(LoopNode::EntryControl), dd);
1433 set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
1435 // Kill the clone's backedge
1436 Node *newcle = old_new[loop_end->_idx];
1437 _igvn.hash_delete( newcle );
1438 Node *one = _igvn.intcon(1);
1439 set_ctrl(one, C->root());
1440 newcle->set_req(1, one);
1441 // Force clone into same loop body
1442 uint max = loop->_body.size();
1443 for( uint k = 0; k < max; k++ ) {
1444 Node *old = loop->_body.at(k);
1445 Node *nnn = old_new[old->_idx];
1446 loop->_body.push(nnn);
1447 if (!has_ctrl(old))
1448 set_loop(nnn, loop);
1449 }
1451 loop->record_for_igvn();
1452 }
1454 //------------------------------do_maximally_unroll----------------------------
1456 void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
1457 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1458 assert(cl->has_exact_trip_count(), "trip count is not exact");
1459 assert(cl->trip_count() > 0, "");
1460 #ifndef PRODUCT
1461 if (TraceLoopOpts) {
1462 tty->print("MaxUnroll %d ", cl->trip_count());
1463 loop->dump_head();
1464 }
1465 #endif
1467 // If loop is tripping an odd number of times, peel odd iteration
1468 if ((cl->trip_count() & 1) == 1) {
1469 do_peeling(loop, old_new);
1470 }
1472 // Now its tripping an even number of times remaining. Double loop body.
1473 // Do not adjust pre-guards; they are not needed and do not exist.
1474 if (cl->trip_count() > 0) {
1475 assert((cl->trip_count() & 1) == 0, "missed peeling");
1476 do_unroll(loop, old_new, false);
1477 }
1478 }
1480 //------------------------------dominates_backedge---------------------------------
1481 // Returns true if ctrl is executed on every complete iteration
1482 bool IdealLoopTree::dominates_backedge(Node* ctrl) {
1483 assert(ctrl->is_CFG(), "must be control");
1484 Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
1485 return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
1486 }
1488 //------------------------------adjust_limit-----------------------------------
1489 // Helper function for add_constraint().
1490 Node* PhaseIdealLoop::adjust_limit(int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl) {
1491 // Compute "I :: (limit-offset)/scale"
1492 Node *con = new (C, 3) SubINode(rc_limit, offset);
1493 register_new_node(con, pre_ctrl);
1494 Node *X = new (C, 3) DivINode(0, con, scale);
1495 register_new_node(X, pre_ctrl);
1497 // Adjust loop limit
1498 loop_limit = (stride_con > 0)
1499 ? (Node*)(new (C, 3) MinINode(loop_limit, X))
1500 : (Node*)(new (C, 3) MaxINode(loop_limit, X));
1501 register_new_node(loop_limit, pre_ctrl);
1502 return loop_limit;
1503 }
1505 //------------------------------add_constraint---------------------------------
1506 // Constrain the main loop iterations so the conditions:
1507 // low_limit <= scale_con * I + offset < upper_limit
1508 // always holds true. That is, either increase the number of iterations in
1509 // the pre-loop or the post-loop until the condition holds true in the main
1510 // loop. Stride, scale, offset and limit are all loop invariant. Further,
1511 // stride and scale are constants (offset and limit often are).
1512 void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *low_limit, Node *upper_limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
1513 // For positive stride, the pre-loop limit always uses a MAX function
1514 // and the main loop a MIN function. For negative stride these are
1515 // reversed.
1517 // Also for positive stride*scale the affine function is increasing, so the
1518 // pre-loop must check for underflow and the post-loop for overflow.
1519 // Negative stride*scale reverses this; pre-loop checks for overflow and
1520 // post-loop for underflow.
1522 Node *scale = _igvn.intcon(scale_con);
1523 set_ctrl(scale, C->root());
1525 if ((stride_con^scale_con) >= 0) { // Use XOR to avoid overflow
1526 // The overflow limit: scale*I+offset < upper_limit
1527 // For main-loop compute
1528 // ( if (scale > 0) /* and stride > 0 */
1529 // I < (upper_limit-offset)/scale
1530 // else /* scale < 0 and stride < 0 */
1531 // I > (upper_limit-offset)/scale
1532 // )
1533 //
1534 // (upper_limit-offset) may overflow or underflow.
1535 // But it is fine since main loop will either have
1536 // less iterations or will be skipped in such case.
1537 *main_limit = adjust_limit(stride_con, scale, offset, upper_limit, *main_limit, pre_ctrl);
1539 // The underflow limit: low_limit <= scale*I+offset.
1540 // For pre-loop compute
1541 // NOT(scale*I+offset >= low_limit)
1542 // scale*I+offset < low_limit
1543 // ( if (scale > 0) /* and stride > 0 */
1544 // I < (low_limit-offset)/scale
1545 // else /* scale < 0 and stride < 0 */
1546 // I > (low_limit-offset)/scale
1547 // )
1549 if (low_limit->get_int() == -max_jint) {
1550 if (!RangeLimitCheck) return;
1551 // We need this guard when scale*pre_limit+offset >= limit
1552 // due to underflow. So we need execute pre-loop until
1553 // scale*I+offset >= min_int. But (min_int-offset) will
1554 // underflow when offset > 0 and X will be > original_limit
1555 // when stride > 0. To avoid it we replace positive offset with 0.
1556 //
1557 // Also (min_int+1 == -max_int) is used instead of min_int here
1558 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1559 Node* shift = _igvn.intcon(31);
1560 set_ctrl(shift, C->root());
1561 Node* sign = new (C, 3) RShiftINode(offset, shift);
1562 register_new_node(sign, pre_ctrl);
1563 offset = new (C, 3) AndINode(offset, sign);
1564 register_new_node(offset, pre_ctrl);
1565 } else {
1566 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1567 // The only problem we have here when offset == min_int
1568 // since (0-min_int) == min_int. It may be fine for stride > 0
1569 // but for stride < 0 X will be < original_limit. To avoid it
1570 // max(pre_limit, original_limit) is used in do_range_check().
1571 }
1572 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1573 *pre_limit = adjust_limit((-stride_con), scale, offset, low_limit, *pre_limit, pre_ctrl);
1575 } else { // stride_con*scale_con < 0
1576 // For negative stride*scale pre-loop checks for overflow and
1577 // post-loop for underflow.
1578 //
1579 // The overflow limit: scale*I+offset < upper_limit
1580 // For pre-loop compute
1581 // NOT(scale*I+offset < upper_limit)
1582 // scale*I+offset >= upper_limit
1583 // scale*I+offset+1 > upper_limit
1584 // ( if (scale < 0) /* and stride > 0 */
1585 // I < (upper_limit-(offset+1))/scale
1586 // else /* scale > 0 and stride < 0 */
1587 // I > (upper_limit-(offset+1))/scale
1588 // )
1589 //
1590 // (upper_limit-offset-1) may underflow or overflow.
