[llvm] Use `GNUInstallDirs` to support custom installation dirs

[Ericson2314]

Summary

This is the patch for LLVM proper in my series for adding GNUInstallDirs support in all project.

Additionally:

Create a new CACHE STRING variable, LLVM_EXAMPLES_INSTALL_DIR, to control where the examples are installed on analogy with the other variables.

---

This patch supersedes D28234, which tried to do the same thing but hand-rolled without GNUInstallDirs.

This patch nearly reverts commit 3 0fc88bf1dc15a72e2d9809d28019d386b7a7cc0, which was a revert of a prior attempt."

(I had to add a space here or else Phabricator detects a reference cycle and won't let me do the form submit.)

[Ericson2314]

Ah this split won't work, because the changes to AddLLVM and friends mean the downstream packages also need to use GNUInstallDirs.

[lebedev.ri]

In D100810#2708650, @Ericson2314 wrote:

Ah this split won't work, because the changes to AddLLVM and friends mean the downstream packages also need to use GNUInstallDirs.

So what? The suggestion to split this up was specifically to simplify review.
Nothing is stopping you from committing everything at once in the end.

[Ericson2314]

Reopen, without llvm_install_symlink changes

[Ericson2314]

Quote variable usages

[Ericson2314]

Fix stray ':' typo

[Ericson2314]

Rebase, no changes

[Ericson2314]

@compnerd Would you like to review this one too (which the other you approved needs)?

[Ericson2314]

Rebased, fixed unintersting conflicts, organized docs better

[Ericson2314]

@phosek would you mind reviewing this one next?

[Ericson2314]

Rebase, fixing conflicts

[Ericson2314]

rebase, fixing conflicts

[compnerd]

llvm/CMakeLists.txt

614–615

Why the change from llvm -> ${project}? (not that it really makes a difference)

llvm/cmake/modules/AddSphinxTarget.cmake

76–77

Nit: trailing slash is unnecessary, CMAKE_INSTALL_MANDIR should be defined, and if not, you do not want installation into / anyway.

llvm/cmake/modules/CMakeLists.txt

4

Why is this variable being put into the cache now?

llvm/cmake/modules/LLVMInstallSymlink.cmake

9

Nit: trailing slash shouldn't be there.

llvm/tools/llvm-config/llvm-config.cpp

361

Why the temporary StringRef? Can you not just initialize Path with the literal?

366

Similar

[Ericson2314]

Fix things in response to comments

[Ericson2314]

llvm/CMakeLists.txt

614–615

To be honest, I forgot. I might have just been OCD deduping on the fly. Happy to change back,

llvm/cmake/modules/CMakeLists.txt

4

I wanted all the installation dirs to be in there for consistency (c.f. Did the same for compiler-rt in D105765).

FWIW I have a yet-unposted commit I want to improve a bit to make it more genuinely user-configurable too (we want the CMake with the headers so it need not be installed runtime)

llvm/tools/llvm-config/llvm-config.cpp

361

I'm not sure. I would think so too, but the old code was also using StringRef so I just followed cargo culted and went with it.

[Ericson2314]

llvm/CMakeLists.txt

614–615

Which would you like me to do, @compnerd?

llvm/tools/llvm-config/llvm-config.cpp

361

Should I, say, submit a separate patch trying to remove the existing one?

[Ericson2314]

llvm/tools/llvm-config/llvm-config.cpp

361

I opened D111322 for this. If that passes CI and lands, I have the next version of this without StringRef ready to go.

[Ericson2314]

Rebase, avoid extra string ref conversions in llvm-config

[Ericson2314]

Removed extraneous StringRef conversion after previous D111322 was landed.

llvm/tools/llvm-config/llvm-config.cpp

361

Fix issue now.

[Ericson2314]

Skip ${project} change

[Ericson2314]

Respond to last open thing

llvm/CMakeLists.txt

614–615

Erred on the size of caution and put it back.

[Ericson2314]

Simple rebase

[compnerd]

llvm/CMakeLists.txt

289

llvm/docs/CMake.rst

270

I'm kinda torn on this. The variables here are all CMake standard and we should redirect users to CMake. Although, this is following the existing pattern, so seems reasonable.

[Ericson2314]

Fix last comment

[mib]

Hi @Ericson2314, I think this patch broke our macOS lldb-incremental bot on GreenDragon (https://green.lab.llvm.org/green/job/lldb-cmake/37560/console).

Could you please take a look ? Thanks!

[mib]

I reverted this patch locally and tried building with clang modules (-DLLVM_ENABLE_MODULES=On) which confirmed it was causing the build failure on the bots.

I had to revert your patch upstream to fix our bots. If you need some help to reproduce the build failure, let me know.

[Ericson2314]

@mib Sorry for not catching this myself. I must admit the error does confuse me. I have an macOS machine I can ssh to, and yes, if if you had some tips on how to reproduce there I would greatly appreciate them.

Thanks.

llvm/docs/CMake.rst

270

Yeah maybe we can redo the section after. "rarely used" is a funny title; shouldn't we be mentioning he most notable CMake variables if any at all?

