[MS ABI] Mangle unnamed enums correctly

Unnamed enums take the name of the first enumerator they define.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290509 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/MicrosoftMangle.cpp

@@ -863,21 +863,28 @@ void MicrosoftCXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND,
         }
       }
 
-      llvm::SmallString<64> Name("<unnamed-type-");
+      llvm::SmallString<64> Name;
       if (DeclaratorDecl *DD =
               Context.getASTContext().getDeclaratorForUnnamedTagDecl(TD)) {
         // Anonymous types without a name for linkage purposes have their
         // declarator mangled in if they have one.
+        Name += "<unnamed-type-";
         Name += DD->getName();
       } else if (TypedefNameDecl *TND =
                      Context.getASTContext().getTypedefNameForUnnamedTagDecl(
                          TD)) {
         // Anonymous types without a name for linkage purposes have their
         // associate typedef mangled in if they have one.
+        Name += "<unnamed-type-";
         Name += TND->getName();
+      } else if (auto *ED = dyn_cast<EnumDecl>(TD)) {
+        auto EnumeratorI = ED->enumerator_begin();
+        assert(EnumeratorI != ED->enumerator_end());
+        Name += "<unnamed-enum-";
+        Name += EnumeratorI->getName();
       } else {
         // Otherwise, number the types using a $S prefix.
-        Name += "$S";
+        Name += "<unnamed-type-$S";
         Name += llvm::utostr(Context.getAnonymousStructId(TD) + 1);
       }
       Name += ">";

test/CodeGenCXX/mangle-ms-cxx11.cpp

@@ -343,3 +343,7 @@ A a;
 
 int call_it = (A::default_args(), 1);
 }
+
+enum { enumerator };
+void f(decltype(enumerator)) {}
+// CHECK-DAG: define void @"\01?f@@YAXW4<unnamed-enum-enumerator>@@@Z"(