[C++4OpenCL] Add extra diagnostics for kernel argument types

[olestrohm]

Summary

Adds extra error diagnostics when using unsupported types in kernel arguments.

This fixes https://bugs.llvm.org/show_bug.cgi?id=48099

[Anastasia]

clang/test/SemaOpenCLCXX/invalid-kernel.clcpp

44

Let's also test atomic and void pointer type since you are checking it in your patch?

This should be extended to references btw since clang implements them as a pointer type so we can allow that too.

Similarly for by-value parameters - let's test an OpenCL type too.

[olestrohm]

Added more exhaustive tests, as well as fixed the diagnostic to allow reference types.

[svenvh]

clang/lib/Sema/SemaDecl.cpp

8673

I am wondering if this should be made conditional on C++ mode? Or is there no possible way that this new return InvalidKernelParam can be triggered from OpenCL C mode?

[Anastasia]

LGTM from my side. I will leave final approval to Sven.

clang/lib/Sema/SemaDecl.cpp

8673

I think it shouldn't because C types are POD types which is a superset of standard layout types.

[olestrohm]

clang/lib/Sema/SemaDecl.cpp

8673

I believe these rules are correct, but just in case they are not, I will make it conditional on C++ mode to not accidentally break OpenCL C.

[olestrohm]

Restricted the checks to C++ for OpenCL and added another test for OpenCL vector types.

[svenvh]

LGTM, thanks!