[LLD][COFF] Generate import modules in PDB

[aganea]

Summary

This patch makes LLD generate a PDB with import modules & coff groups.
This is suitable for hot patching tools like Recode and Live++, which need to extract this information from the PDB. We're using this patch on several productions for a few months now.

---

We generate one debug symbol stream for each imported dll:

                          Streams
============================================================
[...]
  Stream 10 ( 256 bytes): [Module "Import:pdb-publics-import.test.tmp1.dll"]
             Blocks: [9]

We generate two modules for each imported dll:
(currently the first module is empty because llvm-lib does not generate the additional symbol stream, and some descriptors are not imported (remains TODO)

                        Module Stats
============================================================
[...]
Mod 0001 | `pdb-publics-import.test.tmp1.dll`:
  Mod 1 (debug info not present): [pdb-publics-import.test.tmp1.dll]
Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
  Stream 10, 256 bytes

    Symbols
                                       Total:       8 entries (     248 bytes)
    --------------------------------------------------------------------------
                                   S_THUNK32:       2 entries (      72 bytes)
                                       S_END:       2 entries (       8 bytes)
                                   S_OBJNAME:       2 entries (      88 bytes)
                                  S_COMPILE3:       2 entries (      80 bytes)

    Chunks
                                       Total:       0 entries (       0 bytes)
    --------------------------------------------------------------------------

We ensure the modules' first contrib section is properly set (65535 values):

                          Modules
============================================================
[...]
Mod 0001 | `pdb-publics-import.test.tmp1.dll`:
SC[???]  | mod = 65535, 65535:0000, size = -1, data crc = 0, reloc crc = 0
        none
Obj: `F:\svn\build2\tools\lld\test\COFF\Output\pdb-publics-import.test.tmp1.lib`:
debug stream: 65535, # files: 0, has ec info: false
pdb file ni: 0 ``, src file ni: 0 ``
Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
SC[.text]  | mod = 2, 0001:0032, size = 6, data crc = 0, reloc crc = 0
        IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ
Obj: `F:\svn\build2\tools\lld\test\COFF\Output\pdb-publics-import.test.tmp1.lib`:
debug stream: 10, # files: 0, has ec info: false
pdb file ni: 0 ``, src file ni: 0 ``

We generate proper symbol streams for each import module, in the same way as link.exe:

                          Symbols
============================================================
[...]
Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
     4 | S_OBJNAME [size = 44] sig=0, `pdb-publics-import.test.tmp1.dll`
    48 | S_COMPILE3 [size = 40]
         machine = intel x86-x64, Ver = LLVM Linker, language = link
         frontend = 0.0.0.0, backend = 14.10.25019.0
         flags = none
    88 | S_THUNK32 [size = 36] `exportfn1`
         parent = 0, end = 124, next = 0
         kind = thunk, size = 6, addr = 0001:0016
   124 | S_END [size = 4]
   128 | S_OBJNAME [size = 44] sig=0, `pdb-publics-import.test.tmp1.dll`
   172 | S_COMPILE3 [size = 40]
         machine = intel x86-x64, Ver = LLVM Linker, language = link
         frontend = 0.0.0.0, backend = 14.10.25019.0
         flags = none
   212 | S_THUNK32 [size = 36] `exportfn2`
         parent = 0, end = 248, next = 0
         kind = thunk, size = 6, addr = 0001:0032
   248 | S_END [size = 4]

And we also generate COFF groups in the * Linker * section, out from PartialSections (that is, unmerged sections).
(there's a subtly here: the .idata$XXX COFF groups have the "write" flag set, whereas the corresponding .idata section does not have it - this is what link.exe does)

Mod 0003 | `* Linker *`:
[...]
   588 | S_SECTION [size = 28] `.text`
         length = 38, alignment = 12, rva = 4096, section # = 1
         characteristics =
           code
           execute permissions
           read permissions
   616 | S_COFFGROUP [size = 24] `.text`
         length = 8, addr = 0001:0000
         characteristics =
           code
           execute permissions
           read permissions
   640 | S_SECTION [size = 28] `.rdata`
         length = 61, alignment = 12, rva = 8192, section # = 2
         characteristics =
           initialized data
           read permissions
   668 | S_SECTION [size = 28] `.idata`
         length = 145, alignment = 12, rva = 12288, section # = 3
         characteristics =
           initialized data
           read permissions
   696 | S_COFFGROUP [size = 28] `.idata$2`
         length = 40, addr = 0003:0000
         characteristics =
           initialized data
           read permissions
           write permissions
   724 | S_COFFGROUP [size = 28] `.idata$4`
         length = 24, addr = 0003:0040
         characteristics =
           initialized data
           read permissions
           write permissions
   752 | S_COFFGROUP [size = 28] `.idata$5`
         length = 24, addr = 0003:0064
         characteristics =
           initialized data
           read permissions
           write permissions
   780 | S_COFFGROUP [size = 28] `.idata$6`
         length = 24, addr = 0003:0088
         characteristics =
           initialized data
           read permissions
           write permissions
   808 | S_COFFGROUP [size = 28] `.idata$7`
         length = 33, addr = 0003:0112
         characteristics =
           initialized data
           read permissions
           write permissions

[aganea]

Please note this work was started from Stefan Reinalter's D49230 and D49231. We agreed offline with Stefan that I will finish those patches.

[aganea]

The file below shows the remaining differences betwen link and lld-link (with this patch). I've modified lld\test\COFF\Output\pdb-publics-import.test to use link.exe instead of lld-link.exe

pdb-publics-import-compare.zip16 KBDownload

[zturner]

Do you happen to know what these are used for? I'm ok with supporting them just for the sake of compatibility, but it's always nice to know "if these aren't present, X won't work"

[aganea]

In D54802#1305448, @zturner wrote:

Do you happen to know what these are used for? I'm ok with supporting them just for the sake of compatibility, but it's always nice to know "if these aren't present, X won't work"

Some edit-and-continue tools rely on this: Recode and Live++. These tools need to extract and repro the linking with the EXE/PDB alone. They need this information for recompiling TUs that change, and hot patch the process in memory.

