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/ADT/StringRef.h"
20 #include "llvm/MC/MCFragment.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/MathExtras.h"
35 /// MCSymbol - Instances of this class represent a symbol name in the MC file,
36 /// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
37 /// should only be constructed with valid names for the object file.
39 /// If the symbol is defined/emitted into the current translation unit, the
40 /// Section member is set to indicate what section it lives in. Otherwise, if
41 /// it is a reference to an external entity, it has a null section.
44 /// The kind of the symbol. If it is any value other than unset then this
45 /// class is actually one of the appropriate subclasses of MCSymbol.
54 /// A symbol can contain an Offset, or Value, or be Common, but never more
55 /// than one of these.
56 enum Contents : uint8_t {
63 // Special sentinal value for the absolute pseudo fragment.
64 static MCFragment *AbsolutePseudoFragment;
66 /// If a symbol has a Fragment, the section is implied, so we only need
68 /// The special AbsolutePseudoFragment value is for absolute symbols.
69 /// If this is a variable symbol, this caches the variable value's fragment.
70 /// FIXME: We might be able to simplify this by having the asm streamer create
72 /// If this is a section, then it gives the symbol is defined in. This is null
73 /// for undefined symbols.
75 /// If this is a fragment, then it gives the fragment this symbol's value is
76 /// relative to, if any.
78 /// For the 'HasName' integer, this is true if this symbol is named.
79 /// A named symbol will have a pointer to the name allocated in the bytes
80 /// immediately prior to the MCSymbol.
81 mutable PointerIntPair<MCFragment *, 1> FragmentAndHasName;
83 /// IsTemporary - True if this is an assembler temporary label, which
84 /// typically does not survive in the .o file's symbol table. Usually
86 unsigned IsTemporary : 1;
88 /// True if this symbol can be redefined.
89 unsigned IsRedefinable : 1;
91 /// IsUsed - True if this symbol has been used.
92 mutable unsigned IsUsed : 1;
94 mutable unsigned IsRegistered : 1;
96 /// This symbol is visible outside this translation unit.
97 mutable unsigned IsExternal : 1;
99 /// This symbol is private extern.
100 mutable unsigned IsPrivateExtern : 1;
102 /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
103 /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
106 /// True if we have created a relocation that uses this symbol.
107 mutable unsigned IsUsedInReloc : 1;
109 /// This is actually a Contents enumerator, but is unsigned to avoid sign
110 /// extension and achieve better bitpacking with MSVC.
111 unsigned SymbolContents : 2;
113 /// The alignment of the symbol, if it is 'common', or -1.
115 /// The alignment is stored as log2(align) + 1. This allows all values from
116 /// 0 to 2^31 to be stored which is every power of 2 representable by an
118 enum : unsigned { NumCommonAlignmentBits = 5 };
119 unsigned CommonAlignLog2 : NumCommonAlignmentBits;
121 /// The Flags field is used by object file implementations to store
122 /// additional per symbol information which is not easily classified.
123 enum : unsigned { NumFlagsBits = 16 };
124 mutable uint32_t Flags : NumFlagsBits;
126 /// Index field, for use by the object file implementation.
127 mutable uint32_t Index = 0;
130 /// The offset to apply to the fragment address to form this symbol's value.
133 /// The size of the symbol, if it is 'common'.
136 /// If non-null, the value for a variable symbol.
140 // MCContext creates and uniques these.
142 friend class MCContext;
144 /// The name for a symbol.
145 /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit
146 /// system, the name is a pointer so isn't going to satisfy the 8 byte
147 /// alignment of uint64_t. Account for that here.
