Determine set of best gcc optimization flags for the current host.

gcccpuopt.sh

#!/bin/sh

# Print the gcc cpu specific options tailored for the current CPU

# Author:
#    http://www.pixelbeat.org/
# Notes:
#    This script currently supports Linux,FreeBSD,Cygwin
#    This script is x86 (32 bit) specific
#    It should work on any gcc >= 2.95 at least
#    It only returns CPU specific options. You probably also want -03 etc.
# Changes:
#    V0.1, 12 Mar 2003, Initial release
#    V0.2, 01 Jun 2005, Added support for 3.2>=gcc<=4.0
#    V0.3, 03 Jun 2005, Added support for pentium-m
#    V0.4, 03 Jun 2005, Fix silly bugs
#    V0.5, 07 Jun 2005, Clarify/Simplify confusing floating point expr usage
#                       Print warning when CPU only supported on a newer gcc
#    V0.6, 15 Dec 2006, Added support for Intel Core and Core 2 processors
#                       Added support for 4.1>=gcc<=4.3
#                       Added support for gcc -msse3 option
#                       Added support for new gcc -march=native option
#    V0.7, 18 Dec 2006, Changes from Conor McDermottroe
#                         Added support for FreeBSD
#                         Remove bash specific constructs
#                         Better error handling
#    V0.8, 19 Dec 2006, Give warnings and 32 bit -march on 64 bit platforms.
#                       Previously it just gave an invalid blank -march.
#                       Reported and tested by Ewan Oughton.
#    V0.9, 30 Apr 2007, Give error if compiler not present.
#                       Warn about rather than default to -march=native option.
#   V0.92, 08 Nov 2007, Change from Krzysztof Jankowski to support Cygwin.
#                       Added support for AMD family 10 processors.
#                       Add support for gcc -msse4 & -msse5 options.
#                       Use "prescott" rather than "pentium4" for all
#                       models >= 3 in intel family 15, not just model 3.
#   V0.93, 13 Nov 2007, Oops, actually not all intel family 15, model >= 3
#                       are prescotts. Use the sse3 flag to distinguish.
#   V0.94, 31 Dec 2007, Oops, actually all intel family 15, model >= 3
#                       are prescotts. This was indicated by Adam Drzewiecki.
#                       I was confused by a bug in older linux kernels where pni
#                       was not reported for my intel "F41" processor at least.
#   V0.95, 18 Jan 2008, Changes from Conor McDermottroe
#                         Support for Mac OS X
#                         Support for FreeBSD base system
#   V0.96, 17 Dec 2008, Following a report from Alfredo Pons, add support
#                       for newer intel core2 processors (models 23,26,29,...)
#                       by assuming models >= 15 are core2.
#                       Report details of unrecognised CPUs.
#   V0.97, 19 Dec 2008, Use prescott for Intel Atom (model 28).
#                       Ensure all errors are output to stderr.
#   V0.98, 24 Feb 2009, Actually Intel Atom (model 28) is core2 ISA compliant.
#                       It's an in-order core (like i586) so mtune as such.
#   V0.99, 30 Apr 2009, Intel Atom (model 28) is getting a corresponding "atom"
#                       option in GCC 4.5
#   V0.99.3, 11 Aug 2009, Support for AMD Geode LX processor.
#   V0.99.4, 24 Oct 2009, Following a report from Maxime de Roucy, add support
#                         for AMD family 17 (griffin).

if [ "$1" = "--version" ]; then
	echo "0.99.4" && exit
fi

# This table shows when -march options were introduced into _official_ gcc releases.
# Note there are vendor deviations that complicate this.
# For e.g. redhat introduced the prescott option in 3.3-13.
#   gcc-2.95   = i386, i486, i586,pentium, i686,pentiumpro, k6
#   gcc-3.0   += athlon
#   gcc-3.1   += pentium-mmx, pentium2, pentium3, pentium4, k6-2, k6-3, athlon-{tbird, 4,xp,mp}
#   gcc-3.3   += winchip-c6, winchip2, c3
#   gcc-3.4.0 += k8,opteron,athlon64,athlon-fx, c3-2
#   gcc-3.4.1 += pentium-m, pentium3m, pentium4m, prescott, nocona
#   gcc-4.3   += core2, amdfam10, geode
#   gcc-4.5   += atom

