xref: /freebsd/contrib/llvm-project/clang/lib/CrossTU/CrossTranslationUnit.cpp (revision d13def78ccef6dbc25c2e197089ee5fc4d7b82c3) 
1 //===--- CrossTranslationUnit.cpp - -----------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 //  This file implements the CrossTranslationUnit interface.
10 //
11 //===----------------------------------------------------------------------===//
12 #include "clang/CrossTU/CrossTranslationUnit.h"
13 #include "clang/AST/ASTImporter.h"
14 #include "clang/AST/Decl.h"
15 #include "clang/Basic/TargetInfo.h"
16 #include "clang/CrossTU/CrossTUDiagnostic.h"
17 #include "clang/Frontend/ASTUnit.h"
18 #include "clang/Frontend/CompilerInstance.h"
19 #include "clang/Frontend/TextDiagnosticPrinter.h"
20 #include "clang/Index/USRGeneration.h"
21 #include "llvm/ADT/Triple.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/ManagedStatic.h"
25 #include "llvm/Support/Path.h"
26 #include "llvm/Support/raw_ostream.h"
27 #include <fstream>
28 #include <sstream>
29 
30 namespace clang {
31 namespace cross_tu {
32 
33 namespace {
34 
35 #define DEBUG_TYPE "CrossTranslationUnit"
36 STATISTIC(NumGetCTUCalled, "The # of getCTUDefinition function called");
37 STATISTIC(
38     NumNotInOtherTU,
39     "The # of getCTUDefinition called but the function is not in any other TU");
40 STATISTIC(NumGetCTUSuccess,
41           "The # of getCTUDefinition successfully returned the "
42           "requested function's body");
43 STATISTIC(NumUnsupportedNodeFound, "The # of imports when the ASTImporter "
44                                    "encountered an unsupported AST Node");
45 STATISTIC(NumNameConflicts, "The # of imports when the ASTImporter "
46                             "encountered an ODR error");
47 STATISTIC(NumTripleMismatch, "The # of triple mismatches");
48 STATISTIC(NumLangMismatch, "The # of language mismatches");
49 STATISTIC(NumLangDialectMismatch, "The # of language dialect mismatches");
50 STATISTIC(NumASTLoadThresholdReached,
51           "The # of ASTs not loaded because of threshold");
52 
53 // Same as Triple's equality operator, but we check a field only if that is
54 // known in both instances.
55 bool hasEqualKnownFields(const llvm::Triple &Lhs, const llvm::Triple &Rhs) {
56   using llvm::Triple;
57   if (Lhs.getArch() != Triple::UnknownArch &&
58       Rhs.getArch() != Triple::UnknownArch && Lhs.getArch() != Rhs.getArch())
59     return false;
60   if (Lhs.getSubArch() != Triple::NoSubArch &&
61       Rhs.getSubArch() != Triple::NoSubArch &&
62       Lhs.getSubArch() != Rhs.getSubArch())
63     return false;
64   if (Lhs.getVendor() != Triple::UnknownVendor &&
65       Rhs.getVendor() != Triple::UnknownVendor &&
66       Lhs.getVendor() != Rhs.getVendor())
67     return false;
68   if (!Lhs.isOSUnknown() && !Rhs.isOSUnknown() &&
69       Lhs.getOS() != Rhs.getOS())
70     return false;
71   if (Lhs.getEnvironment() != Triple::UnknownEnvironment &&
72       Rhs.getEnvironment() != Triple::UnknownEnvironment &&
73       Lhs.getEnvironment() != Rhs.getEnvironment())
74     return false;
75   if (Lhs.getObjectFormat() != Triple::UnknownObjectFormat &&
76       Rhs.getObjectFormat() != Triple::UnknownObjectFormat &&
77       Lhs.getObjectFormat() != Rhs.getObjectFormat())
78     return false;
79   return true;
80 }
81 
82 // FIXME: This class is will be removed after the transition to llvm::Error.
