[DebugInfo] Support for DW_TAG_generic_subrange

This is needed to support fortran assumed rank arrays which
have runtime rank.

  Summary:
Fortran assumed rank arrays have dynamic rank. DWARF TAG
DW_TAG_generic_subrange is needed to support that.

  Testing:
unit test cases added (hand-written)
check llvm
check debug-info

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D89218

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

@@ -875,6 +875,7 @@ MetadataLoader::MetadataLoaderImpl::lazyLoadModuleMetadataBlock() {
       case bitc::METADATA_OBJC_PROPERTY:
       case bitc::METADATA_IMPORTED_ENTITY:
       case bitc::METADATA_GLOBAL_VAR_EXPR:
+      case bitc::METADATA_GENERIC_SUBRANGE:
         // We don't expect to see any of these, if we see one, give up on
         // lazy-loading and fallback.
         MDStringRef.clear();
@@ -1371,6 +1372,18 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
     NextMetadataNo++;
     break;
   }
+  case bitc::METADATA_GENERIC_SUBRANGE: {
+    Metadata *Val = nullptr;
+    Val = GET_OR_DISTINCT(DIGenericSubrange,
+                          (Context, getMDOrNull(Record[1]),
+                           getMDOrNull(Record[2]), getMDOrNull(Record[3]),
+                           getMDOrNull(Record[4])));
+
+    MetadataList.assignValue(Val, NextMetadataNo);
+    IsDistinct = Record[0] & 1;
+    NextMetadataNo++;
+    break;
+  }
   case bitc::METADATA_ENUMERATOR: {
     if (Record.size() < 3)
       return error("Invalid record");