[Clang][OpenMP][NVPTX] Replace `libomptarget-nvptx-path` with `libomptarget-nvptx-bc-path`

[tianshilei1992]

Summary

D94700 removed the static library so we no longer need to pass
-llibomptarget-nvptx to nvlink. Since the bitcode library is the only device
runtime for now, instead of emitting a warning when it is not found, an error
should be raised. We also set a new option libomptarget-nvptx-bc-path to let
user choose which bitcode library is being used.

[JonChesterfield]

LGTM, thanks!

[tianshilei1992]

Fixed the test issue caused by wrong path seperator on Windows and Linux

[tianshilei1992]

Made test more robust

[tianshilei1992]

Fixed test case

[JonChesterfield]

Still LGTM. A little surprised these are being run on windows, but good to be robust.

[tianshilei1992]

In D95161#2517662, @JonChesterfield wrote:

Still LGTM. A little surprised these are being run on windows, but good to be robust.

It's driver test which only invokes -###. ;-) No actual execution.

clang/docs/ClangCommandLineReference.rst

 .. option:: -iwithprefixbefore<dir>, --include-with-prefix-before <arg>, --include-with-prefix-before=<arg>
 
 Set directory to include search path with prefix
 
 .. option:: -iwithsysroot<directory>
 
 Add directory to SYSTEM include search path, absolute paths are relative to -isysroot
 
-.. option:: --libomptarget-nvptx-path=<arg>
+.. option:: --libomptarget-nvptx-bc-path=<arg>
 
-Path to libomptarget-nvptx libraries
+Path to libomptarget-nvptx bitcode library
 
 .. option:: --ptxas-path=<arg>
 
 Path to ptxas (used for compiling CUDA code)
 
 .. option:: --rocm-path=<arg>
 
 ROCm installation path, used for finding and automatically linking required bitcode libraries.

clang/include/clang/Basic/DiagnosticDriverKinds.td

 def err_drv_invalid_omp_target : Error<"OpenMP target is invalid: '%0'">;
 def err_drv_incompatible_omp_arch : Error<"OpenMP target architecture '%0' pointer size is incompatible with host '%1'">;
 def err_drv_omp_host_ir_file_not_found : Error<
   "The provided host compiler IR file '%0' is required to generate code for OpenMP target regions but cannot be found.">;
 def err_drv_omp_host_target_not_supported : Error<
   "The target '%0' is not a supported OpenMP host target.">;
 def err_drv_expecting_fopenmp_with_fopenmp_targets : Error<
   "The option -fopenmp-targets must be used in conjunction with a -fopenmp option compatible with offloading, please use -fopenmp=libomp or -fopenmp=libiomp5.">;
+def err_drv_omp_offload_target_missingbcruntime : Error<
+  "No library '%0' found in the default clang lib directory or in LIBRARY_PATH. Please use --libomptarget-nvptx-bc-path to specify nvptx bitcode library.">;
+def err_drv_omp_offload_target_bcruntime_not_found : Error<"Bitcode library '%0' does not exist.">;
 def warn_drv_omp_offload_target_duplicate : Warning<
   "The OpenMP offloading target '%0' is similar to target '%1' already specified - will be ignored.">,
   InGroup<OpenMPTarget>;
-def warn_drv_omp_offload_target_missingbcruntime : Warning<
-  "No library '%0' found in the default clang lib directory or in LIBRARY_PATH. Expect degraded performance due to no inlining of runtime functions on target devices.">,
-  InGroup<OpenMPTarget>;
 def err_drv_unsupported_embed_bitcode
     : Error<"%0 is not supported with -fembed-bitcode">;
 def err_drv_bitcode_unsupported_on_toolchain : Error<
   "-fembed-bitcode is not supported on versions of iOS prior to 6.0">;
 
 def err_drv_invalid_malign_branch_EQ : Error<
   "invalid argument '%0' to -malign-branch=; each element must be one of: %1">;
 