83 class IndexErrorCategory : public std::error_category {
84 public:
85   const char *name() const noexcept override { return "clang.index"; }
86 
87   std::string message(int Condition) const override {
88     switch (static_cast<index_error_code>(Condition)) {
89     case index_error_code::unspecified:
90       return "An unknown error has occurred.";
91     case index_error_code::missing_index_file:
92       return "The index file is missing.";
93     case index_error_code::invalid_index_format:
94       return "Invalid index file format.";
95     case index_error_code::multiple_definitions:
96       return "Multiple definitions in the index file.";
97     case index_error_code::missing_definition:
98       return "Missing definition from the index file.";
99     case index_error_code::failed_import:
100       return "Failed to import the definition.";
101     case index_error_code::failed_to_get_external_ast:
102       return "Failed to load external AST source.";
103     case index_error_code::failed_to_generate_usr:
104       return "Failed to generate USR.";
105     case index_error_code::triple_mismatch:
106       return "Triple mismatch";
107     case index_error_code::lang_mismatch:
108       return "Language mismatch";
109     case index_error_code::lang_dialect_mismatch:
110       return "Language dialect mismatch";
111     case index_error_code::load_threshold_reached:
112       return "Load threshold reached";
113     }
114     llvm_unreachable("Unrecognized index_error_code.");
115   }
116 };
117 
118 static llvm::ManagedStatic<IndexErrorCategory> Category;
119 } // end anonymous namespace
120 
121 char IndexError::ID;
122 
123 void IndexError::log(raw_ostream &OS) const {
124   OS << Category->message(static_cast<int>(Code)) << '\n';
125 }
126 
127 std::error_code IndexError::convertToErrorCode() const {
128   return std::error_code(static_cast<int>(Code), *Category);
129 }
130 
131 llvm::Expected<llvm::StringMap<std::string>>
132 parseCrossTUIndex(StringRef IndexPath, StringRef CrossTUDir) {
133   std::ifstream ExternalMapFile(IndexPath);
134   if (!ExternalMapFile)
135     return llvm::make_error<IndexError>(index_error_code::missing_index_file,
136                                         IndexPath.str());
137 
138   llvm::StringMap<std::string> Result;
139   std::string Line;
140   unsigned LineNo = 1;
141   while (std::getline(ExternalMapFile, Line)) {
142     const size_t Pos = Line.find(" ");
143     if (Pos > 0 && Pos != std::string::npos) {
144       StringRef LineRef{Line};
145       StringRef LookupName = LineRef.substr(0, Pos);
146       if (Result.count(LookupName))
147         return llvm::make_error<IndexError>(
148             index_error_code::multiple_definitions, IndexPath.str(), LineNo);
149       StringRef FileName = LineRef.substr(Pos + 1);
150       SmallString<256> FilePath = CrossTUDir;
151       llvm::sys::path::append(FilePath, FileName);
152       Result[LookupName] = FilePath.str().str();
153     } else
154       return llvm::make_error<IndexError>(
155           index_error_code::invalid_index_format, IndexPath.str(), LineNo);
156     LineNo++;
157   }
158   return Result;
159 }
160 
161 std::string
162 createCrossTUIndexString(const llvm::StringMap<std::string> &Index) {
163   std::ostringstream Result;
164   for (const auto &E : Index)
165     Result << E.getKey().str() << " " << E.getValue() << '\n';
166   return Result.str();
167 }
168 
169 bool containsConst(const VarDecl *VD, const ASTContext &ACtx) {
170   CanQualType CT = ACtx.getCanonicalType(VD->getType());
171   if (!CT.isConstQualified()) {
172     const RecordType *RTy = CT->getAs<RecordType>();
173     if (!RTy || !RTy->hasConstFields())
174       return false;
175   }
176   return true;
177 }
178 
179 static bool hasBodyOrInit(const FunctionDecl *D, const FunctionDecl *&DefD) {
180   return D->hasBody(DefD);
181 }
182 static bool hasBodyOrInit(const VarDecl *D, const VarDecl *&DefD) {
183   return D->getAnyInitializer(DefD);
184 }
185 template <typename T> static bool hasBodyOrInit(const T *D) {
186   const T *Unused;
187   return hasBodyOrInit(D, Unused);
188 }
189 
190 CrossTranslationUnitContext::CrossTranslationUnitContext(CompilerInstance &CI)
191     : Context(CI.getASTContext()), ASTStorage(CI) {}
192 
193 CrossTranslationUnitContext::~CrossTranslationUnitContext() {}
194 
195 llvm::Optional<std::string>
196 CrossTranslationUnitContext::getLookupName(const NamedDecl *ND) {
197   SmallString<128> DeclUSR;
198   bool Ret = index::generateUSRForDecl(ND, DeclUSR);
199   if (Ret)
200     return {};
201   return std::string(DeclUSR.str());
202 }
203 
204 /// Recursively visits the decls of a DeclContext, and returns one with the
205 /// given USR.
