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            /// ThreadBSSLocal - Zero-initialized TLS data objects with local linkage.
86            ThreadBSSLocal,
87 
88        /// GlobalWriteableData - Writeable data that is global (not thread
89        /// local).
90 
91            /// BSS - Zero initialized writeable data.
92            BSS,
93 
94                /// BSSLocal - This is BSS (zero initialized and writable) data
95                /// which has local linkage.
96                BSSLocal,
97 
98                /// BSSExtern - This is BSS data with normal external linkage.
99                BSSExtern,
100 
101            /// Common - Data with common linkage.  These represent tentative
102            /// definitions, which always have a zero initializer and are never
103            /// marked 'constant'.
104            Common,
105 
106            /// This is writeable data that has a non-zero initializer.
107            Data,
108 
109            /// ReadOnlyWithRel - These are global variables that are never
110            /// written to by the program, but that have relocations, so they
111            /// must be stuck in a writeable section so that the dynamic linker
112            /// can write to them.  If it chooses to, the dynamic linker can
113            /// mark the pages these globals end up on as read-only after it is
114            /// done with its relocation phase.
115            ReadOnlyWithRel
116   } K : 8;
117 public:
118 
isMetadata()119   bool isMetadata() const { return K == Metadata; }
120 
isText()121   bool isText() const { return K == Text || K == ExecuteOnly; }
122 
isExecuteOnly()123   bool isExecuteOnly() const { return K == ExecuteOnly; }
124 
isReadOnly()125   bool isReadOnly() const {
126     return K == ReadOnly || isMergeableCString() ||
127            isMergeableConst();
128   }
129 
isMergeableCString()130   bool isMergeableCString() const {
131     return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
132            K == Mergeable4ByteCString;
133   }
isMergeable1ByteCString()134   bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
isMergeable2ByteCString()135   bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
isMergeable4ByteCString()136   bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
137 
isMergeableConst()138   bool isMergeableConst() const {
139     return K == MergeableConst4 || K == MergeableConst8 ||
140            K == MergeableConst16 || K == MergeableConst32;
141   }
isMergeableConst4()142   bool isMergeableConst4() const { return K == MergeableConst4; }
isMergeableConst8()143   bool isMergeableConst8() const { return K == MergeableConst8; }
isMergeableConst16()144   bool isMergeableConst16() const { return K == MergeableConst16; }
isMergeableConst32()145   bool isMergeableConst32() const { return K == MergeableConst32; }
146 
isWriteable()147   bool isWriteable() const {
148     return isThreadLocal() || isGlobalWriteableData();
149   }
150 
isThreadLocal()151   bool isThreadLocal() const {
152     return K == ThreadData || K == ThreadBSS || K == ThreadBSSLocal;
153   }
154 
isThreadBSS()155   bool isThreadBSS() const { return K == ThreadBSS || K == ThreadBSSLocal; }
isThreadData()156   bool isThreadData() const { return K == ThreadData; }
isThreadBSSLocal()157   bool isThreadBSSLocal() const { return K == ThreadBSSLocal; }
158 
isGlobalWriteableData()159   bool isGlobalWriteableData() const {
160     return isBSS() || isCommon() || isData() || isReadOnlyWithRel();
161   }
162 
isBSS()163   bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
isBSSLocal()164   bool isBSSLocal() const { return K == BSSLocal; }
isBSSExtern()165   bool isBSSExtern() const { return K == BSSExtern; }
166 
isCommon()167   bool isCommon() const { return K == Common; }
168 
isData()169   bool isData() const { return K == Data; }
170 
isReadOnlyWithRel()171   bool isReadOnlyWithRel() const {
172     return K == ReadOnlyWithRel;
173   }
174 private:
get(Kind K)175   static SectionKind get(Kind K) {
176     SectionKind Res;
177     Res.K = K;
178     return Res;
179   }
180 public:
181 
getMetadata()182   static SectionKind getMetadata() { return get(Metadata); }
getText()183   static SectionKind getText() { return get(Text); }
getExecuteOnly()184   static SectionKind getExecuteOnly() { return get(ExecuteOnly); }
getReadOnly()185   static SectionKind getReadOnly() { return get(ReadOnly); }
getMergeable1ByteCString()186   static SectionKind getMergeable1ByteCString() {
187     return get(Mergeable1ByteCString);
188   }
getMergeable2ByteCString()189   static SectionKind getMergeable2ByteCString() {
190     return get(Mergeable2ByteCString);
191   }
getMergeable4ByteCString()192   static SectionKind getMergeable4ByteCString() {
193     return get(Mergeable4ByteCString);
194   }
getMergeableConst4()195   static SectionKind getMergeableConst4() { return get(MergeableConst4); }
getMergeableConst8()196   static SectionKind getMergeableConst8() { return get(MergeableConst8); }
getMergeableConst16()197   static SectionKind getMergeableConst16() { return get(MergeableConst16); }
getMergeableConst32()198   static SectionKind getMergeableConst32() { return get(MergeableConst32); }
getThreadBSS()199   static SectionKind getThreadBSS() { return get(ThreadBSS); }
getThreadData()200   static SectionKind getThreadData() { return get(ThreadData); }
getThreadBSSLocal()201   static SectionKind getThreadBSSLocal() { return get(ThreadBSSLocal); }
getBSS()202   static SectionKind getBSS() { return get(BSS); }
getBSSLocal()203   static SectionKind getBSSLocal() { return get(BSSLocal); }
getBSSExtern()204   static SectionKind getBSSExtern() { return get(BSSExtern); }
getCommon()205   static SectionKind getCommon() { return get(Common); }
getData()206   static SectionKind getData() { return get(Data); }
getReadOnlyWithRel()207   static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
208 };
209 
210 } // end namespace llvm
211 
212 #endif
213