[lld][CMake] 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 include dir

[Ericson2314]

1. Updating D115568: [lld] 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]

1. Updating D115568: [lld] 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 and simplify

[phosek]

lld/cmake/modules/CMakeLists.txt

31–41

Could we move this to a top-level CMake module in https://github.com/llvm/llvm-project/tree/main/cmake/Modules so we can avoid duplicating this logic in every subproject?

[Ericson2314]

lld/cmake/modules/CMakeLists.txt

31–41

Oh I didn't realize there was such a top-level dir, great!

[Ericson2314]

1. Updating D115568: [lld] 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

factor out functions

[Ericson2314]

lld/cmake/modules/CMakeLists.txt

31–41

This is now done, and I rebased it atop D115746 which does something similar.

(we removed similar project-wide prefix variables in libc++, libc++abi, and libc++ before, but I suppose now that we have this function, if someone were to chime in that they wanted them back after all, it wouldn't be such a nuisance to support.)

[Ericson2314]

1. Updating D115568: [lld] 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 on arc diff of the other

[Ericson2314]

1. Updating D115568: [lld][cmake] 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 D115568: [lld][cmake] 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]

Rebase, no longer need new function

[Ericson2314]

1. Updating D115568: [lld][cmake] 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 D115568: [lld] 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 base cmake import

[stephenneuendorffer]

LGTM

[mstorsjo]

lld/CMakeLists.txt

159

This broke building in my setups.

In my setups, I still symlink the clang/lld directories into llvm/tools instead of invoking them via LLVM_ENABLE_PROJECTS. Thus referring to ${LLD_SOURCE_DIR}/.. ends up at llvm-project/llvm/tools instead of at llvm-project.

Is there some better cmake variable we could use here for unambiguously referring to the monorepo root?

(As backstory - a condition for me for getting away from building in that legacy setup, would be to be able to build things with the main llvm-project directory as main target directory for the cmake invocation. When pointing cmake at llvm-project/llvm, cmake uses relative paths for all files under the llvm subdir, but uses absolute paths for files under e.g. llvm-project/lld. With those tools symlinked under llvm-project/llvm/tools, it ends up using relative paths for all files. Using relative paths for compiling files is vital for being able to use ccache across different source trees, otherwise all built object files are unique for each source tree, due to e.g. paths in assert messages.)

[mstorsjo]

lld/CMakeLists.txt

159

I guess a working, but inelegant, solution would be to use ${LLVM_MAIN_SRC_DIR}/../cmake if it happens to exist, otherwise fall back on ${LLD_SOURCE_DIR}/../cmake. The former would normally work, but could maybe fail if building lld standalone without being invoked from the main llvm tree, and the llvm-project source tree has been moved since llvm itself was built.

[Ericson2314]

lld/CMakeLists.txt

159

Sorry about this. The runtime libraries (compile-rt, libunwind, libcxxabi, etc.) do this already, so I figured it was OK.

As a temp hack, you can symlink the repo-root cmake as llvm/tools/cmake. That should fix the ../cmake, right?

I think the better thing to do is simply make a new CACHE PATH for "shared cmake utils" in each of these projects, so you can set that one however you like.

lld/CMakeLists.txt

+include(GNUInstallDirs)
+
 # Check if lld is built as a standalone project.
 if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(lld)
   cmake_minimum_required(VERSION 3.13.4)
 
   set(CMAKE_INCLUDE_CURRENT_DIR ON)
   set(LLD_BUILT_STANDALONE TRUE)
 
if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   list(GET LLVM_CONFIG_OUTPUT 1 MAIN_INCLUDE_DIR)
   list(GET LLVM_CONFIG_OUTPUT 2 LLVM_CMAKE_DIR)
   list(GET LLVM_CONFIG_OUTPUT 3 MAIN_SRC_DIR)
 
   set(LLVM_OBJ_ROOT ${OBJ_ROOT} CACHE PATH "path to LLVM build tree")
   set(LLVM_MAIN_INCLUDE_DIR ${MAIN_INCLUDE_DIR} CACHE PATH "path to llvm/include")
   set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
 
-  file(TO_CMAKE_PATH ${LLVM_OBJ_ROOT} LLVM_BINARY_DIR)
-  file(TO_CMAKE_PATH ${LLVM_CMAKE_DIR} LLVM_CMAKE_DIR)
+  file(TO_CMAKE_PATH "${LLVM_OBJ_ROOT}" LLVM_BINARY_DIR)
+  file(TO_CMAKE_PATH "${LLVM_CMAKE_DIR}" LLVM_CMAKE_DIR)
 
   if(NOT EXISTS "${LLVM_CMAKE_DIR}/LLVMConfig.cmake")
     message(FATAL_ERROR "LLVMConfig.cmake not found")
   endif()
   include("${LLVM_CMAKE_DIR}/LLVMConfig.cmake")
 
   list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
 

 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
   message(FATAL_ERROR "In-source builds are not allowed. CMake would overwrite "
 "the makefiles distributed with LLVM. 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.")
 endif()
 
