From 6adb42e1ac111305fcba657e6c7fe02fcc9f83e2 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 20 Nov 2014 01:35:11 +0000
Subject: [PATCH] =?utf8?q?When=20mangling=20member-expressions,=20skip=20i?=
 =?utf8?q?mplicit=20accesses=20of=20anonymous=20union=20objects.=20This=20?=
 =?utf8?q?is=20consistent=20with=20GCC's=20behavior.=20Patch=20by=20Tomasz?=
 =?utf8?q?=20Mi=C4=85sko!?=
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llvm-svn: 222402
---
 clang/lib/AST/ItaniumMangle.cpp        | 12 ++++++
 clang/test/CodeGenCXX/mangle-exprs.cpp | 76 ++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+)

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index e6409ce..9e9c171 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2532,6 +2532,18 @@ void CXXNameMangler::mangleMemberExpr(const Expr *base,
   // <expression> ::= dt <expression> <unresolved-name>
   //              ::= pt <expression> <unresolved-name>
   if (base) {
+
+    // Ignore member expressions involving anonymous unions.
+    while (const auto *RT = base->getType()->getAs<RecordType>()) {
+      if (!RT->getDecl()->isAnonymousStructOrUnion())
+        break;
+      const auto *ME = dyn_cast<MemberExpr>(base);
+      if (!ME)
+        break;
+      base = ME->getBase();
+      isArrow = ME->isArrow();
+    }
+
     if (base->isImplicitCXXThis()) {
       // Note: GCC mangles member expressions to the implicit 'this' as
       // *this., whereas we represent them as this->. The Itanium C++ ABI
diff --git a/clang/test/CodeGenCXX/mangle-exprs.cpp b/clang/test/CodeGenCXX/mangle-exprs.cpp
index 089203e..ee7f244 100644
--- a/clang/test/CodeGenCXX/mangle-exprs.cpp
+++ b/clang/test/CodeGenCXX/mangle-exprs.cpp
@@ -217,3 +217,79 @@ namespace test5 {
   template void a<int>(decltype(noexcept(int())));
   // CHECK: void @_ZN5test51aIiEEvDTnxcvT__EE(
 }
+
+namespace test6 {
+  struct X {
+    int i;
+  };
+
+  struct Y {
+    union {
+      int i;
+    };
+  };
+
+  struct Z {
+    union {
+      X ua;
+      Y ub;
+    };
+
+    struct {
+      X s;
+    };
+
+    union {
+      union {
+        struct {
+          struct {
+            X uuss;
+          };
+        };
+      };
+    };
+  };
+
+  Z z, *zp;
+
+  template<typename T>
+  void f1(decltype(T(z.ua.i))) {}
+  template void f1<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f1IiEEvDTcvT_dtdtL_ZNS_1zEE2ua1iE
+
+  template<typename T>
+  void f2(decltype(T(z.ub.i))) {}
+  template void f2<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f2IiEEvDTcvT_dtdtL_ZNS_1zEE2ub1iE
+
+  template<typename T>
+  void f3(decltype(T(z.s.i))) {}
+  template void f3<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f3IiEEvDTcvT_dtdtL_ZNS_1zEE1s1iE
+
+  template<typename T>
+  void f4(decltype(T(z.uuss.i))) {}
+  template void f4<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f4IiEEvDTcvT_dtdtL_ZNS_1zEE4uuss1iE
+
+  template<typename T>
+  void f5(decltype(T(zp->ua.i))) {}
+  template void f5<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f5IiEEvDTcvT_dtptL_ZNS_2zpEE2ua1iE
+
+  template<typename T>
+  void f6(decltype(T(zp->ub.i))) {}
+  template void f6<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f6IiEEvDTcvT_dtptL_ZNS_2zpEE2ub1iE
+
+  template<typename T>
+  void f7(decltype(T(zp->s.i))) {}
+  template void f7<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f7IiEEvDTcvT_dtptL_ZNS_2zpEE1s1iE
+
+  template<typename T>
+  void f8(decltype(T(zp->uuss.i))) {}
+  template void f8<int>(int);
+  // CHECK-LABEL: define weak_odr void @_ZN5test62f8IiEEvDTcvT_dtptL_ZNS_2zpEE4uuss1iE
+}
+
-- 
2.7.4