[Ericson2314]

@mib Can you help me reproduce? I ran

cmake -G Ninja .. -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_INSTALL_PREFIX="$HOME/tmp/out" -DLLDB_TEST_USER_ARGS="--arch;x86_64;--build-dir;$HOME/tmp/out/lldb-test-build.noindex;-t;--env;TERM=vt100" '-DLLDB_ENABLE_PYTHON=On' '-DLLVM_ENABLE_ASSERTIONS:BOOL=TRUE' '-DLLVM_ENABLE_MODULES=On' '-DLLVM_ENABLE_PROJECTS=clang;libcxx;libcxxabi;compiler-rt;lld;lldb;cross-project-tests' "-DLLVM_LIT_ARGS=-v --time-tests --shuffle --xunit-xml-output=$HOME/tmp/test/results.xml" '-DLLVM_VERSION_PATCH=99' '-DCMAKE_C_FLAGS=-Wdocumentation' '-DCMAKE_CXX_FLAGS=-Wdocumentation'

on ssh'd to a macOS machine with perhaps fewer SDKs installed, and where the failure occurred I got:

-- Clang version: 14.0.99
-- Host linker version: 530
# (error was here)
-- Not building amdgpu-arch: hsa-runtime64 not found
-- LLD version: 14.0.99
-- Enable editline support in LLDB: TRUE
-- Enable curses support in LLDB: TRUE

[Ericson2314]

I tried again without lld in the list of enable projects, in case it that made a difference to force it to use ld64 more, but it still worked.

[mib]

In D100810#3186066, @Ericson2314 wrote:

I tried again without lld in the list of enable projects, in case it that made a difference to force it to use ld64 more, but it still worked.

Hi @Ericson2314, I tried reproducing the failure with your patch applied and I couldn't ... May be you can try re-landing this patch and monitor the macOS lldb bots for a failure:

• https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/
• https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake-standalone/

[Ericson2314]

I guess reopening is the better way to redo after revert?

[Ericson2314]

Big rebase and cleanup

[Ericson2314]

1. Updating D100810: [llvm] 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

Mark variables as advanced in doc too

[Ericson2314]

1. Updating D100810: [llvm] 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

Removed one to many ${project}

[Ericson2314]

1. Updating D100810: [llvm] 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 bugs

[Ericson2314]

1. Updating D100810: [llvm] 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 top of D116467

[Ericson2314]

Mark some old threads done.

llvm/cmake/modules/CMakeLists.txt

4

I see I put this back for now, that's good.

[Ericson2314]

1. Updating D100810: [llvm] 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

Robust

[mstorsjo]

llvm/CMakeLists.txt

75

Nit: This looks like a spurious unrelated change to whitespace?

164

Could this bit be split out to separate change, to keep this as small as possible - unless it's strictly needed and tied to this one?

292

Nit: Unrelated and can be split out?

406

Unrelated?

[Ericson2314]

Remove off topic bits

[Ericson2314]

llvm/CMakeLists.txt

75

Doing in D116510 instead.

164

Doing that, I will post the revision later as it is not that important.

292

Yes, will do later.

406

Yes, see above.

[Ericson2314]

Rebase

[Ericson2314]

OK, at long last, I this is the attempt that's gonna make it!

[Ericson2314]

llvm/cmake/modules/AddSphinxTarget.cmake

1

N.B. this already had it from an earlier revision of mine, so didn't need to add it.

[arichardson]

llvm/CMakeLists.txt

5

This seems to be causing the following warning for me:

CMake Warning (dev) at /opt/clion-2021.2/bin/cmake/linux/share/cmake-3.20/Modules/GNUInstallDirs.cmake:236 (message):
  Unable to determine default CMAKE_INSTALL_LIBDIR directory because no
  target architecture is known.  Please enable at least one language before
  including GNUInstallDirs.

[arichardson]

llvm/CMakeLists.txt

5

Moving it below project(LLVM should fix that, but I'm not sure if there is a reason that it's up here.

llvm/CMakeLists.txt

 # See docs/CMake.html for instructions about how to build LLVM with CMake.
 
 cmake_minimum_required(VERSION 3.13.4)
 
+include(GNUInstallDirs)
+
 # CMP0116: Ninja generators transform `DEPFILE`s from `add_custom_command()`
 # New in CMake 3.20. https://cmake.org/cmake/help/latest/policy/CMP0116.html
 if(POLICY CMP0116)
   cmake_policy(SET CMP0116 OLD)
 endif()
 
 set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
 

 # This allows an easy way of setting up a build directory for llvm and another
 # one for llvm+clang+... using the same sources.
 set(LLVM_ALL_PROJECTS "clang;clang-tools-extra;compiler-rt;cross-project-tests;libc;libclc;libcxx;libcxxabi;libunwind;lld;lldb;mlir;openmp;polly;pstl")
 # The flang project is not yet part of "all" projects (see C++ requirements)
 set(LLVM_EXTRA_PROJECTS "flang")
 # List of all known projects in the mono repo
 set(LLVM_KNOWN_PROJECTS "${LLVM_ALL_PROJECTS};${LLVM_EXTRA_PROJECTS}")
 set(LLVM_ENABLE_PROJECTS "" CACHE STRING
-  "Semicolon-separated list of projects to build (${LLVM_KNOWN_PROJECTS}), or \"all\".")
+   "Semicolon-separated list of projects to build (${LLVM_KNOWN_PROJECTS}), or \"all\".")
 foreach(proj ${LLVM_ENABLE_PROJECTS})
   if (NOT proj STREQUAL "all" AND NOT proj STREQUAL "llvm" AND NOT "${proj}" IN_LIST LLVM_KNOWN_PROJECTS)
      MESSAGE(FATAL_ERROR "${proj} isn't a known project: ${LLVM_KNOWN_PROJECTS}")
   endif()
 endforeach()
 foreach(proj "libcxx" "libcxxabi" "libunwind")
   if (${proj} IN_LIST LLVM_ENABLE_PROJECTS)
     message(WARNING "Using LLVM_ENABLE_PROJECTS=${proj} is deprecated now, please use -DLLVM_ENABLE_RUNTIMES=${proj} or "

 unset(SHOULD_ENABLE_PROJECT)
 
