[lld] Fix type server merging with PDBs without IPI stream

[CyberShadow]

Summary

PDBs may not necessarily contain an IPI stream. Handle this case
gracefully.

The test case was verified to work with MS link.exe.

[rnk]

lgtm

I can apply this and do the requested code golf simplification if you like, but I just wanted to confirm that's OK with you. Thanks for the patch!

lld/COFF/PDB.cpp

475–480

Maybe we should have an Optional<pdb::TpiStream &> MaybeIpi variable that we check before passing it into the two mergeIdRecords so we don't have to repeat this error handling code.

[CyberShadow]

Yes, of course. Good idea. Thank you!

lld/COFF/PDB.cpp

if (!It.second)
     return IndexMap; // already merged
 
   // Mark this map as a type server map.
   IndexMap.IsTypeServerMap = true;
 
   Expected<pdb::TpiStream &> ExpectedTpi = PDBFile.getPDBTpiStream();
   if (auto E = ExpectedTpi.takeError())
     fatal("Type server does not have TPI stream: " + toString(std::move(E)));
-  Expected<pdb::TpiStream &> ExpectedIpi = PDBFile.getPDBIpiStream();
-  if (auto E = ExpectedIpi.takeError())
-    fatal("Type server does not have TPI stream: " + toString(std::move(E)));
 
   if (Config->DebugGHashes) {
     // PDBs do not actually store global hashes, so when merging a type server
     // PDB we have to synthesize global hashes.  To do this, we first synthesize
     // global hashes for the TPI stream, since it is independent, then we
     // synthesize hashes for the IPI stream, using the hashes for the TPI stream
     // as inputs.
     auto TpiHashes = GloballyHashedType::hashTypes(ExpectedTpi->typeArray());
-    auto IpiHashes =
-        GloballyHashedType::hashIds(ExpectedIpi->typeArray(), TpiHashes);
 
     Optional<uint32_t> EndPrecomp;
     // Merge TPI first, because the IPI stream will reference type indices.
     if (auto Err =
             mergeTypeRecords(TMerger.GlobalTypeTable, IndexMap.TPIMap,
                              ExpectedTpi->typeArray(), TpiHashes, EndPrecomp))
       fatal("codeview::mergeTypeRecords failed: " + toString(std::move(Err)));
 
     // Merge IPI.
+    if (PDBFile.hasPDBIpiStream()) {
+      Expected<pdb::TpiStream &> ExpectedIpi = PDBFile.getPDBIpiStream();
+      if (auto E = ExpectedIpi.takeError())
+        fatal("Error getting type server IPI stream: " +
+              toString(std::move(E)));
+
+      auto IpiHashes =
+          GloballyHashedType::hashIds(ExpectedIpi->typeArray(), TpiHashes);
+
       if (auto Err = mergeIdRecords(TMerger.GlobalIDTable, IndexMap.TPIMap,
                                     IndexMap.IPIMap, ExpectedIpi->typeArray(),
                                     IpiHashes))
         fatal("codeview::mergeIdRecords failed: " + toString(std::move(Err)));
+    }
   } else {
     // Merge TPI first, because the IPI stream will reference type indices.
     if (auto Err = mergeTypeRecords(TMerger.TypeTable, IndexMap.TPIMap,
                                     ExpectedTpi->typeArray()))
       fatal("codeview::mergeTypeRecords failed: " + toString(std::move(Err)));
 
     // Merge IPI.
+    if (PDBFile.hasPDBIpiStream()) {
+      Expected<pdb::TpiStream &> ExpectedIpi = PDBFile.getPDBIpiStream();
+      if (auto E = ExpectedIpi.takeError())
+        fatal("Error getting type server IPI stream: " +
+              toString(std::move(E)));
+
       if (auto Err = mergeIdRecords(TMerger.IDTable, IndexMap.TPIMap,
                                     IndexMap.IPIMap, ExpectedIpi->typeArray()))
         fatal("codeview::mergeIdRecords failed: " + toString(std::move(Err)));
     }
+  }
 
   return IndexMap;
 }
 
 Error PDBLinker::mergeInPrecompHeaderObj(ObjFile *File,
                                          CVIndexMap *ObjectIndexMap) {
   const PrecompRecord &Precomp =
       retrieveDependencyInfo<PrecompRecord>(File->DebugTypesObj);

lld/test/COFF/Inputs/no-ipi-stream-obj.obj.yaml

+--- !COFF
+header:          
+  Machine:         IMAGE_FILE_MACHINE_I386
+sections:        
+  - Name:            '.debug$T'
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+    Types:           
+      - Kind:            LF_TYPESERVER2
+        TypeServer2:     
+          Guid:            '{01234567-0123-0123-0123-0123456789AB}'
+          Age:             1
+          Name:            'no-ipi-stream-pdb.pdb'
+symbols:         

lld/test/COFF/Inputs/no-ipi-stream-pdb.pdb.yaml

+PdbStream:       
+  Guid:            '{01234567-0123-0123-0123-0123456789AB}'

lld/test/COFF/no-ipi-stream.test

+# RUN: rm -rf %t && mkdir %t
+# RUN: yaml2obj < %p/Inputs/no-ipi-stream-obj.obj.yaml > %t/no-ipi-stream-obj.obj
+# RUN: llvm-pdbutil yaml2pdb %p/Inputs/no-ipi-stream-pdb.pdb.yaml -pdb=%t/no-ipi-stream-pdb.pdb
+# RUN: lld-link /dll /noentry /debug %t/no-ipi-stream-obj.obj