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>

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 74f90a0deeb946f6fbf4ccb0804d3fcbb3efe1cc..e22e689de61e442d76b0c15dcb1b9417c6eba100 100644 (file)
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -113,7 +113,7 @@ struct item {
 };
 
 #define HASHSZ 256
-static struct item *config_hashtab[HASHSZ];
+static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ];
 
 static unsigned int strhash(const char *str, unsigned int sz)
 {
@@ -365,6 +365,10 @@ static void parse_dep_file(char *p, const char *target)
                         * name, which will be the original one, and ignore any
                         * other source names, which will be intermediate
                         * temporary files.
+                        *
+                        * rustc emits the same dependency list for each
+                        * emission type. It is enough to list the source name
+                        * just once.
                         */
                        if (!saw_any_target) {
                                saw_any_target = true;
@@ -372,7 +376,8 @@ static void parse_dep_file(char *p, const char *target)
                                printf("deps_%s := \\\n", target);
                                need_parse = true;
                        }
-               } else if (!is_ignored_file(p, q - p)) {
+               } else if (!is_ignored_file(p, q - p) &&
+                          !in_hashtable(p, q - p, file_hashtab)) {
                        printf("  %s \\\n", p);
                        need_parse = true;
                }