LLVM  6.0.0svn
HexagonTargetObjectFile.cpp
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1 //===-- HexagonTargetObjectFile.cpp ---------------------------------------===//
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 declarations of the HexagonTargetAsmInfo properties.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #define DEBUG_TYPE "hexagon-sdata"
15 
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/BinaryFormat/ELF.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/GlobalObject.h"
24 #include "llvm/IR/GlobalValue.h"
25 #include "llvm/IR/GlobalVariable.h"
26 #include "llvm/IR/Type.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/SectionKind.h"
29 #include "llvm/Support/Casting.h"
31 #include "llvm/Support/Debug.h"
34 
35 using namespace llvm;
36 
37 static cl::opt<unsigned> SmallDataThreshold("hexagon-small-data-threshold",
38  cl::init(8), cl::Hidden,
39  cl::desc("The maximum size of an object in the sdata section"));
40 
41 static cl::opt<bool> NoSmallDataSorting("mno-sort-sda", cl::init(false),
42  cl::Hidden, cl::desc("Disable small data sections sorting"));
43 
44 static cl::opt<bool> StaticsInSData("hexagon-statics-in-small-data",
46  cl::desc("Allow static variables in .sdata"));
47 
48 static cl::opt<bool> TraceGVPlacement("trace-gv-placement",
49  cl::Hidden, cl::init(false),
50  cl::desc("Trace global value placement"));
51 
52 static cl::opt<bool>
53  EmitJtInText("hexagon-emit-jt-text", cl::Hidden, cl::init(false),
54  cl::desc("Emit hexagon jump tables in function section"));
55 
56 static cl::opt<bool>
57  EmitLutInText("hexagon-emit-lut-text", cl::Hidden, cl::init(false),
58  cl::desc("Emit hexagon lookup tables in function section"));
59 
60 // TraceGVPlacement controls messages for all builds. For builds with assertions
61 // (debug or release), messages are also controlled by the usual debug flags
62 // (e.g. -debug and -debug-only=globallayout)
63 #define TRACE_TO(s, X) s << X
64 #ifdef NDEBUG
65 #define TRACE(X) \
66  do { \
67  if (TraceGVPlacement) { \
68  TRACE_TO(errs(), X); \
69  } \
70  } while (false)
71 #else
72 #define TRACE(X) \
73  do { \
74  if (TraceGVPlacement) { \
75  TRACE_TO(errs(), X); \
76  } else { \
77  DEBUG(TRACE_TO(dbgs(), X)); \
78  } \
79  } while (false)
80 #endif
81 
82 // Returns true if the section name is such that the symbol will be put
83 // in a small data section.
84 // For instance, global variables with section attributes such as ".sdata"
85 // ".sdata.*", ".sbss", and ".sbss.*" will go into small data.
86 static bool isSmallDataSection(StringRef Sec) {
87  // sectionName is either ".sdata" or ".sbss". Looking for an exact match
88  // obviates the need for checks for section names such as ".sdatafoo".
89  if (Sec.equals(".sdata") || Sec.equals(".sbss") || Sec.equals(".scommon"))
90  return true;
91  // If either ".sdata." or ".sbss." is a substring of the section name
92  // then put the symbol in small data.
93  return Sec.find(".sdata.") != StringRef::npos ||
94  Sec.find(".sbss.") != StringRef::npos ||
95  Sec.find(".scommon.") != StringRef::npos;
96 }
97 
98 static const char *getSectionSuffixForSize(unsigned Size) {
99  switch (Size) {
100  default:
101  return "";
102  case 1:
103  return ".1";
104  case 2:
105  return ".2";
106  case 4:
107  return ".4";
108  case 8:
109  return ".8";
110  }
111 }
112 
114  const TargetMachine &TM) {
117 
118  SmallDataSection =
122  SmallBSSSection =
126 }
127 
129  const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
130  TRACE("[SelectSectionForGlobal] GO(" << GO->getName() << ") ");
131  TRACE("input section(" << GO->getSection() << ") ");
132 
133  TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "")
134  << (GO->hasLocalLinkage() ? "local_linkage " : "")
135  << (GO->hasInternalLinkage() ? "internal " : "")
136  << (GO->hasExternalLinkage() ? "external " : "")
137  << (GO->hasCommonLinkage() ? "common_linkage " : "")
138  << (GO->hasCommonLinkage() ? "common " : "" )
139  << (Kind.isCommon() ? "kind_common " : "" )
140  << (Kind.isBSS() ? "kind_bss " : "" )
141  << (Kind.isBSSLocal() ? "kind_bss_local " : "" ));
142 
143  // If the lookup table is used by more than one function, do not place
144  // it in text section.
