Mercurial > hg > graal-jvmci-8
comparison graal/Compiler/src/com/sun/c1x/graph/MemoryMap.java @ 2507:9ec15d6914ca
Pull over of compiler from maxine repository.
author | Thomas Wuerthinger <thomas@wuerthinger.net> |
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date | Wed, 27 Apr 2011 11:43:22 +0200 |
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2506:4a3bf8a5bf41 | 2507:9ec15d6914ca |
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1 /* | |
2 * Copyright (c) 2009, 2010, 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 com.sun.c1x.graph; | |
24 | |
25 import static java.lang.reflect.Modifier.*; | |
26 | |
27 import java.util.*; | |
28 | |
29 import com.sun.c1x.ir.*; | |
30 import com.sun.cri.ri.*; | |
31 | |
32 /** | |
33 * The {@code MemoryMap} class is an approximation of memory that is used redundant load and | |
34 * store elimination. In C1, tracking of fields of new objects' fields was precise, | |
35 * while tracking of other fields is managed at the offset granularity (i.e. a write of a field with offset | |
36 * {@code off} will "overwrite" all fields with the offset {@code off}. However, C1X distinguishes all | |
37 * loaded fields as separate locations. Static fields have just one location, while instance fields are | |
38 * tracked for at most one instance object. Loads or stores of unloaded fields kill all memory locations. | |
39 * An object is no longer "new" if it is stored into a field or array. | |
40 * | |
41 * @author Ben L. Titzer | |
42 */ | |
43 public class MemoryMap { | |
44 | |
45 private final HashMap<RiField, Value> objectMap = new HashMap<RiField, Value>(); | |
46 private final HashMap<RiField, Value> valueMap = new HashMap<RiField, Value>(); | |
47 private final IdentityHashMap<Value, Value> newObjects = new IdentityHashMap<Value, Value>(); | |
48 | |
49 /** | |
50 * Kills all memory locations. | |
51 */ | |
52 public void kill() { | |
53 objectMap.clear(); | |
54 valueMap.clear(); | |
55 newObjects.clear(); | |
56 } | |
57 | |
58 /** | |
59 * The specified instruction has just escaped, it can no longer be considered a "new object". | |
60 * @param x the instruction that just escaped | |
61 */ | |
62 public void storeValue(Value x) { | |
63 newObjects.remove(x); | |
64 } | |
65 | |
66 /** | |
67 * Record a newly allocated object. | |
68 * @param n the instruction generating the new object | |
69 */ | |
70 public void newInstance(NewInstance n) { | |
71 newObjects.put(n, n); | |
72 } | |
73 | |
74 /** | |
75 * Look up a load for load elimination, and put this load into the load elimination map. | |
76 * @param load the instruction representing the load | |
77 * @return a reference to the previous instruction that already loaded the value, if it is available; the | |
78 * {@code load} parameter otherwise | |
79 */ | |
80 public Value load(LoadField load) { | |
81 if (!load.isLoaded()) { | |
82 // the field is not loaded, kill everything, because it will need to be resolved | |
83 kill(); | |
84 return load; | |
85 } | |
86 RiField field = load.field(); | |
87 if (load.isStatic()) { | |
88 // the field is static, look in the static map | |
89 Value r = valueMap.get(field); | |
90 if (r != null) { | |
91 return r; | |
92 } | |
93 valueMap.put(field, load); | |
94 } else { | |
95 // see if the value for this object for this field is in the map | |
96 if (objectMap.get(field) == load.object()) { | |
97 return valueMap.get(field); | |
98 } | |
99 objectMap.put(field, load.object()); | |
100 valueMap.put(field, load); | |
101 } | |
102 | |
103 return load; // load cannot be eliminated | |
104 } | |
105 | |
106 /** | |
107 * Insert a new result for a load into the memory map. | |
108 * @param load the load instruction | |
109 * @param result the result that the load instruction should produce | |
110 */ | |
111 public void setResult(LoadField load, Value result) { | |
112 if (load.isLoaded()) { | |
113 RiField field = load.field(); | |
114 if (load.isStatic()) { | |
115 // the field is static, put it in the static map | |
116 valueMap.put(field, result); | |
117 } else { | |
118 // put the result for the loaded object into the map | |
119 objectMap.put(field, load.object()); | |
120 valueMap.put(field, result); | |
121 } | |
122 } | |
123 } | |
124 | |
125 /** | |
126 * Look up a store for store elimination, and put this store into the load elimination map. | |
127 * @param store the store instruction to put into the map | |
128 * @return {@code null} if the store operation is redundant; the {@code store} parameter | |
129 * otherwise | |
130 */ | |
131 public StoreField store(StoreField store) { | |
132 if (!store.isLoaded()) { | |
133 // the field is not loaded, kill everything, because it will need to be resolved | |
134 kill(); | |
135 return store; | |
136 } | |
137 RiField field = store.field(); | |
138 Value value = store.value(); | |
139 if (store.isStatic()) { | |
140 // the field is static, overwrite it into the static map | |
141 valueMap.put(field, value); | |
142 } else { | |
143 if (newObjects.containsKey(store.object())) { | |
144 // this is a store to a new object's field | |
145 if (fieldHasNoStores(field) && value.isConstant() && value.asConstant().isDefaultValue()) { | |
146 // this is a redundant initialization of a new object's field that has not been assigned to | |
147 return null; | |
148 } | |
149 } | |
150 Value obj = objectMap.get(field); | |
151 if (obj == store.object()) { | |
152 // is this a redundant store? | |
153 if (value == valueMap.get(field) && !isVolatile(field.accessFlags())) { | |
154 return null; | |
155 } | |
156 } | |
157 objectMap.put(field, store.object()); | |
158 valueMap.put(field, value); | |
159 } | |
160 storeValue(value); // the value stored just escaped | |
161 return store; // the store cannot be eliminated | |
162 } | |
163 | |
164 private boolean fieldHasNoStores(RiField field) { | |
165 return objectMap.get(field) == null; | |
166 } | |
167 } |