update gpu build and docs

Author: nickdesaulniers

libc/CMakeLists.txt

@@ -50,16 +50,28 @@ set(LIBC_NAMESPACE ${default_namespace}
   CACHE STRING "The namespace to use to enclose internal implementations. Must start with '__llvm_libc'."
 )
 
-
-add_subdirectory(newhdrgen)
-
-
 # We will build the GPU utilities if we are not doing a runtimes build.
 option(LIBC_BUILD_GPU_LOADER "Always build the GPU loader utilities" OFF)
-if(LIBC_BUILD_GPU_LOADER OR (LLVM_LIBC_GPU_BUILD AND NOT LLVM_RUNTIMES_BUILD))
-  add_subdirectory(utils/gpu)
+if(LIBC_BUILD_GPU_LOADER OR NOT LLVM_RUNTIMES_BUILD)
+  foreach(_name ${LLVM_RUNTIME_TARGETS})
+    if("libc" IN_LIST RUNTIMES_${_name}_LLVM_ENABLE_RUNTIMES)
+      if("${_name}" STREQUAL "amdgcn-amd-amdhsa" OR "${_name}" STREQUAL "nvptx64-nvidia-cuda")
+        set(LIBC_NEED_LOADER_UTILS TRUE)
+      endif()
+    endif()
+  endforeach()
+  if("${LIBC_TARGET_TRIPLE}" STREQUAL "amdgcn-amd-amdhsa" OR
+     "${LIBC_TARGET_TRIPLE}" STREQUAL "nvptx64-nvidia-cuda")
+    set(LIBC_NEED_LOADER_UTILS TRUE)
+  endif()
+  if(LIBC_NEED_LOADER_UTILS)
+    add_subdirectory(utils/gpu)
+    return()
+  endif()
 endif()
 
+add_subdirectory(newhdrgen)
+
 option(LIBC_CMAKE_VERBOSE_LOGGING
   "Log details warnings and notifications during CMake configuration." OFF)
 

libc/docs/gpu/building.rst

@@ -63,10 +63,6 @@ targeting the default host environment as well.
 Runtimes cross build
 --------------------
 
-.. note::
-  These instructions need to be updated for new headergen. They may be
-  inaccurate.
-
 For users wanting more direct control over the build process, the build steps
 can be done manually instead. This build closely follows the instructions in the
 :ref:`main documentation<full_cross_build>` but is specialized for the GPU

llvm/CMakeLists.txt

@@ -197,6 +197,10 @@ if("${LIBC_TARGET_TRIPLE}" STREQUAL "amdgcn-amd-amdhsa" OR
    "${LIBC_TARGET_TRIPLE}" STREQUAL "nvptx64-nvidia-cuda")
   set(LLVM_LIBC_GPU_BUILD ON)
 endif()
+if (NOT "libc" IN_LIST LLVM_ENABLE_PROJECTS AND LLVM_LIBC_GPU_BUILD)
+  message(STATUS "Enabling libc project to build libc testing tools")
+  list(APPEND LLVM_ENABLE_PROJECTS "libc")
+endif()
 
 # LLVM_ENABLE_PROJECTS_USED is `ON` if the user has ever used the
 # `LLVM_ENABLE_PROJECTS` CMake cache variable.  This exists for