 # Build llvm with ccache if the package is present
 set(LLVM_CCACHE_BUILD OFF CACHE BOOL "Set to ON for a ccache enabled build")
 if(LLVM_CCACHE_BUILD)
   find_program(CCACHE_PROGRAM ccache)
   if(CCACHE_PROGRAM)
       set(LLVM_CCACHE_MAXSIZE "" CACHE STRING "Size of ccache")
-      set(LLVM_CCACHE_DIR "" CACHE STRING "Directory to keep ccached data")
+      set(LLVM_CCACHE_DIR "" CACHE PATH "Directory to keep ccached data")
       set(LLVM_CCACHE_PARAMS "CCACHE_CPP2=yes CCACHE_HASHDIR=yes"
           CACHE STRING "Parameters to pass through to ccache")
 
       set(CCACHE_PROGRAM "${LLVM_CCACHE_PARAMS} ${CCACHE_PROGRAM}")
       if (LLVM_CCACHE_MAXSIZE)
         set(CCACHE_PROGRAM "CCACHE_MAXSIZE=${LLVM_CCACHE_MAXSIZE} ${CCACHE_PROGRAM}")
       endif()
       if (LLVM_CCACHE_DIR)

 
 option(LLVM_ENABLE_DAGISEL_COV "Debug: Prints tablegen patterns that were used for selecting" OFF)
 option(LLVM_ENABLE_GISEL_COV "Enable collection of GlobalISel rule coverage" OFF)
 if(LLVM_ENABLE_GISEL_COV)
   set(LLVM_GISEL_COV_PREFIX "${CMAKE_BINARY_DIR}/gisel-coverage-" CACHE STRING "Provide a filename prefix to collect the GlobalISel rule coverage")
 endif()
 
 # Add path for custom modules
-set(CMAKE_MODULE_PATH
-  ${CMAKE_MODULE_PATH}
+list(INSERT CMAKE_MODULE_PATH 0
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
+  "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/Modules"
   )
 
 # Generate a CompilationDatabase (compile_commands.json file) for our build,
 # for use by clang_complete, YouCompleteMe, etc.
 set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
 
 option(LLVM_INSTALL_BINUTILS_SYMLINKS
   "Install symlinks from the binutils tool names to the corresponding LLVM tools." OFF)

 
 if (CMAKE_BUILD_TYPE AND
     NOT uppercase_CMAKE_BUILD_TYPE MATCHES "^(DEBUG|RELEASE|RELWITHDEBINFO|MINSIZEREL)$")
   message(FATAL_ERROR "Invalid value for CMAKE_BUILD_TYPE: ${CMAKE_BUILD_TYPE}")
 endif()
 
 set(LLVM_LIBDIR_SUFFIX "" CACHE STRING "Define suffix of library directory name (32/64)" )
 
-set(LLVM_TOOLS_INSTALL_DIR "bin" CACHE STRING "Path for binary subdirectory (defaults to 'bin')")
+set(LLVM_TOOLS_INSTALL_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
+    "Path for binary subdirectory (defaults to '${CMAKE_INSTALL_BINDIR}')")
 mark_as_advanced(LLVM_TOOLS_INSTALL_DIR)
 
-set(LLVM_UTILS_INSTALL_DIR "${LLVM_TOOLS_INSTALL_DIR}" CACHE STRING
+set(LLVM_UTILS_INSTALL_DIR "${LLVM_TOOLS_INSTALL_DIR}" CACHE PATH
     "Path to install LLVM utilities (enabled by LLVM_INSTALL_UTILS=ON) (defaults to LLVM_TOOLS_INSTALL_DIR)")
 mark_as_advanced(LLVM_UTILS_INSTALL_DIR)
 
+set(LLVM_EXAMPLES_INSTALL_DIR "examples" CACHE PATH
+    "Path for examples subdirectory (enabled by LLVM_BUILD_EXAMPLES=ON) (defaults to 'examples')")
+mark_as_advanced(LLVM_EXAMPLES_INSTALL_DIR)
+
 # They are used as destination of target generators.
 set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin)
 set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
 if(WIN32 OR CYGWIN)
   # DLL platform -- put DLLs into bin.
   set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_RUNTIME_OUTPUT_INTDIR})
 else()
   set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_LIBRARY_OUTPUT_INTDIR})

 
 # List of targets with JIT support:
 set(LLVM_TARGETS_WITH_JIT X86 PowerPC AArch64 ARM Mips SystemZ)
 
 set(LLVM_TARGETS_TO_BUILD "all"
     CACHE STRING "Semicolon-separated list of targets to build, or \"all\".")
 
 set(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD ""
     CACHE STRING "Semicolon-separated list of experimental targets to build.")
 
