LLVM  9.0.0svn
SectionKind.h
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1 //===-- llvm/MC/SectionKind.h - Classification of sections ------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_MC_SECTIONKIND_H
10 #define LLVM_MC_SECTIONKIND_H
11 
12 namespace llvm {
13 
14 /// SectionKind - This is a simple POD value that classifies the properties of
15 /// a section. A section is classified into the deepest possible
16 /// classification, and then the target maps them onto their sections based on
17 /// what capabilities they have.
18 ///
19 /// The comments below describe these as if they were an inheritance hierarchy
20 /// in order to explain the predicates below.
21 ///
22 class SectionKind {
23  enum Kind {
24  /// Metadata - Debug info sections or other metadata.
25  Metadata,
26 
27  /// Text - Text section, used for functions and other executable code.
28  Text,
29 
30  /// ExecuteOnly, Text section that is not readable.
31  ExecuteOnly,
32 
33  /// ReadOnly - Data that is never written to at program runtime by the
34  /// program or the dynamic linker. Things in the top-level readonly
35  /// SectionKind are not mergeable.
36  ReadOnly,
37 
38  /// MergableCString - Any null-terminated string which allows merging.
39  /// These values are known to end in a nul value of the specified size,
40  /// not otherwise contain a nul value, and be mergable. This allows the
41  /// linker to unique the strings if it so desires.
42 
43  /// Mergeable1ByteCString - 1 byte mergable, null terminated, string.
44  Mergeable1ByteCString,
45 
46  /// Mergeable2ByteCString - 2 byte mergable, null terminated, string.
47  Mergeable2ByteCString,
48 
49  /// Mergeable4ByteCString - 4 byte mergable, null terminated, string.
50  Mergeable4ByteCString,
51 
52  /// MergeableConst - These are sections for merging fixed-length
53  /// constants together. For example, this can be used to unique
54  /// constant pool entries etc.
55 
56  /// MergeableConst4 - This is a section used by 4-byte constants,
57  /// for example, floats.
58  MergeableConst4,
59 
60  /// MergeableConst8 - This is a section used by 8-byte constants,
61  /// for example, doubles.
62  MergeableConst8,
63 
64  /// MergeableConst16 - This is a section used by 16-byte constants,
65  /// for example, vectors.
66  MergeableConst16,
67 
68  /// MergeableConst32 - This is a section used by 32-byte constants,
69  /// for example, vectors.
70  MergeableConst32,
71 
72  /// Writeable - This is the base of all segments that need to be written
73  /// to during program runtime.
74 
75  /// ThreadLocal - This is the base of all TLS segments. All TLS
76  /// objects must be writeable, otherwise there is no reason for them to
77  /// be thread local!
78 
79  /// ThreadBSS - Zero-initialized TLS data objects.
80  ThreadBSS,
81 
82  /// ThreadData - Initialized TLS data objects.
83  ThreadData,
84 
85  /// GlobalWriteableData - Writeable data that is global (not thread
86  /// local).
87 
88  /// BSS - Zero initialized writeable data.
89  BSS,
90 
91  /// BSSLocal - This is BSS (zero initialized and writable) data
92  /// which has local linkage.
93  BSSLocal,
94 
95  /// BSSExtern - This is BSS data with normal external linkage.
96  BSSExtern,
97 
98  /// Common - Data with common linkage. These represent tentative
99  /// definitions, which always have a zero initializer and are never
100  /// marked 'constant'.
101  Common,
102 
103  /// This is writeable data that has a non-zero initializer.
104  Data,
105 
106  /// ReadOnlyWithRel - These are global variables that are never
107  /// written to by the program, but that have relocations, so they
108  /// must be stuck in a writeable section so that the dynamic linker
109  /// can write to them. If it chooses to, the dynamic linker can
110  /// mark the pages these globals end up on as read-only after it is
111  /// done with its relocation phase.
