[OpenMP][NVPTX] Refined CMake logic to choose compute capabilites

This patch refines the logic to choose compute capabilites via the
environment variable `LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES`. It supports the
following values (all case insensitive):
- "all": Build `deviceRTLs` for all supported compute capabilites;
- "auto": Only build for the compute capability auto detected. Note that this
  requires CUDA. If CUDA is not found, a CMake fatal error will be raised.
- "xx,yy" or "xx;yy": Build for compute capabilities `xx` and `yy`.

If `LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES` is not set, it is equivalent to set
it to `all`.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D95687

diff --git a/openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake b/openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
index 317260c..bc3c5d2 100644 (file)
--- a/openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
+++ b/openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
@@ -118,9 +118,7 @@ endif()
 find_package(CUDA QUIET)
 
 # Try to get the highest Nvidia GPU architecture the system supports
-set(LIBOMPTARGET_NVPTX_AUTODETECT_COMPUTE_CAPABILITY TRUE CACHE BOOL
-  "Auto detect CUDA Compute Capability if CUDA is detected.")
-if (CUDA_FOUND AND LIBOMPTARGET_NVPTX_AUTODETECT_COMPUTE_CAPABILITY)
+if (CUDA_FOUND)
   cuda_select_nvcc_arch_flags(CUDA_ARCH_FLAGS)
   string(REGEX MATCH "sm_([0-9]+)" CUDA_ARCH_MATCH_OUTPUT ${CUDA_ARCH_FLAGS})
   if (NOT DEFINED CUDA_ARCH_MATCH_OUTPUT OR "${CMAKE_MATCH_1}" LESS 35)

diff --git a/openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt b/openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt
index eeda137..b705e0b 100644 (file)
--- a/openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt
+++ b/openmp/libomptarget/deviceRTLs/nvptx/CMakeLists.txt
@@ -10,12 +10,12 @@
 #
 ##===----------------------------------------------------------------------===##
 
-# By default we will not build NVPTX deviceRTL on a non-CUDA
+# By default we will not build NVPTX deviceRTL on a CUDA free system
 set(LIBOMPTARGET_BUILD_NVPTX_BCLIB FALSE CACHE BOOL
-  "Whether build NVPTX deviceRTL on non-CUDA system.")
+  "Whether build NVPTX deviceRTL on CUDA free system.")
 
 if (NOT (LIBOMPTARGET_DEP_CUDA_FOUND OR LIBOMPTARGET_BUILD_NVPTX_BCLIB))
-  libomptarget_say("Not building NVPTX deviceRTL by default on non-CUDA system.")
+  libomptarget_say("Not building NVPTX deviceRTL by default on CUDA free system.")
   return()
 endif()
 
@@ -73,16 +73,22 @@ set(devicertl_common_directory
 set(devicertl_nvptx_directory
   ${devicertl_base_directory}/nvptx)
 
-if (DEFINED LIBOMPTARGET_DEP_CUDA_ARCH)
-  set(default_capabilities ${LIBOMPTARGET_DEP_CUDA_ARCH})
-else()
-  set(default_capabilities 35 37 50 52 53 60 61 62 70 72 75 80)
-endif()
+set(all_capabilities 35 37 50 52 53 60 61 62 70 72 75 80)
 
-set(LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES ${default_capabilities} CACHE STRING
+set(LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES ${all_capabilities} CACHE STRING
   "List of CUDA Compute Capabilities to be used to compile the NVPTX device RTL.")
+string(TOLOWER ${LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES} LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES)
 
-set(nvptx_sm_list ${LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES})
+if (LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES STREQUAL "all")
+  set(nvptx_sm_list ${all_capabilities})
+elseif(LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES STREQUAL "auto")
+  if (NOT LIBOMPTARGET_DEP_CUDA_FOUND)
+    libomptarget_error_say("[NVPTX] Cannot auto detect compute capability as CUDA not found.")
+  endif()
+  set(nvptx_sm_list ${LIBOMPTARGET_DEP_CUDA_ARCH})
+else()
+  string(REPLACE "," ";" nvptx_sm_list "${LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES}")
+endif()
 
 # If user set LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES to empty, we disable the
 # build.
@@ -93,8 +99,8 @@ endif()
 
 # Check all SM values
 foreach(sm ${nvptx_sm_list})
-  if (NOT ${sm} IN_LIST default_capabilities)
-    message(FATAL_ERROR "LIBOMPTARGET-NVPTX: compute capability ${sm} is not supported. Supported values: ${default_capabilities}")
+  if (NOT ${sm} IN_LIST all_capabilities)
+    libomptarget_warning_say("[NVPTX] Compute capability ${sm} is not supported. Make sure clang can work with it.")
   endif()
 endforeach()