148 using NameEntryStorageTy = union {
149 const StringMapEntry<bool> *NameEntry;
150 uint64_t AlignmentPadding;
153 MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)
154 : IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false),
155 IsRegistered(false), IsExternal(false), IsPrivateExtern(false),
156 Kind(Kind), IsUsedInReloc(false), SymbolContents(SymContentsUnset),
157 CommonAlignLog2(0), Flags(0) {
159 FragmentAndHasName.setInt(!!Name);
161 getNameEntryPtr() = Name;
164 // Provide custom new/delete as we will only allocate space for a name
166 void *operator new(size_t s, const StringMapEntry<bool> *Name,
170 void operator delete(void *);
171 /// Placement delete - required by std, but never called.
172 void operator delete(void*, unsigned) {
173 llvm_unreachable("Constructor throws?");
175 /// Placement delete - required by std, but never called.
176 void operator delete(void*, unsigned, bool) {
177 llvm_unreachable("Constructor throws?");
180 MCSection *getSectionPtr() const {
181 if (MCFragment *F = getFragment()) {
182 assert(F != AbsolutePseudoFragment);
183 return F->getParent();
188 /// Get a reference to the name field. Requires that we have a name
189 const StringMapEntry<bool> *&getNameEntryPtr() {
190 assert(FragmentAndHasName.getInt() && "Name is required");
191 NameEntryStorageTy *Name = reinterpret_cast<NameEntryStorageTy *>(this);
192 return (*(Name - 1)).NameEntry;
194 const StringMapEntry<bool> *&getNameEntryPtr() const {
195 return const_cast<MCSymbol*>(this)->getNameEntryPtr();
199 MCSymbol(const MCSymbol &) = delete;
200 MCSymbol &operator=(const MCSymbol &) = delete;
202 /// getName - Get the symbol name.
203 StringRef getName() const {
204 if (!FragmentAndHasName.getInt())
207 return getNameEntryPtr()->first();
210 bool isRegistered() const { return IsRegistered; }
211 void setIsRegistered(bool Value) const { IsRegistered = Value; }
213 void setUsedInReloc() const { IsUsedInReloc = true; }
214 bool isUsedInReloc() const { return IsUsedInReloc; }
219 /// isTemporary - Check if this is an assembler temporary symbol.
220 bool isTemporary() const { return IsTemporary; }
222 /// isUsed - Check if this is used.
223 bool isUsed() const { return IsUsed; }
225 /// Check if this symbol is redefinable.
226 bool isRedefinable() const { return IsRedefinable; }
227 /// Mark this symbol as redefinable.
228 void setRedefinable(bool Value) { IsRedefinable = Value; }
229 /// Prepare this symbol to be redefined.
230 void redefineIfPossible() {
232 if (SymbolContents == SymContentsVariable) {
234 SymbolContents = SymContentsUnset;
237 IsRedefinable = false;
242 /// \name Associated Sections
245 /// isDefined - Check if this symbol is defined (i.e., it has an address).
247 /// Defined symbols are either absolute or in some section.
248 bool isDefined() const { return !isUndefined(); }
250 /// isInSection - Check if this symbol is defined in some section (i.e., it
251 /// is defined but not absolute).
252 bool isInSection() const {
253 return isDefined() && !isAbsolute();
256 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
257 bool isUndefined(bool SetUsed = true) const {
258 return getFragment(SetUsed) == nullptr;
261 /// isAbsolute - Check if this is an absolute symbol.
262 bool isAbsolute() const {
263 return getFragment() == AbsolutePseudoFragment;
266 /// Get the section associated with a defined, non-absolute symbol.
267 MCSection &getSection() const {
268 assert(isInSection() && "Invalid accessor!");
269 return *getSectionPtr();
272 /// Mark the symbol as defined in the fragment \p F.
273 void setFragment(MCFragment *F) const {
274 assert(!isVariable() && "Cannot set fragment of variable");
275 FragmentAndHasName.setPointer(F);
278 /// Mark the symbol as undefined.