[aganea]

This all boils down to iterativity. Using the tools I've mentionned above allows for really quick iterations, when you need to change small bits of code. When you're iterating over some gameplay or UI code, for example.
Without these tools, for testing any small change, you need to: compile the TU, link the whole EXE, start it, load the game map, and do a walkthrough until you're at the right position in the game world. This can take more than 10 minutes.
With these edit-and-continue tools, you don't shut down the game. The player remains at the same position in the game. You simply change the code, the tool applies the changes, and that's it. You can go for hundreds of iterations like this. Live++ even allows the game to save/reload data structures, which means that you can change pretty much anything in the code, including class definitions.

[rnk]

Cool. :)

lld/trunk/COFF/Driver.cpp

1226 ↗

(On Diff #174923)

Do you want to submit this separately? It seems to cause wide ranging mechanical changes to the tests. Feel free to submit it without review.

lld/trunk/COFF/Writer.cpp

758–760 ↗

(On Diff #174923)

This seems like it's really just replicating Map into some longer lived data structure, and then creating a backreference from the output section to the concatenated input section. There are three other helper functions that take a reference to Map, and that type is ridiculously long. I think we could clean this code up significantly if we planned some NFC changes first to make Map a member of Writer and then give it a real key and value type. WDYT? I'm imagining that the type would become: std::map<NameAndChars, InputSection>

That would have the side effect of cleaning up a lot of unreadable Pair.second and Pair.first.first accesses in this code.

Honestly I started looking at this at first just because we copy the Chunks vector again, and I was wondering if that could be avoided, especially for a no-PDB build...

[pcc]

lld/trunk/COFF/Driver.cpp

1226 ↗

(On Diff #174923)

Are you sure that this is what link.exe does? I'm pretty sure I added this here after noticing that this was what link.exe did, see D45737

[aganea]

After further testing, in some scenarios this patch doesn't seem to be enough for Recode to work. I'll pause this patch and follow up with Will (@lantictac) to ensure everything is covered.

lld/trunk/COFF/Driver.cpp

1226 ↗

(On Diff #174923)

import-tests.zip46 KBDownload

@pcc: Please see the zip file above for comparing the output from different linkers.

I figured out a few more things with link.exe along the way:

• S_TRAMPOLINE records are used for jump thunks when incremental linking is active. Of course this makes the produced EXE to execute slower because there are missed function inlining oportunities.
• The * Linker * module has a section contribution in .idata only when incremental linking is specified. Otherwise, there's no contrib section, only a debug stream.
• There's a lot more .text padding (CCCCCC) around functions when incremental linking is active.
• More importantly, link.exe folds .idata sections into .rdata only when /INCREMENTAL:NO is specified. Given that /INCREMENTAL is the default, I thought we should do the same in LLD. I would need to disable that behavior when providing /INCREMENTAL:NO (not in this patch yet).

Doc and defaults for /INCREMENTAL are here.

lld/trunk/COFF/Writer.cpp

758–760 ↗

(On Diff #174923)

Agreed. Will do that.

[aganea]

Actually, the question about folding .idata into .rdata remains open. Should we follow the same behavior as link.exe or not, to reduce variability in the output?

[rnk]

In D54802#1309701, @aganea wrote:

Actually, the question about folding .idata into .rdata remains open. Should we follow the same behavior as link.exe or not, to reduce variability in the output?

I don't think we intend to support incremental linking, so I'd just fold idata into rdata by default as we do now.

[aganea]

In D54802#1309791, @rnk wrote:

I don't think we intend to support incremental linking, so I'd just fold idata into rdata by default as we do now.

I'd say incremental linking is the only major hurdle for widespread LLD adoption on industrial sites. Like we discussed at the LLVM conf., I agree that EXEs/DLLs shouldn't be incrementally linked. But what about incremental PDB generation?

For our typical gameplay developement loop, for a DLL target, this is what we currently see:

  Input File Reading:          1847 ms (  3.7%)
  Code Layout:                  579 ms (  1.2%)
  PDB Emission (Cumulative):  43468 ms ( 87.8%)
    Add Objects:              33074 ms ( 66.8%)
      Type Merging:           28276 ms ( 57.1%)
      Symbol Merging:          4748 ms (  9.6%)
    TPI Stream Layout:         1487 ms (  3.0%)
    Globals Stream Layout:     1789 ms (  3.6%)
    Commit to Disk:            5981 ms ( 12.1%)
  Commit Output File:          2837 ms (  5.7%)
-------------------------------------------------
Total Link Time:              49494 ms (100.0%)

That is for the biggest DLL in the game, and inherently the one that programmers iterate the most on:

-- DLL: 182 MB
-- PDB: 930 MB
-- Merged OBJs: 179 (no GHASH, OBJs are from cl.exe; these are unity/blob .cpp files)
-- Inserted type records: 91,573,186
-- Final unique type records: 3,578,658 (hash table size: 8,388,608)
-- TypeTable.RecordStorage: 1,639,715,884 bytes allocated

For the same thing, link.exe /INCREMENTAL takes about 3 sec to relink any change. If we could at least do the Type/Symbol passes incrementally, that would be a major win.

[aganea]

Sorry that was the wrong timings - that was for MSVC-built LLD. With Clang 7.0 things are a bit better in reality:

  Input File Reading:          1658 ms (  4.7%)
  Code Layout:                  621 ms (  1.8%)
  PDB Emission (Cumulative):  30380 ms ( 86.7%)
    Add Objects:              22615 ms ( 64.6%)
      Type Merging:           19205 ms ( 54.8%)
      Symbol Merging:          3385 ms (  9.7%)
    TPI Stream Layout:          897 ms (  2.6%)
    Globals Stream Layout:     1418 ms (  4.1%)
    Commit to Disk:            4559 ms ( 13.0%)
  Commit Output File:          1717 ms (  4.9%)
-------------------------------------------------
Total Link Time:              35021 ms (100.0%)

I noticed by the way that the default cmake config for Clang/LLVM/LLD comes with /INCREMENTAL and /MD (dll CRT) active. This causes a lot of thunking. I changed that to /INCREMENTAL:NO and /MT and things are a lot better - I'll send another review for that.

