[c++2a] P0515R3: Support for overloaded operator<=>.

No CodeGen support for MSABI yet, we don't know how to mangle this there.

llvm-svn: 319513
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index c804854..0c55c1a 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1192,6 +1192,15 @@
   // <operator-name> ::= ?__L # co_await
   case OO_Coawait: Out << "?__L"; break;
 
+  case OO_Spaceship: {
+    // FIXME: Once MS picks a mangling, use it.
+    DiagnosticsEngine &Diags = Context.getDiags();
+    unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
+      "cannot mangle this three-way comparison operator yet");
+    Diags.Report(Loc, DiagID);
+    break;
+  }
+
   case OO_Conditional: {
     DiagnosticsEngine &Diags = Context.getDiags();
     unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,