clang/include/clang/Driver/Options.td

defm gpu_exclude_wrong_side_overloads : BoolFOption<"gpu-exclude-wrong-side-overloads",
   ResetBy<NegFlag, [], "Exclude wrong side overloads only if there are same side overloads">,
   BothFlags<[HelpHidden], " in overloading resolution for CUDA/HIP">>;
 def gpu_max_threads_per_block_EQ : Joined<["--"], "gpu-max-threads-per-block=">,
   Flags<[CC1Option]>,
   HelpText<"Default max threads per block for kernel launch bounds for HIP">;
 def gpu_instrument_lib_EQ : Joined<["--"], "gpu-instrument-lib=">,
   HelpText<"Instrument device library for HIP, which is a LLVM bitcode containing "
   "__cyg_profile_func_enter and __cyg_profile_func_exit">;
-def libomptarget_nvptx_path_EQ : Joined<["--"], "libomptarget-nvptx-path=">, Group<i_Group>,
-  HelpText<"Path to libomptarget-nvptx libraries">;
+def libomptarget_nvptx_bc_path_EQ : Joined<["--"], "libomptarget-nvptx-bc-path=">, Group<i_Group>,
+  HelpText<"Path to libomptarget-nvptx bitcode library">;
 def dD : Flag<["-"], "dD">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print macro definitions in -E mode in addition to normal output">;
 def dI : Flag<["-"], "dI">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print include directives in -E mode in addition to normal output">,
   MarshallingInfoFlag<PreprocessorOutputOpts<"ShowIncludeDirectives">>;
 def dM : Flag<["-"], "dM">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print macro definitions in -E mode instead of normal output">;
 def dead__strip : Flag<["-"], "dead_strip">;

clang/lib/Driver/ToolChains/Cuda.cpp

void NVPTX::OpenMPLinker::ConstructJob(Compilation &C, const JobAction &JA,
 
   StringRef GPUArch =
       Args.getLastArgValue(options::OPT_march_EQ);
   assert(!GPUArch.empty() && "At least one GPU Arch required for ptxas.");
 
   CmdArgs.push_back("-arch");
   CmdArgs.push_back(Args.MakeArgString(GPUArch));
 
-  // Assume that the directory specified with --libomptarget_nvptx_path
-  // contains the static library libomptarget-nvptx.a.
-  if (const Arg *A = Args.getLastArg(options::OPT_libomptarget_nvptx_path_EQ))
-    CmdArgs.push_back(Args.MakeArgString(Twine("-L") + A->getValue()));
-
   // Add paths specified in LIBRARY_PATH environment variable as -L options.
   addDirectoryList(Args, CmdArgs, "-L", "LIBRARY_PATH");
 
   // Add paths for the default clang library path.
   SmallString<256> DefaultLibPath =
       llvm::sys::path::parent_path(TC.getDriver().Dir);
   llvm::sys::path::append(DefaultLibPath, "lib" CLANG_LIBDIR_SUFFIX);
   CmdArgs.push_back(Args.MakeArgString(Twine("-L") + DefaultLibPath));
 
-  // Add linking against library implementing OpenMP calls on NVPTX target.
-  CmdArgs.push_back("-lomptarget-nvptx");
-
   for (const auto &II : Inputs) {
     if (II.getType() == types::TY_LLVM_IR ||
         II.getType() == types::TY_LTO_IR ||
         II.getType() == types::TY_LTO_BC ||
         II.getType() == types::TY_LLVM_BC) {
       C.getDriver().Diag(diag::err_drv_no_linker_llvm_support)
           << getToolChain().getTripleString();
       continue;
void CudaToolChain::addClangTargetOptions(
 
   if (CudaInstallation.version() >= CudaVersion::UNKNOWN)
     CC1Args.push_back(DriverArgs.MakeArgString(
         Twine("-target-sdk-version=") +
         CudaVersionToString(CudaInstallation.version())));
 
