[ThinLTO][Bitcode] Generate import type in bitcode (#87600)

For distributed ThinLTO, the LTO indexing step generates combined
summary for each module, and postlink pipeline reads the combined
summary which stores the information for link-time optimization.

This patch populates the 'import type' of a summary in bitcode, and
updates bitcode reader to parse the bit correctly.

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index e2754d7..7304eab 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -1400,18 +1400,20 @@ public:
                   llvm::StringRef ModulePath,
                   const std::string &NewModulePath) {
     std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
+    GVSummaryPtrSet DeclarationSummaries;
 
     std::error_code EC;
     gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
-                                     ImportList, ModuleToSummariesForIndex);
+                                     ImportList, ModuleToSummariesForIndex,
+                                     DeclarationSummaries);
 
     raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
                       sys::fs::OpenFlags::OF_None);
     if (EC)
       return errorCodeToError(EC);
 
-    // TODO: Serialize declaration bits to bitcode.
-    writeIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex);
+    writeIndexToFile(CombinedIndex, OS, &ModuleToSummariesForIndex,
+                     &DeclarationSummaries);
 
     if (ShouldEmitImportsFiles) {
       EC = EmitImportsFiles(ModulePath, NewModulePath + ".imports",