SectionKind.h revision a3839bc3714e6a84222f45cf4c0f1a20a88b10cd 
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
18namespace 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///
28class 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        MergeableConst,
59
60            /// MergeableConst4 - This is a section used by 4-byte constants,
61            /// for example, floats.
62            MergeableConst4,
63
64            /// MergeableConst8 - This is a section used by 8-byte constants,
65            /// for example, doubles.
66            MergeableConst8,
67
68            /// MergeableConst16 - This is a section used by 16-byte constants,
69            /// for example, vectors.
70            MergeableConst16,
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           /// Common - Data with common linkage.  These represent tentative
92           /// definitions, which always have a zero initializer and are never
93           /// marked 'constant'.
94           Common,
95
96           /// DataRel - This is the most general form of data that is written
97           /// to by the program, it can have random relocations to arbitrary
98           /// globals.
99           DataRel,
100
101               /// DataRelLocal - This is writeable data that has a non-zero
102               /// initializer and has relocations in it, but all of the
103               /// relocations are known to be within the final linked image
104               /// the global is linked into.
105               DataRelLocal,
106
107                   /// DataNoRel - This is writeable data that has a non-zero
108                   /// initializer, but whose initializer is known to have no
109                   /// relocations.
110                   DataNoRel,
111
112           /// ReadOnlyWithRel - These are global variables that are never
113           /// written to by the program, but that have relocations, so they
114           /// must be stuck in a writeable section so that the dynamic linker
115           /// can write to them.  If it chooses to, the dynamic linker can
116           /// mark the pages these globals end up on as read-only after it is
117           /// done with its relocation phase.
118           ReadOnlyWithRel,
119
120               /// ReadOnlyWithRelLocal - This is data that is readonly by the
121               /// program, but must be writeable so that the dynamic linker
122               /// can perform relocations in it.  This is used when we know
123               /// that all the relocations are to globals in this final
124               /// linked image.
125               ReadOnlyWithRelLocal
126
127  } K : 8;
128public:
129
130  bool isMetadata() const { return K == Metadata; }
131  bool isText() const { return K == Text; }
132
133  bool isReadOnly() const {
134    return K == ReadOnly || isMergeableCString() ||
135           isMergeableConst();
136  }
137
138  bool isMergeableCString() const {
139    return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
140           K == Mergeable4ByteCString;
141  }
142  bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
143  bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
144  bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
145
146  bool isMergeableConst() const {
147    return K == MergeableConst || K == MergeableConst4 ||
148           K == MergeableConst8 || K == MergeableConst16;
149  }
150  bool isMergeableConst4() const { return K == MergeableConst4; }
151  bool isMergeableConst8() const { return K == MergeableConst8; }
152  bool isMergeableConst16() const { return K == MergeableConst16; }
153
154  bool isWriteable() const {
155    return isThreadLocal() || isGlobalWriteableData();
156  }
157
158  bool isThreadLocal() const {
159    return K == ThreadData || K == ThreadBSS;
160  }
161
162  bool isThreadBSS() const { return K == ThreadBSS; }
163  bool isThreadData() const { return K == ThreadData; }
164
165  bool isGlobalWriteableData() const {
166    return isBSS() || isCommon() || isDataRel() || isReadOnlyWithRel();
167  }
168
169  bool isBSS() const { return K == BSS; }
170  bool isCommon() const { return K == Common; }
171
172  bool isDataRel() const {
173    return K == DataRel || K == DataRelLocal || K == DataNoRel;
174  }
175
176  bool isDataRelLocal() const {
177    return K == DataRelLocal || K == DataNoRel;
178  }
179
180  bool isDataNoRel() const { return K == DataNoRel; }
181
182  bool isReadOnlyWithRel() const {
183    return K == ReadOnlyWithRel || K == ReadOnlyWithRelLocal;
184  }
185
186  bool isReadOnlyWithRelLocal() const {
187    return K == ReadOnlyWithRelLocal;
188  }
189private:
190  static SectionKind get(Kind K) {
191    SectionKind Res;
192    Res.K = K;
193    return Res;
194  }
195public:
196
197  static SectionKind getMetadata() { return get(Metadata); }
198  static SectionKind getText() { return get(Text); }
199  static SectionKind getReadOnly() { return get(ReadOnly); }
200  static SectionKind getMergeable1ByteCString() {
201    return get(Mergeable1ByteCString);
202  }
203  static SectionKind getMergeable2ByteCString() {
204    return get(Mergeable2ByteCString);
205  }
206  static SectionKind getMergeable4ByteCString() {
207    return get(Mergeable4ByteCString);
208  }
209  static SectionKind getMergeableConst() { return get(MergeableConst); }
210  static SectionKind getMergeableConst4() { return get(MergeableConst4); }
211  static SectionKind getMergeableConst8() { return get(MergeableConst8); }
212  static SectionKind getMergeableConst16() { return get(MergeableConst16); }
213  static SectionKind getThreadBSS() { return get(ThreadBSS); }
214  static SectionKind getThreadData() { return get(ThreadData); }
215  static SectionKind getBSS() { return get(BSS); }
216  static SectionKind getCommon() { return get(Common); }
217  static SectionKind getDataRel() { return get(DataRel); }
218  static SectionKind getDataRelLocal() { return get(DataRelLocal); }
219  static SectionKind getDataNoRel() { return get(DataNoRel); }
220  static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
221  static SectionKind getReadOnlyWithRelLocal(){
222    return get(ReadOnlyWithRelLocal);
223  }
224};
225
226} // end namespace llvm
227
228#endif
229