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 "opto/addnode.hpp"
26 #include "opto/node.hpp"
27 #include "precompiled.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "opto/callnode.hpp"
30 #include "opto/inlinetypenode.hpp"
31 #include "opto/loopnode.hpp"
32 #include "opto/movenode.hpp"
33 #include "opto/opaquenode.hpp"
34
35
36 //------------------------------split_thru_region------------------------------
37 // Split Node 'n' through merge point.
38 RegionNode* PhaseIdealLoop::split_thru_region(Node* n, RegionNode* region) {
39 assert(n->is_CFG(), "");
40 RegionNode* r = new RegionNode(region->req());
41 IdealLoopTree* loop = get_loop(n);
42 for (uint i = 1; i < region->req(); i++) {
43 Node* x = n->clone();
44 Node* in0 = n->in(0);
45 if (in0->in(0) == region) x->set_req(0, in0->in(i));
46 for (uint j = 1; j < n->req(); j++) {
47 Node* in = n->in(j);
48 if (get_ctrl(in) == region) {
49 x->set_req(j, in->in(i));
50 }
51 }
52 _igvn.register_new_node_with_optimizer(x);
53 set_loop(x, loop);
54 set_idom(x, x->in(0), dom_depth(x->in(0))+1);
55 r->init_req(i, x);
56 }
57
58 // Record region
59 r->set_req(0,region); // Not a TRUE RegionNode
60 _igvn.register_new_node_with_optimizer(r);
61 set_loop(r, loop);
62 if (!loop->_child) {
63 loop->_body.push(r);
64 }
65 return r;
66 }
67
68 //------------------------------split_up---------------------------------------
69 // Split block-local op up through the phis to empty the current block
70 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
71 if( n->is_CFG() ) {
72 assert( n->in(0) != blk1, "Lousy candidate for split-if" );
73 return false;
74 }
75 if (!at_relevant_ctrl(n, blk1, blk2))
76 return false; // Not block local
77 if( n->is_Phi() ) return false; // Local PHIs are expected
78
79 // Recursively split-up inputs
80 for (uint i = 1; i < n->req(); i++) {
81 if( split_up( n->in(i), blk1, blk2 ) ) {
82 // Got split recursively and self went dead?
83 if (n->outcnt() == 0)
84 _igvn.remove_dead_node(n);
85 return true;
86 }
87 }
88
89 if (clone_cmp_loadklass_down(n, blk1, blk2)) {
90 return true;
91 }
92
93 // Check for needing to clone-up a compare. Can't do that, it forces
94 // another (nested) split-if transform. Instead, clone it "down".
95 if (clone_cmp_down(n, blk1, blk2)) {
96 return true;
97 }
98
99 if (subgraph_has_opaque(n)) {
100 Unique_Node_List wq;
101 wq.push(n);
102 for (uint i = 0; i < wq.size(); i++) {
103 Node* m = wq.at(i);
104 if (m->is_If()) {
105 assert(skeleton_predicate_has_opaque(m->as_If()), "opaque node not reachable from if?");
106 Node* bol = clone_skeleton_predicate_bool(m, NULL, NULL, m->in(0));
107 _igvn.replace_input_of(m, 1, bol);
108 } else {
109 assert(!m->is_CFG(), "not CFG expected");
110 for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
111 Node* u = m->fast_out(j);
112 wq.push(u);
113 }
114 }
115 }
116 }
117
118 if (n->Opcode() == Op_OpaqueZeroTripGuard) {
119 // If this Opaque1 is part of the zero trip guard for a loop:
120 // 1- it can't be shared
121 // 2- the zero trip guard can't be the if that's being split
122 // As a consequence, this node could be assigned control anywhere between its current control and the zero trip guard.
123 // Move it down to get it out of the way of split if and avoid breaking the zero trip guard shape.
124 Node* cmp = n->unique_out();
125 assert(cmp->Opcode() == Op_CmpI, "bad zero trip guard shape");
126 Node* bol = cmp->unique_out();
127 assert(bol->Opcode() == Op_Bool, "bad zero trip guard shape");
128 Node* iff = bol->unique_out();
129 assert(iff->Opcode() == Op_If, "bad zero trip guard shape");
130 set_ctrl(n, iff->in(0));
131 set_ctrl(cmp, iff->in(0));
132 set_ctrl(bol, iff->in(0));
133 return true;
134 }
135
136 // See if splitting-up a Store. Any anti-dep loads must go up as
137 // well. An anti-dep load might be in the wrong block, because in
138 // this particular layout/schedule we ignored anti-deps and allow
139 // memory to be alive twice. This only works if we do the same
140 // operations on anti-dep loads as we do their killing stores.
