LLVM  6.0.0svn
MCSymbol.h
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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 
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/MC/MCFragment.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 {
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  };
62 
63  // Special sentinal value for the absolute pseudo fragment.
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.
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  /// \brief 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 };
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 };
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  /// \brief 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;
151  };
152 
154  : IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false),
157  CommonAlignLog2(0), Flags(0) {
158  Offset = 0;
159  FragmentAndHasName.setInt(!!Name);
160  if (Name)
161  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  /// \brief Placement delete - required by std, but never called.
172  void operator delete(void*, unsigned) {
173  llvm_unreachable("Constructor throws?");
174  }
175  /// \brief 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(bool SetUsed = true) const {
181  if (MCFragment *F = getFragment(SetUsed)) {
182  assert(F != AbsolutePseudoFragment);
183  return F->getParent();
184  }
185  return nullptr;
186  }
187 
188  /// \brief 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  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  void setUsed(bool Value) const { IsUsed |= Value; }
225 
226  /// \brief Check if this symbol is redefinable.
227  bool isRedefinable() const { return IsRedefinable; }
228  /// \brief Mark this symbol as redefinable.
230  /// \brief Prepare this symbol to be redefined.
232  if (IsRedefinable) {
234  Value = nullptr;
236  }
237  setUndefined();
238  IsRedefinable = false;
239  }
240  }
241 
242  /// @}
243  /// \name Associated Sections
244  /// @{
245 
246  /// isDefined - Check if this symbol is defined (i.e., it has an address).
247  ///
248  /// Defined symbols are either absolute or in some section.
249  bool isDefined(bool SetUsed = true) const {
250  return getFragment(SetUsed) != nullptr;
251  }
252 
253  /// isInSection - Check if this symbol is defined in some section (i.e., it
254  /// is defined but not absolute).
255  bool isInSection(bool SetUsed = true) const {
256  return isDefined(SetUsed) && !isAbsolute(SetUsed);
257  }
258 
259  /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
260  bool isUndefined(bool SetUsed = true) const { return !isDefined(SetUsed); }
261 
262  /// isAbsolute - Check if this is an absolute symbol.
263  bool isAbsolute(bool SetUsed = true) const {
264  return getFragment(SetUsed) == AbsolutePseudoFragment;
265  }
266 
267  /// Get the section associated with a defined, non-absolute symbol.
268  MCSection &getSection(bool SetUsed = true) const {
269  assert(isInSection(SetUsed) && "Invalid accessor!");
270  return *getSectionPtr(SetUsed);
271  }
272 
273  /// Mark the symbol as defined in the fragment \p F.
274  void setFragment(MCFragment *F) const {
275  assert(!isVariable() && "Cannot set fragment of variable");
276  FragmentAndHasName.setPointer(F);
277  }
278 
279  /// Mark the symbol as undefined.
280  void setUndefined() { FragmentAndHasName.setPointer(nullptr); }
281 
282  bool isELF() const { return Kind == SymbolKindELF; }
283 
284  bool isCOFF() const { return Kind == SymbolKindCOFF; }
285 
286  bool isMachO() const { return Kind == SymbolKindMachO; }
287 
288  bool isWasm() const { return Kind == SymbolKindWasm; }
289 
290  /// @}
291  /// \name Variable Symbols
292  /// @{
293 
294  /// isVariable - Check if this is a variable symbol.
295  bool isVariable() const {
297  }
298 
299  /// getVariableValue - Get the value for variable symbols.
300  const MCExpr *getVariableValue(bool SetUsed = true) const {
301  assert(isVariable() && "Invalid accessor!");
302  IsUsed |= SetUsed;
303  return Value;
304  }
305 
306  void setVariableValue(const MCExpr *Value);
307 
308  /// @}
309 
310  /// Get the (implementation defined) index.
311  uint32_t getIndex() const {
312  return Index;
313  }
314 
315  /// Set the (implementation defined) index.
