From 95a3256ad0259f0b2af2515f011ef7addf4b29a4 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Thu, 19 Feb 2015 21:41:48 +0000
Subject: [PATCH] Itanium ABI: Pack expansions change the arity of expressions
 to unknown

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@229918 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/ItaniumMangle.cpp  | 11 ++++++++---
 test/CodeGenCXX/mangle.cpp |  9 +++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index f4fee77925..95fca00125 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -2796,9 +2796,14 @@ recurse:
       Out << "cl";
     }
 
-    mangleExpression(CE->getCallee(), CE->getNumArgs());
-    for (unsigned I = 0, N = CE->getNumArgs(); I != N; ++I)
-      mangleExpression(CE->getArg(I));
+    unsigned CallArity = CE->getNumArgs();
+    for (const Expr *Arg : CE->arguments())
+      if (isa<PackExpansionExpr>(Arg))
+        CallArity = UnknownArity;
+
+    mangleExpression(CE->getCallee(), CallArity);
+    for (const Expr *Arg : CE->arguments())
+      mangleExpression(Arg);
     Out << 'E';
     break;
   }
diff --git a/test/CodeGenCXX/mangle.cpp b/test/CodeGenCXX/mangle.cpp
index 2cdfd1929a..630a251c20 100644
--- a/test/CodeGenCXX/mangle.cpp
+++ b/test/CodeGenCXX/mangle.cpp
@@ -1062,3 +1062,12 @@ namespace test51 {
   // CHECK-LABEL: @_ZN6test514fun7INS_1EEEEDTcldtcvS1__Esr1EEdnT_EEv
   template void fun8<X>();
 }
+
+namespace test52 {
+struct X {};
+void operator+(X);
+template <typename... T>
+auto f4(T... x) -> decltype(operator+(x...));
+// CHECK-LABEL: @_ZN6test522f4IJNS_1XEEEEDTclonplspfp_EEDpT_
+void use() { f4(X{}); }
+}
-- 
2.40.0