1/*
2 * Copyright (c) 2016, 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/resourceArea.hpp"
27#include "opto/cfgnode.hpp"
28#include "opto/phaseX.hpp"
29#include "opto/replacednodes.hpp"
30
31void ReplacedNodes::allocate_if_necessary() {
32  if (_replaced_nodes == NULL) {
33    _replaced_nodes = new GrowableArray<ReplacedNode>();
34  }
35}
36
37bool ReplacedNodes::is_empty() const {
38  return _replaced_nodes == NULL || _replaced_nodes->length() == 0;
39}
40
41bool ReplacedNodes::has_node(const ReplacedNode& r) const {
42  return _replaced_nodes->find(r) != -1;
43}
44
45bool ReplacedNodes::has_target_node(Node* n) const {
46  for (int i = 0; i < _replaced_nodes->length(); i++) {
47    if (_replaced_nodes->at(i).improved() == n) {
48      return true;
49    }
50  }
51  return false;
52}
53
54// Record replaced node if not seen before
55void ReplacedNodes::record(Node* initial, Node* improved) {
56  allocate_if_necessary();
57  ReplacedNode r(initial, improved);
58  if (!has_node(r)) {
59    _replaced_nodes->push(r);
60  }
61}
62
63// Copy replaced nodes from one map to another. idx is used to
64// identify nodes that are too new to be of interest in the target
65// node list.
66void ReplacedNodes::transfer_from(const ReplacedNodes& other, uint idx) {
67  if (other.is_empty()) {
68    return;
69  }
70  allocate_if_necessary();
71  for (int i = 0; i < other._replaced_nodes->length(); i++) {
72    ReplacedNode replaced = other._replaced_nodes->at(i);
73    // Only transfer the nodes that can actually be useful
74    if (!has_node(replaced) && (replaced.initial()->_idx < idx || has_target_node(replaced.initial()))) {
75      _replaced_nodes->push(replaced);
76    }
77  }
78}
79
80void ReplacedNodes::clone() {
81  if (_replaced_nodes != NULL) {
82    GrowableArray<ReplacedNode>* replaced_nodes_clone = new GrowableArray<ReplacedNode>();
83    replaced_nodes_clone->appendAll(_replaced_nodes);
84    _replaced_nodes = replaced_nodes_clone;
85  }
86}
87
88void ReplacedNodes::reset() {
89  if (_replaced_nodes != NULL) {
90    _replaced_nodes->clear();
91  }
92}
93
94// Perfom node replacement (used when returning to caller)
95void ReplacedNodes::apply(Node* n, uint idx) {
96  if (is_empty()) {
97    return;
98  }
99  for (int i = 0; i < _replaced_nodes->length(); i++) {
100    ReplacedNode replaced = _replaced_nodes->at(i);
101    // Only apply if improved node was created in a callee to avoid
102    // issues with irreducible loops in the caller
103    if (replaced.improved()->_idx >= idx) {
104      n->replace_edge(replaced.initial(), replaced.improved());
105    }
106  }
107}
108
109static void enqueue_use(Node* n, Node* use, Unique_Node_List& work) {
110  if (use->is_Phi()) {
111    Node* r = use->in(0);
112    assert(r->is_Region(), "Phi should have Region");
113    for (uint i = 1; i < use->req(); i++) {
114      if (use->in(i) == n) {
115        work.push(r->in(i));
116      }
117    }
118  } else {
119    work.push(use);
120  }
121}
122
123// Perfom node replacement following late inlining
124void ReplacedNodes::apply(Compile* C, Node* ctl) {
125  // ctl is the control on exit of the method that was late inlined
126  if (is_empty()) {
127    return;
128  }
129  for (int i = 0; i < _replaced_nodes->length(); i++) {
130    ReplacedNode replaced = _replaced_nodes->at(i);
131    Node* initial = replaced.initial();
132    Node* improved = replaced.improved();
133    assert (ctl != NULL && !ctl->is_top(), "replaced node should have actual control");
134
135    ResourceMark rm;
136    Unique_Node_List work;
137    // Go over all the uses of the node that is considered for replacement...
138    for (DUIterator j = initial->outs(); initial->has_out(j); j++) {
139      Node* use = initial->out(j);
140
141      if (use == improved || use->outcnt() == 0) {
142        continue;
143      }
144      work.clear();
145      enqueue_use(initial, use, work);
146      bool replace = true;
147      // Check that this use is dominated by ctl. Go ahead with the
148      // replacement if it is.
149      while (work.size() != 0 && replace) {
150        Node* n = work.pop();
151        if (use->outcnt() == 0) {
152          continue;
153        }
154        if (n->is_CFG() || (n->in(0) != NULL && !n->in(0)->is_top())) {
155          int depth = 0;
156          Node *m = n;
157          if (!n->is_CFG()) {
158            n = n->in(0);
159          }
160          assert(n->is_CFG(), "should be CFG now");
161          while(n != ctl) {
162            n = IfNode::up_one_dom(n);
163            depth++;
164            // limit search depth
165            if (depth >= 100 || n == NULL) {
166              replace = false;
167              break;
168            }
169          }
170        } else {
171          for (DUIterator k = n->outs(); n->has_out(k); k++) {
172            enqueue_use(n, n->out(k), work);
173          }
174        }
175      }
176      if (replace) {
177        bool is_in_table = C->initial_gvn()->hash_delete(use);
178        int replaced = use->replace_edge(initial, improved);
179        if (is_in_table) {
180          C->initial_gvn()->hash_find_insert(use);
181        }
182        C->record_for_igvn(use);
183
184        assert(replaced > 0, "inconsistent");
185        --j;
186      }
187    }
188  }
189}
190
191void ReplacedNodes::dump(outputStream *st) const {
192  if (!is_empty()) {
193    st->print("replaced nodes: ");
194    for (int i = 0; i < _replaced_nodes->length(); i++) {
195      st->print("%d->%d", _replaced_nodes->at(i).initial()->_idx, _replaced_nodes->at(i).improved()->_idx);
196      if (i < _replaced_nodes->length()-1) {
197        st->print(",");
198      }
199    }
200  }
201}
202
203// Merge 2 list of replaced node at a point where control flow paths merge
204void ReplacedNodes::merge_with(const ReplacedNodes& other) {
205  if (is_empty()) {
206    return;
207  }
208  if (other.is_empty()) {
209    reset();
210    return;
211  }
212  int shift = 0;
213  int len = _replaced_nodes->length();
214  for (int i = 0; i < len; i++) {
215    if (!other.has_node(_replaced_nodes->at(i))) {
216      shift++;
217    } else if (shift > 0) {
218      _replaced_nodes->at_put(i-shift, _replaced_nodes->at(i));
219    }
220  }
221  if (shift > 0) {
222    _replaced_nodes->trunc_to(len - shift);
223  }
224}
225