   if (DeviceOffloadingKind == Action::OFK_OpenMP) {
     SmallVector<StringRef, 8> LibraryPaths;
-    if (const Arg *A = DriverArgs.getLastArg(options::OPT_libomptarget_nvptx_path_EQ))
-      LibraryPaths.push_back(A->getValue());
-
     // Add user defined library paths from LIBRARY_PATH.
     llvm::Optional<std::string> LibPath =
         llvm::sys::Process::GetEnv("LIBRARY_PATH");
     if (LibPath) {
       SmallVector<StringRef, 8> Frags;
       const char EnvPathSeparatorStr[] = {llvm::sys::EnvPathSeparator, '\0'};
       llvm::SplitString(*LibPath, Frags, EnvPathSeparatorStr);
       for (StringRef Path : Frags)
         LibraryPaths.emplace_back(Path.trim());
     }
 
     // Add path to lib / lib64 folder.
     SmallString<256> DefaultLibPath =
         llvm::sys::path::parent_path(getDriver().Dir);
     llvm::sys::path::append(DefaultLibPath, Twine("lib") + CLANG_LIBDIR_SUFFIX);
     LibraryPaths.emplace_back(DefaultLibPath.c_str());
 
+    // First check whether user specifies bc library
+    if (const Arg *A =
+            DriverArgs.getLastArg(options::OPT_libomptarget_nvptx_bc_path_EQ)) {
+      std::string LibOmpTargetName(A->getValue());
+      if (llvm::sys::fs::exists(LibOmpTargetName)) {
+        CC1Args.push_back("-mlink-builtin-bitcode");
+        CC1Args.push_back(DriverArgs.MakeArgString(LibOmpTargetName));
+      } else {
+        getDriver().Diag(diag::err_drv_omp_offload_target_bcruntime_not_found)
+            << LibOmpTargetName;
+      }
+    } else {
+      bool FoundBCLibrary = false;
+
       std::string LibOmpTargetName =
           "libomptarget-nvptx-" + GpuArch.str() + ".bc";
-    bool FoundBCLibrary = false;
+
       for (StringRef LibraryPath : LibraryPaths) {
         SmallString<128> LibOmpTargetFile(LibraryPath);
         llvm::sys::path::append(LibOmpTargetFile, LibOmpTargetName);
         if (llvm::sys::fs::exists(LibOmpTargetFile)) {
           CC1Args.push_back("-mlink-builtin-bitcode");
           CC1Args.push_back(DriverArgs.MakeArgString(LibOmpTargetFile));
           FoundBCLibrary = true;
           break;
         }
       }
       if (!FoundBCLibrary)
-      getDriver().Diag(diag::warn_drv_omp_offload_target_missingbcruntime)
+        getDriver().Diag(diag::err_drv_omp_offload_target_missingbcruntime)
             << LibOmpTargetName;
     }
   }
+}
 
 llvm::DenormalMode CudaToolChain::getDefaultDenormalModeForType(
     const llvm::opt::ArgList &DriverArgs, const JobAction &JA,
     const llvm::fltSemantics *FPType) const {
   if (JA.getOffloadingDeviceKind() == Action::OFK_Cuda) {
     if (FPType && FPType == &llvm::APFloat::IEEEsingle() &&
         DriverArgs.hasFlag(options::OPT_fcuda_flush_denormals_to_zero,
                            options::OPT_fno_cuda_flush_denormals_to_zero,

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

 // RUN:          -Xopenmp-target=nvptx64-nvidia-cuda -march=sm_35 %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-FOPENMP-TARGET-COMPILATION %s
 
 // CHK-FOPENMP-TARGET-COMPILATION: ptxas{{.*}}" "--gpu-name" "sm_35"
 // CHK-FOPENMP-TARGET-COMPILATION: nvlink{{.*}}" "-arch" "sm_35"
 
