LLVM 19.0.0git
MCSymbol.h
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1//===- MCSymbol.h - Machine Code Symbols ------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains the declaration of the MCSymbol class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_MC_MCSYMBOL_H
14#define LLVM_MC_MCSYMBOL_H
15
17#include "llvm/ADT/StringRef.h"
18#include "llvm/MC/MCExpr.h"
19#include "llvm/MC/MCFragment.h"
22#include <cassert>
23#include <cstddef>
24#include <cstdint>
25
26namespace llvm {
27
28class MCAsmInfo;
29class MCContext;
30class MCSection;
31class raw_ostream;
32
33/// MCSymbol - Instances of this class represent a symbol name in the MC file,
34/// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
35/// should only be constructed with valid names for the object file.
36///
37/// If the symbol is defined/emitted into the current translation unit, the
38/// Section member is set to indicate what section it lives in. Otherwise, if
39/// it is a reference to an external entity, it has a null section.
40class MCSymbol {
41protected:
42 /// The kind of the symbol. If it is any value other than unset then this
43 /// class is actually one of the appropriate subclasses of MCSymbol.
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 {
61 SymContentsTargetCommon, // Index stores the section index
62 };
63
64 // Special sentinel value for the absolute pseudo fragment.
66
67 /// If a symbol has a Fragment, the section is implied, so we only need
68 /// one pointer.
69 /// The special AbsolutePseudoFragment value is for absolute symbols.
70 /// If this is a variable symbol, this caches the variable value's fragment.
71 /// FIXME: We might be able to simplify this by having the asm streamer create
72 /// dummy fragments.
73 /// If this is a section, then it gives the symbol is defined in. This is null
74 /// for undefined symbols.
75 ///
76 /// If this is a fragment, then it gives the fragment this symbol's value is
77 /// relative to, if any.
78 mutable MCFragment *Fragment = nullptr;
79
80 /// True if this symbol is named. A named symbol will have a pointer to the
81 /// name allocated in the bytes immediately prior to the MCSymbol.
82 unsigned HasName : 1;
83
84 /// IsTemporary - True if this is an assembler temporary label, which
85 /// typically does not survive in the .o file's symbol table. Usually
86 /// "Lfoo" or ".foo".
87 unsigned IsTemporary : 1;
88
89 /// True if this symbol can be redefined.
90 unsigned IsRedefinable : 1;
91
92 /// IsUsed - True if this symbol has been used.
93 mutable unsigned IsUsed : 1;
94
95 mutable unsigned IsRegistered : 1;
96
97 /// True if this symbol is visible outside this translation unit. Note: ELF
98 /// uses binding instead of this bit.
99 mutable unsigned IsExternal : 1;
100
101 /// This symbol is private extern.
102 mutable unsigned IsPrivateExtern : 1;
103
104 /// This symbol is weak external.
105 mutable unsigned IsWeakExternal : 1;
106
107 /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
108 /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
109 unsigned Kind : 3;
110
111 /// True if we have created a relocation that uses this symbol.
112 mutable unsigned IsUsedInReloc : 1;
113
114 /// This is actually a Contents enumerator, but is unsigned to avoid sign
115 /// extension and achieve better bitpacking with MSVC.
116 unsigned SymbolContents : 3;
117
118 /// The alignment of the symbol if it is 'common'.
119 ///
120 /// Internally, this is stored as log2(align) + 1.
121 /// We reserve 5 bits to encode this value which allows the following values
122 /// 0b00000 -> unset
123 /// 0b00001 -> 1ULL << 0 = 1
124 /// 0b00010 -> 1ULL << 1 = 2
125 /// 0b00011 -> 1ULL << 2 = 4
126 /// ...
127 /// 0b11111 -> 1ULL << 30 = 1 GiB
128 enum : unsigned { NumCommonAlignmentBits = 5 };
130
131 /// The Flags field is used by object file implementations to store
132 /// additional per symbol information which is not easily classified.
133 enum : unsigned { NumFlagsBits = 16 };
135
136 /// Index field, for use by the object file implementation.
137 mutable uint32_t Index = 0;
138
139 union {
140 /// The offset to apply to the fragment address to form this symbol's value.
142
143 /// The size of the symbol, if it is 'common'.
145
146 /// If non-null, the value for a variable symbol.
147 const MCExpr *Value;
148 };
149
150 // MCContext creates and uniques these.
