From 52ad36a21973c0b4fbc16b7104bbffec765e5a23 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Sun, 4 Dec 2011 17:44:33 -0500 Subject: [PATCH] Small optimization of generic ELF hash function --- ChangeLog | 1 + sysdeps/generic/dl-hash.h | 47 ++++++++++++++++++++++------------------------- 2 files changed, 23 insertions(+), 25 deletions(-) diff --git a/ChangeLog b/ChangeLog index 0dfff5c..f4b3460 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,6 +1,7 @@ 2011-12-04 Ulrich Drepper * 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 e35bd25..28312ca 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; } } } -- 2.7.4