1 /*
2 * Copyright (c) 1999, 2023, 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/addnode.hpp"
28 #include "opto/callnode.hpp"
29 #include "opto/loopnode.hpp"
30 #include "opto/movenode.hpp"
31 #include "opto/node.hpp"
32 #include "opto/opaquenode.hpp"
33
34 //------------------------------split_thru_region------------------------------
35 // Split Node 'n' through merge point.
36 RegionNode* PhaseIdealLoop::split_thru_region(Node* n, RegionNode* region) {
37 assert(n->is_CFG(), "");
38 RegionNode* 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 }
50 _igvn.register_new_node_with_optimizer(x);
51 set_loop(x, loop);
52 set_idom(x, x->in(0), dom_depth(x->in(0))+1);
53 r->init_req(i, x);
54 }
55
56 // Record region
57 r->set_req(0,region); // Not a TRUE RegionNode
58 _igvn.register_new_node_with_optimizer(r);
59 set_loop(r, loop);
60 if (!loop->_child) {
61 loop->_body.push(r);
62 }
63 return r;
64 }
65
66 //------------------------------split_up---------------------------------------
67 // Split block-local op up through the phis to empty the current block
68 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
69 if( n->is_CFG() ) {
70 assert( n->in(0) != blk1, "Lousy candidate for split-if" );
71 return false;
72 }
73 if (!at_relevant_ctrl(n, blk1, blk2))
74 return false; // Not block local
75 if( n->is_Phi() ) return false; // Local PHIs are expected
76
77 // Recursively split-up inputs
78 for (uint i = 1; i < n->req(); i++) {
79 if( split_up( n->in(i), blk1, blk2 ) ) {
80 // Got split recursively and self went dead?
81 if (n->outcnt() == 0)
82 _igvn.remove_dead_node(n);
83 return true;
84 }
85 }
86
87 if (clone_cmp_loadklass_down(n, blk1, blk2)) {
88 return true;
89 }
90
91 // Check for needing to clone-up a compare. Can't do that, it forces
92 // another (nested) split-if transform. Instead, clone it "down".
93 if (clone_cmp_down(n, blk1, blk2)) {
94 return true;
95 }
96
97 if (subgraph_has_opaque(n)) {
98 Unique_Node_List wq;
99 wq.push(n);
100 for (uint i = 0; i < wq.size(); i++) {
101 Node* m = wq.at(i);
102 if (m->is_If()) {
103 assert(assertion_predicate_has_loop_opaque_node(m->as_If()), "opaque node not reachable from if?");
104 Node* bol = create_bool_from_template_assertion_predicate(m, nullptr, nullptr, m->in(0));
105 _igvn.replace_input_of(m, 1, bol);
106 } else {
107 assert(!m->is_CFG(), "not CFG expected");
108 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
109 Node* u = m->fast_out(j);
110 wq.push(u);
111 }
112 }
113 }
114 }
115
116 if (n->Opcode() == Op_OpaqueZeroTripGuard) {
117 // If this Opaque1 is part of the zero trip guard for a loop:
118 // 1- it can't be shared
119 // 2- the zero trip guard can't be the if that's being split
120 // As a consequence, this node could be assigned control anywhere between its current control and the zero trip guard.
121 // Move it down to get it out of the way of split if and avoid breaking the zero trip guard shape.
122 Node* cmp = n->unique_out();
123 assert(cmp->Opcode() == Op_CmpI, "bad zero trip guard shape");
124 Node* bol = cmp->unique_out();
125 assert(bol->Opcode() == Op_Bool, "bad zero trip guard shape");
126 Node* iff = bol->unique_out();
127 assert(iff->Opcode() == Op_If, "bad zero trip guard shape");
128 set_ctrl(n, iff->in(0));
129 set_ctrl(cmp, iff->in(0));
130 set_ctrl(bol, iff->in(0));
131 return true;
132 }
133
134 // See if splitting-up a Store. Any anti-dep loads must go up as
135 // well. An anti-dep load might be in the wrong block, because in
136 // this particular layout/schedule we ignored anti-deps and allow
137 // memory to be alive twice. This only works if we do the same
138 // operations on anti-dep loads as we do their killing stores.
