[PATCH 1/2] xdiff: refactor xdl_hash_record()
From: Alexander Monakov <hidden>
Date: 2025-07-28 19:12:33
Subsystem:
the rest · Maintainer:
Linus Torvalds
From: Phillip Wood <redacted>
Inline the check for whitespace flags so that the compiler can hoist
it out of the loop in xdl_prepare_ctx(). This improves the performance
by 8%.
$ hyperfine --warmup=1 -L rev HEAD,HEAD^ --setup='git checkout {rev} -- :/ && make git' ': {rev}; GIT_CONFIG_GLOBAL=/dev/null ./git log --oneline --shortstat v2.0.0..v2.5.0'
Benchmark 1: : HEAD; GIT_CONFIG_GLOBAL=/dev/null ./git log --oneline --shortstat v2.0.0..v2.5.0
Time (mean ± σ): 1.670 s ± 0.044 s [User: 1.473 s, System: 0.196 s]
Range (min … max): 1.619 s … 1.754 s 10 runs
Benchmark 2: : HEAD^; GIT_CONFIG_GLOBAL=/dev/null ./git log --oneline --shortstat v2.0.0..v2.5.0
Time (mean ± σ): 1.801 s ± 0.021 s [User: 1.605 s, System: 0.192 s]
Range (min … max): 1.766 s … 1.831 s 10 runs
Summary
': HEAD^; GIT_CONFIG_GLOBAL=/dev/null ./git log --oneline --shortstat v2.0.0..v2.5.0' ran
1.08 ± 0.03 times faster than ': HEAD^^; GIT_CONFIG_GLOBAL=/dev/null ./git log --oneline --shortstat v2.0.0..v2.5.0'
Signed-off-by: Phillip Wood <redacted>
---
xdiff/xutils.c | 7 ++-----
xdiff/xutils.h | 10 +++++++++-
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 444a108f87..e070ed649f 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c@@ -249,7 +249,7 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags) return 1; } -static unsigned long xdl_hash_record_with_whitespace(char const **data, +unsigned long xdl_hash_record_with_whitespace(char const **data, char const *top, long flags) { unsigned long ha = 5381; char const *ptr = *data;
@@ -294,13 +294,10 @@ static unsigned long xdl_hash_record_with_whitespace(char const **data, return ha; } -unsigned long xdl_hash_record(char const **data, char const *top, long flags) { +unsigned long xdl_hash_record_verbatim(char const **data, char const *top) { unsigned long ha = 5381; char const *ptr = *data; - if (flags & XDF_WHITESPACE_FLAGS) - return xdl_hash_record_with_whitespace(data, top, flags); - for (; ptr < top && *ptr != '\n'; ptr++) { ha += (ha << 5); ha ^= (unsigned long) *ptr;
diff --git a/xdiff/xutils.h b/xdiff/xutils.h
index fd0bba94e8..13f6831047 100644
--- a/xdiff/xutils.h
+++ b/xdiff/xutils.h@@ -34,7 +34,15 @@ void *xdl_cha_alloc(chastore_t *cha); long xdl_guess_lines(mmfile_t *mf, long sample); int xdl_blankline(const char *line, long size, long flags); int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags); -unsigned long xdl_hash_record(char const **data, char const *top, long flags); +unsigned long xdl_hash_record_verbatim(char const **data, char const *top); +unsigned long xdl_hash_record_with_whitespace(char const **data, char const *top, long flags); +static inline unsigned long xdl_hash_record(char const **data, char const *top, long flags) +{ + if (flags & XDF_WHITESPACE_FLAGS) + return xdl_hash_record_with_whitespace(data, top, flags); + else + return xdl_hash_record_verbatim(data, top); +} unsigned int xdl_hashbits(unsigned int size); int xdl_num_out(char *out, long val); int xdl_emit_hunk_hdr(long s1, long c1, long s2, long c2,
--
2.44.2