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