1 //===--- DIBuilder.cpp - Debug Information Builder ------------------------===//
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 implements the DIBuilder.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/IR/DIBuilder.h"
14 #include "llvm/IR/IRBuilder.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/Optional.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/BinaryFormat/Dwarf.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DebugInfo.h"
21 #include "llvm/IR/IntrinsicInst.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/Support/Debug.h"
24 
25 using namespace llvm;
26 using namespace llvm::dwarf;
27 
28 cl::opt<bool>
29     UseDbgAddr("use-dbg-addr",
30                llvm::cl::desc("Use llvm.dbg.addr for all local variables"),
31                cl::init(false), cl::Hidden);
32 
33 DIBuilder::DIBuilder(Module &m, bool AllowUnresolvedNodes, DICompileUnit *CU)
34   : M(m), VMContext(M.getContext()), CUNode(CU),
35       DeclareFn(nullptr), ValueFn(nullptr), LabelFn(nullptr),
36       AllowUnresolvedNodes(AllowUnresolvedNodes) {}
37 
38 void DIBuilder::trackIfUnresolved(MDNode *N) {
39   if (!N)
40     return;
41   if (N->isResolved())
42     return;
43 
44   assert(AllowUnresolvedNodes && "Cannot handle unresolved nodes");
45   UnresolvedNodes.emplace_back(N);
46 }
47 
48 void DIBuilder::finalizeSubprogram(DISubprogram *SP) {
49   MDTuple *Temp = SP->getRetainedNodes().get();
50   if (!Temp || !Temp->isTemporary())
51     return;
52 
53   SmallVector<Metadata *, 16> RetainedNodes;
54 
55   auto PV = PreservedVariables.find(SP);
56   if (PV != PreservedVariables.end())
57     RetainedNodes.append(PV->second.begin(), PV->second.end());
58 
59   auto PL = PreservedLabels.find(SP);
60   if (PL != PreservedLabels.end())
61     RetainedNodes.append(PL->second.begin(), PL->second.end());
62 
63   DINodeArray Node = getOrCreateArray(RetainedNodes);
64 
65   TempMDTuple(Temp)->replaceAllUsesWith(Node.get());
66 }
67 
68 void DIBuilder::finalize() {
69   if (!CUNode) {
70     assert(!AllowUnresolvedNodes &&
71            "creating type nodes without a CU is not supported");
72     return;
73   }
74 
75   CUNode->replaceEnumTypes(MDTuple::get(VMContext, AllEnumTypes));
76 
77   SmallVector<Metadata *, 16> RetainValues;
78   // Declarations and definitions of the same type may be retained. Some
79   // clients RAUW these pairs, leaving duplicates in the retained types
80   // list. Use a set to remove the duplicates while we transform the
81   // TrackingVHs back into Values.
82   SmallPtrSet<Metadata *, 16> RetainSet;
83   for (unsigned I = 0, E = AllRetainTypes.size(); I < E; I++)
84     if (RetainSet.insert(AllRetainTypes[I]).second)
85       RetainValues.push_back(AllRetainTypes[I]);
86 
87   if (!RetainValues.empty())
88     CUNode->replaceRetainedTypes(MDTuple::get(VMContext, RetainValues));
89 
90   DISubprogramArray SPs = MDTuple::get(VMContext, AllSubprograms);
91   for (auto *SP : SPs)
92     finalizeSubprogram(SP);
93   for (auto *N : RetainValues)
94     if (auto *SP = dyn_cast<DISubprogram>(N))
95       finalizeSubprogram(SP);
96 
97   if (!AllGVs.empty())
98     CUNode->replaceGlobalVariables(MDTuple::get(VMContext, AllGVs));
99 
100   if (!AllImportedModules.empty())
101     CUNode->replaceImportedEntities(MDTuple::get(
102         VMContext, SmallVector<Metadata *, 16>(AllImportedModules.begin(),
103                                                AllImportedModules.end())));
104 
105   for (const auto &I : AllMacrosPerParent) {
106     // DIMacroNode's with nullptr parent are DICompileUnit direct children.
107     if (!I.first) {
108       CUNode->replaceMacros(MDTuple::get(VMContext, I.second.getArrayRef()));
109       continue;
110     }
111     // Otherwise, it must be a temporary DIMacroFile that need to be resolved.
112     auto *TMF = cast<DIMacroFile>(I.first);
113     auto *MF = DIMacroFile::get(VMContext, dwarf::DW_MACINFO_start_file,
114                                 TMF->getLine(), TMF->getFile(),
115                                 getOrCreateMacroArray(I.second.getArrayRef()));
116     replaceTemporary(llvm::TempDIMacroNode(TMF), MF);
117   }
118 
119   // Now that all temp nodes have been replaced or deleted, resolve remaining
120   // cycles.
121   for (const auto &N : UnresolvedNodes)
122     if (N && !N->isResolved())
123       N->resolveCycles();
124   UnresolvedNodes.clear();
125 
126   // Can't handle unresolved nodes anymore.
127   AllowUnresolvedNodes = false;
128 }
129 
130 /// If N is compile unit return NULL otherwise return N.
131 static DIScope *getNonCompileUnitScope(DIScope *N) {
132   if (!N || isa<DICompileUnit>(N))
133     return nullptr;
134   return cast<DIScope>(N);
135 }
136 
137 DICompileUnit *DIBuilder::createCompileUnit(
138     unsigned Lang, DIFile *File, StringRef Producer, bool isOptimized,
139     StringRef Flags, unsigned RunTimeVer, StringRef SplitName,
140     DICompileUnit::DebugEmissionKind Kind, uint64_t DWOId,
141     bool SplitDebugInlining, bool DebugInfoForProfiling,
142     DICompileUnit::DebugNameTableKind NameTableKind, bool RangesBaseAddress) {
143 
144   assert(((Lang <= dwarf::DW_LANG_Fortran08 && Lang >= dwarf::DW_LANG_C89) ||
145           (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
146          "Invalid Language tag");
147 
148   assert(!CUNode && "Can only make one compile unit per DIBuilder instance");
149   CUNode = DICompileUnit::getDistinct(
150       VMContext, Lang, File, Producer, isOptimized, Flags, RunTimeVer,
151       SplitName, Kind, nullptr, nullptr, nullptr, nullptr, nullptr, DWOId,
152       SplitDebugInlining, DebugInfoForProfiling, NameTableKind,
153       RangesBaseAddress);
154 
155   // Create a named metadata so that it is easier to find cu in a module.