139 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
140 // Get store's memory slice
141 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
142
143 // Get memory-phi anti-dep loads will be using
144 Node *memphi = n->in(MemNode::Memory);
145 assert( memphi->is_Phi(), "" );
146 // Hoist any anti-dep load to the splitting block;
147 // it will then "split-up".
148 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
149 Node *load = memphi->fast_out(i);
150 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
151 set_ctrl(load,blk1);
152 }
153 }
154
155 // Found some other Node; must clone it up
156 #ifndef PRODUCT
157 if( PrintOpto && VerifyLoopOptimizations ) {
158 tty->print("Cloning up: ");
159 n->dump();
160 }
161 #endif
162
163 // ConvI2L may have type information on it which becomes invalid if
164 // it moves up in the graph so change any clones so widen the type
165 // to TypeLong::INT when pushing it up.
166 const Type* rtype = nullptr;
167 if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) {
168 rtype = TypeLong::INT;
169 }
170
171 // Now actually split-up this guy. One copy per control path merging.
172 Node *phi = PhiNode::make_blank(blk1, n);
173 for( uint j = 1; j < blk1->req(); j++ ) {
174 Node *x = n->clone();
175 // Widen the type of the ConvI2L when pushing up.
176 if (rtype != nullptr) x->as_Type()->set_type(rtype);
177 if( n->in(0) && n->in(0) == blk1 )
178 x->set_req( 0, blk1->in(j) );
179 for( uint i = 1; i < n->req(); i++ ) {
180 Node *m = n->in(i);
181 if( get_ctrl(m) == blk1 ) {
182 assert( m->in(0) == blk1, "" );
183 x->set_req( i, m->in(j) );
184 }
185 }
186 register_new_node( x, blk1->in(j) );
187 phi->init_req( j, x );
188 }
189 // Announce phi to optimizer
190 register_new_node(phi, blk1);
191
192 // Remove cloned-up value from optimizer; use phi instead
193 _igvn.replace_node( n, phi );
194
195 // (There used to be a self-recursive call to split_up() here,
196 // but it is not needed. All necessary forward walking is done
197 // by do_split_if() below.)
198
199 return true;
200 }
201
202 // Look for a (If .. (Bool(CmpP (LoadKlass .. (AddP obj ..)) ..))) and clone all of it down.
203 // There's likely a CheckCastPP on one of the branches of the If, with obj as input.
204 // If the (LoadKlass .. (AddP obj ..)) is not cloned down, then split if transforms this to: (If .. (Bool(CmpP phi1 ..)))
205 // and the CheckCastPP to (CheckCastPP phi2). It's possible then that phi2 is transformed to a CheckCastPP
206 // (through PhiNode::Ideal) and that that CheckCastPP is replaced by another narrower CheckCastPP at the same control
207 // (through ConstraintCastNode::Identity). That could cause the CheckCastPP at the If to become top while (CmpP phi1)
208 // wouldn't constant fold because it's using a different data path. Cloning the whole subgraph down guarantees both the
209 // AddP and CheckCastPP have the same obj input after split if.