316  void setIndex(uint32_t Value) const {
317  Index = Value;
318  }
319 
320  uint64_t getOffset() const {
323  "Cannot get offset for a common/variable symbol");
324  return Offset;
325  }
326  void setOffset(uint64_t Value) {
329  "Cannot set offset for a common/variable symbol");
330  Offset = Value;
332  }
333 
334  /// Return the size of a 'common' symbol.
335  uint64_t getCommonSize() const {
336  assert(isCommon() && "Not a 'common' symbol!");
337  return CommonSize;
338  }
339 
340  /// Mark this symbol as being 'common'.
341  ///
342  /// \param Size - The size of the symbol.
343  /// \param Align - The alignment of the symbol.
344  void setCommon(uint64_t Size, unsigned Align) {
345  assert(getOffset() == 0);
346  CommonSize = Size;
348 
349  assert((!Align || isPowerOf2_32(Align)) &&
350  "Alignment must be a power of 2");
351  unsigned Log2Align = Log2_32(Align) + 1;
352  assert(Log2Align < (1U << NumCommonAlignmentBits) &&
353  "Out of range alignment");
354  CommonAlignLog2 = Log2Align;
355  }
356 
357  /// Return the alignment of a 'common' symbol.
358  unsigned getCommonAlignment() const {
359  assert(isCommon() && "Not a 'common' symbol!");
360  return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0;
361  }
362 
363  /// Declare this symbol as being 'common'.
364  ///
365  /// \param Size - The size of the symbol.
366  /// \param Align - The alignment of the symbol.
367  /// \return True if symbol was already declared as a different type
368  bool declareCommon(uint64_t Size, unsigned Align) {
369  assert(isCommon() || getOffset() == 0);
370  if(isCommon()) {
371  if(CommonSize != Size || getCommonAlignment() != Align)
372  return true;
373  } else
374  setCommon(Size, Align);
375  return false;
376  }
377 
378  /// Is this a 'common' symbol.
379  bool isCommon() const {
381  }
382 
383  MCFragment *getFragment(bool SetUsed = true) const {
384  MCFragment *Fragment = FragmentAndHasName.getPointer();
385  if (Fragment || !isVariable())
386  return Fragment;
387  Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
388  FragmentAndHasName.setPointer(Fragment);
389  return Fragment;
390  }
391 
392  bool isExternal() const { return IsExternal; }
393  void setExternal(bool Value) const { IsExternal = Value; }
394 
395  bool isPrivateExtern() const { return IsPrivateExtern; }
396  void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
397 
398  /// print - Print the value to the stream \p OS.
399  void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
400 
401  /// dump - Print the value to stderr.
402  void dump() const;
403 
404 protected:
405  /// Get the (implementation defined) symbol flags.
406  uint32_t getFlags() const { return Flags; }
407 
408  /// Set the (implementation defined) symbol flags.
409  void setFlags(uint32_t Value) const {
410  assert(Value < (1U << NumFlagsBits) && "Out of range flags");
411  Flags = Value;
412  }
413 
414  /// Modify the flags via a mask
415  void modifyFlags(uint32_t Value, uint32_t Mask) const {
416  assert(Value < (1U << NumFlagsBits) && "Out of range flags");
417  Flags = (Flags & ~Mask) | Value;
418  }
419 };
420 
421 inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
422  Sym.print(OS, nullptr);
423  return OS;
424 }
425 
426 } // end namespace llvm
427 
428 #endif // LLVM_MC_MCSYMBOL_H
bool isCOFF() const
Definition: MCSymbol.h:284
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
union { const StringMapEntry< bool > *NameEntry NameEntryStorageTy
The name for a symbol.
Definition: MCSymbol.h:149
void setInt(IntType IntVal)
void setPrivateExtern(bool Value)
Definition: MCSymbol.h:396
uint32_t getIndex() const
Get the (implementation defined) index.
