[libc] newheadergen: cmake config newhdrgen (#99543)

- revert to revert for patch
#98828
- revert to revert #99410
- revert to revert #99413

Author: aaryanshukla

libc/CMakeLists.txt

@@ -73,6 +73,8 @@ if(LIBC_BUILD_GPU_LOADER OR (LLVM_LIBC_GPU_BUILD AND NOT LLVM_RUNTIMES_BUILD))
   add_subdirectory(utils/gpu)
 endif()
 
+option(LIBC_USE_NEW_HEADER_GEN "Generate header files using new headergen instead of the old one" OFF)
+
 set(NEED_LIBC_HDRGEN FALSE)
 if(NOT LLVM_RUNTIMES_BUILD)
   if("libc" IN_LIST LLVM_ENABLE_RUNTIMES)

libc/cmake/modules/LLVMLibCHeaderRules.cmake

@@ -66,7 +66,106 @@ function(add_header target_name)
   )
 endfunction(add_header)
 
-# A rule for generated header file targets.
+function(add_gen_header2 target_name)
+  cmake_parse_arguments(
+    "ADD_GEN_HDR2"
+    "PUBLIC" # No optional arguments
+    "YAML_FILE;DEF_FILE;GEN_HDR" # Single value arguments
+    "DEPENDS"     # Multi value arguments
+    ${ARGN}
+  )
+  get_fq_target_name(${target_name} fq_target_name)
+  if(NOT LLVM_LIBC_FULL_BUILD)
+    add_library(${fq_target_name} INTERFACE)
+    return()
+  endif()
+  if(NOT ADD_GEN_HDR2_DEF_FILE)
+    message(FATAL_ERROR "`add_gen_hdr2` rule requires DEF_FILE to be specified.")
+  endif()
+  if(NOT ADD_GEN_HDR2_GEN_HDR)
+    message(FATAL_ERROR "`add_gen_hdr2` rule requires GEN_HDR to be specified.")
+  endif()
+  if(NOT ADD_GEN_HDR2_YAML_FILE)
+    message(FATAL_ERROR "`add_gen_hdr2` rule requires YAML_FILE to be specified.")
+  endif()
+
+  set(absolute_path ${CMAKE_CURRENT_SOURCE_DIR}/${ADD_GEN_HDR2_GEN_HDR})
+  file(RELATIVE_PATH relative_path ${LIBC_INCLUDE_SOURCE_DIR} ${absolute_path})
+  set(out_file ${LIBC_INCLUDE_DIR}/${relative_path})
+  set(yaml_file ${CMAKE_SOURCE_DIR}/${ADD_GEN_HDR2_YAML_FILE})
+  set(def_file ${CMAKE_CURRENT_SOURCE_DIR}/${ADD_GEN_HDR2_DEF_FILE})
+
+  set(fq_data_files "")
+  if(ADD_GEN_HDR2_DATA_FILES)
+    foreach(data_file IN LISTS ADD_GEN_HDR2_DATA_FILES)
+      list(APPEND fq_data_files "${CMAKE_CURRENT_SOURCE_DIR}/${data_file}")
+    endforeach(data_file)
+  endif()
+
+  set(entry_points "${TARGET_ENTRYPOINT_NAME_LIST}")
+  list(TRANSFORM entry_points PREPEND "--e=")
+
+  add_custom_command(
+    OUTPUT ${out_file}
+    COMMAND ${Python3_EXECUTABLE} ${LIBC_SOURCE_DIR}/newhdrgen/yaml_to_classes.py
+            ${yaml_file}
+            --h_def_file ${def_file}
+            ${entry_points}
+            --output_dir ${out_file}
+    DEPENDS ${yaml_file} ${def_file} ${fq_data_files}
+    COMMENT "Generating header ${ADD_GEN_HDR2_GE2N_HDR} from ${yaml_file} and ${def_file}"
+  )
+  if(LIBC_TARGET_OS_IS_GPU)
+    file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/llvm-libc-decls)
+    file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/llvm-libc-decls/gpu)
+    set(decl_out_file ${LIBC_INCLUDE_DIR}/llvm-libc-decls/${relative_path})
+    add_custom_command(
+      OUTPUT ${decl_out_file}
+      COMMAND ${Python3_EXECUTABLE} ${LIBC_SOURCE_DIR}/newhdrgen/yaml_to_classes.py
+              ${yaml_file}
+              --export-decls
+              ${entry_points}
+              --output_dir ${decl_out_file}
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      DEPENDS ${yaml_file} ${fq_data_files}
+    )
+  endif()
+  
+  if(ADD_GEN_HDR2_DEPENDS)
+    get_fq_deps_list(fq_deps_list ${ADD_GEN_HDR2_DEPENDS})
+    # Dependencies of a add_header target can only be another add_gen_header target
+    # or an add_header target.
+    foreach(dep IN LISTS fq_deps_list)
+      get_target_property(header_file ${dep} HEADER_FILE_PATH)
+      if(NOT header_file)
+        message(FATAL_ERROR "Invalid dependency '${dep}' for '${fq_target_name}'.")
+      endif()
+    endforeach()
+  endif()
+  set(generated_hdr_target ${fq_target_name}.__generated_hdr__)
+  add_custom_target(
+    ${generated_hdr_target}
+    DEPENDS ${out_file} ${fq_deps_list} ${decl_out_file}
+  )
+
+  add_header_library(
+    ${target_name}
+    HDRS
+      ${out_file}
+  )
+
+  add_dependencies(${fq_target_name} ${generated_hdr_target})
+
+  set_target_properties(
+    ${fq_target_name}
+    PROPERTIES
+      HEADER_FILE_PATH ${out_file}
+      DEPS "${fq_deps_list}"
+  )
+
+
+endfunction(add_gen_header2)
+
 # Usage:
 #     add_gen_header(
 #       <target name>