Rename MDValue* to Metadata* (NFC)

Renamed MDValue* to Metadata*, and MDValueToValIDMap to MetadataToIDs,
as per review for r255909.

llvm-svn: 256593
diff --git a/llvm/lib/Bitcode/Writer/ValueEnumerator.h b/llvm/lib/Bitcode/Writer/ValueEnumerator.h
index abe383d..9fb8325 100644
--- a/llvm/lib/Bitcode/Writer/ValueEnumerator.h
+++ b/llvm/lib/Bitcode/Writer/ValueEnumerator.h
@@ -63,7 +63,7 @@
   std::vector<const Metadata *> MDs;
   SmallVector<const LocalAsMetadata *, 8> FunctionLocalMDs;
   typedef DenseMap<const Metadata *, unsigned> MetadataMapType;
-  MetadataMapType MDValueMap;
+  MetadataMapType MetadataMap;
   bool HasMDString;
   bool HasDILocation;
   bool HasGenericDINode;
@@ -93,7 +93,7 @@
   /// before incorporation.
   unsigned NumModuleValues;
 
-  /// When a function is incorporated, this is the size of the MDValues list
+  /// When a function is incorporated, this is the size of the Metadatas list
   /// before incorporation.
   unsigned NumModuleMDs;
 
@@ -117,7 +117,7 @@
     return ID - 1;
   }
   unsigned getMetadataOrNullID(const Metadata *MD) const {
-    return MDValueMap.lookup(MD);
+    return MetadataMap.lookup(MD);
   }
   unsigned numMDs() const { return MDs.size(); }