145  if (EmitLutInText && GO->getName().startswith("switch.table")) {
146  if (const Function *Fn = getLutUsedFunction(GO))
147  return selectSectionForLookupTable(GO, TM, Fn);
148  }
149 
150  if (isGlobalInSmallSection(GO, TM))
151  return selectSmallSectionForGlobal(GO, Kind, TM);
152 
153  if (Kind.isCommon()) {
154  // This is purely for LTO+Linker Script because commons don't really have a
155  // section. However, the BitcodeSectionWriter pass will query for the
156  // sections of commons (and the linker expects us to know their section) so
157  // we'll return one here.
158  return BSSSection;
159  }
160 
161  TRACE("default_ELF_section\n");
162  // Otherwise, we work the same as ELF.
164 }
165 
167  const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
168  TRACE("[getExplicitSectionGlobal] GO(" << GO->getName() << ") from("
169  << GO->getSection() << ") ");
170  TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "")
171  << (GO->hasLocalLinkage() ? "local_linkage " : "")
172  << (GO->hasInternalLinkage() ? "internal " : "")
173  << (GO->hasExternalLinkage() ? "external " : "")
174  << (GO->hasCommonLinkage() ? "common_linkage " : "")
175  << (GO->hasCommonLinkage() ? "common " : "" )
176  << (Kind.isCommon() ? "kind_common " : "" )
177  << (Kind.isBSS() ? "kind_bss " : "" )
178  << (Kind.isBSSLocal() ? "kind_bss_local " : "" ));
179 
180  if (GO->hasSection()) {
181  StringRef Section = GO->getSection();
182  if (Section.find(".access.text.group") != StringRef::npos)
185  if (Section.find(".access.data.group") != StringRef::npos)
188  }
189 
190  if (isGlobalInSmallSection(GO, TM))
191  return selectSmallSectionForGlobal(GO, Kind, TM);
192 
193  // Otherwise, we work the same as ELF.
194  TRACE("default_ELF_section\n");
196 }
197 
198 /// Return true if this global value should be placed into small data/bss
199 /// section.
201  const TargetMachine &TM) const {
202  // Only global variables, not functions.
203  DEBUG(dbgs() << "Checking if value is in small-data, -G"
204  << SmallDataThreshold << ": \"" << GO->getName() << "\": ");
205  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO);
206  if (!GVar) {
207  DEBUG(dbgs() << "no, not a global variable\n");
208  return false;
209  }
210 
211  // Globals with external linkage that have an original section set must be
212  // emitted to that section, regardless of whether we would put them into
213  // small data or not. This is how we can support mixing -G0/-G8 in LTO.
214  if (GVar->hasSection()) {
215  bool IsSmall = isSmallDataSection(GVar->getSection());
216  DEBUG(dbgs() << (IsSmall ? "yes" : "no") << ", has section: "
217  << GVar->getSection() << '\n');
218  return IsSmall;
219  }
220 
221  if (GVar->isConstant()) {
222  DEBUG(dbgs() << "no, is a constant\n");
223  return false;
224  }
225 
226  bool IsLocal = GVar->hasLocalLinkage();
227  if (!StaticsInSData && IsLocal) {
228  DEBUG(dbgs() << "no, is static\n");
229  return false;
230  }
231 
232  Type *GType = GVar->getType();
233  if (PointerType *PT = dyn_cast<PointerType>(GType))
234  GType = PT->getElementType();
235 
236  if (isa<ArrayType>(GType)) {
237  DEBUG(dbgs() << "no, is an array\n");
238  return false;
239  }
240 
241  // If the type is a struct with no body provided, treat is conservatively.
242  // There cannot be actual definitions of object of such a type in this CU
243  // (only references), so assuming that they are not in sdata is safe. If
244  // these objects end up in the sdata, the references will still be valid.
