Fix SourceFileName when loading the FunctionInfoIndex from bitcode.

[mehdi_amini]

Summary

We need to use the SourceFileName recorded in the bitcode, and not the "identifier" of the buffer.

[mehdi_amini]

Nahhh that's wrong, forget it.

lib/Bitcode/Reader/BitcodeReader.cpp

       std::unique_ptr<FunctionSummary> FS = llvm::make_unique<FunctionSummary>(
           getDecodedLinkage(RawLinkage), InstCount);
       // The module path string ref set in the summary must be owned by the
       // index's module string table. Since we don't have a module path
       // string table section in the per-module index, we create a single
       // module path string table entry with an empty (0) ID to take
       // ownership.
       FS->setModulePath(
-          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0));
+          TheIndex->addModulePath(SourceFileName, 0));
       static int RefListStartIndex = 4;
       int CallGraphEdgeStartIndex = RefListStartIndex + NumRefs;
       assert(Record.size() >= RefListStartIndex + NumRefs &&
              "Record size inconsistent with number of references");
       for (unsigned I = 4, E = CallGraphEdgeStartIndex; I != E; ++I) {
         unsigned RefValueId = Record[I];
         uint64_t RefGUID = getGUIDFromValueId(RefValueId);
         FS->addRefEdge(RefGUID);

     }
     // FS_PERMODULE_GLOBALVAR_INIT_REFS: [valueid, linkage, n x valueid]
     case bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS: {
       unsigned ValueID = Record[0];
       uint64_t RawLinkage = Record[1];
       std::unique_ptr<GlobalVarSummary> FS =
           llvm::make_unique<GlobalVarSummary>(getDecodedLinkage(RawLinkage));
       FS->setModulePath(
-          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0));
+          TheIndex->addModulePath(SourceFileName, 0));
       for (unsigned I = 2, E = Record.size(); I != E; ++I) {
         unsigned RefValueId = Record[I];
         uint64_t RefGUID = getGUIDFromValueId(RefValueId);
         FS->addRefEdge(RefGUID);
       }
       uint64_t GUID = getGUIDFromValueId(ValueID);
       auto InfoList = TheIndex->findGlobalValueInfoList(GUID);
       assert(InfoList != TheIndex->end() &&