include/llvm/MC/SectionKind.h

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