yaxunl added a comment. In D67509#1679524 <https://reviews.llvm.org/D67509#1679524>, @tra wrote:
> In D67509#1678394 <https://reviews.llvm.org/D67509#1678394>, @yaxunl wrote: > > > A reduced test case is > > > > struct A { > > A(); > > }; > > > > template <class T> > > struct B > > { > > T a; > > constexpr B() = default; > > }; > > > > B<A> x; > > > > > > > > `B<A>::B()` got implicit `__host__ __device__` attrs due to constexpr > > before entering Sema::inferCUDATargetForImplicitSpecialMember. > > In Sema::inferCUDATargetForImplicitSpecialMember, the inferred hostness of > > `B<A>::B()` is host since `A::A()` is host. This causes discrepancy between > > the inferred hostness and the existing hostness. > > > On one hand `inferCUDATargetForImplicitSpecialMember` is correct here. > On the other hand, `constexpr` being implicitly `__host__ __device__` also > works OK, with the error popping up only if we need to instantiate the B<A> > on device side. > > So, what we want is: > > __host__ void f() {B<A> x;} // This should compile > __device__ void f() {B<A> x;} // This should produce an error. > > struct foo { > __host__ foo() { B<A> x; } // should compile > __device__ foo() { B<A> x; } // ??? > }; > > > We could remove the implicit '__device__' attribute from the function. This > should make `__device__ foo()` fail to compile regardless of whether `struct > foo` is instantiated on device. > Or we can keep the defaulted constexpr function as `__host__ __device__` and > catch the error only if/when `struct foo` is instantiated on device side. > > NVCC (and clang as it is right now) appear to follow the latter -- there's no > error if we don't generate code for the function. > https://godbolt.org/z/aVhvVn > > For the sake of avoiding surprises, I think we should preserve this behavior > and just relax the assertion here. We should be OK to infer stricter set of > attributes, but not to relax them. I will add a lit test to make sure we have the desired behavior. Repository: rL LLVM CHANGES SINCE LAST ACTION https://reviews.llvm.org/D67509/new/ https://reviews.llvm.org/D67509 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
