[flang] Use `GNUInstallDirs` to support custom installation dirs.

[Ericson2314]

Summary

Extracted from D99484. My new plan is to start from the outside and work
inward.

[Ericson2314]

Fix installed config include dir

[MehdiChinoune]

flang/cmake/modules/AddFlang.cmake

1

[MehdiChinoune]

flang/cmake/modules/AddFlang.cmake

1

[Ericson2314]

Fix typo @MehdiChinoune found

Thanks, and sory that was there! I hand-split up my old patch and need to do
some test builds since there are new changes beyond the split like that one
line.

[Ericson2314]

1. Updating D115569: [flang] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

Fix typo

[Ericson2314]

Reuse function from LLD's patch

[Ericson2314]

1. Updating D115569: [flang] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

rebase to hopefully fix pre-merge CI

[Ericson2314]

1. Updating D115569: [flang] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

fix mod inc path

[Ericson2314]

1. Updating D115569: [flang] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

rebase

[Ericson2314]

1. Updating D115569: [flang] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

fix bad import

[stephenneuendorffer]

LGTM

flang/CMakeLists.txt

 cmake_minimum_required(VERSION 3.13.4)
 
 set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
 
 # Flang requires C++17.
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
+include(GNUInstallDirs)
+
 set(FLANG_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR AND NOT MSVC_IDE)
   message(FATAL_ERROR "In-source builds are not allowed. \
           Please create a directory and run cmake from there,\
           passing the path to this source directory as the last argument.\
           This process created the file `CMakeCache.txt' and the directory\
           `CMakeFiles'. Please delete them.")
foreach(lib ${FLANG_LIBS})
     if (NOT LLVM_ENABLE_IDE)
       add_dependencies(install-flang-libraries install-${lib})
     endif()
   endforeach()
 endif()
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/flang
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     COMPONENT flang-headers
     FILES_MATCHING
     PATTERN "*.def"
     PATTERN "*.h"
     PATTERN "*.inc"
     PATTERN "*.td"
     PATTERN "config.h" EXCLUDE
     PATTERN ".git"     EXCLUDE
     PATTERN "CMakeFiles" EXCLUDE)
     
   install(DIRECTORY ${FLANG_INCLUDE_DIR}/flang
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     COMPONENT flang-headers
     FILES_MATCHING
     PATTERN "*.inc"
     )
 endif()

flang/cmake/modules/AddFlang.cmake

+include(GNUInstallDir)
 include(LLVMDistributionSupport)
 
 macro(set_flang_windows_version_resource_properties name)
   if (DEFINED windows_resource_file)
     set_windows_version_resource_properties(${name} ${windows_resource_file}
       VERSION_MAJOR ${FLANG_VERSION_MAJOR}
       VERSION_MINOR ${FLANG_VERSION_MINOR}
       VERSION_PATCHLEVEL ${FLANG_VERSION_PATCHLEVEL}
if (TARGET ${name})
 
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "libflang")
       get_target_export_arg(${name} Flang export_to_flangtargets UMBRELLA flang-libraries)
       install(TARGETS ${name}
         COMPONENT ${name}
         ${export_to_flangtargets}
         LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
         ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
-        RUNTIME DESTINATION bin)
+        RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
 
       if (NOT LLVM_ENABLE_IDE)
         add_llvm_install_targets(install-${name}
                                  DEPENDS ${name}
                                  COMPONENT ${name})
       endif()
 
       set_property(GLOBAL APPEND PROPERTY FLANG_LIBS ${name})
macro(add_flang_tool name)
   endif()
 
   add_flang_executable(${name} ${ARGN})
 
   if (FLANG_BUILD_TOOLS)
     get_target_export_arg(${name} Flang export_to_flangtargets)
     install(TARGETS ${name}
       ${export_to_flangtargets}
-      RUNTIME DESTINATION bin
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
       COMPONENT ${name})
 
     if(NOT LLVM_ENABLE_IDE)
       add_llvm_install_targets(install-${name}
                                DEPENDS ${name}
                                COMPONENT ${name})
     endif()
     set_property(GLOBAL APPEND PROPERTY FLANG_EXPORTS ${name})

flang/cmake/modules/CMakeLists.txt

set(FLANG_CONFIG_INCLUDE_DIRS
   )
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/FlangConfig.cmake.in
   ${flang_cmake_builddir}/FlangConfig.cmake
   @ONLY)
 set(FLANG_CONFIG_CMAKE_DIR)
 set(FLANG_CONFIG_LLVM_CMAKE_DIR)
 
