[CIR][CUDA] Fix CUDA CIR mangling bug (llvm#1396)

Includes function name while mangling C functions to avoid link errors.
[This is the same way OG handles
it](https://github.com/llvm/clangir/blob/c301b4a0d3d2d79b26c9c809c11b8a1137c0a9ec/clang/lib/CodeGen/CodeGenModule.cpp#L1896).

Author: advay168

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -2427,7 +2427,7 @@ static std::string getMangledNameImpl(CIRGenModule &CGM, GlobalDecl GD,
       assert(0 && "NYI");
     } else if (FD && FD->hasAttr<CUDAGlobalAttr>() &&
                GD.getKernelReferenceKind() == KernelReferenceKind::Stub) {
-      Out << "__device_stub__";
+      Out << "__device_stub__" << II->getName();
     } else {
       Out << II->getName();
     }

clang/test/CIR/CodeGen/CUDA/mangling.cu

@@ -0,0 +1,92 @@
+#include "../Inputs/cuda.h"
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir \
+// RUN:            -x cuda -emit-cir -target-sdk-version=12.3 \
+// RUN:            %s -o %t.cir
+// RUN: FileCheck --check-prefix=CIR-HOST --input-file=%t.cir %s
+
+// RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fclangir \
+// RUN:            -fcuda-is-device -emit-cir -target-sdk-version=12.3 \
+// RUN:            %s -o %t.cir
+// RUN: FileCheck --check-prefix=CIR-DEVICE --input-file=%t.cir %s
+
+namespace ns {
+    __global__ void cpp_global_function_1(int a, int* b, float c) {}
+    // CIR-HOST: cir.func @_ZN2ns36__device_stub__cpp_global_function_1EiPif
+    // CIR-DEVICE: cir.func @_ZN2ns21cpp_global_function_1EiPif
+
+    __global__ void cpp_global_function_2(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @_ZN2ns36__device_stub__cpp_global_function_2EiPif
+    // CIR-DEVICE: cir.func @_ZN2ns21cpp_global_function_2EiPif
+
+    __host__ void cpp_host_function_1(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @_ZN2ns19cpp_host_function_1EiPif
+
+    __host__ void cpp_host_function_2(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @_ZN2ns19cpp_host_function_2EiPif
+
+    __device__ void cpp_device_function_1(int a, int* b, float c) {}
+
+    // CIR-DEVICE: cir.func @_ZN2ns21cpp_device_function_1EiPif
+
+    __device__ void cpp_device_function_2(int a, int* b, float c) {}
+
+    // CIR-DEVICE: cir.func @_ZN2ns21cpp_device_function_2EiPif
+}
+
+__global__ void cpp_global_function_1(int a, int* b, float c) {}
+
+// CIR-HOST: cir.func @_Z36__device_stub__cpp_global_function_1iPif
+// CIR-DEVICE: cir.func @_Z21cpp_global_function_1iPif
+
+__global__ void cpp_global_function_2(int a, int* b, float c) {}
+
+// CIR-HOST: cir.func @_Z36__device_stub__cpp_global_function_2iPif
+// CIR-DEVICE: cir.func @_Z21cpp_global_function_2iPif
+
+__host__ void cpp_host_function_1(int a, int* b, float c) {}
+
+// CIR-HOST: cir.func @_Z19cpp_host_function_1iPif
+
+__host__ void cpp_host_function_2(int a, int* b, float c) {}
+
+// CIR-HOST: cir.func @_Z19cpp_host_function_2iPif
+
+__device__ void cpp_device_function_1(int a, int* b, float c) {}
+
+// CIR-DEVICE: cir.func @_Z21cpp_device_function_1iPif
+
+__device__ void cpp_device_function_2(int a, int* b, float c) {}
+
+// CIR-DEVICE: cir.func @_Z21cpp_device_function_2iPif
+
+extern "C" {
+    __global__ void c_global_function_1(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @__device_stub__c_global_function_1
+    // CIR-DEVICE: cir.func @c_global_function_1
+
+    __global__ void c_global_function_2(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @__device_stub__c_global_function_2
+    // CIR-DEVICE: cir.func @c_global_function_2
+
+    __host__ void c_host_function_1(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @c_host_function_1
+
+    __host__ void c_host_function_2(int a, int* b, float c) {}
+
+    // CIR-HOST: cir.func @c_host_function_2
+
+    __device__ void c_device_function_1(int a, int* b, float c) {}
+
+    // CIR-DEVICE: cir.func @c_device_function_1
+
+    __device__ void c_device_function_2(int a, int* b, float c) {}
+
+    // CIR-DEVICE: cir.func @c_device_function_2
+}