[Clang][OpenMP] Require CUDA 9.2+ for OpenMP offloading on NVPTX target

[tianshilei1992]

Summary

In current implementation of deviceRTLs, we're using some functions
that are CUDA version dependent (if CUDA_VERSION < 9, it is one; otheriwse, it
is another one). As a result, we have to compile one bitcode library for each
CUDA version supported. A worse problem is forward compatibility. If a new CUDA
version is released, we have to update CMake file as well.

CUDA 9.2 has been released for three years. Instead of using various weird tricks
to make deviceRTLs work with different CUDA versions and still have forward
compatibility, we can simply drop support for CUDA 9.1 or lower version. It has at
least two benifits:

• We don't need to generate bitcode libraries for each CUDA version;
• Clang driver doesn't need to search for the bitcode lib based on CUDA version.

We can claim that starting from LLVM 12, OpenMP offloading on NVPTX target requires
CUDA 9.2+.

[jdoerfert]

Could you include the simplifications this allows in the openmp subfolder? If it's too much put it in a child revision.

[tianshilei1992]

In D97003#2573090, @jdoerfert wrote:

Could you include the simplifications this allows in the openmp subfolder? If it's too much put it in a child revision.

I prefer to split them as most of changes are in OpenMP.

[grokos]

This change makes much sense. In fact, CUDA 8 was so problematic for use with the nvptx runtime that (if memory serves me well) we declared it unsupported. So essentially this patch drops support for CUDA version 7 (and lower), which is already six years old. If the other reviewers agree, we can accept the patch.

[jdoerfert]

LGTM

[tianshilei1992]

According to D97012, if we want to completely drop CUDA version, it should be CUDA 9.2. Do we want to change the minimum version to CUDA 9.2?

[tianshilei1992]

Update to CUDA 9.2

[tianshilei1992]

Use CUDA 9.1 for failure test

[tianshilei1992]

rebase

[tianshilei1992]

fixed the test

[tianshilei1992]

update test case

[tianshilei1992]

optimize error handle process

[tianshilei1992]

If there is no objection, I’ll merge it.

[JonChesterfield]

LGTM too.

clang/include/clang/Basic/DiagnosticDriverKinds.td

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-%1-bc-path to specify %1 bitcode library.">;
 def err_drv_omp_offload_target_bcruntime_not_found : Error<"Bitcode library '%0' does not exist.">;
+def err_drv_omp_offload_target_cuda_version_not_support : Error<"NVPTX target requires CUDA 9.2 or above. CUDA %0 is detected.">;
 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 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">;
 

clang/lib/Driver/ToolChains/Cuda.cpp

if (LibDeviceFile.empty()) {
 
     getDriver().Diag(diag::err_drv_no_cuda_libdevice) << GpuArch;
     return;
   }
 
   CC1Args.push_back("-mlink-builtin-bitcode");
   CC1Args.push_back(DriverArgs.MakeArgString(LibDeviceFile));
 
+  clang::CudaVersion CudaInstallationVersion = CudaInstallation.version();
   std::string CudaVersionStr;
 
   // New CUDA versions often introduce new instructions that are only supported
   // by new PTX version, so we need to raise PTX level to enable them in NVPTX
   // back-end.
   const char *PtxFeature = nullptr;
-  switch (CudaInstallation.version()) {
+  switch (CudaInstallationVersion) {
 #define CASE_CUDA_VERSION(CUDA_VER, PTX_VER)                                   \
   case CudaVersion::CUDA_##CUDA_VER:                                           \
     CudaVersionStr = #CUDA_VER;                                                \
     PtxFeature = "+ptx" #PTX_VER;                                              \
     break;
     CASE_CUDA_VERSION(112, 72);
     CASE_CUDA_VERSION(111, 71);
     CASE_CUDA_VERSION(110, 70);
default:
     CudaVersionStr = "80";
     PtxFeature = "+ptx42";
   }
   CC1Args.append({"-target-feature", PtxFeature});
   if (DriverArgs.hasFlag(options::OPT_fcuda_short_ptr,
                          options::OPT_fno_cuda_short_ptr, false))
     CC1Args.append({"-mllvm", "--nvptx-short-ptr"});
 
-  if (CudaInstallation.version() >= CudaVersion::UNKNOWN)
-    CC1Args.push_back(DriverArgs.MakeArgString(
-        Twine("-target-sdk-version=") +
-        CudaVersionToString(CudaInstallation.version())));
+  if (CudaInstallationVersion >= CudaVersion::UNKNOWN)
+    CC1Args.push_back(
+        DriverArgs.MakeArgString(Twine("-target-sdk-version=") +
+                                 CudaVersionToString(CudaInstallationVersion)));
 
   if (DeviceOffloadingKind == Action::OFK_OpenMP) {
+    if (CudaInstallationVersion < CudaVersion::CUDA_92) {
+      getDriver().Diag(
+          diag::err_drv_omp_offload_target_cuda_version_not_support)
+          << CudaVersionToString(CudaInstallationVersion);
+      return;
+    }
+
     std::string BitcodeSuffix =
         "nvptx-cuda_" + CudaVersionStr + "-" + GpuArch.str();
     addOpenMPDeviceRTL(getDriver(), DriverArgs, CC1Args, BitcodeSuffix,
                        getTriple());
   }
 }
 
 llvm::DenormalMode CudaToolChain::getDefaultDenormalModeForType(

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

 
 // CHK-NOLIBDEVICE-NOT: error:{{.*}}sm_60
 
 /// ###########################################################################
 
 /// 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_35 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
+// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_102/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-bc-path=.
 // RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
 // RUN:   --libomptarget-nvptx-bc-path=%S/Inputs/libomptarget/libomptarget-nvptx-test.bc \
-// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
+// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_102/usr/local/cuda \
 // RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHK-BCLIB-USER %s
 
-// CHK-BCLIB: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-cuda_80-sm_35.bc
+// CHK-BCLIB: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-cuda_102-sm_35.bc
 // CHK-BCLIB-USER: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-test.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_35 bitcode library should never exist.
 // RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
-// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
+// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_102/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-cuda_80-sm_35.bc' found in the default clang lib directory or in LIBRARY_PATH. Please use --libomptarget-nvptx-bc-path to specify nvptx bitcode library.
+// CHK-BCLIB-WARN: No library 'libomptarget-nvptx-cuda_102-sm_35.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_35 --cuda-path=%S/Inputs/CUDA_80/usr/local/cuda \
+// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_102/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 the error is thrown when CUDA 9.1 or lower version is used.
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda \
+// RUN:   -Xopenmp-target -march=sm_35 --cuda-path=%S/Inputs/CUDA_90/usr/local/cuda \
+// RUN:   -fopenmp-relocatable-target -save-temps -no-canonical-prefixes %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHK-CUDA-VERSION-ERROR %s
+
+// CHK-CUDA-VERSION-ERROR: NVPTX target requires CUDA 9.2 or above. CUDA 9.0 is detected.
+
 /// 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
 // RUN:   %clang -### -no-canonical-prefixes -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target -march=sm_60 %s -g0 2>&1 \