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128 lines
4.7 KiB
Text
128 lines
4.7 KiB
Text
dnl @synopsis AX_CC_MAXOPT
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dnl @summary turn on optimization flags for the C compiler
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dnl @category C
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dnl
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dnl Try to turn on "good" C optimization flags for various compilers
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dnl and architectures, for some definition of "good". (In our case,
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dnl good for FFTW and hopefully for other scientific codes. Modify
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dnl as needed.)
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dnl
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dnl The user can override the flags by setting the CFLAGS environment
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dnl variable.
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dnl
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dnl Note also that the flags assume that ANSI C aliasing rules are
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dnl followed by the code (e.g. for gcc's -fstrict-aliasing), and that
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dnl floating-point computations can be re-ordered as needed.
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dnl
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dnl Requires macros: AX_CHECK_COMPILER_FLAGS, AX_COMPILER_VENDOR,
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dnl
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dnl @version 2011-06-22
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dnl @license GPLWithACException
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dnl @author Steven G. Johnson <stevenj@alum.mit.edu> and Matteo Frigo.
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AC_DEFUN([AX_CC_MAXOPT],
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[
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AC_REQUIRE([AC_PROG_CC])
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AC_REQUIRE([AX_COMPILER_VENDOR])
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AC_REQUIRE([AC_CANONICAL_HOST])
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# Try to determine "good" native compiler flags if none specified via CFLAGS
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if test "$ac_test_CFLAGS" != "set"; then
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CFLAGS=""
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case $ax_cv_c_compiler_vendor in
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dec) CFLAGS="-newc -w0 -O5 -ansi_alias -ansi_args -fp_reorder -tune host"
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;;
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sun) CFLAGS="-native -fast -xO5 -dalign"
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;;
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hp) CFLAGS="+Oall +Optrs_ansi +DSnative"
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;;
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ibm) xlc_opt="-qarch=auto -qtune=auto"
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AX_CHECK_COMPILER_FLAGS($xlc_opt,
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CFLAGS="-O3 -qalias=ansi -w $xlc_opt",
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[CFLAGS="-O3 -qalias=ansi -w"])
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;;
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intel) CFLAGS="-O3"
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# Intel seems to have changed the spelling of this flag recently
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icc_ansi_alias="unknown"
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for flag in -ansi-alias -ansi_alias; do
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AX_CHECK_COMPILER_FLAGS($flag, [icc_ansi_alias=$flag; break])
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done
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if test "x$icc_ansi_alias" != xunknown; then
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CFLAGS="$CFLAGS $icc_ansi_alias"
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fi
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AX_CHECK_COMPILER_FLAGS(-malign-double, CFLAGS="$CFLAGS -malign-double")
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# We used to check for architecture flags here, e.g. -xHost etc.,
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# but these flags are problematic. On icc-12.0.0, "-mavx -xHost"
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# overrides -mavx with -xHost, generating SSE2 code instead of AVX
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# code. ICC does not seem to support -mtune=host or equivalent
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# non-ABI changing flag.
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;;
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clang)
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CFLAGS="-O3 -fomit-frame-pointer"
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AX_CHECK_COMPILER_FLAGS(-mtune=native, CFLAGS="$CFLAGS -mtune=native")
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AX_CHECK_COMPILER_FLAGS(-fstrict-aliasing,CFLAGS="$CFLAGS -fstrict-aliasing")
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;;
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gnu)
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# Default optimization flags for gcc on all systems.
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# Somehow -O3 does not imply -fomit-frame-pointer on ia32
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CFLAGS="-O3 -fomit-frame-pointer"
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# tune for the host by default
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AX_CHECK_COMPILER_FLAGS(-mtune=native, CFLAGS="$CFLAGS -mtune=native")
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# -malign-double for x86 systems
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AX_CHECK_COMPILER_FLAGS(-malign-double, CFLAGS="$CFLAGS -malign-double")
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# -fstrict-aliasing for gcc-2.95+
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AX_CHECK_COMPILER_FLAGS(-fstrict-aliasing,
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CFLAGS="$CFLAGS -fstrict-aliasing")
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# -fno-schedule-insns is pretty much required on all risc
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# processors.
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#
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# gcc performs one pass of instruction scheduling, then a pass of
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# register allocation, then another pass of instruction
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# scheduling. The first pass reorders instructions in a way that
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# is pretty much the worst possible for the purposes of register
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# allocation. We disable the first pass.
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AX_CHECK_COMPILER_FLAGS(-fno-schedule-insns, CFLAGS="$CFLAGS -fno-schedule-insns")
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# flags to enable power ISA 2.07 instructions with gcc (always true with vsx)
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if test "$have_vsx" = "yes"; then
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AX_CHECK_COMPILER_FLAGS(-mcpu=power8, CFLAGS="$CFLAGS -mcpu=power8")
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AX_CHECK_COMPILER_FLAGS(-mpower8-fusion, CFLAGS="$CFLAGS -mpower8-fusion")
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AX_CHECK_COMPILER_FLAGS(-mpower8-vector, CFLAGS="$CFLAGS -mpower8-vector")
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AX_CHECK_COMPILER_FLAGS(-mdirect-move, CFLAGS="$CFLAGS -mdirect-move")
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fi
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;;
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esac
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if test -z "$CFLAGS"; then
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echo ""
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echo "********************************************************"
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echo "* WARNING: Don't know the best CFLAGS for this system *"
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echo "* Use ./configure CFLAGS=... to specify your own flags *"
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echo "* (otherwise, a default of CFLAGS=-O3 will be used) *"
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echo "********************************************************"
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echo ""
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CFLAGS="-O3"
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fi
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AX_CHECK_COMPILER_FLAGS($CFLAGS, [], [
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echo ""
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echo "********************************************************"
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echo "* WARNING: The guessed CFLAGS don't seem to work with *"
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echo "* your compiler. *"
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echo "* Use ./configure CFLAGS=... to specify your own flags *"
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echo "********************************************************"
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echo ""
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CFLAGS=""
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])
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fi
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])
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