210 bool PhaseIdealLoop::clone_cmp_loadklass_down(Node* n, const Node* blk1, const Node* blk2) {
211 if (n->Opcode() == Op_AddP && at_relevant_ctrl(n, blk1, blk2)) {
212 Node_List cmp_nodes;
213 uint old = C->unique();
214 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
215 Node* u1 = n->fast_out(i);
216 if (u1->Opcode() == Op_LoadNKlass && at_relevant_ctrl(u1, blk1, blk2)) {
217 for (DUIterator_Fast jmax, j = u1->fast_outs(jmax); j < jmax; j++) {
218 Node* u2 = u1->fast_out(j);
219 if (u2->Opcode() == Op_DecodeNKlass && at_relevant_ctrl(u2, blk1, blk2)) {
220 for (DUIterator k = u2->outs(); u2->has_out(k); k++) {
221 Node* u3 = u2->out(k);
222 if (at_relevant_ctrl(u3, blk1, blk2) && clone_cmp_down(u3, blk1, blk2)) {
223 --k;
224 }
225 }
226 for (DUIterator_Fast kmax, k = u2->fast_outs(kmax); k < kmax; k++) {
227 Node* u3 = u2->fast_out(k);
228 if (u3->_idx >= old) {
229 cmp_nodes.push(u3);
230 }
231 }
232 }
233 }
234 } else if (u1->Opcode() == Op_LoadKlass && at_relevant_ctrl(u1, blk1, blk2)) {
235 for (DUIterator j = u1->outs(); u1->has_out(j); j++) {
236 Node* u2 = u1->out(j);
237 if (at_relevant_ctrl(u2, blk1, blk2) && clone_cmp_down(u2, blk1, blk2)) {
238 --j;
239 }
240 }
241 for (DUIterator_Fast kmax, k = u1->fast_outs(kmax); k < kmax; k++) {
242 Node* u2 = u1->fast_out(k);
243 if (u2->_idx >= old) {
244 cmp_nodes.push(u2);
245 }
246 }
247 }
248 }
249
250 for (uint i = 0; i < cmp_nodes.size(); ++i) {
251 Node* cmp = cmp_nodes.at(i);
252 clone_loadklass_nodes_at_cmp_index(n, cmp, 1);
253 clone_loadklass_nodes_at_cmp_index(n, cmp, 2);
254 }
255 if (n->outcnt() == 0) {
256 assert(n->is_dead(), "");
257 return true;
258 }
259 }
260 return false;
261 }
262
263 bool PhaseIdealLoop::at_relevant_ctrl(Node* n, const Node* blk1, const Node* blk2) {
264 return ctrl_or_self(n) == blk1 || ctrl_or_self(n) == blk2;
265 }
266
267 void PhaseIdealLoop::clone_loadklass_nodes_at_cmp_index(const Node* n, Node* cmp, int i) {
268 Node* decode = cmp->in(i);
269 if (decode->Opcode() == Op_DecodeNKlass) {
270 Node* loadklass = decode->in(1);
271 if (loadklass->Opcode() == Op_LoadNKlass) {
272 Node* addp = loadklass->in(MemNode::Address);
273 if (addp == n) {
274 Node* ctrl = get_ctrl(cmp);
275 Node* decode_clone = decode->clone();
276 Node* loadklass_clone = loadklass->clone();
277 Node* addp_clone = addp->clone();
278 register_new_node(decode_clone, ctrl);
279 register_new_node(loadklass_clone, ctrl);
280 register_new_node(addp_clone, ctrl);
281 _igvn.replace_input_of(cmp, i, decode_clone);
282 _igvn.replace_input_of(decode_clone, 1, loadklass_clone);
283 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone);
284 if (decode->outcnt() == 0) {
285 _igvn.remove_dead_node(decode);
286 }
287 }
288 }
289 } else {
290 Node* loadklass = cmp->in(i);
291 if (loadklass->Opcode() == Op_LoadKlass) {
292 Node* addp = loadklass->in(MemNode::Address);
293 if (addp == n) {
294 Node* ctrl = get_ctrl(cmp);
295 Node* loadklass_clone = loadklass->clone();
296 Node* addp_clone = addp->clone();
297 register_new_node(loadklass_clone, ctrl);
298 register_new_node(addp_clone, ctrl);
299 _igvn.replace_input_of(cmp, i, loadklass_clone);
300 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone);
301 if (loadklass->outcnt() == 0) {
302 _igvn.remove_dead_node(loadklass);
303 }
304 }
305 }
306 }
307 }
308
309 bool PhaseIdealLoop::clone_cmp_down(Node* n, const Node* blk1, const Node* blk2) {
310 if( n->is_Cmp() ) {
311 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
312 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
313 // sequence can have no other users and it must all reside in the split-if
314 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
315 // private, per-use versions of the Cmp and Bool are made. These sink to
316 // the CMove block. If the CMove is in the split-if block, then in the
317 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
318 Node *bol, *cmov;
319 if (!(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
320 (bol = n->unique_out()->as_Bool()) &&
321 (at_relevant_ctrl(bol, blk1, blk2) &&
322 bol->outcnt() == 1 &&
323 bol->unique_out()->is_CMove() &&
324 (cmov = bol->unique_out()->as_CMove()) &&
325 at_relevant_ctrl(cmov, blk1, blk2)))) {
326
327 // Must clone down
328 #ifndef PRODUCT