156   NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
157   NMD->addOperand(CUNode);
158   trackIfUnresolved(CUNode);
159   return CUNode;
160 }
161 
162 static DIImportedEntity *
163 createImportedModule(LLVMContext &C, dwarf::Tag Tag, DIScope *Context,
164                      Metadata *NS, DIFile *File, unsigned Line, StringRef Name,
165                      SmallVectorImpl<TrackingMDNodeRef> &AllImportedModules) {
166   if (Line)
167     assert(File && "Source location has line number but no file");
168   unsigned EntitiesCount = C.pImpl->DIImportedEntitys.size();
169   auto *M = DIImportedEntity::get(C, Tag, Context, cast_or_null<DINode>(NS),
170                                   File, Line, Name);
171   if (EntitiesCount < C.pImpl->DIImportedEntitys.size())
172     // A new Imported Entity was just added to the context.
173     // Add it to the Imported Modules list.
174     AllImportedModules.emplace_back(M);
175   return M;
176 }
177 
178 DIImportedEntity *DIBuilder::createImportedModule(DIScope *Context,
179                                                   DINamespace *NS, DIFile *File,
180                                                   unsigned Line) {
181   return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_module,
182                                 Context, NS, File, Line, StringRef(),
183                                 AllImportedModules);
184 }
185 
186 DIImportedEntity *DIBuilder::createImportedModule(DIScope *Context,
187                                                   DIImportedEntity *NS,
188                                                   DIFile *File, unsigned Line) {
189   return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_module,
190                                 Context, NS, File, Line, StringRef(),
191                                 AllImportedModules);
192 }
193 
194 DIImportedEntity *DIBuilder::createImportedModule(DIScope *Context, DIModule *M,
195                                                   DIFile *File, unsigned Line) {
196   return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_module,
197                                 Context, M, File, Line, StringRef(),
198                                 AllImportedModules);
199 }
200 
201 DIImportedEntity *DIBuilder::createImportedDeclaration(DIScope *Context,
202                                                        DINode *Decl,
203                                                        DIFile *File,
204                                                        unsigned Line,
205                                                        StringRef Name) {
206   // Make sure to use the unique identifier based metadata reference for
207   // types that have one.
208   return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_declaration,
209                                 Context, Decl, File, Line, Name,
210                                 AllImportedModules);
211 }
212 
213 DIFile *DIBuilder::createFile(StringRef Filename, StringRef Directory,
214                               Optional<DIFile::ChecksumInfo<StringRef>> CS,
215                               Optional<StringRef> Source) {
216   return DIFile::get(VMContext, Filename, Directory, CS, Source);
217 }
218 
219 DIMacro *DIBuilder::createMacro(DIMacroFile *Parent, unsigned LineNumber,
220                                 unsigned MacroType, StringRef Name,
221                                 StringRef Value) {
222   assert(!Name.empty() && "Unable to create macro without name");
223   assert((MacroType == dwarf::DW_MACINFO_undef ||
224           MacroType == dwarf::DW_MACINFO_define) &&
225          "Unexpected macro type");
226   auto *M = DIMacro::get(VMContext, MacroType, LineNumber, Name, Value);
227   AllMacrosPerParent[Parent].insert(M);
228   return M;
229 }
230 
231 DIMacroFile *DIBuilder::createTempMacroFile(DIMacroFile *Parent,
232                                             unsigned LineNumber, DIFile *File) {
233   auto *MF = DIMacroFile::getTemporary(VMContext, dwarf::DW_MACINFO_start_file,
234                                        LineNumber, File, DIMacroNodeArray())
235                  .release();
236   AllMacrosPerParent[Parent].insert(MF);
237   // Add the new temporary DIMacroFile to the macro per parent map as a parent.
238   // This is needed to assure DIMacroFile with no children to have an entry in
239   // the map. Otherwise, it will not be resolved in DIBuilder::finalize().
240   AllMacrosPerParent.insert({MF, {}});
241   return MF;
242 }
243 
244 DIEnumerator *DIBuilder::createEnumerator(StringRef Name, int64_t Val,
245                                           bool IsUnsigned) {
246   assert(!Name.empty() && "Unable to create enumerator without name");
247   return DIEnumerator::get(VMContext, Val, IsUnsigned, Name);
248 }
249 
250 DIBasicType *DIBuilder::createUnspecifiedType(StringRef Name) {
251   assert(!Name.empty() && "Unable to create type without name");
252   return DIBasicType::get(VMContext, dwarf::DW_TAG_unspecified_type, Name);
253 }
254 
255 DIBasicType *DIBuilder::createNullPtrType() {
256   return createUnspecifiedType("decltype(nullptr)");
257 }
258 
259 DIBasicType *DIBuilder::createBasicType(StringRef Name, uint64_t SizeInBits,
260                                         unsigned Encoding,
261                                         DINode::DIFlags Flags) {
262   assert(!Name.empty() && "Unable to create type without name");
263   return DIBasicType::get(VMContext, dwarf::DW_TAG_base_type, Name, SizeInBits,
264                           0, Encoding, Flags);
265 }
266 
267 DIDerivedType *DIBuilder::createQualifiedType(unsigned Tag, DIType *FromTy) {
268   return DIDerivedType::get(VMContext, Tag, "", nullptr, 0, nullptr, FromTy, 0,
269                             0, 0, None, DINode::FlagZero);
270 }
271 
272 DIDerivedType *DIBuilder::createPointerType(
273     DIType *PointeeTy,
274     uint64_t SizeInBits,
275     uint32_t AlignInBits,
276     Optional<unsigned> DWARFAddressSpace,
277     StringRef Name) {
278   // FIXME: Why is there a name here?
