1/*
2 * Copyright (c) 2006, 2012, 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/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  // check for vectorized loops, any unswitching was already applied
66  if (_head->is_CountedLoop() && _head->as_CountedLoop()->do_unroll_only()) {
67    return false;
68  }
69
70  int nodes_left = phase->C->max_node_limit() - phase->C->live_nodes();
71  if ((int)(2 * _body.size()) > nodes_left) {
72    return false; // Too speculative if running low on nodes.
73  }
74  LoopNode* head = _head->as_Loop();
75  if (head->unswitch_count() + 1 > head->unswitch_max()) {
76    return false;
77  }
78  return phase->find_unswitching_candidate(this) != NULL;
79}
80
81//------------------------------find_unswitching_candidate-----------------------------
82// Find candidate "if" for unswitching
83IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {
84
85  // Find first invariant test that doesn't exit the loop
86  LoopNode *head = loop->_head->as_Loop();
87  IfNode* unswitch_iff = NULL;
88  Node* n = head->in(LoopNode::LoopBackControl);
89  while (n != head) {
90    Node* n_dom = idom(n);
91    if (n->is_Region()) {
92      if (n_dom->is_If()) {
93        IfNode* iff = n_dom->as_If();
94        if (iff->in(1)->is_Bool()) {
95          BoolNode* bol = iff->in(1)->as_Bool();
96          if (bol->in(1)->is_Cmp()) {
97            // If condition is invariant and not a loop exit,
98            // then found reason to unswitch.
99            if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {
100              unswitch_iff = iff;
101            }
102          }
103        }
104      }
105    }
106    n = n_dom;
107  }
108  return unswitch_iff;
109}
110
111//------------------------------do_unswitching-----------------------------
112// Clone loop with an invariant test (that does not exit) and
113// insert a clone of the test that selects which version to
114// execute.
115void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {
116
117  // Find first invariant test that doesn't exit the loop
118  LoopNode *head = loop->_head->as_Loop();
119
120  IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);
121  assert(unswitch_iff != NULL, "should be at least one");
122
123#ifndef PRODUCT
124  if (TraceLoopOpts) {
125    tty->print("Unswitch   %d ", head->unswitch_count()+1);
126    loop->dump_head();
127  }
128#endif
129
130  // Need to revert back to normal loop
131  if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {
132    head->as_CountedLoop()->set_normal_loop();
133  }
134
135  ProjNode* proj_true = create_slow_version_of_loop(loop, old_new, unswitch_iff->Opcode());
136
137#ifdef ASSERT
138  Node* uniqc = proj_true->unique_ctrl_out();
139  Node* entry = head->in(LoopNode::EntryControl);
140  Node* predicate = find_predicate(entry);
141  if (predicate != NULL && UseLoopPredicate) {
142    // We may have two predicates, find first.
143    entry = find_predicate(entry->in(0)->in(0));
144    if (entry != NULL) predicate = entry;
145  }
146  if (predicate != NULL) predicate = predicate->in(0);
147  assert(proj_true->is_IfTrue() &&
148         (predicate == NULL && uniqc == head ||
149          predicate != NULL && uniqc == predicate), "by construction");
150#endif
151  // Increment unswitch count
152  LoopNode* head_clone = old_new[head->_idx]->as_Loop();
153  int nct = head->unswitch_count() + 1;
154  head->set_unswitch_count(nct);
155  head_clone->set_unswitch_count(nct);
156
157  // Add test to new "if" outside of loop
158  IfNode* invar_iff   = proj_true->in(0)->as_If();
159  Node* invar_iff_c   = invar_iff->in(0);
160  BoolNode* bol       = unswitch_iff->in(1)->as_Bool();
161  invar_iff->set_req(1, bol);
162  invar_iff->_prob    = unswitch_iff->_prob;
163
164  ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();
165
166  // Hoist invariant casts out of each loop to the appropriate
167  // control projection.
