lld: Let find_package(LLD) work

[arsenm]

Summary

Install a cmake config file. Copied exactly from how clang exports.

I'm slightly confused since it looks like the build is manually
generating a very similar *Targets.cmake to what gets auto-generated
by export(). After generating the build, I see:

build/tools/lld/cmake/modules/CMakeFiles/Export/lib/cmake/lld/LLDTargets.cmake
build/lib/cmake/lld/LLDTargets.cmake
build/tools/clang/cmake/modules/CMakeFiles/Export/lib/cmake/clang/ClangTargets.cmake
build/lib/cmake/clang/ClangTargets.cmake

The cmake generated one "wins" and is what I see in the installed
tree. I'm guessing this is somehow for the benefit of old versions
of cmake?

I also wasn't sure whether the canonical capitalization is "lld" or
"LLD". The project() is still calling this lld, but most places seemed
to capitalize it.

[labath]

I'm afraid I don't know anything about this stuff.

[arsenm]

ping

[smeenai]

LGTM, given it's basically just matching what clang already does.

I'm slightly confused since it looks like the build is manually
generating a very similar *Targets.cmake to what gets auto-generated
by export(). After generating the build, I see:

build/tools/lld/cmake/modules/CMakeFiles/Export/lib/cmake/lld/LLDTargets.cmake
build/lib/cmake/lld/LLDTargets.cmake
build/tools/clang/cmake/modules/CMakeFiles/Export/lib/cmake/clang/ClangTargets.cmake
build/lib/cmake/clang/ClangTargets.cmake

The cmake generated one "wins" and is what I see in the installed
tree. I'm guessing this is somehow for the benefit of old versions
of cmake?

I believe both the CMakeFiles version and the lib version are generated by CMake. The first one should just be an internal CMake file.

lld/CMakeLists.txt

224

Looks like you got rid of the EOF newline

[arsenm]

In D79328#2035234, @smeenai wrote:

LGTM, given it's basically just matching what clang already does.

I'm slightly confused since it looks like the build is manually
generating a very similar *Targets.cmake to what gets auto-generated
by export(). After generating the build, I see:

build/tools/lld/cmake/modules/CMakeFiles/Export/lib/cmake/lld/LLDTargets.cmake
build/lib/cmake/lld/LLDTargets.cmake
build/tools/clang/cmake/modules/CMakeFiles/Export/lib/cmake/clang/ClangTargets.cmake
build/lib/cmake/clang/ClangTargets.cmake

The cmake generated one "wins" and is what I see in the installed
tree. I'm guessing this is somehow for the benefit of old versions
of cmake?

I believe both the CMakeFiles version and the lib version are generated by CMake. The first one should just be an internal CMake file.

Any comment on "lld" vs "LLD"? Should the project() name be capitalized?

[smeenai]

In D79328#2035284, @arsenm wrote:

In D79328#2035234, @smeenai wrote:

LGTM, given it's basically just matching what clang already does.

I'm slightly confused since it looks like the build is manually
generating a very similar *Targets.cmake to what gets auto-generated
by export(). After generating the build, I see:

build/tools/lld/cmake/modules/CMakeFiles/Export/lib/cmake/lld/LLDTargets.cmake
build/lib/cmake/lld/LLDTargets.cmake
build/tools/clang/cmake/modules/CMakeFiles/Export/lib/cmake/clang/ClangTargets.cmake
build/lib/cmake/clang/ClangTargets.cmake

The cmake generated one "wins" and is what I see in the installed
tree. I'm guessing this is somehow for the benefit of old versions
of cmake?

I believe both the CMakeFiles version and the lib version are generated by CMake. The first one should just be an internal CMake file.

Any comment on "lld" vs "LLD"? Should the project() name be capitalized?

Not sure ... I think LLD is more common, but e.g. the directory is named lld. Adding a bunch of LLD COFF and ELF folks to see if they have any opinions there.

