[clang][cmake] Add options to pass in vcs repo and revision info

[zhuhan0]

Summary

Clang may be built in an environment where Git is not available. In our case,
Clang is part of a larger monorepo which is not Git-based, and
GenerateVersionFromVCS was not able to get source info.

Provide options to pass in repo and revision info from cmake.

cmake \
  -DCLANG_VC_REPOSITORY=abc://repo.url.com \
  -DCLANG_VC_REVISION=abcd1234 \
  ...

This would allow us to prepare the source info beforehand and pass it to the
clang binary.

[drodriguez]

clang/lib/Basic/CMakeLists.txt

16–21

I imagine you do not need it, but maybe LLVM should have the same changes? There's a for loop in GenerateVersionFromVCS.cmake that is already going to try to look into LLVM_VC_REPOSITORY/REVISION.

llvm/cmake/modules/GenerateVersionFromVCS.cmake

20–21

While I agree that repository and then revision makes more sense, the existing get_source_info receives them in the opposite order.

22–24

Nit: Looks like tabs were added?

48–50

Tabs?

51

I would recommend changing the flow a little bit:

• Remove path argument from append_info. Leave name, revision, and repository.
• Remove the if(path) get_source_info() endif() part.
• Change this foreach to the following:

foreach(name IN LISTS NAMES)
  if(${name}_VC_REPOSITORY AND ${name}_VC_REVISION)
   set(revision ${${name}_VC_REVISION})
   set(repository ${${name}_VC_REPOSITORY})
  elseif(DEFINED ${name}_SOURCE_DIR)
    get_source_info(${${name}_SOURCE_DIR} revision repository)
  else()
    message(FATAL_ERROR "${name}_SOURCE_DIR is not defined")
  endif()
  append_info(${name} ${revision} ${repository})
endforeach()

[zhuhan0]

llvm/cmake/modules/GenerateVersionFromVCS.cmake

22–24

These are not tabs but spaces. The arrow just means it's further indented.

[zhuhan0]

llvm/cmake/modules/GenerateVersionFromVCS.cmake

51

Looks much better!

[zhuhan0]

Address comments.

[zhuhan0]

The patch failed a build bot which sets LLVM_APPEND_VC_REV=OFF. Fixed with https://reviews.llvm.org/rGee68f612ba682ddb911c5621e63df56039ec5824.

clang/lib/Basic/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
   TargetParser
   )
 
 find_first_existing_vc_file("${LLVM_MAIN_SRC_DIR}" llvm_vc)
 find_first_existing_vc_file("${CLANG_SOURCE_DIR}" clang_vc)
 
 # The VC revision include that we want to generate.
 set(version_inc "${CMAKE_CURRENT_BINARY_DIR}/VCSVersion.inc")
 
 set(generate_vcs_version_script "${LLVM_CMAKE_DIR}/GenerateVersionFromVCS.cmake")
 
 if(llvm_vc AND LLVM_APPEND_VC_REV)
   set(llvm_source_dir ${LLVM_MAIN_SRC_DIR})
 endif()
+if (LLVM_VC_REPOSITORY AND LLVM_VC_REVISION)
+  set(llvm_source_dir ${LLVM_SOURCE_DIR})
+  set(llvm_vc_repository ${LLVM_VC_REPOSITORY})
+  set(llvm_vc_revision ${LLVM_VC_REVISION})
+endif()
 if(clang_vc AND LLVM_APPEND_VC_REV)
   set(clang_source_dir ${CLANG_SOURCE_DIR})
 endif()
+if (CLANG_VC_REPOSITORY AND CLANG_VC_REVISION)
+  set(clang_source_dir ${CLANG_SOURCE_DIR})
+  set(clang_vc_repository ${CLANG_VC_REPOSITORY})
+  set(clang_vc_revision ${CLANG_VC_REVISION})
+endif()
 
 # Create custom target to generate the VC revision include.
 add_custom_command(OUTPUT "${version_inc}"
   DEPENDS "${llvm_vc}" "${clang_vc}" "${generate_vcs_version_script}"
   COMMAND ${CMAKE_COMMAND} "-DNAMES=\"LLVM;CLANG\""
                            "-DLLVM_SOURCE_DIR=${llvm_source_dir}"
                            "-DCLANG_SOURCE_DIR=${clang_source_dir}"
+                           "-DCLANG_VC_REPOSITORY=${clang_vc_repository}"
+                           "-DCLANG_VC_REVISION=${clang_vc_revision}"
                            "-DHEADER_FILE=${version_inc}"
+                           "-DLLVM_VC_REPOSITORY=${llvm_vc_repository}"
+                           "-DLLVM_VC_REVISION=${llvm_vc_revision}"
                            -P "${generate_vcs_version_script}")
 
 # Mark the generated header as being generated.
 set_source_files_properties("${version_inc}"
   PROPERTIES GENERATED TRUE
              HEADER_FILE_ONLY TRUE)
 
 if(CLANG_VENDOR)

llvm/cmake/modules/GenerateVersionFromVCS.cmake

 get_filename_component(LLVM_CMAKE_DIR "${CMAKE_SCRIPT_MODE_FILE}" PATH)
 
 list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
 
 include(VersionFromVCS)
 
 # Handle strange terminals
 set(ENV{TERM} "dumb")
 
-function(append_info name path)
-  if(path)
-    get_source_info("${path}" revision repository)
-  endif()
+function(append_info name revision repository)
   if(revision)
     file(APPEND "${HEADER_FILE}.tmp"
       "#define ${name}_REVISION \"${revision}\"\n")
   else()
     file(APPEND "${HEADER_FILE}.tmp"
       "#undef ${name}_REVISION\n")
   endif()
   if(repository)
     file(APPEND "${HEADER_FILE}.tmp"
       "#define ${name}_REPOSITORY \"${repository}\"\n")
   else()
     file(APPEND "${HEADER_FILE}.tmp"
       "#undef ${name}_REPOSITORY\n")
   endif()
 endfunction()
 
 foreach(name IN LISTS NAMES)
-  if(NOT DEFINED ${name}_SOURCE_DIR)
+  if(${name}_VC_REPOSITORY AND ${name}_VC_REVISION)
+    set(revision ${${name}_VC_REVISION})
+    set(repository ${${name}_VC_REPOSITORY})
+  elseif(DEFINED ${name}_SOURCE_DIR)
+    get_source_info(${${name}_SOURCE_DIR} revision repository)
+  else()
     message(FATAL_ERROR "${name}_SOURCE_DIR is not defined")
   endif()
-  append_info(${name} "${${name}_SOURCE_DIR}")
+  append_info(${name} ${revision} ${repository})
 endforeach()
 
 # Copy the file only if it has changed.
 execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
   "${HEADER_FILE}.tmp" "${HEADER_FILE}")
 file(REMOVE "${HEADER_FILE}.tmp")