For best results, put CPU-specific Cflags in your
/etc/environment file.
Safe Cflags - Gentoo Linux Wiki
For instance, to get the best stable Cflags for a G5 SPARC...
Code:
CHOST="powerpc64-unknown-linux-gnu"
CFLAGS="-mcpu=G5 -O2 -pipe -maltivec -mabi=altivec -fno-strict-aliasing"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O1"