1 /*
2 * Copyright (c) 1999, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "memory/allocation.inline.hpp"
27 #include "opto/callnode.hpp"
28 #include "opto/loopnode.hpp"
29 #include "opto/movenode.hpp"
30
31
32 //------------------------------split_thru_region------------------------------
33 // Split Node 'n' through merge point.
34 Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
35 uint wins = 0;
36 assert( n->is_CFG(), "" );
37 assert( region->is_Region(), "" );
38 Node *r = new RegionNode( region->req() );
39 IdealLoopTree *loop = get_loop( n );
40 for( uint i = 1; i < region->req(); i++ ) {
41 Node *x = n->clone();
42 Node *in0 = n->in(0);
43 if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
44 for( uint j = 1; j < n->req(); j++ ) {
45 Node *in = n->in(j);
46 if( get_ctrl(in) == region )
47 x->set_req( j, in->in(i) );
48 }
49 _igvn.register_new_node_with_optimizer(x);
50 set_loop(x, loop);
51 set_idom(x, x->in(0), dom_depth(x->in(0))+1);
52 r->init_req(i, x);
53 }
54
55 // Record region
56 r->set_req(0,region); // Not a TRUE RegionNode
57 _igvn.register_new_node_with_optimizer(r);
58 set_loop(r, loop);
59 if( !loop->_child )
60 loop->_body.push(r);
61 return r;
62 }
63
64 //------------------------------split_up---------------------------------------
65 // Split block-local op up through the phis to empty the current block
66 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
67 if( n->is_CFG() ) {
68 assert( n->in(0) != blk1, "Lousy candidate for split-if" );
69 return false;
70 }
71 if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
72 return false; // Not block local
73 if( n->is_Phi() ) return false; // Local PHIs are expected
74
75 // Recursively split-up inputs
76 for (uint i = 1; i < n->req(); i++) {
77 if( split_up( n->in(i), blk1, blk2 ) ) {
78 // Got split recursively and self went dead?
79 if (n->outcnt() == 0)
80 _igvn.remove_dead_node(n);
81 return true;
82 }
83 }
84
85 // Check for needing to clone-up a compare. Can't do that, it forces
86 // another (nested) split-if transform. Instead, clone it "down".
87 if( n->is_Cmp() ) {
88 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
89 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
90 // sequence can have no other users and it must all reside in the split-if
91 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
92 // private, per-use versions of the Cmp and Bool are made. These sink to
93 // the CMove block. If the CMove is in the split-if block, then in the
94 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
95 Node *bol, *cmov;
96 if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
97 (bol = n->unique_out()->as_Bool()) &&
98 (get_ctrl(bol) == blk1 ||
99 get_ctrl(bol) == blk2) &&
100 bol->outcnt() == 1 &&
101 bol->unique_out()->is_CMove() &&
102 (cmov = bol->unique_out()->as_CMove()) &&
103 (get_ctrl(cmov) == blk1 ||
104 get_ctrl(cmov) == blk2) ) ) {
105
106 // Must clone down
107 #ifndef PRODUCT
108 if( PrintOpto && VerifyLoopOptimizations ) {
109 tty->print("Cloning down: ");
110 n->dump();
111 }
112 #endif
113 // Clone down any block-local BoolNode uses of this CmpNode
114 for (DUIterator i = n->outs(); n->has_out(i); i++) {
115 Node* bol = n->out(i);
116 assert( bol->is_Bool(), "" );
117 if (bol->outcnt() == 1) {
118 Node* use = bol->unique_out();
119 if (use->Opcode() == Op_Opaque4) {
120 if (use->outcnt() == 1) {
121 Node* iff = use->unique_out();
122 assert(iff->is_If(), "unexpected node type");
123 Node *use_c = iff->in(0);
124 if (use_c == blk1 || use_c == blk2) {
125 continue;
126 }
127 }
128 } else {
129 // We might see an Opaque1 from a loop limit check here
130 assert(use->is_If() || use->is_CMove() || use->Opcode() == Op_Opaque1, "unexpected node type");