 option(BUILD_SHARED_LIBS
   "Build all libraries as shared libraries instead of static" OFF)
 
 option(LLVM_ENABLE_BACKTRACES "Enable embedding backtraces on crash." ON)
 if(LLVM_ENABLE_BACKTRACES)
   set(ENABLE_BACKTRACES 1)
 endif()

 else()
   option(LLVM_ENABLE_THREADS "Use threads if available." ON)
 endif()
 
 set(LLVM_ENABLE_ZLIB "ON" CACHE STRING "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_ENABLE_CURL "OFF" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
 
-set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")
+set(LLVM_Z3_INSTALL_DIR "" CACHE PATH "Install directory of the Z3 solver.")
 
 option(LLVM_ENABLE_Z3_SOLVER
   "Enable Support for the Z3 constraint solver in LLVM."
   ${LLVM_ENABLE_Z3_SOLVER_DEFAULT}
 )
 
 if (LLVM_ENABLE_Z3_SOLVER)
   find_package(Z3 4.7.1)

 option(LLVM_INCLUDE_BENCHMARKS "Generate benchmark targets. If OFF, benchmarks can't be built." ON)
 
 option (LLVM_BUILD_DOCS "Build the llvm documentation." OFF)
 option (LLVM_INCLUDE_DOCS "Generate build targets for llvm documentation." ON)
 option (LLVM_ENABLE_DOXYGEN "Use doxygen to generate llvm API documentation." OFF)
 option (LLVM_ENABLE_SPHINX "Use Sphinx to generate llvm documentation." OFF)
 option (LLVM_ENABLE_OCAMLDOC "Build OCaml bindings documentation." ON)
 option (LLVM_ENABLE_BINDINGS "Build bindings." ON)
 
-set(LLVM_INSTALL_DOXYGEN_HTML_DIR "share/doc/llvm/doxygen-html"
-    CACHE STRING "Doxygen-generated HTML documentation install directory")
-set(LLVM_INSTALL_OCAMLDOC_HTML_DIR "share/doc/llvm/ocaml-html"
-    CACHE STRING "OCamldoc-generated HTML documentation install directory")
+set(LLVM_INSTALL_DOXYGEN_HTML_DIR "${CMAKE_INSTALL_DOCDIR}/llvm/doxygen-html"
+    CACHE PATH "Doxygen-generated HTML documentation install directory")
+set(LLVM_INSTALL_OCAMLDOC_HTML_DIR "${CMAKE_INSTALL_DOCDIR}/llvm/ocaml-html"
+    CACHE PATH "OCamldoc-generated HTML documentation install directory")
 
 option (LLVM_BUILD_EXTERNAL_COMPILER_RT
   "Build compiler-rt as an external project." OFF)
 
 option (LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
   "Show target and host info when tools are invoked with --version." ON)
 
 # You can configure which libraries from LLVM you want to include in the

 
 # Do this last so that all lit targets have already been created.
 if (LLVM_INCLUDE_UTILS)
   add_subdirectory(utils/llvm-lit)
 endif()
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/llvm include/llvm-c
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     COMPONENT llvm-headers
     FILES_MATCHING
     PATTERN "*.def"
     PATTERN "*.h"
     PATTERN "*.td"
     PATTERN "*.inc"
     PATTERN "LICENSE.TXT"
     )
 
   install(DIRECTORY ${LLVM_INCLUDE_DIR}/llvm ${LLVM_INCLUDE_DIR}/llvm-c
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     COMPONENT llvm-headers
     FILES_MATCHING
     PATTERN "*.def"
     PATTERN "*.h"
     PATTERN "*.gen"
     PATTERN "*.inc"
     # Exclude include/llvm/CMakeFiles/intrinsics_gen.dir, matched by "*.def"
     PATTERN "CMakeFiles" EXCLUDE
     PATTERN "config.h" EXCLUDE
     )
 
   if (LLVM_INSTALL_MODULEMAPS)
     install(DIRECTORY include/llvm include/llvm-c
-            DESTINATION include
+            DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
             COMPONENT llvm-headers
             FILES_MATCHING
             PATTERN "module.modulemap"
             )
     install(FILES include/llvm/module.install.modulemap
-            DESTINATION include/llvm
+            DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/llvm"
             COMPONENT llvm-headers
             RENAME "module.extern.modulemap"
             )
   endif(LLVM_INSTALL_MODULEMAPS)
 
   # Installing the headers needs to depend on generating any public
   # tablegen'd headers.
   add_custom_target(llvm-headers DEPENDS intrinsics_gen omp_gen)

llvm/cmake/modules/AddLLVM.cmake

+include(GNUInstallDirs)
 include(LLVMDistributionSupport)
 include(LLVMProcessSources)
 include(LLVM-Config)
 include(DetermineGCCCompatible)
 
 function(llvm_update_compile_flags name)
   get_property(sources TARGET ${name} PROPERTY SOURCES)
   if("${sources}" MATCHES "\\.c(;|$)")
if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ARG_INSTALL_WITH_TOOLCHAIN)
         set(umbrella)
       endif()
 
       get_target_export_arg(${name} LLVM export_to_llvmexports ${umbrella})
       install(TARGETS ${name}
               ${export_to_llvmexports}
               LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
               ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
-              RUNTIME DESTINATION bin COMPONENT ${name})
+              RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" COMPONENT ${name})
 
       if (NOT LLVM_ENABLE_IDE)
         add_llvm_install_targets(install-${name}
                                  DEPENDS ${name}
                                  COMPONENT ${name})
       endif()
     endif()
     set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS ${name})