279   return DIDerivedType::get(VMContext, dwarf::DW_TAG_pointer_type, Name,
280                             nullptr, 0, nullptr, PointeeTy, SizeInBits,
281                             AlignInBits, 0, DWARFAddressSpace,
282                             DINode::FlagZero);
283 }
284 
285 DIDerivedType *DIBuilder::createMemberPointerType(DIType *PointeeTy,
286                                                   DIType *Base,
287                                                   uint64_t SizeInBits,
288                                                   uint32_t AlignInBits,
289                                                   DINode::DIFlags Flags) {
290   return DIDerivedType::get(VMContext, dwarf::DW_TAG_ptr_to_member_type, "",
291                             nullptr, 0, nullptr, PointeeTy, SizeInBits,
292                             AlignInBits, 0, None, Flags, Base);
293 }
294 
295 DIDerivedType *DIBuilder::createReferenceType(
296     unsigned Tag, DIType *RTy,
297     uint64_t SizeInBits,
298     uint32_t AlignInBits,
299     Optional<unsigned> DWARFAddressSpace) {
300   assert(RTy && "Unable to create reference type");
301   return DIDerivedType::get(VMContext, Tag, "", nullptr, 0, nullptr, RTy,
302                             SizeInBits, AlignInBits, 0, DWARFAddressSpace,
303                             DINode::FlagZero);
304 }
305 
306 DIDerivedType *DIBuilder::createTypedef(DIType *Ty, StringRef Name,
307                                         DIFile *File, unsigned LineNo,
308                                         DIScope *Context) {
309   return DIDerivedType::get(VMContext, dwarf::DW_TAG_typedef, Name, File,
310                             LineNo, getNonCompileUnitScope(Context), Ty, 0, 0,
311                             0, None, DINode::FlagZero);
312 }
313 
314 DIDerivedType *DIBuilder::createFriend(DIType *Ty, DIType *FriendTy) {
315   assert(Ty && "Invalid type!");
316   assert(FriendTy && "Invalid friend type!");
317   return DIDerivedType::get(VMContext, dwarf::DW_TAG_friend, "", nullptr, 0, Ty,
318                             FriendTy, 0, 0, 0, None, DINode::FlagZero);
319 }
320 
321 DIDerivedType *DIBuilder::createInheritance(DIType *Ty, DIType *BaseTy,
322                                             uint64_t BaseOffset,
323                                             uint32_t VBPtrOffset,
324                                             DINode::DIFlags Flags) {
325   assert(Ty && "Unable to create inheritance");
326   Metadata *ExtraData = ConstantAsMetadata::get(
327       ConstantInt::get(IntegerType::get(VMContext, 32), VBPtrOffset));
328   return DIDerivedType::get(VMContext, dwarf::DW_TAG_inheritance, "", nullptr,
329                             0, Ty, BaseTy, 0, 0, BaseOffset, None,
330                             Flags, ExtraData);
331 }
332 
333 DIDerivedType *DIBuilder::createMemberType(DIScope *Scope, StringRef Name,
334                                            DIFile *File, unsigned LineNumber,
335                                            uint64_t SizeInBits,
336                                            uint32_t AlignInBits,
337                                            uint64_t OffsetInBits,
338                                            DINode::DIFlags Flags, DIType *Ty) {
339   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
340                             LineNumber, getNonCompileUnitScope(Scope), Ty,
341                             SizeInBits, AlignInBits, OffsetInBits, None, Flags);
342 }
343 
344 static ConstantAsMetadata *getConstantOrNull(Constant *C) {
345   if (C)
346     return ConstantAsMetadata::get(C);
347   return nullptr;
348 }
349 
350 DIDerivedType *DIBuilder::createVariantMemberType(
351     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
352     uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
353     Constant *Discriminant, DINode::DIFlags Flags, DIType *Ty) {
354   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
355                             LineNumber, getNonCompileUnitScope(Scope), Ty,
356                             SizeInBits, AlignInBits, OffsetInBits, None, Flags,
357                             getConstantOrNull(Discriminant));
358 }
359 
360 DIDerivedType *DIBuilder::createBitFieldMemberType(
361     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
362     uint64_t SizeInBits, uint64_t OffsetInBits, uint64_t StorageOffsetInBits,
363     DINode::DIFlags Flags, DIType *Ty) {
364   Flags |= DINode::FlagBitField;
365   return DIDerivedType::get(
366       VMContext, dwarf::DW_TAG_member, Name, File, LineNumber,
367       getNonCompileUnitScope(Scope), Ty, SizeInBits, /* AlignInBits */ 0,
368       OffsetInBits, None, Flags,
369       ConstantAsMetadata::get(ConstantInt::get(IntegerType::get(VMContext, 64),
370                                                StorageOffsetInBits)));
371 }
372 
373 DIDerivedType *
374 DIBuilder::createStaticMemberType(DIScope *Scope, StringRef Name, DIFile *File,
375                                   unsigned LineNumber, DIType *Ty,
376                                   DINode::DIFlags Flags, llvm::Constant *Val,
377                                   uint32_t AlignInBits) {
378   Flags |= DINode::FlagStaticMember;
379   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
380                             LineNumber, getNonCompileUnitScope(Scope), Ty, 0,
381                             AlignInBits, 0, None, Flags,
382                             getConstantOrNull(Val));
383 }
384 
385 DIDerivedType *
386 DIBuilder::createObjCIVar(StringRef Name, DIFile *File, unsigned LineNumber,
387                           uint64_t SizeInBits, uint32_t AlignInBits,
388                           uint64_t OffsetInBits, DINode::DIFlags Flags,
389                           DIType *Ty, MDNode *PropertyNode) {
390   return DIDerivedType::get(VMContext, dwarf::DW_TAG_member, Name, File,
391                             LineNumber, getNonCompileUnitScope(File), Ty,
392                             SizeInBits, AlignInBits, OffsetInBits, None, Flags,
393                             PropertyNode);
394 }
395 
396 DIObjCProperty *
397 DIBuilder::createObjCProperty(StringRef Name, DIFile *File, unsigned LineNumber,
398                               StringRef GetterName, StringRef SetterName,
399                               unsigned PropertyAttributes, DIType *Ty) {
400   return DIObjCProperty::get(VMContext, Name, File, LineNumber, GetterName,
401                              SetterName, PropertyAttributes, Ty);
402 }
403 
404 DITemplateTypeParameter *
405 DIBuilder::createTemplateTypeParameter(DIScope *Context, StringRef Name,
406                                        DIType *Ty) {
407   assert((!Context || isa<DICompileUnit>(Context)) && "Expected compile unit");
408   return DITemplateTypeParameter::get(VMContext, Name, Ty);
