r220595 - CodeGen: Don't form weak dllexport aliases

[David Majnemer]

Author: majnemer
Date: Fri Oct 24 17:05:27 2014
New Revision: 220595

URL: http://llvm.org/viewvc/llvm-project?rev=220595&view=rev
Log:
CodeGen: Don't form weak dllexport aliases

The MS linker cannot do anything interesting with these, it doesn't make
sense to emit them.

This fixes PR21373.

Differential Revision: http://reviews.llvm.org/D5986

Modified:
    cfe/trunk/lib/CodeGen/CGCXX.cpp
    cfe/trunk/test/CodeGenCXX/dllexport.cpp

Modified: cfe/trunk/lib/CodeGen/CGCXX.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCXX.cpp?rev=220595&r1=220594&r2=220595&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGCXX.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGCXX.cpp Fri Oct 24 17:05:27 2014
@@ -119,6 +119,11 @@ bool CodeGenModule::TryEmitDefinitionAsA
   if (!llvm::GlobalAlias::isValidLinkage(Linkage))
     return true;
 
+  // Don't create a weak alias for a dllexport'd symbol.
+  if (AliasDecl.getDecl()->hasAttr<DLLExportAttr>() &&
+      llvm::GlobalValue::isWeakForLinker(Linkage))
+    return true;
+
   llvm::GlobalValue::LinkageTypes TargetLinkage =
       getFunctionLinkage(TargetDecl);
 

Modified: cfe/trunk/test/CodeGenCXX/dllexport.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/dllexport.cpp?rev=220595&r1=220594&r2=220595&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/dllexport.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/dllexport.cpp Fri Oct 24 17:05:27 2014
@@ -3,8 +3,6 @@
 // RUN: %clang_cc1 -triple i686-windows-gnu    -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=GNU --check-prefix=G32 %s
 // RUN: %clang_cc1 -triple x86_64-windows-gnu  -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=GNU --check-prefix=G64 %s
 
-// RUN: %clang_cc1 -triple i686-pc-win32 -O1 -mconstructor-aliases -disable-llvm-optzns -std=c++1y -emit-llvm -o - %s | FileCheck %s --check-prefix=MSC --check-prefix=M32
-
 // Helper structs to make templates more expressive.
 struct ImplicitInst_Exported {};
 struct ExplicitDecl_Exported {};
@@ -607,6 +605,15 @@ template struct __declspec(dllexport) Ex
 USEMEMFUNC(ExplicitlyInstantiatedWithDifferentAttr<int>, f);
 // M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ExplicitlyInstantiatedWithDifferentAttr at H@@QAEXXZ"
 
+// Don't create weak dllexport aliases. (PR21373)
+struct NonExportedBaseClass {
+  virtual ~NonExportedBaseClass();
+};
+NonExportedBaseClass::~NonExportedBaseClass() {}
+
+struct __declspec(dllexport) ExportedDerivedClass : NonExportedBaseClass {};
+// M32-DAG: weak_odr dllexport x86_thiscallcc void @"\01??1ExportedDerivedClass@@UAE at XZ"
+
 
 //===----------------------------------------------------------------------===//
 // Classes with template base classes