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1 //===-- llvm/BinaryFormat/Dwarf.h ---Dwarf Constants-------------*- 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 /// \file
11 /// This file contains constants used for implementing Dwarf
12 /// debug support.
13 ///
14 /// For details on the Dwarf specfication see the latest DWARF Debugging
15 /// Information Format standard document on http://www.dwarfstd.org. This
16 /// file often includes support for non-released standard features.
17 //
18 //===----------------------------------------------------------------------===//
19 
20 #ifndef LLVM_BINARYFORMAT_DWARF_H
21 #define LLVM_BINARYFORMAT_DWARF_H
22 
23 #include "llvm/ADT/Optional.h"
24 #include "llvm/Support/Compiler.h"
25 #include "llvm/Support/DataTypes.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/Format.h"
28 #include "llvm/Support/FormatVariadicDetails.h"
29 
30 namespace llvm {
31 class StringRef;
32 
33 namespace dwarf {
34 
35 //===----------------------------------------------------------------------===//
36 // DWARF constants as gleaned from the DWARF Debugging Information Format V.5
37 // reference manual http://www.dwarfstd.org/.
38 //
39 
40 // Do not mix the following two enumerations sets.  DW_TAG_invalid changes the
41 // enumeration base type.
42 
43 enum LLVMConstants : uint32_t {
44   // LLVM mock tags (see also llvm/BinaryFormat/Dwarf.def).
45   DW_TAG_invalid = ~0U,        // Tag for invalid results.
46   DW_VIRTUALITY_invalid = ~0U, // Virtuality for invalid results.
47   DW_MACINFO_invalid = ~0U,    // Macinfo type for invalid results.
48 
49   // Other constants.
50   DWARF_VERSION = 4,       // Default dwarf version we output.
51   DW_PUBTYPES_VERSION = 2, // Section version number for .debug_pubtypes.
52   DW_PUBNAMES_VERSION = 2, // Section version number for .debug_pubnames.
53   DW_ARANGES_VERSION = 2,  // Section version number for .debug_aranges.
54   // Identifiers we use to distinguish vendor extensions.
55   DWARF_VENDOR_DWARF = 0, // Defined in v2 or later of the DWARF standard.
56   DWARF_VENDOR_APPLE = 1,
57   DWARF_VENDOR_BORLAND = 2,
58   DWARF_VENDOR_GNU = 3,
59   DWARF_VENDOR_GOOGLE = 4,
60   DWARF_VENDOR_LLVM = 5,
61   DWARF_VENDOR_MIPS = 6
62 };
63 
64 /// Constants that define the DWARF format as 32 or 64 bit.
65 enum DwarfFormat : uint8_t { DWARF32, DWARF64 };
66 
67 /// Special ID values that distinguish a CIE from a FDE in DWARF CFI.
68 /// Not inside an enum because a 64-bit value is needed.
69 /// @{
70 const uint32_t DW_CIE_ID = UINT32_MAX;
71 const uint64_t DW64_CIE_ID = UINT64_MAX;
72 /// @}
73 
74 /// Identifier of an invalid DIE offset in the .debug_info section.
75 const uint32_t DW_INVALID_OFFSET = UINT32_MAX;
76 
77 enum Tag : uint16_t {
78 #define HANDLE_DW_TAG(ID, NAME, VERSION, VENDOR) DW_TAG_##NAME = ID,
79 #include "llvm/BinaryFormat/Dwarf.def"
