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1 : // Copyright 2017 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_VISITORS_H_
6 : #define V8_VISITORS_H_
7 :
8 : #include "src/globals.h"
9 : #include "src/objects/code.h"
10 : #include "src/objects/compressed-slots.h"
11 : #include "src/objects/foreign.h"
12 : #include "src/objects/slots.h"
13 :
14 : namespace v8 {
15 : namespace internal {
16 :
17 : class CodeDataContainer;
18 : class MaybeObject;
19 : class Object;
20 :
21 : #define ROOT_ID_LIST(V) \
22 : V(kStringTable, "(Internalized strings)") \
23 : V(kExternalStringsTable, "(External strings)") \
24 : V(kReadOnlyRootList, "(Read-only roots)") \
25 : V(kStrongRootList, "(Strong roots)") \
26 : V(kSmiRootList, "(Smi roots)") \
27 : V(kBootstrapper, "(Bootstrapper)") \
28 : V(kTop, "(Isolate)") \
29 : V(kRelocatable, "(Relocatable)") \
30 : V(kDebug, "(Debugger)") \
31 : V(kCompilationCache, "(Compilation cache)") \
32 : V(kHandleScope, "(Handle scope)") \
33 : V(kDispatchTable, "(Dispatch table)") \
34 : V(kBuiltins, "(Builtins)") \
35 : V(kGlobalHandles, "(Global handles)") \
36 : V(kEternalHandles, "(Eternal handles)") \
37 : V(kThreadManager, "(Thread manager)") \
38 : V(kStrongRoots, "(Strong roots)") \
39 : V(kExtensions, "(Extensions)") \
40 : V(kCodeFlusher, "(Code flusher)") \
41 : V(kPartialSnapshotCache, "(Partial snapshot cache)") \
42 : V(kReadOnlyObjectCache, "(Read-only object cache)") \
43 : V(kWeakCollections, "(Weak collections)") \
44 : V(kWrapperTracing, "(Wrapper tracing)") \
45 : V(kUnknown, "(Unknown)")
46 :
47 : class VisitorSynchronization : public AllStatic {
48 : public:
49 : #define DECLARE_ENUM(enum_item, ignore) enum_item,
50 : enum SyncTag { ROOT_ID_LIST(DECLARE_ENUM) kNumberOfSyncTags };
51 : #undef DECLARE_ENUM
52 : };
53 :
54 : enum class Root {
55 : #define DECLARE_ENUM(enum_item, ignore) enum_item,
56 : ROOT_ID_LIST(DECLARE_ENUM)
57 : #undef DECLARE_ENUM
58 : kNumberOfRoots
59 : };
60 :
61 : // Abstract base class for visiting, and optionally modifying, the
62 : // pointers contained in roots. Used in GC and serialization/deserialization.
63 898194 : class RootVisitor {
64 : public:
65 892760 : virtual ~RootVisitor() = default;
66 :
67 : // Visits a contiguous arrays of pointers in the half-open range
68 : // [start, end). Any or all of the values may be modified on return.
69 : virtual void VisitRootPointers(Root root, const char* description,
70 : FullObjectSlot start, FullObjectSlot end) = 0;
71 :
72 : // Handy shorthand for visiting a single pointer.
73 207621559 : virtual void VisitRootPointer(Root root, const char* description,
74 : FullObjectSlot p) {
75 415243118 : VisitRootPointers(root, description, p, p + 1);
76 207622217 : }
77 :
78 : // Intended for serialization/deserialization checking: insert, or
79 : // check for the presence of, a tag at this position in the stream.
80 : // Also used for marking up GC roots in heap snapshots.
81 : // TODO(ulan): Remove this.
82 3583897 : virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
83 :
84 : static const char* RootName(Root root);
85 : };
86 :
87 : class RelocIterator;
88 :
89 : // Abstract base class for visiting, and optionally modifying, the
90 : // pointers contained in Objects. Used in GC and serialization/deserialization.
91 180127561 : class ObjectVisitor {
92 : public:
93 180659513 : virtual ~ObjectVisitor() = default;
94 :
95 : // Visits a contiguous arrays of pointers in the half-open range
96 : // [start, end). Any or all of the values may be modified on return.
97 : virtual void VisitPointers(HeapObject host, ObjectSlot start,
98 : ObjectSlot end) = 0;
99 : virtual void VisitPointers(HeapObject host, MaybeObjectSlot start,
100 : MaybeObjectSlot end) = 0;
101 :
102 : // Custom weak pointers must be ignored by the GC but not other
103 : // visitors. They're used for e.g., lists that are recreated after GC. The
104 : // default implementation treats them as strong pointers. Visitors who want to
105 : // ignore them must override this function with empty.
106 5046826 : virtual void VisitCustomWeakPointers(HeapObject host, ObjectSlot start,
107 : ObjectSlot end) {
108 5046826 : VisitPointers(host, start, end);
109 5047467 : }
110 :
111 : // Handy shorthand for visiting a single pointer.
112 63691718 : virtual void VisitPointer(HeapObject host, ObjectSlot p) {
113 551797177 : VisitPointers(host, p, p + 1);
114 64055249 : }
115 34795369 : virtual void VisitPointer(HeapObject host, MaybeObjectSlot p) {
116 69590738 : VisitPointers(host, p, p + 1);
117 34378469 : }
118 66194705 : virtual void VisitCustomWeakPointer(HeapObject host, ObjectSlot p) {
119 132389410 : VisitCustomWeakPointers(host, p, p + 1);
120 66103433 : }
121 :
122 29639 : virtual void VisitEphemeron(HeapObject host, int index, ObjectSlot key,
123 : ObjectSlot value) {
124 29639 : VisitPointer(host, key);
125 29639 : VisitPointer(host, value);
126 29631 : }
127 :
128 : // To allow lazy clearing of inline caches the visitor has
129 : // a rich interface for iterating over Code objects ...
130 :
131 : // Visits a code target in the instruction stream.
132 : virtual void VisitCodeTarget(Code host, RelocInfo* rinfo) = 0;
133 :
134 : // Visit pointer embedded into a code object.
135 : virtual void VisitEmbeddedPointer(Code host, RelocInfo* rinfo) = 0;
136 :
137 : // Visits a runtime entry in the instruction stream.
138 3625432 : virtual void VisitRuntimeEntry(Code host, RelocInfo* rinfo) {}
139 :
140 : // Visits an external reference embedded into a code object.
141 3425 : virtual void VisitExternalReference(Code host, RelocInfo* rinfo) {}
142 :
143 : // Visits an external reference.
144 2972274 : virtual void VisitExternalReference(Foreign host, Address* p) {}
145 :
146 : // Visits an (encoded) internal reference.
147 137 : virtual void VisitInternalReference(Code host, RelocInfo* rinfo) {}
148 :
149 : // Visits an off-heap target in the instruction stream.
150 117499564 : virtual void VisitOffHeapTarget(Code host, RelocInfo* rinfo) {}
151 :
152 : // Visits the relocation info using the given iterator.
153 : virtual void VisitRelocInfo(RelocIterator* it);
154 : };
155 :
156 : } // namespace internal
157 : } // namespace v8
158 :
159 : #endif // V8_VISITORS_H_
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