151 friend class MCExpr;
152 friend class MCContext;
153
154 /// The name for a symbol.
155 /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit
156 /// system, the name is a pointer so isn't going to satisfy the 8 byte
157 /// alignment of uint64_t. Account for that here.
158 using NameEntryStorageTy = union {
159 const StringMapEntry<bool> *NameEntry;
161 };
162
168 Offset = 0;
169 HasName = !!Name;
170 if (Name)
171 getNameEntryPtr() = Name;
172 }
173
174 // Provide custom new/delete as we will only allocate space for a name
175 // if we need one.
176 void *operator new(size_t s, const StringMapEntry<bool> *Name,
177 MCContext &Ctx);
178
179private:
180 void operator delete(void *);
181 /// Placement delete - required by std, but never called.
182 void operator delete(void*, unsigned) {
183 llvm_unreachable("Constructor throws?");
184 }
185 /// Placement delete - required by std, but never called.
186 void operator delete(void*, unsigned, bool) {
187 llvm_unreachable("Constructor throws?");
188 }
189
190 /// Get a reference to the name field. Requires that we have a name
191 const StringMapEntry<bool> *&getNameEntryPtr() {
192 assert(HasName && "Name is required");
193 NameEntryStorageTy *Name = reinterpret_cast<NameEntryStorageTy *>(this);
194 return (*(Name - 1)).NameEntry;
195 }
196 const StringMapEntry<bool> *&getNameEntryPtr() const {
197 return const_cast<MCSymbol*>(this)->getNameEntryPtr();
198 }
199
200public:
201 MCSymbol(const MCSymbol &) = delete;
202 MCSymbol &operator=(const MCSymbol &) = delete;
203
204 /// getName - Get the symbol name.
206 if (!HasName)
207 return StringRef();
208
209 return getNameEntryPtr()->first();
210 }
211
212 bool isRegistered() const { return IsRegistered; }
213 void setIsRegistered(bool Value) const { IsRegistered = Value; }
214
215 void setUsedInReloc() const { IsUsedInReloc = true; }
216 bool isUsedInReloc() const { return IsUsedInReloc; }
217
218 /// \name Accessors
219 /// @{
220
221 /// isTemporary - Check if this is an assembler temporary symbol.
222 bool isTemporary() const { return IsTemporary; }
223
224 /// isUsed - Check if this is used.
225 bool isUsed() const { return IsUsed; }
226
227 /// Check if this symbol is redefinable.
228 bool isRedefinable() const { return IsRedefinable; }
229 /// Mark this symbol as redefinable.
231 /// Prepare this symbol to be redefined.
233 if (IsRedefinable) {
235 Value = nullptr;
237 }
238 setUndefined();
239 IsRedefinable = false;
240 }
241 }
242
243 /// @}
244 /// \name Associated Sections
245 /// @{
246
247 /// isDefined - Check if this symbol is defined (i.e., it has an address).
248 ///
249 /// Defined symbols are either absolute or in some section.
250 bool isDefined() const { return !isUndefined(); }
251
252 /// isInSection - Check if this symbol is defined in some section (i.e., it
253 /// is defined but not absolute).
254 bool isInSection() const {
255 return isDefined() && !isAbsolute();
256 }
257
258 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
259 bool isUndefined(bool SetUsed = true) const {
260 return getFragment(SetUsed) == nullptr;
261 }
262
263 /// isAbsolute - Check if this is an absolute symbol.
264 bool isAbsolute() const {
266 }
267
268 /// Get the section associated with a defined, non-absolute symbol.
270 assert(isInSection() && "Invalid accessor!");
271 return *getFragment()->getParent();
272 }
273
274 /// Mark the symbol as defined in the fragment \p F.
275 void setFragment(MCFragment *F) const {
276 assert(!isVariable() && "Cannot set fragment of variable");
277 Fragment = F;
278 }
279
280 /// Mark the symbol as undefined.
281 void setUndefined() { Fragment = nullptr; }
282
283 bool isELF() const { return Kind == SymbolKindELF; }
284
285 bool isCOFF() const { return Kind == SymbolKindCOFF; }
286
287 bool isGOFF() const { return Kind == SymbolKindGOFF; }
288
289 bool isMachO() const { return Kind == SymbolKindMachO; }
290
291 bool isWasm() const { return Kind == SymbolKindWasm; }
292
293 bool isXCOFF() const { return Kind == SymbolKindXCOFF; }
294
295 /// @}
296 /// \name Variable Symbols
297 /// @{
298
299 /// isVariable - Check if this is a variable symbol.
