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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/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"
23 : #include <cassert>
24 : #include <cstddef>
25 : #include <cstdint>
26 :
27 : namespace llvm {
28 :
29 : class MCAsmInfo;
30 : class MCContext;
31 : class MCExpr;
32 : class MCSection;
33 : class raw_ostream;
34 :
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.
38 : ///
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.
42 : class MCSymbol {
43 : protected:
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.
46 : enum SymbolKind {
47 : SymbolKindUnset,
48 : SymbolKindCOFF,
49 : SymbolKindELF,
50 : SymbolKindMachO,
51 : SymbolKindWasm,
52 : };
53 :
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 {
57 : SymContentsUnset,
58 : SymContentsOffset,
59 : SymContentsVariable,
60 : SymContentsCommon,
61 : };
62 :
63 : // Special sentinal value for the absolute pseudo fragment.
64 : static MCFragment *AbsolutePseudoFragment;
65 :
66 : /// If a symbol has a Fragment, the section is implied, so we only need
67 : /// one pointer.
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
71 : /// dummy fragments.
72 : /// If this is a section, then it gives the symbol is defined in. This is null
73 : /// for undefined symbols.
74 : ///
75 : /// If this is a fragment, then it gives the fragment this symbol's value is
76 : /// relative to, if any.
77 : ///
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;
82 :
83 : /// IsTemporary - True if this is an assembler temporary label, which
84 : /// typically does not survive in the .o file's symbol table. Usually
85 : /// "Lfoo" or ".foo".
86 : unsigned IsTemporary : 1;
87 :
88 : /// True if this symbol can be redefined.
89 : unsigned IsRedefinable : 1;
90 :
91 : /// IsUsed - True if this symbol has been used.
92 : mutable unsigned IsUsed : 1;
93 :
94 : mutable unsigned IsRegistered : 1;
95 :
96 : /// This symbol is visible outside this translation unit.
97 : mutable unsigned IsExternal : 1;
98 :
99 : /// This symbol is private extern.
100 : mutable unsigned IsPrivateExtern : 1;
101 :
102 : /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
103 : /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
104 : unsigned Kind : 3;
105 :
106 : /// True if we have created a relocation that uses this symbol.
107 : mutable unsigned IsUsedInReloc : 1;
108 :
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;
112 :
113 : /// The alignment of the symbol, if it is 'common', or -1.
114 : ///
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
117 : /// unsigned.
118 : enum : unsigned { NumCommonAlignmentBits = 5 };
119 : unsigned CommonAlignLog2 : NumCommonAlignmentBits;
120 :
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;
125 :
126 : /// Index field, for use by the object file implementation.
127 : mutable uint32_t Index = 0;
128 :
129 : union {
130 : /// The offset to apply to the fragment address to form this symbol's value.
131 : uint64_t Offset;
132 :
133 : /// The size of the symbol, if it is 'common'.
134 : uint64_t CommonSize;
135 :
136 : /// If non-null, the value for a variable symbol.
137 : const MCExpr *Value;
138 : };
139 :
140 : // MCContext creates and uniques these.
141 : friend class MCExpr;
142 : friend class MCContext;
143 :
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;
151 : };
152 :
153 : MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)
154 11212813 : : IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false),
155 : IsRegistered(false), IsExternal(false), IsPrivateExtern(false),
156 : Kind(Kind), IsUsedInReloc(false), SymbolContents(SymContentsUnset),
157 11212813 : CommonAlignLog2(0), Flags(0) {
158 11212813 : Offset = 0;
159 11212813 : FragmentAndHasName.setInt(!!Name);
160 11212813 : if (Name)
161 6113060 : getNameEntryPtr() = Name;
162 : }
163 :
164 : // Provide custom new/delete as we will only allocate space for a name
165 : // if we need one.
166 : void *operator new(size_t s, const StringMapEntry<bool> *Name,
167 : MCContext &Ctx);
168 :
169 : private:
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?");
174 : }
175 : /// Placement delete - required by std, but never called.