141 if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
142 // Get store's memory slice
143 int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
144
145 // Get memory-phi anti-dep loads will be using
146 Node *memphi = n->in(MemNode::Memory);
147 assert( memphi->is_Phi(), "" );
148 // Hoist any anti-dep load to the splitting block;
149 // it will then "split-up".
150 for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
151 Node *load = memphi->fast_out(i);
152 if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
153 set_ctrl(load,blk1);
154 }
155 }
156
157 // Found some other Node; must clone it up
158 #ifndef PRODUCT
159 if( PrintOpto && VerifyLoopOptimizations ) {
160 tty->print("Cloning up: ");
161 n->dump();
162 }
163 #endif
164
165 // ConvI2L may have type information on it which becomes invalid if
166 // it moves up in the graph so change any clones so widen the type
167 // to TypeLong::INT when pushing it up.
168 const Type* rtype = NULL;
169 if (n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::INT) {
170 rtype = TypeLong::INT;
171 }
172
173 // Now actually split-up this guy. One copy per control path merging.
174 Node *phi = PhiNode::make_blank(blk1, n);
175 for( uint j = 1; j < blk1->req(); j++ ) {
176 Node *x = n->clone();
177 // Widen the type of the ConvI2L when pushing up.
178 if (rtype != NULL) x->as_Type()->set_type(rtype);
179 if( n->in(0) && n->in(0) == blk1 )
180 x->set_req( 0, blk1->in(j) );
181 for( uint i = 1; i < n->req(); i++ ) {
182 Node *m = n->in(i);
183 if( get_ctrl(m) == blk1 ) {
184 assert( m->in(0) == blk1, "" );
185 x->set_req( i, m->in(j) );
186 }
187 }
188 register_new_node( x, blk1->in(j) );
189 phi->init_req( j, x );
190 }
191 // Announce phi to optimizer
192 register_new_node(phi, blk1);
193
194 // Remove cloned-up value from optimizer; use phi instead
195 _igvn.replace_node( n, phi );
196
197 // (There used to be a self-recursive call to split_up() here,
198 // but it is not needed. All necessary forward walking is done
199 // by do_split_if() below.)
200
201 return true;
202 }
203
204 // Look for a (If .. (Bool(CmpP (LoadKlass .. (AddP obj ..)) ..))) and clone all of it down.
205 // There's likely a CheckCastPP on one of the branches of the If, with obj as input.
206 // If the (LoadKlass .. (AddP obj ..)) is not cloned down, then split if transforms this to: (If .. (Bool(CmpP phi1 ..)))
207 // and the CheckCastPP to (CheckCastPP phi2). It's possible then that phi2 is transformed to a CheckCastPP
208 // (through PhiNode::Ideal) and that that CheckCastPP is replaced by another narrower CheckCastPP at the same control
209 // (through ConstraintCastNode::Identity). That could cause the CheckCastPP at the If to become top while (CmpP phi1)
210 // wouldn't constant fold because it's using a different data path. Cloning the whole subgraph down guarantees both the
211 // AddP and CheckCastPP have the same obj input after split if.