80   DW_TAG_lo_user = 0x4080,
81   DW_TAG_hi_user = 0xffff,
82   DW_TAG_user_base = 0x1000 ///< Recommended base for user tags.
83 };
84 
isType(Tag T)85 inline bool isType(Tag T) {
86   switch (T) {
87   case DW_TAG_array_type:
88   case DW_TAG_class_type:
89   case DW_TAG_interface_type:
90   case DW_TAG_enumeration_type:
91   case DW_TAG_pointer_type:
92   case DW_TAG_reference_type:
93   case DW_TAG_rvalue_reference_type:
94   case DW_TAG_string_type:
95   case DW_TAG_structure_type:
96   case DW_TAG_subroutine_type:
97   case DW_TAG_union_type:
98   case DW_TAG_ptr_to_member_type:
99   case DW_TAG_set_type:
100   case DW_TAG_subrange_type:
101   case DW_TAG_base_type:
102   case DW_TAG_const_type:
103   case DW_TAG_file_type:
104   case DW_TAG_packed_type:
105   case DW_TAG_volatile_type:
106   case DW_TAG_typedef:
107     return true;
108   default:
109     return false;
110   }
111 }
112 
113 /// Attributes.
114 enum Attribute : uint16_t {
115 #define HANDLE_DW_AT(ID, NAME, VERSION, VENDOR) DW_AT_##NAME = ID,
116 #include "llvm/BinaryFormat/Dwarf.def"
117   DW_AT_lo_user = 0x2000,
118   DW_AT_hi_user = 0x3fff,
119 };
120 
121 enum Form : uint16_t {
122 #define HANDLE_DW_FORM(ID, NAME, VERSION, VENDOR) DW_FORM_##NAME = ID,
123 #include "llvm/BinaryFormat/Dwarf.def"
124   DW_FORM_lo_user = 0x1f00, ///< Not specified by DWARF.
125 };
126 
127 enum LocationAtom {
128 #define HANDLE_DW_OP(ID, NAME, VERSION, VENDOR) DW_OP_##NAME = ID,
129 #include "llvm/BinaryFormat/Dwarf.def"
130   DW_OP_lo_user = 0xe0,
131   DW_OP_hi_user = 0xff,
132   DW_OP_LLVM_fragment = 0x1000 ///< Only used in LLVM metadata.
133 };
134 
135 enum TypeKind : uint8_t {
136 #define HANDLE_DW_ATE(ID, NAME, VERSION, VENDOR) DW_ATE_##NAME = ID,
137 #include "llvm/BinaryFormat/Dwarf.def"
138   DW_ATE_lo_user = 0x80,
139   DW_ATE_hi_user = 0xff
140 };
141 
142 enum DecimalSignEncoding {
143   // Decimal sign attribute values
144   DW_DS_unsigned = 0x01,
145   DW_DS_leading_overpunch = 0x02,
146   DW_DS_trailing_overpunch = 0x03,
147   DW_DS_leading_separate = 0x04,
148   DW_DS_trailing_separate = 0x05
149 };
150 
151 enum EndianityEncoding {
152   // Endianity attribute values
153   DW_END_default = 0x00,
154   DW_END_big = 0x01,
155   DW_END_little = 0x02,
156   DW_END_lo_user = 0x40,
157   DW_END_hi_user = 0xff
158 };
159 
160 enum AccessAttribute {
161   // Accessibility codes
162   DW_ACCESS_public = 0x01,
163   DW_ACCESS_protected = 0x02,
164   DW_ACCESS_private = 0x03
165 };
166 
167 enum VisibilityAttribute {
168   // Visibility codes
169   DW_VIS_local = 0x01,
170   DW_VIS_exported = 0x02,
171   DW_VIS_qualified = 0x03
172 };
173 
174 enum VirtualityAttribute {
175 #define HANDLE_DW_VIRTUALITY(ID, NAME) DW_VIRTUALITY_##NAME = ID,