1591 // To avoid it min(pre_limit, original_limit) is used
1592 // in do_range_check() for stride > 0 and max() for < 0.
1593 Node *one = _igvn.intcon(1);
1594 set_ctrl(one, C->root());
1596 Node *plus_one = new (C, 3) AddINode(offset, one);
1597 register_new_node( plus_one, pre_ctrl );
1598 // Pass (-stride) to indicate pre_loop_cond = NOT(main_loop_cond);
1599 *pre_limit = adjust_limit((-stride_con), scale, plus_one, upper_limit, *pre_limit, pre_ctrl);
1601 if (low_limit->get_int() == -max_jint) {
1602 if (!RangeLimitCheck) return;
1603 // We need this guard when scale*main_limit+offset >= limit
1604 // due to underflow. So we need execute main-loop while
1605 // scale*I+offset+1 > min_int. But (min_int-offset-1) will
1606 // underflow when (offset+1) > 0 and X will be < main_limit
1607 // when scale < 0 (and stride > 0). To avoid it we replace
1608 // positive (offset+1) with 0.
1609 //
1610 // Also (min_int+1 == -max_int) is used instead of min_int here
1611 // to avoid problem with scale == -1 (min_int/(-1) == min_int).
1612 Node* shift = _igvn.intcon(31);
1613 set_ctrl(shift, C->root());
1614 Node* sign = new (C, 3) RShiftINode(plus_one, shift);
1615 register_new_node(sign, pre_ctrl);
1616 plus_one = new (C, 3) AndINode(plus_one, sign);
1617 register_new_node(plus_one, pre_ctrl);
1618 } else {
1619 assert(low_limit->get_int() == 0, "wrong low limit for range check");
1620 // The only problem we have here when offset == max_int
1621 // since (max_int+1) == min_int and (0-min_int) == min_int.
1622 // But it is fine since main loop will either have
1623 // less iterations or will be skipped in such case.
1624 }
1625 // The underflow limit: low_limit <= scale*I+offset.
1626 // For main-loop compute
1627 // scale*I+offset+1 > low_limit
1628 // ( if (scale < 0) /* and stride > 0 */
1629 // I < (low_limit-(offset+1))/scale
1630 // else /* scale > 0 and stride < 0 */
1631 // I > (low_limit-(offset+1))/scale
1632 // )
1634 *main_limit = adjust_limit(stride_con, scale, plus_one, low_limit, *main_limit, pre_ctrl);
1635 }
1636 }
1639 //------------------------------is_scaled_iv---------------------------------
1640 // Return true if exp is a constant times an induction var
1641 bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
1642 if (exp == iv) {
1643 if (p_scale != NULL) {
1644 *p_scale = 1;
1645 }
1646 return true;
1647 }
1648 int opc = exp->Opcode();
1649 if (opc == Op_MulI) {
1650 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1651 if (p_scale != NULL) {
1652 *p_scale = exp->in(2)->get_int();
1653 }
1654 return true;
1655 }
1656 if (exp->in(2) == iv && exp->in(1)->is_Con()) {
1657 if (p_scale != NULL) {
1658 *p_scale = exp->in(1)->get_int();
1659 }
1660 return true;
1661 }
1662 } else if (opc == Op_LShiftI) {
1663 if (exp->in(1) == iv && exp->in(2)->is_Con()) {
1664 if (p_scale != NULL) {
1665 *p_scale = 1 << exp->in(2)->get_int();
1666 }
1667 return true;
1668 }
1669 }
1670 return false;
1671 }
1673 //-----------------------------is_scaled_iv_plus_offset------------------------------
1674 // Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
1675 bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
1676 if (is_scaled_iv(exp, iv, p_scale)) {
1677 if (p_offset != NULL) {
1678 Node *zero = _igvn.intcon(0);
1679 set_ctrl(zero, C->root());
1680 *p_offset = zero;
1681 }
1682 return true;
1683 }
1684 int opc = exp->Opcode();
1685 if (opc == Op_AddI) {
1686 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1687 if (p_offset != NULL) {
1688 *p_offset = exp->in(2);
1689 }
1690 return true;
1691 }
1692 if (exp->in(2)->is_Con()) {
1693 Node* offset2 = NULL;
1694 if (depth < 2 &&
1695 is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
1696 p_offset != NULL ? &offset2 : NULL, depth+1)) {
1697 if (p_offset != NULL) {
1698 Node *ctrl_off2 = get_ctrl(offset2);
1699 Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
1700 register_new_node(offset, ctrl_off2);
1701 *p_offset = offset;
1702 }
1703 return true;
1704 }
1705 }
1706 } else if (opc == Op_SubI) {
1707 if (is_scaled_iv(exp->in(1), iv, p_scale)) {
1708 if (p_offset != NULL) {
1709 Node *zero = _igvn.intcon(0);
1710 set_ctrl(zero, C->root());
1711 Node *ctrl_off = get_ctrl(exp->in(2));
1712 Node* offset = new (C, 3) SubINode(zero, exp->in(2));
1713 register_new_node(offset, ctrl_off);
1714 *p_offset = offset;
1715 }
1716 return true;
1717 }
1718 if (is_scaled_iv(exp->in(2), iv, p_scale)) {
1719 if (p_offset != NULL) {
1720 *p_scale *= -1;
1721 *p_offset = exp->in(1);
1722 }
1723 return true;
1724 }
1725 }
1726 return false;
1727 }
1729 //------------------------------do_range_check---------------------------------
1730 // Eliminate range-checks and other trip-counter vs loop-invariant tests.
1731 void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
1732 #ifndef PRODUCT
1733 if (PrintOpto && VerifyLoopOptimizations) {
1734 tty->print("Range Check Elimination ");
1735 loop->dump_head();
1736 } else if (TraceLoopOpts) {
1737 tty->print("RangeCheck ");
1738 loop->dump_head();
1739 }
1740 #endif
1741 assert(RangeCheckElimination, "");
1742 CountedLoopNode *cl = loop->_head->as_CountedLoop();
1743 assert(cl->is_main_loop(), "");
1745 // protect against stride not being a constant
1746 if (!cl->stride_is_con())
1747 return;
1749 // Find the trip counter; we are iteration splitting based on it
1750 Node *trip_counter = cl->phi();
1751 // Find the main loop limit; we will trim it's iterations
1752 // to not ever trip end tests
1753 Node *main_limit = cl->limit();
1755 // Need to find the main-loop zero-trip guard
1756 Node *ctrl = cl->in(LoopNode::EntryControl);
1757 assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
1758 Node *iffm = ctrl->in(0);
1759 assert(iffm->Opcode() == Op_If, "");
1760 Node *bolzm = iffm->in(1);
1761 assert(bolzm->Opcode() == Op_Bool, "");
1762 Node *cmpzm = bolzm->in(1);
1763 assert(cmpzm->is_Cmp(), "");
1764 Node *opqzm = cmpzm->in(2);
1765 // Can not optimize a loop if zero-trip Opaque1 node is optimized
1766 // away and then another round of loop opts attempted.