300 bool isVariable() const {
302 }
303
304 /// getVariableValue - Get the value for variable symbols.
305 const MCExpr *getVariableValue(bool SetUsed = true) const {
306 assert(isVariable() && "Invalid accessor!");
307 IsUsed |= SetUsed;
308 return Value;
309 }
310
311 void setVariableValue(const MCExpr *Value);
312
313 /// @}
314
315 /// Get the (implementation defined) index.
317 return Index;
318 }
319
320 /// Set the (implementation defined) index.
321 void setIndex(uint32_t Value) const {
322 Index = Value;
323 }
324
325 bool isUnset() const { return SymbolContents == SymContentsUnset; }
326
330 "Cannot get offset for a common/variable symbol");
331 return Offset;
332 }
336 "Cannot set offset for a common/variable symbol");
337 Offset = Value;
339 }
340
341 /// Return the size of a 'common' symbol.
343 assert(isCommon() && "Not a 'common' symbol!");
344 return CommonSize;
345 }
346
347 /// Mark this symbol as being 'common'.
348 ///
349 /// \param Size - The size of the symbol.
350 /// \param Alignment - The alignment of the symbol.
351 /// \param Target - Is the symbol a target-specific common-like symbol.
352 void setCommon(uint64_t Size, Align Alignment, bool Target = false) {
353 assert(getOffset() == 0);
356
357 unsigned Log2Align = encode(Alignment);
358 assert(Log2Align < (1U << NumCommonAlignmentBits) &&
359 "Out of range alignment");
360 CommonAlignLog2 = Log2Align;
361 }
362
363 /// Return the alignment of a 'common' symbol.
365 assert(isCommon() && "Not a 'common' symbol!");
367 }
368
369 /// Declare this symbol as being 'common'.
370 ///
371 /// \param Size - The size of the symbol.
372 /// \param Alignment - The alignment of the symbol.
373 /// \param Target - Is the symbol a target-specific common-like symbol.
374 /// \return True if symbol was already declared as a different type
375 bool declareCommon(uint64_t Size, Align Alignment, bool Target = false) {
376 assert(isCommon() || getOffset() == 0);
377 if(isCommon()) {
378 if (CommonSize != Size || getCommonAlignment() != Alignment ||
380 return true;
381 } else
382 setCommon(Size, Alignment, Target);
383 return false;
384 }
385
386 /// Is this a 'common' symbol.
387 bool isCommon() const {
390 }
391
392 /// Is this a target-specific common-like symbol.
393 bool isTargetCommon() const {
395 }
396
397 MCFragment *getFragment(bool SetUsed = true) const {
398 if (Fragment || !isVariable() || isWeakExternal())
399 return Fragment;
400 // If the symbol is a non-weak alias, get information about
401 // the aliasee. (Don't try to resolve weak aliases.)
403 return Fragment;
404 }
405
406 bool isExternal() const { return IsExternal; }
407 void setExternal(bool Value) const { IsExternal = Value; }
408
409 bool isPrivateExtern() const { return IsPrivateExtern; }
411
412 bool isWeakExternal() const { return IsWeakExternal; }
413
414 /// print - Print the value to the stream \p OS.
415 void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
416
417 /// dump - Print the value to stderr.
418 void dump() const;
419
420protected:
421 /// Get the (implementation defined) symbol flags.
422 uint32_t getFlags() const { return Flags; }
423
424 /// Set the (implementation defined) symbol flags.
425 void setFlags(uint32_t Value) const {
426 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
427 Flags = Value;
428 }
429
430 /// Modify the flags via a mask
431 void modifyFlags(uint32_t Value, uint32_t Mask) const {
432 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
433 Flags = (Flags & ~Mask) | Value;
434 }
435};
436
438 Sym.print(OS, nullptr);
439 return OS;
440}
441
442} // end namespace llvm
443
444#endif // LLVM_MC_MCSYMBOL_H
This file defines the StringMapEntry class - it is intended to be a low dependency implementation det...
std::string Name
uint64_t Size
Symbol * Sym
Definition: ELF_riscv.cpp:479
#define F(x, y, z)
Definition: MD5.cpp:55
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
This class is intended to be used as a base class for asm properties and features specific to the tar...
