13.12.2010, 18:53, Francesco R viv...@gmail.com:
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 - 21 | grep
march
# echo int main() { return 0; } | gcc -march=core2 -v -Q -x c - 21
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
Note that for some architectures (e.g, PowerPC) you need to add -mcpu case
(-mcpu has the same meaning as -march on x86)
--
Regards,
Konstantin
