[OpenMP][CUDA] Do not forward OpenMP flags for CUDA device actions.

[sfantao]

Summary

This patch prevents OpenMP flags from being forwarded to CUDA device commands. That was causing the CUDA frontend to attempt to emit OpenMP code which is not supported.

This fixes the bug reported in https://llvm.org/bugs/show_bug.cgi?id=28723.

[ABataev]

LG

lib/Driver/Tools.cpp

   // AltiVec-like language extensions aren't relevant for assembling.
   if (!isa<PreprocessJobAction>(JA) || Output.getType() != types::TY_PP_Asm) {
     Args.AddLastArg(CmdArgs, options::OPT_faltivec);
     Args.AddLastArg(CmdArgs, options::OPT_fzvector);
   }
   Args.AddLastArg(CmdArgs, options::OPT_fdiagnostics_show_template_tree);
   Args.AddLastArg(CmdArgs, options::OPT_fno_elide_type);
 
-  // Forward flags for OpenMP
+  // Forward flags for OpenMP. We don't do this if the current action is an
+  // device offloading action.
+  //
+  // TODO: Allow OpenMP offload actions when they become available.
   if (Args.hasFlag(options::OPT_fopenmp, options::OPT_fopenmp_EQ,
-                   options::OPT_fno_openmp, false)) {
+                   options::OPT_fno_openmp, false) &&
+      JA.isDeviceOffloading(Action::OFK_None)) {
     switch (getOpenMPRuntime(getToolChain(), Args)) {
     case OMPRT_OMP:
     case OMPRT_IOMP5:
       // Clang can generate useful OpenMP code for these two runtime libraries.
       CmdArgs.push_back("-fopenmp");
 
       // If no option regarding the use of TLS in OpenMP codegeneration is
       // given, decide a default based on the target. Otherwise rely on the

test/Driver/offloading-interoperability.c

+// REQUIRES: clang-driver
+// REQUIRES: powerpc-registered-target
+// REQUIRES: nvptx-registered-target
+
+//
+// Verify that CUDA device commands do not get OpenMP flags.
+//
+// RUN: %clang -### -x cuda -target powerpc64le-linux-gnu -std=c++11 --cuda-gpu-arch=sm_35 -fopenmp %s 2>&1 \
+// RUN: | FileCheck %s --check-prefix NO-OPENMP-FLAGS-FOR-CUDA-DEVICE
+//
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE:      clang{{.*}}" "-cc1" "-triple" "nvptx64-nvidia-cuda"
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE-NOT:  -fopenmp
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE-NEXT: ptxas" "-m64"
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE-NEXT: fatbinary" "--cuda" "-64"
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE-NEXT: clang{{.*}}" "-cc1" "-triple" "powerpc64le--linux-gnu"
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE:      -fopenmp
+// NO-OPENMP-FLAGS-FOR-CUDA-DEVICE-NEXT: ld" "-z" "relro" "--hash-style=gnu" "--eh-frame-hdr" "-m" "elf64lppc"