+function(extend_delayed_install_path joined_path current_segment)
+  if("${current_segment}" STREQUAL "")
+    set(temp_path "\${FLANG_INSTALL_PREFIX}")
+  elseif(IS_ABSOLUTE "${current_segment}")
+    message(WARNING "Since \"${current_segment}\" is absolute, it overrides FLANG_INSTALL_PREFIX")
+    set(temp_path "${current_segment}")
+  else()
+    set(temp_path "\${FLANG_INSTALL_PREFIX}/${current_segment}")
+  endif()
+  set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()
+
 # Generate FlangConfig.cmake for the install tree.
 set(FLANG_CONFIG_CODE "
   # Compute the installation prefix from this LLVMConfig.cmake file location.
   get_filename_component(FLANG_INSTALL_PREFIX \"\${CMAKE_CURRENT_LIST_FILE}\" PATH)")
 # Construct the proper number of get_filename_component(... PATH)
 # calls to compute the installation prefix.
 string(REGEX REPLACE "/" ";" _count "${FLANG_INSTALL_PACKAGE_DIR}")
 foreach(p ${_count})
   set(FLANG_CONFIG_CODE "${FLANG_CONFIG_CODE}
       get_filename_component(FLANG_INSTALL_PREFIX \"\${FLANG_INSTALL_PREFIX}\" PATH)")
 endforeach(p)
 
 set(FLANG_CONFIG_CMAKE_DIR "\${FLANG_INSTALL_PREFIX}/${FLANG_INSTALL_PACKAGE_DIR}")
 set(FLANG_CONFIG_LLVM_CMAKE_DIR "\${FLANG_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(Flang FLANG_CONFIG_INCLUDE_EXPORTS)
-set(FLANG_CONFIG_INCLUDE_DIRS "\${FLANG_INSTALL_PREFIX}/include")
+extend_delayed_install_path(FLANG_CONFIG_INCLUDE_DIRS "${CMAKE_INCLUDE_DIR}")
 
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/FlangConfig.cmake.in
   ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/FlangConfig.cmake
   @ONLY)
 
 set(FLANG_CONFIG_CODE)
 set(FLANG_CONFIG_CMAKE_DIR)

flang/tools/f18/CMakeLists.txt

add_custom_command(OUTPUT ${base}.mod
     COMMAND flang-new -fc1 -fsyntax-only -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
       ${FLANG_SOURCE_DIR}/module/${filename}.f90
     DEPENDS flang-new ${FLANG_SOURCE_DIR}/module/${filename}.f90 ${depends}
   )
   add_custom_command(OUTPUT ${base}.f18.mod
     DEPENDS ${base}.mod
     COMMAND ${CMAKE_COMMAND} -E copy ${base}.mod ${base}.f18.mod)
   list(APPEND MODULE_FILES ${base}.mod ${base}.f18.mod)
-  install(FILES ${base}.mod ${base}.f18.mod DESTINATION include/flang)
+  install(FILES ${base}.mod ${base}.f18.mod DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang")
 endforeach()
 
 add_custom_target(module_files ALL DEPENDS ${MODULE_FILES})
 
 # This flang shell script will only work in a POSIX shell.
 if (NOT WIN32)
   file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/flang
     DESTINATION ${CMAKE_BINARY_DIR}/bin
     FILE_PERMISSIONS OWNER_EXECUTE OWNER_READ OWNER_WRITE)
-  install(PROGRAMS ${CMAKE_BINARY_DIR}/bin/flang DESTINATION bin)
+  install(PROGRAMS ${CMAKE_BINARY_DIR}/bin/flang DESTINATION "${CMAKE_INSTALL_BINDIR}")
 endif()

flang/tools/flang-driver/CMakeLists.txt

 
 option(FLANG_PLUGIN_SUPPORT "Build Flang with plugin support." ON)
 
 # Enable support for plugins, which need access to symbols from flang-new
 if(FLANG_PLUGIN_SUPPORT)
   export_executable_symbols_for_plugins(flang-new)
 endif()
 
-install(TARGETS flang-new DESTINATION bin)
+install(TARGETS flang-new DESTINATION "${CMAKE_INSTALL_BINDIR}")