Add support for remapping metadata kind IDs when reading in a

bitcode file, so that two bitcode files where the same metadata kind
name happens to have been assigned a different ID can still be
linked together.

Eliminate the restriction that metadata kind IDs can't be 0.

Change MD_dbg from 1 to 0, because we can now, and because it's
less mysterious that way.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108939 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitcodeReader.h

@@ -156,6 +156,9 @@ class BitcodeReader : public GVMaterializer {
   // stored here with their replacement function.
   typedef std::vector<std::pair<Function*, Function*> > UpgradedIntrinsicMap;
   UpgradedIntrinsicMap UpgradedIntrinsics;
+
+  // Map the bitcode's custom MDKind ID to the Module's MDKind ID.
+  DenseMap<unsigned, unsigned> MDKindMap;
   
   // After the module header has been read, the FunctionsWithBodies list is 
   // reversed.  This keeps track of whether we've done this yet.