1 files changed, 8 insertions, 1 deletions
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 21aed799d6fa..76223e88ca1a 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -720,7 +720,14 @@ bool lto::initImportList(const Module &M,
       if (Summary->modulePath() == M.getModuleIdentifier())
         continue;
       // Add an entry to provoke importing by thinBackend.
-      ImportList[Summary->modulePath()].insert(GUID);
+      // Try emplace the entry first. If an entry with the same key already
+      // exists, set the value to 'std::min(existing-value, new-value)' to make
+      // sure a definition takes precedence over a declaration.
+      auto [Iter, Inserted] = ImportList[Summary->modulePath()].try_emplace(
+          GUID, Summary->importType());
+
+      if (!Inserted)
+        Iter->second = std::min(Iter->second, Summary->importType());
     }
   }
   return true;