sepavloff created this revision.
sepavloff added reviewers: rsmith, tra.
sepavloff added a subscriber: cfe-commits.
Current version of clang cannot build the program:
```
template<int n> int var;
int main(int argc, char *argv[]) {
return var<0>;
}
```
as linker does not find `var<0>`, codegen treats it as declaration only.
However this program must build succesfully, because the template
declaration is a definition as none of the conditions mentioned in
[basic.def]p2 is met. With this change codegen generates definitions
for file level variable template specialization even if the declaration
does not contain an initializer.
https://reviews.llvm.org/D24649
Files:
lib/CodeGen/CodeGenModule.cpp
test/CodeGenCXX/dllexport.cpp
test/CodeGenCXX/variable-templates.cpp
Index: test/CodeGenCXX/variable-templates.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/variable-templates.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -std=c++14 %s -triple=x86_64-linux -emit-llvm -o - |
FileCheck %s
+
+// Unused template
+// CHECK-NOT: _Z6var_00ILi0EE
+template<int n> int var_00;
+
+// Definition without initializer
+// CHECK: @_Z6var_01ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_01;
+int use_01a() {
+ return var_01<0>;
+}
+int use_01b() {
+ return var_01<0>;
+}
+
+// Definitions without initializer combined with extern declaration
+
+// CHECK: @_Z6var_02ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> extern int var_02;
+template<int n> int var_02;
+int use_02() {
+ return var_02<0>;
+}
+
+// CHECK: @_Z6var_03ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_03;
+template<int n> extern int var_03;
+int use_03() {
+ return var_03<0>;
+}
+
+// CHECK: @_Z6var_04ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> extern int var_04;
+int use_04() {
+ return var_04<0>;
+}
+template<int n> int var_04;
+
+// CHECK: @_Z6var_05ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_05;
+int use_05() {
+ return var_05<0>;
+}
+template<int n> extern int var_05;
+
+
+int main(int argc, char *argv[]) {
+ return 0;
+}
Index: test/CodeGenCXX/dllexport.cpp
===================================================================
--- test/CodeGenCXX/dllexport.cpp
+++ test/CodeGenCXX/dllexport.cpp
@@ -108,8 +108,8 @@
template<typename T> __declspec(dllexport) int VarTmplDef;
INSTVAR(VarTmplDef<ExplicitInst_Exported>)
-// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" =
external dllexport global
-// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE =
external dllexport global
+// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" =
weak_odr dllexport global
+// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE =
weak_odr dllexport global
template<typename T> __declspec(dllexport) int VarTmplImplicitDef;
USEVAR(VarTmplImplicitDef<ImplicitInst_Exported>)
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1609,7 +1609,11 @@
!VD->hasDefinition() &&
(VD->hasAttr<CUDAConstantAttr>() ||
VD->hasAttr<CUDADeviceAttr>());
- if (!MustEmitForCuda &&
+ bool MustEmitVarInst = isa<VarTemplateSpecializationDecl>(VD) &&
+ !VD->isStaticDataMember() &&
+ !VD->hasDefinition() &&
+ !VD->hasAttr<DLLImportAttr>();
+ if (!(MustEmitForCuda || MustEmitVarInst) &&
VD->isThisDeclarationADefinition() != VarDecl::Definition &&
!Context.isMSStaticDataMemberInlineDefinition(VD)) {
// If this declaration may have caused an inline variable definition to
Index: test/CodeGenCXX/variable-templates.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/variable-templates.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -std=c++14 %s -triple=x86_64-linux -emit-llvm -o - | FileCheck %s
+
+// Unused template
+// CHECK-NOT: _Z6var_00ILi0EE
+template<int n> int var_00;
+
+// Definition without initializer
+// CHECK: @_Z6var_01ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_01;
+int use_01a() {
+ return var_01<0>;
+}
+int use_01b() {
+ return var_01<0>;
+}
+
+// Definitions without initializer combined with extern declaration
+
+// CHECK: @_Z6var_02ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> extern int var_02;
+template<int n> int var_02;
+int use_02() {
+ return var_02<0>;
+}
+
+// CHECK: @_Z6var_03ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_03;
+template<int n> extern int var_03;
+int use_03() {
+ return var_03<0>;
+}
+
+// CHECK: @_Z6var_04ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> extern int var_04;
+int use_04() {
+ return var_04<0>;
+}
+template<int n> int var_04;
+
+// CHECK: @_Z6var_05ILi0EE = linkonce_odr global i32 0, comdat
+template<int n> int var_05;
+int use_05() {
+ return var_05<0>;
+}
+template<int n> extern int var_05;
+
+
+int main(int argc, char *argv[]) {
+ return 0;
+}
Index: test/CodeGenCXX/dllexport.cpp
===================================================================
--- test/CodeGenCXX/dllexport.cpp
+++ test/CodeGenCXX/dllexport.cpp
@@ -108,8 +108,8 @@
template<typename T> __declspec(dllexport) int VarTmplDef;
INSTVAR(VarTmplDef<ExplicitInst_Exported>)
-// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" = external dllexport global
-// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE = external dllexport global
+// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" = weak_odr dllexport global
+// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE = weak_odr dllexport global
template<typename T> __declspec(dllexport) int VarTmplImplicitDef;
USEVAR(VarTmplImplicitDef<ImplicitInst_Exported>)
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1609,7 +1609,11 @@
!VD->hasDefinition() &&
(VD->hasAttr<CUDAConstantAttr>() ||
VD->hasAttr<CUDADeviceAttr>());
- if (!MustEmitForCuda &&
+ bool MustEmitVarInst = isa<VarTemplateSpecializationDecl>(VD) &&
+ !VD->isStaticDataMember() &&
+ !VD->hasDefinition() &&
+ !VD->hasAttr<DLLImportAttr>();
+ if (!(MustEmitForCuda || MustEmitVarInst) &&
VD->isThisDeclarationADefinition() != VarDecl::Definition &&
!Context.isMSStaticDataMemberInlineDefinition(VD)) {
// If this declaration may have caused an inline variable definition to
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