The only effect the project() name would have would be the various variables that CMake sets based on it (https://cmake.org/cmake/help/latest/command/project.html), but I don't think we're using any of those.

[MaskRay]

I usually just follow the executable name and call it lld. In patch subjects, I follow pre-git layout and just use [ELF] and don't bother adding [lld] .
I see LLD is common, too. LLD is the string lld-link and ld.lld --version print:

% ld.lld --version
LLD 11.0.0 (compatible with GNU linkers)

I think either is ok.

---

For this patch, what does it intend to achieve? find_package(LLD), link against lldCOFF, lldELF etc, and call lld::elf::link, lld::wasm::link?

It'd be nice if you have an out-of-tree project or something which demonstrates that find_package(LLD) works, if you do want to use lld this way.

[arsenm]

In D79328#2035419, @MaskRay wrote:

I usually just follow the executable name and call it lld. In patch subjects, I follow pre-git layout and just use [ELF] and don't bother adding [lld] .
I see LLD is common, too. LLD is the string lld-link and ld.lld --version print:

% ld.lld --version
LLD 11.0.0 (compatible with GNU linkers)

I think either is ok.

---

For this patch, what does it intend to achieve? find_package(LLD), link against lldCOFF, lldELF etc, and call lld::elf::link, lld::wasm::link?

It'd be nice if you have an out-of-tree project or something which demonstrates that find_package(LLD) works, if you do want to use lld this way.

This is to fix this

[MaskRay]

lld/cmake/modules/CMakeLists.txt

33

Does this need an indentation?

39

Not indented?

44

This does not need a line wrap.

lld/cmake/modules/LLDConfig.cmake.in

18

Is this used?

[arsenm]

lld/cmake/modules/CMakeLists.txt

33

None of this is indented, although it does look like it is in phabricator for some reason.

lld/cmake/modules/LLDConfig.cmake.in

18

Don't think so. It looks like clang sets this property up itself for generated headers. The tablegen uses in lld look like they only produce private .inc files

[arsenm]

2b2a961309e65fb175fcf8d56507323fa6872425

lld/cmake/modules/LLDConfig.cmake.in

18

Removed this

lld/CMakeLists.txt

 endif()
 
 add_subdirectory(docs)
 add_subdirectory(COFF)
 add_subdirectory(ELF)
 add_subdirectory(MachO)
 add_subdirectory(MinGW)
 add_subdirectory(wasm)
+
+add_subdirectory(cmake/modules)
 No newline at end of file

lld/cmake/modules/AddLLD.cmake

 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)
     if(${name} IN_LIST LLVM_DISTRIBUTION_COMPONENTS OR
         NOT LLVM_DISTRIBUTION_COMPONENTS)
-      set(export_to_lldtargets EXPORT lldTargets)
+      set(export_to_lldtargets EXPORT LLDTargets)
       set_property(GLOBAL PROPERTY LLD_HAS_EXPORTS True)
     endif()
 
     install(TARGETS ${name}
       COMPONENT ${name}
       ${export_to_lldtargets}
       LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
       ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
if (NOT LLD_BUILD_TOOLS)
     set(EXCLUDE_FROM_ALL ON)
   endif()
 
   add_lld_executable(${name} ${ARGN})
 
   if (LLD_BUILD_TOOLS)
     if(${name} IN_LIST LLVM_DISTRIBUTION_COMPONENTS OR
         NOT LLVM_DISTRIBUTION_COMPONENTS)
-      set(export_to_lldtargets EXPORT lldTargets)
+      set(export_to_lldtargets EXPORT LLDTargets)
       set_property(GLOBAL PROPERTY LLD_HAS_EXPORTS True)
     endif()
 
     install(TARGETS ${name}
       ${export_to_lldtargets}
       RUNTIME DESTINATION bin
       COMPONENT ${name})
 