 /// ###########################################################################
 
-/// Check that -lomptarget-nvptx is passed to nvlink.
-// RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp \
-// RUN:          -fopenmp-targets=nvptx64-nvidia-cuda %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=CHK-NVLINK %s
-/// Check that the value of --libomptarget-nvptx-path is forwarded to nvlink.
-// RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp \
-// RUN:          --libomptarget-nvptx-path=/path/to/libomptarget/ \
-// RUN:          -fopenmp-targets=nvptx64-nvidia-cuda %s 2>&1 \
-// RUN:   | FileCheck -check-prefixes=CHK-NVLINK,CHK-LIBOMPTARGET-NVPTX-PATH %s
-
-// CHK-NVLINK: nvlink
-// CHK-LIBOMPTARGET-NVPTX-PATH-SAME: "-L/path/to/libomptarget/"
-// CHK-NVLINK-SAME: "-lomptarget-nvptx"
-
-/// ###########################################################################
-
 /// Check cubin file generation and usage by nvlink
 // RUN:   %clang -### -no-canonical-prefixes -target powerpc64le-unknown-linux-gnu -fopenmp=libomp \
 // RUN:          -fopenmp-targets=nvptx64-nvidia-cuda -save-temps %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-CUBIN-NVLINK %s
 /// Check cubin file generation and usage by nvlink when toolchain has BindArchAction
 // RUN:   %clang -### -no-canonical-prefixes -target x86_64-apple-darwin17.0.0 -fopenmp=libomp \
 // RUN:          -fopenmp-targets=nvptx64-nvidia-cuda %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-CUBIN-NVLINK %s

 /// ###########################################################################
 
 /// Check that the runtime bitcode library is part of the compile line. Create a bogus
 /// bitcode library and add it to the LIBRARY_PATH.
 // RUN:   env LIBRARY_PATH=%S/Inputs/libomptarget %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
 // RUN:   -Xopenmp-target -march=sm_20 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
 // RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-BCLIB %s
-/// The user can override default detection using --libomptarget-nvptx-path=.
-// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda --libomptarget-nvptx-path=%S/Inputs/libomptarget \
+/// The user can override default detection using --libomptarget-nvptx-bc-path=.
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
+// RUN:   --libomptarget-nvptx-bc-path=%S/Inputs/libomptarget/libomptarget-nvptx-sm_20.bc \
 // RUN:   -Xopenmp-target -march=sm_20 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
 // RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-BCLIB %s
 
 // CHK-BCLIB: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-sm_20.bc
 // CHK-BCLIB-NOT: {{error:|warning:}}
 
 /// ###########################################################################
 
 /// Check that the warning is thrown when the libomptarget bitcode library is not found.
 /// Libomptarget requires sm_35 or newer so an sm_20 bitcode library should never exist.
 // RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
 // RUN:   -Xopenmp-target -march=sm_20 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
 // RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-BCLIB-WARN %s
 
-// CHK-BCLIB-WARN: No library 'libomptarget-nvptx-sm_20.bc' found in the default clang lib directory or in LIBRARY_PATH. Expect degraded performance due to no inlining of runtime functions on target devices.
+// CHK-BCLIB-WARN: No library 'libomptarget-nvptx-sm_20.bc' found in the default clang lib directory or in LIBRARY_PATH. Please use --libomptarget-nvptx-bc-path to specify nvptx bitcode library.
+
+/// ###########################################################################
+
+/// Check that the error is thrown when the libomptarget bitcode library does not exist.
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
+// RUN:   -Xopenmp-target -march=sm_20 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
+// RUN:   --libomptarget-nvptx-bc-path=not-exist.bc \
+// RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHK-BCLIB-ERROR %s
+
+// CHK-BCLIB-ERROR: Bitcode library 'not-exist.bc' does not exist.
 
 /// Check that debug info is emitted in dwarf-2
 // RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target -march=sm_60 %s -g -O1 --no-cuda-noopt-device-debug 2>&1 \
 // RUN:   | FileCheck -check-prefix=DEBUG_DIRECTIVES %s
 // RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target -march=sm_60 %s -g -O3 2>&1 \
 // RUN:   | FileCheck -check-prefix=DEBUG_DIRECTIVES %s
 // RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target -march=sm_60 %s -g -O3 --no-cuda-noopt-device-debug 2>&1 \
 // RUN:   | FileCheck -check-prefix=DEBUG_DIRECTIVES %s