[cmake] Support custom package install paths

[Ericson2314]

Summary

Firstly, we we make an additional GNUInstallDirs-style variable. With
NixOS, for example, this is crucial as we want those to go in
${dev}/lib/cmake not ${out}/lib/cmake as that would a cmake subdir
of the "regular" libdir, which is installed even when no one needs to do
any development.

Secondly, we make *Config.cmake robust to absolute package install
paths. We for NixOS will in fact be passing them absolute paths to make
the ${dev} vs ${out} distinction mentioned above, and the
GNUInstallDirs-style variables are suposed to support absolute paths in
general so it's good practice besides the NixOS use-case.

Thirdly, we make ${project}_INSTALL_PACKAGE_DIR CACHE PATHs like other
install dirs are.

[Ericson2314]

Could one of you review this?

[Ericson2314]

Rebase

[Ericson2314]

This comment was removed by Ericson2314.

[Ericson2314]

• Rebase

• Some set -> extend_path

• Fix spelling / comments

[Ericson2314]

@nikic if you are still around, might you want to review this?

[sebastian-ne]

Two comments inline, apart from that it looks good to me.

cmake/Modules/FindPrefixFromConfig.cmake

30

Shouldn’t this set config_code instead of prefix_var, which is the output variable in the generated code?

32

This could use a comment to why it ignores path_to_leave and why CMAKE_INSTALL_PREFIX is the correct choice.

[Ericson2314]

Fix bug, and add comments to both branches for clarity

[Ericson2314]

cmake/Modules/FindPrefixFromConfig.cmake

30

Yes! Silly mistake me cleaning the code up for upstreaming but not yet testing it with our configuration again. Thanks for noticing.

32

Added comments to both branches.

[sebastian-ne]

Thank you, the comments make it clearer what’s happening. LGTM

[sebastian-ne]

I found a regression when llvm is added with CMake’s add_subdirectory. D130555 has a fix.

clang/cmake/modules/CMakeLists.txt

+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(LLVMDistributionSupport)
 include(FindPrefixFromConfig)
 
 # 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 ${Project}Targets.cmake.
-set(CLANG_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/clang)
-set(clang_cmake_builddir "${CMAKE_BINARY_DIR}/${CLANG_INSTALL_PACKAGE_DIR}")
+set(CLANG_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/clang" CACHE STRING
+  "Path for CMake subdirectory for Clang (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/clang')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(clang_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
 
 # 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}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
 
 get_property(CLANG_EXPORTS GLOBAL PROPERTY CLANG_EXPORTS)
 export(TARGETS ${CLANG_EXPORTS} FILE ${clang_cmake_builddir}/ClangTargets.cmake)
 
 # Generate ClangConfig.cmake for the build tree.
 set(CLANG_CONFIG_CMAKE_DIR "${clang_cmake_builddir}")
 set(CLANG_CONFIG_LLVM_CMAKE_DIR "${llvm_cmake_builddir}")
 set(CLANG_CONFIG_INCLUDE_EXPORTS "include(\"${clang_cmake_builddir}/ClangTargets.cmake\")")

 file(COPY .
   DESTINATION ${clang_cmake_builddir}
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )
 
 # Generate ClangConfig.cmake for the install tree.
 find_prefix_from_config(CLANG_CONFIG_CODE CLANG_INSTALL_PREFIX "${CLANG_INSTALL_PACKAGE_DIR}")
-set(CLANG_CONFIG_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}/${CLANG_INSTALL_PACKAGE_DIR}")
-set(CLANG_CONFIG_LLVM_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
+extend_path(CLANG_CONFIG_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}" "${CLANG_INSTALL_PACKAGE_DIR}")
+extend_path(CLANG_CONFIG_LLVM_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(Clang CLANG_CONFIG_INCLUDE_EXPORTS)
 extend_path(base_includedir "\${CLANG_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
 set(CLANG_CONFIG_INCLUDE_DIRS
   "${base_includedir}"
   )
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/ClangConfig.cmake.in
   ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/ClangConfig.cmake