1767 if (opqzm->Opcode() != Op_Opaque1)
1768 return;
1769 assert(opqzm->in(1) == main_limit, "do not understand situation");
1771 // Find the pre-loop limit; we will expand it's iterations to
1772 // not ever trip low tests.
1773 Node *p_f = iffm->in(0);
1774 assert(p_f->Opcode() == Op_IfFalse, "");
1775 CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
1776 assert(pre_end->loopnode()->is_pre_loop(), "");
1777 Node *pre_opaq1 = pre_end->limit();
1778 // Occasionally it's possible for a pre-loop Opaque1 node to be
1779 // optimized away and then another round of loop opts attempted.
1780 // We can not optimize this particular loop in that case.
1781 if (pre_opaq1->Opcode() != Op_Opaque1)
1782 return;
1783 Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
1784 Node *pre_limit = pre_opaq->in(1);
1786 // Where do we put new limit calculations
1787 Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
1789 // Ensure the original loop limit is available from the
1790 // pre-loop Opaque1 node.
1791 Node *orig_limit = pre_opaq->original_loop_limit();
1792 if (orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP)
1793 return;
1795 // Must know if its a count-up or count-down loop
1797 int stride_con = cl->stride_con();
1798 Node *zero = _igvn.intcon(0);
1799 Node *one = _igvn.intcon(1);
1800 // Use symmetrical int range [-max_jint,max_jint]
1801 Node *mini = _igvn.intcon(-max_jint);
1802 set_ctrl(zero, C->root());
1803 set_ctrl(one, C->root());
1804 set_ctrl(mini, C->root());
1806 // Range checks that do not dominate the loop backedge (ie.
1807 // conditionally executed) can lengthen the pre loop limit beyond
1808 // the original loop limit. To prevent this, the pre limit is
1809 // (for stride > 0) MINed with the original loop limit (MAXed
1810 // stride < 0) when some range_check (rc) is conditionally
1811 // executed.
1812 bool conditional_rc = false;
1814 // Check loop body for tests of trip-counter plus loop-invariant vs
1815 // loop-invariant.
1816 for( uint i = 0; i < loop->_body.size(); i++ ) {
1817 Node *iff = loop->_body[i];
1818 if( iff->Opcode() == Op_If ) { // Test?
1820 // Test is an IfNode, has 2 projections. If BOTH are in the loop
1821 // we need loop unswitching instead of iteration splitting.
1822 Node *exit = loop->is_loop_exit(iff);
1823 if( !exit ) continue;
1824 int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
1826 // Get boolean condition to test
1827 Node *i1 = iff->in(1);
1828 if( !i1->is_Bool() ) continue;
1829 BoolNode *bol = i1->as_Bool();
1830 BoolTest b_test = bol->_test;
1831 // Flip sense of test if exit condition is flipped
1832 if( flip )
1833 b_test = b_test.negate();
1835 // Get compare
1836 Node *cmp = bol->in(1);
1838 // Look for trip_counter + offset vs limit
1839 Node *rc_exp = cmp->in(1);
1840 Node *limit = cmp->in(2);
1841 jint scale_con= 1; // Assume trip counter not scaled
1843 Node *limit_c = get_ctrl(limit);
1844 if( loop->is_member(get_loop(limit_c) ) ) {
1845 // Compare might have operands swapped; commute them
1846 b_test = b_test.commute();
1847 rc_exp = cmp->in(2);
1848 limit = cmp->in(1);
1849 limit_c = get_ctrl(limit);
1850 if( loop->is_member(get_loop(limit_c) ) )
1851 continue; // Both inputs are loop varying; cannot RCE
1852 }
1853 // Here we know 'limit' is loop invariant
1855 // 'limit' maybe pinned below the zero trip test (probably from a
1856 // previous round of rce), in which case, it can't be used in the
1857 // zero trip test expression which must occur before the zero test's if.
1858 if( limit_c == ctrl ) {
1859 continue; // Don't rce this check but continue looking for other candidates.
1860 }
1862 // Check for scaled induction variable plus an offset
1863 Node *offset = NULL;
1865 if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
1866 continue;
1867 }
1869 Node *offset_c = get_ctrl(offset);
1870 if( loop->is_member( get_loop(offset_c) ) )
1871 continue; // Offset is not really loop invariant
1872 // Here we know 'offset' is loop invariant.
1874 // As above for the 'limit', the 'offset' maybe pinned below the
1875 // zero trip test.
1876 if( offset_c == ctrl ) {
1877 continue; // Don't rce this check but continue looking for other candidates.
1878 }
1879 #ifdef ASSERT
1880 if (TraceRangeLimitCheck) {
1881 tty->print_cr("RC bool node%s", flip ? " flipped:" : ":");
1882 bol->dump(2);
1883 }
1884 #endif
1885 // At this point we have the expression as:
1886 // scale_con * trip_counter + offset :: limit
1887 // where scale_con, offset and limit are loop invariant. Trip_counter
1888 // monotonically increases by stride_con, a constant. Both (or either)
1889 // stride_con and scale_con can be negative which will flip about the
1890 // sense of the test.
1892 // Adjust pre and main loop limits to guard the correct iteration set
1893 if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
1894 if( b_test._test == BoolTest::lt ) { // Range checks always use lt
1895 // The underflow and overflow limits: 0 <= scale*I+offset < limit
1896 add_constraint( stride_con, scale_con, offset, zero, limit, pre_ctrl, &pre_limit, &main_limit );
1897 if (!conditional_rc) {
1898 // (0-offset)/scale could be outside of loop iterations range.