[rnk]

In D54802#1311401, @aganea wrote:

  Input File Reading:          1658 ms (  4.7%)
  Code Layout:                  621 ms (  1.8%)
  PDB Emission (Cumulative):  30380 ms ( 86.7%)
    Add Objects:              22615 ms ( 64.6%)
      Type Merging:           19205 ms ( 54.8%)
      Symbol Merging:          3385 ms (  9.7%)
    TPI Stream Layout:          897 ms (  2.6%)
    Globals Stream Layout:     1418 ms (  4.1%)
    Commit to Disk:            4559 ms ( 13.0%)
  Commit Output File:          1717 ms (  4.9%)
-------------------------------------------------
Total Link Time:              35021 ms (100.0%)

I think we can optimize copying symbols using the same techniques we've used for optimizing LLD. Symbol records are pretty straightforward: You figure out which .debug$S sections are live, relocate them, process them a bit, and copy the bytes to the PDB in some order. In D54554 I did some work, and that cuts down the "Commit Output File" (13%) and "Symbol Merging" times, but there may be more things to do.

For types, I think this is one of the classic problems where you make a hash table and say "it's O(1) insertion" but really it's order "length of key", and probably with a high constant factor. I think if we looked at the distribution of type record sizes, we'd see a few categories like this:

1. Small records, < 20bytes, i.e. less than a SHA-1, like pointer types, qualified (const/volatile) types, array types, function types, etc. Merging theses in the linker should be cheap, ghash or no ghash.
2. Records with names, like LF_STRUCTURE and LF_PROC_ID. C++ mangled names can get long, but they probably aren't 64K, the max CV record length, bytes long. Think ~4KB.
3. Long field lists. LF_FIELDLIST is a bear. I expect on average most field lists are 32KB plus, since they include the name of every field, method, and typedef. Templates tend to have lots of members, many of which are unused in most instantiations.

The other thing to keep in mind is that type hash table "hits" are common. Most types are duplicates. Given some 64KB field list record, you can expect it will be deduplicated O(#objects) times. Without the content hash, this means you have to memcmp the entire 64KB for every duplicate. With the hash, you do O(length of hash) work, so a 8 or 20 byte memcmp. I think that's where the real ghash gains are coming from. I'm not sure what to do with that information, but it seems like a useful insight.

One thing we talked about a while ago was trying to parallelize type merging. I think the challenge there is it requires a good concurrent hash map implementation, which we'd have to find or implement ourselves.

[thakis]

lld/trunk/COFF/PDB.cpp

1533 ↗

(On Diff #174923)

This regresses PDBs being independent of the build directory, cf r344061

[aganea]

In D54802#1311943, @rnk wrote:

I think the challenge there is it requires a good concurrent hash map implementation, which we'd have to find or implement ourselves.

I can provide that, we have a good lockless, insert-only, DenseHash implemention that we have been using for many years.

Although the issue at stake here is the high memory bandwith, due to the large volume of data to process in a tight loop. Like you are pointing out, GHash uses a smaller key size (8 bytes) which packs more entries per cache line (instead of the {hash, ArrayRef<U8>} key (24 bytes) when GHash isn’t used). I’m not entierely sure multithreading will help a lot, but we can give it a try. Packing more tightly the data in the DenseHash, and avoiding indirections at all cost would probably benefit more in the short term.

lld/trunk/COFF/PDB.cpp

1533 ↗

(On Diff #174923)

Thanks for pointing out!

[mstorsjo]

lld/trunk/test/COFF/hello32.test

60 ↗

(On Diff #174923)

I didn't read the whole patch in detail, but can you give a TL;DR about what's added to the output files in the case when no PDB output is enabled, that shuffles some sections forward now?

[aganea]

I still need to work on this patch. I'll mark it as pending in the meanwhile.

lld/trunk/test/COFF/hello32.test

60 ↗

(On Diff #174923)

Please see lld/trunk/COFF/Driver.cpp, L1226, I initially removed parseMerge(".idata=.rdata");

And the comment above:
"More importantly, link.exe folds .idata sections into .rdata only when /INCREMENTAL:NO is specified. Given that /INCREMENTAL is the default, I thought we should do the same in LLD. I would need to disable that behavior when providing /INCREMENTAL:NO (not in this patch yet)."

However, it was decided that we'll keep the current .idata merging behavior for now.

[mstorsjo]

lld/trunk/test/COFF/hello32.test

60 ↗

(On Diff #174923)

Ok, I see. Thanks!

[aganea]

Simplify & addressed comments.

I took the liberty to remove COFF groups from the MinGW target. This was adding a significant footprint to the PDB, given that each function is in its own .text section.
As an additionnal side-effect, MinGW PDBs are now much smaller, because we don't emit empty debug streams anymore.

As an example, using Martin's test package, I generated libqt_plugin.pdb:

trunk			21 MB
	coff groups	import modules	27.1 MB
(this patch)	no coff groups	import modules	13.5 MB
	no coff groups	no import modules	13.3 MB

The impact is less significat in non-MinGW, on a 1 GB PDB this patch adds 2 MB and scales with the size (actually depends on the number of imported libraries).

[rnk]

lld/trunk/COFF/PDB.cpp

1111 ↗

(On Diff #190888)

Is this relevant to this change?

1566 ↗

(On Diff #190888)

DllModSet, maybe? DllToModuleDbi?

1584–1586 ↗

(On Diff #190888)

Usually we use Twine to avoid the cost of concatenating strings used for debugging purposes, like names for instructions that aren't used in release mode, or log statements. In this case, I think you can use plain old std::string, something like addModuleInfo(std::string("Import:") + File->DLLName. With that simplification, I think the lambda is unnecessary.

llvm/trunk/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp

40–50 ↗

(On Diff #190888)

I don't see the change to add this method to the class in this patch. Was this change intended to be part of this review? It seems unnecessary for import files.

