From 6d2b60a2be21cce7ae856c72ff6a88b8828e1c61 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 12 Jul 2016 16:48:17 +0000
Subject: [PATCH] [ItaniumMangle] Correctly mangle BuiltinTemplateDecls

A BuiltinTemplateDecl has no underlying templated decl and as such they
cannot be relied upon for mangling.  The ItaniumMangler had some bugs
here which lead to crashes.

This fixes PR28519.

llvm-svn: 275190
---
 clang/lib/AST/ItaniumMangle.cpp           |  7 ++++++-
 clang/test/CodeGenCXX/mangle-template.cpp | 11 +++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 015e9d7214f4..5a7c45594e08 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -910,6 +910,8 @@ void CXXNameMangler::mangleUnscopedTemplateName(
     assert(!AdditionalAbiTags &&
            "template template param cannot have abi tags");
     mangleTemplateParameter(TTP->getIndex());
+  } else if (isa<BuiltinTemplateDecl>(ND)) {
+    mangleUnscopedName(ND, AdditionalAbiTags);
   } else {
     mangleUnscopedName(ND->getTemplatedDecl(), AdditionalAbiTags);
   }
@@ -1715,7 +1717,10 @@ void CXXNameMangler::mangleTemplatePrefix(const TemplateDecl *ND,
     mangleTemplateParameter(TTP->getIndex());
   } else {
     manglePrefix(getEffectiveDeclContext(ND), NoFunction);
-    mangleUnqualifiedName(ND->getTemplatedDecl(), nullptr);
+    if (isa<BuiltinTemplateDecl>(ND))
+      mangleUnqualifiedName(ND, nullptr);
+    else
+      mangleUnqualifiedName(ND->getTemplatedDecl(), nullptr);
   }
 
   addSubstitution(ND);
diff --git a/clang/test/CodeGenCXX/mangle-template.cpp b/clang/test/CodeGenCXX/mangle-template.cpp
index 7fa300ae237b..60481b3328f6 100644
--- a/clang/test/CodeGenCXX/mangle-template.cpp
+++ b/clang/test/CodeGenCXX/mangle-template.cpp
@@ -201,3 +201,14 @@ namespace test14 {
 
   int call(bool b) { return inl<void>(b); }
 }
+
+namespace std {
+template <class _Tp, _Tp...> struct integer_sequence {};
+}
+
+namespace test15 {
+template <int N>
+__make_integer_seq<std::integer_sequence, int, N> make() {}
+template __make_integer_seq<std::integer_sequence, int, 5> make<5>();
+// CHECK: define weak_odr void @_ZN6test154makeILi5EEE18__make_integer_seqISt16integer_sequenceiXT_EEv(
+}