1# ===========================================================================
2#          http://www.nongnu.org/autoconf-archive/ax_cc_maxopt.html
3# ===========================================================================
4#
5# SYNOPSIS
6#
7#   AX_CC_MAXOPT
8#
9# DESCRIPTION
10#
11#   Try to turn on "good" C optimization flags for various compilers and
12#   architectures, for some definition of "good". (In our case, good for
13#   FFTW and hopefully for other scientific codes. Modify as needed.)
14#
15#   The user can override the flags by setting the CFLAGS environment
16#   variable. The user can also specify --enable-portable-binary in order to
17#   disable any optimization flags that might result in a binary that only
18#   runs on the host architecture.
19#
20#   Note also that the flags assume that ANSI C aliasing rules are followed
21#   by the code (e.g. for gcc's -fstrict-aliasing), and that floating-point
22#   computations can be re-ordered as needed.
23#
24#   Requires macros: AX_CHECK_COMPILER_FLAGS, AX_COMPILER_VENDOR,
25#   AX_GCC_ARCHFLAG, AX_GCC_X86_CPUID.
26#
27# LICENSE
28#
29#   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
30#   Copyright (c) 2008 Matteo Frigo
31#
32#   This program is free software: you can redistribute it and/or modify it
33#   under the terms of the GNU General Public License as published by the
34#   Free Software Foundation, either version 3 of the License, or (at your
35#   option) any later version.
36#
37#   This program is distributed in the hope that it will be useful, but
38#   WITHOUT ANY WARRANTY; without even the implied warranty of
39#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
40#   Public License for more details.
41#
42#   You should have received a copy of the GNU General Public License along
43#   with this program. If not, see <http://www.gnu.org/licenses/>.
44#
45#   As a special exception, the respective Autoconf Macro's copyright owner
46#   gives unlimited permission to copy, distribute and modify the configure
47#   scripts that are the output of Autoconf when processing the Macro. You
48#   need not follow the terms of the GNU General Public License when using
49#   or distributing such scripts, even though portions of the text of the
50#   Macro appear in them. The GNU General Public License (GPL) does govern
51#   all other use of the material that constitutes the Autoconf Macro.
52#
53#   This special exception to the GPL applies to versions of the Autoconf
54#   Macro released by the Autoconf Archive. When you make and distribute a
55#   modified version of the Autoconf Macro, you may extend this special
56#   exception to the GPL to apply to your modified version as well.
57
58AC_DEFUN([AX_CC_MAXOPT],
59[
60AC_REQUIRE([AC_PROG_CC])
61AC_REQUIRE([AX_COMPILER_VENDOR])
62AC_REQUIRE([AC_CANONICAL_HOST])
63
64AC_ARG_ENABLE(portable-binary, [AC_HELP_STRING([--enable-portable-binary], [disable compiler optimizations that would produce unportable binaries])],
65	acx_maxopt_portable=$withval, acx_maxopt_portable=no)
66
67# Try to determine "good" native compiler flags if none specified via CFLAGS
68if test "$ac_test_CFLAGS" != "set"; then
69  CFLAGS=""
70  case $ax_cv_c_compiler_vendor in
71    dec) CFLAGS="-newc -w0 -O5 -ansi_alias -ansi_args -fp_reorder -tune host"
72	 if test "x$acx_maxopt_portable" = xno; then
73           CFLAGS="$CFLAGS -arch host"
74         fi;;
75
76    sun) CFLAGS="-native -fast -xO5 -dalign"
77	 if test "x$acx_maxopt_portable" = xyes; then
78	   CFLAGS="$CFLAGS -xarch=generic"
79         fi;;
80
81    hp)  CFLAGS="+Oall +Optrs_ansi +DSnative"
82	 if test "x$acx_maxopt_portable" = xyes; then
83	   CFLAGS="$CFLAGS +DAportable"
84	 fi;;
85
86    ibm) if test "x$acx_maxopt_portable" = xno; then
87           xlc_opt="-qarch=auto -qtune=auto"
88	 else
89           xlc_opt="-qtune=auto"
90	 fi
91         AX_CHECK_COMPILER_FLAGS($xlc_opt,
92         	CFLAGS="-O3 -qansialias -w $xlc_opt",
93               [CFLAGS="-O3 -qansialias -w"
94                echo "******************************************************"
95                echo "*  You seem to have the IBM  C compiler.  It is      *"
96                echo "*  recommended for best performance that you use:    *"
97                echo "*                                                    *"
98                echo "*    CFLAGS=-O3 -qarch=xxx -qtune=xxx -qansialias -w *"
99                echo "*                      ^^^        ^^^                *"
100                echo "*  where xxx is pwr2, pwr3, 604, or whatever kind of *"
101                echo "*  CPU you have.  (Set the CFLAGS environment var.   *"
102                echo "*  and re-run configure.)  For more info, man cc.    *"
103                echo "******************************************************"])
104         ;;
105
106    intel) CFLAGS="-O3 -ansi_alias"
107	if test "x$acx_maxopt_portable" = xno; then
108	  icc_archflag=unknown
109	  icc_flags=""
110	  case $host_cpu in
111	    i686*|x86_64*)
112              # icc accepts gcc assembly syntax, so these should work:
113	      AX_GCC_X86_CPUID(0)
114              AX_GCC_X86_CPUID(1)
115	      case $ax_cv_gcc_x86_cpuid_0 in # see AX_GCC_ARCHFLAG
116                *:756e6547:*:*) # Intel
117                  case $ax_cv_gcc_x86_cpuid_1 in
118                    *6a?:*[[234]]:*:*|*6[[789b]]?:*:*:*) icc_flags="-xK";;
119                    *f3[[347]]:*:*:*|*f4[1347]:*:*:*) icc_flags="-xP -xN -xW -xK";;
120                    *f??:*:*:*) icc_flags="-xN -xW -xK";;
121                  esac ;;
122              esac ;;
123          esac
124          if test "x$icc_flags" != x; then
125            for flag in $icc_flags; do
126              AX_CHECK_COMPILER_FLAGS($flag, [icc_archflag=$flag; break])
127            done
128          fi
129          AC_MSG_CHECKING([for icc architecture flag])
130	  AC_MSG_RESULT($icc_archflag)
131          if test "x$icc_archflag" != xunknown; then
132            CFLAGS="$CFLAGS $icc_archflag"
133          fi
134        fi
135	;;
136
137    gnu)
138     # default optimization flags for gcc on all systems
139     CFLAGS="-O3 -fomit-frame-pointer"
140
141     # -malign-double for x86 systems
142     AX_CHECK_COMPILER_FLAGS(-malign-double, CFLAGS="$CFLAGS -malign-double")
143
144     #  -fstrict-aliasing for gcc-2.95+
145     AX_CHECK_COMPILER_FLAGS(-fstrict-aliasing,
146	CFLAGS="$CFLAGS -fstrict-aliasing")
147
148     # note that we enable "unsafe" fp optimization with other compilers, too
149     AX_CHECK_COMPILER_FLAGS(-ffast-math, CFLAGS="$CFLAGS -ffast-math")
150
151     AX_GCC_ARCHFLAG($acx_maxopt_portable)
152
153     # drop to -O1 for gcc 4.2
154     $CC --version |
155	sed -e 's/.* \(@<:@0-9@:>@@<:@0-9@:>@*\)\.\(@<:@0-9@:>@@<:@0-9@:>@*\).*/\1 \2/' |
156	(read major minor
157	    if test $major -eq 4 -a $minor -eq 2; then
158				exit 0
159	    fi
160	    exit 1
161	) && CFLAGS="-O1"
162     ;;
163  esac
164
165  if test -z "$CFLAGS"; then
166	echo ""
167	echo "********************************************************"
168        echo "* WARNING: Don't know the best CFLAGS for this system  *"
169        echo "* Use ./configure CFLAGS=... to specify your own flags *"
170	echo "* (otherwise, a default of CFLAGS=-O3 will be used)    *"
171	echo "********************************************************"
172	echo ""
173        CFLAGS="-O3"
174  fi
175
176  AX_CHECK_COMPILER_FLAGS($CFLAGS, [], [
177	echo ""
178        echo "********************************************************"
179        echo "* WARNING: The guessed CFLAGS don't seem to work with  *"
180        echo "* your compiler.                                       *"
181        echo "* Use ./configure CFLAGS=... to specify your own flags *"
182        echo "********************************************************"
183        echo ""
184        CFLAGS=""
185  ])
186
187fi
188])
189