IR: Add specialized debug info metadata nodes

Add specialized debug info metadata nodes that match the `DIDescriptor`
wrappers (used by `DIBuilder`) closely.  Assembly and bitcode support to
follow soon (it'll mostly just be obvious), but this sketches in today's
schema.  This is the first big commit (well, the only *big* one aside
from the testcase changes that'll come when I move this into place) for
PR22464.

I've marked a bunch of obvious changes as `TODO`s in the source; I plan
to make those changes promptly after this hierarchy is moved underneath
`DIDescriptor`, but for now I'm aiming mostly to match the status quo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228640 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Metadata.def

@@ -51,6 +51,32 @@ HANDLE_MDNODE_LEAF(MDTuple)
 HANDLE_MDNODE_LEAF(MDLocation)
 HANDLE_MDNODE_BRANCH(DebugNode)
 HANDLE_MDNODE_LEAF(GenericDebugNode)
+HANDLE_MDNODE_LEAF(MDSubrange)
+HANDLE_MDNODE_LEAF(MDEnumerator)
+HANDLE_MDNODE_BRANCH(MDScope)
+HANDLE_MDNODE_BRANCH(MDType)
+HANDLE_MDNODE_LEAF(MDBasicType)
+HANDLE_MDNODE_BRANCH(MDDerivedTypeBase)
+HANDLE_MDNODE_LEAF(MDDerivedType)
+HANDLE_MDNODE_BRANCH(MDCompositeTypeBase)
+HANDLE_MDNODE_LEAF(MDCompositeType)
+HANDLE_MDNODE_LEAF(MDSubroutineType)
+HANDLE_MDNODE_LEAF(MDFile)
+HANDLE_MDNODE_LEAF(MDCompileUnit)
+HANDLE_MDNODE_LEAF(MDSubprogram)
+HANDLE_MDNODE_BRANCH(MDLexicalBlockBase)
+HANDLE_MDNODE_LEAF(MDLexicalBlock)
+HANDLE_MDNODE_LEAF(MDLexicalBlockFile)
+HANDLE_MDNODE_LEAF(MDNamespace)
+HANDLE_MDNODE_BRANCH(MDTemplateParameter)
+HANDLE_MDNODE_LEAF(MDTemplateTypeParameter)
+HANDLE_MDNODE_LEAF(MDTemplateValueParameter)
+HANDLE_MDNODE_BRANCH(MDVariable)
+HANDLE_MDNODE_LEAF(MDGlobalVariable)
+HANDLE_MDNODE_LEAF(MDLocalVariable)
+HANDLE_MDNODE_LEAF(MDExpression)
+HANDLE_MDNODE_LEAF(MDObjCProperty)
+HANDLE_MDNODE_LEAF(MDImportedEntity)
 
 #undef HANDLE_METADATA
 #undef HANDLE_METADATA_LEAF

include/llvm/IR/Metadata.h

@@ -62,6 +62,25 @@ public:
     MDTupleKind,
     MDLocationKind,
     GenericDebugNodeKind,
+    MDSubrangeKind,
+    MDEnumeratorKind,
+    MDBasicTypeKind,
+    MDDerivedTypeKind,
+    MDCompositeTypeKind,
+    MDSubroutineTypeKind,
+    MDFileKind,
+    MDCompileUnitKind,
+    MDSubprogramKind,
+    MDLexicalBlockKind,
+    MDLexicalBlockFileKind,
+    MDNamespaceKind,
+    MDTemplateTypeParameterKind,
+    MDTemplateValueParameterKind,
+    MDGlobalVariableKind,
+    MDLocalVariableKind,
+    MDExpressionKind,
+    MDObjCPropertyKind,
+    MDImportedEntityKind,
     ConstantAsMetadataKind,
     LocalAsMetadataKind,
     MDStringKind
@@ -865,9 +884,14 @@ public:
 
   /// \brief Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Metadata *MD) {
-    return MD->getMetadataID() == MDTupleKind ||
-           MD->getMetadataID() == MDLocationKind ||
-           MD->getMetadataID() == GenericDebugNodeKind;
+    switch (MD->getMetadataID()) {
+    default:
+      return false;
+#define HANDLE_MDNODE_LEAF(CLASS)                                              \
+  case CLASS##Kind:                                                            \
+    return true;
+#include "llvm/IR/Metadata.def"
+    }
   }
 
   /// \brief Check whether MDNode is a vtable access.