206 template <typename T>
207 const T *
208 CrossTranslationUnitContext::findDefInDeclContext(const DeclContext *DC,
209                                                   StringRef LookupName) {
210   assert(DC && "Declaration Context must not be null");
211   for (const Decl *D : DC->decls()) {
212     const auto *SubDC = dyn_cast<DeclContext>(D);
213     if (SubDC)
214       if (const auto *ND = findDefInDeclContext<T>(SubDC, LookupName))
215         return ND;
216 
217     const auto *ND = dyn_cast<T>(D);
218     const T *ResultDecl;
219     if (!ND || !hasBodyOrInit(ND, ResultDecl))
220       continue;
221     llvm::Optional<std::string> ResultLookupName = getLookupName(ResultDecl);
222     if (!ResultLookupName || *ResultLookupName != LookupName)
223       continue;
224     return ResultDecl;
225   }
226   return nullptr;
227 }
228 
229 template <typename T>
230 llvm::Expected<const T *> CrossTranslationUnitContext::getCrossTUDefinitionImpl(
231     const T *D, StringRef CrossTUDir, StringRef IndexName,
232     bool DisplayCTUProgress) {
233   assert(D && "D is missing, bad call to this function!");
234   assert(!hasBodyOrInit(D) &&
235          "D has a body or init in current translation unit!");
236   ++NumGetCTUCalled;
237   const llvm::Optional<std::string> LookupName = getLookupName(D);
238   if (!LookupName)
239     return llvm::make_error<IndexError>(
240         index_error_code::failed_to_generate_usr);
241   llvm::Expected<ASTUnit *> ASTUnitOrError =
242       loadExternalAST(*LookupName, CrossTUDir, IndexName, DisplayCTUProgress);
243   if (!ASTUnitOrError)
244     return ASTUnitOrError.takeError();
245   ASTUnit *Unit = *ASTUnitOrError;
246   assert(&Unit->getFileManager() ==
247          &Unit->getASTContext().getSourceManager().getFileManager());
248 
249   const llvm::Triple &TripleTo = Context.getTargetInfo().getTriple();
250   const llvm::Triple &TripleFrom =
251       Unit->getASTContext().getTargetInfo().getTriple();
252   // The imported AST had been generated for a different target.
253   // Some parts of the triple in the loaded ASTContext can be unknown while the
254   // very same parts in the target ASTContext are known. Thus we check for the
255   // known parts only.
256   if (!hasEqualKnownFields(TripleTo, TripleFrom)) {
257     // TODO: Pass the SourceLocation of the CallExpression for more precise
258     // diagnostics.
259     ++NumTripleMismatch;
260     return llvm::make_error<IndexError>(index_error_code::triple_mismatch,
261                                         Unit->getMainFileName(), TripleTo.str(),
262                                         TripleFrom.str());
263   }
264 
265   const auto &LangTo = Context.getLangOpts();
266   const auto &LangFrom = Unit->getASTContext().getLangOpts();
267 
268   // FIXME: Currenty we do not support CTU across C++ and C and across
269   // different dialects of C++.
270   if (LangTo.CPlusPlus != LangFrom.CPlusPlus) {
271     ++NumLangMismatch;
272     return llvm::make_error<IndexError>(index_error_code::lang_mismatch);
273   }
274 
275   // If CPP dialects are different then return with error.
276   //
277   // Consider this STL code:
278   //   template<typename _Alloc>
279   //     struct __alloc_traits
280   //   #if __cplusplus >= 201103L
281   //     : std::allocator_traits<_Alloc>
282   //   #endif
283   //     { // ...
284   //     };
285   // This class template would create ODR errors during merging the two units,
286   // since in one translation unit the class template has a base class, however
287   // in the other unit it has none.