131 Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
132 if (use_c == blk1 || use_c == blk2) {
133 assert(use->is_CMove(), "unexpected node type");
134 continue;
135 }
136 }
137 }
138 if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
139 // Recursively sink any BoolNode
140 #ifndef PRODUCT
141 if( PrintOpto && VerifyLoopOptimizations ) {
142 tty->print("Cloning down: ");
143 bol->dump();
144 }
145 #endif
146 for (DUIterator j = bol->outs(); bol->has_out(j); j++) {
147 Node* u = bol->out(j);
148 // Uses are either IfNodes, CMoves or Opaque4
149 if (u->Opcode() == Op_Opaque4) {
150 assert(u->in(1) == bol, "bad input");
151 for (DUIterator_Last kmin, k = u->last_outs(kmin); k >= kmin; --k) {
152 Node* iff = u->last_out(k);
153 assert(iff->is_If() || iff->is_CMove(), "unexpected node type");
154 assert( iff->in(1) == u, "" );
155 // Get control block of either the CMove or the If input
156 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
157 Node *x1 = bol->clone();
158 Node *x2 = u->clone();
159 register_new_node(x1, iff_ctrl);
160 register_new_node(x2, iff_ctrl);
161 _igvn.replace_input_of(x2, 1, x1);
162 _igvn.replace_input_of(iff, 1, x2);
163 }
164 _igvn.remove_dead_node(u);
165 --j;
166 } else {
167 // We might see an Opaque1 from a loop limit check here
168 assert(u->is_If() || u->is_CMove() || u->Opcode() == Op_Opaque1, "unexpected node type");
169 assert(u->in(1) == bol, "");
170 // Get control block of either the CMove or the If input
171 Node *u_ctrl = u->is_If() ? u->in(0) : get_ctrl(u);
172 assert((u_ctrl != blk1 && u_ctrl != blk2) || u->is_CMove(), "won't converge");
173 Node *x = bol->clone();
174 register_new_node(x, u_ctrl);
175 _igvn.replace_input_of(u, 1, x);
176 --j;
177 }
178 }
179 _igvn.remove_dead_node(bol);
180 --i;
181 }
182 }
183 // Clone down this CmpNode
184 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
185 Node* bol = n->last_out(j);
186 assert( bol->in(1) == n, "" );
187 Node *x = n->clone();
188 register_new_node(x, get_ctrl(bol));
189 _igvn.replace_input_of(bol, 1, x);
190 }
191 _igvn.remove_dead_node( n );
192
193 return true;
194 }
195 }
196
197 // See if splitting-up a Store. Any anti-dep loads must go up as
198 // well. An anti-dep load might be in the wrong block, because in
199 // this particular layout/schedule we ignored anti-deps and allow
200 // memory to be alive twice. This only works if we do the same
201 // operations on anti-dep loads as we do their killing stores.
202 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
203 // Get store's memory slice
204 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
205
206 // Get memory-phi anti-dep loads will be using
207 Node *memphi = n->in(MemNode::Memory);
208 assert( memphi->is_Phi(), "" );
209 // Hoist any anti-dep load to the splitting block;
210 // it will then "split-up".
211 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
212 Node *load = memphi->fast_out(i);
213 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
214 set_ctrl(load,blk1);
215 }
216 }
217
218 // Found some other Node; must clone it up
219 #ifndef PRODUCT
220 if( PrintOpto && VerifyLoopOptimizations ) {
221 tty->print("Cloning up: ");
222 n->dump();
223 }
224 #endif
225
226 // ConvI2L may have type information on it which becomes invalid if
227 // it moves up in the graph so change any clones so widen the type
228 // to TypeLong::INT when pushing it up.
229 const Type* rtype = NULL;
230 if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) {
231 rtype = TypeLong::INT;
232 }
233
234 // Now actually split-up this guy. One copy per control path merging.
235 Node *phi = PhiNode::make_blank(blk1, n);
236 for( uint j = 1; j < blk1->req(); j++ ) {
237 Node *x = n->clone();
238 // Widen the type of the ConvI2L when pushing up.
