[llvm][cmake] Make `install_symlink` workflow work with absolute install dirs

[Ericson2314]

Summary

If CMAKE_INSTALL_BINDIR is a different absolute path per project, as
it is with NixOS when we install every package to its own prefix, the
old way fails when the absolute path gets prepended with CMAKE_INSTALL_PREFIX.

The extend_path function does what we want, but it is currently internal-only. So easier to just inline the one small case of it we need.

Also fix one stray bin -> CMAKE_INSTALL_BINDIR

[Ericson2314]

1. Updating D101070: Make llvm_install_symlink robust with respect to absolute 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]

Much simpler now

Code taken from D99484 and then to D117419 and now to here.

[Ericson2314]

Continuing my bisect of D99484 (since this change was in there at the time it was approved, but failing) I will land this one next.

[Ericson2314]

This seems to be the part of D99484 that wasn't working.

[Ericson2314]

Rebase, hopefully fix, and also fix stray GNUInstallDirs violation

[Ericson2314]

Rebase to retrigger CI

I think it tried to cherry-pick an already-landed patch marked as a parent revision.

[sebastian-ne]

Hi, not sure if you saw D130256, but I needed to extend CMAKE_MODULE_PATH, otherwise the ExtendPath module was not found when running LLVMInstallSymlink.cmake.

[sebastian-ne]

In D101070#3675462, @sebastian-ne wrote:

Hi, not sure if you saw D130256, but I needed to extend CMAKE_MODULE_PATH, otherwise the ExtendPath module was not found when running LLVMInstallSymlink.cmake.

Just checked, if I run ninja install with this patch, it fails with

CMake Error at /llvm-project/llvm/cmake/modules/LLVMInstallSymlink.cmake:5 (include):
  include could not find requested file:

    ExtendPath
Call Stack (most recent call first):
  tools/llvm-ar/cmake_install.cmake:56 (include)
  tools/cmake_install.cmake:49 (include)
  cmake_install.cmake:78 (include)


FAILED: CMakeFiles/install.util

[Ericson2314]

@sebastian-ne Thanks yes I was worried that might happen. I think I will just move the extend_path to the caller then.

[Ericson2314]

Rebase, make caller responsible for making paths absolute

This avoids module resolution issues.

[sebastian-ne]

I get a configure error with this version:

CMake Error at cmake/modules/AddLLVM.cmake:2052 (extend_path):
  Unknown CMake command "extend_path".
Call Stack (most recent call first):
  cmake/modules/AddLLVM.cmake:2148 (llvm_install_symlink)
  cmake/modules/AddLLVM.cmake:2154 (llvm_add_tool_symlink)
  tools/llvm-ar/CMakeLists.txt:22 (add_llvm_tool_symlink)

[Ericson2314]

Oops! ExtendPath was not already imported. Thanks, @sebastian-ne

[Ericson2314]

Also sorry, I had missed D130256 all along!

[sebastian-ne]

No problem, thanks for the fixes!
LGTM

[Ericson2314]

Avoid extend_path

clang/cmake/modules/AddClang.cmake

if (CLANG_BUILD_TOOLS)
     endif()
     set_property(GLOBAL APPEND PROPERTY CLANG_EXPORTS ${name})
   endif()
 endmacro()
 
 macro(add_clang_symlink name dest)
   add_llvm_tool_symlink(${name} ${dest} ALWAYS_GENERATE)
   # Always generate install targets
-  llvm_install_symlink(${name} ${dest} ALWAYS_GENERATE)
+  llvm_install_symlink(${name} ${dest} ${CMAKE_INSTALL_FULL_BINDIR} ALWAYS_GENERATE)
 endmacro()
 
 function(clang_target_link_libraries target type)
   if (CLANG_LINK_CLANG_DYLIB)
     target_link_libraries(${target} ${type} clang-cpp)
   else()
     target_link_libraries(${target} ${type} ${ARGN})
   endif()
 
 endfunction()

flang/cmake/modules/AddFlang.cmake

if (FLANG_BUILD_TOOLS)
     endif()
     set_property(GLOBAL APPEND PROPERTY FLANG_EXPORTS ${name})
   endif()
 endmacro()
 
 macro(add_flang_symlink name dest)
   add_llvm_tool_symlink(${name} ${dest} ALWAYS_GENERATE)
   # Always generate install targets
-  llvm_install_symlink(${name} ${dest} ALWAYS_GENERATE)
+  llvm_install_symlink(${name} ${dest} ${CMAKE_INSTALL_FULL_BINDIR} ALWAYS_GENERATE)
 endmacro()
 

lld/cmake/modules/AddLLD.cmake

if (LLD_BUILD_TOOLS)
     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} ${dest} ALWAYS_GENERATE)
+  llvm_install_symlink(${name} ${dest} ${CMAKE_INSTALL_FULL_BINDIR} ALWAYS_GENERATE)
 endmacro()

llvm/cmake/modules/AddLLVM.cmake

function(llvm_install_library_symlink name dest type)
   endif()
 
   install(SCRIPT ${INSTALL_SYMLINK}
           CODE "install_symlink(${full_name} ${full_dest} ${output_dir})"
           COMPONENT ${component})
 
 endfunction()
 
-function(llvm_install_symlink name dest)
+function(llvm_install_symlink name dest output_dir)
   cmake_parse_arguments(ARG "ALWAYS_GENERATE" "COMPONENT" "" ${ARGN})
   foreach(path ${CMAKE_MODULE_PATH})
     if(EXISTS ${path}/LLVMInstallSymlink.cmake)
       set(INSTALL_SYMLINK ${path}/LLVMInstallSymlink.cmake)
       break()
     endif()
   endforeach()
 
   if(ARG_COMPONENT)
     set(component ${ARG_COMPONENT})
   else()
     if(ARG_ALWAYS_GENERATE)
       set(component ${dest})
     else()
       set(component ${name})
     endif()
   endif()
 
   set(full_name ${name}${CMAKE_EXECUTABLE_SUFFIX})
   set(full_dest ${dest}${CMAKE_EXECUTABLE_SUFFIX})
 
   install(SCRIPT ${INSTALL_SYMLINK}
-          CODE "install_symlink(${full_name} ${full_dest} ${LLVM_TOOLS_INSTALL_DIR})"
+          CODE "install_symlink(${full_name} ${full_dest} ${output_dir})"
           COMPONENT ${component})
 
   if (NOT LLVM_ENABLE_IDE AND NOT ARG_ALWAYS_GENERATE)
     add_llvm_install_targets(install-${name}
                              DEPENDS ${name} ${dest}
                              COMPONENT ${name}
                              SYMLINK ${dest})
   endif()
else()
     set_target_properties(${target_name} PROPERTIES FOLDER Tools)
 
     # Make sure both the link and target are toolchain tools
     if (${link_name} IN_LIST LLVM_TOOLCHAIN_TOOLS AND ${target} IN_LIST LLVM_TOOLCHAIN_TOOLS)
       set(TOOL_IS_TOOLCHAIN ON)
     endif()
 
     if ((TOOL_IS_TOOLCHAIN OR NOT LLVM_INSTALL_TOOLCHAIN_ONLY) AND LLVM_BUILD_TOOLS)
-      llvm_install_symlink(${link_name} ${target})
+      GNUInstallDirs_get_absolute_install_dir(output_dir LLVM_TOOLS_INSTALL_DIR)
+      llvm_install_symlink(${link_name} ${target} ${output_dir})
     endif()
   endif()
 endfunction()
 
 function(llvm_externalize_debuginfo name)
   if(NOT LLVM_EXTERNALIZE_DEBUGINFO)
     return()
   endif()