Wow, gold, Ian Lance Taylor's replacement for the GNU linker ld, is fast.

Firefox builds a large (200mb) shared library called libxul, and creating this is often a bottleneck on my machine. Gold speeds this up significantly:

$ cd toolkit/library
$ rm libxul.so
$ time make

# With ld:
real    5m21.202s
user    0m40.499s
sys     0m50.855s

# With gold:
real    2m8.786s
user    0m19.017s
sys     0m21.341s

This is a 2.5x speedup!

Right now, the only way to get gold is to build binutils from source. It's not too hard; just download from here, configure with --enable-gold, make, and then either make install or add a symlink in your ~/bin to binutils-2.20/gold/ld-new.

Have fun!