239 if (rtype != NULL) x->as_Type()->set_type(rtype);
240 if( n->in(0) && n->in(0) == blk1 )
241 x->set_req( 0, blk1->in(j) );
242 for( uint i = 1; i < n->req(); i++ ) {
243 Node *m = n->in(i);
244 if( get_ctrl(m) == blk1 ) {
245 assert( m->in(0) == blk1, "" );
246 x->set_req( i, m->in(j) );
247 }
248 }
249 register_new_node( x, blk1->in(j) );
250 phi->init_req( j, x );
251 }
252 // Announce phi to optimizer
253 register_new_node(phi, blk1);
254
255 // Remove cloned-up value from optimizer; use phi instead
256 _igvn.replace_node( n, phi );
257
258 // (There used to be a self-recursive call to split_up() here,
259 // but it is not needed. All necessary forward walking is done
260 // by do_split_if() below.)
261
262 return true;
263 }
264
265 //------------------------------register_new_node------------------------------
266 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
267 assert(!n->is_CFG(), "must be data node");
268 _igvn.register_new_node_with_optimizer(n);
269 set_ctrl(n, blk);
270 IdealLoopTree *loop = get_loop(blk);
271 if( !loop->_child )
272 loop->_body.push(n);
273 }
274
275 //------------------------------small_cache------------------------------------
276 struct small_cache : public Dict {
277
278 small_cache() : Dict( cmpkey, hashptr ) {}
279 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
280 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
281 };
282
283 //------------------------------spinup-----------------------------------------
284 // "Spin up" the dominator tree, starting at the use site and stopping when we
285 // find the post-dominating point.
286
287 // We must be at the merge point which post-dominates 'new_false' and
288 // 'new_true'. Figure out which edges into the RegionNode eventually lead up
289 // to false and which to true. Put in a PhiNode to merge values; plug in
290 // the appropriate false-arm or true-arm values. If some path leads to the
291 // original IF, then insert a Phi recursively.
292 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
293 if (use_blk->is_top()) // Handle dead uses
294 return use_blk;
295 Node *prior_n = (Node*)((intptr_t)0xdeadbeef);
296 Node *n = use_blk; // Get path input
297 assert( use_blk != iff_dom, "" );
298 // Here's the "spinup" the dominator tree loop. Do a cache-check
299 // along the way, in case we've come this way before.
300 while( n != iff_dom ) { // Found post-dominating point?
301 prior_n = n;
302 n = idom(n); // Search higher
303 Node *s = cache->probe( prior_n ); // Check cache
304 if( s ) return s; // Cache hit!
305 }
306
307 Node *phi_post;
308 if( prior_n == new_false || prior_n == new_true ) {
309 phi_post = def->clone();
310 phi_post->set_req(0, prior_n );
311 register_new_node(phi_post, prior_n);
312 } else {
313 // This method handles both control uses (looking for Regions) or data
314 // uses (looking for Phis). If looking for a control use, then we need
315 // to insert a Region instead of a Phi; however Regions always exist
316 // previously (the hash_find_insert below would always hit) so we can
317 // return the existing Region.
318 if( def->is_CFG() ) {
319 phi_post = prior_n; // If looking for CFG, return prior
320 } else {
321 assert( def->is_Phi(), "" );
322 assert( prior_n->is_Region(), "must be a post-dominating merge point" );
323
324 // Need a Phi here
325 phi_post = PhiNode::make_blank(prior_n, def);
326 // Search for both true and false on all paths till find one.
327 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
328 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
329 Node *t = _igvn.hash_find_insert(phi_post);
330 if( t ) { // See if we already have this one
331 // phi_post will not be used, so kill it
332 _igvn.remove_dead_node(phi_post);
333 phi_post->destruct();
334 phi_post = t;
335 } else {
336 register_new_node( phi_post, prior_n );
337 }
338 }
339 }
340
341 // Update cache everywhere
342 prior_n = (Node*)((intptr_t)0xdeadbeef); // Reset IDOM walk
343 n = use_blk; // Get path input
344 // Spin-up the idom tree again, basically doing path-compression.
345 // Insert cache entries along the way, so that if we ever hit this
346 // point in the IDOM tree again we'll stop immediately on a cache hit.
347 while( n != iff_dom ) { // Found post-dominating point?
