LLVM 17.0.0git
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
18#include "llvm/ADT/StringRef.h"
19#include "llvm/MC/MCExpr.h"
20#include "llvm/MC/MCFragment.h"
23#include <cassert>
24#include <cstddef>
25#include <cstdint>
26
27namespace llvm {
28
29class MCAsmInfo;
30class MCContext;
31class MCSection;
32class raw_ostream;
33
34/// MCSymbol - Instances of this class represent a symbol name in the MC file,
35/// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
36/// should only be constructed with valid names for the object file.
37///
38/// If the symbol is defined/emitted into the current translation unit, the
39/// Section member is set to indicate what section it lives in. Otherwise, if
40/// it is a reference to an external entity, it has a null section.
41class MCSymbol {
42protected:
43 /// The kind of the symbol. If it is any value other than unset then this
44 /// class is actually one of the appropriate subclasses of MCSymbol.
53 };
54
55 /// A symbol can contain an Offset, or Value, or be Common, but never more
56 /// than one of these.
57 enum Contents : uint8_t {
62 SymContentsTargetCommon, // Index stores the section index
63 };
64
65 // Special sentinal value for the absolute pseudo fragment.
67
68 /// If a symbol has a Fragment, the section is implied, so we only need
69 /// one pointer.
70 /// The special AbsolutePseudoFragment value is for absolute symbols.
71 /// If this is a variable symbol, this caches the variable value's fragment.
72 /// FIXME: We might be able to simplify this by having the asm streamer create
73 /// dummy fragments.
74 /// If this is a section, then it gives the symbol is defined in. This is null
75 /// for undefined symbols.
76 ///
77 /// If this is a fragment, then it gives the fragment this symbol's value is
78 /// relative to, if any.
79 ///
80 /// For the 'HasName' integer, this is true if this symbol is named.
81 /// A named symbol will have a pointer to the name allocated in the bytes
82 /// immediately prior to the MCSymbol.
84
85 /// IsTemporary - True if this is an assembler temporary label, which
86 /// typically does not survive in the .o file's symbol table. Usually
87 /// "Lfoo" or ".foo".
88 unsigned IsTemporary : 1;
89
90 /// True if this symbol can be redefined.
91 unsigned IsRedefinable : 1;
92
93 /// IsUsed - True if this symbol has been used.
94 mutable unsigned IsUsed : 1;
95
96 mutable unsigned IsRegistered : 1;
97
98 /// True if this symbol is visible outside this translation unit. Note: ELF
99 /// uses binding instead of this bit.
100 mutable unsigned IsExternal : 1;
101
102 /// This symbol is private extern.
103 mutable unsigned IsPrivateExtern : 1;
104
105 /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
106 /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
107 unsigned Kind : 3;
108
109 /// True if we have created a relocation that uses this symbol.
110 mutable unsigned IsUsedInReloc : 1;
111
112 /// This is actually a Contents enumerator, but is unsigned to avoid sign
113 /// extension and achieve better bitpacking with MSVC.
114 unsigned SymbolContents : 3;
115
116 /// The alignment of the symbol if it is 'common'.
117 ///
118 /// Internally, this is stored as log2(align) + 1.
119 /// We reserve 5 bits to encode this value which allows the following values
120 /// 0b00000 -> unset
121 /// 0b00001 -> 1ULL << 0 = 1
122 /// 0b00010 -> 1ULL << 1 = 2
123 /// 0b00011 -> 1ULL << 2 = 4
124 /// ...
125 /// 0b11111 -> 1ULL << 30 = 1 GiB
126 enum : unsigned { NumCommonAlignmentBits = 5 };
128
129 /// The Flags field is used by object file implementations to store
130 /// additional per symbol information which is not easily classified.
131 enum : unsigned { NumFlagsBits = 16 };
133
134 /// Index field, for use by the object file implementation.
135 mutable uint32_t Index = 0;
136
137 union {
138 /// The offset to apply to the fragment address to form this symbol's value.
140
141 /// The size of the symbol, if it is 'common'.
143
144 /// If non-null, the value for a variable symbol.
145 const MCExpr *Value;
146 };
147
148 // MCContext creates and uniques these.
149 friend class MCExpr;
150 friend class MCContext;
151
152 /// The name for a symbol.
153 /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit
154 /// system, the name is a pointer so isn't going to satisfy the 8 byte
155 /// alignment of uint64_t. Account for that here.
