[patch][pr19848] Produce explicit comdats in clang.

The llvm IR until recently had no support for comdats. This was a problem when
targeting C++ on ELF/COFF as just using weak linkage would cause quite a bit of
dead bits to remain on the executable (unless -ffunction-sections,
-fdata-sections and --gc-sections were used).

To fix the problem, llvm's codegen will just assume that any weak or linkonce
that is not in an explicit comdat should be output in one with the same name as
the global.

This unfortunately breaks cases like pr19848 where a weak symbol is not
xpected to be part of any comdat.

Now that we have explicit comdats in the IR, we can finally get both cases
right.

This first patch just makes clang give explicit comdats to GlobalValues where
t is allowed to.

A followup patch to llvm will then stop implicitly producing comdats.

llvm-svn: 225705

14 files changed, 100 insertions, 84 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 4a612c9bedf..39052e54ddd 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -206,6 +206,9 @@ llvm::Constant *CodeGenModule::getOrCreateStaticVarDecl(
   GV->setAlignment(getContext().getDeclAlign(&D).getQuantity());
   setGlobalVisibility(GV, &D);
 
+  if (supportsCOMDAT() && GV->isWeakForLinker())
+    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+
   if (D.getTLSKind())
     setTLSMode(GV, D);
 
diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 0e3117400fe..12cdb950978 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -267,15 +267,7 @@ void CodeGenModule::EmitPointerToInitFunc(const VarDecl *D,
   addUsedGlobal(PtrArray);
 
   // If the GV is already in a comdat group, then we have to join it.
-  llvm::Comdat *C = GV->getComdat();
-
-  // LinkOnce and Weak linkage are lowered down to a single-member comdat group.
-  // Make an explicit group so we can join it.
-  if (!C && (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage())) {
-    C = TheModule.getOrInsertComdat(GV->getName());
-    GV->setComdat(C);
-  }
-  if (C)
+  if (llvm::Comdat *C = GV->getComdat())
     PtrArray->setComdat(C);
 }
 
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index a863591aa04..15d383418f2 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1928,6 +1928,31 @@ void CodeGenModule::MaybeHandleStaticInExternC(const SomeDecl *D,
     R.first->second = nullptr;
 }
 
+static bool shouldBeInCOMDAT(CodeGenModule &CGM, const Decl &D) {
+  if (!CGM.supportsCOMDAT())
+    return false;
+
+  if (D.hasAttr<SelectAnyAttr>())
+    return true;
+
+  GVALinkage Linkage;
+  if (auto *VD = dyn_cast<VarDecl>(&D))
+    Linkage = CGM.getContext().GetGVALinkageForVariable(VD);
+  else
+    Linkage = CGM.getContext().GetGVALinkageForFunction(cast<FunctionDecl>(&D));
+
+  switch (Linkage) {
+  case GVA_Internal:
+  case GVA_AvailableExternally:
+  case GVA_StrongExternal:
+    return false;
+  case GVA_DiscardableODR:
+  case GVA_StrongODR:
+    return true;
+  }
+  llvm_unreachable("No such linkage");
+}
+
 void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   llvm::Constant *Init = nullptr;
   QualType ASTTy = D->getType();
@@ -2071,6 +2096,9 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
     setTLSMode(GV, *D);
   }
 
+  if (shouldBeInCOMDAT(*this, *D))
+    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+
   // Emit the initializer function if necessary.
   if (NeedsGlobalCtor || NeedsGlobalDtor)
     EmitCXXGlobalVarDeclInitFunc(D, GV, NeedsGlobalCtor);
@@ -2405,6 +2433,9 @@ void CodeGenModule::EmitGlobalFunctionDefinition(GlobalDecl GD,
 
   MaybeHandleStaticInExternC(D, Fn);
 
+  if (shouldBeInCOMDAT(*this, *D))
+    Fn->setComdat(TheModule.getOrInsertComdat(Fn->getName()));
+
   CodeGenFunction(*this).GenerateCode(D, Fn, FI);
 
   setFunctionDefinitionAttributes(D, Fn);
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index deebab85839..f2ffabcf3e9 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1711,11 +1711,12 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
 
