[OpenMP] Add a driver flag to enable the new device runtime library

This patch adds a driver flag `-fopenmp-target-new-runtime` to optionally enable the new device runtime
bitcode library. This allows users to enable the new experimental runtime
before it becomes the default in the future.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D106793

Author: jhuber6

clang/include/clang/Basic/LangOptions.def

@@ -240,6 +240,7 @@ LANGOPT(OpenMPCUDAForceFullRuntime , 1, 0, "Force to use full runtime in all con
 LANGOPT(OpenMPCUDANumSMs  , 32, 0, "Number of SMs for CUDA devices.")
 LANGOPT(OpenMPCUDABlocksPerSM  , 32, 0, "Number of blocks per SM for CUDA devices.")
 LANGOPT(OpenMPCUDAReductionBufNum , 32, 1024, "Number of the reduction records in the intermediate reduction buffer used for the teams reductions.")
+LANGOPT(OpenMPTargetNewRuntime , 1, 0, "Use the new bitcode library for OpenMP offloading")
 LANGOPT(OpenMPOptimisticCollapse  , 1, 0, "Use at most 32 bits to represent the collapsed loop nest counter.")
 LANGOPT(RenderScript      , 1, 0, "RenderScript")
 

clang/include/clang/Driver/Options.td

@@ -2376,6 +2376,10 @@ def fopenmp_cuda_blocks_per_sm_EQ : Joined<["-"], "fopenmp-cuda-blocks-per-sm=">
   Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
 def fopenmp_cuda_teams_reduction_recs_num_EQ : Joined<["-"], "fopenmp-cuda-teams-reduction-recs-num=">, Group<f_Group>,
   Flags<[CC1Option, NoArgumentUnused, HelpHidden]>;
+defm openmp_target_new_runtime: BoolFOption<"openmp-target-new-runtime",
+  LangOpts<"OpenMPTargetNewRuntime">, DefaultFalse,
+  PosFlag<SetTrue, [CC1Option], "Use the new bitcode library for OpenMP offloading">,
+  NegFlag<SetFalse>>;
 defm openmp_optimistic_collapse : BoolFOption<"openmp-optimistic-collapse",
   LangOpts<"OpenMPOptimisticCollapse">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option]>, NegFlag<SetFalse>, BothFlags<[NoArgumentUnused, HelpHidden]>>;

clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp

@@ -222,7 +222,14 @@ void AMDGPUOpenMPToolChain::addClangTargetOptions(
 
   if (DriverArgs.hasArg(options::OPT_nogpulib))
     return;
-  std::string BitcodeSuffix = "amdgcn-" + GPUArch;
+
+  std::string BitcodeSuffix;
+  if (DriverArgs.hasFlag(options::OPT_fopenmp_target_new_runtime,
+                         options::OPT_fno_openmp_target_new_runtime, false))
+    BitcodeSuffix = "new-amdgcn-" + GPUArch;
+  else
+    BitcodeSuffix = "amdgcn-" + GPUArch;
+
   addOpenMPDeviceRTL(getDriver(), DriverArgs, CC1Args, BitcodeSuffix,
                      getTriple());
 }

clang/lib/Driver/ToolChains/Cuda.cpp

@@ -751,7 +751,13 @@ void CudaToolChain::addClangTargetOptions(
       return;
     }
 
-    std::string BitcodeSuffix = "nvptx-" + GpuArch.str();
+    std::string BitcodeSuffix;
+    if (DriverArgs.hasFlag(options::OPT_fopenmp_target_new_runtime,
+                           options::OPT_fno_openmp_target_new_runtime, false))
+      BitcodeSuffix = "new-nvptx-" + GpuArch.str();
+    else
+      BitcodeSuffix = "nvptx-" + GpuArch.str();
+
     addOpenMPDeviceRTL(getDriver(), DriverArgs, CC1Args, BitcodeSuffix,
                        getTriple());
   }

clang/test/Driver/Inputs/libomptarget/libomptarget-new-nvptx-sm_35.bc

@@ -0,0 +1 @@
+

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

@@ -154,6 +154,11 @@
 // 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
+/// Check with the new runtime enabled
+// 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_102/usr/local/cuda \
+// RUN:   -fopenmp-relocatable-target -fopenmp-target-new-runtime -save-temps -no-canonical-prefixes %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHK-BCLIB-NEW %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 \
@@ -162,6 +167,7 @@
 // RUN:   | FileCheck -check-prefix=CHK-BCLIB-USER %s
 
 // CHK-BCLIB: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-sm_35.bc
+// CHK-BCLIB-NEW: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-new-nvptx-sm_35.bc
 // CHK-BCLIB-USER: clang{{.*}}-triple{{.*}}nvptx64-nvidia-cuda{{.*}}-mlink-builtin-bitcode{{.*}}libomptarget-nvptx-test.bc
 // CHK-BCLIB-NOT: {{error:|warning:}}