This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug libc/4937] New: RFE: micro-efficiency in symbol lookup for GNU_HASH chains
- From: "jreiser at BitWagon dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 19 Aug 2007 14:49:17 -0000
- Subject: [Bug libc/4937] New: RFE: micro-efficiency in symbol lookup for GNU_HASH chains
- Reply-to: sourceware-bugzilla at sourceware dot org
In glibc-2.6.1/elf/do-lookup.h the test on line 193
if ((*hasharr & ~1u) == (new_hash & ~1u))
can be evaluated in one fewer temporary register as
if (0==((*hasharr ^ new_hash) >> 1))
That also saves 1 cycle on a CPU with two-address instructions and only one
execution unit.
Re-writing the same test as
if (*hasharr == (new_hash | (1u & *hasharr)))
enables the low-order bit of hashes to affect comparisons when the current
member is not the last in the hash chain. This may increase search speed when a
chain has more than one member.
--
Summary: RFE: micro-efficiency in symbol lookup for GNU_HASH
chains
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: libc
AssignedTo: drepper at redhat dot com
ReportedBy: jreiser at BitWagon dot com
CC: glibc-bugs at sources dot redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=4937
------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.