409 }
410 
411 static DITemplateValueParameter *
412 createTemplateValueParameterHelper(LLVMContext &VMContext, unsigned Tag,
413                                    DIScope *Context, StringRef Name, DIType *Ty,
414                                    Metadata *MD) {
415   assert((!Context || isa<DICompileUnit>(Context)) && "Expected compile unit");
416   return DITemplateValueParameter::get(VMContext, Tag, Name, Ty, MD);
417 }
418 
419 DITemplateValueParameter *
420 DIBuilder::createTemplateValueParameter(DIScope *Context, StringRef Name,
421                                         DIType *Ty, Constant *Val) {
422   return createTemplateValueParameterHelper(
423       VMContext, dwarf::DW_TAG_template_value_parameter, Context, Name, Ty,
424       getConstantOrNull(Val));
425 }
426 
427 DITemplateValueParameter *
428 DIBuilder::createTemplateTemplateParameter(DIScope *Context, StringRef Name,
429                                            DIType *Ty, StringRef Val) {
430   return createTemplateValueParameterHelper(
431       VMContext, dwarf::DW_TAG_GNU_template_template_param, Context, Name, Ty,
432       MDString::get(VMContext, Val));
433 }
434 
435 DITemplateValueParameter *
436 DIBuilder::createTemplateParameterPack(DIScope *Context, StringRef Name,
437                                        DIType *Ty, DINodeArray Val) {
438   return createTemplateValueParameterHelper(
439       VMContext, dwarf::DW_TAG_GNU_template_parameter_pack, Context, Name, Ty,
440       Val.get());
441 }
442 
443 DICompositeType *DIBuilder::createClassType(
444     DIScope *Context, StringRef Name, DIFile *File, unsigned LineNumber,
445     uint64_t SizeInBits, uint32_t AlignInBits, uint64_t OffsetInBits,
446     DINode::DIFlags Flags, DIType *DerivedFrom, DINodeArray Elements,
447     DIType *VTableHolder, MDNode *TemplateParams, StringRef UniqueIdentifier) {
448   assert((!Context || isa<DIScope>(Context)) &&
449          "createClassType should be called with a valid Context");
450 
451   auto *R = DICompositeType::get(
452       VMContext, dwarf::DW_TAG_structure_type, Name, File, LineNumber,
453       getNonCompileUnitScope(Context), DerivedFrom, SizeInBits, AlignInBits,
454       OffsetInBits, Flags, Elements, 0, VTableHolder,
455       cast_or_null<MDTuple>(TemplateParams), UniqueIdentifier);
456   trackIfUnresolved(R);
457   return R;
458 }
459 
460 DICompositeType *DIBuilder::createStructType(
461     DIScope *Context, StringRef Name, DIFile *File, unsigned LineNumber,
462     uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
463     DIType *DerivedFrom, DINodeArray Elements, unsigned RunTimeLang,
464     DIType *VTableHolder, StringRef UniqueIdentifier) {
465   auto *R = DICompositeType::get(
466       VMContext, dwarf::DW_TAG_structure_type, Name, File, LineNumber,
467       getNonCompileUnitScope(Context), DerivedFrom, SizeInBits, AlignInBits, 0,
468       Flags, Elements, RunTimeLang, VTableHolder, nullptr, UniqueIdentifier);
469   trackIfUnresolved(R);
470   return R;
471 }
472 
473 DICompositeType *DIBuilder::createUnionType(
474     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
475     uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
476     DINodeArray Elements, unsigned RunTimeLang, StringRef UniqueIdentifier) {
477   auto *R = DICompositeType::get(
478       VMContext, dwarf::DW_TAG_union_type, Name, File, LineNumber,
479       getNonCompileUnitScope(Scope), nullptr, SizeInBits, AlignInBits, 0, Flags,
480       Elements, RunTimeLang, nullptr, nullptr, UniqueIdentifier);
481   trackIfUnresolved(R);
482   return R;
483 }
484 
485 DICompositeType *DIBuilder::createVariantPart(
486     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
487     uint64_t SizeInBits, uint32_t AlignInBits, DINode::DIFlags Flags,
488     DIDerivedType *Discriminator, DINodeArray Elements, StringRef UniqueIdentifier) {
489   auto *R = DICompositeType::get(
490       VMContext, dwarf::DW_TAG_variant_part, Name, File, LineNumber,
491       getNonCompileUnitScope(Scope), nullptr, SizeInBits, AlignInBits, 0, Flags,
492       Elements, 0, nullptr, nullptr, UniqueIdentifier, Discriminator);
493   trackIfUnresolved(R);
494   return R;
495 }
496 
497 DISubroutineType *DIBuilder::createSubroutineType(DITypeRefArray ParameterTypes,
498                                                   DINode::DIFlags Flags,
499                                                   unsigned CC) {
500   return DISubroutineType::get(VMContext, Flags, CC, ParameterTypes);
501 }
502 
503 DICompositeType *DIBuilder::createEnumerationType(
504     DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
505     uint64_t SizeInBits, uint32_t AlignInBits, DINodeArray Elements,
506     DIType *UnderlyingType, StringRef UniqueIdentifier, bool IsScoped) {
507   auto *CTy = DICompositeType::get(
508       VMContext, dwarf::DW_TAG_enumeration_type, Name, File, LineNumber,
509       getNonCompileUnitScope(Scope), UnderlyingType, SizeInBits, AlignInBits, 0,
510       IsScoped ? DINode::FlagEnumClass : DINode::FlagZero, Elements, 0, nullptr,
511       nullptr, UniqueIdentifier);
512   AllEnumTypes.push_back(CTy);
513   trackIfUnresolved(CTy);
514   return CTy;
515 }
516 
517 DICompositeType *DIBuilder::createArrayType(uint64_t Size,
518                                             uint32_t AlignInBits, DIType *Ty,
519                                             DINodeArray Subscripts) {
520   auto *R = DICompositeType::get(VMContext, dwarf::DW_TAG_array_type, "",
521                                  nullptr, 0, nullptr, Ty, Size, AlignInBits, 0,
522                                  DINode::FlagZero, Subscripts, 0, nullptr);
523   trackIfUnresolved(R);
524   return R;
525 }
526 
527 DICompositeType *DIBuilder::createVectorType(uint64_t Size,
528                                              uint32_t AlignInBits, DIType *Ty,
529                                              DINodeArray Subscripts) {
530   auto *R = DICompositeType::get(VMContext, dwarf::DW_TAG_array_type, "",
531                                  nullptr, 0, nullptr, Ty, Size, AlignInBits, 0,
532                                  DINode::FlagVector, Subscripts, 0, nullptr);
533   trackIfUnresolved(R);
534   return R;
535 }
536 
537 DISubprogram *DIBuilder::createArtificialSubprogram(DISubprogram *SP) {
538   auto NewSP = SP->cloneWithFlags(SP->getFlags() | DINode::FlagArtificial);
539   return MDNode::replaceWithDistinct(std::move(NewSP));
540 }
541 
542 static DIType *createTypeWithFlags(const DIType *Ty,
543                                    DINode::DIFlags FlagsToSet) {
544   auto NewTy = Ty->cloneWithFlags(Ty->getFlags() | FlagsToSet);
545   return MDNode::replaceWithUniqued(std::move(NewTy));
546 }
547 
548 DIType *DIBuilder::createArtificialType(DIType *Ty) {
549   // FIXME: Restrict this to the nodes where it's valid.
