2010/12/13 Ryan Hill <dirtye...@gentoo.org> > On Sun, 12 Dec 2010 09:01:13 -0400 > "Sergio D. Rodríguez Inclan" <srinc...@gmail.com> wrote: > > > El 12/12/2010 02:46 a.m., Ryan Hill escribió: > > > I think the fewer sources of magic USE flags the better. Maybe we > could > > > document how to figure out what instruction sets a processor supports > in the > > > handbook instead. > > > A good manual would be greatly appreciated :) > > I wrote a guide a couple weeks ago that might be a good starting point. > > http://en.gentoo-wiki.com/wiki/Hardware_CFLAGS > > if I read correctly the article on the wiki it does circa what the script reported below does. would be possible to adopt something similar for automatic C*FLAGS selection if someone step in willing to take the pain to mantain it.
#!/usr/bin/python # Copyright 2010 Gentoo Foundation # Distributed under the terms of the GNU General Public License v2 # Author: Francesco Riosa # extrapolated from http://en.gentoo-wiki.com/wiki/Hardware_CFLAGS, errors are mine # kate: encoding utf-8; eol unix # kate: indent-width 4; mixedindent off; replace-tabs on; # kate: remove-trailing-space on; space-indent on # echo "int main() { return 0; }" | gcc -march=native -v -E - 2>&1 | grep march # echo "int main() { return 0; }" | gcc -march=core2 -v -Q -x c - 2>&1 """ example output: ./hw-cflags.py extrapolating flags for gcc-4.4.5 useful flags: -march=core2 -msse4.1 --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=2048 -mtune=generic redundant: -mcx16 -msahf extrapolating flags for gcc-4.5.1 useful flags: -march=core2 -msse4.1 --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=2048 -mtune=core2 redundant: -mcx16 -msahf """ import os import time import fnmatch from subprocess import Popen, PIPE GCC_PATH = '/usr/bin/' GCC_LIST = fnmatch.filter(os.listdir(GCC_PATH), 'gcc-[0-9].*') GCC_LIST.sort() def extract_flags(gcccmd, header): # get output from gcc buf = '' devnul = open('/dev/null', 'w') p = Popen(gcccmd, stdin=PIPE, stdout=devnul, stderr=PIPE) p.stdin.write("""int main() { return 0; }""") p.stdin.close() while p.poll() is None: t = p.stderr.read() buf = "buf%s" % t time.sleep(0.01) p.stderr.close() devnul.close() # parse it flags = [] add = False for line in buf.split('\n'): if line.startswith(header): add = True flags += line.strip().split(' ') continue if add: if line.startswith(' '): flags += line.strip().split(' ') else: break # extract flags we are interested in t = [] march = '' mtune = '-mtune=generic' for i in xrange(len(flags)): if flags[i].startswith('-m'): if flags[i].startswith('-mtune'): mtune = flags[i] elif flags[i].startswith('-march'): march = flags[i] else: t.append(flags[i]) elif flags[i] == '--param': t.append("%s %s" % (flags[i], flags[i+1])) flags = t return march, mtune, flags for gcc in GCC_LIST: print "extrapolating flags for %s" % gcc gcccmd = [ GCC_PATH + gcc, '-march=native', '-v', '-E', '-', ] header='COLLECT_GCC_OPTIONS' march, mtune, flags_native = extract_flags(gcccmd, header) gcccmd = [ GCC_PATH + gcc, march, '-v', '-Q', '-x', 'c', '-', ] header='options enabled:' t, t, flags_enabled = extract_flags(gcccmd, header) redundant_flags = [] useful_flags = [] for x in flags_native: if x in flags_enabled: redundant_flags.append(x) else: useful_flags.append(x) if gcc < "gcc-4.5.0": mtune = '-mtune=generic' print " useful flags: %s %s %s " % (march, " ".join(useful_flags), mtune) print " redundant: %s" % " ".join(redundant_flags) print