288   if (LangTo.CPlusPlus11 != LangFrom.CPlusPlus11 ||
289       LangTo.CPlusPlus14 != LangFrom.CPlusPlus14 ||
290       LangTo.CPlusPlus17 != LangFrom.CPlusPlus17 ||
291       LangTo.CPlusPlus2a != LangFrom.CPlusPlus2a) {
292     ++NumLangDialectMismatch;
293     return llvm::make_error<IndexError>(
294         index_error_code::lang_dialect_mismatch);
295   }
296 
297   TranslationUnitDecl *TU = Unit->getASTContext().getTranslationUnitDecl();
298   if (const T *ResultDecl = findDefInDeclContext<T>(TU, *LookupName))
299     return importDefinition(ResultDecl, Unit);
300   return llvm::make_error<IndexError>(index_error_code::failed_import);
301 }
302 
303 llvm::Expected<const FunctionDecl *>
304 CrossTranslationUnitContext::getCrossTUDefinition(const FunctionDecl *FD,
305                                                   StringRef CrossTUDir,
306                                                   StringRef IndexName,
307                                                   bool DisplayCTUProgress) {
308   return getCrossTUDefinitionImpl(FD, CrossTUDir, IndexName,
309                                   DisplayCTUProgress);
310 }
311 
312 llvm::Expected<const VarDecl *>
313 CrossTranslationUnitContext::getCrossTUDefinition(const VarDecl *VD,
314                                                   StringRef CrossTUDir,
315                                                   StringRef IndexName,
316                                                   bool DisplayCTUProgress) {
317   return getCrossTUDefinitionImpl(VD, CrossTUDir, IndexName,
318                                   DisplayCTUProgress);
319 }
320 
321 void CrossTranslationUnitContext::emitCrossTUDiagnostics(const IndexError &IE) {
322   switch (IE.getCode()) {
323   case index_error_code::missing_index_file:
324     Context.getDiagnostics().Report(diag::err_ctu_error_opening)
325         << IE.getFileName();
326     break;
327   case index_error_code::invalid_index_format:
328     Context.getDiagnostics().Report(diag::err_extdefmap_parsing)
329         << IE.getFileName() << IE.getLineNum();
330     break;
331   case index_error_code::multiple_definitions:
332     Context.getDiagnostics().Report(diag::err_multiple_def_index)
333         << IE.getLineNum();
334     break;
335   case index_error_code::triple_mismatch:
336     Context.getDiagnostics().Report(diag::warn_ctu_incompat_triple)
337         << IE.getFileName() << IE.getTripleToName() << IE.getTripleFromName();
338     break;
339   default:
340     break;
341   }
342 }
343 
344 CrossTranslationUnitContext::ASTFileLoader::ASTFileLoader(
345     const CompilerInstance &CI)
346     : CI(CI) {}
347 
348 std::unique_ptr<ASTUnit>
349 CrossTranslationUnitContext::ASTFileLoader::operator()(StringRef ASTFilePath) {
350   // Load AST from ast-dump.
351   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
352   TextDiagnosticPrinter *DiagClient =
353       new TextDiagnosticPrinter(llvm::errs(), &*DiagOpts);
354   IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
355   IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
356       new DiagnosticsEngine(DiagID, &*DiagOpts, DiagClient));
357 
358   return ASTUnit::LoadFromASTFile(
359       ASTFilePath, CI.getPCHContainerOperations()->getRawReader(),
360       ASTUnit::LoadEverything, Diags, CI.getFileSystemOpts());
361 }
362 
363 CrossTranslationUnitContext::ASTUnitStorage::ASTUnitStorage(
364     const CompilerInstance &CI)
365     : FileAccessor(CI), LoadGuard(const_cast<CompilerInstance &>(CI)
366                                       .getAnalyzerOpts()
367                                       ->CTUImportThreshold) {}
368 
369 llvm::Expected<ASTUnit *>
370 CrossTranslationUnitContext::ASTUnitStorage::getASTUnitForFile(
371     StringRef FileName, bool DisplayCTUProgress) {
372   // Try the cache first.
373   auto ASTCacheEntry = FileASTUnitMap.find(FileName);
374   if (ASTCacheEntry == FileASTUnitMap.end()) {
375 
376     // Do not load if the limit is reached.
377     if (!LoadGuard) {
378       ++NumASTLoadThresholdReached;
379       return llvm::make_error<IndexError>(
380           index_error_code::load_threshold_reached);
381     }
382 
383     // Load the ASTUnit from the pre-dumped AST file specified by ASTFileName.