550   if (Ty->isArtificial())
551     return Ty;
552   return createTypeWithFlags(Ty, DINode::FlagArtificial);
553 }
554 
555 DIType *DIBuilder::createObjectPointerType(DIType *Ty) {
556   // FIXME: Restrict this to the nodes where it's valid.
557   if (Ty->isObjectPointer())
558     return Ty;
559   DINode::DIFlags Flags = DINode::FlagObjectPointer | DINode::FlagArtificial;
560   return createTypeWithFlags(Ty, Flags);
561 }
562 
563 void DIBuilder::retainType(DIScope *T) {
564   assert(T && "Expected non-null type");
565   assert((isa<DIType>(T) || (isa<DISubprogram>(T) &&
566                              cast<DISubprogram>(T)->isDefinition() == false)) &&
567          "Expected type or subprogram declaration");
568   AllRetainTypes.emplace_back(T);
569 }
570 
571 DIBasicType *DIBuilder::createUnspecifiedParameter() { return nullptr; }
572 
573 DICompositeType *
574 DIBuilder::createForwardDecl(unsigned Tag, StringRef Name, DIScope *Scope,
575                              DIFile *F, unsigned Line, unsigned RuntimeLang,
576                              uint64_t SizeInBits, uint32_t AlignInBits,
577                              StringRef UniqueIdentifier) {
578   // FIXME: Define in terms of createReplaceableForwardDecl() by calling
579   // replaceWithUniqued().
580   auto *RetTy = DICompositeType::get(
581       VMContext, Tag, Name, F, Line, getNonCompileUnitScope(Scope), nullptr,
582       SizeInBits, AlignInBits, 0, DINode::FlagFwdDecl, nullptr, RuntimeLang,
583       nullptr, nullptr, UniqueIdentifier);
584   trackIfUnresolved(RetTy);
585   return RetTy;
586 }
587 
588 DICompositeType *DIBuilder::createReplaceableCompositeType(
589     unsigned Tag, StringRef Name, DIScope *Scope, DIFile *F, unsigned Line,
590     unsigned RuntimeLang, uint64_t SizeInBits, uint32_t AlignInBits,
591     DINode::DIFlags Flags, StringRef UniqueIdentifier) {
592   auto *RetTy =
593       DICompositeType::getTemporary(
594           VMContext, Tag, Name, F, Line, getNonCompileUnitScope(Scope), nullptr,
595           SizeInBits, AlignInBits, 0, Flags, nullptr, RuntimeLang, nullptr,
596           nullptr, UniqueIdentifier)
597           .release();
598   trackIfUnresolved(RetTy);
599   return RetTy;
600 }
601 
602 DINodeArray DIBuilder::getOrCreateArray(ArrayRef<Metadata *> Elements) {
603   return MDTuple::get(VMContext, Elements);
604 }
605 
606 DIMacroNodeArray
607 DIBuilder::getOrCreateMacroArray(ArrayRef<Metadata *> Elements) {
608   return MDTuple::get(VMContext, Elements);
609 }
610 
611 DITypeRefArray DIBuilder::getOrCreateTypeArray(ArrayRef<Metadata *> Elements) {
612   SmallVector<llvm::Metadata *, 16> Elts;
613   for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
614     if (Elements[i] && isa<MDNode>(Elements[i]))
615       Elts.push_back(cast<DIType>(Elements[i]));
616     else
617       Elts.push_back(Elements[i]);
618   }
619   return DITypeRefArray(MDNode::get(VMContext, Elts));
620 }
621 
622 DISubrange *DIBuilder::getOrCreateSubrange(int64_t Lo, int64_t Count) {
623   return DISubrange::get(VMContext, Count, Lo);
624 }
625 
626 DISubrange *DIBuilder::getOrCreateSubrange(int64_t Lo, Metadata *CountNode) {
627   return DISubrange::get(VMContext, CountNode, Lo);
628 }
629 
630 static void checkGlobalVariableScope(DIScope *Context) {
631 #ifndef NDEBUG
632   if (auto *CT =
633           dyn_cast_or_null<DICompositeType>(getNonCompileUnitScope(Context)))
634     assert(CT->getIdentifier().empty() &&
635            "Context of a global variable should not be a type with identifier");
636 #endif
637 }
638 
639 DIGlobalVariableExpression *DIBuilder::createGlobalVariableExpression(
640     DIScope *Context, StringRef Name, StringRef LinkageName, DIFile *F,
641     unsigned LineNumber, DIType *Ty, bool isLocalToUnit, DIExpression *Expr,
642     MDNode *Decl, MDTuple *templateParams, uint32_t AlignInBits) {
643   checkGlobalVariableScope(Context);
644 
645   auto *GV = DIGlobalVariable::getDistinct(
646       VMContext, cast_or_null<DIScope>(Context), Name, LinkageName, F,
647       LineNumber, Ty, isLocalToUnit, true, cast_or_null<DIDerivedType>(Decl),
648       templateParams, AlignInBits);
