francesco biscani <bluesca...@gmail.com> writes: > I'm experiencing a strange behaviour with GCC 4.4.1. Basically I have > some C++ mathematical code which gets a ~x2 performance drop if I > *remove* the following debug line from the code:
This message is not appropriate for the mailing list g...@gcc.gnu.org. It is appropriate for gcc-h...@gcc.gnu.org. Please take any followups to gcc-help. Thanks. In my experience, a performance drop in a tight loop when you remove a line of code means that your loop is extremely sensitive to cache line boundaries. It can be difficult to find the optimal code other than by testing various command line options. Options to particularly test are -falign-loops, -falign-labels, and -falign-jumps. Also, be sure that you are using a -mtune option appropriate for the processor on which you are running. E.g., you mention Core2, so you should be using -mtune=core2. You may also get some benefit from the micro-architectural optimizer at http://code.google.com/p/mao, but note that that is not part of gcc, and it is still under development. Ian