245  if (StructType *ST = dyn_cast<StructType>(GType)) {
246  if (ST->isOpaque()) {
247  DEBUG(dbgs() << "no, has opaque type\n");
248  return false;
249  }
250  }
251 
252  unsigned Size = GVar->getParent()->getDataLayout().getTypeAllocSize(GType);
253  if (Size == 0) {
254  DEBUG(dbgs() << "no, has size 0\n");
255  return false;
256  }
257  if (Size > SmallDataThreshold) {
258  DEBUG(dbgs() << "no, size exceeds sdata threshold: " << Size << '\n');
259  return false;
260  }
261 
262  DEBUG(dbgs() << "yes\n");
263  return true;
264 }
265 
267  return SmallDataThreshold > 0;
268 }
269 
271  return SmallDataThreshold;
272 }
273 
275  bool UsesLabelDifference, const Function &F) const {
276  return EmitJtInText;
277 }
278 
279 /// Descends any type down to "elementary" components,
280 /// discovering the smallest addressable one.
281 /// If zero is returned, declaration will not be modified.
282 unsigned HexagonTargetObjectFile::getSmallestAddressableSize(const Type *Ty,
283  const GlobalValue *GV, const TargetMachine &TM) const {
284  // Assign the smallest element access size to the highest
285  // value which assembler can handle.
286  unsigned SmallestElement = 8;
287 
288  if (!Ty)
289  return 0;
290  switch (Ty->getTypeID()) {
291  case Type::StructTyID: {
292  const StructType *STy = cast<const StructType>(Ty);
293  for (auto &E : STy->elements()) {
294  unsigned AtomicSize = getSmallestAddressableSize(E, GV, TM);
295  if (AtomicSize < SmallestElement)
296  SmallestElement = AtomicSize;
297  }
298  return (STy->getNumElements() == 0) ? 0 : SmallestElement;
299  }
300  case Type::ArrayTyID: {
301  const ArrayType *ATy = cast<const ArrayType>(Ty);
302  return getSmallestAddressableSize(ATy->getElementType(), GV, TM);
303  }
304  case Type::VectorTyID: {
305  const VectorType *PTy = cast<const VectorType>(Ty);
306  return getSmallestAddressableSize(PTy->getElementType(), GV, TM);
307  }
308  case Type::PointerTyID:
309  case Type::HalfTyID:
310  case Type::FloatTyID:
311  case Type::DoubleTyID:
312  case Type::IntegerTyID: {
313  const DataLayout &DL = GV->getParent()->getDataLayout();
314  // It is unfortunate that DL's function take non-const Type*.
315  return DL.getTypeAllocSize(const_cast<Type*>(Ty));
316  }
317  case Type::FunctionTyID:
318  case Type::VoidTyID:
319  case Type::X86_FP80TyID:
320  case Type::FP128TyID:
321  case Type::PPC_FP128TyID:
322  case Type::LabelTyID:
323  case Type::MetadataTyID:
324  case Type::X86_MMXTyID:
325  case Type::TokenTyID:
326  return 0;
327  }
328 
329  return 0;
330 }
331 
332 MCSection *HexagonTargetObjectFile::selectSmallSectionForGlobal(
333  const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
334  const Type *GTy = GO->getType()->getElementType();
335  unsigned Size = getSmallestAddressableSize(GTy, GO, TM);
336 
337  // If we have -ffunction-section or -fdata-section then we should emit the
338  // global value to a unique section specifically for it... even for sdata.
339  bool EmitUniquedSection = TM.getDataSections();
340 
341  TRACE("Small data. Size(" << Size << ")");
342  // Handle Small Section classification here.
343  if (Kind.isBSS() || Kind.isBSSLocal()) {
344  // If -mno-sort-sda is not set, find out smallest accessible entity in
345  // declaration and add it to the section name string.
346  // Note. It does not track the actual usage of the value, only its de-
347  // claration. Also, compiler adds explicit pad fields to some struct
348  // declarations - they are currently counted towards smallest addres-
349  // sable entity.