[ -z "$CC" ] && CC=gcc

try_gcc_options() {
	$CC $* -S -o /dev/null -xc /dev/null >/dev/null 2>&1
}

if ! try_gcc_options; then
	echo "Error: Couldn't execute your compiler ($CC)" >&2
	exit 1
fi

if try_gcc_options -march=native; then
	echo "Warning: Your compiler supports the -march=native option which you may prefer" >&2
fi

if ! try_gcc_options -march=i386; then
	if ! try_gcc_options -m32 -march=i386; then
		echo "Error: This script only supports 32 bit x86 architectures" >&2
		exit 1
	else
		echo "Warning: The optimum *32 bit* architecture is reported" >&2
		m32="-m32 "
	fi
fi

try_line() {
	skip=0
	for arch in $1; do
		if try_gcc_options $m32 -march=$arch; then
			echo $arch
			return
		elif [ "$skip" = "0" ] && [ "$arch" != "native" ]; then
			skip=1
			echo "Warning: Newer versions of GCC better support your CPU with -march=$arch" >&2
		fi
	done
	return 1
}

read_cpu_data_linux() {
	IFS=":"
	while read name value; do
		unset IFS
		name=$(echo $name)
		value=$(echo $value)
		IFS=":"
		if [ "$name" = "vendor_id" ]; then
			vendor_id="$value"
		elif [ "$name" = "cpu family" ]; then
			cpu_family="$value"
		elif [ "$name" = "model" ]; then
			cpu_model="$value"
		elif [ "$name" = "flags" ]; then
			flags="$value"
			break #flags last so break early
		fi
	done </proc/cpuinfo
	unset IFS
}

read_cpu_data_freebsd() {
	local _line _cpu_id

	if [ ! -r /var/run/dmesg.boot ]; then
		echo "Error: /var/run/dmesg.boot does not exist!" >&2
		exit 1
	fi

	IFS="
"
	for _line in $(grep -A2 '^CPU: ' /var/run/dmesg.boot); do
		if [ -n "$(echo $_line | grep '^  Origin = ')" ]; then
			vendor_id="$(echo $_line | sed -e 's/^  Origin = .//' -e 's/[^A-Za-z0-9].*$//')"
			_cpu_id="$(echo $_line | sed -e 's/^.*Id = //' -e 's/ .*$//' -e 'y/abcdef/ABCDEF/')"
			cpu_family=$((($_cpu_id & 0xF0F) >> 8))
			cpu_model=$((($_cpu_id & 0xF0) >> 4))
		fi
		if [ -n "$(echo $_line | grep '^  Features=')" ]; then
flags="$(echo $_line | sed -e 's/^.*<//' -e 's/>.*//' -e 's/,/ /g' | tr 'A-Z' 'a-z')"
		fi
	done
	unset IFS
}

read_cpu_data_darwin() {
	vendor_id="$(/usr/sbin/sysctl -n machdep.cpu.vendor)"
	cpu_family="$(/usr/sbin/sysctl -n machdep.cpu.family)"
	cpu_model="$(/usr/sbin/sysctl -n machdep.cpu.model)"
	flags="$(/usr/sbin/sysctl -n machdep.cpu.features | tr 'A-Z' 'a-z')"
}

read_cpu_data() {
	# Default values
	vendor_id="NotFound"
	cpu_family="-1"
	cpu_model="-1"
	flags=""
	case "$(uname)" in
	Linux | CYGWIN*)
		read_cpu_data_linux
		;;
	FreeBSD)
		read_cpu_data_freebsd
		;;
	Darwin)
		read_cpu_data_darwin
		;;
	*)
		echo "Error: $(uname) is not a supported operating system" >&2
		exit 1
		;;
	esac
}

