1 files changed, 10 insertions, 0 deletions
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 2e670d584ecc0..c7606fd488a0a 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3071,7 +3071,12 @@ void BitcodeReader::saveMetadataList(
   for (unsigned ID = 0; ID < MetadataList.size(); ++ID) {
     Metadata *MD = MetadataList[ID];
     auto *N = dyn_cast_or_null<MDNode>(MD);
+    assert((!N || (N->isResolved() || N->isTemporary())) &&
+           "Found non-resolved non-temp MDNode while saving metadata");
     // Save all values if !OnlyTempMD, otherwise just the temporary metadata.
+    // Note that in the !OnlyTempMD case we need to save all Metadata, not
+    // just MDNode, as we may have references to other types of module-level
+    // metadata (e.g. ValueAsMetadata) from instructions.
     if (!OnlyTempMD || (N && N->isTemporary())) {
       // Will call this after materializing each function, in order to
       // handle remapping of the function's instructions/metadata.
@@ -3080,6 +3085,11 @@ void BitcodeReader::saveMetadataList(
         assert(MetadataToIDs[MD] == ID && "Inconsistent metadata value id");
         continue;
       }
+      if (N && N->isTemporary())
+        // Ensure that we assert if someone tries to RAUW this temporary
+        // metadata while it is the key of a map. The flag will be set back
+        // to true when the saved metadata list is destroyed.
+        N->setCanReplace(false);
       MetadataToIDs[MD] = ID;
     }
   }