[libc] Place headers in the right include directory

[phosek]

Summary

When LLVM_ENABLE_PER_TARGET_RUNTIME_DIR is enabled, place headers
in include/<target> directory, otherwise use include/.

[phosek]

libc/CMakeLists.txt

29

@sivachandra When LIBC_TARGET_ARCHITECTURE_IS_GPU, would it make sense to use gpu-none-llvm instead of LLVM_DEFAULT_TARGET_TRIPLE? It seems like we're effectively treating gpu-none-llvm as a target triple but I wanted to confirm first before making the change.

32–33

@sivachandra Would it make sense to use ${CMAKE_CURRENT_BINARY_DIR}/lib in this case for consistency?

[sivachandra]

libc/CMakeLists.txt

29

If building for the GPU, I think we want the target triple to be fixed to gpu-none-llvm and LLVM_DEFAULT_TARGET_TRIPLE does not matter. I will let @jhuber6 to confirm.

32–33

Agreed.

libc/include/CMakeLists.txt

534

What is this target_include_directories doing? I can see why it could be ${LIBC_INCLUDE_DIR} but I do not understand why ${LLVM_BINARY_DIR}/include.

[jhuber6]

libc/CMakeLists.txt

29

Yes, that was a decision to separate these generates GPU headers from the ones that would be used by the system. Since we don't have a single triple we just made one up.

[jhuber6]

This broke the GPU headers in many ways, I'll need to look into it. It's now installing the headers somewhere completely outside of the CMAKE_PREFIX_PATH because the relative paths are wrong.

[jhuber6]

libc/CMakeLists.txt

22–28

This does not work, this macro isn't defined until line 107 below.

libc/cmake/modules/LLVMLibCHeaderRules.cmake

23 ↗

(On Diff #533476)

The old logic used to create for example this file when doing a runtimes build.

./runtimes/runtimes-bins/libc/include/llvm-libc-types/rpc_opcodes_t.h

Now I get

./include/gpu-none-llvm/llvm-libc-types/rpc_opcodes_t.h

Which is wrong because we should not be building these outside of the runtimes directory when doing a runtimes build, and because of the discrepancy it causes the relative path to be completely wrong. Did you test this with a runtimes build of libc?

[phosek]

libc/cmake/modules/LLVMLibCHeaderRules.cmake

23 ↗

(On Diff #533476)

This is intentional and matches what we do for other runtimes like libc++. Our goal has always been for the layout of the build directory to match the layout of the install directory so you can run the compiler without having to do the install step first. Clang driver looks for headers in <path to clang>/../include/.... If this is undesirable for the GPU target, we can adjust the logic, but we want to keep this for other targets.

libc/CMakeLists.txt

 
 # The top-level source directory.
 set(LIBC_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 # The top-level directory in which libc is being built.
 set(LIBC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 set(LIBC_ENABLE_USE_BY_CLANG OFF CACHE BOOL "Whether or not to place libc in a build directory findable by a just built clang")
 
-if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND LIBC_ENABLE_USE_BY_CLANG)
+if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
+  set(LIBC_INCLUDE_DIR ${LLVM_BINARY_DIR}/include/gpu-none-llvm)
+  set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/gpu-none-llvm)
+  set(LIBC_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/gnu-none-llvm)
+elseif(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND LIBC_ENABLE_USE_BY_CLANG)
+  set(LIBC_INCLUDE_DIR ${LLVM_BINARY_DIR}/include/${LLVM_DEFAULT_TARGET_TRIPLE})
+  set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
   set(LIBC_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
 else()
   if(NOT LIBC_ENABLE_USE_BY_CLANG)
-    set(LIBC_LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
+    set(LIBC_INCLUDE_DIR ${CMAKE_CURRENT_BINARY_DIR}/include)
+    set(LIBC_LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/lib)
   elseif(LLVM_LIBRARY_OUTPUT_INTDIR)
+    set(LIBC_INCLUDE_DIR ${LLVM_BINARY_DIR}/include)
     set(LIBC_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
   else()
+    set(LIBC_INCLUDE_DIR ${CMAKE_BINARY_DIR}/include)
     set(LIBC_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
   endif()
+  set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR})
 endif()
 
 if(LLVM_LIBC_FULL_BUILD OR LIBC_GPU_BUILD OR LIBC_GPU_ARCHITECTURES)
   if(NOT LIBC_HDRGEN_EXE)
     # We need to set up hdrgen first since other targets depend on it.
     add_subdirectory(utils/LibcTableGenUtil)
     add_subdirectory(utils/HdrGen)
   else()

libc/include/CMakeLists.txt

foreach(target IN LISTS ARGN)
     get_all_install_header_targets(nested_deps ${deps})
     list(APPEND all_deps ${nested_deps})
   endforeach()
   list(REMOVE_DUPLICATES all_deps)
   set(${out_var} ${all_deps} PARENT_SCOPE)
 endfunction(get_all_install_header_targets)
 
 get_all_install_header_targets(all_install_header_targets ${TARGET_PUBLIC_HEADERS})
-add_custom_target(libc-headers)
-add_dependencies(libc-headers ${all_install_header_targets})
+add_library(libc-headers INTERFACE)
 foreach(target IN LISTS all_install_header_targets)
   get_target_property(header_file ${target} HEADER_FILE_PATH)
   if(NOT header_file)
     message(FATAL_ERROR "Installable header file '${target}' does not have the "
                         "HEADER_FILE_PATH property set.")
   endif()
   file(RELATIVE_PATH relative_path ${LIBC_INCLUDE_BINARY_DIR} ${header_file})
-  get_filename_component(nested_dir ${relative_path} DIRECTORY)
-  # The GPU headers are installed to 'gpu-none-llvm/' to prevent shadowing the
-  # system headers.
-  if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-    set(nested_dir gpu-none-llvm/${nested_dir})
+  if(LIBC_ENABLE_USE_BY_CLANG)
+    set(dst "${LIBC_INCLUDE_DIR}/${relative_path}")
+    add_custom_command(OUTPUT ${dst}
+      DEPENDS ${header_file}
+      COMMAND ${CMAKE_COMMAND} -E copy_if_different ${header_file} ${dst}
+      COMMENT "Copying C header ${header_file}")
+    list(APPEND _all_includes "${dst}")
   endif()
+  get_filename_component(nested_dir ${relative_path} DIRECTORY)
   install(FILES ${header_file}
-          DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/${nested_dir}
+          DESTINATION ${LIBC_INSTALL_INCLUDE_DIR}/${nested_dir}
           COMPONENT libc-headers)
 endforeach()
+add_custom_target(copy-libc-headers ALL DEPENDS ${_all_includes})
+add_dependencies(libc-headers ${all_install_header_targets} copy-libc-headers)
+target_include_directories(libc-headers SYSTEM INTERFACE ${LIBC_INCLUDE_DIR})