329 if( PrintOpto && VerifyLoopOptimizations ) {
330 tty->print("Cloning down: ");
331 n->dump();
332 }
333 #endif
334 if (!n->is_FastLock()) {
335 // Clone down any block-local BoolNode uses of this CmpNode
336 for (DUIterator i = n->outs(); n->has_out(i); i++) {
337 Node* bol = n->out(i);
338 assert( bol->is_Bool(), "" );
339 if (bol->outcnt() == 1) {
340 Node* use = bol->unique_out();
341 if (use->Opcode() == Op_Opaque4) {
342 if (use->outcnt() == 1) {
343 Node* iff = use->unique_out();
344 assert(iff->is_If(), "unexpected node type");
345 Node *use_c = iff->in(0);
346 if (use_c == blk1 || use_c == blk2) {
347 continue;
348 }
349 }
350 } else {
351 // We might see an Opaque1 from a loop limit check here
352 assert(use->is_If() || use->is_CMove() || use->Opcode() == Op_Opaque1 || use->is_AllocateArray(), "unexpected node type");
353 Node *use_c = (use->is_If() || use->is_AllocateArray()) ? use->in(0) : get_ctrl(use);
354 if (use_c == blk1 || use_c == blk2) {
355 assert(use->is_CMove(), "unexpected node type");
356 continue;
357 }
358 }
359 }
360 if (at_relevant_ctrl(bol, blk1, blk2)) {
361 // Recursively sink any BoolNode
362 #ifndef PRODUCT
363 if( PrintOpto && VerifyLoopOptimizations ) {
364 tty->print("Cloning down: ");
365 bol->dump();
366 }
367 #endif
368 for (DUIterator j = bol->outs(); bol->has_out(j); j++) {
369 Node* u = bol->out(j);
370 // Uses are either IfNodes, CMoves or Opaque4
371 if (u->Opcode() == Op_Opaque4) {
372 assert(u->in(1) == bol, "bad input");
373 for (DUIterator_Last kmin, k = u->last_outs(kmin); k >= kmin; --k) {
374 Node* iff = u->last_out(k);
375 assert(iff->is_If() || iff->is_CMove(), "unexpected node type");
376 assert( iff->in(1) == u, "" );
377 // Get control block of either the CMove or the If input
378 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
379 Node *x1 = bol->clone();
380 Node *x2 = u->clone();
381 register_new_node(x1, iff_ctrl);
382 register_new_node(x2, iff_ctrl);
383 _igvn.replace_input_of(x2, 1, x1);
384 _igvn.replace_input_of(iff, 1, x2);
385 }
386 _igvn.remove_dead_node(u);
387 --j;
388 } else {
389 // We might see an Opaque1 from a loop limit check here
390 assert(u->is_If() || u->is_CMove() || u->Opcode() == Op_Opaque1 || u->is_AllocateArray(), "unexpected node type");
391 assert(u->is_AllocateArray() || u->in(1) == bol, "");
392 assert(!u->is_AllocateArray() || u->in(AllocateNode::ValidLengthTest) == bol, "wrong input to AllocateArray");
393 // Get control block of either the CMove or the If input
394 Node *u_ctrl = (u->is_If() || u->is_AllocateArray()) ? u->in(0) : get_ctrl(u);
395 assert((u_ctrl != blk1 && u_ctrl != blk2) || u->is_CMove(), "won't converge");
396 Node *x = bol->clone();
397 register_new_node(x, u_ctrl);
398 _igvn.replace_input_of(u, u->is_AllocateArray() ? AllocateNode::ValidLengthTest : 1, x);
399 --j;
400 }
401 }
402 _igvn.remove_dead_node(bol);
403 --i;
404 }
405 }
406 }
407 // Clone down this CmpNode
408 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
409 Node* use = n->last_out(j);
410 uint pos = 1;
411 if (n->is_FastLock()) {
412 pos = TypeFunc::Parms + 2;
413 assert(use->is_Lock(), "FastLock only used by LockNode");
414 }
415 assert(use->in(pos) == n, "" );
416 Node *x = n->clone();
417 register_new_node(x, ctrl_or_self(use));
418 _igvn.replace_input_of(use, pos, x);
419 }
420 _igvn.remove_dead_node(n);
421
422 return true;
423 }
424 }
425 return false;
426 }
427
428 //------------------------------register_new_node------------------------------
429 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
430 assert(!n->is_CFG(), "must be data node");
431 _igvn.register_new_node_with_optimizer(n);
432 set_ctrl(n, blk);
433 IdealLoopTree *loop = get_loop(blk);
434 if( !loop->_child )
435 loop->_body.push(n);
436 }
437
438 //------------------------------small_cache------------------------------------
439 struct small_cache : public Dict {
440
441 small_cache() : Dict( cmpkey, hashptr ) {}
442 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
443 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
444 };
445
446 //------------------------------spinup-----------------------------------------
447 // "Spin up" the dominator tree, starting at the use site and stopping when we
448 // find the post-dominating point.
