fixdep: avoid parsing the same file over again
The dep files (*.d files) emitted by C compilers usually contain the
deduplicated list of included files.
One exceptional case is when a header is included by the -include
command line option, and also by #include directive.
For example, the top Makefile adds the command line option,
"-include $(srctree)/include/linux/kconfig.h". You do not need to
include <linux/kconfig.h> in every source file.
In fact, include/linux/kconfig.h is listed twice in many .*.cmd files
due to include/linux/xarray.h having "#include <linux/kconfig.h>".
I did not fix that since it is a small redundancy.
However, this is more annoying for rustc. rustc emits the dependency
for each emission type.
For example, cmd_rustc_library emits dep-info, obj, and metadata.
So, the emitted *.d file contains the dependency for those 3 targets,
which makes fixdep parse the same file 3 times.
$ grep rust/alloc/raw_vec.rs rust/.alloc.o.cmd
rust/alloc/raw_vec.rs \
rust/alloc/raw_vec.rs \
rust/alloc/raw_vec.rs \
To skip the second parsing, this commit adds a hash table for parsed
files, just like we did for CONFIG options.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>