3 files changed, 31 insertions, 4 deletions
diff --git a/include/llvm/Bitcode/BitcodeReader.h b/include/llvm/Bitcode/BitcodeReader.h
index 0e17e9a0a2781..160ddad5761f8 100644
--- a/include/llvm/Bitcode/BitcodeReader.h
+++ b/include/llvm/Bitcode/BitcodeReader.h
@@ -111,9 +111,14 @@ namespace llvm {
 
   struct BitcodeFileContents {
     std::vector<BitcodeModule> Mods;
+    StringRef Symtab, StrtabForSymtab;
   };
 
-  /// Returns the contents of a bitcode file.
+  /// Returns the contents of a bitcode file. This includes the raw contents of
+  /// the symbol table embedded in the bitcode file. Clients which require a
+  /// symbol table should prefer to use irsymtab::read instead of this function
+  /// because it creates a reader for the irsymtab and handles upgrading bitcode
+  /// files without a symbol table or with an old symbol table.
   Expected<BitcodeFileContents> getBitcodeFileContents(MemoryBufferRef Buffer);
 
   /// Returns a list of modules in the specified bitcode buffer.
diff --git a/include/llvm/Bitcode/BitcodeWriter.h b/include/llvm/Bitcode/BitcodeWriter.h
index 7c3c4b2e0cbd3..f8b7fb341e881 100644
--- a/include/llvm/Bitcode/BitcodeWriter.h
+++ b/include/llvm/Bitcode/BitcodeWriter.h
@@ -28,18 +28,34 @@ namespace llvm {
     std::unique_ptr<BitstreamWriter> Stream;
 
     StringTableBuilder StrtabBuilder{StringTableBuilder::RAW};
-    bool WroteStrtab = false;
+
+    // Owns any strings created by the irsymtab writer until we create the
+    // string table.
+    BumpPtrAllocator Alloc;
+
+    bool WroteStrtab = false, WroteSymtab = false;
 
     void writeBlob(unsigned Block, unsigned Record, StringRef Blob);
 
+    std::vector<Module *> Mods;
+
    public:
     /// Create a BitcodeWriter that writes to Buffer.
     BitcodeWriter(SmallVectorImpl<char> &Buffer);
 
     ~BitcodeWriter();
 
+    /// Attempt to write a symbol table to the bitcode file. This must be called
+    /// at most once after all modules have been written.
+    ///
+    /// A reader does not require a symbol table to interpret a bitcode file;
+    /// the symbol table is needed only to improve link-time performance. So
+    /// this function may decide not to write a symbol table. It may so decide
+    /// if, for example, the target is unregistered or the IR is malformed.
+    void writeSymtab();
+
     /// Write the bitcode file's string table. This must be called exactly once
-    /// after all modules have been written.
+    /// after all modules and the optional symbol table have been written.
     void writeStrtab();
 
     /// Copy the string table for another module into this bitcode file. This
diff --git a/include/llvm/Bitcode/LLVMBitCodes.h b/include/llvm/Bitcode/LLVMBitCodes.h
index 4e3e177cac8f1..5435e48ff4242 100644
--- a/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/include/llvm/Bitcode/LLVMBitCodes.h
@@ -22,7 +22,7 @@
 
 namespace llvm {
 namespace bitc {
-// The only top-level block types are MODULE, IDENTIFICATION and STRTAB.
+// The only top-level block types are MODULE, IDENTIFICATION, STRTAB and SYMTAB.
 enum BlockIDs {
   // Blocks
   MODULE_BLOCK_ID = FIRST_APPLICATION_BLOCKID,
@@ -57,6 +57,8 @@ enum BlockIDs {
   STRTAB_BLOCK_ID,
 
   FULL_LTO_GLOBALVAL_SUMMARY_BLOCK_ID,
+
+  SYMTAB_BLOCK_ID,
 };
 
 /// Identification block contains a string that describes the producer details,
@@ -571,6 +573,10 @@ enum StrtabCodes {
   STRTAB_BLOB = 1,
 };
 
+enum SymtabCodes {
+  SYMTAB_BLOB = 1,
+};
+
 } // End bitc namespace
 } // End llvm namespace