threads / patch / 18419

patchMicrooptimize strbuf_cmp

Subject: [PATCH] Microoptimize strbuf_cmp

## tl;dr

3 messages between Mar 19, 2009 and Mar 19, 2009. Diffs are folded; open one to read it.

replies: 2people: 2as markdown or json

Alex Riesen· Mar 19, 2009, 21:09 UTC · lore

Make it inline and cleanup a bit. It is definitely less code including object code, but it is not always measurably faster (but mostly is).

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
---

I have this patch for a long time in my tree and vaguely remember sending it once.

 strbuf.c |   12 ------------
 strbuf.h |    9 ++++++++-
 2 files changed, 8 insertions(+), 13 deletions(-)

Show changes to 2 files +8 −13

strbuf.c, strbuf.h

diff --git a/strbuf.c b/strbuf.c
index 6ed0684..e1f4db7 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -137,18 +137,6 @@ void strbuf_list_free(struct strbuf **sbs)
 	free(sbs);
 }
 
-int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
-{
-	int cmp;
-	if (a->len < b->len) {
-		cmp = memcmp(a->buf, b->buf, a->len);
-		return cmp ? cmp : -1;
-	} else {
-		cmp = memcmp(a->buf, b->buf, b->len);
-		return cmp ? cmp : a->len != b->len;
-	}
-}
-
 void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,
 				   const void *data, size_t dlen)
 {
diff --git a/strbuf.h b/strbuf.h
index 89bd36e..df95960 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -80,11 +80,18 @@ static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
 extern void strbuf_trim(struct strbuf *);
 extern void strbuf_rtrim(struct strbuf *);
 extern void strbuf_ltrim(struct strbuf *);
-extern int strbuf_cmp(const struct strbuf *, const struct strbuf *);
 extern void strbuf_tolower(struct strbuf *);
 
 extern struct strbuf **strbuf_split(const struct strbuf *, int delim);
 extern void strbuf_list_free(struct strbuf **);
+static inline int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
+{
+	int len = a->len < b->len ? a->len: b->len;
+	int cmp = memcmp(a->buf, b->buf, len);
+	if (cmp)
+		return cmp;
+	return a->len < b->len ? -1: a->len != b->len;
+}
 
 /*----- add data in your buffer -----*/
 static inline void strbuf_addch(struct strbuf *sb, int c) {

-- 
1.6.2.1.250.ga1458

Junio C Hamano· Mar 19, 2009, 22:01 UTC · re: Alex Riesen · lore

Re: [PATCH] Microoptimize strbuf_cmp

Alex Riesen <raa.lkml@gmail.com> writes:

> Make it inline and cleanup a bit. It is definitely less code
> including object code, but it is not always measurably faster
> (but mostly is).

The only in-tree user seems to be rerere, so inlining for that single caller will reduce the object side, but I am not sure if this is a good change in the longer term if we want to encourage the use of strbuf library.

The rewrite of the logic does seem worth doing, though.

Alex Riesen· Mar 19, 2009, 22:27 UTC · re: Junio C Hamano · lore

Re: [PATCH] Microoptimize strbuf_cmp

It can be less object code and may be even faster, even if at the moment there is no callers to take an advantage of that. This implementation can be trivially made inlinable later.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
---

Junio C Hamano, Thu, Mar 19, 2009 23:01:40 +0100:

Show 12 quoted lines

> Alex Riesen <raa.lkml@gmail.com> writes:
> 
> > Make it inline and cleanup a bit. It is definitely less code
> > including object code, but it is not always measurably faster
> > (but mostly is).
> 
> The only in-tree user seems to be rerere, so inlining for that single
> caller will reduce the object side, but I am not sure if this is a good
> change in the longer term if we want to encourage the use of strbuf
> library.
> 
> The rewrite of the logic does seem worth doing, though.

But then it is only a half of the micro-optimization. In this case, the cost of call to the function's code is comparable with the change of the code.

Anyway, FWIW.

 strbuf.c |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)

Show changes to strbuf.c +5 −8

diff --git a/strbuf.c b/strbuf.c
index 6ed0684..bfbd816 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -139,14 +139,11 @@ void strbuf_list_free(struct strbuf **sbs)
 
 int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
 {
-	int cmp;
-	if (a->len < b->len) {
-		cmp = memcmp(a->buf, b->buf, a->len);
-		return cmp ? cmp : -1;
-	} else {
-		cmp = memcmp(a->buf, b->buf, b->len);
-		return cmp ? cmp : a->len != b->len;
-	}
+	int len = a->len < b->len ? a->len: b->len;
+	int cmp = memcmp(a->buf, b->buf, len);
+	if (cmp)
+		return cmp;
+	return a->len < b->len ? -1: a->len != b->len;
 }
 
 void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,

-- 
1.6.2.1.237.g7206c6