649   if (!Expr)
650     Expr = createExpression();
651   auto *N = DIGlobalVariableExpression::get(VMContext, GV, Expr);
652   AllGVs.push_back(N);
653   return N;
654 }
655 
656 DIGlobalVariable *DIBuilder::createTempGlobalVariableFwdDecl(
657     DIScope *Context, StringRef Name, StringRef LinkageName, DIFile *F,
658     unsigned LineNumber, DIType *Ty, bool isLocalToUnit, MDNode *Decl,
659     MDTuple *templateParams, uint32_t AlignInBits) {
660   checkGlobalVariableScope(Context);
661 
662   return DIGlobalVariable::getTemporary(
663              VMContext, cast_or_null<DIScope>(Context), Name, LinkageName, F,
664              LineNumber, Ty, isLocalToUnit, false,
665              cast_or_null<DIDerivedType>(Decl), templateParams, AlignInBits)
666       .release();
667 }
668 
669 static DILocalVariable *createLocalVariable(
670     LLVMContext &VMContext,
671     DenseMap<MDNode *, SmallVector<TrackingMDNodeRef, 1>> &PreservedVariables,
672     DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
673     unsigned LineNo, DIType *Ty, bool AlwaysPreserve, DINode::DIFlags Flags,
674     uint32_t AlignInBits) {
675   // FIXME: Why getNonCompileUnitScope()?
676   // FIXME: Why is "!Context" okay here?
677   // FIXME: Why doesn't this check for a subprogram or lexical block (AFAICT
678   // the only valid scopes)?
679   DIScope *Context = getNonCompileUnitScope(Scope);
680 
681   auto *Node =
682       DILocalVariable::get(VMContext, cast_or_null<DILocalScope>(Context), Name,
683                            File, LineNo, Ty, ArgNo, Flags, AlignInBits);
684   if (AlwaysPreserve) {
685     // The optimizer may remove local variables. If there is an interest
686     // to preserve variable info in such situation then stash it in a
687     // named mdnode.
688     DISubprogram *Fn = getDISubprogram(Scope);
689     assert(Fn && "Missing subprogram for local variable");
690     PreservedVariables[Fn].emplace_back(Node);
691   }
692   return Node;
693 }
694 
695 DILocalVariable *DIBuilder::createAutoVariable(DIScope *Scope, StringRef Name,
696                                                DIFile *File, unsigned LineNo,
697                                                DIType *Ty, bool AlwaysPreserve,
698                                                DINode::DIFlags Flags,
699                                                uint32_t AlignInBits) {
700   return createLocalVariable(VMContext, PreservedVariables, Scope, Name,
701                              /* ArgNo */ 0, File, LineNo, Ty, AlwaysPreserve,
702                              Flags, AlignInBits);
703 }
704 
705 DILocalVariable *DIBuilder::createParameterVariable(
706     DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
707     unsigned LineNo, DIType *Ty, bool AlwaysPreserve, DINode::DIFlags Flags) {
708   assert(ArgNo && "Expected non-zero argument number for parameter");
709   return createLocalVariable(VMContext, PreservedVariables, Scope, Name, ArgNo,
710                              File, LineNo, Ty, AlwaysPreserve, Flags,
711                              /* AlignInBits */0);
712 }
713 
714 DILabel *DIBuilder::createLabel(
715     DIScope *Scope, StringRef Name, DIFile *File,
716     unsigned LineNo, bool AlwaysPreserve) {
717   DIScope *Context = getNonCompileUnitScope(Scope);
718 
719   auto *Node =
720       DILabel::get(VMContext, cast_or_null<DILocalScope>(Context), Name,
721                    File, LineNo);
722 
723   if (AlwaysPreserve) {
724     /// The optimizer may remove labels. If there is an interest
725     /// to preserve label info in such situation then append it to
726     /// the list of retained nodes of the DISubprogram.
727     DISubprogram *Fn = getDISubprogram(Scope);
728     assert(Fn && "Missing subprogram for label");
729     PreservedLabels[Fn].emplace_back(Node);
730   }
731   return Node;
732 }
733 
734 DIExpression *DIBuilder::createExpression(ArrayRef<uint64_t> Addr) {
735   return DIExpression::get(VMContext, Addr);
736 }
737 
738 DIExpression *DIBuilder::createExpression(ArrayRef<int64_t> Signed) {
739   // TODO: Remove the callers of this signed version and delete.
