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authorUlrich Drepper <drepper@gmail.com>2011-12-04 17:44:33 -0500
committerUlrich Drepper <drepper@gmail.com>2011-12-04 17:44:33 -0500
commit52ad36a21973c0b4fbc16b7104bbffec765e5a23 (patch)
tree8d71d471da30fa6b86311eef449d5b4ed521ac16
parent52ff5dd0e4ad6436def42b58bc8abe5b534cf739 (diff)
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Small optimization of generic ELF hash function
-rw-r--r--ChangeLog1
-rw-r--r--sysdeps/generic/dl-hash.h47
2 files changed, 23 insertions, 25 deletions
diff --git a/ChangeLog b/ChangeLog
index 0dfff5cfb5..f4b3460a83 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,7 @@
2011-12-04 Ulrich Drepper <drepper@gmail.com>
* sysdeps/generic/dl-hash.h (_dl_elf_hash): Fix attribute.
+ Minor optimizations.
* sunrpc/clnt_unix.c (clntunix_control): Fix aliasing issues.
* sunrpc/clnt_tcp.c (clnttcp_control): Likewise.
diff --git a/sysdeps/generic/dl-hash.h b/sysdeps/generic/dl-hash.h
index e35bd25a33..28312ca1c4 100644
--- a/sysdeps/generic/dl-hash.h
+++ b/sysdeps/generic/dl-hash.h
@@ -29,42 +29,39 @@ __attribute__ ((unused))
_dl_elf_hash (const char *name_arg)
{
const unsigned char *name = (const unsigned char *) name_arg;
- unsigned long int hash = 0;
- if (*name != '\0')
+ unsigned long int hash = *name;
+ if (hash != 0 && name[1] != '\0')
{
- hash = *name++;
- if (*name != '\0')
+ hash = (hash << 4) + name[1];
+ if (name[2] != '\0')
{
- hash = (hash << 4) + *name++;
- if (*name != '\0')
+ hash = (hash << 4) + name[2];
+ if (name[3] != '\0')
{
- hash = (hash << 4) + *name++;
- if (*name != '\0')
+ hash = (hash << 4) + name[3];
+ if (name[4] != '\0')
{
- hash = (hash << 4) + *name++;
- if (*name != '\0')
+ hash = (hash << 4) + name[4];
+ name += 5;
+ while (*name != '\0')
{
+ unsigned long int hi;
hash = (hash << 4) + *name++;
- while (*name != '\0')
- {
- unsigned long int hi;
- hash = (hash << 4) + *name++;
- hi = hash & 0xf0000000;
+ hi = hash & 0xf0000000;
- /* The algorithm specified in the ELF ABI is as
- follows:
+ /* The algorithm specified in the ELF ABI is as
+ follows:
- if (hi != 0)
- hash ^= hi >> 24;
+ if (hi != 0)
+ hash ^= hi >> 24;
- hash &= ~hi;
+ hash &= ~hi;
- But the following is equivalent and a lot
- faster, especially on modern processors. */
+ But the following is equivalent and a lot
+ faster, especially on modern processors. */
- hash ^= hi;
- hash ^= hi >> 24;
- }
+ hash ^= hi;
+ hash ^= hi >> 24;
}
}
}