112  ReadOnlyWithRel
113  } K : 8;
114 public:
115 
116  bool isMetadata() const { return K == Metadata; }
117 
118  bool isText() const { return K == Text || K == ExecuteOnly; }
119 
120  bool isExecuteOnly() const { return K == ExecuteOnly; }
121 
122  bool isReadOnly() const {
123  return K == ReadOnly || isMergeableCString() ||
125  }
126 
127  bool isMergeableCString() const {
128  return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
129  K == Mergeable4ByteCString;
130  }
131  bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
132  bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
133  bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
134 
135  bool isMergeableConst() const {
136  return K == MergeableConst4 || K == MergeableConst8 ||
137  K == MergeableConst16 || K == MergeableConst32;
138  }
139  bool isMergeableConst4() const { return K == MergeableConst4; }
140  bool isMergeableConst8() const { return K == MergeableConst8; }
141  bool isMergeableConst16() const { return K == MergeableConst16; }
142  bool isMergeableConst32() const { return K == MergeableConst32; }
143 
144  bool isWriteable() const {
145  return isThreadLocal() || isGlobalWriteableData();
146  }
147 
148  bool isThreadLocal() const {
149  return K == ThreadData || K == ThreadBSS;
150  }
151 
152  bool isThreadBSS() const { return K == ThreadBSS; }
153  bool isThreadData() const { return K == ThreadData; }
154 
155  bool isGlobalWriteableData() const {
156  return isBSS() || isCommon() || isData() || isReadOnlyWithRel();
157  }
158 
159  bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
160  bool isBSSLocal() const { return K == BSSLocal; }
161  bool isBSSExtern() const { return K == BSSExtern; }
162 
163  bool isCommon() const { return K == Common; }
164 
165  bool isData() const { return K == Data; }
166 
167  bool isReadOnlyWithRel() const {
168  return K == ReadOnlyWithRel;
169  }
170 private:
171  static SectionKind get(Kind K) {
172  SectionKind Res;
173  Res.K = K;
174  return Res;
175  }
176 public:
177 
178  static SectionKind getMetadata() { return get(Metadata); }
179  static SectionKind getText() { return get(Text); }
180  static SectionKind getExecuteOnly() { return get(ExecuteOnly); }
181  static SectionKind getReadOnly() { return get(ReadOnly); }
183  return get(Mergeable1ByteCString);
184  }
186  return get(Mergeable2ByteCString);
187  }
189  return get(Mergeable4ByteCString);
190  }
191  static SectionKind getMergeableConst4() { return get(MergeableConst4); }
192  static SectionKind getMergeableConst8() { return get(MergeableConst8); }
193  static SectionKind getMergeableConst16() { return get(MergeableConst16); }
194  static SectionKind getMergeableConst32() { return get(MergeableConst32); }
195  static SectionKind getThreadBSS() { return get(ThreadBSS); }
196  static SectionKind getThreadData() { return get(ThreadData); }
197  static SectionKind getBSS() { return get(BSS); }
198  static SectionKind getBSSLocal() { return get(BSSLocal); }
199  static SectionKind getBSSExtern() { return get(BSSExtern); }
200  static SectionKind getCommon() { return get(Common); }
201  static SectionKind getData() { return get(Data); }
202  static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
203 };
204 
205 } // end namespace llvm
206 
207 #endif
bool isBSSExtern() const
Definition: SectionKind.h:161
static SectionKind getData()
Definition: SectionKind.h:201
bool isThreadData() const
Definition: SectionKind.h:153
static SectionKind getMergeableConst32()
Definition: SectionKind.h:194
This class represents lattice values for constants.
Definition: AllocatorList.h:23
bool isWriteable() const
Definition: SectionKind.h:144
bool isMergeableConst8() const
Definition: SectionKind.h:140
static SectionKind getMergeableConst8()
Definition: SectionKind.h:192
static SectionKind getMergeableConst16()
Definition: SectionKind.h:193
static SectionKind getMergeable1ByteCString()
Definition: SectionKind.h:182
bool isMergeableCString() const
Definition: SectionKind.h:127
static SectionKind getCommon()
Definition: SectionKind.h:200
static SectionKind getMergeableConst4()
Definition: SectionKind.h:191
bool isMergeable2ByteCString() const
Definition: SectionKind.h:132
static SectionKind getBSS()
Definition: SectionKind.h:197
static SectionKind getMergeable4ByteCString()
Definition: SectionKind.h:188
bool isGlobalWriteableData() const
Definition: SectionKind.h:155
bool isText() const
Definition: SectionKind.h:118
bool isBSSLocal() const
Definition: SectionKind.h:160
bool isMergeableConst32() const
Definition: SectionKind.h:142
static SectionKind getThreadData()
Definition: SectionKind.h:196
bool isReadOnlyWithRel() const
Definition: SectionKind.h:167
static SectionKind getBSSLocal()
Definition: SectionKind.h:198
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:22
bool isMergeableConst16() const
Definition: SectionKind.h:141
bool isThreadBSS() const
Definition: SectionKind.h:152
bool isBSS() const
Definition: SectionKind.h:159
bool isMergeableConst4() const
Definition: SectionKind.h:139
static SectionKind getThreadBSS()
Definition: SectionKind.h:195
bool isMergeable4ByteCString() const
Definition: SectionKind.h:133
bool isCommon() const
Definition: SectionKind.h:163
static SectionKind getMetadata()
Definition: SectionKind.h:178
static SectionKind getReadOnlyWithRel()
Definition: SectionKind.h:202
bool isMetadata() const
Definition: SectionKind.h:116
bool isReadOnly() const
Definition: SectionKind.h:122
static SectionKind getMergeable2ByteCString()
Definition: SectionKind.h:185
bool isMergeableConst() const
Definition: SectionKind.h:135
static SectionKind getBSSExtern()
Definition: SectionKind.h:199
bool isData() const
Definition: SectionKind.h:165
bool isThreadLocal() const
Definition: SectionKind.h:148
bool isMergeable1ByteCString() const
Definition: SectionKind.h:131
bool isExecuteOnly() const
Definition: SectionKind.h:120
static SectionKind getReadOnly()
Definition: SectionKind.h:181
Root of the metadata hierarchy.
Definition: Metadata.h:57
static SectionKind getExecuteOnly()
Definition: SectionKind.h:180
static SectionKind getText()
Definition: SectionKind.h:179