[aganea]

lld/trunk/COFF/PDB.cpp

1111 ↗

(On Diff #190888)

Yes, I think we can remove that comment now, unless @zturner says otherwise.

llvm/trunk/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp

40–50 ↗

(On Diff #190888)

I indeed forgot an include file from the diff. But you're right, this is for supporting empty streams, I should maybe do that in another patch.

[aganea]

Rebased, reduced & adressed comments.

[santagada]

Anything missing for this to be accepted? It seems like this patch is ready.

[rnk]

lgtm, thanks!

In D54802#1440864, @santagada wrote:

Anything missing for this to be accepted? It seems like this patch is ready.

I just missed the update, sorry.

COFF/Writer.cpp

307

Needs wrapping

COFF/Driver.cpp

else
       Driver->addBuffer(std::move(MBOrErr.first), WholeArchive);
   });
 }
 
 void LinkerDriver::addArchiveBuffer(MemoryBufferRef MB, StringRef SymName,
                                     StringRef ParentName) {
   file_magic Magic = identify_magic(MB.getBuffer());
   if (Magic == file_magic::coff_import_library) {
-    Symtab->addFile(make<ImportFile>(MB));
+    InputFile *Imp = make<ImportFile>(MB);
+    Imp->ParentName = ParentName;
+    Symtab->addFile(Imp);
     return;
   }
 
   InputFile *Obj;
   if (Magic == file_magic::coff_object) {
     Obj = make<ObjFile>(MB);
   } else if (Magic == file_magic::bitcode) {
     Obj = make<BitcodeFile>(MB);

COFF/InputFiles.cpp

 static StringRef getBasename(StringRef Path) {
   return sys::path::filename(Path, sys::path::Style::windows);
 }
 
 // Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
 std::string lld::toString(const coff::InputFile *File) {
   if (!File)
     return "<internal>";
-  if (File->ParentName.empty())
+  if (File->ParentName.empty() || File->kind() == coff::InputFile::ImportKind)
     return File->getName();
 
   return (getBasename(File->ParentName) + "(" + getBasename(File->getName()) +
           ")")
       .str();
 }

COFF/PDB.cpp

public:
   void initialize(llvm::codeview::DebugInfo *BuildId);
 
   /// Add natvis files specified on the command line.
   void addNatvisFiles();
 
   /// Link CodeView from each object file in the symbol table into the PDB.
   void addObjectsToPDB();
 
+  /// Link info for each import file in the symbol table into the PDB.
+  void addImportFilesToPDB(ArrayRef<OutputSection *> OutputSections);
+
   /// Link CodeView from a single object file into the target (output) PDB.
   /// When a precompiled headers object is linked, its TPI map might be provided
   /// externally.
   void addObjFile(ObjFile *File, CVIndexMap *ExternIndexMap = nullptr);
 
   /// Produce a mapping from the type and item indices used in the object
   /// file to those in the destination PDB.
   ///
static void scopeStackOpen(SmallVectorImpl<SymbolScope> &Stack,
   S.ScopeOffset = CurOffset;
   S.OpeningRecord = const_cast<ScopeRecord *>(
       reinterpret_cast<const ScopeRecord *>(Sym.content().data()));
   S.OpeningRecord->PtrParent = Stack.empty() ? 0 : Stack.back().ScopeOffset;
   Stack.push_back(S);
 }
 
 static void scopeStackClose(SmallVectorImpl<SymbolScope> &Stack,
-                            uint32_t CurOffset, ObjFile *File) {
+                            uint32_t CurOffset, InputFile *File) {
   if (Stack.empty()) {
     warn("symbol scopes are not balanced in " + File->getName());
     return;
   }
   SymbolScope S = Stack.pop_back_val();
   S.OpeningRecord->PtrEnd = CurOffset;
 }
 
if (auto *SecChunk = dyn_cast_or_null<SectionChunk>(C)) {
     ArrayRef<uint8_t> Contents = SecChunk->getContents();
     JamCRC CRC(0);
     ArrayRef<char> CharContents = makeArrayRef(
         reinterpret_cast<const char *>(Contents.data()), Contents.size());
     CRC.update(CharContents);
     SC.DataCrc = CRC.getCRC();
   } else {
     SC.Characteristics = OS ? OS->Header.Characteristics : 0;
-    // FIXME: When we start creating DBI for import libraries, use those here.
     SC.Imod = Modi;
   }
   SC.RelocCrc = 0; // FIXME
 
   return SC;
 }
 
 static uint32_t
if (HasQ) {
       R.append(A);
     }
     if (HasWS || HasQ)
       R.push_back('"');
   }
   return R;
 }
 
-static void addCommonLinkerModuleSymbols(StringRef Path,
-                                         pdb::DbiModuleDescriptorBuilder &Mod,
-                                         BumpPtrAllocator &Allocator) {
-  ObjNameSym ONS(SymbolRecordKind::ObjNameSym);
-  Compile3Sym CS(SymbolRecordKind::Compile3Sym);
-  EnvBlockSym EBS(SymbolRecordKind::EnvBlockSym);
-
-  ONS.Name = "* Linker *";
-  ONS.Signature = 0;
-
+static void fillLinkerVerRecord(Compile3Sym &CS) {
   CS.Machine = toCodeViewMachine(Config->Machine);
   // Interestingly, if we set the string to 0.0.0.0, then when trying to view
   // local variables WinDbg emits an error that private symbols are not present.
   // By setting this to a valid MSVC linker version string, local variables are
   // displayed properly.   As such, even though it is not representative of
   // LLVM's version information, we need this for compatibility.
   CS.Flags = CompileSym3Flags::None;
   CS.VersionBackendBuild = 25019;
   CS.VersionBackendMajor = 14;
   CS.VersionBackendMinor = 10;
   CS.VersionBackendQFE = 0;
 