384     std::unique_ptr<ASTUnit> LoadedUnit = FileAccessor(FileName);
385 
386     // Need the raw pointer and the unique_ptr as well.
387     ASTUnit *Unit = LoadedUnit.get();
388 
389     // Update the cache.
390     FileASTUnitMap[FileName] = std::move(LoadedUnit);
391 
392     LoadGuard.indicateLoadSuccess();
393 
394     if (DisplayCTUProgress)
395       llvm::errs() << "CTU loaded AST file: " << FileName << "\n";
396 
397     return Unit;
398 
399   } else {
400     // Found in the cache.
401     return ASTCacheEntry->second.get();
402   }
403 }
404 
405 llvm::Expected<ASTUnit *>
406 CrossTranslationUnitContext::ASTUnitStorage::getASTUnitForFunction(
407     StringRef FunctionName, StringRef CrossTUDir, StringRef IndexName,
408     bool DisplayCTUProgress) {
409   // Try the cache first.
410   auto ASTCacheEntry = NameASTUnitMap.find(FunctionName);
411   if (ASTCacheEntry == NameASTUnitMap.end()) {
412     // Load the ASTUnit from the pre-dumped AST file specified by ASTFileName.
413 
414     // Ensure that the Index is loaded, as we need to search in it.
415     if (llvm::Error IndexLoadError =
416             ensureCTUIndexLoaded(CrossTUDir, IndexName))
417       return std::move(IndexLoadError);
418 
419     // Check if there is and entry in the index for the function.
420     if (!NameFileMap.count(FunctionName)) {
421       ++NumNotInOtherTU;
422       return llvm::make_error<IndexError>(index_error_code::missing_definition);
423     }
424 
425     // Search in the index for the filename where the definition of FuncitonName
426     // resides.
427     if (llvm::Expected<ASTUnit *> FoundForFile =
428             getASTUnitForFile(NameFileMap[FunctionName], DisplayCTUProgress)) {
429 
430       // Update the cache.
431       NameASTUnitMap[FunctionName] = *FoundForFile;
432       return *FoundForFile;
433 
434     } else {
435       return FoundForFile.takeError();
436     }
437   } else {
438     // Found in the cache.
439     return ASTCacheEntry->second;
440   }
441 }
442 
443 llvm::Expected<std::string>
444 CrossTranslationUnitContext::ASTUnitStorage::getFileForFunction(
445     StringRef FunctionName, StringRef CrossTUDir, StringRef IndexName) {
446   if (llvm::Error IndexLoadError = ensureCTUIndexLoaded(CrossTUDir, IndexName))
447     return std::move(IndexLoadError);
448   return NameFileMap[FunctionName];
449 }
450 
451 llvm::Error CrossTranslationUnitContext::ASTUnitStorage::ensureCTUIndexLoaded(
452     StringRef CrossTUDir, StringRef IndexName) {
453   // Dont initialize if the map is filled.
454   if (!NameFileMap.empty())
455     return llvm::Error::success();
456 
457   // Get the absolute path to the index file.
458   SmallString<256> IndexFile = CrossTUDir;
459   if (llvm::sys::path::is_absolute(IndexName))
460     IndexFile = IndexName;
461   else
462     llvm::sys::path::append(IndexFile, IndexName);
463 
464   if (auto IndexMapping = parseCrossTUIndex(IndexFile, CrossTUDir)) {
465     // Initialize member map.
466     NameFileMap = *IndexMapping;
467     return llvm::Error::success();
468   } else {
469     // Error while parsing CrossTU index file.
470     return IndexMapping.takeError();
471   };
472 }
473 
474 llvm::Expected<ASTUnit *> CrossTranslationUnitContext::loadExternalAST(
475     StringRef LookupName, StringRef CrossTUDir, StringRef IndexName,
476     bool DisplayCTUProgress) {
477   // FIXME: The current implementation only supports loading decls with
478   //        a lookup name from a single translation unit. If multiple
479   //        translation units contains decls with the same lookup name an
480   //        error will be returned.
481 
482   // Try to get the value from the heavily cached storage.
483   llvm::Expected<ASTUnit *> Unit = ASTStorage.getASTUnitForFunction(
484       LookupName, CrossTUDir, IndexName, DisplayCTUProgress);
485 
486   if (!Unit)
487     return Unit.takeError();
488 
489   // Check whether the backing pointer of the Expected is a nullptr.