156 using NameEntryStorageTy = union {
157 const StringMapEntry<bool> *NameEntry;
159 };
160
165 CommonAlignLog2(0), Flags(0) {
166 Offset = 0;
167 FragmentAndHasName.setInt(!!Name);
168 if (Name)
169 getNameEntryPtr() = Name;
170 }
171
172 // Provide custom new/delete as we will only allocate space for a name
173 // if we need one.
174 void *operator new(size_t s, const StringMapEntry<bool> *Name,
175 MCContext &Ctx);
176
177private:
178 void operator delete(void *);
179 /// Placement delete - required by std, but never called.
180 void operator delete(void*, unsigned) {
181 llvm_unreachable("Constructor throws?");
182 }
183 /// Placement delete - required by std, but never called.
184 void operator delete(void*, unsigned, bool) {
185 llvm_unreachable("Constructor throws?");
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
198public:
199 MCSymbol(const MCSymbol &) = delete;
200 MCSymbol &operator=(const MCSymbol &) = delete;
201
202 /// getName - Get the symbol name.
204 if (!FragmentAndHasName.getInt())
205 return StringRef();
206
207 return getNameEntryPtr()->first();
208 }
209
210 bool isRegistered() const { return IsRegistered; }
211 void setIsRegistered(bool Value) const { IsRegistered = Value; }
212
213 void setUsedInReloc() const { IsUsedInReloc = true; }
214 bool isUsedInReloc() const { return IsUsedInReloc; }
215
216 /// \name Accessors
217 /// @{
218
219 /// isTemporary - Check if this is an assembler temporary symbol.
220 bool isTemporary() const { return IsTemporary; }
221
222 /// isUsed - Check if this is used.
223 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.
229 /// Prepare this symbol to be redefined.
231 if (IsRedefinable) {
233 Value = nullptr;
235 }
236 setUndefined();
237 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 bool isInSection() const {
253 return isDefined() && !isAbsolute();
254 }
255
256 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
257 bool isUndefined(bool SetUsed = true) const {
258 return getFragment(SetUsed) == nullptr;
259 }
260
261 /// isAbsolute - Check if this is an absolute symbol.
262 bool isAbsolute() const {
264 }
265
266 /// Get the section associated with a defined, non-absolute symbol.
268 assert(isInSection() && "Invalid accessor!");
269 return *getFragment()->getParent();
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 bool isELF() const { return Kind == SymbolKindELF; }
282
283 bool isCOFF() const { return Kind == SymbolKindCOFF; }
284
285 bool isGOFF() const { return Kind == SymbolKindGOFF; }
286
287 bool isMachO() const { return Kind == SymbolKindMachO; }
288
289 bool isWasm() const { return Kind == SymbolKindWasm; }
290
291 bool isXCOFF() const { return Kind == SymbolKindXCOFF; }
292
293 /// @}
294 /// \name Variable Symbols
295 /// @{
296
297 /// isVariable - Check if this is a variable symbol.
298 bool isVariable() const {
300 }
301
302 /// getVariableValue - Get the value for variable symbols.
303 const MCExpr *getVariableValue(bool SetUsed = true) const {
304 assert(isVariable() && "Invalid accessor!");
305 IsUsed |= SetUsed;
306 return Value;
307 }
308
309 void setVariableValue(const MCExpr *Value);
310
311 /// @}
312
313 /// Get the (implementation defined) index.
315 return Index;
316 }
317
318 /// Set the (implementation defined) index.
319 void setIndex(uint32_t Value) const {
320 Index = Value;
321 }
322
323 bool isUnset() const { return SymbolContents == SymContentsUnset; }
324
328 "Cannot get offset for a common/variable symbol");
329 return Offset;
330 }
334 "Cannot set offset for a common/variable symbol");
335 Offset = Value;
337 }
338
339 /// Return the size of a 'common' symbol.
341 assert(isCommon() && "Not a 'common' symbol!");
342 return CommonSize;
343 }
344
345 /// Mark this symbol as being 'common'.
346 ///
347 /// \param Size - The size of the symbol.
348 /// \param Alignment - The alignment of the symbol.
349 /// \param Target - Is the symbol a target-specific common-like symbol.
350 void setCommon(uint64_t Size, Align Alignment, bool Target = false) {
351 assert(getOffset() == 0);
354
355 unsigned Log2Align = encode(Alignment);
356 assert(Log2Align < (1U << NumCommonAlignmentBits) &&
357 "Out of range alignment");
358 CommonAlignLog2 = Log2Align;
359 }
360
361 /// Return the alignment of a 'common' symbol.
363 assert(isCommon() && "Not a 'common' symbol!");
365 }
366
367 /// Declare this symbol as being 'common'.
368 ///
369 /// \param Size - The size of the symbol.
370 /// \param Alignment - The alignment of the symbol.
371 /// \param Target - Is the symbol a target-specific common-like symbol.
372 /// \return True if symbol was already declared as a different type
373 bool declareCommon(uint64_t Size, Align Alignment, bool Target = false) {
374 assert(isCommon() || getOffset() == 0);
375 if(isCommon()) {
376 if (CommonSize != Size || getCommonAlignment() != Alignment ||
378 return true;
379 } else
380 setCommon(Size, Alignment, Target);
381 return false;
382 }
383
384 /// Is this a 'common' symbol.
385 bool isCommon() const {
388 }
389
390 /// Is this a target-specific common-like symbol.
391 bool isTargetCommon() const {
393 }
394
395 MCFragment *getFragment(bool SetUsed = true) const {
396 MCFragment *Fragment = FragmentAndHasName.getPointer();
397 if (Fragment || !isVariable())
398 return Fragment;
399 Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
400 FragmentAndHasName.setPointer(Fragment);
401 return Fragment;
402 }
403
404 bool isExternal() const { return IsExternal; }
405 void setExternal(bool Value) const { IsExternal = Value; }
406
407 bool isPrivateExtern() const { return IsPrivateExtern; }
409
410 /// print - Print the value to the stream \p OS.
411 void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
412
413 /// dump - Print the value to stderr.
414 void dump() const;
415
416protected:
417 /// Get the (implementation defined) symbol flags.
418 uint32_t getFlags() const { return Flags; }
419
420 /// Set the (implementation defined) symbol flags.
421 void setFlags(uint32_t Value) const {
422 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
423 Flags = Value;
424 }
425
426 /// Modify the flags via a mask
427 void modifyFlags(uint32_t Value, uint32_t Mask) const {
428 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
429 Flags = (Flags & ~Mask) | Value;
430 }
431};
432
433inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
434 Sym.print(OS, nullptr);
435 return OS;
436}
437
438} // end namespace llvm
439
440#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
#define F(x, y, z)
Definition: MD5.cpp:55
This file defines the PointerIntPair class.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
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:987
MCSection * getParent() const
Definition: MCFragment.h:95
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:41
bool isAbsolute() const
isAbsolute - Check if this is an absolute symbol.
Definition: MCSymbol.h:262
bool isWasm() const
Definition: MCSymbol.h:289
bool isMachO() const
Definition: MCSymbol.h:287
MCSymbol(const MCSymbol &)=delete
const MCExpr * getVariableValue(bool SetUsed=true) const
getVariableValue - Get the value for variable symbols.
Definition: MCSymbol.h:303
void setPrivateExtern(bool Value)
Definition: MCSymbol.h:408
bool isTargetCommon() const
Is this a target-specific common-like symbol.
Definition: MCSymbol.h:391
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:248
bool isInSection() const
isInSection - Check if this symbol is defined in some section (i.e., it is defined but not absolute).
Definition: MCSymbol.h:252
bool isELF() const
Definition: MCSymbol.h:281
void setCommon(uint64_t Size, Align Alignment, bool Target=false)
Mark this symbol as being 'common'.
Definition: MCSymbol.h:350
bool isGOFF() const
Definition: MCSymbol.h:285
void setExternal(bool Value) const
Definition: MCSymbol.h:405
unsigned IsUsed
IsUsed - True if this symbol has been used.
Definition: MCSymbol.h:94
bool isCommon() const
Is this a 'common' symbol.
Definition: MCSymbol.h:385
void modifyFlags(uint32_t Value, uint32_t Mask) const
Modify the flags via a mask.
Definition: MCSymbol.h:427
unsigned IsPrivateExtern
This symbol is private extern.
Definition: MCSymbol.h:103
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:203
void setFragment(MCFragment *F) const
Mark the symbol as defined in the fragment F.
Definition: MCSymbol.h:273
unsigned IsRegistered
Definition: MCSymbol.h:96
unsigned IsUsedInReloc
True if we have created a relocation that uses this symbol.
Definition: MCSymbol.h:110
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:298
uint32_t Flags
Definition: MCSymbol.h:132
@ NumCommonAlignmentBits
Definition: MCSymbol.h:126
unsigned IsRedefinable
True if this symbol can be redefined.
Definition: MCSymbol.h:91
void setFlags(uint32_t Value) const
Set the (implementation defined) symbol flags.
Definition: MCSymbol.h:421
uint32_t getFlags() const
Get the (implementation defined) symbol flags.
Definition: MCSymbol.h:418
unsigned IsExternal
True if this symbol is visible outside this translation unit.