176 #include "llvm/BinaryFormat/Dwarf.def"
177   DW_VIRTUALITY_max = 0x02
178 };
179 
180 enum DefaultedMemberAttribute {
181 #define HANDLE_DW_DEFAULTED(ID, NAME) DW_DEFAULTED_##NAME = ID,
182 #include "llvm/BinaryFormat/Dwarf.def"
183   DW_DEFAULTED_max = 0x02
184 };
185 
186 enum SourceLanguage {
187 #define HANDLE_DW_LANG(ID, NAME, VERSION, VENDOR) DW_LANG_##NAME = ID,
188 #include "llvm/BinaryFormat/Dwarf.def"
189   DW_LANG_lo_user = 0x8000,
190   DW_LANG_hi_user = 0xffff
191 };
192 
193 enum CaseSensitivity {
194   // Identifier case codes
195   DW_ID_case_sensitive = 0x00,
196   DW_ID_up_case = 0x01,
197   DW_ID_down_case = 0x02,
198   DW_ID_case_insensitive = 0x03
199 };
200 
201 enum CallingConvention {
202 // Calling convention codes
203 #define HANDLE_DW_CC(ID, NAME) DW_CC_##NAME = ID,
204 #include "llvm/BinaryFormat/Dwarf.def"
205   DW_CC_lo_user = 0x40,
206   DW_CC_hi_user = 0xff
207 };
208 
209 enum InlineAttribute {
210   // Inline codes
211   DW_INL_not_inlined = 0x00,
212   DW_INL_inlined = 0x01,
213   DW_INL_declared_not_inlined = 0x02,
214   DW_INL_declared_inlined = 0x03
215 };
216 
217 enum ArrayDimensionOrdering {
218   // Array ordering
219   DW_ORD_row_major = 0x00,
220   DW_ORD_col_major = 0x01
221 };
222 
223 enum DiscriminantList {
224   // Discriminant descriptor values
225   DW_DSC_label = 0x00,
226   DW_DSC_range = 0x01
227 };
228 
229 /// Line Number Standard Opcode Encodings.
230 enum LineNumberOps : uint8_t {
231 #define HANDLE_DW_LNS(ID, NAME) DW_LNS_##NAME = ID,
232 #include "llvm/BinaryFormat/Dwarf.def"
233 };
234 
235 /// Line Number Extended Opcode Encodings.
236 enum LineNumberExtendedOps {
237 #define HANDLE_DW_LNE(ID, NAME) DW_LNE_##NAME = ID,
238 #include "llvm/BinaryFormat/Dwarf.def"
239   DW_LNE_lo_user = 0x80,
240   DW_LNE_hi_user = 0xff
241 };
242 
243 enum LineNumberEntryFormat {
244 #define HANDLE_DW_LNCT(ID, NAME) DW_LNCT_##NAME = ID,
245 #include "llvm/BinaryFormat/Dwarf.def"
246   DW_LNCT_lo_user = 0x2000,
247   DW_LNCT_hi_user = 0x3fff,
248 };
249 
250 enum MacinfoRecordType {
251   // Macinfo Type Encodings
252   DW_MACINFO_define = 0x01,
253   DW_MACINFO_undef = 0x02,
254   DW_MACINFO_start_file = 0x03,
255   DW_MACINFO_end_file = 0x04,
256   DW_MACINFO_vendor_ext = 0xff
257 };
258 
259 /// DWARF v5 macro information entry type encodings.
260 enum MacroEntryType {
261 #define HANDLE_DW_MACRO(ID, NAME) DW_MACRO_##NAME = ID,
262 #include "llvm/BinaryFormat/Dwarf.def"
263   DW_MACRO_lo_user = 0xe0,
264   DW_MACRO_hi_user = 0xff
265 };
266 
267 /// DWARF v5 range list entry encoding values.
268 enum RangeListEntries {
269 #define HANDLE_DW_RLE(ID, NAME) DW_RLE_##NAME = ID,
270 #include "llvm/BinaryFormat/Dwarf.def"
271 };
272 
273 /// Call frame instruction encodings.
