MCSymbol.h revision db9835d0895337eb94c19e3a30b7d3fc8fcddfd5 
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
19namespace 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 MCContext;
60    MCSymbol(StringRef name, bool isTemporary)
61      : Name(name), Section(0), Value(0),
62        IsTemporary(isTemporary), IsUsed(false) {}
63
64    MCSymbol(const MCSymbol&);       // DO NOT IMPLEMENT
65    void operator=(const MCSymbol&); // DO NOT IMPLEMENT
66  public:
67    /// getName - Get the symbol name.
68    StringRef getName() const { return Name; }
69
70    /// @name Accessors
71    /// @{
72
73    /// isTemporary - Check if this is an assembler temporary symbol.
74    bool isTemporary() const { return IsTemporary; }
75
76    /// isUsed - Check if this is used.
77    bool isUsed() const { return IsUsed; }
78    void setUsed(bool Value) const { IsUsed = Value; }
79
80    /// @}
81    /// @name Associated Sections
82    /// @{
83
84    /// isDefined - Check if this symbol is defined (i.e., it has an address).
85    ///
86    /// Defined symbols are either absolute or in some section.
87    bool isDefined() const {
88      return Section != 0;
89    }
90
91    /// isInSection - Check if this symbol is defined in some section (i.e., it
92    /// is defined but not absolute).
93    bool isInSection() const {
94      return isDefined() && !isAbsolute();
95    }
96
97    /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
98    bool isUndefined() const {
99      return !isDefined();
100    }
101
102    /// isAbsolute - Check if this is an absolute symbol.
103    bool isAbsolute() const {
104      return Section == AbsolutePseudoSection;
105    }
106
107    /// getSection - Get the section associated with a defined, non-absolute
108    /// symbol.
109    const MCSection &getSection() const {
110      assert(isInSection() && "Invalid accessor!");
111      return *Section;
112    }
113
114    /// setSection - Mark the symbol as defined in the section \arg S.
115    void setSection(const MCSection &S) { Section = &S; }
116
117    /// setUndefined - Mark the symbol as undefined.
118    void setUndefined() {
119      Section = 0;
120    }
121
122    /// setAbsolute - Mark the symbol as absolute.
123    void setAbsolute() { Section = AbsolutePseudoSection; }
124
125    /// @}
126    /// @name Variable Symbols
127    /// @{
128
129    /// isVariable - Check if this is a variable symbol.
130    bool isVariable() const {
131      return Value != 0;
132    }
133
134    /// getValue() - Get the value for variable symbols.
135    const MCExpr *getVariableValue() const {
136      assert(isVariable() && "Invalid accessor!");
137      IsUsed = true;
138      return Value;
139    }
140
141    void setVariableValue(const MCExpr *Value);
142
143    /// @}
144
145    /// print - Print the value to the stream \arg OS.
146    void print(raw_ostream &OS) const;
147
148    /// dump - Print the value to stderr.
149    void dump() const;
150  };
151
152  inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
153    Sym.print(OS);
154    return OS;
155  }
156} // end namespace llvm
157
158#endif
159