168
169  Node_List worklist;
170
171  for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {
172    ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();
173    // Copy to a worklist for easier manipulation
174    for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {
175      Node* use = proj->fast_out(j);
176      if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {
177        worklist.push(use);
178      }
179    }
180    ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();
181    while (worklist.size() > 0) {
182      Node* use = worklist.pop();
183      Node* nuse = use->clone();
184      nuse->set_req(0, invar_proj);
185      _igvn.replace_input_of(use, 1, nuse);
186      register_new_node(nuse, invar_proj);
187      // Same for the clone
188      Node* use_clone = old_new[use->_idx];
189      _igvn.replace_input_of(use_clone, 1, nuse);
190    }
191  }
192
193  // Hardwire the control paths in the loops into if(true) and if(false)
194  _igvn.rehash_node_delayed(unswitch_iff);
195  short_circuit_if(unswitch_iff, proj_true);
196
197  IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();
198  _igvn.rehash_node_delayed(unswitch_iff_clone);
199  short_circuit_if(unswitch_iff_clone, proj_false);
200
201  // Reoptimize loops
202  loop->record_for_igvn();
203  for(int i = loop->_body.size() - 1; i >= 0 ; i--) {
204    Node *n = loop->_body[i];
205    Node *n_clone = old_new[n->_idx];
206    _igvn._worklist.push(n_clone);
207  }
208
209#ifndef PRODUCT
210  if (TraceLoopUnswitching) {
211    tty->print_cr("Loop unswitching orig: %d @ %d  new: %d @ %d",
212                  head->_idx,                unswitch_iff->_idx,
213                  old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);
214  }
215#endif
216
217  C->set_major_progress();
218}
219
220//-------------------------create_slow_version_of_loop------------------------
221// Create a slow version of the loop by cloning the loop
222// and inserting an if to select fast-slow versions.
223// Return control projection of the entry to the fast version.
224ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,
225                                                      Node_List &old_new,
226                                                      int opcode) {
227  LoopNode* head  = loop->_head->as_Loop();
228  bool counted_loop = head->is_CountedLoop();
229  Node*     entry = head->in(LoopNode::EntryControl);
230  _igvn.rehash_node_delayed(entry);
231  IdealLoopTree* outer_loop = loop->_parent;
232
233  Node *cont      = _igvn.intcon(1);
234  set_ctrl(cont, C->root());
235  Node* opq       = new Opaque1Node(C, cont);
236  register_node(opq, outer_loop, entry, dom_depth(entry));
237  Node *bol       = new Conv2BNode(opq);
238  register_node(bol, outer_loop, entry, dom_depth(entry));
239  IfNode* iff = (opcode == Op_RangeCheck) ? new RangeCheckNode(entry, bol, PROB_MAX, COUNT_UNKNOWN) :
240    new IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);
241  register_node(iff, outer_loop, entry, dom_depth(entry));
242  ProjNode* iffast = new IfTrueNode(iff);
243  register_node(iffast, outer_loop, iff, dom_depth(iff));
244  ProjNode* ifslow = new IfFalseNode(iff);
245  register_node(ifslow, outer_loop, iff, dom_depth(iff));
246
247  // Clone the loop body.  The clone becomes the fast loop.  The
248  // original pre-header will (illegally) have 3 control users
249  // (old & new loops & new if).
250  clone_loop(loop, old_new, dom_depth(head), iff);
251  assert(old_new[head->_idx]->is_Loop(), "" );
252
253  // Fast (true) control
254  Node* iffast_pred = clone_loop_predicates(entry, iffast, !counted_loop);
255  _igvn.replace_input_of(head, LoopNode::EntryControl, iffast_pred);
256  set_idom(head, iffast_pred, dom_depth(head));
257
258  // Slow (false) control
259  Node* ifslow_pred = clone_loop_predicates(entry, ifslow, !counted_loop);
260  LoopNode* slow_head = old_new[head->_idx]->as_Loop();
261  _igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow_pred);
262  set_idom(slow_head, ifslow_pred, dom_depth(slow_head));
263
264  recompute_dom_depth();
265
266  return iffast;
267}
268
269LoopNode* PhaseIdealLoop::create_reserve_version_of_loop(IdealLoopTree *loop, CountedLoopReserveKit* lk) {
270  Node_List old_new;
271  LoopNode* head  = loop->_head->as_Loop();
272  bool counted_loop = head->is_CountedLoop();
273  Node*     entry = head->in(LoopNode::EntryControl);
274  _igvn.rehash_node_delayed(entry);
275  IdealLoopTree* outer_loop = loop->_parent;
276
277  ConINode* const_1 = _igvn.intcon(1);
278  set_ctrl(const_1, C->root());
279  IfNode* iff = new IfNode(entry, const_1, PROB_MAX, COUNT_UNKNOWN);
280  register_node(iff, outer_loop, entry, dom_depth(entry));
281  ProjNode* iffast = new IfTrueNode(iff);
282  register_node(iffast, outer_loop, iff, dom_depth(iff));
283  ProjNode* ifslow = new IfFalseNode(iff);
284  register_node(ifslow, outer_loop, iff, dom_depth(iff));
285
286  // Clone the loop body.  The clone becomes the fast loop.  The
287  // original pre-header will (illegally) have 3 control users
288  // (old & new loops & new if).