274 enum CallFrameInfo {
275 #define HANDLE_DW_CFA(ID, NAME) DW_CFA_##NAME = ID,
276 #include "llvm/BinaryFormat/Dwarf.def"
277   DW_CFA_extended = 0x00,
278 
279   DW_CFA_lo_user = 0x1c,
280   DW_CFA_hi_user = 0x3f
281 };
282 
283 enum Constants {
284   // Children flag
285   DW_CHILDREN_no = 0x00,
286   DW_CHILDREN_yes = 0x01,
287 
288   DW_EH_PE_absptr = 0x00,
289   DW_EH_PE_omit = 0xff,
290   DW_EH_PE_uleb128 = 0x01,
291   DW_EH_PE_udata2 = 0x02,
292   DW_EH_PE_udata4 = 0x03,
293   DW_EH_PE_udata8 = 0x04,
294   DW_EH_PE_sleb128 = 0x09,
295   DW_EH_PE_sdata2 = 0x0A,
296   DW_EH_PE_sdata4 = 0x0B,
297   DW_EH_PE_sdata8 = 0x0C,
298   DW_EH_PE_signed = 0x08,
299   DW_EH_PE_pcrel = 0x10,
300   DW_EH_PE_textrel = 0x20,
301   DW_EH_PE_datarel = 0x30,
302   DW_EH_PE_funcrel = 0x40,
303   DW_EH_PE_aligned = 0x50,
304   DW_EH_PE_indirect = 0x80
305 };
306 
307 /// Constants for location lists in DWARF v5.
308 enum LocationListEntry : unsigned char {
309   DW_LLE_end_of_list = 0x00,
310   DW_LLE_base_addressx = 0x01,
311   DW_LLE_startx_endx = 0x02,
312   DW_LLE_startx_length = 0x03,
313   DW_LLE_offset_pair = 0x04,
314   DW_LLE_default_location = 0x05,
315   DW_LLE_base_address = 0x06,
316   DW_LLE_start_end = 0x07,
317   DW_LLE_start_length = 0x08
318 };
319 
320 /// Constants for the DW_APPLE_PROPERTY_attributes attribute.
321 /// Keep this list in sync with clang's DeclSpec.h ObjCPropertyAttributeKind!
322 enum ApplePropertyAttributes {
323 #define HANDLE_DW_APPLE_PROPERTY(ID, NAME) DW_APPLE_PROPERTY_##NAME = ID,
324 #include "llvm/BinaryFormat/Dwarf.def"
325 };
326 
327 /// Constants for unit types in DWARF v5.
328 enum UnitType : unsigned char {
329 #define HANDLE_DW_UT(ID, NAME) DW_UT_##NAME = ID,
330 #include "llvm/BinaryFormat/Dwarf.def"
331   DW_UT_lo_user = 0x80,
332   DW_UT_hi_user = 0xff
333 };
334 
335 enum Index {
336 #define HANDLE_DW_IDX(ID, NAME) DW_IDX_##NAME = ID,
337 #include "llvm/BinaryFormat/Dwarf.def"
338   DW_IDX_lo_user = 0x2000,
339   DW_IDX_hi_user = 0x3fff
340 };
341 
isUnitType(uint8_t UnitType)342 inline bool isUnitType(uint8_t UnitType) {
343   switch (UnitType) {
344   case DW_UT_compile:
345   case DW_UT_type:
346   case DW_UT_partial:
347   case DW_UT_skeleton:
348   case DW_UT_split_compile:
349   case DW_UT_split_type:
350     return true;
351   default:
352     return false;
353   }
354 }
355 
isUnitType(dwarf::Tag T)356 inline bool isUnitType(dwarf::Tag T) {
357   switch (T) {
358   case DW_TAG_compile_unit:
359   case DW_TAG_type_unit:
360   case DW_TAG_partial_unit:
361   case DW_TAG_skeleton_unit:
362     return true;
363   default:
364     return false;
365   }
366 }
367 
368 // Constants for the DWARF v5 Accelerator Table Proposal
369 enum AcceleratorTable {
370   // Data layout descriptors.
371   DW_ATOM_null = 0u,       ///  Marker as the end of a list of atoms.
372   DW_ATOM_die_offset = 1u, // DIE offset in the debug_info section.
373   DW_ATOM_cu_offset = 2u, // Offset of the compile unit header that contains the
374                           // item in question.
