forked from Imagelibrary/binutils-gdb
ccb1ba6229
XXHash is faster than htab_hash_string: ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_xxh3 11 ns 11 ns 65887249 BM_xxh32 19 ns 19 ns 36511877 BM_xxh64 16 ns 16 ns 42964585 BM_hash_string 182 ns 182 ns 3853125 BM_iterative_hash 77 ns 77 ns 9087638 Unfortunately, XXH3 is still experimental (see https://github.com/Cyan4973/xxHash#user-content-new-experimental-hash-algorithm) However, regular XXH64 is still a lot faster than htab_hash_string per my benchmark above. I used the following string for the benchmark: static constexpr char str[] = "_ZZZL13make_gdb_typeP7gdbarchP10tdesc_typeEN16gdb_type_creator19make_gdb_type_flagsEPK22tdesc_type_with_fieldsE19__PRETTY_FUNCTION__"; htab_hash_string is currently 4.35% + 7.98% (rehashing) of gdb startup when attaching to Chrome's content_shell. An additional 5.21% is spent in msymbol_hash, which does not use this hash function. Unfortunately, since it has to lowercase the string, it can't use this hash function. BM_msymbol_hash 52 ns 52 ns 13281495 It may be worth investigating if strlen+XXHash is still faster than htab_hash_string, which would make it easier to use in more places. Debian ships xxhash as libxxhash{0,-dev}. Fedora ships it as xxhash-devel. gdb/ChangeLog: 2019-10-22 Christian Biesinger <cbiesinger@google.com> * Makefile.in: Link with libxxhash. * config.in: Regenerate. * configure: Regenerate. * configure.ac: Search for libxxhash. * utils.c (fast_hash): Use xxhash if present. Change-Id: Icab218388b9f829522ed3977f04301ae6d4fc4ca
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.