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            /// DataRel - This is the most general form of data that is written
103            /// to by the program, it can have random relocations to arbitrary
104            /// globals.
105            DataRel,
106 
107                /// DataRelLocal - This is writeable data that has a non-zero
108                /// initializer and has relocations in it, but all of the
109                /// relocations are known to be within the final linked image
110                /// the global is linked into.
111                DataRelLocal,
112 
113                    /// DataNoRel - This is writeable data that has a non-zero
114                    /// initializer, but whose initializer is known to have no
115                    /// relocations.
116                    DataNoRel,
117 
118            /// ReadOnlyWithRel - These are global variables that are never
119            /// written to by the program, but that have relocations, so they
120            /// must be stuck in a writeable section so that the dynamic linker
121            /// can write to them.  If it chooses to, the dynamic linker can
122            /// mark the pages these globals end up on as read-only after it is
123            /// done with its relocation phase.
124            ReadOnlyWithRel,
125 
126                /// ReadOnlyWithRelLocal - This is data that is readonly by the
127                /// program, but must be writeable so that the dynamic linker
128                /// can perform relocations in it.  This is used when we know
129                /// that all the relocations are to globals in this final
130                /// linked image.
131                ReadOnlyWithRelLocal
132 
133   } K : 8;
134 public:
135 
isMetadata()136   bool isMetadata() const { return K == Metadata; }
isText()137   bool isText() const { return K == Text; }
138 
isReadOnly()139   bool isReadOnly() const {
140     return K == ReadOnly || isMergeableCString() ||
141            isMergeableConst();
142   }
143 
isMergeableCString()144   bool isMergeableCString() const {
145     return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
146            K == Mergeable4ByteCString;
147   }
isMergeable1ByteCString()148   bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
isMergeable2ByteCString()149   bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
isMergeable4ByteCString()150   bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
151 
isMergeableConst()152   bool isMergeableConst() const {
153     return K == MergeableConst4 || K == MergeableConst8 ||
154            K == MergeableConst16;
155   }
isMergeableConst4()156   bool isMergeableConst4() const { return K == MergeableConst4; }
isMergeableConst8()157   bool isMergeableConst8() const { return K == MergeableConst8; }
isMergeableConst16()158   bool isMergeableConst16() const { return K == MergeableConst16; }
159 
isWriteable()160   bool isWriteable() const {
161     return isThreadLocal() || isGlobalWriteableData();
162   }
163 
isThreadLocal()164   bool isThreadLocal() const {
165     return K == ThreadData || K == ThreadBSS;
166   }
167 
isThreadBSS()168   bool isThreadBSS() const { return K == ThreadBSS; }
isThreadData()169   bool isThreadData() const { return K == ThreadData; }
170 
isGlobalWriteableData()171   bool isGlobalWriteableData() const {
172     return isBSS() || isCommon() || isDataRel() || isReadOnlyWithRel();
173   }
174 
isBSS()175   bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
isBSSLocal()176   bool isBSSLocal() const { return K == BSSLocal; }
isBSSExtern()177   bool isBSSExtern() const { return K == BSSExtern; }
178 
isCommon()179   bool isCommon() const { return K == Common; }
180 
isDataRel()181   bool isDataRel() const {
182     return K == DataRel || K == DataRelLocal || K == DataNoRel;
183   }
184 
isDataRelLocal()185   bool isDataRelLocal() const {
186     return K == DataRelLocal || K == DataNoRel;
187   }
188 
isDataNoRel()189   bool isDataNoRel() const { return K == DataNoRel; }
190 
isReadOnlyWithRel()191   bool isReadOnlyWithRel() const {
192     return K == ReadOnlyWithRel || K == ReadOnlyWithRelLocal;
193   }
194 
isReadOnlyWithRelLocal()195   bool isReadOnlyWithRelLocal() const {
196     return K == ReadOnlyWithRelLocal;
197   }
198 private:
get(Kind K)199   static SectionKind get(Kind K) {
200     SectionKind Res;
201     Res.K = K;
202     return Res;
203   }
204 public:
205 
getMetadata()206   static SectionKind getMetadata() { return get(Metadata); }
getText()207   static SectionKind getText() { return get(Text); }
getReadOnly()208   static SectionKind getReadOnly() { return get(ReadOnly); }
getMergeable1ByteCString()209   static SectionKind getMergeable1ByteCString() {
210     return get(Mergeable1ByteCString);
211   }
getMergeable2ByteCString()212   static SectionKind getMergeable2ByteCString() {
213     return get(Mergeable2ByteCString);
214   }
getMergeable4ByteCString()215   static SectionKind getMergeable4ByteCString() {
216     return get(Mergeable4ByteCString);
217   }
getMergeableConst4()218   static SectionKind getMergeableConst4() { return get(MergeableConst4); }
getMergeableConst8()219   static SectionKind getMergeableConst8() { return get(MergeableConst8); }
getMergeableConst16()220   static SectionKind getMergeableConst16() { return get(MergeableConst16); }
getThreadBSS()221   static SectionKind getThreadBSS() { return get(ThreadBSS); }
getThreadData()222   static SectionKind getThreadData() { return get(ThreadData); }
getBSS()223   static SectionKind getBSS() { return get(BSS); }
getBSSLocal()224   static SectionKind getBSSLocal() { return get(BSSLocal); }
getBSSExtern()225   static SectionKind getBSSExtern() { return get(BSSExtern); }
getCommon()226   static SectionKind getCommon() { return get(Common); }
getDataRel()227   static SectionKind getDataRel() { return get(DataRel); }
getDataRelLocal()228   static SectionKind getDataRelLocal() { return get(DataRelLocal); }
getDataNoRel()229   static SectionKind getDataNoRel() { return get(DataNoRel); }
getReadOnlyWithRel()230   static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
getReadOnlyWithRelLocal()231   static SectionKind getReadOnlyWithRelLocal(){
232     return get(ReadOnlyWithRelLocal);
233   }
234 };
235 
236 } // end namespace llvm
237 
238 #endif
239