375   DW_ATOM_die_tag = 3u,   // A tag entry.
376   DW_ATOM_type_flags = 4u, // Set of flags for a type.
377 
378   DW_ATOM_type_type_flags = 5u, // Dsymutil type extension.
379   DW_ATOM_qual_name_hash = 6u,  // Dsymutil qualified hash extension.
380 
381   // DW_ATOM_type_flags values.
382 
383   // Always set for C++, only set for ObjC if this is the @implementation for a
384   // class.
385   DW_FLAG_type_implementation = 2u,
386 
387   // Hash functions.
388 
389   // Daniel J. Bernstein hash.
390   DW_hash_function_djb = 0u
391 };
392 
393 // Constants for the GNU pubnames/pubtypes extensions supporting gdb index.
394 enum GDBIndexEntryKind {
395   GIEK_NONE,
396   GIEK_TYPE,
397   GIEK_VARIABLE,
398   GIEK_FUNCTION,
399   GIEK_OTHER,
400   GIEK_UNUSED5,
401   GIEK_UNUSED6,
402   GIEK_UNUSED7
403 };
404 
405 enum GDBIndexEntryLinkage { GIEL_EXTERNAL, GIEL_STATIC };
406 
407 /// \defgroup DwarfConstantsDumping Dwarf constants dumping functions
408 ///
409 /// All these functions map their argument's value back to the
410 /// corresponding enumerator name or return an empty StringRef if the value
411 /// isn't known.
412 ///
413 /// @{
414 StringRef TagString(unsigned Tag);
415 StringRef ChildrenString(unsigned Children);
416 StringRef AttributeString(unsigned Attribute);
417 StringRef FormEncodingString(unsigned Encoding);
418 StringRef OperationEncodingString(unsigned Encoding);
419 StringRef AttributeEncodingString(unsigned Encoding);
420 StringRef DecimalSignString(unsigned Sign);
421 StringRef EndianityString(unsigned Endian);
422 StringRef AccessibilityString(unsigned Access);
423 StringRef VisibilityString(unsigned Visibility);
424 StringRef VirtualityString(unsigned Virtuality);
425 StringRef LanguageString(unsigned Language);
426 StringRef CaseString(unsigned Case);
427 StringRef ConventionString(unsigned Convention);
428 StringRef InlineCodeString(unsigned Code);
429 StringRef ArrayOrderString(unsigned Order);
430 StringRef LNStandardString(unsigned Standard);
431 StringRef LNExtendedString(unsigned Encoding);
432 StringRef MacinfoString(unsigned Encoding);
433 StringRef RangeListEncodingString(unsigned Encoding);
434 StringRef CallFrameString(unsigned Encoding);
435 StringRef ApplePropertyString(unsigned);
436 StringRef UnitTypeString(unsigned);
437 StringRef AtomTypeString(unsigned Atom);
438 StringRef GDBIndexEntryKindString(GDBIndexEntryKind Kind);
439 StringRef GDBIndexEntryLinkageString(GDBIndexEntryLinkage Linkage);
440 StringRef IndexString(unsigned Idx);
441 /// @}
442 
443 /// \defgroup DwarfConstantsParsing Dwarf constants parsing functions
444 ///
445 /// These functions map their strings back to the corresponding enumeration
446 /// value or return 0 if there is none, except for these exceptions:
447 ///
448 /// \li \a getTag() returns \a DW_TAG_invalid on invalid input.
449 /// \li \a getVirtuality() returns \a DW_VIRTUALITY_invalid on invalid input.
450 /// \li \a getMacinfo() returns \a DW_MACINFO_invalid on invalid input.