   // MSVC also sets the frontend to 0.0.0.0 since this is specifically for the
   // linker module (which is by definition a backend), so we don't need to do
   // anything here.  Also, it seems we can use "LLVM Linker" for the linker name
   // without any problems.  Only the backend version has to be hardcoded to a
   // magic number.
   CS.VersionFrontendBuild = 0;
   CS.VersionFrontendMajor = 0;
   CS.VersionFrontendMinor = 0;
   CS.VersionFrontendQFE = 0;
   CS.Version = "LLVM Linker";
   CS.setLanguage(SourceLanguage::Link);
+}
+
+static void addCommonLinkerModuleSymbols(StringRef Path,
+                                         pdb::DbiModuleDescriptorBuilder &Mod,
+                                         BumpPtrAllocator &Allocator) {
+  ObjNameSym ONS(SymbolRecordKind::ObjNameSym);
+  EnvBlockSym EBS(SymbolRecordKind::EnvBlockSym);
+  Compile3Sym CS(SymbolRecordKind::Compile3Sym);
+  fillLinkerVerRecord(CS);
+
+  ONS.Name = "* Linker *";
+  ONS.Signature = 0;
 
   ArrayRef<StringRef> Args = makeArrayRef(Config->Argv).drop_front();
   std::string ArgStr = quote(Args);
   EBS.Fields.push_back("cwd");
   SmallString<64> cwd;
   if (Config->PDBSourcePath.empty())
     sys::fs::current_path(cwd);
   else
static void addCommonLinkerModuleSymbols(StringRef Path,
   Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       ONS, Allocator, CodeViewContainer::Pdb));
   Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       CS, Allocator, CodeViewContainer::Pdb));
   Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       EBS, Allocator, CodeViewContainer::Pdb));
 }
 
+static void addLinkerModuleCoffGroup(PartialSection *Sec,
+                                     pdb::DbiModuleDescriptorBuilder &Mod,
+                                     OutputSection &OS,
+                                     BumpPtrAllocator &Allocator) {
+  // If there's a section, there's at least one chunk
+  assert(!Sec->Chunks.empty());
+  const Chunk *firstChunk = *Sec->Chunks.begin();
+  const Chunk *lastChunk = *Sec->Chunks.rbegin();
+
+  // Emit COFF group
+  CoffGroupSym CGS(SymbolRecordKind::CoffGroupSym);
+  CGS.Name = Sec->Name;
+  CGS.Segment = OS.SectionIndex;
+  CGS.Offset = firstChunk->getRVA() - OS.getRVA();
+  CGS.Size = lastChunk->getRVA() + lastChunk->getSize() - firstChunk->getRVA();
+  CGS.Characteristics = Sec->Characteristics;
+
+  // Somehow .idata sections & sections groups in the debug symbol stream have
+  // the "write" flag set. However the section header for the corresponding
+  // .idata section doesn't have it.
+  if (CGS.Name.startswith(".idata"))
+    CGS.Characteristics |= llvm::COFF::IMAGE_SCN_MEM_WRITE;
+
+  Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
+      CGS, Allocator, CodeViewContainer::Pdb));
+}
+
 static void addLinkerModuleSectionSymbol(pdb::DbiModuleDescriptorBuilder &Mod,
                                          OutputSection &OS,
                                          BumpPtrAllocator &Allocator) {
   SectionSym Sym(SymbolRecordKind::SectionSym);
   Sym.Alignment = 12; // 2^12 = 4KB
   Sym.Characteristics = OS.Header.Characteristics;
   Sym.Length = OS.getVirtualSize();
   Sym.Name = OS.Name;
   Sym.Rva = OS.getRVA();
   Sym.SectionNumber = OS.SectionIndex;
   Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       Sym, Allocator, CodeViewContainer::Pdb));
+
+  // Skip COFF groups in MinGW because it adds a significant footprint to the
+  // PDB, due to each function being in its own section
+  if (Config->MinGW)
+    return;
+
+  // Output COFF groups for individual chunks of this section.
+  for (PartialSection *Sec : OS.ContribSections) {
+    addLinkerModuleCoffGroup(Sec, Mod, OS, Allocator);
+  }
+}
+
+// Add all import files as modules to the PDB.
+void PDBLinker::addImportFilesToPDB(ArrayRef<OutputSection *> OutputSections) {
+  if (ImportFile::Instances.empty())
+    return;
+
+  std::map<std::string, llvm::pdb::DbiModuleDescriptorBuilder *> DllToModuleDbi;
+
+  for (ImportFile *File : ImportFile::Instances) {
+    if (!File->Live)
+      continue;
+
+    if (!File->ThunkSym)
+      continue;
+
+    std::string DLL = StringRef(File->DLLName).lower();
+    llvm::pdb::DbiModuleDescriptorBuilder *&Mod = DllToModuleDbi[DLL];
+    if (!Mod) {
+      pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
+      SmallString<128> LibPath = File->ParentName;
+      pdbMakeAbsolute(LibPath);
+      sys::path::native(LibPath);
+
+      // Name modules similar to MSVC's link.exe.
+      // The first module is the simple dll filename
+      llvm::pdb::DbiModuleDescriptorBuilder &FirstMod =
+          ExitOnErr(DbiBuilder.addModuleInfo(File->DLLName));
+      FirstMod.setObjFileName(LibPath);
+      pdb::SectionContrib SC =
+          createSectionContrib(nullptr, llvm::pdb::kInvalidStreamIndex);
+      FirstMod.setFirstSectionContrib(SC);
+
+      // The second module is where the import stream goes.
+      Mod = &ExitOnErr(DbiBuilder.addModuleInfo("Import:" + File->DLLName));
+      Mod->setObjFileName(LibPath);
+    }
+
+    DefinedImportThunk *Thunk = cast<DefinedImportThunk>(File->ThunkSym);
+
+    ObjNameSym ONS(SymbolRecordKind::ObjNameSym);
+    Compile3Sym CS(SymbolRecordKind::Compile3Sym);
+    Thunk32Sym TS(SymbolRecordKind::Thunk32Sym);
+    ScopeEndSym ES(SymbolRecordKind::ScopeEndSym);
+
+    ONS.Name = File->DLLName;
+    ONS.Signature = 0;
+
+    fillLinkerVerRecord(CS);
+
+    TS.Name = Thunk->getName();
+    TS.Parent = 0;
+    TS.End = 0;
+    TS.Next = 0;
+    TS.Thunk = ThunkOrdinal::Standard;
+    TS.Length = Thunk->getChunk()->getSize();
+    TS.Segment = Thunk->getChunk()->getOutputSection()->SectionIndex;
+    TS.Offset = Thunk->getChunk()->OutputSectionOff;
+
+    Mod->addSymbol(codeview::SymbolSerializer::writeOneSymbol(
+        ONS, Alloc, CodeViewContainer::Pdb));
+    Mod->addSymbol(codeview::SymbolSerializer::writeOneSymbol(
+        CS, Alloc, CodeViewContainer::Pdb));
+
+    SmallVector<SymbolScope, 4> Scopes;
+    CVSymbol NewSym = codeview::SymbolSerializer::writeOneSymbol(
+        TS, Alloc, CodeViewContainer::Pdb);
+    scopeStackOpen(Scopes, Mod->getNextSymbolOffset(), NewSym);
+
+    Mod->addSymbol(NewSym);
+
+    NewSym = codeview::SymbolSerializer::writeOneSymbol(ES, Alloc,
+                                                        CodeViewContainer::Pdb);
+    scopeStackClose(Scopes, Mod->getNextSymbolOffset(), File);
+
+    Mod->addSymbol(NewSym);
+
+    pdb::SectionContrib SC =
+        createSectionContrib(Thunk->getChunk(), Mod->getModuleIndex());
+    Mod->setFirstSectionContrib(SC);
+  }
 }
 
