[PATCH v3 01/10] gen_compile_commands: parse only the first line of .*.cmd files

Masahiro Yamada
2020-08-22T14:57:58Z

After the allmodconfig build, this script takes about 5 sec on my
machine. Most of the run-time is consumed for needless regex matching.

We know the format of .*.cmd file; the first line is the build command.
There is no need to parse the rest.

With this optimization, now it runs 4 times faster.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
---

(no changes since v2)

Changes in v2:
- Remove the unneeded variable 'line'

scripts/gen_compile_commands.py | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/scripts/gen_compile_commands.py b/scripts/gen_compile_commands.py
index c458696ef3a7..1bcf33a93cb9 100755
--- a/scripts/gen_compile_commands.py
+++ b/scripts/gen_compile_commands.py
@@ -125,11 +125,8 @@ def main():
filepath = os.path.join(dirpath, filename)

with open(filepath, 'rt') as f:
- for line in f:
- result = line_matcher.match(line)
- if not result:
- continue
-
+ result = line_matcher.match(f.readline())
+ if result:
try:
entry = process_line(directory, dirpath,
result.group(1), result.group(2))
--
2.25.1