cmake/Modules/FindPrefixFromConfig.cmake

 # prefix_var:
 #   Name of the variable to define in the returned code (not directory for the
 #   faller!) that will contain the prefix path.
 #
 # path_to_leave:
 #   Path from the prefix to the config file, a relative path which we wish to
 #   go up and out from to find the prefix directory.
 function(find_prefix_from_config out_var prefix_var path_to_leave)
+  if(IS_ABSOLUTE "${path_to_leave}")
+    set(prefix_var
+      "# Installation prefix is fixed absolute path"
+      "set(${prefix_var} \"${CMAKE_INSTALL_PREFIX}\"")
+  else()
     set(config_code
       "# Compute the installation prefix from this LLVMConfig.cmake file location."
       "get_filename_component(${prefix_var} \"\${CMAKE_CURRENT_LIST_FILE}\" PATH)")
     # Construct the proper number of get_filename_component(... PATH)
     # calls to compute the installation prefix.
     string(REGEX REPLACE "/" ";" _count "${path_to_leave}")
     foreach(p ${_count})
       list(APPEND config_code
         "get_filename_component(${prefix_var} \"\${${prefix_var}}\" PATH)")
     endforeach(p)
+  endif()
   string(REPLACE ";" "\n" config_code "${config_code}")
   set("${out_var}" "${config_code}" PARENT_SCOPE)
 endfunction()

cmake/Modules/GNUInstallPackageDir.cmake

+# Mimmick GNUInstallDirs for one more install directory, the one where
+# project's installed cmake subdirs gos.
+
+# These functions are internal functions vendored in from GNUInstallDirs (with
+# new names) lest it changes.
+#
+# The purpose would appear to be making `CACHE PATH` vars in a way that
+# bypasses the legacy oddity that `-D<PATH>` gets canonicalized, despite
+# non-canonical `CACHE PATH`s being perfectly valid.
+
+macro(_GNUInstallPackageDir_cache_convert_to_path var description)
+  get_property(_GNUInstallPackageDir_cache_type CACHE ${var} PROPERTY TYPE)
+  if(_GNUInstallPackageDir_cache_type STREQUAL "UNINITIALIZED")
+    file(TO_CMAKE_PATH "${${var}}" _GNUInstallPackageDir_cmakepath)
+    set_property(CACHE ${var} PROPERTY TYPE PATH)
+    set_property(CACHE ${var} PROPERTY VALUE "${_GNUInstallPackageDir_cmakepath}")
+    set_property(CACHE ${var} PROPERTY HELPSTRING "${description}")
+    unset(_GNUInstallPackageDir_cmakepath)
+  endif()
+  unset(_GNUInstallPackageDir_cache_type)
+endmacro()
+
+# Create a cache variable with default for a path.
+macro(_GNUInstallPackageDir_cache_path var default description)
+  if(NOT DEFINED ${var})
+    set(${var} "${default}" CACHE PATH "${description}")
+  endif()
+  _GNUInstallPackageDir_cache_convert_to_path("${var}" "${description}")
+endmacro()
+
+_GNUInstallPackageDir_cache_path(CMAKE_INSTALL_PACKAGEDIR "lib${LLVM_LIBDIR_SUFFIX}/cmake"
+  "Directories containing installed CMake modules (lib/cmake)")

flang/cmake/modules/CMakeLists.txt

+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(FindPrefixFromConfig)
 
 # 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 ${Project}Targets.cmake.
-set(FLANG_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/flang)
-set(flang_cmake_builddir "${CMAKE_BINARY_DIR}/${FLANG_INSTALL_PACKAGE_DIR}")
+set(FLANG_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/flang" CACHE STRING
+  "Path for CMake subdirectory for Flang (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/flang')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(flang_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/flang")
 
 # 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}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
 
 get_property(FLANG_EXPORTS GLOBAL PROPERTY FLANG_EXPORTS)
 export(TARGETS ${FLANG_EXPORTS} FILE ${flang_cmake_builddir}/FlangTargets.cmake)
 