348 prior_n = n;
349 n = idom(n); // Search higher
350 cache->lru_insert( prior_n, phi_post ); // Fill cache
351 } // End of while not gone high enough
352
353 return phi_post;
354 }
355
356 //------------------------------find_use_block---------------------------------
357 // Find the block a USE is in. Normally USE's are in the same block as the
358 // using instruction. For Phi-USE's, the USE is in the predecessor block
359 // along the corresponding path.
360 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
361 // CFG uses are their own block
362 if( use->is_CFG() )
363 return use;
364
365 if( use->is_Phi() ) { // Phi uses in prior block
366 // Grab the first Phi use; there may be many.
367 // Each will be handled as a separate iteration of
368 // the "while( phi->outcnt() )" loop.
369 uint j;
370 for( j = 1; j < use->req(); j++ )
371 if( use->in(j) == def )
372 break;
373 assert( j < use->req(), "def should be among use's inputs" );
374 return use->in(0)->in(j);
375 }
376 // Normal (non-phi) use
377 Node *use_blk = get_ctrl(use);
378 // Some uses are directly attached to the old (and going away)
379 // false and true branches.
380 if( use_blk == old_false ) {
381 use_blk = new_false;
382 set_ctrl(use, new_false);
383 }
384 if( use_blk == old_true ) {
385 use_blk = new_true;
386 set_ctrl(use, new_true);
387 }
388
389 if (use_blk == NULL) { // He's dead, Jim
390 _igvn.replace_node(use, C->top());
391 }
392
393 return use_blk;
394 }
395
396 //------------------------------handle_use-------------------------------------
397 // Handle uses of the merge point. Basically, split-if makes the merge point
398 // go away so all uses of the merge point must go away as well. Most block
399 // local uses have already been split-up, through the merge point. Uses from
400 // far below the merge point can't always be split up (e.g., phi-uses are
401 // pinned) and it makes too much stuff live. Instead we use a path-based
402 // solution to move uses down.
403 //
404 // If the use is along the pre-split-CFG true branch, then the new use will
405 // be from the post-split-CFG true merge point. Vice-versa for the false
406 // path. Some uses will be along both paths; then we sink the use to the
407 // post-dominating location; we may need to insert a Phi there.
408 void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
409
410 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
411 if( !use_blk ) return; // He's dead, Jim
412
413 // Walk up the dominator tree until I hit either the old IfFalse, the old
414 // IfTrue or the old If. Insert Phis where needed.
415 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
416
417 // Found where this USE goes. Re-point him.
418 uint i;
419 for( i = 0; i < use->req(); i++ )
420 if( use->in(i) == def )
421 break;
422 assert( i < use->req(), "def should be among use's inputs" );
423 _igvn.replace_input_of(use, i, new_def);
424 }
425
426 //------------------------------do_split_if------------------------------------
427 // Found an If getting its condition-code input from a Phi in the same block.
428 // Split thru the Region.
429 void PhaseIdealLoop::do_split_if( Node *iff ) {
430 if (PrintOpto && VerifyLoopOptimizations) {
431 tty->print_cr("Split-if");
432 }
433 if (TraceLoopOpts) {
434 tty->print_cr("SplitIf");
435 }
436
437 C->set_major_progress();
438 Node *region = iff->in(0);
439 Node *region_dom = idom(region);
440
441 // We are going to clone this test (and the control flow with it) up through
442 // the incoming merge point. We need to empty the current basic block.
443 // Clone any instructions which must be in this block up through the merge
444 // point.
445 DUIterator i, j;
446 bool progress = true;
447 while (progress) {
448 progress = false;
449 for (i = region->outs(); region->has_out(i); i++) {
450 Node* n = region->out(i);
451 if( n == region ) continue;
452 // The IF to be split is OK.
453 if( n == iff ) continue;
454 if( !n->is_Phi() ) { // Found pinned memory op or such
455 if (split_up(n, region, iff)) {
456 i = region->refresh_out_pos(i);
457 progress = true;
458 }
459 continue;
460 }
461 assert( n->in(0) == region, "" );
462
463 // Recursively split up all users of a Phi
464 for (j = n->outs(); n->has_out(j); j++) {
465 Node* m = n->out(j);
466 // If m is dead, throw it away, and declare progress
467 if (_nodes[m->_idx] == NULL) {
468 _igvn.remove_dead_node(m);
469 // fall through
470 }
471 else if (m != iff && split_up(m, region, iff)) {
472 // fall through
473 } else {
474 continue;
475 }
476 // Something unpredictable changed.
