1/*
2 * Copyright (c) 2006, 2019, 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.
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23 */
24
25#include "precompiled.hpp"
26#include "memory/allocation.inline.hpp"
27#include "opto/connode.hpp"
28#include "opto/convertnode.hpp"
29#include "opto/loopnode.hpp"
30#include "opto/opaquenode.hpp"
31#include "opto/rootnode.hpp"
32
33//================= Loop Unswitching =====================
34//
35// orig: transformed:
36// if (invariant-test) then
37// predicate predicate
38// loop loop
39// stmt1 stmt1
40// if (invariant-test) then stmt2
41// stmt2 stmt4
42// else endloop
43// stmt3 else
44// endif predicate [clone]
45// stmt4 loop [clone]
46// endloop stmt1 [clone]
47// stmt3
48// stmt4 [clone]
49// endloop
50// endif
51//
52// Note: the "else" clause may be empty
53
54//------------------------------policy_unswitching-----------------------------
55// Return TRUE or FALSE if the loop should be unswitched
56// (ie. clone loop with an invariant test that does not exit the loop)
57bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {
58 if (!LoopUnswitching) {
59 return false;
60 }
61 if (!_head->is_Loop()) {
62 return false;
63 }
64
65 // If nodes are depleted, some transform has miscalculated its needs.
66 assert(!phase->exceeding_node_budget(), "sanity");
67
68 // check for vectorized loops, any unswitching was already applied
69 if (_head->is_CountedLoop() && _head->as_CountedLoop()->is_unroll_only()) {
70 return false;
71 }
72
73 LoopNode* head = _head->as_Loop();
74 if (head->unswitch_count() + 1 > head->unswitch_max()) {
75 return false;
76 }
77 if (phase->find_unswitching_candidate(this) == NULL) {
78 return false;
79 }
80
81 // Too speculative if running low on nodes.
82 return phase->may_require_nodes(est_loop_clone_sz(2));
83}
84
85//------------------------------find_unswitching_candidate-----------------------------
86// Find candidate "if" for unswitching
87IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {
88
89 // Find first invariant test that doesn't exit the loop
90 LoopNode *head = loop->_head->as_Loop();
91 IfNode* unswitch_iff = NULL;
92 Node* n = head->in(LoopNode::LoopBackControl);
93 while (n != head) {
94 Node* n_dom = idom(n);
95 if (n->is_Region()) {
96 if (n_dom->is_If()) {
97 IfNode* iff = n_dom->as_If();
98 if (iff->in(1)->is_Bool()) {
99 BoolNode* bol = iff->in(1)->as_Bool();
100 if (bol->in(1)->is_Cmp()) {
101 // If condition is invariant and not a loop exit,
102 // then found reason to unswitch.
103 if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {
104 unswitch_iff = iff;
105 }
106 }
107 }
108 }
109 }
110 n = n_dom;
111 }
112 return unswitch_iff;
113}
114
115//------------------------------do_unswitching-----------------------------
116// Clone loop with an invariant test (that does not exit) and
117// insert a clone of the test that selects which version to
118// execute.
119void PhaseIdealLoop::do_unswitching(IdealLoopTree *loop, Node_List &old_new) {
120
121 // Find first invariant test that doesn't exit the loop
122 LoopNode *head = loop->_head->as_Loop();
123
124 IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
125 assert(unswitch_iff != NULL, "should be at least one");
126
127#ifndef PRODUCT
128 if (TraceLoopOpts) {
129 tty->print("Unswitch %d ", head->unswitch_count()+1);
130 loop->dump_head();
131 }
132#endif
133
134 // Need to revert back to normal loop
135 if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
136 head->as_CountedLoop()->set_normal_loop();
137 }
138
139 ProjNode* proj_true = create_slow_version_of_loop(loop, old_new, unswitch_iff->Opcode(), CloneIncludesStripMined);
140
141#ifdef ASSERT
142 Node* uniqc = proj_true->unique_ctrl_out();
143 Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
144 Node* predicate = find_predicate(entry);
145 if (predicate != NULL) {
146 entry = skip_loop_predicates(entry);
147 }
148 if (predicate != NULL && UseLoopPredicate) {
149 // We may have two predicates, find first.