279 void setUndefined() { FragmentAndHasName.setPointer(nullptr); }
281 bool isELF() const { return Kind == SymbolKindELF; }
283 bool isCOFF() const { return Kind == SymbolKindCOFF; }
285 bool isMachO() const { return Kind == SymbolKindMachO; }
287 bool isWasm() const { return Kind == SymbolKindWasm; }
290 /// \name Variable Symbols
293 /// isVariable - Check if this is a variable symbol.
294 bool isVariable() const {
295 return SymbolContents == SymContentsVariable;
298 /// getVariableValue - Get the value for variable symbols.
299 const MCExpr *getVariableValue(bool SetUsed = true) const {
300 assert(isVariable() && "Invalid accessor!");
305 void setVariableValue(const MCExpr *Value);
309 /// Get the (implementation defined) index.
310 uint32_t getIndex() const {
314 /// Set the (implementation defined) index.
315 void setIndex(uint32_t Value) const {
319 bool isUnset() const { return SymbolContents == SymContentsUnset; }
321 uint64_t getOffset() const {
322 assert((SymbolContents == SymContentsUnset ||
323 SymbolContents == SymContentsOffset) &&
324 "Cannot get offset for a common/variable symbol");
327 void setOffset(uint64_t Value) {
328 assert((SymbolContents == SymContentsUnset ||
329 SymbolContents == SymContentsOffset) &&
330 "Cannot set offset for a common/variable symbol");
332 SymbolContents = SymContentsOffset;
335 /// Return the size of a 'common' symbol.
336 uint64_t getCommonSize() const {
337 assert(isCommon() && "Not a 'common' symbol!");
341 /// Mark this symbol as being 'common'.
343 /// \param Size - The size of the symbol.
344 /// \param Align - The alignment of the symbol.
345 void setCommon(uint64_t Size, unsigned Align) {
346 assert(getOffset() == 0);
348 SymbolContents = SymContentsCommon;
350 assert((!Align || isPowerOf2_32(Align)) &&
351 "Alignment must be a power of 2");
352 unsigned Log2Align = Log2_32(Align) + 1;
353 assert(Log2Align < (1U << NumCommonAlignmentBits) &&
354 "Out of range alignment");
355 CommonAlignLog2 = Log2Align;
358 /// Return the alignment of a 'common' symbol.
359 unsigned getCommonAlignment() const {
360 assert(isCommon() && "Not a 'common' symbol!");
361 return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0;
364 /// Declare this symbol as being 'common'.
366 /// \param Size - The size of the symbol.
367 /// \param Align - The alignment of the symbol.
368 /// \return True if symbol was already declared as a different type
369 bool declareCommon(uint64_t Size, unsigned Align) {
370 assert(isCommon() || getOffset() == 0);
372 if(CommonSize != Size || getCommonAlignment() != Align)
375 setCommon(Size, Align);
379 /// Is this a 'common' symbol.
380 bool isCommon() const {
381 return SymbolContents == SymContentsCommon;
384 MCFragment *getFragment(bool SetUsed = true) const {
385 MCFragment *Fragment = FragmentAndHasName.getPointer();
386 if (Fragment || !isVariable())
388 Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
389 FragmentAndHasName.setPointer(Fragment);
393 bool isExternal() const { return IsExternal; }
394 void setExternal(bool Value) const { IsExternal = Value; }
396 bool isPrivateExtern() const { return IsPrivateExtern; }
397 void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
399 /// print - Print the value to the stream \p OS.
400 void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
402 /// dump - Print the value to stderr.
406 /// Get the (implementation defined) symbol flags.
407 uint32_t getFlags() const { return Flags; }
409 /// Set the (implementation defined) symbol flags.
410 void setFlags(uint32_t Value) const {
411 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
415 /// Modify the flags via a mask
416 void modifyFlags(uint32_t Value, uint32_t Mask) const {
417 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
418 Flags = (Flags & ~Mask) | Value;
422 inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
423 Sym.print(OS, nullptr);
427 } // end namespace llvm
429 #endif // LLVM_MC_MCSYMBOL_H