     // The ABI says: It is suggested that it be emitted in the same COMDAT group
     // as the associated data object
-    if (!D.isLocalVarDecl() && var->isWeakForLinker() && CGM.supportsCOMDAT()) {
-      llvm::Comdat *C = CGM.getModule().getOrInsertComdat(var->getName());
+    llvm::Comdat *C = var->getComdat();
+    if (!D.isLocalVarDecl() && C) {
       guard->setComdat(C);
-      var->setComdat(C);
       CGF.CurFn->setComdat(C);
+    } else if (CGM.supportsCOMDAT() && guard->isWeakForLinker()) {
+      guard->setComdat(CGM.getModule().getOrInsertComdat(guard->getName()));
     }
 
     CGM.setStaticLocalDeclGuardAddress(&D, guard);
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 06c913e1ced..c80db7d18a1 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1829,18 +1829,10 @@ void MicrosoftCXXABI::EmitThreadLocalInitFuncs(
     llvm::Function *F = CXXThreadLocalInits[I];
 
     // If the GV is already in a comdat group, then we have to join it.
-    llvm::Comdat *C = GV->getComdat();
-
-    // LinkOnce and Weak linkage are lowered down to a single-member comdat
-    // group.
-    // Make an explicit group so we can join it.
-    if (!C && (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage())) {
-      C = CGM.getModule().getOrInsertComdat(GV->getName());
-      GV->setComdat(C);
+    if (llvm::Comdat *C = GV->getComdat())
       AddToXDU(F)->setComdat(C);
-    } else {
+    else
       NonComdatInits.push_back(F);
-    }
   }
 
   if (!NonComdatInits.empty()) {
diff --git a/clang/test/CodeGen/ms-declspecs.c b/clang/test/CodeGen/ms-declspecs.c
index 5dc7787b8fb..328fc835d34 100644
--- a/clang/test/CodeGen/ms-declspecs.c
+++ b/clang/test/CodeGen/ms-declspecs.c
@@ -2,8 +2,8 @@
 
 __declspec(selectany) int x1 = 1;
 const __declspec(selectany) int x2 = 2;
-// CHECK: @x1 = weak_odr global i32 1, align 4
-// CHECK: @x2 = weak_odr constant i32 2, align 4
+// CHECK: @x1 = weak_odr global i32 1, comdat, align 4
+// CHECK: @x2 = weak_odr constant i32 2, comdat, align 4
 
 struct __declspec(align(16)) S {
   char x;
diff --git a/clang/test/CodeGenCXX/cxx11-exception-spec.cpp b/clang/test/CodeGenCXX/cxx11-exception-spec.cpp
index 75f939f93f0..3fb5c15c2ab 100644
--- a/clang/test/CodeGenCXX/cxx11-exception-spec.cpp
+++ b/clang/test/CodeGenCXX/cxx11-exception-spec.cpp
@@ -22,9 +22,9 @@ template<> void S<short>::f() { h(); }
 // CHECK: define {{.*}} @_ZN1SIA2_sE1fEv() [[NUW]]
 template<> void S<short[2]>::f() noexcept { h(); }
 
-// CHECK: define {{.*}} @_Z1fIDsEvv() [[NONE]] {
+// CHECK: define {{.*}} @_Z1fIDsEvv() [[NONE]] comdat {
 template void f<char16_t>();
-// CHECK: define {{.*}} @_Z1fIA2_DsEvv() [[NUW]]  {
+// CHECK: define {{.*}} @_Z1fIA2_DsEvv() [[NUW]] comdat {
 template void f<char16_t[2]>();
 
 // CHECK: define {{.*}} @_ZN1SIDsE1fEv()
@@ -34,9 +34,9 @@ template void S<char16_t>::f();
 template void S<char16_t[2]>::f();
 
 void h() {
-  // CHECK: define {{.*}} @_Z1fIiEvv() [[NUW]] {
+  // CHECK: define {{.*}} @_Z1fIiEvv() [[NUW]] comdat {
   f<int>();
-  // CHECK: define {{.*}} @_Z1fIA2_iEvv() [[NONE]] {
+  // CHECK: define {{.*}} @_Z1fIA2_iEvv() [[NONE]] comdat {
   f<int[2]>();
 