150 Node* n = find_predicate(entry);
151 if (n != NULL) {
152 predicate = n;
153 entry = skip_loop_predicates(entry);
154 }
155 }
156 if (predicate != NULL && UseProfiledLoopPredicate) {
157 entry = find_predicate(entry);
158 if (entry != NULL) predicate = entry;
159 }
160 if (predicate != NULL) predicate = predicate->in(0);
161 assert(proj_true->is_IfTrue() &&
162 (predicate == NULL && uniqc == head && !head->is_strip_mined() ||
163 predicate == NULL && uniqc == head->in(LoopNode::EntryControl) && head->is_strip_mined() ||
164 predicate != NULL && uniqc == predicate), "by construction");
165#endif
166 // Increment unswitch count
167 LoopNode* head_clone = old_new[head->_idx]->as_Loop();
168 int nct = head->unswitch_count() + 1;
169 head->set_unswitch_count(nct);
170 head_clone->set_unswitch_count(nct);
171
172 // Add test to new "if" outside of loop
173 IfNode* invar_iff = proj_true->in(0)->as_If();
174 Node* invar_iff_c = invar_iff->in(0);
175 BoolNode* bol = unswitch_iff->in(1)->as_Bool();
176 invar_iff->set_req(1, bol);
177 invar_iff->_prob = unswitch_iff->_prob;
178
179 ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
180
181 // Hoist invariant casts out of each loop to the appropriate
182 // control projection.
183
184 Node_List worklist;
185
186 for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
187 ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
188 // Copy to a worklist for easier manipulation
189 for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
190 Node* use = proj->fast_out(j);
191 if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
192 worklist.push(use);
193 }
194 }
195 ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
196 while (worklist.size() > 0) {
197 Node* use = worklist.pop();
198 Node* nuse = use->clone();
199 nuse->set_req(0, invar_proj);
200 _igvn.replace_input_of(use, 1, nuse);
201 register_new_node(nuse, invar_proj);
202 // Same for the clone
203 Node* use_clone = old_new[use->_idx];
204 _igvn.replace_input_of(use_clone, 1, nuse);
205 }
206 }
207
208 // Hardwire the control paths in the loops into if(true) and if(false)
209 _igvn.rehash_node_delayed(unswitch_iff);
210 short_circuit_if(unswitch_iff, proj_true);
211
212 IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
213 _igvn.rehash_node_delayed(unswitch_iff_clone);
214 short_circuit_if(unswitch_iff_clone, proj_false);
215
216 // Reoptimize loops
217 loop->record_for_igvn();
218 for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
219 Node *n = loop->_body[i];
220 Node *n_clone = old_new[n->_idx];
221 _igvn._worklist.push(n_clone);
222 }
223
224#ifndef PRODUCT
225 if (TraceLoopUnswitching) {
226 tty->print_cr("Loop unswitching orig: %d @ %d new: %d @ %d",
227 head->_idx, unswitch_iff->_idx,
228 old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
229 }
230#endif
231
232 C->set_major_progress();
233}
234
235//-------------------------create_slow_version_of_loop------------------------
236// Create a slow version of the loop by cloning the loop
237// and inserting an if to select fast-slow versions.
238// Return control projection of the entry to the fast version.
239ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,
240 Node_List &old_new,
241 int opcode,
242 CloneLoopMode mode) {
243 LoopNode* head = loop->_head->as_Loop();
244 bool counted_loop = head->is_CountedLoop();
245 Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
246 _igvn.rehash_node_delayed(entry);
247 IdealLoopTree* outer_loop = loop->_parent;
248
249 head->verify_strip_mined(1);
250
251 Node *cont = _igvn.intcon(1);
252 set_ctrl(cont, C->root());
253 Node* opq = new Opaque1Node(C, cont);
254 register_node(opq, outer_loop, entry, dom_depth(entry));
255 Node *bol = new Conv2BNode(opq);
256 register_node(bol, outer_loop, entry, dom_depth(entry));
257 IfNode* iff = (opcode == Op_RangeCheck) ? new RangeCheckNode(entry, bol, PROB_MAX, COUNT_UNKNOWN) :
258 new IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);
259 register_node(iff, outer_loop, entry, dom_depth(entry));
260 ProjNode* iffast = new IfTrueNode(iff);
261 register_node(iffast, outer_loop, iff, dom_depth(iff));
262 ProjNode* ifslow = new IfFalseNode(iff);
263 register_node(ifslow, outer_loop, iff, dom_depth(iff));
264
265 // Clone the loop body. The clone becomes the fast loop. The
266 // original pre-header will (illegally) have 3 control users
267 // (old & new loops & new if).
268 clone_loop(loop, old_new, dom_depth(head->skip_strip_mined()), mode, iff);
269 assert(old_new[head->_idx]->is_Loop(), "" );
270
271 // Fast (true) control
272 Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop);
273
274 // Slow (false) control
275 Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop);
276
277 Node* l = head->skip_strip_mined();
278 _igvn.replace_input_of(l, LoopNode::EntryControl, iffast_pred);
279 set_idom(l, iffast_pred, dom_depth(l));
280 LoopNode* slow_l = old_new[head->_idx]->as_Loop()->skip_strip_mined();
281 _igvn.replace_input_of(slow_l, LoopNode::EntryControl, ifslow_pred);
282 set_idom(slow_l, ifslow_pred, dom_depth(l));
283
284 recompute_dom_depth();
285
286 return iffast;
287}
288
289LoopNode* PhaseIdealLoop::create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk) {
290 Node_List old_new;
291 LoopNode* head = loop->_head->as_Loop();
292 bool counted_loop = head->is_CountedLoop();
293 Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
294 _igvn.rehash_node_delayed(entry);
295 IdealLoopTree* outer_loop = head->is_strip_mined() ? loop->_parent->_parent : loop->_parent;
296
297 ConINode* const_1 = _igvn.intcon(1);
298 set_ctrl(const_1, C->root());
299 IfNode* iff = new IfNode(entry, const_1, PROB_MAX, COUNT_UNKNOWN);
300 register_node(iff, outer_loop, entry, dom_depth(entry));
301 ProjNode* iffast = new IfTrueNode(iff);
302 register_node(iffast, outer_loop, iff, dom_depth(iff));
303 ProjNode* ifslow = new IfFalseNode(iff);
304 register_node(ifslow, outer_loop, iff, dom_depth(iff));
305
306 // Clone the loop body. The clone becomes the fast loop. The
307 // original pre-header will (illegally) have 3 control users
308 // (old & new loops & new if).