212 bool PhaseIdealLoop::clone_cmp_loadklass_down(Node* n, const Node* blk1, const Node* blk2) {
213 if (n->Opcode() == Op_AddP && at_relevant_ctrl(n, blk1, blk2)) {
214 Node_List cmp_nodes;
215 uint old = C->unique();
216 for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
217 Node* u1 = n->fast_out(i);
218 if (u1->Opcode() == Op_LoadNKlass && at_relevant_ctrl(u1, blk1, blk2)) {
219 for (DUIterator_Fast jmax, j = u1->fast_outs(jmax); j < jmax; j++) {
220 Node* u2 = u1->fast_out(j);
221 if (u2->Opcode() == Op_DecodeNKlass && at_relevant_ctrl(u2, blk1, blk2)) {
222 for (DUIterator k = u2->outs(); u2->has_out(k); k++) {
223 Node* u3 = u2->out(k);
224 if (at_relevant_ctrl(u3, blk1, blk2) && clone_cmp_down(u3, blk1, blk2)) {
225 --k;
226 }
227 }
228 for (DUIterator_Fast kmax, k = u2->fast_outs(kmax); k < kmax; k++) {
229 Node* u3 = u2->fast_out(k);
230 if (u3->_idx >= old) {
231 cmp_nodes.push(u3);
232 }
233 }
234 }
235 }
236 } else if (u1->Opcode() == Op_LoadKlass && at_relevant_ctrl(u1, blk1, blk2)) {
237 for (DUIterator j = u1->outs(); u1->has_out(j); j++) {
238 Node* u2 = u1->out(j);
239 if (at_relevant_ctrl(u2, blk1, blk2) && clone_cmp_down(u2, blk1, blk2)) {
240 --j;
241 }
242 }
243 for (DUIterator_Fast kmax, k = u1->fast_outs(kmax); k < kmax; k++) {
244 Node* u2 = u1->fast_out(k);
245 if (u2->_idx >= old) {
246 cmp_nodes.push(u2);
247 }
248 }
249 }
250 }
251
252 for (uint i = 0; i < cmp_nodes.size(); ++i) {
253 Node* cmp = cmp_nodes.at(i);
254 clone_loadklass_nodes_at_cmp_index(n, cmp, 1);
255 clone_loadklass_nodes_at_cmp_index(n, cmp, 2);
256 }
257 if (n->outcnt() == 0) {
258 assert(n->is_dead(), "");
259 return true;
260 }
261 }
262 return false;
263 }
264
265 bool PhaseIdealLoop::at_relevant_ctrl(Node* n, const Node* blk1, const Node* blk2) {
266 return ctrl_or_self(n) == blk1 || ctrl_or_self(n) == blk2;
267 }
268
269 void PhaseIdealLoop::clone_loadklass_nodes_at_cmp_index(const Node* n, Node* cmp, int i) {
270 Node* decode = cmp->in(i);
271 if (decode->Opcode() == Op_DecodeNKlass) {
272 Node* loadklass = decode->in(1);
273 if (loadklass->Opcode() == Op_LoadNKlass) {
274 Node* addp = loadklass->in(MemNode::Address);
275 if (addp == n) {
276 Node* ctrl = get_ctrl(cmp);
277 Node* decode_clone = decode->clone();
278 Node* loadklass_clone = loadklass->clone();
279 Node* addp_clone = addp->clone();
280 register_new_node(decode_clone, ctrl);
281 register_new_node(loadklass_clone, ctrl);
282 register_new_node(addp_clone, ctrl);
283 _igvn.replace_input_of(cmp, i, decode_clone);
284 _igvn.replace_input_of(decode_clone, 1, loadklass_clone);
285 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone);
286 if (decode->outcnt() == 0) {
287 _igvn.remove_dead_node(decode);
288 }
289 }
290 }
291 } else {
292 Node* loadklass = cmp->in(i);
293 if (loadklass->Opcode() == Op_LoadKlass) {
294 Node* addp = loadklass->in(MemNode::Address);
295 if (addp == n) {
296 Node* ctrl = get_ctrl(cmp);
297 Node* loadklass_clone = loadklass->clone();
298 Node* addp_clone = addp->clone();
299 register_new_node(loadklass_clone, ctrl);
300 register_new_node(addp_clone, ctrl);
301 _igvn.replace_input_of(cmp, i, loadklass_clone);
302 _igvn.replace_input_of(loadklass_clone, MemNode::Address, addp_clone);
303 if (loadklass->outcnt() == 0) {
304 _igvn.remove_dead_node(loadklass);
305 }
306 }
307 }
308 }
309 }
310
311 bool PhaseIdealLoop::clone_cmp_down(Node* n, const Node* blk1, const Node* blk2) {
312 if( n->is_Cmp() ) {
313 assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
314 // Check for simple Cmp/Bool/CMove which we can clone-up. Cmp/Bool/CMove
315 // sequence can have no other users and it must all reside in the split-if
316 // block. Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
317 // private, per-use versions of the Cmp and Bool are made. These sink to
318 // the CMove block. If the CMove is in the split-if block, then in the