 
 
 macro(add_llvm_example name)
   if( NOT LLVM_BUILD_EXAMPLES )
     set(EXCLUDE_FROM_ALL ON)
   endif()
   add_llvm_executable(${name} ${ARGN})
   if( LLVM_BUILD_EXAMPLES )
-    install(TARGETS ${name} RUNTIME DESTINATION examples)
+    install(TARGETS ${name} RUNTIME DESTINATION "${LLVM_EXAMPLES_INSTALL_DIR}")
   endif()
   set_target_properties(${name} PROPERTIES FOLDER "Examples")
 endmacro(add_llvm_example name)
 
 macro(add_llvm_example_library name)
   if( NOT LLVM_BUILD_EXAMPLES )
     set(EXCLUDE_FROM_ALL ON)
     add_llvm_library(${name} BUILDTREE_ONLY ${ARGN})

llvm/cmake/modules/AddSphinxTarget.cmake

 include(GNUInstallDirs)
 
 # Create sphinx target
 if (LLVM_ENABLE_SPHINX)
   message(STATUS "Sphinx enabled.")
   find_package(Sphinx REQUIRED)
   if (LLVM_BUILD_DOCS AND NOT TARGET sphinx)
     add_custom_target(sphinx ALL)
   endif()
set_property(DIRECTORY APPEND PROPERTY
                  "${SPHINX_DOC_TREE_DIR}")
   endif()
 
   if (LLVM_BUILD_DOCS)
     add_dependencies(sphinx ${SPHINX_TARGET_NAME})
 
     # Handle installation
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
       if (builder STREQUAL man)
         # FIXME: We might not ship all the tools that these man pages describe
         install(DIRECTORY "${SPHINX_BUILD_DIR}/" # Slash indicates contents of
                 COMPONENT "${project}-sphinx-man"
                 DESTINATION "${CMAKE_INSTALL_MANDIR}/man1")
 
         if(NOT LLVM_ENABLE_IDE)
           add_llvm_install_targets("install-${SPHINX_TARGET_NAME}"
                                    DEPENDS ${SPHINX_TARGET_NAME}
                                    COMPONENT "${project}-sphinx-man")
         endif()
       elseif (builder STREQUAL html)
         string(TOUPPER "${project}" project_upper)
-        set(${project_upper}_INSTALL_SPHINX_HTML_DIR "share/doc/${project}/html"
-            CACHE STRING "HTML documentation install directory for ${project}")
+        set(${project_upper}_INSTALL_SPHINX_HTML_DIR "${CMAKE_INSTALL_DOCDIR}/${project}/html"
+            CACHE PATH "HTML documentation install directory for ${project}")
 
         # '/.' indicates: copy the contents of the directory directly into
         # the specified destination, without recreating the last component
         # of ${SPHINX_BUILD_DIR} implicitly.
         install(DIRECTORY "${SPHINX_BUILD_DIR}/."
                 COMPONENT "${project}-sphinx-html"
                 DESTINATION "${${project_upper}_INSTALL_SPHINX_HTML_DIR}")
 

llvm/cmake/modules/CMakeLists.txt

+include(ExtendPath)
 include(LLVMDistributionSupport)
 
 set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
 set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
 
 # 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

 # via CMAKE_MODULE_PATH, place API modules next to it.
 # This should be removed in the future.
 file(COPY .
   DESTINATION ${llvm_cmake_builddir}
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )
 
+#
 # Generate LLVMConfig.cmake for the install tree.
-set(LLVM_CONFIG_CODE "
-# Compute the installation prefix from this LLVMConfig.cmake file location.
-get_filename_component(LLVM_INSTALL_PREFIX \"\${CMAKE_CURRENT_LIST_FILE}\" PATH)")
+#
+
+# Find common prefix if relative path, CMAKE_INSTALL_PREFIX if absolute
+if(IS_ABSOLUTE "${LLVM_INSTALL_PACKAGE_DIR}")
+  set(LLVM_CONFIG_CODE
+    "# Installation prefix is fixed absolute path"
+    "set(LLVM_INSTALL_PREFIX \"${CMAKE_INSTALL_PREFIX}\"")
+else()
+  set(LLVM_CONFIG_CODE
+    "# Compute the installation prefix from this LLVMConfig.cmake file location."
+    "get_filename_component(LLVM_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 "${LLVM_INSTALL_PACKAGE_DIR}")
   foreach(p ${_count})
-  set(LLVM_CONFIG_CODE "${LLVM_CONFIG_CODE}
-get_filename_component(LLVM_INSTALL_PREFIX \"\${LLVM_INSTALL_PREFIX}\" PATH)")
+    list(APPEND LLVM_CONFIG_CODE
+      "get_filename_component(LLVM_INSTALL_PREFIX \"\${LLVM_INSTALL_PREFIX}\" PATH)")
   endforeach(p)
-set(LLVM_CONFIG_INCLUDE_DIRS "\${LLVM_INSTALL_PREFIX}/include")
+endif()
+string(REPLACE ";" "\n" LLVM_CONFIG_CODE "${LLVM_CONFIG_CODE}")
+
+# Set path variables for config file
+extend_path(LLVM_CONFIG_INCLUDE_DIRS "\${LLVM_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
 set(LLVM_CONFIG_INCLUDE_DIR "${LLVM_CONFIG_INCLUDE_DIRS}")
 set(LLVM_CONFIG_MAIN_INCLUDE_DIR "${LLVM_CONFIG_INCLUDE_DIRS}")
-set(LLVM_CONFIG_LIBRARY_DIRS "\${LLVM_INSTALL_PREFIX}/lib\${LLVM_LIBDIR_SUFFIX}")
-set(LLVM_CONFIG_CMAKE_DIR "\${LLVM_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
+extend_path(LLVM_CONFIG_LIBRARY_DIRS "\${LLVM_INSTALL_PREFIX}" "lib\${LLVM_LIBDIR_SUFFIX}")
+extend_path(LLVM_CONFIG_CMAKE_DIR "\${LLVM_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
 set(LLVM_CONFIG_BINARY_DIR "\${LLVM_INSTALL_PREFIX}")
-set(LLVM_CONFIG_TOOLS_BINARY_DIR "\${LLVM_INSTALL_PREFIX}/bin")
+extend_path(LLVM_CONFIG_TOOLS_BINARY_DIR "\${LLVM_INSTALL_PREFIX}" "${LLVM_TOOLS_INSTALL_DIR}")
 