 # Generate FlangConfig.cmake for the build tree.
 set(FLANG_CONFIG_CMAKE_DIR "${flang_cmake_builddir}")
 set(FLANG_CONFIG_LLVM_CMAKE_DIR "${llvm_cmake_builddir}")
 set(FLANG_CONFIG_INCLUDE_EXPORTS "include(\"${flang_cmake_builddir}/FlangTargets.cmake\")")

lld/cmake/modules/CMakeLists.txt

+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(FindPrefixFromConfig)
 
 # 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}")
+set(LLD_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/lld" CACHE STRING
+  "Path for CMake subdirectory for LLD (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/lld')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(lld_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/lld")
 
 # 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}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
 
 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_INCLUDE_EXPORTS "include(\"${lld_cmake_builddir}/LLDTargets.cmake\")")
 set(LLD_CONFIG_INCLUDE_DIRS
   "${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)
 
 # Generate LLDConfig.cmake for the install tree.
 find_prefix_from_config(LLD_CONFIG_CODE LLD_INSTALL_PREFIX "${LLD_INSTALL_PACKAGE_DIR}")
-set(LLD_CONFIG_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLD_INSTALL_PACKAGE_DIR}")
-set(LLD_CONFIG_LLVM_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
+extend_path(LLD_CONFIG_CMAKE_DIR "\${LLD_INSTALL_PREFIX}" "${LLD_INSTALL_PACKAGE_DIR}")
+extend_path(LLD_CONFIG_LLVM_CMAKE_DIR "\${LLD_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(LLD LLD_CONFIG_INCLUDE_EXPORTS)
 extend_path(LLD_CONFIG_INCLUDE_DIRS "\${LLD_INSTALL_PREFIX}" "${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)

llvm/cmake/modules/AddLLVM.cmake

function(process_llvm_pass_plugins)
   endforeach()
 
   # Eventually generate the extension headers, and store config to a cmake file
   # for usage in third-party configuration.
   if(ARG_GEN_CONFIG)
 
       ## Part 1: Extension header to be included whenever we need extension
       #  processing.
-      set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
-      set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
+      if(NOT DEFINED LLVM_INSTALL_PACKAGE_DIR)
+          message(FATAL_ERROR "LLVM_INSTALL_PACKAGE_DIR must be defined and writable. GEN_CONFIG should only be passe when building LLVM proper.")
+      endif()
+      # LLVM_INSTALL_PACKAGE_DIR might be absolute, so don't reuse below.
+      set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
       file(WRITE
           "${llvm_cmake_builddir}/LLVMConfigExtensions.cmake"
           "set(LLVM_STATIC_EXTENSIONS ${LLVM_STATIC_EXTENSIONS})")
       install(FILES
           ${llvm_cmake_builddir}/LLVMConfigExtensions.cmake
           DESTINATION ${LLVM_INSTALL_PACKAGE_DIR}
           COMPONENT cmake-exports)
 

llvm/cmake/modules/CMakeLists.txt

+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(LLVMDistributionSupport)
 include(FindPrefixFromConfig)
 
-set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
-set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
 
 # First for users who use an installed LLVM, create the LLVMExports.cmake file.
 set(LLVM_EXPORTS_FILE ${llvm_cmake_builddir}/LLVMExports.cmake)
 get_property(LLVM_EXPORTS GLOBAL PROPERTY LLVM_EXPORTS)
 export(TARGETS ${LLVM_EXPORTS} FILE ${LLVM_EXPORTS_FILE})
 
 # Then for users who want to link against the LLVM build tree, provide the
 # normal targets and the build tree only targets.

mlir/cmake/modules/CMakeLists.txt

+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(LLVMDistributionSupport)
 include(FindPrefixFromConfig)
 
