[Clang][OpenMP] Allow unified_shared_memory for Pascal-generation GPUs.

[Meinersbur]

Summary

The Pascal architecture supports the page migration engine required for unified_shared_memory, as indicated by NVIDIA:

• https://developer.nvidia.com/blog/unified-memory-cuda-beginners/
• https://developer.nvidia.com/blog/beyond-gpu-memory-limits-unified-memory-pascal/
• https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#um-requirements

The limitation was introduced in D54493 which justified the cut-off by the requirement for unified addressing. However, Unified Virtual Addressing (UVA) is already available with sm20 (Fermi. Kepler, Maxwell). Unified shared memory might even be possible with these, but with migration of entire allocations on kernel startup.

To be sure, I enabled the tests for a Pascal GPU which finish successfully.

[JonChesterfield]

Nice. Thanks for including the references.

[Meinersbur]

Will fix the failed required_codegen.cpp test.

[Meinersbur]

• Fix test case

Will wait for D101498 is resolved, otherwise I cannot test this anymore.

clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp

if (Clause->getClauseKind() == OMPC_unified_shared_memory) {
       case CudaArch::SM_20:
       case CudaArch::SM_21:
       case CudaArch::SM_30:
       case CudaArch::SM_32:
       case CudaArch::SM_35:
       case CudaArch::SM_37:
       case CudaArch::SM_50:
       case CudaArch::SM_52:
-      case CudaArch::SM_53:
-      case CudaArch::SM_60:
-      case CudaArch::SM_61:
-      case CudaArch::SM_62: {
+      case CudaArch::SM_53: {
         SmallString<256> Buffer;
         llvm::raw_svector_ostream Out(Buffer);
         Out << "Target architecture " << CudaArchToString(Arch)
             << " does not support unified addressing";
         CGM.Error(Clause->getBeginLoc(), Out.str());
         return;
       }
+      case CudaArch::SM_60:
+      case CudaArch::SM_61:
+      case CudaArch::SM_62:
       case CudaArch::SM_70:
       case CudaArch::SM_72:
       case CudaArch::SM_75:
       case CudaArch::SM_80:
       case CudaArch::SM_86:
       case CudaArch::GFX600:
       case CudaArch::GFX601:
       case CudaArch::GFX602:

clang/test/OpenMP/requires_codegen.cpp

 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm-bc %s -o %t-ppc-host.bc -DREGION_HOST
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_20 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_21 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_30 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_32 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_35 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_37 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_50 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_52 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_53 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
-// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_60 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
-// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_61 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
-// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_62 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_60 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_61 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_62 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_70 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_72 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-nvidia-cuda -fopenmp-targets=nvptx64-nvidia-cuda -target-cpu sm_75 -emit-llvm %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t-out.ll -DREGION_DEVICE_NO_ERR
 
 #if defined(REGION_HOST) || defined(REGION_DEVICE_NO_ERR)
 // expected-no-diagnostics
 #pragma omp requires unified_shared_memory
 #endif
 
 #ifdef REGION_DEVICE
 #pragma omp requires unified_shared_memory // expected-error-re {{Target architecture sm_{{20|21|30|32|35|37|50|52|53|60|61|62}} does not support unified addressing}}
 #endif