 # Generate a default location for lit
 if (LLVM_INSTALL_UTILS AND LLVM_BUILD_UTILS)
   set(LLVM_CONFIG_DEFAULT_EXTERNAL_LIT "${LLVM_CONFIG_TOOLS_BINARY_DIR}/llvm-lit")
 endif()
 
 get_config_exports_includes(LLVM LLVM_CONFIG_INCLUDE_EXPORTS)
 set(LLVM_CONFIG_EXPORTS "${LLVM_EXPORTS}")

llvm/cmake/modules/LLVMInstallSymlink.cmake

 # We need to execute this script at installation time because the
 # DESTDIR environment variable may be unset at configuration time.
 # See PR8397.
 
+include(GNUInstallDirs)
+
 function(install_symlink name target outdir)
   set(DESTDIR $ENV{DESTDIR})
-  set(bindir "${DESTDIR}${CMAKE_INSTALL_PREFIX}/${outdir}/")
+  set(bindir "${DESTDIR}${CMAKE_INSTALL_PREFIX}/${outdir}")
 
   message(STATUS "Creating ${name}")
 
   execute_process(
     COMMAND "${CMAKE_COMMAND}" -E create_symlink "${target}" "${name}"
     WORKING_DIRECTORY "${bindir}" ERROR_VARIABLE has_err)
   if(CMAKE_HOST_WIN32 AND has_err)
     execute_process(
       COMMAND "${CMAKE_COMMAND}" -E copy "${target}" "${name}"
       WORKING_DIRECTORY "${bindir}")
   endif()
 
 endfunction()

llvm/docs/CMake.rst

 Here are some of the CMake variables that are rarely used, along with a brief
 explanation and LLVM-related notes.  For full documentation, consult the CMake
 manual, or execute ``cmake --help-variable VARIABLE_NAME``.
 
 **CMAKE_CXX_STANDARD**:STRING
   Sets the C++ standard to conform to when building LLVM.  Possible values are
   14, 17, 20.  LLVM Requires C++ 14 or higher.  This defaults to 14.
 
+**CMAKE_INSTALL_BINDIR**:PATH
+  The path to install executables, relative to the *CMAKE_INSTALL_PREFIX*.
+  Defaults to "bin".
+
+**CMAKE_INSTALL_INCLUDEDIR**:PATH
+  The path to install header files, relative to the *CMAKE_INSTALL_PREFIX*.
+  Defaults to "include".
+
+**CMAKE_INSTALL_DOCDIR**:PATH
+  The path to install documentation, relative to the *CMAKE_INSTALL_PREFIX*.
+  Defaults to "share/doc".
+
+**CMAKE_INSTALL_MANDIR**:PATH
+  The path to install manpage files, relative to the *CMAKE_INSTALL_PREFIX*.
+  Defaults to "share/man".
+
 .. _LLVM-related variables:
 
 LLVM-related variables
 -----------------------
 
 These variables provide fine control over the build of LLVM and
 enabled sub-projects. Nearly all of these variable names begin with
 ``LLVM_``.

 **LLVM_INSTALL_BINUTILS_SYMLINKS**:BOOL
   Install symlinks from the binutils tool names to the corresponding LLVM tools.
   For example, ar will be symlinked to llvm-ar.
 
 **LLVM_INSTALL_CCTOOLS_SYMLINKS**:BOOL
   Install symliks from the cctools tool names to the corresponding LLVM tools.
   For example, lipo will be symlinked to llvm-lipo.
 
-**LLVM_INSTALL_OCAMLDOC_HTML_DIR**:STRING
+**LLVM_INSTALL_OCAMLDOC_HTML_DIR**:PATH
   The path to install OCamldoc-generated HTML documentation to. This path can
   either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
-  `share/doc/llvm/ocaml-html`.
+  ``${CMAKE_INSTALL_DOCDIR}/llvm/ocaml-html``.
 
-**LLVM_INSTALL_SPHINX_HTML_DIR**:STRING
+**LLVM_INSTALL_SPHINX_HTML_DIR**:PATH
   The path to install Sphinx-generated HTML documentation to. This path can
   either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
-  `share/doc/llvm/html`.
+  ``${CMAKE_INSTALL_DOCDIR}/llvm/html``.
 