   // CHECK: define {{.*}} @_ZN1SIiE1fEv() [[NUW]]
@@ -45,9 +45,9 @@ void h() {
   // CHECK-NOT: [[NUW]]
   S<int[2]>::f();
 
-  // CHECK: define {{.*}} @_Z1fIfEvv() [[NUW]] {
+  // CHECK: define {{.*}} @_Z1fIfEvv() [[NUW]] comdat {
   void (*f1)() = &f<float>;
-  // CHECK: define {{.*}} @_Z1fIdEvv() [[NONE]] {
+  // CHECK: define {{.*}} @_Z1fIdEvv() [[NONE]] comdat {
   void (*f2)() = &f<double>;
 
   // CHECK: define {{.*}} @_ZN1SIfE1fEv() [[NUW]]
@@ -56,9 +56,9 @@ void h() {
   // CHECK-NOT: [[NUW]]
   void (*f4)() = &S<double>::f;
 
-  // CHECK: define {{.*}} @_Z1fIA4_cEvv() [[NUW]] {
+  // CHECK: define {{.*}} @_Z1fIA4_cEvv() [[NUW]] comdat {
   (void)&f<char[4]>;
-  // CHECK: define {{.*}} @_Z1fIcEvv() [[NONE]] {
+  // CHECK: define {{.*}} @_Z1fIcEvv() [[NONE]] comdat {
   (void)&f<char>;
 
   // CHECK: define {{.*}} @_ZN1SIA4_cE1fEv() [[NUW]]
diff --git a/clang/test/CodeGenCXX/dllexport-members.cpp b/clang/test/CodeGenCXX/dllexport-members.cpp
index d913c09ec7b..5b2af1e04bd 100644
--- a/clang/test/CodeGenCXX/dllexport-members.cpp
+++ b/clang/test/CodeGenCXX/dllexport-members.cpp
@@ -110,9 +110,9 @@ public:
 
   // MSC-DAG: @"\01?StaticField@ExportMembers@@2HA"               = dllexport global i32 1, align 4
   // MSC-DAG: @"\01?StaticConstField@ExportMembers@@2HB"          = dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?StaticConstFieldEqualInit@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?StaticConstFieldBraceInit@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?ConstexprField@ExportMembers@@2HB"            = weak_odr dllexport constant i32 1, align 4
+  // MSC-DAG: @"\01?StaticConstFieldEqualInit@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+  // MSC-DAG: @"\01?StaticConstFieldBraceInit@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+  // MSC-DAG: @"\01?ConstexprField@ExportMembers@@2HB"            = weak_odr dllexport constant i32 1, comdat, align 4
   // GNU-DAG: @_ZN13ExportMembers11StaticFieldE                   = dllexport global i32 1, align 4
   // GNU-DAG: @_ZN13ExportMembers16StaticConstFieldE              = dllexport constant i32 1, align 4
   // GNU-DAG: @_ZN13ExportMembers25StaticConstFieldEqualInitE     = dllexport constant i32 1, align 4
@@ -233,9 +233,9 @@ public:
 
   // MSC-DAG: @"\01?StaticField@Nested@ExportMembers@@2HA"               = dllexport global i32 1, align 4
   // MSC-DAG: @"\01?StaticConstField@Nested@ExportMembers@@2HB"          = dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?StaticConstFieldEqualInit@Nested@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?StaticConstFieldBraceInit@Nested@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, align 4
-  // MSC-DAG: @"\01?ConstexprField@Nested@ExportMembers@@2HB"            = weak_odr dllexport constant i32 1, align 4
+  // MSC-DAG: @"\01?StaticConstFieldEqualInit@Nested@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+  // MSC-DAG: @"\01?StaticConstFieldBraceInit@Nested@ExportMembers@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+  // MSC-DAG: @"\01?ConstexprField@Nested@ExportMembers@@2HB"            = weak_odr dllexport constant i32 1, comdat, align 4
   // GNU-DAG: @_ZN13ExportMembers6Nested11StaticFieldE                   = dllexport global i32 1, align 4
   // GNU-DAG: @_ZN13ExportMembers6Nested16StaticConstFieldE              = dllexport constant i32 1, align 4
   // GNU-DAG: @_ZN13ExportMembers6Nested25StaticConstFieldEqualInitE     = dllexport constant i32 1, align 4
@@ -599,21 +599,21 @@ template<typename T> const int MemVarTmpl::StaticVar;
 template<typename T> const int MemVarTmpl::ExportedStaticVar;
 