Definition: MCSymbol.h:311
void setUsedInReloc() const
Definition: MCSymbol.h:213
unsigned IsRegistered
Definition: MCSymbol.h:94
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
PointerTy getPointer() const
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:295
StringMapEntry - This is used to represent one value that is inserted into a StringMap.
Definition: StringMap.h:126
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
void redefineIfPossible()
Prepare this symbol to be redefined.
Definition: MCSymbol.h:231
MCSection & getSection(bool SetUsed=true) const
Get the section associated with a defined, non-absolute symbol.
Definition: MCSymbol.h:268
bool isWasm() const
Definition: MCSymbol.h:288
unsigned getCommonAlignment() const
Return the alignment of a &#39;common&#39; symbol.
Definition: MCSymbol.h:358
SymbolKind
The kind of the symbol.
Definition: MCSymbol.h:46
F(f)
uint64_t CommonSize
The size of the symbol, if it is &#39;common&#39;.
Definition: MCSymbol.h:134
bool isCommon() const
Is this a &#39;common&#39; symbol.
Definition: MCSymbol.h:379
unsigned IsPrivateExtern
This symbol is private extern.
Definition: MCSymbol.h:100
bool isRedefinable() const
Check if this symbol is redefinable.
Definition: MCSymbol.h:227
void setPointer(PointerTy PtrVal)
void setExternal(bool Value) const
Definition: MCSymbol.h:393
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:36
void setFragment(MCFragment *F) const
Mark the symbol as defined in the fragment F.
Definition: MCSymbol.h:274
void setCommon(uint64_t Size, unsigned Align)
Mark this symbol as being &#39;common&#39;.
Definition: MCSymbol.h:344
bool isAbsolute(bool SetUsed=true) const
isAbsolute - Check if this is an absolute symbol.
Definition: MCSymbol.h:263
Context object for machine code objects.
Definition: MCContext.h:59
unsigned IsUsedInReloc
True if we have created a relocation that uses this symbol.
Definition: MCSymbol.h:107
IntType getInt() const
uint64_t Offset
The offset to apply to the fragment address to form this symbol&#39;s value.
Definition: MCSymbol.h:131
This class is intended to be used as a base class for asm properties and features specific to the tar...
Definition: MCAsmInfo.h:56
constexpr bool isPowerOf2_32(uint32_t Value)
Return true if the argument is a power of two > 0.
Definition: MathExtras.h:421
PointerIntPair - This class implements a pair of a pointer and small integer.
void setRedefinable(bool Value)
Mark this symbol as redefinable.
Definition: MCSymbol.h:229
uint32_t Index
Index field, for use by the object file implementation.
Definition: MCSymbol.h:127
unsigned Kind
LLVM RTTI discriminator.
Definition: MCSymbol.h:104
bool isTemporary() const
isTemporary - Check if this is an assembler temporary symbol.
Definition: MCSymbol.h:220
uint64_t getCommonSize() const
Return the size of a &#39;common&#39; symbol.
Definition: MCSymbol.h:335
uint64_t getOffset() const
Definition: MCSymbol.h:320
void setOffset(uint64_t Value)
Definition: MCSymbol.h:326
bool isExternal() const
Definition: MCSymbol.h:392
void setFlags(uint32_t Value) const
Set the (implementation defined) symbol flags.
Definition: MCSymbol.h:409
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static MCFragment * AbsolutePseudoFragment
Definition: MCSymbol.h:64
bool isInSection(bool SetUsed=true) const
isInSection - Check if this symbol is defined in some section (i.e., it is defined but not absolute)...
Definition: MCSymbol.h:255
void setUndefined()
Mark the symbol as undefined.
Definition: MCSymbol.h:280
bool isUndefined(bool SetUsed=true) const
isUndefined - Check if this symbol undefined (i.e., implicitly defined).