1899 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1900 }
1901 } else {
1902 #ifndef PRODUCT
1903 if( PrintOpto )
1904 tty->print_cr("missed RCE opportunity");
1905 #endif
1906 continue; // In release mode, ignore it
1907 }
1908 } else { // Otherwise work on normal compares
1909 switch( b_test._test ) {
1910 case BoolTest::gt:
1911 // Fall into GE case
1912 case BoolTest::ge:
1913 // Convert (I*scale+offset) >= Limit to (I*(-scale)+(-offset)) <= -Limit
1914 scale_con = -scale_con;
1915 offset = new (C, 3) SubINode( zero, offset );
1916 register_new_node( offset, pre_ctrl );
1917 limit = new (C, 3) SubINode( zero, limit );
1918 register_new_node( limit, pre_ctrl );
1919 // Fall into LE case
1920 case BoolTest::le:
1921 if (b_test._test != BoolTest::gt) {
1922 // Convert X <= Y to X < Y+1
1923 limit = new (C, 3) AddINode( limit, one );
1924 register_new_node( limit, pre_ctrl );
1925 }
1926 // Fall into LT case
1927 case BoolTest::lt:
1928 // The underflow and overflow limits: MIN_INT <= scale*I+offset < limit
1929 // Note: (MIN_INT+1 == -MAX_INT) is used instead of MIN_INT here
1930 // to avoid problem with scale == -1: MIN_INT/(-1) == MIN_INT.
1931 add_constraint( stride_con, scale_con, offset, mini, limit, pre_ctrl, &pre_limit, &main_limit );
1932 if (!conditional_rc) {
1933 // ((MIN_INT+1)-offset)/scale could be outside of loop iterations range.
1934 // Note: negative offset is replaced with 0 but (MIN_INT+1)/scale could
1935 // still be outside of loop range.
1936 conditional_rc = !loop->dominates_backedge(iff) || RangeLimitCheck;
1937 }
1938 break;
1939 default:
1940 #ifndef PRODUCT
1941 if( PrintOpto )
1942 tty->print_cr("missed RCE opportunity");
1943 #endif
1944 continue; // Unhandled case
1945 }
1946 }
1948 // Kill the eliminated test
1949 C->set_major_progress();
1950 Node *kill_con = _igvn.intcon( 1-flip );
1951 set_ctrl(kill_con, C->root());
1952 _igvn.replace_input_of(iff, 1, kill_con);
1953 // Find surviving projection
1954 assert(iff->is_If(), "");
1955 ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
1956 // Find loads off the surviving projection; remove their control edge
1957 for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
1958 Node* cd = dp->fast_out(i); // Control-dependent node
1959 if( cd->is_Load() ) { // Loads can now float around in the loop
1960 // Allow the load to float around in the loop, or before it
1961 // but NOT before the pre-loop.
1962 _igvn.replace_input_of(cd, 0, ctrl); // ctrl, not NULL
1963 --i;
1964 --imax;
1965 }
1966 }
1968 } // End of is IF
1970 }
1972 // Update loop limits
1973 if (conditional_rc) {
1974 pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
1975 : (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
1976 register_new_node(pre_limit, pre_ctrl);
1977 }
1978 _igvn.hash_delete(pre_opaq);
1979 pre_opaq->set_req(1, pre_limit);
1981 // Note:: we are making the main loop limit no longer precise;
1982 // need to round up based on stride.
1983 cl->set_nonexact_trip_count();
1984 if (!LoopLimitCheck && stride_con != 1 && stride_con != -1) { // Cutout for common case
1985 // "Standard" round-up logic: ([main_limit-init+(y-1)]/y)*y+init
1986 // Hopefully, compiler will optimize for powers of 2.
1987 Node *ctrl = get_ctrl(main_limit);
1988 Node *stride = cl->stride();
1989 Node *init = cl->init_trip();
1990 Node *span = new (C, 3) SubINode(main_limit,init);
1991 register_new_node(span,ctrl);
1992 Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
1993 Node *add = new (C, 3) AddINode(span,rndup);
1994 register_new_node(add,ctrl);
1995 Node *div = new (C, 3) DivINode(0,add,stride);
1996 register_new_node(div,ctrl);
1997 Node *mul = new (C, 3) MulINode(div,stride);
1998 register_new_node(mul,ctrl);
1999 Node *newlim = new (C, 3) AddINode(mul,init);
2000 register_new_node(newlim,ctrl);
2001 main_limit = newlim;
2002 }
2004 Node *main_cle = cl->loopexit();
2005 Node *main_bol = main_cle->in(1);
2006 // Hacking loop bounds; need private copies of exit test
2007 if( main_bol->outcnt() > 1 ) {// BoolNode shared?
2008 _igvn.hash_delete(main_cle);
2009 main_bol = main_bol->clone();// Clone a private BoolNode
2010 register_new_node( main_bol, main_cle->in(0) );
2011 main_cle->set_req(1,main_bol);
2012 }
2013 Node *main_cmp = main_bol->in(1);
2014 if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
2015 _igvn.hash_delete(main_bol);
2016 main_cmp = main_cmp->clone();// Clone a private CmpNode
2017 register_new_node( main_cmp, main_cle->in(0) );
2018 main_bol->set_req(1,main_cmp);
2019 }
2020 // Hack the now-private loop bounds
2021 _igvn.replace_input_of(main_cmp, 2, main_limit);
2022 // The OpaqueNode is unshared by design
2023 assert( opqzm->outcnt() == 1, "cannot hack shared node" );
2024 _igvn.replace_input_of(opqzm, 1, main_limit);
2025 }
2027 //------------------------------DCE_loop_body----------------------------------
2028 // Remove simplistic dead code from loop body
2029 void IdealLoopTree::DCE_loop_body() {
2030 for( uint i = 0; i < _body.size(); i++ )
2031 if( _body.at(i)->outcnt() == 0 )
2032 _body.map( i--, _body.pop() );
2033 }
2036 //------------------------------adjust_loop_exit_prob--------------------------
2037 // Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
2038 // Replace with a 1-in-10 exit guess.
2039 void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
2040 Node *test = tail();
2041 while( test != _head ) {
2042 uint top = test->Opcode();
2043 if( top == Op_IfTrue || top == Op_IfFalse ) {
2044 int test_con = ((ProjNode*)test)->_con;
2045 assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
2046 IfNode *iff = test->in(0)->as_If();
2047 if( iff->outcnt() == 2 ) { // Ignore dead tests
2048 Node *bol = iff->in(1);
2049 if( bol && bol->req() > 1 && bol->in(1) &&
2050 ((bol->in(1)->Opcode() == Op_StorePConditional ) ||
2051 (bol->in(1)->Opcode() == Op_StoreIConditional ) ||
2052 (bol->in(1)->Opcode() == Op_StoreLConditional ) ||
2053 (bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
2054 (bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
2055 (bol->in(1)->Opcode() == Op_CompareAndSwapP ) ||
2056 (bol->in(1)->Opcode() == Op_CompareAndSwapN )))
2057 return; // Allocation loops RARELY take backedge
2058 // Find the OTHER exit path from the IF
2059 Node* ex = iff->proj_out(1-test_con);
2060 float p = iff->_prob;
2061 if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
2062 if( top == Op_IfTrue ) {
2063 if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
2064 iff->_prob = PROB_STATIC_FREQUENT;
2065 }
2066 } else {
2067 if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
2068 iff->_prob = PROB_STATIC_INFREQUENT;
2069 }
2070 }
2071 }
2072 }
2073 }
2074 test = phase->idom(test);
2075 }
2076 }
2079 //------------------------------policy_do_remove_empty_loop--------------------
2080 // Micro-benchmark spamming. Policy is to always remove empty loops.
