Adjust r194296 to not apply the alias replacement for externally

available always-inline functions. This breaks libc++'s locale
implementation. Code generation for this case should be fixed, but this
is a stop gap fix for clang 3.4.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195501 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 22baa654084978b49c651d6f5b3aba8e80b37a3d..cfb2d6291b8aa80c0c8ed986cf121565d721fae6 100644 (file)
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -140,7 +140,14 @@ bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
 
   // Instead of creating as alias to a linkonce_odr, replace all of the uses
   // of the aliassee.
-  if (llvm::GlobalValue::isDiscardableIfUnused(Linkage)) {
+  if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) &&
+     (TargetLinkage != llvm::GlobalValue::AvailableExternallyLinkage ||
+      !TargetDecl.getDecl()->hasAttr<AlwaysInlineAttr>())) {
+    // FIXME: An extern template instanciation will create functions with
+    // linkage "AvailableExternally". In libc++, some classes also define
+    // members with attribute "AlwaysInline" and expect no reference to
+    // be generated. It is desirable to reenable this optimisation after
+    // corresponding LLVM changes.
     Replacements[MangledName] = Aliasee;
     return false;
   }

diff --git a/test/CodeGenCXX/ctor-dtor-alias.cpp b/test/CodeGenCXX/ctor-dtor-alias.cpp
index 6efd0bf9f870b155922358a2d89d9764ea1721c0..235d1650dec92df4067fdf2f9d20291fc29276c0 100644 (file)
--- a/test/CodeGenCXX/ctor-dtor-alias.cpp
+++ b/test/CodeGenCXX/ctor-dtor-alias.cpp
@@ -1,6 +1,9 @@
 // RUN: %clang_cc1 %s -triple x86_64-linux -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-optzns | FileCheck %s
 // RUN: %clang_cc1 %s -triple x86_64-linux -emit-llvm -o - -mconstructor-aliases | FileCheck --check-prefix=NOOPT %s
 
+// RUN: %clang_cc1 -cc1 -triple x86_64--netbsd -emit-llvm \
+// RUN: -mconstructor-aliases -O2 %s -o - | FileCheck --check-prefix=CHECK-RAUW %s
+
 namespace test1 {
 // test that we don't produce an alias when the destructor is weak_odr. The
 // reason to avoid it that another TU might have no explicit template
@@ -129,3 +132,32 @@ namespace test8 {
   struct zed : public bar {};
   zed foo;
 }
+
+// CHECK-RAUW: @_ZTV1C = linkonce_odr unnamed_addr constant [4 x i8*] [{{[^@]*}}@_ZTI1C {{[^@]*}}@_ZN1CD2Ev {{[^@]*}}@_ZN1CD0Ev {{[^@]*}}]
+// r194296 replaced C::~C with B::~B without emitting the later.
+
+class A {
+public:
+  A(int);
+  virtual ~A();
+};
+
+template <class>
+class B : A {
+public:
+  B()
+      : A(0) {
+  }
+  __attribute__((always_inline)) ~B() {
+  }
+};
+
+extern template class B<char>;
+
+class C : B<char> {
+};
+
+void
+fn1() {
+  new C;
+}