451 ///
452 /// @{
453 unsigned getTag(StringRef TagString);
454 unsigned getOperationEncoding(StringRef OperationEncodingString);
455 unsigned getVirtuality(StringRef VirtualityString);
456 unsigned getLanguage(StringRef LanguageString);
457 unsigned getCallingConvention(StringRef LanguageString);
458 unsigned getAttributeEncoding(StringRef EncodingString);
459 unsigned getMacinfo(StringRef MacinfoString);
460 /// @}
461 
462 /// \defgroup DwarfConstantsVersioning Dwarf version for constants
463 ///
464 /// For constants defined by DWARF, returns the DWARF version when the constant
465 /// was first defined. For vendor extensions, if there is a version-related
466 /// policy for when to emit it, returns a version number for that policy.
467 /// Otherwise returns 0.
468 ///
469 /// @{
470 unsigned TagVersion(Tag T);
471 unsigned AttributeVersion(Attribute A);
472 unsigned FormVersion(Form F);
473 unsigned OperationVersion(LocationAtom O);
474 unsigned AttributeEncodingVersion(TypeKind E);
475 unsigned LanguageVersion(SourceLanguage L);
476 /// @}
477 
478 /// \defgroup DwarfConstantsVendor Dwarf "vendor" for constants
479 ///
480 /// These functions return an identifier describing "who" defined the constant,
481 /// either the DWARF standard itself or the vendor who defined the extension.
482 ///
483 /// @{
484 unsigned TagVendor(Tag T);
485 unsigned AttributeVendor(Attribute A);
486 unsigned FormVendor(Form F);
487 unsigned OperationVendor(LocationAtom O);
488 unsigned AttributeEncodingVendor(TypeKind E);
489 unsigned LanguageVendor(SourceLanguage L);
490 /// @}
491 
492 /// A helper struct providing information about the byte size of DW_FORM
493 /// values that vary in size depending on the DWARF version, address byte
494 /// size, or DWARF32/DWARF64.
495 struct FormParams {
496   uint16_t Version;
497   uint8_t AddrSize;
498   DwarfFormat Format;
499 
500   /// The definition of the size of form DW_FORM_ref_addr depends on the
501   /// version. In DWARF v2 it's the size of an address; after that, it's the
502   /// size of a reference.
getRefAddrByteSizeFormParams503   uint8_t getRefAddrByteSize() const {
504     if (Version == 2)
505       return AddrSize;
506     return getDwarfOffsetByteSize();
507   }
508 
509   /// The size of a reference is determined by the DWARF 32/64-bit format.
getDwarfOffsetByteSizeFormParams510   uint8_t getDwarfOffsetByteSize() const {
511     switch (Format) {
512     case DwarfFormat::DWARF32:
513       return 4;
514     case DwarfFormat::DWARF64:
515       return 8;
516     }
517     llvm_unreachable("Invalid Format value");
518   }
519 
520   explicit operator bool() const { return Version && AddrSize; }
521 };
522 
523 /// Get the fixed byte size for a given form.
524 ///
525 /// If the form has a fixed byte size, then an Optional with a value will be
526 /// returned. If the form is always encoded using a variable length storage
527 /// format (ULEB or SLEB numbers or blocks) then None will be returned.
528 ///
529 /// \param Form DWARF form to get the fixed byte size for.
530 /// \param Params DWARF parameters to help interpret forms.
531 /// \returns Optional<uint8_t> value with the fixed byte size or None if
532 /// \p Form doesn't have a fixed byte size.
533 Optional<uint8_t> getFixedFormByteSize(dwarf::Form Form, FormParams Params);
534 
535 /// Tells whether the specified form is defined in the specified version,
536 /// or is an extension if extensions are allowed.
537 bool isValidFormForVersion(Form F, unsigned Version, bool ExtensionsOk = true);
538 
539 /// Returns the symbolic string representing Val when used as a value
540 /// for attribute Attr.
541 StringRef AttributeValueString(uint16_t Attr, unsigned Val);
542 
543 /// Returns the symbolic string representing Val when used as a value
544 /// for atom Atom.
