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1 //===- MCSymbol.h - Machine Code Symbols ------------------------*- 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 contains the declaration of the MCSymbol class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_MC_MCSYMBOL_H
15 #define LLVM_MC_MCSYMBOL_H
16 
17 #include "llvm/ADT/StringRef.h"
18 
19 namespace llvm {
20   class MCExpr;
21   class MCSection;
22   class MCContext;
23   class raw_ostream;
24 
25   /// MCSymbol - Instances of this class represent a symbol name in the MC file,
26   /// and MCSymbols are created and unique'd by the MCContext class.  MCSymbols
27   /// should only be constructed with valid names for the object file.
28   ///
29   /// If the symbol is defined/emitted into the current translation unit, the
30   /// Section member is set to indicate what section it lives in.  Otherwise, if
31   /// it is a reference to an external entity, it has a null section.
32   class MCSymbol {
33     // Special sentinal value for the absolute pseudo section.
34     //
35     // FIXME: Use a PointerInt wrapper for this?
36     static const MCSection *AbsolutePseudoSection;
37 
38     /// Name - The name of the symbol.  The referred-to string data is actually
39     /// held by the StringMap that lives in MCContext.
40     StringRef Name;
41 
42     /// Section - The section the symbol is defined in. This is null for
43     /// undefined symbols, and the special AbsolutePseudoSection value for
44     /// absolute symbols.
45     const MCSection *Section;
46 
47     /// Value - If non-null, the value for a variable symbol.
48     const MCExpr *Value;
49 
50     /// IsTemporary - True if this is an assembler temporary label, which
51     /// typically does not survive in the .o file's symbol table.  Usually
52     /// "Lfoo" or ".foo".
53     unsigned IsTemporary : 1;
54 
55     /// IsUsed - True if this symbol has been used.
56     mutable unsigned IsUsed : 1;
57 
58   private:  // MCContext creates and uniques these.
59     friend class MCExpr;
60     friend class MCContext;
MCSymbol(StringRef name,bool isTemporary)61     MCSymbol(StringRef name, bool isTemporary)
62       : Name(name), Section(0), Value(0),
63         IsTemporary(isTemporary), IsUsed(false) {}
64 
65     MCSymbol(const MCSymbol&);       // DO NOT IMPLEMENT
66     void operator=(const MCSymbol&); // DO NOT IMPLEMENT
67   public:
68     /// getName - Get the symbol name.
getName()69     StringRef getName() const { return Name; }
70 
71     /// @name Accessors
72     /// @{
73 
74     /// isTemporary - Check if this is an assembler temporary symbol.
isTemporary()75     bool isTemporary() const { return IsTemporary; }
76 
77     /// isUsed - Check if this is used.
isUsed()78     bool isUsed() const { return IsUsed; }
setUsed(bool Value)79     void setUsed(bool Value) const { IsUsed = Value; }
80 
81     /// @}
82     /// @name Associated Sections
83     /// @{
84 
85     /// isDefined - Check if this symbol is defined (i.e., it has an address).
86     ///
87     /// Defined symbols are either absolute or in some section.
isDefined()88     bool isDefined() const {
89       return Section != 0;
90     }
91 
92     /// isInSection - Check if this symbol is defined in some section (i.e., it
93     /// is defined but not absolute).
isInSection()94     bool isInSection() const {
95       return isDefined() && !isAbsolute();
96     }
97 
98     /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
isUndefined()99     bool isUndefined() const {
100       return !isDefined();
101     }
102 
103     /// isAbsolute - Check if this is an absolute symbol.
isAbsolute()104     bool isAbsolute() const {
105       return Section == AbsolutePseudoSection;
106     }
107 
108     /// getSection - Get the section associated with a defined, non-absolute
109     /// symbol.
getSection()110     const MCSection &getSection() const {
111       assert(isInSection() && "Invalid accessor!");
112       return *Section;
113     }
114 
115     /// setSection - Mark the symbol as defined in the section \arg S.
setSection(const MCSection & S)116     void setSection(const MCSection &S) { Section = &S; }
117 
118     /// setUndefined - Mark the symbol as undefined.
setUndefined()119     void setUndefined() {
120       Section = 0;
121     }
122 
123     /// setAbsolute - Mark the symbol as absolute.
setAbsolute()124     void setAbsolute() { Section = AbsolutePseudoSection; }
125 
126     /// @}
127     /// @name Variable Symbols
128     /// @{
129 
130     /// isVariable - Check if this is a variable symbol.
isVariable()131     bool isVariable() const {
132       return Value != 0;
133     }
134 
135     /// getValue() - Get the value for variable symbols.
getVariableValue()136     const MCExpr *getVariableValue() const {
137       assert(isVariable() && "Invalid accessor!");
138       IsUsed = true;
139       return Value;
140     }
141 
142     // AliasedSymbol() - If this is an alias (a = b), return the symbol
143     // we ultimately point to. For a non alias, this just returns the symbol
144     // itself.
145     const MCSymbol &AliasedSymbol() const;
146 
147     void setVariableValue(const MCExpr *Value);
148 
149     /// @}
150 
151     /// print - Print the value to the stream \arg OS.
152     void print(raw_ostream &OS) const;
153 
154     /// dump - Print the value to stderr.
155     void dump() const;
156   };
157 
158   inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
159     Sym.print(OS);
160     return OS;
161   }
162 } // end namespace llvm
163 
164 #endif
165