[ms-cxxabi] Don't consider function templates for name backrefs

They don't seem to be used for back references, presumably because a
function template is unlikely to reoccur, while a class template name
may reoccur as a type.

This fixes a mangling issue for llvm::hash_combine() in Hashing.h.

Reviewers: timurrrr

Differential Revision: http://llvm-reviews.chandlerc.com/D1078

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186233 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/MicrosoftMangle.cpp b/lib/AST/MicrosoftMangle.cpp
index 143472f..88548ae 100644
--- a/lib/AST/MicrosoftMangle.cpp
+++ b/lib/AST/MicrosoftMangle.cpp
@@ -421,7 +421,16 @@
   // Check if we have a template.
   const TemplateArgumentList *TemplateArgs = 0;
   if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
-    // We have a template.
+    // Function templates aren't considered for name back referencing.  This
+    // makes sense since function templates aren't likely to occur multiple
+    // times in a symbol.
+    // FIXME: Test alias template mangling with MSVC 2013.
+    if (!isa<ClassTemplateDecl>(TD)) {
+      mangleTemplateInstantiationName(TD, *TemplateArgs);
+      return;
+    }
+
+    // We have a class template.
     // Here comes the tricky thing: if we need to mangle something like
     //   void foo(A::X<Y>, B::X<Y>),
     // the X<Y> part is aliased. However, if you need to mangle