 # 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 ${Project}Targets.cmake.
-set(MLIR_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/mlir)
-set(mlir_cmake_builddir "${CMAKE_BINARY_DIR}/${MLIR_INSTALL_PACKAGE_DIR}")
+set(MLIR_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/mlir" CACHE STRING
+  "Path for CMake subdirectory for Polly (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/polly')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(mlir_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/mlir")
 
 # 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}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
 
 get_property(MLIR_EXPORTS GLOBAL PROPERTY MLIR_EXPORTS)
 export(TARGETS ${MLIR_EXPORTS} FILE ${mlir_cmake_builddir}/MLIRTargets.cmake)
 
 get_property(MLIR_ALL_LIBS GLOBAL PROPERTY MLIR_ALL_LIBS)
 get_property(MLIR_DIALECT_LIBS GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 get_property(MLIR_CONVERSION_LIBS GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
 get_property(MLIR_TRANSLATION_LIBS GLOBAL PROPERTY MLIR_TRANSLATION_LIBS)

 file(COPY .
   DESTINATION ${mlir_cmake_builddir}
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )
 
 # Generate MLIRConfig.cmake for the install tree.
 find_prefix_from_config(MLIR_CONFIG_CODE MLIR_INSTALL_PREFIX "${MLIR_INSTALL_PACKAGE_DIR}")
-set(MLIR_CONFIG_CMAKE_DIR "\${MLIR_INSTALL_PREFIX}/${MLIR_INSTALL_PACKAGE_DIR}")
-set(MLIR_CONFIG_LLVM_CMAKE_DIR "\${MLIR_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
+extend_path(MLIR_CONFIG_CMAKE_DIR "\${MLIR_INSTALL_PREFIX}" "${MLIR_INSTALL_PACKAGE_DIR}")
+extend_path(MLIR_CONFIG_LLVM_CMAKE_DIR "\${MLIR_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(MLIR MLIR_CONFIG_INCLUDE_EXPORTS)
 extend_path(base_includedir "\${MLIR_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
 set(MLIR_CONFIG_INCLUDE_DIRS
   "${base_includedir}"
   )
 # Ensure that we are using the installed mlir-tblgen. This might not be MLIR_TABLEGEN_EXE
 # if we're building with a host-optimized mlir-tblgen (with LLVM_OPTIMIZED_TABLEGEN).
 set(MLIR_CONFIG_TABLEGEN_EXE mlir-tblgen)

polly/cmake/CMakeLists.txt

 # Keep this in sync with llvm/cmake/CMakeLists.txt!
 
+include(GNUInstallPackageDir)
 include(ExtendPath)
 include(FindPrefixFromConfig)
 
-set(LLVM_INSTALL_PACKAGE_DIR "lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
-set(POLLY_INSTALL_PACKAGE_DIR "lib${LLVM_LIBDIR_SUFFIX}/cmake/polly")
+set(POLLY_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/polly" CACHE STRING
+  "Path for CMake subdirectory for Polly (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/polly')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(polly_cmake_builddir "${POLLY_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/polly")
+
+set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
+  "Path for CMake subdirectory for LLVM (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/llvm')")
+# CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
+set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
+
 if (CMAKE_CONFIGURATION_TYPES)
   set(POLLY_EXPORTS_FILE_NAME "PollyExports-$<LOWER_CASE:$<CONFIG>>.cmake")
 else()
   # avoid conflicts in the build-tree when changing configuration
   set(POLLY_EXPORTS_FILE_NAME "PollyExports-all.cmake")
 endif()
 
 set(POLLY_CONFIG_EXPORTED_TARGETS Polly ${ISL_TARGET})
 if (NOT WIN32 AND LLVM_ENABLE_PIC)
   # LLVMPolly is a dummy target on Win or if PIC code is disabled.
   list(APPEND POLLY_CONFIG_EXPORTED_TARGETS LLVMPolly)
 endif()
 if (POLLY_ENABLE_GPGPU_CODEGEN)
   list(APPEND POLLY_CONFIG_EXPORTED_TARGETS PollyPPCG)
 endif()
 