 // Export implicit instantiation of an exported member variable template.
-// MSC-DAG: @"\01??$ExportedStaticVar@UImplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, align 4
-// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ImplicitInst_ExportedEE       = weak_odr dllexport constant i32 1, align 4
+// MSC-DAG: @"\01??$ExportedStaticVar@UImplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ImplicitInst_ExportedEE       = weak_odr dllexport constant i32 1, comdat, align 4
 int useMemVarTmpl() { return MemVarTmpl::ExportedStaticVar<ImplicitInst_Exported>; }
 
 // Export explicit instantiation declaration of an exported member variable
 // template.
-// MSC-DAG: @"\01??$ExportedStaticVar@UExplicitDecl_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, align 4
-// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ExplicitDecl_ExportedEE       = weak_odr dllexport constant i32 1, align 4
+// MSC-DAG: @"\01??$ExportedStaticVar@UExplicitDecl_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ExplicitDecl_ExportedEE       = weak_odr dllexport constant i32 1, comdat, align 4
 extern template const int MemVarTmpl::ExportedStaticVar<ExplicitDecl_Exported>;
        template const int MemVarTmpl::ExportedStaticVar<ExplicitDecl_Exported>;
 
 // Export explicit instantiation definition of an exported member variable
 // template.
-// MSC-DAG: @"\01??$ExportedStaticVar@UExplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, align 4
-// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ExplicitInst_ExportedEE       = weak_odr dllexport constant i32 1, align 4
+// MSC-DAG: @"\01??$ExportedStaticVar@UExplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+// GNU-DAG: @_ZN10MemVarTmpl17ExportedStaticVarI21ExplicitInst_ExportedEE       = weak_odr dllexport constant i32 1, comdat, align 4
 template const int MemVarTmpl::ExportedStaticVar<ExplicitInst_Exported>;
 
 // Export specialization of an exported member variable template.
@@ -630,15 +630,15 @@ template<> const int MemVarTmpl::ExportedStaticVar<ExplicitSpec_NotExported> = 1
 
 // Export explicit instantiation declaration of a non-exported member variable
 // template.
-// MSC-DAG: @"\01??$StaticVar@UExplicitDecl_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, align 4
-// GNU-DAG: @_ZN10MemVarTmpl9StaticVarI21ExplicitDecl_ExportedEE        = weak_odr dllexport constant i32 1, align 4
+// MSC-DAG: @"\01??$StaticVar@UExplicitDecl_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+// GNU-DAG: @_ZN10MemVarTmpl9StaticVarI21ExplicitDecl_ExportedEE        = weak_odr dllexport constant i32 1, comdat, align 4
 extern template __declspec(dllexport) const int MemVarTmpl::StaticVar<ExplicitDecl_Exported>;
        template __declspec(dllexport) const int MemVarTmpl::StaticVar<ExplicitDecl_Exported>;
 
 // Export explicit instantiation definition of a non-exported member variable
 // template.
-// MSC-DAG: @"\01??$StaticVar@UExplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, align 4
-// GNU-DAG: @_ZN10MemVarTmpl9StaticVarI21ExplicitInst_ExportedEE        = weak_odr dllexport constant i32 1, align 4
+// MSC-DAG: @"\01??$StaticVar@UExplicitInst_Exported@@@MemVarTmpl@@2HB" = weak_odr dllexport constant i32 1, comdat, align 4
+// GNU-DAG: @_ZN10MemVarTmpl9StaticVarI21ExplicitInst_ExportedEE        = weak_odr dllexport constant i32 1, comdat, align 4
 template __declspec(dllexport) const int MemVarTmpl::StaticVar<ExplicitInst_Exported>;
 