289  clone_loop(loop, old_new, dom_depth(head), iff);
290  assert(old_new[head->_idx]->is_Loop(), "" );
291
292  LoopNode* slow_head = old_new[head->_idx]->as_Loop();
293
294#ifndef PRODUCT
295  if (TraceLoopOpts) {
296    tty->print_cr("PhaseIdealLoop::create_reserve_version_of_loop:");
297    tty->print("\t iff = %d, ", iff->_idx); iff->dump();
298    tty->print("\t iffast = %d, ", iffast->_idx); iffast->dump();
299    tty->print("\t ifslow = %d, ", ifslow->_idx); ifslow->dump();
300    tty->print("\t before replace_input_of: head = %d, ", head->_idx); head->dump();
301    tty->print("\t before replace_input_of: slow_head = %d, ", slow_head->_idx); slow_head->dump();
302  }
303#endif
304
305  // Fast (true) control
306  _igvn.replace_input_of(head, LoopNode::EntryControl, iffast);
307  // Slow (false) control
308  _igvn.replace_input_of(slow_head, LoopNode::EntryControl, ifslow);
309
310  recompute_dom_depth();
311
312  lk->set_iff(iff);
313
314#ifndef PRODUCT
315  if (TraceLoopOpts ) {
316    tty->print("\t after  replace_input_of: head = %d, ", head->_idx); head->dump();
317    tty->print("\t after  replace_input_of: slow_head = %d, ", slow_head->_idx); slow_head->dump();
318  }
319#endif
320
321  return slow_head->as_Loop();
322}
323
324CountedLoopReserveKit::CountedLoopReserveKit(PhaseIdealLoop* phase, IdealLoopTree *loop, bool active = true) :
325  _phase(phase),
326  _lpt(loop),
327  _lp(NULL),
328  _iff(NULL),
329  _lp_reserved(NULL),
330  _has_reserved(false),
331  _use_new(false),
332  _active(active)
333  {
334    create_reserve();
335  };
336
337CountedLoopReserveKit::~CountedLoopReserveKit() {
338  if (!_active) {
339    return;
340  }
341
342  if (_has_reserved && !_use_new) {
343    // intcon(0)->iff-node reverts CF to the reserved copy
344    ConINode* const_0 = _phase->_igvn.intcon(0);
345    _phase->set_ctrl(const_0, _phase->C->root());
346    _iff->set_req(1, const_0);
347
348    #ifndef PRODUCT
349      if (TraceLoopOpts) {
350        tty->print_cr("CountedLoopReserveKit::~CountedLoopReserveKit()");
351        tty->print("\t discard loop %d and revert to the reserved loop clone %d: ", _lp->_idx, _lp_reserved->_idx);
352        _lp_reserved->dump();
353      }
354    #endif
355  }
356}
357
358bool CountedLoopReserveKit::create_reserve() {
359  if (!_active) {
360    return false;
361  }
362
363  if(!_lpt->_head->is_CountedLoop()) {
364    if (TraceLoopOpts) {
365      tty->print_cr("CountedLoopReserveKit::create_reserve: %d not counted loop", _lpt->_head->_idx);
366    }
367    return false;
368  }
369  CountedLoopNode *cl = _lpt->_head->as_CountedLoop();
370  if (!cl->is_valid_counted_loop()) {
371    if (TraceLoopOpts) {
372      tty->print_cr("CountedLoopReserveKit::create_reserve: %d not valid counted loop", cl->_idx);
373    }
374    return false; // skip malformed counted loop
375  }
376  if (!cl->is_main_loop()) {
377    bool loop_not_canonical = true;
378    if (cl->is_post_loop() && (cl->slp_max_unroll() > 0)) {
379      loop_not_canonical = false;
380    }
381    // only reject some loop forms
382    if (loop_not_canonical) {
383      if (TraceLoopOpts) {
384        tty->print_cr("CountedLoopReserveKit::create_reserve: %d not canonical loop", cl->_idx);
385      }
386      return false; // skip normal, pre, and post (conditionally) loops
387    }
388  }
389
390  _lp = _lpt->_head->as_Loop();
391  _lp_reserved = _phase->create_reserve_version_of_loop(_lpt, this);
392
393  if (!_lp_reserved->is_CountedLoop()) {
394    return false;
395  }
396
397  Node* ifslow_pred = _lp_reserved->as_CountedLoop()->in(LoopNode::EntryControl);
398
399  if (!ifslow_pred->is_IfFalse()) {
400    return false;
401  }
402
403  Node* iff = ifslow_pred->in(0);
404  if (!iff->is_If() || iff != _iff) {
405    return false;
406  }
407
408  if (iff->in(1)->Opcode() != Op_ConI) {
409    return false;
410  }
411
412  return _has_reserved = true;
413}
414