2081 // The 'DO' part is to replace the trip counter with the value it will
2082 // have on the last iteration. This will break the loop.
2083 bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
2084 // Minimum size must be empty loop
2085 if (_body.size() > EMPTY_LOOP_SIZE)
2086 return false;
2088 if (!_head->is_CountedLoop())
2089 return false; // Dead loop
2090 CountedLoopNode *cl = _head->as_CountedLoop();
2091 if (!cl->is_valid_counted_loop())
2092 return false; // Malformed loop
2093 if (!phase->is_member(this, phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue))))
2094 return false; // Infinite loop
2096 #ifdef ASSERT
2097 // Ensure only one phi which is the iv.
2098 Node* iv = NULL;
2099 for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
2100 Node* n = cl->fast_out(i);
2101 if (n->Opcode() == Op_Phi) {
2102 assert(iv == NULL, "Too many phis" );
2103 iv = n;
2104 }
2105 }
2106 assert(iv == cl->phi(), "Wrong phi" );
2107 #endif
2109 // main and post loops have explicitly created zero trip guard
2110 bool needs_guard = !cl->is_main_loop() && !cl->is_post_loop();
2111 if (needs_guard) {
2112 // Skip guard if values not overlap.
2113 const TypeInt* init_t = phase->_igvn.type(cl->init_trip())->is_int();
2114 const TypeInt* limit_t = phase->_igvn.type(cl->limit())->is_int();
2115 int stride_con = cl->stride_con();
2116 if (stride_con > 0) {
2117 needs_guard = (init_t->_hi >= limit_t->_lo);
2118 } else {
2119 needs_guard = (init_t->_lo <= limit_t->_hi);
2120 }
2121 }
2122 if (needs_guard) {
2123 // Check for an obvious zero trip guard.
2124 Node* inctrl = PhaseIdealLoop::skip_loop_predicates(cl->in(LoopNode::EntryControl));
2125 if (inctrl->Opcode() == Op_IfTrue) {
2126 // The test should look like just the backedge of a CountedLoop
2127 Node* iff = inctrl->in(0);
2128 if (iff->is_If()) {
2129 Node* bol = iff->in(1);
2130 if (bol->is_Bool() && bol->as_Bool()->_test._test == cl->loopexit()->test_trip()) {
2131 Node* cmp = bol->in(1);
2132 if (cmp->is_Cmp() && cmp->in(1) == cl->init_trip() && cmp->in(2) == cl->limit()) {
2133 needs_guard = false;
2134 }
2135 }
2136 }
2137 }
2138 }
2140 #ifndef PRODUCT
2141 if (PrintOpto) {
2142 tty->print("Removing empty loop with%s zero trip guard", needs_guard ? "out" : "");
2143 this->dump_head();
2144 } else if (TraceLoopOpts) {
2145 tty->print("Empty with%s zero trip guard ", needs_guard ? "out" : "");
2146 this->dump_head();
2147 }
2148 #endif
2150 if (needs_guard) {
2151 // Peel the loop to ensure there's a zero trip guard
2152 Node_List old_new;
2153 phase->do_peeling(this, old_new);
2154 }
2156 // Replace the phi at loop head with the final value of the last
2157 // iteration. Then the CountedLoopEnd will collapse (backedge never
2158 // taken) and all loop-invariant uses of the exit values will be correct.
2159 Node *phi = cl->phi();
2160 Node *exact_limit = phase->exact_limit(this);
2161 if (exact_limit != cl->limit()) {
2162 // We also need to replace the original limit to collapse loop exit.
2163 Node* cmp = cl->loopexit()->cmp_node();
2164 assert(cl->limit() == cmp->in(2), "sanity");
2165 phase->_igvn._worklist.push(cmp->in(2)); // put limit on worklist
2166 phase->_igvn.replace_input_of(cmp, 2, exact_limit); // put cmp on worklist
2167 }
2168 // Note: the final value after increment should not overflow since
2169 // counted loop has limit check predicate.
2170 Node *final = new (phase->C, 3) SubINode( exact_limit, cl->stride() );
2171 phase->register_new_node(final,cl->in(LoopNode::EntryControl));
2172 phase->_igvn.replace_node(phi,final);
2173 phase->C->set_major_progress();
2174 return true;
2175 }
2177 //------------------------------policy_do_one_iteration_loop-------------------
2178 // Convert one iteration loop into normal code.
2179 bool IdealLoopTree::policy_do_one_iteration_loop( PhaseIdealLoop *phase ) {
2180 if (!_head->as_Loop()->is_valid_counted_loop())
2181 return false; // Only for counted loop
2183 CountedLoopNode *cl = _head->as_CountedLoop();
2184 if (!cl->has_exact_trip_count() || cl->trip_count() != 1) {
2185 return false;
2186 }
2188 #ifndef PRODUCT
2189 if(TraceLoopOpts) {
2190 tty->print("OneIteration ");
2191 this->dump_head();
2192 }
2193 #endif
2195 Node *init_n = cl->init_trip();
2196 #ifdef ASSERT
2197 // Loop boundaries should be constant since trip count is exact.
2198 assert(init_n->get_int() + cl->stride_con() >= cl->limit()->get_int(), "should be one iteration");
2199 #endif
2200 // Replace the phi at loop head with the value of the init_trip.
2201 // Then the CountedLoopEnd will collapse (backedge will not be taken)
2202 // and all loop-invariant uses of the exit values will be correct.
2203 phase->_igvn.replace_node(cl->phi(), cl->init_trip());
2204 phase->C->set_major_progress();
2205 return true;
2206 }
2208 //=============================================================================
2209 //------------------------------iteration_split_impl---------------------------
2210 bool IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
2211 // Compute exact loop trip count if possible.
2212 compute_exact_trip_count(phase);
2214 // Convert one iteration loop into normal code.
2215 if (policy_do_one_iteration_loop(phase))
2216 return true;
2218 // Check and remove empty loops (spam micro-benchmarks)
2219 if (policy_do_remove_empty_loop(phase))
2220 return true; // Here we removed an empty loop
2222 bool should_peel = policy_peeling(phase); // Should we peel?
2224 bool should_unswitch = policy_unswitching(phase);
2226 // Non-counted loops may be peeled; exactly 1 iteration is peeled.