176 : void operator delete(void*, unsigned, bool) {
177 : llvm_unreachable("Constructor throws?");
178 : }
179 :
180 : MCSection *getSectionPtr() const {
181 18517872 : if (MCFragment *F = getFragment()) {
182 : assert(F != AbsolutePseudoFragment);
183 18517871 : return F->getParent();
184 : }
185 : return nullptr;
186 : }
187 :
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;
193 : }
194 : const StringMapEntry<bool> *&getNameEntryPtr() const {
195 : return const_cast<MCSymbol*>(this)->getNameEntryPtr();
196 : }
197 :
198 : public:
199 : MCSymbol(const MCSymbol &) = delete;
200 : MCSymbol &operator=(const MCSymbol &) = delete;
201 :
202 : /// getName - Get the symbol name.
203 : StringRef getName() const {
204 17492476 : if (!FragmentAndHasName.getInt())
205 : return StringRef();
206 :
207 8739157 : return getNameEntryPtr()->first();
208 : }
209 :
210 18796630 : bool isRegistered() const { return IsRegistered; }
211 8576279 : void setIsRegistered(bool Value) const { IsRegistered = Value; }
212 :
213 5306484 : void setUsedInReloc() const { IsUsedInReloc = true; }
214 8765394 : bool isUsedInReloc() const { return IsUsedInReloc; }
215 :
216 : /// \name Accessors
217 : /// @{
218 :
219 : /// isTemporary - Check if this is an assembler temporary symbol.
220 8722917 : bool isTemporary() const { return IsTemporary; }
221 :
222 : /// isUsed - Check if this is used.
223 350 : bool isUsed() const { return IsUsed; }
224 :
225 : /// Check if this symbol is redefinable.
226 : bool isRedefinable() const { return IsRedefinable; }
227 : /// Mark this symbol as redefinable.
228 828 : void setRedefinable(bool Value) { IsRedefinable = Value; }
229 : /// Prepare this symbol to be redefined.
230 : void redefineIfPossible() {
231 8888995 : if (IsRedefinable) {
232 3 : if (SymbolContents == SymContentsVariable) {
233 3 : Value = nullptr;
234 3 : SymbolContents = SymContentsUnset;
235 : }
236 : setUndefined();
237 3 : IsRedefinable = false;
238 : }
239 : }
240 :
241 : /// @}
242 : /// \name Associated Sections
243 : /// @{
244 :
245 : /// isDefined - Check if this symbol is defined (i.e., it has an address).
246 : ///
247 : /// Defined symbols are either absolute or in some section.
248 : bool isDefined() const { return !isUndefined(); }
249 :
250 : /// isInSection - Check if this symbol is defined in some section (i.e., it
251 : /// is defined but not absolute).
252 9329735 : bool isInSection() const {
253 9329735 : return isDefined() && !isAbsolute();
254 : }
255 :
256 : /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
257 : bool isUndefined(bool SetUsed = true) const {
258 84119792 : return getFragment(SetUsed) == nullptr;
259 : }
260 :
261 : /// isAbsolute - Check if this is an absolute symbol.
262 : bool isAbsolute() const {
263 9090235 : return getFragment() == AbsolutePseudoFragment;
264 : }
265 :
266 : /// Get the section associated with a defined, non-absolute symbol.
267 : MCSection &getSection() const {
268 : assert(isInSection() && "Invalid accessor!");
269 : return *getSectionPtr();
270 : }
271 :
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);
276 : }
277 :
278 : /// Mark the symbol as undefined.
279 : void setUndefined() { FragmentAndHasName.setPointer(nullptr); }
280 :
281 1737 : bool isELF() const { return Kind == SymbolKindELF; }
282 :
283 : bool isCOFF() const { return Kind == SymbolKindCOFF; }
284 :
285 : bool isMachO() const { return Kind == SymbolKindMachO; }
286 :
287 : bool isWasm() const { return Kind == SymbolKindWasm; }
288 :
289 : /// @}
290 : /// \name Variable Symbols
291 : /// @{
292 :
293 : /// isVariable - Check if this is a variable symbol.
294 : bool isVariable() const {
295 87511269 : return SymbolContents == SymContentsVariable;
296 : }
297 :
298 : /// getVariableValue - Get the value for variable symbols.
299 : const MCExpr *getVariableValue(bool SetUsed = true) const {
300 : assert(isVariable() && "Invalid accessor!");
301 30576 : IsUsed |= SetUsed;
302 25926 : return Value;
303 : }
304 :
305 : void setVariableValue(const MCExpr *Value);
306 :
307 : /// @}
308 :
309 : /// Get the (implementation defined) index.
