Debug Info: Add a file: field to DIImportedEntity.

DIImportedEntity has a line number, but not a file field. To determine
the decl_line/decl_file we combine the line number from the
DIImportedEntity with the file from the DIImportedEntity's scope. This
does not work correctly when the parent scope is a DINamespace or a
DIModule, both of which do not have a source file.

This patch adds a file field to DIImportedEntity to unambiguously
identify the source location of the using/import declaration.  Most
testcase updates are mechanical, the interesting one is the removal of
the FIXME in test/DebugInfo/Generic/namespace.ll.

This fixes PR33822. See https://bugs.llvm.org/show_bug.cgi?id=33822
for more context.

<rdar://problem/33357889>
https://bugs.llvm.org/show_bug.cgi?id=33822

Differential Revision: https://reviews.llvm.org/D35583

llvm-svn: 308398

lib/Bitcode/Reader/MetadataLoader.cpp

@@ -1671,15 +1671,17 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
     break;
   }
   case bitc::METADATA_IMPORTED_ENTITY: {
-    if (Record.size() != 6)
+    if (Record.size() != 6 && Record.size() != 7)
       return error("Invalid record");
 
     IsDistinct = Record[0];
+    bool HasFile = (Record.size() == 7);
     MetadataList.assignValue(
         GET_OR_DISTINCT(DIImportedEntity,
                         (Context, Record[1], getMDOrNull(Record[2]),
-                         getDITypeRefOrNull(Record[3]), Record[4],
-                         getMDString(Record[5]))),
+                         getDITypeRefOrNull(Record[3]),
+                         HasFile ? getMDOrNull(Record[6]) : nullptr,
+                         HasFile ? Record[4] : 0, getMDString(Record[5]))),
         NextMetadataNo);
     NextMetadataNo++;
     break;