2227 // This removes loop-invariant tests (usually null checks).
2228 if (!_head->is_CountedLoop()) { // Non-counted loop
2229 if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
2230 // Partial peel succeeded so terminate this round of loop opts
2231 return false;
2232 }
2233 if (should_peel) { // Should we peel?
2234 #ifndef PRODUCT
2235 if (PrintOpto) tty->print_cr("should_peel");
2236 #endif
2237 phase->do_peeling(this,old_new);
2238 } else if (should_unswitch) {
2239 phase->do_unswitching(this, old_new);
2240 }
2241 return true;
2242 }
2243 CountedLoopNode *cl = _head->as_CountedLoop();
2245 if (!cl->is_valid_counted_loop()) return true; // Ignore various kinds of broken loops
2247 // Do nothing special to pre- and post- loops
2248 if (cl->is_pre_loop() || cl->is_post_loop()) return true;
2250 // Compute loop trip count from profile data
2251 compute_profile_trip_cnt(phase);
2253 // Before attempting fancy unrolling, RCE or alignment, see if we want
2254 // to completely unroll this loop or do loop unswitching.
2255 if (cl->is_normal_loop()) {
2256 if (should_unswitch) {
2257 phase->do_unswitching(this, old_new);
2258 return true;
2259 }
2260 bool should_maximally_unroll = policy_maximally_unroll(phase);
2261 if (should_maximally_unroll) {
2262 // Here we did some unrolling and peeling. Eventually we will
2263 // completely unroll this loop and it will no longer be a loop.
2264 phase->do_maximally_unroll(this,old_new);
2265 return true;
2266 }
2267 }
2269 // Skip next optimizations if running low on nodes. Note that
2270 // policy_unswitching and policy_maximally_unroll have this check.
2271 uint nodes_left = MaxNodeLimit - phase->C->unique();
2272 if ((2 * _body.size()) > nodes_left) {
2273 return true;
2274 }
2276 // Counted loops may be peeled, may need some iterations run up
2277 // front for RCE, and may want to align loop refs to a cache
2278 // line. Thus we clone a full loop up front whose trip count is
2279 // at least 1 (if peeling), but may be several more.
2281 // The main loop will start cache-line aligned with at least 1
2282 // iteration of the unrolled body (zero-trip test required) and
2283 // will have some range checks removed.
2285 // A post-loop will finish any odd iterations (leftover after
2286 // unrolling), plus any needed for RCE purposes.
2288 bool should_unroll = policy_unroll(phase);
2290 bool should_rce = policy_range_check(phase);
2292 bool should_align = policy_align(phase);
2294 // If not RCE'ing (iteration splitting) or Aligning, then we do not
2295 // need a pre-loop. We may still need to peel an initial iteration but
2296 // we will not be needing an unknown number of pre-iterations.
2297 //
2298 // Basically, if may_rce_align reports FALSE first time through,
2299 // we will not be able to later do RCE or Aligning on this loop.
2300 bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
2302 // If we have any of these conditions (RCE, alignment, unrolling) met, then
2303 // we switch to the pre-/main-/post-loop model. This model also covers
2304 // peeling.
2305 if (should_rce || should_align || should_unroll) {
2306 if (cl->is_normal_loop()) // Convert to 'pre/main/post' loops
2307 phase->insert_pre_post_loops(this,old_new, !may_rce_align);
2309 // Adjust the pre- and main-loop limits to let the pre and post loops run
2310 // with full checks, but the main-loop with no checks. Remove said
2311 // checks from the main body.
2312 if (should_rce)
2313 phase->do_range_check(this,old_new);
2315 // Double loop body for unrolling. Adjust the minimum-trip test (will do
2316 // twice as many iterations as before) and the main body limit (only do
2317 // an even number of trips). If we are peeling, we might enable some RCE
2318 // and we'd rather unroll the post-RCE'd loop SO... do not unroll if
2319 // peeling.
2320 if (should_unroll && !should_peel)
2321 phase->do_unroll(this,old_new, true);
2323 // Adjust the pre-loop limits to align the main body
2324 // iterations.
2325 if (should_align)
2326 Unimplemented();
2328 } else { // Else we have an unchanged counted loop
2329 if (should_peel) // Might want to peel but do nothing else
2330 phase->do_peeling(this,old_new);
2331 }
2332 return true;
2333 }
2336 //=============================================================================
2337 //------------------------------iteration_split--------------------------------
2338 bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
2339 // Recursively iteration split nested loops
2340 if (_child && !_child->iteration_split(phase, old_new))
2341 return false;
2343 // Clean out prior deadwood
2344 DCE_loop_body();
2347 // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
2348 // Replace with a 1-in-10 exit guess.
2349 if (_parent /*not the root loop*/ &&
2350 !_irreducible &&
2351 // Also ignore the occasional dead backedge
2352 !tail()->is_top()) {
2353 adjust_loop_exit_prob(phase);
2354 }
2356 // Gate unrolling, RCE and peeling efforts.
2357 if (!_child && // If not an inner loop, do not split
2358 !_irreducible &&
2359 _allow_optimizations &&
2360 !tail()->is_top()) { // Also ignore the occasional dead backedge
2361 if (!_has_call) {
2362 if (!iteration_split_impl(phase, old_new)) {
2363 return false;
2364 }
2365 } else if (policy_unswitching(phase)) {
2366 phase->do_unswitching(this, old_new);
2367 }
2368 }
2370 // Minor offset re-organization to remove loop-fallout uses of
2371 // trip counter when there was no major reshaping.
2372 phase->reorg_offsets(this);
2374 if (_next && !_next->iteration_split(phase, old_new))
2375 return false;
2376 return true;
2377 }
2380 //=============================================================================
2381 // Process all the loops in the loop tree and replace any fill
2382 // patterns with an intrisc version.
2383 bool PhaseIdealLoop::do_intrinsify_fill() {
2384 bool changed = false;
2385 for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2386 IdealLoopTree* lpt = iter.current();
2387 changed |= intrinsify_fill(lpt);
2388 }
2389 return changed;
2390 }
2393 // Examine an inner loop looking for a a single store of an invariant
2394 // value in a unit stride loop,
2395 bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
2396 Node*& shift, Node*& con) {
2397 const char* msg = NULL;
2398 Node* msg_node = NULL;
2400 store_value = NULL;
2401 con = NULL;
2402 shift = NULL;
2404 // Process the loop looking for stores. If there are multiple
2405 // stores or extra control flow give at this point.
