tree-walk: finally switch over tree descriptors to contain a pre-parsed entry

This continues 4651ece8 (Switch over tree descriptors to contain a
pre-parsed entry) and moves the only rest computational part

mode = canon_mode(mode)

from tree_entry_extract() to tree entry decode phase - to
decode_tree_entry().

The reason to do it, is that canon_mode() is at least 2 conditional
jumps for regular files, and that could be noticeable should canon_mode()
be invoked several times.

That does not matter for current Git codebase, where typical tree
traversal is

while (t->size) {
sha1 = tree_entry_extract(t, &path, &mode);
...
update_tree_entry(t);
}

i.e. we do t -> sha1,path.mode "extraction" only once per entry. In such
cases, it does not matter performance-wise, where that mode
canonicalization is done - either once in tree_entry_extract(), or once
in decode_tree_entry() called by update_tree_entry() - it is
approximately the same.

But for future code, which could need to work with several tree_desc's
in parallel, it could be handy to operate on tree_desc descriptors, and
do "extracts" only when needed, or at all, access only relevant part of
it through structure fields directly.

And for such situations, having canon_mode() be done once in decode
phase is better - we won't need to pay the performance price of 2 extra
conditional jumps on every t->mode access.

So let's move mode canonicalization to decode_tree_entry(). That was the
final bit. Now after tree entry is decoded, it is fully ready and could
be accessed either directly via field, or through tree_entry_extract()
which this time got really "totally trivial".

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/tree-walk.c b/tree-walk.c
index 79dba1d0f4e729b5e62825d347c7e6a9b1455f1d..4dc86c7fe5f66b858b6bd7834a76b1dbbb63a339 100644 (file)
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -37,7 +37,7 @@ static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned
 
        /* Initialize the descriptor entry */
        desc->entry.path = path;
-       desc->entry.mode = mode;
+       desc->entry.mode = canon_mode(mode);
        desc->entry.sha1 = (const unsigned char *)(path + len);
 }
 

diff --git a/tree-walk.h b/tree-walk.h
index ae04b6417de0ff06391cc7e2d98fcd1b7d5aa633..ae7fb3a824a960c6c03efae799683cd7e18d402c 100644 (file)
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -16,7 +16,7 @@ struct tree_desc {
 static inline const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
 {
        *pathp = desc->entry.path;
-       *modep = canon_mode(desc->entry.mode);
+       *modep = desc->entry.mode;
        return desc->entry.sha1;
 }