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
12namespace 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///
22class SectionKind {
23  enum Kind {
24    /// Metadata - Debug info sections or other metadata.
25    Metadata,
26
27    /// Exclude - This section will be excluded from the final executable or
28    /// shared library. Only valid for ELF / COFF targets.
29    Exclude,
30
31    /// Text - Text section, used for functions and other executable code.
32    Text,
33
34           /// ExecuteOnly, Text section that is not readable.
35           ExecuteOnly,
36
37    /// ReadOnly - Data that is never written to at program runtime by the
38    /// program or the dynamic linker.  Things in the top-level readonly
39    /// SectionKind are not mergeable.
40    ReadOnly,
41
42        /// MergableCString - Any null-terminated string which allows merging.
43        /// These values are known to end in a nul value of the specified size,
44        /// not otherwise contain a nul value, and be mergable.  This allows the
45        /// linker to unique the strings if it so desires.
46
47           /// Mergeable1ByteCString - 1 byte mergable, null terminated, string.
48           Mergeable1ByteCString,
49
50           /// Mergeable2ByteCString - 2 byte mergable, null terminated, string.
51           Mergeable2ByteCString,
52
53           /// Mergeable4ByteCString - 4 byte mergable, null terminated, string.
54           Mergeable4ByteCString,
55
56        /// MergeableConst - These are sections for merging fixed-length
57        /// constants together.  For example, this can be used to unique
58        /// constant pool entries etc.
59
60            /// MergeableConst4 - This is a section used by 4-byte constants,
61            /// for example, floats.
62            MergeableConst4,
63
64            /// MergeableConst8 - This is a section used by 8-byte constants,
65            /// for example, doubles.
66            MergeableConst8,
67
68            /// MergeableConst16 - This is a section used by 16-byte constants,
69            /// for example, vectors.
70            MergeableConst16,
71
72            /// MergeableConst32 - This is a section used by 32-byte constants,
73            /// for example, vectors.
74            MergeableConst32,
75
76    /// Writeable - This is the base of all segments that need to be written
77    /// to during program runtime.
78
79       /// ThreadLocal - This is the base of all TLS segments.  All TLS
80       /// objects must be writeable, otherwise there is no reason for them to
81       /// be thread local!
82
83           /// ThreadBSS - Zero-initialized TLS data objects.
84           ThreadBSS,
85
86           /// ThreadData - Initialized TLS data objects.
87           ThreadData,
88
89           /// ThreadBSSLocal - Zero-initialized TLS data objects with local linkage.
90           ThreadBSSLocal,
91
92       /// GlobalWriteableData - Writeable data that is global (not thread
93       /// local).
94
95           /// BSS - Zero initialized writeable data.
96           BSS,
97
98               /// BSSLocal - This is BSS (zero initialized and writable) data
99               /// which has local linkage.
100               BSSLocal,
101
102               /// BSSExtern - This is BSS data with normal external linkage.
103               BSSExtern,
104
105           /// Common - Data with common linkage.  These represent tentative
106           /// definitions, which always have a zero initializer and are never
107           /// marked 'constant'.
108           Common,
109
110           /// This is writeable data that has a non-zero initializer.
111           Data,
112
113           /// ReadOnlyWithRel - These are global variables that are never
114           /// written to by the program, but that have relocations, so they
115           /// must be stuck in a writeable section so that the dynamic linker
116           /// can write to them.  If it chooses to, the dynamic linker can
117           /// mark the pages these globals end up on as read-only after it is
118           /// done with its relocation phase.
119           ReadOnlyWithRel
120  } K : 8;
121public:
122
123  bool isMetadata() const { return K == Metadata; }
124
125  bool isExclude() const { return K == Exclude; }
126
127  bool isText() const { return K == Text || K == ExecuteOnly; }
128
129  bool isExecuteOnly() const { return K == ExecuteOnly; }
130
131  bool isReadOnly() const {
132    return K == ReadOnly || isMergeableCString() ||
133           isMergeableConst();
134  }
135
136  bool isMergeableCString() const {
137    return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
138           K == Mergeable4ByteCString;
139  }
140  bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
141  bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
142  bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
143
144  bool isMergeableConst() const {
145    return K == MergeableConst4 || K == MergeableConst8 ||
146           K == MergeableConst16 || K == MergeableConst32;
147  }
148  bool isMergeableConst4() const { return K == MergeableConst4; }
149  bool isMergeableConst8() const { return K == MergeableConst8; }
150  bool isMergeableConst16() const { return K == MergeableConst16; }
151  bool isMergeableConst32() const { return K == MergeableConst32; }
152
153  bool isWriteable() const {
154    return isThreadLocal() || isGlobalWriteableData();
155  }
156
157  bool isThreadLocal() const {
158    return K == ThreadData || K == ThreadBSS || K == ThreadBSSLocal;
159  }
160
161  bool isThreadBSS() const { return K == ThreadBSS || K == ThreadBSSLocal; }
162  bool isThreadData() const { return K == ThreadData; }
163  bool isThreadBSSLocal() const { return K == ThreadBSSLocal; }
164
165  bool isGlobalWriteableData() const {
166    return isBSS() || isCommon() || isData() || isReadOnlyWithRel();
167  }
168
169  bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
170  bool isBSSLocal() const { return K == BSSLocal; }
171  bool isBSSExtern() const { return K == BSSExtern; }
172
173  bool isCommon() const { return K == Common; }
174
175  bool isData() const { return K == Data; }
176
177  bool isReadOnlyWithRel() const {
178    return K == ReadOnlyWithRel;
179  }
180private:
181  static SectionKind get(Kind K) {
182    SectionKind Res;
183    Res.K = K;
184    return Res;
185  }
186public:
187
188  static SectionKind getMetadata() { return get(Metadata); }
189  static SectionKind getExclude() { return get(Exclude); }
190  static SectionKind getText() { return get(Text); }
191  static SectionKind getExecuteOnly() { return get(ExecuteOnly); }
192  static SectionKind getReadOnly() { return get(ReadOnly); }
193  static SectionKind getMergeable1ByteCString() {
194    return get(Mergeable1ByteCString);
195  }
196  static SectionKind getMergeable2ByteCString() {
197    return get(Mergeable2ByteCString);
198  }
199  static SectionKind getMergeable4ByteCString() {
200    return get(Mergeable4ByteCString);
201  }
202  static SectionKind getMergeableConst4() { return get(MergeableConst4); }
203  static SectionKind getMergeableConst8() { return get(MergeableConst8); }
204  static SectionKind getMergeableConst16() { return get(MergeableConst16); }
205  static SectionKind getMergeableConst32() { return get(MergeableConst32); }
206  static SectionKind getThreadBSS() { return get(ThreadBSS); }
207  static SectionKind getThreadData() { return get(ThreadData); }
208  static SectionKind getThreadBSSLocal() { return get(ThreadBSSLocal); }
209  static SectionKind getBSS() { return get(BSS); }
210  static SectionKind getBSSLocal() { return get(BSSLocal); }
211  static SectionKind getBSSExtern() { return get(BSSExtern); }
212  static SectionKind getCommon() { return get(Common); }
213  static SectionKind getData() { return get(Data); }
214  static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
215};
216
217} // end namespace llvm
218
219#endif
220