319 // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
320 Node *bol, *cmov;
321 if (!(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
322 (bol = n->unique_out()->as_Bool()) &&
323 (at_relevant_ctrl(bol, blk1, blk2) &&
324 bol->outcnt() == 1 &&
325 bol->unique_out()->is_CMove() &&
326 (cmov = bol->unique_out()->as_CMove()) &&
327 at_relevant_ctrl(cmov, blk1, blk2)))) {
328
329 // Must clone down
330 #ifndef PRODUCT
331 if( PrintOpto && VerifyLoopOptimizations ) {
332 tty->print("Cloning down: ");
333 n->dump();
334 }
335 #endif
336 if (!n->is_FastLock()) {
337 // Clone down any block-local BoolNode uses of this CmpNode
338 for (DUIterator i = n->outs(); n->has_out(i); i++) {
339 Node* bol = n->out(i);
340 assert( bol->is_Bool(), "" );
341 if (bol->outcnt() == 1) {
342 Node* use = bol->unique_out();
343 if (use->Opcode() == Op_Opaque4) {
344 if (use->outcnt() == 1) {
345 Node* iff = use->unique_out();
346 assert(iff->is_If(), "unexpected node type");
347 Node *use_c = iff->in(0);
348 if (use_c == blk1 || use_c == blk2) {
349 continue;
350 }
351 }
352 } else {
353 // We might see an Opaque1 from a loop limit check here
354 assert(use->is_If() || use->is_CMove() || use->Opcode() == Op_Opaque1 || use->is_AllocateArray(), "unexpected node type");
355 Node *use_c = (use->is_If() || use->is_AllocateArray()) ? use->in(0) : get_ctrl(use);
356 if (use_c == blk1 || use_c == blk2) {
357 assert(use->is_CMove(), "unexpected node type");
358 continue;
359 }
360 }
361 }
362 if (at_relevant_ctrl(bol, blk1, blk2)) {
363 // Recursively sink any BoolNode
364 #ifndef PRODUCT
365 if( PrintOpto && VerifyLoopOptimizations ) {
366 tty->print("Cloning down: ");
367 bol->dump();
368 }
369 #endif
370 for (DUIterator j = bol->outs(); bol->has_out(j); j++) {
371 Node* u = bol->out(j);
372 // Uses are either IfNodes, CMoves or Opaque4
373 if (u->Opcode() == Op_Opaque4) {
374 assert(u->in(1) == bol, "bad input");
375 for (DUIterator_Last kmin, k = u->last_outs(kmin); k >= kmin; --k) {
376 Node* iff = u->last_out(k);
377 assert(iff->is_If() || iff->is_CMove(), "unexpected node type");
378 assert( iff->in(1) == u, "" );
379 // Get control block of either the CMove or the If input
380 Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
381 Node *x1 = bol->clone();
382 Node *x2 = u->clone();
383 register_new_node(x1, iff_ctrl);
384 register_new_node(x2, iff_ctrl);
385 _igvn.replace_input_of(x2, 1, x1);
386 _igvn.replace_input_of(iff, 1, x2);
387 }
388 _igvn.remove_dead_node(u);
389 --j;
390 } else {
391 // We might see an Opaque1 from a loop limit check here
392 assert(u->is_If() || u->is_CMove() || u->Opcode() == Op_Opaque1 || u->is_AllocateArray(), "unexpected node type");
393 assert(u->is_AllocateArray() || u->in(1) == bol, "");
394 assert(!u->is_AllocateArray() || u->in(AllocateNode::ValidLengthTest) == bol, "wrong input to AllocateArray");
395 // Get control block of either the CMove or the If input
396 Node *u_ctrl = (u->is_If() || u->is_AllocateArray()) ? u->in(0) : get_ctrl(u);
397 assert((u_ctrl != blk1 && u_ctrl != blk2) || u->is_CMove(), "won't converge");
398 Node *x = bol->clone();
399 register_new_node(x, u_ctrl);
400 _igvn.replace_input_of(u, u->is_AllocateArray() ? AllocateNode::ValidLengthTest : 1, x);
401 --j;
402 }
403 }
404 _igvn.remove_dead_node(bol);
405 --i;
406 }
407 }
408 }
409 // Clone down this CmpNode
410 for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
411 Node* use = n->last_out(j);
412 uint pos = 1;
413 if (n->is_FastLock()) {
414 pos = TypeFunc::Parms + 2;
415 assert(use->is_Lock(), "FastLock only used by LockNode");
416 }
417 assert(use->in(pos) == n, "" );
418 Node *x = n->clone();
419 register_new_node(x, ctrl_or_self(use));
420 _igvn.replace_input_of(use, pos, x);
421 }
422 _igvn.remove_dead_node(n);
423
424 return true;
425 }
426 }
427 return false;
428 }
429
430 //------------------------------register_new_node------------------------------
