1 files changed, 37 insertions, 0 deletions
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 8a50749..62d9904 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -558,6 +558,13 @@ class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
   DenseMap<Function *, std::vector<BasicBlock *>> BasicBlockFwdRefs;
   std::deque<Function *> BasicBlockFwdRefQueue;
 
+  /// These are Functions that contain BlockAddresses which refer a different
+  /// Function. When parsing the different Function, queue Functions that refer
+  /// to the different Function. Those Functions must be materialized in order
+  /// to resolve their BlockAddress constants before the different Function
+  /// gets moved into another Module.
+  std::vector<Function *> BackwardRefFunctions;
+
   /// Indicates that we are using a new encoding for instruction operands where
   /// most operands in the current FUNCTION_BLOCK are encoded relative to the
   /// instruction number, for a more compact encoding.  Some instruction
@@ -881,6 +888,11 @@ Error BitcodeReader::materializeForwardReferencedFunctions() {
   }
   assert(BasicBlockFwdRefs.empty() && "Function missing from queue");
 
+  for (Function *F : BackwardRefFunctions)
+    if (Error Err = materialize(F))
+      return Err;
+  BackwardRefFunctions.clear();
+
   // Reset state.
   WillMaterializeAllForwardRefs = false;
   return Error::success();
@@ -4317,6 +4329,31 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       continue;
     }
 
+    case bitc::FUNC_CODE_BLOCKADDR_USERS: // BLOCKADDR_USERS: [vals...]
+      // The record should not be emitted if it's an empty list.
+      if (Record.empty())
+        return error("Invalid record");
+      // When we have the RARE case of a BlockAddress Constant that is not
+      // scoped to the Function it refers to, we need to conservatively
+      // materialize the referred to Function, regardless of whether or not
+      // that Function will ultimately be linked, otherwise users of
+      // BitcodeReader might start splicing out Function bodies such that we
+      // might no longer be able to materialize the BlockAddress since the
+      // BasicBlock (and entire body of the Function) the BlockAddress refers
+      // to may have been moved. In the case that the user of BitcodeReader
+      // decides ultimately not to link the Function body, materializing here
+      // could be considered wasteful, but it's better than a deserialization
+      // failure as described. This keeps BitcodeReader unaware of complex
+      // linkage policy decisions such as those use by LTO, leaving those
+      // decisions "one layer up."
+      for (uint64_t ValID : Record)
+        if (auto *F = dyn_cast<Function>(ValueList[ValID]))
+          BackwardRefFunctions.push_back(F);
+        else
+          return error("Invalid record");
+
+      continue;
+
     case bitc::FUNC_CODE_DEBUG_LOC_AGAIN:  // DEBUG_LOC_AGAIN
       // This record indicates that the last instruction is at the same
       // location as the previous instruction with a location.