[Comgr] Reduce device_libs_id.py invocation command line lenght (llvm#2486)

Author: jmmartinez

amd/comgr/cmake/DeviceLibs.cmake

@@ -59,7 +59,8 @@ foreach(AMDGCN_LIB_TARGET ${AMD_DEVICE_LIBS_TARGETS})
   add_dependencies(amd_comgr ${AMDGCN_LIB_TARGET}_header)
 
   list(APPEND TARGETS_INCLUDES "#include \"${header}\"")
-  list(APPEND TARGETS_HEADERS "${INC_DIR}/${header}")
+  list(APPEND TARGETS_HEADERS_FILENAME "${header}")
+  list(APPEND TARGETS_HEADERS_REALPATH "${INC_DIR}/${header}")
 endforeach()
 
 list(JOIN TARGETS_INCLUDES "\n" TARGETS_INCLUDES)
@@ -113,8 +114,8 @@ find_package(Python3 REQUIRED Interpreter)
 set(DEVICE_LIBS_ID_SCRIPT "${CMAKE_CURRENT_SOURCE_DIR}/cmake/device-libs-id.py")
 set(DEVICE_LIBS_ID_HEADER ${INC_DIR}/libraries_sha.inc)
 add_custom_command(OUTPUT ${DEVICE_LIBS_ID_HEADER}
-  COMMAND ${Python3_EXECUTABLE} ${DEVICE_LIBS_ID_SCRIPT} --varname DEVICE_LIBS_ID --output ${DEVICE_LIBS_ID_HEADER} ${TARGETS_HEADERS}
-  DEPENDS ${DEVICE_LIBS_ID_SCRIPT} ${TARGETS_HEADERS}
+    COMMAND ${Python3_EXECUTABLE} ${DEVICE_LIBS_ID_SCRIPT} --varname DEVICE_LIBS_ID --output ${DEVICE_LIBS_ID_HEADER} --parent-directory ${INC_DIR} ${TARGETS_HEADERS_FILENAME}
+    DEPENDS ${DEVICE_LIBS_ID_SCRIPT} ${TARGETS_HEADERS_REALPATH}
     COMMENT "Generating ${INC_DIR}/libraries_sha.inc"
 )
 set_property(DIRECTORY APPEND PROPERTY ADDITIONAL_MAKE_CLEAN_FILES ${INC_DIR}/libraries_sha.inc)

amd/comgr/cmake/device-libs-id.py

@@ -4,20 +4,23 @@
 
 from argparse import ArgumentParser
 from hashlib import sha256
-from functools import reduce
+from os.path import join as join_path
 
 if __name__ == "__main__":
     parser = ArgumentParser(description='Generate id by computing a hash of the generated headers')
     parser.add_argument("headers", nargs='+', help='List of headers to generate id from')
+    # On Windows, we cannot list the realpath for every individual header since we hit cmd.exe's
+    # maximum command line lenght. As a workaround, we pass the pwd and the headers separately.
+    parser.add_argument("--parent-directory", help='Parent directory for the headers', required=True)
     parser.add_argument("--varname", help='Name of the variable to generate', required=True)
     parser.add_argument("--output", help='Name of the header to generate', required=True)
 
     args = parser.parse_args()
     args.headers.sort()
 
     hash = sha256()
-    for x in args.headers:
-        hash.update(open(x, 'rb').read())
+    for header in args.headers:
+        hash.update(open(join_path(args.parent_directory, header), 'rb').read())
     digest_uchar = hash.digest()
     digest_elts = ", ".join(map(str, digest_uchar))
     print(f"static const unsigned char {args.varname}[] = {{{digest_elts}, 0}};", file=open(args.output, 'w'))