[OpenMP] Fix nvptx CUDA_VERSION conversion

[jdenny]

Summary

As mentioned in PR#49250, without this patch, ptxas for CUDA 9.1 fails
in the following two tests:

• openmp/libomptarget/test/mapping/lambda_mapping.cpp
• openmp/libomptarget/test/offloading/bug49021.cpp

The error looks like:

ptxas /tmp/lambda_mapping-081ea9.s, line 828; error   : Not a name of any known instruction: 'activemask'

The problem is that our cmake script converts CUDA version strings
incorrectly: 9.1 becomes 9100, but it should be 9010, as shown in
getCudaVersion in clang/lib/Driver/ToolChains/Cuda.cpp. Thus,
openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.cu
inadvertently enables activemask because it apparently becomes
available in 9.2. This patch fixes the conversion.

This patch does not fix the other two tests in PR#49250.

[tianshilei1992]

LGTM with one nit. Thanks for the fix!

openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt

179

You can use libomptarget_error_say("Unrecognized CUDA version format: ${cuda_version}") instead.

[jdenny]

Address @tianshilei1992's review.

Thanks!

openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt

foreach(sm ${nvptx_sm_list})
   # Uncomment the following code and remove those ugly part if the feature
   # is available.
   # foreach(cuda_version ptx_num IN ZIP_LISTS cuda_version_list ptx_feature_list)
   foreach(itr RANGE ${loop_range})
     list(GET cuda_version_list ${itr} cuda_version)
     list(GET ptx_feature_list ${itr} ptx_num)
     set(cuda_flags ${sm_flags})
     list(APPEND cuda_flags -Xclang -target-feature -Xclang +ptx${ptx_num})
-    list(APPEND cuda_flags "-DCUDA_VERSION=${cuda_version}00")
+    if("${cuda_version}" MATCHES "^([0-9]+)([0-9])$")
+      set(cuda_version_major ${CMAKE_MATCH_1})
+      set(cuda_version_minor ${CMAKE_MATCH_2})
+    else()
+      libomptarget_error_say(
+        "Unrecognized CUDA version format: ${cuda_version}")
+    endif()
+    list(APPEND cuda_flags
+      "-DCUDA_VERSION=${cuda_version_major}0${cuda_version_minor}0")
 
     set(bc_files "")
     foreach(src ${cuda_src_files})
       get_filename_component(infile ${src} ABSOLUTE)
       get_filename_component(outfile ${src} NAME)
       set(outfile "${outfile}-cuda_${cuda_version}-sm_${sm}.bc")
 
       add_custom_command(OUTPUT ${outfile}