Use a trivial comdat for C++ tables.

This produces comdats for vtables, typeinfo, typeinfo names, and vtts.

When combined with llvm not producing implicit comdats, not doing this would
cause code bloat on ELF and link errors on COFF.

llvm-svn: 226227

4 files changed, 38 insertions, 25 deletions

diff --git a/clang/lib/CodeGen/CGVTT.cpp b/clang/lib/CodeGen/CGVTT.cpp
index bd280ea14e8..81bd65179b7 100644
--- a/clang/lib/CodeGen/CGVTT.cpp
+++ b/clang/lib/CodeGen/CGVTT.cpp
@@ -94,6 +94,9 @@ CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
   // Set the correct linkage.
   VTT->setLinkage(Linkage);
 
+  if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
+    VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
+
   // Set the right visibility.
   CGM.setGlobalVisibility(VTT, RD);
 }
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 7a97aa64ea9..72d7a6cd8e0 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1828,7 +1828,10 @@ CodeGenModule::CreateOrReplaceCXXRuntimeVariable(StringRef Name,
     
     OldGV->eraseFromParent();
   }
-  
+
+  if (supportsCOMDAT() && GV->isWeakForLinker())
+    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+
   return GV;
 }
 
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 7d8ad465bf3..29d922c68e3 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1256,6 +1256,9 @@ void ItaniumCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
   // Set the correct linkage.
   VTable->setLinkage(Linkage);
 
+  if (CGM.supportsCOMDAT() && VTable->isWeakForLinker())
+    VTable->setComdat(CGM.getModule().getOrInsertComdat(VTable->getName()));
+
   // Set the right visibility.
   CGM.setGlobalVisibility(VTable, RD);
 
@@ -2716,9 +2719,13 @@ llvm::Constant *ItaniumRTTIBuilder::BuildTypeInfo(QualType Ty, bool Force) {
 
   llvm::Constant *Init = llvm::ConstantStruct::getAnon(Fields);
 
+  llvm::Module &M = CGM.getModule();
   llvm::GlobalVariable *GV =
-    new llvm::GlobalVariable(CGM.getModule(), Init->getType(),
-                             /*Constant=*/true, Linkage, Init, Name);
+      new llvm::GlobalVariable(M, Init->getType(),
+                               /*Constant=*/true, Linkage, Init, Name);
+
+  if (CGM.supportsCOMDAT() && GV->isWeakForLinker())
+    GV->setComdat(M.getOrInsertComdat(GV->getName()));
 
   // If there's already an old global variable, replace it with the new one.
   if (OldGV) {
diff --git a/clang/test/CodeGenCXX/vtable-linkage.cpp b/clang/test/CodeGenCXX/vtable-linkage.cpp
index 9c08b3037ca..5cbd3897a1f 100644
--- a/clang/test/CodeGenCXX/vtable-linkage.cpp
+++ b/clang/test/CodeGenCXX/vtable-linkage.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o %t
+// RUN: %clang_cc1 %s -triple=x86_64-pc-linux -emit-llvm -o %t
 // RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -disable-llvm-optzns -O3 -emit-llvm -o %t.opt
 // RUN: FileCheck --check-prefix=CHECK %s < %t
 // RUN: FileCheck --check-prefix=CHECK-OPT %s < %t.opt
@@ -89,10 +89,10 @@ void use_F() {
 
 // C has no key function, so its vtable should have weak_odr linkage
 // and hidden visibility (rdar://problem/7523229).
-// CHECK-DAG: @_ZTV1C = linkonce_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1C = linkonce_odr constant
-// CHECK-DAG: @_ZTI1C = linkonce_odr constant
-// CHECK-DAG: @_ZTT1C = linkonce_odr unnamed_addr constant
+// CHECK-DAG: @_ZTV1C = linkonce_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1C = linkonce_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1C = linkonce_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTT1C = linkonce_odr unnamed_addr constant {{.*}}, comdat{{$}}
 
 // D has a key function that is defined in this translation unit so its vtable is
 // defined in the translation unit.
@@ -110,28 +110,28 @@ void use_F() {
 // E<short> is an explicit template instantiation with a key function
 // defined in this translation unit, so its vtable should have
 // weak_odr linkage.
-// CHECK-DAG: @_ZTV1EIsE = weak_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1EIsE = weak_odr constant
-// CHECK-DAG: @_ZTI1EIsE = weak_odr constant
+// CHECK-DAG: @_ZTV1EIsE = weak_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1EIsE = weak_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1EIsE = weak_odr constant {{.*}}, comdat{{$}}
 
 // F<short> is an explicit template instantiation without a key
 // function, so its vtable should have weak_odr linkage
-// CHECK-DAG: @_ZTV1FIsE = weak_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1FIsE = weak_odr constant
-// CHECK-DAG: @_ZTI1FIsE = weak_odr constant
+// CHECK-DAG: @_ZTV1FIsE = weak_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1FIsE = weak_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1FIsE = weak_odr constant {{.*}}, comdat{{$}}
 
 // E<long> is an implicit template instantiation with a key function
 // defined in this translation unit, so its vtable should have
 // linkonce_odr linkage.
-// CHECK-DAG: @_ZTV1EIlE = linkonce_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1EIlE = linkonce_odr constant
-// CHECK-DAG: @_ZTI1EIlE = linkonce_odr constant
+// CHECK-DAG: @_ZTV1EIlE = linkonce_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1EIlE = linkonce_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1EIlE = linkonce_odr constant {{.*}}, comdat{{$}}
 
 // F<long> is an implicit template instantiation with no key function,
 // so its vtable should have linkonce_odr linkage.
-// CHECK-DAG: @_ZTV1FIlE = linkonce_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1FIlE = linkonce_odr constant
-// CHECK-DAG: @_ZTI1FIlE = linkonce_odr constant
+// CHECK-DAG: @_ZTV1FIlE = linkonce_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1FIlE = linkonce_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1FIlE = linkonce_odr constant {{.*}}, comdat{{$}}
 
 // F<int> is an explicit template instantiation declaration without a
 // key function, so its vtable should have external linkage.
@@ -158,11 +158,11 @@ void use_F() {
 
 // F<char> is an explicit specialization without a key function, so
 // its vtable should have linkonce_odr linkage.
-// CHECK-DAG: @_ZTV1FIcE = linkonce_odr unnamed_addr constant
-// CHECK-DAG: @_ZTS1FIcE = linkonce_odr constant
-// CHECK-DAG: @_ZTI1FIcE = linkonce_odr constant
+// CHECK-DAG: @_ZTV1FIcE = linkonce_odr unnamed_addr constant {{.*}}, comdat,
+// CHECK-DAG: @_ZTS1FIcE = linkonce_odr constant {{.*}}, comdat{{$}}
+// CHECK-DAG: @_ZTI1FIcE = linkonce_odr constant {{.*}}, comdat{{$}}
 
-// CHECK-DAG: @_ZTV1GIiE = linkonce_odr unnamed_addr constant
+// CHECK-DAG: @_ZTV1GIiE = linkonce_odr unnamed_addr constant {{.*}}, comdat,
 template <typename T>
 class G {
 public:
@@ -178,7 +178,7 @@ void G_f0()  { new G<int>(); }
 
 // H<int> has a key function without a body but it's a template instantiation
 // so its VTable must be emitted.
-// CHECK-DAG: @_ZTV1HIiE = linkonce_odr unnamed_addr constant
+// CHECK-DAG: @_ZTV1HIiE = linkonce_odr unnamed_addr constant {{.*}}, comdat,
 template <typename T>
 class H {
 public: