# ===========================================================================
# http://www.gnu.org/software/autoconf-archive/ax_cc_maxopt.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_CC_MAXOPT
#
# DESCRIPTION
#
# Try to turn on "good" C optimization flags for various compilers and
# architectures, for some definition of "good". (In our case, good for
# FFTW and hopefully for other scientific codes. Modify as needed.)
#
# The user can override the flags by setting the CFLAGS environment
# variable. The user can also specify --enable-portable-binary in order to
# disable any optimization flags that might result in a binary that only
# runs on the host architecture.
#
# Note also that the flags assume that ANSI C aliasing rules are followed
# by the code (e.g. for gcc's -fstrict-aliasing), and that floating-point
# computations can be re-ordered as needed.
#
# Requires macros: AX_CHECK_COMPILE_FLAG, AX_COMPILER_VENDOR,
# AX_GCC_ARCHFLAG, AX_GCC_X86_CPUID.
#
# LICENSE
#
# Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
# Copyright (c) 2008 Matteo Frigo
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation, either version 3 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <http://www.gnu.org/licenses/>.
#
# As a special exception, the respective Autoconf Macro's copyright owner
# gives unlimited permission to copy, distribute and modify the configure
# scripts that are the output of Autoconf when processing the Macro. You
# need not follow the terms of the GNU General Public License when using
# or distributing such scripts, even though portions of the text of the
# Macro appear in them. The GNU General Public License (GPL) does govern
# all other use of the material that constitutes the Autoconf Macro.
#
# This special exception to the GPL applies to versions of the Autoconf
# Macro released by the Autoconf Archive. When you make and distribute a
# modified version of the Autoconf Macro, you may extend this special
# exception to the GPL to apply to your modified version as well.
#serial 13
AC_DEFUN([AX_CC_MAXOPT],
[
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AX_COMPILER_VENDOR])
AC_REQUIRE([AC_CANONICAL_HOST])
AC_ARG_ENABLE(portable-binary, [AS_HELP_STRING([--enable-portable-binary], [disable compiler optimizations that would produce unportable binaries])],
acx_maxopt_portable=$enableval, acx_maxopt_portable=no)
# Try to determine "good" native compiler flags if none specified via CFLAGS
if test "$ac_test_CFLAGS" != "set"; then
CFLAGS=""
case $ax_cv_c_compiler_vendor in
dec) CFLAGS="-newc -w0 -O5 -ansi_alias -ansi_args -fp_reorder -tune host"
if test "x$acx_maxopt_portable" = xno; then
CFLAGS="$CFLAGS -arch host"
fi;;
sun) CFLAGS="-native -fast -xO5 -dalign"
if test "x$acx_maxopt_portable" = xyes; then
CFLAGS="$CFLAGS -xarch=generic"
fi;;
hp) CFLAGS="+Oall +Optrs_ansi +DSnative"
if test "x$acx_maxopt_portable" = xyes; then
CFLAGS="$CFLAGS +DAportable"
fi;;
ibm) if test "x$acx_maxopt_portable" = xno; then
xlc_opt="-qarch=auto -qtune=auto"
else
xlc_opt="-qtune=auto"
fi
AX_CHECK_COMPILE_FLAG($xlc_opt,
CFLAGS="-O3 -qansialias -w $xlc_opt",
[CFLAGS="-O3 -qansialias -w"
echo "******************************************************"
echo "* You seem to have the IBM C compiler. It is *"
echo "* recommended for best performance that you use: *"
echo "* *"
echo "* CFLAGS=-O3 -qarch=xxx -qtune=xxx -qansialias -w *"
echo "* ^^^ ^^^ *"
echo "* where xxx is pwr2, pwr3, 604, or whatever kind of *"
echo "* CPU you have. (Set the CFLAGS environment var. *"
echo "* and re-run configure.) For more info, man cc. *"
echo "******************************************************"])
;;
intel) CFLAGS="-O3 -ansi_alias"
if test "x$acx_maxopt_portable" = xno; then
icc_archflag=unknown
icc_flags=""
case $host_cpu in
i686*|x86_64*)
# icc accepts gcc assembly syntax, so these should work:
AX_GCC_X86_CPUID(0)
AX_GCC_X86_CPUID(1)
case $ax_cv_gcc_x86_cpuid_0 in # see AX_GCC_ARCHFLAG
*:756e6547:*:*) # Intel
case $ax_cv_gcc_x86_cpuid_1 in
*6a?:*[[234]]:*:*|*6[[789b]]?:*:*:*) icc_flags="-xK";;
*f3[[347]]:*:*:*|*f4[1347]:*:*:*) icc_flags="-xP -xN -xW -xK";;
*f??:*:*:*) icc_flags="-xN -xW -xK";;
esac ;;
esac ;;
esac
if test "x$icc_flags" != x; then
for flag in $icc_flags; do
AX_CHECK_COMPILE_FLAG($flag, [icc_archflag=$flag; break])
done
fi
AC_MSG_CHECKING([for icc architecture flag])
AC_MSG_RESULT($icc_archflag)
if test "x$icc_archflag" != xunknown; then
CFLAGS="$CFLAGS $icc_archflag"
fi
fi
;;
gnu)
# default optimization flags for gcc on all systems
CFLAGS="-O3 -fomit-frame-pointer"
# -malign-double for x86 systems
# LIBFFI -- DON'T DO THIS - CHANGES ABI
# AX_CHECK_COMPILE_FLAG(-malign-double, CFLAGS="$CFLAGS -malign-double")
# -fstrict-aliasing for gcc-2.95+
AX_CHECK_COMPILE_FLAG(-fstrict-aliasing,
CFLAGS="$CFLAGS -fstrict-aliasing")
# note that we enable "unsafe" fp optimization with other compilers, too
AX_CHECK_COMPILE_FLAG(-ffast-math, CFLAGS="$CFLAGS -ffast-math")
AX_GCC_ARCHFLAG($acx_maxopt_portable)
;;
esac
if test -z "$CFLAGS"; then
echo ""
echo "********************************************************"
echo "* WARNING: Don't know the best CFLAGS for this system *"
echo "* Use ./configure CFLAGS=... to specify your own flags *"
echo "* (otherwise, a default of CFLAGS=-O3 will be used) *"
echo "********************************************************"
echo ""
CFLAGS="-O3"
fi
AX_CHECK_COMPILE_FLAG($CFLAGS, [], [
echo ""
echo "********************************************************"
echo "* WARNING: The guessed CFLAGS don't seem to work with *"
echo "* your compiler. *"
echo "* Use ./configure CFLAGS=... to specify your own flags *"
echo "********************************************************"
echo ""
CFLAGS=""
])
fi
])