DebugInfo: Gut DIDescriptor

PR23080 is almost finished.  With this commit, there's no consequential
API in `DIDescriptor` and its subclasses.  What's left?

  - Default-constructed to `nullptr`.
  - Handy `const_cast<>` (constructed from `const`, but accessors are
    non-`const`).

I think the safe way to catch those is to delete the classes and fix
compile errors.  That'll be my next step, after I delete the `DITypeRef`
(etc.) wrapper around `MDTypeRef`.

llvm-svn: 235069

1 files changed, 4 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 46f3eb3201d..91546529877 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1405,9 +1405,10 @@ void DwarfUnit::constructArrayTypeDIE(DIE &Buffer, DICompositeType CTy) {
   // Add subranges to array type.
   DIArray Elements = CTy->getElements();
   for (unsigned i = 0, N = Elements.size(); i < N; ++i) {
-    DIDescriptor Element = Elements[i];
-    if (Element.getTag() == dwarf::DW_TAG_subrange_type)
-      constructSubrangeDIE(Buffer, cast<MDSubrange>(Element), IdxTy);
+    // FIXME: Should this really be such a loose cast?
+    if (auto *Element = dyn_cast_or_null<DebugNode>(Elements[i]))
+      if (Element->getTag() == dwarf::DW_TAG_subrange_type)
+        constructSubrangeDIE(Buffer, cast<MDSubrange>(Element), IdxTy);
   }
 }