Reapply "[LLVM] Make the GPU loader utilities an LLVM tool (#132096)" (#132277)

Summary:
There were a few issues with the first one, leading to some errors and
warnings. Most importantly, this was building on MSVC which isn't
supported.

Author: jhuber6

libc/CMakeLists.txt

@@ -59,13 +59,6 @@ set(LIBC_NAMESPACE ${default_namespace}
   CACHE STRING "The namespace to use to enclose internal implementations. Must start with '__llvm_libc'."
 )
 
-# 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 ((NOT LLVM_RUNTIMES_BUILD) AND LLVM_LIBC_GPU_BUILD))
-  add_subdirectory(utils/gpu)
-  return()
-endif()
-
 option(LIBC_CMAKE_VERBOSE_LOGGING
   "Log details warnings and notifications during CMake configuration." OFF)
 

libc/src/__support/RPC/rpc_server.h

@@ -20,6 +20,11 @@
 #define __has_builtin(x) 0
 #endif
 
+// Workaround for missing __builtin_is_constant_evaluated in < GCC 10.
+#ifndef __builtin_is_constant_evaluated
+#define __builtin_is_constant_evaluated(x) 0
+#endif
+
 // Configs for using the LLVM libc writer interface.
 #define LIBC_COPT_USE_C_ASSERT
 #define LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY
@@ -28,7 +33,7 @@
 #define LIBC_COPT_PRINTF_DISABLE_INDEX_MODE
 #define LIBC_COPT_PRINTF_DISABLE_STRERROR
 
-// The 'long double' type is 8 byte
+// The 'long double' type is 8 bytes.
 #define LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64
 
 #include "shared/rpc.h"

libc/utils/gpu/CMakeLists.txt

@@ -210,10 +210,6 @@ 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

libc/utils/gpu/loader/CMakeLists.txt

@@ -534,20 +534,6 @@ if(build_runtimes)
   endif()
   if(LLVM_LIBC_GPU_BUILD)
     list(APPEND extra_cmake_args "-DLLVM_LIBC_GPU_BUILD=ON")
-    if("libc" IN_LIST RUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES)
-      if(TARGET amdhsa-loader)
-        list(APPEND extra_cmake_args
-             "-DRUNTIMES_amdgcn-amd-amdhsa_LIBC_GPU_LOADER_EXECUTABLE=$<TARGET_FILE:amdhsa-loader>")
-        list(APPEND extra_deps amdhsa-loader)
-      endif()
-    endif()
-    if("libc" IN_LIST RUNTIMES_nvptx64-nvidia-cuda_LLVM_ENABLE_RUNTIMES)
-      if(TARGET nvptx-loader)
-        list(APPEND extra_cmake_args
-             "-DRUNTIMES_nvptx64-nvidia-cuda_LIBC_GPU_LOADER_EXECUTABLE=$<TARGET_FILE:nvptx-loader>")
-        list(APPEND extra_deps nvptx-loader)
-      endif()
-    endif()
     if(TARGET clang-offload-packager)
       list(APPEND extra_deps clang-offload-packager)
     endif()

libc/utils/gpu/loader/amdgpu/CMakeLists.txt

@@ -9,6 +9,10 @@
 # traversing each directory.
 create_llvm_tool_options()
 
+if(NOT LLVM_COMPILER_IS_GCC_COMPATIBLE)
+  set(LLVM_TOOL_LLVM_GPU_LOADER_BUILD OFF)
+endif()
+
 if(NOT LLVM_BUILD_LLVM_DYLIB AND NOT LLVM_BUILD_LLVM_C_DYLIB)
   set(LLVM_TOOL_LLVM_SHLIB_BUILD Off)
 endif()

libc/utils/gpu/loader/nvptx/CMakeLists.txt

@@ -0,0 +1,46 @@
+set(LLVM_LINK_COMPONENTS
+  BinaryFormat
+  Object
+  Option
+  Support
+  FrontendOffloading
+  TargetParser
+)
+
+add_llvm_tool(llvm-gpu-loader
+  llvm-gpu-loader.cpp
+
+  # TODO: We intentionally split this currently due to statically linking the
+  #       GPU runtimes. Dynamically load the dependencies, possibly using the
+  #       LLVM offloading API when it is complete.
+  PARTIAL_SOURCES_INTENDED
+
+  DEPENDS
+  intrinsics_gen
+)
+
+# Locate the RPC server handling interface.
+include(FindLibcCommonUtils)
+target_link_libraries(llvm-gpu-loader PUBLIC llvm-libc-common-utilities)
+
+# Check for HSA support for targeting AMD GPUs.
+find_package(hsa-runtime64 QUIET 1.2.0 HINTS ${CMAKE_INSTALL_PREFIX} PATHS /opt/rocm)
+if(hsa-runtime64_FOUND)
+  target_sources(llvm-gpu-loader PRIVATE amdhsa.cpp)
+  target_compile_definitions(llvm-gpu-loader PRIVATE AMDHSA_SUPPORT)
+  target_link_libraries(llvm-gpu-loader PRIVATE hsa-runtime64::hsa-runtime64)
+
+  # Compatibility with the old amdhsa-loader name.
+  add_llvm_tool_symlink(amdhsa-loader llvm-gpu-loader)
+endif()
+
+# Check for CUDA support for targeting NVIDIA GPUs.
+find_package(CUDAToolkit 11.2 QUIET)
+if(CUDAToolkit_FOUND)
+  target_sources(llvm-gpu-loader PRIVATE nvptx.cpp)
+  target_compile_definitions(llvm-gpu-loader PRIVATE NVPTX_SUPPORT)
+  target_link_libraries(llvm-gpu-loader PRIVATE CUDA::cuda_driver)
+
+  # Compatibility with the old nvptx-loader name.
+  add_llvm_tool_symlink(nvptx-loader llvm-gpu-loader)
+endif()