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/PointerUnion.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/Support/Compiler.h"
32 /// MCSymbol - Instances of this class represent a symbol name in the MC file,
33 /// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
34 /// should only be constructed with valid names for the object file.
36 /// If the symbol is defined/emitted into the current translation unit, the
37 /// Section member is set to indicate what section it lives in. Otherwise, if
38 /// it is a reference to an external entity, it has a null section.
41 /// The kind of the symbol. If it is any value other than unset then this
42 /// class is actually one of the appropriate subclasses of MCSymbol.
50 // Special sentinal value for the absolute pseudo section.
52 // FIXME: Use a PointerInt wrapper for this?
53 static MCSection *AbsolutePseudoSection;
55 /// If a symbol has a Fragment, the section is implied, so we only need
57 /// FIXME: We might be able to simplify this by having the asm streamer create
59 /// If this is a section, then it gives the symbol is defined in. This is null
60 /// for undefined symbols, and the special AbsolutePseudoSection value for
61 /// absolute symbols. If this is a variable symbol, this caches the variable
64 /// If this is a fragment, then it gives the fragment this symbol's value is
65 /// relative to, if any.
66 mutable PointerUnion<MCSection *, MCFragment *> SectionOrFragment;
68 /// Value - If non-null, the value for a variable symbol.
71 /// IsTemporary - True if this is an assembler temporary label, which
72 /// typically does not survive in the .o file's symbol table. Usually
74 unsigned IsTemporary : 1;
76 /// \brief True if this symbol can be redefined.
77 unsigned IsRedefinable : 1;
79 /// IsUsed - True if this symbol has been used.
80 mutable unsigned IsUsed : 1;
82 mutable bool IsRegistered : 1;
84 /// This symbol is visible outside this translation unit.
85 mutable unsigned IsExternal : 1;
87 /// This symbol is private extern.
88 mutable unsigned IsPrivateExtern : 1;
90 /// True if this symbol is named.
91 /// A named symbol will have a pointer to the name allocated in the bytes
92 /// immediately prior to the MCSymbol.
95 /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
96 /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
99 /// Index field, for use by the object file implementation.
100 mutable uint32_t Index = 0;
103 /// The offset to apply to the fragment address to form this symbol's value.
106 /// The size of the symbol, if it is 'common'.
110 /// The alignment of the symbol, if it is 'common', or -1.
112 // FIXME: Pack this in with other fields?
113 unsigned CommonAlign = -1U;
115 /// The Flags field is used by object file implementations to store
116 /// additional per symbol information which is not easily classified.
117 mutable uint32_t Flags = 0;
119 protected: // MCContext creates and uniques these.
121 friend class MCContext;
123 /// \brief The name for a symbol.
124 /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit
125 /// system, the name is a pointer so isn't going to satisfy the 8 byte
126 /// alignment of uint64_t. Account for that here.
128 const StringMapEntry<bool> *NameEntry;
129 uint64_t AlignmentPadding;
130 } NameEntryStorageTy;
132 MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)
133 : Value(nullptr), IsTemporary(isTemporary),
134 IsRedefinable(false), IsUsed(false), IsRegistered(false),
135 IsExternal(false), IsPrivateExtern(false), HasName(!!Name),
139 getNameEntryPtr() = Name;
142 // Provide custom new/delete as we will only allocate space for a name
144 void *operator new(size_t s, const StringMapEntry<bool> *Name,
149 void operator delete(void *);
150 /// \brief Placement delete - required by std, but never called.
151 void operator delete(void*, unsigned) {
152 llvm_unreachable("Constructor throws?");
154 /// \brief Placement delete - required by std, but never called.
155 void operator delete(void*, unsigned, bool) {
156 llvm_unreachable("Constructor throws?");
159 MCSymbol(const MCSymbol &) = delete;
160 void operator=(const MCSymbol &) = delete;
161 MCSection *getSectionPtr() const {
162 if (MCFragment *F = getFragment())
163 return F->getParent();
164 assert(!SectionOrFragment.is<MCFragment *>() && "Section or null expected");
165 MCSection *Section = SectionOrFragment.dyn_cast<MCSection *>();
166 if (Section || !Value)
168 return Section = Value->findAssociatedSection();
171 /// \brief Get a reference to the name field. Requires that we have a name
172 const StringMapEntry<bool> *&getNameEntryPtr() {
173 assert(HasName && "Name is required");
174 NameEntryStorageTy *Name = reinterpret_cast<NameEntryStorageTy *>(this);
175 return (*(Name - 1)).NameEntry;
177 const StringMapEntry<bool> *&getNameEntryPtr() const {
178 return const_cast<MCSymbol*>(this)->getNameEntryPtr();
182 /// getName - Get the symbol name.