 // Creates a PDB file.
 void coff::createPDB(SymbolTable *Symtab,
                      ArrayRef<OutputSection *> OutputSections,
                      ArrayRef<uint8_t> SectionTable,
                      llvm::codeview::DebugInfo *BuildId) {
   ScopedTimer T1(TotalPdbLinkTimer);
   PDBLinker PDB(Symtab);
 
   PDB.initialize(BuildId);
   PDB.addObjectsToPDB();
+  PDB.addImportFilesToPDB(OutputSections);
   PDB.addSections(OutputSections, SectionTable);
   PDB.addNatvisFiles();
 
   ScopedTimer T2(DiskCommitTimer);
   codeview::GUID Guid;
   PDB.commit(&Guid);
   memcpy(&BuildId->PDB70.Signature, &Guid, 16);
 

COFF/Writer.h

 #include <vector>
 
 namespace lld {
 namespace coff {
 static const int PageSize = 4096;
 
 void writeResult();
 
+class PartialSection {
+public:
+  PartialSection(StringRef N, uint32_t Chars)
+      : Name(N), Characteristics(Chars) {}
+  StringRef Name;
+  unsigned Characteristics;
+  std::vector<Chunk *> Chunks;
+};
+
 // OutputSection represents a section in an output file. It's a
 // container of chunks. OutputSection and Chunk are 1:N relationship.
 // Chunks cannot belong to more than one OutputSections. The writer
 // creates multiple OutputSections and assign them unique,
 // non-overlapping file offsets and RVAs.
 class OutputSection {
 public:
   OutputSection(llvm::StringRef N, uint32_t Chars) : Name(N) {
     Header.Characteristics = Chars;
   }
   void addChunk(Chunk *C);
   void insertChunkAtStart(Chunk *C);
   void merge(OutputSection *Other);
   void setPermissions(uint32_t C);
   uint64_t getRVA() { return Header.VirtualAddress; }
   uint64_t getFileOff() { return Header.PointerToRawData; }
   void writeHeaderTo(uint8_t *Buf);
+  void addContributingPartialSection(PartialSection *Sec);
 
   // Returns the size of this section in an executable memory image.
   // This may be smaller than the raw size (the raw size is multiple
   // of disk sector size, so there may be padding at end), or may be
   // larger (if that's the case, the loader reserves spaces after end
   // of raw data).
   uint64_t getVirtualSize() { return Header.VirtualSize; }
 
   // Returns the size of the section in the output file.
   uint64_t getRawSize() { return Header.SizeOfRawData; }
 
   // Set offset into the string table storing this section name.
   // Used only when the name is longer than 8 bytes.
   void setStringTableOff(uint32_t V) { StringTableOff = V; }
 
   // N.B. The section index is one based.
   uint32_t SectionIndex = 0;
 
   llvm::StringRef Name;
   llvm::object::coff_section Header = {};
 
   std::vector<Chunk *> Chunks;
   std::vector<Chunk *> OrigChunks;
 
+  std::vector<PartialSection *> ContribSections;
+
 private:
   uint32_t StringTableOff = 0;
 };
 
-}
-}
+} // namespace coff
+} // namespace lld
 
 #endif

COFF/Writer.cpp

bool operator<(const PartialSectionKey &Other) const {
     if (C == 1)
       return false;
     if (C == 0)
       return Characteristics < Other.Characteristics;
     return true;
   }
 };
 
-class PartialSection {
-public:
-  PartialSection(StringRef N, uint32_t Chars)
-      : Name(N), Characteristics(Chars) {}
-  StringRef Name;
-  unsigned Characteristics;
-  std::vector<Chunk *> Chunks;
-};
-
 // The writer writes a SymbolTable result to a file.
 class Writer {
 public:
   Writer() : Buffer(errorHandler().OutputBuffer) {}
   void run();
 
 private:
   void createSections();
void OutputSection::setPermissions(uint32_t C) {
   Header.Characteristics |= C;
 }
 
 void OutputSection::merge(OutputSection *Other) {
   for (Chunk *C : Other->Chunks)
     C->setOutputSection(this);
   Chunks.insert(Chunks.end(), Other->Chunks.begin(), Other->Chunks.end());
   Other->Chunks.clear();
+  ContribSections.insert(ContribSections.end(), Other->ContribSections.begin(), Other->ContribSections.end());
+  Other->ContribSections.clear();
 }
 
 // Write the section header to a given buffer.
 void OutputSection::writeHeaderTo(uint8_t *Buf) {
   auto *Hdr = reinterpret_cast<coff_section *>(Buf);
   *Hdr = Header;
   if (StringTableOff) {
     // If name is too long, write offset into the string table as a name.
     sprintf(Hdr->Name, "/%d", StringTableOff);
   } else {
     assert(!Config->Debug || Name.size() <= COFF::NameSize ||
            (Hdr->Characteristics & IMAGE_SCN_MEM_DISCARDABLE) == 0);
     strncpy(Hdr->Name, Name.data(),
             std::min(Name.size(), (size_t)COFF::NameSize));
   }
 }
 