lld/cmake/modules/CMakeLists.txt

+# 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${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
+set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
+
+get_property(LLD_EXPORTS GLOBAL PROPERTY LLD_EXPORTS)
+export(TARGETS ${LLD_EXPORTS} FILE ${lld_cmake_builddir}/LLDTargets.cmake)
+
+# Generate LLDConfig.cmake for the build tree.
+set(LLD_CONFIG_CMAKE_DIR "${lld_cmake_builddir}")
+set(LLD_CONFIG_LLVM_CMAKE_DIR "${llvm_cmake_builddir}")
+set(LLD_CONFIG_EXPORTS_FILE "${lld_cmake_builddir}/LLDTargets.cmake")
+set(LLD_CONFIG_INCLUDE_DIRS
+  "${LLD_SOURCE_DIR}/include"
+  "${LLD_BINARY_DIR}/include"
+  )
+configure_file(
+  ${CMAKE_CURRENT_SOURCE_DIR}/LLDConfig.cmake.in
+  ${lld_cmake_builddir}/LLDConfig.cmake
+  @ONLY)
+set(LLD_CONFIG_CMAKE_DIR)
+set(LLD_CONFIG_LLVM_CMAKE_DIR)
+set(LLD_CONFIG_EXPORTS_FILE)
+
+# Generate LLDConfig.cmake for the install tree.
+set(LLD_CONFIG_CODE "
+# Compute the installation prefix from this LLVMConfig.cmake file location.
+get_filename_component(LLD_INSTALL_PREFIX \"\${CMAKE_CURRENT_LIST_FILE}\" PATH)")
+# Construct the proper number of get_filename_component(... PATH)
+# calls to compute the installation prefix.
+string(REGEX REPLACE "/" ";" _count "${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}")
+set(LLD_CONFIG_EXPORTS_FILE "\${LLD_CMAKE_DIR}/LLDTargets.cmake")
+set(LLD_CONFIG_INCLUDE_DIRS
+  "\${LLD_INSTALL_PREFIX}/include"
+  )
+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)
+set(LLD_CONFIG_EXPORTS_FILE)
+
+if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+  get_property(lld_has_exports GLOBAL PROPERTY LLD_HAS_EXPORTS)
+  if(lld_has_exports)
+    install(EXPORT LLDTargets DESTINATION ${LLD_INSTALL_PACKAGE_DIR}
+            COMPONENT lld-cmake-exports)
+  endif()
+
+  install(FILES
+    ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/LLDConfig.cmake
+    DESTINATION ${LLD_INSTALL_PACKAGE_DIR}
+    COMPONENT lld-cmake-exports)
+
+  if(NOT LLVM_ENABLE_IDE)
+    # Add a dummy target so this can be used with LLVM_DISTRIBUTION_COMPONENTS
+    add_custom_target(lld-cmake-exports)
+    add_llvm_install_targets(install-lld-cmake-exports
+                             COMPONENT lld-cmake-exports)
+  endif()
+endif()

lld/cmake/modules/LLDConfig.cmake.in

+# This file allows users to call find_package(LLD) and pick up our targets.
+
+@LLD_CONFIG_CODE@
+
+find_package(LLVM REQUIRED CONFIG
+             HINTS "@LLD_CONFIG_LLVM_CMAKE_DIR@")
+
+set(LLD_EXPORTED_TARGETS "@LLD_EXPORTS@")
+set(LLD_CMAKE_DIR "@LLD_CONFIG_CMAKE_DIR@")
+set(LLD_INCLUDE_DIRS "@LLD_CONFIG_INCLUDE_DIRS@")
+
+# Provide all our library targets to users.
+include("@LLD_CONFIG_EXPORTS_FILE@")
+
+# By creating lld-tablegen-targets here, subprojects that depend on lld's
+# tablegen-generated headers can always depend on this target whether building
+# in-tree with lld or not.
+if(NOT TARGET lld-tablegen-targets)
+  add_custom_target(lld-tablegen-targets)
+endif()