1 //===- MCSymbol.h - Machine Code Symbols ------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the declaration of the MCSymbol class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_MC_MCSYMBOL_H
15 #define LLVM_MC_MCSYMBOL_H
17 #include "llvm/ADT/PointerIntPair.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/MC/MCExpr.h"
20 #include "llvm/Support/Compiler.h"
30 /// MCSymbol - Instances of this class represent a symbol name in the MC file,
31 /// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
32 /// should only be constructed with valid names for the object file.
34 /// If the symbol is defined/emitted into the current translation unit, the
35 /// Section member is set to indicate what section it lives in. Otherwise, if
36 /// it is a reference to an external entity, it has a null section.
38 // Special sentinal value for the absolute pseudo section.
40 // FIXME: Use a PointerInt wrapper for this?
41 static MCSection *AbsolutePseudoSection;
43 /// Name - The name of the symbol. The referred-to string data is actually
44 /// held by the StringMap that lives in MCContext.
45 const StringMapEntry<bool> *Name;
47 /// The section the symbol is defined in. This is null for undefined symbols,
48 /// and the special AbsolutePseudoSection value for absolute symbols. If this
49 /// is a variable symbol, this caches the variable value's section.
50 mutable MCSection *Section;
52 /// Value - If non-null, the value for a variable symbol.
55 /// IsTemporary - True if this is an assembler temporary label, which
56 /// typically does not survive in the .o file's symbol table. Usually
58 unsigned IsTemporary : 1;
60 /// \brief True if this symbol can be redefined.
61 unsigned IsRedefinable : 1;
63 /// IsUsed - True if this symbol has been used.
64 mutable unsigned IsUsed : 1;
66 mutable bool HasData : 1;
68 /// Index field, for use by the object file implementation.
69 mutable uint64_t Index : 60;
71 /// An expression describing how to calculate the size of a symbol. If a
72 /// symbol has no size this field will be NULL.
73 const MCExpr *SymbolSize = nullptr;
75 /// The alignment of the symbol, if it is 'common', or -1.
77 // FIXME: Pack this in with other fields?
78 unsigned CommonAlign = -1U;
81 /// The offset to apply to the fragment address to form this symbol's value.
84 /// The size of the symbol, if it is 'common'.
88 /// The Flags field is used by object file implementations to store
89 /// additional per symbol information which is not easily classified.
90 mutable uint32_t Flags = 0;
92 /// The fragment this symbol's value is relative to, if any. Also stores if
93 /// this symbol is visible outside this translation unit (bit 0) or if it is
94 /// private extern (bit 1).
95 mutable PointerIntPair<MCFragment *, 2> Fragment;
97 private: // MCContext creates and uniques these.
99 friend class MCContext;
100 MCSymbol(const StringMapEntry<bool> *Name, bool isTemporary)
101 : Name(Name), Section(nullptr), Value(nullptr), IsTemporary(isTemporary),
102 IsRedefinable(false), IsUsed(false), HasData(false), Index(0) {
106 MCSymbol(const MCSymbol &) = delete;
107 void operator=(const MCSymbol &) = delete;
108 MCSection *getSectionPtr() const {
109 if (Section || !Value)
111 return Section = Value->FindAssociatedSection();
115 /// getName - Get the symbol name.
116 StringRef getName() const { return Name ? Name->first() : ""; }
118 bool hasData() const { return HasData; }
120 MCSymbol &getData() const { return *const_cast<MCSymbol *>(this); }
122 /// Initialize symbol data.
124 /// Nothing really to do here, but this is enables an assertion that \a
125 /// MCAssembler::getOrCreateSymbolData() has actually been called before
126 /// anyone calls \a getData().
127 void initializeData() const { HasData = true; }
132 /// isTemporary - Check if this is an assembler temporary symbol.
133 bool isTemporary() const { return IsTemporary; }
135 /// isUsed - Check if this is used.
136 bool isUsed() const { return IsUsed; }
137 void setUsed(bool Value) const { IsUsed = Value; }
139 /// \brief Check if this symbol is redefinable.
140 bool isRedefinable() const { return IsRedefinable; }
141 /// \brief Mark this symbol as redefinable.