Definition: MCSymbol.h:260
MCFragment * getFragment(bool SetUsed=true) const
Definition: MCSymbol.h:383
bool isRegistered() const
Definition: MCSymbol.h:210
unsigned IsUsed
IsUsed - True if this symbol has been used.
Definition: MCSymbol.h:92
uint32_t Flags
Definition: MCSymbol.h:124
unsigned IsExternal
This symbol is visible outside this translation unit.
Definition: MCSymbol.h:97
bool isUsed() const
isUsed - Check if this is used.
Definition: MCSymbol.h:223
unsigned SymbolContents
This is actually a Contents enumerator, but is unsigned to avoid sign extension and achieve better bi...
Definition: MCSymbol.h:111
void setVariableValue(const MCExpr *Value)
Definition: MCSymbol.cpp:48
void dump() const
dump - Print the value to stderr.
Definition: MCSymbol.cpp:85
MCFragment * findAssociatedFragment() const
Find the "associated section" for this expression, which is currently defined as the absolute section...
Definition: MCExpr.cpp:782
unsigned Log2_32(uint32_t Value)
Return the floor log base 2 of the specified value, -1 if the value is zero.
Definition: MathExtras.h:531
bool isMachO() const
Definition: MCSymbol.h:286
void setIsRegistered(bool Value) const
Definition: MCSymbol.h:211
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
bool isUsedInReloc() const
Definition: MCSymbol.h:214
unsigned CommonAlignLog2
Definition: MCSymbol.h:119
bool isDefined(bool SetUsed=true) const
isDefined - Check if this symbol is defined (i.e., it has an address).
Definition: MCSymbol.h:249
unsigned IsRedefinable
True if this symbol can be redefined.
Definition: MCSymbol.h:89
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
void setUsed(bool Value) const
Definition: MCSymbol.h:224
raw_ostream & operator<<(raw_ostream &OS, const APInt &I)
Definition: APInt.h:2018
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:203
uint64_t AlignmentPadding
Definition: MCSymbol.h:150
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const MCExpr * getVariableValue(bool SetUsed=true) const
getVariableValue - Get the value for variable symbols.
Definition: MCSymbol.h:300
MCSymbol & operator=(const MCSymbol &)=delete
LLVM Value Representation.
Definition: Value.h:73
std::underlying_type< E >::type Mask()
Get a bitmask with 1s in all places up to the high-order bit of E&#39;s largest value.
Definition: BitmaskEnum.h:81
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:44
const MCExpr * Value
If non-null, the value for a variable symbol.
Definition: MCSymbol.h:137
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
MCSymbol(SymbolKind Kind, const StringMapEntry< bool > *Name, bool isTemporary)
Definition: MCSymbol.h:153
bool isELF() const
Definition: MCSymbol.h:282
PointerIntPair< MCFragment *, 1 > FragmentAndHasName
If a symbol has a Fragment, the section is implied, so we only need one pointer.
Definition: MCSymbol.h:81
Contents
A symbol can contain an Offset, or Value, or be Common, but never more than one of these...
Definition: MCSymbol.h:56
bool declareCommon(uint64_t Size, unsigned Align)
Declare this symbol as being &#39;common&#39;.
Definition: MCSymbol.h:368
bool isPrivateExtern() const
Definition: MCSymbol.h:395
void setIndex(uint32_t Value) const
Set the (implementation defined) index.
Definition: MCSymbol.h:316
void modifyFlags(uint32_t Value, uint32_t Mask) const
Modify the flags via a mask.
Definition: MCSymbol.h:415
uint32_t getFlags() const
Get the (implementation defined) symbol flags.
Definition: MCSymbol.h:406
unsigned IsTemporary
IsTemporary - True if this is an assembler temporary label, which typically does not survive in the ...
Definition: MCSymbol.h:86
void print(raw_ostream &OS, const MCAsmInfo *MAI) const
print - Print the value to the stream OS.
Definition: MCSymbol.cpp:59