Introduce LIT_SITE_CFG_IN_HEADER

[AlexDenisov]

Summary

At the moment almost every lit.site.cfg.in contains two lines comment:

## Autogenerated by LLVM/Clang configuration.
# Do not edit!

It took me several days and a few attempts to realise that these are not for this file itself, but for files that are generated from this template.

The patch adds variable LIT_SITE_CFG_IN_HEADER, that is replaced from configure_lit_site_cfg with the note and some useful information.

Assigning to Chandler Carruth as CODE_OWNERS.txt states.

If everybody happy with the patch, then I will apply the change to other projects as well (clang/ compiler-rt, lld, and so on).

P.S. Credits for idea go to Mehdi Amini:

[08:05:19] AlexDenisov:	does anybody know how lit.site.cfg.in's are generated?
[08:06:27] joker-eph:	AlexDenisov: the .in file is in the repo the .cfg is generated, is that what you're asking about ?
[08:06:59] AlexDenisov:	@joker-eph I see there "## Autogenerated by LLVM/Clang configuration."
[08:07:21] AlexDenisov:	which probably a part of the template
[08:07:53] joker-eph:	AlexDenisov: I don't know, I modified this file by hand I think
[08:08:06] AlexDenisov:	yepp, that's a bit confusing
[08:08:29] joker-eph:	AlexDenisov: I think it is so that the comment is in the .cfg file in the end
[08:08:33] AlexDenisov:	I think this note intended to be in the output file
[08:08:34] joker-eph:	not nice though.
[08:08:41] joker-eph:	agree
[08:09:51] AlexDenisov:	ok, at least it's a bit clearer now
[08:10:06] AlexDenisov:	need to be documented or noted somehow somewhere
[08:10:47] joker-eph:	I'd rather have the configure_lit_site_cfg() function prepending the comment
[08:11:05] joker-eph:	 But I did my share of cleanup this week, I have real work to do :)
[08:20:41] AlexDenisov:	joker-eph I will try to send patch soon, thank you very much for help :)

[mehdi_amini]

Nice!
Can you do the same thing in clang/test?

[AlexDenisov]

In D19155#402556, @joker.eph wrote:

Nice!
Can you do the same thing in clang/test?

Yes, as well as for compiler-rt, lld, clang-tools-extra and probably dragonegg and lldb.

cmake/modules/AddLLVM.cmake

function(configure_lit_site_cfg input output)
 
   set(HOST_OS ${CMAKE_SYSTEM_NAME})
   set(HOST_ARCH ${CMAKE_SYSTEM_PROCESSOR})
 
   set(HOST_CC "${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ARG1}")
   set(HOST_CXX "${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1}")
   set(HOST_LDFLAGS "${CMAKE_EXE_LINKER_FLAGS}")
 
+  set(LIT_SITE_CFG_IN_HEADER  "## Autogenerated from ${input}\n## Do not edit!")
+
   configure_file(${input} ${output} @ONLY)
 endfunction()
 
 # A raw function to create a lit target. This is used to implement the testuite
 # management functions.
 function(add_lit_target target comment)
   cmake_parse_arguments(ARG "" "" "PARAMS;DEPENDS;ARGS" ${ARGN})
   set(LIT_ARGS "${ARG_ARGS} ${LLVM_LIT_ARGS}")

test/Unit/lit.site.cfg.in

+@LIT_SITE_CFG_IN_HEADER@
+
 import sys
 
-## Autogenerated by LLVM/Clang configuration.
-# Do not edit!
 config.llvm_src_root = "@LLVM_SOURCE_DIR@"
 config.llvm_obj_root = "@LLVM_BINARY_DIR@"
 config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
 config.llvm_build_mode = "@LLVM_BUILD_MODE@"
 config.enable_shared = @ENABLE_SHARED@
 config.shlibdir = "@SHLIBDIR@"
 
 # Support substitution of the tools_dir and build_mode with user parameters.

test/lit.site.cfg.in

+@LIT_SITE_CFG_IN_HEADER@
+
 import sys
 
-## Autogenerated by LLVM/Clang configuration.
-# Do not edit!
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.llvm_src_root = "@LLVM_SOURCE_DIR@"
 config.llvm_obj_root = "@LLVM_BINARY_DIR@"
 config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
 config.llvm_lib_dir = "@LLVM_LIBRARY_DIR@"
 config.llvm_shlib_dir = "@SHLIBDIR@"
 config.llvm_shlib_ext = "@SHLIBEXT@"