Como bien lo sabe la gente de
Gentoo∞, una de las muchas ventajas de Linux es que permite compilar el código según nuestro procesador y asi mejoramos el rendimiento. Esto se hace indicándole los
flags o
banderas a GCC, el compilador de C.
Sin embargo, muchas veces no sabemos exactamente que banderas le corresponden a nuestro procesador.
Pixelbeat ha escrito un BASH script que nos ayuda conocer los flags que corresponden.
El programa sólo funciona para Linux y para procesadores de 32 bits.
Descargar:
gcccpuopt.txt∞
El código:
#!/bin/sh
# Author: pixelbeat
#This script is Linux specific
#It should work on any gcc >= 2.95 at least
#these apply to any arch (just here for reference)
unsafe_math_opts="-ffast-math -fno-math-errno -funsafe-math-optimizations -fno-trapping-math"
gcc_version=`gcc -dumpversion | sed 's/\([0-9]\{1,\}\.[0-9]\{1,\}\)\.*\([0-9]\{1,\}\)\{0,1\}/editor/'`
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="$value"
fi
done < /proc/cpuinfo
unset IFS
if [ "$vendor_id"
"AuthenticAMD" ]; then
if [ "$cpu_family"
"4" ]; then
_CFLAGS="$_CFLAGS -march=i486"
elif [ "$cpu_family"
"5" ]; then
if [ "$cpu_model" -lt "4" ]; then
_CFLAGS="$_CFLAGS -march=pentium"
elif [ "$cpu_model"
"6" ] || [ "$cpu_model"
"7" ]; then
_CFLAGS="$_CFLAGS -march=k6"
elif [ "$cpu_model"
"8" ] || [ "$cpu_model"
"12" ]; then
if expr $gcc_version '>=' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=k6-2"
else
_CFLAGS="$_CFLAGS -march=k6"
fi
elif [ "$cpu_model"
"9" ] || [ "$cpu_model"
"13" ]; then
if expr $gcc_version '>=' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=k6-3"
else
_CFLAGS="$_CFLAGS -march=k6"
fi
fi
elif [ "$cpu_family"
"6" ]; then
if [ "$cpu_model" -le "3" ]; then
if expr $gcc_version '>=' 3. >/dev/null; then
_CFLAGS="$_CFLAGS -march=athlon"
else
_CFLAGS="$_CFLAGS -march=k6"
fi
elif [ "$cpu_model"
"4" ]; then
if expr $gcc_version '>=' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=athlon-tbird"
elif expr $gcc_version '>=' 3. >/dev/null; then
_CFLAGS="$_CFLAGS -march=athlon"
else
_CFLAGS="$_CFLAGS -march=k6"
fi
elif [ "$cpu_model" -ge "6" ]; then #athlon-{4,xp,mp}
if expr $gcc_version '>=' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=athlon-xp"
elif expr $gcc_version '>=' 3. >/dev/null; then
_CFLAGS="$_CFLAGS -march=athlon"
else
_CFLAGS="$_CFLAGS -march=k6"
fi
fi
fi
else #everything else "GenuineIntel"
if [ "$cpu_family"
"3" ]; then
_CFLAGS="$_CFLAGS -march=i386"
elif [ "$cpu_family"
"4" ]; then
_CFLAGS="$_CFLAGS -march=i486"
elif [ "$cpu_family"
"5" ] && expr $gcc_version '<' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=pentium"
elif [ "$cpu_family" -ge "6" ] && expr $gcc_version '<' 3.1 >/dev/null; then
_CFLAGS="$_CFLAGS -march=pentiumpro"
elif [ "$cpu_family"
"5" ]; then
if [ "$cpu_model" != "4" ]; then
_CFLAGS="$_CFLAGS -march=pentium"
else
_CFLAGS="$_CFLAGS -march=pentium-mmx" #No overlap with other vendors
fi
elif [ "$cpu_family"
"6" ]; then
if echo "$flags" | grep -vq cmov; then #gcc incorrectly assumes i686 always has cmov
_CFLAGS="$_CFLAGS -march=pentium -mcpu=pentiumpro" #VIA CPUs exhibit this
else
if [ "$cpu_model"
"0" ] || [ "$cpu_model"
"1" ]; then
_CFLAGS="$_CFLAGS -march=pentiumpro"
elif [ "$cpu_model" -ge "3" ] && [ "$cpu_model" -le "6" ]; then #4=TM5600 at least
_CFLAGS="$_CFLAGS -march=pentium2"
elif [ "$cpu_model" -ge "7" ] && [ "$cpu_model" -le "11" ]; then #9 invalid
_CFLAGS="$_CFLAGS -march=pentium3"
fi
fi
elif [ "$cpu_family"
"15" ]; then
_CFLAGS="$_CFLAGS -march=pentium4"
fi
fi
if expr $gcc_version '>=' 3.1 >/dev/null; then
if echo "$flags" | grep -q sse2; then
_CFLAGS="$_CFLAGS -mfpmath=sse -msse2"
elif echo "$flags" | grep -q sse; then
_CFLAGS="$_CFLAGS -mfpmath=sse -msse"
fi
if echo "$flags" | grep -q mmx; then
_CFLAGS="$_CFLAGS -mmmx"
fi
if echo "$flags" | grep -q 3dnow; then
_CFLAGS="$_CFLAGS -m3dnow"
fi
fi
echo "$_CFLAGS"
