1 //===-- llvm/MC/SectionKind.h - Classification of sections ------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLVM_MC_SECTIONKIND_H
11 #define LLVM_MC_SECTIONKIND_H
15 /// SectionKind - This is a simple POD value that classifies the properties of
16 /// a section. A section is classified into the deepest possible
17 /// classification, and then the target maps them onto their sections based on
18 /// what capabilities they have.
20 /// The comments below describe these as if they were an inheritance hierarchy
21 /// in order to explain the predicates below.
25 /// Metadata - Debug info sections or other metadata.
28 /// Text - Text section, used for functions and other executable code.
31 /// ReadOnly - Data that is never written to at program runtime by the
32 /// program or the dynamic linker. Things in the top-level readonly
33 /// SectionKind are not mergeable.
36 /// MergableCString - Any null-terminated string which allows merging.
37 /// These values are known to end in a nul value of the specified size,
38 /// not otherwise contain a nul value, and be mergable. This allows the
39 /// linker to unique the strings if it so desires.
41 /// Mergeable1ByteCString - 1 byte mergable, null terminated, string.
42 Mergeable1ByteCString,
44 /// Mergeable2ByteCString - 2 byte mergable, null terminated, string.
45 Mergeable2ByteCString,
47 /// Mergeable4ByteCString - 4 byte mergable, null terminated, string.
48 Mergeable4ByteCString,
50 /// MergeableConst - These are sections for merging fixed-length
51 /// constants together. For example, this can be used to unique
52 /// constant pool entries etc.
54 /// MergeableConst4 - This is a section used by 4-byte constants,
55 /// for example, floats.
58 /// MergeableConst8 - This is a section used by 8-byte constants,
59 /// for example, doubles.
62 /// MergeableConst16 - This is a section used by 16-byte constants,
63 /// for example, vectors.
66 /// Writeable - This is the base of all segments that need to be written
67 /// to during program runtime.
69 /// ThreadLocal - This is the base of all TLS segments. All TLS
70 /// objects must be writeable, otherwise there is no reason for them to
73 /// ThreadBSS - Zero-initialized TLS data objects.
76 /// ThreadData - Initialized TLS data objects.
79 /// GlobalWriteableData - Writeable data that is global (not thread
82 /// BSS - Zero initialized writeable data.
85 /// BSSLocal - This is BSS (zero initialized and writable) data
86 /// which has local linkage.
89 /// BSSExtern - This is BSS data with normal external linkage.
92 /// Common - Data with common linkage. These represent tentative
93 /// definitions, which always have a zero initializer and are never
94 /// marked 'constant'.
97 /// This is writeable data that has a non-zero initializer.
100 /// ReadOnlyWithRel - These are global variables that are never
101 /// written to by the program, but that have relocations, so they
102 /// must be stuck in a writeable section so that the dynamic linker
103 /// can write to them. If it chooses to, the dynamic linker can
104 /// mark the pages these globals end up on as read-only after it is
105 /// done with its relocation phase.
110 bool isMetadata() const { return K == Metadata; }
111 bool isText() const { return K == Text; }
113 bool isReadOnly() const {
114 return K == ReadOnly || isMergeableCString() ||
118 bool isMergeableCString() const {
119 return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
120 K == Mergeable4ByteCString;
122 bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
123 bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
124 bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
126 bool isMergeableConst() const {
127 return K == MergeableConst4 || K == MergeableConst8 ||
128 K == MergeableConst16;
130 bool isMergeableConst4() const { return K == MergeableConst4; }
131 bool isMergeableConst8() const { return K == MergeableConst8; }
132 bool isMergeableConst16() const { return K == MergeableConst16; }
134 bool isWriteable() const {
135 return isThreadLocal() || isGlobalWriteableData();
138 bool isThreadLocal() const {
139 return K == ThreadData || K == ThreadBSS;
142 bool isThreadBSS() const { return K == ThreadBSS; }
143 bool isThreadData() const { return K == ThreadData; }
145 bool isGlobalWriteableData() const {
146 return isBSS() || isCommon() || isData() || isReadOnlyWithRel();
149 bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
150 bool isBSSLocal() const { return K == BSSLocal; }
151 bool isBSSExtern() const { return K == BSSExtern; }
153 bool isCommon() const { return K == Common; }
155 bool isData() const { return K == Data; }
157 bool isReadOnlyWithRel() const {
158 return K == ReadOnlyWithRel;
161 static SectionKind get(Kind K) {
168 static SectionKind getMetadata() { return get(Metadata); }
169 static SectionKind getText() { return get(Text); }
170 static SectionKind getReadOnly() { return get(ReadOnly); }
171 static SectionKind getMergeable1ByteCString() {
172 return get(Mergeable1ByteCString);
174 static SectionKind getMergeable2ByteCString() {
175 return get(Mergeable2ByteCString);
177 static SectionKind getMergeable4ByteCString() {
178 return get(Mergeable4ByteCString);
180 static SectionKind getMergeableConst4() { return get(MergeableConst4); }
181 static SectionKind getMergeableConst8() { return get(MergeableConst8); }
182 static SectionKind getMergeableConst16() { return get(MergeableConst16); }
183 static SectionKind getThreadBSS() { return get(ThreadBSS); }
184 static SectionKind getThreadData() { return get(ThreadData); }
185 static SectionKind getBSS() { return get(BSS); }
186 static SectionKind getBSSLocal() { return get(BSSLocal); }
187 static SectionKind getBSSExtern() { return get(BSSExtern); }
188 static SectionKind getCommon() { return get(Common); }
189 static SectionKind getData() { return get(Data); }
190 static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
193 } // end namespace llvm