SectionKind.h revision ce8749e445fdd0493758932874bad50293647df9 
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               /// 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           /// DataRel - This is the most general form of data that is written
104           /// to by the program, it can have random relocations to arbitrary
105           /// globals.
106           DataRel,
107
108               /// DataRelLocal - This is writeable data that has a non-zero
109               /// initializer and has relocations in it, but all of the
110               /// relocations are known to be within the final linked image
111               /// the global is linked into.
112               DataRelLocal,
113
114                   /// DataNoRel - This is writeable data that has a non-zero
115                   /// initializer, but whose initializer is known to have no
116                   /// relocations.
117                   DataNoRel,
118
119           /// ReadOnlyWithRel - These are global variables that are never
120           /// written to by the program, but that have relocations, so they
121           /// must be stuck in a writeable section so that the dynamic linker
122           /// can write to them.  If it chooses to, the dynamic linker can
123           /// mark the pages these globals end up on as read-only after it is
124           /// done with its relocation phase.
125           ReadOnlyWithRel,
126
127               /// ReadOnlyWithRelLocal - This is data that is readonly by the
128               /// program, but must be writeable so that the dynamic linker
129               /// can perform relocations in it.  This is used when we know
130               /// that all the relocations are to globals in this final
131               /// linked image.
132               ReadOnlyWithRelLocal
133
134  } K : 8;
135public:
136
137  bool isMetadata() const { return K == Metadata; }
138  bool isText() const { return K == Text; }
139
140  bool isReadOnly() const {
141    return K == ReadOnly || isMergeableCString() ||
142           isMergeableConst();
143  }
144
145  bool isMergeableCString() const {
146    return K == Mergeable1ByteCString || K == Mergeable2ByteCString ||
147           K == Mergeable4ByteCString;
148  }
149  bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; }
150  bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; }
151  bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; }
152
153  bool isMergeableConst() const {
154    return K == MergeableConst || K == MergeableConst4 ||
155           K == MergeableConst8 || K == MergeableConst16;
156  }
157  bool isMergeableConst4() const { return K == MergeableConst4; }
158  bool isMergeableConst8() const { return K == MergeableConst8; }
159  bool isMergeableConst16() const { return K == MergeableConst16; }
160
161  bool isWriteable() const {
162    return isThreadLocal() || isGlobalWriteableData();
163  }
164
165  bool isThreadLocal() const {
166    return K == ThreadData || K == ThreadBSS;
167  }
168
169  bool isThreadBSS() const { return K == ThreadBSS; }
170  bool isThreadData() const { return K == ThreadData; }
171
172  bool isGlobalWriteableData() const {
173    return isBSS() || isCommon() || isDataRel() || isReadOnlyWithRel();
174  }
175
176  bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; }
177  bool isBSSLocal() const { return K == BSSLocal; }
178  bool isBSSExtern() const { return K == BSSExtern; }
179
180  bool isCommon() const { return K == Common; }
181
182  bool isDataRel() const {
183    return K == DataRel || K == DataRelLocal || K == DataNoRel;
184  }
185
186  bool isDataRelLocal() const {
187    return K == DataRelLocal || K == DataNoRel;
188  }
189
190  bool isDataNoRel() const { return K == DataNoRel; }
191
192  bool isReadOnlyWithRel() const {
193    return K == ReadOnlyWithRel || K == ReadOnlyWithRelLocal;
194  }
195
196  bool isReadOnlyWithRelLocal() const {
197    return K == ReadOnlyWithRelLocal;
198  }
199private:
200  static SectionKind get(Kind K) {
201    SectionKind Res;
202    Res.K = K;
203    return Res;
204  }
205public:
206
207  static SectionKind getMetadata() { return get(Metadata); }
208  static SectionKind getText() { return get(Text); }
209  static SectionKind getReadOnly() { return get(ReadOnly); }
210  static SectionKind getMergeable1ByteCString() {
211    return get(Mergeable1ByteCString);
212  }
213  static SectionKind getMergeable2ByteCString() {
214    return get(Mergeable2ByteCString);
215  }
216  static SectionKind getMergeable4ByteCString() {
217    return get(Mergeable4ByteCString);
218  }
219  static SectionKind getMergeableConst() { return get(MergeableConst); }
220  static SectionKind getMergeableConst4() { return get(MergeableConst4); }
221  static SectionKind getMergeableConst8() { return get(MergeableConst8); }
222  static SectionKind getMergeableConst16() { return get(MergeableConst16); }
223  static SectionKind getThreadBSS() { return get(ThreadBSS); }
224  static SectionKind getThreadData() { return get(ThreadData); }
225  static SectionKind getBSS() { return get(BSS); }
226  static SectionKind getBSSLocal() { return get(BSSLocal); }
227  static SectionKind getBSSExtern() { return get(BSSExtern); }
228  static SectionKind getCommon() { return get(Common); }
229  static SectionKind getDataRel() { return get(DataRel); }
230  static SectionKind getDataRelLocal() { return get(DataRelLocal); }
231  static SectionKind getDataNoRel() { return get(DataNoRel); }
232  static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); }
233  static SectionKind getReadOnlyWithRelLocal(){
234    return get(ReadOnlyWithRelLocal);
235  }
236};
237
238} // end namespace llvm
239
240#endif
241