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 isMetadata()116 bool isMetadata() const { return K == Metadata; } 117 isText()118 bool isText() const { return K == Text || K == ExecuteOnly; } 119 isExecuteOnly()120 bool isExecuteOnly() const { return K == ExecuteOnly; } 121 isReadOnly()122 bool isReadOnly() const { 123 return K == ReadOnly || isMergeableCString() || 124 isMergeableConst(); 125 } 126 isMergeableCString()127 bool isMergeableCString() const { 128 return K == Mergeable1ByteCString || K == Mergeable2ByteCString || 129 K == Mergeable4ByteCString; 130 } isMergeable1ByteCString()131 bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; } isMergeable2ByteCString()132 bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; } isMergeable4ByteCString()133 bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; } 134 isMergeableConst()135 bool isMergeableConst() const { 136 return K == MergeableConst4 || K == MergeableConst8 || 137 K == MergeableConst16 || K == MergeableConst32; 138 } isMergeableConst4()139 bool isMergeableConst4() const { return K == MergeableConst4; } isMergeableConst8()140 bool isMergeableConst8() const { return K == MergeableConst8; } isMergeableConst16()141 bool isMergeableConst16() const { return K == MergeableConst16; } isMergeableConst32()142 bool isMergeableConst32() const { return K == MergeableConst32; } 143 isWriteable()144 bool isWriteable() const { 145 return isThreadLocal() || isGlobalWriteableData(); 146 } 147 isThreadLocal()148 bool isThreadLocal() const { 149 return K == ThreadData || K == ThreadBSS; 150 } 151 isThreadBSS()152 bool isThreadBSS() const { return K == ThreadBSS; } isThreadData()153 bool isThreadData() const { return K == ThreadData; } 154 isGlobalWriteableData()155 bool isGlobalWriteableData() const { 156 return isBSS() || isCommon() || isData() || isReadOnlyWithRel(); 157 } 158 isBSS()159 bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; } isBSSLocal()160 bool isBSSLocal() const { return K == BSSLocal; } isBSSExtern()161 bool isBSSExtern() const { return K == BSSExtern; } 162 isCommon()163 bool isCommon() const { return K == Common; } 164 isData()165 bool isData() const { return K == Data; } 166 isReadOnlyWithRel()167 bool isReadOnlyWithRel() const { 168 return K == ReadOnlyWithRel; 169 } 170 private: get(Kind K)171 static SectionKind get(Kind K) { 172 SectionKind Res; 173 Res.K = K; 174 return Res; 175 } 176 public: 177 getMetadata()178 static SectionKind getMetadata() { return get(Metadata); } getText()179 static SectionKind getText() { return get(Text); } getExecuteOnly()180 static SectionKind getExecuteOnly() { return get(ExecuteOnly); } getReadOnly()181 static SectionKind getReadOnly() { return get(ReadOnly); } getMergeable1ByteCString()182 static SectionKind getMergeable1ByteCString() { 183 return get(Mergeable1ByteCString); 184 } getMergeable2ByteCString()185 static SectionKind getMergeable2ByteCString() { 186 return get(Mergeable2ByteCString); 187 } getMergeable4ByteCString()188 static SectionKind getMergeable4ByteCString() { 189 return get(Mergeable4ByteCString); 190 } getMergeableConst4()191 static SectionKind getMergeableConst4() { return get(MergeableConst4); } getMergeableConst8()192 static SectionKind getMergeableConst8() { return get(MergeableConst8); } getMergeableConst16()193 static SectionKind getMergeableConst16() { return get(MergeableConst16); } getMergeableConst32()194 static SectionKind getMergeableConst32() { return get(MergeableConst32); } getThreadBSS()195 static SectionKind getThreadBSS() { return get(ThreadBSS); } getThreadData()196 static SectionKind getThreadData() { return get(ThreadData); } getBSS()197 static SectionKind getBSS() { return get(BSS); } getBSSLocal()198 static SectionKind getBSSLocal() { return get(BSSLocal); } getBSSExtern()199 static SectionKind getBSSExtern() { return get(BSSExtern); } getCommon()200 static SectionKind getCommon() { return get(Common); } getData()201 static SectionKind getData() { return get(Data); } getReadOnlyWithRel()202 static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); } 203 }; 204 205 } // end namespace llvm 206 207 #endif 208