490   if (!*Unit)
491     return llvm::make_error<IndexError>(
492         index_error_code::failed_to_get_external_ast);
493 
494   return Unit;
495 }
496 
497 template <typename T>
498 llvm::Expected<const T *>
499 CrossTranslationUnitContext::importDefinitionImpl(const T *D, ASTUnit *Unit) {
500   assert(hasBodyOrInit(D) && "Decls to be imported should have body or init.");
501 
502   assert(&D->getASTContext() == &Unit->getASTContext() &&
503          "ASTContext of Decl and the unit should match.");
504   ASTImporter &Importer = getOrCreateASTImporter(Unit);
505 
506   auto ToDeclOrError = Importer.Import(D);
507   if (!ToDeclOrError) {
508     handleAllErrors(ToDeclOrError.takeError(),
509                     [&](const ImportError &IE) {
510                       switch (IE.Error) {
511                       case ImportError::NameConflict:
512                         ++NumNameConflicts;
513                          break;
514                       case ImportError::UnsupportedConstruct:
515                         ++NumUnsupportedNodeFound;
516                         break;
517                       case ImportError::Unknown:
518                         llvm_unreachable("Unknown import error happened.");
519                         break;
520                       }
521                     });
522     return llvm::make_error<IndexError>(index_error_code::failed_import);
523   }
524   auto *ToDecl = cast<T>(*ToDeclOrError);
525   assert(hasBodyOrInit(ToDecl) && "Imported Decl should have body or init.");
526   ++NumGetCTUSuccess;
527 
528   return ToDecl;
529 }
530 
531 llvm::Expected<const FunctionDecl *>
532 CrossTranslationUnitContext::importDefinition(const FunctionDecl *FD,
533                                               ASTUnit *Unit) {
534   return importDefinitionImpl(FD, Unit);
535 }
536 
537 llvm::Expected<const VarDecl *>
538 CrossTranslationUnitContext::importDefinition(const VarDecl *VD,
539                                               ASTUnit *Unit) {
540   return importDefinitionImpl(VD, Unit);
541 }
542 
543 void CrossTranslationUnitContext::lazyInitImporterSharedSt(
544     TranslationUnitDecl *ToTU) {
545   if (!ImporterSharedSt)
546     ImporterSharedSt = std::make_shared<ASTImporterSharedState>(*ToTU);
547 }
548 
549 ASTImporter &
550 CrossTranslationUnitContext::getOrCreateASTImporter(ASTUnit *Unit) {
551   ASTContext &From = Unit->getASTContext();
552 
553   auto I = ASTUnitImporterMap.find(From.getTranslationUnitDecl());
554   if (I != ASTUnitImporterMap.end())
555     return *I->second;
556   lazyInitImporterSharedSt(Context.getTranslationUnitDecl());
557   ASTImporter *NewImporter = new ASTImporter(
558       Context, Context.getSourceManager().getFileManager(), From,
559       From.getSourceManager().getFileManager(), false, ImporterSharedSt);
560   NewImporter->setFileIDImportHandler([this, Unit](FileID ToID, FileID FromID) {
561     assert(ImportedFileIDs.find(ToID) == ImportedFileIDs.end() &&
562            "FileID already imported, should not happen.");
563     ImportedFileIDs[ToID] = std::make_pair(FromID, Unit);
564   });
565   ASTUnitImporterMap[From.getTranslationUnitDecl()].reset(NewImporter);
566   return *NewImporter;
567 }
568 
569 llvm::Optional<std::pair<SourceLocation, ASTUnit *>>
570 CrossTranslationUnitContext::getImportedFromSourceLocation(
571     const clang::SourceLocation &ToLoc) const {
572   const SourceManager &SM = Context.getSourceManager();
573   auto DecToLoc = SM.getDecomposedLoc(ToLoc);
574 
575   auto I = ImportedFileIDs.find(DecToLoc.first);
576   if (I == ImportedFileIDs.end())
577     return {};
578 
579   FileID FromID = I->second.first;
580   clang::ASTUnit *Unit = I->second.second;
581   SourceLocation FromLoc =
582       Unit->getSourceManager().getComposedLoc(FromID, DecToLoc.second);
583 
584   return std::make_pair(FromLoc, Unit);
585 }
586 
587 } // namespace cross_tu
588 } // namespace clang
589