 **LLVM_INSTALL_UTILS**:BOOL
   If enabled, utility binaries like ``FileCheck`` and ``not`` will be installed
   to CMAKE_INSTALL_PREFIX.
 
 **LLVM_INTEGRATED_CRT_ALLOC**:PATH
   On Windows, allows embedding a different C runtime allocator into the LLVM
   tools and libraries. Using a lock-free allocator such as the ones listed below
   greatly decreases ThinLTO link time by about an order of magnitude. It also
   midly improves Clang build times, by about 5-10%. At the moment, rpmalloc,
   snmalloc and mimalloc are supported. Use the path to `git clone` to select
   the respective allocator, for example:
 
   .. code-block:: console
 
     $ D:\git> git clone https://github.com/mjansson/rpmalloc
     $ D:\llvm-project> cmake ... -DLLVM_INTEGRATED_CRT_ALLOC=D:\git\rpmalloc
 
   This flag needs to be used along with the static CRT, ie. if building the
   Release target, add -DLLVM_USE_CRT_RELEASE=MT.
 
 **LLVM_INSTALL_DOXYGEN_HTML_DIR**:STRING
   The path to install Doxygen-generated HTML documentation to. This path can
-  either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
-  `share/doc/llvm/doxygen-html`.
+  either be absolute or relative to the ``CMAKE_INSTALL_PREFIX``. Defaults to
+  ``${CMAKE_INSTALL_DOCDIR}/llvm/doxygen-html``.
 
 **LLVM_LINK_LLVM_DYLIB**:BOOL
   If enabled, tools will be linked with the libLLVM shared library. Defaults
   to OFF. Setting LLVM_LINK_LLVM_DYLIB to ON also sets LLVM_BUILD_LLVM_DYLIB
   to ON.
   This option is not available on Windows.
 
 **LLVM_LIT_ARGS**:STRING
**SPHINX_OUTPUT_MAN**:BOOL
   the man pages are added (but not built by default unless ``LLVM_BUILD_DOCS``
   is enabled). Currently the only target added is ``docs-llvm-man``. Defaults
   to ON.
 
 **SPHINX_WARNINGS_AS_ERRORS**:BOOL
   If enabled then sphinx documentation warnings will be treated as
   errors. Defaults to ON.
 
+Advanced variables
+~~~~~~~~~~~~~~~~~~
+
+These are niche, and changing them from their defaults is more likely to cause
+things to go wrong.  They are also unstable across LLVM versions.
+
+**LLVM_TOOLS_INSTALL_DIR**:PATH
+  The path to install the main LLVM tools, relative to the *CMAKE_INSTALL_PREFIX*.
+  Defaults to *CMAKE_INSTALL_BINDIR*.
+
+**LLVM_UTILS_INSTALL_DIR**:PATH
+  The path to install auxiliary LLVM utilities, relative to the *CMAKE_INSTALL_PREFIX*.
+  Only matters if *LLVM_INSTALL_UTILS* is enabled.
+  Defaults to *LLVM_TOOLS_INSTALL_DIR*.
+
+**LLVM_EXAMPLES_INSTALL_DIR**:PATH
+  The path for examples of using LLVM, relative to the *CMAKE_INSTALL_PREFIX*.
+  Only matters if *LLVM_BUILD_EXAMPLES* is enabled.
+  Defaults to "examples".
+
 CMake Caches
 ============
 
 Recently LLVM and Clang have been adding some more complicated build system
 features. Utilizing these new features often involves a complicated chain of
 CMake variables passed on the command line. Clang provides a collection of CMake
 cache scripts to make these features more approachable.
 

llvm/examples/Bye/CMakeLists.txt

 if(LLVM_BYE_LINK_INTO_TOOLS)
   message(WARNING "Setting LLVM_BYE_LINK_INTO_TOOLS=ON only makes sense for testing purpose")
 endif()
 
 # The plugin expects to not link against the Support and Core libraries,
 # but expects them to exist in the process loading the plugin. This doesn't
 # work with DLLs on Windows (where a shared library can't have undefined
 # references), so just skip this example on Windows.
 if (NOT WIN32)
   add_llvm_pass_plugin(Bye
     Bye.cpp
     DEPENDS
     intrinsics_gen
     BUILDTREE_ONLY
    )
 
-  install(TARGETS ${name} RUNTIME DESTINATION examples)
+  install(TARGETS ${name} RUNTIME DESTINATION "${LLVM_EXAMPLES_INSTALL_DIR}")
   set_target_properties(${name} PROPERTIES FOLDER "Examples")
 endif()