read_cpu_data

if [ "$vendor_id" = "AuthenticAMD" ]; then
	if [ $cpu_family -eq 4 ]; then
		_CFLAGS="-march=i486"
	elif [ $cpu_family -eq 5 ]; then
		if [ $cpu_model -lt 4 ]; then
			_CFLAGS="-march=pentium"
		elif [ \( $cpu_model -eq 6 \) -o \( $cpu_model -eq 7 \) ]; then
			_CFLAGS="-march=k6"
		elif [ \( $cpu_model -eq 8 \) -o \( $cpu_model -eq 12 \) ]; then
			line="k6-2 k6"
		elif [ \( $cpu_model -eq 9 \) -o \( $cpu_model -eq 13 \) ]; then
			line="k6-3 k6-2 k6"
		elif [ $cpu_model -eq 10 ]; then #geode LX
			line="geode k6-2 k6"
			#The LX supports 3dnowext in addition to the k6-2 instructions,
			#however gcc doesn't support explicitly selecting that.
		fi
	elif [ $cpu_family -eq 6 ]; then
		if [ $cpu_model -le 3 ]; then
			line="athlon k6-3 k6-2 k6"
		elif [ $cpu_model -eq 4 ]; then
			line="athlon-tbird athlon k6-3 k6-2 k6"
		elif [ $cpu_model -ge 6 ]; then #athlon-{4,xp,mp} (also geode NX)
			line="athlon-4 athlon k6-3 k6-2 k6"
		fi
	elif [ $cpu_family -eq 15 ]; then #k8,opteron,athlon64,athlon-fx
		line="k8 athlon-4 athlon k6-3 k6-2 k6"
	elif [ $cpu_family -eq 16 ] || #barcelona,amdfam10
		[ $cpu_family -eq 17 ]; then #griffin
		line="amdfam10 k8 athlon-4 athlon k6-3 k6-2 k6"
	fi
elif [ "$vendor_id" = "CentaurHauls" ]; then
	if [ $cpu_family -eq 5 ]; then
		if [ $cpu_model -eq 4 ]; then
			line="winchip-c6 pentium"
		elif [ $cpu_model -eq 8 ]; then
			line="winchip2 winchip-c6 pentium"
		elif [ $cpu_model -ge 9 ]; then
			line="winchip2 winchip-c6 pentium" #actually winchip3 but gcc doesn't support this currently
		fi
	elif [ $cpu_family -eq 6 ]; then
		if echo "$flags" | grep -q cmov; then
			fallback=pentiumpro
		else
			fallback=pentium #gcc incorrectly assumes i686 always has cmov
		fi
		if [ $cpu_model -eq 6 ]; then
			_CFLAGS="-march=pentium" # ? Cyrix 3 (samuel)
		elif [ $cpu_model -eq 7 ] || [ $cpu_model -eq 8 ]; then
			line="c3 winchip2 winchip-c6 $fallback"
		elif [ $cpu_model -ge 9 ]; then
			line="c3-2 c3 winchip2 winchip-c6 $fallback"
		fi
	fi
elif [ "$vendor_id" = "GenuineIntel" ]; then
	if [ $cpu_family -eq 3 ]; then
		_CFLAGS="-march=i386"
	elif [ $cpu_family -eq 4 ]; then
		_CFLAGS="-march=i486"
	elif [ $cpu_family -eq 5 ]; then
		if [ $cpu_model -ne 4 ]; then
			_CFLAGS="-march=pentium"
		else
			line="pentium-mmx pentium" #No overlap with other vendors
		fi
	elif [ $cpu_family -eq 6 ]; then
		if [ \( $cpu_model -eq 0 \) -o \( $cpu_model -eq 1 \) ]; then
			_CFLAGS="-march=pentiumpro"
		elif [ \( $cpu_model -ge 3 \) -a \( $cpu_model -le 6 \) ]; then #4=TM5600 at least
			line="pentium2 pentiumpro pentium-mmx pentium i486 i386"
		elif [ \( $cpu_model -eq 9 \) -o \( $cpu_model -eq 13 \) ]; then #centrino
			line="pentium-m pentium4 pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		elif [ \( $cpu_model -eq 14 \) ]; then #Core
			line="prescott pentium-m pentium4 pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		elif [ $cpu_model -eq 28 ]; then #Atom
			line="atom core2 pentium-m pentium4 pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		elif [ $cpu_model -ge 15 ]; then #Core2
			line="core2 pentium-m pentium4 pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		elif [ \( $cpu_model -ge 7 \) -a \( $cpu_model -le 11 \) ]; then
			line="pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		fi
	elif [ $cpu_family -eq 15 ]; then
		line="pentium4 pentium3 pentium2 pentiumpro pentium-mmx pentium i486 i386"
		if [ $cpu_model -ge 3 ]; then
			line="prescott $line"
		fi
	fi
fi

