[cmake] Use relative cmake binary dir for processing pass plugins

[alan-baker]

Summary

https://reviews.llvm.org/D61446 introduced a new function to process pass plugins that used CMAKE_BINARY_DIR. This is problematic when LLVM is a subproject. Instead use CMAKE_CURRENT_BINARY_DIR to get the right relative directory for cmake.

[serge-sans-paille]

llvm/cmake/modules/AddLLVM.cmake

907

Why CMAKE_CURRENT_BINARY_DIR and not LLVM_BINARY_DIR as in line 903?

909

Same here.

[Meinersbur]

I don't think CMAKE_CURRENT_BINARY_DIR will work. It is different for each subdirectory, such that multiple plugins create separate Extension.def.tmp instead of appending to a central one. LLVM_BINARY_DIR might be the better choice.

[alan-baker]

llvm/cmake/modules/AddLLVM.cmake

907

That they didn't match was a left over mistake from testing. In my setups they evaluated to the same values. I'll switch all uses to LLVM_BINARY_DIR as Meinersbur suggested.

[alan-baker]

Switch to use LLVM_BINARY_DIR instead of CMAKE_CURRENT_BINARY_DIR.

[Meinersbur]

LGTM

[alan-baker]

I do not have commit access. Would it be possible for someone to commit it on my behalf? Thanks.

[Meinersbur]

I changed CMAKE_CURRENT_BINARY_DIR to LLVM_BINARY_DIR in the commit description. Thank you for the patch.

[mgorny]

This broke standalone build of clang. It's trying to write into /include (as in, root directory) now! My guess is that LLVM_BINARY_DIR is undefined at this point of standalone build, later it might be defined to point to directory where LLVM was installed which also wouldn't be correct.

 * ACCESS DENIED:  mkdir:        /include
CMake Error at /usr/lib/llvm/11/lib64/cmake/llvm/AddLLVM.cmake:894 (file):
  file failed to open for writing (No such file or directory):

    /include/llvm/Support/Extension.def.tmp
Call Stack (most recent call first):
  CMakeLists.txt:867 (process_llvm_pass_plugins)

[serge-sans-paille]

@mgorny can you try with https://reviews.llvm.org/D74602 applied?

[mgorny]

In D72109#1876189, @serge-sans-paille wrote:

@mgorny can you try with https://reviews.llvm.org/D74602 applied?

That seems to help. Thanks!

llvm/cmake/modules/AddLLVM.cmake

 # Generate X Macro file for extension handling. It provides a
 # HANDLE_EXTENSION(extension_namespace, ExtensionProject) call for each extension
 # allowing client code to define HANDLE_EXTENSION to have a specific code be run for
 # each extension.
 #
 # Also correctly set lib dependencies between plugins and tools.
 function(process_llvm_pass_plugins)
   get_property(LLVM_EXTENSIONS GLOBAL PROPERTY LLVM_COMPILE_EXTENSIONS)
-  file(WRITE "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "//extension handlers\n")
+  file(WRITE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "//extension handlers\n")
   foreach(llvm_extension ${LLVM_EXTENSIONS})
     string(TOLOWER ${llvm_extension} llvm_extension_lower)
 
     string(TOUPPER ${llvm_extension} llvm_extension_upper)
     string(SUBSTRING ${llvm_extension_upper} 0 1 llvm_extension_upper_first)
     string(SUBSTRING ${llvm_extension_lower} 1 -1 llvm_extension_lower_tail)
     string(CONCAT llvm_extension_project ${llvm_extension_upper_first} ${llvm_extension_lower_tail})
 
     if(LLVM_${llvm_extension_upper}_LINK_INTO_TOOLS)
-        file(APPEND "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "HANDLE_EXTENSION(${llvm_extension_project})\n")
+      file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "HANDLE_EXTENSION(${llvm_extension_project})\n")
 
-        get_property(llvm_plugin_targets GLOBAL PROPERTY LLVM_PLUGIN_TARGETS)
-        foreach(llvm_plugin_target ${llvm_plugin_targets})
-          set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
-          set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
-        endforeach()
     else()
       add_llvm_library(${llvm_extension_lower} MODULE obj.${llvm_extension_lower})
     endif()
 
   endforeach()
-  file(APPEND "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "#undef HANDLE_EXTENSION\n")
+  file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "#undef HANDLE_EXTENSION\n")
 
   # only replace if there's an actual change
-  execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def")
-  file(REMOVE "${CMAKE_BINARY_DIR}/include/llvm/Support/Extension.def.tmp")
+  execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
+    "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp"
+    "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def")
+  file(REMOVE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp")
 endfunction()
 
 function(export_executable_symbols target)
   if (LLVM_EXPORTED_SYMBOL_FILE)
     # The symbol file should contain the symbols we want the executable to
     # export
     set_target_properties(${target} PROPERTIES ENABLE_EXPORTS 1)
   elseif (LLVM_EXPORT_SYMBOLS_FOR_PLUGINS)