Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -1915,7 +1915,7 @@
   if (hasInit())
     return Definition;
 
-  if (hasAttr<AliasAttr>())
+  if (hasAttr<AliasAttr>() || hasAttr<SelectAnyAttr>())
     return Definition;
 
   // A variable template specialization (other than a static data member
@@ -1925,14 +1925,14 @@
       getTemplateSpecializationKind() != TSK_ExplicitSpecialization)
     return DeclarationOnly;
 
-  if (!hasAttr<SelectAnyAttr>() && hasExternalStorage())
+  if (hasExternalStorage())
     return DeclarationOnly;
 
   // [dcl.link] p7:
   //   A declaration directly contained in a linkage-specification is treated
   //   as if it contains the extern specifier for the purpose of determining
   //   the linkage of the declared name and whether it is a definition.
-  if (!hasAttr<SelectAnyAttr>() && isSingleLineLanguageLinkage(*this))
+  if (isSingleLineLanguageLinkage(*this))
     return DeclarationOnly;
 
   // C99 6.9.2p2:
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -2134,7 +2134,8 @@
 }
 
 static bool isVarDeclStrongDefinition(const ASTContext &Context,
-                                      const VarDecl *D, bool NoCommon) {
+                                      CodeGenModule &CGM, const VarDecl *D,
+                                      bool NoCommon) {
   // Don't give variables common linkage if -fno-common was specified unless it
   // was overridden by a NoCommon attribute.
   if ((NoCommon || D->hasAttr<NoCommonAttr>()) && !D->hasAttr<CommonAttr>())
@@ -2159,6 +2160,10 @@
   if (D->hasAttr<WeakImportAttr>())
     return true;
 
+  // A variable cannot be both common and exist in a comdat.
+  if (shouldBeInCOMDAT(CGM, *D))
+    return true;
+
   // Declarations with a required alignment do not have common linakge in MSVC
   // mode.
   if (Context.getLangOpts().MSVCCompat) {
@@ -2227,7 +2232,7 @@
   // C++ doesn't have tentative definitions and thus cannot have common
   // linkage.
   if (!getLangOpts().CPlusPlus && isa<VarDecl>(D) &&
-      !isVarDeclStrongDefinition(Context, cast<VarDecl>(D),
+      !isVarDeclStrongDefinition(Context, *this, cast<VarDecl>(D),
                                  CodeGenOpts.NoCommon))
     return llvm::GlobalVariable::CommonLinkage;
 
Index: test/CodeGen/ms-declspecs.c
===================================================================
--- test/CodeGen/ms-declspecs.c
+++ test/CodeGen/ms-declspecs.c
@@ -6,8 +6,10 @@
 // CHECK: @x2 = weak_odr constant i32 2, comdat, align 4
 
 // selectany turns extern variable declarations into definitions.
-extern __declspec(selectany) int x3;
+__declspec(selectany) int x3;
+extern __declspec(selectany) int x4;
 // CHECK: @x3 = weak_odr global i32 0, comdat, align 4
+// CHECK: @x4 = weak_odr global i32 0, comdat, align 4
 
 struct __declspec(align(16)) S {
   char x;
Index: test/CodeGen/ms-declspecs.cpp
===================================================================
--- test/CodeGen/ms-declspecs.cpp
+++ test/CodeGen/ms-declspecs.cpp
@@ -7,7 +7,9 @@
 extern "C" {
 __declspec(selectany) int x4;
 }
+__declspec(selectany) int x5;
 // CHECK: @"\01?x1@@3HA" = weak_odr global i32 0, comdat, align 4
 // CHECK: @x2 = weak_odr global i32 0, comdat, align 4
 // CHECK: @"\01?x3@@3HA"  = weak_odr global i32 0, comdat, align 4
 // CHECK: @x4 = weak_odr global i32 0, comdat, align 4
+// CHECK: @"\01?x5@@3HA"  = weak_odr global i32 0, comdat, align 4