Only for reference!
If you want to change a compiler setting in Arch Linux, you must config the “makepkg.conf” file.
The file “/etc/makepkg.conf” contains configuration options for make, makepkg and gcc. This file is sourced, so you can include any special compiler flags you wish to use (however, only the variables described below are exported to the build environment). These settings are helpful when building for different architectures and optimizations.
Do keep in mind that not all package Makefiles will use your exported variables. Some of them override them in the original Makefiles or the PKGBUILD.
The default file is fairly well commented, so it may be easiest to simply follow directions given there for customization.
MAKEFLAGS
Has an effect on how many jobs are passed for compilation. Generally -j2, plus 1 for each additional CPU/core is the adequate choice. Optimizing for multiple cores can sometimes increase compiling performance, shortening compile times. However, you should be warned that occasionally using anything but the default can cause compilation problems, though many have agreed that -j3 is fairly safe to use for the majority of packages. E.g., for a dual-core CPU:
MAKEFLAGS=”-j3″
CFLAGS
Arch currently optimizes for i686 and x86-64 architectures. The default makepkg.conf CFLAGS are compatible with all machines within their respective architectures. Further optimizing for CPU type can theoretically enhance performance for packages built with such optimizations, though such gains are most likely not human-perceivable.
As of version 4.3.0, the gcc compiler offers the -march-native switch that enables CPU auto-detection and automatically selects optimizations supported by the local machine at gcc runtime. To use it, just modify the Arch Linux default settings by changing the CFLAGS line as follows:
x86-64 :
CARCH=”x86_64″
CHOST=”x86_64-unknown-linux-gnu”
CFLAGS=”-march=x86-64 -mtune=generic -O2 -pipe”
CXXFLAGS=”${CFLAGS}”
More optimization method :
CFLAGS=”-march=x86-64 -mtune=native -mfpmath=sse -O3 -pipe”
My optimization method :
CFLAGS=”-march=x86-64 -mtune=native -m64 -mmmx -msse3 -msse2 -m3dnow -mfpmath=sse -O3 -pipe -fomit-frame-pointer”
CXXFLAGS=”${CFLAGS}”
Source :
Arch Linux Wiki : http://wiki.archlinux.org/index.php/Makepkg.conf
GCC Offical Document : http://gcc.gnu.org/onlinedocs/gcc-4.3.4/gcc/i386-and-x86_002d64-Options.html