Definition: MCAsmInfo.h:56
Context object for machine code objects.
Definition: MCContext.h:76
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
MCFragment * findAssociatedFragment() const
Find the "associated section" for this expression, which is currently defined as the absolute section...
Definition: MCExpr.cpp:1058
MCSection * getParent() const
Definition: MCFragment.h:96
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:39
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:40
bool isAbsolute() const
isAbsolute - Check if this is an absolute symbol.
Definition: MCSymbol.h:264
@ NumCommonAlignmentBits
Definition: MCSymbol.h:128
bool isWasm() const
Definition: MCSymbol.h:291
unsigned IsWeakExternal
This symbol is weak external.
Definition: MCSymbol.h:105
bool isMachO() const
Definition: MCSymbol.h:289
MCSymbol(const MCSymbol &)=delete
const MCExpr * getVariableValue(bool SetUsed=true) const
getVariableValue - Get the value for variable symbols.
Definition: MCSymbol.h:305
void setPrivateExtern(bool Value)
Definition: MCSymbol.h:410
bool isTargetCommon() const
Is this a target-specific common-like symbol.
Definition: MCSymbol.h:393
void print(raw_ostream &OS, const MCAsmInfo *MAI) const
print - Print the value to the stream OS.
Definition: MCSymbol.cpp:58
bool isDefined() const
isDefined - Check if this symbol is defined (i.e., it has an address).
Definition: MCSymbol.h:250
bool isInSection() const
isInSection - Check if this symbol is defined in some section (i.e., it is defined but not absolute).
Definition: MCSymbol.h:254
bool isELF() const
Definition: MCSymbol.h:283
void setCommon(uint64_t Size, Align Alignment, bool Target=false)
Mark this symbol as being 'common'.
Definition: MCSymbol.h:352
bool isGOFF() const
Definition: MCSymbol.h:287
void setExternal(bool Value) const
Definition: MCSymbol.h:407
unsigned IsUsed
IsUsed - True if this symbol has been used.
Definition: MCSymbol.h:93
bool isCommon() const
Is this a 'common' symbol.
Definition: MCSymbol.h:387
void modifyFlags(uint32_t Value, uint32_t Mask) const
Modify the flags via a mask.
Definition: MCSymbol.h:431
unsigned IsPrivateExtern
This symbol is private extern.
Definition: MCSymbol.h:102
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:205
void setFragment(MCFragment *F) const
Mark the symbol as defined in the fragment F.
Definition: MCSymbol.h:275
unsigned IsRegistered
Definition: MCSymbol.h:95
unsigned IsUsedInReloc
True if we have created a relocation that uses this symbol.
Definition: MCSymbol.h:112
bool isWeakExternal() const
Definition: MCSymbol.h:412
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:300
uint32_t Flags
Definition: MCSymbol.h:134
unsigned IsRedefinable
True if this symbol can be redefined.
Definition: MCSymbol.h:90
void setFlags(uint32_t Value) const
Set the (implementation defined) symbol flags.
Definition: MCSymbol.h:425
uint32_t getFlags() const
Get the (implementation defined) symbol flags.
Definition: MCSymbol.h:422
unsigned IsExternal
True if this symbol is visible outside this translation unit.
Definition: MCSymbol.h:99
bool isRedefinable() const
Check if this symbol is redefinable.
Definition: MCSymbol.h:228
void setVariableValue(const MCExpr *Value)
Definition: MCSymbol.cpp:47
bool isCOFF() const
Definition: MCSymbol.h:285
MaybeAlign getCommonAlignment() const
Return the alignment of a 'common' symbol.
Definition: MCSymbol.h:364
unsigned CommonAlignLog2
Definition: MCSymbol.h:129
uint32_t Index
Index field, for use by the object file implementation.
Definition: MCSymbol.h:137
uint64_t AlignmentPadding
Definition: MCSymbol.h:160
bool isUsed() const
isUsed - Check if this is used.
Definition: MCSymbol.h:225
unsigned HasName
True if this symbol is named.
Definition: MCSymbol.h:82
bool isRegistered() const
Definition: MCSymbol.h:212
void setIndex(uint32_t Value) const
Set the (implementation defined) index.