431 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
432 assert(!n->is_CFG(), "must be data node");
433 _igvn.register_new_node_with_optimizer(n);
434 set_ctrl(n, blk);
435 IdealLoopTree *loop = get_loop(blk);
436 if( !loop->_child )
437 loop->_body.push(n);
438 }
439
440 //------------------------------small_cache------------------------------------
441 struct small_cache : public Dict {
442
443 small_cache() : Dict( cmpkey, hashptr ) {}
444 Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
445 void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
446 };
447
448 //------------------------------spinup-----------------------------------------
449 // "Spin up" the dominator tree, starting at the use site and stopping when we
450 // find the post-dominating point.
451
452 // We must be at the merge point which post-dominates 'new_false' and
453 // 'new_true'. Figure out which edges into the RegionNode eventually lead up
454 // to false and which to true. Put in a PhiNode to merge values; plug in
455 // the appropriate false-arm or true-arm values. If some path leads to the
456 // original IF, then insert a Phi recursively.
457 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
458 if (use_blk->is_top()) // Handle dead uses
459 return use_blk;
460 Node *prior_n = (Node*)((intptr_t)0xdeadbeef);
461 Node *n = use_blk; // Get path input
462 assert( use_blk != iff_dom, "" );
463 // Here's the "spinup" the dominator tree loop. Do a cache-check
464 // along the way, in case we've come this way before.
465 while( n != iff_dom ) { // Found post-dominating point?
466 prior_n = n;
467 n = idom(n); // Search higher
468 Node *s = cache->probe( prior_n ); // Check cache
469 if( s ) return s; // Cache hit!
470 }
471
472 Node *phi_post;
473 if( prior_n == new_false || prior_n == new_true ) {
474 phi_post = def->clone();
475 phi_post->set_req(0, prior_n );
476 register_new_node(phi_post, prior_n);
477 } else {
478 // This method handles both control uses (looking for Regions) or data
479 // uses (looking for Phis). If looking for a control use, then we need
480 // to insert a Region instead of a Phi; however Regions always exist
481 // previously (the hash_find_insert below would always hit) so we can
482 // return the existing Region.
483 if( def->is_CFG() ) {
484 phi_post = prior_n; // If looking for CFG, return prior
485 } else {
486 assert( def->is_Phi(), "" );
487 assert( prior_n->is_Region(), "must be a post-dominating merge point" );
488
489 // Need a Phi here
490 phi_post = PhiNode::make_blank(prior_n, def);
491 // Search for both true and false on all paths till find one.
492 for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
493 phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
494 Node *t = _igvn.hash_find_insert(phi_post);
495 if( t ) { // See if we already have this one
496 // phi_post will not be used, so kill it
497 _igvn.remove_dead_node(phi_post);
498 phi_post->destruct(&_igvn);
499 phi_post = t;
500 } else {
501 register_new_node( phi_post, prior_n );
502 }
503 }
504 }
505
506 // Update cache everywhere
507 prior_n = (Node*)((intptr_t)0xdeadbeef); // Reset IDOM walk
508 n = use_blk; // Get path input
509 // Spin-up the idom tree again, basically doing path-compression.
510 // Insert cache entries along the way, so that if we ever hit this
511 // point in the IDOM tree again we'll stop immediately on a cache hit.
512 while( n != iff_dom ) { // Found post-dominating point?
513 prior_n = n;
514 n = idom(n); // Search higher
515 cache->lru_insert( prior_n, phi_post ); // Fill cache
516 } // End of while not gone high enough
517
518 return phi_post;
519 }
520
521 //------------------------------find_use_block---------------------------------
522 // Find the block a USE is in. Normally USE's are in the same block as the
523 // using instruction. For Phi-USE's, the USE is in the predecessor block
524 // along the corresponding path.