449
450 // We must be at the merge point which post-dominates 'new_false' and
451 // 'new_true'. Figure out which edges into the RegionNode eventually lead up
452 // to false and which to true. Put in a PhiNode to merge values; plug in
453 // the appropriate false-arm or true-arm values. If some path leads to the
454 // original IF, then insert a Phi recursively.
455 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
456 if (use_blk->is_top()) // Handle dead uses
457 return use_blk;
458 Node *prior_n = (Node*)((intptr_t)0xdeadbeef);
459 Node *n = use_blk; // Get path input
460 assert( use_blk != iff_dom, "" );
461 // Here's the "spinup" the dominator tree loop. Do a cache-check
462 // along the way, in case we've come this way before.
463 while( n != iff_dom ) { // Found post-dominating point?
464 prior_n = n;
465 n = idom(n); // Search higher
466 Node *s = cache->probe( prior_n ); // Check cache
467 if( s ) return s; // Cache hit!
468 }
469
470 Node *phi_post;
471 if( prior_n == new_false || prior_n == new_true ) {
472 phi_post = def->clone();
473 phi_post->set_req(0, prior_n );
474 register_new_node(phi_post, prior_n);
475 } else {
476 // This method handles both control uses (looking for Regions) or data
477 // uses (looking for Phis). If looking for a control use, then we need
478 // to insert a Region instead of a Phi; however Regions always exist
479 // previously (the hash_find_insert below would always hit) so we can
480 // return the existing Region.
481 if( def->is_CFG() ) {
482 phi_post = prior_n; // If looking for CFG, return prior
483 } else {
484 assert( def->is_Phi(), "" );
485 assert( prior_n->is_Region(), "must be a post-dominating merge point" );
486
487 // Need a Phi here
488 phi_post = PhiNode::make_blank(prior_n, def);
489 // Search for both true and false on all paths till find one.
490 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
491 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
492 Node *t = _igvn.hash_find_insert(phi_post);
493 if( t ) { // See if we already have this one
494 // phi_post will not be used, so kill it
495 _igvn.remove_dead_node(phi_post);
496 phi_post->destruct(&_igvn);
497 phi_post = t;
498 } else {
499 register_new_node( phi_post, prior_n );
500 }
501 }
502 }
503
504 // Update cache everywhere
505 prior_n = (Node*)((intptr_t)0xdeadbeef); // Reset IDOM walk
506 n = use_blk; // Get path input
507 // Spin-up the idom tree again, basically doing path-compression.
508 // Insert cache entries along the way, so that if we ever hit this
509 // point in the IDOM tree again we'll stop immediately on a cache hit.
510 while( n != iff_dom ) { // Found post-dominating point?
511 prior_n = n;
512 n = idom(n); // Search higher
513 cache->lru_insert( prior_n, phi_post ); // Fill cache
514 } // End of while not gone high enough
515
516 return phi_post;
517 }
518
519 //------------------------------find_use_block---------------------------------
520 // Find the block a USE is in. Normally USE's are in the same block as the
521 // using instruction. For Phi-USE's, the USE is in the predecessor block
522 // along the corresponding path.
