[CUDA][HIP] allow trivial ctor/dtor in device var init (#73140)

Treat ctor/dtor in device var init as host device function
so that they can be used to initialize file-scope
device variables to match nvcc behavior. If they are non-trivial
they will be diagnosed.

We cannot add implicit host device attrs to non-trivial
ctor/dtor since determining whether they are non-trivial
needs to know whether they have a trivial body and all their
member and base classes' ctor/dtor have trivial body, which
is affected by where their bodies are defined or instantiated.

Fixes: #72261

Fixes: SWDEV-432412

Author: yxsamliu

clang/lib/Sema/SemaCUDA.cpp

@@ -225,6 +225,15 @@ Sema::CUDAFunctionPreference
 Sema::IdentifyCUDAPreference(const FunctionDecl *Caller,
                              const FunctionDecl *Callee) {
   assert(Callee && "Callee must be valid.");
+
+  // Treat ctor/dtor as host device function in device var initializer to allow
+  // trivial ctor/dtor without device attr to be used. Non-trivial ctor/dtor
+  // will be diagnosed by checkAllowedCUDAInitializer.
+  if (Caller == nullptr && CurCUDATargetCtx.Kind == CTCK_InitGlobalVar &&
+      CurCUDATargetCtx.Target == CFT_Device &&
+      (isa<CXXConstructorDecl>(Callee) || isa<CXXDestructorDecl>(Callee)))
+    return CFP_HostDevice;
+
   CUDAFunctionTarget CallerTarget = IdentifyCUDATarget(Caller);
   CUDAFunctionTarget CalleeTarget = IdentifyCUDATarget(Callee);
 

clang/test/SemaCUDA/trivial-ctor-dtor.cu

@@ -0,0 +1,57 @@
+// RUN: %clang_cc1 -isystem %S/Inputs  -fsyntax-only -verify %s
+// RUN: %clang_cc1 -isystem %S/Inputs -fcuda-is-device -fsyntax-only -verify %s
+
+#include <cuda.h>
+
+// Check trivial ctor/dtor
+struct A {
+  int x;
+  A() {}
+  ~A() {}
+};
+
+__device__ A a;
+
+// Check trivial ctor/dtor of template class
+template<typename T>
+struct TA {
+  T x;
+  TA() {}
+  ~TA() {}
+};
+
+__device__ TA<int> ta;
+
+// Check non-trivial ctor/dtor in parent template class
+template<typename T>
+struct TB {
+  T x;
+  TB() { static int nontrivial_ctor = 1; }
+  ~TB() {}
+};
+
+template<typename T>
+struct TC : TB<T> {
+  T x;
+  TC() {}
+  ~TC() {}
+};
+
+template class TC<int>;
+
+__device__ TC<int> tc; //expected-error {{dynamic initialization is not supported for __device__, __constant__, __shared__, and __managed__ variables}}
+
+// Check trivial ctor specialization
+template <typename T>
+struct C {
+    explicit C() {};
+};
+
+template <> C<int>::C() {};
+__device__ C<int> ci_d;
+C<int> ci_h;
+
+// Check non-trivial ctor specialization
+template <> C<float>::C() { static int nontrivial_ctor = 1; }
+__device__ C<float> cf_d; //expected-error {{dynamic initialization is not supported for __device__, __constant__, __shared__, and __managed__ variables}}
+C<float> cf_h;