142 void setRedefinable(bool Value) { IsRedefinable = Value; }
143 /// \brief Prepare this symbol to be redefined.
144 void redefineIfPossible() {
148 IsRedefinable = false;
153 /// \name Associated Sections
156 /// isDefined - Check if this symbol is defined (i.e., it has an address).
158 /// Defined symbols are either absolute or in some section.
159 bool isDefined() const { return getSectionPtr() != nullptr; }
161 /// isInSection - Check if this symbol is defined in some section (i.e., it
162 /// is defined but not absolute).
163 bool isInSection() const { return isDefined() && !isAbsolute(); }
165 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
166 bool isUndefined() const { return !isDefined(); }
168 /// isAbsolute - Check if this is an absolute symbol.
169 bool isAbsolute() const { return getSectionPtr() == AbsolutePseudoSection; }
171 /// Get the section associated with a defined, non-absolute symbol.
172 MCSection &getSection() const {
173 assert(isInSection() && "Invalid accessor!");
174 return *getSectionPtr();
177 /// Mark the symbol as defined in the section \p S.
178 void setSection(MCSection &S) {
179 assert(!isVariable() && "Cannot set section of variable");
183 /// setUndefined - Mark the symbol as undefined.
184 void setUndefined() { Section = nullptr; }
187 /// \name Variable Symbols
190 /// isVariable - Check if this is a variable symbol.
191 bool isVariable() const { return Value != nullptr; }
193 /// getVariableValue() - Get the value for variable symbols.
194 const MCExpr *getVariableValue() const {
195 assert(isVariable() && "Invalid accessor!");
200 void setVariableValue(const MCExpr *Value);
204 /// Get the (implementation defined) index.
205 uint64_t getIndex() const {
206 assert(HasData && "Uninitialized symbol data");
210 /// Set the (implementation defined) index.
211 void setIndex(uint64_t Value) const {
212 assert(HasData && "Uninitialized symbol data");
213 assert(!(Value >> 60) && "Not enough bits for value");
217 void setSize(const MCExpr *SS) { SymbolSize = SS; }
219 const MCExpr *getSize() const { return SymbolSize; }
221 uint64_t getOffset() const {
225 void setOffset(uint64_t Value) {
230 /// Return the size of a 'common' symbol.
231 uint64_t getCommonSize() const {
232 assert(isCommon() && "Not a 'common' symbol!");
236 /// Mark this symbol as being 'common'.
238 /// \param Size - The size of the symbol.
239 /// \param Align - The alignment of the symbol.
240 void setCommon(uint64_t Size, unsigned Align) {
241 assert(getOffset() == 0);
246 /// Return the alignment of a 'common' symbol.
247 unsigned getCommonAlignment() const {
248 assert(isCommon() && "Not a 'common' symbol!");
252 /// Is this a 'common' symbol.
253 bool isCommon() const { return CommonAlign != -1U; }
255 /// Get the (implementation defined) symbol flags.
256 uint32_t getFlags() const { return Flags; }
258 /// Set the (implementation defined) symbol flags.
259 void setFlags(uint32_t Value) const { Flags = Value; }
261 /// Modify the flags via a mask
262 void modifyFlags(uint32_t Value, uint32_t Mask) const {
263 Flags = (Flags & ~Mask) | Value;
266 MCFragment *getFragment() const { return Fragment.getPointer(); }
267 void setFragment(MCFragment *Value) const { Fragment.setPointer(Value); }
269 bool isExternal() const { return Fragment.getInt() & 1; }
270 void setExternal(bool Value) const {
271 Fragment.setInt((Fragment.getInt() & ~1) | unsigned(Value));
274 bool isPrivateExtern() const { return Fragment.getInt() & 2; }
275 void setPrivateExtern(bool Value) {
276 Fragment.setInt((Fragment.getInt() & ~2) | (unsigned(Value) << 1));
279 /// print - Print the value to the stream \p OS.
280 void print(raw_ostream &OS) const;
282 /// dump - Print the value to stderr.
286 typedef MCSymbol MCSymbolData;
288 inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
292 } // end namespace llvm