 // Export specialization of a non-exported member variable template.
diff --git a/clang/test/CodeGenCXX/dllexport.cpp b/clang/test/CodeGenCXX/dllexport.cpp
index cfbc7e10078..93bd1f5fe99 100644
--- a/clang/test/CodeGenCXX/dllexport.cpp
+++ b/clang/test/CodeGenCXX/dllexport.cpp
@@ -110,43 +110,43 @@ template<typename T> __declspec(dllexport) int VarTmplImplicitDef;
 USEVAR(VarTmplImplicitDef<ImplicitInst_Exported>)
 
 // Export definition.
-// MSC-DAG: @"\01??$VarTmplInit1@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z12VarTmplInit1I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmplInit1@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z12VarTmplInit1I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> __declspec(dllexport) int VarTmplInit1 = 1;
 INSTVAR(VarTmplInit1<ExplicitInst_Exported>)
 
-// MSC-DAG: @"\01??$VarTmplInit2@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z12VarTmplInit2I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmplInit2@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z12VarTmplInit2I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> int __declspec(dllexport) VarTmplInit2 = 1;
 INSTVAR(VarTmplInit2<ExplicitInst_Exported>)
 
 // Declare, then export definition.
-// MSC-DAG: @"\01??$VarTmplDeclInit@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z15VarTmplDeclInitI21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmplDeclInit@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z15VarTmplDeclInitI21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> __declspec(dllexport) extern int VarTmplDeclInit;
 template<typename T>                              int VarTmplDeclInit = 1;
 INSTVAR(VarTmplDeclInit<ExplicitInst_Exported>)
 
 // Redeclarations
-// MSC-DAG: @"\01??$VarTmplRedecl1@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z14VarTmplRedecl1I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmplRedecl1@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z14VarTmplRedecl1I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> __declspec(dllexport) extern int VarTmplRedecl1;
 template<typename T> __declspec(dllexport)        int VarTmplRedecl1 = 1;
 INSTVAR(VarTmplRedecl1<ExplicitInst_Exported>)
 
-// MSC-DAG: @"\01??$VarTmplRedecl2@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z14VarTmplRedecl2I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmplRedecl2@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z14VarTmplRedecl2I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> __declspec(dllexport) extern int VarTmplRedecl2;
 template<typename T>                              int VarTmplRedecl2 = 1;
 INSTVAR(VarTmplRedecl2<ExplicitInst_Exported>)
 
-// MSC-DAG: @"\01??$ExternalVarTmpl@UExplicitInst_Exported@@@ns@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_ZN2ns15ExternalVarTmplI21ExplicitInst_ExportedEE        = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$ExternalVarTmpl@UExplicitInst_Exported@@@ns@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_ZN2ns15ExternalVarTmplI21ExplicitInst_ExportedEE        = weak_odr dllexport global i32 1, comdat, align 4
 namespace ns { template<typename T> __declspec(dllexport) int ExternalVarTmpl = 1; }
 INSTVAR(ns::ExternalVarTmpl<ExplicitInst_Exported>)
 
-// MSC-DAG: @"\01??$ExternalAutoTypeVarTmpl@UExplicitInst_Exported@@@@3UExternal@@A" = weak_odr dllexport global %struct.External zeroinitializer, align 4
-// GNU-DAG: @_Z23ExternalAutoTypeVarTmplI21ExplicitInst_ExportedE                    = weak_odr dllexport global %struct.External zeroinitializer, align 4
+// MSC-DAG: @"\01??$ExternalAutoTypeVarTmpl@UExplicitInst_Exported@@@@3UExternal@@A" = weak_odr dllexport global %struct.External zeroinitializer, comdat, align 4
+// GNU-DAG: @_Z23ExternalAutoTypeVarTmplI21ExplicitInst_ExportedE                    = weak_odr dllexport global %struct.External zeroinitializer, comdat, align 4
 template<typename T> __declspec(dllexport) auto ExternalAutoTypeVarTmpl = External();
 template External ExternalAutoTypeVarTmpl<ExplicitInst_Exported>;
 
@@ -155,19 +155,19 @@ template<typename T> int VarTmpl = 1;
 template<typename T> __declspec(dllexport) int ExportedVarTmpl = 1;
 