if [ \( -z "$_CFLAGS" \) -a \( -z "$line" \) ]; then
	echo "\
Unrecognised CPU. Please email the following to: P@draigBrady.com
  Vendor:$vendor_id family:$cpu_family model:$cpu_model
  flags:$flags" >&2
	exit 1
fi

[ -z "$_CFLAGS" ] && _CFLAGS="-march=$(try_line "$line")"

#The Atom CPU supports the full core2 instruction set,
#but it's an in-order core, the last one of those being the i586.
#Therefore if gcc hasn't explicit support for the Atom,
#tune it for the i586 architecture.
if ! echo "$_CFLAGS" | grep -q "atom"; then #gcc hasn't specific Atom support
	if echo "$line" | grep -q "core2"; then #atom ISA line
		if [ $cpu_model -eq 28 ]; then #atom
			if echo "$_CFLAGS" | grep -E -q "(core2|pentium[^ ])"; then #gcc chose out of order arch
				_CFLAGS="$_CFLAGS -mtune=pentium" #tune for last in-order core
			fi
		fi
	fi
fi

#SSE is not used for floating point by default in gcc 32 bit
#so turn that on here.
if echo "$flags" | grep -q "sse"; then
	if try_gcc_options "-mfpmath=sse"; then #gcc >= 3.1
		_CFLAGS="$_CFLAGS -mfpmath=sse"
	fi
fi

#The SSE options are mostly selected automatically
#when a particular march option is selected.
#There are a few exceptions unfortunately, which we handle here.
#Note the sse instruction lines are:
#   intel: [sse4.2] [sse4.1] ssse3 sse3 sse2 sse ...
#   amd:   [sse5] sse4a [sse3] sse2 sse ...
# The bracketed ones are only available on some cpus
# in a particular family and so need to be added explicitly.
if echo "$_CFLAGS" | grep -q "amdfam10"; then
	if echo "$flags" | grep -q "sse5"; then
		if try_gcc_options "-msse5"; then #gcc >= 4.3
			_CFLAGS="$_CFLAGS -msse5"
		fi
	fi
elif echo "$_CFLAGS" | grep -E -q "(k8|c3-2)"; then
	if echo "$flags" | grep -E -q "(sse3|pni)"; then
		if try_gcc_options "-msse3"; then #gcc >= 3.3.3
			_CFLAGS="$_CFLAGS -msse3"
		fi
	fi
elif echo "$_CFLAGS" | grep -q "core2"; then
	if echo "$flags" | grep -q "sse4_2"; then
		if try_gcc_options "-msse4"; then #gcc >= 4.3
			_CFLAGS="$_CFLAGS -msse4"
		fi
	elif echo "$flags" | grep -q "sse4_1"; then
		if try_gcc_options "-msse4.1"; then #gcc >= 4.3
			_CFLAGS="$_CFLAGS -msse4.1"
		fi
	fi
fi

echo "$m32$_CFLAGS"