llvm/tools/llvm-config/BuildVariables.inc.in

 #define LLVM_SRC_ROOT "@LLVM_SRC_ROOT@"
 #define LLVM_OBJ_ROOT "@LLVM_OBJ_ROOT@"
 #define LLVM_CPPFLAGS "@LLVM_CPPFLAGS@"
 #define LLVM_CFLAGS "@LLVM_CFLAGS@"
 #define LLVM_LDFLAGS "@LLVM_LDFLAGS@"
 #define LLVM_CXXFLAGS "@LLVM_CXXFLAGS@"
 #define LLVM_BUILDMODE "@LLVM_BUILDMODE@"
 #define LLVM_LIBDIR_SUFFIX "@LLVM_LIBDIR_SUFFIX@"
+#define LLVM_INSTALL_INCLUDEDIR "@CMAKE_INSTALL_INCLUDEDIR@"
 #define LLVM_TARGETS_BUILT "@LLVM_TARGETS_BUILT@"
 #define LLVM_SYSTEM_LIBS "@LLVM_SYSTEM_LIBS@"
 #define LLVM_BUILD_SYSTEM "@LLVM_BUILD_SYSTEM@"
 #define LLVM_HAS_RTTI @LLVM_HAS_RTTI@
 #define LLVM_ENABLE_DYLIB @LLVM_BUILD_LLVM_DYLIB@
 #define LLVM_LINK_DYLIB @LLVM_LINK_LLVM_DYLIB@
 #define LLVM_ENABLE_SHARED @BUILD_SHARED_LIBS@
 #define LLVM_DYLIB_COMPONENTS "@LLVM_DYLIB_COMPONENTS_expanded@"
 #define LLVM_DYLIB_VERSION "@LLVM_DYLIB_VERSION@"
 #define LLVM_TOOLS_INSTALL_DIR "@LLVM_TOOLS_INSTALL_DIR@"

llvm/tools/llvm-config/llvm-config.cpp

case CMakeBuildModeStyle:
       break;
     }
 
     // We need to include files from both the source and object trees.
     ActiveIncludeOption =
         ("-I" + ActiveIncludeDir + " " + "-I" + ActiveObjRoot + "/include");
   } else {
     ActivePrefix = CurrentExecPrefix;
-    ActiveIncludeDir = ActivePrefix + "/include";
-    SmallString<256> path(LLVM_TOOLS_INSTALL_DIR);
-    sys::fs::make_absolute(ActivePrefix, path);
-    ActiveBinDir = std::string(path.str());
+    {
+      SmallString<256> Path(LLVM_INSTALL_INCLUDEDIR);
+      sys::fs::make_absolute(ActivePrefix, Path);
+      ActiveIncludeDir = std::string(Path.str());
+    }
+    {
+      SmallString<256> Path(LLVM_TOOLS_INSTALL_DIR);
+      sys::fs::make_absolute(ActivePrefix, Path);
+      ActiveBinDir = std::string(Path.str());
+    }
     ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
     ActiveCMakeDir = ActiveLibDir + "/cmake/llvm";
     ActiveIncludeOption = "-I" + ActiveIncludeDir;
   }
 
   /// We only use `shared library` mode in cases where the static library form
   /// of the components provided are not available; note however that this is
   /// skipped if we're run from within the build dir. However, once installed,

llvm/tools/lto/CMakeLists.txt

else()
     set(LTO_LIBRARY_TYPE SHARED)
     set(LTO_LIBRARY_NAME LTO)
 endif()
 
 add_llvm_library(${LTO_LIBRARY_NAME} ${LTO_LIBRARY_TYPE} INSTALL_WITH_TOOLCHAIN
     ${SOURCES} DEPENDS intrinsics_gen)
 
 install(FILES ${LLVM_MAIN_INCLUDE_DIR}/llvm-c/lto.h
-  DESTINATION include/llvm-c
+  DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/llvm-c"
   COMPONENT LTO)
 
 if (APPLE)
   set(LTO_VERSION ${LLVM_VERSION_MAJOR})
   if(LLVM_LTO_VERSION_OFFSET)
     math(EXPR LTO_VERSION "${LLVM_VERSION_MAJOR} + ${LLVM_LTO_VERSION_OFFSET}")
   endif()
   set_property(TARGET LTO APPEND_STRING PROPERTY
               LINK_FLAGS
               " -compatibility_version 1 -current_version ${LTO_VERSION}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
 endif()

llvm/tools/opt-viewer/CMakeLists.txt

 set (files
   "opt-diff.py"
   "opt-stats.py"
   "opt-viewer.py"
   "optpmap.py"
   "optrecord.py"
   "style.css")
 
 foreach (file ${files})
   install(PROGRAMS ${file}
-    DESTINATION share/opt-viewer
+    DESTINATION "${CMAKE_INSTALL_DATADIR}/opt-viewer"
     COMPONENT opt-viewer)
 endforeach (file)
 
 add_custom_target(opt-viewer DEPENDS ${files})
 if(NOT LLVM_ENABLE_IDE)
   add_llvm_install_targets("install-opt-viewer"
                            DEPENDS opt-viewer
                            COMPONENT opt-viewer)
 endif()

llvm/tools/remarks-shlib/CMakeLists.txt

if(LLVM_ENABLE_PIC)
   add_llvm_library(Remarks SHARED INSTALL_WITH_TOOLCHAIN ${SOURCES})
 
   if (LLVM_INTEGRATED_CRT_ALLOC AND MSVC)
     # Make sure we search LLVMSupport first, before the CRT libs
     set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -INCLUDE:malloc")
   endif()
   
   install(FILES ${LLVM_MAIN_INCLUDE_DIR}/llvm-c/Remarks.h
-    DESTINATION include/llvm-c
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/llvm-c"
     COMPONENT Remarks)
 
   if (APPLE)
     set(REMARKS_VERSION ${LLVM_VERSION_MAJOR})
     set_property(TARGET Remarks APPEND_STRING PROPERTY
                  LINK_FLAGS
                  " -compatibility_version 1 -current_version ${REMARKS_VERSION}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
   endif()
 
 endif()