477 // Tell the iterators to refresh themselves, and rerun the loop.
478 i = region->refresh_out_pos(i);
479 j = region->refresh_out_pos(j);
480 progress = true;
481 }
482 }
483 }
484
485 // Now we have no instructions in the block containing the IF.
486 // Split the IF.
487 Node *new_iff = split_thru_region( iff, region );
488
489 // Replace both uses of 'new_iff' with Regions merging True/False
490 // paths. This makes 'new_iff' go dead.
491 Node *old_false = NULL, *old_true = NULL;
492 Node *new_false = NULL, *new_true = NULL;
493 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
494 Node *ifp = iff->last_out(j2);
495 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
496 ifp->set_req(0, new_iff);
497 Node *ifpx = split_thru_region( ifp, region );
498
499 // Replace 'If' projection of a Region with a Region of
500 // 'If' projections.
501 ifpx->set_req(0, ifpx); // A TRUE RegionNode
502
503 // Setup dominator info
504 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
505
506 // Check for splitting loop tails
507 if( get_loop(iff)->tail() == ifp )
508 get_loop(iff)->_tail = ifpx;
509
510 // Replace in the graph with lazy-update mechanism
511 new_iff->set_req(0, new_iff); // hook self so it does not go dead
512 lazy_replace(ifp, ifpx);
513 new_iff->set_req(0, region);
514
515 // Record bits for later xforms
516 if( ifp->Opcode() == Op_IfFalse ) {
517 old_false = ifp;
518 new_false = ifpx;
519 } else {
520 old_true = ifp;
521 new_true = ifpx;
522 }
523 }
524 _igvn.remove_dead_node(new_iff);
525 // Lazy replace IDOM info with the region's dominator
526 lazy_replace( iff, region_dom );
527
528 // Now make the original merge point go dead, by handling all its uses.
529 small_cache region_cache;
530 // Preload some control flow in region-cache
531 region_cache.lru_insert( new_false, new_false );
532 region_cache.lru_insert( new_true , new_true );
533 // Now handle all uses of the splitting block
534 for (DUIterator k = region->outs(); region->has_out(k); k++) {
535 Node* phi = region->out(k);
536 if (!phi->in(0)) { // Dead phi? Remove it
537 _igvn.remove_dead_node(phi);
538 } else if (phi == region) { // Found the self-reference
539 continue; // No roll-back of DUIterator
540 } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
541 assert(phi->in(0) == region, "Inconsistent graph");
542 // Need a per-def cache. Phi represents a def, so make a cache
543 small_cache phi_cache;
544
545 // Inspect all Phi uses to make the Phi go dead
546 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
547 Node* use = phi->last_out(l);
548 // Compute the new DEF for this USE. New DEF depends on the path
549 // taken from the original DEF to the USE. The new DEF may be some
550 // collection of PHI's merging values from different paths. The Phis
551 // inserted depend only on the location of the USE. We use a
552 // 2-element cache to handle multiple uses from the same block.
553 handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
554 } // End of while phi has uses
555 // Remove the dead Phi
556 _igvn.remove_dead_node( phi );
557 } else {
558 assert(phi->in(0) == region, "Inconsistent graph");
559 // Random memory op guarded by Region. Compute new DEF for USE.
560 handle_use(phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true);
561 }
562 // Every path above deletes a use of the region, except for the region
563 // self-cycle (which is needed by handle_use calling find_use_block
564 // calling get_ctrl calling get_ctrl_no_update looking for dead
565 // regions). So roll back the DUIterator innards.
566 --k;
567 } // End of while merge point has phis
568
569 assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
570 region->set_req(0, NULL); // Break the self-cycle
571
572 // Any leftover bits in the splitting block must not have depended on local
573 // Phi inputs (these have already been split-up). Hence it's safe to hoist
574 // these guys to the dominating point.
575 lazy_replace( region, region_dom );
576 #ifndef PRODUCT
577 if( VerifyLoopOptimizations ) verify();
578 #endif
579 }