 # Get the target type for every exported target
 foreach(tgt IN LISTS POLLY_CONFIG_EXPORTED_TARGETS)
   get_target_property(tgt_type ${tgt} TYPE)
   string(REPLACE "_LIBRARY" "" tgt_type ${tgt_type})
   set(POLLY_CONFIG_TARGET_${tgt}_TYPE ${tgt_type})
 endforeach()
 
-set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
-set(POLLY_CONFIG_LLVM_CMAKE_DIR "${llvm_cmake_builddir}")
-
 # generate the import code for bundled/undbundled libisl versions
 if (NOT POLLY_BUNDLED_ISL)
   get_property(incl TARGET ISL PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
   get_property(lib TARGET ISL PROPERTY INTERFACE_LINK_LIBRARIES)
   get_property(opt TARGET ISL PROPERTY INTERFACE_COMPILE_OPTIONS)
   set(ISL_CONFIG_CODE "
 add_library(ISL INTERFACE IMPORTED)
 set_property(TARGET ISL APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${incl})
 set_property(TARGET ISL APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${lib})
 set_property(TARGET ISL APPEND PROPERTY INTERFACE_COMPILE_OPTIONS ${opt})")
 else()
   set(ISL_CONFIG_CODE "
 if (NOT TARGET PollyISL)
   add_library(PollyISL ${POLLY_CONFIG_TARGET_PollyISL_TYPE} IMPORTED)
 endif()")
 endif()
 
 # Generate PollyConfig.cmake for the build tree.
 set(POLLY_CONFIG_CODE "")
-set(POLLY_CONFIG_CMAKE_DIR "${CMAKE_BINARY_DIR}/${POLLY_INSTALL_PACKAGE_DIR}")
+set(POLLY_CONFIG_LLVM_CMAKE_DIR "${llvm_cmake_builddir}")
+set(POLLY_CONFIG_CMAKE_DIR "${polly_cmake_builddir}")
 set(POLLY_CONFIG_INCLUDE_DIRS
   ${POLLY_SOURCE_DIR}/include
   ${ISL_INCLUDE_DIRS}
   ${POLLY_BINARY_DIR}/include
   )
 set(POLLY_CONFIG_LIBRARY_DIRS "${POLLY_BINARY_DIR}/lib")
 
 # set locations for imported targets
 foreach(tgt IN LISTS POLLY_CONFIG_EXPORTED_TARGETS)
   get_target_property(tgt_type ${tgt} TYPE)
   if (NOT tgt_type STREQUAL "INTERFACE_LIBRARY")
     set(POLLY_EXPORTS
       "set_target_properties(${tgt} PROPERTIES
               IMPORTED_LOCATION$<$<NOT:$<CONFIG:>>:_$<UPPER_CASE:$<CONFIG>>> $<TARGET_FILE:${tgt}>)
 ${POLLY_EXPORTS}")
   endif()
 endforeach(tgt)
 
 # PollyConfig holds the target definitions and general settings, PollyExports
 # the imported locations
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/PollyConfig.cmake.in
-  ${POLLY_CONFIG_CMAKE_DIR}/PollyConfig.cmake
+  ${polly_cmake_builddir}/PollyConfig.cmake
   @ONLY)
 
 file(GENERATE
-  OUTPUT ${POLLY_CONFIG_CMAKE_DIR}/${POLLY_EXPORTS_FILE_NAME}
+  OUTPUT ${polly_cmake_builddir}/${POLLY_EXPORTS_FILE_NAME}
   CONTENT "${POLLY_EXPORTS}")
 
 
 # Generate PollyConfig.cmake for the install tree.
 unset(POLLY_EXPORTS)
 find_prefix_from_config(POLLY_CONFIG_CODE POLLY_INSTALL_PREFIX "${POLLY_INSTALL_PACKAGE_DIR}")
 extend_path(POLLY_CONFIG_LLVM_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
 extend_path(POLLY_CONFIG_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}" "${POLLY_INSTALL_PACKAGE_DIR}")