-list (APPEND CMAKE_MODULE_PATH "${LLD_SOURCE_DIR}/cmake/modules")
+# Add path for custom modules.
+list(INSERT CMAKE_MODULE_PATH 0
+  "${LLD_SOURCE_DIR}/cmake/modules"
+  "${LLD_SOURCE_DIR}/../cmake/Modules"
+  )
 
 include(AddLLD)
 
 option(LLD_USE_VTUNE
        "Enable VTune user task tracking."
        OFF)
 if (LLD_USE_VTUNE)
   find_package(VTune)

 
 include_directories(BEFORE
   ${CMAKE_CURRENT_BINARY_DIR}/include
   ${CMAKE_CURRENT_SOURCE_DIR}/include
   )
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     FILES_MATCHING
     PATTERN "*.h"
     )
 endif()
 
 add_subdirectory(Common)
 add_subdirectory(tools/lld)
 

lld/cmake/modules/AddLLD.cmake

+include(GNUInstallDirs)
 include(LLVMDistributionSupport)
 
 macro(add_lld_library name)
   cmake_parse_arguments(ARG
     "SHARED"
     ""
     ""
     ${ARGN})
   if(ARG_SHARED)
     set(ARG_ENABLE_SHARED SHARED)
   endif()
   llvm_add_library(${name} ${ARG_ENABLE_SHARED} ${ARG_UNPARSED_ARGUMENTS})
   set_target_properties(${name} PROPERTIES FOLDER "lld libraries")
 
   if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
     get_target_export_arg(${name} LLD export_to_lldtargets)
     install(TARGETS ${name}
       COMPONENT ${name}
       ${export_to_lldtargets}
       LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
       ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
-      RUNTIME DESTINATION bin)
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
 
     if (${ARG_SHARED} AND NOT CMAKE_CONFIGURATION_TYPES)
       add_llvm_install_targets(install-${name}
         DEPENDS ${name}
         COMPONENT ${name})
     endif()
     set_property(GLOBAL APPEND PROPERTY LLD_EXPORTS ${name})
   endif()
macro(add_lld_tool name)
   endif()
 
   add_lld_executable(${name} ${ARGN})
 
   if (LLD_BUILD_TOOLS)
     get_target_export_arg(${name} LLD export_to_lldtargets)
     install(TARGETS ${name}
       ${export_to_lldtargets}
-      RUNTIME DESTINATION bin
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
       COMPONENT ${name})
 
     if(NOT CMAKE_CONFIGURATION_TYPES)
       add_llvm_install_targets(install-${name}
         DEPENDS ${name}
         COMPONENT ${name})
     endif()
     set_property(GLOBAL APPEND PROPERTY LLD_EXPORTS ${name})
   endif()
 endmacro()
 
 macro(add_lld_symlink name dest)
   add_llvm_tool_symlink(${name} ${dest} ALWAYS_GENERATE)
   # Always generate install targets
   llvm_install_symlink(${name} ${dest} ALWAYS_GENERATE)
 endmacro()

lld/cmake/modules/CMakeLists.txt

+include(ExtendPath)
+
 # Generate a list of CMake library targets so that other CMake projects can
 # link against them. LLVM calls its version of this file LLVMExports.cmake, but
 # the usual CMake convention seems to be ${Project}Targets.cmake.
 set(LLD_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/lld)
 set(lld_cmake_builddir "${CMAKE_BINARY_DIR}/${LLD_INSTALL_PACKAGE_DIR}")
 
 # Keep this in sync with llvm/cmake/CMakeLists.txt!
 set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
set(LLD_CONFIG_INCLUDE_DIRS
   )
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/LLDConfig.cmake.in
   ${lld_cmake_builddir}/LLDConfig.cmake
   @ONLY)
 set(LLD_CONFIG_CMAKE_DIR)
 set(LLD_CONFIG_LLVM_CMAKE_DIR)
 
 # Generate LLDConfig.cmake for the install tree.
 set(LLD_CONFIG_CODE "
 # Compute the installation prefix from this LLVMConfig.cmake file location.
 get_filename_component(LLD_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 "${LLD_INSTALL_PACKAGE_DIR}")
 foreach(p ${_count})
   set(LLD_CONFIG_CODE "${LLD_CONFIG_CODE}
 get_filename_component(LLD_INSTALL_PREFIX \"\${LLD_INSTALL_PREFIX}\" PATH)")
 endforeach(p)
 set(LLD_CONFIG_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLD_INSTALL_PACKAGE_DIR}")
 set(LLD_CONFIG_LLVM_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(LLD LLD_CONFIG_INCLUDE_EXPORTS)
-set(LLD_CONFIG_INCLUDE_DIRS "\${LLD_INSTALL_PREFIX}/include")
+extend_path(LLD_CONFIG_INCLUDE_DIRS "\${LLD_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/LLDConfig.cmake.in
   ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/LLDConfig.cmake
   @ONLY)
 set(LLD_CONFIG_CODE)
 set(LLD_CONFIG_CMAKE_DIR)
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)

lld/tools/lld/CMakeLists.txt

target_link_libraries(lld
   lldCOFF
   lldELF
   lldMachO
   lldMinGW
   lldWasm
   )
 
 install(TARGETS lld
-  RUNTIME DESTINATION bin)
+  RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
 
 if(NOT LLD_SYMLINKS_TO_CREATE)
   set(LLD_SYMLINKS_TO_CREATE
       lld-link ld.lld ld64.lld wasm-ld)
 endif()
 
 foreach(link ${LLD_SYMLINKS_TO_CREATE})
   add_lld_symlink(${link} lld)
 endforeach()