350  if (NoSmallDataSorting) {
351  TRACE(" default sbss\n");
352  return SmallBSSSection;
353  }
354 
355  StringRef Prefix(".sbss");
356  SmallString<128> Name(Prefix);
357  Name.append(getSectionSuffixForSize(Size));
358 
359  if (EmitUniquedSection) {
360  Name.append(".");
361  Name.append(GO->getName());
362  }
363  TRACE(" unique sbss(" << Name << ")\n");
364  return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS,
366  }
367 
368  if (Kind.isCommon()) {
369  // This is purely for LTO+Linker Script because commons don't really have a
370  // section. However, the BitcodeSectionWriter pass will query for the
371  // sections of commons (and the linker expects us to know their section) so
372  // we'll return one here.
373  if (NoSmallDataSorting)
374  return BSSSection;
375 
376  Twine Name = Twine(".scommon") + getSectionSuffixForSize(Size);
377  TRACE(" small COMMON (" << Name << ")\n");
378 
379  return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS,
382  }
383 
384  // We could have changed sdata object to a constant... in this
385  // case the Kind could be wrong for it.
386  if (Kind.isMergeableConst()) {
387  TRACE(" const_object_as_data ");
388  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO);
389  if (GVar->hasSection() && isSmallDataSection(GVar->getSection()))
390  Kind = SectionKind::getData();
391  }
392 
393  if (Kind.isData()) {
394  if (NoSmallDataSorting) {
395  TRACE(" default sdata\n");
396  return SmallDataSection;
397  }
398 
399  StringRef Prefix(".sdata");
400  SmallString<128> Name(Prefix);
401  Name.append(getSectionSuffixForSize(Size));
402 
403  if (EmitUniquedSection) {
404  Name.append(".");
405  Name.append(GO->getName());
406  }
407  TRACE(" unique sdata(" << Name << ")\n");
410  }
411 
412  TRACE("default ELF section\n");
413  // Otherwise, we work the same as ELF.
415 }
416 
417 // Return the function that uses the lookup table. If there are more
418 // than one live function that uses this look table, bail out and place
419 // the lookup table in default section.
420 const Function *
422  const Function *ReturnFn = nullptr;
423  for (auto U : GO->users()) {
424  // validate each instance of user to be a live function.
425  auto *I = dyn_cast<Instruction>(U);
426  if (!I)
427  continue;
428  auto *Bb = I->getParent();
429  if (!Bb)
430  continue;
431  auto *UserFn = Bb->getParent();
432  if (!ReturnFn)
433  ReturnFn = UserFn;
434  else if (ReturnFn != UserFn)
435  return nullptr;
436  }
437  return ReturnFn;
438 }
439 
440 MCSection *HexagonTargetObjectFile::selectSectionForLookupTable(
441  const GlobalObject *GO, const TargetMachine &TM, const Function *Fn) const {
442 
444  // If the function has explicit section, place the lookup table in this
445  // explicit section.
446  if (Fn->hasSection())
447  return getExplicitSectionGlobal(Fn, Kind, TM);
448 
449  const auto *FuncObj = dyn_cast<GlobalObject>(Fn);
450  return SelectSectionForGlobal(FuncObj, Kind, TM);
451 }
bool isGlobalInSmallSection(const GlobalObject *GO, const TargetMachine &TM) const
Return true if this global value should be placed into small data/bss section.
StringRef getSection() const
Get the custom section of this global if it has one.
Definition: GlobalObject.h:90
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
7: Labels
Definition: Type.h:64
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:109
static SectionKind getData()
Definition: SectionKind.h:202
bool hasLocalLinkage() const
Definition: GlobalValue.h:427
MCSection * getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Targets should implement this method to assign a section to globals with an explicit section specfied...
bool hasPrivateLinkage() const
Definition: GlobalValue.h:426
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
2: 32-bit floating point type
Definition: Type.h:59
ArrayRef< Type * > const elements() const
Definition: DerivedTypes.h:305
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:313
static const char * getSectionSuffixForSize(unsigned Size)
13: Structures
Definition: Type.h:73
F(f)
4: 80-bit floating point type (X87)
Definition: Type.h:61
1: 16-bit floating point type
Definition: Type.h:58
15: Pointers
Definition: Type.h:75
12: Functions
Definition: Type.h:72
#define TRACE(X)
static cl::opt< bool > EmitJtInText("hexagon-emit-jt-text", cl::Hidden, cl::init(false), cl::desc("Emit hexagon jump tables in function section"))
static cl::opt< bool > NoSmallDataSorting("mno-sort-sda", cl::init(false), cl::Hidden, cl::desc("Disable small data sections sorting"))
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
TypeID getTypeID() const
Return the type id for the type.