309 clone_loop(loop, old_new, dom_depth(head), CloneIncludesStripMined, iff);
310 assert(old_new[head->_idx]->is_Loop(), "" );
311
312 LoopNode* slow_head = old_new[head->_idx]->as_Loop();
313
314#ifndef PRODUCT
315 if (TraceLoopOpts) {
316 tty->print_cr("PhaseIdealLoop::create_reserve_version_of_loop:");
317 tty->print("\t iff = %d, ", iff->_idx); iff->dump();
318 tty->print("\t iffast = %d, ", iffast->_idx); iffast->dump();
319 tty->print("\t ifslow = %d, ", ifslow->_idx); ifslow->dump();
320 tty->print("\t before replace_input_of: head = %d, ", head->_idx); head->dump();
321 tty->print("\t before replace_input_of: slow_head = %d, ", slow_head->_idx); slow_head->dump();
322 }
323#endif
324
325 // Fast (true) control
326 _igvn.replace_input_of(head->skip_strip_mined(), LoopNode::EntryControl, iffast);
327 // Slow (false) control
328 _igvn.replace_input_of(slow_head->skip_strip_mined(), LoopNode::EntryControl, ifslow);
329
330 recompute_dom_depth();
331
332 lk->set_iff(iff);
333
334#ifndef PRODUCT
335 if (TraceLoopOpts ) {
336 tty->print("\t after replace_input_of: head = %d, ", head->_idx); head->dump();
337 tty->print("\t after replace_input_of: slow_head = %d, ", slow_head->_idx); slow_head->dump();
338 }
339#endif
340
341 return slow_head->as_Loop();
342}
343
344CountedLoopReserveKit::CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active = true) :
345 _phase(phase),
346 _lpt(loop),
347 _lp(NULL),
348 _iff(NULL),
349 _lp_reserved(NULL),
350 _has_reserved(false),
351 _use_new(false),
352 _active(active)
353 {
354 create_reserve();
355 };
356
357CountedLoopReserveKit::~CountedLoopReserveKit() {
358 if (!_active) {
359 return;
360 }
361
362 if (_has_reserved && !_use_new) {
363 // intcon(0)->iff-node reverts CF to the reserved copy
364 ConINode* const_0 = _phase->_igvn.intcon(0);
365 _phase->set_ctrl(const_0, _phase->C->root());
366 _iff->set_req(1, const_0);
367
368 #ifndef PRODUCT
369 if (TraceLoopOpts) {
370 tty->print_cr("CountedLoopReserveKit::~CountedLoopReserveKit()");
371 tty->print("\t discard loop %d and revert to the reserved loop clone %d: ", _lp->_idx, _lp_reserved->_idx);
372 _lp_reserved->dump();
373 }
374 #endif
375 }
376}
377
378bool CountedLoopReserveKit::create_reserve() {
379 if (!_active) {
380 return false;
381 }
382
383 if(!_lpt->_head->is_CountedLoop()) {
384 if (TraceLoopOpts) {
385 tty->print_cr("CountedLoopReserveKit::create_reserve: %d not counted loop", _lpt->_head->_idx);
386 }
387 return false;
388 }
389 CountedLoopNode *cl = _lpt->_head->as_CountedLoop();
390 if (!cl->is_valid_counted_loop()) {
391 if (TraceLoopOpts) {
392 tty->print_cr("CountedLoopReserveKit::create_reserve: %d not valid counted loop", cl->_idx);
393 }
394 return false; // skip malformed counted loop
395 }
396 if (!cl->is_main_loop()) {
397 bool loop_not_canonical = true;
398 if (cl->is_post_loop() && (cl->slp_max_unroll() > 0)) {
399 loop_not_canonical = false;
400 }
401 // only reject some loop forms
402 if (loop_not_canonical) {
403 if (TraceLoopOpts) {
404 tty->print_cr("CountedLoopReserveKit::create_reserve: %d not canonical loop", cl->_idx);
405 }
406 return false; // skip normal, pre, and post (conditionally) loops
407 }
408 }
409
410 _lp = _lpt->_head->as_Loop();
411 _lp_reserved = _phase->create_reserve_version_of_loop(_lpt, this);
412
413 if (!_lp_reserved->is_CountedLoop()) {
414 return false;
415 }
416
417 Node* ifslow_pred = _lp_reserved->skip_strip_mined()->in(LoopNode::EntryControl);
418
419 if (!ifslow_pred->is_IfFalse()) {
420 return false;
421 }
422
423 Node* iff = ifslow_pred->in(0);
424 if (!iff->is_If() || iff != _iff) {
425 return false;
426 }
427
428 if (iff->in(1)->Opcode() != Op_ConI) {
429 return false;
430 }
431
432 return _has_reserved = true;
433}
434