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Subject[PATCH v2 6/7] 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/ rust/.alloc.o.cmd
rust/alloc/ \
rust/alloc/ \
rust/alloc/ \

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 <>
Acked-by: Miguel Ojeda <>
Tested-by: Miguel Ojeda <>
Reviewed-by: Vincenzo Palazzo <>

(no changes since v1)

scripts/basic/fixdep.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 74f90a0deeb9..e22e689de61e 100644
--- 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;
 \ /
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