Definition: Type.h:138
Class to represent struct types.
Definition: DerivedTypes.h:201
virtual void Initialize(MCContext &ctx, const TargetMachine &TM)
This method must be called before any actual lowering is done.
bool hasCommonLinkage() const
Definition: GlobalValue.h:431
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
StringRef str() const
Explicit conversion to StringRef.
Definition: SmallString.h:267
Context object for machine code objects.
Definition: MCContext.h:59
bool hasExternalLinkage() const
Definition: GlobalValue.h:413
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool startswith(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:267
Class to represent array types.
Definition: DerivedTypes.h:369
bool isBSSLocal() const
Definition: SectionKind.h:161
bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference, const Function &F) const override
Class to represent pointers.
Definition: DerivedTypes.h:467
bool getDataSections() const
Return true if data objects should be emitted into their own section, corresponds to -fdata-sections...
void append(in_iter S, in_iter E)
Append from an iterator pair.
Definition: SmallString.h:75
11: Arbitrary bit width integers
Definition: Type.h:71
0: type with no size
Definition: Type.h:57
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:406
const Function * getLutUsedFunction(const GlobalObject *GO) const
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
10: Tokens
Definition: Type.h:67
static bool isSmallDataSection(StringRef Sec)
bool hasInternalLinkage() const
Definition: GlobalValue.h:425
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:23
6: 128-bit floating point type (two 64-bits, PowerPC)
Definition: Type.h:63
bool isBSS() const
Definition: SectionKind.h:160
14: Arrays
Definition: Type.h:74
unsigned UseInitArray
UseInitArray - Use .init_array instead of .ctors for static constructors.
16: SIMD &#39;packed&#39; format, or other vector type
Definition: Type.h:76
static cl::opt< unsigned > SmallDataThreshold("hexagon-small-data-threshold", cl::init(8), cl::Hidden, cl::desc("The maximum size of an object in the sdata section"))
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
bool hasSection() const
Check if this global has a custom object file section.
Definition: GlobalObject.h:82
bool isCommon() const
Definition: SectionKind.h:164
static cl::opt< bool > TraceGVPlacement("trace-gv-placement", cl::Hidden, cl::init(false), cl::desc("Trace global value placement"))
static cl::opt< bool > StaticsInSData("hexagon-statics-in-small-data", cl::init(false), cl::Hidden, cl::ZeroOrMore, cl::desc("Allow static variables in .sdata"))
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
8: Metadata
Definition: Type.h:65
Class to represent vector types.
Definition: DerivedTypes.h:393
iterator_range< user_iterator > users()
Definition: Value.h:401
static cl::opt< bool > EmitLutInText("hexagon-emit-lut-text", cl::Hidden, cl::init(false), cl::desc("Emit hexagon lookup tables in function section"))
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool equals(StringRef RHS) const
equals - Check for string equality, this is more efficient than compare() when the relative ordering ...
Definition: StringRef.h:169
uint64_t getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:403
bool isMergeableConst() const
Definition: SectionKind.h:136
static const size_t npos
Definition: StringRef.h:51
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:220
TargetOptions Options
Definition: TargetMachine.h:96
#define I(x, y, z)
Definition: MD5.cpp:58
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
std::string str() const
Return the twine contents as a std::string.
Definition: Twine.cpp:17
const unsigned Kind
3: 64-bit floating point type
Definition: Type.h:60
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:379
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:556
bool isData() const
Definition: SectionKind.h:166
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
#define DEBUG(X)
Definition: Debug.h:118
Primary interface to the complete machine description for the target machine.
Definition: TargetMachine.h:57
MCSection * getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Targets should implement this method to assign a section to globals with an explicit section specfied...
Type * getElementType() const
Definition: DerivedTypes.h:360
MCSection * BSSSection
Section that is default initialized to zero.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
9: MMX vectors (64 bits, X86 specific)
Definition: Type.h:66
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t find(char C, size_t From=0) const
Search for the first character C in the string.
Definition: StringRef.h:298
Type * getElementType() const
Definition: DerivedTypes.h:486
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:265
5: 128-bit floating point type (112-bit mantissa)
Definition: Type.h:62
static SectionKind getText()
Definition: SectionKind.h:180