2406 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2407 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2408 Node* n = lpt->_body.at(i);
2409 if (n->outcnt() == 0) continue; // Ignore dead
2410 if (n->is_Store()) {
2411 if (store != NULL) {
2412 msg = "multiple stores";
2413 break;
2414 }
2415 int opc = n->Opcode();
2416 if (opc == Op_StoreP || opc == Op_StoreN || opc == Op_StoreCM) {
2417 msg = "oop fills not handled";
2418 break;
2419 }
2420 Node* value = n->in(MemNode::ValueIn);
2421 if (!lpt->is_invariant(value)) {
2422 msg = "variant store value";
2423 } else if (!_igvn.type(n->in(MemNode::Address))->isa_aryptr()) {
2424 msg = "not array address";
2425 }
2426 store = n;
2427 store_value = value;
2428 } else if (n->is_If() && n != head->loopexit()) {
2429 msg = "extra control flow";
2430 msg_node = n;
2431 }
2432 }
2434 if (store == NULL) {
2435 // No store in loop
2436 return false;
2437 }
2439 if (msg == NULL && head->stride_con() != 1) {
2440 // could handle negative strides too
2441 if (head->stride_con() < 0) {
2442 msg = "negative stride";
2443 } else {
2444 msg = "non-unit stride";
2445 }
2446 }
2448 if (msg == NULL && !store->in(MemNode::Address)->is_AddP()) {
2449 msg = "can't handle store address";
2450 msg_node = store->in(MemNode::Address);
2451 }
2453 if (msg == NULL &&
2454 (!store->in(MemNode::Memory)->is_Phi() ||
2455 store->in(MemNode::Memory)->in(LoopNode::LoopBackControl) != store)) {
2456 msg = "store memory isn't proper phi";
2457 msg_node = store->in(MemNode::Memory);
2458 }
2460 // Make sure there is an appropriate fill routine
2461 BasicType t = store->as_Mem()->memory_type();
2462 const char* fill_name;
2463 if (msg == NULL &&
2464 StubRoutines::select_fill_function(t, false, fill_name) == NULL) {
2465 msg = "unsupported store";
2466 msg_node = store;
2467 }
2469 if (msg != NULL) {
2470 #ifndef PRODUCT
2471 if (TraceOptimizeFill) {
2472 tty->print_cr("not fill intrinsic candidate: %s", msg);
2473 if (msg_node != NULL) msg_node->dump();
2474 }
2475 #endif
2476 return false;
2477 }
2479 // Make sure the address expression can be handled. It should be
2480 // head->phi * elsize + con. head->phi might have a ConvI2L.
2481 Node* elements[4];
2482 Node* conv = NULL;
2483 bool found_index = false;
2484 int count = store->in(MemNode::Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
2485 for (int e = 0; e < count; e++) {
2486 Node* n = elements[e];
2487 if (n->is_Con() && con == NULL) {
2488 con = n;
2489 } else if (n->Opcode() == Op_LShiftX && shift == NULL) {
2490 Node* value = n->in(1);
2491 #ifdef _LP64
2492 if (value->Opcode() == Op_ConvI2L) {
2493 conv = value;
2494 value = value->in(1);
2495 }
2496 #endif
2497 if (value != head->phi()) {
2498 msg = "unhandled shift in address";
2499 } else {
2500 if (type2aelembytes(store->as_Mem()->memory_type(), true) != (1 << n->in(2)->get_int())) {
2501 msg = "scale doesn't match";
2502 } else {
2503 found_index = true;
2504 shift = n;
2505 }
2506 }
2507 } else if (n->Opcode() == Op_ConvI2L && conv == NULL) {
2508 if (n->in(1) == head->phi()) {
2509 found_index = true;
2510 conv = n;
2511 } else {
2512 msg = "unhandled input to ConvI2L";
2513 }
2514 } else if (n == head->phi()) {
2515 // no shift, check below for allowed cases
2516 found_index = true;
2517 } else {
2518 msg = "unhandled node in address";
2519 msg_node = n;
2520 }
2521 }
2523 if (count == -1) {
2524 msg = "malformed address expression";
2525 msg_node = store;
2526 }
2528 if (!found_index) {
2529 msg = "missing use of index";
2530 }
2532 // byte sized items won't have a shift
2533 if (msg == NULL && shift == NULL && t != T_BYTE && t != T_BOOLEAN) {
2534 msg = "can't find shift";
2535 msg_node = store;
2536 }
2538 if (msg != NULL) {
2539 #ifndef PRODUCT
2540 if (TraceOptimizeFill) {
2541 tty->print_cr("not fill intrinsic: %s", msg);
2542 if (msg_node != NULL) msg_node->dump();
2543 }
2544 #endif
2545 return false;
2546 }
2548 // No make sure all the other nodes in the loop can be handled
2549 VectorSet ok(Thread::current()->resource_area());
2551 // store related values are ok
2552 ok.set(store->_idx);
2553 ok.set(store->in(MemNode::Memory)->_idx);
2555 // Loop structure is ok
2556 ok.set(head->_idx);
2557 ok.set(head->loopexit()->_idx);
2558 ok.set(head->phi()->_idx);
2559 ok.set(head->incr()->_idx);
2560 ok.set(head->loopexit()->cmp_node()->_idx);
2561 ok.set(head->loopexit()->in(1)->_idx);
2563 // Address elements are ok
2564 if (con) ok.set(con->_idx);
2565 if (shift) ok.set(shift->_idx);
2566 if (conv) ok.set(conv->_idx);
2568 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2569 Node* n = lpt->_body.at(i);
2570 if (n->outcnt() == 0) continue; // Ignore dead
2571 if (ok.test(n->_idx)) continue;
2572 // Backedge projection is ok
2573 if (n->is_IfTrue() && n->in(0) == head->loopexit()) continue;
2574 if (!n->is_AddP()) {
2575 msg = "unhandled node";
2576 msg_node = n;
2577 break;
2578 }
2579 }
2581 // Make sure no unexpected values are used outside the loop
2582 for (uint i = 0; msg == NULL && i < lpt->_body.size(); i++) {
2583 Node* n = lpt->_body.at(i);
2584 // These values can be replaced with other nodes if they are used
2585 // outside the loop.
2586 if (n == store || n == head->loopexit() || n == head->incr() || n == store->in(MemNode::Memory)) continue;
2587 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
2588 Node* use = iter.get();
2589 if (!lpt->_body.contains(use)) {
2590 msg = "node is used outside loop";
2591 // lpt->_body.dump();
2592 msg_node = n;
2593 break;
2594 }
2595 }
2596 }
2598 #ifdef ASSERT
2599 if (TraceOptimizeFill) {
2600 if (msg != NULL) {
2601 tty->print_cr("no fill intrinsic: %s", msg);
2602 if (msg_node != NULL) msg_node->dump();
2603 } else {
2604 tty->print_cr("fill intrinsic for:");
2605 }
2606 store->dump();
2607 if (Verbose) {
2608 lpt->_body.dump();
2609 }
2610 }
2611 #endif
2613 return msg == NULL;
2614 }
2618 bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
2619 // Only for counted inner loops
2620 if (!lpt->is_counted() || !lpt->is_inner()) {
2621 return false;
2622 }
2624 // Must have constant stride
2625 CountedLoopNode* head = lpt->_head->as_CountedLoop();
2626 if (!head->is_valid_counted_loop() || !head->is_normal_loop()) {
2627 return false;
2628 }
2630 // Check that the body only contains a store of a loop invariant
2631 // value that is indexed by the loop phi.
