1 //===-- llvm/Target/TargetLoweringObjectFile.h - Object Info ----*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements classes used to handle lowerings specific to common 11 // object file formats. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_MC_SECTIONKIND_H 16 #define LLVM_MC_SECTIONKIND_H 17 18 namespace llvm { 19 20 /// SectionKind - This is a simple POD value that classifies the properties of 21 /// a section. A section is classified into the deepest possible 22 /// classification, and then the target maps them onto their sections based on 23 /// what capabilities they have. 24 /// 25 /// The comments below describe these as if they were an inheritance hierarchy 26 /// in order to explain the predicates below. 27 /// 28 class SectionKind { 29 enum Kind { 30 /// Metadata - Debug info sections or other metadata. 31 Metadata, 32 33 /// Text - Text section, used for functions and other executable code. 34 Text, 35 36 /// ReadOnly - Data that is never written to at program runtime by the 37 /// program or the dynamic linker. Things in the top-level readonly 38 /// SectionKind are not mergeable. 39 ReadOnly, 40 41 /// MergableCString - Any null-terminated string which allows merging. 42 /// These values are known to end in a nul value of the specified size, 43 /// not otherwise contain a nul value, and be mergable. This allows the 44 /// linker to unique the strings if it so desires. 45 46 /// Mergeable1ByteCString - 1 byte mergable, null terminated, string. 47 Mergeable1ByteCString, 48 49 /// Mergeable2ByteCString - 2 byte mergable, null terminated, string. 50 Mergeable2ByteCString, 51 52 /// Mergeable4ByteCString - 4 byte mergable, null terminated, string. 53 Mergeable4ByteCString, 54 55 /// MergeableConst - These are sections for merging fixed-length 56 /// constants together. For example, this can be used to unique 57 /// constant pool entries etc. 58 59 /// MergeableConst4 - This is a section used by 4-byte constants, 60 /// for example, floats. 61 MergeableConst4, 62 63 /// MergeableConst8 - This is a section used by 8-byte constants, 64 /// for example, doubles. 65 MergeableConst8, 66 67 /// MergeableConst16 - This is a section used by 16-byte constants, 68 /// for example, vectors. 69 MergeableConst16, 70 71 /// Writeable - This is the base of all segments that need to be written 72 /// to during program runtime. 73 74 /// ThreadLocal - This is the base of all TLS segments. All TLS 75 /// objects must be writeable, otherwise there is no reason for them to 76 /// be thread local! 77 78 /// ThreadBSS - Zero-initialized TLS data objects. 79 ThreadBSS, 80 81 /// ThreadData - Initialized TLS data objects. 82 ThreadData, 83 84 /// GlobalWriteableData - Writeable data that is global (not thread 85 /// local). 86 87 /// BSS - Zero initialized writeable data. 88 BSS, 89 90 /// BSSLocal - This is BSS (zero initialized and writable) data 91 /// which has local linkage. 92 BSSLocal, 93 94 /// BSSExtern - This is BSS data with normal external linkage. 95 BSSExtern, 96 97 /// Common - Data with common linkage. These represent tentative 98 /// definitions, which always have a zero initializer and are never 99 /// marked 'constant'. 100 Common, 101 102 /// This is writeable data that has a non-zero initializer. 103 Data, 104 105 /// ReadOnlyWithRel - These are global variables that are never 106 /// written to by the program, but that have relocations, so they 107 /// must be stuck in a writeable section so that the dynamic linker 108 /// can write to them. If it chooses to, the dynamic linker can 109 /// mark the pages these globals end up on as read-only after it is 110 /// done with its relocation phase. 111 ReadOnlyWithRel 112 } K : 8; 113 public: 114 isMetadata()115 bool isMetadata() const { return K == Metadata; } isText()116 bool isText() const { return K == Text; } 117 isReadOnly()118 bool isReadOnly() const { 119 return K == ReadOnly || isMergeableCString() || 120 isMergeableConst(); 121 } 122 isMergeableCString()123 bool isMergeableCString() const { 124 return K == Mergeable1ByteCString || K == Mergeable2ByteCString || 125 K == Mergeable4ByteCString; 126 } isMergeable1ByteCString()127 bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; } isMergeable2ByteCString()128 bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; } isMergeable4ByteCString()129 bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; } 130 isMergeableConst()131 bool isMergeableConst() const { 132 return K == MergeableConst4 || K == MergeableConst8 || 133 K == MergeableConst16; 134 } isMergeableConst4()135 bool isMergeableConst4() const { return K == MergeableConst4; } isMergeableConst8()136 bool isMergeableConst8() const { return K == MergeableConst8; } isMergeableConst16()137 bool isMergeableConst16() const { return K == MergeableConst16; } 138 isWriteable()139 bool isWriteable() const { 140 return isThreadLocal() || isGlobalWriteableData(); 141 } 142 isThreadLocal()143 bool isThreadLocal() const { 144 return K == ThreadData || K == ThreadBSS; 145 } 146 isThreadBSS()147 bool isThreadBSS() const { return K == ThreadBSS; } isThreadData()148 bool isThreadData() const { return K == ThreadData; } 149 isGlobalWriteableData()150 bool isGlobalWriteableData() const { 151 return isBSS() || isCommon() || isData() || isReadOnlyWithRel(); 152 } 153 isBSS()154 bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; } isBSSLocal()155 bool isBSSLocal() const { return K == BSSLocal; } isBSSExtern()156 bool isBSSExtern() const { return K == BSSExtern; } 157 isCommon()158 bool isCommon() const { return K == Common; } 159 isData()160 bool isData() const { return K == Data; } 161 isReadOnlyWithRel()162 bool isReadOnlyWithRel() const { 163 return K == ReadOnlyWithRel; 164 } 165 private: get(Kind K)166 static SectionKind get(Kind K) { 167 SectionKind Res; 168 Res.K = K; 169 return Res; 170 } 171 public: 172 getMetadata()173 static SectionKind getMetadata() { return get(Metadata); } getText()174 static SectionKind getText() { return get(Text); } getReadOnly()175 static SectionKind getReadOnly() { return get(ReadOnly); } getMergeable1ByteCString()176 static SectionKind getMergeable1ByteCString() { 177 return get(Mergeable1ByteCString); 178 } getMergeable2ByteCString()179 static SectionKind getMergeable2ByteCString() { 180 return get(Mergeable2ByteCString); 181 } getMergeable4ByteCString()182 static SectionKind getMergeable4ByteCString() { 183 return get(Mergeable4ByteCString); 184 } getMergeableConst4()185 static SectionKind getMergeableConst4() { return get(MergeableConst4); } getMergeableConst8()186 static SectionKind getMergeableConst8() { return get(MergeableConst8); } getMergeableConst16()187 static SectionKind getMergeableConst16() { return get(MergeableConst16); } getThreadBSS()188 static SectionKind getThreadBSS() { return get(ThreadBSS); } getThreadData()189 static SectionKind getThreadData() { return get(ThreadData); } getBSS()190 static SectionKind getBSS() { return get(BSS); } getBSSLocal()191 static SectionKind getBSSLocal() { return get(BSSLocal); } getBSSExtern()192 static SectionKind getBSSExtern() { return get(BSSExtern); } getCommon()193 static SectionKind getCommon() { return get(Common); } getData()194 static SectionKind getData() { return get(Data); } getReadOnlyWithRel()195 static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); } 196 }; 197 198 } // end namespace llvm 199 200 #endif 201