[clang] [CIR] Upstream support for variable template specializations (PR #151069)

[Morris Hafner via cfe-commits]

https://github.com/mmha updated https://github.com/llvm/llvm-project/pull/151069

>From c9bd371217cad933639170a362ad8e23bd8c3fc5 Mon Sep 17 00:00:00 2001
From: Morris Hafner <mhafner at nvidia.com>
Date: Wed, 6 Aug 2025 15:58:44 +0200
Subject: [PATCH 1/2] [CIR] Upstream support for variable template
 specializations

---
 clang/lib/CIR/CodeGen/CIRGenModule.cpp        |  3 +-
 .../variable-template-specialization.cpp      | 32 +++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CIR/CodeGen/variable-template-specialization.cpp

diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index b143682e435d2..fc8f9d056292d 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -1307,7 +1307,8 @@ void CIRGenModule::emitTopLevelDecl(Decl *decl) {
   }
 
   case Decl::Var:
-  case Decl::Decomposition: {
+  case Decl::Decomposition:
+  case Decl::VarTemplateSpecialization: {
     auto *vd = cast<VarDecl>(decl);
     if (isa<DecompositionDecl>(decl)) {
       errorNYI(decl->getSourceRange(), "global variable decompositions");
diff --git a/clang/test/CIR/CodeGen/variable-template-specialization.cpp b/clang/test/CIR/CodeGen/variable-template-specialization.cpp
new file mode 100644
index 0000000000000..f5043779a21f7
--- /dev/null
+++ b/clang/test/CIR/CodeGen/variable-template-specialization.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=c++14 -triple nvptx64-unknown-unknown -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -std=c++14 -triple nvptx64-unknown-unknown -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t-cir.ll %s
+// RUN: %clang_cc1 -std=c++14 -triple nvptx64-unknown-unknown -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=OGCG --input-file=%t.ll %s
+
+struct some_struct {
+    int x;
+};
+
+template<int I>
+int var_template;
+
+template<> int var_template<0>;
+template<> int var_template<1> = 1;
+template<> some_struct var_template<2>;
+
+// CIR: !rec_some_struct = !cir.record<struct "some_struct" {!s32i}>
+// CIR: cir.global external @_Z12var_templateILi0EE = #cir.int<0> : !s32i
+// CIR: cir.global external @_Z12var_templateILi1EE = #cir.int<1> : !s32i
+// CIR: cir.global external @_Z12var_templateILi2EE = #cir.zero : !rec_some_struct
+
+// LLVM: %[[STRUCT_TYPE:.+]] = type { i32 }
+// LLVM: @_Z12var_templateILi0EE = global i32 0
+// LLVM: @_Z12var_templateILi1EE = global i32 1
+// LLVM: @_Z12var_templateILi2EE = global %[[STRUCT_TYPE]] zeroinitializer
+
+// OGCG: %[[STRUCT_TYPE:.+]] = type { i32 }
+// OGCG: @_Z12var_templateILi0EE = global i32 0
+// OGCG: @_Z12var_templateILi1EE = global i32 1
+// OGCG: @_Z12var_templateILi2EE = global %[[STRUCT_TYPE]] zeroinitializer

>From 6c4845154890afd1889e2cf7cfe9fcbe5d7ae426 Mon Sep 17 00:00:00 2001
From: Morris Hafner <mhafner at nvidia.com>
Date: Wed, 6 Aug 2025 15:59:34 +0200
Subject: [PATCH 2/2] Add support for partial specializations

---
 clang/lib/CIR/CodeGen/CIRGenModule.cpp                    | 2 ++
 .../test/CIR/CodeGen/variable-template-specialization.cpp | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index fc8f9d056292d..425250db87da6 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -1343,6 +1343,8 @@ void CIRGenModule::emitTopLevelDecl(Decl *decl) {
   case Decl::StaticAssert:
   case Decl::TypeAliasTemplate:
   case Decl::UsingShadow:
+  case Decl::VarTemplate:
+  case Decl::VarTemplatePartialSpecialization:
     break;
 
   case Decl::CXXConstructor:
diff --git a/clang/test/CIR/CodeGen/variable-template-specialization.cpp b/clang/test/CIR/CodeGen/variable-template-specialization.cpp
index f5043779a21f7..c13ab51ec64c9 100644
--- a/clang/test/CIR/CodeGen/variable-template-specialization.cpp
+++ b/clang/test/CIR/CodeGen/variable-template-specialization.cpp
@@ -30,3 +30,11 @@ template<> some_struct var_template<2>;
 // OGCG: @_Z12var_templateILi0EE = global i32 0
 // OGCG: @_Z12var_templateILi1EE = global i32 1
 // OGCG: @_Z12var_templateILi2EE = global %[[STRUCT_TYPE]] zeroinitializer
+
+template<typename T, int I> int partial_var_template_specialization_shouldnt_hit_codegen;
+template<typename T> int partial_var_template_specialization_shouldnt_hit_codegen<T, 123>;
+template<int I> float partial_var_template_specialization_shouldnt_hit_codegen<float, I>;
+
+// CIR-NOT: partial_var_template_specialization_shouldnt_hit_codegen
+// LLVM-NOT: partial_var_template_specialization_shouldnt_hit_codegen
+// OGCG-NOT: partial_var_template_specialization_shouldnt_hit_codegen