Re: [PATCH] git gc: Speed it up by 18% via faster hash comparisons
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:51:07
Ingo Molnar [off-list ref] writes:
In any case, i'll retract the null case as it really isnt called that often in the tests i've done - updated patch below - it simply falls back on to hashcmp. Thanks, Ingo Signed-off-by: Ingo Molnar <redacted>
Thanks, will queue this version.
quoted hunk
diff --git a/cache.h b/cache.h index 2674f4c..39fa9cd 100644 --- a/cache.h +++ b/cache.h@@ -675,14 +675,24 @@ extern char *sha1_pack_name(const unsigned char *sha1); extern char *sha1_pack_index_name(const unsigned char *sha1); extern const char *find_unique_abbrev(const unsigned char *sha1, int); extern const unsigned char null_sha1[20]; -static inline int is_null_sha1(const unsigned char *sha1) + +static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2) { - return !memcmp(sha1, null_sha1, 20); + int i; + + for (i = 0; i < 20; i++, sha1++, sha2++) { + if (*sha1 != *sha2) + return *sha1 - *sha2; + } + + return 0; } -static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2) + +static inline int is_null_sha1(const unsigned char *sha1) { - return memcmp(sha1, sha2, 20); + return !hashcmp(sha1, null_sha1); } + static inline void hashcpy(unsigned char *sha_dst, const unsigned char *sha_src) { memcpy(sha_dst, sha_src, 20);