 // Export implicit instantiation of an exported variable template.
-// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z15ExportedVarTmplI21ImplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z15ExportedVarTmplI21ImplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 USEVAR(ExportedVarTmpl<ImplicitInst_Exported>)
 
 // Export explicit instantiation declaration of an exported variable template.
-// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z15ExportedVarTmplI21ExplicitDecl_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z15ExportedVarTmplI21ExplicitDecl_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 extern template int ExportedVarTmpl<ExplicitDecl_Exported>;
        template int ExportedVarTmpl<ExplicitDecl_Exported>;
 
 // Export explicit instantiation definition of an exported variable template.
-// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z15ExportedVarTmplI21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$ExportedVarTmpl@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z15ExportedVarTmplI21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template __declspec(dllexport) int ExportedVarTmpl<ExplicitInst_Exported>;
 
 // Export specialization of an exported variable template.
@@ -187,14 +187,14 @@ template<> int ExportedVarTmpl<ExplicitSpec_NotExported>;
 
 
 // Export explicit instantiation declaration of a non-exported variable template.
-// MSC-DAG: @"\01??$VarTmpl@UExplicitDecl_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z7VarTmplI21ExplicitDecl_ExportedE           = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmpl@UExplicitDecl_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z7VarTmplI21ExplicitDecl_ExportedE           = weak_odr dllexport global i32 1, comdat, align 4
 extern template __declspec(dllexport) int VarTmpl<ExplicitDecl_Exported>;
        template __declspec(dllexport) int VarTmpl<ExplicitDecl_Exported>;
 
 // Export explicit instantiation definition of a non-exported variable template.
-// MSC-DAG: @"\01??$VarTmpl@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, align 4
-// GNU-DAG: @_Z7VarTmplI21ExplicitInst_ExportedE           = weak_odr dllexport global i32 1, align 4
+// MSC-DAG: @"\01??$VarTmpl@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
+// GNU-DAG: @_Z7VarTmplI21ExplicitInst_ExportedE           = weak_odr dllexport global i32 1, comdat, align 4
 template __declspec(dllexport) int VarTmpl<ExplicitInst_Exported>;
 
 // Export specialization of a non-exported variable template.
diff --git a/clang/test/CodeGenCXX/dllimport.cpp b/clang/test/CodeGenCXX/dllimport.cpp
index ddd390ad6f3..e5b9f64dcca 100644
--- a/clang/test/CodeGenCXX/dllimport.cpp
+++ b/clang/test/CodeGenCXX/dllimport.cpp
@@ -243,7 +243,7 @@ __declspec(dllimport) __attribute__((noinline)) inline void noinline() {}
 USE(noinline)
 
 // MSC2-NOT: @"\01?alwaysInline@@YAXXZ"()
-// GNU2-NOT: @_Z12alwaysInlinev()
+// GNU-DAG: define linkonce_odr void @_Z12alwaysInlinev() {{.*}} comdat {
 __declspec(dllimport) __attribute__((always_inline)) inline void alwaysInline() {}
 USE(alwaysInline)
 
diff --git a/clang/test/CodeGenCXX/ms-integer-static-data-members-exported.cpp b/clang/test/CodeGenCXX/ms-integer-static-data-members-exported.cpp
index 3f868f36ff6..78bb3a2b1af 100644
--- a/clang/test/CodeGenCXX/ms-integer-static-data-members-exported.cpp
+++ b/clang/test/CodeGenCXX/ms-integer-static-data-members-exported.cpp
@@ -17,6 +17,6 @@ struct __declspec(dllexport) S {
   };
 };
 
-// CHECK: @"\01?x@S@@2FB" = weak_odr dllexport constant i16 42, align 2
-// CHECK: @"\01?y@S@@2W4Enum@@B" = weak_odr dllexport constant i32 2, align 4
+// CHECK: @"\01?x@S@@2FB" = weak_odr dllexport constant i16 42, comdat, align 2
+// CHECK: @"\01?y@S@@2W4Enum@@B" = weak_odr dllexport constant i32 2, comdat, align 4
 // CHECK-NOT: NonExported
diff --git a/clang/test/CodeGenCXX/ms-integer-static-data-members.cpp b/clang/test/CodeGenCXX/ms-integer-static-data-members.cpp
index b02b679d71a..4965f731918 100644
--- a/clang/test/CodeGenCXX/ms-integer-static-data-members.cpp
+++ b/clang/test/CodeGenCXX/ms-integer-static-data-members.cpp
@@ -26,7 +26,7 @@ const int S::x = 5;
 
