[OpenMP] Don't build the offloading driver without a source input

[jhuber6]

Summary

The Clang driver additional stages to build a complete offloading
program for applications using CUDA or OpenMP offloading. This normally
requires either a source file input or a valid object file to be
handled. This would cause problems when trying to compile an assembly or
LLVM IR file through clang with flags that would enable offloading. This
patch simply adds a check to prevent the offloading toolchain from being
used if we don't have a valid source file.

[jdoerfert]

LG

[yaxunl]

HIP toolchain allows clang driver to compile bundled bitcode or assembly for mixed host/device compilation or device-only multi-GPU compilation.

e.g.

clang --hip-link -fgpu-rdc --offload-arch=gfx906 --offload-arch=gfx908 a.bc b.s

Can you add a test to make sure this does not break HIP toolchain? Thanks.

[jhuber6]

In D125705#3519570, @yaxunl wrote:

HIP toolchain allows clang driver to compile bundled bitcode or assembly for mixed host/device compilation or device-only multi-GPU compilation.

e.g.

clang --offload-arch=gfx906 --offload-arch=gfx908 a.bc b.s

Can you add a test to make sure this does not break HIP toolchain? Thanks.

This only changes the new driver, which doesn't support HIP right now anyway. This should be captured by some existing tests but I could try to dig them up

[yaxunl]

In D125705#3519605, @jhuber6 wrote:

In D125705#3519570, @yaxunl wrote:

HIP toolchain allows clang driver to compile bundled bitcode or assembly for mixed host/device compilation or device-only multi-GPU compilation.

e.g.

clang --offload-arch=gfx906 --offload-arch=gfx908 a.bc b.s

Can you add a test to make sure this does not break HIP toolchain? Thanks.

This only changes the new driver, which doesn't support HIP right now anyway. This should be captured by some existing tests but I could try to dig them up

If it is only for the new driver that is fine. Thanks.

clang/lib/Driver/Driver.cpp

const Arg *Mode = Args.getLastArg(options::OPT_offload_host_only,
                                     options::OPT_offload_device_only,
                                     options::OPT_offload_host_device);
   const bool HostOnly =
       Mode && Mode->getOption().matches(options::OPT_offload_host_only);
   const bool DeviceOnly =
       Mode && Mode->getOption().matches(options::OPT_offload_device_only);
 
   // Don't build offloading actions if explicitly disabled or we do not have a
-  // compile action to embed it in. If preprocessing only ignore embedding.
-  if (HostOnly || !(isa<CompileJobAction>(HostAction) ||
-                    getFinalPhase(Args) == phases::Preprocess))
+  // valid source input and compile action to embed it in. If preprocessing only
+  // ignore embedding.
+  if (HostOnly || !types::isSrcFile(Input.first) ||
+      !(isa<CompileJobAction>(HostAction) ||
     return HostAction;
 
   ActionList OffloadActions;
   OffloadAction::DeviceDependences DDeps;
 
   const Action::OffloadKind OffloadKinds[] = {
       Action::OFK_OpenMP, Action::OFK_Cuda, Action::OFK_HIP};
 

clang/test/Driver/openmp-offload-gpu-new.c

 // CHECK-NVIDIA-AMDGPU: "x86_64-unknown-linux-gnu" - "clang", inputs: ["[[INPUT:.+]]"], output: "[[HOST_BC:.+]]"
 // CHECK-NVIDIA-AMDGPU: "nvptx64-nvidia-cuda" - "clang", inputs: ["[[INPUT]]", "[[HOST_BC]]"], output: "[[NVIDIA_PTX:.+]]"
 // CHECK-NVIDIA-AMDGPU: "nvptx64-nvidia-cuda" - "NVPTX::Assembler", inputs: ["[[NVIDIA_PTX]]"], output: "[[NVIDIA_CUBIN:.+]]"
 // CHECK-NVIDIA-AMDGPU: "amdgcn-amd-amdhsa" - "clang", inputs: ["[[INPUT]]", "[[HOST_BC]]"], output: "[[AMD_BC:.+]]"
 // CHECK-NVIDIA-AMDGPU: "x86_64-unknown-linux-gnu" - "Offload::Packager", inputs: ["[[NVIDIA_CUBIN]]", "[[AMD_BC]]"], output: "[[BINARY:.*]]"
 // CHECK-NVIDIA-AMDGPU: "x86_64-unknown-linux-gnu" - "clang", inputs: ["[[HOST_BC]]", "[[BINARY]]"], output: "[[HOST_OBJ:.+]]"
 // CHECK-NVIDIA-AMDGPU: "x86_64-unknown-linux-gnu" - "Offload::Linker", inputs: ["[[HOST_OBJ]]"], output: "a.out"
 
+// RUN:   %clang -x ir -### --target=x86_64-unknown-linux-gnu -ccc-print-bindings -fopenmp --offload-arch=sm_52 -nogpulib %s 2>&1 | FileCheck %s --check-prefix=CHECK-IR
+
+// CHECK-IR: "x86_64-unknown-linux-gnu" - "clang", inputs: ["[[INPUT_IR:.+]]"], output: "[[OBJECT:.+]]" 
+// CHECK-IR: "x86_64-unknown-linux-gnu" - "Offload::Linker", inputs: ["[[OBJECT]]"], output: "a.out"
+
 // RUN:   %clang -### --target=x86_64-unknown-linux-gnu -emit-llvm -S -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target=nvptx64-nvidia-cuda -march=sm_52 -nogpulib %s 2>&1 | FileCheck %s --check-prefix=CHECK-EMIT-LLVM-IR
 // CHECK-EMIT-LLVM-IR: "-cc1"{{.*}}"-triple" "nvptx64-nvidia-cuda"{{.*}}"-emit-llvm"
 
 // RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target=nvptx64-nvida-cuda -march=sm_70 \
 // RUN:          --libomptarget-nvptx-bc-path=%S/Inputs/libomptarget/libomptarget-new-nvptx-test.bc \
 // RUN:          -nogpulib %s -o openmp-offload-gpu 2>&1 \
 // RUN:   | FileCheck -check-prefix=DRIVER_EMBEDDING %s