545 StringRef AtomValueString(uint16_t Atom, unsigned Val);
546 
547 /// Describes an entry of the various gnu_pub* debug sections.
548 ///
549 /// The gnu_pub* kind looks like:
550 ///
551 /// 0-3  reserved
552 /// 4-6  symbol kind
553 /// 7    0 == global, 1 == static
554 ///
555 /// A gdb_index descriptor includes the above kind, shifted 24 bits up with the
556 /// offset of the cu within the debug_info section stored in those 24 bits.
557 struct PubIndexEntryDescriptor {
558   GDBIndexEntryKind Kind;
559   GDBIndexEntryLinkage Linkage;
PubIndexEntryDescriptorPubIndexEntryDescriptor560   PubIndexEntryDescriptor(GDBIndexEntryKind Kind, GDBIndexEntryLinkage Linkage)
561       : Kind(Kind), Linkage(Linkage) {}
PubIndexEntryDescriptorPubIndexEntryDescriptor562   /* implicit */ PubIndexEntryDescriptor(GDBIndexEntryKind Kind)
563       : Kind(Kind), Linkage(GIEL_EXTERNAL) {}
PubIndexEntryDescriptorPubIndexEntryDescriptor564   explicit PubIndexEntryDescriptor(uint8_t Value)
565       : Kind(
566             static_cast<GDBIndexEntryKind>((Value & KIND_MASK) >> KIND_OFFSET)),
567         Linkage(static_cast<GDBIndexEntryLinkage>((Value & LINKAGE_MASK) >>
568                                                   LINKAGE_OFFSET)) {}
toBitsPubIndexEntryDescriptor569   uint8_t toBits() const {
570     return Kind << KIND_OFFSET | Linkage << LINKAGE_OFFSET;
571   }
572 
573 private:
574   enum {
575     KIND_OFFSET = 4,
576     KIND_MASK = 7 << KIND_OFFSET,
577     LINKAGE_OFFSET = 7,
578     LINKAGE_MASK = 1 << LINKAGE_OFFSET
579   };
580 };
581 
582 template <typename Enum> struct EnumTraits : public std::false_type {};
583 
584 template <> struct EnumTraits<Attribute> : public std::true_type {
585   static constexpr char Type[3] = "AT";
586   static constexpr StringRef (*StringFn)(unsigned) = &AttributeString;
587 };
588 
589 template <> struct EnumTraits<Form> : public std::true_type {
590   static constexpr char Type[5] = "FORM";
591   static constexpr StringRef (*StringFn)(unsigned) = &FormEncodingString;
592 };
593 
594 template <> struct EnumTraits<Index> : public std::true_type {
595   static constexpr char Type[4] = "IDX";
596   static constexpr StringRef (*StringFn)(unsigned) = &IndexString;
597 };
598 
599 template <> struct EnumTraits<Tag> : public std::true_type {
600   static constexpr char Type[4] = "TAG";
601   static constexpr StringRef (*StringFn)(unsigned) = &TagString;
602 };
603 } // End of namespace dwarf
604 
605 /// Dwarf constants format_provider
606 ///
607 /// Specialization of the format_provider template for dwarf enums. Unlike the
608 /// dumping functions above, these format unknown enumerator values as
609 /// DW_TYPE_unknown_1234 (e.g. DW_TAG_unknown_ffff).
610 template <typename Enum>
611 struct format_provider<
612     Enum, typename std::enable_if<dwarf::EnumTraits<Enum>::value>::type> {
613   static void format(const Enum &E, raw_ostream &OS, StringRef Style) {
614     StringRef Str = dwarf::EnumTraits<Enum>::StringFn(E);
615     if (Str.empty()) {
616       OS << "DW_" << dwarf::EnumTraits<Enum>::Type << "_unknown_"
617          << llvm::format("%x", E);
618     } else
619       OS << Str;
620   }
621 };
622 } // End of namespace llvm
623 
624 #endif
625