525 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
526 // CFG uses are their own block
527 if( use->is_CFG() )
528 return use;
529
530 if( use->is_Phi() ) { // Phi uses in prior block
531 // Grab the first Phi use; there may be many.
532 // Each will be handled as a separate iteration of
533 // the "while( phi->outcnt() )" loop.
534 uint j;
535 for( j = 1; j < use->req(); j++ )
536 if( use->in(j) == def )
537 break;
538 assert( j < use->req(), "def should be among use's inputs" );
539 return use->in(0)->in(j);
540 }
541 // Normal (non-phi) use
542 Node *use_blk = get_ctrl(use);
543 // Some uses are directly attached to the old (and going away)
544 // false and true branches.
545 if( use_blk == old_false ) {
546 use_blk = new_false;
547 set_ctrl(use, new_false);
548 }
549 if( use_blk == old_true ) {
550 use_blk = new_true;
551 set_ctrl(use, new_true);
552 }
553
554 if (use_blk == NULL) { // He's dead, Jim
555 _igvn.replace_node(use, C->top());
556 }
557
558 return use_blk;
559 }
560
561 //------------------------------handle_use-------------------------------------
562 // Handle uses of the merge point. Basically, split-if makes the merge point
563 // go away so all uses of the merge point must go away as well. Most block
564 // local uses have already been split-up, through the merge point. Uses from
565 // far below the merge point can't always be split up (e.g., phi-uses are
566 // pinned) and it makes too much stuff live. Instead we use a path-based
567 // solution to move uses down.
568 //
569 // If the use is along the pre-split-CFG true branch, then the new use will
570 // be from the post-split-CFG true merge point. Vice-versa for the false
571 // path. Some uses will be along both paths; then we sink the use to the
572 // post-dominating location; we may need to insert a Phi there.
573 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 ) {
574
575 Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
576 if( !use_blk ) return; // He's dead, Jim
577
578 // Walk up the dominator tree until I hit either the old IfFalse, the old
579 // IfTrue or the old If. Insert Phis where needed.
580 Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
581
582 // Found where this USE goes. Re-point him.
583 uint i;
584 for( i = 0; i < use->req(); i++ )
585 if( use->in(i) == def )
586 break;
587 assert( i < use->req(), "def should be among use's inputs" );
588 _igvn.replace_input_of(use, i, new_def);
589 }
590
591 //------------------------------do_split_if------------------------------------
592 // Found an If getting its condition-code input from a Phi in the same block.
593 // Split thru the Region.
594 void PhaseIdealLoop::do_split_if(Node* iff, RegionNode** new_false_region, RegionNode** new_true_region) {
595 if (PrintOpto && VerifyLoopOptimizations) {
596 tty->print_cr("Split-if");
597 }
598 if (TraceLoopOpts) {
599 tty->print_cr("SplitIf");
600 }
601
602 C->set_major_progress();
603 RegionNode *region = iff->in(0)->as_Region();
604 Node *region_dom = idom(region);
605
606 // We are going to clone this test (and the control flow with it) up through
607 // the incoming merge point. We need to empty the current basic block.
608 // Clone any instructions which must be in this block up through the merge
609 // point.
610 DUIterator i, j;
611 bool progress = true;
612 while (progress) {
613 progress = false;
614 for (i = region->outs(); region->has_out(i); i++) {
615 Node* n = region->out(i);
616 if( n == region ) continue;
617 // The IF to be split is OK.
618 if( n == iff ) continue;
619 if( !n->is_Phi() ) { // Found pinned memory op or such
620 if (split_up(n, region, iff)) {
621 i = region->refresh_out_pos(i);
622 progress = true;
623 }
624 continue;
625 }
626 assert( n->in(0) == region, "" );
627
628 // Recursively split up all users of a Phi
629 for (j = n->outs(); n->has_out(j); j++) {
630 Node* m = n->out(j);
631 // If m is dead, throw it away, and declare progress
632 if (_nodes[m->_idx] == NULL) {
633 _igvn.remove_dead_node(m);
634 // fall through
635 } else if (m != iff && split_up(m, region, iff)) {
636 // fall through
637 } else {
638 continue;
639 }
640 // Something unpredictable changed.