+void OutputSection::addContributingPartialSection(PartialSection *Sec) {
+  ContribSections.push_back(Sec);
+}
+
 } // namespace coff
 } // namespace lld
 
 // Check whether the target address S is in range from a relocation
 // of type RelType at address P.
 static bool isInRange(uint16_t RelType, uint64_t S, uint64_t P, int Margin) {
   if (Config->Machine == ARMNT) {
     int64_t Diff = AbsoluteDifference(S, P + 4) + Margin;
if (Name == ".CRT") {
       log("Processing section " + PSec->Name + " -> " + Name);
 
       sortCRTSectionChunks(PSec->Chunks);
     }
 
     OutputSection *Sec = CreateSection(Name, OutChars);
     for (Chunk *C : PSec->Chunks)
       Sec->addChunk(C);
+
+    Sec->addContributingPartialSection(PSec);
   }
 
   // Finally, move some output sections to the end.
   auto SectionOrder = [&](OutputSection *S) {
     // Move DISCARDABLE (or non-memory-mapped) sections to the end of file because
     // the loader cannot handle holes. Stripping can remove other discardable ones
     // than .reloc, which is first of them (created early).
     if (S->Header.Characteristics & IMAGE_SCN_MEM_DISCARDABLE)

test/COFF/pdb-publics-import.test

 Make a DLL that exports a few functions, then make a DLL with PDBs that imports
 them. Check that the __imp_ pointer and the generated thunks appear in the
 publics stream.
 
 RUN: yaml2obj < %p/Inputs/export.yaml > %t1.obj
 RUN: lld-link /out:%t1.dll /dll %t1.obj /implib:%t1.lib \
 RUN:   /export:exportfn1 /export:exportfn2
 RUN: yaml2obj < %p/Inputs/import.yaml > %t2.obj
 RUN: lld-link /out:%t2.exe /pdb:%t2.pdb /pdbaltpath:test.pdb \
 RUN:   /debug /entry:main %t2.obj %t1.lib
-RUN: llvm-pdbutil dump %t2.pdb -publics -section-contribs | FileCheck %s
+RUN: llvm-pdbutil dump %t2.pdb -all | FileCheck %s
+
+CHECK:                             Streams
+CHECK-NEXT: ============================================================
+CHECK-LABEL:   Stream 10 ( 256 bytes): [Module "Import:pdb-publics-import.test.tmp1.dll"]
+
+CHECK:                         Module Stats
+CHECK-NEXT: ============================================================
+CHECK-NEXT: Mod 0000 | `{{.*}}pdb-publics-import.test.tmp2.obj`:
+CHECK-NEXT:   Mod 0 (debug info not present): [{{.*}}pdb-publics-import.test.tmp2.obj]
+CHECK-NEXT: Mod 0001 | `pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT:   Mod 1 (debug info not present): [pdb-publics-import.test.tmp1.dll]
+CHECK-NEXT: Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT:   Stream 10, 256 bytes
+
+CHECK:                           Modules
+CHECK-NEXT: ============================================================
+CHECK-NEXT:   Mod 0000 | `{{.*}}pdb-publics-import.test.tmp2.obj`:
+CHECK-NEXT:   SC[.text]  | mod = 0, 0001:0000, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:           IMAGE_SCN_CNT_CODE | IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_MEM_EXECUTE |
+CHECK-NEXT:           IMAGE_SCN_MEM_READ
+CHECK-NEXT:   Obj: `{{.*}}pdb-publics-import.test.tmp2.obj`:
+CHECK-NEXT:   debug stream: 65535, # files: 0, has ec info: false
+CHECK-NEXT:   pdb file ni: 0 ``, src file ni: 0 ``
+CHECK-NEXT: Mod 0001 | `pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT: SC[???]  | mod = 65535, 65535:0000, size = -1, data crc = 0, reloc crc = 0
+CHECK-NEXT:         none
+CHECK-NEXT: Obj: `{{.*}}pdb-publics-import.test.tmp1.lib`:
+CHECK-NEXT: debug stream: 65535, # files: 0, has ec info: false
+CHECK-NEXT: pdb file ni: 0 ``, src file ni: 0 ``
+CHECK-NEXT: Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT: SC[.text]  | mod = 2, 0001:0032, size = 6, data crc = 0, reloc crc = 0
+CHECK-NEXT:         IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ
+CHECK-NEXT: Obj: `{{.*}}pdb-publics-import.test.tmp1.lib`:
+CHECK-NEXT: debug stream: 10, # files: 0, has ec info: false
+CHECK-NEXT: pdb file ni: 0 ``, src file ni: 0 ``
+CHECK-NEXT: Mod 0003 | `* Linker *`:
+CHECK-NEXT: SC[???]  | mod = 65535, 65535:0000, size = -1, data crc = 0, reloc crc = 0
+CHECK-NEXT:         none
+CHECK-NEXT: Obj: ``:
+CHECK-NEXT: debug stream: 11, # files: 0, has ec info: false
+CHECK-NEXT: pdb file ni: 1 `{{.*}}pdb-publics-import.test.tmp2.pdb`, src file ni: 0 ``
 
 CHECK:                             Public Symbols
 CHECK-NEXT: ============================================================
 CHECK-NEXT:    Records
 CHECK-NEXT:      112 | S_PUB32 [size = 20] `main`
 CHECK-NEXT:            flags = function, addr = 0001:0000
 CHECK-NEXT:       64 | S_PUB32 [size = 24] `exportfn1`
 CHECK-NEXT:            flags = function, addr = 0001:0016
 CHECK-NEXT:       88 | S_PUB32 [size = 24] `exportfn2`
 CHECK-NEXT:            flags = function, addr = 0001:0032
 CHECK-NEXT:       32 | S_PUB32 [size = 32] `__imp_exportfn2`
 CHECK-NEXT:            flags = none, addr = 0002:0136
 CHECK-NEXT:        0 | S_PUB32 [size = 32] `__imp_exportfn1`
 CHECK-NEXT:            flags = none, addr = 0002:0128
 
