[CUDA] Improve clang's ability to detect recent CUDA versions.

CUDA-11.1 does not carry version.txt which causes clang to assume that it's
CUDA-7.0, which used to be the only CUDA version w/o version.txt.

In order to tell CUDA-7.0 apart from the new versions, clang now probes for the
presence of libdevice.10.bc which is not present in the old CUDA versions.

This should keep Clang working for CUDA-11.1.

PR47332: https://bugs.llvm.org/show_bug.cgi?id=47332

Differential Revision: https://reviews.llvm.org/D89752

(cherry picked from commit 65d2064)

Author: Artem-B

clang/lib/Driver/ToolChains/Cuda.cpp

@@ -155,9 +155,14 @@ CudaInstallationDetector::CudaInstallationDetector(
     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> VersionFile =
         FS.getBufferForFile(InstallPath + "/version.txt");
     if (!VersionFile) {
-      // CUDA 7.0 doesn't have a version.txt, so guess that's our version if
-      // version.txt isn't present.
-      Version = CudaVersion::CUDA_70;
+      // CUDA 7.0 and CUDA 11.1+ do not have version.txt file.
+      // Use libdevice file to distinguish 7.0 from the new versions.
+      if (FS.exists(LibDevicePath + "/libdevice.10.bc")) {
+        Version = CudaVersion::LATEST;
+        DetectedVersionIsNotSupported = Version > CudaVersion::LATEST_SUPPORTED;
+      } else {
+        Version = CudaVersion::CUDA_70;
+      }
     } else {
       ParseCudaVersionFile((*VersionFile)->getBuffer());
     }

clang/test/Driver/Inputs/CUDA_111/usr/local/cuda/bin/.keep

@@ -10,6 +10,11 @@
 // RUN:    FileCheck %s --check-prefix=OK
 // RUN: %clang --target=x86_64-linux -v -### --cuda-gpu-arch=sm_60 --cuda-path=%S/Inputs/CUDA-unknown/usr/local/cuda 2>&1 %s | \
 // RUN:    FileCheck %s --check-prefix=UNKNOWN_VERSION
+// CUDA versions after 11.0 (update 1) do not carry version.txt file. Make sure
+// we still detect them as a new version and handle them the same as we handle
+// other new CUDA versions.
+// RUN: %clang --target=x86_64-linux -v -### --cuda-gpu-arch=sm_60 --cuda-path=%S/Inputs/CUDA_111/usr/local/cuda 2>&1 %s | \
+// RUN:    FileCheck %s --check-prefix=UNKNOWN_VERSION
 // Make sure that we don't warn about CUDA version during C++ compilation.
 // RUN: %clang --target=x86_64-linux -v -### -x c++ --cuda-gpu-arch=sm_60 \
 // RUN:    --cuda-path=%S/Inputs/CUDA-unknown/usr/local/cuda 2>&1 %s | \
@@ -65,5 +70,5 @@
 // ERR_SM61: error: GPU arch sm_61 {{.*}}
 // ERR_SM61-NOT: error: GPU arch sm_61
 
-// UNKNOWN_VERSION: Unknown CUDA version 999.999. Assuming the latest supported version
+// UNKNOWN_VERSION: Unknown CUDA version {{.*}}. Assuming the latest supported version
 // UNKNOWN_VERSION_CXX-NOT: Unknown CUDA version