740   SmallVector<uint64_t, 8> Addr(Signed.begin(), Signed.end());
741   return createExpression(Addr);
742 }
743 
744 template <class... Ts>
745 static DISubprogram *getSubprogram(bool IsDistinct, Ts &&... Args) {
746   if (IsDistinct)
747     return DISubprogram::getDistinct(std::forward<Ts>(Args)...);
748   return DISubprogram::get(std::forward<Ts>(Args)...);
749 }
750 
751 DISubprogram *DIBuilder::createFunction(
752     DIScope *Context, StringRef Name, StringRef LinkageName, DIFile *File,
753     unsigned LineNo, DISubroutineType *Ty, unsigned ScopeLine,
754     DINode::DIFlags Flags, DISubprogram::DISPFlags SPFlags,
755     DITemplateParameterArray TParams, DISubprogram *Decl,
756     DITypeArray ThrownTypes) {
757   bool IsDefinition = SPFlags & DISubprogram::SPFlagDefinition;
758   auto *Node = getSubprogram(
759       /*IsDistinct=*/IsDefinition, VMContext, getNonCompileUnitScope(Context),
760       Name, LinkageName, File, LineNo, Ty, ScopeLine, nullptr, 0, 0, Flags,
761       SPFlags, IsDefinition ? CUNode : nullptr, TParams, Decl,
762       MDTuple::getTemporary(VMContext, None).release(), ThrownTypes);
763 
764   if (IsDefinition)
765     AllSubprograms.push_back(Node);
766   trackIfUnresolved(Node);
767   return Node;
768 }
769 
770 DISubprogram *DIBuilder::createTempFunctionFwdDecl(
771     DIScope *Context, StringRef Name, StringRef LinkageName, DIFile *File,
772     unsigned LineNo, DISubroutineType *Ty, unsigned ScopeLine,
773     DINode::DIFlags Flags, DISubprogram::DISPFlags SPFlags,
774     DITemplateParameterArray TParams, DISubprogram *Decl,
775     DITypeArray ThrownTypes) {
776   bool IsDefinition = SPFlags & DISubprogram::SPFlagDefinition;
777   return DISubprogram::getTemporary(VMContext, getNonCompileUnitScope(Context),
778                                     Name, LinkageName, File, LineNo, Ty,
779                                     ScopeLine, nullptr, 0, 0, Flags, SPFlags,
780                                     IsDefinition ? CUNode : nullptr, TParams,
781                                     Decl, nullptr, ThrownTypes)
782       .release();
783 }
784 
785 DISubprogram *DIBuilder::createMethod(
786     DIScope *Context, StringRef Name, StringRef LinkageName, DIFile *F,
787     unsigned LineNo, DISubroutineType *Ty, unsigned VIndex, int ThisAdjustment,
788     DIType *VTableHolder, DINode::DIFlags Flags,
789     DISubprogram::DISPFlags SPFlags, DITemplateParameterArray TParams,
790     DITypeArray ThrownTypes) {
791   assert(getNonCompileUnitScope(Context) &&
792          "Methods should have both a Context and a context that isn't "
793          "the compile unit.");
794   // FIXME: Do we want to use different scope/lines?
795   bool IsDefinition = SPFlags & DISubprogram::SPFlagDefinition;
796   auto *SP = getSubprogram(
797       /*IsDistinct=*/IsDefinition, VMContext, cast<DIScope>(Context), Name,
798       LinkageName, F, LineNo, Ty, LineNo, VTableHolder, VIndex, ThisAdjustment,
799       Flags, SPFlags, IsDefinition ? CUNode : nullptr, TParams, nullptr,
800       nullptr, ThrownTypes);
801 
802   if (IsDefinition)
803     AllSubprograms.push_back(SP);
804   trackIfUnresolved(SP);
805   return SP;
806 }
807 
808 DICommonBlock *DIBuilder::createCommonBlock(
809     DIScope *Scope, DIGlobalVariable *Decl, StringRef Name, DIFile *File,
810     unsigned LineNo) {
811   return DICommonBlock::get(
812       VMContext, Scope, Decl, Name, File, LineNo);
813 }
814 
815 DINamespace *DIBuilder::createNameSpace(DIScope *Scope, StringRef Name,
816                                         bool ExportSymbols) {
817 
818   // It is okay to *not* make anonymous top-level namespaces distinct, because
819   // all nodes that have an anonymous namespace as their parent scope are
820   // guaranteed to be unique and/or are linked to their containing
821   // DICompileUnit. This decision is an explicit tradeoff of link time versus
822   // memory usage versus code simplicity and may get revisited in the future.
823   return DINamespace::get(VMContext, getNonCompileUnitScope(Scope), Name,
824                           ExportSymbols);
825 }
826 
827 DIModule *DIBuilder::createModule(DIScope *Scope, StringRef Name,
828                                   StringRef ConfigurationMacros,
829                                   StringRef IncludePath,
830                                   StringRef ISysRoot) {
831  return DIModule::get(VMContext, getNonCompileUnitScope(Scope), Name,
832                       ConfigurationMacros, IncludePath, ISysRoot);
833 }
834 
835 DILexicalBlockFile *DIBuilder::createLexicalBlockFile(DIScope *Scope,
836                                                       DIFile *File,
837                                                       unsigned Discriminator) {
838   return DILexicalBlockFile::get(VMContext, Scope, File, Discriminator);
839 }
840 
841 DILexicalBlock *DIBuilder::createLexicalBlock(DIScope *Scope, DIFile *File,
842                                               unsigned Line, unsigned Col) {
843   // Make these distinct, to avoid merging two lexical blocks on the same
844   // file/line/column.
845   return DILexicalBlock::getDistinct(VMContext, getNonCompileUnitScope(Scope),
846                                      File, Line, Col);
847 }
848 
849 Instruction *DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
850                                       DIExpression *Expr, const DILocation *DL,
851                                       Instruction *InsertBefore) {
852   return insertDeclare(Storage, VarInfo, Expr, DL, InsertBefore->getParent(),
853                        InsertBefore);
854 }
855 
856 Instruction *DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
857                                       DIExpression *Expr, const DILocation *DL,
858                                       BasicBlock *InsertAtEnd) {
859   // If this block already has a terminator then insert this intrinsic before
860   // the terminator. Otherwise, put it at the end of the block.
861   Instruction *InsertBefore = InsertAtEnd->getTerminator();
862   return insertDeclare(Storage, VarInfo, Expr, DL, InsertAtEnd, InsertBefore);
863 }
864 
865 Instruction *DIBuilder::insertLabel(DILabel *LabelInfo, const DILocation *DL,
866                                     Instruction *InsertBefore) {
867   return insertLabel(
868       LabelInfo, DL, InsertBefore ? InsertBefore->getParent() : nullptr,
869       InsertBefore);
870 }
871 
872 Instruction *DIBuilder::insertLabel(DILabel *LabelInfo, const DILocation *DL,
873                                     BasicBlock *InsertAtEnd) {
874   return insertLabel(LabelInfo, DL, InsertAtEnd, nullptr);
875 }
876 
877 Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V,
878                                                 DILocalVariable *VarInfo,
879                                                 DIExpression *Expr,
880                                                 const DILocation *DL,
881                                                 Instruction *InsertBefore) {
882   return insertDbgValueIntrinsic(
883       V, VarInfo, Expr, DL, InsertBefore ? InsertBefore->getParent() : nullptr,
884       InsertBefore);
885 }
886 
887 Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V,
888                                                 DILocalVariable *VarInfo,
889                                                 DIExpression *Expr,
890                                                 const DILocation *DL,
891                                                 BasicBlock *InsertAtEnd) {
892   return insertDbgValueIntrinsic(V, VarInfo, Expr, DL, InsertAtEnd, nullptr);
893 }
894 
895 /// Return an IRBuilder for inserting dbg.declare and dbg.value intrinsics. This
896 /// abstracts over the various ways to specify an insert position.