Definition: MCSymbol.h:321
bool isUndefined(bool SetUsed=true) const
isUndefined - Check if this symbol undefined (i.e., implicitly defined).
Definition: MCSymbol.h:259
void setRedefinable(bool Value)
Mark this symbol as redefinable.
Definition: MCSymbol.h:230
void setUsedInReloc() const
Definition: MCSymbol.h:215
unsigned SymbolContents
This is actually a Contents enumerator, but is unsigned to avoid sign extension and achieve better bi...
Definition: MCSymbol.h:116
uint32_t getIndex() const
Get the (implementation defined) index.
Definition: MCSymbol.h:316
MCFragment * Fragment
If a symbol has a Fragment, the section is implied, so we only need one pointer.
Definition: MCSymbol.h:78
Contents
A symbol can contain an Offset, or Value, or be Common, but never more than one of these.
Definition: MCSymbol.h:56
@ SymContentsCommon
Definition: MCSymbol.h:60
@ SymContentsOffset
Definition: MCSymbol.h:58
@ SymContentsUnset
Definition: MCSymbol.h:57
@ SymContentsTargetCommon
Definition: MCSymbol.h:61
@ SymContentsVariable
Definition: MCSymbol.h:59
void setUndefined()
Mark the symbol as undefined.
Definition: MCSymbol.h:281
MCSection & getSection() const
Get the section associated with a defined, non-absolute symbol.
Definition: MCSymbol.h:269
static MCFragment * AbsolutePseudoFragment
Definition: MCSymbol.h:65
SymbolKind
The kind of the symbol.
Definition: MCSymbol.h:44
void setOffset(uint64_t Value)
Definition: MCSymbol.h:333
void redefineIfPossible()
Prepare this symbol to be redefined.
Definition: MCSymbol.h:232
uint64_t getCommonSize() const
Return the size of a 'common' symbol.
Definition: MCSymbol.h:342
unsigned IsTemporary
IsTemporary - True if this is an assembler temporary label, which typically does not survive in the ....
Definition: MCSymbol.h:87
void dump() const
dump - Print the value to stderr.
Definition: MCSymbol.cpp:84
bool isTemporary() const
isTemporary - Check if this is an assembler temporary symbol.
Definition: MCSymbol.h:222
union { const StringMapEntry< bool > *NameEntry NameEntryStorageTy
The name for a symbol.
Definition: MCSymbol.h:159
bool declareCommon(uint64_t Size, Align Alignment, bool Target=false)
Declare this symbol as being 'common'.
Definition: MCSymbol.h:375
MCSymbol(SymbolKind Kind, const StringMapEntry< bool > *Name, bool isTemporary)
Definition: MCSymbol.h:163
bool isUnset() const
Definition: MCSymbol.h:325
bool isExternal() const
Definition: MCSymbol.h:406
const MCExpr * Value
If non-null, the value for a variable symbol.
Definition: MCSymbol.h:147
void setIsRegistered(bool Value) const
Definition: MCSymbol.h:213
uint64_t CommonSize
The size of the symbol, if it is 'common'.
Definition: MCSymbol.h:144
bool isXCOFF() const
Definition: MCSymbol.h:293
uint64_t Offset
The offset to apply to the fragment address to form this symbol's value.
Definition: MCSymbol.h:141
uint64_t getOffset() const
Definition: MCSymbol.h:327
bool isPrivateExtern() const
Definition: MCSymbol.h:409
bool isUsedInReloc() const
Definition: MCSymbol.h:216
MCSymbol & operator=(const MCSymbol &)=delete
unsigned Kind
LLVM RTTI discriminator.
Definition: MCSymbol.h:109
MCFragment * getFragment(bool SetUsed=true) const
Definition: MCSymbol.h:397
StringMapEntry - This is used to represent one value that is inserted into a StringMap.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
Target - Wrapper for Target specific information.
LLVM Value Representation.
Definition: Value.h:74
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
unsigned encode(MaybeAlign A)
Returns a representation of the alignment that encodes undefined as 0.
Definition: Alignment.h:217
MaybeAlign decodeMaybeAlign(unsigned Value)
Dual operation of the encode function above.
Definition: Alignment.h:220
raw_ostream & operator<<(raw_ostream &OS, const APFixedPoint &FX)
Definition: APFixedPoint.h:293
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
This struct is a compact representation of a valid (power of two) or undefined (0) alignment.
Definition: Alignment.h:117