523 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
524 // CFG uses are their own block
525 if( use->is_CFG() )
526 return use;
527
528 if( use->is_Phi() ) { // Phi uses in prior block
529 // Grab the first Phi use; there may be many.
530 // Each will be handled as a separate iteration of
531 // the "while( phi->outcnt() )" loop.
532 uint j;
533 for( j = 1; j < use->req(); j++ )
534 if( use->in(j) == def )
535 break;
536 assert( j < use->req(), "def should be among use's inputs" );
537 return use->in(0)->in(j);
538 }
539 // Normal (non-phi) use
540 Node *use_blk = get_ctrl(use);
541 // Some uses are directly attached to the old (and going away)
542 // false and true branches.
543 if( use_blk == old_false ) {
544 use_blk = new_false;
545 set_ctrl(use, new_false);
546 }
547 if( use_blk == old_true ) {
548 use_blk = new_true;
549 set_ctrl(use, new_true);
550 }
551
552 if (use_blk == nullptr) { // He's dead, Jim
553 _igvn.replace_node(use, C->top());
554 }
555
556 return use_blk;
557 }
558
559 //------------------------------handle_use-------------------------------------
560 // Handle uses of the merge point. Basically, split-if makes the merge point
561 // go away so all uses of the merge point must go away as well. Most block
562 // local uses have already been split-up, through the merge point. Uses from
563 // far below the merge point can't always be split up (e.g., phi-uses are
564 // pinned) and it makes too much stuff live. Instead we use a path-based
565 // solution to move uses down.
566 //
567 // If the use is along the pre-split-CFG true branch, then the new use will
568 // be from the post-split-CFG true merge point. Vice-versa for the false
569 // path. Some uses will be along both paths; then we sink the use to the
570 // post-dominating location; we may need to insert a Phi there.
571 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 ) {
572
573 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
574 if( !use_blk ) return; // He's dead, Jim
575
576 // Walk up the dominator tree until I hit either the old IfFalse, the old
577 // IfTrue or the old If. Insert Phis where needed.
578 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
579
580 // Found where this USE goes. Re-point him.
581 uint i;
582 for( i = 0; i < use->req(); i++ )
583 if( use->in(i) == def )
584 break;
585 assert( i < use->req(), "def should be among use's inputs" );
586 _igvn.replace_input_of(use, i, new_def);
587 }
588
589 //------------------------------do_split_if------------------------------------
590 // Found an If getting its condition-code input from a Phi in the same block.
591 // Split thru the Region.
592 void PhaseIdealLoop::do_split_if(Node* iff, RegionNode** new_false_region, RegionNode** new_true_region) {
593
594 C->set_major_progress();
595 RegionNode *region = iff->in(0)->as_Region();
596 Node *region_dom = idom(region);
597
598 // We are going to clone this test (and the control flow with it) up through
599 // the incoming merge point. We need to empty the current basic block.
600 // Clone any instructions which must be in this block up through the merge
601 // point.
602 DUIterator i, j;
603 bool progress = true;
604 while (progress) {
605 progress = false;
606 for (i = region->outs(); region->has_out(i); i++) {
607 Node* n = region->out(i);
608 if( n == region ) continue;
609 // The IF to be split is OK.
610 if( n == iff ) continue;
611 if( !n->is_Phi() ) { // Found pinned memory op or such
612 if (split_up(n, region, iff)) {
613 i = region->refresh_out_pos(i);
614 progress = true;
615 }
616 continue;
617 }
618 assert( n->in(0) == region, "" );
619
620 // Recursively split up all users of a Phi
621 for (j = n->outs(); n->has_out(j); j++) {
622 Node* m = n->out(j);
623 // If m is dead, throw it away, and declare progress
624 if (_loop_or_ctrl[m->_idx] == nullptr) {
625 _igvn.remove_dead_node(m);
626 // fall through
627 }628 else if (m != iff && split_up(m, region, iff)) {
629 // fall through
630 } else {
631 continue;
632 }
633 // Something unpredictable changed.