897 static IRBuilder<> getIRBForDbgInsertion(const DILocation *DL,
898                                          BasicBlock *InsertBB,
899                                          Instruction *InsertBefore) {
900   IRBuilder<> B(DL->getContext());
901   if (InsertBefore)
902     B.SetInsertPoint(InsertBefore);
903   else if (InsertBB)
904     B.SetInsertPoint(InsertBB);
905   B.SetCurrentDebugLocation(DL);
906   return B;
907 }
908 
909 static Value *getDbgIntrinsicValueImpl(LLVMContext &VMContext, Value *V) {
910   assert(V && "no value passed to dbg intrinsic");
911   return MetadataAsValue::get(VMContext, ValueAsMetadata::get(V));
912 }
913 
914 static Function *getDeclareIntrin(Module &M) {
915   return Intrinsic::getDeclaration(&M, UseDbgAddr ? Intrinsic::dbg_addr
916                                                   : Intrinsic::dbg_declare);
917 }
918 
919 Instruction *DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
920                                       DIExpression *Expr, const DILocation *DL,
921                                       BasicBlock *InsertBB, Instruction *InsertBefore) {
922   assert(VarInfo && "empty or invalid DILocalVariable* passed to dbg.declare");
923   assert(DL && "Expected debug loc");
924   assert(DL->getScope()->getSubprogram() ==
925              VarInfo->getScope()->getSubprogram() &&
926          "Expected matching subprograms");
927   if (!DeclareFn)
928     DeclareFn = getDeclareIntrin(M);
929 
930   trackIfUnresolved(VarInfo);
931   trackIfUnresolved(Expr);
932   Value *Args[] = {getDbgIntrinsicValueImpl(VMContext, Storage),
933                    MetadataAsValue::get(VMContext, VarInfo),
934                    MetadataAsValue::get(VMContext, Expr)};
935 
936   IRBuilder<> B = getIRBForDbgInsertion(DL, InsertBB, InsertBefore);
937   return B.CreateCall(DeclareFn, Args);
938 }
939 
940 Instruction *DIBuilder::insertDbgValueIntrinsic(
941     Value *V, DILocalVariable *VarInfo, DIExpression *Expr,
942     const DILocation *DL, BasicBlock *InsertBB, Instruction *InsertBefore) {
943   assert(V && "no value passed to dbg.value");
944   assert(VarInfo && "empty or invalid DILocalVariable* passed to dbg.value");
945   assert(DL && "Expected debug loc");
946   assert(DL->getScope()->getSubprogram() ==
947              VarInfo->getScope()->getSubprogram() &&
948          "Expected matching subprograms");
949   if (!ValueFn)
950     ValueFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_value);
951 
952   trackIfUnresolved(VarInfo);
953   trackIfUnresolved(Expr);
954   Value *Args[] = {getDbgIntrinsicValueImpl(VMContext, V),
955                    MetadataAsValue::get(VMContext, VarInfo),
956                    MetadataAsValue::get(VMContext, Expr)};
957 
958   IRBuilder<> B = getIRBForDbgInsertion(DL, InsertBB, InsertBefore);
959   return B.CreateCall(ValueFn, Args);
960 }
961 
962 Instruction *DIBuilder::insertLabel(
963     DILabel *LabelInfo, const DILocation *DL,
964     BasicBlock *InsertBB, Instruction *InsertBefore) {
965   assert(LabelInfo && "empty or invalid DILabel* passed to dbg.label");
966   assert(DL && "Expected debug loc");
967   assert(DL->getScope()->getSubprogram() ==
968              LabelInfo->getScope()->getSubprogram() &&
969          "Expected matching subprograms");
970   if (!LabelFn)
971     LabelFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_label);
972 
973   trackIfUnresolved(LabelInfo);
974   Value *Args[] = {MetadataAsValue::get(VMContext, LabelInfo)};
975 
976   IRBuilder<> B = getIRBForDbgInsertion(DL, InsertBB, InsertBefore);
977   return B.CreateCall(LabelFn, Args);
978 }
979 
980 void DIBuilder::replaceVTableHolder(DICompositeType *&T,
981                                     DIType *VTableHolder) {
982   {
983     TypedTrackingMDRef<DICompositeType> N(T);
984     N->replaceVTableHolder(VTableHolder);
985     T = N.get();
986   }
987 
988   // If this didn't create a self-reference, just return.
989   if (T != VTableHolder)
990     return;
991 
992   // Look for unresolved operands.  T will drop RAUW support, orphaning any
993   // cycles underneath it.
994   if (T->isResolved())
995     for (const MDOperand &O : T->operands())
996       if (auto *N = dyn_cast_or_null<MDNode>(O))
997         trackIfUnresolved(N);
998 }
999 
1000 void DIBuilder::replaceArrays(DICompositeType *&T, DINodeArray Elements,
1001                               DINodeArray TParams) {
1002   {
1003     TypedTrackingMDRef<DICompositeType> N(T);
1004     if (Elements)
1005       N->replaceElements(Elements);
1006     if (TParams)
1007       N->replaceTemplateParams(DITemplateParameterArray(TParams));
1008     T = N.get();
1009   }
1010 
1011   // If T isn't resolved, there's no problem.
1012   if (!T->isResolved())
1013     return;
1014 
1015   // If T is resolved, it may be due to a self-reference cycle.  Track the
1016   // arrays explicitly if they're unresolved, or else the cycles will be
1017   // orphaned.
1018   if (Elements)
1019     trackIfUnresolved(Elements.get());
1020   if (TParams)
1021     trackIfUnresolved(TParams.get());
1022 }
1023