1 /*
2 * Copyright (c) 2009, 2011, 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 package org.graalvm.compiler.lir;
24
25 import java.util.ArrayList;
26 import java.util.Arrays;
27 import java.util.List;
28
29 /**
30 * A buffer to enqueue updates to a list. This avoids frequent re-sizing of the list and copying of
31 * list elements when insertions are done at multiple positions of the list. Additionally, it
32 * ensures that the list is not modified while it is, e.g., iterated, and instead only modified once
33 * after the iteration is done.
34 * <p>
35 * The buffer uses internal data structures to store the enqueued updates. To avoid allocations, a
36 * buffer can be re-used. Call the methods in the following order: {@link #init}, {@link #append},
37 * {@link #append}, ..., {@link #finish()}, {@link #init}, ...
38 * <p>
39 * Note: This class does not depend on LIRInstruction, so we could make it a generic utility class.
40 */
41 public final class LIRInsertionBuffer {
42
43 /**
44 * The lir list where ops of this buffer should be inserted later (null when uninitialized).
45 */
46 private List<LIRInstruction> lir;
47
48 /**
49 * List of insertion points. index and count are stored alternately: indexAndCount[i * 2]: the
50 * index into lir list where "count" ops should be inserted indexAndCount[i * 2 + 1]: the number
51 * of ops to be inserted at index
52 */
53 private int[] indexAndCount;
54 private int indexAndCountSize;
55
56 /**
57 * The LIROps to be inserted.
58 */
59 private final List<LIRInstruction> ops;
60
61 public LIRInsertionBuffer() {
62 indexAndCount = new int[8];
63 ops = new ArrayList<>(4);
64 }
65
66 /**
67 * Initialize this buffer. This method must be called before using {@link #append}.
68 */
69 public void init(List<LIRInstruction> newLir) {
70 assert !initialized() : "already initialized";
71 assert indexAndCountSize == 0 && ops.size() == 0;
72 this.lir = newLir;
73 }
74
75 public boolean initialized() {
76 return lir != null;
77 }
78
79 public List<LIRInstruction> lirList() {
80 return lir;
81 }
82
83 /**
84 * Enqueue a new instruction that will be appended to the instruction list when
85 * {@link #finish()} is called. The new instruction is added <b>before</b> the existing
86 * instruction with the given index. This method can only be called with increasing values of
87 * index, e.g., once an instruction was appended with index 4, subsequent instructions can only
88 * be appended with index 4 or higher.
89 */
90 public void append(int index, LIRInstruction op) {
91 int i = numberOfInsertionPoints() - 1;
92 if (i < 0 || indexAt(i) < index) {
93 appendNew(index, 1);
94 } else {
95 assert indexAt(i) == index : "can append LIROps in ascending order only";
96 assert countAt(i) > 0 : "check";
97 setCountAt(i, countAt(i) + 1);
98 }
99 ops.add(op);
100
101 assert verify();
102 }
103
104 /**
105 * Append all enqueued instructions to the instruction list. After that, {@link #init(List)} can
106 * be called again to re-use this buffer.
107 */
108 public void finish() {
109 if (ops.size() > 0) {
110 int n = lir.size();
111 // increase size of instructions list
112 for (int i = 0; i < ops.size(); i++) {
113 lir.add(null);
114 }
115 // insert ops from buffer into instructions list
116 int opIndex = ops.size() - 1;
117 int ipIndex = numberOfInsertionPoints() - 1;
118 int fromIndex = n - 1;
119 int toIndex = lir.size() - 1;
120 while (ipIndex >= 0) {
121 int index = indexAt(ipIndex);
122 // make room after insertion point
123 while (fromIndex >= index) {
124 lir.set(toIndex--, lir.get(fromIndex--));
125 }
126 // insert ops from buffer
127 for (int i = countAt(ipIndex); i > 0; i--) {
128 lir.set(toIndex--, ops.get(opIndex--));
129 }
130 ipIndex--;
131 }
132 indexAndCountSize = 0;
133 ops.clear();
134 }
135 lir = null;
136 }
137
138 private void appendNew(int index, int count) {
139 int oldSize = indexAndCountSize;
140 int newSize = oldSize + 2;
141 if (newSize > this.indexAndCount.length) {
142 indexAndCount = Arrays.copyOf(indexAndCount, newSize * 2);
143 }
144 indexAndCount[oldSize] = index;
145 indexAndCount[oldSize + 1] = count;
146 this.indexAndCountSize = newSize;
147 }
148
149 private void setCountAt(int i, int value) {
150 indexAndCount[(i << 1) + 1] = value;
151 }
152
153 private int numberOfInsertionPoints() {
154 assert indexAndCount.length % 2 == 0 : "must have a count for each index";
155 return indexAndCountSize >> 1;
156 }
157
158 private int indexAt(int i) {
159 return indexAndCount[(i << 1)];
160 }
161
162 private int countAt(int i) {
163 return indexAndCount[(i << 1) + 1];
164 }
165
166 private boolean verify() {
167 int sum = 0;
168 int prevIdx = -1;
169
170 for (int i = 0; i < numberOfInsertionPoints(); i++) {
171 assert prevIdx < indexAt(i) : "index must be ordered ascending";
172 sum += countAt(i);
173 }
174 assert sum == ops.size() : "wrong total sum";
175 return true;
176 }
177 }