[HIP] Diagnose unsupported host triple

[rjmccall]

LGTM.

include/clang/Basic/DiagnosticDriverKinds.td

 def err_drv_no_cuda_libdevice : Error<
   "cannot find libdevice for %0. Provide path to different CUDA installation "
   "via --cuda-path, or pass -nocudalib to build without linking with libdevice.">;
 def err_drv_cuda_version_unsupported : Error<
   "GPU arch %0 is supported by CUDA versions between %1 and %2 (inclusive), "
   "but installation at %3 is %4.  Use --cuda-path to specify a different CUDA "
   "install, pass a different GPU arch with --cuda-gpu-arch, or pass "
   "--no-cuda-version-check.">;
-def err_drv_cuda_nvptx_host : Error<"unsupported use of NVPTX for host compilation.">;
+def err_drv_cuda_host_arch : Error<"unsupported architecture '%0' for host compilation.">;
 def err_drv_invalid_thread_model_for_target : Error<
   "invalid thread model '%0' in '%1' for this target">;
 def err_drv_invalid_linker_name : Error<
   "invalid linker name in argument '%0'">;
 def err_drv_invalid_pgo_instrumentor : Error<
   "invalid PGO instrumentor in argument '%0'">;
 def err_drv_invalid_rtlib_name : Error<
   "invalid runtime library name in argument '%0'">;

lib/Driver/Driver.cpp

 
     bool initialize() override {
       // We don't need to support CUDA.
       if (!C.hasOffloadToolChain<Action::OFK_Cuda>())
         return false;
 
       const ToolChain *HostTC = C.getSingleOffloadToolChain<Action::OFK_Host>();
       assert(HostTC && "No toolchain for host compilation.");
-      if (HostTC->getTriple().isNVPTX()) {
-        // We do not support targeting NVPTX for host compilation. Throw
+      if (HostTC->getTriple().isNVPTX() ||
+          HostTC->getTriple().getArch() == llvm::Triple::amdgcn) {
+        // We do not support targeting NVPTX/AMDGCN for host compilation. Throw
         // an error and abort pipeline construction early so we don't trip
         // asserts that assume device-side compilation.
-        C.getDriver().Diag(diag::err_drv_cuda_nvptx_host);
+        C.getDriver().Diag(diag::err_drv_cuda_host_arch)
+            << HostTC->getTriple().getArchName();
         return true;
       }
 
       ToolChains.push_back(C.getSingleOffloadToolChain<Action::OFK_Cuda>());
 
       Arg *PartialCompilationArg = Args.getLastArg(
           options::OPT_cuda_host_only, options::OPT_cuda_device_only,
           options::OPT_cuda_compile_host_device);

test/Driver/cuda-bad-arch.cu

 // Checks errors generated by passing a bad value for --cuda-gpu-arch.
 // REQUIRES: clang-driver
 // REQUIRES: x86-registered-target
 // REQUIRES: nvptx-registered-target
+// REQUIRES: amdgpu-registered-target
 
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-gpu-arch=compute_20 -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix BAD %s
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-gpu-arch=sm20 -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix BAD %s
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-gpu-arch=sm_19 -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix BAD %s
 
 // BAD: error: Unsupported CUDA gpu architecture
 
 // RUN: %clang -### -v --target=x86_64-linux-gnu --cuda-gpu-arch=sm_21 \
 // RUN:   --cuda-path=%S/Inputs/CUDA_90/usr/local/cuda %s 2>&1 \
 // RUN: | FileCheck -check-prefix BAD_CUDA9 %s
 
 // BAD_CUDA9: GPU arch sm_21 is supported by CUDA versions between 7.0 and 8.0
 
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-gpu-arch=sm_20 -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix OK %s
 // RUN: %clang -### -target x86_64-linux-gnu --cuda-gpu-arch=sm_52 -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix OK %s
 // RUN: %clang -### -target x86_64-linux-gnu -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix OK %s
 
-// We don't allow using NVPTX for host compilation.
+// We don't allow using NVPTX/AMDGCN for host compilation.
 // RUN: %clang -### --cuda-host-only -target nvptx-nvidia-cuda -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix HOST_NVPTX %s
+// RUN: %clang -### --cuda-host-only -target amdgcn-amd-amdhsa -c %s 2>&1 \
+// RUN: | FileCheck -check-prefix HOST_AMDGCN %s
 
 // OK-NOT: error: Unsupported CUDA gpu architecture
-// HOST_NVPTX: error: unsupported use of NVPTX for host compilation.
+// HOST_NVPTX: error: unsupported architecture 'nvptx' for host compilation.
+// HOST_AMDGCN: error: unsupported architecture 'amdgcn' for host compilation.