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#include "llvm/Support/Compiler.h"
19
20namespace llvm {
21  class MCExpr;
22  class MCSection;
23  class MCContext;
24  class raw_ostream;
25
26  /// MCSymbol - Instances of this class represent a symbol name in the MC file,
27  /// and MCSymbols are created and unique'd by the MCContext class.  MCSymbols
28  /// should only be constructed with valid names for the object file.
29  ///
30  /// If the symbol is defined/emitted into the current translation unit, the
31  /// Section member is set to indicate what section it lives in.  Otherwise, if
32  /// it is a reference to an external entity, it has a null section.
33  class MCSymbol {
34    // Special sentinal value for the absolute pseudo section.
35    //
36    // FIXME: Use a PointerInt wrapper for this?
37    static const MCSection *AbsolutePseudoSection;
38
39    /// Name - The name of the symbol.  The referred-to string data is actually
40    /// held by the StringMap that lives in MCContext.
41    StringRef Name;
42
43    /// Section - The section the symbol is defined in. This is null for
44    /// undefined symbols, and the special AbsolutePseudoSection value for
45    /// absolute symbols.
46    const MCSection *Section;
47
48    /// Value - If non-null, the value for a variable symbol.
49    const MCExpr *Value;
50
51    /// IsTemporary - True if this is an assembler temporary label, which
52    /// typically does not survive in the .o file's symbol table.  Usually
53    /// "Lfoo" or ".foo".
54    unsigned IsTemporary : 1;
55
56    /// IsUsed - True if this symbol has been used.
57    mutable unsigned IsUsed : 1;
58
59  private:  // MCContext creates and uniques these.
60    friend class MCExpr;
61    friend class MCContext;
62    MCSymbol(StringRef name, bool isTemporary)
63      : Name(name), Section(nullptr), Value(nullptr),
64        IsTemporary(isTemporary), IsUsed(false) {}
65
66    MCSymbol(const MCSymbol&) LLVM_DELETED_FUNCTION;
67    void operator=(const MCSymbol&) LLVM_DELETED_FUNCTION;
68  public:
69    /// getName - Get the symbol name.
70    StringRef getName() const { return Name; }
71
72    /// @name Accessors
73    /// @{
74
75    /// isTemporary - Check if this is an assembler temporary symbol.
76    bool isTemporary() const { return IsTemporary; }
77
78    /// isUsed - Check if this is used.
79    bool isUsed() const { return IsUsed; }
80    void setUsed(bool Value) const { IsUsed = Value; }
81
82    /// @}
83    /// @name Associated Sections
84    /// @{
85
86    /// isDefined - Check if this symbol is defined (i.e., it has an address).
87    ///
88    /// Defined symbols are either absolute or in some section.
89    bool isDefined() const {
90      return Section != nullptr;
91    }
92
93    /// isInSection - Check if this symbol is defined in some section (i.e., it
94    /// is defined but not absolute).
95    bool isInSection() const {
96      return isDefined() && !isAbsolute();
97    }
98
99    /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
100    bool isUndefined() const {
101      return !isDefined();
102    }
103
104    /// isAbsolute - Check if this is an absolute symbol.
105    bool isAbsolute() const {
106      return Section == AbsolutePseudoSection;
107    }
108
109    /// getSection - Get the section associated with a defined, non-absolute
110    /// symbol.
111    const MCSection &getSection() const {
112      assert(isInSection() && "Invalid accessor!");
113      return *Section;
114    }
115
116    /// setSection - Mark the symbol as defined in the section \p S.
117    void setSection(const MCSection &S) { Section = &S; }
118
119    /// setUndefined - Mark the symbol as undefined.
120    void setUndefined() {
121      Section = nullptr;
122    }
123
124    /// setAbsolute - Mark the symbol as absolute.
125    void setAbsolute() { Section = AbsolutePseudoSection; }
126
127    /// @}
128    /// @name Variable Symbols
129    /// @{
130
131    /// isVariable - Check if this is a variable symbol.
132    bool isVariable() const {
133      return Value != nullptr;
134    }
135
136    /// getVariableValue() - Get the value for variable symbols.
137    const MCExpr *getVariableValue() const {
138      assert(isVariable() && "Invalid accessor!");
139      IsUsed = true;
140      return Value;
141    }
142
143    // AliasedSymbol() - If this is an alias (a = b), return the symbol
144    // we ultimately point to. For a non-alias, this just returns the symbol
145    // itself.
146    const MCSymbol &AliasedSymbol() const;
147
148    void setVariableValue(const MCExpr *Value);
149
150    /// @}
151
152    /// print - Print the value to the stream \p OS.
153    void print(raw_ostream &OS) const;
154
155    /// dump - Print the value to stderr.
156    void dump() const;
157  };
158
159  inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
160    Sym.print(OS);
161    return OS;
162  }
163} // end namespace llvm
164
165#endif
166