From: Dan McGee <dpmcgee@gmail.com>
To: git@vger.kernel.org
Cc: Dan McGee <dpmcgee@gmail.com>
Subject: [PATCH 4/5] tree-walk: unroll get_mode since loop boundaries are well-known
Date: Wed, 30 Mar 2011 20:38:00 -0500 [thread overview]
Message-ID: <1301535481-1085-4-git-send-email-dpmcgee@gmail.com> (raw)
In-Reply-To: <1301535481-1085-1-git-send-email-dpmcgee@gmail.com>
We know our mode entry in our tree objects should be 5 or 6 characters
long. This change both enforces this fact and also unrolls the parsing
of the information giving the compiler more room for optimization of the
operations.
Signed-off-by: Dan McGee <dpmcgee@gmail.com>
---
tree-walk.c | 41 ++++++++++++++++++++++++++++++++++-------
1 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/tree-walk.c b/tree-walk.c
index f386151..41383b0 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -9,16 +9,43 @@ static const char *get_mode(const char *str, unsigned int *modep)
unsigned char c;
unsigned int mode = 0;
- if (*str == ' ')
- return NULL;
-
- while ((c = *str++) != ' ') {
- if (c < '0' || c > '7')
- return NULL;
+ /*
+ * Unroll what looks like a loop since the bounds are
+ * well-known. There should be at least 5 and at most 6
+ * characters available in any valid mode, as '40000' is the
+ * shortest while '160000' (S_IFGITLINK) is the longest.
+ */
+ /* char 1 */
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
+ mode = (mode << 3) + (c - '0');
+ /* char 2 */
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
+ mode = (mode << 3) + (c - '0');
+ /* char 3 */
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
+ mode = (mode << 3) + (c - '0');
+ /* char 4 */
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
+ mode = (mode << 3) + (c - '0');
+ /* char 5 */
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
+ mode = (mode << 3) + (c - '0');
+ /* char 6, optional */
+ if (*str != ' ') {
+ c = *str++;
+ if (c < '0' || c > '7') return NULL;
mode = (mode << 3) + (c - '0');
}
+
+ if (*str != ' ') return NULL;
+
*modep = mode;
- return str;
+ return str + 1;
}
static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size)
--
1.7.4.2
next prev parent reply other threads:[~2011-03-31 1:38 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-31 1:37 [PATCH 1/5] diff_tree_sha1: skip diff_tree if old == new Dan McGee
2011-03-31 1:37 ` [PATCH 2/5] tree-walk: drop unused parameter from match_dir_prefix Dan McGee
2011-08-30 18:55 ` Dan McGee
2011-03-31 1:37 ` [PATCH 3/5] tree-walk: micro-optimization in tree_entry_interesting Dan McGee
2011-04-03 4:01 ` Nguyen Thai Ngoc Duy
2011-04-03 18:55 ` Junio C Hamano
2011-04-05 0:22 ` Dan McGee
[not found] ` <CAEik5nOKrpFycZYVnSu4_5LYWxn0JS_hVXyiQH-80Bu-C4k8VQ@mail.gmail.com>
2011-08-30 19:51 ` Dan McGee
2011-08-30 20:40 ` Junio C Hamano
2011-09-09 2:02 ` [PATCH 1/2] tree-walk: drop unused parameter from match_dir_prefix Dan McGee
2011-09-09 2:02 ` [PATCH 2/2] tree-walk: micro-optimization in tree_entry_interesting Dan McGee
2011-04-04 14:46 ` [PATCH] tree_entry_interesting: inline strncmp() Nguyễn Thái Ngọc Duy
2011-03-31 1:38 ` Dan McGee [this message]
2011-04-02 9:28 ` [PATCH 4/5] tree-walk: unroll get_mode since loop boundaries are well-known Nguyen Thai Ngoc Duy
2011-04-02 17:28 ` Dan McGee
2011-04-03 4:07 ` Nguyen Thai Ngoc Duy
2011-04-04 10:29 ` Erik Faye-Lund
2011-04-04 12:30 ` Andreas Ericsson
2011-04-04 16:55 ` Junio C Hamano
2011-04-05 5:33 ` Dan McGee
2011-04-05 23:55 ` Antriksh Pany
2011-04-06 20:45 ` Dan McGee
2011-03-31 1:38 ` [PATCH 5/5] tree-walk: match_entry microoptimization Dan McGee
2011-04-02 9:06 ` Nguyen Thai Ngoc Duy
2011-04-02 17:54 ` Dan McGee
2011-03-31 12:58 ` [PATCH 1/5] diff_tree_sha1: skip diff_tree if old == new Nguyen Thai Ngoc Duy
2011-03-31 13:56 ` Dan McGee
2011-04-01 22:28 ` Junio C Hamano
[not found] ` <AANLkTinPSqDPdGi5nA3sH1D2wMSW1SQc+5gRqdLy++y0@mail.gmail.com>
2011-04-02 18:38 ` Fwd: " Dan McGee
2011-05-03 7:34 ` Nguyen Thai Ngoc Duy
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