r315996 - [CMake][OpenMP] Customize default offloading arch

[Ahmed Bougacha via cfe-commits]

Hi Jonas,

On Tue, Oct 17, 2017 at 6:37 AM, Jonas Hahnfeld via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: hahnfeld
> Date: Tue Oct 17 06:37:36 2017
> New Revision: 315996
>
> URL: http://llvm.org/viewvc/llvm-project?rev=315996&view=rev
> Log:
> [CMake][OpenMP] Customize default offloading arch
>
> For the shuffle instructions in reductions we need at least sm_30
> but the user may want to customize the default architecture.
>
> Differential Revision: https://reviews.llvm.org/D38883
>
> Modified:
>     cfe/trunk/CMakeLists.txt
>     cfe/trunk/include/clang/Config/config.h.cmake
>     cfe/trunk/lib/Driver/ToolChains/Cuda.cpp
>     cfe/trunk/lib/Driver/ToolChains/Cuda.h
>
> Modified: cfe/trunk/CMakeLists.txt
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/CMakeLists.txt?rev=315996&r1=315995&r2=315996&view=diff
> ==============================================================================
> --- cfe/trunk/CMakeLists.txt (original)
> +++ cfe/trunk/CMakeLists.txt Tue Oct 17 06:37:36 2017
> @@ -235,6 +235,17 @@ endif()
>  set(CLANG_DEFAULT_OPENMP_RUNTIME "libomp" CACHE STRING
>    "Default OpenMP runtime used by -fopenmp.")
>
> +# OpenMP offloading requires at least sm_30 because we use shuffle instructions
> +# to generate efficient code for reductions.
> +set(CLANG_OPENMP_NVPTX_DEFAULT_ARCH "sm_30" CACHE STRING
> +  "Default architecture for OpenMP offloading to Nvidia GPUs.")
> +string(REGEX MATCH "^sm_([0-9]+)$" MATCHED_ARCH "${CLANG_OPENMP_NVPTX_DEFAULT_ARCH}")
> +if (NOT DEFINED MATCHED_ARCH OR "${CMAKE_MATCH_1}" LESS 30)
> +  message(WARNING "Resetting default architecture for OpenMP offloading to Nvidia GPUs to sm_30")

This warning is pretty noisy and doesn't affect most people: I don't
know what it means but I get it in every cmake run.
Can we somehow restrict or disable it?

Thanks!
-Ahmed

> +  set(CLANG_OPENMP_NVPTX_DEFAULT_ARCH "sm_30" CACHE STRING
> +    "Default architecture for OpenMP offloading to Nvidia GPUs." FORCE)
> +endif()
> +
>  set(CLANG_VENDOR ${PACKAGE_VENDOR} CACHE STRING
>    "Vendor-specific text for showing with version information.")
>
>
> Modified: cfe/trunk/include/clang/Config/config.h.cmake
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Config/config.h.cmake?rev=315996&r1=315995&r2=315996&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Config/config.h.cmake (original)
> +++ cfe/trunk/include/clang/Config/config.h.cmake Tue Oct 17 06:37:36 2017
> @@ -20,6 +20,9 @@
>  /* Default OpenMP runtime used by -fopenmp. */
>  #define CLANG_DEFAULT_OPENMP_RUNTIME "${CLANG_DEFAULT_OPENMP_RUNTIME}"
>
> +/* Default architecture for OpenMP offloading to Nvidia GPUs. */
> +#define CLANG_OPENMP_NVPTX_DEFAULT_ARCH "${CLANG_OPENMP_NVPTX_DEFAULT_ARCH}"
> +
>  /* Multilib suffix for libdir. */
>  #define CLANG_LIBDIR_SUFFIX "${CLANG_LIBDIR_SUFFIX}"
>
>
> Modified: cfe/trunk/lib/Driver/ToolChains/Cuda.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ToolChains/Cuda.cpp?rev=315996&r1=315995&r2=315996&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Driver/ToolChains/Cuda.cpp (original)
> +++ cfe/trunk/lib/Driver/ToolChains/Cuda.cpp Tue Oct 17 06:37:36 2017
> @@ -542,9 +542,9 @@ CudaToolChain::TranslateArgs(const llvm:
>    // flags are not duplicated.
>    // Also append the compute capability.
>    if (DeviceOffloadKind == Action::OFK_OpenMP) {
> -    for (Arg *A : Args){
> +    for (Arg *A : Args) {
>        bool IsDuplicate = false;
> -      for (Arg *DALArg : *DAL){
> +      for (Arg *DALArg : *DAL) {
>          if (A == DALArg) {
>            IsDuplicate = true;
>            break;
> @@ -555,14 +555,9 @@ CudaToolChain::TranslateArgs(const llvm:
>      }
>
>      StringRef Arch = DAL->getLastArgValue(options::OPT_march_EQ);
> -    if (Arch.empty()) {
> -      // Default compute capability for CUDA toolchain is the
> -      // lowest compute capability supported by the installed
> -      // CUDA version.
> -      DAL->AddJoinedArg(nullptr,
> -          Opts.getOption(options::OPT_march_EQ),
> -          CudaInstallation.getLowestExistingArch());
> -    }
> +    if (Arch.empty())
> +      DAL->AddJoinedArg(nullptr, Opts.getOption(options::OPT_march_EQ),
> +                        CLANG_OPENMP_NVPTX_DEFAULT_ARCH);
>
>      return DAL;
>    }
>
> Modified: cfe/trunk/lib/Driver/ToolChains/Cuda.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ToolChains/Cuda.h?rev=315996&r1=315995&r2=315996&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Driver/ToolChains/Cuda.h (original)
> +++ cfe/trunk/lib/Driver/ToolChains/Cuda.h Tue Oct 17 06:37:36 2017
> @@ -76,17 +76,6 @@ public:
>    std::string getLibDeviceFile(StringRef Gpu) const {
>      return LibDeviceMap.lookup(Gpu);
>    }
> -  /// \brief Get lowest available compute capability
> -  /// for which a libdevice library exists.
> -  std::string getLowestExistingArch() const {
> -    std::string LibDeviceFile;
> -    for (auto key : LibDeviceMap.keys()) {
> -      LibDeviceFile = LibDeviceMap.lookup(key);
> -      if (!LibDeviceFile.empty())
> -        return key;
> -    }
> -    return "sm_20";
> -  }
>  };
>
>  namespace tools {
>
>
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