[libc-commits] [libc] [libc] Remove CUDA Toolkit dependency for NVPTX build (PR #208497)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Joseph Huber (jhuber6)

<details>
<summary>Changes</summary>

Summary:
This was problemtatic because these CMake headers were never intended to
be used from a GPu target. We had to hack around this to suppress
threads, but all this is used for is getting the default CUDA path, so
just do this directly.


---
Full diff: https://github.com/llvm/llvm-project/pull/208497.diff


1 Files Affected:

- (modified) libc/cmake/modules/prepare_libc_gpu_build.cmake (+13-7) 


``````````diff
diff --git a/libc/cmake/modules/prepare_libc_gpu_build.cmake b/libc/cmake/modules/prepare_libc_gpu_build.cmake
index 36ab321e4994c..aba4d11bf41a1 100644
--- a/libc/cmake/modules/prepare_libc_gpu_build.cmake
+++ b/libc/cmake/modules/prepare_libc_gpu_build.cmake
@@ -73,12 +73,18 @@ set(LIBC_GPU_TARGET_ARCHITECTURE "${gpu_test_architecture}")
 set(LIBC_GPU_CODE_OBJECT_VERSION "6" CACHE STRING "AMDGPU Code object ABI to use")
 
 if(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
-  # FIXME: This is a hack required to keep the CUDA package from trying to find
-  #        pthreads. We only link the CUDA driver, so this is unneeded.
-  add_library(CUDA::cudart_static_deps IMPORTED INTERFACE)
-
-  find_package(CUDAToolkit QUIET)
-  if(CUDAToolkit_FOUND)
-    get_filename_component(LIBC_CUDA_ROOT "${CUDAToolkit_BIN_DIR}" DIRECTORY ABSOLUTE)
+  # Respect the standard CUDAToolkit_ROOT override if the user provided one,
+  # otherwise ask the compiler which CUDA installation it detected.
+  if(CUDAToolkit_ROOT)
+    set(LIBC_CUDA_ROOT "${CUDAToolkit_ROOT}")
+  else()
+    execute_process(
+      COMMAND ${CMAKE_CXX_COMPILER} -v --print-resource-dir
+      OUTPUT_QUIET ERROR_VARIABLE cuda_search_output)
+    string(REGEX MATCH "Found CUDA installation: ([^,]+), version"
+      cuda_search_match "${cuda_search_output}")
+    if(CMAKE_MATCH_1)
+      set(LIBC_CUDA_ROOT "${CMAKE_MATCH_1}")
+    endif()
   endif()
 endif()

``````````

</details>


https://github.com/llvm/llvm-project/pull/208497