634 // Tell the iterators to refresh themselves, and rerun the loop.
635 i = region->refresh_out_pos(i);
636 j = region->refresh_out_pos(j);
637 progress = true;
638 }
639 }
640 }
641
642 // Now we have no instructions in the block containing the IF.
643 // Split the IF.
644 RegionNode *new_iff = split_thru_region(iff, region);
645
646 // Replace both uses of 'new_iff' with Regions merging True/False
647 // paths. This makes 'new_iff' go dead.
648 Node *old_false = nullptr, *old_true = nullptr;
649 RegionNode* new_false = nullptr;
650 RegionNode* new_true = nullptr;
651 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
652 Node *ifp = iff->last_out(j2);
653 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
654 ifp->set_req(0, new_iff);
655 RegionNode* ifpx = split_thru_region(ifp, region);
656
657 // Replace 'If' projection of a Region with a Region of
658 // 'If' projections.
659 ifpx->set_req(0, ifpx); // A TRUE RegionNode
660
661 // Setup dominator info
662 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
663
664 // Check for splitting loop tails
665 if( get_loop(iff)->tail() == ifp )
666 get_loop(iff)->_tail = ifpx;
667
668 // Replace in the graph with lazy-update mechanism
669 new_iff->set_req(0, new_iff); // hook self so it does not go dead
670 lazy_replace(ifp, ifpx);
671 new_iff->set_req(0, region);
672
673 // Record bits for later xforms
674 if( ifp->Opcode() == Op_IfFalse ) {
675 old_false = ifp;
676 new_false = ifpx;
677 } else {
678 old_true = ifp;
679 new_true = ifpx;
680 }
681 }
682 _igvn.remove_dead_node(new_iff);
683 // Lazy replace IDOM info with the region's dominator
684 lazy_replace(iff, region_dom);
685 lazy_update(region, region_dom); // idom must be update before handle_uses
686 region->set_req(0, nullptr); // Break the self-cycle. Required for lazy_update to work on region
687
688 // Now make the original merge point go dead, by handling all its uses.
689 small_cache region_cache;
690 // Preload some control flow in region-cache
691 region_cache.lru_insert( new_false, new_false );
692 region_cache.lru_insert( new_true , new_true );
693 // Now handle all uses of the splitting block
694 for (DUIterator k = region->outs(); region->has_out(k); k++) {
695 Node* phi = region->out(k);
696 if (!phi->in(0)) { // Dead phi? Remove it
697 _igvn.remove_dead_node(phi);
698 } else if (phi == region) { // Found the self-reference
699 continue; // No roll-back of DUIterator
700 } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
701 assert(phi->in(0) == region, "Inconsistent graph");
702 // Need a per-def cache. Phi represents a def, so make a cache
703 small_cache phi_cache;
704
705 // Inspect all Phi uses to make the Phi go dead
706 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
707 Node* use = phi->last_out(l);
708 // Compute the new DEF for this USE. New DEF depends on the path
709 // taken from the original DEF to the USE. The new DEF may be some
710 // collection of PHI's merging values from different paths. The Phis
711 // inserted depend only on the location of the USE. We use a
712 // 2-element cache to handle multiple uses from the same block.
713 handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
714 } // End of while phi has uses
715 // Remove the dead Phi
716 _igvn.remove_dead_node( phi );
717 } else {
718 assert(phi->in(0) == region, "Inconsistent graph");
719 // Random memory op guarded by Region. Compute new DEF for USE.
720 handle_use(phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true);
721 }
722 // Every path above deletes a use of the region, except for the region
723 // self-cycle (which is needed by handle_use calling find_use_block
724 // calling get_ctrl calling get_ctrl_no_update looking for dead
725 // regions). So roll back the DUIterator innards.
726 --k;
727 } // End of while merge point has phis
728
729 _igvn.remove_dead_node(region);
730
731 if (new_false_region != nullptr) {
732 *new_false_region = new_false;
733 }
734 if (new_true_region != nullptr) {
735 *new_true_region = new_true;
736 }
737
738 DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
739 }
--- EOF ---