+CHECK:                           Symbols
+CHECK-NEXT: ============================================================
+CHECK-NEXT:   Mod 0000 | `{{.*}}pdb-publics-import.test.tmp2.obj`:
+CHECK-NEXT:   Error loading module stream 0.  The specified stream could not be loaded. Module stream not present
+CHECK-NEXT: Mod 0001 | `pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT: Error loading module stream 1.  The specified stream could not be loaded. Module stream not present
+CHECK-NEXT: Mod 0002 | `Import:pdb-publics-import.test.tmp1.dll`:
+CHECK-NEXT:      4 | S_OBJNAME [size = 44] sig=0, `pdb-publics-import.test.tmp1.dll`
+CHECK-NEXT:     48 | S_COMPILE3 [size = 40]
+CHECK-NEXT:          machine = intel x86-x64, Ver = LLVM Linker, language = link
+CHECK-NEXT:          frontend = 0.0.0.0, backend = 14.10.25019.0
+CHECK-NEXT:          flags = none
+CHECK-NEXT:     88 | S_THUNK32 [size = 36] `exportfn1`
+CHECK-NEXT:          parent = 0, end = 124, next = 0
+CHECK-NEXT:          kind = thunk, size = 6, addr = 0001:0016
+CHECK-NEXT:    124 | S_END [size = 4]
+CHECK-NEXT:    128 | S_OBJNAME [size = 44] sig=0, `pdb-publics-import.test.tmp1.dll`
+CHECK-NEXT:    172 | S_COMPILE3 [size = 40]
+CHECK-NEXT:          machine = intel x86-x64, Ver = LLVM Linker, language = link
+CHECK-NEXT:          frontend = 0.0.0.0, backend = 14.10.25019.0
+CHECK-NEXT:          flags = none
+CHECK-NEXT:    212 | S_THUNK32 [size = 36] `exportfn2`
+CHECK-NEXT:          parent = 0, end = 248, next = 0
+CHECK-NEXT:          kind = thunk, size = 6, addr = 0001:0032
+CHECK-NEXT:    248 | S_END [size = 4]
+CHECK-NEXT: Mod 0003 | `* Linker *`:
+CHECK-NEXT:      4 | S_OBJNAME [size = 20] sig=0, `* Linker *`
+CHECK-NEXT:     24 | S_COMPILE3 [size = 40]
+CHECK-NEXT:          machine = intel x86-x64, Ver = LLVM Linker, language = link
+CHECK-NEXT:          frontend = 0.0.0.0, backend = 14.10.25019.0
+CHECK-NEXT:          flags = none
+CHECK-NEXT:     64 | S_ENVBLOCK [size = {{[0-9]+}}]
+CHECK:  {{[0-9]+}} | S_SECTION [size = 28] `.text`
+CHECK-NEXT:          length = 38, alignment = 12, rva = 4096, section # = 1
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            code
+CHECK-NEXT:            execute permissions
+CHECK-NEXT:            read permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 24] `.text`
+CHECK-NEXT:          length = 8, addr = 0001:0000
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            code
+CHECK-NEXT:            execute permissions
+CHECK-NEXT:            read permissions
+CHECK-NEXT: {{[0-9]+}} | S_SECTION [size = 28] `.rdata`
+CHECK-NEXT:          length = 209, alignment = 12, rva = 8192, section # = 2
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 28] `.idata$2`
+CHECK-NEXT:          length = 40, addr = 0002:0061
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT:            write permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 28] `.idata$4`
+CHECK-NEXT:          length = 24, addr = 0002:0104
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT:            write permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 28] `.idata$5`
+CHECK-NEXT:          length = 24, addr = 0002:0128
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT:            write permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 28] `.idata$6`
+CHECK-NEXT:          length = 24, addr = 0002:0152
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT:            write permissions
+CHECK-NEXT: {{[0-9]+}} | S_COFFGROUP [size = 28] `.idata$7`
+CHECK-NEXT:          length = 33, addr = 0002:0176
+CHECK-NEXT:          characteristics =
+CHECK-NEXT:            initialized data
+CHECK-NEXT:            read permissions
+CHECK-NEXT:            write permissions
+
 CHECK:                         Section Contributions
 CHECK-NEXT: ============================================================
     main
 CHECK-NEXT:   SC[.text]   | mod = 0, 0001:0000, size = 8, data crc = 0, reloc crc = 0
 CHECK-NEXT:                 IMAGE_SCN_CNT_CODE | IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_MEM_EXECUTE |
 CHECK-NEXT:                 IMAGE_SCN_MEM_READ
     exportfn1 thunk
-CHECK-NEXT:   SC[.text]   | mod = 1, 0001:0016, size = 6, data crc = 0, reloc crc = 0
+CHECK-NEXT:   SC[.text]   | mod = 3, 0001:0016, size = 6, data crc = 0, reloc crc = 0
 CHECK-NEXT:                 IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ
     exportfn2 thunk
-CHECK-NEXT:   SC[.text]   | mod = 1, 0001:0032, size = 6, data crc = 0, reloc crc = 0
+CHECK-NEXT:   SC[.text]   | mod = 3, 0001:0032, size = 6, data crc = 0, reloc crc = 0
 CHECK-NEXT:                 IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ
     .rdata debug directory data chunks
-CHECK-NEXT:   SC[.rdata]  | mod = 1, 0002:0000, size = 28, data crc = 0, reloc crc = 0
-CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
-CHECK-NEXT:   SC[.rdata]  | mod = 1, 0002:0028, size = 33, data crc = 0, reloc crc = 0
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0000, size = 28, data crc = 0, reloc crc = 0
 CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0028, size = 33, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0061, size = 20, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0081, size = 20, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0104, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0112, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0120, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0128, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0136, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0144, size = 8, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0152, size = 12, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0164, size = 12, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+CHECK-NEXT:   SC[.rdata]  | mod = 3, 0002:0176, size = 33, data crc = 0, reloc crc = 0
+CHECK-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