2632 Node* store = NULL;
2633 Node* store_value = NULL;
2634 Node* shift = NULL;
2635 Node* offset = NULL;
2636 if (!match_fill_loop(lpt, store, store_value, shift, offset)) {
2637 return false;
2638 }
2640 #ifndef PRODUCT
2641 if (TraceLoopOpts) {
2642 tty->print("ArrayFill ");
2643 lpt->dump_head();
2644 }
2645 #endif
2647 // Now replace the whole loop body by a call to a fill routine that
2648 // covers the same region as the loop.
2649 Node* base = store->in(MemNode::Address)->as_AddP()->in(AddPNode::Base);
2651 // Build an expression for the beginning of the copy region
2652 Node* index = head->init_trip();
2653 #ifdef _LP64
2654 index = new (C, 2) ConvI2LNode(index);
2655 _igvn.register_new_node_with_optimizer(index);
2656 #endif
2657 if (shift != NULL) {
2658 // byte arrays don't require a shift but others do.
2659 index = new (C, 3) LShiftXNode(index, shift->in(2));
2660 _igvn.register_new_node_with_optimizer(index);
2661 }
2662 index = new (C, 4) AddPNode(base, base, index);
2663 _igvn.register_new_node_with_optimizer(index);
2664 Node* from = new (C, 4) AddPNode(base, index, offset);
2665 _igvn.register_new_node_with_optimizer(from);
2666 // Compute the number of elements to copy
2667 Node* len = new (C, 3) SubINode(head->limit(), head->init_trip());
2668 _igvn.register_new_node_with_optimizer(len);
2670 BasicType t = store->as_Mem()->memory_type();
2671 bool aligned = false;
2672 if (offset != NULL && head->init_trip()->is_Con()) {
2673 int element_size = type2aelembytes(t);
2674 aligned = (offset->find_intptr_t_type()->get_con() + head->init_trip()->get_int() * element_size) % HeapWordSize == 0;
2675 }
2677 // Build a call to the fill routine
2678 const char* fill_name;
2679 address fill = StubRoutines::select_fill_function(t, aligned, fill_name);
2680 assert(fill != NULL, "what?");
2682 // Convert float/double to int/long for fill routines
2683 if (t == T_FLOAT) {
2684 store_value = new (C, 2) MoveF2INode(store_value);
2685 _igvn.register_new_node_with_optimizer(store_value);
2686 } else if (t == T_DOUBLE) {
2687 store_value = new (C, 2) MoveD2LNode(store_value);
2688 _igvn.register_new_node_with_optimizer(store_value);
2689 }
2691 Node* mem_phi = store->in(MemNode::Memory);
2692 Node* result_ctrl;
2693 Node* result_mem;
2694 const TypeFunc* call_type = OptoRuntime::array_fill_Type();
2695 int size = call_type->domain()->cnt();
2696 CallLeafNode *call = new (C, size) CallLeafNoFPNode(call_type, fill,
2697 fill_name, TypeAryPtr::get_array_body_type(t));
2698 call->init_req(TypeFunc::Parms+0, from);
2699 call->init_req(TypeFunc::Parms+1, store_value);
2700 #ifdef _LP64
2701 len = new (C, 2) ConvI2LNode(len);
2702 _igvn.register_new_node_with_optimizer(len);
2703 #endif
2704 call->init_req(TypeFunc::Parms+2, len);
2705 #ifdef _LP64
2706 call->init_req(TypeFunc::Parms+3, C->top());
2707 #endif
2708 call->init_req( TypeFunc::Control, head->init_control());
2709 call->init_req( TypeFunc::I_O , C->top() ) ; // does no i/o
2710 call->init_req( TypeFunc::Memory , mem_phi->in(LoopNode::EntryControl) );
2711 call->init_req( TypeFunc::ReturnAdr, C->start()->proj_out(TypeFunc::ReturnAdr) );
2712 call->init_req( TypeFunc::FramePtr, C->start()->proj_out(TypeFunc::FramePtr) );
2713 _igvn.register_new_node_with_optimizer(call);
2714 result_ctrl = new (C, 1) ProjNode(call,TypeFunc::Control);
2715 _igvn.register_new_node_with_optimizer(result_ctrl);
2716 result_mem = new (C, 1) ProjNode(call,TypeFunc::Memory);
2717 _igvn.register_new_node_with_optimizer(result_mem);
2719 // If this fill is tightly coupled to an allocation and overwrites
2720 // the whole body, allow it to take over the zeroing.
2721 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, this);
2722 if (alloc != NULL && alloc->is_AllocateArray()) {
2723 Node* length = alloc->as_AllocateArray()->Ideal_length();
2724 if (head->limit() == length &&
2725 head->init_trip() == _igvn.intcon(0)) {
2726 if (TraceOptimizeFill) {
2727 tty->print_cr("Eliminated zeroing in allocation");
2728 }
2729 alloc->maybe_set_complete(&_igvn);
2730 } else {
2731 #ifdef ASSERT
2732 if (TraceOptimizeFill) {
2733 tty->print_cr("filling array but bounds don't match");
2734 alloc->dump();
2735 head->init_trip()->dump();
2736 head->limit()->dump();
2737 length->dump();
2738 }
2739 #endif
2740 }
2741 }
2743 // Redirect the old control and memory edges that are outside the loop.
2744 Node* exit = head->loopexit()->proj_out(0);
2745 // Sometimes the memory phi of the head is used as the outgoing
2746 // state of the loop. It's safe in this case to replace it with the
2747 // result_mem.
2748 _igvn.replace_node(store->in(MemNode::Memory), result_mem);
2749 _igvn.replace_node(exit, result_ctrl);
2750 _igvn.replace_node(store, result_mem);
2751 // Any uses the increment outside of the loop become the loop limit.
2752 _igvn.replace_node(head->incr(), head->limit());
2754 // Disconnect the head from the loop.
2755 for (uint i = 0; i < lpt->_body.size(); i++) {
2756 Node* n = lpt->_body.at(i);
2757 _igvn.replace_node(n, C->top());
2758 }
2760 return true;
2761 }