183 StringRef getName() const {
187 return getNameEntryPtr()->first();
190 bool isRegistered() const { return IsRegistered; }
191 void setIsRegistered(bool Value) const { IsRegistered = Value; }
196 /// isTemporary - Check if this is an assembler temporary symbol.
197 bool isTemporary() const { return IsTemporary; }
199 /// isUsed - Check if this is used.
200 bool isUsed() const { return IsUsed; }
201 void setUsed(bool Value) const { IsUsed = Value; }
203 /// \brief Check if this symbol is redefinable.
204 bool isRedefinable() const { return IsRedefinable; }
205 /// \brief Mark this symbol as redefinable.
206 void setRedefinable(bool Value) { IsRedefinable = Value; }
207 /// \brief Prepare this symbol to be redefined.
208 void redefineIfPossible() {
211 SectionOrFragment = nullptr;
212 IsRedefinable = false;
217 /// \name Associated Sections
220 /// isDefined - Check if this symbol is defined (i.e., it has an address).
222 /// Defined symbols are either absolute or in some section.
223 bool isDefined() const { return getSectionPtr() != nullptr; }
225 /// isInSection - Check if this symbol is defined in some section (i.e., it
226 /// is defined but not absolute).
227 bool isInSection() const { return isDefined() && !isAbsolute(); }
229 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
230 bool isUndefined() const { return !isDefined(); }
232 /// isAbsolute - Check if this is an absolute symbol.
233 bool isAbsolute() const { return getSectionPtr() == AbsolutePseudoSection; }
235 /// Get the section associated with a defined, non-absolute symbol.
236 MCSection &getSection() const {
237 assert(isInSection() && "Invalid accessor!");
238 return *getSectionPtr();
241 /// Mark the symbol as defined in the section \p S.
242 void setSection(MCSection &S) {
243 assert(!isVariable() && "Cannot set section of variable");
244 assert(!SectionOrFragment.is<MCFragment *>() && "Section or null expected");
245 SectionOrFragment = &S;
248 /// Mark the symbol as undefined.
249 void setUndefined() {
250 SectionOrFragment = nullptr;
253 bool isELF() const { return Kind == SymbolKindELF; }
255 bool isCOFF() const { return Kind == SymbolKindCOFF; }
257 bool isMachO() const { return Kind == SymbolKindMachO; }
260 /// \name Variable Symbols
263 /// isVariable - Check if this is a variable symbol.
264 bool isVariable() const { return Value != nullptr; }
266 /// getVariableValue() - Get the value for variable symbols.
267 const MCExpr *getVariableValue() const {
268 assert(isVariable() && "Invalid accessor!");
273 void setVariableValue(const MCExpr *Value);
277 /// Get the (implementation defined) index.
278 uint32_t getIndex() const {
282 /// Set the (implementation defined) index.
283 void setIndex(uint32_t Value) const {
287 uint64_t getOffset() const {
291 void setOffset(uint64_t Value) {
296 /// Return the size of a 'common' symbol.
297 uint64_t getCommonSize() const {
298 assert(isCommon() && "Not a 'common' symbol!");
302 /// Mark this symbol as being 'common'.
304 /// \param Size - The size of the symbol.
305 /// \param Align - The alignment of the symbol.
306 void setCommon(uint64_t Size, unsigned Align) {
307 assert(getOffset() == 0);
312 /// Return the alignment of a 'common' symbol.
313 unsigned getCommonAlignment() const {
314 assert(isCommon() && "Not a 'common' symbol!");
318 /// Declare this symbol as being 'common'.
320 /// \param Size - The size of the symbol.
321 /// \param Align - The alignment of the symbol.
322 /// \return True if symbol was already declared as a different type
323 bool declareCommon(uint64_t Size, unsigned Align) {
324 assert(isCommon() || getOffset() == 0);
326 if(CommonSize != Size || CommonAlign != Align)
329 setCommon(Size, Align);
333 /// Is this a 'common' symbol.
334 bool isCommon() const { return CommonAlign != -1U; }
336 MCFragment *getFragment() const {
337 return SectionOrFragment.dyn_cast<MCFragment *>();
339 void setFragment(MCFragment *Value) const {
340 SectionOrFragment = Value;
343 bool isExternal() const { return IsExternal; }
344 void setExternal(bool Value) const { IsExternal = Value; }
346 bool isPrivateExtern() const { return IsPrivateExtern; }
347 void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
349 /// print - Print the value to the stream \p OS.
350 void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
352 /// dump - Print the value to stderr.
356 /// Get the (implementation defined) symbol flags.
357 uint32_t getFlags() const { return Flags; }
359 /// Set the (implementation defined) symbol flags.
360 void setFlags(uint32_t Value) const { Flags = Value; }
362 /// Modify the flags via a mask
363 void modifyFlags(uint32_t Value, uint32_t Mask) const {
364 Flags = (Flags & ~Mask) | Value;
368 inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
369 Sym.print(OS, nullptr);
372 } // end namespace llvm