Definition: MCSymbol.h:100
bool isRedefinable() const
Check if this symbol is redefinable.
Definition: MCSymbol.h:226
PointerIntPair< MCFragment *, 1 > FragmentAndHasName
If a symbol has a Fragment, the section is implied, so we only need one pointer.
Definition: MCSymbol.h:83
void setVariableValue(const MCExpr *Value)
Definition: MCSymbol.cpp:47
bool isCOFF() const
Definition: MCSymbol.h:283
MaybeAlign getCommonAlignment() const
Return the alignment of a 'common' symbol.
Definition: MCSymbol.h:362
unsigned CommonAlignLog2
Definition: MCSymbol.h:127
uint32_t Index
Index field, for use by the object file implementation.
Definition: MCSymbol.h:135
uint64_t AlignmentPadding
Definition: MCSymbol.h:158
bool isUsed() const
isUsed - Check if this is used.
Definition: MCSymbol.h:223
bool isRegistered() const
Definition: MCSymbol.h:210
void setIndex(uint32_t Value) const
Set the (implementation defined) index.
Definition: MCSymbol.h:319
bool isUndefined(bool SetUsed=true) const
isUndefined - Check if this symbol undefined (i.e., implicitly defined).
Definition: MCSymbol.h:257
void setRedefinable(bool Value)
Mark this symbol as redefinable.
Definition: MCSymbol.h:228
void setUsedInReloc() const
Definition: MCSymbol.h:213
unsigned SymbolContents
This is actually a Contents enumerator, but is unsigned to avoid sign extension and achieve better bi...
Definition: MCSymbol.h:114
uint32_t getIndex() const
Get the (implementation defined) index.
Definition: MCSymbol.h:314
Contents
A symbol can contain an Offset, or Value, or be Common, but never more than one of these.
Definition: MCSymbol.h:57
@ SymContentsCommon
Definition: MCSymbol.h:61
@ SymContentsOffset
Definition: MCSymbol.h:59
@ SymContentsUnset
Definition: MCSymbol.h:58
@ SymContentsTargetCommon
Definition: MCSymbol.h:62
@ SymContentsVariable
Definition: MCSymbol.h:60
void setUndefined()
Mark the symbol as undefined.
Definition: MCSymbol.h:279
MCSection & getSection() const
Get the section associated with a defined, non-absolute symbol.
Definition: MCSymbol.h:267
static MCFragment * AbsolutePseudoFragment
Definition: MCSymbol.h:66
SymbolKind
The kind of the symbol.
Definition: MCSymbol.h:45
void setOffset(uint64_t Value)
Definition: MCSymbol.h:331
void redefineIfPossible()
Prepare this symbol to be redefined.
Definition: MCSymbol.h:230
uint64_t getCommonSize() const
Return the size of a 'common' symbol.
Definition: MCSymbol.h:340
unsigned IsTemporary
IsTemporary - True if this is an assembler temporary label, which typically does not survive in the ....
Definition: MCSymbol.h:88
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:220
union { const StringMapEntry< bool > *NameEntry NameEntryStorageTy
The name for a symbol.
Definition: MCSymbol.h:157
bool declareCommon(uint64_t Size, Align Alignment, bool Target=false)
Declare this symbol as being 'common'.
Definition: MCSymbol.h:373
MCSymbol(SymbolKind Kind, const StringMapEntry< bool > *Name, bool isTemporary)
Definition: MCSymbol.h:161
bool isUnset() const
Definition: MCSymbol.h:323
bool isExternal() const
Definition: MCSymbol.h:404
const MCExpr * Value
If non-null, the value for a variable symbol.
Definition: MCSymbol.h:145
void setIsRegistered(bool Value) const
Definition: MCSymbol.h:211
uint64_t CommonSize
The size of the symbol, if it is 'common'.
Definition: MCSymbol.h:142
bool isXCOFF() const
Definition: MCSymbol.h:291
uint64_t Offset
The offset to apply to the fragment address to form this symbol's value.
Definition: MCSymbol.h:139
uint64_t getOffset() const
Definition: MCSymbol.h:325
bool isPrivateExtern() const
Definition: MCSymbol.h:407
bool isUsedInReloc() const
Definition: MCSymbol.h:214
MCSymbol & operator=(const MCSymbol &)=delete
unsigned Kind
LLVM RTTI discriminator.
Definition: MCSymbol.h:107
MCFragment * getFragment(bool SetUsed=true) const
Definition: MCSymbol.h:395
PointerIntPair - This class implements a pair of a pointer and small integer.
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:292
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