310 0 : uint32_t getIndex() const {
311 0 : return Index;
312 : }
313 :
314 : /// Set the (implementation defined) index.
315 0 : void setIndex(uint32_t Value) const {
316 700256 : Index = Value;
317 0 : }
318 :
319 : bool isUnset() const { return SymbolContents == SymContentsUnset; }
320 :
321 0 : uint64_t getOffset() const {
322 : assert((SymbolContents == SymContentsUnset ||
323 : SymbolContents == SymContentsOffset) &&
324 : "Cannot get offset for a common/variable symbol");
325 0 : return Offset;
326 : }
327 : void setOffset(uint64_t Value) {
328 : assert((SymbolContents == SymContentsUnset ||
329 : SymbolContents == SymContentsOffset) &&
330 : "Cannot set offset for a common/variable symbol");
331 7789561 : Offset = Value;
332 7789561 : SymbolContents = SymContentsOffset;
333 : }
334 :
335 : /// Return the size of a 'common' symbol.
336 0 : uint64_t getCommonSize() const {
337 : assert(isCommon() && "Not a 'common' symbol!");
338 0 : return CommonSize;
339 : }
340 :
341 : /// Mark this symbol as being 'common'.
342 : ///
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);
347 667 : CommonSize = Size;
348 667 : SymbolContents = SymContentsCommon;
349 :
350 : assert((!Align || isPowerOf2_32(Align)) &&
351 : "Alignment must be a power of 2");
352 667 : unsigned Log2Align = Log2_32(Align) + 1;
353 : assert(Log2Align < (1U << NumCommonAlignmentBits) &&
354 : "Out of range alignment");
355 667 : CommonAlignLog2 = Log2Align;
356 : }
357 :
358 : /// Return the alignment of a 'common' symbol.
359 : unsigned getCommonAlignment() const {
360 : assert(isCommon() && "Not a 'common' symbol!");
361 648 : return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0;
362 : }
363 :
364 : /// Declare this symbol as being 'common'.
365 : ///
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
369 597 : bool declareCommon(uint64_t Size, unsigned Align) {
370 : assert(isCommon() || getOffset() == 0);
371 597 : if(isCommon()) {
372 5 : if(CommonSize != Size || getCommonAlignment() != Align)
373 1 : return true;
374 : } else
375 : setCommon(Size, Align);
376 : return false;
377 : }
378 :
379 : /// Is this a 'common' symbol.
380 : bool isCommon() const {
381 1393718 : return SymbolContents == SymContentsCommon;
382 : }
383 :
384 181595734 : MCFragment *getFragment(bool SetUsed = true) const {
385 181595734 : MCFragment *Fragment = FragmentAndHasName.getPointer();
386 181595734 : if (Fragment || !isVariable())
387 : return Fragment;
388 5782 : Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
389 : FragmentAndHasName.setPointer(Fragment);
390 5782 : return Fragment;
391 : }
392 :
393 6297 : bool isExternal() const { return IsExternal; }
394 259234 : void setExternal(bool Value) const { IsExternal = Value; }
395 :
396 1676 : bool isPrivateExtern() const { return IsPrivateExtern; }
397 22 : void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
398 :
399 : /// print - Print the value to the stream \p OS.
400 : void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
401 :
402 : /// dump - Print the value to stderr.
403 : void dump() const;
404 :
405 : protected:
406 : /// Get the (implementation defined) symbol flags.
407 31072341 : uint32_t getFlags() const { return Flags; }
408 :
409 : /// Set the (implementation defined) symbol flags.
410 : void setFlags(uint32_t Value) const {
411 : assert(Value < (1U << NumFlagsBits) && "Out of range flags");
412 3220245 : Flags = Value;
413 : }
414 :
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 1470 : Flags = (Flags & ~Mask) | Value;
419 : }
420 : };
421 :
422 : inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
423 25 : Sym.print(OS, nullptr);
424 : return OS;
425 : }
426 :
427 : } // end namespace llvm
428 :
429 : #endif // LLVM_MC_MCSYMBOL_H
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