[CUDA] Add CUDA 10.2 detection

[tra]

This looks like an elaborate way to achieve the effect of -Wno-unknown_cuda_version. :-)

Similar change has been discussed recently. See https://reviews.llvm.org/D74571#1875340 which details why I think it's not a good idea.

[tambre]

Thanks for the context!

To avoid other people stepping into this trap, maybe it'd make sense to reword this warning to say "unsupported" instead of "unknown"?
Or maybe add detection for newer versions, but introduce a separate warning for unsupported versions?

clang/include/clang/Basic/Cuda.h

enum class CudaVersion {
   CUDA_70,
   CUDA_75,
   CUDA_80,
   CUDA_90,
   CUDA_91,
   CUDA_92,
   CUDA_100,
   CUDA_101,
-  LATEST = CUDA_101,
+  CUDA_102,
+  LATEST = CUDA_102,
 };
 const char *CudaVersionToString(CudaVersion V);
 // Input is "Major.Minor"
 CudaVersion CudaStringToVersion(const llvm::Twine &S);
 
 enum class CudaArch {
   UNKNOWN,
   SM_20,

clang/lib/Basic/Cuda.cpp

const char *CudaVersionToString(CudaVersion V) {
   case CudaVersion::CUDA_91:
     return "9.1";
   case CudaVersion::CUDA_92:
     return "9.2";
   case CudaVersion::CUDA_100:
     return "10.0";
   case CudaVersion::CUDA_101:
     return "10.1";
+  case CudaVersion::CUDA_102:
+    return "10.2";
   }
   llvm_unreachable("invalid enum");
 }
 
 CudaVersion CudaStringToVersion(const llvm::Twine &S) {
   return llvm::StringSwitch<CudaVersion>(S.str())
       .Case("7.0", CudaVersion::CUDA_70)
       .Case("7.5", CudaVersion::CUDA_75)
       .Case("8.0", CudaVersion::CUDA_80)
       .Case("9.0", CudaVersion::CUDA_90)
       .Case("9.1", CudaVersion::CUDA_91)
       .Case("9.2", CudaVersion::CUDA_92)
       .Case("10.0", CudaVersion::CUDA_100)
       .Case("10.1", CudaVersion::CUDA_101)
+      .Case("10.2", CudaVersion::CUDA_102)
       .Default(CudaVersion::UNKNOWN);
 }
 
 const char *CudaArchToString(CudaArch A) {
   switch (A) {
   case CudaArch::LAST:
     break;
   case CudaArch::UNKNOWN:
static CudaVersion ToCudaVersion(llvm::VersionTuple Version) {
   case 91:
     return CudaVersion::CUDA_91;
   case 92:
     return CudaVersion::CUDA_92;
   case 100:
     return CudaVersion::CUDA_100;
   case 101:
     return CudaVersion::CUDA_101;
+  case 102:
+    return CudaVersion::CUDA_102;
   default:
     return CudaVersion::UNKNOWN;
   }
 }
 
 bool CudaFeatureEnabled(llvm::VersionTuple  Version, CudaFeature Feature) {
   return CudaFeatureEnabled(ToCudaVersion(Version), Feature);
 }

clang/lib/Driver/ToolChains/Cuda.cpp

void CudaToolChain::addClangTargetOptions(
   CC1Args.push_back("-mlink-builtin-bitcode");
   CC1Args.push_back(DriverArgs.MakeArgString(LibDeviceFile));
 
   // 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()) {
-    case CudaVersion::CUDA_101:
-      PtxFeature = "+ptx64";
-      break;
-    case CudaVersion::CUDA_100:
-      PtxFeature = "+ptx63";
-      break;
-    case CudaVersion::CUDA_92:
-      PtxFeature = "+ptx61";
-      break;
-    case CudaVersion::CUDA_91:
-      PtxFeature = "+ptx61";
-      break;
-    case CudaVersion::CUDA_90:
-      PtxFeature = "+ptx60";
-      break;
-    default:
-      PtxFeature = "+ptx42";
+  case CudaVersion::CUDA_102:
   }
   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(