1 files changed, 24 insertions, 3 deletions
diff --git a/llvm/include/llvm/Bitcode/BitstreamReader.h b/llvm/include/llvm/Bitcode/BitstreamReader.h
index 6f478b72127..a0bbe9b397b 100644
--- a/llvm/include/llvm/Bitcode/BitstreamReader.h
+++ b/llvm/include/llvm/Bitcode/BitstreamReader.h
@@ -58,15 +58,27 @@ public:
   BitstreamReader() : IgnoreBlockInfoNames(true) {
   }
 
-  BitstreamReader(const unsigned char *Start, const unsigned char *End) {
-    IgnoreBlockInfoNames = true;
+  BitstreamReader(const unsigned char *Start, const unsigned char *End)
+      : IgnoreBlockInfoNames(true) {
     init(Start, End);
   }
 
-  BitstreamReader(StreamableMemoryObject *bytes) {
+  BitstreamReader(StreamableMemoryObject *bytes) : IgnoreBlockInfoNames(true) {
     BitcodeBytes.reset(bytes);
   }
 
+  BitstreamReader(BitstreamReader &&Other) {
+    *this = std::move(Other);
+  }
+
+  BitstreamReader &operator=(BitstreamReader &&Other) {
+    BitcodeBytes = std::move(Other.BitcodeBytes);
+    // Explicitly swap block info, so that nothing gets destroyed twice.
+    std::swap(BlockInfoRecords, Other.BlockInfoRecords);
+    IgnoreBlockInfoNames = Other.IgnoreBlockInfoNames;
+    return *this;
+  }
+
   void init(const unsigned char *Start, const unsigned char *End) {
     assert(((End-Start) & 3) == 0 &&"Bitcode stream not a multiple of 4 bytes");
     BitcodeBytes.reset(getNonStreamedMemoryObject(Start, End));
@@ -123,6 +135,15 @@ public:
     BlockInfoRecords.back().BlockID = BlockID;
     return BlockInfoRecords.back();
   }
+
+  /// Takes block info from the other bitstream reader.
+  ///
+  /// This is a "take" operation because BlockInfo records are non-trivial, and
+  /// indeed rather expensive.
+  void takeBlockInfo(BitstreamReader &&Other) {
+    assert(!hasBlockInfoRecords());
+    BlockInfoRecords = std::move(Other.BlockInfoRecords);
+  }
 };