 
 // Inline initialization.
-// CHECK-INLINE: @"\01?x@S@@2HB" = linkonce_odr constant i32 5, align 4
+// CHECK-INLINE: @"\01?x@S@@2HB" = linkonce_odr constant i32 5, comdat, align 4
 
 // Out-of-line initialization.
 // CHECK-OUTOFLINE: @"\01?x@S@@2HB" = constant i32 5, align 4
diff --git a/clang/test/CodeGenCXX/split-stacks.cpp b/clang/test/CodeGenCXX/split-stacks.cpp
index 3e120344d6b..76e1b79b8f1 100644
--- a/clang/test/CodeGenCXX/split-stacks.cpp
+++ b/clang/test/CodeGenCXX/split-stacks.cpp
@@ -18,7 +18,7 @@ int nosplit() {
 
 // CHECK-SEGSTK: define i32 @_Z3foov() [[SS:#[0-9]+]] {
 // CHECK-SEGSTK: define i32 @_Z7nosplitv() [[NSS1:#[0-9]+]] {
-// CHECK-SEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] {
+// CHECK-SEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] comdat {
 // CHECK-SEGSTK-NOT: [[NSS1]] = { {{.*}} "split-stack" {{.*}} }
 // CHECK-SEGSTK-NOT: [[NSS2]] = { {{.*}} "split-stack" {{.*}} }
 // CHECK-SEGSTK: [[SS]] = { {{.*}} "split-stack" {{.*}} }
@@ -27,7 +27,7 @@ int nosplit() {
 
 // CHECK-NOSEGSTK: define i32 @_Z3foov() [[NSS0:#[0-9]+]] {
 // CHECK-NOSEGSTK: define i32 @_Z7nosplitv() [[NSS1:#[0-9]+]] {
-// CHECK-NOSEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] {
+// CHECK-NOSEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] comdat {
 // CHECK-NOSEGSTK-NOT: [[NSS1]] = { {{.*}} "split-stack" {{.*}} }
 // CHECK-NOSEGSTK-NOT: [[NSS2]] = { {{.*}} "split-stack" {{.*}} }
 // CHECK-NOSEGSTK-NOT: [[NSS3]] = { {{.*}} "split-stack" {{.*}} }
diff --git a/clang/test/CodeGenCXX/static-init.cpp b/clang/test/CodeGenCXX/static-init.cpp
index a9debe3de76..66ff5b3fbab 100644
--- a/clang/test/CodeGenCXX/static-init.cpp
+++ b/clang/test/CodeGenCXX/static-init.cpp
@@ -7,10 +7,8 @@
 // CHECK: @_ZZN5test31BC1EvE1u = internal global { i8, [3 x i8] } { i8 97, [3 x i8] undef }, align 4
 // CHECK: @_ZZN5test1L6getvarEiE3var = internal constant [4 x i32] [i32 1, i32 0, i32 2, i32 4], align 16
 
-// CHECK: @_ZZ2h2vE1i = linkonce_odr global i32 0
-// CHECK-NOT: comdat
-// CHECK: @_ZGVZ2h2vE1i = linkonce_odr global i64 0
-// CHECK-NOT: comdat
+// CHECK: @_ZZ2h2vE1i = linkonce_odr global i32 0, comdat, align
+// CHECK: @_ZGVZ2h2vE1i = linkonce_odr global i64 0, comdat{{$}}
 
 struct A {
   A();
@@ -37,8 +35,7 @@ void h() {
   static const int i = a();
 }
 
-// CHECK: define linkonce_odr void @_Z2h2v()
-// CHECK-NOT: comdat
+// CHECK: define linkonce_odr void @_Z2h2v() {{.*}} comdat {
 inline void h2() {
   static int i = a();
 }