------- Additional Comments From dank at kegel dot com 2005-06-18 06:38 ------- To be clear, here are the two most worrying rows from the above table, expanded a bit. These are the runtimes of foo4.i in seconds. The cpu family, model, and name are as shown by /proc/cpuinfo.
cpu family 15, model 2, Intel(R) Xeon(TM) CPU 2.60GHz: -fPIC -mtune=pentium4 -O3 gcc-2.95.3: 1.91 seconds gcc-3.4.3: 3.89 gcc-4.0.0: 3.27 cpu family 6, model 8, Pentium III (Coppermine) -fPIC -mtune=pentium3 -O3 gcc-2.95.3: 9.15 gcc-3.4.3: 10.10 gcc-4.0.0: 13.20 gcc-4.0.0 produces code that runs 1.7 and 1.4 times slower than gcc-2.95.3 on these (fairly common!) cpus, even when the proper -mtune is used. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19923