641 // Tell the iterators to refresh themselves, and rerun the loop.
642 i = region->refresh_out_pos(i);
643 j = region->refresh_out_pos(j);
644 progress = true;
645 }
646 }
647 }
648
649 // Now we have no instructions in the block containing the IF.
650 // Split the IF.
651 RegionNode *new_iff = split_thru_region(iff, region);
652
653 // Replace both uses of 'new_iff' with Regions merging True/False
654 // paths. This makes 'new_iff' go dead.
655 Node *old_false = NULL, *old_true = NULL;
656 RegionNode* new_false = NULL;
657 RegionNode* new_true = NULL;
658 for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
659 Node *ifp = iff->last_out(j2);
660 assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
661 ifp->set_req(0, new_iff);
662 RegionNode* ifpx = split_thru_region(ifp, region);
663
664 // Replace 'If' projection of a Region with a Region of
665 // 'If' projections.
666 ifpx->set_req(0, ifpx); // A TRUE RegionNode
667
668 // Setup dominator info
669 set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
670
671 // Check for splitting loop tails
672 if( get_loop(iff)->tail() == ifp )
673 get_loop(iff)->_tail = ifpx;
674
675 // Replace in the graph with lazy-update mechanism
676 new_iff->set_req(0, new_iff); // hook self so it does not go dead
677 lazy_replace(ifp, ifpx);
678 new_iff->set_req(0, region);
679
680 // Record bits for later xforms
681 if( ifp->Opcode() == Op_IfFalse ) {
682 old_false = ifp;
683 new_false = ifpx;
684 } else {
685 old_true = ifp;
686 new_true = ifpx;
687 }
688 }
689 _igvn.remove_dead_node(new_iff);
690 // Lazy replace IDOM info with the region's dominator
691 lazy_replace(iff, region_dom);
692 lazy_update(region, region_dom); // idom must be update before handle_uses
693 region->set_req(0, NULL); // Break the self-cycle. Required for lazy_update to work on region
694
695 // Now make the original merge point go dead, by handling all its uses.
696 small_cache region_cache;
697 // Preload some control flow in region-cache
698 region_cache.lru_insert( new_false, new_false );
699 region_cache.lru_insert( new_true , new_true );
700 // Now handle all uses of the splitting block
701 for (DUIterator k = region->outs(); region->has_out(k); k++) {
702 Node* phi = region->out(k);
703 if (!phi->in(0)) { // Dead phi? Remove it
704 _igvn.remove_dead_node(phi);
705 } else if (phi == region) { // Found the self-reference
706 continue; // No roll-back of DUIterator
707 } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
708 assert(phi->in(0) == region, "Inconsistent graph");
709 // Need a per-def cache. Phi represents a def, so make a cache
710 small_cache phi_cache;
711
712 // Inspect all Phi uses to make the Phi go dead
713 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
714 Node* use = phi->last_out(l);
715 // Compute the new DEF for this USE. New DEF depends on the path
716 // taken from the original DEF to the USE. The new DEF may be some
717 // collection of PHI's merging values from different paths. The Phis
718 // inserted depend only on the location of the USE. We use a
719 // 2-element cache to handle multiple uses from the same block.
720 handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
721 } // End of while phi has uses
722 // Remove the dead Phi
723 _igvn.remove_dead_node( phi );
724 } else {
725 assert(phi->in(0) == region, "Inconsistent graph");
726 // Random memory op guarded by Region. Compute new DEF for USE.
727 handle_use(phi, region, ®ion_cache, region_dom, new_false, new_true, old_false, old_true);
728 }
729 // Every path above deletes a use of the region, except for the region
730 // self-cycle (which is needed by handle_use calling find_use_block
731 // calling get_ctrl calling get_ctrl_no_update looking for dead
732 // regions). So roll back the DUIterator innards.
733 --k;
734 } // End of while merge point has phis
735
736 _igvn.remove_dead_node(region);
737
738 if (new_false_region != NULL) {
739 *new_false_region = new_false;
740 }
741 if (new_true_region != NULL) {
742 *new_true_region = new_true;
743 }
744
745 #ifndef PRODUCT
746 if( VerifyLoopOptimizations ) verify();
747 #endif
748 }